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+# --- Contents
+
+|                                                                            |    |
+|----------------------------------------------------------------------------|----|
+| Foreword .....                                                             | 4  |
+| 1 Scope.....                                                               | 5  |
+| 2 References.....                                                          | 5  |
+| 3 Definitions and abbreviations .....                                      | 6  |
+| 3.1 Abbreviations .....                                                    | 6  |
+| 4 General .....                                                            | 6  |
+| 5 Adaptive Multi-Rate speech codec transcoding functions.....              | 8  |
+| 6 Adaptive Multi-Rate speech codec ANSI C-code .....                       | 8  |
+| 7 Adaptive Multi-Rate speech codec test vectors .....                      | 8  |
+| 8 Adaptive Multi-Rate speech codec source controlled rate operation .....  | 9  |
+| 9 Adaptive Multi-Rate speech codec voice activity detection.....           | 9  |
+| 10 Adaptive Multi-Rate speech codec comfort noise insertion .....          | 10 |
+| 11 Adaptive Multi-Rate speech codec error concealment of lost frames ..... | 10 |
+| 12 Adaptive Multi-Rate speech codec frame structure .....                  | 10 |
+| 13 Adaptive Multi-Rate speech codec interface to RAN.....                  | 10 |
+| 14 Adaptive Multi-Rate speech codec performance characterisation.....      | 11 |
+| Annex A (informative): Change history.....                                 | 12 |
+
+# --- Foreword
+
+This Technical Specification has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- 1 Scope
+
+The present document is an introduction to the speech processing parts of the narrowband telephony speech service employing the Adaptive Multi-Rate (AMR) speech coder. A general overview of the speech processing functions is given, with reference to the documents where each function is specified in detail.
+
+# --- 2 References
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+- For a specific reference, subsequent revisions do not apply.
+- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+
+- [1] GSM 03.50: "Digital cellular telecommunications system (Phase 2); Transmission planning aspects of the speech service in the GSM Public Land Mobile Network (PLMN) system".
+- [2] 3GPP TS 26.090: "Transcoding functions".
+- [3] 3GPP TS 26.073: "Adaptive Multi-Rate (AMR); ANSI C source code".
+- [4] 3GPP TS 26.074: "Adaptive Multi-Rate (AMR); Test sequences".
+- [5] 3GPP TS 26.093: "Source Controlled Rate operation".
+- [6] 3GPP TS 26.094: "AMR Speech Codec; Voice Activity Detector".
+- [7] 3GPP TS 26.092: "Mandatory Speech Codec speech processing functions; AMR Speech Codec; Comfort noise aspects".
+- [8] 3GPP TS 26.091: "Mandatory Speech Codec speech processing functions; AMR Speech Codec; Error concealment of lost frames".
+- [9] 3GPP TS 26.101: "Frame Structure".
+- [10] 3GPP TS 26.102: "AMR Speech Codec; Interface to Iu and Uu".
+- [11] 3GPP TS 26.901: "AMR wideband speech codec feasibility study report".
+- [12] ITU-T Recommendation G.711: "Pulse code modulation (PCM) of voice frequencies".
+- [13] ITU-T Recommendation H.324: "Terminal for low bit-rate multimedia communication".
+
+# --- 3 Definitions and abbreviations
+
+## 3.1 Abbreviations
+
+For the purposes of this TS, the following abbreviations apply:
+
+|       |                                                                                                 |
+|-------|-------------------------------------------------------------------------------------------------|
+| ACELP | Algebraic Code Excited Linear Prediction                                                        |
+| AMR   | Adaptive Multi-Rate                                                                             |
+| BFI   | Bad Frame Indication                                                                            |
+| CHD   | Channel Decoder                                                                                 |
+| CHE   | Channel Encoder                                                                                 |
+| GSM   | Global System for Mobile communications                                                         |
+| ITU-T | International Telecommunication Union – Telecommunication standardisation sector (former CCITT) |
+| PCM   | Pulse Code Modulation                                                                           |
+| PLMN  | Public Land Mobile Network                                                                      |
+| PSTN  | Public Switched Telephone Network                                                               |
+| RX    | Receive                                                                                         |
+| SCR   | Source Controlled Rate                                                                          |
+| SPD   | SPeech Decoder                                                                                  |
+| SPE   | SPeech Encoder                                                                                  |
+| TC    | Transcoder                                                                                      |
+| TX    | Transmit                                                                                        |
+| UE    | User Equipment (terminal)                                                                       |
+
+# --- 4 General
+
+The AMR speech coder consists of the multi-rate speech coder, a source controlled rate scheme including a voice activity detector and a comfort noise generation system, and an error concealment mechanism to combat the effects of transmission errors and lost packets.
+
+The multi-rate speech coder is a single integrated speech codec with eight source rates from 4.75 kbit/s to 12.2 kbit/s, and a low rate background noise encoding mode. The speech coder is capable of switching its bit-rate every 20 ms speech frame upon command.
+
+A reference configuration where the various speech processing functions are identified is given in Figure 1. In this figure, the relevant specifications for each function are also indicated.
+
+In Figure 1, the audio parts including analogue to digital and digital to analogue conversion are included, to show the complete speech path between the audio input/output in the User Equipment (UE) and the digital interface of the network. The detailed specification of the audio parts is not within the scope of the present document. These aspects are only considered to the extent that the performance of the audio parts affect the performance of the speech transcoder.
+
+![Figure 1: Overview of audio processing functions. The diagram is split into TRANSMIT SIDE and RECEIVE SIDE. The TRANSMIT SIDE shows the flow from BSS side only (GSM 06.60.AMR) and MS side only (GSM 03.50) through various processing blocks like LPF, A/D, 8bit/A-law to 13-bit uniform, and into the Speech Encoder (GSM 06.60.AMR). It also includes Voice Activity Detector (VAD) (GSM 06.82.AMR), Comfort Noise TX Functions (GSM 06.62.AMR), and DTX Control and Operation (GSM 06.81.AMR) blocks, resulting in outputs for SP flag and Info. bits. The RECEIVE SIDE shows the reverse process, starting from Info. bits, BFI, SID, and TAF inputs into the DTX Control and Operation block, followed by Speech frame substitution, Speech Decoder (GSM 06.60.AMR), and Comfort Noise RX Functions (GSM 06.62.AMR), leading to the final output through D/A and LPF blocks (GSM 03.50) to the BSS side only (GSM 06.60.AMR).](997233d405f0d4b89ddeb7683e047f66_img.jpg)
+
+Figure 1: Overview of audio processing functions. The diagram is split into TRANSMIT SIDE and RECEIVE SIDE. The TRANSMIT SIDE shows the flow from BSS side only (GSM 06.60.AMR) and MS side only (GSM 03.50) through various processing blocks like LPF, A/D, 8bit/A-law to 13-bit uniform, and into the Speech Encoder (GSM 06.60.AMR). It also includes Voice Activity Detector (VAD) (GSM 06.82.AMR), Comfort Noise TX Functions (GSM 06.62.AMR), and DTX Control and Operation (GSM 06.81.AMR) blocks, resulting in outputs for SP flag and Info. bits. The RECEIVE SIDE shows the reverse process, starting from Info. bits, BFI, SID, and TAF inputs into the DTX Control and Operation block, followed by Speech frame substitution, Speech Decoder (GSM 06.60.AMR), and Comfort Noise RX Functions (GSM 06.62.AMR), leading to the final output through D/A and LPF blocks (GSM 03.50) to the BSS side only (GSM 06.60.AMR).
+
+**Figure 1: Overview of audio processing functions**
+
+- 1) 8-bit A-law or  $\mu$ -law PCM (ITU-T Recommendation G.711 [12] ), 8 000 samples/s;
+- 2) 13-bit uniform PCM, 8 000 samples/s;
+- 3) Voice Activity Detector (VAD) flag;
+- 4) Encoded speech frame, 50 frames/s, number of bits/frame depending on the AMR codec mode;
+- 5) Silence Descriptor (SID) frame;
+- 6) TX\_TYPE, 2 bits, indicates whether information bits are available and if they are speech or SID information;
+- 7) Information bits delivered to the 3G AN;
+- 8) Information bits received from the 3G AN;
+- 9) RX\_TYPE, the type of frame received quantized into three bits.
+
+# 5 Adaptive Multi-Rate speech codec transcoding functions
+
+The adaptive multi-rate speech codec is described in [2]. The technical content is identical to that of 3GPP TS 26.090.
+
+As shown in Figure 1, the speech encoder takes its input as a 13-bit uniform Pulse Code Modulated (PCM) signal either from the audio part of the UE or on the network side, from the Public Switched Telephone Network (PSTN) via an 8-bit A-law or  $\mu$ -law to 13-bit uniform PCM conversion. The encoded speech at the output of the speech encoder is packetized and delivered to the network interface. In the receive direction, the inverse operations take place.
+
+The detailed mapping between input blocks of 160 speech samples in 13-bit uniform PCM format to encoded blocks (in which the number of bits depends on the presently used codec mode) and from these to output blocks of 160 reconstructed speech samples is described in [2]. The coding scheme is Multi-Rate Algebraic Code Excited Linear Prediction. The bit-rates of the source codec are listed in Table 1.
+
+An AMR speech codec capable UE shall support all source rates listed in Table 1.
+
+**Table 1: Source codec bit-rates for the AMR codec.**
+
+| Codec mode | Source codec bit-rate    |
+|------------|--------------------------|
+| AMR_12.20  | 12,20 kbit/s (GSM EFR)   |
+| AMR_10.20  | 10,20 kbit/s             |
+| AMR_7.95   | 7,95 kbit/s              |
+| AMR_7.40   | 7,40 kbit/s (IS-641)     |
+| AMR_6.70   | 6,70 kbit/s (PDC-EFR)    |
+| AMR_5.90   | 5,90 kbit/s              |
+| AMR_5.15   | 5,15 kbit/s              |
+| AMR_4.75   | 4,75 kbit/s              |
+| AMR_SID    | 1,80 kbit/s (see note 1) |
+
+NOTE 1: Assuming SID frames are continuously transmitted
+
+NOTE 2: GSM-EFR is the 3GPP TS 26.090 Enhanced Full Rate Speech Codec (also identical to the TTA TDMA-US1 Enhanced speech codec)
+
+NOTE 3: IS-641 is the TTA/EIA IS-641 TDMA Enhanced Full Rate Speech Codec
+
+NOTE 4: PDC-EFR is the ARIB 6.7 kbit/s Enhanced Full Rate Speech Codec
+
+# 6 Adaptive Multi-Rate speech codec ANSI C-code
+
+The ANSI-C code of the speech codec, VAD and CNG system are described in [3]. The ANSI C-code is mandatory. The ANSI C-code is identical to that of 3GPP TS 26.073 [3].
+
+# 7 Adaptive Multi-Rate speech codec test vectors
+
+A set of digital test sequences is specified in [4], thus enabling the verification of compliance, i.e. bit-exactness, to a high degree of confidence. The test vectors are identical to those of 3GPP TS 26.074 [4].
+
+The test sequences are defined separately for:
+
+- The speech codec described in [2],
+- The VAD described in [6],
+- The CN generation described in [7].
+
+The adaptive multi-rate speech transcoder, VAD, SCR system and comfort noise parts of the audio processing functions (see Figure 1) are defined in bit exact arithmetic. Consequently, they shall react on a given input sequence always with
+
+the corresponding bit exact output sequence, provided that the internal state variables are also always exactly in the same state at the beginning of the test.
+
+The input test sequences provided shall force the corresponding output test sequences, provided that the tested modules are in their home-state when starting.
+
+The modules may be set into their home states by provoking the appropriate homing-functions.
+
+NOTE: This is normally done during reset (initialisation of the codec).
+
+Special inband signalling frames (encoder-homing-frame and decoder-homing-frame) described in [2] have been defined to provoke these homing-functions also in remotely placed modules.
+
+At the end of the first received homing frame, the audio functions that are defined in a bit exact way shall go into their predefined home states. The output corresponding to the first homing frame is dependent on the codec state when the frame was received. Any consecutive homing frames shall produce corresponding homing frames at the output.
+
+# --- 8 Adaptive Multi-Rate speech codec source controlled rate operation
+
+The source controlled rate operation of the adaptive multi-rate speech codec is defined in [5].
+
+During a normal telephone conversation, the participants alternate so that, on the average, each direction of transmission is occupied about 50 % of the time. Source controlled rate (SCR) is a mode of operation where the speech encoder encodes speech frames containing only background noise with a lower bit-rate than normally used for encoding speech. A network may adapt its transmission scheme to take advantage of the varying bit-rate. This may be done for the following two purposes:
+
+- 1) In the UE, battery life will be prolonged or a smaller battery could be used for a given operational duration.
+- 2) The average required bit-rate is reduced, leading to a more efficient transmission with decreased load and hence increased capacity.
+
+The following functions are required for the source controlled rate operation:
+
+- a Voice Activity Detector (VAD) on the TX side;
+- evaluation of the background acoustic noise on the TX side, in order to transmit characteristic parameters to the RX side;
+- generation of comfort noise on the RX side during periods when no normal speech frames are received.
+
+The transmission of comfort noise information to the RX side is achieved by means of a Silence Descriptor (SID) frame, which is sent at regular intervals.
+
+# --- 9 Adaptive Multi-Rate speech codec voice activity detection
+
+The adaptive multi-rate VAD function is described in [6].
+
+The input to the VAD is the input speech itself together with a set of parameters computed by the adaptive multi-rate speech encoder. The VAD uses this information to decide whether each 20 ms speech coder frame contains speech or not.
+
+The VAD algorithm is described in [6], and the corresponding C code is defined in [3]. The verification of compliance to [6], is achieved by use of digital test sequences applied to the same interface as the test sequences for the speech codec.
+
+# --- 10 Adaptive Multi-Rate speech codec comfort noise insertion
+
+The adaptive multi-rate comfort noise insertion function is described in [7].
+
+When speech is absent, the synthesis in the speech decoder is different from the case when normal speech frames are received. The synthesis of an artificial noise based on the received non-speech parameters is termed comfort noise generation.
+
+The comfort noise generation process is as follows:
+
+- the evaluation of the acoustic background noise in the transmitter;
+- the noise parameter encoding (SID frames) and decoding, and
+- the generation of comfort noise in the receiver.
+
+The comfort noise processes and the algorithm for updating the noise parameters during speech pauses are defined in detail in [7], and the corresponding C code is defined in [3]. The comfort noise mechanism is based on the adaptive multi-rate speech codec defined in [2].
+
+# --- 11 Adaptive Multi-Rate speech codec error concealment of lost frames
+
+The adaptive multi-rate speech codec error concealment of lost frames is described in [8].
+
+Frames may be lost due to transmission errors or frame stealing in a wireless environment. Actions which shall be taken in these cases, both for lost speech frames and for lost SID frames are described in [8]. Error concealment actions shall be used also in the case of lost speech packets in the transport network. The methods described in [8] may with some modifications be used as a basis for such actions.
+
+In order to mask the effect of isolated lost frames, the speech decoder shall be informed and the error concealment actions shall be initiated, whereby a set of predicted parameters are used in the speech synthesis. Insertion of speech signal independent silence frames is not allowed. For several subsequent lost frames, a muting technique shall be used to indicate to the listener that transmission has been interrupted.
+
+# --- 12 Adaptive Multi-Rate speech codec frame structure
+
+The adaptive multi-rate speech frame structure is described in [9]. The output interface format from the encoder and input interface format to the decoder is divided into two parts; the core speech data part, which is the speech coded bits, and the other part is an additional data part with mode information.
+
+The interface format described in [9] is termed AMR interface format 1 (AMR IF1).
+
+Annex A of [9] describes an octet aligned frame format which shall be used in applications requiring octet alignment, such as for ITU-T Recommendation H.324 [13]. This format is termed AMR interface format 2 (AMR IF2).
+
+# --- 13 Adaptive Multi-Rate speech codec interface to RAN
+
+The adaptive multi-rate speech service interface to RAN is described in [10].
+
+# --- 14 Adaptive Multi-Rate speech codec performance characterisation
+
+The adaptive multi-rate speech channel performance characterisation is described in [11].
+
+# Annex A (informative): Change history
+
+| <b>Document history</b> |                 |                                           |           |            |                                      |            |            |  |
+|-------------------------|-----------------|-------------------------------------------|-----------|------------|--------------------------------------|------------|------------|--|
+| V.0.1.0                 | March 1999      | First Draft                               |           |            |                                      |            |            |  |
+| V.0.1.1                 | April 1999      | References changed                        |           |            |                                      |            |            |  |
+| V.1.0.0                 | April 22, 1999  | Editorial changes                         |           |            |                                      |            |            |  |
+| V.2.0.0                 | June 15, 1999   | Minor Editorial changes                   |           |            |                                      |            |            |  |
+| V.3.0.0                 | June 22, 1999   | Approved at 3GPP TSG SA#4 Plenary meeting |           |            |                                      |            |            |  |
+| V.3.0.1                 | August 22, 1999 | Reformatted                               |           |            |                                      |            |            |  |
+| <b>Change history</b>   |                 |                                           |           |            |                                      |            |            |  |
+| <b>Date</b>             | <b>TSG #</b>    | <b>TSG Doc.</b>                           | <b>CR</b> | <b>Rev</b> | <b>Subject/Comment</b>               | <b>Old</b> | <b>New</b> |  |
+| 03-2001                 | 11              |                                           |           |            | Rel-4 version                        |            | 4.0.0      |  |
+| 06-2002                 | 16              |                                           |           |            | Rel-5 version                        | 4.0.0      | 5.0.0      |  |
+| 12-2004                 | 26              |                                           |           |            | Rel-6 version                        | 5.0.0      | 6.0.0      |  |
+| 06-2007                 | 36              |                                           |           |            | Rel-7 version                        | 6.0.0      | 7.0.0      |  |
+| 07-2007                 |                 |                                           |           |            | Correction to version shown on cover | 7.0.0      | 7.0.1      |  |
+| 12-2008                 | 42              |                                           |           |            | Rel-8 version                        | 7.0.1      | 8.0.0      |  |
+| 12-2009                 | 46              |                                           |           |            | Rel-9 version                        | 8.0.0      | 9.0.0      |  |
+| 03-2011                 | 51              |                                           |           |            | Rel-10 version                       | 9.0.0      | 10.0.0     |  |
+| 09-2012                 | 57              |                                           |           |            | Rel-11 version                       | 10.0.0     | 11.0.0     |  |

marked/Rel-11/26_series/26091/raw.md

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+# Contents
+
+|                                                                           |    |
+|---------------------------------------------------------------------------|----|
+| Foreword .....                                                            | 4  |
+| 1 Scope.....                                                              | 5  |
+| 2 References.....                                                         | 5  |
+| 3 Definitions and abbreviations .....                                     | 5  |
+| 3.1 Definitions.....                                                      | 5  |
+| 3.2 Abbreviations .....                                                   | 5  |
+| 4 General.....                                                            | 6  |
+| 5 Requirements .....                                                      | 6  |
+| 5.1 Error detection.....                                                  | 6  |
+| 5.2 Lost speech frames.....                                               | 6  |
+| 5.3 First lost SID frame .....                                            | 6  |
+| 5.4 Subsequent lost SID frames .....                                      | 6  |
+| 6 Example ECU/BFH Solution 1 .....                                        | 6  |
+| 6.1 State Machine.....                                                    | 7  |
+| 6.2 Assumed Active Speech Frame Error Concealment Unit Actions .....      | 8  |
+| 6.2.1 BFI = 0, prevBFI = 0, State = 0.....                                | 8  |
+| 6.2.2 BFI = 0, prevBFI = 1, State = 0 or 5 .....                          | 8  |
+| 6.2.3 BFI = 1, prevBFI = 0 or 1, State = 1...6 .....                      | 9  |
+| 6.2.3.1 LTP-lag update .....                                              | 9  |
+| 6.2.3.2 Innovation sequence .....                                         | 9  |
+| 6.3 Assumed Non-Active Speech Signal Error Concealment Unit Actions ..... | 10 |
+| 6.3.1 General .....                                                       | 10 |
+| 6.3.2 Detectors.....                                                      | 10 |
+| 6.3.2.1 Background detector.....                                          | 10 |
+| 6.3.2.2 Voicing detector.....                                             | 10 |
+| 6.3.3 Background ECU Actions .....                                        | 10 |
+| 6.4 Substitution and muting of lost SID frames .....                      | 10 |
+| 7 Example ECU/BFH Solution 2 .....                                        | 11 |
+| 7.1 State Machine.....                                                    | 11 |
+| 7.2 Substitution and muting of lost speech frames.....                    | 11 |
+| 7.2.1 BFI = 0, prevBFI = 0, State = 0.....                                | 11 |
+| 7.2.2 BFI = 0, prevBFI = 1, State = 0 or 5 .....                          | 11 |
+| 7.2.3 BFI = 1, prevBFI = 0 or 1, State = 1...6 .....                      | 12 |
+| 7.2.3.1 LTP-lag update .....                                              | 12 |
+| 7.2.4 Innovation sequence .....                                           | 12 |
+| 7.3 Substitution and muting of lost SID frames .....                      | 12 |
+| Annex A (informative): Change history.....                                | 13 |
+
+# --- Foreword
+
+This Technical Specification has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- 1 Scope
+
+The present document defines an error concealment procedure, also termed frame substitution and muting procedure, which shall be used by the AMR speech codec receiving end when one or more lost speech or lost Silence Descriptor (SID) frames are received.
+
+The requirements of the present document are mandatory for implementation in all networks and User Equipment (UE)s capable of supporting the AMR speech codec. It is not mandatory to follow the bit exact implementation outlined in the present document and the corresponding C source code.
+
+# --- 2 References
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+- For a specific reference, subsequent revisions do not apply.
+- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+
+- [1] 3GPP TS 26.102: "AMR Speech Codec; Interface to Iu and Uu".
+- [2] 3GPP TS 26.090: "Transcoding functions".
+- [3] 3GPP TS 26.093: "Source Controlled Rate operation".
+- [4] 3GPP TS 26.101: "Frame Structure".
+
+# --- 3 Definitions and abbreviations
+
+## 3.1 Definitions
+
+For the purposes of the present document, the following terms and definitions apply:
+
+**N-point median operation:** consists of sorting the N elements belonging to the set for which the median operation is to be performed in an ascending order according to their values, and selecting the  $(\text{int}(N/2) + 1)$  -th largest value of the sorted set as the median value
+
+Further definitions of terms used in the present document can be found in the references.
+
+## 3.2 Abbreviations
+
+For the purposes of the present document, the following abbreviations apply:
+
+|          |                                                                |
+|----------|----------------------------------------------------------------|
+| AN       | Access Network                                                 |
+| BFH      | Bad Frame Handling                                             |
+| BFI      | Bad Frame Indication from AN                                   |
+| BSI_netw | Bad Sub-block Indication obtained from AN interface CRC checks |
+| CRC      | Cyclic Redundancy Check                                        |
+| ECU      | Error Concealment Unit                                         |
+| medianN  | N-point median operation                                       |
+| PDFI     | Potentially Degraded Frame Indication                          |
+| prevBFI  | Bad Frame Indication of previous frame                         |
+| RX       | Receive                                                        |
+| SCR      | Source Controlled Rate (operation)                             |
+| SID      | Silence Descriptor frame (Background descriptor)               |
+
+# --- 4 General
+
+The purpose of the error concealment procedure is to conceal the effect of lost AMR speech frames. The purpose of muting the output in the case of several lost frames is to indicate the breakdown of the channel to the user and to avoid generating possible annoying sounds as a result from the error concealment procedure.
+
+The network shall indicate lost speech or lost SID frames by setting the RX\_TYPE values [3] to SPEECH\_BAD or SID\_BAD. If these flags are set, the speech decoder shall perform parameter substitution to conceal errors.
+
+The network should also indicate potentially degraded frames using the flag RX\_TYPE value SPEECH\_PROBABLY\_DEGRADED. This flag may be derived from channel quality indicators. It may be used by the speech decoder selectively depending on the estimated signal type.
+
+The example solutions provided in paragraphs 6 and 7 apply only to bad frame handling on a complete speech frame basis. Sub-frame based error concealment may be derived using similar methods.
+
+# --- 5 Requirements
+
+## 5.1 Error detection
+
+If the most sensitive bits of the AMR speech data (class A in [4]) are received in error, the network shall indicate RX\_TYPE = SPEECH\_BAD in which case the BFI flag is set. If a SID frame is received in error, the network shall indicate RX\_TYPE = SID\_BAD in which case the BFI flag is also set. The RX\_TYPE = SPEECH\_PROBABLY\_DEGRADED flag should be set appropriately using quality information from the channel decoder, in which case the PDFI flag is set.
+
+## 5.2 Lost speech frames
+
+Normal decoding of lost speech frames would result in very unpleasant noise effects. In order to improve the subjective quality, lost speech frames shall be substituted with either a repetition or an extrapolation of the previous good speech frame(s). This substitution is done so that it gradually will decrease the output level, resulting in silence at the output. Clauses 6, and 7 provide example solutions.
+
+## 5.3 First lost SID frame
+
+A lost SID frame shall be substituted by using the SID information from earlier received valid SID frames and the procedure for valid SID frames be applied as described in [3].
+
+## 5.4 Subsequent lost SID frames
+
+For many subsequent lost SID frames, a muting technique shall be applied to the comfort noise that will gradually decrease the output level. For subsequent lost SID frames, the muting of the output shall be maintained. Clauses 6 and 7 provide example solutions.
+
+# --- 6 Example ECU/BFH Solution 1
+
+The C code of the following example is embedded in the bit exact software of the codec. In the code the ECU is designed to allow subframe-by-subframe synthesis, thereby reducing the speech synthesis delay to a minimum.
+
+## 6.1 State Machine
+
+This example solution for substitution and muting is based on a state machine with seven states (Figure 1).
+
+The system starts in state 0. Each time a bad frame is detected, the state counter is incremented by one and is saturated when it reaches 6. Each time a good speech frame is detected, the state counter is reset to zero, except when we are in state 6, where we set the state counter to 5. The state indicates the quality of the channel: the larger the value of the state counter, the worse the channel quality is. The control flow of the state machine can be described by the following C code (**BFI** = bad frame indicator, **State** = state variable):
+
+```
+if(BFI != 0 )  
+    State = State + 1;  
+else if(State == 6)  
+    State = 5;  
+else  
+    State = 0;  
+if(State > 6 )  
+    State = 6;
+```
+
+In addition to this state machine, the **Bad Frame Flag** from the previous frame is checked (**prevBFI**). The processing depends on the value of the **State**-variable. In states 0 and 5, the processing depends also on the two flags **BFI** and **prevBFI**.
+
+The procedure can be described as follows:
+
+![Figure 1: State machine for controlling the bad frame substitution. The diagram shows a vertical sequence of seven rectangular boxes representing states. Each box contains three lines of text: 'S' followed by a number (0-6), 'BFI', and 'KBF1'. Arrows indicate transitions between states: a downward arrow from each state to the next, and a self-loop arrow at the top of the first state. Horizontal arrows point from the right side of each state to the right side of the state above it. From the bottom of the sixth state, two horizontal arrows point to two separate horizontal ovals containing 'K' and 'BFI'.](35a7554182eb055209552843f341a1ae_img.jpg)
+
+Figure 1: State machine for controlling the bad frame substitution. The diagram shows a vertical sequence of seven rectangular boxes representing states. Each box contains three lines of text: 'S' followed by a number (0-6), 'BFI', and 'KBF1'. Arrows indicate transitions between states: a downward arrow from each state to the next, and a self-loop arrow at the top of the first state. Horizontal arrows point from the right side of each state to the right side of the state above it. From the bottom of the sixth state, two horizontal arrows point to two separate horizontal ovals containing 'K' and 'BFI'.
+
+Figure 1: State machine for controlling the bad frame substitution
+
+## 6.2 Assumed Active Speech Frame Error Concealment Unit Actions
+
+### 6.2.1 BFI = 0, prevBFI = 0, State = 0
+
+No error is detected in the received or in the previous received speech frame. The received speech parameters are used in the normal way in the speech synthesis. The current frame of speech parameters is saved.
+
+### 6.2.2 BFI = 0, prevBFI = 1, State = 0 or 5
+
+No error is detected in the received speech frame, but the previous received speech frame was bad. The LTP gain and fixed codebook gain are limited below the values used for the last received good
+
+$$\text{subframe: } g^p = \begin{cases} g^p, & g^p \leq g^p(-1) \\ g^p(-1), & g^p > g^p(-1) \end{cases} \quad (1)$$
+
+where  $g^p$  = current decoded LTP gain,  $g^p(-1)$  = LTP gain used for the last good subframe (BFI = 0), and
+
+$$g^c = \begin{cases} g^c, & g^c \leq g^c(-1) \\ g^c(-1), & g^c > g^c(-1) \end{cases} \quad (2)$$
+
+where  $g^c$  = current decoded fixed codebook gain and  $g^c(-1)$  = fixed codebook gain used for the last good subframe (BFI = 0).
+
+The rest of the received speech parameters are used normally in the speech synthesis. The current frame of speech parameters is saved.
+
+### 6.2.3
+
+#### BFI = 1, prevBFI = 0 or 1, State = 1...6
+
+An error is detected in the received speech frame and the substitution and muting procedure is started. The LTP gain and fixed codebook gain are replaced by attenuated values from the previous subframes:
+
+$$g^p = \begin{cases} P(state) g^p(-1), & g^p(-1) \leq median5(g^p(-1), \dots, g^p(-5)) \\ P(state) median5(g^p(-1), \dots, g^p(-5)), & g^p(-1) > median5(g^p(-1), \dots, g^p(-5)) \end{cases} \quad (3)$$
+
+where  $g^p$  = current decoded LTP gain,  $g^p(-1), \dots, g^p(-n)$  = LTP gains used for the last n subframes,  $median5()$  = 5-point median operation,  $P(state)$  = attenuation factor ( $P(1) = 0.98, P(2) = 0.98, P(3) = 0.8, P(4) = 0.3, P(5) = 0.2, P(6) = 0.2$ ),  $state$  = state number, and
+
+$$g^c = \begin{cases} C(state) g^c(-1), & g^c(-1) \leq median5(g^c(-1), \dots, g^c(-5)) \\ C(state) median5(g^c(-1), \dots, g^c(-5)), & g^c(-1) > median5(g^c(-1), \dots, g^c(-5)) \end{cases} \quad (4)$$
+
+where  $g^c$  = current decoded fixed codebook gain,  $g^c(-1), \dots, g^c(-n)$  = fixed codebook gains used for the last n subframes,  $median5()$  = 5-point median operation,  $C(state)$  = attenuation factor ( $C(1) = 0.98, C(2) = 0.98, C(3) = 0.98, C(4) = 0.98, C(5) = 0.98, C(6) = 0.7$ ), and  $state$  = state number.
+
+The higher the state value is, the more the gains are attenuated. Also the memory of the predictive fixed codebook gain is updated by using the average value of the past four values in the memory:
+
+$$ener(0) = \frac{1}{4} \sum_{i=1}^4 ener(-i) \quad (5)$$
+
+The past LSFs are shifted towards their mean:
+
+$$lsf\_q1(i) = lsf\_q2(i) = \alpha past\_lsf\_q(i) + (1 - \alpha)mean\_lsf(i), \quad i = 0 \dots 9 \quad (6)$$
+
+where  $\alpha = 0.95$ ,  $lsf\_q1$  and  $lsf\_q2$  are two sets of LSF-vectors for current frame,  $past\_lsf\_q$  is  $lsf\_q2$  from the previous frame, and  $mean\_lsf$  is the average LSF-vector. Note that two sets of LSFs are available only in the 12.2 mode.
+
+#### 6.2.3.1 LTP-lag update
+
+The LTP-lag values are replaced by the past value from the 4th subframe of the previous frame (12.2 mode) or slightly modified values based on the last correctly received value (all other modes).
+
+#### 6.2.3.2 Innovation sequence
+
+The received fixed codebook innovation pulses from the erroneous frame are used in the state in which they were received when corrupted data are received. In the case when no data were received random fixed codebook indices should be employed.
+
+## 6.3 Assumed Non-Active Speech Signal Error Concealment Unit Actions
+
+### 6.3.1
+
+### General
+
+The Non-Active Speech ECU is used to reduce the negative impact of amplitude variations and tonal artefacts when using the conventional Active Speech ECU in non-voiced signals such as background noise and unvoiced speech. The background ECU actions are only used for the lower rate Speech Coding modes.
+
+The Non-Active Speech ECU actions are done as postprocessing actions of the Active Speech ECU, actions thus ensuring that the Active Speech ECU states are continuously updated. This will guarantee instant and seamless switching to the Active Speech ECU. The detectors and state updates have to be running continuously for all speech coding modes to avoid switching problems.
+
+Only the differences to the Active Speech ECU are stated below.
+
+### 6.3.2
+
+### Detectors
+
+#### 6.3.2.1 Background detector
+
+An energy level and energy change detector is used to monitor the signal. If the signal is considered to contain background noise and only shows minor energy level changes, a flag is set. The resulting indicator is the **inBackgroundNoise** flag which indicates the signal state of the previous frame.
+
+#### 6.3.2.2 Voicing detector
+
+The received LTP gain is monitored and used to prevent the use of the background ECU actions in possibly voiced segments. A median filtered LTP gain value with a varying filter memory length is thresholded to provide the correct voicing decision. Additionally, a counter **voicedHangover** is used to monitor the time since a frame was presumably voiced.
+
+### 6.3.3
+
+#### Background ECU Actions
+
+The BFI, and DFI indications are used together with the flag **inBackgroundNoise** and the counter **voicedHangover** to adjust the LTP part and the innovation part of the excitation. The actions are only taken if the previous frame has been classified as background noise and sufficient time has passed since the last voiced frame was detected.
+
+The background ECU actions are: energy control of the excitation signal, relaxed LTP lag control, stronger limitation of the LTP gain, adjusted adaptation of the Gain-Contour-Smoothing algorithm and modified adaptation of the Anti-Sparseness Procedure.
+
+## 6.4
+
+### Substitution and muting of lost SID frames
+
+In the speech decoder a single frame classified as SID\_BAD shall be substituted by the last valid SID frame information and the procedure for valid SID frames be applied. If the time between SID information updates (updates are specified by SID\_UPDATE arrivals and occasionally by SID\_FIRST arrivals see 06.92) is greater than one second this shall lead to attenuation.
+
+# 7 Example ECU/BFH Solution 2
+
+This is an alternative example solution which is a simplified version of Example ECU/BFH Solution 1.
+
+## 7.1
+
+### State Machine
+
+This example solution for substitution and muting is based on a state machine with seven states (Figure 1, same state machine as in Example 1).
+
+The system starts in state 0. Each time a bad frame is detected, the state counter is incremented by one and is saturated when it reaches 6. Each time a good speech frame is detected, the state counter is reset to zero, except when we are in state 6, where we set the state counter to 5. The state indicates the quality of the channel: the larger the state counter, the
+
+worse the channel quality is. The control flow of the state machine can be described by the following C code (**BFI** = bad frame indicator, **State** = state variable):
+
+```
+
+if(BFI != 0 )
+    State = State + 1;
+else if(State == 6)
+    State = 5;
+else
+    State = 0;
+if(State > 6 )
+    State = 6;
+
+```
+
+In addition to this state machine, the **Bad Frame Flag** from the previous frame is checked (**prevBFI**). The processing depends on the value of the **State**-variable. In states 0 and 5, the processing depends also on the two flags **BFI** and **prevBFI**.
+
+## 7.2 Substitution and muting of lost speech frames
+
+### 7.2.1 BFI = 0, prevBFI = 0, State = 0
+
+No error is detected in the received or in the previous received speech frame. The received speech parameters are used normally in the speech synthesis. The current frame of speech parameters is saved.
+
+### 7.2.2 BFI = 0, prevBFI = 1, State = 0 or 5
+
+No error is detected in the received speech frame but the previous received speech frame was bad. The LTP gain and fixed codebook gain are limited below the values used for the last received good subframe:
+
+$$g^p = \begin{cases} g^p, & g^p \leq g^p(-1) \\ g^p(-1), & g^p > g^p(-1) \end{cases} \quad (7)$$
+
+where  $g^p$  = current decoded LTP gain,  $g^p(-1)$  = LTP gain used for the last good subframe (BFI = 0), and
+
+$$g^c = \begin{cases} g^c, & g^c \leq g^c(-1) \\ g^c(-1), & g^c > g^c(-1) \end{cases} \quad (8)$$
+
+where  $g^c$  = current decoded fixed codebook-gain and  $g^c(-1)$  = fixed codebook gain used for the last good subframe (BFI = 0).
+
+The rest of the received speech parameters are used normally in the speech synthesis. The current frame of speech parameters is saved.
+
+### 7.2.3 BFI = 1, prevBFI = 0 or 1, State = 1...6
+
+An error is detected in the received speech frame and the substitution and muting procedure is started. The LTP gain and fixed codebook gain are replaced by attenuated values from the previous subframes:
+
+$$g^p = \begin{cases} P(state) g^p(-1), & g^p(-1) \leq median5(g^p(-1), \dots, g^p(-5)) \\ P(state) median5(g^p(-1), \dots, g^p(-5)), & g^p(-1) > median5(g^p(-1), \dots, g^p(-5)) \end{cases} \quad (9)$$
+
+where  $g^p$  = current decoded LTP gain,  $g^p(-1), \dots, g^p(-n)$  = LTP gains used for the last n subframes,  $median5()$  = 5-point median operation,  $P(state)$  = attenuation factor ( $P(1) = 0.98, P(2) = 0.98, P(3) = 0.8, P(4) = 0.3, P(5) = 0.2, P(6) = 0.2$ ),  $state$  = state number, and
+
+$$g^c = \begin{cases} C(state) g^c(-1), & g^c(-1) \leq median5(g^c(-1), \dots, g^c(-5)) \\ C(state) median5(g^c(-1), \dots, g^c(-5)), & g^c(-1) > median5(g^c(-1), \dots, g^c(-5)) \end{cases} \quad (10)$$
+
+where  $g^c$  = current decoded fixed codebook gain,  $g^c(-1), \dots, g^c(-n)$  = fixed codebook gains used for the last  $n$  subframes,  $median5()$  = 5-point median operation,  $C(state)$  = attenuation factor ( $C(1) = 0.98$ ,  $C(2) = 0.98$ ,  $C(3) = 0.98$ ,  $C(4) = 0.98$ ,  $C(5) = 0.98$ ,  $C(6) = 0.7$ ), and  $state$  = state number.
+
+The higher the state value is, the more the gains are attenuated. Also the memory of the predictive fixed codebook gain is updated by using the average value of the past four values in the memory:
+
+$$ener(0) = \frac{1}{4} \sum_{i=1}^4 ener(-i) \quad (11)$$
+
+The past LSFs are used by shifting their values towards their mean:
+
+$$lsf\_q1(i) = lsf\_q2(i) = \alpha past\_lsf\_q(i) + (1 - \alpha)mean\_lsf(i), \quad i = 0 \dots 9 \quad (12)$$
+
+where  $\alpha = 0.95$ ,  $lsf\_q1$  and  $lsf\_q2$  are two sets of LSF-vectors for current frame,  $past\_lsf\_q$  is  $lsf\_q2$  from the previous frame, and  $mean\_lsf$  is the average LSF-vector. Note that two sets of LSFs are available only in the 12.2 mode.
+
+#### 7.2.3.1 LTP-lag update
+
+The LTP-lag values are replaced by the past value from the 4th subframe of the previous frame (12.2 mode) or slightly modified values based on the last correctly received value (all other modes).
+
+### 7.2.4 Innovation sequence
+
+The received fixed codebook innovation pulses from the erroneous frame are used in the state in which they were received when corrupted data are received. In the case when no data were received random fixed codebook indices should be employed.
+
+## 7.3 Substitution and muting of lost SID frames
+
+In the speech decoder a single frame classified as SID\_BAD shall be substituted by the last valid SID frame information and the procedure for valid SID frames be applied. If the time between SID information updates (updates are specified by SID\_UPDATE arrivals and occasionally by SID\_FIRST arrivals) is greater than one second this shall lead to attenuation.
+
+# Annex A (informative): Change history
+
+| Tdoc                  | SPEC   | CR       | RE | VER   | SUBJECT                                                | CAT    | NEW    |
+|-----------------------|--------|----------|----|-------|--------------------------------------------------------|--------|--------|
+| SP-99570              | 26.091 | A001     |    | 3.0.1 | Use of random excitation when RX_NODATA and not in DTX | F      | 3.1.0  |
+| <b>Change history</b> |        |          |    |       |                                                        |        |        |
+| Date                  | TSG #  | TSG Doc. | CR | Rev   | Subject/Comment                                        | Old    | New    |
+| 03-2001               | 11     |          |    |       | Version for Release 4                                  |        | 4.0.0  |
+| 06-2002               | 16     |          |    |       | Version for Release 5                                  | 4.0.0  | 5.0.0  |
+| 12-2004               | 26     |          |    |       | Version for Release 6                                  | 5.0.0  | 6.0.0  |
+| 06-2007               | 36     |          |    |       | Version for Release 7                                  | 6.0.0  | 7.0.0  |
+| 12-2008               | 42     |          |    |       | Version for Release 8                                  | 7.0.0  | 8.0.0  |
+| 12-2009               | 46     |          |    |       | Version for Release 9                                  | 8.0.0  | 9.0.0  |
+| 03-2011               | 51     |          |    |       | Version for Release 10                                 | 9.0.0  | 10.0.0 |
+| 09-2012               | 57     |          |    |       | Version for Release 11                                 | 10.0.0 | 11.0.0 |

marked/Rel-11/26_series/26102/raw.md

@@ -0,0 +1,1021 @@
+
+
+
+
+
+
+# Contents
+
+|                                                                                      |    |
+|--------------------------------------------------------------------------------------|----|
+| Foreword .....                                                                       | 5  |
+| 1 Scope.....                                                                         | 6  |
+| 2 References.....                                                                    | 6  |
+| 3 Definitions and abbreviations .....                                                | 7  |
+| 3.1 Definitions.....                                                                 | 7  |
+| 3.2 Abbreviations .....                                                              | 8  |
+| 4 General.....                                                                       | 8  |
+| 5 RAB aspects.....                                                                   | 10 |
+| 6 Iu Interface User Plane (RAN) .....                                                | 11 |
+| 6.1 Frame structure on the Iu UP transport protocol.....                             | 11 |
+| 6.1.1 Initialisation.....                                                            | 11 |
+| 6.1.2 Time Alignment Procedure .....                                                 | 11 |
+| 6.2 Mapping of the bits .....                                                        | 11 |
+| 6.3 Frame handlers .....                                                             | 13 |
+| 6.3.1 Handling of frames from TC to Iu interface (downlink).....                     | 13 |
+| 6.3.1.1 Frame Quality Indicator.....                                                 | 13 |
+| 6.3.1.2 Frame Type.....                                                              | 13 |
+| 6.3.1.3 Codec Mode Indication.....                                                   | 13 |
+| 6.3.1.4 Codec Mode Request.....                                                      | 13 |
+| 6.3.1.5 Optional internal 8 bits CRC .....                                           | 14 |
+| 6.3.1.6 Mapping of Speech or Comfort Noise parameter bits .....                      | 14 |
+| 6.3.2 Handling of frames from Iu interface to TC (uplink).....                       | 14 |
+| 6.3.2.1 Frame Quality Indicator.....                                                 | 14 |
+| 6.3.2.2 Frame Type.....                                                              | 14 |
+| 6.3.2.3 Codec Mode Indication.....                                                   | 14 |
+| 6.3.2.4 Codec Mode Request.....                                                      | 15 |
+| 6.3.2.5 Optional internal 8 bits CRC .....                                           | 15 |
+| 6.3.2.6 Speech and Comfort noise parameter bits .....                                | 15 |
+| 7 Uu Interface User Plane (UE).....                                                  | 15 |
+| 8 Nb Interface User Plane (CN) of a BICC-based Circuit Switched Core Network .....   | 15 |
+| 8.1 Frame structure on the Nb UP transport protocol .....                            | 15 |
+| 8.1.1 Initialisation.....                                                            | 16 |
+| 8.1.2 Time Alignment Procedure .....                                                 | 16 |
+| 8.1.3 SID Frame Generation.....                                                      | 16 |
+| 8.2 Mapping of the bits .....                                                        | 16 |
+| 8.2.1 Mapping for AMR frames.....                                                    | 16 |
+| 8.2.2 Mapping for PCM Coded Speech .....                                             | 16 |
+| 8.2.3 Mapping for GSM_EFR frames .....                                               | 17 |
+| 8.2.4 Mapping for GSM_FR frames .....                                                | 18 |
+| 8.2.5 Mapping for GSM_HR frames.....                                                 | 18 |
+| 8.3 Frame handlers .....                                                             | 20 |
+| 9 Nb Interface User Plane (CN) of a SIP-I -based Circuit Switched Core Network ..... | 20 |
+| 9.1 Overview .....                                                                   | 20 |
+| 9.1.1 Time Alignment Procedure .....                                                 | 21 |
+| 9.1.2 SID Frame Generation.....                                                      | 21 |
+| 9.1.3 Initial Codec Mode.....                                                        | 22 |
+| 9.2 AMR.....                                                                         | 22 |
+| 9.3 AMR-WB.....                                                                      | 23 |
+| 9.4 GSM_EFR.....                                                                     | 24 |
+| 9.5 GSM_FR .....                                                                     | 24 |
+| 9.6 GSM_HR.....                                                                      | 24 |
+| 9.7 PCM .....                                                                        | 25 |
+| 9.8 Telephone-Event .....                                                            | 25 |
+
+10 A-Interface User Plane over IP .....25  
+10.1 Overview ..... 25  
+10.1.1 Time Alignment Procedure ..... 26  
+10.1.2 SID Frame Generation..... 26  
+10.1.3 Initial Codec Mode ..... 26  
+10.2 AMR..... 27  
+10.3 AMR-WB..... 27  
+10.4 GSM\_EFR..... 28  
+10.5 GSM\_FR ..... 28  
+10.6 GSM\_HR..... 28  
+10.7 PCM ..... 28  
+Annex A (informative): Change history .....29
+
+# --- Foreword
+
+This Technical Specification (TS) has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- 1 Scope
+
+The present document specifies the mapping of the AMR generic frame format (3GPP TS 26.101) to the Iu Interface (3GPP TS 25.415 [7]), the Uu Interface and the Nb Interface (3GPP TS 29.415). It further specifies the mapping of Enhanced Full Rate (GSM\_EFR) coded speech and of PCM 64 kBit/s (ITU-T G.711 [9]) coded speech to the Nb Interface in a BICC-based circuit switched core network.
+
+The present document also specifies the mapping of Full Rate (GSM\_FR) coded speech and of Half Rate (GSM\_HR) coded speech to the Nb Interface in a BICC-based circuit switched core network.
+
+The present document also specifies the transport of the AMR Codec Types, the AMR-WB Codec Types, the GSM\_EFR Codec, the GSM\_FR Codec, the GSM\_HR Codec and the ITU-T G.711 Codec over the A-Interface over IP (3GPP TS 48.002 [11]) and the Nb-Interface in a SIP-I-based circuit switched core network (3GPP TS 23.231 [12]).
+
+# --- 2 References
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+- For a specific reference, subsequent revisions do not apply.
+- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+
+- [1] 3GPP TS 25.415: "Iu Interface CN-UTRAN User plane Protocols".
+- [2] 3GPP TS 26.101: "AMR Speech Codec, Frame structure".
+- [3] 3GPP TS 23.107: "QoS Concept and Architecture".
+- [4] 3GPP TS 46.051: "Enhanced Full Rate (EFR) speech processing functions; General Description"
+- [5] 3GPP TS 28.062: "Inband Tandem Free Operation (TFO) of speech codecs; Service description; Stage 3".
+- [6] 3GPP TS 23.153: "Out of band transcoder control, Stage 2".
+- [7] 3GPP TS 29.415: "Core Network Nb Interface User Plane Protocols".
+- [8] ITU-T I.366.2: "AAL type 2 service specific convergence sublayer for trunking".
+- [9] ITU-T Recommendation G.711: "Pulse code modulation (PCM) of voice frequencies".
+- [10] 3GPP TS 29.414: "Core Network Nb data transport and transport signalling".
+- [11] 3GPP TS 48.002: "Base Station System - Mobile-services Switching Centre (BSS - MSC) interface; Interface principles".
+- [12] 3GPP TS 23.231: "SIP-I based circuit-switched core network; Stage 2".
+- [13] 3GPP TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".
+- [14] 3GPP TS 26.103: "Speech codec list for GSM and UMTS ".
+- [15] IETF RFC 3264 (2002): "An Offer/Answer Model with the Session Description Protocol (SDP)", J. Rosenberg and H. Schulzrinne.
+
+- [16] IETF RFC 3550 (2003): "RTP: A Transport Protocol for Real-Time Applications", H. Schulzrinne, S. Casner, R. Frederick and V. Jacobson.
+- [17] IETF RFC 3551 (2003): "RTP Profile for Audio and Video Conferences with Minimal Control", H. Schulzrinne and S. Casner.
+- [18] void
+- [19] IETF RFC 4566 (2006): "SDP: Session Description Protocol", M. Handley, V. Jacobson and C. Perkins.
+- [20] IETF RFC 4733 (2006): "RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals", H. Schulzrinne and T. Taylor.
+- [21] IETF RFC 4867 (2007): "RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs", J. Sjoberg, M. Westerlund, A. Lakanieniemi and Q. Xie.
+- [22] IETF RFC 5993 (2010) "RTP Payload Format for Global System for Mobile Communications Half Rate (GSM-HR)".
+- [23] 3GPP TS 46.010: "Full rate speech; Transcoding".
+- [24] 3GPP TS 46.020: "Half rate speech; Half rate speech transcoding".
+- [25] 3GPP TS 46.041: "Half rate speech; Discontinuous Transmission (DTX) for half rate speech traffic channels".
+- [26] 3GPP TS 48.060: "In-band control of remote transcoders and rate adaptors for full rate traffic channels".
+- [27] 3GPP TS 48.061: "In band control of remote transcoders and rate adaptors for half rate traffic channels".
+- [28] 3GPP TS 46.012: "Full rate speech; Comfort noise aspect for full rate speech traffic channels".
+- [29] 3GPP TS 46.022: "Half rate speech; Comfort noise aspects for half rate speech traffic channels".
+- [30] 3GPP TS 46.062: "Comfort noise aspects for Enhanced Full Rate (EFR) speech traffic channels".
+- [31] 3GPP TS 26.093: "Adaptive Multi-Rate (AMR) speech codec; Source controlled rate operation".
+- [32] 3GPP TS 26.193: "Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Source controlled rate operation".
+- [33] 3GPP TS 48.008: "Mobile Switching Centre - Base Station System (MSC-BSS) interface".
+- [34] 3GPP TS 48.103: "Base Station System – Media GateWay (BSS-MGW) interface; User Plane transport mechanism".
+- [35] 3GPP TS 45.009: "Radio Access Network; Link adaptation"
+- [36] 3GPP TS 46.060: "EFR Speech Codec; Speech Transcoding Functions"
+
+# --- 3 Definitions and abbreviations
+
+## 3.1 Definitions
+
+For the purposes of the present document the following terms and definitions apply:
+
+**AMR Generic Frame Interface:** this interface transports the AMR IF1 generic frame as defined in 3GPP TS 26.101
+
+## 3.2 Abbreviations
+
+For the purposes of the present document, the following abbreviations apply:
+
+|         |                                                                                  |
+|---------|----------------------------------------------------------------------------------|
+| AAL2    | ATM Adaptation Layer 2                                                           |
+| ACS     | Active Codec Set                                                                 |
+| AMR     | Adaptive Multi-Rate                                                              |
+| AoIP    | A-Interface user plane transport over RTP/UDP/IP                                 |
+| AS      | Access Stratum                                                                   |
+| ATM     | Asynchronous Transfer Mode                                                       |
+| BFH     | Bad Frame Handling                                                               |
+| CDMA    | Code Division Multiple Access                                                    |
+| CMI     | Codec Mode Indication                                                            |
+| CMR/CMC | Codec Mode Request or Codec Mode Command                                         |
+| CN      | Core Network                                                                     |
+| DRC     | Downlink Rate Command                                                            |
+| FDD     | Frequency Duplex Division                                                        |
+| FQC     | Frame Quality Classification (Iu Interface)                                      |
+| FQI     | Frame Quality Indication (AMR IF1)                                               |
+| GSM     | Global System for Mobile communications                                          |
+| ITU-T   | International Telecommunication Union – Telecommunication standardisation sector |
+| MGW     | Media GateWay                                                                    |
+| NboIP   | Nb-Interface user plane transport over RTP/UDP/IP when SIP-I is used on Nc       |
+| PCM     | Pulse Code Modulation, synonym for 64 kBit/s coded speech (see ITU-T G.711 [9])  |
+| PDC     | Personal Digital Communication                                                   |
+| PLMN    | Public Land Mobile Network                                                       |
+| QoS     | Quality of Service                                                               |
+| RAB     | Radio Access Bearer                                                              |
+| RAN     | Radio Access Network                                                             |
+| RF      | Radio Frequency                                                                  |
+| RFC     | RAB sub-flow Combination                                                         |
+| RFCI    | RFC Indicator                                                                    |
+| RFCS    | RFC Set                                                                          |
+| RX      | Receive                                                                          |
+| SCR     | Source Controlled Rate                                                           |
+| SDU     | Source Data Unit                                                                 |
+| SID     | Silence Insertion Descriptor                                                     |
+| SMpSDU  | Support Mode for Predefined SDU sizes                                            |
+| SPD     | SPeech Decoder                                                                   |
+| SPE     | SPeech Encoder                                                                   |
+| TC      | Transcoder                                                                       |
+| TDD     | Time Duplex Division                                                             |
+| TDMA    | Time Division Multiple Access                                                    |
+| TFO     | Tandem Free Operation                                                            |
+| TrFO    | Transcoder Free Operation                                                        |
+| TX      | Transmit                                                                         |
+| UE      | User Equipment (terminal)                                                        |
+| URC     | Uplink Rate Command                                                              |
+
+# --- 4 General
+
+The Iu-Interface is defined in two different variants for speech telephony,
+
+- for the ATM bearer with Iu-framing and
+- for the IP bearer with Iu-framing.
+
+The Nb-Interface is defined in three different variants for speech telephony,
+
+- for the ATM bearer with Nb-framing in a BICC-based Core Network,
+- for the IP bearer with Nb-framing in a BICC-based Core Network and
+- for the IP bearer with RTP packetization in a SIP-I -based Core Network, also called NboIP.
+
+The mapping of the AMR Speech Codec parameters to the Iu interface specifies the frame structure of the speech data exchanged between the RNC and the TC inside the MGW in case of normal operation. This mapping is independent from the radio interface in the sense that it has the same structure for both FDD and TDD modes of the UTRAN.
+
+The mapping between the Speech Codec and the Radio Access Network within the UE is not an open interface and need not to be detailed.
+
+The mapping on the Nb Interface in a BICC based Core Network is identical to the one on the Iu Interface in case of Transcoder Free Operation, with the MGW relaying the SDUs unaltered between Iu and Nb Interfaces.
+
+PCM coded speech is mapped onto the Nb-Interface in packets of 40 octets (5ms packetization time) or 160 octets (20ms packetization time). With Nb-framing (i.e. in a BICC-based Circuit Switched Core Network, IP or ATM) the default packetization time for PCM-coded speech is 5ms; 20ms is an additional option. For NbIP (i.e. RTP packetization in a SIP-I -based Circuit Switched Core Network) the default packetization time for PCM-coded speech is 20ms; 5ms is an additional option.
+
+The packetization time of PCM-coded speech for AoIP is 20ms without any other option.
+
+For the 3GPP Codec Types (GSM\_FR, GSM\_HR, GSM\_EFR, AMR and AMR-WB) the framing is always 20ms and also the packetization time is 20ms in all versions of the Nb-Interface and the A-Interface over IP. The mapping of GSM\_FR, GSM\_HR and GSM\_EFR Speech Codec parameters is defined on the A Interface over IP and all versions of the Nb-Interface, but not on the Iu Interface.
+
+# --- 5 RAB aspects
+
+During the RAB Assignment procedure initiated by the CN to establish the RAB for AMR, the RAB parameters are defined. The AMR RAB is established with one or more RAB co-ordinated sub-flows with predefined sizes and QoS parameters. In this way, each RAB sub-flow Combination corresponds to one AMR frame type. For AMR, subject to operator tuning, the first RAB sub-flow (sub-flow 1) corresponds with the Class A bits. In case there are three RAB
+
+sub-flows, subject to operator tuning, the third RAB sub-flow (sub-flow 3) corresponds with the Class C bits. On the Iu interface, these RAB parameters define the corresponding parameters regarding the transport of AMR frames.
+
+Some of the QoS parameters in the RAB assignment procedure are determined from the Bearer Capability Information Element used at call set up. These QoS parameters as defined in [3], can be set as follows:
+
+Table 5-1: Example of mapping of BC IE into QoS parameters for UMTS AMR
+
+| <b>RAB service attribute</b> | <b>RAB service attribute value</b>                        |                                  |                                  | <b>Comments</b>                                                                                                         |
+|------------------------------|-----------------------------------------------------------|----------------------------------|----------------------------------|-------------------------------------------------------------------------------------------------------------------------|
+| Traffic Class                | Conversational                                            |                                  |                                  |                                                                                                                         |
+| RAB Asymmetry Indicator      | Symmetric, bidirectional                                  |                                  |                                  | Symmetric RABs are used for uplink and downlink                                                                         |
+| Maximum bit rate             | 12.2 / 10.2 / 7.95 / 7.4 / 6.7 / 5.9 / 5.15 / 4.75 kbit/s |                                  |                                  | This value depends on the highest mode rate in the RFCS                                                                 |
+| Guaranteed bit rate          | 12.2 / 10.2 / 7.95 / 7.4 / 6.7 / 5.9 / 5.15 / 4.75 kbit/s |                                  |                                  | One of the values is chosen, depending on the lowest rate controllable SDU format (note 2)                              |
+| Delivery Order               | Yes                                                       |                                  |                                  | (note 1)                                                                                                                |
+| Maximum SDU size             | 244 / 204 / 159 / 148 / 134 / 118 / 103 / 95 bits         |                                  |                                  | Maximum size of payload field in Iu UP, according to the highest mode rate in the RFCS                                  |
+| Traffic Handling Priority    | Not applicable                                            |                                  |                                  | Parameter not applicable for the conversational traffic class. (note 1)                                                 |
+| Source statistics descriptor | Speech                                                    |                                  |                                  | (note 1)                                                                                                                |
+| SDU Parameters               | RAB sub-flow 1<br>(Class A bits)                          | RAB sub-flow 2<br>(Class B bits) | RAB sub-flow 3<br>(Class C bits) | The number of SDU, their number of RAB sub-flow and their relative sub-flow size is subject to operator tuning (note 3) |
+| SDU error ratio              | $7 \cdot 10^{-3}$                                         | -                                | -                                | (note 3)                                                                                                                |
+| Residual bit error ratio     | $10^{-6}$                                                 | $10^{-3}$                        | $5 \cdot 10^{-3}$                | (note 3 – applicable for every sub-flow)                                                                                |
+| Delivery of erroneous SDUs   | yes                                                       | -                                | -                                | Class A bits are delivered with error indication;<br>Class B and C bits are delivered without any error indication.     |
+| SDU format information 1-9   |                                                           |                                  |                                  | (note 4)                                                                                                                |
+| Sub-flow SDU size 1-9        | (note 5)                                                  | (note 5)                         | (note 5)                         |                                                                                                                         |
+
+NOTE 1: These parameters apply to all UMTS speech codec types.  
+NOTE 2: The guaranteed bit rate depends on the periodicity and the lowest rate controllable SDU size.  
+NOTE 3: These parameters are subject to operator tuning.  
+NOTE 4: SDU format information has to be specified for each AMR core frame type (i.e. with speech bits and comfort noise bits) included in the RFCS as defined in [2].  
+NOTE 5: The sub-flow SDU size corresponding to an AMR core frame type indicates the number of bits in the class A, class B and class C fields. The assigned SDU sizes shall be set so that the SCR operation is always possible.
+
+The RAB parameters shall be set so that the SCR operation is always possible.
+
+The conversational traffic class shall be used for the speech service, which is identified by the ITC parameter of the bearer capability information element in the SETUP message. This shall apply for all UMTS speech codec types.
+
+The parameters traffic class, transfer delay, traffic handling priority and source statistics descriptor shall be the same for all speech codec types applicable for UMTS.
+
+# 6 Iu Interface User Plane (RAN)
+
+The data structure exchanged on the Iu interface are symmetrical, i.e. the structure of the uplink data frames is identical to that of the downlink data frames.
+
+## 6.1 Frame structure on the Iu UP transport protocol
+
+### 6.1.1 Initialisation
+
+At the initialisation of the SMpSDU mode of operation, several parameters are set by the CN. The initialisation procedure is described in [1].
+
+- RFCS:
+
+In the case of AMR, the RFCS corresponds to the Active Codec Set (ACS) plus potentially SCR authorised in the communication. Annex A of [1] gives an illustration of the usage of RFCI for AMR speech RAB. RFCS used in downlink may differ from that in uplink.
+
+- Delivery of erroneous SDUs:
+
+This parameter shall be set to YES. Erroneous speech frames may be used to assist the error concealment procedures. Therefore, according to [1], PDU type 0 (containing a payload CRC) shall be used for transport of AMR data.
+
+### 6.1.2 Time Alignment Procedure
+
+The TC should adjust the timing of the speech data transmission in downlink direction according to the time alignment frames sent by the RNC.
+
+Time alignment procedure shall be dismissed in case of TFO and TrFO.
+
+## 6.2 Mapping of the bits
+
+The mapping of the bits between the generic AMR frames and the PDU is the same for both uplink and downlink frames.
+
+The following table gives the correspondence of the bit fields between the generic AMR frames at the TC interface and the PDU exchanged with the Iu transport layer.
+
+**Table 6-1: Mapping of generic AMR frames onto Iu PDUs**
+
+| PDU field                    | Corresponding field within the generic AMR frame | Comment   |
+|------------------------------|--------------------------------------------------|-----------|
+| PDU Type                     | N/A                                              | Type 0    |
+| Frame Number                 | N/A                                              |           |
+| FQC                          | Frame Quality Indicator                          |           |
+| RFCI                         | Frame Type                                       |           |
+| Payload CRC                  | N/A                                              |           |
+| Header CRC                   | N/A                                              |           |
+|                              |                                                  |           |
+| Payload Fields (N Sub-flows) | Class A or SID payload<br>Class B<br>Class C     |           |
+| SDU #1                       | Most important speech bits come first            | Mandatory |
+| SDU #2                       | Next bits follow                                 | Optional  |
+| ...                          | ...                                              | Optional  |
+| SDU #N                       | Least important speech bits                      | Optional  |
+
+The number of RAB sub-flows, their corresponding sizes, and their attributes such as "Delivery of erroneous SDUs" shall be defined at the RAB establishment and signalled in the RANAP RAB establishment request, as proposed in clause 5. The number of RAB sub-flows is corresponding to the desired bit protection classes. The total number of bits in all sub-flows for one RFC shall correspond to the total number given in 3GPP TS 26.101, generic AMR frame, format IF1, for the corresponding Codec Mode, respectively Frame Type.
+
+The class division and relative subjective importance of the encoded bits is given in 3GPP TS 26.101 and provides guidance for setting the number of bits in each RAB sub-flow.
+
+The following two tables are examples of mapping of RAB sub-flows.
+
+Table 6-2 gives three examples of sub-flow mapping.
+
+The RFCI definition is given in order of increasing SDU sizes.
+
+- Example 1 describes Codec Type UMTS\_AMR, with all eight codec modes foreseen in the Active Codec Set (ACS) and provision for Source Controlled Rate operation (SCR). In this example, Blind Transport Format Detection is supported and the sub-flow mapping follows the 3GPP TS 26.101 class division.
+- Example 2 describes Codec Type GSM\_EFR, with one codec mode, including SCR.
+
+- Example 3 describes Codec Type FR\_AMR, including AMR SCR
+
+**Table 6-2: Example for AMR with SCR and three sub-flows, according to subjective class division indication of 3GPP TS 26.101**
+
+| UMTS_AMR<br>RFCI<br>Example 1 | GSM_EFR<br>RFCI<br>Example 2 | FR_AMR<br>RFCI<br>Example 3 | RAB sub-flows                    |                                  |                                  | Total size of<br>bits/RAB sub-<br>flows<br>combination<br>(Mandatory) | Source rate   |
+|-------------------------------|------------------------------|-----------------------------|----------------------------------|----------------------------------|----------------------------------|-----------------------------------------------------------------------|---------------|
+|                               |                              |                             | RAB sub-<br>flow 1<br>(Optional) | RAB sub-<br>flow 2<br>(Optional) | RAB sub-<br>flow 3<br>(Optional) |                                                                       |               |
+| 2                             |                              | 2                           | 42                               | 53                               | 0                                | 95                                                                    | AMR 4,75 kbps |
+| 3                             |                              |                             | 49                               | 54                               | 0                                | 103                                                                   | AMR 5,15 kbps |
+| 4                             |                              | 3                           | 55                               | 63                               | 0                                | 118                                                                   | AMR 5,9 kbps  |
+| 5                             |                              | 4                           | 58                               | 76                               | 0                                | 134                                                                   | AMR 6,7 kbps  |
+| 6                             |                              |                             | 61                               | 87                               | 0                                | 148                                                                   | AMR 7,4 kbps  |
+| 7                             |                              |                             | 75                               | 84                               | 0                                | 159                                                                   | AMR 7,95 kbps |
+| 8                             |                              | 5                           | 65                               | 99                               | 40                               | 204                                                                   | AMR 10,2 kbps |
+| 9                             | 2                            |                             | 81                               | 103                              | 60                               | 244                                                                   | AMR 12,2 kbps |
+| 1                             |                              | 1                           | 39                               | 0                                | 0                                | 39                                                                    | AMR SID       |
+|                               | 1                            |                             | 43                               | 0                                | 0                                | 43                                                                    | GSM-EFR SID   |
+
+Table 6-3 gives one example of sub-flow mapping that supports Equal Error Protection. The RFCI definition is given in order of increasing SDU sizes.
+
+- Example 4 describes Codec Type PDC\_EFR and the corresponding Source Controlled Rate operation (SCR).
+
+**Table 6-3: Example of SDU sizes for PDC\_EFR with SCR and Equal Error Protection**
+
+| PDC_EFR<br>RFCI<br>Example 4 | RAB sub-flow<br>RAB sub-<br>Flow 1<br>(Mandatory) | Total size of<br>bits/RAB sub-flows<br>combination<br>(Mandatory) | Source rate  |
+|------------------------------|---------------------------------------------------|-------------------------------------------------------------------|--------------|
+|                              |                                                   |                                                                   |              |
+|                              | 95                                                | 95                                                                | AMR 4,75kbps |
+|                              | 103                                               | 103                                                               | AMR 5,15kbps |
+|                              | 118                                               | 118                                                               | AMR 5,9kbps  |
+| 2                            | 134                                               | 134                                                               | AMR 6,7kbps  |
+|                              | 148                                               | 148                                                               | AMR 7,4kbps  |
+|                              | 159                                               | 159                                                               | AMR 7,95kbps |
+|                              | 204                                               | 204                                                               | AMR 10,2kbps |
+|                              | 244                                               | 244                                                               | AMR 12,2kbps |
+|                              | 39                                                | 39                                                                | AMR SID      |
+|                              | 43                                                | 43                                                                | GSM-EFR SID  |
+|                              | 38                                                | 38                                                                | TDMA-EFR SID |
+| 1                            | 37                                                | 37                                                                | PDC-EFR SID  |
+
+## 6.3 Frame handlers
+
+In PDU Frame handling functions are described in 3GPP TS 25.415 [1]. This section describes the mandatory frame handling functions at the AMR Generic frame interface.
+
+### 6.3.1 Handling of frames from TC to Iu interface (downlink)
+
+The frames from the TC in generic AMR frame format IF1 are mapped onto the Iu PDU as follows.
+
+#### 6.3.1.1 Frame Quality Indicator
+
+The Frame Quality Indicator (FQI) from the TC is directly mapped to the Frame Quality Classification (FQC) of the Iu frame according to Table 6-4.
+
+**Table 6-4: FQI AMR to FQC Iu PDU mapping**
+
+| FQI AMR | FQI value<br>(1 bit) | FQC PDU | FQC value<br>(2 bit) |
+|---------|----------------------|---------|----------------------|
+| GOOD    | 1                    | GOOD    | 00                   |
+| BAD     | 0                    | BAD     | 01                   |
+
+#### 6.3.1.2 Frame Type
+
+The received Frame Type Index  $l$  is mapped onto the RFCI  $j$  thanks to the assigned RFCS table: the correspondence between Codec Mode, Frame Type Index  $l$  and RFCI  $j$  is defined at RAB assignment.
+
+#### 6.3.1.3 Codec Mode Indication
+
+The Codec Mode Indication is not used.
+
+#### 6.3.1.4 Codec Mode Request
+
+Codec Mode Request (CMR) in downlink direction is forwarded to the rate control procedure when it changes, or when it is commanded so by the TC in case of TFO, see 3G TS 28.062.
+
+#### 6.3.1.5 Optional internal 8 bits CRC
+
+The internal AMR Codec CRC is not used on the Iu interface.
+
+#### 6.3.1.6 Mapping of Speech or Comfort Noise parameter bits
+
+Let us define the  $N$  payload fields of the  $N$  sub-flows for RFCI  $j$  as follows:
+
+$U_i(k)$  shall be the bits in sub-flow  $i$ , for  $k = 1$  to  $M_i$
+
+$M_i$  shall be the size of sub-flow  $i$ , for  $i = 1$  to  $N$
+
+$d(k)$  shall be the bits of the speech or comfort noise parameters of the corresponding Frame Type  $l$  in decreasing subjective importance, as defined in the generic AMR frame format IF1, see TS 26.101 [2].
+
+Then the following mapping in pseudo code applies:
+
+$U_1(k) = d(k-1)$  with  $k = 1, \dots, M_1$
+
+$U_2(k) = d(k-1+M_1)$  with  $k = 1, \dots, M_2$
+
+$U_3(k) = d(k-1+M_2)$  with  $k = 1, \dots, M_3$
+
+...
+
+$U_N(k) = d(k-1+M_{N-1})$  with  $k = 1, \dots, M_N$
+
+### 6.3.2 Handling of frames from Iu interface to TC (uplink)
+
+The uplink Iu frames are mapped onto generic AMR frames, format IF1, as follows.
+
+#### 6.3.2.1 Frame Quality Indicator
+
+At reception of Iu PDU the Iu frame handler function set the Frame Quality Classification according to the received FQC, Header-CRC check, and Payload-CRC check (see 25.415). AMR Frame Type and Frame Quality Indicator are determined according to the following table:
+
+**Table 6-5: FQC Iu PDU type 0 to AMR FQI and AMR Frame Type mapping**
+
+| FQC       | FQC value (2 bits) | Resulting FQI | FQI value (1 bit) | resulting Frame Type |
+|-----------|--------------------|---------------|-------------------|----------------------|
+| GOOD      | 00                 | GOOD          | 1                 | from RFCI            |
+| BAD       | 01                 | BAD           | 0                 | NO_DATA              |
+| BAD Radio | 10                 | BAD           | 0                 | from RFCI            |
+| Reserved  | 11                 | BAD           | 0                 | Reserved             |
+
+#### 6.3.2.2 Frame Type
+
+The received RFCI j is mapped onto the Frame Type Index I thanks to the RFCS table.
+
+#### 6.3.2.3 Codec Mode Indication
+
+The Codec Mode Indication is not used.
+
+#### 6.3.2.4 Codec Mode Request
+
+The received Downlink Rate Control command (DRC) is mapped onto the Codec Mode Request (CMR) towards the AMR Codec. In case a new DRC is received it is mapped into the corresponding CMR of the generic AMR frame format. It is remembered by the TC until the next DRC is received. In each new frame that is sent to the AMR Codec, the stored CMR is resent, in order to control the Codec Mode for the downlink direction.
+
+#### 6.3.2.5 Optional internal 8 bits CRC
+
+The internal AMR Codec CRC is not used on the Iu interface.
+
+#### 6.3.2.6 Speech and Comfort noise parameter bits
+
+The speech and Comfort noise parameter bits are mapped from the sub-flows to the payload of the generic AMR frames with the reverse function of clause 6.3.1.6.
+
+# 7 Uu Interface User Plane (UE)
+
+The interface between the UE AMR speech codec (see 3GPP TS 26.101) and the Radio Access Network is an internal UE interface and is not detailed. The mapping is corresponding to the mapping described in clause 6 for the Iu interface.
+
+Even though the details of Uu interface are not detailed, there are some functional requirements for the UE that need to be considered, when an AMR codec type (i.e. UMTS AMR2) is being used in a conversational speech call. These requirements are related to the mapping of AMR Generic frame format handling functions. The requirements are
+
+1. The set of available codec modes (bitrates) that the UE may use are configured by UTRAN. The UE shall select, from the configured set of codec modes, a mode that is supported by the current TX power conditions as defined in 3GPP TS25.133. The highest available mode should be used for best speech quality.
+2. The lowest configured codec mode is always to be considered supported.
+
+3. When the codec mode is being adapted during a call, the used mode should be changed in a step-by-step fashion within the configured set of codec modes, i.e. by stepping one mode up or down within the configured set. This avoids disruptions on AMR decoding in GSM side, if TFO or TrFO operation is ongoing.
+
+# --- 8 Nb Interface User Plane (CN) of a BICC-based Circuit Switched Core Network
+
+The data structures exchanged on the Nb interface are symmetrical, i.e. the structures of the sent and received data frames are identical.
+
+The Nb-Interface is defined in a BICC-based Core Network in two different variants, a) for the ATM bearer with Nb-framing, b) for the IP bearer with Nb-framing. The Nb-framing and the use of PDU Type 0 for the speech payload and PDU Type 14 [7] for AMR Rate Control is common for both versions of the Nb-Interface here. These two versions also share the principle of "Nb\_Init", where the Nb-Interface is initialized on User Plane level and where the Initial Codec Mode for AMR and/or AMR-WB is signalled.
+
+## 8.1 Frame structure on the Nb UP transport protocol
+
+Delivery of erroneous SDUs for AMR- and AMR-WB-coded speech, as well as for GSM\_FR-, GSM\_HR-, GSM\_EFR-coded speech and for PCM-coded speech on the Nb-Interface shall be set to: "YES" in a BICC-based Circuit Switched Core Network. Erroneous speech frames may be used to assist the error concealment procedures. Therefore, according to [1] and [7], PDU Type 0 (with payload CRC) shall be used for the transport of AMR, AMR-WB, GSM\_FR, GSM\_HR and GSM\_EFR coded speech on the Nb interface. PDU Type 0 (with payload CRC) shall be used for the transport of PCM coded speech on the Nb interface, too.
+
+### 8.1.1 Initialisation
+
+The initialisation procedure is used for support mode. At the initialisation several parameters are set by the CN. The initialisation procedure for the Nb Interface is described in [7].
+
+### 8.1.2 Time Alignment Procedure
+
+The handling of Time Alignment on the Nb Interface is described in [7].
+
+The Time alignment procedure shall be dismissed in case of TFO and TrFO.
+
+### 8.1.3 SID Frame Generation
+
+All 3GPP Codec Types include a standardized Discontinuous Transmission (DTX) with Voice Activity Detection, Silence Description (by SID frames) and Comfort Noise Generation to fill the speech pauses. If speech inactivity is detected by the Encoder, then (speech) frames are not transmitted, but the transmission is suspended in order to save battery life time in the mobile station, reduce interference on the radio interface and reduce load on all links. The receiving Decoder fills these transmission pauses with Comfort Noise to minimize the contrast between pauses and active speech. Silence Descriptor (SID) frames need to be sent during speech inactivity to keep the Comfort Noise decently well aligned with the background noise at sender side. This is especially important at the onset of the next talkspurt and therefore SID frames should not be too old, when speech starts again.
+
+The generation of SID frames for the AMR and AMR-WB families of Codecs is determined by the Speech Encoder as specified in TS 26.093 [31], respectively TS 26.193 [32]. The radio subsystem does not influence this timing! SID frames come during speech pauses in uplink and downlink about every 160ms. Also an AMR Encoder in the Media Gateway generates and sends SID frames about every 160ms.
+
+The generation of SID frames for GSM\_FR, GSM\_HR and GSM\_EFR in the GSM radio network is determined by the GSM mobile station and the GSM radio subsystem, not primarily by the Speech Encoder! SID frames come during speech pauses in uplink from the mobile station about every 480ms. In downlink to the mobile station, when they are generated by the Speech Encoder of the GSM radio subsystem, SID frames are sent every 20ms to the GSM base station, which then picks only one every 480ms for downlink radio transmission. For other applications, like transport over Nb, it is more appropriate to send the SID frames less often than every 20ms, but 480ms may be too sparse. As a compromise it is recommended that an Encoder in the Media Gateway should generate and send SID frames every 160ms.
+
+## 8.2 Mapping of the bits
+
+### 8.2.1 Mapping for AMR frames
+
+The mapping of the bits between the generic AMR frames and the PDU for the Nb Interface is identical to the mapping on the Iu Interface. In case of TrFO the MGW relays the AMR frames from the Iu Interface unaltered to the Nb Interface and vice versa, as described in [7].
+
+### 8.2.2 Mapping for PCM Coded Speech
+
+The mapping for the PCM coded speech in 5ms frames on the Nb Interface shall be as defined in Table 8-1.
+
+**Table 8-1: Mapping of PCM Coded Speech in 5 ms frames onto Nb PDU, Type 0**
+
+| PDU field     | Comment                                                  |
+|---------------|----------------------------------------------------------|
+| PDU Type      | Type 0 (with Payload CRC)                                |
+| Frame Number  | as defined in [7]                                        |
+| FQC           | set to "good", i.e. value 0                              |
+| RFCI          | initialise by MGW, see [7],<br>one value required        |
+| Header CRC    | as defined in [7]                                        |
+| Payload CRC   | as defined in [7]                                        |
+|               |                                                          |
+| Payload Field | 320 bits of PCM coded speech,<br>in accordance with [8]. |
+
+The mapping for the PCM coded speech in 20ms frames on the Nb Interface shall be as defined in Table 8-2.
+
+**Table 8-2: Mapping of PCM Coded Speech in 20ms frames onto Nb PDU, Type 0**
+
+| PDU field     | Comment                                                    |
+|---------------|------------------------------------------------------------|
+| PDU Type      | Type 0 (with Payload CRC)                                  |
+| Frame Number  | as defined in [7]                                          |
+| FQC           | set to "good", i.e. value 0                                |
+| RFCI          | initialised by MGW, see [7],<br>one value required         |
+| Header CRC    | as defined in [7]                                          |
+| Payload CRC   | as defined in [7]                                          |
+|               |                                                            |
+| Payload Field | 4x320 bits of PCM coded speech,<br>in accordance with [8]. |
+
+5ms is the default packetization time to be supported for PCM encoded speech over Nb in a BICC based Core Network. 20ms is an additional optional packetization time for PCM encoded speech in a BICC based Core Network over IP Nb bearer that may be negotiated during bearer establishment as specified in [10].
+
+NOTE: the use of 20ms packetization time will result in some call scenarios in higher delays over the speech path compared to the 5ms packetization time. This potentially higher delay should be taken into account in the overall end to end (ear to mouth) delay budget.
+
+### 8.2.3 Mapping for GSM\_EFR frames
+
+The mapping of the bits between the generic GSM\_EFR frames and the PDUs for the Nb Interface follows the same principles as the mapping of AMR frames. The PDU for the GSM\_EFR speech frame is identical to the PDU for AMR Mode 12.2 kbps.
+
+The PDU for the GSM\_EFR SID frame is similar to the PDU for AMR SID, with 43 instead of 39 bits in the payload field. The contents of GSM\_EFR SID is the Comfort Noise Parameter set ( $s(i)$ ) as defined in [36]. The Comfort noise parameters are computed as described in [30] by the GSM\_EFR speech encoder and are denoted as  $s(i) = \{s(1), s(2), \dots, s(38), s(87), s(88), \dots, s(91)\}$ . The notation  $s(i)$  follows that of [36] (Table 6). The notation  $d(j) = \{d(1) \dots d(43)\}$  of the SID frame is local to the present document and is formed as defined by the pseudo code below.
+
+```
+
+for j = 1 to 38
+  d(j) := s(j); /* LSP parameters in s(1) to s(38) */;
+
+for j = 39 to 43
+  d(j) := s(j+48); /* fixed codebook gain parameter in s(87)-s(91) */
+
+```
+
+The payload within the PDU shall be the vector  $d(j)$  constructed above. The first bit in the vector  $d(j)$  shall be supplied first in the payload within the PDU.
+
+NOTE: The Payload field for Nb frames for GSM\_EFR in a BICC-based Circuit Switched Core Network is filled differently to the RTP payload according to RFC3551 [17], used in AoIP and NboIP.
+
+### 8.2.4 Mapping for GSM\_FR frames
+
+The mapping of GSM\_FR-coded speech in 20ms frames on the Nb Interface shall be as defined in Table 8.2.4.1.
+
+**Table 8.2.4.1: Mapping of GSM\_FR-coded speech in 20ms frames onto Nb PDU, Type 0**
+
+| PDU field     | Comment                                                                                                      |
+|---------------|--------------------------------------------------------------------------------------------------------------|
+| PDU Type      | Type 0 (with Payload CRC)                                                                                    |
+| Frame Number  | as defined in [7]                                                                                            |
+| FQC           | see below                                                                                                    |
+| RFCI          | initialise by MGW, see [7], two values required (Speech and SID)                                             |
+| Header CRC    | as defined in [7]                                                                                            |
+| Payload CRC   | as defined in [7]                                                                                            |
+|               |                                                                                                              |
+| Payload Field | 264 bits if Nb PDU contains a speech frame, see below.<br>42 bits if Nb PDU contains a SID frame, see below. |
+
+#### Payload field with speech frame:
+
+The 260 bits of GSM\_FR-coded speech (b1...b260) are defined in TS 46.010, chapter 1.7. They and a "signature" are copied into the 33 octets of the Payload field as follows. The four most significant bits (bit 8...5) of the first octet (octet 1) of the Nb Payload field are set to a "signature" of 0b1101 = 0xD. Then the four most significant bits (b6...b3) of the first GSM\_FR parameter (LAR 1) are copied into the next bits (bit 4...1) of the first octet. The two least significant bits of the first GSM\_FR parameter (LAR 1) are copied into the next octet (octet 2) into the 2 MSBs (bit 8...7), and so on. Each GSM\_FR parameter is copied bit by bit with its most significant bit first. The least significant bit of the last GSM\_FR parameter (b258 of RPE-pulse no.13) is placed in the LSB (bit 1) of octet 33.
+
+#### Payload field with SID frame:
+
+The GSM\_FR SID frames are defined in chapter 5.2 of [28] and in chapter 1.7 of [23] and are denoted as  $b(i) = \{b(1), b(2), \dots, b(36), b(48), b(49), \dots, b(53)\}$ . Each GSM\_FR SID parameter is copied bit by bit with its most significant bit first. The notation  $d(j) = \{d(1) \dots d(42)\}$  of the SID frame is local to the present document and is formed by the pseudo code below.
+
+```
+
+for j = 1 to 36
+  d(j) := b(j); /* averaged log area coefficients in b(1) to b(36) */;
+
+for j = 37 to 42
+  d(j) := b(j+11); /* averaged block amplitude values in b(48)-b(53) */
+
+```
+
+The payload within the PDU shall be the vector  $d(j)$  constructed above. The first bit in the vector  $d(j)$  shall be supplied first in the payload within the PDU.
+
+NOTE: The Payload field for Nb frames for GSM\_FR containing SID frame in a BICC-based Circuit Switched Core Network is filled differently to the Payload field in RTP Packets according to RFC3551 [17], used in AoIP and NboIP.
+
+#### FQC:
+
+The FQC (see Nb UP [7]) is set by the MGW depending on the call case:
+
+1. FQC is set to "good", i.e. value 0, if the GSM\_FR-compression and coding is performed within the MGW
+2. FQC is set to "good", i.e. value 0, if GSM\_FR-coded speech is received without frame quality indication
+
+3. FQC is derived from the input frame, if FQC or a similar frame quality indication is specified there. In case of GSM\_FR-coded speech received via TFO frames (see TS 28.062 [5]) the FQC is derived from the "Bad Frame Indication" (BFI) of these TFO frames. Speech frames and SID frames marked with BFI set to "good" shall be sent with FQC set to "good", i.e. value 0. Speech frames and SID frames marked with BFI set to "bad" shall not be sent in order to save bandwidth on Nb.
+
+### 8.2.5 Mapping for GSM\_HR frames
+
+The mapping of GSM\_HR-coded speech in 20ms frames on the Nb Interface shall be as defined in Table 8.2.5.1.
+
+**Table 8.2.5.1: Mapping of GSM\_HR-coded speech in 20ms frames onto Nb PDU, Type 0**
+
+| PDU field     | Comment                                                                                                      |
+|---------------|--------------------------------------------------------------------------------------------------------------|
+| PDU Type      | Type 0 (with Payload CRC)                                                                                    |
+| Frame Number  | as defined in [7]                                                                                            |
+| FQC           | see below                                                                                                    |
+| RFCI          | initialise by MGW, see [7], two values required (Speech and SID)                                             |
+| Header CRC    | as defined in [7]                                                                                            |
+| Payload CRC   | as defined in [7]                                                                                            |
+| Payload Field | 112 bits if Nb PDU contains a Speech frame, see below.<br>33 bits if Nb PDU contains a SID frame, see below. |
+
+#### Payload field with speech frame:
+
+The 112 bits of GSM\_HR-coded speech ( $b(1)\dots b(112)$ ) are defined in TS 46.020, Annex B, in the order of occurrence. The first bit ( $b(1)$ ) of the first parameter is placed in bit 8 (the MSB) of the first octet (octet 1) of the Nb Payload field; the second bit is placed in bit 7 of the first octet and so on. The last bit ( $b(112)$ ) is placed in the LSB (bit 1) of octet 14.
+
+NOTE 1: The Payload field for Nb frames for GSM\_HR with speech frame in a BICC-based Circuit Switched Core Network is identical to the "speech data section" of the RTP payload. It is done according to [22], used in AoIP and NboIP.
+
+#### Payload field with SID frame:
+
+The GSM\_HR SID frames are defined in [24] and [29] and are denoted as  $b(i) = \{b(1), b(2), \dots, b(33)\}$ . The notation  $d(j) = \{d(1) \dots d(33)\}$  of the SID frame is local to the present document and is formed by the pseudo code as follows.
+
+```
+
+for  $j = 1$  to 5
+   $d(j) := b(j)$ ; /* R0 parameter in  $b(1)$  to  $b(5)$  */
+
+for  $j = 6$  to 16
+   $d(j) := b(j)$ ; /* LPC1 parameter in  $b(6)$ - $b(16)$  */
+
+for  $j = 17$  to 25
+   $d(j) := b(j)$ ; /* LPC2 parameter in  $b(17)$ - $b(25)$  */
+
+for  $j = 26$  to 33
+   $d(j) := b(j)$ ; /* LPC3 parameter in  $b(26)$ - $b(33)$  */
+
+```
+
+The payload within the PDU shall be the vector  $d(j)$  constructed above. The first bit in the vector  $d(j)$  shall be supplied first in the payload within the PDU.
+
+NOTE 2: The Payload field for Nb frames for GSM\_HR with SID frame in a BICC-based Circuit Switched Core Network is not filled in the same way as the "speech data section" of the RTP payload used in AoIP and NboIP. For both AoIP and NboIP packing is according to [22].
+
+#### FQC:
+
+The FQC (see Nb UP [7]) is set by the MGW depending on the call case:
+
+1. FQC is set to "good", i.e. value 0, if the GSM\_HR-compression and coding is performed within the MGW.
+2. FQC is set to "good", i.e. value 0, if GSM\_HR-coded speech is received without frame quality indication.
+3. FQC is derived from the input frame, if FQC or a similar frame quality indication is specified there. In case of GSM\_HR-coded speech received via TFO frames (see TS 28.062 [5]) the FQC is derived from
+
+the "Extended control bits" (XC1 to XC5) for 8kbps submultiplexing (specified in TS 48.061, chapter 5.2.4.1.1 and partly reprinted here for ease of reading) as defined in table 8.2.5.2.
+
+**Table 8.2.5.2: The FQC for GSM\_HR-coded Nb frames derived from TFO frames**
+
+| FQC  | XC1 | XC2 | XC3 | XC4 | XC5 | Meaning (in Abis frames with 8kbps submultiplexing)                                                                                                                                                            |
+|------|-----|-----|-----|-----|-----|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| good | 0   | 0   | 0   | 0   | 0   | Good speech frame with UFI = 0<br>(BFI=0, SID=0, TAF=1)<br>(BFI=0, SID=0, TAF=0)                                                                                                                               |
+| bad* | 0   | 0   | 0   | 0   | 1   | Unreliable speech frame (if speech decoder is in speech decoding mode) or unusable frame (if speech decoder is in comfort noise insertion mode) with UFI = 1<br>(BFI=0, SID=0, TAF=1)<br>(BFI=0, SID=0, TAF=0) |
+| good | 0   | 0   | 0   | 1   | 0   | Valid SID frame with UFI = 0<br>(BFI=0, SID=2, TAF=1)<br>(BFI=0, SID=2, TAF=0)                                                                                                                                 |
+| bad  | 0   | 0   | 0   | 1   | 1   | Invalid SID frame with UFI = 1<br>(BFI=0, SID=2, TAF=1)<br>(BFI=0, SID=2, TAF=0)                                                                                                                               |
+| bad  | 0   | 1   | 0   | 0   | 0   | Invalid SID frame at TAF=0 with UFI = 0<br>(BFI=0, SID=1, TAF=0)<br>(BFI=1, SID=1, TAF=0)<br>(BFI=1, SID=2, TAF=0)                                                                                             |
+| bad  | 0   | 1   | 0   | 0   | 1   | Invalid SID frame at TAF=0 with UFI = 1<br>(BFI=0, SID=1, TAF=0)<br>(BFI=1, SID=1, TAF=0)<br>(BFI=1, SID=2, TAF=0)                                                                                             |
+| bad  | 0   | 1   | 0   | 1   | 0   | Invalid SID frame at TAF=1 with UFI = 0<br>(BFI=0, SID=1, TAF=1)<br>(BFI=1, SID=1, TAF=1)<br>(BFI=1, SID=2, TAF=1)                                                                                             |
+| bad  | 0   | 1   | 0   | 1   | 1   | Invalid SID frame at TAF=1 with UFI = 1<br>(BFI=0, SID=1, TAF=1)<br>(BFI=1, SID=1, TAF=1)<br>(BFI=1, SID=2, TAF=1)                                                                                             |
+| bad* | 0   | 1   | 1   | 0   | 0   | Bad speech frame or unusable frame at TAF = 0 with UFI = 0<br>(BFI=1, SID=0, TAF=0)                                                                                                                            |
+| bad* | 0   | 1   | 1   | 0   | 1   | Bad speech frame or unusable frame at TAF = 0 with UFI = 1<br>(BFI=1, SID=0, TAF=0)                                                                                                                            |
+| bad* | 0   | 1   | 1   | 1   | 0   | Bad speech frame or unusable frame at TAF = 1 with UFI = 0<br>(BFI=1, SID=0, TAF=1)                                                                                                                            |
+| bad* | 0   | 1   | 1   | 1   | 1   | Bad speech frame or unusable frame at TAF = 1 with UFI = 1<br>(BFI=1, SID=0, TAF=1)                                                                                                                            |
+
+Speech frames and SID frames marked in Table 8.2.5.2 with FQC set to "good", i.e. value 0, shall be sent.
+
+Frames marked in Table 8.2.5.2 with FQC set to "bad\*" or "bad" shall not be sent in order to save bandwidth on Nb.
+
+NOTE 3: the abbreviations "UFI" (unreliable frame indication), "BFI" (bad frame indication), "SID" (Silence Descriptor) and "TAF" (Time Alignment Flag) are defined in 3GPP TS 46.041 [25].
+
+## 8.3 Frame handlers
+
+Nb PDU Frame handling functions are described in [7].
+
+# 9 Nb Interface User Plane (CN) of a SIP-I -based Circuit Switched Core Network
+
+## 9.1 Overview
+
+The SIP-I -based Circuit Switched Core Network is specified in 3GPP TS 23.231 [12]. The User Plane in this Core Network is further specified in 3GPP TS 29.414 [10]. RTP is specified in IETF RFC 3550 [16].
+
+RTP is used in a SIP-I -based Circuit Switched Core Network as framing protocol at the Nb-Interface (without Nb-framing protocol). The rules for the usage of RTP and RTCP in 3GPP TS 29.414 [10] are applicable in combination with further Codec-specific rules provided in the present specification.
+
+Table 9.1.1 lists the applicable 3GPP Codec Types for a SIP-I -based Circuit Switched Core Network. Codecs for data transport are described in 3GPP TS 29.007 [13].
+
+**Table 9.1.1 Supported Codec Types in a SIP-I -based Circuit Switched Core Network**
+
+| Payload Type Name     | References         | Remarks                                                        | Support                                                                                                         |
+|-----------------------|--------------------|----------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------|
+| audio/AMR             | IETF RFC 4867 [21] | Applicable for FR_AMR, HR_AMR, OHR_AMR, UMTS_AMR and UMTS_AMR2 | Mandatory.<br>Not all AMR Configurations are mandatory. Some Configurations are preferred, see below.           |
+| audio/AMR-WB          | IETF RFC 4867 [21] | Applicable for FR_AMR-WB, OHR_AMR-WB, OFR_AMR-WB, UMTS_AMR-WB  | Optional.<br>AMR-WB is mandatory, if WB speech is supported. Not all WB Configurations are mandatory, see below |
+| audio/GSM_EFR         | IETF RFC 3551 [17] | Useful if an A-interface over IP is attached or TFO is used.   | Optional                                                                                                        |
+| audio/GSM_FR          | IETF RFC 3551 [17] | Useful if an A-interface over IP is attached or TFO is used.   | Optional                                                                                                        |
+| audio/GSM_HR          | IETF RFC 5993 [22] | Useful if an A-interface over IP is attached or TFO is used.   | Optional                                                                                                        |
+| audio/PCMA            | IETF RFC 3551 [17] | ITU-T G.711 Alaw                                               | Mandatory                                                                                                       |
+| audio/PCMU            | IETF RFC 3551 [17] | ITU-T G.711 ulaw                                               | Mandatory                                                                                                       |
+| audio/telephone-event | IETF RFC 4733 [20] | Used to transport DTMF                                         | Mandatory                                                                                                       |
+
+The RTP "Payload Type" number for the Nb-Interface is either static (for PCMA, PCMU and GSM\_FR) or determined by the MSC-S (dynamic Payload Type).
+
+### 9.1.1 Time Alignment Procedure
+
+Time Alignment (and AMR Phase Alignment) is not specified in a SIP-I -based Circuit Switched Core Network.
+
+### 9.1.2 SID Frame Generation
+
+All 3GPP Codec Types include standardized Discontinuous Transmission (DTX) with Voice Activity Detection, Silence Description (by SID frames) and Comfort Noise Generation to fill the speech pauses. If speech inactivity is detected by the Encoder, then (speech) frames are not transmitted, but the transmission is suspended in order to save battery life time in the mobile station, reduce interference on the radio interface and reduce load on all links. The receiving Decoder fills these transmission pauses with Comfort Noise to minimize the contrast between pauses and active speech. Silence Descriptor frames need to be sent during speech inactivity to keep the Comfort Noise decently well aligned with the background noise at sender side. This is especially important at the onset of the next talkspurt and therefore SID frames should not be too old, when speech starts again.
+
+The generation of SID frames for the AMR and AMR-WB families of Codecs is determined by the Speech Encoder as specified in TS 26.093 [31], respectively TS 26.193 [32]. The radio subsystem does not influence this timing! SID frames come during speech pauses in uplink and downlink about every 160ms. Also an AMR Encoder in the Media Gateway generates and sends SID frames about every 160ms.
+
+The generation of SID frames for GSM\_FR, GSM\_HR and GSM\_EFR in the GSM radio network is determined by the GSM mobile station and the GSM radio subsystem, not primarily by the Speech Encoder! SID frames come during speech pauses in uplink from the mobile station about every 480ms. In downlink to the mobile station, when they are generated by the Speech Encoder of the GSM radio subsystem, SID frames are sent every 20ms to the GSM base station, which then picks only one every 480ms for downlink radio transmission. For other applications, like transport over Nb, it is more appropriate to send the SID frames less often than every 20ms, but 480ms may be too sparse. As a compromise it is recommended that an Encoder in the Media Gateway should generate and send SID frames every 160ms.
+
+### 9.1.3 Initial Codec Mode
+
+NOTE: At the Nb-Interface in a SIP-I -based Core Network, direct RTP packetization without Nb-framing is applied. Therefore the use of PDU Type 0 for the speech payload and PDU Type 14 [7] for AMR Rate Control is here not applicable. Also the principle of "Nb\_Init" is not applicable for a SIP-I -based Core Network.
+
+The Initial Codec Mode for AMR and AMR-WB shall be derived by pre-defined rules from the AMR Configuration (Active Codec Set), see TS 45.009 [35], chapter 3.4.3 "Initial Codec Mode Selection at Call Setup and Handover".
+
+Start of extract from TS 45.009 [35] for information and ease of reading:
+
+"If the Initial Codec Mode is not signalled, then the default Initial Codec Mode is given by the following implicit rule. If the Active Codec Set contains:
+
+- 1 mode, then this shall be the Initial Codec Mode;
+- 2 or 3 modes, then the Initial Codec Mode shall be the most robust mode of the set (with lowest bit rate);
+- 4 modes, then the Initial Codec Mode shall be the second most robust mode of the set (with second lowest bit rate."
+
+End of extract from TS 45.009 [35].
+
+In case of FR\_AMR (Set 1), i.e. Config-NB-Code 1, see below, this is the AMR Mode with 5.90kbps.
+
+## 9.2 AMR
+
+AMR (FR\_AMR, HR\_AMR, OHR\_AMR, UMTS\_AMR and UMTS\_AMR2) shall be packed according to IETF RFC 4867 [21].
+
+The AMR Codec Types can be used in conversational speech telephony services in a number of different Codec Configurations. The set of preferred AMR Codec Configurations is defined in TS 28.062 [5], Table 7.11.3.1.3-2. One of these preferred Configurations, **Config-NB-Code 1**, is recommended for TFO-TrFO harmonisation between GSM and UMTS networks. This Configuration shall be supported in a SIP-I based circuit switched core network to ensure interoperability with an AoIP-based BSS. However, it is recommended that nodes in the core network support all AMR modes for maximum interoperability.
+
+The bandwidth efficient mode of RFC 4867 shall be used. CRC and robust sorting shall not be applied.
+
+To avoid delay, a single frame (Speech or SID\_FIRST or SID\_UPDATE or ONSET) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20ms shall be applied. No\_Data frames should not be sent, except when needed for urgent Rate Control.
+
+Nodes in the core network (e.g. MGWs) transcoding between AMR and some other Codec shall observe the following rules:
+
+- An AMR Encoder (sender) in the core network shall obey an AMR Codec Mode change period of 40ms, i.e. Codec Mode changes by the AMR Encoder (sender) in this core network node are only permissible at every second frame. This ensures maximum interoperability with any AMR receiver.
+- An AMR Decoder (receiver) shall, however, be able to accept Codec Mode changes at any time. Variations of the Codec Mode period in receive direction may happen due to handover or other events during a conversation. The UMTS\_AMR Codec Type (only allowed in R99 UTRAN-only terminals) may change its Codec Mode any time. Other application of the AMR Codec Types (e.g. MTSI) may perform Codec Mode changes any time. This ensures maximum interoperability with any AMR sender.
+- An AMR Encoder shall only change the Codec Mode to a neighbouring mode of the defined AMR Configuration (one step up or one step down), regardless which Rate Control command it receives. If necessary the AMR Encoder shall apply several Codec Mode changes in a row, if the received Rate Control command requests a change of more than one step. This ensures maximum interoperability with any AMR receiver, especially within GSM terminals.
+- An AMR Decoder (receiver) shall, however, be able to accept Codec Mode changes in any step size. Variations of the Codec Mode in receive direction may happen due to handover or other events during a
+
+conversation. Other application of the AMR Codec Types (e.g. MTSI) may perform any Codec Mode changes. This ensures maximum interoperability with any AMR sender.
+
+- DTX (SCR) shall be supported in send and receive direction.
+
+AMR Rate Control shall use the CMR bits inside the RTP payload, both, in send and receive direction. RTCP shall not be used for AMR Rate Control in a CS core network.
+
+Rate Control Commands coming from an Nb-Interface of a BICC-based Core Network, or an Iu-Interface, or an IMS-Interface, or an general VoIP-Interface, shall be converted to CMR and shall be send continuously inside RTP packets together with the next Speech or SID\_FIRST or SID\_UPDATE or ONSET frame.
+
+NOTE: In a SIP-I -based Circuit Switched Core Network no Nb-framing is applied and so also no "PDU Type 14" [7] exists for Rate Control Commands.
+
+It is allowed to send an artificially inserted No\_Data frame to transport an urgent CMR in RTP. Please note that a GSM radio subsystem connected via AoIP can not send No\_Data frames across the radio interface and will typically ignore such No\_Data frames. The use of No\_Data frames for CMR is especially helpful inside the Core Network at call setup to control the downlink mode for the Encoder inside the terminating MGW for the compression of the ringback tone or an announcement, when the originating MGW still blocks the speech path in forward direction to prevent fraud.
+
+## 9.3 AMR-WB
+
+AMR-WB (FR\_AMR-WB, OHR\_AMR-WB, OFR\_AMR-WB, UMTS\_AMR-WB) shall be packed according to IETF RFC 4867 [21].
+
+The AMR-WB Codec Types can be used in conversational speech telephony services in a number of different Codec Configurations. The set of AMR-WB Codec Configurations is defined in TS 26.103 [14], Table 5.7-1. One of these Configurations, **Config-WB-Code 0**, shall be supported by all nodes supporting the AMR-WB codec in a SIP-I based circuit switched core network to ensure interoperability. However, it is recommended that nodes in the core network support all AMR-WB modes for maximum interoperability.
+
+The bandwidth efficient mode of RFC 4867 [21] shall be used. CRC and robust sorting shall not be applied.
+
+To avoid delay, a single frame (Speech or SID\_FIRST or SID\_UPDATE or ONSET) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20ms shall be applied. No\_Data frames should not be sent, except when needed for urgent Rate Control.
+
+Nodes in the core network (e.g. MGWs) transcoding between AMR-WB and some other Codec shall observe the following rules:
+
+- An AMR-WB Encoder (sender) in the core network shall obey an AMR-WB Codec Mode change period of 40ms, i.e. Codec Mode changes by the AMR-WB Encoder (sender) in this core network node are only permissible at every second frame. This ensures maximum interoperability with any AMR-WB receiver.
+- An AMR-WB Decoder (receiver) shall, however, be able to accept Codec Mode changes at any time. Variations of the Codec Mode period in receive direction may happen due to handover or other events during a conversation. Other application of the AMR-WB Codec Types (e.g. MTSI) may perform Codec Mode changes any time. This ensures maximum interoperability with any AMR-WB sender.
+- An AMR-WB Encoder shall only change the Codec Mode to a neighbouring mode of the defined AMR-WB Configuration (one step up or one step down), regardless which Rate Control command it receives. If necessary the AMR-WB Encoder shall apply several Codec Mode changes in a row, if the received Rate Control command requests a change of more than one step. This ensures maximum interoperability with any AMR-WB receiver, especially within GSM terminals.
+- An AMR-WB Decoder (receiver) shall, however, be able to accept Codec Mode changes in any step size. Variations of the Codec Mode in receive direction may happen due to handover or other events during a conversation. Other application of the AMR-WB Codec Types (e.g. MTSI) may perform any Codec Mode changes. This ensures maximum interoperability with any AMR-WB sender.
+- DTX (SCR) shall be supported in send and receive direction.
+
+AMR-WB Rate Control shall use the CMR bits inside the RTP payload, both, in send and receive direction. RTCP shall not be used for AMR-WB Rate Control in a CS core network.
+
+Rate Control Commands coming from an Nb-Interface of a BICC-based Core Network, or an Iu-Interface, or an IMS-Interface, or an general VoIP-Interface, shall be converted to CMR and shall be sent continuously inside RTP packets together with the next Speech or SID\_FIRST or SID\_UPDATE or ONSET frame.
+
+NOTE: In a SIP-I -based Circuit Switched Core Network no Nb-framing is applied and so also no "PDU Type 14" [7] exists for Rate Control Commands.
+
+It is allowed to send an artificially inserted No\_Data frame to transport an urgent CMR in RTP. Please note that a GSM radio subsystem connected via AoIP can not send No\_Data frames across the radio interface and will typically ignore such No\_Data frames. The use of No\_Data frames for CMR is especially helpful on the AoIP-Interface in uplink and inside the Core Network at call setup to control the downlink mode for the Encoder inside the terminating MGW for the compression of the ringback tone or an announcement, when the originating MGW still blocks the speech path in forward direction to prevent fraud.
+
+## 9.4 GSM\_EFR
+
+GSM\_EFR shall be packed according to IETF RFC 3551 [17].
+
+The coding of SID frames is based on the coding of Speech frames by setting the 95 bits of the so called "SID-Codeword" all to "1", see TS 46.062 [30].
+
+To avoid delay, a single frame (Speech or SID) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20 ms shall be applied. No\_Data frames shall not be sent.
+
+DTX shall be supported in send and receive direction.
+
+GSM\_EFR frames received from some interface (e.g. a GSM radio interface via TFO) with a bad frame indication set to "bad" shall not be forwarded on the Nb-Interface in a SIP-I -based Circuit Switched Core Network, but silently discarded.
+
+NOTE: RFC 3551 [17] does not support the concept of Bad Frame Indication.
+
+## 9.5 GSM\_FR
+
+GSM\_FR shall be packed according to IETF RFC 3551 [17].
+
+The coding of SID frames is based on the coding of Speech frames by setting the 95 bits of the so called "SID-Codeword" all to "0", see TS 46.012 [28].
+
+To avoid delay, a single frame (Speech or SID) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20ms shall be applied. No\_Data frames shall not be sent.
+
+DTX shall be supported in send and receive direction.
+
+GSM\_FR frames received from some interface (e.g. a GSM radio interface via TFO) with a bad frame indication set to "bad" shall not be forwarded on the Nb-Interface in a SIP-I based Circuit Switched Core Network, but silently discarded.
+
+NOTE: RFC 3551 [17] does not support the concept of Bad Frame Indication.
+
+## 9.6 GSM\_HR
+
+GSM\_HR shall be packed according to [22].
+
+The options specified in [22] are not applied inside the Circuit Switched Core Network, but set to pre-defined values as follows:
+
+A single frame (Speech or SID) shall be included in one RTP packet, FEC and Interleaving (redundancy) shall not be used, Encryption shall not be used, a packetization time of 20ms shall be applied. No\_Data frames shall not be sent.
+
+DTX shall be supported in send and receive direction.
+
+GSM\_HR frames received from some interface (e.g. a GSM radio interface via TFO) with a bad frame indication set to "bad" shall not be forwarded on the Nb-Interface in a SIP-I -based Circuit Switched Core Network, but silently discarded.
+
+NOTE: [22] does not support the concept of Bad Frame Indication.
+
+## 9.7 PCM
+
+PCMU and PCMA shall be packed according to IETF RFC 3551 [17].
+
+The PCM packetization time for a SIP-I -based Core Network is negotiated via SDP. The mandatory, default value is 20ms; 5ms is one other, optional value; no other packetization time shall be used. To avoid delay, a single frame of length equal to the packetization time shall be included in one RTP packet, Interleaving (redundancy) shall not be used.
+
+The usage of DTX for PCM-coded speech is not recommended for NboIP.
+
+## 9.8 Telephone-Event
+
+Telephony-Event (DTMF) shall be encoded according to IETF RFC 4733 [20].
+
+The audio/telephone-event payload type in IETF RFC 4733 [20] with default events and default rate shall be used to encode DTMF, if compressed speech is used in a SIP-I -based Core Network. Only in case of PCM-coded speech on NboIP the Telephone-Event is optional, i.e. also inband DTMF tones may be used (see TS 23.231 [12]).
+
+# 10 A-Interface User Plane over IP
+
+## 10.1 Overview
+
+The A interface User Plane over IP (AoIP) is standardised in the 3GPP TS 48-series (mainly in TS 48.008) [33] for the Control Plane and in TS 48.103 [34] for the User Plane).
+
+For AoIP the same Codecs as described in Clause 9 are applicable, except telephone-event, see table 10.1.1. Those Codecs shall also be applied in the same manner as described in Clause 9, unless otherwise specified in the present Clause 10.
+
+**Table 10.1.1 Supported Codec Types for the A interface User Plane over IP**
+
+| Payload Type Name | References         | Remarks                                          | Support                                                                                                                    |
+|-------------------|--------------------|--------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------|
+| audio/AMR         | IETF RFC 4867 [21] | Applicable for FR_AMR, HR_AMR, OHR_AMR           | Optional.<br>Not all AMR Configurations are mandatory. Some Configurations are preferred, see chapter 9.                   |
+| audio/AMR-WB      | IETF RFC 4867 [21] | Applicable for FR_AMR-WB, OHR_AMR-WB, OFR_AMR-WB | Optional.<br>AMR-WB is mandatory, if WB speech is supported.<br>Not all AMR-WB Configurations are mandatory, see chapter 9 |
+| audio/GSM_EFR     | IETF RFC 3551 [17] |                                                  | Optional                                                                                                                   |
+| audio/GSM_FR      | IETF RFC 3551 [17] |                                                  | Mandatory                                                                                                                  |
+| audio/GSM_HR      | IETF RFC 5993 [22] |                                                  | Optional                                                                                                                   |
+| audio/PCMA        | IETF RFC 3551 [17] | ITU-T G.711 Alaw                                 | Optional                                                                                                                   |
+| audio/PCMU        | IETF RFC 3551 [17] | ITU-T G.711 ulaw                                 | Optional                                                                                                                   |
+
+The RTP "Payload Type" for AoIP is pre-determined by 3GPP TS 48.103 [34] for all Codec Types (static payload type).
+
+### 10.1.1 Time Alignment Procedure
+
+Time Alignment (and AMR Phase Alignment) is not specified for AoIP.
+
+### 10.1.2 SID Frame Generation
+
+All 3GPP Codec Types include standardized Discontinuous Transmission (DTX) with Voice Activity Detection, Silence Description (by SID frames) and Comfort Noise Generation to fill the speech pauses. If speech inactivity is detected by the Encoder, then (speech) frames are not transmitted, but the transmission is suspended in order to save battery life time in the mobile station, reduce interference on the radio interface and reduce load on all links. The receiving Decoder fills these transmission pauses with Comfort Noise to minimize the contrast between pauses and active speech. Silence Descriptor frames need to be sent during speech inactivity to keep the Comfort Noise decently well aligned with the background noise at sender side. This is especially important at the onset of the next talk spurt and therefore SID frames should not be too old, when speech starts again.
+
+The generation of SID frames for the AMR and AMR-WB families of Codecs is determined by the Speech Encoder as specified in TS 26.093 [31], respectively TS 26.193 [32]. The radio subsystem does not influence this timing! SID frames come during speech pauses in uplink and downlink about every 160ms. Also an AMR Encoder in the Media Gateway generates and sends SID frames about every 160ms.
+
+The generation of SID frames for GSM\_FR, GSM\_HR and GSM\_EFR in the GSM radio network is determined by the GSM mobile station and the GSM radio subsystem, not primarily by the Speech Encoder! SID frames come during speech pauses in uplink from the mobile station about every 480ms. In downlink to the mobile station, when they are generated by the Speech Encoder of the GSM radio subsystem, SID frames are sent every 20ms to the GSM base station, which then picks only one every 480ms for downlink radio transmission. For other applications, like transport over the A-Interface, it is more appropriate to send the SID frames less often than every 20ms, but 480ms may be too sparse. As a compromise it is recommended that an Encoder in the Media Gateway should generate and send SID frames every 160ms.
+
+### 10.1.3 Initial Codec Mode
+
+The Initial Codec Mode for AMR and AMR-WB shall be derived by pre-defined rules from the AMR Configuration (Active Codec Set), see TS 45.009 [35], chapter 3.4.3 "Initial Codec Mode Selection at Call Setup and Handover".
+
+Start of extract from TS 45.009 [35] for information and ease of reading:
+
+"If the Initial Codec Mode is not signalled, then the default Initial Codec Mode is given by the following implicit rule. If the Active Codec Set contains:
+
+- 1 mode, then this shall be the Initial Codec Mode;
+- 2 or 3 modes, then the Initial Codec Mode shall be the most robust mode of the set (with lowest bit rate);
+- 4 modes, then the Initial Codec Mode shall be the second most robust mode of the set (with second lowest bit rate."
+
+End of extract from TS 45.009 [35].
+
+In case of FR\_AMR (Set 1), i.e. Config-NB-Code 1, see below, this is the AMR Mode with 5.90 kbps.
+
+## 10.2 AMR
+
+AMR (FR\_AMR, HR\_AMR, OHR\_AMR) shall be packed according to IETF RFC 4867 [21].
+
+The AMR Codec Types can be used in conversational speech telephony services in a number of different Codec Configurations. The set of preferred AMR Codec Configurations is defined in TS 28.062 [5], Table 7.11.3.1.3-2. One of these preferred Configurations, **Config-NB-Code 1**, is recommended for TFO-TrFO harmonisation between GSM and UMTS networks. This Configuration shall be supported in an AoIP supporting BSS and an AoIP supporting Circuit Switched Core Network to ensure interoperability. However, it is recommended that a BSS and Circuit Switched Core Network supports all AMR modes for maximum interoperability.
+
+The bandwidth efficient mode of RFC 4867 [21] shall be used. CRC and robust sorting shall not be applied.
+
+To avoid delay, a single frame (Speech or SID\_FIRST or SID\_UPDATE or ONSET) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20ms shall be applied. No\_Data frames should not be sent downlink across AoIP, except to transport an urgent CMR in RTP. The use of No\_Data frames for CMR is especially helpful on the AoIP-Interface in uplink and inside the Core Network at call setup to control the
+
+downlink mode for the Encoder inside the terminating MGW for the compression of the ringback tone or an announcement, when the originating MGW still blocks the speech path in forward direction to prevent fraud.
+
+Please note that a GSM radio subsystem can not send No\_Data frames across the radio interface and will typically ignore such No\_Data frames in downlink direction.
+
+DTX (SCR) shall be supported in send and receive direction.
+
+AMR Rate Control shall use the CMR bits inside the RTP payload, both, in send and receive direction. RTCP shall not be used for AMR Rate Control in a CS network.
+
+## 10.3 AMR-WB
+
+AMR-WB (FR\_AMR-WB, OHR\_AMR-WB, OFR\_AMR-WB) shall be packed according to IETF RFC 4867 [21].
+
+The AMR-WB Codec Types can be used in conversational speech telephony services in a number of different Codec Configurations. The set of AMR-WB Codec Configurations is defined in TS 26.103 [14], Table 5.7-1. One of these Configurations, **Config-WB-Code 0**, shall be supported by all nodes supporting the AMR-WB codec in an AoIP-supporting BSS and an AoIP-supporting Circuit Switched Core Network to ensure interoperability. However, it is recommended that nodes in the Core Network support all AMR-WB modes for maximum interoperability.
+
+The bandwidth efficient mode of RFC 4867 [21] shall be used. CRC and robust sorting shall not be applied.
+
+To avoid delay, a single frame (Speech or SID\_FIRST or SID\_UPDATE or ONSET) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20ms shall be applied. No\_Data frames should not be sent downlink across AoIP, except to transport an urgent CMR in RTP. The use of No\_Data frames for CMR is especially helpful on the AoIP-Interface in uplink and inside the Core Network at call setup to control the downlink mode for the Encoder inside the terminating MGW for the compression of the ringback tone or an announcement, when the originating MGW still blocks the speech path in forward direction to prevent fraud.
+
+Please note that a GSM radio subsystem can not send No\_Data frames across the radio interface and will typically ignore such No\_Data frames in downlink direction.
+
+DTX (SCR) shall be supported in send and receive direction.
+
+AMR-WB Rate Control shall use the CMR bits inside the RTP payload, both, in send and receive direction. RTCP shall not be used for AMR-WB Rate Control in a Circuit Switched Core Network.
+
+## 10.4 GSM\_EFR
+
+GSM\_EFR shall be packed according to IETF RFC 3551 [17].
+
+The coding of SID frames is based on the coding of Speech frames by setting the 95 bits of the so called "SID-Codeword" all to "1", see TS 46.062 [30].
+
+To avoid delay, a single frame (Speech or SID) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20 ms shall be applied. No\_Data frames shall not be sent.
+
+DTX shall be supported in send and receive direction.
+
+NOTE: RFC 3551 [17] does not support the concept of Bad Frame Indication. Therefore missing GSM\_EFR frames in the AoIP downlink direction (e.g. discarded by a network node due to the missing bad frame indication) need to be properly treated within the BSS before sending downlink on the radio interface. Details are not specified.
+
+## 10.5 GSM\_FR
+
+GSM\_FR shall be packed according to IETF RFC 3551 [17].
+
+The coding of SID frames is based on the coding of Speech frames by setting the 95 bits of the so called "SID-Codeword" all to "0", see TS 46.012 [28].
+
+To avoid delay, a single frame (Speech or SID) shall be included in one RTP packet, Interleaving (redundancy) shall not be used, and a packetization time of 20 ms shall be applied. No\_Data frames shall not be sent.
+
+DTX shall be supported in send and receive direction.
+
+NOTE: RFC 3551 [17] does not support the concept of Bad Frame Indication. Therefore missing GSM\_EFR frames in the AoIP downlink direction (e.g. discarded by a network node due to the missing bad frame indication) need to be properly treated within the BSS before sending downlink on the radio interface. Details are not specified.
+
+## 10.6 GSM\_HR
+
+GSM\_HR shall be packed according to [22].
+
+The options specified in [22] are not applied on AoIP, but set to pre-defined values as follows:
+
+A single frame (Speech or SID) shall be included in one RTP packet, FEC and Interleaving (redundancy) shall not be used, Encryption shall not be used, a packetization time of 20ms shall be applied. No\_Data frames shall not be sent.
+
+DTX shall be supported in send and receive direction.
+
+NOTE: [22] does not support the concept of Bad Frame Indication. Therefore missing GSM\_HR frames in the AoIP downlink direction (e.g. discarded by a network node due to the missing bad frame indication) need to be properly treated within the BSS before sending downlink on the radio interface. Details are not specified.
+
+## 10.7 PCM
+
+PCMU and PCMA shall be packed according to IETF RFC 3551 [17].
+
+A packetization time of 20ms shall be applied for PCM on AoIP. The packetization time is not negotiated for AoIP. To avoid delay, a single frame of 20ms shall be included in one RTP packet, Interleaving (redundancy) shall not be used.
+
+The usage of DTX for PCM-coded speech is not allowed on AoIP.
+
+# Annex A (informative): Change history
+
+| Change history |       |           |      |     |                                                                                |        |        |
+|----------------|-------|-----------|------|-----|--------------------------------------------------------------------------------|--------|--------|
+| Date           | TSG # | TSG Doc.  | CR   | Rev | Subject/Comment                                                                | Old    | New    |
+| 1999-12        | 6     | SP-99563  |      |     | Approved at TSG-SA#6 Plenary                                                   |        | 3.0.0  |
+| 2000-03        | 7     | SP-000025 | 001  | 3   | Introduction of QoS parameters used at RAB assignment                          | 3.0.0  | 3.1.0  |
+| 2000-03        | 7     | SP-000025 | 002  |     | Introduction of different RFCS set on Iu User Plane                            | 3.0.0  | 3.1.0  |
+| 2000-03        | 7     | SP-000025 | 003  | 2   | Introduction of Time Alignment                                                 | 3.0.0  | 3.1.0  |
+| 2000-12        | 10    | SP-000575 | 005  | 1   | AMR interface to Iu                                                            | 3.1.0  | 3.2.0  |
+| 2001-03        | 11    | SP-010103 | 006  | 2   | Removal of TFO and TrFO from Release 99, and removal of Initial Time Alignment | 3.2.0  | 3.3.0  |
+| 2001-03        | 11    | SP-010103 | 008  | 1   | Introduction of TFO and TrFO                                                   | 3.3.0  | 4.0.0  |
+| 2002-06        | 16    |           |      |     | Version for Release 5                                                          | 4.0.0  | 5.0.0  |
+| 2002-12        | 18    | SP-020689 | 012  | 2   | Correction of RAB parameter assignment for AMR                                 | 5.0.0  | 5.1.0  |
+| 2003-03        | 19    | SP-030087 | 015  | 2   | AMR Rate Adaptation of Rel-5                                                   | 5.1.0  | 5.2.0  |
+|                |       |           |      |     |                                                                                |        |        |
+| 2004-04        | 25    | SP-040645 | 016  | 1   | Mapping of GSM_EFR SID on Nb Interface                                         | 5.2.0  | 6.0.0  |
+|                |       |           |      |     |                                                                                |        |        |
+| 2005-12        | 30    | SP-050791 | 0017 |     | 20 ms packetisation time for PCM coded speech over IP Nb                       | 6.0.0  | 7.0.0  |
+| 2006-06        | 32    | SP-060358 | 0018 | 1   | Supplement of 20 ms packetisation time for PCM coded speech over IP Nb         | 7.0.0  | 7.1.0  |
+| 2008-06        | 41    | SP-080475 | 0019 | 2   | Addition of CS over IP User Plane                                              | 7.1.0  | 8.0.0  |
+| 2008-06        | 41    | SP-080475 | 0020 | 1   | Nb-framing for GSM_FR and GSM_HR                                               | 7.1.0  | 8.0.0  |
+| 2008-12        | 42    | SP-080678 | 0021 | 3   | Corrections to CS over IP User Plane                                           | 8.0.0  | 8.1.0  |
+| 2009-09        | 45    | SP-090568 | 0023 | 1   | Clarification of RAB sub-flow numbering for AMR                                | 8.1.0  | 8.2.0  |
+| 2009-12        | 46    | SP-090703 | 0024 | 1   | Correction of payload field size for mapping of GSM FR on Nb interface         | 8.2.0  | 8.3.0  |
+| 2009-12        | 46    |           |      |     | Version for Release 9                                                          | 8.3.0  | 9.0.0  |
+| 2010-03        | 47    | SP-100018 | 0026 |     | Corrections and clarifications of Nb frames                                    | 9.0.0  | 9.1.0  |
+| 2011-03        | 51    | SP-110034 | 0028 |     | Correction of reference for GSM-HR payload format                              | 9.1.0  | 9.2.0  |
+| 2011-03        | 51    |           |      |     | Version for Release 10                                                         | 9.2.0  | 10.0.0 |
+| 2012-09        | 57    | SP-120508 | 0029 | 2   | Clarification of Text Regarding Bit Protection Classes and RAB sub-flows       | 10.0.0 | 11.0.0 |

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+
+
+
+
+
+
+# Contents
+
+|                                                                                                          |           |
+|----------------------------------------------------------------------------------------------------------|-----------|
+| Foreword .....                                                                                           | 4         |
+| 1 Scope.....                                                                                             | 5         |
+| 2 Normative references .....                                                                             | 5         |
+| 3 Definitions and Abbreviations .....                                                                    | 6         |
+| 3.1 Definitions.....                                                                                     | 6         |
+| 3.2 Abbreviations .....                                                                                  | 6         |
+| 4 General .....                                                                                          | 7         |
+| 5 3GPP Codec List for OoBTC in a BICC-based Circuit Switched Core Network and for AoIP .....             | 9         |
+| 5.1 GSM Full Rate Codec Type (GSM FR).....                                                               | 9         |
+| 5.2 GSM Half Rate Codec Type (GSM HR) .....                                                              | 9         |
+| 5.3 GSM Enhanced Full Rate Codec Type (GSM EFR).....                                                     | 9         |
+| 5.4 Five Adaptive Multi-Rate Codec Types (FR AMR, HR AMR, UMTS AMR, UMTS AMR2, OHR AMR) .....            | 10        |
+| 5.5 TDMA Enhanced Full Rate Codec Type (TDMA EFR) .....                                                  | 13        |
+| 5.6 PDC Enhanced Full Rate Codec Type (PDC_EFR) .....                                                    | 13        |
+| 5.7 Four Adaptive Multi-Rate Wideband Codec Types (FR AMR-WB, UMTS AMR-WB, OFR AMR-WB, OHR AMR-WB) ..... | 13        |
+| 5.8 MuMe Dummy Codec (3G.324M).....                                                                      | 16        |
+| 5.9 MuMe2 Dummy Codec (3G.324M2).....                                                                    | 17        |
+| 5.10 Codec Extension.....                                                                                | 17        |
+| 5.11 CSData Dummy Codec (AoIP).....                                                                      | 17        |
+| 6 Codec List for the Call Control Protocol .....                                                         | 17        |
+| 6.1 System Identifiers for GSM and UMTS .....                                                            | 17        |
+| 6.2 Codec Bitmap.....                                                                                    | 18        |
+| 6.3 Selected Codec Type.....                                                                             | 19        |
+| 7 3GPP Codecs for OoBTC in a SIP-I -based Circuit Switched Core Network.....                             | 20        |
+| 7.1 Overview .....                                                                                       | 20        |
+| 7.2 AMR.....                                                                                             | 20        |
+| 7.3 AMR-WB.....                                                                                          | 21        |
+| 7.4 GSM_EFR .....                                                                                        | 21        |
+| 7.5 GSM_FR .....                                                                                         | 21        |
+| 7.6 GSM_HR.....                                                                                          | 21        |
+| 7.7 PCM .....                                                                                            | 22        |
+| 7.8 Telephone-Event .....                                                                                | 22        |
+| <b>Annex A (informative): Example Supported Codec List for UMTS.....</b>                                 | <b>23</b> |
+| Annex B (informative): Change history.....                                                               | 25        |
+
+# --- Foreword
+
+This Technical Specification has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- 1 Scope
+
+The present Technical Specification outlines the Codec Lists in 3GPP including both systems, GSM and UMTS, to be used by the Out of Band Transcoder Control (OoBTC) protocol to set up a call or modify a call in **Transcoder Free Operation** (TrFO) and in "transcoder at the edge" scenarios.
+
+The TS also specifies the SDP description of 3GPP Codecs to be used within a SIP-I -based circuit switched core network as specifies in 3GPP TS 23.231 [14].
+
+The TS further specifies the coding of the Supported Codec List Information Elements for the UMTS radio access technology.
+
+The TS further reserves the Code Point for the CSData (dummy) Codec Type for the negotiation of A-Interface Type and the RTP redundancy for CS Data and Fax services, see 3GPP TS 48.008 [23].
+
+The Supported Codec List IE includes Codec\_Types from the TDMA and PDC systems, to support TFO or TrFO between UMTS and TDMA, or UMTS and PDC.
+
+# --- 2 Normative references
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+- For a specific reference, subsequent revisions do not apply.
+- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+
+- [1] 3GPP TS 26.090: "AMR Speech Codec; Speech Transcoding Functions".
+- [2] 3GPP TS 26.093: "AMR Speech Codec; Source Controlled Rate Operation".
+- [3] 3GPP TS 26.101: "Mandatory Speech Codec Speech Processing Functions; AMR Speech Codec Frame Structure".
+- [4] 3GPP 46.0xx: "Enhanced Full Rate Codec Recommendations".
+- [5] 3GPP 26.0xx: "Adaptive Multi-Rate Codec Recommendations".
+- [6] "ITU Q.765.5: "Use of Application Transport Mechanism for Bearer Independent Call Control"
+- [7] 3GPP TS 28.062: "In-band Tandem Free Operation (TFO) of Speech Codecs, Stage 3 - Service Description".
+- [8] 3GPP TS 23.153: "Out of Band Transcoder Control - Stage 2".
+- [9] 3GPP TS 24.008: "Mobile radio interface layer 3 specifications, Core Network Protocols"
+- [10] 3GPP TS 26.190: "AMR Wideband Speech Codec; Speech Transcoding Functions".
+- [11] 3GPP TS 26.193: "AMR Wideband Speech Codec; Source Controlled Rate Operation".
+- [12] 3GPP TS 26.201: "Mandatory Speech Codec Speech Processing Functions; AMR Wideband Speech Codec Frame Structure".
+- [13] 3GPP TS 23.172: "CS multimedia service UDI/RDI fallback and service modification; Stage 2".
+- [14] 3GPP TS 23.231: "SIP-I based circuit-switched core network; Stage 2".
+
+- [15] 3GPP TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".
+- [16] IETF RFC 3264 (2002): "An Offer/Answer Model with the Session Description Protocol (SDP)", J. Rosenberg and H. Schulzrinne.
+- [17] IETF RFC 3551 (2003): "RTP Profile for Audio and Video Conferences with Minimal Control", H. Schulzrinne and S. Casner.
+- [18] void
+- [19] IETF RFC 4566 (2006): "SDP: Session Description Protocol", M. Handley, V. Jacobson and C. Perkins.
+- [20] IETF RFC 4733 (2006): "RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals", H. Schulzrinne and T. Taylor.
+- [21] IETF RFC 4867 (2007): "RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs", J. Sjoberg, M. Westerlund, A. Lakaniemi and Q. Xie.
+- [22] IETF RFC 5993 (2010) "RTP Payload Format for Global System for Mobile Communications Half Rate (GSM-HR)".
+- [23] 3GPP TS 48.008: "Mobile Switching Centre - Base Station System (MSC-BSS) interface".
+- [24] 3GPP TS 26.102: "Adaptive Multi-Rate (AMR) speech codec; Interface to Iu, Uu and Nb".".
+
+# --- 3 Definitions and Abbreviations
+
+## 3.1 Definitions
+
+**Codec Type:** defines a specific type of a speech Coding algorithm, applied on a specific radio access technology (e.g. GSM FR, (GSM) FR AMR).
+
+**Codec Mode:** defines a specific mode of a Codec Type (e.g. 12,2 kBit/s Mode of the (GSM) FR AMR).
+
+**Codec Configuration:** defines a specific set of attributes to a certain Codec Type (e.g. the combination of ACS and DTX="on" for (GSM) FR AMR).
+
+**Organisation Identifier (OID):** Identifies the standard organisation (e.g. 3GPP) producing a specification for a Codec List. ITU-T is responsible for maintaining the list of Organisation Identifiers.
+
+**System Identifier (SysID):** Identifies the radio access technology (e.g. GSM or UMTS) for which the supported Codec List is defined.
+
+Other definitions are given in TS 23.153 [8].
+
+## 3.2 Abbreviations
+
+For the purposes of the present document, the following abbreviations apply:
+
+|        |                                           |
+|--------|-------------------------------------------|
+| ACS    | Active Codec (mode) Set                   |
+| AoIP   | A-Interface User Plane over IP            |
+| BWM    | BandWidth Multiplier                      |
+| CoID   | Codec Identifier                          |
+| CSData | Circuit Switched Data and Fax dummy Codec |
+| DTX    | Discontinuous Transmission                |
+
+|       |                                                                                                                 |
+|-------|-----------------------------------------------------------------------------------------------------------------|
+| GSM   | Global System for Mobile communication                                                                          |
+| MuMe  | Multi-Media                                                                                                     |
+| NbIoP | Nb-Interface User Plane transport over IP in a SIP-I -based network                                             |
+| OID   | Organisation IDeNtifier (e.g. ITU-T, 3GPP)                                                                      |
+| OoBTC | Out of Band Transcoder Control                                                                                  |
+| PDC   | Personal Digital Communication (synonym for ...)                                                                |
+| RX    | Receive                                                                                                         |
+| SCR   | Source Controlled Rate operation (synonym to DTX )                                                              |
+| SID   | Silence Descriptor                                                                                              |
+| SysID | System Identifier                                                                                               |
+| TDMA  | Time Division Multiple Access (synonym for ...)                                                                 |
+| TFO   | <b>T</b> andem <b>F</b> ree <b>O</b> peration<br>(also sometimes called "Transcoder-Through" or "Codec-Bypass") |
+| TrFO  | <b>T</b> ranscoder <b>F</b> ree <b>O</b> peration                                                               |
+| TX    | Transmit                                                                                                        |
+| UMTS  | Universal Mobile Telecommunications System                                                                      |
+
+# --- 4 General
+
+The present Technical Specification (TS) outlines the 3GPP internal Codec Lists for both, GSM and UMTS, to be used by the Out of Band Transcoder Control (OoBTC) protocol a BICC-based Circuit Switched Core Network to set up a call or modify a call in Transcoder Free Operation (TrFO). The Codec List is also used in the Codec Negotiation for the A-Interface User Plane over IP (AoIP), see 3GPP TS 48.008 [23].
+
+The TS specifies the SDP parameters for the 3GPP Codecs for OoBTC in a SIP-I -based Circuit Switched Core Network, see 3GPP TS 23.231 [14].
+
+The TS further specifies the coding of the Supported Codec List Information Elements as defined in 3GPP TS 24.008 for the UMTS radio access technology.
+
+Transcoder Free Operation allows the transport of speech signals in the coded domain from one user equipment (UE) to the other user equipment through the radio access network (RAN) and core network (CN), possibly through a transit network (TN). This enables high speech quality, low transmission costs and high flexibility.
+
+The necessary Codec Type selection and resource allocation are negotiated out of band before and after call setup. Possible Codec (re-)configuration, Rate Control and DTX signalling may be performed after call setup by additional inband signalling or a combination of inband and out-of-band signalling.
+
+Up to release '99 GSM does not support Transcoder Free Operation, but specifies the Tandem Free Operation (TFO). Tandem Free Operation enables similar advantages, but is based on pure inband signalling after call setup. The parameters defined in this Technical Specification allow interaction between TrFO and TFO. They further provide an evolutionary path for GSM towards Transcoder Free Operation.
+
+The GERAN and UTRAN standards define fourteen different Speech Codec Types, see table 4.1.
+
+In addition to these Speech Codec Types some "dummy" Codec Types are defined to support the negotiation for data, fax and multimedia applications.
+
+**Table 4.1: Support of Codec Types in Radio Access Technologies**
+
+|                       | <b>TDMA<br/>EFR</b> | <b>UMTS<br/>AMR 2</b>                  | <b>UMTS<br/>AMR</b> | <b>(GSM)<br/>HR AMR</b> | <b>(GSM)<br/>FR AMR</b> | <b>GSM<br/>EFR</b> | <b>GSM<br/>HR</b> | <b>GSM<br/>FR</b> |
+|-----------------------|---------------------|----------------------------------------|---------------------|-------------------------|-------------------------|--------------------|-------------------|-------------------|
+| <b>CoID</b>           | <b>0x07</b>         | <b>0x06</b>                            | <b>0x05</b>         | <b>0x04</b>             | <b>0x03</b>             | <b>0x02</b>        | <b>0x01</b>       | <b>0x00</b>       |
+| <b>GERAN<br/>GMSK</b> | not defined         | not possible                           | not possible        | yes, 1..4 modi          | yes, 1..4 modi          | yes                | yes               | yes               |
+| <b>GERAN<br/>8PSK</b> | not defined         | not possible                           | not possible        | not defined             | not defined             | not defined        | not defined       | not defined       |
+| <b>UTRAN</b>          | not defined         | yes, 1..8 modi<br>1..4 modi<br>recomm. | R99, UTRAN-only UEs | not defined             | not defined             | not defined        | not defined       | not defined       |
+
+|                       | <b>Codec<br/>Extension</b> |             | <b>OHR<br/>AMR-WB</b> | <b>OFR<br/>AMR-WB</b> | <b>OHR<br/>AMR</b> | <b>UMTS<br/>AMR-WB</b> | <b>FR<br/>AMR-WB</b> | <b>PDC<br/>EFR</b> |
+|-----------------------|----------------------------|-------------|-----------------------|-----------------------|--------------------|------------------------|----------------------|--------------------|
+| <b>CoID</b>           | <b>0x0F</b>                | <b>0x0E</b> | <b>0x0D</b>           | <b>0x0C</b>           | <b>0x0B</b>        | <b>0x0A</b>            | <b>0x09</b>          | <b>0x08</b>        |
+| <b>GERAN<br/>GMSK</b> | reserved                   | spare       | not defined           | not defined           | not defined        | not possible           | yes3 modi            | not defined        |
+| <b>GERAN<br/>8PSK</b> | reserved                   | spare       | yes, 3 modi           | yes, 3 modi           | yes, 1..4 modi     | not possible           | not defined          | not defined        |
+| <b>UTRAN</b>          | reserved                   | spare       | not defined           | not defined           | not defined        | yes 3..4 modi          | not defined          | not defined        |
+
+CoID is reprinted here in hexadecimal notation. It is defined in section 5.
+
+Up to date the following Code Points are defined:
+
+**Table 4.2. Defined Code Points**
+
+| <b>Hexadecimal<br/>Notation</b> | <b>Binary<br/>Notation</b>        | <b>Codec Name</b>     | <b>Remark</b>    |
+|---------------------------------|-----------------------------------|-----------------------|------------------|
+| 0x00h                           | 0x0000.0000                       | GSM_FR                |                  |
+| 0x01h                           | 0x0000.0001                       | GSM_HR                |                  |
+| 0x02h                           | 0x0000.0010                       | GSM_EFR               |                  |
+| 0x03h                           | 0x0000.0011                       | (GSM) FR_AMR          |                  |
+| 0x04h                           | 0x0000.0100                       | (GSM) HR_AMR          |                  |
+| 0x05h                           | 0x0000.0101                       | UMTS_AMR              |                  |
+| 0x06h                           | 0x0000.0110                       | UMTS_AMR2             |                  |
+| 0x07h                           | 0x0000.0111                       | TDMA_EFR              |                  |
+| 0x08h                           | 0x0000.1000                       | PDC_EFR               |                  |
+| 0x09h                           | 0x0000.1001                       | (GSM) FR_AMR-WB       |                  |
+| 0x0Ah                           | 0x0000.1010                       | UMTS_AMR-WB           |                  |
+| 0x0Bh                           | 0x0000.1011                       | OHR_AMR               |                  |
+| 0x0Ch                           | 0x0000.1100                       | OFR_AMR-WB            |                  |
+| 0x0Dh                           | 0x0000.1101                       | OHR_AMR-WB            |                  |
+| 0x0Eh                           | 0x0000.1110                       | Spare, for future use |                  |
+| 0x0Fh                           | 0x0000.1111                       | Codec Extension       | For AoIP and TFO |
+| 0x10h ...<br>0xFCh              | 0x0001.0000<br>...<br>0x1111.1100 | Spare, for future use |                  |
+| 0xFDh                           | 0x1111.1101                       | CSData                | For AoIP only    |
+| 0xFEh                           | 0x1111.1110                       | MuMe2                 | For OoBTC only   |
+| 0xFFh                           | 0x1111.1111                       | MuMe                  | For OoBTC only   |
+
+# --- 5 3GPP Codec List for OoBTC in a BICC-based Circuit Switched Core Network and for AoIP
+
+The definition of the common Codec List for Out of Band Transcoder Control (3GPP TS 23.153, [8]) in 3GPP for GSM and UMTS follows the specifications given in ITU Q.765.5: The most preferred Codec Type is listed first, followed by the second preferred one, and so on. An informative example for a codec list for UMTS can be found in Annex A.
+
+The Codec Identification codes (CoIDs) are specified in two versions: the long form (8 bits) for the use in OoBTC and the short form (the 4 LSBs of the long form) for the use in TFO and AoIP.
+
+## 5.1 GSM Full Rate Codec Type (GSM FR)
+
+The Codec Identification (CoID) code is defined to be: FR\_CoID := 0x0000.0000.
+
+The GSM Full Rate Codec Type has no additional parameters.
+
+For information (for exact details see GSM Recommendations):
+
+The GSM Full Rate Codec Type supports one fixed Codec Mode with 13.0 kBit/s.
+
+DTX may be enabled in uplink and in downlink independently of each other. DTX on or off is defined by the network on a cell basis and can not be negotiated at call setup or during the call. The DTX scheme uses one SID frame to mark the end of a speech burst and to start Comfort Noise Generation. Identical SID frames for comfort noise updates are sent in speech pauses about every 480 ms, aligned with the cell's TDMA frame structure. The defined Tandem Free Operation allows the reception of GSM FR DTX information for the downlink direction in all cases. The TFO respectively TrFO partner is prepared to receive DTX information as well.
+
+## 5.2 GSM Half Rate Codec Type (GSM HR)
+
+The Codec Identification (CoID) code is defined to be: HR\_CoID := 0x0000.0001.
+
+The GSM Half Rate Codec Type has no additional parameters.
+
+For information (for exact details see GSM Recommendations):
+
+The GSM Half Rate Codec Type supports one fixed Codec Mode with 5.60 kBit/s.
+
+DTX may be enabled in uplink and in downlink independently of each other. DTX on or off is defined by the network on a cell basis and can not be negotiated at call setup or during the call. The DTX scheme uses one SID frame to mark the end of a speech burst and to start Comfort Noise Generation. Identical SID frames for comfort noise updates are sent in speech pauses about every 480 ms, aligned with the cell's TDMA frame structure. The defined Tandem Free Operation allows the reception of GSM HR DTX information for the downlink direction in all cases. The TFO respectively TrFO partner shall be prepared to receive DTX information as well.
+
+## 5.3 GSM Enhanced Full Rate Codec Type (GSM EFR)
+
+The Codec Identification (CoID) code is defined to be: EFR\_CoID := 0x0000.0010.
+
+The GSM Enhanced Full Rate Codec Type has no additional parameters.
+
+For information (for exact details see GSM Recommendations):
+
+The GSM Enhanced Full Rate Codec Type supports one fixed Codec Mode with 12.2 kBit/s.
+
+DTX may be enabled in uplink and in downlink independently of each other. DTX on or off is defined by the network on a cell basis and can not be negotiated at call setup or during the call. The DTX scheme uses one SID frame to mark the end of a speech burst and to start Comfort Noise Generation. It is important to note that the Comfort Noise parameters for this start of the comfort noise generation are calculated at transmitter side from the previous eight speech frames. A DTX hangover period needs to be applied therefore at transmitter side before sending the first SID frame. SID frames with incremental information for comfort noise updates are sent in speech pauses about every 480 ms, aligned with the cell's TDMA frame structure. The defined Tandem Free Operation allows the reception of GSM EFR
+
+DTX information for the downlink direction in all cases. The TFO respectively TrFO partner shall be prepared to receive DTX information as well.
+
+## 5.4 Five Adaptive Multi-Rate Codec Types (FR AMR, HR AMR, UMTS AMR, UMTS AMR2, OHR AMR)
+
+The Adaptive Multi-Rate Codec algorithm is applied in GERAN-GMSK, GERAN-8PSK and UTRAN in five different Codec Types.
+
+The Codec Identification (CoID) codes are defined to be:
+
+FR\_AMR\_CoID := 0x0000.0011.  
+ HR\_AMR\_CoID := 0x0000.0100.  
+ UMTS\_AMR\_CoID := 0x0000.0101.  
+ UMTS\_AMR\_2\_CoID := 0x0000.0110.  
+ OHR\_AMR\_CoID := 0x0000.1011.
+
+The AMR Codec Types can be used in conversational speech telephony services in a number of different configurations. The set of preferred configurations is defined in TS 28.062, Table 7.11.3.1.3-2. One of these preferred configurations, Config-NB-Code 1, is recommended for TFO-TrFO harmonisation between GSM and UMTS networks, it is mandatory for an AoIP-supporting BSS, see 3GPP TS 48.008 [23], an AoIP-supporting BICC-based Circuit Switched Core Network and for any SIP-I -based Circuit Switched Core Network.
+
+The Single Codec Information Element for AMR Codec Types may have several additional parameters. These parameters are optional in the Supported Codec List (BICC) and in the Available Codec List (BICC), but these parameters shall specify exactly one AMR Configuration for the Selected Codec (BICC), see [8].
+
+**Active Codec Set, ACS:** eight bits.
+
+Each bit corresponds to one AMR Mode. Setting the bit to "1" means the mode is included, setting the bit to "0" means the mode is not included in the ACS.
+
+Note: Except for HR\_AMR all eight AMR modes may be selected, for the HR\_AMR only the six lower modes.
+
+**Supported Codec Set, SCS:** eight bits.
+
+Each bit corresponds to one AMR Mode, as in the ACS. Setting the bit to "1" means the mode is supported, setting the bit to "0" means the mode is not supported. The SCS shall at least contain all modes of the ACS.
+
+**Maximal number of codec modes in the ACS, MACS:** three bits.
+
+MACS shall be used in the Supported Codec List (BICC) and the Available Codec List (BICC), when it is necessary to restrict the maximum number of modes for the (future) Selected Codec (BICC).
+
+For FR AMR, HR AMR and OHR AMR one up to four, for the UMTS AMR and UMTS AMR2 one up to eight Codec Modes are allowed.
+
+Coding: "001": one, "010": two, ... "111": seven, "000": eight Codec Modes allowed.
+
+**Optimisation Mode for ACS, OM:** one bit.
+
+OM indicates, whether the sending side supports the modification (optimisation) of its offered ACS for the needs of the distant side.
+
+Coding: "0": Optimisation of the ACS not supported, "1": Optimisation of the ACS supported.
+
+If OM is specified as "Optimisation of the ACS not supported", then SCS and MACS have no meaning for this Single Codec Information Element; then the SCS shall at least contain all modes of the offered ACS; MACS shall be equal to or larger than the number of modes in the offered ACS.
+
+**Usage of this Single Codec Information Element in OoBTC.**
+
+In the Single Codec Information Element for the Selected Codec (BICC) the ACS shall be specified exactly.
+
+For FR AMR, HR\_AMR and OHR AMR at least one, but not more than four modes shall be included.
+
+For UMTS AMR and UMTS AMR2 at least one, but not more than four modes should be included.
+
+OM shall be set to "Optimisation of the ACS not supported".
+
+In the Single Codec Information Element for the Supported Codec List (BICC) and the Available Codec List (BICC) one of the following codings shall be used
+
+- either all parameters (ACS, SCS, MACS and OM) are omitted.
+
+Then per default all possible AMR modes shall be treated as included in ACS and SCS, MACS shall be treated as set to its allowed maximum and OM shall be treated as set to "Optimisation of the ACS
+
+supported".
+
+- or only the ACS is specified:  
+Then per default all possible AMR modes shall be treated as included in the SCS, MACS shall be treated as set to its allowed maximum and OM shall be treated as set to "Optimisation of the ACS supported".
+- or ACS and SCS are specified.  
+Then per default MACS shall be treated as set to its allowed maximum and OM shall be treated as set to "Optimisation of the ACS supported".
+- or all parameters (ACS, SCS, MACS and OM) are specified.
+
+### Procedures in OoBTC
+
+The procedures for handling of these Single Codec Information Element in the originating, intermediate and terminating nodes are specified in TS 23.153 [8].
+
+The "Single Codec" information element consists of 5 to 8 octets in case of the AMR Codec Types (table 5.4):
+
+**Table 5.4: Coding of "Single Codec" for the Adaptive Multi-Rate Codec Types**
+
+| Octet | Parameter         | MSB 8                                                                  | 7       | 6       | 5       | 4    | 3    | 2    | 1 LSB |
+|-------|-------------------|------------------------------------------------------------------------|---------|---------|---------|------|------|------|-------|
+| 1 m   | Single Codec      | Single Codec (see ITU-T Q.765.5)                                       |         |         |         |      |      |      |       |
+| 2 m   | Length Indication | 3, 4, 5, 6                                                             |         |         |         |      |      |      |       |
+| 3 m   | Compat. Info      | Compatibility Information                                              |         |         |         |      |      |      |       |
+| 4 m   | OID               | ETSI OID (See ITU-T Q.765.5 [6])                                       |         |         |         |      |      |      |       |
+| 5 m   | CoID              | FR_AMR_CoID, HR_AMR_CoID, UMTS_AMR_CoID, UMTS_AMR_2_CoID, OHR_AMR_CoID |         |         |         |      |      |      |       |
+| 6 o   | ACS               | 12.2                                                                   | 10.2    | 7.95    | 7.40    | 6.70 | 5.90 | 5.15 | 4.75  |
+| 7 o   | SCS               | 12.2                                                                   | 10.2    | 7.95    | 7.40    | 6.70 | 5.90 | 5.15 | 4.75  |
+| 8 o   | OM, MACS          | (spare)                                                                | (spare) | (spare) | (spare) | OM   | MACS |      |       |
+
+with "m" = mandatory and "o" = optional
+
+For information on GSM procedures (for exact details see GSM Recommendations):
+
+The GSM AMR Codec Types comprise eight (Full Rate), respectively six (Half Rate) different Codec Modes: 12,2 ... 4,75 kBit/s.
+
+The active Codec Mode is selected from the Active Codec Set (ACS) by the network (Codec Mode Command) with assistance by the mobile station (Codec Mode Request). This Codec Mode Adaptation, also termed Rate Control, can be performed every 40 ms by going one Codec Mode up or down within the ACS. The Codec Modes in uplink and downlink at one radio leg may be different. In Tandem Free Operation both radio legs (A and B) are considered for the optimal selection of the active Codec Mode in each direction (uplink A and then downlink B, respectively vice versa) by the "Distributed Rate Decision" algorithm. The worst of both radio legs determines the highest allowed Codec Mode, respectively the maximally allowed rate ("Maximum Rate Control"). All rate control commands are transmitted inband: on the radio interface, the BTS-TRAU interface and the TRAU-TRAU interface.
+
+The Active Codec Set is configured at call setup or reconfigured during the call. It consists of one up to maximally four Codec Modes (MACS) at a given time, selected from the Supported Codec Set. The maximal number of Codec Modes and the Supported Codec Set may be constrained by the network to consider resources and radio conditions. The Active Codec Sets in uplink and downlink are identical.
+
+First, at start up of Tandem Free Operation, Active Codec Sets, the Supported Codec Sets, the MACSs and the OMs are taken into account to determine the optimal common Active Codec Set. In a later phase the Codec Lists of both radio legs may be taken into account to find the optimum configuration. For exact details see 3GPP TS 28.062. All configuration data and update protocols are transmitted inband.
+
+The DTX scheme of the Adaptive Multi-Rate Codec Type marks with a specific SID\_FIRST frame the end of a speech burst. SID\_FIRST does not contain Comfort Noise parameters. This SID\_FIRST starts the comfort noise generation
+
+with parameters that are calculated at receiver side (!) from the latest received seven speech frames. A DTX hangover period needs to be applied therefore at transmitter side before sending of this SID\_FIRST.
+
+Absolutely coded SID\_UPDATE frames follow about every eighth frame (160 ms) in speech pauses. SID\_UPDATE frames are sent independently of the cell's TDMA frame structure and are related only to the source signal.
+
+An ONSET frame (typically) precedes in uplink direction the beginning of a new speech burst. DTX on or off is defined by the network on a cell basis. The defined Tandem Free Operation allows the reception of GSM-AMR DTX information for the downlink direction in all cases.
+
+Note: The DTX scheme of the Enhanced Full Rate Codec Type is not compatible with the DTX scheme of the Adaptive Multi-Rate Codec Type in Codec Mode 12.2 kBit/s, although the speech modes of these two Codec Types are bit exact identical.
+
+#### **Informative for terminals of R99 that support only UTRAN access ("UTRAN-only" terminals):**
+
+UTRAN-only terminals of R99 may either use UMTS AMR or UMTS AMR2 as default speech version in UTRAN access.
+
+#### **Normative for terminals that support GSM and UTRAN radio access ("dual-mode" terminals):**
+
+Dual-mode terminals of R99 and onwards shall use the UMTS AMR2 as the default speech version in UTRAN access. They need not to support the UMTS AMR, because the UMTS AMR2 in terminals is a fully compatible replacement.
+
+**Normative for all UMTS terminals of REL-4 and onwards:** The UMTS AMR2 shall be the default speech version in UTRAN access in all terminals, UTRAN-only and dual-mode (GSM and UTRAN) of REL-4 and onwards.
+
+For information on UMTS procedures (for exact details see 3GPP TS 28.062 (TFO) and 3GPP TS 23.153 (TrFO)):
+
+The active Codec Mode is selected from the Active Codec Set (ACS) by the network. This Codec Mode Adaptation, also termed Rate Control, can be performed for the UMTS AMR every 20 ms by going to another Codec Mode within the ACS. For the UMTS AMR 2 this Codec Mode Adaptation can be performed every 20ms for the downlink traffic channel, but only every 40ms for the uplink radio channel. The UE selects at call setup one of the two possible phases for Codec Mode Adaptation (odd or even frames). During the call changes of the Codec Mode in uplink direction are only allowed in this selected phase. Rate Control commands received in downlink direction are considered at the next possible phase.
+
+By this definition the UMTS AMR 2 Codec Type is TFO and TrFO compatible to the FR AMR, HR AMR, OHR AMR and UMTS AMR 2 Codec Types. In any multi-mode configuration the UMTS\_AMR shall be regarded as only compatible to itself, not to any other AMR codec Type, to avoid incompatibilities in TFO-TrFO-TFO interworking scenarios. In single mode configuration, UMTS AMR and UMTS AMR 2 are compatible, when both codec types use the same single rate ACS.
+
+The Codec Modes in uplink and downlink at one radio leg may be different. In Tandem Free Operation or Transcoder Free Operation both radio legs (A and B) are considered for the optimal selection of the active Codec Mode in each direction (uplink A and then downlink B, respectively vice versa) by a "Distributed Rate Decision" algorithm. The worst of both radio legs determine the highest allowed Codec Mode, respectively the maximally allowed rate. All rate control commands are transmitted inband on the Iu and Nb interfaces and out of band on the radio interface.
+
+The Active Codec Set is configured at call setup or reconfigured during the call. It consists of one up to maximally eight Codec Modes (MACS) at a given time, selected from the Supported Codec Set. The maximal number of Codec Modes and the Supported Codec Set may be constrained by the network to consider resources and radio conditions.
+
+The Active Codec Sets in uplink and downlink are typically identical.
+
+At call setup the Originating Side sends the AMR parameter set (included in the Codec List). The Terminating side then selects a suitable ACS from the given information and sends it back. In case the terminating side does not support TrFO a transcoder is allocated in the path at a suitable position, preferably as close as possible to the terminating side. This transcoder may by inband signalling install a Tandem Free Operation after call setup. Then, at start up of Tandem Free Operation, both Active Codec Sets, the Supported Codec Sets, the MACSs and the OMs are taken into account to determine the optimal common Active Codec Set. In a later phase the Codec Lists of both radio legs may be taken into account to find the optimum configuration. All configuration data and update protocols are transmitted inband on the TFO interface, but out of band within the UMTS network. For information on Tandem Free Operation see 3GPP TS 28.062 and on Transcoder Free Operation see 3GPP TS 23.153.
+
+The SCR scheme of the Adaptive Multi-Rate Codec Types mark with a specific SID\_FIRST frame the end of a speech burst. SID\_FIRST does not contain Comfort Noise parameters. This SID\_FIRST starts the comfort noise generation with parameters that are calculated at receiver side (!) from the latest received seven speech frames. A DTX hangover period needs to be applied therefore at transmitter side before sending of this SID\_FIRST.
+
+Absolutely coded SID\_UPDATE frames follow about every eighth frame (160 ms) in speech pauses. SID\_UPDATE
+
+frames are sent independently of the cell's timing structure and are related only to the source signal.
+
+An ONSET frame does (typically) not exist in UMTS networks, but may be received in TFO from the distant partner. It marks the beginning of a speech burst. The uplink SCR operation is always activated for UMTS AMR and UMTS AMR2 codec types. The defined Tandem Free Operation and Transcoder Free Operation allows the reception of AMR SCR information for the downlink direction in all cases.
+
+The SCR scheme of the UMTS AMR2 Codec Type is fully compatible to the SCR scheme of the UMTS AMR in UMTS and the DTX schemes of the FR AMR, HR AMR and OHR AMR Codec Types.
+
+## 5.5 TDMA Enhanced Full Rate Codec Type (TDMA EFR)
+
+The Codec IDentification (CoID) code is defined to be: TDMA\_EFR\_CoID := 0x0000.0111.
+
+The TDMA Enhanced Full Rate Codec Type has no additional parameters.
+
+For information (for exact details see TDMA Recommendations):
+
+The TDMA Enhanced Full Rate Codec Type supports one fixed Codec Mode with 7.4 kBit/s. This codec mode is bit exact identical with AMR codec mode at 7.4 kBit/s.
+
+In a TDMA system DTX may be enabled in uplink, but not in downlink. The DTX scheme uses one SID frame to mark the end of a speech burst and to start or continue Comfort Noise Generation.
+
+The defined Tandem Free Operation allows the reception of TDMA EFR DTX information for the downlink direction in all cases. In TDMA systems the transcoder has to generate comfort noise in speech like frames to be sent downlink. In UMTS the downlink DTX shall always be supported and the transcoder can therefore stay transparently in TFO.
+
+## 5.6 PDC Enhanced Full Rate Codec Type (PDC\_EFR)
+
+The Codec IDentification (CoID) code is defined to be: TDMA\_EFR\_CoID := 0x0000.1000.
+
+The PDC Enhanced Full Rate Codec Type has no additional parameters.
+
+For information (for exact details see PDC Recommendations):
+
+The PDC Enhanced Full Rate Codec Type supports one fixed Codec Mode with 6.7 kBit/s. This codec mode is bit exact identical with AMR codec mode at 6.7 kBit/s.
+
+In a PDC system DTX may be enabled in uplink, but not in downlink. The DTX scheme uses one SID frame to mark the end of a speech burst and to start or continue Comfort Noise Generation.
+
+The Tandem Free Operation allows the reception of PDC EFR DTX information for the downlink direction in all cases. In PDC systems the transcoder has to generate comfort noise in speech like frames to be sent downlink. In UMTS the downlink DTX shall always be supported and the transcoder can therefore stay transparently in TFO.
+
+## 5.7 Four Adaptive Multi-Rate Wideband Codec Types (FR AMR-WB, UMTS AMR-WB, OFR AMR-WB, OHR AMR-WB)
+
+The Adaptive Multi-Rate - WideBand Codec algorithm is applied in GERAN-GMSK, GERAN-8PSK and UTRAN in four different Codec Types.
+
+The Codec IDentification (CoID) codes are defined to be:
+
+FR\_AMR-WB\_CoID := 0x0000.1001.
+
+UMTS\_AMR-WB\_CoID := 0x0000.1010.
+
+OFR\_AMR-WB\_CoID := 0x0000.1100.
+
+OHR\_AMR-WB\_CoID := 0x0000.1101.
+
+The AMR-WB Codec Types can be used in conversational speech telephony services in a number of different configurations. The set of allowed configurations is defined in Table 5.7-1.
+
+**Table 5.7-1: Allowed Configurations for the Adaptive Multi-Rate – Wideband Codec Types**
+
+| Configuration →<br>(Config-WB-Code) | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
+|-------------------------------------|---|---|---|---|---|---|---|---|---|---|----|----|----|----|----|----|
+| ↓ Codec Mode                        |   |   |   |   |   |   |   |   |   |   |    |    |    |    |    |    |
+| 23,85                               |   |   |   |   | 1 | 1 |   |   |   |   |    |    |    |    |    |    |
+| 15,85                               |   |   | 1 | 1 |   |   |   |   |   |   |    |    |    |    |    |    |
+| 12,65                               | 1 | 1 | 1 | 1 | 1 | 1 |   |   |   |   |    |    |    |    |    |    |
+| 8,85                                | 1 | 1 | 1 | 1 | 1 | 1 |   |   |   |   |    |    |    |    |    |    |
+| 6,60                                | 1 | 1 | 1 | 1 | 1 | 1 |   |   |   |   |    |    |    |    |    |    |
+| OM                                  | F | A | F | A | F | A |   |   |   |   |    |    |    |    |    |    |
+| FR_AMR-WB,<br>OHR_AMR-WB            | Y |   |   |   |   |   |   |   |   |   |    |    |    |    |    |    |
+| OFR_AMR-WB,<br>UMTS_AMR-WB          | Y | Y | Y | Y | Y | Y |   |   |   |   |    |    |    |    |    |    |
+
+The "1" in the table indicates that the Codec Mode is included in the Active Codec Set of the Configuration.
+
+The parameters "OM" (Optimisation Mode) define whether the indicated Configuration can be changed to any of the other Allowed ones (OM == A) or if the change is Forbidden (OM == F).
+
+The "Y" in the table indicates, which Configuration is defined for which Codec Type.
+
+Please note that Configurations 0 to 5 are immediately fully compatible with respect to TFO/TrFO due to the specification of Maximum Rate Control.
+
+Table 5.7-2 defines the Coding of the "Single Codec" information element for the AMR-WB Codec Types.
+
+**Table 5.7-2: Coding of "Single Codec" for the Adaptive Multi-Rate - WideBand Codec Types**
+
+| Octet | Parameter         | MSB 8                                                                       | 7       | 6       | 5       | 4              | 3 | 2 | 1 LSB |
+|-------|-------------------|-----------------------------------------------------------------------------|---------|---------|---------|----------------|---|---|-------|
+| 1 m   | Single Codec      | Single Codec (see ITU-T Q.765.5)                                            |         |         |         |                |   |   |       |
+| 2 m   | Length Indication | 4                                                                           |         |         |         |                |   |   |       |
+| 3 m   | Compat. Info      | Compatibility Information                                                   |         |         |         |                |   |   |       |
+| 4 m   | OID               | ETSI OID (See ITU-T Q.765.5 [6])                                            |         |         |         |                |   |   |       |
+| 5 m   | CoID              | FR_AMR-WB_CoID or UMTS_AMR-WB_CoID or<br>OHR_AMR-WB_CoID or OFR_AMR-WB_CoID |         |         |         |                |   |   |       |
+| 6 m   | Config-WB         | (spare)                                                                     | (spare) | (spare) | (spare) | Config-WB-Code |   |   |       |
+
+with "m" = mandatory
+
+An AMR-WB speech telephony service is only possible when the whole path allows a digitally transparent transport of the AMR-WB speech parameters end to end.
+
+Normative for GERAN terminals for FR\_AMR-WB, OHR\_AMR-WB and OFR\_AMR-WB.
+
+If a GERAN terminal offers one of these Codec Types in the capability list, then all AMR-WB Configurations that are defined for the offered Codec Type shall be supported by this terminal.
+
+Normative for GERAN infrastructure for FR\_AMR-WB, OHR\_AMR-WB and OFR\_AMR-WB.
+
+If a GERAN infrastructure supports one of these Codec Types, then at least AMR-WB Configuration 0 shall be supported. The other AMR-WB Configurations are not normative, but optional for OFR\_AMR-WB.
+
+For information on GERAN A/Gb mode procedures for FR\_AMR-WB, OHR\_AMR-WB and OFR\_AMR-WB (for exact details see GSM Recommendations):
+
+The active Codec Mode is selected from the Active Codec Set (ACS) by the network (Codec Mode Command) with assistance by the mobile station (Codec Mode Request). This Codec Mode Adaptation, also termed Rate Control, can be performed every 40 ms by going one Codec Mode up or down within the ACS. The Codec Modes in uplink and downlink at one radio leg may be different. In Tandem Free Operation both radio legs (A and B) are considered for the optimal selection of the active Codec Mode in each direction (uplink A and then downlink B, respectively vice versa) by the "Distributed Rate Decision" algorithm. The worst of both radio legs determines the highest allowed Codec Mode, respectively the maximally allowed rate ("Maximum Rate Control"). All rate control commands are transmitted inband: on the radio interface, the BTS-TRAU interface and the TRAU-TRAU interface.
+
+The Active Codec Set is configured at call setup or reconfigured during the call. It consists of three or four Codec Modes at a given time, selected from the set of allowed Configurations. The selection of the Configuration may be constrained by the network to consider resources and radio conditions. The configurations (Active Codec Sets) in uplink and downlink are identical.
+
+First, at start up of Tandem Free Operation both Active Codec Sets are taken into account to determine the common Active Codec Set. The set of allowed AMR-WB configurations guarantees that WB-TFO is always possible. In a later phase the Codec Lists of both radio legs may be taken into account to find the optimum configuration. For exact details see 3GPP TS 28.062. All configuration data and update protocols are transmitted inband.
+
+The DTX scheme of the Adaptive Multi-Rate Wideband Codec Type marks with a specific SID\_FIRST frame the end of a speech burst. SID\_FIRST does not contain Comfort Noise parameters. This SID\_FIRST starts the comfort noise generation with parameters that are calculated at receiver side from the latest received seven speech frames. A DTX hangover period needs to be applied therefore at transmitter side before sending of this SID\_FIRST.
+
+Absolutely coded SID\_UPDATE frames follow about every eighth frame (160 ms) in speech pauses. SID\_UPDATE frames are sent independently of the cell's TDMA frame structure and are related only to the source signal.
+
+An ONSET frame (typically) precedes in uplink direction the beginning of a new speech burst. DTX on or off is defined by the network on a cell basis. The defined Tandem Free Operation allows the reception of FR\_AMR-WB DTX information for the downlink direction in all cases.
+
+Normative for UTRAN terminals for UMTS\_AMR-WB.
+
+If an UTRAN terminal offers Codec Type UMTS\_AMR-WB in the capability list, then all allowed AMR-WB Configurations shall be supported by this terminal.
+
+Normative for UTRAN infrastructures for UMTS\_AMR-WB.
+
+If an UTRAN infrastructure supports Codec Type UMTS\_AMR-WB, then at least AMR-WB Configuration 0 shall be supported. The other AMR-WB Configurations are not normative, but optional.
+
+For information on UMTS procedures for UMTS\_AMR-WB (for exact details see 3GPP TS 28.062 (TFO) and 3GPP TS 23.153 (TrFO)):
+
+The active Codec Mode is selected from the Active Codec Set (ACS) by the network. This Codec Mode Adaptation, also termed Rate Control, can be performed for the UMTS\_AMR-WB every 20 ms for the downlink traffic channel, but only every 40ms for the uplink traffic channel by going to another Codec Mode within the ACS. The UE selects at call setup one of the two possible phases for Codec Mode Adaptation (odd or even frames). During the call changes of the Codec Mode in uplink direction are only allowed in this selected phase. Rate Control commands received in downlink direction are considered at the next possible phase. By this definition the UMTS\_AMR-WB Codec Type is TFO and TrFO compatible to the FR\_AMR-WB, the OHR\_AMR-WB and OFR\_AMR-WB and the UMTS\_AMR-WB Codec Types.
+
+The Codec Modes in uplink and downlink at one radio leg may be different. In Tandem Free Operation or Transcoder Free Operation both radio legs (A and B) are considered for the optimal selection of the active Codec Mode in each direction (uplink A and then downlink B, respectively vice versa) by a "Distributed Rate Decision" algorithm. The worst of both radio legs determine the highest allowed Codec Mode, respectively the maximally allowed rate. All rate control commands are transmitted inband on the Iu and Nb interfaces and out of band on the radio interface.
+
+The Active Codec Set is selected at call setup or reselected during the call. It consists of three or four Codec Modes at a given time, selected from the allowed configurations. The selection of the configuration may be constrained by the network to consider resources and radio conditions.
+
+The Active Codec Sets in uplink and downlink are typically identical.
+
+At call setup with TrFO negotiation the Originating Side sends its preferred AMR-WB configuration and indicates whether it allows a change of this preferred configuration or not (included in the Codec List). The Terminating side then selects a suitable configuration from the given information and sends it back. In case the terminating side does not support TrFO a transcoder is allocated in the path at a suitable position, preferably as close as possible to the terminating side. This transcoder may by inband signalling install a Tandem Free Operation after call setup. The set of allowed AMR-WB configurations guarantees that WB-TFO is always possible. In a later phase the Codec Lists of both radio legs may be taken into account to find the optimum configuration. All configuration data and update protocols are transmitted inband on the TFO interface, but out of band within the UMTS network. For information on Tandem Free Operation see 3GPP TS 28.062 and on Transcoder Free Operation see 3GPP TS 23.153.
+
+The SCR scheme of the Adaptive Multi-Rate WideBand Codec Types mark with a specific SID\_FIRST frame the end of a speech burst. SID\_FIRST does not contain Comfort Noise parameters. This SID\_FIRST starts the comfort noise generation with parameters that are calculated at receiver side from the latest received seven speech frames. A DTX hangover period needs to be applied therefore at transmitter side before sending of this SID\_FIRST.
+
+Absolutely coded SID\_UPDATE frames follow about every eighth frame (160 ms) in speech pauses. SID\_UPDATE frames are sent independently of the cell's timing structure and are related only to the source signal.
+
+An ONSET frame does (typically) not exist in UMTS networks, but may be received in TFO from the distant partner. It marks the beginning of a speech burst. "SCR on" is always defined by the network. The defined Tandem Free Operation and Transcoder Free Operation allows the reception of AMR-WB SCR information for the downlink direction in all cases.
+
+The SCR scheme of the UMTS AMR-WB Codec Type is fully compatible to the DTX schemes of FR AMR-WB, OHR AMR-WB and OFR AMR-WB.
+
+The exact details of these Codec Types and their related procedures (DTX, Rate Control, etc) are described in the respective standard documentation.
+
+## 5.8 MuMe Dummy Codec (3G.324M)
+
+The Codec Identification (CoID) code is defined to be: MuMe\_CoID:= 0x1111.1111.
+
+The MuMe codec has one additional mandatory parameter:
+
+**B/W Multiplier, BWM:** eight bits.
+
+This defines the required bandwidth for the bearer; the value is a factor of 64K b/s when not equal to 0. When equal to zero then a 32k b/s.
+
+The "Single Codec" information element consists of 6 octets in case of the MuMe Dummy Codec (table 5.8):
+
+**Table 5.8: Coding of "Single Codec" for the MuMe Dummy Codec Type**
+
+| Octet | Parameter         | MSB 8                            | 7 | 6 | 5 | 4 | 3 | 2 | 1 LSB |
+|-------|-------------------|----------------------------------|---|---|---|---|---|---|-------|
+| 1 m   | Single Codec      | Single Codec (see ITU-T Q.765.5) |   |   |   |   |   |   |       |
+| 2 m   | Length Indication | 4                                |   |   |   |   |   |   |       |
+| 3 m   | Compat. Info      | Compatibility Information        |   |   |   |   |   |   |       |
+| 4 m   | OID               | ETSI OID (See ITU-T Q.765.5 [6]) |   |   |   |   |   |   |       |
+| 5 m   | CoID              | MuMe_CoID                        |   |   |   |   |   |   |       |
+| 6 m   | BWM               | BandWidth Multiplier – see note1 |   |   |   |   |   |   |       |
+
+with "m" = mandatory
+
+### Note 1:
+
+BWM == 0 => 32Kb/s
+
+BWM == 1-255 => factor n (multiplier of 64Kb/s)
+
+The procedures for use of this codec are defined in TS 23.172 [13].
+
+This MuMe Dummy codec type is only for use in Core Network OoBTC procedures it shall NOT be used across the radio interface.
+
+The MuMe Dummy codec indicates that an Unrestricted multimedia path (UDI) is required, subsequent codec negotiation may occur within this path using MuMe protocols, e.g. H.324M. There are no encoding properties or codec specifications associated to this codec type; it is purely an indication for a MuMe pipe.
+
+## 5.9 MuMe2 Dummy Codec (3G.324M2)
+
+The Codec Identification (CoID) code is defined to be: MuMe2\_CoID:= 0x1111.1110. Otherwise, the Coding is identical to the MuME Dummy Codec described in Clause 5.8.
+
+The Procedural description provided for MuME Dummy Codec in Clause 5.8 is also applicable for the MuMe2 Dummy Codec. The MuMe2 Dummy Codec is used in core network procedures to indicate that a service change to multimedia was indicated by the network. The procedures for use of this codec are defined in TS 23.172 [13].
+
+## 5.10 Codec Extension
+
+The Codec Identification (CoID) code is defined to be: Codec\_Extension\_CoID:= 0x0000.1111 in the "long form" and 0x1111 = 0xFh in the "short form".
+
+In TFO, see 3GPP TS 28.062 [7] and in AoIP, see 3GPP TS 48.008 [23] the Codec Lists use in general the short form (4 bits) for the Codec Identifier. In order to allow future extensions of this Codec Lists beyond 16 Codec Types the "Codec\_Extension" is defined. These Codec Lists may contain a certain CoID in the range [0x0h, 0xEh] or they may contain the so called "Codec\_Extension" (0xFh), in which case the real Codec Type follows in the next octet in its long form (8 bits).
+
+## 5.11 CSData Dummy Codec (AoIP)
+
+The Codec Identification (CoID) code is defined to be: CSData\_CoID:= 0x1111.1101.
+
+The CSData Dummy Codec has one mandatory parameter of one octet length, for details see TS 48.008 [23].
+
+# --- 6 Codec List for the Call Control Protocol
+
+For call control on the air interface the Codec Lists need to be specified for each radio access technology separately, because it can not be expected that an UE supports the same Codec Types in different radio access technologies.
+
+*3GPP TS 24.008 [9] defines the call control signalling and how to use the "Supported Codec List Information Element" (IE).* It contains Codec Lists (in form of Codec Bitmaps) for each supported radio access technology (identified by a SysID).
+
+The coding of this IE is given here. It is also used for TFO in 3GPP TS 28.062 [7].
+
+## 6.1 System Identifiers for GSM and UMTS
+
+The system identifiers for the radio access technologies supported by this specification are:
+
+SysID for GSM: 0x0000.0000 (bit 8 .. bit 1)
+
+SysID for UMTS: 0x0000.0100 (bit 8 .. bit 1)
+
+These values are selected in accordance with [7] (3GPP TS 28.062).
+
+## 6.2 Codec Bitmap
+
+The Codec Types are coded in the first and second octet of the Codec List Bitmap as follows:
+
+| 8        | 7          | 6        | 5      | 4      | 3       | 2      | bit 1  |         |
+|----------|------------|----------|--------|--------|---------|--------|--------|---------|
+| TDMA EFR | UMTS AMR 2 | UMTS AMR | HR AMR | FR AMR | GSM EFR | GSM HR | GSM FR | Octet 1 |
+
+| bit 16     | 15         | 14         | 13         | 12      | 11          | 10        | bit 9   |         |
+|------------|------------|------------|------------|---------|-------------|-----------|---------|---------|
+| (reserved) | (reserved) | OHR AMR-WB | OFR AMR-WB | OHR AMR | UMTS AMR-WB | FR AMR-WB | PDC EFR | Octet 2 |
+
+A Codec Type is supported, if the corresponding bit is set to "1". All reserved bits shall be set to "0".
+
+## 6.3 Selected Codec Type
+
+The Selected Codec Type in a BICC-based OoBTC negotiation is coded as shown in Table 6.3-1. The same coding is used also in 3GPP TS 28.062 [7].
+
+**Table 6.3-1: Coding of the selected Codec\_Type (long form)**
+
+| Bit 8...Bit 1<br>CoID | Codec_Type                                                                                    | Name                                  |
+|-----------------------|-----------------------------------------------------------------------------------------------|---------------------------------------|
+| 0000.0000             | GSM Full Rate (13.0 kBit/s)                                                                   | GSM FR                                |
+| 0000.0001             | GSM Half Rate (5.6 kBit/s)                                                                    | GSM HR                                |
+| 0000.0010             | GSM Enhanced Full Rate (12.2 kBit/s)                                                          | GSM EFR                               |
+| 0000.0011             | Full Rate Adaptive Multi-Rate                                                                 | FR AMR                                |
+| 0000.0100             | Half Rate Adaptive Multi-Rate                                                                 | HR AMR                                |
+| 0000.0101             | UMTS Adaptive Multi-Rate                                                                      | UMTS AMR                              |
+| 0000.0110             | UMTS Adaptive Multi-Rate 2                                                                    | UMTS AMR 2                            |
+| 0000.0111             | TDMA Enhanced Full Rate (7.4 kBit/s)                                                          | TDMA EFR                              |
+| 0000.1000             | PDC Enhanced Full Rate (6.7 kBit/s)                                                           | PDC EFR                               |
+| 0000.1001             | Full Rate Adaptive Multi-Rate WideBand                                                        | FR AMR-WB                             |
+| 0000.1010             | UMTS Adaptive Multi-Rate WideBand                                                             | UMTS AMR-WB                           |
+| 0000.1011             | 8PSK Half Rate Adaptive Multi-Rate                                                            | OHR AMR                               |
+| 0000.1100             | 8PSK Full Rate Adaptive Multi-Rate WideBand                                                   | OFR AMR-WB                            |
+| 0000.1101             | 8PSK Half Rate Adaptive Multi-Rate WideBand                                                   | OHR AMR-WB                            |
+| 0000.1110             | spare, for future use                                                                         |                                       |
+| 0000.1111             | Reserved for Codec_Extension                                                                  | for AoIP and<br>TFO,<br>not for OoBTC |
+| Up to<br>1111.1100    | spare for future use                                                                          |                                       |
+| 1111.1101             | Reserved for CSData dummy Codec Type                                                          | for AoIP,<br>not for OoBTC            |
+| 1111.1110             | Reserved for MuMe2 dummy Codec Type<br><br>NOTE: codec not to be used across radio interface. | MuMe2                                 |
+| 1111.1111             | Reserved for MuMe dummy Codec Type<br><br>NOTE: codec not to be used across radio interface.  | MuMe                                  |
+
+# 7 3GPP Codecs for OoBTC in a SIP-I -based Circuit Switched Core Network
+
+## 7.1 Overview
+
+In a SIP-I -based Circuit Switched Core Network, as specified in 3GPP TS 23.231 [14], SDP (IETF RFC 4566 [19]) and SDP offer-answer procedures (IETF RFC 3264 [16]) are applied for Out of Band Transcoder Control as specified in 3GPP TS 23.153 [8].
+
+Table 7.1.1 lists the supported 3GPP Speech Codecs for a SIP-I -based Circuit Switched Core Network.
+
+**Table 7.1.1 Supported 3GPP Codecs in a SIP-I -based Circuit Switched Core Network**
+
+| Payload Type Name     | References         | Remarks                                                        | Support                                                                                                     |
+|-----------------------|--------------------|----------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------|
+| audio/AMR             | IETF RFC 4867 [21] | Applicable for FR_AMR, HR_AMR, OHR_AMR, UMTS_AMR and UMTS_AMR2 | Mandatory. Not all AMR configurations are mandatory. Some configurations are preferred, see below.          |
+| audio/AMR-WB          | IETF RFC 4867 [21] | Applicable for FR_AMR-WB, OHR_AMR-WB, OFR_AMR-WB, UMTS_AMR-WB  | Optional. AMR-WB is Mandatory if WB speech is supported. Not all WB configurations are mandatory, see below |
+| audio/GSM-EFR         | IETF RFC 3551 [17] | Useful if an A-interface over IP is attached or TFO is used.   | Optional                                                                                                    |
+| audio/GSM-FR          | IETF RFC 3551 [17] | Useful if an A-interface over IP is attached or TFO is used.   | Optional                                                                                                    |
+| audio/GSM-HR          | IETF RFC 5993 [22] | Useful if an A-interface over IP is attached, or TFO is used   | Optional                                                                                                    |
+| audio/PCMA            | IETF RFC 3551 [17] | ITU-TG.711, Alaw                                               | Mandatory                                                                                                   |
+| audio/PCMU            | IETF RFC 3551 [17] | ITU-T G.711, ulaw                                              | Mandatory                                                                                                   |
+| audio/telephone-event | IETF RFC 4733 [20] | Used to transport DTMF                                         | Mandatory                                                                                                   |
+
+## 7.2 AMR
+
+AMR (FR\_AMR, HR\_AMR, OHR\_AMR, UMTS\_AMR and UMTS\_AMR2) shall be encoded in SDP according to the MIME registration in IETF RFC 4867 [21]. The SDP offer-answer related rules in this RFC apply.
+
+The bandwidth efficient mode of RFC 4867 shall be used. To offer the bandwidth-efficient mode, the octet-align parameter should be omitted in SDP.
+
+The AMR Codec Types can be used in conversational speech telephony services in a number of different configurations. Configuration related procedures in Clause 5.4 shall be applied also within a SIP-I based CS CN. The set of preferred configurations is defined in TS 28.062 [7], Table 7.11.3.1.3-2. The configuration is encoded in SDP in the mode-set parameter.
+
+One of these preferred configurations, **Config-NB-Code 1**, is recommended for TFO-TrFO harmonisation between GSM and UMTS networks. This configuration shall be supported in a SIP-I based circuit switched core network to ensure interoperability with an AoIP-based BSS.
+
+However, it is recommended that nodes in the core network (MSC-S and MGW) support all AMR modes for maximum interoperability.
+
+To offer the AMR codec in different configurations, the AMR codec may be included several times with different configurations in an SDP m-line.
+
+A core network node performing a transcoding free interworking towards an A-Interface (TFO towards any A-Interface or TrFO towards an IP-based A-Interface) shall provide the parameters "mode-change-period=2" and "mode-change-neighbour=1" in offer or answer. The parameter "mode-change-capability=2" shall be included by all other CS CN
+
+nodes in the offer to ensure interoperability unless they received an offer from other nodes without this parameter and do not transcode.
+
+## 7.3 AMR-WB
+
+AMR-WB (FR\_AMR-WB, OHR\_AMR-WB, OFR\_AMR-WB, UMTS\_AMR-WB) shall be encoded in SDP according to the MIME registration in IETF RFC 4867 [21]. The SDP offer-answer related rules in this RFC apply.
+
+The bandwidth efficient mode of RFC 4867 shall be used. To offer the bandwidth-efficient mode, the octet-align parameter should be omitted in SDP.
+
+The AMR-WB Codec Types can be used in conversational speech telephony services in a number of different configurations. Configuration related procedures in Clause 5.7 shall be applied also within a SIP-I based CS CN. The set of configurations is defined in Table 5.7-1. The configuration is encoded in SDP in the mode-set parameter.
+
+One of these configurations, **Config-WB-Code 0**, shall be supported by all nodes supporting the AMR-WB codec in a circuit switched core network to ensure interoperability.
+
+However, it is recommended that a node in the core network supports all AMR-WB modes for maximum interoperability.
+
+To offer the AMR-WB codec in different configurations, the AMR-WB codec may be included several times with different configurations in an SDP m-line.
+
+A core network node performing a transcoding free interworking towards an A-Interface (TFO towards any A-Interface or TrFO towards an IP-based A-Interface) shall provide the parameters "mode-change-period=2" and "mode-change-neighbour=1" in offer or answer. The parameter "mode-change-capability=2" shall be included by all other CS CN nodes in the offer to ensure interoperability unless they received an offer from other nodes without this parameter and do not transcode
+
+## 7.4 GSM\_EFR
+
+GSM\_EFR shall be encoded in SDP using either the fixed payload type assigned in IETF RFC 3551 [17] or a dynamic payload type described according to the MIME registration in IETF RFC 3551 [17]
+
+The GSM\_EFR standard comprises a DTX scheme with VAD, SID frames and Comfort Noise generation that is automatically included in this SDP negotiation. For User Plane details see 3GPP TS 26.102 [24]. No other DTX scheme shall be negotiated in SDP for GSM\_EFR.].
+
+## 7.5 GSM\_FR
+
+GSM\_FR shall be encoded in SDP using either the fixed payload type assigned in IETF RFC 3551 [17] or a dynamic payload type described according to the MIME registration in IETF RFC 3551 [17]
+
+The GSM\_FR standard comprises a DTX scheme with VAD, SID frames and Comfort Noise generation that is automatically included in this SDP negotiation. For User Plane details see 3GPP TS 26.102 [24]. No other DTX scheme shall be negotiated in SDP for GSM\_FR.].
+
+## 7.6 GSM\_HR
+
+GSM\_HR shall be encoded in SDP according to the MIME registration in [22]. GSM\_HR shall be encoded in SDP using a dynamic payload type described according to the MIME registration in [22]. The options specified in [22] are not applied inside the Circuit Switched Core Network and not across the A-Interface, but set to pre-defined values as follows: a single frame (Speech or SID) shall be included in one RTP packet, FEC and Interleaving (redundancy) shall not be used, Encryption shall not be used, a packetization time of 20ms shall be applied.
+
+The GSM\_HR standard comprises a DTX scheme with VAD, SID frames and Comfort Noise generation that is automatically included in this SDP negotiation. For User Plane details see [22] and 3GPP TS 26.102 [24]. No other DTX scheme shall be negotiated in SDP for GSM\_HR.
+
+## 7.7 PCM
+
+PCMU and PCMA shall be encoded in SDP using either the fixed payload type assigned in IETF RFC 3551 [ee] or a dynamic payload type described according to the MIME registration in IETF RFC 3551 [ee].
+
+## 7.8 Telephone-Event
+
+Telephony-Event shall be encoded in SDP according to the MIME registration in IETF RFC 4733 [20].
+
+The MIME type audio/telephone-event in IETF RFC 4733 [20] with default events and default rate shall be used to encode DTMF. Therefore, the rate and event parameters do not need to be supplied.
+
+# Annex A (informative): Example Supported Codec List for UMTS
+
+This Annex gives some informative examples how the Codec List for UMTS may look like for the OoBTC protocol in a BICC-based Circuit Switched Core Network.
+
+In this example the UMTS Circuit Switched Core Network does support: UMTS AMR2(set1), (GSM) FR AMR(set1) and (GSM) HR AMR(set1) and GSM EFR. It supports PCM, i.e. ITU-T G.711, here in the Alaw version, with transcoding. It may support also UMTS\_AMR(set7), GSM FR, and GSM\_HR (not included in the list).
+
+One "Supported Codec List" (with arbitrarily selected Codec Type preference) could look at Originating side like:
+
+| Octet | Parameter              | MSB 8                                | 7       | 6       | 5       | 4       | 3       | 2       | 1 LSB   |  |  |  |
+|-------|------------------------|--------------------------------------|---------|---------|---------|---------|---------|---------|---------|--|--|--|
+| 1     | Codec List             | Codec List (see ITU-T Q.765.5)       |         |         |         |         |         |         |         |  |  |  |
+| 2     | Length Indication (LI) | 30                                   |         |         |         |         |         |         |         |  |  |  |
+| 3     | Compat. Info           | Compatibility Information            |         |         |         |         |         |         |         |  |  |  |
+| 4     | Single Codec           | Single Codec (see ITU-T Q.765.5)     |         |         |         |         |         |         |         |  |  |  |
+| 5     | LI                     | 6                                    |         |         |         |         |         |         |         |  |  |  |
+| 6     | Compat. Info           | Compatibility Information            |         |         |         |         |         |         |         |  |  |  |
+| 7     | OID                    | ETSI OID (See ITU-T Q.765.5 [6])     |         |         |         |         |         |         |         |  |  |  |
+| 8     | CoID                   | UMTS_AMR2 CoID                       |         |         |         |         |         |         |         |  |  |  |
+| 9     | ACS (set1)             | 12.2(1)                              | 10.2(0) | 7.95(0) | 7.40(1) | 6.70(0) | 5.90(1) | 5.15(0) | 4.75(1) |  |  |  |
+| 10    | SCS (set1)             | 12.2(1)                              | 10.2(0) | 7.95(0) | 7.40(1) | 6.70(0) | 5.90(1) | 5.15(0) | 4.75(1) |  |  |  |
+| 11    | MACS                   | (spare)                              | (spare) | (spare) | (spare) | OM(0)   | MACS(4) |         |         |  |  |  |
+| 12    | Single Codec           | Single Codec (see ITU-T Q.765.5)     |         |         |         |         |         |         |         |  |  |  |
+| 13    | LI                     | 3                                    |         |         |         |         |         |         |         |  |  |  |
+| 14    | Compat. Info           | Compatibility Information            |         |         |         |         |         |         |         |  |  |  |
+| 15    | OID                    | ITU-T OID (See ITU-T Q.765.5 [6])    |         |         |         |         |         |         |         |  |  |  |
+| 16    | CoID                   | Codec Identifier for PCM Alaw 64kbps |         |         |         |         |         |         |         |  |  |  |
+| 17    | Single Codec           | Single Codec (see ITU-T Q.765.5)     |         |         |         |         |         |         |         |  |  |  |
+| 18    | LI                     | 6                                    |         |         |         |         |         |         |         |  |  |  |
+| 19    | Compat. Info           | Compatibility Information            |         |         |         |         |         |         |         |  |  |  |
+| 20    | OID                    | ETSI OID (See ITU-T Q.765.5 [6])     |         |         |         |         |         |         |         |  |  |  |
+| 21    | CoID                   | FR_AMR CoID                          |         |         |         |         |         |         |         |  |  |  |
+| 22    | ACS (set1)             | 12.2(1)                              | 10.2(0) | 7.95(0) | 7.40(1) | 6.70(0) | 5.90(1) | 5.15(0) | 4.75(1) |  |  |  |
+| 23    | SCS (set1)             | 12.2(1)                              | 10.2(0) | 7.95(0) | 7.40(1) | 6.70(0) | 5.90(1) | 5.15(0) | 4.75(1) |  |  |  |
+| 24    | MACS                   | (spare)                              | (spare) | (spare) | (spare) | OM(0)   | MACS(4) |         |         |  |  |  |
+| 25    | Single Codec           | Single Codec (see ITU-T Q.765.5)     |         |         |         |         |         |         |         |  |  |  |
+| 26    | LI                     | 6                                    |         |         |         |         |         |         |         |  |  |  |
+| 27    | Compat. Info           | Compatibility Information            |         |         |         |         |         |         |         |  |  |  |
+| 28    | OID                    | ETSI OID (See ITU-T Q.765.5 [6])     |         |         |         |         |         |         |         |  |  |  |
+| 29    | CoID                   | HR_AMR CoID                          |         |         |         |         |         |         |         |  |  |  |
+| 30    | ACS (set1)             | (spare)                              | (spare) | 7.95(0) | 7.40(1) | 6.70(0) | 5.90(1) | 5.15(0) | 4.75(1) |  |  |  |
+| 31    | SCS (set1)             | (spare)                              | (spare) | 7.95(0) | 7.40(1) | 6.70(0) | 5.90(1) | 5.15(0) | 4.75(1) |  |  |  |
+| 32    | MACS                   | (spare)                              | (spare) | (spare) | (spare) | OM(0)   | MACS(3) |         |         |  |  |  |
+| 33    | Single Codec           | Single Codec (see ITU-T Q.765.5)     |         |         |         |         |         |         |         |  |  |  |
+| 34    | LI                     | 3                                    |         |         |         |         |         |         |         |  |  |  |
+| 35    | Compat. Info           | Compatibility Information            |         |         |         |         |         |         |         |  |  |  |
+| 36    | OID                    | ETSI OID (See ITU-T Q.765.5 [6])     |         |         |         |         |         |         |         |  |  |  |
+| 37    | CoID                   | EFR_CoID                             |         |         |         |         |         |         |         |  |  |  |
+
+The Terminating Side selects one of the Codec Types and returns it, together with the selected codec attributes.
+
+The AMR Codec Types may have very similar, if not identical codec attributes at Originating side. The UMTS as Originating side can, however, already decide, which configuration would be preferred in case the Terminating side is
+
+UMTS or GSM. A GSM Circuit Switched Core Network as Originating side can not offer UMTS AMR (unless it provides local transcoding) and the Codec attributes for FR AMR and HR AMR may be quite different.
+
+# Annex B (informative): Change history
+
+| Change history |         |           |      |     |                                                                        |        |        |
+|----------------|---------|-----------|------|-----|------------------------------------------------------------------------|--------|--------|
+| Date           | TSG SA# | TSG Doc.  | CR   | Rev | Subject/Comment                                                        | Old    | New    |
+| 12-2000        | 10      | SP-000576 | 004  |     | Introduction of Codec Type Bit-Map for Codec Negotiation               | 3.0.0  | 4.0.0  |
+| 12-2000        | 10      | SP-000576 | 005  |     | Introduction of Selected Codec Type for Codec Negotiation              | 3.0.0  | 4.0.0  |
+| 12-2000        | 10      | SP-000576 | 006  |     | Clarification for the use of the Codec List Information Element        | 3.0.0  | 4.0.0  |
+| 03-2001        | 11      | SP-010104 | 007  |     | Simplification of the Optimisation Mode Field                          | 4.0.0  | 4.1.0  |
+| 03-2001        | 11      | SP-010199 | 008  | 3   | Introduction of UMTS_AMR_2                                             | 4.0.0  | 4.1.0  |
+| 03-2001        | 11      | SP-010199 | 009  |     | Introduction of AMR Wideband                                           | 4.1.0  | 5.0.0  |
+| 03-2002        | 15      | SP-020078 | 015  |     | Introduction of GERAN-8PSK Codec Types into Codec List                 | 5.0.0  | 5.1.0  |
+| 03-2002        | 15      | SP-020078 | 017  |     | Introduction of codepoint for Dummy Codec for CS Multi Media (3G 324M) | 5.0.0  | 5.1.0  |
+| 06-2002        | 16      | SP-020223 | 014  | 2   | UMTS_AMR2 is default Codec Type in all terminals of Rel-4 and onwards  | 5.1.0  | 5.2.0  |
+| 09-2002        | 17      | SP-020437 | 020  | 1   | TrFO-Signalling for allowed AMR-WB Configurations                      | 5.2.0  | 5.3.0  |
+| 12-2002        | 18      | SP-020690 | 021  | 1   | Correction of uplink SCR activation for UMTS AMR                       | 5.3.0  | 5.4.0  |
+| 12-2002        | 18      | SP-020690 | 022  |     | Correction to the Codec ID Table                                       | 5.3.0  | 5.4.0  |
+| 09-2004        | 25      | SP-040646 | 028  | 1   | Correction of Size and Reference of MuMe Codec                         | 5.4.0  | 5.5.0  |
+| 09-2004        | 25      | SP-040646 | 023  | 2   | Harmonisation of AMR Configurations                                    | 5.5.0  | 6.0.0  |
+| 09-2004        | 25      | SP-040646 | 025  | 1   | Error Fixes                                                            | 5.5.0  | 6.0.0  |
+| 09-2004        | 25      | SP-040646 | 029  | 1   | Correction of Size and Reference of MuMe Codec                         | 5.5.0  | 6.0.0  |
+| 12-2004        | 26      | SP-040845 | 032  |     | TFO/TrFO Compatibility of UMTS_AMR and UMTS_AMR2                       | 6.0.0  | 6.1.0  |
+| 12-2004        | 26      | SP-040847 | 036  | 1   | Clarifications for AMR                                                 | 6.0.0  | 6.1.0  |
+| 03-2006        | 31      | SP-060008 | 0037 |     | 3G-324.M2 Codec for Indication of Network-Initiated Service Change     | 6.1.0  | 6.2.0  |
+| 06-2007        | 36      |           |      |     | Version for Release 7                                                  | 6.2.0  | 7.0.0  |
+| 09-2008        | 41      | SP-080475 | 0038 | 2   | Addition of CS over IP User Plane                                      | 7.0.0  | 8.0.0  |
+| 12-2008        | 42      | SP-080678 | 0039 | 2   | Corrections to CS over IP User Plane                                   | 8.0.0  | 8.1.0  |
+| 12-2009        | 46      |           |      |     | Version for Release 9                                                  | 8.1.0  | 9.0.0  |
+| 03-2011        | 51      | SP-110034 | 0041 |     | Correction of reference for GSM-HR payload format                      | 9.0.0  | 9.1.0  |
+| 03-2011        | 51      |           |      |     | Version for Release 10                                                 | 9.1.0  | 10.0.0 |
+| 09-2012        | 57      |           |      |     | Version for Release 11                                                 | 10.0.0 | 11.0.0 |

marked/Rel-11/26_series/26104/raw.md

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+
+
+
+
+
+
+# --- Contents
+
+|                                                                    |    |
+|--------------------------------------------------------------------|----|
+| Foreword .....                                                     | 4  |
+| 1 Scope.....                                                       | 5  |
+| 2 Normative references.....                                        | 5  |
+| 3 Definitions and abbreviations .....                              | 6  |
+| 3.1 Definitions.....                                               | 6  |
+| 3.2 Abbreviations .....                                            | 6  |
+| 4 C code structure .....                                           | 6  |
+| 4.1 Contents of the C source code.....                             | 6  |
+| 4.2 Program execution .....                                        | 7  |
+| 4.3 Coding style .....                                             | 7  |
+| 4.4 Code hierarchy .....                                           | 7  |
+| 4.5 Variables, constants and tables .....                          | 10 |
+| 4.5.1 Description of constants used in the C code.....             | 11 |
+| 4.5.2 Description of fixed tables used in the C code.....          | 11 |
+| 4.5.3 Static variables used in the C code.....                     | 13 |
+| 5 Homing procedure .....                                           | 16 |
+| 6 File formats .....                                               | 22 |
+| 6.1 Speech file (encoder input / decoder output) .....             | 22 |
+| 6.2 Mode control file (encoder input) .....                        | 22 |
+| 6.3 Parameter bitstream file (encoder output / decoder input)..... | 22 |
+| Annex A (informative): Change History.....                         | 23 |
+
+# --- Foreword
+
+This Technical Specification (TS) has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- 1 Scope
+
+This Technical Standard (TS) contains an electronic copy of the ANSI-C code for a floating-point implementation of the Adaptive Multi-Rate codec. This floating-point codec specification is mainly targeted to be used in multimedia applications such as the 3G-324M terminal specified in 3GPP TS 26.110, or in packet-based (e.g., H.323) applications. The bit-exact fixed-point ANSI-C code in 3GPP TS 26.073 remains the preferred implementation for all applications, but the floating-point codec may be used instead of the fixed-point codec when the implementation platform is better suited for a floating-point implementation. It has been verified that the fixed-point and floating-point codecs interoperate with each other without any artefacts.
+
+The floating-point ANSI-C code in this specification is the only standard conforming non-bit-exact implementation of the Adaptive Multi Rate speech transcoder (3GPP TS 26.090 [2]), Voice Activity Detection (3GPP TS 26.094 [6]), comfort noise generation (3GPP TS 26.092 [4]), and source controlled rate operation (3GPP TS 26.093 [5]). The floating-point code also contains example solutions for substituting and muting of lost frames (3GPP TS 26.091 [3]).
+
+**The fixed-point specification in 26.073 shall remain the only allowed implementation for the 3G mandatory speech service and the use of the floating-point codec is strictly limited to other services.**
+
+The floating-point encoder in this specification is a non-bit-exact implementation of the fixed-point encoder producing quality indistinguishable from that of the fixed-point encoder. The decoder in this specification is functionally a bit-exact implementation of the fixed-point decoder, but the code has been optimized for speed and the standard fixed-point libraries are not used as such.
+
+# --- 2 Normative references
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+- For a specific reference, subsequent revisions do not apply.
+- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+
+- [1] 3GPP TS 26.074: "AMR Speech Codec; Test sequences".
+- [2] 3GPP TS 26.090: "AMR Speech Codec; Speech transcoding".
+- [3] 3GPP TS 26.091: "AMR Speech Codec; Substitution and muting of lost frames".
+- [4] 3GPP TS 26.092: "AMR Speech Codec; Comfort noise aspects".
+- [5] 3GPP TS 26.093: "AMR Speech Codec; Source controlled rate operation".
+- [6] 3GPP TS 26.094: "AMR Speech Codec; Voice Activity Detection".
+- [7] 3GPP TS 26.073: "ANSI-C code for the Adaptive Multi Rate speech codec".
+- [8] 3GPP TS 26.101: "AMR Speech Codec Frame Structure".
+- [9] RFC 3267: "A Real-Time Transport Protocol (RTP) Payload Format and File Storage Format for Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs", June 2002.
+
+# --- 3 Definitions and abbreviations
+
+## 3.1 Definitions
+
+Definition of terms used in the present document, can be found in 3GPP TS 26.090 [2], 3GPP TS 26.091 [3], 3GPP TS 26.092 [4], 3GPP TS 26.093 [5], and 3GPP TS 26.094 [6].
+
+## 3.2 Abbreviations
+
+For the purpose of the present document, the following abbreviations apply:
+
+|      |                                         |
+|------|-----------------------------------------|
+| ANSI | American National Standards Institute   |
+| ETS  | European Telecommunication Standard     |
+| GSM  | Global System for Mobile communications |
+| I/O  | Input/Output                            |
+| RAM  | Random Access Memory                    |
+| ROM  | Read Only Memory                        |
+
+# --- 4 C code structure
+
+This clause gives an overview of the structure of the floating-point C code and provides an overview of the contents and organization of the C code attached to this document. The basic structure of the floating-point C code follows that of the bit-exact fixed-point code [7].
+
+The C code has been verified on the following systems:
+
+- IBM PC/AT compatible computers with Windows NT40 and Microsoft Visual C++ v.5.0 compiler;
+- HP workstations and GNU gcc compiler;
+- IBM PC/AT compatible computers with Linux operating system and GNU gcc compiler;
+
+ANSI-C 9899 was selected as the programming language because portability was desirable
+
+## 4.1 Contents of the C source code
+
+The C code distribution has all files in the root level.
+
+The files with suffix "c" contain the source code and the files with suffix "h" are the header files. The ROM data is contained in "rom" files with suffix "h".
+
+The C code does not contain any speech coder installation verification data files. Verification for the bit-exact decoder is defined in specification 3GPP TS 26.073 [7].
+
+Makefiles are provided for the platforms in which the C code has been verified (listed above). Once the software is installed, this directory will have a compiled version of encoder and decoder and all the object files.
+
+## 4.2 Program execution
+
+The Adaptive Multi-Rate codec is implemented in two programs:
+
+- (*encoder*) speech encoder;
+- (*decoder*) speech decoder.
+
+The programs should be called like:
+
+```
+encoder [-dtx] mode speech_file bitstream_file
+```
+
+or
+
+```
+encoder [-dtx] -modefile=mode_file speech_file bitstream_file
+```
+
+```
+decoder <parameter file> <speech output file>
+```
+
+The speech files contain 16-bit linear encoded PCM speech samples and the parameter files contain encoded speech data and some additional flags.
+
+See the file *readme.txt* for more information on how to run the *encoder* and *decoder* programs.
+
+## 4.3 Coding style
+
+The C code has been written according to structuring conventions used in 3GPP TS 26.073 [7]. Encoder and decoder state structures are allocated and initialized with special initializing functions. There are no separate functions for each module, as opposed to the fixed-point implementation in 3GPP TS 26.073 [7].
+
+## 4.4 Code hierarchy
+
+The code hierarchy follows the one specified in 3GPP TS 26.073 [7].
+
+Figures 1 to 4 are call graphs that show the functions used in the speech codec, including the functions of VAD, DTX, and comfort noise generation.
+
+Each column represents a call level and each cell a function. The functions contain calls to the functions in rightwards neighbouring cells. The time order in the call graphs is from the top downwards as the processing of a frame advances. All standard C functions, such as *printf()*, *fwrite()*, etc., have been omitted.
+
+The encoder call graph is broken down into three separate call graphs, shown in Tables 1 to 3.
+
+**Table 1: Speech encoder call structure**
+
+|                     |             |                     |                   |                           |                           |
+|---------------------|-------------|---------------------|-------------------|---------------------------|---------------------------|
+| Speech_Encode_Frame | Pre_Process |                     |                   |                           |                           |
+|                     | cod_amr     | vad                 | filter_bank       | first_filter_stage        |                           |
+|                     |             |                     |                   | filter5                   |                           |
+|                     |             |                     |                   | filter3                   |                           |
+|                     |             |                     |                   | level_calculation         |                           |
+|                     |             |                     | vad_decision      | complex_estimate_adapt    |                           |
+|                     |             |                     |                   | complex_vad               |                           |
+|                     |             |                     |                   | noise_estimate_update     | update_cntrl              |
+|                     |             |                     |                   | hangover_addition         |                           |
+|                     |             | tx_dtx_handler      |                   |                           |                           |
+|                     |             | lpc                 | Autocorr          |                           |                           |
+|                     |             |                     | Levinson          |                           |                           |
+|                     |             | lsp                 | Az_lsp            | Chebps                    |                           |
+|                     |             |                     | Q_plsf_5          | Lsp_lsf                   |                           |
+|                     |             |                     |                   | Lsf_wt                    |                           |
+|                     |             |                     |                   | Vq_subvec                 |                           |
+|                     |             |                     |                   | Vq_subvec_s               |                           |
+|                     |             |                     |                   | Reorder_lsf               |                           |
+|                     |             |                     |                   | Lsf_lsp                   |                           |
+|                     |             |                     | Int_lpc_1and3_2   | Lsp_az                    | Get_lsp_pol               |
+|                     |             |                     | Int_lpc_1and3     | Lsp_az                    | Get_lsp_pol               |
+|                     |             |                     | Q_plsf_3          | Lsp_lsf                   |                           |
+|                     |             |                     |                   | Lsf_wt                    |                           |
+|                     |             |                     |                   | Vq_subvec3                |                           |
+|                     |             |                     |                   | Vq_subvec4                |                           |
+|                     |             |                     |                   | Reorder_lsf               |                           |
+|                     |             |                     |                   | Lsf_lsp                   |                           |
+|                     |             |                     | Int_lpc_1to3_2    | Lsp_az                    | Get_lsp_pol               |
+|                     |             |                     | Int_lpc_1to3      | Lsp_az                    | Get_lsp_pol               |
+|                     |             | dtx_buffer          | Dotproduct40      |                           |                           |
+|                     |             | dtx_enc             | Lsp_lsf           |                           |                           |
+|                     |             |                     | Reorder_lsf       |                           |                           |
+|                     |             |                     | Lsf_lsp           |                           |                           |
+|                     |             |                     | Q_plsf_3          | Lsp_lsf                   |                           |
+|                     |             |                     |                   | Lsf_wt                    |                           |
+|                     |             |                     |                   | Vq_subvec3                |                           |
+|                     |             |                     |                   | Vq_subvec4                |                           |
+|                     |             |                     |                   | Reorder_lsf               |                           |
+|                     |             |                     |                   | Lsf_lsp                   |                           |
+|                     |             | check_lsp           |                   |                           |                           |
+|                     |             | pre_big             | Weight_Ai         |                           |                           |
+|                     |             |                     | Residu            |                           |                           |
+|                     |             |                     | Syn_filt          |                           |                           |
+|                     |             | ol_ltp              | Pitch_ol          | vad_tone_detection_update |                           |
+|                     |             |                     |                   | Lag_max                   | vad_tone_detection        |
+|                     |             |                     |                   | comp_corr                 |                           |
+|                     |             |                     |                   | hp_max                    |                           |
+|                     |             |                     | Pitch_ol_wgh      | comp_corr                 |                           |
+|                     |             |                     |                   | Lag_max_wght              | vad_tone_detection_update |
+|                     |             |                     |                   | gmed_n                    | vad_tone_detection        |
+|                     |             |                     |                   | hp_max <sup>2</sup>       |                           |
+|                     |             | vad_pitch_detection |                   |                           |                           |
+|                     |             | subframePreProc     | Weight_Ai         |                           |                           |
+|                     |             |                     | Syn_filt          |                           |                           |
+|                     |             |                     | Residu            |                           |                           |
+|                     |             | cl_ltp              | Pitch_fr          | getRange                  |                           |
+|                     |             |                     |                   | Norm_Corr                 | Dotproduct40              |
+|                     |             |                     |                   | searchFrac                | Interpol_3or6             |
+|                     |             |                     |                   | Enc_lag3                  |                           |
+|                     |             |                     |                   | Enc_lag6                  |                           |
+|                     |             |                     | Pred_lt_3or6      |                           |                           |
+|                     |             |                     | G_pitch           | Dotproduct40              |                           |
+|                     |             |                     | check_gp_clipping |                           |                           |
+|                     |             |                     | q_gain_pitch      |                           |                           |
+|                     |             | cbsearch            | see Table 2       |                           |                           |
+|                     |             | gainQuant           | see Table 3       |                           |                           |
+|                     |             | update_gp_clipping  | Copy              |                           |                           |
+|                     |             | subframePostProc    | Syn_filt          |                           |                           |
+|                     |             | Pred_lt_3or6        |                   |                           |                           |
+|                     |             | Convolve            |                   |                           |                           |
+
+**Table 2: cbsearch call structure**
+
+|          |                   |                         |              |
+|----------|-------------------|-------------------------|--------------|
+| cbsearch | code_2i40_9bits   | cor h_x                 | Dotproduct40 |
+|          |                   | set_sign                |              |
+|          |                   | cor h                   | Dotproduct40 |
+|          |                   | search 2i40_9bits       |              |
+|          |                   | build_code 2i40_9bits   |              |
+|          | code_2i40_11bits  | cor h_x                 | Dotproduct40 |
+|          |                   | set_sign                |              |
+|          |                   | cor h                   | Dotproduct40 |
+|          |                   | search 2i40_11bits      |              |
+|          |                   | build_code 2i40_11bits  |              |
+|          | code_3i40_14bits  | cor h_x                 | Dotproduct40 |
+|          |                   | set_sign                |              |
+|          |                   | cor h                   | Dotproduct40 |
+|          |                   | search 3i40             |              |
+|          |                   | build_code 3i40_14bits  |              |
+|          | code_4i40_17bits  | cor h_x                 | Dotproduct40 |
+|          |                   | set_sign                |              |
+|          |                   | cor h                   | Dotproduct40 |
+|          |                   | search 4i40             |              |
+|          |                   | build_code 4i40         |              |
+|          | code_8i40_31bits  | cor h_x                 | Dotproduct40 |
+|          |                   | set_sign12k2            | Dotproduct40 |
+|          |                   | cor h                   | Dotproduct40 |
+|          |                   | search 8i40             |              |
+|          |                   | build_code 8i40_31bits  |              |
+|          |                   | compress_code           | compress10   |
+|          | code_10i40_35bits | cor h_x                 | Dotproduct40 |
+|          |                   | set_sign12k2            | Dotproduct40 |
+|          |                   | cor h                   | Dotproduct40 |
+|          |                   | search 10i40            |              |
+|          |                   | build_code 10i40_35bits |              |
+|          |                   | g_p                     |              |
+
+**Table 3: gainQuant call structure**
+
+|           |                       |                           |              |
+|-----------|-----------------------|---------------------------|--------------|
+| gainQuant | gc_pred               | Dotproduct40              |              |
+|           | calc_filt_energies    | Dotproduct40              |              |
+|           | Dotproduct40          |                           |              |
+|           | MR475_update_unq_pred |                           |              |
+|           | MR475_gain_quant      | gc_pred                   | Dotproduct40 |
+|           | g_gain_code           |                           |              |
+|           | MR795_gain_quant      | g_gain_pitch              |              |
+|           |                       | MR795_gain_code_quant3    |              |
+|           |                       | calc_unfilt_energies      | Dotproduct40 |
+|           |                       | gain_adapt                | Gmed_n_f     |
+|           |                       | MR795_gain_code_quant_mod |              |
+|           | Qua_gain              |                           |              |
+
+**Table 4: Speech decoder call structure**
+
+|                     |             |                         |                         |              |  |
+|---------------------|-------------|-------------------------|-------------------------|--------------|--|
+| Speech_Decode_Frame | Decoder_amr | rx_dtx_handler          |                         |              |  |
+|                     |             | Decoder_amr_reset       |                         |              |  |
+|                     |             | dtx_dec                 | Copy                    |              |  |
+|                     |             |                         | Lsf_lsp                 |              |  |
+|                     |             |                         | D_plsf_3                | Lsf_lsp      |  |
+|                     |             |                         | pseudonoise             |              |  |
+|                     |             |                         | Lsp_lsf                 |              |  |
+|                     |             |                         | Reorder_lsf             |              |  |
+|                     |             |                         | Lsp_Az                  | Get_lsp_pol  |  |
+|                     |             |                         | A_Refl                  |              |  |
+|                     |             |                         | Log2                    | Log2_norm    |  |
+|                     |             |                         | Pow2                    |              |  |
+|                     |             |                         | Build_CN_code           | pseudonoise  |  |
+|                     |             |                         | Syn_filt                |              |  |
+|                     |             | Lsf_lsp                 |                         |              |  |
+|                     |             | Lsp_avg                 |                         |              |  |
+|                     |             | Build_CN_param          |                         |              |  |
+|                     |             | D_plsf_3                | Lsf_lsp                 |              |  |
+|                     |             | Int_lpc_1to3            | Lsp_Az                  | Get_lsp_pol  |  |
+|                     |             | D_plsf_5                | Reorder_lsf             |              |  |
+|                     |             |                         | Lsf_lsp                 |              |  |
+|                     |             | Int_lpc_1and3           | Lsp_Az                  | Get_lsp_pol  |  |
+|                     |             | Dec_lag3                |                         |              |  |
+|                     |             | Pred_lt_3or6_40         |                         |              |  |
+|                     |             | Dec_lag6                |                         |              |  |
+|                     |             | decode_2140_9bits       |                         |              |  |
+|                     |             | decode_2140_11bits      |                         |              |  |
+|                     |             | decode_3140_14bits      |                         |              |  |
+|                     |             | decode_4140_17bits      |                         |              |  |
+|                     |             | decode_8140_31bits      | decompress_codewords    | decompress10 |  |
+|                     |             | ec_gain_pitch           | gmed_n                  |              |  |
+|                     |             | d_gain_pitch            |                         |              |  |
+|                     |             | ec_gain_pitch_update    |                         |              |  |
+|                     |             | decode_10140_35bits     |                         |              |  |
+|                     |             | Dec_gain                | Log2                    | Log2_norm    |  |
+|                     |             |                         | gc_pred                 | Log2         |  |
+|                     |             |                         |                         | Log2_norm    |  |
+|                     |             |                         | Pow2                    |              |  |
+|                     |             |                         | gc_pred_update          |              |  |
+|                     |             | ec_gain_code            | gmed_n                  |              |  |
+|                     |             |                         | gc_pred_average_limited |              |  |
+|                     |             |                         | gc_pred_update          |              |  |
+|                     |             | ec_gain_code_update     |                         |              |  |
+|                     |             | d_gain_code             | gc_pred                 | Log2         |  |
+|                     |             |                         |                         | Log2_norm    |  |
+|                     |             |                         | Pow2                    |              |  |
+|                     |             |                         | gc_pred_update          |              |  |
+|                     | Post_Filter | Int_lsf                 |                         |              |  |
+|                     |             | Cb_gain_average         |                         |              |  |
+|                     |             | ph_disp                 |                         |              |  |
+|                     |             | sqrt_l_exp              |                         |              |  |
+|                     |             | Ex_ctrl                 | gmed_n                  |              |  |
+|                     |             | agc2                    | Inv_sqrt                |              |  |
+|                     |             | Syn_filt                |                         |              |  |
+|                     |             | Bgn_scd                 | gmed_n                  |              |  |
+| Post_Process        |             | dtx_dec_activity_update | Copy                    |              |  |
+|                     |             |                         | Log2                    | Log2_norm    |  |
+|                     |             | Lsp_avg                 |                         |              |  |
+|                     |             | Residu40                |                         |              |  |
+|                     |             | Syn_filt                |                         |              |  |
+|                     |             | agc                     | energy_new              | energy_old   |  |
+|                     |             |                         | Inv_sqrt                |              |  |
+
+## 4.5 Variables, constants and tables
+
+The data types of variables and tables used in the floating-point implementation are signed integers in 2's complement representation, defined by:
+
+**Word8** 8 bit variable
+
+**UWord8** 8 bit unsigned variable
+
+**Word16** 16 bit variable
+
+**Word32** 32 bit variable
+
+Floating-point numbers use the IEEE (Institute of Electrical and Electronics Engineers) format:
+
+**Float32** 8 bit exponent, 23 bit mantissa, 1 bit sign
+
+**Float64** 11 bit exponent, 52 bit mantissa, 1 bit sign
+
+Furthermore some **enum** types are used, all possible to represent with one byte, and a Boolean **Flag**.
+
+### 4.5.1 Description of constants used in the C code
+
+Constants for the codec are defined in rom (h) files.
+
+### 4.5.2 Description of fixed tables used in the C code
+
+This section contains a listing of all fixed tables sorted by source file name and table name.
+
+**Table 5: Speech encoder fixed tables**
+
+| File      | Table name           | Type[Length]   | Description                                                           |
+|-----------|----------------------|----------------|-----------------------------------------------------------------------|
+| rom_enc.h | trackTable           | Word8[4*5]     | track table for algebraic code book search (MR475, MR515)             |
+| rom_enc.h | gamma1               | Float32[10]    | spectral expansion factors                                            |
+| rom_enc.h | gamma1_12k2          | Float32[10]    | spectral expansion factors                                            |
+| rom_enc.h | gamma2               | Float32[10]    | spectral expansion factors                                            |
+| rom_enc.h | b60                  | Float32[61]    | interpolation filter coefficients                                     |
+| rom_enc.h | startPos1            | Word16[2]      | track start search position for first pulse                           |
+| rom_enc.h | startPos2            | Word16[4]      | track start search position for second pulse                          |
+| rom_enc.h | startPos             | Word16[16]     | track start search position                                           |
+| rom_enc.h | corrweight           | Float32[251]   | weighting of the correlation function in open loop LTP search (MR102) |
+| rom_enc.h | qua_gain_pitch       | Float32[16]    | adaptive codebook gain quantization table (MR795)                     |
+| rom_enc.h | qua_gain_pitch_MR122 | Float32[16]    | adaptive codebook gain quantization table (MR122)                     |
+| rom_enc.h | qua_gain_code        | Float32[64]    | fixed codebook gain quantization table (MR122, MR795)                 |
+| rom_enc.h | gray                 | Word8[8]       | gray coding table                                                     |
+| rom_enc.h | grid                 | Float32[61]    | grid points at which Chebyshev polynomials are evaluated              |
+| rom_enc.h | b24                  | Float32[25]    | interpolation filter coefficients                                     |
+| rom_enc.h | lag_wind             | Float32[10]    | lag window table                                                      |
+| rom_enc.h | lsp_init_data        | Float32[10]    | initialization table for lsp history in DTX                           |
+| rom_enc.h | past_rq_init         | Float32[80]    | initialization table for the MA predictor in DTX                      |
+| rom_enc.h | mean_lsf_3           | Float32[10]    | LSF means (not in MR122)                                              |
+| rom_enc.h | mean_lsf_5           | Float32[10]    | LSF means (MR122)                                                     |
+| rom_enc.h | pred_fac             | Float32[10]    | LSF prediction factors (not in MR122)                                 |
+| rom_enc.h | dico1_lsf_3          | Float32[3*256] | 1 <sup>st</sup> LSF quantizer (not in MR122 and MR795)                |
+| rom_enc.h | dico2_lsf_3          | Float32[3*512] | 2 <sup>nd</sup> LSF quantizer (not in MR122)                          |
+| rom_enc.h | dico3_lsf_3          | Float32[4*512] | 3 <sup>rd</sup> LSF quantizer (not in MR122, MR515 and MR475)         |
+| rom_enc.h | mr515_3_lsf          | Float32[4*128] | 3 <sup>rd</sup> LSF quantizer (MR515 and MR475)                       |
+| rom_enc.h | mr795_1_lsf          | Float32[3*512] | 1 <sup>st</sup> LSF quantizer (MR795)                                 |
+| rom_enc.h | dico1_lsf_5          | Float32[4*128] | 1 <sup>st</sup> LSF quantizer (MR122)                                 |
+| rom_enc.h | dico2_lsf_5          | Float32[4*256] | 2 <sup>nd</sup> LSF quantizer (MR122)                                 |
+| rom_enc.h | dico3_lsf_5          | Float32[4*256] | 3 <sup>rd</sup> LSF quantizer (MR122)                                 |
+| rom_enc.h | dico4_lsf_5          | Float32[4*256] | 4 <sup>th</sup> LSF quantizer (MR122)                                 |
+| rom_enc.h | dico5_lsf_5          | Float32[4*64]  | 5 <sup>th</sup> LSF quantizer (MR122)                                 |
+| rom_enc.h | table_gain_MR475     | Float32[4*256] | gain quantization table (MR475)                                       |
+| rom_enc.h | table_gain_highrates | Float32[128*3] | gain quantization table (MR67, MR74 and MR102)                        |
+| rom_enc.h | table_gain_lowrates  | Float32[64*3]  | gain quantization table (MR515 and MR59)                              |
+| rom_enc.h | window_200_40        | Float32[240]   | LP analysis window (not in MR122)                                     |
+| rom_enc.h | window_160_80        | Float32[240]   | 1 <sup>st</sup> LP analysis window (MR122)                            |
+| rom_enc.h | window_232_8         | Float32[240]   | 2 <sup>nd</sup> LP analysis window (MR122)                            |
+| rom_enc.h | corrweight           | Float32[251]   | correlation weights                                                   |
+| rom_enc.h | mode_dep_parm        | Word8[8*9]     | parameters defining the adaptive codebook search per mode             |
+
+**Table 6: Speech decoder fixed tables**
+
+| File      | Table name           | Type[Length]  | Description                                                   |
+|-----------|----------------------|---------------|---------------------------------------------------------------|
+| rom_dec.h | dtx_log_en_adjust    | Word16[9]     | level adjustments for each mode                               |
+| rom_dec.h | cdown                | Word32[7]     | attenuation factors for codebook gain                         |
+| rom_dec.h | pdown                | Word32[7]     | attenuation factors for adaptive codebook gain                |
+| rom_dec.h | pred                 | Word32[4]     | algebraic code book gain MA predictor coefficients            |
+| rom_dec.h | pred_MR122           | Word32[4]     | algebraic code book gain MA predictor coefficients (MR122)    |
+| rom_dec.h | gamma3_MR122         | Word32[10]    | spectral expansion factors                                    |
+| rom_dec.h | gamma3               | Word32[10]    | spectral expansion factors                                    |
+| rom_dec.h | gamma4_MR122         | Word32[10]    | spectral expansion factors                                    |
+| rom_dec.h | gamma4               | Word32[10]    | spectral expansion factors                                    |
+| rom_dec.h | bitno_MR475          | Word16[17]    | number of bits per parameter to transmit (MR475)              |
+| rom_dec.h | bitno_MR515          | Word16[19]    | number of bits per parameter to transmit (MR515)              |
+| rom_dec.h | bitno_MR59           | Word16[19]    | number of bits per parameter to transmit (MR59)               |
+| rom_dec.h | bitno_MR67           | Word16[19]    | number of bits per parameter to transmit (MR67)               |
+| rom_dec.h | bitno_MR74           | Word16[19]    | number of bits per parameter to transmit (MR74)               |
+| rom_dec.h | bitno_MR795          | Word16[23]    | number of bits per parameter to transmit (MR795)              |
+| rom_dec.h | bitno_MR102          | Word16[39]    | number of bits per parameter to transmit (MR102)              |
+| rom_dec.h | bitno_MR122          | Word16[57]    | number of bits per parameter to transmit (MR122)              |
+| rom_dec.h | bitno_MRDTX          | Word16[5]     | number of bits per parameter to transmit (MRDTX)              |
+| rom_dec.h | qua_gain_pitch       | Word32[16]    | adaptive codebook gain quantization table (MR122, MR795)      |
+| rom_dec.h | qua_gain_code        | Word32[96]    | fixed codebook gain quantization table (MR122, MR795)         |
+| rom_dec.h | gray                 | Word8[8]      | gray coding table                                             |
+| rom_dec.h | dgray                | Word8[8]      | gray decoding table                                           |
+| rom_dec.h | sqrt_table           | Word32[49]    | table to compute sqrt(x)                                      |
+| rom_dec.h | inv_sqrt_table       | Word32[49]    | table used in inverse square root computation                 |
+| rom_dec.h | log2_table           | Word32[33]    | table used in base 2 logarithm computation                    |
+| rom_dec.h | pow2_table           | Word32[33]    | table used in 2 to the power computation                      |
+| rom_dec.h | cos_table            | Word32[65]    | table to compute cos(x) in Lsf_lsp()                          |
+| rom_dec.h | acos_slope           | Word32[64]    | table to compute acos(x) in Lsp_lsf()                         |
+| rom_dec.h | ph_imp_low_MR795     | Word32[40]    | phase dispersion impulse response (MR795)                     |
+| rom_dec.h | ph_imp_mid_MR795     | Word32[40]    | phase dispersion impulse response (MR795)                     |
+| rom_dec.h | ph_imp_low           | Word32[40]    | phase dispersion impulse response (MR475 - MR67)              |
+| rom_dec.h | ph_imp_mid           | Word32[40]    | phase dispersion impulse response (MR475 - MR67)              |
+| rom_dec.h | past_rq_init         | Word32[80]    | initialization table for the MA predictor in DTX              |
+| rom_dec.h | mean_lsf_3           | Word32[10]    | LSF means (not in MR122)                                      |
+| rom_dec.h | mean_lsf_5           | Word32[10]    | LSF means (MR122)                                             |
+| rom_dec.h | pred_fac             | Word32[10]    | LSF prediction factors (not in MR122)                         |
+| rom_dec.h | dico1_lsf_3          | Word32[3*256] | 1 <sup>st</sup> LSF quantizer (not in MR122 and MR795)        |
+| rom_dec.h | dico2_lsf_3          | Word32[3*512] | 2 <sup>nd</sup> LSF quantizer (not in MR122)                  |
+| rom_dec.h | dico3_lsf_3          | Word32[4*512] | 3 <sup>rd</sup> LSF quantizer (not in MR122, MR515 and MR475) |
+| rom_dec.h | mr515_3_lsf          | Word32[4*128] | 3 <sup>rd</sup> LSF quantizer (MR515 and MR475)               |
+| rom_dec.h | mr795_1_lsf          | Word32[3*512] | 1 <sup>st</sup> LSF quantizer (MR795)                         |
+| rom_dec.h | dico1_lsf_5          | Word32[4*128] | 1 <sup>st</sup> LSF quantizer (MR122)                         |
+| rom_dec.h | dico2_lsf_5          | Word32[4*256] | 2 <sup>nd</sup> LSF quantizer (MR122)                         |
+| rom_dec.h | dico3_lsf_5          | Word32[4*256] | 3 <sup>rd</sup> LSF quantizer (MR122)                         |
+| rom_dec.h | dico4_lsf_5          | Word32[4*256] | 4 <sup>th</sup> LSF quantizer (MR122)                         |
+| rom_dec.h | dico5_lsf_5          | Word32[4*64]  | 5 <sup>th</sup> LSF quantizer (MR122)                         |
+| rom_dec.h | table_gain_MR475     | Word32[4*256] | gain quantization table (MR475)                               |
+| rom_dec.h | table_gain_highrates | Word32[128*4] | gain quantization table (MR67, MR74 and MR102)                |
+| rom_dec.h | table_gain_lowrates  | Word32[64*4]  | gain quantization table (MR515 and MR59)                      |
+| rom_dec.h | inter_6              | Word32[61]    | interpolation filter coefficients                             |
+| rom_dec.h | window_200_40        | Word32[240]   | LP analysis window (not in MR122)                             |
+| rom_dec.h | table_speech_bad     | UWord8[9]     | comparison optimisation table in DTX                          |
+| rom_dec.h | table_SID            | UWord8[9]     | comparison optimisation table in DTX                          |
+| rom_dec.h | table_DTX            | UWord8[9]     | comparison optimisation table in DTX                          |
+| rom_dec.h | table_mute           | UWord8[9]     | comparison optimisation table in DTX                          |
+
+### 4.5.3 Static variables used in the C code
+
+In this section, two tables that specify the static variables for the speech encoder and decoder, respectively, are shown. All static variables are declared within a C **struct**.
+
+**Table 7: Speech encoder static variables**
+
+| Struct name                  | Variable           | Type[Length]     | Description                                                            |
+|------------------------------|--------------------|------------------|------------------------------------------------------------------------|
+| Speech_Encode_<br>FrameState | cod_amr_state      | cod_amrState     | see below in this table                                                |
+|                              | pre_state          | Pre_ProcessState | see below in this table                                                |
+|                              | dtx                | Word32           | Is set if DTX functionality is used                                    |
+| Pre_ProcessState             | y2                 | Float32          | filter state                                                           |
+|                              | y1                 | Word16 Float32   | filter state                                                           |
+|                              | x0                 | Float32          | filter state                                                           |
+|                              | x1                 | Float32          | filter state                                                           |
+| cod_amrState                 | old_speech         | Float32 [320]    | speech buffer                                                          |
+|                              | speech             | Float32*         | pointer to current frame in old_speech                                 |
+|                              | p_window           | Float32*         | pointer to LPC analysis window in old_speech                           |
+|                              | p_window_12k2      | Float32*         | pointer to LPC analysis window with no lookahead in old_speech (MR122) |
+|                              | new_speech         | Float32*         | pointer to the last 160 speech samples in old_speech                   |
+|                              | old_wsp            | Float32 [303]    | buffer holding spectral weighted speech                                |
+|                              | wsp                | Float32*         | pointer to the current frame in old_wsp                                |
+|                              | old_lags           | Word32[5]        | open loop LTP states                                                   |
+|                              | ol_gain_flg        | Float32 [2]      | enables open loop pitch lag weighting (MR102)                          |
+|                              | old_exc            | Float32 [314]    | excitation vector                                                      |
+|                              | exc                | Float32*         | current excitation                                                     |
+|                              | ai_zero            | Float32 [51]     | history of weighted synth. filter followed by zero vector              |
+|                              | zero               | Float32*         | zero vector                                                            |
+|                              | h1                 | Float32*         | impulse response of weighted synthesis filter                          |
+|                              | hvec               | Float32 [80]     | zero vector followed by impulse response                               |
+|                              | lpcSt              | lpcState         | see below in this table                                                |
+|                              | lspSt              | lspState         | see below in this table                                                |
+|                              | clLtpSt            | clLtpState       | see below in this table                                                |
+|                              | gainQuantSt        | gainQuantState   | see below in this table                                                |
+|                              | pitchOLWghtSt      | pitchOLWghtState | see below in this table                                                |
+|                              | tonStabSt          | tonStabState     | see below in this table                                                |
+|                              | vadSt              | vadState         | see below in this table                                                |
+|                              | vadSt2             | vadState2        | see below in this table                                                |
+|                              | dtx                | Word32           | is set if DTX functionality is used                                    |
+|                              | dtx_encSt          | dtx_encState     | see below in this table                                                |
+|                              | mem_syn            | Float32 [10]     | synthesis filter memory                                                |
+|                              | mem_w0             | Float32 [10]     | weighting filter memory (applied to error signal)                      |
+|                              | mem_w              | Float32 [10]     | weighting filter memory (applied to input signal)                      |
+|                              | mem_err            | Float32 [50]     | filter memory for production of error vector                           |
+|                              | error              | Float32*         | error signal (input minus synthesized speech)                          |
+|                              | sharp              | Float32          | pitch sharpening gain                                                  |
+| vadState                     | bckr_est           | Float32 [9]      | background noise estimate                                              |
+|                              | ave_level          | Float32 [9]      | averaged input components for stationary estimation                    |
+|                              | old_level          | Float32 [9]      | input levels of the previous frame                                     |
+|                              | sub_level          | Float32 [9]      | input levels calculated at the end of a frame (lookahead)              |
+|                              | a_data5            | Float32 [6]      | memory for the filter bank                                             |
+|                              | a_data3            | Float32 [5]      | memory for the filter bank                                             |
+|                              | burst_count        | Word16           | counts length of a speech burst                                        |
+|                              | hang_count         | Word16           | hangover counter                                                       |
+|                              | stat_count         | Word16           | stationary counter                                                     |
+|                              | vadreg             | Word32           | 15 flags for intermediate VAD decisions                                |
+|                              | pitch              | Word32           | 15 flags for pitch detection                                           |
+|                              | tone               | Word16           | 15 flags for tone detection                                            |
+|                              | complex_high       | Word16           | flags for complex detection                                            |
+|                              | complex_low        | Word16           | flags for complex detection                                            |
+|                              | oldlag_count       | Word32           | variables for pitch detection                                          |
+|                              | oldlag             | Word32           | variables for pitch detection                                          |
+|                              | complex_hang_count | Word16           | complex hangover counter, used by VAD                                  |
+|                              | complex_hang_timer | Word16           | hangover initiator, used by CAD                                        |
+
+| Struct name      | Variable            | Type[Length]   | Description                                      |
+|------------------|---------------------|----------------|--------------------------------------------------|
+|                  | best_corr_hp        | Float32        | filtered value                                   |
+|                  | speech_vad_decision | Word16         | final decision                                   |
+|                  | complex_warning     | Word16         | complex background warning                       |
+|                  | sp_burst_count      | Word16         | counts length of a speech burst incl HO addition |
+|                  | corr_hp_fast        | Word16         | filtered value                                   |
+| dtx_encState     | lsp_hist            | Float32[80]    | LSP history (8 frames)                           |
+|                  | log_en_hist         | Float32 [8]    | logarithmic frame energy history (8 frames)      |
+|                  | hist_ptr            | Word16         | pointer to the cyclic history vectors            |
+|                  | log_en_index        | Word16         | Index for logarithmic energy                     |
+|                  | init_lsf_vq_index   | Word32         | initial index for lsf predictor                  |
+|                  | lsp_index           | Word16[3]      | lsp indecies to the three code books             |
+|                  | dtxHangoverCount    | Word16         | is decreased in DTX hangover period              |
+|                  | decAnaElapsedCount  | Word16         | counter for elapsed speech frames in DTX         |
+| lpcState         | LevinsonSt          | LevinsonState  | see below                                        |
+| LevinsonState    | old_A               | Float32[11]    | last frames direct form coefficients             |
+| lspState         | lsp_old             | Float32 [10]   | old LSP vector                                   |
+|                  | lsp_old_q           | Float32 [10]   | old quantized LSP vector                         |
+|                  | qSt                 | Q_plsfState    | see below in this table                          |
+| Q_plsfState      | past_rq             | Float32[10]    | past quantized LSF prediction error              |
+| clLtpState       | pitchSt             | Pitch_frState  | see below in this table                          |
+| tonStabState     | count               | Word16         | count consecutive (potential) resonance frames   |
+|                  | gp                  | Float32[7]     | pitch gain history                               |
+| Pitch_frState    | T0_prev_subframe    | Word32         | integer. pitch lag of previous subframe          |
+| gainQuantState   | sf0_gcode0          | Float32        | subframe 0/2 codebook gain                       |
+|                  | sf0_target_en       | Float32        | subframe 0/2 target energy                       |
+|                  | sf0_coeff           | Float32 [5]    | subframe 0/2 energy coefficient                  |
+|                  | gain_idx_ptr        | Word16*        | pointer to gain index value in parameter frame   |
+|                  | gc_predSt           | gc_predState   | see below in this table                          |
+|                  | gc_predUncSt        | gc_predState   | see below in this table                          |
+|                  | adaptSt             | GainAdaptState | see below in this table                          |
+| gc_predState     | past_qua_en         | Float32[4]     | MA predictor memory (20*log10(pred. error))      |
+| GainAdaptState   | onset               | Word16         | onset counter                                    |
+|                  | prev_alpha          | Float32        | previous adaptor output                          |
+|                  | prev_gc             | Float32        | previous codebook gain                           |
+|                  | ltpg_mem            | Float32 [5]    | pitch gain history                               |
+| pitchOLWghtState | old_T0_med          | Word32         | weighted open loop pitch lag                     |
+|                  | ada_w               | Float32        | weigthing level depeding on open loop pitch gain |
+|                  | wght_flg            | Word16         | switches lag weighting on and off                |
+
+**Table 8: Speech decoder static variables**
+
+| Struct name              | Variable            | Type[Length]         | Description                                     |
+|--------------------------|---------------------|----------------------|-------------------------------------------------|
+| Speech_Decode_FrameState | decoder_amrState    | Decoder_amrState     | see below in this table                         |
+|                          | post_state          | Post_FilterState     | see below in this table                         |
+|                          | postHP_state        | Post_ProcessState    | see below in this table                         |
+| Decoder_amrState         | old_exc             | Word32[194]          | excitation vector                               |
+|                          | exc                 | Word32*              | current excitation                              |
+|                          | lsp_old             | Word32[10]           | LSP vector of previous frame                    |
+|                          | mem_syn             | Word32[10]           | synthesis filter memory                         |
+|                          | sharp               | Word32               | pitch sharpening gain                           |
+|                          | old_T0              | Word32               | pitch sharpening lag                            |
+|                          | prev_bf             | Word16               | previous value of "bad frame" flag              |
+|                          | prev_pdf            | Word16               | previous value of "pot. dangerous frame" flag   |
+|                          | state               | Word16               | ECU state (0..6)                                |
+|                          | excEnergyHist       | Word32[9]            | excitation energy history                       |
+|                          | T0_lagBuff          | Word32               | received pitch lag for ECU                      |
+|                          | inBackgroundNoise   | Word32               | background noise flag                           |
+|                          | voicedHangover      | Word32               | hangover flag                                   |
+|                          | ltpGainHistory      | Word32[9]            | pitch gain history                              |
+|                          | background_state    | Bgn_scdState         | see below in this table                         |
+|                          | Cb_gain_averState   | Cb_gain_averageState | see below in this table                         |
+|                          | lsp_avg_st          | lsp_avgState         | see below in this table                         |
+|                          | lsfState            | D_plsfState          | see below in this table                         |
+|                          | ec_gain_p_st        | ec_gain_pitchState   | see below in this table                         |
+|                          | ec_gain_c_st        | ec_gain_codeState    | see below in this table                         |
+|                          | pred_state          | gc_predState         | see table 7                                     |
+|                          | nodataSeed          | Word16               | seed for CN generator                           |
+|                          | ph_disp_st          | ph_dispState         | see below in this table                         |
+|                          | dtxDecoderState     | dtx_decState         | see below in this table                         |
+| dtx_decState             | since_last_sid      | Word16               | number of frames since last SID frame           |
+|                          | true_sid_period_inv | Word16               | inverse of true SID update rate                 |
+|                          | log_en              | Word32               | logarithmic frame energy                        |
+|                          | old_log_en          | Word32               | previous value of log_en                        |
+|                          | pn_seed_rx          | Word32               | random number generator seed                    |
+|                          | lsp                 | Word32[10]           | LSP vector                                      |
+|                          | lsp_old             | Word32[10]           | previous LSP vector                             |
+|                          | lsf_hist            | Word32[80]           | LSF vector history (8 frames)                   |
+|                          | lsf_hist_ptr        | Word16               | index to beginning of LSF history               |
+|                          | lsf_hist_mean       | Word32[80]           | mean-removed LSF history (8 frames)             |
+|                          | log_pg_mean         | Word16               | mean-removed logarithmic prediction gain        |
+|                          | log_en_hist         | Word32[8]            | logarithmic frame energy history                |
+|                          | log_en_hist_ptr     | Word16               | index to beginning of log. frame energy history |
+|                          | log_en_adjust       | Word16               | mode-dependent frame energy adjustment          |
+|                          | dtxHangoverCount    | Word16               | counts down in hangover period                  |
+|                          | decAnaElapsedCount  | Word16               | counts elapsed speech frames after DTX          |
+|                          | sid_frame           | Word16               | flags SID frames                                |
+|                          | valid_data          | Word16               | flags SID frames containing valid data          |
+|                          | dtxHangoverAdded    | Word16               | flags hangover period at end of speech          |
+|                          | dtxGlobalState      | enum DTXStateType    | DTX state flags                                 |
+|                          | data_updated        | Word16               | flags CNI updates                               |
+| Bgn_scdState             | frameEnergyHist     | Word32[60]           | history of synthesis frame energy               |
+|                          | bgHangover          | Word16               | number of frames since last speech frame        |
+| Cb_gain_averageState     | cbGainHistory       | Word32[7]            | codebook gain history                           |
+|                          | hangVar             | Word16               | counts length of talkspurt in subframes         |
+|                          | hangCount           | Word16               | number of subframes since last talkspurt        |
+| lsp_avgState             | lsp_meanSave        | Word32[10]           | averaged LSP vector                             |
+| D_plsfState              | past_r_q            | Word32[10]           | past quantized LSF prediction vector            |
+|                          | past_lsf_q          | Word32[10]           | past dequantized LSF vector                     |
+| ec_gain_pitchState       | pbuf                | Word32[5]            | pitch gain history                              |
+|                          | past_gain_pit       | Word32               | previous pitch gain (limited to 1.0)            |
+|                          | prev_gp             | Word32               | previous good pitch gain                        |
+| ec_gain_codeState        | gbuf                | Word32[5]            | codebook gain history                           |
+|                          | past_gain_code      | Word32               | previous codebook gain                          |
+|                          | prev_gc             | Word32               | previous good codebook gain                     |
+| ph_dispState             | gainMem             | Word32[5]            | pitch gain history                              |
+|                          | prevState           | Word32               | previously used impulse response                |
+|                          | prevCbGain          | Word32               | previous codebook gain                          |
+|                          | lockFull            | Word16               | force maximum phase dispersion                  |
+|                          | onset               | Word16               | onset counter                                   |
+|                          | res2                | Word32[40]           | LP residual                                     |
+| Post_FilterState         | mem_syn_pst         | Word32[10]           | synthesis filter memory                         |
+|                          | synth_buf           | Word16[170]          | synthesis filter work area                      |
+|                          | agc_state           | agcState             | see below in this table                         |
+|                          | preemph_state       | preemphasisState     | see below in this table                         |
+| agcState                 | past_gain           | Word16               | past agc gain                                   |
+| preemphasisState         | mem_pre             | Word16               | filter state                                    |
+
+| Struct name       | Variable | Type[Length] | Description              |
+|-------------------|----------|--------------|--------------------------|
+| Post_ProcessState | y2_hi    | Word32       | filter state, upper word |
+|                   | y2_lo    | Word32       | filter state, lower word |
+|                   | y1_hi    | Word32       | filter state, upper word |
+|                   | y1_lo    | Word32       | filter state, lower word |
+|                   | x0       | Word32       | filter state             |
+|                   | x1       | Word32       | filter state             |
+
+# 5 Homing procedure
+
+The principles of the homing procedures are described in 3GPP TS 06.090 [2]. This specification only includes a detailed description of the 8 decoder homing frames. For each AMR codec mode, the corresponding decoder homing frame has a fixed set of speech parameters shown in table 9a-9h. The bit allocation within these parameters is identical to the corresponding bit allocation of the source encoder output parameters given in 3GPP TS 06.090 [2].
+
+In the following tables, the following naming convention is used for the individual parameters. Letters in *italics* indicate numbers.
+
+- LPC *n* index of *n*th LSF submatrix
+- LTP-LAG *m* adaptive codebook index for subframe *m*
+- LTP-GAIN *m* adaptive codebook gain index in subframe *m*
+- FCB-GAIN *m* fixed codebook gain index in subframe *m*
+- GAIN\_VQ *m* codebook gain VQ index in subframe *m* (subframe *m* and *m+1* for MR475)
+- POS *m\_n* position index of *n*th pulse in subframe *m*
+- POS *m\_n\_k* position index of *n*th and *k*th pulse in subframe *m*
+- POS *m\_n\_k\_l\_j* position index of *n*th, *k*th, *l*th, and *j*th pulse in subframe *m*
+- SIGN *m\_n\_k* sign information for *n*th and *k*th pulse in subframe *m*
+- SIGN *m\_n\_k\_l\_j* sign information for *n*th, *k*th, *l*th, and *j*th pulse in subframe *m*
+- SIGN *m\_n\_k\_POS\_m\_n* sign information for *n*th and *k*th pulse and position index for *n*th pulse in subframe *m*
+
+**Table 9a: Parameter values for the decoder homing frame (MR475)**
+
+| Parameter  | Value (LSB=b0) |
+|------------|----------------|
+| LPC 1      | 0x00F8         |
+| LPC 2      | 0x009D         |
+| LPC 3      | 0x001C         |
+| LTP-LAG 1  | 0x0066         |
+| POS 1_1_2  | 0x0000         |
+| SIGN_1_1_2 | 0x0003         |
+| GAIN-VQ 1  | 0x0028         |
+| LTP-LAG 2  | 0x000F         |
+| POS 2_1_2  | 0x0038         |
+| SIGN_2_1_2 | 0x0001         |
+| LTP-LAG 3  | 0x000F         |
+| POS 3_1_2  | 0x0031         |
+| SIGN_3_1_2 | 0x0002         |
+| GAIN-VQ 3  | 0x0008         |
+| LTP-LAG 4  | 0x000F         |
+| POS 4_1_2  | 0x0026         |
+| SIGN_4_1_2 | 0x0003         |
+
+**Table 9b: Parameter values for the decoder homing frame (MR515)**
+
+| <b>Parameter</b> | <b>Value (LSB=b0)</b> |
+|------------------|-----------------------|
+| LPC 1            | 0x00F8                |
+| LPC 2            | 0x009D                |
+| LPC 3            | 0x001C                |
+| LTP-LAG 1        | 0x0066                |
+| POS 1_1_2        | 0x0000                |
+| SIGN_1_1_2       | 0x0003                |
+| GAIN-VQ 1        | 0x0037                |
+| LTP-LAG 2        | 0x000F                |
+| POS 2_1_2        | 0x0000                |
+| SIGN_2_1_2       | 0x0003                |
+| GAIN-VQ 2        | 0x0005                |
+| LTP-LAG 3        | 0x000F                |
+| POS 3_1_2        | 0x0037                |
+| SIGN_3_1_2       | 0x0003                |
+| GAIN-VQ 3        | 0x0037                |
+| LTP-LAG 4        | 0x000F                |
+| POS 4_1_2        | 0x0023                |
+| SIGN_4_1_2       | 0x0003                |
+| GAIN-VQ 4        | 0x001F                |
+
+**Table 9c: Parameter values for the decoder homing frame (MR59)**
+
+| <b>Parameter</b> | <b>Value (LSB=b0)</b> |
+|------------------|-----------------------|
+| LPC 1            | 0x00F8                |
+| LPC 2            | 0x00E3                |
+| LPC 3            | 0x002F                |
+| LTP-LAG 1        | 0x00BD                |
+| POS 1_1_2        | 0x0000                |
+| SIGN_1_1_2       | 0x0003                |
+| GAIN-VQ 1        | 0x0037                |
+| LTP-LAG 2        | 0x000F                |
+| POS 2_1_2        | 0x0001                |
+| SIGN_2_1_2       | 0x0003                |
+| GAIN-VQ 2        | 0x000F                |
+| LTP-LAG 3        | 0x0060                |
+| POS 3_1_2        | 0x00F9                |
+| SIGN_3_1_2       | 0x0003                |
+| GAIN-VQ 3        | 0x0037                |
+| LTP-LAG 4        | 0x000F                |
+| POS 4_1_2        | 0x0000                |
+| SIGN_4_1_2       | 0x0003                |
+| GAIN-VQ 4        | 0x0037                |
+
+**Table 9d: Parameter values for the decoder homing frame (MR67)**
+
+| <b>Parameter</b> | <b>Value (LSB=b0)</b> |
+|------------------|-----------------------|
+| LPC 1            | 0x00F8                |
+| LPC 2            | 0x00E3                |
+| LPC 3            | 0x002F                |
+| LTP-LAG 1        | 0x00BD                |
+| POS 1_1_2_3      | 0x0002                |
+| SIGN_1_1_2_3     | 0x0007                |
+| GAIN-VQ 1        | 0x0000                |
+| LTP-LAG 2        | 0x000F                |
+| POS 2_1_2_3      | 0x0098                |
+| SIGN_2_1_2_3     | 0x0007                |
+| GAIN-VQ 2        | 0x0061                |
+| LTP-LAG 3        | 0x0060                |
+| POS 3_1_2_3      | 0x05C5                |
+| SIGN_3_1_2_3     | 0x0007                |
+| GAIN-VQ 3        | 0x0000                |
+| LTP-LAG 4        | 0x000F                |
+| POS 4_1_2_3      | 0x0318                |
+| SIGN_4_1_2_3     | 0x0007                |
+| GAIN-VQ 4        | 0x0000                |
+
+**Table 9e: Parameter values for the decoder homing frame (MR74)**
+
+| <b>Parameter</b> | <b>Value (LSB=b0)</b> |
+|------------------|-----------------------|
+| LPC 1            | 0x00F8                |
+| LPC 2            | 0x00E3                |
+| LPC 3            | 0x002F                |
+| LTP-LAG 1        | 0x00BD                |
+| POS 1_1_2_3_4    | 0x0006                |
+| SIGN_1_1_2_3_4   | 0x000F                |
+| GAIN-VQ 1        | 0x0000                |
+| LTP-LAG 2        | 0x001B                |
+| POS 2_1_2_3_4    | 0x0208                |
+| SIGN_2_1_2_3_4   | 0x000F                |
+| GAIN-VQ 2        | 0x0062                |
+| LTP-LAG 3        | 0x0060                |
+| POS 3_1_2_3_4    | 0x1BA6                |
+| SIGN_3_1_2_3_4   | 0x000F                |
+| GAIN-VQ 3        | 0x0000                |
+| LTP-LAG 4        | 0x001B                |
+| POS 4_1_2_3_4    | 0x0006                |
+| SIGN_4_1_2_3_4   | 0x000F                |
+| GAIN-VQ 4        | 0x0000                |
+
+**Table 9f: Parameter values for the decoder homing frame (MR795)**
+
+| Parameter      | Value (LSB=b0) |
+|----------------|----------------|
+| LPC 1          | 0x00C2         |
+| LPC 2          | 0x00E3         |
+| LPC 3          | 0x002F         |
+| LTP-LAG 1      | 0x00BD         |
+| POS_1_1_2_3_4  | 0x0006         |
+| SIGN_1_1_2_3_4 | 0x000F         |
+| LTP-GAIN 1     | 0x000A         |
+| FCB-GAIN 1     | 0x0000         |
+| LTP-LAG 2      | 0x0039         |
+| POS_2_1_2_3_4  | 0x1C08         |
+| SIGN_2_1_2_3_4 | 0x0007         |
+| LTP-GAIN 2     | 0x000A         |
+| FCB-GAIN 2     | 0x000B         |
+| LTP-LAG 3      | 0x0063         |
+| POS_3_1_2_3_4  | 0x11A6         |
+| SIGN_3_1_2_3_4 | 0x000F         |
+| LTP-GAIN 3     | 0x0001         |
+| FCB-GAIN 3     | 0x0000         |
+| LTP-LAG 4      | 0x0039         |
+| POS_4_1_2_3_4  | 0x09A0         |
+| SIGN_4_1_2_3_4 | 0x000F         |
+| LTP-GAIN 4     | 0x0002         |
+| FCB-GAIN 4     | 0x0001         |
+
+**Table 9g: Parameter values for the decoder homing frame (MR102)**
+
+| <b>Parameter</b> | <b>Value (LSB=b0)</b> |
+|------------------|-----------------------|
+| LPC 1            | 0x00F8                |
+| LPC 2            | 0x00E3                |
+| LPC 3            | 0x002F                |
+| LTP-LAG 1        | 0x0045                |
+| SIGN_1_1_5       | 0x0000                |
+| SIGN_1_2_6       | 0x0000                |
+| SIGN_1_3_7       | 0x0000                |
+| SIGN_1_4_8       | 0x0000                |
+| POS_1_1_2_5      | 0x0000                |
+| POS_1_3_6_7      | 0x0000                |
+| POS_1_4_8        | 0x0000                |
+| GAIN-VQ_1        | 0x0000                |
+| LTP-LAG 2        | 0x001B                |
+| SIGN_2_1_5       | 0x0000                |
+| SIGN_2_2_6       | 0x0001                |
+| SIGN_2_3_7       | 0x0000                |
+| SIGN_2_4_8       | 0x0001                |
+| POS_2_1_2_5      | 0x0326                |
+| POS_2_3_6_7      | 0x00CE                |
+| POS_2_4_8        | 0x007E                |
+| GAIN-VQ_2        | 0x0051                |
+| LTP-LAG 3        | 0x0062                |
+| SIGN_3_1_5       | 0x0000                |
+| SIGN_3_2_6       | 0x0000                |
+| SIGN_3_3_7       | 0x0000                |
+| SIGN_3_4_8       | 0x0000                |
+| POS_3_1_2_5      | 0x015A                |
+| POS_3_3_6_7      | 0x0359                |
+| POS_3_4_8        | 0x0076                |
+| GAIN-VQ_3        | 0x0000                |
+| LTP-LAG 4        | 0x001B                |
+| SIGN_4_1_5       | 0x0000                |
+| SIGN_4_2_6       | 0x0000                |
+| SIGN_4_3_7       | 0x0000                |
+| SIGN_4_4_8       | 0x0000                |
+| POS_4_1_2_5      | 0x017C                |
+| POS_4_3_6_7      | 0x0215                |
+| POS_4_4_8        | 0x0038                |
+| GAIN-VQ_4        | 0x0030                |
+
+**Table 9h: Parameter values for the decoder homing frame (MR122)**
+
+| <b>Parameter</b>    | <b>Value (LSB=b0)</b> |
+|---------------------|-----------------------|
+| LPC1                | 0x0004                |
+| LPC2                | 0x002A                |
+| LPC3                | 0x00DB                |
+| LPC4                | 0x0096                |
+| LPC5                | 0x002A                |
+| LTP-LAG 1           | 0x0156                |
+| LTP-GAIN 1          | 0x000B                |
+| SIGN_1_1_6_POS_1_1  | 0x0000                |
+| SIGN_1_2_7_POS_1_2  | 0x0000                |
+| SIGN_1_3_8_POS_1_3  | 0x0000                |
+| SIGN_1_4_9_POS_1_4  | 0x0000                |
+| SIGN_1_5_10_POS_1_5 | 0x0000                |
+| POS 1_6             | 0x0000                |
+| POS 1_7             | 0x0000                |
+| POS 1_8             | 0x0000                |
+| POS 1_9             | 0x0000                |
+| POS 1_10            | 0x0000                |
+| FCB-GAIN 1          | 0x0000                |
+| LTP-LAG 2           | 0x0036                |
+| LTP-GAIN 2          | 0x000B                |
+| SIGN_2_1_6_POS_2_1  | 0x0000                |
+| SIGN_2_2_7_POS_2_2  | 0x000F                |
+| SIGN_2_3_8_POS_2_3  | 0x000E                |
+| SIGN_2_4_9_POS_2_4  | 0x000C                |
+| SIGN_2_5_10_POS_2_5 | 0x000D                |
+| POS 2_6             | 0x0000                |
+| POS 2_7             | 0x0001                |
+| POS 2_8             | 0x0005                |
+| POS 2_9             | 0x0007                |
+| POS 2_10            | 0x0001                |
+| FCB-GAIN 2          | 0x0008                |
+| LTP-LAG 3           | 0x0024                |
+| LTP-GAIN 3          | 0x0000                |
+| SIGN_3_1_6_POS_3_1  | 0x0001                |
+| SIGN_3_2_7_POS_3_2  | 0x0000                |
+| SIGN_3_3_8_POS_3_3  | 0x0005                |
+| SIGN_3_4_9_POS_3_4  | 0x0006                |
+| SIGN_3_5_10_POS_3_5 | 0x0001                |
+| POS 3_6             | 0x0002                |
+| POS 3_7             | 0x0004                |
+| POS 3_8             | 0x0007                |
+| POS 3_9             | 0x0004                |
+| POS 3_10            | 0x0002                |
+| FCB-GAIN 3          | 0x0003                |
+| LTP-LAG 4           | 0x0036                |
+| LTP-GAIN 4          | 0x000B                |
+| SIGN_4_1_6_POS_4_1  | 0x0000                |
+| SIGN_4_2_7_POS_4_2  | 0x0002                |
+| SIGN_4_3_8_POS_4_3  | 0x0004                |
+| SIGN_4_4_9_POS_4_4  | 0x0000                |
+| SIGN_4_5_10_POS_4_5 | 0x0003                |
+| POS 4_6             | 0x0006                |
+| POS 4_7             | 0x0001                |
+| POS 4_8             | 0x0007                |
+| POS 4_9             | 0x0006                |
+| POS 4_10            | 0x0005                |
+| FCB-GAIN 4          | 0x0000                |
+
+# 6 File formats
+
+This section describes the file formats used by the encoder and decoder programs. The test sequences defined in [2] also use the file formats described here.
+
+## 6.1 Speech file (encoder input / decoder output)
+
+Speech files read by the encoder and written by the decoder consist of 16-bit words where each word contains a 13-bit, left aligned speech sample. The byte order depends on the host architecture (e.g. MSByte first on SUN workstations, LSByte first on PCs etc.). Both the encoder and the decoder program process complete frames (of 160 samples) only.
+
+This means that the encoder will only process  $n$  frames if the length of the input file is  $n*160 + k$  words, while the files produced by the decoder will always have a length of  $n*160$  words.
+
+## 6.2 Mode control file (encoder input)
+
+The encoder program can optionally read in a mode control file which specifies the encoding mode for each frame of speech processed. The file is a text file containing one line per speech frame. Each line contains one of the mode names from the list {MR475, MR515, MR59, MR67, MR74, MR795, MR102, MR122}.
+
+## 6.3 Parameter bitstream file (encoder output / decoder input)
+
+The files produced by the speech encoder/expected by the speech decoder contain an arbitrary number of frames in the format described in RFC 3267 [9], sections 5.1 and 5.3.
+
+By using preprocessor definition encoder/decoder can optionally use AMR Interface Format 2. The format is described in TS 26.101 [8] Annex A.
+
+By using another preprocessor definition encoder/decoder can optionally use format compatible with the existing AMR fixed-point C-code. Frame format is following.
+
+|            |    |    |     |      |           |                |     |                |
+|------------|----|----|-----|------|-----------|----------------|-----|----------------|
+| FRAME_TYPE | B1 | B2 | ... | B244 | MODE_INFO | <i>unused1</i> | ... | <i>unused4</i> |
+|------------|----|----|-----|------|-----------|----------------|-----|----------------|
+
+Each box corresponds to one `Word16` value in the bitstream file, for a total of 250 words or 500 bytes per frame. The fields have the following meaning:
+
+**FRAME\_TYPE** transmit frame type, which is one of
+
+- TX\_SPEECH (0x0000)**
+- TX\_SID\_FIRST (0x0001)**
+- TX\_SID\_UPDATE (0x0002)**
+- TX\_NO\_DATA (0x0003)**
+
+**B0...B244** speech encoder parameter bits (i.e. the bitstream itself). Each B $x$  either has the value 0x0000 or 0x0001. Only mode MR122 really uses all 244 bits; for the other modes, only the first  $n$  bits are used ( $35 \le n \le 204$ ). The remaining bits are unused (written as 0x0000)
+
+**MODE\_INFO** encoding mode information, which is one of
+
+- MR475 (0x0000)**
+- MR515 (0x0001)**
+- MR59 (0x0002)**
+- MR67 (0x0003)**
+- MR74 (0x0004)**
+- MR795 (0x0005)**
+- MR102 (0x0006)**
+- MR122 (0x0007)**
+
+***unused1...4*** unused, written as 0x0000
+
+As indicated in section 6.1 above, the byte order depends on the host architecture.
+
+# Annex A (informative): Change History
+
+| TSG<br>SA# | Tdoc      | CR   | Rev | Cat | PH     | Vers  | New<br>Vers | Subject                                                                |
+|------------|-----------|------|-----|-----|--------|-------|-------------|------------------------------------------------------------------------|
+| 10         | SP-000577 | 002  |     | A   | Rel-4  | 3.0.0 | 4.0.0       | AMR Core Frame bit ordering (AMR speech Codec; Floating point C-Code   |
+| 12         | SP-010306 | 004  | 1   | A   | Rel-4  | 4.0.0 | 4.1.0       | Limiting predicted codebook gain computing in encoder                  |
+| 12         | SP-010306 | 006  | 1   | A   | Rel-4  | 4.0.0 | 4.1.0       | Correction of decoder operation in error concealment of lost frames    |
+| 12         | SP-010306 | 008  | 1   | A   | Rel-4  | 4.0.0 | 4.1.0       | Correction of mode state bug in AMR decoder                            |
+| 12         | SP-010306 | 012  | 1   | A   | Rel-4  | 4.0.0 | 4.1.0       | Correction of decoder Reset                                            |
+| 12         | SP-010306 | 014  | 1   | A   | Rel-4  | 4.0.0 | 4.1.0       | Correction of comfort noise parameter interpolation bug of AMR decoder |
+| 12         | SP-010306 | 016  | 1   | A   | Rel-4  | 4.0.0 | 4.1.0       | Correction of the TX_TYPE and RX_TYPE identifiers                      |
+|            | MCC       |      |     |     | Rel-4  | 4.1.0 | 4.1.1       | Correction of bugs in code                                             |
+| 13         | SP-010452 | 010  | 1   | A   | Rel-4  | 4.1.1 | 4.2.0       | Correction to make encoder and decoder memories independent            |
+| 13         | SP-010452 | 018  |     | A   | Rel-4  | 4.1.1 | 4.2.0       | Correction of decoder operation in error concealment of lost frames    |
+| 15         | SP-020079 | 019  |     | A   | Rel-4  | 4.2.0 | 4.3.0       | Maintaining bit-exactness with TS 26.073                               |
+| 16         |           |      |     |     |        |       | 5.0.0       | Version for Release 5                                                  |
+| 19         | SP-030088 | 21   | 1   | F   | Rel-5  | 5.0.0 | 5.1.0       | MMS compatible i/o format option                                       |
+| 19         | SP-030088 | 24   |     | A   | Rel-5  | 5.0.0 | 5.1.0       | Correction to floating-point implementation of sp_dec.c                |
+| 20         | SP-030214 | 26   |     | A   | Rel-5  | 5.1.0 | 5.2.0       | Correction on codec mode handling during DTX                           |
+| 22         | SP-030681 | 29   | 1   | F   | Rel-5  | 5.2.0 | 5.3.0       | Correction on the implementation of the interface of decoder.c         |
+| 22         | SP-030682 | 30   | 1   | D   | Rel-6  | 5.3.0 | 6.0.0       | Correction on the default behaviour of the unix makefile               |
+| 23         | SP-040198 | 32   |     | A   | Rel-6  | 6.0.0 | 6.1.0       | Correction of floating point AMR DTX functionality                     |
+| 36         | SP-070321 | 0033 | 1   | F   | Rel-7  | 6.1.0 | 7.0.0       | Bit order of Mode Indication in AMR comfort noise frames               |
+| 42         |           |      |     |     | Rel-8  |       | 8.0.0       | Version for Release 8                                                  |
+| 46         |           |      |     |     | Rel-9  |       | 9.0.0       | Version for Release 9                                                  |
+| 51         |           |      |     |     | Rel-10 |       | 10.0.0      | Version for Release 10                                                 |
+| 57         |           |      |     |     | Rel-11 |       | 11.0.0      | Version for Release 11                                                 |

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+
+
+
+
+
+
+# --- Contents
+
+|                                                            |           |
+|------------------------------------------------------------|-----------|
+| Foreword .....                                             | 4         |
+| Introduction .....                                         | 4         |
+| 1 Scope.....                                               | 5         |
+| 2 References.....                                          | 5         |
+| 3 Definitions and abbreviations .....                      | 6         |
+| 3.1 Definitions.....                                       | 6         |
+| 3.2 Abbreviations .....                                    | 6         |
+| 4 General.....                                             | 7         |
+| 5 ITU-T H.324 .....                                        | 8         |
+| 6 Modifications to H.324 (3GPP TS 26.111).....             | 8         |
+| 7 Call set-up requirements .....                           | 8         |
+| 8 Terminal implementor's guide (3GPP TR 26.911).....       | 8         |
+| <b>Annex A (informative): Background information .....</b> | <b>9</b>  |
+| A.1 Video I/O Equipment.....                               | 9         |
+| A.2 Video Codec.....                                       | 9         |
+| A.2.1 H.261 .....                                          | 10        |
+| A.2.2 H.263 .....                                          | 10        |
+| A.2.3 MPEG-4 .....                                         | 10        |
+| A.3 Audio I/O Codec .....                                  | 10        |
+| A.4 Speech Codec.....                                      | 10        |
+| A.4.1 3GPP AMR .....                                       | 10        |
+| A.4.2 G.723.1 .....                                        | 11        |
+| A.5 User Data Applications .....                           | 11        |
+| A.5.1 Data conferencing – T.120.....                       | 11        |
+| A.5.2 Text conversation – T.140.....                       | 12        |
+| A.6 Data Protocols.....                                    | 12        |
+| A.7 System Control.....                                    | 12        |
+| A.8 Call Set-up.....                                       | 12        |
+| A.9 H.245.....                                             | 12        |
+| A.10 H.223.....                                            | 12        |
+| A.10.1 Level 0.....                                        | 13        |
+| A.10.2 Level 1.....                                        | 13        |
+| A.10.3 Level 2.....                                        | 13        |
+| A.10.4 Level 3.....                                        | 13        |
+| <b>Annex B (informative): Bibliography .....</b>           | <b>13</b> |
+| Annex C (informative): Change history.....                 | 14        |
+
+# --- Foreword
+
+This Technical Specification has been produced by the 3GPP.
+
+The present document introduces the set of specifications which apply to 3G-324M multimedia terminals within the 3GPP system.
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of this TS, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version 3.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 Indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the specification;
+
+# --- Introduction
+
+This document contains a specification for H.324 based multimedia codecs for circuit switched 3GPP networks. The term codec is usually associated with a single media type. However, many multimedia services require a close integration of disparate media types. In this sense, the representations of these media types (in the form of media streams) are at least logically bound into a single multimedia stream. As such, a H.324 based multimedia codec must handle multiplexing/de-multiplexing and skew. It will also have to provide codecs for each of the derived media streams. End-to-end, in-band control is also required for the purposes of configuration and establishing individual media streams. Finally, since 3GPP networks are inherently error prone, error detection and/or correction must also be provided by the multimedia codec since it has a comprehensive view of the bit stream it produces and therefore can apply the most efficient form of error detection and/or correction.
+
+# --- 1 Scope
+
+This specification introduces the set of specifications which apply to 3G-324M multimedia terminals.
+
+# --- 2 References
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+  - For a specific reference, subsequent revisions do not apply.
+  - For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+- [1] ITU-T Recommendation H.223: "Multiplexing protocol for low bitrate multimedia communication"
+- [2] ITU-T Recommendation H.223 — Annex A: "Multiplexing protocol for low bitrate multimedia communication over low error-prone channels"
+- [3] ITU-T Recommendation H.223 — Annex B: "Multiplexing protocol for low bitrate multimedia communication over moderate error-prone channels"
+- [4] ITU-T Recommendation H.223 — Annex C: "Multiplexing protocol for low bitrate multimedia communication over highly error-prone channels"
+- [5] ITU-T Recommendation H.223 — Annex D: "Optional multiplexing protocol for low bitrate multimedia communication over highly error-prone channels"
+- [6] ITU-T Recommendation H.245: "Control protocol for multimedia communication"
+- [7] ITU-T Recommendation G.723.1: "Dual rate speech coder for multimedia communication transmitting at 5.3 & 6.3 kbit/s"
+- [8] ITU-T Recommendation H.263: "Video coding for low bitrate communication"
+- [9] ITU-T Recommendation H.261: "Video CODEC for audiovisual services at p X 64 kbit/s"
+- [10] ITU-T Recommendation H.324: "Terminal for low bitrate multimedia communication"
+- [11] 3GPP TS 26.111: "Modifications to H.324"
+- [12] 3GPP TR 26.911: "Terminal Implementor's Guide"
+- [13] ITU-T Recommendation X.691: "Information Technology - ASN.1 Encoding Rules - Specification of Packed Encoding Rules (PER)"
+- [14] International Standard ISO/IEC 14494-2: "Information technology — Generic coding of audiovisual object — Part 2: Visual, 1999"
+- [15] 3GPP TS 26.071: "Mandatory Speech Codec; General Description"
+- [16] 3GPP TS 26.090: "Mandatory Speech Codec; Speech Transcoding Functions"
+- [17] 3GPP TS 26.073: "Mandatory Speech Codec; ANSI C-Code"
+- [18] ITU-T T.140 (1998) Presentation protocol for text conversation application.
+- [19] 3GPP TS 22.226: "Global Text Telephony; Stage 1"
+- [20] 3GPP TS 24.008: "Mobile Radio Interface - Layer 3 MM/CC Specification".
+
+- [21] 3GPP TS 27.001: "General on Terminal Adaptation Functions (TAF) for Mobile Stations (MS)".
+- [22] 3GPP TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".
+- [23] 3GPP TS 23.108: "Mobile radio interface layer 3 specification; Core Network protocols; stage 2".
+- [24] ITU-T Recommendation G.712: "Transmission performance characteristics of pulse code modulation channels".
+- [25] ITU-T Recommendation T.120: "Data protocols for multimedia conferencing".
+
+# --- 3 Definitions and abbreviations
+
+## 3.1 Definitions
+
+For the purposes of the present document, the following terms and definitions apply.
+
+**H.324 terminal:** ITU-T H.324 recommendation, including Annex C
+
+**3G-324M terminal:** Based on ITU-T H.324 recommendation modified by 3GPP for purposes of 3GPP circuit switched network based video telephony
+
+## 3.2 Abbreviations
+
+For the purposes of the present document, the following abbreviations apply:
+
+|          |                                                   |
+|----------|---------------------------------------------------|
+| ACELP    | Algebraic-Code-Excited Linear-Prediction          |
+| ADC      | Analogue Digital Converter                        |
+| AEC      | Acoustic Echo Cancellation                        |
+| AL       | Adaptation Layer                                  |
+| CCSRL    | Control Channel Segmentation and Reassembly Layer |
+| CELP     | Code-Excited Linear-Prediction                    |
+| CT       | Correlation Threshold                             |
+| DAC      | Digital Analogue Converter                        |
+| DCT      | Discrete Cosine Transformation                    |
+| EI       | Error Indication                                  |
+| EOB      | End Of Block                                      |
+| FEC      | Forward Error Correction                          |
+| GOB      | Group Of Blocks                                   |
+| GQUANT   | Group Quantizer information                       |
+| GTT      | Global Text Telephony                             |
+| HDLC     | High-Level Data Link Control                      |
+| HEC      | Header Error Control                              |
+| ISDN     | Integrated Services Digital Network               |
+| LAPM     | Link Access Procedure for Modems                  |
+| LC       | Logical Channel                                   |
+| MC       | Multiplex Code                                    |
+| MCU      | Multipoint Communication Unit                     |
+| MP-MLQ   | Multipulse Maximum Likelihood Quantization        |
+| MPL      | Multiplex Payload Length                          |
+| MR-ACELP | Multi-rate ACELP                                  |
+| PC       | Personal Computer                                 |
+| MCU      | Multipoint Conference Unit                        |
+| MUX      | H.223 Multiplex layer                             |
+| PDU      | Protocol Data Unit                                |
+| SN       | Sequence Number                                   |
+| VLC      | Variable Length Code                              |
+
+# 4 General
+
+3G-324M terminals provide real-time video, audio, or data, in any combination, including none, over 3GPP circuit-switched, radio networks. They are based on ITU-T H.324 with Annex C, and Annex H when mobile multilink operation is supported. Communication may be either 1-way or 2-way. Such terminals may be part of a portable device or integrated into an automobile or other non fixed location device. They may also be fixed, stand-alone devices; for example, a video telephone or kiosk. 3G-324M terminals may also be integrated into PCs and workstations.
+
+In addition to 3G-324M to 3G-324M communication, interoperation with other types of multimedia telephone terminals is possible, however a gateway may be required.
+
+Multipoint communication between more than two 3G-324M terminals is possible using a Multipoint Communication Unit (MCU). MCU functionality is for further study.
+
+3G-324M terminals are based on ITU-T H.324 with Annex C, and Annex H when mobile multilink operation is supported. For performance reasons and to reference the call set-up procedures, some modifications to H.324 were made. These are described in 3GPP TS 26.111, except call set-up procedures are described in 3GPP TS 24.008, 27.001, 29.007 and 23.108. 3G-324M terminals shall conform to these specifications. Because of the many options in H.324, an implementor's guide, 3GPP TR 26.911, provides preferred options for 3G-324M implementations.
+
+Figure 1 below shows the functional components of a generic 3GPP multimedia terminal. The video, speech, data and multilink components are optional. If a media type is supported, the standards indicated are mandatory except those enclosed in square brackets are optional.
+
+![Figure 1: Scope of circuit switched multimedia 3GPP specification. The diagram shows the functional components of a generic 3GPP multimedia terminal. A central dashed box labeled '3GPP TS 26.111' contains several functional blocks. On the left, four input blocks are shown: 'Video I/O Equipment', 'Audio I/O Equipment', 'User Data Applications [T.120, ...]', and 'System Control'. The 'Video I/O Equipment' connects to a 'Video Codec H.263, [MPEG-4, H.261 ...]'. The 'Audio I/O Equipment' connects to a 'Speech Codec 3GPP-AMR, [G.723.1 ...]'. The 'Speech Codec' connects to an 'Optional Receive Path Delay' block, which then connects to a 'Multiplex/Demultiplex H.223, H.223 Annex A, H.223 Annex B, [H.223 Annex C, H.223 Annex D]' block. The 'User Data Applications' connect to 'Data Protocols [V.14, LAPM, ...]', which also connect to the 'Multiplex/Demultiplex' block. The 'System Control' connects to an 'H.245' block, which connects to 'CCSRL', which connects to 'NSRP[LAP M/V.42]', which then connects to the 'Multiplex/Demultiplex' block. The 'Multiplex/Demultiplex' block connects to an 'Optional Multilink H.324 Annex H' block, which in turn connects to the '3GPP Network'. The 'System Control' also connects to a 'Call Set-up' block, which connects to the '3GPP Network'.](ca4d4ff86cf319ed7cc36a1ecda29101_img.jpg)
+
+Figure 1: Scope of circuit switched multimedia 3GPP specification. The diagram shows the functional components of a generic 3GPP multimedia terminal. A central dashed box labeled '3GPP TS 26.111' contains several functional blocks. On the left, four input blocks are shown: 'Video I/O Equipment', 'Audio I/O Equipment', 'User Data Applications [T.120, ...]', and 'System Control'. The 'Video I/O Equipment' connects to a 'Video Codec H.263, [MPEG-4, H.261 ...]'. The 'Audio I/O Equipment' connects to a 'Speech Codec 3GPP-AMR, [G.723.1 ...]'. The 'Speech Codec' connects to an 'Optional Receive Path Delay' block, which then connects to a 'Multiplex/Demultiplex H.223, H.223 Annex A, H.223 Annex B, [H.223 Annex C, H.223 Annex D]' block. The 'User Data Applications' connect to 'Data Protocols [V.14, LAPM, ...]', which also connect to the 'Multiplex/Demultiplex' block. The 'System Control' connects to an 'H.245' block, which connects to 'CCSRL', which connects to 'NSRP[LAP M/V.42]', which then connects to the 'Multiplex/Demultiplex' block. The 'Multiplex/Demultiplex' block connects to an 'Optional Multilink H.324 Annex H' block, which in turn connects to the '3GPP Network'. The 'System Control' also connects to a 'Call Set-up' block, which connects to the '3GPP Network'.
+
+**Figure 1 Scope of circuit switched multimedia 3GPP specification. Items in [brackets] are optional.**
+
+Short descriptions of ITU-T H.324, 3GPP TS 26.111, and 3GPP TR 26.911 are given below.
+
+# 5 ITU-T H.324
+
+ITU-T H.324 describes terminals for low bitrate multimedia communication. That ITU-T recommendation contains “ANNEX C, Multimedia Telephone Terminals Over Error Prone Channels” (sometimes referred to as H.324/M) and “ANNEX H, Mobile Multilink Operation”. These annexes are considered an integral part of the recommendation.
+
+Therefore, herewith H.324 shall mean ITU-T H.324 with Annex C. When multilink operation is utilized, H.324 shall also mean to include H.324 Annex H.
+
+Originally designed for V.34 modems, H.324 now supports ISDN and wireless networks. Therefore, it is well suited as a basis for 3GPP multimedia codecs. Relevant to wireless networks, H.324 describes the overall system architecture and introduces control (H.245), mux (H.223), video (H.261 and H.263), text (T.140), and audio (G.723.1).
+
+Annex A provides a short overview of H.324 and multimedia codecs.
+
+# --- 6 Modifications to H.324 (3GPP TS 26.111)
+
+To enable cost-effective, high-quality H.324 terminals for 3GPP networks, some modifications were made to H.324. These modifications are described in 3GPP TS 26.111. Terminals adhering to this specification are herewith known as 3G-324M terminals. 3G-324M terminals shall conform to 3GPP TS 26.111.
+
+# --- 7 Call set-up requirements
+
+H.324 does not describe call set-up procedures for 3GPP networks. These are described in 3GPP TS 24.008, 27.001, 29.007, 23.108 and shall be used for 3G-324M terminals.
+
+# --- 8 Terminal implementor's guide (3GPP TR 26.911)
+
+A successful 3G-324M terminal will have to function well at bandwidths as low as 32 KBPS and in potentially high error rate environments. 3G-324M contains many options that may be employed by an implementor. To help choose which options and combinations of options are useful, an implementor's guide is provided in 3GPP TR 26.911.
+
+# --- Annex A (informative): Background information
+
+The section is intended for informational purposes only. This is not an integral part of this specification. Each section below relates to the functional components in figure 1.
+
+---
+
+## A.1 Video I/O Equipment
+
+For a video telephone this would most likely consist of a video camera and display monitor. Other possible input sources could be a VCR or disk drive. While most applicable I/O equipment relies on a standard format for the video signal or bit stream, this format is likely to differ from that mandated by the video codec. In such cases, circuitry or software is used to transcode between the two formats.
+
+---
+
+## A.2 Video Codec
+
+ITU-R 601 (NTSC or PAL) is a typical video input signal and represents a bit stream of 20.7 Mbyte/s for the actual image (excluding blanking intervals). The first order of compression occurs by reducing the resolution of the input signal.<sup>1</sup> For example, CIF resolution at 30 fps produces a bit stream 4.6 Mbyte/s. Additional savings occur by dropping frames. In a videoconference, where motion is relatively slow, 10 fps is considered adequate. Thus, the original signal of 20.7 Mbytes/s could be reduced to 1.5 Mbyte/s with just these techniques. However, this is still 188 times greater than can be transmitted on, for example, a 64 KBPS channel. Substantial compression is still required, especially considering that framing, control, and audio would as well require a portion of the available bandwidth.
+
+To achieve the degree of compression required for video telephony, all of the video codecs that can currently be employed in a 3GPP multimedia codec use a combination of spatial and temporal redundancy reduction to reduce the bandwidth required by the video media stream. Spatial redundancy can be reduced by converting the input signal from the time domain to the frequency domain using a DCT. This produces a DC value and other coefficients, where most of the scene energy is concentrated in the coefficients corresponding to the lower frequencies. Next, a coarse quantizer is applied (which, in this domain, has little effect on image quality). This results in many of the coefficients being encoded to 0. The significant coefficients are encoded to a much smaller range of values. The coefficients are then reordered so that, typically, the larger magnitude values will occur first followed by 0 value coefficients. Finally, the coefficients are replaced with a count of the number of zero value coefficients followed by the value of a nonzero coefficient. This combination is translated into a VLC. Applying this type of compression to the entire video frame produces an intra frame.
+
+Despite the efficiency of intra coding, significantly more compression is required. In addition to removing spatial redundancy, all video codecs apply temporal reduction as well. This is achieved by comparing the current frame to the previous and estimating the set of vectors which when applied to their respective areas of the scene would create the new, current frame based on the old, previous frame. The match is usually not perfect, so an error component is transmitted as well. The error component is also transformed to the frequency domain, so the same compression efficiency achieved in the intra frame is achieved here as well — enhanced by the fact the range of error coefficients is less than intra coefficients. Since generally only a few areas of a scene change from frame to frame, high compression can be achieved by sending a series of inter frames. If the error component for a particular block is too large, it can be encoded as an intra block.
+
+Since, by their nature, VLCs are not fixed length, a single bit error can make it impossible to decode an entire frame. Unfortunately, each inter coded frame relies on its previous frame to be decoded. Thus, a single bit error can destroy the entire remaining bit stream. Video codecs have various ways of handling errors. The simplest is to use error detection to determine if a frame contains an error. The transmitter is then signalled that an error occurred. It then sends an intra coded frame, which does not depend on any previous frames. This approach consumes considerable bandwidth and is only practical for very low error networks. Other, more sophisticated schemes are available using the video codecs available to 3G-324M terminals.
+
+---
+
+<sup>1</sup> Note that ITU-R 601 represents 16 bit precision colour, whereas true colour is usually considered to require 24 bit precision. Also, the spatial resolution of ITU-R 601 is substantially less than can be achieved with normal human vision.
+
+### A.2.1 H.261
+
+H.261 supports CIF and QCIF images as input. It provides good video quality at 64 kbit/s or higher. It uses BCH codes for Forward Error Correction (FEC). However, this is not recommended for H.324.
+
+### A.2.2 H.263
+
+H.263 is an extension of H.261. It allows sub-QCIF, 4CIF and 16CIF as additional input formats. H.263, in its original version, provides four annexes that describe optional modes for enhanced coding.
+
+- Advanced prediction mode (Annex F) provides half-pel motion estimation, median-based motion vector prediction, 4 motion vectors per macroblock (one per block), and overlapped block motion compensation
+- Unrestricted motion vectors (Annex D) work in conjunction with advanced prediction mode and allow motion vectors to point outside the picture area
+- Arithmetic coding (Annex E) can be used instead of variable length coding
+- PB-frames (Annex G) allow bi-directional prediction similar to MPEG
+
+Other significant differences exist, but require a level of detail to explain that renders them outside the scope of this document.
+
+A second version of H.263 (known as H.263+) adds annexes I through T, some of which address error prone environments and are therefore of special interest to 3GPP multimedia codecs.
+
+### A.2.3 MPEG-4
+
+MPEG-4 Visual (ISO/IEC 14496-2) is a generic video codec. One of its target areas is mobile communications. Error resiliency and high efficiency make this codec particularly well suited for 3G-324M.
+
+MPEG-4 Visual is organised into Profiles. Within a Profile, various Levels are defined. Profiles define subsets of tool sets. Levels are related to computational complexity. Among these Profiles, Simple Visual Profile provides error resilience (through data partitioning, RVLC, resynchronization marker and header extension code) and low complexity.
+
+MPEG-4 allows various input formats, including general formats such as QCIF and CIF. It is also baseline compatible with H.263.
+
+## --- A.3 Audio I/O Codec
+
+Generally, a video telephone would require a handset, headset, or microphone and speaker. Often, integrated circuits are employed that convert the typically analogue input signal to a PCM format bit stream (ADC) and convert PCM to an analogue signal for acoustic output (DAC). This is helpful since many speech codecs use PCM for input and output. Video telephones often use a separate microphone and speaker. This allows the user to be seen without a handset or headset. However, if this is so, AEC will be required.
+
+## --- A.4 Speech Codec
+
+### A.4.1 3GPP AMR
+
+The AMR codec uses eight source codecs with bit-rates of 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kbit/s. The coder operates on speech frames of 20 ms corresponding to 160 samples at the sampling frequency of 8000 sample/s. It performs the mapping from input blocks of 160 speech samples in 13-bit uniform PCM format to encoded blocks of 95, 103, 118, 134, 148, 159, 204, and 244 bits and from encoded blocks of 95, 103, 118, 134, 148, 159, 204, and 244 bits to output blocks of 160 reconstructed speech samples. The coding scheme for the multi-rate coding modes is the so-called Algebraic Code Excited Linear Prediction Coder (ACELP). The multi-rate ACELP coder is referred to as MR-ACELP. At each 160 speech samples, the speech signal is analysed to extract the parameters of the CELP model (LP filter coefficients, adaptive and fixed codebooks' indices and gains). These parameters are encoded and transmitted. At the decoder, these parameters are decoded and speech is synthesised by filtering the reconstructed excitation signal through the LP synthesis filter.
+
+The adaptive multi-rate speech codec is described in a bit-exact arithmetic in form of a fixed-point ANSI-C code to allow for easy type approval as well as general testing purposes of the adaptive multi-rate speech codec.
+
+The DTX mechanism includes a Voice Activity Detector (VAD) on the TX side; evaluation of the background acoustic noise on the TX side, in order to transmit characteristic parameters to the RX side; and generation of comfort noise on the RX side during periods where the radio transmission is turned off.
+
+The AMR specification contains error concealment. The purpose of frame substitution is to conceal the effect of lost AMR speech frames. The purpose of muting the output in the case of several lost frames is to indicate the breakdown of the channel to the user and to avoid generating possible annoying sounds as a result from the frame substitution procedure.
+
+### A.4.2 G.723.1
+
+G.723.1 can be used for compressing the speech or other audio signal component of multimedia services at a very low bitrate as part of H.324. This coder has two bit-rates associated with it, 5.3 and 6.3 kbit/s. The higher bitrate has greater quality. The lower bit-rate gives good quality and provides system designers with additional flexibility. Both rates are a mandatory part of the encoder and decoder. It is possible to switch between the two rates at any frame boundary. An option for variable rate operation using discontinuous transmission and noise fill during non-speech intervals is also possible using a series of silence frames or a single silence frame followed by no frames until speech is detected.
+
+G.723.1 encodes speech or other audio signals in frames using linear predictive analysis-by-synthesis coding. The excitation signal for the high rate coder is Multipulse Maximum Likelihood Quantization (MP-MLQ) and for the low rate coder is Algebraic-Code-Excited Linear-Prediction (ACELP). The frame size is 30 ms and there is an additional look ahead of 7.5 msec,. This coder is designed to operate with a digital signal obtained by first performing telephone bandwidth filtering (ITU-T Recommendation G.712) of the analogue input, then sampling at 8000 Hz and then converting to 16-bit linear PCM for the input to the encoder. The output of the decoder is converted back to analogue by similar means.
+
+G.723.1 has been designed to be robust for indicated frame erasures. An error concealment strategy for frame erasures has been included in the decoder. However, this strategy must be triggered by an external indication that the bit stream for the current frame has been erased. This can be achieved in H.324 using the AL2 Error Indication (EI) flag and the optional AL2 Sequence Number (SN). Because the coder was designed for burst errors, there is no error correction mechanism provided for random bit errors. If a frame erasure has occurred, the decoder switches from regular decoding to frame erasure concealment mode.
+
+G.723.1 contains three annexes. Annex A describes the silence compression system designed for the G.723.1 speech coder (mentioned above). Annex B describes an alternative implementation of G.723.1 contained in floating point C source code. Annex C specifies a channel coding scheme which can be used with the triple rate speech codec G.723.1. The channel codec is scalable in bit-rate and is designed for mobile multimedia applications as a part of the overall H.324 family of standards.
+
+## --- A.5 User Data Applications
+
+### A.5.1 Data conferencing – T.120
+
+An example of a User Data Application is T.120. This protocol allows multipoint data conferencing that includes data and image transferral. Other functions, such as shared whiteboards and applications, are possible.
+
+### A.5.2 Text conversation – T.140
+
+The real time text conversation application, is supported by the presentation protocol ITU-T T.140 [19]. The Global Text Telephony feature is implemented in the CS Multimedia environment by applying T.140, as specified in H.324. The text stream may be opened simultaneously with voice, video and other data applications. Text-only sessions are also possible. Further requirements applicable to the Global Text Telephony feature are specified in TS 22.226 [20].
+
+The data protocol for T.140 is specified in H.324 to be AL1.
+
+## --- A.6 Data Protocols
+
+Various data protocols can be supported. These always support data applications (see A.5 User Data Applications). A specific protocol or set of protocols is often stipulated by the data application. Each protocol provides varying degrees of error detection and/or correction.
+
+## --- A.7 System Control
+
+In general, system control constitutes the overall state machine for the terminal. It usually has to be aware of when a connection has been established. At that point it can begin H.245 procedures such as master/slave determination, capabilities exchange, and opening logical channels. Upon call termination, either initiated at the near or far ends, system control generally initiates H.245 end session procedures.
+
+## --- A.8 Call Set-up
+
+All out-of-band network signalling for the purpose of call control is handled by call set-up, which is usually implemented as a state machine. This includes initiating, answering, and tearing down calls.
+
+## --- A.9 H.245
+
+H.245 specifies the syntax and semantics for in-band, terminal-to-terminal control messages and the procedures for their use. Most importantly, H.245 is used for master/slave determination, capabilities exchange, H.223 mux table transmission, and opening and closing logical channels. There is also a large array of general control and indication messages. H.245 addresses a wide range of terminals and applications. Therefore, only a subset of the messages listed in H.245 pertain to 3G-324M terminals. Messages fall into one of four categories: Request (requires a Response), Response (in response to a Request), Command (requires an action), and Indication (informative only).
+
+H.245 messages are carried on a single logical channel within the H.223 mux. This channel is labelled LC 0 and is considered to be open upon establishing digital communications end-to-end and survives until digital communication is terminated. Due to the characteristics of the H.223 mux, bandwidth for H.245 messages is allocated on an as-needed basis. Since most H.245 traffic occurs at the beginning and end of the session, this conserves much needed bandwidth for video and audio. Error control is not provided for within H.245 and is specified elsewhere.
+
+## --- A.10 H.223
+
+H.223 describes the multiplexing protocol used between H.324 terminals. It is packet oriented and each packet can contain a subset of a maximum of 65536 LCs. Each LC represents a single media, information, or control channel. The H.223 protocol is split into two layers, the lowest being the Multiplex Layer.
+
+The Multiplex Layer exchanges data with the end terminal via MUX-PDUs. Multiplex table entries, of which there are 16 (and can be changed during a session), describe which octets from within the PDU are allocated to which logical channels. The multiplex table entry employed for a particular PDU is indicated by the 4 bit MC field in the MUX-PDU header. MUX-PDUs contain an integer number of octets. Errors within the MUX-PDU header are controlled using the HEC field in the MUX-PDU header. H.324 terminals utilising the V.34 transmission protocol frame MUX-PDUs with HDLC. Bit stuffing is used for data transparency in this case.
+
+Above the Multiplex Layer is the Adaptation Layer, of which there are three different types.
+
+- 1) AL1 is designed primarily for control information and data protocols. It can be either framed or unframed and does not provide any error control.
+- 2) AL2 is designed primarily for the transfer of digital audio. AL2 PDUs contain 1 octet for an 8-bit CRC and an optional octet for a sequence number.
+- 3) AL3 is designed primarily for the transfer of digital video. AL3 PDUs contain 2 octets for a 16-bit CRC. There is also optionally 1 or 2 octets for control. AL3 also allows limited retransmission.
+
+For purposes of video telecommunications over wireless networks, four annexes to H.223 have been created. These create four levels of error detection and error correction.
+
+### A.10.1 Level 0
+
+Level 0 applies to H.223 as described above.
+
+### A.10.2 Level 1
+
+Level 1, described in Annex A, replaces HDLC framing with 1 or 2 16 bit flags. Unlike HDLC, Level 1 does not guarantee data transparency. However, if the MUX-PDU header is constructed in such a way as to make emulating the Level 1 framing flags impossible, data transparency can be achieved by correctly decoding the MUX-PDU. Should there be an error in the MUX-PDU header, resynchronization techniques will have to be applied.
+
+### A.10.3 Level 2
+
+Level 2, described in Annex B, uses the same framing as Level 1, but utilises a 3 octet header. This header starts with a 4 bit MC, which is the same as in Level 0. This is followed by an 8-bit MPL-field, with a range of values 0 – 254. Lastly, a 12 bit extended Golay code is used for parity bits. The PM in Level 2 is signalled through the polarity of the MUX-PDU flag. If the output of the correlator is greater than or equal to CT, the PM is 0. If it is less than or equal to -CT, the PM equals 1. After the parity bits, there can be an optional MUX-PDU header for the previous (corrupted) MUX-PDU. This 1 octet field uses the format described in Level 0. Level 2 also offers enhanced packet resynchronization.
+
+### A.10.4 Level 3
+
+Level 3, described in Annexes C and D, provides error correction capabilities at the mux level.
+
+# --- Annex B (informative): Bibliography
+
+(void)
+
+# Annex C (informative): Change history
+
+| Change history |       |           |     |     |                                                                   |        |        |
+|----------------|-------|-----------|-----|-----|-------------------------------------------------------------------|--------|--------|
+| Date           | TSG # | TSG Doc.  | CR  | Rev | Subject/Comment                                                   | Old    | New    |
+| 06-1999        | 04    |           |     |     | Approved at TSG-SA#4                                              |        | 3.0.0  |
+| 09-2000        | 09    | SP-000395 | 001 |     | CS Multimedia Codec specification for real time text conversation | 3.0.1  | 4.0.0  |
+| 03-2001        | 011   | SP-010105 | 002 | 1   | Support of mobile multi-link operation in 3G-324M                 | 4.0.0  | 4.1.0  |
+| 03-2001        | 011   | SP-010105 | 004 | 1   | Correction of incorrect reference                                 | 4.0.0  | 4.1.0  |
+| 06-2002        | 016   |           |     |     | Version for Release 5                                             | 4.1.0  | 5.0.0  |
+| 12-2004        | 026   |           |     |     | Version for Release 6                                             | 5.0.0  | 6.0.0  |
+| 06-2007        | 036   |           |     |     | Version for Release 7                                             | 6.0.0  | 7.0.0  |
+| 12-2008        | 042   |           |     |     | Version for Release 8                                             | 7.0.0  | 8.0.0  |
+| 12-2009        | 046   |           |     |     | Version for Release 9                                             | 8.0.0  | 9.0.0  |
+| 03-2011        | 051   |           |     |     | Version for Release 10                                            | 9.0.0  | 10.0.0 |
+| 09-2012        | 057   |           |     |     | Version for Release 11                                            | 10.0.0 | 11.0.0 |

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+
+
+
+
+
+
+# --- Contents
+
+|                                                       |    |
+|-------------------------------------------------------|----|
+| Foreword .....                                        | 4  |
+| Introduction .....                                    | 4  |
+| 1 Scope.....                                          | 5  |
+| 2 References.....                                     | 5  |
+| 3 Definitions and abbreviations .....                 | 6  |
+| 3.1 Definitions.....                                  | 6  |
+| 3.2 Abbreviations .....                               | 6  |
+| 4 General .....                                       | 6  |
+| 5 Document structure .....                            | 6  |
+| 6 Functional requirements.....                        | 7  |
+| 6.1 Required elements .....                           | 7  |
+| 6.2 Information streams.....                          | 7  |
+| 6.3 Modem .....                                       | 7  |
+| 6.4 Multiplex .....                                   | 7  |
+| 6.5 Control channel .....                             | 7  |
+| 6.6 Video channels .....                              | 7  |
+| 6.6.1 MPEG-4 interface to multiplex .....             | 10 |
+| 6.6.2 H.264 (MPEG-4 AVC) interface to multiplex ..... | 10 |
+| 6.7 Audio channels.....                               | 11 |
+| 6.8 Data channels .....                               | 11 |
+| 7 Terminal procedures .....                           | 11 |
+| 8 Optional enhancements .....                         | 11 |
+| 9 Interoperation with other terminals.....            | 11 |
+| 10 Multipoint considerations .....                    | 11 |
+| 11 Maintenance.....                                   | 12 |
+| Annex A (informative): Change History.....            | 13 |
+
+# --- Foreword
+
+This Technical Specification (TS) has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- Introduction
+
+In the present document is described additions, deletions, and changes made to ITU-T Recommendation H.324 [10] with annex C for the purpose of using that recommendation as a basis for the technical specification for circuit switched multimedia service in 3GPP networks. The present document does not address call setup procedures, but references to the specifications which cover call setup are found in 3GPP TS 26.110 [11].
+
+# --- 1 Scope
+
+In ITU-T Recommendation H.324 [10] with annex C describes a generic multimedia codec for use in error-prone, wireless networks. The scope of the present document are the changes, deletions, and additions to those texts necessary to fully specify a multimedia codec for use in 3GPP networks. Note that this implicitly excludes the network interface and call setup procedures. Also excluded are any general introductions to the system components.
+
+# --- 2 References
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+  - For a specific reference, subsequent revisions do not apply.
+  - For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+- [1] ITU-T Recommendation H.223: "Multiplexing protocol for low bit rate multimedia communication".
+- [2] ITU-T Recommendation H.223 - Annex A: "Multiplexing protocol for low bit rate multimedia mobile communication over low error-prone channels".
+- [3] ITU-T Recommendation H.223 - Annex B: "Multiplexing protocol for low bit rate multimedia mobile communication over moderate error-prone channels".
+- [4] ITU-T Recommendation H.223 - Annex C: "Multiplexing protocol for low bit rate multimedia mobile communication over highly error-prone channels".
+- [5] ITU-T Recommendation H.223 - Annex D: "Optional multiplexing protocol for low bit rate multimedia mobile communication over highly error-prone channels".
+- [6] ITU-T Recommendation H.245: "Control protocol for multimedia communication".
+- [7] ITU-T Recommendation G.723.1: "Dual rate speech coder for multimedia communication transmitting at 5,3 and 6,3 kbit/s".
+- [8] ITU-T Recommendation H.263: "Video coding for low bitrate communication".
+- [9] ITU-T Recommendation H.261: "Video CODEC for audiovisual services at px64 kbit/s".
+- [10] ITU-T Recommendation H.324: "Terminal for low bitrate multimedia communication".
+- [11] 3GPP TS 26.110: "Codec for Circuit Switched Multimedia Telephony Service; General description".
+- [12] 3GPP TR 26.911: "Codec for circuit switched multimedia telephony service; terminal implementor's Guide (Release 4)".
+- [13] ITU-T Recommendation X.691: "Information Technology - ASN.1 Encoding Rules - Specification of Packed Encoding Rules (PER)".
+- [14] ISO/IEC 14496-2: "Information technology - Coding of audio-visual objects - Part 2: Visual".
+- [15] 3GPP TS 26.071: "General description".
+- [16] 3GPP TS 26.090: "Transcoding functions".
+- [17] 3GPP TS 26.073: "Adaptive Multi-Rate (AMR); ANSI C source code".
+
+- [18] 3GPP TS 26.171: "AMR Wideband Speech codec; General Description".
+- [19] ITU-T Recommendation H.264 (2003): "Advanced video coding for generic audiovisual services" | ISO/IEC 14496-10:2003: "Information technology – Coding of audio-visual objects – Part 10: Advanced Video Coding".
+- [20] ITU-T Recommendation H.241 (2003): "Extended video procedures and control signals for H.300 series terminals".
+- [21] ITU-T Recommendation G.722.2 Annex F (2002): "AMR-WB usage in H.245".
+- [22] 3GPP TS 26.201 : "Adaptive Multi-Rate – Wideband (AMR-WB) speech codec ; Frame Structure."
+
+# --- 3 Definitions and abbreviations
+
+## 3.1 Definitions
+
+For the purposes of the present document, the following terms and definitions apply:
+
+**H.324:** ITU-T H.324 [10] with annex C
+
+**3G-324M terminal:** based on ITU-T H.324 [10] recommendation modified by 3GPP for purposes of 3GPP circuit switched network based video telephony
+
+## 3.2 Abbreviations
+
+For the purposes of the present document, the following abbreviations apply:
+
+|        |                              |
+|--------|------------------------------|
+| AMR    | Adaptive Multi-Rate          |
+| AMR-WB | AMR Wide-Band                |
+| AVC    | Advanced Video Codec         |
+| FLC    | Fixed Length Code            |
+| RVLC   | Reverse Variable Length Code |
+| DP     | Data Partitioning            |
+| RM     | Resynchronization Marker     |
+| MCU    | Multipoint Control Unit      |
+
+# --- 4 General
+
+The present document contains any deviations to ITU-T H.324 [10] required for the specification of 3G-324M Terminals.
+
+# --- 5 Document structure
+
+The structure of H.324 [10] is followed in the present document. Where there are no differences in a specific section, that section is skipped. Where differences are minor, only the differences are described. Where major differences exist, the section is rewritten in the present document. It is important to note that for wireless terminals, Annex C of H.324 [10] supersedes respective portions of the main body of H.324 [10] For the present document, these modifications are treated as if they are part of the main body of H.324 [10] Therefore, a reader must keep in mind both the main body and Annex C of H.324 [10] when reading the present document.
+
+# --- 6 Functional requirements
+
+## 6.1 Required elements
+
+3G-324M implementations are not required to have each functional element except a wireless interface, H.223 [1] with Annex A and B multiplex, and H.245 [6] version 3 or later versions for system control protocol.
+
+3G-324M terminals offering audio communication shall support the AMR audio codec. Support for G.723.1 [7] is not mandatory, but recommended.
+
+3G-324M terminals offering video communication shall support the H.263 [8] video codec. Support for MPEG-4 simple profile and H.261 [9] is optional.
+
+3G-324M terminals shall support H.223 [1] with annex A and annex B.
+
+3G-324M terminals shall support at least 32 kbit/s minimum bit rate at the mux to wireless network interface.
+
+## 6.2 Information streams
+
+V.25ter discussion does not apply.
+
+## 6.3 Modem
+
+Does not apply.
+
+## 6.4 Multiplex
+
+3G-324M terminals shall support H.223 [1] with annex A and annex B. All other aspects shall follow H.324 [10] with annex C. H.223 [1] Annex C and D are optional.
+
+## 6.5 Control channel
+
+No differences with H.324 [10].
+
+Should it not be possible to signal an element of the 3G-324M terminal using a published version of H.245 [6], a procedure will be defined here.
+
+## 6.6 Video channels
+
+Support for H.261 [9] is optional.
+
+Support for MPEG-4 Visual is optional. When supported, MPEG-4 Visual codecs shall support Simple Profile @ Level 0. The FLC code 0000 1000 in Table G-1 – "FLC table for profile\_and\_level\_indication" in ISO/IEC 14496-2 [14] is assigned to it. Additional information can be found in [14].
+
+MPEG-4 Visual Simple Profile @ level 0 provides error concealment as part of the simple profile through Data Partitioning (DP), Reversible Variable Length Coding (RVLC), Resynchronization Marker (RM) and header extension code. MPEG-4 Visual is baseline compatible with H.263 [8].
+
+When opening a logical channel for MPEG-4 Visual, configuration information (Visual Object Sequence Header, Visual Object Header, and Video Object Layer Header) shall be sent in the decoderConfigurationInformation parameter. The same information shall also be sent in the MPEG-4 video bitstream. If the operational mode of MPEG-4 Visual encoder needs to be changed, the existing MPEG-4 video logical channel shall be closed and H.245 [6] procedures for opening a new MPEG-4 video logical channel shall be started. The new operational mode shall be indicated in the parameters of the new logical channel.
+
+Support for H.264 (MPEG-4 AVC) [19] is optional. When supported, H.264 codecs shall support Baseline level 1, without requirements on output timing conformance (Annex C of [19]).
+
+Support for H.264 [19] shall be signalled according to H.241 chapter 8 "Capability Exchange signalling" [20].
+
+When opening a logical channel for H.264 [19], initial sequence parameter set(s) and picture parameter set(s) should be sent in a H.264 DecoderConfigurationInformation (DCI) defined in Table 1 below, amending H.241 parameters [20]. Additionally, decoder capabilities may be sent in a H.264 AcceptRedundantSlices and a H.264 ProfileIOP defined in Table 2 and 3 below, amending H.241 parameters [20].
+
+NOTE: The H.264 DCI parameter can also be used when either party signals a H.245 [6] MasterSlaveDetermination terminalType parameter greater than 128, such as e.g. a Multipoint Conference Unit (MCU).
+
+A sequence parameter set or a picture parameter set with a particular value of seq\_parameter\_set\_id or pic\_parameter\_set\_id, respectively, sent in the H.264 [19] DCI shall be identical to the earliest occurrence of the sequence parameter set or picture parameter set with the same value of seq\_parameter\_set\_id or pic\_parameter\_set\_id, respectively, sent in the H.264 bitstream.
+
+If DCI was used when a H.264 [19] logical channel was opened and H.264 sequence parameter sets need to be changed or new sets need to be added during the session, the existing H.264 logical channel shall be closed and H.245 [6] procedures for opening a new H.264 logical channel shall be started, in which sequence parameter set(s) and picture parameter set(s) shall be sent in a DCI. Each sequence parameter set of H.264 [19] shall contain the vui\_parameters syntax structure including the num\_reorder\_frames syntax element set equal to 0.
+
+If H.264 picture parameter sets need to be changed or new sets need to be added during a session, it may be done either by opening a new logical channel using the same procedure as described above or within the current channel, by including picture parameter set NAL units directly in the bitstream.
+
+**Table 1 / TS 26.111 – H.264 Capability Parameter – DecoderConfigurationInformation (DCI)**
+
+|                            |                                                                                                                                                                                                                                                                                                                                                                                                                                           |
+|----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name             | DecoderConfigurationInformation                                                                                                                                                                                                                                                                                                                                                                                                           |
+| Parameter description      | This is a nonCollapsing GenericParameter.<br><br>DecoderConfigurationInformation indicates how to configure the decoder for a particular H.264 video sequence [19]. It contains sequence parameter set NAL units, picture parameter set NAL units, or both, using the byte stream format specified in Annex B/H.264, separating NAL units with a start code. The use of a start code before the first parameter set NAL unit is optional. |
+| Parameter identifier value | 43                                                                                                                                                                                                                                                                                                                                                                                                                                        |
+| Parameter status           | Optional. Shall not be present for Capability Exchange and Mode Request. May be present exactly once for Logical Channel Signalling.                                                                                                                                                                                                                                                                                                      |
+| Parameter type             | OctetString                                                                                                                                                                                                                                                                                                                                                                                                                               |
+| Supersedes                 | -                                                                                                                                                                                                                                                                                                                                                                                                                                         |
+
+A decoder may indicate its' capability to make use of H.264 redundant slices by the following parameter.
+
+**Table 2 / TS 26.111 – H.264 Capability Parameter – AcceptRedundantSlices**
+
+|                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+|----------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name             | AcceptRedundantSlices                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
+| Parameter description      | <p>This is a collapsing GenericParameter.</p> <p>AcceptRedundantSlices indicates the capability to use H.264 redundant slices and corresponds to the MIME video/H264 parameter “redundant-pic-cap”.</p> <p>When False or when the parameter is not present, it indicates that the receiver makes no attempt to use redundant coded pictures to correct incorrectly decoded primary coded pictures and a sender should not send redundant slices.</p> <p>When True, it indicates that the receiver is capable of decoding any such redundant slice that covers a corrupted area in a primary decoded picture (at least partly), and a sender may send redundant slices.</p> <p>When using a H.264 profile (or subset of a profile as indicated by the H.264 ProfileIOP parameter defined in Table 3) and level that disallows the use of redundant slices, this parameter shall be ignored.</p> |
+| Parameter identifier value | 44                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
+| Parameter status           | Optional. May be present exactly once for Capability Exchange Signalling.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
+| Parameter type             | Logical                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
+| Supersedes                 | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
+
+NOTE: An encoder should only code redundant slices if it knows that the far-end decoder makes use of this feature. Encoders should also pay attention to potential implications on end-to-end delay.
+
+A decoder may indicate additional limitations that only the common subset of the algorithmic features and limitations of the Baseline level 1 are supported by the following parameter.
+
+**Table 3 / TS 26.111 – H.264 Capability Parameter – ProfileIOP**
+
+|                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
+|----------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name             | ProfileIOP                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
+| Parameter description      | <p>ProfileIOP indicates that the capability to decode H.264 streams is limited to a common subset of the algorithmic features included in the indicated profile and level.</p> <p>This parameter is a Boolean array.</p> <p>bit 1 (value 128) is constraint_set0_flag.</p> <p>bit 2 (value 64) is constraint_set1_flag.</p> <p>bit 3 (value 32) is constraint_set2_flag.</p> <p>All other bits are reserved, shall be set to 0, and shall be ignored by receivers.</p> <p>constraint_set0_flag, constraint_set1_flag and constraint_set2_flag are defined in [18].</p> <p>As an example, a receiver indicating decoding support of the intersection of the baseline and main profile will signal value 11000000 (constraint_set0_flag = 1, constraint_set1_flag = 1, constraint_set2_flag = 0).</p> |
+| Parameter identifier value | 46                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
+| Parameter status           | Optional. May be present exactly once for Capability Exchange Signalling.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
+| Parameter type             | BooleanArray                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
+| Supersedes                 | -                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
+
+A terminal supporting H.264 encoding should respond to all `videoFastUpdatePicture` commands received via the H.245 control channel. If an H.264 encoder responds to `videoFastUpdatePicture`, it shall use the procedure specified in subclause 6.2.2 of H.241.
+
+A terminal supporting H.264 shall start decoding immediately when it receives data (even if the stream does not start with an IDR access unit) or alternatively no later than it receives the next IDR access unit or the next recovery point SEI message, whichever is earlier in decoding order. The decoding process for a stream not starting with an IDR access unit shall be the same as for a valid H.264 bitstream. However, the client shall be aware that such a stream may contain references to picture not available in the decoded picture buffer. The display behaviour of the client is out of scope of this specification.
+
+NOTE: Terminals may use full-frame freeze and full-frame freeze release SEI messages of H.264 to control the display process.
+
+### 6.6.1 MPEG-4 interface to multiplex
+
+As H.263 [8] encoders align picture start codes with the start of an AL-SDU, the same concept applies to MPEG-4 encoders. The following are the requirements of the MPEG-4 interface to the H.223 [1] multiplex.
+
+- Each 3G-324M MPEG-4 encoder shall align each `visual_object_sequence_start_code` with the start of an AL-SDU.
+- Each 3G-324M MPEG-4 encoder shall align each `group_of_vop_start_code` (the beginning of a GOV field) with the start of an AL-SDU unless the GOV field immediately follows configuration information.
+- Each 3G-324M MPEG-4 encoder shall align each `vop_start_code` with the start of an AL-SDU unless the `vop_start_code` immediately follows configuration information or a GOV field.
+
+In these requirements, GOV stands for `Group_of_VideoObjectPlane()` and Configuration information consists of Visual Object Sequence Header, Visual Object Header, and Video Object Layer Header.
+
+### 6.6.2 H.264 (MPEG-4 AVC) interface to multiplex
+
+Shall conform to the byte stream format according to H.241 chapter 7.1.5 "Transport of H.264 streams in H.324 systems" [20].
+
+More strict alignment of AL-SDU and NAL units may optionally be used. To signal capability for and use of this mode, the generic parameter described in Table 3 shall be used, amending the H.264 Generic Capability in H.241 [20].
+
+**Table 3 / TS 26.111 – H.264 Capability Parameter – NalAlignedMode**
+
+|                            |                                                                                                                                                                                                                                                                                                                                                                                                                |
+|----------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name             | NalAlignedMode                                                                                                                                                                                                                                                                                                                                                                                                 |
+| Parameter description      | This is a collapsing GenericParameter.<br><br>NalAlignedMode indicates that every AL-SDU carrying H.264 shall contain an integer number of NAL units and that the start of the AL-SDU shall be aligned with the start of a NAL. Individual NAL units within the AL-SDU shall be separated by start codes as described in Annex B/H.264. The use of a start code before the first NAL in an AL-SDU is optional. |
+| Parameter identifier value | 45                                                                                                                                                                                                                                                                                                                                                                                                             |
+| Parameter status           | Optional. May be present exactly once for Capability Exchange, Logical Channel, or Mode Request Signalling.                                                                                                                                                                                                                                                                                                    |
+| Parameter type             | Logical                                                                                                                                                                                                                                                                                                                                                                                                        |
+| Supersedes                 | -                                                                                                                                                                                                                                                                                                                                                                                                              |
+
+## 6.7 Audio channels
+
+AMR is the mandatory speech codec. Support for G.723.1 [7] is not mandatory, but recommended. Support for AMR-WB [18] is also recommended.
+
+When AMR-WB is supported, the AMR-WB speech data shall be carried in IF2 frame format as defined in Annex A of 3GPP TS 26.201 [22], and the signalling for AMR-WB shall be according to G.722.2 Annex F [21] with the following additional restrictions:
+
+- octetAlign shall be present
+- The following parameters are not compatible with IF2 frame format, and so shall not be used:
+  - crc
+  - robustSorting
+  - interleaving
+
+When both the receiving and transmitting terminals support multiple codecs in common, the use of AMR and AMR-WB is preferred:
+
+- If both the receiving and transmitting terminals support AMR and other codecs (e.g. G.723.1) but not AMR-WB, then AMR shall be used.
+- If both the receiving and transmitting terminals support AMR and other codecs including AMR-WB, either AMR or AMR-WB shall be used.
+
+Asymmetric configurations with one codec in one direction and another one in the other direction (e.g. AMR in one direction and AMR-WB in the other direction) are allowed, if supported by both terminals.
+
+This applies to connections without an Multipoint Control Unit (MCU).
+
+## 6.8 Data channels
+
+No differences with H.324 [10].
+
+# --- 7 Terminal procedures
+
+See 3GPP TS 26.110 [11].
+
+# --- 8 Optional enhancements
+
+No differences with H.324 [10].
+
+# --- 9 Interoperation with other terminals
+
+For further study.
+
+# --- 10 Multipoint considerations
+
+For further study.
+
+# --- 11 Maintenance
+
+No differences with H.324 [10].
+
+# Annex A (informative): Change History
+
+| History |           |        |                  |              |      |     |                                                                  |
+|---------|-----------|--------|------------------|--------------|------|-----|------------------------------------------------------------------|
+| TSG_#   | TSG_DOC   | SPEC   | VERS_CURRE<br>NT | VERS_<br>NEW | CR   | REV | SUBJECT                                                          |
+| SP-05   | SP-99359  | 26.111 | 3.0.1            | 3.0.2        | 001  |     | Changes to editorial notes.                                      |
+| SP-06   | SP-99434  | 26.111 | 3.0.2            | 3.1.0        | 002  | 2   | Specification of coding parameters for MPEG-4 video codec        |
+| SP-06   | SP-99514  | 26.111 | 3.0.2            | 3.1.0        | 003  |     | Transmission of MPEG-4 configuration information in 3G-324M      |
+| SP-08   | SP-00263  | 26.111 | 3.1.0            | 3.2.0        | 004  |     | Changes to editorial notes                                       |
+| SP-09   | SP-000396 | 26.111 | 3.2.0            | 3.3.0        | 006  |     | MPEG-4 interface to multiplex                                    |
+| SP-10   | SP-000653 | 26.111 | 3.3.0            | 3.4.0        | 005  | 1   | MPEG4 visual simple profile @ level 0                            |
+| SP-11   |           |        |                  | 4.0.0        |      |     | Version for Release 4                                            |
+| SP-16   |           |        | 4.0.0            | 5.0.0        |      |     | Version for Release 5                                            |
+| SP-20   | SP-030215 | 26.111 | 5.0.0            | 5.1.0        | 009  | 1   | Removal of Reference to TS 26.112                                |
+|         |           |        |                  |              |      |     |                                                                  |
+| SP-25   | SP-040659 | 26.111 | 5.1.0            | 6.0.0        | 010  | 3   | 3G-324M Improvements                                             |
+| SP-25   | SP-040648 | 26.111 | 5.1.0            | 6.0.0        | 011  | 1   | 3G-324M Improvements: Addition of optional AMR-WB support        |
+| SP-26   | SP-040842 | 26.111 | 6.0.0            | 6.1.0        | 012  | 1   | Addition of the missing signalling of H.264 decoder capabilities |
+| SP-26   | SP-040842 | 26.111 | 6.0.0            | 6.1.0        | 013  | 1   | Reference Corrections                                            |
+| SP-36   |           |        | 6.1.0            | 7.0.0        |      |     | Version for Release 7                                            |
+| SP-40   | SP-080247 | 26.111 | 7.0.0            | 7.1.0        | 0015 | 1   | Use of AMR-WB in 3G-324M                                         |
+| SP-42   |           |        | 7.1.0            | 8.0.0        |      |     | Version for Release 8                                            |
+| SP-46   |           |        | 8.0.0            | 9.0.0        |      |     | Version for Release 9                                            |
+| SP-51   |           |        | 9.0.0            | 10.0.0       |      |     | Version for Release 10                                           |
+| SP-57   |           |        | 10.0.0           | 11.0.0       |      |     | Version for Release 11                                           |

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+
+
+
+
+
+
+# --- Contents
+
+- Foreword ..... 4
+- Introduction ..... 4
+- 1 Scope..... 5
+- 2 References..... 5
+- 3 Abbreviations ..... 5
+- 4 Interfaces..... 5
+- 5 Narrow Band Speech Telephony Network Echo Control ..... 6
+- 5.1 GSTN Network Echo Cancellation ..... 6
+- Annex A (informative): Change history..... 7
+
+# --- Foreword
+
+This Technical Specification has been produced by the 3<sup>rd</sup> Generation Partnership Project (3GPP).
+
+The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows:
+
+Version x.y.z
+
+where:
+
+- x the first digit:
+  - 1 presented to TSG for information;
+  - 2 presented to TSG for approval;
+  - 3 or greater indicates TSG approved document under change control.
+- y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
+- z the third digit is incremented when editorial only changes have been incorporated in the document.
+
+# --- Introduction
+
+The present document specifies minimum performance requirements for the transmission planning aspects of 3G speech and multi-media services.
+
+The objective is to reach a quality as close as possible to ITU-T standards for PSTN circuits. However, due to technical and economic factors, there cannot be full compliance with the general characteristics of international telephone connections and circuits recommended by the ITU-T.
+
+The performance requirements are specified the main body of the text; the test methods and considerations are described in [tbd].
+
+# --- 1 Scope
+
+The present document specifies minimum performance requirements for the gateway echo control of 3G speech and multi-media services. The present document is applicable to any narrow band speech telephony or multimedia service.
+
+# --- 2 References
+
+The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
+
+- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
+  - For a specific reference, subsequent revisions do not apply.
+  - For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document *in the same Release as the present document*.
+- [1] ITU-T Recommendation G.114 (2000): "One-way transmission time".
+- [2] ITU-T Recommendation G.168 (2000): "Digital network echo cancellers".
+- [3] ITU-T Recommendation G.131 (1996): "Control of talker echo".
+- [4] ITU-T Recommendation G.703 (1998): "Physical/electrical characteristics of hierarchical digital interfaces".
+- [5] ITU-T Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice frequencies".
+
+# --- 3 Abbreviations
+
+For the purposes of the present document, the following abbreviations apply:
+
+|      |                                      |
+|------|--------------------------------------|
+| ADC  | Analogue to Digital Converter        |
+| DAC  | Digital to Analogue Converter        |
+| DTX  | Discontinuous Transmission           |
+| EC   | Echo Canceller                       |
+| EEC  | Electrical Echo Control              |
+| EL   | Echo Loss                            |
+| ERL  | Echo Return Loss                     |
+| ERLE | Echo Return Loss Enhancement         |
+| PCM  | Pulse Code Modulation                |
+| POI  | Point of Interconnection (with PSTN) |
+| PSTN | Public Switched Telephone Network    |
+| TCL  | Terminal Coupling Loss               |
+| TX   | Transmission                         |
+
+# --- 4 Interfaces
+
+The POI with the public switched telephone network (PSTN) will generally be at the 2 048 kbits/ level at an interface in accordance with ITU-T Recommendation G.703 [4]/G.704 or STM1 155Mbit/s. At this point, which is considered to have a relative level of 0 dBr, the analogue signals will be represented by 8-bit A-law or  $\mu$ -law according to ITU-T Recommendation G.711 [5]. Analogue measurements may be made at this point using a standard send and receive side, as defined in ITU-T Recommendations.
+
+# --- 5 Narrow Band Speech Telephony Network Echo Control
+
+## 5.1 GSTN Network Echo Cancellation
+
+Narrow band speech calls from the 3G mobile system to the public GSTN are terminated on local switch line cards where two to four wire conversion takes place. The hybrid used to carry out this function is never perfect and echo is generated which degrades the speech call quality for the 3G mobile user. To overcome this situation an echo cancellation device should be used at the gateway from the 3G mobile network to the GSTN. This echo control device shall conform to ITU-T G.168 [2].
+
+NOTE: Acoustic Echo Control: Narrow band speech calls from the 3G mobile network to the public GSTN involve a high delay. The only echo path that is audible to the GSTN user is the acoustic echo path in the UE. To overcome this echo a Terminal Coupling Loss (TCL) of 46dB should be achieved by the terminal. This provides adequate echo protection for calls up to a delay of 300ms as defined by ITU-T Recommendation G.131 [3].
+
+# --- Annex A (informative): Change history
+
+| Change history |       |           |    |     |                                                       |        |        |
+|----------------|-------|-----------|----|-----|-------------------------------------------------------|--------|--------|
+| Date           | TSG # | TSG Doc.  | CR | Rev | Subject/Comment                                       | Old    | New    |
+| -              | 07    | SP-000020 | -  | -   | Approved at TSG SA #7 and placed under Change Control | -      | 3.0.0  |
+| 03-2001        | 11    | -         | -  | -   | Version for Release 4                                 | 3.0.0  | 4.0.0  |
+| 06-2002        | 16    | -         | -  | -   | Version for Release 5                                 | 4.0.0  | 5.0.0  |
+| 12-2004        | 26    | -         | -  | -   | Version for Release 6                                 | 5.0.0  | 6.0.0  |
+| 06-2007        | 36    | -         | -  | -   | Version for Release 7                                 | 6.0.0  | 7.0.0  |
+| 12-2008        | 42    | -         | -  | -   | Version for Release 8                                 | 7.0.0  | 8.0.0  |
+| 12-2009        | 46    |           |    |     | Version for Release 9                                 | 8.0.0  | 9.0.0  |
+| 03-2011        | 51    |           |    |     | Version for Release 10                                | 9.0.0  | 10.0.0 |
+| 09-2012        | 57    |           |    |     | Version for Release 11                                | 10.0.0 | 11.0.0 |