hash stringlengths 32 32 | doc_id stringlengths 7 13 | section stringlengths 3 121 | content stringlengths 0 2.2M |
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6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.2.1 Outer Encoding (BCH) | [6] clause 6.1.1, Outer Encoding (BCH), details the outer encoding requirements for normal and short codewords (FECFrames). For the CMTS, only short codewords are required. The CMTS shall meet the outer encoding requirements for short FECFrames specified in [6] clause 6.1.1, Outer Encoding (BCH). |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.2.2 Inner Coding (LDPC) | [6] clause 6.1.2, Inner Encoding, and clause 6.1.2.2, Inner Coding for Short FECFrame, detail the inner coding requirements for short codewords. For DOCSIS 3.1 codewords, the CMTS shall meet the inner coding requirements for short codewords and code rate 8/9 specified in [6] clause 6.1.2, Inner Encoding, and clause 6.1... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.2.3 Support for Codeword Shortening | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.2.3.0 Codeword Shortening for Insufficient Data | Codeword shortening is used for two purposes: • Create shortened codewords when there is insufficient data to fill complete codewords. • Achieve strong burst noise protection. The full FEC block size for the FEC code rate of 8/9 is provided in table 7.18. Codeword shortening is accomplished by shortening the uncoded bl... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.3 Bit Interleaving | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.3.1 Bit Interleaving for Non-Shortened Codewords | For non-shortened codewords that are not of the mixed-modulation type the CMTS shall apply parity interleaving, followed by column-twist interleaving as detailed in [6] clause 6.1.3, Bit Interleaver, with the number of rows, columns and column twisting parameters specified in this clause. The number of rows and columns... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.3.2 Bit Interleaving for Non-Shortened Mixed Modulation Codewords | To support non-shortened mixed-modulation codewords, the bit interleaver specified in [6] has been modified. For non- shortened mixed-modulation codewords, the CMTS shall apply parity interleaving followed by column-twist interleaving as detailed in [6] clause 6.1.3, Bit Interleaver, and in the following discussion. Be... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.3.3 Bit Interleaving for Shortened Codewords | Shortened codewords fall into one of the following three types: • Square modulation • Non-square modulation • Mixed modulation The CMTS shall interleave all types of shortened codewords as described in this clause. The CMTS shall interleave the 1 800 parity bits as described in [6] clause 6.1.3, Bit Interleaver. Becaus... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.4 Downstream Receiver FEC Processing | Downstream data is encoded for FEC by the CMTS. The CM shall decode the FEC-applied codeword to correct for any bit errors introduced by noise and interference in the transmission medium. This process is discussed in this clause. The FEC decoder at the CM operates on the QAM subcarriers of OFDM symbols to generate an e... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5 Mapping Bits to QAM Constellations | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.0 Bits to QAM Mapping Methods | This clause describes the method used in DOCSIS 3.1 to map bits onto QAM constellations. It is based on [6] clause 6.2, Mapping Bits onto Constellations, and is used here with the following modifications: • Parameters for mapping bits onto non-square constellations have been added • Parameters for mapping bits of short... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.1 Modulation Formats | The CMTS modulator shall support 16-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, 1024-QAM, 2048-QAM, and 4096-QAM. The CMTS modulator may support 8192-QAM and 16384-QAM. The CM demodulator shall support 16-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, 1024-QAM, 2048-QAM, and 4096-QAM. The CM demodulator may support 8192-QAM and 1... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.2 Bit-to-Cell Word Demultiplexer | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.2.1 Non-shortened Codewords | For non-shortened codewords that are not of the mixed-modulation type, the CMTS shall demultiplex the bit stream vi from the bit interleaver into Nsubstreams sub-streams, using the value of Nsubstreams as defined in table 7.27 and the description following that table. Table 7.27: Number of Sub-Streams in Demultiplexer ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.2.2 Shortened Codewords and Mixed-Modulation Codewords | It is important to emphasize that shortened codewords can have square modulation, non-square modulation or may be of the mixed-modulation type. The CMTS shall bypass the bit-to-cell demultiplexer and apply the bit-to-cell mapping described in this clause for all types of shortened codewords, as well as for non-shortene... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.3 Randomization | The CMTS shall randomize cell words of data subcarriers, NCP subcarriers and PLC subcarriers, just before mapping these onto QAM constellations, as described in this clause. The CMTS shall also introduce BPSK-modulated subcarriers for the following subcarriers during the randomization process, as described in this clau... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.4 Cell Word Mapping into I/Q Constellations | The CMTS shall modulate each randomized cell word ( . . ) from the randomizer described in clause 7.5.5.3 using a BPSK, QPSK, 16-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, 1024-QAM, 2048-QAM, 4096-QAM, 8192-QAM or 16384-QAM constellation as described in Annex A. D0 α 12-bit 12-bit D1 ETSI ETSI TS 103 311-2 V1.1.... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.5 Transmitter Bit Loading for Symbol Mapping | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.5.0 Overview of Transmitter Bit Loading for Symbol Mapping | All subcarriers of an OFDM symbol may not have the same constellation; the constellation for each subcarrier is given in a table that details the bit loading pattern. This bit-loading pattern may change from profile to profile. This clause describes how the bits to symbol mapping is performed, with reference to a bit-l... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.5.1 Bit Loading | The bit loading pattern defines the QAM constellations assigned to each of the 4 096 or 8 192 subcarriers of the OFDM transmission. This bit loading pattern can change from profile to profile. Continuous pilot locations, PLC locations and exclusion bands are defined separately, and override the values defined in the bi... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.5.5.2 NCP Insertion | Next Codeword Pointers (NCPs) point to the beginning of codewords in a symbol, counting only data subcarriers of that symbol, not including the locations reserved for the scattered pilots. The format of an NCP is described in clause 8.3.4, which also describes the FEC applied to the NCP. Each FEC encoded NCP is 48 bits... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.6 Interleaving and De-interleaving | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.6.0 Interleaving and De-interleaving Overview | To minimize the impacts of burst noise and ingress on the DOCSIS signals, time and frequency interleaving are applied to OFDM symbols in the following order: time interleaving, then frequency interleaving. These interleaving methods are discussed in this clause. The time interleaver is a convolutional interleaver that ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.6.1 Time Interleaving | The CMTS shall time interleave as described been mapped to QAM constellations and befo The time interleaver is a convolutional interle interleaver is M, then there are M branches, a Figure The CMTS shall support a maximum value o 16 for 40 µs symbol duration (25 kHz subcar The CMTS shall support all values of M from Ea... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.7 IDFT | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.7.1 Downstream Transmitter Inverse Discrete Fourier Transform | The CMTS transmitter shall use the IDFT definition and subcarrier referencing method described in this clause. This clause defines the inverse discrete Fourier transform (IDFT) used in the CMTS transmitter for DOCSIS 3.1. OFDM subcarrier referencing for other definitions such as PLC location, continuous pilots, exclusi... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.7.2 Subcarrier Referencing | It is necessary to refer to specific OFDM subcarriers for several definitions: a) Defining continuous pilot locations b) Defining exclusion bands and excluded individual subcarriers c) Defining bit loading profiles Each of these definitions uses the index k of the equation defined in the preceding section to refer to a... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.8 Cyclic Prefix and Windowing | This clause describes how cyclic prefixes are inserted and how a window is applied to the output of the IDFT at the CMTS and how they are handled by the CM. The addition of a cyclic prefix enables the receiver to overcome the effects of inter-symbol-interference caused by micro-reflections in the channel. Windowing max... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.9 Fidelity Requirements | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.9.0 Fidelity Requirements Overview | For the purposes of the present document, the number of occupied CEA channels of an OFDM channel is the occupied bandwidth of the OFDM channel divided by 6 MHz. CMTSs capable of generating N-channels of legacy DOCSIS plus NOFDM-channels of OFDM per RF port, for purposes of the DRFI output electrical requirements, the d... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.9.2 Power per Channel for CMTS | A CMTS shall generate an RF output with power capabilities as defined in table 7.37. The CMTS shall be capable of adjusting channel RF power on a per channel basis as stated in table 7.37. If the CMTS has independent modulation capability on a per channel basis for legacy DOCSIS channels, then the CMTS shall be capable... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.9.3 Out-of-Band Noise and Spurious Requirements for CMTS | One of the goals of the DOCSIS DRFI specification is to provide the minimum intended analog channel CNR protection of 60 dB for systems deploying up to 119 DRFI-compliant QAM channels. A new DOCSIS 3.1 PHY goal is to provide protection for legacy DOCSIS channels and for high density constellations of OFDM channel block... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.10 CMTS Transmitter Output Requirements | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.10.0 CMTS Transmitter Output Requirements | CMTSs capable of generating N-channels of legacy DOCSIS plus NOFDM-channels of OFDM per RF port, for purposes of the output electrical requirements, the device is said to be capable of generating Neq-channels per RF port, where Neq = N + 32*NOFDM "equivalent legacy DOCSIS channels. ETSI ETSI TS 103 311-2 V1.1.1 (2017-0... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.10.1 CMTS Output Electrical Requirements | A CMTS shall output an RF modulated signal with the characteristics defined in table 7.39. The condition for these requirements is the entire OFDM block commanded to a constant power spectral density, except for Phase Noise, Diagnostic Carrier Suppression, and power difference requirements (table 7.37), and except as d... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.11 Cable Modem Receiver Input Requirements | The CM shall be able to accept any range of OFDM subcarriers defined between Lower Frequency Boundary and Upper Frequency Boundary simultaneously. Active subcarrier frequencies, loading, and other OFDM characteristics are described by OFDM configuration settings and CM exclusion bands and profile definition. The OFDM s... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.12 Cable Modem Receiver | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.12.0 Cable Modem Receiver Capabilities | The required level for CM downstream post-FEC error ratio is defined as less than or equal to 10-6 PER (packet error ratio) with 1 500 byte Ethernet packets. This clause describes the conditions at which the CM is required to meet this error ratio. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 143 |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.12.1 CM Error Ratio Performance in AWGN Channel | Implementation loss of the CM shall be such that the CM achieves the required error ratio when operating at a CNR as shown in table 7.41, under input load and channel conditions as follows: • Any valid transmit combination (frequency, subcarrier clock frequency, transmit window, cyclic prefix, pilot, PLC, subcarrier ex... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13 Physical Layer Link Channel (PLC) | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.0 PLC Overview | This clause contains the description of the Physical layer Link Channel (PLC) that the CMTS follows during the construction of the PLC. The aim of the PLC is for the CMTS to convey to the CM the physical properties of the OFDM channel. In a blind acquisition, that is, in an acquisition without prior knowledge of the ph... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.1 PLC Placement | The CMTS shall transmit a PLC for every downstream OFDM channel. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 144 The CMTS shall place the PLC at the centre of a 6 MHz encompassed spectrum with no excluded subcarriers. For 4K FFT OFDM, this 6 MHz will contain 56 subcarriers followed by the 8 PLC subcarriers followed by anot... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.2 PLC Structure | The CMTS shall place the PLC so that it occupies the same set of contiguous subcarriers in every OFDM symbol. The CMTS shall place 8 OFDM subcarriers in the PLC of every OFDM symbol when using 4K FFT OFDM (i.e. a subcarrier spacing of 50 kHz). The CMTS shall place 16 OFDM subcarriers in the PLC of every OFDM symbol whe... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.3 PLC Preamble Modulation | The CMTS shall modulate the subcarriers in the PLC preamble using binary phase-shift keying (BPSK), as described in this clause. For 4K FFT, the preamble size is 8 subcarriers. Thus, an array of size (8 x 8) is defined as follows: Table 7.43: PLC Preamble for 4K FFT Symbol 1 Symbol 2 Symbol 3 Symbol 4 Symbol 5 Symbol 6... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.4 PHY Parameters Carried by the PLC | The PLC carries two sets of PHY parameters from the CMTS to cable modems: the Downstream Profile Descriptor and the OFDM Channel Descriptor. Contents of each of these descriptors are described in [4]. This clause contains only a brief description of the physical layer parameters carried by the PLC. For formatting and o... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.5 Mapping of Bytes to a Bit Stream | The CMTS shall convert the stream of bytes received by the PLC into a stream of bits, MSB first, as illustrated in figure 7.58. Figure 7.58: Mapping Bytes into a Bit Stream for FEC Encoding |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.6 Forward Error Correction code for the PLC | The CMTS shall encode the PLC data using (384,288) puncturing LDPC encoder, see clause 7.4.4.3 for the definition of puncturing encoder. The puncturing encoder uses the same mother encoder for fine ranging FEC (see clause 7.4.16.2.3), that is the rate 3/5 (480,288) LDPC encoder listed by table 7.15. Denote the informat... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.7 Block Interleaving of the PLC Subcarriers | The preceding section shows 240 data bits entering the LDPC encoder and 384 encoded bits exiting the LDPC encoder. This sequence is in effect is time-reversed order. The time-ordered sequence takes the form shown in figure 7.60. The CMTS shall map these 384 data bits into 96 4-bit nibbles {u , i = 0,1, … , 95} as descr... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.8 Randomizing the PLC Subcarriers | The CMTS shall randomize QAM symbols forming the data section of the PLC frame using a copy of the linear feedback shift register in GF[212] used for randomizing the data subcarriers. This is shown in figure 7.63. 6 Frequency Time 16 u0 u1 u5 u6 u7 u11 u90 u91 u95 ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 153 Figure 7.63... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.9 Mapping to 16-QAM Subcarriers | The CMTS shall map each randomized nibble {yyyy } into a complex number using the 16-QAM constellation mapping shown in figure 9.6. The CMTS shall multiply the real and imaginary parts by 1/√10 to ensure that mean-square value of the QAM constellation is unity. D0 α 12-bit 12-bit D1 ETSI ETSI TS 103 311-2 V1.1.1 (... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.13.10 PLC Timestamp Reference Point | The PLC subcarriers following the preamble may contain a timestamp. The CMTS shall define this timestamp with reference to the first OFDM symbol following the preamble if such a timestamp exists. This OFDM symbol is indicated by an arrow in figure 7.64. Figure 7.64: Time - Frequency Plane Representation of PLC Timestam... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14 Next Codeword Pointer | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14.1 Mapping of Bytes to Bits | Each NCP consists of three bytes as defined in clause 8.3.4. The first byte (Byte 0) contains the profile identifier as the four MSBs and four control bits as the four LSBs. The other two bytes (Byte 1 and Byte 2) contain the start pointer. The CMTS shall map the three NCP bytes into 24-bit serial bit stream {a a … ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14.2 CRC-24-D | The last NCP in the NCP field of each symbol contains a CRC-24-D message which is calculated across all NCPs in the NCP field of the symbol as specified in Annex E. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 156 NCP data is fed into the CRC-24-D encoder in the same order as the FEC encoder, as depicted in figure 7.68. Fig... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14.2 Forward Error Correction code for the NCP | The CMTS shall encode the 24 information bits of a Next Codeword Pointer using (48, 24) shortening and puncturing LDPC encoder, see clause 7.4.16.1.4 for the definition of shortening and puncturing encoder. The shortening puncturing encoder uses the same mother encoder for initial ranging FEC (see clause 7.4.4.3), that... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14.3 Mapping LDPC Encoded Bits into OFDM Subcarriers | The LDPC encoder outputs a stream of 48 bits: {b b … b b b … b a a … a} The NCP QAM constellation can be a member of the set {QPSK, QAM-16, QAM-64}. For QAM-64 the CMTS shall map the LDPC encoded bits into eight 6-bit QAM constellation points as defined below: y, y, y, y, y, y, = {a a a... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14.4 Placement of NCP Subcarriers | The CMTS shall place the NCP subcarriers beginning from the frequency location of the highest frequency active data subcarrier of the OFDM symbol, and going downwards along active data subcarriers of the OFDM symbols before they are time and frequency interleaved. Therefore the first subcarrier of the first NCP occupie... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.14.5 Randomization and Interleaving of NCP Subcarriers | The CMTS shall randomize the NCP constellation points {yi,j} described in clause 7.5.14.3 using the algorithm applied to the data subcarriers, described in clause 7.5.5.3. The CMTS shall time and frequency interleave the NCP subcarriers using the algorithm applied to data subcarriers and this is described in the interl... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15 Downstream Pilot Patterns | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.0 Overview | Downstream pilots are subcarriers modulated by the CMTS with a defined modulation pattern that is known to all the CMs in the system to allow interoperability. There are two types of pilots: continuous and scattered. Continuous pilots occur at fixed frequencies in every symbol. Scattered pilots occur at different frequ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.1 Scattered Pilots | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.1.0 Scattered Pilots Overview | The main purpose of scattered pilots is the estimation of the channel frequency response for the purpose of equalization. There are two scattered pilot patterns, one for 4K FFT and one for 8K FFT. Although these pilots occur at different frequency locations in different OFDM symbols, the patterns repeat after every 128... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.1.1 Scattered Pilot Pattern for 4K FFT | The CMTS shall create scattered pilots for 4K FFTs in the manner described in this clause. Figure 7.74 shows the 4K FFT scattered pilot pattern for OFDM transmissions. The scattered pilot pattern is synchronized to the PLC as shown in figure 7.74. The first OFDM symbol after the PLC preamble has a scattered pilot in th... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.1.2 Scattered Pilot Pattern for 8K FFT | The CMTS shall create scattered pilots for 8K FFTs in the manner described in this clause. Figure 7.75 shows a scattered pilot pattern that may be used for OFDM transmissions employing 8K FFT. This is used here for explanation purposes only and to help with the derivation of the scattered pilot pattern actually used in... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.2 Continuous Pilots | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.2.0 Continuous Pilots Overview | Continuous pilots occur at the same frequency location in all symbols and are used for receiver synchronization. Placement of continuous pilots is determined in two ways: a) Predefined continuous pilot placement around the PLC b) Continuous pilot placement defined via PLC messages Note that continuous and scattered pil... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.2.1 Predefined Continuous Pilots Around the PLC | As discussed in clause 7.5.13.1, the PLC is placed at the centre of a 6 MHz spectral region. Four pairs of predefined continuous pilots are placed symmetrically around the PLC as shown in figure 7.77. The spacing between each pilot pair and the PLC are different to prevent all pilots from being impacted at the same tim... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.2.2 Continuous Pilot Placement Defined by PLC Message | The CMTS shall define a set of continuous pilots distributed as uniformly as possible over the entire OFDM spectrum in addition to the predefined continuous pilots described in the preceding section. Frequency PLC Time d1 d2 d3 d4 d4 d3 d2 d1 ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 167 The CMTS shall ensure that there ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.3 Pilot Modulation | For both continuous and scattered pilots, the CMTS shall modulate these subcarriers as described in the following section. Continuous and scattered pilots are BPSK modulated using a pseudo-random sequence. This pseudo-random sequence is generated using a 13-bit linear feedback shift register, shown in figure 7.78 with ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.15.4 Pilot Boosting | The CMTS shall multiply the real and imaginary components of continuous and scattered pilots by a real-valued number such that the amplitude of the continuous and scattered pilots is twice the root-mean-square value of the amplitude of other subcarriers of the OFDM symbol; that is, continuous and scattered pilots are b... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8 PHY-MAC Convergence | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.1 Scope | The present document defines the electrical characteristics and signal processing operations for a cable modem (CM) and Cable Modem Termination System (CMTS). It is the intent of the present document to define an interoperable CM and CMTS such that any implementation of a CM can work with any CMTS. It is not the intent... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2 Upstream | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.1 Profiles | Upstream profiles are comprised of multiple minislots, and are characterized by bit loading and pilot pattern. Bit loading and pilot patterns can vary between minislots within the profile. The bit loading and pilot pattern assignment of minislots can also vary between profiles. An upstream profile maps to an Interval U... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.2 Upstream Subcarrier Numbering Conventions | Subcarriers are numbered from lower frequency to higher frequency within a FFT block. All subcarriers within the 102,4 MHz bandwidth are numbered, including the outside excluded subcarriers. Numbering starts at 0 and goes to 2 047 for 2K FFT, and 0 to 4 095 for 4K FFT. Data codewords are mapped into minislots - prior t... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3 Minislots | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.0 Minislots Overview | Minislots are defined by a size in terms of the number of symbols and number of subcarriers. They include data carried on data subcarriers, pilots carried on pilot subcarriers and complementary pilots that can carry data but at a lower modulation order. In this clause, BW is defined as the encompassed spectrum on a sin... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.1 Minislot Parameters | The CMTS shall define minislot parameters according to table 8.1. The CMTS communicates minislot definition to the CM in UCD messages as defined in [4]. The CM shall use the minislot structure defined by the UCD messages received from the CMTS. The CMTS shall be capable of receiving minislots structured according to ta... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.2 Minislot Structure | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.2.1 Number of OFDM Symbols per Minislot | The CMTS shall follow the rules listed below for the range of the frame size in number of symbols (K): • K is configurable between 6 (minimal value) and one of the following values: With 20 µs FFT duration (2K FFT) - Kmax = 18 for BW > 72 MHz - Kmax = 24 for 48 MHz < BW < 72 MHz - Kmax = 36 for BW < 48 MHz With 40 µs F... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.2.2 Number of subcarriers per minislot | The CMTS signals the number of subcarriers per minislot to the CM in the UCD. The CMTS shall use 16-subcarrier minislots when the subcarrier spacing is 25 kHz. The CMTS shall use 8-subcarrier minislots when the subcarrier spacing is 50 kHz. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.3 Modulation of Data Subcarriers | With the exception of pilots and complementary pilots, bit loading is constant within a minislot. The CMTS shall use the same modulation order for all data subcarriers in a minislot. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.4 Location of Pilots | A set of pilot patterns is defined from which the CMTS or operator can select to match the frequency response of the network. Pilot patterns are described in clause 7.4.17. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.5 Modulation Order of Pilots | The CMTS shall use BPSK modulation for pilots. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.6 Location of Complementary Pilots | The CMTS shall place complementary pilots as defined by the chosen minislot pattern. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.7 Modulation Order of Complementary Pilots | The CMTS shall use a modulation order equal to (data modulation order - 4) for complementary pilots. The CMTS shall use a minimum modulation order of BPSK for complementary pilots. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.8 Pilot Overhead | Pilot overhead is dependent on the chosen minislot pattern. Capacity and pilot overhead vary with the length of the minislot (number of symbols) and with the number of subcarriers (8 or 16). Minimum capacity and largest pilot overhead occur with the shortest minislot length (8 symbols). |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.9 Mapping Minislots to Subcarriers | The CMTS shall construct minislots using only contiguous subcarriers. There is no subcarrier exclusion within a minislot. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.3.10 Ordering of Data Bits within a Minislot | With the exception of initial ranging transmissions, the CM shall fill minislots as follows: prior to interleaving, data would be filled across all symbol periods, subcarrier by subcarrier, transmitted symbol period by symbol period, with complementary pilots filled inline. The fill order is illustrated in figure 8.1. ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.4 Subslots | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.2.4.1 Subslot Structure | The minislot can be subdivided along time in requests, as shown in Figure 8.2. The subslot along the time axis. Leftover symbols are not minislot is granted to IUCs 1 or 2. Gaps betw Fi The subslot length is fixed at 2 symbols with employ 8 subcarriers. 8.2.4.2 Data Mapping Amon The data mapping within a subslot is as ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3 Downstream | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.1 Operation | An example implementation of the downstream convergence layer for DOCSIS 3.1 and its association with the stages before and after it is shown in figure 8.5. This block diagram is intended to demonstrate functionality; while it represents one style of implementation, there are no requirements that an implementation need... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.2 MAC Frame to Codewords | The downstream LDPC codeword shown in figure 8.6 is referred to as (16 200, 14 400). This means that a full codeword is 2 025 bytes (16 200 bits) that are divided into 225 bytes (1 800 bits) of parity and 1 800 bytes (14 400 bits) of LDPC payload. That payload is further divided into 21 bytes (168 bits) of BCH parity, ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.3 Subcarrier Numbering Conventions | Subcarriers are numbered from lower frequency to higher frequency within a FFT block. All subcarriers within the 204,8 MHz bandwidth are numbered, including the outside excluded subcarriers. Numbering starts at 0 and goes to 4 095 for 4K FFT, and 0 to 8 191 for 8K FFT. Data codewords are mapped to subcarriers - prior t... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.4 Next Codeword Pointer | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.4.0 NCP Overview | When the data codewords are mapped to subcarriers within a symbol, a pointer is needed to identify where a data codeword starts. This is known as the Next Codeword Pointer (NCP). The collection of NCP message blocks within a symbol is known as the NCP field. There are a variable number of NCP message blocks (MBs) on ea... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.4.2 NCP Field with CRC and FEC | The last NCP message block is a dedicated CRC block. This block is shown in figure 8.10. Time Symbol -130 -129 -128 -127 -126 -125 -124 … -4 --3 -2 -1 0 1 2 U-bit 0 0 1 0 1 1 1 … 0 1 0 1 0 0 0 128 symbols New NCP Profile ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 180 Figure 8.10: NCP CRC Message Block The CMTS shall inclu... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.4.3 NCP Usage | The CMTS shall not place more than 11 NCP data message blocks plus a CRC for a total of 12 NCP MBs in an 8K OFDM symbol. The CMTS shall not place more than 12 NCP data message blocks plus two CRCs for a total of 14 NCP MBs in any two successive 4K OFDM symbols. In the case of an 8K FFT OFDM symbol, the 12 NCP MBs will ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 8.3.4.4 NCP Example | Figure 8.12 shows some examples of how the NCP field is used. This view is prior to interleaving. Figure 8.12: NCP Examples NCP blocks are mapped to sub-carriers starting with the first non-excluded subcarrier at the top of the spectrum and then down in frequency. After the last NCP MB is a CRC-24-D. Data is mapped to ... |
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