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 | 7.4.3.4 Upstream Subcarrier Clock Frequency | The CM shall lock the Upstream Subcarrier Clock Frequency (25 kHz or 50 kHz) to the 10,24 MHz Master Clock via the Downstream Subcarrier Clock, subject to the carrier phase noise and frequency offset requirements in this clause. The subcarrier frequency is specified as locked to the 10,24 MHz reference and given with 2... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4 Forward Error Correction | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4.0 Upstream Codword Parameters | DOCSIS 3.1 uses three Quasi-Cyclic Low-Density Parity-Check codes (QC-LDPC) for the upstream transmission, as depicted in table 7.3. Table 7.3: Upstream Codeword Parameters Code Code rate Codeword size in bits (Ni) Information bits (Ki) Parity bits (Pi) Long code 89 % (8/9) 16 200 14 400 1 800 Medium code 85 % (28/33) ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4.1 FEC Codeword Selection | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4.1.0 FEC Codeword Size | The choice of codeword sizes to be used in any given burst is based on the grant in the MAP message. The grant indicates which minislots are assigned to a given burst and which upstream profile is to be used. The CM and CMTS use this information to determine the total number of bits in the grant which are available to ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4.1.1 FEC Codeword Selection Algorithm | The FEC codeword selection algorithm is given by: % The total number of bits in the grant is given by rgrant_size % set values for codeword sizes % total bits = size including parity % info bits = information bits only % thresholds - if more bits than threshold, shorten this cw instead of % using a smaller one ETSI ETS... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4.2 FEC Encoding | All three LDPC encoders are systematic. Every encoder encodes N-M information bits into a codeword by adding m parity bits obtained so that , where is an m*n parity check matrix. The parity-check matrix can be divided into blocks of L*L submatrices, where L represents the submatrix size or lifting factor. The parity-ch... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.4.3 Shortening of LDPC Codewords | Shortening of LDPC codewords is useful in order to optimize FEC protection for the payload. If a shortened codeword is required, the CM shall construct it as follows: 1) Binary zeros are appended to a reduced number of information bits at the input of the encoder. 2) The encoder calculates the parity bits. 3) The appen... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.5 Data Randomization | The CM shall implement a randomizer in the upstream modulator shown in figure 7.4 where the 23-bit seed value is programmable. At the beginning of each grant, the register is cleared and the seed value is loaded. The CM shall use the seed value to calculate the scrambler bit which is combined in an XOR with the first b... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.6 Time and Frequency Interleaving and De-interleaving | Upstream transmissions can be affected by burst noise that reduces the SNR of all the subcarriers of a few successive OFDMA symbols. Upstream transmissions may also be impacted by ingress, i.e. relatively narrowband interferers, that can last for several symbol periods and therefore reduce the SNR of a subset of subcar... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.7 Mapping of Bits to Cell Words | CMs are granted transmission opportunities by minislots, and minislots are associated with subcarriers. All subcarriers of a specific type (data subcarriers, pilots, complementary pilots) within a minislot have the same modulation order, although different minislots may have different modulation orders; the modulation ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.8 Mapping and De-mapping Bits to/from QAM Subcarriers | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.8.0 Minislots Structure | CMs are granted transmission opportunities by minislots, and minislots are associated with subcarriers. All subcarriers of a specific type (i.e. data subcarriers, pilots, complementary pilots or zero-valued subcarriers) within a minislot have the same modulation order, although different minislots may have different mo... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.8.1 Modulation Formats | The CM modulator shall support zero valued subcarriers of upstream OFDMA channels. The CM modulator shall support BPSK, QPSK, 8-QAM, 16-QAM, 32-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, 1024-QAM, 2048-QAM, and 4096-QAM for subcarriers of upstream OFDMA channels. BPSK is used for pilots and complimentary pilots only, and ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.8.2 Constellation Mapping | The CM shall encode the bit stream such that the first bit is the most-significant bit of the first QAM subcarrier constellation m-tuple. Figure 7.10: Bitstream to QAM M-Tuple Mapping The CM shall modulate the interleaved m-tuples onto subcarriers using QAM constellation mappings described in Annex A. The CM shall ensu... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.9 REQ Messages | REQ messages are short messages used by the CM to request transmission opportunities from the CMTS. These messages have a different structure than the data messages: they are always 56 bits long, they always use QPSK modulation, do not apply any FEC, and are block interleaved. REQ message processing is described in fig... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.10 IDFT | The upstream OFDMA signal transmitted by the CM is described using the following IDFT equation: = √ ∑ ! exp (" ) , = 0, 1, … , ( −1) Where N equals 2 048 with 50 KHz subcarrier spacing and 4 096 with 25 KHz subcarrier spacing. The resulting time domain discrete signal, x(i), is a baseba... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.11 Cyclic Prefix and Windowing | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.11.0 Background and General Requirements | Cyclic prefix and windowing are applied in the upstream transmission. Cyclic prefix is added in order to enable the receiver to overcome the effects of inter-symbol interference (ISI) and caused by micro-reflections in the channel. Windowing is applied in order to maximize channel capacity by sharpening the edges of th... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.11.1 Cyclic Prefix and Windowing Algorithm | The algorithm for cyclic prefix extension and windowing is described here with reference to figure 7.14. The CM shall support cyclic prefix extension and windowing as described in this clause. Figure 7.14: Cyclic Prefix and Windowing Algorithm Processing begins with the N-point output of the IDFT. Let this be: { 0, ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.11.2 Parameter Optimization | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.11.2.1 Impacts of Cyclic Prefix and Windowing | The combination of cyclic prefix insertion and windowing can impact OFDM symbol duration: once the CP and RP additions have been made, the length of the extended OFDM symbol is (N + NCP + NRP) samples. Of this, (NRP/2) samples are within the preceding symbol, and (NRP/2) samples are within the following symbol. This yi... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.11.2.2 Joint Optimization of Cyclic Prefix and Windowing Parameters | It is clear from the clause above that the parameters and have to be jointly optimized for given channel, taking into account the following properties of the channel: a) Bandwidth of the transmitted signal b) Number of exclusion zones in the transmitted bandwidth c) Channel micro-reflection profile d) QAM const... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.12 Burst Timing Convention | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.12.0 OFDMA Transmission | The start time of an OFDMA transmission by a CM is referenced to an OFDMA frame boundary that corresponds to the starting minislot of the transmission opportunity. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 68 For all transmissions, except Fine Ranging and Requests in subslots not at the start of a frame, the CM transmits... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.12.1 Upstream Time Reference of an OFDMA Frame | The upstream time reference is defined as the first sample of the first symbol of an OFDMA frame, pointed to by the dashed arrow of figure 7.16. The parameter NFFT refers to the length of the FFT duration which is either 2 048 or 4 096, and the parameter NCP is the length of the configurable cyclic prefix. The sample r... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.12.2 Upstream Time Reference of an OFDMA Symbol | The upstream time reference for construction of each OFDMA symbol is defined as the first sample of each FFT duration of each OFDMA symbol, pointed to by the dotted arrow of figure 7.16. Figure 7.16: Time References for OFDMA Symbol and Frame |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13 Fidelity Requirements | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.0 CM Transmit Channel Set | A DOCSIS 3.1 CM is required to generate up to 8 channels of legacy DOCSIS plus up to 2 OFDMA channels as defined in clauses 6.2.1 and 7.2.1. A CM's Transmit Channel Set (TCS) is the combination of legacy channels and OFDMA channels being transmitted by the CM. With BWlegacy being the combined occupied bandwidth of the ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.1 Maximum Scheduled Minislots | While transmitting on the large upstream spectrum supported by DOCSIS 3.1, a CM can encounter large upstream attenuation and can have a power deficit when attempting to reach the CMTS receiver at the nominal OFDMA channel set power. A CMTS has several options in dealing with such CMs: it can limit the TCS to the channe... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.2 Transmit Power Requirements | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.2.0 Transmit Power Requirements Overview | The transmit power requirements are a function of the number and occupied bandwidth of the OFDMA and legacy channels in the TCS. The minimum highest value of the total power output of the CM Pmax is 65 dBmV, although higher values are allowed. The total maximum power is distributed among the channels in the TCS, based ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.2.1 Transmit Power Requirements with Multiple Transmit Channel Mode Enabled | The following requirements apply with Multiple Transmit Channel mode enabled. Requirements with Multiple Transmit Channel mode disabled are addressed in [5]. The CM shall support varying the amount of transmit power. Requirements are presented for 1) range of reported transmit power per channel; 2) step size of power c... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.3 OFDMA Transmit Power Calculations | In OFDMA mode the CM determines its target transmit power per channel P1.6t_n, as follows, for each channel which is active. Define for each active channel, for example, upstream channel n: P1.6r_n = reported power level (dBmV) of CM for channel n. P1.6hi = Pmax/Neq. P1.6low_n = P1.6low. The CM updates its reported pow... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.4 Global Reconfiguration Time for OFDMA Channels | "Global reconfiguration time" is defined as the inactive time interval provided between active upstream transmissions, which simultaneously satisfies the requirement in clause 6.2.20 for all TDMA channels in the TCS and the requirement in clause 6.2.20 for all S-CDMA channels in the TCS and the requirement here for OFD... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.5 OFDMA Fidelity Requirements | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.5.0 TCS Fidelity Requirements | The following requirements assume that any pre-equalization is disabled, unless otherwise noted. When channels in the TCS are commanded to the same equivalent powers, the reference signal power in the "dBc" definition is to be interpreted as the measured equivalent to the reported power as defined in clause 7.4.13.2.1.... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.5.1 Spurious Emissions | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.5.1.0 Spurious Emissions Requirements | The noise and spurious power generated by the CM shall not exceed the levels given in tables 7.6, 7.7 and 7.8. Up to five discrete spurs can be excluded from the emissions requirements listed in tables 7.6, 7.7 and 7.8 and have to be less than -42 dBc relative to a single subcarrier power level. SpurFloor is defined as... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.5.2 Spurious Emissions During Burst On/Off Transients | The CM shall control spurious emissions prior to and during ramp-up, during and following ramp-down, and before and after a burst. The CM's on/off spurious emissions, such as the change in voltage at the upstream transmitter output, due to enabling or disabling transmission, shall be no more than 50 mV. The CM's voltag... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.13.5.3 MER Requirements | 7.4.13.5.3.0 Modulation Error Ratio Overview Transmit modulation error ratio (TxMER or just MER) measures the cluster variance caused by the CM during upstream transmission due to transmitter imperfections. The terms "equalized MER" and "unequalized MER" refer to a measurement with linear distortions equalized or not e... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.14 Cable Modem Transmitter Output Requirements | The CM shall output an RF Modulated signal with characteristics delineated in table 7.11. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 83 Table 7.11: CM Transmitter Output Signal Characteristics Parameter Value Frequency Support and be configurable to a permitted subset (see clause 7.2.3 for allowed combinations) of the fol... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.15 CMTS Receiver Capabilities | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.15.1 CMTS Receiver Input Power Requirements | The CMTS Upstream Demodulator shall operate with an average input signal level, including ingress and noise to the upstream demodulator, up to 31 dBmV. The CMTS shall be settable according to table 7.12 for intended received power normalized to 6,4 MHz of bandwidth. The CMTS Upstream demodulator shall operate within it... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.15.2 CMTS Receiver Error Ratio Performance in AWGN Channel | The required level for CMTS upstream post-FEC error ratio is defined for AWGN 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 CMTS is required to meet this error ratio. Implementation loss of the CMTS receiver shall be such that ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16 Ranging | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.0 Ranging Procedure | Ranging in DOCSIS 3.1 is divided into three steps, as illustrated in figure 7.17: • Initial ranging is used by the CMTS to identify a new admitting CM and for coarse power and timing ranging. • Fine ranging is used after initial ranging has been completed, to fine-tune timing and power. • Probing is used during admissi... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.1 Initial Ranging | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.1.1 Initial Ranging Zone | The initial ranging zone consists of N by M contiguous minislots in the upstream frame. N and M are configured by the CMTS. Minislots in the initial ranging zone do NOT the initial ranging signal, as illustrated in figu Figu 7.4.16.1.2 Initial Ranging Sign The initial ranging signal consists of a pream O-INIT-RNG-REQ a... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.1.5 Padding and Randomizing | The CM shall pad and randomize the 128 encoded bits as described below. The CM shall calculate the number of symbols required to transmit the INIT-RNG-REQ message as follows: Nuid_sym = ceiling (128/Nir) where Nir is the number of subcarriers allocated for the INIT-RNG-REQ message. CM shall pad the remaining bits with ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.1.6 Symbol Duplicating Cyclic Prefix and Windowing | The CM shall repeat each Initial Ranging OFDMA symbol twice. A cyclic prefix of Ncp samples is appended before the first repeated OFDMA symbol. A cyclic suffix of Nrcp (Nrcp = Ncp + Nrp) samples is appended after the second repeated OFDMA symbol. ) , , ( 79 0 a a L ) , , , , , ( 159 80 79 0 b b a a L L 159 80 , , b b L... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2 Fine Ranging | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.0 Fine Ranging Operations | This clause describes fine ranging operations for the CM transmitter. Fine ranging is used by the CMTS for the second step of the admission of a new CM process, following successful initial ranging. During this step, a fine ranging signal is transmitted by a new CM joining the network, according to transmission paramet... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.1 Fine Ranging Signal | Figure 7.24 illustrates a fine ranging signal. Symbol X0 Symbol X0 Symbol X0 Symbol X0 Symbol X0 Cyclic Prefix X0 Cyclic Suffix X0 Repeat OFDM symbol N N N N N Ncp Ncp Nrcp = Ncp + Nrp Add Prefix and Postfix Symbol X0 Symbol X0 Nrcp Add Windowing 2*(N+Ncp) Symbol X+1 ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 90 Figure 7.... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.2 Transmission of the Fine Ranging Signal | The CM shall duplicate the OFDMA symbols at the output of the IFFT as described in clause 7.4.16.1.6, adding a Cyclic Prefix to symbols 2n, and a Cyclic Suffix to symbols 2n+1, for n=0, 1, 2, … The CM shall apply windowing as described in clause 7.4.16.1.6. The CM shall add the Cyclic Prefix as described in clause 7.4.... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.3 Fine Ranging FEC | The CM shall encode the 34 bytes of fine ranging information data using (362,272) shortening and puncturing LDPC encoder. Shortening and puncturing encoder consists of three steps. In this step, the shortening step, one or more information bits are filled with 0 and the rest are filled with input bits. Then all informa... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.4 Padding and Randomizing | The CM shall calculate the total number of data bits that can be transmitted in the fine ranging signal as follows: Number_of_allocated_bits = Nfr* floor((K-4)/2)*2. If the number of allocated bits is greater than 362, the CM shall pad the 362 bits output from the LDPC encoder with ones so that the encoded data and the... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.5 Exclusion Bandwidths | Transmission of the fine ranging signal around exclusion bands is allowed, using same processing as explained in clause 7.4.16.2.2 with the same values of Nfr and Ngb. ) , , ( 287 0 a a L ) , , , , , ( 479 288 287 0 b b a a L L 479 288 , , b b L 0 287 273 272 = = = = a a a L 271 0 , , a a L 53 1 0 , , , a a a L 479 433... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.6 Allowed Values and Ranges for Configuration Parameters | The CMTS shall configure the initial and fine ranging signal with the following limitations: • The maximum number of subcarriers for initial ranging, not including the guardband, shall not exceed 64 subcarriers with 50 kHz subcarrier spacing • The maximum number of subcarriers for initial ranging, not including the gua... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.2.7 Power and Time Adjustments | Algorithms for power and time adjustments (such as number of fine ranging trials, frequency allocations, etc.) are vendor-specific implementation. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.3 Probing | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.3.0 Probing Usage | Probing is used during admission and steady state for pre-equalization configuration and periodic transmission power and time-shift ranging. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.3.1 Probing Frame | A probing frame consists of K contiguous probing symbols (OFDM symbols), where K is the number of symbols in the minislot. The probing frame is aligned with the minislot boundaries in the time domain. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.3.2 Probing Symbol Pilots | Probing symbol pilots are BPSK subcarriers, generated from the PRBS generation scheme described in clause 7.4.16.3.3. The CM shall use the generation scheme detailed in clause 7.4.16.3.3 to generate 2 048/4 096 subcarriers for 2K/4K FFT. The CM shall use the same BPSK modulation for a specific subcarrier in all probing... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.3.3 PRBS Generation Scheme | The polynomial definition for the PRBS scheme is X12 + X9 + X8+ X5+ 1, where the seed is 3 071. The period of the PRBS is 212-1 bits, which is sufficient to create one probe symbol without repetitions. The sequence is illustrated in figure 7.30. The CM's linear feedback shift register shall be clocked after every subca... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.16.3.4 Probing Information | The CMTS shall allocate a specific probing symbol within the probing frame and instruct the CM to transmit the probing sequence in that symbol. The CMTS shall specify the probing symbol within the probing frame through the parameter "Symbol in Frame". The CMTS shall send three parameters to the CM: "st", "Start Subcarr... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17 Upstream Pilot Structure | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17.0 Edge and Body Minislots | Pilots are used by the CMTS receiver to adapt to channel conditions and frequency offset. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 97 DOCSIS 3.1 specifies two minislot types, differing in the number of subcarriers per minislot, 8- and 16-subcarrier minislots. Two types of minislots are defined for each minislot size: ed... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17.1 Pilot Patterns for 8-Subcarrier Minislots | Figure 7.34 and figure 7.35 define the pilot patterns for edge and body minislots with 8 subcarriers. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 98 The CM shall support pilot patterns 1-7. The CMTS shall support pilot patterns 1-4. The CMTS SHOULD support pilot patterns 5-7. The CMTS shall use either pilots pattern 1-4 or... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17.2 Pilot patterns for 16-Subcarrier Minislots | Figure 7.36 and figure 7.37 define the pilot patterns for minislots with 16 subcarriers. The CM shall support pilot patterns 8-14. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 99 The CMTS shall support pilot patterns 8-11. The CMTS should support pilot patterns 12-14. The CMTS shall use either pilots pattern 8-11 or pilot p... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17.3 Pilot Boosting | The CM shall use higher power (pilot boost) when transmitting pilots and complementary pilots with pilot patterns 5-7 and patterns 12-14, with the following exception: The CM shall use boosted power for the pilot and normal power for the complementary pilot when both are used in the same symbol and in the same minislot... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17.4 Pilot Patterns for 8-Subcarrier Subslots | Subslots are used to carry REQ messages which are always 7 bytes or 56 bits long. Data subcarriers are always QPSK- modulated, and are not encoded by any FEC but are randomized using the randomizer described in clause 7.4.5. Figure 7.38 depicts the pilot pattern for a subslot with 8 subcarriers. The CM shall support th... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.4.17.6 Pilot Modulation | The CM shall BPSK modulate the pilots usin illustrated in figure 7.30. This feedback shift equation of clause 7.4.10. It is then clocked o this is BPSK modulated with the output of th of 1 mapping to (-1 + j0). 7.4.18 Upstream Pre-Equa A CM shall implement a linear pre-equalizer The CMTS shall be able to direct a CM to... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5 Downstream Transmit and Receive | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.1 Overview | This clause specifies the downstream electrical and signal processing requirements for the transmission of OFDM modulated RF signals from the CMTS to the CM. ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 103 |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2 Signal Processing | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.0 Downstream PHY Processing | Serial data signals received from the PHY-MAC Convergence Layer are received and processed by the PHY as illustrated in figure 7.40. This process yields OFDM symbols with 4 096 subcarriers for the 4K FFT mode and 8 192 subcarriers for the 8K FFT mode, with each symbol consisting of: • Data subcarriers • Scattered pilot... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.1 Forward Error Correction (FEC) Encoding | The PHY begins processing incoming data by FEC encoding data bits to form encoded codewords. Forward error correction adds redundancy to the transmitted data; these redundant bits can be used by the receiver to detect and correct errors in the transmission. For DOCSIS 3.1, FEC encoding applies a concatenated BCH-LDPC e... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.2 Symbol Mapping to QAM Constellations | Once FEC encoded codewords have been created, the codewords are placed into OFDM symbols. Because each subcarrier in an OFDM symbol can have a different QAM modulation, the codewords are to be first demultiplexed into parallel cell words; these cell words are then mapped into constellations based on the corresponding b... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.3 Scattered Pilot Placeholder Insertion | OFDM transmission requires the insertion of scattered pilots to enable channel estimation and equalization in the receiver. While the insertion happens after time and frequency interleaving, since these pilots are not in the same spectral location in every symbol, insertion of these scattered pilots disrupt the spectra... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.4 Next Codeword Pointer Insertion | Detecting where the next codeword begins in an OFDM symbol can be difficult: more than one codeword may map into one OFDM symbol, the number of codewords per OFDM symbol may not be an integer, a codeword can overflow from one OFDM symbol to another, and the codeword could be shortened. Therefore, the transmitter is to ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.5 Interleaving | These OFDM symbols, comprised of data subcarriers, scattered pilot placeholders, and NCPs, are then subjected to time and frequency interleaving. Time interleaving mitigates the impact of burst noise, while frequency interleaving mitigates the effect of ingress. Time interleaving disperses the subcarriers of an input s... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.6 Insertion of Pilots and Exclusion Sub-Bands | When interleaving is complete, placeholders for continuous pilots are inserted. These will be subject to modulation later, together with the placeholders already inserted for scattered pilots. Continuous pilots are pilots that occur at the same subcarrier location in every symbol. These are needed for receiver synchron... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.7 Encoding and Insertion of the PLC | The PLC is constructed within the convergence layer in parallel with the functions already discussed, relating to the main data channel. The PLC occupies the same contiguous set of subcarriers in every OFDM symbol. The PLC data is encoded for error correction, and then mapped into 16-QAM PLC data subcarriers. The PLC d... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.8 IDFT Transformation and Cyclic Prefix Insertion | In this stage each OFDM symbol is transformed into the time domain using a 4 096-point or 8 192-point inverse discrete Fourier transform (IDFT). This 4 096 or 8 192 sample sequence is referred to below as the IDFT output. This process is described in clause 7.5.7. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.2.9 Cyclic Prefix and Windowing | A segment at the end of the IDFT output is prepended to the IDFT, and this is referred to as the Cyclic Prefix (CP) of the OFDM symbol. There are five possible values for the length of the CP and the choice depends on the delay spread of the channel - a longer delay spread requires a longer cyclic prefix. For windowing... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3 Time and Frequency Synchronization | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.0 Timing and Frequency Synchronization Requirements | This clause specifies the timing and frequency synchronization requirements for DOCSIS 3.1 CMTS transmitters and CM receivers. The purpose of this clause is to ensure that the CMTS transmitter can provide proper timing and frequency references for DOCSIS 3.1 downstream OFDM operation and that the CM receiver can acquir... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.1 Downstream sampling rate | The CMTS shall lock the 204,8 MHz Downstream OFDM Clock to the 10,24 MHz CMTS Master Clock (see table 7.1). |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.2 OFDM RF Transmission Synchronization | The CMTS shall lock the Downstream OFDM RF transmissions to the 10,24 MHz CMTS Master Clock (see table 7.1). |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.3 Downstream OFDM Symbol Clock Jitter | The CMTS shall adhere to the following clock jitter requirements for the downstream OFDM symbol clock over the specified frequency ranges: • < [-21 + 20*log (fDS /204,8)] dBc (i.e. < 0,07 ns RMS) 10 Hz to 100 Hz ETSI ETSI TS 103 311-2 V1.1.1 (2017-02) 107 • < [-21 + 20*log (fDS /204,8)] dBc (i.e. < 0,07 ns RMS) 100 Hz ... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.4 Downstream Timing Acquisition Accuracy | The downstream clock timing is defined with respect to downstream PLC frame. The CM shall be able to adjust its clock to synchronize its own clock timing with PLC frame for proper operation. The CM shall be able to acquire downstream clock timing from downstream traffic (pilots, preambles, or mixed pilots, preambles, a... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.5 Downstream Carrier Frequency Acquisition | The CM shall be able to acquire the carrier frequency from downstream (pilots, preambles, or mixed pilots, preambles and data). |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.3.6 Downstream Acquisition Time | The CM shall achieve downstream signal acquisition (frequency and time lock) in less than 60 s for a device with no previous network frequency plan knowledge. Nonetheless, it is expected that the CM would be able to achieve downstream acquisition in less than 30 s. |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4 Downstream Forward Error Correction | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.0 FEC Scheme | This clause describes the downstream forward error correction scheme used for DOCSIS 3.1. It is based on [6] clause 6.1, FEC Encoding; it is used here with the following modifications: • A codeword will be the size of the short FEC Frame (16 200 bits); the "normal" FEC Frame (64 800 bits) is not used. • Only the code r... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.1 Definitions | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.1.1 Mixed-Modulation Codewords | Before downstream FEC can be defined, it is important to understand what a mixed-modulation codeword is, as these codewords are handled differently. A mixed-modulation codeword belongs to a profile that does not use the same modulation constellation for all sub-carriers of the OFDM symbol. Note that subcarrier zero bit... |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.2 FEC Encoding | |
6bff1d8e6adfce5063e1e51e244276b5 | 103 311-2 | 7.5.4.2.0 FEC Encoding Requirements and Parameters | [6] clause 6.1, FEC Encoding, describes the FEC encoding requirements for the CMTS transmitter. The CMTS shall meet the portion of [6] clause 6.1, FEC Encoding, as described below: The CMTS shall support the 8/9 code rate for the short codeword (Nldpc = 16,200 bits) only. Support for other code rates and codeword sizes... |
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