1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T J.195.2 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2014) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Cable modems and home networking Physical layer specifi
2、cation for high speed transmission over coaxial networks Recommendation ITU-T J.195.2 Rec. ITU-T J.195.2 (10/2014) i Recommendation ITU-T J.195.2 Physical layer specification for high speed transmission over coaxial networks Summary Recommendation ITU-T J.195.2 specifies the physical (PHY) layer spe
3、cification for high-speed data transmission over coaxial cable as part of the high performance network over coax (HiNoC). The HiNoC architecture consists of a HiNoC bridge (HB) and HiNoC modems (HMs), and the HiNoC protocol stack includes the media access control (MAC) layer and PHY layer. HiNoC uti
4、lizes the unassigned spectrum of the “last 100-meter“ coaxial network to provide more bandwidth and improve spectral efficiency. This document contains descriptions for the signal transmission mode of the PHY layer, including frame structure, channel coding and modulation techniques. History Edition
5、 Recommendation Approval Study Group Unique ID* 1.0 ITU-T J.195.2 2014-10-29 9 11.1002/1000/12311 Keywords HiNoC, PHY layer _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/han
6、dle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T J.195.2 (10/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector
7、 (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every f
8、our years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, t
9、he necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary.
10、 However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the neg
11、ative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the u
12、se of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendatio
13、n, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/w
14、ww.itu.int/ITU-T/ipr/. ITU 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T J.195.2 (10/2014) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1
15、 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 2 5 Conventions 3 6 PHY layer structure 3 6.1 Overview 3 6.2 Scrambler 3 6.3 FEC code 4 6.4 Constellation mapping 5 6.5 OFDM modulation and cyclic prefix insertion 7 7 Physical layer frame format 8 7.1 Overview 8 7.2 Preamble
16、 A . 9 7.3 Preamble B . 10 7.4 Payload A . 12 7.5 Payload B 13 8 Spectrum mask 13 Annex A Constellation mapping . 15 Annex B Constellation mapping table 21 Rec. ITU-T J.195.2 (10/2014) 1 Recommendation ITU-T J.195.2 Physical layer specification for high speed transmission over coaxial networks 1 Sco
17、pe This Recommendation specifies the physical (PHY) layer protocol and is part of a series of high performance network over coax (HiNoC) Recommendations for high-speed data transmission over coaxial cable. This Recommendation applies to bi-directional high-performance wideband access digital systems
18、 that use coaxial cable connected between fibre-to-the-building (FTTB) and HiNoC modems (HMs). Frequency planning, safety and electromagnetic compatibility (EMC) requirements are a national matter and are not covered by this Recommendation. Compliance remains the operators responsibility. 2 Referenc
19、es The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users o
20、f this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendati
21、on does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.972 Recommendation ITU-T G.972 (2011), Definition of terms relevant to optical fibre submarine cable systems. ITU-T J.112 Recommendation ITU-T J.112 (1998), Transmission systems for interactive cable television s
22、ervices. ITU-T J.195.1 Recommendation ITU-T J.195.1 (2013), Functional requirements for high speed transmission over coaxial networks connected with fibre to the building. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 constellation ma
23、pping ITU-T J.195.1: The process of mapping the data bits to the constellation symbol. 3.1.2 cyclic redundancy check ITU-T J.112: A method of error detection using cyclic code. 3.1.3 forward error correction ITU-T G.972: A technique which consists of transmitting the data in an encoded form such tha
24、t the redundancy added by the coding allows the decoding to detect and correct errors. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 available sub-carrier: Sub-carriers of OFDM symbol for data bearing. 3.2.2 control frame: Frame of the MAC layer used
25、 for access control and channel allocation. 2 Rec. ITU-T J.195.2 (10/2014) 3.2.3 cyclic prefix: Data located at the front of an OFDM symbol, which is a copy of the data from the end of the OFDM symbol. 3.2.4 data frame: Frame of the MAC layer used to carry data of the upper layer. 3.2.5 downlink: Li
26、nk from HiNoC bridge (HB) to HiNoC modem (HM). 3.2.6 frame check sequence: A redundant sequence that is used for verifying the correctness of the received data. 3.2.7 Pd cycle: A time interval between two adjacent downlink probe frames. 3.2.8 probe frame: Frame of the physical layer used for carryin
27、g signalling frames of the MAC layer. 3.2.9 scrambler: Process that randomizes data using a pseudo-random binary sequence. 3.2.10 signalling frame: Frame of the MAC layer used for node admission, node quitting/deletion and link maintenance. 3.2.11 unavailable sub-carrier: Sub-carriers of OFDM symbol
28、 for adjacent channel protection and zero frequency sub-carrier. 3.2.12 uplink: Link from HiNoC modem (HM) to HiNoC bridge (HB). 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: BCH Bose-Chaudhuri-Hocquenghem CP Cyclic Prefix CRC Cyclic Redundancy Check
29、 Dd downlink Data DQPSK Differential Quadrature Phase-Shift Keying Du uplink Data FCS Frame Check Sequence FEC Forward Error Correction FTTB Fibre-To-The-Building HB HiNoC Bridge HiNoC High performance Network over Coax HM HiNoC Modem IFFT Inverse Fast Fourier Transform MAC Media Access Control OFDM
30、 Orthogonal Frequency Division Multiplexing Pd downlink Probe PSD Power Spectral Density Pu uplink Probe QAM Quadrature Amplitude Modulation QPSK Quadrature Phase-Shift Keying Rec. ITU-T J.195.2 (10/2014) 3 RF Radio Frequency 5 Conventions The keywords “is/are required to“ indicate a requirement whi
31、ch must be strictly followed and from which no deviation is permitted if conformance to this Recommendation is to be claimed. The keywords “is recommended“ indicate a requirement which is recommended but which is not absolutely required. Thus this requirement need not be present to claim conformance
32、. The keywords “is prohibited from“ indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this Recommendation is to be claimed. The keywords “can optionally“ indicate an optional requirement which is permissible, without implying any sense
33、of being recommended. This term is not intended to imply that the vendors implementation must provide the option and the feature can be optionally enabled by the network operator/service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with the spe
34、cification. In the body of this Recommendation and its annexes, the words shall, shall not, should, and may sometimes appear, in which case they are to be interpreted, respectively, as is required to, is prohibited from, is recommended, and can optionally. The appearance of such phrases or keywords
35、in an appendix or in material explicitly marked as informative are to be interpreted as having no normative intent. 6 PHY layer structure 6.1 Overview A functional block diagram of the transmitter is shown in Figure 1. Figure 1 Functional Block Diagram of the Transmitter The data streams (service da
36、ta and signalling data from the media access control (MAC) layer) are transmitted in the following process: scrambler, optional forward error correction (FEC) coding, constellation mapping, orthogonal frequency division multiplexing (OFDM) modulation, cyclic prefix (CP) insertion, framing (into diff
37、erent types of PHY packets) and up conversion to radio frequency (RF) signals. 6.2 Scrambler The data entering into the transmitter is scrambled using the pseudo-random binary sequence that is defined by the generator polynomial 15141)( xxxp . The structure of scrambler is shown in Figure 2. Prior t
38、o the first bit of each frame, the scrambler shifting register is required to be initialized to initial phase 010010011011000 (from bit 15 to bit 1) as shown in Figure 2. For each input bit, the scrambler is shifted 1 position. The input bits are combined with the scrambling sequence through an excl
39、usive-or operator (XOR), resulting in the randomized output bits. 4 Rec. ITU-T J.195.2 (10/2014) Figure 2 Structure of the Scrambler 6.3 FEC code 6.3.1 Overview The FEC encoder is required to support three truncated Bose-Chaudhuri-Hocquenghem (BCH) codes with the following code parameters: (508.472)
40、, (504.432), and (392.248). 6.3.2 (508.472) truncated BCH code The (508.472) BCH code is truncated from (511.475) BCH code, a systematic code with the generator polynomial as shown in Equation (1). 1)( 578111516192021232530313435361 xxxxxxxxxxxxxxxxxg (1) The octal representation for the generator p
41、olynomial is (1630256304641)8. 6.3.3 (504.432) truncated BCH code The (504.432) BCH code is truncated from (511.439) BCH code, a systematic code with the generator polynomial as shown in Equation (2). 1)(2567910131718192021222324252627283233353940414344474950575960616367686971722xxxxxxxxxxxxxxxxxxxx
42、xxxxxxxxxxxxxxxxxxxxxg(2) The octal representation for the generator polynomial is (1561350064670543777423345)8. 6.3.4 (392.248) truncated BCH code The (392.248) BCH code is truncated from (511.367) BCH code, a systematic code with the generator polynomial as shown in Equation (3). 1)(23578161718212
43、4262729303135383943444649505153545659616466687071728182838490919496971001011031041061071081101141161181241261271281291311331341361371391411443xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxg(3) The octal representation for the generator polynomial is (11266572025056663230170016
44、52245562614435511600655)8. 6.3.5 Encoding procedure The truncated BCH encoding procedure is shown in Figure 3. Suppose that the (n, k) truncated BCH code comes from the (ns, ks) systematic BCH code. Input bits enter the BCH encoder in order of110 , kddd . And kks zeros are added in front of 0d to fo
45、rm ks information bits. Then ks information Rec. ITU-T J.195.2 (10/2014) 5 bits are encoded to an sn bits code as per the original BCH code. Finally, the added kks zeros are deleted to get n bits output sequence 110 , nccc . Figure 3 Encoding procedure of truncated BCH code 6.4 Constellation mapping
46、 6.4.1 Overview The constellation mapping unit is required to support differential quadrature phase-shift keying (DQPSK), quadrature phase-shift keying (QPSK), 8 quadrature amplitude modulation (8QAM), 16QAM, 32QAM, 64QAM, 128QAM, 256QAM, 512QAM, and 1024QAM constellations. The input bit order of co
47、nstellation mapping is shown in Figure 4. Figure 4 Input bit order of constellation mapping The input bit stream is in the order of c0, ., cn-1, According to different constellation modes, n bits 01,.,bbn are taken from the bit stream and mapped into a 2n QAM symbol, where bn-1 is the first bit sent
48、 to the constellation mapping unit. 6.4.2 DQPSK For the DQPSK constellation, the modulated symbol sn is taken as the reference symbol, and two input bits b1b0 are mapped into symbol sn+1 according to the mapping table shown in Table 1. Table 1 DQPSK mapping Sn b1b0 00 01 10 11 +1 +1 +j j 1 1 1 j +j
49、+1 +j +j 1 +1 j j j +1 1 +j As shown in Figure A.1 of Annex A, the four DQPSK symbols +1, +j, 1, j correspond to the four points on the axis and the corresponding phases are 0, 2/ , , 2/3 . The initial reference symbol 6 Rec. ITU-T J.195.2 (10/2014) 0s is set to +1 and 0s should not be output. The DQPSK mapping is initialized at the beginning of each frame.
