1、 International Telecommunication Union ITU-T J.381TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (09/2012) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Digital transmission of television signals Requirements for advanced digital cable transmi
2、ssion technologies Recommendation ITU-T J.381 Rec. ITU-T J.381 (09/2012) i Recommendation ITU-T J.381 Requirements for advanced digital cable transmission technologies Summary Recommendation ITU-T J.381 specifies the requirements that should be considered for advanced digital cable transmission tech
3、nologies (ACTTs) to provide high spectral efficiency schemes designed to save transmission resource in hybrid fibre/coax (HFC)-based networks. History Edition Recommendation Approval Study Group 1.0 ITU-T J.381 2012-09-22 9 ii Rec. ITU-T J.381 (09/2012) FOREWORD The International Telecommunication U
4、nion (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions
5、 and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on
6、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, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the e
7、xpression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or appli
8、cability) 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 negative equivalents are used to express requirements. The use of such words does not suggest that compliance with t
9、he Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicab
10、ility 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 Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implemen
11、t 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:/www.itu.int/ITU-T/ipr/. ITU 2013 All rights reserved. No part of this publication may be reproduced, by any means
12、 whatsoever, without the prior written permission of ITU. Rec. ITU-T J.381 (09/2012) iii Table of Contents Page 1 Scope 1 1.1 Reference architecture 1 1.2 Considerations 2 2 References. 3 3 Definitions 3 3.1 Terms defined elsewhere 3 3.2 Terms defined in this Recommendation . 3 4 Abbreviations and a
13、cronyms 3 5 Conventions 4 6 General requirements 4 7 Performance and efficiency requirements 5 8 Requirements of downstream PHY 6 9 Requirements of upstream PHY . 6 Appendix I Examples of transmission regarding downstream throughput improvement of ACTT compared to Annex B of ITU-T J.83 8 Bibliograph
14、y. 9 iv Rec. ITU-T J.381 (09/2012) Introduction As the demand from consumers for high-quality broadcast and multicast services increases, cable system operators are seeking more efficient ways to transmit those services through hybrid fibre/coax (HFC)-based networks. Representative examples of high-
15、quality broadcast services could be 3DTV and ultra high definition TV (UHDTV), and those of multicast services could be Data over Cable Service Interface Specification (DOCSIS) 3.0, standard definition/high definition (SD/HD), video on demand (VoD), switched digital video (SDV) and Internet protocol
16、 TV (IPTV). There are several solutions that have been developed to solve the issues described above. First, some approaches are focusing on efficient compression of audio/video data so that more contents can be transmitted using the same channel bandwidth. Examples of this approach are Recommendati
17、on ITU-T H.264 and high efficiency video coding (HEVC). Second, some technologies aim to extend the usable frequency spectrum in HFC-based networks. In most cases, multiple system operators (MSOs) are using the frequency bandwidth up to 860 MHz, optionally up to 1 GHz, for their broadcasting and dat
18、a services. These kinds of technologies can provide more transmission resources by increasing the usable frequency spectrum. The third approach focuses on improvement of spectral efficiency per hertz (i.e., bits per second per hertz). In order to improve spectral efficiency, these kinds of technolog
19、ies usually support higher order modulation, stronger FEC schemes, more efficient framing structures and so on. Regarding the modulation and coding scheme, the current transmission technology, which is widely used in the cable industry, is Recommendation ITU-T J.83. This Recommendation was developed
20、 and deployed in the 1990s and can support up to 39 Mbit/s per 6 MHz channel when using a 256-QAM modulation scheme. Rec. ITU-T J.381 (09/2012) 1 Recommendation ITU-T J.381 Requirements for advanced digital cable transmission technologies 1 Scope Among the three options described in the introduction
21、, this Recommendation limits the scope to the employed technologies to improve spectral efficiency for downstream and upstream over hybrid fibre/coax (HFC)-based networks. The requirements stated herein are intended to be technology neutral. Furthermore, this Recommendation defines the requirements
22、for advanced digital cable transmission technologies on the physical layer, which includes modulation, channel coding, transmission schemes and frame structure for providing higher spectral efficiency. 1.1 Reference architecture Figure 1 shows a reference architecture of advanced digital cable trans
23、mission technologies. The headend part is composed of downstream Tx PHY and upstream Rx PHY. Furthermore, the user terminal is composed of the downstream Rx PHY and the upstream Tx PHY. As Figure 1 shows, the downstream Tx PHY includes a downstream framer, a downstream FEC encoder and a downstream m
24、odulator. The downstream framer that receives multiple stream formats, such as MPEG-2 transport streams and Ethernet packet streams, will have a function of framing these kinds of streams. The downstream framer is followed by the downstream FEC encoder, which will have the function of encoding to pr
25、otect information data from channel noise through the HFC networks. The downstream modulator will have multiple functions, including mapping for improving spectral efficiency, interleaving for protecting information data from burst noise in both time and frequency domains, and so on. The downstream
26、Rx PHY includes a downstream demodulator, a downstream FEC decoder, and a downstream deframer. The downstream demodulator will have the functions of timing offset recovery, frequency offset recovery, phase offset recovery, a demapper to retrieve transmission information, de-interleaver (the counterp
27、art of the interleaver), and so on. The downstream demodulator is followed by the downstream FEC decoder, which will have the function of error correction from channel noise in the HFC network. The downstream deframer will rebuild multiple format streams, such as MPEG-2 transport and Ethernet packet
28、 streams from the frame structure for transmitting signals through HFC-based networks. The upstream Tx PHY, which includes an upstream framer, an upstream FEC encoder and an upstream modulator, will have a function similar to the downstream Tx PHY. Furthermore, the upstream Rx PHY, which has an upst
29、ream demodulator, an upstream FEC decoder and an upstream deframer, will have a similar function of the downstream Rx PHY. 2 Rec. ITU-T J.381 (09/2012) Figure 1 A reference architecture of advanced digital cable transmission technologies 1.2 Considerations Advanced digital cable transmission technol
30、ogies should take into account the following considerations. Cable operators are seeking advanced technologies for highly efficient frequency spectrum utilization over their HFC-based networks. An improvement figure of 30% or greater is deemed to be the minimal impetus for cable operators to deploy
31、advanced technologies into their networks. Since many countries consider HFC-based networks as one of the primary means for delivering broadcasting contents to their citizens, retransmission of terrestrial and satellite broadcasting over HFC will be necessary. There are various packet formats used i
32、n delivering broadcasting and multicasting services in other networks, so the advanced digital cable transmission technologies need to accommodate these input formats. A channel-bonding scheme is very useful for delivering high-volume content over HFC-based networks along with utilization of the ava
33、ilable frequency spectrum. Interactive services such as gaming or IPTV are very sensitive to time latency. From the user experience viewpoint, acceptable delay for video channel switching and delivery of a visually stable image to the display device is deemed to be approximately 300 ms. Currently, c
34、able operators use DOCSIS for providing interactive data services, so the advanced digital cable transmission technologies need to harmonize with DOCSIS transport systems. For developing practical transmission technologies, it is necessary to take into account HFC-based networks which are characteri
35、zed and modelled on a global (e.g., North America, Asia and Europe) level (including customer premises networks) and realistic cable channel models, which include: deployment of analogue PAL/SECAM/NTSC television channels; deployment of different digital signals (such as ITU-T J.83, DOCSIS, DAVIC) a
36、nd the associated signal back-off ratios to analogue signals; Rec. ITU-T J.381 (09/2012) 3 different noise types (e.g., white, burst, impulse), non-linearities, and other impairments present in current and future networks. 2 References The following ITU-T Recommendations and other references contain
37、 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 of this Recommendation are therefore encouraged to investigate the p
38、ossibility 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 Recommendation does not give it, as a stand-alone document, the status of a Rec
39、ommendation. ITU-T J.83 Recommendation ITU-T J.83 (2007), Digital multi-programme systems for television, sound and data services for cable distribution. ITU-T J.222.1 Recommendation ITU-T J.222.1 (2007), Third-generation transmission systems for interactive cable television services IP cable modems
40、: Physical layer specification. ITU-T Resolution 73 ITU-T Resolution 73 (2008), Information and communication technologies and climate change. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following term defined elsewhere: 3.1.1 DOCSIS ITU-T J.222.1: Data Over Cable Service
41、Interface Specifications. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 advanced digital cable transmission technology (ACTT): Advanced digital cable transmission technology on the physical layer, which includes modulation, channel coding, transmissi
42、on schemes and frame structure to provide higher spectral efficiency. 3.2.2 HFC-based networks: HFC-based networks include legacy cable networks such as hybrid fibre coax; recent technology deployments such as radio frequency over glass (RFoG); and cable network technologies that may be deployed in
43、the near future. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: 3DTV Three Dimensional Television ACM Adaptive Coding and Modulation ACTT Advanced digital Cable Transmission Technology CMTS Cable Modem Termination System DOCSIS Data Over Cable Service
44、 Interface Specification FEC Forward Error Correction HD High Definition HDTV High Definition Television 4 Rec. ITU-T J.381 (09/2012) HEVC High Efficiency Video Coding HFC Hybrid Fibre/Coax IPTV IP Packet Television MSO Multiple System Operators PHY Physical Layer QAM Quadrature Amplitude Modulation
45、 RF Radio Frequency RFoG Radio Frequency over Glass Rx Receiver SD Standard Definition SDTV Standard Definition Television SDV Switched Digital Video Tx Transmitter UHD Ultra High Definition UHDTV Ultra High Definition Television VoD Video on Demand 5 Conventions In this Recommendation: The keywords
46、 “is required to“ indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed. The keywords “is recommended“ indicate a requirement which is recommended but which is not absolutely required. Thus, this requirement n
47、eed not be present to claim conformance. The keywords “is prohibited from“ indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed. The keywords “can optionally“ indicate an optional requirement which is permiss
48、ible, without implying any sense 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 sti
49、ll claim conformance with the specification. In the body of this Recommendation, 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 in an appendix or in material explicitly marked as informative is to be interpreted as having no normative intent. 6 General requirements ACTT-GER-001 ACTT is required to be applied to HFC-based networks. ACTT-GER-002 ACT
