ITU-T J 141-1999 Performance Indicators for Data Services Delivered over Digital Cable Television Systems - Series J Transmission of Television Sound Programme and Other Multimediaic.pdf

1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU J.141 (09/99) SERIES J: TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Measurement of the quality of service Performance indicators for data services delivered over digital cable tel

2、evision systems ITU-T Recommendation J.141 (Previously CCITT Recommendation) INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STAN DARD IZATI ON SECTOR OF ITU J.141 (09/99) SERIES J: TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Measurement of the quality of s

3、ervice Performance indicators for data services delivered over digital cable television systems ITU-T Recommendation J.141 (Previously CCITT Recommendation) ITU-T J-SERIES RECOMMENDATIONS TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS General Recommendations General specifi

4、cations for analogue sound-programme transmission Performance characteristics of analogue sound-programme circuits Equipment and lines used for analogue sound-programme circuits Digital encoders for analogue sound-programme signals Digital transmission of sound-programme signals Circuits for analogu

5、e television transmission Analogue television transmission over metallic lines and interconnection with radio-relay links Digital transmission of television signals Ancillary digital services for television transmission Operational requirements and methods for television transmission Interactive sys

6、tems for digital television distribution Transport of WEG-2 signals on packetised networks Measurement of the quality of service Digital television distribution through local subscriber networks J. 1-J.9 J.10-J.19 5.20-5.29 5.30-J.39 5.40-5.49 J.50-J.59 J.60-J.69 J.70-J.79 J.80-J.89 J.90-J.99 J. 100

7、-J. 109 J.110-J.129 5.130-J.139 J.14oJ.149 J. 150-J. 159 For further details, please re to ITU-T List of Recommendations. ITU-T RECOMMENDATION 5.141 PERFORMANCE INDICATORS FOR DATA SERVICES DELIVERED OVER DIGITAL CABLE TELEVISION SYSTEMS Summary This Recommendation describes some performance indicat

8、ors to be used to evaluate the performance of digital modems in a hybrid fibrekoax cable television network in the presence of continuous or impulsive noise. Source ITU-T Recommendation 5.141 was prepared by ITU-T Study Group 9 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure o

9、n 16 September 1999. Recommendation 5.141 (09/99) 1 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- cations. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the IT. The ITU-T is responsible fo

10、r 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 Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T St

11、udy Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are

12、prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that

13、 the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The 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 Recommen

14、dation development process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest informatio

15、n and are therefore strongly urged to consult the TSB patent database. o ITU 2000 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the IT. 11

16、Recommendation 5.141 (09/99) _ CONTENTS Page 1 Scope 1 2 References 1 3 Definitions 1 4 Abbreviations and acronyms 1 Appendix I - Example of the use of the recommended performance indicators . 5 Performance Indicators . 1 2 Recommendation 5.141 (09/99) . 111 Recommendation 5.141 PERFORMANCE INDICATO

17、RS FOR DATA SERVICES DELIVERED OVER DIGITAL CABLE TELEVISION SYSTEMS (Geneva, 1999) 1 Scope Recommendation J. 1 1 1 “Network independent protocols for interactive systems“ specifies some characteristics for the modems to be used for the delivery of data services over digital television cable. This R

18、ecommendation recommends some performance indicators to be used to evaluate the performance of those modems in a hybrid fibrekoax (HFC) cable television network in the presence of continuous or impulsive noise. 2 References The following ITU-T Recommendations and other references contain provisions

19、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; all users of this Recommendation are therefore encouraged to investigate the possibili

20、ty 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. - ITU-T Recommendation J. 1 1 1 (1998), Network independent protocolsfor interactive systems. 3 Definitions This Recommendation

21、 defines the following terms: 3.1 when the data frames are transmitted over a noisy channel. frame loss ratio (FLR): The ratio of errored data frames with respect to total number of frames transmitted, 3.2 terms of amount of data transmitted through the unit of bandwidth per unit of time (bits/s/Hz)

22、. bandwidth efficiency (BWE): The amount of data that can be transmitted through a channel, expressed in 4 Abbreviations and acronyms This Recommendation uses the following abbreviations: BWE Bandwidth Efficiency CNR Carrier-to-Noise Ratio FEC Forward Error Correction FLR Frame Loss Ratio 5 Performa

23、nce Indicators Three important indicators have been in successful use and are listed below. Carrier-to-Noise Ratio (CNR) - This is the widely used indicator of the noise level of a transmission channel. Depending on the characteristics of the noise in the channel, it can be expressed in terms of add

24、itive white Gaussian noise, or of impulsive noise bursts of specified duration and repetition rate. This is an indicator of the performance of the transmission network, and it can only be improved by changing the network or improving its maintenance. Recommendation 5.141 (09/99) 1 Frame Loss Raiio (

25、FLR) - The frame loss ratio is the ratio of errored data frames with respect to total number of frames transmitted, when the data fiames are transmitted over a noisy channel. This indicator is often referred to Ethernet-type frames consisting of 64 bytes each, but it is also customary to refer to 53

26、-byte fiames as used in some regions, or to 1518-byte fiames, which are also supported by Ethernet. The value of this indicator is dictated by the desired quality of service that the network should provide for a given service. Banwidth Eflciency (B WE) - The bandwidth efficiency indicates the data c

27、apacity that can be transmitted through the channel. It is expressed in terms of the amount of data transmitted through the unit of bandwidth per unit of time (bits/s/Hz). The value of this indicator is governed by the design of the modem. It should be noted that the usable data includes only the us

28、eful message data. It does not include any overhead needed for forward error correction (FEC) and control. Of course, the greater the percent overhead, the less the useful data that can be delivered. A modem without provision for FEC overhead will have a high bandwidth efficiency, but it will rapidl

29、y fail on a noisy transmission channel. A compromise FLR and bandwidth efficiency must be found case by case. The three indicators above are related to each other and bounded by Shannons law: when the value of CNR is known, the limit to the value of BWE at an arbitrarily small FLR can be computed by

30、 applying that law, The values of the three indicators can be plotted on a three-dimensional graph. In practice, cross sections of the three- dimensional graph, perpendicular to the FLR axis, are often used instead, for the sake of convenience. The line that represents Shannons law can also be plott

31、ed on those bidimensional cross-section graphs; that line describes the maximum theoretical performance possible for any combination of BWE and CNR at an arbitrarily low FLR approaching zero. An example of the use of the described performance indicators is provided in Appendix I. Appendix I Example

32、of the use of the recommended performance indicators - Different services have different error-performance requirements and different data rates. For example, a service, such as status monitoring or polling, may be able to tolerate more errors than a time-critical application, such as video telephon

33、y or “twitch“ video games, where re-transmission of errored frames cannot be tolerated. A system designer engaged in the design of a digital transmission facility intended to provide a given service will try to optimize his choice of values for the three indicators above, through a trial-and-error p

34、rocess based on the steps described below. Create tables or graphs, of the type described above, corresponding to the error performance needed for the service to be provided. This will determine a lower boundary plane, orthogonal to the FLR axis, on the three-dimensional graph described in clause 5.

35、 Characterize the quality of the HFC cable television plant from a CNR and burst-noise distribution point of view. This will determine a lower boundary plane, orthogonal to the C/N axis, on the same graph. Determine the minimum acceptable data rate for the service and the amount of bandwidth which c

36、an be dedicated to that particular service. There are several issues associated with this decision. The bandwidth decision may be limited to a range between strong ingress sources. The service to be provided may be a low revenue-generating service, to which only a modest bandwidth can be dedicated,

37、or the service may be a high revenue-generating service, to which a full channel may be dedicated in the best part of the spectrum. It may be necessary to fit the return channels of all the bidirectional services into a limited return band. Recommendation 5.141 (09/99) 4) Calculate the required band

38、width efficiency by dividing the required bit rate by the available bandwidth. This will determine a lower boundary plane, orthogonal to the BWE axis, on the three-dimensional graph. - The system designer can then plot the performance indicators of the various available modem models on the bidimensi

39、onal cross-section of the three-dimensional graph, applicable to the required FLR value. The designer can focus his choice on those modem models that fall in the area bounded by the lines that correspond to the measured CNR and to the minimum required BWE and thus simultaneously meet or exceed the m

40、inimum identified requirements for CNR, FLR and BWE. The designers attention should particularly focus on those modems that, while meeting the condition above, appear to be closest to the upper boundary of theoretical performance represented by Shannons law. .in 3.5 - 3.0 - N I, 2.5 - t e v L .- 2.0

41、 E al .- E 5 ps 1.5 c m m 1.0 0.5 Vendor D QPSK mode 1 1 I 8 O Figure I. 1 provides an example of such a bidimensional cross-section graph and its use. Vendor A 16-QAM 4 I DOCSIS 16-QAM* 4 DOCSIS 16-QAM t=2* + DOCSIS 16-QAM t=4* + DOCSIS 16-QAM t=10“ 4 4 Vendor A QPSK - DOCSIS QPSK*+ DOCSIS QPSK t=2

42、* 4 - DOCSIS QPSK t=4 Vendor D QAM - DOCSIS QPSK t=10*+ Vendor C QPSK no FEC 4 - Vendor C QPSK FEC t=2 4 4 Vendor D QPSK mode 2 I 4 Vendor 0 QPSK - I I 1 I I I Figure 1.VJ.141 -Bandwidth efficiency vs. CNR for 1% FLR It should be noted that several available modems have a set bandwidth and a set FEC

43、 capability. Therefore, the system designer is limited to what is available. However, some modems have varying parameters that can be used to move to different points on the three-dimensional graph. For the modems with several modes, the system engineer could add points to create more of a continuou

44、s trace and could choose the operating point to be somewhere along the trace. While it would be convenient to choose any arbitrary bandwidth and power efficiency, ail these modems operate with a discrete set of parameters. In an operational system, FEC options, data rates, or bandwidths, can be cont

45、rolled dynamically to adjust for the changing channel conditions. Recommendation 5.141 (09/99) 3 Series A Series B Series C Series D Series E Series F Series G Series H Series I Series J Series K Series L Series M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Serie

46、s X Series Y Series Z ITU-T RECOMMENDATIONS SERIES Organization of the work of the ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors Non-tele

47、phone telecommunication services Transmission systems and media, digital systems and networks Audiovisual and multimedia systems Integrated services digital network Transmission of television, sound programme and other multimedia signals Protection against interference Construction, installation and

48、 protection of cables and other elements of outside plant TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Maintenance: international sound programme and television transmission circuits Specifications of measuring equipme

49、nt Telephone transmission quality, telephone installations, local line networks Switching and signalling Telegraph transmission Telegraph services terminal equipment Terminals for telematic services Telegraph switching Data communication over the telephone network Data networks and open system communications Global information infrastructure Languages and general software aspects for telecommunication systems *17660* Printed in Switzerland Geneva, 2000