1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU J.142 (OW2 O0 O) SERIES J: TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Measurement of the quality of service Methods for the measurement of parameters in the transmission of digit
2、al cable television signals ITU-T Recommendation J. 142 (Formerly CCITT Recommendation) ITU-T J-SERIES RECOMMENDATIONS TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS General Recommendations General specifications for analogue sound-programe transmission Performance characte
3、ristics of analogue sound-programme circuits Equipment and lines used for analogue sound-programme circuits Digital encoders for analogue sound-programe signals Digital transmission of sound-programme signals Circuits for analogue television transmission Analogue television transmission over metalli
4、c 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 systems for digital television distribution TransDort of WEG-2 signals on
5、Dacketised networks u Measurement of the quaiiy of service Digital television distribution through local subscriber networks J. 1-J.9 J. 10-J. 19 5.20-5.29 5.30-5.39 5.40-5.49 J.50-J.59 5.60-5.69 5.70-J.79 J.80-J.89 J.90-J.99 J. 100-J. 109 J.110-J.129 J. 130-5.139 J. 150-J. 159 For further details,
6、please rer to the list of ITD-T Recommendations. ITU-T Recommendation 5.142 Methods for the measurement of parameters in the transmission of digital cable television signals Summary This Recommendation specifies objective methods for the measurement of parameters in the transmission of digital cable
7、 television signals. The Recommendation is applicable for Digital Cable Television Signals using PSK, QAM and OFDM modulation. Measurement of mutual interference between analogue and digital television signals is also described in the Appendices. Source ITU-T Recommendation J.142 was prepared by ITU
8、-T Study Group 9 (1997-2000) and approved under the WTSC Resolution 1 procedure on 18 May 2000. ITU-T 5.142 (05/2000) 1 FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sect
9、or (U-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 Conference (WTSC), which meets every
10、 four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of U-T Recommendations is covered by the procedure laid down in WTSC Resolution 1. In some areas of information technology which fall within U-Ts purview, the
11、 necessary standards are 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 ITU draws attention to
12、 the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. U takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by U members or others outside of
13、 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 implement this Recommendation. However, implementors are cautioned that this may not represent the latest i
14、nformation and are therefore strongly urged to consult the TSB patent database. o mu 2001 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 ITU
15、. 11 ITU-T 5.142 (05/2000) CONTENTS Page 1 Scope . 2 Informative references 1 3 Terms and definitions . 4 Abbreviations 5 Objective methods for measurements of parameters in the transmission of digital cable television signals . End to end measurement of PSK. QAM modulated television signals Mutual
16、isolation between system outlets . Amplitude response within a channel 5.1.3 RF carrier power Carrier to Noise Ratio (C/N) . Bit Error Ratio (BER) 5.1.8 Noise margin Modulation Error Ratio (MER) . 5.1 5.1.1 5.1.2 5.1.4 RF noise power 5.1.5 5.1.6 5.1.7 BER versus all users of this Recommendation are
17、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. - - ITU-T J. 82 (1 996), Transport of MPEG-2 constant bit rate television sign
18、als in B-ISDN. ITU-T J. 83 (1 997), Digital multi-programme systems for television, sound and data services for cable distribution. ITU-T J. 13 1 (1 998), Transport of MPEG-2 signals in PDH networks. ITU-T J. 132 (1998), Transport of MPEG-2 signals in SDH networks. ITU-T J. 140 (1998), Subjective pi
19、cture quality assessment for digital cable television systems. - ITU-T P.9 1 O (1 999), Subjective video quality assessment methods for multimedia applications. - - - 3 Terms and definitions This Recommendation defines the following terms: 3.1 cable television: Communications systems distributes bro
20、adcast and non-broadcast signals, as well as a multiplicity of satellite signals originating programming and other signals by means of coaxial cable andor optical fibre. ITU-T 5.142 (0900) 1 3.2 MPEG-2: Coding system of video and audio signals defined in ISO/IEC Standard 13818, 3.3 multiplex: A stre
21、am of all the digital data carrying one or more services within a single physical channel. 3.4 service information (SI): Digital data describing the delivery system, content and schedulinghiming to broadcast data streams etc. It includes WEG-2 Program Specific Information (PSI) together with indepen
22、dently defined extensions. 3.5 transport stream (TS): TS is a Transport Stream. 3.6 mutual isolation: The attenuation between specified system outlets at any frequency within the range of the system under investigation. It is always specified, for any particular installation, as the minimum value ob
23、tained within specified frequency limits. ITU-T H.222 and H.262. 4 Abbreviations This Recommendation uses the following abbreviations: 8-VSB BER BPSK BW C/N CATV COFDM cso CTB cw dB dBc dBm dBmV dBpV DVB DVB-SI Eb EB ES FEC GHz Hz VQ ITU-R ITU-T kHz Eight Vestigial SideBand Bit Error Rate Binary Pha
24、se Shift Keying Bandwidth Carrier to Noise ratio Cable Television Coded Orthogonal Frequency Division Multiplex Composite Second Order beat Composite Triple beat Continuous Wave Decibels Decibels below a Carrier used as reference Decibels referred to a 1 mW power Decibels referred to a 1 millivolt r
25、ms signal level Decibels referred to a 1 microvolt rms signal level Digital Video Broadcasting Digital Video Broadcasting - Service Information Energy per bit Errored Block Errored Second Forward Error Correction Giga Hertz (1 O Hertzs) Hertz (1 cycle per second) In-Phase/Quadrature-Phase Internatio
26、nal Telecommunication Union - Radiocommunication Sector International Telecommunication Union - Telecommunication Standardization Sector kilo Hertz (1 O00 Hz) 2 ITU-T 5.142 (05/2000) MATV MER MHz MMDS MPEG MVDS mW NM No O OFDM PRBS PSI PSK QAM QEF QPSK RF RMS R-S S/N SDP SES SHF SI SMATV TCSPSK TCM
27、TEV TS ut XM Master Antenna Television Modulation Error Ratio Mega Hertz (1 O6 Hz) Multichannel Multipoint Distribution System Motion Picture Experts Group Multichannel Video Distribution System Milliwatt Noise Margin Noise power normalized to 1 Hz Degrees Celsius Orthogonal Frequency Division Multi
28、plex Pseudo Random Binary Sequence Program Specific Information Phase Shift Keying Quadrature Amplitude Modulation Quasi Error Free Quaternary Phase-Shift Keying Radio Frequency Root Mean Square Reed- Solomon Signal to Noise ratio Severely Disturbed Period Severely Errored Second Super High Frequenc
29、y Service Information Satellite Master Antenna Television Trellis Coded 8 Phase Shift Keying Trellis Coded Modulation Target Error Vector Transport Stream Unavailable time Cross Modulation 5 Objective methods for measurements of parameters in the transmission of digital cable television signals Over
30、view of cabled distribution system is shown in Figure 5-1. Regardless of system complexity, the method for measurement of parameters shall be specified uniquely for end to end measurement. As a sub-system of cabled distribution system, the SMATVMTV system is shown in Figure 5-2. This Recommendation
31、is applicable to any digital cabled distribution system (including individual receiving systems) having a coaxial cable output and primarily intended for television and sound signals operating between about 30 MHz and 2150 MHz. ITU-T 5.142 (0900) 3 An extension of the frequency range to that fi-om 5
32、 MHz to 3000 MHz will be considered for future work. This Recommendation lays down the basic methods of measurement of the operational characteristics of digital cabled distribution systems having coaxial cable outputs in order to assess the performance of those systems and their performance limits.
33、 5.1 The methods of measurement listed below are applicable to PSK and QAM digitally modulated signals. Specific measurement methods may be required for the transmission of VSB signals on cable; these are under study. - - - RF Carrier power; - RF Noise power; - - Bit Error Rate (BER); - BER versus E
34、bN,; - Noise Margin; - Modulation Error Ratio (MER); - - RF Phase Jitter; - Echoes. End to end measurement of PSK, QAM modulated television signals Mutual isolation between system outlets; Amplitude response within a channel; Carrier to Noise ratio (CN); Signal to noise ratio (SN); 4 ITU-T 5.142 (05
35、/2000) ;I1 rn il n I I I ITU-T 5.142 (0900) 5 6 ITU-T 5.142 (05/2000) The methods of measurement for digitally modulated signals differ from those for analogue modulation for several reasons: a) except in the case of VSB transmission, the carrier is either not present in the modulated signal and the
36、refore cannot be measured (i.e. systems using PSK or QAM modulation as in ITU-T J.83), or there are thousands of modulated carriers .e. systems using OFDM including pilots and BPSK, QPSK and QAM modulation); the modulated signal has a spectrum that is flat in the bandwidth and is similar to noise; t
37、he parameters that affect the quality of the received signal are related to the bit and word errors introduced by the channel (noise, amplitude and phase response inequalities, echoes, etc.) before demodulation and error correction. b) c) The methods of measurement for digitally modulated signals ar
38、e based on the assumption that: a) the MPEG-2 Transport Stream (TS) is the specified input and output signal for all the baseline systems, i.e. for satellite, cable, SMATV/MATV, MMDS/MVDS and terrestrial distribution; the digitally modulated signals received by satellite are modulated in the PSK for
39、mat, i.e. for the QPSK format, and can be distributed in the same format in cable systems (SMATVMATV Systems); the digitally modulated signals received by satellite are distributed in CATV systems in the QAM format; the digitally modulated signals received from terrestrial broadcasting in the OFDM f
40、ormat are distributed in SMATVKATV systems in the same OFDM format; an VQ baseband signal source for PSK or QAM or OFDM format is available, appropriate interfaces are accessible and are consistent with the relevant SI documents; a reference receiver for PSK or QAM or OFDM format is available where
41、appropriate interfaces are indicated; the decoder implementation will not affect the consistency of the results. b) c) d) e) f) g) 5.1.1 Isolation will usually be measured between: a) b) c) adjacent looped system outlets. The method of measurement is based on the use of a sweep generator as for anal
42、ogue modulated signals. Mutual isolation between system outlets system outlets connected to adjacent subscribers taps; system outlets connected to the same multiple subscribers tap; 5.1.2 The method described is applicable to the measurement of the amplitude response of cabled distribution systems o
43、ver the frequency range of an individual channel between two specified points within the system. However, where input signals to the system are demodulated to baseband, and subsequently modulated onto the system carrier frequencies, the response of any demodulator and modulator shall not be included
44、. If it is required to include the characteristics of these items, a separate assessment shall be made using test techniques applicable to such equipment. Where the system contains frequency changing equipment between the antenna input and the system outlet at which the tests are to be made, the cal
45、ibration of the equipment shall be carried out at the output frequencies, having first checked that the output of the frequency generator is also flat over the input channel. Amplitude response within a channel ITU-T 5.142 (0900) 7 The method of measurement is based on the use of a sweep generator a
46、s for analogue modulated signals. 5.1.3 RF carrier power The RF power for digitally modulated carriers (wanted power) is defined by the mean power as measured by a thermal power meter. It can also be measured with a spectrum analyser by integrating the spectrum power in the nominal bandwidth of the
47、channel. (This facility is available in several models of spectrum analysers) The bandwidth of the channel (BW) for PSK, QPSK and QAM signals is defined as the symbol rate times (1 + a). Where a (alpha), the excess bandwidth of the filter, is defined in each application. The bandwidth for OFDM signa
48、ls is the band contained between the two outermost carriers. The RF Carrier power is expressed in dBm (dB relative to 1 mW of power). A vector signal analyser, or any other suitable device designed and calibrated for measurement of the RF power of digitally modulated signals can also be used. Some p
49、recautions have to be taken into account when measuring the RF carrier power, see 1.2. The measurement can be performed at the system outlet, at the outlet of distribution equipment (passive or active), at the outlet of the headend or at the outlet of an outdoor unit (SHF receiver) for satellite reception. 5.1.4 RF noise power Noise is always present in any transmission system and causes important impairments on the transmitted signals. The noise power (or unwanted power) is defined by the mean power as a thermal power meter measures it. It can also be measured with a spect
