1、Rec. ITU-R SNG.1421 RECOMMENDATION ITU-R SNG.1421* 1 COMMON OPERATING PARAMETERS TO ENSURE INTEROPERABILITY FOR TRANSMISSION OF DIGITAL TELEVISION SATELLITE NEWS GATHERING (Question ITU-R 249/4) The ITU Radiocommunication Assembly, (1999) considering that to facilitate the international coverage of
2、news, it is necessary to adopt uniform operating parameters for a) digital satellite news gathering (SNG), to ensure interoperability between equipment from different manufacturers; b) that Recommendation ITU-R SNG. 1007 gives uniform technical standard (digital) for SNG, recommends that the digital
3、 SNG equipment should comply with the uniform operating parameters described in Annex 1. 1 ANNEX 1 1 Scope According to Recommendation ITU-R SNG.770, SNG is defined as “Temporary and occasional transmission with short notice of television or sound for broadcasting purposes, using highly portable or
4、transportable uplink earth stations .”. The equipment should be capable of uplinking the video programme (or programmes) with its associated sound or sounds programme signals. Limited receiving capability should be available in the uplink terminal to assist in pointing the antenna and to monitor the
5、 transmitted signal, where possible. The equipment should be capable of providing two-way communication circuits and data transmission according to Q 4. Maximum commonality with Recommendation ITU-R BO. 121 1 is maintained, such as transport stream multiplexing, scrambling for energy dispersal, conc
6、atenated error protection strategy based on Reed-Solomon (RS) coding, convolutional interleaving and inner convolutional coding. The baseline system includes all the transmission formats included in Recommendation ITU-R B0.1211, based on quaternary phase shift keying (QPSK) modulation. Nevertheless
7、it is possible to use more spectrum efficient modulation schemes like eight-phase shift keying (8-PSK) modulation and sixteen-quadrature amplitude modulation (16-QAM) for some specific applications. The following warnings should be taken into account while using the high spectrum efficiency modes, 8
8、-PSK they require higher transmitted e.i.r.p.s and/or receiving antenna diameters, because of their intrinsic sensitivity to noise and interferences; they are more sensitive to linear and non-linear distortions; in particular 16-QAM cannot be used on transponders driven near saturation; and 16-QAM:
9、- - * This Recommendation should be brought to the attention of Radiocommunication Study Group 11 and Working Party 2 of Telecommunication Standardization Study Group 9. 2 Rec. ITU-R SNG.1421 - they are more sensitive to phase noise, especially at low symbol rates; therefore high-quality frequency c
10、onverters should be used; the system modulationkoding schemes are not rotationally-invariant, so that cycle-slips and phase snaps in the chain can produce service interruptions; therefore frequency conversions and demodulation carrier recovery systems should be designed to avoid cycle-slips and phas
11、e snaps. - The system is suitable for use on different satellite transponder bandwidths, either in single carrier per transponder or in multiple carriers per transponder (frequency division multiplex (FDM) configuration. Appendix 1 gives examples of possible use of the system. Satellite operators sh
12、ould also consider providing appropriate satellite capacity. The use of conditional access systems and other service components, such as auxiliary data or vertical blanking interval data, are outside the scope of this Recommendation. 2 Source encoding, service information and multiplexing 2.1 Video
13、encoding Video encoding to MPEG-2 main profile at main level (MPML) is in accordance with existing standards (ITU-T Recommendation H.222). The use of MPEG-2 4:2:2PML may also be considered. Video source, bit rate, (horizontal and vertical resolution) do not affect interoperability. These parameters
14、are not specified in this Recommendation as integrated receiver decoders (IRD) should handle these automatically. 2.2 Audio encoding Audio encoding to MPEG layer I or II is in accordance with existing standards (ITU-T Recommendation H.222). Audio channel configuration, source and bit rate do not aff
15、ect interoperability. These parameters are not specified in this Recommendation as IRD should handle these automatically. 2.3 Data encoding Subject for further study. 2.4 Program Specific Information (PSI) and Service Information (SI) 2.4.1 General PSI and SI should conform to all relevant requireme
16、nts in accordance with applicable standards and guidelines. The following tables are mandatory for MPEG-2 DVB-S compliance: PAT: Program Association Table PMT: Program Map Table CAT: Conditional Access Table NIT: SDT: TDT: Time and Date Table EIT: Some of these service information tables or their co
17、ntents may not be relevant to digital SNG service, but they are still required. This Recommendation does not specify values or syntax of the service information tables but recommends that wherever possible default values should be used by the equipment to facilitate simple and rapid deployment of di
18、gital SNG. Network Information Table, actual delivery system Service Description Table, (actual transport stream) Event Information Table, presentlfollowing actual transport stream. Rec. ITU-R SNG.1421 3 In digital SNG transmissions, editing of the SI tables in the field may be impossible due to ope
19、rational problems. Therefore, only the following MPEG-2 defined SI tables PAT, PMT and SDT transport stream Service Description Table are mandatory. 2.4.2 First SDT descriptor The first descriptor in the SDT descriptor loop contains the descriptor which identifies the transport stream as of type “CO
20、NA (with reference to the CONtribution Application). Syntax No. of bits Identifier transport-stream-descriptor () descriptor-tag 8 uimsbf descriptor-length 8 uimsbf for (i=O;i Time - For rates 5/6 and 8/9, bit mapping in the 8-PSK constellation shall comply with Fig. 7. If the normalization factor i
21、/ 0.36 dB due to the RS outer code) and include the modem implementation margins. For QPSK the figures are derived from Recommendation ITU-R B0.1211. For 8-PSK and 16-QAM, modem implementation margins which increase with the spectrum efficiency are adopted, to cope with the larger sensitivity associ
22、ated with these schemes. QEF means approximately less than one uncorrected error event per hour at the input of the MPEG-2 demultiplexer. Other residual error rate targets could be defined for contribution quality transmissions. The BER of 2 x lo4 before RS decoding corresponds approximately to a by
23、te error ratio between 7 x lo4 and 2 x 8-PSK rate 819 is suitable for satellite transponders driven near saturation, while 16-QAM rate 314 offers better spectrum efficiency for quasi-linear transponders, in frequency division multiplex access. (2) depending on the coding scheme. 16-QAM (optional) TA
24、BLE 6 DVB transmission Set-up examples 314) 2.76 1.5 9.0 718 3.22 2.1 10.7 Bit rate Ru (after MUX) (MbiVs) MPEG-2 coding profile Modulation MPML I MPML I 8.2941 I QPSK 3.0719 QPSK I MPML I 8.4480 I QPSK MPML MPML I 4:2:2PML I 21.5030 I QPSK 4.6078 QPSK 6.3120 QPSK Symbol Total bandwidth Code rate ra
25、te R, 1.35 R, 2.222 3.000 314 314 3.333 4.500 4.566 6.160 314 I 6.000 I 8.100 314 I 6.1113 I 8.250 718 I 13.3332 I 18.000 Informative note: For bit rates and symbol rates typical accuracy is f 18 Mi-SETUP (ISOG) Rec. ITU-R SNG.1421 TABLE 7 ISOG transmission Set-up example MPML 8.448 QPSK 314 6.1113
26、8.25 Bit rate Ru() Symbol Total (Mbitls) coding profile (I) See ITU-T Recommendation H.262 and Recommendation ITU-R B0.1211. 4 Two-way communication channels Subject for further study. APPENDIX 1 TO ANNEX 1 (Information) Examples of possible use of the system In single carrier per transponder config
27、urations, the transmission symbol rate, R, can be matched to given transponder bandwidth, BW (at -3 dB), to achieve the maximum transmission capacity compatible with the acceptable signal degradation due to transponder bandwidth limitations. To take into account possible thermal and ageing instabili
28、ties, reference can be made to the frequency response mask of the transponder. In the multi-carrier FDM configuration, R, can be matched to the frequency slot, BS, allocated to the service by the frequency plan, to optimize the transmission capacity while keeping the mutual interference between adja
29、cent carriers at an acceptable level. Table 8 gives examples of the maximum useful bit rate capacity Ru achievable by the system versus the allocated bandwidths BW or BS. The figures for very low and very high bit rates may be irrelevant for specific applications. In these examples the adopted BWIR,
30、 or BSIR, ratios are q = 1 + a = 1.35, where a is the roll-off factor of the modulation. This choice allows to obtain a negligible typical figures are of the order of 0.5 to 1.5 dB. 20 Rec. ITU-R SNG.1421 Satellite BW (MHz) 36 36 36 36 72 Quasi-constant envelope modulations, such as QPSK and 8-PSK,
31、are power efficient in single carrier per transponder configuration, since they can operate on transponders driven near saturation. Conversely, 16-QAM is not power efficient since it can only operate on quasi-linear transponders (i.e. with large output-back-off (OBO). The use of the narrow roll- off
32、 a = 0.25 with 8-PSK can produce a larger non-linear degradation by satellite. Slot Number Bit rate Eb/No(l Ru (specification) BSIR, rate Video System coding mode (MBd) (Hz/Bd) (mit/s) (dB) BS of slots (MHz) in BW 9 4 MPML QPSK 6.1113 1.47 8.4480 5.5 rate 314 18 2 4:2:2PML QPSK 13.3332 1.35 21.5030
33、6.4 rate 718 12 3 4:2:2PML 8-QPSK 9.3332 1.28 21.5030 8.9 rate 516 9 4 4:2:2PML 16-QAM 6.6666 1.35 21.5030 10.7 rate 718 18 4 4:2:2PML QPSK 13.3332 1.35 21.5030 6.4 rate 718 Table 10 considers possible examples of use of the system in the multi-carrier FDM configuration and in SCPC mode. Different m
34、odulationkoding modes are given with the relevant bit rates. TABLE 10 Examples of system configurations by satellite: multi-carrier FDM transmissions, SCPC mode (1 The Eb/No figures refer to the IF loop specification for QEF (see 3 5). Overall linear, non-linear and interference degradations by sate
35、llite should be evaluated on a case-by-case basis; typical figures are of the order of 0.5 dB to 1.5 dB. In the FDM configuration, the satellite transponder must be quasi-linear (i.e. with large OSO) to avoid excessive intermodulation interference between signals. Therefore 16-QAM may be used. The s
36、ystem, when operating in 8-PSK and 16-QAM modes, is more sensitive to phase noise than in QPSK modes. Figure 13 shows an example transmit phase noise mask for carriers with information rates 2 048 Mbids, taken from the INTELSAT IESS-3 10 specification fr pragmatic trellis coded 8-PSK modulations. Re
37、c. ITU-R SNG.1421 21 -30 ,X -50 .3 3 -a % -60 .3 a al 3 2 -90 .3 w -100 10 FIGURE 13 Example of continuous single sideband phase noise mask (for carriers with information rates less than or equal to 2 048 Mbit/s) 1 o2 1 o3 1 o4 1 o5 Frequency from centre (Hz) 1 o6 1 o7 142 1 - 13 NOTE 1 - Equipment designers should take account of the total system phase noise requirements, that is arising in the modulator, up/down converters, satellite and the receiver oscillators.
