Recommendation itu-r sng. 1561 Digital transmission of high-definition television for satellite news gathering and outside broadcasting




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Rec. ITU-R SNG.1561

RECOMMENDATION ITU-R SNG.1561

Digital transmission of high-definition television for satellite news


gathering and outside broadcasting

(Question ITU R 226/4)

(2002)
The ITU Radiocommunication Assembly,

considering

a) that in point to point video transmission via satellite, quality of service objectives are fixed on the basis of large sized transmitting and receiving station antennas;

b) that the introduction of highly portable transmitting stations is essential particularly for news gathering operations and can provide a satisfactory technical solution;

c) that the special characteristics needed for portable and transportable stations and the reduced link availability characteristics of highly portable stations may necessitate acceptance of reduced transmission performance objectives;

d) that it may be necessary to provide, on the same satellite bearer, the auxiliary signals required for the operation of portable and transportable transmitting stations but that these auxiliary signals should not have a perceptible effect on the transmission quality of the television signals;

e) that throughout the world, where news events take place, standardized and uniform technical and operating procedures should be established to ensure prompt activation of satellite news gathering (SNG) and outside broadcasting services;

f) that to facilitate the international coverage of news, it is necessary to adopt uniform operating parameters for high definition television (HDTV) digital SNG, to ensure interoperability between equipment from different manufactures,

noting

a) that Recommendation ITU R SNG.1007 provides uniform technical standards for SNG;

b) that Recommendation ITU-R SNG.1421 gives common operating parameters to ensure interoperability for transmission of digital conventional television SNG,

recommends

1 that when requiring international interoperability, the HDTV digital SNG equipment should comply with the uniform operating parameters described in Annex 1.

ANNEX 1

1 Scope


The system is based on the following technical requirements:

– The system should be applicable to all possible satellite transponders, including future planned ones.

– The source coding system should conform to the MPEG 2 systems1.

– The channel coding system should be as flexible as possible, with the highest possible efficiency for the intended application. It should be selectable by the user according to the characteristics of the transmission channel.

– The user bit rate should meet the picture quality requirements which may be requested from other relevant ITU Study Groups.

– The information bit rate with outer coding should be defined, taking account of connectivity with existing international digital hierarchies as well as coding performance.

 The SNG system may include the auxiliary channels, such as communication channels.

2 Source encoding, service information and multiplexing

2.1 Video encoding


Video encoding in accordance with MPEG-2 4:2:2P@HL is recommended. The use of MPEG 2 MP@HL may also be considered.

Video source and bit rate (horizontal and vertical resolution) do not affect interoperability. These parameters are not specified in this Recommendation as integrated receiver decoders (IRD) should handle these automatically.


2.2 Audio encoding


Audio encoding to MPEG-1 Layers I and II, MPEG-2 Layers I and II, MPEG-2 AAC, or AC 3 should be used.

Audio channel configuration, source and bit rate do not affect 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 requirements in accordance with applicable standards and guidelines.

The following tables are mandatory for MPEG-2 digital video broadcasting using satellite (DVB S) compliance:

PAT: Program Association Table

PMT: Program Map Table

CAT: Conditional Access Table

NIT: Network Information Table, actual delivery system

SDT: Service Description Table, (actual transport stream)

TDT: Time and Date Table

EIT: Event Information Table, present/following actual transport stream.

Some of these service information tables or their contents 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 digital SNG.

In digital SNG transmissions, editing of the SI tables in the field may be impossible due to operational 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


See Recommendation ITU-R SNG.1421.

2.4.3 Second SDT descriptor


See Recommendation ITU-R SNG.1421.

2.4.4 Guidelines

2.4.4.1 Guidelines for the usage of the SDT (transport stream Service Description Table) within digital SNG streams


SDTs are repeated at least every 10 s.

The station_identification_char field contains the following items, comma-separated and in the following order:

usual station code;

– SNG headquarter;

– SNG provider.

The usual station code is the code assigned to the station by the satellite operator with which the station is most frequently used.

The SNG headquarter (operating during the transmission period) is the control centre through which the station can uniquely be identified (by giving its usual station code) and quickly located. The SNG provider is the owner of the SNG station.

IRDs should be flexible enough to handle at least the mandatory service information table, and intelligent enough to ignore optional service information that they have not been designed to utilize.

Digital SNG IRDs shall be able to decode and interpret the SDT and the descriptors specified.

2.4.4.2 Guidelines to achieve compatibility with consumer IRDs


If compatibility with consumer IRDs is required, the SDT shall contain three descriptors:

– The first descriptor is a transport stream descriptor [0x67] containing the ASCII string “DVB”. The presence of this descriptor implies that all SI tables shall be present according to the DVB-SI specification.

– The second descriptor is the transport stream descriptor [0x67] containing the ASCII string “CONA”. The presence of this descriptor indicates that the transmission is of contribution nature.

– For digital SNG transmissions, the third descriptor is the digital SNG descriptor [0x68].


2.5 Multiplexing


The system input stream is organized in fixed length packets, following the MPEG-2 transport multiplexer MUX (see ITU-T Recommendation H.222). The total packet length of the MPEG 2 transport multiplex packet is 188 bytes.

3 Transmission system


The system is defined as the functional block of equipment performing the adaptation of the baseband TV signal, from the output of the MPEG-2 transport multiplexer (see ITU T Recommendation H.222), to the satellite channel characteristics.

The system transmission frame is synchronous with the MPEG-2 multiplex transport packets (see ITU-T Recommendation H.222).

The system uses 8-phase shift keying (8 PSK) modulation, and optionally quadrature (QPSK) or 16 quadrature amplitude modulation (16 QAM) modulations, and the concatenation of convolutional and Reed-Solomon (RS) codes. For 8-PSK and 16-QAM, pragmatic trellis coding applies, optimizing the error protection of the convolutional code defined in Recommendation ITU R BO.1211. The convolutional code is able to be configured flexibly, allowing the optimization of the system performance for a given satellite transponder bandwidth.

All the transmission systems are according to Recommendation ITU-R SNG.1421 (see Fig. 1).



The following processes are applied to the data stream (see Fig. 1):

– transport multiplex adaptation and randomization for energy dispersal (according to Recommendation ITU R BO.1211);

– outer coding (i.e. RS) (according to Recommendation ITU-R BO.1211);

– convolutional interleaving (according to Recommendation ITU-R BO.1211);

– inner coding:

– punctured convolutional coding (according to Recommendation ITU-R BO.1211);

– pragmatic trellis coding associated with 8-PSK and 16-QAM (optional);

– bit mapping into constellations:

– 8-PSK;


– QPSK (optional);

– 16-QAM (optional);

– squared-root raised-cosine baseband shaping:

– roll-off factor   0.35 according to Recommendation ITU-R BO.1211 for QPSK, 8 PSK and 16-QAM;

– additional optional roll-off factor   0.25 (for the modulations 8-PSK and 16-QAM);

– quadrature modulation (according to Recommendation ITU-R BO.1211).

If the received signal is above C/N and C/I threshold, the forward error correction technique adopted in the system is designed to provide a quasi-error-free (QEF) quality target. The QEF means less than one uncorrected error-event per transmission hour, corresponding to bit error ratio  1  10–10 to 1  10–11 at the input of the MPEG-2 demultiplexer.

3.1 Adaptation to satellite transponder characteristics


The symbol rate is matched to given transponder characteristics, and, in the case of multiple carriers per frequency division multiplexing (FDM) transponder, to the adopted frequency plan. Examples of possible use of the system are given in Appendix 1.

3.2 Interfacing


See Recommendation ITU-R SNG.1421.

3.3 Channel coding


See Recommendation ITU-R SNG.1421.

3.4 Baseband shaping and quadrature modulation


See Recommendation ITU-R SNG.1421 taking into account that 8-PSK is the recommended modulation scheme.

3.5 Error performance


See Recommendation ITU-R SNG.1421 taking into account that 8-PSK is the recommended modulation scheme.

3.6 Transmission set-ups for emergency situations


At least one set of operating parameters should be defined for preset or default mode of operation.

4 Two-way communication channels


Subject for further study.

APPENDIX 1



TO ANNEX 1

Examples of possible use of the system

In single carrier per transponder configurations, the transmission symbol rate, Rs 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 instabilities, reference can be made to the frequency response mask of the transponder.

In the multi-carrier FDM configuration, Rs 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 adjacent carriers at an acceptable level.

Table 1 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 BW/Rs or BS/Rs ratios are   1    1.35, where  is the roll-off factor of the modulator. This choice allows to obtain a negligible Eb/N0 degradation due to transponder bandwidth limitations, and also to adjacent channel interference on a linear channel. Higher bit rates can be achieved with the narrow roll-off factor   0.25 (optional for 8-PSK and 16-QAM) and BW/Rs or BS/Rs equal to   1    1.25.

Table 2 considers possible examples of use of the system in the single carrier per transponder configuration. Different modulation and inner code rates are given with the relevant bit rates. According to typical practical applications, a BW/Rs ratio equal to 1.31 is considered, offering a slightly better spectrum efficiency than the examples of Table 1 for the same modulation/coding schemes. The considered transponder bandwidth of 36 MHz is wide enough to allow high quality 4:2:2P@HL single channel per carrier (SCPC) transmissions, as well as MP@HL and 4:2:2P@HL multiple channels per carrier (MCPC) transmissions.

Table 3 gives useful transmission set-up examples conformed for the use of BW/Rs ratio equal to 1.207.



TABLE 1

Examples of maximum bit rates versus transponder BW or BS,
for BW/Rs or BS/Rs    1.35 (applicable for HDTV)



BW
or
BS
(MHz)


Rs  
BW/1.35
(MBd)(1)


Ru (Mbit/s)(2)

QPSK

8-PSK

16-QAM

Rate
1/2


Rate
2/3


Rate
3/4


Rate
5/6


Rate
7/8


Rate
2/3


Rate
5/6


Rate
8/9(3)


Rate
3/4


Rate
7/8


72

53.333

49.1503

65.5338

73.7255

81.9172

86.0131

98.3007

122.876

131.068

147.451

172.026

54

40.000

36.8627

49.1503

55.2941

61.4379

64.5098

73.7255

92.1568

98.3007

110.588

129.020

46

34.074

31.4016

41.8688

47.1024

52.3360

54.9528

62.8032

78.5040

83.7376

94.2047

109.906

41

30.370

27.9884

37.3178

41.9826

46.6473

48.9797

55.9768

69.971

74.6357

83.9651

97.9593

36

26.666

24.5752

32.7669

36.8627

40.9586

43.0065

49.1503

61.4379

65.5338

73.725

86.0131

33

24.444

22.5272

30.0363

33.7908

37.5454

39.4227

45.0545

56.3181

60.0726

67.5817

78.8453

30

22.222

20.4793

27.3057

30.7190

34.1322

35.8388

40.9586

51.1983

54.6115

61.4379

71.6776

27

20.000

18.4314

24.5752

27.6471

30.7190

32.2549

36.8627

46.0784

49.1503

55.2941

64.5098

18

13.333



16.3834

18.4314

20.4793

21.5030

24.5752

30.7190

32.7669

36.8627

43.0065

15

11.111







17.0661

17.9194

24.5752

25.5991

27.3057

30.7190

35.8388

12

8.888











16.3834

20.4793

21.8446

24.5752

28.6710

9

6.666















16.3834

18.4314

21.5033

(1) BW/Rs or BS/Rs ratios different from 1   may be adopted for different service requirements. The adoption of BS/Rs figures significantly lower than 1   (e.g. BS/Rs  1.207 associated with   0.35), to improve the spectrum exploitation, should be carefully studied on a case-by-case basis, since severe performance degradations may arise due to bandwidth limitations and/or adjacent channel interference, especially with 8 PSK and 16 QAM modulations and high coding rates (e.g. 5/6 or 7/8).

(2) Ru stands for the useful bit rate (188-byte format) after MPEG-2 MUX. Rs (symbol rate) corresponds to the  3 dB bandwidth of the modulated signal. Rs (1  ) corresponds to the theoretical total signal bandwidth after the modulator.

(3) 8-PSK rate 8/9 is suitable for satellite transponders driven near saturation, while 16-QAM rate 3/4 offers better spectrum efficiency for quasi-linear transponders, in frequency division multiple access configuration.

TABLE 2


Examples of system configurations by satellite: single carrier per transponder


Satellite BW
(at –3 dB)
(MHz)


System mode

Symbol rate
Rs
(MBd)


Bit rate Ru
(after MUX)
(Mbit/s)


Eb/N0(1)
(specification)
(dB)


36

QPSK rate 3/4

27.500

38.015

5.5

36

8-PSK rate 2/3

27.500

50.686

6.9

(1) The Eb/N0 figures refer to the IF loop specification for QEF. Overall linear, non-linear and interference performance degradations by satellite should be evaluated on a case-by-case basis; typical figures are of the order of 0.5 to 1.5 dB.

Quasi-constant envelope modulations, such as QPSK and 8-PSK, 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   0.25 with 8-PSK can produce a larger non-linear degradation by satellite.

TABLE 3

Transmission set-up examples


BW
or
BS
(MHz)


Rs  BW/1.207
(MBd)


Ru (Mbit/s)

QPSK

8-PSK

Rate
1/2


Rate
2/3


Rate
3/4


Rate
5/6


Rate
7/8


Rate
2/3


Rate
5/6


Rate
8/9


27

22.368

20.6136



30.9205





41.2273





36

29.824

27.4849



41.2273





54.9697





Table 4 considers possible examples of use of the system in the multi-carrier FDM configuration and in SCPC mode. Different modulation/coding modes are given with the relevant bit rates.

TABLE 4

Examples of system configurations by satellite:
multi-carrier FDM transmissions, SCPC mode



Satellite
BW (MHz)


Slot
BS
(MHz)


Number
of slots
in BW


Video
coding


System
mode


Symbol
rate
(MBd)


BS/Rs
(Hz/Bd)


Bit rate
Ru
(Mbit/s)


Eb/N0(1)
(specification)
(dB)


36

18

2

4:2:2P@HL

QPSK
rate 7/8

13.3332

1.35

21.5031

6.4

36

12

3

4:2:2P@HL

8-QPSK
rate 5/6

9.3332

1.28

21.5030

8.9

36

9

4

4:2:2P@HL

16-QAM
rate 7/8

6.6666

1.35

21.5030

10.7

72

18

4

4:2:2P@HL

QPSK
rate 7/8

13.3332

1.35

21.5031

6.4

(1) The Eb/N0 figures refer to the IF loop specification for QEF. Overall linear, non-linear and interference degradations by satellite 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 OBO) to avoid excessive intermodulation interference between signals. Therefore 16-QAM may be used.



The system, when operating in 8-PSK and 16-QAM modes, is more sensitive to phase noise than in QPSK modes.

1 MPEG-2 refers to ITU T Recommendations H.222 and H.262, or ISO/IEC 13818.


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