1、ITU-R RECMN*SNG. 1007-1 95 = 4855212 0525832 368 m Re. ITU-R SNG.1007-1 1 RECOMMENDATION ITU-R SNG. 1007- 1 * UNIFORM TECHNICAL STANDARDS (DIGITAL) FOR SATELLITE NEWS GATHERING (SNG) (Question -R 22814) (1993-1995) The Radiocommunication Assembly, considering a) that Satellite News Gathering (SNG) u
2、sing portable transmitting earth stations is essential for broadcast operations and provides a valuable method of transmission for the rapid acquisition and broadcasting of news events; b) that to facilitate the international coverage of news and to optimize the design of equipment, it would be desi
3、rable to adopt uniform technical standards for digital SNG, taking into account the possibility for interference to other satellites and systems and the need to be interoperable; c) that digital SNG requirements include various communication and transmission support systems and that it is necessary
4、to provide, preferably on the same satellite transponder, auxiliary signals for the operation of digital SNG earth stations; d) that digital SNG earth stations operate mainly in the fixed-satellite service, and should comply with the relevant provisions of the Radio Regulations, and any relevant dom
5、estic regulations requirements; e) that digital SNG transmissions should conform to certain technical criteria with regard to off-axis e.i.r.p. and other antenna characteristics; f) that the technical characteristics of an appropriate identification signal should be specified; g) that digital SNG vi
6、deo terminals could require less transmission power and can use smaller antennas and lighter equipment than analogue SNG video terminals; h) that digital SNG video terminals could utilize less power and bandwidth from the satellite; j) that digital SNG transmissions have lower interference potential
7、 than analogue transmissions, recommends that digital SNG earth-station transmissions should comply with the uniform technical standards as described that digital SNG earth stations equipped to provide two-way satellite communications circuits should comply 1 in Annex 1 ; 2 with Recommendation ITU-R
8、 SNG.77 1. * This Recommendation should be brought to the attention of Radiocommunication Study Groups 10 and 11. ITU-R RECMN*SNG- 1007-1 75 m 4855212 0525833 2T4 m 2 Rec. WU-R SNG.1007-1 ANNEX 1 Technical parameters applicable to digital SNG terminals 1 General performance A digital SNG terminal mu
9、st be able to be rapidly deployed, to transmit (with a minimum of impairments) vision and associated sound or sound programme signals, to provide limited receiving capability to assist in the pointing of the antenna and to monitor (where possible) the transmitted signals, and to provide two-way comm
10、unications for operation and supervision. Digital SNG terminals using a flat (usually phased array antenna) or parabolic antenna consist of the following main units: - - - antenna and feed system with polarization adjustment, antenna mount with azimuth/elevation adjustment, optional antenna tracking
11、 system. (in the case of a flat antenna automatic tracking may be achieved by use of a beacon signal. The satellite uplink and downlink contours must overlap. In the case of a loss of the beacon signal, specific procedures should be initiated in order to avoid interference to other systems), high po
12、wer amplifier/solid state power amplifier (HPNSSPA) for multiplexed visionhounddata channels, receiver unit in order to assist antenna pointing, basebandcoding and modulation equipment and IF to RF upconverter, two-way communication equipment for voicddata, - - - - - system locailremote control pane
13、l, - optional power generator. 2 Transmission performance requirements The baseband digital signal shall be transmitted with a minimum of impairment by adhering to the performance requirements as described in 8 3. 3 RF performance requirements 3.1 Off-axis e.i.r.p. density Shall comply with Recommen
14、dation ITU-R S.524 or the satellite operators requirements, whichever is more stringent. 3.2 Polarization discrimination Some satellites use overlapping channels with orthogonal polarization discrimination. The cross-polarization design for linearly polarized antennas should be better than 30 dB wit
15、hin the -1 dB points of the main axis of the beam and 25 dB elsewhere. 3.3 E.i.r.p. The necessary e.i.r.p. of the digital SNG terminal depends on the required uplink carrier-to-noise ratio C/N and satellite Gfl. However, e.i.r.p. is often limited by the off-axis e.i.r.p. density limits as indicated
16、in 8 3.1. 3.4 Necessary RF bandwidth The necessary RF bandwidth for digital SNG can be determined by taking into account the RF spectrum of the digital signal and the number of associated carriers for auxiliary circuits. ITU-R RECMN*SNG. 1007-1 95 m 4855212 0525834 130 Rec. ITU-R SNG.1007-1 3 3.5 Ou
17、t-of-band e.i.r.p. density The system should be designed with a sufficient output back-off of the amplifier in order to limit the out-of-band emissions due to the output amplifier non-linearity. The exact limit for the permitted out-of-band e.i.r.p. density is determined by the satellite operator. 4
18、 Modulation characteristics The modulation of the carrier with the multiplexed vision, sound and auxiliary data signal shall be fully compatible with the specifications as defined below. The main characteristics are: - - FEC convolution encoding, - - optional outer coding, - coherent QPSK modulation
19、 (other modulation methods may be used), soft decision decoding, e.g. Viterbi, scrambling of data for energy dispersal. 5 Range of bit rates SNG is primarily a contribution link, and as such, the integrity of the original source signal must be maintained throughout the satellite link. For contributi
20、on quality, at least 34 Mbit/s is recommended (see IT-T Recommen- dation J.8 1). It is also desirable to minimize the number of coding/decoding processes. Where possible, large bit rate reduction should be avoided at the beginning of the chain in order to enable good overall performance. The use of
21、lower bit rates (e.g. WEG-2, main profile at main level) will allow small terminals, and will allow to operate them with low power. Equipment with variable or adaptive transmission bit rates can optimize operating conditions. In such cases, the system can be optimized to allow for the best operating
22、 conditions depending on external conditions such as rain attenuation and power limitations. The same precautions should be taken for the audio signals. 6 Identification signal Transmitted by suitable means (method to be further studied). 7 Antenna and feed system The antenna should be small in diam
23、eter, light weight, easy to assemble and easy to transport. The ahtenna radiation patterns in the plane of the orbital arc at the earth station location are such that the off-axis radiation will comply with Q 3.1. The cross-polarization discrimination shall comply with 8 3.2. Repeated assembly and d
24、isassembly of the antenna shall not affect the radiation and cross-polarization discrimination performance. 8 Beacon signal Flat antennas using electronic tracking techniques rely on the presence of an appropriate stable beacon signal. ITU-R RECMNUSNG. 1007-II 95 4855232 0525835 077 I I 9 Auxiliary
25、communications (see Recommendation ITU-R SNG.77 1) 4 Rec. ITU-R SNG.1007-1 Digital SNG uplink signals are often originated from remote areas. In these cases, communication using the public switched telephone network (PSTN) is difficult or impossible. The digital SNG terminal should therefore be equi
26、pped to provide all of its own communications through the satellite to both the satellite operators communication control centre and the broadcasters premises, with the following facilities: - between digital SNG terminals and the satellite operators communication control centre: a minimum of one, t
27、wo- way narrow-band, voiddata communication circuit. This should be available at all times and not be restricted to the transponder booked times. It is desirable that these circuits are provided in the same transponder as the programme vision and sound; between the digital SNG terminal and the broad
28、casters premises: it is desirable to have four (4) two-way, narrow-band, voice/data communication circuits. These circuits should be available for a short time before and after as well as during the transponder booked times. It is essential that these circuits are provided in the same transponder as
29、 the programme vision and sound. - 9.1 Digital SNG terminals require two-way communication channels, in addition to the vision and associated sound, to provide for communications capability with satellite operators communications control centre and the broadcasters facilities. Communication channels
30、 for supervision and coordination The digital SNG terminals are assumed to be located in the downlink footprint. If the digital SNG terminal is not in the downlink footprint, other solutions, as described in Annex 2 to Recommen- dation IT-R SNG.77 1, are required. It should be noted that several dom
31、estic systems are presently in operation using various communication techniques. 9.2 Liaison with the satellite operators communications control centre should be available at all times and should not be restricted to the duration of the transponder booking. For this purpose it is desirable that coor
32、dination circuits, in each direction, be provided preferably in the same transponder as the programme vision and sound. If it is necessary to provide these carriers elsewhere on the satellite, and linear polarization is being used, they should be provided on the appropriate polarization to avoid the
33、 need for a dual polarization feed on digital SNG terminals. Circuits between digital SNG terminai and satellite operator 9.3 Circuits between digital SNG terminal and broadcasters premises For the purpose of communicating with the broadcasters premises, typically up to four (4) two-way (duplex) voi
34、ce/data circuits are required per broadcaster. These circuits generally operate for brief periods before and after transponder bookings and during actual programme transmissions. These “two-way” circuits between the digital SNG terminal and the broadcasters premises could be used for: - production c
35、oordination, - engineering coordination, - programme-related data transmission, - more than one broadcaster, - more than one language. 10 Video/audio/RF monitoring equipment To allow the digital SNG terminal operator to properly set up the terminal, monitoring equipment is essential. To simulate the
36、 satellite transponder it is advantageous to provide a loop-test translator and video/audio receiver to verify the performance of the uplink equipment. Due to the low Gfl of the digital SNG antenna system and the particular operational configuration of the satellite system, it is normally not possib
37、le to monitor the transmitted video and audio signals at full quality. However, G/T should be adequate for communication channels. ITU-R RECMNUSNG. 1007-1 95 W 4855212 0525836 TO3 RC. ITU-R SNG.1007-1 5 11 Other design considerations The digital SNG terminal can be designed with all the equipment ne
38、xt to the antenna or with the high power amplifiedsolid state power amplifier (HPAISSPA) at the antenna and the other equipment located some distance (e.g. less than 50 m) away from the antenna. The latter option, which is operationally preferable, allows the digital SNG terminal to be operated and
39、monitored from indoors after antenna alignment. The HPA/SSPA must be located as close as possible to the antenna to minimize the waveguide losses. The system should be designed to accept redundant radio-frequency power amplifiers. System interconnections must be reduced to a minimum to allow quick a
40、nd easy Set-up under ali weather conditions, all external connections must be waterproof. It is desirable that the digital SNG terminal can accept a power input of 100-250 V/50-60 Hz. The design of the shipping cases should allow the terminai to be operated in direct rain with the lids removed. The
41、cases must provide a controlled environment for the electronics to allow proper operation during extremes of both high and low temperatures. The digital SNG terminai must be designed to offer the maximum possible safety to the operator. 12 Additional technical parameters Considerations on pointing a
42、ccuracy, polarization plane alignment and spurious emission are to be developed. 12.1 The small SNG terminal using a flat antenna is designed for easy portability, rapid deployment and prompt activation. By receiving a beacon signal transmitted via satellite by a “hub” station, it is only necessary
43、to orient the flat antenna to within only a few degrees (for example: less than about 5”) of the satellites orbital position at which point the system automatically adjusts for optimum orientation and polarization alignment. Digital SNG terminal using a flat antenna equipped with electronic tracking facilities
