1、ITU-R RECNN*77L-L * .I 4655232 0520959 935 16 Rw. ITU-R SNG.771-1 RECOMMENDATION IT-R SNG.77 1- 1 * AUXILIARY COORDmATION SATELLITE CIRCUITS FOR !ING TERMINALS (Question ITU-R 225/4)* (1992-1993) The ITU Radiocommunication Assembly, co mide ring a) that Satellite News Gathering (SNG) using portable
2、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 SNG is temporary and occasional and its activation often cannot be determined long in advance; cl that SNG operators req
3、uire the use of auxiliary full duplex coordination circuits between the SNG terminal and the satellite operator and broadcasters premises; d) that SNG terminals are often deployed to remote areas where expeditious access to the public switched telephone network can be difficult or impossible; e) tha
4、t throughout the world, where news events take place, uniform technical and operational standards for communication should be established to ensure prompt activation of the SNG serviu:; fi that the technical and operational standards for SNG are defined in other F:ecommendations 770 and 722; s) that
5、 there is a general trend towards the use of digital carriers for the transmission of both data and voice information (see Note 1); Note i - Currently most of the SNG systems are using analogue modulation techniques. Until suitable digital communications systems are widely available, analogue modula
6、tion systems may be used. recommends 1. that SNG earth stations should be equipped to provide two-way satellite immmunication circuits which must be available prior to, during, and after, the transmission of the vision and associatedl sound or sound programme signal. These circuits will provide comm
7、unication between the SNG operator, the satellite operator and the broadcaster; 2. that two or more duplex circuits should be provided, whenever possible within the same transponder as the programme vision and associated sound or sound programme signal; 3. that these communication circuits should be
8、 in compliance with Recomme:ndation ITU-T G.703, i.e. 64 kbids; 4. that the modulation of the communication channel chers should comply with the specification summarized in Annex 1; 5. that for occasions when these circuits cannot be provided in the same transponder with the programme vision and ass
9、ociated sound or sound programme signal, the alternative arrangements detailed in Annex 2 should be followed. * This Recommendation should be brought to the attention of Radiocommunication Study Groups 10 and 11. Formerly Question ITU-R 33-fCMT. * ITU-R RECMN*771-1 93 4855222 0520b0 657 - Rec. ITU-R
10、 SNG.771-1 17 ANNEX 1 The modem used for modulation of the 64 kbitis carriers shall be fully compatible with the current INTELSAT Standard IESS-308. ANNEX 2 There will be occasions when the return communications to the SNG terminai cannot be provided in the same transponder as the video. In these ci
11、rcumstances it may be possible to provide the return communications in another transponder in the same frequency band on the same satellite. In this case the return communications should be provided on the appropriate polarization to avoid the need for a duai polarization feed on the SNG terminais.
12、If it is not possible to provide the communications in the same frequency band as the video signai a number of other solutions are proposed. 1. 6/4 GHz band In one such solution, the communication channel could be provided on a 614 GHz band transponder with global coverage. One particular scheme cur
13、rently under investigation is the use of small (circa 0.8 m) micro terminals employing spread-spectrum modulation. This would support a single 64 kbitis duplex circuit, which may itself include multiple low bit-rate voice duplex circuits. A second solution to this problem, which has been proposed, i
14、s the implemcmtation of a “partial“ dual band feed (Le. 14/12-11 GHz band Ta, 6/4 GHz band Rx) on the SNG terminal. This solution would augment the normal 14/12-11 GHz band transmitireceive capability of the SNG terminai with a 6/4 GHz band receive only capability, thereby enabling the reception of
15、6/4 GHz band transmissions. initiai studies in this area indicate that multiple 64 kbits carriers could be supported with this approach using existing commercially available digital modem technology. Note I - Tx : transmit, Rx : receive. 2. Land mobile earth station (LMES) On some occasions a solution could bc provided by using a land mobile earth station operating at 64 kbitis or an LMES which can support voice grade communication capability.
