According to ITU-R Recommendation SNG.770-1, Satellite News Gathering (SNG) is defined as "Temporary and
occasional transmission with short notice of television or sound for broadcasting purposes, using highly portable or
transportable up-link earth stations ¿". EN 301 210 [2] describes the frame structure, channel coding and modulation
system for Digital Satellite News gathering (DSNG).
For SNG technical and/or programme co-ordination, and interruptible feed-back, ITU-R Recommendation SNG.771-1
recommends "that SNG earth stations should be equipped to provide two-way satellite communication circuits which
must be available prior to, during and after, the transmission of the vision and associated sound or sound programme
signal. These circuits will provide communications between the SNG operator, the satellite operator and the
broadcaster; 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". The same Recommendation considers "that
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 service". The availability of co-ordination
(communication) circuits by satellite may be particularly useful in areas where access to the public switched or cellular
telephone networks is difficult or impossible. For these purposes, the same antennas of the DSNG stations may often be
used, and the same frequency resources (or at least the same satellite transponder) as the main DSNG signal may be
exploited. Other frequency resources may also be chosen according to the operational conditions and requirements.
To achieve a two-way (i.e. full-duplex) communication channel, two independent carriers have to be transmitted, one
from the DSNG terminal, the other from a fixed station. Dependin (...abbreviated)