scope:

The present document describes the modulation and channel coding system (denoted the "System" for the purposes of the present document) for Digital Satellite News Gathering (DSNG) and other contribution applications by satellite.

According to ITU-R Recommendation SNG.770-1 [12], SNG is defined as "Temporary and occasional transmission with short notice of television or sound for broadcasting purposes, using highly portable or transportable uplink earth stations...". The equipment should be capable of uplinking the video programme (or programmes) with its associated sound or sound programme signals. Optionally it should be capable of providing two-way co-ordination (communication) circuits and data transmission according to EN 301 222 [6] (see bibliography). The equipment should be capable of being set up and operated by a crew of no more than two people within a reasonably short time. Limited receiving capability should be available in the uplink terminal to assist in pointing the antenna and to monitor the transmitted signal, where possible.

Digital television contribution applications by satellite consist of point-to-point or point-to-multipoint transmissions, connecting fixed or transportable uplink and receiving stations, not intended to be received by the general public.

Although these applications often transmit a single TV service, the Transport Stream multiplex flexibility also allows multi-programme TV services with associated sound, including commentary sound channels and data services; in this case multiple service components are Time Division Multiplexed (TDM) on a single digital carrier.

Maximum commonality with EN 300 421 [3] is maintained, such as Transport Stream multiplexing [1], scrambling for energy dispersal, concatenated error protection strategy based on Reed-Solomon coding, convolutional interleaving and inner convolutional coding. The baseline System compatibly includes (as a subset) all the transmission formats specified by EN 300 421 [3], based on Quaternary Phase Shift Keying (QPSK) modulation and is suitable for DSNG services as well as for other contribution applications by satellite. Nevertheless, other optional (annex C explains the meaning of "optional" within the present document) transmission modes are added, using Eight Phase Shift Keying (8PSK) modulation and Sixteen Quadrature Amplitude Modulation (16QAM), in order to fulfil specific application requirements. These optional modes can be very efficient in certain contribution applications by satellite.

The following warnings should be taken into account while using the high spectrum efficiency modes, 8PSK and 16QAM:

• they require higher transmitted EIRPs 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 16QAM cannot be used on transponders driven near saturation;
• they are more sensitive to phase noise, especially at low symbol rates; therefore high quality frequency converters should be used (see annex E);
• the System modulation/coding 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 phase 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. Annex E gives examples of possible use of the System.

The present document:

- gives a general description of the System;

- specifies the digitally modulated signal in order to allow compatibility between pieces of equipment developed by different manufacturers. This is achieved by describing in detail the signal processing principles at the modulator side, while the processing at the receive side is left open to different implementation solutions. However, it is necessary in the present document to refer to certain aspects of reception;

- identifies the global performance requirements and features of the System, in order to meet the service quality targets.