DVB-S/S2

The DVB-S standard EN 300 421 was introduced in 1994, and the DVB-DSNG standard EN 301 210 in 1997. The DVB-S standard specifies QPSK modulation and concatenated convolutional and Reed-Solomon channel coding, and has since been used by most satellite operators worldwide for television and data broadcasting services. DVB-DSNG specifies, in addition to DVB-S format, the use of 8PSK and 16QAM modulation for satellite news gathering and contribution services.

Since 1997, digital satellite transmission technology has evolved significantly:

• New channel coding schemes, combined with higher-order modulation, promise more powerful alternatives to the DVB-S/ DVB-DSNG coding and modulation schemes. The result is a capacity gain in the order of 30 % at a given transponder bandwidth and transmitted EIRP, depending on the modulation type and code rate.
• Variable coding and modulation (VCM) may be applied to provide different levels of error protection to different service components (e.g. SDTV and HDTV, audio, multimedia).
• In the case of interactive and point-to-point applications, the VCM functionality may be combined with the use of return channels to achieve adaptive coding and modulation (ACM). This technique provides the best-suited channel protection and dynamic link adaptation to propagation conditions, targeting each individual receiving terminal. ACM systems promise satellite capacity gains of as much as 100 % to 200 %. In addition, service availability may be extended compared to a constant coding and modulation system (CCM) such as DVB-S or DVB-DSNG. Such gains are achieved by informing the satellite uplink station of the channel condition (e.g. C/(N+I)) of each receiving terminal via the satellite or terrestrial return channels.
• DVB-S and DVB-DSNG are strictly focused on a unique data format, the MPEG transport stream (ISO/ IEC 13818-1). Extended flexibility to cope with other input data formats (such as multiple transport streams, or generic data formats) is now possible without a significant increase in complexity.

The DVB-S2 standard EN 302 307 defines a "second generation" modulation and channel coding system to make use of the improvements that have emerged since the publication of the DVB-S standard. DVB-S2 is a single, very flexible standard covering a variety of applications by satellite.

It is characterized by:

• A flexible input stream adapter, suitable for operation with single and multiple input streams of various formats (packetized or continuous).
• A powerful FEC system based on low-density parity check (LDPC) codes concatenated with BCH codes, allowing quasi-error-free operation at approx. 0.7 dB to 1 dB from the Shannon limit, depending on the transmission mode (AWGN channel, modulation constrained Shannon limit).
• A wide range of code rates (from 1/4 up to 9/10).
• Four constellations, ranging in spectrum efficiency from 2 bit/s/Hz to 5 bit/s/Hz, optimized for operation over non-linear transponders.
• A set of three spectrum shapes with roll-off factors 0.35, 0.25, and 0.20.
• Adaptive coding and modulation (ACM) functionality, optimizing channel coding and modulation on a frame-by-frame basis.

The system has been optimized for digital multiprogram television broadcast services and high definition television (HDTV) broadcast services to be used for primary and secondary distribution in the fixed satellite service (FSS) and the broadcast satellite service (BSS) bands.