Field Guide · protocol

Also known as: DVB-S, DVB-S2, DVB-S2X

DVB-S (Digital Video Broadcasting — Satellite) and its successor DVB-S2 are the ETSI standards for digital television delivered from geostationary satellites.1 Because a satellite transponder is power-limited but bandwidth-rich, DVB-S uses constant-envelope phase modulation — QPSK, or 8PSK and higher APSK orders in DVB-S2 — wrapped in strong forward error correction so the link closes with a small dish under rain fade.

QPSK — 4 phases, 2 bits/symbol downlink satellite dish
DVB-S carries data as satellite-friendly phase modulation; DVB-S2 adds LDPC coding to squeeze near-Shannon capacity from each transponder.

Overview

A DVB-S signal occupies a whole satellite transponder — commonly 27 to 36 MHz — and runs at a symbol rate of tens of millions of symbols per second. The original DVB-S used only QPSK with a concatenated code: an outer Reed–Solomon block code protecting an inner punctured convolutional code. DVB-S2 replaced that with a BCH-plus-LDPC stack and added 8PSK, 16-APSK, and 32-APSK, together with adaptive coding and modulation, so the transmitter can pick the most efficient constellation the current link margin allows.

Technical characteristics

Property Value
Modulation QPSK (S); +8PSK/16-APSK/32-APSK (S2)
Inner FEC Convolutional (S); LDPC (S2)
Outer FEC Reed–Solomon (S); BCH (S2)
Symbol rate ≈ 1–45 Msym/s (transponder-dependent)
Roll-off 35% (S); 35/25/20% (S2); down to 5% (S2X)
Payload MPEG transport stream / generic stream (S2)
Efficiency gain S2 ≈ 30% more capacity than S

History

The DVB Project standardised DVB-S as ETSI EN 300 421 in 1994; it became the workhorse of satellite TV worldwide. DVB-S2 followed in 2005 as EN 302 307, one of the first mass-market systems to adopt LDPC codes, bringing performance within a fraction of a decibel of the Shannon limit.2 The DVB-S2X extension (2014) added finer code rates, lower roll-off, and higher-order constellations for professional and high-throughput links.

Deployment

DVB-S/S2 dominates direct-to-home satellite platforms across Europe, Asia, Africa, the Middle East, and Latin America, and underpins satellite news gathering and broadcast contribution feeds. Ku-band and Ka-band downlinks are received with dishes from 45 cm upward, the size set by the frequency, transponder power, and required rain-fade margin.

Decoding it with GopherTrunk

GopherTrunk does not decode DVB-S; it targets terrestrial land-mobile trunking, not MPEG satellite video. The downlink is nonetheless a favourite of SDR hobbyists: after a low-noise block downconverter shifts the Ku-band signal to an L-band IF, a wideband receiver plus dedicated software can lock a transponder and even display its QPSK/8PSK constellation. The terrestrial and cable siblings are covered under DVB-T and DVB-C.

Sources

  1. DVB-S2 — Wikipedia, for the satellite DVB standards, their phase-modulation constellations, and the move to LDPC coding. ↩

  2. EN 302 307 (DVB-S2) — ETSI, the primary standard defining DVB-S2 channel coding, LDPC/BCH FEC, and modulation. ↩

See also