A.1 Overview - Comtech EF Data CDM-710 Installation And Operation Manual

Appendix A. FORWARD
ERROR CORRECTION
A.1 Overview
The CDM-710 Broadcast Satellite Modem operates with error correction based
on DVB standards:
• DVB-S – QPSK with concatenated Viterbi and Reed Solomon.
• DVB-DSNG – 8PSK and 16QAM with concatenated Viterbi and Reed
Solomon.
• DVB-S2 – QPSK, 8PSK, 16APSK and 32APSK with concatenated Low
Density Parity Code (LDPC) and Bose-Chaudhuri-Hocquenghem (BCH).
DVB-S and DVB-DSNG anchored one the most widely adopted modulation and
coding schemes deployed, and were universally employed for satellite broadcast
and related applications. DVB-S2 now defines the latest generation of
performance that boosts throughput by about 30% over the same transponders,
using a new type coding that exceeds the capability of concatenated Viterbi and
Reed Solomon coding.
A.2 Viterbi and Reed Solomon
The concatenated Viterbi and Reed Solomon coding technique produces
significant improvement over Viterbi decoding alone. Simplistically, a Reed
Solomon block decoder follows the convolutional Viterbi decoder to further
enhance error correction. Errors exiting the Viterbi decoder tend to occur in
OPTIONS
A–1