CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
FEC (Forward Error Correction) Options B–1 MN-CDM570A
Appendix B. FEC (FORWARD
ERROR CORRECTION) OPTIONS
B.1 Overview
The CDM-570A/570AL Satellite Modem is equipped with VersaFEC (short-block LDPC), Turbo
Product Code (TPC), Viterbi, Reed-Solomon (Closed Network), and Trellis with concatenated
Reed-Solomon Forward Error Correction encoders/decoders. The constraint lengths and
encoding polynomials are Closed Network compatible with the vast majority of existing modems
from other manufacturers. Comtech EF Data has performed compatibility testing to ensure inter-
operability.
Turbo Product 0.95 Code Rate (TPC) is available via an optional plug-in card.
While the performance of LDPC is exceptional in terms of coding gain, its higher latency is
considered disadvantageous in some applications. For this reason, Comtech EF Data and
Comtech AHA Enterprise Products Group have jointly developed a family of short-block LDPC
codes called VersaFEC
®
. (The name VersaFEC
is a trademark registered to Comtech AHA
Enterprise Products Group.)
VersaFEC is ideal for lower data rates that demand the shortest possible latency, and is available
as a FAST option. It represents the best Forward Error Correction (FEC) technology currently
available, and is offered with a sufficient range of code rates and modulation types that link
performance can be optimized under almost any conditions.
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