Premier Mounts CDM-600 specifications Forward Error Correction Options, Viterbi

Chapter 7. FORWARD ERROR CORRECTION OPTIONS

7.1Introduction

As standard, the CDM-600 Modem is equipped with four Forward Error Correction encoders/decoders – Viterbi, Sequential, concatenated Reed-Solomon and Trellis (which is available with the 8-PSK FAST option). The constraint lengths and encoding polynomials are not only Open Network compatible, but are also 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 Coding represents a very significant development in the area of FEC, and optionally, the CDM-600 may be fitted with one of two Turbo Product Codecs They are plug-in daughter cards (SIMM modules), both field upgradeable. The Low Rate option provides data rate capability up to 5 Mbps, and code rates limited to Rate 5/16 (BPSK, Rate 21/44 (BPSK) and Rate 3/4 (QPSK, OQPSK, 8-PSK and 16-QAM). The High Rate option provides data rate capability up to 20 Mbps, in addition to Rate 7/8 and Rate 0.95 capability.

Now, Low-Density Parity Check (LDPC) coding is being offered in addition to the TPC options. In some instances this provides even better performance than TPC. A third option card, again field upgradeable, combines LDPC and TPC together on one module. This povides the best Forward Error Correction technology currently available, and is offered with a sufficient range of code rates and modulation types that link performance can be optimized under any conditions.

7.2Viterbi

The combination of convolutional coding and Viterbi decoding has become an almost universal standard for satellite communications. The CDM-600 complies with the Intelsat

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