Performance of Sequentially Decoded Long Constraint Length Codes for a Satellite Communications Link in a Scintillated Channel.

摘要

Convolutional codes with long constraint lengths, on the order of 25 to 30, can be decoded using the Fano sequential decoding algorithm. While some increase in coding gain over short codes may be achieved for small probabilities of bit error, sequential decoding is not optimum and does not perform as well as the Viterbi decoding algorithm. However, because of power limitations on satellite downlinks, the possibility of achieving some additional gain with long constraint length codes for the scintillated signal channel is receiving increasing interest. This report presents an analysis of the performance and implementation trade-offs between short codes with Viterbi decoding and long codes with sequential decoding in an additive white Gaussian noise channel and a scintillation channel created by a high-altitude nuclear detonation. Performance is provided for and EHF, 2400 bps, DBPSK modulated satellite communications link in terms of bit error rates and decoded bit processing delays.