Adaptive rate error control for the land-mobile satellite channel

An adaptive rate error control system is presented for communication over a land mobile satellite channel described by a finite state Markov chain. In channel states where the fading is moderate, the code rate is high thus providing increased throughput. In channel states where the fading is more severe, a low rate code is used to provide the necessary error protection. Retransmission requests used by hybrid-ARQ error control are incorporated into the Viterbi decoder following a modification proposed by Yamamoto and Itoh (1980). The decision to change code rates is made by a sequential statistical test which monitors the frequency of retransmissions. The essentials are presented in an example which illustrates the significant performance improvements realized by the adaptive system