Error protection for low rate speech transmission over a mobile satellite channel

The authors examine the error protection strategies for a high-quality code-excited linear predictive (CELP) vocoder to be used for mobile satellite communications. The speech coder has a data rate of 4.8 kb/s and an overall rate of 6.4 kb/s, including error protection coding. The error protection strategies involve selective error correction and error detection along with speech parameter smoothing. Candidate coding strategies are evaluated by examining their performance against burst errors common to a mobile channel and against random errors with fairly high bit-error rates (BERs). It is found that a hybrid parity check coding scheme performs best under these channel conditions. The error protection strategies have been found to work well under burst error conditions designed to simulate a land mobile environment. The proposed coding technique can provide good performance under random error conditions as high as 0.01 BER.