Channel decoding using adaptive interframe and intraframe bit prediction in GSM system

Abstract

The goal of source controlled channel decoding is to improve the performance of the channel decoder by using the residual redundancy of the speech encoded data. The original approach exploits only the interframe correlation between bits and few simple schemes have been devised in order to use the intraframe correlation. In this contribution, we present an efficient method to exploit the intraframe correlation during the channel decoding process. We predict the soft value of the bit being decoded from the bits already decoded along the trellis path. Our estimator of bit correlation is adaptively estimated from the soft bits values at the decoder output. Finally, the combination of interframe and intraframe prediction is applied to the full-rate and enhanced full-rate speech codecs in the GSM system.