Joint source-channel decoding by channel-coded optimal estimation (CCOE) for a CELP speech codec

A new algorithm called Channel-Coded Optimal Estimation (CCOE) is adapted to a CELP speech codec. The CCOE-algorithm performs joint source-channel decoding by optimal estimation using bit-reliability informations (soft-bits) and source statistics. The basic algorithm for a simple transmission scenario with a single scalar quantizer has been recently stated by the author. In this paper the basic idea is extended for the use in a CELP speech-codec that was developed for enhanced speech transmission in the GSM mobile radio channel. Simulation results based on informal listening tests are given which show that the new algorithm achieves substantial gains over separate error correction with hard decisions prior to source decoding and classical techniques for error detection and bad frame handling as widely used in the present mobile-radio systems.