A multimode voice communications system with source-matched error protection for mobile communications

This paper presents the design of a source matched error protection code, tailoring the encoding operations to suit the different sensitivities of source bits to channel errors, in applications involving channels with time-varying error characteristics. The source coding algorithm selected for the qualitative analysis is a fast variable rate CELP coder (FVR-CELP), developed by CSELT S.p.A. in the UMTS Code Division Testbed (CODIT) project. We determine, on the basis of the quality degradation tolerated by each bit-group of the FVR-CELP coder, the unequal error protection needed by these bit-groups in different channel conditions. The FEC (forward error correction) protection chosen for the analysis are a set of source-sensitivity matched binary Bose-Chaudhury-Hocquenghem (BCH) codecs.