Realtime robust speech communication based on iterative joint source-channel decoding and demodulation algorithm for MELP vocoder

Realtime speech communications require high efficient compression algorithms to encode speech signals. As the compressed speech parameters are highly sensitive to transmission errors, robust source and channel decoding and demodulation schemes are both important and of practical use. In this paper, an iterative joint source-channel decoding and demodulation algorithm is proposed for mixed excited linear prediction (MELP) vocoder by both exploiting the residual redundancy and passing soft information throughout the receiver while introducing systematic global iteration process to further enhance the performance. Being fully compatible with existing transmitter structure, the proposed algorithm does not introduce additional bandwidth expansion and transmission delay. Simulations show substantial error correcting performance and synthesized speech quality improvement over conventional separate designed systems in delay and bandwidth constraint channels by using the joint source-channel decoding and demodulation (JSCCM) algorithm.