Channel adaptive joint source-channel coding of speech

Abstract

We present a novel joint source-channel coding scheme for speech signals. The source coder is a perceptually based sub-band coder producing bits with different error sensitivities. The channel encoder is a rate compatible punctured trellis code (RCPT) that permits unequal error protection. The RCPT code design naturally incorporates large constellations, allowing a high information rate per symbol. The source coder is robust to acoustic noise, adapts automatically every 20 ms and produces good quality speech for a wide range of channel conditions. The paper presents a method for finding the optimal puncturing architecture for different source bit rates and channel conditions. The resulting joint source-channel coder is suitable for situations where the channel is time varying such as in mobile communications.