Low complexity decoding of variable length source-channel codes

Soft source decoders, in conjunction with error correcting channel codes, can be used to improve the error resilience of digital communication systems based on variable length codes. In this paper, we present a novel approach to reduce the complexity of maximum a posteriori variable length decoders implemented on a bit-symbol trellis. The decoding algorithm is implemented in a narrow corridor along the trellis diagonal to reduce the decoder complexity. Furthermore, by periodically adjusting the corridor boundaries, a significant reduction in complexity is achieved at the price of a small degradation in decoding performance.