Constrained Viterbi Algorithm and its Application in SPIHT Coded Images Transmission

The Viterbi algorithm (VA) is a kind of efficient maximum likelihood (ML) decoding method for finite state signals observed in noise environments. But the decoding complexity grows exponentially while the memory size increases and it doesn ´t work well when dealing with burst errors. Constrained Viterbi algorithm (C-VA) was proposed in a novel product code scheme to overcome the drawback. The main idea of constrained Viterbi algorithm is to make full use of some bits which are known to be decoded correctly first. It has been proved that once the reliable constraint condition can be given, the C-VA has great advantages for image transmission. In this paper, by adding constraint condition directly and simply for C-VA in the encoder, a new scheme is proposed for error resilient transmission of set partitioning in hierarchical trees (SPIHT) coded images. Experiments show that it is useful when the channel condition is extremely inferior.