Study On Constraint Viterbi Algorithm And Its Application

The channel coding is one of important topics in communication research, and it usually falls into two classes: block codes and convolutional codes. Many of communication systems take the convolutional code and Viterbi algorithm as the channel coding scheme. The Viterbi algorithm decoding is a kind of maximum likelihood decoding, and its performance is good over Additive White Gaussian Noise (AWGN) channel, but when burst errors occur, the decoding performance may be greatly degraded.In this paper, the constraint Viterbi algorithm is studied from the project Research on a Novel Product Code and Decode which is a project of National Natural Science Foundation of China, experiment results show that it can overcome the drawback and reduce the decoding complexity while keeping the good characteristic of conventional Viterbi algorithm. The constraint Viterbi algorithm makes full use of the information which is known to be correctly decoded. A constraint flag array is used based on normal Viterbi algorithm. Simulations over coding channel show that the more correct bits we know the better the performance is.The key point of constraint Viterbi algorithm is how to provide the reliable constraint condition and make full use of it. According the product code scheme proposed in NSFC projects, in that scheme, the product code has a special structure and uses the Cyclic Redundancy Check (CRC)to detect whether the information is decoded correctly. The columns and rows are constrained by each other. The simulations over Binary Symmetric Channe(lBSC)and Gilbert-Elliott Channel (GEC) shows the performance is great improved, especially over burst error channel Peak Signal to Noise Ratio ( PSNR ) is improved more. It is tried to be used in wireless communication system. In the IS95 protocol, because of the different rate in the wireless communication system, a symbol repetition is used to adjust the frame length to the same. In the scheme proposed in this paper, a symbol...