Comparison And Analysis Of The Decoding Algorithm Of Turbo-codes And Its Application In CPM

The technology of Error-Correcting Coding has been widely used in the digital communications as an effective means of decreasing bit error rates. In 1993, a Frenchman named C.Berrou advanced an exciting coding structure called Turbo-codes. The Turbo-codes' encoder is comprised of Recursive Systematic Convolutional Codes, which is connected by an interweaver. And the decoding algorithm of Turbo-codes, such as (log) MAP, Max-log-MAP and SOVA, are all based on the soft input and soft output (SISO) module.First of all, the research emphasis of this paper is placed on the performance comparison of some kinds of decoding algorithm of Turbo-codes such as (log-)MAP, Max-log-MAP and SOVA in a wide range. And through simulation, this paper proves that: (1) The distribution of LLR sequence of Log-MAP is unorderly, compared with that of BCJR decoding algorithm. (2) The performance of Log-MAP is hardly influenced by the accuracy of the estimation of noise's power in AWGN channel. (3) The mean and the variance of LLR sequence of Log-MAP decoding algorithm change with the SNR in approximately linear order respectively.On the other hand, this paper also does some research on the technology of the combination of Turbo-codes and CPM. The research emphasis is placed on the Minimum Euclidean Distance of the modulated signals and the best Turbo codes, and the result from computer research is compared with the one of convolutional coded CPM, which has strongly proved the better performance of Turbo-codes.