The Study Of Turbo Theory And Its Performance Of Quantization On Decoding

Turbo codes is a new class of error-correcting codes that can approach the Shannon bound. It is considered as the most exciting and potentially important development in code theory in recent years. Its invention has changed the conventional design principles of the coding scheme from the attempt to increase the minimum Hamming distance of the code to the goal of reducing the number of code words with low Hamming weights. This thesis investigates some problems of turbo codes with emphasis on the turbo theory, the quantization of the turbo decoder and its performance, the performance of turbo codes on Rayleigh fading channel and the turbo codes with OFDM and so on. The main results and contents of this dissertation covers the follows: 1. The development on the theory and technique of channel coding is outlined, the development and application of turbo codes is also discussed. 2. The theory of iterative decoding of turbo codes is shown, and the decoding algorithm of turbo codes over AWGN channel is displayed. 3 For different decoding algorithm and different signal, different quantization scheme is used. The nonuniform quantization method for the special property signal is put forward for the first time. 4. According to the characteristic of Rayleigh fading channel and combine with the channel property, the decoding algorithm of turbo codes on fading channel is discussed and its performance is also shown. 5. In the future application, the theory of turbo codes with OFDM is introduced, a new scheme of TTCM with OFDM is also suggested. As the selected code of 3GPP, the study of turbo code is of great significance. The application of turbo code still faces some problems. The study of quantization and decoding on AWGN channel is intended to solve the application problems. There are many problems left on the turbo theory which need advanced study. Now a days, OFDM has become into a hot area in the High Speed Digital Transmitting, the combination of turbo codes with OFDM can be applied to the HSDT. We have little work on this title, and great effort will be done to this problem.