Analysis And Study Of Multidimensional Turbo Codes

Turbo code is an important error correcting code in modern communication system. The coding system is a novel combination of iterative decoding with Soft input/ Soft output (SISO) algorithms and Recursive Systematic Convolutional (RSC) codes in parallel connected by an interleaver. With these components, Turbo codes can approach to Shannon limit in AWGN channels. Multiple Turbo codes are one of the important researches in Turbo code, so it attracts many experts and researchers who are in communication system to follow and research.We research the method of encoding and decoding of Multiple Turbo codes in this thesis, and optimize the performance of Multiple Turbo codes in Rayleigh fading channel. First of all, we introduce the theory of channel coding and the structure of encoding and decoding of traditional turbo code. Secondly, we also introduce the decoding algorithm of the component code of traditional turbo code: MAP algorithm, LOG-MAP algorithm and MAX-LOG MAP algorithm, and then, we discuss a reformative MAP algorithm to prove that this algorithm can reduce the time delay without losing the performance, and we will use this method in decoding of Multiple Turbo codes. Next we will have a research in encoding and decoding of Multiple Turbo codes, and analysis several parts of Multiple Turbo codes which are different from traditional turbo code: choice of the component code that the multi-component codes decide multi-structure of decoding, different structure of decoding gained different performance, the extended serial (ES) the best structure of decoding and the reformative MAP algorithm can meliorate the time delay in the use of Multiple Turbo code. Meanwhile, we have many simulation experimentations of Multiple Turbo codes with different parameters, and gained many simulation results,such as the component code, interleaver length, rate , trellis termination and iterative times, all of these are very important factors to effect the performance of Multiple Turbo codes.Multiple Turbo codes have achieved excellent performance over additive White Gaussian noise channels, but the channels of wireless and deep-space communication are fading channels, so the research of Multiple Turbo codes in fading channels is more valuable. In the sixth chapter, we introduce the history of Joint Coded Modulation and combine with Multiple Turbo Codes. And then, we simulated many different rotated angles in Rayleigh fading channel, and we found that MTCs-coded systems exhibit minimum BER performance at the optimum rotated angle. We have a conclusion that optimizing the performance of Multiple Turbo codes in Rayleigh fading channel is to search a best rotated angle.