Research On Key Techniques Of Turbo Code And The Application Of Turbo Principle

Turbo code, which utilizes the condition of random coding and decoding of Shannon noisy channel coding theorem, has obtained the performance near to Shannon theoretic limit. The performance of turbo code is the best one in all presented coding methods. The present of it is viewed as landmark in the development of the theory of channel coding.In the dissertation, the principle of coding and decoding for turbo codes are introduced. Based on the simulation results, the key techniques for the design of turbo codes, including the choice of component codes, the design of interleaver, trellis termination schemes and puncturing methods, are discussed deeply. By measuring the statistical characteristic of extrinsic information from component decoders, new iterative stopping criteria and SNR estimation updator are devised. Also, it is used to implement synchronization of carrier phase. At last, Turbo equalization is analysed simply.The main content of the dissertation includes:1. The channel capacity of AWGN channel and Rayleigh fading channel with binary input and continuous output are derived and the Shannon capacity limits for different code rate are provided.2. The principle of coding and decoding for turbo codes, including PCCC, SCCC and HCCC, are discussed; Based on the introduction of the modified and simplified MAP algorithms on AWGN channel for turbo codes, multiplicative and additive SISO decoding algorithms adapted to general iterative decoding are derived.3. The effect of different parameters to the performance of turbo codes is analyzed. The parameters include generator polynomial of component codes, interleave length and the type of interleavers, iterative decoding algorithms and iteration number, code rates and channel models et al.4. The research for key techniques of turbo codes is processed. It includes,· The design of optimal component codes and the performance of asymmetric turbo codes are analyzed;· A search algorithm for short random interleaver based on the distance spectrum and IDS criteria is carried out and simplified;· Random puncturing method to improve the weight distribution of turbo codes with some special code rates is analyzed and simulated.· The effect of different schemes of trellis termination to the performance of turbo codes is analyzed;· A new low complexity decoder structure is provided;5. The statistical characteristic of extrinsic information from component decoders is discussed. Based on it,· It is explained that the related curves of input-output SNR could be used to measure the performance and convergence of iterative decoding;· Two types of turbo iterative stopping criteria are designed;· The methods to updating SNR estimation in the process of iterative decoding is provided;· A way to implement synchronization of carrier phase by serial concatenation scheme is devised.6. The basic principle of turbo equalization is discussed and the SISO equalization algorithms based on a posteriori probability and interference cancellation are derived. At last, the simulation results are provided.