Research On Encoding And Decoding Technology Of TPC Based On Modified Lookup Table Decoding Algorithm Of BCH Code

Error control coding (i.e. Channel-coding, ECC) is a technology to enhance the reliability of the data transmission, which is widely applied in various communication and computer system. In various channel coding technology, the turbo product code (TPC) has become the focus in the ECC field and has a very broad application prospect which dues to its relatively simple coding and decoding method and error correction ability near the Shannon limit. But there are still some problems, such as high complexity, large delay and a large amount of memory requirements in the decoding of the TPC, which is mainly dependent on the decoding complexity of the component-code decoder. Therefore, this thesis focuses on how to reduce the complexity and delay of component-code decoders to improve the decoding speed of TPC.Firstly, an overview of development history of EEC is introduced, and then the development of BCH and the basic knowledge of TPC are summarized.Secondly, the decoding algorithms of the BCH code which is commonly used as the component-codes of the TPC, are deeply researched, and a fast decoding algorithm of the binary BCH code is proposed based on lookup talbe method. The data in the lookup table consists of syndrome patterns and corresponding error patterns which only occure in the message block of the received codeword. The proposed algorithm makes use of the lookup table and the weight of syndromes. It often results in a significant reduction in the memory requirements and lower complexity comparing with the traditional lookup table or other algebraic decoding methods. Moreover, the simulation of (15,5,7) BCH code based on MATLAB software shows that such a novel method can increase about 158% decode speed comparing with the traditional full lookup table searching algorithm, which indicates that the proposed algorithm is a good trade-off between memory requirements and decode time. The improved decoding algorithm is simulated on (15,5,7) BCH code under Quartusâ…¡, The FPGA simulation shows that the decoding process can be accomplished in two clocks when the system clock is 50MHz.Lastly, the basic principle of TPC iterative decoding algorithm based on the Chase algorithm, and the basic steps of the implementation of this decoding algorithm are given. And then, the calculation of the extrinsic informations and the iterative structure of this algorithm are discussed. On these bases, take (31,21,5) BCH code as the component-codes, the proposed algorithm is introduced into the iterative decoding of TPC. The MATLAB simulation shows that the TPC iterative soft-decision decoding algorithm based on the Chase algorithm can enhance a 2.7dB gain comparing with the traditional iterative hard-decision decoding algorithm with 10-5 BER, and in the performance of frame error rate, the former is much better than the later. It is concluded that the proposed algorithm can not only reduce the memory requirements of the component-code decoders, but also improve the decoding speed of TPC greatly.