Ldpc Code Decoding Compatibility Study And Research

Channel coding is always an important part of communication system. Turbo codes and LDPC codes are two of the most popular channel coding. They both have near Shannon limit performance. But, because they have different decoders, a multiple system communicates equipment needs both Turbo decoder and LDPC decoder, which leads more complexity and to a great extent limits the choosing of channel coding in communication system. In order to solve this problem, the compatibility of LDPC decoder is studied and the main works in this thesis are:First, a LDPC decoder compatible with Turbo codes is proposed in this paper. In the proposed decoder, the Turbo code is transformed into the LDPC code completely. A parity-check splitting method is used to eliminate all of the length-4cycles in the check matrix of the transformed LDPC codes. Simulation results show that the performance of the proposed decoder compared to the BCJR decoder is lost1dB. Nevertheless, the proposed decoder in this paper gives a new and convenient alternative way for compatible with the different communication standards.Moreover, based on the decoder we proposed in this thesis, designing LDPC codes can be more flexible. A LDPC design method based on adding short cycles is proposed. A large number of short cycles are added in LDPC codes which gained from PEG algorithm, which results in LDPC codes with excellent performance in the decoder proposed in this thesis.Furthermore, the proposed LDPC decoder is developed to eliminate the influence of length-6cycles by clustering nodes in these cycles temporarily, which make the decoder apply to LDPC codes with a large number of length-4and length-6cycles. Simulation results show that LDPC codes with length-4and length-6cycles have better performance in the developed decoder than standard BP decoder. Also, LDPC codes which transformed from Turbo codes have better performance in the developed decoder.