Performance Of LDPC Codes On Rayleigh Fading Channels

Channel coding is a fundamental technique in modern digital communication systems. Low density parity check (LDPC) codes can approach the Shannon's capacity limit, when decoded with the iterative decoding algorithm with low complexity. Due to the advantages of LDPC codes, their applications in reliable communications have received great interests and have become one of most attractive field in channel coding community.This thesis investigates some aspects of LDPC codes with emphases on the performance of LDPC codes on Rayleigh fading channels and LDPC assisted MIMO and OFDM systems. The main results and contents are summarized as follows:1. The simulation models of LDPC codes on the Rayleigh fading channels and the improved sum-product algorithm are presented. The performances of the LDPC codes on the fading channels are systematically analyzed.2. We propose a concatenated scheme of LDPC codes and STBC codes and the improved sun-product algorithm based on MAP, then analyze its performance on the Rayleigh fading channels. The performance of the system can be substantially enhanced.3. Based on the existing knowledge of the OFDM, we propose a LDPC assisted OFDM systems for high data rate wireless transmission and the related sum-product algorithm. The computer simulate result show the algorithm is right and efficiency.Although LDPC codes are superior to Turbo codes when their code lengths are long enough, it is not the case for short LDPC codes. So founding a short LDPC codes with excellent performance is the core task for the channel coding community. How to optimize the LDPC codes for communicate on Rayleigh fading condition and when it is concatenated with STBC codes or OFDM systems is a challenge.