| Channel code is one of the key technologies in the future wide-band wireless communication system. As a class of error-correcting codes that has performance approaching Shannon limit, low-density-parity-check (LDPC) codes is a hot topic in the research area of channel code.Follow in a short background introduction of channel coding and the basic knowledge of the LDPC codes, the thesis deeply analyzes the encoding and decoding principle of LDPC codes. According to the block characteristic of parity check matrices of LDPC codes used in IEEE802.16e standard, the thesis deeply researches two encoding algorithms and designs a LDPC(n=2304,rate=1/2) encoding module with Richardson-Urbanke encoding algorithm. Based on theoretical analyzes and the implement on FPGA, the results show that: the LDPC codes in the IEEE802.16e can be effectively encoded with the linear time. As for normalization min-sum (NMS) algorithm multiplies the fixed normalized factor in the checking-node updating formulas, leading to the normalized ? m ?n,NMS is far form the ? m ?n,BP in the situation of the least input is much smaller than the other input. The thesis proposes a Revised-NMS decoding algorithm and compares the revised algorithm to the NMS algorithm. Simulation results show that: the Revised-NMS decoding algorithm achieves a good performance very close to that of the BP algorithm with a little algorithm's complexity increased. At last, the configuration of LDPC decoder for IEEE802.16e based on the revised decoding algorithm is proposed, the key parameters of the decoder and main module are also designed. |
