The Implementation Of Encoding And Decoding System Of LDPC Codes Based On DSP

Low Density Parity Check (LDPC) codes are a class of capacity approaching error correcting codes of which the decoding performance can get near Shannon limit. For long code length, LDPC codes can even outperform Turbo codes. Based on belief propagation, the complexity of decoding algorithms is very low. Due to these advantages, the application of LDPC codes in reliable communication have received great interest and have become one of the most attractive fields in channel coding community. Now the application of LDPC codes has been put on the agenda.The creative work of this paper is mainly manifested in two aspects: the improvement of decoding algorithm and the implementation of encoding and decoding system of LDPC codes based on DSP.First of all, this paper introduces the basic principles of LDPC codes and various simplified decoding algorithms are thoroughly analyzed and compared. On this basis, the paper innovatively proposed a new decoding algorithm called M-NMS (Modified Normalized Min-Sum). For short regular LDPC codes, simulation results show that the improved algorithm outperforms the LLR BP algorithm with only a modest increase in computation complexity.According to the application requirement, this paper implements both the encoding and decoding system on DSP rather than DSP combined with FPGA, which means the reduction of system cost. To realize the system, efficient methods of parameters'storage and matrix operations are put forward. Furthermore, the results of optimization of the program are presented and analyzed.Finally, a PC-based test platform is designed using LabWindows/CVI of American National Instrument Company as the software development tool. Offering a friendly human-computer interface, the test platform has a variety of functions, such as setting the parameters of serial communication, generating data to be encoding, adding noise, analyzing and displaying results and so on. Thus the whole encoding and decoding system of LDPC codes is accomplished.