Research On Encoding And Decoding Algorithm For LDPC Codes In CMMB System

CMMB, which is short for China Mobile Multimedia Broadcast, is a research production by our own country.It has a wide range of applications in the field of mobile multimedia broadcast services.CMMB is a new generation of multimedia broadcasting technology and supports a variety of mobile terminals. CMMBis aimed at small-screen handheldterminals, such as MP4, mobile phones and GPS. However, providing more reliable and accurateservices to meet the demands of clientsbecomes the key difficulty for the CMMB.The improvement and optimization of the technology of physical layer transportation which decides the reliability of CMMB transportation is the most significant problem to be solved.So this thesis does a deep research on the encoding and decoding algorithms for LDPC codes on the physical layer of CMMB system.Firstly, the basic concepts of mobile multimedia broadcasting and the standard of mobile multimedia broadcasting in China are introduced, and the development of the LDPC and its applications are described. Secondly, the basic principles of the CMMB system are presented. Then the basic principles of LDPC codes in the physical layer of the CMMB are introduced, including its check matrix construction method, the traditional encoding and decoding algorithms. In specific, the encoding and decoding of LDPC are studied in details. Because of the inadequacies of traditional encoding algorithms, a more suitable coding algorithm of LDPC for CMMB standard--the coding method based on LU decomposition is proposed. Meanwhile, it can be deduced the superiority of LU decomposition from the respective of resource consumption and coding efficiency. The normalized offset Min-Sum algorithm of low complexity is proposed. The simulation results show that the new algorithm can reduce the complexity of the hardware realization at the premises of ensuring the decoding performance.