Research On The OFDM-based Encoding And Decoding Theory Of LDPC Codes

Orthogonal Frequency Division Multiplexing technology is one of the most core technologiesof multi-carrier wireless communication, now it is regarded as the most potential4th Generationmobile communication technology. Low-Density Parity Check code is a linear block errorcorrecting code based on a sparse parity check matrix. LDPC has excellent performanceapproaching Shannon limit, and now it has been considered as the best performance of the channelerror correction code. When combine LDPC and the sub-carriers of OFDM, the system will beimproved in terms of performance due to the influence of the multi-path effects on some of thespecific frequency of the carrier channel.This Paper describes the basic concepts of OFDM and its key technologies, includingsynchronization, channel estimation, adaptive modulation and average peak suppression technology.The Paper also shows the use of OFDM system. Then describe the LDPC code’s definition and itsrelated concepts, and do further research for the LDPC encoding and decoding.Through the research for different algorithms of encoding and decoding about LDPC, the Paperdesigns a new method for decoding after redesign the formula in Log-Likelihood Ratio-BeliefPropagation algorithm. This improved method reduces the complexity of the algorithm. Withdifferent environment and parameters on LDPC-COFDM system, it shows the improved Bit ErrorRate at high SNR.