Research On The Loop Removal Among The Low Degree Nodes For Irregular LDPC Codes And Its Related Techniques

Low-density parity-check (LDPC) codes—first discovered by Gallager and rediscovered by Sipser etal. and MacKay etal. have created much interest recently since they are shown to have a remarkable performance close to the Shannon limit over additive white Gaussian noise (AWGN) channels. The existence of short loop leading to LDPC codes are error-ping layer effect of the main reasons. This article systematically studied the loop and related issues.This article reads as follows:1) A detailed introduction of a very effective edge function value calculation method. Use function factorization map mode, when the function of the factorization picture is a tree, through the message passing algorithm can be very effective for calculating the value of the edge function. Pointed out that the LDPC code decoding problem can be modeled for that model and gave a decoding of the message transmission rules for the binary memoryless channel. Finally, when the corresponding Tanner picture shows the tree-type LDPC decoding performance should not be satisfied. So the existence of ring is necessary for the good LDPC code.2) Put forward the innovative methods of loop removal from part. Irregular codes decoding performance than the regular code, but also because of loop for a small degree of the node is greater than the impact of large degree nodes, so give priority to ensuring that loops among the low degree nodes have to maximize is meaningful. On this point, this paper, based on matrix multiplication and graph of the correspondence between the paths through the switching nodes between the edges, we propose two innovative implementation program of loop removal from part and some job to do the following for the loop removal from part:2.1) Give two loop removal from part program implementation specific algorithm, and pointed out that the actual operation of the program is much larger than one program of the feasibility of two.2.2) Analysis of the algorithm complexity, derived algorithm for the long code is also realistic.2.3) Give a partial elimination of the theoretical limit. Simulation results show that the theoretical limit is not compact, but has a certain significance.2.4) Simulations.: The simulation results show that loop removal from part compared to the overall elimination of the LDPC code decoding performance gain must have.