Design and analysis of structured irregular LDPC code ensembles

好一 坂庭, KOHICHI SAKANIWA

隆之 野崎, T. Nozaki, 健太 笠井 +3 more

健太 笠井, Kenta Kasai

Li Peng, Guangxi Zhu

In this paper we present three optimization techniques of improving the performance of some irregular low-density parity-check ensemble with determinate structure and finite block length. Firstly, its permutation matrix optimization. We present a new random permutation matrix called as the Q-matrix. We substituted Q-matrix for identity matrix in base matrix array which can be expanded into H-matrix of the irregular QC-LDPC codes recommended in IEEE 802.16e standard draft and can make the performance of this QC-LDPC codes improve about 0.4 dB. Secondly, it is large girth optimization technique. We design H-matrix of the irregular LDPC ensemble and make it at least not include 8-cycle. Thirdly, its column weight optimization technique in H-matrix of the irregular LDPC ensemble. For the presented irregular LDPC ensemble, it is not such case that the larger the column weight is and the better the performance is, but the column weight should be a moderate value.

健太 笠井, Kenta Kasai

Yingjian Xue, Haige Xiang

In this paper, we are concerned with the finite-length analysis of low-density parity-check (LDPC) codes when used over additive white Gaussian noise (AWGN) channels. We present the iterative decoding algorithm of LDPC codes, and we also discuss the encoding methods and the bipartite graph representation of LDPC codes ensemble. Finite-length LDPC code performances are investigated, and the influence of cycle is pointed out. Simulation results show that irregular LDPC codes with variable and check node degree distribution optimized for infinite-length codes are not optimal for finite-length LDPC codes, and the error patterns of both regular and irregular codes are investigated as an effort to improve the performance and design methodology of finite-length LDPC codes.