Improving performance of some irregular LDPC codes by means of three optimization techniques

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.