Efficient construction of irregular LDPC codes with midterm block length and nearly optimal performance

In this paper, we propose a general method for constructing irregular LDPC codes with midterm or short block lengths. It is a Monte-Carlo simulation based optimization procedure called Downhill Simplex which uses PEG (Progressive Edge Growth) method for Tanner graph construction in cost function evaluations. It outperforms DE (Density Evolution) method in both efficiency and performance. The efficiency of our proposal mostly depends on the Monte-Carlo simulation time which due to the midterm block lengths is relatively small compared to the time delay of conventional DE method. Simulation results show that for block length of 3200 and a relatively low code rate 3/8, LDPC codes constructed using our proposal noticeably outperform those constructed with DE method by more than 0.2dB in the entire SNR range under AWGN channel.