Construction of Short Block Length IRA Codes Based on Modified IPEG Algorithm

Based on the particular structure of irregular repeat-accumulate (IRA) codes, a weight function is given for codeword weight computing. Then, we propose a modification to the improved progressive-edge-growth (IPEG) algorithm. The modified IPEG algorithm gives degree-2 variable nodes more protection and tries to avoid low weight code-words corresponding to weight-one and weight-two encoder inputs. Simulation results show that the proposed algorithm improves the performance of short block length IRA codes at high signal-to-noise ratio (SNR) region with no sacrifice in low-SNR performance.