Construction of EIRA codes with enlarged dual diagonal distance by EXIT charts

An improved construction scheme of efficient extended irregular repeat-accumulate (eIRA) codes with easy check matrix encoding is proposed in this paper. At the dual diagonal parts of the right check matrices of the codes, the distances of the nodes are enlarged in their corresponding Tanner graphs by increasing the distances between the adjacent “1” of the matrices. Thus, the probabilities of small loops in the Tanner graphs of the codes are reduced. Therefore, it decreases the error self-feedback and obtains good decoding performance. Moreover, with an extrinsic information transfer (EXIT) chart method, the degree profile of the code can be optimally designed to meet the requirement of optimal decoding performance. Simulation results show that our proposed coding scheme slightly outperforms the contrast original eIRA code about 0.05–0.1 dB at a bit-error-ratio (BER) of 10⁻⁵ with the same binary phase shift keying (BPSK) system in an additive white Gaussian noise (AWGN) channel. In addition, it obtains lower encoding and decoding complexity since it employs the sparse check matrices for encoding and applies the easy addressing operations both for encoding and decoding. Therefore, the proposed scheme of constructing eIRA codes can be efficiently applied in wireless digital communications.