Improvements on construction of quasi cyclic irregular non binary LDPC codes

Non Binary Low Density Parity Check (NB-LDPC) codes, a category of LDPC codes have better decoding performance in high order Galois field. A construction method called hierarchically diagonal matrix (HDM) is proposed in this paper. The constructed HDM is analyzed for IEEE 802.11 n specification of code length 648, rate 1/2 over GF (4). Codes constructed based on the hierarchical matrix perform well over the AWGN channel with FFT based sum product iterative decoding (FFT-SPA) algorithm. The computation complexity of the HDM is analyzed. The average number of multiplications and additions involved in the HDM of check node unit and variable node unit has reduced to 62% and 48% when compared with random matrix.