Abstract:

The irregularLDPC codes over GF(q) are an extension of the binary irregularLDPC codes which have been proved to outperform the binary irregularLDPC codes with the same code length and code rate. How to analyze the performance of the iterative decoding algorithm of the irregularLDPC codes over GF(q) is the key issue on whether it can be efficiently applied or not. Based on the structure of iterative decoding, this paper studies an EXIT analysis method of the irregularLDPC codes over GF(q) in the AWGN channel and derives the calculation expressions. Moreover, a union optimized rule considering the bit variables and check variables simultaneously is presented. The experimental results show that the EXIT analysis method can attain a convergence threshold the same as the density evolution methods do, but can reduce the computing complexity a lot. Moreover, under the same communication conditions, the performance of the irregularLDPC codes over GF(q) designed by the union optimized rule is superior to that of the binary irregularLDPC codes. The SNR corresponding to the convergence threshold attained by the EXIT chart is very near to the Shannon limit, which validates the superiority of EXIT.

Key words: irregularlow density parity check codes;density evolution;extrinsic information transfer;convergence threshold;GF(q);Shannon limit