GF(q)域上非规则LDPC码EXIT图分析方法研究

GF(q)域上非规则LDPC码是二进制非规则LDPC码在有限域GF(q=2p)上的扩展,在码长和码率相等的情况下,具有比二进制非规则LDPC码更优异的性能。如何分析GF(q)域上非规则LD-PC码的迭代译码性能是其能否有效应用的关键。基于迭代译码结构,本文研究了AWGN信道下GF(q)域上非规则LDPC码的EXIT图分析方法,推导了其计算表达式;提出了利用EXIT图变量节点与校验节点联合优化准则。仿真结果表明,相对密度进化方法,该方法计算出的收敛门限值的精度稍有下降,却极大地降低了计算复杂度;在相同通信条件下,通过联合优化准则设计的GF(q)域上的非规则LDPC性能优于二进制非规则LDPC码;得到的收敛门限对应的信噪比非常接近香农限,进一步验证了EXIT图分析工具的优越性。

An Extrinsic Information Transfer (EXIT)Chart Analysis Method of theIrregular-LDPC Codes over GF(q)

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.