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首先从理论上分析了硬判决译码算法和软判决译码算法的性能然后对BCH(Bose,Ray-Chaudhuri,Hocquenghem)码的网格结构以及BCJR(Bahl,Cocke,Jelinek and Raviv)算法进行了详细地分析及推导。实验结果表明,在光信道环境中,在误比特率为10-5时,当仅提高最小汉明距离码率相同或者仅减小码率最小汉明距离相同时,BCJR算法相对于硬判决译码算法的编码增益分别在之前的编码增益基础上又增加了0.15dB和0.25dB。因此设计级联码方案时,应尽可能选择纠错能力较大的内码。此外也可以采用适当增加内码的冗余度相应减小外码的冗余度的方法,在获得更高的编码增益的同时保证整个系统的带宽利用率不变。
Firstly, the performance of hard decision decoding algorithm and soft decision decoding algorithm is analyzed theoretically. Then the grid structure of BCH (Bose, Ray-Chaudhuri, Hocquenghem) codes and BCJR (Bahl, Cocke, Jelinek and Raviv) Detailed analysis and derivation. The experimental results show that in the optical channel environment, when the bit error rate is 10-5, when the minimum Hamming distance is increased only or the minimum Hamming distance is the same, the BCJR algorithm is better than the hard decision translation The coding gain of the code algorithm adds another 0.15dB and 0.25dB respectively to the previous coding gain. Therefore, the design of cascaded code scheme, the error correction capability should be as large as possible to select the internal code. In addition, a method of appropriately increasing the redundancy of the inner code and correspondingly reducing the redundancy of the outer code may also be used to ensure higher coding gain while ensuring the same system bandwidth utilization.