Cooperative LDPC Codes Design for Decode-and-forward Half-duplex Relay Channels
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摘要: 为逼近解码前传半双工中继信道容量，该文提出一种协作LDPC编码结构及度分布优化方法。与双层删除LDPC码不同，该结构将中继校验比特视为协作LDPC码的一部分，目的端利用从信源和中继接收的消息进行联合译码获得信源信息。为了分析协作LDPC码性能，拓展传统外信息转移(EXIT)图，推导了基于消息错误概率的双层EXIT图噪声门限分析方法。在此基础上，提出了协作LDPC码度分布优化方法，采用差分进化算法搜索了一组具有最大噪声门限的协作LDPC码。实验仿真证明，与双层删除LDPC码相比，协作LDPC码的性能得到了不同程度的改善。Abstract: In order to approach the theoretical limit of decode-and-forward strategy for the half-duplex relay channel, a cooperative LDPC coding structure and its corresponding optimization scheme is proposed. Different from the structure of Bilayer-Expurgated LDPC (BE-LDPC) codes, new structure makes the extra parity bits generated by the relay as a part of the overall code. Using the messages from both source and relay nodes, the destination node can decode the information of the source node. To analyze the performance of cooperative LDPC codes，bilayer EXtrinsic Information Transfer (EXIT) charts based on message-error rate is devised as an extension of standard EXIT. Based on bilayer-EXIT chart, a design methodology for cooperative LDPC codes is proposed, in which the degree distribution with maximum noise threshold is iteratively improved through Differential Evolution (DE). The experiment results show that the cooperative LDPC codes always outperform the BE-LDPC codes.
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