基于低密度格码的编码协作中继系统

Coded cooperation relay scheme based on low density lattice code

提出一种联合低密度奇偶校验码(low density parity check,LDPC)的低密度格码编码协作(low density lattice code coded cooperation,LDLC-CC)改进方案。中继对源节点广播的LDLC码字进行译码,并向目的节点转发基于LDPC和LDLC编码的增强校验信息。通过利用校验矩阵下三角结构特性,源节点和中继节点可以简单地通过各自的校验矩阵进行整形和编码,且采用的LDLC校验矩阵可以构成高维下三角结构校验矩阵。此外,设计了目的节点联合迭代软译码算法。该算法建立了LDLC联合译码与LDPC软译码之间的联系,相比LDPC硬译码可以获得显著的编码增益。仿真结果显示,在瑞利慢衰落信道下提出的联合LDPC的LDLC-CC系统相比传统无协作直传LDLC系统最大可以取得近5dB性能增益。

An improved low density pari ty check （LDPC）-aided low density lattice code coded cooperation （LDLC-CC） scheme is proposed for the relay cooperative system. The relay node decodes the LDLC codeword transmitted from the source node and forwards the additional parity check information based on LDPC and LDLC encoding to the destination. By taking advantage of the characteristics of parity check matrix with lower triangular structure, the shaping and encoding operations in source and relay can be simply implemented base on corresponding parity check matrices. Furthermore, the LDLC parity check matrices constitute a higher-dimen-sional matrix with lower triangular structure. A joint iterative soft decoding algorithm is also proposed in desti-nation. It establishes the connection between LDLC decoding and LDPC soft decoding and achieves obvious coding gain than that with hard decoding. Simulation results show that the proposed LDPC-aided LDLC-CC scheme can achieve up to 5 dB gain compared to the conventional direct transmission LDLC scheme without co-operation in Rayleigh slow fading channel.