传统协作通信常采用译码转发(DF)协议.而该协议在源-中继节点链路通信质量较差情况下,易出现误码传播现象.为了改进该问题,该文提出可应用于编码协作(CC)机制的Raptor编码协作方案,其可在高信噪比下获得较大编码增益和满分集增益.它在源节点和中继节点使用不同Raptor编码,使中继节点新编码码字为源节点码字的部分校验信息,使接收端所得码字独立不等.因此,目的节点在分别接收来自不同独立链路消息后,可根据码字间固有关系联合译码,以获得额外发送空间分集增益.为了降低复杂度,Raptor码的预编码还可采用整数序列构造的准循环低密度奇偶校验(QC-LDPC)码,从而获得较低线性预编码复杂度.仿真表明:在误比特率(BER)为10-4时,所提Raptor编码协作方案较传统DF协议Raptor方案,Raptor与分布式空时分组码(DSTBC)结合方案,分别有2 dB和1 dB增益.此外,当中断概率为10-2时,其性能较CC,DF协作方案提高了约2 dB和7 dB.%Traditionally,the cooperative communications usually uses Decode-and-Forward (DF) strategy.However,there is easily error propagation phenomenon by the strategy,when the quality of the communication link between source and relay is poor.To solve the problem,a novel Raptor coded cooperation scheme,which can be used in the Coded Cooperation (CC) strategy,is proposed to achieve rather high coding gains and full diversity gains in high Signal-to-Noise Ratio (SNR) regime.In this scheme,different Raptor codes are employed at the source and relay nodes,so the codeword at each node is independent and unequal.Meanwhile,the codeword at relay node is the parity check section of the codeword at the source node.Therefore,after receiving the data transmitted from different independent links,the destination node tries to decode them jointly by the intrinsic relationship among them,to obtain additionally spatial diversity gains in transmission.In addition,in order to reduce the complexity of Raptor encoding and decoding,the Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) codes are constructed by integer sequence and employed as the pre-coding.Simulations indicate that the proposed Raptor CC scheme achieves 2 dB and 1 dB performance gains compared with those of the traditional DF based one and a scheme with the combination of a Raptor code and a Distributed Space-Time Block Code (DSTBC),respectively,at Bit Error Rate (BER) of 10-4.Moreover,the performance improves about 2 dB and 7 dB at the outage of 10-2,when compared with those of the CC strategy and DF strategy,respectively.
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