半双工译码转发中继信道下的空间耦合RA码设计

Design of Spatially Coupled RA Codes for Decode-and-Forward in Half-duplex Relay Channels

针对半双工译码转发中继信道,提出了一种可逼近三节点中继信道容量限的空间耦合RA码的设计方法。针对二进制删除信道,源节点分别向中继节点和目的节点发送空间耦合RA码,中继节点先正确恢复出源节点发送的空间耦合RA,然后再次编码产生额外的校验比特并转发给目的节点;目的节点结合中继节点发送的额外校验比特和源节点发送的空间耦合RA码进行译码,正确恢复出源节点的信息。为了评估所设计的空间耦合RA码在三节点中继信道下的渐近性能,推导了密度进化算法用于计算阈值。阈值分析结果表明,所提出的空间耦合RA码能够同时逼近源到中继链路和源到目的链路的容量限。同时,基于半双工二进制删除中继信道,仿真了所设计的空间耦合RA码的误码性能,结果表明,其误码性能与所推导的密度进化算法计算的阈值结果一致,呈现出逼近于容量限的优异性能,且优于采用空间耦合低密度奇偶校验(Low Density Parity Check,LDPC)码的性能。

The design method of capacity-approaching spatially coupled RA(SC-RA)codes for half-duplex decode-and-forward relay channel is proposed.For binary erasure channels,the source node sends one SC-RA code to the relay node and the destination node respectively.After receiving the information from the source node,the relay node first correctly recovers the information and then encodes it to generate additional check bits sent to the destination node.The destination node can correctly recover the information from the source node by combining the additional check bits sent by the relay node with the information sent by the source node.To evaluate the asymptotic performances of the proposed SC-RA codes in the three-node relay channel,a modified density evolution algorithm is derived to compute the decoding thresholds.The threshold analysis results show that the proposed SC-RA codes can approach the capacity of the source-to-relay link and the source-to-destination link simultaneously.Moreover,the decoding performances over the binary erasure half-duplex relay channels are also simulated to demonstrate the threshold analysis results.Simulation results show that the bit error rate performance of the designed SC-RA codes is consistent with the decoding thresholds obtained by the Derived Density Evolution Algorithm,the codes exhibit excellent capacity-approaching performances and also are better than spatially coupled low density parity check(LDPC)codes.