基于差分编码调制的多址中继网络编码方法

现有多址接入中继信道（multiple-access relay channel,MARC）的网络编码技术多采用非差分调制,相干解调时会产生相位模糊。引用差分调制可克服此问题,但解调性能会损失约2.5 dB。为了弥补此损失,文中提出一种基于差分调制的比特交织编码调制迭代译码（bit-interleaved coded modulation scheme with iterative decoding,BICM-ID）方法。利用外信息转移图分析比较了两种编码（卷积码和低密度校验（low density parity check,LDPC）码）结合差分正交幅度调制（differential quadrature amplitude modulation,DQAM）在格雷和改进集合分割（modified set partitioning, MSP）映射下的性能,并做仿真对比。结果表明,对于差分调制,格雷映射比MSP映射更优。对于格雷映射,卷积码比LDPC码更优,有0.7dB的增益,且复杂度更低。

Network coding method based on differential modulation in multiple-access relay channel

Most existing network coding schemes based on the multiple-access relay channel (MARC) employ non-differential modulation, which have the phase ambiguity problem. Differential modulation can solve this problem, but its demodulation performance is degraded with a cost of 2.5 dB degradation. To make up for the performance loss, a kind of bit-interleaved coded modulation scheme with iterative decoding (BICM ID) based on differential modulation is proposed. We research two channel codes including convolution codes and low density parity check (LDPC) codes， matching differential quadrature amplitude modulation (DQAM) under gray and modified set partitioning (MSP) mappings. We analyze their convergence performance via extrinsic information transfer chart, and compare their error performance via simulation. Analysis and simulation results show that, for the DQAM,the gray mapping scheme outperforms that the MSP mapping scheme for both channel codes; for the gray mapping, the convolution coding DQAM scheme outperforms that LDPC coding scheme by 0.7dB gains, and it is of much lower complexity as well.