Abstract:

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.