Spatial Modulation-Aided Cooperative NOMA: Performance Analysis and Comparative Study

The combination of non-orthogonal multiple access (NOMA) and multiple-input multiple-output (MIMO) signaling is capable of providing significantly improved spectral efficiency and effective multiple access. However, conventional MIMO-NOMA entails significantly increased power consumption and implementation complexity. Inspired by the essence of spatial modulation (SM), in this paper, a novel three-node cooperative relaying system (CRS) using SM-aided NOMA, termed CRS-SM-NOMA, is proposed, in which the messages for two users are conveyed by two different information-bearing units of SM. As the reference scheme, conventional CRS-NOMA is further re-investigated with multiple receive antennas. Besides the achievable rate, which is adopted by most of the existing NOMA works as the performance metric, the bit error rate (BER) of CRS-SM-NOMA and CRS-NOMA is analyzed assuming maximum-likelihood detection. Approximate bit error probability expressions are derived in closed form for both users. Simulation results verify the analysis and show that the proposed CRS-SM-NOMA outperforms conventional CRS-NOMA and SM-OMA in terms of the BER as well as ergodic sum rate.