Downlink Index Modulation aided NOMA for MIMO Transmission

Spatial modulation uses index modulation (IM)-based transmission scheme to reduce transmitted power and radio-frequency (RF) chains in multiple antenna systems. In this paper, we propose IM and non-orthogonal multiple access (NOMA) based IM-NOMA system (I-NOMA) to support massive connectivity in a wireless network. In the proposed downlink I-NOMA, users are multiplexed using both the transmit antenna index and different power levels at base station. The symbol error rate (SER) and sum rate performances of the proposed I-NOMA are analyzed and compared with the IMbased orthogonal multiple access (OMA) system. Impact of various system parameters such as modulation order, transmit antennas, imperfect channel estimation are studied in I-NOMA. Results show that the proposed I-NOMA can yield better sum rate performances than the conventional IM-OMA with good SER and low complexity transceivers.