Comparative Analysis of Ergodic Sum Capacity of Cooperative NOMA Aided with Spatial Modulation

Abstract

Non-Orthogonal Multiple Access (NOMA) is one of the upsurging various access techniques for beyond 5G networks due to its high spectral efficiency. Combining Multiple-Input and Multiple-Output (MIMO) and NOMA provides significantly effective multiple access with improved spectral efficiency. While implementing MIMO-NOMA, it results with increased power consumption due to a greater number of Radio Frequency (RF) chains which increase the complexity of detection. This further leads to Inter-Channel Interference (ICI) and Inter Antenna Synchronization (IAS). A possible candidate to avoid these issues is implementing Index Modulation (IM) technique such as Spatial Modulation (SM) in NOMA system. A three-node User Relaying Cooperative NOMA system with SM named UR-SM-CNOMA is proposed in this paper. A recursive algorithm for maximizing the sum capacity of UR-CNOMA to obtain the optimal power allocation factor. With the analytical results obtained, simulation compares the proposed system and conventional User Relaying Cooperative NOMA (UR-CNOMA) system, which ensures the effectiveness of the proposed method. Simulation results of the sum capacity of UR-SM-CNOMA for different spatial locations of NU2 are depicted, and conditions for the site of NU2 and FU1 are obtained to outperform SM-OMA.