Selective non-orthogonal multiple access (NOMA) and spatial modulation (SM) for improved spectral efficiency

Non-orthogonal multiple access (NOMA) is a promising candidate for future radio networks, as it effectively utilizes frequency and time resources and has higher spectral efficiency. In this problem we address a problem in NOMA based communication systems when both the users has the same channel gain, in which case NOMA performance degrades considerably. To solve this issue a switching mechanism between NOMA and spatial modulation (SM) is introduced. Simulation results shows that better spectral efficiency can be achieved using the proposed switching scheme.