Exploration of Different Combination of Antenna Diversity Techniques for MIMO-PD-NOMA with Experimental Validation

The conjunction of Multiple-Input-Multiple-Output (MIMO) with Non-Orthogonal Multiple Access (NOMA) scheme enhances the performance of latter in terms of higher spectral efficiency, improved reliability and lower latency. This makes MIMO-NOMA a more promising choice for beyond 5G networks for both broadband and machine-to-machine type communication. Diversity techniques are a fundamental asset of MIMO technology and hence, have been applied to MIMO-NOMA systems so that the benefits offered by these techniques can be experienced by the users sharing the resources through the NOMA principle. In this paper, the concept of antenna diversity techniques, that deals with employing multiple antennas at the transmitter and/or receiver, is explored in association with power-domain NOMA (PD-NOMA), entailing Constrained Optimization Power Allocation (COPA) mechanism, for a downlink scenario. The performance of different combinations of transmitter and receiver antenna diversity techniques, on a two-user MIMO-PD-NOMA paradigm, is analyzed on grounds of system Bit Error Rate (BER) and sum capacity, for various modulation schemes. The optimum diversity pair is also experimentally validated on a Software Defined Radio (SDR) kit, named WARP v3.