NOMA-based downlink relaying with media-based modulation

In recent years, non-orthogonal multiple access (NOMA) has attracted considerable attention as a promising multi-access technique for next generation wireless communication systems. Media-based modulation (MBM), which is an emerging index modulation concept, is another technique that can be considered for next generation wireless communication systems due to its high spectral and energy efficiency. In this paper, we propose a NOMA-based decode-and-forward relaying system, where MBM is applied at the source to improve error performance at the relay. We consider a topology consisting of a single source with a single transmit antenna equipped with multiple radio frequency (RF) mirrors, one relay equipped with a single transmit and multiple receive antennas, and multiple users equipped with multiple receive antennas. Pairwise error probability expression for NOMA with multiple receive antennas is derived and the union bound on bit error rate (BER) for the overall system with imperfect successive interference cancellation (SIC) is obtained in closed-form. Analytical results are in agreement with the Monte Carlo simulation results. Moreover, two power allocation optimization problems are formulated in terms of user fairness and quality of service requirements of the users. BER performance of the proposed system is also investigated using the optimum coefficients according to the formulated problems. It is shown that the proposed system outperforms the conventional cooperative NOMA system in terms of error performance as the data rate increases.