Application of Non-orthogonal Multiplexing to mmWave Multi-user Systems

Limited wireless spectrum in future networks is an issue that millimeter-Wave (mmWave) frequencies can resolve. Beamforming is a challenging operation for mmWave systems. Both analogue and hybrid solutions have been proposed. Apart from Orthogonal Multiple Access (OMA) systems, the Non-Orthogonal Multiple Access (NOMA) scheme has been recently considered as an alternative and can outperform OMA in many cases. Our contribution is the application of NOMA to a hybrid precoder design in mmWave indoor scenarios with multiple users. Introducing to our system appropriate user grouping and scheduling schemes, we show that the NOMA outperforms, in terms of spectral efficiency, OMA by providing a 17.1% improvement for high SNR values. Finally, applying NOMA with fair power allocation improves the rate of users with weak channel conditions by around 1 bps/Hz for SNR > 5dB, without degrading the overall spectral efficiency in the cell.