On the Impact of Line-of-Sight and Spatial Correlation on NOMA Performance

Non-orthogonal multiple access based zero-forcing beamforming (NOMA-ZFBF) systems require both semi- orthogonal users (SU) in beams and highly correlated (HC) users within a beam to maximize the spectral efficiency of the system. Hence, channel models where different users are likely to experience both similar and near-orthogonal channel vectors are likely to give good NOMA performance. In order to explore this, we analyze the variance of the interference power between two users, where a large variance indicates this channel behavior is more likely. Moreover, we have compared the Rician and Rayleigh channels in correlated and independent and identically distributed (I.I.D.) environments in order to provide some new insights into the role of line- of-sight (LoS) and correlated components with respect to NOMA beam formation and clustering of HC users. Analysis and numerical results show that correlated channels with similar channel statistics result in a higher variance that in turn increases the cluster percentage and enhances the cluster rate.