Cluster Grouping and Power Control For Angle-Domain MmWave MIMO NOMA Systems

This paper investigates the performance of angle-domain millimeter-wave (mmWave) multi-input multi-output nonorthogonal multiple access systems in the presence of angular estimation error. A closed-form expression for the achievable rate is presented, based on which an asymptotic approximation is derived. The analytical findings indicate that, as the number of BS antennas goes to infinity, the achievable rate is mainly determined by the antenna number to beam number ratio (ANTBNR) as well as the spatial direction distance. In particular, a large ANTBNR would cause a severe rate loss, and the achievable rate is an increasing function with respect to the spatial direction distance. Capitalizing on this key observation, a novel cluster grouping scheme is designed to mitigate the intercluster interference, which shows a great advantage over a random cluster grouping scheme. Furthermore, a max-min power control scheme is proposed, aiming at enhancing user fairness. Finally, simulation results are provided to corroborate the analytical results.