Performance Evaluation of Massive MIMO With Beamforming and Nonorthogonal Multiple Access Based on Practical Channel Measurements

This letter presents a comprehensive performance analysis of a massive multiple-input-multiple-output (MIMO) system using nonorthogonal multiple access (NOMA) in both indoor and outdoor environments, based on practical channel measurements. The latter are performed using frequency-domain channel sounding experiments conducted at 3.5 GHz with 18 MHz bandwidth. Multiuser beamforming and NOMA clustering are used in the massive MIMO system. The system performance is evaluated in terms of sum-rate capacity for two precoding schemes-zero-forcing (ZF) and maximum ratio transmission (MRT). Two interbeam power allocation (PA) schemes are investigated-equal PA and water filling. Fractional transmit PA is used to perform intracluster PA between paired users. This study allows the identification of practical scenarios that are propitious to NOMA with beamforming. Results show that NOMA is particularly interesting with MRT, compared to ZF, especially when combined with water filling. However, ZF generally outperforms MRT for all system configurations.