Rate and Energy Efficiency Improvements of Massive MIMO-Based Stochastic Cellular Networks With NOMA

Non-orthogonal multiple access (NOMA) coupled with massive multiple-input multiple-output (MIMO) base stations hold immense potential in increasing the spectral and energy efficiencies while enabling massive access of future cellular networks. To this end, we investigate the rate performance of a system employing multi-user NOMA and massive MIMO base stations distributed under a Poisson process. We adopt a time-division-duplexing mode, and employ matched filter based precoding in the downlink of the cellular network. We investigate two power allocation scenarios for the individual users while keeping the overall power usage of a NOMA cluster constant: 1) pre-defined power allocation and 2) power allocation based on user-base station distance. Considering imperfect successive interference cancellation, pilot contamination, and error propagation for the two power allocation scenarios, we characterize the average rate of a NOMA user and the signal detection probability under asymptotic conditions for the number of antennas. Furthermore, we derive the moment generating function of the out-of-cell interference caused by pilot contamination. We show that NOMA improves the rate performance and by extension the energy efficiency under most system conditions. Moreover, the rate can be increased further through denser network deployments, while the user fairness is greatly impacted by the power allocation scheme.