Performance Analysis and Power Allocation Strategy for Downlink NOMA Systems in Large-Scale Cellular Networks

In this paper, downlink non-orthogonal multiple access (NOMA) systems in large-scale cellular networks are considered and an analytical framework to evaluate the outage performance is developed. Different from the previous work where the users’ distribution is assumed to be completely independent of the Base Station (BS) locations, the deployment of the BSs and the location of NOMA-user pair are modeled as Poisson Cluster Process so that the relation between system throughput and the density of BSs could be effectively formulated and clearly revealed. Under the proposed system model, the closed-form expressions of outage probabilities are derived for 2-user downlink NOMA systems. Furthermore, the power allocation strategy is proposed for minimizing the maximal outage probability among NOMA users. And the average area spectral efficiency is also defined and derived to evaluate the throughput of the network. The accuracy of the theoretical results is verified by the simulations.