Downlink NOMA for Stochastic Cellular Networks under Millimeter Wave Channels

Non-orthogonal multiple access (NOMA) and millimeter wave communications are key technologies for the fifth generation (5G) of cellular networks in order to increase the spectral efficiency, ensure massive connectivity, and to provide large bandwidths to mobile internet services. However, the coexistence of these two techniques is critical, especially under increasingly random dense base station assignments. To this end, this paper characterizes the system coverage for users utilizing NOMA in a stochastic multi cell set-up under millimeter wave frequencies. We employ the Poisson point process (PPP) to model the base stations and user devices. Moreover, our system model considers the power allocation, imperfections in the successive interference cancellation (SIC), and blockages that affect the channel path loss and fading characteristics. The aggregate co-channel interference experienced at a user is characterized based on the moment generating function, and the outage probability is derived for a two user NOMA scenario. Analytical and numerical results show that NOMA is a feasible candidate technique to increase the spectral efficiency under millimeter wave channels if careful power allocation is implemented, with limited performance penalties for each user. It is also shown that the performance is further improved by utilizing a dense base station deployment.