Placement and Power Allocation for NOMA-UAV Networks

Unmanned aerial vehicles (UAVs) can be used as flying base stations to provide ubiquitous connections for mobile devices in over-crowded areas. On the other hand, non-orthogonal multiple access (NOMA) is a promising technique to support massive connectivity. In this letter, the placement and power allocation (PA) are jointly optimized to improve the performance of the NOMA-UAV network. Since the formulated joint optimization problem is non-convex, the location of the UAV is first optimized, with the total path loss from the UAV to users minimized. Then, the PA for NOMA is optimized using the optimal location of the UAV to maximize the sum rate of the network. Simulation results are presented to show the effectiveness and efficiency of the proposed scheme for NOMA-UAV networks.

I. Introduction

To satisfy the increasing demand for data services, the 5G networks are being standardized to provide wider coverage, support more devices, and achieve higher throughput. Meanwhile, unmanned aerial vehicle (UAV) communication is an emerging technique which can help 5G achieve better performances, due to its mobility, flexibility and good channel condition [1], [2]. Recently, much research has already been conducted on UAV communications [3]–[7]. In [3], to minimize the number of UAVs, a 2-D placement optimization algorithm was proposed for multiple UAVs. In [4], the UAV trajectory was studied to offload traffic for base stations (BSs). Through trajectory optimization, the energy trade-off problem of ground-to-UAV communications was studied in [5]. In [6], a fundamental tradeoff was made between the throughput and delay in UAV networks with cyclical multiple access. In [7], a blind beam tracking approach for a Ka-band UAV-satellite communication system was proposed.