Power Allocation for Multi-Cell Non-Orthogonal Multiple Access Networks: Energy Efficiency vs. Throughput vs. Power Consumption.

The pressing need for more energy-efficient networks requires understanding the trade-offs maintained by emerging technologies that are expected to help serve an increasing number of connected devices and meet their rate requirements. While spectral efficiency is typically a key performance indicator, hence used for optimal resource allocation, energy efficiency and power consumption of a wireless network should also be considered while deciding on the potential adoption of a new technology. In this paper, we focus on non-orthogonal multiple access (NOMA) as it is considered as a candidate radio access scheme due to its promise to improve spectral efficiency. With a goal of understanding whether joint transmission offers benefits over conventional NOMA, we investigate the performance of joint-transmission NOMA and NOMA considering three objectives: throughput maximization (SumRate), energy efficiency maximization (EE), and power minimization (minP). Different from the literature, we incorporate a power consumption model that accounts for the overhead introduced by successive interference cancellation that is necessary to distinguish the intended signal of a NOMA receiver from the interfering signals aimed for other users in the same cluster. After formulating the optimal power allocation problems, we present our solution steps to make the original problems convex for solving them optimally. Our numerical analysis shows that, for the studied two-cell scenario, joint-transmission offers a benefit only in terms of finding a feasible power allocation while NOMA fails in more cases irrespective of the considered objective. Additionally, our investigation of trade-offs between the investigated problems shows orders of magnitude difference in energy efficiency and throughput for small variations in power consumption.