Distributed energy-efficiency maximization in energy-harvesting uplink NOMA relay ad-hoc networks: Game-theoretic modeling and analysis

Abstract

In this paper, the problem of distributed energy-efficiency maximization in energy-harvesting uplink non-orthogonal multiple-access (NOMA) relay ad-hoc networks is considered. Particularly, the aim is to allow each user to maximize its energy-efficiency (EE) in a distributed manner over an energy-harvesting amplify-and-forward relay, while satisfying its quality-of-service (QoS) constraint. To this aim, the centralized energy-efficiency maximizing power allocation (C-EE-MAX-PA) problem is formulated as a multi-objective optimization problem, which is NP-complete, and thus is computationally-expensive. In turn, a distributed game-theoretic power control algorithm is proposed, whereby each user iteratively updates its transmit energy such that its EE is maximized, ultimately converging to the unique generalized Nash equilibrium (GNE), and with proven Pareto-optimality. Simulation results are presented to validate the proposed algorithm, which is shown to yield the Pareto-optimal solution of the C-EE-MAX-PA problem; however, at lower computational-complexity, while satisfying the users’ QoS constraints. Moreover, light is shed on the effect of the minimum rate requirement as well as the relay harvested energy on the energy-efficiency of the network users. Lastly, this work constitutes a step towards developing sustainable and computationally-efficient algorithmic solutions for EE maximization in NOMA relay ad-hoc networks, and thus, discussions on some of the potential applications as well as practical aspects of the proposed algorithm are given.