Spectral-Energy Efficiency Trade-off-based Beamforming Design for MISO Non-Orthogonal Multiple Access Systems

Abstract

Energy efficiency (EE) and spectral efficiency (SE)are two of the key performance metrics in future wirelessnetworks, covering both design and operational requirements.For previous conventional resource allocation techniques, thesetwo performance metrics have been considered in isolation,resulting in severe performance degradation in either of thesemetrics. Motivated by this problem, in this paper, we proposea novel beamforming design that jointly considers the trade-offbetween the two performance metrics in a multiple-input singleoutputnon-orthogonal multiple access system. In particular, weformulate a joint SE-EE based design as a multi-objective optimization(MOO) problem to achieve a good trade-off betweenthe two performance metrics. However, this MOO problem is notmathematically tractable and, thus, it is difficult to determinea feasible solution due to the conflicting objectives, where bothneed to be simultaneously optimized. To overcome this issue, weexploit a priori articulation scheme combined with the weightedsum approach. Using this, we reformulate the original MOOproblem as a conventional single objective optimization (SOO)problem. In doing so, we develop an iterative algorithm tosolve this non-convex SOO problem using the sequential convexapproximation technique. Simulation results are provided todemonstrate the advantages and effectiveness of the proposedapproach over the available beamforming designs