Uplink Data Rate Maximization with Channel Uncertainties in BackCom NOMA System

Abstract

This paper investigates a backscatter communication non-orthogonal multiple access (BackCom NOMA) system with a multi-antenna single access point (AP), where both downlink users and BackCom devices (BDs) have one antenna, and users possess perfect channel state information (CSI) while the AP has imperfect channel information. We optimize the sum uplink rate by adjusting beamforming vectors and reflection indices. Utilizing the S-procedure to address channel uncertainties and applying semidefinite relaxation (SDR) for problem convexification, we achieve a sub-optimal solution via an alternating optimization approach. Simulation results demonstrate the superiority of our proposed scheme compared to traditional user-focused power allocation strategies in sum uplink rate.