Sum Rate Maximization for IRS-Assisted Uplink NOMA

Abstract

An intelligent reflecting surface (IRS) consists of a large number of\nlow-cost reflecting elements, which can steer the incident signal\ncollaboratively by passive beamforming. This way, IRS reconfigures the wireless\nenvironment to boost the system performance. In this paper, we consider an\nIRS-assisted uplink non-orthogonal multiple access (NOMA) system. The objective\nis to maximize the sum rate of all users under individual power constraint. The\nconsidered problem requires a joint power control at the users and beamforming\ndesign at the IRS, and is nonconvex. To handle it, semidefinite relaxation is\nemployed, which provides a near-optimal solution. Presented numerical results\nshow that the proposed NOMA-based scheme achieves a larger sum rate than\northogonal multiple access (OMA)-based one. Moreover, the impact of the number\nof reflecting elements on the sum rate is revealed.\n