Robust Beamforming Techniques for Non-Orthogonal Multiple Access Systems with Bounded Channel Uncertainties

TL;DR

This paper introduces a robust beamforming method for NOMA MISO downlink systems that accounts for channel uncertainties, ensuring reliable service despite imperfect CSI, by transforming a non-convex problem into a convex one using LMI and S-Procedure.

Contribution

It presents a novel robust beamforming design for NOMA systems with bounded channel uncertainties, employing a convex reformulation via LMI and S-Procedure.

Findings

The proposed scheme effectively minimizes power while maintaining QoS.

Simulation results confirm the robustness and efficiency of the design.

The method handles channel uncertainties without significant performance loss.

Abstract

In this letter, we propose a robust beamforming design for non-orthogonal multiple access (NOMA) based multiple-input single-output (MISO) downlink systems. In particular, the robust power minimization problem is studied with imperfect channel state information (CSI), where the beamformers are designed by incorporating norm-bounded channel uncertainties to provide the required quality of service at each user. This robust scheme is developed based on the worst-case performance optimization framework. In terms of beamforming vectors, the original robust design is not convex and therefore, the robust beamformers cannot be obtained directly. To circumvent this non-convex issue, the original intractable problem is reformulated into a convex problem, where the non-convex constraint is converted into a linear matrix inequality (LMI) by exploiting S-Procedure. Finally, simulation results are provided to demonstrate the effectiveness of the proposed robust design.