Joint Beamforming Design and Power Allocation for Full-Duplex NOMA Cognitive Relay Systems

TL;DR

This paper proposes a joint beamforming and power allocation scheme for full-duplex NOMA cognitive relay systems, enhancing user rate regions by optimizing relay and transmission parameters while mitigating interference.

Contribution

It introduces a novel joint optimization framework for beamforming and power allocation in full-duplex NOMA cognitive relays, improving interference management and user rate performance.

Findings

Joint optimization significantly reduces residual self-interference.

Proposed method enlarges the near-far user rate region.

Compared to fixed beamforming, the approach yields better rate performance.

Abstract

In this paper, we consider a non-orthogonal multiple access cognitive radio network, where a full-duplex multi-antenna relay assists transmission from a base station (BS) to a cognitive far user, whereas, at the same time, the BS transmits to a cognitive near user. Our objective is to enlarge the far-near user rate region by maximizing the rate of the near user under a constraint that the rate of the far user is above a certain threshold. To this end, a non-convex joint optimization problem of relay beamforming and the transmit powers at the BS and cognitive relay is solved as a semi-definite relaxation problem, in conjunction with an efficiently solvable line-search approach. For comparisons, we also consider low complexity fixed beamformer design, where the optimum power allocation between the BS and cognitive relay is solved. Our results demonstrate that the proposed joint optimization can significantly reduce the impact of the residual self-interference at the FD relay and inter-user interference in the near user case.