Relay selection and power allocation for secrecy sum rate maximization in underlying cognitive radio with cooperative relaying NOMA

Abstract

Cooperative communication that integrates cognitive radio and non-orthogonal multiple access is recognized as an emerging technology for fifth-generation and beyond wireless networks. However, security is still a critical issue because of the risk that confidential information will be overheard in wireless transmission environments. Thus, physical-layer security appears as a powerful alternative to complement, or even replace, the traditional use of encryption-based approaches. In this paper, we investigate a particle swarm optimization-based power allocation and relay-selection scheme to enhance physical-layer security by maximizing the secrecy sum-rate in a cooperative relaying cognitive radio-non-orthogonal multiple access system. First, we formulate the optimization problem subject to the constraints of minimum data rate at each secondary user and maximum transmission power at the secondary base station and the relay, provided that the interference induced by the base station and the relay on the primary users' receivers is below an acceptable level. Afterward, we describe the cooperative relaying cognitive radio orthogonal multiple access system to compare the secrecy sum-rate performance of the proposed system with that of the orthogonal multiple access baseline scheme. Satisfactorily, simulation results show that by applying the non-orthogonal multiple access transmission strategy, our proposed scheme reaches higher secrecy sum-rate than the baseline scheme. CO 2020 Elsevier B.V. All rights reserved.