| With the vigorous development of mobile communication technology and Io T technology,a variety of key multiple access technologies have been proposed for the new generation of mobile communication systems.Among them,RSMA technology can support high spectral efficiency and large-scale connections,and is a more universal and robust transmission method.In addition,IRS are composed of multiple reflective elements integrated on a plane,including atomic layer,control layer,and gateway layer.By generating reflected beamforming for reflected signals,IRS achieves intelligent wireless propagation,with greater coverage,higher transmission reliability,higher spectral efficiency,and energy efficiency.Therefore,applying IRS to RSMA systems can effectively improve the performance of CR systems.This paper will use IRS-CR-RSMA transmission to improve the system’s outage performance.Firstly,this paper discusses a proposed solution,known as IRS-CR-RSMA,for the uplink communication system in RSMA.The solution considers the deployment of IRS to assist cognitive secondary users in communication with the BS,while satisfying the Qo S requirements of the primary user.To improve the outage performance of secondary users,the optimal power allocation for reflection,target rate allocation,and successive interference cancellation decoding order of the IRS-CR-RSMA scheme are jointly optimized to achieve the maximum achievable rate for cognitive secondary users.Additionally,the closed-form expression for the outage probability of the secondary user is derived,taking into account the reflection channel gain of the IRS.The paper then analyzes the impact of deploying IRS on the outage performance of cognitive secondary users.The simulation results suggest that the proposed IRS-CR-RSMA solution significantly improves the outage performance of cognitive secondary users compared to RSMA technology without IRS assistance.The second contribution of this paper is to further extend the design of cognitive RSMA with a single IRS to a multi-IRS assisted CR-RSMA system,where two IRSs are deployed to respectively assist the primary user and the secondary user transmission.This achieves an improvement in the secondary user’s outage performance under the Qo S constraint of the primary user.In order to address the difficulty of improving user outage performance in communication systems,this paper proposes a method of using IRS to increase the tolerable interference power threshold of the primary user,thereby improving the achievable rate of the secondary user,by leveraging the ability of IRS to flexibly change the wireless transmission channel environment.Then,the optimal power allocation,target rate allocation,and successive interference cancellation decoding order for the secondary user are analyzed.By applying the central limit theorem,a closed-form expression for the secondary user’s outage probability is obtained,which clearly reveals the impact of deploying multiple IRSs on the secondary user’s outage probability.Simulation results show that the proposed IRS-CR-RSMA scheme outperforms CR-RSMA scheme in terms of outage performance. |
