Performance Analysis Of Reconfigurable Intelligent Surface Assisted Wireless Communication System Based On Stochastic Geometry

Reconfigurable Intelligent Surface(RIS)is one of the key technologies for future 6G wireless communication systems.RIS can change the amplitude/phase of incoming electromagnetic waves to reconstruct the wireless signal propagation environment and enhance the communication performance of target users.Due to the dense deployment of cellular networks,improving the quality of service for cell-edge users is an important challenge,and the spatial locations of closely related communication nodes need to be modeled by the spatial point process of stochastic geometry theory for theoretical evaluation.However,the introduction of RIS makes the interference environment of cellular networks even more complex,thereby affecting the overall performance of the network.Therefore,it is an urgent and critical issue to characterize the statistical properties of interference and effectively evaluate the performance of RIS-assisted cellular networks.In this regard,this paper focuses on the RIS-assisted cellular network and symbiotic cellular network performance using stochastic geometry tools.The main innovative contributions of this paper include:Firstly,for the RIS-assisted cellular communication system,the performance of cell-edge users is analyzed,and the successful coverage probability of edge users is derived.Firstly,the positions of base stations and users are modeled using the Poisson point process(PPP),and the central users and edge users are divided by the hole structure.RIS is deployed near the edge of the cell to enhance the communication performance of edge users.The edge user and RIS positions are modeled using the Poisson hole process(PHP),and the downlink composite signal model received by the cell-edge user when RIS is used as an auxiliary path service is derived.Then,based on the correlation statistical properties of PPP and PHP,the Laplace transform expressions of the useful signal power and interference signal power received by users are derived,and the expression of the average successful communication probability of users in the cellular system is derived.The accuracy of the theoretical derivation is verified by simulation,and the impact of different system parameters on signal gain and coverage probability is also analyzed.Secondly,for the RIS-assisted symbiotic radio cellular system,the performance of primary receiver(PR)and Internet-of-Things receiver(IR)users is studied,and the analytical expressions of successful communication probabilities of PR and IR in symbiotic communication are derived.Firstly,the positions of base stations and PR are modeled using the homogeneous Poisson point process(HPPP),and the RIS and IR positions are modeled using the Poisson bipolar network.The signal model received by PR and IR in the symbiotic communication scenario of base stations and RIS is derived.Then,based on the related statistical characteristics of PPP and Poisson bipolar network,the expression of PR’s signalto-interference plus noise ratio(SINR)and IR’s signal-to-noise ratio(SNR)under RIS random phase and heuristic phase design is derived,and the expression of the system average successful probability is derived.The research results indicate that the phase design of RIS can significantly improve the communication performance of PR and IR,especially under the high RIS elements design,the coverage probability of communication system can be significantly improved.