Deployment Strategy And Placement Optimization For Reconfigurable Intelligent Surface In Smart Factory

As the fifth generation(5G)wireless communication networks are deployed worldwide,intelligent wireless services are becoming more prevalent,and the data transmission rate requirements of wireless networks are increasing.As a key driver of the future intelligent information society,the next generation wireless communication system(6G)is expected to provide 1000 times more network capacity than existing systems,and in order to cope with the sustainable growth of future wireless network capacity.To achieve ultra-reliable communications and reduce costs,complexity and energy consumption,we urgently need to develop disruptive and innovative technologies.In recent years,driven by artificial intelligence,emerging materials and integrated antennarelated technologies(especially the further development of information metamaterials),a new wireless transmission technology for 6G,Reconfigurable Intelligent Surface(RIS),has emerged as a revolutionary technology.RIS is a technology that enables wireless signal optimization in wireless transmission networks,where a large number of low-cost passive reflective elements can skillfully adjust signal reflections to intelligently configure the wireless propagation environment to improve communication system performance.Compared with traditional access points,RIS is a more promising technology solution to use as an auxiliary device in wireless networks that can be flexibly integrated into the network,transforming the existing heterogeneous network with only active components into a new hybrid architecture with active and passive components working together in an intelligent manner.That means,RIS provides great flexibility and compatibility with existing wireless systems(e.g.,cellular or WiFi).In this thesis,we introduce the RIS-aided path loss model for wireless communication,the hardware architecture,and the potential applications of RIS in wireless networks,with a focus on RIS deployment.In this thesis,we use an electromagnetic theory-based RIS path loss model(hereafter referred to as a comprehensive path loss model)to improve the performance of wireless communication systems in multiple scenarios by optimizing the deployment location of RIS.First,in the single-user communication scenario,this thesis explores the key factors affecting the user channel conditions in the comprehensive path loss model and proposes two novel deployment schemes,i.e.,ceiling deployment and vertical deployment.The optimal deployment locations that maximize the user rate under different deployment schemes are derived.And in some specific scenarios,the phase design of RIS metasurface based on beam broadening technique is proposed to improve the coverage of the deployment scheme and compensates for the array gain by increasing the number of metasurfaces.Second,in the multi-user communication scenario,this thesis solves the multi-user Weighted Sum-Rate(WSR)maximization problem by jointly optimizing the access point(AP)active beamforming,RIS passive beamforming and RIS deployment locations.A two-stage optimization is proposed in the ceiling deployment scheme,and the first stage jointly optimizes the active beamforming and RIS deployment locations.After determining the RIS deployment location,the second phase further jointly optimizes the active beamforming and RIS passive beamforming.In the vertical deployment scheme,the spatial geometry of the deployment scheme is exploited to simplify the channel model,and an efficient algorithm is proposed to jointly optimize the BS active beamforming and RIS passive beamforming using block coordinate descent(BCD)and successive convex approximation(SCA)techniques.The simulation results show that the RIS-assisted communication channel model is dependent on many factors such as radiation pattern,distance,and reflection coefficient,and the traditional free-space path loss model,which only considers the distance,is no longer applicable.In the single-user system,all three deployment schemes have their own advantages.After analyzing the strengths and limitations of wall deployment,this paper innovatively proposes two schemes:ceiling deployment and vertical deployment.The former mainly solves the problem of long-distance movement along the wall deployment,while the latter further solves the problem of small coverage area of ceiling deployment.In specific deployment scenarios,the use of beam broadening technology and increased meta-surface amounts can provide stable link support for users within a certain coverage area.In the multi-user system,a optimization algorithm based on BCD and SCA is proposed to solve the joint optimization problem of active beamforming and RIS location.Shown from the simulation results,the system performance is greatly improved.