Research On Communication Performance Analysis And Channel Modeling Based On Reconfigurable Intelligent Surfaces

In recent years,with the commercial deployment and popularization of 5G,a large number of wireless devices have been connected to the Internet,resulting in the rapid growth of data and an increasing shortage of spectrum resources.It is urgent to develop new spectrum resources.Millimeter wave and terahertz frequency bands have rich spectrum resources,high transmission rates,but high absorption loss and are easy to be interfered by obstacles.At the same time,the traditional transceiver is no longer suitable for high frequency communication,and the hardware architecture needs to be redesigned,which is expensive and extremely complex.RIS,as a possible new paradigm in future wireless networks,can be designed as relays and transceivers to solve the above problems.RIS,as an emerging technology that has been extensively studied in recent years,is similar to but very different from traditional relays when it is used as a relay to assist communication.Therefore,it is necessary to conduct a detailed study on these differences from qualitative and quantitative aspects.Meanwhile,the communication performance will be affected by the communication channels.Before the development of new equipment system and network deployment,it is necessary to have a comprehensive understanding of the channel characteristics of the channel.Accurate channel models can provide simulation alternative environment for real communication scenarios and evaluation approaches for equipment research and development,which is very important for the design of the whole communication system.Therefore,the main research work and innovation of this thesis are as follows:(1)In the first two chapters,the background of the whole project is described in detail,the basic knowledge of RIS and relay is listed,and a macro comparison is made between RIS and relays.At the same time,geometry-based stochastic models are emphasized.(2)A comprehensive quantitative comparison and analysis of RIS and four different relay modes,including signal-to-noise ratio,achievable rate,transmitted power,total power consumption,and energy efficiency,are carried out.The condition of equal achievable rate between RIS and half duplex decode and forward relay is judged,and the optimal number of RIS with minimum total power is deduced and simulated.In addition,the optimization of energy efficiency in SISO and MISO scenarios are explored.Through the derivation and analysis of different parameters and modes,some inspirations of RIS deployments in corresponding scenarios are obtained.(3)A new 3D wideband non-stationary stochastic channel model is proposed,which is suitable for RIS-assisted communication in outdoor scenarios.Scatterers in motion space are modeled as twin-clusters and the birth and death evolutions of twin-clusters in time and antenna array domains are all considered.When RIS is placed on the surface of a moving receiver,RIS and receiver move at the same speed.Therefore,RIS and receiver have the same initial cluster,where birth and death evolutions take place respectively.The corresponding channel characteristic parameters are deduced,and the correctness of the deduced model is verified by comparing the simulation model with the reference model,and the time-varying non-stability of the channel model is revealed.