Beamforming And Performance Analysis Of Communication System With IRS

Although the current 5G communication technology significantly improves the spectral efficiency of wireless networks,it also brings more energy consumption and higher hardware costs.Therefore,the intelligent reflecting surface that meets the needs of energy saving,green demand and high efficiency are coming out in the next generation of communication technology.By integrating a large number of inexpensive electromagnetic reflection elements,the intelligent reflecting surface can adjust the amplitude or/and phase of the incident signal in real time,realize the reconstruction of the wireless communication channel,and improve the quality of signal reception.However,when it is introduced into the existing mobile communication technology,the traditional communication theory may no longer apply.Therefore,it is very necessary to research the transmission optimization scheme and performance analysis in the communication system assisted by the intelligent reflecting surface.This paper mainly considers the scenario of deploying distributed intelligent reflecting surface,and conducts a series of studies on the signal processing and performance of the transmitter and receiver of the communication system.First,the physical properties of intelligent reflecting surface are studied and the existing optimization algorithms are verified.The physical properties of reconfigurable intelligent reflecting surface and the practical meaning of smart wireless environments are explained in detail using the knowledge of electromagnetism and materials science.By elaborating the working mechanism and system modeling method of the intelligent reflecting surface,the principle of how the intelligent reflecting surface scattering incident waves and controlling the directionality of the scattered waves is explained.The mathematical theory combining communication and electromagnetism is also introduced.By validating a fair comparison between the intelligent reflecting surface and the conventional relay,we determine the size of an intelligent reflecting surface needed to outperform a conventional relay.Finally,aiming at the maximum problem of formulating the weighted sum rate by jointly designing active beamforming and passive beamforming,an alternate iterative method is proposed to verify the effectiveness of this scheme.Secondly,the communication system using multi-intelligent reflecting surface with random geometric distribution is studied.Tools from stochastic geometry are used to study the performance of a single-cell system with one base station(BS)aided by multiple IRSs with predictive receiver mobility.The ergodic rate of the network with phase shifts is analyzed deviating from the ideal values according to a uniform distribution.An exact expression for characterizing the ergodic rate is also derived.Furthermore,large phase shift errors due to the user movement increase the cancellation among the different channels through IRS in the form of a sinc function,while large reflecting elements,suitble IRS dense,and predictive user mobility can narrow this loss.The handover between the BS and IRSs is analyzed under random deployment and an expression of the effective area spectral efficiency is given.This representation allows for theoretical analysis of the performance and can help the system designer study the interplay between performance,the distribution of phase errors,and the number of reflectors.Numerical results confirm the theoretical prediction and show that the performance is remarkably robust with predictable mobility.Lastly,passive beamforming and performance optimization of the communication system assisted by distributed intelligent reflecting surfaces are studied.A multiple-input-single-output system using statistical channel state information is considered,the passive beamforming of multiple intelligent reflecting surface is designed,and its performance on the receiver is analyzed.In particular,we first propose a low complexity passive beamforming design,which only uses the statistical correlation information of the channel.Then,considering the channel estimation error of the receiver,we analyze the ergodic rate of the network under the system.Finally,the exact closed expression of ergodic rate is obtained.In addition,we also find that the ergodic rate increases significantly with the increase of the number of line-of-sight paths from the base station to the intelligent reflecting surface and from the intelligent reflecting surface to the user.The advantages of distributed intelligent reflecting surface over centralized intelligent reflecting surface are verified,because the former increases the possibility of line-of-sight channel.