Optimization Technology In Intelligent Reflecting Surface Assisted Wireless Communication System

In contemporary wireless communication systems,with the development of material technology,intelligent reflecting surface(IRS)has gradually become a significant part in the system.As an emerging technology,IRS can effectively improve capacity and reliable of wireless communication,especially when the communication systems have complicated network interference issues.For example,when there are lots of active nodes in a system,IRS can easily optimize the communication between them.Although researches on IRS have been very popular nowadays,the situation of users with different importance in communication system is not common.This thesis closely follows the research trend.It takes the total information rate of wireless communication system as the optimization goal,and proposed a solution for the parameter design of IRS assisted user system when the users have different weights.For the design of IRS units,beamforming of base station’s antennas and other parameters,this paper proposed a solution to optimize it by using convex optimization techniques such as semidefinite relaxation(SDR).In the same time,a joint optimization algorithm is designed for optimization to improve the performance of the communication system.At the same time,because the IRS’s location of placement also has a great impact on the performance of the communication,this thesis designs an optimization algorithm for its location of placement,and uses convex optimization technology and numerical algorithm to optimize the IRS’s location of placement in the system,so as to further improve the communication performance.At the same time,as a relatively mature technology,unmanned aerial vehicle(UAV)has become an indispensable part in wireless communication system.Unlike the previous situation that the IRS is placed in a fixed position and the IRS is separated from the UAV,this thesis innovatively designs a wireless communication system in which IRS is carried by UAV,which provides a better capacity and reliable for the wireless communication system.This thesis aims to improve the worst communication performance of the BS-user group in the whole communication system.Firstly,the flight trajectory of UAV is studied and solved by using successive convex optimization algorithm and other technologies.After solve the problem of flight trajectory,it will be easy to obtain the information about the channel.Then we can further design the beamforming of the BS’s antenna and the phase shift of the IRS unit.At last,this thesis designs a joint optimization algorithm to optimize the whole communication system by combining the three parts to find the optimal flight trajectory of the UAV,the beamforming of the antenna and the phase shift of the IRS unit.It can effectively improve worst communication performance of the BS-user group,then the overall communication performance and capacity of the system can be effectively improved.In this end of thesis,many simulations have verified the reliability and effectiveness of the two proposed algorithms.This thesis provides a feasible solution for the situation when there are multi users in the IRS assisted communication system.For the design of the communication system of UAV equipped with IRS,this thesis also provides an effective solution.