Research On Joint Optimization Algorithm Of Intelligent Reflective Surface-assisted Wireless Communication System

In future wireless networks,sixth generation(6G)mobile communication networks will need to provide superior performance over fifth generation(5G)networks due to high data traffic and massive connections for applications such as Internet of Things(IoT)and Integrated Sensing and Communications(ISAC).To meet these needs,further development of large-scale multiple-input multiple-output(MIMO)technology and deeper exploration of the high-frequency spectrum is a recognized path for the development of 6G.Intelligent reflecting surface,as a potentially cost-effective solution,are considered as an evolutionary extension of large-scale MIMO.This paper first investigates the theoretical performance improvement of the system with the addition of intelligent reflecting surfaces for assisted communication between base station and user in point-topoint communication.Through mathematical modeling of the intelligent reflecting surface-assisted communication system,a joint optimization of the base station transmits precoding and the intelligent reflecting surface phase shift matrix is performed to maximize the user’s communication rate under the maximum transmit power constraint of the base station.Then the problem of difficult channel estimation of the intelligent reflecting surface-assisted communication system and the difficulty in engineering the continuous phase shift parameter of the intelligent reflecting surface reflecting unit are added into consideration,and the problem of maximizing the communication rate under the imperfect channel state information and discrete phase shift parameter of the intelligent reflecting surface reflecting unit is investigated and the performance of the intelligent reflecting surface reflecting unit under different resolutions is explored.Finally,the single-user communication scenario is extended to the multi-user communication scenario,and the joint parameter optimization problem is explored for adding the intelligent reflecting surface for auxiliary communication when the base station transmits and receives with multiple singleantenna users at the same time.A block coordinate descent(BCD)-based algorithm is proposed to jointly optimize the base station transmit precoding matrix and the phase shift matrix of the intelligent reflecting surface under the constraint of maximum total transmit power of the base station with the objective of maximizing the weighted sum-rate(WSR)of users.Simulation results show that effective optimization of the phase shift parameters of the intelligent reflecting surface can bring good performance improvement to the communication system.