Research On Resource Allocation Algorithms In Intelligent Reflecting Surface-Aided Communication Systems

With the rapid development of fifth-generation mobile communication networks,the number of network users and mobile data volumes have proliferated.Higher transmission rates and higher bandwidths need to be achieved to improve the experience of user.However,it causes serious energy consumption problems.Therefore,the design of wireless communication systems not only needs to concentrate on the improvement of spectrum efficiency or capacity,but also the improvement of energy efficiency.And energy efficiency has become an important performance indicator in communication networks.In recent years,Intelligent Reflecting Surface(IRS)technology with passive characteristics has attracted much attention for its high spectral efficiency and high energy efficiency.The resource allocation problems are investigated in IRS-assisted wireless communication systems with spectrum efficiency and energy efficiency as the optimization objectives.The main work and innovations of are as follows.1.In IRS-assisted multi-user downlink communication system,Base Station(BS)precoding,IRS phase shift and transmit power allocation problems are optimized jointly to maximize the spectrum efficiency.First,the joint resource allocation problem is modeled as a spectrum efficiency maximization problem.Then,to suppress the inter-user interference,the Zero-Forcing precoder is proposed to design the BS precoding matrix.Next,given the BS precoding matrix,a joint optimization strategy of IRS phase shift and power allocation based on the alternating iteration algorithm is proposed.Specifically,for the IRS phase shift optimization design problem,the Riemannian trust Region algorithm is proposed by embedding the unit modulus constraint into the search space using the manifold optimization technique;for the transmit power allocation problem,a power allocation scheme based on the Water Fullfilling algorithm is proposed.Finally,simulation results show that the proposed algorithm effectively improves the spectral efficiency of the system.2.In multi-IRSs-assisted downlink communication system,the IRS phase shift,BS transmit power and IRS ON-OFF switch selection problems are optimized jointly to maximize energy efficiency.First,the resource allocation problem for energy-efficiency maximization is modeled.Then,an alternating iteration algorithm is proposed to solve the joint optimization problem of IRS phase shift,BS transmit power,and IRS ON-OFF switch selection.For the IRS phase shift optimization design problem,a successive convex approximation algorithm is adopted.For the BS transmit power problem,the optimal solution of transmit power is found based on the Dinkelbach method.For the IRS ON-OFF switch selection problem,the greedy algorithm is proposed to find the solution of this problem.Finally,the simulation results show that the proposed algorithm effectively improves the energy efficiency of the system.