Intelligent Reflecting Surface Assisted Wireless Powered Communication Networks

摘要

In this paper, we propose to use an intelligent reflecting surface (IRS) in a wireless powered communication network to boost both downlink energy transfer (ET) and uplink information transmission (IT) efficiency, where the IRS consisting of a large number of low-cost passive reflecting elements is deployed between a hybrid access point (HAP) and multiple wireless-powered users. In particular, all passive reflecting elements collaboratively adjust their phase shifts to first construct beamforming for ET from the HAP to all users and then provide additional transmission links for IT from the users to the HAP. Then, we formulate a sum-rate maximization problem by jointly optimizing the time scheduling for network, the phase shift matrix for ET, and the phase shift matrices for all users' IT. Since the formulated problem is non-convex, we first design the phase shift matrices for IT independently by exploiting the characteristics of IT and obtain an approximate solution by using the semidefinite relaxation technique and the Gaussian randomization method. After that, we propose a block coordinated decent based algorithm to solve the simplified problem by iteratively optimizing the time scheduling and the ET's phase shift matrix, the convergence of which is further analyzed. Simulation results confirm that the proposed scheme can achieve up to 350% sum- rate gain compared to the benchmarks.