摘要：面向无线供电通信网络（WPCN），混合接入点（HAP）和无线设备之间常存在障碍物的遮挡，这导致HAP 和无线设备之间无法直接通信。针对该问题，提出了两跳智能反射面（IRS）辅助的传输方案，即在HAP 和无线设备附近分别放置IRS，使得HAP、IRS 和无线设备之间构成反射链路，从而实现HAP 到无线设备的下行能量传输和无线设备到HAP 的上行信息传输。为了最大化系统吞吐量，建立了关于能量和信息传输的时隙分配、IRS 的相位和无线设备信息传输功率的联合优化问题。为了解决该非凸优化问题，提出了两阶段交替优化算法，以有效求得该问题的局部最优解。仿真结果表明，相较于参照方案，所提出的最优方案可以有效提升系统性能。
Abstract: In wireless powered communication networks (WPCN), there may exist obstacles between the hybrid access point (HAP) and wireless devices, which makes it impossible for them to communicate directly. To address this issue, two intelligent reflecting surfaces (IRSs) are used to establish a dual-hop relaying transmission link between the HAP and wireless devices. In particular, IRSs are deployed near HAP and wireless devices respectively, which realize the downlink energy transfer from the HAP to wireless devices and the uplink information transmission from wireless devices to the HAP. The system throughput is maximized by jointly optimizing the time scheduling of energy and information transmission, the phase shifts of IRSs, and the transmit power for information transmission of wireless devices. In order to tackle the non-convexity of the formulated problem, a two-stage alternating programming method is proposed to obtain the local optimal solution. Numerical results demonstrate the proposed scheme can achieve significant system throughput gain compared with the benchmark scheme.
Keywords: dual-hop intelligent reflecting surface; wireless powered communication network; phase shift optimization; energy harvesting