Joint Energy and Information Beamforming Design for RIS-assisted Wireless Powered Communication

In the wireless powered communication network (WPCN), the wireless energy acquisition is weak due to the fading characteristic of the wireless link, which is hard to supply energy to wireless sensor. Reconfifigurable intelligent surface (RIS) is a promising performance enhancing technology for WPCN, which can improve the energy and spectral effificiency, expand the network coverage, and thus improve the throughput. This paper proposes a new framework for energy harvesting and information transmission of non-orthogonal multiple access (NOMA) based WPCN aided by the RIS. The total transmission capacity is maximized by joint optimization energy beamforming, information beamforming and the RIS phase shift, which turns out to be a non-convex problem. By exploiting the iterative optimization and maximal ratio combining (MRC) algorithm, the energy beamforming and information beamforming are determined for single- and multi-user system, respectively. Numerical results prove that compared with the non-RIS-aided system, the proposed scheme can increase the throughput of the multi-user system.