Achieving Multi-Beam Gain in Intelligent Reflecting Surface Assisted Wireless Energy Transfer

Intelligent reflecting surface (IRS) is a promising technology to boost the efficiency of wireless energy transfer (WET) systems. However, for multiuser WET system, simultaneous multi-beam transmission generally required achieve maximum performance, which may not be implemented by using IRS having only single set coefficients. As result, it remains unknown how exploit approach such performance upper bound. To answer this question, we aim maximize total harvested system subject user fairness constraints and non-linear harvesting model. We first consider static beamforming scheme, shows that optimal reflection matrix obtained applying semidefinite relaxation indeed high rank in general as number receivers (ERs) increases, due resulting rank-one solution Gaussian Randomization lead significant loss. gain, then propose time-division based novel framework exploiting IRS's dynamic passive beamforming. Moreover, able good balance between complexity controlling shift patterns. Finally, also multiple access (TDMA) design comparison. Simulation results demonstrate necessity superiority proposed scheme over existing schemes.