Multi-Antenna Wireless Powered Relaying: Low Complexity and Near Optimal Techniques for Generic EH Models

We investigate Wireless Powered Multi-Relay Networks (WPRNs) equipped with multiple antennas both at the Source and the Relay and propose two different communication schemes. These schemes are based on the combination of Time Switching (TS) and Self-Energy Recycling (SER) and extend existing ones that have been developed for single-antenna sources. Following that, by adopting only the very generic assumption that the Energy Harvesting Model (EHM) is described by any non-decreasing function, we focus on the instantaneous rate maximization problem and design near-optimal beamforming and wireless power transfer-time determination algorithms for our schemes. A common characteristic of the presented algorithms is their low complexity and implementation simplicity. Given the generality of our EHM assumptions, our algorithms are applicable for all popular EHMs found in the literature, which are normally described using non-decreasing functions, without being specific to any of them. Various simulation results are presented that allow to evaluate the two schemes and compare them with existing benchmarks for different popular EHMs and relay availability scenarios. Finally, we bound the suboptimality of our solutions and verify their near-optimal performance for different EHMs.