On the Throughput of Wireless Powered Communication Systems With a Multiple Antenna Bidirectional Relay

We consider an amplify-and-forward-based relay network comprising a hybrid access point, multi-antenna bidirectional relay and user terminal (UT). The relay first harvests energy using a power splitting (PS) scheme and then transfers power wirelessly to the UT. We analyze the throughput assuming maximum ratio combining in conjunction with a linear combination of information beamforming and energy beamforming at the relay. In particular, we derive two new closed-form approximations for the ergodic throughput in the asymptotic regime for a large number of antennas at the relay. We also present new solutions for the optimal beamforming vector and PS factor that maximize throughput. Finally, all the analytical results are corroborated through simulations.