Time-to-Recharge Analysis for Energy-Relay-Assisted Energy Harvesting

The performance of two energy relaying schemes, namely backscatter relaying and store-and-forward relaying are compared with the system where no relaying is incorporated by considering time-to-recharge as a performance metric. The non-linearity of energy harvesting efficiency and its dependency on the waveform of energy signal and received power are taken into consideration while evaluating the performance of the relay assisted schemes as well as no relay scenario. Additionally, we considered a multi-antenna energy transmitter and formulated optimization problems for finding the optimal beamforming vectors that maximize the received power for the relay assisted schemes. Exploiting the structure of the optimization problems, we also derived analytical expressions that characterize the optimal solutions. Finally, using numerical results we demonstrated the effectiveness of the presented relaying schemes in comparison with the no relay scheme.