Bidirectional Wireless Information and Power Transfer With a Helping Relay

This letter studies a wireless powered communication system with a bidirectional relay, where the relay helps forward wireless power from the access point (AP) to the user, and also amplify-and-forward information from the user to the AP in the reverse direction. We propose two protocols based on power splitting and time switching at the relay, respectively. The optimal power splitting and time switching ratios are derived in each case to maximize the information throughput from the user to the AP subject to the energy harvesting and consumption balance constraint at both the relay and the user. Numerical results show that a significant throughput gain is achieved by the optimized power splitting scheme over the optimized time switching scheme.