Multi-antenna Enabled Cluster-based Cooperation in Wireless Powered Communication Networks

In this paper, we consider a wireless powered communication network (WPCN) consisting of a multi-antenna hybrid access point (HAP) that transfers wireless energy in the downlink to wireless devices (WDs), and receives the information transmissions from the WDs in the uplink. To enhance the throughput performance of some far-away WDs, we allow one of the WDs acting as the cluster head that helps relay the information transmitted by the other cluster members. This cluster-based cooperation can effectively enhance the throughput performance of some far-away WDs. However, its performance is also limited by the high energy consumption of the cluster head. To tackle this energy imbalance issue, we propose in this paper to exploit the capability of multi-antenna energy beamforming technique at the HAP, which focuses more transferred power to the cluster head to balance the energy consumption of all the WDs. Specifically, we derive the throughput performance of the proposed scheme and demonstrate through simulations that the proposed multi-antenna enabled cluster-based cooperation can effectively improve the throughput fairness performance of the WPCNs.