Group Cooperation and Resource Allocation in Wireless Powered Communication Networks

Abstract

This paper focuses on the optimal wireless powered communication network (WPCN) design. A network composed of two communication groups is considered, where the first group has sufficient power supply but no available bandwidth, and the second group has licensed bandwidth but very limited power. By introducing power and bandwidth cooperation between the two groups, both groups can accomplish their expected information delivering. Multiple antennas are employed at the hybrid access point (H-AP) to enhance both energy and information transfer efficiency and the cooperative relaying is employed to help the power-limited group to enhance its information transmission throughput. To explore the information transmission performance limit of the system, we formulate an optimization problem to maximize the system weighted sum-rate (WSR) by jointly optimizing the time assignment, power allocation, and energy beamforming under the available power constraint and the quality of service (QoS) requirement constraints of both groups. As the problem is non-convex and has no known solutions, we solve it by using proper variable substitutions and the semi-definite relaxation (SDR). We theoretically prove that our proposed solution method can guarantee to find the global optimal solution. Extensive experimental results are provided to discuss the system performance behaviors, which provide some useful insights for future WPCN design. It also shows that in such a WPCN, relay should be placed closer to the multi-antenna HAP to achieve higher WSR.