Wireless Powered Communication Networks with Inter-Node Energy Charging

Wireless sensor networks (WSNs) are used in many surveillance tasks, such as air quality monitoring and control systems, smart building, smart agriculture, and habitat monitoring. However, in the classic WSN, the nodes are dependent on non-rechargeable batteries with a limited energy storage capacity. Since it is difficult to replace onboard batteries, the use of wireless harvested energy is desirable. Wireless powered communication networks (WPCNs) is proposed to break the limitation of the lifetime of battery-powered WSNs in many applications. In this paper, we present a time allocation scheme with inter-node energy charging using particle swarm optimization (PSO) for the WPCN that consists of a hybrid access point (HAP) and sensor nodes. The HAP is responsible to deliver energies to charge the nodes and receive data from the nodes in the network. Besides, the nodes can obtain the needed energy from the HAP and the other transmitting nodes. The round-time is divided into two major parts. One portion of it is assigned to the HAP to deliver energies to nodes. In another portion, all nodes complete their transmissions by evenly occupying the time. During one node is transmitting data to the HAP, other nodes can charge energy from the radio signal. The optimum allocation is obtained by applying the PSO algorithm. Simulation results show that the number of nodes has a direct impact on the system throughput. As more nodes are present in the network, more charging energies are available to the transmitting node with an increase in the system throughput.