Design On Energy Harvesting Wireless Energy Transfer System For Wireless Sensor Networks

Wireless sensor networks(WSNs) have quickly become an area of great interest because of the great economic benefits and convenience they can bring us. One major problem of WSNs is the energy problem. WSNs are always expected to have a long lifetime while sensor nodes and other embedded systems are commonly powered by batteries, which have limited energy.Energy harvesting(EH) is a technology that enables sensor nodes to harvest energy from the energy source so as to have infinite energy and prolong their lifetime. EH systems have three main categories:(a) harvest-use(HU),(b) harvest-store-use(HSU), and(c) harvest-use-store(HUS). This thesis analyzes factors and conditions for EH system designing and show the characteristics of each category. Power management algorithms are given for HSU-EH system, in order to help the system achieve a better performance.Wireless energy transfer(WET) is a kind of EH that allows devices to harvest electromagnetic energy through wireless communication links. Since the path loss increases exponentially with the distance between harvester and receiver, devices only can receive a small portion of energy when using conventional wireless transfer framework. This thesis proposes a new massively distributed antenna system(MDAS) architecture to achieve a high efficiency energy transmission. Antenna selection, energy beamforming and power management are used to improve the performance of energy transfer in MDAS. This thesis also shows the outperformance of data transmission in MDAS when compared with traditional framework.A practical use of EH in WSNs is demonstrated in this thesis. The thesis applies WET on Point-to-Point(P2P) communication systems in WSNs. It analyzes the throughput of the system when using HU and HSU. Optimal energy allocation policy is proposed to maximize the system capacity.