Optimal Energy Transmitters Placement Schemes For RF-energy Harvesting Wireless Sensor Networks

Wireless Sensor Network(WSN)has a lot of potential applications in different fields.The sensor nodes in the traditional WSN are usually powered by the battery.However,once the energy of battery is used up,the node becomes useless.In many applications,the replacement of battery is very hard or even impossible.In recent years,the WSN which is able to harvest the environmental energy has attracted more and more attention.Among such type of WSNs,Radio Frequency Energy Harvesting Wireless Sensor Network(RF-EHWSN)is quiet attractive.This work focuses on RF-EHWSN which is powered by the specially deployed energy transmitters(ETs).In the considered RF-EHWSN,on one hand,the cost of ETs is quite high.On the other hand,the placement positions of ETs greatly determine the energy harvesting rate of nodes.Therefore,how to deploy the ETs as few as possible so as to guarantee the normal work of nodes is worthy to be studied.This work aims to RF-EHWSN where the nodes have different demands on the energy harvesting rates,and study the ETs deployment problems.The main contributions are listed as follows.(1)Study how to deploy omni-directional(i.e.RF energy is radiated in all directions)EnergyTransmitters(ETs)so that the power output requirements of all nodes are satisfied and thenumber of ETs is minimized at the same time.This paper first formulates this ETsplacement problem so as to deeply and theoretically understand this problem,and thenpresents a low-complexity greedy scheme and a particle swarm optimization(PSO)-basedscheme with relatively high complexity.(2)Study how to deploy directional ETs so that the power output requirements of all nodes aresatisfied and the number of ETs is minimized at the same time.This paper first formulatesthis ETs placement problem and then presents a low-complexity random scheme and agreedy scheme with relatively high complexity.The proposed schemes not only have acceptable computational complexity,but also can find the feasible ETs deployment solutions which have relative small number of ETs?...