Power Allocation Strategies In Energy Harvesting Wireless Sensor Networks

Wireless sensor network(WSN)is a distributed network which is composed of a large number of miniature and cheap sensor nodes.Sensor nodes in the WSN can monitor the targets in monitoring area and use wireless communication technology to transmit monitoring data to the department of information management by the form of single or multiple hops.Nowadays,WSN is widely used in various fields due to its good flexibility,excellent self-adaptive ability and self-organizing ability.The sensor nodes in WSN are usually powered by batteries with limited energy.Therefore,the energy consumption problem of sensor nodes gradually becomes an important factor which restricts the development of WSN,which make the WSN can't be deployed in some special environments such as enemy battlefields,buildings and the human bodies.In this context,energy harvesting wireless sensor network came into being.It is a new type of network which equipped with wireless energy harvesting devices based on the traditional WSN.It can make the sensor nodes in WSN collect the energy in our surroundings spontaneously and convert the natural resources into electrical energy which can be used to power the network.Based on the theory of energy harvesting technology and cooperative transmission technology,the power allocation strategies of energy harvesting WSN system is studied in this passage.The common power allocation algorithms include independent non-cooperative transmission algorithm,equal power allocation algorithm,water filling power allocation algorithm and channel inversion power allocation algorithm,in which water filling algorithm achieves the greatest network throughput.However,the traditional water filling algorithm does not consider the new constraints imposed by harvested energy of the system.On this background,an improving energy-transferring power allocation algorithm is proposed in this paper.The main contents and research results are as follows:(1)In the energy harvesting WSN,the realization of the simultaneous power and information delivery need to use integrated information and energy receiver architecture or separated information and energy receiver architecture.The separated information and energy receiver architecture can be divided into time switching-based receiver and power splitting-based receiver.With the assistance of power splitting-based receiver,this paper derived the expression of outage probability in multi-users and single-relay node cooperative system,which use independent non-cooperative transmission algorithm,equal power allocation algorithm,water filling power allocation algorithm respectively in the decode-and-forward(DF)mode and amplify-and-forward(AF)mode.The simulation results show that the performance of the system using water filling power allocation algorithm isbetter than that using equal power allocation algorithm and independent non-cooperative transmission algorithm.(2)The power allocation problems of the energy harvesting WSN require additional consideration of the new constraints imposed by harvested energy.The energy consumed by the system at any moment cannot be the total energy collected at the current moment.The improving energy-transferring power allocation(IETPA)algorithm based on the water filling power allocation algorithm considers the new constraints imposed by harvested energy and couples the power allocation factors of each time slot,which made the power allocation of each time slot is not only related to the energy collected in the previous time slot and affects the power allocation in the next time slot.The simulation results show that the improving energy-transferring power allocation algorithm not only can completely applied to energy harvesting WSN,but also can further improve network throughput,reduce system outage probability,and improve system stability.