Packet Length Adaptation For Improving The Energy Efficiency In Wireless Sensor Networks

As a fundamental and supporting technology for the Internet of things underlyinglayer, Wireless Sensor Networks have received widely attention of the world. Differfrom the other wireless technologies, Wireless Sensor Networks are generally chargedby battery. Once energy is depleted, the sensor will fail and stop working. So, how toperform better energy efficiency is crucial for WSNs research. To improve the energyefficiency of WSNs, we start from the three basic elements of communication procedure,and an analytical model of energy efficiency is established for describing energyconsumption from hardware, useful information, control packets and retransmission.Based on the model, a high energy efficiency packet length adaptation algorithm isproposed and designed by using dynamic gradient. The simulation results show that thealgorithm can improve energy efficiency obviously. The contributions are as follows.(1) The current basic background and scientific significance of wireless sensornetworks are introduced, including the basic concept, characteristic and architecture.The significance of energy efficiency research for wireless sensor networks is analyzed.Meanwhile, the techniques for improving energy efficiency are summarized. A detailcurrent state of the art for energy efficiency analytical model and packets lengthadaptation algorithm are presented and discussed.(2)The key factors that affect and decide the performance of wireless sensornetwork energy efficiency are discussed and derived, including the selection of channelmodel, the hidden terminal problem in IEEE802.15.4. Considering the three scenario,the packet error rate caused by channel bit error rate and collision rate caused bychannel access and hidden terminal are computed. Finally, the packet drop rate isobtained under the retransmission mechanism.(3)The basic idea for designing the energy efficiency analytical model of WSNs ispresent and the detail deriving procedure under retransmission mechanism for energyefficiency is presented. The energy efficiency parameters can be divided into twoclasses, i.e. the parameters depending on the network protocols and the parameters thatindependent on the network protocol. With the method of simulation, the significanceimpact of packet length, number of nodes, the maximum retransmission limitation andretransmission mechanism on network performance is analyzed. (4)A packet length adaptation scheme based on dynamic gradient is proposed. Theinfluences caused by variation of network state are divided into three situations, i.e.increase, decrease and invariant. Targeting each different situation, correspondingstrategies are formulated. Meanwhile, because the gradient of packet length is adaptive,it can improve the convergence rate of packet length adaptation and avoid trapping inlocal optimum. By simulation with OMNeT++, the energy efficiency using VG-PLA isimproved by11.7%and4.8%respectively compared with fixed packet length algorithmand adaptive packet length algorithm but with fixed gradient (FG-PLA).