Research On Energy Hole Based On PMRC In Wireless Sensor Network

With the rapid development of wireless network, sensor network, as a boominginformation collection technology, has been given a great amount of attention increasingly andpopularized powerfully in many fields recent years.One of the main research directions isto solve the energy hole problem.Wireless sensor network applications have a predominant traffic pattern: aggregation, inwhich sensor nodes send reports to the base station. aggregation causes energy hole problem,nodes closer to the base station incur heavier workload and deplete their energy more quickly,which impairs network lifetime. This thesis proposes two strategy, which can improve networklifetime without sacrificing end-to-end delay and throughput.The main work and innovation of this paper are summarized as follows.Previous literatures are mainly based on corona network model, while this thesis adoptsthe PMRC network model. In the model, all the sensor nodes are homogeneous and have thesame capability. Nodes are partitioned into layers according to their distance to the Sink. Acluster is composed of sensor nodes in the same layer and a cluster head in the upstream layer.Once the residual energy of a cluster head drops below a pre-defined threshold, the Sink willinitiate the network formation process in a new round. If there is one sensor node that cannotfind any candidate cluster head during the process, the network is considered partitioned.A new strategy, DP strategy, is proposed which takes the energy consumed for idlelistening and transmitting data into consideration. This approach is designed based on energyconsumed by both traffic and idle listening. It assigns different duty cycles for nodes atdifferent distances from the base station to address the energy hole problem. The duty cycledifferentiation requires nodes in different coronas to deploy different duty cycles. The resultsof simulation experiment on the platform OMNET++indicate that our strategy, compared tothe original approach, can prolong network lifetime and maintain network performancewithout sacrificing end-to-end delay and throughput.The unbalanced energy depletion among all the nodes in the network is unavoidable.Even if the nodes in the inner coronas of the network have used up their energy simultaneously,the ones in the outermost corona may still have unused energy. This is due to the intrinsicmany-to-one traffic pattern of WSN. Nevertheless, nearly balanced energy depletion in thenetwork is possible if the number of nodes increases in geometric progression from the outercoronas to the inner ones except the outermost one circle. Based on this, another strategy, LPstrategy, is proposed which prolongs the network lifetime by balancing the energyconsumption of all nodes, especially the nodes in inner coronas. In the inner coronas more nodes will be deployed in the range where the average load is higher. From the fourth coronasto the outmost coronas, the number of nodes in each corona and derive the ratio between thenode densities in the adjacent coronas. Extensive simulations on OMNET++have beenperformed to validate the performance of the LP strategy.