Research On Energy Hole Mitigation Mechanism For Wireless Sensor Networks With Cost Balance

In Wireless Sensor Networks(WSNs for short),how to effectively use the limited energy of the nodes in the network to maximize the overall effectiveness of the network and extend the network life cycle has been a key issue in WSNs research.As parts of the nodes in the network consume prematurely the energy of their own reserves,resulting in the "energy hole" phenomenon which reduces the network coverage rate or could not transmit data collected by the node to the Sink.At present,the "energy hole" phenomenon has become a hot issue in Sensor Networks.In this thesis,two methods have been proposed to alleviate the "energy hole" phenomenon in circular and rectangular networks respectively.(1)The mitigation method for "energy hole" phenomenon based on circular sensor networks with virtual annuluses.A type of energy hole mitigation method based on synchronization of nodes in adjacent annuluses(SNAA for short)is proposed.The circular network is divided into several virtual annuluses with the same width.Nodes are deployed non-uniformly in each annulus and the number of them increases in geometric progression from the outer annuluses to the inner ones which could effectively reduce the work load on nodes near the center.Moreover,each node could select its optimal parent by considering the residual energy of each candidate as well as the distance between the two nodes in adjacent annuluses.In addition,on the basis of synchronization of nodes between adjacent annuluses during their transmitting and receiving phases,a sleep scheduling strategy is also proposed to further reduce the energy consumption of nodes in idle listening mode.Simulation results show that SNAA has a superior performance on energy consumption balance compared to the algorithm proposed(Liu et al.,Wu et al.)and it could also mitigate the "energy hole" phenomenon in WSNs.(2)The mitigation method for "energy hole" phenomenon based on rectangular sensor network with mobile Sink.First of all,the rectangular network is divided into several virtual grids and nodes in the same grid form a cluster.Subsequently,a data collection tree is constructed with the mobile Sink as its root.The cluster head in each grid is assumed as an intermediate node or a leaf node.The mobile Sink calculates the communication cost on all data collection trees,and moves to the grid where the tree has the minimum cost.Simulation results show that the data collection tree of the proposed method is energy efficient in multi-hop sensor networks,and can effectively alleviate the "energy hole" phenomenon in the rectangular network.