| Underwater Wireless Sensor networks(UWSNs) are one aquatic environment monitoring network system that consists of many nodes with data acquisition,signal processing,storage,wireless acoustic transmission.UWSNs have extensive applications in information acquisition of aquatic environment,ocean exploitation,surveillance of ocean military and underwater disaster prediction.In recent years,UWSNs have been widely concerned by the government,industry and academia in coastal state.The researches of UWSNs mostly relate to routing protocol,topology control,node positioning technology and node deployment.Meanwhile,the node deployment is not only directly related to the quality of network monitoring but also dramatically affects subsequent processing on the design of all kinds of protocols and algorithms.Therefore,in this study,this crucial and basic problem is further investigated,namely,node deployment.The node deployment is the process of improving the network performances by optimizing the location of nodes.However,based on the assumption of node mobility,the existing deployment algorithms can be classified into three categories,namely,static deployment,free movement deployment,and vertical movement deployment.This study mainly aimed at different deployment requirements and scenarios to design some relevant deployment algorithms.Then,the main research works are as follow:(1)Firstly,for the vertical movement deployment,we proposed a node depth adjustment deployment algorithm based on two-dimensional convex hull and spanning tree.This algorithm uses the geometric characteristics of a two-dimensional convex hull and empty circle to find the optimal location of a sleep node and activate it,minimizes the network coverage overlaps of the two-dimensional plane,and then increases the coverage rate until the first layer coverage threshold is reached.At the same time,this algorithm guarantees the connectivity between father node and its child nodes in the process of depth adjustment.The simulation results show that the proposed algorithm can maintain full network connectivity with high coverage rate and low energy consumption of communication,as well as improved network average node degree,thus increasing network reliability.(2)Secondly,for the free movement deployment,we proposed an uneven cluster deployment algorithm based network layered for event coverage.This algorithm evaluates several characteristics for the existing deployment algorithms based on event coverage,according to the energy consumption requirement of the communication load at different depths of the underwater network.Then it obtained the expected value of deployment nodes and the distribution density of each layer network after theoretical analysis and deduction.Afterward,the network is divided into multilayers based on uneven clusters,and the heterogeneous communication radius of nodes can improve the network connectivity rate.The recovery strategy is used to balance the energy consumption of nodes in the cluster and can efficiently reconstruct the network topology,which ensures that the network has a high network coverage and connectivity rate in a long period of data acquisition.(3)Finally,for the network coverage preserving routing after initial node deployment,we proposed coverage preserving routing algorithm based on decision tree.This algorithm generates the decision tree routing based on multivariable characteristic,and then selects the optimal path of information routing.Furthermore,pruning decision tree is utilized to simplify the network routing model and reduces duplication of transmitted information.The simulation results show that the proposed algorithm can ensure the network is in a relatively high coverage rate in a long period.At the same time,the proposed algorithm can balance the energy consumptions of overall network,thus prolonging the network lifetime. |
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