Research On Node Location And Fault Connectivity Recovery In Wireless Sensor Networks

Wireless Sensor Network(WSN)technology plays an important role in the field of Internet of Things because of its high practicability.The application scenarios of wireless sensor networks are usually complex external environments,so it is inevitable to encounter various problems during deployment and operation.In the application process of wireless sensor networks,there are some unknown nodes in the network that can't get the position information through satellite positioning system.Positioning the unknown nodes without satellite positioning system can effectively guarantee the operation of the network and expand the use value of wireless sensor networks.However,in the process of locating unknown nodes in sensor networks,a large number of nodes are sometimes damaged due to the influence of the harsh external environment,thus dividing the whole network into a plurality of disconnected partitions.Therefore,it is also a problem to be solved how to restore the connectivity of the network after the network breaks down and ensure the robustness of the network after the connectivity is restored.To sum up,in view of the above two problems in wireless sensor networks,this paper proposes the following methods to improve:1.Aiming at the problem that the distance difference between each anchor node and its unknown node in the process of locating unknown nodes by the traditional centroid algorithm,a three-dimensional weighted centroid localization algorithm based on polyhedron centroid replacement(TW-CLA-PCR algorithm)is proposed by optimizing and improving the traditional centroid localization algorithm.Firstly,the number of anchor nodes in the communication range is determined.When n<4,unknown nodes with different numbers of anchor nodes are located by using maximum likelihood estimation method and centroid estimation method respectively.When n?4,the centroid of all anchor nodes in the communication range of unknown nodes is solved,and the anchor node farthest from the unknown node is replaced by this centroid,which is solved and replaced repeatedly,and finally stopped when the set threshold condition is reached.At this time,the weighted centroid is solved by combining the RSSI(Received Signal Strength Indication)values of each anchor node,and the centroid is taken as the estimated position of the unknown node.2.Aiming at the problem that wireless sensor networks are vulnerable to severe environmental damage and the energy loss of each key node is much larger than that of other nodes after connectivity restoration,a connectivity restoration algorithm based on Steiner tree and Tyson polygon(CRAST algorithm)is proposed.Firstly,the algorithm abstracts the partitioned nodes into discrete points,enumerates all the nondegenerate quadrilaterals in the discrete point area,and then deploys relay nodes to these nondegenerate quadrilaterals by using quadrilateral Steiner tree structure to achieve connectivity recovery.Then,the algorithm constructs Delaunay triangulation with key nodes,and constructs the Tyson polygon topology of the whole wireless sensor network through Delaunay triangulation.Finally,mobile standby relay nodes are deployed at all vertices of the Tyson polygon.When the key nodes are damaged,spare nodes to be moved are selected by comparing the proportion of spare nodes to all spare nodes corresponding to the key nodes,and the damaged key nodes are replaced by mobile standby relay nodes.