Anchor-free Localization Algorithm In Wireless Sensor Networks

Node positioning technology is one of the key supporting technologies of wireless sensor network.In the common node positioning technology,anchor node positioning can be divided into anchor-based positioning and anchor-free positioning according to whether anchor node is needed or not.The anchor node localization algorithm requires some sensor nodes in the network to be equipped with positioning modules such as GPS or beidou navigation.In the anchor-free positioning algorithm,the sensor node can be positioned without needing to be equipped with a positioning module which has little dependence on the hardware.In this paper,based on the connectivity between sensor nodes,a low-cost and large-scale node positioning algorithm named virtual anchor node positioning algorithm is proposed.In the virtual anchor node positioning algorithm,five virtual anchor nodes need to be selected from ordinary nodes at first,and the selection of these five virtual anchor nodes can be realized only by the wireless transceiver of the node itself.After the virtual anchor node is selected,the relative coordinate system can be established.Other nodes in the network can use the distance from the virtual anchor node to calculate the node's own position through the triangular measurement method.In order to reduce the positioning error,the algorithm proposed in this paper corrects the hops between the unknown node and the virtual anchor node and the hops distance between the unknown node and the virtual anchor node in combination with the neighbor node density.After the unknown node obtains the estimated position,the contact position is optimized by the Taylor series expansion method to achieve the positioning accuracy.After the establishment of relative coordinate system,the backup node is selected according to the number of neighbors and the composite index of residual energy of the node,and the virtual anchor node is required for backup.After the establishment of relative coordinate system of node,it can be converted into absolute coordinates by sink node.The effect of the positioning algorithm is verified by the experimental simulation,and the positioning error of the nodes is analyzed.