Research On Mobile Anchor-aided Range-based Localization Technologies For Wireless Sensor Networks

Node localization is one of the key supporting technologies for the widespread Wireless Sensor Networks(WSN),and has been attached great importance to by technology researchers all the time.Nowadays,the enlarging coverage of wireless network signal and the successive application of new-type ranging methods with high accuracy and at low cost such as UWB,provide an opportunity for the development of high accurate WSN positioning system.According to the implementation of WSN,this paper proposes Two-step Weighed Least-square algorithm With Lagrange Multiplier(TWLS-WLM)and joint algorithm of clock synchronization and node localization,in order to solve the problems in mobile WSN,such as anchors' clock synchronization,anchors' relative localization,tags' hyperbolic localization and the resume of networks' whole topology.(1)TWLS-WLM algorithm converts tags' hyperbolic localization into seeking polar angle and polar radius of curves' intersection.Applying constraints between angular parameters,this algorithm obtains and solves a real coefficient quartic equation of Lagrange multiplier,then gets in two steps the estimates of angular parameters and polar radius.Theoretically,this algorithm is iteration-free,and can provide analytic solution in closed form.Simulation results show that it has an actual calculation load between Fang algorithm and Taylor series algorithm,and a performance in locating accuracy and effective coverage much better than that of Fang algorithm and close to that of Taylor series algorithm,and suffers no hazard of divergence as well.(2)Joint algorithm of clock synchronization and node localization,constructs the information-collecting model for centralized computation by introducing the connectivity of anchors to backbone networks.Then with signals' TOA of several blink rounds applied in linear model of anchor clocks,clock parameters' estimates are obtained,thus make sure bench synchronization of anchors' clock in the compensation sense,which in turn gives support to pseudo TOF range between anchors,the relative multilateration of anchors and hyperbolic location of tags.This algorithm employs centralized operation,with its simple principle,small calculation load and clear physical meaning of each parameter.Simulation shows that it provides a position-estimating accuracy close to that of similar algorithm with anchors' positions known and clocks synchronized.The advantage of this algorithm also lies in that it gets rid of the dependence of anchors on the GPS,which reduces greatly the cost of WSN,and in that it adopts the inverse-GPS structure for TDO A range,which reduces the hardware requirement and energy consumption of tags,and augments the capacity of WSN for tags.Both theoretical analysis and simulation results show that the mobile anchor-aided range-based localization algorithm for WSN proposed in this paper solves to certain extent some practical problems in WSN localization.This algorithm is simple and effective,with its performance close to that of synchronous algorithm,and minimized energy consumption and cost of the system,thus holds a wide application scope in the development of WSN positioning system.