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Distributed Localization Using a Moving Beacon in Wireless Sensor Networks. + Bin Xiao, + Hekang Chen and *Shuigeng Zhou + Department of Computing, Hong Kong Polytechnic University, Hong Kong. * Department of Computer Science and Engineering, Fudan University.
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Distributed Localization Using a Moving Beacon in Wireless Sensor Networks +Bin Xiao, +Hekang Chen and *Shuigeng Zhou + Department of Computing, Hong Kong Polytechnic University, Hong Kong. * Department of Computer Science and Engineering, Fudan University. IEEE Transactions on Parallel and Distributed System, Vol. 19, No. 5, May 2008
Outline • Introduction • Distributed Localization using a Moving Beacon • Movement Patterns of the Beacon • Localization in the Real Environment • Performance Evaluation • Conclusions
Introduction • The techniques used to identify the position of each sensor node are central to such location-aware operations. • where events take place • tracking moving targets • assisting traffic routing • providing the network geographic coverage
Introduction • It is not infeasible to equip each node in a network with a Global Positioning System. • Constraints of cost and power consumption • Sensor nodes may be used to identify the position of other nodes in a sensor network. • Range-based • Range-free
Introduction • In this paper, the authors propose distributed method to localization of sensor nodes • low hardware cost • use moving beacon • feasible and accurate
Distributed Localization –using a Moving Beacon Static sensor Moving beacon
Distributed Localization–using a Moving Beacon Static sensor Arrival and Departure Overlap (ADO) Moving beacon arrival position prearrival position post departure position departure position
Distributed Localization –using a Moving Beacon Static sensor Moving beacon
Movement Patterns of the Beacon • Sparse-Straight-Line (SSL) • Dense-Straight-Line (DSL) • Random movement pattern
SSL Movement Patterns Arrival and Departure Overlap (ADO) upper HADO lower HADO
Distributed Localization –using a Moving Beacon Static sensor upper HADO Moving beacon lower HADO
SSL Movement Patterns Moving beacon
Line 3 Line 2 Line 1 SSL Movement Patterns Moving beacon • Rule 1. If B is in the row immediately above the (i-1)th line, the position of A is below the ith line. B B
Line 3 Line 2 Line 1 SSL Movement Patterns Moving beacon • Rule 2. If HADO(B) cannot contact HADOupper(A), theposition of A is below the ith line. A A’
Line 3 Line 2 Line 1 SSL Movement Patterns Moving beacon • Rule 3. If HADO(C) can contact HADOupper(A), theposition of A is below the ith line. C A A’
DSL Movement Patterns Moving beacon
Uncovered Space Moving beacon
Random movement pattern Static sensor Moving beacon A (previous position, current position, next position) (prearrival, arrival, departure, postdeparture)
Random movement pattern • The overlap of ADOs creates a single kernel overlap area(KOA) • Suppose that the KOA consists of n vertices. Let the coordinates of those n vertices (from v1 to vn) be (x1, y1), (x2, y2), . . . ,(xn, yn)
Random movement pattern • If node G can acquire the information of kADOs • k prearrival positions • k arrival positions • k departure positions • k postdeparture positions • OutPoints as a set to encompass both the prearrival and postdeparture positions • InPoints as a set to encompass both the arrival and departure positions • Point set P contain all the intersection points of these 4k circles.
Random movement pattern • Given a point u in P, its initial degree is set to0. • If the distance between u and an InPoint is not more than r, its degree is increased by 1 • If the distance between u and an OutPoint is not less than r, its degree is increased by 1
Localization in the Real Environment Arrival position Out of range In range
Performance Evaluation • 300 nodes • 500 m x 500 m • Transmission range r:30~50 m • Beacon interval s:1~9 m
Comparisons of the Three Movement Patterns SSL DSL Random
Detailed Estimate ErrorInformation s=0.3 m s=0.6 m
Conclusions • The authors present a distributed range-free localization method • use only one moving beacon • feasible and accurate • The basic idea is to narrow down the possible location of a node • use the arrival and departure constraint • SSL pattern • DSL pattern • Random movement pattern