GPS-Free Node Localizationin Mobile Wireless Sensor Networks

H¨useyin Akcan1, Vassil Kriakov1,Herv´e Br¨onnimann1, Alex Delis2

1CIS Department Polytechnic University2Dept. of Informatics & Telecom. University of Athens

ACM MobiDE’06

Outline

Introductions Localization Algorithm Simulations Conclusion

Introduction

Wireless sensor networks are composed of hundreds sensor nodes.

Sensor nodes are capable of measuring various physical

values. are communicating with each other and

organizing themselves to achieve mission. find routing path by their relation between each

other.

Introduction

Many applications require sensor network mobility in environments.

Some place there are not deployed sensor. Ex.

The scene of a fire. Emergency incident.

Introduction Motivation

preserve network formation during directed mobility in mobile sensor networks.

Goals provide directional neighbor localization in a network wide coordinate system. work under fairly large motion and distance measurement errors. unaffect by the speed of nodes. work for any network size. support a stable network in mobility problems.

Introduction

Explore accident location

Introduction

Introduction Assumptions in this paper

Each mobile sensor node has a compass pointing North can measure the distance to their neighbors using (TOA). allows each node to move a specific distance in a specific

direction. has no additional positioning equipment or infrastructure is

required. Actuator, compass and distance measurements are

subject to errors caused by various real world disturbances.

Localization Algorithm

Core localization algorithm Verification algorithm Exceptional configurations

Localization Algorithm

d1

d2

d1

T=2

T=1

T=3

α2

V2v1

Localization Algorithm

Core localization algorithm

A

(X0 , Y0)

Bd1

A Bd2

α1

α2

V2v1

Localization Algorithm

A

(X0 , Y0)

Bd1

A Bd2

α1

(X1 , Y1)

Localization Algorithm

α2

V2v1

A

(X0 , Y0)

Bd1

A Bd2

α1

(X1 , Y1)

(X2 , Y2)

(X3 , Y3)

Localization Algorithm

Localization Algorithm

Localization Algorithm

CoreLocalization(n1, n2, v1,α1)

1: d1 inter-distance(n1, n2)

2: Move node n1 by v1 and α1

3: d2 inter-distance(n1, n2)

4: Retrieve v2 and α2 from n2

5: Calculate positions of n2 using equations (4),(5) and (6)

Localization Algorithm

α2

V2 v1

A

(X0 , Y0)

Bd1

AB d2

α1

(X1 , Y1)

(X2 , Y2)

(X3 , Y3)

Localization Algorithm

Two possible position

AB

AB A B

A B

Localization Algorithm Verification (NeighborList NL) 1: for each neighbor pair (m, n) in NL do 2: if m and n are neighbors then 3: dm,n measured inter-distance(m, n) 4: for each position pair {mi, nj | i, j = 1, 2} do 5: Compute Euclidean distance D between

mi and nj

6: if D = dm,n then 7: mark mi and nj as exact positions

Find dBC which are equal to d3.

Localization Algorithm

AB

AB A B

A B

CdBC

C

dBC

Localization Algorithm

Exceptional configurations If A=0 and B=0 then D=0

A

A

B

B

B

B

Localization Algorithm

Exceptional configurations If E2-DF<0 or G2-DH<0 Node skip this round and make necessary

adjustments.

Localization Algorithm

d1

d5

d2 d3

d4

T=1 T=2

V3

V2

V1

Simulations

Environment Compare with absolute position algorithm Sensor radio range 6 100 x 100 area 100 run

Each round random speed [0,5) random angle [0,2π)

Simulations

Simulations

Random movement

Simulations

Directed movement

Simulations

Directed trajectory of nodes performing

zig-zag movement.

Simulations

Absolute positioning algorithm

Simulations

Our localization algorithm

Conclusion

In this paper, they are the first GPS-free localization algorithm

work on mobile nodes. propose a straightforward and robust algorithm

that requires only a single round of node movement to localize all neighbor nodes.