Localization algorithms for wireless sensor networks M.Srbinovska, C.Gavrovski Ss.Cyril and...

Localization algorithms for wireless sensor networks

M.Srbinovska, C.GavrovskiSs.Cyril and Methodius University,

SkopjeFaculty of Electrical Engineering and IT-

Skopje, R. Macedonia

NIS, 2010 210/04/23

OUTLINE

Introduction Propagation models Measurement uncertainty for position

estimation Experimental results Conclusion

Projekt „ISSNBS“

DAADDeutscher Akademischer Austausch DienstGerman Academic Exchange Service

NIS, 2010 310/04/23

Introduction

Wireless sensor networks monitor large areas, monitoring the environment, air, water

and soil. GPS (global positioning system) does not

work indoors. Define the coordinates during the

instalation.



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Wireless channel model

Three propagation models are used: Free space propagation model

Two – Ray ground model

Log-distance model

Projekt „ISSNBS


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Received Signal Strength Indicator (RSSI)

RSSI – power of the signal at the receiver Direct path

n- path loss exponent



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Received Signal Strength Indicator (RSSI)

The RSSI can be used to characterize the channel status.

Friis’ free space transmission equation is:

10RSSI 10 n(log d) A RSSI dBm



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Multilateration

2n

21n

2n

21n

2n

21n

2n

21

2n

21

2n

21

1nn1nn

1n1n

yyxxd~

d~

yyxxd~

d~

y

x

yyxx

yyxx

2

iii dd~

Minimizing the mean square error:

BAxAA TT



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Measured vs. calculated RSSI with different n

-110

-100

-90

-80

-70

-60

-50

-40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

RSS

I (d

Bm

)

distance (m)

RSSI as a function of distance

n=1 n=2 n=2.25 n=3 n=4 measured

Measured vs. calculated RSSI with different n



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Root mean square error between theoretical and measured RSSI with different n

0

2

4

6

8

10

12

14

1 2 2.15 2.25 2.375 2.5 2.625 2.75 2.875 3 4

dB

m

n



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Received Signal Strength Indicator

Sensor node

• It works at the 2.4 GHz ISM Band.

• Each board features :

• Silicon laboratories C8051F121 microcontroller

• Chipcon CC2420 2.4 GHz 802.15.4 transceiver.

Position of sensor nodes

X3

X1X2

A4

A5A6



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Measurement uncertainty for position estimation

)x(ux

fu i

2n

1i iy

R

tf P

PCd

2P2

R

f

ft

R2p

R

f

ft

R2P

R

2P

td )u

P

C

CP

P

2

1()u

P

C

CP

P

2

1()u

P

d()u

P

d(u

RtRt

n

1i

2iX xx

1n

1

n

1

n

ss)x(u

)x,....,x,....,x,x(fy ni21



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Experimental results

Distance uncertainties of the sensor nodes

0

0.2

0.4

0.6

0.8

1

1.2

15.9 16.4 18.7 19 23.6 24.2 28.7 29.5

Loca

lizati

on e

rror

(m)

Distance (m)



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Conclusion

The relationship between RSSI and distance was determined through practical experiments.

Distance uncertainties of the sensor nodes through experimental measurements

were presented.

Wireless sensor networks are widely applicable to many practical

applications including environmental monitoring, military applicationsetc. in which sensors may need

to know their geographical locations

NIS, 2010 1410/04/23

Thank You for your attention!

Localization algorithms for wireless sensor networks M.Srbinovska, C.Gavrovski Ss.Cyril and...

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