17-10-07 Sadaf Tanvir-INPG 20071 ENERGY EFFICIENT INDOOR LOCALIZATION IN WIRELESS SENSOR NETWORKS...

17-10-07 Sadaf Tanvir-INPG 2007 1

ENERGY EFFICIENT INDOOR LOCALIZATION IN

WIRELESS SENSOR NETWORKS

Ph.D Student: Sadaf TANVIR

Co-Supervisor: Benoît PONSARD

Supervisor: Andrzej Duda


Localization in WSNs

To achieve

Better interpretation of sensed dataQuality of network coverageGeographic RoutingTarget movement Monitoring

Environment/forest monitoring

Smart battlefield

Inventory monitoring

Smart hospital

Machine survillance

Courtesy: www.timedomain.com


Contents

Introduction

Preliminary WorkLocalization using:

Beacon approach

Beaconless approach

Conceived steps of future work


IntroductionTypes of localization processes:

Intrinsic

Extrinsic

-Endogenous process

-Exogenous process

Coordinate systemAbsolute Relative


Related work

Localization approaches:

Exogenous systemsActive badge Active batRADAR

Endogenous systemsCricketGPS based.

GPS less


Anchor Nodes

Unlocalized Nodes

Our focusGPS based localization process involving:

• Anchor/beacon nodes• Unlocalized/free/unknown/blindfolded nodes


The Process

1D Measurement

2-3D Local Process

Collaborative Process

MA

C

Position R

efinement


1D Measurement

2 Techniques of Distance Measurement:

Range free methodFor achieving coarse grained accuracy3 methods of distance estimation

– Sum-Dist– DV-hop– Euclidean

Range based methodFor fine grained accuracy

– TOA/TOF

– TDOA

– RSSI

– AOA


Ranging Implementation

UltrasoundRadio frequencyMany others

RF TOF -Provides long range

-Good wall penetration-No additional hardware required-Pair wise roundtrip TOF do not require clock synchronization-Ranging accuracy is reported to be between 1-3m(rms)-To pave way for Ultra wide band(UWB) systems


2-3D Local Process

Coversion of 1D distances in 2-3D coordinates

If range-free 1D techniques are used Centriod/proximityDV-hopAmporphous PositioningApproximate Point in Triangulation

If range based 1D techniques are usedTrilaterationMaximum Likelihood/Minimum Least SquaresMany others



Iterative propagation of information across the network through collaboration of neighboring nodesEnables each unlocalized node of the network to calculate its position

1

2

34

5

6


Position Refinement

Causes of errors in pair wise TOF

Interference, obstruction and multipath fading

Clock drift

Two kinds of errors

Ranging errors

Localization errors

1D Measurement

2-3D Local Process


MA

CP

osition Refinem

ent


Indoor Localization

Active Research Area

More difficult

GPS signals not available

Signals are affected by walls, furniture, people

Reflection, refraction, diffraction and scattering cause interference of RF signals


Energy Consumption

Major source of energy consumptionThe radio transceiver

1D measurement

2-3D local Process


MA

C

Position refinem

ent


Our Objectives

Design and evaluate indoor WSN localization techniques that are energy efficient

To evaluate the Accuracy vs. Energy Consumption trade-off of our suggested approaches


Preliminary work

Understanding the localization phenomenon

Localization using: Beacon messages

Beaconless approach


Beacon Approach(1/2)based on the work of L. De Nardis and M.-G. Di Benedetto

UN

AN: Anchor node

UN: Unlocalized node

AN1

AN2

AN3

ANs broadcast beacon messages(BM)

UN gathers BMs from the three ANs

BM from AN1BM from AN2BM from AN3

UN Broadcasts Query message(QM)

ANs receive Query message and reply

with a unicast response message

(RM)

UN estimates 1D distance between itself and the anchor nodes


Beacon Approach(2/2)

Pros

The UN only broadcasts QM when there is

surety of getting 1D measurement through 2 way ranging process

Addition of new nodes is easy

Cons

Constant emission of BM

RM emission by LN on its scheduled time

highly unsuitable for the 2 way ranging process.


Simulation Results

Energy consumption measured as the no. of messages exchangedNode degree(η) =14

B_Tx_msg_600_18_200_200

0

20

40

60

80

100

120

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tx

msg

s

B_convergence latency_600_18_200_200

050

100150200250300350400450

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tim

e(s)

B_Rx_msgs_600_18_200_200

0

10

20

30

40

50

60

70

0 18 36 54 72 90 108 126 144 162

Distance(m)

Rx

msg

s


Beaconless Approach(1/2)

UN

AN: Anchor node

UN: Unlocalized node

AN1

AN2

AN3

UN starts the process by broadcasting Query

message(QM)ANs receive Query message and reply

with a unicast response message

(RM)UN estimates 1D distance between itself and the anchor nodes


Beaconless Approach(2/2)

Pros

Energy not wasted in broadcasting Beacon messages

RM emission by LN: a reaction to the QM

making 1D measurement possible

Addition of new nodes is easy once the network has converged

Cons

Redundant QM emission from UNs far from the Anchor group


Simulation Results

BL_Convergence Latency_600_18_200_200

0

20

40

60

80

100

120

140

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tim

e(s)

BL_Tx_msgs_600_18_200_200

05

1015

2025

3035

40

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tx

msg

s

Node degree(η) =14

BL_Rx_msgs_600_18_200_200

0

10

20

30

40

50

0 18 36 54 72 90 108 126 144 162

Distance(m)

Rx

msg

s


Comparison of Beacon vs. Beaconless approach

Convergence Latency

B_convergence latency_600_18_200_200

050

100150200250300350400450

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tim

e(s)

BL_Convergence Latency_600_18_200_200

0

20

40

60

80

100

120

140

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tim

e(s)


Tx/Rx messages

B_Tx_msg_600_18_200_200

0

20

40

60

80

100

120

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tx

msg

s

BL_Tx_msgs_600_18_200_200

05

1015

2025

3035

40

0 18 36 54 72 90 108 126 144 162

Distance(m)

Tx

msg

s

B_Rx_msgs_600_18_200_200

0

10

20

30

40

50

60

70

0 18 36 54 72 90 108 126 144 162

Distance(m)

Rx

msg

s

BL_Rx_msgs_600_18_200_200

0

10

20

30

40

50

0 18 36 54 72 90 108 126 144 162

Distance(m)

Rx

msg

s


Scope of Current Work

1D measurement

2-3D local Process


MA

C

Position R

efinement

Only analyses MAC level message exchange


Drawback of Current Approach

Information propagation over a large number of hops

Error accumulation and poor accuracy


Future work Step 1: Study AN placement in the

networkIts effect on:

1. Accuracy of location estimation2. Communication cost3. Convergence latency

1D measurement

2-3D local Process


MA

C

Position refinem

ent


Future workStep 2: Study and analyse the energy consumption

during collaborative process

1D measurement

2-3D local Process


MA

C

Position R

efinement

Through the use of

Robust least squares


Future workStudy comunication cost, convergence latency and accuracy w.r.t AN placement in the network

Implement the RLS approach and evaluate it in terms of Accuracy achieved vs. Energy consumed

Evaluate our suggested approach on energy efficient MAC protocol designed for WSNs and realistic indoor propagation models

Direct my work towards application oriented localization e.g.

Localization for geographic routing


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THANK YOU!

17-10-07 Sadaf Tanvir-INPG 20071 ENERGY EFFICIENT INDOOR LOCALIZATION IN WIRELESS SENSOR NETWORKS...

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