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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
17-10-07 Sadaf Tanvir-INPG 2007 2
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
17-10-07 Sadaf Tanvir-INPG 2007 3
Contents
Introduction
Preliminary WorkLocalization using:
Beacon approach
Beaconless approach
Conceived steps of future work
17-10-07 Sadaf Tanvir-INPG 2007 4
IntroductionTypes of localization processes:
Intrinsic
Extrinsic
-Endogenous process
-Exogenous process
Coordinate systemAbsolute Relative
17-10-07 Sadaf Tanvir-INPG 2007 5
Related work
Localization approaches:
Exogenous systemsActive badge Active batRADAR
Endogenous systemsCricketGPS based.
GPS less
17-10-07 Sadaf Tanvir-INPG 2007 6
Anchor Nodes
Unlocalized Nodes
Our focusGPS based localization process involving:
• Anchor/beacon nodes• Unlocalized/free/unknown/blindfolded nodes
17-10-07 Sadaf Tanvir-INPG 2007 7
The Process
1D Measurement
2-3D Local Process
Collaborative Process
MA
C
Position R
efinement
17-10-07 Sadaf Tanvir-INPG 2007 8
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
17-10-07 Sadaf Tanvir-INPG 2007 9
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
17-10-07 Sadaf Tanvir-INPG 2007 10
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
17-10-07 Sadaf Tanvir-INPG 2007 11
Collaborative Process
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
17-10-07 Sadaf Tanvir-INPG 2007 12
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
Collaborative Process
MA
CP
osition Refinem
ent
17-10-07 Sadaf Tanvir-INPG 2007 13
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
17-10-07 Sadaf Tanvir-INPG 2007 14
Energy Consumption
Major source of energy consumptionThe radio transceiver
1D measurement
2-3D local Process
Collaborative Process
MA
C
Position refinem
ent
17-10-07 Sadaf Tanvir-INPG 2007 15
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
17-10-07 Sadaf Tanvir-INPG 2007 16
Preliminary work
Understanding the localization phenomenon
Localization using: Beacon messages
Beaconless approach
17-10-07 Sadaf Tanvir-INPG 2007 17
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
17-10-07 Sadaf Tanvir-INPG 2007 18
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.
17-10-07 Sadaf Tanvir-INPG 2007 19
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
17-10-07 Sadaf Tanvir-INPG 2007 20
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
17-10-07 Sadaf Tanvir-INPG 2007 21
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
17-10-07 Sadaf Tanvir-INPG 2007 22
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
17-10-07 Sadaf Tanvir-INPG 2007 23
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)
17-10-07 Sadaf Tanvir-INPG 2007 24
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
17-10-07 Sadaf Tanvir-INPG 2007 25
Scope of Current Work
1D measurement
2-3D local Process
Collaborative Process
MA
C
Position R
efinement
Only analyses MAC level message exchange
17-10-07 Sadaf Tanvir-INPG 2007 26
Drawback of Current Approach
Information propagation over a large number of hops
Error accumulation and poor accuracy
17-10-07 Sadaf Tanvir-INPG 2007 27
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
Collaborative Process
MA
C
Position refinem
ent
17-10-07 Sadaf Tanvir-INPG 2007 28
Future workStep 2: Study and analyse the energy consumption
during collaborative process
1D measurement
2-3D local Process
Collaborative Process
MA
C
Position R
efinement
Through the use of
Robust least squares
17-10-07 Sadaf Tanvir-INPG 2007 29
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
17-10-07 Sadaf Tanvir-INPG 2007 30
Comments
Feed back
Questions
Critique
THANK YOU!