1. ENERGY EFFICIENT INDOOR LOCALIZATION IN WIRELESS SENSOR NETWORKS
Ph.D Student: Sadaf TANVIR
Co-Supervisor: Benoît PONSARD
Supervisor: Andrzej Duda
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Sadaf Tanvir-INPG 2007

2. Localization in WSNs To achieve Better interpretation of sensed data
Inventory monitoring
Environment/forest monitoring
Smart battlefield
To achieve
Better interpretation of sensed data
Quality of network coverage
Geographic Routing
Target movement Monitoring
Machine survillance
Smart hospital
Capability of WSNs to self organize
Soil moisture monitoring system at Camalie Vineyards California
Courtesy:
Sadaf Tanvir-INPG 2007

3. Contents Introduction Preliminary Work Conceived steps of future work
Localization using:
Beacon approach
Beaconless approach
Conceived steps of future work
Sadaf Tanvir-INPG 2007

4. Introduction Types of localization processes: Intrinsic Extrinsic
-Endogenous process
-Exogenous process
Extrinsic more approapriate for WSN
Coordinate system
Absolute
Relative
Sadaf Tanvir-INPG 2007

5. Related work Localization approaches: Exogenous systems
Active badge
Active bat
RADAR
Endogenous systems
Cricket
GPS based.
GPS less
GPS-less: Netwide wide coherence(Relative coordinate system)
GPS-based: A percentage of networks nodes know their position: Anchor nodes (Absolute coordinate system)
Sadaf Tanvir-INPG 2007

6. Our focus GPS based localization process involving:
Anchor/beacon nodes
Unlocalized/free/unknown/blindfolded nodes
Unlocalized Nodes
Anchor Nodes
Sadaf Tanvir-INPG 2007

7. Collaborative Process
The Process
1D Measurement
Position Refinement
MAC
2-3D Local Process
Collaborative Process
Sadaf Tanvir-INPG 2007

8. 1D Measurement Range free method Range based method
2 Techniques of Distance Measurement:
Range free method
For achieving coarse grained accuracy
3 methods of distance estimation
Sum-Dist
DV-hop
Euclidean
Range based method
For fine grained accuracy
TOA/TOF
TDOA
RSSI
AOA
Sadaf Tanvir-INPG 2007

9. Ranging Implementation
Ultrasound
Radio frequency
Many 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
(infrared,Laser, Bluetooth, ,RFID)
Nonradio frquency Communication
Optical medium
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/proximity
DV-hop
Amporphous Positioning
Approximate Point in Triangulation
If range based 1D techniques are used
Trilateration
Maximum Likelihood/Minimum Least Squares
Many others
Taxonomy of techniques available for position estimation from 1D distance measurement
Sadaf Tanvir-INPG 2007

11. Collaborative Process
Iterative propagation of information across the network through collaboration of neighboring nodes
Enables each unlocalized node of the network to calculate its position 5 1 4 3 6 2
Sadaf Tanvir-INPG 2007

12. Collaborative Process
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
MAC
Position Refinement
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
Sadaf Tanvir-INPG 2007

14. Collaborative Process
Energy Consumption
Major source of energy consumption
The radio transceiver
1D measurement
Position refinement
MAC
2-3D local Process
Collaborative Process
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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
Sadaf Tanvir-INPG 2007

16. Preliminary work Understanding the localization phenomenon
Localization using:
Beacon messages
Beaconless approach
Sadaf Tanvir-INPG 2007

17. Beacon Approach(1/2) based on the work of L. De Nardis and M. -G
Beacon Approach(1/2) based on the work of L. De Nardis and M.-G. Di Benedetto
UN gathers BMs from the three ANs
BM from AN1
BM from AN2
BM from AN3
AN1
AN2
AN3 UN
AN: Anchor node
UN: Unlocalized node
ANs receive Query message and reply with a unicast response message (RM)
ANs broadcast beacon messages(BM)
UN Broadcasts Query message(QM)
UN estimates 1D distance between itself and the anchor nodes
Sadaf Tanvir-INPG 2007

18. Beacon Approach(2/2) The UN only broadcasts QM when there is
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.
Sadaf Tanvir-INPG 2007

19. Simulation Results
Energy consumption measured as the no. of messages exchanged
Node degree(η) =14
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20. Beaconless Approach(1/2)
AN3 UN
AN: Anchor node
UN: Unlocalized node
AN2
UN starts the process by broadcasting Query message(QM)
AN1
ANs receive Query message and reply with a unicast response message (RM)
UN estimates 1D distance between itself and the anchor nodes
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
Sadaf Tanvir-INPG 2007

22. Simulation Results
Node degree(η) =14
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23. Comparison of Beacon vs. Beaconless approach
Convergence Latency
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24. Tx/Rx messages
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25. Scope of Current Work Only analyses MAC level message exchange
1D measurement
Position Refinement
MAC
2-3D local Process
Collaborative Process
Sadaf Tanvir-INPG 2007

26. Drawback of Current Approach
Information propagation over a large number of hops
Error accumulation and poor accuracy
Sadaf Tanvir-INPG 2007

27. Collaborative Process
Future work
Step 1:
Study AN placement in the network
Its effect on:
Accuracy of location estimation
Communication cost
Convergence latency
1D measurement
2-3D local Process
Collaborative Process
MAC
Position refinement
Sadaf Tanvir-INPG 2007

28. Future work
Step 2:
Study and analyse the energy consumption during collaborative process
1D measurement
Position Refinement
MAC
Through the use of Robust least squares
2-3D local Process
Collaborative Process
Sadaf Tanvir-INPG 2007

29. Future work
Study 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
To evaluate the accuracy vs. Energy trade-off
Sadaf Tanvir-INPG 2007

30. THANK YOU! Questions Comments Feed back Critique 17-10-07
Sadaf Tanvir-INPG 2007