Some Results on Some Results on Source Source Localization Localization Soura Dasgupta, U of Iowa Soura Dasgupta, U of Iowa With: Baris Fidan, Brian With: Baris Fidan, Brian Anderson, Shree Divya Chitte Anderson, Shree Divya Chitte and Zhi Ding and Zhi Ding
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Some Results on Source Localization Soura Dasgupta, U of Iowa With: Baris Fidan, Brian Anderson, Shree Divya Chitte and Zhi Ding.
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Some Results on Some Results on Source LocalizationSource Localization
Soura Dasgupta, U of IowaSoura Dasgupta, U of IowaWith: Baris Fidan, Brian Anderson, With: Baris Fidan, Brian Anderson,
Shree Divya Chitte and Zhi DingShree Divya Chitte and Zhi Ding
NICTA/ANU August 8, 2008
Outline
• Localization– What– Why– How
• Issues• Linear algorithm
– Conceptually simple– Poor performance
• Goal• New nonlinear algorithm
– Characterize conditions for convergence
• Estimating Distance from RSS
NICTA/ANU August 8, 2008
What is Localization?Source Localization:• Sensors with known position• Source at unknown location• Sensors must estimate source
location Sensor Localization:• Anchors with known position• Sensor at unknown location• Sensor must estimate its location Need some relative position
information
NICTA/ANU August 8, 2008
Why localize?
• To process a signal in a sensor network sensors must locate the signal source– Bioterrorism
• A sensor in a sensor network must know its own position for– Routing
– Rescue
– Target tracking
– Enhanced network coverage
NICTA/ANU August 8, 2008
Wireless Localization
• Emerging multibillion dollar market• E911• Mobile advertising• Asset tracking for advanced public safety• Fleet management: taxi, emergency vehicles• Location based access authority for network
security• Location specific billing
NICTA/ANU August 8, 2008
Some Existing Technology
• Manual configuration– Infeasible in large scale sensor networks
– Nodes move frequently
• GPS– LOS problems
– Expensive hardware and power
– Ineffective for indoor problems
NICTA/ANU August 8, 2008
What Information?
Bearing
Power level
TDOA
Distance
NICTA/ANU August 8, 2008
How to measure distance?Many methods
One example• Emit a signal• Wait for reflection to returnSecond example• Source emits a signal• Signal strength=A/dc
– A=signal strength at d=1– d=distance– c a constant– Received Signal Strength (RSS)
NICTA/ANU August 8, 2008
How to localize from distances?
• One distance– Circle
• Two distances– Flip ambiguity
• Three distances– Specified
– Unless collinear
• In 3-d– Need 4
– Noncoplanar
NICTA/ANU August 8, 2008
Outline
• Localization– What– Why– How
• Issues• Linear algorithm
– Conceptually simple– Poor performance
• Goal• New nonlinear algorithm
– Characterize conditions for convergence
• Estimating Distance from RSS
NICTA/ANU August 8, 2008
Issues
• Sensor/Anchor Placement• Fast efficient localization• Achieve large geographical coverage• Past work
– Distance from an anchor available if within range
– Place anchors in a way that sufficient number of distances available to each sensor
• Enough to have the right number of distances?• With Linear algorithms yes
– Linear algorithms have problems
NICTA/ANU August 8, 2008
Outline
• Localization– What– Why– How
• Issues
• Linear algorithm– Conceptually simple– Poor performance