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Tian He @ Honeywell ACS Fellows Symposium Event-Driven Localization Techniques Tian He Department of Computer Science and Engineering University of Minnesota www.cs.umn.edu/~tianhe
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Tian He @ Honeywell ACS Fellows Symposium Motivation “ Location is everything” Interactive Gaming– WII (center meters) Location-aware services Location-aware Services (10 meters) Military Surveillance (meters)
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Tian He @ Honeywell ACS Fellows Symposium Existing Solutions Outdoor GPSPositioning with Wifi Hotspots Range-Based use absolute distance estimates or angle estimates Expensive, Precise Range-Free use only connectivity and proximity Cheap, Inaccurate
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Tian He @ Honeywell ACS Fellows Symposium The limitations of existing solutions The main issue: High Location Accuracy ≡ High Cost Current limitations: Sophisticated hardware: time-synch with satellites (GPS) Short Range, highly directional (ultrasound) Hefty price for a 1-time event Larger Form Factor (requires additional hardware) In-Situ Impact on the Accuracy.
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Tian He @ Honeywell ACS Fellows Symposium Event-Driven Localization A new localization paradigm for low-cost sensor nodes Achieving High Location Accuracy without High Cost Main idea Localize sensor nodes by externally disseminating controlled events
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Tian He @ Honeywell ACS Fellows Symposium Overview of the talk Event-Based Spotlight System [SenSys 05] Image-Based Passive Stardust System [SenSys 06] Sequence-based MSP System [SenSys 07]
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Tian He @ Honeywell ACS Fellows Symposium Spotlight @ 2005 Main Idea: Generate controlled events in the field according to known spatiotemporal (time/location) mapping. A node timestamps when it detects a controlled event Obtain spatial information (i.e., location) for a node
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Tian He @ Honeywell ACS Fellows Symposium Generates Events Timestamp Events Report Timestamps Compute Location Report Location Spotlight System Architecture Event Distribution Function: the core of SpotlightWe propose 3 Functions System Design (3)
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Tian He @ Honeywell ACS Fellows Symposium Event Distribution Functions: Point Scan Area Cover Line Scan 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 System Design (4)
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Tian He @ Honeywell ACS Fellows Symposium Spotlight System Spotlight Device: Projector Laptop Mica2 motes Short range (10-20m) Versatile, it generates: Point Scan Line Scan Area Cover Purpose: Investigate Capabilities System Implementation (1)
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Tian He @ Honeywell ACS Fellows Symposium Spotlight System Spotlight Device: Telescope Mount Diode Laser Laptop XSM motes Long range (>1000m) It generates: Point Scan Line Scan (recently) System Implementation (2)
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Tian He @ Honeywell ACS Fellows Symposium Highlight of Spotlight Performance Indoor accuracy is as low as 0.5 centimeter! Outdoor localization accuracy is about a few feet (over a range of football court). Require no cost at sensor node A 900$ spotlight device (amortizable )
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Tian He @ Honeywell ACS Fellows Symposium Star-Dust System @ 2006 Localization based on the Position of the light-Spot
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Tian He @ Honeywell ACS Fellows Symposium StarDust Design 0.01$ Corner-Cube Retroreflector Self-righting enclosure design Multiple color filtering Below 0.1$
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Tian He @ Honeywell ACS Fellows Symposium ID ? Concept of Operation ID ?
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Tian He @ Honeywell ACS Fellows Symposium A football stadium where we deploy 6 sensor nodes in a 3x2 grid. The distance between the lighting device and the sensor nodes is approximately 500ft. Without illuminationWith illumination How it works Deployment area
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Tian He @ Honeywell ACS Fellows Symposium Each pixel P is described by an RGB Value The light reflected back by CCR has highest intensity. Edge Detection is applied to identify the location of light spot DifferenceEdge Detection How it works
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Tian He @ Honeywell ACS Fellows Symposium Mapping: Positions ↔ Nodes It is necessary to associate spots with sensor IDs. Solution: apply Label relaxation algorithm on a set of different constraints Color constraints Connectivity constraints Spatial Deployment constraints Temporal constraints ID matching turns out to be a very difficult problem!
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Tian He @ Honeywell ACS Fellows Symposium Highlight of StarDust Performance Accuracy Error is mainly caused by the error in mapping. 5 feet error under 12 colors with 91% correctness in mapping Range The effective range is 1500 ~4500 ft, depending on clearness of the atmosphere Time Milliseconds with unique colors. Cost less than 0.01$ per node if buy in a large quantity
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Tian He @ Honeywell ACS Fellows Symposium MSP: Multi-Sequence Positioning @ 2007 The issue Event-driven localization (such as spotlight) needs externally disseminating precisely controlled events, which would be hard to realized The idea MSP: A new event driven solution that requires no precise control of event generation.
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Tian He @ Honeywell ACS Fellows Symposium MSP: Multi-Sequence Positioning
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Tian He @ Honeywell ACS Fellows Symposium Indoor Implementation Laser line dissemination over a 360-node sensor network testbed
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Tian He @ Honeywell ACS Fellows Symposium Outdoor Implementation Sound Wave Dissemination
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Tian He @ Honeywell ACS Fellows Symposium Highlight of MSP Performance Sub-foot accuracy indoor A few feet accuracy outdoor. Require no cost at sensor nodes Require no precise control at event dissemination devices Work with different event dissemination methods Laser Sound ….
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Tian He @ Honeywell ACS Fellows Symposium Comparison Chart Hardware Cost Ad HocRangePowerAccuracyFast Soft Cost Ideal +++++++ Spotlight ++++++/-- StarDust +++++/-++ MSP +++++/-++ Range Free +++/-+-+ UltraS -+--+++/- WiFi --+/---+ GPS -++-+++/- High Cost High accuracy ; Low cost Low Accuracy Even Driven Localization: Low cost and High Accuracy
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Tian He @ Honeywell ACS Fellows Symposium Conclusion Existing localization paradigms (range-free and range- based) suffer the conflict between cost and accuracy Event-Based Localization is a novel and effective paradigm which can achieve high accuracy and low cost simultaneously as shown in Spotlight [Sensys 2005], Stardust [SenSys 2006] and MSP [SenSys 2007]. High accurate, low cost localization without LOS requirement is yet an open problem to solve.
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Tian He @ Honeywell ACS Fellows Symposium http://mess.cs.umn.edu
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