Localization in Sensor Networking. John Quintero. Application-driven, data-centric sensor networks frequently require location information tied to sensor data: Wildlife Tracking Weather Monitoring Location-based Authentication. Applications. Triangulation
2D position requires three distance measurements.
3D position requires four distance measurements.Triangulation: Lateration
2D position requires two angle + one distance measurement.
3D position requires two angle + one length + one azimuth measurement.Triangulation: Angulation
Static: observations matched to features recorded in a database with corresponding locations.
Differential: examine differences between two successive scenes to calculate location.
Passive observation => better privacy, low power requirents.
Requires compiling a database of features: extensive infrastructure.Scene Analysis
Physical contact: pressure sensors, capacitance field detector. Smart Floor.
Monitoring access point = ‘in-range’ proximity. Active Badge.
Automatic ID Systems: RFID badges, UPC scanning, phone & computer logs. Location of scanner, badge, computer, phone, identifies location of object.Proximity
Absolute vs Relative reference frame.
Accuracy or granularity eg: within 1 meter.
Precision or repeatability eg: within 1 meter 75% of the time.Location Properties
Local sensor-based computation: better privacy, but higher computational, power, cost requirements.
Infrastructure-based computation: remove computational , power costs to the wired infrastructure. Allows smaller, cheaper sensors.
CostLocation System Properties
Cricket [Priyantha ]:Lateration using time of flight, ultrasonic with radio synchronization. Sensor-based computation; no centralized coordination. Four-foot accuracy.Research
Heterogeneous Sensor Network Systems
Use a combination of few high-powered beacon sensors broadcasting known location (GPS, etc) and many low-powered sensors to form a cooperative localization system.Research
Propagation circles (or triangles) allow calculating location as the center position of all received signals.
Each beacon broadcasts a packet with its location and a hop count, initialized to one.
The hop-count is incremented by each node as the packet is forwarded.
Each node maintains a table of minimum hop-count distances to each beacon.Ad-Hoc Positioning System
30 + 60
3 + 4
The beacon broadcasts the average distance per hop, which is forwarded to all nodes.
Individual nodes use the average distance per hop, along with the hop count to known beacons, to calculate their local position using lateration.Ad-Hoc Positioning System
Jeffrey Hightower, Gaetano Borriello, A Survey and Taxonomy of Location Systems for Ubiquitous Computing, IEEE Computer, Aug 2001.
N.B. Priyantha, A Chakraborty, H. Baladrishnan, The Cricket Location-Support System, in Proceedings of MOBICOM, ‘00, Aug 2000.
P.Bahl, V.N. Padmanabhan, RADAR: An In-Building RF-Based User Location and Tracking System, in Proceedings of IEEE INFOCOM ‘00, March 2000.
N. Bulusu, J. Heidemann, D. Estrin, GPS-less Low Cost Outdoor Localization for Very Small Devices, IEEE Personal Communications Magazine, Oct 2000.
Tian He, Chengdu Huang, Brian M. Blum, Range-Free Localization Schemes for Large-Scale Sensor Networks, MOBICOM 2003.References