WIRELESS SENSOR NETWORK 1 ASIS KUMAR TRIPATHY Department of Information Technology

2 Module-II Localization

3 Overview Localization: To determine the location of objects. This is measured as a tuple of,Where S:Spatial Location f the measurement T:Time of the measurement M:Measurement value Location Information is necessary/useful for many functions: – Location stamps – Quality of coverage – Load balancing – Tracking and locating objects – Cluster formation – Efficient Addressing – Efficient Querying and Routing

4 Localization Issues What to localize?: Unknown node Vs. Reference Node – Mobile Vs. Static nodes – Node localization Vs. Network Localization – Cooperative Vs. Non-cooperative nodes When to localize? – Static Vs. Dynamic How well to localize? – Coarse grained Vs. Fine Grained Where to localize? – Central server (Location Tracking) Vs. Localizing Object (Location Support) How to localize? – What technology to use?: RF, IR, Ultrasound etc. – What methodology to use?

5 Node Localization Approaches Coarse-grained – Use minimal information – Use minimal computation power Fine-grained – Gather and use as much information as possible – Requires higher computation power Trade-off: – Accuracy Vs. Implementation/Computation/Cost

6 Coarse-Grained Node Localization Binary Proximity Centroid Geometric Constraints Approximate Point in Triangle (APIT) Identifying Codes (ID Codes) Several techniques provide approximate solutions for node localization based on the use of minimal information:

7 Coarse-Grained Node Localization Binary Proximity – Location of the closest reference node is the location of the unknown node. Centroid: – Center of gravity of reference nodes in the radio range of the unknown node.

8 Geometrics Constraints

9 Approximate Point In Triangle (APIT)

10 Identifying Codes (ID Codes)