The Cricket Location-Support System By: Min Chen 10/28/03

Goal User Privacy Decentralized administration Network heterogeneity Low cost Room-sized granularity

System Architecture Beacon: Disseminate the string of space information about a geographic space to listeners. Listener: Infer its current location from the set of beacons. Use combination of RF and ultrasound to provide a location-support service to users. Approach

Related Problem and Method Collision of RF transmissions from different beacons Randomization Wrong correlation of the RF data of one beacon with the ultrasonic signal of another System parameters Listener Inference Algorithms

use a relatively sluggish RF data transmission rate. System Parameters Selection

Interference Scenarios RF-A:US-RA Align the beacons RF-A:US-I Using RF signal with long range RF-A:US-RI Ensure less than 5 beacons within range of each other

Listener Inference Algorithm Majority Picks the beacon with highest frequency of occurrence MinMean Selects the beacon with the minimum mean value MinMode Compute the per-beacon statistical mode over the past n samples.

Implementation : Beacon Positioning and Configuration

Implementation : Ultrasound Deployment

Experiment: Boundary Performance

Experiment: Static Performance

Experiment: Static Performance (Cont)

Experiment: Mobile Performance

Comments Concerns when apply to sensor network 2D Constrain Power Consideration Calibration On the Transmitter. Kalman Filter for the Mobile Algorithm