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

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

3. 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

4. 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

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

6. 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

7. 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.

8. Implementation : Beacon Positioning and Configuration

9. Implementation : Ultrasound Deployment

10. Experiment: Boundary Performance

11. Experiment: Static Performance

12. Experiment: Static Performance (Cont)

13. Experiment: Mobile Performance

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