1. Outline Location sensing techniques Location systems properties Existing systems overview WiFi localization techniques WPI precision personnel locator

2. Location sensing techniques 1. Triangulation Lateration Direct Time of flight Attenuation Angulation 2. Scene analysis 3. Proximity (ex. CC, RFID tags,…)

3. Location systems properties Physical Vs symbolic location Absolute Vs relative location Accuracy (mt) and precision (%) Localized Vs centralized computation Cost Scale (object located by certain amount of infrastructure) Limitations

4. LBS – Location Based Services GPS Satellite-based Wireless Network-based WiFi Inertial GSM Existing infrastructure Ad-hoc hw ultrasounds IR UWB

5. TechnologyTechniqueAccuracy/ Precision CostLimits GPSMicrowave time- of-flight lateration 5-15 mt (95- 99%) LowNot indoors or in densely built areas GSM (E911)Lateration or Angulation or Scene analysis 150-300 mt (95%) LowCell coverage Wi-Fi (RADAR, Ekahau PS) Triangulation/ Scene analysis 3-4 mt (50%) LowCalibration / fingerprinting cost Existing infrastructure

6. TechnologyTechniqueAccuracy/ Precision CostLimits IR (Active Badge) Proximity5-15 mt (95- 99%) HighSunlight interference, high base station cost Ultrasounds (Active Bat) Time-of-flight lateration 9 cm (95%) HighHigh base station cost MC-UWB (WPI PPL) Lateration0.5 mt (99%) HighRequires outdoor base units, high hw costs Inertial (WPI PPL) Local computation of location (Enhanced ?)LowFast drifting: enhancer for existing systems? Ad hoc infrastructure

7. WiFi RSSI lateration RSSI-based distance estimation from at least 3 base stations / access points Simple intersection computation Indoor problems Distance attenuation Penetration losses (walls, windows,...) Reflection and multipath  Complex propagation modeling

8. WiFi RSSI fingerprinting 1. Training phase: map of RSSI measured at reference points 2. Online phase: comparation of collected RSSI with the training data NN algorithms Probabilistic algorithms Neural networks  Training phase to be repeated if APs are moved  Slightly better accuracy than in the lateration approach

9. WiFi TOA lateration 1. Estimate TOA assuming clock synchronization 2. Calculate distance and then trilaterate  Needs additional hw for clock accuracy

10. WPI Precision Personnel Locator Locators 3 or more reference units (deployed outside the building) Base Station (trilateration algorithm)

11. WPI Precision Personnel Locator Multicarrier Ultra-wide band signal between locators and reference stations TDOA recovery from phase shift (at least 2 carriers required) Multicarrier = multipath immunity Low bandwidth consumption Improvement with inertial sensors?