1 CSCE 5013: Hot Topics in Mobile and Pervasive Computing Nilanjan Banerjee Hot Topic in Mobile and Pervasive Computing University of Arkansas Fayetteville, AR

2 What is localization, aka location? absolute location (lat, long) relative location context location

3 Why should I care about localization? social application advertisements podcasting

4 What can I use to localize my phone? GPS Cell tower Wi-Fi Bluetooth RFID Sound Ambience

5 How does these technologies work (Centroid scheme) a b c Wi-Fi B.S #1 Wi-Fi B.S #2Wi-Fi B.S #3 You distance from BSs position of the BSs

6 Position of the BSs Find position of the APs and cell towers –Based on databases already available (Placelab Intel Research) –Cell phone companies know the position of their cell towers

7 Distance measures Received Signal Strength Indication (RSSI) –Correlation between RSSI and distance Time to propagation –Amount of time for signal to propagate from source to destination –Distance = time * speed of propagation

8 Alternate method purely based on profiling… Take extensive measurements of your environment War driving Similar to what Jonathan and Warner are doing Collect tuples,, ….> Scan and look for APs or cell towers Match with your measurements Compare with the signal strength and set of APs in the scan and your measurements Choose location which matches closely to the collected measurements

9 Relative positioning of individuals Bluetooth/Wi-Fi/sound/Infrared Placing people in a two dimensional plane Application to localization in ad hoc networks

10 Trade-offs between some of these schemes… Energy hungry Very accurate Works outdoors Energy hungry Moderately accurate Works outdoor and indoor No Energy cost Very inaccurate Works outdoor and indoor low energy accurate very short range

11 Challenges… High Accuracy of localization Energy-Efficiency Distance measure RSSI? Location Privacy

12 Papers we will cover under localization SurroundSense: Mobile Phone Localization via Ambience Fingerprinting BeepBeep: A High Accuracy Acoustic Ranging System using COTS Mobile Devices Sherlock: Automatically locating objects for human Ambient sources RFID Sound

13 Next class Reviews due for the following paper SurroundSense paper Review due by 11:59 p.m. tomorrow Extra class on iptables tomorrow in 239 from 3:30-4:30