1. Spatio-Temporal WiFi Localization
Demetris Zeinalipour
Assistant Professor
Data Management Systems Laboratory
Department of Computer Science
University of Cyprus
University of Piraeus
Final Conference of MOVE COST Action IC903, Vienna, Austria, Sept 30-Oct 1, 2013

2. Motivation
People spend 80-90% of their time inside buildings, while 70% of cellular calls and 80% of data connections originate from indoors.
GPS has low availability indoors due to the blockage or attenuation of the satellite signals, alternative geolocation solutions are required.
Smartphones can nowadays localize off-the-shelf with onboard sensors and WiFi signal fingerprints (coined Hybrid Localization)
New Applications:
In-building Navigation (Malls, Airports, Museums, Schools, etc.)
Asset Tracking and Inventory Management (Hospitals, etc)
Elderly support for Ambient and Assisted Living (AAL)
Augmented Reality (Firefighters), Social Networking, etc.

3. Demo at ACM Mobisys'13, Taiwan
Related Work
Cywee / Airplace
Indoor Localization using proprietary infrastructure: Infrared, Bluetooth, Visual or Acoustic Analysis, RFID, Inertial Measurement Units, Ultra-Wide-Band, Wireless Sensor Network, Wireless LAN,
IMU+WifI (acceler., gyro, digital compass) MapMatching, Magnetic Data, pedometer
Smartphone Localization:
Demo at ACM Mobisys'13, Taiwan
Good
The Cywee/Airplace Positioning platform performs multi-dimensional (i.e., 3-axis accelerometer, gyroscope and digital compass) motion sensor fusion for calculating the user orientation in real-time and implements an in-house pedometer algorithm for pedestrian trajectory tracking.

4. RadioMap (Server Side)
The Server maintains a 2-D MATRIX[N][M] by recording the RSS values of M APs at N geo-locations (x,y)
For example, Radiomap MATRIX format:
AP1, AP2, .... APM => x1,y1
AP1, AP2, .... APM => x2,y2
AP1, AP2, .... APM => x3,y3
....
AP1, AP2, .... APM => xN,yN
typically constructed by centrally overlaying several RSS vectors.

5. RadioMap (Server-Side)
I can see these Reference Points, where am I?
Cellular
WiFi
(x,y)!
RadioMap Service
...
User u
Cellular

6. Anyplace Indoor Navigation
TU Wien Demo!
RadioMap (Client-site)

7. Temporal VectorMap (TVM)
Demo!
Bloom Filter (u's APs)
WiFi
WiFi
K=3 Positions
RadioMap (server-side)
...
User u
WiFi

8. TVM – Bloom Filters Bloom filters – basic idea:
allocate a vector of b bits, initially all set to 0
use h independent hash functions to hash every Access Point seen by a user to the vector.
To test whether an element is a member of a set:
compare the vector of the query to the RadioMap on the server.
AP1
AP1
AP2
AP2 b 1

9. TVM – Bloom Filters
The most significant feature of Bloom filters is that there is a clear tradeoff between b and the probability of a false positive
Given h optimal hash functions, b bits for the Bloom filter and the number M of elements we can calculate the amount of false positives produced by the Bloom filter:
False Positive Ratio:
Size of vector:

10. TVM Continuous

11. References Anyplace Website: http://anyplace.cs.ucy.ac.cy/
Privacy-Preserving Indoor Localization on Smartphones with Vectormap, Andreas Konstantinidis, Paschalis Mpeis, Demetrios Zeinalipour-Yazti and Yannis Theodoridis, in preparation.
"Demo: Indoor Geolocation on Multi-Sensor Smartphones", C.-L. Li, C. Laoudias, G. Larkou, Y.-K. Tsai, D. Zeinalipour-Yazti and C. G. Panayiotou, In ACM Mobisys '13, Taipei, Taiwan, 2013.
"The Airplace Indoor Positioning Platform for Android Smartphones", C. Laoudias, G. Constantinou, M. Constantinides, S. Nicolaou, D. Zeinalipour-Yazti, C. G. Panayiotou, In IEEE MDM'12, Bangalore, India, 2012 (Best Demo Award)
"Towards planet-scale localization on smartphones with a partial radiomap", A. Konstantinidis, G. Chatzimilioudis, C. Laoudias, S. Nicolaou and D. Zeinalipour-Yazti. In ACM HotPlanet'12, in conjunction with ACM MobiSys '12, ACM, Pages: 9--14, 2012.
"Demo: the airplace indoor positioning platform", C. Laoudias, G. Constantinou, M. Constantinides, S. Nicolaou, D. Zeinalipour-Yazti and C. G. Panayiotou, In ACM Mobisys'12, 2012

12. SmartLab: http://smartlab.cs.ucy.ac.cy/
Testbed Issues
SmartLab:
Static Androids
Mobile Androids
["Demo: a programming cloud of smartphones", A. Konstantinidis, C. Costa, G. Larkou, D. Zeinalipour-Yazti, In ACM Mobisys'12.
"Managing Smartphone Testbeds with SmartLab", G. Larkou, C. Costa, P. Andreou, A. Konstantinidis, D. Zeinalipour-Yazti , In USENIX LISA'13.

13. Testbed Issues

14. Spatio-Temporal WiFi Localization
Thanks!
Questions?
Demetris Zeinalipour
University of Piraeus
Final Conference of MOVE COST Action IC903, Vienna, Austria, Sept 30-Oct 1, 2013