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Spatial Analysis of WiFi Networks

Spatial Analysis of WiFi Networks. Spatial Extent. Greater Fremont Parts of Mountain View for comparison. The Network. Mostly made up of personal APs Restaurants, etc. offer free WiFi Municipal Networks. The Network. IEEE 802.11b/g 84.5Mc @ 2.4Gc :: 2.401Gc – 2.495Gc c = Hz

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Spatial Analysis of WiFi Networks

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  1. Spatial Analysis of WiFi Networks

  2. Spatial Extent • Greater Fremont • Parts of Mountain View for comparison

  3. The Network • Mostly made up of personal APs • Restaurants, etc. offer free WiFi • Municipal Networks

  4. The Network • IEEE 802.11b/g • 84.5Mc @ 2.4Gc :: 2.401Gc – 2.495Gc • c = Hz • Amateur Overlap • 13cm band :: 2.310Gc – 2.450Gc • Why 2.4Gc? • Unlicensed spectrum • Potential Problems

  5. IEEE 802.11b/g Spectrum

  6. Municipal Networks

  7. Method Used • Hardware • Software • Issues • Ideas

  8. Hardware • Laptop • Orinoco 802.11g/b cardbus /w antenna “patch” • Power inverter for extended logging periods • NMEA-0183 GPS + WAAS • WGS84 datum / Albert Equal Area projection • 1 pps

  9. Software • Commercial • NONE • Open Source • Kismet – WiFi probe • GPSd – GPS data logger Kismet reads from • GRASS GIS – Data analysis and visualization software • Python - Scripting

  10. Issues • Kismet generates bad data until a GPS lock is acquired • Some Windows drivers leak memory into the SSID, rendering them useless for naming • Assumes isotropic radiator given the bounds of GPS coordinates • GPS can “wander” • DGPS preferred

  11. Ideas • Use external gain antenna for improved reception • Must have card with antenna “patch” or willingness to destroy card • Must use high quality, extremely low loss coax with shortest runs possible • And/or mount AP in vehicle trunk and mount antenna directly above • Difficult, but can be done

  12. Interesting Facts • Number of AP Manufacturers: 17 • Number of APs: 3575 • Number of public APs: 44 :: 1.2% • Number of open APs: 1129 :: 32% • “Seven Words”: 3 • Number of amusing SSIDs: Not enough

  13. AP Types

  14. AP Manufacturers

  15. South Bay AP Density

  16. Fremont AP Density

  17. 3D View – Fremont APs

  18. What's Next? • Log more data • Trending • Time-series analysis • Better AP spatial approximation • Make more maps with reasonable resolution • Mount external gain omni antenna • Extrude AP range to 3D for visualization

  19. References • Kismet – http://kismetwireless.net • GRASS GIS - http://grass.itc.it • Dylan Beaudette - http://casoilresource.lawr.ucdavis.net • Matt Perry - http://perrygeo.net/wordpress • FCC - http://fcc.gov

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