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Spatial Analysis of WiFi Networks in Greater Fremont

Study of WiFi networks in Fremont and parts of Mountain View, comparing personal and municipal networks, issues with hardware/software, and ideas for improvement using IEEE 802.11b/g spectrum.

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Spatial Analysis of WiFi Networks in Greater Fremont

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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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