Spatial Analysis of WiFi Networks

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Spatial Analysis of WiFi Networks
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Spatial Extent

• Greater Fremont
• Parts of Mountain View for comparison

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The Network

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

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The Network

• IEEE 802.11b/g
• 84.5Mc _at_ 2.4Gc 2.401Gc 2.495Gc
• c Hz
• Amateur Overlap
• 13cm band 2.310Gc 2.450Gc
• Why 2.4Gc?
• Unlicensed spectrum
• Potential Problems

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IEEE 802.11b/g Spectrum
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Municipal Networks
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Method Used

• Hardware
• Software
• Issues
• Ideas

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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

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Software

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

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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

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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

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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

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AP Types
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AP Manufacturers
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South Bay AP Density
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Fremont AP Density
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3D View Fremont APs
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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

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References

• Kismet http//kismetwireless.net
• GRASS GIS - http//grass.itc.it
• Dylan Beaudette - http//casoilresource.lawr.ucdav
  is.net
• Matt Perry - http//perrygeo.net/wordpress
• FCC - http//fcc.gov