A Measurement Study of
Vehicular Internet Access using
In Situ Wi-Fi Network
Vladimir Bychkovsky, Bret Hull, Allen
Miu, Hari Balakrishnan and Samuel
Madden
Presented By: Galileo Namata
Basic Problem
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Can a “grassroots” wireless Internet service,
provided by users who “open-up” their 802.11
(Wi-Fi) AP, be created for mobile clients?
Can such an unplanned network service
provide reasonable performance to clients at
vehicular speeds?
What is the expected performance for users
in automobiles as they move?
Motivation
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Cartel
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Cartel is a mobile sensor computing system
designed to collect, process, deliver and visualize
data from in car sensors
Reference:
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Bret Hull, Vladimir Bychkovskiy, Kevin Chen, Michel
Goraczko, Eugene Shih, Yang Zhang, Hari Balakrishnan,
Samuel Madden. CarTel: A Distributed Mobile Sensor
Computing System. In Proceedings of SenSys, 2006.
http://db.csail.mit.edu/pubs/fp02-hull.pdf
CarTel In A Nutshell
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Computer
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266 MHz with 128 MB of RAM and 1 GB of flash memory
Varied Sensors
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GPS Receiver, OBD-II Interface, Wi-Fi Interface, Digital
Camera
CarTel In A Nutshell
CarTel In A Nutshell
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Commute Time Analysis
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Traffic Hot Spot Heuristic
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Identify Traffic Areas automatically
Image Acquisition
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Researcher shortened his commute
Google Maps with Pictures
Wi-Fi Measurement
Automotive Diagnostics
CarTel Example
Communication
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CarTel data is set up to be automated
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Don’t need to be plugged in to get data
Want to be able to get current data
Use In Situ Wi-Fi Networks
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In Situ – Latin “in the place”
All data, sent through open networks
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Updates and queries to CarTel nodes
Data from sensors to main server
What’s the Performance?
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Experiment:
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Use CarTel system in and around Boston
Metropolitan Area and Seattle
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9 cars total, 290 “drive hours”
Measure Time For:
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Scan
Association
Address Configuration
Single End to End Ping
Connectivity and uploads
Network Activity Timeline
Geographic Coverage
IP Address Acquisition
Latency
Effects of Speed
AP Connectivity
Throughput
Related Work
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Ott and Kutscher – Controlled experiment
measuring network connection from fixed
test bed
Gass et al – Similar measurement but in
California desert
“War Driving Maps”
Wardriving
Discussion
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Open Wi-Fi Networks
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Don’t wanna get sued
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Don’t wanna get in trouble with ISP
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Fon System (http://en.fon.com)
Public Free Internet?
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“Safe Harbor” Laws
Google in SF
Don’t Wanna Get Hacked?
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Specialized, easy to manage hardware