mobisteer: using steerable beam directional antenna for vehicular network access samir r. das...
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![Page 1: MobiSteer: Using Steerable Beam Directional Antenna for Vehicular Network Access Samir R. Das Computer Science Department Stony Brook University Joint](https://reader030.vdocuments.net/reader030/viewer/2022032523/56649d7f5503460f94a62c52/html5/thumbnails/1.jpg)
MobiSteer: Using Steerable Beam Directional Antenna
for Vehicular Network Access
Samir R. DasComputer Science Department
Stony Brook University
Joint work with Vishnu Navda, Anand Prabhu Subramanian, Kannan Dhanasekaran, and Andreas Timm-Giel
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Vehicle to Roadside Communication
Problems:• Poor link quality: 80% delivery ratio. • Short connectivity duration: 13 sec avg. • High handoff cost: 1-2 sec.
• MIT CarTel Project [MobiCom06]
• WiFi client in car accessing WiFi APs in the neighborhood
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Use Steerable Beam Directional Antenna
Omni Directional Beam
High transmit and receive gain withdirectional antenna translate to better SNR
Beam steering
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Optimal Beam Steering and AP Selection
AP1
• Goal: Maximize overall throughput. • Both online and offline approaches possible.
AP2AP3
AP4
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Offline Approach: Cached Mode Operation
• Scan and collect tuples during idle mode.
<location, beam, channel, AP, SNR>
RF Signature Database
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Offline Approach: Cached Mode Operation
• Run optimal beam steering and AP selection algo during operational mode.
Route from navigation system
<beam, AP>at every point on route
RF Signature Database
<location, beam, channel, AP, SNR>
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Mobisteer Prototype
• Phocus Array Steerable Antenna system from Fidelity Comtech– 8 Beams - 45° beam
width/ 15dBi gain– Atheros 802.11b/g
radio– 250usec beam steering
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Controlled Outdoor Experiments
5m Segments
Mobisteer
Omni
Beam1
Nu
mb
er
of
pa
cke
ts a
t b
it-r
ate
s
Beam2
Beam3
Beam4
Beam5
Beam6
Beam7
Beam8
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Overall Performance Improvement
• Experiments with APs under our control– 2-4 times improvement in throughput.
• Experiments with neighborhood APs– More than 2 times increase in
connectivity duration. – +15dB gain in SNR.
[ACM MobiSys 2007 (best paper award)]
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Drive-by Localization of Neighborhood APs
• Challenge: Handling reflections. • Localization Error: 10-30m. Compare with
Place Lab (error 13-40m in spite of elaborate RF fingerprinting).
[Submitted for publication. Send email for a copy.]
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Conclusions
Directional antenna beam steering + moving vehicle = Potential for good performance + interesting applications.