vtube : towards the media rich city life with autonomous vehicular content distribution
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VTube : Towards the Media Rich City Life with Autonomous Vehicular Content Distribution. Tom H. Luan * , Lin X. Cai * , Jiming Chen § , Xuemin (Sherman) Shen * , and Fan Bai † * University of Waterloo, ON, Canada § Zhejiang University, China † General Motors Corporation, MI, USA. - PowerPoint PPT PresentationTRANSCRIPT
VTube: Towards the Media Rich City Life with Autonomous Vehicular Content Distribution
Tom H. Luan*, Lin X. Cai*, Jiming Chen§, Xuemin (Sherman) Shen*, and Fan Bai†
*University of Waterloo, ON, Canada§ Zhejiang University, China
†General Motors Corporation, MI, USA
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Roadmap: Motivation of the research Methodology – system model and algorithms Simulation Conclusion and Q&A
Goal and RoadmapGoal: To design a large-scale cost-
effective infrastructure-based content distribution network using
off-the-shelve technologies
VTube: Cost-effective Vehicular Content DistributionSECON’11
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The Dream: to download file contents for free at high speed Contents such as video clips (like using YouTube),
MP3s, HD images, flyers, magazines … The Reality, the bandwidth is
Expensive: Rogers: 50 CAD for 500MB; AT&T: 60 USD for 5GB
Unreliable: pure vehicle-to-vehicle (V2V) or ad hoc content distribution is unreliable and far to be practical
Can we achieve large-scale content distribution in the urban area with low-cost? Download everywhere in the city with no need to pay
VTube: Cost-effective Vehicular Content DistributionSECON’11
Motivation: Dream v.s. Reality
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Roadside Buffers (RSB) Low cost infrastructure
installed on the roadside: buffer storage (e.g., 20GB) + wireless interface
Store contents and distribute to subscribed users
Components of the System Vehicles
With caching storage and wireless interface
Download/upload contents from/to RSBs, and swap contents among each other
Transport contents cross the city
50 USD
30 USD
+
(e.g., flyers)(deployed by the store)
(deployed by the bus company to distribute bus schedules)
(interested in the contents)
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RSBs are bought and deployed by distributed entities like movie theatres, malls, hotels, schools, to distribute their
own information content, like movie trailers, room pictures in hotels
RSBs distributedly deployed cross the city forms VTube, an integrated infrastructure for content distribution
Why would stores like to buy RSBs? Because they are Cheap: Lump sum of 80 dollars on devises and no further fees
No extra charge on the bandwidth (not connected to Internet) No messy cabling works (simply mount RSBs high on a pole and configure
them using wireless communications) Profitable:
Upload contents, like advertisements, flyers, …, and distribute to users on the street for free
VTube: Cost-Effective ApproachShare costs to build
the content distribution
infrastructure
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Contents are published by distributed entities through the RSBs which
they have deployed transported by vehicles and spread in the city to vehicles
and RSBs at different locations A distributedly and additively built network
Entities deploy their own RSBs without any coordination with others
New RSBs work distributedly and can be additively incorporated into the existing system
Design Problem: How to enable RSBs to distributedly and selectively cache contents from vehicular networks to minimize the average download delay of contents?
VTube: Autonomous System
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Compared with femtocells and infostations [1, 2] no connections to the Internet focusing on content replications and buffer management with V2V
(vehicle-to-vehicle) and V2R (vehicle-to-RSB) communications built in a decentralized and additively manner by distributed
entities Compared with the V2V content distribution [3, 4]
RSB as the content injection points focusing on the design of RSBs and can be incorporated with the
V2V schemes proposed can also be used to distribute contents to PDAs, tablets, etc
Compared with the existing infrastructure-based vehicular content distribution network [5, 6] incorporate V2V communications in the content distribution propose a detailed and practical system architecture
Comparison with Related Works
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Design of VTube: Model RSBs: randomly deployed with
equal buffer to store L files at most : set of files published in the city : portion of vehicles that
subscribe to download file i : portion of vehicles have file i
stored in their buffer : probability that a RSU stores
file i in its buffer : average download delay of file
i is function of and
: buffer storage of RSB given
i
ixX
otherwise
cachedisifilexi ,0
,1
At any given time
Design at each RSB to minimize the overall delay of content dissemination
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Design of VTube: Assumptions A homogeneous network
Files have equal size RSBs are homogeneous with
equal buffer storage and follow the same policy to store files
Each RSB selects a file i to store with the probability
How to evaluate ? How to solve the optimization
problem How to design distributed
algorithm
Design at each RSB to minimize the overall delay of content dissemination
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Each file is of equal size and chopped into k pieces Randomly select a vehicle to examine the download
delay of file i (time to download all k pieces of file i) Model the file download of the vehicle by a 2D
Markov process with state (X(t), Y(t)) X(t): number of blocks downloaded Y(t): Y(t) = 1, if the vehicle is inside a RSB, and 0, otherwise
Model of Average Download Delay
Download rate of file i outside any RSBs
Download rate of file i inside a RSB
Rate to depart the coverage of an RSB
Rate to drive into the coverage of an RSB
AVERAGE DOWNLOAD
DELAY (MEAN FIRST PASSAGE
TIME)
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Using the Markov model, we can derive the expression of download delay represented by the file availability at vehicles and RSBs : portion of vehicles with file i stored in local
buffer : probability that a RSB store file i in its buffer
Apply this result, Chebyshev inequality and KKT to
we have an optimal solution of as
Centralized Content Distribution
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Select file i to store in RSBs with probability
Random walk based approach1) RSBs issue walkers to the vehicular networks2) Walkers are forwarded among files stored at
vehicles for TTL steps3) The files with stopped walkers are select to
be uploaded to RSBs
Decentralized Algorithm
( )
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Trace-driven Session level simulator coded in C++ 1000 vehicles randomly selected in the Shanghai taxi trace
within 24-hour period on Feb. 20th, 2010 200 RSBs are randomly deployed in a region of 50
30 km2
(download demand of file i) follows the Zipf-like distribution
Simulation Verification
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Average Download Delay
portion of vehicles subscribe to download file i
utilityaverage download delay of file i
• Global: store files based on b*
• Distributed algorithm: random walk based algorithm
• Local greedy: RSB always select the files with the largest di to download
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While wireless networking and various personal electronics (e.g., PDA, tablet, smartphones) have proliferated in the past decade, low-cost content distribution is still unavailable
A content distribution infrastructure is necessary Traditional cellular networks are expensive whereas the
pure ad hoc networks are unreliable and not practical so far
We propose to build distributed infrastructure with shared expenses
VTube: Roadside Buffers + vehicular networks Optimal content replication with central information Distributed content replication using the random walk
algorithm
Conclusions
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Q&A
VTube: Towards the Media Rich City Life with Autonomous Vehicular Content Distribution
Tom H. Luan*, Lin X. Cai*, Jimin Chen§, Xuemin (Sherman)
Shen*, and Fan Bai†*University of Waterloo, ON, Canada
§ Zhejiang University, China†General Motors Corporation, MI, USA