Vehicular networks content distribution and data retrieval
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Vehicular Networks - Content distribution and data retrieval. Slides are integrated from researchers at UCLA. Outline. Urban Grid Car Torrent. Urban Grid “opportunistic” ad hoc networking. From Wireless to Wired network Via Multihop. Opportunistic piggy rides in the urban mesh.

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Vehicular networks content distribution and data retrieval

Vehicular Networks -Content distribution and data retrieval

Slides are integrated from researchers at UCLA


Outline

Outline

  • Urban Grid

  • Car Torrent


Urban grid opportunistic ad hoc networking

Urban Grid “opportunistic” ad hoc networking

From Wireless to

Wired network

Via Multihop


Opportunistic piggy rides in the urban mesh

Opportunistic piggy rides in the urban mesh

  • Pedestrian transmits a large file in blocks to passing cars, busses

  • The carriers deliver the blocks to the hot spot


Car to car communications for safe driving

Car to Car communications for Safe Driving

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 65 mphAcceleration: - 5m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 75 mphAcceleration: + 20m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Alert Status: None

Alert Status: None

Alert Status: Inattentive Driver on Right

Alert Status: Slowing vehicle ahead

Alert Status: Passing vehicle on left

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 45 mphAcceleration: - 20m/sec^2Coefficient of friction: .65Driver Attention: NoEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 75 mphAcceleration: + 10m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Alert Status: Passing Vehicle on left


Dsrc ieee 802 11p enabler of novel applications

DSRC*/IEEE 802.11p : Enabler of Novel Applications

  • Car-Car communications at 5.9Ghz

  • Derived from 802.11a

  • three types of channels: Vehicle-Vehicle service, a Vehicle-Gateway service and a control broadcast channel .

  • Ad hoc mode; and infrastructure mode

  • 802.11p: IEEE Task Group that intends to standardize DSRC for Car-Car communications

    * DSRC: Dedicated Short Range Communications


Dsrc channel characteristics

DSRC Channel Characteristics


Vehicular networks content distribution and data retrieval

Hot Spot

Hot Spot

Vehicular Grid as Opportunistic Ad Hoc Net


Vehicular networks content distribution and data retrieval

Power

Blackout

Power

Blackout

Hot Spot

Hot Spot

Vehicular Grid as Emergency Net


Vehicular networks content distribution and data retrieval

Power

Blackout

Power

Blackout

Vehicular Grid as Emergency Net


Cartorrent opportunistic ad hoc networking to download large multimedia files

CarTorrent : Opportunistic Ad Hoc networking to download large multimedia files

Published 2005


You are driving to vegas you hear of this new show on the radio video preview on the web 10mb

You are driving to VegasYou hear of this new show on the radioVideo preview on the web (10MB)


Highway infostation download

Highway Infostation download

Internet

file


Incentive for ad hoc networking

Incentive for “ad hoc networking”

Problems:

Stopping at gas station to download is a nuisance

Downloading from GPRS/3G too slow and quite expensive

Observation: many other drivers are interested in download sharing (like in the Internet)

Solution: Co-operative P2P Downloading via Car-Torrent


Cartorrent basic idea

CarTorrent: Basic Idea

Internet

Download a piece

Outside Range of Gateway

Transferring Piece of File from Gateway


Co operative download

Co-operative Download

Internet

Vehicle-Vehicle Communication

Exchanging Pieces of File Later


Bit torrent review

Bit Torrent review

  • Swarming: Parallel downloads among a mesh of cooperating peers

    • Scalable: System capacity increases with increase in number of peers

  • Tracker

    • Handles peer discovery

  • Centralized Tracker, single point of failure

  • Observation: Might not work for Wireless scenarios, because of intermittent connectivity

  • Issue: Mobility increases churn of nodes participating in a download


Bittorrent a picture

BitTorrent…. A picture..

Uploader/downloader

Uploader/downloader

Uploader/downloader

Tracker

Uploader/downloader

Uploader/downloader


Cartorrent gossip protocol

CarTorrent: Gossip protocol

A Gossip message containing Torrent ID, Chunk list

and Timestamp is “propagated” by each peer

Problem: how to select the peer for downloading


Peer selection strategies

Peer Selection Strategies

Possible selections:

  • 1) Rarest First:BitTorrent-like policy of searching for the rarest bitfield in your peerlist and downloading it

  • 2) Closest Rarest: download closest missing piece (break ties on rarity)

  • 3) Rarer vs Closer:weighs the rare pieces based on the distance to the closest peer who has that piece.


Experimental evaluation

Experimental Evaluation


Impact of selection strategy

Impact of Selection Strategy


Analytical model

n

√n

log n

Analytical Model


Why is the car torrent solution attractive

Why is the Car-Torrent solution attractive?

  • Bandwidth at the infostation is limited and “not convenient”

    • It can become congested if all vehicles stop

    • It is a nuisance as I must stop and waste time

  • GPRS and 3G bandwidth is also limited and expensive

  • The car to car bandwidth on the freeway is huge and practically unlimited!

  • Car to car radios already paid for by safe navigation requirement

  • CarTorrent transmissions are reliable - they involve only few hops (proximity routing)


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