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Effects of power conservation, wireless coverage
and cooperation on data dissemination among
mobile devices2001

• Authors Maria Papadopouli and Henning
  Schulzrinne
• Presented by
• Taylor Perkins

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About Me

• Taylor Perkins
• 5th Year Co-op Computer Science Major
• Specializations UI Databases
• From Roswell, GA
• Interests
• Anything new and interesting
• More high-level, less low-level

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Problem

• Increase in non-voice data
• News, traffic, weather, sports, etc.
• Sparse coverage or high cost
• Requires connectivity to the Internet
• Lots of Power Usage
• How to increase data access, but not increase
  power usage?

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Solution

• Share data between roaming users
• Motivation
• High spatial locality of info
• Different information providers
• Not necessarily cooperating with each other
• Imagine A Train or Airport
• High spatial locality News, sports, schedules
• Popular info Music Video games

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7DS P2P sharing system

• 7DS is an architecture, a set of protocols, and
  an implementation enabling the exchange of data
  among peers that are not necessarily connected to
  the Internet.
• Application
• Mobile Stationary Devices
• Anticipate information needs, searches among
  peers for this information.

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How it Works

• Two modes
• Prefetch
• Anticipate information needs
• On-demand
• Search among peers after fetch from Internet
  fails
• Two interaction types
• Peer-to-peer (P-P) 7DSs main focus
• Data sharing
• Message forwarding
• Caching popular information
• Server-Client (S-C) Servers also connected to
  other servers
• Data sharing
• Message forwarding
• Caching popular information

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More Details

• Device forms queries based on URL of request
• Also predicts future URLs
• Multicasts these queries to other devices
• Host can select subset of requests to listen to
  (Saves power)
• 7DS-enabled servers can broadcast that they have
  data (advertisement)
• 7DS organizes and manages device cache
• User can view, browse and manage cache through GUI

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How it Saves Power

• Trades power for data only when battery is above
  threshold.
• Reduce energy consumption
• Idle periods
• Low expectation of data
• Battery life below threshold
• Periodically turn off network interface
• Reduce collaboration (Thresholds)
• Above 75 Battery Active querying
• 50-75 Passive querying (only responds)
• Below 50 Stops participation in 7DS

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Some Results
Experiment Setup 1km x 1km test space. One
node has data, which all other nodes are
interested in getting.
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Some More Results
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And More Results
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Criticism

• 7 Years old
• More power, more bandwidth
• Requires other 7DS users
• Software install
• Cooperation
• Hard to Perform Experiments
• Requires simulation