Energy-Aware Adaptation for Mobile Applications

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Energy-Aware Adaptation for Mobile Applications

• Aida Vosoughi
• Britt Antley

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Conserving Energy in Mobile Devices

• There has always been a desire to conserve energy
  in devices reliant on their battery
• First approaches dealt with purely hardware
  solutions
• Soon realized that this would not be enough
• OS needed to interact with hardware to achieve
  more efficient energy usage
• Needed to consider higher level approach and thus
  software solutions began to be explored

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Adaptive Disk Spin-Down

• Monitors the spin-down threshold and adjusts it
  to keep a balance between energy consumption and
  unacceptable spin-ups.

Wireless Communication Suspension

• Transport Layer Protocol (TLP) that conserves
  power by choosing short periods of time to
  suspend communications
• Collaboration between TLP and mobile host to
  enable queuing of data when communication is
  suspended
• Up to 83 communication power savings, resulting
  in overall savings of 6-9 in laptops and 40
  mobile device

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Energy-Aware Adaptation for Mobile Applications

• The idea is to modify the applications' behavior
  dynamically to conserve energy.
• According to the energy supply and demand a
  decision is made
• Use less energy if energy is scarce
• Use more energy otherwise (better user
  experience)
• OS is monitoring the energy and guide the
  applications to yield a battery-life of interest

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Odyssey

• Introduced in 1997 by B. D. Noble et al.
• A software platform which supports adaptation for
  a broad range of mobile applications.
• Integrated into Linux as a new file system, along
  with a set of API extensions.
• Monitors resources such as bandwidth, CPU cycles,
  battery power, etc makes tradeoffs
• Adaptation is achieved by trading of data quality
  for resource consumption.
• Fidelity the degree to which data presented at a
  client matches the reference copy at a server.
• Fidelity is type-specific
• Odyssey allows each application to specify the
  fidelity levels it supports.

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Odyssey Architecture

• Viceroy Responsible for monitoring the
  availability of resources and managing their use.
• Wardens Encapsulate type-specific functionality.
  There is one warden for each data type.

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1 J. Flinn and M. Satyanarayanan. Energy-aware
adaptation for mobile applications.
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PowerScope

• Introduced in 1999 by J. Flinn et al.
• A tool for profiling energy usage by
  applications.
• A sample energy profile

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2 J. Flinn and M. Satyanarayanan, "PowerScope
a tool for profiling the energy usage of mobile
applications
2
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Experiments

• Question Does lowering data fidelity lead to
  better energy savings?

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QuickTime Video 35 reduction through hardware
management, compression, and reduced window size
Speech Recognition 69-80 reduction mainly
through lower fidelity and turning off screen
network
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Map Viewer 46-70 reduction by hardware filtering
(most efficient by removing minor and secondary
roads) cropping
Web Browser 29-34 reduction by hardware fidelity
reduction
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Zoned Backlighting

• Selectively control lighting on parts of screen
• Break screen into multiple "zones" which can be
  lit or not based on need
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• Theoretical power savings of up to 50

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Goal-Directed Energy Adaptation
Determine the residual energy

• A mobile user has an estimate of how long a
  battery needs to last.
• Goals
• To ensure that Odyssey meets the specified time
  duration.
• To provide the best user experience possible.
• Two requirements
• Applications should offer as high a fidelity as
  possible at all times
• The user should not be jarred by frequent
  adaptations.

Predict future energy demand
Decide if applications should change fidelity
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OdysseyPredicting future energy demand

• Exponential smoothing function new (1-a)(this
  sample)(a)(old).
• History-based prediction Empirical approach to
  predict energy consumption of a specific
  application as a function of fidelity
• Application-specific logging/training randomly
  sample the fidelity space and recording energy
  consumption at each sample point
• Offline/Online learning using machine learning
  algorithms

• Simplest such predictor is linear. (E c0 c1S
  c2fS, where S is a constant e.g. size of image
  and f is fidelity)

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OdysseyTriggering Adaptation

• Predicted demand gt Residual energy Up-calls so
  that applications can adapt to reduce energy
  usage.
• Residual energy gt Predicted demand Applications
  are notified to increase data fidelity.
• Level of hysteresis in Odysseys adaptation
  strategy
• Bias toward stability when energy is plentiful
  and toward agility when it is scarce.
• Odyssey caps fidelity improvements at a maximum
  rate of once every 15 seconds.
• When multiple applications are executing
  concurrently, Odyssey must decide which to
  notify.

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Example of Goal-Directed Adaptation

• Application priorities
• Web browser
• Map viewer
• Video player
• Speech recognizer

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Modern Implementations

• Focus on uses in modern mobile OS

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Energy Management in Mobile Devices with the
Cinder Operating System

• Controlling energy allocation is crucial feature
  for mobile OS's
• Introduces abstraction of reserves and taps
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• Modification of HiStar OS running on ARM
  processor (Android G1)

• Used to achieve 3 properties of control
• Isolation
• Delegation
• Subdivision

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Power Guru Implementing Smart Energy Management
on the Android Platform

• Implement smart power management app on Android
• Monitor all apps and their power use
• Give user suggestion on which apps to kill to
  optimize battery life
• Apps are given Power Rating based on their CPU
  utilization and hardware usage
• User can Prioritize certain apps to not be killed
  and other apps are ranked based on Power Rating

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Context-aware Battery Management for Mobile Phones

• Battery meter/ battery low audio signals are
  not enough anymore
• CABMAN Problem Will the battery last until the
  next charging opportunity is encountered?
• Next charging opportunity? Call time
  requirements? Discharge speedup factor?

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Summary

• The main goal is to converse energy without
  affecting usability
• High level solutions are effective
• Fidelity adaptation
• Context-aware battery management
• Application energy allotment
• Giving user suggestions for power savings
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References
1 Jason Flinn and M. Satyanarayanan. 1999.
Energy-aware adaptation for mobile applications.
In Proceedings of the seventeenth ACM symposium
on Operating systems principles (SOSP '99). ACM,
New York, NY, USA, 48-63. 2 Flinn, J.
Satyanarayanan, M. , "PowerScope a tool for
profiling the energy usage of mobile
applications," Mobile Computing Systems and
Applications, 1999. Proceedings. WMCSA '99.
Second IEEE Workshop on , vol., no., pp.2-10,
25-26 Feb 1999 3 Kravets, Robin Krishnan, P.,
"Power Management Techniques for Mobile
Communication," MobiCom 1998. pp. 157-168. 4
Arjun Roy Stephen M. Rumble Ryan Stutsman
Philip Levis David Mazières Nickolai Zeldovich
"Energy Management in Mobile Devices with the
Cinder Operating System," EuroSys '11. April
10-13 2011. 5 Ravi, N. Scott, J. Lu Han
Iftode, L. , "Context-aware Battery Management
for Mobile Phones," Pervasive Computing and
Communications, 2008. PerCom 2008. Sixth Annual
IEEE International Conference on , vol., no.,
pp.224-233, 17-21 March 2008 6 D. Narayanan, J.
Flinn, and M. Satyanarayanan. 2000. Using history
to improve mobile application adaptation. In
Proceedings of the Third IEEE Workshop on Mobile
Computing Systems and Applications (WMCSA'00)
(WMCSA '00). IEEE Computer Society, Washington,
DC, USA 7 Brian Noble, M. Satyanarayanan, and
Morgan Price. 1995. A Programming Interface for
Application-Aware Adaptation in Mobile Computing.
In Proceedings of the 2nd Symposium on Mobile and
Location-Independent Computing (MLICS '95).
USENIX Association, Berkeley, CA, USA, 57-66. 8
Brian D. Noble, M. Satyanarayanan, Dushyanth
Narayanan, James Eric Tilton, Jason Flinn, and
Kevin R. Walker. 1997. "Agile application-aware
adaptation for mobility". SIGOPS Oper. Syst. Rev.
31, 5 (October 1997)  9  Unelsroed, Hans
Fredrik Roeine, Per Christian Ghani, Fahad.
"Power Guru Implementing Smart Power Management
on the Android Platform."