Users and batteries interactions and adaptive power management in mobile systems
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Users and Batteries : Interactions and Adaptive Power Management in Mobile Systems Nilanjan Banerjee 1 , Ahmad Rahmati 2 , Mark Corner 1 , Sami Rollins 3 , Lin Zhong 2 1 University of Massachusetts, Amherst 2 Rice University 3 University of San Francisco

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Users and batteries interactions and adaptive power management in mobile systems l.jpg

Users and Batteries : Interactions and Adaptive Power Management in Mobile Systems

Nilanjan Banerjee1, Ahmad Rahmati2, Mark Corner1,

Sami Rollins3, Lin Zhong2

1University of Massachusetts,

Amherst

2 Rice University

3University of San Francisco

http://prisms.cs.umass.edu/llama


Scenario why did my laptop switch of l.jpg
Scenario: why did my laptop switch of ? Management in Mobile Systems

  • You are riding a bus to work and you are five minutes away

  • you are working on your laptop finishing a presentation

  • Suddenly your laptop turns of ! Grrr … !!!

  • your laptop battery was running low

  • You would have charged your laptop within 5 minutes anyway

  • you could have completed your presentation


Scenario working on an airplane l.jpg
Scenario : working on an airplane Management in Mobile Systems

  • You are working on your presentation on a flight to Austria

  • Midway through your flight your laptop turns of

  • your battery could only last for three hours

  • Wish your laptop adapted to your charging behavior !


Problem power management vs user l.jpg
Problem : power management Vs user Management in Mobile Systems

  • Power management for mobile systems are not user-centric

  • do not adapt to changing user behavior and device modalities

  • No understanding of how users use energy of their mobile device

  • assumption: users desire maximum lifetime out of batteries

User

Battery


Solution energy for the user l.jpg
Solution: energy for the user Management in Mobile Systems

energy management

user behavior

  • Understand user-battery interaction in mobile systems

  • when, why and where do users recharge

  • Built user-centric power management policy for mobile systems

  • policy which adapts to varying user-battery behavior


Outline l.jpg
Outline Management in Mobile Systems

  • User-study on laptops and mobile phone

  • research methods for user-study

  • Insights from the user study

  • when, where, and why do users recharge batteries

  • how predictable are recharge patterns

  • User-centric power management

  • design and implementation, and evaluation of Llama

  • Related work

  • Conclusions


Study of user battery interaction l.jpg
Study of user-battery interaction Management in Mobile Systems

  • Goal : examine where, when, and why people recharge

  • subjects recruited from friends, family, mailing lists

  • used three complimentary research methods

In-situ survey

Trace Collection

User Interviews

56 Laptops

15-150 days

10 Mobile phones

42-77 days

10 Laptops

10 Mobile phone

age 20-26 years

10 Laptop

415 response

10 Mobile phone

91 responses


Trace collection l.jpg
Trace collection Management in Mobile Systems

  • Goal : collect quantitative records of battery level

  • Laptop implementation is Java based

  • runs on Microsoft Windows and Apple OS X

  • records measurements periodically

  • uploads data automatically to a central server once a day

  • Mobile phone tool is written in C++

  • runs on Microsoft Windows Mobile

  • tool distributed pre-installed on T-Mobile MDA phones

  • aggressive : wakes the phone very minute to take reading


User interviews l.jpg
User interviews Management in Mobile Systems

  • Gather qualitative data regarding user-battery interaction

  • understand context of recharge

  • Provided sample scenarios to participants to think about

  • last time the user was faced with a low battery condition ?

  • what impact did it have on their future behavior ?

  • Questions about when, why, and where users recharge ?

  • Encouraged users to tell their stories and anecdotes


In situ pop up survey l.jpg
In-situ pop-up survey Management in Mobile Systems

  • Filtered out intervals of less than 5 minutes between recharges

Goal: In-situ information about why users recharge

Laptop

Mobile Phone

Disappears after a minute


Outline11 l.jpg
Outline Management in Mobile Systems

  • User-study on laptops and mobile phone

  • research methods for user-study

  • Insights from the user study

  • when, where, and why do users recharge batteries

  • how predictable are recharge patterns

  • User-centric power management

  • design and implementation, and evaluation of Llama

  • Related work

  • Conclusions


Users have energy to spare l.jpg
Users have energy to spare Management in Mobile Systems

Laptops

50% of the recharges occur when the battery is half full

Fraction of users use their laptops like desktops


Users have energy to spare13 l.jpg
Users have energy to spare Management in Mobile Systems

Mobile Phones

60% of the recharges occur when the battery is half full

Most recharges occur between 25-75 %


Recharges are context driven l.jpg
Recharges are context driven Management in Mobile Systems

Limited Opportunities Ahead

Limited Opportunities Ahead

System Reminder

System Reminder

Low Battery

Low Battery

Convenient location

Convenient Time

Convenient location

Convenient Time

Mobile Phones

Laptops

Fraction of recharges are driven by context

Low battery corresponded to 40% of the battery remaining


Variations across users and devices l.jpg
Variations across users and devices Management in Mobile Systems

Laptops

Mobile Phones

Variation in recharge pattern across mobile phones and laptops

Variation across recharge patterns across users


Summary of the user study l.jpg
Summary of the user-study Management in Mobile Systems

  • Recharges occur with significant energy remaining in batteries

  • Charging is mostly driven by context and battery levels

  • Users and devices show significant variation in battery usage

  • power management should adapt with users and devices

I usually charge in the office when the indicator shows 1 bar

I always recharge every night


User centric power management l.jpg
User-centric power management Management in Mobile Systems

  • Users charge their system with significant battery left

  • accurately predict excess energy left in the battery

  • proactively use the remaining energy to improve QoS

  • Optimization framework for power management

  • maximize the excess energy usable by applications

  • minimize the probability of running out of battery

  • try to avoid true low battery levels


Llama design and implementation l.jpg
Llama : design and implementation Management in Mobile Systems

  • Example Scenario

  • Confidence of not exceeding battery capacity = 0.95

  • Llama determines present battery percentage (Cp) = 30%

  • creates a histogram of recharges below Cp (H)

  • Llama calculates 95% of the time user recharges by 10%

  • devote 10% to Llama application


Llama applications and deployment l.jpg
Llama applications and deployment Management in Mobile Systems

Screen Brightness

excess energy to adjust screen brightness

Web prefetching

prefetching a random webpage

download interval determines aggressiveness

Health monitoring

reports preprogrammed data

upload interval determines aggressiveness


Llama deployment demographics l.jpg
Llama deployment demographics Management in Mobile Systems


Llama evaluation l.jpg
Llama evaluation Management in Mobile Systems

Laptops

Mobile Phones

Llama used energy depending on battery left at recharge

Beneficial use of Llama

more web data, and brighter display


Post llama recharge behavior l.jpg
Post-Llama recharge behavior Management in Mobile Systems


Feedback loop with user l.jpg
Feedback loop with user Management in Mobile Systems

Recharge cycle becomes shorter and shorter, frustrating the user

Plan to address the problem in future versions of Llama


Post llama user study l.jpg
Post-Llama user study Management in Mobile Systems

  • Interviews to evaluate negative effects of Llama

  • impact of Llama on battery lifetime

  • All mobile phone users but one showed similar satisfaction

  • “The battery lifetime was better last month, I have to recharge it every day now, but it used to be every day and a half”

Laptop user

Even though I didn’t notice it, I would definitely care in situations where I require maximum battery life

It must have been small, since I didn’t notice it


Future work l.jpg
Future work Management in Mobile Systems

  • Evaluate the positive effects of Llama

  • what are the user-perceived benefits of Llama ?

  • Improve the prediction algorithm of Llama

  • use contextual information such as location, work patterns

  • Experiment on different mobile devices like music players

  • less biased or demographically weighted subject selection


Related work l.jpg
Related work Management in Mobile Systems

  • MyExperience in-situ survey tool [Mobisys 2007]

  • tool for in-situ profiling and survey

  • Human factor in energy management

  • user-interface design on energy efficiency [Vallero et al.]

  • visual perception to reduce energy of LCDs [Chen et al.]

  • Tools for studying mobile users in natural settings

  • logging tool for studying HCI [Demumieux et al.]

  • Balance performance and system-wide energy consumption

  • Odyssey [Flinn et al.], Ecosystem [Zeng et al.]


Conclusions l.jpg
Conclusions Management in Mobile Systems

  • First glimpse of user-battery interaction

  • traces would be available through the traces.cs project

  • User study produced three key observations

  • users leave excess energy in the battery on recharge

  • charging behavior is driven by opportunity and context

  • significant variations across users and systems

  • Built an user-centric energy management system called Llama

  • it can scale energy usage to user behavior


Users and batteries interactions and adaptive power management in mobile systems28 l.jpg

Users and Batteries : Interactions and Adaptive Power Management in Mobile Systems

Nilanjan Banerjee1, Ahmad Rahmati2, Mark Corner1,

Sami Rollins3, Lin Zhong2

1University of Massachusetts,

Amherst

2 Rice University

3University of San Francisco

http://prisms.cs.umass.edu/llama


Hotmobile 2008 l.jpg
HotMobile 2008 Management in Mobile Systems

Napa, CA, February 25-26, 2008Submissions: October 16, 2007


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