Turducken: Hierarchical Power Management for Mobile Devices Jacob Sorber, Nilanjan Banerjee, Mark Corner, Sami Rollins University of Massachusetts, Amherst Presentation prepared by: Kip Coonley Paper appears in “Proceedings of the Third International Conference on Mobile Systems, Applications, and Services” (MobiSys 05), Seattle, WA, USA, June, 2005 Additional figures from

Key issue: Battery Lifetime vs. Mobility Scenarios and photos care of Nilanjan Banerjee Scenario 2Scenario 3 Key question: Which device to use? laptop phone Mote Scenario 1

40W 2W 0.04W Sensor PDA Laptop Simple computation and storage Download Web Pages Very complex computation Send/Recv Mail Tasks requiring large memory or storage space Power Needs Choosing the right device for the job

Wake-On-Wireless [Shih, et al] Low-power radio receives wakeup messages Requires in-network support Focus on when to wake up Possible Solutions (Related Work) WiFi Power Save Mode (PSM) Local Availability of data Staleness issue Battery technology Energy scavenging Wireless optimizations [Anand, et al], Disk Spindown [Helmbold, et al], Multiple radios [Pering, et al], Multiple processor cores [Mayo & Ranganathan] none provide orders-of-magnitude scaling of power

A New Approach: Turducken – 3 devices in 1 WiFi detector Mica2 Mote PDA Laptop Example: Mote checks for a network, PDA checks for mail server, Laptop remains asleep until user reads the mail

Integrate multiple independent platforms Pass control between tiers Suspend unneeded tiers The Idea: Hierarchical Power Management Reducible Power – Power that can be eliminated Reducible vs. Non-Reducible Power Non-reducible Power – Required for computation LCD Screen, Wireless power, Caching Power supply, On-board oscillators, Memory, I/O buses, Voltage & Current regulation

Time Synchronization Can be completely performed by the mote Lowest tier periodically synchronizes with remote time server Web Prefetching More complicated application which requires at least PDA Mote detects wireless networks PDA periodically fetches updates to frequently accessed pages Involves user interaction Both incoming and outgoing updates Laptop accesses mail via proxy on the PDA 3 Applications

Laptop Laptop+Mote Laptop+PDA+Mote 3 Configurations A Tiered Approach Note on Methodology: Time dilation used to extrapolate data

Power Draw Comparisons of Turducken Tiers Wakeup Interval vs. Lifetime for Integrated Turducken System Availability of Wireless Networks and its impact on the Turducken System 3 Experiments

LaptopLaptop+MoteFull Turducken Power-By-Tier

Wake Synchronization Time of Device Time Synchronization Mote is the right device for the job Laptop & PDA always suspended

Wake Synchronization Time of Device Web Caching 5MB storage = 15 websites cached For always-on operation, Turducken lasts up to 10 times longer Waking every 6 minutes, Turducken lasts 3 times longer

Wake Synchronization Time of Device Laptop wakes 2 min every hr, 4MB of mail stored Due to laptop user input, overall system lifetimes much less For waking every 6 minutes, Turducken lasts 1.5 times longer

Availability of Wireless Network (Web caching only, 12 minute wake interval preset) Probability of WiFi Lifetime (hours) With no network, mote prevents laptop from waking Turducken performs well over a variety of connectivity patterns

Conclusions & Thoughts Turducken extends laptop lifetime up to 10x (Always-on)! Where Turducken Wins - Laptop on > 17 min/hr Hierachical Power Management & Reducible vs. Non-Reducible Power Sleep/Wake power costs – this work averages Device portability/weight integration of tiers Device reliability with integration of tiers

Turducken: Hierarchical Power Management for Mobile Devices Jacob Sorber, Nilanjan Banerjee, Mark Corner, Sami Rollins Paper appears in “Proceedings of the Third International Conference on Mobile Systems, Applications, and Services” (MobiSys 05), Seattle, WA, USA, June, 2005

One more experiment: Reachability of Wireless Network (Web caching only, 12 minute wake interval preset, always available) Similar results to Availability of WiFi except… Mote cannot access WiFi -only detect it - PDA must work more