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SMERT: Energy-Efficient Design of a Multimedia Messaging System for Mobile Devices

SMERT: Energy-Efficient Design of a Multimedia Messaging System for Mobile Devices. Lin Zhong Rice University Bin Wei A&T Labs-Research Michael Sinclair Microsoft Research. Multimedia Messaging. 1. Compelling media sources. 1. 2. Relevant pieces constructed. 3.

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SMERT: Energy-Efficient Design of a Multimedia Messaging System for Mobile Devices

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  1. SMERT: Energy-Efficient Design of a Multimedia Messaging System for Mobile Devices Lin Zhong Rice University Bin WeiA&T Labs-Research Michael Sinclair Microsoft Research

  2. Multimedia Messaging 1 Compelling media sources 1 2 Relevant pieces constructed 3 Rich content imposes more challenges on power usage ? 3 2 Tuesday, May 28, 2006 8:31PM TeleComm(96 seconds) In carefully worded statement, BellSouth, AT&T, and now Verizon have challenged a report that said the companies gave tens of millions of consumers' phone records to the National Security Agency as part of the war on terrorism after 9/11. news program text, images, audio, and video

  3. Device power profile Communications 1600mW, GPRS System 370mW, Busy User interfaces 212mW, Display Messaging service Energy Cost Message Text KFrames Video Size 140 10K 696K Auto Dnld (J) ~0.03 ~1.2 ~80 Manu Dnld (J) ~0.08 ~1.7 ~114 Consum. cost (J) ~5 ~10 ~48 Our Goal: Optimizing multimedia messaging services,given the constraint of battery lifetime

  4. Our Approach • Reconstruct message content • Different levels • Selective and incremental, instead of all-or-none • Utilize low-power user interface device • A wrist-worn low-power user interface device • Limited content with control interface • Reduce user interruptions • Battery-aware message fetching • Automatic downloading without energy consumption on display

  5. MediaAlert messaging system Watch SMS Notification Fetching Media-alerts of different qualities/formats Web server Mobile device SMERT: A hierarchical multimedia messaging system for mobile users SMERT: A SMart alERT Messaging System

  6. SMERT SMS vs. MMS/SMS • 140 Bytes • Short description of the message • URL to richer content • Different from conventional MMS/SMS • SMS: short message + control information • MMS: more detailed content • The device can choose when to download the content with which wireless interface • MMS is limited to the use of cellular networks • Our device can choose to use Wi-Fi, which can consume 10 times less energy than GPRS in data transfer if available

  7. Cache-Watch • Cache-Watch • Caches messages from phone • Data cache • Low-power secondary interface to phone • Interface cache • 100 X 132 Dot Matrix LCD • Three series of touch sensors • 1: mode switching • 2 and 3: displayed content manipulation • Browse/delete/confirm cached information • Synchronized with the phone periodically Cache-watch 1.0

  8. Watch with Invisible Technology • Tech-heavy watches yet to prove wide social acceptance Invisible text Fossil Palm Watch SPOT/MSN-Direct Fossil • A watch with usual appearance but one line of digital text display • Short text messages • Caller IDs

  9. 2x8 character low-power LCD Debugging board Both software and hardware will be OPEN-SOURCE! New Development at Rice

  10. 3 Equivalent # of 20-second phone SMS access per hour 2.3 2 # of phone SMS accesses 1.4 1 0.7 0.6 0.5 0 0.5 1 3 5 10 Phone-CacheWatch synchronization interval (minute) Energy Efficiency Benefit • Phone outsources simple-yet-frequent interactive tasks to Cache-Watch • Display usage reductionenergy reduction One reduction in phone text message accesses per two hour will justify Bluetooth connection every 10 minutes Benefit increases if lower power wireless personal-area technologies are used

  11. MediaAlert Messaging system Watch SMS Notification Fetching Media-alerts of different qualities/formats Web server Mobile device SMERT: Fetching and Notification • Fetching and Notification • Prioritize messages • Battery awareness (Evaluate battery) • Adaptive synchronization scheme

  12. Message Prioritization • Priority is determined by match quality and quantity • Keywords are grouped in levels of different urgency • Matches are counted across groups; higher level dominates lower ones; more matches contribute more. • Delay-Tolerance Score (DTS) • Priority score is (1-DTS) which is between 1 (most urgent) and 0 (least urgent). Informative (5-0) Deferrable (10-0) Critical (1-0) l m n ∑ C + E * ∑ I + F * ∑ D i i i i = 1 i = 1 i = 1 DTS = d *(l + m + n) Critical: 1/10, 1/20, 1/30, 1/40, … Informative: 5/10, 9/20, 12/30, 14/40,… Deferrable: 10/10, 19/20, 27/30, 33/40…

  13. Battery Evaluation • Energy Optimism Score (EOS) • Battery-aware policies need information from both angles. • Priority score – the application perspective. • Energy optimism score – the device perspective. RBC EOS = ECR * EWT RBC: Remaining battery capacity ECR: Energy consumption rate EWT: Expected work time

  14. Battery-Aware Policies Messages arrive as SMS Phone-watch synchronization schedule Notification policy Through phone Send to wrist Fetching policy Bluetooth Decision sent back to phone User decision Fetch Delete CacheWatch Default message notification Message Gator on phone

  15. S 6 10 Battery-Aware Fetching and Notification • Notification policy depends on priority score and EOS. • Ignore low priority messages when EOS is low • Notify the user through the phone when priority is high • Automatic or user directed fetching • Tradeoffs among priority, EOS and message size, as Y<0, P*EOS <= 0.5: immediate P*EOS >0.5: k-frames 0<Y<0.5: k-frames Y>1.5: clip Fetching Factor (Y) = P * EOS - P: priority score EOS: energy-optimism score S: the size of the smallest video format

  16. Communication Need w.r.t. Message Delay 1000 900 800 Fixed interval 700 Adaptive-MAX=20, STEP=1 600 Adaptive-MAX=40, STEP=1 Total # of phone-watch communications 500 Adaptive-MAX=40, STEP=2 400 300 200 100 0 0 5 10 15 20 25 30 35 Average message delay (minutes)

  17. Design Lessons • Looking beyond the mobile device itself • Energy efficiency coupled with usability • Energy efficiency != less energy consumption • Maximize messaging services while achieving the targeted battery lifetime

  18. Conclusion and future work • SMERT: an energy-efficient multimedia messaging system • Targets: • Reduce communication requirement • Minimize interruptions to the user • Methods: • Device hierarchy • Information richness versus battery usage • Future work • User studies • Multiple wireless networks for higher energy efficiency (supported by SMERT)

  19. Measuring power consumption • Hardware • 0.1 ohm resistor in series inside battery • 1 KHz sampling rate • USB measurement device

  20. Thermal challenge Every One Watt increases surface temperature by about 13 deg C Simulation using FloTherm Phone case temperature will be 40 deg C higher for a three-watt SMT5600. Fuel cell batteries have <50% efficiency: one-watt heat for one-watt electricity

  21. Adaptive Communication Scheme • Dynamically adjust phone-watch communication intervals • Traces

  22. Related Work • Internet alerts • Google alerts, Yahoo alerts, etc. • Most of them rely on email • Balancing application quality and energy conservation • Keeping track of power demand, supply, and usage history • Computation offloaded from mobile devices to wall-powered computers • Standard messaging framework • IMS

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