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SMERT: Energy-Efficient Design of a Multimedia Messaging System for Mobile Devices
Lin Zhong Rice University
Bin Wei A&T Labs-ResearchMichael Sinclair Microsoft Research
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Multimedia Messaging
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
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1 Compelling media sources
2 Relevant pieces constructed
3 Rich content imposes more challenges on power usage
text, images, audio, and video
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Energy Cost
Device power profile Communications
1600mW, GPRS System
370mW, Busy User interfaces
212mW, Display
Messaging service
Message Text KFrames VideoSize 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
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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
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SMERT: A SMart alERT Messaging System
Notification
SMS
Fetching
Media-alerts of different qualities/formats
Web server
Mobile device
Watch
SMERT: A hierarchical multimedia messaging system for mobile users
MediaAlert messaging
system
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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
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Cache-Watch Cache-Watch
Caches messages from phone
Data cache Low-power secondary
interface to phone Interface cache
Cache-watch 1.0
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
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Watch with Invisible Technology Tech-heavy watches yet to prove wide social acceptance
Fossil Palm Watch SPOT/MSN-Direct Fossil
A watch with usual appearance but one line of digital text display
•Short text messages
•Caller IDs
Invisible text
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New Development at Rice
2x8 character low-power LCD
Debugging board
Both software and hardware will be OPEN-SOURCE!
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Energy Efficiency Benefit Phone outsources simple-yet-frequent interactive tasks to
Cache-Watch Display usage reductionenergy reduction
One reduction in phone text message accesses per two hour will justify Bluetooth connection
every 10 minutes
2.3
1.4
0.70.6
0.5
0
1
2
3
0.5 1 3 5 10
Phone-CacheWatch synchronization interval (minute)
# of
pho
ne S
MS
acce
sses
Equivalent # of 20-second phone SMS access per hour
Benefit increases if lower power wireless personal-
area technologies are used
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SMERT: Fetching and Notification
Fetching and Notification Prioritize messages Battery awareness (Evaluate battery)
Adaptive synchronization scheme
Notification
SMS
Fetching
Media-alerts of different qualities/formats
Web server
Mobile device
WatchMediaAlert Messaging
system
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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).
Message Prioritization
∑ C + E * ∑ I + F * ∑ Di i ii = 1 i = 1 i = 1
ml n
d *(l + m + n)DTS =
Critical (1-0)
Informative (5-0)Deferrable (10-0)
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…
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Energy Optimism Score (EOS)
Battery-aware policies need information from both angles. Priority score – the application perspective. Energy optimism score – the device perspective.
Battery Evaluation
EOS =RBC
ECR * EWT
RBC: Remaining battery capacity
ECR: Energy consumption rate
EWT: Expected work time
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Battery-Aware Policies
Notification policy
Fetching policy
User decision
Through phoneSend to wrist
Fetch
Default message notification
Delete
Decision sent back to phone
Phone-watch synchronization
schedule
Messages arrive as SMS
Message Gator on phone
Bluetooth
CacheWatch
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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
Fetching Factor (Y) = P * EOS -6
S
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P: priority score
EOS: energy-optimism score
S: the size of the smallest video format
Y<0, P*EOS <= 0.5: immediate
P*EOS >0.5: k-frames
0<Y<0.5: k-frames
Y>1.5: clip
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Communication Need w.r.t. Message Delay
0
100
200
300
400
500
600
700
800
900
1000
0 5 10 15 20 25 30 35
Average message delay (minutes)
Tota
l # o
f pho
ne-w
atch
com
mun
icat
ions
Fixed interval
Adaptive-MAX=20, STEP=1
Adaptive-MAX=40, STEP=1
Adaptive-MAX=40, STEP=2
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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
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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)
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Measuring power consumption Hardware
0.1 ohm resistor in series inside battery 1 KHz sampling rate USB measurement device
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Thermal challengeEvery One Watt increases surface
temperature by about 13 deg C
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
Simulation using FloTherm
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Adaptive Communication Scheme Dynamically adjust phone-watch communication intervals Traces
0.1
1
10
100
1000
0 500 1000 1500 2000 2500 3000 3500
Time (minutes)
Mes
sage
arr
ival
/Pho
ne-w
atch
com
mun
icat
ion
inte
rval
(min
utes
)
Alert arrivalAdaptive-MAX=20, STEP=1Adaptive-MAX=40, STEP=1Adaptive-MAX=40, STEP=2
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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