1. smert: energy-efficient design of a multimedia messaging system for mobile devices lin zhongrice...
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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
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Multimedia MessagingMultimedia 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 CostEnergy Cost
Device power profile Communications
1600mW, GPRS System
370mW, Busy User interfaces
212mW, Display
Messaging service
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
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Our ApproachOur 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 SystemSMERT: 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/SMSSMERT 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-WatchCache-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 TechnologyWatch 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 RiceNew Development at Rice
2x8 character low-power LCD
Debugging board
Both software and hardware will be OPEN-SOURCE!
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Energy Efficiency BenefitEnergy 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)
# o
f p
ho
ne
SM
S a
cc
es
se
s
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 NotificationSMERT: 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 PrioritizationMessage 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 EvaluationBattery Evaluation
EOS =RBC
ECR * EWT
RBC: Remaining battery capacity
ECR: Energy consumption rate
EWT: Expected work time
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Battery-Aware PoliciesBattery-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 NotificationBattery-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 DelayCommunication 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)
To
tal
# o
f p
ho
ne-
wat
ch c
om
mu
nic
atio
ns
Fixed interval
Adaptive-MAX=20, STEP=1
Adaptive-MAX=40, STEP=1
Adaptive-MAX=40, STEP=2
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Design LessonsDesign 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 workConclusion 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 consumptionMeasuring power consumption
Hardware 0.1 ohm resistor in series inside battery 1 KHz sampling rate USB measurement device
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Thermal challengeThermal challenge
Every 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 SchemeAdaptive 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
sag
e ar
riva
l/P
ho
ne-
wat
ch c
om
mu
nic
atio
n
inte
rval
(m
inu
tes)
Alert arrivalAdaptive-MAX=20, STEP=1Adaptive-MAX=40, STEP=1Adaptive-MAX=40, STEP=2
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Related WorkRelated 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