1

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

3

?3

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

1

2

1 Compelling media sources

2 Relevant pieces constructed

3 Rich content imposes more challenges on power usage

text, images, audio, and video

4

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

5

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

6

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

7

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

8

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

9

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

10

New Development at Rice

2x8 character low-power LCD

Debugging board

Both software and hardware will be OPEN-SOURCE!

11

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

12

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

13

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…

14

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

15

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

16

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

10

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

17

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

18

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

19

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)

20

Measuring power consumption Hardware

0.1 ohm resistor in series inside battery 1 KHz sampling rate USB measurement device

21

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

22

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

23

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