CoolSpots Mobisys06 External

8/17/2019 CoolSpots Mobisys06 External

1/21

CoolSpots

Yuvraj Agarwal, CSE, UCSDTrevor Pering, Intel Research

Rajesh Gupta, CSE, UCSD

Roy Want, Intel Research


2/21

CoolSpots

Motivation: Wireless Power Is a Problem!

Power breakdown for a fully connected

mobile device in idle mode, with LCD

screen and backlight turned off.

Depending on the usage

model, the power

consumption of emerging

mobile devices can beeasily dominated by the

wireless interfaces!


3/21

CoolSpots

Many devices already have multiple wireless interfaces

• P!A"s #P h$%&& 'G(M)GPR(, *T, +&-../

• Mo0ile Phones 1 Motorola 23$& '*T, +&-.., G(M/

• 4aptops 'Wi15i, *T, G(M, /

Opportunity: Devices With Multiple Radios

These radios typically function as isolated

systems, but what if their operation was

coordinated to provide a unified network

connection?


4/21

CoolSpots

Properties o Common Radio Standards

Higher throughput radios have a lower energybit value

have a higher idle power consumption

…and they have different range characteristics!


5/21

CoolSpots

ow"power #ccess Within a Wi$i %ot"spot

Wi-Fi

HotSpot

Mobile Device

(e.g., cell-phone)

CoolSpots


6/21

CoolSpots

Your entire house

would be covered

by a WiFi HotSpot…

Your TV would be a

Bluetooth-enabled

CoolSpot!


7/21

CoolSpots

WiFi

Active

CoolSpots implement inter -technology power mngement

on top o! intra-technology techni"#es to reli$e better

power % per!ormnce thn ny single r&io technology.

WiFi

Active

WiFi

'SM

WiFi

Active

Active

WiFi

Active

Sni!!

Bluetooth Wi-Fi

CoolSpots

Inter&Intra 'echnolo(y Power Mana(ement

" #W $$% #W&' #W()& #W


8/21

CoolSpots

CoolSpots )etwor* #rchitecture

"nfrastructure

Computers

Cool#pot

$ccess Point

BT WiFi

BT WiFi %obile

Device

"P address on

&ackbone #ubnet

Low'power &luetooth link

(always maintained, when

possible)

'

%obile devicemonitors channel

and implements

switching policy

*i+i link isdynamically activated

based on switching

determination

*

$ccess point changes routing

table on switch- message

from mobile device

"

#witching is transparent

applications always use the "P

address of the local subnet.

(

&ackbone /etwork


9/21

CoolSpots

Switchin( Overview

Three main components contri0ute to the 0ehavior ofa multi1radio system6 where, what, and when

Position6 Where you are

• 3eed to address the difference in range 0etween *luetooth and Wi5i

+enchmar*s6 What you are doing

• Application traffic patterns greatly affect underlying policies

Policies6 When to switch interfaces

• A non1intrusive way to tell which interface to use


10/21

CoolSpots

Where: Position

*luetooth and Wi5i have verydifferent operating ranges7'appro8- .&m vs- .&&m/

• 9ptimal switching point willdepend on e8act operating

conditions, not just range• :8periments and 'effective/

policies will measure andta;e into account a varietyof operating conditions

Position 0

Position 1

&luetooth channel

capacity depends on

range, so the further

away you are, the

sooner you need to

switch

&ase

#tation

"n some situations,

&luetooth will not

be functional and

*i+i will be the

only alternative

Position 2


11/21

CoolSpots

What: +enchmar*s

Baseline: target underlying strengths

of wireless technologies

3 "dle connected, but no data transfer

3 4ransfer bulk 4CP data transfer

WWW: realistic combination of idle

and data transfer conditions

3 "dle think time-

3 #mall transfer basic web'pages

3 &ulk transfer documents or media

Video: range of streaming

bit'rates varying video 5uality

3 026k, 278k, 169k datarates

3 #treaming data, instant start


12/21

CoolSpots

When: Policies

The switching policy determines how the system will reactunder different operating conditions

bluetooth'fi:ed (using sniff mode)

wifi C$% (normali;ation baseline)

wifi'fi:ed (using P#%)

bandwidth'< cap'static'< cap'dynamic

k b p s = <

k b p s > <

k b p s >

<

t i m e

= ?

t i m e

= ?

k b p s > @

@ A k b p

s

Bse *i+i Channel

Bse &luetooth Channel


13/21

CoolSpots

,-perimental Setup

Multiple Policies> !ifferent locations

> (uite of 0enchmar; applications

?&&Mh= processor, $?M* RAM, 4inu8

> Allows detailed power measurement


14/21

CoolSpots

Switchin( ,-ample: MP,./ streamin(

Switch +

Wi-Fi -, BT

Bluetooth

*i'+i' #imple bandwidth policy

' #witch from *i+i to &4 when

application has buffered enough data

Demonstrates how

switching is

transparent to

unmodified

applications!


15/21

CoolSpots

Results Overview (Intermediate Location)

3 blue-fixed does well in ter#s o ener.y but at the cost o increased latency

3 cap-dynamic does well in ter#s o both ener.y and increased latency


16/21

CoolSpots

Impact o Ran(e&Distance

/issin. data indicates ailure o at least one application0

and thereore an ineective policy!


17/21

CoolSpots

Results across various benchmar*s

wifi-fixed consu#es lowest ener.y or data transer0 any bluetooth policy or idle

1verall0 cap-dynamic does well ta2in. into account ener.y and latency

Video bench#ar2s really hi.hli.ht proble#s with wifi-fixed and bandwidth-x


18/21


19/21


20/21

CoolSpots

Conclusions

• A dynamic system can leverage the different underlying radiocharacteristics to reduce communication energy while stillmaintaining good performance

• Advanced policies can adapt well to changing operating conditions

> Application 0ehavior

> Radio lin; Kuality

• :valuation of CoolSpots policies shows around a J&L reduction inenergy consumption over the present power management scheme in

Wi5i 'P(M/ across a range of situations


21/21

CoolSpots

'han* you!

5uestions6

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