2016 lecture3 mobile computing models

8/18/2019 2016 Lecture3 Mobile Computing Models

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Mobile and Pervasive Computing

CNT5517 - Section 1G92CIS4930 - Section 1376

Lecture 3

Mobile Computing Models

Dr. Sumi HelalComputer & Information Science & Engineering

Department

niversit! of "lorida# $ainesville# "L 3%''

(elal)cise.u*.edu

© 2016 Dr. Sumi Hell ! "o#ile n$ %er&'i&e Com(utin)


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+utline

• Client/Server Computing Model

• Mobile Computing Models

– Unaware Client/Server Model

– Client/Proxy/Server Model

– Thin Client/Server Model – Disonneted !peration

– Mobile "gents

– !pportunisti Computing Model

– #roadast Des$s

– Cloud%Mobile & Cyber 'oraging Models

• Cast Studies(

– Coda

– !dyssey


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)

*eview( Client/Server Computing

Request

Reply

Cache Coherency: - cache invalidation

- update propagation

clientcache

Client

Server

Client

State

TLI

RPC

Sockets

RESTful

Fixed Network

server

cache

TLI

RPC

Sockets

RESTful


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+

Client/Server Design

• Stateless/state,ull lient/server design

• Cahing and ahe invalidation

–server invalidates lient ahe and/or – lient re-uests server to validate its ahe.

– ,ile system ahing( writes 0 update propagation

• Connetionless/Connetion%oriented design

• 1nter,aes 2TCP/1P3 *PC3 *4ST,ul3 et.5• !ther issues( multi%threading & deadlo$s

*eview( Client/Server Computing


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6

'ixed 7etwor$ Client/Server

"ssumptions

• Client Connetivity – lient is always onneted with availability

omparable to the server8s. Server an always

invalidate the lient ahe• Server "vailability & *eliability

– server is highly available. *eliable i, stateless 2butstate in,o is exhanged in every C/S interation53 or

i, implements reovery proedures 2may re-uirelient availability5

• 7etwor$ *eliability – ,ast93 reliable93 #4* : ;


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A

The Unaware Client/Server Model

• 'ull lient on mobile host and ,ull server on,ixed networ$ 2SB1P/PPP C/S5

• Client and Server are not mobility%aware

• Client ahing does not wor$ as the lient anbe disonneted when the server invalidatesthe ahe

• 7ot reliable and o, unpreditable per,ormane

• Requires special cache invalidation algorithmsto enable caching despite long clientdisconnections


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The Client/Proxy/Server Model

• "dding mobility%awareness between the lient and theserver. Client and server are not mobility%aware.

• Proxy ,untions as a lient to the ,ixed networ$ server3

and as a mobility%aware server to the mobile lient• Proxy may be plaed in the mobile host 2Coda8s

enus53 or the ,ixed networ$3 or both 2Eeb4xpress5

• "ppliation%dependent

• Proxy embodies $nowledge o, limitations o, the lientand the wireless networ$ and the trans,ormations andadaptations neessary to ahieve good per,ormane.


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F

Thin Client/Server Model

• Thin lient ,its in resoure poor mobile devies

• *e-uires at least wea$ onnetion3 but

generates bounded ommuniation tra,,i• 4xamples( C1T*1G Ein'rame and 1C" thin

lientH 1n,oPad

Keyboard and mouse events

Display eventsServer

Thin

Client


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Send keystroke k ,(in Client

Manager

,(in Client

Server

2. Send Keystroke “k” to word

3. rab t!e window as a bitmap

". #ake t!e di$$erence btw. bitmaps

%. Compress & Send di$$erence to

client

'. #ype k

(. )ecompress di$$erence

*. +erlay t!e di$$erence

Compressed di$$erence

kk

Ho- does ,C /or01


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Eireless T/C Challenges

• "tive Components

• 1ntense 1nterations

• Total Disonnetion

;;


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T/C BoaliIation Jradient

MobileComputing

Connected

WeaklyConnected

Disconnected

LocalizationLocalization


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BoaliIation Spae

Applications Events

Data

Others

Mouse KB Voice

eplica !ragmentCache

"ocali#ations


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"tive Components

Display $or% seconds Display $or

% seconds


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Jeneral "pproah

• Detet reurring displays

• 4xtrat ative

omponents separately

• Client simulates ative

omponents loally

• Trans,er only non%

repeating parts o, the

sreen

Blinking Cursor

Animated GIFs


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Boop Detetion

Deterministi Boops

Server #u,,er

Client #u,,er

&

%

&

%

&

%%

&"oop o$ % states


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Boop Detetion7on%Deterministi Boops

Server #u,,er

Client #u,,er

&

%

'

%

&

'

%

&

(D)"oop o$ ' states

'

Display *mage +%

Display *mage +&

Display *mage +'


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State 4xplosion

• More than two ative omponents

– Di,,erent number o, states

– Di,,erent ,re-uenies

– Two K%state ative omponents annot be

aptured in ,our states

– Eith ) ative omponents3 a bu,,er o, 0;


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San Bine "lgorithm "$soy et al9

• Detet ative omponents on eah

bu,,ered image

• Pass san lines %0 4nlosing retangles

• ertial and horiIontal san lines an

produe extra ative omponents or big

enlosing retangles

C. 20so! and 2. Helal# +ptimi4ing ,(in Clients for /ireless 2ctive5media 2pplications# Proceedings of t(e ,(ird IEEE /or0s(op on

Mobile Computing S!stems and 2pplications 6/MCS27889# (eld inMontere C2 Dec :5; %888. df

http://www.icta.ufl.edu/projects/publications/wmcsa2000.pdfhttp://www.icta.ufl.edu/projects/publications/wmcsa2000.pdf


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Scan Lines


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Scan Lines


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Second Step Scan Lines


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"C 4xtration

• 'or eah ative omponent

– Searh bu,,er ,or the same enlosing

retangles

– Compare the bitmaps in the retangles todetet states

– Use bu,,er timing in,ormation to extrat timing

o, the ative omponent


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"tive Components

• )K3;KF3KF3;


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Leyboard BoaliIation

• BoaliIation begins only i, intense L#

ativity is deteted 2L# #litI3 *amamourthy et al5

• Then L# is ,ully loaliIed and periodiallysyned and re%assessed

• The L# #litI test involves – hoosing L#%#litI Eindow 2how muh o, typing needs

monitoring5 – the $ind o, $eys typed3 and

– the speed o, the typing

K6


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L#%#litI BoaliIation *e-uirements

• The loaliIation system should implement

as muh o, its ,untionality at the server

• Display o, loaliIed typing must resemble

the orresponding display when typing is

handled by server

• Subtle ,eatures should be provided to

reate user awareness o, any loaliIationta$ing plae


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Leyboard & Mouse BoaliIation

this is an *CA client getting ,etting

a bit $aster - thanks to KB Blit#"ocali#ation by .ivaamamourthy


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K

The Disonneted !peration Model

• pproac! /

– Provide ,ull lient and a thin version o, the server on themobile plat,orm. 1n addition3 needed data is repliatedinto the mobile plat,orm. Upon reonnetion3 updatedreplias are synhroniIed with the home server. Con,litresolution strategies are needed 2Coda01enus &+racle ite5

• pproac! /

– Provide a ,ull lient and a mobility agent that intereptsre-uests to the unreahable server3 emulates theserver3 bu,,ers the re-uests3 and transmit them uponreonnetion 2+racle Mobile gents5


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!pportunisti Computing Model

• "n ad%ho networ$ o, mobile devies is

,ormed3 eah devie o,,ers servies

• Some servies may be o, interest to

mobile users3 or other servies

• 1mpromptu servie omposition based on

opportunity rules and user interations

• Servie deomposition and tear down

)<

C. Lee# 2. Helal# . 2rslan# ?onar0@ 2 S!stemand Protocols for Device Independent# Peer5to5Peer Discover! andDeliver! of Mobile Services# t(e IEEE ,ransaction on S!stems# Man

and C!bernatics# =olume 33#


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);

#roadast Dis$s

• Push data dissemination virtual devie

• 1ndexing on air • Client ahing strategies and ahe

invalidation algorithms


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)K

Push/Pull Data Dissemination

upstreamdownstream

B!

• Pull data delivery( lients re-uest 2validate5 data bysending uplin$ msgs to server

• Push data delivery( servers push data 2and validationreports5 through a broadast hannel3to a ommunityo, lients


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))

#roadast Dis$s

"eriodic broadcast o# one or more dis$s using a broadcast channel

%ach dis$ can be bcast at di##erent speed

Dis$ speed can be changed based on client access pattern


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)+

inx inx

inxinx inx

inx

inx inx

inx inx

1ndexing on "ir

• Server dynamially ad@usts broadast hotspot

•Clients read the index3 enter into doIe mode3 andthen per,orm selective tuning – Query Time( time ta$en ,rom point a lient issues a -uery until

answer is reeived

– Listening Time( time spent by lient listening to the hannel.


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)6

Cahing in Mobile Client/Server(

Problems

• Cashing is ritial to many appliations suh as Eebbrowsing and ,ile and database systems

• Classial ahe invalidation tehni-ues do not wor$

e,,etively in the mobile environment beause o,( – lient disonnetion 2call-backs do not wor$5

– slow and limited up%lin$ bandwidth ,or lientinvalidation 2detection approach is ine,,iient5

– very limited salability ,or appliation servers with

a large number o, lients – limited ahing apaity due to lient memory and

power onsumption limitations


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)=

Cahing in Mobile Client/Server(

Solutions

• ariable granularity o, aheohereny 2Coda5

• #roadast dis$s based aheinvalidation

J , C


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)A

aried Jranularity o, Cahe

Cohereny in oda

• Server maintains version stamps ,or eah ob@etand its ontaining volume. Ehen an ob@et isupdated3 the server updates its version stamp

and that o, its ontaining volume.• 1n antiipation o, disonnetion3 lients ahe

volume version stamps

• Upon reonnetion3 lients present volume

version stamps to server ,or validation• 1, valid3 so is every ob@et ahed at the lient3

otherwise3 ahed ob@ets are invalidatedindividually


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)

#C Dis$ based Cahe 1nvalidationCahe 1nvalidation *eports

• Server bast invalidation report showing all items

updated within preeding w seonds

• Client onneted( invalidation is straight,orward

• Clients must invalidate their entire ahe i, their

disonnetion period exeeds w seonds.

id& tsid& tsid& tsid& tsid& ts

Broadcast periodTime !indow


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Cloud5Mobile & C!ber "oraging

Models

• Similar to t(in client but it is notBuite t(in.

• =irtuali4ed replica of t(e MobilePlatform 6or client9

• +utsourced computations performedon t(e cloud replica using cloud

resources onl! results are s!nced. ason "linn# C!ber "oraging@ >ridging Mobile and Cloud Computing#FPervasive and Mobile Computing S!nt(esis lectures. September %8'% 6pdf 92. 2bu0mail and 2. Helal# Energ! Management for Mobile Devicest(roug( Computation +utsourcing -it(in Pervasive Smart Spaces#F.

6pdf 9

http://www.morganclaypool.com/doi/pdf/10.2200/S00447ED1V01Y201209MPC010http://www.icta.ufl.edu/projects/publications/IEEE%20TOMC-abukmail%20paper.pdfhttp://www.icta.ufl.edu/projects/publications/IEEE%20TOMC-abukmail%20paper.pdfhttp://www.morganclaypool.com/doi/pdf/10.2200/S00447ED1V01Y201209MPC010


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Case Studies

+<


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+;

'ile System Proxy in oda

Disconnected oeration '(enus): hoarding& emulating& reintegrating

!eakly connected oeration: both ob*ect and volume call-bac$s

Isolation"#nly Transactions


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+K

1solation%!nly Transations

in oda

Isolation"#nly Transactions $ AC I D%& no #ailure atomicity guarantees+

,lso Durability is guaranteed only conditionally+


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Eeb Proxy in !eb"xpress

The !eb%press .ntercept /odel


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!dyssey

• !dyssey lient arhiteture

• !dyssey system omponents

• !dyssey appliations(

– ideo player

– Eeb browser


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+6

!dyssey Client "rhiteture

Cache /anager

(iceroy 0eneric Support

,". %tensions 'Kernel)

,pplications

!ardens Type-Speci#icSupport


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+=

Main 'eatures o, !dyssey

• "ppliation%aware adaptation approah

• !dyssey monitors system resoures andnoti,ies appliations o, relevant hanges

• "ppliations deide when and how to adapt3 tomaintain ertain level o, ,idelity

• Jeneral support ,or adaptation( #iceroy

• Type%spei,i support( !arden

• Cahing support


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+A

!dyssey System Components

• !dyssey !b@ets

• Client "P1 to allow appliations to(

– operate on !dyssey ob@ets

– express resoure needs 2expetations5

– be noti,ied when needed resoures are no

longer available – respond by hanging levels o, ,idelity


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!dyssey "P1

Request( in path, in resource_descriptor, out request_id)

Cancel(in request_id)

Resource_id

lower bound

upper bound

name of upcall handler

Tsop( in path, in opcode, in insize, in inbuf, in out outsize, out outbuf)

Handle( in request_id, in resource_id, in resource-level)

etwor! "andwidth b#tes$second

etwor! %atenc# microseconds

&is! cache 'pace ilob#tes

C* '+CCint

"atter# ower minutes

.one# cents

Resource Ne'otiation #erations

(eneric Resources in #dyssey

Resource Descritor Fileds

Tye"secific #erations

)call *andler


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+F

ideo Player in !dyssey


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6<

!eb Browser in 1dyssey


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!dyssey( Summary

,pplications 2ile system access& video playing& and !eb browsing+

,daptation ,pplication-aware adaptation with the systemsupport that provides resource monitoring& noti#ies

applications o# resource changes& and en#orces

resource allocation decisions+

/odel Classic client-server architecture+

/obile Data Distilled server data delivery based on the client

2eedbac$s+

2016 lecture3 mobile computing models

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