Wilamowski B.M., Irwin J.D. The Industrial Electronics Handbook. Second Edition: Industrial Communication Systems

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4-2 Industrial Communication Systems

•. Wireless metropolitan area networks.are.a.type.of.network.that.connects.several.Wireless.LANs..

WiMAX.is.the.term.used.to.refer.to.WMAN.and.is.covered.in.IEEE.802.16d/802.16e.

•

. Wireless wide area networks.with.technologies.such.as.universal.mobile.telecommunication.system.

(UMTS.),.general.packet.radio.service.(GPRS),.and.global.system.for.mobile.communication.(GSM).

.further.increase.radio.coverage.for.clients.and.facilitate.ease.of.movement,.wireless.mesh.networks.

(WMN).are.used..WMNs.span.all.segments.and.are.a.completely.at.and.nonhierarchical.organization.

formed.to.cover.all.areas,.and.for.this.reason.it.is.outside.the.previous.classication..A.WMN.has.been.

dened.as.a.network.composed.of.mesh.routers.and.mesh.clients..Mesh.routers.have.minimal.mobility.

and.form.the.backbone.of.the.network,.and.the.mesh.clients.may.be.stationary.or.mobile,.and.can.form.

a.client.mesh.network.among.themselves.and.with.mesh.routers..In.this.scheme,.each.node.operates.not.

only.as.a.host.but.also.as.a.router,.forwarding.packets.on.behalf.of.other.nodes.that.may.not.be.within.

direct.wireless.transmission.range.of.their.destinations.[AWW05]..In.mesh.networks,.full.physical.layer.

connectivity.is.not.required;.a.mesh.network.employs.one.of.two.connection.arrangements,.full.mesh.

topology.or.partial.mesh.topology..As.long.as.a.node.is.connected.to.at.least.one.other.node.in.a.mesh.

network,.it.will.have.full.connectivity.to.the.entire.network.because.each.mesh.node.forwards.packets.

to.other.nodes.in.the.network.as.required.

 ere

.are.many.dierent.types.of.mesh.networks..Mesh.networks.can.be.wired.or.wireless..For.wire-

less

.networks,.there.are.ad.hoc.mobile.mesh.networks.or.wireless.sensor.networks,*.and.permanent.

infrastructure. mesh. networks.. Regarding. radio. transmission,. there. is. another. classication:. single.

radio.mesh.networks,.dual-radio.mesh.networks,.and.multi-radio.mesh.networks.

WMNs

.can.widely.nd.applications.in.WLANs,.WMANs,.WPANs,.and.wireless.sensor.networks.

(WSNs).. Major. industrial. organizations. are. actively. working. on. introducing. multi-hop. mesh. ele-

ments

.in.their.next.generation.standards..For.example,.IEEE.has.created.a.working.group.to.dene.

how.the.mesh.works.in.802.11.networks.(WLAN)..802.11s.[AESSM].networks.also.include.two.routing.

In.ad.hoc.networks.and.sensor.networks.every.node.functions.as.a.router.

WPAN

WiMax

tower

WLAN

WWANWMAN

(UMTS, GPRS, GSM)

FIGURE 4.1 Wireless.network.classication.(WPAN,.WLAN,.WMAN,.WWAN).

Routing in Wireless Networks 4-3

mechanisms,. through.an. Ad. hoc.On-Demand.Distance.Vector. (AODV).and. Optimized.Link-State.

Routing.Protocol.(OLSR).hybrid.solution.[MZKD04].. e.standard.802.16.(WMAN).supports.a.mesh.

form.of.working.[LMAN04],.although.it.is.not.compatible.with.the.standard.IEEE.802.16e.for.wireless.

metropolitan.networks.. e.IEEE.802.15.standard.denes.the.physical.layer.and.media.access.control.

(MAC).of.the.WPANs.and.the.working.group.IEEE.802.15.5.[TG5].is.studying.how.to.establish.a.mesh.

architecture.in.this.type.of.network..Figure.4.2.shows.how.the.four.types.of.wireless.networks.(WPAN,.

WLAN,.WMAN,.WWAN).and.the.WMNs.live.side.by.side..In.the.case.of.WMNs,.mesh.routers.are.

distinguished.from.mesh.clients.

.we.use.the.term.WMN.in.a.wide.sense.to.denote.any.kind.of.multi-hop.network,.regardless.of.

the.wireless.technology.used.or.the.hardware.features.of.the.related.devices,.an.ad.hoc.network.can.

be.understood.as.a.subset.of.WMNs,.since.no.infrastructure.exists.in.an.ad.hoc.network.[AWW05]..

Amobile.ad.hoc.network.(MANET).is.a.collection.of.wireless.mobile.hosts.forming.a.temporary.

network.without.the.aid.of.any.centralized.administration.or.standard.support.services..In.such.an.

environment,.it.may.be.necessary.for.one.mobile.host.to.enlist.the.aid.of.others.in.forwarding.a.packet.

to.its.destination.due.to.the.limited.propagation.range.of.each.mobile.host’s.wireless.transmissions..

Routing.in.a.MANET.is.challenging.because.of.the.dynamic.topology.and.the.lack.of.an.existing.xed.

infrastructure..For.this.reason,.conventional.routing.protocols.are.not.useful.in.ad.hoc.networks..In.this.

chapter,.there.is.a.brief.description.of.the.routing.protocols.in.ad.hoc.networks,.which.are.currently.

undergoing.a.standardization.process.

WSNs

.can.be.understood.as.a.subset.of.WMNs.. ese.share.similarities.with.ad.hoc.wireless.networks..

 e.dominant.communication.method.in.both.is.multi-hop.networking,.but.several.important.distinc-

tions

.can.be.drawn.between.the.two.. ese.dierences.result.from.both.the.technological.structure.of.

sensor.nodes.and.from.the.intended.application.scenarios..Ad.hoc.networks.typically.support.routing.

between.any.pair.of.nodes,.whereas.sensor.networks.have.a.more.specialized.communication.pattern.

[AY05];.for.this.reason,.new.protocols.have.been.designed.to.be.used.in.WSNs.. ree.of.these.protocols.are.

introduced.in.this.chapter.

WiMAX

tower

WPAN

WLAN

WMN (mesh routers)

(UMTS, GPRS, GSM)

WLAN

WPAN

WLAN

INTERNET

WiMAX

tower

WPAN

WMN (mesh clients)

Wireless LAN

WPAN

FIGURE 4.2 Wireless.networks.

4-4 Industrial Communication Systems

4.2 routing Protocols and Classication

 e.purpose.of.routing.protocols.is.to.determine.the.best.path.from.source.to.destination.. e.routing.

prot

ocols

.have.to.enab

.rout

ers

.to.comm

unicate

.with.each.othe

.exch

anging

.topo

logy

.and.stat

.info

rma-

tion.

. ere.is.a.dive

rse

.rang

.of.rout

ing

.prot

ocols,

.whic

.may.be.clas

sied

.accor

ding

.to.sever

.die

rent

char

acteristics.

Depending

.on.the.type.of.rout

ing

.algo

rithms

.used

.rout

ing

.proto

cols

.can.be.divi

ded

.into.thre

.fami

lies:

.dis

tance

.vec

tor,

.lin

.sta

te,

.and.sou

rce

.rou

ting:

•

. Proto

cols

.that.use.the.dist

ance vector

.tech

nique

.main

tain

.a.tabl

.for.comm

unication

.and.empl

diu

sion

.(no

.oo

ding)

.for.inf

ormation

.exc

hanged

.bet

ween

.the

.nei

ghbors.

•

. Link

state

.tech

nique

.main

tains

.a.tabl

.with.the.enti

.topol

ogy

.netw

ork.

. e.topol

ogy

.is.buil

by.nding.the.shortest.path.in.terms.of.link.cost.. is.cost.is.periodically.exchanged.among.all.

the.node

.thro

ugh

.a.ood

ing

.tech

nique.

.Each.node.upda

tes

.its.rout

ing

.tabl

.using.the.link.cost.

info

rmation.

. is.tech

nique

.can.caus

.loop

.in.netw

orks

.that.chan

.the.topol

ogy

.quic

kly

.[M95

•

. In.the.sour

ce routing

.tech

nique,

.all.the.data.pack

ets

.have.the.rout

ing

.info

rmation

.on.the.head

ers.

 e.sour

.node.make

.the.rout

.deci

sion.

.With.this.tech

nique,

.loop

.can.be.avoi

ded,

.but.the.pro-

col

.over

head

.is.quit

.signi

cant.

. is.tech

nique

.is.not.eci

ent

.for.fast.movi

.topol

ogies

.due.to.

rout

.inv

alidation

.aro

und

.the.pat

.of.a.pac

ket.

However,

.the

.are.oth

.cla

ssications

.tha

.tak

.into.acc

ount

.oth

.cha

racteristics.

•

. Dyna

mic

.or.stat

ic.

.A.dyna

mic

.or.adapt

ative

.rout

ing

.proto

col

.chan

ges

.its.beha

vior

.acco

rding

.to.the.

netw

ork

.sta

te,

.whi

.a.sta

tic

.one.doe

.not

•

. Cent

ralized

.or.dist

ributed.

.Dyna

mic

.rout

ing

.proto

cols

.can.also.be.clas

sied

.as.cent

ralized

.or.

dist

ributed.

. e.clas

sication

.is.base

.on.whic

.node.make

.the.rout

ing

.deci

sions.

.In.a.dist

rib-

uted

.rout

ing

.proto

col,

.all.node

.are.resp

onsible

.for.maki

.thei

.own.rout

ing

.deci

sions.

.In.a.cen-

ralized

.rout

ing

.proto

col,

.the.deci

sions

.take.plac

.at.a.cent

ral

.node

.One.exam

ple

.of.cent

ralized

rout

ing

.proto

cols

.is.the.clus

ter-based

.rout

ing

.proto

cols,

.wher

.the.cent

ral

.node.is.the.so-c

alled

clus

terhead.

.It.is.res

ponsible

.for.the.rou

ting

.pro

cess.

Routing

.in.wire

less

.netw

orks

.is.of.grow

ing

.impo

rtance

.as.curr

ently

.more.and.more.appl

ications

invo

lve

.clie

.mobi

lity.

.This.mean

.the.impl

ementation

.of.rout

ing

.mech

anisms

.that.faci

litate

.com-

unication

.betw

een

.node

.and.whic

.can.adap

.to.the.part

icular

.char

acteristics

.of.this.type.of.

medi

um.

.It.is.beca

use

.of.this.that.wire

less

.envi

ronments

.cann

.use.the.clas

sic

.rout

ing

.prot

ocols.

Thes

.clas

sic

.prot

ocols

.must.be.adap

ted

.to.meet.the.requ

irements

.of.the.new.wire

less

.envi

ronment.

Ther

.foll

ows

.a.desc

ription

.of.some.of.the.prob

lems

.and.char

acteristics

.to.be.foun

.in.wire

less

envi

ronments

.[CM9

9]:

•

. Firs

tly,

.as.the.node

.are.mobi

.elem

ents,

.the.netw

ork

.topo

logy

.chan

ges

.cont

inuously,

.and.ther

fore

.the.lin

.bet

ween

.nod

.are.cre

ated

.and.bro

ken

.dyn

amically.

•

. e.bandwidth.available.in.a.wireless.interface.is.less.than.that.with.a.wired.interface..Sometimes,.

the.maxi

mum

.avai

lable

.band

width

.is.in.the.orde

.of.tens.and.hund

reds

.of.Kbps.and.is.unde

ruti-

lized

.due.to.redu

ction

.and.inte

rference

.in.the.elec

tromagnetic

.signa

ls.

.As.the.dist

ance

.betw

een

the.user.and.its.peer.link.enti

.grow

.the.avai

lable

.band

width

.decr

eases

.due.to.the.need.for.a.

robu

.cod

ing

.due.to.a.sma

ller

.sign

al-to-noise

.and.int

erference

.(SN

IR)

.rat

io.

•

. e.link

latency

.is.high.due.prin

cipally

.to.the.exte

nsive

.proc

essing

.requ

ired

.at.the.physi

cal

.laye

.of.

thes

.net

works

.and.due.to.the.tra

nsmission

.del

ays

.in.the.rad

.acc

ess

.net

work.

•

. In.wire

less

.link

.loss

.due.to.corr

uption

.may.occu

.even.in.stat

.cond

itions,

.due.to.seve

ral

phen

omena

.suc

.as.fad

ing,

.mul

tipath,

.and.att

enuation.

Routing in Wireless Networks 4-5

•. On.some.occasions,.a.mobile.user.may.experience.a.link outage.in.some.situations,.such.as.driving.

thro

ugh

.a.tunn

.or.bein

.in.an.elev

ator.

.Duri

.thes

.peri

ods,

.the.user.has.no.radi

.conn

ectiv-

ity,

.and.if.such.peri

ods

.have.a.dura

tion

.grea

ter

.than.appl

ication

.time

rs,

.ongo

ing

.comm

unications

may.be.abo

rted.

•

. Dela

y jitter

.may.be.cau

sed

.by.a.numb

.of.rea

sons

.whe

.usin

.wir

eless

.tec

hnologies.

•

. Some.or.all.of.the.node

.will.be.powe

red

.by.batt

eries,

.whic

.mean

.that.ener

.savi

.is.an.impo

tant

.fact

.when.deal

ing

.with.this.type.of.netw

ork.

.As.ener

.cons

umption

.is.direc

tly

.prop

ortional

to.the.dist

ance

.betw

een

.host

.(pro

portional

.to.radi

.squar

ed),

.sing

le-hop

.tran

smissions

.betw

een

two.host

.requ

ire

.a.lot.of.powe

.caus

ing

.inte

rference

.with.othe

.host

.To.avoi

.this.prob

lem

.in.rout

ing,

.two.host

.can.use.a.mult

i-hop

.tran

smission

.to.comm

unicate

.with.each.othe

.via.othe

.node

in.the.netw

ork.

•

. Prob

lems

.rela

ted

.to.secu

rity

.are.acce

ntuated

.in.wire

less

.netw

orks.

.As.it.is.a.shar

.envi

ronment

.to.

whic

.any

body

.can.hav

.acc

ess,

.con

dentiality

.of.dat

.is.an.imp

ortant

.con

sideration.

•

. When.we.work.with.wire

less

.netw

orks,

.we.must.consi

der

.some.prob

lems

.such.as.hidd

en termi-

nals,

.whic

.occu

.when.ther

.are.two.node

.with

.comm

unication

.rang

.of.a.thir

.node.but.not.

of.each.othe

.Both.may.try.to.comm

unicate

.with.the.thir

.node.simul

taneously

.and.migh

.not.

dete

.any.inte

rference

.in.the.wire

less

.medi

um.

. us,.the.signa

.coll

ide

.at.the.thir

.node

.whic

will.not.be.able.to.rece

ive

.the.tran

smissions

.from.eith

.node.[P99

. e.typi

cal

.solu

tion

.is.that.the.

term

inals

.coo

rdinate

.the

.tra

nsmissions,

.by.mea

.of.req

uest

.to.sen

d/clear

.to.sen

.(RT

S/CTS).

•

. Supposing.node.B.communicates.with.node.A,.and.node.C.wants.to.transmit.a.packet.to.node.D..

Duri

.the.tran

smission

.betw

een

.node.B.and.node.A,.node.C.perc

eives

.the.chan

nel

.as.busy

Node.C.fals

ely

.conc

ludes

.that.it.may.not.send.to.node.D,.even.thou

.both.tran

smissions

woul

.succ

eed.

.Bad.rece

ption

.woul

.only.occu

.in.the.zone.betw

een

.node.B.and.node.C,.

wher

.neit

her

.of.the.rece

ivers

.are.loca

ted.

. at.is.the.prob

lem

.of.the.expo

sed terminals,

.and.

this. toge

ther

.with.the.hidd

.term

inal

.caus

.sign

icant

.redu

ction

.of.netw

ork

.thro

ughput

when.the.tra

.load.is.high

4.3 routing Protocol Families for ad Hoc Networks

MANET.routing.protocols.are.traditionally.divided.into.three.main.categories.[AWD04].depending.on.

the.type.of.info

rmation

.bein

.exch

anged

.and.the.freq

uency

.with.whic

.it.is.done

.proa

ctive

.or.glob

proto

cols,

.reac

tive

.or.on-d

emand

.proto

cols,

.and.hybr

.proto

cols.

. e.rst.grou

.aims.to.main

tain

.up-

to-

date

.rout

ing

.info

rmation

.in.the.node

.thro

ugh

.peri

odic

.cont

rol

.mess

age

.exch

ange,

.whil

.the.seco

atte

mpts

.to.nd.rout

.on.dema

nd.

. ere.are.also.hybr

.rout

ing

.proto

cols,

.whic

.combi

.feat

ures

from.bot

.pro

active

.and.rea

ctive

.app

roaches.

4.3.1 Proactive routing Protocols

In.proactive.routing.protocols,.each.node.keeps.the.routing.tables.constantly.up-to-date.. e.routing.

tabl

.cont

ain

.the.rout

ing

.info

rmation

.for.ever

.othe

.node.in.the.netw

ork,

.whic

.is.upda

ted

.peri

odi-

cally

.and.when.ther

.are.chan

ges

.in.the.topol

ogy

.of.the.netw

ork.

. e.rout

ing

.info

rmation

.can.be.kept.

in.diff

erent

.rout

ing

.tabl

.depe

nding

.on.the.rout

ing

.prot

ocol.

.Proa

ctive

.tech

niques

.typi

cally

.use.

algo

rithms

.suc

.as.dis

tance

.vec

tor

.and.lin

.sta

te.

.type.of.proto

col

.will.oper

ate

.in.netw

orks

.in.whic

.it.is.nece

ssary

.for.the.rout

.disc

overy

.proc

dure

.to.not.have.exce

ssive

.late

ncy,

.and.this.type.of.proto

col

.is.appr

opriate

.in.term

.of.cons

umption

.of.

reso

urces

.such.as.band

width

.and.ener

gy.

.In.most.of.the.proa

ctive

.rout

ing

.proto

cols,

.the.cont

rol

.mess

age

over

head

.gro

.as.O(N

),.where.N.represents.the.number.of.nodes.in.the.network.

.die

rence

.betw

een

.thes

.proto

cols

.is.in.the.mann

.that.the.rout

ing

.info

rmation

.is.upda

ted,

dete

cted,

.and.the.typ

.of.inf

ormation

.tha

.is.stor

.in.eac

.rou

ting

.tab

le.

4-6 Industrial Communication Systems

4.3.2 reactive routing Protocols

Reactive.or.on-demand*.routing.protocols.were.designed.to.reduce.the.overhead.of.the.proactive.routing.

prot

ocols;

.they.main

tain

.info

rmation

.on.acti

.rout

.only

.When.one.node.want

.to.comm

unicate

.with.

anot

her

.node

.one.rout

.to.the.dest

ination

.is.dema

nded.

.Alth

ough

.netw

ork

.resou

rces

.such.as.ener

.and.

band

width

.are.used.more.eci

ently

.than.in.the.proa

ctive

.prot

ocols,

.the.dela

.in.the.rout

ing

.disco

very

proc

edure

.incr

eases.

. e.rout

.disco

very

.proc

edure

.is.usua

lly

.made.by.ood

ing

.a.rout

.requ

est

.pack

thro

ugh

.the.netw

ork.

.If.a.node.with.a.rout

.to.the.dest

ination

.(or.the.dest

ination

.itsel

.recei

ves

.the.rout

requ

est

.pack

et,

.it.sends.back.a.rout

.repl

.pack

.to.the.sourc

.node.usin

.the.link.reve

rsal

.if.the.pack

has.trav

eled

.thro

ugh

.bidi

rectional

.link

. e.rout

.repl

.pack

.cont

ains

.the.desi

red

.rout

. e.rout

ing

algo

rithms

.foun

.amon

.the.reac

tive

.rout

ing

.prot

ocols

.are.dist

ance

.vecto

.and.sourc

.rout

ing.

Reactive

.rout

ing

.prot

ocols

.are.divi

ded

.into.two.grou

ps,

.sourc

e-based

.and.hop-

by-hop

.or.poin

t-to-point.

•

. In.sourc

e-based

.on-d

emand

.prot

ocols,

.each.data.pack

.tran

sports

.in.its.head

.the.comp

lete

.sourc

to.the.dest

ination,

.that.is,.the.info

rmation

.of.ever

.neig

hboring

.node.from.the.sourc

.to.the.dest

ina-

tion.

.Ever

.inte

rmediate

.pack

.cons

ults

.the.head

.pack

.to.know.wher

.to.forw

ard

.it.to.. ere

fore,

ther

.is.no.need.for.the.inte

rmediate

.node

.to.keep.the.rout

ing

.info

rmation

.cont

inuously

.up.to.date.

by.mean

.of.forw

arding

.rout

ing

.mess

ages

.peri

odically

.as.in.proa

ctive

.rout

ing

.prot

ocols.

.In.cont

rast,

in.larg

.ad.hoc.netw

orks,

.the.prob

ability

.of.link.fail

ures

.occur

ring

.incr

eases

.with.the.numb

.of.

node

.As.the.numb

.of.inte

rmediate

.node

.incr

eases,

.the.size.of.the.head

.pack

.incr

eases

.too..

 is.kind.of.prot

ocol

.is.not.recom

mended

.in.larg

.netw

orks

.with.a.lot.of.hops.and.high.mobi

lity

becau

.they.do.not.scale.well

•

. In.the.hop-b

y-hop

.rout

ing

.proto

cols,

.the.pack

.only.carr

ies

.the.dest

ination

.addr

ess

.and.the.next.

hop.addr

ess;

.in.this.way,.ever

.inte

rmediate

.node.that.part

icipates

.in.the.rout

.woul

.cons

ult

.its.

rout

ing

.tabl

.to.deci

.whic

.way.to.send.the.pack

et.

. e.adva

ntage

.is.that.ever

.inte

rmediate

node.keep

.its.rout

ing

.tabl

.up.to.date.cont

inuously

.and.inde

pendently,

.so.that.when.a.pack

reac

hes

.an.inte

rmediate

.node

.it.can.deci

.how.to.rout

.it.acco

rding

.to.the.curr

ent

.stat

.of.the.

netw

ork;

.the.rout

.can.ther

efore

.adapt.to.the.dyna

mic

.topol

ogy

.of.this.kind.of.rout

.more.easil

 e.draw

back

.is.that.ever

.inte

rmediate

.node.alon

.the.rout

.must.cons

tantly

.upda

.its.rout

ing

tabl

.by.mea

.of.bea

coning

.mes

sages.

.rout

.disc

overy

.over

head

.can.grow.O(N.+.M).if.a.link.reve

rsal

.is.possi

ble,

.wher

.N.repr

esents

.the.

numbe

.of.node

.in.the.netw

ork

.and.M.the.numbe

.of.node

.in.the.repl

.path

;

.for.unid

irectional

.link

the.dis

covery

.ove

rhead

.is.O(2N).

.3.2.1 Hybrid routing Protocols

Hybrid

.rout

ing

.proto

cols

.are.a.new.gene

ration

.of.proto

cols

.that.use.the.char

acteristics

.of.reac

tive

.and.

proa

ctive

.proto

cols.

. ese.are.desig

ned

.to.incr

ease

.scal

ability

.and.redu

.the.over

load

.invo

lved

.in.rout

disc

overy.

. is.is.pos

sible

.by.mea

.of.pro

active

.rou

.mai

ntenance

.for.the.clo

ser

.nod

.and.a.det

ermi-

nation

.of.rou

tes

.for.the.mor

.dis

tant

.nod

.by.mea

.of.a.rou

.dis

covery

.str

ategy.

Most

.of.the.hybr

.prot

ocols

.are.zone.base

.that.is,.the.netw

ork

.is.divi

ded

.into.a.numb

.of.zone

each.cont

aining

.one.node.that.is.sele

cted

.to.be.in.char

.of.all.the.mobi

.node

.with

.thei

.tran

smis-

sion

.rang

.or.a.subs

.of.them

.Othe

.hybr

.rout

ing

.prot

ocols

.grou

.the.node

.into.tree

.or.clus

ters.

4.4 routing Protocol Families for Wireless Sensor Networks

Routing.in.sensor.networks.is.very.challenging.due.to.a.number.of.characteristics.that.distinguish.them.

from.con

temporary

.com

munication

.and.wir

eless

.ad.hoc.net

works.

Note.that.the.terms.reactive.and.on.demand.are.used.interchangeably.

Routing in Wireless Networks 4-7

Firstly,.due.to.the.relatively.large.number.of.sensor.nodes,.it.is.not.possible.to.build.a.global.addressing.

sche

.for.the.depl

oyment

.of.a.larg

.numbe

.of.sens

.node

.as.the.over

head

.of.ID.main

tenance

.is.high

 ere

fore,

.cla

ssic

.IP-b

ased

.pro

tocols

.can

not

.be.app

lied

.to.sen

sor

.net

works.

Secondly,

.in.cont

rast

.to.typi

cal

.comm

unication

.netw

orks,

.almo

.all.appl

ications

.of.sens

.netw

orks

requ

ire

.the.ow.of.dat

.fro

.mul

tiple

.sou

rces

.to.a.par

ticular

.bas

.sta

tion.

 irdly,

.sens

.node

.are.tigh

tly

.cons

trained

.in.term

.of.ener

gy,

.proc

essing,

.and.stora

.capa

cities

and.this.must.be.consi

dered

.when.desig

ning

.a.rout

ing

.proto

col.

. e.next.consi

deration

.is.that.in.most.

appl

ication

.scen

arios,

.node

.in.WSNs.are.gene

rally

.stat

ionary

.aer.depl

oyment

.exce

.for.a.few.mobi

node

. e.next.char

acteristic

.is.that.sens

.netw

orks

.are.appl

ication

.spec

ic

.(the.requ

irements

.chan

acco

rding

.to.the.appl

ication).

.Posit

ion

.awar

eness

.of.sens

.node

.is.also.impo

rtant

.since.data.coll

ection

is.norm

ally

.base

.on.the.loca

tion.

.Fina

lly,

.data.coll

ected

.by.many.sens

ors

.in.WSNs.is.typi

cally

.base

on.comm

.phen

omena,

.so.ther

.is.a.high.prob

ability

.that.this.data.has.some.redu

ndancy.

. is.char

acteristic

.mus

.be.use

.by.the.rou

ting

.pro

tocols

.to.imp

rove

.ene

rgy

.and.ban

dwidth

.uti

lization

.[AK

04].

Due

.to.such.die

rences,

.many.new.algo

rithms

.have.been.prop

osed

.for.the.prob

lem

.of.rout

ing

.data.in.

sens

.netw

orks.

. e.thre

.main.cate

gories

.are.at,.hier

archical,

.and.loca

tion

.base

.alth

ough

.ther

.are.

seve

ral

.oth

ers

.bas

.on.net

work

.ow.or.qua

lity

.of.ser

vice

.(Qo

.awa

reness.

4.4.1 Flat routing Protocols

In.at.networks,.each.node.normally.plays.the.same.role.and.sensor.nodes.collaborate.to.perform.the.

sensi

.task

.Due.to.the.larg

.numb

.of.node

.it.is.not.feas

ible

.to.assi

.a.glob

.iden

tier

.to.each.node..

 is.cons

ideration

.has.led.to.data

-centric

.rout

ing,

.wher

.the.base.stat

ion

.sends.quer

ies

.to.cert

ain

.regi

ons

and.wait

.for.data.from.the.sensor

.loca

ted

.in.the.select

.regi

ons.

.Sinc

.data.are.bein

.requ

ested

.thro

ugh

quer

ies,

.attr

ibute-based

.nami

.is.neces

sary

.to.speci

.the.prop

erties

.of.data

4.4.2 Hierarchical routing Protocols

 e.hierarchical.routing.protocols.use.methods.originally.proposed.in.wireline.networks.. ese.are.

well

-known

.tech

niques

.with.spec

ial

.adva

ntages

.rela

ted

.to.scal

ability

.and.eci

ent

.comm

unication.

. e.

conc

ept

.of.hier

archical

.or.clus

ter-based

.rout

ing

.is.also.util

ized

.to.perf

orm

.ener

gy-ecient

.rout

ing

.in.

WSNs

.In.this.type.of.arch

itecture,

.high

er-energy

.node

.are.used.to.proc

ess

.and.send.the.info

rmation,

whil

.low-

energy

.node

.can.be.used.to.perf

orm

.the.sensi

.in.the.prox

imity

.of.the.targ

et.

. e.crea

tion

of.clus

ters

.and.assi

gning

.speci

.task

.to.clus

ter

.head

.can.grea

tly

.cont

ribute

.to.over

all

.syst

.scala

bility,

life

time,

.and.ene

rgy

.ec

iency.

4.4.3 Location-Based routing Protocols

Sensor.nodes.that.use.this.routing.protocol.are.addressed.by.means.of.their.location.. e.distance.

betw

een

.neig

hboring

.node

.is.esti

mated

.acco

rding

.to.signa

.stre

ngths.

.Coor

dinates

.of.the.neig

hboring

node

.can.be.obta

ined

.by.exch

anging

.info

rmation

.betw

een

.neig

hbors.

.Some.proto

cols

.use.GPS.to.nd.

the.loca

tion

.of.neig

hboring

.node

.In.orde

.to.save.ener

.in.some.loca

tion-based

.sche

mes,

.the.node

that.are.not.act

ive

.go.into.sle

.mod

4.5 Summary of the Main routing Protocols

in Wireless Networks

 e.most.common.MANET.routing.protocols.are.described.in.this.chapter.. ese.are.promoted.by.the.

IETF.MANE

.Work

ing

.Grou

.by.publ

ishing

.them.as.expe

rimental

.RFC,.and.are.OLSR

.Topo

logy

.dis-

emination

.Base

.on.Reve

rse

.Path.Forw

arding

.(TBR

PF),

.AODV

.and.Dyna

mic

.Sour

.Rout

ing

.(DSR

4-8 Industrial Communication Systems

Aer.this,.a.new.one.is.explained—Dynamic.MANET.On-Demand.(DYMO),.which.has.been.published.

as.Standard.Track.RFC.

Along

.similar.lines,.three.more.routing.protocols.used.in.WSNs.are.explained.. ese.are.Sensor.

Protocols.for.Information.via.Negotiation.(SPIN),.which.are.classied.as.at.routing.protocols,.and.Low.

Energy.Adaptive.Clustering.Hierarchy.(LEACH).protocol,.and.Geographic.Adaptive.Fidelity.(GAF),.

which.is.a.location-based.routing.protocol.

4.5.1 Optimized Link-State routing Protocol

OLSR.[JMC01].is.a.proactive.routing.protocol.based.on.the.link.state.algorithm..It.is.in.experimental.

state.in.the.IETF.Working.Group.[CJ03].

Each

.node.maintains.a.route.to.the.rest.of.the.nodes.in.the.ad.hoc.network.. e.nodes.forming.

the.network.exchange.messages.about.the.link.state.periodically,.but.they.use.the.multipoint.relaying.

(MPR).strategy.to.minimize.both,.the.routing.message.size.and.the.number.of.nodes.that.resend.the.

routing.messages.in.broadcast.mode..In.the.MPR.[BCGS04].strategy,.each.node.uses.“Hello”.messages.

to.nd.out.which.nodes.are.placed.at.one.hop.distance.and.a.list.is.created,.see.Figure.4.3.

Each

.node.selects.in.that.list.a.subset.of.neighbor.nodes.able.to.reach.every.node.at.a.distance.of.

two.hops.from.the.node.that.is.making.the.selection..Only.these.selected.neighbor.nodes.will.be.used.

to.retransmit.the.routing.messages,.and.these.are.called.multipoint.relays.. e.rest.of.the.neighboring.

nodes.will.process.the.routing.messages.they.receive,.but.they.will.be.unable.to.retransmit.them..Each.

node.determines.the.best.route.(in.number.of.hops).for.each.destination,.using.the.information.stored.

(in.the.routing.table.of.the.topology.and.in.that.of.their.neighbors).[AWD04],.and.stores.that.informa-

tion

.in.a.routing.table,.so.that.it.is.available.at.the.precise.moment.when.a.node.wants.to.start.sending.

data.. is.protocol.selects.bidirectional.links.to.send.messages.[ChCL03],.dispensing.with.unidirec-

tional

.links..OLSR.is.well.suited.to.large,.dense.mobile.networks..Because.of.the.use.of.MPRs,.larger.and.

denser.networks.link.state.routing.oers.optimum.performance.

4.5.2 topology Dissemination Based on reverse Path Forwarding

Topology.Dissemination.Based.on.Reverse-Path.Forwarding.[OTL04].is.a.proactive,.link-state.rout-

ing

.protocol.designed.for.mobile.ad.hoc.networks,.which.provides.hop-by-hop.routing.along.shortest.

paths.to.each.destination..Each.node.running.TBRPF.computes.a.source.tree.based.on.partial.topology.

information.stored.in.its.topology.table,.using.a.modication.of.Dijkstra’s.algorithm..To.minimize.over-

head,

.each.node.reports.only.part.of.its.source.tree.to.neighbors..TBRPF.uses.a.combination.of.periodic.

and.dierential.updates.to.keep.all.neighbors.informed.of.the.reported.part.of.its.source.tree..Each.

node.also.has.the.option.to.report.additional.topology.information,.to.provide.improved.robustness.

MPR nodes

Source node

FIGURE 4.3 OLSR.multipoint.relay.selection.

Routing in Wireless Networks 4-9

in.highly.mobile.networks..TBRPF.performs.neighbor.discovery.using.“dierential”.HELLO.messages.

tha

.rep

ort

.onl

.cha

nges

.in.the.sta

tus

.of.nei

ghbors.

. is.res

ults

.in.HEL

.mes

sages

.tha

.are.muc

sma

ller

.th

ose

.of.ot

her

.li

nk-state

.ro

uting

.pr

otocols.

4.5.3 Dynamic Source routing Protocol

 is.protocol.was.created.in.1996.[JM96,JM01],.and.like.other.protocols,.it.has.been.widely.studied.and.

als

.mod

ied

.[DR

L03].

.Cur

rently,

.its.sta

.is.exp

erimental

.[JH

M07],

.lik

.tha

.of.OLS

.DSR.is.a.rea

ctive

rou

ting

.pro

tocol.

.An.imp

ortant

.cha

racteristic

.to.con

sider

.is.tha

.thi

.pro

tocol

.req

uires

.tha

.eac

.mes

sage

.sen

.con

tains

.the.com

plete

.add

ress

.fro

.the.sou

rce

.nod

.to.the.des

tination

.nod

.(so

urce

.bas

ed).

Whe

.a.nod

.nee

.to.kno

.the.pat

.to.the.des

tination,

.it.sen

.a.Rou

.Req

uest

.(RR

EQ)

.mes

sage

.and.

the.rou

.dis

covery

.pro

cedure

.is.ini

tiated.

.Eac

.nod

.add

.its.own.ide

ntier

.whe

.the.RRE

.is.res

ent,

and.in.th

.wa

.th

.ro

ute

.re

cord

.is.cr

eated.

.det

ect

.RRE

.dup

licates,

.eac

.nod

.in.the.net

work

.mai

ntains

.a.lis

.wit

.the.pai

.[so

urce

.add

ress,

req

uest_id].

.Whe

.a.nod

.rec

eives

.a.RRE

.mes

sage,

.it.fol

lows

.the.fol

lowing

.ste

ps:

.(1).If.the.pai

[so

urce

.add

ress,

.req

uest_id]

.for.thi

.rou

.dis

covery

.are.in.the.rec

ent

.sea

rch

.lis

.of.thi

.nod

.it.dis

misses

.it.and.doe

.not.pro

cess

.the.RRE

.mes

sage.

.(2).If.the.add

ress

.of.thi

.nod

.is.in.the.rou

.rec

ord

of.the.RRE

.mes

sage,

.it.dis

misses

.it.and.doe

.not.pro

cess

.it..(3).If.the.sea

rch

.obje

ctive

.is.the.nod

add

ress,

.the.rou

.rec

ord

.alr

eady

.con

tains

.the.rou

.fro

.sou

rce

.to.des

tination

.and.the.rou

.rep

(RR

EP)

.mes

sage

.is.sen

.(4).Oth

erwise,

.thi

.nod

.add

.its.own.add

ress

.in.the.rou

.rec

ord

.of.the.RRE

mes

sage

.and.res

ends

.the.sea

rch.

.the.nod

.tha

.rec

eives

.the.RRE

.is.the.des

tination

.or.it.con

tains

.inf

ormation

.abo

.the.des

tina-

tion,

.it.rep

lies

.wit

.a.RRE

.mes

sage.

. e.RRE

.mes

sage

.is.sen

.thr

ough

.the.sam

.pat

.tha

.has.bee

dis

covered,

.and.thi

.sam

.mes

sage

.hol

.the.rou

.fro

.the.sou

rce

.nod

.to.the.des

tination.

.If.the.

lin

.is.not.bid

irectional,

.a.new.rou

.dis

covery

.is.car

ried

.out.to.sen

.the.RRE

.mes

sage.

.Whe

.the.

source.node.receives.the.RREP,.it.stores.the.route.from.source.to.destination.included.in.the.RREP.

in.the.rou

.cac

he.

.Whi

.RRE

.and.RRE

.mes

sages

.pas

.thr

ough

.int

ermediate

.nod

es,

.the

.sto

.the.

inf

ormation

.in.the

.rou

.cac

he.

.Whi

.wai

ting

.for.the.rou

.dis

covery

.to.ni

sh,

.the.nod

.can.con

tinue

.sen

ding

.and.rec

eiving

.mes

sages

.to/

from

.oth

.nod

es.

.Whe

.the.sou

rce

.nod

.rec

eives

.the.RRE

mes

sage,

.it.can.sen

.dat

.pac

kets

.to.the.des

tination

.nod

.and.the.hea

der

.of.tho

.pac

kets

.inc

ludes

.the.

rou

.the

.hav

.to.fol

low.

. is.way

.int

ermediate

.nod

.use.the.rou

.inc

luded

.in.the.pac

ket

.to.dec

ide

whi

.nod

.the

.hav

.to.sen

.the.pac

ket

.to..Whe

.the.pac

ket

.rea

ches

.its.des

tination,

.it.is.del

ivered

.to.

the.net

work

.lay

er.

Each

.nod

.has.a.rou

.cac

.whe

.the.pat

.to.a.des

tination

.nod

.is.sto

red.

.Eac

.ent

.in.the.rou

.cac

has.an.asso

ciated

.lif

etime

.ae

.whi

.the.ent

.is.del

eted

.fro

.the.cac

he.

. e.use.of.thi

.rou

.cac

.in.

eac

.nod

.oe

.two.adva

ntages:

.Fir

stly,

.mor

.spe

.in.the.rou

.disc

overy—if

.a.nod

.tha

.rece

ives

.a.RRE

for.a.pat

.to.des

tination

.tha

.is.alr

eady

.kno

.(bec

ause

.it.alr

eady

.has.it.in.its.cac

he),

.it.can.rep

.wit

.a.

RREP

.usi

.the.loc

.rou

ting

.cac

he.

.Seco

ndly,

.the.tra

nsmission

.of.RRE

.is.redu

ced,

.beca

use

.if.the.pat

.to.

the.des

tination

.is.alr

eady

.kno

.beca

use

.a.nod

.has.it.sto

red

.in.its.rou

.cac

he,

.the

.is.no.need.to.con

tinue

tra

nsmitting

.RRE

.mes

sages.

.If.a.rou

.bre

aks,

.the.sour

.nod

.can.con

sider

.ano

ther

.rou

.tha

.it.has.in.

its.cac

.for.the.sam

.add

ress.

.If.it.doe

.not.hav

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overy

.aga

in.

.Fig

ure

.4.4.

sho

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mple

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.based.on.the.rou

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blem,

.if.a.nod

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.and.is.not.the.obj

ective

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inning

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ained

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he.

4-10 Industrial Communication Systems

4.5.4 ad Hoc On-Demand Distance Vector routing Protocol

 e. AODV. protocol. is. built. on.the. destination-sequenced. distance-vector. (DSDV). protocol.. e.

improvement.here.is.to.minimize.the.number.of.transmissions.required.to.create.routes,.because.

as.they.are.on.demand,.the.nodes.that.are.not.placed.in.the.chosen.path.do.not.have.to.maintain.

the.route.or.participate.in.table.interchanges..Several.studies.on.this.protocol.have.been.carried.out.

[PR99,RP99,RP00],.and.it.has.been.modied.[SWL03].several.times..Currently,.it.is.a.protocol.in.

experimental.state.[PBD03].

When

.a.node.wants.to.transmit.to.a.destination.and.it.does.not.have.a.valid.route,.it.must.start.the.

path.discovery.process..To.do.this,.in.the.rst.place,.it.broadcasts.a.RREQ.message.to.its.neighbors,.

which.in.turn.sends.it.to.their.own.neighbors.and.so.on,.until.it.gets.to.the.destination.or.to.an.interme-

diate

.node.that.has.a.route.to.the.destination..Like.DSDV,.it.uses.sequence.numbers.to.identify.the.most.

recent.routes.and.delete.loops..Each.node.maintains.two.counters:.the.node’s.sequence.number.(to.avoid.

loops).and.Broadcast_ID.that.is.increased.when.a.transmission.is.initiated.in.the.node.

.identify.a.single.RREQ,.it.uses.the.Broadcast_ID.and.the.IP.address.of.the.source.node.. e.

RREQ.contains.the.following.elds:.source_addr,.number_sequence_#,.broadcast_id,.dest_addr,.dest_

sequence_#,

.and.hop_cnt..Intermediate.nodes.only.reply.to.RREQ.messages.if.they.have.a.route.to.the.

destination.with.a.sequence.number.greater.or.equal.to.the.one.stored.in.the.RREQ,.in.other.words,.only.

if.they.have.equal.routes.(in.age).or.more.recent..While.the.RREQ.is.sent,.intermediate.nodes.increase.

the.“hop_cnt”.eld,.and.they.also.register.in.their.routing.table.the.address.of.the.neighbor.from.which.

they.rst.received.the.message,.to.establish.the.Reverse.Path,.where.RREQs.are.still.sent,.and.at.the.same.

time,.the.Reverse.Path.is.being.established.. e.copies.of.the.same.RREQ.received.aer.that.coming.

from.other.neighbors.are.dismissed.

Once

.the.“destination.node/intermediate.node.with.recent.route”.has.been.found,.it.replies.with.a.uni-

cast

.packet.known.as.RREP.to.the.neighbor.from.which.it.received.the.rst.RREQ.. e.RREP.uses.the.

links.that.had.been.established.before.as.reverse.path.. e.RREP.contains.the.following.elds:.source_addr,.

dest_addr,.dest_sequence_#,.hop_cnt,.and.lifetime.or.expiration.time.for.the.Reverse.Path.. e.RREP.uses.

the.reverse.path.established.to.the.source.node..In.its.route,.all.the.nodes.the.RREP.passes.through.write.

the.Reverse.Path.as.the.most.recent.route.to.the.destination.node..From.that.we.can.conclude.that.the.

AODV.holds.only.bidirectional.links..In.Figure.4.5,.the.AODV.route.discovery.procedure.is.shown.

.a.source.node.moves,.it.is.able.to.restart.the.discovery.protocol.to.nd.a.new.route.to.the.destina-

tion.

.If.an.intermediate.node.moves,.its.previous.neighbor.(in.the.source-destination.direction).broadcasts.

(until.the.source.node.is.reached).a.not-requested.RREP.with.a.“recent”.sequence.number.(in.other.words,.

greater.than.the.sequence.number.known).and.with.a.number.of.hops.to.the.destination.equal.to.innite..

 at.way,.the.source.node.restarts.the.route.discovery.process.in.the.case.that.it.still.needs.the.route.

When

the

link

breakage

happens,

the

node

must

invalidate

the

existing

route

the

routing

table

entry.. e.node.must.list.the.aected.destinations.and.determine.which.neighbors.can.be.aected.by.

[C, S]

[S, E, F, J, D]

[E, F, J, D]

[F, J, D], [F, E, S]

[J, F, E, S]

[G, C, S]

FIGURE 4.4 Example.of.the.route.cache.in.the.DSR.protocol.

Routing in Wireless Networks 4-11

this.breakage..Finally,.the.node.must.send.the.route.error.(RERR).message.to.the.corresponding.neigh-

bors.

. e.RERR.message.can.be.broadcasted.if.there.are.many.neighbors.that.need.that.information.

or.unicasted.if.there.is.only.one.neighbor.. e.sequence.numbers.for.the.entries.in.the.routing.table.for.

the.unreachable.destinations.must.be.set.to.invalid.lifetime..When.the.link.breakage.happens,.then.the.

host.can.try.to.locally.repair.the.link.if.the.destination.is.no.further.than.a.specied.amount.of.hops..

If.the.RREP.message.is.not.received,.then.it.changes.the.routing.table.status.for.the.entry.to.“invalid.”.If.

the.host.receives.the.RREP.message,.then.the.hop.count.measurement.is.compared..If.the.hop.measure-

ment

.from.the.message.is.greater.than.the.previous.one,.then.the.RERR.with.the.N.eld.that.is.set.up.is.

broadcasted.. e.N.eld.in.the.RERR.message.indicates.that.the.host.has.been.locally.repaired,.and.the.

link.and.the.entry.in.the.table.should.not.be.deleted.

.additional.feature.is.the.use.of.“Hello”.messages.(periodical.broadcast).to.inform.a.mobile.node.

about.every.neighboring.node.. ese.are.a.special.kind.of.not-requested.RREPs,.whose.sequence.num-

ber

.is.equal.to.the.last.RREP.sent.(the.sequence.number.is.not.increased).and.that.have.a.time-to-live.

(TTL).=.1.to.not.ood.the.net.. ey.can.be.used.for.the.network.route.maintenance.

4.5.5 Dynamic MaNEt On-Demand routing Protocol

DYMO.[ChP08].is.a.reactive.protocol.that.inherits.most.of.its.functionality.from.its.predecessors,.AODV.

and.DSR..It.is.intended.for.use.by.mobile.nodes.in.wireless.multi-hop.networks..It.oers.adaptation.to.

changing.network.topology.and.determines.unicast.routes.between.nodes.within.the.network..One.of.

the.main.features.of.this.protocol.is.path.accumulation,.which.consists.of.the.following.mechanism..

During.the.RREQ.dissemination.process,.each.intermediate.node.records.a.route.to.the.originating.

node..When.the.target.node.receives.the.RREQ,.it.responds.with.a.RREP.unicast.toward.the.originating.

node..It.is.expected.that.since.intermediate.nodes.learn.routes.gratuitously.from.RREQs.and.RREPs,.

protocol.overhead.will.be.small.since.part.of.the.route.discovery.processes.is.avoided.

.Table.4.1,.there.is.a.comparison.of.the.ve.routing.protocols.for.ad.hoc.networks.presented.in.this.

section.. is.table.also.summarizes.the.routing.algorithm.used.and.the.family.protocol.of.every.routing.

protocol.presented.

RREP

RREQ

FIGURE 4.5 ADOV.route.discovery.procedure.

TABLE 4.1 Routing.Protocols.in.Wireless.Sensor.Networks

Routing.Protocols.in.Wireless.Sensor.Networks

SPIN LEACH GAF

Routing

.algorithm Resource.

adaptative

Cluster.based Energy.aware.

location.based

Routing

.protocol.family Flat Hierarchical Location.based