Routing in WirelessSensor Networks

Matthias HandyMatthias HandyUniversity of RostockUniversity of Rostock

matthias.handy@unimatthias.handy@uni--rostock.derostock.de

22

Overview

•• Problem Problem FormulationFormulation

•• ChallengesChallenges

•• ClassificationClassification

•• FlatFlat RoutingRouting

•• HierarchicalHierarchical RoutingRouting

•• LocationLocation BasedBased RoutingRouting

•• OtherOther

•• Open Research Open Research IssuesIssues

•• SummarySummary

33

Problem Formulation

Deployment Area

Base Station

Sensor node Sensor node in event regionSensor node outside the event region with routing task

44

Challenges for RPs in WSN

•• NodeNode deploymentdeployment

•• EnergyEnergy vs. vs. QualityQuality

•• DataData reportingreporting methodmethod•• timetime--drivendriven

•• eventevent--drivendriven

•• queryquery--drivendriven

•• NodeNode heterogeneityheterogeneity

•• Fault Fault tolerancetolerance

•• ScalabilityScalability

•• NetworkNetwork dynamicsdynamics

55

Challenges ctd.

•• Transmission media (MAC)Transmission media (MAC)

•• ConnectivityConnectivity

•• CoverageCoverage

•• DataData aggregationaggregation

66

Classification of RPs for WSN

RoutingProtocols

in WSN

NetworkStructure

ProtocolOperation

FlatNetworkRouting

HierarchicalNetworkRouting

LocationBased

Routing

NegotiationBased

Routing

MultipathBased

Routing

QueryBased

Routing

QoSBased

Routing

CoherentBased

Routing

Source: Al-Karaki / Kamal, 2004

77

Flat Routing: Characteristics

•• No No distinctdistinct rolesroles•• DataData--centriccentric routingrouting vs. vs. addressaddress--centriccentric routingrouting•• Evolution of Evolution of flatflat routingrouting: :

•• FloodingFlooding, , GossipingGossiping•• SPIN & SPIN & DirectedDirected DiffusionDiffusion

Sink

Source 1

Source 2

A B

C

1

2

2

1+2

Source 1

Source 2

Sink

A B

C1

1

2

2

2

Address-centric Data-centric

88

Flat Routing: Flooding & Gossiping

•• FloodingFlooding::•• NodeNode A A sendssends datadata to all to all neighborsneighbors

•• NeighborsNeighbors of A send of A send datadata to all to all theirtheir neighborsneighbors ……

•• UntilUntil all all nodesnodes receivedreceived thethe datadata

•• GossipingGossiping::•• basesbases on on floodingflooding

•• datadata isis onlyonly forwardedforwarded to to oneonerandomlyrandomly selectedselected neighborneighbor

•• savessaves energyenergy

Gossiping Example

99

Flat Routing: SPIN•• SSensor ensor PProtocolsrotocols forfor IInformation via nformation via NNegotiationegotiation

(Kulik et al. 2002)(Kulik et al. 2002)•• Motivation: Problems of Motivation: Problems of classicclassic floodingflooding

•• ImplosionImplosion•• OverlapOverlap•• ResourceResource BlindnessBlindness

•• Solution: Solution: SPIN SPIN protocolprotocol familyfamily•• SPINSPIN--PP (PP (forfor pointpoint--toto--pointpoint media)media)•• SPINSPIN--EC (SPINEC (SPIN--PP PP withwith a a lowlow energyenergy thresholdthreshold))•• SPINSPIN--BC (BC (forfor broadcastbroadcast media)media)•• SPINSPIN--RL (SPINRL (SPIN--BC BC forfor lossylossy networksnetworks))

•• Key Key featuresfeatures of SPIN of SPIN protocolsprotocols•• NegotiationNegotiation ((metameta datadata) ) Implosion, Implosion, OverlapOverlap•• ResourceResource adaptationadaptation ResourceResource BlindnessBlindness

•• 3 3 messagemessage typestypes::•• ADVADV•• REQREQ•• DATADATA

A

B C

D

(a)

(a)

(a)

(a)

source

sink

Implosion

Overlap

B

C

A

qr

s

(q,r) (r,s)

1010

Flat Routing: SPIN (2)SPIN-PP optimized for networks using point-to point transmission media

B

A

(1)

B

A

(2)

B

A

(3)

B

A

(5)

B

A

(6)

ADVREQ

DATA

REQREQ

REQ

B

A

(4)

ADVADV

ADV

AD

V

ADV

DATADATA

DATA

SPIN-EC: a node participates only in the three-stage SPIN-PP-protocol,if it believes that in complete all three stages

1111

Flat Routing: SPIN (3)SPIN-BC optimized for networks using broadcast transmission media

B

C

EA

D

(1)ADV B

C

EA

DREQ

(2)

B

C

EA

D

(3)DATA B

C

EA

D

(4)

G F

nodes with data

nodes without data

nodes waiting to tx REQ

transmission range

• nodes receiving ADV set arandom timer before broad-casting REQ

• a node cancels its timer whenit overhears a REQ from adifferent node on the sameADV

• DATA is broadcasted onlyonce, regardless how manyREQs are broadcasted

SPIN-RL

• SPIN-BC for lossy networks• adjustments for reliability:

• nodes request data ofoverheard, not answeredREQ messages

• multiple REQs for the samedata are answered

1212

Flat Routing: Directed Diffusion•• Elements of DDElements of DD ((IntanagonwiwatIntanagonwiwat 2001)2001)

•• DataData isis namednamed usingusing attributeattribute--valuevalue pairspairs•• interestsinterests areare disseminateddisseminated througoutthrougout thethe

wsnwsn•• disseminationdissemination setssets up up gradientsgradients to "to "drawdraw" "

eventsevents fromfrom sourcessources to to sinkssinks alongalong multiple multiple pathspaths

•• thethe networknetwork reinforcesreinforces subsetsubset of of availableavailablepathespathes fromfrom sourcesource to sinkto sink

type = four-legged animal

interval = 20 ms

duration = 10 seconds

rect = [-100, 100, 200, 400]

A simple task in a DD network

a) Interest propagation b) Initial gradients set-up c) Data delivery

Interest is 'injected' into the network at the sink node!

1313

3. gradient(data rate,

neighbor ID)

1. interest x

Flat Routing: Directed Diffusion (2)

Interests and Gradients

1

sink

2. interest cache lookup*

* if entry and gradient exist, onlytimestamp and duration are updated

4. interest x

neighbor selection for interest forwarding• broadcast (flooding)• geographic routing• use cached data

Data Propagation

source

1

rect rect

type = four-legged animal interval = 1s

rect = [-100, 100, 200, 400] timestamp = 01:20:40

expiresAt = 01:30:40

Inte

rest

x

1. target detection2. interest cache lookup

3. data msg

4. interest cache & data cache lookup

4. data msg

type = four-legged animal

instance = goat

location = [125, 220]

intensity = 0.6

confidence = 0.85

timestamp = 01:22:40

Data msg

1414

Flat Routing: Directed Diffusion (3)

Reinforcement & Negative Reinforcement

- sink may reinforce one particular neighbor(not path!)

- for higher data rate- sink re-sends interest with smaller interval to

selected node(in the picture: thick path is reinforced)

• Negative reinforcement to 'repair' degraded links by

• timeout high data rate gradients(implicit degradation)

• re-sending interest with lower data rate(explicit degradation)

All interactions in Directed Diffusion are based on local rules!

1515

Flat Routing: GBR•• GGradientradient BBasedased RRoutingouting ((SchurgersSchurgers, , SrivastavaSrivastava 2001)2001)•• BasedBased on on DirectedDirected DiffusionDiffusion

•• DD'sDD's interestinterest messagesmessages countcount hops to hops to thethe sinkssinks•• heightheight of of thethe nodenode = = hophop countcount to sink (to sink (minimumminimum))•• gradientgradient of a link = of a link = heightheight differencedifference of of bothboth link link endpointsendpoints

•• reducesreduces DD'sDD's energyenergy consumptionconsumption byby•• DataData CombiningCombining EntitiesEntities (DCE)(DCE)•• NetworkNetwork TrafficTraffic SpreadingSpreading (NTS)(NTS)

2

2

3

3

2

1 01

1

1

10

1

0

10

Packet is forwarded on the link with the largest gradient!

1

1Gradient

1 Node w. height

3 Source

Sink3

1616

Flat Routing: GBR (2)

B = Area length, R = Tx range

Data Combining Entities (DCE)

Idea: Nodes with multiple streams fromthe same event flowing through themcombine the data

sink source

DCE

DCEs reduce energy consumption but increase delay!

1717

Flat Routing: GBR (3) Network Traffic Spreading (NTS)

Stochastic scheme:

2

3 2

1 01

1

1

1

1

0

source

sink

source chooses next hop randomly

Energy-Based scheme:

2

3 3

1 01

1

1

1

0

0source

sink

remaining energy

• low-energy nodes increase height• neighbor's heights are updated

Stream-based scheme:

2

3 2

1 01

1

1

10

source

sink

1

** height = 3

• Idea: divert new streams from nodesthat are currently part of the path ofother streams

• stream node tells all neighbors(except stream origin) thatits height has increased

1818

Classification

RoutingProtocolsin WSN

NetworkStructure

ProtocolOperation

FlatNetworkRouting

HierarchicalNetworkRouting

LocationBased

Routing

NegotiationBased

Routing

MultipathBased

Routing

QueryBased

Routing

QoSBased

Routing

CoherentBased

Routing

Source: Al-Karaki / Kamal, 2004

1919

Hierarchical Routing: Characteristics

•• IntendIntend to to increaseincrease flatflatnetworksnetworks''•• efficiencyefficiency

•• scalabilityscalability

•• rolerole basedbased routingrouting schemesschemes•• Cluster Cluster headsheads

•• Cluster Cluster membersmembers

•• OftenOften stepstep--wisewise organizedorganized::•• 1. Cluster 1. Cluster formationformation

•• 2. 2. RoutingRouting

•• ChallengesChallenges•• SelectionSelection of of CHsCHs

•• Cluster Cluster formationformation

•• Medium Medium accessaccess

CM

CH

Sink

2-level hierarchical routing scheme

2020

Hierarchical Routing: LEACH

•• LLowow--EEnergynergy AAdaptive daptive CClusteringlustering HHierarchyierarchy ((HeinzelmanHeinzelman '00)'00)

•• RotatingRotating--CHCH--SchemeScheme / / CHsCHs changechange fromfrom roundround to to roundround

CM

CH

Network Model

Base Station

Threshold Computation

( ) GnnT ∉∀= 0

( ) Gn

PrP

PnT ∈∀

−

=1

mod1

P = cluster head probability

r = number of current round (notframe!)

G = nodes that have not beenclusterhead in the last 1/P rounds

2121

Hierarchical Routing: LEACH (2)Evaluation: NS2-Simulations

Tot

al e

nerg

ydi

ssip

ated

in s

yste

m[J

]

Network diameter

LEACH energy dissipation

100 nodes, message-length 2kb

Energy savings mainly depend ondata aggregation ratio in clusterheads!

2222

Hierarchical Routing: LEACH (3)

•• XLEACH XLEACH –– eXtendedeXtended LEACH (Handy et al. 2002)LEACH (Handy et al. 2002)

•• clustercluster headhead selectionselection basedbased on on energyenergy levellevel::

( )

−

+

−

=max_

_

_

_ 11

1mod1 n

currentns

xman

currentn

E

E

Pdivr

E

E

PrP

PnT

energy level correction

574

746

1104

1337

0

500

1000

1500

LEACH Improved CHS

Life

tim

e (R

ound

s)

FNDHNA

XLEACH

Nodes: 200Area: 200m*200mBase Station Pos.: (100,300)mInitial Energy / Node: 1 JMessage Length: 200 bitCH-Probability: 0.05Path-Loss (intra-cluster): 2Path-Loss (to BS): 2.5

FND=First Node Dies, HNA=Half Nodes Alive

2323

Hierarchical Routing: TEEN / APTEEN

•• TThresholdhreshold sensitive sensitive EEnergynergy EEfficientfficient sensorsensor NNetworketworkprotocolprotocol ((ManjeshwarManjeshwar//AgrawalAgrawal '01)'01)

•• LEACHLEACH--basedbased withwith MultiMulti--LevelLevel--CHsCHs

Network Model

Base Station

simple node 1st level CH 2nd level CH

Principles:

• LEACH: One sensor sample / frame and node (Periodic)

• TEEN: sample sending depends on thresholds (Event-driven)

• Hard Threshold (H) / Soft Threshold (S)

Cluster change

time

Para-meters

Attribute > H

CH receives

msg

(Attr. > H)&

(|Attr.-SV|>S)

CH receives

msg

2424

Hierarchical Routing: TEEN / APTEEN (2)

•• TEEN'sTEEN's drawbackdrawback: no : no transmissionstransmissions belowbelow thresholdsthresholds

•• Solution: Solution: AAdaptive daptive PPeriodiceriodic TThresholdhreshold--sensitivesensitive EEnergynergyEEfficientfficient sensorsensor NNetworketwork protocolprotocol (APTEEN)(APTEEN)

•• CH CH broadcastsbroadcasts::•• AttributesAttributes

•• ThresholdsThresholds

•• TDMATDMA--ScheduleSchedule

•• CountCount Time Time max. max. periodperiod betweenbetween twotwo successivesuccessive reportsreports

Cluster change

time

Parameters& TDMA-Sched.

Attribute > H

CH receives

msg

(Attr. > H)&

(|Attr.-SV|>S)

CH receives

msg

CH receives

msg

Slot fornode i

CH receives

msg

Slot fornode i

2525

Hierarchical Routing: TEEN / APTEEN (3)

Evaluation: NS2-Simulations

Time (s)

Num

ber

of N

odes

Aliv

e

Number of Nodes Alive

• APTEEN/TEEN perform betterthan LEACH because of event-driven operation

• TEEN performs better thanAPTEEN because of no periodic transmissions

• TEEN/APTEEN parametersallow energy/quality trade-offs

• TDMA-schedule requires clocksynchronization

Results:

2626

Hierarchical Routing: Sensor Aggregates Routing

•• Fang/Zhao/Fang/Zhao/GuibasGuibas '03'03•• Sensor Sensor aggregateaggregate: : setset of of nodesnodes in a in a networknetwork satisfyingsatisfying a a groupinggrouping predicatepredicate•• ProtocolsProtocols: : DAMDAM, EBAM, EMLAM, EBAM, EMLAM

Target Monitoring Scenario

Task: Determine number and appr.location of targets in a 2D-field

• targets are signal sources• each single target is assigned

to a 'cluster leader'

DAM: Distributed Aggregate Management

Purpose: Elect local cluster leaders

Leader election by comparing node's heightin the signal field 'landscape'(Leader is higher than all its neighbors)

sample signalamplitude field

Only one packet type for DAM: the 'DAM-packet'

2727

Hierarchical Routing: Sensor Aggregated Routing (2)

DAM: Distributed Aggregate Management

DAM-Packet:

MaxPr MaxID TransPr TransID

stored sensor state at each node:• maxPrHeard, leaderID, • myPr, myID, myParent• participating

A node forwards a received DAM-packet p only if:

p.maxPr > maxPrHeard && p.transPr + δ > myPr

δ = threshold to filter out tiny spurious peaks

DAM problem: undercounting (multiple targets belong to a single cluster leader)

2828

Hierarchical Routing: Sensor Aggregated Routing (3)

EBAM: Energy based activity monitoring

• DAM problem: undercounting (multiple targets belong to a single cluster leader)• EBAM solution: estimate volume of each cluster

single sourcesignal profile

superposedsignal

ceiling

EBAM operation• after DAM-phase, each leaf sensor

reports its reading (up to ceiling) to itsparent

• parents aggregate reports of all leafsand report to their parents

• until cluster leader (root) is reached

leaf 1st level parent 2nd level parent

3rd protocol EMLAM:incorporates target's movement

cluster leader

2929

Classification

RoutingProtocolsin WSN

NetworkStructure

ProtocolOperation

FlatNetworkRouting

HierarchicalNetworkRouting

LocationBased

Routing

NegotiationBased

Routing

MultipathBased

Routing

QueryBased

Routing

QoSBased

Routing

CoherentBased

Routing

Source: Al-Karaki / Kamal, 2004

3030

Location Based Routing: Characteristics

•• NodesNodes addressedaddressed byby locationlocation

•• LocationLocation obtainedobtained byby•• Distance Distance estimationestimation

•• NeighborNeighbor discoverydiscovery

•• BeaconsBeacons

•• GPSGPS

•• Frank Frank saidsaid itit beforebefore ;;--))

3131

Location Based Routing: GAF

•• GGeographicaleographical AAdaptive daptive FFidelity (idelity (XuXu et al. 2001)et al. 2001)

•• Motivation:Motivation: IdleIdle energyenergy dominatesdominates energyenergy consumptionconsumption in in AdAd--hochoc--networksnetworks

•• GAFGAF--SolutionSolution:: putput redundant redundant nodesnodes in in sleepsleep mode mode byby usingusing a a virtualvirtual gridgrid

12

3

45

nominal radio range

if node 2 is awake 3 and 4are extraneous for communicationbetween 1 and 5

Discover redundant nodes with a virtual grid:

12

3

45

A B C

r

r r r

5Rr ≤

R=nominal radio range

Virtual grid size:

3232

Location Based Routing: GAF (2)

GAF state transitions

Three states in GAF:• sleeping: power down radio• discovery: find nodes within the

same grid (initial state)• active: node participates in routing

• node starts in discovery state• after Td , node

• broadcasts discovery message• enters active state• sets Timer Ta• periodically re-broadcasts discovery

message while in active state• timer can be suppressed by other discovery

messages• after Ta , node returns to discovery state• active node can change to sleep state,

when a higher-ranked node handles routing

3333

Other: DCP (Bluetooth)•• DDataata CCollectionollection PProtocolrotocol (Handy '04)(Handy '04)•• CooperationCooperation StrategyStrategy: Clustering: Clustering

•• Cluster Cluster HeadHead, Cluster , Cluster MembersMembers

•• PeriodicPeriodic Cluster Cluster ReorganizationReorganization•• EnergyEnergy consumptionconsumption•• TopologyTopology changeschanges

•• DCP DCP doesdoes notnot maintainmaintain connectionsconnections duringduringsteadysteady--statestate ((unlikeunlike BluetoothBluetooth scatternetsscatternets!)!)

1

32

cluster head

clustermembers

Cluster

- Cluster head selection- Cluster formation- PFA delivery

Collection of Sensor Data

Setup Phase Steady-State Phase

3434

Other: DCP (Bluetooth)

B

12 3

4

57

6

810

9

11

1. Cluster Head Selection

randomly determined

2. Base station Inquiry

detect CH and 1-hop-CM

3. Base station transmits PFAfirst CMs (1,3,4) then CHs (2)

4. Discovered nodes turn off I-Scan"invisible" mode

5. 1-hop-distant CH inquiryCM and CH discovered by BS are not

detected

6. 1-hop-distant CH transmit PFAfirst CMs (6) then CHs (5,7)

BS-Cluster

12

Abbrevations:BS = Base StationCM = Cluster MemberCH = Cluster HeadPFA = Packet Forward Address

Setup Phase in Detail

3535

Other: DCP (Bluetooth)

Steady State Phase in Detail

•• CM CM transfertransfer sensorsensor datadata to CHto CH

•• CH CH preprocesspreprocess sensorsensor datadata ((datadatacompressioncompression//fusionfusion))

•• CH CH forwardforward aggregatedaggregated datadata to PFA/BSto PFA/BS

B

12 3

4

57

6

810

9

11

BS-Cluster

12

Nodes disconnect immediately• clusters are not limited to piconet size• energy savings for low data rates• reduced interference

(How many Bluetooth piconets fit into a room?)

Periodical or event-triggered transmission schemes are applicable!

3636

Open Research Issues*

•• ExploitExploit RedundancyRedundancy•• TieredTiered ArchitecturesArchitectures•• ExploitExploit spatialspatial diversitydiversity and and densitydensity of of sensorsensor//actuatoractuator

networksnetworks•• AchieveAchieve desireddesired global global behaviorbehavior withwith adaptive adaptive localizedlocalized

algorithmsalgorithms•• LeverageLeverage datadata processingprocessing insideinside thethe networknetwork and and exploitexploit

computationcomputation nearnear datadata sourcessources•• Time and Time and locationlocation synchronizationsynchronization•• SelfSelf--configurationconfiguration•• SecureSecure routingrouting

* taken from: Al-Karaki & Kamal 2004

3737

Summary

•• RoutingRouting protocolsprotocols forfor wiredwired networksnetworks and and adad--hochoc networksnetworks areare notnotapplicableapplicable forfor sensorsensor networksnetworks

•• RoutingRouting protocolsprotocols forfor sensorsensor networksnetworks havehave to to bebe•• energyenergy conservingconserving

•• scalablescalable

•• robustrobust

•• fault tolerantfault tolerant

•• selfself--organizingorganizing

•• Most Most routingrouting protocolsprotocols forfor sensorsensor networksnetworks cancan bebe categorizedcategorized intointo•• flatflat ((datadata--centriccentric))

•• hierarchicalhierarchical

•• locationlocation--basedbased

•• DirectedDirected Diffusion, SPIN and LEACH Diffusion, SPIN and LEACH areare ""ancestorsancestors" of " of manymanymodern modern routingrouting protocolsprotocols forfor sensorsensor networksnetworks

3838

•• ThankThank YouYou!!

•• ContactContact: : matthias.handy@unimatthias.handy@uni--rostock.derostock.de