Architectures and Applications for Wireless Sensor Networks (01204525) Network Architecture

Architectures and Architectures and Applications for Applications for Wireless Sensor Wireless Sensor

Networks (01204525)Networks (01204525)

Network ArchitectureNetwork Architecture

Chaiporn JaikaeoChaiporn [email protected]@ku.ac.th

Department of Computer EngineeringDepartment of Computer EngineeringKasetsart UniversityKasetsart University

Materials taken from lecture slides by Karl and Willig

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OutlineOutline Network scenariosNetwork scenarios Optimization goalsOptimization goals Design principlesDesign principles Service interfaceService interface Gateway conceptsGateway concepts

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Typical Views of WSNTypical Views of WSN Self-organizing mobile ad hoc Self-organizing mobile ad hoc

networks (MANETs)networks (MANETs) Peer-to-peer networksPeer-to-peer networks Multi/mobile agent systems and Multi/mobile agent systems and

swarm intellegenceswarm intellegence

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Sensor Network Sensor Network ScenariosScenarios SourcesSources: Any entity that provides : Any entity that provides

data/measurementsdata/measurements SinksSinks: Nodes where information is : Nodes where information is

required required

Source

SinkInternet

Sink

Source

Sink

Source

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Single-Hop vs. Single-Hop vs. MMulti-ulti-hophop Multi-hop networksMulti-hop networks

Send packets to an intermediate nodeSend packets to an intermediate node Intermediate node forwards packet to its Intermediate node forwards packet to its

destinationdestination Store-and-forward Store-and-forward multi-hop networkmulti-hop network Store & forward Store & forward multi-hopping multi-hopping NOT the only NOT the only possible possible solutionsolution E.g., E.g.,

collaborative collaborative networking, networking, network codingnetwork coding

Source

Sink

Obstacle

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Multi-hopping Always Multi-hopping Always Efficient?Efficient? Obvious idea: Multi-hopping is more Obvious idea: Multi-hopping is more

energy-efficient than direct energy-efficient than direct communicationcommunication Suppose we put a relay at distance Suppose we put a relay at distance dd/2/2 Energy for distance Energy for distance dd is reduced from is reduced from cdcd

to 2to 2cc((dd/2)/2)

cc - some constant - some constant - path loss coefficient (- path loss coefficient ( 2) 2)

Usually wrong, or over-simplifiedUsually wrong, or over-simplified Need to take constant offsets for Need to take constant offsets for

powering transmitter, receiver into powering transmitter, receiver into accountaccount

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Multiple Sinks, Multiple Multiple Sinks, Multiple sourcessources

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Different sources of Different sources of mobilitymobility Node mobilityNode mobility Sink mobilitySink mobility Event mobility Event mobility

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Sink Mobility Sink Mobility

Request

Movementdirection

Propagationof answers

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WSN Event MobilityWSN Event Mobility

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Goal: Goal: Quality of ServiceQuality of Service QoS in WSN is more complicated QoS in WSN is more complicated

(compared to MANET)(compared to MANET) Event detection/reporting probabilityEvent detection/reporting probability Event classification error, detection delayEvent classification error, detection delay Probability of missing a periodic reportProbability of missing a periodic report Approximation accuracy (e.g, when WSN Approximation accuracy (e.g, when WSN

constructs a temperature map)constructs a temperature map) Tracking accuracy (e.g., difference between Tracking accuracy (e.g., difference between

true and conjectured position of the pink true and conjectured position of the pink elephant)elephant)

Related goal: robustnessRelated goal: robustness Network should withstand failure of some Network should withstand failure of some

nodesnodes

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Goal: Goal: Energy efficiencyEnergy efficiency Many definitionsMany definitions

Energy per correctly received bitEnergy per correctly received bit Energy per reported (unique) eventEnergy per reported (unique) event Delay/energy tradeoffsDelay/energy tradeoffs Network lifetimeNetwork lifetime

Time to first node failureTime to first node failure Network half-life (how long until 50% of the Network half-life (how long until 50% of the

nodes died?)nodes died?) Time to partitionTime to partition Time to loss of coverageTime to loss of coverage Time to failure of first event notificationTime to failure of first event notification

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Sharpening the DropSharpening the Drop Sacrifice long lifetimes in return for Sacrifice long lifetimes in return for

an improvement in short lifetimesan improvement in short lifetimes

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Goal: Goal: ScalabilityScalability Network should be operational regardless of Network should be operational regardless of

number of nodesnumber of nodes At high efficiencyAt high efficiency

Typical node numbers difficult to guessTypical node numbers difficult to guess MANETs: 10s to 100s MANETs: 10s to 100s WSNs: 10s to 1000s, maybe moreWSNs: 10s to 1000s, maybe more

Requiring to scale to large node numbers Requiring to scale to large node numbers has has seriousserious consequences for network consequences for network architecturearchitecture Might not result in the most efficient solutions Might not result in the most efficient solutions

for small networks!for small networks! Carefully consider actual application needs Carefully consider actual application needs

before looking for scalable solutionsbefore looking for scalable solutions

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Distributed Distributed Organization Organization WSN participants should cooperate in WSN participants should cooperate in

organizing the networkorganizing the network Centralized approach usually not feasibleCentralized approach usually not feasible

Potential shortcomingsPotential shortcomings Not clear whether distributed or Not clear whether distributed or

centralized organization achieves better centralized organization achieves better energy efficiency energy efficiency

Option: Option: “limited centralized”“limited centralized” solution solution Elect nodes for local coordination/controlElect nodes for local coordination/control Perhaps rotate this function over timePerhaps rotate this function over time

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In-Network ProcessingIn-Network Processing WSNs are expected to provide WSNs are expected to provide

informationinformation Gives additional optionsGives additional options E.g., E.g., manipulatemanipulate or or processprocess the data the data

in the networkin the network Main example: aggregation Main example: aggregation

Apply aggregation functions to a Apply aggregation functions to a collection tree in a network collection tree in a network

Typical functions: minimum, maximum, Typical functions: minimum, maximum, average, sum, … average, sum, …

Not amenable functions: median Not amenable functions: median

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Aggregation ExampleAggregation Example

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1

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1

6

1

1

11

1

1

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Signal ProcessingSignal Processing Another form of in-network processingAnother form of in-network processing E.g.,E.g.,

Edge detectionEdge detection Tracking/angle detection of signal sourceTracking/angle detection of signal source

Exploit Exploit temporaltemporal and and spatial spatial correlationcorrelation Observed signals might vary only slowly in Observed signals might vary only slowly in

time time Signals of neighboring nodes are often Signals of neighboring nodes are often

quite similarquite similar Compressive sensingCompressive sensing

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Adaptive FidelityAdaptive Fidelity Adapt data processing effort based on Adapt data processing effort based on

required accuracy/fidelityrequired accuracy/fidelity E.g., event detectionE.g., event detection

When event occurs, increase rate of When event occurs, increase rate of message exchangesmessage exchanges

E.g., temperatureE.g., temperature When temperature is in acceptable When temperature is in acceptable

range, only send temperature values at range, only send temperature values at low resolutionlow resolution

When temperature becomes high, When temperature becomes high, increase resolution and thus message increase resolution and thus message lengthlength

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Data Centric Data Centric NetworkingNetworking Interactions in typical networks are Interactions in typical networks are

addressed to the addressed to the identities identities of nodesof nodes Known as Known as node-centricnode-centric or or address-address-

centriccentric networking paradigm networking paradigm In WSN, specific source of events In WSN, specific source of events

might not be importantmight not be important Several nodes can observe the same Several nodes can observe the same

areaarea Focus on data/results insteadFocus on data/results instead

Data-centric networkingData-centric networking Principal design changePrincipal design change

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Implementation Implementation OptionsOptions Publish/subscribe (NDN – Named Publish/subscribe (NDN – Named

Data Networking)Data Networking) Nodes can Nodes can publishpublish data, can data, can

subscribe subscribe to any particular kind of to any particular kind of datadata

Once data of a certain type has been Once data of a certain type has been published, it is delivered to all published, it is delivered to all subscriberssubscribers

DatabasesDatabases SQL-based requestSQL-based request

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Other Design PrinciplesOther Design Principles Exploit location informationExploit location information Exploit activity patternsExploit activity patterns Exploit heterogeneityExploit heterogeneity

By constructionBy construction By evolutionBy evolution

Cross-layer optimization of protocol Cross-layer optimization of protocol stacks for WSNstacks for WSN Goes against grain of standard Goes against grain of standard

networkingnetworking Promises big performance gainsPromises big performance gains

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Interfaces to Protocol Interfaces to Protocol StacksStacks The world’s all-purpose network interface: The world’s all-purpose network interface:

socketssockets Good for transmitting data from one sender to one Good for transmitting data from one sender to one

receiverreceiver Not well matched to WSN needs (ok for ad hoc Not well matched to WSN needs (ok for ad hoc

networks)networks)

App as another componentApp as another component Well-designed interfaceWell-designed interface

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Gateways in Gateways in WSN/MANETWSN/MANET Allow remote access to/from the WSNAllow remote access to/from the WSN Bridge the gap between different Bridge the gap between different

interaction semanticsinteraction semantics E.g., data vs. address-centric networkingE.g., data vs. address-centric networking

Need support for different radios/protocolsNeed support for different radios/protocols

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WSN to Internet WSN to Internet CommunicationCommunication E.g., deliver an alarm message to an Internet hostE.g., deliver an alarm message to an Internet host IssuesIssues

Need to find a gateway (integrates routing & service discovery)Need to find a gateway (integrates routing & service discovery) Choose “best” gateway if several are availableChoose “best” gateway if several are available How to find Alice or Alice’s IP?How to find Alice or Alice’s IP?

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Internet to WSN Internet to WSN communication communication How to find the right WSN to answer a How to find the right WSN to answer a

need? need? How to translate from IP protocols to WSN How to translate from IP protocols to WSN

protocols, semantics? protocols, semantics?

Gatewaynodes

Remote requester

Internet Gateway

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Gatewaynodes

Internet

Gateway

WSN tunnelingWSN tunneling Use the Internet to “tunnel” WSN Use the Internet to “tunnel” WSN

packets between two remote WSNs packets between two remote WSNs

6LoWPAN6LoWPAN IPvIPv66 over over LoLow-power w-power WWireless ireless

PPersonal ersonal AArea rea NNetworksetworks Nodes communicate using IPv6 Nodes communicate using IPv6

packetspackets An IPv6 packet is carried in the An IPv6 packet is carried in the

payload of IEEE 802.15.4 data payload of IEEE 802.15.4 data framesframes

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Example 6LoWPAN Example 6LoWPAN SystemsSystems

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SummarySummary Network architectures for WSNs look quite Network architectures for WSNs look quite

different from typical networks in many different from typical networks in many aspectsaspects

Data-centric paradigm opens new Data-centric paradigm opens new possibilities for protocol designpossibilities for protocol design

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Architectures and Applications for Wireless Sensor Networks (01204525) Network Architecture