sensor networks unit wise 4 ppt units ppt

CONTENTS:
1.1. Challenges for wireless sensor networks
1.2. Characteristics requirements-required mechanisms,
1.3. Difference between mobile ad-hoc and sensor networks,
1.4. Applications of sensor networks-
1.5 Enabling technologies for wireless sensor networks
UNIT-I
OUTCOMES:
To understand network architecture, node discovery and localization, deployment strategies, fault
tolerant and network security

UNIT-I
OUTCOMES:
To understand network architecture, node discovery and localization, deployment strategies, fault
tolerant and network security
•Wireless sensor networks combine sensing, processing and networking over miniaturized
embedded devices → sensor nodes.
Wireless sensor networks are networks that consists of sensors which are distributed in an ad
hoc manner. These sensors work with each other to sense some physical phenomenon and then
the information gathered is processed to get relevant results.
Wireless sensor networks consists of protocols and algorithms with self-organizing capabilities.

1.1. Challenges for wireless sensor networks
INTRODUCTION:
Wirelesssensornetworks
(WSNs)havebeenconsideredas
oneofthemostimportant
technologiesthatareenabledby
recentadvancesin–
Micro-electronic-mechanical-
systems(MEMS) Wireless
Communicationtechnologies.

.
Introduction
Infrastructure Based Wireless Network
Typical Wireless Network: Based on Infrastructure -Eg: GSM , UMTS
Base stations connected to a wired backbone network

.
Introduction
Infrastructure Free Wireless Network
Military Networking: Tanks, Soldiers, etc.,
Finding out empty parking lots in a city, without asking a server
Search and Rescue in an advance
Personal Area Networking (Watch, Glasses, PDA, Medical Appliances….etc.,)

.
1.1. Challenges for wireless sensor networks
WSNcanhandlesuchawiderangeofapplicationtypes.Nonetheless,certaincommontraits
appear,especiallywithrespecttothecharacteristicsandtherequiredmechanismsofsuch
systems.
Realizingthesecharacteristicswithnewmechanismsisthemajorchallengeofthevisionof
wirelesssensornetworks.
Characteristicrequirements:Thefollowingcharacteristicsaresharedamongmostofthe
applicationexamplesdiscussedabove:
1. Type of service
2. Quality of service
3. Fault tolerance
4.Lifetime
5. Scalability
6. Wide range of densities
7. Programmability
8. Maintainability

.
1.1. Challenges for wireless sensor networks
Heterogeneity
The devices deployed maybe of various types and need to collaborate with each other.
Distributed Processing
The algorithms need to be centralized as the processing is carried out on different
nodes.
Low Bandwidth Communication
The data should be transferred efficiently between sensors
Large Scale Coordination
The sensors need to coordinate with each other to produce required results
Utilization of Sensors
The sensors should be utilized in a ways that produce the maximum performance and use less
energy.
Real Time Computation
The computation should be done quickly as new data is always being generated.

.
1.1. Challenges for wireless sensor networks
Energy Efficiency
Limited storage and computation
Low bandwidth and high error rates
Errors are common
-Wireless communication
-Noisy measurements
-Node failure are expected
Scalability to a large number of sensor nodes
Survivability in harsh environments
Experiments are time-and space-intensive

.
1.2. Characteristics requirements-required mechanisms
Required mechanisms
Torealizetheserequirements,innovativemechanismsforacommunicationnetworkhavetobe
found,aswellasnewarchitectures,andprotocolconcepts.
Aparticularchallengehereistheneedtofindmechanismsthataresufficientlyspecifictothe
idiosyncrasiesofagivenapplicationtosupportthespecificqualityofservice,lifetime,and
maintainabilityrequirements.
Some of the mechanisms that will form typical parts of WSNs are:
Multi-hop wireless communication
Energy-efficient operation
Auto-configuration
Collaboration and in-network processing
Data centric
Locality
Exploit trade-offs

.
1.2. Characteristics requirements-required mechanisms
Conventional Networks WSN
General purpose design (many
applications)
Serving a single application or a bouquet of
applications
Network Performance and Latency Energy is the primary challenge
Devices and networks operate in controlled
/ mild environments (or over an
appropriate infrastructure)
Unattended, harsh conditions & hostile
environments
Easily accessible Physical access is difficult / undesirable
Global knowledge is feasible and
centralized management is possible
Localized decisions –no support by central entity
Differences between Conventional and Wireless sensor networks

.
1.3. Difference between mobile ad-hoc and sensor networks
Anadhocnetworkisanetworkthatissetup,foraspecificpurpose,tomeetaquicklyappearing
communicationneed.
Thesimplestexampleofanadhocnetworkisperhapsasetofcomputersconnectedtogethervia
cablestoformasmallnetwork,likeafewlaptopsinameetingroom.Inthisexample,theaspectof
self-configurationiscrucial–thenetworkisexpectedtoworkwithoutmanualmanagementor
configuration.
Wirelesssensornetworksmainlyusebroadcastcommunicationwhileadhocnetworks
usepoint-to-pointcommunication.
Unlikeadhocnetworkswirelesssensornetworksarelimitedbysensorslimitedpower,
energyandcomputationalcapability.
SensornodesmaynothaveglobalIDbecauseofthelargeamountofoverheadandlarge
numberofsensors.

.
1.3 . Difference between mobile ad-hoc and sensor networks
Key characteristic that distinguishes them from remaining networks is the
reasoning of existence:
Collect information from the physical environment –regardless of
how easily accessible that is;
Couple the end-users directly to the sensor measurements ( cyber to physical space);
Provide information that is precisely localized (in spatio-temporal
terms) according to the application demands;
Establish a bi-directional link with the physical space (remote & adaptable actuation
based on the sensing stimulus)

.
1.4. Applications of sensor networks
Examples of Wireless sensor Networks

.
1.4. Applications of sensor networks
The applications can be divided in three categories:
1. Monitoring of objects.
2. Monitoring of an area.
3. Monitoring of both area and objects.
Monitoring Area:
1. Environmental and Habitat Monitoring
2. Precision Agriculture
3. Indoor Climate Control
4. Military Surveillance
5. Treaty Verification
6. Intelligent Alarms

.
1.4. Applications of sensor networks
•Precisionagricultureaimsatmaking
culturaloperationsmoreefficient,
whilereducingenvironmental
impact.
•Theinformationcollectedfrom
sensorsisusedtoevaluateoptimum
sowingdensity,estimatefertilizers
andotherinputsneeds,andtomore
accuratelypredictcropyields.

.Monitoring objects:
1.4. Applications of sensor networks
Structural Monitoring
Eco-physiology
Condition-based Maintenance
Medical Diagnostics
Urban terrain mapping
Example: Condition-based Maintenance: Intel fabrication plants
Sensors collect vibration data, monitor wear and tear; report data in real-time
Reduces need for a team of engineers; cutting costs by several orders of magnitude

.
1.4. Applications of sensor networks
Monitoring Interactions between Objects and Space
Wildlife Habitats
Disaster Management
Emergency Response
Ubiquitous Computing
Asset Tracking
Health Care
Manufacturing Process Flows

.
1.4. Applications of sensor networks
The Zebra-Net Project
Collar-mounted sensors monitor zebra movement
in Kenya

.
1.4. Applications of sensor networks
Future of WSN: Smart Home / Smart Office
Sensors controlling appliances and
electrical devices in the house.
Better lighting and heating in office
buildings.
The Pentagon building has used
sensors extensively.

.
1.5 Enabling technologies for wireless sensor networks
Exploit spatially and temporally dense, in situ, sensing and actuation
Buildingsuchwirelesssensor
networkshasonlybecome
possiblewithsomefundamental
advances in enabling
technologies.
•Miniaturization of hardware
•Energy Scavenging
Cost
MEMS’isakeytechnologyformanufacturingtiny,low-cost,andlow–powersensor
nodes.Byintegratingdifferentcomponentstogetherintoasingleprocess,thesizeofa
sensornodecansignificantlybereduced.

.
1.5 Enabling technologies for wireless sensor networks
Smallerfeaturesizesinchipshavedrivendownthepowerconsumptionofthebasic
componentsofasensornode-likemicrocontrollers,memorychips,radiomodems,etc.;have
becomemuchmoreenergyefficient.
Reduced chip size and improved energy efficiency is accompanied by reduced cost, which is
necessary to make redundant deployment of nodes affordable.
Next to processing and communication, the actual sensing equipment is the third relevant
technology.
Thesethreebasicpartsofasensornodehavetoaccompanybypowersupply.Thisrequires,
dependingonapplication,highcapacitybatteriesthatlastforlongtimes,thatis,haveonlya
negligibleself-dischargerate,andthatcanefficientlyprovidesmallamountsofcurrent.

.
1.5 Enabling technologies for wireless sensor networks
To achieve low -power consumption at the node level, it is necessary to incorporate power
awareness and energy optimization in hardware design for sensor networks.
Power consumption can further be reduced through efficiently operating various system
resources using some dynamic power management (DPM) technique
•Ideally, a sensor node also has a device for energy scavenging, recharging the battery
with energy gathered from the environment –solar cells or vibration-based power
generation are conceivable options.
Such a concept requires the battery to be efficiently chargeable with small amounts of
current, which is not a standard ability

1. Discuss challenges and hurdles for wireless sensor networks.
2. Explain the historical background of sensor networks.
3. Various applications of wireless sensor networks.
4. Explain Industrial Automation
5. Discuss about Home Automation
Assignment Question

Sensor node Architectures
AWirelessSensorNetworkisonekindofwirelessnetworkincludesalargenumber
ofcirculating,self-directed,minute,lowpowereddevicesnamedsensornodes
calledmotes.
Thesenetworkscertainlycoverahugenumberofspatiallydistributed,little,
battery-operated,embeddeddevicesthatarenetworkedtocaringlycollect,process,
andtransferdatatotheoperators,andithascontrolledthecapabilitiesof
computing&processing.Nodesarethetinycomputers,whichworkjointlytoform
thenetworks.

Contents:
2.1. Single-node architecture -hardware components,
2.2. Energy consumption of sensor nodes,
2.3. Operating systems and Execution environments
2.4. Network architecture -sensor network scenarios,
2.5. Optimization goals and figures of merit, gateway concepts.
Architectures

2.1. Single-node architecture -hardware components
.
•ControllerA controller to
process all the relevant data,
capable of executing arbitrary
code.
•MemorySome memory to store
programs and intermediate data;
usually, different types of
memory are used for programs
and data.
•Sensors and actuatorsThe actual interface to the physical world: devices that can observe or
control physical parameters of the environment.
•CommunicationTurning nodes into a network requires a device for sending and receiving
information over a wireless channel

.
2.1. Single-node architecture -hardware components
•Thesensornodeisamulti-functional,energyefficientwirelessdevice.Theapplicationsofmotes
inindustrialarewidespread.
•Acollectionofsensornodescollectsthedatafromthesurroundingstoachievespecific
applicationobjectives.
•Thecommunicationbetweenmotescanbedonewitheachotherusingtransceivers.Ina
wirelesssensornetwork,thenumberofmotescanbeintheorderofhundreds/eventhousands.
•Incontrastwithsensornetworks,AdHocnetworkswillhavefewernodeswithoutany
structure.
PowersupplyAsusuallynotetheredpowersupplyisavailable,someformsofbatteriesare
necessarytoprovideenergy.Sometimes,someformofrechargingbyobtainingenergyfromthe
environmentisavailableaswell(e.g.solarcells).
Eachofthesecomponentshastooperatebalancingthetrade-offbetweenassmallanenergy
consumptionaspossibleontheonehandandtheneedtoful-filtheirtasksontheotherhand.
Forexample,boththecommunicationdeviceandthecontrollershouldbeturnedoffaslongas
possible.

2.1. Single-node architecture -hardware components
Hardware Components:
Power supply
Microcontrollers vs Microprocessors, FPGAs and ASIC
Memory
Communication devices
Sensors & Actuators
-Passive omni-directional sensors
-Passive narrow-beam sensors
-Active sensors
-Actuators
Memory
Thememorycomponentisfairlystraightforward.Evidently,thereisaneedforRandomAccess
Memory(RAM)tostoreintermediatesensorreadings,packetsfromothernodes,andsoon.
WhileRAMisfast,itsmaindisadvantageisthatitlosesitscontentifpowersupplyisinterrupted.
ProgramcodecanbestoredinRead-OnlyMemory(ROM)or,moretypically,inElectricallyErasable
ProgrammableRead-OnlyMemory(EEPROM)orflashmemory(thelaterbeingsimilartoEEPROM
butallowingdatatobeerasedorwritteninblocksinsteadofonlyabyteatatime).

2.1. Single-node architecture -hardware components
Communication device:
Choice of transmission medium
Thecommunicationdeviceisusedtoexchangedatabetweenindividualnodes.Insomecases,
wiredcommunicationcanactuallybethemethodofchoiceandisfrequentlyappliedinmany
sensorNetworklikesettings(usingfieldbuseslikeProfi-bus,LON,CAN,orothers).
Thecommunicationdevicesforthesenetworksarecustomoff-the-shelfcomponents.
Transceivers
Foractualcommunication,bothatransmitterandareceiverarerequiredinasensornode.The
essentialtaskistoconvertabitstreamcomingfromamicrocontroller(orasequenceofbytesor
frames)andconvertthemtoandfromradiowaves.
Forpracticalpurposes,itisusuallyconvenienttouseadevicethatcombinesthesetwotasksin
asingleentity.Suchcombineddevicesarecalledtransceivers.
Usually,half-duplexoperationisrealizedsincetransmittingandreceivingatthesametimeona
wirelessmediumisimpracticalinmostcases(thereceiverwouldonlyheartheowntransmitter
anyway).

.
2.1. Single-node architecture -hardware components
Transceiver tasks and characteristics
To select appropriate transceivers, a number of characteristics should be taken into account.
The most important ones are:
Service to upper layer
Power consumption and energy efficiency
Carrier frequency and multiple channels
State change times and energy
Data rates
Modulations
Coding
Noise figure The noise figure
Gain
Power efficiency
Receiver sensitivity
Range
Blocking performance
Out of band emission
Carrier sense and RSSI
Frequency stability and Voltage range

.
2.1. Single-node architecture -hardware components
A fairly common structure of transceivers is
into the Radio Frequency (RF) front end and
the baseband part:
• The radio frequency front end performs
analog signal processing in the actual radio
frequency band, whereas
• The baseband processor performs all signal processing in the digital domain and
communicates with a sensor node’s processor or other digital circuitry.

. Transceiver operational states:
many transceivers can distinguish four operational states :
Transmitin the transmit state, the transmit part of the transceiver is active and the antenna radiates
energy.
Receivein the receive state the receive part is active.
2.1. Single-node architecture -hardware components
IdleA transceiver that is ready to receive but is not currently receiving anything is said to be in an
idle state.
SleepInthesleepstate,significantpartsofthetransceiverareswitchedoff.
Therearetransceiversofferingseveraldifferentsleepstates,seereferenceforadiscussionof
sleepstatesforIEEE802.11transceivers.Thesesleepstatesdifferintheamountofcircuitry
switchedoffandintheassociatedrecoverytimesandstartupenergy

.
2.1. Single-node architecture -hardware components
Sensors and actuators
Without the actual sensors and actuators, a wireless sensor network would be beside the point
entirely.
But as the discussion of possible application areas has already indicated, the possible range of
sensors is vast.
It is only possible to give a rough idea on which sensors and actuators can be used in a WSN
Sensors
Sensors can be roughly categorized into three categories
Passive, omni-directional sensors
Passive, narrow-beam sensors
Active sensors

.
2.1. Single-node architecture -hardware components
Power supply of sensor nodes
Foruntetheredwirelesssensornodes,thepowersupplyisacrucialsystem
component.Thereareessentiallytwoaspects:First,storingenergyandproviding
powerintherequiredform;
second,attemptingtoreplenishconsumedenergyby“scavenging”itfromsomenode-
externalpowersourceovertime.
Storing power is conventionally done using batteries. As a rough orientation, a normal
AA battery stores about 2.2–2.5 Ah at 1.5 V.
Storing energy: Batteries
Traditional batteries
Capacity
Capacity under load
Self-discharge
Efficient recharging, Relaxation, Unconventional energy stores and DC–DC Conversion

.
2.1. Single-node architecture -hardware components
Energy scavenging
Someoftheunconventionalenergy
storesdescribedabove–fuelcells,micro
heatengines,radioactivity
–convertenergyfromsomestored,
secondaryformintoelectricityinaless
directandeasytousewaythananormal
batterywoulddo.Theentireenergy
supplyisstoredonthenodeitself–once
thefuelsupplyisexhausted,thenode
fails.
Toensuretrulylong-lastingnodesand
wirelesssensornetworks,suchalimited
energystoreisunacceptable.Rather,
energyfromanode’senvironmentmust
betappedintoandmadeavailable
tothenode–energyscavenging
shouldtakeplace.
A MEMS device for converting vibrations to electrical
energy, based on a variable capacitor .Reproduced by
permission of IEEE

.
2.2 Energy Consumption of Sensor Nodes
Attimet1,thedecisionwhetheror
notacomponent(say,the
microcontroller)istobeputinto
sleepmodeshouldbetakento
reducepowerconsumptionfrom
PactivetoPsleep.
Ifitremainsactiveandthenext
eventoccursattimetevent,then
atotalenergyofEactive=
Pactive(tevent−t1)hasbespent
uselesslyidling.
Puttingthecomponentintosleepmode,ontheotherhand,requiresatimeτdownuntilsleepmode
hasbeenreached;asasimplification,assumethattheaveragepowerconsumptionduringthisphase
is(Pactive+Psleep)/2.
Then,Psleepisconsumeduntiltevent.Intotal,τdown(Pactive+Psleep)/2+(tevent−t1−
τdown)Psleepenergyisrequiredinsleepmodeasopposedto(tevent−t1)Pactivewhenremaining
active.

.
2.2 Energy Consumption of Sensor Nodes
Microcontroller energy consumption
Basic power consumption in discrete operation
states:
Intel Strong ARM
The Intel Strong ARM ,In normal mode, all parts of
the processor are fully powered.
Power consumption is up to 400 mW.
• In idle mode, clocks to the CPU are stopped; clocks that pertain to peripherals are active. Any
interrupt will cause return to normal mode. Power consumption is up to 100 mW.
• In sleep mode, only the real-time clock remains active. Wakeup occurs after a timer interrupt and
takes up to 160 ms. Power consumption is up to 50 μW.
Energy per operation with dynamic power scaling on an Intel
Strong ARM SA-1100

2.3 Operating systems and Execution Environments
1.Embeddedoperatingsystems:The
traditionaltasksofanoperatingsystem
arecontrollingandprotectingtheaccess
toresources(includingsupportfor
input/output)andmanagingtheir
allocationtodifferentusersaswellasthe
supportforconcurrentexecutionof
severalprocessesandcommunication
betweentheseprocesses.
2.2.Programming paradigms and
applicationprogramming interfaces
(concurrentprogramming):
-Process-basedconcurrency
-Event-basedprogramming
-Interfacestotheoperating
systems

.
2.3 Operating systems and Execution Environments
Event based programming
model:
Suchaneventhandlercaninterrupt
theprocessingofanynormalcode,but
asitisverysimpleandshort,itcanbe
requiredtoruntocompletioninall
circumstanceswithoutnoticeably
disturbingothercode
Event handlers cannot interrupt each other (as this would in turn require complicated stack
handling procedures) but are simply executed one after each other.

CONTENTS:
2.4. Network architecture -sensor network scenarios,
2.5. Optimization goals and figures of merit, gateway concepts
OUTCOMES:
Unit 2:Network Architecture
To Discuss About network architecture and optimization goals with the figure of Merit Concepts

.
2.4. Network architecture -sensor network scenarios
Three types of sinks in a very simple single-hop sensor network
Types of Sources and sinks:
-Single hop versus Multi hop
Fromthebasicsofradiocommunicationandtheinherentpowerlimitationofradiocommunication
followsalimitationonthefeasibledistancebetweenasenderandareceiver.Becauseofthis
limiteddistance,thesimple,directcommunicationbetweensourceandsinkisnotalwayspossible,
specificallyinWSNs,whichareintendedtocoveralotofground(e.g.inenvironmentalor
agricultureapplications)orthatoperateindifficultradioenvironmentswithstrongattenuation

.Multi hop network:
2.4. Network architecture -sensor network scenarios
Toovercomesuchlimiteddistances,anobvious
wayoutistouserelaystations,withthedata
packetstakingmultihopsfromthesourcetothe
sink.
Thisconceptofmulti-hopnetworks is
particularlyattractiveforWSNsasthesensor
nodesthemselvescanactassuchrelaynodes,
foregoingtheneedforadditionalequipment
Depending on the particular application, the likelihood of having an intermediate sensor node at
the right place can actually be quite high

.
2.4. Network architecture -sensor network scenarios
Multiple sources and/or multiple sinks
Inmanycases,therearemultiplesourcesand/ormultiplesinkspresent.Inthemostchallenging
case,multiplesourcesshouldsendinformationtomultiplesinks,whereeitherallorsomeofthe
informationhastoreachallorsomeofthesinks.Figureillustratesthesecombinations.

.
2.4. Network architecture -sensor network scenarios
Three types of
Mobility
Node mobility
Sink mobility
Event mobility
Communicationprotocols
forWSNswillhaveto
render appropriate
supportfortheseformsof
mobility.
Inparticular,event
mobility is quite
uncommon,comparedto
previousformsofmobile
orwirelessnetworks.
A mobile sinks moves through a mobile sensor network as a
information being retrieves on its behalf

.
2.5. Optimization goals and figures of merit, gateway concepts
Forallthesescenariosandapplicationtypes,differentformsofnetworkingsolutionscanbefound.
Thechallengingquestionishowtooptimizeanetwork,howtocomparethesesolutions,howto
decidewhichapproachbettersupportsagivenapplication,andhowtoturnrelativelyimprecise
optimizinggoalsintomeasurablefiguresofmerit?Whileageneralanswerappearsimpossible
consideringthelargevarietyofpossibleapplications,afewaspectsarefairlyevident
1.Quality of service
-Event detection/reporting probability
-Event classification error
-Event detection delay
-Missing reports
-Approximation accuracy
-Tracking accuracy
2. Energy efficiency
-Energy/correctly received
-Energy/reported event
-Delay
-N/w Life time
3. Scalability
4. Robustness

Area of sensor nodes detecting an event-an elephant-that moves through the network along
with the event source
2.5. Optimization goals and figures of merit, gateway concepts

2.5. Optimization goals and figures of merit, gateway concepts
NeedforGateways
Forpracticaldeployment,asensornetworkonlyconcernedwithitselfisinsufficient.Thenetwork
ratherhastobeabletointeractwithotherinformationdevices,
forexample,auserequippedwithaPDAmovinginthecoverageareaofthenetworkorwitha
remoteuser,tryingtointeractwiththesensornetworkviatheInternet(thestandardexampleisto
readthetemperaturesensorsinone’shomewhiletravelingandaccessingtheInternetviaa
wirelessconnection).Figureshowsthisnetworkingscenario.

.
2.5. Optimization goals and figures of merit, gateway concepts
1. WSN to Internet communication
Asensornodewantstodeliveranalarm
messagetosomeInternethost.
Thefirstproblemtosolveisakintoad
hocnetworks,namely,howtofindthe
gatewayfromwithinthenetwork.
Basically, a routing problem to a node that offers a specific service has to be solved, integrating
routing and service discovery

.
2.5. Optimization goals and figures of merit, gateway concepts
2. Internet to WSN communication
ThecaseofanInternet-basedentitytrying
toaccessservicesofaWSNisevenmore
challenging.
Thisisfairlysimpleifthisrequesting
terminalisabletodirectlycommunicate
withtheWSN,forexample,amobile
requesterequippedwithaWSNtransceiver,
andalsohasallthenecessaryprotocol
componentsatitsdisposal
In this case, the requesting terminal can be a direct part of the WSN and no particular treatment is
necessary

.
2.5. Optimization goals and figures of merit, gateway concepts
3. WSN tunneling
Inadditiontothesescenariosdescribing
actualinteractionsbetweenaWSNand
Internetterminals,thegatewayscanalso
actassimpleextensionsofoneWSNto
anotherWSN.
Theideaistobuildalarger,“virtual”WSN
outofseparateparts,transparently
“tunneling”allprotocolmessagesbetween
thesetwonetworksandsimplyusingthe
Internetasatransportnetwork.
This can be attractive, but care has to be taken not to confuse the virtual link between two gateway
nodes with a real link; otherwise, protocols that rely on physical properties of a communication
link can get quite confused.

.
Assignment Question
1.Write short notes on Berkeley Motes.
2.Explain single node architecture.
3.Explain Gateway concepts.
4.Explain network architecture and sensor network scenarios.
5.What is the function of controller in sensor node architecture.

INTRODUCTION:
The physical layer is mostly concerned with modulation and demodulation of digital data; this task
is carried out by so-called transceivers. In sensor networks, the challenge is to find modulation
schemes and transceiver architectures that are simple, low cost, but still robust enough to provide
the desired service.
Medium Access Control (MAC) protocols is the first protocol layer above the Physical Layer (PHY)
and consequently MAC protocols are heavily influenced by its properties. The fundamental task of
any MAC protocol is to regulate the access of a number of nodes to a shared medium in such a way
that certain application-dependent performance requirements are satisfied.
UNIT-III: Physical Layer and MAC Protocols

Contents:
3.1. physical layer and transceiver design considerations,
3.2. MAC protocols for wireless sensor networks,
3.3. Low duty cycle protocols and wakeup concepts -S-MAC,
-Zigbee: IEEE 802.15.4 MAC layer,
-the mediation device protocol,
-wakeup radio concepts,
3.4. Address and name management,
3.5. Assignment of MAC addresses,
3.6. Routing protocols
-Energy-efficient routing,
-Geographic routing.
UNIT-III: Physical Layer and MAC Protocols

In sensor networks, the challenge is to find modulation schemes and transceiver architectures that
are simple, low cost, but still robust enough to provide the desired service.
Wirelesschannelandcommunicationfundamentals:
1.Frequencyallocation
2.Modulationanddemodulation
3.Wavepropagationeffectsandnoise
-Reflection,diffraction,scattering,dopplerfading
-Pathlossandattenuation
-Noiseandinterference
-Symbolsandbiterrors
4.Channelmodels
5.Spread-spectrumcommunications
-Direct Sequence Spread Spectrum (DSSS) and
-Frequency Hopping Spread Spectrum (FHSS)
6. Packet transmission and synchronization
-Carrier synchronization
-Bit/symbol synchronization
-Frame synchronization
INTRODUCTION

Introduction: For actual communication, both a transmitter and a receiver are required in a sensor
node. The essential task is to convert a bit stream coming from a and convert them to and from radio
waves. For practical purposes, it is usually convenient to use a device that combines these two tasks
in a single entity. Such combined devices are called “transceivers”
3.1. Physical Layer and Transceiver Design Considerations
Some of the most crucial points influencing PHY design in wireless sensor networks are:
• Low power consumption.
• As one consequence: small transmit power and thus a small transmission range.
• As a further consequence: low duty cycle. Most hardware should be switched off or operated in
a low-power standby mode most of the time.
• Comparably low data rates, on the order of tens to hundreds kilobits per second, required.
• Low implementation complexity and costs.
• Low degree of mobility.
• A small form factor for the overall node

In general, in sensor networks, the challenge is to find modulation schemes and transceiver
architectures that are simple, low-cost but still robust enough to provide the desired service.
3.1. Physical Layer and Transceiver Design Considerations
1.Energyusageprofile:
Thechoiceofasmalltransmitpowerleadstoanenergyconsumptionprofiledifferentfrom
otherwirelessdeviceslikecellphones.
Theradiatedenergyissmall,typicallyontheorderof0dBm(correspondingto1mW).On
theotherhand,theoveralltransceiver(RFfrontendandbasebandpart)consumesmuch
moreenergythanisactuallyradiated.
Asecondkeyobservationisthatforsmalltransmitpowersthetransmitandreceivemodes
consumemoreorlessthesamepower;itisevenpossiblethatreceptionrequiresmore
powerthantransmission.
Athirdkeyobservationistherelativecostsofcommunicationsversuscomputationina
sensornode.Clearly,acomparisonofthesecostsdependsforthecommunicationpartonthe
BERrequirements,range,transceivertype,andsoforth,andforthecomputationpartonthe
processortype,theinstructionmix,andsoon.

2. Choice of modulation scheme:
A crucial point is the choice of modulation scheme. Several factors have to be balanced
here: the required and desirable data rate and symbol rate, the implementation
complexity, the relationship between radiated power and target BER, and the expected
channel characteristics.
Table:BandwidthefficiencyηBWandEb/N0[dB]requiredatthereceivertoreachaBERof10−6overanAWGNchannel
form-aryorthogonalFSKandPSK
3.1. Physical Layer and Transceiver Design Considerations

3. Dynamic modulation scaling
To determine the optimal scheme for a given combination of BER target, range, packet sizes and so
forth, such an optimum is only valid for short time; as soon as one of the constraints changes, the
optimum can change, too.
In addition, other constraints like delay or the desire to achieve high throughput can dictate to
choose higher modulation schemes.
Therefore, it is interesting to consider methods to adapt the modulation scheme to the current
situation. Such an approach, called dynamic modulation scaling.
4. Antenna considerations
If the antenna is much smaller than the carrier’s wavelength, it is hard to achieve good antenna
efficiency, that is, with ill-sized antennas one must spend more transmit energy to obtain the same
radiated energy.
with small sensor node cases, it will be hard to place two antennas with suitable distance to achieve
receive diversity
3.1. Physical Layer and Transceiver Design Considerations

Medium access control (MAC) protocols solve a seemingly simple task: they coordinate
the times where a number of nodes access a shared communication medium
an “un-overseeable” number of protocols have emerged in more than thirty years of
research in this area. They differ, among others, in the types of media they use and in the
performance requirements for which they are optimized.
Medium Access Control (MAC) protocols is the first protocol layer above the Physical
Layer (PHY) and consequently MAC protocols are heavily influenced by its properties.
The fundamental task of any MAC protocol is to regulate the access of a number of nodes
to a shared medium in such a way that certain application-dependent performance
requirements are satisfied
3.2. MAC PROTOCOLS for WSN

The most important performance requirements for MAC protocols are throughput ,
efficiency,
stability,
fairness,
low access delay and
low transmission delay
as well as a low overhead
The overhead in MAC protocols can result from per-packet overhead (MAC headers and trailers),
collisions, or from exchange of extra control packets.
Collisions can happen if the MAC protocol allows two or more nodes to send packets at the same
time. Collisions can result in the inability of the receiver to decode a packet correctly, causing the
upper layers to perform a retransmission.
For time-critical applications, it is important to provide deterministic or stochastic guarantees on
delivery time or minimal available data rate.
Sometimes, preferred treatment of important packets over unimportant ones is required, leading
to the concept of priorities
3.2.Requirements and design constraints for wireless MAC protocols

3.2.Requirements and design constraints for wireless MAC protocols
1. Hidden Terminal Problem
2. Exposed terminal scenario
wehavethreenodesA,B,andCthatarearrangedsuchthatAandBareinmutualrange,Band
Careinmutualrange,butAandCcannotheareachother.AssumethatAstartstotransmita
packettoBandsometimelaternodeCalsodecidestostartapackettransmission.Acarrier-
sensingoperationbyCshowsanidlemediumsinceCcannothearA’ssignals.WhenCstartsits
packet,thesignalscollideatBandbothpacketsareuseless.

Important classes of MAC protocols:
1.Fixed assignment protocols
-TDMA, FDMA, CDMA, and SDMA.
2.Demand assignment protocols
-HIPERLAN/2 protocol
-DQRUMA
-MASCARA protocol
-polling schemes
3. Random access protocols
-CSMA protocols
-non-persistent CSMA
-persistent CSMA
3.2.Requirements and design constraints for wireless MAC protocols

TheRTS/CTShandshakeasusedinIEEE802.11isbasedontheMACAWprotocol
anditusesonlyasinglechannelandtwospecialcontrolpackets.
3.2.Requirements and design constraints for wireless MAC protocols
RTS/CTS handshake
in IEEE 802.11

FurtherproblemoftheRTS/CTShandshakeisitssignificantoverheadoftwocontrolpacketsper
datapacket,notcountingtheacknowledgmentpacket.Ifthedatapacketissmall,thisoverhead
mightnotpayoffanditmaybesimplertousesomeplainCSMAvariant
3.2 Requirements and Design constraints for wireless MAC
Two problems in
RTS/CTS Handshake

3.2 MAC Protocols for WSN
Balance of requirements
Energy problems on the MAC layer
-Collisions
-Overhearing
-Protocol overhead
-Idle listening
Structure
-contention-based
-schedule-based protocols

Balance of requirements:
3.2 MAC Protocols for WSN
Thebalanceofrequirementsisdifferentfromtraditional(wireless)networks.
Additionalrequirementscomeup,firstandforemost,theneedtoconserveenergy.
TheimportanceofenergyefficiencyforthedesignofMACprotocolsisrelativelynew
andmanyofthe“classical”protocolslikeALOHAandCSMAcontainnoprovisions
towardthisgoal.
Othertypicalperformancefigureslikefairness,throughput,ordelaytendtoplaya
minorroleinsensornetworks.
FairnessisnotimportantsincethenodesinaWSNdonotrepresentindividuals
competingforbandwidth,buttheycollaboratetoachieveacommongoal.
Theaccess/transmissiondelayperformanceistradedagainstenergy
conservation,andthroughputismostlynotanissueeither.

3.2 MAC Protocols for WSN
Energy problems on the MAC layer
Further important requirements for MAC protocols are scalability and robustness
against frequent topology changes, as caused for example by nodes powering down
temporarily to replenish their batteries by energy scavenging, mobility, deployment of
new nodes, or death of existing nodes.
The need for scalability is evident when considering very dense sensor networks with
dozens or hundreds of nodes in mutual range.
Nodestransceiverconsumesasignificantshareofenergy.
Transceivercanbeinoneofthefourmainstates:transmitting,receiving,idling,or
sleeping.
Transmittingiscostly,receivecostsoftenhavethesameorderofmagnitudeas
transmitcosts,idlingcanbesignificantlycheaperbutalsoaboutasexpensiveas
receiving,andsleepingcostsalmostnothingbutresultsina“deaf”node.

3.2 MAC Protocols for WSN
Collisions:
Collisionsincuruselessreceivecostsatthedestinationnode,uselesstransmitcosts
atthesourcenode,andtheprospecttoexpendfurtherenergyuponpacket
retransmission.
Hence,collisionsshouldbeavoided,eitherbydesign(fixedassignment/TDMAor
demandassignmentprotocols)orbyappropriatecollisionavoidance/hidden-
terminalproceduresinCSMAprotocols.
Overhearing:
Uni-castframeshaveonesourceandonedestinationnode.
However,thewirelessmediumisabroadcastmediumandallthesource’sneighbors
thatareinreceivestatehearapacketanddropitwhenitisnotdestinedtothem;these
nodesoverhearthepacket.
Forhighernodedensitiesoverhearingavoidancecansavesignificantamountsof
energy.Ontheotherhand,overhearingissometimesdesirable.

3.2 MAC Protocols for WSN
Protocol overhead :
ProtocoloverheadisinducedbyMAC-relatedcontrolframeslike,forexample,
RTSandCTSpacketsorrequestpacketsindemandassignmentprotocols,and
furthermorebyper-packetoverheadlikepacketheadersandtrailers.
Idlelistening:
Anodebeinginidlestateisreadytoreceiveapacketbutisnotcurrentlyreceiving
anything.
Thisreadinessiscostlyanduselessincaseoflownetworkloads;formanyradio
modems,theidlestatestillconsumessignificantenergy.
Switchingoffthetransceiverisasolution;however,sincemodechangesalsocost
energy,theirfrequencyshouldbekeptat“reasonable”levels.

3.2 MAC Protocols for WSN
Someotherprotocolsareclassifiedintoeithercontention-basedorschedule-
basedprotocols.
Thisdistinctionistobeunderstoodbythenumberofpossiblecontendersupona
transmitopportunitytowardsareceivernode:
Incontention-basedprotocols,anyofthereceiver’sneighborsmighttryitsluck
attheriskofcollisions.
Accordingly,thoseprotocolscontainmechanismstoavoidcollisionsortoreduce
theirprobability.
Inschedule-basedprotocols,onlyoneneighborgetsanopportunityandcollisions
areavoided.TheseprotocolshaveaTDMAcomponent,whichprovidesalsoan
implicitidlelisteningavoidancemechanism:whenanodeknowsitsallocatedslots
andcanbesurethatitcommunicates(transmits/receives)onlyintheseslots,itcan
safelyswitchoffitsreceiveratallothertimes

.
3.3. Low duty cycle protocols and wakeup concepts
Low duty cycle
protocols try to avoid
spending (much) time
in the idle state and to
reduce the
communication
activities of a sensor
node to a minimum.
In an ideal case, the sleep state is left only when a node is about to transmit or receive
packets. To achieve this WAKEUP RADIO Concept is introduced.
In several protocols, a periodic wakeup scheme is used. Such schemes exist in
different flavors.
This approach, nodes spend most of their time in the sleep mode and wake up periodically
to receive packets from other nodes. Specifically, a node A listens onto the channel during
its listen period and goes back into sleep mode when no other node takes the
opportunity to direct a packet to A.
.

•.
3.3. Low duty cycle protocols and wakeup concepts
By choosing a small duty cycle, the transceiver is in sleep mode most of the time,
avoiding idle listening and conserving energy.
• By choosing a small duty cycle, the traffic directed from neighboring nodes to a
given node concentrates on a small time window (the listen period) and in heavy
load situations significant competition can occur.
• Choosing a long sleep period induces a significant per-hop latency, since a
prospective transmitter node has to wait an average of half a sleep period before
the receiver can accept packets. In the multi-hop case, the per-hop latencies add up
and create significant end-to-end latencies.
• Sleep phases should not be too short lest the start-up costs outweigh the benefits
Thereisalsoaperiodicwakeupbutnodescanbothtransmitandreceiveduringtheir
wakeupphases.Whennodeshavetheirwakeupphasesatthesametime,thereisno
necessityforanodewantingtotransmitapackettobeawakeoutsidethesephasesto
rendezvousitsreceiver.

.
3.2 Sparse topology and energy management (STEM)
The Sparse Topology and Energy Management (STEM) protocol does not cover all
aspects of a MAC protocol but provides a solution for the idle listening problem
STEM duty cycle for a single node
STEM targets networks that are deployed to wait for and report on the behavior of a
certain event.

TheS-MAC(Sensor-MAC)protocolprovidesmechanismstocircumventidle
listening,collisions,andoverhearing.AsopposedtoSTEM,itdoesnotrequiretwo
differentchannels.
S-MAC (Sensor –MAC)
S-MAC principle

.
S-MAC (Sensor –MAC)
S-MACadoptsaperiodicwakeupscheme,thatis,eachnodealternatesbetweena
fixed-lengthlistenperiodandafixed-lengthsleepperiodaccordingtoitsschedule,as
opposedtoSTEM,thelistenperiodofS-MACcanbeusedtoreceiveandtransmit
packets.
S-MACattemptstocoordinatetheschedulesofneighboringnodessuchthattheir
listenperiods
Startatthesametime.Anodex’slistenperiodissubdividedintothreedifferent
phases:
. •Inthefirstphase(SYNCHphase),
•Inthesecondphase(RTSphase),
•Inthethirdphase(CTSphase),

S-MAC (Sensor –MAC)
S-MAC fragmentation and NAV setting

3.2 The Mediation device protocol
The mediation device protocol is compatible with the peer-to-peer
communication mode of the IEEE 802.15.4 low-rate WPAN standard. It allows each
node in a WSN to go into sleep mode periodically and to wake up only for short times
to receive packets from neighbor nodes. There is no global time reference, each node
has its own sleeping schedule, and does not take care of its neighbors sleep schedules

3.2 The Mediation device protocol
Uponeachperiodicwakeup,anodetransmitsashortquerybeacon,indicating
itsnodeaddressanditswillingnesstoacceptpacketsfromothernodes.Thenode
staysawakeforsomeshorttimefollowingthequerybeacon,toopenupawindow
forincomingpackets.Ifnopacketisreceivedduringthiswindow,thenodegoes
backintosleepmode.
Dynamicsynchronization
Mediationdevice(MD)
Thedynamicsynchronizationapproachachievesthissynchronizationwithout
requiringthetransmittertobeawakepermanentlytodetectthedestinationsquery
beacon.
Toachievethis,amediationdevice(MD)isused.

.
3.3 Wakeup radio concepts
Theidealsituationwouldbeifanodewerealwaysinthereceivingstatewhena
packetistransmittedtoit,inthetransmittingstatewhenittransmitsapacket,andin
thesleepstateatallothertimes;theidlestateshouldbeavoided.
Thewakeupradioconceptstrivestoachievethisgoalbyasimple,“powerless”
receiverthatcantriggeramainreceiverifnecessary
OneproposedwakeupMACprotocolassumesthepresenceofseveralparalleldata
channels,separatedeitherinfrequency(FDMA)orbychoosingdifferentcodesina
CDMAschemes.
Anodewishingtotransmitadatapacketrandomlypicksoneofthechannelsand
performsacarriersensingoperation.Ifthechannelisbusy,thenodemakesanother
randomchannelchoiceandrepeatsthecarrier-sensingoperation.
After a certain number of unsuccessful trials, the node backs off for a random time
and starts again.

3.2 Wakeup radio concepts
Ifthechannelisidle,thenodesendsawakeupsignaltotheintendedreceiver,
indicatingboththereceiveridentificationandthechanneltouse.
Thereceiverwakesupitsdatatransceiver,tunestotheindicatedchannel,andthe
datapackettransmissioncanproceed.
Afterward,thereceivercanswitchitsdatatransceiverbackintosleepmode.This
wakeupradioconcepthasthesignificantadvantagethatonlythelow-powerwakeup
transceiverhastobeswitchedonallthetimewhilethemuchmoreenergyconsuming
datatransceiverisnonsleepingifandonlyifthenodeisinvolvedindatatransmissions.
Furthermore,thisschemeisnaturallytrafficadaptive,thatis,theMACbecomes
moreandmoreactiveasthetrafficloadincreases.Periodicwakeupschemesdo
nothavethisproperty.
Therearealsosomedrawbacks.First,toourknowledge,thereisnorealhardware
yetforsuchanultralowpowerwakeuptransceiver.Second,therangeofthewakeup
radioandthedataradioshouldbethesame.
Iftherangeofthewakeupradioissmallerthantherangeofthedataradio,possibly
notallneighbornodescanbewokenup.

3.2 IEEE 802.15.4 MAC protocol
IEEEfinalizedtheIEEE802.15.4standardinOctober2003,thestandardcoversthe
physicallayerandtheMAClayerofalow-rateWirelessPersonalAreaNetwork
(WPAN).
Zig-BeeusestheservicesofferedbyIEEE802.15.4andaddsnetworkconstruction
(starnetworks,peer-to-peer/meshnetworks,cluster-treenetworks),security,
applicationservices,andmore.
ThetargetedapplicationsforIEEE802.15.4areintheareaofwirelesssensor
networks,homeautomation,homenetworking,connectingdevicestoaPC,
homesecurity,andsoon.
Mostoftheseapplicationsrequireonlylow-to-mediumbitrates(uptosomefew
hundredsofkbps),moderateaveragedelayswithouttoostringentdelayguarantees,
andforcertainnodesitishighlydesirabletoreducetheenergyconsumptiontoa
minimum.

.
3.2 IEEE 802.15.4 MAC protocol
The physical layer offers:
Bitrates of 20 kbps (a single channel in the frequency range 868–868.6 MHz),
40 kbps (ten channels in the range between 905 and 928 MHz) and
250 kbps (16 channels in the 2.4 GHz ISM band between 2.4 and 2.485 GHz with
5-MHz spacing between the center frequencies).
There are a total of 27 channels available,
But the MAC protocol uses only one of these channels at a time;
It is not a multichannel protocol.
The MAC protocol combines both schedule-based as well as contention-based
schemes

.IEEE 802.15.4 MAC Protocol:
Network architecture and types/roles of nodes:
3.2 IEEE 802.15.4 MAC protocol
The standard distinguishes on the MAC layer two types of nodes:
• A Full Function Device (FFD) can operate in three different roles: it can be a PAN
coordinator (PAN = Personal Area Network), a simple coordinator or a device.
• A Reduced Function Device (RFD) can operate only as a device.
Network architecture and types/roles of nodes
Super-frame structure
GTS management
Data transfer procedures
Slotted CSMA-CA protocol
Non-beaconed mode

3.2 IEEE 802.15.4 MAC protocol
1.Network architecture and types/roles of nodes:
Adevicemustbeassociatedtoacoordinatornode(whichmustbeaFFD)and
communicatesonlywiththis,thiswayformingastarnetwork.Coordinatorscan
operateinapeer-to-peerfashionandmultiplecoordinatorscanformaPersonal
AreaNetwork(PAN).
ThePANisidentifiedbya16-bitPANIdentifierandoneofitscoordinatorsis
designatedasaPANcoordinator.
A coordinator handles among others the following tasks:
It manages a list of associated devices.
It allocates short addresses to its devices.
In the beaconed mode of IEEE 802.15.4, it transmits regularly frame beacon
packets announcing the PAN identifier, a list of outstanding frames, and other
parameters.
It exchanges data packets with devices and with peer coordinators.

.
3.2 IEEE 802.15.4 MAC protocol
2. Super frame structure:
Super frame structure of IEEE 802.15.4
Thecoordinatorofastarnetworkoperatinginthebeaconedmodeorganizes
channelaccessanddatatransmissionwiththehelpofasuperframe.
All super frames have the same length. The coordinator starts each super frame by
sending a frame beacon packet.
The frame beacon includes a super frame specification describing the length of the
various components of the following super frame:
1.Active period
2.Inactive period.
The active period is subdivided into
16 time slots.
The first time slot is occupied
by the beacon frame and
the remaining time slots
1. CAP
2. GTSs

.
3.3 IEEE 802.15.4 MAC protocol
3.GTSmanagement:
ThecoordinatorallocatesGTStodevicesonlywhenthelattersendappropriate
requestpacketsduringtheCAP.
Oneflagintherequestindicateswhethertherequestedtimeslotisatransmitslot
orareceiveslot.
Inatransmitslot,thedevicetransmitspacketstothecoordinatorandina
receiveslotthedataflowsinthereversedirection.Anotherfieldintherequest
specifiesthedesirednumberofcontiguoustimeslotsintheGTSphase.
Thecoordinatoranswerstherequestpacketintwosteps:Animmediate
acknowledgmentpacketconfirmsthatthecoordinatorhasreceivedtherequestpacket
properlybutcontainsnoinformationaboutsuccessorfailureoftherequest.
Afterreceivingtheacknowledgmentpacket,thedeviceisrequiredtotrackthe
coordinator’sbeaconsforsomespecifiedtime(calledAgtsDescPersistenceTime).

3.3 IEEE 802.15.4 MAC protocol
4.Datatransferprocedures:
Devicewantstotransmitadatapackettothecoordinator,Ifthedevicehasan
allocatedtransmitGTS,itwakesupjustbeforethetimeslotstartsandsendsitspacket
immediatelywithoutrunninganycarrier-senseorothercollision-avoidingoperations.
However,thedevicecandosoonlywhenthefulltransactionconsistingofthedata
packetandanimmediateacknowledgmentsentbythecoordinatoraswellas
appropriateInterFrameSpaces(IFSs)fitintotheallocatedtimeslots.
Theothercaseisadatatransferfromthecoordinatortoadevice.Ifthedevicehas
allocatedareceiveGTSandwhenthepacket/acknowledgment/IFScyclefitsintothese,
thecoordinatorsimplytransmitsthepacketintheallocatedtimeslotwithoutfurther
coordination.Thedevicehastoacknowledgethedatapacket.

3.3 IEEE 802.15.4 MAC protocol
Handshake between coordinator and device
when the device retrieves a packet
When the coordinator is not able to use a
receive GTS:
Thecoordinatorannouncesabufferedpacketto
adevicebyincludingthedevicesaddressintothe
pendingaddressfieldofthebeaconframe.
The device’s address is included as long as the
device has not retrieved the packet or a certain
timer has expired.
When the device finds its address in the
pending address field, it sends a special data
request packet during the CAP.
Thecoordinatoranswersthispacketwith
anacknowledgmentpacketandcontinueswith
sendingthedatapacket

•5. Slotted CSMA-CA protocol:
3.3 IEEE 802.15.4 MAC protocol
Nodeshavetosenddataor
management/controlpackets
duringtheCAP,theyusea
slottedCSMAprotocol.
Theprotocolcontainsno
provisionsagainsthidden-
terminalsituations.
ForExamplethereisno
RTS/CTShandshake.To
reducetheprobabilityof
collisions,theprotocoluses
randomdelays;itisthusa
CSMA-CAprotocol.
Thetimeslotsmakingup
theCAParesubdividedinto
smallertimeslots,called
back-offperiods.

.
3.3 IEEE 802.15.4 MAC protocol
6. Non-beaconed mode:
The IEEE 802.15.4 protocol offers a Non-beaconed mode besides the beaconed
mode.
Some important differences between these modes are the following:
1.In the non-beaconed mode, the coordinator does not send beacon frames nor is
there any GTS mechanism.
2.All packets from devices are transmitted using an un slotted (because of the lack of
time synchronization) CSMA-CA protocol.
3.Coordinators must be switched on constantly but devices can follow their own
sleep schedule.
4.Deviceswakeupfortworeasons:(i)tosendadata/controlpackettothe
coordinators,or(ii)tofetchapacketdestinedtoitselffromthecoordinatorby
usingthedatarequest/acknowledgment/data/acknowledgmenthandshake

.
3.3. Address and name management
Namingandaddressingaretwofundamentalissuesinnetworking.
Namesareusedtodenotethings(forexample,nodes,data,transactions).
Addressessupplytheinformationneededtofindthesethings.
Useofaddressesandnamesin(sensor)networks:
Inmostcomputerandsensornetworks,thefollowingtypesofnames,addresses,
andidentifierscanbefound:
1.UniqueNodeIdentifier(UID)
2.MACaddress
3.Networkaddress
4.Networkidentifiers
5.Resourceidentifiers
The fundamental tasks of address
management, which are independent of
the type of addresses:
1.Address allocation
2.Address de-allocation
3.Address representation
4.Conflict detection/resolution
5.Binding

.
3.3. Address and name management
Example for network partition
Anyaddressmanagementschemefor
sensorandadhocnetworksis
occasionallyfacedwithnetwork
partitionsandnetworkmergeevents.
Uniqueness of addresses:
The following uniqueness
requirementsfornetworknamesand
addresses.
1.Globallyunique
2.Networkwideunique
3.Locallyunique

.
3.3. Address and name management in wireless sensor networks
MACaddressesareindispensableiftheMACprotocolshallemployoverhearing
avoidanceandgointosleepmodeasoftenaspossible.However,doMACaddresses
needtobegloballyornetworkwideunique.
sincethescopeofaMACprotocoliscommunicationbetweenneighboringnodesand
itissufficientthataddressesarelocallyuniquewithinatwo-hopneighborhood.
Thisrequirementensuresthatnotwoneighborsofaselectednodehavethesame
MACaddress
Itisnotreallynecessaryinwirelesssensornetworkssinceafterallthewholenetwork
isnotacollectionofindividualnodesbelongingtoindividualusersbutthenodes
collaboratetoprocesssignalsandeventsfromthephysicalenvironment.
The users ultimately are interested in the data and not in the individual or groups of
nodes delivering them, the data can also influence the operation of protocols, which is
the essence of data-centric networking.
Data-centric or content-based addressing schemes are important.

3.4. Assignment of MAC addresses
The assignment of globally unique MAC addresses is undesirable in sensor networks
with mostly small packets.
An a priori assignment of network wide unique addresses is feasible only if it can be
done with reasonable effort.
But there is still the problem that the overhead to represent addresses can be
considerable although not as large as in globally unique addresses
Dynamicanddistributedassignmentofnetworkwideandlocaladdresses.
Noderandomlypicksanaddressfromagivenaddressrangeandhopesthatthis
addressisunique.
Thisaddressrangeisgivenbytheintegersbetween0and2
m
−1andanaddresscan
thusberepresentedwithmbits.Theaddressspacehasasizeofn=2
m
addresses.
A node chooses its address without any prior information, in which case it is best to
use a uniform distribution on the address range since this has maximum entropy.

.
3.5. Routing protocols
Inamultihopnetwork,intermediatenodeshavetorelaypacketsfromthesource
tothedestinationnode.
Suchanintermediatenodehastodecidetowhichneighbortoforwardan
incomingpacketnotdestinedforitself.
Typically,routingtablesthatlistthemostappropriateneighborforanygiven
packetdestinationareused.
Theconstructionandmaintenanceoftheseroutingtablesisthecrucialtaskofa
distributedroutingprotocol
Asimpleexampleofroutingina
multi-hopnetwork–nodeSsends
packetstonodeD

.1. Energy-efficient uni-cast:
3.5. Routing protocols
Various example routes for communication
between nodes A and H, showing energy costs per
packet for each link and available battery capacity
for each node
Energy-efficientuni-cast
routingappearstobea
simpleproblem:takethe
networkgraph,assignto
eachlinkacostvalue
thatreflectstheenergy
consumptionacrossthis
link,andpickany
algorithmthatcomputes
least-costpathsina
graph.

.
3.5. Routing protocols
There are various aspects how energy or power efficiency can be conceived of in a
routing context:
Minimize energy per packet
Maximize network lifetime
-Time until the first node fails.
-Time until there is a spot that is not covered by the network (loss of coverage, a
useful metric only for redundantly deployed networks).
-Time until network partition (when there are two nodes that can no longer
communicate with each other)
Routing considering available battery energy
-Maximum Total Available Battery Capacity
-Minimum Battery Cost Routing (MBCR)
-Min–Max Battery Cost Routing (MMBCR)
-Conditional Max–Min Battery Capacity Routing (CMMBCR)
-Minimize variance in power levels
Minimum Total Transmission Power Routing (MTPR)

The idea behind the relatively large class of geographic routing protocols is twofold:
1. For many applications, it is necessary to address physical locations, for example, as
“any node in a given region” or “the node at/closest to a given point”. When such
Requirements exist, they have to be supported by a proper routing scheme.
3.5. Routing protocols
2. Geographic Routing:
Whenthepositionofsourceanddestinationisknownasarethepositionsof
intermediatenodes,thisinformationcanbeusedtoassistintheroutingprocess.
Todoso,thedestinationnodehastobespecifiedeithergeographically(asabove)oras
someformofmapping–alocationservice–betweenanotherwisespecified
destination(e.g.byitsidentifier)andits(conjectured)currentpositionisnecessary

3.5. Routing protocols-Geographic Routing:
Basics of position-based routing
Simple greedy geographic forwarding
Most forward within r:

.
3.5. Routing protocols-Geographic Routing:
Nearest with forward progress
Directional routing
The problem of dead ends
Restricted flooding
Right-hand rule to recover greedy routing –GPSR
Performance guarantees of combined greedy/face routing
Combination with ID-based routing, hierarchies
Randomized forwarding and adaptive node activity –GeRaF
Geographic routing without positions –GEM
Simple greedy geographic
forwarding fails in presence of
obstacles

3.5. Routing protocols-Geographic Routing:
Example for GPSR
Illustrateshowa
packetwouldbe
routedfromnodeA
tonodeZ.
Whileatnode
A,thepacketcanbe
greedilyforwarded
tonodeD.AtnodeD,
greedyforwarding
fails,sothepacket
hastoberouted
aroundtheperimeter
oftheinteriorface
definedbyBFGCD.

3.5. Routing protocols-Geographic Routing:
Geo-casting
Geo-casting–sendingdatatoasubsetofnodesthatarelocatedinanindicatedregion
isevidentlyanexampleofmulticastingandthuswouldnotrequireanyfurther
attention.
Similartothecaseofposition-basedrouting,positioninformationofthedesignated
regionandtheintermediatenodescanbeexploitedtoincreaseefficiency
Location Based Multicast:
-Static zone
-Adaptive zone
-Adaptive distances
Finding the right direction
Tessellating the plane
Mesh-based geo-casting
Geo-casting using a uni-cast protocol –GeoTORA
Trajectory-based forwarding (TBF)

.
Assignment Question
1.Explain in detail about S-MAC Protocol
2.Briefly explain IEEE 802.15.4 MAC Layer.
3.Explain Low duty cycle protocols.
4.What are differences between Zigbee and Bluetooth Technology?
5.Explain sparse topology and energy management protocol.

INTRODUCTION:
UNIT-IV:INFRASTRUCTURE ESTABLISHMENT
OUTCOMES:
To understand the performance of sensor network and identify bottlenecks.
•Inadenselydeployedwirelessnetwork,asinglenodehasmanyneighboringnodeswithwhich
directcommunicationwouldbepossiblewhenusingsufficientlylargetransmissionpower.This
is,however,notnecessarilybeneficial:hightransmissionpowerrequireslotsofenergy,many
neighborsareaburdenforaMACprotocol,androutingprotocolssufferfromvolatilityinthe
networkwhennodesmovearoundandfrequentlyformorsevermanylinks.
•Toovercometheseproblems,topologycontrolcanbeapplied.Theideaistodeliberatelyrestrict
thesetofnodesthatareconsideredneighborsofagivennode.Thiscanbedonebycontrolling
transmissionpower,byintroducinghierarchiesinthenetworkandsignalingoutsomenodesto
takeovercertaincoordinationtasks,orbysimplyturningoffsomenodesforacertaintime.

Contents:
4.1.Topology control, clustering,
4.2. Time synchronization,
4.3. localization and positioning,
4.4. sensor tasking and control.
4.5. Operating systems for wireless sensor networks,
4.6. sensor node hardware –berkeleymotes,
4.7 programming challenges,
4.8. Node-level software platforms, node-level simulators, state-centric programming
OUTCOMES
UNIT-IV:INFRASTRUCTURE ESTABLISHMENT
Toevaluatetheperformanceofsensornetworkandidentifybottlenecks.

CONTENTS:
4.1.Topology control, clustering,
OUTCOMES:
To know the basics of topology and clustering of network
MODULE-I

.
4.1.Topology control, clustering
In a very dense networks, too many nodes might be in range for an efficient operation
•Toomanycollisions/toocomplexoperationforaMACprotocol,toomanypathsto
choosefromforaroutingprotocol.
Idea: Make topology less complex
•Topology: Which node is able/allowed to communicate with which other nodes
•Topology control needs to maintain invariants, e.g., connectivity
•A sensor network node that first wakes up executes a protocol to discover which other
nodes it can communicate with (bi directionally).
•This set of neighbors is determined by the radio power of the nodes as well as the local
topography and other conditions that may degrade radio links

4.1.Topology control, clustering
Options for
Topology control
•Theproblemoftopologycontrolforasensornetworkishowtosettheradiorangeforeach
nodesoastominimizeenergyusage,whilestillensuringthatthecommunicationgraphofthe
nodesremainsconnectedandsatisfiesotherdesirablecommunicationproperties.

Alternative: Selectively discard some links
•Usually done by introducing hierarchies
4.1.Topology control, clustering
Flat Networks:
Main option: Control transmission power
•Do not always use maximum power
•Selectively for some links or for a node as a
whole
•Topology looks “thinner”
•Less interference.

.Hierarchical networks –backbone:
4.1.Topology control, clustering
Construct a backbonenetwork
•Some nodes “control” their neighbors –they form
a (minimal) dominating set
•Each node should have a controlling neighbor.
Controlling nodes have to be connected
(backbone)
Only links within backbone and from backbone to
controlled neighbors are used

4.1.Topology control, clustering
Aspects of topology-control algorithms:
Connectivity –If two nodes connected in G, they have to be connected in G
0
resulting from
topology control
Stretch factor –should be small
Hop stretch factor: how much longer are paths in G
0
than in G?
Energy stretch factor: how much more energy does the most energy-efficient path
need?
Throughput –removing nodes/links can reduce throughput, by how much?
Robustness to mobility
Algorithm overhead

.
4.1.Topology control, clustering
Construct clusters
Partition nodes into groups (“clusters”)
Each node in exactly one group
•Except for nodes “bridging” between two or more groups
Groups can have cluster heads
Typically: all nodes in a cluster are direct neighbors of their cluster head
Cluster heads are also a dominating set, but should be separated from each other –they
form an independent set
Formally: Given graph G=(V,E), construct C ½ V such that

4.1.Topology control, clustering
Further options
How do clusters communicate? Some nodes need to
act asgatewaysbetween clusters.
If clusters may not overlap, two nodes need to jointly
act as a distributed gateway
Partition nodes into groups of nodes –Clusters
Many options for details
Are there cluster heads? –One controller/representative node per cluster
May cluster heads be neighbors? If no: cluster heads form an
independent set C:
Typically: cluster heads form
a maximum independent set
May clusters overlap?
Do they have nodes in common?

. Maximum independent set:
4.1.Topology control, clustering
ComputingamaximumindependentsetisNP-complete
Canbeapproximatewithin(+3)/5forsmall,within(loglog/log)else;bounded
degree
Show:Amaximumindependentsetisalsoadominatingset
Maximumindependentsetnotnecessarilyintuitivelydesired
solution
Example:Radialgraph,withonly(v0,vi)2E

.
4.1.Topology control, clustering
•Use some attribute of nodes to break local
symmetries.
•Node identifiers, energy reserve, mobility,
weighted combinations… -matters not for
the idea as such (all types of variations have
been looked at).
•Make each node a cluster head that locally
has the largest attribute value.
•Once a node is dominated by a cluster-
head, it abstains from local competition,
giving other nodes a chance.
Determining gateways to connect clusters:
Rotating cluster heads
•Multi-hop clusters
•Passive clustering
•Adaptive node activity

CONTENTS:
4.2. Time synchronization,
OUTCOMES:
To discusses the time synchronization problem in wireless sensor
networks
MODULE-2

4.2. Time synchronization
Timeisanimportantaspectformanyapplicationsandprotocolsfoundin
wirelesssensornetworks.
Nodescanmeasuretimeusinglocalclocks,drivenbyoscillators.
Becauseofrandomphaseshiftsanddriftratesofoscillators,thelocaltime
readingofnodeswouldstarttodiffer–theyloosesynchronization–without
correction
Thetimesynchronizationproblemisastandardproblemindistributedsystems.
Ex: Determination of angle of arrival of a
distant sound event by an array of acoustic
sensors

4.2. Time synchronization
There are at least two ways to get a more reliable estimate. The first one (and the one
focused on in this chapter) is to keep the sensors clocks as tightly synchronized as
possible, using dedicated time synchronization algorithms.
The second one is to combine the readings of multiple sensors and to “average out”
the estimation errors
Itisimportanttonotethatthetimeneededinsensornetworksshouldadhereto
physicaltime,thatistwosensornodesshouldhavethesameideaaboutthe
durationof1sandadditionallyasensornode’ssecondshouldcomeascloseas
possibleto1sofrealtimeorcoordinateduniversaltime(UTC).
The physical time has to be distinguished from the concept of logical time that allows
to determine the ordering of events in a distributed system but does not necessarily
show any correspondence to real time.

Node Clocks and the Problem of Accuracy:
-Oscillator
-Counter Register
-Hardware clock
-Software clock
4.2. Time synchronization
Properties and structure of time synchronization algorithms;
Physical time Vs Logical time
External Vs Internal Synchronization
Global Vs Local
Absolute Vs Relative
Hardware Vs soft ware
A priori Vs A posteriori
Deterministic Vs Stochastic
Local clock update discipline
performance metrics:
Precision
Energy Costs
Memory requirements
Fault tolerance

.
4.2. Time synchronization
Time synchronization in wireless sensor networks:
•Analgorithmmustscaletolargemult-ihopnetworksofunreliableandseverely
energy-constrainednodes.
•Thescalabilityrequirementreferstoboththenumberofnodesaswellastothe
averagenodedegree/nodedensity.
•Theprecisionrequirementscanbequitediverse,rangingfrommicrosecondsto
seconds.
•Theuseofextrahardwareonlyfortimesynchronizationpurposesismostlyruledout
becauseoftheextracostandenergypenaltiesincurredbydedicatedcircuitry.
•Thedegreeofmobilityislow.
•Therearemostlynofixedupperboundsforpacketdeliverydelay.
•Thepropagationdelaybetweenneighboringnodesisnegligible.
•Manualconfigurationofsinglenodesisnotanoption.
•Itwillturnoutthattheaccuracyoftimesynchronizationalgorithmscriticallydepends
onthedelaybetweenthereceptionofthelastbitofapacketandthetimewhenitistime
stamped.

CONTENTS:
4.3 Localization and Positioning
4.4 operating systems for wireless sensor networks
OUTCOMES:
To discuss the operating systems for wireless sensor networks and andobjectives for a WSN
operating system.
MODULE-3

4.3 Localization and Positioning
In many circumstances, it is useful or even necessary for a node in a wireless sensor
network to be aware of its location in the physical world.
Properties of localization and positioning procedures:
Physical position versus symbolic location
Absolute versus relative coordinates
Localized versus centralized computation
Accuracy and precision
Scale
Limitations
Costs

4.3 Localization and Positioning
Possible Approaches:
1.Proximity
2.Trilateration and Triangulation
3.Scene Analysis
Determining the position of sensor nodes with
the assistance from some anchor points; not all
nodes are necessarily in contact with all anchors

.
4.3 Localization and Positioning
Positioning in Multi hop Environment:
1.Connectivity in multihopnetwork
2.Multihoprange estimation
3.Iterative and collabrativemutilateraion
4.Probabilistic Positioning description and propagation

4.3 Localization and Positioning

.
4.4 Operating Systems for Wireless Sensor Networks
WSNscanbeusedtomonitorand/orcontrolphysicalenvironmentinaspace
whereitisdifficultorimpossibletodosomanually.
AWSNisgenerallycomposedofacentralizedstation(sink)andtens,hundreds,or
perhapsthousandsoftinysensornodessuchasMoteandMica2.
WSNs are a special type of distributed network system that is similar to database,
real-time, and embedded systems.
ThebasicfunctionofWSNsistocollectinformationandtosupportcertain
applicationsspecifictothetaskofWSNdeployment.
Commerciallyavailablesensornodesarecategorizedintofourgroups:

4.4 Operating Systems for Wireless Sensor Networks
1.SpecializedsensingplatformssuchastheSpecnodedesignedattheUniversityof
California–Berkeley.
2.GenericsensingplatformssuchasBerkeleymotes
3.High-bandwidthsensingplatformssuchasiMote
4.GatewayplatformssuchasStargate
Thedifferencesinthesensortypesaboveareinthefunctionofthesensor,frequencyofthe
microprocessor,memorysize,andtransceiverbandwidth.
Althoughthesenodeshavedifferentcharacteristics,theirbasichardwarecomponentsarethe
same:aphysicalsensor,amicroprocessorormicrocontroller,amemory,aradiotransceiver,anda
battery.
Each sensor node needs an operating system (OS) that can control the hardware, Provide
hardware abstraction to application software, and fill in the gap between applications and the
underlying hardware

.
4.4 Operating Systems for Wireless Sensor Networks
Operating system design issues:
Traditionaloperatingsystemsaresystemsoftware,includingprogramsthatmanage
computingresources,controlperipheraldevices,andprovidesoftwareabstractionto
theapplicationsoftware.
TraditionalOSfunctionsarethereforetomanageprocesses,memory,CPUtime,file
system,anddevices..
Thisisoftenimplementedinamodularandlayeredfashion,includingalowerlayer
ofkernelsandahigherlayerofsystemlibraries.
TraditionalOSsarenotsuitableforwirelesssensornetworksbecauseWSNshave
constrainedresourcesanddiversedata-centricapplications,inadditiontoavariable
topology.
WSNsneedanewtypeofoperatingsystem,consideringtheirspecialcharacteristics.

4.4 Operating Systems for Wireless Sensor Networks
Operating system design issues:
1.Process management and scheduling 2.Memory management
3. kernel model 4. Application program interface (API).
5. Code upgrade and reprogramming
Sensor operating systems (SOS) should embody the following functions:
1.Should be compact and small in size since the sensor nodes have very small
memory.
2.Should provide real-time support, since there are real-time applications, especially
when actuators are involved
3.Should provide efficient resource management mechanisms in order to allocate
microprocessor time and limited memory.
4.Should support reliable and efficient code distribution since the functionality
performed by the sensor nodes may need to be changed after deployment.
5.Should support power management, which helps to extend the system lifetime and
improve its performance.
6.Should provide a generic programming interface up to sensor middleware or
application software.

.
4.4 Operating Systems for Wireless Sensor Networks
Examples of Operating Systems:
1. TinyOS
2 .Mate,
3 .MagnetOS,
4 .MANTIS,
5 .OSPM
6 .EYES OS
7 .SenOS,
8 .EMERALDS
9 . PicOS
ThemajorissuesforthedesignofoperationsystemsforWSNsaresize(memory
requirement),energy-efficientIPCsandtaskscheduling,effectivecodedistribution
andupgrades,andfinally,genericapplicationprogramminginterfaces.

.TinyOS:
4.4 Operating Systems for Wireless Sensor Networks
Thedesignoftinyosallowsapplicationsoftwaretoaccesshardware
directlywhenrequired.
TinyosisatinymicrothreadedOSthatattemptstoaddress
twoissues:howtoguaranteeconcurrentdataflowsamonghardwaredevices,and
howtoprovidemodularizedcomponentswithlittleprocessingandstorage
overhead.
TinyOS uses an event-based model to support high levels of concurrent application in a
very small amount of memory.
It includes a tiny scheduler and a set of components.
The scheduler schedules operation of those components. Each component consists of
four parts: command handlers, event handlers, an encapsulated fixed-size frame, and a
group of tasks.

CONTENTS:
4.5 Sensor Node architecture
4.6 Programming Challenges
OUTCOMES:
To explaining about architecture of sensor node and challenges
MODULE-3

.
4.5 Sensor Node Hardware
Sensor node hardware can be grouped into threecategories, each of which entails a
different set of trade-offs in the design choices:
1.Augmented general-purpose computers
Ex: low power PCs, embedded PCs (e.g., PC104), custom-designed PCs and
various personal digital assistants (PDA).
2. Dedicated embedded sensor nodes
Ex: Berkeley mote family , the UCLA Medusa family , Ember nodes, and MIT μAMP
3. System-on-chip (SoC) nodes
Ex:smartdust,theBWRCpicoradionode,andthePASTAnode
Amongthesehardwareplatforms,theBerkeleymotes,duetotheirsmallformfactor,
opensourcesoftwaredevelopment,andcommercialavailability,havegainedwide
popularityinthesensornetworkresearchcommunity.

4.5 Sensor Node Hardware-Berkeley Motes
The Berkeley motes are a family of embedded sensor nodes sharing roughly the same
architecture.
A comparison of Berkeley motes

MICA MOTE: MICA motes have a two-CPU design
4.5 Sensor Node Hardware-Berkeley Motes
MCU: an Atmel ATmega103L
-512 KB flash memory
-4 KB of data memory
TR1000 chip set:
-operating at 916 MHz
-Max 50 kbps raw data rate
-40 kbps transmission rate
supports a 51 pin I/O
A sensor/ actuator board can
host :
-a temperature sensor,
-a light sensor,
-an accelerometer,
-a magnetometer,
-a microphone, and
-a beeper
serial I/O (UART)

The energy consumption of various components on a MICA mote.
4.5 Sensor Node Hardware-Berkeley Motes
MATRUSRI
ENGINEERING COLLEGE
ARadiotransmissionbearsthemaximumpowerconsumption.
Anotherobservationisthattherearehugedifferencesamongthepower
consumptionlevelsintheactivemode,theidlemode,andthesuspendmodeofthe
MCU

Traditional programming technologies rely on operating systems to provide abstraction
for processing, I/O, networking, and user interaction hardware
4.6. Programming Challenges
MATRUSRI
ENGINEERING COLLEGE
Traditional embedded system programming interface

4.6 Programming Challenges
MATRUSRI
ENGINEERING COLLEGE
When applying traditional model to programming networked embedded systems, such
as sensor networks, the application programmers need to explicitly deal with:
message passing,
event synchronization,
interrupt handing, and
sensor reading
An application is typically implemented as a finite state machine (FSM) that covers
all extreme cases:
unreliable communication channels,
long delays,
irregular arrival of messages,
simultaneous events

4.6 Programming Challenges
MATRUSRI
ENGINEERING COLLEGE
Forresource-constrainedEmbeddedsystemswithreal-timerequirements,several
mechanismsareusedinembeddedoperatingsystemsto
reducecodesize,
improveresponsetime,and
reduceenergyconsumption
Embeddedoperatingsystemstendtoexposemorehardwarecontrolstothe
programmers,whonowhavetodirectlyfacedevicedriversandschedulingalgorithms,
andoptimizecodeattheassemblylevel.
Althoughthesetechniquesmayworkwellforsmall,stand-aloneembeddedsystems,
theydonotscaleupfortheProgrammingofsensornetworksfortworeasons:
1.Sensor networks are large-scale distributed systems, where global properties are
derivable from program execution in a massive number of distributed nodes.
2.Assensornodesdeeplyembedintothephysicalworld,asensornetworkshouldbe
abletorespondtomultipleconcurrentstimuliatthespeedofchangesofthephysical
phenomenaofinterest.

CONTENTS:
4.7. Node-level software platforms
4.8. Node-level simulator
4.9 Sate centric Programming
OUTCOMES:
To understand the concepts of node-level software and simulations
MODULE-4
MATRUSRI
ENGINEERING COLLEGE

4.7. Node-level software platforms
MATRUSRI
ENGINEERING COLLEGE
Mostdesignmethodologiesforsensornetworksoftwarearenodecentric,where
programmersthinkintermsofhowanodeshouldbehaveintheenvironment.
Anode-levelplatformcanbeanodecentricoperatingsystem,whichprovides
hardwareandnetworkingabstractionsofasensornodetoprogrammers,oritcanbe
alanguageplatform,whichprovidesalibraryofcomponentstoprogrammers.
Typicaloperatingsystemabstractsthehardwareplatformbyprovidingasetof
servicesforapplications,including
-filemanagement,
-memoryallocation,
-taskscheduling,
-peripheraldevicedrivers,and
-networking.

4.7. Node-level software platforms
MATRUSRI
ENGINEERING COLLEGE
Operating System: TinyOS
TinyOSaimsatsupportingsensornetworkapplicationsonresourceconstrained
hardwareplatforms,suchastheBerkeleymotes.
Toensurethatanapplicationcodehasanextremelysmallfootprint,TinyOSchooses
tohavenofilesystem,supportsonly
staticmemoryallocation,
implementsasimpletaskmodel,and
providesminimaldeviceand
networkingabstractions

.
4.7. Node-level software platforms
MATRUSRI
ENGINEERING COLLEGE
TheFieldMonitor
application for
sensingandsending
measurements

4.8 Node-Level Simulators
MATRUSRI
ENGINEERING COLLEGE
Node-leveldesignmethodologiesareusuallyassociatedwithsimulatorsthatsimulate
thebehaviorofasensornetworkonaper-nodebasis.
Usingsimulation,designerscanquicklystudytheperformance(intermsoftiming,
power,bandwidth,andscalability)ofpotentialalgorithmswithoutimplementing
themonactualhardwareanddealingwiththevagariesofactualphysicalphenomena.
A node-level simulator typically has the following components:
Sensor node model
Communication model
Physical environment model:
Statistics and visualization
Asensornetworksimulatorsimulatesthebehaviorofasubsetofthesensornodeswith
respecttotime.
Dependingonhowthetimeisadvancedinthesimulation,therearetwotypesof
executionmodels:
Cycle-drivensimulation(CD)and
Discrete-eventsimulation(DE)

.
4.8 Node-Level Simulators
MATRUSRI
ENGINEERING COLLEGE
ACycle-driven(CD)simulationdiscretizesthecontinuousnotionofrealtimeinto
(typicallyregularlyspaced)ticksandsimulatesthesystembehaviorattheseticks.
Ateachtick,thephysicalphenomenaarefirstsimulated,andthenallnodesare
checkedtoseeiftheyhaveanythingtosense,process,orcommunicate.
ADiscrete-event(DE)simulatorassumesthatthetimeiscontinuousandan
eventmayoccuratanytime.Aneventisa2-tuplewithavalueandatimestamp
indicatingwhentheeventissupposedtobehandled.
There is no general CD simulator that fits all sensor network simulation tasks. We have
come across a number of homegrown simulators written in
Matlab,
Java, and
C++
Many of them are developed for particular applications and exploit application-specific
assumptions to gain efficiency.

.
4.8 Node-Level Simulators
MATRUSRI
ENGINEERING COLLEGE
DEsimulationsaresometimesconsideredasgoodasactualimplementations,
becauseoftheircontinuousnotionoftimeanddiscretenotionofevents.Thereare
severalopen-sourceorcommercialsimulatorsavailable.
Oneclassofthesesimulatorscomprisesextensionsofclassicalnetworksimulators,
suchas
ns-2,
J-Sim(previouslyknownasJavaSim),and
GloMoSim/QualNet.8
(Thefocusofthesesimulatorsisonnetworkmodeling,protocolsstacks,and
simulationperformance).
Anotherclassofsimulators,sometimescalledsoftwarein-the-loopsimulators,
incorporatetheactualnodesoftwareintothesimulation.Forthisreason,theyare
typicallyattachedtoparticularhardwareplatformsandarelessportable.Examplesin
TOSSIMforBerkeleymotesand
Em*(pronouncedemstar)forLinux-basednodessuchasSensoriaWINSNG
platforms

Ns-2 simulator and its sensor network extensions:
4.8 Node-Level Simulators-NS 2
MATRUSRI
ENGINEERING COLLEGE
The simulator ns-2 is an open-source network simulatorthat was originally
designed for wired, IP networks.
Extensions have been made to simulate Wireless/mobile networks (e.g., 802.11 MAC
and TDMA MAC) and more recently sensor networks.
Whiletheoriginalns-2onlysupportslogicaladdressesforeachnode,the
wireless/mobileextensionofitintroducesthenotionofnodelocationsandasimple
wirelesschannelmodel.
Thisisnotatrivialextension,sinceoncethenodesmove,thesimulatorneedstocheck
foreachphysicallayereventwhetherthedestinationnodeiswithinthe
communicationrange.
Foralargenetwork,thissignificantlyslowsdownthesimulationspeed.

MATRUSRI
ENGINEERING COLLEGE
4.8 Node-Level Simulators
Thereareatleasttwoeffortstoextendns-2tosimulatesensornetworks:
1.SensorSimfromUCLA9and
2.NRLsensornetworkextensionfromtheNavyResearchLaboratory
SensorSimaims at providing an energy model for sensor nodes and communication,
so that power properties can be simulated .
It also supports hybrid simulation.
NRLsensornetworkextensionprovidesaflexiblewayofmodelingphysical
phenomenainadiscreteeventsimulator.
Physicalphenomenaaremodeledasnetworknodeswhichcommunicatewithreal
nodesthroughphysicallayers.
Thereceivingnodessimplyhaveasensorstackparalleltothenetworkstackthat
processestheseevents.

4.8 Node-Level Simulators
MATRUSRI
ENGINEERING COLLEGE
Themainfunctionalityofns-2isimplementedinC++,whilethedynamicsofthe
simulation(e.g.,time-dependentapplicationcharacteristics)iscontrolledbyTcl
scripts.
Basiccomponentsinns-2arethelayersintheprotocolstack.Theyimplementthe
handlersinterface,indicatingthattheyhandleevents.
Eventsarecommunicationpacketsthatarepassedbetweenconsecutivelayerswithin
onenode,orbetweenthesamelayersacrossnodes.
Advantage of ns-2 is its rich libraries of protocols for nearly all network layers and for
many routing mechanisms.
TCP: reno, tahoe, vegas, and SACK implementations
• MAC: 802.3, 802.11, and TDMA
• Ad hoc routing: DSDV,DSR, AODV routing, and TORA
• Sensor network routing: Directed diffusion, geographical routing (GEAR) and
geographical adaptive fidelity (GAF) routing.

.
4.8 Node-Level Simulators-TOSSIM
MATRUSRI
ENGINEERING COLLEGE
TOSSIMisadedicatedsimulatorforTinyOSapplicationsrunningononeormore
Berkeleymotes.
ThekeydesigndecisionsonbuildingTOSSIMweretomakeitscalabletoanetworkof
potentiallythousandsofnodes,andtobeabletousetheactualsoftwarecodeinthe
Simulation.
To achieve these goals, TOSSIM takes a cross-compilation approach that compiles the
nesC source code into components in the simulation
The event-driven execution model of TinyOS greatly simplifies the design of TOSSIM.
By replacing a few low-level components, such as the A/D conversion (ADC), the system
clock, and the radio front end, TOSSIM translates hardware interrupts into discrete event
simulator events.
The simulator event queue delivers the interrupts that drive the execution of a node. The
upper-layer TinyOS code runs unchanged.

4.8 Node-Level Simulators-TOSSIM
MATRUSRI
ENGINEERING COLLEGE
TOSSIMusesasimplebutpowerfulabstractiontomodelawirelessnetwork.A
networkisadirectedgraph,whereeachvertexisasensornodeandeachdirected
edgehasabit-errorrate.Eachnodehasaprivatepieceofstaterepresentingwhatit
hearsontheradiochannel.
Bysettingconnectionsamongtheverticesinthegraphandabiterrorrateoneach
connection,wirelesschannelcharacteristics,suchas
imperfectchannels,
hiddenterminalproblems,and
asymmetriclinks,canbeeasilymodeled.
Wirelesstransmissionsaresimulatedatthebitlevel.Ifabiterroroccurs,the
simulatorflipsthebit.
TOSSIMhasavisualizationpackagecalledTinyViz,whichisaJavaapplicationthat
canconnecttoTOSSIMsimulations.

.
4.9 State-centric programming
MATRUSRI
ENGINEERING COLLEGE
Manysensornetworkapplications,suchastargettracking,arenotsimplygeneric
distributedprogramsoveranadhocnetworkofenergy-constrainednodes.
Deeplyrootedintheseapplicationsisthenotionofstatesofphysicalphenomenaand
modelsoftheirevolutionoverspaceandtime.
Someofthesestatesmayberepresentedonasmallnumberofnodesandevolveover
time,asinthetargettrackingproblemwhileothersmayberepresentedoveralarge
andspatiallydistributednumberofnodes,asintrackingatemperaturecontour.
A distinctive property of physical states, such as location, shape, and motion of objects,
is their continuity in space and time.
Their sensing and control is typically done through sequential state updates.

.
4.9 State-centric programming
MATRUSRI
ENGINEERING COLLEGE
System theories, the basis for most signal and information processing algorithms,
provide abstractions for state update, such as:
where x is the state of a system, u are the inputs, y are the outputs, k is an integer update
index over space and/or time, f is the state update function, and g is the output or observation
function.
Thisformulationisbroadenoughtocaptureawidevarietyofalgorithmsinsensor
fusion,signalprocessing,andcontrol(e.g.,Kalmanfiltering,Bayesianestimation,
systemidentification,feedbackcontrollaws,andfinite-stateautomata).
However, in distributed real-time embedded systems such as sensor networks, the
formulation is not so clean as represented in those equations.
The relationships among subsystems can be highly complex and dynamic over space
and time.

4.10 State-centric programming
MATRUSRI
ENGINEERING COLLEGE
Thefollowingconcernsmustbeproperlyaddressedduringthedesignto
ensurethecorrectnessandefficiencyoftheresultingsystems:
Where are the state variables stored?
Where do the inputs come from?
Where do the outputs go?
Where are the functions f and g evaluated?
How long does the acquisition of inputs take?
Are the inputs in uk collected synchronously?
Do the inputs arrive in the correct order through communication?
What is the time duration between indices k and k + 1? Is it a constant?
Theseissues,addressingwhereandwhen,ratherthanhow,toperformsensing,
computation,andcommunication,playacentralroleintheoverallsystemperformance.
However,these“nonfunctional”aspectsofcomputation,relatedtoconcurrency,
responsiveness,networking,andresourcemanagement,arenotwellsupportedby
traditionalprogrammingmodelsandlanguages.State-centricprogrammingaimsat
providingdesignmethodologiesandframeworksthatgivemeaningfulabstractions
fortheseissues,sothatsystemdesignerscancontinuetowritealgorithmsliketopofan
intuitiveunderstandingofwhereandwhentheoperationsareperformed.

.
4.9 State-centric programming
MATRUSRI
ENGINEERING COLLEGE
CollaborationGroups:
Acollaborationgroupisasetofentitiesthatcontributetoastateupdate.These
entitiescanbephysicalsensornodes,ortheycanbemoreabstractsystem
componentssuchasvirtualsensorsormobileagentshoppingamongsensors.Inthis
context,theyareallreferredtoasagents.
ExampleofGroups:
GeographicallyConstrainedGroup.
N-hopNeighborhoodGroup.
Publish/SubscribeGroup.
AcquaintanceGroup.
Using Multiple Types of Groups
PIECES: A State-Centric Design Framework
Principal Groups
Mobility
PIECES Simulator

1.What are the design issues for an operating system for WSN.
2. Explain about Berkeley motes .
3. Briefly explain bout Localization and Positioning
4. Discuss about Sensor tasking and control
5. Explain about Sensor tasking and control
Assignment Question
MATRUSRI
ENGINEERING COLLEGE

Questions & Answers
MATRUSRI
ENGINEERING COLLEGE
S.NO QUESTION Blooms
Taxonomy
Level
Course
Outcome
1.What are the design factors for routing protocol of
WSN.
L1 CO4
2.Explain Clustering. L2 CO4
3.Whatis the Topology L1 CO4
4.What are the performance metrics for WSN. L1 CO4
5.Explain enabling technologies for WSN. L1 CO4
Short answer questions

Questions & Answers
MATRUSRI
ENGINEERING COLLEGE
S.NO QUESTION Blooms
Taxonomy
Level
Course
Outcome
1.What do you mean by state centric programming and
explain its significance over generic distributed
systems.
L1 CO4
2.Explain how multi-target tracking problem is solved
using state centric programming.
L2 CO4
3.Write aboutMICA motes. L3 CO4
4.What are optimization goals and figures of merit in
WSN.
L1 CO4
5.Explain node level software platforms. L2 CO4
Long answer questions

INTRODUCTION:
UNIT-V:Security Issues In Wireless Sensor Networks
OUTCOMES:
Evaluate concepts of security in sensor networks
MATRUSRI
ENGINEERING COLLEGE
WSNssufferfrommanyconstraints,includinglowcomputationcapability,small
memory,limitedenergyresources,susceptibilitytophysicalcapture,andtheuseof
insecurewirelesscommunicationchannels.Theseconstraintsmakesecurityin
WSNsachallenge.

CONTENTS:
Introduction
OUTCOMES:
To understand concepts of security in sensor networks.
MODULE-I
MATRUSRI
ENGINEERING COLLEGE

Contents:
5.1. Security architectures
5.2. Survey of Security protocols for Wireless Sensor Networks and their Comparisons
OUTCOMES
Evaluateconceptsofsecurityinsensornetworks
UNIT-V:Security Issues In Wireless Sensor Networks
MATRUSRI
ENGINEERING COLLEGE
.

.
INTRODUCTION
MATRUSRI
ENGINEERING COLLEGE
Advancesinwirelesscommunicationandelectronicshaveenabledthedevelopment
oflow-cost,lowpower,multifunctionalsensornodes.
Thesetinysensornodes,consistingofsensing,dataprocessing,andcommunication
components,makeitpossibletodeployWirelessSensorNetworks(WSNs),which
representasignificantimprovementovertraditionalwiredsensornetworks.
WSNscangreatlysimplifysystemdesignandoperation,astheenvironmentbeing
monitoreddoesnotrequirethecommunicationorenergyinfrastructureassociated
withwirednetworks.
WSNsareexpectedtobesolutionstomanyapplications,suchasdetectingandtracking
thepassageoftroopsandtanksonabattlefield,monitoringenvironmentalpollutants,
measuringtrafficflowsonroads,andtrackingthelocationofpersonnelinabuilding.
Manysensornetworkshavemission-criticaltasksandthusrequirethatsecuritybe
considered.

INTRODUCTION
MATRUSRI
ENGINEERING COLLEGE
Thedifferencesbetweensensornetworksandadhocnetworksaregreatlyaffect
howsecuredata-transfer.
Thelimitedenergyandprocessingpowerofnodesmakestheuseofpublickey
cryptographynearlyimpossible.
Publickeycryptographymightbefeasibleinsensornetworksitremainsforthe
mostpartinfeasibleinWSNsmostsecurityschemesmakeuseofsymmetrickey
cryptography.
Onethingrequiredineithercaseistheuseofkeysforsecurecommunication.
ManagingkeydistributionisnotuniquetoWSNs,butagainconstraintssuchas
smallmemorycapacitymakecentralizedkeyingtechniquesimpossible.
Straightpairwisekeysharingbetweeneverytwonodesinanetworkdoesnotscale
tolargenetworkswithtensofthousandsofnodes,asthestoragerequirementsare
toohigh.AsecurityschemeinWSNsmustprovideefficientkeydistributionwhile
maintainingtheabilityforcommunicationbetweenallrelevantnodes.

INTRODUCTION
MATRUSRI
ENGINEERING COLLEGE
Inadditiontokeydistribution,secureroutingprotocolsmustbeconsidered.These
protocolsareconcernedwithhowanodesendsmessagestoothernodesorabase
station.Akeychallengeisthatofauthenticatedbroadcast.
Existingauthenticatedbroadcastmethodsoftenrelyonpublickeycryptographyand
includehighcomputationaloverheadmakingtheminfeasibleinWSNs.
SecureroutingprotocolsproposedforuseinWSNs,suchasSPINS,mustconsider
thesefactors.
Additionally,theconstraintonenergyinWSNsleadstothedesirefordata
aggregation.Thisaggregationofsensordataneedstobesecureinordertoensure
informationintegrityandconfidentiality.
While this is achievable through cryptography, an aggregation scheme must take into
account the constraints in WSNs and the unique characteristics of the cryptography
and routing schemes.

.
5.1 Security Architecture
MATRUSRI
ENGINEERING COLLEGE
.AWSNisusuallycomposed
ofhundredsorthousands
ofsensornodes.These
sensornodesareoften
denselydeployedina
sensorfieldandhavethe
capabilitytocollectdata
androutedatabacktoa
basestation(BS).Asensor
consistsoffourbasicparts:
asensingunit,aprocessing
unit,atransceiverunit,and
apowerunit.Itmayalso
have additional
application- dependent
componentssuchasa
locationfindingsystem,
powergenerator,and
mobilizer

5.1 Security Architecture
MATRUSRI
ENGINEERING COLLEGE
Theprotocolstackusedinsensornodescontainsphysical,datalink,network,
transport,andapplicationlayersdefinedasfollows[4]:
•Physicallayer:responsibleforfrequencyselection,carrierfrequencygeneration,
signaldeflection,modulation,anddataencryption
•Datalinklayer:responsibleforthemultiplexingofdatastreams,dataframe
detection,mediumaccess,anderrorcontrol;aswellasensuringreliablepoint-to-
pointandpoint-to-multipointconnections
•Networklayer:responsibleforspecifyingtheassignmentofaddressesandhow
packetsareforwarded
•Transportlayer:responsibleforspecifyinghowthereliabletransportofpackets
willtakeplace
•Applicationlayer:responsibleforspecifyinghowthedataarerequestedand
providedforbothindividualsensornodesandinteractionswiththeenduser

.
5.1 Security Architecture-Constraints in WSNs
MATRUSRI
ENGINEERING COLLEGE
Constraints in WSNs
Variety of real-life sensor nodes
IndividualsensornodesinaWSNareinherentlyresourceconstrained.
Theyhavelimitedprocessingcapability,storagecapacity,andcommunication
bandwidth.
Eachoftheselimitationsisdueinparttothetwogreatestconstraints—limited
energyandphysicalsize.

.
5.1 Security Architecture-Constraints in WSNs
MATRUSRI
ENGINEERING COLLEGE
The design of security services in WSNs must consider the hardware constraints of
the sensor nodes:
• Energy:
Energy consumption in sensor nodes can be categorized into three parts:
–Energy for the sensor transducer
–Energy for communication among sensor nodes
–Energy for microprocessor computation
Computation:
The embedded processors in sensor nodes are generally not as powerful as those in
nodes of a wired or ad hoc network.
Memory:
Transmission range:

5.2 Survey of Security protocols for WSN-Security requirements
MATRUSRI
ENGINEERING COLLEGE
ThegoalofsecurityservicesinWSNsistoprotecttheinformationandresourcesfrom
attacksandmisbehavior.
ThesecurityrequirementsinWSNsinclude:
Availability,
Authorization
Authentication
Confidentiality
Integrity,
Non-repudiation
Freshness
As new sensors are deployed and old
sensors fail, we suggest that forward and
backward secrecy should also be
considered:
Forward secrecy
Backward Secrecy

5.2 Survey of Security protocols for WSN: Threat model
MATRUSRI
ENGINEERING COLLEGE
InWSNs,itisusuallyassumedthatanattackermayknowthesecuritymechanisms
thataredeployedinasensornetwork;theymaybeabletocompromiseanodeoreven
physicallycaptureanode.
once a node is compromised, the attacker is capable of stealing the key materials
contained within that node.
Base stations in WSNs are usually regarded as trustworthy.
Attacksinsensornetworkscanbeclassifiedintothefollowingcategories:
• Outsider versus insider attacks:
•Passive versus active attacks:
•Mote-class versus laptop-class attacks:

5.2 Survey of Security protocols for WSN:Evaluation
MATRUSRI
ENGINEERING COLLEGE
ThefollowingmetricstoevaluatewhetherasecurityschemeisappropriateinWSNs:
Security:
Resiliency:
Energy efficiency:
Flexibility:
Scalability:
Fault-tolerance:
Self-healing:
Assurance:

5.2 Survey of Security protocols for WSN: Attacks in sensor networks
MATRUSRI
ENGINEERING COLLEGE
WSNsarevulnerabletovarioustypesofattacks.Accordingtothesecurityrequirements
inWSNs,theseattackscanbecategorizedas:
Attacksonsecrecyandauthentication:
Attacksonnetworkavailability:
Stealthyattacksagainstserviceintegrity:
Intheseattacks,keepingthesensornetworkavailableforitsintendeduseis
essential.DoS(Denial-of-service)attacksagainstWSNsmaypermitreal-world
damagetothehealthandsafetyofpeople.
TheDoSattackusuallyreferstoanadversary’sattempttodisrupt,subvert,or
destroyanetworkHowever,aDoSattackcanbeanyeventthatdiminishesor
eliminatesanetwork’scapacitytoperformitsexpectedfunction.
Sensornetworksareusuallydividedintolayers,andthislayeredarchitecture
makesWSNsvulnerabletoDoSattacks,asDoSattacksmayoccurinanylayerofa
sensornetwork.

.
5.2 Survey of Security protocols for WSN: Attacks in sensor networks
MATRUSRI
ENGINEERING COLLEGE
PHYSICAL LAYER
Jamming
Tampering
LINK LAYER
Collisions
Exhaustion
Unfairness
NETWORK AND ROUTING LAYER: The network and routing layer of sensor networks
is usually designed according to the following principles.
•Power efficiency is an important consideration.
• Sensor networks are mostly data-centric.
• An ideal sensor network has attribute-based addressing
and location awareness.

5.2 survey of security protocols for WSN :Attacks in sensor networks
MATRUSRI
ENGINEERING COLLEGE
Sensor network layers and denial-of-service defenses

5.2 Survey of Security protocols for WSN: Attacks in sensor networks
MATRUSRI
ENGINEERING COLLEGE
The attacks in the network and the routing layer include the following:
Spoofed, Altered, or Replayed Routing Information
Selective Forwarding
Sinkhole
Sybil
Wormholes
Hello Flood Attacks
Acknowledgment Spoofing
TRANSPORT LAYER:
Flooding
De-synchronization

CONTENTS:
5.2 survey of security protocols for WSN: CRYPTOGRAPHY in WSNs
OUTCOMES:
Discuss about survey of security protocols of WSNs
.
MODULE-3
MATRUSRI
ENGINEERING COLLEGE

5.2 Survey of Security protocols for WSN: Cryptography in WSNs
MATRUSRI
ENGINEERING COLLEGE
Selectingthemostappropriatecryptographic
methodisvitalinWSNsbecauseallsecurity
servicesareensuredbycryptography.
CryptographicmethodsusedinWSNsshould
meettheconstraintsofsensornodesandbe
evaluated
bycodeSize,
Datasize,
Processingtime,and
Powerconsumption
Publickeycryptography,
Symmetrickeycryptography.
Public key cryptography:
average ECC
and RSA execution times
Public key cryptography:
average energy costs of
digital signature and
key exchange omputations

.
5.2 Survey of Security protocols for WS:Cryptography
MATRUSRI
ENGINEERING COLLEGE
Symmetric key cryptography: average
RC5 and skipjack execution times
Symmetric key cryptography: average
energy numbers for AES and SHA-1
Tables shows the
execution time and
energy cost of two
symmetric
cryptography
protocols on an
Atmel ATmega128
processor
Theperformanceofsymmetrickeycryptographyismainlydecidedbythefollowing
factors:
•Embeddeddatabuswidth
•Instructionset

5.2 Survey of Security protocols for WSN : Key management protocols
MATRUSRI
ENGINEERING COLLEGE
Keymanagementisacoremechanismtoensurethesecurityofnetworkservicesand
applicationsinWSNs.Thegoalofkeymanagementistoestablishrequiredkeys
betweensensornodeswhichmustexchangedata.
According to the
network structure,
the protocol scan
be divided into
centralized key
schemes and
distributed
key schemes.
Taxonomy of key management protocols in WSNs

5.3 Classification and comparison of key management protocols in WSNs
MATRUSRI
ENGINEERING COLLEGE

5.2 Survey of Security protocols for WSN :Secure routing protocols
MATRUSRI
ENGINEERING COLLEGE
Many routing protocols have been specifically designed for WSNs. These routing
protocols can be divided into three categories according to the network structure:
flat-based routing,
hierarchical-based routing, and
location-based routing
Inflat-basedrouting,allnodesaretypicallyassignedequalrolesorfunctionality.
Inhierarchical-basedrouting,nodesplaydifferentrolesinthenetwork.
In location-based routing, sensor node positions are used to route data in the
network.
Mostnetworklayerattacksagainstsensornetworksfallintooneofthecategories
describedabove,namely:
• Spoofed, altered, or replayed routing information • Wormholes
• Selective forwarding • Sybil
• Sinkhole • Acknowledgment spoofing
• Hello flood attacks

.
5.2 Survey of Security protocols for WSN :Secure routing protocols
MATRUSRI
ENGINEERING COLLEGE
Asecureroutingprotocoldependsonanappropriatekeymanagementschemeina
WSN,whichhasbeendiscussedearlier.
Beforearoutingprotocolstarts,sensornodesshouldhavebeenloadedwithproper
keys(e.g.,thekeyforconfidentiality,authentication,etc.).Oneofthefundamental
securityservicesinsensornetworksisbroadcastauthentication,whichenablesthe
basestationtobroadcastauthenticateddatatotheentiresensornetwork.
Using a time-released key chain for source authentication
Broadcast authentication
Authenticated broadcast are impractical
in WSNs for the following reasons:
• Most proposals rely on public key
cryptography for the
authentication. However, public key
cryptography is
impractical for WSNs;
• Even one-time signature schemes that are
based on symmetric
key cryptography have too much overhead.

:
5.2 Survey of Security protocols for WSN :Secure routing protocols
MATRUSRI
ENGINEERING COLLEGE
Securerouting
Thegoalofasecureroutingprotocolistoensuretheintegrity,authentication,and
availabilityofmessages.
SNEPoffersthefollowingproperties:
semanticsecurity,
dataauthentication,
replayprotection,
weakfreshness,and
lowcommunicationoverhead.

5.2 Survey of Security protocols for WSN :Secure routing protocols
MATRUSRI
ENGINEERING COLLEGE
Comparison of secure routing protocols
SPINSidentifiestwotypesoffreshness:
weakfreshnessandstrongfreshness.
Weakfreshnessprovidespartialmessageorderingandcarriesnodelayinformation
whilestrongfreshnessprovidesatotalorderonarequest–responsepairandallows
fordelayestimation.

5.2 Survey of Security protocols for WSN : Secure data aggregation
MATRUSRI
ENGINEERING COLLEGE
Secure data aggregation in WSNs:
Dataaggregation(fusion)protocolsaimateliminatingredundantdata
transmittedacrossthenetworkandareessentialforenergy-constrainedWSNs.
Traditionaldataaggregationtechniquesincludesimpletypesofqueriessuchas
SUM,COUNT,AVERAGE,andMIN/MAX.
According to the protocol
operation, secure
data aggregation can be classified
into two categories:
Plaintext based and
Cipher based

.
Assignment Question
MATRUSRI
ENGINEERING COLLEGE
1.Explain the Hardware components of Security Architecture
2.Classification and comparison of key management protocols in WSNs.
3.What are the Security Routing Protocols.
4.Discuss about Cryptography in WSNs.
5.What are the Design constraints of security services in WSNs

Questions & Answers
MATRUSRI
ENGINEERING COLLEGE
S.NO QUESTION Blooms
Taxonomy
Level
Course
Outcome
1.What are the security requirements? L1 CO5
2.Draw the block diagram of key management
Protocols in WSNs
L1 CO5
3.Discuss about Secure Data Aggregation. L3 CO5
4.List out the Attacks in Wireless sensor networks.L1 CO5
5.What are the metrics to evaluate the security of
WSNs
L1 CO5
Short answer questions

Questions & Answers
MATRUSRI
ENGINEERING COLLEGE
S.NO QUESTION Blooms
Taxonomy
Level
Course
Outcome
1.Differences between WSNs security protocols L3 CO5
2.Draw and Explain about WSN Security architecturesL2 CO5
3.Explain the attacks in Sensor Networks L2 CO5
4.Discuss about Cryptography in WSNs L4 CO5
5.Explain about Key Management Protocols L2 CO5
Long answer questions

sensor networks unit wise 4 ppt units ppt

About This Presentation

Slide Content

Tags

Categories

Download

Quick Actions

Statistics

Related Slideshows

sensor networks unit wise 4 ppt units ppt

About This Presentation

Slide Content

Slide 1

Slide 2

Slide 3

Slide 4

Slide 5

Slide 6

Slide 7

Slide 8

Slide 9

Slide 10

Slide 11

Slide 12

Slide 13

Slide 14

Slide 15

Slide 16

Slide 17

Slide 18

Slide 19

Slide 20

Slide 21

Slide 22

Slide 23

Slide 24

Slide 25

Slide 26

Slide 27

Slide 28

Slide 29

Slide 30

Slide 31

Slide 32

Slide 33

Slide 34

Slide 35

Slide 36

Slide 37

Slide 38

Slide 39

Slide 40

Slide 41

Slide 42

Slide 43

Slide 44

Slide 45

Slide 46

Slide 47

Slide 48

Slide 49

Slide 50

Slide 51

Slide 52

Slide 53

Slide 54

Slide 55

Slide 56

Slide 57

Slide 58

Slide 59

Slide 60

Slide 61

Slide 62

Slide 63

Slide 64

Slide 65

Slide 66

Slide 67

Slide 68

Slide 69

Slide 70

Slide 71

Slide 72

Slide 73

Slide 74

Slide 75

Slide 76

Slide 77