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8/8/2019 2007 Sensor Networks
http://slidepdf.com/reader/full/2007-sensor-networks 1/31
Taking Sensor Networks from
the Lab to the Jungle
Vamshi NadipelliPreethi Tiwari
ECE-695
Mobile Wireless Networks
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W hat is a Sensor Network?
A sensor network is a collection of sensor nodes
equipped with sensing, communication (short range
radio) and processing capabilities.
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Outline
IntroductionThe System
Areas of ApplicationChallenges
TechnicalSystem
Conclusion
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IntroductionChain Home - B ritain¶s Radar Network WW II
Cold War:SOSUS ± The Pacific Ocean
N ORAD ± Cheyenne MountainNational Power GridInvolves
Devices with multiple sensorsNetwork via wireless/physical links
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The Systems involved
Sensor Node Internals
Operating System
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Sensor Node Internals
SENSOR
POWERSUPPLY
CPU
COMMUN ICAT ION
NODE
ELECTRO-MAGNETICINTERFACE
Some Current Node Platforms:
1. Sensoria WINS
2. Smart Dust ± Dust Inc. Berkeley
3. UC Berkeley mote ± Crossbow (www.xbow.com)
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Op erating System - Tiny OS
Custom built at UC, B erkeley for wirelesssensor nodesComponent -based architecture: ensuresminimum code sizeComponent library includes:
Network protocolsSensor drivers
Data acquisition toolsDistributed services
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Physical Size
AWACS
LWIM III AWAIRS IWINS
NG 2.0
Berkley
Motes
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Applications
B order MonitoringB attlefield Observation
Forest Fire DetectionEnvironment and Habitat MonitoringInfrastructure securityIndustrial sensing
Medical Applications
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Border Monitoring Most widely cited application
US -Mexico B order (3100 km)Requires Full length Surveillance
Detection can be based onsound or vibration
With in a range of 10m
Estimated need of 440,000sensors
Air dropped biannually (battery life
6months)Not cost effectiveShould distinguish humans fromwild animals
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Battlefield surveillance
Observing enemy activities in a battle field.Unmanned aerial vehicles (UAV)
Coverage problem (limited radio range)
10,000 nodes were required to monitor just 1 squarekilometer
For large areas:
cost
Many nodes implies large number of UAV¶s operatingsimultaneously.
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Forest Fire Detection
A sensor network is more feasible as an early warning system for
forests.
Carefully placing nodes (close to vulnerable areas such as hilltops)
Reduce the number of sensors required to cover a large geographic
area.
Important aspect is lifetime
Must operate for a very long period of time to discover a
comparatively rare event
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Nodes are subjected to random failures
Due to battery exhaustion
Disorientation of antennas (falling branches, wind etc)
So, Networks relay messages hop by hop failure of severalclosely spaced nodes could partition the network into non
communicating subnetworks
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Environment and Habitat Monitoring
Environmental monitoring involves collecting readings over time across a
volume of large space enough to exhibit significant internal variation.
Environmental sensors are used to monitor relative humidity, barometricpressure and temperature.
They study vegetation responses related to climatic trends and diseases
Whereas the imaging sensors can identify, track and measure the populationof birds and other species.
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Monitoring nesting
Large number of burrows.
Long time observation
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Migration pattern of zebrasThey generally move in wide areaLong term observation
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I nfrastructure Security
Early detection of chemical, biological and nuclear threats.
Protection of power plants and communication centers.
Networks of video, acoustic and other sensors are deployed around thesefacilities.
When compared to Fixed sensors, Ad hoc networks can provide moreflexibility and additional coverage.
MULT IPLE SENSORS provide Improved coverage, detection, and reducedfalse alarm rate.
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Industrial Sensing
Goals of commercial industryLower costImproved performanceMaintainability
It involves continuous monitoring of vibrations, lubrication levels and insertinsensors into regions inaccessible by humans.
Spectral and Optical sensors are generally used in industrial applications
because inputs from hundreds or thousands of sensors can be fed into thedatabases that can be accessed in any number of ways to show the real tim
information (called MULT IPO INT OR MATR IX SENS ING ).
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Medical applications
Heart rateOxygen saturationEnhances emergency
medical care.
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Technical challenges
Changing network topology:Node failuresIntroduction of additional nodes variations in sensor locationChanges to cluster allocations in response to network demandsrequires the adaptability of underlying network structures and
operations.
Advanced communication protocolsTo support high level services and real - time operation
(to adapt rapidly to changes in network conditions).
Resource optimization:To minimize cost, power and network traffic loadsEnsuring network reliability and adequate sensor resolution for dataaccuracy.
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Limitations:Power, Memory, processing power, life - time. These physical constraints
may be minimized through further technological breakthroughs inmaterials and sensor hardware designs.
Failure prone :Individual sensors are unreliable, particularly in harsh and unpredictableenvironments.
Addressing sensor reliability can reduce the level of redundancyrequired for a network to operate with the same level of reliability.
Network congestion resulting from dense network
deployment :The quantity of data gathered may exceed the requirements of thenetwork and so evaluation of the data and transmission of only relevantand adequate information needs to be performed.
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Self-organization
Ability to adapt to dynamic environments as well as ad hoc distributionand connectivity scenarios.
Self-operating and self-maintaining
This functionality is desired in order to minimize further humaninteraction beyond network deployment.
Security
It is a critical factor in sensor networks.
An effective compromise must be obtained, between the low bandwidthrequirements of sensor network applications and security demands.
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Conclusion
Sensor networks are application specific
Key application characteristics
Lifetime, cost, data rate, environment, network
topology, user interaction
Must address the system aspects of wireless sensor network design