sensors overview
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Wireless Sensor Networks
Lecturer : M ichael O'Grady
Course: MSc Ubiquitous & Multimedia Systems
Unit: Context Sensitive Service Delivery
Lecture:
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Objectives
Sensor Components
WSN Components
Design issues Applications
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Some Thoughts
Recall Weisers vision for Ubiq. Computing Sense physical phenomena
Two Objectives: Ubiquity inject computation into the physical
environment with a high spatial density
Invisibility- computational nodes operate autonomously
Recall Ambient Intelligence..
How will this happen? One potential Solution = Wireless Sensor
Networks (WSNs)
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Classification of Sensor Networks
Event DetectionReport specified event
Periodic MeasurementsReport measurements at certain time intervals
Function approximationValue approximation using a sample temperature
Isothermal points identify edge of forest fire
Tracking Surveillance
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Architecture of a WSN
Three Components (for this discussion!)
Node
Sink
Task Node Manager
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Sensor Node: Tasks
Computation
Storage
CommunicationSensing/Actuation
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Sensor Node: Characteristics
Small Size
Battery
Limited CPUWireless communications capability
One or more sensors (temperature etc)
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Sensor Node: Components
Sensing Unit
Processing Unit
Power Unit
Transceiver
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Node - Sensing Unit
Senses or measures certain physicalphenomenon
Light
Sound
Et c etc
Analogue signal generated by Sensor
Signal digitised and sent to the Processing Unit
ADC Analogue-to-Digital Converter (ADC)
Note: alternative Sensor architectures available
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Node - Processing Unit
Processes sensed data
Collaborates with other Nodes to achieveWSNs objectives.
ComponentsMicrocontrollers/Microprocessors
FPGA (Field programmable Gate Arrays)
Reprogrammable / reconfigurable
Memory
Flash (low cost / storage capacity)
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Node - Power Unit
BatteriesAlkalinewide voltage range
Large physical sizeLithiumConstant voltage supply
Low currents
Major Challenge: How to effectively preserveand capture power in a WSN?????
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Node - Transceiver
Three popular communication schemesOptical Communication (Laser)
Low energy requirement (no antenna)
secure
Line of Sight required Sensitive to atmospheric conditions
Infra-Red (IR) No antenna
Limited in its broadcasting capacity
Radio Freuency (RF)Antenna required
Easy to use
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WSN - Sink
Sink
A node that data should be delivered to
Base station
Cluster head
Gateway Node
InternetCellular network
PSTN
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WSN- Task Node Manager
Management
Administration
InterfaceWSN health
WSN status
Alarms
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Design Issues I
Fault ToleranceSustain WSN operation despite individual node
failure
ScalabilityMaintain performance regardless of WSN size
Production CostsDirectly proportional to the cost of the node
Ideally
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Design Issues II
Sensor Network TopologyDeployment StrategiesPre-deployment
How? Plane?, one by one?
Post-deployment Topology changes
Position
Reachability
Energy
Malfunctionality Task
Redeployment how?
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Design Issues III
Environment Close to observed phenomenon
Transmission Media
RF Infrared
optical
Power Consumption
Strategy for power management/conversationThree domainsSensing
Communication
Data processing
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Applications of WSNs
Disaster Relief
Environmental monitoring
Intelligent Buildings
Facility management
Machine monitoring
Precision agriculture
Medicine
Logistics
Telematics
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Unconventional Power Sources
Power - an Achilles heel for WSNs?
Recall Energy Scavenging
Photovoltaics (solar)
Temperature gradients
Vibrations Mechanical energy
Pressure Variation Piezoelectric generator
Shoe
Air/liquid flowMiniature gas turbines
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Autonomic Computing
What is Autonomic Computing?
What was the motivation for itsdevelopment?
What are its 4 essential characteristics?
Why integrate Autonomic computingconcepts with Wireless Sensor Networks?
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Some Readings
Culler, D., Estrin, D., Srivastava, M. Overviewof Sensor Networks
Akyildiz, I. F.; Su, W.; Sankarasubramaniam,
Y.; and Cayirci, E. A. 2002.A survey onsensor networks. IEEE CommunicationsMagazine 40(8):102-114.
Kephart, J. O. and Chess, D. M. 2003. TheVision of Autonomic Computing. Computer36, 1 (Jan. 2003), 41-50.
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The End
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Project Demonstration
Wednesday 28th November 2006
Format
Short overview of the project
Demo of the project
Individual Contributions
Final Report
Due this coming Monday 6.00 PM
Remember - names & Students Numbers
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Provisional Exam Timetable
COMP40320 Adaptive Personalisation
Tuesday 12th December 2006
RDS 12.0013.45
COMP40300 - Context Sensitive ServiceDelivery
Saturday 16th December 2006
RDS 12.00-13.45
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