sensors overview

7/28/2019 Sensors Overview

1/25

Wireless Sensor Networks

Lecturer : M ichael O'Grady

Course: MSc Ubiquitous & Multimedia Systems

Unit: Context Sensitive Service Delivery

Lecture:


2/25

Objectives

Sensor Components

WSN Components

Design issues Applications


3/25

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)


4/25

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


5/25

Architecture of a WSN

Three Components (for this discussion!)

Node

Sink

Task Node Manager


6/25

Sensor Node: Tasks

Computation

Storage

CommunicationSensing/Actuation


7/25

Sensor Node: Characteristics

Small Size

Battery

Limited CPUWireless communications capability

One or more sensors (temperature etc)


8/25

Sensor Node: Components

Sensing Unit

Processing Unit

Power Unit

Transceiver


9/25

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


10/25

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)


11/25

Node - Power Unit

BatteriesAlkalinewide voltage range

Large physical sizeLithiumConstant voltage supply

Low currents

Major Challenge: How to effectively preserveand capture power in a WSN?????


12/25

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


13/25

WSN - Sink

Sink

A node that data should be delivered to

Base station

Cluster head

Gateway Node

InternetCellular network

PSTN


14/25

WSN- Task Node Manager

Management

Administration

InterfaceWSN health

WSN status

Alarms


15/25

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


16/25

Design Issues II

Sensor Network TopologyDeployment StrategiesPre-deployment

How? Plane?, one by one?

Post-deployment Topology changes

Position

Reachability

Energy

Malfunctionality Task

Redeployment how?


17/25

Design Issues III

Environment Close to observed phenomenon

Transmission Media

RF Infrared

optical

Power Consumption

Strategy for power management/conversationThree domainsSensing

Communication

Data processing


18/25

Applications of WSNs

Disaster Relief

Environmental monitoring

Intelligent Buildings

Facility management

Machine monitoring

Precision agriculture

Medicine

Logistics

Telematics


19/25

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


20/25

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?


21/25

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.


22/25

The End


23/25

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


24/25

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


25/25

sensors overview

Documents