Introduction to Theory and Applications of Self Organizing Wireless Sensor Networks Vijay K. Devabhaktuni & James W. Haslett Department of Electrical and.

Introduction to Theory and Applications of Self Organizing

Wireless Sensor Networks

Vijay K. Devabhaktuni & James W. Haslett

Department of Electrical and Computer Engineering

University of Calgary

13 July 2004

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Agenda

Introduction

Self Organizing Wireless Sensor Networks

Experimental System

Wireless Sensor Networks in Patient Monitoring

Demonstration

Summary

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Wireless Sensor Network (WSN)

A wireless sensor network consists of a large number of nodes deployed in the environment being sensed and controlled through wireless communication.

Typically, a WSN consists of

• A number of remote nodes (we refer to them as motes)

• Base station

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Features:The remote nodes self-assemble into a network.

The sensor information is propagated to the base station.

Nodes collaborate i.e. intermediate nodes assist distant nodes to reach the base station.

Routing Tree Link

Connectivity

Base Station

Self Organizing WSN

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Highlights

• Micro-sensors, on-board processing and wireless interface are all possible at very small scale!

• WSN are able to monitor a phenomena up-close

• Spatio-temporally dense environmental monitoring becomes a reality

• Networked sensing can reveal certain previously unobservable phenomena of our nature

Seismic structure response

Contaminant transportation

Marine microorganisms

Eco-system’s biocomplexity

Application Domains

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Sensor ADC Radio

Battery

Event detectionWireless communication with other nodes & base

In-node processing

Mote: Structure & Function

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Enabling TechnologiesTechnological advances have facilitated

• Smaller & cheaper electronic components

• Systems on a single chip

• Integrated low-power communication modules

The above trends enabled WSN characterized by

• Smaller physical size

• Multi-functional behavior & concurrent operation

• Wireless communication

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UCLA, 1996 UCLA, 1998

Sensoria, 2001UCB, 2000

(Crossbow Tech.)

It’s Just a Beginning

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Time

log

(p

eo

ple

pe

r c

om

pu

ter)

“Streaming informationto/fromphysical world”

Number crunchingData storage

ProductivityInteractive

Mainframe

Minicomputer

Workstation

PC

Laptop

PDA

Roadmap

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Flexible integration of sensors

Low-cost & energy-efficient processors

Robust communication over radio

Lifetime source with each mote

A Dream Network!

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4× Mica2 Motes

3× Sensor Boards(MTS300)

Mote to PC Interfaceand Programming Board

(MIB500)

2× Prototyping Boards(MDA500)

4× Mica2Dot Motes

Experimental Hardware

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Generations of Crossbow Motes

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Mica2dot

• Battery

• Memory and Processor

• Sensor modules (externally integrated)

• 916/433 radio transceiver

• 10-bit ADC

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Base Station

Base station includes an interface board that allows

• Mote connectivity

• RS-232 serial programming interface

• Aggregation of network data on a PC

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Sensor interfacing

Radio messaging

Routing

Power management

Time

Debug

Required Software Services

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Developed taking the following aspects into account

• Efficient resource utilization

• Small foot print to run on small processors

Key Features:

• Set of services

• Simple operating system

• Open-source development environment

• nesC programming language

Tiny Operating System (TinyOS)

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Designed for low-power ad hoc WSNResponsive to stimuli, event oriented, scaleable

Key elementsSensing, computation, communication, power

Resource constrainedPower, memory, processing

Adapt to changing technologyModularity & re-use

TinyOS Architecture

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Dialect of C

TOS syntax and structure aware– Variables, tasks, calls, events, signals– Component wiring

A pre-processor– nesC output is a c program file, which is

compiled and linked using gcc tool

nesC - The TinyOS Language

Application Example

A Wireless Patient Monitoring System for the Ward of the 21st Centuryof the Calgary Foothills Hospital

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Doctors wish to continuously monitor variations in

• Temperature

• Heart rate

• Blood oxygenation

• Respiratory rate

Toward this end, we developed a wireless framework.

Patient’s Vital Medical Parameters

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The Comprehensive Wireless Framework

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Key Features

The framework includes

Real-time sensing of patient’s vital parameters using precision-sensors interfaced to the motes

Wireless transmission of such critical information over radio frequencies to the base-station

Subsequent data processing on a PC to allow detection of medical emergencies and alerting of medical staff

Note: Emergency detection is enabled using neural networks

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Deliverables

A self-organizing wireless system capable of continuous patient-monitoring

Patients can move about in the hospital space, thanks to the “multi-hop” feature of WSN

A smart hospital bed with automation in terms of emergency detection

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Temperature Sensor

Ear temperature is quick to read and reliable!

Our initial temperature sensor design involved:

• Thermistor modeling

• Linearization of output voltage

• Initial prototype is operational

• Future work will include packaging of thermistor using a silicon enclosure to protect from ear wax, and other non-intrusive methods of measuring body temperature

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Heart Rate & Blood Oxygenation

This instrument is being interfaced to a wireless mote

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Potential applications for Ad hoc WSN are vast

Low-power transceiver designs become essential

• “Low-power” versus “Performance”

Fully-integrated low-power relaxation VCO• Ken Townsend presented measured results

Low-Power Transceivers

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ADXL202AE dual-axis accelerometers (±2g) from Analog Devices are interfaced to the motes

Mica2dot motes are programmed to read sensor data via ADC3 and wirelessly transmit such data

Nominal reading of sensors is +1500mV at 0g. Sensitivity characteristic is ±150mV/g

Targeted application is the R&D of 6-axis motion of human feet that helps understand Parkinson’s

Concept Demonstration

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(1324,1245)

Two types of nodes– Tripwire nodes

that always sense• Low-power

presence sensing

– Tracker nodes that sense on-demand

Future of Power Management

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Acknowledgements

NSERC

iCORE

TRLabs

Calgary Health Region

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Conclusions

In this project, WSN technology is exploited for developing a framework for wireless patient-monitoring.

Results are expected to significantly help the healthcare personnel to cope with today’s shortage of resources.

The WSN paradigm and its advancements promise many other key applications in the healthcare sector.

The research area opens the doors for novel R&D activities in the microelectronics arena.