WSN Programming Course

Introduction to Wireless Sensor Networks

Manuel Fernández

UAH, 18th September 2013

Contents

• What are Wireless Sensor Networks? • WSN Advantages & Challenges • Applications • Future of WSN • What are Motes? • WSN Evolution • IEEE 802.15.4 • IEEE 802.15.4 vs. ZigBee • Future of IEEE 802.15.4 • Embedded Operating Systems • Introduction to TinyOS 2.x

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• A Wireless Sensor Network (WSN) is a wireless network of small autonomous devices spatially distributed over a certain area that cooperatively monitor physical or environmental variables through their attached sensors, and transmit this information to a main location.

What are WSNs?

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• Advantages:

• Low cost devices • Low power • Easy and quick to deploy • Scalability (increase network robustness)

• Challenges:

• Energy constrained • Limited memory and computation • Low Bandwidth

WSN Advantages &Challenges

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• Monitoring of objects • Monitoring of areas • Monitoring of objects and areas

Applications

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Monitoring of objects • Structural Monitoring • Condition-based Maintenance • Medical Diagnostics • Urban terrain mapping Example: Condition-based Maintenance 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

Applications

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Monitoring of areas • Environmental and Habitat Monitoring • Precision Agriculture • Indoor Climate Control • Military Surveillance • Treaty Verification • Intelligent Alarms

Example: Precision agriculture • Precision agriculture aims at making agricultural operations more

efficient and cost effective, while reducing environmental impact. • The information collected from sensors is used to evaluate

optimum sowing density, estimate fertilizers and other inputs needs, and to more accurately predict crop yields.

Applications

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Monitoring of objects and areas • Wildlife Habitats • Disaster Management • Emergency Response • Ubiquitous Computing • Asset Tracking • Health Care • Manufacturing Process Flows • …

Applications

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Smart Home/Smart Office • Sensors controlling appliances and electrical devices in the house • Better lighting and heating in office buildings. Biomedical/Medical • Health Monitors: Glucose /Heart rate • Chronic disease: artificial retina/ cochlear implants • Hospital sensors: monitor vital signs/ record anomalies Traffic management & monitoring • Traffic flow • Real time routing update Industrial & Commercial •Agricultural crop conditions •Inventory tracking •Plant equipment maintenance monitoring •Automated problem monitoring

Future of WSN

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• Low cost and power computer • Sensors • Radio module • Storage • Power unit

What are Motes?

CONTROL

SENSOR 3

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• CM5000

What are Motes?

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WSN Evolution

• First developments for military applications • At the end of the 90’s, the possibilities of this technology were very evident for researches & the industry across the globe. • In 2003 the IEEE 802.15.4 standard was formulated. The first embedded operating systems are developed • First WSN designs are distributed systems • Newest designs focus on in-node processing and actuation, and multipoint communication

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• In 2003 the IEEE 802.15.4 standard was formulated, as an answer to the industry needs for a common communication stack among small devices

• This stack is aimed towards low power consumption, and low data transfer rates

• The communication stack focuses on the definition of the frequencies of operation, and how they physically access the medium

IEEE 802.15.4

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IEEE 802.15.4

802.15.4 802.11

(Wi-Fi) Bluetooth

UWB (Ultra

Wide Band) Wireless USB IR Wireless

Data Rate 20, 40, and 250

Kbits/s

11 & 54

Mbits/sec 1 Mbits/s 100-500 Mbits/s 62.5 Kbits/s

20-40 Kbits/s

115 Kbits/s

4 & 16 Mbits/s

Range 10-800 meters 50-100 meters 10 meters <10 meters 10 meters

<10 meters (line

of sight)

Networking Topology

Ad-hoc, peer to

peer, star, or

mesh

Point to hub

Ad-hoc, very

small networks Point to point Point to point Point to point

Operating Frequency

868 MHz

(Europe)

900-928 MHz

(NA), 2.4 GHz

(worldwide)

2.4 and 5 GHz 2.4 GHz 3.1-10.6 GHz 2.4 GHz 800-900 nm

Complexity (Device

and application

impact)

Low High High Medium Low Low

Power Consumption

(Battery option and

life)

Very low (low

power is a design

goal)

High Medium Low Low Low

IEEE 802.15.4

Tech comparison:

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IEEE 802.15.4 vs. ZigBee

IEEE 802.15.4 IS NOT THE SAME AS ZIGBEE!!!

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• IPv6 over 802.15.4 • 6LoWPAN • Blip • RPL (IETF ) • ….

• Industrial Automation with IEEE 802.15.4 • WirelessHART • ISA100 • …

Future of IEEE 802.15.4

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• Embedded OS run inside the mote and take care of most of most of the operations, always focusing on achieving a low power state

• This allows the programmer to focus on developing applications, and staying away from low power tinkering

• Among the most popular, TinyOS and Contiki lead the research

Embedded Operating Systems

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Introduction to TinyOS-2.x

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Overview •One of the first OSs to target WSNs – currently the most widespread • Emphasis is on memory consumption – both program and data memory • Open-source w/ rich component library • Memory efficient • Rich tool-chain • Large code-base and user community

TinyOS Features: • TinyOS is programmed in nesC • nesC is a C-style language • nesC provides the programming abstractions – component based • Split-phase execution – return values arrive asynchronously through events • Tasks provide the unit of concurrency – typically spawned by events – can be pre-empted by asynchronous events – FIFO scheduling • Pre-emptive threaded model with TOSThreads

Introduction to TinyOS-2.x

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• TinyOS abstracts everything as a component:

– Components can be reused

– Components can be replaced

– Components can be hardware or software

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Introduction to TinyOS-2.x

Component-oriented Programming

• Object-Oriented Programming:

– Focuses on the relationships between classes that are combined into one large binary executable

• Component-Oriented Programming:

– Focuses on interchangeable code modules that work independently and don't require you to be familiar with their inner workings to use them.

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Introduction to TinyOS-2.x

TinyOS Architecture

Sensing Comms Other Libraries

Application

Main (scheduler)

Hardware Abstractions (ADC, CLOCK, I2C, LEDS, PHOTO, UART, SPI)

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Introduction to TinyOS-2.x

Compiling

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Introduction to TinyOS-2.x

Contact Info: Manuel Fernández

manuel.fernandez@advanticsys.com

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