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
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