Elec6076 wireless sensor networks

Nadège Barrage - [email_address] ELEC6076

Definition
Network topologies
Standards
Applications
Conclusion
Nadège Barrage – ELEC6076 – Wireless Sensor Networks

A wireless sensor network (WSN) = various wireless nodes communicating with base stations via radio link. It is an ad-hoc network : nodes act as forwarder, relaying data to a base station. Nadège Barrage – ELEC6076 – Wireless Sensor Networks

Each node is equipped with:
One or two sensors
A wireless commu-nications device
A small micro-controller
An energy source
The sensors can measure various conditions: temperature, sound, vibration, pressure, motion, pollutants… Nadège Barrage – ELEC6076 – Wireless Sensor Networks

Main functions of the microcontroller:
Managing data collection from the sensors
Performing power management functions
Interfacing the sensor data to the physical layer
Managing the radio network protocol
Nodes are really cheap. Their interface and their components are very basic, so they don’t need a lot of resources (which is not the case for base stations).

Star Network:
One base station
The remote nodes can only send or receive a message from the base station
Advantages: simple, minimum power consumption
Disadvantages: the base station must be within radio transmission range of all individual nodes

Mesh Network:
Any node can transmit to any other node (if the node is within its radio transmission range): multihop communications
Advantages: redundancy, scalability
Disadvantages: power consumption higher for the nodes implementing the multihop communications (battery life limited)

Hybrid Star-Mesh Network:
The lowest power sensor nodes cannot forward messages
The other nodes are enabled with multihop capability so that the messages can be forwarded from the low power nodes to other nodes on the network
Robust and versatile network, power consumption minimum. Nadège Barrage – ELEC6076 – Wireless Sensor Networks

Standards -> interoperability among multiple companies networks
Predominant standards for WSN communication:
Wi-Fi (IEEE802.11): for local area and high bandwidth data transfer between computers and other devices.
Data transfer rate ranges : 1 Mbps-50 Mbps
Typical transmission range: 300 feet
Disadvantages: power requirements quite high
Bluetooth (IEEE802.15.1 and .2): PAN lower power than Wi-Fi using a star network topology.
Disadvantages: can only support 7 nodes and relatively high power for a short transmission range

Zigbee (IEEE802.15.4): specifies the IEEE802.15.4 as the physical and MAC layer. It can support both star and hybrid star-mesh networks. IEEE802.15.4 is specifically designed for the requirement of wireless sensing applications. The hardware is designed to allow for the radio to be put to sleep.
Transmission frequencies: 868 MHz/902-928 MHz/2.48-2.5 GHz
Data rates: 20 Kbps, 50 Kbps and 250 Kbps
WirelessHART: used for industrial environments, it adopts the IEEE802.15.4 as the physical layer but defines its own time-synchronized MAC layer. It uses self-healing mesh network and meets the stringent requirements of industrial control.

Area monitoring:
Common application of WSNs
Nodes are deployed over a region where a phenomenon needs to be monitored
Event detected (pressure, vibration…) -> a base station receives the information and can take appropriate action
Environmental monitoring:
Landslide detection:
WSNs used to detect the slight movements of soil
Data gathered by the base station -> the occurrence of landslides can be known long before it actually happens

Environmental monitoring:
Greenhouse monitoring:
WSNs used to control the temperature and humidity levels in greenhouses
Fall of temperature or humidity below a specific level -> information transmitted by the node to the base station which can send a notification to the greenhouse manager
WSNs easy to move -> ideal for this kind of application
Glacsweb:
Project at the University of Southampton using WSNs to monitor glacier behaviour.
Nodes are placed on and under glaciers in Norway.

Industrial monitoring:
Structural health monitoring:
Sensors embedded into machines, structures and previously inaccessible locations -> condition-based maintenance
Expensive method but can prevent the cost of catastrophic failure of one of the machine or structure.
WSNs can also be used for health monitoring of large civil structures, using strain gauges.

Industrial monitoring:
Industrial automation:
Use of wired sensors too cumbersome for a production line environment
Example of use: measurement of gaps where rubber seals are to be placed

Smart home:
A future application !
It could control almost everything in a house!

Wireless sensing networks are very versatile.
Widespread development of WSNs in the future
Low power system absolutely necessary ; it is one of wireless sensor networks’ main challenges right now

Internet:
http://en.wikipedia.org/wiki/Wireless_sensor_network
http:// www.ece.ncsu.edu/wireless/wsn.html
http:// microstrain.com/white/Wilson-chapter-22.pdf
http://www.cs.utexas.edu/~ shan/paper/rtas08.pdf
http://envisense.org/glacsweb/index.html
Books:
Lewis, F.L., « Wireless Sensor Networks » , Smart Environ-ments: Technologies, Protocols, and Applications ed. D.J. Cook and S.K. Das, John Wiley, New York, 2004.

Elec6076 wireless sensor networks

by Tristan De Candé

Accessibility

Categories

Upload Details

Usage Rights

Statistics

Elec6076 wireless sensor networks Presentation Transcript