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).
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.
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.