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Sensors organise themselves into wireless networks
Published:  01 August, 2003

Sensors organise themselves into wireless networks

A US company has developed a cable-free sensing technology, based on tiny, low-power devices which organise themselves into wireless networks, without human intervention, to transmit sensor information around a plant.

Millennial Net, founded in 2000 by a group of graduates from the Massachusetts Institute of Technology (MIT), says that its i-Bean system will allow OEMs and systems integrators to create easily-maintained, low data-rate wireless and control networks, at a low cost. It will be also allow them to place sensors in locations which are impossible to reach using conventional technologies.

The system has three main hardware elements:

Endpoints, which fit inside sensors and actuators to transmit analogue or digital data over a range of 30m or more. The coin-sized devices (shown above) are self-contained miniature computers with a power source, flash memory, and peripherals, including a digital I/O interface, analogue-to-digital converter, and radio-frequency transceiver for two-way communications. The devices, powered by calculator batteries, draw less than 50µA at 3V, giving an expected operating life of at least ten years.

Routers, which can extend the network`s operating range to hundreds of metres, as well as routing signals around obstacles, and providing back-up routes in the event of device failures or network congestion.

Gateways, which link i-Bean networks to LANs, host controllers, or the Internet. They gather data from the network and act as a portal to monitor performance and to configure network parameters.

When an i-Beans network is first powered up, the components organise themselves into a star-mesh network with redundant routes. The technology also supports other network architectures, including simple mesh structures (where power and battery life are not major concerns), linear arrangements (for monitoring installations such as pipelines) and simple stars (where redundancy is not essential).

If devices are added to or removed from a network, or are moved, the network reconfigures itself automatically. It also adapts to changes in network traffic and radio propagation conditions. The gateways support interfaces including RS-232, Ethernet and GSM.

The technology uses a variety of radio technologies, including micro-power, narrowband systems, as well as the "wireless personal area network" (WPAN) system, as defined in IEEE 802.15.4. Data rates of up to 500 kb/s are possible.

Millennial Net has recently secured $6m in backing from a group of venture capitalists.

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