Mitsubishi preps Zigbee for enterprise security apps

Mitsubishi is developing Zigbee-based networks for office and industrial use and one application includes positioning and distance measuring.

Mitsubishi Electric intends to commercialize in 2007 ZigBee-based sensor networks that have location and positioning applications, the company said Tuesday.

Mitsubishi Electric has added microcomputers with software algorithms to ZigBee sensors that enables them to measure the distance between each other, said Noriyuki Kushiro, manager at Mitsubishi Electric's Living Environment Systems Lab.

ZigBee is a wireless system based on the 802.15.4 standard approved by the Institute of Electrical and Electronics Engineers. It is designed to carry data at up to 250K bps (bits per second) and use very little power so that ZigBee equipment can run for years on standard household batteries.

In an experimental network made by the company, the chips on the sensors are able to measure distances between themselves through the different strengths of the signals, Kushiro said.

The chips used on the sensors are 16-bit microprocessors made by Renesas Technology and each combined chip and senor is powered by 2 AA batteries, according to the company.

The target price for the ZigBee sensor and chip unit is YEN 300 (US$2.85), but the company has not decided how much more it will charge for the algorithm for distance measurement, said Travis Woodward, a company spokesman.

The chips are able to calculate the distance to an accuracy of about 80 percent. For example, if two sensors are a meter apart, they can calculate the distance between them to an accuracy of 20 centimeters. If two sensors are 10 meters apart, the error is up to two meters, Kushiro said.

The experiment is being conducted on a floor of offices and rooms in a research building in Ofuna, west of Tokyo. The experimental network has 40 sensors that feed into a central processing unit that can real-time monitor where the sensors are, he said.

Mitsubishi believes the technology could be used for industrial applications such as monitoring the position of warehoused goods. Enterprises could network the floor of a building with about 200 sensors that could be attached to important or valuable equipment so that the network could be used for security applications, he said.

"You could attach the sensors even to chairs or people, for example, to find who is attending a meeting," he said.

One of the problems with ZigBee technology is that signals can't pass through building walls, Kushiro said.

In a different experiment at the Ofuna site, the company has linked a ZigBee network placed on machinery outside a building to one inside the building via a wire running along a refrigeration pipe, he said.

The two networks are connected through gateways at either end of the wire. When signals are transmitted through the wired connection, the 2.4GHz ZigBee frequency is changed to a series of frequencies that enable the signal to cope with interference and noise caused by the pipe, equipment and machinery, he said.

In this experiment, the sensors only check atmospheric conditions such as temperature and humidity and don't support the distance and position application. The wired link can extend up to 150 meters and transmit data speeds up to 400K bps (kilobits per second), according to experimental results, the company said.

Mitsubishi is running both experiments from January until August. If everything goes to plan, it wants to put the technologies on sale in Japan and internationally some time 2007, Kushiro said.

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