Highlighting capabilities of mobile nodes

Paul Boughton

Cambridge Consultants is demonstrating how Zigbee's networking attributes can be exploited to implement sophisticated 'home monitoring networks' for the elderly and vulnerable.

This emerging wireless application is said to offer a major market opportunity for OEMs, as well as being a powerful aid that could reduce the load on stretched healthcare resources while helping people preserve their independence.

The demonstration illustrates a concept mobile node in such a network. Worn by the elderly or vulnerable, the wireless node monitors physiological signs and additionally provides zonal location sensing to identify which room the wearer is in. Combined with a few other fixed Zigbee nodes - a load sensor on the bed, for example - pictures of typical daily activity can be constructed. These could be used by relatives, building supervisors and carers to monitor vulnerable people and identify deviations from patterns in advance of problems, as well as providing the familiar panic button facility.

Zigbee is seen as a key technology for home automation and sensor networksbut its characteristics can be extremely valuable in some healthcare applications as well"notes Cambridge Consultants' Paul Williamson. "Research is establishing how modern wireless networks can enhance today's panic-button type systems. Our demonstration of personal monitoring combined with position sensing illustrates that Zigbee provides a practical platform for every aspect of such systemsincluding sophisticated body sensor nodes."

For mobile nodes attached to peopleZigbee has the data rates to allow 'person down' alarms to be complemented by sophisticated functions ranging from monitoring blood pressureto breathing or heart rate; for exampleCambridge Consultants' demonstration uses 250 millisecond updates to monitor breathingin addition to transmitting the data required for position updates. In conjunction with data from simple sensors such as load cells on beds and chairsand current flow sensors on electronic appliancestypical behaviour patterns in the home can be readily constructed - as research from Imperial College is showing.

Raw data can be transmitted to a central location using a broadband lineor analysed and stored locally for review on demand. This information can then be used by social services or doctors to monitor when intervention might be requiredor to notify carers of significant changes in activity patterns.

Zigbee's support for ultra-low-power devices that can operate for years from a small cell makes it particularly suitable for wireless networking of such devices. The designed-for-purpose nature of Zigbee means that all the sensor nodes can be implemented using single-chip radio-plus-microcontroller devices costing a few Euros.

In conjunction with Zigbee's support for 'ad-hoc' mesh topologieswhich allows installation without any specialised skillsthese factors make it possible to design easily installed home monitoring networkswith consumer resale prices starting at a few hundred Euros.

The zonal location capability is based on a proprietary Cambridge Consultants algorithm that runs on standard Zigbee hardware and uses the standard Zigbee protocol stack. Zonal location can be used in the home or professional care environments to monitor behaviour and allow rapid response to alarmsand can be added to existing Zigbee infrastructure at low cost to the developer.

For more informationvisit www.cambridgeconsultants.com

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