ZigBee at Heart of Home Monitoring Networks for the Vulnerable

The wireless developer Cambridge Consultants is demonstrating how ZigBee’s unique networking attributes can be exploited to implement sophisticated ‘home monitoring networks’ for the elderly and vulnerable. This emerging wireless application offers 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 caregivers to monitor vulnerable people and identify deviations to 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 networks, but 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 systems, including sophisticated body sensor nodes.”

For mobile nodes attached to people, ZigBee has the data rates to allow ‘person down’ alarms to be complemented by sophisticated functions ranging from monitoring blood pressure, to breathing or heart rate; Cambridge Consultants’ demonstration uses 250 millisecond updates to monitor breathing for example, in addition to transmitting the data required for position updates. In conjunction with data from simple sensors such as load cells on beds and chairs, and current flow sensors on electronic appliances, typical 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 line, or 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 required, or 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 ideal for wireless networking 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 dollars.

In conjunction with ZigBee’s support for ad-hoc mesh topologies, which allows installation without any specialised skills, these factors make it possible to design easy-install home monitoring networks, with consumer resale prices starting at a few hundred dollars.

The zonal location capability is based on a proprietary Cambridge Consultants algorithm that runs on standard ZigBee hardware, and using 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 alarms, and can be added to existing ZigBee infrastructure, at low cost to the developer.

Cambridge Consultants is a member of the Design Alliance program of qualified developers for Freescale’s embedded solutions, and the company’s Tim Whittaker is presenting a paper on the ZigBee demonstration on the 24th July.

Cambridge Consultants Ltd, Science Park, Milton Road, Cambridge, CB4 0DW, UK. Tel: +44 (0)1223 420024; Fax: +44 (0)1223 423373

Cambridge Consultants Inc., 451 D Street, Boston MA 02210, USA. Tel: +1 617 532 4700; Fax: +1 617 737 9889.