The Continua Health Alliance has approved two wireless formats for their next generation standard for personal and clinic medical devices. The two formats are Bluetooth Low Power, when the specification and protocol is finalized and all the currently available ZigBee protocols.

PAN is aimed at device-to-device communication for body-worn devices, while ZigBee includes low-power LAN applications for device-to-device and device-to-station communication.

Freescale was a key participant in the creation of the demo for qualification and adoption of the ZigBee (IEEE 802.15.4 format) supporting the ISO/IEEE 11073 for point-of-care medical device communication standard. The solution that was presented at the Barcelona meeting was based on not only the technology merits of the communication method, but also availability of parts and sub-systems, component and IP providers, software providers, and products that are incorporating the technology.

Freescale makes sensors, low-power embedded processors and battery-saving power-management technologies that are used extensively in pulse-oximeters, glucose meters, insulin pumps, infusion pumps, blood pressure monitors and personal monitoring products such as activity monitors, gait sensors and wearable panic alarms. Several end product providers, both smaller start-ups and large established medical device providers such as Philips, presented to support the ZigBee adoption.

The ZigBee solution is based on a mesh network format that includes both device/patient identification as unique network elements, but also data-transfer protocols. The use of the mesh network format provides for high reliability multi-path data communication to base options for home, fitness center, retirement communities, nursing homes and a variety of medical care facilities where direct line of sight is often interrupted by temporary obstructions such as people, fixtures and movable metal objects (chairs, lights, poles, etc). The use of the mesh network environment, in addition to the data collection capability, allows for location and proximity identification, which are key aspects of patient monitoring and management for ageing and chronic disease care. In order to address privacy and HIPA compliance, the ZigBee protocols support multiple types of data security including 128 bit AES encryption.

The adoption of the ZigBee protocol by Continua Health Alliance and their device certification means that devices using the wireless solutions from Freescale, Philips, Texas Instruments and others will be able to interact on the network without conflict or interference.

The ZigBee Device Object (ZDO) is a predefined class of functionality so the product developer can focus on writing on the application code rather than low-level details. The Health Care targeting has created a custom Application Support Sub-layer (APS). The ZDO is responsible for starting the APS, and the Network layer and the Security Service Provider in the communication channel. The figure, highlights in Blue, the ZigBee Health Care definitions based on the Zigbee specification. This figure is from the ZigBee Alliance Web site in the white paper on application for Health and Wellness. Compliance with the IEE 11073-20601 protocol provides methods for: (1) establishing logical connections betwen devices, (ii) presenting capabilities of the devices, and (iii) servicing the communications needs.

Figure: ZigBee Wireless Sensor Applications for Health, Wellness and Fitness – March 2009

Pallab Chatterjee is the Coordinating Regional Editor for Chip Design magazine. He has been an independent consultant in the EDA and Mixed Signal design space for over 20 years. He holds a BSEE from UC Berkeley and an MSEE from San Jose State University.