ZigBee-radio-module

Medical Design has a nice overview article on ZigBee, promoting the technology for medical devices. There are currently ZigBee based RTLS systems from a number of vendors, but to date I'm not aware of any medical devices using ZigBee radios.

ZigBee's low power consumption is attractive, but the technology is also intended for low duty cycle sensors, active less than 1% of the time. This eliminates ZigBee for many clinical applications. The examples mentioned in the article are all generalized facilities management applications that apply to the manufacturing floor as well as the nursing floor.

ZigBee networks carry different types of traffic with unusual characteristics,
such as data that is periodic, intermittent, and repetitive low-latency.

  • Periodic data is information usually defined by the application such as
    a wireless sensor or meter. It typically is handled using a beaconing system
    in which a sensor wakes at a set time, checks for the beacon, exchanges data,
    and returns sleep.
  • Intermittent data is either application or external stimulus, such as a
    wireless light switch. Data can be handled in a beaconless or disconnected
    system. In disconnected operations, the device only attaches to the network
    when communication is required, saving energy.
  • Repetitive low-latency data uses time-slot allocations as needed by security
    systems. These applications may use guaranteed time slots. It is a quality-of-service
    method that gives each device a specific duration as defined by the PAN coordinator
    (a network organizer) in the Super-frame to do whatever it requires without
    contention or latency.

Reading a meter, for instance, represents periodic traffic with data from water
or gas meters transmitted to a line-powered electric meter which passes the
data over a power line to a central location. For this operation, the RFD meter
wakes up and listens for the beacon from the PAN coordinator. When received,
the RFD requests to join the network. The coordinator accepts the request. Once
connected, the device passes its meter information and returns to sleep.

Oops, the medical mask fell right off!

Pictured right is a ZigBee radio module with antenna.

UPDATE:  In the comment below, connectologist Arnaud Houette notes why his firm (Capsule Technologie) evaluated ZigBee and passed.