The Outdoor Wireless Healthcare Monitoring System for Hospital Patients Based on ZigBee

Zigbee

The name of ZigBee comes from the zigzagging path a bee (a data packet) takes to get from flower to flower (or node to node) (Niagara, 2005). ZigBee is primarily intended low power and low duty-cycle sensors. ZigBee nodes can active for less than 1% of the time. For instance, an off-line node can connect to a network in about 30 ms. Waking up a sleeping node takes about 15 ms, as does accessing a channel and transmitting data. Our healthcare system will get benefit from this technology. In large outdoor monitoring area, not all of nodes should work all the times. These nodes could go to sleep, and wake up until a new task coming.

As an IEEE 802.15.4 based standard, ZigBee is described by referring to the 7-layer OSI model for layered communication systems. But not all of the 7 layers are defined, ZigBee Alliance only specifies four layers (Physical, Data Link, Network, and Application), as well the Application Layer (APL) that allows end-developers design custom applications that use the services provided by the lower layers. It should be noted that the ZigBee Alliance choose to use an already existing data link and physical layers specification. These are published IEEE 802.15.4 (IEEE Standard 2003) standards for low-rate personal area networks. The network and application layer are defined by the alliance itself.