Wireless Personal Area Networks (WPAN)
WPAN protocols run over low cost, low power, and low data rate radio links, typically in wireless control and sensor networks. WPAN radios save power by sleeping (powering down) at low duty cycles, by transmitting short (less than 128B) packets, and by using just enough transmit power to reach their nearest neighbor in a mesh topology. The radios operate in unlicensed ISM frequencies in the 858, 915 and 2450 MHz bands at data rates less than 250kbps.
The first version of IEEE 802.15.4 was ratified in 2003. The ZigBee 1.0 specification was ratified in 2004.
The IEEE 801.15.4 protocol
The ZigBee protocol