Communications in Medical Applications 30-11
communicate with each other and with the PAN coordinator. Furthermore, cluster heads can route
packets from/to their own cluster, other clusters, or the PAN coordinator. Sensor nodes, cluster heads,
and the PAN coordinator communicate with each other and with the outside world by employing a
superframe structure containing an active part, used for contention-based (CSMA/CA) or conten-
tion-free communications, and an inactive part where the transceiver can be turned o for power sav-
ing. is superframe is bounded by beacon frames periodically transmitted by the PAN coordinator,
which conveys the sensor network information to other systems by means of a (PC) gateway enabled
with TCP/IP communica