Z-wave

Z-wave is a radio protocol in the category of WHAN networks that is used primarily for home automation. It uses then a slave-master topology.

The master sends commands to the slaves that executes the commands and the slaves are unable to send information directly to other slaves. The Home ID is a 32 bit unique identifier that is pre-programmed in all controller devices and a node ID is an 8 bit value. The masters and the slaves can only communicate within the same Home ID. It means that within the same area, it's possible to have 232 masters that each control 28 devices. This can be an advantage for a particular application where many controllers are needed for different slaves in the same network. It also uses a ACK mechanism, and has a bit rate of 40 kbps.

Source
http://www.z-wave.com/

http://www.zwaveproducts.com/