Overview of Z-Wave

Z-Wave is a wireless RF-based communications technology designed for control and status reading applications in residential and light commercial environments. Z-Wave delivers reliable wireless networking at a fraction of the cost of other similar technologies, by focusing on narrow bandwidth applications and substituting costly hardware. Z-Wave transforms any stand-alone device into an intelligent network node that can be controlled and monitored wirelessly.

Applications for Z-Wave intelligence include home entertainment systems, lighting and appliance control, HVAC systems, security and access control, meter reading and digital home health care.

Radio specifications
Bandwidth: 9,600 bit/s or 40 Kbit/s, fully interoperable
Modulation: GFSK
Range: Approximately 100 feet (or 30 meters) assuming "open air" conditions, with reduced range indoors depending on building materials, etc.
Frequency band: The Z-Wave Radio uses the 900 MHz ISM band: 908.42MHz (USA); 868.42MHz (Europe); 919.82MHz (Hong Kong); 921.42MHz (Australia/New Zealand).

Radio specifics
In Europe, the 868 MHz band has a 1% duty cycle limitation, meaning that a Z-wave unit can only transmit 1% of the time. This limitation is not present in the US 908 MHz band, but US legislation imposes a 1 mW transmission power limit (as opposed to 25 mW in Europe). Z-wave units can be in power-save mode and only be active 0.1% of the time, thus reducing power consumption dramatically.

Topology and routing
Z-wave uses an intelligent Mesh network topology and has no master node. A message from node A to node C can be successfully delivered even if the two nodes are not within range providing that a third node B can communicate with nodes A and C. If the preferred route is unavailable, the message originator will attempt other routes until a path is found to the "C" node. Therefore a Z-wave network can span much further than the radio range of a single unit. In order for Z-wave units to be able to route unsolicited messages, they cannot be in sleep mode. Therefore, most battery-operated devices will opt not to be repeater units. A Z-wave network can consist of up to 232 units with the option of bridging networks if more units are required.