Z-Wave is a proprietary wireless communications protocol designed for home automation, specifically to remote control applications in residential and light commercial environments. The technology uses a low-power RF radio embedded or retrofitted into home electronics devices and systems, such as lighting, home access control, entertainment systems and household appliances.
The Z-Wave Alliance is an international consortium of manufacturers that provide interoperable Z-Wave enabled devices.
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Z-Wave communicates using a low-power wireless technology designed specifically for remote control applications. The Z-Wave wireless protocol is optimized for reliable, low-latency communication of small data packets, unlike Wi-Fi and other IEEE 802.11-based wireless LAN systems that are designed primarily for high-bandwidth data flow. Z-Wave operates in the sub-gigahertz frequency range, around 900 MHz. This band competes with some cordless telephones and other consumer electronics devices, but avoids interference with Wi-Fi and other systems that operate on the crowded 2.4 GHz band. Z-Wave is designed to be easily embedded in consumer electronics products, including battery operated devices such as remote controls, smoke alarms and security sensors.
Z-Wave is currently supported by over 200 manufacturers worldwide and appears in a broad range of consumer products in the U.S. and Europe. The standard itself is not open and is available only to Zensys customers under non-disclosure agreement.[1] Some Z-Wave product vendors have embraced the open source and hobbyist communities.[2]
Z-Wave is a mesh networking technology where each node or device on the network is capable of sending and receiving control commands through walls or floors and use intermediate nodes to route around household obstacles or radio dead spots that might occur in the home. Z-Wave devices can work individually or in groups, and can be programmed into scenes or events that trigger multiple devices, either automatically or via remote control. Some common applications for Z-Wave include:
Z-Wave mesh networks can begin with a single controllable device and a controller. Additional devices can be added at any time, as can multiple controllers, including traditional hand-held controllers, key-fob controllers, wall-switch controllers and PC applications designed for management and control of a Z-Wave network.
A device must be "included" to the Z-Wave network before it can be controlled via Z-Wave. This process (also known as "pairing" and "adding") is usually achieved by pressing a sequence of buttons on the controller and the device being added to the network. This sequence only needs to be performed once, after which the device is always recognized by the controller. Devices can be removed from the Z-Wave network by a similar process of button strokes.
This inclusion process is repeated for each device in the system. Because the controller is learning the signal strength between the devices during the inclusion process, the devices themselves should be in their intended final location before they are added to the system.
However, once a device has been introduced into a network, it can become troublesome to remove the unit without actually having the functional unit present. A number of Z-Wave users have complained that a Z-Wave controller can be functionally destroyed by the bulb that it controls blowing and any controlling units then report errors every time a command that would affect that unit is sent, i.e., group commands / scene commands / all-on / all-off, etc. The only way to restore the service to a non-error reporting state is to factory reset all controllers and then relearn all Z-Wave devices.
The Z-Wave Alliance is a consortium of over 160 independent manufacturers who have agreed to build wireless home control products based on the Z-Wave standard. Principal members include Cooper Wiring Devices, Danfoss, Fakro, Ingersoll-Rand, Intermatic, Leviton, Universal Electronics, Wayne-Dalton, Z-Wave and Zensys.
Products and applications from the Z-Wave Alliance fall into all major market sectors for residential and light commercial control applications. These include lighting, HVAC and security control, as well as home theaters, automated window treatments, pool and spa controls, garage and access controls and more.
In Europe, the 868 MHz band has a 1% duty cycle limitation, thus a Z-Wave unit can only transmit 1% of the time. This limitation is absent in the U.S. 908 MHz band, but U.S. legislation imposes a 1 mW transmission power limit, contrary 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 substantially.
Z-Wave uses a source-routed mesh network topology and has one or more master controllers that control routing and security. Devices can communicate to another by using intermediate nodes to actively route around and circumvent household obstacles or radio dead spots that might occur. 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 farther than the radio range of a single unit; however with several of these hops a delay may be introduced between the control command and the desired result. In order for Z-Wave units to be able to route unsolicited messages, they cannot be in sleep mode. Therefore, most battery-operated devices are not designed as repeater units. A Z-Wave network can consist of up to 232 devices with the option of bridging networks if more devices are required.
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