Z-Wave
Z-Wave is a wireless communications standard designed for home automation, specifically to remote control applications in residential and light commercial environments. The technology, which is developed by Danish company Zensys, 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 technology has been standardized by the Z-Wave Alliance, an international consortium of manufacturers that oversees interoperability between Z-Wave products and enabled devices.
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Overview
Z-Wave is a low-power wireless technology designed specifically for remote control applications. Unlike Wi-Fi and other IEEE 802.11-based wireless LAN systems that are designed primarily for high-bandwidth data flow, the Z-Wave RF system operates in the sub Gigahertz frequency range and is optimized for low-overhead commands such as on-off (as in a light switch or an appliance) and raise-lower (as in a thermostat or volume control), with the ability to include device metadata in the communications. Because Z-Wave operates apart from the 2.4 GHz frequency of 802.11 based wireless systems, it is largely impervious to interference from common household wireless electronics, such as Wi-Fi routers, cordless telephones and Bluetooth devices that work in the same frequency range. This freedom from household interference allows for a standardized low-bandwidth control medium that can be reliable alongside common wireless devices. On other hand, 2.4GHz frequency usage allows unlicensed devices usage in most countries, this is convenient to customers and allows wider technology adoption and reduced deployment costs. This could be not true for other frequencies and could easily turn into a strong drawback if licensing is required or frequency is occupied. That's one of reason why competing 2.4GHz technologies became so popular.
As a result of its low power consumption and low cost of manufacture, Z-Wave is 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.<ref>http://www.zwaveworld.com/ask/ask26.php</ref> Some Z-Wave product vendors have embraced the open source and hobbyist communities.<ref>http://www.zwaveworld.com/ask/ask8.php</ref>
Applications
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 around household obstacles or radio dead spots that might occur in the home. Z-Wave devices can work singly 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:
Remote Home Control And Management
By adding Z-Wave to home electronics such as lighting, climate and security systems, it is possible to control and monitor these household functions via remote control, based on manual or automated decisions. The control can be applied to a single device or group of devices, in a single room or zone or throughout the entire home. One of the benefits of Z-Wave over powerline communication technologies is the ability to function in older houses lacking a neutral wire. Z-Wave devices can also be monitored and controlled from outside of the home by way of a gateway that combines Z-Wave with broadband Internet access.
Energy Conservation
Z-Wave is envisioned as a key enabling technology for energy management in the green home. As an example, Z-Wave enabled thermostats are able to raise or lower automatically based on commands from Z-Wave enabled daylight sensors. Grouped scene controls can ensure that unnecessary energy consumption is minimized by various all-off states for systems throughout the home such as lighting, appliances and home entertainment systems.
Home Safety And Security Systems
Because Z-Wave can transceive commands based on real time conditions, and is able to control devices in intelligent groupings, it allows novel extensions of traditional home security concepts. As an example, the opening of a Z-Wave enabled door lock can de-activate a security system and turn on lights when children arrive home from school, and send a notification to a parent's PC or cell phone via the Internet. Opening a Z-Wave enabled garage door can trigger exterior and interior home lights, while a Z-Wave motion detector can trigger an outdoor security light and a webcam, which would allow the end user to monitor the home while away.
Home Entertainment
Z-Wave’s ability to command multiple devices as a unified event makes it well suited for home audio and video applications. For example, a simple “Play DVD” command on the remote control could turn on the needed components, set them to the correct inputs and even lower motorized shades and dim the room lights. Z-Wave’s RF technology is also well suited as an evolution of conventional infrared (IR) based remote controls for home electronics, as it is not constrained by IR’s line of sight and distance limitations. In January of 2008, Zensys announced a single-chip solution that pairs Z-Wave with IR control, positioning the technology as an all encompassing solution for home remote controls.
Setting Up A Z-Wave network
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 zwave users have complained that a zwave 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 zwave devices. <ref>http://board.homeseer.com/showthread.php?t=100212</ref>
Z-Wave Alliance
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, Intel, 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.
Radio specifications
Bandwidth: 9,600 bit/s or 40 Kbit/s, fully interoperable
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. Devices can communicate to another around 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 further 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.
See also
- Insteon - dual-mesh technology from SmartLabs
- ZigBee - standards-based protocol based on IEEE 802.15.4.
- EnOcean - an alternative to Zigbee, mostly for battery-less switches.
- ONE-NET - An open source alternative
External links
- Z-Wave Alliance, open consortium of over 160 manufacturers of Z-Wave products
- Zensys, the creator of Z-Wave
- Z-wave European Portal
- Z-wave United States Portal
- Z-wave vs Insteon
- First Look: Catch the Home Automation Z-Wave
- Information and Z-Wave products for 230V
