Z-Wave
Z-Wave is a wireless communication standard developed by Sigma Designs and the Z-Wave Alliance for home automation . Radio communication is optimized for low energy consumption and high communication security. Through a comprehensive specification of all communication aspects and certification of the products, interoperability of all devices communicating via Z-Wave is achieved.
history
Z-Wave was developed in 2001 by two Danish engineers who wanted to bring their own home automation solution to the market. The radio technology was sold to other companies as an OEM supplier by the company Zen-Sys, based in Copenhagen / Denmark . These OEMs use the hardware and a development environment with shared libraries and reference designs. In 2004 the first products came onto the market. In 2005 the Z-Wave alliance was founded. The first European manufacturer of Z-Wave devices was the Danish company Danfoss in 2007, the first German manufacturer the electrical company Merten GmbH (now part of Schneider Electric ) in 2008. In 2009 Sigma Designs took over the company Zen-Sys .
With more than 2100 such certified products, Z-Wave is the world's largest system platform for interoperable radio-based products. The hardware-related protocol layers (MAC and PHY) have been defined by the ITU-T as the G.9959 standard since 2012 .
On the one hand, the “Z-Wave Plus Standard” was introduced to increase user-friendliness. This makes the "inclusion" of the devices much easier. On the other hand, since 2016 the smart home software “ Z-Way ” has included ready-made apps. This means that the smart home can be implemented with almost no programming knowledge.
implementation
The various manufacturers specify and develop their products on the basis of a Z-Wave System on a Chip ASIC (SOC). This is offered by Sigma Designs and, as a licensee, also by Mitsumi . The SOC contains the radio transceiver according to ITU-T G.9959, an 8051 -compatible microcontroller and a large number of peripheral interfaces. Most Z-Wave devices implement all of their functionality in this SOC. However, there are also devices that use a second processor to control the device functions. The control software on the SOC consists of a program library that can be used by every compatible Z-Wave device for communication and the actual device-specific application.
Z-Wave Alliance
The Z-Wave Alliance is an association of over 600 manufacturers and service providers who manufacture and develop products for wireless home automation using Z-Wave. The alliance is based in Milpitas / California . The main members (so-called "Principal Members") are Fakro, Linear Technologies, Ingersoll-Rand , Jasco Products Company , Evolve and Sigma Designs. There is also a normal and a so-called affiliate membership. The alliance organizes joint marketing and trade fair appearances for its members, conducts development and application training, and develops the Z-Wave standard through internal working groups. The newest members of the alliance are the Samsung subsidiary SmartThings and the Finnish network equipment supplier Nokia.
PHY and MAC layer
Z-Wave uses radio frequencies between 850 and 950 MHz. These are either in the ISM band (Industry Science Medicine) or in the SRD frequency band ( Short Range Devices ). Compared to the 2.4 GHz frequency band used as an alternative to radio technology, these frequencies offer significantly better penetration through walls and less losses due to reflections. The disadvantage is that there is no uniform radio frequency available worldwide in these frequency bands. All European countries and a large part of the Asian countries use the frequency of the SRD band of 868.4 MHz or 869 MHz , which has been approved by the CEPT organization . Alternative frequencies in North America are in the ISM band at 908 MHz or in South America at 921 MHz.
Z-Wave uses frequency shift keying (FSK) with a frequency spacing of 20 kHz. Data rates of 100 kbit / s, 40 kbit / s and 9.6 kbit / s are used on different frequencies, which are switched dynamically according to the existing radio situation.
The radio power of Z-Wave is limited to a few mW, although the SRD band with 25 mW would allow a significantly higher transmission power. The result is a radio range of approx. 150 m in the open air. A radio range of 40 m in closed buildings is a minimum requirement for Z-Wave devices.
Network functions
The Z-Wave devices are addressed using a shared 4-byte home ID and a 1-byte node ID that is only valid within the network. This means that several radio networks can be operated in parallel in one house. The process of assigning a common home ID and an individual node ID to a new device is called inclusion at Z-Wave and is controlled by the primary controller organizing the network. A mobile remote control can be used as the primary controller in small networks . In larger networks, a central control with IP access is usually used to configure and control the house. A total of 232 individual devices can be addressed in a network. About Bridges different Z-Wave networks can be interconnected.
Z-Wave uses two-way communication with reconfirmation. Only successfully confirmed datagrams are considered to have been sent successfully. In the event of communication errors, the transmission process is repeated up to three times. As a network topology, Z-Wave implements radio meshing, in which every network-operated device can forward datagrams from other devices in its own network. The resulting meshed network is also controlled by the primary controller and the routes are updated when the network changes. Routes can extend over up to 4 intermediate hops.
All network-operated devices are always radio-active and can therefore serve as routers . Battery-operated sensors and actuators are mostly inactive and wake up periodically to receive and send commands.
Application level
A special feature of Z-Wave is the standardization of the user level in order to guarantee the interoperability of devices from different manufacturers. Z-Wave devices are divided into different device classes, which in turn have to implement certain mandatory commands and functions. Each manufacturer can add their own additional functions and commands; must implement this according to the Z-Wave specification. The certification of the Z-Wave devices checks whether the mandatory functions of the selected device class have been implemented correctly and completely and whether all other functions offered correspond to the specification. Each device can offer functions in up to 128 function channels in order to be able to correctly map identical functions (such as several switching relays in one device).
safety
With security-relevant devices, communication between the devices is encrypted and tap-proof according to the Z-Wave specification Security Architecture Version 2. After the inclusion, it is not possible to intercept the network key. In May 2018, the so-called Z-Shave security gap became known, through which attackers can manipulate the initialization of communication between devices (inclusion) and eavesdrop in plain text. According to the manufacturer, the time window for this attack is in the millisecond range.
Areas of application
The main area of application is the home automation of private houses and apartments, i.e. the wireless control of heating, ventilation, lighting, alarm and air conditioning systems. In addition, wireless control of audio and video devices and energy meters is also possible. Because of the low bandwidth, Z-Wave is not suitable for the transmission of audio or video data. However, the secure transmission of the data enables use in access and security systems.
See also
literature
- Christian Pätz: Z-Wave: The radio technology for the smart home. Books on Demand 2017, ISBN 978-3-7386-0194-7 .
Web links
Individual evidence
- ↑ a b About Z-Wave Technology . Z-Wave Alliance. Retrieved February 4, 2018.
- ↑ Press Release Sigma Designs: Sigma Designs' Z-Wave Technology Recognized by International Telecommunication Union (ITU) . Marketwired. January 12, 2012. Retrieved April 20, 2012.
- ↑ Z-Wave Plus Standard
- ↑ Z-Wave.me opens the App Store , February 1, 2016.
- ↑ Press Release Sigma Designs: Sigma Designs Licenses Mitsumi as Second Source for Z-Wave Technology . Marketwired. May 23, 2011. Retrieved April 20, 2014.
- ↑ Z-Shave: Attackers could spy on the Z-Wave radio standard Message from May 29, 2018 on Heise Online, accessed on June 6, 2018
- ^ Z-Shave. Exploiting Z-Wave downgrade attacks Very detailed analysis by the IT security consultancy Pen Test Partners LLP, Buckingham / Great Britain, which discovered the Z-Shave vulnerability, from May 23, 2018, accessed on June 6, 2018