Chapter 1



Z-Wave is an international standard for wireless communication in Smart Homes. It interconnects different devices such as lighting, heating, climate control, media and entertainment, safety installations and security systems. The interconnection of all these systems creates a smart home where different devices from different vendors work together to increase safety, security, convenience and life quality of the people living in this environment. Above and beyond this, a smart home helps to save energy and to protect human life and environment.

The key to a Smart Home is the interconnection of all different devices in the home and the ability to control all of them through a single user interface that may be a web browser, a wall touch panel, a dedicated remote control or a mobile phone.

The interconnection of devices in a residential home requires a common communication media. There exist three different approaches:

  • Wired solutions require dedicated cables that need to be installed during the construction or a major house renovation. Wired solutions such as BACNet (BACNet is a protocol, it runs on different media types), certain versions of LON or KNX resp. Instabus in Europe are typically expensive and therefore only used in commercial installations and very few high-end residential homes.
  • Powerline communication is using the 110 V or 230 V mains power installation as communication media. Certain standards such as HomeplugAV become more common but rather used as a replacement for Ethernet technology applied for media distributions such as TV, Video and Audio.
  • Wireless solutions show the biggest growth in the market since they are both reliable and affordable and can be applied in homes without major refurbishments. Additionally, certain technologies such as intelligent door locks or sensors can hardly be installed with wires because they are on moving devices such as doors or they shall be applied on places where no wires are available.

That’s why this book focuses on wireless technologies as technology of choice for interconnecting devices in a Smart Home.

1.1 What is a Smart Home?

Smart Home is a term often used along with the more descriptive term home automation. Wikipedia defines home automation as:

“ Home automation is the residential extension of “building automation”. It is automation of the home, housework or household activity. Home automation may include centralized control of lighting, HVAC (heating, ventilation and air conditioning), appliances, and other systems, to provide improved convenience, comfort, energy efficiency and security. Home automation for the elderly and disabled can provide increased quality of life for persons who might otherwise require caregivers or institutional care. A home automation system integrates electrical devices in a house with each other. The techniques employed in home automation include those in building automation as well as the control of domestic activities, such as home entertainment systems, houseplant and yard watering, pet feeding, changing the ambiance “scenes” for different events (such as dinners or parties), and the use of domestic robots. Devices may be connected through a computer network to allow control by a personal computer, and may allow remote access from the Internet. Through the integration of information technologies with the home environment, systems and appliances are able to communicate in an integrated manner, which results in convenience, energy efficiency, and safety benefits. ”   [SmartHome]

The definition is accurate but not very insightful. Let’s start with the obvious: In the good old time, the controlling part and the controlled part of a function in the home were located in the same device. A candle was lit right at the candle and the light came right from the candle. A door knocker was operated right at the device and generated noise right at the same device.

The advent of electricity in the last 100 years has partly changed this reality. The electronic door bell is operated at the door by pressing a button and the more or less ugly sound of the bell comes from a ’bell’ connected with the door button by an electrical circuit. The electrical light is typically controlled by a wall switch that is not longer located right next to the light bulb but on a convenient location next to the door where the resident can easily access it when entering the room. The wall switch is again connected to the light bulbs via an electrical circuit.

Other examples are the control of the window blinds, the wall thermostats controlling the heat in the room or a simple remote control turning on and off devices that are inconvenient to access directly. The home is mixed with various devices that are still controlled and operated right at the devices. Examples of such devices include dishwasher, washing machine, dryer or electric stove. TVs moved out of this category about 40 years ago when the infrared remote control became the standard device to control them.

Figure 1.1: Traditional Home of the late Nineties of the 20th century

Figure 1.1: Traditional Home of the late Nineties of the 20th century

Image 1.1 shows the situation in a traditional home of the early twenty-first century reflecting the different ways to control devices in the home. The Smart Home or home automation changes this situation in multiple ways.

First of all, the direct relationship between device and control of the device is relaxed. The light switch may not longer only control a light but as well other functions of the room. A remote control is not longer dedicated to one single device but to multiple entertainment devices and home functions such as light or climate control.

Figure 1.2: First step into smart home

Figure 1.2: First step into smart home

Image 1.2 demonstrates this first step into smart home.

This first step offers a first simplification of usage and control to the resident. It unifies the operations concept and allows using single point of controls that are more convenient to use. Good examples of such single point of controls are mobile phones that have become more and more the central point of control to various functions and services in people’s lives.

The second step into a Smart Home is the use of sensors that give further information about the status of the home and actions to be undertaken to improve the convenience and security of the resident. By no means this is a new concept. Wall thermostats have a temperature sensor inside that is used to control the heating in the room and the smoke detector is also a sensor as such. The concept of a Smart Home brings the idea of sensor controlling the room to a new level. Motion detectors control the light if people are in a room or turn down or even off the heating when people have left the room. Air quality sensors control windows and ventilation to guarantee enough oxygen in the room when occupied. This second step is represented by Image 1.3.

Figure 1.3: Second step into smart home

Figure 1.3: Second step into smart home

Diese zweite Funktion ist in Abbildung 1.3 dargestellt.

Last but not least the core function of a smart home is the automation. An intelligent entity interconnects the different information given either by sensors or by the resident’s interactions – e.g. operating a button to create intelligent control of the different functions of the home. It is connecting different functions, already unified in their manual operation by the first aspect of smart home into a self-thinking entity that makes sure that the home is executing functions automatically and independent of dedicated user interaction.

A good example is the control of a roof window. In wintertime, the windows shall be closed with shutters during the night to preserve as much energy as possible. During the day, the window blinds may go up and at noon, if the outside temperature is sensed to be high enough, the windows open automatically to bring fresh air into the building. A rain and a wind sensor provide information to keep the window closed during heavy wind or rain. In summer time, the automation may be different. Now the window shall be closed during daytime with blinds down to prevent overheating and it shall open up at night to get fresh air into the building. Of course, rain and wind protection are provided as well. If the automation control knows that the resident is not in the building, the windows may be closed 24 hours for security reasons. Beside the control of the home the interconnected system of sensors and acting devices – also referred to as actuators – can provide information about certain measurement values to status of the home and the resident. This may help to further optimize the functions of the home but also inform the user about the safety and security and help to conserve energy when possible.

Figure 1.4: Final step into smart home

Figure 1.4: Final step into smart home

Image 1.4 shows this final step into a smart home. Home owners want to be informed about what is going on and contemporary ’user interfaces’ such as wall panels or mobile phones shall provide information about the status of the home and also alert in case of events

The characteristics of a smart home can be defined as

“ Different unified user interfaces control different actions in the home using the users interaction, sensor data and intelligent decisions made by the control itself. The same time the smart home provides useful information for the resident to help to make smarter decisions such as conserving energy. ”

There is no clear borderline when a home starts to become a Smart Home. When wired communication technologies are used, the homebuilder has to decide prior to the construction what kind of intelligent or non-intelligent functions he wants to apply in the building. Particularly, the use of wireless technology allow however to step by step introduce new functions and make the living or working environment more and more intelligent.


1.2 Smart Home Definitions

Smart Home

There are some common characteristics and basic language used in every smart home environment.

  • Sensor: A sensor is a device that generates information and delivers it to other devices in the network using a communication network. Examples of such sensors are the temperature sensor in the room thermostat, motion detectors, door sensors or smoke detectors.
  • Controllers: Controllers are devices that control other devices using the communication network between them. They typically provide a user interface. Examples of controllers are remote controls, keypads or wall switches.
  • Actors: Actors – also referred to as actuators – are devices that perform an action. They switch, dim, turn on or off, wind up, shut down etc. Examples of actors are window motors, light switches, light dimmers, electronic door locks.
  • Control Network: The network is the communication medium that interconnects actors, controllers and sensors.
  • Gateways: Gateways interconnect the home communication network to other communication networks such as TCP/IP (Transmission Control Protocol/Internet Protocol) based Internet or the cell phone network.

The intelligence of the home control network may reside in one single device. This is typically the gateway because it needs higher computing power anyway. However the function may also be distributed amongst various devices.

Certain devices may also mix different functions in one single hardware device. Multiple sensors – e.g. temperature or humidity are very common. Another example of such a hybrid device is a room thermostat that typically combines a temperature sensor with a user interface to set the desired temperature in the room.

1.3 General Layer Model of wireless communication network

Wireless communication systems are complex and consist of a huge number of functions. To structure all these functions communication engineers cluster them into a layer stack or protocol stack. The idea of the layer stack is that one layer is using the services of the underlying layer and is providing a function to the layer above. Their functions are well defined so that it is – at least in theory – possible to replace one implementation of a layer by another different implementation without changing the rest of the stack. Each layer has its defined functions to be performed and these functions define the services one layer is offering to the upper layer. For communication networks in Smart Homes a four layer structure is very usable:

  1. Radio Layer: This layer defines the way a signal is exchanged between a transmitter and a receiver. This includes issues like frequency, encoding, hardware access, etc. The service the radio layer is providing is the transport of different bits and bytes from one device to another device.
  2. Network Layer: This layer makes sure that data are transmitted securely and reliably from the source to the destination. In a wireless radio network this may require to use certain devices as wireless repeaters. The functions of the network layer include the organization of the network (who is in, who is out), addressing, routing, encryption, data retransmission and data.
  3. Application Layer: The application layer defines the meaning of the data transmitted by the network layer and subsequently the radio layer. The network layer only knows bytes. The application layer defines the meaning of the bytes and how they form a command. Application layer defines the format of metering and measuring values, the different commands used to perform certain actions.
  4. User interface: The user interface layer acts as interface to the user itself. It defines how certain functions of the network and certain status information are presented on different user interfaces such as cell phone or tablet screen or even on a wall switch. User interface defines things like meanings of icons, LED blinking sequences, number and speed of needed button presses etc.
    Figure 1.5: Generic four layers of a wireless communication network

    Figure 1.5: Generic four layers of a wireless communication network

    This four layer structure is shown in Figure 1.5. This book will organize the description of the Z-Wave wireless communication world using this layer model.

1.4 Requirements of a wireless system for home control

The communication network of a smart home needs to meet a set of important requirements. Since wireless technologies are the clear winning choice compared with wire based technology, the following comparison will focus on wireless technologies.

Requirements are:

  1. Reliability of the communication: It is essential for important functions such as door locks, alarm and heating to be reliable. In order to ensure this reliability it is essential that all messages will reach their destination and are confirmed by the receiving device back to the transmitter. This two-way communication, where every message sent is confirmed or acknowledged back to the transmitter, this is what defines a reliable communication. Not all wireless network technologies comply to this requirement.
  2. Security of communication: It must be guaranteed that an unauthorized third party cannot on purpose or accidentally intercept or interfere with the communication of the communication system. Typically encoding or encryption technologies and handshake mechanisms ensure this.
  3. Low power radio emission: It is essential for health and safety as well as for interference with other wireless devices such as phones, radios and TVs that the wireless technology for home automation is as low power as possible. This is also helpful in achieving extended battery life for battery powered devices.
  4. Simple usage: Home Automation shall make the life of the user easier and not more complicated.
  5. Adequate price: That is an obvious point to ensure broad acceptance of the technology.
  6. Protection of investment: Home automation solutions are typically installed during the construction of new buildings or renovation and need to comply with typical product life cycles of home installation equipment. It is important to make sure, that the user can replace devices or extend their systems even after years and do not run into compatibility issues.
  7. Interoperability: Home Automation functions such as heating, lighting or window control are implemented with products from different vendors each with expertise in their respective areas. It is not acceptable to be forced to stick with one vendor and buy – as an example – heating technology from a vendor with core competence in lighting just to enable interoperability of all system devices. Each installed wireless technology has to be used independent from several manufacturers. Cross vendor interoperability is ensured by strong technology standards and product certification programs. Good examples of interoperability are WiFi, Bluetooth and Z-Wave.

1.5 Alternatives for wireless home control networks

On the market there are various wireless communication technologies for Smart Homes that comply more or less with the requirements just outlined.

1.5.1 Analogue Control using 27 MHz or 433 MHz frequency band

Analogue wireless systems are typically available from no-name vendors and have a remarkably low price. The strong focus on entry level performance and the price typically results in low manufacturing quality and very poor security. Because the frequency is used is often shared with baby monitor radios or CB transceivers, interference is common and the behavior of this equipment becomes unpredictable. Because of these limitations analogue wireless systems are not widely used for more serious installations in homes. They are more and more replaced by digital systems that are more reliable and have higher levels of performance and flexibility.

  1. Reliability of communication: no
  2. Security of communication: no
  3. Low radio emission: yes
  4. Simple usage: yes
  5. Low price: yes
  6. Protection of investment: no
  7. Interoperability: no

1.5.2 Proprietary digital protocols from different vendors

Multiple manufacturers have developed their own proprietary digital solution for wireless control and some of them offer a variety of different products. Some of these protocols have implemented a two-way reliable communication with full acknowledge of transmission.

By far the biggest disadvantage of these solutions is the fact that the communication technology used is proprietary or private to one or a very small number of vendors. This does not pose a problem for a simple solution but often prevents the implementation of a complete automation or control solution. Not only will types of products be limited having one vendor it bears a great risk for long-term availability of products. It is not uncommon to see vendors change protocols and make the former products obsolete. Nevertheless proprietary technologies play their role in the market mainly because of substantial marketing efforts from the companies owning these technologies and their one-stop simplicity in purchasing.

  1. Reliability of communication: partly
  2. Security of communication: partly
  3. Low radio emission: yes
  4. Simple usage: yes
  5. Low price: yes
  6. Protection of investment: no
  7. Interoperability: no

1.5.3 Wifi or WLAN


Wireless LAN (WLAN) is most likely the technology with the highest market penetration. Virtually all notebooks, netbooks, all tablet PCs, almost all smart phones have WLAN interface built in. This bears the obvious question why smart homes are not utilizing WLAN as the standard communication network. Actually there are three reasons:

(1) WLAN is designed for transmitting a large amount of data and therefore is using a lot of energy for transmissions and reception. The clear focus on speed, high security and large transmission ratio comes at a big price: WLAN takes way too much energy for a home control network that is at least partly built on battery powered devices or even devices using energy harvesting. WLAN therefore can be used in parts of the smart home where devices are mains powered but it cannot cover the whole range of applications. The interconnection of smart home devices to cell phones or tablets is typically done using WLAN to a gateway device and then some other lower speed, lower power technology is used from the gateway to the end devices, the sensors and actuators. There are various attempts to decrease the power consumption of WLAN but none of them comes nearly to a level where battery operated devices can be used at a reasonable battery life time.

(2) WLAN is using the 2.4 GHz and 5 GHz radio spectrum and that spectrum or band is getting more and more saturated. At the moment this is not yet a big problem in typical residential homes but more and more high energy WLAN transmitters are getting deployed usually for digital media streaming, Netflicks, WirelessHD and the like hence creating a big future risk for any technology that shares this spectrum. Exhibitors at trade shows such as CES, CeBit or Light + Building already know that a certain amount of active WLAN devices in a room will certainly shut down all WLAN communication.

(3) WLAN only specifies the radio layer and the network layer. So far there is no generally accepted application layer specification for smart homes based on WLAN. This means that different devices using WLAN can work in one single network but cannot interoperate with each other. The Internet Engineering Task Force (IETF) as standardization body of the Internet application layers is working on this issue but so far there is no widely accepted standard available. The only currently available link between Internet/WLAN technology and Smart Home is the so called 6LoWPAN specification [6LoWPAN]. 6LoPAn defines how to map an IP address to the addresses used in the Internet and to wireless technologies typically used in Smart Homes. The aim is to create the Internet of things where each and every device in the home has its own IP address and is reachable from the Internet. The reader may decide whether this is a desirable solution from the security and privacy point of view.

Reliability of communication: mainly yes

  1. Security of communication: yes
  2. Low radio emission: no
  3. Simple usage: yes
  4. Low price: yes
  5. Protection of investment: no proprietary application layers
  6. Interoperability: no proprietary application layers

1.5.4 IEEE 802.15.4 based communication networks

IEEE 802.15.4

The IEEE 802.15.4 standard defines a reliable low power low data rate communication link that is used as the underlying layers for a variety of different home automation communication network technologies. The specification leaves plenty of room for proprietary implementation because it only specifies the radio layer. This limits the specification benefit of the common hardware use that can result in lower prices. Indeed IEEE 802.15.4 radios are by far the most deployed small band radios thanks to this benefit. A lot of proprietary wireless communication solutions are based on this protocol. Since there is no definition of higher communication layers, the standard cannot be referred as complete communication network solution.

1.5.5  ZigBee


ZigBee is one of many communication standards that use or reference IEEE 802.15.4 as their radio layer. Essentially ZigBee is a specification of a network layer using the IEEE 802.15.4 radio layer. When ZigBee was originally specified the application protocol specification was not covered. This results in the situation that a broad variety of ZigBee implementations coexists in the market. None of these different implementations is interoperable with other implementations of ZigBee due to the lack of a specified application layer protocol. More recently ZigBee standard has added the specification of so called profiles to cover the application layer. Unfortunately, there are many different profiles such as the Smart Energy Profile (SEP versions 1 and 2). the Home Automation Profile and the Lighting Profile that have limited interoperability between them and to date a limited number of vendors who have adopted them.

Manufacturers are not required to follow a certain profile but have the freedom to use their own proprietary profile – e.g. application layer protocol and still refer to themselves as ZigBee.

ZigBee is a great technology for wireless communication where interoperability is not required or needed. Its therefore well adopted in proprietary solutions as often found in commercial or industrial applications. In residential homes, where typically different devices and solutions from different manufacturers must interoperate in one network, ZigBee due to its many non-interoperable profiles and low vendor adoption of these profiles is not a good choice and has been slow to gain acceptance where application layer interoperability is important.

The following list shows all the specifications and standards currently available and labeled as ZigBee (according to wikipedia).

  1. Various Specs
    1. ZigBee Home Automation 1.2
    2. ZigBee Smart Energy 1.1b
    3. ZigBee Telecommunication Services 1.0
    4. ZigBee Health Care 1.0
    5. ZigBee RF4CE � Remote Control 1.0
    6. ZigBee RF4CE � Input Device 1.0
    7. ZigBee Light Link 1.0
    8. ZigBee IP 1.0
    9. ZigBee Building Automation 1.0
  2. Specs in development
    1. ZigBee Smart Energy 2.0
    2. ZigBee Retail Services
    3. ZigBee Smart Energy 1.2/1.3
    4. ZigBee Light Link 1.1
    5. ZigBee Home Automation 1.3
  1. Reliability of communication: usually yes
  2. Low radio emission: yes
  3. Simple usage: not yet
  4. Low price: not yet
  5. Protection of investment: not yet
  6. Interoperability: yes at radio layer, not yet at application layer due to too many profiles and low vendor adoption of profiles

1.5.6  EnOcean


EnOcean GmbH is a spin-off company from the German company, Siemens AG, founded in 2001. EnOcean actors and sensors work without battery using energy harvesting techniques, means energy generated out of thin air. The claim of battery free devices using energy from the air has great appeal in an environment oriented society. This claim however comes as its cost: The communication is not as reliable as other technologies such as ZigBee or Z-Wave and the devices are comparably costly. The low power available from energy harvesting such as piezo effect for buttons solar panels or peltier elements generating energy out of temperature differences also heavily limits the wireless range of EnOcean. The company offers however repeaters to overcome this restriction. The low radio range and low communication security caused by the lack of energy make EnOcean only interesting in application where security and range is less important. This is the case for light control, particularly in industrial buildings, where the company has its sweet spot. EnOcean tries to enter the residential market but the higher price of the components has blocked the road so far.

  1. Reliability of communication: no
  2. Security of communication: no
  3. Low radio emission: yes
  4. Simple usage: yes
  5. Low price: no
  6. Protection of investment: yes
  7. Interoperability: yes

1.5.7  DECT ULE


Digital Enhanced Cordless Telecommunications (DECT, initially Digital European Cordless Telephony) is an international standard for cordless phones (with base station in the room or in the house, NOT for mobile phones).

The market for cordless phones is declining, primarily due to the increasing use of normal mobile phones and WLAN based devices within private homes. The vendors of the technology have therefore looked for a new use of their investment and knowledge. In 2011 the initially power hungry DECT technology was enhanced by power reducing functions and the new protocol was called DECT ULE (ULE = ultra low energy). DECT ULE is suitable for battery operated devices now.

The big advantage of DECT is the possession of an own frequency band around 1800 MHz that is not jammed by higher power radio products such as WLAN.

An industry alliance – the DECT ULE alliance tries to standardize the application functions of DECT but by today there is no market relevance of this technology. The deployment of other technologies such as ZigBee or Z-Wave has shown that this process takes many years. It may be that DECT ULE is simply too late for the Smart Home market.

  1. Reliability of communication: yes
  2. Security of communication: yes
  3. Low radio emission: yes
  4. Simple usage: not known
  5. Low price: not known
  6. Protection of investment: likely
  7. Interoperability: not known yet

1.5.8  Z-Wave


Z-Wave was particularly designed as wireless communication technology for residential homes. No wonder that it has all the ingredients to perfectly service this market place. The main advantages of Z-Wave are

  • Used sub 1GHz frequency avoiding the heavily congested 2.4 GHz and 5 GHz bands where WLAN and ZigBee are positioned.
  • Offers secure and reliable two way communication using message acknowledgement and mesh networking (for definition and explanation of mesh network please refer to 3.2)
  • Comes at a reasonable price point, certainly higher than the low end analog technologies but substantially lower than high end technologies such as EnOcean that are dedicated to professional building market.
  • Z-Wave ensures 100 % interoperability as its core value. All devices that implement Z-Wave will work together in one single network and can be controlled from every controller that uses Z-Wave as well.
  1. Reliability of communication: yes
  2. Security of communication: yes
  3. Low radio emission: yes
  4. Simple usage: yes
  5. Low price: not yet
  6. Protection of investment: yes
  7. Interoperability: yes
AnaloginexpensiveUnreliable, not interoperable
DigitalProprietaryNot interoperable
WLANWidely used, available in cell phones, etc, low priceNot interoperable, high energy consumption / no batteries possible
ZigBeeStable standard, lots low cost chipsNot interoperable
Z-WaveInteroperable, reliableCost higher than analog systems, not (yet) available in notebooks, cell phones, …
DECT ULEInteroperable, reliableno devices yet, a late comer
EnOceanNo batteries, interoperableHigh price, low security

Table 1.1: Summary of Pros and Cons of different radio technologies

Table 1.1 summarizes the pros and cons of the different protocols.

1.6 History of Z-Wave

Z-Wave is a development of a Danish company called Zen-Sys. Two Danish engineers founded Zen-Sys at the end of the 1990s. From the initial idea of developing their own home automation solution the company soon evolved into becoming a communications technology provider selling to companies that wanted to develop interoperable control solutions. Making this reliable and interoperable technology available to manufacturers world-wide has resulted in the largest ecosystem of manufacturers with compatible products.

Figure 1.6: Zen-Sys radio chip Series 400

Figure 1.6: Zen-Sys radio chip Series 400

In Figure 1.6 a Zen-Sys radio chip is illustrated. The first generation of Zen-Sys hardware was sold from 2003 – at that time still as a combination of a standard microcontroller (Atmel) and a radio transceiver. This hardware platform was extended during the following years with the chip generations 100 (2003), 200 (2005), 300 (2007), 400 (2009) and last 500 (2013).

Zen-Sys found the first big customers in the USA where – thanks to an early powerline carrier home automation protocol called X10 – a relevant market and market awareness already existed for home automation.

The first larger Z-Wave device manufacturer in Europe was the Danish thermostat maker Danfoss. Since the beginning of 2005 the market dynamics has strongly increased in US and Europe and Z-Wave is finding more and more adopters in Asia. This is also fostered by the purchase of Zen-Sys by the much larger US based chip manufacturer Sigma Designs.


Figure 1.7: Z-Wave Alliance Website (as of 2013)

Figure 1.7: Z-Wave Alliance Website (as of 2013)

One other landmark of the Z-Wave development was the foundation of the Z-Wave Alliance in 2005. In this industrial Alliance the manufacturers of Z-Wave compatible products are gathered. The Alliance had more than 250 manufacturers by the end of 2013. The Z-Wave Alliance enhances the standard and also takes care of central marketing events such as trade shows. Another central duty of the Z-Wave Alliance is the maintenance of the interoperability of the devices on the basis of the Z-Wave protocol. This is guaranteed by a certification program, which results in a logo on the device guaranteeing the compliance to the Z-Wave standard. Figure 1.7 shows the Z-Wave Alliance Website.

Figure 1.8: Z-Wave Compatibility Program

Figure 1.8: Z-Wave Compatibility Program

This logo is shown by Figure 1.8. While most manufacturers base their products on the hardware of Sigma Designs, they have some freedom to implement application.

Sigma Designs defines the radio level with the line encodings and also defines the functions to organize the network itself. Precompiled firmware libraries accomplish this. The manufacturers cannot change them. Z-Wave also defines application specific functions (e.g. switch A is switched when button B is pressed) but the manufacturers are responsible to implement this. Most manufacturers optimize and enhance functions on application layer.

Hence, the certification process focuses to make sure that the application layer functions of the device comply with the standard to allow and guarantee interoperability across functionality and manufacturers boundaries.

1.7 Z-Wave becomes open standard

Figure 1.9: Steps from proprietary solution to public standard

Figure 1.9: Steps from proprietary solution to public standard

Initially, Z-Wave started as a proprietary system only available to those manufacturers that agreed with the original supplier Zen-Sys to design products based on Zen-Sys technology.

With the adoption of the Z-Wave technology in the market and the increasing success of Z-Wave as an eco system the technology has opened up more and more.

The first step into this direction was certainly the incorporation of the Z-Wave Alliance that now acts as the central marketing engine and collection of vendors in the market. More than 250 different companies from all parts of the world have joined the Alliance since its start in 2005. An interesting fact is the broad diversity of the alliance. World market leaders are found beside little start ups and companies from different backgrounds such as security, marketing, light switches, plastic molding, TV, remote control business, software, test house etc. are all lined up in support of this interoperable standard.

The next step in opening up the Z-Wave world was the availability of a second source for the Z-Wave SOC chip. In 2011 Mitsumi from Japan announced the availability of a certified SOC from its factories. [MITSUMI2011]

In 2012 Z-Wave became an open and public standard. The radio and MAC layer were standardized as standard G.9959 by the international telecommunication union ITU-T. [ITU2012]