Introduction of Z-Wave smart home

Z-Wave smart home is an international standard for wireless home automation. Home automation allows to interconnect all functions dealing with electricity such as light, heating, cooking, cooling, security etc with each other and to apply automation of these functions. This results in more security and more convenience in homes and offices. Home automation also helps to save energy and other resources.

The interconnection of all these functions can be accomplished using wires or a wireless technology. Particularly for wired home automation the so-called European Installation bus or KNX is very popular and the defacto standard. Wired solutions are very reliable but require proper planning of wires and devices during the construction of the home and the installation of all the utilities.
For retrofitting or partial solutions a wired home automation system is not applicable. Here wireless solutions come into play. Unfortunately there is no clear standard for wireless home automation protocol in the market yet.

1.1 Requirements of a wireless system for home control

To identify a good wireless technology for house automation a list of requirements must be considered. These are:

1. Reliability of the communication:

Important functions such as window blind or even security installations are to be controlled via wireless signal. Hence it is essential that all messages will reach its destination and will be confirmed by the received device back to the transmitter. Not all wireless protocols comply with this requirement.

2. Security of communication:

It must be guaranteed that an unauthorized third party cannot – on purpose or accidently – intercept or interfere the communication of the wireless system. Typically encoding technologies and handshake mechanisms ensures this.

3. Low radio emission:

Wireless technology for home automation is used on living rooms; hence issues like electromagnetic emission need to be taken into account.

4. Simple usage:

Home automation shall make the life of the user easier and not more complicated.

5. Adequate price:

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 extends 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 of different vendors with expertise in their respective area. 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. Each installed wireless technology has to be used independent from several manufacturers.

Alternatives for wireless home control

On the market there are various wireless technologies, which comply more or less with the requirements just outlined.

Analogue Control using 27 MHz or 433 MHz frequency band

Analogue wireless systems, which are available from no-name vendors, have a remarkably low price. The strong focus on the price will result in low manufacturing quality and very poor security.
Because a frequency is used which is shared with baby sitter radio or CB transceivers malfunctions are typical and the behaviour of this
equipment becomes unpredictable. Analogue products are there not widely used for more serious installations in homes.

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

Proprietary Protocols of different vendors

Multiple manufacturers have developed their own proprietary solution for wireless control and some of them offer a variety of different products. Some names from this category are Intertechno, Free Control (Kopp), Homeeasy, FS 20, Homematic (both ELV) or Xcomfort (Eaton). Most of these protocols use the frequency of 868 MHz and communicate digitally.

Some protocols have implemented a two-way communication. The by far biggest disadvantage of these solutions is the limitation of few or even one single vendor. While this may be attractive for the installation “out of one hand” it bears a great risk for long-term availability of components and stability of the protocol. Several vendors have already proven their willingness to change protocols and make the former products obsolete.

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

Power line

The so-called power line communication uses the 230 V mains lines as communication medium. This is not a wireless technology but it competes with wireless automation technologies. The first and still important technology for power line communication is called X10. It was introduced almost 20 years ago in the US and still has plenty of users both in US and Europe. X10 has reached its end of life since the bandwidth is very limited and the protocol has problems with the modern switched power supplies of PCs injecting a lot of electrical noise into the power network.

Modern power line communication technology uses digital signal coding and is more robust against noise. Unfortunately multiple different “standards” exists which are not compatible with each other. Furthermore the compatibility to the CE regulation on cable emission is questionable.

Another initiative based on power line is called Digitalstrom. This is a development from the University of Zurich and has gained some
awareness in the press. As of today the technology hasn’t yet proven its stability in real environments beyond prototype installations.

1. Reliability of communication: questionable
2. Security of communication: questionable
3. Low radio emission: yes
4. Simple usage: yes
5. Low price: yes
6. Protection of investment: yes
7. Interoperability: yes

Zigbee

„ZigBee“ is quite a new player on the block, with the first products on the market in the beginning of 2005. „ZigBee“ is an open wireless networking protocol which works similarly, but better than Bluetooth. Whereas Bluetooth will pair up with a mere seven devices, „ZigBee“ can pair with many hundred!

A part of the functionality is based on the IEEE specification IEEE 802.15.4, which enables to connect household appliances, sensors, etc. on short distances (10 to 100 metres). The downside is ZigBee devices from different manufacturers are not compatible with each other because Zigbee standardises only the lower protocol layers (radio layer), whereas different manufacturers have defined their own higher software layers.

1. Reliability of communication: usually yes
2. Security of communication: yes
3. Low radio emission: yes
4. Simple usage: –
5. Low price: not yet
6. Protection of investment: –
7. Interoperability: no

En-Ocean

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.

In the meantime, more than 100 manufacturers, primarily from Europe, adopt EnOcean. Pricewise Enocean tries to align with the higher pricing level of KNX.

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

Z-Wave Smart Home

Z-Wave Smart Home technology is the key to having complete control over your home security and energy solutions, with the minimum of fuss. With a Z-Wave Smart Home, home automation system, you can program all major electrical elements of the home, such as light, heating, cooking, cooling and even your home security.

The benefits don‘t end there, although its a sophisticated system, it is simple to use, and works out to be an energy efficient and cost effective option.

The system works via a remote control, and uses low-powered radio waves. Its mesh network covers all areas of the home, as the radio
waves travel easily through walls, floors and furniture, making connectivity 100% reliable.

This freedom of connectivity means that you can easily start with a basic package, and build it up over time with additional components, personalizing your home energy and security system, unique to your home and at your convenience. Each Z-Wave Smart Home module can act as an RF repeater and commands can route through a maximum of four devices.

This gives the system a maximum range of 400 ft. and routing is managed automatically. Components include sockets, switches, remote controls, and the Z-Wave Internet Gateway VERA where you can create scenes, events and timer settings to personalize your electrical appliances as you would your home. In terms of pricing Z-Wave Smart Home products ranges above proprietary solutions of some manufacturers but are clearly lower than comparable solutions by ZigBee or Enocean.

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

History and Characteristics of Z-Wave Smart Home

Z-Wave Smart Home is a development of the Danish company of Zen-Sys. Two Danish engineers founded Zen-Sys at the end of the nineties of the last century. From the initial idea of developing their own home automation solution the company soon evolved into becoming a chip provider selling a home automation ASIC together with own firmware to other manufacturers. This formed an ecosystem of manufacturers with compatible products.

Figure 1.1: 3rd Generation Zen-Sys Chip

The first generation of Zensys 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) and last 400 (2009).

Zen-Sys found the first big customers in the USA where – thanks to X10 – a relevant market and market awareness already existed for
home automation.
The first larger Z-Wave Smart Home device manufacturer in Europe was the German switch manufacturer Merten (now a part of Schneider Electric), which publicly introduced the Z-Wave based lighting system CONNECT in the end of 2007. Since beginning of 2009 the market dynamics has strongly increased in Europe and Z-Wave Smart Home also gets more and more adopters in Asia. This is also fostered by the takeover of Zen-Sys by the Asian-influenced chip manufacturer Sigma Designs. Sigma bought the venture capital funded Zen-Sys – among other funded by Intel Ventures – in December 2008.

Figure 1.2: Z-Wave Alliance Website (as of 2009)

One other landmark of the Z-Wave development was the foundation of the Z-Wave Smart Home Alliance in 2005. In this industrial alliance the manufacturers of Z-Wave compatible products are gathered. The alliance had more than 200 manufacturers in the end of 2009. The Z-Wave alliance enhances the standard and also takes care of central marketing events such 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 Smart Home protocol. This is guaranteed by a certification program, which results in a logo on the device guaranteeing the compliance to the Z-Wave protocol.

Figure 1.3: Z-Wave Compatibility Program

While all manufacturers base their products on the hardware of ZenSys, they have some freedom to implement application. Zen-Sys 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 Smart Home 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 tests concentrate 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.

General Layer Model of wireless communication

Wireless systems are complex and consist of a huge number of functions. As you have already read, there are numerous routes to choose from, but importantly, whatever you choose, has to be compatible with the products you are using. To help manage the huge number of functions, its useful to split them into different layers.

The lowest layer is always used for communication media. In the case of a wireless protocol, this is the air. The highest layer is always the user, in this case, a human being. In case of Z-Wave a three-layer structure has turned out to be useful.

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.

2. Network Layer:

This layer defines how real control data are exchanged between two communication partners. This includes issues like addressing, network organization, routing, etc.

3. Application Layer:

This layer defines which messages need to be exchanged to specific applications such as switching a light or increasing the temperature of a heating device.

Figure 1.4: General model of an communication architecture