Chapter 3

3 Key Concepts

From a technical perspective, home automation consists of five building blocks:

  • devices under control (DUC)
  • sensors and actuators
  • the control network
  • the controller
  • remote control devices.

3.1 Devices under Control 

Devices under control are all components, such as home appliances, consumer electronics, lighting, or window blinds, which are connected to and controlled by the home automation system. An increasing number of things come with this functionality built in through integrated web-servers, WLAN-, Bluetooth- or Z-Wave-interfaces. Components without such built in control capabilities can often be equipped with adapters in order to integrate them with the smart home infrastructure.

3.2 Sensors and Actuators 

Sensors are the eyes and ears of the home network. There are sensors for a wide range of applications such as measuring temperature, humidity, light, liquid, gas, detecting movement or noise.

Actuators are the hands of the home network. They are the means of how the smart network can actually do things in the real world. Depending on the type of interaction required, there are mechanical actuators such as pumps and electrical motors or electronic actuators such as electric switches and dimmers.

3.3 Control Networks 

The control network provides the connectivity between devices under control, sensors, and actuators on the one hand and the controller along with remote control devices on the other hand. There are three technology options for home and building automation control networks:

  • powerline communication
  • wireless communication
  • wireline communication

3.3.1 Power Line Communication 

The power line communication principle uses existing electric power lines in buildings to transmit carrier wave signals in the frequency range of 20 kHz to 100 MHz. The long dominant, decades old, low speed power line standard X.10, while still widely installed, has been finally replaced by HomePlug, which became the IEEE 1901 standard in 2010. AV2, the latest version of HomePlug, is able to achieve transmission speeds of up to 500 MBit/s. The main advantage of power line communication is the low price for its components and that fact, that no additional wiring is required. The downside is that power line distribution units can significantly impact transmission speeds. In some cases the design of the electric wiring can even prohibit the coverage of parts of the electric power line infrastructure in a building.

3.3.2 Wireless Communication 

Today, there are a large number of wireless communication technologies available for building and home automation. Transmission speeds and distance depend on transmission frequency and modulation of the very technology and range from 20 kBit/s to 250 kBit/s and 60 ft (20 m) to 3000 ft (1000 m) respectively. Other important considerations are power consumption and location accuracy. Technological advances have significantly improved all performance aspects of wireless transmission technologies over the past 10 years. The main drivers for wireless technologies gaining popularity in home automation are:

  • proprietary home automation systems migrating towards Internet technologies
  • the main building automation systems becoming open, international standards
  • new standards releases increasing throughput and reducing power consumption
  • cost and size of components coming down
  • integration with wireline based building automation standards through gateways

While wireless building control for years has been plan B for lower end, post-construction projects, the adoption of new, reliable low power technologies has changed the industry. Today, Z-Wave, ZigBee, BLE (Bluetooth low energy), and RFID interfaces are available fully integrated in controllable power-outlets, light switches, and household appliances. Many audio and video consumer electronic devices come with WLAN (Wi-Fi), ready to stream content from the Internet, and ready to be fully controlled via smartphones. In 2016 the Wi-Fi Alliance announced 802.11ah (HaLow), a new standard optimized for Home Automation and Internet of Things (IoT) applications. It features a number of benefits compared to current Wi-Fi technologies. Using the 900 MHz band (other than conventional Wi-Fi networks operating in the 2.4 GHz and 5 GHz bands) it allows wireless signals to reach almost twice as far as current Wi-Fi radios while using less power to broadcast. This will impact not just Wi-Fi routers, which will become far more efficient at killing dead spots, but also mobile phones and IoT devices that will be able to communicate over greater distances while conserving battery life.

A new generation of energy harvesting technology based devices such as EnOcean are even capable of operating wireless control links exclusively with energy retrieved from the environment through temperature changes, light changes or the mechanical energy when pressing a switch. Table 3.1 lists the main open standards used for wireless building automation today.

T3.1 Wireless Building Automation Standards

Table 3.1 Wireless Building Automation Standards (click for larger view)

(*)LR-WPAN (Low Rate Wireless Personal Area Networks)
(**) heavily depends on topology, frequency and distortion of the sensor

3.3.3 Wire Line Building Automation

The main open standards for wire line based building automation are KNX,, LON and HomePNA. KNX is a European (EN50090, 2003) and international (ISO/IEC 14543-3, 2006) standard for home and building automation. The abbreviation KNX stands for Konnex, and replaces the older European standards EIB (European Installation Bus), Batibus (primarily used in France), and EHS (European Home Systems). Today in Europe, more than 75% of industrial building automation solutions as well as upscale residential smart homes are realized using KNX. Over the past years, KNX has started to be adopted in many regions of the world outside of Europe as well.

LON (Local Operating Network), originally introduced in 1990 by Echolon Corporation and an ISO/IEC 14908 standard since 2008, is the building automation solution of choice for large scale automation projects such as airports, stadiums, or street lightning. Contrary to the hierarchical KNX architecture, it uses a decentralized approach. In large installations, local information can be processed locally, without being sent to a central control node. This allows for the scalability and redundancy needed in public installations with high availability requirements.

Another wireline transmission standard for the networked home, which has been primarily deployed in North America, is HomePNA. Specified by the Home Phoneline Networking Alliance its first release was published in 1990. For almost twenty years it was mainly used to transmit IPTV services over telephone wires, since 2006 also over coaxial cables. In an effort to put an end to the multitude of non-interoperable home networking technologies, the ITU-T working group G developed a single transmission standard for home networks, which can be used over any type of wire (telephone, coax, power line and fiber): (hn – home network). The initial release of was published in 2010. The industry alliance behind the standard is the HomeGrid Forum (HGF). In 2013 the Home Phoneline Networking Alliance merged with the Home Grid Forum. provides data transmission rates of between 250 MBit/s and 2 Gbit/s, depending on the physical medium.

3.3.4 Control Networks: Summary

All three control network technology categories– power line, wireless, and wire line – have significantly improved in transmission speed, reliability and interoperability through standardization efforts over the past ten years. In general, control networks based on power line communication and wireless transmission are dominant in residential home automation due to lower component prices and installation cost. Wire line based control networks, on the other hand, are found in the premium residential segment and in control applications for industrial buildings. Wireless technologies are used for partial or point solutions involving components which are not mission critical for building operation.

3.4 Controller

The controller is the computer system which acts as the brain of the building automation system. It collects information through sensors and receives commands through remote control devices. It acts based on commands or a set of predefined rules using actuators or means of communication such as loud speaker, email, or telephone. For residential home automation, the controller typically is an always-on standalone or embedded Linux / Windows / OS-X computer, running the control application for the house. Higher end residential and industrial buildings use dedicated high availability, redundant controller systems with uninterruptible power supplies (UPS). In the consumer segment for residential homes some vendors also offer controllers in form of cloud applications, which connect to the building through the Internet.

3.5 Remote Control Devices

One of the main reasons for the increased acceptance of home automation systems in the residential segment is, that with the omnipresence of smart phones and tablets, the need for dedicated automation control devices has vanished. Within a few years, literally all home automation systems on the market have introduced smartphone and tablet based control applications. In addition, advances in voice recognition have finally brought voice based control to smart homes as well. The remote control devices act by connecting to the home automation application, which reside on the home controller. They do this by either connecting to the controller through the building control network itself, or through any other interface the controller provides, such as WLAN, the Internet, or the telephone network. As a side affect of using smartphones as remote control, building control from outside of the house via the mobile telephony network or the public Internet comes as a standard feature set.

3.6 Market Trends

The traditional differentiation between expensive, proprietary industrial building control systems and residential smart homes automation is blurring. Over the past ten years these two market segments have changed drastically and are increasingly overlapping. Expensive proprietary solutions have become more open standards based and less expensive. Low end solutions for residential customers have become more sophisticated and are using the same technologies as industrial systems. A development similar to what happened when the markets for professional and home PCs blended a few decades ago. While the requirements for reliability, redundancy and robustness of professional building control systems have led to the development of many proprietary standards, now the pace of the digital evolution has caught up with these requirements. In addition, new requirements for smart building control are arriving at speeds, which proprietary standards cannot match anymore. Recent examples are

  • integration of smart grid and smart meters
  • integration of web/IP enabled home appliances
  • integration of web/IP enabled consumer electronics
  • integration of Internet based information and services such as supply demand based energy prices or weather, traffic and location information.

3.7. Smart Homes for the Masses: Google, Apple, Samsung and more …

While the smart home market has experienced double digit growth rates in recent years, it was the year 2014, by when it truly became mainstream. It was the year when three of the largest consumer product and service companies made bold entries into the smart home market. Apple introduced it’s HomeKit architecture, Samsung spent more than 200 million US$ for home automation startup SmartThings and Google acquired learning thermostat maker Nest Labs for 3.2 billion US$.

3.7.1 Google’s Nest Labs

Nest Labs was founded in 2010 by two former Apple engineers with the focus on self learning thermostats. The key innovation of Nest Labs centered around the fact that most people do not program their thermostats because it is too complicated. Nest thermostats automatically create a heating or cooling schedule based on the daily routines of the residents. Initially the residents frequently set the target room temperature by turning the Nest thermostat wheel several times a day. Storing these settings the thermostat is capable of building a temperature schedule. Nest thermostats have to be connected to the Internet to receive software updates. Since part of their functionality requires location information determined by postal zip-codes, international deployment outside of the US has been slow. At the end of 2014 Nest acquired streaming video camera maker Dropcam and has since integrated its products with Dropcam’s surveillance capabilities. Dropcam recordings can now be triggered by Nest smoke detector alarms and Dropcam motion alerts are turned on when Nest thermostats are being set to „away“.

Nest devices communicate using Nest Lab’s Thread protocol (, which is based on the 6LoWPAN standard (IPv6 over IEEE 802.15.4 LR-WPAN). With that it uses the same transport protocol as ZigBee and WirelessHART. With that Existing 802.15.4 products could be upgraded to the Thread protocol via software update.

3.7.2 One More Thing … Apple HomeKit

With its HomeKit framework Apple has made a strategic move to enter the smart home market. The large installed base of smartphones and tablets with the powerful voice assistant Siri provide the platform for a basic, easy to use, plug and play type smart home solution. The core of Apples HomeKit consists of the three components

  • home configuration database
  • HAP HomeKit Accessory Protocol
  • API for HomeKit Apps

As transport protocol Apple has specified IP (LAN, WiFi) and BLE (Low Energy Bluetooth). Using the HomeKit API third party developers can build iOS applications, which discover HomeKit compliant accessories and add them to the home configuration database, access the database and  communicate with configured accessories and services. In addition to iOS applications Apples voice assistant Siri has also access to HomeKit, allowing for voice based smart home control.

Accessories which are not HomeKit compliant can connect to the HomeKit infrastructure through bridging devices (HomeKit Bridges). However this approach is limited to accessories which

  • offer no user control
  • have no physical access (such as door locks)
  • and which use non competing transport layer technologies such as ZigBee or Z-Wave

This basically restricts HomeKit bridging to simple sensors, which do not use WiFi or BLE. All WiFi or BLE based sensors as well as all smart home components which offer active user control (e.g. thermostat controllers, light switches, door locks) will have to implement the HAP protocol and enter the Apple MFi (Made-for-iPhone/iPad ) program. Software bridges to integrate HomeKit with wireline smart home technologies such as KNX or HomePlug are currently not on the roadmap. The Apple TV hardware is taking over the part of the smart home hub for remote access to smart home accessories. With the addition of HomeKit capabilities it functions as a relay between the local smart home accessories and a HomeKit cloud account, which in turn can be accessed by the smartphone HomeKit app from anywhere (Figure 3.1).


Figure 3.1 Apple’s smart home framework HomeKit (click for larger view)

3.7.3 Samsung’s SmartThings

The third large consumer products company in 2014 to make a serious effort towards smart home technologies was Samsung with it’s acquisition of US startup SmartThings ( Core of the SmartThing solution is an easy to use smartphone app (iOS, Android), which communicates to the SmartThing Hub, which in turn controls Z-Wave and Zigbee compliant smart home accessories. The SmartThings Hub can directly communicate with the smartphone app as long as it is within its range. In parallel it connects to a cloud account,  which serves as the communication hub when communicating with the building from away.

3.8 A Future Proof Smart Home Architecture

In spite of the trends towards open standards, for the realization of smart home projects the variety of wireline and wireless standards in combination with proprietary vendor solutions remains a challenge. Any architecture with the objective to go beyond point solutions, which control garage doors or lights using a smartphone, will need to be built upon a central, rule based home server, capable of connecting to devices via multiple technologies. In most homes at least part of the control infrastructure will be based on WLAN (WiFi) and wireline technologies for the foreseeable future. Examples are the latest generation of consumer electronic devices such as  audio equipment, TV sets and appliances (ovens, refrigerators, dish washers, washing machines) which are all equipped with WLAN interfaces ready to be integrated in smart home infrastructures. The full line of WiFi connected appliances from General Electric (, Samsung’s series of SmartTV sets, or the Denon and Marantz music systems are just a few representatives for this market reality. In newly built residential homes as well as in commercial and public buildings for security and reliability reasons wireline technologies will continue to serve as the backbone for the control of key building infrastructure elements such as power outlets, lighting and HVAC (heating, ventilation and air conditioning). The smart home solutions of new market entrants such as Nest, Apple or the many new smart home startups typically provide point solutions for specific needs. They are capable of providing a quick and inexpensive initial step towards home automation with restricted functionality and limited customization capabilities. Most of these solutions can be at least partially integrated in server based scalable multi technology solutions such as OpenRemote. However, their reliance on wireless technology and cloud based control limits their use from a security and reliability perspective. An example is the attenuation of the popular 2.4 GHz frequency band through rain and plants. The 900 MHz band on the other hand suffers from low data rates. And last but not least, any wireless technology is prone to denial of service attacks through signal jammers, which anybody can buy on the Internet for a few dollars.

Equally critical from a security and privacy perspective is the usage of cloud accounts for smart home control and communication. A prominent example is Nest Labs, which officially passes user data stored on the thermostats of its customers to its parent company Google. And even independent of the wide spread practice of selling customer data and profiles, cloud based solutions represent a significant risk from a security and reliability perspective. It is a fact that cloud based services frequently suffer from outages caused by technical problems or hacker attacks. Just take a look at InfoWorld’s annual listing of the top ten cloud service outages.

To summarize, a reliable and secure architecture needs to be based on a local smart home controller with wireline control links to the key home infrastructure components such as power outlets, lighting, HVAC, surveillance and door locks. Since most consumer electronics and appliances with integrated power supply will continue to offer connectivity using WiFi, WLAN integration is mandatory. In addition a new generation of mobile, battery powered devices are coming to the market, which provide connectivity through low power technologies such as BLE or EnOcean. Some of these devices are based on proprietary vendor implementations such as Apple’s HomeKit or Nest’s Thread protocol. The degree to which they can or should be integrated in an overall smart home architecture needs to be looked at on a case per case basis. Perhaps the biggest downside of these proprietary plug and play solutions is their lack of customization capabilities. The price for being easy to install and for using proprietary technology is, that they cannot be used to build an integrated rule base, which delivers meaningful interaction between residents, environment and building infrastructure. And without that, the fact that the garage door can now be opened using smart phone based voice control, cannot conceal that such a smart home solution is a mere remote control. Figure 3.2 shows how an integrated smart home architecture as discussed above could look like.

3.9 Where do we go from here?

With the above trends and developments, the slow moving market of building automation has changed radically.  New players and start-ups are taking on the opportunities, which the intersection of new technologies and new demands are offering in home automation. It looks like that finally the vision of an Internet of Things, seamlessly integrating with our life, handling daily routines, while saving energy, is becoming reality.

3.2 HTS-the-Big-Picture-web

Figure 3.2 An integrated smart home architecture (click for larger view)

(1) 24/7 Home controller with rule database interfacing actuators and sensors via multiple technologies

(2) WiFi (WLAN) network interfacing to power supply based devices (consumer electronics, home appliances)

(3) 2nd generation wireless technologies (z-wave, ZigBee) interfacing to small devices and sensors

(4) Local smartphone / tablet based home control app connected to controllable devices through the home server

(5) Proprietary smart home components (e.g. Apple’s  HomeKit) connected to select devices and integrated to the home network using bridges

(6) 3rd generation low energy wireless technologies (e.g. Bluetooth LE, EnOcean) connected to mobile, battery powered devices providing services such as location tracking.

(7) Remote smartphone based home control app connected to the home server via 3G/Internet/VPN connections

(8) Smart meter reporting on supply & demand based tariffs and the availability of local generated power (e.g. roof based solar energy). Connectivity to utilities via 2G/3G or DSL/Internet and to the home server via  wireline connections.

(9) Wireline based control of the building infrastructure (Lighting, HVAC, wall outlets, door locks, alarm system)

(10) Integration of data from public and private Internet based services (calendar, sport, medical, weather, traffic, etc.) to the home automation rule base.

(11) The automatic generation of reports on key operating parameters plays a vital role in monitoring and optimizing building operation and the continued development of the automation rule base.

3.10 Bibliography

Weiping Sun, Munhwan Choi and Sunghyun Choi (2013): 802.ah – A long range 802.11 WLAN. IEEE 802.ah: A long range 802.11 WLAN

Home Grid Forum (2013): Converging Technologies. Converging Technologies – Moving from HomePNA to

IEEE Computer Society (2011): IEEE Standard for Local and metropolitan area networks Part 15.4: Low-Rate Wireless Personal Area Networks (LR-WPANs).

International Telecommunication Union (2012): Recommendation ITU-T G.9959 Short range narrow-band digital radio communication transceivers – PHY and MAC layer specifications.

Enocean Alliance (2013): EnOcean Wireless Standard ISO/IEC 14543-3-10.