RTC Magazine

More applications for smartphones are becoming available every day, making the smartphone a centerpiece of communication for the future smart, connected home. Some of these applications intend to “check and control things at home,” like temperature control as in changing the setting of the thermostat, security—making sure that doors are locked—or energy management like lighting controls. However, in spite of the longstanding promise of the home of the future, many of the electric devices at home still live on isolated islands, disconnected from the Internet and unable to connect to each other.

But, this is rapidly changing! More and more home devices are equipped with networking capabilities like Wi-Fi and ZigBee, allowing them to connect to the Internet via a set-top box and/or a home router. The recent arrival of IPv6, which is replacing IPv4, has solved the bottleneck that existed because there were not enough web “addresses” available, marking the transition from “The Internet of People” to “The Internet of Things.” Once connected to the Internet, all these devices can be reached with any mobile web device or smartphone from anywhere in the world (Figure 1).

Wi-Fi or ZigBee?

For the home environment, the immediate question is: what networking will be best used in the home? One may think that Wi-Fi and ZigBee are competing with each other. The reality however is that both technologies have their own place.

Wi-Fi, based on IEEE 802.11, has been developed with a focus on a high-speed data rate (100 Mbit/s and beyond) optimized to distribute content through the home from browsing the Internet to downloading movies. Wi-Fi-connected devices are typically connected to the power mains and therefore energy consumption has only been a secondary consideration.

The focus of ZigBee (based on IEEE 802.15.4) has been very complementary to Wi-Fi. Developed for sensor and control networks, the data rate (250 Kbit/s) has been secondary to battery life, and therefore the battery life of ZigBee devices can easily be measured in years, or even exceeding the lifetime of the device it is used in. In contrast, the battery life of even “energy-efficient” Wi-Fi implementations is usually expressed in weeks or months. This makes ZigBee an attractive candidate to complement Wi-Fi in the home as the management network of choice.

The Changing Role of the Set-Top Box or Home Router

The roles of the set-top box and the home router are going to change. Currently these two devices—or a single device integrating both—are focused on content distribution.

There are a variety of technology players here, but in particular the cable operators are recognizing the opportunity to offer new services to the consumer for security, energy management and lighting control. As a first step, operators are already equipping their set-top boxes with ZigBee Radio Frequency for Consumer Electronics (RF4CE), obsoleting the good old infrared-based remote control and allowing two-way communication with the set-top box. Comcast is a good example of an operator that is already on track with their roll-out.

The next step is to further expand the set-top box with ZigBee Pro and to connect other devices to the set-top box. The set-top box or home router transforms into a home control box equipped with both ZigBee and Wi-Fi, and responsible for both distribution of content as well as the management of information through the home and relaying this to the Internet cloud.

Here the clear advantages of ZigBee stand out since it was developed as a networking standard covering a complete home and with a range that is very comparable to Wi-Fi. In addition ZigBee has mesh networking capabilities. In case there are regions in the home that cannot be directly reached from the home control box, a message from a ZigBee node that is out of reach can be relayed via an intermediate ZigBee node.

The Role of ZigBee

ZigBee is the standard owned by the ZigBee Alliance, an open, non-profit association that has more than 400 members. These include many of the chip makers, networking software developers and a significant number of product companies implementing the standard in useful end-products for consumers and businesses. 

Wi-Fi is a relatively monolithic application: Internet content distribution for computers, smartphones and TVs, with usually a lot of available computing power. In contrast, ZigBee is the best solution for a wide range of very diverse applications, supporting many different types of devices with usually little to no computer power around. This includes washing machines and refrigerators to electricity meters, and from remote controls to simple garage door openers or light switches with no computer power at all. Some of these devices are connected to the mains power, some are on battery and others may not require any batteries at all.

Therefore it should come as no surprise that these different applications are using different forms of ZigBee, like ZigBee Home Automation, ZigBee Smart Energy, ZigBee Light Link or ZigBee Remote Control. However, these implementations of ZigBee all use the same underlying radio technology based on IEE 802.15.4.

To accommodate the different requirements at the networking layers, there are a few different ZigBee Network Layer implementations, of which at this moment ZigBee Pro and ZigBee RF4CE are the most important and ZigBee IP (based on IPv6) can be expected soon. These different networking technologies can easily be bridged and connected, thanks to the common underlying radio technology (Figure 2).

ZigBee RF4CE Network Layer Features 

ZigBee RF4CE provides a multi-vendor interoperable solution for consumer electronics featuring a simple, robust and low-cost communication network for two-way wireless connectivity. ZigBee RF4CE is a full member of the ZigBee family and is based on the IEEE 802.15.4 specification. It is specifically designed for consumer electronics devices and was developed for simple, two-way device-to-device control applications that do not require full-featured mesh networking capabilities. RF4CE has already found its way into TVs, set-top boxes and remote controls. ZigBee RF4CE can be characterized by ease of installation, a very high level of reliability over a longer range and a very long battery life. It has special features included to avoid Wi-Fi interference rejection (channel agility among others). ZigBee RF4CE offers low memory size requirements thereby enabling low-cost implementations.

A practical benefit is that the two-way communications capability of RF4CE can support new applications. One highly desirable application is to have a “Find Me” button on a TV or set-top box that, once pressed, would cause the remote device to make a sound so the viewer can easily locate it—probably under the couch, where your children left it.

More sophisticated applications that offer interactive viewer participation could also be built into the remote control, using the two-way communication capabilities: tele-voting and gaming, personal messages and reminders, real-time sports results, stock information and residential sensor network monitoring. It also enables operators to create new opportunities for advertising revenues via server initiated commercial push messages on the consumers’ remote control.

The interoperability offered by the ZigBee industry standard allows a remote control to work with more systems in a house and can be used as the basis for home automation. Although the main applications of RF4CE are consumer electronics based, there are no technical restrictions to also control other devices like lights, heating/air-conditioning, and some of these implementations are already in the market today. Leveraging the open ZigBee RF4CE standard, the remote will eventually become the dashboard for the home.

ZigBee Pro Network Layer Features

The ZigBee Pro network layer supports Home Automation, Smart Energy and Light Link application profiles. It is IEEE 802.15.4 compliant, has excellent range and can cover a complete home with multiple floors. It handles dead-spots or Wi-Fi interference via mesh networking: the capability where one node can find its way to the home control box via other nodes and is even capable of doing this dynamically. If one route is blocked it will automatically and instantaneously find another route, if that exists, without any user interaction required.

The ZigBee Pro Feature Set is currently probably the most popular choice for most ZigBee developed applications. It maximizes all the capabilities of the standard ZigBee feature set and also facilitates ease-of-use and advanced support for larger networks comprised of thousands of devices. This also makes it suitable for industrial applications and building automation. 

The wide range of application profiles that ZigBee Pro supports in the home space make it a very complete standard. These also include the so-called Green Power applications. Take, for example, battery-free light switches where the energy for the data communications is generated by energy harvesting techniques from flipping the switch itself.  These switches offer a new generation of self-powered, battery-free and therefore green and maintenance-free ZigBee products. Green Power is an option of the ZigBee Pro standard. As there is no need to run and install power cables, this also makes it easy for the consumer to position and move light switches, without needing the services of an electrician.

Future Directions

The ZigBee standard is rapidly expanding. Already defined are bridge and router devices that allow for concatenating networks for use in larger building environments. To this end the Building Automation profile has been developed that runs on top of ZigBee Pro, and provides wireless connectivity between equipment controllers, lighting controllers, sensors and other devices within commercial buildings. This allows professional building owners to control a large number of devices in applications that benefit from wireless monitoring, control and automation of energy-efficient building systems. 

Smart home technology will allow all sorts of devices and appliances to communicate with each other and perform a variety of tasks. More traditional home appliances like refrigerators, ovens and washers are following the path to smartness, and the smartphone or tablet device is on its way to becoming a portal for connecting, monitoring and controlling other household appliances, both remotely and via the cloud. 

A fine example of this emerging trend is the smart refrigerator that helps people manage their diets by connecting their food storage status to their smartphone. A smart refrigerator is just one of many high-tech appliances that will make life in an intelligent house easier. The various features of smart home appliances can make homes greener, more efficient and even ensure that you never run out of milk and eggs. Again, interoperability of the communication technology for the smart applications under one technology platform will be paramount for the future success in smart home technology. 

In the foreseeable future, continued integration will take place between ZigBee RF4CE and ZigBee Pro via gateway capabilities that can be easily and cost-effectively implemented in the Home Control Box.  

GreenPeak Technologies
Utrecht, The Netherlands.
+31 30 262 1157.
[www.greenpeak.com].