Connected Technology Entering Home Automation

　　The dream of a smart home that automatically controls the living environment and responds to each person's preferences has been around since the advent of the microcontroller. However, high costs, reliability issues, limited functionality, and a lack of standards have limited the market, making home automation more of a fantasy than a reality. Now, with advances in wireless technology, the emergence of home networking standards, and the pull of the entertainment and energy markets, efforts are being revived to make the dream a reality, although industry players are still divided on how to achieve it.

　　The first attempts at home automation provided simple remote control of basic functions such as dimming lights, adjusting fan speeds, and turning appliances on and off. Pico Electronics of Scotland first introduced X10 power line signaling technology in 1975, which was the basis of these early attempts.

The X10 control system transmits data at a rate of 1 b/8.33 ms (limited to 16 commands) and can control up to 256 devices on a network. However, despite these limitations, X10 products have enjoyed limited but continuing success in the market and are still available for consumers to purchase and install.

　　In order to provide more powerful and comprehensive control functions for home applications, the EIA (Electronic Industries Association), now known as the Consumer Electronics Association CEA, began to develop a set of standards in 1984, which is a common command language for controlling a range of devices. This work also defined many media communication methods, including twisted pair, infrared, RF and power line signal transmission. The CEbus standard emerged and was adopted by the industry as the EIA-600 standard in 1994. It is aimed at remote controls, remote instruments, security systems, energy management, and other entertainment systems that carry entertainment content lines.

　　Unfortunately, CEbus proved to be too complex and too advanced. It was expensive to implement and did not gain widespread support, as it seemed that the consumer market had not yet accepted the concept of the Internet and networking. Its support has gradually faded. For example, Domosys, a CEbus product supplier, eventually abandoned CEbus in favor of its own proprietary PowerBus networking technology. The CEbus industry organization's website (www.cebus.org) is now non-functional.

　　Other technologies have emerged in the field of home networking, the most successful of which is Echelon's LonWorks platform. LonWorks is not only for home automation, but can also be used for industrial and automotive control, and has achieved considerable success in these two fields. The LonWorks platform, combined with its physical layer signal transmission on power lines and twisted pair cables, has gathered multiple industrial and building standards, including ANSI/EIA709.1B for control networks, the European EN14908 building automation standard, and even IEEE 1473-L for train control.

　　Despite these successes, neither LonWorks nor any other home networking technology has taken off in the market. There are many reasons for the stagnation of home automation. One is that no single technology offers all the features consumers demand. Another is the lack of a killer application that will gain immediate widespread adoption, one that will continue to drive down costs, continue to improve public awareness, and encourage innovations that will encourage competition.

　　To be successful in a consumer market like home automation, a technology must have the following characteristics:

　　Affordability: The technology must provide sufficient benefits at a low enough price that consumers are willing to invest in it.
　　Ease of use: The technology should be simple enough to install and work right out of the box for the average consumer.
　　Reliability: Once installed, the technology should work as expected without interruption or needing consumer attention.
　　Flexibility: Consumers expect to be able to decide where and how the technology is applied based on their wishes, without major restrictions.
　　Longevity: Consumers expect their investment to pay off over months or years. For devices that operate on batteries, long battery life is the foundation of consumer satisfaction.
　　Interoperability: Consumers expect technology components to be purchased from multiple competitive sources and to work easily together.
　　Capabilities: Consumers expect newly adopted technologies to provide multiple important benefits and useful features, and that the capabilities and features of the technology to increase steadily over time.

　　All existing home automation technologies have one or more drawbacks, but advocates are continually working to address them. Sometimes the drawbacks are simply the communications medium. Home automation systems use one or more of three mediums: wires and cables, power lines, and wireless (usually RF). Each approach has its own advantages and disadvantages.

　　Wire and cable media used for home automation include twisted pair, coaxial cable, and fiber optic. The advantages of these media are high data capacity and a relatively low-noise communications channel for network transmission. The main disadvantage is cost. It is estimated that the cost of installing cable in a building ranges from $65 per foot in a residential home to $300 per foot in an industrial building. The cost of installing cable in new construction is lower, but still too high for most consumers.

　　The second disadvantage of wire and cable media is the lack of flexibility. Consumers cannot freely rearrange control devices or terminal equipment according to their wishes. The installed wiring restricts the layout, and the cost of re-routing cables is too high.

　　Power line signal transmission

　　To address the shortcomings of cable wiring, home automation technology attempts to use a type of wiring that exists in every home: power lines. Power lines have two advantages as a networking medium. First, they are already laid and are almost everywhere where end devices are located. Second, end devices do not require an external power source, such as a battery. Both of these factors help meet the requirements of low cost and ease of use for consumer technology. [page]

　　But powerline networking has its own challenges. The medium is noisy, with voltage spikes when lights and motors are switched on and off, loads change, and interference from the power grid can be transmitted to the home. Because of this noise, powerline networking technology limits signal transmission bandwidth while also requiring complex and expensive noise reduction and error correction strategies.

　　The X10 standard is an example of the first approach, bandwidth limitation. To avoid noise, X10 signaling is transmitted during the zero crossing of the AC power supply. It is transmitted in 120 kHz bursts of 120 cycles and repeated at the next zero crossing to suppress noise, with the presence of signal representing a 1 and the absence of signal representing a 0. This results in a raw data rate of 60 bps, with the added overhead of synchronization, framing, and addressing bits, which reduces the available data rate by 60%. This low data rate makes the network incapable of handling most basic control and

detection function, and adds considerable delay in implementing a command string.

　　SmartLabs' Insteon is a similar solution (Figure 1) that transmits a 24-bit packet during the zero-crossing interval, with each bit encoded as 10 cycles of 131.65 kHz. It achieves a continuous 2880 bps bit rate, which greatly improves availability and latency over X10. In addition, the similarity in technology allows an Insteon network to control X10 devices, providing the interoperability features that consumers demand.

　　The third variant is the Universal Powerline Bus from Powerline Control Systems. This system adds a 40V-dc spike to the zero-crossing interval of the power line, using pulse position modulation to encode 2 bits per zero-crossing interval. Filtering can prevent the spike from generating excessive EMI on the power line. The data rate is on the order of 100 bps.

　　However, these low data rates limit the performance of the network, thus failing to provide consumers with the expected technical performance. In addition, achieving higher data bandwidths with powerline solutions requires a more complex signal transmission method and protocol. For example, Echelon's PL3120 powerline transceiver includes a DSP-enhanced processor for data recovery and noise reduction, achieving a stable data rate of up to 5.4 kbps.

　　Higher data rates have been emerging over the past few years. The HomePlug Powerline Alliance's new HomePlug AV standard uses Intellon's technology to generate signals using orthogonal frequency division multiplexing to achieve sustained data rates of up to 200 Mbps. This speed far exceeds the requirements of the network for simple control of lights and power, and can be used as a communication channel for entertainment media such as IPTV (Internet Protocol Television). However, it still needs to prove that the cost of this complexity will be reduced to a level that can be widely accepted.

　　Powerline signaling has other drawbacks that could limit its long-term success. For example, U.S. homes are wired for 120V on two different phases and a neutral line. This allows demanding appliances, such as furnaces and dryers, to run at 240V while keeping standard appliances running at a safe 120V. The result is that the home's power lines are shared between the two phases, and signals cannot be reliably transmitted across the phases unless bridge nodes or high-frequency shunts are used between the phases. This adds complexity and cost, and consumers may not tolerate such a home network implementation.

　　Powerline signaling has another limitation in terms of installation flexibility: it requires power lines to be present at every node in the system. This limits the placement of control nodes, such as light switches and thermometers. The ideal solution in the minds of consumers is to place anything anywhere without restrictions.

　　This level of flexibility is one of the main advantages of the wireless RF medium. There are several wireless home automation network technologies available, including Z-Wave and ZigBee. In addition, home network technologies such as Echelon's LonWorks, SmartLabs' Insteon, and Europe's KNX all use wireless signal transmission methods other than power lines to gain more flexibility.

　　But until recently, RF-based networking technologies have faced considerable reliability challenges. To avoid licensing issues, RF-based networks usually operate in an open frequency band, such as the band used for products such as microwave ovens and cordless phones. For example, the Z-Wave solution operates in the 900 MHz ISM (Industrial/Scientific/Medical) band, which is different in the United States and Europe. ZigBee also operates in this band, but will move to the 2.4 GHz band in the future, which is a universal frequency band throughout the world, so global RF equipment can be designed. But in both cases, there are other users in these open bands, which can cause serious interference problems.

　　RF supporters have been working to solve the interference problem and now appear to be getting closer. For example, ZigBee Alliance members Ember, Freescale, Microchip and Texas Instruments have reported that the latest revision of the specification, ZigBee 2006, can ensure reliable operation even in the presence of interference from other users in the band, such as WiFi. Components based on ZigBee 2006 became available last December and will soon be available for design into home automation products.

　　Software can also play a role in resolving interference issues and ensuring reliable network operation. Officials at Airbee Wireless, a ZigBee application software provider, noted that the implementation of the ZigBee protocol can affect the performance of the network in a mixed RF environment. For example, Airbee's software includes network management capabilities that can measure signal strength and dynamically respond to interference sources through channel selection and message routing. Fixed routers can also use signal strength for triangulation and determine the source of interference and notify users.

　　There are other issues as well. Proponents of the powerline approach point to the limited range of RF devices and their battery power requirements as significant drawbacks to the RF approach. But because RF home automation networks use a self-configuring mesh architecture, proponents claim that distance is not an issue. Simply adding nodes with message relay capabilities in appropriate locations ensures full connectivity (Figure 2).

　　For supporters of RF home networking, battery life is a bigger concern. An RF-based home network may contain hundreds of nodes, many of which are battery-powered. Consumers don’t want to switch on and off every time they see a battery.

Dozens of batteries need to be replaced every few months.

　　There are a number of approaches to extending battery life. For example, the Z-Wave approach keeps nodes inactive most of the time to save power. They wake up when an event requires a response (such as a key press) and periodically check to see if there is network traffic addressed to them, remaining in a low-power state the rest of the time. ZigBee nodes have a similar approach. The underlying IEEE 802.15.4 radio standard operates at a low duty cycle, transmitting energy only in bursts. In both cases, relay nodes need to remain continuously active to maintain the link, but these nodes are generally not battery powered.

　　Other new approaches to extending battery life include designing microcontrollers and other ICs specifically for implementing home networking nodes with dynamic power management capabilities. Texas Instruments' Extremely Low-Power MSP430 Microcontroller Division offers microcontroller devices that minimize power consumption by keeping only those functional blocks that are needed active at any given time. For example, TI divides its MSP430FG461x series of microcontrollers into multiple functional blocks (Figure 3) that can complete their tasks without intervention from the core processor. This approach reduces power consumption and allows nodes to operate on batteries for years without having to be replaced.

　　This technological advancement has brought various home networking solutions to a new level, which will make the dream of smart home finally become a reality. However, there are still two roadblocks: one is the interoperability problem. Many companies' solutions are based on proprietary technologies, which limits the number of suppliers that consumers can choose. The second is the lack of attractive applications that can start the market.

　　To address interoperability issues, home automation technology vendors have turned to standards organizations and trade groups. Echelon's LonWorks technology has been supported by the Digital Home Alliance, which provides a broad vendor community and interoperability certification between devices. The Z-Wave Alliance provides similar capabilities for Zensys Z-Wave technology. The HomePlug Powerline Alliance supports Intellon's HomePlug technology. Other industry groups include the UPnP (Universal Plug and Play) Forum and the ZigBee Alliance, both of which are committed to ensuring interoperability and continuously refining their standards.

　　At a higher level, international groups are also trying to establish global standards to tie together all aspects of home networking. The ISO/IEC JTC (International Organization for Standardization/International Electrotechnical Commission Joint Technical Committee) has formed JTC1/SC25/WG (Working Group) 1 to define a set of standards needed to establish a single network for all electronic and electrical devices in the home. The scope of the proposed standards includes heating and air conditioning equipment, as well as home appliances and home entertainment devices connected to home computers and the Internet. This definition work is in progress, but some standards have been published publicly.

　　However, developers should review the certification levels required by the standards and provided by trade organizations to ensure they are designing for the right goals. For example, ZigBee has multiple levels of compliance, not all of which guarantee interoperability in a home network application. The ZigBee protocol relies on the IEEE 802.15.4 radio frequency standard, with application software sitting on top of the protocol stack (Figure 4). ZigBee Platform Certification ensures that compliant devices can interoperate in a network, but says nothing about their applications. Certification of a manufacturer's specific platform ensures that a device will not interfere with other ZigBee devices, but does not guarantee application-level interoperability. For a device to guarantee the kind of interoperability that consumers expect, it must be certified for the common features for a given application.

　　Yet, while the standards are still unclear and in competition, the field is poised to offer home automation advocates things they never dreamed possible. A wide range of media options ensures flexible and low-cost installation options. Data rates are high enough to ensure distribution of entertainment content and data, as well as control functions over the network. RF signal strength triangulation allows the system to monitor and adapt to the user's location, such as turning on lights when someone enters the room and off when they leave, and switching music from room to room as people move through the room. Developers are building links to the Internet for remote operation of systems and downloading media for many home automation solutions now on the market.

　　Killer app?

　　However, while these possibilities may seem exciting, from a consumer's perspective, they are just spice. They will not kick-start the market. The real meat of home automation (the killer app) must make the technology widely accepted.

　　Such an application may be emerging. Electric utilities in Southern California and Texas are seeking to use ZigBee technology to help them achieve load control and pricing based on household needs. These companies will establish a ZigBee link at the meter entrance, hoping to provide customers with real-time feedback on electricity usage and prices, and to adjust user needs by remotely adjusting the temperature meter up and down, shutting off the water supply and pool heaters, etc.

　　As energy prices continue to climb, this type of home automation application will become increasingly attractive and may become a government mandate. It's a humble start, not as exciting as a smart home that senses your presence and preferences, but it may be the entry point the home automation industry needs to gain into consumers' homes. From here, the solutions that best meet consumers' technology needs will see all kinds of growth opportunities, just as the PC industry enjoyed in the late 20th century.