August 19, 2004

ZigBee Takes It Easy

Short-range wireless "ZigBee" networks are ready to unwire your house.

By Eric S. Brown

Five years ago, the ZigBee short-range wireless communications standard might have been hawked as a magic key that could unlock the wonders of pervasive computing, a dream of a future in which devices and appliances anticipate their users every need. In todays more careful atmosphere, however, its developers are wisely focusing on a smaller, more attainable goal: letting builders and homeowners cheaply install portable light switches, thermostats, and security systems. If ZigBee wins big in this lighting and control space, however, it may well go on to play a major role in product tracking, medical monitoring, and industrial sensor networks.

The ZigBee Alliance, which totals nearly 100 companies, including Honeywell, Mitsubishi, Motorola, Philips, and Samsung, is hoping to tame a still-fledgling home-automation market confused by a hodgepodge of proprietary technologies. This summer over a dozen ZigBee-ready prototype products been released, and more should arrive by years end. By next summer, builders should have complete certified kits at their disposal. According to ABI Research, over 80 million ZigBee-enabled devices will ship by the end of 2006.

ZigBee allows small, low-cost devices to quickly transmit small amounts of data such as temperature readings for thermostats, on/off requests for light switches, or keystrokes for a wireless keyboard. Based on a recently approved international packet radio standard, ZigBee uses the same unlicensed 900MHz and 2.4GHz frequencies as many cordless telephones to send data over distances up to 20 meters. ZigBee devices, typically battery-powered, can actually transmit information much farther than 20 meters because each device within listening distance passes the message along to any other device within range. Only the intended device acts upon the message.

Given enough devices spread around a house, this multi-hop mesh networking approach can use redundant pathways to make sure the message gets through even if one of the devices is out of order. For example, if you were sitting in bed and flipped a portable switch to preheat the hot tub in the back yard, the message might normally pass through a node in the kitchen. However, if your kitchen ZigBees battery died, the message could still get through in a wireless version of an end-around play. By simultaneously transmitting the message to the den, your tub switch could bypass the kitchen transmitter, still getting the on message to the tub. But because another major ZigBee innovation is power efficiency, the kitchen battery is not likely to go dead in the first place. By instructing nodes to wake up only for those split second intervals when theyre needed, ZigBee is so chintzy with electricity that batteries might last for years.

While the technology could well emerge as a bedrock wireless automation standard for transmitting status messages in sensor networks for manufacturing, health care, shipping, homeland defense, and more, the ZigBee Alliance is initially keeping its focus small. The Alliance would love to have ZigBee in every widget in the world, says Jon Adams, director of radio technology and strategy for Freescale Semiconductor, a Motorola spinoff that recently released the first ZigBee development kit. The challenge, he says, is drawing attention to ZigBee in an era of proliferating wireless standardsand at a time when manufacturers and consumers have learned to distrust any technology billed as a panacea. So, weve chosen to limit our reach, Adams says.

ZigBees first applications will be in professional installation kits for lighting controls, heating, ventilation, air conditioning, and security. According to Adams, huge cost savings will be found in both new construction and in redesigning commercial spaces. The cost of laying cable ranges between $20 and $200 a foot, and you have to move a lot of conduits in order to get the light controls and other mechanisms into the right spots, says Adams. The advantage of a wireless, peel-and-stick light switch is very powerful.

Similar technologies are available, such as Zensyss Z-Wave mesh network, Smarthomes Insteon, or on the high end, the Intel-backed TinyOS operating system popular in sensor networks used for academic research. Even the Bluetooth short-range wireless technology found in laptops and cell phones has been held out as a home automation solution, although according to Adams, it lacks the affordability, power savings, and mesh-networking capabilities of ZigBee. Builders appear to be drawn to ZigBee due to its frugal use of battery power, its use of open standards, and the support of home automation giants such as Honeywell and Philips.

Once established in the construction industry, ZigBee is likely to appear in home-networking upgrade kits for consumers, perhaps around 2006. ZigBee will also move into industrial maintenance networks, which can benefit from wireless sensors that dont need to be regularly checked by technicians. ZigBee devices can be strung together in networks of up to 65,000 nodes, enabling quality-control engineers to scatter ZigBee units throughout a factory to monitor vibrations that might indicate an imminent equipment failure or let building managers control campus-wide electrical and security systems from a single computer. It could even enable sensor networks to monitor environmental conditions on large farms or to blanket a city to check for bioterror hazards.

In the meantime, however, if ZigBee companies can maintain their focus, the technology will start working its way into new homes and renovations by next summer. That will mean more flexibility and cost savings for consumers, and the potential for far greater control over household appliances. The pervasive stuffand the hypecan come later.