ZigBee Moves From Monogamy To Polygamy

In its early days, ZigBee networking was the ZigBee Alliance’s core technology.

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ZigBee’s initial strategy was to become the gold standard for sensor networking. IEEE 802 specifications, promulgated by the Institute of Electrical and Electronics Engineers, do not address networking; most IEEE 802 devices simply use transmission control protocol/Internet protocol (TCP/IP). However, the 802.15.4 specification targeted low-power, small footprint devices that, at the time, could not be expected to manage a TCP/IP network stack. Many sensor network start-up companies began to commercialize their own proprietary networking technologies. ZigBee saw itself as a way to eliminate such fragmentation.

ZigBee-defined networking, though standardized, was not optimal for many applications, so other networking technologies persisted.

One application in which ZigBee networking proved unsuitable was remote controls for consumer electronics (CE). Infrared (IR) technology had been used for years in remote controls. Leading CE manufacturers wanted to shift to radio frequency (RF)-based remote controls for their high-end products, especially large flat-panel TVs, some of which had difficulty working with IR remotes.

In January 2008, Freescale Semiconductor announced that it would share its 802.15.4 RF remote control technology. This initiative produced the RF4CE Consortium (Radio Frequency for Consumer Electronics). In March 2009, ZigBee announced that it would incorporate RF4CE into its specifications. While, in the future, the ZigBee and RF4CE specifications will be developed together, at present, they are entirely distinct technologies and do not support interoperability between ZigBee and RF4CE devices.

Demand for IP

Besides consumer electronics, the other application with huge promise for ZigBee is Advanced Metering Infrastructure (AMI) and home energy management. AMI is poised to grow rapidly. ARC’s most recent study, “Advanced Metering Infrastructure and Smart Grid North American Market Outlook,” forecasts five-year compound annual growth rate (CAGR) of more than 25 percent, despite tepid growth in 2009. Major U.S. electric utilities are well into major AMI programs.

ZigBee sees its role in AMI as providing networking and interoperability between the utility endpoint (the meter) and home energy devices. Indeed, this June, the U.S. National Institute of Standards and Technology (NIST) included ZigBee’s Smart Energy Profile as the preferred home automation standard in its Smart Grid Interoperability Standards Framework. ZigBee’s problem was that the customers (electric utilities) were attracted mainly to the interoperability technology derived from ZigBee profiles, and were cool, at best, to ZigBee networking technology.

Furthermore, in 2007 and 2008, the Internet Protocol (IP) made great strides in sensor networking. In September 2007, while these AMI projects were being developed, the Internet Engineering Task Force (IETF) published RFC 4944 “Transmission of IPv6 Packets over IEEE 802.15.4 Networks.” IP had come to sensor networks.

North American utilities were much more comfortable with IP, and they pressured the ZigBee organization for support. This past April, ZigBee announced that it would incorporate global information technology (IT) standards from the IETF into its specification portfolio, and indicated that this meant “native IP support” for wireless devices. In other words, CAP-like (Compact Application Protocol) functionality. This pleased the utilities, but added a third network protocol to the expanding “ZigBee portfolio.”

The key takeaway from all of this activity is that the term “ZigBee” does not mean the same thing that it did a year ago. In the near future, ZigBee-compliant devices may use IP rather than ZigBee networking. They may also use any and all physical layers presently used with IP (Ethernet, 802.11 and others) along with the 802.15.4 physical layer they now use.

The role of the ZigBee Alliance will change as well. It will move toward managing the development of specifications that support multiple network layer protocols. It will raise in importance the ZigBee-defined device profiles that support interoperability and the defined integration of these profiles with IP and RF4CE networks.

Harry Forbes, hforbes@arcweb.com, is a Senior Analyst with ARC Advisory Group Inc., in Dedham, Mass.

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