ZigBee (Almost) Arrives
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802.15.4 is one of the many personal area network (PAN) standards around like Bluetooth and ultrawideband (UWB). Like most IEEE 802 standards, the wireless industry knew what the IEEE was doing (or didn't do in the case of UWB) was not enough.
Thus was born the ZigBee Alliance, a consortium of well over 100 companies that looked at what the short range, low power radio frequency (RF) 802.15.4 could do, and built upon it to make something completely interoperable between multiple vendors.
The many months of work have paid off, and as of this week, ZigBee 1.0 is official as a standard.
However, it's not exactly the same as 802.15.4 any more. An 802.15.4 chip without the ZigBee standard might work fine as a radio, but will not have the security layers and mesh networking functions to make it interoperable with any and all ZigBee products of the future. A company can't make a ZigBee product without being a member of the alliance.
Unlike with 802.11, where things like TCP/IP traffic were intended, and thus you could just about assume everyone following a specification like 802.11b would interoperate, that's not the case with 802.15. Bob Heile, the chairman of the ZigBee Alliance, says the group had to spend a lot of time building on the "upper stack" to make ZigBee as simple as possible, and small enough to work with storage of just a few KB.
"The hard part was coming up with an efficient network layer for self-organizing networks," says Heile. "And it had to stay small."
Having such a short range (70-100 meters) and being relatively slow (only 250Kilobits per second), ZigBee isn't going to overtake Wi-Fi anytime soon in home networks. That's not the intention, anyway. Heile says one target market is replacing the line-of-sight infrared technology used in remote controls.
Initially, the technology is likely to become a cornerstone of control and sensing tools in homes and buildings.
"Think about what you want to know the status of," says Heile. "You can do it now with ZigBee and get a lot more information than before. Put a wireless light control where you want it, not where the builder put it." It could essentially go into anything that you don't want to change a battery in very often: smoke detectors, keyless entry, garage doors, thermostats, hot water tanks, and on windows and doors to see if they're open and closed, to name just a few applications.
ABI Research analyst Chris Lopez said in an ABI Insights newsletter that the technology has "the potential to function in a whole variety of applications that are only limited by one's imagination."
ZigBee's potential means it has to be able to scale from a few nodes in a home to potentially thousands in a commercial building.
Knowing the scope of things to come led to what Heile considers a primary ZigBee principle: "It had to be brain-dead simple and brain-dead cheap. It had to be self-organizing—you couldn't install it manually. And parts break, so it had to self-heal."
One area that ZigBee is likely not gunning for is the Bluetooth or Wi-Fi space. While ZigBee could handle some of what Bluetooth does, its slower speed and lack of TCP/IP for network communications mean it is not going to do much data transfer anytime soon that would compete.
ZigBee could be ubiquitous quite fast—analysts are saying anywhere from 5 to 100 million ZigBee chips could ship in the next few years.
The Alliance was originally hoping to have the standard done earlier, but ABI's Lopez said that it was "postponed several times... to ensure that the final product would be complete and foolproof. This is important to ZigBee's success in the marketplace because most consumers will simply return any ZigBee product that does not easily work with multiple vendors."
ZigBee is facing the same issue now that Wi-Fi has faced in the past many times (and faces again with 802.11n)—companies have already started to release chips and products in a "pre-standard" form. The ZigBee specification from the Alliance has been pretty solid for a while, so they felt they could get a jump on things. Heile points out that all claims by ZigBee vendors should at this point be considered with "A grain of salt on capability. It's everyone jockeying for position... No one has anything that has met our test suite. That's our next piece to do."
Testing for interoperability will be a core tenet of why the ZigBee Alliance exists, much like its Wi-Fi counterpart. The group says it's 90 percent ready for two test houses to get started.
Alliance member companies will also be expected to participate in the Zigfest, a product plug-fest where everyone working on the platform comes together to demonstrate that the hardware can easily interoperate.
"The test will tell us a lot," says Heile, "but we're not sure it's enough to say they're interoperable. We want this real-world thing on top of the test."
Until everyone has been through both, "no one can say they have the first of anything" in ZigBee, he concludes. An 802.15.4 chip could come out tomorrow without the ZigBee standard and work fine as a radio, but will not have the security layers and mesh functions to make it interoperable with ZigBee.
That, of course, hasn't stopped anyone. Airbee Wireless, for example, announced a software platform for ZigBee this week that it says will be hardware-independent, working with any 802.15.4 radio to make it ZigBee-compliant. Freescale Semiconductor is already claiming that its ZigBee platform can outperform the specification's range by going up to 378 meters.
ABI says that Freescale and others like Figure 8 Wireless, CompXs, Eaton, and Atmel have had a headstart because they're heavily involved in the Alliance, and will need only minimal changes to be fully ZigBee-compliant.
Competition isn't fierce in this wireless control space, but players like Zensys with its Z-Wave system are out there, and will likely give ZigBee someone to play against—which is all the better for the consumers of the technology.
The IEEE 802.15 Working Group is already at work on 802.15.4a, an update to the "Low Rate Alternative PHY" that ZigBee is based on. Considering the time it takes the IEEE to push through a new spec, however, Heile's confident it won't have much of an impact on what they're doing in ZigBee for a long while. He says, "When ZigBee takes its next step, 4a might be ready. But don't expect ZigBee 2.0 anytime soon."