TAIPEI, Taiwan — The ZigBee Alliance released an updated specification Wednesday (Sept. 27) that should help system developers targeting the home automation market. But those interested in large-scale deployments in the industrial and building-automation markets may opt to wait for another release, due early next year.

Called ZigBee 2006 or "enhanced" ZigBee, the update includes some significant changes from the spec first issued in 2004. Those changes mean that the two versions are also incompatible, which could cause problems for companies that already have products in the market.

Alliance members were quick to downplay the incompatibility issue, saying that there aren't many products on the market at this early stage of ZigBee development and that the new spec's incompatibility probably won't matter much even for companies that have already rolled ZigBee offerings. "Most of the ZigBee 2004 implementations are in confined spaces . . . where interoperability isn't high on the priority list," said Bob Heile, chairman of the ZigBee Alliance and chairman of the IEEE 802.15 Working Group on Wireless Personal Area Networks.

Future releases of the spec will be backward-compatible. Heile also noted that it is possible to create a compatibility mode if developers are willing to increase memory to run a slightly larger code base. "Then you can have complete compatibility," Heile said.

One of the main differences between the 2006 and 2004 versions is a change in the addressing scheme, said Andy Wheeler, chief technology officer of Ember Corp., a provider of ZigBee chips and software. ZigBee is meant to accommodate 65,000 nodes on a network, but developers found that the larger networks were becoming unstable over time. That's because initially ZigBee used a tree structure for addressing, which restricted the number of addresses to well below what was theoretically available, Wheeler said.

In the 2006 spec, a random addressing scheme is used, with built-in address conflict resolution.

That will be key to large deployments of ZigBee in industrial markets because it allows for many more network nodes. However, developers in the industrial market may still wait for the ZigBee Pro stack, which will include features aimed at industrial and commercial building automation, such as higher levels of security and improved frequency hopping.

Most of the leading makers of 802.15.4 radios using the ZigBee protocol stack believe that development will begin to move more quickly toward full ZigBee implementation now that the 2006 version has been finalized. To date, most of the activity has been for 802.15.4 with proprietary protocol stacks and applications.

The 2006 spec is immediately available to ZigBee Alliance members. It will be released to the public in the first quarter.