Discord over ZigBee Smart Energy Profile could delay market for home-area network products
and 802.15.4 module/chipset shipments
|| 7 million
|2008|| 13.2 million
|2008|| 18.4 million
|2010|| 36.5 million (preliminary)
|2014||120 million to 180 million (forecast)|
HANs (home area networks) could represent an even bigger market, both for smart energy devices that would monitor household power usage and communicate that to the meter, presumably through ZigBee, and for devices embedded in a range of household appliances, ranging from TVs to home security to dishwashers. The latter could use any of a variety of networking technologies, including WiFi and power line.
But debate over the technical details of SEP 2.0 is holding up the HAN market, according to market observers and some participants.
ZigBee's future in the smart grid was assured in early 2010, when its SEP was included as one of 16 consensus standards in the smart grid interoperability framework being developed by NIST (National Institute of Standards and Technology). There was only one problem - NIST wants everything in the smart grid to use the IP (Internet Protocol), and ZigBee does not. So the Alliance has been working with the IETF (Internet Engineering Task Force) to re-develop the ZigBee protocol stack.
The job is technically complex, according to Bob Gohn, director of smart grid research at Pike Research. "With ZigBee, all the [protocol] layers are tied together in a way that IETF protocols are not," he explained. Even though SEP 2.0 "technically refers to just that application layer on top of the protocol stack, in reality from a development perspective it means a redevelopment of the whole megillah - the whole protocol stack on top of the 15.4 radio."
In April, the ballot process revealed significant disagreement over technical details. Specifically, one faction, presumably those who had developed the original ZigBee standard, wanted to use UDP (user datagram protocol) as the transport layer, whereas the other group was arguing for TCP (transmission control protocol). But the use of TCP would require more memory than the original ZigBee standard. That could make it difficult to upgrade those 20 million smart meters already in the field, because their chips don't have enough memory for the new standard.
Chips for the earlier ZigBee standard have about 160k of flash and 8k of RAM, according to Matt Maupin, senior marketing manager at Freescale Semiconductor. The new standard with TCP would require 256k of flash and 16k of RAM.
It's not unusual for technical disagreements to surface during the balloting process of a standard, noted Bob Heile, chairman of the ZigBee Alliance. Nevertheless, the alliance has taken some unusual steps to try to get past the issue. First, it has hired an expert facilitator. "This is somebody to help the two opposing camps hear each other better and find common ground," he said. Second, the alliance has created a leadership task force to look at the business drivers that are behind the technical differences of opinion. "Each [utility] has built a separate business case that they have filed with their public service commission." The goal of the task force is to try to find alignment among those business cases, he said.
Those business drivers vary significantly, noted Gohn. Some companies involved in the standard have no installed base of ZigBee chips to worry about. But "if I'm responsible for 30 million meters that are already out in the field, or my bread and butter happens to be making 15.4 chips, I'm not liking this," said Gohn. "Tempers have really flared up."
Meter manufacturers and chip vendors say they can devise workarounds. Stephen Johnson, product line manager for consumer energy management at Itron, says there is a spectrum of options. One emerging compromise is to use a gateway that is equipped to handle either TCP or UDP, he noted. "What we're trying to do is make sure that we not only open the door to more advanced applications but we also don't strand the assets that have already been deployed."
As for HAN devices, one approach that many chip makers are adopting is to split the protocol stack between the ZigBee chip and a secondary microcontroller in the home device, said Maupin. "You just have to make sure that the customer is putting enough flash on the host IC to handle this."
But that's not a solution for HAN devices that are already deployed. Some 70% of utilities surveyed by ON Research already offer or plan to offer in-home energy management systems that integrate with home-area networks. Utilities that have installed for their customers free or low-cost devices like thermostats that communicate with their smart meter are now concerned about how or whether those devices can be upgraded to 2.0, noted Johnson. They may not have been built with enough memory.
Indeed, questions over how to migrate from SEP 1.0 to SEP 2.0 are holding up the market for such devices, said Maupin. "I would've expected at least a 10% attach rate [one household device attached for every 10 smart meters deployed] by now, maybe even 15 or 20%," said Maupin. Instead, he estimated it's closer to 5%.
Heile insisted that the disagreements will be resolved, and said the alliance is still on track to have the standard ready by late this year or early 2012.
Meanwhile, however, the HAN market is on hold.
"The whole market for HAN devices, which are getting to point of substantial implementation, is hanging in limbo until this new standard comes out," said Gohn.
Editor's note: Shortly after this story was published, the ZigBee Alliance announced progress in achieving agreement on a proposal involving the way HTTP and CoAP are used in the draft of the Smart Energy version 2 standard. This agreement means the draft can advance into the next ballot, scheduled to begin on July 11. See this statement for more information.