Higher memory requirements may strand the installed base of home-area network smart-energy devices.

Tam Halbert — EDN, June 14, 2011

The
smart meter market has been a boon for ZigBee chips, and could lead to an even
greater market in energy-related home-area network equipment. But how soon that
happens may depend on how recent wrinkles in the development of the ZigBee SEP
(Smart Energy Profile) 2.0 standard work out.

Last
year saw 13 million smart meters shipped in the North America, most of them incorporating
ZigBee chips, according to Mareca Hatler, director of research at ON World Inc, which tracks the market for
wireless sensors and networks. Another market researcher, Pike Research, estimates that about 20
million smart meters shipped in North America from 2008 to 2010 and forecasts
another 60 million to 65 million will ship from 2011 to 2015, with more than
70% of them using ZigBee chips.

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.