Practical Chip Design

With all the doom-and-gloom talk in the UWB wireless USB market it's important to understand that WUSB is its own specific market with its own specific dynamic, not an avatar of the entire short-range wireless network market. At Electronica last week this point was clearly illustrated by a conversation with Jim Lindop, CEO of wireless transceiver chip company Jennic.

Wireless USB is tied closely to the personal computer and consumer markets—an unfortunate association at the moment. But 802.15.4, with shorter theoretical range, considerably lower data rates, several different air interfaces, and significantly lower power than the typical WUSB configuration, has lived in another world. Lindop said that the majority of the applications for the protocol have been in sensor networks for industrial or medical applications, as a MAC/PHY for Zigbee PRO, for industrial asset-tracking applications, for smart energy applications such as building-level energy management, and, in the consumer world, as an RF replacement for IR remote controls.

The contrast between these last two applications is rather remarkable, Lindop said. While the cost and performance of 802.15.4 are both excellent for banishing the IR link from home entertainment, that market has slowed dramatically with the vanishing of the consumer. But Lindop claimed that the cost of energy and concern over carbon footprint have triggered an acceleration in the energy-management market that shows no sign of slowing with the recession. Apparently there is so much low-hanging fruit for many organizations in simply doing intelligent things with their lights, heat, coffee-makers and office equipment that a wireless sense-and-command network to control loads and reduce electrical consumption has a very short payback. Organizations can justify the investment because of the recession, rather than in spite of it.

An illustration of this point is a recently-concluded project in which Jennic assisted in creating a wireless network controlling heating at the City of London School for Girls. The company claims that because the installation is wireless, it was done at a fraction of the cost of pulling wire, and in a fraction of the time. This of course not only reduces front-end cost—in simple command-and-sense networks installation can be a significant portion of the initial cost—but it accelerates the return on investment and the reduction in carbon release.

This particular example illustrates another point on which Lindop had interesting thoughts. This particular sensor network, like many examples where both sensor data patterns and command information are relatively simple, does not require anywhere near the entire flexibility of the Zigbee PRO protocol stack. For such applications, Jennic has created a significantly simpler stack, which they call JenNet, and to which they have just added some significant extensions. The proprietary stack offers a much smaller memory footprint, as well as the possibility of reduced energy per transfer.

Lindop sees a number of areas in which there may be further work on specialized protocol stacks for the 802.15.4 standard. One such is support of IP-to-Zigbee interoperability. Another is the need for deterministic latency when the wireless link is actually inside a real-time control loop in sense-and-control applications. And of course there is the continual pressure, especially in areas such as asset tracking, for lower energy consumption.