Dash7 Wireless Networking Gains Momentum

Get ready for yet another low-power radio protocol

Photo: Savi Technology

MANIFEST DESTINY: At one time, cargo lists existed only on paper. Now these records are not only electronic, they can reside on radio-frequency identification tags attached to the cargo itself. Dash7-based RFID tags, like the one shown here, have been helping to address the military's many logistical challenges. They may soon become popular in the commercial sector.

Wireless data networks are sprouting up like daisies. Wi-Fi hot spots have proliferated. Bluetooth personal-area networks are everywhere. And the push to make electric grids smarter is bringing with it a proliferation of ZigBee radios that use the airwaves to connect electric meters, lamps, light switches, thermostats, and appliances. So it might come as a surprise that yet another wireless-networking scheme, called Dash7, is entering the fray—and appears to be gaining traction. The International Organization for Standardization (ISO) first ratified the standard behind Dash7 in 2004, and it continues to be refined. Like Bluetooth and ZigBee, it's intended for low-power, low-bandwidth digital communications. But Dash7 hardware is designed to use even less power than other schemes, making it especially appropriate for such things as radio-frequency identification (RFID) tags, which must work for years without any external power source.

Whereas the familiar RFID tags used today for such things as door keys are passive devices (they draw their energy from the radio waves their readers emit), Dash7 tags are active, meaning that they make use of small batteries instead. So Dash7 readers don't have to transmit high RF power levels and consequently can be manufactured inexpensively—yet they can communicate with tags located hundreds of meters away or even farther when conditions are right.

Dash7 operates at around 433 megahertz, a globally available frequency also used, for example, in many keyless entry systems for automobiles. The corresponding wavelength is about 70 centimeters, which makes it difficult to design efficient antennas that are conveniently compact. Dash7 supporters say that the advantage of using a wavelength this long is that it can penetrate such obstacles as concrete walls and work in environments with large amounts of metallic clutter. This, the Dash7 advocates contend, is more of a problem for ZigBee, which employs 868 MHz, 915 MHz, or most popularly, 2.4 gigahertz, the last of which is also used for many Wi-Fi networks. Using "2.4 GHz is really nasty in environments with a lot of metal," says Pat Burns, vice president of marketing and licensing for Savi Technology, the Mountain View, Calif., company that first devised the Dash7 technology.

Jon Adams, Freescale Semiconductor's director of business development for wireless connectivity operations and a former vice chairman of the ZigBee Alliance, is, however, skeptical. "Wavelength is only part of the equation," he says, adding that if the only way for a radio signal to pass into or out of a room is through a window, a shorter wavelength may, in fact, work better. "I think some of what we're hearing about Dash7 is market positioning," he says.

The search for a market for Dash7 isn't new. Savi began developing this technology two decades ago, intending it initially as a way for parents to keep track of their kids during family outings. But that application proved a dud. According to Burns, advisors told Savi's founders, recent graduates of Stanford, "You guys have to do a reboot and find a different business model." So they shifted plans, and following the first Gulf War, they began selling active RFID tags to the U.S. Department of Defense for tracking shipments of war materials.

The U.S. military embraced this radio tagging system and has been employing it increasingly. This, of course, has been a boon for Savi. But in 2006, the Defense Department pressured Savi to license its patents to several other companies so that the military wouldn't be dependent on a single supplier. In January of 2009, the DOD awarded a US $428 million contract for Dash7 RFID devices, software, and services to four companies: Savi, Northrop Grumman, Systems & Process Engineering Corp., and Unisys.

In a move to expand its reach into the commercial sector, Savi joined with other companies to form the Dash7 Alliance this past March. Savi also liberalized its licensing arrangements in October, removing up-front fees and reducing royalties to as little as 5 cents per tag, which, according to Burns, has made dozens of companies eager to use Dash7 in their equipment.

One is RFind Systems, of Kelowna, B.C., Canada, which began more than four years ago to develop RFID tags that broadcast their positions whenever they are moved. Customers might use this system to locate pallets within a factory or cars on a dealer's lot, for example.

According to Sharon Barnes, RFind's chief executive officer, the company's original tags employed a proprietary protocol to communicate with one another and to determine their location with respect to a small set of fixed tags. Now RFind is adopting Dash7 to do the same.

The new technology has clearly helped this company refine its product line, but Dash7's general claims for far less power use than ZigBee depend on the details of how the particular wireless network is set up. And its promise of better range, too, hinges on the environment in which it is used. But one uncontested attribute of Dash7 is that its name has a clear and sensible derivation: It's a catchy contraction for ISO 18000-7. That's something that neither Wi-Fi, nor Bluetooth, nor ZigBee can boast.

This article originally appeared in print as "Wireless Networking Dashes in a New Direction."

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