Bob Trebilcock

What's next for ultra wide band RTLS
February 21, 2008

That's not the kind of feedback most reporters are hoping for when they publish their work, me included.

But that was the response back in October to an article I wrote about UBISense, a provider of real-time location systems using ultra-wide band (UWB) RFID technology. While I’ve written about the RTLS market for the last couple of years, UWB technology was a new one to me. But since getting flamed, I’ve come across a number of articles by technology writers who are a lot better informed than I am and who believe in the technology, so I thought I’d take a second shot at the topic. Most, you’ll notice, are out of the UK, where the adoption of RFID technology seems to be ahead of those of us here in the States. 

The promise of UWB technology is that it offers much more precise tracking and locating capabilities than competing technologies—vendor like Ubisense and Time Domain say they can track an object’s location to within a foot or less. This compares to tracking objects to within 3, 10 or 30 feet with other technologies. If you’re trying to locate a big object, like a lift truck or shipping trailer, getting to within 30 feet may be good enough. If you’re trying to locate a mission critical tool or tote for a manufacturing line, you may need more precision. 

How does it work? To find out, I talked to Adrian Jennings, Time Domain’s chief technology officer.

According to Jennings, UWB uses a tracking method know as time difference of arrival (TDOA). Also known as triangulation, TDOA solutions use three RFID readers to receive a signal coming from an active RFID tag. The readers record the time when they receive the signals and forward that to a central location, where the time difference between the three signals is used to triangulate a location. TDOA solutions require a direct line of sight between the tag and the reader. For that reason, they work best out of doors, or in facilities with high ceilings and open spaces

Other providers of RTLS technology, including WhereNet and AeroScout, use this method to locate assets. They, however, operate over different radio frequencies than UWB. In a manufacturing or logistics environment, where there’s lots of metal racking, and those objects can cause the radio signals to bounce around. “They can overlap, and a receiver may have a difficult time distinguishing which pulse it’s listening to,” says Jennings.

UWB tags transmit ultra short pulses that are on and off very quickly. Those short pulses are more easily read by readers, and allow the readers to track many more tags than is possible using other technologies. For that reason, Jennings says, it’s ideally suited to manufacturing operations. In fact, one of the company’s first customers is an aircraft parts manufacturer that uses the technology to make sure that a part in a jig is lined up properly to get pushed into a manufacturing cell. “They’re getting accuracy to within 8 inches,” says Jennings.

The catch: Accuracy comes at a price. “In general, there is an increasing cost of installation versus accuracy,” says Jennings. “UWB is at the high end of both spectrums—its’ the most accurate and it’s the most expensive.”

For that reason, it’s primarily being used to address real pain points, rather than general use.

Is your company investigating RTLS solutions or UWB? Let us know what you’re finding in the marketplace.

Posted by Bob Trebilcock on February 21, 2008 | Comments (0)