Data Intelligence: Choosing a Real-Time Locating System

Feb. 1, 2007
"While it's tempting to think that WiFi-based systems are the more ‘open' standard, the real magic is the software."

You probably think you know what moveable assets you have, where they are and how efficiently they're being used. In some instances, you might be right. In others, however, you could be costing your company money. Big money.

Now, it's not entirely your fault. Moveable assets are, by definition, moveable. So, whether they're freight containers in a yard, infusion pumps in a hospital or returnable containers in the shipping department, it's enough of a challenge keeping track of what you have, let alone how it's being used or where someone decided to put it.

This is where real-time locating systems (RTLS) can help. A lot.

A case in point: Lynn DeRose of GE Aerospace says that 41% of the time a gauge is checked out, it isn't used. But each checkout counts against a mandatory calibration schedule. This means that an expensive and time-consuming calibration process must be performed nearly twice as often as it really needs to be.

Another example: as reported by Dr. In Mun of Aventura (Fla.) Hospital and Medical Center, the hospital's inventory of infusion pumps always seemed to be inadequate. The hospital, therefore, budgeted new equipment purchases every year. After implementing a trial of RTLS for these pumps, the hospital discovered that it actually had 30% excess inventory.

There are, in fact, many case studies demonstrating the cost savings associated with the use of RTLS. Sometimes the ROI can be easily proven in advance. Other times, however, as with Aventura Hospital, the cost savings are evident only after a trial or pilot. The point of this column, however, isn't as much about ROI or the benefits of an RTLS—you can figure that out for yourself— it's more about choosing an RTLS.

There are two basic types of RTLS: proprietary network and WiFi-based. And there are many different configurations of each. While it's tempting to think that WiFi-based systems are the more "open" standard, the real magic in the system is the software. And each vendor offers a different package.

WhereNet (, now owned by Zebra Technologies) is the leading proponent of proprietary communications. Most other RTLS suppliers, such as PanGo Systems (, Ekahau ( and AeroScout (, are in the WiFi camp.

Both types of systems employ active tags that periodically broadcast (or "beacon") their identity. Using this signal, received by one or more antennas, the system calculates relative signal strength or time differential to determine the relative location of the tag.

Typically, the more antennas, the more precise the location. Some systems can get by with only one antenna if, say, you're looking for a large item in a restricted space. Once you're in the general location, you can probably find it. Greater precision, including X,Y,Z location, may be required for locations where items are smaller or more densely packed.

WiFi systems can use an existing WiFi infrastructure and enable bi-directional communication with the tag. The limitation with WiFi systems is that a high density of tags in a given area and a frequent rate of "beaconing" can overwhelm the system. They may also require more antennas for better precision.

Proprietary communications don't have the same potential to overwhelm an existing data communications infrastructure and may offer greater range than WiFi, reducing the number of antennas required or providing greater precision. The disadvantage is that such systems require installation of a standalone infrastructure.

While RTLS offer tremendous benefits, systems today still vary greatly and do not interoperate. Care needs to be taken in evaluating the software and physical environment to determine the most appropriate system. It's a lot of work but it can result in a lot less wasted effort and resources.

Bert Moore is a 20-year veteran of the AIDC industry. He is director of IDAT Consulting & Education, Alpharetta, Ga.

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