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Why Zone-Based Real-time Location Systems Are Superior

For indoor applications, zone-based approaches provide far more reliable results than triangulation-based methods, and at a cheaper cost.
By Abraham Blonder
The zoning method is mostly used for passageways (doors) or indoor environments, such as office spaces, hospitals and so forth. Tuning the reader for each room at the installation allows for precise and stable room-level accuracy. Even if a tag located close to a wall could be detected by the reader covering the adjacent room, the signal's intensity—after passing through the wall—would be significantly lower than that of the signal received by the reader within the same zone. The software application will thus consider that the tag is in the correct area.

Dynamic filtering is also used to further increase localization reliability. Such algorithms take into account the localization of the previous tag signals, in case of complex situations. Practically speaking, readers deployed using the zoning method, along with RSSI and sophisticated software, can warrant approximately 99 percent accuracy in tag localization, whether situated on a person or on an asset.

The communication protocols used by active tags for first-generation zoning systems are normally unidirectional—that is, they talk to the reader, but the reader can not call the tag ("tag talks first"). Such tags have the advantage of being rather inexpensive compared with other types of active tags. A zoning system's installation is simple and stable, which is also a cost-savings factor. The big disadvantage for this type of system is that it requires a single reader per room, which implies the device's cost, plus the expense of a network point and an electricity point.

Second-Generation Zoning
The active tags employed in second-generation zoning systems are bidirectional—that is, they can both emit and receive signals. A single interrogator is installed and tuned to cover a large area—typically, a circle with a radius of 15 meters to 20 meters (49 feet to 66 feet), passing through several walls.

USER COMMENTS

Glenn Tamir 2011-08-25 01:44:20 PM
The important question however is , does the accuracy meet t It may be possible to achieve incredible levels of accuracy with certain active RFID systems. However, the question that often does NOT get asked is, what is the need of the customer and the application? Does it really matter if one system can show which floor tile an IV pump is sitting on if all the customer needs to know id where it is located in a general area??? It's not about hitting the bullseye but meeting the needs of the customer and the application.
Glenn Tamir 2011-08-26 12:58:08 AM
I Completely agree with this article In this very well-researched article, it is clear that the Second-Generation Zoning method is the least expensive and most reliable system for healthcare applications and other indoor environments. LogiTag Systems, Inc., which has been specializing in RFID technology since 2004, has designed it RTLS system called "LogiTrack" based on this very technology. Thank you for validating that the direction LogiTag has been pursuing is the right course to take. It is reassuring to know this and bodes well for our future as we enter the US Market.
Jack Vandenberghe 2011-10-05 11:12:34 AM
What about for a warehouse? I like this artilce and am just wondering how RTLS could be applied not to single rooms, but to a large warehouse area that is not partioned into rooms?

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