Radio Frequency Identification tags have carved out a niche for themselves in several location-based technology sectors, most notably in supply chain management and ERP. The compelling value point of RFID, compared to other wireless technologies, has been cost, with chips running as little as 35 cents apiece for some varieties.
However, there have been problems. Limited range, reader glitches, and what to do with the incredible volume of data created by RFID systems have all been issues with which engineers have struggled. The answer has been application of RFID in different models, based on need and desired functionality.
The National Institute of Standards and Technology has produced an overview, RFID-based Localizaton and Tracking Technologies, which outlines four basic models of RFID implementation. The article is available free to IT Business Edge members here in the IT Downloads library.
The article runs through the basic component of RFID technology-the differences between active and passive tags and the range limitations of reader antennae-and then breaks down the four basic models of RFID location-tracking implementations that have emerged:
Tag-based systems require the target to carry a (typically active) RFID tag that periodically transmits beacon messages. These systems tend to also employ reference tags to help verify the position of targets as they move through the survey area. You can see a schematic of a typical tag-based layout in the image below.
Reader-based systems require the target to carry a portable RFID reader, to gather information from nearby tags. This is sometimes referred to as reverse RFID. It tends to be employed where building and maintaining a very large network of fixed readers in implausible. Reference tags are just much cheaper.
Transceiver-free technologies can localize targets without requiring them to carry any device. It is appropriate in very static environments and relies on interruption of wireless wave to predict movement of the target. Kinda like RFID radar.
Hybrid technologies integrate RFID technologies with other technologies such as inertial navigation systems and WSNs. These systems were developed largely to mitigate problems with RFID range limitations, or to use a steady stream of RFID data to correct "drift" of other localization technologies.
The article goes on to spell out the challenges that still face RFID, such as tracking multiple objects in the same closed space and interference by the million or so devices that generate radio waves. It's a quick yet comprehensive read at seven pages and well worth a look if you are considering any localization technologies.