For years, the RFID industry worked tirelessly to improve RFID read rates just so that an RFID tag on a piece of inventory or asset could be read as it passed a reader. The first few generations worked exclusively on picking up this small, weak signal, and declared “VICTORY” when the tag could finally be read with precision.
Then something happened. As the industry gained knowledge, tags and readers improved, and more antenna choices became available. This led to expanded read ranges. Now, that tag that could barely be read at 5 feet away from the antenna is read at 20 feet away. At last, improved long-range reading was a reality. However, long-range reading produced a problem — a problem bigger than the problem of not reading the tag at all: Reading the tag accidently.
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Unfortunately, RF energy, as much as we hope and wish, can’t be controlled enough to limit the reading of unwanted tags simply by changing the reader power or limiting the receive signal strength of tags (RSSI). The read zone characteristics change regularly. The classic example of this is the effects of a forklift as it drives through a dock door read zone. The metal characteristics of the forklift bounce the RF energy for a short period, creating read events from tags outside the reader’s normal field of view.
So, how do you fix the issue and enable more accurate reading? It is necessary to apply more filtering in order to determine what a “valid” tag read looks like. Note that a “raw” tag read does NOT equate to a valid tag read; a valid tag read creates actionable data. Raw tag reads become valid tag reads if they fit the profile of a valid read event. A raw read that does not meet the criteria of a valid tag read needs to be tossed aside, as it is nothing more than pure noise to the system. If undetected, this creates false read events and bad data, and requires manual manipulation to correct the error. Invalid read events that are passed as valid events essentially remove most of the ROI the RFID system was designed to provide.
I spend an extraordinary amount of time with customers helping define the algorithms for a Valid read event for a specific read zone. Those characteristics take into account many of the following parameters:
- Tag Header
- Read count by antenna
- Number of antennas
- RSSI
- Only movement from distinct zone to another distinct zone
- Persist time in the RFID read zone
Furthermore, the RFID server must have the ability to manipulate all of these criteria to form a decision on a valid read event. For this reason, RFID software is always deployed in a solution that requires something more than a simple raw read event.
Buyer beware of the data collection sales person that offers a reader and states, “The reader can do all of that for you.” The readers are smart — no doubt — and an important tool to limit some of the raw reads. But, the readers can’t collaborate enough to make some of these valid event decisions.
Lastly, as you are looking at different RFID system, remember to ask yourself, “What is a valid read within my operation and how can I filter the unwanted reads?”
Tom O’Boyle is Director of RFID at Barcoding, Inc.
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