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Six Sigma and the Single Tag
How do you achieve flawless read performance from your RFID system? By making sure it interrogates only one tag at a time.
The reasons RFID data can be unreliable are twofold.
First, the interrogator's RF field is not uniform, and is even distorted by the mere object in the field and nearby. The RFID reader sends out a beacon that would look like a flashlight beam if your eyes could see it. The energy in that beacon in absorbed and/or reflected by everything in its path. RFID tags in the field of the beacon absorb the energy and interact with the reader.
Since the field is nonuniform and can vary over time, then even if you were to introduce the same tags over and over again, you would still run the risk of missing one of them at any given time. This is kind of like the camera in the early days of the bar code. You could have a perfect bar code but might not be able to decode it because the image the camera produced was illegible, causing you instead to read a different bar code on the edge of the field of view because its image is clearer. Thus, if multiple tags are in the field and you read them, you cannot be certain you actually read all of the tags.
Second, nonuniformity and uncertainty of the RFID tags' performance occurs due to environmental conditions. Many, many conferences now teach about dielectric packaging materials and the influences of water, metal, soap and other things on RFID performance.
(Note: This article does not discuss poorly manufactured tags or readers, but rather assumes we are speaking purely about reliable, certified and acceptable readers and tags. And while I do make that assumption, in reality, many tags and readers are known to be of poor quality, even noncompliant with FCC requirements. Imagine if you added poor quality readers or tags to the equation above? The first advice I would give anyone new to RFID would be to work only with certified reliable tags and readers. If you receive anything other than that, send it back.)
If you now imagine that the goal is to read variably performing tags, in a nonuniform and varying field, then you have the recipe for disaster. This is where most people find themselves today.
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