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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.
By Pat King
The Problem
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.


Sanjay Chawla 2006-01-30 01:36:23 PM
Six Sigma and the Single Tag If reading RFID tags one at a time becomes a requirement for reliability, then barcode is a better solution. It is much cheaper and you can see what your are reading. The case studies, presented in the article, supporting RFID will not be enough to overcome the cost factor.
Damon McDaniel 2006-10-24 12:58:29 PM
Singulation Mr. King, Your performance issues and therefore basis for your article is that RFID reads are NOT reliable (enough) and the only way to get there is to read all cases/items separately. Let me ask a question of you. Might you be referring to Gen 1 tags (class 1 & class 0)? And, at what frequency(ies)? I'm not a RF engineer, so because of that I HAVE to do a ton of reading & researching to keep abreast of the technology. From what I read - most of the relaiability issues have either been solved by Gen 2 developments or were truly site environment circumstances that may have called for a particular solution/frequency and because individuals were rushing to do RFID - were applying the wrong solution attempting to get the reads they were looking for. Apologies if that was confusing - but for example - look at the developments of near-field UHF vs. far. Here - the liquids pose no problem whatsoever and even metals can actually be used to ENHANCE the read ability. I don't think it matters much if you have 1,000 reads per second ability or 400. From a practical perspective - no one has proposed having a scanner sit on top of a truck bay and scan the entire truck contents for item-level tags. You probably would have reliability issues. You'd definitely also have data overload. Anyway - when a forktruck removes a pallet from a truck - usually what is desired is the pallet scan to confirm the ASN & determine it's routing - 100% reliable (if I assume proper function as you did). If the pallet requires "breakdown", then a further scan will usually capture the read on a moving conveyor to obtain the case read (also now 100% reliable in most properly constructed zones). True Six Sigma reliability will only happen when the tags & the rest of the supporting infrastructure are 100% reliable. The readers are almost there today (with proper construct). Think also of the developing RuBee & other technologies and how they will continue to improve performance issues. I felt like you were insuating that bar codes are "Six Sigma" reliable and the scanning process ususally is. But, for item level tracking - how many times have you purchased something like kids' flavored drinks - assorted flavors, yet the scanning clerk says "How many did you get?" - scans 1 and multiplies or repeats that over by your Qty? Item-level Six Sigma just disappeared. So, yes - RFID can & should be more reliable than bar codes and avail much to organizations as they discover creative ways to take advantage of the data as it becomes available. Warm Regards, Damon McDaniel

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