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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
Jan 30, 2006We often read or hear about how one RFID system is better than another because the first can read 500, 600 or even 1,000 tags concurrently. This is a point RFID equipment marketers are constantly making in print and at conferences. The most frequently referenced applications are luggage at airports and the holy grail of reading, an entire shopping carriage as it rolls past a portal. There is a small problem with all of this, though, and it pertains to read reliability.

The inability to read multiple tags reliably is why Wal-Mart and the U.S. Department of Defense have focused on reading only the pallet tag rather than the tags of all cases on a given pallet, and on reading the case tags only when the boxes are on a conveyor. They are subscribing to singulation—making sure only one tag is in an interrogator's read field at a time—and not knowing it.

RFID vendors still drone on about their systems' ability to read hundreds of tags simultaneously. Unfortunately, RFID is being promoted as a confidence game, and we are naively rushing to a sad ending.

Why? Are we inherently stupid? I think not. Is it because we lust for automation and advances in technology? Perhaps, to some degree, but it's not the only reason. Then what is going on?

Most of the world has begun to take bar codes for granted. This is the first part of the problem. When you fail to understand the base solution we live with and how it actually works and doesn't work, you set yourself up to be conned and duped.

Let me take you back for a moment. The bar code actually dates back to antiquity, but the really old part is not pertinent. We will fast-forward to the late 1970s and early 1980s. In that period, companies imagined a new printing market based on item identification. They created symbols such as black and white lines or bars that varied in thickness, width and/or pitch. They standardized them and called them Code 39 and Code 128. They convened U.S. and ISO standards groups, all along making sure they could sell more and more labels with these new bar codes.

Well, they forgot one thing—namely, how the heck do you read a bar code? The early solution was with a camera or line scanner/wand. The first cameras were costly boxes, and the handhelds were boxes with handles. They were ugly and costly, and they were unreliable because cameras had limitations regarding such things as ranges for depth-of-field, depth-of-focus, contrast, dynamic range, etc. The early industrial cameras tended to capture too much or too little information, or the lighting was wrong, or the image was fuzzy, and so forth. Most people rejected bar codes as ever being useful. The wand worked OK, but was very manual and labor intensive.

The big technological breakthrough came with the invention of the galvo-laser reader. This device sent out a single scanning beam that ran across the surface of a bar code, reflecting back any laser light not absorbed. The black absorbed the light, and the white reflected it back to the galvo-mirror optics. Suddenly, you could reliably scan a single bar code. This laser scanner, which we take for granted today, continued to improve in the usual ways: smaller, lower cost, improved performance, etc. As a result, you can plug one of these modules today into almost any electronic device and reliably read a bar code.

So why don't bar codes work, and why do we passionately want to replace them? Well, bar codes do have some flaws. These flaws are normally either the first or the second slide in most recent PowerPoint presentations at conferences. They include line-of-sight requirements, distorted/soiled or damaged bar codes, lost bar codes and, finally, the inability to write additional data to a bar code. Most of those are described as being solved by RFID within the next two slides at the same conference.

These days, we are so enamored with RFID's potential that we lose sight of one important fact: When we receive a data read, it must have Six Sigma reliability. Manufacturers attain Six Sigma in many of their applications today. They still want to improve but cannot go backward in terms of data reliability.


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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