RFID for libraries: HF or UHF? (2)

Finally! With the European tender wrapped up, Autocheck Systems chosen as our partner, our RFID project is finally on its way. Now I can share a little more on the technology choice, following up on a post from, *cough*, one year ago.

When we started preparing, it looked like UHF had great potential to overcome some of the shortcomings of HF. To check whether this would work in practice, we organized a test in our stacks with UHF gear together with one of the major vendors. The test looked specifically at speed and reliability of inventory with a hand-held device. Unfortunately, the test resulted in a muddled answer: UHF showed great potential indeed, but needed more finetuning to get consistent results. Meanwhile, other HF vendors were showing that they were still able to tweak their systems further to reach speeds that, although not as high as UHF's, were still closing the gap to the point where reading with a hand-held was becoming notably faster than checking by eye.

Because of this, we decided not to specify HF or UHF in the tender. Instead, we asked for vendors to specify the performance of their system in terms of speed and accuracy for three scenarios. The lower the speed and the higher the accuracy, the more points could be earned, calculated on a logarithmic scale, starting from zero at 98% accuracy and a different number of seconds for each scenario, via hundreds or so for expected HF speeds to thousands for UHF.

To prevent a vendor bluffing, these numbers would need to be proven in a trial setup, failing which would lead to automatic exclusion. You could say that we tested the trust the vendors had in their systems.

Now I obviously can't give out details of the bids, but here's the general outcome. UHF vendors scored well, but at a relatively high price. And some - though not all! - HF vendors wrote in with a performance higher than expected for HF, though still below the UHF figures. The clear winner, Autocheck, was one of these high-performing HF vendors. They scored best on the combination of high HF performance with a very decent pricetag (needless to say, they were able to prove their performance figures).

So, an interesting outcome, not quite what we expected. A side effect is that it changed my opinion on the European tendering process. Yes, it is tedious, bureaucratic and can lead to unexpected results. But by tendering for functional requirements, rather than for a specific technology, we actually ended up with a good deal. That it was not what we expected is all the better. The trick is to properly investigate what you want and specify that, rather than how you want it done.

We have a tender!

Quite a long time ago I started what I hoped would be a series on UHF vs HF RFID. That proved most optimistic, and the real world came in the way.

However, after a *lot* of work the past weeks and months, which I could not write about - oh the horror - I can safely announce that we have sent our Tender Request off to TED (Tenders European Daily). This is the followup to an earlier pre-announcement we made on TED - which is handy, because having pre-announced, we can shave off some time off the procedure that follows. Unfortunately, not much time to write about it now - but if you're interested, keep an eye on TED for the publication.

And what came of the HF vs UHF question? In the end, we decided to specify on functionality rather than choosing ourselves, leaving it to the companies to propose the best system for our wishes. In our quality demands, we do value speed and reliability with a formula which multiplies the squared values for these. This makes for an interesting challenge, we hope - a functioning UHF system that lives up to the expectations could earn a *lot* of points, but it would need to be both fast and reliable for that. And the values need to be proven in a proof of concept.

More later... interesting times!

RFID for libraries: HF or UHF? (1)

Using RFID tags in libraries has become common nowadays, at least for public libraries. The high circulation rates make the math simple: introducing self-service for patrons increases the efficiency significantly enough to pay back.

For research libraries with a much lower circulation rate, this advantage is not that great, and as a result, RFID adoption is trailing. But, as a famous dutch philosopher would say, every disadvantage has its advantage (and vice versa...).

HF: the de facto standard

There are several types of RFID, each operating in a different wave spectrum. The most important ones are HF and UHF, operating respectively the High and the Ultra High Frequency bands. Though the basic technique is the same, the different wavelengths make quite a difference in the details.

The de facto standard for library RFID use is to use HF-based techniques. This can be considered proven tech these days, and there is a healthy marketplace with numerous vendors offering systems. This is historical: when libraries started adopting RFID, HF was the more mature technology, and it was foreseen that its shortcomings for inventory would be solved in the future. This, however, has not happened. HF RFID works well for patron self-service, but is still not reliable enough for inventory.

For research libraries, the advantage of introducing RFID are much less in the area of self-service, and much more in warehousing. Research libraries keep their books for a much longer time, if not indefinitely, and have large closed stack warehouses. This is where it gets interesting.

UHF vs HF

In recent years, UHF technology has also matured, and has become the RFID type of choice for industries where tracking and tracing is the most important goal. All the big name-projects use UHF: Wal-Mart, Metro, Marks & Spencers', as well as numerous other ones. UHF can scan hundreds of objects per second, and more importantly, it can do it reliably. And here we come to the big difference: the way read failures are handled. With HF, failures are caused by tags too close to each other, parallel, to the shelf or a wall. These tags are effectively skipped.

UHF also has its share errors. However, the tags are much less prone to distortion caused by being placed too close together; and also the reading speed makes the scanner effectively retry reading a difficult tags numerous times. The main reading errors of UHF are caused by field distortion. Certain types of materials and shapes can work as a conduit, effectively extending the field in which the reader operates in a seemingly random direction. When that happens, the reader will also pick up tags from a number of meters away, rather than just the ones close by.

This causes its share of problems - but they are of a different category. The importance is that where HF fails with silent reading errors, UHF fails by reading too many. Reading tags that turn out to be several shelves away are a problem when looking for a specific misplaced book. However, silent errors are deadly when taking inventory. When you have too many results, you can try to filter the unwanted ones out; when you have too few, there's nothing you can do.

UHF has the promise to deliver. Yet HF is the proven technology. What to do?

To be continued...