During the past 18 months, our team has helped a number of companies with people tracking, personnel tracking, and employee tracking, including a North American retail store tracking 40,000+ employees in 3,000+ locations. We have tested over a dozen RFID badge tags, six different stationary RFID readers, and four different RFID handheld readers. What we found is that traditional passive RFID badge tags can read up to about 15 feet away, but when you put them close to your body, the read range is not only reduced, but in some situations the tag can't be read at all.
CSL claims that their new Class 1 Generation 2 battery assisted passive (BAP) RFID badge tag can be read up to 16 feet away in your pocket. In this edition of the RFID Network, our team puts the CSL BAP RFID badge tags to the test.
These badge tags are specifically designed for personnel identification and tracking. Because they contain a battery, they read more reliability than traditional passive tags when working with RF challenging conditions, such as when the badge is placed next to a person’s body: either clipped on, using a lanyard, or when placed in a shirt pocket. These badge tags are the same size as a credit card and although they contain a battery, they are still extremely thin. It’s important to point out that these tags are not a proprietary technology, but fully compliant with the ISO 18000-6C and EPCglobal Class 1 Generation 2 standards.
Traditional passive RFID tags rely on gathering energy from the RFID reader’s signal to wake up the chip and provide the backscatter required for identification. BAP RFID tags contain their own integrated power source. BAP RFID tags can backscatter about 90% of the energy that they receive. Traditional passive tags typically backscatter 10-15% of the signal that reaches them. In real world terms, that means BAP RFID tags can be read from further away and more importantly, they provide increased reliability and read rates even in the most challenging environments, such as those containing liquids and metals.
It’s important not to confuse BAP RFID tags with active RFID tags. Active RFID tags transmit a beacon at a defined interval. BAP RFID tags do not transmit. They use the battery to improve the signal strength when they respond to a reader.
Our team did performance testing of the CSL BAP RFID Badge tag using two different stationary RFID readers as well as two different handheld RFID readers. In free space, the BAP RFID tag read an average of 80 feet away using the stationary RFID readers and 30 feet away with the handheld RFID readers. In a shirt pocket, the BAP RFID tag read an average of 29 feet away using the stationary RFID readers and 18 feet away with the handheld RFID readers. Given this kind of performance, our team highly recommends the CSL BAP RFID tag for personnel tracking. Our only caution goes to those that have RFID readers with poor sensitivity, which we will explain more about below.
Editor's Note: After publishing this article, we had a number of companies contact us for details regarding the handheld and stationary RFID readers performance. Overall, our team found the Impinj Speedway Revolution provided the longest read distances with these BAP RFID tags. We also found that the CSL CS101 achieved 2 to 3 times the read range of the Motorola 9090-Z handheld RFID reader. Given the CS101 is less than half the price Motorola handheld, we prefer the CS101 for Gen2 BAP RFID.
Plus, the RFID Network is not alone in our findings. Since publishing this article, we have received feedback from other industry experts that have achieved similar results...
The Expert Perspective
"This is the first RFID tag in any format that can be placed in your wallet, sandwiched between two short-range PROX door-badge type cards, and still read perfectly when passing through a doorway from about 10'. We had pretty much given up on tracking using an RFID badge. This makes tracking not just possible -- but, reliable."
Carl Brown, President SimplyRFID.com
Over the years, The RFID Network team has done performance testing with numerous BAP RFID tags and RFID readers. The most important point to understand about BAP tags is: the RFID reader you’re using must have good sensitivity. Preferably -90db or better.
We have worked with many clients that have tried BAP tags using RFID readers with poor sensitivity, only to find that the BAP tags don’t read any further than traditional passive tags. Unfortunately, these companies had to replace entire infrastructures of RFID readers to achieve the performance they need. This is one of the reasons it is vital for companies to carefully consider RFID equipment before making a purchase.
While doing performance testing of the CSL BAP RFID badge tag, we were working in a very tag dense environment, surrounded by hundreds of RFID tags - all of the pallets are tagged as well as the items on the pallets. This makes it more difficult for the RFID reader to hear the faint signals aong the strong signals. This kind of test is what you would find in the real world when employees are surrounded by RFID tagged products. Be aware that many RFID tag manufacturers publish read distances from testing a single tag in an anechoic chamber. These results are typically not even close to real world environments. Our series of tests used both handheld and stationary readers with the tag in free space and in a shirt pocket.
Obviously, some RFID readers perform better than others, but this is especially true when working with BAP tags. Because of the high sensitivity of the BAP tag, the RFID reader's receiver sensitivity also should be high to be able to receive this signal. Keep in mind that high sensitivity does not help the performance of standard passive labels because performance in this case is limited by the reader-to-tag link. This is why our team is using the Impinj Speedway Revolution RFID reader. Other, lower sensitivity readers will still work, but they will provide lower performance.
BAP tags will also achieve better performance when using RFID readers that support bi-static modes of operation. That’s where one antenna is always transmitting and another is always receiving.
When The RFID Network published our first article about BAP RFID in 2009, our engineers recommended Battery Assisted Passive (BAP) RFID tags kits without a specific RFID reader. This has resulted in dozens of support calls to our engineers because the sensitivity of most ISO/IEC 18000-6 UHF RFID readers is not high enough to take advantage BAP tags and resulted in performance less than what we have published here. As a result, our engineers only recommend RFID readers with high sensitivity when working with BAP RFID tags.
With handhelds RFID readers, BAP tags will still outperform most passive tags but the difference in read range will be less significant. The reason for degradation is that the small size of the handheld limits the size of the antenna which in turn limits the gain and beam width of the antenna. Additionally, many handheld readers limit the output power of the reader in order to conserve battery life. That’s why our team recommends the CSL CS101: it not only has a larger antenna, but allows full control over the transmit power.
If you would like to try BAP tags in your environment, CSL offers a kit with 10 Battery Assisted passive RFID tags. CSL can also print up to 4 color graphics on the tags, pre-program them, and offers pricing discounts for quantity purchases. Please contact CSL for more information.