Well Designed RFID System- Converting Weakness into Strength
Posted by P. Krishna on Thu, Apr 07, 2011
Mike Tyson once said “My biggest weakness is my sensitivity. I am too sensitive a person.” RFID should not have that problem – a well designed RFID system should convert the dramatically improved tag sensitivities into its strength. But better chips on the tags doesn't always mean better system performance when people deploy RFID without understanding the physics.
A passive RFID system is forward link (link for the reader to the tag) limited, which basically means that the read range is limited by the receive sensitivity of the tag. Higher the sensitivity (negative number !), longer the read range. Over the past five years, considerable innovation has occurred in the RFID tag and RFID reader space. As you can see in the graph, RFID read range has increased 3x during that period. My kudos to the RFID tag manufacturers for continuously pushing the envelope.
RFID tag range is a proxy for reliability of RFID tag reads under stressful environmental conditions. Given a choice, customers should always pick the tag with the best sensitivity. RFID tag to RFID reader link is the foundation of any RFID system - and the RFID tag sensitivity is one of the key determinants of the robustness of that foundation.
At the tag-reader level, RFID is fundamentally a probabilistic acquisition system, where the read range of the RFID tag is the random variable. Under favorable conditions, the read range could be higher than the free-space loss based limit, and under unfavorable conditions, the read range could be zero.
This randomness leads to two fundamental events that a RFID system has to deal with:
- False-positive: When a tag is read by an unintended antenna
- False-negative: When a tag is not read by an intended antenna
False-negatives lead to missed RFID reads, and false-positives lead to locationing errors. Both are bad for business applications. Thankfully, increased sensitivity will reduce the false-negatives – i.e., going forward we should see lower rates of missed reads – which is fantastic for the overall industry. RFID software that sits on the RFID reader processing at the edge can also make a big differnece.
However, with the proliferation of higher-sensitivity RFID tags in the environment, there will be a much higher rate of false-positives – i.e., leading to increased rate of locationing errors. This thankfully can be corrected using intelligent algorithms that take a systemic view to the problem by analyzing in real time the tag’s observations from all relevant readers to determine the accurate location of the tag. This is exactly what the algorithms in the EasyTAP do. We worked for six years and have ten patents granted for this sophisitcated and stable software platform.
Buyers beware: A sub-optimal RFID system can be severely hampered by this jump in RFID tag performance and would resort to poor implementation choices such as reducing transmit power, receive quelching at the RFID reader etc. They basically are reducing the performance of the RFID tag-reader link to match the capabilities of their sub-optimal system. It is like letting an amateur drive a Formula 1 car … or a quad core intel i7 base gaming PC with just 500MB RAM … or …. You get my point! Think of old generation RFID Middleware as that lame RAM in the gaming PC. It's not pretty.
A well-designed RFID system, on the other hand, effectively leverages the improvements in RFID tag sensitivity to dramatically improve the system performance, resulting in a high-performing, accurate RFID system for business applications.