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The Longer the UII, the Slower the Read Rate

A new study examines the consequences of adopting a unique ID number or EPC larger than 96 bits for ISO-18000-6c/EPC Gen 2 tags.
By Patrick King
The tool is currently in global use, and has also already provided major inputs to standardization at ISO/IEC, EPCglobal and ETSI. As the simulation tool has been aligned with real-world RFID readers and tags, it could utilize the major advantage of performing hundreds of application operation simulations with a high number of tags for various data rates, as required for the different global RF regulations, with very little man-power, but only with computing time. This results in a very cost-optimized evaluation, compared to real setups.

One of the study's major findings is that throughput, in terms of anticollision rate (that is, the number of tags that can be singulated within a particular span of time—e.g., one second), degrades by approximately 30 percent if the UII length is increased from 96 bits to 240 bits. This also has a severe impact on mixed population environments of tags with 96-bit or 240-bit unique IDs, compared with an environment of 96-bit tags only, since the reader reliability for the 240-bit tags is lower than for the 96-bit tags, thereby resulting in missed reads requiring multiple attempts.

Therefore, in order to have a fast anticollision rate, end users should keep the UII as short as possible. This would also improve the performance for a mixed population of tags, as well as for those tags for which the reading of user memory can be skipped.

Furthermore, the study noted that an interrogator is able to read user memory only during tag singulation (anticollision), which means that user memory handling always results in a significant decrease in application performance, versus an application requiring no user memory. What's more, for applications in which a tag's user memory needs to be read, there is no difference between having information stored in the UII (MB01) or user memory (MB11).

The summary recommendation is that any industry considering creating UII serial numbers larger than 96 bits needs to read this report and be forewarned. There should be serious consideration of using the UII as an anticollision feature, and actually assigning all relevant data to MB11. For tires, the request would be for Michelin (and others) to provide their own UII in MB01, with MB11 available for any and all additional serial identifications required for the same tire.

A complete copy of the report can downloaded by clicking here, or by e-mailing a request to CISC at j.preishuber-pfluegl@cisc.at. For a discussion of other issues involving ISO-18000-6c/EPC Gen 2 RFID tags, see Hex Is Not the Standard and Identifying RFID's Biggest Threats.

Patrick King is the current leader for global electronics strategies at Michelin, and the tire maker's representative to EPCglobal. Dedicated to sustainable mobility, Michelin designs, manufactures and sells tires for every type of vehicle, including airplanes, automobiles, bicycles, earthmovers, farm equipment, heavy-duty trucks, motorcycles and the space shuttle.


Patrick Taylor 2010-02-04 02:47:42 AM
Unintended Consequences Hopefully this work will prevent the fracturing of the standard so recently agreed. It does beg the question of whether this "mission creep" could have been foreseen and dealt with.

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