ETSI Tests Show EPC Scaleable in Europe

The alternate scheme uses five channels: Interrogators would transmit their signals over channels 4, 6, 8, 10 and 12, while the tags could send responses over a single channel, either 5, 7, 9, 11 or 13—again, as instructed by the reader's signal. A mixture of these two schemes could not work, since they use conflicting channels. Thus, TG34 needed to settle on one.

The four-channel approach is optimized for high-tag performance, says Husak, since the tags would have two responding channels between each interrogator channel, whereas the five-channel approach gives more bandwidth to the readers, but less for the tags. Falck says the group debated the merits of each before settling on a four-channel approach, which is the one being written into the technical specification. Current users of RFID, however, will be grandfathered in rather than be subject to using a synchronized approach. They will and may continue to use all 10 channels within the UHF band for either interrogator or tag transmissions.

The second phase of testing was meant to determine if the hard-wired and wireless synchronization approaches worked, both on their own and in mixed environment, where readers would use a combination of hard-wired and wireless approaches to synchronization. The results indicate that both approaches did, say Falck and Husak. "For example," says Falck, "a central controller can initiate a pre-pulse at the same time that it instructs the hard-wired readers to transmit. This gives the system a capability to work with portable devices such as forklift trucks,"

Lastly, each hardware provider involved in the tests—Feig, Impinj, Intermec, Reva, Sirit and Symbol—was given an opportunity to test its products, using any of the approved synchronization schemes and employing software they each had newly developed to enable those synchronization schemes, in a large-scale deployment dock-door test. This meant establishing portal interrogation zones at 20 separate dock doors in the Metro DC, then having 20 forklift drivers each move a single pallet carrying 62 tagged cases through each dock door simultaneously. The results were "nothing short of miraculous," says Falck. "Typically, they got better than 1.5 percent missed tags, and in some instances, less than 1 percent missed." And the results might have been even better if the reader makers had more time to optimize the synchronization algorithms they used, he adds.

"On a whole, the reading performance [using the synchronized approach] is meeting the requirements of the end user, and it can probably only get better, because the reader makers say they did not have time to debug the new software," says Falck. "The manufacturers were under enormous pressure to get equipment ready for the test."

Falck presented the results of the tests at a policy meeting in Montegrotto Terme, Italy, late last month. The ERM TG34 will now write a technical specification to be added to ETSI TR 102 436. This document provides recommendations to system integrators and installers regarding the installation and commissioning of RFID systems operating at UHF and under the ETSI standard EN 302 208 for spectrum usage. The latter will describe the synchronization approaches and how they can be implemented. Falck hopes the specification will be approved by March of next year.