Communication Breakdown

By Ari Juels

Not all EPC Gen 1 readers can be upgraded to handle EPC Gen 2's dense reader mode. Here's what you need to know.

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Right now, you might be able to count on one hand how many readers you’ve installed in your facilities. But down the road, you will require many more readers in warehouses, distribution centers or manufacturing facilities. To help make sure they’ll operate without interfering with one another, you’ll want to buy Gen 2 readers that can operate in dense-reader mode—and you’ll probably want to ensure your current readers can be upgraded to support dense-reader mode.

Not all of the first Gen 2 readers to hit the market will be able to operate in dense-reader mode. Under the Gen 2 standard, readers can operate under three different settings that define how the reader transmits RF signals: single-reader mode, multi-reader mode and dense-reader mode. In the dense-reader mode, readers communicate through specific communication channels in order to avoid interfering with other readers in the vicinity. EPCglobal developed its dense-reader mode based on the European Telecommunications Standards Institute’s and the U.S. Federal Communications Commission’s RF transmission regulatory requirements, which are designed to keep channels on the radio spectrum free from congestion.

The Gen 2 standard says readers must operate in the dense-reader mode whenever there are 50 or more of them operating within 1 square kilometer, or 0.39 square mile. But even if your RFID plans call for fewer than 50 readers, it’s a good idea to use readers that operate in dense-reader mode wherever you have many tags and readers in close proximity. That way, you’ll generate less noise and therefore achieve faster and more accurate reads.

Some readers that are already on the market will be able to operate in dense-reader mode through a firmware upgrade to Gen 2. But others will operate only in single-reader mode or, after a firmware upgrade, only in single- and multi-reader modes. For those readers to operate in dense-reader mode, they’ll require a hardware change, and that could be costly, depending on how many readers need to be upgraded.

“We tried to design [the Gen 2 standard] so that hardware can be firmware upgraded, but some of the more basic readers will require a hardware upgrade to reach all the functionality described in Gen 2,” says Sue Hutchinson, director of product development for EPCglobal US, in Lawrenceville, N.J. “So a key question for an end user with many readers to ask a vendor is whether the readers they already have are dense-reader upgradable and, if not, can they be through a firmware or hardware upgrade?”