If there are multiple RFID or NFC readers in an area, how can I know which is active or reading a tag?
There is no global numbering system to ensure that every radio frequency identification reader has a unique identifier for the purposes of identifying which reader is interrogating a tag.
I reached out to Sanjiv Dua, the president of training and systems integration firm RFID4U, for information about how systems identify which reader is doing the interrogating. Sanjiv points out that ultrahigh-frequency (UHF) readers are network devices, so the factory-configured unique Mac ID and host name can identify these readers uniquely. Similarly, for Near Field Communication (NFC) readers in phones, the International Mobile Equipment Identity (IMEI) number can be a unique number. But for all practical purposes, software applications typically identify each reader uniquely.
"Whether you use UHF, HF [high-frequency] or NFC RFID, you typically write a software application to manage the reader functions," Sanjiv explains. "Within the software application, you define the reader ID or name. So whenever the reader captures a tag read, the reader provides its own ID or name along with the values captured from the tag or tags."
In other words, the software tells the reader when to turn on and read, and when not to read. This can also be triggered by an electronic eye or some other input. The software identifies each reader in the system. You can even assign values to each antenna in a multipart antenna, and tell the reader to report which antenna read the tag. This is useful if you use one reader with eight antenna ports to cover two dock doors. If the tag is read by antennas 1, 2, 3 or 4, for instance, then you know the item came through dock door 1.
—Mark Roberti, Founder and Editor, RFID Journal
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