RFID readers communicate with tags through an RF channel to obtain identifying information. Depending on the type of tag, this communication may be a simple ping or may be a more complex multi-round protocol. In environments with many tags, a reader may have to perform an anti-collision protocol to ensure that communication conflicts to not occur. Anti-collision protocols permit readers to rapidly communicate with many tags in serial order.
Readers often power what are called passive tags through their RF communication channel.
These types of tags carry no on-board power and rely solely on a reader to operate. Since
these tags are so limited, may subsequently rely on a reader to perform computation as well.
Readers come in many forms, operate on many different frequencies, and may offer a wide
range of functionality. Readers may have their own processing power and internal storage,
and may offer network connectivity. Readers might be a simple conduit to an external
system, or could store all relevant data locally.
Currently, many applications rely on fixed reading devices. Early trials of EPC at a major
supermarket chain integrated fixed readers into docking-bay entrances. These readers scan
tags at the pallet level as shipments of products arrive. In the long term, readers may be
integrated at a shelf level as a “smart shelf ”. Smart shelves would scan for tags at the item
level and monitor when they are added and removed from a shelf.
RFID readers may also be integrated into hand-held mobile devices. These mobile readers
would allow someone to, for example, take inventory of a warehouse by walking through its
aisles. The cellular phone manufacturer Nokia is already offering RFID-reading functionality
in some of their cell phones [16]. If EPC-type tags become highly successful, interesting and
useful consumer applications might arise. If this occurs, RFID reading functionality might
become a common feature on cellular phones, PDAs, or other handheld computing devices.