EPC Gen 2 Architecture

The architecture of an EPC Gen 2 RFID network is shown in figure. It has two key components: tags and readers. RFID tags are small, inexpensive devices that have a unique 96-bit EPC identifier and a small amount of memory that can be read and written by the RFID reader. The memory might be used to record the location history of an item, for example, as it moves through the supply chain.

Often, the tags look like stickers that can be placed on, for example, pairs of jeans on the shelves in a store. Most of the sticker is taken up by an antenna that is printed onto it. A tiny dot in the middle is the RFID integrated circuit. Alternatively, the RFID tags can be integrated into an object, such as a driver’s license. In both cases, the tags have no battery and they must gather power from the radio transmissions of a nearby RFID reader to run. This kind of tag is called a ‘‘Class 1’’ tag to distinguish it from more capable tags that have batteries.

RFID architecture

The readers are the intelligence in the system, analogous to base stations and access points in cellular and WiFi networks. Readers are much more powerful than tags. They have their own power sources, often have multiple antennas, and are in charge of when tags send and receive messages. As there will commonly be multiple tags within the reading range, the readers must solve the multiple access problem. There may be multiple readers that can contend with each other in the same area, too.

The main job of the reader is to inventory the tags in the neighborhood, that is, to discover the identifiers of the nearby tags. The inventory is accomplished with the physical layer protocol and the tag-identification protocol that are outlined in the following sections.