EPC Gen2 Session
The EPC Gen2 standard defines four sessions (0-3) for inventorying tags. Each session serves two purposes:
- Determines when a tag will respond to a query from the reader: This ensures that tags do not respond simultaneously, reducing collisions and improving inventory efficiency.
- Allows tags to maintain independent states when communicating with multiple readers at the same time: This enables tags to keep track of their state (e.g., whether they have been inventoried or not) even when communicating with multiple readers.
Session Persistence
Session persistence refers to the time a tag remains in a specific state (e.g., “B” state) after being inventoried before reverting back to the initial state (e.g., “A” state). Persistence time is affected by both the search mode and session used.
Session Modes
Understanding EPC Gen2 Search Modes and Sessions highlights the differences between each session and search mode. For example:
- Session 0 is the default session, and inventorying occurs in a single pass.
- Session 1 and Session 2 have extended persistence, allowing tags to remain energized and ready for inventory even after the reader frequency-hops.
- Session 3 has the longest persistence, ensuring that tags remain energized and ready for inventory even after multiple frequency-hops.
Reader Commands and Sessions
EPC Gen2 reader commands, such as Select and Inventory, operate within a single session at a time. These commands allow readers to control which tags are read, filter tags, and send commands back to tags (e.g., writing to user memory).