Figure 1
From: Bit Level Synchronized MAC Protocol for Multireader RFID Networks
Reader-Tag Collision Problem: responses of a tag to a reader when queried are drowned out by the interfering signal from another concurrently operating reader in the vicinity. In this example, Tag 2 is within the read range of Reader 2. Reader 2 is also in the interfering range of Reader 1. After Reader 2 queries Tag 2 for its ID, the response of Tag 2 at Reader 2 is interfered with by the signal from Reader 1 which was querying Tag 1 at the same time. [1].