A fair reader collision avoidance protocol for RFID dense reader environments

TDMA‐SDMA‐based RFID algorithm for fast detection and efficient collision avoidance

“…After completing this step, the identification of group #2 of tags will start, and so on, until the full coverage of the reader zone. Notice that the IDs of all already identified tags are sent in a beacon message to other neighboring beams for reader collision avoidance …”

“…According to the reader collision can be divided into three types: Interference of frequency or reader‐to‐reader interference (RRI) when the readers are close to each other or operating at the same frequency. If just few readers are involved, the problem can easily be solved, but in dense RFID environments, eg, wireless sensor networks, reader collision can dramatically affect the RFID system performance. To better address this issue, it is crucial to distinguish between transmission range, which represents the reading area of a given reader, and the interference range in which the reader produces interference.…”

“…Collision occurrence is a multi‐access drawback in communication channel . To efficiently address this issue, various anti‐collision algorithms have been suggested through the last few years . They mainly involve multiple‐access techniques based on time (TDMA), frequency (FDMA), coding (CDMA), or space (SDMA) division .…”

“…This classification is usually based on the way they access the channel. However, one can select another criterion and distinguish the techniques based on tag collision from those that deal with reader collision . Most of time‐based algorithms involve tag‐to‐tag collision (also known as tag interference or tag collision) knowing that reader collision algorithms (ie, reader‐to‐tag or reader‐to‐reader collision) imply different parameters to mitigate the collision issues, such as the required power to activate tags according to the capture effect, and the distance between tags and readers or between readers .…”

“…However, one can select another criterion and distinguish the techniques based on tag collision from those that deal with reader collision . Most of time‐based algorithms involve tag‐to‐tag collision (also known as tag interference or tag collision) knowing that reader collision algorithms (ie, reader‐to‐tag or reader‐to‐reader collision) imply different parameters to mitigate the collision issues, such as the required power to activate tags according to the capture effect, and the distance between tags and readers or between readers . In the case of tag collision, Aloha‐based algorithms suffer from relatively low performance when large number of tags are involved, while deterministic algorithms can exhibit better performance by progressively decreasing the bits of collision in a given tag ID using a suitable coding scheme such as Manchester coding; yet their efficiency is still limited because of their relatively slow detection time .…”