On RFID tag reading by a mobile reader in a warehouse

Protocols are introduced to improve the tag reading efficiency of an RFID system consisting of a mobile reader that is constantly moving at a reasonable speed in a warehouse containing many thousands of items tagged with RFID. The warehouse is divided into storage areas with aisles separating these areas and the mobile reader tries to capture as many tag identifiers (IDs) as possible during this process. We execute ALOHA based protocols as the reader moves along the aisles and our goal is to read all the tags using a minimal number of laps, where a lap is the arrival of mobile reader at a location in the warehouse. To reduce the number of laps, we store the ALOHA protocols´ status information (for example, the number of idle, collided, and successful slots) along with the location of the mobile reader at the mobile reader. During the next visit to the same location, the mobile reader uses the information (instead of executing the ALOHA based protocols from start) to improve the reading ability. We have further enhanced our protocol by segregating tags into zones (which is automatically done by the mobile reader) and allowing only tags within particular zones to participate in the ALOHA based protocols. This segregation results in lesser collisions and hence contributes to minimizing the number of laps required to complete the reading process. We have provided simulation results involving thousands of tags in a warehouse and the results show that our protocol reduces the number of laps by approximately 1/3^rd in comparison with the standard ALOHA based protocols.