QTS ALOHA: A Hybrid Collision Resolution Protocol for Dense RFID Networks

The performances of the frame slotted ALOHA based and tree based protocols are unsatisfactory in resolving the collision occurring in dense RFID networks made up of hundreds or even thousands RFID tags. QTS ALOHA, a hybrid collision resolution protocol which combines both the query tree protocol and the dynamic frame slotted ALOHA protocols, is proposed to achieve the rapid identification of a large amount memory-less RFID tags. For the identification of a group of tags, based on the data already collected, the population of tags in the group is estimated, and according to the identification accuracy required by the application system, the group of tags may be split into multiple subgroups through some binary suffix strings, dynamic slotted ALOHA protocol is performed to identify tags and collect data in the group or subgroups. This collision resolution process is performed repeatedly until the required identification accuracy is achieved. Numeric simulation verifies that this hybrid protocol outperforms othr protocols in frames and slots consumed to identify different number of tags, keeps a high throughput in each identification frame, and is especially suitable for the collision resolution in dense memory-less passive RFID networks.