Passive RFID tags, which have no self-battery and just backscatter the energy from a reader, share a common channel. It causes a tag-to-tag collision problem when at least two or more tags communicate to the reader simultaneously. The dynamic frame slotted Aloha (DFS-Aloha) protocol is one of the well-known anti-collision algorithms to solve this problem.
To maximize the system performance and enhance the reading speed of Aloha protocols, we propose a frame grouping algorithm, called grouped frame Aloha (GF-Aloha), which splits a large-frame of Aloha into several groups. The tags are allocated to each group according to their collision information at the previous frame. To implement the idea, tag structure and GF-Aloha protocol are designed based on the EPC Class 1 Generation 2. In addition, we also suggest a frame size estimator that enhances the Q-Algorithm and find the best parameters of the proposed estimation algorithm. Finally, combining the GF-Aloha and the proposed estimation algorithm, we suggest high speed anti-collision protocol for low-cost RFID tags.
Simulation results show that the GF-Aloha algorithm outperforms the conventional non-grouped Aloha protocol and the proposed estimation algorithm also enhances the system performance. Moreover, the combination of GF-Aloha and the proposed estimation algorithm takes less identification time than DFS-Aloha with Q-Algorithm based on EPC Class 1 Generation 2 protocol.
In conclusion, the proposed schemes enhances the identification time of DFS-Aloha for low-cost RFID systems. Moreover, the proposed anti-collision protocol can be adopted to not only supply chain management using low-cost RFID but also Aloha-based sensor network as an fast multiple access protocol.