Improved physical layer collision recovery receivers for RFID readers

Abstract

Radio Frequency Identification (RFID) systems usually operate in a multiple RFID tag environment. If multiple tags respond simultaneously, a collision occurs and the information is discarded. In this paper, we propose a novel physical layer collision recovery mechanism. We analyse theoretical limits of the inventory time and show how our new method can approach such theoretical maxima. We propose a method that resolves more colliding tags by making collisions less destructive. In this method a postprocessing of the received signal by beamforming is performed. Furthermore, we investigate the influence of the proposed method on the system performance by means of simulations. We show that our method considerably shortens the time necessary to interrogate tags.

An Efficient Tag Search Protocol in Large-Scale RFID Systems With Noisy Channel

“…A number of recent papers [22]- [27] focus on collision recovery (CR) techniques, which enable the resolution of multiple tag IDs from a collision slot. Benefiting from the CR techniques, the identification throughput can be dramatically improved up to 3.1 tags per slot in [26].…”

“…Therefore, the search process of ITSP-rem contains at least (37) rounds. Also, we can derive (38) With , , , and , , the search time of ITSP-rem can be calculated using (31), (26), and (27).…”

“…We compare our protocol ITSP to CATS [11], the polling protocol (Section III-B), the optimal DFSA, and a tag identification protocol with collision recovery [27], denoted as CR, which identifies 4.8 tags per slot on average, about 13 times the speed of the optimal DFSA. For ITSP and CATS, their Bloom filters (or filtering vectors) constitute most of the overall transmission overhead, while other transmission cost, such as transmission of hash seeds, is comparatively negligible.…”

“…Hence, we do not count the estimation time of in the simulation results because it is relatively small and does not affect fair comparison as both protocols need it. Consequently, the key metric concerning the time efficiency is the total size of Bloom filters or filtering vectors, and then (8) can be used for calculating the search time required by CATS, while (27) for ITSP.…”

“…As a result, the maximal theoretical throughput is 3.1 tags per slot. In the follow-up work [27], the received signal is post-processed by a beamformer to further improve collision recovery. With this strategy, the maximal throughput is increased to 4.8 tags per slot using four receiving antennas.…”