Adaptive Aloha anti-collision algorithms for RFID systems

Abstract

In this paper, we propose two adaptive frame size Aloha algorithms, namely adaptive frame size Aloha 1 (AFSA1) and adaptive frame size Aloha 2 (AFSA2), for solving radio frequency identification (RFID) multiple-tag anti-collision problem. In AFSA1 and AFSA2, the frame size in the next frame is adaptively changed according to the real-time collision rate measured in the current frame. It is shown that AFSA1 and AFSA2 can significantly improve the transmission efficiency of RFID systems compared to the static Aloha, and AFSA2 produces transmission efficiency similar to that of the electronic product code (EPC) Q-selection algorithm (Variant II), while the mean identification delay of AFSA2 is much smaller than that of EPC Q-selection algorithm (Variant II). It is also shown that the transmission efficiency of AFSA2 and EPC Variant II is very close to its upper bound which is obtained by assuming that the reader knows the number of unidentified tags. It is worth noting that when the threshold of the collision rate is chosen to be 0.5 or 0.6, AFSA2 can maintain the transmission efficiency well above 0.65 for the case of a typical EPC code length of 96 bits and for the investigated range of tag population, i.e., from 2 to 1000, while keeping the mean identification delay below ten transmit contentions. Very light computational burden at the reader is needed: the reader needs only to measure the collision rate in the current frame and then to double or halve the frame size accordingly. No additional computational burden is required at the tag side.

Improving Efficiency of Passive RFID Tag Anti-Collision Protocol Using Dynamic Frame Adjustment and Optimal Splitting

“…These protocols treat tags at different slots by separating the access time of tags. In slotted ALOHA, tags respond prior to time slots [ 10 , 12 , 21 ], whereas in frame slotted ALOHA (FSA), time slots are further grouped into frames inside which tags respond [ 29 , 30 ]. In the ALOHA based protocols, identification efficiency is based on the quantity of tags as well as the number of slots, whose performance may be lowered when the quantity of tags is less than the number of slots, resulting in idle slots, or when the quantity of tags is more than number of slots, inducing collision occurrence.…”

Interference Sources in Congested Environments and its Effects in UHF-RFID Systems: A Review

“…Since passive tags cannot detect collisions it is necessary a kind of anticollision protocol that enables the recognition of tags with some collisions, but since frame sizes in the protocol are limited, the framed slotted ALOHA algorithm is limited, and also when the number of tags is large, the number of slots required to read tags increases exponentially as the number of tags does. Some methods are proposed, such as [20], in order to try solving such problem, but always including complexity into the system.…”

A bit arbitration tree anti-collision protocol in radio frequency identification systems

“…The first category is Aloha-based anti-collision protocols. [19][20][21][22][23] Zheng and Kaiser 19 proposed two adaptive frame size Aloha protocols, in which the following frame size was adaptively changed according to the real-time collision rate in the current frame. Su et al 20 investigated how to determine the optimality of the current frame size and proposed a detected sector-based DFSA.…”