Radio Frequency IDentification (RFID) systems are becoming more and more popular in the field of ubiquitous computing, in particular for objects identification. An RFID system is composed by one or more readers and a number of tags. One of the main issues in an RFID network is the fast and reliable identification of all tags in the reader range. The reader issues some queries, and tags properly answer. Then, the reader must identify the tags from such answers. This is crucial for most applications. Since the transmission medium is shared, the typical problem to be faced is a MAC-like one, i.e. to avoid or limit the number of tags transmission collisions. We propose a protocol which, under some assumptions about transmission techniques, always achieves a 100 perfomance. It is based on a proper recursive splitting of the concurrent tags sets, until all tags have been identified. The other approaches present in literature have performances of about 42 in the average at most. The counterpart is a more sophisticated hardware to be deployed in the manufacture of low cost tags.
In @cite_2 , the bi-slotted query tree algorithm, and bi-slotted collision tracking tree algorithm are proposed. They reduce the prefix overhead for fast tag identification.
@cite_2
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This paper is intended to present bi-slotted tree based RFID tag anti-collision protocols, bi-slotted query tree algorithm (BSQTA) and bi-slotted collision tracking tree algorithm (BSCTTA). Diminishing prefix overhead and iteration overhead is a significant issue to minimize the anti-collision cost. For fast tag identification, BSQTA and BSCTTA use time divided responses depending on whether the collided bit is 0' or 1' at each tag ID. According to the simulation results, BSQTA and BSCTTA require less time consumption for tag identification than the other tree based RFID tag anti-collision protocols In this paper, we propose a hybrid query tree protocol that combines a tree based query protocol with a slotted backoff mechanism. The proposed protocol decreases the average identification delay by reducing collisions and idle time. To reduce collisions, we use a 4-ary query tree instead of a binary query tree. To reduce idle time, we introduce a slotted backoff mechanism to reduce the number of unnecessary query commands. For static scenarios of tags, we extended the proposed protocol by adopting two phases. First, in leaf query phase for existing tags, the interrogator queries leaf-nodes directly to reuse query strings in the previous session. Second, in root query phase for new arriving tags, the interrogator starts the query process from the roof-node. Simulation reveals that the proposed protocol achieves lower identification delay than existing tag collision arbitration protocols regardless of whether tags are mobile or not. In this paper we present a new tree search-based protocol for the anti-collision problem of RFID systems. This protocol builds a binary search tree according to the prefixes chosen randomly by tags rather than using their ID-based prefixes. Therefore, the tag identification time of the proposed protocol is no longer limited by the tag ID distribution and ID length as the conventional tree search protocol. The time complexity of the protocol is derived and shown that it can identify tags faster than the Query-Tree protocol. In this paper, we approach the problem of identifying a set of objects in an RFID network. We propose a modified version of slotted aloha protocol to reduce the number of transmission collisions. All tags select a slot to transmit their ID by generating a random number. If there is a collision in a slot, the reader broadcasts the next identification request only to tags which collided in that slot. Simulation results show that our approach performs better than framed slotted aloha and query tree based protocols, in terms of number of slots needed to identify all tags, which is a commonly used metric, strictly related to delay.