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.
The frame size affects the performance of Aloha based algorithms. A small frame size results in many collisions, and so increases the required total number of slots when the number of tags is high. In contrast, a large frame size may result in more idle time slots, when the number of tags is small. Different methods estimating the number of unread tags, permit to the reader of choosing an optimal frame size for the next read cycle, are presented in @cite_11 @cite_3 @cite_24 .
@cite_24 @cite_3 @cite_11
2133365802 2107154877 2108365714 2114005194
In RFID system, one of the problems that we must solve is the collision between tags which lowers the efficiency of the RFID system. One of the popular anti-collision algorithms is ALOHA-type algorithms, which are simple and shows good performance when the number of tags to read is small. However, they generally require exponentially increasing number of slots to identify the tags as the number of tag increases. In the paper, we propose a new anti-collision algorithm called enhanced dynamic framed slotted ALOHA (EDFSA) which estimates the number of unread tags first and adjusts the number of responding tags or the frame size to give the optimal system efficiency. As a result, in the proposed method, the number of slots to read the tags increases linearly as the the number of tags does. Simulation results show that the proposed algorithm improves the slot efficiency by 85 spl sim 100 compared to the conventional algorithms when the number of tags is 1000. We propose two ALOHA-based Dynamic Framed Slotted ALOHA algorithms (DFSA) using tag estimation method (TEM), which estimates the number of tags around the reader, and dynamic slot allocation (DSA), which dynamically allocates the frame size for the number of tags. We compare the performance of the proposed DFSA with the conventional Framed Slotted ALOHA algorithm (FSA) using simulation. According to the analysis, two proposed DFSA algorithms show better performance than FSA algorithm regardless of the number of tags We propose the ALOHA-based Dynamic Framed Slotted ALOHA algorithm (DFSA) using proposed Tag Estimation Method (TEM) which estimates the number of tags around the reader. We describe the conventional Tag Estimation Method and Dynamic Slot Allocation (DSA), which is the method to dynamically allocate the frame size according to the number of tags. We compare the performance of the proposed DFSA algorithm with the conventional algorithms using simulation. According to the analysis, the proposed DFSA algorithm shows better performance than other conventional algorithms regardless of the number of tags because the proposed algorithm has lower complexity and better delay performance. This paper analyses the practical faults existing in enhanced dynamic frame slotted ALOHA (EDFSA) algorithms, and discusses the strategy to improve the efficiency of anti-collision algorithm in RFID system. EDFSA algorithm divides the tags into a number of groups and allows only one group of tags to respond when the number of tags is much larger than optimal efficiency tags. However the efficiency of the system can still be improved. We propose a new anti-collision algorithm called by the name of variant enhanced dynamic frame slotted ALOHA algorithm (VEDFSA) to improve the efficiency of the system that can solve the problem above by dynamic divide tags into groups during the anti-collision solving procedure.