UHF Passive RFID System Research Articles

RFID Tags Estimation through the Statistics Method for ALOHA

One of the key problems that affect the data integrity of passive RFID systems is the collision among the tags. A popular anti-collision algorithm which dominates the standards in HF and UHF passive RFID systems is framed slotted Aloha (FSA) and some variations of FSA. Throughput of the RFID system which determines the performance/efficiency of the system is reduced rapidly when the number of tags inside the interrogation zone is increased. Using larger frame sizes is not always the solution. The best performance can be achieved when the slot number is equal to the tag number for FSA algorithm. In order to estimate the number of tags, a lot of work has been done. The existing algorithm about the tags estimation has been discussed in this paper. And an idle slot number based estimation algorithm is proposed. The idle slot number based estimation algorithm uses the idle slots in a frame. For performance analysis, the idle slot number based estimation algorithm was evaluated with the parameters of 128 slots to estimate the number of tags. The proposed method considers two situation, one is applied only 128 slots in a frame and all of them are used to estimate the number of tags; the other is applied the first 128 slots in a frame with 1024 slots frame. The results showed that the proposed algorithm can improve the efficiency of the number of RFID tag estimation and provide a reliable solution for cases with a high density of tags in the area.

Power Transmission of UHF Passive Embedded RFID in Tires

UHF passive RFID tags embedded in tires have a deep impact on tire life cycle management and tire monitoring. In this work, we present the power transmission of UHF passive embedded RFID in tires. In UHF passive embedded RFID systems in tires, the bidirectional radio link between reader and tags goes through air and tires. The total path loss contains reflection loss at tire-air boundaries and attenuation loss in the tires. The power transmission is based on the permittivity of tires and tire-air boundary conditions. We give an OCP method for measuring the permittivity of tires. By analyzing the radio link for UHF passive RFID, we establish a model of wave propagation of UHF embedded RFID in tires and make numerical analyses. Numerical analyses show that the error of the OCP methods for measuring the permittivity of tires is small, the parallel polarization and normal incidence of wave are chosen for improving the performance of the UHF embedded RFID in tires, and distance is chosen to keep power transmission function from locating valley.

Anti-collision Algorithm for RFID Based on Continuous Collision Detection

Tag estimation can improve the throughput of the UHF passive RFID systems. It plays an important role in anti-collision algorithm. In order to reduce the complexity of the estimation algorithm and the hardware support, a new algorithm based on the continuous detection mechanism has been proposed. According to the different probability of the collision and idle, the number of the continuous detected slots must be set independently. This scheme can simplify the system and reduce the extra consumption by less detecting timeslot. Simulation results indicate the proposed scheme can improve the efficiency without complicate system. DOI: http://dx.doi.org/10.11591/telkomnika.v11i12.3661 Full Text: PDF

Multiple RFID Tags Access Algorithm

One of the main problems that affect the data integrity of passive RFID systems is the collision between the tags. A popular anticollision algorithm which dominates the standards in HF and UHF passive RFID systems is framed slotted Aloha (FSA) and some variations of FSA. Throughput and average time delay of the RFID system which determines the performance/efficiency of the system are reduced rapidly when the number of tags inside the interrogation zone is increased. Using larger frame sizes is not always the solution. This paper discusses and compares the existing protocols, and proposes a variation of FSA, called progressing scanning (PS) algorithm. The PS algorithm divides the tags in the interrogation zone into smaller groups and gives the reader the ability to communicate with each of them. For performance analysis, the PS algorithm was evaluated with the parameters of a typical passive RFID system at 2.5 GHz. The results showed that the PS algorithm can improve the efficiency of the RFID system and provide a reliable solution for cases with a high density of tags in the area (over 800 tags).

Application of Quasi Log-Periodic Antenna for UHF Passive RFID Tag Design Featuring Constant Power Transmission Coefficient Over Broadband Operation

Quasi log-periodic antenna configuration was adopted to design passive UHF RFID tag for the first time. With proper adjustment of the physical parameters which in turn adjusted the induced coupling levels to the dipole-based radiator, the designed antenna was capable of providing constant reactance from 860 MHz to 960 MHz covering the whole spectrum of UHF passive RFID system. In addition to the omni-directional radiation pattern and good overall radiation efficiency provided by the antenna, the proposed design features constant power transmission coefficient over 860 MHz to 960 MHz which is essential to guarantee consistent read range in passive RFID systems.

A Frequency Diverse Gen2 RFID System with Isolated Continuous Wave Emitters

The “Gen2” specification for UHF passive RFID systems released by EPCglobal has become an intense research interest. A Gen2 tag derives its power from the RF wave emitted by a Gen2 RFID reader and responds its modulated backscatter signals to the reader. Due to the large propagation loss, the accessible range of a Gen2 tag is hence limited. Moreover, the readability of a Gen2 tag is often influenced by the multipath fading problem. In order to mitigate the problems, a multi-carrier UHF passive RFID system utilizing the frequency diverse backscatter ability of a Gen2 tag is proposed in a prior work. In this work, a thorough analysis of the system is given. Especially, the appropriate powers of the transceiver and CWEs are derived to make the system more feasible in practical applications.