Novel tag estimation method by use of Manchester coding in RFID systems

Abstract

Radio frequency identification suffers from tag collision issue. ALOHA-based algorithms are useful and practical groups of tag anti-collision algorithm among others. Some standards such as EPCglobal Class-1 Generation-2 use some kind of dynamic framed slotted ALOHA (DFSA) to cope with tag collision. DFSA efficiency depends on estimating the number of unidentified tags in each identification cycle accurately. So tag estimation is one of the challenging issues in DFSA. In this paper, we use Manchester coding to compute the lower bound of collided tags in a frame and then add α as an additional value to computed value according to the difference between optimal number of collision slots and calculated number of collision slots. Then, we evaluate and compare our method with other proposed methods. KEYWORDS DFSA, RFID, tag anti-collision, tag estimation | INTRODUCTIONThe automatic identification and data capture (AIDC) technology was introduced to simplify the way of identification. Among other members of this technology including optical character recognition (OCR), barcode and infrared identification technologies, and the radio frequency identification (RFID) could be called the rising star in this family because of its characteristics: nonline-of-sight and contactless reading data. 1 RFID comprises three elements: tags that store data, reader that reads/writes data from/to tags within its interrogation zone, and a server to analyze received data from reader. The basic of identification process in RFID is easy to understand; first, reader transmits adequate energy to power up the tags, then communicate with tags to demand, and receive their identifiers (ID). One of the benefits of RFID rather than some other auto ID technologies like barcode is reading more than one tag simultaneously via a reader. But this benefit causes side effects like collision. It is reported that in typical RFID deployments, the tag read rate is usually about 60% to 70%. 2 There are two main types of collision: tag collision and reader collision. Tag collision happens when more than one tag within interrogation zone of a reader transmit their data to that reader simultaneously. Result of this transmission is receiving of corruption signals by reader. Reader collision happens when one tag is within interrogation zone of two or more readers and they want to read that tag simultaneously. Both reader and tag collision are depicted in Figure 1. To address this issue tag and reader anti-collision is proposed, but our focus in this paper is on tag anti-collision algorithms. There are four types of tag anti-collision algorithms: ALOHA-based, tree-based, counter-based, and some algorithms that are made by combination of the first three types, called hybrid algorithms. 3 ALOHA-based algorithms like framed slotted ALOHA (FSA) use frame that comprises some slots, and then, each tag can transmit its data in a slot. These algorithms are probabilistic. 4-7 Tree-based algorithms like query tree divide all collided tags to two groups according to bits of thei...

LC-DFSA: Low Complexity Dynamic Frame Slotted Aloha Anti-Collision Algorithm for RFID System

“…Wang [14] Normal Normal Good Chen [15] Low Low Normal HajMirzaei [16] High Low Good Chen [17] Normal High Good LC-DFSA Low Low Good…”

“…Thus, it lowers the complexity of the passive RFID system. The results of the analyses and simulations show that the complexity of LC-DFSA is lower than that of Chen [15] and HajMirzaei [16], and the access efficiency of the proposed LC-DFSA achieves 0.345 for the massive tags scenario, which outperforms Chen [15] and HajMirzaei [16].…”

“…Chen [15] performed once early judgment to adjust frame sizes. HajMirzaei [16] proposed a TEM based on Manchester encoding, and Chen [17] Sensors 2020, 20, 228 2 of 13 used the Maximum a Posteriori (MAP) to estimate the tag number. They are either with low efficiency or with high complexity considering the limited power in passive RFID systems.…”

Suffix-based double reader tag movement RFID anti-collision method

“…Wong [20] proposed a bit slot ALOHA algorithm based on bit sequences. In DSFA algorithms, Chen [21] proposed a method by the Maximum a Posteriori (MAP) to estimate the tag number, HajMirzaei [22] proposed an efficient method to estimate the lower bound of collided tags by Manchester coding, Wang [23] proposed the secant-iteration-based adaptive and dynamic frame slotted Aloha method (SIADA), Yang [24] proposed a low complexity dynamic frame slotted Aloha (LC-DFSA) anti-collision algorithm. The algorithm proposed in this paper will be compared with the algorithms proposed in recent years, reflecting the good performance of the algorithm in TMRS.…”