一种基于不等长时隙的射频识别防碰撞算法

该文提出了一种基于不等长时隙的射频识别(Radio Frequency Identification, RFID)动态帧时隙ALOHA (Dynamic Framed-Slotted ALOHA, DFSA)防碰撞算法。算法考虑到大量碰撞时隙和空闲时隙对系统效率的影响,采用帧内时隙长度不等的优化策略,由时隙优化参数和未读标签数确定帧长,通过优化的切比雪夫不等式法进行标签估计,并基于马尔科夫链分析标签识别过程,来实现读取周期的控制。分析和仿真结果表明,该算法比时隙优化前的DFSA算法效率更高,平均识别时间更短,标签数估计比下限值法、Schoute法和碰撞率法更准确。     

一种时间高效的易于实现的多标签射频识别技术

多标签碰撞问题严重影响射频识别RFID系统的识别效率.在研究子帧观测机制的基础上,针对常规动态帧时隙Aloha多标签防碰撞算法存在的复杂度高、时间效率低等问题,提出了一种基于子帧的动态帧时隙Aloha算法,其在识别过程中采取设定的子帧观测,运用空闲与碰撞时隙数的关系估计剩余标签数,再依据预估的结果优化设置新的帧长,显著提升了大容量多标签RFID系统的识别效率.该算法的运算复杂度低、计算量小,易于在常规RFID读写器中实现,工程应用前景广阔.仿真结果表明：同传统的Aloha类防碰撞算法相比,提出的算法具有复杂度低、稳定好、识别效率高等优势.     

一种改进的RFID标签防碰撞算法

在已有RFID标签防碰撞ALOHA算法基础上,提出了一种改进的带中断机制的动态帧时隙ALOHA(ⅡDFSA)算法,一方面通过优化设置系统效率临界因子和参考碰撞时空比,比较系统效率判断是否改变帧的大小;另一方面通过比较碰撞时空比来判断帧大小的改变方向,从而有效降低标签识别时间,提高识别效率。计算机仿真结果表明,与传统的动态帧时隙ALOHA算法相比,当标签数低于200和高于800时,采用ⅡDFSA算法可以有效降低系统总识别时间,提高系统效率。当标签数介于200~800之间时,与传统的动态帧时隙ALOHA算法相当。     

按需时隙分配RFID防碰撞协议研究

为进一步提高射频识别阅读器的标签识别效率,提出一种按需时隙分配高效防碰撞协议.该协议将识别循环分为预约帧时隙阶段和在帧时隙内读取标签两个阶段,通过帧前预约机制消除读取阶段的空闲时隙,采用预约冲突捕获机制有效地减少了读取阶段的碰撞时隙数.在此基础上,通过选择最优预约时隙随机码位数和最优预约时隙数,实现了该防碰撞协议的识别效率最优化,分析了该协议标签电路复杂性,并给出了适用于本协议的标签数估计方法.性能评估表明:该防碰撞协议的平均识别效率达到91.28%,在通信复杂性和识别速度方面明显优于现有典型防碰撞协议.     

RFID系统多标签识别防碰撞算法

进行了全面的基于动态帧时隙 ALOHA(DFSA)的无源 RFID 系统多标签识别防碰撞算法研究,并将其中的标签数目估计技术进行序贯加权处理,通过仿真比较了改进前后 DFSA算法的性能,并确定了最佳遗忘因子。仿真结果表明,该改进措施缩短了 RFID识别标签所需时间,提高了系统的工作效率,可有效地应用于港口码头、车站或物流中心的集装箱管理或物流配送管理,以改善由于 RFID系统多标签碰撞而导致的货物流通缓慢或拥堵问题。     

改进型帧时隙ALOHA防碰撞算法研究

为进一步提高RFID系统中电子标签防碰撞算法的识别效率,对帧时隙ALOHA防碰撞算法的性能进行分析,提出一种结合精确标签估计和二进制搜索的改进型帧时隙ALOHA算法.将识别过程分为标签估计和标签识别两个阶段,在标签估计算法中引入碰撞概率上、下限参数,并精确估计标签数量对初始帧时隙大小进行优化;在标签识别阶段,利用二进制搜索算法对时隙内的碰撞标签进行快速识别.通过对识别过程进行仿真结果表明:改进的算法改善了防碰撞性能,提高了RFID系统的标签识别效率.     

改进的基于ALOHA的RFID防碰撞算法

为了解决RFID系统中电子标签识别效率不高的问题,对基于ALOHA的随机性防碰撞算法进行了详细分析,提出了一种新的ALOHA防碰撞算法.在该算法中,针对标签估计,采用动态调整的方式自动改变标签估计式中的系数,使得标签估计个数随着已识别的标签数动态变化,从而估计下一帧待识别标签数;而对于帧长调整,根据估计的标签数,通过帧长与标签数分组的关系确定.通过MATLAB进行仿真,结果表明,该算法能明显提高系统的吞吐率和稳定性.     

RFID高频读写器防碰撞算法研究

基于对RFID(无线射频识别,Radio Frequency Identification)高频读写器防碰撞性能提高的目的,介绍了二进制搜索算法原理,并基于二进制搜索算法详尽研究了一种符合ISO/IEC 14443A规范的比特帧防碰撞算法,比特帧防碰撞算法能有效的实现高频读写器的防碰撞功能。此方法为解决RFID高频防碰撞问题,提高高频读写器性能具有重要的实用意义和指导意义。     

超高频RFID读写器设计

为满足市场需求,提高读写器读写效率,降低成本,提出了一种基于ISO/IEC 18000-6C的射频身份识别(RFID)读写器方案.该读写器适用于超高频段,支持跳频,发送通路来用射频发送芯片,接收回路采用相关解调,用分离元件搭建,成本较低,结构简单,易于实现.采用随机槽时隙陈计数器算法进行防碰撞设计,在多标签环境下能够识别标签,并与其成功通信.相对于采用传统随机碰撞算法的读写器,此读写器能够在多标签环境下顺利读取标签,防碰撞性能具有一定提高.     

可并行识别的分组动态帧时隙ALOHA标签防碰撞算法

该文针对现有动态帧时隙ALOHA标签防碰撞算法的系统吞吐率低、算法效率低等问题,提出一种可并行识别的分组动态帧时隙ALOHA(PIGDFSA)标签防碰撞算法。该文以实验为基础,探索了待识别标签数、标签分组数、帧长对系统吞吐率与标签碰撞率的影响,研究了提升系统吞吐率与降低标签碰撞率的策略与方法。结合射频识别(RFID)的多天线系统,引入FastICA技术,从而实现碰撞时隙重新定义,并以此为基础,利用未识别标签数目自适应确定分组数与帧长。仿真结果表明:PIGDFSA算法在标签数达到2000时,算法吞吐率仍能稳定在92%以上,与FSA-256, GDFSA, BSDBG等算法相比具有更高的算法吞吐率,更少的空隙时隙,更高的算法效率。     

Optimal Dynamic Framed Slotted ALOHA Based Anti-collision Algorithm for RFID Systems

In Radio Frequency IDentification (RFID) system, one of the most important issues that affect the data integrity is the collision resolution between the tags when these tags transmit their data to reader. In majority of tag anti-collision algorithm, Dynamic Framed Slotted Aloha (DFSA) has been employed as a popular collision resolution algorithm to share the medium when multiple tags respond to the reader’s signal command. According to previous works, the performance of DFSA algorithm is optimal when the frame size equals to the number of un-identified tags inside the interrogation zone. However, based on our research results, when the frame size equals to number of tags, collision occurs frequently, and this severely affects the system performance because it causes power consumption and longer tag reading time. Since the proper choice of the frame size has a great influence on overall system performance, in this paper we develop an analytical model to study the system throughput of DFSA based RFID systems, and then we use this model to search for an optimal frame size that maximizes the system throughput based on current number of un-identified tags. In addition to theoretical analysis, simulations are conducted to evaluate its performance. Comparing with the traditional DFSA anti-collision algorithm, the simulation results show that the proposed scheme reaches better performance with respect to the tag collision probability and tag reading time.     

Accurate tag estimation for dynamic framed-slotted ALOHA in RFID systems

Dynamic Framed-Slotted ALOHA (DFSA) is one of the most popular algorithms to resolve tag collision in RFID systems. In DFSA, it is widely known that the optimal performance is achieved when the frame size is equal to the number of tags. So, a reader dynamically adjusts the next frame size according to the current number of tags. Thus it is important to estimate the number of tags accurately. In this paper, we propose a novel tag estimation method for DFSA. We compare the performance of the proposed method with those of other existing methods. And, simulation results show that our scheme improves the accuracy of tag estimation and the speed of tag identification.     

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

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.     

Gen2‐Based Tag Anti‐collision Algorithms Using Chebyshev's Inequality and Adjustable Frame Size

Arbitration of tag collision is a significant issue for fast tag identification in RFID systems. A good tag anti‐collision algorithm can reduce collisions and increase the efficiency of tag identification. EPCglobal Generation‐2 (Gen2) for passive RFID systems uses probabilistic slotted ALOHA with a Q algorithm, which is a kind of dynamic framed slotted ALOHA (DFSA), as the tag anti‐collision algorithm. In this paper, we analyze the performance of the Q algorithm used in Gen2, and analyze the methods for estimating the number of slots and tags for DFSA. To increase the efficiency of tag identification, we propose new tag anti‐collision algorithms, namely, Chebyshev's inequality, fixed adjustable framed Q, adaptive adjustable framed Q, and hybrid Q. The simulation results show that all the proposed algorithms outperform the conventional Q algorithm used in Gen2. Of all the proposed algorithms, AAFQ provides the best performance in terms of identification time and collision ratio and maximizes throughput and system efficiency. However, there is a tradeoff of complexity and performance between the CHI and AAFQ algorithms.     

Bi-slotted tree based anti-collision protocols for fast tag identification in RFID systems

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