RFID阅读器的软件设计及防碰撞算法研究

发布时间：2018-10-30 08:37

【摘要】：自动识别中最具有优势的无线射频识别(Radio Frequency Identification,RFID)技术是一种非接触式识别方法。它利用发射信号的电感(电磁)耦合原理或信号的反射特性来识别目标物体。其以信号的距离长、识别容量大、安全程度高、多标签可同时识别,并具有较强的穿透能力等优点被广泛地应用于人类生活中的多个领域。例如物流仓库、安全交通、商场支付等。但是伴随着RFID技术高速发展,它也逐渐暴露出了一些亟待解决的问题。当RFID在某区域内多个阅读器同时与大量电子标签进行信息交换时,可能会出现信号相互干扰的碰撞问题。为此研究员们提出了RFID防碰撞算法,它不但解决通信过程中标签碰撞问题,而且减少了电子标签的识别时间、提高通道的利用效率和系统的吞吐率。电子标签防碰撞算法解决了多个标签在阅读器工作范围内产生的碰撞问题。论文深入研究了二进制搜索算法、ALOHA算法等防碰撞算法,提出了分组混合查询防碰撞算法和基于帧时隙的HQT算法并完成了阅读器的软件设计。本文的主要研究内容包括:(1)对阅读器进行了软件设计。根据我国自主标准协议,实现了以32位STM32F207为基础的逻辑控制单元的软件架构设计。其中底层驱动实现STM32F207与FPGA之间通信,采用SPI串行接口进行通信。基带的逻辑控制单元与上位机之间的数据传输是基于以太网采用无线通信方式和TCP/IP协议实现。协议层是采取我国自主的标准空中接口协议,实现阅读器与标签的通信状态机制和处理过程的协议命令,同时对标签与阅读器之间的交互式处理进行分析、执行。(2)在传统的射频识别二进制多叉树防碰撞算法和QT算法的基础上,本文提出了一种基于分组的混合查询防碰撞算法。考虑到当碰撞位在标签中所占的位数较多时,直接使用多叉树算法会产生较多的查询次数。在此基础上提出先分组后使用改进的HQT算法能减少查询次数。通过不断的异或分组再用最高位和次高碰撞位的组合信息对标签进行时隙延迟响应,这样就错开了大量标签的碰撞。仿真结果表明,新算法较HQT算法和QT算法有明显的改进,在系统的查询次数上相较QT算法明显减少,对比HQT算法也有一定的减少;系统吞吐率明显提高。(3)在传统的ALOHA防碰撞算法和二进制搜索防碰撞算法基础上,本文提出了基于分组的帧时隙HQT算法。该算法首先通过对标签数量进行预估计决定是否将标签分组,这样减少碰撞机率、提高系统识别效率;在进行不确定性算法时采用多组随机数,减少空闲时隙,然后再对产生碰撞的时隙进行无空时隙的HQT防碰撞算法,这样能够提高系统的识别效率、减少空时隙数以及数据传输量。仿真结果表明对比动态帧时隙ALOHA算法,改进算法在系统的吞吐率由36%提高到57%左右;随着电子标签的增加识别时隙数增加并不明显,远小于动态帧时隙ALOHA算法。
[Abstract]:Radio Frequency Identification (Radio Frequency Identification,RFID) technology, which has the most advantages in automatic identification, is a non-contact identification method. It uses the inductance (electromagnetic) coupling principle of the transmitting signal or the reflection characteristic of the signal to identify the target object. It is widely used in many fields of human life because of its long distance, large recognition capacity, high level of security, simultaneous recognition of multiple tags and strong penetration ability. Such as logistics warehouse, safe transportation, shopping mall payment and so on. However, with the rapid development of RFID technology, it has gradually exposed some problems to be solved. When multiple readers in a certain area exchange information with a large number of tags simultaneously, there may be a collision problem in which the signals interfere with each other. For this reason, RFID anti-collision algorithm is proposed, which not only solves the problem of tag collision in communication process, but also reduces the identification time of electronic tag, improves the efficiency of channel utilization and the throughput of the system. The anti-collision algorithm solves the collision problem caused by multiple tags in the reader range. In this paper, the anti-collision algorithms such as binary search algorithm, ALOHA algorithm and so on are studied, and the anti-collision algorithm of grouping mixed query and HQT algorithm based on frame slot are proposed, and the software design of reader is completed. The main contents of this paper are as follows: (1) the software design of reader is carried out. According to the independent standard protocol of our country, the software architecture design of the logical control unit based on 32 bit STM32F207 is realized. The bottom driver realizes the communication between STM32F207 and FPGA, and uses SPI serial interface to communicate. The data transmission between the base band logic control unit and the host computer is realized by wireless communication mode and TCP/IP protocol based on Ethernet. The protocol layer adopts our country's own standard air interface protocol to realize the communication state mechanism between reader and tag and the protocol command of processing process. At the same time, the interactive processing between tag and reader is analyzed. (2) based on the traditional anti-collision algorithm of binary multitree and QT algorithm, a hybrid query anti-collision algorithm based on grouping is proposed in this paper. When the collision bit takes up more bits in the tag, the multi-tree algorithm can generate more query times. On this basis, it is proposed that the improved HQT algorithm can reduce the number of queries. Using the combination information of the highest bit and the second high collision bit, the time-slot delay response of the tag is carried out by the constant XOR grouping, so a large number of tag collisions are staggered. The simulation results show that the new algorithm is better than the HQT algorithm and the QT algorithm, the query times of the system are obviously reduced compared with the QT algorithm, and the HQT algorithm is also reduced to some extent. The throughput of the system is improved obviously. (3) based on the traditional ALOHA anti-collision algorithm and binary search anti-collision algorithm, a frame slot HQT algorithm based on packet is proposed in this paper. In this algorithm, the number of tags is estimated in advance to decide whether to group the tags, which reduces the probability of collision and improves the efficiency of system recognition. In order to reduce the free time slot, the HQT anti-collision algorithm is applied to the collision time slot, which can improve the recognition efficiency of the system. Reduce the number of slots and the amount of data transmitted. The simulation results show that compared with the dynamic frame slot ALOHA algorithm, the throughput of the improved algorithm increases from 36% to 57%, and with the increase of tag, the number of identifying slots is not obviously increased, which is much smaller than the dynamic frame slot ALOHA algorithm.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP391.44

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