【作者】 尹君；

【导师】 陈洪云；

【作者基本信息】 湖南大学 ， 电工理论与新技术， 2009， 硕士

【摘要】 射频识别技术(Radio Frequency Identification, RFID)作为一种非接触式的自动识别技术,它通过射频信号自动识别目标对象并获取相关数据。RFID具有条形码无可比拟的优点:无需接触,直接读取信息;可在恶劣环境下工作;穿透能力强;可同时处理多个目标等。但作为一种新兴的应用技术,RFID技术尚不成熟,还存在一些不足,如识别准确率不高;标准化进程缓慢等等。其中,由于复杂环境下标签碰撞和读写器碰撞带来的系统工作效率低下问题成了RFID技术应用推广的瓶颈。因此,研究快速、准确、可靠的防碰撞问题解决方案,对于RFID技术的发展有着至关重要的意义。本文核心内容是关于RFID系统防碰撞算法的研究,包括标签的算法和读写器的算法。针对单读写器作用范围内,多标签通讯的防碰撞问题,文中结合RFID标准(主要是UHF频段的EPC Gen2和ISO18000-6标准),详细研究了已有的ALOHA算法和二进制树搜索算法及其改进算法,深入分析每种算法的性能、优缺点及适用场合。在此基础上,本文提出了一种基于动态帧时隙的改进算法,当标签数量很多时,通过分组限制响应标签个数可达到较高的识别效率。仿真结果表明,当标签数达到1000时,本文提出的算法相对于传统的时隙算法可以使时隙利用率提高80%以上。另外,对于多读写器环境下的防碰撞问题,尽管它类似于移动通讯中蜂窝网的频率分配问题,但RFID系统也有它自身的特性,如低效的标签引发的标签干扰和读写器在实际工作中的限制等等。本文参考相关国内外文献,定义和分析几种读写器碰撞类型,并利用图论中的着色理论建立读写器碰撞模型。接着研究分析了Color-wave和HiQ这两种解决读写器碰撞问题的算法,为今后研究多读写器与多标签通讯以及移动读写器的通讯过程这些复杂问题打下了基础。更多还原

【Abstract】 Radio Frequency Identification (RFID) is a kind of non-touching automatic identifying technology. It can automatically identify the target and get information through radio-frequency signal. RFID has unexampled advantages compared to barcode, such as reading information directly without touching; working under bad environment; the better penetrability and identifying more objects simultaneously. As one applied technology, it’s immature yet, and still has some shortcomings, like the poor accuracy rate of identifying, the slow progress of RFID standardization, etc. Among those elements, in the dense environment due to tag-collision and reader-collision problem, the lower efficiency of system will become bottleneck to the RFID technology’s application and promotion. Therefore finding a fast, accurate and reliable solution to solve the anti-collision problem is of very important significance in developing the RFID technology.The main contents of this thesis are about the research on anti-collision algorithm of RFID systems, including tag’s and reader’s. According to the anti-collision problem of multi-tags communication Within the reading range of a single reader, the paper combine with RFID standard (mainly UHF frequencies as EPC Gen2 and ISO18000-6), and detailedly discuss ALOHA algorithm and Binary tree search algorithm along with algorithms which improved from them. Besides the performance of advantages and disadvantages and their application situation are also analyzed. Based on those work, an improved Dynamic Frame Slotted ALOHA algorithm is put forward. The proposed algorithm compared to conventional ones, when there are a large number of tags in the field, can achieve high system efficiency by grouping to restrict the number of unread tags. Simulation results show that the proposed algorithm improves the slot efficiency above 80% at least compared to the conventional algorithms when the number of tags reach 1000.Otherwise, the anti-collision problem with respect to the environment of multi-readers, although it’s similar to the Frequency Assignment Problem experienced in cellular telephone networks, but RFID system has its own unique features, like tag interference due to the lower functionality of tag and the practical system operating constraints. Making reference to domestic and foreign literature, several types of readers collision are defined and analyzed, moreover utilizing graph coloring theory to establish collision model of readers. Subsequently, both Colorwave and HiQ algorithm which used to solve the problem of reader-collision are discussed in detail, and it will pave the way for future research on those more complicated problems, like the communication between multi-tags and multi-readers, and the communication process of mobile reader device etc.更多还原