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    Title: 無線射頻辨識網路中讀取器佈署與防碰撞之研究
    Other Titles: Research on reader deployment and anti-collision in RFID networks
    Authors: 蔡維庭;Tsai, Wei-Ting
    Contributors: 淡江大學電機工程學系碩士班
    莊博任;Chuang, Po-Jen
    Keywords: 讀取器網路;讀取器佈署;讀取器防碰撞;RFID Networks;Reader Deployment;Anti-collision
    Date: 2015
    Issue Date: 2016-01-22 15:06:42 (UTC+8)
    Abstract: 無線射頻辨識網路(Radio Frequency Identification Networks, RFID Networks)是利用讀取器(Reader)發送無線電波訊號,而標籤(Tag)接收到無線電波訊號後則將標籤內的資訊回傳給讀取器。相較於傳統的二維條碼(Barcode)擁有快速辨識的特點,也因此被大量應用於大型商場、物流業等等之中,在未來也被認為是實現物聯網(Internet of Things, IoTs)的核心技術之一。
    在大多數的物聯網應用中,都需要使用大量的讀取器,但由於讀取器過於密集造成讀取碰撞與讀取率過低的問題產生,這種現象稱為讀取器干擾問題。因此如何避免讀取器干擾發生是相當重要的議題。為了解決讀取器干擾的問題需要從兩個層面著手,首先必須要對讀取器網路佈署,佈署後得以減緩讀取器干擾,但若僅依靠讀取器佈署來避免干擾發生,這會使得硬體的建置成本大幅提升,因此還需從軟體方面著手,也就是讀取器網路防碰撞演算法,唯有從軟體與硬體這兩層面著手,才能夠使讀取器干擾盡可能降到最低。
    讀取器佈署問題下,現有的方式皆是採取最佳化演算法(如GA)求解,其中的目標函數為評估拓樸的核心,目前大多數的成本目標都會造成拓樸偏頗,因此我們提出另一種成本評估方式,並改良出新的最佳化演算法(IGAA),使得讀取器網路佈署可以較符合需求,最後也提出一種階段性的最佳化演算法。
    讀取器防碰撞問題下,現有的TDMA方法有DCS、ColorWave、ColorTable等等,這些方法中由於動態調整時槽數造成傳輸成功率不穩定,並且讀取器網路在越複雜環境下,會因為改選方式的關係造成kick連鎖效應,因此我們提出交換改選方式來取代現有的改選方式並引入四色理論來解決這些問題,最後為了找出最好的效能,我們將所提的演算法與現有的演算法做混合。
    最後實驗結果證實,在讀取器佈署問題下,我們所提新成本目標與IGAA能得到更好的拓樸,而所提階段性的最佳化演算法能夠以少量時間且使各目標發展更明確。另一方面證實,在讀取器防碰撞問題下,我們所提出的交換改選方式能夠減少kick連鎖效應、應用四色理論後能夠解決動態調整時槽數的問題,且混合式演算法確實能夠得到較高的成功率與吞吐量。
    The radio Frequency Identification (RFID) Networks send radio signals to tags via readers. After tags receive radio signals, they will respond their information to readers. Compared with the two-dimensional barcode, the RFID has high efficiency. Thus, the RFID has been considered as one of the principal building blocks for realizing the Internet of Things (IoTs) concept.
    In IoTs, most RFID applications (for instance, a supermarket or logistics management) use multiple readers to read the IDs of multiple tags and form the RFID network. Unguarded reader deployment (for instance, readers are largely or randomly deployed) may generate over-crowded readers in the RFID network and therefore brings up interferences. How to avoid interferences between any two readers that is an important topic. The RFID network has to deploy topology which is called the reader deployment in order to solve interferences. Interferences can be reduced after the reader deployment, but it makes high cost of hardware. The RFID network thus has to consider software solution which is called the reader anti-collision. They can minimize interferences when the reader deployment and the reader anti-collision were solved.
    In the reader deployment, solutions use optimization algorithms (for instance, the GA) in existing literatures. Optimization algorithms use objective fitness function to evaluate topology, but the cost objective function may lead to biased reader deployment in existing literatures. We thus propose a new cost objective function and improved optimization algorithm (IGAA), which can create a suitable RFID network topology. Finally, we propose a non- optimization algorithm.
    In the reader anti-collision, TDMA solutions have DCS, ColorWave, ColorTable and so on. They are the kick effect problem and the dynamic MaxColor problem in complex RFID networks. We thus propose a switch mechanism and the four-color theorem to solve these problems. Finally, we propose a new hybrid algorithm which combines existing algorithms with ours in order to find the best performance.
    Simulation results show the cost objective function and IGAA have better performance in the reader deployment. The non-optimization algorithm can reduce processing time and obtain competitive performance. On the other hand, the switch mechanism and the four-color theorem can solve the kick effect problem and the dynamic MaxColor problem in the reader anti-collision. Our hybrid algorithm can obtain favorable performance and achieve high throughput.
    Appears in Collections:[電機工程學系暨研究所] 學位論文

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