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Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38.

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Presentation on theme: "Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38."— Presentation transcript:

1 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 王正誠

2 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 RFID 介紹 RFID collision problem 探討 Conclusion Future work Reference 2

3 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 RFID – Radio Frequency Identification – 無線射頻識別 – 利用空間電磁感應或電磁傳播進行通信,以達 到自動識別標識物體的目的 3

4 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 RFID 主要有三個組成元件 1. 電子標籤 (Tag)  RFID 詢答器 (RFID Transponder) 、非接觸 ID 標籤 (Contactless ID Tag) 2. 感應器 (Reader)  辨識器、讀碼器 3. 天線 (Antenna) 4

5 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 依本身具電源與否區分為三類 1. 主動式 RFID  電池型  通訊距離可達十公尺  可自行處理和傳送資料 2. 被動式 RFID  免電池型  由讀寫器的天線接收電力後才能動作,通訊距離較 短  不能自行處理和傳送資料 5

6 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 半主動式 RFID  電池支援式  標籤內部數位電路供電  不能自行發送資料 6

7 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 感應器 (Reader) – 讀取電子標籤 – 射頻信號,不需要與電子標籤接觸及可讀取資 料 – 感應器會與電腦連接,得到的資料傳送至系統 作辨識或後續處理 7

8 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 天線 (Antenna) – 傳遞電子標籤和感應器之間的射頻信號 8

9 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 儲存資訊量多 2. 非接觸式、穿透性 3. 可辨識數個 RFID 標籤、標籤可覆寫 4. 使用期限長 5. 體積小、多變的形狀 6. 讀取速度快 7. 安全性高 9

10 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 有效距離 – 標籤和讀取裝置的通訊距離 2. 成本價格較高 – RFID 的標籤成本較傳統條碼高 3. 易受干擾 – 電磁波無處不在 10

11 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 醫療 – 追蹤傳染性疾病患者、病患辨識、醫療廢棄物 品追蹤 零售 – RFID 標籤取代條碼標籤,追蹤商品,防缺貨 監控保全 – RFID 技術與無線區域網路結合,取代傳統巡邏 11

12 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Differentiate between two main forms of communication. – Multi-access to a reader – Broadcast mode 12

13 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Data from many individual tag to reader 13

14 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 At beginning of identification, reader broadcast to tags in its range and tags return message to reader. 14

15 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Three cases 1.Only one tag to respond reader. 2.At the same time have more tag to respond to the reader that result collision. 3.After reader’s broadcasting no tag respond. 15

16 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Active tag – Detect other between tags to avoid collision. Passive tags – Not detect other between tags to avoid collision. 16

17 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 FSA (Framed Slotted ALOHA) – Reader broadcast a frame size to tags, all tags select a random number(less than frame size). – Tag have own random number, slot equal to the number, tag transmit message to reader. – Tag transmit to reader stagger. – Avoid collision caused by tag. – Tags 17 Reader 12 34

18 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 When collision occur, reader skip collision tags until next cycle, and then reader broadcast again and collision tags select random number and transmit again. Repeat step until all tags are identified by the reader. 18

19 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / Issue – Additional memory to save the random number except the ID of tag.

20 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / Reader broadcasts a prefix and queries the tags. ID of tag is same as prefix, reader recognize it. Query again until completing.

21 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / Issue – Not like ALOHA, need extra memory to save number of tag. – Whole identification process check ID with prefix one by one. ID of tags is similar, identification process of tag maybe cost long time. But ALOHA type not impact by ID.

22 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 DFSA (Dynamic Framed Slotted ALOHA) – Estimate through algorithm can estimate remaining number tags after each round of identification. – Frame size change according to result. 22

23 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / Issue – Frame size is no longer fixed, make whole identification process more efficient.

24 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Based on ALOHA. Solve collision immediately when collisions occur. When collision occur, system restart another identification process(new cycle and abandon previous cycle). – Estimate collision tags and reader broadcast a new frame size to tags. Tag generate random number again and transmit message. Reduce collision tag to collide again in next round to make more collisions. 24

25 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 n : passive tags(have unique ID) – Reader does not know number of tags but can estimate. N i : frame size at the beginning – Reader broadcast frame size N i to tags, tag generate a number between 1 and N i. n c : estimate number of collision tag – Reader use n c to differentiate frame size N c, tag generate number between 1 and N c. 25

26 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 26

27 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Referring to [2], range of frame size can be decided. Frame size is close number of tag, efficiency of identification is better. 27

28 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Command “throw_away” – Execute of proposed method. What reader do when reader detects collision? c : greater than zero, mean collisions occur ad : count value to aim at collision tags //Reader: //broadcast “throw_away” if (c > 0) tag_respond = tag(throw_away); if (tag_respond > 0) ad = ad + 1; tag(ad); start a new round; broadcast Nc; 28

29 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 What tag do when the reader broadcasts command “throw_away” to collision tag? ct : limit collision tags to respond to reader //Tag: //Receive initial parameters from reader ct = 1; transmission: receive frame size; generate random number; //must <= frame size if (ct == ad) transmit message; ct = 0; if (receive “throw_away”) ct = ct + 1; goto transmission; 29

30 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / Worst case

31 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Analyze probability of worst case Number of tags is between 3 and 32 31

32 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / ≦ n ≦ 300, N i =16 32

33 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / N i ={16,64,128}

34 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / ≦ n ≦ 1000, N i =16

35 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 The method of anti-collision algorithm of RFID system – Base on ALOHA protocol. – Cost fewer slots than DFSA about 54% and efficiency of whole process is about 35% when number of tags is increased to

36 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Anti-collision algorithm for RFID Position of RFID 36

37 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 [1] Chuen-Ching Wang, Te-Yuan Wang, Tien-Hao Lien, Rong-Ming Su, "A Simple and Efficient Anti-collision Algorithm for RFID System," iih-msp, pp , 2010 Sixth International Conference on Intelligent Information Hiding and Multimedia Signal Processing, 2010 [2] Wen-Tzu Chen, Guan-Hung Lin “An Efficient Anti-Collision Method for Tag Identification in a RFID System,” IEICE Transactions on Communications, Volume E89-B, no.12, pp , Dec [3] Klaus Finkenzeller, RFID Handbook Fundamentals and Applications in Contactless Smart Cards and Identification,Second Edition, Wiley, [4] 龔哲幀著,「主動式 RFID 室內定位追蹤演算法與系統設計」,碩 士論文,國立台北科技大學資訊工程研究所,台北, 2010 。 37

38 Wireless and Broadband Networks Laboratory ◆ Department of Computer Science and Information Engineering ◆ National Taipei University of Technology / 38 Q & A 38


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