RFID

RFID Collision 2010.12.31 Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 381OutlineRFID RFID collision problem ConclusionFuture work Reference

2Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 382RFID?RFIDRadio Frequency Identification3Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 383RFIDRFID(Tag) RFID(RFID Transponder)ID(Contactless ID Tag)(Reader)(Antenna)

4Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 384RFID TagRFIDRFID5

Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 385RFID Tag (contd)RFID

6Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 386RFID Reader(Reader)7

Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 387RFID Antenna(Antenna)

8Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 388RFIDRFID9Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 389RFIDRFID10Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3810RFIDRFIDRFID11Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3811RFIDDifferentiate between two main forms of communication.Multi-access to a readerBroadcast mode

12Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3812RFID Multi-accessData from many individual tag to reader13

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

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Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 38RFID Broadcast (contd) Three casesOnly one tag to respond reader.At the same time have more tag to respond to the reader that result collision.After readers broadcasting no tag respond.

15Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3815RFID Tag & CollisionActive tagDetect other between tags to avoid collision.Passive tagsNot detect other between tags to avoid collision.16Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3816Anti-Collision Algorithm FSA (1/3)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. Tags17Reader1234Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3817

Anti-Collision Algorithm FSA (2/3)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.18Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3818Anti-Collision Algorithm FSA (3/3)19IssueAdditional memory to save the random number except the ID of tag.Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3819

Anti-Collision Algorithm Query tree (1/2)20Reader broadcasts a prefix and queries the tags. ID of tag is same as prefix, reader recognize it. Query again until completing.Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3820Anti-Collision Algorithm Query tree (2/2)21IssueNot 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.

Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3821

Anti-Collision Algorithm DFSA (1/2)DFSA (Dynamic Framed Slotted ALOHA)Estimate through algorithm can estimate remaining number tags after each round of identification.Frame size change according to result.

22Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3822Anti-Collision Algorithm DFSA (2/2)23IssueFrame size is no longer fixed, make whole identification process more efficient.Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3823Simple & Efficient Anti-Collision Algorithm (1/8) 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.24Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3824Simple & Efficient Anti-Collision Algorithm (2/8)n : passive tags(have unique ID) Reader does not know number of tags but can estimate.Ni : frame size at the beginningReader broadcast frame size Ni to tags, tag generate a number between 1 and Ni.nc : estimate number of collision tagReader use nc to differentiate frame size Nc, tag generate number between 1 and Nc.25Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 38Simple & Efficient Anti-Collision Algorithm (3/8)26

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

Simple & Efficient Anti-Collision Algorithm (4/8)Referring to [2], range of frame size can be decided.Frame size is close number of tag, efficiency of identification is better. 27Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3827Simple & Efficient Anti-Collision Algorithm (5/8)Command throw_away Execute of proposed method.What reader do when reader detects collision?c : greater than zero, mean collisions occurad : count value to aim at collision tags

//Reader://broadcast throw_awayif (c > 0) tag_respond = tag(throw_away);if (tag_respond > 0)ad = ad + 1;tag(ad);start a new round;broadcast Nc;28Wireless and Broadband Networks Laboratory Department of Computer Science and Information Engineering National Taipei University of Technology/ 3828Simple & Efficient Anti-Collision Algorithm (6/8)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 readerct = 1;transmission:receive frame size;generate random number; //must