Lesson Title: Singulation

Dale R. ThompsonComputer Science and Computer Engineering Dept.

University of Arkansas

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This material is based upon work supported by the National Science Foundation under Grant No. DUE-0736741.

Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).

Copyright © 2008 by Dale R. Thompson {d.r.thompson@ieee.org}

Singulation

• Singulation is the process that a reader performs to identify and/or communicate with a particular tag in the presence of multiple tags that are in range of the reader.

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Anti-collision Algorithm/Protocol

• An anti-collision protocol is the protocol used to prevent two or more devices from interfering with each other in a common communication channel to share the medium. They are also called medium access control (MAC) protocols.

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Time division multiplexing (TDM)

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Frequency division multiplexing (FDM)

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Polling

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Random access

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Pure Aloha

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Pure Aloha Efficiency

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Slotted Aloha

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Slotted Aloha Efficiency

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Pure Aloha vs Slotted Aloha

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Questions

• What is the difference between pure and slotted Aloha?

• Which is more efficient, pure or slotted Aloha?

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Framed slotted Aloha

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Framed slotted Aloha Efficiency

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Questions

• What is the difference between slotted Aloha and framed slotted Aloha?

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Gen-2 Anti-Collision Protocol (media access control)

• Select phase– Single out particular tag population with one or more bits with query tree protocol

• Inventory phase – identify individual tag using Q protocol (slotted-aloha based)– Reader sends Query with parameter Q and Session number (Q=4 is suggested default)– Reader creates slotted time– Tags pick random 16-bit number for handle– Tags in requested session pick a random number in the range [0,2^Q-1] for slot_number– If slot_number = 0, backscatter handle– If slot_number != 0, wait that number of slots to backscatter handle– Reader ACKs individual tag with handle and goes to access phase. All other tags wait.– If more that one tag answers, reader can send same Q again or send modified Q

• Access phase– Reader interacts with tags requesting EPC number and any other information

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Gen-2 Select (Query Tree)

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Time slice 0 1 2 3 4 5

Reader-to-Tag 0**   00*   01*  

Tag-to-Reader 

collision

  no answer  collisio

n

Tag1 (ID = 010)   010       010

Tag2 (ID = 011)   011       011

Tag3 (ID = 100)            Time slice 6 7 8 9 10 11

Reader-to-Tag 010   011   1**  

Tag-to-Reader   010   011   100

Tag1 (ID = 010)   010        

Tag2 (ID = 011)       011    

Tag3 (ID = 100)           100

Gen-2 Select (Query Tree)

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Gen-2 Inventory (Q protocol, form of slotted Aloha)

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Time slice 0 1 2 3 4 5 6 7

Slot number     0 1 2 3    

Reader-to-Tag Query Q=2           ACK handle1  

Tag-to-Reader     handle1 collision empty empty   EPC1

Tag1   slot=0 handle1         EPC1

Tag2   slot=1   handle2        

Tag3   slot=1   handle3        

Time slice 8 9 10 11 12 13 14 15

Slot number     0 1 2 3    

Reader-to-TagQueryAdjus

t          ACK handle2  

Tag-to-Reader     empty handle2 empty handle3   EPC2

Tag1 (ID = 010)   wait            

Tag2 (ID = 011)   slot=1   handle2       EPC2

Tag3 (ID = 100)   slot=3       handle3    

Q-protocol efficiency

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Question

• What is the relationship between Q and the number of users?

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Contact InformationDale R. Thompson, Ph.D., P.E.Associate ProfessorComputer Science and Computer Engineering Dept.JBHT – CSCE 5041 University of ArkansasFayetteville, Arkansas 72701-1201

Phone: +1 (479) 575-5090FAX: +1 (479) 575-5339E-mail: d.r.thompson@ieee.orgWWW: http://comp.uark.edu/~drt/

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Copyright Notice, Acknowledgment, and Liability Release

• Copyright Notice– This material is Copyright © 2008 by Dale R. Thompson. It may be freely redistributed in its entirety

provided that this copyright notice is not removed. It may not be sold for profit or incorporated in commercial documents without the written permission of the copyright holder.

• Acknowledgment– These materials were developed through a grant from the National Science Foundation at the

University of Arkansas. Any opinions, findings, and recommendations or conclusions expressed in these materials are those of the author(s) and do not necessarily reflect those of the National Science Foundation or the University of Arkansas.

• Liability Release– The curriculum activities and lessons have been designed to be safe and engaging learning

experiences and have been field-tested with university students. However, due to the numerous variables that exist, the author(s) does not assume any liability for the use of this product. These curriculum activities and lessons are provided as is without any express or implied warranty. The user is responsible and liable for following all stated and generally accepted safety guidelines and practices.

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