1 EPCglobal Training Suite

2 Introduction Tag Protocol - UHF Class 1 Gen 2 Ultra High Frequency (UHF) Generation 2 (Generation 1 is deprecated) Class 1 ClassificationActive/PassiveDescription Class 1PassiveWrite Once, Read Many Times Class 2PassiveRead / Write Class 3Semi-PassiveRead / Write with battery power to enhance range Class 4ActiveRead / Write active transmitter

3 Tag Memory Four Memory Banks Reserved Bank (00) Uses for Tag operation control EPC Bank (01) Uses for storing EPC TID Bank (10) Uses for storing unique Tag Identification (TID) User Bank (11) Uses for storing user defined fields

4 Tag Memory Reserved Memory [00-1F] Kill Password [20-3F] Access Password EPC Bank [00-0F] Cyclic-Redundancy Check [10-1F] Protocol Control [20-xx] Electronic Product Code

5 Tag Memory TID Bank [00-xx] Tag Identification User Bank [00-07] Data Storage Format Identifier (DSFID) [08-xx] User Defined Fields

6 Tag State Diagram

7 Reader Commands Select Commands Selects Tag groups to communicating Inventory Commands Collecting EPC of Tags in reading range Access Commands Access data of specified Tag

8 Reader Commands Select Commands Selects Tag groups to communicating Commands Select

9 Reader Commands Select Commands Select can assert or deassert a Tag’s SL flag, or it can set a Tag’s inventoried flag to either A or B in any one of the four sessions. The conditions to check a tag is matching or non-matching Tag’s flags

10 Reader Commands Inventory Commands Collecting EPC of Tags in reading range Commands Query, QueryAdjust, QueryRep, ACK, NAK

11 Reader Commands Query Query initiates and specifies an inventory round. Choose a group of tags Tag will pick a random value (slot) in the range2 Q − 1 If Tag’s slot = 0, the Tag reply RN16.

12 Reader Commands QueryAdjust QueryAdjust adjusts Q without changing any other round parameters. Tag will pick a NEW random value in the range2 Q − 1 If Tag’s slot = 0, the Tag reply RN16.

13 Reader Commands QueryRep QueryRep instructs Tags to decrement their slot counters. If slot = 0 after decrementing, it will backscatter an RN16 to Interrogater. If Tag’s slot = 0, the Tag reply RN16.

14 Reader Commands ACK ACK echoes the Tag’s backscattered RN16. Tag reply to a successful ACK command

15 Reader Commands NAK Any Tag that receives a NAK shall return to the arbitrate state without changing its inventoried flag (unless the Tag is in ready or killed).

16 Reader Commands Command Sequence (Inventory) ReaderTag1Tag2Tag3 Query (Q=1) Slot=0, Reply RN16Slot=1 ACK (RN16(1)) Reply EPC QueryRep Slot=0, Reply RN16 QueryAdj(Q=2) 12 QueryRep Slot=0, Reply RN16Slot=1 ACK(RN16(2)) ReplyEPC QueryRep Slot=0, Reply RN16 ACK(RN16(3)) Reply EPC QueryRep

17 Reader Commands Access Commands Access data of specified Tag Commands Req_RN, Read, Write, Kill, Lock, Access, BlockWrite, BlockErase

18 Reader Commands Access Access Password (32 bits) Using access password before accessing Tag data Read MemBank Select which Tag Memory Bank to be read WordPtr Specify start reading point. A word is 16 bits WordCount Specify how many words to be read Write MemBank Select which Tag Memory Bank to be write WordPtr Specify start writing point. A word is 16 bits Data The data to be written in MemBank. Writing a word (16 bits) at a time

19 Reader Commands Kill Kill Password (32 bits) Req_RN Instructs a Tag to backscatter a new RN16. Lock Lock / Unlock / PermaLock Mask (10 bits) and Action (10 bits)

20 Reader Commands BlockWrite MemBank Select which Tag Memory Bank to be written WordPtr Specify start writing point WordCount Specify how many words to be written Data The data to be written in MemBank. Data length is ( 16 bits * WordCount ) BlockErase MemBank Select which Tag Memory Bank to be erased WordPtr Specify start erasing point WordCount Specify how many words to be erased

21 Collision Problem What is Collision? Readers and Tags can not resolve noise signal into correct messages The radio interference, the noise, is occurred when multiple radio signal of the same frequency are raised at the same time Reader Collision Two or more Readers communication with the same Tag Tag Collision Two or more Tags communication with the same Reader

22 Solutions of Collision Problem Reader Collision Time Division Multiple Access (TDMA) Readers send commands in different time slot Frequency Division Multiple Access (FDMA) Readers send commands by different radio frequency Tag Collision Slotted Aloha Tags send messages in different time slot Tree Walk The Tags have the number that Reader specified can response