1. EPC Radio Frequency Identify Protocols Class1 Generation-2 UHF RFID 860 MHZ – 960 MHZ
EPCglobal

2. Introduction RFID Tag classes Class-1: Identity Tags
Passive-backscatter Tags
EPC / Tag Identifier(TID) / ‘kill’ function / Optional(password/user memory)
Higher-class Tags
Class-2: Higher-Functionality Tags
Passive Tags
Extended TID / Extended user memory / authenticated access control
Class-3: Semi-Passive Tags
An internal power source / integrated sensing circuitry
Class-4: Active Tags
Tag-to-Tag communications / Active communications / ad-hoc networking capabilities

3. Terminologies Interrogator RFID reader Cover-coding
A method by which an Interrogator obscures information that it is transmitting to a Tag
Cover-coded string = data (EXOR) random number of the tag
Data transmits the cover-coded string
Inventory round
The period between successive Query commands
Slotted random anticollision
Random number based anti-collision algorithm
Generates RN  into a slot counter  decrement based on Interrogator cmds  Tags reply when slot reaches zero Q
Interrogator uses to regulate the probability of Tag response
Tags load a Q-bit random number
Session
Interrogator chooses on of four sessions and inventories Tags within that session
Inventoried flag
Indicates whether a Tag may respond to an Interrogator
Tags maintain a separate inventoried flag for each of four sessions
Singulation
Identifying an individual Tag in a multiple-Tag environment
R=>T
Interrogator => Tag
T=>R
Tag => Interrogator
Permalock or permalocked
A memory location whose lock status is unchangeable
i.e. memory is permanently locked

4. Protocol Overview ISO/IEC 18000-6 EPC Class 1 Gen 1 protocol
Type A for Class 0 / Type B for Class 1
EPC Class 1 Gen 2 protocol
Single standard protocol
Type C ( c)
Physical layer
DSB-ASK, SSB-ASK, PR-ASK
PIE format (Pulse-interval encoding)
Tag-Identification layer
Select: choosing a Tag population for inventory and access
Inventory: identifying Tags
Access : communicating with a Tag

5. ISO/IEC 18000-6 ISO/IEC Type A, B, EPC Class Gen2 규격 비교(시스템)
Parameters
ISO/IEC
EPC
Type A
Type B
Class 1 Gen2
Collision arbitration
ALOHA
Binary Tree
Slotted Random Anti-collision
Anti-collision type
Probabilistic
Collision arbitration linearity
Up to 250 tags
Up to 2256
Up to 215
Communication hopping
Half duplex FHSS
Tag memory
Read & write by blocks
Read & Write (multiple of 16bits)
Tag type
Passive
Class1(Passive)
Class2(Passive)
Class3(Semi-passive)
Class4(Active)

6. ISO/IEC 18000-6 ISO/IEC Type A, B, EPC Class Gen2 규격 비교(Forward link)
Parameters
ISO/IEC
EPC
Type A
Type B
Class 1 Gen2
Operating frequency range
860 MHz ~ 960 MHz
860 MHz ~ 960 MHz as local regulation
Modulation
ASK
DSB / SSB or PR-ASK
Modulation index / depth
27% to 100%
18% or 100%
Min 80%, Max 100%
Data coding
PIE
Manchester bi-phase
Data rate
33 Kbits/s (mean)
10 or 40 Kbit/s (according to local regulations)
26.7 kbps to 128 kbps
Preamble
No preamble
9 bits of Manchester 0 in NRZ format
Required
Bit period
0 = 20㎲, 1 = 40㎲, SOF=EOF=80㎲
25㎲
6.25㎲, 12.5㎲, 25㎲
Error detection
5 bit CRC for all commands
16 bit CRC
CRC-5 & CRC-16
Command bits
6 bits
8 bits
Variable length
Parity bit
Not supported
Password for Kill command
32 bit password supported by kill command

7. ISO/IEC 18000-6 ISO/IEC Type A, B, EPC Class Gen2 규격 비교(Reverse link)
Parameters
ISO/IEC
EPC
Type A
Type B
Class 1 Gen2
Operating frequency range
860 MHz ~ 960 MHz
860 MHz ~ 960 MHz inclusive
Modulation
Bi-state amplitude modulated backscatter
ASK and / or PSK modulation
Data coding
Bi-phase space (FM0)
Baseband FM0 or Miller modulated subcarrier
Data rate
40kbits/s
40kbits/s or 160kbits/s
FM0 : 40kbits/s to 640kbits/s
Subcarrier : 5kbits/s to 320kbits/s
Preamble
16 bits Sequence of backscatter modulation
Required
Error detection
16 bit CRC
CRC-16
Minimum tag receiver bandwidth
BW tag dependent

8. Protocol Overview (cont’d)
Protocol parameters
Physical and MAC
R=>T
Operating Frequency Range: 860~960MHz
Operating Channels(Spread-spectrum systems): 50 channels
T=>R
Logical
Who talks first: Interrogator (ITF)
Tag EPC: Contained in Tag memory
EPC Length/Format: specified in EPCTM Tag Data Standards
Read/Write size: multiples of 16 bits
Error detection: CRC-16 / CRC-5 / None
Collision management
Type(probabilistic or Deterministic): Probabilistic

9. Example of Tag inventory and access
Example inventory and access of a single Tag

10. Interrogator Operating Modes
Single Interrogator Mode
Multi Interrogator Mode
# of Interrogators < # of channels
Dense Interrogator Mode
# of Interrogators > # of channels
Designed to prevent readers from interfering with one another

11. Tag memory
Separated into four distinct banks
UII
UII
UII
UII

12. Tag memory (cont’d) Reserved memory Kill password
Interrogator shall use a kill password once to kill the tag
Tag shall not execute a kill operation if its password is zero
Access password
Default value shall be zero
Interrogator have to issue this password before transitioning to the secured state

13. Tag memory (cont’d) EPC memory CRC-16
Interrogator/Tag uses when protecting certain R=>T /T=>R
PC (Protocol control)
Bits 10h-14h: the length of (PC+EPC) that a Tag backscatters, in words
000002: one word ~ : 32 words
Bits 15h-16h: RFU (shall be set to 002 for Class-1 Tags)
Bits 17h-1Fh:
if(17h == 0) contain EPCglobalTM Header
Else if(17h == 1) contain the entire AFI defined in ISO/IEC 15961
EPC

14. Tag memory (cont’d) TID memory
8-bit ISO/IEC allocation class identifier
for EPCglobal
User memory
User-specific data storage

15. 3.if(RNS == 0) backscatter RNF
Singulation Process
Singulation
Identifying an individual Tag in a multiple-Tag environment
1.Select (Q)
Random Number
RNF: 0 ~ 65,535
RNS: 0 ~ 2Q-1
3.if(RNS == 0) backscatter RNF
2.Generate RNS
4.ACK
5.Backscatter PC,EPC,CRC
7.if(RNs > 0)
decrement RNs
6.QueryRep

16. Tag states and slot counter
Ready state
Arbitrate state
Reply state
Acknowledged state
Open state
Secured state
Killed state
Slot counter
15-bit
Query or QueryAdjust command a Tag shall preload a value between 0 and 2Q-1
Q is an integer in the range (0,15)

17. Managing Tag populations
Select
The process by which an Interrogator selects a Tag population for inventory and access
Inventory
The process by which an Interrogator identifies Tags
Access
The process by which an Interrogator transacts with (read / write) individual Tags

18. Interrogator algorithm for choosing Q
Example algorithm an Interrogator might use to choose Q
Qfp is a floating-point representation of Q; an Interrogator rounds Qfp to an integer value and substitutes this integer value for Q in the Query.
Typical values for C are 0.1 < C < 0.5. An Interrogator typically uses small values of C when Q is large, and larger values of C when Q is small.