1

EPC Radio Frequency Identify ProtocolsClass1 Generation-2 UHF RFID860 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 algorith

m• Generates RN into a slot counter

decrement based on Interrogator cmds Tags reply when slot reaches zero

• Q– Interrogator uses to regulate the probability o

f 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 (18000-6c)

• 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 Probabilistic Probabilistic

Collision arbitration linearity

Up to 250 tags Up to 2256 Up to 215

Communication hopping

Half duplex FHSS Half duplex FHSS Half duplex FHSS

Tag memory Read & write by blocks Read & write by blocks

Read & Write (multiple of 16bits)

Tag type Passive 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 860 MHz ~ 960 MHz as local regulation

Modulation ASK 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 PIE

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 Not supported Not supported

Password for Kill command

Not supported Not supported 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 860 MHz ~ 960 MHz inclusive

Modulation Bi-state amplitude modulated backscatter

Bi-state amplitude modulated backscatter

ASK and / or PSK modulation

Data coding Bi-phase space (FM0) Bi-phase space (FM0) Baseband FM0 or Miller modulated subcarrier

Data rate 40kbits/s 40kbits/s or 160kbits/s

FM0 : 40kbits/s to 640kbits/sSubcarrier : 5kbits/s to 320kbits/s

Preamble 16 bits Sequence of backscatter modulation

16 bits Sequence of backscatter modulation

Required

Error detection 16 bit CRC 16 bit CRC CRC-16

Minimum tag receiver bandwidth

860 MHz ~ 960 MHz 860 MHz ~ 960 MHz 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– Operating Frequency Range: 860~960MHz– Operating Channels(Spread-spectrum systems): 50 channels

– 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 ~ 111112: 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 15963 allocation class identifier– 111000102 for EPCglobal

• User memory– User-specific data storage

15

Singulation Process

• Singulation– Identifying an individual Tag in a multiple-Tag environment

Reader

1.Select (Q)

Random Number RNF: 0 ~ 65,535 RNS: 0 ~ 2Q-12.Generate RNS

3.if(RNS == 0) backscatter RNF

4.ACK

5.Backscatter PC,EPC,CRC

6.QueryRep7.if(RNs > 0) decrement RNs

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 betwe

en 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.

19

20