Radio Frequency Identification_图文

发布于:2021-05-15 03:52:51

RFID Technology

Matthias Handy
Institute of Applied Microelectronics & CS University of Rostock
RFID-Workshop, 30.9./1.10.04, Berlin

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Agenda
Introduction Characteristics Operating Principles Applications & Standards Summary

Radio Frequency Identification
RFID: Automatic identification technology where information is carried by radio waves.

Other Auto-ID-Technologies:
- Bar Code - Smart Cards - Biometrics (e.g. fingerprint)

Special Characteristics of Radio Communication:
- No physical contact - No line-of-sight - Imperceptible

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Elements of an RFID-System
Transponder T T T Application
TCP/IP TCP/IP Network Network

Data Clock Energy

Reader

Transponder T T T Application Data Clock Energy Reader

Transponder Power Supply
Active (battery-assisted) Transponders
own energy source (e.g. battery) transponder transmits radio signal higher read range finite lifetime

Passive Transponders
no power supply "on board" transponder reflects/modulates radio signal from reader shorter read range lifetime not limited by energy source

X

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Passive Transponders – What's inside?
T

Coupling Element

Control Logic RF Interface Control Memory
Memory Interface Control

RF Interface Volt. Regulator Modulator Demodulator Clock

Access Control

Integrated Circuit

Transponder Construction Formats (Examples)
Disks

Cylinders

Cards

Key Fobs /Rings Glass

Smart Labels

Pictures: Texas Instruments, Matrics, Philips

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Readers – What's inside?
Reader

Special reader design depends on: ? type of coupling ? communication sequence ? type of data transmission transponder reader ? operating frequency

Coupling Element

RF Interface Transmitter Receiver Clock Generator Voltage Regulator

Control Logic & Memory Microcontroller App. Interface Driver
Application

Memory

Supply Voltage

Communication Model (Passive)
Energy from RF field T1 T2 T3 Responses
Transponders

Commands Reader

Communication Example: ? Application Reader: ? "Show me IDs of all tags in range!" ? Reader Tags: ? "Deliver your ID!" ? Tags Reader: ? "T1", "T2", "T3" ? Reader Application: ? "IDs of tags in range: T1, T2, T3"

Commands

Responses

Application

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Agenda
Introduction Characteristics Operating Principles Applications & Standards Summary

Overview of RFID System Characteristics
Operating Frequency Method of Coupling Transmission Range Data Storage Capacity Power Supply (Active, Passive) Read Only / Read-Write Transmission Types (HDX, FDX, SEQ)

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Selected Operating Frequencies (1)
< 135 kHz (LF)
? ? ? ? ? ? ? ? ? ? Short range Low data (read-) rates Penetrate non-metallic materials (e.g. water) Do not penetrate / transmit around metals E.g. for animal identification ISM Band Higher data rates and range (than <135 kHz-systems) Penetrate non-metallic materials (e.g. water) Do not penetrate / transmit around metals E.g. for contactless smart cards

13,56 MHz (HF)

Selected Operating Frequencies (2)
860-930 MHz (UHF)
? ? ? ? ? ? ? ? ? ? High data rate / long range Effective around metals Do not penetrate water Differences in frequency (Europe, USA, Japan) E.g. for logistics ISM Band (same as Bluetooth, WLAN) High data rate, long range Effective around metals Do not penetrate water E.g. for logistics

2,45 GHz (UHF)

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System Ranges - Classification
Close Coupling Systems
? ? ? ? ? ? ? ? ? ? ? ? Range: < 1cm Frequencies: DC ... 30 MHz Based on inductive or capacitive coupling E.g. for door locking systems Range: < 1m Frequencies: 135 kHz or 13,56 MHz Mostly based on inductive coupling E.g. for contactless smart cards Range: > 1m Also known as backscatter systems Frequencies: 860-930 MHz or 2,45 GHz E.g. for logistics

Remote Coupling Systems

Long Range Systems

RFID Tag as Data Storage Device
T

Coupling Element

Control Logic RF Interface Control Memory
Memory Interface Control

RF Interface Volt. Regulator Modulator Demodulator Clock

Access Control

Integrated Circuit

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RFID Tag as Data Storage Device
Most RFID-Tags store (U)ID – Unique IDentifier
Mostly read only Factory programmed

Some tags can store user data
Mostly read/write EPC, Product information

Memory Technologies:
EEPROM, RAM, ROM, FRAM

RFID-Tag Memory (Example)
Texas Instr. Tag-It HF-I (passive smart label; 13,56 MHz)

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Example Storage Capacities
Manufacturer Philips Philips Alien Technologies Matrics Texas Instruments Tag Name U-CODE I-CODE ALB-2482 Type passive smart label passive smart label batt. assisted (8cm x 2.5cm x 1.5cm) passive smart label passive smart card Frequency 2,45 GHz 13,56 MHz 2,45 GHz Memory (user data) 2048 bit up to 1024 bit 4 kByte RAM

I2010-LBL RI-TH1-CB1A

860-960MHz 13,56 MHz

256 bit 2048 bit

Agenda
Introduction Characteristics Operating Principles Applications & Standards Summary

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Coupling Overview
Close Coupling Systems
? ? ? ? ? ? ? ? ? ? ? ? Range: < 1cm Frequencies: DC ... 30 MHz Based on inductive or capacitive coupling E.g. for door locking systems Range: < 1m Frequencies: 135 kHz or 13,56 MHz Mostly based on inductive coupling E.g. for contactless smart cards Range: > 1m Also known as backscatter systems Frequencies: 860-930 MHz or 2,45 GHz E.g. for logistics

Remote Coupling Systems

Long Range Systems

Inductive Coupling (close coupling & remote coupling systems)
Transponder's power supply: 1. Reader generates magnetic alternating field. 2. This field induces a voltage in tag's antenna coil power supply

Data transfer from transponder reader: 1. Resonant transponder draws energy from magnetic alternating field. 2. This can be detected in reader's antenna (voltage drop) 3. Switching a load resistor on and off at the transponder amplitude modulation of voltage at the reader antenna (load modulation)

Tag

Reader

Tag modulates inductive coupling

Reader detects load modulation

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Electromagn. Backscatter Coupling (long range)
Transponder's power supply: Tag draws energy from electromagnetic field of the reader. Tag may be battery-assisted. Data transfer from transponder reader: Similar to radar technology Incoming power at the tag antenna is reflected partially. Reflection characteristics depend on load connected to the antenna. Load resistor in parallel with the antenna can modulate the amplitude of the reflected power (modulated backscatter).

Tag: Reflects electromagnetic waves

Reader: Detects Changes in reflected power

Tag

Reader

Anticollision
The Problem: A reader is only able to communicate with one single tag at a time! The Solution: Use anticollision (singulation) protocols!
Tags

Tag Tag Tag Tag

Reader

Common anticollision techniques: - (Slotted) ALOHA - Binary Search
Reader

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Anticollision: Slotted ALOHA
Tags only transmit packets at pre-defined points in time (slots) Synchronized by reader Example: 1 Reader, 5 Tags, 8-bit ID
Reader-Slot

Slot 1

Slot 2

Slot 3

Reader-Slot SELECT 10000001

Reader Tag 1 Tag 2 Tag 3 Tag 4 Tag 5

INVENTORY

11110110
collision!

10000001

11010110
collision!

10010001 11110111
slot length

t

Anticollision: Binary Search
"Tree Walking" Recursive depth-first search Requirement: Reader is able to detect bit position of a collision Example: 1 Reader, 3 Transponder, 3-bit ID Received data at reader
1 10 11 Bit number 1st iteration 2nd iteration 2 X 0 0 1 X X 0 0 X 1 1

collision!

0
collision!

00

01

000

001

010

011

100

101 110

111

3rd iteration

Tag present

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Anticollision: Blocker Tag
A. Juels, R. Rivest, M. Szydlo; 2003 (Selective) Blocking of RFID tags Only works with binary search anticollision Simulates the full set of 2k possible RFIDtag serial numbers Reader cannot tell which tags are really present Example: 48 bit ID, Reader reads 1000 tags/s: > 8000 years reading all tags
collision!

Blocker Tag

Tag Tag Tag Tag

Reader

0
collision!

1
collision! collision! collision!

collision!

00

01

10

11
collision!

Anticollision protocol recursively asks: "What is your next bit?" Blocker tag always answers: "Both 1 and 0!"

000

001

010

011

100

101 110

111

Agenda
Introduction Characteristics Operating Principles Applications & Standards Summary

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Applications

RFID Standards
Standards for logistics applications
ISO/IEC 18000 ISO/IEC 15961-15963 ISO/IEC 15418

Standards for automatic livestock identification
ISO 11784 ISO 11785 ISO 14223

Standards for vicinity coupling cards
ISO/IEC 10373 ISO/IEC 10536 ISO/IEC 14443 ISO/IEC 15693

Supply Chain Management
EPC (under development)

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Summary
There's no typical RFID-System Main differentiation characteristics
Tag's power supply Frequency Range! Type of Coupling Data storage capacity

Operating Principles
Inductive coupling Electromagnetic Backscatter coupling

Anticollision techniques
Slotted ALOHA Binary Search

References
K. Finkenzeller; RFID-Handbook; John Wiley & Sons, 2003. M. Reynolds; Physics of RFID, MIT RFID Privacy Workshop, Cambridge, MA, November 2003. C.K. Harmon; Basics of RFID Technology, MIT RFID Privacy Workshop, Cambridge, MA, November 2003. R. Bridgelall; RADAR Technology for Commodity Goods; 2004. A. Juels, R.L. Rivest, M. Szydlo, The Blocker Tag: Selective Blocking of RFID Tags for Consumer Privacy, ACM Press, 2003. A. Juels; RFID Tags: Privacy and Security without Cryptography; MIT RFID Privacy Workshop, Cambridge, MA, November 2003. Texas Instruments; Tag-it HF-I Transponder Inlays Reference Guide.

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Contact Information

Matthias Handy Institute of Applied Microelectronics & Computer Science University of Rostock matthias.handy@uni-rostock.de

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