RK_zhaw2007_v1.0 1

RFID: Schlüssel zum Internet der Dinge

Prof. Roland KuengContact: roland.kueng@zhaw.ch

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Centralized Control Distributed Control

Change of Paradigm

• Goods and Objects: From External Control to Self-Control

• Information on Goods: Everywhere and Anytime through Internet

• Data relating to objects and processes are stored on a chip, read over an air interface

and fed into an IT network.

• Ability to combine the data collected through RFID in different applications together

in one network.

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Market Vision

• Evolving connectivity at anytime, any place, anyone to seamless connectivity to anything.

•Radio Frequency IDentification is seen as one of the pivotal enabler of the Internet of Things.

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0 51234567890

Wanted: Smart Wireless Electronic Barcode which allows to create and operate an Internet-of-Things

Needs: Ultra low cost Tags with a Global Standard behind

to tag all goods and items

Future: Upgrade Tag with Sensors

Starting Motivation

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The “Big Bang” of Internet of Things

The Electronic Product Code (EPC)

• EPC provides unique numbering scheme for physical objects

• EPC is only an ID, the information is stored on the network

96 bit = 1029 different codes

- Age of earth is 1017 s- Diameter of universe is 1029 cm- 1019 ID’s available per person in this world- Total capacity of chip manufacturers is 1013 tags/year

RFID Basics

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UHF & µµµµWaveInductive RFInductive LF

passivepassive

passive

active

Kueng Classification of RFID

RFID

ZigBeeRuBee NFC WLAN

Semi-passiveSemi-passive Semi-active

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Needs battery power problem

Sub-Categories helping to save power

Active RFID

Active RFID

Semi-active

- Built-in wake-up detector active- Tag switched off

Semi-passive

- Built-in wake-up detector passive- Tag switched off

True Active

- Own RF Oscillator- Tag toggles between

receive and sleep mode

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Tag contains just identifier (ID)

like Barcode

Read only

R&W ↔↔↔↔ Read Only Tag

Read ID only

• contains a unique ID

• low power - fast read

Limited write capability

• write once or by contact

• write data memory only

Tag memory

Read&Write

Near Field

• reactive

• storage energy

MaxwellFar Field

• radiated

• propagating energy

What Maxwell tells us

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What Maxwell tells us

(Dipol)

β = ω/c = 2π/λ

Radiation term:

E ~ ω/r

Power is proportional to (1/d)2

doubling the distance d means 1/4 of available power

(for given antenna and Impedance matching)

Note: |E| limited by

regulations (EIRP)

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Frequency Boundary

135 kHz LF 135 m

13.5 MHz RF 3.5 m

868 MHz UHF 5.5 cm

2.4 GHz µµµµW 1.9 cm

The Distance Game: Near Field - Far Field Boundary

Plane Wave

Electric Field

Magnetic Field

Magnetic Field

(Inductive)

Electric Field

(Capacitive)

Transition region

0.1 1.0 10

Zo = 377 ΩΩΩΩ

10

100

1000

10000

times

Impedance

distance

„Radio Modem“

„Plate Capacitor“

„Transformer“

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Inductive System: Signal & Power Transfer

Power is proportional to (1/d3)2

doubling the distance d means 1/64 of available power

(if d > coil diameter)

Design Rule:

make θθθθ small & antenna r2 big

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Best what Radiation can do

• The fundamental formula (d>> λλλλ) :

• Pr = received power

• Pt = transmitted power

• Gt = transmit antenna gain

• Gr = receive antenna gain

• λλλλ = wavelength

• d = distance

• n = propagation exponent

• L = system loss factor

• do = breakpoint distance for n>2

G = 4ππππ·Ae/λλλλ2

Pt ·Gt = EIRP (limited by regulations*)

λλλλ2/(4ππππ)2d2 Free space attenuation, n = 2

Ld

doGrGtPtPr

n

n

⋅⋅

⋅⋅⋅⋅=

−

2

22

)4( π

λ

*Regulations: ETSI EN 320 208

US FCC Part 15

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Gain = 7 dB

Path Loss 49 dB @ 8 m

- 16 dBm received at tag *

+ 33 dBm

(2 W)

Path Loss 49 dB @ 8 m- 71 dBm

(0.1 nW)

S/N = 35 dB

-22 dBm (6 μμμμW)

backscatter signal

Ld

GrGtPtPr

⋅⋅

⋅⋅⋅=

22

2

)4( π

λ* EPC Class 1 Gen 2

-13…-17 dBm

Receiver Noise: -99 dBm

(F = 25 dB, B = 100 kHz)

Reality: Additionally orientation losses, system losses, fading, n > 2 ... Additional noise sources, amplitude phase, TX to RX coupling

Passive UHF RFID: Limited by Tag Power Consumption

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Gain = 7 dB

Path Loss 71 dB @ 100 m

- 38 dBm received at tag *

+ 33 dBm

(2 W)

Path Loss 71 dB @ 100 m- 113 dBm

(5 fW)

S/N = 10 dB

- 42 dBm (50 nW)

backscatter signal

Ld

GrGtPtPr

⋅⋅

⋅⋅⋅=

22

2

)4( π

λ

Receiver Noise: -116 dBm

(F = 8 dB, B = 100 kHz)

Semi-Active UHF RFID: limited by Backward Link

* ZHAW TWD

-50…-54 dBm

Reality: Additionally orientation losses, system losses, fading, n > 2... Additional noise sources, amplitude phase, TX to RX coupling

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⋅

⋅⋅⋅

⋅

⋅⋅⋅=

d

hh

d

GGPP

rtrtt

r

λ

π

π

λ 2sin

)4(

4 2

22

2

Fading - Problem for Passive Solutions

Simple 2-Ray Model

RFID Tag

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control

&

signal

processing

unit

memorybackscatter

modulator

DC power

sub carrier with

data from reader

sub carrier with

data from tag

RADIATING ANTENNA

UHF Passive Tag Block Diagram

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Backscatter Modulation Principle

• UHF carrier f0 from reader

• f0 is ASK or BPSK modulated with sub carrier fC

• Sub carrier fC used to filter out f0 in reader

• Sub carrier modulation fD is ASK, PSK, FSK

• Backscatter loss 3…9 dB

fD

fCfO

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Tag Zoo

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UHF Semi-active Tag Block Diagram

state

machine

CRC

decoderManchester

decoder

BP filter &

wake up detector Battery

backscatter

mismatch

switch

driver

FSK

encoder

reader-to-tag:

data or CW

illumination

tag-to-reader:

data as modulated

backscatter

RADIATING ANTENNA

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Semi passive / active tags

RFID Reader

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UHF Reader Block Diagram

signal

processor

direct

conversion

receiver

modulation

switch

TX antenna

RX antenna

I Q

RADIATING ANTENNA

synthesizer

Air Interface Options:

• 2 Separated Antennas

• 1 Antenna and Circulator

• 1 Antenna and Directional Coupler

D

A

power amp

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Details Reader Architecture

UHF Frontend

- Direct Conversion Receiver

- Carrier Suppression

- Multi Antenna

Signal Processing

- Sample Level on FPGA

- Symbol Level on DSP

- Air Protocol on DSP

RISC Processor

- MAC

- Reader Protocol

- Interfaces

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FPGADSP

Xscale

Synthesizer

Circulator

TX Amp

ADC

DC-RX

DAC

Supply

4 Antenna PortsEthernet USB RS232

Modern Reader Example

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Reader to Tag Modulation: ASK

• DSB-ASK, SSB-ASK, or PR-ASK modulation

• Pulse Interval Encoding = PIE

• 6.25µs < Tari < 25µs

1 Tari 1.5 …2 Tari

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• ASK or PSK modulation

• Baseband-FM0 for single reader per frequency channel saves bandwidth

• Miller sub carrier encoding for dense reader environment no collisions, filtering

• 5 kbps < data rate < 640 kbps

Tag to Reader: Sub Carrier Encoding

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Tag to Reader Modulation: ASK or PSK

UHF Gen2 Protocol

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Multi-Tag Reading Procedure

• Tag has no means to

- detect other tags

- to talk first (EPC)

• Reader does not know

- number of tags in field

- ID address of the tags

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Play the Inventory Game

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Slotted ALOHA Singulation Concept

same

RN16

sent

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Inventory Command Example

same

RN16

sent

RFID Antenna and Propagation

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UHF Signal Propagation

• Test fixture with 73 Gen2 tags,

equally spaced in air medium

• Target read time: < 1 second

Material

Orientation

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UHF Signal Propagation

Multi-path reflections from metal (reinforcing in floors/ dock levellers and other objects), cause nulls and peaks that get worse with distance from the antenna.

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Why Circular Polarized Antennas

Typical gate using1 reader with 4 antennas

Detail near one antenna

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Allowed Orientation of Tag

Reader Antenna is circular polarized

Tag antenna is often dipole

Red locations are readable

RFID Systems

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RFID Systems up to Edgeware

RFID Reader System

Enterprise Application Integration

Decoupling Line to RFID - Application

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System Architecture for RFID

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EPC Standards and Protocols Overview

Hardware

Edgeware

Middleware

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UHF Challenge in Europe

Optimal spectrum usage is pivotal

Optimal spectrum usage is pivotal

Scarce available spectrumwithin Europe

Scarce available spectrumwithin Europe

865 MHz 866 MHz 867 MHz 868 MHz

865.6 MHz 867.6 MHz

Ch

.4

Ch

.5

Ch

.6

Ch

.7

Ch

.8

Ch

.9

Ch

.1

0

Ch

.1

1

Ch

.1

2

Ch

.1

3

Frequency

100 mWERP

500mWERP

2 W ERP

1 2 314 15

14 155 6 8 9 11 121 2 3

865 MHz 866 MHz 867 MHz 868 MHz

865.6 MHz 867.6 MHz

Ch

.4

Ch

.7

Ch

.1

0

Ch

.1

3

Frequency

25 mWERP

2 W ERP

Multiple Readers must use

same channel at same timeMultiple Readers must use

same channel at same time

2007

2006

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Example: Dock Door Application

Reader related risks

• Mutual interference among

readers

• Co-channel interference

• Adjacent channel

interferences

• Intersystem interferences

3 m

Intra-System

Interference

Channel e.g. Nr. 4

Channel e.g. Nr. 10

Carrier Frequencies

Inter-System

Interference

9 m

Channel e.g. Nr. 13

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European Regulatory Requirements

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Optimal network performance in dense reader environments - Facility SoundingTM

Just like the sound of each instrument in a symphonic orchestra is optimally adjusted to the concert hall, each reader tunes itself to avoid interference from other readers.

• Facility SoundingTM provides automatic optimization of the RFID network performance

• Detection of any potential interference sources and scheduling reading events for optimal reading performance

Toward Internet of Things

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advanced functionalitye.g. sensors

ability to communicatewith other tags

wireless ID networks

2006

2009

EPC Tag Classification

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The Next Step: RFID & Location

Staff workflow tracking

Process tracking

Location based alerting and paging

Personnel

Tracking

Asset tracking

Location Finding

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And it Continues: Class IV Active Tags with Sensors

Similarity to: Wireless Sensor Networks

Topics arising:

- Topologies…

- Mesh networks

- AdHoc networks

- Redundancy….

Master Reader

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E-grain, Smart Dust & Co: What Makes Sense ?

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And finally there might be Risks!?

Switzerland, Postulat vom 9. März 2005

Der Bundesrat wird beauftragt, zu prüfen, welcher Handlungsbedarf sich aus

dem absehbaren flächendeckenden Einsatz der RFID-Technologie ergibt.

RFID: Der Schnüffel-Chip im JoghurtbecherMONITOR Nr. 513 am 8. Januar 2004

Prada Pulls RFID Because of Privacy Concerns

Australien Financial Review, Tuesday, October 21 2003

Risks:- Health: Electromagnetic Radiation- Environment: Waste Treatment- Unemployment: Full automation - Privacy: Tracking

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Internet of Things Will Move the World

Questions ?