ranging and positioning of uhf rfid...

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RANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, K. Witrisal Ass.Prof. Dr. Holger Arthaber [email protected] Vienna University of Technology Institute of Electrodynamics, Microwave and Circuit Engineering Microwave Engineering Group Gusshausstrasse 25/354 1040 Vienna, Austria Assoc.Prof. Dr. Klaus Witrisal [email protected] Graz University of Technology Signal Processing and Speech Communication Lab Inffeldgasse 16c 8010 Graz, Austria RFID Real-Time Localization for Flexible Production Environments (REFlex)

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Page 1: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

RANGING AND POSITIONING OFUHF RFID TAGS

H. Arthaber, K. Witrisal

Ass.Prof. Dr. Holger [email protected]

Vienna University of TechnologyInstitute of Electrodynamics, Microwave and Circuit EngineeringMicrowave Engineering GroupGusshausstrasse 25/3541040 Vienna, Austria

Assoc.Prof. Dr. Klaus [email protected]

Graz University of TechnologySignal Processing and Speech Communication Lab

Inffeldgasse 16c8010 Graz, Austria

RFID Real-Time Localization for Flexible Production Environments (REFlex)

Page 2: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 3: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 4: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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Applications for Accurate Indoor Positioning Systems

Manufacturing Retail

Process monitoringProcess control

Real-time inventoryRecommender systemTheft control

Manufacturing Logistics

Positioning / NavigationSafetyFlexible processes

Pick-and-place Assisted Living

Error detectionFlexible processes

Fall detectionMedication managementBehavior monitoring

Emergency response systems

SafetyCoordinationMonitoring

Requirements:Accuracy (5 – 20 cm); Reliability(90 – 100%)

Technologies:RFID; active transponders (IoT;UWB); 5G wireless systems

Objectives:Positioning and navigation;activity recognition; control

Images: Ubisense, SSI Schaefer, brighamyen.com, Witrisal, Jungheinrich, slashgear.com

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• Potential future applications for RFID

– Positioning of massive tag populations

– Activity recognition (humans interacting with goods)

• Sales floor

– Recommender systems for “brick and mortar” stores

• Warehouses

– Pick-and-place stations

• Requirements:

– large read volumes (entire rooms); decimeter-range accuracies

Ranging/Positioning Applications

Images: SSI Schaefer, brighamyen.com

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• Traditional RFID applications domains – ranging allows for:

• RFID Gates

– distance bounding, range gating reduce false detects

– movement direction detection

• Conveyor belts

– ordering on conveyor belt

– distance bounding for parallel belts

• Requirements:

– confined read volumes; 0.5 – 1 m accuracy; (typically) ~100 % reliability

Ranging/Positioning Applications

Images: intermec

Page 7: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 8: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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Monostatic configuration: Bistatic configuration:

Problems:

• „Multipath“: several ways/paths from antenna to tag

• „Reflectors“: introduce multipath and/or „blind“ the RFID reader

• „Dead spots“: no communication zones due to interference

The UHF RFID Radio Szenario

red ……. unmodulated signal from readergreen … signal with tag-modulation on it

line of sight pathother paths, e.g. via reflectors

Page 9: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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How does the signal look like at the RX-antenna?

• Radio waves are described by– Frequency (e.g. 868 MHz)

– Magnitude

– Phase

• RX antenna receives unmodulated TX signal and tag‘s modulated response

The UHF RFID Radio Szenario

large signal(dominated by TX-RX-coupling)

very small signal, shown enlarged(dominated by line-of-sight path)

combined signal(tag response almost invisible)

+ =

Page 10: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 11: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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2D Positioning Methods

1) Angle based (Triangulation)– requires at least 2 RFID readers at

exactly known positions and orientations

2) Distance based (Trilateration)– requires at least 2(3) RFID readers at

exactly known positions

3) Combination of Angle + Distance– works with a single reader

Passive UHF RFID Ranging/Positioning – Overview

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Received Signal Strength (RSSI)

• Uses the received signal power

• Gives a distance estimate

Problems:

• Multipath results in inaccuracy

• Antenna pattern influence

• Tag‘s reflection is not constant

• Many RFID reader chipsets aren‘t capableof vector measurements (they either use real or imaginary part)

Passive UHF RFID Ranging/Positioning – Received Signal Strength (RSSI)

?

?

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Passive UHF RFID Ranging/Positioning – Angle of Arrival (AoA)

Angle of Arrival (AoA)

• Uses at least two antennas

• phase difference of tag’s signal gives an angle estimate

Problems:

• Multiple antennas needed

• Multipath will result in wrong power readings

• Many RFID readers aren‘t capable of vectormeasurements ?

Page 14: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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Time of Flight (ToF)

• An experiment:

– Transmission of an ultra-short pulse in an indoor environment

– Signal reflections lead to multipath propagation

Passive UHF RFID Ranging/Positioning – Time of Flight (ToF)

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Passive UHF RFID Ranging/Positioning – Time of Flight (ToF)

• Influence of bandwidth:

– Time/range resolution changes vastly

• Impact of multipath propagation onto ToF ranging:

– Ultra-wideband (> 500 MHz): line-of-sight signal is clearly seen

– 10 – 100 MHz: signal distortions and fading

– Narrowband (<= 1 MHz): flat fading (only)

• Conclusion: (very) large bandwidth is needed

Page 16: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 17: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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1 range 1 range

1 TRX 1 TRX

Positioning with Multiple Antennas

1 TRX 1 TRX

1 bi

1 TX; 1 RX 1 TX; 1 RX

2 bistatic1 range 1 range4 range 4 range

2 TX, 2 RX 2 TX, 2 RX

8 bistatic

Multi-antenna systems improve the ranging and positioning performance

Three reader configurationswith 2 reader positions arecompared. Each reader has:

1) – combined TX/RX antenna

2 range measurements

2) – separated TX/RX antennas

2 range + 2 bistatic meas.

3) – 2 pairs of separated TX/RX ant.

2 x 4 independent range plus8 independent bistatic meas.

Error ellipses: 95% of measurements are inside

positioning error at 50 MHz ranging bandwidth

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Comparison of numeric results over entire test area:

Always statistical errors – There is no 100% guarantee!

Multiple antennas improve performance dramatically, but

Require complex infrastructure (antennas mounted at exact positions)

Positioning performance with 50 MHz bandwidth sufficient for most applications

Positioning with Multiple Antennas

95% error 99% error

2 x monostatic 34 cm 38 cm

4 x bistatic 26 cm 30 cm

16 x bistatic 13 cm 15 cm

Page 19: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 20: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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What’s new?

• Direct time-of-flight measurement with 50 MHz bandwidth

• Works with standard EPC Gen2 tags

• Independent on tag chip manufacturer

• Performs ranging with a single antenna

• Measures the “echo” from the tag’s antenna and suppresses other echos

A new Time-of-Flight Ranging Method for Passive UHF Tags

Page 21: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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How does the ranging signal look like?

• Spectrum of RFID and ranging signal:

• Without any changes, the signal violates EPC standard and radio standards an extremely low power ranging signal must be used this reduces signal to noise ratio expect noisy distance measurements

A new Time-of-Flight Ranging Method for Passive UHF Tags

RFID communication

unattenuated ranging signal

reduced power ranging signal

Page 22: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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Nice theory… But can this work?

Ranging Enabled RFID Reader Prototype:

– EPC compliant 868/915 MHz reader

– Real-time positioning of standard UHF EPC tags

– FPGA implementation

– Research platform:

• RF-Frontend not yet optimized

• Positioning algorithms

A new Time-of-Flight Ranging Method for Passive UHF Tags

SPS IPC Drives 2015, Nuremburg

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Measurement results

• NXP UCODE 7 tags

• 5 tags in different distances

A new Time-of-Flight Ranging Method for Passive UHF Tags

95

(0.5) ± 1.2 cm

1.14 ± 4.8 cm

2.06 ± 4.2 cm

2.84 ± 6.2 cm

4.22 ± 8.8 cm

Page 24: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Ranging/Positioning Applications

• The UHF RFID Radio Szenario

• Passive UHF RFID Ranging/Positioning Methods

• Positioning with Multiple Antennas

• A new Time-of-Flight Ranging Method for Passive UHF Tags

• Summary

Contents

Page 25: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

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• Basic ranging principles explained

– Distance based

– Angle based

• Ranging/positioning accuracy is limited by multipath transmission

– Always statistical errors, no 100% guarantee

– More bandwidth better accuracy

– More antennasmore accuracy

• New ToF-based ranging method

– Promising results for standard EPC Gen2 tags

Summary

Page 26: RANGING AND POSITIONING OF UHF RFID TAGSrainrfid.org/wp-content/uploads/2016/03/RAIN-RFID-TUGraz.pdfRANGING AND POSITIONING OF UHF RFID TAGS H. Arthaber, ... RFID Real-Time Localization

Thank You For Your Attention!

RFID Real-Time Localization for Flexible Production Environments (REFlex)

parts of the shown results were done in the funded research project: