tagoram: real-time tracking of mobile rfid tags to high ... · tagoram: real-time tracking of...

Tagoram: Real-Time Tracking of Mobile

RFID Tags to High-Precision Accuracy

Using COTS Devices

Xiang-Yang Li

Lei Yang, Yekui Chen, Xiang-Yang Li, Chaowei Xiao, Mo Li, Yunhao Liu

Sep. 9, 2014

Movement with known track04.

Outline

State-of-the-art02.

Overview03.

Implementation & Evaluation06.

Movement with unknown track05.

Motivation01.

Pilot Study07.

Conclusion08.

Motivation

Human-computer interface

Imagine you can localize RFIDs to within 0.1cm to 1 cm!

Baggage sortation in airport


Goal-line technology


Demonstration

http://young.tagsys.org/tracking/tagoram/youtube

High-Precision RFID Tracking Using COTS Devices

30cm40cm

Drawing in the Air

TrackPoint Deployed at Airports

Reader

Industrial

computer

State-of-the-art

RFID Tracking & LocalizationState-of-the-art

2004 2014201320112010

[1] Lionel M. Ni, Yunhao Liu, etal

LANDMARC: Indoor Location Sensing

Using Active RFID

Wireless Networks

1120mm

LANDMARC Lionel M. Ni


2004 2014201320112010



Using Active RFID

Wireless Networks

1120mm

LANDMARC Lionel M. Ni

[3] P.Nikitin, etal

Phase based spatial identification of uhf

rfid tags.

IEEE RFID 2010.

680mm

[2] C.Hekimian-Williams, elta

Accurate localization of rfid tags using

phase difference.

IEEE RFID 2010.

280mm

Diff basedC. H.Williams

Spatial basedP. Nikitin


2004 2014201320112010



Using Active RFID

Wireless Networks

1120mm [3] P.Nikitin, etal


rfid tags.

IEEE RFID 2010.

680mm



phase difference.

IEEE RFID 2010.

280mm

Diff basedC. H.Williams

Spatial basedP. Nikitin

[4] Salah Azzouzi, etal

New measurement results for the

localization of uhf RFID transponders

using an angle of arrival (aoa) approach

IEEE RFID 2011.

300mm

210mm

[5] R. Miesen etal.

Holographic localization of passive uhf

rfid transponders.

IEEE RFID 2011.

AOA basedS. Azzouzi

HolographicR. Miesen


2004 2014201320112010



Using Active RFID

Wireless Networks

1120mm





IEEE RFID 2011.

300mm

210mm

[5] R. Miesen etal.


rfid transponders.

IEEE RFID 2011.

AOA basedS. Azzouzi

HolographicR. Miesen

[6] Jue Wang, etal

Dude, where's my card?: RFID positioning

that works with multipath and non-line of

sight

ACM SIGCOMM 2013

110mm

12.8mm

[7] Jue Wang, etal

RF-compass: robot object manipulation

using RFIDs

ACM MobiCom 2013

PinItJue Wang

RF-CompassJue Wang

680mm



phase difference.

IEEE RFID 2010.

280mm

[3] P.Nikitin, etal


rfid tags.

IEEE RFID 2010.


2004 2014201320112010



Using Active RFID

Wireless Networks

1120mm





IEEE RFID 2011.

300mm

210mm

[5] R. Miesen etal.


rfid transponders.

IEEE RFID 2011.

[6] Jue Wang, etal



sight

ACM SIGCOMM 2013

110mm

27.6mm

[7] Jue Wang, etal


using RFIDs

ACM MobiCom 2013

[8] Tianci Liu, etal,

Anchor-free Backscatter Positioning for

RFID Tags with High Accuracy

IEEE INFOCOM 2014

128mm

[9] Jue Wang, etal,

RF-Idaw: Virtual Touch Screen in the Air

Using RF Signals

IEEE INFOCOM 2014

37mm

BackPosTianci Liu

RF-IDRawJue Wang

[3] P.Nikitin, etal


rfid tags.

IEEE RFID 2010.

680mm



phase difference.

IEEE RFID 2010.

280mm

PinItJue Wang

RF-CompassJue Wang


2004 2014201320112010



Using Active RFID

Wireless Networks

1120mm





IEEE RFID 2011.

300mm

210mm

[5] R. Miesen etal.


rfid transponders.

IEEE RFID 2011.

[6] Jue Wang, etal



sight

ACM SIGCOMM 2013

110mm

27.6mm

[7] Jue Wang, etal


using RFIDs

ACM MobiCom 2013

[8] Tianci Liu, etal,

Anchor-free Backscatter Positioning for

RFID Tags with High Accuracy

IEEE INFOCOM 2014

128mm

[9] Jue Wang, etal,

RF-Idaw: Virtual Touch Screen in the Air

Using RF Signals

IEEE INFOCOM 2014

37mm

BackPosTianci Liu

RF-IDRawJue Wang

WE ARE HERE

7mm

[3] P.Nikitin, etal


rfid tags.

IEEE RFID 2010.

680mm



phase difference.

IEEE RFID 2010.

280mm

State-of-the-art Techniques

RSS based Methods1

RSS is not a reliable location indicatorespecially for UHF tags

RSSOrientation VS

Phase based Methods2

PinIt (SIGCOMM 2013) RF-Compass (MobiCom 2013)

Needs to deploy dense reference tags

State-of-the-art Techniques

Summary of Challenges

Need mm-level localization accuracy achieved• especially for mobile tags.

Small overhead, COTS devices• infeasible for using many references for a trackingsystem spanning a long pipeline.

Fast-changing environment• multipath reflection of RF signals• varied orientation of tags• Doppler effect

How Tagoram works?Overview the basic idea

Backscatter Communication

❷ Double distance

❶ 𝑩𝒂𝒕𝒕𝒆𝒓𝒚 𝒇𝒓𝒆𝒆

❸ Continuous wave

❹ Device diversity

COTS RFID Reader

0.0015 radians (4096 bits)

≈ 𝟎. 𝟎𝟑𝟖𝒎𝒎accuracy

𝑰𝒎𝒑𝒊𝒏𝒋 𝑹𝒆𝒂𝒅𝒆𝒓

Problem definition

Surveillance region

Reader antenna

{ 𝜃1,1, 𝑡1,1 , (𝜃1,2, 𝑡1,2)⋯ , (𝜃1,𝑁, 𝑡1,𝑁)}

{ 𝜃2,1, 𝑡2,1 , (𝜃2,2, 𝑡2,2)⋯ , (𝜃2,𝑁, 𝑡2,𝑁)}

{ 𝜃𝑀,1, 𝑡𝑀,1 , (𝜃𝑀,2, 𝑡𝑀,2)⋯ , (𝜃𝑀,𝑁, 𝑡𝑀,𝑁)}

⋮ ⋮ ⋮

𝑀 ×𝑁

Utilizing antennas’ locations, sampled phase values and timestamps to find out the tag’s trajectory 𝒇(𝒕)?

Tagoram

Controllable CaseCase 1.

Uncontrollable CaseCase 2.

Movement with

Known TrackControllable case

Virtual Antenna Matrix

Conveyor

Inverse Synthetic Aperture Radar

𝒇(𝒕𝟎)𝑉

𝐴1

𝐴2

𝐴1,1 𝐴1,2 𝐴1,3 𝐴1,4

𝐴2,1 𝐴2,2 𝐴2,3 𝐴2,4

Initial

position

RF Hologram

𝑳

𝑾

𝑾

𝑳

𝒙𝒘,𝒍

Surveillance region𝑾× 𝑳 grids

RF Hologram𝑾× 𝑳 pixels

How to define the likelihood?

The key is

RF Hologram

Naïve Hologram

Augmented Hologram

DifferentialAugmented Hologram

Thermal noise

Device diversity

Naïve Hologram

𝐴 𝑇

𝑒𝑱𝜃 The real signal

𝐴 𝑋𝑒𝑱ℎ(𝐴,𝑋)

The theoretical signal

𝐴 𝑋𝑒𝑱(ℎ 𝐴,𝑋 −𝜃)A virtual interfered signal

Naïve Hologram

Virtual interfered signal

Sum of all signals

Naïve Hologram

If 𝑿 is the initial location, the waves add up constructively.

Real axis

Imaginary axis

𝑒𝑱(𝒉 𝑿,𝑨𝟏,𝟏 −𝜽𝟏,𝟏)

𝑒𝑱(𝒉 𝑿,𝑨𝟏,𝟐 −𝜽𝟏,𝟐)

𝑒𝑱(𝒉 𝑿,𝑨𝟒,𝟒 −𝜽𝟒,𝟒)𝑒𝑱(𝒉 𝑿,𝑨𝟒,𝟑 −𝜽𝟒,𝟑)

Naïve Hologram

Real axis

Imaginary axis

𝑒𝑱(𝒉 𝑿,𝑨𝟏,𝟏 −𝜽𝟏,𝟏)

𝑒𝑱(𝒉 𝑿,𝑨𝟏,𝟐 −𝜽𝟏,𝟐)

𝑒𝑱(𝒉 𝑿,𝑨𝟒,𝟒 −𝜽𝟒,𝟒)

𝑒𝑱(𝒉 𝑿,𝑨𝟒,𝟑 −𝜽𝟒,𝟑)

If 𝑿 is not the initial location, the waves canceled out.

Naïve Hologram

High PSNR

−𝟕𝟎 ∼ −𝟑𝟎𝒅𝒃𝒎

Influence from Thermal Noise

Experiment Observations

CDFModeling

varying with 𝒅 𝝈 = 𝟎. 𝟏

𝜃 ∼ 𝒩(𝜇, 𝜎) 𝐹(𝜃; 𝜇, 𝜎)

𝟎∘~𝟒𝟎∘

𝟗𝟐𝟎 ∼ 𝟗𝟐𝟔𝑴𝑯𝒛

100 tags

How to deal with thermal noise?Augmented Hologram

Augmented Hologram

A probabilistic weight

𝒉 𝑿, 𝑨 − 𝜽 ∼ 𝓝(𝟎, 𝟎. 𝟏)

Probability of 𝑻 → 𝑨

Augmented Hologram

Ground truth Result

Shift

scattered

Influence from Tag Diversity

Experiment Observations

Random testModeling

At same position

70 tags 100 times

Tag diversity

Pass KS-test to be verifiedover a uniform distributionwith 0.5 significant level.

How to eliminate tag diversity?Differential Augmented Hologram

Differential Augmented Hologram

Using the difference of phase values

Differential Augmented Hologram

Result

Ground truth

Movement with

Unknown TrackUncontrollable case

Overview

Estimating Speeds,

Fitting tag’s trajectory

1

Selecting the optimal trajectory2

Implementation & EvaluationPurely based on COTS devices

Hardware & Software Introduction

ImpinJ R420 reader.

4 directional antennas

Reader Tag

Alien 2 × 2 Inlay

Alien Squiggle Inlay

Software

EPCglobal LLRP

Java

Linear Track

• A mobile object is emulated via a toy train on which a tag is attached.

• The system triggers the camera to take a snapshot on the train when firstly read.

• A camera is installed above the track to capture the ground truth.

Tracking Accuracy in Linear Track

Improve the accuracy by 𝟒𝟖 ×, 𝟑𝟎 ×, 𝟐𝟖 × 𝒂𝒏𝒅 𝟖. 𝟓 ×in comparison to RSS, OTrack, PinIt and BackPos.

DAH

𝟒

𝟏𝟑 𝟏𝟒

Controllable Case with Nonlinear Track

• The track’s internal diameter is 540mm

• The distance varies from 𝟏𝒎to 𝟏𝟓𝒎

Nonlinear track

DAH

𝟒. 𝟗𝟖 𝟐. 𝟗𝟓

𝟕. 𝟐𝟗

Under Uncontrollable Case

Achieve a median of 12.3cm accuracy with astandard deviation of 5cm.

Pilot StudyIn two airports

Current workflow – Manual sortation

Sortation carousel Sorting baggage

It is error-prone step to find the baggagefrom the carousel in manual sortation.

Our system: TrackPoint

Reader

Industrial

computer

Tracking Visualization

Pilot site

Beijing Capital International Airport

Sanya Phoenix International Airport

Setup

• Each airport contains 5 TrackPoints, 4visualization screens, and 22 RFIDPrinters.

• The two-year pilot study totallyspent more than $600,000

Setup

•Consumed 110,000 RFID tags.

• Involved 53 destination airports, 93air lines, and 1,094 flights.

Tracking Accuracy

Tagoram achieves a median accuracy of6.35cm in practice.

• Provides real-time tracking of mobile tags withaccuracy to mm-level.

• Limits almost all negative impacts.• Multipath effect

• Doppler effect

• Thermal noise

• Device diversity

• Implemented purely based on COTS RFID products.

• Systematically evaluated under indoor environment and at two airports.

Conclusion

Not well-studied before

Questions?

hank you T

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