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
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.
Motivation1
Human-computer interface
Imagine you can localize RFIDs to within 0.1cm to 1 cm!
Baggage sortation in airport
Imagine you can localize RFIDs to within 0.1cm to 1 cm!
Goal-line technology
Imagine you can localize RFIDs to within 0.1cm to 1 cm!
Demonstration
http://young.tagsys.org/tracking/tagoram/youtube
High-Precision RFID Tracking Using COTS Devices
30cm40cm
Drawing in the Air
TrackPoint Deployed at AirportsReader
Industrial computer
State-of-the-art2
RFID Tracking & LocalizationState-of-the-art
2004 2014201320112010
[1] Lionel M. Ni, Yunhao Liu, etalLANDMARC: Indoor Location Sensing Using Active RFIDWireless Networks
1120mm
LANDMARC Lionel M. Ni
RFID Tracking & LocalizationState-of-the-art
2004 2014201320112010
[1] Lionel M. Ni, Yunhao Liu, etalLANDMARC: Indoor Location Sensing Using Active RFIDWireless Networks
1120mm
LANDMARC Lionel M. Ni
[3] P.Nikitin, etalPhase based spatial identification of uhf rfid tags.IEEE RFID 2010.
680mm
[2] C.Hekimian-Williams, eltaAccurate localization of rfid tags using phase difference. IEEE RFID 2010.
280mm
Diff basedC. H.Williams
Spatial basedP. Nikitin
RFID Tracking & LocalizationState-of-the-art
2004 2014201320112010
[1] Lionel M. Ni, Yunhao Liu, etalLANDMARC: Indoor Location Sensing Using Active RFIDWireless Networks
1120mm [3] P.Nikitin, etalPhase based spatial identification of uhf rfid tags.IEEE RFID 2010.
680mm
[2] C.Hekimian-Williams, eltaAccurate localization of rfid tags using phase difference. IEEE RFID 2010.
280mm
Diff basedC. H.Williams
Spatial basedP. Nikitin
[4] Salah Azzouzi, etalNew measurement results for the localization of uhf RFID transponders using an angle of arrival (aoa) approachIEEE RFID 2011.
300mm
210mm
[5] R. Miesen etal. Holographic localization of passive uhf rfid transponders. IEEE RFID 2011.
AOA basedS. Azzouzi
HolographicR. Miesen
RFID Tracking & LocalizationState-of-the-art
2004 2014201320112010
[1] Lionel M. Ni, Yunhao Liu, etalLANDMARC: Indoor Location Sensing Using Active RFIDWireless Networks
1120mm
[4] Salah Azzouzi, etalNew measurement results for the localization of uhf RFID transponders using an angle of arrival (aoa) approachIEEE RFID 2011.
300mm
210mm
[5] R. Miesen etal. Holographic localization of passive uhf rfid transponders. IEEE RFID 2011.
AOA basedS. Azzouzi
HolographicR. Miesen
[6] Jue Wang, etalDude, where's my card?: RFID positioning that works with multipath and non-line of sightACM SIGCOMM 2013
110mm
12.8mm
[7] Jue Wang, etalRF-compass: robot object manipulation using RFIDsACM MobiCom 2013
PinItJue Wang
RF-CompassJue Wang
680mm
[2] C.Hekimian-Williams, eltaAccurate localization of rfid tags using phase difference. IEEE RFID 2010.
280mm
[3] P.Nikitin, etalPhase based spatial identification of uhf rfid tags.IEEE RFID 2010.
RFID Tracking & LocalizationState-of-the-art
2004 2014201320112010
[1] Lionel M. Ni, Yunhao Liu, etalLANDMARC: Indoor Location Sensing Using Active RFIDWireless Networks
1120mm
[4] Salah Azzouzi, etalNew measurement results for the localization of uhf RFID transponders using an angle of arrival (aoa) approachIEEE RFID 2011.
300mm
210mm
[5] R. Miesen etal. Holographic localization of passive uhf rfid transponders. IEEE RFID 2011.
[6] Jue Wang, etalDude, where's my card?: RFID positioning that works with multipath and non-line of sightACM SIGCOMM 2013
110mm
27.6mm
[7] Jue Wang, etalRF-compass: robot object manipulation using RFIDsACM MobiCom 2013
[8] Tianci Liu, etal,Anchor-free Backscatter Positioning for RFID Tags with High AccuracyIEEE INFOCOM 2014
128mm
[9] Jue Wang, etal,RF-Idaw: Virtual Touch Screen in the Air Using RF SignalsIEEE INFOCOM 2014
37mm
BackPosTianci Liu
RF-IDRawJue Wang
[3] P.Nikitin, etalPhase based spatial identification of uhf rfid tags.IEEE RFID 2010.
680mm
[2] C.Hekimian-Williams, eltaAccurate localization of rfid tags using phase difference. IEEE RFID 2010.
280mm
PinItJue Wang
RF-CompassJue Wang
RFID Tracking & LocalizationState-of-the-art
2004 2014201320112010
[1] Lionel M. Ni, Yunhao Liu, etalLANDMARC: Indoor Location Sensing Using Active RFIDWireless Networks
1120mm
[4] Salah Azzouzi, etalNew measurement results for the localization of uhf RFID transponders using an angle of arrival (aoa) approachIEEE RFID 2011.
300mm
210mm
[5] R. Miesen etal. Holographic localization of passive uhf rfid transponders. IEEE RFID 2011.
[6] Jue Wang, etalDude, where's my card?: RFID positioning that works with multipath and non-line of sightACM SIGCOMM 2013
110mm
27.6mm
[7] Jue Wang, etalRF-compass: robot object manipulation using RFIDsACM MobiCom 2013
[8] Tianci Liu, etal,Anchor-free Backscatter Positioning for RFID Tags with High AccuracyIEEE INFOCOM 2014
128mm
[9] Jue Wang, etal,RF-Idaw: Virtual Touch Screen in the Air Using RF SignalsIEEE INFOCOM 2014
37mm
BackPosTianci Liu
RF-IDRawJue Wang
WE ARE HERE
7mm
[3] P.Nikitin, etalPhase based spatial identification of uhf rfid tags.IEEE RFID 2010.
680mm
[2] C.Hekimian-Williams, eltaAccurate localization of rfid tags using phase difference. IEEE RFID 2010.
280mm
State-of-the-art Techniques
RSS based Methods1
RSS is not a reliable location indicator especially 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 tracking
system spanning a long pipeline.
Fast-changing environment • multipath reflection of RF signals • varied orientation of tags• Doppler effect
How Tagoram works?3Overview the basic idea
Backscatter Communication
Double distance
❶𝑩𝒂𝒕𝒕𝒆𝒓𝒚 𝒇𝒓𝒆𝒆
Continuous wave
Device diversity
COTS RFID Reader
0.0015 radians (4096 bits)
accuracy
𝑰𝒎𝒑𝒊𝒏𝒋 𝑹𝒆𝒂𝒅𝒆𝒓
Problem definition
Surveillance region
Reader antenna
{(𝜃1,1 ,𝑡 1,1 ) ,(𝜃1,2 , 𝑡1,2)⋯ , (𝜃1, 𝑁 ,𝑡 1 ,𝑁)}
{(𝜃2,1 ,𝑡 2,1 ) ,(𝜃2,2 ,𝑡 2,2)⋯ ,(𝜃2 ,𝑁 ,𝑡 2 ,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 ?
Tagoram
Controllable CaseCase 1.
Uncontrollable CaseCase 2.
Movement with Known TrackControllable case
4
Our goal is to find the
tag’s trajectory with
a known track.
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 region grids
RF Hologram pixels
How to define the likelihood?
The key is
RF Hologram
Naïve Hologram
Augmented Hologram
DifferentialAugmented Hologram
Thermal noise
Device diversity
Naïve Hologram
-1.5
-1
-0.5
0
0.5
1
1.5
Chart Title
𝐴 𝑇
𝑒 𝑱 𝜃 The real signal
-1.5
-1
-0.5
0
0.5
1
1.5
Chart Title
𝐴 𝑋𝑒 𝑱 h(𝐴 , 𝑋 ) The theoretical signal
-2
0
2Chart Title
𝐴 𝑋𝑒 𝑱 (h ( 𝐴 ,𝑋 )−𝜃 )A virtual interfered signal
Naïve Hologram
Virtual interfered signal
Sum of all signals
Naïve Hologram
If is the initial location, the waves add up constructively.
Real axis
Imaginary axis
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟏 ,𝟏 )−𝜽𝟏 ,𝟏)
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟏 ,𝟐 )−𝜽𝟏 ,𝟐)
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟒 ,𝟒 )−𝜽𝟒 ,𝟒)𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟒 ,𝟑 )−𝜽𝟒,𝟑 )
Naïve Hologram
Real axis
Imaginary axis
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟏 ,𝟏 )−𝜽𝟏 ,𝟏)
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟏 ,𝟐 )−𝜽𝟏 ,𝟐)
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟒 ,𝟒 )−𝜽𝟒 ,𝟒)
𝑒 𝑱 (𝒉 ( 𝑿 , 𝑨𝟒 ,𝟑 )−𝜽𝟒,𝟑 )
If is not the initial location, the waves canceled out.
Naïve Hologram
High PSNR
−𝟕𝟎∼−𝟑𝟎𝒅𝒃𝒎
Influence from Thermal Noise
Experiment Observations CDF Modeling
varying with 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
Augmented Hologram
Ground truth Result
Shift
scattered
Influence from Tag Diversity
Experiment Observations
Random testModeling
At same position
70 tags times
Tag diversity
Pass KS-test to be verified over a uniform distribution with 0.5 significant level.
How to eliminate tag diversity?Differential Augmented Hologram
Differential Augmented Hologram
Using the difference of phase values
Differential Augmented Hologram
ResultGround truth
Movement with Unknown TrackUncontrollable case
5
Overview
Estimating Speeds, Fitting tag’s trajectory
1
Selecting the optimal trajectory2
Implementation & EvaluationPurely based on COTS devices6
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 in comparison to RSS, OTrack, PinIt and BackPos.
DAH02468
10121416
Chart Title
DAH
𝟒
𝟏𝟑𝟏𝟒
Controllable Case with Nonlinear Track
• The track’s internal diameter is 540mm
• The distance varies from to
Nonlinear track
DAH02468
10121416
Chart Title
DAH
𝟒 .𝟗𝟖𝟐 .𝟗𝟓
𝟕 .𝟐𝟗
Under Uncontrollable Case
Achieve a median of 12.3cm accuracy with a standard deviation of 5cm.
Pilot StudyIn two airports7
Current workflow – Manual sortation
Sortation carousel Sorting baggage
It is error-prone step to find the baggage from the carousel in manual sortation.
Our system: TrackPointReader
Industrial computer
Tracking Visualization
Pilot site
Beijing Capital International Airport
Sanya Phoenix International Airport
Setup
• Each airport contains 5 TrackPoints, 4 visualization screens, and 22 RFID Printers.
• The two-year pilot study totally spent more than $600,000
Setup
• Consumed 110,000 RFID tags.
• Involved 53 destination airports, 93 air lines, and 1,094 flights.
Tracking Accuracy
Tagoram achieves a median accuracy of 6.35cm in practice.
• Provides real-time tracking of mobile tags with accuracy 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