1
Position Estimationfor Goods Tracking System
using Mobile Detectors
Hiroshi Mineno, Kazuo Hida, Miho Mizutani, Naoto Miyauchi,Kazuhiro Kusunoki, Akira Fukuda, Tadanori Mizuno
Shizuoka University, JapanMitsubishi Electric Corporation
Kyushu University, Japan
Hiroshi Mineno, Kazuo Hida, Miho Mizutani, Naoto Miyauchi,Kazuhiro Kusunoki, Akira Fukuda, Tadanori Mizuno
Shizuoka University, JapanMitsubishi Electric Corporation
Kyushu University, Japan
†
‡†
†‡
2
Outline
Introduction – location awareness -Related workMobiTra overviewHierarchical trackingPosition estimationPrototype testbedExperimental resultSimulation resultConclustion
3
Introduction
Location awareness is useful to applicationsLibraries: guide readers to books they chooseHospitals: keep track of patients or nursesMolls: guide parents to their lost childHome: guide us to something looking for
Context aware ubiquitous service
Pervasive Sentient Invisible
Accurate positioning, tracking systemAccurate positioning, tracking system
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Related workActive badge:
Infrared signal, room level granularity
Active bat, cricket:TDoA between RF and ultrasound
RADAR:RSSI of 802.11 RF, several meters
RF based proximity:The location is given as a centroid.
Requiring special devices to track the objectTrade-off between position accuracy and the number of sensing devices
Reader
Tag
Large Expensive Hard to install
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Solution is RFID tags
Categorized by existence of battery
Active RFID tags Passive RFID tagsMerit Long read range No battery, small, lightweight
Demerit Need battery exchange, expensive
Short read range
Tag readers will be commonly mobileSmall and lightweight have been developed
Ubiquitous Communicator byYRP Ubiquitous Networking Lab.
2004.9.15 2005.3.2Trial model
Compact Flash type Cell phone with tag reader by KDDI
6
MobiTra overview
UserUser
ObjectsObjects
Mobile tag readers (MTRs)Mobile tag readers (MTRs)
MobiTra Server
Internet
PassiveRFID tags
Hierarchicaltracking
Sensing EnvironmentSensing Environment Traditionalresearch
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Position estimation
204738C10:15
204020C10:15
204532A10:13
203030A10:18
202512A10:13
203433B10:09
205050C10:15
205050C10:15
201525A10:17
204040B10:16
201010A10:18
……………
Read range
MTR’s y-coordinate
MTR’s x-coordinateObject IDTime
MTRs’ Detection histories (i)
(ii)
(iii)
(iv)
Estimated area
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Position estimation methods
AA
B
B
(a) Sensing constraint (b) Connectivityconstraint
(c) Negative constraint
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Prototype testbed
Target object
Mobile active RFID tag reader
(MTR)
Tracking environment
for MTRs
Passive RFID tag reader
Passive RFID tag reader
Passive RFID tags(at 20cm intervals)Passive RFID tags(at 20cm intervals)
Active RFID tagActive RFID tag
Active RFID tag reader
Active RFID tag reader
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Experimental result
The number of applied detection histories
1.0
0.8
0.6
0.4
0.2
00 1 2 3 4 5 6 7 8
◆
◆
◆
◆ ◆
◆ ◆ ◆ ◆
Ext
inct
ion
ratio
of e
stim
ated
are
a
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Simulation result
0
0.5
1
1.5
2
2.5
3
3.5
4
0 80 160
240
320
400
Elapsed time (sec)
0
0.5
1
1.5
2
2.5
3
3.5
4
0 80 160
240
320
400
(a) Tags at four corners
Estim
ated
are
a (m
^2)
Estim
ated
are
a (m
^2)
(b) Other tags
Using negative constraintsNot using negative constraints
Elapsed time (sec) Elapsed time (sec)
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Detailed analysis
(a) Tags not at four corners( Connectivity constraints)
(b) Tags at four corners(Connectivity constraints)
Target object
MTR
Estimated area
(c) Tags at four corners(Negative constraints)
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Conclusion
This presentation showed:Hierarchical goods tracking system using RFID tags and mobile detectorsEffect of position estimation is evaluated through prototype testbedand simulation
Future work:Developing MobiTra v.2 (TDoA, Web I/F)
Evaluate estimated location accuracyNew position estimation method
B
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MobiTra v.2
User
Beacon
MTR
Wireless LANAccess Point
MobiTra server
Tag reader
Listener
PDATDoA
Web browser
Objects
Position estimation
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Interval v.s. Num of MTR
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
3 4 5 6 7 8 9 10
Square on a side (m)
Elapsed time to detect all targets (s) Num of MTR: 1
Num of MTR: 2
Num of MTR: 3
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
3 4 5 6 7 8 9 10
Square on a side (m)
Elapsed time to detect all targets (s) Num of MTR: 1
Num of MTR: 2
Num of MTR: 3
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
3 4 5 6 7 8 9 10
Square on a side (m)
Elapsed time to detect all targets (s) Num of MTR: 1
Num of MTR: 2
Num of MTR: 3
Interval: 10sec
Interval: 20sec
Interval: 5sec
Num of MTR: 1
Interval: 20sec
Interval: 10sec
Interval: 5sec
MTR × 1
MTR × 2
MTR × 3
MTR × 1
MTR × 2MTR × 3
MTR × 1MTR × 2MTR × 3
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
3 4 5 6 7 8 9 10
Square on a side (m)
Elapsed time to detect all targets (s) Interval: 1sec
Interval: 3sec
Interval: 5sec
Interval: 10sec
Interval: 20sec
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Effect of Negative Constraint
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Applied detection histories
Decrease of estimated area (%) Square on a side: 3m
Square on a side: 4m
Square on a side: 5m
Square on a side: 6m
Square on a side: 7m
Square on a side: 8m
Square on a side: 9m
Square on a side: 10m
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Applied detection histories
Decrease of estimated area (%) Square on a side: 3m
Square on a side: 4m
Square on a side: 5m
Square on a side: 6m
Square on a side: 7m
Square on a side: 8m
Square on a side: 9m
Square on a side: 10m
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Detailed analysis
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Applied detection histories
Decrease of estimated area (%)
Square on a sede: 3m Square on a side: 4m
Square on a side: 5m Square on a side: 6m
Square on a side: 7m Square on a side: 8m
Square on a side: 9m Square on a side: 10m
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Applied detection histories
Decrease of estimated area (%) Square on a side: 3m
Square on a side: 4mSquare on a side: 5mSquare on a side: 6m
Square on a side: 7mSquare on a side: 8mSquare on a side: 9mSquare on a side: 10m
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Applied detection histories
Decrease of estimated area (%)
Square on a side: 3mSquare on a side: 4mSquare on a side: 5mSquare on a side: 6mSquare on a side: 7mSquare on a side: 8mSquare on a side: 9mSquare on a side: 10m
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100 150 200 250
Applied detection histories
Decrease of estimated area (%) Square on a side: 3m
Square on a side: 4m
Square on a side: 5m
Square on a side: 6m
Square on a side: 7m
Square on a side: 8m
Square on a side: 9m
Square on a side: 10m
Connectivity constraints (others)
Negative constraints (at 4 corners)
Negative constraints (others)
Connectivity constraints (at 4 corners)
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Solution is RFID tags
Active type Passive typeMerit Long read range No battery, small, lightweight
Demerit Need battery exchange, expensive
Short read range
~135kHz 13.56MHz 860~930MHz 2.45GHz
Communication method
Electromagnetic induction Electromagnetic wave propagation
Read range ~10cm ~30cm ~3m ~1.5mDirectivity ○ ○ ◎ ◎
Water resistance
◎ ○ △ ×
Metal resistance
◎ ○ △ ×
(LF) (HF) (UHF)
Categorized by existence of battery
Categorized by radio frequency
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A)無線ICタグとの交信距離と指向性2
読取り可能なタグ方向(電磁誘導方式)
無指向性アンテナ 指向性アンテナ(低周波)
標準的なゲートアンテナ
×
○○
○○
○○
○
2つのゲートアンテナ
アンテナ交信範囲と指向性 距離
幅
指向性アンテナ(高周波)
距離
幅
交信可能時間
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A)無線ICタグとの交信距離と指向性3
ある程度の検知率を得るためには,指向性が弱く,交信距離が1m程度の検知器が望ましい?
RF Code社 Spider Reader IIIAタグリーダ & タグアクティブタグ(約20g),303.825MHz帯電波(UHF)2本のヘリカルアンテナを用いて指向性の調整可能10cm~10mで8段階に交信距離を調整可能複数同時読み取り(最大1,000個)バッテリ内臓(約4時間),約450gタグ内のコイン型電池交換可能
タグID送信間隔7秒(△)