Presenter Ho-lin Chang

• Introduction• Design• Implementation• Evaluation• Conclusion and future Work

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• Indoor location-based service

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Healthcare Security Warehouse

• Existed indoor localization technique– UWB– Ultrasound– WiFi

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UWB

WiFi

Ultrasound

• UWB (Ubisense)– Accuracy: 10 ~ 20 cm– Time difference of arrival– Expensive specialized

hardware (10,000 USD)

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• Ultrasonic (Cricket)– Accuracy: 10 ~ 20 cm– Short range– Non-line of sight problem

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• WiFi (Ekahau, RADAR)– RSS fingerprinting– Accuracy: 3 ~ 5m– Low cost– Offline training

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Technologies Accuracy Properties

UWB 15 cm • Specialized hardware

Ultrasound 15 cm• Short range• Non-line of sight problem

WiFi 300~500 cm • Offline training

? cm range• Low cost• Radio• No offline training

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• Develop a novel localization system – Spinning beacon (RF)– Indoor environment– Sub-meter accuracy• 50% < 39 cm• 90% < 70 cm

– Low cost• Low cost motes (100 USD)• Rotation motor

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S

S

S

XX

RR

XX

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The location of XThe location of X

X

S v

f vproject

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X

Δf = 0 HzΔf = 0 HzΔf = 30 HzΔf = -30 Hz

timeΔf (t) = ?30Hz

0Hz

0Hz

-30Hz

vS

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v(t)

S

X

α

x

y

dr

S : (r cosθ, r sinθ)v(t) = (-ωr sinθ, ωr

cosθ)

θ(t) = ωt+φ

X : (d cosα, d sinα)

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S

v(t) X

αx

y

RRβ

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S

S

S

XX

RR

XX

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The location of X

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500 Hz

A 900 MHz

900 MHz + 500 HzBThe location of X

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The location of X

• Hardware–Crossbow MICA2

–Rotational motor

• Software– TinyOS 1.x–C/C++

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• Testbed– 國發所地下室停車場– Three spinning beacons– 30 sample points (2m grid)

• 10 position samples (300 samples)• 3 angles (900 angles)

• Evaluation metrics– Positional error– Angular error

• Parameter Tuning

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50% < 3 degrees

90% < 10 degrees

50% < 3 degrees

90% < 10 degrees

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50% < 3 degrees

90% < 10 degrees

50% < 39 cm

90% < 70 cm

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• Data collection time• Rotational velocity

• Interference frequency

• Angulation filtering threshold– Minimum distance as a quality indicator

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Lower frequency estimation precision

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• Track fast moving targets• Rotational device

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• Develop a novel localization system– Spinning beacon– Indoor environment– Low cost– Sub-meter accuracy• 39cm / 70cm

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• Reduce the localization latency–Reduce the routing time• Distributed version• Data compression

• Track the fast moving targets

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r/d

0.10.30.5

0

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k

A

B

Xv

fA

fB

|fA-fB||fA + ΔfX - fB|

R

S A

S

S

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Time

Signal strength

• Each infrastructure perceives different Doppler shift.

• Localize the target by different Doppler shifts

Xv

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I

I

I

II

I

Maximum Doppler shiftf : 900 MHz ω : 2.5 round/secr : 30 cm ~ 50 cm

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0.3 ~ 1.5 sec 8 ~ 10 sec1st Doppler angulation

2nd Doppler angulation3rd Doppler angulation

Localization

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v(t)

S

X

α

x

y

dr

S : (r cosθ, r sinθ, 0)v(t) = (-ωr sinθ, ωr cosθ, 0)

θ(t) = ωt+φ

X : (d cosα, d sinα, h)

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