Zhongli Liu, UMass Lowell
Yinjie Chen, UMass Lowell
Benyuan Liu, UMass Lowell
Chengyu Cao, University of Connecticut
Xinwen Fu, UMass Lowell


Introduction

HAWK - a mini Helicopter-based Aerial
Wireless Kit

Evaluation

Conclusion
CS@UML
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Infrastructure :
GPS Constellation
Target : smartphone
Infrastructure :
WiFi Access Points



Self-positioning: target calculates its own position
Infrastructure positioning: the infrastructure calculates the target’s position
Third party wireless localization of target
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Localization via received signal strength (RSS)
Broad applications in public safety, cyber forensics, network management
CS@UML
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
Introduction

HAWK - a mini Helicopter-based Aerial
Wireless Kit

Evaluation

Conclusion
CS@UML
5

Problem Definition: How to locate a wireless target device by HAWK
Basic idea: Use the location where HAWK senses the strongest signal strength sending from target device as the location of the target
CS@UML
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1.
What is the flight route for the helicopter?
2.
How to ensure a target will be detected?
3.
How to implement reliable waypoints?
4.
What is target location?
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1. What is the flight route for the helicopter?
Moore space filling curve can be used as a flight route
Reasons:
 It is a space-filling curve
 A level n Moore curve covers all unit squares with the shortest distance
 It begins and ends at the same point
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2. How to ensure a target will be detected?
 Principle 1: During the flight in a unit square, HAWK senses at least one packet from target in that unit square
 Principle 2: To save battery power, a proper level of Moore curve is critical while satisfying Principle 1
 Proper level: flight speed v, square side width d, transmission radius R and transmission interval t




 d
 n
2 2 d
2 n
 vt
2
R
(1)
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3. How to implement reliable waypoints?
 Moore curve is a direct application of the waypoints functionality
 Factors such as wind may affect helicopter’s movement during flight
 Three parameters of the mini helicopter, pitch, roll, and yaw can be adjusted
 PI-control law is written as:
  p
 i
 t u ( ) k
0
( )
(2)
P roportional I ntegral
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4. What is target location?
 We use the location where the strongest RSS is sensed as the target device’s location
 A target device may be located in the unit square where the strongest RSS from the target is sensed or one of its eight surrounding unit squares
CS@UML
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
Introduction

HAWK - a mini Helicopter-based Aerial
Wireless Kit

Evaluation

Conclusion
CS@UML
12

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



Helicopter: Draganflyer X6 with GPS
Wireless sniffer: Nokia N900
Handheld controller: emergency controller
Software controller on a laptop: control takeoff and flight and receive telemetry including GPS from helicopter
Locator on the laptop: show route on Google map in real time, and download data from N900 for location calculation
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 Mini helicopter, with sniffer, flied over buildings
 Sniffer ran Kismet
 HAWK identified APs
 Google Map showed flight route and APs’ locations
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Experiments to locate 12 smart phones on track field
Result:
 One Nokia N900 with Kismet
 Warwalking on the tracks and three different flight routes
 Five meters localization accuracy on average for a level 3 Moore curve
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http://www.youtube.com/watch?v=ju86xnHbEq0
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Disadvantages of W.A.S.P (Wi-Fi Aerial Surveillance
Platform):
 A mini airplane that has to fly at a relatively high speed in order to float in the air
 Limited localization and surveillance capability because W.A.S.P cannot satisfy Formula (1)
CS@UML
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
Introduction

HAWK - a mini Helicopter-based Aerial
Wireless Kit

Evaluation

Conclusion
CS@UML
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 Developed a fully functional Mini Helicopter-based Aerial
Wireless Kit (HAWK)
 Proposed a suite of theories for HAWK conducting accurate localization
 Moore curve based flight route, considering flight velocity, target transmission interval and target transmission range
 Customized PI control laws for reliable navigation
 Conducted extensive real-world experiments to validate the feasibility of HAWK for localization
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Student Research Competition Silver Medal at Mobicom 2011
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Simulations to validate the hot area (nine unit squares) theory
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Disadvantages of W.A.S.P (Wi-Fi Aerial Surveillance
Platform):
 A mini airplane that has to fly at a relatively high speed in order to float in the air
 Limited localization and surveillance capability because W.A.S.P cannot satisfy Formula (1)
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Comparison of localization strategy for accuracy
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