1 Bandwidth-aware Breach-free Barrier Construction with VANET nodes for Realtime Fugitive Search Donghyun Kim*, Junggab Son*, Wei Wang** , Deying Li***, Alade O. Tokuta*, Sunghyun Cho + * Department of Mathematics and Physics, North Carolina Central University, Durham, NC, USA ** Schoo of Mathematics and Statistics, Xi'an Jiaotong University, Xi'an, China *** School of Information, Renmin University of China, China + Department of Computer Science and Engineering, Hanyang University, South Korea
Transcript
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Bandwidth-aware Breach-free Barrier Construction with VANET nodes for
Realtime Fugitive Search
Donghyun Kim*, Junggab Son*, Wei Wang** , Deying Li***, Alade O. Tokuta*, Sunghyun Cho+
* Department of Mathematics and Physics, North Carolina Central University, Durham, NC, USA** Schoo of Mathematics and Statistics, Xi'an Jiaotong University, Xi'an, China
*** School of Information, Renmin University of China, China+ Department of Computer Science and Engineering, Hanyang University, South Korea
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Agenda
• Introduction• Problem Formulation
– Abstraction of Metropolitan Area Topology– Breach of Sensor Barriers– Formal Definition of Problem
• Main Contribution – Polynomial Time Exact Algorithm– Checking Integrity of a VANET Barrier– Barrier-breach between Two VANET Barriers– Scheduling Subsets for Breach-free Barrier
• Concluding Remarks
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Introduction
• Vehicular Ad hoc NETwork (VANET)– An adhoc network of highly mobile nodes, in particular
• VANET applications– Remote vehicle personalization and diagnostics– Internet access– Digital map downloading– On-demand-basis real-time visual data collection
• Pics-on-wheel (POW): mobile cloud-based real-time street visual data collection system [2]
• Vehicle Witnesses as a Service (VWaaS): privacy enhanced version of POW [3]
– and many more.
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Introduction
• Q: Collecting Real-time Visual Images of Suspects Who Are Trying to Leave Area of Interest using VANET nodes?– VANET nodes are expected to have visual sensors and
wireless transceivers
Image source: http://humandrama.tistory.com/975
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Introduction
– People care their privacy• Normally, reluctant to reveal their current locations and/or their
future travel schedule
– Under urgent/emergent situation, e.g. Boston Bombing• Previous experiences show many people may voluntarily
disclose their locations and give up their privacy
Image source: http://ipvm.com/
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Introduction
• Still, the future trajectories of VANET nodes may not be controllable, but may provide their current locations and short-term future trajectories
• Asking all nodes to transmit real-time video would generate too much network traffic
– Abstraction of Metropolitan Area Topology– Breach of Sensor Barriers– Formal Definition of Problem
• Main Contribution – Polynomial Time Exact Algorithm– Checking Integrity of a VANET Barrier– Barrier-breach between Two VANET Barriers– Scheduling Subsets for Breach-free Barrier
• Concluding Remarks
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Problem Formulation
• Problem Statement– How to operate a subset of VANET nodes
• to provide (inside-out) barrier-coverage over an area of interest to detect fugitives leaving an area of interest during a given mission period
– Assume• the area of interest is a huge metropolitan area,• the mission period consists of a series of time slots,• the travel schedule of each VANET node is known for next T
time slots,• each participating VANET node is with visual sensors and
wireless connectivity to the central authority, and• are either moving on the road and parked on a parking lot,
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Problem Formulation
• Abstraction of Metropolitan Area Topology– Assume the shape of the map M of a metropolitan area
is a rectangle– Partition M into regular squares whose length and
width are r– Construct a topology graph G=(V, E)
(a)
(b)
r
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Problem Formulation
• Barrier coverage of a sensor network and breach [27]
a
b
c
d
e
1g
2g
x
y
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Problem Formulation
• Adoption of the Concept of Breach to Our Context
p p
(a) (b) (c)
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Problem Formulation
• Seamless VANET barrier coverage problem (SVBCP)– Given
• the location of each VANET node at each time slot in [0, T], • find a VANET node operation schedule (a collection of subsets
of nodes) which does not have two subsets at t-time slot and (t+1)-time slot, between which there exists a breach, and (b) the size of each subset does not exceed a network limit, b.
(a) (b)
q
p1a
2a3a
4a5a
6a7a
8a
9a 10a
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Problem Formulation
• Seamless VANET barrier coverage problem (SVBCP)
q
p
q
p
Q: There might be more than one choice from one slot to the next slot – which one does not lead to the dead end?
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Agenda
• Introduction• Problem Formulation
– Abstraction of Metropolitan Area Topology– Breach of Sensor Barriers– Formal Definition of Problem
• Main Contribution – Polynomial Time Exact Algorithm– Checking Integrity of a VANET Barrier– Barrier-breach between Two VANET Barriers– Scheduling Subsets for Breach-free Barrier
• Concluding Remarks
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Main Contributions
• Three Key Questions– Given a city map abstraction , the initial location , and a
subset of nodes , the locations of participating VANET nodes at the -th time slot, how to determine if provides a (inside-out) barrier coverage over against ?
– Given and two barriers and , how to determine if there is no breach when is replaced by .
– How to design a polynomial time exact algorithm for SVBCP?
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Checking Integrity of a VANET Barrier
– Given a city map abstraction , the initial location , and a subset of nodes , the locations of participating VANET nodes at the -th time slot, how to determine if provides a (inside-out) barrier coverage over against ?
• Step 1: modify to a directional graph
• Step 2: compute a path from to – the existence of such path implies the existence of a covert
path for the fugitive
such that any incoming directional edge to a VANET node in is removed
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Barrier-breach between Two VANET Barriers
• In our context, – a breach between two barriers is a node in such that
• used to reachable to , but not reachable to , but• now, not reachable to , but reachable to (outside the current
barrier, and thus get to almost immeidately)
q
p
q
p
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Scheduling Subsets for Breach-free Barrier
• For each i-th time slot – find all possible configurations (a subset with size b)– edge from one configuration at i-th time slot to another
configuration at i+1 time slot– find s-t path 0S 1S 2S TS
… … … …
…
10,s
20,s 21,s
11,s
… ts
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Analysis
• Theorem 1– The proposed strategy solves the SVBCP correctly.
• Theorem 2– The running time of the proposed algorithm is
polynomial
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Agenda
• Introduction• Problem Formulation
– Abstraction of Metropolitan Area Topology– Breach of Sensor Barriers– Formal Definition of Problem
• Main Contribution – Polynomial Time Exact Algorithm– Checking Integrity of a VANET Barrier– Barrier-breach between Two VANET Barriers– Scheduling Subsets for Breach-free Barrier
• Concluding Remarks
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Concluding Remarks
• Proposed a polynomial exact algorithm for SVBCP
• Will Consider– Smaller running time– Less assumptions
• more sophisticated assumption for network bandwidth• more practical VANET node mobility• unpredictability
