Event:
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PhD Defense:
Time: Monday, February 21,  2011,   10:00 AM
Location:   E&CS Building 1st Floor Auditorium

PhD Student:
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Khaled Ibrahim

Committee Members:
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Dr. Michele C. Weigle ( Advisor)
Prof. Kurt Maly
Prof. Hussein Abdel-Wahab
Prof. Stephan Olariu
Dr. Tamer Nadeem

Thesis Title:
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"Data Aggregation and Dissemination in Vehicular Ad-Hoc Networks"

Abstract
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Vehicular Ad-Hoc Networks (VANETs) is a fast growing technology that many
governments and automobile manufacturers are investing in to provide not only
safer and more secure roads, but also informational and entertainment-based
applications for drivers. The applications developed for VANET can be
classified into multiple categories (safety, informational, and infotainment,
etc.). Most VANET applications, regardless of their category, depend on
having certain vehicular data (vehicular speed, X position and Y position)
available. Although these applications seem to use the same vehicular data,
the characteristics of this data (i.e. data accuracy, data refresh or update
rate and data amount) will vary based on the application category. For
example, safety applications need an accurate version of the vehicular data
with high frequency, but for short distances. Informational applications
relax the data frequency constraint as they need the vehicular data to be
reasonably accurate with less frequency, but for longer distances. If each
of these applications shares the vehicular data with only its peers using
its own mechanism, this behavior will not only introduce redundant
functionalities (sending, receiving, processing, etc.) for handling the same
data, but also wastefully consume the bandwidth by broadcasting the same
data multiple times. Despite the differences in the data characteristics
needed by each application, this data can be still shared. Vehicular
networks introduce the potential for many co-existing applications. If we do
not address the problem of data redundancy early, it may hinder the
deployment and usefulness of many of these applications.

Therefore, we designed and developed a framework, CASCADE, for efficiently
aggregating and disseminating commonly-used vehicular data. CASCADE is
architected as a layer that provides applications with a customized version of
the vehicular data. CASCADE customizes the vehicular data passed to each
application to satisfy the data characteristics needed by each based on certain
parameters that each application registers with CASCADE. Additionally, the
framework performs the common data handling functionalities (data sending,
receiving, aggregating, etc.) needed by the applications.

This dissertation makes the following contributions:
- a lossless data compression technique based on differential encoding that is
  a good fit for the characteristics of vehicular data
- a syntactic data aggregation mechanism that can represent the vehicular data
  in a 1.5km area in one IEEE 802.11 frame
- a light-weight position verification technique that quickly detects false
  data with very low false positives
- a probabilistic data dissemination technique that alleviates the spatial
   broadcast storm problem and effectively uses the bandwidth to disseminate data
   to distant areas in a short amount of time in addition to having less
   redundancy and more coverage than other techniques.
- a mechanism for recovering from the communication discontinuity problem in
  short time based on the traffic density in the opposite direction
- an investigation of the possible data structures for representing the
  vehicular data in a searchable format
- a parametric mechanism for matching the vehicular data and providing a
  customized version of the data that satisfies certain characteristics based on
  the parameter value

CASCADE through its four major components, local view, extended view, data
security and data dissemination, provides an efficient solution for problem of
scalability for VANET applications.