Title: Incorporating Design Knowledge into Genetic Algorithm-based White-Box Software Test Case Generators
Speaker: Matthew C. Makai
Date: April 24th 2008, 2pm, NVC Room 322
Title: Design and Analysis of Adaptive Fault Tolerant QoS Control Algorithms for Query Processing in Wireless Sensor Networks
Speaker: Anh Phan Speer
Date: April 17, 2008, 1pm, NVC Room 320
Title: Design and Analysis of Adaptive Fault Tolerant QoS Control Algorithms for Query Processing in Wireless Sensor Networks
Speaker: Anh Phan Speer
Date: Dec. 20 2007, 11am, NVC Room 320
Title: Service-Oriented Sensor-Actuator Networks
Speaker: Abdelmounaam Rezgui
Date: November 29th 2007, 10am, NVC Room 106
Title: Multi-channel Mobile Access to Web Services
Speaker: Xu Yang
Date: November 26th 2007, 5pm, NVC Room 111
Title: Empirical Analysis of Value and Reference Semantics
Speaker: Neha Khedekar
Date: August 10th 2007, 2pm, NVC Room 314
Title: A component-based approach to proving the correctness of the Schorr-Waite algorithm
Speaker: Amrinder Singh
Date: August 9th 2007, 2pm, NVC Room 325
Title: Support for Subjective Views in Collaborative Virtual Environments
Speaker: Jianghui Ying
Date: July 19 2007,5pm, NVC Room 111
Title: Multi-channel Mobile Access to Web Services
Speaker: Xu Yang
Date: June 14, 5pm, 2007, Room 103
Title: Design and Analysis of QoS-Aware Key Management and Intrusion Detection Protocols for Secure Mobile Group Communications in Wireless Networks
Speaker: Jin-Hee Cho
Date: May 9, 10am, 2007. Room 320
Title: A Framework for Resource and Pricing Management for Revenue Optimization with QoS Guarantees for Multiple Service Classes in Wireless Networks
Speaker: Okan Yilmaz
Date: March 21, 2pm, 2007. Room 207
Title: MOBILITY AND SERVICE MANAGEMENT FOR FUTURE ALL-IP BASED WIRELESS NETWORKS
Speaker: Weiping He
Date: Dec. 12, 2pm, 2006. Room 324
Title: Abnormal Pattern Recognition in Spatial Data
Speaker: Yufeng Kou
Date: Nov. 29, 10am, 2006. Room 103
Title: Efficient Concurrent Operations in Spatial Databases
Speaker: Jing Dai
Date: Oct. 30, 10am, 2006. Room 103
Title: Design and Analysis of Adaptive Fault Tolerant QoS Control Algorithms for Query Processing in Wireless Sensor Networks
Speaker: Anh Phan Speer
Date: Oct. 20, 1pm, 2006. Room 320
Title: Software Agents for DLNET Content Review - Study and Experiment
Speaker: Seema Mitra
Date: August 31, 1pm, 2006. Room 204 (max cap. 30)
Title: The Design and Implementation of the Tako Language and Compiler
Speaker: Jyotindra Vasudeo
Date: May 5th, 12:30pm, 2006
Title: Managing Changes to Service Oriented Enterprises
Speaker: M. Salman Akram
Title: Design and Analysis of Algorithms for Efficient Location and Service Management in Mobile Wireless Systems
Speaker: Baoshan Gu
Date: Sep. 30th 1:00pm-3:00pm
You are cordially
invited to attend Matthew’s MS Defense
April 24th 2008, 2pm, NVC Room 322
Speaker: Matthew C. Makai
Title:
Incorporating Design Knowledge into Genetic
Algorithm-based White-Box Software Test Case
Generators
Abstract:
This thesis shows how design knowledge can be
extracted from Unified Modeling Language sequence
diagrams and incorporated into genetic
algorithm-based automated test case generators to
increase the coverage of their test cases. Automated
generation of test data through evolutionary testing
was proven feasible in prior research studies. In
those previous investigations, the metrics used for
determining the test generation method effectiveness
were the percentages of testing statement and branch
code coverage achieved. However, the code coverage
realized in those preceding studies often converged
at suboptimal percentages due to a lack of guidance
in conditional statements. This study examines a
tool known as the Evolutionary Test Case Generator,
or ETCG (pronounced "e-tee-see-gee"), which provides
an improved method for automatically producing test
case suites using genetic algorithms. Test case
production is accomplished by a novel method for
incorporating design knowledge into the evolutionary
test case generation process. In this study, common
Unified Modeling Language sequence diagrams provide
design knowledge to direct the heuristic search
process and facilitate the production of test cases.
The design knowledge, measured by the number of
sequence diagrams associated with the source code
incorporated into the generation process, provides
guidance to the searches for apposite test cases.
When the generator uses design knowledge, the
resulting test cases converge at higher code
coverage percentages that are unattainable when the
design knowledge is not utilized.
You are cordially
invited to attend Ahn’s PhD Final Defense
April 17, 2008, 1pm, NVC Room 320
Speaker: Anh Phan Speer
Title:
Design and Analysis of Adaptive Fault
Tolerant QoS Control Algorithms for Query Processing
in Wireless Sensor Networks
Abstract:
Wireless sensor networks (WSNs) present several
unique characteristics such as resource-constrained
sensors, random deployment, and data-centric
communication protocols. These characteristics pose
unprecedented challenges in the area of query
processing in WSNs. This dissertation presents the
design and validation of adaptive fault tolerant QoS
control algorithms with the objective to achieve the
desired quality of service (QoS) requirements and
maximize the system lifetime in query-based WSNs.
Data sensing and retrieval in WSNs have a great
applicability in military, environmental, medical,
home and commercial applications. In query-based
WSNs, a user would issue a query with QoS
requirements in terms of reliability and timeliness,
and expect a correct response to be returned within
the deadline. Satisfying these QoS requirements
requires that fault tolerance mechanisms through
redundancy be used, which may cause the energy of
the system to deplete quickly. We analyze the effect
of redundancy on the mean time to failure (MTTF) of
query-based cluster-structured WSNs, defined as the
mean number of queries that a WSN is able to answer
correctly until it fails due to channel faults,
sensor faults, or sensor energy depletion. We show
that a tradeoff exists between redundancy and MTTF.
Furthermore, an optimal redundancy level exists such
that the MTTF of the system is maximized.
We develop a hop-by-hop data delivery (HHDD)
mechanism and an Adaptive Fault Tolerant Quality of
Service Control (AFTQC) algorithm in which we
utilize "source" and "path" redundancies with the
goal to satisfy application QoS requirements while
maximizing the lifetime of WSNs. We also compare and
contrast AFTQC without acknowledgment vs. AFTQC with
acknowledgement and identify conditions under which
AFTQC should couple with acknowledgement to maximize
the system MTTF.
To deal with network dynamics, we investigate
proactive and reactive methods to dynamically
collect channel and delay conditions to determine
the optimal redundancy level at runtime. AFTQC can
adapt to network dynamics that cause changes to the
node density, residual energy, sensor failure
probability, and radio range due to energy
consumption, node failures, and change of node
connectivity. Further, AFTQC can deal with software
faults, concurrent query processing with distinct
QoS requirements, and data aggregation.
We compare our design with a baseline design without
redundancy based on acknowledgement for data
transmission and geographical routing for relaying
packets to demonstrate the feasibility. We validate
analytical results with extensive simulation
studies. When given QoS requirements of queries in
terms of reliability and timeliness, our AFTQC
design allows optimal "source" and "path"
redundancies to be identified and applied
dynamically in response to network dynamics such
that not only query QoS requirements are satisfied,
as long as adequate resources are available, but
also the lifetime of the system is maximized.
You are cordially
invited to attend Ahn’s PhD Research Defense
Dec. 20 2007, 11am, NVC Room 320
Speaker: Anh Phan Speer
Title:
Design and Analysis of Adaptive Fault
Tolerant QoS Control Algorithms for Query Processing
in Wireless Sensor Networks
Abstract:
Wireless sensor networks (WSNs) present several
unique characteristics such as resource-constrained
sensors, random deployment, and data-centric
communication protocols. These characteristics pose
unprecedented challenges in the area of query
processing in WSNs. This dissertation presents the
design and validation of adaptive fault tolerant QoS
control algorithms with the objective to achieve the
desired quality of service (QoS) requirements and
maximize the system lifetime in query-based WSNs.
Data sensing and retrieval in WSNs have a great
applicability in military, environmental, medical,
home and commercial applications. In query-based
WSNs, a user would issue a query with QoS
requirements in terms of reliability and timeliness,
and expect a correct response to be returned within
the deadline. Satisfying these QoS requirements
requires that fault tolerance mechanisms through
redundancy be used, which may cause the energy of
the system to deplete quickly. We analyze the effect
of redundancy on the mean time to failure (MTTF) of
query-based cluster-structured WSNs, defined as the
mean number of queries that a WSN is able to answer
correctly until it fails due to channel faults,
sensor faults, or sensor energy depletion. We show
that a tradeoff exists between redundancy and MTTF.
Furthermore, an optimal redundancy level exists such
that the MTTF of the system is maximized.
We develop a hop-by-hop data delivery (HHDD)
mechanism and an Adaptive Fault Tolerant Quality of
Service Control (AFTQC) algorithm in which we
utilize "source" and "path" redundancies with the
goal to satisfy application QoS requirements while
maximizing the lifetime of WSNs. We also compare and
contrast AFTQC without acknowledgment vs. AFTQC with
acknowledgement and identify conditions under which
AFTQC should couple with acknowledgement to maximize
the system MTTF.
To deal with network dynamics, we investigate
proactive and reactive methods to dynamically
collect channel and delay conditions to determine
the optimal redundancy level at runtime. AFTQC can
adapt to network dynamics that cause changes to the
node density, residual energy, sensor failure
probability, and radio range due to energy
consumption, node failures, and change of node
connectivity. Further, AFTQC can deal with software
faults, concurrent query processing with distinct
QoS requirements, and data aggregation.
We compare our design with a baseline design without
redundancy based on acknowledgement for data
transmission and geographical routing for relaying
packets to demonstrate the feasibility. We validate
analytical results with extensive simulation
studies. When given QoS requirements of queries in
terms of reliability and timeliness, our results
allow optimal "source" and "path" redundancies to be
identified by AFTQC such that not only QoS
requirements are satisfied, but also the lifetime of
the system is prolonged. Finally AFTQC is
demonstrated to maximize the MTTF of the system
despite the presence of network dynamics.
You are cordially
invited to attend Abdelmounaam’s PhD Final Defense
November 29th 2007, 10am, NVC Room 106
Speaker: Abdelmounaam Rezgui
Title:
Service-Oriented Sensor-Actuator Networks
Abstract:
For decades since their inception, sensor-actuator
networks (SANETs) have been closed networks owned,
maintained, and used by a single party, e.g., a
government agency, a research institution, or a
private company. Typically, the network is designed
and deployed to serve one or a few applications with
a specic set of characteristics. In subsequent
years, the need to decouple SANETs from the
applications using them led to the emergence of
generic SANETs, an alternative design model where an
application-independent query system is deployed on
each node of the SANET. In this model, the query
system is designed to answer queries from any
application. Both application-specic and generic
SANET architectures are inherently inadequate to
support the next-generation of open, interoperable,
pervasive, multi-purpose, Web-accessible SANETs.
Indeed, application-specic SANETs provide limited
reusability, are not cost eective, and may require
extensive reprogramming eorts when new applications
need to use the network. Generic SANETs usually
require that a sizeable code be deployed on the
nodes regardless of the specic requirements of the
application at hand. More importantly, they may not
be optimized to fully exploit the specic
characteristics and query patterns of a given
application. We argue that the next-generation of
SANETs require customizable architectures where
SANETs may consist of nodes that have heterogeneous
hardware and software components and are managed by
autonomous entities. Customizable SANETs would
provide developers the ability to select individual
software components from several SANETs that are
already deployed and integrate these components in
new applications. These SANETs must expose their
capabilities to developers at an adequate level of
abstraction and, yet, achieve high eciency,
scalability and reusability. In this dissertation,
we propose service-oriented SANETs (SOSANETs) as a
novel approach for building customizable SANETs. In
SOSANETs, nodes expose their capabilities to
applications in the form of service proles. A node's
service prole consists of a set of services (i.e.
sensing and actuation capabilities) that it provides
and the quality of service (QoS) parameters
associated with those services (delay, accuracy,
freshness, etc.). Services are lightweight code
units deployed directly on top of the operating
system of nodes. SOSANETs provide the benets of both
application-specic SANETs (e.g., energy eciency,
scalability) and generic SANETs (e.g., reusability),
and avoid most of their limitations. Developing
SOSANETs entails, in particular, three major
research challenges: (i) defining a query model and
a system architecture to support that model, (ii)
developing new routing protocols, and (iii)
developing new query processing techniques. In this
research, we address each of these challenges and
demonstrate SOSANETs's potential in supporting the
next-generation of sensor infrastructures.
Our contributions may be summarized as follows:
1. Service-Oriented Query Model and Architecture for
SANETs: We introduce service-oriented
sensor-actuator networks as a new paradigm for
building the next generation of open, interoperable,
customizable sensor-actuator networks. We dene a
query model for SOSANETs and propose an architecture
that supports that model. The proposed query model
oers a simple, uniform query interface whereby
applications specify sensing and actuation queries
independently from any specic deployment of the
underlying SOSANET.
2. Routing Protocols: We developed RACER (Reliable
Adaptable serviCe-driven Efficient Routing), a
routing protocol suite for SOSANETs. RACER consists,
essentially, of three routing protocols, namely,
SARP (Service-Aware Routing Protocol), TARP
(Trust-Aware Routing Protocol), and CARP
(Context-Aware Routing Protocol). RACER uses an
ecient service-aware routing approach that
aggressively reduces downstream trac (from the sink
to the network's nodes) by translating service
proles into ecient paths for queries. To support
QoS, RACER dynamically adapts each node's routing
behavior and service prole according to the current
context of that node, i.e. number of pending queries
and number and type of messages to be routed.
Finally, RACER improves end-to-end reliability
through a scalable reputation-based approach in
which each node is able to locally estimate the next
hop of the most reliable path to the sink.
3. Query Processing and Optimization: We introduce a
set of query optimization techniques that contribute
to the ecient execution of queries. These techniques
include service-driven sleep scheduling,
service-based multi-query processing, and
multi-event detection.
4. Implementation and Evaluation: To validate our
work, we implemented TinySOA, a prototype SOSANET
built on top of TinyOS 1.1.15 with RACER as its
routing mechanism. A design approach that has proved
its merit in wireless networks is cross- layer
optimization. Given the promise of this design
approach and the advantages of layered design, we
designed and implemented TinySOA as a set of layers
with a loose interaction model that enables several
cross-layer optimization options. We conducted an
evaluation of TinySOA that included a comparison
with TinyDB, an established query processing system
for sensor networks. The obtained empirical results
show that TinySOA achieves signicant improvements on
many aspects including energy consumption,
scalability, reliability and response time.
Sensor-actuator networks are an integral component
in the vision of ubiquitous service environments. As
they mature, SANETs will be used in a wide spectrum
of applications. This will transform SANETs into a
"utility" that will support much of the societal
activities. Providers will deliver this utility to
"consumers" as a service. To SANET providers and
consumers, the challenges will be the same:
improving eciency, reliability, scalability, and
interoperability while reducing development and
maintenance cost. This will translate into a host of
new requirements. Current architectures are
inherently unable to support those requirements.
They also are not able to properly exploit the
benets of recent and future advances in related
technologies. The architecture and protocols
proposed in this dissertation are a fundamental
departure from all existing approaches for SANET
architectures and protocols. Theoretical and
empirical results show that a service-oriented
architecture design is a viable candidate to support
the requirements of tomorrow's sensor-actuator
networks. We regard our work as a milestone in
demonstrating the potential of SOSANETs. We expect
its impact to be signicant on the design,
development, and deployment of future SANETs. This
impact will span several aspects including cost,
development time, eciency, interoperability, and
scalability. In fact, our work readily applies to
any SANET-like wireless networks where the main
characteristics are nodes with limited energy supply
and lossy communication links. We anticipate that
this work will foster research that would
reformulate and address many of the problems
encountered in developing and deploying today's
sensor systems.
You are cordially
invited to attend Xu’s PhD Final Defense
November 26th 2007, 5pm, NVC Room 111
Speaker: Xu Yang
Title:
Multi-channel Mobile Access to Web Services
Abstract:
To support wireless-oriented services, a new
generation of Web services called Mobile services
(M-services) has emerged. M-services provide mobile
users access to services through wireless networks.
One of the important issues in M-service environment
is how to discover and access M-services
efficiently. In this dissertation, we propose time
and power efficient access methods for M-services.
We focus on methods for accessing broadcast based
M-services from multiple wireless channels. We first
discuss efficient access methods in data-oriented
wireless broadcast sys- tems. We then discuss how to
extend current wireless broadcast systems to support
simple M-services. We present a novel infrastructure
that provides a multi-channel broadcast framework
for mobile users to effectively discover and access
composite M-services. Multi-channel algorithms are
proposed for efficiently accessing composite
services. We define a few semantics that have impact
on access efficiency in the pro- posed
infrastructure. We discuss semantic access to
composite services. Broadcast channel organizations
suitable for discovering and accessing composite
services are proposed. We also derive analytical
models for these channel organizations. To provide
practical study for the proposed infrastructure and
access methods, a testbed is developed for
simulating accessing M-services in a broadcast-based
environment. Extensive experiments have been
conducted to study the proposed access methods and
broadcast channel organizations. The experimental
results are presented and discussed.
You are cordially
invited to attend Neha’s MS Defense
August 10th 2007, 2pm, NVC Room 314
Speaker: Neha Khedekar
Title:
Empirical Analysis of Value and
Reference Semantics
Abstract:
In this thesis, we attempt to measure the impact of
reference semantics on programming and reasoning.
There is a lot of anecdotal evidence that references
and aliasing complicate both formal and informal
reasoning, but there is a lack of empirical data on
the topic. In this thesis, we have designed a survey
that is used to compare how well programmers perform
under different programming paradigms. Two of the
programming paradigms studied in the survey, copying
and swapping, use value semantics, while the third,
referencecopying, uses reference semantics. We have
given the survey to over 25 people who have various
levels of Java programming experience. The results
of the survey seem to support the anecdotal evidence
that programming with value semantics is easier than
programming with reference semantics.
You are cordially
invited to attend Amrinder’s MS Defense
August 9th 2007, 2pm, NVC Room 325
Speaker: Amrinder Singh
Title:
A component-based approach to proving the
correctness of the Schorr-Waite algorithm
Abstract:
This thesis presents a component-based approach to
proving the correctness of programs involving
pointers. Unlike previous work, our component-based
approach supports modular reasoning, which is
essential to the scalability of systems.
Specifically, we specify the behavior of a
graph-marking algorithm known as the Schorr-Waite
algorithm, implement it using a component that
captures the behavior and performance benefits of
pointers, and prove that the implementation is
correct with respect to the specification. We use
the Resolve language in our example, which is an
integrated programming and specification language
that supports modular reasoning. The behavior of the
algorithm is fully specified using custom
definitions, pre- and post-conditions, and a complex
loop invariant. Additional operations for the
Resolve pointer component are introduced that
preserve the accessibility of a system. These
operations are used in the implementation of the
algorithm. They simplify the proof of correctness
and make the code shorter.
You are cordially
invited to attend Jianghui’s PhD Research Defense
July 19 2007, 5pm, NVC Room 111
Speaker: Jianghui Ying
Title:
Support for Subjective Views in
Collaborative Virtual Environments
Abstract:
Collaborative Virtual Environments (CVEs) use a
shared virtual world to support interactions and
collaboration among users. The majority of CVEs
provide a highly objective virtual environment. That
is, each user is presented with the same virtual
world in the same way, albeit from diRerent
viewpoints. This is partly due to the fact that
multi-user Virtual Reality (VR) systems have evolved
from single-user systems that have been extended to
support a number of users. The development trend of
VR systems is similar to the way that groupware
systems evolved from 2D single-user systems that
simply replicated the single-user interface to
multiple users. WYSIWIS (What You See Is What I See)
is the foundational abstraction that guided the
multi-user interface design of early groupware
systems. WYSIWIS is critical for collaboration.
However, some research has indicated that the strict
objectivity is too inXexible. In some cases it may
even hinder collaboration if all users are forced to
work on the same representation without the
capability to tailor the view to meet their own
needs. This has led to the development of the
Relaxed-WYSIWIS 2D user interface design. Just as
the strict WYSIWIS proved too limited in 2D shared
user interface, there is a need to extend current
multi-user virtual environments to support
subjectivity. The concept of "Subjective View" is
introduced to give users ability to control the
presentation of the virtual world to best suit their
needs. In a CVE interface, subjectivity is a dicult
issue. It can provide great benet to users, however,
it might also pose problems for users' cooperation
if used inappropriately. The goal of this research
is to explore the approach of supporting appropriate
subjective views in Collaborative Virtual
Environments (CVEs). The hypothesis of this research
is that, under certain conditions, subjective views
can improve user and task performance over certain
tasks in CVEs compared to the corresponding
objective view.
Our approach is based on the assumption that in a
CVE, only a subset of information, core information,
about the environment is needed to support
collaboration. The rest of the informa- tion,
auxiliary information, is not important for
collaboration tasks. Auxiliary information can be
presented in diRerent ways without impacting on the
collaboration tasks. To build an eRective Subjective
Views CVE (SVCVE) system, we need to maintain
consistent awareness among collaborative users under
subjective views. To achieve that, we look at a CVE
as composed of two layers: the syntax layer, which
is the cooperative interface specic information, and
the semantics layer, which is the underlying
application functionality. In a subjective
environment, what users see from the syntax layer
could be very diRerent. However, from the semantics
level, all users should get the same or nearly the
same knowledge. We believe the semantics associated
with the CVE is the foundation to maintain
consistency. The CVE semantic is modeled using a
formal method - Petri net. Petri net is a promising
formal model. It is a state-oriented formal
specication notation. The Petri net model provides a
foundation for our work. In order to support a
general way of building SVCVE systems, we presented
a framework sup- porting the process of going from
analyzing initial 3D content describing the virtual
environment to creating corresponding subjective
views for the CVE. We discussed a general subjective
views CVE model and a corresponding Petri net based
hierarchical model to describe the relationship
among diRerent views in SVCVE system. Based on that,
a SVCVE system implementation framework is proposed.
In order to illustrate the process and the
implementation framework, we implemented a prototype
system and used it for case studies. Furthermore, we
discussed how to analyze SVCVE system
characteristics using Petri net inherent properties
such as reachability, reinitiability, boundedness,
etc. We also performed a pilot study using a simple
case study to evaluate user and task performance in
diRerent subjective views. when providing views with
suitable degree of subjectivity in CVE, user would
have better performance in certain collaborative
tasks. In future work, in order to prove the above
hypothesis, we will evaluate the user and task
performance by applying subjective views under two
conditions: symmetric condition (same resources such
as platforms, input/output devices, etc.) and
asymmetric condition (diRerent resources). Under
symmetric condition, we will focus on how users'
personal preferences will help to improve the
performance while maintaining semantic consistency.
Under asymmetric condition, we will focus on
leveraging subjective views to minimize the semantic
inconsistency caused by system diRerence in order to
better support eRective collaboration.
You are cordially
invited to attend Xu’s PhD Research Defense
June 14, 5pm, 2007, Room 103
Speaker: Xu Yang
Title:
Multi-channel Mobile Access to Web Services
Abstract:
To support wireless-oriented services, a new
generation of Web services called Mobile services
(M-services) has emerged. M-services provide mobile
users access to services through wireless networks.
One of the important issues in M-service environment
is how to discover and access M-services
efficiently. The aim of our research is to
investigate time and power efficient access methods
to M-services. We focus on methods for accessing
broadcast based M-services from multiple wireless
channels. We also aim to provide a generic broadcast
based M-service infrastructure for delivering
services to mobile users. In our preliminary work,
we have discussed efficient data access methods and
how to organize and access simple M-services in a
broadcast based environment. In this report, we
focus on efficient access to composite services. We
first demonstrate the major challenges of
efficiently accessing broadcast-based composite
services. Then we present an enhanced M-services
infrastructure that provides a framework for mobile
users to effectively discover and access
broadcast-based composite M-services. The proposed
infrastructure uses multiple broadcast channels to
deliver required wireless information. Multi-channel
algorithms are proposed for efficiently accessing
composite services. We define a few semantics that
have impact on access efficiency in the proposed
infrastructure. We discuss semantic access to
composite services. Broadcast channel organizations
suitable for discovering and accessing composite
services are proposed. Analytical models for these
channel organizations are derived. To provide
practical study for the proposed infrastructure and
access methods, a testbed is implemented for
simulating accessing composite services in a
broadcast- based environment. Extensive experiments
have been conducted to study the proposed semantic
access method and broadcast channel organizations.
The experimental results are presented and
discussed.
You are cordially
invited to attend Jin-Hee’s PhD
Preliminary Exam defense
May 9, 10am, 2007. Room 320
Speaker: Jin-Hee Cho
Title:
Design and Analysis of QoS-Aware Key Management
and Intrusion Detection Protocols for Secure Mobile
Group Communications in Wireless Networks
Abstract:
Many mobile applications in wireless networks such as military battlefield, emergency response, mobile
commerce, online gaming, and collaborative work are based the notion of group communications. Designing security
protocols for secure group communications in wireless networks faces many technical challenges due to unique
characteristics of wireless networks including resource-constrained environments in bandwidth, memory size, battery
life, computational power, etc., openness to eavesdropping and security threats, unreliable communication, and, for
mobile ad hoc networks with no infrastructure support, rapid changes in topology due to user mobility which can
cause group merge/partition events to occur dynamically.
While satisfying security requirements is crucial for secure group communications in wireless systems,
mobile group applications often have application-specific performance requirements in terms of timeliness, reliability,
and system reconfigurability. Often there exists a tradeoff between security vs. performance goals since security
protocols may introduce undue computational and network overheads which may prevent performance goals from
being met.
Unlike traditional security protocols which concern security properties only, in this dissertation research we
propose and analyze a class of QoS-aware protocols for secure group communications in wireless networks with the
goal to satisfy not only security requirements in terms of secrecy, confidentiality, authentication, availability, and
data integrity, but also performance requirements in terms of latency, network traffic, response time, and
reconfigurability for secure group communication systems in wireless networks. These QoS-aware protocols are
adaptive in nature with designs to allow the system to dynamically adjust operational settings, under which both the
system’s security and performance requirements can be best satisfied, leveraging the inherent tradeoff between
performance vs. security goals.
This dissertation research has three contributions. First, we propose and analyze efficient, QoS-aware key
management protocols for secure group communications in wireless networks to deal with outsider attacks. In order
to efficiently reduce the network communication cost caused by rekeying operations (to change a group key), three
“threshold-based” periodic batch rekeying protocols are proposed and analyzed. The aim of these protocols is to
satisfy application security requirements while minimizing the network communication cost. Instead of individual
rekeying, i.e., performing a rekeying operation right after each group join or leave request, these protocols perform
batch rekeying periodically. We demonstrate that an optimal rekey interval exists for each protocol that would satisfy
an imposed security requirement while minimizing the network communication cost. We further compare these
protocols against individual rekeying to identify the best protocol that can minimize the communication cost of
rekeying while satisfying application requirements when given a set of parameter values characterizing the
operational and environmental conditions of the system. We report results for the case in which a centralized key
server exists in wireless networks. Future work will remove this restriction and investigate designs to apply these
threshold-based periodic batch rekeying protocols to infrastructure-less mobile ad hoc networks without a centralized
key server.
Second, we propose and analyze QoS-aware intrusion detection protocols for secure group communications
in wireless networks to deal with insider attacks. These protocols explore the tradeoff of security vs. performance
properties with the goal to determine the best periodic interval for performing intrusion detection. Specifically, we
consider a class of intrusion detection protocols including host-based and voting-based protocols for detecting and
evicting compromised nodes and examine their effect on the mean time to security failure (MTTSF) vs. the response
time performance metric. Our analysis reveals that there exists an optimal intrusion detection interval under which
the MTTSF metric can be best traded off for the response time performance metric, or vice versa. Furthermore, the
intrusion detection interval can be dynamically adjusted based on the attacker behaviors to maximize MTTSF while
satisfying a system-imposed response time requirement. We report results for the case in which all nodes are covered
by a single-hop peer-to-peer wireless network. Future work involves extending the design and analysis to the case in
which mobile nodes communicate with each other through multi-hop in mobile ad hoc networks.
Third, we propose and analyze a scalable and efficient region-based group key management protocol for
managing mobile groups in mobile ad hoc networks. For scalability and dynamic reconfigurability, we take a regionbased
approach by which group members are broken into region-based subgroups, and leaders in subgroups securely
communicate with each other to agree on a group key in response to membership change and member mobility
events. This key management protocol is proposed to identify the optimal size of a region that minimizes the
network communication cost while satisfying the application security requirements. Further, it allows mobile groups
to react to network partitioning/merging events for reconfigurability and survivability while still maintaining the
design goal of secure group communications in mobile ad hoc networks.
We propose to extend and integrate our research in periodic batch rekeying (for dealing with outsider
attacks) and distributed intrusion detection (for dealing with insider attacks) into the region-based group key
management protocol for secure group communications in mobile ad hoc networks. The target mobile group
communication system will be built upon our proposed two-level hierarchical key management structure for
scalability, reconfigurability and efficiency, as well as for adaptability to allow the system to dynamically choose the
best operational setting in response to runtime network conditions to trade performance off for security, or vice versa,
to best satisfy the application imposed performance and security requirements. We propose to perform comparative
analyses against secure group communication protocols that do not consider security vs. performance tradeoffs,
including those based on individual rekeying, static intrusion detection, and/or no-region designs. We propose to
evaluate the merits of our proposed QoS-aware security protocols for mobile group communications through modelbased
mathematical analyses with simulation validation.
You are cordially
invited to attend Yilmaz’s PhD
Preliminary Exam defense
March 21, 2pm, 2007. Room 207
Speaker: Okan Yilmaz
Title: A Framework for Resource and Pricing Management for
Revenue Optimization with QoS Guarantees for Multiple
Service Classes in Wireless Networks
Abstract:
We develop a framework for resource and pricing management
for revenue optimization with Quality of Service (QoS)
guarantees in personal communication service (PCS) wireless
networks that provide multiple service classes to roaming
mobile users.
The framework proposed in the dissertation research consists
of three parts. The first part is the development of a
workload characterization algorithm for calculating the
arrival and departure rates of multiple multimedia service
class from data statistically collected by individual mobile
users and the system. The workload characterization
algorithm provides information for the system to make
resource management decisions to admit or reject service
calls made by mobile users with the objective of maximizing
revenue with QoS guarantees.
he second part of the research is the development of a
class of admission control algorithms that make acceptance
decisions to new and handoff calls of multiple service
classes to satisfy specified QoS constraints in terms of the
dropping probability of handoff calls and the blocking
probability of new calls. We utilize these call admission
control algorithms to determine the maximum revenue
obtainable by each cell of the PCS system while satisfying
the QoS constraints, when given predetermined prices for
multiple service classes.
The third part of the research is to develop and analyze a
constraint-based search algorithm to efficiently determine
optimal pricing that maximizes the system revenue with QoS
guarantees. This algorithm first determines a number of
possible price values for each service class, thus creating
a search space consisting of possible price combinations of
all multimedia services. Then it explores the search space
guided by QoS constraints and a service demand-price
correlation scheme to effectively reduce the search
complexity without degrading the solution optimality. The
constraint-based algorithm is shown to effectively search
for optimal pricing that maximizes the system revenue with
QoS guarantees in all cells of the PCS system.
We propose to use mathematical modeling and analysis methods
to obtain analytical results and compare the proposed set of
algorithms developed for the framework with baseline
algorithms in the literature. We plan to use simulation to
validate analytical results.
You are cordially
invited to attend He’s PhD
Preliminary Exam defense
Dec. 12, 2pm, 2006. Room 324
Speaker: Weiping He
Title: MOBILITY AND SERVICE MANAGEMENT FOR FUTURE ALL-IP BASED WIRELESS NETWORKS
Abstract:
The next generation wireless network will provide not
only voice but also data services. With the success of
the Internet, it is widely believed that IP will become
the foundation of next generation wireless networks.
With the help of IETF standardization, IP-based
wireless networks can benefit from existing and
emerging IP related technologies and services. One key
issue is how to provide uninterrupted, reliable and
efficient data services to a mobile node (MN) in
wireless networks. This dissertation concerns two major
system-support mechanisms in future all-IP based
wireless networks, namely, mobility management and
service management.
Mobility management addresses the issues of how to
track and locate a mobile node efficiently. Service
management addresses the issues of how to efficiently
deliver services to mobile nodes. This dissertation
aims to design and analyze integrated mobility and
service management schemes for future all-IP based
wireless systems. We propose and analyze per-user
regional registration schemes for integrated mobility
and service management with the goal to minimize the
network signaling and packet delivery cost in future
all-IP based wireless networks. We show that, when
given a set of parameters characterizing the
operational and workload conditions of a MN, there
exists an optimal regional area size for the MN such
that the network communication cost is minimized for
serving mobility and service management operations of
the MN.
If access routers in future all-IP based wireless
networks are restricted to perform network layer
functions only, we investigate the design of
intelligent routers, called dynamic mobility anchor
points (DMAPs), to implement per-user regional
management in IP wireless networks. These DMAPs are
access routers (ARs) chosen by individual MNs to act
as regional routers to reduce the signaling overhead
for intra-regional movements. The DMAP domain size,
i.e., the number of subnets covered by a DMAP, is based
on a MN's mobility and service characteristics. A MN
optimally determines when and where to launch a DMAP to
minimize the network cost in serving the user's
mobility and service management operations. We show
that there exists an optimal DMAP domain size for each
individual MN.
If access routers are powerful and flexible in future
all-IP based networks to perform network-layer and
application-layer functions, we propose the use of
per-user proxies that can run on access routers. The
user proxies can carry service context information such
as cached data items and Web processing objects, and
perform context-aware functions such as content
adaptation for services engaged by the MN to help
application executions. Under the proxy-based regional
management scheme, a client-side proxy is created on a
per-user basis to serve as a gateway between a MN and
all services engaged by the MN. Leveraging Mobile IP
with route optimization, the proxy runs on a foreign
agent/access router and cooperates with the home agent
and foreign agent/access router of the MN to maintain
the location information of the MN, in order to
facilitate data delivery by services engaged by the MN.
Further, the proxy optimally determines when to move
with the MN so as to minimize the network cost
associated with the user's mobility and service
management operations.
The proxy-based scheme supports query processing mobile
applications. To improve query performance, the MN
stores frequently used data in its cache. The MN's
proxy receives invalidation reports or updated data
objects from application servers, i.e., corresponding
nodes (CN) for cached data objects stored in the MN.
If the MN is connected, the proxy will forward
invalidation reports or fresh data objects to the MN.
If the MN is disconnected, the proxy will store the
invalidation reports or fresh data objects, and, once
the MN is reconnected, the proxy will forward the
latest cache invalidation report or data objects to the
MN. We show that there is an optimal ``service area''
under which the overall cost including query processing
cost and mobility management cost is minimized.
We demonstrate that our proposed per-user regional
management scheme outperforms basic Mobile IPv6, Mobile
IPv6 Regional Registration, and Hierarchical Mobile
IPv6 that do not consider integrated mobility and
service management and that use static regional routers
to serve all MNs in the system. We will develop a
simulation model based on ns2 to validate analytical
results. We will also investigate mobile applications
to which the proposed integrated mobility and service
management scheme can be applied in Mobile IP systems.
You are cordially
invited to attend Kou’s PhD
Final Exam Defense
Nov. 29, 10am, 2006. Room 103
Speaker: Yufeng Kou
Title: Abnormal Pattern Recognition in Spatial Data
Abstract:
In the recent years, abnormal spatial pattern
recognition has received a great deal of attention from
both industry and academia, and has become an important
branch of data mining. Abnormal spatial patterns, or
spatial outliers, are those observations whose
characteristics are markedly dierent from their spatial
neighbors. The identication of spatial outliers can be
used to reveal hidden but valuable knowledge in many
applications. For example, it can help locate extreme
meteorological events such as tornadoes and hurricanes,
identify aberrant genes or tumor cells, discover
highway trac congestion points, pinpoint military
targets in satellite images, determine possible
locations of oil reservoirs, and detect water pollution
incidents. Numerous traditional outlier detection
methods have been developed, but they cannot be
directly applied to spatial data in order to extract
abnormal patterns. Traditional outlier detection mainly
focuses on "global comparison" and identies deviations
from the remainder of the entire data set. In contrast,
spatial outlier detection concentrates on discovering
neighborhood instabilities that break the spatial
continuity. In recent years, a number of techniques
have been proposed for spatial outlier detection.
However, they have the following limitations. First,
most of them focus primarily on single-attribute
outlier detection. Second, they may not accurately
locate outliers when multiple outliers exist in a
cluster and correlate with each other. Third, the
existing algorithms tend to abstract spatial objects as
isolated points and do not consider their geometrical
and topological properties, which may lead to inexact
results.
This dissertation reports a study of the problem of
abnormal spatial pattern recognition, and proposes a
suite of novel algorithms. Contributions include: (1)
formal denitions of various spatial outliers, including
single-attribute outliers, multi-attribute outliers,
and region outliers; (2) a set of algorithms for the
accurate detection of single-attribute spatial
outliers; (3) a systematic approach to identifying and
tracking region outliers in continuous meteorological
data sequences; (4) a novel Mahalanobis-distance-based
algorithm to detect outliers with multiple attributes;
(5) a set of graph-based algorithms to identify point
outliers and region outliers; and (6) extensive
analysis of experiments on several spatial data sets
(e.g., West Nile virus data and NOAA meteorological
data) to evaluate the eectiveness and eciency of the
proposed algorithms.
You are cordially
invited to attend Dai’s PhD
Preliminary Exam defense
Oct. 30, 10am, 2006. Room 103
Speaker: Jing Dai
Title: Efficient Current Operations in Spaital Databases
Abstract:
Nowadays, demanded by the applications such as GIS, CAD, ecology analysis, and space research, efficient spatial data access methods have attracted a lot of research efforts. Especially, complex spatial operations and continuous spatial queries are becoming highlighted in spatial database area. However, most of the existing spatial query processing approaches were designed for single-user environments, which may not ensure the correctness and the data consistency in multiple-user environments. This research focuses on designing efficient concurrent operations on spatial data sets.
Current multidimensional data access methods can be categorized into two types: 1) pure multidimensional indexing structure such as the R-tree family and grid file; 2) linear spatial access methods, represented by Space-Filling Curve (SFC) combined with B-trees. Concurrency control protocols have been designed for some pure multidimensional indexing structures, but none of them is suitable for variants of R-trees with object clipping, which are efficient in searching. On the other hand, there is no concurrency control protocol designed for linear spatial indexing structures, where the one-dimensional concurrency control protocols can not be directly applied.
In the proposed research, sound solutions for efficient concurrent access frameworks on both types of spatial indexing structures will be provided, as well as the spatial-temporal component, continuous query operations on moving objects, for multiple-user environment. These two concurrent access frameworks can satisfy the concurrency control requirements, meanwhile providing outstanding performance for concurrent queries. Major contributions include: (1) a new efficient spatial indexing approach with object clipping technique, ZR+-tree, that outperforms R-tree and R+-tree on searching; (2) complete concurrency control protocol, GLIP, to provide high throughput and phantom update protection on spatial indexing with object clipping; (3) efficient fundamental and complex concurrent operations for indexing based on linear spatial access methods, which form up the CLOCK protocol; (4) efficient concurrent continuous queries on moving objects for both concurrent spatial access framework.
You are cordially
invited to attend Speer’s PhD
Preliminary Exam defense
Oct. 20, 1pm, 2006. Room 320
Speaker: Anh Phan Speer
Title: Design and Analysis of Adaptive Fault Tolerant
QoS Control Algorithms for Query Processing in Wireless
Sensor Networks
Abstract:
Wireless sensor networks (WSNs) present several unique
characteristics such as extremely resource-constrained
sensors, large-scale random deployment, and
data-centric communication protocols. These
characteristics pose unprecedented challenges in the
area of query processing in WSNs. This dissertation
presents the design and validation of adaptive fault
tolerant QoS control algorithms to achieve the desired
quality of service (QoS) requirements and maximize the
system lifetime in query-based WSNs.
Data sensing and retrieval in WSNs have a widespread
application in areas such as security and surveillance
monitoring, as well as command and control in
battlefield situations. In query-based WSNs, a user
would issue a query with QoS requirements in terms of
reliability and timeliness, and expect a correct
response to be returned within the deadline. Satisfying
these QoS requirements requires that fault tolerance
mechanisms through redundancy be used, which may cause
the energy of the system to deplete quickly.
We analyze the effect of redundancy on the mean time to
failure (MTTF) of a WSN with clustering, defined as the
mean number of queries that the WSN is able to answer
correctly until it fails due to channel faults, sensor
faults, or sensor energy depletion. When the knowledge
of query arrival rate is available, this metric can be
translated into the conventional lifetime measure. In
particular, we analyze the effect of redundancy on the
MTTF of query-based cluster-structured WSNs. We show
that a tradeoff exists between redundancy and MTTF.
Furthermore, an optimal redundancy level exists such
that the MTTF of the system is maximized.
We develop a hop-by-hop data delivery mechanism in
which we utilize "source" and "path" redundancies with
the goal to satisfy application QoS requirements while
maximizing the lifetime of the WSN. When given QoS
requirements of a query in terms of reliability and
timeliness, we identify optimal "source" and "path"
redundancies such that not only QoS requirements are
satisfied, but also the lifetime of the system is
prolonged. Numerical data are presented to demonstrate
the feasibility of our approach.
To deal with network dynamics, we investigate proactive
and reactive methods for cluster heads to dynamically
collect channel and delay conditions to determine the
optimal redundancy at runtime. We also design
mechanisms to adapt to status changes of sensor nodes
due to energy consumption and node failures. We
validate our proposed adaptive fault tolerant QoS
control algorithms with simulation studies based on
J-Sim.
You are cordially
invited to attend Vasudeo’s Master’s
thesis defense
12:30pm, May 5, 2006
Speaker: Mr. Jyotindra Vasudeo Vasudeo
Title: The Design and Implementation of the Tako Language and Compiler
Abstract:
Aliasing complicates both formal and informal
reasoning. Aliasing is a particular problem in
object-oriented languages, where variables denote
references to objects rather than object values.
Researchers have proposed various approaches to the
aliasing problem in object-oriented languages ranging
from alias-control, where the effects of aliasing are
isolated, to alias avoidance, where common sources of
aliasing are avoided. The Tako language is an example
of an object-oriented language that incorporates alias
avoidance methodology. In this thesis we describe the
design and implementation of the Tako language and
compiler. We discuss the features of the language,
describe the implementation of the Tako compiler in
Java, and give proof rules for common statements in the
language. We also present a brief case study that
illustrates the paradigm shifts involved when moving
from Java to Tako.
You are cordially
invited to attend Salman’s Master’s
thesis defense
10:00 AM, Monday, May 23, 2005
Room 113
Speaker: Mr. M. Salman Akram
Title: Managing Changes to Service Oriented Enterprises
Abstract:
In our thesis, we present a framework for managing
changes in Service Oriented Enterprises (SOEs). A service oriented enterprise outsources and composes its functionality from third-party
Web service providers. We focus on
changes initiated or triggered by these member Web services. We present a taxonomy of changes that occur in service oriented
enterprises. We use a combination
of several types of Petri nets to model the triggering changes and ensuing
reactive changes. The techniques
presented in our work are implemented in WebBIS, a
prototype for composing and managing e-business Web services.
You are cordially invited to
attend the PhD thesis defense
1:00pm-3:00pm, Sep. 30th, 2005
NVC Room 113
Speaker: Baoshan Gu
gubs@vt.edu
Title:
Design and Analysis of Algorithms for Efficient Location and Service Management in Mobile Wireless Systems
Committee:
Dr. Ing-Ray Chen, Committee Chair
Dr. Luiz A. DaSilva
Dr. Denis Gracanin
Dr. Chang-Tien Lu
Dr. Scott F. Midkiff
Abstract:
Mobile wireless environments present several characteristics different from wired distributed systems, including unreliable wireless communication, disconnection, mobile and heterogeneous devices, and limited resources. These characteristics make design and validation of appropriate system supports for facilitating development of wireless mobile applications a challenging problem. This dissertation concerns two major system-support mechanisms in mobile wireless networks, namely, location management and service management.
Location management addresses the issues of how to track and locate a mobile user efficiently. Service management addresses the issues of how to efficiently deliver services to mobile user through limited wired and wireless network resources. This dissertation aims to design and analyze location and service management schemes that are efficient for cellular personal communication service (PCS) systems. We propose to address this research issue by considering three topics: location management, service management, and integrated location and service management.
A location management scheme must effectively and efficiently handle both user location-update and location-search operations. We propose to analyze existing location management algorithms by quantitatively evaluating the network signaling overhead for each of these algorithms and identifying conditions under which one algorithm may perform better than others. From insight leaned from the quantitative analysis, we design and analyze a hybrid algorithm that outperforms individual algorithms and show that such a hybrid algorithm can be uniformly applied to all mobile users with distinct call and mobility characteristics to simplify the system design without sacrificing performance.
For service management, we propose and analyze the notion of location-aware personal proxies with the goal to minimize the overall network signaling and communication cost caused by both location and service management operations. The idea is for each mobile user to use personal proxies as intelligent client-side agents to communication with services engaged by the mobile user. A personal proxy cooperates with the underlying location management system so that it is location-aware and can optimally decide when and how often it should move with the roaming user. We show that for cellular wireless networks that provide packet services, when given a set of model parameters characterizing the network and workload conditions, there exists an optimal proxy service area size for service handoffs such that the overall network signaling and communication cost for servicing location and service operations is minimized. These proxy-based mobile service management schemes are shown to outperform non-proxy-based schemes over a wide range of identified conditions. Moreover, when the mobile user is concurrently engaged in multiple services, the per-service proxy scheme, which uses a separate proxy for each service, outperforms the aggregate proxy scheme, which uses a single proxy to interact with multiple services taking their aggregate service characteristics into consideration.
Taking the lesson learned from designing location and service management algorithms, we investigate how location and service management can be more tightly integrated, i.e., by co-locating location databases with service proxies in order to further reduce the overall network signaling and communication cost due to managing both location and service operations. Four integrated location and service management schemes are proposed and analyzed in this dissertation for PCS cellular systems and validated with simulation and sensitivity analysis. We show that, when given an MH's mobility and service characteristics, there exists an optimal integrated location and service management scheme that would minimize the overall network communication cost as a result of executing the MH's location and service operations. We also demonstrate that the best integrated location and service scheme identified always performs better than the best decoupled scheme that considers location and service managements separately. By simulation, we show that these results obtained are insensitive to the residence time distribution. Moreover, these results obtained are valid when we use the random waypoint model, instead of the random movement model, for modeling user mobility.