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Virginia Tech
1.
Anyanwu, Uchenna Kevin.
A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms.
Degree: MS, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/33744
► Wireless communications technology ranging from satellite communications to sensor networks has benefited from the development of flexible, SDR platforms. SDR is used for military applications…
(more)
▼ Wireless communications technology ranging from satellite communications to sensor
networks has benefited from the development of flexible, SDR platforms. SDR is used for
military applications in radio devices to reconfigure waveforms, frequency, and modulation
schemes in both software and hardware to improve communication performance in
harsh environments. In the commercial sector, SDRs are present in cellular infrastructure,
where base stations can reconfigure operating parameters to meet specific cellular coverage
goals. In response to these enhancements, industry leaders in cellular (such as Lucent,
Nortel, and Motorola) have embraced the cost advantages of implementing SDRs in their
cellular technology. In the future, there will be a need for more capable SDR platforms on
inexpensive hardware that are able to balance work loads between several computational
processing elements while minimizing power cost to accomplish multiple goals.
This thesis will present the development of a random access MAC protocol for the IRIS
platform. An assessment of different SDR hardware and software platforms is conducted.
From this assessment, we present several SDR technology requirements for networking
research and discuss the impact of these requirements on future SDR platforms. As a
consequence of these requirements, we choose the USRP family of SDR hardware and the
IRIS software platform to develop our two random access MAC implementations: Aloha
with Explicit ACK and Aloha with Implicit ACK. A point-to-point link was tested with
our protocol and then this link was extended to a 3-hop (4 nodes) network. To improve
our protocolsâ efficiency, we implemented carrier sensing on the FPGA of the USRP E100,
an embedded SDR hardware platform. We also present simulations using OMNeT++
software to accompany our experimental data, and moreover, show how our protocol
scales as more nodes are added to the network.
Advisors/Committee Members: MacKenzie, Allen B. (committeechair), DaSilva, Luiz A. (committee member), Dietrich, Carl B. (committee member).
Subjects/Keywords: Random Access MAC; Wireless Networks; Software Defined Radio
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APA (6th Edition):
Anyanwu, U. K. (2012). A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33744
Chicago Manual of Style (16th Edition):
Anyanwu, Uchenna Kevin. “A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms.” 2012. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/33744.
MLA Handbook (7th Edition):
Anyanwu, Uchenna Kevin. “A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms.” 2012. Web. 24 Jan 2021.
Vancouver:
Anyanwu UK. A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/33744.
Council of Science Editors:
Anyanwu UK. A Reconfigurable Random Access MAC Implementation for Software Defined Radio Platforms. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/33744

Virginia Tech
2.
Good, Stephen D.
A Study into the Tradeoffs Between TDM / MF-SCPC and TDM / MF-TDMA Transport Options to Support IP-Based Multimedia Applications Under Different Load Conditions Within a Point-to-Multipoint Satellite Network.
Degree: MS, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/32730
► This thesis provides the reader with an overview of the many elements that are involved in geosynchronous satellite point-to-multipoint Internet Protocol (IP)-based multimedia communications design…
(more)
▼ This thesis provides the reader with an overview of the many elements that are involved in geosynchronous satellite point-to-multipoint Internet Protocol (IP)-based multimedia communications design and also takes a deep dive into the analysis of a real-life scenario, using the TDM / MF-SCPC and TDM / MF-TDMA media access techniques.
This thesis starts with a discussion of satellite network topologies utilized within point-to-multipoint satellite communications followed by an overview of the satellite communications channel. A discussion on the intelligent and proper selection of modulation and coding follows. Descriptions and characteristics of the satellite access technologies chosen to be analyzed are next followed by a detailed description of Forward Error Correction (FEC) techniques and a discussion on network-wide tradeoffs so selecting different options.
The thesis then presents the results of a real-life scenario, investigating both TDM / MF-SCPC and TDM / MF-TDMA media access technique options, pointing out the tradeoffs brought to the forefront earlier in the study. The major takeaway is that there does not exist a one-size-fits-all solution that works for each and every scenario.
Advisors/Committee Members: Midkiff, Scott F. (committee member), Zaghloul, Amir I. (committeecochair), DaSilva, Luiz A. (committeecochair).
Subjects/Keywords: MF-TDMA; MF-SCPC; TDM; VSAT networks; Satellite
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APA ·
Chicago ·
MLA ·
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Export
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APA (6th Edition):
Good, S. D. (2012). A Study into the Tradeoffs Between TDM / MF-SCPC and TDM / MF-TDMA Transport Options to Support IP-Based Multimedia Applications Under Different Load Conditions Within a Point-to-Multipoint Satellite Network. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32730
Chicago Manual of Style (16th Edition):
Good, Stephen D. “A Study into the Tradeoffs Between TDM / MF-SCPC and TDM / MF-TDMA Transport Options to Support IP-Based Multimedia Applications Under Different Load Conditions Within a Point-to-Multipoint Satellite Network.” 2012. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/32730.
MLA Handbook (7th Edition):
Good, Stephen D. “A Study into the Tradeoffs Between TDM / MF-SCPC and TDM / MF-TDMA Transport Options to Support IP-Based Multimedia Applications Under Different Load Conditions Within a Point-to-Multipoint Satellite Network.” 2012. Web. 24 Jan 2021.
Vancouver:
Good SD. A Study into the Tradeoffs Between TDM / MF-SCPC and TDM / MF-TDMA Transport Options to Support IP-Based Multimedia Applications Under Different Load Conditions Within a Point-to-Multipoint Satellite Network. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/32730.
Council of Science Editors:
Good SD. A Study into the Tradeoffs Between TDM / MF-SCPC and TDM / MF-TDMA Transport Options to Support IP-Based Multimedia Applications Under Different Load Conditions Within a Point-to-Multipoint Satellite Network. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/32730

Virginia Tech
3.
Naik, Apoorv.
Orchestra Framework: Protocol Design for Ad Hoc and Delay Tolerant Networks using Genetic Algorithms.
Degree: MS, Electrical and Computer Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/43409
► Protocol designs targeted at a specific network scenario or performance metric appear promising on paper, but the complexity and cost of implementing and tuning a…
(more)
▼ Protocol designs targeted at a specific network scenario or performance metric appear promising on paper, but the complexity and cost of implementing and tuning a routing protocol from scratch presents a major bottleneck in the protocol design process. A unique framework called 'Orchestra` is proposed in the literature to support the testing and development of novel routing designs. The idea of the Orchestra framework is to create generic and reusable routing functional components which can be combined to create unique protocol designs customized for a specific performance metric or network setting. The first contribution of this thesis is the development of a generic, modular, scalable and extensible architecture of the Orchestra framework.
Once the architecture and implementation of the framework is completed, the second contribution of this thesis is the development of functional components and strategies to design and implement routing protocols for delay tolerant networks (DTNs). DTNs are a special type of ad hoc network characterized by intermittent connectivity, long propagation delays and high loss rate. Thus, traditional ad hoc routing approaches cannot be used in DTNs, and special features must be developed for the Orchestra framework to support the design of DTN routing protocols.
The component-based architecture of Orchestra can capture a variety of modules that can be used to assemble a routing protocol. However, manually assembling these components may result in suboptimal designs, because it is difficult to determine what the best combination is for a particular set of performance objectives and network characteristics. The third contribution of the thesis addresses this problem. A genetic algorithm based approach to automate the process of routing protocol design is developed and its performance is evaluated in the context of the Orchestra framework.
Advisors/Committee Members: DaSilva, Luiz A. (committeechair), Hou, Yiwei Thomas (committee member), Yang, Yaling (committee member).
Subjects/Keywords: Delay Tolerant Networks; Genetic Algorithms; Component-based Software Engineering; Ad hoc Networks
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Naik, A. (2011). Orchestra Framework: Protocol Design for Ad Hoc and Delay Tolerant Networks using Genetic Algorithms. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/43409
Chicago Manual of Style (16th Edition):
Naik, Apoorv. “Orchestra Framework: Protocol Design for Ad Hoc and Delay Tolerant Networks using Genetic Algorithms.” 2011. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/43409.
MLA Handbook (7th Edition):
Naik, Apoorv. “Orchestra Framework: Protocol Design for Ad Hoc and Delay Tolerant Networks using Genetic Algorithms.” 2011. Web. 24 Jan 2021.
Vancouver:
Naik A. Orchestra Framework: Protocol Design for Ad Hoc and Delay Tolerant Networks using Genetic Algorithms. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/43409.
Council of Science Editors:
Naik A. Orchestra Framework: Protocol Design for Ad Hoc and Delay Tolerant Networks using Genetic Algorithms. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/43409

Virginia Tech
4.
Meuleners, Michael.
Design and Implementation of a Distributed Tdoa-Based Geolocation System Using Ossie and Low-Cost Usrp Boards.
Degree: MS, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/32731
► The Software Communications Architecture (SCA) specification defines a framework that allows modular software components to be developed and assembled to build larger radio applications. The…
(more)
▼ The Software Communications Architecture (SCA) specification defines a framework that allows modular software components to be developed and assembled to build larger radio applications. The specification allows for these components to be distributed among a set of computing hardware and to be connected by standard interfaces. This research aims to build a spatially distributed SCA application for the Open Source SCA Implementation: Embedded (OSSIE) implementation using low-cost Universal Software Radio Peripheral (USRP) hardware. The system collects signals from multiple spatially distributed collection devices and use those signals to compute precision estimates for the location of emitters using time difference of arrival (TDOA) computations. Several OSSIE components and tools are developed to support this research. Results are presented showing the capabilities of the geolocation system.
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Dietrich, Carl B. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Geolocation; TDOA; OSSIE; SDR; SCA
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Meuleners, M. (2012). Design and Implementation of a Distributed Tdoa-Based Geolocation System Using Ossie and Low-Cost Usrp Boards. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32731
Chicago Manual of Style (16th Edition):
Meuleners, Michael. “Design and Implementation of a Distributed Tdoa-Based Geolocation System Using Ossie and Low-Cost Usrp Boards.” 2012. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/32731.
MLA Handbook (7th Edition):
Meuleners, Michael. “Design and Implementation of a Distributed Tdoa-Based Geolocation System Using Ossie and Low-Cost Usrp Boards.” 2012. Web. 24 Jan 2021.
Vancouver:
Meuleners M. Design and Implementation of a Distributed Tdoa-Based Geolocation System Using Ossie and Low-Cost Usrp Boards. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/32731.
Council of Science Editors:
Meuleners M. Design and Implementation of a Distributed Tdoa-Based Geolocation System Using Ossie and Low-Cost Usrp Boards. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/32731

Virginia Tech
5.
Zhou, Bin.
Computational Analysis of LC-MS/MS Data for Metabolite Identification.
Degree: MS, Electrical and Computer Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/36109
► Metabolomics aims at the detection and quantitation of metabolites within a biological system. As the most direct representation of phenotypic changes, metabolomics is an important…
(more)
▼ Metabolomics aims at the detection and quantitation of metabolites within a biological system. As the most direct representation of phenotypic changes, metabolomics is an important component in system biology research. Recent development on high-resolution, high-accuracy mass spectrometers enables the simultaneous study of hundreds or even thousands of metabolites in one experiment. Liquid chromatography-mass spectrometry (LC-MS) is a commonly used instrument for metabolomic studies due to its high sensitivity and broad coverage of metabolome.
However, the identification of metabolites remains a bottle-neck for current metabolomic studies. This thesis focuses on utilizing computational approaches to improve the accuracy and efficiency for metabolite identification in LC-MS/MS-based metabolomic studies. First, an outlier screening approach is developed to identify those LC-MS runs with low analytical quality, so they will not adversely affect the identification of metabolites. The approach is computationally simple but effective, and does not depend on any preprocessing approach. Second, an integrated computational framework is proposed and implemented to improve the accuracy of metabolite identification and prioritize the multiple putative identifications of one peak in LC-MS data. Through the framework, peaks are likely to have the m/z values that can give appropriate putative identifications. And important guidance for the metabolite verification is provided by prioritizing the putative identifications. Third, an MS/MS
spectral matching algorithm is proposed based on support vector machine classification. The approach provides an improved retrieval performance in spectral matching, especially in the presence of data heterogeneity due to different instruments or experimental settings used during the MS/MS spectra acquisition.
Advisors/Committee Members: Wang, Yue J. (committeechair), Lu, Chang-Tien (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Liquid chromatography-mass spectrometry; Metabolomics; Spectral matching; Outlier screening; Support vector machine
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zhou, B. (2011). Computational Analysis of LC-MS/MS Data for Metabolite Identification. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36109
Chicago Manual of Style (16th Edition):
Zhou, Bin. “Computational Analysis of LC-MS/MS Data for Metabolite Identification.” 2011. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/36109.
MLA Handbook (7th Edition):
Zhou, Bin. “Computational Analysis of LC-MS/MS Data for Metabolite Identification.” 2011. Web. 24 Jan 2021.
Vancouver:
Zhou B. Computational Analysis of LC-MS/MS Data for Metabolite Identification. [Internet] [Masters thesis]. Virginia Tech; 2011. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/36109.
Council of Science Editors:
Zhou B. Computational Analysis of LC-MS/MS Data for Metabolite Identification. [Masters Thesis]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/36109

Virginia Tech
6.
Irwin, Ryan.
Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks.
Degree: PhD, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/26601
► This dissertation addresses the problem of channel assignment in multi-hop, multi-transceiver wireless networks. We investigate (1) how channels can be assigned throughout the network to…
(more)
▼ This dissertation addresses the problem of channel assignment in multi-hop, multi-transceiver wireless networks. We investigate (1) how channels can be assigned throughout the network to ensure that the network is connected and (2) how the channel assignment can be adapted to suit the current traffic demands. We analyze a traffic-aware method for channel assignment that addresses both maintaining network connectivity and adapting the topology based on dynamic traffic demands.
The traffic-aware approach has one component that assigns channels independently of traffic conditions and a second component that assigns channels in response to traffic conditions. The traffic-independent (TI) component is designed to allocate as few transceivers or radios as possible in order to maintain network connectivity, while limiting the aggregate interference induced by the topology. The traffic-driven (TD) component is then designed to maximize end-to-end flow rate using the resources remaining after the TI assignment is complete. By minimizing resources in the TI component, the TD component has more resources to adapt the topology to suit the traffic demands and support higher end-to-end flow rate.
We investigate the fundamental tradeoff between how many resources are allocated to maintaining network connectivity versus how many resources are allocated to maximize flow rate. We show that the traffic-aware approach achieves an appropriately balanced resource allocation, maintaining a baseline network connectivity and adapting to achieve near the maximum theoretical flow rate in the scenarios evaluated.
We develop a set of greedy, heuristic algorithms that address the problem of resource- minimized TI assignment, the first component of the traffic-aware assignment. We develop centralized and distributed schemes for nodes to assign channels to their transceivers. These schemes perform well as compared to the optimal approach in the evaluation. We show that both of these schemes perform within 2% of the optimum in terms of the maximum achievable flow rate.
We develop a set of techniques for adapting the networkâ s channel assignment based on traffic demands, the second component of the traffic-aware assignment. In our approach, nodes sense traffic conditions and adapt their own channel assignment independently to support a high flow rate and adapt when network demand changes. We demonstrate how our distributed TI and TD approaches complement each other in an event-driven simulation.
Advisors/Committee Members: DaSilva, Luiz A. (committeechair), Reed, Jeffrey Hugh (committee member), Hou, Yiwei Thomas (committee member), Gracanin, Denis (committee member), MacKenzie, Allen B. (committeecochair).
Subjects/Keywords: Topology Control; Traffic-aware; Channel assignment; Cognitive Networks; Multi-channel Networks
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Irwin, R. (2012). Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26601
Chicago Manual of Style (16th Edition):
Irwin, Ryan. “Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks.” 2012. Doctoral Dissertation, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/26601.
MLA Handbook (7th Edition):
Irwin, Ryan. “Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks.” 2012. Web. 24 Jan 2021.
Vancouver:
Irwin R. Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/26601.
Council of Science Editors:
Irwin R. Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/26601

Virginia Tech
7.
Lazem, Shaimaa.
Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics.
Degree: PhD, Computer Science, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/26732
► The rapid evolution of portable devices and social media has enabled pervasive forms of distributed cooperation. A group could perform a task using a heterogeneous…
(more)
▼ The rapid evolution of portable devices and social media has enabled pervasive forms of distributed cooperation. A group could perform a task using a heterogeneous set of the devices (desktop, mobile), connections (wireless, wired, 3G) and software clients. We call this form of systems Distributed Dynamic Cooperative Environments (DDCEs).
Content in DDCEs is created and shared by the users. The content could be static (e.g., video or audio), dynamic (e.g.,wikis), and/or Objects with behavior. Objects with behavior are programmed objects that take advantage of the available computational services (e.g., cloud-based services).
Providing a desired Quality of Experience (QoE) in DDCEs is a challenge for cooperative systems designers. DDCEs are expected to provide groups with the utmost flexibility in conducting their cooperative activities. More flexibility at the user side means less control and predictability of the groupsâ behavior at the system side.
Due to the lack of Quality of Service (QoS) guarantees in DDCEs, groups may experience changes in the system behavior that are usually manifested as delays and inconsistencies in the shared state. We question the extent to which cooperation among group members is sensitive to system changes in DDCEs. We argue that a QoE definition for groups should account for cooperation emergence and sustainability.
An experiment was conducted, where fifteen groups performed a loosely-coupled task that simulates social traps in a 3D virtual world. The groups were exposed to two forms of system delays. Exo-content delays are exogenous to the provided content (e.g., network delay). Endo-content delays are endogenous to the provided content (e.g., delay in processing time for Objects with behavior). Groups' performance in the experiment and their verbal communication have been recorded and analyzed.
The results demonstrate the nonlinearity of groups' behavior when dealing with endo-content delays. System interventions are needed to maintain QoE even though that may increase the cost or the required resources.
Systems are designed to be used rather than understood by users. When the system behavior changes, designers have two choices. The first is to expect the users to understand the system behavior and adjust their interaction accordingly. That did not happen in our experiment. Understanding the system behavior informed groups' behavior. It partially influenced how the groups succeeded or failed in accomplishing its goal. The second choice is to understand the semantics of the application and provide guarantees based on these semantics. Based on our results, we introduce the following design guidelines for QoE provision in DDCEs.
â ¢If possible the system should keep track of information about group goals and add guarding constraints to protect these goals.
â ¢QoE guarantees should be provided based on the semantics of the user-generated content that constitutes the group activity.
â ¢Users should be given the option to define the content that is sensitive to system changes…
Advisors/Committee Members: Gracanin, Denis (committeechair), DaSilva, Luiz A. (committee member), Cao, Yong (committee member), Tilevich, Eli (committee member), Harrison, Steven R. (committee member).
Subjects/Keywords: Mixed-Motive Tasks; Social Traps; Social Dilemmas; Dynamics of Cooperation; Group Dynamics; Quality of Experience; Delays; Online 3D Virtual Worlds; Quality of Service
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lazem, S. (2012). Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26732
Chicago Manual of Style (16th Edition):
Lazem, Shaimaa. “Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics.” 2012. Doctoral Dissertation, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/26732.
MLA Handbook (7th Edition):
Lazem, Shaimaa. “Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics.” 2012. Web. 24 Jan 2021.
Vancouver:
Lazem S. Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/26732.
Council of Science Editors:
Lazem S. Analysis of the Relationships between Changes in Distributed System Behavior and Group Dynamics. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/26732

Virginia Tech
8.
Hassan Eltarras, Rami M.
BioSENSE: Biologically-inspired Secure Elastic Networked Sensor Environment.
Degree: PhD, Electrical and Computer Engineering, 2011, Virginia Tech
URL: http://hdl.handle.net/10919/27790
► The essence of smart pervasive Cyber-Physical Environments (CPEs) is to enhance the dependability, security and efficiency of their encompassing systems and infrastructures and their services.…
(more)
▼ The essence of smart pervasive Cyber-Physical Environments (CPEs) is to enhance the dependability, security and efficiency of their encompassing systems and infrastructures and their services. In CPEs, interactive information resources are integrated and coordinated with physical resources to better serve human users. To bridge the interaction gap between users and the physical environment, a CPE is instrumented with a large number of small devices, called sensors, that are capable of sensing, computing and communicating. Sensors with heterogeneous capabilities should autonomously organize on-demand and interact to furnish real-time, high fidelity information serving a wide variety of user applications with dynamic and evolving requirements. CPEs with their associated networked sensors promise aware services for smart systems and infrastructures with the potential to improve the quality of numerous application domains, in particular mission-critical infrastructure domains. Examples include healthcare, environment protection, transportation, energy, homeland security, and national defense.
To build smart CPEs, Networked Sensor Environments (NSEs) are needed to manage demand-driven sharing of large-scale federated heterogeneous resources among multiple applications and users. We informally define NSE as a tailorable, application agnostic, distributed platform with the purpose of managing a massive number of federated resources with heterogeneous computing, communication, and monitoring capabilities. We perceive the need to develop scalable, trustworthy, cost-effective NSEs. A NSE should be endowed with dynamic and adaptable computing and communication services capable of efficiently running diverse applications with evolving QoS requirements on top of federated distributed resources. NSEs should also enable the development of applications independent of the underlying system and device concerns. To our knowledge, a NSE with the aforementioned capabilities does not currently exist.
The large scale of NSEs, the heterogeneous node capabilities, the highly dynamic topology, and the likelihood of being deployed in inhospitable environments pose formidable challenges for the construction of resilient shared NSE platforms. Additionally, nodes in NSE are often resource challenged and therefore trustworthy node cooperation is required to provide useful services. Furthermore, the failure of NSE nodes due to malicious or non-malicious conditions represents a major threat to the trustworthiness of NSEs. Applications should be able to survive failure of nodes and change their runtime structure while preserving their operational integrity. It is also worth noting that the decoupling of application programming concerns from system and device concerns has not received the appropriate attention in most existing wireless sensor network platforms.
In this dissertation, we present a Biologically-inspired Secure Elastic Networked Sensor Environment (BioSENSE) that synergistically integrates: (1) a novel bio-inspired construction of…
Advisors/Committee Members: Eltoweissy, Mohamed Y. (committeechair), Midkiff, Scott F. (committee member), Chen, Ing-Ray (committee member), Riad, Sedki Mohamed (committee member), DaSilva, Luiz A. (committee member), Youssef, Moustafa (committee member).
Subjects/Keywords: Resilient Architecture; Adaptability; Software Diversity; Middleware; Routing; Biologically-Inspired Design; Sensor Networks
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hassan Eltarras, R. M. (2011). BioSENSE: Biologically-inspired Secure Elastic Networked Sensor Environment. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27790
Chicago Manual of Style (16th Edition):
Hassan Eltarras, Rami M. “BioSENSE: Biologically-inspired Secure Elastic Networked Sensor Environment.” 2011. Doctoral Dissertation, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/27790.
MLA Handbook (7th Edition):
Hassan Eltarras, Rami M. “BioSENSE: Biologically-inspired Secure Elastic Networked Sensor Environment.” 2011. Web. 24 Jan 2021.
Vancouver:
Hassan Eltarras RM. BioSENSE: Biologically-inspired Secure Elastic Networked Sensor Environment. [Internet] [Doctoral dissertation]. Virginia Tech; 2011. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/27790.
Council of Science Editors:
Hassan Eltarras RM. BioSENSE: Biologically-inspired Secure Elastic Networked Sensor Environment. [Doctoral Dissertation]. Virginia Tech; 2011. Available from: http://hdl.handle.net/10919/27790

Virginia Tech
9.
Mahajan, Rahul.
Cross-Layer Optimization: System Design and Simulation Methodologies.
Degree: MS, Electrical and Computer Engineering, 2006, Virginia Tech
URL: http://hdl.handle.net/10919/35920
► An important aspect of wireless networks is their dynamic behavior. The conventional protocol stack is inflexible as various protocol layers communicate in a strict manner.…
(more)
▼ An important aspect of wireless networks is their dynamic behavior. The conventional protocol stack is inflexible as various protocol layers communicate in a strict manner. In such a case the layers are designed to operate under the worst conditions as opposed to adapting to changing conditions. This leads to inefficient use of spectrum and energy. Adaptation represents the ability of network protocols and applications to observe and respond to channel conditions.
Traditional simulation methodologies independently model the physical and higher layers. When multiple layer simulations are required, an abstraction of one layer is inserted into the other to provide the multiple layer simulation. However, recent advances in wireless communication technologies, such as adaptive modulation and adaptive antenna algorithms, demand a cross layer perspective to this problem in order to provide a sufficient level of fidelity. However, a full simulation of both layers often results in excessively burdensome simulation run-times. The benefits and possible parametric characterization issues arising due to the cross-layer integration of lower physical and higher network layers are investigated in this thesis. The primary objective of investigating cross-layer simulation techniques is to increase the fidelity of cross-layer network simulations while minimizing the simulation runtime penalties.
As a study of cross-layer system design a medium access control (MAC) scheme is studied for a MANET wherein the nodes are equipped with smart antennas. Traditional MAC protocols assume the use of omnidirectional antennas. Nodes with directional antennas are capable of transmitting in certain directions only and significantly reduce the chances of collision and increase the effective network capacity. MANETs using omni-directional antennas severely limit system performance as the entire space around a node up to its radio range is seen as a single logical channel. In this research a MAC protocol is studied that exploits space division multiple access at the physical layer. This is a strong example where physical and MAC design must be carried out simultaneously for adequate system performance.
Power control is a very important in the design of cellular CDMA systems which suffer from the near-far problem. Finally, the interaction between successive interference cancellation (SIC) receivers at the physical layer and power control, which is a layer 2 radio resource management issue, is studied. Traffic for future wireless networks is expected to be a mix of real-time traffic such as voice, multimedia teleconferencing, and games and data traffic such as web browsing, messaging, etc. All these applications will require very diverse quality of service guarantees. A power control algorithm is studied, which drives the average received powers to those required, based on the QoS requirements of the individual users for a cellular CDMA system using SIC receivers.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Tranter, William H. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Mobile Ad-Hoc Networks with Smart Antennas; Power Control for Successive Interference Cancell; Medium Access Control with Directional Antennas
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APA (6th Edition):
Mahajan, R. (2006). Cross-Layer Optimization: System Design and Simulation Methodologies. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35920
Chicago Manual of Style (16th Edition):
Mahajan, Rahul. “Cross-Layer Optimization: System Design and Simulation Methodologies.” 2006. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/35920.
MLA Handbook (7th Edition):
Mahajan, Rahul. “Cross-Layer Optimization: System Design and Simulation Methodologies.” 2006. Web. 24 Jan 2021.
Vancouver:
Mahajan R. Cross-Layer Optimization: System Design and Simulation Methodologies. [Internet] [Masters thesis]. Virginia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/35920.
Council of Science Editors:
Mahajan R. Cross-Layer Optimization: System Design and Simulation Methodologies. [Masters Thesis]. Virginia Tech; 2006. Available from: http://hdl.handle.net/10919/35920

Virginia Tech
10.
Shukla, Umesh Kumar.
Backpressure Policies for Wireless ad hoc Networks.
Degree: MS, Electrical and Computer Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/31982
► Interference in ad hoc wireless networks causes the performance of traditional networking protocols to suffer. However, some user applications in ad hoc networks demand high…
(more)
▼ Interference in ad hoc wireless networks causes the performance of traditional networking protocols to suffer. However, some user applications in ad hoc networks demand high throughput and low end-user delay. In the literature, the backpressure policy, i.e. queue backlog differential-based joint routing and scheduling, is known to be throughput-optimal with robust support for traffic load fluctuations . Unfortunately, many backpressure-based algorithms cannot be implemented due to high end-user delay, inaccurate assumptions for interference, and high control overhead in distributed scenarios. We develop new backpressure based approaches to address these issues. We first propose a heuristic packet forwarding scheme that solves the issue of high end-user delay and still provides near-optimal throughput. Next we develop a novel interference model that provides simple yet accurate interference relationships among users. Such a model is helpful in designing a simple backpressure scheduling algorithm that does not violate realistic interference constraints. Finally we develop distributed backpressure algorithms based on our proposed ideas. Our distributed algorithms provide throughput performance close to the optimal and have low control overhead and simple implementation.
Advisors/Committee Members: MacKenzie, Allen B. (committeechair), Buehrer, R. Michael (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Interference models; Backpressure; Routing; Scheduling; Wireless networks
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APA (6th Edition):
Shukla, U. K. (2010). Backpressure Policies for Wireless ad hoc Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31982
Chicago Manual of Style (16th Edition):
Shukla, Umesh Kumar. “Backpressure Policies for Wireless ad hoc Networks.” 2010. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/31982.
MLA Handbook (7th Edition):
Shukla, Umesh Kumar. “Backpressure Policies for Wireless ad hoc Networks.” 2010. Web. 24 Jan 2021.
Vancouver:
Shukla UK. Backpressure Policies for Wireless ad hoc Networks. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/31982.
Council of Science Editors:
Shukla UK. Backpressure Policies for Wireless ad hoc Networks. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/31982

Virginia Tech
11.
Kumar, Nishant.
MAC and Physical Layer Design for Ultra-Wideband Communications.
Degree: MS, Electrical and Computer Engineering, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/9934
► Ultra-Wideband has recently gained great interest for high-speed short-range communications (e.g. home networking applications) as well as low-speed long-range communications (e.g. sensor network applications). Two…
(more)
▼ Ultra-Wideband has recently gained great interest for high-speed short-range communications (e.g. home networking applications) as well as low-speed long-range communications (e.g. sensor network applications). Two flavors of UWB have recently emerged as strong contenders for the technology. One is based on Impulse Radio techniques extended to direct sequence spread spectrum. The other technique is based on Orthogonal Frequency Division Multiplexing. Both schemes are analyzed in this thesis and modifications are proposed to increase the performance of each system. For both schemes, the issue of simultaneously operating users has been investigated.
Current MAC design for UWB has relied heavily on existing MAC architectures in order to maintain backward compatibility. It remains to be seen if the existing MACs adequately support the UWB PHY (Physical) layer for the applications envisioned for UWB. Thus, in this work we propose a new MAC scheme for an Impulse Radio based UWB PHY, which is based on a CDMA approach using a code-broker in a piconet architecture. The performance of the proposed scheme is compared with the traditional CSMA scheme as well as the receiver-based code assignment scheme.
A new scheme is proposed to increase the overall performance of the Multiband-OFDM system. Two schemes proposed to increase the performance of the system in the presence of simultaneously operating piconets (namely Half Pulse Repetition Frequency and Time spreading) are studied. The advantages/disadvantages of both of the schemes are discussed.
Advisors/Committee Members: Buehrer, R. Michael (committeechair), Sweeney, Dennis G. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Impulse Radio; Ultra-Wideband; Multiband-OFDM; Medium Access Control; CDMA; CSMA
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Kumar, N. (2004). MAC and Physical Layer Design for Ultra-Wideband Communications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/9934
Chicago Manual of Style (16th Edition):
Kumar, Nishant. “MAC and Physical Layer Design for Ultra-Wideband Communications.” 2004. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/9934.
MLA Handbook (7th Edition):
Kumar, Nishant. “MAC and Physical Layer Design for Ultra-Wideband Communications.” 2004. Web. 24 Jan 2021.
Vancouver:
Kumar N. MAC and Physical Layer Design for Ultra-Wideband Communications. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/9934.
Council of Science Editors:
Kumar N. MAC and Physical Layer Design for Ultra-Wideband Communications. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/9934

Virginia Tech
12.
Al-Saleh, Mohammad.
Sensor Package Analysis and Simulation for Direct Sensor-to-Satellite Links.
Degree: MS, Electrical and Computer Engineering, 2007, Virginia Tech
URL: http://hdl.handle.net/10919/76907
► This thesis investigates the design and the performance of low-power microsensors that communicate directly to a satellite or a constellation of satellites. Information is spread…
(more)
▼ This thesis investigates the design and the performance of low-power microsensors that communicate directly to a satellite or a constellation of satellites. Information is spread using pseudo noise (PN) or Barker codes. The sensors use a single circular microstrip patch element with a wide beamwidth or a miniature phased array antenna that continuously scans to access the satellite(s). The array beam is controlled with a beam-forming network (BFN), which contains 3 or 4-bit phase shifters, which can be made in micro-electro-mechanical systems (MEMS) or in monolithic microwave integrated circuits (MMIC). The antennas are designed using array simulation program called 'ARRAY' and the results are used in another simulation program called Advanced Design System (ADS) to simulate the whole sensor package that uses one of the antennas. The simulation results show that a sensor as small as 2.35 cm in diameter is able to send information with data rate of 1 kbps at bit error rate less than 10?? to low-earth orbit (LEO) satellites with a transmitted power of 27.5 microwatts (-15.6 dBm).
Advisors/Committee Members: Zaghloul, Amir I. (committeechair), DaSilva, Luiz A. (committee member), Midkiff, Scott F. (committee member).
Subjects/Keywords: Circular Microstrip Patch Arrays; LEO Satellite; DSSS; MEMS; Miniature Sensor
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Al-Saleh, M. (2007). Sensor Package Analysis and Simulation for Direct Sensor-to-Satellite Links. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76907
Chicago Manual of Style (16th Edition):
Al-Saleh, Mohammad. “Sensor Package Analysis and Simulation for Direct Sensor-to-Satellite Links.” 2007. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/76907.
MLA Handbook (7th Edition):
Al-Saleh, Mohammad. “Sensor Package Analysis and Simulation for Direct Sensor-to-Satellite Links.” 2007. Web. 24 Jan 2021.
Vancouver:
Al-Saleh M. Sensor Package Analysis and Simulation for Direct Sensor-to-Satellite Links. [Internet] [Masters thesis]. Virginia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/76907.
Council of Science Editors:
Al-Saleh M. Sensor Package Analysis and Simulation for Direct Sensor-to-Satellite Links. [Masters Thesis]. Virginia Tech; 2007. Available from: http://hdl.handle.net/10919/76907

Virginia Tech
13.
Thorp, Brian J.
Application Layer Multipoint Extension for the Session Initiation Protocol.
Degree: MS, Electrical and Computer Engineering, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/42245
► The Session Initiation Protocol (SIP) was first published in 1999, by the Internet Engineering Task Force (IETF), to be the standard for multimedia transfers. SIP…
(more)
▼ The Session Initiation Protocol (SIP) was first published in 1999, by the Internet Engineering Task Force (IETF), to be the standard for multimedia transfers. SIP is a peer-to-peer signaling protocol that is capable of initiating, modifying, and terminating media sessions. SIP utilizes existing Internet Protocols (IP) such as Domain Name Service (DNS) and the Session Description Protocol (SDP), allowing it to seamlessly integrate into existing IP networks.
As SIP has matured and gained acceptance, its deficiencies when functioning as a multipoint communications protocol have become apparent. SIP currently supports two modes of operation referred to as conferencing and multicasting. Conferencing is the unicast transmission of session information between conference members. Multicasting uses IP multicast to distribute session information. This thesis proposes an extension for the Session Initiation Protocol that improves functionality for multipoint communications.
When using conferencing, a SIP user-agent has limited information about the conference it is taking part in. This extension increases the awareness of a SIP node by providing it with complete conference membership information, the ability to detect neighboring node failures, and the ability to automatically repair conference partitions. Signaling for conferencing was defined and integrated into a standard SIP implementation where it was used to demonstrate the above capabilities. Using a prototype implementation, the additional functionality was shown to come at the cost of a modest increase in transaction message size and processing complexity.
IP multicast has limited deployment in todayâ s networks reducing the usability of this useful feature. Since IP multicast support is not guaranteed, the use of application layer multicast protocols is proposed to replace the use of IP multicast. An efficient means of negotiating an application layer protocol is proposed as well as the ability to provide the protocol with session information to begin operation. A ring protocol was defined and implemented using the proposed extension. Performance testing revealed that the application layer protocol had slightly higher processing complexity than conferencing, but on average had a smaller transaction message size.
Advisors/Committee Members: Midkiff, Scott F. (committeechair), DaSilva, Luiz A. (committee member), Hou, Yiwei Thomas (committee member).
Subjects/Keywords: application layer multicast; conferencing; Session Initiation Protocol
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Thorp, B. J. (2005). Application Layer Multipoint Extension for the Session Initiation Protocol. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42245
Chicago Manual of Style (16th Edition):
Thorp, Brian J. “Application Layer Multipoint Extension for the Session Initiation Protocol.” 2005. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/42245.
MLA Handbook (7th Edition):
Thorp, Brian J. “Application Layer Multipoint Extension for the Session Initiation Protocol.” 2005. Web. 24 Jan 2021.
Vancouver:
Thorp BJ. Application Layer Multipoint Extension for the Session Initiation Protocol. [Internet] [Masters thesis]. Virginia Tech; 2005. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/42245.
Council of Science Editors:
Thorp BJ. Application Layer Multipoint Extension for the Session Initiation Protocol. [Masters Thesis]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/42245

Virginia Tech
14.
Thomschutz, Hans Olaf Rutger.
Security in Packet-Switched Land Mobile Radio Backbone Networks.
Degree: MS, Electrical and Computer Engineering, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/33591
► Spurred by change in government regulations and to leverage lower-cost technology and services, many land mobile radio (LMR) operators have begun transitioning from circuit-switched to…
(more)
▼ Spurred by change in government regulations and to leverage lower-cost technology and services, many land mobile radio (LMR) operators have begun transitioning from circuit-switched to packet-switched backbone networks to handle their future communication needs. Due to the unique demands of packet-switched backbone networks for LMR, it may not be wise to carry over the previously implemented security methods used with circuit-switch systems or to treat an LMR backbone as a regular packet-switched network. This thesis investigates security in packet-switched LMR backbone networks to identify security issues in packet-switched LMR networks and provide possible solutions for them. Security solutions that are examined include different types of virtual private networks (VPNs), various encryption and keying procedures for safe communication, and logic behind how and where to implement security functions within the network. Specific schemes examined include IP Security (IPSec), OpenVPN, Virtual Tunnel (VTun), and Zebedee. I also present a quantitative analysis of the effects that the solutions have on packet-switched networks, in terms of link utilization, and on voice traffic, in terms of delay and delay jitter. In addition, I evaluate, in general terms, the additional cost or complexity that is introduced by the different security solutions.
Simulation with OPNET Modeler was used to evaluate how the various security schemes affect voice communication and network performance as a whole. Since OPNET Modeler does not provide models of security functions, the source code of the transceiver system models was modified to introduce additional overhead that is representative of the various security solutions. Through experimentation, simulation, and analysis of the security schemes considered, it was found that the most effective security scheme overall for a packet-switched LMR backbone network would either be IPSec or OpenVPN implemented at the base stations and end-hosts. Both security schemes provide strong encryption, flexibility, and are actively supported. However, if bandwidth is scarce and flexibility is less important, then a security solution with less overhead, such as VTun, should be considered. Thus, one has to balance performance with security to choose the most effective security solution for a particular application.
Advisors/Committee Members: Midkiff, Scott F. (committeechair), DaSilva, Luiz A. (committee member), Abbott, A. Lynn (committee member).
Subjects/Keywords: VPN; OPNET Modeler; packet-switched; circuit-switched; validation; first responders; public safety; simulation; Project 25; P25; APCO; Radio over IP
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Thomschutz, H. O. R. (2005). Security in Packet-Switched Land Mobile Radio Backbone Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33591
Chicago Manual of Style (16th Edition):
Thomschutz, Hans Olaf Rutger. “Security in Packet-Switched Land Mobile Radio Backbone Networks.” 2005. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/33591.
MLA Handbook (7th Edition):
Thomschutz, Hans Olaf Rutger. “Security in Packet-Switched Land Mobile Radio Backbone Networks.” 2005. Web. 24 Jan 2021.
Vancouver:
Thomschutz HOR. Security in Packet-Switched Land Mobile Radio Backbone Networks. [Internet] [Masters thesis]. Virginia Tech; 2005. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/33591.
Council of Science Editors:
Thomschutz HOR. Security in Packet-Switched Land Mobile Radio Backbone Networks. [Masters Thesis]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/33591

Virginia Tech
15.
Hia, Henry Erik.
Secure SNMP-Based Network Management in Low Bandwidth Networks.
Degree: MS, Electrical and Computer Engineering, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/32126
► This research focuses on developing a secure, SNMP-based network management system specifically tailored for deployment in internetworks that rely on low-bandwidth backbone networks. The network…
(more)
▼ This research focuses on developing a secure, SNMP-based network management system specifically tailored for deployment in internetworks that rely on low-bandwidth backbone networks. The network management system developed uses a two-level hierarchy of network management applications consisting of one top-level management application communicating with several mid-level management applications strategically distributed throughout the internetwork. Mid-level management applications conduct routine monitoring chores on behalf of the top-level management application and report results in a way that makes intelligent use of the limited bandwidth available on the backbone network. The security framework is based on using SNMPv2c over IPSec. This research shows that the other security alternative considered, SNMPv3, consumes as much as 24 percent more network capacity than SNMPv2c over IPSec. The management framework is based on the Management by Delegation (MbD) model and is implemented using the IETF DISMAN Script MIB. This research demonstrates that the MbD-based management framework consumes only 2 percent of the network capacity required by the traditional, centralized management scheme.
Advisors/Committee Members: Midkiff, Scott F. (committeechair), DaSilva, Luiz A. (committee member), Davis, Nathaniel J. IV (committee member).
Subjects/Keywords: Network Management; SNMP; DISMAN Script MIB; IPSec
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APA ·
Chicago ·
MLA ·
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hia, H. E. (2001). Secure SNMP-Based Network Management in Low Bandwidth Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32126
Chicago Manual of Style (16th Edition):
Hia, Henry Erik. “Secure SNMP-Based Network Management in Low Bandwidth Networks.” 2001. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/32126.
MLA Handbook (7th Edition):
Hia, Henry Erik. “Secure SNMP-Based Network Management in Low Bandwidth Networks.” 2001. Web. 24 Jan 2021.
Vancouver:
Hia HE. Secure SNMP-Based Network Management in Low Bandwidth Networks. [Internet] [Masters thesis]. Virginia Tech; 2001. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/32126.
Council of Science Editors:
Hia HE. Secure SNMP-Based Network Management in Low Bandwidth Networks. [Masters Thesis]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/32126

Virginia Tech
16.
Dham, Vikram.
Link Establishment in Ad Hoc Networks Using Smart Antennas.
Degree: MS, Electrical and Computer Engineering, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/32310
► Traditionally medium access control protocols for ad hoc networks have been designed for nodes using omni directional antennas. Through the use of directional antennas, it…
(more)
▼ Traditionally medium access control protocols for ad hoc networks have been designed for nodes using omni directional antennas. Through the use of directional antennas, it is possible to obtain higher efficiency. In this thesis we investigate the impact of these antennas on aggregate throughput and end-to-end delay. The use of omni-directional antennas not only results in lower power efficiency, but also decreases network efficiency due to interference caused by the transmission of packets in undesired directions. This thesis explores the effect of using smart antennas and proposes a signaling mechanism for forming the extended links using the network layer. For the performance assessment of the wireless networks using directional antennas, baseline models of phased array antenna and channel have been developed using the discrete event simulator OPNET ModelerTM 8.0. Simulation scenarios have been created for single hop as well as multihop networks. From the results of the simulation we observe that although the nodes forming the extended link experience decrease in end-to-end delay, the data successfully transmitted using extended link is correlated to the spatial distribution of nodes.
Advisors/Committee Members: DaSilva, Luiz A. (committeechair), Midkiff, Scott F. (committee member), Annamalai, Annamalai Jr. (committee member).
Subjects/Keywords: XuDSR; extended link; WLAN; simulation; directional antenna; DSR
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APA (6th Edition):
Dham, V. (2003). Link Establishment in Ad Hoc Networks Using Smart Antennas. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32310
Chicago Manual of Style (16th Edition):
Dham, Vikram. “Link Establishment in Ad Hoc Networks Using Smart Antennas.” 2003. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/32310.
MLA Handbook (7th Edition):
Dham, Vikram. “Link Establishment in Ad Hoc Networks Using Smart Antennas.” 2003. Web. 24 Jan 2021.
Vancouver:
Dham V. Link Establishment in Ad Hoc Networks Using Smart Antennas. [Internet] [Masters thesis]. Virginia Tech; 2003. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/32310.
Council of Science Editors:
Dham V. Link Establishment in Ad Hoc Networks Using Smart Antennas. [Masters Thesis]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/32310

Virginia Tech
17.
Cho, Jin-Hee.
Design, Implementation and Analysis of Wireless Ad Hoc Messenger.
Degree: MS, Computer Science, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/10058
► Popularity of mobile devices along with the presence of ad hoc networks requiring no infrastructure has contributed to recent advances in the field of mobile…
(more)
▼ Popularity of mobile devices along with the presence of ad hoc networks requiring no infrastructure has contributed to recent advances in the field of mobile computing in ad hoc networks. Mobile ad hoc networks have been mostly utilized in military environments. The recent advances in ad hoc network technology now introduce a new class of applications.
In this thesis, we design, implement and analyze a multi-hop ad hoc messenger application using Pocket PCs and Microsoft .Net Compact Framework. Pocket PCs communicate wirelessly with each other using the IEEE 802.11b technology without the use of an infrastructure. The main protocol implemented in this application is based on Dynamic Source Routing (DSR), which consists of two important mechanisms, Route Discovery and Route Maintenance. We adopt DSR since DSR operates solely based on source routing and "on-demand" process, so each packet does not have to transmit any periodic advertisement packets or routing information. These characteristics are desirable for the ad hoc messenger application for which a conversation is source-initiated on-demand.
To test our application easily, we have developed a testing strategy by which a mobility configuration file is pre-generated describing the mobility pattern of each node generated based on the random waypoint mobility model. A mobility configuration file thus defines topology changes at runtime and is used by all nodes to know whether they can communicate with others in a single-hop or multi-hops during an experimental run.
We use five standard metrics to test the performance of the wireless ad hoc messenger application implemented based on DSR, namely, (1) average latency to find a new route, (2) average latency to deliver a data packet, (3) delivery ratio of data packets, (4) normalized control overhead, and (5) throughput. These metrics test the correctness and efficiency of the wireless ad hoc messenger application using the DSR protocol in an 802.11 ad hoc network that imposes limitations on bandwidth and resources of each mobile device.
We test the effectiveness of certain design alternatives for implementing the ad hoc messenger application with these five metrics under various topology change conditions by manipulating the speed and pause-time parameters in the random waypoint model. The design alternatives evaluated include (1) Sliding Window Size (SWS) for end-to-end reliable communication control; (2) the use of per-hop acknowledgement packets (called receipt packets) deigned for rapid detection of route errors by intermediate nodes; and (3) the use of cache for path look-up during route discovery and maintenance.
Our analysis results indicate that as the node speed increases, the system performance deteriorates because a higher node speed causes the network topology to change more frequently under the random waypoint mobility model, causing routes to be broken. On the other hand, as the pause time increases, the system performance improves due to a more stable network topology. For the design alternatives…
Advisors/Committee Members: Chen, Ing-Ray (committeechair), DaSilva, Luiz A. (committee member), Gracanin, Denis (committee member).
Subjects/Keywords: network routing protocols; mobile ad hoc networks; dynamic source routing (DSR); instant messaging; random waypoint mobility model; wireless communication
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Cho, J. (2004). Design, Implementation and Analysis of Wireless Ad Hoc Messenger. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/10058
Chicago Manual of Style (16th Edition):
Cho, Jin-Hee. “Design, Implementation and Analysis of Wireless Ad Hoc Messenger.” 2004. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/10058.
MLA Handbook (7th Edition):
Cho, Jin-Hee. “Design, Implementation and Analysis of Wireless Ad Hoc Messenger.” 2004. Web. 24 Jan 2021.
Vancouver:
Cho J. Design, Implementation and Analysis of Wireless Ad Hoc Messenger. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/10058.
Council of Science Editors:
Cho J. Design, Implementation and Analysis of Wireless Ad Hoc Messenger. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/10058

Virginia Tech
18.
Saleh, Areej.
A Location-aided Decision Algorithm for Handoff Across Heterogeneous Wireless Overlay Networks.
Degree: MS, Electrical and Computer Engineering, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/10043
► Internetworking third generation (3G) technologies with wireless LAN (WLAN) technologies such as Universal Mobile Telecommunication Systems (UMTS) and IEEE 802.11, respectively, is an emerging trend…
(more)
▼ Internetworking third generation (3G) technologies with wireless LAN (WLAN) technologies such as Universal Mobile Telecommunication Systems (UMTS) and IEEE 802.11, respectively, is an emerging trend in the wireless domain. Its development was aimed at increasing the UMTS network'Âs capacity and optimizing performance. The increase in the number of wireless users requires an increase in the number of smaller WLAN cells in order to maintain an acceptable level of QoS. Deploying smaller cells in areas of higher mobility (e.g., campuses, subway stations, city blocks, malls, etc.) results in the user only spending a short period of time in each cell, which significantly increases the rate of handoff. If the user does not spend sufficient time in the discovered WLAN's coverage area, the application cannot benefit from the higher data rates. Therefore, the data interruption and performance degradation associated with the handoff cannot be compensated for. This counters the initial objective for integrating heterogeneous technologies, thus only handoffs that are followed by a sufficient visit to the discovered WLAN should be triggered. The conventional RF-based handoff decision method does not have the necessary means for making an accurate decision in the type of environments described above. Therefore, a location-aided handoff decision algorithm was developed to prevent the triggering of handoffs that result from short visits to discovered WLAN's  coverage area. The algorithm includes a location-based evaluation that runs on the network side and utilizes a user's location, speed, and direction as well as handoff-delay values to compute the minimum required visit duration and the user'Âs trajectory. A WLAN coverage database is queried to determine whether the trajectory's end point falls within the boundaries of the discovered WLAN's coverage area. If so, the mobile node is notified by the UMTS network to trigger the handoff. Otherwise, the location-based evaluation reiterates until the estimated trajectory falls within the boundaries of the discovered WLAN'Âs coverage area, or the user exits the coverage area. By taking into consideration more then merely RF-measurements, the proposed algorithm is able to predict whether the user'Âs visit to the WLAN will exceed the minimum requirements and make the decision accordingly. This allows the algorithm to prevent the performance degradation and cost associated with unbeneficial/unnecessary handoffs.
Advisors/Committee Members: Davis, Nathaniel J. IV (committeechair), Midkiff, Scott F. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Heterogeneous; Handoff; 3G; IEEE 802.11; Location-aided; UMTS; WLAN
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APA (6th Edition):
Saleh, A. (2004). A Location-aided Decision Algorithm for Handoff Across Heterogeneous Wireless Overlay Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/10043
Chicago Manual of Style (16th Edition):
Saleh, Areej. “A Location-aided Decision Algorithm for Handoff Across Heterogeneous Wireless Overlay Networks.” 2004. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/10043.
MLA Handbook (7th Edition):
Saleh, Areej. “A Location-aided Decision Algorithm for Handoff Across Heterogeneous Wireless Overlay Networks.” 2004. Web. 24 Jan 2021.
Vancouver:
Saleh A. A Location-aided Decision Algorithm for Handoff Across Heterogeneous Wireless Overlay Networks. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/10043.
Council of Science Editors:
Saleh A. A Location-aided Decision Algorithm for Handoff Across Heterogeneous Wireless Overlay Networks. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/10043

Virginia Tech
19.
Ballapuram, Vijayanand Sreenivasan.
Impact of Queuing Schemes and VPN on the Performance of a Land Mobile Radio VoIP System.
Degree: MS, Electrical and Computer Engineering, 2007, Virginia Tech
URL: http://hdl.handle.net/10919/33033
► Land mobile radio (LMR) systems are used for communication by public safety and other government and commercial organizations. LMR systems offer mission-critical or even life-critical…
(more)
▼ Land mobile radio (LMR) systems are used for communication by public safety and other government and commercial organizations. LMR systems offer mission-critical or even life-critical service in the day-to-day activities of such organizations. Traditionally, a variety of different LMR systems have been deployed by different organizations, leading to a lack of radio interoperability. A voice application that connects LMR systems via a packet-switched network is called an LMR Voice over IP (LMRVoIP) system and is a potential solution to the interoperability problem. LMRVoIP systems are time critical, i.e., are delay and jitter sensitive. Transmission of LMRVoIP traffic in a congested packet-switched network with no quality of service (QoS) or priority mechanisms in place could lead to high delays and extreme variations in delay, i.e., high jitter, thus resulting in poor application performance. LMRVoIP systems may also have performance issues with the use of virtual private networks (VPNs). To the best of our knowledge, there has been no prior thorough investigation of the performance of an LMRVoIP system with different queuing schemes for QoS and with the use of VPN. In this thesis, we investigate the performance of an LMRVoIP system with different queuing schemes and with the use of VPN.
An experimental test bed was created to evaluate four QoS queuing schemes: first-in first-out queuing (FIFO), priority queuing (PQ), weighted fair queuing (WFQ), and class-based weighted fair queuing (CBWFQ). Quantitative results were obtained for voice application throughput, delay, jitter, and signaling overhead. Results show that, compared to a baseline case with no background traffic, LMRVoIP traffic suffers when carried over links with heavy contention from other traffic sources when FIFO queuing is used. There is significant packet loss for voice and control traffic and jitter increases. FIFO queuing provides no QoS and, therefore, should not be used for critical applications where the network may be congested. The situation can be greatly improved by using one of the other queuing schemes, PQ, WFQ, or CBWFQ, which perform almost equally well with one voice flow. Although PQ has the best overall performance, it tends to starve the background traffic. CBWFQ was found to have some performance benefits over WFQ in most cases and, thus, is a good candidate for deployment.
The LMRVoIP application was also tested using a VPN, which led to a modest increase in latency and bandwidth utilization, but was found to perform well.
Advisors/Committee Members: Midkiff, Scott F. (committeechair), DaSilva, Luiz A. (committee member), Park, Jung-Min Jerry (committee member).
Subjects/Keywords: Quality of Service; Voice Over IP; Land Mobile Radio; Virtual Private Networks
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ballapuram, V. S. (2007). Impact of Queuing Schemes and VPN on the Performance of a Land Mobile Radio VoIP System. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33033
Chicago Manual of Style (16th Edition):
Ballapuram, Vijayanand Sreenivasan. “Impact of Queuing Schemes and VPN on the Performance of a Land Mobile Radio VoIP System.” 2007. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/33033.
MLA Handbook (7th Edition):
Ballapuram, Vijayanand Sreenivasan. “Impact of Queuing Schemes and VPN on the Performance of a Land Mobile Radio VoIP System.” 2007. Web. 24 Jan 2021.
Vancouver:
Ballapuram VS. Impact of Queuing Schemes and VPN on the Performance of a Land Mobile Radio VoIP System. [Internet] [Masters thesis]. Virginia Tech; 2007. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/33033.
Council of Science Editors:
Ballapuram VS. Impact of Queuing Schemes and VPN on the Performance of a Land Mobile Radio VoIP System. [Masters Thesis]. Virginia Tech; 2007. Available from: http://hdl.handle.net/10919/33033

Virginia Tech
20.
Edwards, Samuel Zachary.
Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques.
Degree: MS, Electrical and Computer Engineering, 2006, Virginia Tech
URL: http://hdl.handle.net/10919/33223
► The U.S. Coast Guard maintains a network structure to connect its nation-wide assets. This paper analyzes and models four highly aggregate traces of the traffic…
(more)
▼ The U.S. Coast Guard maintains a network structure to connect its nation-wide assets. This paper analyzes and models four highly aggregate traces of the traffic to/from the Coast Guard Data Network ship-shore nodes, so that the models may be used to predict future system demand. These internet traces (polled at 5â 40â intervals) are shown to adhere to a Gaussian distribution upon detrending, which imposes limits to the exponential distribution of higher time-resolution traces. Wavelet estimation of the Hurst-parameter is shown to outperform estimation by another common method (Sample-Variances). The First Differences method of detrending proved problematic to this analysis and is shown to decorrelate AR(1) processes where 0.65< phi1 <1.35 and correlate AR(1) processes with phi1 <-0.25. The Hannan-Rissanen method for estimating (phi,theta) is employed to analyze this series and a one-step ahead forecast is generated.
Advisors/Committee Members: Mili, Lamine M. (committeechair), DaSilva, Luiz A. (committee member), Bell, Amy E. (committee member).
Subjects/Keywords: Long-range Dependence; Self-Similarity; Short-range Dependence; Hurst parameter; Time Series Analysis; Fractals; Wavelets; Forecast
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Edwards, S. Z. (2006). Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33223
Chicago Manual of Style (16th Edition):
Edwards, Samuel Zachary. “Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques.” 2006. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/33223.
MLA Handbook (7th Edition):
Edwards, Samuel Zachary. “Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques.” 2006. Web. 24 Jan 2021.
Vancouver:
Edwards SZ. Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques. [Internet] [Masters thesis]. Virginia Tech; 2006. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/33223.
Council of Science Editors:
Edwards SZ. Forecasting Highly-Aggregate Internet Time Series Using Wavelet Techniques. [Masters Thesis]. Virginia Tech; 2006. Available from: http://hdl.handle.net/10919/33223

Virginia Tech
21.
Phanse, Kaustubh Suhas.
Simulation Study of an ADSL Network Architecture: TCP/IP Performance Characterization and Improvements using ACK Regulation and Scheduling Mechanisms.
Degree: MS, Electrical and Computer Engineering, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/35733
► Asymmetric digital subscriber line (ADSL) is a broadband access technology capable of delivering large bandwidth over existing copper telephone line infrastructure. This research aims at…
(more)
▼ Asymmetric digital subscriber line (ADSL) is a broadband access technology capable of delivering large bandwidth over existing copper telephone line infrastructure. This research aims at characterizing and analyzing TCP/IP performance in presence of a new protocol stack (TCP/IP
over PPP and ATM) being promoted for one of the ADSL network architectures.
Using extensive simulations, we verify the adverse effects of asymmetric links on the
performance of TCP and additional throughput degradation caused by the overhead at the AAL5-
ATM layers. This study involves unidirectional as well as bi-directional data transfer using
different traffic mixes including bursty and non-bursty types of traffic. Bi-directional data transfer over asymmetric links results in ACK compression wherein TCP acknowledgements (ACKs) get bunched together behind larger data packets, further exacerbating the effect of asymmetry on
TCP performance. By implementing the simulation model for PPP encapsulation over AAL5, we
characterize its effect in terms of throughput degradation and excessive delay.
We quantify the improvement in the throughput obtained by delaying the TCP ACKs and by
TCP/IP header compression. These techniques being effective for unidirectional traffic over
asymmetric links, however, do not prove as effective when ATM enters the scenario or in
presence of bi-directional data transfer. Further, we implemented a simulation model of the Smart ACK Dropper (SAD), a technique to regulate the flow of TCP ACKs. Considerable improvement
in performance especially in the presence of unidirectional data transfer is achieved using the
SAD technique. Although the improvement is to a lesser extent in the presence of bi-directional
data traffic, SAD helps the network in quickly recovering from the impact of ACK compression.
We also propose and implement certain customized queuing/scheduling and policing mechanisms to enable differentiated servicing of TCP ACKs and data packets, and mitigate the effect of ACK compression. While providing considerable TCP performance improvement in presence of SAD, custom queuing also allows fair sharing of bandwidth between TCP flows, unlike priority queuing, which starves the low priority flow. The committed access rate (CAR)policing scheme provides considerable performance improvement when used with SAD, and is especially useful when TCP ACKs compete with bursty data traffic over the slower upstream.
Advisors/Committee Members: DaSilva, Luiz A. (committeechair), Jacobs, Ira (committee member), Midkiff, Scott F. (committee member).
Subjects/Keywords: differentiated service; ACK Regulation; PPP; simulation; TCP/IP; ATM; ADSL
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Phanse, K. S. (2000). Simulation Study of an ADSL Network Architecture: TCP/IP Performance Characterization and Improvements using ACK Regulation and Scheduling Mechanisms. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35733
Chicago Manual of Style (16th Edition):
Phanse, Kaustubh Suhas. “Simulation Study of an ADSL Network Architecture: TCP/IP Performance Characterization and Improvements using ACK Regulation and Scheduling Mechanisms.” 2000. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/35733.
MLA Handbook (7th Edition):
Phanse, Kaustubh Suhas. “Simulation Study of an ADSL Network Architecture: TCP/IP Performance Characterization and Improvements using ACK Regulation and Scheduling Mechanisms.” 2000. Web. 24 Jan 2021.
Vancouver:
Phanse KS. Simulation Study of an ADSL Network Architecture: TCP/IP Performance Characterization and Improvements using ACK Regulation and Scheduling Mechanisms. [Internet] [Masters thesis]. Virginia Tech; 2000. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/35733.
Council of Science Editors:
Phanse KS. Simulation Study of an ADSL Network Architecture: TCP/IP Performance Characterization and Improvements using ACK Regulation and Scheduling Mechanisms. [Masters Thesis]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/35733

Virginia Tech
22.
Chattha, Jawwad Nasar.
Characterization of Selfish Behavior in Mobile Ad Hoc Networks through Virtual Emulation.
Degree: MS, Electrical and Computer Engineering, 2009, Virginia Tech
URL: http://hdl.handle.net/10919/34666
► Unlike infrastructure-based networks, mobile ad hoc networks consist of nodes independent of any infrastructure. Cooperation among these nodes is essential for the sustenance of multi…
(more)
▼ Unlike infrastructure-based networks, mobile ad hoc networks consist of nodes independent of any infrastructure. Cooperation among these nodes is essential for the sustenance of multi hop communication. However, battery and bandwidth constraints may lead nodes in an ad hoc network to adopt energy- and bandwidth-conserving strategies. As routing and packet forwarding are end results of cooperation, network performance is affected when nodes in the network behave selfishly to conserve their resources.
Our work involves characterizing selfish behavior by nodes in ad hoc networks and assessing the effectiveness of adopting tit for tat based strategies, which are meant to discourage selfish behavior in the network. We show that in an ad hoc network where other nodes act selfishly to conserve their resources, a node can benefit by adopting a generous tit for tat strategy. We also show that a node can gain benefit by avoiding selfish nodes in an ad hoc network, adopting a strategy that we call generous tit for tat with selfish avoidance (GTFT-SA).
To analyze the effectiveness of cooperation strategies in selfish ad hoc networks we create an emulation environment based on virtualization. Such an emulation environment is more flexible to changes and is simpler to replicate than real life testbeds, while providing higher fidelity than simulations.
Advisors/Committee Members: DaSilva, Luiz A. (committeechair), Eltoweissy, Mohamed Y. (committee member), Midkiff, Scott F. (committee member).
Subjects/Keywords: Emulation; Generous tit for tat.; Virtualization
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Chattha, J. N. (2009). Characterization of Selfish Behavior in Mobile Ad Hoc Networks through Virtual Emulation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34666
Chicago Manual of Style (16th Edition):
Chattha, Jawwad Nasar. “Characterization of Selfish Behavior in Mobile Ad Hoc Networks through Virtual Emulation.” 2009. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/34666.
MLA Handbook (7th Edition):
Chattha, Jawwad Nasar. “Characterization of Selfish Behavior in Mobile Ad Hoc Networks through Virtual Emulation.” 2009. Web. 24 Jan 2021.
Vancouver:
Chattha JN. Characterization of Selfish Behavior in Mobile Ad Hoc Networks through Virtual Emulation. [Internet] [Masters thesis]. Virginia Tech; 2009. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/34666.
Council of Science Editors:
Chattha JN. Characterization of Selfish Behavior in Mobile Ad Hoc Networks through Virtual Emulation. [Masters Thesis]. Virginia Tech; 2009. Available from: http://hdl.handle.net/10919/34666

Virginia Tech
23.
Chugh, Sarabjeet Singh.
Impact of Network Address Translation on Router Performance.
Degree: MS, Electrical and Computer Engineering, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/35307
► Network Address Translation (NAT) is a method by which Internet Protocol (IP) addresses are ranslated from one group to another, in a manner transparent to…
(more)
▼ Network Address Translation (NAT) is a method by which Internet Protocol (IP) addresses are ranslated from one group to another, in a manner transparent to the end users. It translates the source and destination addresses and ports in the Internet Protocol datagram. There are several benefits for using NAT. NAT can be installed without changes to hosts or routers, it allows reuse of globally routable addresses, it facilitates easy migration or addition of new networks and it provides a method to keep private network addresses hidden from the outside world.
NAT, however, is a processor- and memory-intensive activity for any device that implements it. This is because NAT involves reading from and writing to the header and payload information of every IP packet to do the address translation, a performance-intensive activity. It causes an increase in Central Processing Unit (CPU) and memory utilization and may impair throughput and increase the latency experienced by a packet. Thus, understanding the performance impact of NAT on a network device (in particular, a router) becomes an important factor when implementing NAT in any live network.
This thesis aims to understand and quantify the impact of Network Address Translation on a network router by doing a series of performance tests after specifying the performance parameters to measure and, then, clearly defining the performance testing methodology that is used to study each of the performance parameters. After a discussion of previous research, the measurement system and subsequent measurement results are described.
Advisors/Committee Members: DaSilva, Luiz A. (committeechair), Midkiff, Scott F. (committee member), Annamalai, Annamalai Jr. (committee member).
Subjects/Keywords: Utilization; Network; Delay; CPU; Throughput
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Chugh, S. S. (2003). Impact of Network Address Translation on Router Performance. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35307
Chicago Manual of Style (16th Edition):
Chugh, Sarabjeet Singh. “Impact of Network Address Translation on Router Performance.” 2003. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/35307.
MLA Handbook (7th Edition):
Chugh, Sarabjeet Singh. “Impact of Network Address Translation on Router Performance.” 2003. Web. 24 Jan 2021.
Vancouver:
Chugh SS. Impact of Network Address Translation on Router Performance. [Internet] [Masters thesis]. Virginia Tech; 2003. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/35307.
Council of Science Editors:
Chugh SS. Impact of Network Address Translation on Router Performance. [Masters Thesis]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/35307

Virginia Tech
24.
Filippi, Geoffrey George.
A High-Availability Architecture for the Dynamic Domain Name System.
Degree: MS, Electrical and Computer Engineering, 2008, Virginia Tech
URL: http://hdl.handle.net/10919/32869
► A High-Availability Architecture for the Dynamic Domain Name System DNS, DDNS, BGP, anycast, DHCP, replication, LDAP, multi-master, high-availability, reliability The Domain Name System (DNS) provides…
(more)
▼ A High-Availability Architecture for the Dynamic Domain Name System
DNS, DDNS, BGP, anycast, DHCP, replication, LDAP, multi-master, high-availability, reliability
The Domain Name System (DNS) provides a mapping between host names and Internet Protocol
(IP) addresses. Hosts that are configured using the Dynamic Host Configuration Protocol
(DHCP) can have their assigned IP addresses updated in a Dynamic DNS (DDNS). DNS and
DDNS are critical components of the Internet. Most applications use host names rather than IP
addresses, allowing the underlying operating system (OS) to translate these host names to IP
addresses on behalf of the application. When the DDNS service is unavailable, applications that
use DNS cannot contact the hosts served by that DDNS server. Unfortunately, the current DDNS
implementation cannot continue to operate under failure of a master DNS server. Although a
slave DNS server can continue to translate names to addresses, new IP addresses or changes to
existing IP addresses cannot be added. Therefore, those new hosts cannot be reached by the
DDNS.
A new architecture is presented that eliminates this single point of failure. In this design, instead
of storing resource records in a flat text file, all name servers connect to a Lightweight Directory
Access Protocol (LDAP) directory to store and retrieve resource records. These directory servers
replicate all resource records across each other using a multi-master replication mechanism. The
DHCP servers can add records to any of the functioning DNS servers in event of an outage.
In this scheme, all DNS servers use the anycast Border Gateway Protocol (BGP). This allows
any of the DNS servers to answer queries sent to a single IP address. The DNS clients always use
the same IP address to send queries. The routing system removes routes to non-functional name
servers and delivers the request to the closest (according to network metrics) available DNS
server.
This thesis also describes a concrete implementation of this system that was created to
demonstrate the viability of this solution. A reference implementation was built in a laboratory to
represent an Internet Service Provider (ISP) with three identical regions. This implementation
was built using Quagga as the BGP routing software running on a set of core routers and on each
of the DNS servers. The Berkeley Internet Name Daemon (BIND) was used as an
implementation of the DNS. The BIND Simplified Database Backend (SDB) interface was used
to allow the DNS server to store and retrieve resource records in an LDAP directory. The Fedora
Directory Server was used as a multi-master LDAP directory. DHCP service was provided by
the Internet Systems Consortium's (ISC) DHCP server.
The objectives for the design were high-availability, scalability and consistency. These
properties were analyzed using the metrics of downtime during failover, replication overhead,
and latency of replication. The downtime during failover was less than one second. The precision
of this metric was limited by the…
Advisors/Committee Members: Midkiff, Scott F. (committeechair), DaSilva, Luiz A. (committee member), Eltoweissy, Mohamed Y. (committee member).
Subjects/Keywords: DNS; DDNS; BGP; anycast; DHCP; replication; LDAP; multi-master; high-availability; reliability
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Filippi, G. G. (2008). A High-Availability Architecture for the Dynamic Domain Name System. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32869
Chicago Manual of Style (16th Edition):
Filippi, Geoffrey George. “A High-Availability Architecture for the Dynamic Domain Name System.” 2008. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/32869.
MLA Handbook (7th Edition):
Filippi, Geoffrey George. “A High-Availability Architecture for the Dynamic Domain Name System.” 2008. Web. 24 Jan 2021.
Vancouver:
Filippi GG. A High-Availability Architecture for the Dynamic Domain Name System. [Internet] [Masters thesis]. Virginia Tech; 2008. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/32869.
Council of Science Editors:
Filippi GG. A High-Availability Architecture for the Dynamic Domain Name System. [Masters Thesis]. Virginia Tech; 2008. Available from: http://hdl.handle.net/10919/32869

Virginia Tech
25.
Srivastava, Vikash Umeshchandra.
Smart Antennas & Power Management in Wireless Networks.
Degree: MS, Electrical and Computer Engineering, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/31244
► The proliferation of wireless ad-hoc networks especially wireless LAN (IEEE 802.11b Standard) in the commercial market in recent years has reached a critical mass. The…
(more)
▼ The proliferation of wireless ad-hoc networks especially wireless LAN (IEEE 802.11b Standard) in the commercial market in recent years has reached a critical mass. The adoption and strong support of wireless IEEE 802.11 standard, coupled with the consequent decline in costs, has made wireless LAN deployment as one of the fastest growth area in communication access technology. With the ever increasing use of wireless LAN technology the various networks are reaching their full capacity in terms of network throughput, number of users and interference level in the wireless channel.
In this thesis work I propose to the use smart antenna technology and a power management scheme in the wireless ad-hoc networks to increase the network capacity in terms of throughput, number of simultaneous communication and to lower the average transmit power and consequently co-channel interference. Power management scheme can be used to maximize the power efficiency of the transmitter by choosing an optimum transmit power level. Smart antenna or adaptive antenna array technology has reached a level of sophistication that it is feasible to use it on small mobile terminals like handheld PDA, LAPTOP and other mobile devices with limited battery power.
The simulation results of various ad â hoc network scenario shows that there are significant gains to be had if these technologies can be integrated in the existing wireless LAN physical layer and/or in the standard them self. Smart antennas along with slight modification in channel access scheme reduce co-channel interference dramatically and increases the number of simultaneous transmissions hence improves network throughput. Power management algorithm is shown to improve average transmission of a node.
We present a mathematical framework to characterize the outage probability of cellular mobile radio system with selective co-channel interference receiver in overloaded array environments. The mathematical framework outlines a general numerical procedure for computing the probability of outage of a cellular mobile radio system that is equipped with a smart antenna to suppress a few strongest co-channel interferers (CCI) out of a total of NI active interferers by null steering.
Advisors/Committee Members: Annamalai, Annamalai Jr. (committeechair), DaSilva, Luiz A. (committee member), Reed, Jeffrey Hugh (committee member).
Subjects/Keywords: Wireless Communications; Ad-Hoc Network; Indoor Propagation Environment; Network Throughput; Wireless LAN802.11b; Smart Antenna; Adaptive Beam-Forming
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Srivastava, V. U. (2003). Smart Antennas & Power Management in Wireless Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31244
Chicago Manual of Style (16th Edition):
Srivastava, Vikash Umeshchandra. “Smart Antennas & Power Management in Wireless Networks.” 2003. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/31244.
MLA Handbook (7th Edition):
Srivastava, Vikash Umeshchandra. “Smart Antennas & Power Management in Wireless Networks.” 2003. Web. 24 Jan 2021.
Vancouver:
Srivastava VU. Smart Antennas & Power Management in Wireless Networks. [Internet] [Masters thesis]. Virginia Tech; 2003. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/31244.
Council of Science Editors:
Srivastava VU. Smart Antennas & Power Management in Wireless Networks. [Masters Thesis]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/31244

Virginia Tech
26.
Samal, Savyasachi.
Mobility Pattern Aware Routing in Mobile Ad Hoc Networks.
Degree: MS, Computer Science, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/34984
► A mobile ad hoc network is a collection of wireless nodes, all of which may be mobile, that dynamically create a wireless network amongst them…
(more)
▼ A mobile ad hoc network is a collection of wireless nodes, all of which may be mobile, that dynamically create a wireless network amongst them without using any infrastructure. Ad hoc wireless networks come into being solely by peer-to-peer interactions among their constituent mobile nodes, and it is only such interactions that are used to provide the necessary control and administrative functions supporting such networks. Mobile hosts are no longer just end systems; each node must be able to function as a router as well to relay packets generated by other nodes. As the nodes move in and out of range with respect to other nodes, including those that are operating as routers, the resulting topology changes must somehow be communicated to all other nodes as appropriate. In accommodating the communication needs of the user applications, the limited bandwidth of wireless channels and their generally hostile transmission characteristics impose additional constraints on how much administrative and control information may be exchanged, and how often. Ensuring effective routing is one of the greatest challenges for ad hoc networking.
As a practice, ad hoc routing protocols make routing decisions based on individual node mobility even for applications such as disaster recovery, battlefield combat, conference room interactions, and collaborative computing etc. that are shown to follow a pattern.
In this thesis we propose an algorithm that performs routing based on underlying mobility patterns. A mobility pattern aware routing algorithm is shown to have several distinct advantages such as: a more precise view of the entire network topology as the nodes move; a more precise view of the location of the individual nodes; ability to predict with reasonably accuracy the future locations of nodes; ability to switch over to an alternate route before a link is disrupted due to node movements.
Advisors/Committee Members: Mishra, Amitabh (committeechair), DaSilva, Luiz A. (committee member), Varadarajan, Srinidhi (committeecochair).
Subjects/Keywords: DSDV; Random Motion; Routing Algorithms; Mobility Pattern; Ad Hoc Networks
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APA (6th Edition):
Samal, S. (2003). Mobility Pattern Aware Routing in Mobile Ad Hoc Networks. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34984
Chicago Manual of Style (16th Edition):
Samal, Savyasachi. “Mobility Pattern Aware Routing in Mobile Ad Hoc Networks.” 2003. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/34984.
MLA Handbook (7th Edition):
Samal, Savyasachi. “Mobility Pattern Aware Routing in Mobile Ad Hoc Networks.” 2003. Web. 24 Jan 2021.
Vancouver:
Samal S. Mobility Pattern Aware Routing in Mobile Ad Hoc Networks. [Internet] [Masters thesis]. Virginia Tech; 2003. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/34984.
Council of Science Editors:
Samal S. Mobility Pattern Aware Routing in Mobile Ad Hoc Networks. [Masters Thesis]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/34984

Virginia Tech
27.
Kawser, Mohammad Tawhid.
Investigation of a Novel Dual Band Microstrip/Waveguide Hybrid Antenna Element.
Degree: MS, Electrical and Computer Engineering, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/33660
► Microstrip antennas are low in profile, light in weight, conformable in structure and are now developed for many applications. The main difficulty of the microstrip…
(more)
▼ Microstrip antennas are low in profile, light in weight, conformable in structure and are now developed for many applications. The main difficulty of the microstrip antenna is its narrow bandwidth. Several modern applications like satellite communications, remote sensing and multi-function radar systems will find it useful if there is dual band antenna operating from a single aperture. Some applications require covering both transmitting and receiving frequency bands which are spaced apart. Providing multiple antennas to handle multiple frequencies and polarizations becomes especially difficult if the available space is limited as with airborne platforms and submarine periscopes.
Dual band operation can be realized from a single feed using slot loaded or stacked microstrip antenna or two separately fed antennas sharing a common aperture. The former design, when used in arrays, has certain limitations like complicated beam forming or diplexing network and difficulty to realize good radiation patterns at both the bands. The second technique provides more flexibility with separate feed system as beams in each frequency band can be controlled independently. Another desirable feature of a dual band antenna is easy adjustability of upper and lower frequency bands.
This thesis presents investigation of a new dual band antenna, which is a hybrid of microstrip and waveguide radiating elements. The low band radiator is a Shorted Annular Ring (SAR) microstrip antenna and the high band radiator is an aperture antenna. The hybrid antenna is realized by forming a waveguide radiator in the shorted region of the SAR microstrip antenna. It is shown that the upper to lower frequency ratio can be controlled by the proper choice of various dimensions and dielectric material. Operation in both linear and circular polarization is possible in either band. Moreover, both broadside and conical beams can be generated in either band from this antenna element.
Finite Element Method based software, HFSS and Method of Moments based software, FEKO were employed to perform parametric studies of the proposed dual band antenna. The antenna was not tested physically. Therefore, in most cases, both HFSS and FEKO were employed to corroborate the simulation results.
Advisors/Committee Members: Zaghloul, Amir I. (committeechair), Davis, William A. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: FEKO; HFSS; Dual Band; Shorted Annular Ring Patch
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kawser, M. T. (2005). Investigation of a Novel Dual Band Microstrip/Waveguide Hybrid Antenna Element. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33660
Chicago Manual of Style (16th Edition):
Kawser, Mohammad Tawhid. “Investigation of a Novel Dual Band Microstrip/Waveguide Hybrid Antenna Element.” 2005. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/33660.
MLA Handbook (7th Edition):
Kawser, Mohammad Tawhid. “Investigation of a Novel Dual Band Microstrip/Waveguide Hybrid Antenna Element.” 2005. Web. 24 Jan 2021.
Vancouver:
Kawser MT. Investigation of a Novel Dual Band Microstrip/Waveguide Hybrid Antenna Element. [Internet] [Masters thesis]. Virginia Tech; 2005. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/33660.
Council of Science Editors:
Kawser MT. Investigation of a Novel Dual Band Microstrip/Waveguide Hybrid Antenna Element. [Masters Thesis]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/33660

Virginia Tech
28.
Sprinkle, Matthew.
Design Considerations in a Modern Land Mobile Radio System.
Degree: MS, Electrical and Computer Engineering, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/33847
► Modern Land Mobile Radio has the potential for large growth in the near future. Current regulations have set the stage for a required transition to…
(more)
▼ Modern Land Mobile Radio has the potential for large growth in the near future. Current regulations have set the stage for a required transition to more spectrally efficient
technologies. While several organizations are working to ease this transition, there still
remain many details and feature sets which the end user must decide amongst and often
there is no clear dividing line between these choices.
This thesis provides a high-level view of the distinguishing components in modern LMR
systems. Discussions related to trunked channel allocation, coverage, costs, security, and
other capabilities are given. The application to and effect on everyday users is also
considered. Several quantitative examples are provided to assist the end-user in
determining when a solution is viable. The discussion and analysis included reaffirm that
LMR design is complex and wide-ranging. Ultimately, the designer must evaluate needs
and technologies to provide a course of action which is optimum and justifiable.
Advisors/Committee Members: Woerner, Brian D. (committeechair), DaSilva, Luiz A. (committee member), Reed, Jeffrey Hugh (committee member).
Subjects/Keywords: Trunking; Encryption; Security; Land Mobile Radio; Analysis; Push-to-Talk; Cost; Coverage
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Sprinkle, M. (2003). Design Considerations in a Modern Land Mobile Radio System. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33847
Chicago Manual of Style (16th Edition):
Sprinkle, Matthew. “Design Considerations in a Modern Land Mobile Radio System.” 2003. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/33847.
MLA Handbook (7th Edition):
Sprinkle, Matthew. “Design Considerations in a Modern Land Mobile Radio System.” 2003. Web. 24 Jan 2021.
Vancouver:
Sprinkle M. Design Considerations in a Modern Land Mobile Radio System. [Internet] [Masters thesis]. Virginia Tech; 2003. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/33847.
Council of Science Editors:
Sprinkle M. Design Considerations in a Modern Land Mobile Radio System. [Masters Thesis]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/33847

Virginia Tech
29.
Wang, Xiao.
Simulation of Simultaneously Negative Medium Metamaterials.
Degree: MS, Electrical and Computer Engineering, 2009, Virginia Tech
URL: http://hdl.handle.net/10919/35301
► Metamaterials are artificial materials and named by those who work in the microwave material area. According to existing documentation, the metamaterials have relative permittivity and/or…
(more)
▼ Metamaterials are artificial materials and named by those who work in the microwave material area. According to existing documentation, the metamaterials have relative permittivity and/or relative permeability of values less than 1, including negative values. If the material has negative permittivity and permeability at the same time, the material is also referred to as simultaneously negative medium (DNG medium). Such medium has several features that any natural medium is not equipped with: negative refraction, backward phase, and evanescent wave amplification [5]. Though the medium does not exist in nature, it seems that it can be artificially made through synthesizing metallic insertions inside the natural dielectrics [2]. Due to its unique feature of negative refraction and this feature is not equipped with any reported natural medium, the concept of making perfect lenses with metamaterials has attracted attentions in recent years. However a number of questions need to be answered: How can we quantize the refractive index of the metamaterial given that the permittivity and permeability are known or vice versa; can the metamaterial be made isotropic medium under effects of different incident angles? The answer to the first question will help us to define the dimension of the lenses more efficiently; and the answer to the latter question will help determine if such medium is capable of being used to make lenses.
Previous publications from others demonstrated the negative refraction phenomenon of metamaterials though this phenomenon is restricted to a very narrow band [4] [11]. The derivation of the negative refractive index through full-wave simulation and comparison with its value through calculating the simulated negative permittivity and permeability obtained from the simulated scattering matrix have not been reported. The work carried in this thesis fully explored the ways to address this and answer those questions mentioned in previous paragraph. To fully understand the negative refraction effect of metamaterial, the author built a mathematical geometric model to calculate refractive index for rectangular metamaterial slab. With this approach, the refractive index can be obtained provided that incident and peak-receive angle are known. In order to achieve a metamaterial with isotropy property, the author also presented three different types of metamaterial slabs: parallel-arranged, vertical-arranged and cross-arranged slab of capacitive-loaded-loops (CLL) in front of standing probes or posts, which are also called CLL-P slabs. The three arrangements are differentiated by the way unit cell is oriented. With the geometric model, the author obtained refractive indexes for three metamaterial slabs at different incident angles through numerical simulation. The refractive indexes have negative values at all circumstance, which shows the negative refraction phenomena unique to the metamaterial. Unlike the other two CLL-P slabs, the cross-arranged CLL-P slab has near constant refractive index and constant received…
Advisors/Committee Members: Zaghloul, Amir I. (committeechair), Mili, Lamine M. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: Simultaneously Negative; Medium; Simulation; Metamaterials; DNG Medium
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wang, X. (2009). Simulation of Simultaneously Negative Medium Metamaterials. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35301
Chicago Manual of Style (16th Edition):
Wang, Xiao. “Simulation of Simultaneously Negative Medium Metamaterials.” 2009. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/35301.
MLA Handbook (7th Edition):
Wang, Xiao. “Simulation of Simultaneously Negative Medium Metamaterials.” 2009. Web. 24 Jan 2021.
Vancouver:
Wang X. Simulation of Simultaneously Negative Medium Metamaterials. [Internet] [Masters thesis]. Virginia Tech; 2009. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/35301.
Council of Science Editors:
Wang X. Simulation of Simultaneously Negative Medium Metamaterials. [Masters Thesis]. Virginia Tech; 2009. Available from: http://hdl.handle.net/10919/35301

Virginia Tech
30.
Vasudevan, Srinivasan.
A Simulator for analyzing the throughput of IEEE 802.11b Wireless LAN Systems.
Degree: MS, Electrical and Computer Engineering, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/31054
► Wireless Local Area Networks (WLAN) have proliferated in the last 5 years. The IEEE 802.11b products have become commonplace both in the residential and business…
(more)
▼ Wireless Local Area Networks (WLAN) have proliferated in the last 5 years. The IEEE 802.11b products have become commonplace both in the residential and business places for untethered Internet access. However the end user experience has often been less satisfactory than what the technology can offer. The degradation in the performance of the system is mainly attributed to the poor network design. The current network design is primarily RF centric. There are two factors that need to be in the incorporated in the design. Firstly a clear understanding of the traffic sources in the network such as the peak load of the system is necessary. Secondly the design should account for the limitations of the indoor propagation such as interference and multipath.
The goal of this thesis is to develop a simulator which will predict the performance (throughput) of an end user. The throughput is predicted for a given topology and traffic source. The simulator is built on object oriented design. To validate the simulator a measurement campaign was conducted. The campaign was conducted in two different channel conditions, office space and open hall. The channel measurements were also performed at these locations to understand the multipath.
Comparative studies indicate that the choice of the rate adaptation algorithm hugely influences the predicted throughput. The simulator results match very well with the measurement results for the open space scenario. For the office space scenario the simulator varied by roughly 20% from the measurement results. This was due to existence of multipath leading to Inter Symbol Interference.
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Robert, Pablo M. (committee member), DaSilva, Luiz A. (committee member).
Subjects/Keywords: channel characteristics; IEEE 802.11b; throughput measurement; Wireless LAN
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Vasudevan, S. (2005). A Simulator for analyzing the throughput of IEEE 802.11b Wireless LAN Systems. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31054
Chicago Manual of Style (16th Edition):
Vasudevan, Srinivasan. “A Simulator for analyzing the throughput of IEEE 802.11b Wireless LAN Systems.” 2005. Masters Thesis, Virginia Tech. Accessed January 24, 2021.
http://hdl.handle.net/10919/31054.
MLA Handbook (7th Edition):
Vasudevan, Srinivasan. “A Simulator for analyzing the throughput of IEEE 802.11b Wireless LAN Systems.” 2005. Web. 24 Jan 2021.
Vancouver:
Vasudevan S. A Simulator for analyzing the throughput of IEEE 802.11b Wireless LAN Systems. [Internet] [Masters thesis]. Virginia Tech; 2005. [cited 2021 Jan 24].
Available from: http://hdl.handle.net/10919/31054.
Council of Science Editors:
Vasudevan S. A Simulator for analyzing the throughput of IEEE 802.11b Wireless LAN Systems. [Masters Thesis]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/31054
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