Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 120-122). Also available via the Internet.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 120-129). Also available in electronic version.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2005. / Thesis Advisor(s): Frank Kragh, Herschel H. Loomis. Includes bibliographical references (p. 55-56). Also available online.

An ad hoc network is maintained by the combined efforts of all the mobile nodes themselves, who often operate under severe constraints, such as limited battery power, variable link quality, and limited storage capacity. As a result, there is a growing need for enhanced fault and configuration management solutions to help in tracking problems as well as solving them. Viable network architecture for a wireless ad-hoc environment, which takes advantages of both hierarchical and distributed architectures, has been investigated. A complete design solution is proposed which makes ad-hoc environments less susceptible to faults. Results shows that by applying the proposed power saving technique, network load due to control traffic may be significantly reduced. Based on other gathered statistics, we can set the optimal value of maximum number of nodes allowed in a cluster for efficient performance to be 35 for a specific scenario.

Testimonies of “wireless catching up with wireline” have begun. However, the nonstationary and hostile nature of the wireless channel impose the greatest threat to reliable data transmission over wireless links. The performance of a digital modulation scheme is degraded by many transmission impairments including fading, delay spread, co-channel interference and noise. Two powerful techniques for improving the quality of service over the wireless network are investigated: diversity reception and adaptive error control schemes. Owing to the growing interest in wireless communications, the importance of exact theoretical analysis of such systems cannot be understated. In light of these considerations, this dissertation focuses on accurate and efficient analysis of wireless digital communication systems in multiuser and multipath fading environments. The evaluation of error probabilities in digital communication systems is often amenable to calculating a generic error probability of the form Pr {X ≤ 0}, where X is a random variable whose probability distribution is known. We advocate a simple numerical approach based on the Fourier or Laplace inversion formulas and Gauss-Chebychev quadratures (GCQ) for computing this error probability. Using this result, and by formulating the outage probability of cellular mobile radio networks in the framework of statistical decision theory, we can unify the outage performance analysis for cellular mobile radio systems in generalized fading channels without imposing any restrictions on the desired signal and interferers statistics. Next, we develop two unified analytical frameworks for evaluating the bit or symbol error probability (SER) of a broad class of coherent, differentially coherent and noncoherent digital communication systems with diversity reception in generalized fading channels. The exact SER is mostly expressed in terms of a single finite-range integral, and in some cases in the form of double finite-range integrals. Virtually “exact” closed-form expressions (in terms of a rapidly converging series) are also derived. This offers a convenient method to perform a comprehensive study of all common diversity combining techniques (maximal-ratio combining (MRC), equal-gain combining (EGC), selection combining (SDC) and switched combining (SWC)) with different modulation formats in a myriad of fading scenarios. In particular, our unified approach based on characteristic function (CHF) method allows us to unify the above problem in a single common framework. Nevertheless, the moment generating function (MGF) method often yields a more concise solution than the CHF approach in the analysis of MRC, SDC and SWC diversity systems. Subsequently, we examine the performance of a maximum amplitude selection diversity (MA/SD) rake receiver configuration in indoor wireless channels. The proposed low-complexity receiver structure is practically appealing because of its simplicity as well as its ability to operate effectively even at high signalling rates. We have also devised a robust packet combining mechanism to enhance the throughput and delay performance of spread-spectrum radio networks without incurring a substantial penalty in receiver complexity. A simple indirect method to estimate the channel state condition for successful implementation of a self-reconfigurable automatic repeat-request (ARQ) system, such as mixed-mode ARQ protocol or adaptive packet length strategy in a slowly varying mobile radio environment is also studied. / Graduate

With the growing commercial importance of the Internet and the development of new real-time, connection-oriented services like IP-telephony and electronic commerce resilience is becoming a key issue in the design of TP-based networks. Two emerging technologies, which can accomplish the task of efficient information transfer, are Multiprotocol Label Switching (MPLS) and Differentiated Services. A main benefit of MPLS is the ability to introduce traffic-engineering concepts due to its connection-oriented characteristic. With MPLS it is possible to assign different paths for packets through the network. Differentiated services divides traffic into different classes and treat them differently, especially when there is a shortage of network resources. In this thesis, a framework was proposed to integrate the above two technologies and its performance in providing load balancing and improving QoS was evaluated. Simulation and analysis of this framework demonstrated that the combination of MPLS and Differentiated services is a powerful tool for QoS provisioning in IP networks.

This thesis presents a novel approach towards providing a collaboration environment by using Grid Computing. The implementation includes the deployment of a cluster attached to a mural display for high performance computing and visualization and a Grid-infrastructure for sharing storage space across a wide area network and easing the remote use of the computing resources. A medical data processing application is implemented on the platform. The outcome is enhanced use of remote storage facilities and quick return time for computationally-intensive problems. The central issue of this thesis work is thus one that focuses on the development of a secure distributed system for data management and visualization to respond to the need for more efficient interaction and collaboration between technical researchers and medical professionals. The proposed networked solution is envisioned such as to provide synergy for more collaboration on theoretical and experimental issues involving analysis, visualization, and data sharing across sites.

M.Ing. (Electrical & Electronic Engineering) / Please refer to full text to view abstract

A thesis submitted in fulfilment of the requirements for the Degree of MA in Communication Science, University of Zululand, 2001. / In this thesis I focus on the introduction of Electronic Cornmunication as part of an envisaged Communication Science curriculum in the Language, Literacy and Communication Learning area of the Further Education and Training band. In the course of my thesis I will show that the requisite elements of verbal and written cornmunication are dispersed throughout the Language, Literacy and Communication learning area in the General Education and Training band, and that they can be utilised as basis for formally introducing Communication Science, as a subject in the Language, literacy and Communication learning area in the Further Education and Train¬ing band. I also show that electronic communication will form a crucial area of study in such a Communication Science curriculum. I argue that due to the diversity of cultures in South Africa, cross-cultural cornmunication is required in such a curriculum. I also argue that by the very na¬ture of Outcomes-Based Education it is necessary to have a subject into our school curriculum that will form an interface with conceptual learning and experiential learning, that will contextu-alise language study within the more comprehensive scope of forms of human communication, and that will form an interface between the humanities and science to prevent the humanities from becoming soft options in Further Education and Training band learning programmes. To this effect I focus on the crucial role of Constructivism as integrating theory to account for vari¬ous approaches to motivational learning, the primary form of learning required in Outcomes-Based Education. I examine the principles of curriculum construction in OBE and its associated culture of learn¬ing against the backdrop of the theory of Situated Cognition. This presents a platform to argue the case for Electronic Communication as part of Communication Science in the Further Edu¬cation and Training band curricula in South African schools. / National Research Foundation

Spectrum sharing among cellular users has been a promising approach to attain better efficiency in the use of the limited spectral bands. The existing dynamic spectrum access techniques include sharing of the licensed spectrum bands by allowing other 'secondary' users to use the bands if the licensee 'primary' user is idle. This primary-secondary spectrum sharing is limited in terms of design space, and may not be sufficient to meet the ever-increasing demand of connectivity and high signal quality to improve the end-users' wireless experience. The next step to increase spectrum efficiency is to design markets where sharing takes place pervasively among primary providers rather than leaving it to the limited case of when the primary licensee is idle. Attaining contractual pervasive spectrum sharing among primary providers, a.k.a. co-primary spectrum sharing (Co-PSS), involves additional costs for the users, e.g., roaming fee. Co-PSS without additional charge to the users poses two major challenges: 1) regulatory approaches must be introduced to incentivize and encourage providers for sharing spectrum resources, and 2) small providers in Co-PSS markets may freeride on large providers' networks as the customers of the small providers may be using the spectrum and infrastructure resources of large providers. Such freeriding opportunities in Co-PSS markets must be minimized to realize the benefits of primary-level sharing. This dissertation considers a subsidy-based spectrum sharing (SBSS) market to facilitate Co-PSS where providers are explicitly incentivized to share spectrum resources. It focuses on minimizing freeriding in SBSS markets by introducing a novel game-theoretic and heuristic algorithm. It proposes ''Proof of Sharing (PoS)'', an architecture to account spectrum sharing. It also demonstrates how to utilize PoS-like crowdsourced data to predict cellular tower locations which help to generate a truthful coverage map. Finally, this dissertation extends Co-PSS to two new models with government infrastructure and spectrum as rewards.