Thesis (M.S.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaf 39)

Thesis (M.S.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 73-75)

Thesis (M.S.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 148-150)

Thesis (M.S.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 51-52)

This dissertation addresses the issue of optimum system design to achieve reliable communication in the presence of various types of interference. Multiobjective formulation is used with noncooperative and cooperative approaches owing to the nature of the problems under consideration. Since intentional Jamming is one of the most severe kinds of interference, anti-jam techniques are crucial for communications in a hostile environment. The jam and anti-jam problem is modeled as a two-person zero-sum game in which the communicator and the jammer have antagonistic objectives and are viewed as the two players. The concept of Nash equilibrium is introduced and its characterizations such as existence, uniqueness, stability, robustness, and sensitivity are investigated. This model is then applied to a frequency-hop spread spectrum M-ary frequency-shift-keying system where ratio-threshold diversity is used to combat partial-band noise and multitone jamming. Equilibrium performance in terms of cutoff rate and bit error rate is shown to be superior to that predicted by worst-case analysis. When mutual interference caused by simultaneous transmissions is the major concern in a heterogeneous packet network, a multiobjective framework is proposed in this dissertation with the objectives and constraints of the individual users taken into consideration. Near-far effect and Rayleigh fading may occasion packet capture and therefore create unfairness in favor of closer users. Thus, multiobjective optimality is introduced, in which criterion of fairness is embedded. Optimum strategies controlling transmission probability and/or power are examined to yield the Pareto optimal solution in a slotted ALOHA network. Then, the same control strategies are studied with the channel utilization being the maximization objective. Optimization results are obtained in various situations, and effectiveness of different strategies is compared. A multimedia direct-sequence spread spectrum system may support multiple services with different transmission rates and diverse quality-of-service requirements. To facilitate multimedia applications and maximize the system capacity, average power control, error correction coding, and time diversity are incorporated into the system. The capacity of such a system is evaluated in multipath Rayleigh fading channels. Average bit error rate, outage probability, and corresponding information theoretic bounds are discussed. Concatenation of Reed-Solomon codes and convolutional codes is considered for error correction to account for different quality and delay constraints. It is shown through a numerical example that the system capacity can be increased significantly by an appropriate system design. / Graduate

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

Various wireless networks are widely deployed world wide. Current technologies employed in these networks vary widely in terms of bandwidths, latencies, frequencies, and media access methods. Most existing wireless network technologies can be divided into two categories: those that provide a low-bandwidth service over a wide geographic area, for example UMTS, and those that provide a high bandwidth service over a narrow geographic area, for example 802.11. Although it would be desirable to provide a high- bandwidth service over a wide coverage region to mobile users all the time, no single wireless network technology simultaneously satisfies these require- ments. Wireless Overlay Networks, a hierarchical structure of wireless personal area, local area, and wide area data networks, is considered as an efficient and scalable way to solve this problem. Due to the wide deployment of UMTS and 802.11 WLAN, this study attempts to combine them to implement the concept of Wireless Overlay Net- works. Furthermore, the information transmitted over this Wireless Overlay Networks is protected in terms of authentication, integrity and confidentiality. To achieve this goal, this study aims to combine GPRS, Mobile IP and IPSec to propose a framework for secure mobility in Wireless Overlay Networks. The framework is developed in three steps: Firstly, this study addresses the problem of combining GPRS and Mo- bile IP, so that GPRS users are provided with Mobile IP service. This results in presenting a uniform Mobile IP interface to peers regardless of whether mobile users use UMTS or 802.11 WLAN. Secondly, this study discovers the existing problem when combining Mobile IP and IPSec, and proposes a Dual Home Agent Architecture to achieve secure mobility. Finally, based on the output of the previous two steps, a complete framework is proposed, which achieves secure mobility in Wireless Overlay Networks, specifically, in UMTS and 802.11 WLAN. The framework also implements seamless handover when mobile users switch between UMTS and 802.11. This results in UMTS and 802.11 WLAN looking like a single network when participating in this framework, and presents seamless and secure mobility.

Video surveillance systems have been commonly used in transportation systems to support traffic monitoring, speed estimation, and incident detection. However, there are several challenges in developing and deploying such systems, including high development and maintenance costs, bandwidth bottleneck for long range link, and lack of advanced analytics. In this thesis, I leverage current wireless, video camera, and analytics technologies, and present a wireless traffic monitoring system. I first present an overview of the system. Then I describe the site investigation and several test links with different hardware/software configurations to demonstrate the effectiveness of the system. The system development process was documented to provide guidelines for future development. Furthermore, I propose a novel speed-estimation analytics algorithm that takes into consideration roads with slope angles. I prove the correctness of the algorithm theoretically, and validate the effectiveness of the algorithm experimentally. The experimental results on both synthetic and real dataset show that the algorithm is more accurate than the baseline algorithm 80% of the time. On average the accuracy improvement of speed estimation is over 3.7% even for very small slope angles.

The analysis of radio wave propagation is a crucial part in designing an efficient wireless communication system. The Geographic Information System (GIS) can be incorporated into this procedure because most of the factors in radio wave propagation are geographic features. In this research, a commercial wireless planning software is tested in a field driving test carried out in Montgomery County, VA. The performance of current wireless planning software is evaluated based on field measurement. The received signal strength data collected during this driving test are then analyzed in a GIS environment in a statistical approach. The effects of local geographic features are modeled in GIS by appropriate spatial analyses. / Master of Science

No description available.