Browsing by Subject "Digital communications"
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Item A computer based data acquisition system for fast pulsed power experiments(Texas Tech University, 1981-05) Auyeung, Alex KamlunNot availableItem Channel equalization to achieve high bit rates in discrete multitone systems(2004) Ding, Ming; Evans, Brian L.Multicarrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) and discrete multi-tone (DMT) modulation are attractive for high-speed data communications due to the ease with which MCM can combat channel dispersion. With all the benefits MCM could give, DMT modulation has an extra ability to perform dynamic bit loading, which has the potential to exploit fully the available bandwidth in a slowly time-varying channel. In broadband wireline communications, DMT modulation is standardized for asymmetric digital subscribe line (ADSL) and very-high-bit-rate digital subscriber line (VDSL) modems. ADSL and VDSL standards are used by telephone companies to provide high speed data service to residences and offices. In an ADSL receiver, an equalizer is required to compensate for the channel’s dispersion in the time domain and the channel’s distortion in the frequency domain of the transmitted waveform. This dissertation proposes design methods for linear equalizers to increase the bit rate of the connection. The methods are amenable to implementation on programmable fixed-point digital signal processors, which are employed in ADSL/VDSL transceivers. A conventional ADSL equalizer consists of a time-domain equalizer, a fast Fourier transform, and a frequency domain equalizer. The time domain equalizer (TEQ) is a finite impulse response filter that when coupled with a discretized channel produces an equivalent channel whose impulse response is shorter than that of the discretized channel. This channel shortening is required by the ADSL standards. In this dissertation, I first propose a linear phase TEQ design that exploits symmetry in existing eigen-filter approaches such as minimum mean square error(MMSE), maximum shortening signal to noise ratio (MSSNR) and minimum intersymbol interference (Min-ISI) equalizers. TEQs with symmetric coefficients can reach the same performance as non-symmetric ones with much lower training complexity. Second, I improve Min-ISI design. I reformulate the cost function to make long TEQs design feasible. I remove the dependency of transmission delay in order to reduce the complexity associated with delay optimization. The quantized weighting is introduced to further lower the complexity. I also propose an iterative optimization procedure of Min-ISI that completely avoids Cholesky decomposition hence is better suited for a fixed-point implementation. Finally I propose a dual-path TEQ structure, which designs a standard singleFIR TEQ to achieve good bit rate over the entire transmission bandwidth, and designs another FIR TEQ to improve the bit rate over a subset of subcarriers. Dualpath TEQ can be viewed as a special case of a complex valued filter bank structure that delivers the best bit rate of existing DMT equalizers. However, dual-path TEQ provides a very good tradeoff between achievable bit rate vs. implementation complexity on a programmable digital signal processor.Item Coded and filtered quadrature amplitude modulation signaling(Texas Tech University, 2001-12) Harris, JasonIn this thesis, the performance of several modified digital baseband transmission signals will be evaluated against each other with respect to their bandwidth and error probability characteristics. This is accompHshed via a transmission simulator designed specifically for this purpose. Hybrid signals incorporating a combination of signaling techniques such as Walsh Coding, Pre-filtering, and QAM signaling will be simulated and analyzed with a focus on Walsh Coded Gaussian QAM signals.Item Design of a clock synchronization circuit(Texas Tech University, 2001-08) Elahi, Noor-EWith the advent of digital networks and the transmission and reception of binary pulses (Is and Os), it became important to devise some method for detecting these signals accurately at the receiver. The ideal system is one in which the binary pulses arrive at the receiver in a very precise and concise manner. This means that the receiver knows the exact time when the signal (a binary 1 or 0) manifests itself at the receiver interface. Fortunately, it is relatively easy to determine this timing, because the receiver can derive the clock from the incoming bit stream by examining when the pulses arrive at the receiver. This function is called cock recovery. The rest ofthe data can be detected using this clock. However, errors can occur if the clock is not aligned with the signal or data. This leads to wrong information in the receiver about the timing of received data. This problem is usually called phase variation, and may translate into an incorrect interpretation of the binary Is and Os in the transmission stream. So it is vital for digital transmission that the data transmitted should be aligned to a pure clock, which has no phase variations. As shown in Figure 1.1, the signal and the clock are perfectly aligned to a clock with no phase variations. The positive edge ofthe clock is at the middle of each 1 or 0. This clock is referred to as a reference clock.Item Mixed-signal signature analysis for systems-on-a-chip(2001-08) Roh, Jeongjin, 1966-; Abraham, Jacob A.Item Multiple-station digital wireless power metering system(Texas Tech University, 1999-08) Dávila, Adrián Arnoldo PinedaThis thesis describes the design of a multiple station digital wireless power metering system for industrial plants. The objective of this thesis is the design of a flexible multiple station digital wireless power metering system. Efficient use of electrical energy and reduction of energy costs can be achieved by knowing the behavior of a plant's load. To run efficiently, industrial plant managers must know load factor, power factor, the peak and average demand of the plant among other variables. A monitoring system that provides the data necessary to calculate these parameters is useful while one that is flexible and low cost is indispensable. This project has been designed for and coordinated with the Department of Electrical Engineering Division of the Efficient Use of Electrical Energy of the Institute Tecnologico y de Estudios Superiores de Monterrey (I.T.E.S.M.) Campus Monterrey, Nuevo Leon Mexico. This thesis manifests the continuation of a thesis at I.T.E.S.M. entitled "Go-Back-N ARQ Multiple Station Digital Wireless Power Monitoring System Design" by Adrian Amoldo Pineda Davila, M.S.E.E.Item Predicting the effect of digital conversion on U.S. television stations(Texas Tech University, 2002-08) Schultz, Bradley EThe study investigated the effect of the conversion from analog to digital transmission at television stations across the United States. This effect was studied based on Oliver's model of how organizations respond to outside pressures or influences. Based on the findings, there was a close relationship in several areas between the Oliver model and television station response. This was most notable for religious and low-power stations. Those areas where the model did not fit as well were best explained by factors of causation an context, along with Greve's theory of mimetic adoption.