Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 44 for “"Frequency offset"”.
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Compensation of nonlinear distortion and frequency offset in OFDM systems
Orthogonal frequency division multiplexing (OFDM) systems exhibit many advantages in wireless as well as wireline environments. However, two crucial limiting issues should be overcomed for applicaiton of OFDM scheme to wireless systems: sensitivities to nonlinear distortion and frequency offset. …
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Analysis and mitigation of carrier frequency offset for uplink of OFDMA
Orthogonal Frequency Division Multiplexing (OFDM) is being used in many wireless standards because of its immunity to multipath fading, high spectral efficiency and simple implementation, making it suitable for high data rate multimedia wireless applications. One of the significant drawbacks of the …
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A new data rotation syncrhonization scheme for CP based OFDM systems
… rotation scheme for symbol timing and carrier frequency offset (CFO) estimation of orthogonal frequency-division multiplexing (OFDM) systems. We first analyze Beeka??s cyclic prefix (CP) based joint ML estimator [2] and find that its performance can be improved when the average energy of the CP …
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Digital Signal Processing for Front-end Non-idealities in Coherent Optical OFDM system
… in CO-OFDM systems, including carrier frequency offset, linear phase noise and IQ mismatch. Firstly, we propose a novel frequency offset compensation method, which is successfully demonstrated through experiment. Our algorithm achieves the widest estimation range with one training …
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Spectrally Modulated Spectrally Encoded Framework Based Cognitive Radio in Mobile Environment
… such as NC-OFDM (non-contiguous Orthogonal Frequency Division Multiplexing), NC-MC-CDMA (non-contiguous multi-carrier code division multiple access) and NC-SC-OFDM (non-contiguous single carrier OFDM), allow the SUs to utilize the available spectrum. Spectrally Modulated Spectrally Encoded …
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FPGA-based DOCSIS upstream demodulation
… are explored. In particular, algorithms for frequency recovery and equalization are developed. The many data-aided feedforward frequency offset estimators analyzed in the literature have not considered intersymbol interference (ISI) caused by micro-reflections in the channel. It is shown in …
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Control of a Nonlinear Mach-Zehnder Interferometer for Regeneration Using Digital Signal Processing
… them both. To use a NMZI as a regenerator, the frequency of the pump signal must be kept close to that of the data carrier and the phase difference between the data and pump signals needs to be aligned with the phase transfer curve. A digital signal processing (DSP) based control method is …
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Spectrum Sensing and Blind Automatic Modulation Classification in Real-Time
… with no prior knowledge of the signal's center frequency, bandwidth, or symbol rate. An energy detector forms the initial approximations of the signal parameters. The energy detector used in the wideband sweep is reused to obtain fine estimates of the center frequency and bandwidth of the …
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Advanced classification of OFDM and MIMO signals with enhanced second order cyclostationarity detection
… of number of subcarriers, CP length, timing and frequency offset and the oversampling factor for the OFDM signal. For the second part of the thesis, we improve the statistical signal processing techniques that were used in the first part. Particularly, the second order cyclostationarity based …
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Performance of GMSK and 7/4-DQPSK Modulations in Land Mobile Radio Channels
… are analog in nature. These systems employ frequency modulation. As the spectrum gets crowded, bandwidth efficient digital systems will find increasing application. Gaussian Minimum Shift Keying (GMSK) and 7r/4-Differential Quadrature Phase Shift Keying (7r/ 4-DQPSK) have been identified as …
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On the performance and capacity of space-time block coded multicarrier CDMA communication systems
… STBC MC-CDMA systems in the presence of carrier frequency offset (CFO). Then various multirate access schemes, multicode, variable spreading gain (VSG) and multiple symbol rate (MSR), are investigated. Next, the thesis looks into some of design and implementation issues of STBC MC-CDMA systems. …
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Simulation of Adaptive Array Algorithms for CDMA Systems
… the test situations (e.g., AWGN channel, timing offset case, frequency offset case, and multipath environment). It is also shown that these two algorithms have less complexity and can converge faster than the other algorithms.
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Techniques for low coherence pulsed Doppler lidar
… reason is the expense and bulk of the single frequency injection locked lasers currently used. These are required to ensure coherence is maintained between the reference and measurement beams over long pathlength differences. In order to reduce the cost and size of lidar systems, we have …
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Blind CFO Estimation for Zero-Padded OFDM over Underwater Acoustic Channels
… and complexity of three existing blind carrier-frequency-offset (CFO) estimators when they are applied to estimate the residual Doppler shift for zero-padded OFDM transmissions over underwater acoustic channels: the null subcarrier based method, the O-M algorithm, and the Y-G algorithm. …
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Efficient Radiometric Signature Methods for Cognitive Radio Devices
… characteristics of the radio, including the frequency offset, modulated phase offset, in-phase/quadrature-phase offset from the origin, and magnitude. Our method provides stable and robust identification by developing individual identifiers (classifiers) that may each be weak (i.e., incurring …
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Implementation of a Software Defined Spread Spectrum Communication System
… algorithm is capable of determining the code and frequency offset in a received (DSSS) signal. We also find that the carrier tracking loop is capable of tracking the received carrier when the signal has a high (SNR). We conclude that GNU Radio as a technology can be used to prototype transceivers …
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Terahertz beam-steering imager using a scalable 2D-coupled architecture and multi- functional heterodyne pixels
… receiving, sub-harmonic mixing, and intermediate frequency (IF) signal extraction. Each pixel consumes 10 mW power and achieves a sensitivity of 2.9 pW in simulation. The local oscillator (LO) of the pixel is phase coupled with its neighbors; the whole oscillator array is then stabilized by an …
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Development and Analysis of Adaptive Interference Rejection Techniques for Direct Sequence Code Division Multiple Access Systems
… the adaptive receiver in the presence of carrier frequency offsets is analyzed. The performance of several new adaptive receiver structures for frequency offset compensation is also studied in this research. Analysis of the minimum mean-squared error receiver is carried out to provide a better …
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