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 58 for “"OFDM systems"”.
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Outphase power amplifiers in OFDM systems
A trade-off between linearity and efficiency exists in conventional power amplifiers. The outphase amplifying concept overcomes this trade-off by enabling the use of high efficiency, non-linear power amplifiers for linear amplification. An amplitude modulated signal is first decomposed into two …
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Radio Resource Allocation in Wireless OFDM Systems
… radio resource allocation problems in wireless OFDM systems using both centralized optimization and game theoretic approaches. In our work we consider only integer numbers for bit-loading for practical purpose. The subcarrier, bit and power allocation (SBPA) problem in single-cell and multi-cell …
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Channel Estimation for OFDM Systems With Transmitter Diversity
Orthogonal Frequency-Division Multiplexing (OFDM) is now regarded as a feasible alternative to the conventional single carrier modulation techniques for high data rate communication systems, mainly because of its inherent equalisation simplicity. Transmitter diversity can effectively combat …
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Channel modeling and resource allocation in OFDM systems
… for high data rate in wireless communication systems gives rise to broadband communication systems. The radio channel is plagued by multipath propagation, which causes frequency-selective fading in broadband signals. Orthogonal Frequency-Division Multiplexing (OFDM) is a modulation scheme …
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Channel estimation for Gigabit Multi-user MIMO-OFDM Systems
… with Orthogonal Frequency Division Multiplexing (OFDM).However, the superior performance promised by the MIMO-OFDM technology relies on the availability of accurate Channel State Information (CSI) at the receiver. In the literature, the Mean Square Error (MSE) performance of MIMO-OFDM CSI …
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Performance evaluation of detection algorithms for MOMI OFDM systems
… Orthogonal Frequency Division Multiplexing (OFDM) as the base air interface method for Next Generation Network (NGN) will face a number of challenges from hostile channel conditions to interference from other users. This would result in an increase of detection complexity required for mobile …
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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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Fast peak-power reduction for MIMO-OFDM systems with diversity
… (SISO) orthogonal frequency-division modulated (OFDM) signals by extending the outer constellation points in a way that minimizes the PAPR of an OFDM transmit signal, without reducing the bandwidth or increasing bit error rate (BER). Recent work includes extensions of the concept of ACE using a …
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A new data rotation syncrhonization scheme for CP based OFDM systems
… 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 increases. We then propose a new data rotation scheme, where we intentionally …
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A comparison of timing methods in orthogonal frequency division multiplexing (OFDM) systems
Orthogonal frequency division multiplexing (OFDM) is being used by wireless local area network (WLAN) standards, such as IEEE 802.11a, and wireless metropolitan area network (MAN) standards, such as IEEE 802.16a. OFDM is a very efficient communications scheme for wireless ADHOC networks. However, …
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Simulation of Adaptive Array Algorithms for OFDM and Adaptive Vector OFDM Systems
… Orthogonal frequency division multiplexing (OFDM) is well-known to be effective against multipath distortion. It is a multicarrier communication scheme, in which the bandwidth of the channel is divided into subcarriers and data symbols are modulated and transmitted on each subcarrier …
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Iterative receivers with channel estimation for MIMO and multi-user OFDM systems
… used. The use of multiple antenna (MIMO) systems and iterative (turbo) receivers has significantly improved the realizable system performance. Still, many challenges exist in the development of efficient wireless receivers. In this thesis, which is written in the form of a collection of …
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Intercarrier Interference Suppression for the OFDM Systems in Time-Varying Multipath Fading Channels
… orthogonal frequency division multiplexing (OFDM) has served as one of the major modulation schemes for the modern communication systems. In the future, the wireless OFDM systems are expected to operate at high carrier-frequencies, high speed and high throughput mobile reception, where the …
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Low-Complexity Algorithms for Channel Estimation in Optimised Pilot-Assisted Wireless OFDM Systems
Orthogonal frequency division multiplexing (OFDM) has recently become a dominant transmission technology considered for the next generation fixed and mobile broadband wireless communication systems. OFDM has an advantage of lessening the severe effects of the frequency-selective (multipath) fading …
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Performance analysis of diversity techniques in wireless communication systems: Cooperative systems with CCI and MIMO-OFDM systems
… performance of ecient digital commu- nication systems, the performance analysis includes the bit error rate (BER) of dier- ent binary and M-ary modulation schemes, and the average channel capacity (ACC) under dierent adaptive transmission protocols, namely, the simultaneous power and rate …
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New methods of partial transmit sequence for reducing the high peak-to-average-power ratio with low complexity in the ofdm and f-ofdm systems
… frequency division multiplexing system (OFDM) is one of the most important components for the multicarrier waveform design in the wireless communication standards. Consequently, the OFDM system has been adopted by many high-speed wireless standards. However, the high peak-to-average- …
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I/Q imbalance mitigation for space-time block coded communication systems
… block coded (STBC) wireless communication systems provide reliable data transmissions by exploiting the spatial diversity in fading channels. However, due to component imperfections, the in-phase/quadrature (I/Q) imbalance caused by the non-ideal matching between the relative amplitudes and …
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Online Machine Learning for Wireless Communications: Channel Estimation, Receive Processing, and Resource Allocation
… detection algorithms are designed for MIMO-OFDM and massive MIMO-OFDM systems by utilizing reservoir computing, extreme learning machine, multi-mode reservoir computing, and StructNet; 2) Channel estimation, where residual learning-based offline method is introduced for WiFi-OFDM systems, …
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New Techniques for Multicarrier Communication Systems
Common to all OFDM systems is a large peak-to-average-power ratio (PAR) problem, which can lead to low power efficiency and nonlinear distortion at the transmit power amplifier. Tone reservation uses unavailable or reserved tones to design a peak-cancelling signal that lowers the PAR of a transmit …
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