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1
Kosa, Irfan. "Performance of IEEE 802.11a wireless LAN standard over frequency-selective, slowly fading Nakagami channels in a pulsed jamming environment". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Dec%5FKosa.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2002.Thesis advisor(s): R. Clark Robertson, Tri Ha. Includes bibliographical references (p. 107-108). Also available online.
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Bemani, Ali. "Affine Frequency Division Multiplexing (AFDM) for Wireless Communications". Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS610.pdf.
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La recherche de nouvelles formes d'onde robustes, lorsque utilisées sur des canaux doublement sélectifs, est primordiale. De telles formes d'onde permettraient donc d'assurer des communications fiables pour les réseaux sans fil de nouvelle génération dans les scénarios de haute mobilité. Dans cette thèse, une nouvelle solution, le affine frequency division multiplexing (AFDM), est proposée. Cette nouvelle forme d'onde de type multichirps est basée sur la transformée de Fourier affine discrète (DAFT), une variante de la transformée de Fourier discrète caractérisée par deux paramètres pouvant être adaptés pour mieux faire face aux canaux doublement dispersifs. Cette thèse offre une enquête complète sur les principes de l'AFDM au sein des communications à haute mobilité. Elle fournit un aperçu de la relation explicite entrée-sortie dans le domaine DAFT, révélant l'impact conséquent des paramètres de l'AFDM. Le manuscrit détaille le réglage précis des paramètres DAFT qui permette d'assurer une représentation complète délai-Doppler du canal de propagation sans fil. À travers des démonstrations analytiques, il est affirmé que l'AFDM atteint de manière optimale l'ordre de diversité des canaux doublement dispersifs en raison de la représentation complète délai-Doppler du canal qu'il permet d'obtenir. La thèse propose également deux algorithmes de détection à faible complexité pour l'AFDM, tirant parti de la parcimonie inhérente du canal. Le premier est un détecteur de type minimum mean squared error (MMSE) à faible complexité basé sur la factorisation LDL. Le deuxième est un égaliseur de type decision feedback equalizer (DFE) à faible complexité basé sur la combinaison cohérente, grace à la méthode maximum ratio combining (MRC), de différentes copies des symboles d'entrée du canal ayant été altérés par différents trajets de ce dernier. De plus, la thèse présente une technique de type embedded d'estimation de canal pour les systèmes AFDM, exploitant la capacité de l'AFDM à obtenir une représentation complète délai-Doppler du canal. Dans cette approche, un seul symbole pilote est inséré dans le domain DAFT du symbole AFDM, et les interférences que ce pilote pourrait générer pour les symboles de donnée sont évitées par des intervalles de garde. Un algorithme pratique d'estimation de canal, compatible avec ce schéma de transmission de pilote et basé sur une approche de type approximate maximum likelihood (ML), est aussi proposé. La thèse est conclue en se penchant sur de possibles applications de l'AFDM au delà de celles conçues pour les environnements marqués par une haute mobilité, spécifiquement les applications de type integrated sensing and communication (ISAC) et les communications dans les bandes de hautes fréquences. Il est démontré que pour identifier tous les composants de délai et de Doppler liés au milieu de propagation, on peut utiliser soit le signal AFDM complet, soit seulement sa partie pilote constituée d'un symbole de domaine DAFT et de son intervalle de garde. De plus, la nature chirp de l'AFDM permet une annulation simple de l'auto-interférence, éliminant ainsi le besoin de méthodes coûteuses normalement nécessaires dans les systèmes full duplex. La thèse met également en évidence les bonnes performances de l'AFDM pour les communications sans fil dans les bandes de hautes fréquences sans ou avec mobilité, grâce à la répartition maximale du signal AFDM en temps et en fréquences, assurant un gain de couverture. Contrairement à d'autres formes d'onde, l'AFDM ne fournit pas seulement une répartition maximale temps-fréquences mais assure également une détection robuste et efficace et une résilience au décalage de fréquence de porteuse et au bruit de phaseIn the realm of next-generation wireless systems (beyond 5G/6G), the vision is clear: to support a broad range of services and applications. This includes ensuring reliable communications in environments marked by high mobility, such as high-speed railway systems and various vehicular communications. Despite the deployment of various multicarrier techniques like orthogonal frequency division multiplexing (OFDM) and single-carrier frequency division multiple access (SC-FDMA) in standardized communication systems, the challenge persists. These techniques, while effective in time-invariant frequency selective channels, face performance degradation in high mobility scenarios due to the destruction of orthogonality among subcarriers caused by significant Doppler frequency shifts. Addressing this, the search for new, robust modulation techniques is paramount. It stands as a key area of investigation aiming to resolve the reliable communications issue for next-generation wireless networks within doubly-selective wireless channels. In this thesis, a novel solution, affine frequency division multiplexing (AFDM), is proposed. This new chirp-based multicarrier waveform is based on the discrete affine Fourier transform (DAFT), a variant of the discrete Fourier transform characterized with two parameters that can be adapted to better cope with doubly dispersive channels. This thesis provides a comprehensive investigation into the principles of AFDM within high mobility communications. It provides insight into the explicit input-output relation in the DAFT domain, unveiling the consequential impact of AFDM parameters. The manuscript details the precise setting of DAFT parameters, ensuring a full delay-Doppler representation of the channel. Through analytical demonstrations, it asserts that AFDM optimally achieves the diversity order in doubly dispersive channels due to its full delay-Doppler representation. The thesis also proposes two low-complexity detection algorithms for AFDM, taking advantage of its inherent channel sparsity. The first is a low complexity MMSE detector based on LDL factorization. The second is a low complexity iterative decision feedback equalizer (DFE) based on weighted maximal ratio combining (MRC) of the channel impaired input symbols received from different paths. Additionally, the thesis presents an embedded channel estimation strategy for AFDM systems, leveraging AFDM's ability to achieve full delay-Doppler representation of the channel. In this approach, an AFDM frame contains a pilot symbol and data symbols, with zero-padded symbols employed as guard intervals to prevent interference. A practical channel estimation algorithm based on an approximate maximum likelihood (ML) approach and compatible with this pilot scheme is also provided. The thesis concludes by delving into the expanded applications of AFDM, specifically in integrated sensing and communication (ISAC) and extremely high frequency (EHF) band communications. It is demonstrated that to identify all delay and Doppler components linked with the propagation medium, one can use either the full AFDM signal or only its pilot part consisting of one DAFT domain symbol and its guard interval. Furthermore, the chirp nature of AFDM allows for unique and simple self-interference cancellation with a single pilot, eliminating the need for costly full-duplex methods. The thesis also highlights AFDM's efficient performance in high-frequency bands (with or without mobility), where the maximal spreading of its signal in time and frequency ensures a coverage gain. Unlike other waveforms, AFDM not only provides maximal time-frequency spreading but also ensures robust and efficient detection, characterized by one-tap equalization and resilience to carrier frequency offset (CFO) and phase noise
3
Qin, Tianrui. "Over-the-air computation via broadband channels". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/26460.
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As the scale of the current network keeps increasing at a dramatic rate, the future Internet-of-Things applications will need to connect billions of sensor nodes. This brings great challenges to the traditional "transmit then compute" mode, as communication latency will be excessive for a large-scale communication network.
The massive access points will also exhaust bandwidth resources in a conventional multiple-access scheme. By exploiting the superposition property of a multi-access channel, Over-the-Air Computation (AirComp) has been recognized as a low-latency solution for wireless sensor data fusion, where multiple sensors simultaneously send their measurement signals to a receiver for computation. Most existing work only considered performing AirComp over a single frequency channel. However, for a sensor network with a massive number of nodes, a single frequency channel may not be sufficient to accommodate the large number of sensors, and the AirComp performance will be very limited. So it is highly desirable to have more frequency channels for large-scale AirComp systems to benefit from multi-channel diversity.
In this thesis, we propose an M-frequency AirComp system where each sensor selects a subset of the M frequencies and broadcasts its signal over these channels under a certain power constraint. We derive the optimal sensors' transmission and receiver's signal processing methods separately, and develop an algorithm for joint design to achieve the best AirComp performance. We further investigate the property of the optimal design problem to reduce its complexity. Numerical results show that increasing one frequency channel can improve the AirComp performance threefold compared to the single-frequency case.
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Ekinci, Umut Utku. "Code Aided Frame Synchronization For Frequency Selective Channels". Thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611951/index.pdf.
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Frame synchronization is an important problem in digital communication systems. In frame synchronization, the main task is to find the frame start given the flow of the communication symbols. In this thesis, frame synchronization problem is investigated for both additive white Gaussian noise (AWGN) channels and frequency selective channels. Most of the previous works on frame synchronization consider the simple case of AWGN channels. The algorithms developed for this purpose fail in frequency selective channels. There is limited number of algorithms proposed for the frequency selective channels. In this thesis, existing frame synchronization techniques are investigated for both AWGN and frequency selective channels. Code-aided frame synchronization techniques are combined with the methods for frequency selective channels. Mainly two types of code-aided frame synchronization schemes are considered and two new system structures are proposed for frame synchronization. One of the proposed structures performs better than the alternative methods for frequency selective channels. The overall system for this new synchronizer is composed of a list synchronizer which generates the possible frame starts, a channel estimator, a soft output MLSE equalizer, and a soft output Viterbi decoder. A mode separation algorithm is used to generate the statistics for the selection of the true frame start. Several experiments are done and the performance is outlined for a variety of scenarios.
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Chen, Xuan. "Adaptive equalization of frequency selective indoor wireless channels". Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10132.
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In this thesis, we examine the performance of adaptive linear, T/2 fractionally spaced, and decision feedback equalizers (LE, FSE and DFE) for digital communication systems over indoor wireless channels affected by frequency selective fading. The channel is modeled as both fixed and time varying channels, and the data transmission rate is 10 M bits/s. The simulation results show that, with differential encoding, the quadrature phase shift keying (DQPSK) modulation scheme outperforms 4-state and 8-state 8PSK-based trellis coded modulations (D8PTCM4 and D8PTCM8), when the DFE with the least-mean-square (LMS) algorithm (DFELMS) is used. While D8PTCM4 has better BER performance than D8PTCM8 with the DFELMS over time varying channels, the reverse conclusion can be obtained over fixed channels. When the recursive least-square (RLS) algorithm is applied instead of the LMS algorithm, the systems with the DFERLS can achieve slightly better bit error rate (BER) performance than those with the DFELMS.
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So, Daniel Ka Chun. "MIMO wireless communications in frequency selective fading channels /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20SO.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 136-144). Also available in electronic version. Access restricted to campus users.
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Liu, Shoumin. "Soft-decision equalization techniques for frequency selective MIMO channels /". Available online. Click here, 2005. http://sunshine.lib.mtu.edu/ETD/DISS/lius/Dissertation.pdf.
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Xu, Ying Lin 1975. "OFDMA schemes with diversity in frequency-selective fading channels". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81577.
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By using sufficiently long prefix and orthogonal narrow-band sub-carriers with adaptive bit loading, orthogonal frequency-division multiple-access (OFDMA) can offer high bandwidth efficiency required for broadband wireless access communications in frequency-selective fading channels. However, when deep fading occurs in a frequency slot, it can create data loss in one or more sub-carriers. Diversity techniques could be used to enhance the performance of OFDMA in the presence of deep fades.The research presented in this thesis aims to provide diversity in OFDMA for broadband wireless access communications in frequency-selective fading channels. First, the diversity characteristics in OFDMA are examined to establish the diversity equivalence in the time and frequency domains. Based on these characteristics, suitable techniques to achieve the full diversity gain in OFDMA are developed. When channel information is available to transmitters, a group-optimal adaptive-tone-diversity OFDMA (GO-ATD-OFDMA) scheme that combines adaptive diversity gain and bit loading, is proposed. It is shown that the GO-ATD-OFDMA can offer a better performance than the conventional time-domain Rake receiver. In the case of unavailable channel information, spreading is combined with diversity in the proposed group-spreading OFDMA (GS-OFDMA) scheme to provide both diversity protection and interference suppression. The GS-OFDMA has a comparable performance to the group-orthogonal multi-carrier code-division multiple-access (GO-MC-CDMA) scheme but with a reduced transmitted peak-to-average power ratio (PAR). Performance of the proposed schemes in terms of error rates, spectral efficiency, achievable system throughput, and computational complexity is investigated by analysis and simulations.
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Davies, Martin. "Polynomial matrix decomposition techniques for frequency selective MIMO channels". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6047.
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For a narrowband, instantaneous mixing multi-input, multi-output (MIMO) communications system, the channel is represented as a scalar matrix. In this scenario, singular value decomposition (SVD) provides a number of independent spatial subchannels which can be used to enhance data rates or to increase diversity. Alternatively, a QR decomposition can be used to reduce the MIMO channel equalization problem to a set of single channel equalization problems. In the case of a frequency selective MIMO system, the multipath channel is represented as a polynomial matrix. Thus conventional matrix decomposition techniques can no longer be applied. The traditional solution to this broadband problem is to reduce it to narrowband form by using a discrete Fourier transform (DFT) to split the broadband channel into N narrow uniformly spaced frequency bands and applying scalar decomposition techniques within each band. This describes an orthogonal frequency division multiplexing (OFDM) based system. However, a novel algorithm has been developed for calculating the eigenvalue decomposition of a para-Hermitian polynomial matrix, known as the sequential best rotation (SBR2) algorithm. SBR2 and its QR based derivatives allow a true polynomial singular value and QR decomposition to be formulated. The application of these algorithms within frequency selective MIMO systems results in a fundamentally new approach to exploiting spatial diversity. Polynomial matrix decomposition and OFDM based solutions are compared for a wide variety of broadband MIMO communication systems. SVD is used to create a robust, high gain communications channel for ultra low signal-to-noise ratio (SNR) environments. Due to the frequency selective nature of the channels produced by polynomial matrix decomposition, additional processing is required at the receiver resulting in two distinct equalization techniques based around turbo and Viterbi equalization. The proposed approach is found to provide identical performance to that of an existing OFDM scheme while supporting a wider range of access schemes. This work is then extended to QR decomposition based communications systems, where the proposed polynomial approach is found to not only provide superior bit-error-rate (BER) performance but significantly reduce the complexity of transmitter design. Finally both techniques are combined to create a nulti-user MIMO system that provides superior BER performance over an OFDM based scheme. Throughout the work the robustness of the proposed scheme to channel state information (CSI) error is considered, resulting in a rigorous demonstration of the capabilities of the polynomial approach.
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Litchfield, Charan. "Single user diversity receivers for frequency selective WCDMA channels". Thesis, University of Kent, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443772.
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Assimi, Abdel Nasser. "Diversity techniques for HARQ transmissions over frequency-selective channels". Cergy-Pontoise, 2009. http://biblioweb.u-cergy.fr/theses/09CERG0428.pdf.
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Nous considérons dans cette thèse le problème de la transmission fiable de données par paquets en utilisant une transmission mono-porteuse sur des canaux sélectifs en fréquence à évanouissements. Notre objectif est de concevoir des couples émetteurs-récepteurs permettant d'améliorer les performances de la détection en l'absence d'information sur le canal à la transmission et ceci en exploitant la diversité temporelle disponible dans le cadre des protocoles de retransmission hybrides (HARQ). En analysant les performances du système de transmission avec un récepteur à maximum de vraisemblance, nous établissons un critère pertinent pour l'étude des performances du système basé sur les statistiques de la distance Euclidienne à la sortie du canal sélectif en fréquence. A partir de ce cadre théorique, nous proposons un nouveau schéma de diversité entre les différentes retransmissions, nommé précodage de phase, qui permet de combattre l'interférence entre symboles pour les canaux lentement variables dans le temps. Puis, à l'aide de nos outils d'analyse, nous revisitons un autre schéma de diversité qu'est la diversité d’entrelacement. En particulier, nous soulignons le double avantage offert par ce schéma, à savoir la diversité de modulation et la réduction de l'interférence entre symboles. Nous réalisons ensuite une étude comparative entre les deux schémas de diversité précédents sous traitement itératif ou non itératif au récepteur. Enfin, nous introduisons un nouveau protocole de retransmission adaptative pour les transmissions dîtes multi-couches afin de réduire l'interférence entre couches pour les canaux rapidement variant dans le temps utilisant des informations de retour limitéesIn this thesis, we consider the problem of reliable data packets transmission using single-carrier signaling over frequency-selective fading channels. Our objective is to design enhanced transceivers with improved detection performance in the absence of channel state information at the transmitter by exploiting the available time-diversity in Chase combining Hybrid Automatic Repeat reQuest (HARQ) protocols. By analyzing the performance of the transmission scheme using an optimal maximum-likelihood receiver, we establish a suitable criterion for the study of system performance based on the statistics of the Euclidean distance at the output of a frequency-selective channel. From this theoretical framework, we propose a novel transmit-diversity scheme between subsequent HARQ transmissions, called phase-precoding, which allows the mitigation of intersymbol interference for slow time-varying channels. Then, with the help of our analytical tools, we revisit another transmit-diversity scheme which is the bit-interleaving diversity scheme. In particular, we emphasize the double advantage offered by this diversity scheme including the inherent modulation diversity in addition to the intersymbol interference reduction. Subsequently, we perform a comparative study between phase-precoding and bit-interleaving diversity schemes under iterative and non-iterative receiver structures. Finally, we introduce a new adaptive retransmission protocol for a multi-layer transmission scheme for the mitigation of inter-layers interference for rapidly time-varying channels using limited feedback information
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Zhu, Xu. "Wireless MIMO antenna systems for frequency selective fading channels /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202003%20ZHU.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.Includes bibliographical references (leaves 116-118). Also available in electronic version. Access restricted to campus users.
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Liu, Yuan. "FREQUENCY DOMAIN INDEPENDENT COMPONENT ANALYSIS APPLIED TO WIRELESS COMMUNICATIONS OVER FREQUENCY-SELECTIVE CHANNELS". Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3150.
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In wireless communications, frequency-selective fading is a major source of impairment for wireless communications. In this research, a novel Frequency-Domain Independent Component Analysis (ICA-F) approach is proposed to blindly separate and deconvolve signals traveling through frequency-selective, slow fading channels. Compared with existing time-domain approaches, the ICA-F is computationally efficient and possesses fast convergence properties. Simulation results confirm the effectiveness of the proposed ICA-F. Orthogonal Frequency Division Multiplexing (OFDM) systems are widely used in wireless communications nowadays. However, OFDM systems are very sensitive to Carrier Frequency Offset (CFO). Thus, an accurate CFO compensation technique is required in order to achieve acceptable performance. In this dissertation, two novel blind approaches are proposed to estimate and compensate for CFO within the range of half subcarrier spacing: a Maximum Likelihood CFO Correction approach (ML-CFOC), and a high-performance, low-computation Blind CFO Estimator (BCFOE). The Bit Error Rate (BER) improvement of the ML-CFOC is achieved at the expense of a modest increase in the computational requirements without sacrificing the system bandwidth or increasing the hardware complexity. The BCFOE outperforms the existing blind CFO estimator [25, 128], referred to as the YG-CFO estimator, in terms of BER and Mean Square Error (MSE), without increasing the computational complexity, sacrificing the system bandwidth, or increasing the hardware complexity. While both proposed techniques outperform the YG-CFO estimator, the BCFOE is better than the ML-CFOC technique. Extensive simulation results illustrate the performance of the ML-CFOC and BCFOE approaches.Ph.D.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
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Zheng, Jun. "Analysis of coded OFDM system over frequency-selective fading channels". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1137.
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This thesis considers the analysis of system performance and resource allocation for a coded OFDM system over frequency selective fading channels. Due to the inseparable role taken by channel coding in a coded OFDM system, an information theoretical analysis is carried out and taken as the basis for the system performance and throughput.
Based on the results of the information theoretical analysis, the optimal system BER performance of a coded OFDM system is first shown to converge to the outage probability for large OFDM block lengths. Instead of evaluating the outage probability numerically, we provide in this thesis a simple analytical closed form approximation of the outage probability for a coded OFDM system over frequency selective quasi-static fading channels. Simulation results of the turbo-coded OFDM systems further confirm the approximation of the outage probability.
By taking the instantaneous channel capacity as the analytical building block, system throughput of a coded OFDM system is then provided. With the aim to compare the performance difference between adaptive and uniform resource allocation strategies, the system throughput of different allocation schemes under various channel conditions is analyzed. First, it is demonstrated that adaptive power allocation over
OFDM sub-carriers at the transmitter achieves very little gain in terms of throughput over a uniform power distribution scheme. Theoretical analysis is then provided of the throughput increase of adaptive-rate schemes compared with fixed-rate schemes under various situations. Two practical OFDM systems implementing rate-compatible-punctured-turbo-code-based (RCPT-based) hybrid automatic-repeat-request (Hybrid-ARQ) and redundancy incremental Hybrid-ARQ protocols are also provided to verify the analytical results.
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Szubbocsev, Zoltan. "The EM algorithm for frequency selective, quasi-static fading channels /". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111503.
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A fractional iterative channel estimation and data detection algorithm is proposed for frequency selective, quasi-static MIMO channels. It is shown that due to the correlation of the noise samples after pulse matched filtering and sampling, the complexity of the derived receiver, based on the Expectation-Maximization (EM) algorithm with fractional sampling, is the same as that of the ML receiver, which requires an exhaustive search. It is shown that by using a noise whitening filter to whiten the noise samples, the algorithm can be efficiently implemented using the Viterbi algorithm instead of using an exhaustive search technique. Due to spectral zeros of the autocorrelation function of the noise sequence, noise whitening filter designed by spectral factorization are not practical for the square-root raised cosine pulses and similar shapes. An alternative prediction-error whitening filter is proposed solving the Yule-Walker equations. We analyze the performance of the proposed receiver via numerical simulations. It is observed that when the channel is perfectly known, the performance of the fractional ML receiver, with five-tap whitening filter, is only 0.5 dB worse than that of the optimal ML receiver at a BER of 10-4. When the path delays are fixed and the channel is unknown, the fractional iterative scheme outperforms the symbol rate iterative scheme between 0 and 16 dB, and between BERs of 2 x 10-1 and 2 x 10 -4. With varying path delays, the fractional scheme is better for all simulated SNR values. However, both schemes experience a severe error flooring. Application of the EM algorithm to iteratively estimate frequency selective channels and detect the transmitted information sequence improves the efficiency of pilot symbols. By using additional iterations, the BER is lowered with the same number of pilot symbols. We also compare the performance of the iterative receiver that uses the correct tap covariance matrix with the one that assumes a diagonal covariance matrix. It is observed that with fixed path delays the performance is identical with both models. With varying path delays and fractional sampling the diagonal assumption results in a performance loss of 0.5 dB.**This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation).
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Count, Patrick A. "Performance analysis of OFDM in frequency selective, slowly fading Nakagami Channels". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA401365.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, December 2001.Thesis Advisor(s): Ha, Tri T. ; Robertson, R. Clark. "December 2001." Includes bibliographical references (p. 109-110). Also available in print.
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Liu, Hong. "Frequency-domain equalization of single carrier transmissions over doubly selective channels". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187064126.
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Chu, Alice Pin-Chen. "High-Rate Space-Time Block Codes in Frequency-Selective Fading Channels". Thesis, University of Canterbury. Electrical and Computer Engineering, 2012. http://hdl.handle.net/10092/10360.
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The growing popularity of wireless communications networks has resulted in greater bandwidth contention and therefore spectrally efficient transmission schemes are highly sought after by designers.
Space-time block codes (STBCs) in multiple-input, multiple-output (MIMO) systems are able to increase channel capacity as well as reduce error rate. A general linear space-time structure known as linear dispersion codes (LDCs) can be designed to achieve high-data rates and has been researched extensively for flat fading channels. However, very little research has been done on frequency-selective fading channels. The combination of ISI, signal interference from other transmitters and noise at the receiver mean that maximum likelihood sequence estimation (MLSE) requires high computational complexity. Detection schemes that can mitigate the signal interference can significantly reduce the complexity and allow intersymbol interference (ISI) equalization to be performed by a Viterbi decoder.
In this thesis, detection of LDCs on frequency-selective channels is investigated. Two predominant detection schemes are investigated, namely linear processing and zero forcing (ZF). Linear processing depends on code orthogonality and is only suited for short channels and small modulation schemes. ZF cancels interfering signals when a sufficient number of receive antennas is deployed. However, this number increases with the channel length. Channel decay profiles are investigated for high-rate LDCs to ameliorate this limitation. Performance improves when the equalizer assumes a shorter channel than the actual length provided the truncated taps carry only a small portion of the total channel power.
The LDC is also extended to a multiuser scenario where two independent users cooperate over half-duplex frequency-selective channels to achieve cooperative gain. The cooperative scheme transmits over three successive block intervals. Linear and zero-forcing detection are considered.
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Song, Hui. "On statistical characterization of EESM effective SNR over frequency selective channels". Thesis, University of Bedfordshire, 2010. http://hdl.handle.net/10547/135260.
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With frequency selective fading, the SNRs of each sub-carrier would vary over the time and frequency. It would then cause fluctuations of the effective SNR. As the decision of MeS in LA is based on the effective SNR, the study of the statistical characterization of effective SNR over frequency selective fading channels would be very important, This problem forms the basis of investigation in this thesis. The methodology used in this thesis is generally divided into two parts. The first part is to investigate the method in obtaining the distribution of EESM over frequency selective fading channels. Such approach will be very helpful for the second part of the work which is to obtain the exact distribution of the EESM effective SNR for a specified fading model. In this case, Nakagami-m fading model is used. The choice of this model is based due to its simplicity and experimental consistency. One of the important features of the distribution is that the SNR of a signal under Nakagami fading is gamma distributed. Thus, in performance evaluation involving Nakagami fading, one can often rely on established results (in the statistics literature) of the gamma distribution. An important special case of the Nakagami distribution is the Rayleigh distribution, which arises in the situation of where the line-of-sight (LOS) component between the transmitter and the receiver is absent, i.e., when all of the received power stems from scattered components. The corresponding distribution for the SNR is the exponential distribution. The research in this thesis represents an effort to provide a statistical characterization of EESM effective SNR which has not appeared in any existing literatures. The goals of this thesis is to Characterize the statistics of EESM effective SNR over frequency selective channels. Obtain the distribution of EESM effective SNR over correlated Nakagami-m fading channels. Theoretically analyze the performance (Le. average SNR, outage probability and Symbol Error Rate (SER) etc.) of EESM over correlated Nakagami-m fading channels. Provide simple approximations to the proposed analytical results. Try to find extension and application of the results.
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Ahmed, Alaa Hussain. "Physical layer network coding based communication systems in frequency selective channels". Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3871.
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The demand for wireless communications is growing every day which requiresmore speed and bandwidth. In two way relay networks (TWRN), physical layer network coding (PLNC) was proposed to double the bandwidth. A TWRN is a system where two end users exchange data through a middle node called the relay. The two signals are allowed to be physically added before being broadcasted back to the end users. This system can work smoothly in flat fading channels, but can not be applied straightforward in frequency selective channels. In a multipath multi-tap FIR channel, the inter-symbol interference (ISI) spreads through several symbols. In this case, the symbols at the relay are not just an addition of the sent symbols but also some of the previous symbols from both sides. This not only causes a traditional PLNC to fail but also a simple one equalizer system will not solve the problem. Three main methods have been proposed by other researchers. The OFDM based PLNC is the simplest in terms of implementation and complexity but suffers from the disadvantages of the OFDMlike cyclic prefix overhead and frequency offset. The main disadvantage, however is the relatively low BER performance because it is restricted to linear equalizers in the PLNC system. Another approach is pre-filtering or pre-equalization. This method also has some disadvantages like complexity, sensitivity to channel variation and the need of a feedback channel for both end nodes. Finally, the maximum likelihood sequence detector was also proposed but is restricted to BPSK modulation and exponentially rising complexity are major drawbacks. The philosophy in this work is to avoid these disadvantages by using a time domain based system. The DFE is the equalizer of choice here because it provides a non-trivial BER performance improvement with very little increase in complexity. In this thesis, the problem of frequency selective channels in PLNC systems can be solved by properly adjusting the design of the system including the DFE. The other option is to redesign the equalizer to meet that goal. An AF DFE system is proposed in this work that provides very low complexity especially at the relay with little sensitivity to channel changes. A multi-antenna DNF DFE system is also proposed here with an improved performance. Finally, a new equalizer is designed for very low complexity and cost DNF approach with little sacrifice of BER performance. Matlab was used for the simulations with Monte Carlo method to verify the findings of this work through finding the BER performance of each system. This thesis opens the door for future improvement on the PLNC system. More research needs to be done like testing the proposed systems in real practical implementation and also the effect of adding channel coding to these systems.
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Viteri, Mera Carlos Andres. "Beamforming Techniques for Frequency-Selective and Millimeter-Wave Indoor Broadcast Channels". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu152344603415358.
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Le, Bidan Raphaël. "Turbo-equalization for bandwidth-efficient digital communications over frequency-selective channels". Rennes, INSA, 2003. http://www.theses.fr/2003ISAR0012.
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Cette thèse traite de la combinaison des fonctions d'égalisation et décodage pour les transmissions haut-débits avec modulations codées sur canaux sélectifs en fréquence. Nous considérons la Turbo-Egalisation, qui instaure un échange itératif d'information entre l'égaliseur et le décodeur. Nous étudions dans un premier temps le turbo-égaliseur reposant sur le critère maximum-a-posteriori, et montrons que ce récepteur offre des gains de performances importants en comparaison avec les récepteurs traditionnels. Nous considérons ensuite une seconde classe de turbo-égaliseurs de moindre complexité reposant sur des égaliseurs à base de filtres linéaires, optimisés selon le critère de la minimisation de l'erreur quadratique moyenne (MEQM). Nos études montrent que ce récepteur constitue une solution attractive pour les transmissions à grande efficacité spectrale sur canaux sélectifs en fréquence. Finalement, nous présenterons la mise en oeuvre d'un turbo-égaliseur MEQM sur un DSP virgule-fixe.
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Rattray, George G. K. "Joint diversity trellis-coded modulation for frequency selective environments". Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366060.
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Katayama, Masaaki. "Keynote: “Power line channels: frequency and time selective” Part 2.-Noise statistics of indoor PLC channels". IEEE, 2007. http://hdl.handle.net/2237/9424.
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SUGAHARA, TOMIE. "DETECTION OF TRELLIS-COBE MODULATED SIGNAL IN FREQUENCY NON-SELECTIVE FADING CHANNELS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8513@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREste trabalho examina uma nova estratégia para detenção de Sinais TCM em presença de desvanecimento não-seletivo em freqüência. Esta estratégia faz uso de um conjunto de estimativas da distorção do canal, cada uma associada a um estado da treliça de decodificação, que são utilizadas simultaneamente no processo de decodificação. No método proposto, a cada intervalo de símbolo calcula-se uma estimativa de canal para cada percurso sobrevivente, usando os sinais associados a este percurso como decisões dos sinais transmitidos até então, juntamente com um algoritmo do tipo Filtro de Kalman. O método é descrito inicialmente para uso em sistemas sem intercalação- desintercalação. Uma versão modificada é proposta para permitir o uso da nova estratégia em associação com esquemas de intercalação-desintercalação. Resultados de desempenho obtidos, via simulação, com os métodos propostos são comparados com os resultados obtidos supondo- se o conhecimento ideal das distorções introduzidas pelo canal bem como os resultados apresentados na literatura, referentes a outros métodos de deteção.
We look into a new strategy for detecting trellis-code modulated signal in the presence of frequency non- selective fading which makes simultaneous use in the decoding procedure of a set of channel distortion estimates, each one associated to a trellis state. During each symbol interval, based on a Kalman Filter-type algorithm, a distinct channel estimate is recursively generated for each survivor path using this path symbols as the truly transmitted symbols. A method is first proposed for use in non-interleaved systems. A modified version for interleaved systems. A modified version for interleaved systens is then presented. Performances are evaluated by computer simulations and comparisons mede to curves pertaining to other methods in the literature and to curves obteined under ideal channel state information assumption.
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Aktas, Emre. "Channel estimation and equalization for wireless communication systems in frequency selective channels /". The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486546889382902.
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Iyer, Karthik S. "Iterative equalization and decoding for modified D-BLAST in frequency selective MIMO channels". Ann Arbor, Mich. : ProQuest, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1432940.
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Thesis (M.S. in Electrical Engineering)--S.M.U.Title from PDF title page (viewed July 9, 2007). Source: Masters Abstracts International, Volume: 44-04, page: 1928. Adviser: Dinesh Rajan. Includes bibliographical references.
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Tung, Tai-Lai, Kung Yao y Don Whiteman. "MULTIPLE-ANTENNA SPATIO-TEMPORAL PROCESSING FOR OFDM COMMUNICATIONS OVER FREQUENCY-SELECTIVE FADING CHANNELS". International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/606486.
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International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaIn this paper, we propose applying the spatio-temporal signal processing and OFDM techniques to a multiple-antenna system in order to achieve high data rate and high performance transmission capability. In order to perform real time processing for this system, we also propose a complexity reduced QR beamforming algorithm. The performance of the proposed system has been investigated for a two-ray frequency-selective fading model by extensive computer simulations. These results show that significant benefits can be realized in terms of lower bit error rate and higher data transmission rate.
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Gao, Wei, Shih-Ho Wang y Kamilo Feher. "BLIND EQUALIZATION FOR FQPSK AND FQAM SYSTEMS IN MULTIPATH FREQUENCY SELECTIVE FADING CHANNELS". International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/607298.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaBlind adaptive equalization with application for Non-Linearly Amplified (NLA) quadrature amplitude modulation (QAM) systems in multipath selective fading channels is presented. With an offset sampling strategy in the receiver, the proposed blind equalization using Constant Modulus Algorithm (CMA) exhibits a fast convergent speed for a family of quadrature modulated systems in NLA and multipath fading channels. Feher’s patented Quadrature Phase Shift Keying (FQPSK) and Feher’s Quadrature Amplitude Modulation (FQAM) which correspond respectively to 4-state and 16-state QAM are used due to their higher Radio Frequency (RF) power and spectral efficiency in NLA channel. It has been shown that blind adaptive equalization can significantly open the eye signals in multipath frequency selective fading channels.
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Eddaghel, Masoud. "Mitigating PAPR in cooperative wireless networks with frequency selective channels and relay selection". Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16339.
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The focus of this thesis is peak-to-average power ratio (PAPR) reduction in cooperative wireless networks which exploit orthogonal frequency division multiplexing in transmission. To reduce the PAPR clipping is employed at the source node. The first contribution focuses upon an amplify-and-forward (AF) type network with four relay nodes which exploits distributed closed loop extended orthogonal space frequency block coding to improve end-to-end performance. Oversampling and filtering are used at the source node to reduce out-of-band interference and the iterative amplitude reconstruction decoding technique is used at the destination node to mitigate in-band distortion which is introduced by the clipping process. In addition, by exploiting quantized group feedback and phase rotation at two of the relay nodes, the system achieves full cooperative diversity in addition to array gain. The second contribution area is outage probability analysis in the context of multi-relay selection in a cooperative AF network with frequency selective fading channels. The gains of time domain multi-path fading channels with L paths are modeled with an Erlang distribution. General closed form expressions for the lower and upper bounds of outage probability are derived for arbitrary channel length L as a function of end-to-end signal to noise ratio. This analysis is then extended for the case when single relay selection from an arbitrary number of relay nodes M is performed. The spatial and temporal cooperative diversity gain is then analysed. In addition, exact form of outage probability for multi-path channel length L = 2 and selecting the best single relay from an arbitrary number of relay nodes M is obtained. Moreover, selecting a pair of relays when L = 2 or 3 is additionally analysed. Finally, the third contribution context is outage probability analysis of a cooperative AF network with single and two relay pair selection from M available relay nodes together with clipping at the source node, which is explicitly modelled. MATLAB and Maple software based simulations are employed throughout the thesis to support the analytical results and assess the performance of algorithms and methods.
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Pham, Edward Carleton University Dissertation Engineering Electrical. "SER prediction for transmission of PSAM 16-QAM in frequency selective fading channels". Ottawa, 1992.
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Song, Liying Tugnait Jitendra K. "Channel estimation and equalization for doubly-selective channels using basis expansion models". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Electrical_and_Computer_Engineering/Dissertation/Song_Liying_29.pdf.
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D'Amours, Claude. "Differential and coherent RAKE receivers for DS-CDMA in frequency-selective Rayleigh fading channels". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/10753.
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The performance of digital communications over frequency-selective Rayleigh fading channels can be quite poor, thus diminishing, the capacity of a DS-CDMA system. This thesis compares differential detection, multiple symbol differential detection and pilot symbol-aided coherent detection of a direct-sequence spread spectrum signal for this channel. Diversity reception is obtained through RAKE reception, and both equal gain and maximal gain diversity combining are considered. The improvement provided by some error correcting convolutional codes arid interleaving are also studied.
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Kao, Chi-Han. "Performance of IEEE 802.11a wireless LAN standard over frequency-selective, slow, ricean fading channels". Thesis, Monterey California. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/5020.
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Approved for public release, distribution is unlimitedWith the rapidly growing demand for more reliable and higher data rate wireless communications, the Institute of the Electrical and Electronics Engineers (IEEE) 802.11 working group approved a standard for 5 GHz band, wireless local area networks (WLAN) in 1999. This standard, IEEE 802.11a, supports data rates from 6 up to 54 Mbps, and uses orthogonal frequency division multiplexing (OFDM) for transmission in indoor wireless environments. This thesis examines the performance of the IEEE 802.11a standard for different combinations of sub-carrier modulation type and code rate and determines the signal-to-noise ratio required to obtain a probability of bit error b P of 10-5. The channel is modeled as a frequency-selective, slow, Ricean fading channel with additive white Gaussian noise (AWGN). Contrary to expectations, for the combinations of sub-carrier modulation type and code rate utilized by the IEEE 802.11a standard, some of the higher data rate combinations outperform some of the lower data rate combinations. On the other hand, the results also show significant coding gain when applying convolutional coding with Viterbi decoding, and hence highlight the importance of forward error correction (FEC) coding to the performance of wireless communications systems.
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Rice, Michael, Gaston David de, Adam Davis, Gus German y Christian Bettwieser. "ARTM CHANNEL SOUNDING RESULTS – AN INVESTIGATION OF FREQUENCY SELECTIVE FADING ON AERONAUTICAL TELEMETRY CHANNELS". International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/608746.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaInitial results of wideband channel sounding experiments sponsored by the Advanced Range Telemetry (ARTM) program are presented. Data collected at Edwards EAFB during the Winter 1998-1999, are analyzed in the frequency domain to estimate the number, strength, and delays of the significant multipath reflections observed during the experiments. We observe that the channel is adequately modeled using two or three multipath reflections. The multipath fade events are correlated with recorded bit error rates and transmitter location to provide a comprehensive overview of the channel characteristics. Summaries from two test flights are included where it is seen that the 2- and 3-ray channel models provide excellent models for the data. In general, the 3-ray model captures the essential features of the multipath interference. In this model the first multipath is a strong specular reflection with relative amplitude greater than 0.5 and relative delay in the 30 to 70 ns range. The second multipath is a much weaker reflection with relative amplitude less than 0.5 and relative delay in the 175 to 325 ns range.
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Kao, Chi-han. "Performance of IEEE 802.11a wireless LAN standard over frequency-selective, slow, ricean fading channels /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FKao.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2002.Thesis advisor(s): R. Clark Robertson, Roberto Cristi. Includes bibliographical references (p. 93-94). Also available online.
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Wavegedara, Kapila Chandika B. "Advanced receivers for space-time block-coded single-carrier transmissions over frequency-selective fading channels". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/620.
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In recent years, space-time block coding (STBC) has emerged as an effective transmit-diversity technique to combat the detrimental effects of channel fading. In addition to STBC, high-order modulation schemes will be used in future wireless communication systems aiming to provide ubiquitous-broadband wireless access. Hence, advanced receiver schemes are necessary to achieve high performance. In this thesis, advanced and computationally-efficient receiver schemes are investigated and developed for single-carrier space-time (ST) block-coded transmissions over frequency-selective fading (FSF) channels.
First, we develop an MMSE-based turbo equalization scheme for Alamouti ST block-coded systems. A semi-analytical method to estimate the bit error rate (BER) is devised. Our results show that the proposed turbo equalization scheme offers significant performance improvements over one-pass equalization. Second, we analyze the convergence behavior of the proposed turbo equalization scheme for Alamouti ST block-coded systems using the extrinsic information transfer (EXIT)-band chart technique.
Third, burst-wise (BW)-STBC is applied for uplink transmission over FSF channels in block-spread-CDMA systems with multiuser interference-free reception. The performances of different decision feedback sequence estimation (DFSE) schemes are investigated. A new scheme combining frequency-domain (FD) linear equalization and modified unwhitened-DFSE is proposed. The proposed scheme is very promising as the error-floor behavior observed in the existing unwhitened DFSE schemes is eliminated.
Fourth, we develop a FD-MMSE-based turbo equalization scheme for the downlink of ST block-coded CDMA systems. We adopt BW-STBC instead of Alamouti symbol-wise (SW)-STBC considered for WCDMA systems and demonstrate its superior performance in FSF channels. Block spreading is shown to be more desirable than conventional spreading to improve performance using turbo equalization. We also devise approximate implementations (AprxImpls) that offer better trade-offs between performance and complexity. Semi-analytical upper bounds on the BER are derived.
Fifth, turbo multicode detection is investigated for ST block-coded downlink transmission in DS-CDMA systems. We propose symbol-by-symbol and chip-by-chip FD-MMSE-based multicode detectors. An iterative channel estimation scheme is also proposed. The proposed turbo multicode detection scheme offers significant performance improvements compared with non-iterative multicode detection. Finally, the impact of channel estimation errors on the performance of MMSE-based turbo equalization in ST block-coded CDMA systems is investigated.
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Pham, Tri. "Soft Detection of Trellis Coded CPM in Frequency-SelectiveChannels". Thesis, University of Canterbury. Electrical and Electronic Engineering, 2012. http://hdl.handle.net/10092/7178.
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Non-linear continuous phase modulation has constant envelope and spectral efficiency, which are desirable for public safety communication systems where both bandwidth and power are limited. A practical design of an innovation based receiver for partial response CPM was recently developed for public
safety applications. It is in the form of a linear predictive demodulator with a coefficient look up table. The demodulator shows great performance over multipath fading channels without channel equalization and promises a significant
contribution to public safety communication.
The work in this thesis is focussed on developing and analyzing modern techniques to improve the receiver performance while maintaining a feasible implementation complexity. Suitable soft output algorithms are incorporated into the demodulator allowing a subsequent convolutional decoder to perform soft
decoding. By modifying the design criteria of the predictive demodulator and introducing a feedback loop, an iterative detection scheme is formed for the concatenated structure of demodulator, deinterleaver and decoder.
Spatial diversity combining techniques are summarized and a very low complexity combining scheme is developed. It selects the best received sample sequence by considering the average energy of each sequence. In addition, the demodulator is extended to have dual coefficient look up tables supporting its
detection by having parallel prediction processes and combining their results. This leads to an improvement in overall demodulator performance. A theoretical proof that only half the number of coefficients need to be stored in memory is also given.
Matlab simulations on a Rayleigh fast fading multipath channel have shown that the proposed techniques significantly improve the overall detection accuracy. Each of them provides a good gain in signal to noise ratio or delay spread and when combined, a significant performance gain is achieved.
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Liang, Yan. "Integrated Frequency-Selective Conduction Transmission-Line EMI Filter". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26360.
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The multi-conductor lossy transmission-line model and finite element simulation tool are used to analyze the high-frequency attenuator and the DM transmission-line EMI filter. The insertion gain, transfer gain, current distribution, and input impedance of the filter under a nominal design are discussed. In order to apply the transmission-line EMI filter to power electronics systems, the performance of the filter under different dimensions, material properties, and source and load impedances must be known. The influences of twelve parameters of the DM transmission-line EMI filter on the cut-off frequency, the roll-off slope, and other characteristics of the insertion gain and transfer gain curves are investigated. The most influential parameters are identified. The current sharing between the copper and nickel conductors under different parameters are investigated. The performance of the transmission-line EMI filter under different source and load impedances is also explored.
The measurement setups of the DM transmission-line EMI filter using a network analyzer have been discussed. The network analyzer has a common-ground problem that influences the measured results of the high-frequency attenuator. However, the common-ground problem has a negligible influence on the measured results of the DM transmission-line EMI filter. The connectors and copper strips between the connectors and the filter introduce parasitic inductance to the measurement setup. Both simulated and measured results show that transfer gain curve is very sensitive to the parasitic inductance. However, the insertion gain curve is not sensitive to the parasitic inductance. There are two major methods to reduce the parasitic inductance of the measurement setup: using small connectors and applying a four-terminal measurement setup. The transfer gain curves of three measurement setups are compared: the two-terminal measurement setup with BNC connectors, the two-terminal measurement setup with Sub Miniature version B (SMB) connectors, and the four-terminal measurement setup with SMB connectors. The four-terminal measurement setup with SMB connectors is the most accurate one and is applied for all the transfer gain measurements in this dissertation.
This dissertation also focuses on exploring ways to improve the performance of the DM transmission-line EMI filter. Several improved structures of the DM transmission-line EMI filter are investigated. The filter structure without insulation layer can greatly reduce the thickness of the filter without changing its performance. The meander structure can increase the total length of the filter without taking up too much space and results in the cut-off frequency being shifted lower and achieving more attenuation. A prototype of the two-dielectric-layer filter structure is built and measured. The measurement result confirms that a multi-dielectric-layer structure is an effective way to achieve a lower cut-off frequency and more attenuation.
This dissertation proposes a broadband DM EMI filter combining the advantages of the discrete reflective LC EMI filter and the transmission-line EMI filter. Two DM absorptive transmission-line EMI filters take the place of the two DM capacitors in the discrete reflective LC EMI filter. The measured insertion gain of the prototype has a large roll-off slope at low frequencies and large attenuation at high frequencies. The dependence of the broadband DM EMI filter on source and load impedances is also investigated. Larger load (source) impedance gives more attenuation no matter it is resistive, inductive or capacitive. The broadband DM EMI filter always has more high-frequency attenuation than the discrete reflective LC EMI filter under different load (source) impedances.Ph. D.
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Gong, Yi. "Space-time coding for high data-rate wireless communications over space and frequency selective fading channels /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202002%20GONG.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 105-114). Also available in electronic version. Access restricted to campus users.
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Manglani, Manish. "Wavelet Modulation in Gaussian and Rayleigh Fading Channels". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34396.
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Wavelet Modulation (WM)---also referred to as fractal modulation---simultaneously sends data at multiple rates through an unknown channel. This novel multirate diversity strategy offers improved message recovery over conventional modulation techniques: if the message is not received at one rate due to the channel disturbances, it can be received at another rate where the channel is clear. Previous research has demonstrated the performance of wavelet modulation in Gaussian channels.
This paper extends the investigation to the performance of wavelet modulation in time varying channels. We show that bit error rate (BER) wavelet demodulation performance in the additive, white, Gaussian noise (AWGN) channel is comparable to theoretical binary phase shift keying. Our results depict the improvement in performance that can be realized for time varying channels by utilizing the various rates of wavelet modulation; BER versus SNR curves for each fading channel show how the message at one rate can be more accurately recovered than at another rate. Furthermore, we also present results indicating the dramatic improvement in wavelet demodulation performance when multiple rates are available and utilized for demodulation. This improvement in performance is highly visible in BER performance for the AWGN and flat fading channels.
Finally, a comparison of binary phase shift keying (BPSK) and WM in a frequency selective channel is performed. The BER improvement of WM is shown when demodulation is done at rates which are least corrupted by ISI. We illustrate our new algorithm that: identifies the channel characteristics; determines which rates are maximally corrupted by ISI; and, utilizes only those uncorrupted copies in demodulation.Master of Science
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Siyau, Ming Fei. "A novel training-based MIMO channel estimation scheme for layered space-time systems in frequency selective wireless channels". Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/3464.
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New development in wireless technology using multiple antennas with appropriate space-time processing has recently become the new frontier of wireless communication systems due to the potential for providing very high spectral efficiency and enormous capacity improvement over the conventional wireless radio communications. The technical advances in using the multiple-input multiple-output (MIMO) wireless links present a promising breakthrough in resolving the bottleneck of current capacity limitation for future intensive wireless networks. The MIMO wireless systems utilize multiple antennas at both side of the transmitter and the receiver for enormous gains in spectral efficiency as well as system capacity in terms of higher data throughput by exploiting the multipath diversity in a rich scattering environment. A number of MIMO systems have been proposed to permit very high transmission rate, far exceeding the conventional communication technique. In particular, the Bell Laboratories layered space-time (BLAST) architecture has been presented that uses concept of spatial diversity and successive interference cancellation technique to improve the quality of signal reception over the flat-fading or the frequency selective fading channel. However, in order to achieve the quoted capacity gains in MIMO systems, the channeli nformation in terms of the multiple channeli mpulse responses(C IRs) and their fading coefficients must be known or estimated, which requires the design of a suitable channele stimator.T hus far, existing MIMO channele stimations chemesh aveb eenm ostly limited to the flat-fading case or cater specifically for coded space-time systems such as space-timeb lock code systems.I n this thesis,t he work is to considert he existing MIMO channel estimation techniques (used in the flat fading condition) and extend them to cater for a more realistic time-varying, frequency selective fading channel. The focus of this thesis has been the design and development of suitable training-based MIMO channel estimation scheme as well as the formulation of a new pilot code to enable effective estimation for the frequency selective channel. The novel channel estimator is also incorporatedi nto the BLAST architecturet o allow the practical assessmenotf using nonidealized channel to be studied and analysed for the performance of the MIMO systems. The driver for this work has been the recognition of the importance of channel knowledge for all the MIMO system to be used in practical application.
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LI, XIANGTAO. "PERFORMANCE ANALYSIS OF DECORRELATING DETECTORS FOR DUAL-RATE SYNCHRONOUS DS/CDMA SYSTEMS OVER FREQUENCY-SELECTIVE RAYLEIGH FADING CHANNELS". University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1028644891.
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Siyau, M. F. "A Novel training-based MIMO channel estimation scheme for layered space-time systems in frequency selective wireless channels". Thesis, Department of Aerospace, Power & Sensors, 2009. http://hdl.handle.net/1826/3464.
Texto completoResumen
New development in wireless technology using multiple antennas with appropriate
space-time processing has recently become the new frontier of wireless communication
systems due to the potential for providing very high spectral efficiency and enormous
capacity improvement over the conventional wireless radio communications. The technical
advances in using the multiple-input multiple-output (MIMO) wireless links present a
promising breakthrough in resolving the bottleneck of current capacity limitation for future
intensive wireless networks. The MIMO wireless systems utilize multiple antennas at both
side of the transmitter and the receiver for enormous gains in spectral efficiency as well as
system capacity in terms of higher data throughput by exploiting the multipath diversity in
a rich scattering environment. A number of MIMO systems have been proposed to permit
very high transmission rate, far exceeding the conventional communication technique. In
particular, the Bell Laboratories layered space-time (BLAST) architecture has been
presented that uses concept of spatial diversity and successive interference cancellation
technique to improve the quality of signal reception over the flat-fading or the frequency
selective fading channel.
However, in order to achieve the quoted capacity gains in MIMO systems, the
channeli nformation in terms of the multiple channeli mpulse responses(C IRs) and their
fading coefficients must be known or estimated, which requires the design of a suitable
channele stimator.T hus far, existing MIMO channele stimations chemesh aveb eenm ostly
limited to the flat-fading case or cater specifically for coded space-time systems such as
space-timeb lock code systems.I n this thesis,t he work is to considert he existing MIMO
channel estimation techniques (used in the flat fading condition) and extend them to cater
for a more realistic time-varying, frequency selective fading channel. The focus of this
thesis has been the design and development of suitable training-based MIMO channel
estimation scheme as well as the formulation of a new pilot code to enable effective
estimation for the frequency selective channel. The novel channel estimator is also
incorporatedi nto the BLAST architecturet o allow the practical assessmenotf using nonidealized
channel to be studied and analysed for the performance of the MIMO systems.
The driver for this work has been the recognition of the importance of channel knowledge
for all the MIMO system to be used in practical application.
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Chi, Xuan. "The Impact of Channel Estimation Error on Space-Time Block and Trellis Codes in Flat and Frequency Selective Channels". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33963.
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Recently multiple antenna systems have received significant attention from researchers as a means to improve the energy and spectral efficiency of wireless systems. Among many classes of schemes, Space-Time Block codes (STBC) and Space-Time Trellis codes (STTC) have been the subject of many investigations.Both techniques provide a means for combatting the effects of multipath fading without adding much complexity to the receiver. This is especially useful in the downlink of wireless systems. In this thesis we investigate the impact of channel estimation error on the performance of both STBC and STTC.
Channel estimation is especially important to consider in multiple antenna systems since (A) for coherent systems there are more channels to estimate due to multiple antennas and (B) the decoupling of data streams relies on correct channel estimation. The latter effect is due to the intentional cross-talk introduced into STBC.
Master of Science
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Fhima, Hayfa. "Study and implementation of widely linear (WL) receiver for filter bank based multicarrier (FBMC-OQAM) modulations over frequency selective channels". Electronic Thesis or Diss., Paris, CNAM, 2019. http://www.theses.fr/2019CNAM1266.
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Parmi les principales raisons qui ont aboutit au progrès technique et au développement des systèmes de communication sans fils modernes, on trouve la forte demande des besoins et des exigences des différents utilisateurs. Ainsi, depuis les systèmes de deuxième génération (2G), de nombreux changements ont eu lieu, principalement, le passage des modulations (WF) mono-porteuses aux modulations multi-porteuses (MC) introduites pour la transmission de la 4G en sens descendant.En effet, l'idée d'introduire les formes d'ondes MC est de se débarrasser des effets du canal de propagation, en relâchant le processus d’égalisation par la transmission des symboles de données sur des sous-canaux ou des sous-porteuses à évanouissements plats. En outre, la modulation MC la plus répandue est l'orthogonal frequency division multiplexing (OFDM), qui est devenu très dominante et largement utilisée dans de nombreuses normes sans fil, telles que long term evolution (LTE)- Advanced (LTE-A) et le Wi-Fi. Ce succès de l'OFDM est du grâce à ses avantages présentés dans la simple implémentation par le biais de l'utilisation de la transformée de Fourrier rapide inverse (IFFT) à la transmission et de la transformé de Fourrier rapide à la réception. De plus, avec l'utilisation du préfixe cyclique (CP), la transmission est ainsi sans interférences inter-symboles (ISI).Malgré la dominante utilisation de l'OFDM MW, néanmoins, elle présente des inconvénients. En effet, cette technique souffre de la perte de l'efficacité spectrale à cause de l'utilisation du CP, sans oublier la mauvaise localisation fréquentielle à cause de la mise en forme rectangulaire du filtre prototype utilisé dans OFDM. Ces inconvénients ont été une source de motivation pour les chercheurs pour la conception d'une nouvelle MC WF, ayant une meilleure localisation fréquentielle, une meilleure robustesse au synchronisme des utilisateurs, tout en conservant une complexité de mise en oeuvre modérée. Dans ce contexte, un nombre élevé de MC WF post-OFDM ont été proposés et mis en œuvre pour répondre aux scénarios et aux exigences de la 5G d'une manière flexible.Ainsi, la modulation multi-porteuse à base des bancs de filtres (FBMC-OQAM) a été proposée en tant qu'une solution alternative à l'OFDM WF et ce pour surmonter ses inconvénients. En effet, la modulation FBMC-OQAM utilise un filtre prototype (Phydyas) qui lui permet d'avoir une meilleure localisation fréquentielle ce que lui offre une meilleure performance en supportant les phénomènes d'asynchronisme entre les utilisateurs ainsi que la transmission avec différentes numérologies. En outre, l'efficacité spectrale est améliorée grâce à la non utilisation du CP et de bandes de garde larges. De plus, l'orthogonalité dans le domaine réel est garantie grâce à l'utilisation de la modulation OQAM. Cependant, cette orthogonalité est perdue dans les canaux sélectifs en fréquence, ce qui nécessite des techniques d'égalisation avancées.Dans ce contexte, l'objectif de cette thèse est d'étudier plusieurs types d'égalisation appliqués aux systèmes FBMC-OQAM. Vu que la modulation utilisée en FBMC-OQAM peut être considérée comme la transmission de deux flux de modulation M-PAM sur la même sous porteuse et comme le traitement largement linéaire est plus performant par rapport au traitement classique pour la modulatyion M-PAM, on va se concentrer sur les avantages de ce traitement largement linéaire utilisé pour le système FBMC-OQAM. En outre, en se basant qur e caractère cyclo-stationnaire du signal FBMC-OQAM, nous avons proposés une structure d'égalisation avancée basée sur le traitement FRESH qui a été appliqué sur un système FBMC-OQAM utilisant différente numélogiesThe increasing demand of user’s requirements is one of the main reasons in technical progress and development of modern wireless communication systems. Thus, since 2G and beyond, there have been many changes, especially, the switch from the mono carrier to the multi-carrier (MC), introduced for the Down-Link (DL) 4G transmission. Indeed, the predo- minant idea behind introducing MC waveforms (WF) is to get rid of the propagation channel effects, by relaxing the equalization process through the transmission of the data symbols over flat fading sub-channels or sub-carriers. Furthermore, the widely adopted MC WF is the ortho- gonal frequency division multiplexing (OFDM), which became very popular and widely used in many wireless standards like long term evolution (LTE)- Advanced (LTE-A) andWi-Fi. The standardization of OFDM, for these applications and also for some others, is related to the ad- vantages shown by this MC WF. One of these advantages is its simple implementation through the use of the inverse fast Fourier transform (IFFT) at the transmitter side, and a FFT at the receiver side. Also, OFDM introduces a cyclic prefix (CP), making the transmission free from inter-symbol-interference (ISI).Despite the large success of the OFDM WF, this technique suffers from the loss of spec- tral efficiency due to the use of the CP. Besides, it suffers from bad frequency localization due the use of a rectangular prototype filter. These OFDM drawbacks, have motivated researchers to design new MC WF, with better frequency domain localization, better robustness to user’s synchronism, while keeping moderate implementation complexity. In this context, high num- ber of post-OFDM MC WF have been proposed and implemented to meet 5G scenarios and requirements in a flexible manner.Therefore, the offset-quadratureamplitudemodulation-based filter-bankmulti-carrier(FBMC- OQAM) has been proposed as an alternative to overcome some drawbacks of the OFDM WF. Indeed, FBMC-OQAM is characterized by owning one of the best frequency localiza- tion among all the post-OFDM WFs, thanks to its prototype filter (Phydyas), providing then the best performance in supporting asynchronous and mixed numerologies transmissions. Be- sides, it offers high spectrum efficiency since it avoids the use of CP and large guard bands. Furthermore, the orthogonality in real domain is guaranteed thanks to the use of the OQAM modulation. However, this orthogonality is lost under frequency selective channels which re- quires advanced equalization techniques.In this context, the main objective of this thesis is to study different types of equalization applied on FBMC-OQAM system. Since the modulation used in the FBMC-OQAM system can be seen as the transmission of two M−PAM modulations over one single carrier and since the widely linear processing outperforms the classical one for M−PAM modulation, we will focus on the advantages of using the widely linear processing over FBMC-OQAM system. Ad- ditionally, and based on the cyclo-stationarity of the FBMC-OQAM signal, we have proposed an advanced equalization structure based on FRESH processing that have been applied in to a FBMC-OQAM system using different numerologies
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Franklin, Daniel Robert. "Enhancements to channel models, DMT modulation and coding for channels subject to impulsive noise". School of Electrical, Computer & Telecommunications Engineering - Faculty of Informatics, 2007. http://ro.uow.edu.au/theses/18.
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DMT modulation is an OFDM-based modulation scheme used in ADSL and proposed for various other high-speed broadband access systems. Existing mathematical models for transmission lines make a number of simplistic assumptions about the distribution of noise, in particular, the assumption that impulsive noise originates at either end of the transmission line. It is therefore desirable to improve the accuracy of the transmission-line model to allow better prediction of broadband modem performance, and to further improve the bit-allocation algorithms and equaliser designs used in DMT-based modems. This Thesis presents a new channel model particularly well-suited for simulation of high-speed digital subscriber line systems. The model extends a commonly-used physical channel model by distributing the points of noise ingress along the physical length of the transmission line. Simulation results are presented for a highspeed multicarrier modem operating on channels modelled with both the conventional and new models. Comparison with the same modem operating over a real channel demonstrates that the new model provides a better estimate of the bit error rates and temporal error distribution expected on actual telephone lines than is possible with the conventional model. A number of improvements to modulation and coding schemes for DMT modems are also presented in this Thesis, including a robust frequency-domain decision feedback equaliser, a new algorithm for allocating bits to sub-carriers based on a measurement of per-carrier BER, and a technique for encoding data with fractional numbers of bits ii Abstract iii per symbol, thereby providing additional channel capacity.
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Kalogrias, Christos. "Performance analysis of the IEEE 802.11A WLAN standard optimum and sub-optimum receiver in frequency-selective, slowly fading Nakagami channels with AWGN and pulsed noise jamming". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FKalogrias.pdf.
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Thesis (M.S. in Electrical Engineering and M.S. in Systems Engineering)--Naval Postgraduate School, March 2004.Thesis advisor(s): Clark Robertson. Includes bibliographical references (p. 143). Also available online.
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Fung, Victor. "Bit error simulation of FSK, BPSK, and pi/4 DQPSK in flat and frequency-selective fading mobile radio channels using two-ray and measurement- based impulse response models". Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08142009-040410/.
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Osman, Ammar. "Low-complexity OFDM transceiver design for UMTS-LTE". Thesis, Blekinge Tekniska Högskola, Avdelningen för signalbehandling, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3716.
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Over the past two decades the mobile wireless communication systems has been growing fast and continuously. Therefore, the standardization bodies together with wireless researchers and mobile operators around the globe have been constantly working on new technical specifications in order to meet the demand for this rapid growth. The 3rd Generation Partnership Project (3GPP) one of the largest of such standardization bodies, works on developing the current third generation (3G) mobile telecommunication systems towards the future 4th generation. Research towards meeting the higher demands for higher data rates was the main reason for the birth of an evolution technology towards the 4th generation mobile systems. This evolution to the current 3rd generation UMTS systems was given the name E-UTRA/UTRAN Long Term Evolution (LTE) by the 3GPP. This thesis research has been carried out at the Telecommunications Research Center (ftw.) in Vienna. It was conducted in the framework of the C10 project “Wireless Evolution Beyond 3G”. One of the fields of research within this project is to have a special focus on the OFDM modulation schemes that are discussed under the new evolution technology (LTE) of the UMTS mobile networks. Therefore, this thesis focuses mainly in analyzing the new requirements, and evaluating them by designing a low-complexity UMTS-LTE OFDM based transceiver. This thesis aims mainly in studying the feasibility of this technology by means of simulation.Tel: +46-704469795 Email: osman@ftw.at,amos04@student.bth.se, ammarmao@gmail.com