Bibliographies thématiques / Time /Frequency Selective Broadband Channels

Littérature scientifique sur le sujet « Time /Frequency Selective Broadband Channels »

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Publié le 25 mai 2024

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Articles de revues sur le sujet "Time /Frequency Selective Broadband Channels"

Fateh, Rachid, Anouar Darif, Ahmed Boumezzough, Said Safi et Miloud Frikel. « A Novel Kernel Algorithm for Finite Impulse Response Channel Identiﬁcation ». Journal of Telecommunications and Information Technology, n^o 2 (29 juin 2023) : 84–93. http://dx.doi.org/10.26636/jtit.2023.169823.

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Over the last few years, kernel adaptive ﬁlters have gained in importance as the kernel trick started to be used in classic linear adaptive ﬁlters in order to address various regression and time-series prediction issues in nonlinear environments.In this paper, we study a recursive method for identifying ﬁnite impulse response (FIR) nonlinear systems based on binary-value observation systems. We also apply the kernel trick to the recursive projection (RP) algorithm, yielding a novel recursive algorithm based on a positive deﬁnite kernel. For purposes, our approach is compared with the recursive projection (RP) algorithm in the process of identifying the parameters of two channels, with the ﬁrst of them being a frequency-selective fading channel, called a broadband radio access network (BRAN B) channel, and the other being a a theoretical frequency-selective channel, known as the Macchi channel. Monte Carlo simulation results are presented to show the performance of the proposed algorithm.

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Perov, Sergey Yu, Olga V. Belaya, Quirino Balzano et Nina B. Rubtsova. « The problems of mobile communication electromagnetic field exposure assessment today and tomorrow ». Russian Journal of Occupational Health and Industrial Ecology 60, n^o 9 (7 octobre 2020) : 597–99. http://dx.doi.org/10.31089/1026-9428-2020-60-9-597-599.

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New and necessary improvements of electromagnetic exposure assessment principles and methods are considered and presented. The electromagnetic field exposure assessment is the physical basis for hygienic and biological research and needs s to consider the new technological features of emerging 5G mobile systems in addition to existing 2-4G systems. The new generation of telecommunication networks will cause significantly novel electromagnetic field exposure, in particular for time-frequency and spatial parameters. A complex exposure assessment based on refined broadband measurements seems to be the proper and necessary approach to the enhancement of Russian EMF assessment guidelines. Simple broadband EMF measurements are the common approach for present exposure assessment and cannot be used any longer as the only measure for multiple 5G sources exposure evaluation. Then again broadband measurements are the simple and practical approach for mm wave in-situ exposure assessment. Frequency-selective and code-selective measurements provide detailed EMF level distribution in separate frequency channels, telecommunication services or sources and are a promising approach for objective exposure assessment.

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Zhang, Zilong, Xiaodong Xu et Yanan Wu. « Transmit Beamforming Optimization Design for Broadband Multigroup Multicast System ». Mathematical Problems in Engineering 2015 (2015) : 1–13. http://dx.doi.org/10.1155/2015/563863.

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Spectral efficient transmission techniques are necessary and promising for future broadband wireless communications, where the quality of service (QoS) and/or max-min fair (MMF) of intended users are often considered simultaneously. In this paper, both the QoS problem and the MMF problem are investigated together for transmit beamforming in broadband multigroup multicast channels with frequency-selective fading characters. We first present a basic algorithm by directly using the results in frequency-flat multigroup multicast systems (Karipidis et al., 2008), namely, the approximation algorithms in this paper, for both problems, respectively. Due to high computational consumption nature of the approximation algorithms, two reduced-complexity algorithms for each of the two problems are proposed separately by introducing the time-frequency correlations. In addition, parameters in the new time-frequency formulations, such as the number of optimization matrix variables and the taps of the beamformer with finite impulse response (FIR) structure, can be used to make a reasonable tradeoff between computational burden and system performance. Insights into the relationship between the two problems and some analytical results of the computational complexity of the proposed algorithms are also studied carefully. Numerical simulations indicate the efficiency of the proposed algorithms.

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Xing, Kang, Shiyan Li, Zhijie Qu et Xiaojuan Zhang. « Time-Domain Electromagnetic Noise Suppression Using Multivariate Variational Mode Decomposition ». Remote Sensing 16, n^o 5 (25 février 2024) : 806. http://dx.doi.org/10.3390/rs16050806.

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Noise suppression is essential in time-domain electromagnetic (TDEM) data processing and interpretation. TDEM data are typically in broadband signal, which makes it difficult to separate the signal in the whole frequency band. The conventional methods tend to process data trace by trace, ignoring the lateral continuity between channels. This paper proposes a workflow based on multivariate variational mode decomposition (MVMD) and multivariate detrended fluctuation analysis (MDFA) to deal with the noise in 2-D TDEM data. The proposed method initially employs MVMD to decompose TDEM signals into a series of intrinsic mode functions (IMFs). Subsequently, MDFA is used to calculate the scaling exponent of each IMF, facilitating the selection of signal-dominant IMFs. Finally, the signal IMFs are summed up to reconstruct the TDEM signal. Both simulation and field results demonstrate that, by considering the lateral continuity of data across channels, the proposed method is more effective at noise removal than other single-channel data processing techniques.

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Cobacho-Ruiz, Pablo, Francisco Javier Cañete, Eduardo Martos-Naya et Unai Fernández-Plazaola. « OFDM System Design for Measured Ultrasonic Underwater Channels ». Sensors 22, n^o 15 (29 juillet 2022) : 5703. http://dx.doi.org/10.3390/s22155703.

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In this paper, we present the development of a multicarrier modulation system of low complexity for broadband underwater acoustic communications (UAC), whose frequency band is located in the ultrasonic range, specifically between 32 kHz and 128 kHz. Underwater acoustic channels are recognized among the most hostile communication channels due to their strong time and frequency selectivity and, hence, the design of high-performance systems is a challenge that is difficult to resolve at the present time with state-of-art technology. The aim of the proposed system is to reach a reasonable bit rate, between 40 and 50 Kbps, over these channels that allows, for instance, the transmission of video signals of limited quality. We describe an orthogonal frequency division multiplexing (OFDM) modem prototype with a parameter setting and design specifically adapted to the channel nature. For this purpose, actual measurements carried out at the Mediterranean sea, on shallow waters, have been used to evaluate the system performance and to optimize the design. A discussion on several modulations and OFDM configurations is presented that leads to the selection of differential and non-differential quadri-phase shift keying (QPSK) as good candidates depending on synchronization capabilities.

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Nwanekezie, Nnamdi, Oluyomi Simpson, Gbenga Owojaiye et Yichuang Sun. « Co-Efficient Vector Based Differential Distributed Quasi-Orthogonal Space Time Frequency Coding ». Sensors 23, n^o 17 (30 août 2023) : 7540. http://dx.doi.org/10.3390/s23177540.

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Distributed space time frequency coding (DSTFC) schemes address problems of performance degradation encountered by cooperative broadband networks operating in highly mobile environments. Channel state information (CSI) acquisition is, however, impractical in such highly mobile environments. Therefore, to address this problem, designers focus on incorporating differential designs with DSTFC for signal recovery in environments where neither the relay nodes nor destination have CSI. Traditionally, unitary matrix-based differential designs have been used to generate the differentially encoded symbols and codeword matrices. Unitary based designs are suitable for cooperative networks that utilize the amplify-and-forward protocol where the relay nodes are typically required to forego differential decoding. In considering other scenarios where relay nodes are compelled to differentially decode and re-transmit information signals, we propose a novel co-efficient vector differential distributed quasi-orthogonal space time frequency coding (DQSTFC) scheme for decode-and-forward cooperative networks. Our proposed space time frequency coding scheme relaxes the need for constant channel gain in the temporal and frequency dimensions over long symbol periods; thus, performance degradation is reduced in frequency-selective and time-selective fading environments. Simulation results illustrate the performance of our proposed co-efficient vector differential DQSTFC scheme under different channel conditions. Through pair-wise error probability analysis, we derive the full diversity design criteria for our code.

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Tuzlukov, Vyacheslav. « Performance of Generalized Receiver Employed by Broadband Multicarrier DS-CDMA System Using Space-Time Spreading-Assisted Transmit Diversity ». WSEAS TRANSACTIONS ON COMMUNICATIONS 20 (29 septembre 2021) : 152–71. http://dx.doi.org/10.37394/23204.2021.20.21.

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In this paper the multicarrier direct-sequence code-division multiple access (MC DS-CDMA) using space-time spreading assisted transmit diversity is investigated in the context of broadband wireless communi-cations systems constructed based on the generalized approach to signal processing in noise over frequency-se-lective Rayleigh fading channels. We consider the issue of parameter design for the sake of achieving high-ef-ficiency communications in various dispersive environments. In contrast to the conventional MC DS-CDMA wireless communication system employing the time (T)-domain spreading only, in the present paper the broad-band wireless MC DS-CDMA wireless communication schemes employ both the time (T)-domain and frequen-cy (F)-domain spreading, i.e., employ the TF-domain spreading. The bit-error rate (BER) performance of the space-time spreading assisted broadband MC DS-CDMA wireless communications system is investigated for down-link transmissions associated with the single user and multiuser generalized detectors and is compared with that of the single user correlation detector and the multiuser decorrelating detector. Our study demonstra-tes that with appropriately selecting the system parameters, the broadband MC DS-CDMA wireless communi-cation system using the space-time spreading assisted transmit diversity constitutes a promising downlink tran-smission scheme. This scheme is capable to support ubiquitous communications over diverse communication environments without the BER performance degradation

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Chien, Wei, Tzong-Tyng Hsieh, Chien-Ching Chiu, Yu-Ting Cheng, Yang-Han Lee et Qiang Chen. « Theoretical Derivation and Optimization Verification of BER for Indoor SWIPT Environments ». Symmetry 12, n^o 7 (17 juillet 2020) : 1185. http://dx.doi.org/10.3390/sym12071185.

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Symmetrical antenna array is useful for omni bearing beamforming adjustment with multiple receivers. Beam-forming techniques using evolution algorithms have been studied for multi-user resource allocation in simultaneous wireless information and power transfer (SWIPT) systems. In a high-capacity broadband communication system there are many users with wearable devices. A transmitter provides simultaneous wireless information and power to a particular receiver, and the other receivers harvest energy from the radio frequency while being idle. In addition, the ray bounce tracking method is used to estimate the multi-path channel, and the Fourier method is used to perform the time domain conversion. A simple method for reducing the frequency selective effort of the multiple channels using the feed line length instead of the digital phase shifts is proposed. The feed line length and excitation current of the transmitting antennas are adjusted to maximize the energy harvest efficiency under the bit error rate (BER) constraint. We use the time-domain multipath signal to calculate the BER, which includes the inter symbol interference for the wideband system. In addition, we use multi-objective function for optimization. To the best of our knowledge, resource allocation algorithms for this problem have not been reported in the literature. The optimal radiation patterns are synthesized by the asynchronous particle swarm optimization (APSO) and self-adaptive dynamic differential evolution (SADDE) algorithms. Both APSO and SADDE can form good patterns for the receiver for energy harvesting. However, APSO has a faster convergence speed than SADDE.

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Dobreva, Marina S., William E. O'Neill et Gary D. Paige. « Influence of aging on human sound localization ». Journal of Neurophysiology 105, n^o 5 (mai 2011) : 2471–86. http://dx.doi.org/10.1152/jn.00951.2010.

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Errors in sound localization, associated with age-related changes in peripheral and central auditory function, can pose threats to self and others in a commonly encountered environment such as a busy traffic intersection. This study aimed to quantify the accuracy and precision (repeatability) of free-field human sound localization as a function of advancing age. Head-fixed young, middle-aged, and elderly listeners localized band-passed targets using visually guided manual laser pointing in a darkened room. Targets were presented in the frontal field by a robotically controlled loudspeaker assembly hidden behind a screen. Broadband targets (0.1–20 kHz) activated all auditory spatial channels, whereas low-pass and high-pass targets selectively isolated interaural time and intensity difference cues (ITDs and IIDs) for azimuth and high-frequency spectral cues for elevation. In addition, to assess the upper frequency limit of ITD utilization across age groups more thoroughly, narrowband targets were presented at 250-Hz intervals from 250 Hz up to ∼2 kHz. Young subjects generally showed horizontal overestimation (overshoot) and vertical underestimation (undershoot) of auditory target location, and this effect varied with frequency band. Accuracy and/or precision worsened in older individuals for broadband, high-pass, and low-pass targets, reflective of peripheral but also central auditory aging. In addition, compared with young adults, middle-aged, and elderly listeners showed pronounced horizontal localization deficiencies (imprecision) for narrowband targets within 1,250–1,575 Hz, congruent with age-related central decline in auditory temporal processing. Findings underscore the distinct neural processing of the auditory spatial cues in sound localization and their selective deterioration with advancing age.

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Qiu, Chencheng, Liu Liu, Botao Han, Jiachi Zhang, Zheng Li et Tao Zhou. « Broadband Wireless Communication Systems for Vacuum Tube High-Speed Flying Train ». Applied Sciences 10, n^o 4 (18 février 2020) : 1379. http://dx.doi.org/10.3390/app10041379.

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A vactrain (or vacuum tube high-speed flying train) is considered as a novel proposed rail transportation approach in the ultra-high-speed scenario. The maglev train can run with low mechanical friction, low air resistance, and low noise mode at a speed exceeding 1000 km/h inside the vacuum tube regardless of weather conditions. Currently, there is no research on train-to-ground wireless communication system for vactrain. In this paper, we first summarize a list of the unique challenges and opportunities associated with the wireless communication for vactrain, then analyze the bandwidth and Quality of Service (QoS) requirements of vactrain’s train-to-ground communication services quantitatively. To address these challenges and utilize the unique opportunities, a leaky waveguide solution with simple architecture but excellent performance is proposed for wireless coverage for vactrains. The simulation of the leaky waveguide is conducted, and the results show the uniform phase distribution along the horizontal direction of the tube, but also the smooth field distribution at the point far away from the leaky waveguide, which can suppress Doppler frequency shift, indicating that the time-varying frequency-selective fading channel could be approximated as a stationary channel. Furthermore, the train-to-ground wireless access architectures based on leaky waveguide are studied and analyzed. Finally, the moving scheme is adopted based on centralized, cooperative, cloud Radio Access Network (C-RAN), so as to deal with the extremely frequent handoff issue.

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Thèses sur le sujet "Time /Frequency Selective Broadband Channels"

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 phase
In 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

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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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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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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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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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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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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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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.

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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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Chayot, Romain. « Synchronisation, détection et égalisation de modulation à phase continue dans des canaux sélectifs en temps et en fréquence ». Thesis, Toulouse, INPT, 2019. http://oatao.univ-toulouse.fr/24188/1/Chayot_Romain.pdf.

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Si les drones militaires connaissent un développement important depuis une quinzaine d’année, suivi depuis quelques années par les drones civiles dont les usages ne font que se multiplier, en réalité les drones ont un siècle avec le premier vol d’un avion équipé d’un système de pilotage automatique sur une centaine de kilomètre en 1918. La question des règles d’usage des drones civiles sont en cours de développement malgré leur multiplication pour des usages allant de l’agriculture, à l’observation en passant par la livraison de colis. Ainsi, leur intégration dans l’espace aérien reste un enjeu important, ainsi que les standards de communication avec ces drones dans laquelle s’inscrit cette thèse. Cette thèse vise en effet à étudier et proposer des solutions pour les liens de communications des drones par satellite.L’intégration de ce lien de communication permet d’assurer la fiabilité des communications et particulièrement du lien de Commande et Contrôle partout dans le monde, en s’affranchissant des contraintes d’un réseau terrestre (comme les zones blanches). En raison de la rareté des ressources fréquentielles déjà allouées pour les futurs systèmes intégrant des drones, l’efficacité spectrale devient un paramètre important pour leur déploiement à grande échelle et le contexte spatiale demande l’utilisation d’un système de communication robuste aux non-linéarités. Les Modulations à Phase Continue permettent de répondre à ces problématiques. Cependant, ces dernières sont des modulations non-linéaire à mémoire entraînant une augmentation de la complexité des récepteurs. Du fait de la présence d’un canal multi-trajet (canal aéronautique par satellite), le principal objectif de cette thèse est de proposer des algorithmes d’égalisation (dans le domaine fréquentiel pour réduire leur complexité) et de synchronisation pour CPM adaptés à ce concept tout en essayant de proposer une complexité calculatoire raisonnable. Dans un premier temps, nous avons considéré uniquement des canaux sélectifs en fréquence et avons étudier les différents égaliseurs de la littérature. En étudiant leur similitudes et différences, nous avons pu développer un égaliseur dans le domaine fréquentiel qui proposant les mêmes performances a une complexité moindre. Nous proposons également des méthodes d’estimation canal et une méthode d’estimation conjointe du canal et de la fréquence porteuse. Dans un second temps nous avons montré comment étendre ces méthodes à des canaux sélectifs en temps et fréquence permettant ainsi de conserver une complexité calculatoire raisonnable.

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Livres sur le sujet "Time /Frequency Selective Broadband Channels"

Silva, Fabio, Rui Dinis et Paulo Montezuma. Frequency-Domain Receiver Design for Doubly Selective Channels. Taylor & Francis Group, 2017.

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Frequency-Domain Receiver Design for Doubly Selective Channels. Taylor & Francis Group, 2017.

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Silva, Fabio, Rui Dinis et Paulo Montezuma. Frequency-Domain Receiver Design for Doubly Selective Channels. Taylor & Francis Group, 2017.

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Silva, Fabio, Rui Dinis et Paulo Montezuma. Frequency-Domain Receiver Design for Doubly Selective Channels. Taylor & Francis Group, 2017.

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Silva, Fabio, Rui Dinis et Paulo Montezuma. Frequency-Domain Receiver Design for Doubly Selective Channels. Taylor & Francis Group, 2019.

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Chapitres de livres sur le sujet "Time /Frequency Selective Broadband Channels"

Chang, Kapseok, et Youngnam Han. « Throughput Enhancement Scheme in an OFCDM System over Slowly-Varying Frequency-Selective Channels ». Dans Information Networking. Convergence in Broadband and Mobile Networking, 697–706. Berlin, Heidelberg : Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/978-3-540-30582-8_73.

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Egle, Jochem, Markus Reinhardt et Jürgen Lindner. « Equalization and Coding for Extended MC-CDMA Over Time and Frequency Selective Channels ». Dans Multi-Carrier Spread-Spectrum, 127–34. Boston, MA : Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-6231-3_15.

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Priyatam, Kumar, R. M. Banakar et B. Shankaranand. « ISI Cancellation in 4G Wireless Mobiles ». Dans Handbook of Research in Mobile Business, Second Edition, 354–67. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-156-8.ch033.

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Physical layer issues of broadband wireless communication systems form the bottleneck in providing fast and reliable communication over wireless channel. Critical performance limiting challenges are time selective fading channels, frequency selective fading channels, noise, inter symbol interference (ISI), inter carrier interference, power, and bandwidth. Addressing these challenges of wireless broadband communication systems, one can provide faster data processing with lower computational complexity, higher data throughput, and improved performance in terms of bit error rate (BER). In this chapter an effective technique (SISO estimation) to handle interference cancellation is developed. ISI is caused by multi-path propagation. It can be reduced by using a channel equalizer which provides the receiver with the prior knowledge of the channel. Channel estimation is a technique to acquire behavior of the channel. Accuracy of the channel estimation improves the system performance. At BER of 10-4 SISO estimator provide an improvement of 2dB as compared with MMSE DFE estimator.

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Rohling, Hermann. « OFDM Transmission Technique ». Dans Mobile Computing, 3561–87. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-054-7.ch260.

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The orthogonal frequency division multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA; FDMA; and CDMA approaches with the OFDM modulation procedure; which is especially important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting sub-carrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM signal. The OFDM transmission technique is used for the time being in some broadcast applications (DVB-T; DAB; DRM) and wireless local loop (WLL) standards (HIPERLAN/2; IEEE 802.11a) but OFDM has not been used so far in cellular communication networks. The general idea of the OFDM scheme is to split the total bandwidth into many narrowband sub-channels which are equidistantly distributed on the frequency axis. The sub-channel spectra overlap each other but the sub-carriers are still orthogonal in the receiver and can therefore be separated by a Fourier transformation. The system flexibility and use of sub-carrier specific adaptive modulation schemes in frequency selective radio channels are some advantages which make the OFDM transmission technique a strong and technically attractive candidate for the next generation of mobile communications. The objective of this chapter is to describe an OFDM-based system concept for the fourth generation (4G) of mobile communications and to discuss all technical details when establishing a cellular network which requires synchronization in time and frequency domain with sufficient accuracy. In this cellular environment a flexible frequency division multiple access scheme based on OFDM-FDMA is developed and a radio resource management (RRM) employing dynamic channel allocation (DCA) techniques is used. A purely decentralized and self-organized synchronization technique using specific test signals and RRM techniques based on co-channel interference (CCI) measurements has been developed and will be described in this chapter.

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« LINEAR STBC FOR FREQUENCY-SELECTIVE CHANNELS ». Dans Space-Time Block Coding for Wireless Communications, 130–56. Cambridge University Press, 2003. http://dx.doi.org/10.1017/cbo9780511550065.011.

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Oestges, Claude, et Bruno Clerckx. « Space—time coding for frequency selective channels ». Dans MIMO Wireless Communications, 369–402. Elsevier, 2007. http://dx.doi.org/10.1016/b978-012372535-6/50014-3.

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Clerckx, Bruno, et Claude Oestges. « Space-Time Coding for Frequency Selective Channels ». Dans Mimo Wireless Networks, 385–418. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-385055-3.00011-0.

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Ma, Xiaoli, et Georgios B. Giannakis. « Space-time coding for time- and frequency-selective MIMO channels ». Dans Space-Time Wireless Systems, 218–38. Cambridge University Press, 2001. http://dx.doi.org/10.1017/cbo9780511616815.012.

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SivachandarK., V. Amudha, B. Ramesh, Jose Anand, M. ShanmugaSundari et Jerril Gilda S. « MIMO-IDMA System Performance for SUI and LTE Frequency Selective Channels ». Dans Advances in Parallel Computing Algorithms, Tools and Paradigms. IOS Press, 2022. http://dx.doi.org/10.3233/apc220059.

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The spectrum used by Code Division Multiple Access (CDMA) allows for a signal with a greater bandwidth by spreading electromagnetic energy. Multi-Carrier CDMA (MC-CDMA) is a telecommunications numerousentrée strategy that spreads each user symbol across the frequency domain with distinct codes. Cognitive Radio (CR) is a vibrant spectrum admittance enabling technology by dynamically allocating space for fundamental users by modifying its settings and base station. Two models for people on the cognitive spectrum are Opportunistic Spectrum Access (OSA) and Concurrent Spectrum Access (CSA). Using Co-Channel Interference (CCI) and Adjacent Channel Interference (ACI), the MC-CDMA system is an effective accessing strategy for multi-user data transmission (ACI). Multiple-Input Multiple-Output (MIMO) involving Space-Time Transmit Diversity (STTD), Spatial Multiplexing (SM), and collaborative MIMO is used for numerous data communication, and dependable Bit Error Rate (BER) presentation is attained. STBC (Space Time Block Coding) is equipped with two antennas and codes for data transmission across multiple antennas. At the receiver, STBC offers channel state information while maintaining a low level of complexity. The image’s pixels will be shuffled using Arnold’s Cat Map (ACM) encryption method. When compared to other compression methods, Integer Wavelet Transform (IWT) compression is stress-free. The Internet of Things (IoT) is used to examine tracklatency and power stages, STTD MC-CDMA faultoutput utilizing cognitive spectrum, and channel simulated parameterization. The output on fault levels with patient caring using Stanford University Interim (SUI) and Long Term Evolution (LTE) techniques with a Double STTD (DSTTD) assisted MC-CDMA cognitive spectrum system.

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Abualhaol, Ibrahim Y., et Mustafa M. Matalgah. « Resource Allocation for a Cooperative Broadband MIMO-OFDM System ». Dans Cooperative Communications for Improved Wireless Network Transmission, 382–98. IGI Global, 2010. http://dx.doi.org/10.4018/978-1-60566-665-5.ch014.

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In this chapter, a cooperative broadband relay-based resource allocation technique is proposed for adaptive bit and power loading multiple-input-multiple-output/orthogonal frequency division multiplexing (MIMO-OFDM) system. In this technique, sub-channels allocation, M-QAM modulation order, and power distribution among different sub-channels in the relay-based MIMO-OFDM system are jointly optimized according to the channel state information (CSI) of the relay and the direct link. The transmitted stream of bits is divided into two parts according to a suggested cooperative protocol that is based on sub-channel-division. In this protocol, the first part is sent directly from the source to the destination, and the second part is relayed to the destination through an indirect link. Such a cooperative relay-based system enables us to exploit the inherent system diversities in frequency, space and time to maximize the system power efficiency. The BER performance using this cooperative sub-channel-division protocol with adaptive sub-channel assignment and adaptive bit/power loading are presented and compared with a noncooperative ones. The use of cooperation in a broadband relay-based MIMO-OFDM system showed high performance improvement in terms of BER.

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Actes de conférences sur le sujet "Time /Frequency Selective Broadband Channels"

Lerner, I. M., A. N. Khairullin, R. R. Fayzullin, D. V. Shushpanov et V. I. Il’in. « Resolution Time Theory Broadband Communications in Problem of Data Dependent Jitter in Frequency Selective Channels with PAM-n-Signals ». Dans 2023 Systems of Signals Generating and Processing in the Field of on Board Communications. IEEE, 2023. http://dx.doi.org/10.1109/ieeeconf56737.2023.10092097.

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Li, Qian, Kwok H. Li et Kah C. Teh. « Noncoherent Space-Frequency Codes for Broadband MIMO Systems over Frequency-Selective Fading Channels ». Dans 2008 IEEE Vehicular Technology Conference (VTC 2008-Spring). IEEE, 2008. http://dx.doi.org/10.1109/vetecs.2008.125.

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Peng Sun et Daoben Li. « Space time interleaving code in frequency selective channels ». Dans 2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications - (PIMRC 2011). IEEE, 2011. http://dx.doi.org/10.1109/pimrc.2011.6139749.

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Larsson, Stoica, Lindskog et Jian Li. « Space-time block coding for frequency-selective channels ». Dans IEEE International Conference on Acoustics Speech and Signal Processing ICASSP-02. IEEE, 2002. http://dx.doi.org/10.1109/icassp.2002.1005169.

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Larsson, Erik G., Petre Stoica, Erik Lindskog et Jian Li. « Space-time block coding for frequency-selective channels ». Dans Proceedings of ICASSP '02. IEEE, 2002. http://dx.doi.org/10.1109/icassp.2002.5745131.

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Tourki, Kamel, Rostom Zakaria et Merouane Debbah. « LVDM Time-Frequency Equalizers for Doubly Selective Channels ». Dans 2020 IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications. IEEE, 2020. http://dx.doi.org/10.1109/pimrc48278.2020.9217145.

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Zaman, Md Sayem Uz, Himadri Shekhar Mondal, Md Ali Hasan et Mohammad Ismat Kadir. « Multicarrier multiantenna space-time architectures for frequency-selective channels ». Dans 2017 4th International Conference on Innovations in Information, Embedded and Communication Systems (ICIIECS). IEEE, 2017. http://dx.doi.org/10.1109/iciiecs.2017.8276034.

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Giese et Skoglund. « Space-time code design for unknown frequency-selective channels ». Dans IEEE International Conference on Acoustics Speech and Signal Processing ICASSP-02. IEEE, 2002. http://dx.doi.org/10.1109/icassp.2002.1005171.

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Giese, Jochen, et Mikael Skoglund. « Space-time code design for unknown frequency-selective channels ». Dans Proceedings of ICASSP '02. IEEE, 2002. http://dx.doi.org/10.1109/icassp.2002.5745133.

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Fang, Kun, et Geert Leus. « Space-time block coding for frequency-selective and time-varying channels ». Dans 2009 Conference Record of the Forty-Third Asilomar Conference on Signals, Systems and Computers. IEEE, 2009. http://dx.doi.org/10.1109/acssc.2009.5469913.

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