Bibliografías temáticas / Time-Frequency fading

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Literatura académica sobre el tema "Time-Frequency fading"

Autor: Grafiati

Publicado: 25 de mayo de 2024

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Artículos de revistas sobre el tema "Time-Frequency fading"

Zhiqiang Liu, Yan Xin y G. B. Giannakis. "Space-time-frequency coded OFDM over frequency-selective fading channels". IEEE Transactions on Signal Processing 50, n.º 10 (octubre de 2002): 2465–76. http://dx.doi.org/10.1109/tsp.2002.803332.

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Hongbin Li. "Differential space-time-frequency modulation over frequency-selective fading channels". IEEE Communications Letters 7, n.º 8 (agosto de 2003): 349–51. http://dx.doi.org/10.1109/lcomm.2003.814711.

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ISHII, K. "Space-Time-Frequency Turbo Code over Time-Varying and Frequency-Selective Fading Channel". IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E88-A, n.º 10 (1 de octubre de 2005): 2885–95. http://dx.doi.org/10.1093/ietfec/e88-a.10.2885.

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Chu, James. "Frequency-Selective and Time-Selective Fading [Book\/Software Reviews]". IEEE Microwave Magazine 19, n.º 5 (julio de 2018): 87–103. http://dx.doi.org/10.1109/mmm.2018.2821089.

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TAO, X., C. ZHANG, J. LU y N. SUEHIRO. "Adaptive CI-OSDM in Time-Frequency Selective Fading Channel". IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E91-A, n.º 12 (1 de diciembre de 2008): 3712–22. http://dx.doi.org/10.1093/ietfec/e91-a.12.3712.

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Borah, D. K. y B. D. Hart. "Receiver structures for time-varying frequency-selective fading channels". IEEE Journal on Selected Areas in Communications 17, n.º 11 (1999): 1863–75. http://dx.doi.org/10.1109/49.806817.

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Al-nahari, A. Y., F. E. Abd El-Samie y M. I. Dessouky. "Distributed Space-Time/Frequency Coding Schemes for Single-Carrier Frequency Division Multiple Access Systems". ISRN Communications and Networking 2011 (4 de abril de 2011): 1–10. http://dx.doi.org/10.5402/2011/549706.

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The single carrier-frequency division multiple access (SC-FDMA) system is a new system that was adopted in the standardization of the upcoming 3GPP long-term evolution (LTE). Designing diversity-achieving schemes for the SC-FDMA system is a challenging task. The codes adopted should not affect the peak-to-average power ratio (PAPR) among other constraints. In this paper, we consider the design of cooperative diversity schemes for SC-FDMA systems in the uplink direction. Specifically, two relay-assisted distributed space-time/frequency codes are proposed. The proposed distributed space-frequency code (SFC) achieves full spatial diversity in the uplink fast-fading channels, where a diversity of order three can be achieved. The proposed code keeps a low PAPR, which is a good feature of the system. A minimum mean square error (MMSE) decoder is used at the receiver of the destination node. Moreover, we propose a bandwidth-efficient distributed space-time code (STC) for slow-fading relay channels. A decode-and-forward (DF) protocol is used at the relay node, and the possibility of erroneous decoding is taken into account. Simulation results demonstrate the performance improvement of the proposed schemes.

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Sun, Zeng You y Xia Ling. "Time-Varying Channel Multi-Carrier Modulation Technology Research". Applied Mechanics and Materials 513-517 (febrero de 2014): 2680–86. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.2680.

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With frequency selective fading from multi-path characteristic and time selective fading from high speed mobility, double selective channel has become the typical context for the current wireless communication system. To realize high performance transmission in time-varying channel, this paper presents DAFT-OFDM multicarrier modulation scheme. The simulation results show that the scheme is applicable to time-varying fading channel, in which each path experiences independent Doppler spread. The scheme can also reduce ICI effectively.

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Fokin, G. "Modeling multi-beam radio channel". Telecom IT 9, n.º 1 (31 de marzo de 2021): 59–78. http://dx.doi.org/10.31854/2307-1303-2021-9-1-59-78.

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In this work, a simulation model of a radio channel with fading is implemented for use in research of the multipath channel, as well as for assessing the noise immunity of transmission, recep-tion and processing systems in modern and future mobile communication and radio access networks. Formalization of mathematical models of a radio channel with fading, including the Rayleigh amplitude distribution, uniform phase distribution and a given Doppler spectrum, made it possible to visualize the time-frequency and probabilistic characteristics of a radio channel with fading. The implementation of the procedures for delaying and attenuating copies of signals in a multipath radio channel made it pos-sible to reproduce scenarios of flat and frequency selective fading, which are widely used in practice in assessing the noise immunity of signals with given frequency and time characteristics.

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Kim, Minhyuk y Sekchin Chang. "A real-time locating system for localization of high-speed mobile objects". International Journal of Distributed Sensor Networks 14, n.º 5 (mayo de 2018): 155014771877447. http://dx.doi.org/10.1177/1550147718774475.

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This article addresses a novel real-time locating system for localization of high-speed mobile objects in fading environments. The proposed locating system exploits time difference of arrival measurements based on ultra-wideband signals. However, the ultra-wideband signals cause a frequency-selective fading due to their short time duration, which induces severe inter-symbol interference. Moreover, high-speed objects cause fast fading due to large Doppler spread. Therefore, the fading cases considerably reduce the localization performance. The presented locating system relies on a new localization approach in order to overcome the fading issues, which utilizes a modification of extended Kalman filtering. Especially, the suggested locating method works well even in the zero time difference of arrival case, which occurs due to a very deep fading. Experiment results verify that the proposed real-time locating system gives excellent localization performance in severe fading environments. The results also exhibit that the presented locating system is superior to the conventional locating systems in the localization of high-speed mobile objects under fading environments.

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Tesis sobre el tema "Time-Frequency fading"

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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Lee, King F. "Space-time and space-frequency coded orthogonal frequency division multiplexing transmitter diversity techniques". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14981.

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Zheng, Changqing 1979. "Optimum spreading bandwidth for DS-CDMA on time and frequency fading channels". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16870.

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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
Includes bibliographical references (p. 69-70).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
by Changqing Zheng.
M.Eng.and S.B.

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Shang, Lei y lei shang@ieee org. "Modelling of Mobile Fading Channels with Fading Mitigation Techniques". RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061222.113303.

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This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems.

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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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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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Nguyen, Linh Trung. "Estimation and separation of linear frequency- modulated signals in wireless communications using time - frequency signal processing". Queensland University of Technology, 2004. http://eprints.qut.edu.au/15984/.

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Signal processing has been playing a key role in providing solutions to key problems encountered in communications, in general, and in wireless communications, in particular. Time-Frequency Signal Processing (TFSP) provides eective tools for analyzing nonstationary signals where the frequency content of signals varies in time as well as for analyzing linear time-varying systems. This research aimed at exploiting the advantages of TFSP, in dealing with nonstationary signals, into the fundamental issues of signal processing, namely the signal estimation and signal separation. In particular, it has investigated the problems of (i) the Instantaneous Frequency (IF) estimation of Linear Frequency-Modulated (LFM) signals corrupted in complex-valued zero-mean Multiplicative Noise (MN), and (ii) the Underdetermined Blind Source Separation (UBSS) of LFM signals, while focusing onto the fast-growing area of Wireless Communications (WCom). A common problem in the issue of signal estimation is the estimation of the frequency of Frequency-Modulated signals which are seen in many engineering and real-life applications. Accurate frequency estimation leads to accurate recovery of the true information. In some applications, the random amplitude modulation shows up when the medium is dispersive and/or when the assumption of point target is not valid; the original signal is considered to be corrupted by an MN process thus seriously aecting the recovery of the information-bearing frequency. The IF estimation of nonstationary signals corrupted by complex-valued zero-mean MN was investigated in this research. We have proposed a Second-Order Statistics approach, rather than a Higher-Order Statistics approach, for IF estimation using Time-Frequency Distributions (TFDs). The main assumption was that the autocorrelation function of the MN is real-valued but not necessarily positive (i.e. the spectrum of the MN is symmetric but does not necessary has the highest peak at zero frequency). The estimation performance was analyzed in terms of bias and variance, and compared between four dierent TFDs: Wigner-Ville Distribution, Spectrogram, Choi-Williams Distribution and Modified B Distribution. To further improve the estimation, we proposed to use the Multiple Signal Classification algorithm and showed its better performance. It was shown that the Modified B Distribution performance was the best for Signal-to-Noise Ratio less than 10dB. In the issue of signal separation, a new research direction called Blind Source Separation (BSS) has emerged over the last decade. BSS is a fundamental technique in array signal processing aiming at recovering unobserved signals or sources from observed mixtures exploiting only the assumption of mutual independence between the signals. The term "blind" indicates that neither the structure of the mixtures nor the source signals are known to the receivers. Applications of BSS are seen in, for example, radar and sonar, communications, speech processing, biomedical signal processing. In the case of nonstationary signals, a TF structure forcing approach was introduced by Belouchrani and Amin by defining the Spatial Time- Frequency Distribution (STFD), which combines both TF diversity and spatial diversity. The benefit of STFD in an environment of nonstationary signals is the direct exploitation of the information brought by the nonstationarity of the signals. A drawback of most BSS algorithms is that they fail to separate sources in situations where there are more sources than sensors, referred to as UBSS. The UBSS of nonstationary signals was investigated in this research. We have presented a new approach for blind separation of nonstationary sources using their TFDs. The separation algorithm is based on a vector clustering procedure that estimates the source TFDs by grouping together the TF points corresponding to "closely spaced" spatial directions. Simulations illustrate the performances of the proposed method for the underdetermined blind separation of FM signals. The method developed in this research represents a new research direction for solving the UBSS problem. The successful results obtained in the research development of the above two problems has led to a conclusion that TFSP is useful for WCom. Future research directions were also proposed.

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Nguyen, Linh-Trung. "Estimation and separation of linear frequency- modulated signals in wireless communications using time - frequency signal processing". Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15984/1/Nguyen_Linh-Trung_Thesis.pdf.

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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.
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Sokoya, Oludare Ayodeji. "Performance analysis of channel codes in multiple antenna OFDM systems". Thesis, University of Pretoria, 2012. http://hdl.handle.net/2263/25431.

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Multiple antenna techniques are used to increase the robustness and performance of wireless networks. Multiple antenna techniques can achieve diversity and increase bandwidth efficiency when specially designed channel codes are used at the scheme’s transmitter. These channel codes can be designed in the space, time and frequency domain. These specially designed channel codes in the space and time domain are actually designed for flat fading channels and in frequency selective fading channel, their performance may be degraded. To counteract this possible performance degradation in frequency selective fading channel, two main approaches can be applied to mitigate the effect of the symbol interference due to the frequency selective fading channel. These approaches are multichannel equalisation and orthogonal frequency division multiplexing (OFDM). In this thesis, a multichannel equalisation technique and OFDM were applied to channel codes specially designed for multiple antenna systems. An optimum receiver was proposed for super-orthogonal space-time trellis codes in a multichannel equalised frequency selective environment. Although the proposed receiver had increased complexity, the diversity order is still the same as compared to the code in a flat fading channel. To take advantage of the multipath diversity possible in a frequency selective fading channel, super-orthogonal block codes were employed in an OFDM environment. A new kind of super-orthogonal block code was proposed in this thesis. Super-orthogonal space-frequency trellis-coded OFDM was proposed to take advantage of not only the possible multipath diversity but also the spatial diversity for coded OFDM schemes. Based on simulation results in this thesis, the proposed coded OFDM scheme performs better than all other coded OFDM schemes (i.e. space time trellis-coded OFDM, space-time block coded OFDM, space-frequency block coded OFDM and super-orthogonal space-time trellis-coded OFDM). A simplified channel estimation algorithm was proposed for two of the coded OFDM schemes, which form a broad-based classification of coded OFDM schemes, i.e. trelliscoded schemes and block-coded schemes. Finally in this thesis performance analysis using the Gauss Chebychev quadrature technique as a way of validating simulation results was done for super-orthogonal block coded OFDM schemes when channel state information is known and when it is estimated. The results obtained show that results obtained via simulation and analysis are asymptotic and therefore the proposed analysis technique can be use to obtain error rate values for different SNR region instead of time consuming simulation.
Thesis (PhD)--University of Pretoria, 2012.
Electrical, Electronic and Computer Engineering
unrestricted

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Capítulos de libros sobre el tema "Time-Frequency fading"

Sayeed, Akbar M. y Behnaam Aazhang. "Communication over Multipath Fading Channels: A Time-Frequency Perspective". En Wireless Communications, 73–98. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4757-2604-6_4.

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Chen, Fa-Tang y Lei Ma. "Research on Time and Frequency Synchronization for 3GPP LTE TDD System over Multipath Fading Channel". En Proceedings of the 2012 International Conference on Communication, Electronics and Automation Engineering, 1269–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-31698-2_179.

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Zhang, Xiuyan y Guobin Tao. "The Research of Adaptive Modulation Technology in OFDM System". En Proceeding of 2021 International Conference on Wireless Communications, Networking and Applications, 739–48. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2456-9_74.

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AbstractOrthogonal frequency division multiplexing (OFDM) as a special multi-carrier transmission technology has good resistance to narrow-band interference and frequency selective fading ability. Compared with traditional modulation techniques, adaptive modulation can enhance bandwidth efficiency and system capacity. Therefore, applying adaptive modulation in OFDM systems can take full advantage of spectrum resources, and it is suitable for the high-speed and reliable mobile communication systems in the future. The purpose of this paper is to improve traditional OFDM adaptive algorithms (Hughes-Hartogs, Chow) to realize bits allocation, power allocation better. In this paper, simulation results demonstrated that the improved Levin-Campello algorithm lowers algorithm’s complexity greatly and owns better flexibility, at the same time, it guarantees good the bit error rate (BER) performance and can be applied to speech communication (fixed rate) and data communication (variable rate) in wireless communication systems.

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"Satellite Channels Based on IEEE 802.16 Standard". En Recent Advances in Satellite Aeronautical Communications Modeling, 133–66. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8214-4.ch003.

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This chapter considers the modeling of RPAS/Aircraft data transmission via channels based on IEEE 802.16 standard. RPAS communication channel with a fading was analyzed using original model. Dependencies of a SNR in ground receiver on a SNR in downlink for different types of RPAS amplifier nonlinearity were obtained. Signals constellations of received signals were compared for different Doppler shifts. The influence of the aircraft transmitter nonlinearity for different types of fading in the channel was studied using “80216dstbc Rayleigh,” “80216dstbc Rician,” “80216d Rayleigh,” and “80216d Rician” models. The possibility of the nonlinearity correction using pre-distortion was revealed. The impact of space-time diversity (MISO 2x1) for different types of fading in the channels was investigated. The effect of the Doppler's frequency shift on the operation of communication channels was analyzed.

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Priyatam, Kumar, R. M. Banakar y B. Shankaranand. "ISI Cancellation in 4G Wireless Mobiles". En 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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Papazafeiropoulos, Anastasios. "Channel Characterization and Modelling for Mobile Communications". En Handbook of Research on Heterogeneous Next Generation Networking, 382–413. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-108-7.ch017.

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As a consequence of the growing interest in wireless communications systems, much effort is being devoted to the channel characterization and modelling. This is obvious since the performance depends fundamentally on the channels under consideration, so a communication system design must be preceded by the study of channel characteristics. This chapter considers the propagation environment in which a wireless system operates. In other words, we are primarily interested in the characterization of radio links between the transmitter and the receiver antenna that will be modelled by randomly time-variant linear systems. Wireless communication channels are usually described by considering three separable phenomena, namely, path loss, shadowing, and multipath fading. In the following, we briefly overview various efforts to characterize such aspects of wireless communication channels. Firstly, in this chapter we address the estimation of signal decay due to propagation loss which is very important in the determination of the necessary transmission power and the coverage area. Although propagation loss models are sometimes quite accurate, they generally fail to predict signal fluctuations due to the effect of the terrain near the antenna. Such a phenomenon of signal fluctuations is usually called shadowing. However, the effect of multipath fading is generally more complex because it does not only change in time but also varies over frequency. As a result, this topic will also be presented in enough depth and a number of statistical models will be studied. Moreover, the various categories of fading will be discussed. Finally, a novel small-scale model derived by the author is presented in order to give a recent application of the theory.

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"Carrier frequency oset estimation of utilizing Subcarrier Residual Power for OFDM systems over time-varying multipath fading channel". En Network Security and Communication Engineering, 293–94. CRC Press, 2015. http://dx.doi.org/10.1201/b18660-72.

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"Parameters Estimation of Aircraft and RPAS Satellite Channels Based on IEEE 802.11a Standard". En Recent Advances in Satellite Aeronautical Communications Modeling, 65–132. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8214-4.ch002.

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This chapter deals with parameters estimation of satellite channels based on IEEE 802.11a standard. Dependencies of a signal to noise ratio on free space path loss for different types of modulation (BPSK, QPSK, 16QAM, 64QAM), noise temperatures, number of OFDM symbols, Doppler frequency offsets, satellite amplifier gain, and aircraft antenna diameter were received using model “OFDM_FSPL_Sat_FSPL_802.11a.” A method for parameters estimation of satellite OFDM communication channel was proposed. The spectrums and signals constellations of received signals were compared for different types of the amplifier nonlinearity. The developed model allows predicting spectral regrowth of digitally modulated OFDM signals due to the amplifier nonlinearity. Channel parameters were received for the Rayleigh and Rician fading, different types of Doppler spectrum, the gain of multipath channels, the delay time of message flow using models “OFDM_Multipath_Sat_Multipath_802.11a,” “OFDM_AWGN_Sat_Multipath_802.11a,” and “OFDM_FSPL_Sat_Rician_802.11a.”

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Omer, Ala Eldin. "Review of Spectrum Sensing Techniques in Cognitive Radio Networks". En Advances in Wireless Technologies and Telecommunication, 85–107. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-5354-0.ch005.

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Most frequency spectrum bands are licensed to certain services to avoid the interference between various networks, but the spectrum occupancy measurements show that few portions of this spectrum are fully efficiently used. Cognitive radio is a future radio technology that is aware of its environment, internal state, and can change its operating behavior (transmitter parameters) accordingly. Through this technology the unlicensed users can use the underutilized spectrum without causing any harmful interference to the licensed users. Its key domains are sensing, cognition, and adaptation. The spectrum sensing problem is one of the most challenging issues in cognitive radio systems to detect the available frequency bands. This chapter introduces the concepts of various transmitter detection techniques, namely energy detection, matched filter detection, and cyclostationary feature detection. The chapter also discusses other sensing techniques that are introduced to enhance the detection performance of the conventional energy detector. Additionally, the introduced sensing techniques are implemented using extensive MATLAB simulations and their performances are evaluated and compared in terms of sensing time, detection sensitivity, and ease of implementation. The implementation is based on BPSK and QPSK modulation schemes under various SNR values for AWGN noisy channel with Rayleigh fading.

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Sharma, Shree Krishna, Symeon Chatzinotas y Björn Ottersten. "Exploiting Polarization for Spectrum Awareness in Cognitive Satellite Communications". En Advances in Wireless Technologies and Telecommunication, 856–83. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-6571-2.ch033.

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The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the satellite paradigm, cognitive satellite communications has been considered as a promising technique. In addition to the existing spectrum sharing dimensions such as frequency, time, and space, polarization can be exploited as an additional degree of freedom in order to explore the spectral gaps in the under-utilized licensed spectrum. In this context, this chapter firstly provides an overview of the existing works in polarization-based spectrum sharing. Secondly, it presents the theoretical analysis of energy detection technique for dual polarized Additive White Gaussian Noise and Rayleigh fading channels considering the spectral coexistence scenarios of dual and hybrid satellite systems. Thirdly, it provides the comparison of different combining techniques in terms of the sensing performance. Finally, it provides interesting future research directions in this domain.

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Actas de conferencias sobre el tema "Time-Frequency fading"

Park, Jinwoo, Joungmoon Lee, Inho Ha y Sang-Kook Han. "Mitigation of Dispersion-Induced Power Fading in Broadband Intermediate-Frequency-over-Fiber Transmission using Space-Time Block Coding". En Optical Fiber Communication Conference. Washington, D.C.: Optica Publishing Group, 2024. http://dx.doi.org/10.1364/ofc.2024.m3f.4.

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STBC with optical I-Q modulator for dispersion-induced power fading mitigation is proposed and experimentally demonstrated in broadband IFoF system. 9.5GHz bandwidth IFoF signal transmission with 8.5% EVM in fading-affected band of 50km transmission was demonstrated.

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Tulino, Antonia, Giuseppe Caire, Shlomo Shamai y Sergio Verdu. "The capacity of the frequency/time-selective fading channel". En 2010 IEEE Information Theory Workshop on Information Theory (ITW). IEEE, 2010. http://dx.doi.org/10.1109/itwksps.2010.5503142.

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Tao, X., C. Zhang y J. Lu. "Adaptive SD-OFDM in Time-Frequency Selective Fading Channel". En 2008 IEEE International Conference on Communications. IEEE, 2008. http://dx.doi.org/10.1109/icc.2008.398.

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Leus, G., Shengli Zhou y G. B. Giannakis. "Multiple access regardless of time- and frequency-selective fading". En Conference Record. Thirty-Fifth Asilomar Conference on Signals, Systems and Computers. IEEE, 2001. http://dx.doi.org/10.1109/acssc.2001.987727.

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Ng, Benjamin K. y Chan Tong Lam. "Single-carrier time-interleaved space-time code for frequency-selective fading channels". En 2014 IEEE 8th Sensor Array and Multichannel Signal Processing Workshop (SAM). IEEE, 2014. http://dx.doi.org/10.1109/sam.2014.6882387.

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Shrivastava, Neeraj, Sapna Bishoriya y Aditya Trivedi. "Space-time-frequency turbo coded MIMO-OFDM systems over frequency selective fading channels". En 2012 Ninth International Conference on Wireless and Optical Communications Networks - (WOCN). IEEE, 2012. http://dx.doi.org/10.1109/wocn.2012.6331895.

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Binggang Huang, Zhijie Zhou, Wenqiang Zhang y Hao Zhang. "Performance of differential space-frequency modulation under time-varying frequency-selective fading channels". En 2008 International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE, 2008. http://dx.doi.org/10.1109/icmmt.2008.4540882.

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Schulze, Henrik. "A simulation model for space-time-frequency variant fading channels". En 2010 International ITG Workshop on Smart Antennas (WSA 2010). IEEE, 2010. http://dx.doi.org/10.1109/wsa.2010.5456426.

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Saemi, A., V. Meghdadi, J. P. Cances, M. R. Zahabi y J. M. Dumas. "ML Time-Frequency Synchronization for MIMO-OFDM Systems in Unknown Frequency Selective Fading Channels". En 2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications. IEEE, 2006. http://dx.doi.org/10.1109/pimrc.2006.254010.

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Huang, Tao, Chaowei Yuan y Chuanglu Sun. "Multiuser Bit-Interleaved Space-Time-Frequency Coding System for Frequency Selective Block Fading Channels". En 2006 International Conference on Wireless Communications, Networking and Mobile Computing. IEEE, 2006. http://dx.doi.org/10.1109/wicom.2006.65.

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