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Artículos de revistas sobre el tema "Frequency Selective Broadband Channels"

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Publicado: 25 de mayo de 2024

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1

Jiang, Ting, Maozhong Song, Xiaorong Zhu y Xu Liu. "Channel Estimation for Broadband Millimeter Wave MIMO Systems Based on High-Order PARALIND Model". Wireless Communications and Mobile Computing 2021 (23 de noviembre de 2021): 1–12. http://dx.doi.org/10.1155/2021/6408442.

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Channel state information (CSI) is important to improve the performance of wireless transmission. However, the problems of high propagation path loss, multipath, and frequency selective fading make it difficult to obtain the CSI in broadband millimeter-wave (mmWave) system. Based on the inherent multidimensional structure of mmWave multipath channels and the correlation between channel dimensions, mmWave multiple input multiple output (MIMO) channels are modelled as high-order parallel profiles with linear dependence (PARALIND) model in this paper, and a new PARALIND-based channel estimation algorithm is proposed for broadband mmWave system. Due to the structural property of PARALIND model, the proposed algorithm firstly separates the multipath channels of different scatterers by PARALIND decomposition and then estimates the channel parameters from the factor matrices decomposed from the model based on their structures. Meanwhile, the performance of mmWave channel estimation is analysed theoretically. A necessary condition for channel parameter estimation is given based on the uniqueness principle of PARALIND model. Simulation results show that the proposed algorithm performs better than traditional compressive sensing-based channel estimation algorithms.

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2

Hu, Yuze, Mingyu Tong, Siyang Hu, Weibao He, Xiang’ai Cheng y Tian Jiang. "Multidimensional engineered metasurface for ultrafast terahertz switching at frequency-agile channels". Nanophotonics 11, n.º 7 (22 de febrero de 2022): 1367–78. http://dx.doi.org/10.1515/nanoph-2021-0774.

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Abstract The ability to actively manipulate free-space optical signals by using tunable metasurfaces is extremely appealing for many device applications. However, integrating photoactive semiconductors into terahertz metamaterials still suffers from a limited functionality. The ultrafast switching in picosecond timescale can only be operated at a single frequency channel. In the hybrid metasurface proposed here, we experimentally demonstrate a dual-optically tunable metaphotonic device for ultrafast terahertz switching at frequency-agile channels. Picosecond ultrafast photoswitching with a 100% modulation depth is realized at a controllable operational frequency of either 0.55 THz or 0.86 THz. The broadband frequency agility and ultrafast amplitude modulation are independently controlled by continuous wave light and femtosecond laser pulse, respectively. The frequency-selective, temporally tunable, and multidimensionally-driven features can empower active metamaterials in advanced multiplexing of information, dual-channel wireless communication, and several other related fields.

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3

Semmar, A., M. Lecours y H. T. Huynh. "Performance of coherent QPSK communications over frequency-selective fading channels for broadband PCS". Canadian Journal of Electrical and Computer Engineering 22, n.º 2 (abril de 1997): 51–54. http://dx.doi.org/10.1109/cjece.1997.7101978.

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4

Boutalline, Mohammed, Belaid Bouikhalene y Said Safi. "Channel Identification and Equalization based on Kernel Methods for Downlink Multicarrier-CDMA Systems". Journal of Electronic Commerce in Organizations 13, n.º 2 (abril de 2015): 14–29. http://dx.doi.org/10.4018/jeco.2015040102.

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In this paper the authors are focused on channel identification and equalization for Multi-Carrier Code Division Multiple Access (MC-CDMA) system. For this, they identify the impulse response of two practical selective frequency fading channels called Broadband Radio Access Network (BRAN A and BRAN B) normalized by the European Telecommunications Standards Institute (ETSI). To identify the channel parameters, they have the positive definite kernels to build on algorithm. The simulations show that the presented method confirms the good performance for different SNR values. In part of equalization, the authors use the Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) equalizers.

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5

Perov, Sergey Yu, Olga V. Belaya, Quirino Balzano y 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 de octubre de 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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6

Fateh, Rachid, Anouar Darif, Ahmed Boumezzough, Said Safi y Miloud Frikel. "A Novel Kernel Algorithm for Finite Impulse Response Channel Identiﬁcation". Journal of Telecommunications and Information Technology, n.º 2 (29 de junio de 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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7

Zidane, Mohammed, Said Safi, Mohamed Sabri y Ahmed Boumezzough. "Bit Error Rate Analysis of MC-CDMA Systems with Channel Identification Using Higher Order Cumulants". Indonesian Journal of Electrical Engineering and Computer Science 1, n.º 1 (1 de enero de 2016): 138. http://dx.doi.org/10.11591/ijeecs.v1.i1.pp138-152.

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The aim of this paper is to contribute to study the problems of the blind identification and equalization using Higher Order Cumulants (HOC) in downlink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems. For this problem, two blind algorithms based on HOC for Broadband Radio Access Network (BRAN) channel are proposed. In the one hand, to assess the performance of these approaches to identify the parameters of non minimum phase channels, we have considered two theoretical channels, and one practical frequency selective fading channel called BRAN C, driven by non gaussian signal. In the other hand, we use the Minimum Mean Square Error (MMSE) equalizer technique after the channel identification to correct the channel distortion. Theoretical analysis and numerical simulation results, in noisy environment and for different signal to noise ratio (SNR), are presented to illustrate the performance of the proposed methods.

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8

Fateh, Rachid, Anouar Darif y Said Safi. "Performance Evaluation of MC-CDMA Systems with Single User Detection Technique using Kernel and Linear Adaptive Method". Journal of Telecommunictions and Information Technology 4, n.º 2021 (30 de diciembre de 2021): 1–11. http://dx.doi.org/10.26636/jtit.2021.151621.

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Among all the techniques combining multi-carrier modulation and spread spectrum, the multi-carrier code division multiple access (MC-CDMA) system is by far the most widely studied. In this paper, we present the performance of the MC-CDMA system associated with key single-user detection techniques. We are interested in problems related to identification and equalization of mobile radio channels, using the kernel method in Hilbert space with a reproducing kernel, and a linear adaptive algorithm, for MC-CDMA systems. In this context, we tested the efficiency of these algorithms, considering practical frequency selective fading channels, called broadband radio access network (BRAN), standardized for MC-CDMA systems. As far as the equalization problem encountered after channel identification is concerned, we use the orthogonality restoration combination (ORC) and the minimum mean square error (MMSE) equalizer techniques to correct the distortion of the channel. Simulation results demonstrate that the kernel algorithm is efficient for practical channels.

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9

Yan, Qiuna, Yu Sun y Dian-Wu Yue. "LOS-Based Equal Gain Transmission and Combining in General Frequency-Selective Ricean Massive MIMO Channels". Electronics 8, n.º 1 (10 de enero de 2019): 79. http://dx.doi.org/10.3390/electronics8010079.

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In general frequency-selective Ricean fading environments with doubly-ended spatial correlation, this paper investigates the spectral efficiency of a broadband massive multiple-input multiple-output (MIMO) system. In particular, in order to reduce overhead of channel estimation effectively, it proposes a scheme of equal gain transmission and combining, which is only based on line- of-sight (LOS) component and has low hardware complexity. With the scheme, several interesting transmit power scaling properties without and with spatial correlation are derived when the number of antennas at the transmitter or the number of antennas at the receiver grows in an unlimited way. Furthermore, the asymptotical rate analysis is extended to the cooperative relaying scenarios with decode-and-forward and amplify-and-forward protocols, respectively, and then two novel power scaling laws are given.

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10

Fateh, Rachid, Anouar Darif y Said Safi. "An Extended Version of the Proportional Adaptive Algorithm Based on Kernel Methods for Channel Identification with Binary Measurements". Journal of Telecommunications and Information Technology 3, n.º 2022 (29 de septiembre de 2022): 47–58. http://dx.doi.org/10.26636/jtit.2022.161122.

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In recent years, kernel methods have provided an important alternative solution, as they offer a simple way of expanding linear algorithms to cover the non-linear mode as well. In this paper, we propose a novel recursive kernel approach allowing to identify the finite impulse response (FIR) in non-linear systems, with binary value output observations. This approach employs a kernel function to perform implicit data mapping. The transformation is performed by changing the basis of the data In a high-dimensional feature space in which the relations between the different variables become linearized. To assess the performance of the proposed approach, we have compared it with two other algorithms, such as proportionate normalized least-meansquare (PNLMS) and improved PNLMS (IPNLMS). For this purpose, we used three measurable frequency-selective fading radio channels, known as the broadband radio access Network (BRAN C, BRAN D, and BRAN E), which are standardized by the European Telecommunications Standards Institute (ETSI), and one theoretical frequency selective channel, known as the Macchi’s channel. Simulation results show that the proposed algorithm offers better results, even in high noise environments, and generates a lower mean square error (MSE) compared with PNLMS and IPNLMS.

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11

Zidane, Mohammed, Said Safi, Mohamed Sabri, Ahmed Boumezzough y Miloud Frikel. "Adaptive Algorithms Versus Higher Order Cumulants for Identification and Equalization of MC-CDMA". Journal of Telecommunications and Information Technology, n.º 3 (30 de septiembre de 2014): 53–62. http://dx.doi.org/10.26636/jtit.2014.3.1034.

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In this paper, a comparative study between a blind algorithm, based on higher order cumulants, and adaptive algorithms, i.e. Recursive Least Squares (RLS) and Least Mean Squares (LMS) for MultiCarrier Code Division Multiple Access (MC-CDMA) systems equalization is presented. Two practical frequency-selective fading channels, called Broadband Radio Access Network (BRAN A, BRAN B) normalized for MC-CDMA systems are considered. In the part of MC-CDMA equalization, the Zero Forcing (ZF) and the Minimum Mean Square Error (MMSE) equalizer techniques were used. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the blind algorithm gives approximately the same results obtained by adaptive algorithms. However, the proposed algorithm presents the advantage to estimate the impulse response of these channels blindly except that the input excitation is non-Gaussian, with the low calculation cost, compared with the adaptive algorithms exploiting the information of input and output for the impulse response channel estimation.

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12

Zhang, Zilong, Xiaodong Xu y 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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13

Perov, Sergey Yu y Olga V. Belaya. "Instrumental assessment of mobile communication base station electromagnetic field exposure". Russian Journal of Occupational Health and Industrial Ecology 60, n.º 11 (3 de diciembre de 2020): 853–56. http://dx.doi.org/10.31089/1026-9428-2020-60-11-853-856.

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Introduction. Monitoring and ensuring safe operating conditions of modern base stations for occupational and general public exposure is relevant with the use of methods for measuring electromagnetic fields, which allow to assess the contribution of different sources to the overall level of the electromagnetic background, taking into account the dynamic features of base stations and the spectral electromagnetic characteristics. The aim of study is the levels of electromagnetic fields assessment from modern base stations using broadband and selective measurement methods, as well as the possibility of predicting the worst exposure conditions. Materials and methods. The levels of electromagnetic fields from base stations according to the LTE2600 standard were evaluated at the maximum transmission traffic (laboratory mearements) and at real variable traffic (field measurements). For broadband measurements, the power density (PD) was estimated, for selective measurements, the PD level in the LTE frequency channel (frequency-selective measurements) and the PD level of the reference signal (code-selective measurements) were evaluated. The theoretical maximum PD level was calculated from the maximum value of the reference signal. Results. When simulating the maximum intensity of data traffic, the PD level in the LTE channel was 94.51-101.39% of the calculated maximum value. According to field measurements, the values of electromagnetic field levels obtained from frequency-selective measurements in the LTE frequency channel were less than the corresponding values estimated from the results of broadband measurements, and were no more than 25% of the theoretical maximum. Conclusions. The use of selective approach and measurement methods made it possible to estimate the maximum possible contribution of a single source to the overall level of the electromagnetic background and to predict the worst conditions for human exposure.

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14

Hao, Wenhui, Yi Peng, Shaohua Wang y Xia Liu. "RF Frequency Selective Switch by Multiple PMIM Conversions". Applied Sciences 13, n.º 4 (14 de febrero de 2023): 2472. http://dx.doi.org/10.3390/app13042472.

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Nowadays, broadband and multi-channel radio frequency (RF) processing has been widely used in communication, radar, countermeasure, and other applications. At present, multiple-input and multiple-output (MIMO)-oriented microwave photonic signal processing technology is relatively scarce, so this paper proposes an RF frequency selective switch (FSS) based on multiple phase modulation to intensity modulation (PMIM) conversions. PMIM conversion has been used in narrowband microwave photonic filtering in the past. We extend it to a wideband and arbitrarily reconfigurable RF spectrum processing unit through an optical frequency comb and periodic optical filter. Although we use the incoherent combination of a multi-wavelength light source, we can obtain any frequency response including rectangles only by using all positive tap coefficients. Using an optical wavelength selective switch (WSS), we obtain RF FSS, and the spectral resolution of RF FSS is much better than that of optical WSS, which is improved by more than two orders of magnitude. The above principles, including single-channel reconfigurable filtering and multi-channel RF FSS, are verified by experiments. Our technology provides a stable solution for future RF MIMO signal processing.

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Cobacho-Ruiz, Pablo, Francisco Javier Cañete, Eduardo Martos-Naya y Unai Fernández-Plazaola. "OFDM System Design for Measured Ultrasonic Underwater Channels". Sensors 22, n.º 15 (29 de julio de 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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Safi, Said, Miloud Frikel, Abdelouhab Zeroual y Mohammed M’Saad. "Higher Order Cumulants for Identification and Equalization of Multicarrier Spreading Spectrum Systems". Journal of Telecommunications and Information Technology, n.º 2 (27 de junio de 2023): 74–84. http://dx.doi.org/10.26636/jtit.2011.2.1148.

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This paper describes two blind algorithms for multicarrier code division multiple access (MC-CDMA) system equalization. In order to identify, blindly, the impulse response of two practical selective frequency fading channels called broadband radio access network (BRAN A and BRAN E) normalized for MC-CDMA systems, we have used higher order cumulants (HOC) to build our algorithms. For that, we have focussed on the experimental channels to develop our blind algorithms able to simulate the measured data with high accuracy. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the proposed algorithms are able to estimate the impulse response of these channels blindly (i.e., without any information about the input), except that the input excitation is i.i.d. (identically and independent distributed) and non-Gaussian. In the part of MC-CDMA, we use the zero forcing and the minimum mean square error equalizers to perform our algorithms. The simulation results demonstrate the effectiveness of the proposed algorithms.

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17

Xing, Kang, Shiyan Li, Zhijie Qu y Xiaojuan Zhang. "Time-Domain Electromagnetic Noise Suppression Using Multivariate Variational Mode Decomposition". Remote Sensing 16, n.º 5 (25 de febrero de 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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18

Liu, Tao, Yong-Jian Wang y Yu-Fei Zhao. "Channel Estimation Based on Compressed Sensing Technique for Low-Voltage Power Line Communication". Journal of Nanoelectronics and Optoelectronics 13, n.º 10 (1 de octubre de 2018): 1468–72. http://dx.doi.org/10.1166/jno.2018.2468.

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Broadband low-voltage power line communication (PLC) has many advantages including less investment cost, construction speed, and convenient access. Since the orthogonal frequency division multiplexing (OFDM) technology has strong anti-jamming and anti-frequency selective fading characteristics naturally it becomes a better low voltage power line communication solution. We proposed an OFDM channel estimation method based on compressed sensing (CS) technique according to the channel characteristics of low-voltage power lines. CS algorithm in OFDM system was discussed and an orthogonal matching pursuit (OMP) algorithm was applied to reconstruct the PLC channel information. The simulation results showed that the communication channel estimation method based on CS technique was feasible in PLC system, and the validity of information transmission in OFDM systems can be enhanced.

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Dobreva, Marina S., William E. O'Neill y Gary D. Paige. "Influence of aging on human sound localization". Journal of Neurophysiology 105, n.º 5 (mayo de 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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Nwanekezie, Nnamdi, Oluyomi Simpson, Gbenga Owojaiye y Yichuang Sun. "Co-Efficient Vector Based Differential Distributed Quasi-Orthogonal Space Time Frequency Coding". Sensors 23, n.º 17 (30 de agosto de 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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Chien, Wei, Tzong-Tyng Hsieh, Chien-Ching Chiu, Yu-Ting Cheng, Yang-Han Lee y Qiang Chen. "Theoretical Derivation and Optimization Verification of BER for Indoor SWIPT Environments". Symmetry 12, n.º 7 (17 de julio de 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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Wang, Xianhai, Teng Wang, Chuan Yin, Jun Han, Qiao Meng y Chen Wang. "Broadband Spectral Analysis Algorithm with High-Frequency Resolution for Elimination of Overlap Interference between Adjacent Channels". Applied Sciences 11, n.º 21 (1 de noviembre de 2021): 10262. http://dx.doi.org/10.3390/app112110262.

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Spectral lines can be analysed to determine the physical properties of molecular clouds and the astrochemical processes in the formation area of massive stars. To improve the observation technology of radio astronomy, this paper proposes and compares two spectral analysis algorithms (improved weighted overlap-add (IWOLA) + FFT and IWOLA + weighted overlap-add (WOLA)). The proposed algorithms can obtain an ultra-high-frequency resolution for real-valued wideband signals, eliminate the signal overlapping interference between adjacent channels, substantially decrease the required hardware resources, especially multipliers, adders, and memory resources, and reduce the system design complexity. The IWOLA + FFT algorithm consists of an improved weighted overlap-add (IWOLA) filter bank, fast Fourier transform (FFT), a specific decimation for the output data from the IWOLA filter bank, and a selection for part of the output data from the FFT. The IWOLA + WOLA algorithm consists of the same modules as the IWOLA + FFT algorithm, with the second-stage FFT replaced by the modules of the weighted overlap-add (WOLA) filter bank and the accumulation for each sub-band. Based on an analysis of the underlying principles and characteristics of both algorithms, the IWOLA + FFT algorithm demonstrated a spectrum with a high frequency resolution and a comparable performance to an ultra-large-scale FFT, based on two smaller FFTs and a flexible architecture instead of a ultra-large-scale FFT. The IWOLA + WOLA algorithm contains the same function as the IWOLA + FFT algorithm and demonstrates a higher performance. The proposed algorithms eliminated the interference between the adjacent channels within the entire Nyquist frequency bandwidth. The simulation results verify the accuracy and spectral analysis performances of the proposed algorithms.

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Qiu, Chencheng, Liu Liu, Botao Han, Jiachi Zhang, Zheng Li y Tao Zhou. "Broadband Wireless Communication Systems for Vacuum Tube High-Speed Flying Train". Applied Sciences 10, n.º 4 (18 de febrero de 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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24

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 de septiembre de 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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25

Gui, Guan, Li Xu, Lin Shan y Fumiyuki Adachi. "Compressive Sensing Based Bayesian Sparse Channel Estimation for OFDM Communication Systems: High Performance and Low Complexity". Scientific World Journal 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/927894.

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In orthogonal frequency division modulation (OFDM) communication systems, channel state information (CSI) is required at receiver due to the fact that frequency-selective fading channel leads to disgusting intersymbol interference (ISI) over data transmission. Broadband channel model is often described by very few dominant channel taps and they can be probed by compressive sensing based sparse channel estimation (SCE) methods, for example, orthogonal matching pursuit algorithm, which can take the advantage of sparse structure effectively in the channel as for prior information. However, these developed methods are vulnerable to both noise interference and column coherence of training signal matrix. In other words, the primary objective of these conventional methods is to catch the dominant channel taps without a report of posterior channel uncertainty. To improve the estimation performance, we proposed a compressive sensing based Bayesian sparse channel estimation (BSCE) method which cannot only exploit the channel sparsity but also mitigate the unexpected channel uncertainty without scarifying any computational complexity. The proposed method can reveal potential ambiguity among multiple channel estimators that are ambiguous due to observation noise or correlation interference among columns in the training matrix. Computer simulations show that proposed method can improve the estimation performance when comparing with conventional SCE methods.

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26

Fateh, Rachid, Anouar Darif y Said Safi. "Channel Identification of Non-linear Systems with Binary-Valued Output Observations Based on Positive Definite Kernels". E3S Web of Conferences 297 (2021): 01020. http://dx.doi.org/10.1051/e3sconf/202129701020.

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Nowadays, the kernel methods are increasingly developed, they are a significant source of advances, not only in terms of computational cost but also in terms of the obtained efficiencies in solving complex tasks, they are founded on the theory of reproducing kernel Hilbert spaces (RKHS). In this paper, we propose an algorithm for recursive identification of finite impulse response (FIR) nonlinear systems, whose outputs are detected by binary value sensors. This algorithm is based on a nonlinear transformation of the data using a kernel function. This transformation performs a basic change that allows the data to be projected into a new space where the relationships between the variables are linear. To test the accuracy of the proposed algorithm, we have compared it with another algorithm proposed in the literature, for that, we employ the practical frequency selective fading channel, called Broadband Radio Access Network (BRAN). Monte Carlo simulation results, in noisy environment and for various data length, demonstrate that the proposed algorithm can give better precision.

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27

Seddik, K. y K. J. R. Liu. "Distributed Space-Frequency Coding over Broadband Relay Channels". IEEE Transactions on Wireless Communications 7, n.º 11 (noviembre de 2008): 4748–59. http://dx.doi.org/10.1109/t-wc.2008.071205.

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28

G. P. Neto, José Jaime, Antonio Luiz P. S. Campos, Ruann Victor de A. Lira, Alfredo Gomes Neto y Maurício W. B. Silva. "Absorb/Transmit Broadband Type Frequency Selective Surface". Journal of Microwaves, Optoelectronics and Electromagnetic Applications 22, n.º 1 (marzo de 2023): 1–12. http://dx.doi.org/10.1590/2179-10742023v22i1268430.

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29

Xi, Xinyu, Dehong Li, Dongwen Chen y Yong Li. "Application of frequency optimization neural network method on power line communication". E3S Web of Conferences 300 (2021): 01018. http://dx.doi.org/10.1051/e3sconf/202130001018.

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The quality of broadband power line carrier communication mainly depends on the carrier communication frequency. However, there is a lack of fast and effective optimal carrier frequency selection method. One frequency selection method based on frequency point optimization neural network is proposed by this paper. This method combines transmission line theory and voltage partial reflection theory to build a power line carrier channel mathematical model of the distribution network. The input frequency point sample set is used as the training set of the frequency point optimization neural network to obtain a neural network model that can predict the local optimal frequency point set. Then the actual distribution network is taken as an example for simulation analysis. When inputting any frequency range, the model outputs the corresponding optimal frequency point set. Simulation results show that the algorithm saves a lot of input impedance or channel strength testing time, while the error rate is limited to about 3%.

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30

Jibing Wang, E. Biglieri y Kung Yao. "Asymptotic performance of space-frequency codes over broadband channels". IEEE Communications Letters 6, n.º 12 (diciembre de 2002): 523–25. http://dx.doi.org/10.1109/lcomm.2002.806463.

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31

Gasilin, D. V. "IMPROVING OF THE FREQUENCY-SELECTIVE BROADBAND RECIVER STRUCTURE". Electronic engineering. Series 2. Semiconductor devices 248, n.º 1 (2018): 68–71. http://dx.doi.org/10.36845/2073-8250-2018-248-1-68-71.

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32

Qian, Guangxu, Junming Zhao, Xiaomei Ren, Ke Chen, Tian Jiang, Yijun Feng y Ying Liu. "Switchable Broadband Dual-Polarized Frequency-Selective Rasorber/Absorber". IEEE Antennas and Wireless Propagation Letters 18, n.º 12 (diciembre de 2019): 2508–12. http://dx.doi.org/10.1109/lawp.2019.2941661.

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33

Loof, Joseph L. y Thomas G. Pratt. "Frequency-Hopped Signal Source Identification in Frequency-Selective Channels". IEEE Transactions on Aerospace and Electronic Systems 55, n.º 6 (diciembre de 2019): 3316–29. http://dx.doi.org/10.1109/taes.2019.2907392.

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34

Schober, R., L. H. J. Lampe, W. H. Gerstacker y S. Pasupathy. "Modulation diversity for frequency-selective fading channels". IEEE Transactions on Information Theory 49, n.º 9 (septiembre de 2003): 2268–76. http://dx.doi.org/10.1109/tit.2003.815786.

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35

Shayevitz, O. y M. Feder. "Universal Decoding for Frequency-Selective Fading Channels". IEEE Transactions on Information Theory 51, n.º 8 (agosto de 2005): 2770–90. http://dx.doi.org/10.1109/tit.2005.851741.

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36

Gore, D., S. Sandhu y A. Paulraj. "Delay diversity code for frequency selective channels". Electronics Letters 37, n.º 20 (2001): 1230. http://dx.doi.org/10.1049/el:20010860.

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37

Malik, Wasim. "MIMO capacity convergence in frequency-selective channels". IEEE Transactions on Communications 57, n.º 2 (febrero de 2009): 353–56. http://dx.doi.org/10.1109/tcomm.2009.02.070105.

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38

Wing Seng Leon, U. Mengali y D. P. Taylor. "Equalization of linearly frequency-selective fading channels". IEEE Transactions on Communications 45, n.º 12 (1997): 1501–3. http://dx.doi.org/10.1109/26.650220.

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39

Hu, Jun y Tolga Duman. "Cooperation over frequency-selective fading relay channels". IEEE Transactions on Wireless Communications 7, n.º 12 (diciembre de 2008): 5072–81. http://dx.doi.org/10.1109/t-wc.2008.071141.

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40

Zakharov, Y. V. y T. C. Tozer. "Linear multiuser detector for frequency selective channels". Electronics Letters 36, n.º 12 (2000): 1081. http://dx.doi.org/10.1049/el:20000767.

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41

Tulino, Antonia M., Giuseppe Caire, Shlomo Shamai y Sergio Verdu. "Capacity of Channels With Frequency-Selective and Time-Selective Fading". IEEE Transactions on Information Theory 56, n.º 3 (marzo de 2010): 1187–215. http://dx.doi.org/10.1109/tit.2009.2039041.

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42

Friedlander, B. y A. Zeira. "Detection of broadband signals in frequency and time dispersive channels". IEEE Transactions on Signal Processing 44, n.º 7 (julio de 1996): 1613–22. http://dx.doi.org/10.1109/78.510610.

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43

Feteiha, M. F. y M. Uysal. "Cooperative transmission for broadband vehicular networks over doubly selective fading channels". IET Communications 6, n.º 16 (6 de noviembre de 2012): 2760–68. http://dx.doi.org/10.1049/iet-com.2012.0115.

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44

Venugopal, Kiran, Nuria Gonzalez-Prelcic y Robert W. Heath. "Optimal Frequency-Flat Precoding for Frequency-Selective Millimeter Wave Channels". IEEE Transactions on Wireless Communications 18, n.º 11 (noviembre de 2019): 5098–112. http://dx.doi.org/10.1109/twc.2019.2932932.

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45

Viswanathan, H. y R. Krishnamoorthy. "A frequency offset estimation technique for frequency-selective fading channels". IEEE Communications Letters 5, n.º 4 (abril de 2001): 166–68. http://dx.doi.org/10.1109/4234.917102.

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46

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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47

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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48

JIAO, Jian, Nianxi XU, Xin CHEN y Jinsong GAO. "Broadband frequency selective surface based on composite coupling structure". Optics and Precision Engineering 30, n.º 7 (2022): 773–79. http://dx.doi.org/10.37188/ope.20223007.0773.

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49

Alonso-Gonzalez, Leticia, Samuel Ver-Hoeye, Miguel Fernandez-Garcia y Fernando Las-Heras Andres. "Broadband Flexible Fully Textile-Integrated Bandstop Frequency Selective Surface". IEEE Transactions on Antennas and Propagation 66, n.º 10 (octubre de 2018): 5291–99. http://dx.doi.org/10.1109/tap.2018.2858141.

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50

Xu, Yang, Jinsong Gao, Nianxi Xu, Dongzhi Shan y Naitao Song. "A novel broadband bi-mode active frequency selective surface". AIP Advances 7, n.º 5 (mayo de 2017): 055012. http://dx.doi.org/10.1063/1.4980020.

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