Log in

Relevant bibliographies by topics / Time /Frequency Selective Broadband Channels / Journal articles

Journal articles on the topic 'Time /Frequency Selective Broadband Channels'

To see the other types of publications on this topic, follow the link: Time /Frequency Selective Broadband Channels.

Author: Grafiati

Published: 25 May 2024

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Time /Frequency Selective Broadband Channels.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Fateh, Rachid, Anouar Darif, Ahmed Boumezzough, Said Safi, and Miloud Frikel. "A Novel Kernel Algorithm for Finite Impulse Response Channel Identiﬁcation." Journal of Telecommunications and Information Technology, no. 2 (June 29, 2023): 84–93. http://dx.doi.org/10.26636/jtit.2023.169823.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

2

Perov, Sergey Yu, Olga V. Belaya, Quirino Balzano, and Nina B. Rubtsova. "The problems of mobile communication electromagnetic field exposure assessment today and tomorrow." Russian Journal of Occupational Health and Industrial Ecology 60, no. 9 (October 7, 2020): 597–99. http://dx.doi.org/10.31089/1026-9428-2020-60-9-597-599.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

3

Zhang, Zilong, Xiaodong Xu, and 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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

4

Xing, Kang, Shiyan Li, Zhijie Qu, and Xiaojuan Zhang. "Time-Domain Electromagnetic Noise Suppression Using Multivariate Variational Mode Decomposition." Remote Sensing 16, no. 5 (February 25, 2024): 806. http://dx.doi.org/10.3390/rs16050806.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

5

Cobacho-Ruiz, Pablo, Francisco Javier Cañete, Eduardo Martos-Naya, and Unai Fernández-Plazaola. "OFDM System Design for Measured Ultrasonic Underwater Channels." Sensors 22, no. 15 (July 29, 2022): 5703. http://dx.doi.org/10.3390/s22155703.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

6

Nwanekezie, Nnamdi, Oluyomi Simpson, Gbenga Owojaiye, and Yichuang Sun. "Co-Efficient Vector Based Differential Distributed Quasi-Orthogonal Space Time Frequency Coding." Sensors 23, no. 17 (August 30, 2023): 7540. http://dx.doi.org/10.3390/s23177540.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

7

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 (September 29, 2021): 152–71. http://dx.doi.org/10.37394/23204.2021.20.21.

Full text

Abstract:

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

APA, Harvard, Vancouver, ISO, and other styles

8

Chien, Wei, Tzong-Tyng Hsieh, Chien-Ching Chiu, Yu-Ting Cheng, Yang-Han Lee, and Qiang Chen. "Theoretical Derivation and Optimization Verification of BER for Indoor SWIPT Environments." Symmetry 12, no. 7 (July 17, 2020): 1185. http://dx.doi.org/10.3390/sym12071185.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

9

Dobreva, Marina S., William E. O'Neill, and Gary D. Paige. "Influence of aging on human sound localization." Journal of Neurophysiology 105, no. 5 (May 2011): 2471–86. http://dx.doi.org/10.1152/jn.00951.2010.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

10

Qiu, Chencheng, Liu Liu, Botao Han, Jiachi Zhang, Zheng Li, and Tao Zhou. "Broadband Wireless Communication Systems for Vacuum Tube High-Speed Flying Train." Applied Sciences 10, no. 4 (February 18, 2020): 1379. http://dx.doi.org/10.3390/app10041379.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

11

Tulino, Antonia M., Giuseppe Caire, Shlomo Shamai, and Sergio Verdu. "Capacity of Channels With Frequency-Selective and Time-Selective Fading." IEEE Transactions on Information Theory 56, no. 3 (March 2010): 1187–215. http://dx.doi.org/10.1109/tit.2009.2039041.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Friedlander, B., and A. Zeira. "Detection of broadband signals in frequency and time dispersive channels." IEEE Transactions on Signal Processing 44, no. 7 (July 1996): 1613–22. http://dx.doi.org/10.1109/78.510610.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Zhiqiang Liu, Yan Xin, and G. B. Giannakis. "Space-time-frequency coded OFDM over frequency-selective fading channels." IEEE Transactions on Signal Processing 50, no. 10 (October 2002): 2465–76. http://dx.doi.org/10.1109/tsp.2002.803332.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Hongbin Li. "Differential space-time-frequency modulation over frequency-selective fading channels." IEEE Communications Letters 7, no. 8 (August 2003): 349–51. http://dx.doi.org/10.1109/lcomm.2003.814711.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Diggavi, S. N., N. Al-Dhahir, A. Stamoulis, and A. R. Calderbank. "Differential space-time coding for frequency-selective channels." IEEE Communications Letters 6, no. 6 (June 2002): 253–55. http://dx.doi.org/10.1109/lcomm.2002.1010872.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Hongbin Li. "Differential space-time modulation over frequency-selective channels." IEEE Transactions on Signal Processing 53, no. 6 (June 2005): 2228–42. http://dx.doi.org/10.1109/tsp.2005.847853.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Coloma, J., and R. A. Carrasco. "MLP equaliser for frequency selective time-varying channels." Electronics Letters 30, no. 6 (March 17, 1994): 503–4. http://dx.doi.org/10.1049/el:19940352.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Semmar, A., M. Lecours, and H. T. Huynh. "Performance of coherent QPSK communications over frequency-selective fading channels for broadband PCS." Canadian Journal of Electrical and Computer Engineering 22, no. 2 (April 1997): 51–54. http://dx.doi.org/10.1109/cjece.1997.7101978.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Xi, Xinyu, Dehong Li, Dongwen Chen, and 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.

Full text

Abstract:

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%.

APA, Harvard, Vancouver, ISO, and other styles

20

Leus, G., Shengli Zhou, and G. B. Giannakis. "Orthogonal multiple access over time- and frequency-selective channels." IEEE Transactions on Information Theory 49, no. 8 (August 2003): 1942–50. http://dx.doi.org/10.1109/tit.2003.814477.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Abe, T., and T. Matsumoto. "Space-time turbo equalization in frequency-selective mimo channels." IEEE Transactions on Vehicular Technology 52, no. 3 (May 2003): 469–75. http://dx.doi.org/10.1109/tvt.2003.813227.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Qin, M., and R. S. Blum. "Properties of Space-Time Codes for Frequency-Selective Channels." IEEE Transactions on Signal Processing 52, no. 3 (March 2004): 694–702. http://dx.doi.org/10.1109/tsp.2003.821109.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Lozano, A., and C. Papadias. "Layered space-time receivers for frequency-selective wireless channels." IEEE Transactions on Communications 50, no. 1 (2002): 65–73. http://dx.doi.org/10.1109/26.975751.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Borah, D. K., and B. D. Hart. "Receiver structures for time-varying frequency-selective fading channels." IEEE Journal on Selected Areas in Communications 17, no. 11 (1999): 1863–75. http://dx.doi.org/10.1109/49.806817.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Hu, Yuze, Mingyu Tong, Siyang Hu, Weibao He, Xiang’ai Cheng, and Tian Jiang. "Multidimensional engineered metasurface for ultrafast terahertz switching at frequency-agile channels." Nanophotonics 11, no. 7 (February 22, 2022): 1367–78. http://dx.doi.org/10.1515/nanoph-2021-0774.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

26

Rainish, D., and J. M. Perl. "Generalized cutoff rate of time- and frequency-selective fading channels." IEEE Transactions on Communications 37, no. 5 (May 1989): 449–67. http://dx.doi.org/10.1109/26.24596.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Fragouli, C., N. Al-Dhahir, S. N. Diggavi, and W. Turin. "Prefiltered space-time M-BCJR equalizer for frequency-selective channels." IEEE Transactions on Communications 50, no. 5 (May 2002): 742–53. http://dx.doi.org/10.1109/tcomm.2002.1006556.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Baas, Nicholas, and Desmond Taylor. "Adaptive MLSE for DPSK in time- and frequency-selective channels." IEEE Transactions on Communications 56, no. 9 (September 2008): 1478–86. http://dx.doi.org/10.1109/tcomm.2008.060159.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Viteri-Mera, Carlos A., and Fernando L. Teixeira. "Space-Time Block Diagonalization for Frequency-Selective MIMO Broadcast Channels." IEEE Access 4 (2016): 6602–13. http://dx.doi.org/10.1109/access.2016.2618722.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Viteri-Mera, Carlos A., and Fernando L. Teixeira. "Equalized Time Reversal Beamforming for Frequency-Selective Indoor MISO Channels." IEEE Access 5 (2017): 3944–57. http://dx.doi.org/10.1109/access.2017.2682160.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Hart, B. D., and S. Pasupathy. "Innovations-based MAP detection for time-varying frequency-selective channels." IEEE Transactions on Communications 48, no. 9 (2000): 1507–19. http://dx.doi.org/10.1109/26.870018.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

WU, Jinsong, Steven D. BLOSTEIN, Qingchun CHEN, and Pei XIAO. "Joint Time-Frequency Diversity for Single-Carrier Block Transmission in Frequency Selective Channels." IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E95.A, no. 11 (2012): 1912–20. http://dx.doi.org/10.1587/transfun.e95.a.1912.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Cuji, Diego A., Zhengnan Li, and Milica Stojanovic. "Multi-user transmit beamforming for broadband acoustic systems." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A345. http://dx.doi.org/10.1121/10.0019100.

Full text

Abstract:

Multi-user transmit beamforming for acoustic systems based on orthogonal frequency division multiplexing (OFDM) modulation is studied and demonstrated. Transmit beamforming consists of assigning weight coefficients to multiple transmit elements, such that the signals transmitted from the array add constructively at the users' receive sides. In an optimal setting, the transmitter assigns weights that are proportional to the channel transfer functions to the users. However, the assumption of complete channel knowledge is not entirely accurate, as the transmitter obtains the channels via feedback from the users. Thus, the transmitter has partial knowledge of the channels, as their estimates are not only noisy, but can be outdated if the channels have changed during the time it took to close the feedback loop. These adversities are notably pronounced in time-varying acoustic channels, as the feedback delay is large as compared to the channel coherence time due to the low speed of sound propagation. To counteract this problem, a technique that targets only those features of the channels that can withstand the feedback delay is proposed. Such features are the users' angles of arrival of the principal propagation paths. The principal paths are stable paths that do not experience rapid fluctuations and are thus varying sufficiently slowly that they can tolerate long feedback delays. The design concepts are demonstrated using experimental over-the-air transmissions in an indoor environment of an acoustic communications testbed.

APA, Harvard, Vancouver, ISO, and other styles

34

Yan, Qiuna, Yu Sun, and Dian-Wu Yue. "LOS-Based Equal Gain Transmission and Combining in General Frequency-Selective Ricean Massive MIMO Channels." Electronics 8, no. 1 (January 10, 2019): 79. http://dx.doi.org/10.3390/electronics8010079.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

35

Shao, Chao, Cheng Cheng Zhang, Cun Yao Xu, and Yu Ming Liu. "Performance of Two Space-Time-Frequency the Coding Schemes in Frequency Selective Channel." Advanced Materials Research 684 (April 2013): 571–74. http://dx.doi.org/10.4028/www.scientific.net/amr.684.571.

Full text

Abstract:

Discussion of two classic space-time-frequency coding (STFC) scheme in frequency selective channel transmission problems is given. One utilized the data order inversion and conjugation transform, which makes the quadrature data encoder can no longer be interpreted as orthogonality of channel parameter matrix. Another has data orthogonal pre-processing, which makes each symbol spreading stream uniformly to all sub-channels. The computer simulation results illustrate the theoretical analysis of the paper.

APA, Harvard, Vancouver, ISO, and other styles

36

Baas, N. J., and D. P. Taylor. "Pulse Shaping for Wireless Communication Over Time- or Frequency-Selective Channels." IEEE Transactions on Communications 52, no. 9 (September 2004): 1477–79. http://dx.doi.org/10.1109/tcomm.2004.833133.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Zhiqiang Liu and G. B. Giannakis. "Space-time block-coded multiple access through frequency-selective fading channels." IEEE Transactions on Communications 49, no. 6 (June 2001): 1033–44. http://dx.doi.org/10.1109/26.930633.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Bauch, G., and N. Al-Dhahir. "Reduced-complexity space-time turbo-equalization for frequency-selective MIMO channels." IEEE Transactions on Wireless Communications 1, no. 4 (October 2002): 819–28. http://dx.doi.org/10.1109/twc.2002.805094.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Rhee, D., H. G. Hwang, Y. J. Sang, and K. S. Kim. "Multiuser adaptive transmission technique for time-varying frequency-selective fading channels." Signal Processing 88, no. 8 (August 2008): 2095–107. http://dx.doi.org/10.1016/j.sigpro.2008.02.014.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Li, Yong-zhao, Gui-sheng Liao, and Wen-ning Tong. "Space-time coded eigenbeamforming for downlink frequency-selective correlated fading channels." Journal of Shanghai University (English Edition) 10, no. 6 (December 2006): 500–505. http://dx.doi.org/10.1007/s11741-006-0046-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Reinhardt, Markus, Jochem Ecle, and JÜRcen Lindner. "Transformation Methods, Coding and Equalization for Time- and Frequency-Selective Channels." European Transactions on Telecommunications 11, no. 6 (November 2000): 555–65. http://dx.doi.org/10.1002/ett.4460110606.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Mheidat, Hakam, Murat Uysal, and Naofal Al-Dhahir. "Quasi-Orthogonal Time-Reversal Space–Time Block Coding for Frequency-Selective Fading Channels." IEEE Transactions on Signal Processing 55, no. 2 (January 2007): 772–78. http://dx.doi.org/10.1109/tsp.2006.885766.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

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

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

44

Zhang, Wei, Xiang-Gen Xia, and P. C. Ching. "High-Rate Full-Diversity Space–Time–Frequency Codes for Broadband MIMO Block-Fading Channels." IEEE Transactions on Communications 55, no. 1 (January 2007): 25–34. http://dx.doi.org/10.1109/tcomm.2006.885058.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Nouh, Mostafa. "Multichannel frequency-selective beaming in time-modulated electroacoustic phased arrays." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A155. http://dx.doi.org/10.1121/10.0010954.

Full text

Abstract:

Acoustic phased arrays have been a cornerstone of non-destructive evaluation, sonar communications, and medical imaging for years. Conventional arrays work by imparting a static phase gradient across a set of acoustic transceivers to steer a self-created wavefront in a desired direction. In a reception mode, they abide by basic reciprocity principles and exhibit the strongest gain for waves incident from the same direction to which they transmit. This talk sheds light on a class of dynamic phased arrays which is capable of (a) generating multiple scattered harmonics of a single-frequency voltage input which simultaneously propagate in different directional lanes and (b) exhibiting non-identical TX/RX patterns. We will show that such lanes emerge in the form of artificially-synthesized directional channels each with a distinct frequency signature that can be predicted a priori. To achieve this, we devise a class of phase shifters, which augment the array elements with a dynamic phase modulation using an array of piezo-wafer discs bonded to an elastic medium. The scattered beams propagate simultaneously in the transmitted wave field but can be visualized using an FFT of the time-transient measurements via laser Doppler vibrometry. The experimental realization illustrates the array’s ability to guide incident waves within tunable frequency channels that are commensurate with the modulation rate and along the intended directions.

APA, Harvard, Vancouver, ISO, and other styles

46

Matos, Marcílio Castro de, Oswaldo Davogustto, Kui Zhang, and Kurt J. Marfurt. "Detecting stratigraphic discontinuities using time-frequency seismic phase residues." GEOPHYSICS 76, no. 2 (March 2011): P1—P10. http://dx.doi.org/10.1190/1.3528758.

Full text

Abstract:

Spectral decomposition is a proven, powerful means of identifying strong amplitude anomalies at specific frequencies that are otherwise buried in the broadband response. Most publications focus on using spectral magnitude instead of phase components to identify lateral changes in stratigraphy, wavefield attenuation from the quality factor Q, and unconformities between geologic formations. Although seismic acquisition and processing preserve phase very well, little has been published about interpreting the phase components resulting from spectral decomposition. Morlet complex wavelet transform phase residues can improve seismic spectral decomposition interpretation by detecting the phase discontinuities in the joint time-frequency spectral phase component. Phase singularities can be associated with geologic features, and work with phase residues can improve interpretation of the Anadarko basin Red Fork channels of Oklahoma, U.S.A.

APA, Harvard, Vancouver, ISO, and other styles

47

Li, Meng, Mudar A. Al-Joumayly, and Nader Behdad. "Broadband True-Time-Delay Microwave Lenses Based on Miniaturized Element Frequency Selective Surfaces." IEEE Transactions on Antennas and Propagation 61, no. 3 (March 2013): 1166–79. http://dx.doi.org/10.1109/tap.2012.2227444.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Steendam, H., and M. Moeneclaey. "Analysis and optimization of the performance of OFDM on frequency-selective time-selective fading channels." IEEE Transactions on Communications 47, no. 12 (1999): 1811–19. http://dx.doi.org/10.1109/26.809701.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Li, Cong, and Yasunori Iwanami. "Linear and Nonlinear Time Domain Block Equalizers on MIMO Frequency Selective Channels." International Journal of Communications, Network and System Sciences 06, no. 03 (2013): 119–27. http://dx.doi.org/10.4236/ijcns.2013.63014.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Shengli Zhou and G. B. Giannakis. "Single-carrier space-time block-coded transmissions over frequency-selective fading channels." IEEE Transactions on Information Theory 49, no. 1 (January 2003): 164–79. http://dx.doi.org/10.1109/tit.2002.806158.

Full text

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!