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Artykuły w czasopismach na temat „Doppler spreads”

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Data publikacji: 6 września 2023

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1

Zhang, Yan, Zunwen He, Wancheng Zhang, Limin Xiao i Shidong Zhou. "Measurement-Based Delay and Doppler Characterizations for High-Speed Railway Hilly Scenario". International Journal of Antennas and Propagation 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/875345.

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This paper presents results for delay and Doppler spread characterization in high-speed railway (HSR) hilly scenario. To investigate the propagation characteristics in this specific terrain, a measurement campaign is conducted along the “Guangzhou-Shenzhen” HSR in China. A wideband channel sounder with 40 MHz bandwidth is used to collect raw data at 2.4 GHz band. The delay spread and Doppler frequency features are analyzed based on measured data. It is found that there are abundant multipath components (MPCs) in this scenario. We present the relationship between the delay spreads and the transceiver distances. The measured route can be divided into four areas with different delay and Doppler characteristics. Finally, a tapped delay line (TDL) model is proposed to parameterize the channel responses in the HSR hilly environment, which is supposed to provide criterions for evaluations of the radio interface and development of wireless communication system.

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2

Guo, Huaihai, Ali Abdi, Aijun Song i Mohsen Badiey. "Delay and Doppler spreads in underwater acoustic particle velocity channels". Journal of the Acoustical Society of America 129, nr 4 (kwiecień 2011): 2015–25. http://dx.doi.org/10.1121/1.3533721.

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3

Bernado, Laura, Thomas Zemen, Fredrik Tufvesson, Andreas F. Molisch i Christoph F. Mecklenbrauker. "Delay and Doppler Spreads of Nonstationary Vehicular Channels for Safety-Relevant Scenarios". IEEE Transactions on Vehicular Technology 63, nr 1 (styczeń 2014): 82–93. http://dx.doi.org/10.1109/tvt.2013.2271956.

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4

Karlsson, Kristian, Xiaoming Chen, Jan Carlsson i Anton Skarbratt. "On OTA Test in the Presence of Doppler Spreads in a Reverberation Chamber". IEEE Antennas and Wireless Propagation Letters 12 (2013): 886–89. http://dx.doi.org/10.1109/lawp.2013.2272716.

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5

Borah, D. K. "Estimation of Frequency-Selective CDMA Channels With Large Possible Delay and Doppler Spreads". IEEE Transactions on Vehicular Technology 55, nr 4 (lipiec 2006): 1126–36. http://dx.doi.org/10.1109/tvt.2006.877473.

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6

Weitzen, J., M. Sowa, R. Scofidio i J. Quinn. "Characterizing the Multipath and Doppler Spreads of the High-Latitude Meteor Burst Communication Channel". IEEE Transactions on Communications 35, nr 10 (październik 1987): 1050–58. http://dx.doi.org/10.1109/tcom.1987.1096690.

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7

Zhang, Mi, Xiaochen Xia, Kui Xu, Xiaoqin Yang, Wei Xie, Yunkun Li i Yang Liu. "A Structured Sparse Bayesian Channel Estimation Approach for Orthogonal Time—Frequency Space Modulation". Entropy 25, nr 5 (6.05.2023): 761. http://dx.doi.org/10.3390/e25050761.

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Orthogonal time–frequency space (OTFS) modulation has been advocated as a promising waveform for achieving integrated sensing and communication (ISAC) due to its superiority in high-mobility adaptability and spectral efficiency. In OTFS modulation-based ISAC systems, accurate channel acquisition is critical for both communication reception and sensing parameter estimation. However, the existence of the fractional Doppler frequency shift spreads the effective channels of the OTFS signal significantly, making efficient channel acquisition very challenging. In this paper, we first derive the sparse structure of the channel in the delay Doppler (DD) domain according to the input and output relationship of OTFS signals. On this basis, a new structured Bayesian learning approach is proposed for accurate channel estimation, which includes a novel structured prior model for the delay-Doppler channel and a successive majorization–minimization (SMM) algorithm for efficient posterior channel estimate computation. Simulation results show that the proposed approach significantly outperforms the reference schemes, especially in the low signal-to-noise ratio (SNR) region.

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8

Rejeb, Nessrine Ben, Ines Bousnina, Mohamed Bassem Ben Salah i Abdelaziz Samet. "Mean angle of arrival, angular and Doppler spreads estimation in multiple‐input multiple‐output system". IET Signal Processing 9, nr 5 (lipiec 2015): 395–402. http://dx.doi.org/10.1049/iet-spr.2014.0173.

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9

Donnelly, M. J., O. K. Rediniotis, S. A. Ragab i D. P. Telionis. "The Interaction of Rolling Vortices With a Turbulent Boundary Layer". Journal of Fluids Engineering 117, nr 4 (1.12.1995): 564–70. http://dx.doi.org/10.1115/1.2817302.

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Laser-Doppler velocimetry is employed to measure the periodic field created by releasing spanwise vortices in a turbulent boundary layer. Phase-averaged vorticity and turbulence level contours are estimated and presented. It is found that vortices with diameter of the order of the boundary layer quickly diffuse and disappear while their turbulent kinetic energy spreads uniformly across the entire boundary layer. Larger vortices have a considerably longer life span and in turn feed more vorticity into the boundary layer.

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10

Linnartz, J. P. M. G. "Performance analysis of synchronous MC-CDMA in mobile Rayleigh channel with both delay and Doppler spreads". IEEE Transactions on Vehicular Technology 50, nr 6 (2001): 1375–87. http://dx.doi.org/10.1109/25.966570.

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11

Shui, Yishui, Fang Li, Junyi Yu, Wei Chen, Changzhen Li, Kun Yang i Fuxing Chang. "Vehicle-to-Vehicle Radio Channel Characteristics for Congestion Scenario in Dense Urban Region at 5.9 GHz". International Journal of Antennas and Propagation 2018 (2018): 1–14. http://dx.doi.org/10.1155/2018/1751869.

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This paper reports the results of a car-following measurement of the wireless propagation channel at 5.9 GHz on a seriously congested urban road in Wuhan, China. The small-scale amplitude-fading distribution was determined to be a Ricean distribution using the Akaike information criterion. This result shows that this car-following scenario can be regarded as a line-of-sight radio channel. Moreover, the statistical K-factor features follow a Gaussian distribution. According to the power delay profile and average power delay profile, we found that street buildings in this dense urban environment contributed to very strong reflection phenomena. The impact of a powerful reflection is analyzed through path loss, delay, and Doppler spreads in the channel statistical properties. In the frequency domain, we observe a U-shape delay-Doppler spectrum that proved that the dense urban scenario consists of scattering channels. All these results are summarized in tabular form that will be useful in the modeling of vehicle-to-vehicle wireless communication systems.

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12

Yang, Jingya, Bo Ai, Danping He, Longhe Wang, Zhangdui Zhong i Andrej Hrovat. "A Simplified Multipath Component Modeling Approach for High-Speed Train Channel Based on Ray Tracing". Wireless Communications and Mobile Computing 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/8517204.

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High-speed train (HST) communications at millimeter-wave (mmWave) band have received a lot of attention due to their numerous high-data-rate applications enabling smart rail mobility. Accurate and effective channel models are always critical to the HST system design, assessment, and optimization. A distinctive feature of the mmWave HST channel is that it is rapidly time-varying. To depict this feature, a geometry-based multipath model is established for the dominant multipath behavior in delay and Doppler domains. Because of insufficient mmWave HST channel measurement with high mobility, the model is developed by a measurement-validated ray tracing (RT) simulator. Different from conventional models, the temporal evolution of dominant multipath behavior is characterized by its geometry factor that represents the geometrical relationship of the dominant multipath component (MPC) to HST environment. Actually, during each dominant multipath lifetime, its geometry factor is fixed. To statistically model the geometry factor and its lifetime, the dominant MPCs are extracted within each local wide-sense stationary (WSS) region and are tracked over different WSS regions to identify its “birth” and “death” regions. Then, complex attenuation of dominant MPC is jointly modeled by its delay and Doppler shift both which are derived from its geometry factor. Finally, the model implementation is verified by comparison between RT simulated and modeled delay and Doppler spreads.

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13

Smirnov, Y. A., T. M. Bogacheva i R. G. Valeev. "Ultrasonography in assessing the cervical cancer extent". Kazan medical journal 93, nr 5 (15.10.2012): 735–38. http://dx.doi.org/10.17816/kmj1699.

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Aim. To study the potentials of complex ultrasonography in assessing the extent of cervical cancer, defining typical ultrasonographic features of cervical cancer. Methods. 75 patients with the diagnosis of morphologically confirmed cervical cancer were examined. Continuous sampling method was used to recruit the patients. Patients underwent transabdominal, transvaginal and transrectal ultrasonography with the use of color Doppler and power Doppler modes. Results. 57 (76,5%) patients were diagnosed with squamous cell non-keratinous carcinoma, 12 (16%) - with squamous cell keratinous carcinoma, 6 (8%) - with adenocarcinoma. 43 (57,3%) patients had cancer stages I-II, 32 (42,7%) - cancer stages III-IV. The certain features of ultrasonographic images were found at different stages of cervical cancer. At cancer stage I the most typical findings were: low echogenicity area, diffuse heterogeneity of stroma, area of hypervascularity at the place of cervical cancer. Increased blood flow at the cancer site is typical for cervical cancer because of tumor vasculature hyperplasia and neoangiogenesis, the increase in number of blood vessels is proportional to tumor size. Cervix hypertrophy, fuzzy and irregular contouring, no flexion angle between the fundus and cervix were characteristic for cervical cancer stages II-III. Corpus uteri echo-structure at the tumor site portrays the tumor structure. Infiltrates in parametrium can be seen. At stage IV tumor spreads to urine bladder and rectum walls. In advanced stages uretеrs can be involved, pyelectasis and ureterectasis can develop. Conclusion. Complex ultrasonography allows to diagnose cervical cancer quite reliably and to estimate the extent of cervical cancer.

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14

Stocker, A. J., E. M. Warrington i D. R. Siddle. "Observations of Doppler and delay spreads on HF signals received over polar cap and trough paths at various stages of the solar cycle". Radio Science 48, nr 5 (wrzesień 2013): 638–45. http://dx.doi.org/10.1002/2013rs005264.

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15

Dang, Qun, i Xiao Li Lei. "Doppler Frequency Shift Tolerance Extension in Burst Spread Spectrum Communication System". Advanced Materials Research 443-444 (styczeń 2012): 237–40. http://dx.doi.org/10.4028/www.scientific.net/amr.443-444.237.

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A method to extend Doppler frequency discrimination tolerance is proposed for quick acquirement PN-code and Doppler frequency in TDMA burst spread spectrum communication system. According to Doppler’s different impacts on the correlation Peak and data demodulation, PN-code is acquired through single channel matched-filters, and parallel multi-channel correlators are used in the data demodulation branch channel. Thus, with using frame head prior information in data channel instead of traditional Cross-Product Automatic Frequency Control (CPAFC), the Doppler frequency shift discrimination tolerance is extended. Simulation and experiment show that frequency and PN-code can be acquired in several data periods, and synchronous time and the resources consumption are effectively reduced.

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16

Ayadi, Raouia, Inès Kammoun i Mohamed Siala. "Efficient Offline Waveform Design Using Quincunx/Hexagonal Time-Frequency Lattices". Wireless Communications and Mobile Computing 2017 (2017): 1–16. http://dx.doi.org/10.1155/2017/9207108.

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Conventional orthogonal frequency division multiplexing (OFDM) may turn to be inappropriate for future wireless cellular systems services, because of extreme natural and artificial impairments they are expected to generate. Natural impairments result from higher Doppler and delay spreads, while artificial impairments result from multisource transmissions and synchronization relaxation for closed-loop signaling overhead reduction. These severe impairments induce a dramatic loss in orthogonality between subcarriers and OFDM symbols and lead to a strong increase in intercarrier interference (ICI) and intersymbol interference (ISI). To fight against these impairments, we propose here an optimization of the transmit/receive waveforms for filter-bank multicarrier (FBMC) systems, with hexagonal time-frequency (TF) lattices, operating over severe doubly dispersive channels. For this, we exploit the Ping-pong Optimized Pulse Shaping (POPS) paradigm, recently applied to rectangular TF lattices, to design waveforms maximizing the signal-to-interference-plus-noise ratio (SINR) for hexagonal TF lattices. We show that FBMC, with hexagonal lattices, offers a strong improvement in SINR with respect to conventional OFDM and an improvement of around 1 dB with respect to POPS-FBMC, with rectangular lattices. Furthermore, we show that hexagonal POPS-FBMC brings more robustness to frequency synchronization errors and offers a 10 dB reduction in out-of-band (OOB) emissions, with respect to rectangular POPS-FBMC.

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17

Kára, J., S. Zharikov, M. Wolf, H. Kučáková, P. Cagaš, A. L. Medina Rodriguez i M. Mašek. "The period-gap cataclysmic variable CzeV404 Her: A link between SW Sex and SU UMa systems". Astronomy & Astrophysics 652 (sierpień 2021): A49. http://dx.doi.org/10.1051/0004-6361/202140958.

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Context. We present a new study of the eclipsing cataclysmic variable CzeV404 Her (Porb = 0.098 d) that is located in the period gap. Aims. This report determines the origin of the object and the system parameters and probes the accretion flow structure of the system. Methods. We conducted simultaneous time-resolved photometric and spectroscopic observations of CzeV404 Her. We applied our light-curve modelling techniques and the Doppler tomography method to determine the system parameters and analyse the structure of the accretion disk. Results. We found that the system has a massive white dwarf MWD = 1.00(2) M⊙, a mass ratio of q = 0.16, and a relatively hot secondary with an effective temperature T2 = 4100(50) K. The system inclination is i = 78.8°. The accretion disk spreads out to the tidal limitation radius and has an extended hot spot or line region. The hot spot or line is hotter than the remaining outer part of the disk in quiescence or in intermediate state, but does not stand out completely from the disk flux in (super)outbursts. Conclusions. We claim that this object represents a link between two distinct classes of SU UMa-type and SW Sex-type cataclysmic variables. The accretion flow structure in the disk corresponds to the SW Sex systems, but the physical conditions inside the disk fit the behaviour of SU UMa-type objects.

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18

Benani, Abdelmoumen, Andre Carr i Martin Quenneville. "Doppler spread technique". IEEE Vehicular Technology Magazine 4, nr 1 (marzec 2009): 78–86. http://dx.doi.org/10.1109/mvt.2008.931621.

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19

Patil, Ameykumar Arunrao. "Robust Transmission using Efficient Adaptive Modulation and Coding in Modern OFDM Systems". International Journal for Research in Applied Science and Engineering Technology 11, nr 5 (31.05.2023): 3364–76. http://dx.doi.org/10.22214/ijraset.2023.52336.

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Abstract: OFDM (Orthogonal Frequency Division Multiplexing) as a special multi-carrier transmission technology has good resistance to narrow-band interference and frequency selective fading ability. Using adaptive modulation and coding in an OFDM systems in comparison with traditional fixed modulation techniques, it becomes possible to take full advantage of spectrum resources enhancing bandwidth efficiency and system capacity making it suitable for the high-speed and reliable mobile communication systems in the future. In AMC (Adaptive Modulation and Coding) technique, modulation method, coding rate, and/or other signal transmission parameters are dynamically adapted to the channel conditions to increase the system performance in terms of Bit Error Rate (BER) and throughput (bps) in various conditions such as channel mismatch, Doppler spreads, fading, etc. The purpose of this paper is to investigate the effect of adaptive modulation and coding in an OFDM system in terms of bit error rate and SNR over fading communication channels. In this paper, we have considered fixed and adaptive modulation technique in an OFDM system over AWGN and RICEAN channel with convolutional and BCH coding. An OFDM system model is simulated in MATLAB programming environment to obtain the simulation result. From the comparative simulation result analysis in terms of BER v/s SNR, it can be concluded that Adaptive modulation with Convolutional coding over RICEAN channel significantly reduces bit error rate giving better trade-off between SNR and BER than all other options considered here.

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20

Krasny, L., H. Arslan, D. Koilpillai i S. Chennakeshu. "Doppler spread estimation in mobile radio systems". IEEE Communications Letters 5, nr 5 (maj 2001): 197–99. http://dx.doi.org/10.1109/4234.922758.

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21

Howard, S. J., i K. Pahlavan. "Doppler spread measurements of indoor radio channel". Electronics Letters 26, nr 2 (1990): 107. http://dx.doi.org/10.1049/el:19900074.

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22

KO, Y. C. "Doppler Spread Estimation in Mobile Communication Systems". IEICE Transactions on Communications E88-B, nr 2 (1.02.2005): 724–28. http://dx.doi.org/10.1093/ietcom/e88-b.2.724.

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23

Hines, Colin O. "The Doppler spread theory and parameterization revisited". Journal of Atmospheric and Solar-Terrestrial Physics 66, nr 11 (lipiec 2004): 949–56. http://dx.doi.org/10.1016/j.jastp.2004.02.005.

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24

Bhadouria, Vijay Singh, Monika Agrawal i Ritesh Kumar. "An unsupervised clustering-based scale-lag receiver design approach for the doubly selective underwater acoustic channel". Journal of the Acoustical Society of America 152, nr 1 (lipiec 2022): 342–53. http://dx.doi.org/10.1121/10.0012349.

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This paper details the architecture of a novel scale-lag rake receiver for the doubly selective underwater acoustic (UWA) channel. The shallow UWA channel is known to have a large Doppler spread. The cause of this is primarily due to the large spread of the angle of arrival of the received signal's paths. The Doppler scale value is dependent on the angle of arrival of the received signal. The Doppler spread is significant, and multiple Doppler scales are present in the UWA channel. Therefore, the receivers operating with only a single Doppler scale compensation perform sub-optimally. The optimal receiver should incorporate all possible Doppler scales for better performance. The receiver needs to have multiple sampling rates to incorporate all Doppler scales. It is usually done by having multiple receive channels, one for each sampling rate. It requires tremendous resources as its complexity increases exuberantly. This paper shows that these Doppler scales are clustered and that an optimal receiver is implemented using fewer receiver channels, each corresponding to one such cluster. It reduces the receiver's complexity. The simulation results demonstrate that using the Doppler scale value associated with the path of the highest magnitude per cluster yields the best performance.

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25

Yang, Guang, Feng Zhou, Gang Qiao, Yunjiang Zhao, Yufei Liu, Yinheng Lu i Yuanan He. "Optimized Doppler Estimation and Symbol Synchronization for Mobile M-ary Spread Spectrum Underwater Acoustic Communication". Journal of Marine Science and Engineering 9, nr 9 (13.09.2021): 1001. http://dx.doi.org/10.3390/jmse9091001.

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In mobile underwater acoustic (UWA) communications, the Doppler effect causes severe signal distortion, which leads to carrier frequency shift and compresses/broadens the signal length. This situation has a more severe impact on communication performance in the case of low signal-to-noise ratio and variable-speed movement. This paper proposes a non-data-aided Doppler estimation method for M-ary spread spectrum UWA communication systems in mobile scenarios. The receiver uses the spread spectrum codes dedicated to transmitting signals with different frequency offsets as local reference signals. Correlation operations are performed symbol by symbol with the received signal. The decoding and Doppler estimation of the present symbol are achieved by searching the correlation maximum in the code domain and frequency domain. The length of the current symbol is corrected for the next symbol synchronization using the estimated Doppler coefficient. To optimize the process of Doppler estimation and symbol synchronization, a heuristic search method is used. By adjusting the Doppler factor search step size, setting the threshold value, and using the Doppler factor estimation of the previous symbol, the search range can be significantly reduced and the computational complexity decreased. The Fisher-Yates shuffle algorithm is used to traverse the search range to ensure reliability of the results. Simulation results show that enlarging the frequency-domain search step size in some degree does not affect the decoding accuracy. On 15 May 2021, a shallow-water mobile UWA spread spectrum communication experiment was conducted in Weihai, China. The horizontal distance between the transmitter and the receiver is 3.7–4.0 km, and the communication rate is 41.96 bits per second. The transmitting ship moves at a speed of 0–3 m/s, and the bit error rate (BER) is lower than 1e−3, which is better than that of the sliding correlation despreading method with average Doppler compensation.

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26

Wu, Xing Cun, Ping Gong, Hai Jun Song i Hui Zhi Zou. "An FFT-Based Approach for Carrier Frequency Domain Acquisition in Spread Spectrum TT&C System". Applied Mechanics and Materials 135-136 (październik 2011): 211–16. http://dx.doi.org/10.4028/www.scientific.net/amm.135-136.211.

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Acquisition time of precision ranging code is long under the conditions of large Doppler shift, the carrier frequency domain FFT-based fast acquisition theory was analyzed, and the method of carrier Doppler compensation estimates to complete the PN code Doppler compensation was directly used in spread spectrum ranging signal acquisition. Comparing with the traditional parallel acquisition approach, the Doppler frequency estimation accuracy and acquisition speed is greatly improved, the acquisition time is shorter than long code segment with the traditional parallel acquisition method. Comparing with the method of short code supporting for long code, the channel energy is saved.

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27

Liu, Bei Jia, Xiao Wang, Xue Zhi Tan i Yang Yu. "An Adaptive Channel Estimation Based on Polynomial Fitting for LTE Uplink in High Doppler Spread Scenario". Advanced Materials Research 756-759 (wrzesień 2013): 3522–26. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.3522.

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Channel estimation plays a crucial role in improving the overall system performance in long term evolution (LTE) systems. However, it is demonstrated that conventional channel estimation algorithms have poor performance in the presence of a large Doppler frequency shift. To mitigate the adverse effect of Doppler frequency shift on transmission signals, an adaptive anti-Doppler shift method based on polynomial fitting for LTE uplink is proposed in this paper. Furthermore, an adaptive strategy is exploited to improve estimation accuracy and reduce estimation mean square error (MSE), achieving better system performance. Simulations results validate the effectiveness of anti-Doppler algorithm.

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28

Rice, Joseph, Paul Baxley, Homer Bucker, Richard Shockley, Dale Green, John Proakis i John Newton. "Doppler spread in an undersea acoustic transmission channel". Journal of the Acoustical Society of America 103, nr 5 (maj 1998): 2782. http://dx.doi.org/10.1121/1.422266.

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29

Baddour, K. E., i N. C. Beaulieu. "Robust Doppler spread estimation in nonisotropic fading channels". IEEE Transactions on Wireless Communications 4, nr 6 (listopad 2005): 2677–82. http://dx.doi.org/10.1109/twc.2005.858362.

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30

Huang, Pengda, Dinesh Rajan i Joseph Camp. "An Autoregressive Doppler Spread Estimator for Fading Channels". IEEE Wireless Communications Letters 2, nr 6 (grudzień 2013): 655–58. http://dx.doi.org/10.1109/wcl.2013.091113.130593.

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Okada, Minoru, Hideaki Takayanagi i Heiichi Yamamoto. "Array antenna assisted doppler spread compensator for OFDM". European Transactions on Telecommunications 13, nr 5 (wrzesień 2002): 507–12. http://dx.doi.org/10.1002/ett.4460130511.

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32

Frigyes, I., B. G. Molnár, R. Vallet, Z. Herczku i Z. Bodnár. "Doppler spread characteristics of satellite personal communication channels". International Journal of Satellite Communications 19, nr 3 (maj 2001): 251–62. http://dx.doi.org/10.1002/sat.685.

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Yoon, Eunchul, Soonbum Kwon, Unil Yun i Sun-Yong Kim. "Doppler Spread Estimation Based on Machine Learning for an OFDM System". Wireless Communications and Mobile Computing 2021 (21.09.2021): 1–15. http://dx.doi.org/10.1155/2021/5586029.

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In this paper, we propose a Doppler spread estimation approach based on machine learning for an OFDM system. We present a carefully designed neural network architecture to achieve good performance in a mixed-channel scenario in which channel characteristic variables such as Rician K factor, azimuth angle of arrival (AOA) width, mean direction of azimuth AOA, and channel estimation errors are randomly generated. When preprocessing the channel state information (CSI) collected under the mixed-channel scenario, we propose averaged power spectral density (PSD) sequence as high-quality training data in machine learning for Doppler spread estimation. We detail intermediate mathematical derivatives of the machine learning process, making it easy to graft the derived results into other wireless communication technologies. Through simulation, we show that the machine learning approach using the averaged PSD sequence as training data outperforms the other machine learning approach using the channel frequency response (CFR) sequence as training data and two other existing Doppler estimation approaches.

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34

TAO, X., C. ZHANG i J. LU. "Doppler Diversity in MC-CDMA Systems with T-ZCZ Sequences for Doppler Spread Cancelation". IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E90-A, nr 11 (1.11.2007): 2361–68. http://dx.doi.org/10.1093/ietfec/e90-a.11.2361.

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35

Andonov, Antonio. "Accelerated synchronization in system with SSS (spread spectrum signal) with optimized structure". Journal scientific and applied research 1, nr 1 (3.03.2012): 47–53. http://dx.doi.org/10.46687/jsar.v1i1.16.

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In the systems with spread spectrum signal the quasi-coherent acceptance can not be made without prior synchronization, because in the real conditions the phase, position of time and Doppler shift frequency are unknown. For the purposes of processing of quasi-coherent SSS should make the introduction of tracking devicesin step with an accuracy determined by the area of the grip devices. The accuracy of determining the frequency and the delay of the received signal must be determined by the appropriate intervals of the correlation of the signal. To minimize the time for initial synchronization, the signal should be changed so that the autocorrelation function at each stage to be agreed with the necessary increase in aposteriority density.

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36

Wang, Ke, Chan-Tong Lam i Benjamin K. Ng. "Positioning Information Based High-Speed Communications with Multiple RISs: Doppler Mitigation and Hardware Impairments". Applied Sciences 12, nr 14 (13.07.2022): 7076. http://dx.doi.org/10.3390/app12147076.

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In this paper, we consider a multiple reconfigurable intelligent surface (RIS)-assisted system using positioning information (PI) to explore the potential of Doppler effect mitigation and spectral efficiency (SE) enhancement in high-speed communications (HSC) in the presence of hardware impairments (HWI). In particular, we first present a general multi-RIS-assisted system model for HSC with HWI. Then, based on PI, different phase shift optimization strategies are designed and compared for maximizing SE, eliminating Doppler spread, and maintaining a very low delay spread. Moreover, we compare the performance of different numbers of RISs with HWI in terms of SE and delay spread. Finally, we extend our channel model from line-of-sight to the Rician channel to demonstrate the effectiveness and robustness of our proposed scheme. Numerical results reveal that the HWI of RISs increases the delay spread, but has no impact on Doppler shift and spread. Additionally, the multiple RIS system not only suffers a more severe delay spread, but is limited in SE due to the HWI. When the number of RISs increases from 2 to 16, the range of average spectral efficiency and delay spread are from 4 to 4.6 Bit/s/Hz and from 0.7 μs to 2.5 μs, respectively. In contrast to conventional RIS-assisted systems that require channel estimation, the proposed PI-based RIS system offers simplicity without compromising effectiveness and robustness in both SE enhancement and Doppler mitigation.

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SHENG, Bin, Pengcheng ZHU i Xiaohu YOU. "An Enhanced Doppler Spread Estimation Method for OFDM Systems". IEICE Transactions on Communications E95.B, nr 12 (2012): 3911–14. http://dx.doi.org/10.1587/transcom.e95.b.3911.

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Yanovsky, F. J., C. M. H. Unal, H. W. J. Russchenberg i L. P. Ligthart. "Doppler-Polarimetric Weather Radar: Returns from Wide Spread Precipitation". Telecommunications and Radio Engineering 66, nr 8 (2007): 715–27. http://dx.doi.org/10.1615/telecomradeng.v66.i8.20.

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Eller, Anthony I., i Ellen M. Daley. "Effects of scattering‐induced frequency spread on Doppler performance". Journal of the Acoustical Society of America 98, nr 5 (listopad 1995): 2912. http://dx.doi.org/10.1121/1.414197.

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Mohammadkarimi, Mostafa, Ebrahim Karami, Octavia A. Dobre i Moe Z. Win. "Doppler Spread Estimation in MIMO Frequency-Selective Fading Channels". IEEE Transactions on Wireless Communications 17, nr 3 (marzec 2018): 1951–65. http://dx.doi.org/10.1109/twc.2017.2787539.

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Zhang, Wei, Huiyong Li, Guohao Sun i Zishu He. "Enhanced Detection of Doppler-Spread Targets for FMCW Radar". IEEE Transactions on Aerospace and Electronic Systems 55, nr 4 (sierpień 2019): 2066–78. http://dx.doi.org/10.1109/taes.2019.2925433.

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Hong Zhang i A. Abdi. "Cyclostationarity-based doppler spread estimation in mobile fading channels". IEEE Transactions on Communications 57, nr 4 (kwiecień 2009): 1061–67. http://dx.doi.org/10.1109/tcomm.2009.04.070255.

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Reyes, Hector, Naima Kaabouch i Wen-Chen Hu. "Spectrum Channel Characterization Using Delay and Doppler Spread Parameters". Journal of Communications 9, nr 3 (2014): 234–40. http://dx.doi.org/10.12720/jcm.9.3.234-240.

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Reddi, C. R., M. S. S. R. K. N. Sarma i K. Niranjan. "HF Doppler radar observations of low-latitude spread F". Radio Science 44, nr 3 (9.05.2009): n/a. http://dx.doi.org/10.1029/2007rs003777.

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ZHANG, P., X. XU, G. BI, X. CAO i J. ZHAO. "Iterative Joint Correlation Interval Selection and Doppler Spread Estimation". IEICE Transactions on Communications E89-B, nr 11 (1.11.2006): 3156–59. http://dx.doi.org/10.1093/ietcom/e89-b.11.3156.

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Capoglu, I. R., Ye Li i A. Swami. "Effect of Doppler spread in OFDM-based UWB systems". IEEE Transactions on Wireless Communications 4, nr 5 (wrzesień 2005): 2559–67. http://dx.doi.org/10.1109/twc.2005.853978.

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Robertson, Patrick, i Stefan Kaiser. "Analysis of Doppler Spread Perturbations in OFDM(A) Systems". European Transactions on Telecommunications 11, nr 6 (listopad 2000): 585–92. http://dx.doi.org/10.1002/ett.4460110609.

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Li, Jie, Fangjiong Chen, Songzuo Liu, Hua Yu i Fei Ji. "Estimation of Overspread Underwater Acoustic Channel Based on Low-Rank Matrix Recovery". Sensors 19, nr 22 (15.11.2019): 4976. http://dx.doi.org/10.3390/s19224976.

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In this paper, the estimation of overspread, i.e., doubly spread underwater acoustic (UWA) channels of strong dispersion is considered. We show that although the UWA channel dispersion causes the degeneration of channel sparsity, it leads to a low-rank structure especially when the channel delay-Doppler-spread function is separable in delay and Doppler domain. Therefore, we introduce the low-rank criterion to estimate the UWA channels, which can help to improve the estimation performance in the case of strong dispersion. The estimator is based on the discrete delay-Doppler-spread function representation of channel, and is formulated as a low-rank matrix recovery problem which can be solved by the singular value projection technique. Simulation examples are carried out to demonstrate the effectiveness of the proposed low-rank-based channel estimator.

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Tsay, Lok Wai Jacky, Shiigi Tomoo, Zichen Huang, Hiroaki Nakanishi, Tetsuhito Suzuki, Keiichiro Shiraga, Yuichi Ogawa i Naoshi Kondo. "An Acoustic Based Local Positioning System for Dynamic UAV in GPS-Denied Environments". Applied Engineering in Agriculture 39, nr 3 (2023): 315–23. http://dx.doi.org/10.13031/aea.15397.

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Highlights A positioning system for mobile UAVs is needed in a GPS-denied environment. A Doppler shift compensation algorithm was proposed. The successful detection rate and positioning errors were 90.2% and 75.9 ± 39.1 mm, respectively. The system performance meets the requirements for mobile UAVs in an indoor environment. Abstract. An alternative positioning system, the Spread Spectrum Sound-based Local Positioning System (SSSLPS), was developed to extend the usage of UAVs in GPS-denied environments, such as greenhouses. To date, it has been proven that the SSSLPS could provide a centimeter-level locational accuracy of static objects and dynamic ground robots. In this research, the ranging and positioning performance of SSSLPS were evaluated with the system mounted on a UAV. Meanwhile, to minimize the Time of Arrival (ToA) estimation error and improve positioning accuracy, a novel Doppler shift compensation algorithm was proposed. Experiments were conducted, and the measurement accuracy was evaluated by comparing the measurement of the motion capture system. The results show a successful detection rate of 90.2% using the proposed algorithm and a position error of 75.9 mm. These results demonstrate that the SSSLPS with spectrum peak algorithm can improve positioning accuracy and enable the SSSLPS to be an accurate positioning system for UAVs in a greenhouse. Keywords: Dopper shift, Greenhouse robots, Positioning system, ToA estimation, UAV.

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Zhao, Pengyu, Xiaoyong Wang, Kai Zhang, Yanliang Jin i Guoxin Zheng. "Doppler Modeling and Simulation of Train-to-Train Communication in Metro Tunnel Environment". Sensors 22, nr 11 (4.06.2022): 4289. http://dx.doi.org/10.3390/s22114289.

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The communication system of urban rail transit is gradually changing from train-to-ground (T2G) to train-to-train (T2T) communication. The subway can travel at speeds of up to 200 km/h in the tunnel environment, and communication between trains can be conducted via millimeter waves with minimum latency. A precise channel model is required to test the reliability of T2T communication over a non-line-of-sight (NLoS) Doppler channel in a tunnel scenario. In this paper, the description of the ray angle for a T2T communication terminal is established, and the mapping relationship of the multipath signals from the transmitter to the receiver is established. The channel parameters including the angle, amplitude, and mapping matrix from the transmitter to the receiver are obtained by the ray-tracing method. In addition, the channel model for the T2T communication system with multipath propagations is constructed. The Doppler spread simulation results in this paper are consistent with the RT simulation results. A channel physics modelling approach using an IQ vector phase shifter to achieve Doppler spread in the RF domain is proposed when paired with the Doppler spread model.

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