Artykuły w czasopismach: „Orthogonal time frequency space”

1

Tiwari, S., i S. S. Das. "Circularly pulse‐shaped orthogonal time frequency space modulation". Electronics Letters 56, nr 3 (luty 2020): 157–60. http://dx.doi.org/10.1049/el.2019.2503.

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Aksoy, K., i Ü Aygölü. "Super-orthogonal space-time-frequency trellis coded OFDM". IET Communications 1, nr 3 (2007): 317. http://dx.doi.org/10.1049/iet-com:20060094.

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Fazel, F., i H. Jafarkhani. "Quasi-Orthogonal Space-Frequency and Space-Time-Frequency Block Codes for MIMO OFDM Channels". IEEE Transactions on Wireless Communications 7, nr 1 (styczeń 2008): 184–92. http://dx.doi.org/10.1109/twc.2008.060420.

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Ren, Huarong, Weikai Xu i Lin Wang. "Multiple-Mode Orthogonal Time Frequency Space with Index Modulation". Electronics 11, nr 16 (19.08.2022): 2600. http://dx.doi.org/10.3390/electronics11162600.

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Recently, orthogonal time frequency space modulation with index modulation (OTFS-IM) has been proposed to improve the bit-error-rate (BER) performance of the OTFS system. However, only some of the grids in the OTFS-IM system are activated, resulting in low spectral efficiency (SE). In order to solve this problem, a new scheme called multiple-mode OTFS-IM (MM-OTFS-IM) is proposed in this paper. In the proposed scheme, all grids are activated to transmit modulation bits. Each grid in the subblock adopts a different modulation mode, and the index bits are transmitted implicitly by the combination of different constellation modes. At the receiver, a distance-based signal detection algorithm is designed, which uses the distance matrix to find the combination of the minimum sum of elements to recover the index bits. The simulation results demonstrate the enhanced performance of the proposed scheme in the time-varying channels.

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5

Zhendong Luo, Junshi Liu, Ming Zhao, Yuanan Liu i Jinchun Gao. "Double-orthogonal coded space-time-frequency spreading CDMA scheme". IEEE Journal on Selected Areas in Communications 24, nr 6 (czerwiec 2006): 1244–55. http://dx.doi.org/10.1109/jsac.2005.864007.

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Shao, Chao, Cun Yao Xu i Xin Shi. "A Column Orthogonality Space-Time-Frequency Coding Schemes". Advanced Materials Research 846-847 (listopad 2013): 1044–47. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.1044.

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A column orthogonal space-time-frequency coding scheme is presented, its induced cost207 transmit environment channel matrix has greater determinant value, which will lead result in amplifying the signal-to noise ratio of system, and improving the performance of the system. Computer simulations confirm the theory of the article.

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7

An, Changyoung, i Heung-Gyoon Ryu. "Design and Performance Evaluation of MIMO(Multiple Input Multiple Output) System Using OTFS(Orthogonal Time Frequency Space) Modulation". Journal of Korean Institute of Electromagnetic Engineering and Science 28, nr 6 (czerwiec 2017): 444–51. http://dx.doi.org/10.5515/kjkiees.2017.28.6.444.

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Zhao, Hang, Dongxuan He, Ziqi Kang i Hua Wang. "Orthogonal Time Frequency Space (OTFS) With Dual-Mode Index Modulation". IEEE Wireless Communications Letters 10, nr 5 (maj 2021): 991–95. http://dx.doi.org/10.1109/lwc.2021.3053981.

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Wei, Zhiqiang, Weijie Yuan, Shuangyang Li, Jinhong Yuan, Ganesh Bharatula, Ronny Hadani i Lajos Hanzo. "Orthogonal Time-Frequency Space Modulation: A Promising Next-Generation Waveform". IEEE Wireless Communications 28, nr 4 (sierpień 2021): 136–44. http://dx.doi.org/10.1109/mwc.001.2000408.

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Li, Qiao, Zheng Xiang, Peng Ren i Wanlu Li. "Variational autoencoder based receiver for orthogonal time frequency space modulation". Digital Signal Processing 117 (październik 2021): 103170. http://dx.doi.org/10.1016/j.dsp.2021.103170.

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Shen, Wenqian, Linglong Dai, Jianping An, Pingzhi Fan i Robert W. Heath. "Channel Estimation for Orthogonal Time Frequency Space (OTFS) Massive MIMO". IEEE Transactions on Signal Processing 67, nr 16 (15.08.2019): 4204–17. http://dx.doi.org/10.1109/tsp.2019.2919411.

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Tran, Le Chung, Alfred Mertins i Tadeusz A. Wysocki. "Quasi-orthogonal space-time-frequency codes in MB-OFDM UWB". Computers & Electrical Engineering 36, nr 4 (lipiec 2010): 766–74. http://dx.doi.org/10.1016/j.compeleceng.2008.11.014.

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Yuan, Weijie, Zhiqing Wei, Jiamo Jiang, Shun Zhang, Jinhong Yuan i Pingzhi Fan. "Guest editorial: Orthogonal time frequency space modulation in 6G era". China Communications 20, nr 1 (styczeń 2023): iii—vi. http://dx.doi.org/10.23919/jcc.2023.10038836.

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Koroupi, Farokh, Alireza Morsali, Vida Niktab, Mostafa Shahabinejad i Siamak Talebi. "Quasi-orthogonal space–frequency and space–time–frequency block codes with modified performance and simplified decoder". IET Communications 11, nr 11 (3.08.2017): 1655–61. http://dx.doi.org/10.1049/iet-com.2016.0277.

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

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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.

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Mheidat, Hakam, Murat Uysal i Naofal Al-Dhahir. "Quasi-Orthogonal Time-Reversal Space–Time Block Coding for Frequency-Selective Fading Channels". IEEE Transactions on Signal Processing 55, nr 2 (styczeń 2007): 772–78. http://dx.doi.org/10.1109/tsp.2006.885766.

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Wei, Zhiqiang, Weijie Yuan, Shuangyang Li, Jinhong Yuan i Derrick Wing Kwan Ng. "Transmitter and Receiver Window Designs for Orthogonal Time-Frequency Space Modulation". IEEE Transactions on Communications 69, nr 4 (kwiecień 2021): 2207–23. http://dx.doi.org/10.1109/tcomm.2021.3051386.

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Ebi Elias J, Robinson. "Quasi-Orthogonal Space-Time-Frequency Trellis Codes for Mimo-OFDM Systems". International Journal of Software Engineering & Applications 3, nr 3 (31.05.2012): 23–33. http://dx.doi.org/10.5121/ijsea.2012.3303.

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19

Liang, Wei, Xuan Liu, Jia Shi, Lixin Li i Junfan Hu. "Underlying Security Transmission Design for Orthogonal Time Frequency Space (OTFS) Modulation". Sensors 22, nr 20 (18.10.2022): 7919. http://dx.doi.org/10.3390/s22207919.

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With the aim of ensuring secure transmission in high-mobility wireless scenarios, this paper proposes a 2D permutation-aided Orthogonal Time Frequency Space (OTFS) secure transmission scheme, which uses the Gosudarstvennyi Standard (GOST) algorithm to perform disturbance control on the OTFS modulation domain. Furthermore, we develop an improved SeLective Mapping (SLM) algorithm, which can significantly improve the Peak-to-Average Power Ratio (PAPR) problem with very low complexity. In addition, we carry out the security analysis, investigating the proposed scheme’s resistance performance to a range of effective attacks. Finally, our numerical results show that our proposed transmission scheme can guarantee the underlying security property of OTFS.

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20

Raviteja, P., Khoa T. Phan, Yi Hong i Emanuele Viterbo. "Interference Cancellation and Iterative Detection for Orthogonal Time Frequency Space Modulation". IEEE Transactions on Wireless Communications 17, nr 10 (październik 2018): 6501–15. http://dx.doi.org/10.1109/twc.2018.2860011.

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21

Lee, Keonkook, Youngok Kim i Joonhyuk Kang. "A novel orthogonal space-time-frequency block code for OFDM systems". IEEE Communications Letters 13, nr 9 (wrzesień 2009): 652–54. http://dx.doi.org/10.1109/lcomm.2009.090680.

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22

Flores, Jorge, Jaime Sanchez i Hamid Jafarkhani. "Quasi-Orthogonal Space-Time-Frequency Trellis Codes for Two Transmit Antennas". IEEE Transactions on Wireless Communications 9, nr 7 (lipiec 2010): 2125–29. http://dx.doi.org/10.1109/twc.2010.07.090774.

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23

Li, Jun, Miaowen Wen, Xueqin Jiang i Wei Duan. "Space-Time Multiple-Mode Orthogonal Frequency Division Multiplexing With Index Modulation". IEEE Access 5 (2017): 23212–22. http://dx.doi.org/10.1109/access.2017.2761845.

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Lampel, Franz, Hamdi Joudeh, Alex Alvarado i Frans M. J. Willems. "Orthogonal Time Frequency Space Modulation Based on the Discrete Zak Transform". Entropy 24, nr 12 (22.11.2022): 1704. http://dx.doi.org/10.3390/e24121704.

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In orthogonal time frequency space (OTFS) modulation, information-carrying symbols reside in the delay-Doppler (DD) domain. By operating in the DD domain, an appealing property for communication arises: time-frequency (TF) dispersive channels encountered in high-mobility environments become time-invariant. OTFS outperforms orthogonal frequency division multiplexing (OFDM) in high-mobility scenarios, making it an ideal waveform candidate for 6G. Generally, OTFS is considered a pre- and postprocessing step for OFDM. However, the so-called Zak transform provides the fundamental relation between the DD and time domain. In this work, we propose an OTFS system based on the discrete Zak transform (DZT). To this end, we discuss the DZT and establish the input–output relation for time-frequency (TF) dispersive channels solely by the properties of the DZT. The presented formulation simplifies the derivation and analysis of the input–output relation of the TF dispersive channel in the DD domain. Based on the presented formulation, we show that operating in the DD incurs no loss in capacity.

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25

Yeh, Hen-Geul. "Tutorial for Space-Time ICI Parallel Cancellation Techniques for OFDM Systems". International Journal of Interdisciplinary Telecommunications and Networking 15, nr 1 (12.05.2023): 1–14. http://dx.doi.org/10.4018/ijitn.322788.

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Orthogonal frequency division multiplexing (OFDM) expects the subcarriers to be orthogonal. However, the factors, such as residual carrier frequency, offset time variations due to Doppler shift or phase noise leads to a loss in the orthogonality between subcarriers and results in inter-carrier interference (ICI). Further developing the parallel cancellation (PC) scheme to mitigate the ICI of OFDM systems, the authors expand this OFDM symbol-based PC scheme into a space-time (ST) coded system. This simple space-time parallel cancellation (STPC) scheme is a technique that combines the useful properties of ST and PC schemes together. Computer simulations indicate that OFDM systems using the STPC scheme outperform the regular PC and ST systems in slow and fast frequency selective fading channels, specifically at a high signal-noise ratio (SNR). Furthermore, the error floor of the STPC-OFDM system is significantly lower than that of the regular ST systems without increasing computational load.

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26

Nwanekezie, Nnamdi, Oluyomi Simpson, Gbenga Owojaiye i Yichuang Sun. "Co-Efficient Vector Based Differential Distributed Quasi-Orthogonal Space Time Frequency Coding". Sensors 23, nr 17 (30.08.2023): 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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27

B. Oluwafemi, Ilesanmi, i Stanley H. Mneney. "Hybrid Concatenated Super-orthogonal Space-time Frequency Trellis Coded MIMO-OFDM Systems". Research Journal of Applied Sciences, Engineering and Technology 8, nr 4 (25.07.2014): 530–40. http://dx.doi.org/10.19026/rjaset.8.1002.

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28

Yang, Yingchao, Zhiquan Bai, Ke Pang, Piming Ma, Haixia Zhang, Xinghai Yang i Dongfeng Yuan. "Design and analysis of spatial modulation based orthogonal time frequency space system". China Communications 18, nr 8 (sierpień 2021): 209–23. http://dx.doi.org/10.23919/jcc.2021.08.015.

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29

Bandeira, Dayse, Didier Le Ruyet, Mylene Pischella i João Mota. "Performance Evaluation of Low-Complexity Algorithms for Orthogonal Time-Frequency Space Modulation". Journal of Communication and Information Systems 35, nr 1 (2020): 138–49. http://dx.doi.org/10.14209/jcis.2020.15.

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Yuan, Weijie, Zhiqiang Wei, Jinhong Yuan i Derrick Wing Kwan Ng. "A Simple Variational Bayes Detector for Orthogonal Time Frequency Space (OTFS) Modulation". IEEE Transactions on Vehicular Technology 69, nr 7 (lipiec 2020): 7976–80. http://dx.doi.org/10.1109/tvt.2020.2991443.

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31

Farhang, Arman, Ahmad RezazadehReyhani, Linda E. Doyle i Behrouz Farhang-Boroujeny. "Low Complexity Modem Structure for OFDM-Based Orthogonal Time Frequency Space Modulation". IEEE Wireless Communications Letters 7, nr 3 (czerwiec 2018): 344–47. http://dx.doi.org/10.1109/lwc.2017.2776942.

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32

Yuan, Weijie, Jiaqi Zou, Yuanhao Cui, Xinyu Li, Junsheng Mu i Kaifeng Han. "Orthogonal Time Frequency Space and Predictive Beamforming-Enabled URLLC in Vehicular Networks". IEEE Wireless Communications 30, nr 2 (kwiecień 2023): 56–62. http://dx.doi.org/10.1109/mwc.005.2200408.

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Raslan, Walid, i Heba Abdel-Atty. "Performance Evaluation of Data Detection Methods for Orthogonal Time Frequency Space Modulation". Delta University Scientific Journal 6, nr 1 (1.04.2023): 162–80. http://dx.doi.org/10.21608/dusj.2023.291035.

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Li, Shuo, Lixia Xiao, Yangyang Liu, Guanghua Liu, Pei Xiao i Tao Jiang. "Performance analysis for orthogonal time frequency space modulation systems with generalized waveform". China Communications 20, nr 4 (kwiecień 2023): 57–72. http://dx.doi.org/10.23919/jcc.fa.2022-0452.202304.

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35

Zhao Li, 赵黎, 柯熙政 Ke Xizheng i 王惠琴 Wang Huiqin. "A Free Space Optical Communication-Orthogonal Frequency Devision Muitiplexing Model Based on Time Frequency Code". Chinese Journal of Lasers 36, nr 10 (2009): 2757–62. http://dx.doi.org/10.3788/cjl20093610.2757.

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36

Hu, Junfan, Jia Shi, Shuai Ma i Zan Li. "Secrecy Analysis for Orthogonal Time Frequency Space Scheme Based Uplink LEO Satellite Communication". IEEE Wireless Communications Letters 10, nr 8 (sierpień 2021): 1623–27. http://dx.doi.org/10.1109/lwc.2021.3072902.

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37

Deka, Kuntal, Anna Thomas i Sanjeev Sharma. "OTFS-SCMA: A Code-Domain NOMA Approach for Orthogonal Time Frequency Space Modulation". IEEE Transactions on Communications 69, nr 8 (sierpień 2021): 5043–58. http://dx.doi.org/10.1109/tcomm.2021.3075237.

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ZHANG, Yang, Qunfei ZHANG, Yingjie WANG, Chengbing HE i Wentao SHI. "A low-complexity orthogonal time frequency space modulation method for underwater acoustic communication". Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 39, nr 5 (październik 2021): 954–61. http://dx.doi.org/10.1051/jnwpu/20213950954.

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Compared with the orthogonal frequency division multiplexing (OFDM) modulation, the orthogonal time frequency space(OTFS) modulation has a lower peak-to-average power ratio. It can effectively resist the time selective fading caused by the Doppler effect and has significant performance advantages over doubly dispersive channels. However, the conventional OTFS linear minimum mean square error (LMMSE) method has a high complexity and is not easy to process in real time. In order to solve this problem, we propose a low-complexity equalization algorithm with infinite norm constraints based on the optimal coordinate reduction. The equalization algorithm not only obtains the optimal solution through a certain number of iterations and avoids direct matrix inversion but also equalizes infinite norm constraints to improve the symbol detection performance gains. At the same time, the OTFS delay-Doppler channel matrix we utilize is sparse and the two-norm squares of each column vector equally reduces the complexity of optimal coordinate descent. Finally, the simulation in the underwater acoustic communication scenario we designed verify the effectiveness of the proposed equalization algorithm. The simulation results show that the performance of the proposed equalization algorithm is close to that of the LMMSE method, while its low complexity is ensured.

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39

Yuan, Weijie, Zhiqiang Wei, Shuangyang Li, Jinhong Yuan i Derrick Wing Kwan Ng. "Integrated Sensing and Communication-Assisted Orthogonal Time Frequency Space Transmission for Vehicular Networks". IEEE Journal of Selected Topics in Signal Processing 15, nr 6 (listopad 2021): 1515–28. http://dx.doi.org/10.1109/jstsp.2021.3117404.

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Yuan, Weijie, Zhiqiang Wei, Shuangyang Li, Jinhong Yuan i Derrick Wing Kwan Ng. "Integrated Sensing and Communication-Assisted Orthogonal Time Frequency Space Transmission for Vehicular Networks". IEEE Journal of Selected Topics in Signal Processing 15, nr 6 (listopad 2021): 1515–28. http://dx.doi.org/10.1109/jstsp.2021.3117404.

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Srivastava, Suraj, Rahul Kumar Singh, Aditya K. Jagannatham i Lajos Hanzo. "Bayesian Learning Aided Sparse Channel Estimation for Orthogonal Time Frequency Space Modulated Systems". IEEE Transactions on Vehicular Technology 70, nr 8 (sierpień 2021): 8343–48. http://dx.doi.org/10.1109/tvt.2021.3096432.

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42

Oluwafemi, IlesanmiB, i StanleyH Mneney. "Review of Space-time Coded Orthogonal Frequency Division Multiplexing Systems for Wireless Communication". IETE Technical Review 30, nr 5 (2013): 417. http://dx.doi.org/10.4103/0256-4602.123126.

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Ozgul, Bariss, Mutlu Koca i Hakan Delic. "Orthogonal space-time block coding for continuous phase modulation with frequency-domain equalization". IEEE Transactions on Communications 57, nr 12 (grudzień 2009): 3579–84. http://dx.doi.org/10.1109/tcomm.2009.12.080524.

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Liu, Yusha, Lie-Liang Yang i Lajos Hanzo. "Sparse Space-Time-Frequency-Domain Spreading for Large-Scale Non-Orthogonal Multiple Access". IEEE Transactions on Vehicular Technology 69, nr 10 (październik 2020): 12327–32. http://dx.doi.org/10.1109/tvt.2020.3010437.

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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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46

Yadav, Sarita, Ashish Nema i Jitendra Mishra. "Space Time Trellis Code Frequency Index Modulation with Neuro-LS Channel Estimation in OFDM". SMART MOVES JOURNAL IJOSCIENCE 5, nr 9 (14.09.2019): 7. http://dx.doi.org/10.24113/ijoscience.v5i9.226.

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In wireless communication, orthogonal frequency division multiplexing (OFDM) plays a major role because of its high transmission rate. In space-time shift keying (STSK), the information is conveyed by both the spatial and time dimensions, which can be used to strike a trade-off between the diversity and multiplexing gains. On the other hand, orthogonal frequency division multiplexing (OFDM) relying on index modulation (IM) conveys information not only by the conventional signal constellations as in classical OFDM, but also by the indices of the subcarriers. In this paper compressed sensing(CS) is studied in order to increase throughput and bit-error performance by transmitting extra information bits in each subcarrier block as well as to decrease the complexity of the detector. In this paper, soft trellis decoding algorithm is implemented with channel estimation using Neuro-LS technique. The result analysis shows the better performance of trellis decoder with respect to BER and Neuro-LS channel estimation with respect to BER.

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47

Jia, Xizi, Gui Cheng, Yuanfa Ji, Xiyan Sun i Jianhui Wu. "GNSS Single-Frequency, Single-Epoch Attitude Determination Method with Orthogonal Constraints". Mathematical Problems in Engineering 2022 (1.03.2022): 1–9. http://dx.doi.org/10.1155/2022/4426987.

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Attitude determination is one of the most considerable applications in high-precision GNSS (Global Navigation Satellite System) positioning and navigation. For rigid-body applications, the baseline is approximately fixed on the same plane and its relative position does not change over time. This provides an important constraint that can be exploited to directly aid the attitude determination process. This study provides an attitude determination algorithm with orthogonal constraints for single frequency and single epoch by fully integrating the baseline orthogonal constraints into the observation equations. Carrier phase and pseudo-range measurement from more than two antennas are used to construct the double-difference observation equations. Given the inclusion analysis of the two search spaces, the LAMBDA algorithm is used to transform the non-ellipsoid space search into the ellipsoid space search. The attitude matrix is solved directly by the Lagrange multiplier method and the optimal solution is selected by search space verification. The analysis focuses on single-frequency, single-epoch, rigid-body attitude accuracy and calculation amount. Experimental results demonstrate that the proposed approach can effectively improve the success rate and reliability of single-frequency and single-epoch attitude resolution.

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48

Liu, Hui, Jing Shan Jiao, Fu Chun Zhang i Ling Zhou. "Channel Estimating Based on Space-Time-Frequency Pilot for MIMO-OFDM". Advanced Materials Research 429 (styczeń 2012): 179–85. http://dx.doi.org/10.4028/www.scientific.net/amr.429.179.

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The pilots that are transmitted by different transmitting antennas must be orthogonal after being shifted. So the time domain channel estimating solution is deduced through LS based on the MIMO-OFDM channel estimating model. The time domain solution need the inverse operation of matrix, and its operating quantity is large. So the three dimensions pilot based on space domain, time domain and frequency domain is designed. The method need not the inverse operation of matrix for the time domain channel estimating solution and can reduce the complexity of channel estimating and make the channel estimating error minimum. It is shown from the simulation that the channel estimating method of this paper based on space domain, time space and frequency domain pilot has better MSE and BER performances compared with the traditional LS algorithm and the document algorithm.

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49

Solyman, Ahmad AA, Hani Attar, Mohammad R. Khosravi i Baki Koyuncu. "MIMO-OFDM/OCDM low-complexity equalization under a doubly dispersive channel in wireless sensor networks". International Journal of Distributed Sensor Networks 16, nr 6 (czerwiec 2020): 155014772091295. http://dx.doi.org/10.1177/1550147720912950.

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In this article, three novel systems for wireless sensor networks based on Alamouti decoding were investigated and then compared, which are Alamouti space–time block coding multiple-input single-output/multiple-input multiple-output multicarrier modulation (MCM) system, extended orthogonal space–time block coding multiple-input single-output MCM system, and multiple-input multiple-output system. Moreover, the proposed work is applied over multiple-input multiple-output systems rather than the conventional single-antenna orthogonal chirp division multiplexing systems, based on the discrete fractional cosine transform orthogonal chirp division multiplexing system to mitigate the effect of frequency-selective and time-varying channels, using low-complexity equalizers, specifically by ignoring the intercarrier interference coming from faraway subcarriers and using the LSMR iteration algorithm to decrease the equalization complexity, mainly with long orthogonal chirp division multiplexing symbols, such as the TV symbols. The block diagrams for the proposed systems are provided to simplify the theoretical analysis by making it easier to follow. Simulation results confirm that the proposed multiple-input multiple-output and multiple-input single-output orthogonal chirp division multiplexing systems outperform the conventional multiple-input multiple-output and multiple-input single-output orthogonal frequency division multiplexing systems. Finally, the results show that orthogonal chirp division multiplexing exhibited a better channel energy behavior than classical orthogonal frequency division multiplexing, thus improving the system performance and allowing the system to decrease the equalization complexity.

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Liu, Weiqiang, Pinrong Lin, Qingtian Lü, Rujun Chen, Hongzhu Cai i Jianhua Li. "Time Domain and Frequency Domain Induced Polarization Modeling for Three-dimensional Anisotropic Medium". Journal of Environmental and Engineering Geophysics 22, nr 4 (grudzień 2017): 435–39. http://dx.doi.org/10.2113/jeeg22.4.435.

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Time domain induced polarization (TDIP) and frequency domain induced polarization (FDIP) synthetic models, incorporating three-dimensional (3D) anisotropic medium, were tested. In TDIP modeling, both resistivity and chargeability of the medium were anisotropic, and the apparent chargeability values were calculated by carrying out two resistivity forward calculations using resistivity with and without an IP effect. We analyzed the TDIP response of a 3D isotropic cube model embedded in the anisotropic subsurface half-space. In FDIP modeling, the complex resistivity of the medium at various frequencies was anisotropic. The complex resistivity was determined by a Cole-Cole model with anisotropic model parameters. We then analyzed the FDIP response of a 3D anisotropic cube model embedded in an isotropic subsurface half-space. Both of the TDIP and FDIP simulation results suggest that IP responses acquired in two orthogonal directions on the surface are different when the same arrays are used and acquisition in orthogonal directions helps resolve the presence of anisotropy. The anisotropy should be taken into account in practice for TDIP and FDIP exploration.

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