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Journal articles on the topic 'Modulation OTFS'

Author: Grafiati

Published: 30 November 2024

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1

Siluveru, Mounika, Dharavath Nanda, and RadhaKrishna Karne. "Study and Analysis of OTFS and OFDM." Journal of Artificial Intelligence, Machine Learning and Neural Network, no. 26 (November 29, 2022): 13–23. http://dx.doi.org/10.55529/jaimlnn.26.13.23.

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High mobility wireless communication systems have been proposed to be robust to channel-induced Doppler shift using Orthogonal Time Frequency Space (OTFS) modulation. The OTFS modulation technique is described in this paper. In addition to being in the delay-Doppler (DD) domain, OTFS has a unique and important feature. The OTFS modulation offers maximum diversity over frequency and time when coupled with an equalizer. This technique converts fading, time-varying wireless channels into time-independent, non-fading interactions that reveal their underlying geometry. Even in challenging 5G deployment settings, OTFS achieves Massive MIMO throughput gains by scaling throughput linearly with MIMO order. An analysis of peak to average power ratio (PAPR) of OFTS modulation wave forms is presented in this paper. OTFS with rectangular pulses is characterized analytically using the complementary cumulative distribution function (CCDF). The simulated CCDF for the PAPR of OTFS is compared with that for orthogonal frequency division multiplexing (OFDM) for different pulse shapes. The results show that OTFS has a better PAPR than OFDM.

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2

Ren, Huarong, Weikai Xu, and Lin Wang. "Multiple-Mode Orthogonal Time Frequency Space with Index Modulation." Electronics 11, no. 16 (August 19, 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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3

Raviteja, P., Yi Hong, Emanuele Viterbo, and Ezio Biglieri. "Effective Diversity of OTFS Modulation." IEEE Wireless Communications Letters 9, no. 2 (February 2020): 249–53. http://dx.doi.org/10.1109/lwc.2019.2951758.

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4

Ramadhan, Ali J., and Ali TaeiZadeh. "The Orthogonal Time Frequency Space (OTFS) Technique In 6G Wireless Communications." BIO Web of Conferences 97 (2024): 00128. http://dx.doi.org/10.1051/bioconf/20249700128.

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The orthogonal time-frequency space (OTFS) technique is a potential waveform modulation method that modulates data in the delaydoppler (DD) domain. OTFS differs from traditional multiplexing techniques by utilizing two-dimensional modulation to switch between the time-frequency (TF) domain and the delay-Doppler domain. This allows for handling Doppler shifts caused by fast-moving objects, a capability lacking in traditional modulation techniques like orthogonal frequency division multiplexing (OFDM). The primary goal of this paper is to offer an overview and short survey of this new topic, highlighting its system model. We also examine key aspects of OTFS modulation such as data detection methods, channel estimation, MIMO, and multiuser systems.

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5

Guo, Xiaopeng, Biao Wang, Yunan Zhu, Zide Fang, and Zhaoyue Han. "Hamming Distance Optimized Underwater Acoustic OTFS-IM Systems." Entropy 25, no. 7 (June 24, 2023): 972. http://dx.doi.org/10.3390/e25070972.

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The orthogonal time frequency space (OTFS) modulation technique can provide reliable communication in time-varying channels. Due to the dispersive characteristics of underwater acoustic channels, this paper proposes an OTFS-IM underwater acoustic communication system based on Hamming distance optimization to reduce the impact of dispersion in underwater acoustic communication. Firstly, the OTFS-IM underwater acoustic communication system is introduced, which introduces index modulation into the Delay–Doppler (DD) domain to make the OTFS system have stronger anti-Delay–Doppler capability. In contrast, since there is index sequence redundancy in a specific index combination, a Hamming distance optimization model is used to eliminate the redundant combination in the specific index combination sequence and further improve the bit error rate performance of the system. In addition, the Hamming distance optimized OTFS-IM underwater acoustic communication system is verified by simulation analysis. The results show that the proposed Hamming distance optimized OTFS-IM can achieve more reliable bit error rate performance.

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6

Lian, Dianbin, Yan Gao, and Jie Lian. "Cross-Water–Air Optical Wireless Communication Using Orthogonal Time–Frequency Space Modulation." Symmetry 16, no. 5 (May 7, 2024): 571. http://dx.doi.org/10.3390/sym16050571.

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This paper examines the communication difficulties encountered in cross-media wireless optical transmission through simulated research on the utilization of orthogonal time and frequency space (OTFS) modulation technology. Our analysis and comparison demonstrate that OTFS significantly improves the reliability and throughput of data transmission in intricate multipath channel settings. In contrast to conventional orthogonal frequency division multiplexing (OFDM) technology, OTFS displays better resilience and transmission effectiveness. We foresee additional enhancements and progress in OTFS technology to present a sturdier and more efficient resolution for wireless communication, thereby providing valuable perspectives and encouragement for associated research initiatives. Our results underscore the capability of OTFS technology to transform wireless communication systems in demanding multipath channel conditions.

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7

Xue, Yukang, and Yahong R. Zheng. "Orthogonal time-frequency space (OTFS) modulation for underwater mobile acoustic communications." Journal of the Acoustical Society of America 154, no. 4_supplement (October 1, 2023): A249. http://dx.doi.org/10.1121/10.0023445.

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This paper investigates the Orthogonal Time-Frequency Space (OTFS) Modulation for Underwater Mobile Acoustic Communications where the communication channel suffers from severe multipath and Doppler effects simultaneously. Practical OTFS modulation schemes with different parameters are designed for acoustic transmission at a center frequency of 115 kHz and a bandwidth of 11.5 kHz. The schemes are tested in lake experiments where the transmitter was anchored and the receiver was towed by a boat at a speed of approximately 1 m/s or 3.6 km/h. The receiver utilizes low-complexity channel estimation and equalization algorithms, such as NLMS (Normalized Least Mean Squares) and IPNLMS (improved proportionate NLMS) algorithms. The results show some insights of the OTFS scheme for acoustic communications. First, the mobile acoustic channel characteristics are different in the 2D delay-Doppler domain than those in the 1D time and frequency domains for the Single-Carrier Coherent Modulation (SCCM) and the Orthogonal frequency division modulation (OFDM), respectively. Second, in mobile scenarios, the OTFS scheme receiver effectively and significantly reduces the accuracy requirements of the Doppler compensation algorithm and provides better frequency-selective fading suppression and Doppler effect robustness compared to SCCM and OFDM schemes. Third, the OTFS scheme has better anti-multipath performance and reduces multipath interference by effectively differentiating signals on different paths in the 2D delay-Doppler domain.

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8

Mohammadi, Abderrahim, Saad Chakkor, Ahmed El Oualkadi, Mohamed Moussaoui, Aziz Dkiouak, and Mostafa Baghouri. "Performance Evaluation of OTFS and OFDM for 6G Waveform." ITM Web of Conferences 48 (2022): 01015. http://dx.doi.org/10.1051/itmconf/20224801015.

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Orthogonal time frequency space (OTFS) modulation is a coming technique addressing the challenges of 5G and 6G. It’s appeared to bring about outstanding error performance in delay – Doppler (DeDo) channels. Still, a really fair comparison with its competitor's direct orthogonal frequency division multiplexing and is extensively used in this participation, we will make a comparison of the performance of OTFS and OFDM with the digital modulation format in terms of bit error rate (BER) versus signal-to-noise rate (SNR) for the 16- QAM technique. From the numerical simulations under MATLAB, the results showed that the OTFS admits a small BER to the OFDM in given cases

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9

Zhang, Ji, Leqi Cai, and Huanyou Liu. "Integrated Sensing and Communication via Orthogonal Time Frequency Space Signaling with Hybrid Message Passing Detection and Fractional Parameter Estimation." Sensors 23, no. 24 (December 16, 2023): 9874. http://dx.doi.org/10.3390/s23249874.

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For the orthogonal time frequency space (OTFS) modulation, we generally multiplex symbols on a new type of carrier waveform in the delay-Doppler (DD) domain. These two parameters can be used to infer the range (R) and velocity (V) of the communication user and sensing target; thus, it is natural for the OTFS to be implemented in integrated sensing and communication (ISAC). A framework for ISAC based on OTFS modulation is proposed in this paper, in which the matched filter scheme with fractional parameter estimation is implemented for radar sensing. In addition, the hybrid message passing (MP) detection algorithm is developed for OTFS symbol demodulation. According to the simulation results, fractional DD shifts associated with multiple targets can be accurately obtained through the proposed framework. Meanwhile, the bit error rate under the proposed detector is less than 10−4 when the signal-to-noise ratio is high enough.

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10

Zhang, Mi, Xiaochen Xia, Kui Xu, Xiaoqin Yang, Wei Xie, Yunkun Li, and Yang Liu. "A Structured Sparse Bayesian Channel Estimation Approach for Orthogonal Time—Frequency Space Modulation." Entropy 25, no. 5 (May 6, 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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11

Liang, Wei, Xuan Liu, Jia Shi, Lixin Li, and Junfan Hu. "Underlying Security Transmission Design for Orthogonal Time Frequency Space (OTFS) Modulation." Sensors 22, no. 20 (October 18, 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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12

Lampel, Franz, Hamdi Joudeh, Alex Alvarado, and Frans M. J. Willems. "Orthogonal Time Frequency Space Modulation Based on the Discrete Zak Transform." Entropy 24, no. 12 (November 22, 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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13

Wang, Siqiang, Jing Guo, Xinyi Wang, Weijie Yuan, and Zesong Fei. "Pilot Design and Optimization for OTFS Modulation." IEEE Wireless Communications Letters 10, no. 8 (August 2021): 1742–46. http://dx.doi.org/10.1109/lwc.2021.3078527.

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14

Mohammed, Saif Khan. "Derivation of OTFS Modulation From First Principles." IEEE Transactions on Vehicular Technology 70, no. 8 (August 2021): 7619–36. http://dx.doi.org/10.1109/tvt.2021.3069913.

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15

Surabhi, G. D., and A. Chockalingam. "Low-Complexity Linear Equalization for OTFS Modulation." IEEE Communications Letters 24, no. 2 (February 2020): 330–34. http://dx.doi.org/10.1109/lcomm.2019.2956709.

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16

Liu, Lei, Chao Ma, Yong Duan, Xinyu Liu, and Xin Qing. "Channel Estimation and Iterative Decoding for Underwater Acoustic OTFS Communication Systems." Journal of Marine Science and Engineering 12, no. 9 (September 5, 2024): 1559. http://dx.doi.org/10.3390/jmse12091559.

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Orthogonal Time–Frequency Space (OTFS) is an innovative modulation method that ensures efficient and secure communication over a time-varying channel. This characteristic inspired us to integrate OTFS technology with underwater acoustic (UWA) communications to counteract the time-varying and overspread characteristics of UWA channels. However, implementing OTFS in UWA communications presents challenges related to overspread channels. To handle these challenges, we introduce a specialized OTFS system and offer frame design recommendations for UWA communications in this article. We propose a Doppler compensation method and a dual-domain joint channel estimation method to address the issues caused by severe Doppler effects in UWA communication. Additionally, we propose an OTFS system detection approach. This approach incorporates an iterative detection process which facilitates soft information exchange between a message passing (MP) detector and a low-density parity check (LDPC) decoder. By conducting simulations, we demonstrate that the proposed UWA OTFS system significantly outperforms Orthogonal Frequency-Division Multiplexing (OFDM), Initial Estimate Iterative Decoding Feedback (IE-IDF-MRC), and two-dimensional Passive Time Reversal Decision Feedback Equalization (2D-PTR-DFE) in UWA channels.

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17

Li, Shuangyang, Weijie Yuan, Zhiqiang Wei, Jinhong Yuan, Baoming Bai, Derrick Wing Kwan Ng, and Yixuan Xie. "Hybrid MAP and PIC Detection for OTFS Modulation." IEEE Transactions on Vehicular Technology 70, no. 7 (July 2021): 7193–98. http://dx.doi.org/10.1109/tvt.2021.3083181.

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18

Surabhi, G. D., Rose Mary Augustine, and Ananthanarayanan Chockalingam. "Peak-to-Average Power Ratio of OTFS Modulation." IEEE Communications Letters 23, no. 6 (June 2019): 999–1002. http://dx.doi.org/10.1109/lcomm.2019.2914042.

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19

Shang, Huichao, Ruifeng Chen, Haoxiang Zhang, Guoyu Ma, Ruisi He, Bo Ai, and Zhangdui Zhong. "OTFS modulation and PAPR reduction for IoT-railways." China Communications 20, no. 1 (January 2023): 102–13. http://dx.doi.org/10.23919/jcc.2023.01.009.

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20

Zhang, Yuzhi, Shumin Zhang, Bin Wang, Yang Liu, Weigang Bai, and Xiaohong Shen. "Deep Learning-Based Signal Detection for Underwater Acoustic OTFS Communication." Journal of Marine Science and Engineering 10, no. 12 (December 6, 2022): 1920. http://dx.doi.org/10.3390/jmse10121920.

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Orthogonal time frequency space (OTFS) is a novel two-dimensional (2D) modulation technique that provides reliable communications over time- and frequency-selective channels. In underwater acoustic (UWA) channel, the multi-path delay and Doppler shift are several magnitudes larger than wireless radio communication, which will cause severe time- and frequency-selective fading. The receiver has to recover the distorted OTFS signal with inter-symbol interference (ISI) and inter-carrier interference (ICI). The conventional UWA OTFS receivers perform channel estimation explicitly and equalization to detect transmitted symbols, which requires prior knowledge of the system. This paper proposes a deep learning-based signal detection method for UWA OTFS communication, in which the deep neural network can recover the received symbols after sufficient training. In particular, it cascades a convolutional neural network (CNN) with skip connections (SC) and a bidirectional long short-term memory (BiLSTM) network to perform signal recovery. The proposed method extracts feature information from received OTFS signal sequences and trains the neural network for signal detection. The numerical results demonstrate that the SC-CNN-BiLSTM-based OTFS detection method performs with a lower bit error rate (BER) than the 2D-CNN, FC-DNN, and conventional signal detection methods.

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21

Kulaç, Selman, and Müjdat Şahin. "Bit Error Rate Performance Improvement for Orthogonal Time Frequency Space Modulation with a Selective Decode-and-Forward Cooperative Communication Scenario in an Internet of Vehicles System." Sensors 24, no. 16 (August 17, 2024): 5324. http://dx.doi.org/10.3390/s24165324.

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Orthogonal time frequency space (OTFS) modulation has recently found its place in the literature as a much more effective waveform in time-varying channels. It is anticipated that OTFS will be widely used in the communications of smart vehicles, especially those considered within the scope of Internet of Things (IoT). There are efforts to obtain customized traditional point-to-point single-input single-output (SISO)-OTFS studies in the literature, but their BER performance seems a bit low. It is possible to use cooperative communications in order improve BER performance, but it is noticeable that there are very few OTFS studies in the area of cooperative communications. In this study, to the best of the authors’ knowledge, it is addressed for the first time in the literature that better performance is achieved for the OTFS waveform transmission in a selective decode-and-forward (SDF) cooperative communication scenario. In this context, by establishing a cooperative communication model consisting of a base station/source, a traffic sign/relay and a smart vehicle/destination moving at a constant speed, an end-to-end BER expression is derived. SNR-BER analysis is performed with this SDF-OTFS scheme and it is shown that a superior BER performance is achieved compared to the traditional point-to-point single-input single-output (SISO)-OTFS structure.

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22

Maršálek, Roman, Radim Zedka, Erich Zöchmann, Josef Vychodil, Radek Závorka, Golsa Ghiaasi, and Jiří Blumenstein. "Persistent Homology Approach for Human Presence Detection from 60 GHz OTFS Transmissions." Sensors 23, no. 4 (February 16, 2023): 2224. http://dx.doi.org/10.3390/s23042224.

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Orthogonal Time Frequency Space (OTFS) is a new, promising modulation waveform candidate for the next-generation integrated sensing and communication (ISaC) systems, providing environment-awareness capabilities together with high-speed wireless data communications. This paper presents the original results of OTFS-based person monitoring measurements in the 60 GHz millimeter-wave frequency band under realistic conditions, without the assumption of an integer ratio between the actual delays and Doppler shifts of the reflected components and the corresponding resolution of the OTFS grid. As the main contribution of the paper, we propose the use of the persistent homology technique as a method for processing gathered delay-Doppler responses. We highlight the advantages of the persistent homology approach over the standard constant false alarm rate target detector for selected scenarios.

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23

S Bhat, Vighnesh, Surabhi Garudanagiri Dayanand, and Ananthanarayanan Chockalingam. "Performance Analysis of OTFS Modulation With Receive Antenna Selection." IEEE Transactions on Vehicular Technology 70, no. 4 (April 2021): 3382–95. http://dx.doi.org/10.1109/tvt.2021.3063546.

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24

ZHANG, Yang, Qunfei ZHANG, Yingjie WANG, Chengbing HE, and 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, no. 5 (October 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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25

An, Changyoung, and Heung-Gyoon Ryu. "Design and Performance Evaluation of OTFS Modulation System using 2D iDFT and DFT." Journal of the Institute of Electronics and Information Engineers 54, no. 9 (September 30, 2017): 14–20. http://dx.doi.org/10.5573/ieie.2017.54.9.14.

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26

Zhao, Hang, Dongxuan He, Ziqi Kang, and Hua Wang. "Orthogonal Time Frequency Space (OTFS) With Dual-Mode Index Modulation." IEEE Wireless Communications Letters 10, no. 5 (May 2021): 991–95. http://dx.doi.org/10.1109/lwc.2021.3053981.

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27

Zhang, Yang, Qunfei Zhang, Chengbing He, Yi Zhou, and Lianyou Jing. "Delay-Doppler domain decision feedback turbo equalization for OTFS modulation." Physical Communication 52 (June 2022): 101699. http://dx.doi.org/10.1016/j.phycom.2022.101699.

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28

Ramachandran, M. K., G. D. Surabhi, and A. Chockalingam. "OTFS: A New Modulation Scheme for High-Mobility Use Cases." Journal of the Indian Institute of Science 100, no. 2 (April 2020): 315–36. http://dx.doi.org/10.1007/s41745-020-00167-4.

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29

Zhang, Yuzhi, Shumin Zhang, Yang Wang, Qingyuan Liu, and Xiangxiang Li. "Model-Driven Deep-Learning-Based Underwater Acoustic OTFS Channel Estimation." Journal of Marine Science and Engineering 11, no. 8 (August 1, 2023): 1537. http://dx.doi.org/10.3390/jmse11081537.

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Accurate channel estimation is the fundamental requirement for recovering underwater acoustic orthogonal time–frequency space (OTFS) modulation signals. As the Doppler effect in the underwater acoustic channel is much more severe than that in the radio channel, the channel information usually cannot strictly meet the compressed sensing sparsity assumption in the orthogonal matching pursuit channel estimation algorithm. This deviation ultimately leads to a degradation in system performance. This paper proposes a novel approach for OTFS channel estimation in underwater acoustic communications, utilizing a model-driven deep learning technique. Our method incorporates a residual neural network into the OTFS channel estimation process. Specifically, the orthogonal matching pursuit algorithm and denoising convolutional neural network (DnCNN) collaborate to perform channel estimation. The cascaded DnCNN denoises the preliminary channel estimation results generated by the orthogonal matching pursuit algorithm for more accurate OTFS channel estimation results. The use of a lightweight DnCNN network with a single residual block reduces computational complexity while still preserving the accuracy of the neural network. Through extensive evaluations conducted on simulated and experimental underwater acoustic channels, the outcomes demonstrate that our proposed method outperforms traditional threshold-based and orthogonal matching pursuit channel estimation techniques, achieves superior accuracy in channel estimation, and significantly reduces the system’s bit error rate.

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30

Surabhi, G. D., Rose Mary Augustine, and A. Chockalingam. "On the Diversity of Uncoded OTFS Modulation in Doubly-Dispersive Channels." IEEE Transactions on Wireless Communications 18, no. 6 (June 2019): 3049–63. http://dx.doi.org/10.1109/twc.2019.2909205.

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31

Shi, Jia, Xinyang Hu, Zhuangzhuang Tie, Xuankai Chen, Wei Liang, and Zan Li. "Reliability performance analysis for OTFS modulation based integrated sensing and communication." Digital Signal Processing 144 (January 2024): 104280. http://dx.doi.org/10.1016/j.dsp.2023.104280.

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32

Sun, Teng, Jiebiao Lv, and Tao Zhou. "A Transformer-Based Channel Estimation Method for OTFS Systems." Entropy 25, no. 10 (October 7, 2023): 1423. http://dx.doi.org/10.3390/e25101423.

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Orthogonal time frequency space (OTFS) is a novel modulation scheme that enables reliable communication in high-mobility environments. In this paper, we propose a Transformer-based channel estimation method for OTFS systems. Initially, the threshold method is utilized to obtain preliminary channel estimation results. To further enhance the channel estimation, we leverage the inherent temporal correlation between channels, and a new method of channel response prediction is performed. To enhance the accuracy of the preliminary results, we utilize a specialized Transformer neural network designed for processing time series data for refinement. The simulation results demonstrate that our proposed scheme outperforms the threshold method and other deep learning (DL) methods in terms of normalized mean squared error and bit error rate. Additionally, the temporal complexity and spatial complexity of different DL models are compared. The results indicate that our proposed algorithm achieves superior accuracy while maintaining an acceptable computational complexity.

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33

Zheng, Yuanbing, Jizhe Wang, Jian Wang, Lu Chen, Chongchong Wu, Xue Li, Yong Liao, Peng Lu, and Shaohua Wan. "GAMP-Based Low-Complexity Sparse Bayesian Learning Channel Estimation for OTFS Systems in V2X Scenarios." Electronics 12, no. 23 (November 21, 2023): 4722. http://dx.doi.org/10.3390/electronics12234722.

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Vehicle to everything (V2X) is widely regarded as a critical application for future wireless communication networks. In V2X, large relative speeds between vehicles may severely deteriorate the performance of communication between vehicles. Orthogonal time frequency space (OTFS) modulation, which converts time- and frequency-selective channels into non-selective channels in the delay-Doppler (DD) domain, provides a solution for establishing reliable wireless communications in V2X scenarios. However, in the complex multi-scattering scenarios, the channel also suffers from a serious inter-Doppler interference (IDI) problem, which poses a great challenge to the accurate demodulation of OTFS receiver signals. To address the above problems, this paper considers the variation of Doppler sampling points within one symbol when deriving the channel model, which effectively overcomes the IDI problem, and employs a basis expansion model (BEM) to convert the channel estimation into a sparse recovery problem for the basis coefficients. In addition, to better utilize the sparse nature of the OTFS channel, a generalized approximate message passing-sparse Bayesian learning (GAMP-SBL)-based algorithm is employed to estimate the basis coefficients of the channel. The complexity of this algorithm is greatly reduced compared to the conventional SBL algorithm. Finally, system simulation results are reported to verify the superiority of the proposed scheme.

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Gu, Peng, Lin Guo, Shen Jin, Guangzu Liu, and Jun Zou. "OTFS-IM Modulation Based on Four-Dimensional Spherical Code in Air-to-Ground Communication." Drones 7, no. 10 (October 10, 2023): 631. http://dx.doi.org/10.3390/drones7100631.

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Unmanned aerial vehicles (UAVs) have been widely utilized for their various advantages. However, UAVs exhibit high mobility and energy storage restrictions in some applications, which can compromise the quality and reliability of communication links. This is a challenge that future aircraft and low-orbit aircraft will inevitably encounter. To effectively address the issue of dynamic Doppler spread in air-to-ground communication, this paper creatively introduces four-dimensional spherical code modulation into the orthogonal time–frequency space with an index modulation (OTFS-IM) system. The fundamental concept of the four-dimensional spherical code is elaborated in detail. Multiple resource symbols can be jointly used to increase the modulation dimension, thereby achieving a larger minimum Euclidean distance between constellation points. Furthermore, detailed analysis is conducted on the bit error rate (BER) and the peak-to-average-power ratio (PAPR) expressions of the proposed system to evaluate its performance and provide theoretical guidance. The proposed scheme not only adapts well to high-speed scenarios but also achieves better power consumption efficiency. The simulation results demonstrate that our proposed scheme outperforms conventional methods. Its robustness and generalization ability are also validated.

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Zhang, Haojian, and Tingting Zhang. "A Low-Complexity Message Passing Detector for OTFS Modulation With Probability Clipping." IEEE Wireless Communications Letters 10, no. 6 (June 2021): 1271–75. http://dx.doi.org/10.1109/lwc.2021.3063904.

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Yuan, Weijie, Zhiqiang Wei, Jinhong Yuan, and Derrick Wing Kwan Ng. "A Simple Variational Bayes Detector for Orthogonal Time Frequency Space (OTFS) Modulation." IEEE Transactions on Vehicular Technology 69, no. 7 (July 2020): 7976–80. http://dx.doi.org/10.1109/tvt.2020.2991443.

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Shi, Wentao, Mingqi Jin, Lianyou Jing, Nan Tu, and Chengbing He. "Adaptive Channel Estimation Based on Multidirectional Structure in Delay-Doppler Domain for Underwater Acoustic OTFS System." Remote Sensing 16, no. 17 (August 27, 2024): 3157. http://dx.doi.org/10.3390/rs16173157.

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Time-varying underwater acoustic (UWA) channels are the key challenge of underwater acoustic communication (UAC). Although UAC exhibits time-variance characteristics significantly in time domains, its delay-Doppler (DD) domain representation tends to be time-invariant. Orthogonal time–frequency space (OTFS) modulation has recently been proposed and has acquired widespread interest due to its excellent performance over time-varying channels. In the UWA OTFS system, the novel DD domain channel estimation algorithm that employs a multidirectional adaptive moving average scheme is proposed. Specifically, the proposed scheme is cascaded by a channel estimator and moving average filter. The channel estimator can be employed to estimate the time-invariant channel of the DD domain multidirectionally, improving proportionate normalized least mean squares (IPNLMS). Meanwhile, the moving average filter is used to reduce the output noise of the IPNLMS. The performance of the proposed method is verified by simulation experiments and real-world lake experiments. The results demonstrate that the proposed channel estimation method can outperform those of benchmark algorithms.

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Deka, Kuntal, Anna Thomas, and Sanjeev Sharma. "OTFS-SCMA: A Code-Domain NOMA Approach for Orthogonal Time Frequency Space Modulation." IEEE Transactions on Communications 69, no. 8 (August 2021): 5043–58. http://dx.doi.org/10.1109/tcomm.2021.3075237.

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Li, Chengjie, Lidong Zhu, Cheng Guo, Tao Liu, and Zhen Zhang. "Intelligent blind source separation technology based on OTFS modulation for LEO satellite communication." China Communications 19, no. 7 (July 2022): 89–99. http://dx.doi.org/10.23919/jcc.2022.07.008.

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Tang, Zuping, Hengyou Kong, Ziyu Wu, and Jiaolong Wei. "Superimposed Perfect Binary Array-Aided Channel Estimation for OTFS Systems." Entropy 25, no. 8 (August 3, 2023): 1163. http://dx.doi.org/10.3390/e25081163.

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Orthogonal time-frequency space (OTFS) modulation outperforms orthogonal frequency-division multiplexing in high-mobility scenarios through better channel estimation. Current superimposed pilot (SP)-based channel estimation improves the spectral efficiency (SE) when compared to that of the traditional embedded pilot (EP) method. However, it requires an additional non-superimposed EP delay-Doppler frame to estimate the delay-Doppler taps for the following SP-aided frames. To handle this problem, we propose a channel estimation method with high SE, which superimposes the perfect binary array (PBA) on data symbols as the pilot. Utilizing the perfect autocorrelation of PBA, channel estimation is performed based on a linear search to find the correlation peaks, which include both delay-Doppler tap information and complex channel gain in the same superimposed PBA frame. Furthermore, the optimal power ratio of the PBA is then derived by maximizing the signal-to-interference-plus-noise ratio (SINR) to optimize the SE of the proposed system. The simulation results demonstrate that the proposed method can achieve a similar channel estimation performance to the existing EP method while significantly improving the SE.

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Zhang, Xiaoqi, Haifeng Wen, Ziyu Yan, Weijie Yuan, Jun Wu, and Zhongjie Li. "A Novel Joint Channel Estimation and Symbol Detection Receiver for Orthogonal Time Frequency Space in Vehicular Networks." Entropy 25, no. 9 (September 20, 2023): 1358. http://dx.doi.org/10.3390/e25091358.

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A vehicular network embodies a specialized variant of wireless network systems, characterized by its capability to facilitate inter-vehicular communication and connectivity with the encompassing infrastructure. With the rapid development of wireless communication technology, high-speed and reliable communication has become increasingly important in vehicular networks. It has been demonstrated that orthogonal time frequency space (OTFS) modulation proves effective in addressing the challenges posed by high-mobility environments, as it transforms the time-varying channels into the delay-Doppler domain. Motivated by this, in this paper, we focus on the theme of integrated sensing and communication (ISAC)-assisted OTFS receiver design, which aims to perform sensing channel estimation and communication symbol detection. Specifically, the estimation of the sensing channel is accomplished through the utilization of a deep residual denoising network (DRDN), while the communication symbol detection is performed by orthogonal approximate message passing (OAMP) processing. The numerical results demonstrate that the proposed ISAC system exhibits superior performance and robustness compared to traditional methods, with a lower complexity as well. The proposed system has great potential for future applications in wireless communication systems, especially in challenging scenarios with high mobility and interference.

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An, Changyoung, and 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, no. 6 (June 2017): 444–51. http://dx.doi.org/10.5515/kjkiees.2017.28.6.444.

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Xie, Jianli, Yong Hao, Cuiran Li, and Huiqin Wang. "Research on an Algorithm for High-Speed Train Positioning and Speed Measurement Based on Orthogonal Time Frequency Space Modulation and Integrated Sensing and Communication." Electronics 13, no. 22 (November 9, 2024): 4397. http://dx.doi.org/10.3390/electronics13224397.

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The Doppler effect caused by the rapid movement of high-speed rail services has a great impact on the accuracy of train positioning and speed measurement. Existing train positioning algorithms require a large number of trackside equipment and sensors, resulting in high construction and maintenance costs. Aiming to solve the above two problems, this article proposes a train positioning algorithm based on orthogonal time–frequency space (OTFS) modulation and integrated sensing and communication (ISAC). Firstly, based on the OTFS, the positioning and speed measurement architecture of communication awareness integration is constructed. Secondly, a two-stage estimation (TSE) algorithm is proposed to estimate the delay Doppler parameters of HST. In the first stage, a low-complexity coarse grid search is used, and in the second stage, a refined off-grid search is used to obtain the delay Doppler parameters. Then, the time difference of arrival/frequency difference of arrival (TDOA/FDOA) algorithm based on multiple base stations is used to locate the target, the weighted least square method is used to calculate the location, and the Cramér–Rao lower bound (CRLB) for positioning and speed measurement is derived. The simulation results demonstrate that, compared to GNSS/INS and OFDM radars, the algorithm exhibits enhanced positioning and speed measurement accuracy.

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Gao, Shuang, and Jianping Zheng. "Peak-to-Average Power Ratio Reduction in Pilot-Embedded OTFS Modulation Through Iterative Clipping and Filtering." IEEE Communications Letters 24, no. 9 (September 2020): 2055–59. http://dx.doi.org/10.1109/lcomm.2020.2993036.

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Utsuro, Hidetoshi, Toshiyuki Ando, Yoshizo Takai, Ryuichi Shimizu, and Takashi Ikuta. "Theoretical background of defocus image modulation processing (DIMP) based on three dimensional optical transfer functions (3D-OTFs)." Optik 112, no. 2 (2001): 67–75. http://dx.doi.org/10.1078/0030-4026-00012.

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Li, Tianshi, Ruisi He, Bo Ai, Mi Yang, Zhangdui Zhong, and Haoxiang Zhang. "OTFS modulation performance in a satellite-to-ground channel at sub-6-GHz and millimeter-wave bands with high mobility." Frontiers of Information Technology & Electronic Engineering 22, no. 4 (April 2021): 517–26. http://dx.doi.org/10.1631/fitee.2000468.

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Liu, Bowen, Taoming Guo, Yueshan Qin, Yangkun Hou, Hanbin Ma, and Chen Jiang. "50‐3: Invited Paper: An Active‐Matrix High‐Channel‐Count Neurostimulation System Enabled by Flexible Thin‐Film Transistors." SID Symposium Digest of Technical Papers 55, no. 1 (June 2024): 685–88. http://dx.doi.org/10.1002/sdtp.17617.

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Advanced neurostimulation systems require intimate interface with brain or peripheral nervous system to provide a therapeutic modulation for patients experiencing neural function loss. To achieve these, it requires stimulators with high‐channel counts and mechanical flexibility. In this invited paper, we showed a 4T1C neurostimulation pixel circuit with an active‐matrix architecture, offering the opportunity for high‐channel counts. In addition, a 4‐mask photolithographic process for highly uniform organic thin‐film transistor (OTFT) integrated system was demonstrated for mechanical flexibility, which shows a high device yield of 100% (50/50) and small device variation in threshold voltage of 0.64 V and in mobility of 4.9%. By implementing OTFTs to this novel neurostimulation architecture, we fabricated an OTFT‐based high‐channel‐count neurostimulation system, showing a high stimulator yield of 71.0% and small variation of 15.6% for the output stimulation currents among pixels.

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Kim, Hoon, Hee-Jun Kim, and Won-Sup Chung. "Pulsewidth Modulation Circuits Using CMOS OTAs." IEEE Transactions on Circuits and Systems I: Regular Papers 54, no. 9 (September 2007): 1869–78. http://dx.doi.org/10.1109/tcsi.2007.904677.

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Otsu, Takahiro. "From justification to modulation." Pragmatics and Cognition 25, no. 2 (December 31, 2018): 337–62. http://dx.doi.org/10.1075/pc.17028.ots.

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Abstract The English discourse marker after all and the Japanese discourse marker datte have been commonly claimed to give a reason or justification to the preceding utterance, and therefore, these two expressions are regarded as the equivalent translation counterparts to each other. This paper first attempts to propose that such an equated account is motivated by these two discourse markers constructing a similar inferential schema involved in the interpretation of the utterance including them. In fact, datte and after all make manifest similar polyfunctions according to the syntactic position although they encode different lexical information. This is because these two discourse markers are indicators that contribute to the inferential phase of communication by various degrees of modulation of a cognitive gap between two different assumptions. Another aim of this paper is to differentiate a procedural constraint these two indicators encode on the interpretation of the utterance.

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Papadopoulos, Christos, Panagiotis A. Karas, Sotirios Vasileiadis, Panagiota Ligda, Anastasios Saratsis, Smaragda Sotiraki, and Dimitrios G. Karpouzas. "Host Species Determines the Composition of the Prokaryotic Microbiota in Phlebotomus Sandflies." Pathogens 9, no. 6 (May 29, 2020): 428. http://dx.doi.org/10.3390/pathogens9060428.

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Phlebotomine sandflies are vectors of the humans’ and mammals’ parasite Leishmania spp. Although the role of gut microbiome in the biological cycle of insects is acknowledged, we still know little about the factors modulating the composition of the gut microbiota of sandflies. We tested whether host species impose a strong structural effect on the gut microbiota of Phlebotomus spp. Sandflies were collected from the island of Leros, Greece, and classified to P. papatasi, P. neglectus, P. tobbi, and P. similis, all being negative to Leishmania spp. The prokaryotic gut microbiota was determined via 16S rRNA gene amplicon sequencing. Phlebotomus species supported distinct microbial communities (p < 0.001). P. papatasi microbiota was the most distinct over-dominated by three Spiroplasma, Wolbachia and Paenibacillus operational taxonomic units (OTUs), while another Wolbachia OTU prevailed in P. neglectus. Conversely, the microbiota of P. tobbi and P. similis was composed of several less dominant OTUs. Archaea showed low presence with the dominant OTUs belonging to methanogenic Euryarcheota, ammonia-oxidizing Thaumarcheota, and Nanoarchaeota. We provide first insights into the composition of the bacterial and archaeal community of Phlebotomus sandflies and showed that, in the absence of Leishmania, host genotype is the major modulator of Phlebotomus sandfly gut microbiota.

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