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space-time coding Design for RIS-Assisted Integrated Sensing and Communication System

IEEE WIRELESS COMMUNICATIONS LETTERS 2024年第7期13卷 1943-1947页

作者： Liu, Yifei Wu, Liang Zhang, Zaichen Dang, Jian Zhu, Bingcheng Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Peoples R China Southeast Univ Nanjing 211111 Peoples R China

This letter designs a reconfigurable intelligent surface (RIS) assisted integrated sensing and communication (ISAC) system, where time division multiplexing cooperated with the space-time coding for the RIS is employed. In the communication subframe, the RIS is utilized to realize quadrature phase shift keying (QPSK) modulation. During the sensing, the angle information corresponding to the location of the user is extracted by controlling the space-time code of the RIS. Addressing the instability and low sensing accuracy of the traditional random coding strategy, this letter proposes a spatial codebook design scheme, which improves the sensing performance greatly. Besides, the transmitter performs beamforming based on the sensing information, achieving the synergistic enhancement of the communication quality and sensing accuracy.

关键词： Sensors Symbols Vectors Encoding Antenna arrays Wireless communication Array signal processing Integrated sensing and communication (ISAC) reconfigurable intelligent surface (RIS) space-time coding sensing codebook

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DOA Estimation Method Based on space-time coding Antennas With Orthogonal Codes

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2024年第2期72卷 1173-1181页

作者： Fang, Zuqi Zhou, Qunyan Dai, Jun Yan Qi, Zhen Jie Zhang, Jianan Cheng, Qiang Cui, Tie Jun Southeast Univ State Key Lab Millimeter Waves Nanjing 210096 Peoples R China

Recently, direction-of-arrival (DOA) estimation has been widely employed in wireless communication networks, electromagnetic (EM) environment management, and radar tracking. However, traditional DOA estimation algorithms and systems are based on multiple digital receivers with expensive hardware. To overcome this challenge, we propose a novel DOA estimation method based on a space-time coding antenna. With the aid of space-time coding antenna and orthogonal codes, the received signal of each antenna element can be reproduced with high accuracy, helping to obtain more information on the incident waves. In this case, traditional super-resolved DOA estimation algorithms can be employed to estimate more complicated signals using the space-time coding antenna. Compared to the previous studies on similar accuracy, the proposed method has lower complexity and higher flexibility due to the reproduction of complete element information and the use of multiple signal classification (MUSIC) algorithm. The method can operate in the azimuth angle between -60(degrees) and 60(degrees), with angle estimation errors of less than 1.5(degrees), the estimation RMSE of 0.7(degrees), and high reliability for different modulated signals.

关键词： Estimation Direction-of-arrival estimation Encoding Antennas Signal processing algorithms Antenna measurements Receiving antennas Antenna array direction of arrival (DOA) estimation multiple signal classification (MUSIC) algorithm orthogonal codes space-time coding

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A Novel space-time coding Echo Separation Scheme with Orthogonal Frequency Division Multiplexing Chirp Waveforms for Multi-Input Multi-Output Synthetic Aperture Radar

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SENSORS 2025年第6期25卷 1717-1717页

作者： Yao, Kai Liu, Chang Chinese Acad Sci Aerosp Informat Res Inst Beijing 100094 Peoples R China Univ Chinese Acad Sci Sch Elect Elect & Commun Engn Beijing 100049 Peoples R China

Multi-input Multi-output Synthetic Aperture Radar (MIMO-SAR) systems significantly improve the performance of traditional SAR systems by providing more system freedom. However, in the working mode of the simultaneous transceiver, each receiving antenna will receive the scattered echoes of all transmitting antennas, resulting in the overlapping of echo data and serious related interference, which becomes the main obstacle to the further development and application of MIMO-SAR system. Therefore, achieving effective echo separation is the key technical challenge faced by the MIMO-SAR system. space-time coding (STC) uses multiple dimensions, such as space, time, and frequency. Through the process of encoding and decoding in these dimensions, channel information can be obtained, and echo separation can be realized. STC is suitable for MIMO-SAR system on different platforms, such as airborne, and has wide applicability. When the traditional scheme uses STC as a coding scheme, it is generally limited by the two-dimensional sending and receiving matrix of Alamouti code. To solve this problem, a new STC scheme based on complex orthogonal matrix design is proposed in this paper. The scheme can form a multidimensional orthogonal STC matrix, recover the superposed signal by echo decoding, and improve the echo signal-to-noise ratio (SNR) of MIMO-SAR. In addition, the use of orthogonal frequency division multiplexing (OFDM) waveform can further reduce cross-correlation interference to achieve effective separation of MIMO-SAR echoes. The effectiveness of the waveform scheme is verified by numerical experiments.

关键词： space-time coding MIMO-SAR OFDM waveform SNR

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Ultra-Wideband Simultaneous Manipulations of Fundamental and Harmonic Waves Based on space-time coding Metasurface: Basic Principles and mmWave Applications

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LASER & PHOTONICS REVIEWS 2025年第8期19卷

作者： Liu, Yujie Wang, Yu Fu, Xiaojian Luo, Jiang Zhu, Ziyi Xu, Hang Wang, Peng Fu, Yuan Cao, Liu Xu, Yongjun Cui, Tie Jun Southeast Univ State Key Lab Millimeter Waves Nanjing 210096 Peoples R China Southeast Univ Inst Electromagnet Space Nanjing 210096 Peoples R China Hangzhou Dianzi Univ Sch Elect & Informat Hangzhou 310018 Peoples R China Chongqing Univ Posts & Telecommun Sch Commun & Informat Engn Chongqing 400065 Peoples R China

A 2-bit millimeter-wave (mmWave) space-time coding metasurface (STCM) based on an innovative theoretical mechanism and encoding strategy to boost the performance of wireless communications is proposed. Specifically, this metasurface can switch between four different modes by controlling the working states of the active components loaded on the metasurface element. Combined with a simple, efficient, and robust mechanism and encoding strategy, it achieves arbitrary phase controls of the fundamental and harmonic frequencies over an ultra-wideband range. Based on these developments, a single-aperture, multi-channel mmWave wireless communication system is constructed that basically spans the entire V-band. It is demonstrated that different data are transmitted under the quadrature phase shift keying modulation scheme at the fundamental and harmonic frequencies, with an operating bandwidth exceeding 25 GHz. Furthermore, the research has achieved an ultrafast single-aperture communication rate, while seamlessly integrating information modulation and beamforming into the system. The proposed mmWave STCM-based communication architecture, both compact and miniaturized, offers an efficient and low-complexity solution for achieving comprehensive coverage, affordability, high capacity, and reliable communications in the next-generation wireless networks.

关键词： dual channel metasurface millimeter wave space-time coding wireless communications

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Toward Sub-Terahertz: space-time coding Metasurface Transmitter for Wideband Wireless Communications

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ADVANCED SCIENCE 2023年第29期10卷 e2304278页

作者： Liu, Yujie Wang, Yu Fu, Xiaojian Shi, Lei Yang, Fei Luo, Jiang Zhou, Qun Yan Fu, Yuan Chen, Qi Dai, Jun Yan Zhang, Lei Cheng, Qiang Cui, Tie Jun Southeast Univ State Key Lab Millimeter Waves Nanjing 210096 Peoples R China Southeast Univ Inst Electromagnet Space Nanjing 210096 Peoples R China Hangzhou Dianzi Univ Sch Elect & Informat Hangzhou 310018 Peoples R China

A space-time coding metasurface (STCM) operating in the sub-terahertz band to construct new-architecture wireless communication systems is proposed. Specifically, a programmable STCM is designed with varactor-diode-tuned metasurface elements, enabling precise regulation of harmonic amplitudes and phases by adjusting the time delay and duty cycle of square-wave modulation signal loaded on the varactor diodes. Independent electromagnetic (EM) regulations in the space and time domains are achieved by STCM to realize flexible beam manipulations and information modulations. Based on these features, a sub-terahertz wireless communication link is constructed by employing STCM as a transmitter. Experimental results demonstrate that the STCM supports multiple modulation schemes including frequency-shift keying, phase-shift keying, and quadrature amplitude modulations in a wide frequency band. It is also shown that the STCM is capable of realizing wide-angle beam scanning in the range of & PLUSMN;45(o), which offers an opportunity for user tracking during the communication. Thus, the STCM transmitter with high device density and low power consumption can provide low-complexity, low-cost, low-power, and low-heat solutions for building the next-generation wireless communication systems in the sub-terahertz frequency and even terahertz band.

关键词： metasurface space-time coding sub-terahertz wireless communications

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space-time coding design for multiple source nodes full-duplex cooperative communication 95

Space-time coding design for multiple source nodes full-dupl...

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IEEE 95th Vehicular Technology Conference: (VTC-Spring)

作者： Liu, Ligang Qu, Qing Zhou, Bin Zhao, Yu Bu, Zhiyong Chinese Acad Sci Shanghai Inst Microsyst & Informat Technol Shanghai 200050 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

ISBN: (数字)9781665482431

ISBN: (纸本)9781665482431

Cooperative communication is a promising technology to improve the performance of resource-limited or cost-sensitive single antenna wireless equipment. Moreover, full duplex (FD) could theoretically double the spectral efficiency of a cooperative communication system comparing to the conventional half duplex (HD) communication. Although researchers have studied FD cooperative communication with two source nodes, and proposed an Alamouti-style space-time code, there is not much works on multiple source nodes scenarios yet. This article presents our results on the FD cooperative communication with multiple source nodes. We provide two orthogonal space-time block codes (OSTBC) for both three and four source nodes scenarios. The proposed codes skillfully share data in as less time slots as possible by taking advantages of the FD communication. Consequently, spectral efficiency of the FD cooperation is improved. Furthermore, the proposed codes provide full diversity in addition to a simple ML decoding. Finally, computer simulations verify the performance of the proposed OSTBC design.

关键词： cooperative communication virtual MIMO full duplex space-time coding distributed space-time coding

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Adaptive Beamforming Based on space-time coding Metasurface Antenna with Hadamard Codes 15

Adaptive Beamforming Based on Space-Time Coding Metasurface ...

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15th Global Symposium on Millimeter-Waves & Terahertz (GSMM)

作者： Fang, Zuqi Southeast Univ State Key Lab Millimeter Waves Nanjing Peoples R China

ISBN: (纸本)9798350384963;9798350384956

A novel adaptive beamforming method utilizing the space-time coding metasurface and Hadamard codes is presented. By the modulation of the signal received by each element, the sum modulated signal can be received by single receiver. Then, the sum signal is used to reproduce each element's received signal. Ultimately, the reproduced signals are employed in adaptive beamforming, with the weighting vectors obtained from the traditional adaptive beamforming algorithm. Compared with the traditional adaptive beamforming method with digital array, the proposed method requires only single receiver, which greatly simplifies the receiver structure. In the end, the simulation proves the feasibility of the proposed adaptive beamforming method.

关键词： Beamforming space-time coding orthogonal codes metasurface

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space-time coding Technique for Coherent Frequency Diverse Array

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2021年 69卷 5994-6008页

作者： Wang, Huake Quan, Yinghui Liao, Guisheng Zhu, Shengqi Xu, Jingwei Huang, Lei Xidian Univ Xian 710071 Peoples R China Xidian Univ Natl Key Lab Radar Signal Proc Xian 710071 Shaanxi Peoples R China Shenzhen Univ Coll Informat Engn Shenzhen 518060 Peoples R China

Coherent frequency diverse array (FDA) radar is able to cover all directions with a stable gain by transmitting a single frequency-shifted waveform. However, it is revealed in this work that the range resolution scales linearly with the number of elements, which is limited by the fixed element number. By leveraging the relationship between the beam direction and the signal frequency, we link the sub-bands of the emitted signal to angular sectors. Based on the fact, a novel transmit diversity technique, referred to as two-dimensional (2-D) space-time coding (STC), is proposed to improve the range resolution. For a specific observation direction, the frequency band of each pulse is shifted by STC to synthesize a full bandwidth after the pulse accumulation. Furthermore, the piecewise LFM (linear frequency modulation) waveform design can be combined with the STC technique to synthesize the transmit beampattern flexibly without range resolution degradation for each pulse. Compared with the state-of-the-art technologies, the proposed STC technique has superiorities in range resolution improvement, ultra-low range sidelobe level, interference suppression, and beampattern design capability. In addition, multi-dimensional ambiguity functions are derived to assess the performance in range-angle-Doppler domain, including the range and angle resolutions, the sidelobe level (SLL) and the angular coverage. To satisfy practical demands, the general receive processing procedures are also designed. The proposed method and corresponding theoretical analysis are verified by extensive numerical results.

关键词： Encoding Radar Frequency diversity Signal resolution Array signal processing Frequency modulation time-frequency analysis Transmit diversity technique range resolution space-time coding transmit beampattern design coherent frequency diverse array

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MIMO Waveform Design for Dual Functions of Radar and Communication With space-time coding

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2022年第6期40卷 1906-1917页

作者： Wu, Wenhua Han, Guojun Cao, Yunhe Huang, Yongwei Yeo, Tat-Soon Guangdong Univ Technol Sch Informat Engn Guangzhou 510006 Peoples R China Xidian Univ Natl Lab Radar Signal Proc Xian 710071 Peoples R China Natl Univ Singapore Dept Elect & Comp Engn Singapore 119077 Singapore

Sharing a multiple-input multiple-output (MIMO) radar, the single platform can achieve dual functions of radar and communication (DFRC) within the same frequency spectrum, via the same transmit waveforms. In this paper, a space-time coding scheme is developed for transmit beamforming of DFRC and embedding communication information, without their cross-interference. For transmit beampattern design of DFRC, the shape approximation and integrated power approximation criteria are adopted respectively for waveforms optimization with the constant-envelope constraints of transmit waveforms and the equivalent signal in the communication direction. Based on the space-time coding scheme, the direct constellation mapping (DCM) and phase-rotation constellation mapping (PRCM) methods are proposed to embed information symbols. It turns out that the proposed space-time coding scheme for information constellation mapping can prevent missing information symbols and have better performance in bit-error rate (BER), compared to the existing information-embedding techniques. Moreover, the scheme can reduce the dependence of the communication data rate on radar pulse repetition frequency (PRF). Simulation results are presented to demonstrate the effectiveness of the proposed methods.

关键词： Radar Radar antennas Encoding spaceborne radar Codes Array signal processing MIMO radar MIMO waveform design transmit beamforming space-time coding constellation mapping

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High-Precision Terahertz Beam Steering via space-time coding HEMT-Metasurfaces

High-Precision Terahertz Beam Steering via Space-Time Coding...

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2023 Cross Strait Radio Science and Wireless Technology Conference, CSRSWTC 2023

作者： Nie, Xiaolei Lan, Feng Zhang, Yaxin Yang, Ziqiang Wang, Luyang Song, Tianyang Yang, Munan School of Electronic Science and Engineering Sichuan THz Communication Technology Engineering Research Center University of Electronic Science and Technology of China Chengdu China Huzhou China

ISBN: (纸本)9798350358971

Terahertz space-time coding metasurfaces (TSTCM) exhibit exquisite beam reconstruction capabilities in microwave and quasi-optical bands and have broad application prospects in wireless communications, reprogrammable holographic imaging, and direct transmission of digital information. Fourier analysis of periodic modulated signals in the time domain shows that the time delay and duty ratio independently control the incident wave. Herein, we propose an equivalent multi-bit space-time coding metasurface which based on high electron mobility transistors (HEMTs), implemented positive and negative first-order harmonic beam scanning in farfield simulation. We demonstrate the scanning result with a scanning range of ±80° and a step accuracy of 0.5°, which matched well with the designed device from 0.16THz to 0.23THz. © 2023 IEEE.

关键词： beam scanning HEMTs metasurface space-time coding

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