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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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space-time coding for high-throughput interleave division multiplexing aided multi-source co-operation

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ELECTRONICS LETTERS 2008年第5期44卷 367-369页

作者： Zhang, R. Hanzo, L. Univ Southampton Sch ECS Southampton SO17 1BJ Hants England

Designed is an error-resilient, yet high-throughput interleave division multiplexing based space-time code suitable for multi-source co-operation. Its achievable rate, power efficiency and flexibility have been charac... 详细信息

关键词： space-time coding high-throughput interleave division multiplexing multisource cooperation Codes space-time code space-time codes

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space-time coding with receive combiner bank for multiple-input-multiple-output system under multi-user cochannel interference

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IET COMMUNICATIONS 2013年第2期7卷 180-186页

作者： Wang, Jui Teng Natl Chi Nan Univ Grad Inst Commun Engn Puli Nantou Taiwan

space-time coding with receive combiner bank (STC-RCB), in which a bank of receive combiners is added before the space-time decoder for interference-plus-noise suppression, is proposed. Without loss of generality, the author consider space-time block code (STBC) to be the representative of STC and study the performance for (STBC-RCB). The author derive the output signal to interference-plus-noise ratio (SINR) (of the space-time decoder) for STBC-RCB under multi-user cochannel interference. By regarding STBC as a special case of STBC-RCB, the author also derive the output SINR for STBC under multi-user cochannel interference. Simulation results show that the output SINR of STBC-RCB can be much larger than that of STBC, also, they show that STBC-RCB can adopt the appropriate receive combining strategy in the RCB to further improve the performance.

关键词： time coding outgoing signal Cochannel interference SINR space time block coding combiner output system space-time coding multiple input multiple output systems

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space-time coding ambiguities in joint adaptive channel estimation and detection

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2004年第2期52卷 372-384页

作者： Gazor, S Rad, HS Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

This paper studies the error propagation effect that is caused by certain ambiguities in joint data detection-channel tracking algorithms for transmission diversity schemes. Here, we use a space-time (ST) receiver based on the maximum a posteriori (MAP) method that takes into account the channel estimation error assuming the unknown channel to have a given complex multivariate Gaussian probability density function (pdf) (i.e., a Ricean channel). The decision criterion that is expressed in quadratic form represents either a linear detector or a noncoherent-nonlinear detector in extreme cases. Then, the channel pdf for the next iteration is updated by estimates of the second-order statistics of the channel coefficients, and a very simple decision-directed adaptive algorithm is derived for adaptive channel estimation. The adaptive algorithm can efficiently track a fast Rayleigh fading channel and, as a result, achieves robust performance. However, the occurrence of two types of ambiguities initiated in deep fades result in error propagation. Some remedies called space-time ambiguity remedies (STARs) are proposed to prevent error propagation. A new time-varying space-time coding (TVST) scheme is suggested as a bandwidth-efficient method to combat the permutation ambiguity impairment. This coding scheme, in conjunction with a differential detector, can resolve the ambiguity problem.

关键词： joint adaptive data detection-channel estimation permutation ambiguity phase ambiguity space-time ambiguity space-time ambiguity remedy space-time coding time-varying space-time coding transmit diversity

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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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space-time coding over correlated fading channels with antenna selection

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2006年第1期5卷 34-39页

作者： Bahceci, I Altunbasak, Y Duman, TM Univ Waterloo Dept Elect Engn Waterloo ON N2L 3G1 Canada Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA Arizona State Univ Dept Elect Engn Tempe AZ 85287 USA

In a previous paper by Bahceci et al., antenna selection for multiple-antenna transmission systems under the assumption that the subchannels between antenna pairs fade independently was studied. In this paper, the performance of such systems when the subchannels experience correlated fading is considered. It is assumed that the channel-state information (CSI) is available only at the receiver, the antenna selection is performed only at the receiver, and the selection is based on the instantaneous received signal power. The effects of channel correlations on the diversity and coding gain when the receiver system is a subset of the antennas are quantified. Theoretical results indicate that the correlations in the channel do not degrade the diversity order, provided that the channel is full rank. However, it does result in some performance loss in the coding gain.

关键词： antenna selection diversity multiple-antenna communications multiple-input-multiple-output (MIMO) systems pairwise error probability (PEP) space-time coding spatial fading correlation

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space-time coding waveform design for MIMO radar transmit beamforming with minimum MFL

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DIGITAL SIGNAL PROCESSING 2019年 89卷 124-130页

作者： Wu, Wenhua Cao, Yunhe Wu, Chun-lin Wang, Yu Xidian Univ Natl Lab Radar Signal Proc Xian 710071 Shaanxi Peoples R China Naval Aeronaut Univ Qingdao Campus Qingdao 266041 Shandong Peoples R China

In this paper, we utilize a space-time coding (STC) scheme to synthesize the multiple-input multiple-output (MIMO) radar transmit beampattern and meanwhile consider the matched filtering loss (MFL) of equivalent signal in waveform design. To solve the MFL optimization problem, we propose a simulated annealing based (SA-based) algorithm to effectively find the optimal solution of STC waveform matrix. Our STC method for waveform design has suppressed the fluctuation of equivalent signal so that has the advantage of achieving the minimum MFL nearly, compared to the conventional methods for constant-envelope constraint waveform design (e.g. cyclic algorithm (CA) method). Simulation results demonstrate the effectiveness of the proposed algorithm. (C) 2019 Elsevier Inc. All rights reserved.

关键词： Multiple-input multiple-output radar space-time coding Transmit beamforming Matched filtering loss

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space-time coding MIMO-OFDM SAR for High-Resolution Imaging

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2011年第8期49卷 3094-3104页

作者： Wang, Wen-Qin Univ Elect Sci & Technol China Sch Commun & Informat Engn Chengdu 611731 Peoples R China

Multiple-input and multiple-output (MIMO) radar has received renewed attention in recent years, but little work on MIMO synthetic aperture radar (SAR) remote sensing has been reported. This paper presents a scheme of space-time coding MIMO orthogonal frequency division multiplexing (OFDM) SAR for high-resolution imaging. This system employs MIMO configuration in the elevation direction and the Alamouti space-time coding scheme in the azimuth direction, along with the use of OFDM waveform diversity and displaced phase center antenna (DPCA) techniques. As an orthogonal transmission waveform is required for this novel space-time coding MIMO-OFDM SAR system, one kind of OFDM linearly frequency modulated waveforms is investigated. The matched filtering and multibeam forming in the elevation direction are detailed. Additionally, the corresponding mathematical relations and signal models for high-resolution imaging are formed. In this way, efficient spatial diversity gain and improved range resolution are obtained by the MIMO configuration, and the requirement of pulse repeated frequency for wide-swath remote sensing is reduced by the DPCA technique. The feasibility is validated by numerical simulation results.

关键词： High resolution and wide swath multiple-input and multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) synthetic aperture radar (SAR) MIMO radar MIMO SAR space-time coding waveform diversity

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

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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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