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Deep learning based channel equalization method for wireless UV MIMO scattering turbulence channel

OPTICS COMMUNICATIONS 2025年 583卷

作者： Zhao, Taifei Chen, Yuqi Sun, Yuxin Pan, Feixiang Xian Univ Technol Dept Automat & Informat Engn Xian 710048 Shaanxi Peoples R China Xian Key Lab Wireless Opt Commun & Network Res Xian 710000 Shaanxi Peoples R China Shaanxi Univ Key Lab Photon Power Devices & Discharge Regulat Taiyuan Peoples R China

Aiming at the problems of traditional equalization methods for ultraviolet (UV) multiple-input multiple-output (MIMO) channels in turbulent environments, such as their strong dependence on a priori knowledge of the channel and the low accuracy in coping with the modeling of complex nonlinear channels, this paper proposes a deep-learning-based equalization method for wireless UV-scattering MIMO channels. The method transforms the MIMO signal into a two-dimensional time series, takes the bidirectional long short-term memory (BiLSTM) with bidirectional sequence feature extraction capability as the core, and supplements it with deep neural network for nonlinear modeling to construct a deep learning network model suitable for UV MIMO channel equalization, so as to realize the accurate recovery of the original MIMO signal. Simulation results show that the scheme exhibits stronger BER and MSE performance compared with the least mean square(LMS) algorithm, recursive least squares(LMS) algorithm, and the equalization scheme based on multilayer long and short-term memory(multiLSTM). At SNR of 9 dB, the scheme reduces the BER by about 67.9%, compared with the equalization scheme based on multi-LSTM, and has stable equalization effects in turbulence environments with different intensities.

关键词： Wireless ultraviolet communication Scattering channel multiple-input multiple-output Deep learning Channel equalization Non-line-of-sight

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Hybrid Vector Message Passing for Cascaded Channel Estimation in RIS-Aided Multi-User MIMO-OFDM Systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2025年第5期24卷 4174-4189页

作者： Jiang, Wenjun Yuan, Xiaojun Di Renzo, Marco Univ Elect Sci & Technol China Natl Key Lab Wireless Commun Chengdu 611731 Peoples R China Univ Paris Saclay CNRS Cent Supelec Lab Signaux & Syst F-91192 Gif Sur Yvette France Kings Coll London Ctr Telecommun Res Dept Engn London WC2R 2LS England

This paper investigates the fundamental problem of cascaded channel estimation in reconfigurable intelligent surface (RIS) aided multi-user (MU) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. To address the high pilot overhead required by existing methods, we introduce appropriate auxiliary variables to decompose the received signal model into a subcarrier-wise bilinear sub-model and two linear sub-models with respect to the MU-to-RIS and RIS-to-base-station (BS) cascaded channels. The proposed model decomposition maintains the matrix factorization structure of the two cascaded channels and avoids the problem of parameter expansion in exiting methods. In the two linear sub-models, in addition, the cascaded channels are transformed into the delay-angle domain to leverage the joint sparsity. Based on the established models, we consider the problem of simultaneously estimating the MU-to-RIS and RIS-to-BS channel matrices as a bilinear estimation problem. To tackle this problem, we formulate a Bayesian inference framework and develop a hybrid message-passing (HVMP) algorithm to achieve approximate Bayesian inference by leveraging the Bethe method. Notably, the HVMP algorithm infers the two cascaded channels iteratively, where the covariance of each cascaded channel matrix is estimated to characterize the correlation of the matrix elements. Simulation results show that the proposed algorithm achieves accurate channel estimation with low pilot overhead while state-of-the-art baseline schemes exhibit poor performance. Furthermore, the proposed algorithm can approach the estimation oracle bound of the MU-to-RIS (or RIS-to-BS) channel which assumes perfect knowledge of the RIS-to-BS (or MU-to-RIS) channel.

关键词： Channel estimation Estimation MIMO Reconfigurable intelligent surfaces OFDM Probability density function Covariance matrices Bayes methods Europe Vectors Reconfigurable intelligent surface multiple-input multiple-output orthogonal frequency-division multiplexing cascaded channel estimation message passing

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A 1T2R High-Sensitivity and Dual-Channel Transceiver for Backscatter Communication Systems

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IEEE ACCESS 2024年 12卷 141841-141850页

作者： Lai, Sijia Zhao, Yuxiao Liu, Meng Xu, Shengliang Tang, Kuangfeng Min, Hao Fudan Univ Sch Microelect State Key Lab ASIC & Syst Shanghai 200120 Peoples R China

Owing to the rapid development of the ambient Internet of Things (IoT) industry, Backscatter Communication Systems (BCS) require higher receiver sensitivity for large-scale IoT scenarios than traditional Radio Frequency Identification (RFID) systems. This paper proposes a method of using multiple-input multiple-output (MIMO) technology to compensate for reflected signals in the 920 MHz backscatter communication systems. The researcher first created a MATLAB model to verify the theoretical feasibility and then built a One-Transmitter Two-Receiver (1T2R) BCS transceiver system compatible with the EPC global protocol for practical verification on LabVIEW. The ITIR and 1T2R tests were conducted using the National Instrument (NI) USRP-2952R device, the directional antennas, and the standard RF electronic tags. Through the process of superimposing and utilizing the phase shift between the two reflected carriers, it has been confirmed that the overall signal strength can be enhanced from 2.2 mV to 4.13 mV and 4.37 mV (nearly reaching 4.70 mV by using two Rx antennas in ideal conditions). After calculation, this advancement increases signal strength from -40.14 dBm (when using a single Rx antenna) to -34.18 dBm (when using two Rx antennas). The improvement in signal strength can provide a gain of 5.96 dB to the backscatter communication systems. Experimental results demonstrate that utilizing MIMO technology to the backscatter communication systems can effectively enhance the sensitivity of the receiver at 920 MHz.

关键词： Backscatter Transceivers Communication systems Radiofrequency identification Internet of Things Receiving antennas Sensitivity MIMO ambient Internet of Things backscatter communication systems radio frequency identification multiple-input multiple-output

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Concrete Feedback Layers: Variable-Length, Bit-Level CSI Feedback Optimization for FDD Wireless Communication Systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2024年第10期23卷 15353-15366页

作者： Ji, Dong Jin Chung, Byung Chang Seoul Natl Univ Sci & Technol Dept Semicond Engn Seoul 01811 South Korea Gyeongsang Natl Univ Dept Intelligence & Commun Engn Tongyeong 53064 South Korea

In this work, we present the innovative Concrete Feedback Layers, designed to enable genuine bit-level, end-to-end Channel State Information (CSI) feedback using deep learning techniques. Overcoming the limitations of traditional discrete operations that impede gradient flow, these layers leverage the concrete distribution to facilitate efficient learning processes. Our extensive simulations reveal that these layers significantly enhance digital CSI feedback, achieving superior performance in terms of Normalized Mean Squared Error (NMSE) and cosine similarity compared to conventional feedback models. Furthermore, the integration of the Concrete Feedback Layers with the Feedback Bit Masking Unit (FBMU) allows for authentic bit-level variable-length CSI feedback, while maintaining a single adaptable model for various feedback lengths. This advancement marks a major leap forward in deep learning-based CSI feedback methods, potentially revolutionizing 6G communication systems with its flexibility and efficiency.

关键词： Machine learning for communications deep learning channel feedback multiple-input multiple-output variable-length feedback 6G wireless systems channel state information (CSI) end-to-end learning neural network architectures channel feedback multiple-input multiple-output variable-length feedback 6G wireless systems channel state information (CSI) end-to-end learning neural network architectures

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Enhanced transmitter designs for indoor MIMO-VLC systems

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OPTICS COMMUNICATIONS 2025年 575卷

作者： Zhao, Yinan Zeng, Zhihong Cao, Hailin Chen, Chen Chongqing Univ Sch Microelect & Commun Engn Chongqing 400044 Peoples R China Natl Univ Singapore Dept Elect & Comp Engn Singapore 117576 Singapore

multiple-input multiple-output (MIMO) technology, a fundamental element of 6G, has been widely implemented invisible light communication (VLC) systems. However, actual MIMO-VLC systems face significant challenges due to severe channel correlation. To tackle this issue, in this paper, we propose two enhanced transmitter designs for performance improvement of indoor MIMO-VLC systems, including single transmitter partial coverage (STPC) and enhanced STPC. For the STPC scheme, a single LED transmitter only needs to cover part of the receiving plane, instead of covering the whole receiving plane as in the conventional single transmitter full coverage (STFC) scheme. For the enhanced STPC scheme, each light-emitting diode (LED) is replaced with an LED subarray so as to further improve the system performance. Our simulation results reveal that the system performance is influenced by the LED array spacing, LED subarray spacing, and the LED semi-angle at half power. We identify the optimal combinations of these parameters to maximize the average achievable spectrum efficiency of the system. Notably, the STPC and Enhanced STPC schemes demonstrate increases in average achievable spectrum efficiency of 478.14% and 589.49%, respectively, compared to the benchmark STFC scheme.

关键词： Visible light communication multiple-input multiple-output Single transmitter partial coverage Distributed LED array

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IA Solution in Closed-Form for Optimum DoF in the Multi-User MIMO Interference Network

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KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS 2025年第2期19卷 657-670页

作者： Liu, Weihua Zhang, Shilin Song, Wenjun Li, Baona Huang, Lixun Huang, Daoying Zhengzhou Univ Light Ind Sch Elect & Informat Zhengzhou Peoples R China Luoyang Normal Univ Sch Math Sci Luoyang Peoples R China

In the wireless communication network, interference alignment (IA) represents a technology for the management of interference that can attain the optimum degrees of freedom (DoF). The iterative IA design is highly complex and requires significant computing resources in multiple-user multiple-input multiple-output (MIMO) communication networks. The IA in closed-form design scheme has low complexity of computation, which hasn't been solved well in general multiple-user communication networks. A scheme in closed-form is proposed for the multi-user MIMO interference channel, in which an IA solution is employed to eliminate interference by the precoding sub-matrix chain and achieve the optimum DoF further. The precoding sub-matrix chain is precisely designed, and the exact solution in closed-form is obtained by the solution of linear equations. Eventually, the efficacy of the designed solution scheme is validated through simulation experiments.

关键词： Degrees of freedom interference alignment multiple-input multiple-output precoding sub-matrix chain solution in closed-form

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Block Iterative Support Detection for Uplink Grant-Free MIMO-NOMA

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IEEE WIRELESS COMMUNICATIONS LETTERS 2025年第4期14卷 1264-1268页

作者： Lei, Ruibin Zhang, Xiaoxu Shi, Fengwen Zhou, Xiangwei Zhou, Zhengchun Liu, Jiaqi Southwest Jiaotong Univ Prov Key Lab Informat Coding & Transmiss Chengdu 611756 Peoples R China Louisiana State Univ Div Elect & Comp Engn Baton Rouge LA 70803 USA Avionics Co Ltd China Elect Technol Grp Corp Commun Nav & Surveillance Dept Chengdu 611731 Peoples R China

Grant-Free-Non-orthogonal multiple access (GF-NOMA) is a powerful means to reduce signaling overhead, provide a large number of connections, and support low latency requirements in 6G Internet of Things applications. However, the accuracy of multi-user detection (MUD) remains a challenge. In this letter, we propose a Block Iterative Support Detection (BISD) MUD algorithm for GF-NOMA, which exploits the spatial diversity gain and block sparsity provided by multiple-input multiple-output (MIMO) to improve the MUD accuracy of the traditional Iterative Support Detection (ISD) algorithm. The proposed BISD algorithm efficiently updates the active support set by block-wise non-zero judgment in each iteration to improve detection accuracy. Simulation results show that BISD improves the detection performance with faster convergence speed, compared with ISD and other traditional MUD algorithms for GF-NOMA.

关键词： Multiuser detection Vectors Accuracy MIMO Indexes Transmitting antennas Simulation Receiving antennas NOMA Internet of Things multiple-input multiple-output non-orthogonal multiple access multi-user detection compressive sensing

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Spatial and Wavelength Division Joint multiplexing System Design for MIMO-OFDM Visible Light Communications

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IEEE ACCESS 2024年 12卷 109526-109543页

作者： Chen, Cheng Huang, Shenjie Tavakkolnia, Iman Safari, Majid Haas, Harald Univ Cambridge Dept Engn Elect Engn Div Cambridge CB3 0FA England Univ Edinburgh Inst Imaging Data & Commun IDCOM Sch Engn Edinburgh EH9 3FD Scotland

The low-pass characteristics of front-end elements including light-emitting diodes (LEDs) and photodiodes (PDs) limit the transmission data rate of visible light communication (VLC) and Light Fidelity (LiFi) systems. Using multiplexing transmission techniques, such as spatial multiplexing (SMX) and wavelength division multiplexing (WDM), is a solution to overcome bandwidth limitation. However, spatial correlation in optical wireless channels and optical filter bandpass shifts typically limit the achievable multiplexing gain in SMX and WDM systems, respectively. In this paper, we consider a multiple-input multiple output (MIMO) joint multiplexing VLC system that exploits available degrees-of-freedom (DoFs) across space, wavelength and frequency dimensions simultaneously. Instead of providing a new precoder/post-detector design, we investigate the considered joint multiplexing system from a system configuration perspective by tuning system parameters in both spatial and wavelength domains, such as LED positions and optical filter passband. We propose a novel spatial clustering with wavelength division (SCWD) strategy which enhances the MIMO channel condition. We propose to use a state-of-the-art black-box optimization tool: Bayesian adaptive direct search (BADS) to determine the desired system parameters, which can significantly improve the achievable rate. The extensive numerical results demonstrate the superiority of the proposed method over conventional SMX and WDM VLC systems.

关键词： Visible light communication optical wireless communication multiple-input multiple-output orthogonal frequency division multiplexing spatial multiplexing wavelength division multiplexing optical wireless communication multiple-input multiple-output orthogonal frequency division multiplexing spatial multiplexing wavelength division multiplexing

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Dual-Polarized IRS-Assisted MIMO Network

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2024年第4期23卷 2519-2532页

作者： Munawar, Muteen Lee, Kyungchun Seoul Natl Univ Sci & Technol Res Ctr Elect & Informat Technol Dept Elect & Informat Engn Seoul 01811 South Korea

This study considers a dual-polarized intelligent reflecting surface (DP-IRS)-assisted multiple-input multiple-output (MIMO) single-user wireless communication system. The transmitter and receiver are equipped with DP antennas, and each antenna features a separate phase shifter for each polarization. We attempt to maximize the system's spectral efficiency (SE) by optimizing the operations of the reflecting elements at the DP-IRS, precoder/combiner at the transmitter/receiver, and vertical/horizontal phase shifters at the DP antennas. To address this problem, we propose a three-step alternating optimization (AO) algorithm based on the semi-definite relaxation method. Next, we consider asymptotically low/high signal-to-noise ratio (SNR) regimes and propose low-complexity algorithms. In particular, for the low-SNR regime, we derive computationally low-cost closed-form solutions. According to the obtained numerical results, the proposed algorithm outperforms the various benchmark schemes. Specifically, our main algorithm exhibits a 65.6% increase in the SE performance compared to random operations. In addition, we compare the SE performance of DP-IRS with that of simple IRS (S-IRS). For $N = 50$ , DP-IRS achieves 24.8%, 28.2%, and 30.3% improvements in SE for 4 x 4 , 8 x 8 , and 16 x 16 MIMO, respectively, compared to S-IRS.

关键词： Intelligent reflecting surface dual polarization multiple-input multiple-output alternating optimization

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Data-driven calibration of decoupling matrix for MIMO precision motion stages

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ISA TRANSACTIONS 2024年 150卷 223-231页

作者： Liu, Kaixin Liu, Yang Song, Fazhi Tan, Jiubin Harbin Inst Technol Dept Control Sci & Engn Harbin 15001 Peoples R China Harbin Inst Technol Ultraprecis Optoelect Instrument Engn Harbin 15080 Peoples R China

Decoupling control is a commonly employed technique for achieving high precision in multiple -input multipleoutput (MIMO) motion control systems. A static decoupling matrix, which can be determined using geometric construction, is widely used due to its practicality and simplicity. However, inaccurate geometric parameters will lead to a coarse decoupling matrix, and result in interactions among the system axes and performance deterioration. To tackle this challenge, various attempts have been undertaken to calibrate the decoupling matrix. Data -driven on-line approaches have gained considerable attention for their ability to calibrate the decoupling matrix without interrupting the normal operation of the system. This paper presents a data -driven approach to calibrate the decoupling matrix for MIMO and linear time invariant (LTI) systems. Through some reasonable assumptions, a calibrated static decoupling matrix can be derived to improve the performance of the system. Moreover, considering the inevitable presence of measurement noise, the consistency of the proposed method has been analyzed. As a result, the instrument variable is introduced in the improved method to eliminate the impact of the measurement noise. Finally, the effectiveness and practicality of the proposed method are demonstrated through both numerical simulations and experiments carried out on an ultraprecision wafer stage.

关键词： Calibration Data-driven Decoupling matrix multiple-input multiple-output Precision motion stage

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