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IEEE PHOTONICS JOURNAL 2022年第5期14卷 1页

作者： Krohn, Adrian Harlakin, Andrej Arms, Steffen Pachnicke, Stephan Hoeher, Peter A. Univ Kiel Dept Comp Sci Chair Informat & Coding Theory Chair Commun D-24143 Kiel Germany

In visible light communication systems, the ability to suppress interference caused by other light sources is a major benefit towards performance improvements. Especially for large transmitter arrays or even multi-cell arrangements, the interference problem needs to be handled. In previous work, we have presented a liquid crystal display (LCD) used as an adaptive interference-suppression filter mounted in front of each photodetector. The display elements are switched on and off in such a way that light emitted by unwanted light sources ideally is blocked, but light emitted by desired light sources reaches the detector. The pattern generated by the LC display has strong impact on the system performance. In this paper, we propose combined precoding in conjunction with LCD-based interference suppression in order to increase the signal-to-interference-plus-noise ratio and to ensure user fairness in massive MIMO scenarios. The suggested precoding strategy uses a new heuristic optimization approach based on the Santa Claus problem on unrelated machines known from computer sciences, and employs only binary entries in the weighting matrix. Corresponding results are compared with a genetic evolutionary optimization strategy and with conventional zero-forcing precoding. Regarding performance evaluation, we perform numerical ray-tracing simulations and present a room-scale VLC testbed for experimental verification.

关键词： Light emitting diodes Receivers Precoding Photodetectors Lighting Interference Visible light communication Free-space optical communication free-space optics interference suppression liquid crystal display multiple-input multiple-output optical communication optical wireless communication visible light communication

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Pairwise Error Probability Analysis of Dual Hop Relaying Network over Time Selective Nakagami-m Fading Channel with Imperfect CSI and Node Mobility

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TRAITEMENT DU SIGNAL 2019年第3期36卷 281-295页

作者： Shankar, Ravi Kumar, Indrajeet Mishra, Ritesh Kumar Madanapalle Inst Technol & Sci Madanapalle 517325 India Natl Inst Technol Patna Patna 800005 Bihar India

We investigate the end-to-end performance of the selective decode and forward (S-DF) relaying network over time selective independent but not necessarily identically distributed (i.n.i.d.) Nakagami-m fading channel considering practical communication constraints such as mobile nodes and imperfect channel state information (CSI). The per block average pairwise error probability (PEP) is investigated for both optimal and equal power allocation scenarios. Simulation results have been presented for various values of fading severity parameter and channel variance. The end-to-end performance is examined for various node mobility scenarios and for various antenna configurations at the source, relay and destination nodes. Simulation results confirm the accuracy of the analytical results.

关键词： selective decode-and-forward multiple-input multiple-output channel state information diversity order signal to noise ratio

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Block Sparse Bayesian Learning Based Joint User Activity Detection and Channel Estimation in Grant-Free MIMO-NOMA

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DRONES 2023年第1期7卷 27-27页

作者： Chen, Shuo Li, Haojie Zhang, Lanjie Zhou, Mingyu Li, Xuehua Beijing Informat Sci & Technol Univ Key Lab Modern Measurement & Control Technol Minist Educ Beijing 100101 Peoples R China Baicells Technol Co Ltd Beijing 100094 Peoples R China

In the massive machine type of communication (mMTC), grant-free non-orthogonal multiple access (NOMA) is receiving more and more attention because it can skip the complex grant process to allocate non-orthogonal resources to serve more users. To address the limited wireless resources and substantial connection challenges, combining grant-free NOMA and multiple-input multiple-output (MIMO) is crucial to further improve the system's capacity. In the grant-free MIMO-NOMA system, the base station should obtain the relevant information of the user before data detection. Thus, user activity detection (UAD) and channel estimation (CE) are two problems that should be solved urgently. In this paper, we fully consider the sparse characteristics of signals and the spatial correlation between multiple antennas in the grant-free MIMO-NOMA system. Then, we propose a spatial correlation block sparse Bayesian learning (SC-BSBL) algorithm to address the joint UAD and CE problems. First, by fully mining the block sparsity of signals in the grant-free MIMO-NOMA system, we model the joint UAD and CE problem as a three-dimensional block sparse signal recovery problem. Second, we derive the cost function based on the hierarchical Bayesian theory and spatial correlation. Finally, to estimate the channel and the set of active users, we optimize the cost function with fast marginal likelihood maximization. The simulation results indicate that, compared with the existing algorithms, SC-BSBL can always fully use the signal sparsity and spatial correlation to accurately complete UAD and CE under various user activation probabilities, SNRs, and the number of antennas. The normalized mean square error of CE can be reduced to 0.01, and the UAD error rate can be less than 10(-5).

关键词： sparse Bayesian learning grant-free multiple-input multiple-output non-orthogonal multiple access channel estimation user active detection

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Efficient control of a nonlinear solid oxide fuel cell system using an adaptive model predictive controller

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INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS 2021年第11期31卷

作者： Gupta, Preeti Pahwa, Vivek Verma, Yajvender Pal Panjab Univ Univ Inst Engn & Technol Chandigarh India

Over the years, the solid oxide fuel cell (SOFC) is growing commercially due to its high fuel flexibility, lesser maintenance requirement, and environmental friendliness feature. However, its control is challenging due to its nonlinear behavior and simultaneous management of its operational constraints. Therefore, in this work, an adaptive model predictive control is designed systematically to handle the SOFC's behavior while optimizing its operational constraints such as fuel input, utilization factor, and change in pressure of hydrogen and oxygen. This model-oriented control linearizes, augments, and discretizes the SOFC during run time while estimating the states using a time-varying Kalman filter. Finally, it optimizes the control problem for predicting the internal states of the SOFC using successive linearization. The simulation results show that the proposed controller gives better performance of the SOFC in linear region, and significantly improved performance in nonlinear region in comparison to the conventional model predictive controller. The validation of the work has been done through real-time simulation using OPAL-RT's hardware setup. Using such control is beneficial as it enhances the efficiency of the SOFC significantly. Thus, this advanced controller is most suited for these kinds of nonlinear systems due to its superior performance.

关键词： adaptive model predictive control dynamic model fuel utilization factor linearly time-invariant multiple-input multiple-output model predictive control nonlinear system solid oxide fuel cell time-variant Kalman filter

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Secrecy enhancement in MIMO-OFDM-IM systems with limited RF chains

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PHYSICAL COMMUNICATION 2019年 35卷 100706-000页

作者： Gao, Zhenzhen Shen, Di Liao, Xuewen Xi An Jiao Tong Univ Dept Informat & Commun Engn Xian 710049 Shaanxi Peoples R China

A physical layer security scheme is proposed to resist eavesdropping of a multiple-input multiple-output (MIMO) system using orthogonal frequency-division multiplexing with index modulation (OFDM-IM) in the presence of a multiple-antenna passive eavesdropper, where limited number of radio frequency (RF) chains is required and additional bits are conveyed through the indices of activated transmit antennas. The secure transmission against eavesdropping is achieved by injecting artificial noise (AN) in the frequency and spatial domains. When 2 RF chains are used, the structure of quadrature spatial modulation (QSM) is exploited. The generated OFDM-IM symbols are split into two orthogonal parts, and precoded ANs are injected into each part to produce combined symbols for transmission. The secure scheme is extended to general scenarios when other number of RF chains are available based on the idea of generalized spatial modulation (GSM) and AN. The secrecy rates of the proposed schemes are analyzed, and a closed-form approximation for the ergodic secrecy rate is derived to reduce the computation complexity. The power allocation ratio and design parameters are discussed through numerical simulations. Compared to the existing secure OFDM-IM scheme (modified for MIMO systems), the proposed secure MIMO OFDM-IM shows better performance against eavesdropping when the eavesdropping and legitimate links have the same channel quality and the eavesdropping-legitimate channel correlation is considered. When 2 RF chains are available, the secure scheme based on QSM is recommended since it outperforms the secure scheme based on GSM with 2 RF chains. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Orthogonal frequency division multiplexing Index modulation multiple-input multiple-output Physical layer security

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Two-Stage Channel Estimation for Semi-Passive RIS-Assisted Millimeter Wave Systems

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SENSORS 2022年第15期22卷 5908-5908页

作者： Peng, Chengzuo Deng, Honggui Xiao, Haoqi Qian, Yuyan Zhang, Wenjuan Zhang, Yinhao Cent South Univ Sch Phys & Elect Lushan South Rd Changsha 410083 Peoples R China

In a reconfigurable intelligent surface (RIS) assisted millimeter Wave (mmWave) communication system, the channel coefficient increases exponentially with the number of RIS elements which results in expensive pilot overhead. Most previous works have proposed some channel estimation algorithms for the estimation accuracy of cascaded channels, which have improved the estimation accuracy, but the pilot overhead is discouraging in the estimation process. To improve the channel estimation accuracy with reduced pilot overhead, we propose a two-stage channel estimation protocol by exploiting semi-passive elements and the coherent time difference of the channel, where the quasi-static channel between the base stations (BS) and RIS is estimated at the RIS, and the user (UE)-RIS time-varying channel is estimated at the BS. In the first stage, we formulate the BS-RIS channel estimation as a mathematical optimization problem by an iterative weighting method and then propose a gradient descent (GD)-based algorithm to solve it. In the second stage, we first transform the received the UE-RIS signal model into an equivalent parallel factor (PARAFAC) tensor model and estimate the UE-RIS channel by the least-squares (LS) algorithm. The simulation results show that the proposed method has better estimation accuracy than the LS, compression sensing (CS) and minimum mean square error (MMSE) methods with less pilot overhead, and the spectral efficiency is improved by at least 10.5% compared to the other three methods.

关键词： reconfigurable intelligent surface semi-passive channel estimation multiple-input multiple-output

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Deep Learning-Aided OFDM-Based Generalized Optical Quadrature Spatial Modulation

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2022年第1期14卷 1页

作者： Chen, Chen Zeng, Lin Zhong, Xin Fu, Shu Liu, Min Du, Pengfei Chongqing Univ Sch Microelect & Commun Engn Chongqing 400044 Peoples R China A STAR Singapore Inst Mfg Technol Singapore 138634 Singapore

In this paper, we propose an orthogonal frequency division multiplexing (OFDM)-based generalized optical quadrature spatial modulation (GOQSM) technique for multiple-input multiple-output optical wireless communication (MIMO-OWC) systems. Considering the error propagation and noise amplification effects when applying maximum likelihood and maximum ratio combining (ML-MRC)-based detection, we further propose a deep neural network (DNN)-aided detection for OFDM-based GOQSM systems. The proposed DNN-aided detection scheme performs the GOQSM detection in a joint manner, which can efficiently eliminate the adverse effects of both error propagation and noise amplification. The obtained simulation results successfully verify the superiority of the deep learning-aided OFDM-based GOQSM technique for high-speed MIMO-OWC systems.

关键词： Light emitting diodes Optical transmitters Optical modulation Modulation High-speed optical techniques Adaptive optics Spatial indexes Optical wireless communication orthogonal frequency division multiplexing multiple-input multiple-output deep neural network

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High-isolation eight-element MIMO array for unbroken metal-rimmed smartphone applications

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2022年第12期32卷 e23404-e23404页

作者： Ren, Aidi Yang, Lixia Huang, Zhixiang Yu, Hong-wei Chen, Qian Liu, Ying Anhui Univ Informat Mat & Intelligent Sensing Lab Anhui Prov Hefei 230601 Peoples R China China Elect Technol Corp Res Inst 38 Hefei Peoples R China Xidian Univ Natl Key Lab Antennas & Microwave Technol Xian Peoples R China

ABSTARCT In this paper, a high-isolation eight-unit multiple-input multiple-output (MIMO) array is proposed, which applies to future smartphones with unbroken metal frames. Two types of elements (inverted H-shaped slot antenna [IHSA] and modified top-loaded monopole [MTLM]) are adopted to realize low mutual coupling, and the detailed decoupling mechanism is also presented. The IHSA with a better-reduced ground effect is utilized, which contributes to suppressing mutual coupling. To further enhance isolation, the MTLM without ground clearance is exploited, which cannot excite the radiated mode of the IHSA. To mitigate the effects of an unbroken metal frame, a shorting strip is introduced, which not only improves the impedance matching but also reduces the profile of the MTLM. Ultimately, the proposed MIMO system integrated with an unbroken metal frame is constituted by four IHSAs and four MTLMs, which offers a measured isolation of more than 20 dB. What's more, the calculated envelop correlation coefficients (ECCs) are less than 0.013.

关键词： 5G communication high isolation multiple-input multiple-output unbroken metal frame

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Scalp-Implanted Ultra-Wideband Circularly Polarized MIMO Antenna for Biotelemetry Systems

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SENSORS 2024年第23期24卷 7522页

作者： Song, Zhiwei Shi, Youwei Zheng, Xianren Wang, Yuchao Xinjiang Univ Sch Elect Engn Shengli Rd 666 Urumqi 830046 Peoples R China

This paper presents an innovative, compact, dual-element, implantable, ultra-wideband, circularly polarized multiple-input multiple-output (MIMO) antenna designed to operate within the 2.45 GHz industrial, scientific, and medical band, and both of its radiating units are circularly polarized antennas with polarization diversity. Specifically, antenna-1 exhibits left-handed circular polarization properties, while antenna-2 demonstrates right-handed circular polarization properties. The slots in the radiating patch and ground plane help the antenna achieve 690 MHz (2.14-2.83 GHz) ultra-wide bandwidth characteristics and circularly polarized characteristics. Additionally, a slit connecting two U-slots on the ground plane allows the antenna to achieve a wide effective circularly polarized axial ratio bandwidth of 400 MHz (2.23-2.63 GHz). The antenna is compact, with dimensions of 0.065 x 0.057 x 0.0042 lambda 03 (lambda 0 represents the free-space wavelength corresponding to the lowest operating frequency). The proposed antenna system's performance was evaluated with a seven-layer homogeneous human head model, a real human head model, and minced pork. This evaluation revealed that the antenna attained a peak gain of -24.1 dBi and an isolation level of 27.5 dB. Furthermore, the assessment included the antenna's link margin (LM), key MIMO channel characteristics, and Specific Absorption Rate (SAR) metrics. The results indicate that the antenna performs exceptionally well.

关键词： biotelemetry circular polarization multiple-input multiple-output polarization diversity ultra wideband

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Optical spatial modulation design

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PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 2020年第2169期378卷 20190195-20190195页

作者： Cogalan, T. Haas, H. Panayirci, E. Univ Edinburgh Li Fi R&D Ctr Edinburgh EH9 3J1 Midlothian Scotland Kadir Has Univ Dept Elect & Elect Engn TR-34083 Istanbul Turkey

Visible light communication (VLC) systems are inherently signal-to-noise ratio (SNR) limited due to link budget constraints. One favourable method to overcome this limitation is to focus on the pre-log factors of the channel capacity. multiple-input multiple-output (MIMO) techniques are therefore a promising avenue of research. However, inter-channel interference in MIMO limits the achievable capacity. Spatial modulation (SM) avoids this limitation. Furthermore, the performance of MIMO systems in VLC is limited by the similarities among spatial channels. This limitation becomes particularly severe in intensity modulation/direct detection (IM/DD) systems because of the lack of phase information. The motivation of this paper is to propose a system that results in a multi-channel transmission system that enables reliable multi-user optical MIMO SM transmission without the need for a precoder, power allocation algorithm or additional optics at the receiver. A general bit error performance model for the SM system is developed for an arbitrary number of light-emitting diodes (LEDs) in conjunction with pulse amplitude modulation. Based on this model, an LED array structure is designed to result in spatially separated multiple channels by manipulating the transmitter geometry. This article is part of the theme issue 'Optical wireless communication'.

关键词： light-fidelity multiple-input multiple-output spatial modulation intensity modulation and direct detection pulse amplitude modulation multi-user multiple-input multiple-output

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