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On the Spectral Efficiency of Orbital Angular Momentum With Mode Offset

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2021年第11期70卷 11748-11760页

作者： Almradi, Ahmed Abbasi, Muhammad Ali Babar Matthaiou, Michail Fusco, Vincent F. BT Labs Ipswich IP5 3RE Suffolk England Queens Univ Inst Elect Commun & Informat Technol ECIT Belfast BT3 9DT Antrim North Ireland

Thanks to its low transceiver complexity, mode division multiplexing (MDM) using orbital angular momentum (OAM) has been recently investigated as a new physical layer wireless transmission technique. This is due to the fact that different OAM modes are spatially orthogonal to each other, thus, perfectly suitable for spatial multiplexing and/or diversity. The orthogonality amongst different OAM modes is achieved in the absence of any mode offset between the transceivers' phase-shifting feeding networks. However, the inherent presence of OAM mode offset destroys the orthogonality between different modes, which gives rise to inter-mode interference (IMI). Therefore, in this paper, in order to theoretically analyze the negative impact of OAM mode offset of MDM-OAM systems on the spectral efficiency of line-of-sight free-spacewireless communication systems, an explicit signal-to-interference-plus-noise ratio expression for each OAM mode is derived, through which the spectral efficiency degradation is evaluated. Furthermore, in order to support our theoretical analysis, a 9 x 9 MDM-OAM practical communication experiment for different OAM mode settings is carried out at a microwave frequency of 5.8 GHz. In addition, by leveraging the fact that all circulant matrices always have the same eigendirections, regardless of the entries of the matrix, a low-complexity optimal OAM mode selection scheme is proposed which significantly improves the spectral efficiency of the system. Finally, in order to completely null-out the impact of OAM mode offset, a baseband zero-forcing stage is embedded at the receiver.

关键词： Mode division multiplexing multiple-input multiple-output systems orbital angular momentum spatial multiplexing uniform circular antenna array zero-forcing

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A non-stationary relay-based 3D MIMO channel model with time-variant path gains for human activity recognition in indoor environments

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ANNALS OF TELECOMMUNICATIONS 2021年第11-12期76卷 827-837页

作者： Hicheri, Rym Abdelgawwad, Ahmed Patzold, Mathias Univ Agder Fac Sci & Engn NO-4898 Grimstad Norway

Extensive research showed that the physiological response of human tissue to exposure to low-frequency electromagnetic fields is the induction of an electric current in the body segments. As a result, each segment of the human body behaves as a relay, which retransmits the radio-frequency (RF) signal. To investigate the impact of this phenomenon on the Doppler characteristics of the received RF signal, we introduce a new three-dimensional (3D) non-stationary channel model to describe the propagation phenomenon taking place in an indoor environment. Here, the indoor space is equipped with a multiple-input multiple-output (MIMO) system. A single person is moving in the indoor space and is modelled by a cluster of synchronized moving point scatterers, which behave as relays. We derive the time-variant (TV) channel transfer function (CTF) with TV path gains and TV path delays. The expression of the TV path gains is obtained from the instantaneous total received power at the receiver side. This TV total received power is expressed as the product of the TV power of the RF signal initially transmitted and received by a body segment and the TV received power of the redirected signal. These TV powers are determined according the free-space path-loss model. Also, a closed-form approximate solution to the spectrogram of the TVCTF is derived. Here, we analyse the effect of the motion of the person and the validity of the relay assumption on the spectrogram, the TV mean Doppler shift (MDS), and the TV Doppler shift (DS) of the TVCTF. Simulation results are presented to illustrate the proposed channel model.

关键词： Non-stationary channels Doppler characteristics Time-variant path gains Spectrogram multiple-input multiple-output systems Human activities recognition

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Field-Programmable System-on-Chip-Based Control System for Real-Time Distortion Correction in Optical Imaging

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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS 2021年第4期68卷 3370-3379页

作者： Radner, Hannes Stange, Johannes Buttner, Lars Czarske, Jurgen Tech Univ Dresden Fac Elect & Comp Engn Lab Measurement & Sensor Syst Tech D-01062 Dresden Germany

The digital transition requires real-time control of complex systems with short loop time and low latency in various applications. Field-programmable gate arrays (FPGAs) are, in principle, capable of complying with this task but demand, on the other hand, a high programming effort. In this article, we propose a field-programmable system on chip (FPSoC) as a hybrid solution of an FPGA and a central processing unit (CPU) on a single monolithic die to combine the strengths of both architectures. An FPSoC-based adaptive optical wavefront correction system is presented as a case study to correct camera images in real time that are distorted by time-varying aberrations. While a short total loop time is achieved by interfacing the camera and a deformable mirror on a low level directly with the FPGA, all computationally nonintensive tasks are implemented on the CPU to keep the flexibility, reusability, and development expense low. The system corrects the optical distortion of water surface waves with up to 3600 control cycles per second and spatially attenuates the distortion up to Zernike polynomial 14 with up to 150 Hz. The FPSoC system enables fast spatiotemporal aberration correction in technical processes and offers a perspective for measuring complex flows through fluctuating interfaces.

关键词： Optical distortion Optical surface waves Adaptive optics Optical sensors Optical imaging Mirrors Distortion measurement Adaptive optics field-programmable system on chip (FPSoC) multiple-input multiple-output systems wavefront correction

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Channel correlation relied grouped spatial modulation for massive MIMO systems

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IET COMMUNICATIONS 2020年第8期14卷 1241-1250页

作者： Zuo, Xingxuan Zhang, Jiankang Mu, Xiaomin Yang, Lie-Liang Zhengzhou Univ Sch Informat Engn Zhengzhou 450001 Henan Peoples R China Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

Massive multiple-input multiple-output (MIMO) systems with hundreds of correlated antennas at base station are capable of offering abundant spatial resources. When spatial-domain modulation is applied to these systems, the spatial modulation (SM) using only one radiofrequency chain benefits practical implementation, but suffers from significantly reduced multiplexing gain offered by the massive number of antennas. By contrast, the generalised SM (GSM) allows to simultaneously activate multiple transmit antennas, which improves spatial multiplexing gain, but degrades the achievable error performance, as its design pays no attention to the antenna correlation. The authors propose an antenna grouped SM (GrSM) scheme, which is capable of circumventing the shortcomings of both the SM and GSM schemes suffered in massive MIMO scenarios. In the proposed GrSM scheme, transmit antennas are partitioned into multiple groups, where the relatively strongly correlated antennas within individual groups are used to implement component SM schemes, while the relatively weakly correlated antennas in different groups are beneficial to obtain multiplexing gain. In order to further improve the spectral efficiency, adaptive modulation is integrated with GrSM to form the adaptive GrSM (AGrSM). The achievable error and spectral efficiency performance of GrSM and AGrSM systems are investigated based on both mathematical analysis and Monte-Carlo simulations, which are also compared with that of the conventional SM and GSM schemes, when massive MIMO communication scenarios are considered. Their studies and performance results show that GrSM is a promising transmit scheme for massive MIMO, which can outperform both the SM and GSM schemes.

关键词： MIMO communication transmitting antennas multiplexing Monte Carlo methods adaptive modulation mathematical analysis antenna arrays wireless channels channel correlation spatial modulation massive MIMO systems multiple-input multiple-output systems base station abundant spatial resources spatial-domain modulation radiofrequency chain benefits practical implementation reduced multiplexing gain generalised SM multiple transmit antennas spatial multiplexing gain achievable error performance antenna correlation SM scheme GSM schemes massive MIMO scenarios GrSM scheme relatively strongly correlated antennas individual groups component SM schemes relatively weakly correlated antennas adaptive modulation adaptive GrSM spectral efficiency performance AGrSM systems conventional SM massive MIMO communication scenarios promising transmit scheme

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Constellation coordination and pilot reuse for multi-cell large-scale MIMO systems

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IET COMMUNICATIONS 2020年第2期14卷 357-363页

作者： Xu, Fangmin Wang, Haiquan Wang, Honggang Cao, Haiyan Hangzhou Dianzi Univ Inst Commun Engn Hangzhou Zhejiang Peoples R China Univ Massachusetts UMass Dartmouth Dept Elect & Comp Engn Dartmouth MA USA

To alleviate pilot contamination for multi-cell large-scale multiple-input multiple-output (MIMO) systems, here the authors propose a constellation coordination scheme according to a constellation coordination constraint (CC constraint) on the large-scale fading factors. In fact, a detailed analysis of the uplink process introduces the CC constraint, which reveals that if the CC constraint cannot be satisfied, the error probability will be larger than a threshold. Otherwise, the error probability goes to zero if both the number of antennas at the base station and signal-to-noise ratio go to infinity. Furthermore, by modelling the location of users as a Poisson point process, the authors derive a safe area threshold according to the CC constraint, through which an adaptive pilot reuse is proposed. In this scheme, users outside the dynamic safe area threshold are allowed to reuse the pilot, while other users are not allowed. Simulation results show that the CC scheme alleviates the pilot contamination effectively and the proposed pilot reuse scheme based on the safe area threshold improves the uplink achievable rate of the system significantly.

关键词： MIMO communication channel estimation cellular radio antenna arrays error statistics CC constraint large-scale fading factors uplink process error probability signal-to-noise ratio Poisson point process adaptive pilot reuse dynamic safe area threshold CC scheme pilot contamination pilot reuse scheme large-scale MIMO systems multiple-input multiple-output systems constellation coordination scheme constellation coordination constraint

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QOSTBC coded MIMO system with reduced complexity and optimised decoding for rank deficient channels

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IET COMMUNICATIONS 2020年第4期14卷 646-654页

作者： Gupta, Bhasker Balyan, Vipin Saini, Davinder S. CCET ECE Dept Sect 26 Chandigarh India Cape Peninsula Univ Technol EEC Dept Cape Town South Africa

In multiple-input multiple-output (MIMO) systems, rank deficient channels are the most common and key areas of research. In these channels, the number of transmit antennas (M-Tx) is higher than receive antennas (M-Rx) and subsequently the unknown variables are more than the number of equations. In such situations, the conventional sphere decoder (SD) fails due to the presence of zero diagonal elements in Cholesky decomposition. This study analyses the quasi-orthogonal space-time block code (QOSTBC) of symbol rate-2 for M-Tx = 4 with modified double-layer SD detection to overcome rank deficiency problem. The first half of transmitted symbols is detected using two partially dependent SDs with optimised search radii. The remaining half is detected by employing single symbol maximum likelihood detection. Simulation and analytical results indicate that the proposed detection scheme reduces bit error rate and complexity compared to existing techniques.

关键词： channel coding space-time block codes maximum likelihood detection decoding transmitting antennas MIMO communication receiving antennas error statistics antenna arrays communication complexity search problems rank deficient channels multiple-input multiple-output systems transmitting antennas sphere decoder zero diagonal elements quasiorthogonal space-time block code symbol rate-2 modified double-layer SD detection rank deficiency problem single symbol maximum likelihood detection bit error rate QOSTBC coded MIMO system search radii optimisation receiving antennas Cholesky decomposition

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Low-complexity signal detection for large-scale MIMO systems with second-order Richardson method

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ELECTRONICS LETTERS 2020年第9期56卷 467-469页

作者： Khoso, Imran A. Zhang, Xiaofei Shaikh, Abdul Hayee Nanjing Univ Aeronaut & Astronaut Coll Elect & Informat Engn Nanjing 211100 Peoples R China

Linear minimum mean-square error (MMSE) detection achieves near-optimal performance in large-scale multiple-input multiple-output (LS-MIMO) systems but entails high computational complexity due to large matrix inversion operations. In this Letter, a novel computationally efficient algorithm based on second-order Richardson method is proposed to solve the LS-MIMO detection problem. While no a priori information for the first iteration of the second-order Richardson method is available, the conjugate gradient scheme is exploited that greatly reduces the number of iterations to achieve the desired performance. Moreover, the eigenvalue-based acceleration parameters are proposed to further accelerate the convergence rate. Numerical results demonstrate that the proposed detector outperforms the existing methods and approaches the performance of MMSE with a small number of iterations.

关键词： mean square error methods least mean squares methods signal detection matrix inversion MIMO communication iterative methods computational complexity eigenvalues and eigenfunctions large-scale MIMO systems second-order Richardson method linear minimum mean-square error detection achieves near-optimal performance multiple-input multiple-output systems high computational complexity matrix inversion operations computationally efficient algorithm LS-MIMO detection problem eigenvalue-based acceleration parameters low-complexity signal detection

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Multi-class import vector machine for transmit antenna selection in MIMO systems

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ELECTRONICS LETTERS 2020年第2期56卷 62-65页

作者： Yang, Xiaofeng Zhao, Feng Yulin Normal Univ Sch Phys & Telecommun Engn Yulin Guangxi Peoples R China

Antenna selection is a promising solution to reduce the high cost of multiple RF chains in multiple-input multiple-output (MIMO) systems while maintaining the benefits of spatial diversity and multiplexing gain. By modelling the problem of transmit antenna selection as a multi-class classification and/or decision-making task, this Letter proposed a multi-class import vector machine (IVM) based approach to maximise the average received signal-to-noise ratio (SNR). Simulation results prove that IVM outperforms the conventional optimisation driven algorithm and the state-of-the-art learning-based scheme of support vector machine in terms of average received SNR performance with feasible complexity and sparsity.

关键词： pattern classification transmitting antennas MIMO systems antenna arrays learning (artificial intelligence) MIMO communication multiplexing support vector machines transmit antenna selection MIMO systems multiple RF chains multiple-input multiple-output systems spatial diversity multiplexing gain multiclass import vector machine based approach IVM support vector machine average received SNR performance

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Joint source-and-relay beamforming for multiple-input multiple-output systems with single-antenna distributed relays

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IET COMMUNICATIONS 2012年第1期6卷 62-68页

作者： Li, C. Wang, X. Yang, L. Zhu, W. -P. Southeast Univ Minist Educ Key Lab Underwater Acoust Signal Proc Nanjing 210096 Peoples R China Southeast Univ Sch Informat Sci & Engn Nanjing 210096 Peoples R China Nanjing Univ Dept Math Nanjing 210093 Peoples R China Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada

A joint source-and-relay beamforming scheme is proposed for multiple-input multiple-output ( MIMO) systems with distributed single-antenna relays. First, a lower-bound of the signal-to-noise ratio at the destination is derived as an objective function to formulate a constrained beamforming optimisation problem. The joint beamforming problem is then divided into two sub-optimisation problems corresponding to the source and the relay beamforming, respectively. The first sub-problem is shown to be a quadratic concave minimisation, and is tackled by developing an iterative algorithm with each iteration solving a linear problem. The second one corresponds to a Rayleigh-Ritz ratio problem which is then solved by the generalised singular-value decomposition in a closed form. Based on the solutions to the subproblems, a global iterative algorithm is designed to implement the joint source-and-relay beamforming. Simulation results show that the proposed method outperforms some existing relaying schemes in terms of the capacity and outage probability of the whole MIMO relay system.

关键词： multiple-input multiple-output systems suboptimisation problems Rayleigh-Ritz ratio problem minimisation signal-to-noise ratio joint source-and-relay beamforming scheme global iterative algorithm quadratic concave minimisation MIMO relay system linear problem Optimisation techniques probability single-antenna distributed relays generalised singular-value decomposition iterative methods concave programming constrained beamforming optimisation problem antenna arrays Antenna arrays array signal processing Interpolation and function approximation (numerical analysis) lower-bound Radio links and equipment outage probability MIMO communication Other topics in statistics

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Exploiting transformation optics for arbitrary manipulation of antenna radiation pattern

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IET MICROWAVES ANTENNAS & PROPAGATION 2019年第9期13卷 1271-1279页

作者： Barati, Hooman Fakheri, Mohammad Hosein Abdolali, Ali Iran Univ Sci & Technol Sch Elect Engn Appl Electromagnet Lab Tehran *** Iran

Using transformation optics, a general method for tailoring the radiation pattern of a monopole antenna encompassed by a coating layer is proposed. Unlike previous studies, the propounded approach is not restricted to special patterns and can produce arbitrary radiation pattern with customisable beam parameters such as number, direction, and directivity in both azimuthal and elevation planes. A linear coordinate transformation is established to simplify the coating layer realisation via offering homogeneous materials. As proof-of-principle, two different antennas capable of generating multiple beams and a single-directive beam, are elaborately acquired by a meta-structure consisting of a split-ring resonator-wire array composite. It was observed that the experimental results corroborate numerical simulations. The proposed approach is believed to have potential applications in antenna technologies, satellite communication, and multiple-input multiple-output systems.

关键词： MIMO communication monopole antennas antenna radiation patterns metamaterial antennas strip line resonators multiple beams single-directive beam meta-structure consisting split-ring resonator-wire array composite antenna technologies multiple-input multiple-output systems transformation optics antenna radiation pattern monopole antenna arbitrary radiation pattern customisable beam parameters linear coordinate transformation coating layer realisation homogeneous materials azimuthal planes elevation planes

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