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A combinatorial precoding scheme of cell-free massive MIMO with channel aging

IET COMMUNICATIONS 2022年第16期16卷 1889-1900页

作者： Fang, Hao Hu, Han Yang, Longxiang Zhang, Yao Qiao, Xu Nanjing Univ Posts & Telecommun Wireless Commun Key Lab Jiangsu Prov Nanjing 210003 Peoples R China Zhejiang Normal Univ Coll Phys & Elect Engn Jinhua Zhejiang Peoples R China

Here, we investigate the precoding schemes for the downlink data transmission of a time-division duplex cell-free massive multiple-input multiple-output (MIMO) system with channel aging, which arises from the user mobility. Closed-form spectral efficiency (SE) expressions of the downlink with the normalized conjugate beamforming (NCB), and the full-pilot zero-forcing (FZF), are derived, which are used for the analytical system performance evaluation. Then, a novel combinatorial precoding scheme with enhanced system SE performance, which adopts either NCB or FZF according to each user channel aging condition, is proposed. Moreover, a pilot allocation strategy is proposed to alleviate the extra interference brought by the combinatorial precoding scheme. Also, a statistical channel cooperative power control is employed to further improve the performance for all the above precoding schemes. Numerical results show that the proposed precoding scheme can substantially improve the average downlink SE.

关键词： power control analytical system performance evaluation user channel aging condition user mobility wireless channels enhanced system SE performance time-division duplex cell-free MIMO communication statistical analysis NCB ageing array signal processing precoding combinatorial precoding scheme closed-form spectral efficiency expressions combinatorial mathematics statistical channel cooperative power control multiple-input multiple-output system average downlink SE cooperative communication cell-free massive MIMO novel combinatorial downlink data transmission

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How orbital angular momentum modes are boosting the performance of radio links

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IET MICROWAVES ANTENNAS & PROPAGATION 2018年第10期12卷 1625-1632页

作者： Drysdale, Timothy D. Allen, Ben Stevens, Chris Berry, Simon J. Smith, Francis C. Coon, Justin Open Univ Sch Engn & Innovat Walton Hall Milton Keynes MK4 2BB Bucks England Univ Oxford Dept Engn Sci Parks Rd Oxford OX1 3PJ England QinetiQ Adv Serv & Prod Cody Technol Pk Farnborough GU14 0LX Hants England

This study focuses on the application of orbital angular momentum (OAM) modes for enhancing radio communications. It is shown that OAM modes can enhance the spectral efficiency of line-of-sight links where there is limited or no diversity gain, and also increase physical layer security. multiple-input multiple-output systems, in comparison, can struggle to give spectral efficiency improvements in line-of-sight links because they are not typically configured to exploit OAM modes. The concept of specifically using OAM modes shows great promise provided that several challenges are addressed. This study aims to clarify OAM in the context of applications to which it is well suited, such as high-capacity point-to-point links alongside transport infrastructure, within data centres, and between buildings.

关键词： angular momentum radio links telecommunication security MIMO communication orbital angular momentum mode radio link OAM mode radio communication line-of-sight link physical layer security multiple-input multiple-output system high-capacity point-to-point link transport infrastructure

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Variation of measured indoor MIMO capacity with receive direction and position at 5.2 GHz

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ELECTRONICS LETTERS 2002年第21期38卷 1283-1285页

作者： Herdin, M Özcelik, H Hofstetter, H Bonek, E Vienna Tech Univ Inst Nachrichtentech & Hochfrequenztech A-1040 Vienna Austria FTW A-1220 Vienna Austria

Using a directional receive (RX) antenna array the channel capacity of an 8 x 8 multiple-input multiple-output (MIMO) system in an office scenario at 5.2 GHz for different RX directions and positions is measured. The average MIMO capacity can be related to dominant-wave propagation. However, when path-loss is normalised out, MIMO capacity is nearly independent of RX direction and position.

关键词： indoor radio microstrip antenna arrays directional receive antenna array multiple-input multiple-output system Radiowave propagation channel capacity path-loss receiving antennas office scenario MIMO capacity RX direction RX position RX antenna Antenna arrays dominant wave propagation eight-element uniform linear patch array MIMO systems directive antennas microwave propagation Radio links and equipment linear antenna arrays 5.2 GHz

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Large random matrix-based channel estimation for massive MIMO-OFDM uplink

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IET COMMUNICATIONS 2018年第9期12卷 1035-1041页

作者： Sure, Pallaviram Babu, Narendra C. Bhuma, Chandra Mohan MS Ramaiah Univ Appl Sci Fac Engn Bengaluru India Bapatla Engn Coll Dept Elect & Commun Engn Bapatla India

This study investigates the benefits offered by random matrix theory (RMT) towards the design of reliable channel estimation algorithms for a multi-user massive multiple-input multiple-out (MIMO)-orthogonal frequency-division multiplexing uplink. Assuming no a priori knowledge of channel statistics (KCS) at the massive base station, the authors propose RMT-aided minimum mean square estimation (MMSE) and RMT-aided sparse Bayesian learning (SBL) approaches for massive channel estimation. These approaches render efficient channel estimates, as illustrated through mean square error (MSE) performance, extracted via Monte-Carlo simulations. The results also show that with increasing antennas at the base station, MSE from the RMT-aided MMSE approach decreases, suggesting its aptness to massive MIMO systems. To further enhance the MSE performance, the MMSE and SBL estimated channel impulse responses are pruned using threshold computed from RMT analysis. The authors characterise MSE degradation due to the randomness in the threshold, with the help of the Marcenko-Pastur law-based non-asymptotic framework and concentration inequalities. Analysis results show that, for channels with approximate sparse common support, this MSE degradation is quite insignificant. Altogether, the study demonstrates that RMT analysis is competent in improving channel estimation at a massive MIMO system, when a priori KCS is completely unavailable.

关键词： random processes matrix algebra channel estimation MIMO communication OFDM modulation wireless channels radio links telecommunication network reliability statistical analysis least mean squares methods Bayes methods learning (artificial intelligence) Monte Carlo methods antenna arrays large random matrix-based channel estimation algorithm multiuser massive MIMO-OFDM uplink RMT multiple-input multiple-output system orthogonal frequency-division multiplexing knowledge of channel statistics KCS minimum mean square estimation MMSE sparse Bayesian learning approach SBL approach Monte-Carlo simulation antenna channel impulse response Marcenko-Pastur law-based nonasymptotic framework

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MMV-Based Sequential AoA and AoD Estimation for Millimeter Wave MIMO Channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2022年第6期70卷 4063-4077页

作者： Zhang, Wei Dong, Miaomiao Kim, Taejoon City Univ Hong Kong Dept Elect Engn Hong Kong Peoples R China Nanyang Technol Univ Sch Elect & Elect Engn Singapore 639798 Singapore Univ Kansas Dept Elect Engn & Comp Sci Lawrence KS 66045 USA

The fact that the millimeter-wave (mmWave) multiple-input multiple-output (MIMO) channel has sparse support in the spatial domain has motivated recent compressed sensing (CS)-based mmWave channel estimation methods, where the angles of arrivals (AoAs) and angles of departures (AoDs) are quantized using angle dictionary matrices. However, the existing CS-based methods usually obtain the estimation result through one-stage channel sounding that have two limitations: (i) the requirement of large-dimensional dictionary and (ii) unresolvable quantization error. These two drawbacks are irreconcilable;improvement of the one implies deterioration of the other. To address these challenges, we propose, in this paper, a two-stage method to estimate the AoAs and AoDs of mmWave channels. In the proposed method, the channel estimation task is divided into two stages, Stage I and Stage II. Specifically, in Stage I, the AoAs are estimated by solving a multiple measurement vectors (MMV) problem. In Stage II, based on the estimated AoAs, the receive sounders are designed to estimate AoDs. The dimension of the angle dictionary in each stage can be reduced, which in turn reduces the computational complexity substantially. We then analyze the successful recovery probability (SRP) of the proposed method, revealing the superiority of the proposed framework over the existing one-stage CS-based methods. We further enhance the reconstruction performance by performing resource allocation between the two stages. We also overcome the unresolvable quantization error issue present in the prior techniques by applying the atomic norm minimization method to each stage of the proposed two-stage approach. The simulation results illustrate the substantially improved performance with low complexity of the proposed two-stage method.

关键词： Channel estimation Estimation Dictionaries Receivers Transmitters Matching pursuit algorithms Sensors Millimeter wave communications compressed sensing channel estimation multiple-input multiple-output system support recovery sequential estimation

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The boundary surface control principle and its applications

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2005年第7期E88A卷 1656-1664页

作者： Ise, S Kyoto Univ Fac Engn Kyoto 6068501 Japan

In order to control a sound field using multiple sources and microphones, we must choose the optimum values of parameters such as the numbers of sources and microphones, the location of the sources and the microphones and the filter tap length. Because there is a huge number of possible combinations of these conditions, the boundary surface control principle can be useful as a basis of a design method of such a system. In this paper, a design method of sound field reproduction and active noise control based on the BSC principle are described and several example of its application are presented.

关键词： boundary surface control principle sound field reproduction active noise control multiple-input multiple-output system

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Data-driven optimal PEMFC temperature control via curriculum guidance strategy-based large-scale deep reinforcement learning

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IET RENEWABLE POWER GENERATION 2022年第7期16卷 1283-1298页

作者： Li, Jiawen Yang, Shengchun Yu, Tao Zhang, Xiaoshun South China Univ Technol Coll Elect Power Guangzhou 510640 Peoples R China China Elect Power Res Inst Nanjing Nanjing Peoples R China Shantou Univ Coll Engn Shantou Peoples R China

As the proton exchange membrane fuel cell (PEMFC) is a nonlinear, time-varying, multiple-input multiple-output system, an advanced controller with strong robustness and adaptability is required for controlling PEMFC stack temperature and achieve a high operation efficiency. In this paper, a data driven optimal controller is proposed for controlling the stack temperature, which is based on large-scale deep reinforcement learning. In addition, a new deep reinforcement learning algorithm termed curriculum guidance strategy large-scale dual-delay deep deterministic policy gradient (CGS-L4DPG) algorithm is proposed for this controller. The design of this algorithm introduces the concepts of the curriculum guidance strategy and imitation learning, and its inclusion improves the performance and robustness of the proposed controller. The simulation results show that, taking advantage of the high adaptability and robustness of CGS-L4DPG algorithm, the proposed controller can more effectively control the PEMFC stack temperature than existing control algorithms.

关键词： deep learning (artificial intelligence) optimal controller learning (artificial intelligence) strong robustness optimisation proton exchange membrane fuel cell advanced controller controlling PEMFC stack temperature proton exchange membrane fuel cells optimal control temperature control CGS-L4DPG algorithm control algorithms curriculum guidance strategy-based large-scale reinforcement learning deep deterministic policy gradient high adaptability data-driven optimal PEMFC temperature control large-scale deep reinforcement learning curriculum guidance strategy large-scale dual-delay gradient methods imitation learning nonlinear time-varying multiple-input multiple-output system deep reinforcement learning algorithm high operation efficiency

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Design and analysis of a low-profile directive antenna array for multi-element terminals

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IET MICROWAVES ANTENNAS & PROPAGATION 2014年第8期8卷 611-620页

作者： Brzezina, Greg Basri, Amir Ali Ghasemi, Amir Sydor, John Vukovic, Alex Commun Res Ctr Ottawa ON K2H 8S2 Canada

The authors verify the benefits of directivity for a 4 x 4 multiple-input multiple-output (MIMO) system in a non-line-of-sight indoor propagation environment. A novel prototype with four directive antennas has been designed to have full aggregate azimuth coverage, which is conveniently achieved without the need for electronic or mechanical beam-steering. In this way, it captures similar multipath content to that of an equivalent omnidirectional device as confirmed by the field measurements. This coupled with the inherently larger gain of directive antennas renders the prototype a better choice for multi-antenna receivers. The prototype design makes it possible to use a simple but effective power-based antenna selection algorithm. Importantly, this algorithm achieves close to the theoretical maximum channel capacity when only two radio frequency chains are available at the receiver. For the first time, these results show that in an MIMO indoor environment directive receive antennas are a viable option.

关键词： MIMO communication directive antennas indoor radio beam steering omnidirectional antennas radio receivers receiving antennas low-profile directive receive antenna array multielement terminal multiple-input multiple-output system nonline-of-sight indoor propagation electronic beam-steering mechanical beam-steering omnidirectional device multiantenna receiver power-based antenna selection algorithm MIMO indoor environment

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Ergodic Capacity Evaluation of Multi-Hop Decode-and-Forward MIMO-OFDM Relaying Network

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Computers, Materials & Continua 2021年第9期68卷 3133-3145页

作者： Latif Jan Mohammad Haseeb Zafar Abdul Waheed Mahdi Zareei Faisal Alanazi Department of Electrical Engineering University of Engineering&TechnologyPeshawar25120Pakistan Department of Information Technology Hazara UniversityMansehra21120Pakistan Tecnologico de Monterrey School of Engineering and SciencesZapopan45201Mexico Department of Electrical Engineering Prince Sattam Bin Abdulaziz UniversityCollege of EngineeringAl Kharj16278Saudi Arabia

Spatial diversity plays a significant role in wireless communication systems,including the Fourth Generation(4G)and Fifth Generation(5G)systems,and it is expected to be a fundamental part of the future wireless communication systems as *** multiple-input multiple-output(MIMO)technology,which is included in the IEEE 802.16j standard,still holds the most crucial position in the 4G spectrum as it promises to improve the throughput,capacity,spectral,and energy efficiency of wireless communication systems in the *** makes MIMO a viable technology for delay constrained medical and health care *** paper presents an approximate closed-form expression of the ergodic capacity for the Decode-and-Forward(DF)protocol MIMO-Orthogonal Frequency Division multiplexing(OFDM)relaying *** MIMO-OFDM is highly valuable for modern high-speed wireless communication systems,especially in the medical sciences,its performance degrades in multi-hop relay ***,in this paper,an approximate closed-form expression is derived for an end-to-end ergodic capacity of multi-hop DF MIMO-OFDM wireless communication system has been ***-Carlo simulations are conducted to verify the performance of the presented analysis regarding the capacity(bits/s/Hz)for different SNR-dB values for single,2×2,4×4,and multi-hop DF MIMOOFDM *** presented results provide useful insights for the research on the end-to-end ergodic capacity evaluation.

关键词： multiple-input multiple-output system decode-and-forward protocol orthogonal frequency division multiplexing ergodic capacity

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On Feasibility Conditions for Linear Interference Alignment over Cognitive Interference Channel: A DoF Analysis with Diversity Tradeoff

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IETE JOURNAL OF RESEARCH 2016年第3期62卷 278-287页

作者： Akbari, Mohammad Falahati, Abolfazl IUST Dept Elect Engn Narmak Tehran Iran

In a multiple-antennas cognitive radio network, the rate of the primary link is maximized by water-filling power allocation along the spatial directions associated with the singular values of primary channel matrix. Due to transmitter power constraint, even when the primary user occupies the entire spectrum, some spatial opportunities remain that can be utilized by secondary users. This scheme is called opportunistic interference alignment (OIA). The feasibility issue of OIA in a general symbol-extended system considering the diversity tradeoff, in particular, is the topic that is considered in this paper. An outer bound on the achievable degrees of freedom and also a necessary condition on the feasibility of a multiuser OIA network are presented analytically. In the remaining parts of the paper, the diversity and rate tradeoff is considered. In order to achieve diversity, it is assumed that the paired nodes utilize a space-time coder before the OIA pre-coder. A closed-form relation is presented that relates the minimum achievable diversity to interference alignment quality and code rate.

关键词： Cognitive radio network degrees of freedom diversity feasibility analysis multiple-input multiple-output system opportunistic interference alignment

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