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Pre-Scaling Optimization for Space Shift Keying Based on Semidefinite Relaxation

IEEE TRANSACTIONS ON COMMUNICATIONS 2015年第11期63卷 4231-4243页

作者： Garcia-Rodriguez, Adrian Masouros, Christos Hanzo, Lajos UCL Dept Elect & Elect Engn London WC1E 7JE England Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

The performance of space shift keying (SSK) is known to be dominated by the minimum Euclidean distance (MED) in the received SSK constellation. In this paper, we propose a method of enhancing the MED in the received SSK constellation and improving both the attainable performance and the power efficiency by means of symbol scaling at the transmitter. To this aim, we formulate a pair of optimization problems, one for maximizing the MED subject to a specific transmit power constraint and one for minimizing the transmit power subject to a MED threshold. As these problems are NP-hard, we re-formulate their optimization using semidefinite relaxations, which results in convex problem formulations that can be efficiently solved using standard approaches. Moreover, we design pre-scaling techniques for imperfect channel state information at the transmitter, where the existing approaches are inapplicable. Our results show that the proposed schemes substantially improve the power efficiency of SSK systems with respect to state-of-the-art techniques by offering an improved performance for specific transmit power requirements or, equivalently, a transmit power reduction for a given MED threshold.

关键词： Space shift keying constellation shaping multiple-input multiple-output pre-scaling imperfect CSI

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A Low-Complexity Digital Predistorter for Large-Scale MIMO Systems With Crosstalk

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2023年第10期72卷 13203-13213页

作者： Zhao, Linshan Qian, Hua Feng, Weifeng Li, Mingqi Kang, Kai Chinese Acad Sci Shanghai Adv Res Inst Shanghai 201210 Peoples R China Univ Chinese Acad Sci Beijing 101408 Peoples R China Wuxi Grand Microelect Wuxi 214000 Jiangsu Peoples R China

Massive multiple-input multiple-output (MIMO) technology is a key enabler for future wireless communication systems. On the other hand, crosstalk is inevitable in the highly integrated large-scale antenna array. The nonlinearity of power amplifiers (PAs) coupled with crosstalk is much more complicated when the number of antennas is large. Digital predistortion (DPD) can compensate for the PA nonlinearity without sacrificing efficiency and is widely applied in both base stations and mobile devices. Extending existing solutions to the large-scale MIMO system usually suffers from performance degradation or greatly increased complexity. In this paper, we consider the nonlinearity with crosstalk for the large-scale MIMO scenario. A much simplified DPD model is proposed by ignoring the high-order crosstalk terms generated from the complete nonlinear model. Compared to existing solutions, the proposed DPD can compensate for both the nonlinear and linear crosstalk of the system. It achieves satisfactory linearization performance with much reduced computational complexity. The complexity of the proposed DPD is linearly related to the number of transmitter branches. Thus, it is scalable in the large-scale MIMO scenario. Moreover, the proposed DPD can be extended to the partially-connected hybrid beamforming system with crosstalk. Simulation results validate the effectiveness of the proposed DPD scheme.

关键词： multiple-input multiple-output power amplifier crosstalk digital predistortion nonlinearity

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Mutual-Coupling Isolation Using Embedded Metamaterial EM Bandgap Decoupling Slab for Densely Packed Array Antennas

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IEEE ACCESS 2019年 7卷 51827-51840页

作者： Alibakhshikenari, Mohammad Khalily, Mohsen Virdee, Bal Singh See, Chan Hwang Abd-Alhameed, Raed A. Limiti, Ernesto Univ Roma Tor Vergata Elect Engn Dept Via Politecn 1 I-00133 Rome Italy Univ Surrey Inst Commun Syst Home 5G Innovat Ctr Guildford GU2 7XH Surrey England London Metropolitan Univ Sch Comp & Digital Media Ctr Commun Technol & Math London N7 8DB England Edinburgh Napier Univ Sch Engn & Built Environm Edinburgh EH10 5DT Midlothian Scotland Univ Bolton Sch Engn Bolton BL3 5AB England Univ Bradford Fac Engn & Informat Bradford BD7 1DP W Yorkshire England Basra Univ Dept Commun & Informat Engn Coll Sci & Technol Basra 61004 Iraq

This paper presents a unique technique to enhance isolation between transmit/receive radiating elements in densely packed array antenna by embedding a metamaterial (MTM) electromagnetic bandgap (EMBG) structure in the space between the radiating elements to suppress surface currents that would otherwise contribute towards mutual coupling between the array elements. The proposed MTM-EMBG structure is a cross-shaped microstrip transmission line on which are imprinted two outward facing E-shaped slits. Unlike other MTM structures, there is no short-circuit grounding using via-holes. With this approach, the maximum measured mutual coupling achieved is -60 dB @ 9.18 GHz between the transmit patches (#1 & #2) and receive patches (#3 & #4) in a four-element array antenna. Across the antenna's measured operating frequency range of 9.12-9.96 GHz, the minimum measured isolation between each element of the array is 34.2 dB @ 9.48 GHz, and there is no degradation in radiation patterns. The average measured isolation over this frequency range is 47 dB. The results presented confirm the proposed technique is suitable in applications such as synthetic aperture radar and multiple-input multiple-output systems.

关键词： Metamaterial electromagnetic bandgap array antennas decoupling slab mutual coupling synthetic aperture radar multiple-input multiple-output

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On successive machine learning process for predicting strength and displacement of rectangular reinforced concrete columns subjected to cyclic loading

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COMPUTERS AND CONCRETE 2023年第5期32卷 513-525页

作者： Ju, Bu-seog Kwag, Shinyoung Lee, Sangwoo Kyung Hee Univ Dept Civil Engn Yongin Gyeonggi Do South Korea Hanbat Natl Univ Dept Civil & Environm Engn Daejeon South Korea

Recently, research on predicting the behavior of reinforced concrete (RC) columns using machine learning methods has been actively conducted. However, most studies have focused on predicting the ultimate strength of RC columns using a regression algorithm. Therefore, this study develops a successive machine learning process for predicting multiple nonlinear behaviors of rectangular RC columns. This process consists of three stages: single machine learning, bagging ensemble, and stacking ensemble. In the case of strength prediction, sufficient prediction accuracy is confirmed even in the first stage. In the case of displacement, although sufficient accuracy is not achieved in the first and second stages, the stacking ensemble model in the third stage performs better than the machine learning models in the first and second stages. In addition, the performance of the final prediction models is verified by comparing the backbone curves and hysteresis loops obtained from predicted outputs with actual experimental data.

关键词： bagging ensemble machine learning multiple-input multiple-output reinforced concrete column stacking

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Sparse Bayesian Learning Kalman Filter-based Channel Estimation for Hybrid Millimeter Wave MIMO Systems: A Frequency Domain Approach

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IETE JOURNAL OF RESEARCH 2023年第7期69卷 4243-4253页

作者： Ali, K. Shoukath Sampath, P. Bannari Amman Inst Technol Dept Elect & Commun Engn Erode 638401 Tamil Nadu India

In this paper, channel estimation for Millimeter Wave (mmWave) multiple input multiple output (MIMO) communication system is presented. In the frequency domain, the Sparse Bayesian Learning-based Kalman Filter (SBL-KF) scheme is developed to estimate the sparse channel vector of hybrid mmWave MIMO architecture. The mmWave MIMO hybrid architecture provides reduced power loss and achievable data rates at mmWave frequencies. Frequency-selective channels are sparse at mmWave frequencies. The recovery of the sparse channel is estimated using different channel estimation methods. The hybrid precoding technique achieves both multiplexing gain and array gain in mmWave channels. Simulation results of the proposed SBL-KF scheme show low estimation error over the existing Orthogonal Matching Pursuit, Simultaneous Orthogonal Matching Pursuit, Simultaneous Weighted Orthogonal Matching Pursuit algorithm and SBL scheme. The complexity of the online estimation SBL-KF algorithm is low and it is ideally suited for implementation in an efficient mmWave MIMO system.

关键词： Kalman filter Millimeter wave multiple-input multiple-output Orthogonal matching pursuit Sparse Bayesian learning

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Joint CIR, CFO, DCO and FI/FS Rx IQ imbalance estimation

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IET COMMUNICATIONS 2016年第15期10卷 2025-2033页

作者： Ali, Muhammad Asim Arif, Muhammad Kumar, Wanod Sukkur Inst Business Adm Fac Engn Sukkur Pakistan Mehran Univ Engn & Technol Biomed Engn Jamshoro Pakistan Mehran Univ Engn & Technol Elect Engn Jamshoro Pakistan

The aim of this study is to design a receiver architecture which can jointly estimate the frequency selective (FS) channel impulse response (CIR), frequency independent (FI)/FS Receiver (Rx) Inphase Quadrature (IQ) imbalance, carrier frequency offset (CFO) and direct current offset using long training sequences. All of these problems are typical for low-cost radio-frequency front-ends. This study proposes a set of two scalable solutions to estimate CFO, whereas FS CIR and FI/FS Rx IQ imbalance are estimated in tandem through a closed-form expression. A low-complexity single stage equaliser is also proposed which can mitigate the effects of CFO and equalise the CIR along with FI/FS IQ imbalance in a single step. The proposed solutions are also extended to multiple-input-multiple-output-orthogonal frequency division multiplexing systems. The simulation results illustrate that solutions proposed in this study provide an excellent performance/complexity trade-off.

关键词： MIMO communication OFDM modulation channel estimation radio receivers transient response channel impulse response joint CIR carrier frequency offset joint CFO direct current offset joint DCO frequency selective frequency independent FI FS Rx IQ imbalance estimation receiver architecture design radio frequency front-ends closed-form expression multiple-input multiple-output orthogonal frequency division multiplexing systems

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Exact Outage Probability Analysis of Dual-Transmit-Antenna V-BLAST With Optimum Ordering

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2019年第1期68卷 977-982页

作者： Ozyurt, Serdar Torlak, Murat Yildirim Beyazit Univ Fac Engn & Nat Sci TR-06010 Ankara Turkey Univ Texas Dallas Dept Elect Engn Richardson TX 75083 USA

An exact outage probability analysis of zero-forcing V-BLAST technique with two transmit antennas and r receive antennas (r >= 2) is provided under a decoding order that is optimum in the sense of minimizing the outage probability. Different from the earlier approximated analyses, an exact closed-form expression on the outage probability is attained without neglecting the effect of error propagation. Assuming a one-bit feedback from the receiver to the transmitter, the optimal power and rate allocation values are numerically computed based on the exact outage probability expression under different objective functions. The presented results are also applicable for the corresponding dual scenarios that may involve antenna selection and/or user scheduling.

关键词： multiple-input multiple-output outage probability zero-forcing V-BLAST optimum ordering order statistics

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An investigation of S-DF cooperative communication protocol over keyhole fading channel

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PHYSICAL COMMUNICATION 2018年 29卷 120-140页

作者： Shankar, Ravi Mishra, Ritesh Kumar Natl Inst Technol Elect & Commun Engn Dept Patna Bihar India

This paper investigates the keyhole or pinhole effect on the pairwise error probability (PEP) performance of the multiple-input multiple-output (MIMO) space-time block-code (STBC) based selective decode and forward (S-DF) protocol. The closed form PEP expressions are derived for several configurations in terms of number of hops, phases, and relays over Nakagami-m fading channel, with perfect and imperfect channel state information (CSI), and with and without the keyhole condition. Further, a framework is developed for deriving the diversity order (DO) for each configuration. It demonstrates that full DO for cooperation protocol can be achieved when there is a knowledge of perfect CSI. A convex optimization framework is formulated for obtaining the optimal source-relay power allocation factors which significantly improve the end-to-end reliability of the system under power constraint scenarios. Monte Carlo simulations are performed for both equal and optimal power allocation factors and results show the substantial improvement in PEP performance with an increase in the value of the shape parameter and relay to destination (RD) link channel variance. Results show an improved PEP performance by increasing the RD link channel variance in comparison to increasing the source to relay (SR) link channel variance. Also PEP performance degrades for keyhole Nakagami-m fading channel as compared to Nakagami-m fading channel. Simulation results are in close agreement with the analytical results at high signal to noise ratio (SNR) regimes. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Monte Carlo simulation Keyhole effects Pairwise error probability Channel state information Selective decode and forward multiple-input multiple-output Space-time block-code

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Semi-Blind Adaptive Spatial Equalization for MIMO Systems with High-Order QAM Signalling

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第11期7卷 4486-4491页

作者： Chen, S. Yao, W. Hanzo, L. Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

This contribution investigates semi-blind adaptive spatial filtering or equalisation for multiple-input multiple-output (MIMO) systems that employ high-throughput quadrature amplitude modulation (QAM) signalling. A minimum number of training symbols, equal to the number of receivers (we assume that the number of transmitters is no more than that of receivers), are first utilized to provide a rough least squares channel estimate of the system's MIMO channel matrix for the initialization of the spatial equalizers' weight vectors. A constant modulus algorithm aided soft decision-directed blind algorithm, originally derived for blind equalization of single-input single-output and single-input multiple-output systems employing high-order QAM signalling, is then extended to adapt the spatial equalizers for MIMO systems. This semi-blind scheme has a low computational complexity, and our simulation results demonstrate that it converges fast to the minimum mean-square-error spatial equalization solution.

关键词： multiple-input multiple-output quadrature amplitude modulation spatial equalisation semi-blind adaptive algorithm concurrent constant modulus algorithm and soft decision-directed scheme

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Deep learning-based channel estimation in MIMO system for pilot decontamination

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INTERNATIONAL JOURNAL OF AD HOC AND UBIQUITOUS COMPUTING 2023年第3期44卷 148-166页

作者： Reddy, Gondhi Navabharat Kumar, C. V. Ravi Vellore Inst Technol Sch Elect Engn Embedded Technol SENSE Vellore 632014 India

The next-generation wireless communication system makes use of the upcoming technology known as massive multiple-input multiple-output (MIMO). The imprecise channel estimation leads to enormous error in communication, and this cause pilot contamination (PC), which is a major concern in the massive MIMO system. An efficient invasive shuffled shepherd optimisation (ISSO)-deep maxout-based channel estimate approach is proposed, which chooses the optimal channel in the massive MIMO system to avoid interference among nearby cells, reducing contamination of pilot sequences. Shuffled shepherd optimisation (SSO) and improved invasive weed optimisation (IWO) are combined to develop the proposed ISSO method. The deep maxout network is trained using the proposed ISSO technique, and the weight factors are computed using the loss function. The proposed channel estimation methodology produced bit error rate (BER) and mean square error (MSE) results for the Rayleigh channel of 0.0009 and 0.00070 and for the Rician channel of 0.0009 and 0.0007.

关键词： channel estimation pilot contamination PC deep learning massive MIMO multiple-input multiple-output shuffled shepherd optimisation SSO invasive shuffled shepherd optimisation ISSO invasive weed optimisation IWO

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