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Design of superimposed training sequence for spatially correlated multiple-input-multiple-output channels under interference-limited environments

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IET COMMUNICATIONS 2015年第10期9卷 1259-1268页

作者： Mishra, Himanshu B. Vasudevan, K. Indian Inst Technol Dept Elect Engn Kanpur 208016 Uttar Pradesh India

In this study, the design of a superimposed training (ST) for an interference-limited spatially correlated multiple-input-multiple-output (MIMO) system is addressed and a closed-form solution for designing the training signal is proposed in a sub-optimal way. Earlier papers have considered noise limited MIMO systems. The authors also propose random/orthogonal variable spread factor (OVSF) codes as a choice for the ST signal. The mean-squared error of the channel estimate and symbol error rate performances are obtained through simulation. Considering the power allocation issue between the data and training symbols, a sub-optimal average training power that maximises the lower bound on the effective signal-to-interference ratio is also proposed. Simulation results show that the bit error rate performance of the ST is indistinguishable from the OVSF/random ST sequence.

关键词： MIMO communication radiofrequency interference wireless channels mean square error methods superimposed training sequence spatially correlated multiple-input-multiple-output channels interference limited environments ST multiple-input-multiple-output MIMO system random orthogonal variable spread factor OVSF mean squared error symbol error rate

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Analysis and Improvement of Indoor multiple-input-multiple-output Path Loss Prediction Model for 2.4-Ghz 802.11n Network

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ELECTROMAGNETICS 2013年第5期33卷 353-369页

作者： Mardeni, R. Solahuddin, Y. F. Multimedia Univ Fac Engn Cyberjaya 63100 Malaysia Univ Teknol Mara Fac Elect Engn George Town Malaysia

In telecommunication systems, indoor propagation models have been addressed by many researchers in different approaches for signal prediction purposes. However, the use of those models is limited at different environments and conditions. Enhancement of the models is needed since the environment and mobile technologies are increasing drastically and need to suit the current generation and satisfy mobile users. The 802.11n network features multiple-input-multiple-output, which is not presented in any previous wireless local area network standards;it is considered imperative to figure out a suitable prediction model for the 802.11n network. In this article, development of indoor path loss prediction model for the IEEE 802.11n network at 2.4 GHz is presented. The work based on simulation and measurement. Validation of the developed model has been tested at different office buildings, and it showed good accuracy and consistency with a mean error of 2.21 dB and a standard deviation of 2.02 dB. This new model is found to be suitable for predicting indoor signal loss in an 802.11n wireless local area network system and is useful for telecommunication providers to improve their service for better capacity and mobile user satisfaction.

关键词： 802.11 multiple-input-multiple-output model comparisons wireless local area network

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Modified circular common element four-port multiple-input-multiple-output antenna using diagonal parasitic element

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2019年第2期29卷 e21527-e21527页

作者： Chouhan, Sanjay Panda, Debendra Kumar Kushwah, Vivek Singh Amity Univ Dept Elect & Commun Engn Gwalior Madhya Pradesh India Medi Caps Univ Dept Elect & Commun Engn Indore Madhya Pradesh India

A four-port multiple input multiple-output (MIMO) antenna with common radiating element is proposed for 2.4 GHz Wi-Fi applications. It comprises a modified circular radiator fed by four identical modified feedlines, partial ground planes, and a diagonal parasitic element (DPE). The parasitic element is used to enhance the interport isolation. The antenna has a 2:1 Voltage standing wave ratio (VSWR) impedance band 2.34-2.56GHz and nearly omnidirectional radiation patterns. The radiation efficiency is more than 79% and gain is 2 dBi at resonant 2.43GHz. The isolation in the given frequency band is 10 dB. At the 2.43GHz, the isolation between adjacent ports (1, 2 and 1, 4) is 14dB and between opposite ports (1, 3) is 12dB. The mean effective gain (MEG)-2.7 dB and envelope correlation coefficient is <0.01. The -10 dB total active reflection coefficient bandwidth is 202MHz. The antenna is designed for a Wi-Fi device and the effectiveness of antenna has been checked for distance of 1/2 feet from the human head. The specific absorption rate (SAR) is found to be 0.17W/Kg by CST simulation tool.

关键词： common element antenna envelop correlation coefficient isolation mean effective gain multiple-input-multiple-output Wi-Fi applications

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A New multiple-input-multiple-output Uniform Theory of Diffraction Based Channel Model for multiple Building Diffraction in Urban Environments

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ELECTROMAGNETICS 2014年第7期34卷 553-567页

作者： Tajvidy, Ali Haghbin, Afrooz Pourmina, Mohammad Ali Sadeghzadeh, Ramezan Ali Islamic Azad Univ Sci & Res Branch Dept Elect Engn Tehran *** Iran

This article introduces a new channel model in urban environments that considers multiple antennas in both the transmitter and receiver;moreover, the uniform theory of diffraction is used for modeling rays that impinge on buildings. Against prior models, this model calculates sub-channels of the channel matrix rigorously and does not use any random variables or distribution functions. This model can predict channel and correlation matrixes and channel capacity in a multiple-input-multiple-output system. Furthermore, the 3GPP spatial channel measurement-based model, which is statistical, is compared with the simulation results of this study. The comparison between the two models shows that the proposed model accuracy is enough for further design of different aspects of the multiple-input-multiple-output system. Therefore, the proposed model can successfully be used to improve theoretical methods for predicting a more realistic multiple-input-multiple-output channel matrix in cellular mobile communications, where diffraction from a number of buildings has to be considered.

关键词： channel modeling channel capacity diffraction multiple-input-multiple-output urban environments uniform theory of diffraction

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Compact sub-6 GHz 5G-multiple-input-multiple-output antenna system with enhanced isolation

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2020年第8期30卷 e22246-e22246页

作者： Saurabh, Arun Kumar Meshram, Manoj Kumar Banaras Hindu Univ Indian Inst Technol Dept Elect Engn Varanasi Uttar Pradesh India

A compact two-element multiple-input-multiple-output (MIMO) antenna system with improved impedance matching and isolation is presented for future sub-6 GHz 5G applications. The two identical tapered microstrip line fed modified rhombus-shaped radiating elements are placed in the same orientation at a compact substrate area of 0.24 lambda(0) x 0.42 lambda(0) (where, lambda(0) at 3.6 GHz) on a shared rectangular ground. A remodeled T-shaped ground stub is placed between a pair of radiating element to achieve improved impedance bandwidth and isolation. Further, a split U-shaped stub connected to center of each radiating element to achieve the desired resonant frequency of 3.6 GHz. The proposed antenna covers a -10 dB operating band of 3.34 to 3.87 GHz (530 MHz) with more than 20 dB isolation between a pair of elements. MIMO performances are also analyzed and experimentally validated. The measured performances of a prototype are found in good agreement with simulated performances. Further, the simulation study is carried out to see the effect of housing and extended ground plane on two-element MIMO antenna for practical application. An idea of realization of 12-element MIMO is also studied using the proposed two-element MIMO antenna.

关键词： correlation isolation multiple-input-multiple-output mutual coupling stub 5G communication

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Equivalence of Frequency-Domain Turbo Equalization Schemes for Single-Carrier multiple-input-multiple-output Systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2017年第1期66卷 95-106页

作者： Chen, Zhenrui Zheng, Yahong Rosa Wang, Jintao Song, Jian Missouri Univ Sci & Technol Rolla MO 65409 USA Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China Missouri Univ Sci & Technol Dept Elect & Comp Engn Rolla MO 65409 USA

This paper investigates two typical frequency-domain turbo equalization (FDTE) schemes, i.e., frequency-domain equalization (FDE) with parallel interference cancelation (FDE-PIC) and FDE with frequency-domain decision feedback (FDE-FDDF) in single-carrier (SC) multiple-input-multiple-output (MIMO) systems. These two FDTE schemes are proven to be equivalent under the condition that we derived. We discover that the covariance matrix of the low-complexity FDE-PIC scheme and the correlation matrix of the FDE-FDDF scheme satisfy a unique relationship for constant-modulus modulations, and the original FDE-FDDF scheme suffers numerical instability for non-constant-modulus modulations because the estimation of the correlation matrices leads to the inversion of ill-conditioned matrices. By proposing a new estimation method of the correlation matrices, we guarantee that the non-constant-modulus FDE-FDDF scheme is numerically stable and that the relationship between these two FDTE schemes holds for both constant-modulus and non-constant-modulus modulations. Furthermore, we prove that the FDE-PIC and FDE-FDDF schemes are equivalent under this relationship. The equivalence of these two FDTE schemes is also verified through numerical simulations in terms of bit error rate (BER) at each turbo iteration and the estimation of the correlation matrices.

关键词： Frequency domain equalization multiple-input-multiple-output turbo equaliztion

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Reconfigurable miniaturized UWB multiple-input-multiple-output antenna system design and study using characteristics mode analysis

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2022年第9期32卷 e23287-e23287页

作者： Mohanty, Asutosh Behera, Bikash Ranjan Nasimuddin, Nasimuddin KIIT Deemed Univ Sch Elect Engn Bhubaneswar India Ctr Adv Post Grad Studies BPUT Dept Elect & Commun Engn Rourkela Odisha India ASTAR Inst Infocomm Res Singapore Singapore

In this article, a miniaturized reconfigurable 4-element ultra-wideband (UWB) multiple-input-multiple-output (MIMO) antenna is proposed to operate from 2.52 to 24 GHz, and studied using characteristics mode analysis (CMA). Initially, a 1-element antenna is designed and then extended to 4-element MIMO configuration. The MIMO antenna achieves design merits by orthogonally sorting fractal radiators for miniaturization, a Gamma-shaped slot for band-notching and rotationally symmetric connected ground for isolation. CMA is explored to study the band-notched behavior effect in antenna, which shows two operating modes, NM-mode and NB-mode (NM: normal-mode, NB: Notched-mode). The modal metrics is discussed for both modes giving an insights on the bandwidth and radiation potentials. Four RF p-i-n diodes are mounted at the Gamma-shaped slot orifice on each antennas, to control the band-notched operation. At OFF-state, the antenna is with wide-band-rejection from 3.7 to 8.87 GHz and at ON-state, it works in pure UWB mode. To demonstrate its feasibility, a fabricated antenna of size 24 mm x 24 mm is experimented which are in good agreements with simulated results.

关键词： characteristics mode analysis multiple-input-multiple-output reconfigurable antenna UWB antenna

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Networked multiple-input-multiple-output for optical wireless communication systems

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PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 2020年第2169期378卷 20190189-20190189页

作者： Wang, Zhaocheng Chen, Jiaxuan Tsinghua Univ Beijing Natl Res Ctr Informat Sci & Technol Dept Elect Engn Beijing 100084 Peoples R China Tsinghua Shenzhen Int Grad Sch Shenzhen 518055 Peoples R China

With the escalation of heterogeneous data traffic, the research on optical wireless communication (OWC) has attracted much attention, owing to its advantages such as wide spectrum, low power consumption and high security. Ubiquitous optical devices, e.g. light-emitting diodes (LEDs) and cameras, are employed to support optical wireless links. Since the distribution of these optical devices is usually dense, multiple-input-multiple-output (MIMO) can be naturally adopted to attain spatial diversity gain or spatial multiplexing gain. As the scale of OWC networks enlarges, optical MIMO can also collaborate with network-level operations, like user/AP grouping, to enhance the network throughput. Since OWC is preferred for short-range communications and is sensitive to the directions/rotations of transceivers, optical MIMO links vary frequently and sharply in outdoor scenarios when considering the mobility of optical devices, raising new challenges to network design. In this work, we present an overview of optical MIMO techniques, as well as the cooperation of MIMO and user/AP grouping in OWC networks. In consideration of the challenges for outdoor OWC, key technologies are then proposed to facilitate the adoption of optical MIMO in outdoor scenarios, especially in vehicular ad hoc networks. Lastly, future applications of MIMO in OWC networks are discussed. This article is part of the theme issue 'Optical wireless communication'.

关键词： multiple-input-multiple-output optical wireless communications optical networks

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Dual-element circularly polarized multiple-input-multiple-output-dielectric resonator antenna with high interport isolation for sub-6 GHz applications

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INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING 2022年第11期32卷 e23387-e23387页

作者： Mali, Ravi Sahu, Nikesh Kumar Suman, Kundan Kumar Gangwar, Ravi Kumar IIT ISM Dhanbad Dept Elect Engn Dhanbad 826004 Jharkhand India

This work presents a dual-element multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) for sub-6 GHz applications. The proposed MIMO-DRA has two major features: (i) circular polarization (CP);and (ii) high interport isolation. The proposed MIMO-DRA is formed by two identical antenna elements. Each element is composed of a cylindrical dielectric resonator (DR) which is fed by a microstrip line via the underneath octagonal aperture. A modified L-shaped strip along with the octagonal aperture delivers the desired CP characteristics. Meanwhile, a novel defected ground geometry (DGG) is utilized to enhance the inter-port isolation across the operating frequency bandwidth. The proposed MIMO-DRA has an inter-port isolation of greater than 21 dB over the operating 10-dB impedance band of 4.18-6.12 GHz. Furthermore, the proposed MIMO-DRA features broadside radiation patterns, satisfactory broadside gains, and well-acceptable values of envelope correlation coefficients (ECCs).

关键词： circular polarization dielectric resonator inter-port isolation multiple-input-multiple-output

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Review of optical multiple-input-multiple-output techniques in multimode fiber

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OPTICAL ENGINEERING 2011年第10期50卷 102001-102001页

作者： Amphawan, Angela Univ Utara Malaysia Internetworks Res Grp Sintok 06010 Kedah Malaysia

The success of optical multiple-input-multiple output (MIMO) systems in wireless communications has motivated interesting investigations of MIMO in optical fiber communications. This paper reviews various optical MIMO techniques in multimode fiber. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3631045]

关键词： multiple-input-multiple-output bandwidth increase multimode fiber

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