• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1061-1068
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• 2013

In this paper, we propose a $M{\times}M$ beam-space multiple input multiple output (BS-MIMO) system using electronically steerable parasitic array radiator (ESPAR) antenna. Conventional MIMO method required multiple RF chains because it map the transmission signals onto multiple antennas. So, conventional MIMO system has high cost for design and high energy consumption at RF circuit. Also, It is difficult to use MIMO system in battery based mobile terminals with limited physical area. In order to solve these problems, BS-MIMO technique which map the data signal onto bases in beam space domain was proposed using ESPAR antenna with single RF chain. This paper, we design and analyze the performance of extended $M{\times}M$ BS-MIMO technique. Simulation results show that the proposed BS-MIMO system has similar BER performance compare to conventional MIMO scheme. Therefore, BS-MIMO system with single RF chain will has a low RF power consumption and low cost for RF hardware design as compared with conventional MIMO technique with multiple RF chains.

• ETRI Journal
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• v.37 no.4
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• pp.647-656
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• 2015

This paper proposes a single-RF MIMO receiver that adopts a beam-switching antenna (BSA) instead of a conventional array antenna. The beauty of the proposed single-RF MIMO receiver with BSA is that it can be deployed in a very small physical space while achieving a full spatial multiplexing gain. Our analysis has revealed that the use of a BSA inevitably results in the spectrum spreading effect at the RF output, which in turn causes an SNR decrease and adjacent channel interference (ACI). Two novel receiver techniques are proposed to mitigate the issues of redundant sub-band suppression and ACI avoidance. Numerical analysis results verify the performance improvement from the proposed receiver techniques.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.81-86
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• 2014

A smart phone subscriber needs wide bandwidth services for more fast data communication on the internet. The conventional MIMO system is now developing to resolve these problems with limited device space for antenna and frequency band environment reserved. One of way to make it practically is to add the number of antennas theoretically. But it is difficult to increase the antenna element as a limited space on the system. Therefore an active beam forming scheme is known as a way of constructing a Compact MIMO system for that. In this paper, the fast switching control block was suggested to adjust a reactance of the antenna element and verified experimentally the effects by switching signal on an orthogonal beam forming through a spatial domain.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.219-224
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• 2020

In this paper, we studied the compact MIMO(: Multi-Input Multi-Output) antenna for multi-beam pattern generation and control in narrow space. The characteristics and performance of the basic Dipole SPA and Monopole SPA structures are shown. We implemented a monopole SPA antenna and measured its performance in an 802.11g system. When the average transmission rate was measured using the SPA antenna, the SPA antenna improved the best performance by 8.7 times compared to commercial antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.5
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• pp.220-228
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• 2014

ESPAR(Electronically Steerable Parasitic Array Radiator) antenna is the technique for overcoming the problems of space limitation and energy efficiency due to the multiple RF-chain. Conventional MIMO system with multiple antenna requires a large number of RF-chain for transmitting the multiple data because it transmits the data in proportion to the number of antenna. Beamspace MIMO system using the ESPAR antenna which has single RF-chain was proposed for solving the problems caused by using the multiple antenna and RF-chain. In this paper, therefore we propose 2x2 beamspace MIMO system using the 16, 64-QAM modulation and evaluate the performance of this system to reveal that it is possible that beamspace MIMO system can use not only PSK modulation but also QAM modulation. We confirm that QAM symbol can be generated by adjusting reactance of parasitic elements and making reactance set and also we confirm that performance of beamspace MIMO system is similar to the conventional MIMO system by transmitting the QAM symbol made by reactance set through the simulation.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.53-60
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• 2013

In this paper, the new multi-beamforming is proposed for Multiple-input multiple-output (MIMO) Multicarrier-Code division multiple access(MC-CDMA) systems to overcome the decrease of performance due to multiuser interference and multiple-antenna interference. Installing the number of multi-beamformer which is equal to the number of multi-transmitter antennas and exploiting the proposed approach at the receiver of MIMO MC-CDMA, the multi-beams are formed toward each multi-antenna of desired user and null beam are formed to other interference. Therefore, the performance of MIMO MC-CDMA system is improved as removing the interference signal. BER performance improvement is investigated through computer simulation by the proposed approach to MIMO MC-CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.425-431
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• 2015

Beamspace Multiple-Input Multiple Output(MIMO) system can transmit multiple data by using Electronically Steerable Parasitic Array Radiator(ESPAR) antenna which has single Radio Frequency(RF)-chain. Beamspace MIMO system can reduce complexity of the system and size of antenna in comparison with the conventional MIMO system because of characteristic of ESPAR antenna using the single antenna and the RF-chain. Heretofore, only the research of transmitting single-carrier has been conducted by the use of beamspace MIMO system. Therefore, in this paper, we propose beamspace MIMO system based on Orthogonal Frequency Division Multiplexing(OFDM) for transmitting the multi-carrier and analysis the performance of this system. We find a proper reactance value which has good performance because proposed system changes the performance by the reactance values of parasitic elements. and we confirm that performance of the proposed system is similar to conventional MIMO system based on OFDM.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.1-9
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• 2006

In this paper, we propose a MIMO-OFDMA (Multi Input Multi Output-Orthogonal Frequency Division Multiple Access) system based on beamforming for performance improvement of downlink real-time traffic transmission in harsh channel conditions with low CIR (Carrier-to-Interference Ratio). In the proposed system, we first consider the M-GTA-SBA (Modified-Grouped Transmit Antenna-Simple Bit Allocation) using effective CSI (Channel State Information) calculation procedure based on spatial resource grouping, which is adequate for the combination of MRT (Maximum Ratio Transmission) in the transmitter and MRC (Maximum Ratio Combining) in the receiver. In addition, to reduce feedback information for the beamforming, we also apply QEGT (Quantized Equal Gain Transmission) based on quantization of amplitudes and phases of beam weights. Furthermore, considering multi-user environments, we propose the P-SRA (Proposed-Simple Resource Allocation) algorithm for fair and efficient resource allocation. Simulation results reveal that the proposed MIMO-OFDMA system achieves significant improvement of spectral efficiency in low CRI region as compared to a typical open-loop MIMO-OFDMA system using pseudo-orthogonal space time block code and H-ARQ IR (Hybrid-Automatic Repeat Request Incremental Redundancy).

• ETRI Journal
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• v.41 no.4
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• pp.536-548
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• 2019

In this study, an electronically steerable parasitic array radiator (ESPAR) antenna via analog radio frequency (RF) switches for a single RF chain MIMO system is presented. The proposed antenna elements are spaced at ${\lambda}/64$, and the antenna size is miniaturized via a dielectric radome. The optimum reactance load value is calculated via the beamforming load search algorithm. A switch simplifies the design and implementation of the reactance loads and does not require additional complex antenna matching circuits. The measured impedance bandwidth of the proposed ESPAR antenna is 1,500 MHz (1.75 GHz-3.25 GHz). The proposed antenna exhibits a beam pattern that is reconfigurable at 2.48 GHz due to changes in the reactance value, and the measured peak antenna gain is 4.8 dBi. The reception performance is measured by using a $4{\times}4$ BPSK signal. The measured average SNR is 17 dB when using the proposed ESPAR antenna as a transmitter, and the average SNR is 16.7 dB when using a four-conventional monopole antenna.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.370-382
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• 2013

Distributed massive MIMO systems, which have high bandwidth efficiency and can accommodate a tremendous amount of traffic using algorithms such as zero-forcing beam forming (ZFBF), may be deployed in large public venues with the antennas mounted under-floor. In this case the channel gain matrix H can be modeled as a multi-banded matrix, in which off-diagonal entries decay both exponentially due to heavy human penetration loss and polynomially due to free space propagation loss. To enable practical implementation of such systems, we present a multi-banded matrix inversion algorithm that substantially reduces the complexity of ZFBF by keeping the most significant entries in H and the precoding matrix W. We introduce a parameter p to control the sparsity of H and W and thus achieve the tradeoff between the computational complexity and the system throughput. The proposed algorithm includes dense and sparse precoding versions, providing quadratic and linear complexity, respectively, relative to the number of antennas. We present analysis and numerical evaluations to show that the signal-to-interference ratio (SIR) increases linearly with p in dense precoding. In sparse precoding, we demonstrate the necessity of using directional antennas by both analysis and simulations. When the directional antenna gain increases, the resulting SIR increment in sparse precoding increases linearly with p, while the SIR of dense precoding is much less sensitive to changes in p.