• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.507-513
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• 2015

In this paper, we present the bit-error rate (BER) performance of quasi-orthogonal space-time block code (QOSTBC) massive multiple-input multiple-output (MIMO) system employing up to 32 transmit and receive antennas. The QOSTBC, due to its advantages in transmission rate and decoding complexity, is an important transmit diversity scheme for more than 2 transmit antennas. As massive MIMO implies very large number of antennas, practically at least more than 15 antennas, a different number of transmit and receive antennas (i.e. $2{\times}2$, $4{\times}4$, $8{\times}8$, $16{\times}16$ and $32{\times}32$) using QOSTBC for the massive MIMO system are considered. The BER performance of the massive MIMO with antennas up to $32{\times}32$ using BPSK modulation scheme is analyzed. Simulation results show that the full-rate massive MIMO systems with QOSTBC give a significant performance improvement due to increasing diversity effect, compared with previously considered massive MIMO systems.

• ETRI Journal
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• v.38 no.2
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• pp.280-290
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• 2016

To implement high-order multiuser multiple input and multiple output (MU-MIMO) for massive MIMO systems, there must be a feedback scheme that can warrant its performance with a limited signaling overhead. The interference-to-noise ratio can be a basis for a novel form of Codebook (CB)-based MU-MIMO feedback scheme. The objective of this paper is to verify such a scheme's performance under a practical system configuration with a 3D channel model in various radio environments. We evaluate the performance of various CB-based feedback schemes with different types of overhead reduction approaches, providing an experimental ground with which to optimize a CB-based MU-MIMO feedback scheme while identifying the design constraints for a massive MIMO system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1164-1171
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• 2006

In this paper, a simple and nonlinear MMSE detector is derived from the conventional linear MMSE detector to improve the system performance in turbo processing MIMO system and a new turbo processing MIMO system with nonlinear MMSE detector and Gaussian approximation is proposed. In turbo coded turbo processing MIMO system, the proposed system of M=N=4 performs about 0.5 dB better than the conventional system and the proposed system of M=N=8 performs about 0.4 dB better than conventional system at 1 % FER. In addition, the average number of outer iterations of proposed system shows lower than that of conventional system. This is caused by the fact that the nonlinear MMSE detector of proposed system decides soft-outputs of coded bits based on the observation of received signals, so that it can reduce the uncertainty region in estimating the coded bits.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.4
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• pp.121-127
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• 2012

In this paper, we propose a new beamforming method which is used in Multiple User-Multiple Input Multiple Output (MU-MIMO) system. An experimental system consists of LTE based TDD base-station which has 2 MIMO elements each of which contains 10-array antennas and 2 mobile terminals each of which has a single antenna. We demonstrate that the Multiple Access Interference can further be reduced by appending a beamforming procedure in MU-MIMO system in which various users share a given channel resource. The proposed algorithm is the ordinary Lagrange beamforming algorithm combined with Zero-Forcing. It is demonstrated that the proposed beamforming method outperforms a conventional method which is the ZF at least by 8dB in terms of SNR through computer simulations. From experimental tests, we verify the feasibility of the proposed beamforming algorithm for realizing a practical LTE based TDD base-station for utilizing channel resources more efficiently.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.426-435
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• 2013

In this paper, we propose the MIMO circular polarization feed network to enhance the communication performances from the previous $2{\times}2$ MIMO channel to $4{\times}4$ channel for Land Mobile Satellite communication system. The only possibility to extend the communication channel is to use the additional satellite because of the limitation of satellite spaces to install additional antennas. For overcoming this problems, we propose the MIMO circular polarization feed network to secure the isolation characteristics without the distant antenna space. The port isolation characteristics and each port impedance matching conditions are numerically verified and we suggest the $4{\times}4$ MIMO channel model of the proposed system and the performances are verified. The fabricated circular polarization patch antennas with the proposed feed network are measured in the reverberation chamber and 7~10 dB of diversity gain and 80 % increasement of channel capacity are obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1022-1030
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• 2004

The next generation cellular radio systems require high data rate transmission and large system capacity In order to meet these requirements, multiple antennas can be used at the base and mobile stations, forming MIMO(multiple-input, multiple-output) channels This paper considers a downlink MIMO system assuming a large number of base station antennas, a small number of mobile station antennas, and rich-scattering, quasi-stationary, and flat-fading channel environments When the channel state information is given at the base station in a single user system, a MIMO technique with SVD(singular value decomposition) and water-filling can achieve the maximal downlink channel capacity. In multi-user environments, however, SDMA(space division multiple acces) technique can be used to further increase the total channel capacity supported by the base station This paper proposes a MIMO SDMA technique which can transmit parallel data streams to each of multiple users. The proposed method. can achieve higher total channel capacity than SVD-based MIMO techniques or conventional SDMA using smart antennas.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.564-571
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• 2015

In this paper, we propose a multiple-input, multiple-output(MIMO) interferometric radar network system to generate three-dimensional (3-D) MIMO interferometric inverse synthetic aperture radar(InISAR) image. In the MIMO interferometric radar network system, the MIMO InISAR image can be formed by an incoherent summation of multiple bistatic InISAR images that show 3-D scatterers of a target observed at different bistatic interfermetric configurations, respectively. Because bistatic-sccattering physics of a target at different viewpoints are visible in the 3-D MIMO InISAR image, it can provide various scatterering physics properties of a target, and can be used for target classification as a useful feature vector. Simulations validate that our proposed method successfully finds locations of scatterers of a target in MIMO radar interferometric network system.

• Journal of Broadcast Engineering
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• v.22 no.6
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• pp.755-764
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• 2017

In this paper, we design transmitter and receiver structures for a $2{\times}2$ multiple-input multiple-output (MIMO) in ATSC 3.0 systems and analyze the performance of the $2{\times}2$ MIMO system. In the ATSC 3.0 MIMO systems, spatial diversity and multiplexing gains can be obtained using the spatial demultiplexer and precoder. In this paper, we present the structures of the transmitter and receiver for ATSC 3.0 MIMO systems. Also, we present performance results of the $2{\times}2$ MIMO system through computer simulations.

• The Journal of the Korea Contents Association
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• v.5 no.1
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• pp.201-208
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• 2005

Tn this paper, we evaluate the peak-to-average power ratio (PAPR) performance in a space-time block code (STBC) multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system using selected mapping (SLM) and partial transmit sequences (PTS) approaches. SLM and PTS methods are used to decrease the nonlinear distortion and to improve the power efficiency of the nonlinear high power amplifier(HPA) in the MIMO-OFDM system. In simulation result, when compared with the existing MIMO-OFDM system using QPSK, the PTS method reduces the PAPR about 5dB while the SLM method can reduce about 3.5 dB. Also, we find the BER performance of the MIMO-OFDM system with and without the predistorter in front of the HPA. When the predistorter is used, the input back-off (IBO) of 4 dB is required in the PTS method, and IBO of 6 dB in the SLM method to closely conform to the linear amplifier. If the method of improving the PAPR is not used, the value of IBO of 8 dB is required.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.10
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• pp.579-584
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• 2014

In this paper, we propose beamsapce MIMO(mulitple input multiple output) system using patch ESPAR(Electronically Steerable Parasitic Array Radiator) antenna. When using conventional monopole ESPAR antenna, we have advantages cost of hardware and power consumption of RF cirsuit because of single RF chian. But it is difficult to apply to small portable mobile device. Therefore we design patch ESPAR antenna in order to reducing volume and analyze performance of BS MIMO system that is able to MIMO communication with single RF chain. In This paper, we confirm beam pattern of designed patch ESPAR antenna is steered as ${\pm}15^{\circ}$ elevation angle. Furthermore, we design BS MIMO system using this ESPAR antenna and confirm BER performance of this system.