• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.404-412
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• 2014

Exploiting multiple antennas at mobile devices is difficult due to limited size and power. In this paper, a distributed MIMO protocol achieving the capacity of conventinal MIMO systems is proposed and analyzed. For exploiting distributed MIMO features, Quantize-Map-and-Forward (QMF) scheme shows improved performance than Amplify-and-Forward (AF) scheme. Also, the protocol based on multiple access channel (MAC) is proposed to improve the multiplexing gain. We showed that sufficient condition of the number of slave nodes to achieve the gain of a MAC based protocol. Because the base station can support multiple clusters operating in distributed MIMO, the total cellular capacity can be extremely enhanced in proportional to the number of clusters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.748-757
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• 2015

MIMO systems utilizing multiple antenna transmission and reception is one of the key technologies to enhance the capacity of 5G wireless communications. In order to obtain an appropriate performance evaluation of MIMO techniques, the usage of wireless channel model reflecting spatial channel characteristics is required, such as the 3-dimensional spatial channel model(3D SCM) proposed by 3GPP TR36.873 documentation. In this paper, we implement and verify the channel simulation environment based on 3D SCM, to present and compare the characteristics of UMi and UMa environments. We also apply MIMO transmission to the UMa scenario to investigate the channel correlation among antenna elements with different array distances and to identify the corresponding throughput changes. By evaluating the channel power correlations for randomly distributed users within the sector for different horizontal and vertical antenna distances, we present the statistical characteristics which determine the transmission performance under the SCM environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.494-499
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• 2009

In this paper, we provide an efficient method of user selection for achieving the maximum system throughput in downlink multiuser Multiple-Input Multiple-Output (MIMO) systems. A proposed method is for selecting a fine user set only with powers of each user channel and angles between them. This algorithm is simpler than SUS because there is no considering about the optimal value of correlation. The proposed method finds the user set toward maximizing system throughput, so it has high performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1092-1099
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• 2006

Future wireless communication systems will employ spatial multiplexing with multiple antennas at both transmitter and receiver to take advantage of larger capacity gains as compared to the systems that use a single antenna. However, in order to reduce higher hardware costs and computational burden, it will require an efficient transmit-receive antenna selection algorithm, which we propose in this paper. Through simulation and comparative analysis of various existing methods and the one we propose in this paper, the algorithm we propose was validated as nearer to the optimal selection technique than existing nearly optimal antenna selection schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1565-1573
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• 2011

In this paper, we present a MIMO-OFDM broadband power line communication (BPLC) for Smart Grid and its associated applications and analyze its performance over the 3-phase 4-wire power line channels. For practical BPLC system simulation, we adopt the statistical power line fading channel model instead of the existing deterministic fading channel models (Zimmermann model, MTL model, and so on). In this paper, we implement $2{\times}2$ and $3{\times}3$ MIMO schemes using 3-phase 4-wire power lines. We investigate the capacity loss and BER performance of the proposed MIMO system by considering the effect of cross-talk between antenna paths. We choose space-frequency coding in order to reduce frequency interference between subcarriers and employ maximum ratio combining (MRC) that achieves both multiple antenna path diversity gain and multiple fading path diversity gain. We evaluate the proposed system performance through computer simulation in terms of the impulse noise index and the capacity loss ratio and compare the different signal combining schemes including MRC, equal gain combing (EGC), and selection combining (SC).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1161-1166
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• 2005

In this paper, for spatial multiplexing with limited feedback, we propose subspace based precoding in which the active bases are selected at the receiver from a finite number of basis sets known at both receiving and transmitting ends, conveyed to the transmitter using limited feedback, and assembled into a preceding matrix at the transmitter. The selected bases are conveyed to the transmitter using feedback information on both the index of a basis set, which indicates the most appropriate set of coordinates for describing a MIMO channel, and the active bases having the significant amounts of energy in the selected basis set. We show that the proposed subspace based precoding provides capacity similar to that of the closed-loop MIMO even with limited feedback.

• Journal of KIISE:Information Networking
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• v.41 no.4
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• pp.192-201
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• 2014

User scheduling boosts the Multi-User Multi-Input Multi-Output (MU-MIMO) gain by selecting an optimal set of users to increase the 802.11 Wi-Fi system capacities. Many kinds of user scheduling algorithms, however, fail to realize the advantages of MU-MIMO due to formidable Channel State Information (CSI) overhead. In this paper, we propose a user scheduling method considering such CSI exchange overhead and its MAC protocol, called ACE (Active CSI Exchange based User Scheduling for MU-MIMO Transmission). Unlike most proposals, where user scheduling is performed after an Access Point (AP) receives CSI from all users, ACE determines the best user set during the CSI exchange phase. In particular, the AP broadcasts a channel hint about previously scheduled users, and the remaining users actively send CSI reports according to their Effective Channel Gains (ECGs) calculated from the hint. Through trace-driven MATLAB simulations, we prove that the proposed scheme improves the throughput gain significantly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.712-723
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• 2013

Recent exploration of smart-phone user is fueling the deployment of long term evolution (LTE) service that offers higher data rates service over 3G HSPA networks. In particular, Korea, mobile powerhouse, recently launched the service of LTE-Advanced (LTE-A) which is the latest release in LTE standard. Multiple-input-multiple-output (MIMO) technology is the one of key enablers for LTE and LTE-A for achieving high data rate. MIMO technology has received much attention since it is possible to achieve channel capacity in proportion to the number of antennas without increasing frequency and power. In this paper, we overview of the theoretical background of MIMO technology regarding from single-user MIMO, multiuser MIMO, and massive MIMO and design considerations to implement the communication system.

• Electronics and Telecommunications Trends
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• v.21 no.3 s.99
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• pp.48-58
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• 2006

다중 송수신 안테나 시스템은 추가적인 주파수나 송신전력의 할당 없이도 채널 용량을 안테나 수에 비례하여 증가시킬 수 있는 장점으로 인해 차세대 통신기술의 핵심으로 부각되고 있다. 본 원고에서는 이동통신 시스템에서 다중 송수신 안테나간 채널 특성을 활용하여 무선링크의 신뢰도와 전송률을 증대시키는 다중 송수신 안테나 전송기술과 전체 채널용량을 증가시키기 위한 다중사용자 다중 송수신 안테나 전송기술의 내용 및 동향을 소개한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.3-9
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• 2012

In this paper, we present novel analysis results of sonar communication using parametric array. We consider transducer diameter, primary frequency, difference frequency and acoustic power as analysis parameters of communication performance. We calculate theoretical BER(Bit Error Rate) and channel capacity of MIMO(Multi Input and Multi Output) communication system. By considering practical parameters, we obtain optimum difference frequency generation condition. The obtained primary frequency is 560 kHz, difference frequency 45kHz and acoustic power is 28.05Watt. For BER of $10^{-4}$, the range gain of parametric array communication is 3.35km compared to primary frequency communication. For channel capacity of 10bps/Hz, the SISO and $2{\times}2$ MIMO communication range of parametric array communication are 3.8km and 3.98km respectively, while primary frequency communication range is 0.83km.