• ETRI Journal
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• v.31 no.4
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• pp.472-474
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• 2009

In this letter, an ordered successive interference cancellation (OSIC) scheme is applied for multiple-input multiple-output (MIMO) detection in ultra-wideband (UWB) communication systems. The error rate expression of an OSIC receiver on a log-normal multipath fading channel is theoretically derived in a closed form solution. Its bit error rate performance is analytically compared with that of a zero forcing receiver in the UWB MIMO detection scheme followed by RAKE combining.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.46-49
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• 2007

Multiple Antenna Technologies such as Multiple-Input Multiple-Output (MIMO) and Beamforming provide the increase of channel capacity and the reliability of wireless link. To obtain these advantages, WiBro, Mobile WiMAX and $4^{th}$ Generation System are employing multiple antenna technologies. There exist, however, many technical issues in considering the application of the technologies or the providing of services using them. In this paper, various technical topics are discussed and simple solutions are proposed. Beamforming has several technical issues which include coverage imbalance, difficulties in providing Multicast-Broadcast Service (MBS). In Addition, network planning is a critical point from a cell extension and initial network entry point of view. In case of MIMO, network deployment is discussed in that cellular data network such as WiBro has many repeaters. MIMO mode selection for maximizing the cell capacity is also covered.

• 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.28 no.4
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• pp.351-354
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• 2017

In this paper, a compact MIMO(Multiple Input Multiple Output) antenna for smart glasses is proposed. The proposed MIMO antenna is designed using T-shaped isolator inserted between two closely located Inverted-F Antenna(IFA) and using two slots located in the ground for isolation enhancement and impedance matching characteristic. The proposed antenna has only the overall dimensions of $35mm{\times}9mm{\times}0.8mm$ and operates in the 2.4 GHz industrial, scientific, and medical(ISM) band. To verify human body effect, the phantom is used for antenna performance. The measured specific absorption rate(SAR) value is 1.38 W/kg with an input power of 18 dBm. The performance of the proposed antenna is compared with that of previous works for verification.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.7
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• pp.2365-2382
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• 2014

While single-user spatial multiplexing multiple-input multiple-output (SU-MIMO) allows spatially multiplexed data streams to be transmitted to one node at a time, multi-user spatial multiplexing MIMO (MU-MIMO) enables the simultaneous transmission to multiple nodes. However, if the transmission time required to send packets to each node varies considerably, MU-MIMO may fail to utilize the available MIMO capacity to its full potential. The transmission time typically depends upon two factors: the link quality of the selected channel and the data length (packet size). To utilize the cumulative capacity of multiple channels in MIMO applications, the assignment of channels to each node should be controlled according to the measured channel quality or the transmission queue status of the node.A MAC protocol design that can switch between MU-MIMO and multiple SU-MIMO transmissions by considering the channel quality and queue status information prior to the actual data transmission (i.e., by exchanging control packets between transmitter and receiver pairs) could address such issues in a simple but in attractive way. In this study, we propose a new MAC protocol that is capable of performing such switching and thereby improve the system performance of very high throughput WLANs. The detailed performance analysis demonstrates that greater benefits can be obtained using the proposed scheme, as compared to conventional MU-MIMO transmission schemes.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.51-58
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• 2003

Generally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity reception and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, multiple-input multiple-output (MIMO) scheme is devised to exploit multi-path in a scattering wireless channel. In this paper, we have evaluated the channel capacity of MIMO Multi-Carrier CDMA system in path correlation fading channel. And, the channel capacity of MIMO system is compared with single-input single-output (SISO) system. From the results, the MIMO multi-carrier CDMA system with path correlation yields better performance with respect to channel capacity than a SISO system.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.535-539
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• 2008

Recently mobile devices can transmit mass data contained multi-media contents. According these flow, a demand for fast data transmission is being risen, so we acutely require remarkable technology that overcome mobile communication's poor environment and rise data transmission volume. Because it can be satisfied these needs, the OFDM(Orthogonal Frequency Division Multiplexing) that rise data transmission volume using efficient frequency, and MIMO(Multiple Input Multiple Output) that rise transmission confidence and data transmission volume using numbers of antenna is attended. Before design of MIMO-OFDM System we want to make an analysis for theory of its systems, and we want to design MIMO-OFDM simulator for verify an ability of modulation, data volume and numbers of antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.341-349
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• 2010

In this paper, we studied on the optimization of the output power of Mobile WiMAX (IEEE 802.16) base station considering the technical condition of base station and wireless channel condition. The optimum power of base station can be estimated based on the link budget calculation of downlink and uplink in the Mobile WiMAX communication system. We investigated the optimum output power of base station in the case of 2Tx-2Rx base station with $2{\times}2$ MIMO(multiple input multiple output) technology, 2Tx-4Rx base station with improved receiver sensitivity, and 4Tx-4Rx base station with beamforming technology.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.168-186
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• 2016

In this paper, we investigate the degrees of freedom (DoF) of a two-cluster multiple-input multiple-output (MIMO) multiway relay interference channel (mRIC), where there are two relays and two users per cluster. In this channel, users within the same cluster exchange messages among themselves with the help of two relays.We first obtain the DoF upper bound of the considered MIMO mRIC based on cut-set bound. Then, we propose a novel transmission strategy, blind interference neutralization (BIN), to approach the DoF upper bound. This new method utilizes the overheard information at two relays and focuses on the beamforming matrix designs at two relays so that the channel state information (CSI) at users is not required. Through theoretical analysis and numerical simulations, we show that the DoF upper bound can be obtained by using the BIN scheme. From simulation results, we show that the proposed BIN scheme can provide significant performance gain over the conventional time division multiple access (TDMA) scheme in terms of DoF. In addition, we show that the BIN scheme is a superior approach to the existing signal space alignment (SSA) schemes for the considered mRIC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.706-711
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• 2012

The current visible light communication (VLC) systems have a short transmission distance and a low data rate. To overcome this, we studied on the method of appling MIMO technology to VLC. However, it is difficult to apply the original MIMO technology used in RF frequency to wireless VLC. In VLC system, a lens can be used to separate the transmitted signals. And, if we use an image sensor as the receiver, MIMO technology can be applied to LED wireless visible light communication. In this paper, we report an experiment of $2{\times}2$ LED wireless visible light communication using a commercial image sensor receiver. We show the experimental demonstration with a transmission length of 10.5 m and a data rate of 200 bit/s.