• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.239-244
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• 2014

The conventional clustering approaches are mostly based on minimizing total dissimilarity of input and output. However, the clustering approach may not be helpful in some cases of clustering decision making units (DMUs) with production feature converting multiple inputs into multiple outputs because it does not care converting functions. Data envelopment analysis (DEA) has been widely applied for efficiency estimation of such DMUs since it has non-parametric characteristics. We propose a new clustering method to identify groups of DMUs that are similar in terms of their input-output profiles. A real world example is given to explain the use and effectiveness of the proposed method. And we calculate similarity value between its result and the result of a conventional clustering method applied to the example. After the efficiency value was added to input of K-means algorithm, we calculate new similarity value and compare it with the previous one.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.87-87
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• 2000

In this paper, an integrated design of fault detection, diagnosis and reconfigurable control tot multi-input and multi-output system is proposed. It is based on the interacting multiple model estimation algorithm, which is one of the most cost-effective adaptive estimation techniques for systems involving structural and/or parametric changes. This research focuses on the method to recover the performance of a system with failed actuators by switching plant models and controllers appropriately. The proposed scheme is applied to a fault tolerant control design for flight control system.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.105-111
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• 2020

In most multiple input/output systems, one input affects two or more different outputs. Therefore, there are many inconveniences in using the actual system. In order to solve this problem, a controller that makes an input signal and an output correspond 1:1 is called a decoupling controller. In this paper, I try to implement a relatively simple decoupling controller using a cross-compensator, that is, a compensator that takes an uncorresponding output as an input value. And this cross-compensator has a gain scheduler structure in order to increase the performance. In addition, this system is designed with a distributed control structure using CAN communication, so that it can be manufactured and operated in an easier way when implementing an actual experimental system. The proposed structure is applied to the modified new Arago's disk system and tested, and through this, the effectiveness is confirmed and reported.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.520-530
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• 2016

Since FDD massive MIMO (multiple-input multiple-output) system deploys hundreds of transmit antennas at base station (BS) compared to conventional MIMO system, the overhead of transmitting channel state information reference signal (CSI-RS) increases proportionally to the number of transmit-antennas. To overcome these disadvantages, we proposed beamforming based CSI-RS transmission technique for FDD massive MIMO system which transmit CSI-RS by limited amount of downlink resources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.841-849
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• 2012

This paper proposes an low-complexity soft-output multiple-input multiple-output (soft-MIMO) detection algorithm for achieving soft-output maximum-likelihood (soft-ML) performance under max-log approximation. The proposed algorithm is based on a parallel tree-search (PTS) applying a channel ordering by a sorted-QR decomposition (SQRD) with altered sort order. The empty-set problem that can occur in calculation of log-likelihood ratio (LLR) for each bit is solved by inserting additional nodes at each search level. Since only the closest node is inserted among nodes with opposite bit value to a selected node, the proposed node insertion scheme is very efficient in the perspective of computational complexity. The computational complexity of the proposed algorithm is approximately 37-74% of that of existing algorithms, and from simulation results for a $4{\times}4$ system, the proposed algorithm shows a performance degradation of less than 0.1dB.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2621-2624
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• 2003

In this paper, we designed 12Bit DAC(Digital to Analog Converter) that applied to multiple-valued logic system to Binary system. The proposed D/A Converter structure consists of the Binary to Quaternary Converter(BQC) and Quaternary to Analog Converter(QAC). The BQC converts the two input binary signals to the one Digit Quaternary output signal. The QAC converts the Quaternary input signal to the Analog output signal. The proposed DAC structure can implement voltage mode DAC that high resolution low power consumption with reduced chip area. And also, it has advantage of the easy expansion of resolution and fast settling time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.6
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• pp.2546-2566
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• 2016

This paper investigates an efficient transmission scheme for the remote wireless sensors to receive information which is rarely discussed in the integrated remote wireless sensor and multibeam satellite networks (IWSMSNs). The networks can be employed to exchange sensing information for emergency scenario, ocean scenario, and so on, which are isolated from available terrestrial networks. As the efficient transmission link is important to the IWSMSNs, we propose a hybrid full frequency (HFF) precoding by taking advantage of frequency reuse and multiple-input multiple-output (MIMO) precoding. Considering energy efficiency and sinks fairness are crucial to transmission link, thus the HFF precoding problems are formulated as transmit power minimization (TPM) and max-min fair (MMF) received signal to interference plus noise ratio (SINR) problems, which can be transformed to indefinite quadratic optimization programs. Then this paper presents a semi-definite programming (SDP) algorithm to solve the problems for the IWSMSNs. The promising potential of HFF for the real IWSMSNs is demonstrated through simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1534-1542
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• 2009

In this paper we achieve experimental data evaluation using SSB(Single-side band) modulation in the ocean. Present research in underwater communication is applying digital modulation, OFDM(Orthogonal Frequency Division Modulation) and MIMO(Multiple Input Multiple Output) system. However, Commercial modems using analog modulation techniques in oceans. So, we achieved experimental for modem appliance development of correct high quality in South Korea sea characteristics. This experimets achievd useing SSB analog modulation in Jin-hae shore of shallow water condition. We analyzed Doppler effects, reverberation and transmission characteristics for real channel effect analysis. As a result, reverberation and ships self-noise are disturbed factors for underwater communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.607-613
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• 2004

The future wireless communication systems will use spatial multiplexing with Multiple Input Multiple Output(MIMO) system to take advantage of high spectral efficiencies. In such systems it will be desirable to select a sub-set of available transmit or receive antennas to reduce cost and complexity. In this paper we propose a novel transmit antenna selection schemes for MIMO systems which is suitable for multipath environment. The proposed transmit antenna selection schemes offer better BER performance than that of MIMO systems without antenna selection and with traditionally proposed antenna selection schemes.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.130-139
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• 2010

Environmental issues and the need to reduce energy consumption for lowering operating costs have pushed power efficiency to become one of the major issues of current research in the field of wireless networks. This paper addresses a number of multiple input multiple output (MIMO) precoding and scheduling techniques across the PHY and MAC layers that can operate under a reduced link budget and collectively improve the transmit power efficiency of a base station, while maintaining the same levels of service. Different MIMO transmission and precoding schemes proposed for LTE, achieving varying degrees of multiuser diversity in both the time, frequency as well as the space domain, are examined. Several fairness-aware resource allocation algorithms are applied to the considered MIMO schemes and a detailed analysis of the tradeoffs between power efficiency and quality of service is presented. This paper explicitly examines the performance of a system serving real-time, VoIP traffic under different traffic loading conditions and transmit power levels. It is demonstrated that by use of efficient scheduling and resource allocation techniques significant savings in terms of consumed energy can be achieved, without compromising QoS.