• Steel and Composite Structures
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• v.51 no.6
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• pp.619-645
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• 2024

In the construction industry, composite structures have revolutionized traditional design principles, opening innovative possibilities. The Concrete Encased - Concrete Filled Steel Tubular (CE-CFST) column stands out as a distinctive composite structure, offering structural stability and resilience for various engineering applications. Comprising Reinforced Concrete (RC) and Concrete Filled Steel Tubular (CFST) components, CE-CFST columns are valued for their inherent properties, including ductility and rigidity, CE-CFST is commonly used in the construction of bridges, high-rise buildings, and more. This article aims to provide a concise overview of the evolutionary development of CE-CFST columns and their performance in structural applications. Through a comprehensive review, the study delves into the behaviour of CE-CFST columns under different scenarios. It examines the influences of key parameters such as size, infills, cross section, failure causes, and design codes on the performance of CE-CFST columns, highlighting their enhanced functionality and future potential. Moreover, the review meticulously examines previous applications of CE-CFST columns, offering insights into their practical implementation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.84-90
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• 2012

Since the major cellular data service providers in U.S, Japan as well as in Korea started the LTE (Long Term Evolution) service, there has been more strong need for the methods that can accurately measure the MIMO (Multi Input-Multi Outout) OTA (Over The Air) performance of LTE handsets because the performance of the MIMO antenna determines the packet data rates in the downlink and therefore the higher system throughput of the network. In this regard, there has been a lot discussions in 3GPP on the candidate MIMO OTA test solutions. In this paper, a faire comparison has been done for the conventional method, the Envelop Correlation Coefficient (ECC) measurements, and the anechoic chamber based MIMO OTA test solution, one of the candidate system being discussed in 3GPP. The evaluations and the comparisons are conducted by numerically and experimentally.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.10-18
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• 2010

The polar transmitter is applied to the narrowband communication systems such as GSM (Global System for Mobile Communications), EDGE (Enhanced Data Rates for GSM Evolution), and GPRS (General Packet Radio Service). To apply polar transmitter for the wideband communication like OFDM (Orthogonal Frequency Division Multiplexing) where the high PAPR (Peak-to-Average Power Ratio) problem occurs, this paper proposes a windowed-sinc function based PAPR reduction scheme. The proposed algorithm mitigates the effect of excessive suppression due to successive peaks or relatively high peaks of the signal. The BER (Bit Error Rate) and EVM (Error Vector Magnitude) performances are measured for various window types and lengths. The simulation results demonstrate that the proposed algorithm achieves significant improvement in terms of BER and PAPR reduction performance with similar spectrum performance to the conventional peak windowing scheme.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.9-16
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• 2013

Long term evolution (LTE) and LTE-Advanced (LTE-A) systems adopt closed-loop multiple-input multiple-output antenna techniques. Equal gain transmission which has equal gain property is the key factor in their codebook design. In this paper, a novel differential codebook structure which maintains the codebook design requirements of LTE or LTE-A systems. Especially, eight-phase shift keying (8-PSK) constellations are used as elements of codewords, which not only maintain equal gain property but also reduce the computation complexity of precoding and decoding function blocks. The equal gain property is very important to uplink because the performance of uplink is very sensitive to the peak-to-average power ratio (PAPR). Moreover, the operation of the proposed differential codebook is explained as a rotation-lock structure. As the results of computer simulations, the steady-state throughput performance of the proposed codebook shows at least 0.9dB of SNR better than those of the conventional LTE codebook with the same amount of feedback information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.7
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• pp.723-731
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• 2016

A core technological base to provide enhanced data rates required by 5G mobile wireless communications is the improved bandwidth efficiency using massive multiple-input multiple-output (MIMO) transmission. MIMO transmission requires the channel estimation using the channel state information reference signaling (CSI-RS) and appropriate beamforming, thus the design of the codebook defining proper beamforming vectors is an important issue. In this paper, we propose a multi-rank codebook based on the discrete Fourier transform (DFT) matrix, by utilizing statistical properties of the channel generated by the spatial channel model (SCM). The proposed method includes a structural change of the precoding matrix indicator (PMI) by considering the phase difference distributions between adjacent antenna elements, as well as the selected codevector characteristics of each transmission layer. Performance gain of the proposed method is evaluated and verified by making the performance comparison to the 3GPP standard codebooks adopted by Long-Term Evolution (LTE) systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.25-33
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• 2018

In this paper, we propose an iterative self-interference (SI) channel estimation method for in-band full-duplex cellular systems that employ orthogonal frequency division multiple access (OFDMA) on downlink (DL) and single-carrier frequency division multiple access (SC-FDMA) on uplink (UL), as in Long Term Evolution (LTE) systems. The proposed method first acquires coarse estimates of SI channels using DL signals and UL pilots, which are known to the base stations, and then refines the estimates by consecutively exploiting averaging in the frequency domain and channel truncation in the time domain. In addition, the method enhances the estimates further by iteratively executing this estimation procedure, and does not require any radio resources dedicated to SI channel estimation. Simulation results demonstrate that by significantly improving the SI channel estimation performance without requiring exact knowledge of the SI channel length, the proposed method achieves UL channel estimation performance and signal-to-interference-plus-noise ratio (SINR) performance very close to those in perfect SI cancellation.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.3-9
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• 2016

Current mobile communication systems utilize the multiple-input multiple-output (MIMO) transmission technique as an important means to enhance the bandwidth efficiency. Accurate beamforming via channel estimation contributes to the signal-to-interference-plus-noise ratio (SINR) increase and the system performance improvement when MIMO transmission techniques are employed. Therefore, determination of beamforming vectors as well as the design of appropriate codebooks defining these codevectors play an important role in system operation. In this paper, we statistically analyze the phase difference between the channels corresponding to adjacent antenna elements in order to design an efficient codebook for uniform circular arrays (UCAs). We introduce new parameters which compensate for the additional phase difference observed in its probability density functions (PDFs). The performance of the proposed codebook is tested using the spatial channel model (SCM) to demonstrate its gain over the standard codebooks adopted in the long term evolution (LTE) Releases 8 and 10.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.397-407
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• 2017

A dimensionally stable anode based on the $RuO_2$ electrocatalyst is an important electrode for generating chlorine. The $RuO_2$ is well-known as an electrode material with high electrocatalytic performance and stability. In this study, sonoelectrodeposition is proposed to synthesize the $RuO_2$ electrodes. The electrode obtained by this novel process shows better electrocatalytic properties and stability for generating chlorine compared to the conventional one. The high roughness and outer surface area of the $RuO_2$ electrode from a new fabrication process leads to increase in the chlorine generation rate. This enhanced performance is attributed to the accelerated mass transport rate of the chloride ions from electrolyte to electrode surface. In addition, the electrode with sonodeposition method showed higher stability than the conventional one, which might be explained by the mass coverage enhancement. The effect of sonodeposition time was also investigated, and the electrode with longer deposition time showed higher electrocatalytic performance and stability.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.28-32
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• 2014

In this paper, we analyzed the performance of cyclostationary signal detection scheme for LTE system. We applied the cyclostationary signal detection scheme to the cognitive radio(CR) technology, which improves the usage efficiency of spectrums and shares frequencies, and we detected the signal in the long term evolution(LTE) band. LTE system has been designated as the standard to improve the maximum data rate and provide the low latency in the 3rd generation partnership project(3GPP). In this paper, we generated the LTE signals based on the orthogonal frequency division multiple access(OFDMA) and analyzed the performance of signal detection in accordance with the segment and threshold of the generated signals. Gaussian channel was used in the simulation and we discussed the future studies to apply the CR to the LTE system.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.4
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• pp.7-15
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• 2010

This study proposes a rad o resource management scheme to maximize the performance of the LTE(Long Term Evolution) uplink, using SC-FDMA(Single Carrier-Frequency Division Multiple Access). Rather than the single-cell SC-FDMA system the existing studies are mainly concerning, this study focuses on multi-cell system which needs considering the interaction among cells. Radio resource management is divided into two phases, planning and operation phases. The former is for the master eNB(e-NodeB) to allocate RBs(radio bearer) to eNB, the latter for eNB to assign RBs to the mobiles in the cell. For each phase, an optimization model and greedy algorithm are proposed. Optimization models aim to maximize the system performance while satisfying the constraints for both QoS and RB continuity. The greedy algorithms, like generic ones, move from a solution to a neighboring one having the best objective value among neighboring ones. From the numerous numerical experiments, the performance and characteristics of the algorithms are analyzed. This study is expected to play a volunteering role in radio resource management for the multi-cell SC-FDMA system.