• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1198-1204
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• 2006

In this paper, we extend SVR-MMSE detection scheme which is proposed in MIMO system to MIMO-OFDM system, and evaluate performance of the system in frequency selective fading channel. First of all, we explain about typical MIMO-OFDM system and detection scheme of constant modulus signals in this system. And compare proposed SVR-MMSE with Zero Forcing, Minimum Mean Square Error which is conventional detection scheme. we identify that the performance of the proposed system is shown different by varying doppler frequency in frequency selective fading channel using jakes channel model. The result of detection performance by the proposed SVR-MMSE in this simulation, it shows that proposed algorithm have a good performance in MIMO-OFDM systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.431-436
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• 2014

In this paper, we propose a compressive sensing-based channel quantization feedback mechanism that is appropriate for practical massvie multiple-input multiple-output (MIMO) systems. We assume that the base station (BS) has a compact uniform square array that has a highly correlated channel. To serve multiple users, the BS uses a zero-forcing precoder. Our proposed channel feedback algorithm can reduce the feedback overhead as well as a codebook search complexity. Numerical simulations confirm our analytical results.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.639-644
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• 2000

An experiment on the enhancement of turbulent flow with ultrasonic forcing was carried out by using PIV measurement in a coaxial circular pipe which could offer characteristics of the turbulence flow plentifully through its jet. A large transparent acryl tank and a coaxial circular pipe nozzle were made for the above research. city water of $25^{\circ}C$ was selected as an experimental liquid and the front flow field of the coaxial circular pipe was divided vertically as 3 measuring regions to observe characteristics of flow phenomena. characteristics of fluid flow such as velocity vector distribution, kinetic energy, turbulent intensity and etc. were visualized, observed, examined and considered at 5 kinds of Re No. such as $Re=1{\times}10^3,\;2{\times}10^3,\;3{\times}10^3,\;5{\times}10^3,\;1{\times}10^4$. In result it was proved that ultrasonic vibration affected the enhancement of turbulent flow.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.2275-2293
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• 2020

This paper focuses on the simplified receiver design for multi-user circular block oversampled filter bank (CB-OSFB) uplink systems. Through application of discrete Fourier transform (DFT), the special banded structure and circular properties of the modulation matrix in the frequency domain of each user are derived. By exploiting the newly derived properties, a simplified zero-forcing (ZF) receiver is proposed for multi-user CB-OSFB uplink systems in the multipath channels. In the proposed receiver, the matrix inversion operation of the large dimension multi-user equivalent channel matrix is transformed into DFTs and smaller size matrix inversion operations. Simulation is given to show that the proposed ZF receiver can dramatically reduce the computational complexity while with almost the same symbol error rate as that of the traditional ZF receiver.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.15-20
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• 2016

Compared to the MIMO system using the spatial multiplexing methods and the MIMO system using the diversity scheme achieved a high rate, but the lower the diversity gain to improve the data transmission reliability should separate the spatial stream at the MIMO receiver. In this paper, we compared Channel capacity detection methods with the Lattice code, the 3-user interference channel and linear channel interference detection methods ZF (Zero Forcing) and MMSE (Minimum Mean Square Error) detection methods. The channel is a Diagonal channel. In other words, Diagonal channel is confirmed by the inverse matrix satisfies the properties of Jacket are element-wise inverse to $[H]_N[H]_N^{-1}=[I]_N$.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.6
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• pp.70-75
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• 2000

This paper examines the performance of adaptive filtering algorithms in relation to the asymptotic relative efficiency (ARE) of estimators. The adaptive filtering algorithms are Hybrid II and modified zero forcing (MZF) algorithms. The Hybrid II and MZF algorithms are simplified forms of the LMS algorithm, which use the polarity of the input signal, and polarities of the error and input signals, respectively. The ARE of estimators for each algorithm is analyzed under the condition of the same convergence speed. Computer simulations for adaptive equalization are performed to check the validity of the theory. The explicit expressions for the ARE values of the Hybrid II and MZF algorithms are derived, and its results have similar values to the results of computer simulation. It also revealed that the ARE values depend on the correlation coefficients between input signal and error signal.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.675-678
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• 2008

The effect of wave and current interactions on jet-like current flowing against waves was investigated based on numerical simulations. The numerical simulations are conducted by a combined model system of REF/DIF(a wave model) plus SHORECIRC(a current model) and a Boussinesq equation model, FUNWAVE. In the simulations, regular and irregular waves refracted due to the jet-like opposing current were focused along the core region of current, and the jet-like current was earlier spreaded when the waves had larger wave heights. The numerical results show that the rapid change of wave height distribution in transverse direction near current inlet plays a significant role to spread the jet-like current. In other words, the gradients of radiation stress forcing in transverse direction have a more significant effect on the jet-like current than its relatively small gradients forcing in flowing direction, which tend to accelerate the current, do. In conclusion, it is indispensible to take into account the interaction effect of wave transformation and current characteristics when waves meet the opposing jet-like current such as river mouth.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.658-667
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• 2006

Fractional derivative models, which are used to describe the viscoelastic behavior of material, have received considerable attention. Thus it is necessary to put forward the analysis solutions of dynamic systems containing a fractional derivative. Although previously reported such kind of fractional calculus-based constitutive models, it only handles the particularity of rational number in part, has great limitation by reason of only handling with particular rational number field. Simultaneously, the former study has great unreliability by reason of using the complementary error function which can't ensure uniform real number. In this paper, a new approach is proposed for an analytical scheme for dynamic system of a spring-mass-damper system of single-degree of freedom under general forcing conditions, whose damping is described by a fractional derivative of the order $0<{\alpha}<1$ which can be both irrational number and rational number. The new approach combines the fractional Green's function and Laplace transform of fractional derivative. Analytical examples of dynamic system under general forcing conditions obtained by means of this approach verify the feasibility very well with much higher reliability and universality.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.2
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• pp.235-247
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• 2006

Aerosol indirect radiative forcing of climate change is considered the most uncertain forcing of climate change over the industrial period, despite numerous studies demonstrating such modification of cloud properties and several studies quantifying resulting changes in shortwave radiative fluxes. Detection of this effect is made difficult by the large inherent variability in cloud liquid water path (LWP): the dominant controlling influence of LWP on optical depth and albedo masks any aerosol influences. Here we have used ground-based remote sensing of cloud optical depth (${\tau}_c$) by narrowband radiometry and LWP by microwave radiometry to determine the dependence of optical depth on LWP, thereby permitting examination of aerosol influence. The method is limited to complete overcast conditions with liquid-phase single layer clouds, as determined mainly by millimeter wave cloud radar. The results demonstrate substantial (factor of 2) day-to-day variation in cloud drop effective radius at the ARM Southern Great Plains site that is weakly associated with variation in aerosol loading as characterized by light-scattering coefficient at the surface. The substantial scatter suggests the importance of meteorological influences on cloud drop size as well, which should be analyzed in the further intensive studies. Meanwhile, it is notable that the decrease in cloud drop effective radius results in marked increase in cloud albedo.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.169-174
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• 2002

It has known that the DCMP(Directionally Constrained Minimization of power)and the ZF(Zero Forcing) can improve the SINR performance of an array antenna system by using spatial signature of wireless channel. This paper analyzes performance of DCMP and ZF in multiple scattering environments. To obtain the spatial signature of wireless channel. bothe DOA(Directional of Arrival) and AS(Angular Spread) of the received signals were estimated by using ESPRIT. The performance of the DCMP and the ZF was analyzed theoretically. Through computer simulation, the SINR performance were evaluated.