• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.408-422
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• 2000

In this paper, we propose a generalized vector channel model for wireless communication systems using antenna arrays. The proposed channel model reflects path loss. spatial-temporal variation of shadowing, multipath fading , Doppler effect, spatial distribution of local scatterers and delay spread due to remote dominant scatterers. In addition, we use a discrete ray model in which respective ray signal experiences independent shadowing, fading and Doppler shift, and impinges on antenna arrays at a distinct angle. Based on the proposed mode. we derive the relations on the spatial and temporal correlations of the received signals and implement a spatial channel simulator. By comparing the theoretical values with the simulated ones, we verify the effectiveness of the implemented simulator. The simulator is then used to generate an arbitrary channel impulse response and to analyze the channel characteristics under various environments.

• Journal of Convergence for Information Technology
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• v.7 no.2
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• pp.53-58
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• 2017

This paper describes the design of a simulator for analyzing the accuracy of a correlative interferometer(CI) direction finder. CI direction finder is robust to noise, so it is often used in aircraft or ships where complex antenna installation is required, and the direction finding accuracy is very high. When the radio wave is incident at a specific azimuth angle, the phase difference calculated in a noiseless environment and the phase difference measured in a real environment with noise are fused to estimate the largest correlation coefficient as the azimuth angle of the radio wave. The simulator receives RF frequency, the number of antennas, the antenna coordinates, the transmission signal intensity, the bandwidth of the receiver, the gain and the payload effect, and calculates the direction finding accuracy of 0-360 degrees azimuth and 0-60 degree elevation with 0.5 degree. accuracy.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.7
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• pp.827-834
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• 2014

In this paper, a triple-band U-shaped monopole antenna with T-shaped stub for WLAN(Wireless Local Area Networks)/WiMAX(World interoperability for Microwave Access) applications. The proposed antenna is based on a planar monopole design, and composed of U-shaped of radiating patch, T-shaped strip in U-shaped, for triple-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that greatly effect antenna characteristics. Using the obtained parameters, the antenna is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. And characteristics of gain and radiation patterns are determined for WLAN/WiMAX application.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.219-224
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• 2017

Recently, the importance of DRAM is very significant not only in embedded systems and mobile devices but also in high-end modern microprocessors and multicore processors. To keep up with this, both industry and academia have actively studied various types of future DRAMs. Therefore, accurate DRAM model is requisite when evaluating the microprocessor performance. In this paper, a microprocessor trace-driven simulator which can couple with the cycle-accurate DRAM simulator has been developed. Using SPEC 2000 benchmarks as input, the effect of cycle-accurate DDR3 model on the microprocessor performance has been evaluated.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.203-208
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• 2017

Recently, the importance of DRAM is very significant in multicore processors which are widely used in computers, laptops, tablet PCs, and mobile devices. To keep up with this, both industry and academia have actively studied various types of future DRAMs. Therefore, accurate DRAM model is requisite when evaluating the multicore processor performance. In this paper, a multicore processor trace-driven simulator which can couple with the cycle-accurate DRAM simulator has been developed. Using SPEC 2000 benchmarks as input, the effect of cycle-accurate DDR3 model on the multicore processor performance has been evaluated.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.7
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• pp.987-994
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• 2013

In this paper, a dual-band open-ended circular ring moNopole antenna for WLAN(Wireless Local Area Networks) applications. The proposed antenna is based on a planar moNopole design, and composed of open-ended one circular ring of radiating patches for dual-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that effect antenna characteristics. Using the obtained parameters, the proposed antenna is fabricated. The fabricated antenna is measured at the operating frequencies(2.4-2.484 GHz, 5.15-5.825 GHz), and the return loss coefficient, gain, and radiation patterns are determined.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.57-61
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• 2009

This paper has presented the subthreshold current model of FinFET using the potential variation in the doped channel based on the analytical solution of three dimensional Poisson's equation. The model has been verified by the comparison with the data from 3D numerical device simulator. The variation of subthreshold current with front and back gate bias has been studied. The variation of subthreshold swing and threshold voltage with front and back gate bias has been investigated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.337-342
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• 2001

This paper provides a comprehensive study of the effect of time delay on adaptive transmission methods. By adaptive we mean that the transmission of data is made adaptive according to channel conditions. That is, the modulation level at the transmitter is carefully controlled for maximizing bandwidth efficiency, on the basis of the observation of instantaneous channel characteristics. By making use of the simulator developed for the present work, a large number of channel propagation environments including the models proposed in 3GPP were submitted to the simulator and the performance with respect to both time delay and SNR is observed. The results show that the performance is very sensitive to channel delay and in some cases the performance shows irreducible BER (IBER). A large amount of delay together with a high fading rate greatly affects the performance of adaptive transmission systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.72-77
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• 2014

There are two main technologies to implement cloud effect in flight simulator, cloud modeling using particle system and texture mapping. In former case, this approach may cause a low frame rate while unrealistic cloud effect is observed in latter case. To Solve this problem, in this paper, we propose how to apply fog effect into camera to display more realistic cloud effect with high frame rate. The proposed method is tested with massive terrain database environment through implemented software by using OpenSceneGraph. As a result, compared to texture mapping method, the degree of difference on frame rate is 1 or 2Hz while the cloud effect is significantly improved as realistic as particle system.

• Journal of information and communication convergence engineering
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• v.19 no.4
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• pp.263-268
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• 2021

Although the compact capacitance model of point tunneling types of tunneling field-effect transistors (TFET) has been proposed, those of line tunneling types of TFETs have not been reported. In this study, a compact capacitance model of an L-shaped TFET (LTFET), a line tunneling type of TFET, is proposed using the previously developed surface potentials and current models of P- and L-type LTFETs. The Verilog-A LTFET model for simulation program with integrated circuit emphasis (SPICE) was also developed to verify the validation of the compact LTFET model including the capacitance model. The SPICE simulation results using the Verilog-A LTFET were compared to those obtained using a technology computer-aided-design (TCAD) device simulator. The current-voltage characteristics and capacitance-voltage characteristics of N and P-LTFETs were consistent for all operational bias. The voltage transfer characteristics and transient response of the inverter circuit comprising N and P-LTFETs in series were verified with the TCAD mixed-mode simulation results.