• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.12
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• pp.1947-1955
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• 1989

With the increasing complexity of cabling at sensory level in process control and manufacturing automation, field buses were introduced to replace the traditional point to point links from each sensor or acruator to its controlling equipments by a single link on which all information is transmitted seriall and multiplexed in time. In this papr, we introduce the BITBUS network as a field bus. For the service discipline of the BITBUS network, two service strategies are proposed to obtain the performance of the network. They are the equal priority cyclic service strategy and the non-equal priority cyclic service strategy. The former assigns equal priority to each node for polling and the latter assumes non-equal priority. The BITBUS network was modeled as a cyclic queueing model and it is analyzed by two methods: the Kuehn's and the Boxma's. Computer simulation was also done for the cyclic queueing model and simulation results were compared with those. Under mathematically non-analyzable environment, only the computer simulation was done. From the simulation result, in order to meet the response time requirement of 5 msec imposed by International Electrotechnical Commission when each node has the average traffic of 5000 messages/sec in manufacturing automation the number of slave nodes should be smaller than 10 at the transmission rate of 2.5 Mbps.

• Journal of IKEEE
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• v.20 no.1
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• pp.26-30
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• 2016

In this paper, an inter-orthogonal frequency division multiplexing (OFDM) sub-carrier distortion due to fiber chromatic dispersion is investigated. The fiber chromatic dispersion induces phase difference among OFDM sub-carriers, resulting in non-symmetric peak to average power ratio (PAPR) inducing inter-OFDM distortion. Experiments to confirm the fiber dispersion are performed in a direct-detection optical front-haul link. Quadrature phase shift keying (QPSK) encoded OFDM symbols at 25 Gbit/s are transmitted over 100 km fiber and the resulting error vector magnitude (EVM) of 40 % is observed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1612-1620
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• 2003

This papers describes a nonlinear transfer function modelling of designed GaAs FET power amplifier by measured and simulated values of designed PA amplifier for multi­carrier transmission system, With the results of PA nonlinearity characteristic, we can estimates AM­AM and AM­PM of designed PA. According to the estimated nonlinear characteristics, we can analysis the ACPR of PA for spectral regrowth, the error vector measurement(EVM) of constallation signals and bit error rate of QPSK and 64­QAM. The suggested nonlinear modelling results are used to get an accurate estimate of digital characteristics between PA amplifier and wireless multi­carrier transmission system using OFDM.

• Fire Science and Engineering
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• v.31 no.4
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• pp.7-11
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• 2017

The use of special gas masks such as PAPR is strongly required for the safe and efficient work of fire-fighters in removing fire residue and rescue activity. Special gas masks commonly use canisters with carbon activated particles. This paper analyzed the pressure distribution, velocity distribution and pressure loss characteristics in canisters using CFD simulation, and showed pressure drops are affected by inlet air velocity, canister geometry and increase dramatically especially with the decrease of particle diameters and volume fractions.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.6
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• pp.2453-2459
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• 2014

Ginsenoside Rg1 is one effective anticancer and antioxidant constituent of total saponins of Panax ginseng (TSPG), which has been shown to have various pharmacological effects. Our previous study demonstrated that Rg1 had anti-tumor activity in K562 leukemia cells. The aim of this study was designed to investigate whether Rg1 could induce apoptosis in TF-1/Epo cells and further to explore the underlying molecular mechanisms. Here we found that Rg1 could inhibit TF-1/Epo cell proliferation and induce cell apoptosis in vitro in a concentration and time dependent manner. It also suppressed the expression of EpoR on the surface membrane and inhibited JAK2/STAT5 pathway activity. Rg1 induced up-regulation of Bax, cleaved caspase-3 and C-PAPR protein and down-regulation of Bcl-2 and AG490, a JAK2 specific inhibitor, could enhance the effects of Rg1. Our studies showed that EpoR-mediated JAK2/STAT5 signaling played a key role in Rg1-induced apoptosis in TF-1/Epo cells. These results may provide new insights of Rg1 protective roles in the prevention a nd treatment of leukemia.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.89-95
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• 2017

UFMC is known as a candidate for the 5G wireless communication system because it is robust against ICI and better performs in asynchronous situation than OFDM. In the UFMC system, the filtering is performed for each subband so the performance of the filter is very important. The Dolph-Chebyshev filter has been used in conventional UFMC system because of its small out-of-band radiation. However it has distortion in the sub-band and skirt characteristics is not good enough. Therefore, it is necessary to study a new type of UFMC filter which reduces the distortion in the subband and has sharp skirt characteristics. In this paper we analyze the effect of filter frequency response in UFMC system and suggest the wavelet based type of filter that substitutes the Dolph-ChebyShev filter used in the conventional UFMC system. The simulation results show that wavelet filter has better BER performance in multipath fading channels than conventional filters.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.755-761
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• 2005

In this paper, we propose a high-speed adaptive PTS method which eliminates high PAR (Peak-to-Average Power Ratio) and we compare the proposed method with other conventional methods. In addition, we have designed a combined type SLM-PTS scheme to reduce PAR and evaluate the performance. The system used for evaluating PAR performance can be constructed as COFDM (Coded Orthogonal Frequency Division Multiplexing) applying ETD(Enhabced Time Diversity)-Turbo coding scheme. All the analyses in this paper are focused on the system characteristics according to IFFT's point and modulation method and the performance evaluation are based on the PAR reduction rates. As a result, the SLM-PTS combination method reveals good PAR reduction rate and remarkable reduction in the amount of calculations. Especially, in the case of combine-3 scheme, we can achieve approximately $3.7\~3.9$ dB PAR reduction on a basis of 10-5 BER level. Moreover, we can eliminate the side information in COFDM system because of its adaptive characteristics in evaluating PAR reduction rate, so that the additional errors can be omitted.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.668-676
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• 2018

In satellite communications, a modulation technique with a low peak-to-average power ratio, high transmission efficiency, and low bit error rate(BER) is required, and differential amplitude and phase shift keying(DAPSK) modulation technique has been appraised as a technology that meets these requirements. However, because conventional DAPSK modulation uses a regular constellation diagram, the Euclidean distance between the symbols in the inner concentric circles of the constellation are quite short. Such a characteristic degrades the BER. In this paper, we propose a DAPSK system that uses an efficient constellation assignment to improve the performance of existing DAPSK systems and evaluate the performance of the proposed scheme. From the simulation results, we confirm that the proposed 16-DAPSK system achieves an signal-to-noise ratio gain of 0.8 dB over the conventional approach at a BER condition of $10^{-4}$ when the number of symbols used in the symbol detector of the receiver is 2.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.3
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• pp.339-345
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• 2016

This paper presents a two-stage power amplifier MMIC using a $0.4{\mu}m$ GaN-HEMT process. The two-stage structure provides high gain and compact circuit size using an integrated inter-stage matching network. The size and loss of the inter-stage matching network can be reduced by including bond wires as part of the matching network. The two-stage power amplifier MMIC was fabricated with a chip size of $2.0{\times}1.9mm^2$ and was mounted on a $4{\times}4$ QFN carrier for evaluation. Using a downlink LTE signal with a PAPR of 6.5 dB and a channel bandwidth of 10 MHz for the 2.6 GHz band, the power amplifier MMIC exhibited a gain of 30 dB, a drain efficiency of 32%, and an ACLR of -31.4 dBc at an average output power of 36 dBm. Using two power amplifier MMICs for the carrier and peaking amplifiers, a Doherty power amplifier was designed and implemented. At a 6 dB back-off output power level of 39 dBm, a gain of 24.7 dB and a drain efficiency of 43.5% were achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.906-914
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• 2009

SC-FDMA is employed in the 3GPP-LTE standard as the uplink transmission scheme. SC-FDMA has advantages that the signal has a low PAPR property and a simple equalizer such as FD-LE can be implemented. But FD-LE has inferior performance to Hybrid-DFE composed of frequency-domain feedforward filter and time-domain feedback filter. Recently, several IB-DFE algorithms have been proposed to overcome the disadvantages of implementation and processing complexity of Hybrid-DFE and to obtain superior performance to FD-LE. In this paper, we apply several IB-DFE algorithms to 3GPP-LTE uplink system and compare their performance by calculating BER. We investigate the effects of channel estimation errors and Doppler shift on performance. Finally, by analyzing computational complexity of IB-DFEs, we present some criteria to choose appropriate algorithm and to decide the number of iterative processes.