• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1097-1100
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• 2008

We demonstrate that the performance of amorphous indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFT) can be optimized by controlling the interfaces between IGZO and sandwiching insulators and by proper deposition of IGZO layer. Specifically, contact and channel resistances are decreased by reducing IGZO bulk resistance and optimizing dry-etch process, respectively. Field-effect mobility ($\mu_{FE}$) and subthreshold gate swing (S) are further enhanced by fine-tuning IGZO deposition condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.813-822
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• 2003

Conventional TCPs are designed to work efficiently on wired network where any transmission errors rarely take place. However, the probability of transmission error in a wireless network is much higher than in a wired network, due to pass loss, multipath fading, and many kinds of interference. There were many researches on preventing the degradation of TCP performance in these wireless networks with bad channel condition. One of these researches is the SNOOP protocol which is link-layer solution for achieving high throughput of TCP. However, this SNOOP protocol is apt to retransmit some TCP segments unnecessarily, which could cause some increased traffic loads in a wireless network. In this paper, we propose a new algorithm to prevent the unnecessary retransmission of TCP segments and to achieve increased performance of TCP.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.39-44
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• 2010

In this paper, we analyze the performance of the cooperative cognitive radio relay system which is adapted the recently highly focused cognitive radio system. The performance comparison is made between the system with and that without the opportunistic transmission relay. Especially the selection combining is considered at the destination for simple implementation. In this case, the effect of the channel state information (CSI) delay, which is caused essentially by the process during the CSI delivery, to the system performance is considered. It is noticed that the performance of the system with the opportunistic relay degrades up to 0.6 dB at a given condition compared to the system without the opportunistic relay. And it is shown that the system performance is more sensitive to the CSI delay compared to the frequency acquisition probability of the cognitive radio relay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.183-187
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• 2000

In this paper, the performance of DS-CDMA system and FH-CDMA system has been comparision analyzed in a channel environment which is characterized by Multi-User environment and Rayleigh fading environment. The techniques of improvement of the performance has been comperision analysis evaluated when adopting MRC diversity techniques. In same condition, We are analyzed the BER(Bit Error Rate) as increase Use's number due to comparing performance of two systems by Same communication band(300KHz), jamming signal(JSR) 10∼20dB, user data-rate 300bps. In the result, the performance of DS and FH systems in multiuser and Rayleigh fading environment is improved performance when adopting MRC diversity techniques. Especially DS system has been improved performance about 9.5 times than FH system when adopting MRC diversity techniques.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.222-227
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• 2012

In this paper, we analyze the total performance according to duty cycle of interfering transmitter in hetero systems. We analyze this criteria as a parameter for co-use when hetero systems share the same frequency channels. In order to make an analysis of relationship between duty cycle and performances of two systems. We take into consideration on the case that WiBro is an victim receiver and WLAN is a interfering transmitter. Analyzed coexistence results may be widely applied into the technique developed to get the coexisting condition for wireless devices using many communication protocols in same frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.967-973
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• 2009

Recently, as 3rd-generation mobile communication services using high-speed data rate system are widely employed, the demand for a variety of real-time data services such as VoIP service are also increased. Unlike typical data packets, VoIP packets have delay bound and low loss rate requirement. In this paper we propose a new scheduling algorithm that schedule two deferent kinds of packets efficiently, considering the characteristics of VoIP. Basically this algorithm considers both time delay and channel condition and gives priority depending on the time delay. Simulation results show that the proposed algorithm works more efficiently than conventional algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.665-671
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• 2006

In this paper, we propose and observe a system that adopts Independent-MCS (Modulation and Coding Scheme) level for each layer in the combined AMC-V-BLAST (Adaptive Modulation and Coding-Vertical-Bell-lab Layered Space-Time) system. Also, comparing with the combined system using Common-MCS level, we observe throughput performance improvement. As a result of simulation, Independent-MCS level case adapts modulation and coding scheme for maximum throughput to each channel condition in separate layer, resulting in improved throughput compared to Common-MCS level case. Especially, the results show that the combined AMC-V-BLAST system with Independent-MCS level achieves a gain of 700kbps in $7dB{\sim}9dB$ SNR (Signal-to-Noise Ratio) range.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.3
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• pp.232-238
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• 2008

Research has been proceeded on fuel cell which is fueled by hydrogen. Polymer electrolyte membrane fuel cell (PEMFC) is promising power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, temperature dependent performance. These problems could be solved by experiment which is useful for analysis and optimization of fuel cell performance and heat management. In this paper, when hydrogen flows constantly at the stoichiometry of ${\xi}=1.6$, the performance of the fuel cell stack was increased and the voltage difference between each cells was decreased according to the increase of air stoichiometry by 2.0, 2.5, 3.0. Therefore, the control of air flow rate in the same gas channel is important to get higher performance. Purpose of this research is to expect operation temperature, flow rate, performance and mass transportation through experiment and to help actual manufacture of PEM fuel cell stack.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.136-147
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• 2015

Dead-ended operation of Proton Exchange Membrane Fuel Cell(PEMFC) provides the simplification of fuel cell systems to reduce fuel consumption and weight of fuel cell. However, the water accumulation within the channel prohibits a uniform supply of fuel. Optimization of the purge strategy is required to increase the fuel cell efficiency since fuel and water are removed during the purge process. In this study, we investigated the average voltage output which depends on two interrelated conditions, namely, the supply gas pressure, purging valve open time. In addition, flow visualization was performed to better understand the water build-up on the anode side and cathode side of PEMFC in terms of a variety of the current density. We analyzed the correlation between the purge condition and water flooding.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.104-108
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• 2009

In this paper, we investigate the performance of ARQ-aided downlink Time Switched Transmit Diversity (TSTD) in the WCDMA LCR-TDD system. Proposed TSTD system applies the ARQ scheme in which the receiver sends the response signal (ACK or NACK signal) to the transmitter and predicts the channel condition based on response signal after receiver checks the error, then it re-sends data. Simulation results demonstrate that the proposed TSTD scheme yields about 5.5dB performance gain, compared with the conventional TSTD in term of the frame error rate(FER) for a mobile speed of 3km/h and an FER value of 1%. In addition, 7% of throughput gain is shown when Eb/N0=7dB.