• Journal of the Korea Society of Computer and Information
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• v.6 no.2
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• pp.84-89
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• 2001

In this paper, an improved protocol of Multi-Link Switching Method is proposed by supplementing a concurrent processing function. This protocol is proposed to complement the shortcomings of the conventional Multi-Link Switching Method which is used for the medium access in LAN. We analyzed the improved protocol in channel utilization viewpoint and compared the result with that of the conventional protocol From this result, we showed that the channel utilization of the improved protocol is superior to that of the conventional protocol when the maximum normalized propagation delay is increased.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.79-81
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• 2002

현재의 이동전화망의 연결 방식은 Circuit Switching에 가깝다고 할 수 있다. 이것을 Fully Packet Switching 방식으로 변경했을 경우, 현재의 Channel Utilization Model로 원하는 음성통화의 품질을 제공할 수 있을 지에 대해서는 아직 충분한 검증이 이뤄진 바가 없다. DiffServ를 적용하는 것이 하나의 해결책이 될 수 있는데. 본 논문에서는 Simulation을 통해 이 방법의 효용성을 보였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.31-37
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• 2009

In the two-way relay channel, the relay employ Amplify-and-Forward (AF) or Decode-and-Forward (DF) protocol, and broadcast the network-coded signal to both user. In the system, DF protocol provides maximum throughput at low signal to noise ratio(SNR). On the other hand, at high SNR, AF protocol provides maximum throughput. The paper propose active transmission scheme which employ Amplify-and-Forward or Decode-and-Forward protocol based on received SNR at the relay over Two-way relay channel. The optimal threshold is investigated numerically for switching the protocol. Through numerical results, we confirm that the proposed scheme outperforms conventional schemes over two-way relay channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.66-71
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• 2008

In this paper, an antenna-switching scheme using negative acknowledgement for hybrid automatic repeat request (H-ARQ) is proposed and analyzed in the Vertical Bell Labs Layered Space-Time(V-BLAST) system, in which the transmit antenna is alternatively switched under retransmission. By analytically evaluating the channel capacity of the proposed scheme over correlated fading channels, it is shown that the adverse effect of the channel correlation is alleviated by the antenna switching scheme. Simulation results demonstrate that the average throughput may be improved in a correlated fading channel without adding much complexity to the process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.907-915
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• 2003

A very efficient packet transmission scheme is needed in the radio environment where radio resource is insufficient as compared with the environment of the wired communication. In general, dual mode packet transmission scheme is used broadly. Packets are transmitted through the dedicated or common chamois according to a switching criterion. The general criteria are the length and generation frequency of packet, that is, large and frequent packets are transmitted using a dedicated channel and small and infrequent packets are transmitted using a common channel. The performance of dual mode packet transmission scheme is closely related to the switching criteria. However, it is very difficult to find the optimal switching point because that is not fixed but variable according to the environment such as traffic load, length of generated packets, and the number of channels. In this paper, a new scheme for the dual mode packet transmission scheme using a dynamic switching threshold is proposed where the switching threshold is not fixed but variable according to the network environment. The performance of the proposed method is analyzed using a simulation. From the simulation results, it is shown that the performance of the proposed scheme is not very influenced by the network environment unlike the conventional dual mode packet transmission scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.292-300
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• 2009

This paper presents an LED BLU driving circuit with a local-dimming structure. The efficiency of the proposed LED driver has been improved by parallel driving 8 serial-connected LED arrays. It employed the soft-switching boost converter topology to reduce the switching power loss of the hard switching boost converter. Soft- and hard-switching converters have the same structure except that the free-wheeling diode in the hard-switching converter is replaced with the n-channel MOSFET in the soft-switching one. The proposed boost converter was compared with the hard switching converter. The soft-switching converter reveals superior ripple and efficiency. A smaller inductance can be used for the soft-switching converter contrasting to the hard-switching one. We also studied on an over-voltage protection circuit of the output of the driver at the no load condition. The protection circuit was applied to the proposed driver, and its operation was confirmed by experiment. Using a local-dimming technique, power consumption of LCD BLUs can be reduced as low as possible according to the brightness of its image.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.31-35
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• 2020

This study demonstrates metal-oxide based memtransistor device and the gate tunable memristive characteristic using atomic layer deposition (ALD) and ZnO n-type oxide semiconductor. We fabricated a memtransistor device having channel width 70 ㎛, channel length 5 ㎛, back gate, using 40 nm thick ZnO thin film, and measured gate-tunable memristive characteristics at each gate voltage (50V, 30V, 10V, 0V, -10V, -30V, -50V) under humidity of 40%, 50%, 60%, and 70% respectively, in order to investigate the relation between a memristive characteristic and hydrogen doping effect on the ZnO memtransistor device. The electron mobility and gate controllability of memtransistor device decreased with an increase of humidity due to increased electron carrier concentration by hydrogen doping effect. The gate-tunable memristive characteristic was observed under humidity of 60% 70%. Resistive switching ratio increased with an increase of humidity while it loses gate controllability. Consequently, we could obtain both gate controllability and the large resistive switching ratio under humidity of 60%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.249-258
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• 2013

In multi-hop ad hoc networks, multi-interface multi-channel architecture is being noticing as methodology to improve the effective bandwidth and end-to-end throughput, But since existing routing metrics designed for networks based on single-interface exactly can not reflects the nature of networks based on multi-interface multi-channel, we are not expected the effect of throughput improvement. there had been proposal of MCR that discover high throughput by using metrics such as channel diversity and interface switching cost. however, MCR have an problem that is degraded it's performance in congested networks, because it not reflects the impact of traffic load. in this paper, we propose MAMCR metric, which select high throughput paths under congested conditions by combination MCR with channel access time metric, and conform it's the effect of performance improvement by ns-2 simulation.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.2
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• pp.139-146
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• 2002

The third generation mobile communication needs to provide multimedia service with increased data rates. Thus an efficient allocation of radio and network resources is very important. This paper models the 'burst switching' as an efficient radio resource allocation scheme and the performance is compared to the circuit and packet switching. In burst switching, radio resource is allocated to a call for the duration of data bursts rather than an entire session or a single packet as in the case of circuit and packet switching. After a stream of data burst, if a packet does not arrive during timer2 value ($\tau_{2}$), the channel of physical layer is released and the call stays in suspended state. Again if a packet does not arrive for timerl value ($\tau_{1}$) in the suspended state, the upper layer is also released. Thus the two timer values to minimize the sum of access delay and queuing delay need to be determined. In this paper, we focus on the decision of $\tau_{2}$ which minimizes the access and queueing delay with the assumption that traffic arrivals follow Poison process. The simulation, however, is performed with Pareto distribution which well describes the bursty traffic. The computational results show that the delay and the packet loss probability by the burst switching is dramatically reduced compared to the packet switching.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.51-58
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• 2003

In this paper, we propose a group scheduling scheme to efficiently utilize network resources for core nodes in optical burst switching networks. This scheme schedules multiple bursts utilizing an interval graph to obtain the maximum stable set using the information such as arrival times and burst lengths from the collected header packets. Simultaneous scheduling of multiple bursts in a scheduling window results in lower burst loss probability and increased channel utilization than those proposed previously using one-to-one mapping. Simulation results for both cases of variable and fixed burst sizes show that the group scheduling scheme is better than the immediate scheduling, so called Latest Available Unused Channel with Void Filling, scheme in both performance metrics above mentioned.