• Journal of Communications and Networks
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• v.9 no.3
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• pp.312-318
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• 2007

In this paper, we propose the optimal offset-time decision (OOD) algorithm which can effectively reduce the pre-transmission delay compared to the perfect isolation model, and can also be extended to general n priority classes while the target loss probability of each class is guaranteed for the variable offered load. In order to drive the OOD algorithm, we first analyze the loss probability of each priority class through class aggregation and iteration method; the analytic results obtained through the proposed algorithm are then validated with results garnered from extensive simulation tests.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2828-2833
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• 1997

In this paepr, we have proposed an enhanced TDM with WDM hybrid photonic switching architecture, which has much simpler configuration and requires less hard ware. the basic module consists of arrayed waveguide grating (AWG) for wavelength division, compressor and fiber delay lines for time division. When compared with other systems, we proved that the proposed switch is suitable for large capacity photonic switching system due to less complexity and lower cost in implementation than the previous ones.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.22-23
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• 2006

Proton irradiation technology was used for improvement of switching characteristics of the PT-IGBT. Proton irradiation was carried out at 5.56 MeV energy with $1{\times}10^{12}/cm^2$ doze from the back side of the wafer. Characterization of the device was performed by I-V, breakdown voltage, threshold voltage, and turn-off delay time measurement. For irradiated device by 5.56 MeV energy, the breakdown voltage and the threshold voltage were 730 V and 6.5~6.6 V, respectively. The turn-off time has been reduced to 170 ns, which was original $6\;{\mu}s$ for the un-irradiated device.

• Macromolecular Research
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• v.10 no.6
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• pp.345-358
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• 2002

The electrical conductivity during vulcanization process was measured as a function of time for the system of TiC loaded styrene-butadiene rubber (SBR) composites. The phenomenon of negative and positive temperature coefficients of conductivity and its conduction mechanism were also studied for the SBR polymeric composites. The current-voltage characteristics of the polymeric composites were non-linear in high voltage and showed a switching effect. The effects of temperature on the thermal conductivity and effective dielectric constant were measured. The measured parameters were found to be dependent on TiC concentration. The electromagnetic wave shielding (EMS) of the SBR-TiC polymeric composite was also examined. The SBR filled with TiC could be expected to be promising novel smart polymeric composites for self-electrical heating, temperature sensor, time delay switching, and electro-magnetic wave shielding effectiveness.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.348-352
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• 1998

By employing the Berreman's backflow model, we investigated the effect of liquid crystal parameters on the optical switching characteristics of a bistable twisted-nematic liquid crystal cell. We found that d/p is the most important parameter for high speed operation.

• Annual Conference of KIPS
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• 2009.11a
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• pp.679-680
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• 2009

Radio jamming attack is the most effective and easiest Denial-of-Service (DOS) attack in wireless network. In this paper, we proposed a multi-channel MAC protocol to mitigate the jamming attacks by using cognitive radio. The Cognitive Radio (CR) technology supports real-time spectrum sensing and fast channel switching. By using CR technologies, the legitimate nodes can perform periodic spectrum sensing to identify jamming free channels and when the jamming attack is detected, it can switch to un-jammed channel with minimum channel switching delay. In our proposed protocol, these two CR technologies are exploited for thwarting the jamming attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2473-2492
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• 2012

Energy conservation is a vital issue in wireless sensor networks. Recently, employing mobile sinks for data gathering become a pervasive trend to deal with this problem. The sink can follow stochastic or pre-defined paths; however the controlled mobility pattern nowadays is taken more into consideration. In this method, the sink moves across the network autonomously and changes its position based on the energy factors. Although the sink mobility would reduce nodes' energy consumption and enhance the network lifetime, the overhead caused by topological changes could waste unnecessary power through the sensor field. In this paper, we proposed EEDARS, an energy-efficient dual-sink algorithm with role switching mechanism which utilizes both static and mobile sinks. The static sink is engaged to avoid any periodic flooding for sink localization, while the mobile sink adaptively moves towards the event region for data collection. Furthermore, a role switching mechanism is applied to the protocol in order to send the nearest sink to the recent event area, hence shorten the path. This algorithm could be employed in event-driven and multi-hop scenarios. Analytical model and extensive simulation results for EEDARS demonstrate a significant improvement on the network metrics especially the lifetime, the load and the end-to-end delay.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.57-64
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• 2004

In this paper, we propose a RZ/HRZ mixture data transmission method for the asynchronous circuit design to reduce Power consumption. The dual-rail data with Rf decoding scheme is used to design asynchronous circuit, and it is easy to get a completion signal of the data validity from the native data as contrasted with sin91e-rail. However, the dual-rail scheme suffers from large chip area and increasing of Power consumption from all signals by the switching of the return-to-zero. We need to diminish number of circuit switching. The proposed RZ/HRZ data transmission reduces a switching activity to about 50% and it shows 23% lower power consumption than the conventional dual-rail coding with RZ's.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.59-66
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• 2003

We propose the novel optical burst switching scheme to guarantee a minimum bandwidth for multiple classes. To date, QoS studies on OBS network are capable of differentiating two classes, but have difficulties in providing a minimum bandwidth lot several classes because of lower classes' collision with the highest class bursts in the networks. To solve that problem, in our proposed scheme we assign time zones in a data channel for each class periodically, making one burst have top priority at least its zone. Also, the new burst assembling algorithm, as well as the way of managing data channel, is necessarily proposed to coordinate with the proposed OBS scheme. Through the evaluation, we show that the worst-case end-to-end delay is small enough and the received bandwidth of the lower classes is still assured regardless of the traffic load of the highest class.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.8-15
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• 2003

In this paper, we address how to provide absolute differentiated services for optical burst switching (OBS) networks based on dynamic wavelength assignment. Unlike existing quality of service (QoS), such as buffer-based and offset-time based scheme, our proposed dynamicvirtual lambda partitioning (DVLP) scheme does not mandate any buffer or extra offset time, but can achieve absolute service differentiation between classes. This new DVLP scheme shares wavelength resources based on several different priority of classes in an efficient and QoS guaranteed manner. The performance results show that the proposed scheme effectively guarantees a target blocking probability of each traffic classes both in Poisson and Self-similar traffic environment.