• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.93-96
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• 2008

This paper describes an efficient design of a multi-standard Viterbi decoder that supports multiple constraint lengths and code rates. The Viterbi decode. is parameterized for the code rates 1/2, 1/3 and constraint lengths 7, 9, thus it has four operation modes. In order to achieve low hardware complexity and low power, an efficient architecture based on hardware sharing techniques is devised. Also, the optimization of ACCS (Accumulate-Subtract) circuit for the one-point trace-back algorithm reduces its area by about 35% compared to the full parallel ACCS circuit. The parameterized Viterbi decoder core has 79,818 gates and 25,600 bits memory, and the estimated throughput is about 105 Mbps at 70 MHz clock frequency.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.11
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• pp.527-539
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• 2008

This paper presents a performance estimation technique based on queuing analysis for on-chip bus matrix architectures of Multi-Processor System-on-Chips(MPSoCs). Previous works relying on time-consuming simulation are not able to explore the vast design space to cope with increasing time-to-market pressure. The proposed technique gives accurate estimation results while achieving faster estimation time than cycle -accurate simulation by order of magnitude. We consider the followings for the modeling of practical memory subsystem: (1) the service time with the general distribution instead of the exponential distribution and (2) multiple-outstanding transactions to achieve high performance. The experimental results show that the proposed analysis technique has the accuracy of 94% on average and much shorter runtime ($10^5$ times faster at least) compared to simulation for the various examples: the synthetic traces and real-time application, 4-channel DVR.

• The KIPS Transactions:PartD
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• v.12D no.6 s.102
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• pp.921-930
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• 2005

In this paper, a general purpose molecular simulation system which has been developed by the author, are described. One of the most advantageous features is that the molecular simulation system can handle a coarse-grained model as well as an all-atom mode. Therefore, we can simulate mesoscopic phenomena as well as microscopic phenomena with the help of Langevin dynamics simulation and dissipative particle dynamics simulation techniques. Thus we could study anesthesia, protein folding, biopolymer flow in microchannel with single framework, which spans from microscopic to mesoscopic scales. We expect that we can also simulate many other bio/nano systems of technological importance which are not feasible by means of molecular dynamics simulation technique. Finally, performance data are shown and a bottleneck is identified for future optimization.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.103-113
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• 2006

The numerical methods of finding the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are proposed, which are able to effectively compensate overall channels in $8{\times}40$ Gbps WDM system with non zero-dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that two optimal parameters depend on each other, but less related with the searching procedure. The methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which is a serious problem but the condition in the case of applying the OPC into multi-channels WDM system.

• Convergence Security Journal
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• v.12 no.1
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• pp.35-42
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• 2012

Increase of data traffic and the advent of new real-time services require to change from the traditional TDM-based (Time Division Multiplexing) networks to the optical networks that soft and dynamic configuration. Voice and lease line services are main service area of the traditional TDM-based networks. This optical network became main infrastructure that offer many channel that can convey data, video, and voice. To provide high resilience against failures, Packet-optical networks must have an ability to maintain an acceptable level of service during network failures. Fast and resource optimized lightpath restoration strategies are urgent requirements for the near future Packet-optical networks with a Generalized Multi-Protocol Label Switching(GMPLS) control plane. The goal of this paper is to provide packet-optical network with a hierarchical multi-layer recovery in order to fast and coordinated restoration in packet-optical network/GMPLS, focusing on new implementation information. The proposed schemes do not need an extension of optical network signaling (routing) protocols for support.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.135-141
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• 2014

In this paper, the device design guideline to reduce the threshold voltage variation with fin width in junctionless MuGFET has been suggested. It has been observed that the threshold voltage variation was increased with increase of fin width in junctionless MuGFETs. To reduce the threshold voltage variation with fin width in junctionless MuGFETs, 3-dimensional device simulation with different gate dielectric materials, silicon film thickness, and an optimized fin number has been performed. The simulation results showed that the threshold voltage variation can be reduced by the gate dielectric materials with a high dielectric constant such as $La_2O_3$ and the silicon film with ultra-thin thickness even though the fin width is increased. Particularly, the reduction of the threshold voltage variation and the subthreshold slope by reducing the fin width and increasing the fin numbers is known the optimized device design guideline in junctionless MuGFETs.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.10
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• pp.23-28
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• 2010

In this paper, we investigated the polarization effects on the electrical and structural characteristics of AlGaN/GaN HEMT. Both the Al mole-fraction and the barrier thickness of AlGaN, which determine the profiles of a two-dimensional electron gas, were simulated to obtain the optimum HEMT structure affecting the polarization effect. As a results, we found that the amount of bound sheet charges was increased by 16% and the maximum drain current density ($I_D$,max) was increased by more than 37%, while AI mole fractions are changed from 0.3 to 0.4. We also observed a 37% improvement in maximum drain current density ($I_D$,max) by increasing AIGaN layer thickness from 17 to 38 nm. However when AlGaN layer thickness reached the critical thickness, DC characteristics were dramatically lowered due to 'bulk' relaxation in AlGaN layer.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.2
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• pp.55-67
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• 2005

Separation between computation and communication in system design allows the system designer to explore the communication architecture independently of component selection and mapping. In this paper we present an iterative two-step exploration methodology for bus-based on-chip communication architecture and memory allocation, assuming that memory traces from the processing elements are given from the mapping stage. The proposed method uses a static performance estimation technique to reduce the large design space drastically and quickly, and applies a trace-driven simulation technique to the reduced set of design candidates for accurate Performance estimation. Since local memory traffics as well as shared memory traffics are involved in bus contention, memory allocation is considered as an important axis of the design space in our technique. The viability and efficiency of the proposed methodology arc validated by two real -life examples, 4-channel digital video recorder (DVR) and an equalizer for OFDM DVB-T receiver.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.965-970
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• 2012

In this study, the water distribution in the cathode side of a direct methanol fuel cell (DMFC) is visualized using a neutron imaging technique at the Neutron Radiography Facility (NRF), KAERI. It is difficult to quantify the water content in the cathode side because of $CO_2$ gas. A compared open circuit voltage (OCV) image, relative $CO_2$, and water distribution can be visualized by the neutron imaging technique. This means that the neutron imaging technique is useful for the optimization of the flow field design and the establishment of water management, and, in turn, for the improvement of the cell performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.567-574
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• 2003

It is important to design and evaluate the chip waveform with the minimum MAI under the bandwidth constraint in the interference-limited DS-CDMA system. In this paper, by approximation we present the analytical chip waveforms that are proposed and optimized in the reference. Their performances are compared with performances of three conventional chip waveforms: rectangular, half-sine and raised-cosine. Waveform 1 of the proposed chip waveform outperforms the conventional ones. BER and throughput performance are evaluated in the Rayleigh and Nakagami-m fading channels when DPSK modulation is used. When the required BER is 10$\^$-3/ in two fading channels, the capacity of the waveform 1 is improved about 20 % rather than raised-cosine one. When the offered traffic is 30 and the number of packet per bit(N$\sub$d/) is 14, maximum throughput of the waveform 1 is better than raised-cosine chip waveform about 18 % in two fading channels.