• 전자공학회논문지A
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• 제33A권6호
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• pp.32-41
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• 1996

We propose the improved GMSK (gaussian-filtered minimum shift keying) quadrature modulator using the FIR(finite impulse response )filter whose coefficients are obtained form the differnce of phase response, and design its ASIC (applicaton specific integrated circuit) which can be used for GSM (global system for mobile communication) digital cellular system and DCS 1800 (digital cellular system at 1800MHz) personal communication system. Input data become quantized I and Q channel 10 bit signal through cosine and sine ROM mapping after being filtered by the FIR filter whose normalized bandwidth is 0.3 and designed by considering intersymbol interference as well as sampling ratio. These two signals become the GMSK modulated I and Q channel signal through DAC (digital-to-analog converter) and 7th order analog chebyshev LPF(low pass filter) respectively. The difference between the ideal analog signal and its digitized signal is analyzed in terms of sampling noise, quantization noise, truncation noise and coefficient noise. And the effect of the LPF following the DAC is considered. The ASIC design of the GMSK quadrature modulator is also confirmed by an experiment.

• Molecules and Cells
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• 제40권7호
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• pp.441-449
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• 2017

Proteolysis in eukaryotic cells is mainly mediated by the ubiquitin (Ub)-proteasome system (UPS) and the autophagy-lysosome system (hereafter autophagy). The UPS is a selective proteolytic system in which substrates are recognized and tagged with ubiquitin for processive degradation by the proteasome. Autophagy is a bulk degradative system that uses lysosomal hydrolases to degrade proteins as well as various other cellular constituents. Since the inception of their discoveries, the UPS and autophagy were thought to be independent of each other in components, action mechanisms, and substrate selectivity. Recent studies suggest that cells operate a single proteolytic network comprising of the UPS and autophagy that share notable similarity in many aspects and functionally cooperate with each other to maintain proteostasis. In this review, we discuss the mechanisms underlying the crosstalk and interplay between the UPS and autophagy, with an emphasis on substrate selectivity and compensatory regulation under cellular stresses.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.158-163
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• 1998

This paper is our first attempt to construct a information processing system such as the living creatures' brain based on artificial life technique. In this paper, we propose a method of constructing neural networks using bio-inspired emergent and evolutionary concept, Ontogeny of living things is realized by cellular automata model and Phylogeny that is living things adaptation ability themselves to given environment, are realized by evolutionary algorithms. Proposing evolving cellular automata neural systems are calledin a word ECANS. A basic component of ECANS is 'cell' which is modeled on chaotic neuron with complex characteristics, In our system, the states of cell are classified into eight by method of connection neighborhood cells. When a problem is given, ECANS adapt itself to the problem by evolutionary method. For fixed cells transition rule, the structure of neural network is adapted by change of initial cell' arrangement. This initial cell is to become a network b developmental process. The effectiveness and the capability of proposed scheme are verified by applying it to pattern classification and robot control problem.

• Journal of Communications and Networks
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• 제8권1호
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• pp.13-20
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• 2006

In cellular mobile communications, how to achieve optimum system capacity with limited frequency spectrum is one of the main research issues. Many dynamic channel assignment (DCA) schemes have been proposed and studied to allocate the channels more efficiently, thus, the capacity of cellular systems is improved. Reuse partitioning (RP) is another technique to achieve higher capacity by reducing the overall reuse distance. In this paper, we present a network-based DCA scheme with the implementation of RP technique, namely dynamic reuse partitioning with interference information (DRP-WI). The scheme aims to minimize the effect of assigned channels on the availability of channels for use in the interfering cells and to reduce their overall reuse distances. The performance of DRP-WI is measured in terms of blocking probability and system capacity. Simulation results have confirmed the effectiveness of DRP-WI scheme. Under both uniform and non-uniform traffic distributions, DRP-WI exhibits outstanding performance in improving the system capacity. It can provide about 100% capacity improvement as compared to conventional fixed channel assignment scheme with 70 system channels.

• 한국통신학회논문지
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• 제28권5A호
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• pp.276-283
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• 2003

본 논문은 여러 계층의 셀을 고려하는 실제적인 CDMA 셀룰라 시스템을 시뮬레이션 하기위해 최소 개수의 셀을 사용하여 수행 시간을 줄이지만 충분한 셀 수로 구성했을 때와 동일한 결과를 얻을 수 있는 시뮬레이션 방식의 제안과 이를 적용 했을 때 시스템 알고리즘 성능에 대한 영향을 살펴보는 내용이다. 제안된 셀 구성과 나머지 셀 간섭 보정 방식을 사용하면 중심 셀과 한 이웃 계층만 사용하더라도 간섭 보정에 의해 최대 셀 구성 시의 시뮬레이션 결과와 동일한 총 간섭량, SIR 값, Outage 확률, 그리고 셀 용량 결과를 얻을 수 있으며 시뮬레이션 시간을 극소화 할 수 있다는 결론을 얻었다.

• 한국통신학회논문지
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• 제30권7A호
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• pp.587-596
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• 2005

본 논문에서는 사용자를 주파수로 구분하고 데이터를 주파수 영역 확산으로 다중화하는 OFDMA/CDM 기반 셀룰라 시스템을 제안하다. 셀 구분을 위해 랜덤코드를 이용하며, 시스템 성능 향상을 위하여 전치등화를 적용한다. 송신전력이 제한된 다중셀 환경에 적합한 전치등화 방법과 효율적인 전력할당 방식을 제안한다. 다중셀 환경에서 각 등화방법 및 전력할당 방식에 따른 성능을 분석하곤 특히 셀 중심으로부터의 거리에 따른 성능 변화, 다중화 데이터 개수에 따른 성능 분석을 통괘 다중셀 환검 적용 타당성을 분석한다. 끝으로 시간지연에 따른 성능저하를 전치와 후치 등화를 모두 사용한 전/후치등화를 적용하여 줄일 수 있음을 보인다.

• 한국항행학회논문지
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• 제15권2호
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• pp.307-312
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• 2011

본 논문은 매크로/펨토 셀룰러 망에서 모든 셀들 간의 서비스 공평성을 유지함으로써 시스템을 안정화하고 데이터 전송속도를 향상시키기 위한 채널 분배 기법을 제안한다. 특히 매크로셀과 펨토셀 간에 분배하는 채널의 비율이 시스템에 주는 구체적인 영향을 파악하기 위하여 IP 기반의 매크로/펨토 셀룰러 망에 대한 대기행렬 모형을 제시한다. 이를 바탕으로 실질적인 채널 분배 전략을 제안하고, 실험을 통하여 다양하게 변화하는 시스템 환경에 따라 제안 기법의 동작을 분석한다. 또한 그 결과를 통하여 효율적인 시스템 구조의 설계 방향에 대하여 논의한다.

• Journal of Communications and Networks
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• 제18권6호
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• pp.926-937
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• 2016

In this paper, we study the feasibility of receiver diversity for application to downlink cellular networks, where low-energy devices are equipped with information decoding and energy harvesting receivers for simultaneous wireless information and power transfer. We compare several options that are based on selection combining and maximum ratio combining, which provide different implementation complexities. By capitalizing on the Frechet inequality, we shed light on the advantages and limitations of each scheme as a function of the transmission rate and harvested power that need to be fulfilled at the low-energy devices. Our analysis shows that no scheme outperforms the others for every system setup. It suggests, on the other hand, that the low-energy devices need to operate in an adaptive fashion, by choosing the receiver diversity scheme as a function of the imposed requirements. With the aid of stochastic geometry, we introduce mathematical frameworks for system-level analysis. We show that they constitute an important tool for system-level optimization and, in particular, for identifying the diversity scheme that optimizes wireless information and power transmission as a function of a sensible set of parameters. Monte Carlo simulations are used to validate our findings and to illustrate the trade-off that emerge in cellular networks with simultaneous wireless information and power transfer.

• 한국컴퓨터정보학회논문지
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• 제22권9호
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• pp.41-47
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• 2017

In this paper, we consider the case where D2D users and the cellular user share the uplink of the cellular system. We propose an iterative power control algorithm that converges to the optimum power value. Each user iteratively updates its transmit power level according to the interference function. Finally, all D2D users and cellular user that participate in the transmission get the optimum transmit power level. We first investigate the interference structure and define the interference function. Then, we show that the considered interference function belongs to the standard interference function that converges the unique transmit power level. Through numerical examples, the convergence of the proposed power control algorithm is examined in the various transmission scenarios.

• Journal of Communications and Networks
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• 제9권3호
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• pp.247-253
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• 2007

In this paper, downlink capacity of time duplex division (TDD) based cellular wireless networks utilizing fixed hopping stations is investigated. In the network, a number of fixed subscriber stations act as hopping transmission stations between base stations and far away subscribers, forming a cellular and ad hoc mobile network model. At the radio layer, TDD code division multiple access (CDMA) is selected as the radio interface due to high efficiency of frequency usage. In order to improve the system performance in terms of downlink capacity, we propose different time slot allocation schemes with the usage of fixed hopping stations, which can be selected by either random or distanced dependent schemes. Performance results obtained by computer simulation demonstrate the effectiveness of the proposed network to improve downlink system capacity.