• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.26-34
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• 2011

In Femtocell that provides high quality of indoor communications with low transmitted power, there are two typical Access modes; Closed Access mode and Open Access mode. In this paper, we propose resource allocation scheme, which mitigates difference of performance between Access modes and improves overall cell performance, according to Access mode. We give more wireless resources to Open Access mode Femtocell, which improves performance of other users, than Closed Access mode Femtocell. If Open Access mode Femtocell uses more resource, there is trade-off between improvement of user using Open Access mode Femtocell and increase of interference that other users receive. So, we solve the optimal value for resource allocation and analyze performance of conventional scheme and proposed scheme applying the optimal value. Eventually, proposed scheme can improve overall cell performance relative to conventional scheme.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.495-500
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• 2006

본 논문에서는 셀 환경에서 QoS를 보장하기 위해 통합된 페이징과 루프 정보 관리 캐시를 사용하는 Cellular IP 특성을 가진 Cellular-IP/PRC 네트워크를 제안한다. 제안한 호 수락 방식은, 이동 노드의 홈 기지국 용량이 충분하고, 인접 셀 이동 노드가 흠 기지국에서 호가 수락되었다고 가정할 경우 받을 간섭의 증가량을 고려해 통화 품질이 보장될 때, 홈 기지국은 새로운 호를 이동 노드의 송신 전력 예측에 기반을 둔 호 수락 방식이다. 무선인터넷 네트워크 내의 페이징과 라우터를 관리하기 위해 사용되었던 PC(Paging Cache)와 RC(Routing Cache)를 하나의 PRC(Paging Router Cache)로 통합 관리하고, 모든 노드 내에 구성하여 운용토록 하고, 이동 노드의 핸드 오프 및 로밍 상태를 효율적으로 관리 할 수 있도록 이동 노드에 핸드오프 상태 머신을 추가하고, 노드에서 관련 기능을 수행하도록 하였다. 시스템 환경에서 통화량에 영향을 주는 인자를 각 링크 통화권 및 불균형 정도를 예측, 하향링크에 의해 통화권이 제한을 판단하여 송수신 전력을 기반으로 한 알고리즘과 제안한 알고리즘을 비교하여 QoS가 호 차단 확률과 호 탈락 확률, GoS, 셀 용량의 효율을 예측할 수 있는 QoS로 성능 개선을 연구한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.289-294
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• 2014

In this paper, we investigate the user scheduling, transmit beamforming, and receive beamforming of uplink space division multiple access (SDMA) systems where multiple users are allowed to transmit their signal to a base station (BS) using the same frequency band simultaneously. The BS performs a receive beamforming using the predetermined pseudo-random pattern and select users with a specific criterion. Especially, in this paper, we propose the threshold-based transmit power control, in which a user decrease its transmit power according if its generating interference to other users's signal is larger than a predetermined threshold. Assuming that the TDD system is used, the channel state information (CSI) can be obtained at each user from pilot signals from the BS. Simulation results show that the proposed technique significantly outperforms the existing user scheduling algorithms.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.256-262
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• 2006

This paper proposes a new predistortion linearizer to compensate for AM/AM and AM/PM in the nonlinear characteristics of amplifier. This consists of common-emitter amplifier and schottky diode that is connected between emitter and ground. When effective resistance of the schottky diode with bias condition varies, common-emitter amplifier with series feedback has a increase of amplitude and expansion of phase. This makes a amplifier nonlinear characteristics are to be improved. The proposed linearizer and amplifier has been manufactured and tested to operate in cellular base station frequency (869~894MHz). The test results show that third order intermodulation distortion (IMD3) cab be removed by more than 10.4dB in case of CW 2-tone signals ${\Delta}f$=1MHz, and the adjacent channel power ratio (ACPR) also can be improved by more than 9.6dB for CDMA IS-95 1FA signals.

• Journal of the Korea Society for Simulation
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• v.25 no.3
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• pp.41-51
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• 2016

In this study, we propose an improved Floor Field Model(FFM) that considers the physical characteristics of pedestrians, i.e., body size, shape, and posture. Also we analyse limits of FFM and features of improved model compared with existing evacuation simulation models. FFM is a typical microscopic pedestrian model using CA, but it does not reflect the physical characteristics of pedestrians. Because of this, FFM is difficult to modeling phenomena such as collision, friction between pedestrians. As a result, FFM calculates a very short evacuation time when compared with the other models. We performed a computational experiment to compare improved model with other models such as FFM, Simulex, Pathfinder in an actual campus building. We carried out a comparison of evacuation aspect according to the change in number of evacuees. Also we compared evacuation aspect by exit. Finally, we confirmed that improved model reflects physical phenomena which were not reflected in FFM. Especially, experimental results were very similar to the Simulex.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.558-563
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• 2021

Quantum-Dot Cellular Automata is a next-generation nanocircular design technology that is drawing attention from many research organizations not only because it is possible to design efficient circuits by overcoming the physical size limitations of existing CMOS circuits, but also because of its energy-efficient features. In this paper, one of the existing digital circuits, T flip-flop circuit, is proposed using QCA. The previously proposed T flip-flops are designed based on the majority gate, so the circuits are complex and have long delays. Therefore, the design of the XOR gate-based T flip-flop using cell interaction reduces circuit complexity and minimizes latency. The proposed circuit is simulated using QCADesigner, and the performance is compared and analyzed with the existing proposed circuits.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1254-1260
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• 2019

Recently, 5G cellular systems have been attracted great attention as a key enabler for Industry 4.0. In this paper, we propose a novel random access based on pilot-assisted opportunistic transmission to support internet-of-things (IoT) scenario in cellular networks. A key feature of our proposed scheme is to enable each of IoT devices to attempt opportunistic transmission of its data packet in Step 3 with randomly selected uplink pilot signal. Both the opportunistic transmission and the pilot randomization in Step 3 are effective to significantly mitigate the occurrence of packet collisions. We mathematically analyze our proposed scheme in terms of packet collision probability and uplink resource efficiency. Through simulations, we verify the validity of our analysis and evaluate the performance of our proposed scheme. Numerical results show that our proposed scheme outperforms other competitive schemes.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.10
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• pp.895-903
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• 2017

Quantum Cellular Automata(QCA) is one of the proposed techniques as an alternative solution to the fundamental limitations of CMOS. QCA has recently been extensively studied along with experimental results, and is attracting attention as a nano-scale size and low power consumption. Although the XOR gates proposed in the previous paper can be designed using the minimum area and the number of cells, there is a disadvantage that the number of added cells is increased due to the stability and the accuracy of the result. In this paper, we propose a gate that supplement for the drawbacks of existing XOR gates. The XOR gate of this paper reduces the number of cells by arranging AND gate and OR gate with square structure and propose a half-adder by adding two cells that serve as simple inverters using the proposed XOR gate. Also This paper use QCADesginer for input and result accuracy. Therefore, the proposed half-adder is composed of fewer cells and total area compared to the conventional half-adder, which is effective when used in a large circuit or when a half - adder is needed in a small area.

• The Korean Journal of Mycology
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• v.46 no.3
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• pp.281-294
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• 2018

Molecular analysis using the internal transcribed spacer region sequences revealed that the strains used in this study, which were formerly identified as Panellus serotinus, are Panellus edullis. After Universal Fungal PCR Fingerprinting (UFPF) analysis, eight strains of P. edulis were divided into two groups. We conducted fundamental research on mycelial growth and sawdust cultivation to understand the cultural characteristics of eight wild P. edulis strains collected from Korean forests. All strains showed faster and denser mycelial growth on potato dextrose agar (PDA) than on other media (malt extract agar, Sabouraud dextrose agar). Optimal conditions for mycelial growth were: $20^{\circ}C$ on PDA, $25^{\circ}C$ on potato dextrose broth (PDB), and pH 5~8 on PDB at $25^{\circ}C$. Two strains (NIFoS 2407, 3993) were selected as excellent strains based on mycelial growth and density on PDA. NIFoS 2792 showed high cellulase activities on carboxymethyl cellulose (CMC) agar, and NIFoS 2387 and 2804 exhibited high laccase activities on ABTS-containing agar media. The mycelial growth of P. edulis was the fastest on Quercus acutissima and Q. mongolica sawdust media, and mycelial density was the highest on Quercus spp. sawdust-containing media. Sawdust cultivation of P. edulis was successful. The conditions were 80~85 days of cultivation period after spawn inoculation, 10~11 days for primordial formation at $17{\sim}18^{\circ}C$, and 15~20 days for fruiting growth. NIFoS 2804 and 3993 were selected as good strains in terms of cultivation period and mushroom production. These results could be useful for the artificial cultivation of P. edulis.

• Journal of the Korean Geographical Society
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• v.47 no.4
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• pp.606-624
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• 2012

The main objective of this paper is to provide an adequate and comprehensive review of what has been done in South Korea in the field of geospatial analysis and modeling. This review focuses on spatial data analysis and spatial statistics, spatial optimization, and geosimulation among various aspects of the field. It is recognized that geospatial analysis and modeling in South Korea got through the initial stage during the 1990s when computer and analytical cartography and GIS were introduced, moved to the growth stage during the first decade of the $21^{st}$ century when there was a surge of relevant researches, and now is heading for its maturity stage. In spatial data analysis and spatial statistics, various topics have been addressed for spatial point pattern data, areal data, geostatistical data, and spatial interaction data. In spatial optimization, modeling and applications related to facility location problems, districting problems, and routing problems have been mostly researched. Finally, in geosimulation, while most of research has focused on cellular automata, studies on agent-based model and simulation are in beginning stage. Among all these works, some have fostered methodological advances beyond simple applications of the standard techniques.