• 대한전자공학회논문지TC
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• 제44권10호
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• pp.1-7
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• 2007

WCDMA 시스템에서 하향링크 저력할당은 치국(置局) 셀 용량 영역, 시스템 성능에 직접적인 영향을 준다. 제한된 송신전력 최대의 가입자를 수용하기 위해서 하향링크 전력을 최소로 유지하면서 셀 사용자의 요구 신호 대 잡음비를 만족시켜야 한다. 본 논문에서는 시스템에 접속하여 통화 중인 사용자의 수에 따라 하향링크 전력의 할당이 가변적이어야 함을 수식으로 증명하고, 동적 하향 링크 전력 할당 방법을 채택할 것을 제안한다. 또한 상향 및 하향 링크가 평형을 이루기 위한 파일롯 신호 및 단말기 전송전력 세기를 분석한다.

• 한국통신학회논문지
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• 제24권7A호
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• pp.996-1004
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• 1999

본 논문에서는 레일레이 다중경로 페이딩 채널 환경하에서 직교 확산 방식과 레이크 수신를 채용하는 역방향 링크 동기화 (synchronous) DS-CDMA 시스템의 성능을 분석하고 이를 비동기 (asynchronous) 전송 시스템과 비교하고자 한다. 이상적인 이진 부호화 변조라 가정할 때, 시스템 성능은 평균비트오율과 수용용량으로 계산되어진다. 본 논문에서는 주로 다중경로 강도 프로파일 (MIP) 모양과 레이크 탭의 수가 동기화 전송 시스템의 성능에 미치는 영향을 분석하고자 한다. 분석 결과 경로간 간섭이 존재하는 경우일지라도, 비동기 DS-CDMA 시스템보다 역방향 링크 동기화 DS-CDMA시스템이 우월한 성능을 가짐을 확인할 수 있었다.

• 한국군사과학기술학회지
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• 제14권3호
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• pp.492-500
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• 2011

The airborne backbone network(ABN) provides communication transport services between airborne nodes, surface nodes and satellite nodes. Such ABN is generally constructed with wide-body and high-capacity planes such as AWACS, which can fly long-term along pre-defined flight paths. In this paper, we propose an efficient method to improve routing performances by reconfiguring routing path before link failure based on the prediction of link state with the information of pre-defined backbone nodes' trajectories. Since the proposed method does not need additional information exchange between airborne nodes in order to acknowledge the link failure, it can be effectively used for airborne backbone network with limited bandwidths.

• Steel and Composite Structures
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• 제12권1호
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• pp.13-29
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• 2012

This paper is an experimental study on the behavior of vertical shear link in normal (steel section with and without stiffener) and composite (steel section with concrete located at the area limited to web and flanges of the section) configurations. This study is mainly aimed to perceive failure mechanism, collect laboratory data, and consider the effect of number of transverse reinforcements on strength and ductility of composite vertical links. There have been four specimens selected for examining the effects of different details. The first specimen was an I section with no stiffener, the second composed of I section with stiffeners provided according to AISC 2005. The third and fourth specimens were composed of I sections with reinforced concrete located at the area between its flanges and web. The tests carried out were of quasi-static type and conducted on full scale specimens. Experimental findings show remarkable increase in shear capacity and ductility of the composite links as compared to the normal specimens.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권8호
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• pp.3766-3788
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• 2017

A blockchain is an underlying technology and basic infrastructure of the Bitcoin system. At present, blockchains and their applications are developing rapidly. However, the basic research of blockchain technology is still in the early stages. The efficiency and reliability of blockchain communication is one of the research problems that urgently need to be studied and addressed. Existing algorithms may be less feasible for blockchain-based communication because they only consider a single communication factor (node communication capability or node trust degree) and only focus on a single communication performance parameter(communication time or communication reliability). In this paper, to shorten the validation time of blockchain transactions and improve the reliability of blockchain-based communication, we first establish a multi-link concurrent communication model based on trust degree, and then we propose a novel integrated factor communication tree algorithm (IFT). This algorithm comprehensively considers the node communication link number and the node trust degree and selects several nodes with powerful communication capacity and high trust as the communication sources to improve the concurrency and communication efficiency. Simulation results indicate that the IFT algorithm outperforms existing algorithms. A blockchain communication routing scheme based on the IFT algorithm can increase communication efficiency by ensuring communication reliability.

• Advances in concrete construction
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• 제1권3호
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• pp.253-272
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• 2013

The use of steel bracing systems is a popular method for the strengthening of existing reinforced concrete (RC) frames and may lead to a substantial increase of both strength and stiffness. However, in most retrofitting cases, the main target is the increase of the energy dissipation capacity. This paper studies numerically the efficiency of a specific strengthening methodology which utilizes a steel link element having a cross-section of various shapes, connected to the RC frame through bracing elements. The energy is dissipated through the yielding of the steel link element. The case studied is a typical one bay, single-storey RC frame, constructed according to older code provisions, which is strengthened through two different types of link elements. The presented numerical models are based on tests which are simulated in order to gain a better insight of the behaviour of the strengthened structures, but also in order to study the effects of different configurations for the link element. The behaviour of the strengthened frames is studied with respect to the one of the original bare frame. Moreover, the numerically obtained results are compared to the experimentally obtained ones, in order to verify the effectiveness of the applied simulation methodology.

• 전기전자학회논문지
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• 제23권1호
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• pp.99-106
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• 2019

본 논문에서는 UPQC 시스템과 SVC를 결합한 새로운 형태의 보상장치를 제안하고자 한다. 기존의 UPQC는 직렬형 인버터, 병렬형 인버터, DC 링크로 구성되어 있어있으며 우수한 전력품질 보상 성능을 보이지만 높은 인버터 정격을 요구한다. 제안된 방식은 직렬형 인버터, 병렬형 인버터와 DC 링크 그리고 병렬형 인버터의 출력단에 결합된 SVC로 구성되어 있으며, 기존 UPQC에 비해 넓은 무효전력 보상 범위와 낮은 DC 링크 전압의 장점을 가지고 있다. 또한, SVC가 결합된 새로운 UPQC의 구성은 Matlab 시뮬레이션을 통해 성능을 검증하였다.

• ETRI Journal
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• 제43권5호
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• pp.799-811
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• 2021

This paper considers a challenging problem: to simultaneously optimize the cost and the quality of service in opaque wavelength division multiplexing (WDM) networks. An optimization problem is proposed that takes the information including network topology, traffic between end nodes, and the target level of congestion at each link/ node in WDM networks. The outputs of this problem include routing, link channel capacities, and the optimum number of switch ports locally added/dropped at all switch nodes. The total network cost is reduced to maintain a minimum congestion level on all links, which provides an efficient trade-off solution for the network design problem. The optimal information is utilized for dynamic traffic in WDM networks, which is shown to achieve the desired performance with the guaranteed quality of service in different networks. It was found that for an average link blocking probability equal to 0.015, the proposed model achieves a net channel gain in terms of wavelength channels (𝛾_w) equal to 35.72 %, 39.09 %, and 36.93 % compared to shortest path first routing and 𝛾_w equal to 29.41 %, 37.35 %, and 27.47 % compared to alternate routing in three different networks.

• 전력전자학회논문지
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• 제26권3호
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• pp.205-213
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• 2021

Due to the advantage of reducing the voltage applied to the switch semiconductor, the input series and output parallel combination is widely used in systems with high input voltage and large output current. On the other hand, the LLC converter is widely used as a high-efficiency power converter, and when connected by ISOP combination, there is a possibility that input voltage imbalance may occur due to a mismatch of passive devices. To avoid damaging the switching device, this study analyzed the DC-link voltage imbalance of a high-capacity supply using an ISOP LLC converter. In addition, the case where DC-link unbalance control was applied and the case not applied was analyzed respectively. Based on this analysis, an initial start-up algorithm was proposed to prevent input power semiconductor device damage due to DC-link over-voltage. The effectiveness of the proposed algorithm has been verified through simulations and experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권8호
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• pp.2666-2687
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• 2022

As a new alternative communication scheme in 5G, unmanned aerial vehicle (UAV) is used as a relay in the remote base station (BS) for assistant communication. In order to ameliorate the quality of the backhaul link, a UAV backhaul transmission scheme based on improved Nash equilibrium (NE) strategy is proposed. First, the capacity of air-to-ground (A2G) channel by the link preprocess is maximized. Then, the maximum utility function of each UAV is used as the basis of obtaining NE point according to the backhaul channel and the backhaul congestion. Finally, the improved NE strategy is applied in multiple iterations until maximum utility functions of all the UAVs are reached, and the UAVs which are rejected by air-to-air (A2A) link during the process would participate in the source recovery process to construct a multi-hop backhaul network. Simulation results show that average effective backhaul rate, minimum effective backhaul rate increases by 10%, 28.5% respectively in ideal A2G channel, and 11.8%, 42.3% respectively in fading channel, comparing to pure NE strategy. And the average number of iterations is decreased by 5%.