• Journal of Communications and Networks
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• 제17권1호
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• pp.84-92
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• 2015

Multi-hop relay networks have been widely considered as a promising solution to extend the coverage area and to reduce the deployment cost by deploying the relay stations (RSs) in mobile communication systems. Suitable deployment for the RSs is one of the most important features of the demand nodes (DNs) to obtain a high data transmission rate in such systems. Considering a tradeoff among the network throughput, the deployment budget, and the overall coverage of the systems, efficient RS deployment schemes and corresponding algorithms must be developed and designed. A novel cluster-based RS deployment scheme is proposed in this paper to select the appropriate deployment locations for the relay stations from the candidate positions. To make an ideal cluster distribution, the distances between the DNs are calculated when deploying the RSs. We take into account the traffic demands and adopt a uniform cluster concept to reduce the data transmission distances of the DNs. On the basis of the different candidate positions, the proposed scheme makes an adaptive decision for selecting the deployment sites of the RSs. A better network throughput and coverage ratio can be obtained by balancing the network load among the clusters. Simulation results show that the proposed scheme outperforms the previously known schemes in terms of the network throughput and the coverage ratio. Additionally, a suitable deployment budget can be implemented in multi-hop relay networks.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.371-375
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• 2007

In this paper, we have implemented the device management system to upgrade T-PAK software in mobile phone. The hybrid scheduling method and selective upgrade method are proposed. Hybrid scheduling method is based on distribution of delivery data in accordance with network traffic load and service priority from device management server to mobile phone. Selective upgrade method manages DSL classified by T-PAK software version to be upgrade using version management established in OMA DM SCOMO. Key mechanism of selective upgrade method is to only deliver DSL to be replaced to the mobile phone. We made an experiment on two methods using MS-700T terminals. The experimental result shows that the proposed method is faster than normal from delivery time standpoint.

• 한국통신학회논문지
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• 제29권2C호
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• pp.283-290
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• 2004

웹(Web)이 급속히 발전함에 따라 웹상에서 단순한 텍스트 파일 뿐 아니라 이미지, 오디오, 비디오 등의 멀티미디어 서비스에 대한 사용자의 요구도 기하급수적으로 증가하고 네트워크 대여폭의 수요도 급격히 증가하고 있다. 이러한 상황에서 콘텐츠의 빠른 전송과 적은 트래픽 발생을 위하여 Caching, P2P, CDN 등의 기술이 대두되었다. 본 연구에서는 콘텐츠가 여러 복제 웹 서버에 분산 배치되어 있는 환경에서 클라이언트의 요청에 가장 적절한 서비스를 해 줄 수 있는 웹 서버를 선택하기 위한 리다이렉션 시스템을 설계하고 구현하였다. 본 리다이렉션 시스템은 클라이언트의 요청을 토폴로지 상 가깝고 부하가 적은 복제 웹 서버로 리다이렉트 함으로써 클라이언트가 기대하는 응답시간을 단축시켰다. 이러한 연구는 지속적으로 증가하고 있는 대규모 멀티미디어 콘텐츠의 안정적이고 빠른 전송에 기여할 것이다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1606-1609
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• 2002

MAC state models appeared with an effort to overcome technical demerits of CDMA in provisioning packet data service. In the scenario of sojourn and transition on MAC states, the design of state sojourn time is a critical issue for an efficient utilization of limited recource; a longer sojourn time leads to more resource being preserved for inactive stations, while more connection components should be recovered with a shorter sojourn time. Thus, the sojourn time at each MAC state must be optimized in consideration of these two conflicting arguments. In this paper, we first present a generic MAC state model. Secondly, based on the generic model, we reveal a relation of inactive period and the delay time of the last packet served in pre- ceding active period and specify a loss function reflect-ing two antinomic features that result from a change of state sojourn time. Using the proposed loss function, we construct a decision problem to find an optima3 rule for state sojourn times. Finally, we present a way of computing Bayes rule by use of the posterior distribution of inactivity duration for given observation on the delay time of last packet. Furthermore, Bayes rules are explicitly expressed for special arrival processes and investigated with respect to traffic load and loss parameters.

• 대한전자공학회논문지TC
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• 제41권9호
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• pp.9-16
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• 2004

본 논문에서는 IPSec 가속기를 보안서버에 장착하였을 경우의 성능분석모델을 제안하였다. 제안된 보안서버는 M/M/1 시스템으로 모델링하였으며 트래픽 로드는 포아송분포를 이용하였다 보안서버의 성능변수를 통합하여 디코딩지연이라고 정의하였으며 IPSec 가속기인 BCM5820의 실측 결과와 비교하여 15%정도의 차이를 갖는 디코딩지연을 추출하였다 디코딩 지연을 제안된 성능분석모델에 대입하여 시뮬레이션 하였을 경우 보안연결은 BCM5820의 발표된 성능의 75%의 처리량을 보였다. 그리고 데이터전달은 발표된 성능의 각각 3.125%(패킷크기 64byte), 14.28%(패킷크기 1024byte)의 처리량을 보였다.

• Structural Engineering and Mechanics
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• 제48권3호
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• pp.395-414
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• 2013

The present study fundamentally investigated the mechanical performance of the rib-stiffened super-wide bridge deck with twin box girders in concrete, which is a very popular application to efficiently widen the bridges with normal span. The shear lag effects of the specific cross-sections were firstly studied. The spatial stress distribution and local stiffness of the bridge deck with twin box girders were then investigated under several typical wheel load conditions. Meanwhile, a comparative study for the bridge deck with and without stiffening ribs was also carried out during the investigation; thereby, a design optimization for the stiffening ribs was further suggested. Finally, aiming at the preliminary design, an approximate methodology to manually calculate the bending moments of the rib-stiffened bridge deck was analytically proposed for engineers to quickly assess its performance. This rib-stiffened bridge deck with twin box girders can be widely applied for concrete (especially concrete cable-stayed) bridges with normal span, however, requiring a super-wide bridge width due to the traffic flow.

• Computers and Concrete
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• 제23권5호
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• pp.329-334
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• 2019

Traffic flow capacity of some old road bridges is insufficient due to limited deck width. In such cases bridge deck widening is a common solution. For multi-girder reinforced concrete (RC) bridges it is possible to add steel-concrete composite girders as the new outermost girders. The deck widening may be combined with bridge strengthening thanks to thickening of the existing deck slab. Joint action of the existing and the added parts of such bridge span must be ensured. It refers especially to the horizontal plane at the interface of the existing slab and the added concrete layer as well as to the vertical planes at the external surfaces of the initially outermost girders where the added girders are connected to the existing bridge span. Since the distribution of the added concrete is non-uniform in the span cross-section the structure is particularly sensitive to the added concrete shrinkage. The shrinkage induces shear forces in the aforementioned planes. Widening of a 12 m long RC multi-girder bridge span is numerically analysed to assess the influence of the added concrete shrinkage. The analysis results show that: a) in the vertical plane of the connection of the added and the existing deck slab the longitudinal shear due to the shrinkage of the added concrete is comparable with the effect of live load, b) it is necessary to provide appropriate longitudinal reinforcement in the deck slab over the added girders due to tension induced by the shrinkage of the added concrete.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권9호
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• pp.3043-3067
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• 2022

With the mobile traffic in the network increases exponentially, multi-access edge computing (MEC) develops rapidly. MEC servers are deployed geo-distribution, which serve many mobile terminals locally to improve users' QoE (Quality of Experience). When the cache space of a MEC server is full, how to replace the cached videos is an important problem. The problem is also called the cache replacement problem, which becomes more complex due to the dynamic video popularity and the varied video sizes. Therefore, we proposed a new cache replacement scheme based on local video popularity and video size to solve the cache replacement problem of MEC servers. First, we built a local video popularity model, which is composed of a popularity rise model and a popularity attenuation model. Furthermore, the popularity attenuation model incorporates a frequency-dependent attenuation model and a frequency-independent attenuation model. Second, we formulated a utility based on local video popularity and video size. Moreover, the weights of local video popularity and video size were quantitatively analyzed by using the information entropy. Finally, we conducted extensive simulation experiments based on the proposed scheme and some compared schemes. The simulation results showed that our proposed scheme performs better than the compared schemes in terms of hit rate, average delay, and server load under different network configurations.

• 정보처리학회논문지A
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• 제16A권4호
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• pp.263-272
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• 2009

스마트 홈 인프라를 기반으로 유비쿼터스 컴퓨팅 환경을 구축하기 위해, 여러 연구기관과 산업체에서는 홈 네트워크에 대한 다양한 연구를 진행하고 있다. 이로 인해 다수의 홈 네트워크 미들웨어들이 제안되었으며, 이는 홈 네트워크 표준화를 지연시켰고, 이러한 표준화의 지연은 이 기종 미들웨어 간 상호운용성 문제를 해결할 수 있는 미들웨어 브리지를 요구하였다. 현재 두 미들웨어에 대한 상호운용성을 지원하는 일대일 브리지, 다수의 미들웨어에 대한 상호운용성을 지원하는 일대다 브리지 등 여러 미들웨어 브리지에 대한 개발과 상호운용성 지원 기법에 대한 연구가 진행되고 있다. 하지만 기존의 시스템과 기법들은 특히 스마트 홈 환경에서 요구되는 동적 확장성과 성능에 대한 고려가 부족하다. 미들웨어 브리지는 전문적인 지식이 없는 사용자를 위해 브리지의 수정 없이 쉽게 새 미들웨어를 추가할 수 있는 브리지 확장성을 제공해야 한다. 또한 브리지는 메시지 집중을 해결할 수 있는 부하 분산 기법 역시 제공해야 한다. 본 논문에서는 홈 네트워크 환경에서의 동적 확장성과 부하분산을 위한 다중 미들웨어 브리지(Multi-Middleware Bridge, MMB)를 제안한다. MMB는 분산 구조를 통해 브리지 확장성과 부하 분산 기능을 제공한다. 또한 이에 대한 구현과 평가를 통해, 상호운용성 지원 기능과 브리지 확장성, 부하분산 알고리즘의 성능을 검증한다.

• 한국산업융합학회 논문집
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• 제25권4_2호
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• pp.587-594
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• 2022

In the 2000s, a lot of cable-type grand bridges are being built in consideration of economic aspects such as the reduction of logistics costs and the distribution of traffic volume due to rapid economic development. In addition, because the recently installed grand bridges are designed in an aesthetic form that matches the surrounding environment as well as the original function of the road bridge, and serves as a milestone in an area and is used as an excellent tourism resource, attracting many vehicles and people, there is an urgent need for a safety structure that can ensure the safety of not only vehicles but also people. In order to make cable-stayed bridge safe on wind for additional five safety structures, main girder models with and without safety structures for wind-tunnel experiments was made, and wind tunnel experiments was carried out to measure aerodynamic force coefficients. Also, wind-resistant analyses of 3D cable-stayed bridge were performed on the basis of wind-tunnel experiment results. From the wind tunnel experiments for the aerodynamic force coefficients of main girder with five safety structures and the wind resistant analyses of cable-stayed bridge without safety structure and with safety structure, it was concluded that the best form of wind-resistant safety was shown in the order of mesh, standard, bracing, hollow, and closed type. And wind-resistant safety of cable-stayed bridge with hollow and closed type on design wind speed 68.0m/sec was not secured. Finally, as five safety structures are installed, maximum rate of stress increments was shown in the order of steel main beam, steel floor beam, concrete floor beam and cables.