• 한국통신학회논문지
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• 제21권6호
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• pp.1480-1489
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• 1996

In ATM networks there are two methods in traffic control as schemes advancing the quality of service. One is reactive control after congestion and the other which is generally recommended, is preventive control before congestion, including connection admission control on call leel and usage parameter control, network parameter control, priority control and congestion control on cell level. In particular, usage parameter control is required for restricting the peak cell rate of bursy tracffic to the parameter negotiated at call set-up phase since the peak cell rate significantly influences the network quality of service. The scheme for progressing quality of service by usage parameter control is themethod using VSA(Virtual Scheduling Algorlithm) recommended ITU-T. The method using VSSA(Virtual Scheduling Suggested Algorlithm) in this paper is suggested by considering cell delay variation and token rate of leaky bucket, compared VSA and VSANT(Virtual Scheduling Algolithm with No Tolerance) with VSSA which polices violated cell probability of conformed peak cell rate and intentionally excessive peak cell rate. VSSA method using IPP(Interruped Poisson Process) model of input traffic source showed more quality of service than VSA and VSANT methods as usage parameter control because the suggested method reduced the violated cell probability of contformed peak cell rate and intentionally excessive peak cell rate.

• 한국통신학회논문지
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• 제31권6B호
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• pp.517-526
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• 2006

본 논문에서는 가상 셀(Virtual Cell)이라는 새로운 개념을 도입하여 사용자의 움직임에 따라 셀(Cell)이 동적으로 바뀌어서 핸드오프의 문제가 없으며, 사용자 간, 셀 간에 야기되는 간섭을 모니터링 할 수 있고 또한 상호 간섭을 최소화하도록 제어할 수 있어서 기존 셀룰라 시스템이 안고 있는 간섭 문제를 효과적으로 극복할 수 있는 분산무선통신시스템에 관하여 소개한다. 그리고 이러한 분산무선시스템을 기반으로 하여 사용자 통신의 링크 품질을 지속적으로 유지하면서 용량을 향상시키고자 하는 Dual Virtual Cell(DVC) 개념과 운용 방안을 제안하였다. DVC 시스템은 단말의 실제 트래픽을 위한 Active Virtual Cell 외에, 사용자 통신의 다음 시점의 도달 범위 예측과 사용자 무선링크의 품질저하 및 단절을 방지하기 위한 후보군의 분산안테나들의 집합인 Candidate Virtual Cell을 도입하여 이러한 이중구조의 가상 셀을 동시에 관리함으로써, 채널정보 획득에 대한 단말의 부담을 줄이고 채널추정정보에 대한 시간지연과 단말의 이동으로 인한 무선링크 단절 및 품질 저하를 방지하며 신속한 통신채널 변경을 지원할 수 있다. 제안하는 시스템에서는 DVC의 안테나 구성을 위하여 안테나 선택기법을 이용하고 있으며, 시스템 오차 확률 개선을 위하여 Space-Time Trellis Code를 도입하였다.

• 전자공학회논문지B
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• 제33B권11호
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• pp.106-115
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• 1996

In this paper, the method using virtual scheduling suggested algorithm (VSSA) is suggested by considering cell delay variation and token rate of leaky bucket. This method is compared with virtual scheduling algorithm (VSA) and virtual scheduling algorithm with no tolerance excessive peak cell rate. As a result, the research shows that the usage parameter control using vSSA makes quality of service better than the usage parameter control using vSA or VSANT does because the suggested method reduces the violated cell probability of conformed peak cell rate and intentionally excessive peak cell rate.

• 한국정보과학회논문지:정보통신
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• 제29권2호
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• pp.181-187
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• 2002

Connection admission control(CAC), which decides whether or not to accept a new call request, is one of the most Important preventive congestion control techniques in asynchronous transfer mode(ATM) networks. To develop a practical CAC scheme, first we propose a "Modified Cell Loss Probability MP${\nu}"$, which is based on "Virtual Cell Loss Probability P${\nu}"$, taking into account mean burst duration of input traffic source and buffer size in ATM networks. MP${\nu}"$ computes more accurate cell loss probability than P${\nu}"$ without increasing computational complexity, since P${\nu}"$ is formulated simply form the maximum and the average cell rate of input traffic. P${\nu}"$ is overestimated as compared to the real cell loss probability when the mean burst duration is relatively small to the buffer capacity. Then, we Propose a CAC scheme, based on "Modified Virtual Bandwidth(MVB)" method, which may individualize the cell loss probabilities in heterogeneous traffic environments. For the proposed approach, we define the interference intensity to identify interferences between heterogeneous traffic sources and use it as well as MP${\nu}"$ to compute MVB. Our approach is well suitable for ATM networks since it provides high bandwidth utilization and guarantees simple and real time CAC computation for heterogeneous traffic environments.heterogeneous traffic environments.

• 한국통신학회논문지
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• 제38A권6호
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• pp.535-544
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• 2013

본 논문은 단일 송신안테나를 갖는 다수의 모바일 터미널이 가상 MIMO 링크를 구성하는 MIMO 시스템에서의 역방향 전력 제어 방법을 제안한다. 기존의 성능을 향상 시키기 위하여 전력 벌칙 항을 추가하는 게임이론 기반의 전력 제어 방식과 달리, 전체 유효 간섭 전력에 대한 제한 조건 하에서 선형 수신 빔형성을 이용한 전송율의 유틸리티 함수를 최대화 하는 방법을 고려하였다. 또한, 전력제어 과정에 이너시아를 도입하여 제안 전력 제어가 수렴함을 보였다. 모의 실험을 통하여 간섭이 지배적인 다중셀 시스템에서 제안 전력 제어 방법이 시스템의 성능을 크게 향상 시킴을 입증하였다.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.31-39
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• 2013

A virtual chassis platform for Fuel Cell Hybrid Electric Vehicles(FCHEV) has been developed, and a virtual platform similar to the actual system has been composed. In addition, major components such as a motor, fuel cell and battery for the virtual platform have been constructed by using a mathematical formulation. The FCHEV virtual platform using a detailed model based on the mathematical formula is capable of simulating various conditions according to changes of the control logic and component modules to evaluate performance, considering the vehicle dynamic characteristics. Usability of the mathematical model has been verified by comparative simulations according to the motor current control variation. In addition, reliability of the developed virtual chassis platform has been verified by simulating its fuel consumption with the UDDS(Urban Dynamometer Driving Schedule) FTP-72 velocity profile.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.4703-4723
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• 2018

In recent years, dense small cell network has been deployed to address the challenge that has resulted from the unprecendented growth of mobile data traffic and users. It has proven to be a cost efficeient solution to offload traffic from macro-cells. Software defined heterogeneous wireless network can decouple the control plane from the data plane. The control signal goes through the macro-cell while the data traffic can be offloaded by small cells. In this paper, we propose a framework for cell virtualization and user association in order to satisfy versatile requirements of multiple tenants. In the proposed framework, we propose an interference graph partioning based virtual-cell association and customized physical-cell association for multi-homed users in a software defined small cell network. The proposed user association scheme includes 3 steps: initialization, virtual-cell association and physical-cell association. Simulation results show that the proposed virtual-cell association outperforms the other schemes. For physical-cell association, the results on resource utilization and user fairness are examined for mobile users and infrastructure providers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1354-1358
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• 2003

The process equipment for handling high level radioactive materials like spent fuels is operated in a hot cell, due to high radioactivity. Thus, this equipment should be maintained and repaired optimally by a remotely operated manipulator. The master-slave manipulators(MSM) are widely used as a remote handling device in the hot cell. The equipment in the hot cell should be optimally placed within the workspace of the wall-mounted slave manipulator for the maintenance operation. But, because of the complexity in the hot cell, there would be some parts of the equipment that are not reached by the MSM. In this study, the maintenance process for these parts of the equipment is developed using virtual prototyping technology. To analyze the workspace of the maintenance device in the hot cell and to develop the maintenance processes for the process equipment, the virtual mock-up of the hot cell for the spent fuel handling process is implemented using IGRIP. For the implementation of the virtual mock-up, the parts of the equipment and maintenance devices such as the MSM and servo manipulator are modeled and assembled in 3-D graphics, and the appropriate kinematics are assigned. Also, the virtual workcell of the spent fuel management process is implemented in the graphical environment, which is the same as the real environment. Using this mock-up, the workspace of the manipulators in the hot cell and the operator's view through the wall-mounted lead glass are analyzed. Also, for the dedicated maintenance operation, the analyses for the detailed area of the end effectors in accordance with the slave manipulator's position and orientation are carried out. The parts of the equipment that are located outside of the MSM's workspace are specified and the maintenance process of the parts using the servo manipulator that is mounted in the hot cell is proposed. To monitor the process in the hot cell remotely, the virtual display system by a virtual camera in the virtual work cell is also proposed. And the graphic simulation using a virtual mock-up is performed to verify the proposed maintenance process. The maintenance process proposed in this study can be effectively used in the real hot cell operation and the implemented virtual mock-up can be used for analyzing the various hot cell operations and enhancing the reliability and safety of the spent fuel management.

• 융합신호처리학회논문지
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• 제2권1호
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• pp.71-79
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• 2001

장거리 링크를 가지는 ATM 망에서는 긴 전파지연의 영향을 고려하여 설정된 가상종단시스템을 이용하여 ABR 서비스를 제공할 수 있다. 본 논문에서는 가상종단시스템을 이용하여 ABR 서비스를 제공하는 데에 필요한 조건인 많은 개수의 가상연결들에 대한 ABR 서비스 제어 기능을 설계하기 위한 제반 고려 사항들을 살펴보고 구현을 위한 설계 구조를 제시하였다. 제시한 설계 구조에서는 많은 개수의 가상연결들에 대해 ABR 서비스를 수용해 줄 수 있도록 공유 메모리 구조를 이용한 셀 송출 제어 구조를 적용하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.73.2-73
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• 2001

Nowadays, one of the major technical issues in manufacturing is how to implement an virtual plant as an well-designed, integrated environment for sharing information and engineering collaboration among diverse engineering activities. The systematic approaches to make a virtual plant based on a 3-dimensional CAD, cell and line simulation, database and internet technologies are proposed in this paper. To do that, measuring and 3D CAD modeling technologies of many equipments, facilities and structures of the building are developed, effective management of information including models and related files in WWW environment is implemented, and precise simulations of unit cell and whole structured plant are performed. For the beginning of implementing a Virtual Automotive Plant, the Virtual Plant for the Body Shop of a Korean automotive company is constructed and implemented, Using this Virtual Plant ...