• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.505-508
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• 2000

We discuss simulation results concerning the performance of the TCP protocol when running over high-speed HFC networks. Hybrid Fiber Coaxial are likely to provide fast and cost effective sup-port to a variety of applications including Video on demand, interactive computer games, and internet-type applications such as Webbrowsing, ftp, and telephony. Since most of these applications, use TCP as the transport later protocol, the key to their success largely depends on the effectiveness of the TCP protocol. In all simulation scenarios the TCP traffic is maxed with some background traffic whose level is taken as a variable parameter. Both the background traffic and TCP traffic are either unshaped, or shaped according to the GCRA algorithm. The effect of the background traffic on the TCP protocol performance is discussed varying the buffering capacity with nodes as well as the peak bit rate that each TCP connection is allowed to use.

• 대한교통학회지
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• 제33권6호
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• pp.554-563
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• 2015

본 연구는 확률적 모수를 고려한 음이항 모형을 이용하여 지방부 신호교차로에서 발생한 교통사고에 대한 모형을 개발하는데 목적이 있다. 교통사고 모형개발에 사용되는 기존의 가산모형(대표적으로 포아송/음이항모형)의 단점은 시간적 변화 혹은 각 지점/구간이 가진 고유한 특성에 대한 변화를 통합하여 설명하지 못한다는 것이다. 이로 인해, 추정되는 계수의 표준오차가 과소추정되어 결과적으로 모형 전체의 신뢰성을 하락시킨다. 이러한 문제점을 개선하기 위하여 이 연구에서는 각 대상 지점/구간의 이질성을 고려 할 수 있는 random parameter를 적용하여 기존 가산모형의 한계점을 개선하였다. 분석결과 교통량의 증가와 는 부도로의 보행자 시설들은 사고발생 증가에 영향을 미치고, 좌회전 전용차로 및 중앙분리대는 교통사고 감소에 효과가 있음을 확인할 수 있었다. 본 연구결과를 토대로 본 연구에서는 random parameter를 적용한 모형개발방법이 효과적임을 확인할 수 있었다. 하지만 본 연구에서는 기하구조의 변경 관련 자료의 부재로, 이들에 대한 영향까지는 확인하지 못한 한계가 있다.

• Geomechanics and Engineering
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• 제5권1호
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• pp.71-86
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• 2013

For rock materials, a transversely isotropic failure criterion established through the extended Lade-Duncan failure criterion incorporating an anisotropic state scalar parameter, which is a joint invariant of deviatoric microstructure fabric tensor and normalized deviatoric stress tensor, is verified with the results of triaxial compressive data on Tournemire shale. For torsional shear mode with $0{\leq}b{\leq}0.75$, rock shear strengths decrease with ${\alpha}$ increasing until the rock shear strength approaches minimum value at ${\alpha}{\approx}40^{\circ}$, and after this point, the rock shear strengths increase as ${\alpha}$ increases further. For the torsional shear mode with b > 0.75, rock shear strengths are almost constant for ${\alpha}{\leq}40^{\circ}$, but it increases with increase in ${\alpha}$ afterwards. The rock shear strength variation against ${\alpha}$ agrees with shear strength changing tendency of heavily OCR natural London Clays tested before. Prediction results show that the transversely isotropic failure criterion proposed in the paper is reasonable.

• 한국통신학회논문지
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• 제22권2호
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• pp.259-267
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• 1997

The advent of B-ISDN using ATM(asynchronous transfer mode) made possible a variety of new multimedia services, however it also created a problem of congestion control due to bursty nature of various traffic sources. To tackle this problem, UPC/NPC(user parameter control/network parameter control) have been actively studied and DRLB(dynamic rate leaky bucket) algorithm, in which the token generation rate is changed according to states of data source andbuffer occupancy, is a good example of the UPC/NPC. However, the DRLB algorithm has drawbacks of low efficiency and difficult real-time implementation for bursty traffic sources because the determination of token generation rate in the algorithm is based on the present state of network. In this paper, we propose a more plastic and effective congestion control algorithm by combining the DRLB algorithm and neural network based prediction to remedy the drawbacks of the DRLB algorithm, and verify the efficacy of the proposed method by computer simulations.

• 전자공학회논문지A
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• 제33A권2호
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• pp.23-31
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• 1996

This paper proposes a new UPC(usage parameter control) mechanism that varies the token generation rate of leaky bucket by observing virtual buffer, thus achieving an improvement of performance. An acceptance of a call in B-ISDN is determined by call admission control. A UPC that polices the agreed traffic parameters of a call and takes appropriate actions to prevent congestion in networks. The cell loss probability of conventional UPC is far from that of ideal UPC. The proposed mechanism has a better policing ability and response time for nonconforming call. The proposed mechanism uses ON-OFF model as input traffic. The results of simulation show the efficiency of the proposed mechanism.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.29-34
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• 2007

This paper proposes a MAC protocol for real-time VBR (rt-VBR) services in wireless ATM networks. The proposed protocol is characterized by a contention-based mechanism of the reservation request, a contention-free polling scheme for transferring the dynamic parameters, and a priority scheme of the slot allocation. The design objective of the proposed protocol is to guarantee the real-time constraint of rt-VBR traffic. The scheduling algorithm uses a priority scheme based on the maximum cell transfer delay parameter. The wireless terminal establishes an rt-VBR connection to the base station with a contention-based scheme. The base station scheduler allocates a dynamic parameter minislot to the wireless terminal for transferring the residual lifetime and the number of requesting slots as the dynamic parameters. Based on the received dynamic parameters, the scheduler allocates the uplink slots to the wireless terminal with the most stringent delay requirement. The simulation results show that the proposed protocol can guarantee the delay constraint of rt-VBR services along with its cell loss rate significantly reduced.

• 대한교통학회지
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• 제26권3호
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• pp.17-29
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• 2008

통행지체함수는 도로상의 교통량과 통행시간과의 관계를 나타내는 함수로 통행자들의 경로선택행위를 모형화한 통행배정(traffic assignment)모형에 주로 사용되고 있으며, 이를 위해서는 기본적으로 통행지체함수를 현실에 맞게 정산해야 한다. 본 연구는 기종점 통행자료를 구축하는 과정에서 중요한 역할을 하는 통행지체함수(volumedelay function)의 파라미터를 추정하고, 검증하는데 연구의 목적이 있다. 이를 위하여 본 연구에서는 전구간을 탐색하는 열거법에 황금분할법(golden section method)을 결합시켜 효율적으로 해를 찾는 방법을 제시하였으며 몇 가지 검증지표를 이용하여 현재 사용하고 있는 파라미터와 비교 분석하였다. 분석을 위하여 2006년 국가교통DB의 기종점 통행량(OD) 및 네트워크와 2006년 도로교통량 통계연보 자료를 이용하였으며, 분석결과 새롭게 추정된 파라미터값이 좀 더 현실적임을 보여 주었다.

• 산업융합연구
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• 제18권3호
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• pp.53-61
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• 2020

통행속도는 도로의 교통상황을 측정하고, 교통사고와 같은 돌발상황 발생을 검지하는데 활용되는 중요한 정보이다. 본 논문에서 영상처리 기술을 활용하여 도로구간의 통행속도를 정확하게 측정하는 모델을 제안하였다. 제안 모델은 교통 CCTV 영상에서 차량 객체를 추출하고, 딥러닝 기술 등을 활용하여 차량을 추적하여, 도로구간의 통행속도 및 교통량 등과 같은 교통정보를 수집한다. 또한, 새로운 모델은 데이터 융합기술을 활용하여 정확한 구간통행속도를 수집하여 사용자에게 제공하는 것이 가능하다. 제안 모델을 서울시 오금교에서 현장실험한 결과, 기존 교통정보센터 통행속도 정확도(62.8%)보다 새 모델의 정확도가 높은 것(83.6%)을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권12호
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• pp.2355-2373
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• 2011

Vision-based vehicle detector systems are becoming increasingly important in ITS applications. Real-time operation, robustness, precision, accurate estimation of traffic parameters, and ease of setup are important features to be considered in developing such systems. Further, accurate vehicle detection is difficult in varied complex traffic environments. These environments include changes in weather as well as challenging traffic conditions, such as shadow effects and jams. To meet real-time requirements, the proposed system first applies a color background to extract moving objects, which are then tracked by considering their relative distances and directions. To achieve robustness and precision, the color background is regularly updated by the proposed algorithm to overcome luminance variations. This paper also proposes a scheme of feedback compensation to resolve background convergence errors, which occur when vehicles temporarily park on the roadside while the background image is being converged. Next, vehicle occlusion is resolved using the proposed prior split approach and through reasoning for rule-based tracking. This approach can automatically detect straight lanes. Following this step, trajectories are applied to derive traffic parameters; finally, to facilitate easy setup, we propose a means to automate the setting of the system parameters. Experimental results show that the system can operate well under various complex traffic conditions in real time.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.86-89
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• 1998

Multiple types of information in a multimedia service are delivered though multiple virtual connections on ATM network, while each virtual connection may be controlled independently. A multimedia service requires an associative relationship among multiple information streams to provide required harmonization. There may be required additional traffic descriptors to guarantee the required harmonization among multiple information streams in a multimedia service. For buffering of large bandwidth information stream(e.g., video), extremely large buffer size is necessary, but this approach should not be efficient way to compensate a severely delayed cells/blocks experienced at network. The best way to solve this problem will be minimization of relative-delayed-transfer of cells/blocks to application processes through ATM network control. To minimize a delayed transfer the mapping between relative delay parameter(i.e., associative Group QoS parameters) and per-VC traffic descriptor will be necessary. This paper is present additional functions and parameters to interpret the mapping between relative delay parameters(i.e., associative Group QoS parameters) and per-VC traffic descriptors in ATM API for multimedia application services.