• ETRI Journal
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• 제28권1호
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• pp.31-44
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• 2006

In a packet switching network, congestion is unavoidable and affects the quality of real-time traffic with such problems as delay and packet loss. Packet fair queuing (PFQ) algorithms are well-known solutions for quality-of-service (QoS) guarantee by packet scheduling. Our approach is different from previous algorithms in that it uses hardware time achieved by sampling a counter triggered by a periodic clock signal. This clock signal can be provided to all the modules of a routing system to get synchronization. In this architecture, a variant of the PFQ algorithm, called digitized delay queuing (DDQ), can be distributed on many line interface modules. We derive the delay bounds in a single processor system and in a distributed architecture. The definition of traffic contribution improves the simplicity of the mathematical models. The effect of different time between modules in a distributed architecture is the key idea for understanding the delay behavior of a routing system. The number of bins required for the DDQ algorithm is also derived to make the system configuration clear. The analytical models developed in this paper form the basis of improvement and application to a combined input and output queuing (CIOQ) router architecture for a higher speed QoS network.

• 한국컴퓨터정보학회논문지
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• 제21권11호
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• pp.65-71
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• 2016

This paper proposes a novel traffic and resource management scheme based on Service Level Agreement (SLA) which allows to guarantee the quality of experience (QoE) for various high-quality mobile multimedia service users to a certain level. For this purpose, QoE-SLA coupling structure is considered and a novel scheme is suggested to suppress the processing delay of the mobile terminal and to decrease the transfer delay in the transmission network. According to simulation results, our proposed scheme can increase the total throughput and decrease the average delay by adjusting SLA.

• 한국산업융합학회 논문집
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• 제5권4호
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• pp.329-337
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• 2002

It is the actual condition that the increasing traffic delay and accident caused by inefficient management on various construction by occupying the roadways. Since almost roadway improvements are for the public convenient, negative effects by them are ignored. But now due to the increase of traffics demand and limitation of road supply, the positive management scheme and treatment plan on the constructions must be considered. Thus, to the extent of this study divides uninterrupted flow into freeways and the Highway, yielding the time spread between under construction and not, that is delay time, we build capacity and delay model in the change of traffic volume and occupying length.

• 한국멀티미디어학회논문지
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• 제20권7호
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• pp.1030-1037
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• 2017

Traffic flows of real-time multimedia services such as Internet phone and IPTV are bounded on the end-to-end delay. Packets violating their delay limits will be dropped at a router because of not useful anymore. Service providers promise the quality of their providing services in terms of SLA(Service Level Agreement), and they, especially, have to guarantee the packet loss rates listed in the SLA. This paper is about a method to guarantee the required packet loss rate of each traffic flow keeping the high network resource utilization as well. In details, it assures the required loss rate by adjusting adaptively the timestamps of packets of the flow according to the difference between the required and measured loss rates in the lossy Weighted Fair Queuing(WFQ) scheduler. The proposed method is expected to be highly applicable because of assuring the packet loss rates regardless of the fluctuations of offered traffic load in terms of quality of services and statistical characteristics.

• Journal of Communications and Networks
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• 제5권3호
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• pp.230-239
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• 2003

In this paper, we propose a framework to study how to route packets efficiently in multipath communication networks. Two traffic congestion control techniques, namely, flow assignment and packet scheduling, have been investigated. The flow assignment mechanism defines an optimal splitting of data traffic on multiple disjoint paths. The resequencing delay and the usage of the resequencing buffer can be reduced significantly by properly scheduling the sending order of all packets, say, according to their expected arrival times at the destination. To illustrate our model, and without loss of generality, Gaussian distributed end-to-end path delays are used. Our analytical results show that the techniques are very effective in reducing the average end-to-end path delay, the average packet resequencing delay, and the average resequencing buffer occupancy for various path configurations. These promising results can form a basis for designing future adaptive multipath protocols.

• 한국통신학회논문지
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• 제30권2B호
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• pp.11-20
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• 2005

Strict priority scheduling scheme is a good candidate for the implementation of service differentiation in an Internet because of simplicity in implementation and the capability to guarantee the delay requirement of the highest class of traffic. However, it is also blown that strict priority starves the lower-class traffic at the cost of prioritizing the higher-class traffic. The purpose of this work is to propose an analytic method which can estimate the average delay performance of Diffserv service architecture and shows that strict priority scheme does not sacrifice the lower class traffic over a diverse condition of the load. From the numerical experiments for three-class Diffserv network we validate our argument that strict priority scheme may be applied to a service differentiation scheme for the future Internet.

• 대한교통학회지
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• 제34권5호
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• pp.449-464
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• 2016

본 연구의 목적은 혼잡 교차로에 직결형 회전교차로의 적용 가능성을 평가하고 적용 가능한 교통량 범위를 산정하여 도입기준을 마련하는데 있다. 이를 위해 진입 교통량 및 주 부도로 교통량 비율, 좌회전 교통량 비율에 따라 다양한 시나리오를 작성하고 직결형 회전교차로와 회전교차로, 신호교차로에 대한 시뮬레이션을 수행하여 지체시간을 비교 분석하였다. 분석 결과 주 부도로 교통량 비율이 6:4인 경우의 차로당 교통량이 400대/시에서는 좌회전 비율 30%까지, 500대/시에서는 20%까지, 600대/시에서는 10%까지 직결형 회전교차로의 지체시간이 가장 작게 나타났다. 주 부도로 비율이 7:3인 경우에는 차로당 교통량이 400-600대/시에는 6:4와 동일하게 나타났으나 300대/시의 좌회전 비율 30%, 700대/시인 경우의 10%에서 직결형 회전교차로가 가장 작게 나타났다. 주 부도로 비율 8:2인 경우에는 차로당 교통량이 400-500대/시, 700대/시인 경우에는 7:3과 동일하게 나타났으나 300대/시의 10-30%, 600대/시에는 좌회전 비율이 20% 인 경우에도 가장 작게 나타났다. 종합해보면 주 부도로의 교통량 비율 차이가 커질수록 좌회전 교통량 비율과 교통량이 적을수록 직결형 회전교차로의 교통 처리 능력이 높게 나타났다. 따라서 주 부도로 교통량 차이가 크고 주도로 직진교통량 비율이 큰 혼잡교차로에 직결형 회전교차로의 도입 시 효과가 클 것으로 기대된다.

• Journal of Communications and Networks
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• 제10권3호
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• pp.351-361
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• 2008

This paper presents a delay-margin based traffic engineering (TE) approach to provide end-to-end quality of service (QoS) in multi-protocol label switching (MPLS) networks using differentiated services (DiffServ) at the link level. The TE, including delay, class, and route assignments, is formulated as a nonlinear optimization problem reflecting the inter-class and inter-link dependency introduced by DiffServ and end-to-end QoS requirements. Three algorithms are used to provide a solution to the problem: The first two, centralized offline route configuration and link-class delay assignment, operate in the convex areas of the feasible region to consecutively reduce the objective function using a per-link per-class decomposition of the objective function gradient. The third one is a heuristic that promotes/demotes connections at different links in order to deal with concave areas that may be produced by a trunk route usage of more than one class on a given link. Approximations of the three algorithms suitable for on-line distributed TE operation are also derived. Simulation is used to show that proposed approach can increase the number of users while maintaining end-to-end QoS requirements.

• 한국도로학회논문집
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• 제12권2호
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• pp.1-7
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• 2010

본 연구는 도시교통수요예측에 있어 비신호교차로 지체를 다루고 있다. 본 연구의 목적은 비신호교차로 지체식을 개발하고, 이 지체식의 적용결과를 비교분석하는데 있다. 이를 위해 이 연구에서는 한국도로용량편람(KHCS)에 의한 시뮬레이션과 EMME/2를 이용한 청주시 사례연구에 중점을 두고 있다. 주요 연구결과는 다음과 같다. 첫째, 총 480회의 시뮬레이션을 통해 통계적으로 유의한 8개의 지체식이 개발되었다. 둘째, 비신호교차로의 지체식을 적용한 추정치가 관측 교통량 자료에 가장 적합한 것으로 분석되었다.

• 한국도로학회논문집
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• 제15권6호
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• pp.125-133
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• 2013

PURPOSES : The purpose of this study is to propose delay-minimizing operation methodology of a signalized intersection based upon optimization of lane-uses on approaching lanes for an intersection. METHODS : For the optimization model of lane-uses, a set of constraints are set up to ensure feasibility and safety of the lane-uses, traffic flow, and signal settings. Minimization of demand to saturation flow ratio of a dual-ring signal control system is introduced to the objective function for delay minimization and effective signal operation. Using the optimized lane-uses, signal timings are optimized by delay-based model of TRANSYT-7F. RESULTS : It was found that the proposed objective function is great relation with delay time for an intersection. From the experimental results, the method was approved to be effective in reducing delay time. Especially, cases for two left-turn lanes reduced greater delays than those for a left turn lane. It is noticed that the cases for different traffic volume by approach reduced greater delays than those for the same traffic volume by approach. CONCLUSIONS : It was concluded that the objective function is proper for lane-uses optimizing model and the operation method is effective in reducing delay time for signalized intersections.