• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권11호
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• pp.3913-3934
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• 2021

Real-time prediction of Web service of quality (QoS) provides more convenience for web services in cloud environment, but real-time QoS prediction faces severe challenges, especially under the cold-start situation. Existing literatures of real-time QoS predicting ignore that the QoS of a user/service is related to the QoS of other users/services. For example, users/services belonging to the same group of category will have similar QoS values. All of the methods ignore the group relationship because of the complexity of the model. Based on this, we propose a real-time Matrix Factorization based Clustering model (MFC), which uses category information as a new regularization term of the loss function. Specifically, in order to meet the real-time characteristic of the real-time prediction model, and to minimize the complexity of the model, we first map the QoS values of a large number of users/services to a lower-dimensional space by the PCA method, and then use the K-means algorithm calculates user/service category information, and use the average result to obtain a stable final clustering result. Extensive experiments on real-word datasets demonstrate that MFC outperforms other state-of-the-art prediction algorithms.

• 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.

• International Journal of Reliability and Applications
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• 제3권2호
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• pp.99-112
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• 2002

Traffic congestion is one of critical factors in Internet applications to guarantee their QoS and provide reliable services. This paper discusses many existing congestion control algorithms and proposes a new ISDA. The algorithm is analyzed in respect of queue length, throughput and fairness. The proposed algorithm is working well with TCP and UDP traffics to offer QoS guarantee and fairness.

• 한국정보과학회논문지:정보통신
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• 제28권4호
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• pp.477-488
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• 2001

무선 네트워크 환경에서는 네트워크의 제한된 대역폭과 이동 호스트의 잦은 셀 간 이동으로 인하여, 각 호스트가 요구하는 서비스의 질(Quality of Service)을 보장하기 힘들다. 이런 무선 통신의 특성에서도, 실시간 서비스와 같은 특정 종류의 서비스의 경우에는 요구되어지는 범위 내에서 그 서비스의 질이 반드시 보장되어야 한다. 본 논문에서는 무선 이동 네트워크 환경에서 각 서비스의 서비스 율을 어떻게 조정할 것인가에 대해 논의한다. 무선 네트워크 환경에서 이동 호스트가 다른 셀로 이동하였을 경우, 부족한 대역폭을 고려하여 호스트의 서비스 율이 조정된다. 본 논문에서 각 플로우의 QoS Spec을 고려하여 서비스 율을 할당하는 알고리즘을 제안한다. 제안된 알고리즘에서는 각 플로우가 요구하는 QoS spec 값에 비례하도록 서비스 율을 정하여 부족한 네트워크 자원을 동적으로 할당함으로써, 무선 네트워크 자원을 보다 효율적으로 사용할 수 있게 한다.

• 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.

• 한국항행학회논문지
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• 제14권4호
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• pp.521-529
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• 2010

본 논문에서는 OFDM 시스템에서 인접 셀 간 간섭을 줄이기 위한 새로운 스케줄링 알고리즘을 제안한다. 제안된 알고리즘은 스케줄링을 할 때에 셀 별로 서로 다른 부채널 할당 순서를 적용하며 정수계획법을 이용하여 인접한 셀 간의 간섭을 최소화시키는 파라미터를 도출하며 이에 기반하여 스케줄링을 수행하는 방식이다. 시스템 시뮬레이션을 통하여 제안한 방식의 성능을 도출하였으며, 시뮬레이션 결과 제안한 스케줄링 알고리즘은 기존의 알고리즘들에 비해서 평균 전송율 외에 사용자별 공평성 측면에서 개선이 되고 이로 인해서 가입자 QoS 지원을 더 강화할 수 있음을 보였다.

• 융합보안논문지
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• 제7권2호
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• pp.39-47
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• 2007

본 논문에서는 광대역통합 네트워크(BcN：Broadband Convergence Network)을 이용하는 사용자에게 서비스품질을 제공하기 위한 스케쥴링 기법의 성능을 비교, 분석한다. 이를 위하여 트래픽의 등급별 분류, 입력큐에서의 처리, 등급별 가중치 부여 등과 같은 주요 서비스품질 관리 기법들을 분석하고 최근 멀티미디어 인터넷 통신을 위해 우선 고려되고 있는 주요 스케쥴링 기법(Round Robin, Priority, Weighted Round Robin)들의 동작원리를 분석한다. NS-2를 이용한 시뮬레이션을 통하여 각 스케쥴링 기법들의 성능을 분석한 결과, 단순히 하나의 서비스 등급에 대하여 Priority 스케쥴링 기법을 사용하는 것보다 등급별로 적절한 가중치를 두어 자원을 사용하는 것이 바람직함을 알 수 있다.

• 산업공학
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• 제23권2호
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• pp.193-202
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• 2010

The quality of service(QoS) model should be presented with the optimal network design to effectively provide the multimedia data services between users and converged services with mobile or TV in the next-generation Internet. In specific, the method to provide differentiated services for each user is needed in the given Internet node to offer the previously negotiated QoS with the user. In this paper, the performance of the QoS enabling technologies in the differentiated services(DiffServ) network domain is analyzed. The QoS offering model and QoS metrics are presented to analyze the performance of the major scheduling algorithms. Under the real network topology and virtual service scenarios in the university, the NS-2 network simulation based on the discrete-event is performed. The results show that the ratio-based scheduling method is more effective rather than the bandwidth-assignment method.

• 한국통신학회논문지
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• 제28권6B호
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• pp.553-562
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• 2003

멀티미디어 응용 서비스의 요구가 증대됨에 따라 멀티미디어 QoS (Quality of Service) 제공이 중요한 문제로 다루어지고 있다. 이에 따라 양끝단 시스템의 응용계층에서 혼잡 제어를 통하여 QoS를 제공하려는 많은 연구가 진행되고 있다. 본 논문에서는 송신측과 수신측이 적절한 협력을 바탕으로 전송 속도를 조절함으로서 혼잡에 대응하는 유니케스트 응용에 적합한 새로운 혼잡 제어 알고리즘인 RRC-OTT (Receiver-based Rate Control with One-way Trip Time)를 제안하였다. RRC-OTT 알고리즘은 수신측에서 받아들이는 패킷의 도착 분포를 분석하여 네트워크의 혼잡 상황을 파악하고 이에 따라 적절한 시기에 송신측으로 회신 정보 (ACK 패킷)를 보내줌으로서 전송 속도를 조절하도록 설계되었다. 시뮬레이션을 통하여 RRC-OTT 알고리즘이 기존의 송신측 중심 흔잡제어 알고리즘인 RAP (Rate Adaptation Protocol)에 비하여 ACK 패킷 오버헤드를 현저히 줄일 수 있었고 멀티미디어 QoS 측면에서 훨씬 낮은 지터 분포를 나타냄을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권7호
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• pp.1252-1273
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• 2011

In Web Service Composition (WSC) area, services selection aims at selecting an appropriate candidate from a set of functionally-equivalent services to execute the function of each task in an abstract WSC according to their different QoS values. In despite of many related works, few of previous studies consider transactional constraints in QoS-aware WSC, which guarantee reliable execution of Composite Web Service (CWS) that is composed by a number of unpredictable web services. In this paper, we propose a novel global selection-optimal approach in WSC by considering both transactional constraints and end-to-end QoS constraints. With this approach, we firstly identify building rules and the reduction method to build layer-based Directed Acyclic Graph (DAG) model which can model transactional relationships among candidate services. As such, the problem of solving global optimal QoS utility with transactional constraints in WSC can be regarded as a problem of solving single-source shortest path in DAG. After that, we present Graph-building algorithms and an optimal selection algorithm to explain the specific execution procedures. Finally, comprehensive experiments are conducted based on a real-world web service QoS dataset. The experimental results show that our approach has better performance over other competing selection approaches on success ratio and efficiency.