• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.281-284
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• 2004

This paper presents the design and implementation of a QoS based enhanced collaboration system in MDO. This is an efficient distributed communication tool between designers. It supports text communication, audio/video communication, file transfer and XML data sending/receiving. Specially, this system supports a dynamic QoS self-adaptation by using the improved direct adjustment algorithm (DAA+). The original direct adjustment algorithm adjusts the transmission rate according to the congestion level of the network, based on the end to end real time transport protocol (RTP), and controls the transmission rate by using the information of loss ratio in real time transport control protocol (RTCP). But the direct adjustment algorithm does not consider when the RTCP packets are lost. We suggest an improved direct adjustment algorithm to solve this problem. We apply our improved direct adjustment algorithm to our of QoS (Quality of Service) [1] based collaboration system and show the improved performance of transmission rate and loss ratio.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권3호
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• pp.891-910
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• 2021

Previous QoS-aware service composition methods mainly focus on how to generate composite service with the optimal QoS efficiently for a single request. However, in the real application scenarios, there are multiple service requests and multiple service providers. It is more important to compose services with suboptimal QoS and maintain the load balance between services. To solve this problem, in this paper, we propose a service composition method, named as dynamically change and balancing composition method (DCBC). It assumes that the QoS of service is not static, and the services can adjust the value of QoS to gain more opportunities to be selected for composition. The method mainly includes two steps, which are the preprocessing step and the service selection step. In the preprocessing step, a backward global best QoS calculation is performed which regarding the static and dynamic QoS respectively; then guided by the global QoS, the feasible services can be selected efficiently in the service selection step. The experiments show that the DCBC method can not only improve the overall quality of composite services but also guarantee the fulfill ratio of requests and the load balance of services.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제15권5호
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• pp.370-374
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• 2009

본 논문에서는 IEEE 802.16 OFDMA 시스템에서 QoS를 제공해 주기 위해서 표준에서 정의해 놓은 서비스 클래스 별 대역폭 할당 기법 중에서 UGS 클래스의 대역폭 할당 기법에서의 문제점을 지적하고 이를 해결하기 위한 알고리즘을 제시한다. 802.16 시스템에서는 다섯 가지 트래픽 클래스를 정의하고 이 중에서 UGS 클래스의 서비스 우선 순위를 가장 높게 처리하고 있다. 하지만, 기존의 UGS 클래스를 위한 대역폭 할당 방식에서는 다수개의 UGS 클래스가 존재할 때의 대역폭 할당 주기가 겹치는 문제에 대한 고려를 하고 있지 않다. 이로 인해서 오히려 UGS 클래스의 QoS 서비스를 제공해 줄 수 없는 상황이 발생하게 된다. 본 논문에서는 이런 문제점의 발생을 성능측정을 통해서 보여 주고 이를 해결하기 위한 알고리즘을 제시한다. 또한, 성능 비교를 통해서 제안하는 알고리즘 적용 시에 성능 향상이 있음을 보여 주고자 한다. 본 알고리즘의 적용을 통해서 실제 시스템 적용 시에 발생할 수 있는 문제점을 해결함으로써 보다 안정적인 QoS 서비스를 제공할 수 있는 802.16 시스템이 되리라 기대한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.528-531
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• 2004

This paper presents the design and implementation of a QoS based IrDA in mobile phones. The IrDA standards have arised from the need to connect various mobile devices together. But currently, we have a difficult to connecting various mobile devices together. The difficult thing is to adjust the minimum turn around time. The minimum turn around time in IrDA deals with the time needed for a receiver circuit to recover following saturation by transmissions from the same device (turn around latency). This parameter corresponds to the required time delay between the last byte of the last frames sent by a station and the point at which it is ready the first byte of a frame from another station. This parameter comes into play when the link is turned around and is negotiated independency for each station. We solve this matter by using the Dynamic Adjustment Algorithm (DAA). The dynamic adjustment algorithm adjusts the minimum turn around time according to the numbers of devices. We apply our direct adjustment algorithm to our QoS based IrDA in mobile phones and show the improved performance of connection with various mobile phones together.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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• pp.4144-4165
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• 2018

Software-defined networking (SDN) has emerged as a promising technology for network programmability and experiments. In this work, we focus on virtual network embedding in multiple controllers SDN network. In SDN virtualization environment, virtual SDN networks (vSDNs) operate on the shared substrate network and managed by their each controller, the placement and load of controllers affect vSDN embedding process. We consider controller placement, vSDN embedding, controller adjustment as a joint problem, together considering different quality of service (QoS) requirement for users, formulate the problem into mathematical models to minimize the average time delay of control paths, the load imbalance degree of controllers and embedding cost. We propose a heuristic method which places controllers and partitions control domains according to substrate SDN network, embeds different QoS constraint vSDN requests by corresponding algorithms, and migrates switches between control domains to realize load balance of controllers. The simulation results show that the proposed method can satisfy different QoS requirement of tenants, keep load balance between controllers, and work well in the acceptance ratio and revenue to cost ratio for vSDN embedding.

• 한국통신학회논문지
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• 제39B권2호
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• pp.61-74
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• 2014

In recent years, development of femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improvement in the quality of service for users. In 3GPP LTE-Advanced (LTE-A) system, to efficiently utilize the bandwidth, femtocell and macro cell uses the same frequency band, but this deployment poses a technical challenge of cross-tier interference to macro users. In this paper, the novel quality of service based fractional power control (QoS-FPC) scheme under the heterogeneous networks environment is proposed, which considers the users priority and QoS-requirements during the power allocation. The proposed QoS-FPC scheme has two focal points: firs, it protects the macrocell users uplink communication by limiting the cross-tier interference at eNB below a given threshold, and second, it ensures the optimization of femtocell users power allocation at each power adjustment phase. Performance gain is demonstrated with extensive system-level simulations to show that the proposed QoS-FPC scheme significantly decreases the cross-tier intereference and improves the overall users throughput.

• Journal of Communications and Networks
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• 제9권3호
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• pp.319-329
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• 2007

This paper presents a price-based quality-of-service (QoS) control framework for two-class network services, in which circuit-switched and packet-switched services are defined as "premium service class" and "best-effort service class," respectively. Given the service model, a customer may decide to use the other class as a perfect or an imperfect substitute when he or she perceives the higher utility of the class. Given the framework, fixed-point problems are solved numerically to investigate how static pricing can be used to control the demand and the QoS of each class. The rationale behind this is as follows: For a network service provider to determine the optimal prices that maximize its total revenue, the interactions between the QoS-dependent demand and the demand-dependent QoS should be thoroughly analyzed. To test the robustness of the proposed model, simulations were performed with gradually increasing customer demands or network workloads. The simulation results show that even with substantial demands or workloads, self-adjustment mechanism of the model works and it is feasible to obtain fixed points in equilibrium. This paper also presents a numerical example of guaranteeing the QoS statistically in the short term-that is, through the implementation of pricing strategies.

• 한국정보과학회논문지:정보통신
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• 제41권4호
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• pp.151-166
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• 2014

기존의 QoE(Quality of Experience) 측정 방식은 서비스 제공 서버에서부터 사용자가 서비스를 받는 단말기 까지 전체 구간을 묶어 측정 하였다. 이는 단순히 QoE 품질의 좋고 나쁨만을 판단할 수 있었으며 QoE 품질이 나빠질 경우 해결 방안을 제시 할 수 없었다. 또한 QoE 지표가 무수히 많기 때문에 어떻게 사용해야 하는 국제적 규정이 없다. 본 논문은 QoE 지표를 네트워크와 사용자 관점에서 분석하여 서비스를 제공하는 서버부터 라우터 까지, 라우터에서 서비스 받는 단말기 까지, 서비스 라우터에서 사용자 라우터 까지 3부분으로 나누고 각각의 영역에 맞는 QoE 지표 프레임을 제시한다. 이를 통하여 KOREN-CERNET 환경에서 QoE 네트워크를 설계 및 구현하고 QoE 네트워크의 안정성, 사용자 불만해결 시간 단축, 네트워크 변화에 따른 컨텐츠 적응 효과를 입증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3551-3567
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• 2016

The Low Earth Orbit satellite network has the unique characteristics of the non-uniform and time-variant traffic load distribution, which often causes severe link congestion and thus results in poor performance for delay-sensitive flows, especially when the network is heavily loaded. To solve this problem, a novel adaptive routing algorithm, referred to as the delay-oriented adaptive routing algorithm (DOAR), is proposed. Different from current reactive schemes, DOAR employs Destination-Sequenced Distance-Vector (DSDV) routing algorithm, which is a proactive scheme. DSDV is extended to a multipath QoS version to generate alternative routes in active with real-time delay metric, which leads to two significant advantages. First, the flows can be timely and accurately detected for route adjustment. Second, it enables fast, flexible, and optimized QoS matching between the alternative routes and adjustment requiring flows and meanwhile avoids delay growth caused by increased hop number and diffused congestion range. In addition, a retrospective route adjustment requesting scheme is designed in DOAR to enlarge the alternative routes set in the severe congestion state in a large area. Simulation result suggests that DOAR performs better than typical adaptive routing algorithms in terms of the throughput and the delay in a variety of traffic intensity.

• 전자공학회논문지CI
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• 제48권1호
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• pp.33-43
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• 2011

본 논문에서는 IEEE 802.11e에서 전송 흐름을 고려한 능동적 자원할당 방법을 제안한다. IEEE 802.11e에서는 비디오나 음성 데이터의 QoS를 제공하기 위해 우선순위가 높은 노드에게 정해진 시간동안 연속해서 보낼 수 있도록 TXOP 파라메터 값을 정해놓고 있다. 해당 시간동안 연속해서 데이터를 전송하므로써 채널의 점유를 위한 경쟁을 줄임으로써 충돌의 횟수가 줄어들어 빠른 데이터 전송의 장점은 있지만, 해당노드의 채널 상태가 좋지 못한 경우 전체 네트워크의 전송률은 떨어지고 우선순위는 낮지만 채널 상태가 좋은 노드의 경우 기다리는 시간이 길어지는 문제가 발생하게 된다. 이러한 문제점을 해결하기 위해 채널 상태에 따라 TXOP를 조정하여 우선순위는 낮지만 채널 상태가 좋은 노드에게도 점차적으로 할당함으로써 채널을 최대한으로 활용하도록 하였고 자원의 능동적인 할당으로 전송률 향상에 기여하는 알고리듬을 제안하였다.