• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1113-1119
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• 2007

In this paper, first, we proposed various possible candidate schemes for determining initial sleep window size and varying sleep window size in sleep mode for power saving class I of IEEE 802.16e. Then, we analyzed and compared the power saving performances of those schemes. The schemes used for the comparisons are EICV of IEEE 802.16e, and other comparable schemes such as EIED, EILD, LIED and LILD. Experimental results show that LILD and EIED outperform other comparable schemes. Especially, EIED shows the better performances for the case of high traffic intensity environments, while LILD does for the low traffic intensity case.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.1-8
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• 2001

Adaptive and Strict Packet Dropping mechanism we proposed in this paper drops adaptively packets for the congestion control, as predicting traffic pattern between each cycle. Therefore the proposed mechanism makes up for the drawback of RIO mechanism and minimizes the wastes of the bandwidth being capable of predicting in Dynamic and Strict Packet Dropping (DSPD) mechanism. And we executed a simulation and analyzed the throughput and packet drop rate based on the Sending Drop Precedence changing dynamically depending on the network traffic and compared RIO and the DSPD. The results show that the proposed mechanism provides better performance on drop precedence levels and stricter drop precedence policy for AF class than RIO and the DSPD mechanism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8B
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• pp.752-759
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• 2002

The capacity of the cell varies with the load of the home and neighboring cells. But most call admission control (CAC) algorithms do not consider the cell loading. In this paper a dynamic call admission control is proposed in a WCDMA system with traffic asymmetry. The proposed algorithm changes the CAC thresholds of new call and handoff call based on channel condition. The blocking and dropping probabilities can be controlled by adjusting these thresholds. The proposed algorithm guarantees the Qos of call class and priority between new call and handoff call. In addition, it can minimize the grade of service (GOS) value with the system throughput maintained.

• Journal of Communications and Networks
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• v.4 no.2
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• pp.128-135
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• 2002

We propose a new space priority mechanism, and analyze its performance in a single Constant Bit Rate (CBR) server. The arrival process is derived from the superposition of two types of traffics, each in turn results from the superposition of homogeneous ON-OFF sources that can be approximated by means of a two-state Markov Modulated Poisson Process (MMPP). The buffer mechanism enables the Asynchronous Transfer Mode (ATM) layer to adapt the quality of the cell transfer to the Quality of Service (QoS) requirements and to improve the utilization of network resources. This is achieved by "Selective-Delaying and Pushing-ln"(SDPI) cells according to the class they belong to. The scheme is applicable to schedule delay-tolerant non-real time traffic and delay-sensitive real time traffic. Analytical expressions for various performance parameters and numerical results are obtained. Simulation results in term of cell loss probability conform with our numerical analysis.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.6
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• pp.719-726
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• 1999

본 논문은 교통 신호 제어 알고리즘들의 성능을 비교하기 위한 복합교차로 시뮬레이터를 구현하였다. 기존의 교통 시뮬레이터들은 단일교차로를 대상으로 하거나 텍스트 모드로 동작하는 경우가 많았다. 논문의 시뮬레이터는 Visual C++의 MFC 라이브러리를 사용하여 n $\times$ n 형태를 갖는 복합교차로에 적합하도록 객체지향적으로 구현되었으며, 성능 비교를 위하여 제어 알고리즘들을 별개의 윈도우에서 처리하기 쉽도록 MDI 방식을 사용하였다. 개발한 시뮬레이터는 그래프 윈도우와 맵 윈도우의 편리한 사용자 인터페이스, 논리시간 설정을 통한 다목적 시뮬레이션, 다양한 성능평가 출력 등의 특징을 갖는다. Abstract In this paper, we implemented a multiple crossroad simulator to evaluate the performance of the traffic signal control algorithms. Most of existing traffic simulators were operated in text-mode or at a single intersection. We developed the object-oriented simulator suitable for multiple crossroads with n $\times$ n intersections by using MFC (Microsoft Foundation Class) library in Visual C++. The simulator was implemented by using MDI (Multiple Document Interface) scheme in order to process both control algorithms in separate windows respectively. Our simulator has the following features: user friendly interface with graph window and map window, multi-purpose simulations by setting logical time, and various forms of performance evaluation.

• Journal of the Korea Safety Management & Science
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• v.14 no.4
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• pp.125-136
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• 2012

In most child-care facilities, homeroom teachers take the responsibilities for safety education, which has been conducted in class hours on a regular basis. It was found that most homeroom teachers are lacking in teacher training opportunities, and the younger they are, the less training experience they get. Teachers with fewer teaching careers had a greater interest in safety education and training courses. In addition, homeroom teachers have been utilizing monthly toddler magazines as a method to acquire knowledges for safety education and prevention of safety accidents. The safety accidents which have most frequently occurred in care-care facilities turned out to be stumble and tear, and infants aged 3 years or younger were found to be easily exposed to the safety accidents mainly due to the frolic between peers during the free-choice activity time. The homeroom teachers recognized only traffic safety education among the range of safety training courses, which varied depending on teaching career such as traffic safety education and indoor/outdoor safety environment training, etc. In addition, it turned out that the safety training methods were limited to the utilization of discussion techniques, role-playing, description and demonstration.

• Journal of IKEEE
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• v.5 no.2 s.9
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• pp.136-145
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• 2001

As with appearing new applications that requires QoS guarantee such as VoIP, VPN in Internet, problems of IP QoS has been one of most important issues in next-generation Internet. IETF has proposed integrated services model(Int-Serv) and differentiated service(Diff-Serv) to supply IP QoS in Internet. Int-Serv model uses the state information of each IP flow, so satisfies QoS according to traffic characteristics, but increases the amount of flow state information with increasing flow number. Diff-Serv model uses PHP(Per Hop Behavior), and there are well-defined classes to provide differentiated traffics with different services according to delay and loss sensitivity. Diff-Serv model can provide diverse services in Internet because of having no the state and signal information of each flow. As MPLS uses the packet forwarding technique based-on label, it implements the traffic engineering in the networks easily. The MPLS can set up the path with different traffic parameters, and assign each path to particular Class of Services. Therefore it is possible to support the Diff-Serv model with well-defined classes. In this paper we investigate the performance improvement of Diff-Serv function in the MPLS network to guarantee class of services in Internet.

• The Journal of Information Technology
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• v.4 no.3
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• pp.87-100
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• 2001

IETF has proposed integrated services model(Int-Serv) and differentiated service(Diff-Serv) to supply IP QoS in Internet[1][2]. Int-Serv model uses state information of each IP flow, so satisfies QoS according to traffic characteristics, but increases the amount of flow state information with increasing flow number. Diff-Serv uses PHP(Per Hop Behaviour) and there are well-defined classes to provide differentiated traffics with different services according to delay and loss sensitivity. Diff-Serv model can provide diverse services in Internet because of having no the state and signal information of each flow. As MPLS uses the packet forwarding technology based on label, it implements the forwarding engine of high performance easily. The MPLS can set up the path having different and variable bandwidth and assign each path to particular CoS (Class of Service). Therefore it is possible to support the Diff-Serv model of well- defined classes that can provide the differentiated traffic with different services according to delay and loss sensitivity in IP QoS models of IETF. In this paper we propose a scheme that can accommodate Diff-Serv model to provide QoS. The system performance has been estimated by scheduling plan according to traffic classes.

• The Journal of the Korea Contents Association
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• v.8 no.1
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• pp.169-176
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• 2008

In this paper, we develop radio resource management queueing model in IEEE 802.IS networks considering both connection and packet level. In the upper level connection, we model connection admission control depending on availability of bandwidth and priority queue in each service class. In the lower level packet, we model dynamic bandwidth allocation considering threshold and availability of bandwidth in each service class simultaneously. Hierarchical model is built using an extended Petri Nets, SRN (Stochastic Reward Nets). Bandwidth utilization and normal throughput as performance index for all service classes of traffic are calculated and numerical results are obtained.

• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.863-870
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• 2004

UMTS(Universal Mobile Telecommunication System) is recently recognized as a standard for 3rd generation of wireless networks and DSCH(Down-link Shared Chanel) is considered as a very effective multiplexing method in UMTS. So, it is inevitable to develope an effective packet scheduling algorithms for DSCH in UMTS. This paper describes an improved packet scheduling algorithm for DSCH of UMTS. The algorithm takes consideration in channel state for each mobile terminal to maximize link utilization, delay threshold for class 3 traffic and throughput for class 4 to get long term fairness. To verify the algorithm, we programmed a simulator using PARSEC simulation tool and got some simulation results by it. The simulation results show that the algorithm has reasonable characteristics in both of link utilization and fair-ness by trade-off.