• Journal of the Korea Society of Computer and Information
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• v.6 no.1
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• pp.45-50
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• 2001

Congestion may take place in the ATM network because of high-speed cell transmission features, and cell delay and loss also can be caused by unexpected traffic variation. Thus. traffic control mechanisms are needed. One of them to decrease congestion is the cell shaping. This paper proposes a hybrid type cell shaper composed of a Leaky Bucket with token pool, EWMA with time window, and a spacing control buffer. The simulator BONeS with the ON/OFF traffic source model evaluates the performance of the proposed cell shaping method. Simulation results show that the cell shaping concerning the respective source traffics is adapted to and then controlled on the mean bit rate.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.7
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• pp.36-45
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• 1999

In order to control the flow of traffics in ATM networks and optimize the usage of network resources, an efficient control mechanism is necessary to cope with congestion and prevent the degradation of network performance caused by congestion. In this paper, Buffered Leaky Bucket which applies the same control scheme to a variety of traffics requiring the different QoS(Quality of Service) and Neural Networks lead to the effective buffer utilization and QoS enhancement in aspects of cell loss rate and mean transfer delay. And the cell scheduling algorithms such as DWRR and DWEDF for multiplexing the incoming traffics are enhanced to get the better fair delay. The network congestion information from cell scheduler is used to control the predicted traffic loss rate of Neural Leaky Bucket, and token generation rate and buffer threshold are changed by the predicted values. The prediction of traffic loss rate by neural networks can enhance efficiency in controlling the cell loss rate and cell transfer delay of next incoming cells and also be applied for other traffic controlling schemes. Computer simulation results performed for random cell generation and traffic prediction show that QoSs of the various kinds of traffcis are increased.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.1
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• pp.20-33
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• 2002

Usage of ATM AAL2 packets becomes dominant to increase transmission efficiency of voice traffic in the backbone network. In case of voice service that uses AAL2 mechanism, if resources of network are enough, connection of new call is accepted. However, due to packets generated by the new call, transmission delay of packets from old calls can increase sharply. To control this behavior, in this paper we present an AAL2 buffer management scheme that allocates a virtual buffer to each call and after calculating its propagation delay variation(PDV), decides to drop packets coming from each call according to the PDV value. We show that this packet dropping algorithm can effectively prevent abrupt QoS degradation of old calls. To do this, we analyze AAL2 packet composition process to find a critical factor in the process that influences the end-to-end delay behavior and model the process by K-policy M/D/1 queueing system and MIN(K, Tc)-policy M/D/1 queueing system. From the mathematical model, we derive the probability generating function of AAL2 packets in the buffer and mean waiting time of packets in the AAL2 buffer. Analytical results show that the AAL2 packet dropping algorithm can provide stable AAL2 packetization delay and ATM cell generation time even if the number of voice sources increases dramatically. Finally we compare the analytical result to simulation data obtained by using the COMNET Ⅲ package.

• Journal of the Korea Computer Industry Society
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• v.3 no.1
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• pp.95-104
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• 2002

This paper presents some studies on the Internet TCP/IP(Transmission Control Protocol-Internet Protocol) traffic over ATM(Asynchronous Transfer Mode) UBR(Unspecified Bit Rate) and ABR(Available Bit Rate) classes of service. Fuzzy logic prediction has been used to improve the efficiency and fairness of traffic throughput. For TCP/IP over UBR, a novel fuzzy logic based cell dropping scheme is presented. This is referred to as fuzzy logic selective cell drop (FSCD). A key feature of the scheme is its ability to accept or drop a new incoming packet dynamically based on the predicted future buffer condition in the switch. This is achieved by using fuzzy logic prediction for the production of a drop factor. Packet dropping decision is then based on this drop factor and a predefined threshold value. Simulation results show that the proposed scheme significantly improves TCP/IP efficiency and fairness. To study TCP/IP over ABR, we applied the fuzzy logic ABR service buffer management scheme from our previous work to both approximate and exact fair rate computation ER(Explicit cell Rate) switch algorithms. We then compared the performance of the fuzzy logic control with conventional schemes. Simulation results show that on zero TCP packet loss, the fuzzy logic control scheme achieves maximum efficiency and perfect fairness with a smaller buffer size. When mixed with VBR traffic, the fuzzy logic control scheme achieves higher efficiency with lower cell loss.

• Journal of the Korea Society of Computer and Information
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• v.7 no.3
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• pp.143-148
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• 2002

Congestion may take place in the ATM network because of high-speed cell transmission features, and cell delay and loss also can be caused by unexpected traffic variation. Thus, traffic control mechanisms are needed. One of them to decrease congestion is the Cell shaping. This paper proposes a hybrid type cell shaper composed of a Leaky Bucket with token pool, Tn with time window, and a spacing control buffer. The simulator BONeS with the ON/OFF traffic source model evaluates the performance of the proposed cell shaping method. Simulation results show that the cell shaping concerning the respective source traffics is adapted to and then controlled on the mean bit rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.5A
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• pp.817-827
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• 2001

본 논문에서는 무선 ATM 망의 핸드오버를 위해 제시된 대표적인 동적 교차 스위치 (COS : Crossover Switch) 선택 방식들을 4가지 유형으로 분류하였다. 그리고 ATM 포럼에서 제안된 순방향 및 역방향을 위한 손실 방지 핸드오버와 손실 허용 핸드오버 방식에 대해 COS의 위치에 따른 영향을 핸드오버 지연, 사용자의 서비스 중단 시간, 셀 버퍼링 양 및 셀 손실 관점에서 수학적으로 분석하였다. 이러한 분석을 바탕으로 무선 ATM의 핸드오버에 대한 동적 COS 선택 기준을 각 핸드오버 방식별 및 성능 평가 요소별로 제시하였다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.375-377
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• 1999

본 논문에서는 지금까지 제시된 다양한 동적 COS (CrossOver Switch) 선택 방식들을 4가지 유형을 분류하였다. 그리고 ATM 포럼에서 제안된 순방향 핸드오버와 역방향 핸드오버의 손실 방지 핸드오버와 손실허용 핸드오버 방식에 대해 COS의 위치에 따른 영향을 핸드오버 지연, 사용자의 서비스 중단 시간, 셀 버퍼링양 및 셀 손실 관점, 그리고 경로 재사용 효율과 종단간 전송 지연 관점에서 수식적으로 분석하였다. 이러한 분석을 바탕으로 무선 ATM의 역방향 핸드오버에 대한 적절한 COS 선택 기준을 각 방식별/성능 평가 요소별로 제시되었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.80-90
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• 1996

The efficienty of ATM is based on the statical multiplexing of fixed-length packets, which are called cells. The most important technical point for realizing ATM switching network is an arrangement of the buffers and switches. Current most ATM switching networks are being achieved by using the switching modules based on the unit switch of $8{\times}8$ 150Mb/s or $16{\times}16$ 150Mb/s, the unit switch of $32{\times}32$150Mb/s for a large scale system is under study in many countries. In this paper, we proposed a new $32{\times}32$(4.9Gb/s throughput) ATM switch using Shared buffer memory switch which provides superior traffic characteristics in the cell loss, delay and throughput performance and easy LSI(Large Scale Integrated circuit). We analytically estimated and simulated by computer the buffer size into it. We also proposed the configuration of the large capacity ATM switching network($M{\times}M$.M>1,000) consisting of multistage to improve the link speed by non-blocking.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.394-397
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• 2003

In this paper, we describe the implementation of high performance buffer manager that is used in an advanced input-queued switch fabric. The designed buffer manager provides wire-speed cell/packet routing with low cost and tolerates the transmission pipeline latency of request and grant data. The buffer manager is implemented in a FPGA chip and supports the speed of OC-48c, 2.5Gbps per port.

• Journal of Korea Multimedia Society
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• v.6 no.5
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• pp.842-848
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• 2003

The Guaranteed Frame Rate(GFR) service has been designed to accomodate non-real-time applications, such as TCP/IP based traffic in ATM networks. One of the important factors is buffer management for guaranteeing QoS in GFR service. In this paper, we propose a buffer management scheme which can improve the fairness and the throughput through the traffic control in GFR service. For the evaluation of the proposed scheme, we compare proposed scheme with the existing scheme in the fairness and the throughput. Simulation results show that proposed scheme can improve the fairness and throughput than the existing scheme.