• Journal of the Institute of Convergence Signal Processing
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• v.4 no.1
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• pp.9-14
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• 2003

APON, the subscriber network using bus or tree topology, requires MAC protocol, because it shares the uplink channel for many subscribers to transmit data to OLT. Although various MAC schemes, which consider each QoS characteristics of traffic are proposed considering transmission characteristics of ATM traffic class, existing schemes reduce the network efficiency by increasing transmission overhead in frame. In this paper, we propose new MAC scheme, which shows similar performance as those of existing schemes but does not increase transmission overhead. To prevent increasing transmission overhead, the proposed scheme encodes the information about each cell information of traffic of the local queue in RAU transmitted periodically from ONU to OLT Thus, the proposed MAC scheme shows similar performance as those of existing ones and increases efficiency of entire network.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.362-364
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• 1998

최근의 네트워크의 특징은 '광대역 통합 서비스 네트워크'라 할 수 있다. 뿐만 아니라, 최근의 ATM연결은 점대점 연결은 물론, 점대다점 연결을 특징으로 하고 있다. 이 논문에서는 하나의 ATM 멀티캐스트 (MVCC)세션 내에서, ATM계층 상위에 TCP와 같은 LAN기반 네트워크 연동에 대해 다룬다. ATM네트워크 상에 멀티캐스트 연결을 설정할 경우, 공유 트리 방식에 의해 연결 트리를 구성하고, AAL5 계층을 사용하므로 CIP 가 발생한다. 이 문제를 해결하기 위해 ABT/IT RM셀을 이용한 블록단위의 전송을 고려한다. 또한, ATM VC 위에 LAN 기반 네트워크 연동 서비스를 제공하기 위해 UBR 클래스를 이용하게 되는데. 그 속성상 QoS를 보장하지 못하고 네트워크에 혼잡 발생시에 우선적으로 폐기되며 단지 EPD메커니즘과 같은 버퍼 관리 방식만을 사용할 뿐이다. 따라서, ABT RM 셀을 통한 블록 단위 전송을 이용하게 되면 CIP를 해결할 뿐만 아니라. 여러 응용 트래픽 유형을 고려한 스케줄링을 통해 네트워크 상에 혼잡이 발생할 경우에 UBR 트래픽이 무차별적으로 폐기되는 현상을 막고, 효율적이고 공평한 서비스를 제공할 수 있다. 이을 위해.ATM스위치 내에 하나의 멀티캐스트 세션에 대한 블록 스케줄링 알고리즘을 제안한다.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.847-856
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• 2002

Cellular network applications are growing drastically and this requires a fast and efficient transport method between the base station and the mobile switching center. One possible solution is to use ATM links. The low data rate and small-sized packets in the typical cellular applications imply that significant amount of link bandwidth would be wasted, if this small sized packet is carried by one ATM cell. For efficient operation for such cellular and low bit rate applications, a new type of ATM Adaptation Layer, AAL Type 2, has been proposed. In this paper, the principles of AAL Type 2 are briefly described along with the introduction of other alternatives which have formed the basis for this new AAL. The result from the simulation to study the performance of the AAL Type 2 is discussed from the view point of packet delay and ATM cell use efficiency. Due to the variable size of packets in this application, the fairness issue in serving variable sized packets is also discussed along with the effect of fair queueing algorithm implemented at AAL Type 2.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2B
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• pp.167-173
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• 2004

This paper reports on the development of a 60㎓ wide bandwidth wireless transceiver using NRD waveguide. We fabricated a wireless transceiver using NRD waveguide, which consists of a 3 dB directional coupler, a bandpass filter, a Gunn oscillator, an ASK modulator, and a Balanced Mixer. The new transceiver is capable of transmitting an output power of 10mW to a distance of more than 1 Km, operating in 60㎓ frequency and bandwidth of 2㎓. The value of BER reached approximately 10 when the transceiver was tested at the 155.52Mbps ATM(OC 3) at the communication distance of 1 km. It demonstrated an impressively stable transmission feature of BER l0$^{6}$ even in the heavy rainfall.

• Journal of the Korea Society of Computer and Information
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• v.7 no.3
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• pp.80-91
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• 2002

A general goal of the AT%(Asynchronous Transfer Mode) network is to support connect across various network. On ATM networks, ABR services are provided using the remained ban after allocation CBR and VBR traffic. Realtime services such as transmitting audio or video data may be provided using CBR ado VBR which have a constrained transmission delay, but in these cases, the communications bandwidth may be wasted. In this paper a simulation has been performed to compare and evaluate the performance between the ERICA(Explicit Rate Indicate Avoidance) and EPRCA(Enhanced Proportional Rate Control Algorithm) switches which use Explicit Rate switch algorithm for ABR switch. The variation of the ACR at the source end system, the queue length, the utilization rate of the link bandwidth and the share fairness at the transient and steady states are used as the evaluation criteria for the simulation. As a result of simulation, ERICA algorithm switch was ten times long compared to ERPCA switch to achieve assigned fair share. so EPRCA switch is superior to ERICA about load response. For Fair share and stability, ERICA switch is excellent to EPRCA switch.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.117-120
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• 2001

In this paper, a contention-based reservation MAC protocol is proposed for non-real-time bursty traffic services in the wireless ATM networks. In order to reduce the collisions of the reservation request packets, the base station scheduler calculates the transmission probability using the number of RAS minislots and the estimated load of the reservation request packets. And it broadcasts the calculated transmission probability through the downlink control channel. Mobile terminals, which have a traffic burst, select randomly a RAS minislot and transmit the reservation request packet with the received transmission probability. The reservation request packet contains the number of packets in the buffer. The base station allocates slots based on the buffer status of the received reservation request packets.

• The KIPS Transactions:PartC
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• v.10C no.7
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• pp.937-942
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• 2003

In this paper, we measured and examined RTT delays and packet losses according to the changes of stationary loads for two typical stream-type traffics, a DV and a MPGE2 on the R＆D Gigabit Network testbed, JGN. As the result of our actual measurements, we realized that the packet size of stationary load have no effects on a DV and a MPGE2 stream on the very high-speed network(50Mbps, IP over ATM). When its bandwidth and stationary load exceeds 95％ of network bandwidth, packet losses appeared and RTT delay increased rapidly. Also we realized that the number and size of Receive ＆ Transmit buffer on the end systems have no effects on packet losses and RTT delays.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.487-497
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• 1999

In this paper, the performances of MC-CDMA systems for wireless ATM(WATM) is analyzed through computer simulations. The proposed MC-CDMA systems can support the 25 Mbps data rate with about 18.2 MHz bandwidth at 5 GHz carrier frequency, satisfying the specifications of wireless physical layer proposed by Wireless ATM Working Group(WATM WG). For the channel coding strategies, convolutional code, TCM and Turbo TCM(T-TCM) are explored and their performances are compared. From the simulation results, T-TCM becomes superior to the other coding schemes as interative decoding is performed.

• Electronics and Telecommunications Trends
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• v.14 no.4 s.58
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• pp.10-22
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• 1999

본 고에서는 ATM 교환기에서 비실시간 트래픽를 수용하기 위한 버퍼 관리방법에 대하여 조사하고 분석하였다. ATM 교환기는 고속으로 교환하지만 트래픽이 많을 경우 혼잡이 발생할 수 있으므로 비실시 간 트래픽을 제어하여 사용자가 요구하는 다양한 서비스 품질(Quality of Service: QoS)을 제공해야 한다. TCP는 대표적인 비실시간 트래픽으로서 교환 및 전송중에 패킷 손실이 발생하는 경우 양 종단의 TCP에서 재전송 및 TCP 흐름 제어를 한다. 본 고에서는 ATM 교환기에서 제한된 버퍼를 효율적으로 활용하기 위하여 버퍼 부족현상이 예견되는 경우 패킷 폐기 정책에 따라 패킷을 폐기함으로써 TCP 계층에서의 처리량(goodput)을 증대시키는 방법을 검토하였다. 아울러 다중점대점 연결을 제공하는 가 상채널 병합(VC merging) 기능을 구현하기 위한 ATM 교환기의 버퍼 요구사항과 지연에 대하여 살펴 보았다.

• Information and Communications Magazine
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• v.12 no.4
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• pp.48-62
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• 1995

본고에서는 B-ISDN의 기반기술인 ATM(Asynchronous Transfer Mode)을 기반으로 하는 광대역 지역망 교환 시스팀(ATM-MSS)의 교환 및 관리 구조에 대하여 기술한다. 먼저 ATM-MSS의 기본 구조 및 기능을 개괄적으로 살펴본 후, 이러한 교환 및 전송기능을 관리하는 ATM-MSS 관리 기능을 구조 및 기능면에서 기술한다. 또한 ATM 교환장치를 사용한 망 개념인 ATM-Highway를 통한 ATM-MSS의 활용방안에 대하여 설명한다.