• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.17-23
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• 2000

Wireless link has high bit error rate compared with wired link and many users share this limited bandwidth. So it needs more powerful error control code and efficient media access control(MAC) to provide multimedia service reliably. In this paper we proposed efficient MAC frame format based on TDMA using mini-slot for request access. The number of mini-slots is variable based on the result of collision in the previous frame. This dynamic allocation of request mini-slots helps resolve the contention situation quickly and avoids the waste of bandwidth that may occur when there are several unneeded request mini-slots. The simulation results are also presented in terms of channel utilization, call blocking probability and cell transmission delay for mixed traffic environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.466-474
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• 2003

In this paper, we develope the simulation model for Ethernet passive optical networks (Ethernet-PON) by using OPNET. Ethernet-PON is an emerging access network technology that provides a low-cost method of deploying optical access lines. The simulator uses a Request/Grant TDMA MAC protocol based on IEEE 802.3ah EFM. It also executes registration, ranging and dynamic bandwidth allocation algorithm by exchanging control packets between OLT and ONUs. We have evaluated for success ratio of initial registration process and delay of late registration process. We also have simulated for dynamic TDMA protocol and static TDMA protocol in terms of channel utilization and queueing delay. We expect that this simulator can help to determine various parameters which are considered for designing Ethernet-PON system.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.1
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• pp.53-63
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• 1999

ATM 네트워크에서 다양한 트래픽을 특성과 QoS 요구사항을 갖는 멀티미디어 서비스의 종단간 품질을 만족시키면서 망 자원을 효율적으로 이용하기 위해서는 가상경로(virtual path : VP) 의 적절한 배치 및 대역 할당을 통한 논리적 망의 구성, 호 접속 시의 종적 경로 설정, 그리고 그와 연계된 효율적인 동적 대역 관리가 필수적으로 요구된다. 본 논문에서는 새로운 호가 시도될 때 논리적 망의 설계에서 설정된 가상경로의 대역으로 호의 품질 요구사항을 만족 시킬수 없거나 또는 미리 설정해 놓은 가상경로연결(VP Connection) 이 존재하지 않을 경우에 물리적 링크의 잔여용량을 기반으로 적절한 가상경로를 선택하여 용량을 재조정하기 위한 최적 관리 모델로서 MHR (Minimum Hop Route), MCR(Maximum Capacity Route), 그리고 MRCR (MaxMin Residual Capacity Route)방식을 제안하고 이에 대한 최적화 정식을 제안하였다. 제안된 각 최적화 모델에 대한 해를 노드의 수가 m인 네트워크에서 O(m2)의 복잡도로 구할 수 있는 알고리즘을 제시하고 시뮬레이션을 통해 제안된 최적화 모델이 망의 성능에 미치는 영향을 평균 호 차단률 평균 이용 링크의 수 , 그리고 노드 쌍간의 호 차단률의 분산등에 의해 망 운용의 효율성과 공평성등을 비교분석하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1477-1480
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• 2001

기존 통신사업자가 급변하는 통신시장에 대응하기 위한 구체적 접근방법에 초점을 맞추어 통신기술의 변화와 이에 따른 기존망을 어떻게 개선하여야만 수익성에 차질을 빚지 않을 수 있느냐가 전재 조건이 된다. 먼저 통신기술의 변화에 따른 망의 진화방향을 음성의 패킷화 실현, 망 구조의 단순화 및 통합화를 통한 운용비용의 절감, 향후 신규서비스의 수용에 용이한 방향이 있어야 한다. 본 논문에서는 ATM을 중심으로 한 차세대 교환망에서 음성과 데이터가 동일 패킷망을 사용하므로서 망 대역폭을 효율적으로 활용하는 방법과 유효 대역 사용률을 향상하는 유연한 대역관리 방법에 대해 개괄적으로 논하였으며, 이를 바탕으로 대역폭 할당 프로토콜을 분석한 수 있는 모델을 제안하고, 주어진 음성 및 데이터 트래픽의 요구와 제약을 조건으로 시스템 파라미터를 최적화하기 위해 update interval 시간과 음성과 데이터 트래픽에 예약된 슬롯의 수를 사용하였다. 분석적인 모델은 성능에 관한 트래픽 유형들의 영향뿐만 아니라 혼합 트래픽 시스템의 동적 할당 방법과 대역관리 방법을 제공한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.782-793
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• 2000

This paper presents a simple dynamical prediction scheme of the signal level which is attenuated and varied due to rain fading in satellite communication links using above 10GHz frequency bands. The proposed prediction scheme has four functional blocks for discrete-time low-pass filtering, slope-based prediction, mean-error correction and hybrid fixed/variable prediction margin allocation. Through simulations using Ka-band attenuation data obtained from the data measured over Ku-band by frequency-scaling, it is shown that the slope-based prediction with the mean-error correction has as small standard deviation of prediction error as below 1 dB, and that the error is about 1.5 to 2.5 times as small as that without the mean-error correction. The hybrid prediction margin allocation requires smaller average margin than those of both fixed and variable methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.820-829
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• 2000

In this paper, DSPA(Dynamic Signalling Period Allocation) algorithm that has been proposed by the authors for MAC(Medium Access Control) protocols in W-ATM(Wireless Asynchronous Transfer Mode) is applied to mixed traffic conditions composed of various service classes. We investigate the bandwidth utilization efficiency and quality of service(QoS) fulfillment by the DSPA algorithm used in W-ATM MAC protocols. Simulation results indicate that the DSPA algorithm significantly increases the throughput of the system with the minimum control overhead. Moreover, QoS of each service class is well satisfied by proper and fair channel allocation to different service classes according to their requirements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3B
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• pp.191-199
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• 2003

In this paper, a channel access control algorithm and a dynamic slot allocation algorithm are proposed for rt_VBR services and ABR services in the wireless ATM networks. In the proposed algorithm, rt_VBR terminals that require real-time services transmit a reservation request packet by a RAS minislot. An rt_VBR terminal, which transmitted the reservation request packet, transmits the dynamic parameters by DPS minislot without contention. On the other hand, ABR terminals that have a non-real-time traffic burst transfer a reservation request packet with contention basis. Based on the received dynamic parameters, the base station scheduler allocates uplink data slots as well as DPS minislot into rt_VBR terminals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8B
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• pp.507-513
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• 2005

As the rapid increasement of the number of internet users has occured recently, many multimedia application services have been emerging. To improve quality of service, traffic can be suggested to be classified with priority in EPON(Ethernet Passive Optical Network), which is supporting the multimedia application services. In this paper, multimedia application services treat bandwidth classifying device in serving both delay sensitive traffic for real-time audio, video and voice data such as Von(Voice over Internet Protocol), and for real-time traffic such as BE(Best Effort). With looking through existing mechanisms, new mechanism to improve the quality will be suggested. The delay performances and packet losses of traffic achieved by supporting bandwidth allocation of upstream traffic in suggested mechanism will be analized with simulations.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.162-163
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• 2005

One of the most important things in EPON(Ethernet Passive Optical Network) is that ONUs(Optical Network Units) have to share a channel in upstream direction. We proposed a new algorithm of Dynamic Bandwidth Allocation using Multiple LLID(Logical Link IDentifier). We show how to allocate bandwidth in Queues for improving performance from Bandwidth using Multiple LLID.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.9-9
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• 2004