• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.127-130
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• 2006

EPON의 상향 전송 방식에서는 다수의 ONU가 OLT로부터 공유된 채널에 대한 권한을 할당받아 데이터를 전송하게 되므로 EPON에서는 각각의 ONU들에게 공유된 대역폭을 공평하고 효율적으로 할당하기 위한 DBA 알고리즘이 필수적이다. 우리는 본 논문에 앞서 기존의 DBA알고리즘들의 문제점을 보안하여 Request-Counter Dynamic Bandwidth Assignment 알고리즘을 새롭게 제안하여 성능평가 및 비교 분석을 하였다. 본 논문에서는 제안된 RC-DBA 알고리즘을 적용하여 OLT의 MAC 스케줄러를 설계하고 Corebell 사의 LDS2000 FPCA ver.1.0 보드에 구현하였다. 또한 이를 검증하기 위해서 임베디드 리눅스 기반의 검증 시스템을 개발하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.605-607
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• 2003

파장 다중 분할 Ethernet PON(Passive Optical Network)은 최근 들어 활발하게 연구되고 있는 경제적이고 효율적인 가입자망 구조이다. 가입자망의 구조가 다양하게 진화하고 광 이더넷 기술이 발전하면서 가입자에게 최적의 대역폭을 할당하기 위해 파장 다중 분할 Ethernet PON에서도 서비스별 대역폭 할당방식을 제공해야 할 필요성이 커지고 있다. 따라서, 본 논문에서는 사용자의 대역폭 요구에 따라 OLT(Optical Line Termination)가 각 ONU(Optical Network Unit)에게 서로 다른 방식으로 대역폭을 할당하는 과장 다중 분할 Ethernet PON 모델을 제시하고 구현한다. 그리고, ONU의 큐잉 지연과 단대단 Etherent 지연에 대한 분석을 통해 모델의 효율성을 제시한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.150-151
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• 2014

This paper evaluates performance of a dynamic wavelength and bandwidth allocation algorithm of TWDM PON (time and wavelength division multiplexed passive optical network) which consists of an OLT (optical line termination) and multiple ONU (optical network unit). The allocation algorithm reduces the number of upstream wavelengths to save power. Using self-similar traffic, we simulate TWDM PON systems and measure the average packet delay and the average number of upstream wavelengths.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.422-430
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• 2007

WDM-PON has been receiving much attention as a key technology to FTTH. As the cost of WDM-PON heavily depends on the number of transceivers implemented at ONU, one of its shortcomings comes from the fixed provision of wavelength resource, which is tightly coupled with costly transceivers. In this paper, we propose a cost-effective WDM-PON architecture for dynamic resource provision. The proposed architecture is based on hierarchical grouping of multiple ONUs into a logical group and hierarchical sharing the resource. For high utilization of dynamic resource, the dynamic resource allocation algorithm is also proposed. We analyze the system efficiency in term of dynamism of system resource and system cost. We also verify that the proposed resource allocation algorithm achieves a high dynamism on resource allocation, and at the same time maintains the fairness between ONUs.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.7
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• pp.261-272
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• 2003

An Ethernet PON(Passive Optical Network) is an economical and efficient access network that has received significant research attention in recent years. A MAC(Media Access Control) protocol of PON , the next generation access network, is based on TDMA(Time Division Multiple Access) basically and can classify this protocol into a fixed length slot assignment method suitable for leased line supporting QoS(Quality of Service) and a variable length slot assignment method suitable for LAN/MAN with the best effort. For analyzing the performance of these protocols, we design an Ethernet PON model using OPNET tool. To establish the maximum efficiency of a network, we verify a MAC protocol and determine the optimal number of ONUs(Optical Network Unit) that can be accepted by one OLT(Optical Line Terminal) and propose the suitable buffer size of ONU based on analyzing the end-to-end Ethernet delay, queuing delay, throughput, and utilization.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.223-232
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• 2004

In this paper we propose the hierarchical-based dynamic bandwidth allocation algorithm for multi-class services in Ethernet-PON. The proposed algorithm consists of the high level scheduler in OLT and the low level scheduler in ONU. The hierarchical architecture is able to provide scalability and resource efficiency in Ethernet-PON which has the distributed nature of the scheduling domain, with queues and the scheduler located at a large distance from each other. We also propose three dynamic bandwidth allocation algorithms for the low level scheduler: Proportional Allocation algorithm, Maximum Request First Allocation (MRFA) algorithm and High Priority First Allocation (HPFA) algorithm. We implement the Ethernet-PON standardized in the IEEE 802,3ah using OPNET. We also evaluate and analyze the performance for the proposed algorithms in terms of channel utilization, queuing delay and the amount of remainder.

• Korean Journal of Environment and Ecology
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• v.32 no.2
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• pp.231-243
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• 2018

This study was conducted to determine and compare the perceived number of users (PNU) and evaluative standards for each type of visitors to "Healing Field" of Jangseong Pyunbaek Healing Forest (JPHF). Data were collected from 158 samples selected by convenient sampling method from the users of "Healing Field" in JPHF during September 2017. Visitors to "Healing Field" consisted of 49.3% for recreation (VR), 15.3% for healing (VH), and 35.3% for both recreation and healing (VRH). Respondents' average PNU was 23.8 (median: 20.0), and the range of average PNU by visitor type was 21.1-27.8 (median: 20.0). Respondents' PNU showed low correlations with perceived crowding (PC) (r=0.23) and perceived interference of healing experience (PIHE) (r=0.20). There were no differences in the optimal number of users (ONU) of "Healing Field" among the types of visitors. The overall average ONU was 28.9(median: 25.0), and the range of average ONU by types of visitors was 25.4-31.4 (median: 25.0-27.5). The overall maximum acceptable number of users (MANU) was 38.1, and MANU for VR, VH, and VRH was 36.9, 32.0, and 38.0, respectively. Respondents' mean PC was 2.73 (SD: 3.26, 9-point scale) while mean PIHE was 3.26 (SD: 1.77, 9-point scale). The VRH group showed a higher PC and PIHE than the VR group. The group with greater PNU than ONU showed higher PC and PIHE than the other groups. Based on the results, this paper presented some managerial implications, discussed the limitations of the study, and suggested the further studies.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.12
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• pp.1-9
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• 2001

In the APON(ATM Passive Optical Network), the transmission of the upstream traffic is based on a TDMA(Time Division Multiple Access) method that an OLT(Optical Line Termination) permits ONUs(Optical Network Units) sending cells by allocating time slots. Because the upstream is not a streaming mode, the cell synchronizer has to be operated in the burst mode. Also, the cell phase monitor is required to prevent collisions between cells which are transmitted by multiple ONUs through a single optical fiber. In this paper, a TDMA burst cell synchroniser is implemented with the FPGA(Field Programmable Gate Array) being used in the APON based on G.983.1 for transmitting upstream cells. It has two main functions which are the upstream data recovery and the phase monitoring. The former is to recover the upstream data and clock in the OLT by seeking the preamble which is the overhead of the upstream time slot and by aligning the phase of the bit and cell with the system clock. The latter is to provide the information to the ONU to compensate for the equalization delay by monitoring continuously the phase difference between adjacent cells to avoid the cell collision on the upstream.

• Information and Communications Magazine
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• v.24 no.8
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• pp.53-58
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• 2007

본고에서는FTTH의 최근 기술현황과 장비에 사용되는 GE-PON ONU와 OLT 광(光)송수신모듈의 기술에 대하여 알아본다.