• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4B
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• pp.323-332
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• 2006

In this paper, we consider a WDM based metro ring connecting broadband access networks by using FT-TR (Fixed Transmitter-Tunable Receiver) type access nodes and a new MAC protocol for fair transmission is proposed. The basic channel access scheme is CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) and the transferred optical slot is changed to be empty slot by SS(Source-Stripping) which drops a packet from ring-rotated slot. This empty slot can be either used to send head-of-line packet in buffer or transmitted to next access node. In former cases, there is the improvement of network throughput, but latter case leads unfairness problem of transmission. Thus the proposed MAC protocol exploits the advantages form tow cases. It gives downstream access nodes chance to use empty slots and limits the unconditional usage of empty slots at upstream access nodes with probability as called p-Persistent MAC protocol. We use a numerical analysis to evaluate bandwidth efficiency and maximum node throughput and compares simulation results in terms of node throughput, fairness factor, transfer delay depending on probability. Under two different FT-TR type architectures for metro ring network the proposed MAC protocol is evaluated and compared.

• Electronics and Telecommunications Trends
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• v.28 no.6
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• pp.63-74
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• 2013

모바일, 클라우드, 빅데이터 등 최근 IT 산업의 패러다임의 변화로 인해 매년 25% 이상 증가하는 트래픽 추세에 따라 광 가입자망의 전송 기술도 빠르게 진화하고 있다. 가입자 망의 영역 확장을 위해 분기 수, 전송 거리 확대를 위한 기술개발 및 표준화 노력 또한 끊임없이 이어지고 있다. 링크당 40Gbps 이상의 전송 속도를 요구하는 차세대 광 가입자망 기술 중의 하나인 OFDM 기반 PON은 멀티캐리어 방식으로 대용량, 장거리 전송이 가능하며, 서브캐리어 별로 서비스를 분리할 수 있고, 유연한 서브캐리어 관리를 통해 동적 대역 할당이 가능하므로 향후 유무선 융합 가입자 망에 적합한 기술로써, 기존 광 분배망의 구조 및 시설 교체없이 WDM(Wavelength Division Multiplexing)-PON(Passive Optical Network), T(Time)DM-PON 기술과 융합하여, 전송 용량을 확장할 수 있는 큰 장점을 가지고 있다. 본고에서는 OFDMA-PON 기술을 소개하고, EU, 미국 등 선진 연구 기관의 연구동향을 소개하고 향후 전망에 대해 논하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9A
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• pp.704-711
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• 2009

In this paper, we report the results of the field trial test of 1GbpsX16channels Injection locking FP-LD based WDM-PON system which could guarantee 40Mbps minimum bandwidth per subscriber, We have confirmed the system reliability, also verified that the system could reliably deliver the service such as internet, VoD through the systems during the field trial test.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.23-24
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• 2007

Ethernet passive optical network (EPON) is a technology to solve the access network bottleneck and to realize fiber to the home (FTTH). In EPON, the dynamic bandwidth allocation (DBA) is important because all users share common line in upstream. In this paper, we propose new DBA named as modified EPON dynamic scheduling algorithm (MEDSA) and simulate new DBA using Matlab.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.954-957
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• 2008

EPON(Ethernet Passive Optical Network)은 저비용의 Ethernet 장치와 광섬유 인프라를 융합한 네트워크로서 차세대 광대역 액세스 네트워크에서 'last mile'의 병목현상을 해결하기 위해 개발된 기술이다. EPON에서는 업스트림 방향으로 하나의 파장을 이용해 전송해야 하므로 TDMA(Time-Division Multiple Access) 방식을 이용하는데, 한정된 대역폭을 효율적으로 할당하기 위해서 주로 할당하는 윈도우의 크기에 비중을 두었으나, 본지에서는 할당하는 순서에 연구의 초점을 두었다. 제안 방식은 ONU(Optical Network Unit)들을 여러개의 그룹으로 나누고 요구량에 따라 최대 최소를 찾아 최대는 가장 먼저 최소는 가장 늦게 폴링하게 한다. 제안하는 방식은 기존 DBA(Dynamic Bandwidth Allocation) 알고리즘과의 성능평가 결과를 놓고 볼 때, 지연시간과 처리율면에서 높은 향상을 보인다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.59-67
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• 2006

We demonstrate bidirectional long-reach 35-channel dense wavelength division multiplexing-passive optical network(DWDM-PON) based on wavelength-locked Fabry-Perot laser diodes (F-P LDs). The mode control of F-P LD enhances output power at decreased the required injection power. We show packet-loss-free transmission in all 70 channels at 125 Mb/s per channel line rate through 70 km of single mode fiber without optical amplifier The DWDM-PON can consolidate a metro network into an access network by bypassing the central offices within its reach. The proposed DWDM-PON can accommodate about 80 subscribers with an EDFA-based broadband light source. Further expansion up to 100 subscribers is possible with a semiconductor-based BLS.

• Journal of Convergence for Information Technology
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• v.10 no.1
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• pp.22-27
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• 2020

With the deployment of 5G infrastructure, content delivery network (CDN) will be a key role to provide explosive growing services for the independent media and YouTube which contain high-speed mobile contents. Without a local cache, the mobile backhaul and fronthaul should endure huge burden of bandwidth request for users as the increase number of direct accesses from contents providers. To deal with this issue, this paper fist presents both fronthaul solutions for CDN that use dark fibers and a passive optical network (PON). On top of that, we propose the aggregated content request specialized for PON caching and evaluate and compare its performance to legacy schemes through the simulation. The proposed PON caching scheme can reduce average access time of up to 0.5 seconds, 1/n received request packets, and save 60% of backhaul bandwidth compared to the no caching scheme. This work can be a useful reference for service providers and will be extended to further improve the hit ratio of cache in the future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2492-2512
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• 2018

Multicast communication can effectively reduce network resources consumption in contrast with unicast. With the advent of SDN, current researches on multicast traffic are mainly conducted in the SDN scenario, thus to mitigate the problems of IP multicast such as the unavoidable difficulty in traffic engineering and high security risk. However, migration to SDN cannot be achieved in one step, hybrid SDN emerges as a transitional networking form for ISP network. In hybrid SDN, for acquiring similar TE and security performance as in SDN multicast, we redirect every multicast traffic to an appropriate SDN node before reaching the destinations of the multicast group, thus to build up a core-based multicast tree substantially which is first introduced in CBT. Based on the core SDN node, it is possible to realize dynamic control over the routing paths to benefit traffic engineering (TE), while multicast traffic manageability can also be obtained, e.g., access control and middlebox-supported network services. On top of that, multiple core-based multicast trees are constructed for each multicast group by fully taking advantage of the routing flexibility of SDN nodes, in order to further enhance the TE performance. The multicast routing and splitting (MRS) algorithm is proposed whereby we jointly and efficiently determine an appropriate core SDN node for each group, as well as optimizing the traffic splitting fractions for the corresponding multiple core-based trees to minimize the maximum link utilization. We conduct simulations with different SDN deployment rate in real network topologies. The results indicate that, when 40% of the SDN switches are deployed in HSDN as well as calculating 2 trees for each group, HSDN multicast adopting MRS algorithm can obtain a comparable TE performance to SDN multicast.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1207-1211
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• 2017

Long-Reach PON (LR-PON) is a broadband access network using passive optical network (PON) technology which the reach is extended to 100 km or higher. A major challenge in LR-PON is that the propagation delay between OLT and ONUs is increased by a very significant amount. To effectively and fairly distribute the upstream bandwidth dynamically in LR-PON, we propose a new periodic and multi-thread polling based dynamic bandwidth allocation (DBA) algorithm. We compare the proposed algorithm with traditional DBAs and show its advantage on average packet delay. Numerical results are analyzed under varying offered loads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1216-1221
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• 2011

We propose a multiplexed fiber Bragg grating (FBG) sensor network for vessel monitoring to measure the variation of strain and temperature by environmental perturbation based on code division multiple access (CDMA). The center wavelength of FBG was linearly changed by environmental perturbation such as strain and temperature variation so that we could be monitoring the state of sensors. A RSOA was used as optical broadband source and which was modulated by using pseudo random binary sequence (PRBS) signal. The correlation peak of reflected signal from sensor networks was measured. In this paper, we used the sliding correlation techniques for high speed response and dynamic rage of sensors.