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Low-cost bidirectional optical amplifier using a unidirectional Er-doped fiber amplifier and a fiber Mach-Zehnder interferometer

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IEEE PHOTONICS TECHNOLOGY LETTERS 2001年第1期13卷 76-78页

作者： Lee, ST Chae, CJ Korea Telecom Access Networks Lab Yusung Gu Taejon 305348 South Korea Univ Melbourne Australian Photon Cooperat Res Ctr Dept Elect & Elect Engn Photon Res Lab Parkville Vic 3052 Australia

We propose a cost-effective bidirectional optical amplifier consisting of a single unidirectional Er-doped fiber amplifier and a fiber Mach-Zehnder interferometer (MZI), We demonstrated its feasibility by observing the optical spectra and measuring bit error rates when four optical signals were bidirectionally transmitted at 2.5 Gb/s over a 160-km single-mode fiber. A net gain of 17 dB and a power penalty of 0.5 db were obtained.

关键词： bidirectional optical amplifier bidirectional transmission Er-doped fiber amplifier Mach-Zehnder interferometer wavelength division multiplexing

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Clustering-based low-complexity resource allocation in two-tier femtocell networks with QoS provisioning

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INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS 2017年第4期30卷 1-22页

作者： Fu, Fengchao Lu, Zhaoming Xie, Yuanbao Jing, Wenpeng Wen, Xiangming Beijing Univ Posts & Telecommun Beijing Key Lab Networks Syst Architecture & Conv Beijing Peoples R China Guangzhou Res Inst China Telecom Guangzhou Guangdong Peoples R China

In this paper, we study the resource allocation problem of the uplink transmission with delay quality-of-service constraints in two-tier femtocell networks. Particularly, to provide statistical delay guarantees, the effective capacity is employed as the network performance measure instead of the conventional Shannon capacity. To make the problem computationally efficient and numerically tractable, we decompose the problem into three subproblems, namely, cluster configuration subproblem, intra-cluster subchannel allocation subproblem and inter-cluster power control subproblem. Firstly, we develop a low-complexity heuristic semi-dynamic clustering scheme, where the delay of the channel state information feedback via backhaul is considered. We model such system in the framework of networked partial observation Markov decision process and derive a strategy to reduce the search range for the best cluster configuration. Then, for a given cluster configuration, the cluster heads deal with subchannel allocation and power control within each cluster. We propose a subchannel allocation scheme with proportional fairness. Thereafter, the inter-cluster power control subproblem is modeled as a set of exact potential games, and a channel quality related pricing mechanism is presented to mitigate inter-cluster interference. The existence and uniqueness of Nash equilibriums for the proposed game are investigated, and an effective decentralized algorithm with guaranteed convergence is designed. Simulation results demonstrate that the proposed algorithms not only have much lower computational complexity but also perform close to the exhaustive search solutions and other existing schemes. Copyright (C) 2015 John Wiley & Sons, Ltd.

关键词： delay QoS effective capacity exact potential game femtocells resource allocation semi-dynamic clustering

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Aligned Reverse Frame Structure for Interference Mitigation in Dynamic TDD Systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第10期16卷 6967-6978页

作者： Lee, Kwonjong Park, Yosub Na, Minsoo Wang, Hanho Hong, Daesik Yonsei Univ Sch Elect & Elect Engn Informat Telecommun Lab Seoul 03722 South Korea SK Telecom Tech Lab 5G Corp Res & Dev Ctr Seoul 04539 South Korea Sangmyung Univ Dept Informat & Telecommun Engn Seoul 31066 South Korea

The dynamic time division duplex (TDD) system has been proposed as a way to meet today's asymmetrically and dynamically changing traffic demand. However, this approach causes cross-link interference, because neighboring base stations and user elements transmit in opposite directions. In this paper, we investigate and analyze the characteristics of cross-link interference in dynamic TDD systems. Based on this observation, we propose an aligned reverse frame structure to utilize and cancel the cross-link interference. Mathematical analysis and numerical results verify that the proposed scheme achieves performance enhancement in terms of capacity compared with conventional dynamic TDD systems.

关键词： Dynamic TDD cross-link interference HetNet asynchronized system LTE-TDD

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Zinc diffusion process investigation of InP-based test structures for high-speed avalanche photodiode fabrication

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MICROELECTRONICS JOURNAL 2000年第8期31卷 635-639页

作者： Yun, I Hyun, KS Yonsei Univ Sch Elect & Mech Engn Elect Engn Div Seoul 120749 South Korea Telecom Basic Res Lab Elect & Telecommun Res Inst Yusung Ku Taejon 305350 South Korea

The characterization of zinc diffusion processes for three different test structures has been investigated. The comparison between the different diffusion process conditions for different test structures were explored. The zinc diffusion profiles, such as the diffusion depth and the zinc dopant concentration, were examined using secondary ion mass spectrometry with varying the amount of Zn3P2 source, the ampoule volume, and the diffusion time. It is observed that the diffusion profiles are severely impacted on the process parameters, such as the amount of Zn3P2 source, the ampoule volume, and the diffusion time, as well as material parameters, such as doping concentration of the diffusion layer. These results from the Zn diffusion process can be utilized for the high-speed InP/InGaAs avalanche photodiodes fabrication. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： zinc diffusion III-V compound semiconductor avalanche photodiode semiconductor manufacturing

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telecommunication node clustering with node compatibility and network survivability requirements

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MANAGEMENT SCIENCE 2000年第3期46卷 363-374页

作者： Park, K Lee, K Park, S Lee, H Korea Telecom Telecommun Network Res Lab Yusong Gu Taejon 305348 South Korea Elect & Telecommun Res Inst Yusong Gu Taejon 305350 South Korea Korea Adv Inst Sci & Technol Dept Ind Engn Yusong Gu Taejon 305701 South Korea Hankuk Univ Foreign Studies Dept Ind Engn Kyunggi Do 449791 South Korea

We consider the node clustering problem that arises in designing a survivable two-level telecommunication network. The problem simultaneously determines an optimal partitioning of the whole network into clusters (local networks) and hub locations in each cluster. Intercluster traffic minimization is chosen as the clustering criterion to improve the service quality. Various constraints on the clustering are considered which reflect both the physical structures of local networks, such as the connectivity requirement, and the node compatibility relations such as community of interest or policy. Additional constraints may be imposed on the hub selection to ensure network survivability. We propose an integer programming formulation of the problem by decomposing the entire problem into a master problem and a number of column generation problems. The master problem is solved by column generation and the column generation problems by branch-and-cut. We develop and use strong cutting-planes for the cluster generation subproblems. Computational results using real data are reported.

关键词： network design clustering column generation branch-and-cut

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Reliability of planar InP-InGaAs avalanche photodiodes with recess etching

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IEEE PHOTONICS TECHNOLOGY LETTERS 2002年第8期14卷 1160-1162页

作者： Jung, JH Kwon, YH Hyun, KS Yun, I Yonsei Univ Dept Elect & Elect Engn Seoul 120749 South Korea Elect & Telecommun Res Inst Telecom Basic Res Lab Taejon 305600 South Korea Sejong Univ Sch Elect & Informat Engn Seoul 143747 South Korea

This letter presents the reliability of planar InP-InGaAs avalanche photodiodes (APDs) with recess etching, which is very crucial for the commercial 10-Gb/s optical receiver application. The reliability is examined by accelerated life tests by monitoring dark current and breakdown voltage. The activation energy of the degradation mechanism and device median lifetime were estimated. Based on the test results, it is concluded that the planar InP-InGaAs APDs with recess etching shows the sufficient reliability for practical 10-Gb/s optical receivers.

关键词： avalanche photodiodes recess etching reliability testing

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An efficient LKH tree balancing algorithm for group key management

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IEEE COMMUNICATIONS LETTERS 2006年第3期10卷 222-224页

作者： Kwak, Deuk-Whee Lee, SeungJoo Kim, JongWon Jung, Eunjin KT Telecommun Networks Lab Backbone Network Res Team Taejon South Korea Dept Informat & Commun Kwangju South Korea Univ Texas Dept Comp Sci Austin TX 78712 USA

The efficiency and security of secure group communication are dependent on the group key manager (GKM), which manages the group keys and membership. Although a GKM can employ any kind of group key management algorithm, we adopt the logical key hierarchy (LKH) for its efficiency and scalability. LKH is a tree-based group key management algorithm, which is more efficient when the key tree is balanced. However, only-a few papers or documents have dealt with practical tree balancing techniques so far. In this letter, we propose LKHTreeManager, an LKH key tree balancing algorithm that is efficient for a large and highly dynamic secure group.

关键词： secure group communication logical key hierarchy group key management

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ANALYSIS OF THE M(X)/G/1 QUEUE WITH N-POLICY AND MULTIPLE VACATIONS

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JOURNAL OF APPLIED PROBABILITY 1994年第2期31卷 476-496页

作者： LEE, HW LEE, SS PARK, JO CHAE, KC ETRI SWITCHING METHODS SECT TAEJON 305606 SOUTH KOREA KOREA TELECOM RES CTR TELECOMMUN NETWORK RES LAB SEOUL 137792 SOUTH KOREA KAIST DEPT MANAGEMENT SCI TAEJON 305701 SOUTH KOREA

We consider an M(X)/G/1 queueing system with N-policy and multiple vacations. As soon as the system empties, the server leaves for a vacation of random length V. When he returns, if the queue length is greater than or equal to a predetermined value N(threshold), the server immediately begins to serve the customers. If he finds less than N customers, he leaves for another vacation and so on until he finally finds at least N customers. We obtain the system size distribution and show that the system size decomposes into three random variables one of which is the system size of ordinary M(X)/G/1 queue. The interpretation of the other random variables will be provided. We also derive the queue waiting time distribution and other performance measures. Finally we derive a condition under which the optimal stationary operating policy is achieved under a linear cost structure.

关键词： SYSTEM SIZE QUEUE WAITING TIME OPTIMAL OPERATING POLICY

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Adaptive switching technique for space-time/frequency coded OFDM systems

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IEICE TRANSACTIONS ON COMMUNICATIONS 2008年第2期E91B卷 633-636页

作者： Chang, Namseok Gil, Gye-Tae Kang, Joonhyuk Yu, Gangyoul Informat & Commun Univ Sch Engn Taejon South Korea Korea Telecom Res Ctr Taejon South Korea Samsung Elect Co Ltd Telecommun R&D Ctr Syst Lab 4G Suwon South Korea

In this letter, a switched transmission technique is presented that can provide the orthogonal frequency division multiplexing (OFDM) systems with additional diversity gain. The space-time block coding (STBC) and space-frequency block coding (SFBC) are considered for the transmission of the OFDM signals. A proper coding scheme is selected based on the estimated normalized delay spread and normalized Doppler spread. The selection criterion is derived empirically. It is shown through computer simulations that the proposed switching technique can improve the bit error rate (BER) performance of an OFDM system when the corresponding wireless channel has some time variation of time selectivity as well as frequency selectivity.

关键词： OFDM space-time block code space-frequency block code

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A Weighted Scheduling Mechanism to Reduce Multicast Packet Loss in IPTV Service over EPON

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ETRI JOURNAL 2009年第4期31卷 469-471页

作者： Kwon, YoungHwan Choi, Jun Kyun Choi, Seong Gon Um, Tai-Won Jong, Sang Gug Korea Adv Inst Sci & Technol Sch Engn Taejon 305701 South Korea Chungbuk Natl Univ Sch Elect & Comp Engn Cheongju South Korea ETRI Broadcasting & Telecommun Convergence Res Lab Taejon South Korea Korea Telecom Cent R&D Lab Taejon South Korea

This letter proposes a weighted scheduling mechanism for Internet protocol television (IPTP) to improve the loss performance of multicast transmission over an Ethernet passive optical network (EPON). We propose anew weight policy from the number of multicast receivers to proportionally allocate the downstream bandwidth of LPTV traffic. The proposed mechanism is used in an optical line terminal to decrease lost packets of favorite IPTV services because the lost multicast packets are proportional to the number of receivers. The total proportion of lost multicast packets is reduced by up to 73% in an EPON.

关键词： Weighted scheduling IPTV multicast EPON packet loss

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