• International Journal of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.43-48
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• 2019

We design a reconfigurable optical node for metropolitan WDM networks, and numerically study the capability of the node in the optical signal level. Unlike a long-haul WDM system, major limitations of metropolitan WDM systems are power loss, fiber dispersion and optical signal-to-noise ratio(OSNR) degradation due to EDFAs. Therefore, we include the behaviors of transmitter and receiver, and fiber, EDFAs, and optical filters(MUX/DeMux) in numerical simulations with varying parameters over wide range. From simulation results, we can identify the maximum span numbers for OC-48 and OC-192 to achieve $BER<10^{-12}$ using the node structure at various received powers and residual dispersions.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.585-592
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• 1996

This paper analyzes the impact of digitalization on networks in Seoul Metropolitan Area by considering facility investment together with operatinng costs. A stepwise evolution method toward a digitalized double-homming architecture is proposed to accommodate most efficiently with existing analog-oriented networks.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.377-382
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• 2009

In this paper, theoretical analysis for metropolitan optical networks is performed. First, analytical optical SNR is derived assuming each node consists of an EDFA, an optical filter, an optical switch, and a VOA, and then the relationship between OSNR and BER is studied. In a metropolitan optical network, an optical signal can be dropped to deliver data, and we also studied the effect of drop loss on system performance. When the drop loss is relatively small, the receiver structure of the node can be treated as a preamplifier receiver which is widely used in long-haul systems. In that case, ASE noise from EDFAs is the dominant noise source in the receiver. However, system performance is relatively insensitive to OSNR when the drop loss is significant because of the noise sources in the receiver (thermal and shot noise).

• Journal of the Korean association of regional geographers
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• v.22 no.1
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• pp.102-119
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• 2016

This paper aims at analyzing the role of Korean ethnic network in the settlement process of Korean immigrants, and elucidating their activation strategies. through the case study of Korean Immigrants in London metropolitan area. The main results of this study are as follows. Firstly, the majority of respondents use Korean ethnic networks in the initial immigration process. Secondly, respondents more frequently use Korean ethnic network in the activities such as church, shopping and education. Thirdly, considering the cognition of respondents about the necessity of Korean ethnic networks, respondents prefer supports of Koran government as activation strategies of Korean ethnic network. Finally, a model of activation strategies of Korean ethnic networks is proposed, which is a differentiated and integrated model according to the maturity stage.

• Korea Trade Review
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• v.47 no.6
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• pp.377-393
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• 2022

This study aims to identify the effect of growth of the land transportation industry on economic growth and to provide implications for Korea's metropolitan region policy. The effect of each metropolitan region on the integrated region where each metropolitan region is integrated is as follows. First, The integrated region where each metropolitan region was integrated with the Southeast region and the Daegyeong region had the greatest economic growth effect due to the growth of the land transportation industry in terms of value added, but the effect of the integrated region with the Chungcheong region was the least. In the case of capital such as roads, the integrated metropolitan regions with the Chungcheong region showed the greatest economic effect. However, the impact of the integrated regions with Jeolla region and the Seoul metropolitan region is insignificant. These results suggest that the synergy effect of metropolitan regional integration by spillover effect such as networks should be considered in the land transportation industry policy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1348-1356
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• 1991

The need for MAN(Metropolitan Area Network)has been increased by demands for high performance comuter communication. According to the definition of MAN by IEEE 802.6 MANs have diameter of about 50km, bandwidth of more than 1Mbps, and limited delay, Because optical fibers have unique characteristics that make them attractive for the implementation of MANs several fiber optic networks suitable for MAN application have been proposed. Those networks have drawbacks such as unlimited delay, many processing nodes and limited number of stations. Also IEEE 802.6 proposals and oters improved networks were proposed, but they have complicated access procedures and data buffering and difficulties in implementation. This paper descrives the design of Fiber Optic Metropolitan Area Network in Seoul(Seoul FOMAN) to overcome the drawback, Seoul FOMAN is hierarchical MAN and designed based on the topology of 43 end offices in Seoul. We propose MAN topology, proper access protocol and analyze the performance.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1997.10a
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• pp.239-242
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• 1997

Subscriber network investment cost is a main cost element among those constituting the access charges in telephone networks. The purpose of this paper to estimate the investment cost of installing a subscriber network in a typical metropolitan area and to develop a cost modeling framework. To this aim, a metropolitan area in Seoul was investigated. The main cost elements were identified and their relationships with the cable technology, geographical characteristics, and the number of subscribers were analyzed. The findings could be used to design an enhanced cost proxy models for estimating the access charges in a multi-operator environment.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.1-12
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• 2005

Ethernet is being deployed in metropolitan area networks (MANs) as a lower-cost alternative to SONET-based infrastructures. MANs are usually required to support common communication services, such as voice and frame relay, based on legacy synchronous TDM technology in addition to asynchronous packet data transport. This paper addresses the clock synchronization problem that arises when transporting synchronous services over an asynchronous packet infrastructure, such as Ethernet. A novel algorithm for clock synchronization is presented combining time-stamp methods used in the network time protocol (NTP) with signal processing techniques applied to measured packet interarrival times. The algorithm achieves the frequency accuracy, stability, low drift, holdover performance, and rapid convergence required for viable emulation of TDM circuit services over Ethernet.

• Journal of the Korea Society for Simulation
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• v.17 no.1
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• pp.17-22
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• 2008

Double-binary turbo code has been adopted as an error control code of various future communication systems including wireless metropolitan area networks(WMAN) due to its powerful error correction capability. One of the components affecting the performance of turbo code is internal interleaver. In 802.16 d/e system, an almost regular permutation(ARP) interleaver has been included as a part of specification, however it seems that the interleaver is not optimized in terms of decoding performance. In this paper, we propose three optimization methods for the interleaver based on spatial distance, spread and minimum distance between original and interleaved sequence. We find optimized interleaving parameters for each optimization method and evaluate the performances of the proposed methods by computer simulation under additive white Gaussian noise(AWGN) channel. Optimized parameters can provide up to 1.0 dB power gain over the conventional method and furthermore the obtainable gain does not require any additional hardware complexity.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.613-623
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• 2013

This study is purposed to evaluate the airborne asbestos concentrations in life environment surroundings in Seoul. In study, we investigated airborne asbestos concentrations in thirteen subway stations, four monitoring networks and each vicinity roadside, six stream surroundings, four tunnels quarterly and we also investigated relationship between the airborne asbestos concentrations and ambient temperature in monitoring networks and time-based airborne asbestos concentration variability for two typical monitoring networks, two subway stations transferred and used by lots of people through Phase Contrast Microscopy (PCM) and Transmission Electron Microscopy (TEM). The airborne asbestos concentrations by PCM for 4 objects of study were less than the detection limit (7 fiber/$mm^2$) in 111 (50%) out of 223 samples. The highest concentration was 0.0130 f/cc. But additional TEM analysis result for samples exceeding the guideline value for indoor air quality (0.01 f/cc) proposed by the Ministry of Environment (Korea), no asbestos was detected. Similarly TEM analysis result for 124 samples, no asbestos was detected. The average airborne asbestos concentrations by PCM in subway stations, monitoring networks, streams and tunnels were $0.0041{\pm}0.0027$ f/cc, $0.0015{\pm}0.0011$ f/cc, $0.0024{\pm}0.0012$ f/cc and $0.0016{\pm}0.0020$ f/cc. All objects of study were satisfied with the guideline value for indoor air quality. The relationship between the airborne asbestos concentrations and ambient temperature in monitoring networks was generally positive correlation (r = 0.660). The higher ambient temperature was and the more transient population was, the airborne asbestos concentrations by time for two subway stations were increased. While the airborne asbestos concentrations for two monitoring networks showed no variation pattern according to time.