• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.728-736
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• 2014

Due to the recent development of mobile wireless telecommunication, RRHs(Remote Radio Heads) are widely being utilized to expand the cell coverage. Wire-link, an existing connection between DU(Digital Unit) and RRH through fiber cables, is considered to have limitations in relation to cost for a wide range of applications. This paper focuses on replacing the wire-link by wireless transmission using millimeter-wave, and implementing cellular network system through RRH from a remote location. After an influence element analysis on millimeter-wave wireless link transmissions, a comparative analysis between wireless link and an existing fiber link method will be made by utilizing currently commercialized LTE(Long Term Evolution), to prove the compatibility of millimeter-wave wireless link RRH method in replacing fiber link method without a significant decline in data transmission performance.

• Archives of design research
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• v.12 no.4
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• pp.61-68
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• 1999

Most of the time, developers spend their energy to analyze the main function of the system or make source codes. As a result, they can not consider user interface on their own system and this is true in most programmer's world. But we want to consider the design concept in developing mechanism. In this case we have to upgrade the legacy system which maintaining the transmission system using the copper cables, and add the transmission system using the optical fiber cables. Therefore we design the user interface make easy for end users who are using the maintaining system on copper cables not to confuse the new system which include optical fibers. Especially, we are consider the developing model of design policy and real user to make easy to use new system. In this paper we will describe the instance to adapt the design concept on Broadband Access Network Operation Support System.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.128-134
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• 2014

Recently, design and construction of street tunnels tend to focus on cost reduction and preservation of nature. Accordingly, research is actively being carried out to quickly detect fires when they occur in tunnels, which have partially closed structures. Among such research, fire detection methods using optical fiber sensors have a wide bandwidth and fast transmission speed, while using light as a medium. Therefore, it does not receive electrical interference and there is almost no loss of information during transmission, while also having little noise as well. In relation to this, a fire monitoring system that can accurately detect the location of fires in real time using shape memory alloy and optical cables was developed in this study. In order to verify the developed method, light loss measurement test was conducted according to indoor temperature changes, while also conducting fire simulation tests by installing test beds in common underground zones with different external environments of temperature and distance. Upon carrying out experiments, the fire monitoring system developed in this study was found to be able to detect fires in long distance sections in real time.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.86-95
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• 2006

Brillouin backscatter is a type of reflection that occurs when light is shone into an optical fibre. Brillouin reflections are very sensitive to changes in the fibre arising from external effects, such as temperature, strain and pressure. We report here several case studies on the measurement of strain using Brillouin reflections. A mechanical bending test of an I beam, deployed with both fiber optic sensors and conventional strain gauge rosettes, was performed with the aim of evaluating: (1) the capability and technical limit of the DTSS technology for strain profile sensing; (2) the reliability of strain measurement using fiber optic sensor. The average values of strains obtained from both DTSS and strain gauges (corresponding to the deflection of I beam) showed a linear relationship and an excellent one-to-one match. A practical application of DTSS technology as an early warning system for land sliding or subsidence was examined through a field test at a hillside. Extremely strong, lightweight, rugged, survivable tight-buffered cables, designed for optimal strain transfer to the fibre, were used and clamped on the subsurface at a depth of about 50cm. It was proved that DTSS measurements could detect the exact position and the progress of strain changes induced by land sliding and subsidence. We also carried out the first ever distributed dynamic strain measurement (10Hz) on the Korean Train eXpress(KTX) railway track in Daejeon, Korea. The aim was to analyse the integrity of a section of track that had recently been repaired. The Sensornet DTSS was used to monitor this 85m section of track while a KTX train passed over. In the repaired section the strain increases to levels of 90 microstrain, whereas in the section of regular track the strain is in the region of 30-50 microstrain. The results were excellent since they demonstrate that the DTSS is able to measure small, dynamic changes in strain in rails during normal operating conditions. The current 10km range of the DTSS creates a potential to monitor the integrity of large lengths of track, and especially higher risk sections such as bridges, repaired track and areas at risk of subsidence.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.201-206
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• 2010

A project for construction of Korea Geodetic VLBI has officially started in Oct. 2008. The construction of all system will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room where an H-maser frequency standard is located is in a building separated from an antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with diminishing the effect of path length variations. KVG's round-trip system is designed not only available to use either metal or optical fiber cables, but also available to measure path length variations directly by using K5/VSSP32 sampler. We will present principle of round-trip system and the new type of round trip system for KVG.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.220-235
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• 2005

Internet Service Quality has been constantly the center of attention to Internet Service Providers. The KII project plan (Korea Information Infrastructure) aims to build broadband backbone networks mainly through optical fiber cables and ATM switches and to Provide the government ministries, local authorities and non-profit organizations with high-speed, highly capable broadband access to these networks at reasonable rates. The KB service model, however, is different from other Internet Service models much in the same way SP (Service Provider) and NP (Network Provider) differ from each other. In this paper, we evaluate KII service according to various customer satisfaction indicators under the methodologies and categories as put forth in both the ACSI (American Customer Satisfaction Index) and SEM (Structural Equation Model). We use a structural equation model (SEM) to demarcate the Korea Information Infrastructure Customer Satisfaction Index (KIICSI) in relation to network service quality. The results of our study suggest some strategies for the KII Project need to be modified and effectively implemented in order to increase the satisfaction level of the KII customers.