• TTA Journal
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• s.62
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• pp.78-94
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• 1999

본고는 `99 하반기 시범 서비스를 눈앞에 둔 WLL 시장전망 및 표준화 동향 소개를 목적으로 하였다. 기존의 음성/동회선으로 표현되는 가입자망(Access Network)은 유선망 제공 서비스의 무선망에서의 요구, 데이터 트래픽의 음성 트래픽 추월, 그리고 음성과 데이터 통합 서비스 요구 등 다양한 사용자 요구에 대응하기 위하여 새로운 전환기를 맞이하게 되었다. 그러므로 이와 같은 가입자망 진화 추세에 부응하고 가입자망의 경쟁을 도입하기 위한 정책으로 WLL(Wireless Local Loop)이라는 기술이 대안으로 고려되어지고 있다. 이 기술은 선진국에서는 신규사업자의 우회회선으로, 개발도상국에서는 POTS용으로 필요성이 대두되고 있으나 경제성 여부는 찬반이 일고 있다. 따라서, 본 논고는 ITU/AMD 조사에 기반하여 WLL 시장전망 및 경제성에 관하여 살펴본 후, 엔지니어링 입장에서 구현 기술 및 시스템 특성에 관한 표준화 동향을 소개하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.10
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• pp.1028-1039
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• 2014

After DTV transition, frequency allocation to efficiently utilize 700 MHz band, which is remained as Digital Dividend, is in progress domestically and internationally. This paper investigates global frequency allocation of 700 MHz band and utilization of the band, and analyzes domestic wireless technology methods and requested frequency bandwidth by use. In addition, the paper suggests what needs to be considered in case of building public integrated radio network that focuses on disaster and safety network; the integrated radio network also includes railway network and e-Navigation.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.35-42
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• 2014

This paper analyzes the hazard related to train control, the functional requirements for atrain control system(TCS) and the automatic train protection(ATP) functional allocation that ensures the interoperability of a radio communications-based TCS. In addition, the interoperability can be obtained using wireless communications technology standards and standardized functional allocations of TCS performed on the wayside and onboard. Using this information, an integrated operating system for a rail network can be constructed. The functional allocations of TCS that support interoperability, require hazard analysis of TCS and definition of the system requirements. The hazard factors for a TCS are confirmed through setting the train safety space control and train speed limit excess. Furthermore, this paper determines the impact of the hazard factors on the TCS and, defines the functional requirements for the TCS subsystems and the ATP wayside and onboard functional allocations.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.550-552
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• 2005

ENUM(tElephone Number Mapping)은 차세대 인터넷 주소체계로서 기존의 인터넷 응용 서비스를 하나의 식별체계로 통합하고, 공영성 및 유일성을 보장하는 일반 공중망 전화번호 체계이다. E.164는 전화번호 체계를 인터넷 주소 체계로 변환해 주는 프로토콜로써 다양한 인터넷 관련기술을 접목시킴으로 사용자가 인터넷 전화, 팩스, 무선 인터넷 등 다양한 서비스를 사용할 수 있게 해 준다. 본 논문에서는 이런 ENUM의 다양한 응용 서비스 중 VoIP(Voice over IP)와의 연동 기술에 대해 살펴보고, 해당 기술의 부가 서비스 분야에 대해서 제안하도록 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.903-909
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• 2018

In December 2017, the world's first LTE-R for 250km/h high-speed railway was commercialized with the opening of Wonju-Gangneung high-speed railway. LTE-R has many advantages such as voice and video call, high-speed data transmission, coverage redundancy and DU redundancy. But it requires efficient use of radio resources because of a limited bandwidth of 10MHz for UL and DL, respectively. The existing unicast scheme has limited high frequency efficiency so when the number of users increases, service is limited due to the network load, which could be a problem for LTE-R in terms of stability and reliability. On the other hand, the multicast scheme via eMBMS can provide stable service even if the number of video users is high. This paper derives the number of unicast scheme users considering the LTE-R network with LAB test and calculation result, and proposes implementation plans and considerations for eMBMS commercialization on LTE-R.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2085-2094
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• 2012

In this paper, we propose a wireless access network virtualization algorithm based on a digital unit (DU)-radio unit (RU) separated network structure in a cellular network with multiple radio access technologies (RATs). The proposed wireless access network virtualization algorithm consists of a baseline access network virtualization, RAT virtualization, and access path migration algorithms. Final wireless access network virtualization is performed by sequentially performing these procedures. Through system-level simulations which assume 3GPP LTE and WiMAX systems, the performance of the proposed wireless access network virtualization is evaluated in terms of system throughput for two scenarios according to asymmetry of network traffic load. Numerical results show that our proposed wireless access network virtualization algorithm achieves significant system throughput gain even in asymmetric traffic load and user distribution situations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2405-2410
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• 2012

The 4th generation mobile communication system, LTE, does not support an additional core network to provide voice service, and it is merged into a packet network based on all IP. Although Voice service over LTE can be supported by VoIP, it will be provided by the existing 3G networks because of the discontinuity of LTE coverage. However, it is inevitable to adopt VoIP over LTE to provide high quality voice service. In this paper, we investigate the capacity of VoIP over LTE. Our results indicate that spectral efficiency can be significantly improved as channel bandwidth increases in terms of VoLTE capacity. In addition, we can achieve higher VoLTE capacity without decreasing control channel capacity.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.15-21
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• 2015

Due to the appearance of various mobile terminals like smartphone, smartpad, and smartwatch and tremendous development of WiFi technology, data utilization rate on WiFi network is significantly increasing. As a result, users are wanting to use WiFi network using only a simple identification at a visited place as if they are at their home institute. In this paper, we review the domestic status of eduroam service which supports global extension of wireless network access environment and present the future development perspective of the service in Korea. Besides, we shed light on the current status of WiFi sharing service between domestic universities and propose some methods to facilitate the join of domestic universities in eduroam service.

• Korean Security Journal
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• no.44
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• pp.169-198
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• 2015

The purpose of present study is to provide an efficient 'Disaster Emergency Communication System' (below DECS) to deal with serious disaster situations in national levels. Currently, DECSs such as the VHF, UHF, and TRS are worked to control some disaster situations in the world. However, new system such as for sending the correct image and big data is more likely to need than current the DECSs in the comtemporary societies. Several serious disaster events such as the Sam-Poong Department Store Collapse, Daegu Subway Fire, and Sewol Submerge event, nevertheless, there was not the DECS based on the field in South Korea. In July 2014, finally, South Korean government started to provide a PS-LTE system which is the new and one system with fire fighting, police, army, railway. however, there are no many academic studies for DECSs to deal with disaster situations in South Korea. The present research highlights to explore an efficient DECS of Korean styles to fix some national security and public safety. The paper provides three key findings: first is how to make a unified Korean DECS based on PS-LTE. Second is how to make sure the frequency of 700MHz levels to communicate in the shady areas. Three is what kinds of communication facility is adequate for fixing PS-LTE DECS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.298-306
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• 2014

The railway signalling system for safe train operation regulates the train speed to ensure the safety distance between consecutive trains by using wayside facilities such as track circuits and interlocking systems. In addition, this signalling system controls the trackside equipment such as a railway point along the train line. This ground-equipment-based train control systems require high CAPEX and OPEX. To deal with these problems, the train control system using the on-board controller has been recently proposed and its related technologies have been widely studied. The on-board-controller-based train control system is that the on-board controller can directly control the trackside equipment on the train line. In addition, if this system is used, the wayside facilities can be simplified, and as a result, the efficient and cost-effective train control system can be realized. To this end, we have developed the prototypes of the on-board controller and wayside object control units which control the point and crossing gate and performed the integrated operation simulation in a testbed. In this paper, before the field test of the on-board-controller-based train control system, we perform the preliminary field trial including the installation test, wireless access test, interface test with other on-board devices, and normal operation test.