• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.323-332
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• 2003

We have proposed and implemented a novel cost-effective optical subcarrier mutiplexing transceiver for base station without light sources in which optical signal can be transmitted bidirectionally over a single optical fiber. Modulated optical signal is retransmitted from the base station to the central office using a ring-type base station which consists of a circulator and an Mach-Zehnder modulator, where the optical source is supplied from the central office. In order to investigate the feasibility of the proposed base station without light sources, we have measured adjacent channel power ratio and carrier to noise ratio by transmitting the IS-95 CDMA signal and 14 tones carrier signal bidirectionally through the system.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.4
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• pp.183-192
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• 2019

In fingerprint-based wireless positioning, it is necessary to establish a DB of the unmeasured area. To this end, a method of estimating the position of a base station based on a signal propagation model, and a method of estimating the information of the received signal in the unmeasured area based on the estimated position of the base station have been investigating. The purpose of this paper is to estimate the position of the base station using the measured information and to analyze the performance of the positioning. Vehicles equipped with a GPS receiver and signal measuring equipment travel the service area and acquire location-based Reference Signal Received Power (RSRP) measurements. We propose a method of estimating the position of the base station using the measured information. And the performance of the proposed method is analyzed on a simulation basis. The simulation results confirm that the accuracy of the positioning is affected by the measured area and the Dilution of Precision (DOP), the accuracy of the position information obtained by the GPS receiver, and the errors of the signal included in the RSRP. Based on the results of this paper, we can expect that the position of the base station can be estimated and the DB of the unmeasured area can be constructed based on the estimated position of the base stations and the signal propagation model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.341-349
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• 2010

In this paper, we studied on the optimization of the output power of Mobile WiMAX (IEEE 802.16) base station considering the technical condition of base station and wireless channel condition. The optimum power of base station can be estimated based on the link budget calculation of downlink and uplink in the Mobile WiMAX communication system. We investigated the optimum output power of base station in the case of 2Tx-2Rx base station with $2{\times}2$ MIMO(multiple input multiple output) technology, 2Tx-4Rx base station with improved receiver sensitivity, and 4Tx-4Rx base station with beamforming technology.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.636-641
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• 2008

In this paper, the analysis methods of available information are reviewed and it is elicited to the method of which the analysis results are applied to the Autonomous Decentralized Train Management System for the optimization at the point of the route control time and for making the efficiency shunting plan in the Autonomous Centralized Station Operation Control System. As the statistics and estimated information which are got through the utilizable information analysis are applied for the automatic route control function and the shunting plan management of the station operation control system, it is possible to use efficiently the station information by the autonomous route control system. And as the exact forecast information needed for the shunting plan establishment and the operation is provided to the operator, it is established to the efficient train operation plan.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.624-634
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• 2008

The mobile station which is about to do handover in IEEE 802.16e networks scans its neighboring base station channels to decide its next target base station. However, due to the lack of location information of its subscribers, the serving base station cannot provide any reliable candidate channel which is actually attachable by the scanning mobile stations, which makes the mobile station suffer from the long scanning time. Sometimes, long scanning time may cause the degradation of quality of service due to repeatable scan-duration or failure to start the handover procedure in time. To overcome these problems, in this paper, we propose a new protocol so called fast group scanning scheme, in which multiple mobile stations form a group to scan their neighboring base station channels simultaneously. Main contribution of this proposal is to find and decide a reliable target base station within a short scanning time. The fast group scanning scheme can be deployed to the cell network of the serving base station with a dynamic neighboring base station list management.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.282-288
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• 2014

The DGPS reference station is a national infrastructure generating GPS correctional information and transmitting the signal for Differential GPS. Currently, Korea has applied and operated the software-based DGPS reference station as a standard of the next generation proposed by the USCG in order to improve the hardware-based DGPS reference system. However, software-based DGPS reference station proposed by USCG was changed in software method, only for form. There is no advantage to changing software-based because the most critical part of architecture has not been improved. In this paper, we have designed a new software-based marine DGPS station architecture that a reference station software and a monitor station were integrated. The new marine DGPS station architecture based on software is a more simplified structure than it used to be and can be utilized in the DGPS reference station.

• Journal of Information Technology Services
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• v.7 no.2
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• pp.181-195
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• 2008

The rapid growth of mobile communication technology has provided the expansion of mobile internet services, particularly mobile realtime transaction takes much weight among mobile fields. There is an increasing demand for various mobile applications to process transactions in a mobile computing fields. Thus, During transmission in wireless networks a base station failure inevitably causes data loss of the base station buffer. It is required to compensate the loss for communication. The existing methods for a base station failure are not adequate because they all suffer from too much overhead and resolve only the link failure. In this paper, we study an efficient recovry systems for a mobile DBMS. We propose SLL (Segment Log List) that enables the mobile host to compensate data loss efficiently in the case of base station failure. In SLL, a base station deliveries an output information of data cells to a mobile host. when a base station fails, the mobile host can retransmit just next data cells. We also prove the efficiency of new method.

• Information and Communications Magazine
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• v.30 no.11
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• pp.15-23
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• 2013

최근 전 세계적으로 도로교통의 안전성 제고와 효율성 증진, 환경성 및 지속가능성 확보를 목적으로 추진되고 있는 C-ITS의 동향분석을 통해 C-ITS의 아키텍처 및 ITS Station 구성내용을 정리하였다. C-ITS 핵심요소인 ITS Station의 구성방안은 유럽의 DRIVE C2X, 미국의 Connected Vehicle Program의 Model Deployment인 Safety Pilot 프로젝트, 일본의 C-ITS 추진계획, 한국의 SMART Highway 연구개발 사례를 통해 도출하였다. 국내외 C-ITS 연구개발 사례와 국내 도로교통여건 및 현 ITS 환경을 고려한 C-ITS 아키텍처와 ITS Station 구성방안을 4가지 구성요소별로 제시하였고 차량용 ITS Station과 노변 ITS Station의 주요 고려사항과 요구기능으로 현 ITS를 적극적으로 수용하면서 C-ITS 단말의 보급률을 확대하는 방안으로 제안하였다.

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.181-184
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• 2007

In this paper, a CSSMA/AI MAC protocol in packet CDMA network is presented. The main features of this protocol are the code status sensing and reservation for reducing the packet collision. The base station broadcasts the code status on a frame-by-frame basis just before the beginning of each preamble transmission, and the mobile station transmits a preamble for reserving a code based on the received code status. After having transmitted the preamble, the mobile station listens to the downlink of the selected code and waits the base station reply. If this reply indicates that the code has been correctly acquired, it continues the packet transmission for the rest of the frame. If there are other packets waiting for transmission, the base station broadcasts the status of the code as reserved, and the mobile station transmits a packet on a reserved code for the successive frames.

• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.4
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• pp.87-92
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• 2018

One of the problems with the base station equipment is that there is a large difference between the replacement time of the hardware equipment such as the base station equipment and the radio access equipment, and the evolution period of the communication standard. Therefore, the base station communication platform must be flexible enough to handle the evolving communication standards after purchase. Recent research on reconfigurable communications platforms has focused on the efficient architecture of the communications platform to meet these requirements through software downloads while still using existing hardware. This paper presents a prototype of a base station communications platform based on the ETSI standard reconfigurable architecture. The communication platform presented in this paper is implemented as an ETSI standard reconfigurable architecture using a general-purpose DSP (Digital Signal Processor). In the implemented prototype, we verify the real-time feasibility of communication protocol updates through software reconfiguration.