• Journal of Digital Convergence
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• v.10 no.9
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• pp.375-381
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• 2012

If a mobile station requests a channel allocation in its mobile networks, the switching center assigns a channel to a mobile station that belongs to each base station. There are three kinds of channel allocation schemes; a fixed channel allocation, a dynamic channel allocation and a hybrid combination of these two forms. In assigning a good frequency, it is our intention to provide quality service to our customers as well as to use resources efficiently. This paper proposes methods of assigning frequencies that minimize interference between channels and that also minimize the amount of searching time involved. In this paper, we propose an algorithm to per specific equipment, regardless of the number of channels that can be used as a general-purpose system, such as base stations, control stations, central office model is proposed, the existing operators manner similar to the fixed channel allocation based statistics and assigned when the conventional method and the improved method is proposed. Different ways and compared via simulations to verify the effectiveness of the proposed approach.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.273-279
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• 2007

As the number of mobile telephone users increases, technologies fur increasing quality of services between a mobile terminal and the base station transceiver system become more important than ever. The important criteria of quality of service includes minimum interference of base station, the success rate of network access and portability between different mobile companies. Among many factors, the successful rate of network connection between a mobile terminal and the base station is the most important. In this paper, we introduce an analysis system of mobile terminals using RS-232C communication after considering such environments. This application software simulates the communicational signals between and mobile terminals and the base station and shows the results through the graphs. Using this system, the task about testing communication performance of mobile terminals will be easy since it helps to analyze the status of communication.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.14-19
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• 2020

This paper proposes a precise drone-positioning technique using a differential global positioning system (DGPS). The proposed system consists of a reference station for error correction data production, and a mobile station (a drone), which is the target for real-time positioning. The precise coordinates of the reference station were acquired by post-processing of received satellite data together with the reference station location data provided by government infrastructure. For the system's implementation, low-cost commercial GPS receivers were used. Furthermore, a Zigbee transmitter/receiver pair was used to wirelessly send control signals and error correction data, making the whole system affordable for personal use. To validate the system, a drone-tracking experiment was conducted. The results show that the average real-time position error is less than 0.8 m.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.313-315
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• 2000

무선 컴퓨팅은 무선 통신의 발전으로 미래의 컴퓨팅 산업에서 보다 중요하게 인식될 것이고, WWW은 인터넷 응용의 개발과 인트라넷 통합을 위해 널리 사용될 매우 유망한 기술이다. 본 논문에서는 이동 컴퓨팅과 WWW을 통합한 무선 인터넷에서 이동 단말의 기지국들간에 캐시 재배치를 통하여 웹브라우징을 향상시키는 기법을 설계하고 모의실험을 통하여 제안하는 방법의 성능을 평가한다. 여기서는 이동 단말의 재배치에 필요한 시그널링 트래픽을 줄이고 광역 무선 인터넷 환경에 적합하도록 이동단말이 현재 거주하는 기지국에서의 이동 단말의 경로 예측에 기초하여 캐시 재배치를 실행한다.

• Electronics and Telecommunications Trends
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• v.11 no.3 s.41
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• pp.45-55
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• 1996

본 고에서는 이동국과 기지국간 신호방식에 적용되는 PCS 이동성 관리 프로토콜에 대하여 기술하였다. 기술의 내용으로는 Proposed W-CDMA PCS 표준화를 기본으로 하여 이동성 관리 프로토콜 기능 및 구조 그리고 기본호 절차, 메시지 포맷 및 내용으로 이루어져 있으며, 오류처리에 대해서도 기술하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.5
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• pp.451-458
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• 2016

Urban railway can be divided into ground and underground sections. In particular, the center of the metropolitan has been built mostly underground stations and tunnels. Underground section is difficult to measure the position because GPS signal is unavailable, so it is necessary to apply the indoor positioning technology. For this purpose, we analyzed the positioning technologies which are based on Wi-Fi and mobile base stations. The positing technology for smart phone which uses mobile base station' information is developed in the underground area of urban railway where the core technique is to implement base station ID into the positing technology by considering hand-off point.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.32-38
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• 1996

우리나라 전파 이용현황은 사회경제의 발전, 전파 이용기술의 진보등에 의하여 비약적으로 증가하고 있으며, 전파이용 시스템의 기능은 다양화, 고도화 되고 있다. 1995년 현재 우리나라 무선국 수는 2,021,771국이며, 특히 육상 이동국은 1,768,260국이다. 이런 상 황에서 안정되게 주파수 공급을 도모하기 위하여 이용할 수 있는 주파수 대역의 양적 확대 뿐만 아니라 주파수 유효 이용기술을 개발할 필요가 있다. 일본에서는 전파를 최대한 능률적으로 이용할 목적으로 1991년부터 전문 연구회를 조직하여 전파이용 지능화에 필요한 기술, 기술개발 과제, 제도상의 과제, 기술개발과 도입을 위한 대책에 관한 조사연구를 수년간 활발하게 수행하였다. 우리나라에서는 1992년부터 전파지원 이용기술 개발에 관한 연구를 수행하고 있으나 전파이용 지능화 기술에 관한 연구를 하지 못하였다. 외국의 전파이용 지능화 기술 개발현황을 고찰하여, 우리나라 전파 이용 지능화 기술개발의 기반을 확립할 필요가 있다. 전파이용 지능화를 위하여 중점적으로 개발하여야 할 기술로서 기지국 안테나 제어기술이 제시되어 있다. 전파이용 지능화를 위한 기지국 안테나 제어기술에 관하여, 통신시스템을 요구되는 조건, 방식 및 효과, 특징 및 특성 등을 고찰한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.6
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• pp.617-624
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• 2008

In general, RTK-GPS(Real Time Kinematic GPS) based on the single reference station is able to determinate the high accurate position of rover on the spot using error correction information of transmitted carrier phase from the base station via wireless modem. However, single reference station method has some weak points to decrease positioning accuracy because it must be obtained carrier phase from the each satellite continuously, allowed to transmit without obstacle and limited to short base line distance between base and rover station. This paper aims to attempt network based GPS carrier phase differential positioning using three multi reference stations to overcome the method of single reference station and RTK network is realized by real time monitoring program with Visual C++. The optimum error correction value of three multi reference stations by RTK networking is selected automatically to correct the position of rover station. In this paper, this algorithm is applied to determine sea water level using GPS buoy, and the accuracy results of water level change were analyzed and compared with each other using single and multi reference stations.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.135-139
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• 2012

A majority of 4G Mobile communication manufacturers have launched separated-type base stations composed of DU (digital unit) and RU (ratio unit). DUs are usually installed in the central office, while RUs with antennas are installed on the top of building or pole. Therefore, the allowable distance between DU and RU is very important for cell planning. In this paper, we analyze the allowable distance between DU and RU induced by closed-loop MIMO (mulitple input multiple output) technology in 4G FDD (frequency division duplexing) mobile communication systems. In conclusion, the distance limit between DU and RU is dependent on the frequency of the wireless communication, and the allowable distance is about 11 km when assuming the operating frequency is 2 GHz.

• Journal of KIISE:Software and Applications
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• v.26 no.9
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• pp.1073-1084
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• 1999

이동 컴퓨팅 환경에서 이동 호스트는 제한된 대역폭을 효율적으로 사용하고 이동 트랜잭션의 응답 시간을 향상시키기 위하여 캐쉬를 이용한다. 그리고 이동 호스트에 캐슁된 데이타가 이동 지구국에서 갱신되면 이동 호스트의 캐쉬 일관성을 유지하기 위하여 이동 지구국은 무효화 메시지를 방송한다. 그러나 이동 지구국에서 주기적으로 무효화 메시지를 방송하는 방법은 이동 트랜잭션의 빠른 처리를 위하여 이동 지구국으로부터 데이타를 즉시 캐슁하는 경우에 이동 트랜잭션의 직렬가능한 수행을 보장할 수 없는 경우가 발생한다. 본 연구에서는 캐슁된 데이타를 이용하여 이동 트랜잭션을 수행하는 경우에 록을 이용하여 이동 트랜잭션의 직렬가능한 수행을 보장하는 UCL-MT 방법과 록 관리 방법을 제안한다. 제안하는 UCL-MT 방법은 이동 트랜잭션을 완료하기 이전에 이동 트랜잭션이 접근한 데이타 정보를 이용하여 지구국에서 사이클을 탐지함으로써 이동 트랜잭션의 직렬가능한 수행을 보장한다. 또한 제안하는 록 관리 방법은 이용할 수 있는 대역폭의 크기에 따른 무효화 메시지 내용의 변화에 유연하게 적용될 수 있다. Abstract In mobile computing environments, a mobile host caches the data to use the narrow bandwidth efficiently and improve the response time of a mobile transaction. If the cached data in mobile host is updated at a mobile support station, the mobile support station broadcasts an invalidation message for maintaining the cache consistency of a mobile host. But when a mobile transaction accesses the data which is not in cache, if a mobile host caches the data immediately from a mobile support station for processing a mobile transaction rapidly, the method that a mobile support station broadcasts an invalidation message periodically, happens to the case that can not guarantee the serializable execution of a mobile transaction. In this paper, we propose the UCL-MT method and lock management method, as a mobile transaction is executed using cached data. Since, using the data a mobile transaction accessed, the UCL-MT method detects a cycle in a mobile support station before the completion of the mobile transaction, it guarantees the serializable execution of the mobile transaction. Also, proposing lock management method can be adapted flexibly at the change of invalidation message content, according to the available bandwidth.