• Review of KIISC
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• v.30 no.6
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• pp.23-30
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• 2020

2G에서부터 5G 이동 통신 시대까지 허위 기지국 공격의 위협은 이어져 왔다. 허위 기지국은 정상 기지국으로 위장하여 사용자의 정보를 수집하거나 서비스 거부 공격 등을 수행하는 기지국을 말한다. 바로 이전 세대인 LTE에서는 가짜 재난 문자, 멀웨어 전파, Device Bidding Down 공격 등의 사례가 발표 또는 보고되었다. 5G에서도 LTE의 공격 사례와 같은 공격들이 발생할 수 있어 이에 대한 보안 대책이 연구될 필요가 있다. 현재 3GPP TR 33.809 문서에서 5G에서의 허위 기지국 관련 주요 이슈와 솔루션들이 논의되고 있다. 본 논문에서는 TR 33.809 문서를 바탕으로 5G의 보안을 위한 허위 기지국 대응에 대한 주요 이슈들을 중심으로 분석한다.

• The Journal of the Acoustical Society of Korea
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• v.18 no.7
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• pp.92-100
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• 1999

In the microcell mobile communication, we propose algorithms processing operational disposition to exactly analysis propagation environments from the base station to mobile stations. Algorithms are developed by the triangle analysis method can operate variable propagation paths and reflect numbers. For simulation, we suppose that mobile stations are located in the shadow region of the line of sight and the area of the non-line of sight sloping against the line of sight area at variable angles. By analyzing the results of simulation using proposed algorithms, we can be applied to the optimal position selection of the base station in the microcell mobile communication.

• 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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.440-450
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• 2006

In this paper, the frequency sharing issue between time division duplex-orthogonal frequency division multiplexing/orthogonal frequency division multiple access(TDD-OFDM/OFDMA) based systems beyond third generation(B3G) and fixed Satellite Service(FSS) earth station has been studied. The conventional advanced minimum coupling loss(A-MCL) is adopted to assess the interference from a single base station(BS) of B3G systems. The aggregated interferences from base stations and mobile stations(MS) are evaluated by applying the extended A-MCL and analysed with a cumulative density function(CDF). The minimum distances that enable a single FSS earth station to sharing the frequency with a single BS are between 4 and 53.3 km. In the case of 20 MS per sector, the BS-to-BS distance and the minimum distance between a ES and BS are 6.5 and 2.8 km, respectively.

• Journal of IKEEE
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• v.17 no.2
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• pp.163-167
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• 2013

As the mobile services have been increased, the interference of the neighboring base stations is increased and the PIMD(Passive Inter-Modulation Distortion) has been a main issue for the design of base station antenna systems. In this paper, it is proposed the PIMD test method for the active basestation antenna whose radiators are directly connected with main active parts including amplifiers, and we presents its test results using a developed active basestation antenna. From the results, the active basestation antenna has the better PIMD performance than conventional passive structure by 8.4dB. The proposed PIMD test method can be used to get the accurate PIMD test result because the test environment is very similar with real basestation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.212-219
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• 2002

In this paper, how to perform beamforming and power control for the systems with smart antennas is introduced in consideration of macro-diversity, and cell capacity of the systems is analyzed. In the result, as the number of the base stations linked to mobiles increases, capacity increases in the reverse link. On the other hand, macro diversity causes capacity loss in forward link. It is expected that the result of this work may be used in designing the next generation mobile communication systems for high quality services such as multi media data and wireless internet etc.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2340-2342
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• 2003

본 논문에서는 최적 전력 제어를 이용하여 이동국과 기지국간 최소의 소비 전력과 최대의 채널용량을 유지할 수 있는 알고리즘을 제안하고자 한다. 이동통신 시스템은 한 기지국 안에 속한 가입자 사이에 간섭이 발생할 뿐 아니라 동일한 대역을 사용하는 기지국 사이에도 간섭이 발생하게 된다. 또한 이동통신 시스템은 열악한 무선 환경을 기반으로 수시로 변화하는 가입자 요구를 수용해야 한다. 따라서 가입자 요구에 적절히 대응하는 최적 전력 제어가 이루어져야 원활한 서비스를 가입자들에게 제공할 수 있다. 즉, 동시 통화를 시도하는 여러 가입자들 간의 간섭을 받지 않고 알맞은 통화의 질을 제공받을 수 있도록 하는 전력 제어의 과정이 필수적이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.500-511
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• 2003

To prevent performance degradation of TCP due to packet losses in the smooth handoff by the route optimization extension of Mobile IP protocol, a buffering of packets at a base station is needed. A buffering of packets at a base station recovers those packets dropped during handoff by forwarding buffered packets at the old base station to the mobile user. But, when the mobile user moves to a congested base station in a new foreign subnetwork, those buffered packets forwarded by the old base station are dropped and the wireless link utilization performance degrades due to increased congestion by those forwarded packets. In this paper, considering the case that a mobile user moves to a congested base station in a new foreign subnetwork, we propose an Implicit Priority Packet Forwarding to improve TCP performance in mobile networks. In the proposed scheme, the old base station marks a buffered packet as a priority packet during handoff. In addition, RED (Random Early Detection) at the new congested base station does not include priority packets in queue size and does not drop those packets randomly based on average queue size. Simulation results show that wireless link utilization performance of mobile hosts can be improved without modification to Mobile IP protocol by applying proposed Implicit Priority Packet Forwarding.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.227.2-231
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• 1998

서비스 반경이 1[km]이내인 마이크로셀 방식은 실제 이동국이 70[%]이상 전파 음영지역에 위치하기 때문에, 셀 반경내에 있는 지형과 구조물들에 의해 매우 큰 영향을 받는다. 그러므로, 셀내 지형지물의 형상에 따라 달라지는 전파경로를 추적하여 이동통신 전파환경을 분석함으로써 최적 기지국 위치를 선정할 필요가 있다. 따라서, 본 연구에서는 이동국이 가시거리 영역의 전파 음영지역 또는 가시거리 영역과 일정 경사각으로 기울어져 있는 비가시거리 영역에 위치한 경우로 구분하고, 삼각해석법에 의해 각 영역에서의 반사횟수의 전파 경로를 각각 연산처리하는 알고리즘을 개발하여 마이크로셀 PCS 이동통신 도심 전파환경에서 시뮬레이션하고, 그 결과를 분석함으로써 마이크로셀 이동통신 최적 기지국의 위치 선정 조건을 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.125-133
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• 2007

In this paper, the frequency sharing issue between cellular time division duplex-orthogonal frequency division multiple access (TDD-OFDMA) Systems and terrestrial Fixed Systems has been studied. The conventional advanced minimum coupling loss (A-MCL) includes only the formulation to calculate the interference from one interfering system. Therefore, A-MCL must be modified to assess the aggregated interference from base stations(BS) and mobile stations(MS). By applying the modified model, the coexistence analysis are done according to the average number of MS per sector, BS-to-BS distance, and the main beam direction of the terrestrial fixed system. In the case of 20 MS per sector, the BS-to-BS distance and the minimum distance between a terrestrial fixed system and BS are 5.8 km and 2.5 km, respectively. It is about 25dB that the difference between maximum and minimum interference signal power which varies with the main beam direction of the terrestrial fixed system. Moreover, for 40% of the main beam direction of the terrestrial fixed system, interference signal power is less than the maximum permissible interference.