• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.1491-1494
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• 2005

이동 컴퓨팅 시스템에 결함 내성 기능을 제공하기 위한 많은 방법들이 제안되어졌다. 그 중 하나가 이동 에이전트를 이용하여 이동 호스트의 검사점과 메시지 로그를 분산 관리하는 방법이다. 이동 에이전트 기반의 결함 내성 서비스는 기존 기지국 기반의 서비스에 비해, 비동기적인 복구 정보의 이동 및 복구 정보의 유연한 분산 관리 등의 장점이 있으나, 이동 에이전트 자체의 이동 비용 등이 문제가 될 수 있다. 따라서 본 논문에서는 기존의 기지국 기반 복구 정보 관리 기법과 이동 에이전트 기반 복구 정보 관리 기법의 성능을 비교 평가한다. 특히, 다양한 시스템 환경에서 이동 에이전트 자체 비용이 결함 내성 서비스의 성능에 미치는 영향을 분석한다.

• Ingenium
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• v.29 no.1
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• pp.23-26
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• 2022

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1354-1362
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• 2015

Heterogeneous network technology is expected to be a core technology for 5G mobile communications. 5G mobile network would be composed of many base stations even have mobility, then the operator should connect base stations through the wireless backhaul technology. This paper presents Ultra Wide Area Wireless Backhaul Network System with massive array antenna. We conducted link budget analysis for Ultra Wide Area Wireless Backhaul Network and performance analysis of massive array antenna system through the transmission simulator based on beamforming technology. In wide area ($10km^2$) wireless backhaul system composed of massive antenna, we achieved 5 bps/Hz average spectral efficiency with 1 W transmission power per beam.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1969-1977
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• 2016

We study the connection time of vehicle-to-mobile roadside unit (V2MR) communications which can reduce the significant cost of the fixed RSU by installing a gateway of mobile network into a transit bus called the mobile RSU. In the V2MR communications, the connectivity of a commute vehicle can be improved via ad-hoc connection to a nearby mobile RSU. In this paper, we present a new analysis model to estimate the connection time between a commute vehicle and a mobile RSU, when there is a bus station in the overlapping route. Since the connection time between two vehicles is highly dynamic and unpredictable, our analysis will provide a fundamental basis of connection-time estimation of V2MR communications. Numerical results obtained from VEINS simulation show that our analysis can estimate the connection time of V2MR communications with the average error below 1.0 percent. Moreover, we show that the average connection time of V2MR communications can be extended to approximately 3.85 times of that of V2R communications.

• 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.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.45-50
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• 2006

A satellite and ground stations which are developed in a program are tested whether the interface between the satellite and ground is well established before satellite operations. These compatibility tests are performed when the satellite is connected with the ground stations after all satellite and ground stations requirements are verified. The content of the RF compatibility test is to check whether the interface requirements which are described on the Interface Control Document are well developed. During the early operation phase and tentative contingency operations of the satellite, KARI ground station uses other oversea ground stations which are located worldwide according to contract between the KARI and the contractor. Since oversea ground stations were not developed for the designated space program, system integrator should check whether the oversea ground stations are satisfied with interface requirements. Using the RF suitcase, RF interface and the content of RF communication can directly be verified during RF compatibility test on oversea ground station without KARI ground station's support. The RF compatibility test using RF suitcase was performed oversea ground stations as well as KARI ground station located on Korea. The content of RF compatibility test was standardized in order to be used at any oversea ground stations, especially fitted for the operations concept of launch and early operations phase. The test content would be RF characteristics, protocol, command loop test, telemetry loop test, and ground station interface test.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8A
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• pp.632-638
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• 2012

In a mobile communication system, we analyze the performance of uplink transmit power control mechanisms for various environments when a mobile station is during soft handoff. The quality of data frames at the receiver side can be better at a base station controller (BSC) than at its base stations (BSs) if the BSC combines selectively the data frames transmitted from the BSs. And, in order to achieve the target frame error rate (FER), the outer loop power control should be done at the BSC instead of at the BSs. It can save the energy consumption of a mobile station during the soft handoff.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.660-667
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• 2000

This paper aims at analyzing the traffic of CDMA base station. RTD(Round Trip Delay) method, used for the study, is one of the developed tool for calculating the call setup time between the BTS(Base Station TransceiverSubsystem) and mobile station.We compare the calculated call setup time in air with the field experiments.And we suggest the RTD method for dividing the traffic of the connected repeater from that of the BTS, andwe can testify it by the experiment which analyze the difference of the received time between the base stationand the repeater including the forced delay elements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.135-143
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• 2009

Integrating the Global Positioning System (GPS) and Inertial Navigation System (INS) sensor technologies using the precise GPS Carrier phase measurements is a methodology that has been widely applied in those application fields requiring accurate and reliable positioning and attitude determination; ranging from 'kinematic geodesy', to mobile mapping and imaging, to precise navigation. However, such integrated system may not fulfil the demanding performance requirements when the baseline length between reference and mobil user GPS receiver is grater than a few tens of kilometers. This is because their positioning/attitude determination is still very dependent on the errors of the GPS observations, so-called "baseline dependent errors". This limitation can be remedied by the integration of GPS and INS sensors, using multiple reference stations. Hence, in order to derive the GPS distance dependent errors, this research proposes measurement processing algorithms for multiple reference stations, such as a reference station ambiguity resolution procedure using linear combination techniques, a error estimation based on Kalman filter and a error interpolation. In addition, all the algorithms are evaluated by processing real observations and results are summarized in this paper.

• The Journal of the Acoustical Society of Korea
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• v.14 no.3
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• pp.105-113
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• 1995

For the case of using analog FM system and CDMA system together in the mobile communications, we experimentally calculate the appropriate frequency offset to improve the frequency efficiency by analizing the interference between both systems. As the results of the analysis, we obtained that frequency offset is 840KHz(Path Loss : 80dB) and 720KHz(Path Loss : 120dB) for the Path Loss when a output of CDMA Base Station is 0.91 W ERP. Therefore, to minimize the frequency offset, a output of Base Station will be controlled corresponding to Cover Area.