• ETRI Journal
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• v.39 no.3
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• pp.383-389
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• 2017

A small dual-polarized base station antenna with a simple isolation patch is presented. A high isolation is achieved when using a shorted metallic isolation patch. The experimental results indicate that the measured impedance bandwidth of the proposed antenna is 1.72 GHz to 1.89 GHz for small cell systems and that the isolation is more than 30 dB. The proposed antenna exhibits good radiation patterns with a peak gain of 8 dBi.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.475-488
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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 TCP transmission performance of a mobile user in the congested base station degrades due to increased congestion by those forwarded burst packets. In this paper, considering the general case that a mobile user moves to a congested base station, we analyze the influence of packet buffering on TCP performance according to handoff arrival distribution for Drop-tail and RED (Random Early Detection) buffer management schemes. Simulation results show that RED scheme can reduce the congestion increased by those forwarded burst packets comparing Drop-Tail, but RED scheme cannot avoid Global Synchronization due to forwarded burst packets by the old base station and new buffer management scheme to avoid it is needed in Mobile IP based networks.

• Journal of the Korea Society of Computer and Information
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• v.9 no.1
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• pp.87-93
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• 2004

In the design of mobile wireless communication network, BSC(Base Station Location), BSC(Base Station Controller) and MSC(Mobile Switching Center) are the most important parameters. Designing base station location, the cost must be minimized by combining various, complex parameters. We can solve this Problem by combining optimization algorithm, such as Simulated Annealing, Tabu Search, Genetic Algorithm, Random Walk Algorithm that have been used extensively for global optimization. This paper shows the 4 kinds of algorithm to be applied to the optimization of base station location for communication system and then compares, analyzes the results and shows optimization process of algorithm.

• 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.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.5
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• pp.103-108
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• 2016

In this paper, we propose a resource allocation scheme that guarantees transmission rate for each mobile stations by mitigating interference between a base station-to-mobile station link and a relay station-to-mobile station link. Specifically, we dynamically adjust the boundary between access zone and relay zone using signal to interference plus noise ratio. Moreover, we cluster the mobile stations under sever interference and manage the channel quality of these mobile stations by allocating additional radio resource. Our simulation results show that the proposed scheme can improve the efficiency of radio resources and ensure fairness among mobile stations.

• 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.

• ETRI Journal
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• v.45 no.5
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• pp.781-794
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• 2023

Uncrewed aerial vehicles (UAVs) have become a vital element in nonterrestrial networks, especially with respect to 5G communication systems and beyond. The use of UAVs in support of 4G/5G base station (uncrewed aerial vehicle base station [UAV-BS]) has proven to be a practical solution for extending cellular network services to areas where conventional infrastructures are unavailable. In this study, we introduce a UAV-BS system that utilizes a high-capacity wireless backhaul operating in millimeter-wave frequency bands. This system can achieve a maximum throughput of 1.3 Gbps while delivering data at a rate of 300 Mbps, even at distances of 10 km. We also present the details of our testbed implementation alongside the performance results obtained from field tests.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.499-505
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• 2003

In the design of mobile wireless communication system, base station location is one of the most important parameters. Designing base station location, the cost must be minimized by combining various, complex parameters. We can solve this problem by combining optimization algorithm, such as Simulated Annealing, Tabu Search, Genetic Algorithm, Random Walk Algorithm that have been used extensively fur global optimization. This paper shows the 4 kinds of algorithm to be applied to the optimization of base station location for communication system and then compares, analyzes the results and shows optimization process of algorithm.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.461-464
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• 2003

This paper explains the impact of frequency error on the performance of WCDMA mobile communication systems and what brings about the frequency error between the base station and the mobile station, and then presents automatic frequency error correction method in mobile receiver. On the basis of system requirement related to frequency stability, the integration test between the base station and the mobile station was accomplished. After applying automatic frequency error correction to mobile receiver, 4 Hz of frequency error at transmitting frequency was obtained. The result met frequency error requirement of 0.1ppm(about 200 Hz). Performance degradation due to frequency error was measured by means of Error Vector Magnitude (EVM)

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.288-300
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• 2006

In this paper, we consider a channel ordering problem that seeks to minimize the total interference in mobile radio networks. If a base station receives connection request from a mobile user, one of the empty channels that are fixed to the base station is assigned to the mobile user. Among several channels available, we can choose one that seems to make least interference with other channels assigned to adjacent base stations. However, a pair of channels that are not separated enough do not generate interference if both of them are not simultaneously used by mobile users. That is, interference between channels may vary depending on the channel assignment sequence for each base station and on the distribution of mobile users. To find a channel assignment sequence that seems to generate minimum interference, we develop an optimization model considering various scenarios of mobile user distribution. Simulation results show that channel assignment sequence determined by the scenario based optimization model significantly reduces the interference provided that scenarios and interference costs are properly generated.