• Journal of Digital Contents Society
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• v.7 no.3
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• pp.161-168
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• 2006

Wibro(Wibro - Wireless Broadband Internet ) is a system that can accept effectively the IP-based Wireless data traffic with upward / downward asymmetric transfer characteristic by using a Wirelss broadband transfer technology in OFDMA/TDD (Orthogonal frequency Division Multiple Access/Time Division Duplex). Wibro service should support handover to maintain connection continuously in movement because the service is based on If system which is different from cellular system. Current Micro Mobility system and general Mobile If system has got a problem of delayed speed and lost packets during handover. IETF protocol has been proposed for minimizing this problem and its standardization is under process, mainly focused on Mip4, Mip6 and Mipshop WG. This article studies and analyzes an effective method of minimizing handover delay to improve the problem of WiBro system and its revitalization & outlook.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.5
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• pp.528-533
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• 2010

Currently the telephone service using Internet grows and the recent introduction of a smart phone is expected to accelerate the trend. In particular, considering the domestic situation that the wireless broadband (WiBro) system deployed over the nation, the telephone service over WiBro can be a solution toward its fast expansion. Unlike telephone service over a conventional telephone network or mobile network, however, internet telephone cannot guarantee it service quality, which can be severer in a wireless environment such as a WiBro network. Therefore, a more strict and systematic management for controlling the quality of internet telephone service over WiBro in a more efficient way. As the first step to establish the management system, this paper proposes a scheme to manage the quality of internet telephone service over WiBro and introduces a software developed for the purpose. The developed software is installed on a user terminal and facilitates efficient service quality management by measuring the quality of internet telephone service over WiBro in terms of VoIP metric, network metric, and wireless metric.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1445-1450
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• 2013

In this paper, a broadband series-fed bow-tie dipole pair (SBDP) antenna operating in the band of 1.7-2.7 GHz for mobile communication base station applications is proposed. The proposed antenna uses bow-tie-shaped dipole elements instead of straight strip dipole ones used in a conventional series-fed dipole pair (SDP) antenna. The simulation results show that the lowest operating frequency is shifted toward lower frequency as the flare angle increases, and so the lengths of the bow-tie dipole elements can be reduced in proportion to the frequency shift toward lower frequency. An SBDP antenna with a flare angle of 10 degrees is fabricated on an FR4 substrate (dielectric constant = 4.4 and thickness = 1.6 mm) and total width of the fabricated antenna is reduced by 10% compared to that of the conventional SDP antenna. The measured impedance bandwidth for voltage standing wave ratio (VSWR) < 2 is 48.8% (1.69-2.78 GHz), gain is 5.8-6.3 dBi, and the front-to-back ratio (FBR) is 14-17 dB.

• ETRI Journal
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• v.26 no.1
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• pp.48-52
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• 2004

In this letter, we consider a new packet scheduling algorithm for an orthogonal frequency division multiplexing access/frequency division duplex (OFDMA/FDD)-based system, e.g., mobile broadband wireless access or high-speed portable internet systems, in which the radio resources of both time and frequency slots are dynamically shared by all users under a proper scheduling policy. Our design objective is to increase the number of non-realtime service (e.g., WWW) users that can be supported in the system, especially when the minimum bit rate requirement is imposed on them. The simulation results show that our proposed algorithm can provide a significant improvement in the average outage probability performance for the NRT service, i.e., significantly increasing the number of NRT users without much compromising of the cell throughput.

• ETRI Journal
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• v.36 no.4
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• pp.572-580
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• 2014

Mobile operators in saturated markets increasingly favor mobile network sharing (MNS) over facility-based competition. Previous research examining MNS primarily focused on its positive effects, while the negative effects were largely overlooked. This study proposes a decision-making model using an analytic hierarchy process technique to evaluate decision-making criteria among various types of MNS policies. The decision-making model was applied to Wireless Broadband services in Korea to determine the relative importance of both positive and negative evaluation criteria and preference among multiple types of MNS policies. Positive evaluation criteria (that is, efficiency) were far greater in importance than negative evaluation criteria (that is, competition harm). The preference for adopting MNS among five alternative approaches was also revealed. The study findings offer immediate policy insights in Korea and provide a decision-making framework for policy makers in other countries to utilize.

• Journal of Communications and Networks
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• v.5 no.1
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• pp.55-64
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• 2003

Mobile IP has several inefficiencies, and was not originally designed for situations where both peers are highly mobile. We present a mobility management solution that retains compatibility with existing Internet protocols, whilst increasing the efficiency of communications between two GPRS mobile hosts. Our proposal eradicates triangle routing and minimizes handover latency. We show by numerical analysis that the routing optimization improves the performance of TCP controlled data flows, reducing buffering requirements and minimizing the recovery time after a handover occurs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.926-931
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• 2005

In this paper, the printed-sleeve monopole antenna which has the small size and the broadband characteristics, is presented and its radiation characteristics are investigated. To conform the broadband characteristics of the proposed antenna, the experimental antenna is designed, fabricated, and its radiation characteristics are measured in PCS band (1.75 GHz${\~}$1.87 GHz). It is shown that the designed antenna has the non-directional pattern in the horizontal plane, the directional pattern in the vertical plane, VSWR less than 1.5, and gain in 2.14 dBi${\~}$3.4 dBi. From these results, the proposed antenna is conformed as a broadband antenna which can be used for the mobile communication indoor antenna extensively.

• ETRI Journal
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• v.21 no.4
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• pp.23-28
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• 1999

In this paper, we analyze the performance benefits of broadband ATM networks when the call control and management flows are separated from user data flows. The virtual path tunneling concept for control and management flows are applied to the same physical ATM networks. The behaviors of channel throughput and transfer delay are analyzed. It results that the proposed virtual short-cut paths can maintain the network being stable with acceptable bandwidth. They are very useful to provide the stable control and management capabilities for Internet and mobile applications in the broadband ATM networks. In our numerical results, the effective throughputs of the proposed virtual shout-ut channel are about three times than those of end-to-end user data channels with hop distances of 10, and about two times than those with hop distance of 5 when the link blocking probability increases to 0.1. It concludes that the effective channel bandwidth are greatly reduced down while physical links are not stable and user traffic flows are occasionally overflowed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.11
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• pp.1774-1784
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• 1993

This paper presents the design, fabrication and measured results of the broadband microstrip array with a conical radiation pattern and the circular array composed of six square microstrip antenna elements. Each element antenna has the stacked structure with a parasitic element to achieve a broadband characteristic and a branch line quadrature hybrid is attached to it for the circular polarization. The design procedures and measured results of the scheme for obtaining the conical radiation pattern which is useful for the mobile communication via the satellite. Finally, the performance of the fabricated antenna is measured and compared with the theory.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.2
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• pp.11-20
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• 1997

It is a recent trend that mobile communications and PCS are intergrated into the broadband network. Broadband mutlimedia traffic will be transported over the integrated network. In this paper, we propose a connection re-routing method for fast inter-switch hadoffs and dynamic resurce reservation scheme, which is based on the proposed re-routing method, for the ATM-based personal communications network. To reduce the delay for re-routing method, for the ATM-based personal communications network. To reduce the delay for re-routing, the proposed re-routing method is to reserve VPI/VCIs for possible inter-swich handoff calls in advance. Our reservation scheme is to statistically reserve the fixed resources for possible inter-switch handoff calls, according to the QoS of the handoff calls. The simmulation reslts show that our proposed scheme satisfies the required QoS of handoff calls and keep the dropping probability of handoff calls lower than other schemes.