• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.1
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• pp.42-49
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• 2000

A major technical issue related to supporting multiple classes of service in IMT-2000 is the efficient management of limited channel. The selection of channel access control technique has a significant impact on user QOS, system capacity, and is therefore an important design parameter. In this paper, to achieve the service at resonable QOS level, while utilizing channel resource effectively, some improved methods are proposed by analyzing of the recently released methods.

• Journal of Information Technology Services
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• v.12 no.3
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• pp.111-126
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• 2013

As the gaps become narrower in interconnection fee and volume rate, the MNOs began to introduce flat pricing for unlimited voice traffic competitively in Korea wireless telecommunication market : 'unlimited talks within intra-network' by the 1st operator, followed by the 3rd operator's 'unlimited talks over all networks'. As a result, subscribers tip in toward the third ranked operator and could bring a substantial change to steadfast market structure over the last decade in Korea. This paper aims to develop a simple economic model to analyze competition with flat pricing for unlimited voice traffic, and to check whether the pricing can be appropriate for the MNOs. The results show that MNOs already step in the necessary conditions to launch flat pricing for voice traffic. It also predicts that the MNOs compete with unlimited talk over all networks and set a single fee in an equilibrium. At present, the MNOs run virtually identical pricing for unlimited talk over all networks, considering their differentiation with respect to service quality, coverage and brand preference.

• Journal of the Korea Society of Computer and Information
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• v.19 no.4
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• pp.71-79
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• 2014

This paper investigates wideband dual-polarized microstrip antenna with H-shaped coupling slot. These types of antennas are used to prevent deterioration of transmission quality caused by terminal interference or multipath fading, which usually occur when many terminals are used in limited space such as hot-spot zones. The experimental results show that the impedance bandwidth ($SWR{\leq}2$) of 33.98% and the peak gain of 8.58 dBi (at 2.11 GHz) were obtained by the frequency band under 2.7 GHz. The proposed antenna is designed originally for multiple service bands with simple structure and easily be mass-produced for various commercial applications.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.275-280
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• 2009

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner Femtocells can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage. TThe frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) forapplications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. The IEEE 1588 specification provides a low-cost means for clock synchronisation over a broadband Internet connection. The Time of Packet (ToP) specified in IEEE 1588 is able to synchronize distributed clocks with an accuracy of less than one microsecond in packet networks. However, the timing synchronization over packet switched networks is a difficult task because packet networks introduce large and highly variable packet delays. This paper proposes an enhanced filter algorithm to reduce ths packet delay variation effects and maintain ToP slave clock synchronization performance. The results are presented to demonstrate in the intra-networks and show the improved performance case when the efficient ToP filter algorithm is applied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.35-57
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• 2014

Multi-criteria decision making (MCDM) algorithms play an important role in ensuring quality of service in an integrated HetNets (Heterogeneous Networks). The primary objective of this paper is to develop a multi-criteria vertical handoff decision algorithm (VHDA) for best access network selection in an integrated Wireless Local Area Network (WLAN)/Universal Mobile Telecommunications System (UMTS)/Worldwide Interoperability for Microwave Access (WiMAX) system. The proposed design consists of two parts, the first part is the evaluation of an Analytic Hierarchy Process (AHP) to decide the relative weights of handoff decision criteria and the second part computes the final score of the weights to rank network alternatives using Simple Additive Weighting (SAW). SAW ranks the network alternatives in a faster and simpler manner than AHP. The AHP-SAW mathematical model has been designed, evaluated and simulated for streaming video type of traffic. For other traffic type, such as conversational, background and interactive, only simulation results have been discussed and presented in brief. Simulation results reveal that the hierarchical modelling and computing provides optimum solution for access network selection in an integrated environment as obtained results prove to be an acceptable solution to what could be expected in real life scenarios.

• Smart Media Journal
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• v.5 no.4
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• pp.90-95
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• 2016

Recently, the quality of cultural experience can be improved through a stereoscopic information service provided by the latest mobile-based Information Telecommunication technology without the human cultural commentators, which was used in order to enhance the understanding of our cultural heritage. The purpose of this paper is to produce contents that introduce cultural heritage using the Android-based GPS and augmented reality. In this paper we propose a culture content creation method that is based on location information such as user/cultural anomalies using GPS and augmented reality based on Markerless Tracking. Marker Detection Technology and Markerless Tracking Technology are used for smart phone's rapid recognition of augmented real world and accurate recognition according to the state of the cultural heritage. Also, the Google Map of Android is used to locate the user. The strength of this method lies in that it can be used for a variety of subjects while the existing methods are limited to certain kinds of augmented reality contents.

• Journal of Broadcast Engineering
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• v.13 no.4
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• pp.501-515
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• 2008

Recently, as users' requests for high quality mobile multimedia services are rapidly increasing and additional bandwidth can be provided by adopting the hierarchical modulation transmission technology, the research on the Advanced Terrestrial DMB (AT-DMB) service using the SVC (Scalable Video Coding) scheme is being actively studied. But, in order to realize a compatible video service and to accelerate the successful standardization and commercialization, it is necessary to simplify the compatible encoder structure. In this parer, we propose a fast mode decision method by constraining the redundant coding modes in the spatial scalable encoder that keeps the current T-DMB video in base layer. The proposed method is based on the statistical characteristics of each coding mode at both base and enhancement layers, inter-layer predictions, which are derived by investigating macroblock-layer coding modes of the spatial scalable encoder's functional structure. Through computer simulations, it is shown that a simplified encoder model that reduces the heavy computational burden can be found, while keeping the objective visual quality very high.