• Journal of KIISE:Computer Systems and Theory
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• v.34 no.1
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• pp.19-27
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• 2007

Entering the 21st century, the demand on information service via mobile devices is skyrocketing along with the popularization of computers and mobile communication devices and the rapid development of wireless communication technology. In particular, as mobile device service such as LBS and Telematics becomes highlighted, the management of mobile devices is ever more drawing attention. However, since there is no fixed standard on geographical space data, many commercialized monitoring systems do not use common geographical space data but independent geographic information. Furthermore, as it is impossible to save location information of each mobile device by integrating such information after acquiring them, it is difficult to trace management. Therefore, in this paper, geographic data with DXF. DWG and SHP format, which are commonly used files, were created and visualized by GML format, OGC standard advice. And then, TMS(Trace Monitoring System of Mobile Device) that can trace and manage information after acquiring and saving space information that show the movement of users was implemented.

• The Journal of Society for e-Business Studies
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• v.10 no.1
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• pp.121-134
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• 2005

The MANET has many problems in security despite of its many advantages such as supporting the mobility of nodes, independence of the fixed infrastructure, and quick network establishment. In particular, in establishing security, the traditional certification service has many difficult problems in applying to the MANET because of its safety, expandability, and availability. In this paper, a secure and effective distributed certification service method was proposed using the Secret Sharing scheme and the Threshold Digital Signature scheme in providing certification services in the MANET. In the proposed distributed certification service, certain nodes of relatively high safety among the mobile nodes consisting of the MANET, were set as privileged nodes, from which the process of issuing a certification started. The proposed scheme solved problem that the whole network security would be damaged by the intrusion to one node in the Centralized Architecture and the Hierarchical Architecture. And it decreased the risk of the exposure of the personal keys also in the Fully Distributed Architecture as the number of the nodes containing the partial confidential information of personal keys decreased. By the network simulation, the features and availability of the proposed scheme was evaluated and the relation between the system parameters was analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1128-1135
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• 2010

The relay based cellular system has been introduced to provide the service to satisfy the user requirement. The main reasons of using relay station are to expand a service coverage and to increase a system throughput with satisfying the service requirement level. This paper proposes a new resource allocation algorithm which supports the users' throughput fairness and service coverage in the Fixed Relay Based Cellular system with OFDMA. The performance of proposed algorithm is compared with the performances of proportional fairness(PF) algorithm. The simulation result shows that the proposed algorithm increases the number of active users in the service coverage while paying small amount of throughput loss.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.169-175
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• 2011

This paper addresses mobile IP router which communicate between nodes in Ad Hoc network as well as supply attachment to outer Internet. Ad Hoc network is one which exchanges information through cooperations among nodes without wire infrastructure, mobile IP router considers the network as one mobile unit, and supports Internet connection in mobile as well as fixed spaces. Therefore, this router can accommodate the routing of Ad Hoc network, and provide nodes in Ad Hoc network with Internet connection. So mobile IP router can provide Ad-Hoc terminals with the diverse wireless services, such as Internet connection service, routing, mobility, and so on.

• Journal of Broadcast Engineering
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• v.20 no.2
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• pp.310-339
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• 2015

In this paper, the possibility of a terrestrial fixed 4K UHD (Ultra High Definition) and mobile HD (High Definition) convergence broadcasting service through a single channel employing the FEF (Future Extension Frame) multiplexing technique in DVB (Digital Video Broadcasting)-T2 (Second Generation Terrestrial) systems is examined. The performance of such a service is also investigated. FEF multiplexing technology can be used to adjust the FFT (fast Fourier transform) and CP (cyclic prefix) size for each layer, whereas M-PLP (Multiple-Physical Layer Pipe) multiplexing technology in DVB-T2 systems cannot. The convergence broadcasting service scenario, which can provide fixed 4K UHD and mobile HD broadcasting through a single terrestrial channel, is described, and transmission requirements of the SHVC (Scalable High Efficiency Video Coding) technique are predicted. A convergence broadcasting transmission system structure is described by employing FEF and transmission technologies in DVB-T2 systems. Optimized transmission parameters are drawn to transmit 4K UHD and HD convergence broadcasting by employing a convergence broadcasting transmission structure, and the reception performance of the optimized transmission parameters under AWGN (additive white Gaussian noise), static Brazil-D, and time-varying TU (Typical Urban)-6 channels is examined using computer simulations to find the TOV (threshold of visibility). From the results, for the 6 and 8 MHz bandwidths, reliable reception of both fixed 4K UHD and mobile HD layer data can be achieved under a static fixed and very fast fading multipath channel.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.733-742
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• 2002

It has been known that the host mobility feature has very significant impact on the QoS (Quality of Service), which is usually required to a real-time multimedia application. The existing QoS support mechanisms to provide the real-time services to fixed network environment, like as RSVP, are inadequate to accommodate the mobile hosts which can frequently change their point of attachments to the fixed network. So, MRSVP (Mobile RSVP) protocol has been proposed to reduce the impacts of host mobility on QoS guarantees, in which a mobile host needs to make advance resource reservations at multiple locations it may possibly visit during the lifetime of the connection. This paper proposes a dynamic dual anchor node (DDAN) architecture which integrates the MRSVP and RSVP tunnel, in addition to the Mobile IP Regional Registration protocol. By limiting the resource reserved in local area, it preserves the lower level of resource reservation, but provides approximately the same degree of QoS support as the existing MRSVP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.261-270
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• 2007

The Delay Threshold-based Priority Queueing (DTPQ) scheme has been shown useful for scheduling both real-time (RT) and non-real-time (NRT) service traffic in mobile broadband wireless access (MBWA) systems. The overall system capacity can be maximized subject to their QoS requirement by the DTPQ scheme, which takes the urgency of the RT service into account only when their head-of-line (HOL) packet delays exceed a given delay threshold. In practice, the optimum delay threshold must be configured under the varying service scenarios and a corresponding traffic load, e.g., the number of RT and NRTusers in the system. In this paper, we propose an adaptive version of DTPQ scheme, which updates the delay threshold by taking the urgency and channel conditions of RT service users into account. By evaluating the proposed approach in an orthogonal frequency division multiple access/time division duplex (OFDM/TDD)-based broadband mobile access system, it has been found that our adaptive scheme significantly improves the system capacity as compared to the existing DTPQ scheme with a fixed delay threshold.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.49-53
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• 2007

The Next generation IP-based wireless access network proposed Mobile IP(IPv4) protocols to support mobility of node. Because Mobile IPv4 operates on th basis deigned IP in fixed network, it causes performance drop like triangle routing and handover delay. Therefore Mobile IPv4 needs scheme to complement this problems and to support service guaranteed QoS. Concerns about using MPLS networks in the next generation IP-based wireless access network are increasing. In our previous research, we proposed MCS&MUMCA, IP mobility management scheme. In this paper, we linkage the MCS&MUMCA in MPLS network and analyze its the performance.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.11-17
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• 2011

In this paper, we consider the frequency sharing feasibility of Fixed Satellite Service (FSS) with Microwave Landing System (MLS) allocated in the C-band. On the basis of characteristics of MLS and FSS suggested by ITU and safety standards of MLS by ICAO, three interference scenarios are built and numerical simulations are carried out for investigating the frequency sharing between the two systems. From the simulation results, we calculate the separation distance between MLS and FSS ground antennas, required for frequency sharing by employing standard protection limits regulating the interference to noise ratio (I/N) of the receiver.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.4
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• pp.507-515
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• 1999

통신 기술의 발달로 인하여 고정망 뿐만 아니라 이동망에서도 지능망 서비스를 제공하는 것이 중요하게 생각되고 이에 대한 많은 연구가 진행중이다. 이 논문은 이동망에서의 지능망 서비스를 효율적으로 제공하기 위한 네트워크 모델을 제안한다. 제안하는 모델에서는 MSC/SSP와 SCP/HLR 사이의 두 가지 신호 구조를 고려한다. 이러한 모델에서 지능망 서비스를 제공하는 것이 효율적임을 보이기 위하여 먼저 VLR을 사용한 지능망 서비스의 제공 방안을 제시한 후, 두 가지 모델에서의 지능망 서비스 관리에 관한 성능을 분석해 보고자 한다. 이러한 방법은 SCP에 저장된 지능망 서비스 프로파일들을 VLR로 다운로드 하여 사용자로부터의 지능망 서비스 요청시에 SCP로의 연결을 줄이는 것이다. 제시한 방법은 SCP/HLR의 부하를 감소시켜 지능망 서비스 관리면에서 IMT-2000 보다 훨씬 더 나은 성능을 보인다.Abstract As the communication technology has been developed, it is necessary to provide the IN service in the mobile network as well as the fixed network and many researches are in progress. In this paper we propose the network model to efficiently provide IN service in the mobile network. There are two signaling architectures between MSC/SSP and SCP/HLR. To show that it is efficient to provide the IN service in the proposed model, we propose IN service provision method using VLR and analyze the performance of IN service management in two architectures. These methods are to download the IN service profiles that are saved in SCP to VLR and to decrease the connection to SCP when the user requests the IN service. The proposed methods show that the load of SCP/HLR is decreased and our method is better than IMT-2000 in the aspect of IN service management.