• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.43-48
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• 2017

Recently, demands on civilian UAV (Unmanned Aerial Vehicle) has been increasing and appropriate communication system is required for the UAV. In this paper, the performance of the UAV communication system using commercial wireless mobile network is discussed. The main service area of the wireless mobile network is ground level however the flying range of the UAV is normally in high altitude. Because of this mismatch of service area the performance of the UAV communication system is degraded in high altitude. To compensate performance degradation of the UAV communications system in high altitude, adaptive array antenna is introduced which is able to overcome altitude limitation of the UAV communication system.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.956-961
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• 2009

When construction engineers perform their work in the jobsite, they have to record as-built conditions in the project log (Data Collection). On the other hand, the engineers often have to refer to the construction documents when necessary at the job faces (Data Access). The practice of Data Collection and Data Access in the jobsite can be greatly enhanced by utilizing mobile computing with wireless communications. In this paper, two cases of mobile computing applications for construction field management are presented; Mobile Specifications System and Mobile Data Collection System. The demonstration of the process for developing two mobile applications is the primary purpose of the paper. The problems and issues involved with adopting mobile computing for construction field are also presented. The simple information framework for mobile computing has been also proposed as an outcome of the research. As for development tools, readily available relational database and wireless network have been used. The use of commercial mobile broadband was examined for data communication where local area network is not available.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.64-68
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• 2007

Commercial WiBro and 3G HSDPA services are launched last year in order to provide high speed wireless Internet access and multimedia service. Currently mobile communication service providers concentrate on the deployment of indoor mobile network since indoor traffic is remarkably increased. For fine indoor wireless communication, an installation of access point system via Public IP network which is called Femtocell is required. The development of indoor Femtocell system must be considered in the viewpoint of low hardware complexity, cost reduction, interlocking with WiBro/HSDPA network without change of network component and easy element management. In this paper, we review the implementation issue and technology of dual mode AP which provides WiBro and HSDPA signal to the user simultaneously. Especially, we describe on the HSDPA Femtocell standardization status and possible 3 types of HSDPA communication module development design. Furthermore we analyze the merits and demerits of each HSDPA Femtocell design type and propose a system which enables handover between indoor HSDPA Femtocell and outdoor commercial HSDPA mobile network.

• Journal of Biomedical Engineering Research
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• v.30 no.3
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• pp.185-190
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• 2009

Biomedical mobile devices for ubiquitous healthcare consist of biomedical sensors and communication terminal. They have two types of configuration. One is the sensor-network type device using wired or wireless communication with intelligent sensors to acquire biomedical data. The other is the sensor embedded type device, where the data can be acquired directly by itself. There are many examples of sensor network type, such as, fall detection sensor, blood glucose sensor, and ECG sensors networked with commercial PDA phone and commercial phone terminal for ubiquitous healthcare. On the other hand, sensor embedded type mounts blood glucose sensor, accelerometer, and etc. on commercial phone. However, to enable true ubiquitous healthcare, motion sensing is essential, because users go around anywhere and their signals should be measured and monitored, when they are affected by the motion. Therefore, in this paper, two biomedical mobile devices with motion monitoring function were addressed. One is sensor-network type with motion monitoring function, which uses Zigbee communication to measure the ECG, PPG and acceleration. The other is sensor-embedded type with motion monitoring function, which also can measure the data and uses the built-in cellular phone network modem for remote connection. These devices are expected to be useful for ubiquitous healthcare in coming aged society in Korea.

• Journal of Digital Contents Society
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• v.10 no.1
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• pp.87-96
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• 2009

Digital Broadcast Service is being very popular and the delivery mechanism for digital broadcast content through IP network has progressed constantly, due to the advance of video and audio compression and network technologies. From these trends, in Korea, the commercial IPTV service starts in this year after the law related to IPTV is enacted last year. Since IPTV service, which integrates broadcast and communication services, can give an infrastructure for fusion of communication and interactive multimedia data service, IPTV service is attractive. Recently, by the advent of various wireless connection technologies and the mobile devices of high capability, Mobile IPTV, which has an advantage of not only IPTV but also mobile TV, has gained much interest. In this paper, we review a necessary ingredient for Mobile IPTV in the next generation wired/wireless convergence network environment which consists of heterogeneous wireless access networks. In addition, we propose the scheme for user mobility and service session mobility management using RTSP protocol and introduce the service gateway concept to guarantee the extension of IPTV service platform.

• Journal of Korea Multimedia Society
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• v.11 no.2
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• pp.214-227
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• 2008

As cellular network technologies continue to evolve, various network standards coexist in most CDMA-based cellular networks. This means that mobile device users access mobile services over different network bandwidths according to the users' positions or the mobile devices' network access capabilities. Such differences of network bandwidths cause big differences in service response times. To address this problem, we present a framework called CANS (Context-Aware framework for mobile Navigation Services), which takes into account the user's network profile to adapt the contents for CDRG(Centrally Determined Route Guidance) navigation services for cellular phones. To the best of the authors' knowledge, CANS is the first context-aware framework to make mobile navigation services more feasible. The experimental results under commercial CDMA network show that CANS is able to provide similar service response times regardless of type of wireless network to which users connect by adapting the contents to network bandwidths.

• Journal of information and communication convergence engineering
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• v.6 no.3
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• pp.255-260
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• 2008

In the recently years, there has been a big interest in ad hoc wireless network as they have tremendous military and commercial potential. An Ad hoc wireless network is composed of mobile computing devices that use having no fixed infrastructure of a multi-hop wireless network formed. So, the fact that limited resource could support the network of robust, simple framework and energy conserving etc. In this paper, we propose a new ad hoc multicast routing protocol for based on the ontology scheme called inference network. Ontology knowledge-based is one of the structure of context-aware. And the ontology clustering adopts a tree structure to enhance resilient against mobility and routing complexity. This proposed multicast routing protocol utilizes node locality to be improve the flexible connectivity and stable mobility on local discovery routing and flooding discovery routing. Also attempts to improve route recovery efficiency and reduce data transmissions of context-awareness. We also provide simulation results to validate the model complexity. We have developed that proposed an algorithm have design multi-hierarchy layered networks to simulate a desired system.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.471-478
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• 2003

Traditionally,, analysis, simulation and measurement have all been used to evaluate the performance of network protocols and functional entities that support mobile wireless service. Simulation methods are useful for testing the complex systems which have the very complicate interactions between components. To develop a mobile call simulator which is used to examine, validate, and predict the performance of mobile wireless call procedures must have the teletraffic model, which is to describe the mobile communication environments. Mobile teletraffic model is consists of 2 sub-models, traffic source and network traffic model. In this paper, we analyzed the network traffic data which are gathered from selected Base Stations (BSs) to define the mobile teletraffic model. We defined 4 types of cell location-Residential, Commercial, Industrial, and Afforest zone. We selected some Base Stations (BSs) which are represented cell location types in Seoul city, and gathered real data from them And then, we present the call rate per hour, cail distribution pattern per day, busy hours, loose hours, the maximum number of call, and the minimum number of calls based on defined cell location types. Those parameters are very important to test the mobile communication system´s performance and reliability and are very useful for defining the mobile network traffic model or for working the existed mobile simulation programs as input parameters.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1217-1226
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• 2000

Traditionally, Mobile Teletraffic model consists of two sub-models, i.e. the network traffic model and the traffic source model. In this paper, we present the traffic source model by developing MobCall (Mobile Call Simulator) which analyses various mobile wireless environments based on regional characteristics that the base stations are located. User mobility is presented by regional average vehicle speeds and the transportation share rate. Moreover, the user mobility on subway, which is increasing in urban area, is considered in MobCall. And also, user's movements on highway are considered in MobCall. The object-oriented simulation platform, C++SIM, is used to implement MobCall. Using MobCall, the accumulated number of calls in residential and commercial regions, the handoff rate with respect to traffic sources of Seoul, the handoff rate on highway, and the handoff rate according to the call duration are presented. MobCall enables the simulation of dynamic handoff buffering and functional entity control of one base station according to the changes in user's calling pattern at the design phase. Also, when a new town is under construction by a detailed plan, MobCall is used to design the mobile network with regional characteristics and user mobility considered.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.118-126
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• 2007

An ad hoc network is a system of wireless mobile nodes that dynamically self-organize in arbitrary and temporary network topologies allowing people and devices to internetwork without any preexisting communication infrastructure. Although ad hoc network is attractive solution, there are still some major flaws that prevent commercial growth. Security is one of these main barriers; ad hoc networks are known to be particularly vulnerable to security attack. It is difficult to establish a centralized key distribution center and a trusted certification authority to provide cryptographic keys and digital certificates to nodes. To prevent attacks in ad hoc routing protocols, many algorithms have been used. In this paper, we have depicted a secure framework for multipath routing in wireless multihop network, which is comprehensive solution for secure data forwarding in wireless multihop networks. With the simulation results, the proposed scheme is compared with existing source routing scheme.