• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.1
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• pp.31-37
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• 2008

In this paper, we propose an entropy-based routing protocol to effectively support both stable route construction and route lifetime in Mobile Ad-hoc Wireless Sensor Networks (MAWSN). The basic idea and feature of the proposed routing protocol are as follows. First, we construct the stable routing routes based on entropy concept using mobility of mobile nodes. Second, we consider a realistic approach, in the points of view of the MAWSN, based on mobile sensor nodes as well as fixed sensor nodes in sensor fields while the conventional research for sensor networks focus on mainly fixed sensor nodes. The performance evaluation of the proposed routing protocol is performed via simulation using OPNET(Optimized Network Engineering Tool) and analysis. The results of the performance evaluation show that the proposed routing protocol can efficiently support both the construction of stable route and route lifetime in mobile ad-hoc wireless networks.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.2 s.302
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• pp.1-10
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• 2005

This paper presents a technique for localization of a mobile robot using a single ultrasonic sensor. The mobile robot is designed for operating in a well-structured environment that can be represented by planes, edges, corners and cylinders in the view of structural features. In the case of ultrasonic sensors, these features have the range information in the form of the arc of a circle that is generally named as RCD (Region of Constant Depth). Localization is the continual provision of a knowledge of position which is deduced from it's a priori position estimation. The environment of a robot is modeled into a two dimensional grid map. we defines a physically-based sonar sensor model and employs an extended Kalman filter to estimate position of the robot. The performance and simplicity of the approach is demonstrated with the results produced by sets of experiments using a mobile robot.

• The KIPS Transactions:PartC
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• v.13C no.3 s.106
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• pp.383-388
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• 2006

Most of GIS services have been operated in single applications, and as data processing and computer and mobile technologies have developed rapidly, users request for efficient sharing between each GIS's own data and various different GIS's. However, since many GIS applications maintain their own data formats, they are incapable of processing data formats different with each other, and do not have a filtering function for mobile GIS. This paper designs an integrated preprocessor, SMP to accept features of various current formats of geographic information such as DXF(Drawing eXchange Format), DWG(DraWinG), SHP(SHaPefile), etc., and to extract core information for describing maps. The geographic information extracted by SMP(Synthetic Map Preprocessor) shows consistency in various formats by visualizing through the integrated view. By generating the extracted core data in GML, it supports rapid access to mobile devices and extensibility of file formats overcoming heterogeneity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.641-655
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• 1992

In this paper, the performance of the various multiple accesstechniques for the mobile computer network has been studied in the consideration of the characteristics. Of the mobile communication channel. In the case of the hidden node occurring, it could be seen that the performance of the code division multiple access(CDMA) technique. With simultaneous access function is better than that of the other packet access methods such as carrier sensed multiple access(CAMA). Busy tone mulitiple access(BTMA)and idle signal muitiple access(ISMA) in the view of the throuhtput and mean delay time. Also it has been shown that the performance of the CDMA method is superior to that of other packet access techniques such as multiple access(CSMA).etc when the fading effect or impulsive noise exists in the mobile channel. Especially in the case of the distributed mobile network. It has been shown that the receiver-transmitter based CDMA method using the characteristics of CDMA effectively has better throughput and less mean delay time than the commontransmitter based CDMA technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1330-1336
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• 2021

Media sharing platform such as YouTube have grown significantly in the mobile environment. This is a platform that allows users to select and view broadcast programs that are only available on TV through network-connected PCs and mobiles, and share their media content to communicate. Currently, in the era where mobile and TV broadcasts can be viewed equally, there is a time difference between the video and real-time screen transmitted to TV and mobile, different from the actual situation.We want this time difference to be realized in the same way as the real time, and there is a need for a system that can broadcast in a free environment at any time. Therefore, in this paper, a broadcasting system was designed and implemented in a mobile environment. The result of reducing the delay time difference due to the improvement of the processing method was obtained.

• Journal of Convergence for Information Technology
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• v.12 no.1
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• pp.7-14
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• 2022

Unlike general maps, the underground geospatial Information is a system made to view underground information in a 3D shape. This system is managed by a tile maps to lighten the data. But there are various underground structures in the basement, and the structures are made of 3D data, so the data size is large. Therefore, when a client mobile program requests a tile map, the service server fetches the requested tile map from the DB server and transmits ti to the client, but there is a transmission delay time problem. In this paper, we design the tile cache method to improve the request response speed for the tile map data provided to the client in the mobile underground geospatial information system. We propose a method in which a service server predicts and prefetchs the next tile map while the client is viewing tile map, and stores the prefetching data in the memory of client mobile terminal. Then, the transmission delay time problem can be solved.

• The Journal of the Korea Contents Association
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• v.22 no.5
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• pp.125-135
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• 2022

The number of domestic users of OTT services is gradually increasing, and users can consume content more freely through OTT services that can consume content in various ways unlike existing broadcasting systems. As the service utilization rate increases and consumption patterns diversify, useful and convenient UI design and usability should be considered from the user's point of view, but research on the app UI design of OTT service is still insufficient. Therefore, in this study, UI design components were compared and analyzed for the top five mobile apps in Korea's OTT platform utilization rate, and usability evaluation was conducted through surveys and in-depth interviews with 10 people in their 20s. Based on the analysis results, the direction of improvement of OTT service mobile apps in the future was presented, and the results of this study are expected to be used as basic data for improving UI design and usability of OTT mobile apps in the future.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.463-476
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• 2001

To support the mobility, mobile computers are generally equipped with lower capability than desktop PCs or workstations in terms of the size of a display, the processing power of CPU and so on. This may give a rise to limitation in mobile computers of supporting multimedia services such as World Wide Web which users would otherwise fully enjoy in desktop PCs. Approaches to reducing the limitations are distillating original multimedia data or converting them to text. Conventional proxy servers for mobile computer simply send distillated image files with the fixed size regardless of the display size of a target mobile computer. Since the cached data is kept separately for each user, they cannot be shared among users with the same display configuration and thus the proxy server could be overloaded. In this paper, we first classify various mobile computers based on their display capability in terms of display sizes and colors. We propose an enhanced proxy server called Class-based proxy that provides a mobile computer with distillated image files in proportion to its class display capacity. The proposed proxy server allows a mobile computer user to have a homepage view similar to that in PC or Workstation. Mobile computers with the same class share the cached image files, which are distillated appropriately for that class. This helps the proxy server to get higher cache hit ratio with improved efficiency and scalability.

• Journal of Internet Computing and Services
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• v.7 no.2
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• pp.81-92
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• 2006

Recently, the number of mobile phone and PDA users has been rapidly increased. Such monitoring and control applications as geographical and traffic information systems are being used widely with wireless devices. In this paper, we introduce the mobile M/VC application framework that supports the rapid constructions of mobile monitoring and control (M/VC) applications. The mobile M/VC application framework uses the mobile Observer/Observable pattern that extends the Java's Observer/Observable for automatic interactions of server and client objects in wireless environments. It also provides the Multiplexer and Demultiplexer classes that supports the assembly feature of Observer and Observable objects. To construct an application using the framework, developers just need to create necessary objects from the Observable and MobileObserver classes and inter-connect them structurally(like the plug-and-play style) through the Multiplexer and Demultiplexer objects. Then, the state change of Observable objects is notified to the connected Observer objects and user's input with Observer objects is propagated to Observable objects. These mechanism is the main process for monitoring and control applications. Therefore, the mobile M/VC application framework can improve the productivity of mobile applications and enhance the reusability of such components as Observer and Observable objects in wireless environments.

• Journal of the Korea Society of Computer and Information
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• v.14 no.11
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• pp.233-245
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• 2009

The number of subscribers and the level of service usage are moderately low though WiBro service, as a new mobile Internet service, has been provided to mobile Internet users since June 2006. Considering this situation, the study was to identify, in exploratory point of view, which critical success factors are considered by mobile Internet users as the most important one to facilitate WiBro service, and to examine the perception of critical success factors of WiBro service varies according to their demographic characteristics. The study also was to suggest a few of research propositions on the relationships between critical success factors of WiBro service and characteristics of mobile Internet users, based on various statistical analyses. To accomplish these research purposes, the study defined research variables such as demographic characteristic of mobile Internet users, types of user, and critical success factors of WiBro service based on the review of mobile Internet service related studies. And then, the study performed various statistical analyses using survey questionnaires on mobile Internet users. The analyses show that there are little differences in perception on critical success factors of WiBro service among the mobile Internet users grouped by job and residential region, and that only the relationship between occupation of mobile Internet users and critical success factors of WiBro service is moderated by the types of user. Finally, the study proposed some research propositions, based on these analysis results, that could be used in the future studies.