• Journal of the Korea Society of Computer and Information
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• v.17 no.8
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• pp.41-50
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• 2012

Most of the developed countries and Korea have continued to invest much money in developing low-carbon vehicles such as electric car, methanol car and hydrogen car to replace the conventional fossil fuel vehicles. Government and local governments of each country, however, grope to construct roads for bicycle and public bicycle rental systems because bicycle is the only ultimate and feasible non-pollution transportation. Most of the current bicycle monitoring systems have achieved automation of rental process in bicycle stations, but they can not monitor bicycles in use. This paper develops GPS-CDMA modem combined terminals and implements a LBS-based bicycle monitoring system using them for public bicycle rental system. The monitoring system collects location information from GPS-CDMA modem combined terminals attached on bicycles and presents the moving tracks of bicycles on a GIS map for easy return and redistribution of bicycles. Also, the system helps to prevent from theft and vandalism of bicycles and to recommend the nearest bicycle station.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.245-257
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• 2004

Driven by the growing number of the mobile subscribers, efficient channel resource management plays a key role for provisioning multimedia service in the next generation personal communication systems. To reuse limited channel resources, diminishing the coverage areas of cells seems to be the ultimate solution. Thus, however, causes more handover events. To provide seamless connection environment for mobile terminals and applications, this article presents a novel handover scheme called the intelligent channel reservation (ICR) scheme, which exploits the location prediction technologies to accurately reserve channel resources for handover connections. Considering the fact that each mobile terminal has its individual mobility characteristic, the ICR scheme utilizes a channel reserving notification procedure (CRNP) to collect adequate parameters for predicting the future location of individual mobile terminals. These parameters will be utilized by the handover prediction function to estimate the expected handover blocking rate and the expected number of idle channels. Based on the handover prediction estimations, a cost function for calculating the damages from blocking the handover connections and idling channel resources, and a corresponding algorithm for minimizing the cost function are proposed. In addition, a guard channel decision maker (GCDM) determines the appropriate number of guard channels. The experimental results show that the ICR scheme does reduce the handover-blocking rate while keeping the number of idle channels small.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.109-114
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• 2007

A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio($E_r/E_s$) and computer simulation show the strategy outperform the conventional cooperative system.

• Journal of Broadcast Engineering
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• v.27 no.5
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• pp.762-772
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• 2022

Current disaster alert broadcasting based on mobile communication systems targets personal mobile terminals such as smartphones. However, smart cities require IoT-based services such as smart homes and offices. Therefore, when severe disasters such as earthquakes occur, smart cities must quickly perform appropriate control and respond to buildings and factories. For this, a disaster warning broadcasting technique for IoT terminals for smart cities is required. In this paper, we propose a disaster alert transmission method based on 4G/5G mobile communication for IoT terminals for smart cities. The proposed method effectively utilizes the image display method for CBS, a cell-based broadcasting service, and shows the superiority of the proposed approach through simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4122-4143
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• 2018

Because of the increment in network scale and test expenditure, simulators gradually become main tools for research on key problems of wireless networking, such as radio resource management (RRM) techniques. However, existing simulators are generally event-driven, causing unacceptably large simulation time owing to the tremendous number of events handled during a simulation. In this article, a mass-processing framework for RRM simulations is proposed for the scenarios with a massive amount of terminals of Internet of Things accessing 5G communication systems, which divides the time axis into RRM periods and each period into a number of mini-slots. Transmissions within the coverage of each access point are arranged into mini-slots based on the simulated RRM schemes, and mini-slots are almost fully occupied in dense scenarios. Because the sizes of matrices during this process are only decided by the fixed number of mini-slots in a period, the time expended for performance calculation is not affected by the number of terminals or packets. Therefore, by avoiding the event-driven process, the proposal can simulate dense scenarios in a quite limited time. By comparing with a classical event-driven simulator, NS2, we show the significant merits of our proposal on low time and memory costs.

• The Transactions of the Korea Information Processing Society
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• v.3 no.1
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• pp.191-199
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• 1996

In this paper, We assume that the closed computer system model composed of multiprocessor system is analyzed by BCMP queueing network theory with priority levels. In this system that contains terminals, processors and I/O devices, We show maximum throughput and the number of active terminals in the optimum multiprogramming levels. It is compared the performance with the other. In the result, it is obtained the optimum number of processors and active terminals. Therefore, the system model consisted of the optimum number of processor and multiprogramming level m is analyzed by the servers with a priority level. Each server is applied to the type of server which is characterized terminal, processor I/O device etc.. This model is analyzed by the server with a probability ditribution. Ideal state is proposed by the modeling for priority levels. Finally, we try to increase the performance in overload system.

• Journal of Intelligence and Information Systems
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• v.12 no.4
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• pp.91-107
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• 2006

This study introduces a software system for supporting the engineering process of container terminals. The design procedure consists of data input, capacity requirements, alternative design, alternative evaluation, and results output. In order to design and evaluate alternatives rapidly, a set of libraries for container terminals was developed. The libraries consist of Wharf, Yard, TravellingArea, and Gate. The architecture of the set of libraries was designed by an object-oriented approach. Various types of container terminal models can be constructed by using a user friendly interface, the CAD based environment, and the combinations of the elements of the libraries. Alternative models can be evaluated by a simulation.

• Information Systems Review
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• v.6 no.1
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• pp.155-166
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• 2004

As the necessity of such mobile wireless terminals as PDAs or Cellular phones drastically increases, the terminals play important role in various business areas. In this paper, a bidding system in mobile wireless environments is constructed. However, with many mobile wireless terminals modifying at the same time their (duplicated) bidding values for a given data item, data coherency for the data item becomes essential. Therefore, in this paper, a bidding system using SyncML data synchronization mechanism is proposed and constructed. SyncML is one of data synchronization mechanisms proposed by the SyncML Initiative, a consortium of mobile wireless mobile technology leaders for universal data synchronization. The bidding system is implemented and tested in LINUX, C++, and PocketPC 2000 emulator programming environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.529-540
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• 2015

The NGN should support an ubiquitous environment in which users can use multiple devices. Especially, services should be provided to users in a seamless manner across multiple devices which are dynamically found in users' vicinity. Therefore, supporting service continuity is essential in the NGN. Currently the IMS, which is a session control layer for the NGN, deals with session control procedures in detail for service continuity. However, the IMS provides limited methods how users can find target terminals for transferring the session. The target terminals tend to be located near in user's physical location, and could be shared among different users. For providing better service experience in the NGN, The NGN needs to encompass methods to enable for users to use the dynamically-found terminals in users' vicinity seamlessly. In this paper, we introduce a novel registration method based on virtual ISIM by which the target terminals in user's vicinity can register themselves to the IMS, and also we discuss how service continuity is supported.

• ETRI Journal
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• v.36 no.1
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• pp.155-158
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• 2014

This letter presents an antenna design method for an orthogonally-polarized dual antenna for use in mobile stations (MSs) and includes a verification method for improving the link-level throughput performance of an MS that uses a proposed multiple-input multiple-output antenna. The link-level throughput performance of an MS is strongly related to the correlation between antenna branches, which is determined by the cross polarization discrimination of the second branch antenna, both numerically and experimentally.