• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.279-289
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• 2021

GNSS receivers capable of tracking multiple Global Navigation Systems (GNSSs) simultaneously are widely used. In order to estimate accurate user position and velocity, it is necessary to consider the key elements that contribute to the interoperability of the different GNSSs. Typical examples are the time system and the coordinate system. Each GNSS is operated based on its own reference time system depending on when the system was developed and whether the leap seconds are applied. In addition, each GNSS is designed based on its own coordinate system based on earth model constant values. This paper addresses the interoperability issues from the viewpoint of Single Point Positioning (SPP) users utilizing multiple GNSS signals from GPS, GLONASS, BeiDou, and Galileo. Since the broadcast ephemerides of each GNSS are based on their own time and coordinate systems, the time and the coordinate systems should be unified for any user algorithm. For this purpose, this paper proposes a method of converting each GNSS coordinate system into the reference coordinate system through Helmert transformation. The error of the broadcast ephemerides was calculated with the precise ephemerides provided by the International GNSS Service (IGS). The effectiveness of the proposed multi-GNSS correction and transformation method is verified using the Multi-GNSS Experiment (MGEX) station data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.201-209
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• 2000

In this paper, the bit error rate (BER) performance of Multicode DS/CDMA-BPSK communication system is investigated in the presence of multi user interference and Nakagami fading channel environments. The DS/CDMA-BPSK communication system adopts multicode technique to enhance the data transmission rate. Using the calculated BER performance, BER figures of Multicode DS/CDMA-BPSK communication system are shown to discuss the effect of the number of multi user interference, Nakagami fading index, and data transmission rate. From the results, the transmission rate of DS/CDMA-BPSK signal improve by adopting Multicode technique. And we know that the major parameter of BER performance degradation in Multicode DS/CDMA system is the effect of multi user interference than the fading depth.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.2063-2081
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• 2018

A resource allocation algorithm is proposed in this paper to simultaneously minimize the total system power consumption and maximize the system throughput for the downlink of multi-user multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. With the Lagrange dual decomposition method, we transform the original problem to its convex dual problem and prove that the duality gap between the two problems is zero, which means the optimal solution of the original problem can be obtained by solving its dual problem. Then, we use convex optimization method to solve the dual problem and utilize bisection method to obtain the optimal dual variable. The numerical results show that the proposed algorithm is superior to traditional single-objective optimization method in both the system throughput and the system energy consumption.

• Journal of Internet Computing and Services
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• v.23 no.1
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• pp.19-29
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• 2022

Natural user interface (NUI) is used for the natural motion interface without using a specific device or tool like a mouse, keyboards, and pens. Recently, as non-contact sensor-based interaction technologies for recognizing human motion, gestures, voice, and gaze have been actively studied, an environment has been prepared that can provide more diverse contents based on various interaction methods compared to existing methods. However, as the number of sensors device is rapidly increasing, the system using a lot of sensors can suffer from a lack of computational resources. To address this problem, we proposed a real-time multi-device control system for natural interactive platform. In the proposed system, we classified two types of devices as the HC devices such as high-end commercial sensor and the LC devices such astraditional monitoring sensor with low-cost. we adopt each device manager to control efficiently. we demonstrate a proposed system works properly with user behavior such as gestures, motions, gazes, and voices.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.306-310
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• 2008

Since the preference for information recommendation service can change according to the context, we should know the user context before providing information recommendation. This paper proposes recommender system that considers multi-user preference in mobile environment and attempted to apply it to restaurant recommendation. To model the preference of individual users in mobile environment, we have used Bayesian network, and restaurant recommendation mostly should consider not an individual user but several users, so this paper has used AHP of multi-criteria decision making process to obtain the preference of several users based on one of individual users. For experiments, we conducted recommendation in 10 different situations, and finally, we confirmed that the proposed system was evaluated as a good one using a usability test of SUS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.350-364
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• 2022

Traditionally, in multi-user multi-carrier systems, the neighboring subband will be gapped by one subcarrier, which is set as guard band to reduce multiple access interference (MAI) between neighboring subbands. The empty subcarrier for guard band will degrade the spectral efficiency of the whole system. In order to enhance the spectral efficiency of multi-user filter bank multiple carrier (FBMC) systems, a new subband allocation method is introduced, in which the neighboring subband is gapped by half subcarrier instead of one subcarrier. Meanwhile, in order to implement the proposed resource allocation scheme, an optimized FBMC prototype filter is designed to decrease the inter-subband interference to the neighboring subband. The detailed simulations about the comparison between the proposed spectrum assignment and traditional FBMC are given, as well as the performance in the different interference scenarios. The simulation results show that the combination of the proposed spectrum assignment scheme and the optimized filter has better performance compared to the traditional scheme. The proposed scheme can be used in the system which serves massive users to get higher spectrum efficiency.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.461-471
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• 2010

Recently, Augmented Reality(AR) technologies have been emerged, which shows the types of digital contents integrating real and virtual worlds. To maximize the effect of AR technology, tangible user interface, which enables users to interact with the contents in the same way in which they manipulate objects in real world, is applied. In particular, we expect that the technologies are able to enhance learners' interests and degree of immersion, and produce new learning contents in order to maximize the effect of learning. In this paper, we propose a learning system for scientific experiments with multi-touch screen and tangible user interface. The system consists of an experiment table equipped with a large multi-touch screen and a realistic learning device that can detect the user's simple gestures. In real world, some scientific experiments involve high cost, long time or dangerous objects, but this system will overcome such hindrance and provide learners with a variety of experiment experience in realistic ways.

• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.35-41
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• 2003

A multi-agent technology has emerged as a new paradigm that can flexibly and promptly cope with various environmental changes and complex problems. Accordingly, many researches are being made to establish multi-agent systems in an effort to solve dynamic problems in many fields. However, most previous researches on the multi-agent frameworks aimed at, on behalf of a user, exchanging and sharing information between agents, reusing agents, and suggesting job cooperation in order to integrate and assimilate heterogeneous agents. That is to say, their frameworks mainly focused on the basic functions of general multi-agent. Therefore, they are not suitable to the development of the proper system for a specific field such ,.s a negotiation. In an effort to solve this problem, this research has tried to design a multi-agent framework-base negotiation system, so that for the sake of a user it can evaluate the negotiation messages, manage the negotiation messages, and quickly and exactly exchange messages between negotiation agents. First of all, we have made research on the basic functions hat are necessary in the development of a negotiation system, and then have analyzed the limitations of existing multi-agent frameworks when trying to apply them to a negotiation system. After these efforts, this study suggests a design of multi-agent framework to develop a negotiation system.

• Journal of Korea Entertainment Industry Association
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• v.5 no.2
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• pp.87-95
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• 2011

Recently, the issue has been tangible game environment due to the various interactive interface developments. In this paper, we propose the multi card touch based interactive arcade system by using marker recognition interface and multi-touch interaction interface. For our system, the card's location and orientation information is recognized through DI-based recognition algorithm. In addition, the user's hand gesture tracking informations are provided by the various interaction metaphors. The system provides the user with a higher engagement offers a new experience. Therefore, our system will be used in the tangible arcade game machine.

• Water Engineering Research
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• v.5 no.4
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• pp.157-176
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• 2004

This research presents a prototype development and implementation of Decision Support System (DSS) for integrated river basin water management for the flood control. The DSS consists of Relational Database Management System, Hydrologic Data Monitoring System, Spatial Analysis Module, Spatial and Temporal Analysis for Rainfall Event Tool, Flood Forecasting Module, Real-Time Operation of Multi Reservoir System, and Dialog Module with Graphical User Interface and Graphic Display Systems. The developed DSS provides an automated process of alternative evaluation and selection within a flexible, fully integrated, interactive, centered relational database management system in a user-friendly computer environment. The river basin decision-maker for the flood control should expect that she or he could manage the flood events more effectively by fully grasping the hydrologic situation throughout the basin.