• Journal of information and communication convergence engineering
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• v.11 no.3
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• pp.167-172
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• 2013

Recently, mobile communication systems are suffering from exponentially increasing data traffic. As a promising solution to the increase in data traffic, a coordinated multi-point transmission and reception (CoMP) scheme has been proposed. Although a great deal of research has been done on this new technology, the performance of mobile communication systems with CoMP has not been evaluated properly in a typical indoor environment. To address this, we have developed a system-level simulator and evaluated the performance of mobile communication systems with CoMP. Unlike previous works, we have used an actual antenna pattern in our simulator and link-level results are properly taken into account through link-level abstraction. By using a system-level simulator, we have evaluated the performance of mobile communication systems with CoMP in an indoor environment and found that unlike an outdoor cellular environment, CoMP may not improve the performance of overall mobile communication systems in an indoor environment.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.2
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• pp.75-82
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• 2016

Visible light communication (VLC) using LED lamps is suitable for implementing an indoor positioning system in an indoor environment where the global positioning system (GPS) signal does not reach. In this paper, we present an indoor positioning system for mobile robots using a VLC beacon and fuzzy rules. This system consists of an autonomous mobile robot, VLC modules, and device application software. Fuzzy rules are applied to plan the global and local paths along which the mobile robot navigates indoors. The VLC transmitter modules are attached to the wall or the ceiling as beacons to transmit their own location information. The variable pulse position modulation (VPPM) algorithm is used to transmit data, which is a new modulation scheme for VLC providing a dimming control mechanism for flicker-free optical communication. The mobile robot has a receiver module to receive the location information while performing its mission in the environment where VLC transmitters are deployed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.1
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• pp.16-22
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• 2017

In this paper, we first introduce a mobile data traffic offload method called Local IP Access (LIPA) with femtocell networks. Then, we evaluate the traffic transmission time and probability of mobile data traffic that is transmitted to the core network (CN) when mobile devices transmit the mobile data traffic to indoor devices in three different scenarios, i.e., conventional systems, femtocell based systems, and femtocell and LIPA based systems. Through performance results, it is shown that the next generation mobile network with the femtocell and LIPA not only decrease the density of the mobile data traffic in CNs but also reduce the total transmission time of the mobile data traffic in indoor environments. That is, for the traffic transmission time, the conventional systems and femtocell based systems have 3 and 4 times higher than the femtocell and LIPA based systems, respectively, when the Internet delay is 10ms while 14 and 26 times higher than that, respectively, when the Internet delay is 100ms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1881-1903
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• 2015

With the fast-developing of mobile terminals, positioning techniques based on fingerprinting method draws attention from many researchers even world famous companies. To conquer some shortcomings of the existing fingerprinting systems and further improve its performance, we propose a radio map building and updating technique, which is able to customize the spatial and temporal dependency of radio maps. The method includes indoor propagation and penetration modeling and the analysis of human traffic. Based on the combination of Ray-Tracing Algorithm, Finite-Different Time-Domain and Rough Set Theory, the approach of indoor propagation modeling accurately represents the spatial dependency of the radio map. In terms of temporal dependency, we specifically study the factor of moving people in the interest area. With measurement and statistics, the factor of human traffic is introduced as the temporal updating component. We improve our existing indoor positioning system with the proposed building and updating method, and compare the localization accuracy. The results show that the enhanced system can conquer the influence caused by moving people, and maintain the confidence probability stable during week, which enhance the actual availability and robustness of fingerprinting-based indoor positioning system.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.53-63
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• 1994

In indoor radio systems, vehicular communication systems, and land mobile systems, a very important problem is that of maintaining stable communications at all locations. Therefore solutions for the indoor propagation problem are important aspects of the mobile communication system. leaky coxial cables are finding increasing use in communications systesm involving mines, tunnels, tailroads, and highways, and in new obstacle detection, or guided radar, schemes for ground transportation and perimenter surveilance. In this paper a leaky coaxial cable having periodic slots in the outer conductor is described to obtain the propagation modes in the various environments. We use aneccentric cylindrical model to develop the theory for surface-wave propagation on the cable. Numerical Results are also included for the propagation constants, field distribution and current distribution. First, we derive the electromagnetic equation for leaky coaxial cable having symmetrical periodic slots using mode-matching method and Floquet's theorem, and then find various modes, propagation constants, field distribution, etc.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.64-69
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• 2013

Recently, users who are interested in the service at indoor spaces is increasing. An indoor positioning system can minimize a range of positioning error using a variety of wireless communication infrastructure. Also, the system improves an indoor positioning accuracy by combining a mobile communication network. However, flexible positioning technologies regardless of an environment are insufficient. Therefore, this is time for a systematic study on an indoor positioning system business model. This paper classify differences between an indoor positioning system technology and outdoor positioning system technology. And we research a construction and application of the indoor positioning system that is adapted a wireless communication system (Wi-Fi, Bluetooth, RFID, UWE, Fingerprint, etc.) in domestic and foreign. We present a successful model of indoor positioning system and the development for future systems.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.586-591
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• 2015

In recent years, along with the rapid development of LED technology, indoor positioning systems based on visible light communication (VLC) have been researched. In this paper, we propose an accurate indoor positioning method using white-light LEDs and a dual image sensor. Indoor LED lights are located at the ceiling in a room and broadcast information on their positions using VLC technology. A mobile device with a dual image sensor receives LED position information by VLC and estimates its position and azimuth angle. Simulation and experimental results are given to show the performance of the proposed indoor positioning system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.5
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• pp.1317-1340
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• 2024

With the rapid development of information technology, people's demands on precise indoor positioning are increasing. Wireless sensor network, as the most commonly used indoor positioning sensor, performs a vital part for precise indoor positioning. However, in indoor positioning, obstacles and other uncontrollable factors make the localization precision not very accurate. Ultra-wide band (UWB) can achieve high precision centimeter-level positioning capability. Inertial navigation system (INS), which is a totally independent system of guidance, has high positioning accuracy. The combination of UWB and INS can not only decrease the impact of non-line-of-sight (NLOS) on localization, but also solve the accumulated error problem of inertial navigation system. In the paper, a fused UWB and INS positioning method is presented. The UWB data is firstly clustered using the Fuzzy C-means (FCM). And the Z hypothesis testing is proposed to determine whether there is a NLOS distance on a link where a beacon node is located. If there is, then the beacon node is removed, and conversely used to localize the mobile node using Least Squares localization. When the number of remaining beacon nodes is less than three, a robust extended Kalman filter with M-estimation would be utilized for localizing mobile nodes. The UWB is merged with the INS data by using the extended Kalman filter to acquire the final location estimate. Simulation and experimental results indicate that the proposed method has superior localization precision in comparison with the current algorithms.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.2
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• pp.24-33
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• 1993

In indoor radio systems, vehicular communication systems, and land mobile systems, a very important problem is that of maintaing stable communications at all locations. Therefore solutions for the indoor propagation problem are an important aspects of the mobile communication system. Leaky coaxial cables finding increasing use in communications systems involving mines, tunnels, railroads, and highways, and in new obstacle detection, or guided radar, schemes for ground transpor- tation and perimeter surveilance. In this paper a leaky coaxial cable having periodic slots in the outer conductor is described to obtain the propagation modes in the various environments. We use an essentric cylindrical model to develop the theory for surface-wave propagation on the cable. Numerical Results are also included for the propagation constants, field distribution and impedance as functions of various parameters. First, we derive the electromagnetic equation for leaky coaxial cable having periodic slots using mode-matching method and Floguet's theorem, and then find various modes, propagation constants, field distribution, etc.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2563-2568
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• 2013

Recently, various solutions to support explosively growing mobile data traffic have attracted intensive attentions. However, the range of spectrum which can be exploited for mobile communications is very limited. Small cell networks are actively investigated because they can efficiently offload mobile data traffic from macro cells without using additional spectrum. In this paper, we developed a system-level simulator considering small cell networks in the indoor environments. We compare the performance of outage probability when a load-balancing algorithm is utilized or not. We can reduce the outage probability of congested BS with the load-balancing algorithm. In addition, overall outage probability of whole wireless systems can be reduced by using the proposed load-balancing algorithm.