• ETRI Journal
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• v.37 no.6
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• pp.1055-1064
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• 2015

We demonstrate a next-generation high-capacity mobile fronthaul based on radio over fiber (RoF) technology, which links between a digital unit and a radio unit supporting two frequency assignments and $2{\times}2$ multiple input, multiple output antennas. To confirm the technical feasibility of a mobile fronthaul, we experimentally investigate its down- and uplink end-to-end performances including the optical and radio frequency (RF) signal path. Frequency-dependent performance deviations, error vector magnitude variations, overall system performance variations caused by optical to electrical conversion, and intermediate frequency to RF conversions are examined. Experimental verifications on multiple LTE uplink signals are performed for the first time. We also demonstrate several commercial mobile Internet services, YouTube video streaming, and file transfers using off-the-shelf mobile devices, through a mobile fronthaul based on RoF.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2340-2346
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• 2011

This paper presents a user-friendly authentication system using a flexible USIM. In the proposed method and its system, the flexible USIM utilizes personalized data such as Mobile Directory Number(MDN) and social security number as the key to user authentication. The authentication method proposed in this paper permits limited times of use and/or limited duration of use. A simple simulation model shows that the proposed algorithm works well and shows high compatibility with existing authentication methods. In addition, an alternative or more advanced authentication system can be developed with the proposed flexible USIM card. It is seen that this simple alternative method will eventually be able to make wireless communication networks more easily accessible for subscribers, irrespective of user environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.760-770
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• 2011

The existing mobility management schemes do not fully support the next generation network, which is composed of IP-based core network and various access networks. Currently, ETRI has been developing the AIMS (Access Independent Mobility Service) system which satisfies the ITU-T requirements of mobility management in the next generation network. The AIMS system is designed to provide a mobile host with a fast and reliable mobility service among heterogeneous access networks. Recently, many user devices have multiple communication interfaces, e.g., 3G and WLAN, and thus they can make two or more network connections at the same time. In this paper, we design a scheme of flow mobility, i.e., the movement of selected data flows from one access technology to another, to be applied in the AIMS system, and verify the proposed scheme through the NS-3 simulation study. From the simulation results, we can know that the proposed flow mobility scheme can utilize the network resource efficiently in the heterogeneous mobile networks.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.119-123
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• 2001

The CDMA system with time division duplex mode (CDMA/TDD system) is a highly attractive solution to support the next generation cellular mobile systems providing multimedia services where the traffic unbalance between downlink and uplink exists. In this paper, the capacity of the CDMA/TDD system is analyzed in general multicell environments. For this analysis, the interference for a time slot is analyzed, and a time slot and channel allocation problem is mathematically formulated and solved using simulated annealing technique. Computational experiments provide a promising result.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.668-675
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• 2001

Recently, the performance of the commercial PCS(Personal Communication Service) system has been improved to the uppermost limit and ultimately the next generation mobile communication is to be realized by IMT-2000 (International Mobile Communication-2000) to provide multimedia services. Therefore, the new type receiving system is researched actively and one of the most important part in a receiver is direct conversion method. The direct conversion method is suitable for low power consumption, small size, MMIC, and low price, which is to be adopted to the next generation mobile communication systems. In this case, however, several problems occur due to DC-offset. The DC-offset suppresses amplification of the required signal because of the leakage signal of frequency synthesizer in the system. In this thesis, the removing method of DC-offset was considered. There are four removing techniques of DC-offset, which are AC-coupling, large capacitor, DC-feedback loop, and DC-free coding. Among these, the AC-coupling method is the most simplest method and the DC-feedback loop method has the best performance. Then, the performance of the AC-coupling method and DC-feedback loop method are evaluated by HP's ADS simulation tool. As a result, the AC-coupling method cannot be used to the digital communication systems due to data loss. On the other hand, it was confirmed that the DC-feedback loop method is suitable for the direct conversion receiver.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.27-33
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• 2010

We have successfully demonstrated a high-pin-count and thin embedded-LSI package to realize next generation's mobile terminals. The following three design key points were applied: (i) Using Cu posts, (ii) Using the coreless structure, (iii) Using a Cu plate as the ground plane. In order to quantitatively determine the contribution of the three points, the five-stage process for reducing the number of metal layers is described by means of the electrical simulation. The point-(i) and (ii) are effective from the viewpoint of the power integrity (PI); that is, these points play important roles in reducing the number of metal layers, and especially the point-(ii) contributes at least twice as the point-(i). The point-(iii) is not effective in the PI, but has a few effects on the signal integrity (SI). For reducing the number of metal layers, we should, at first, pay attention whether the PI characteristics fulfill the specification, and then we should confirm the SI characteristics.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.36 no.3
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• pp.126-132
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• 2013

In this paper, efficiencies of core technology development projects, conducted by Ministry of Trade, Industry and Energy, are compared. In the process, DEA (Data Envelopment Analysis) is utilized as a main technique for comparing efficiencies. For DEA, input oriented BCC Model is adopted with government grant, recipient expenditure, the number of participating institutions, and project duration as input factors, and the number of patents, the number of papers, and occurred sales as output factors. As a result, next generation mobile communication project turns out to be the most efficient project of all. Therefore, next generation mobile communication project should be benchmarked for the other projects to follow. However, these results should be used only for reference data since every project has a different objective and, of course, is run under a different environment.

• Electronics and Telecommunications Trends
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• v.34 no.2
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• pp.73-82
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• 2019

Airport is shifted airport 1.0 to airport 4.0 called smart airport and services paradigm is changed into direction to point the customer targeted benefits. Smart airports make use of integrated Internet of Things components to provide added-value services. By integrating smart components, airports are being exposed to a larger attack surface and new attack vectors. Self-services such as web or mobile check-in, self check-in/tagging/back drop/boarding, etc. should be strengthened to make airport processes smarter, and technologies such as automatic immigration, smart security search, and automatic AI-based baggage search should be applied. In this paper, we describe the necessity and importance of smart airports and next generation security screening technology. Further, we describe a walk through-type smart security screening system.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.7
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• pp.656-663
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• 2007

A new dynamic balancing algorithm has been proposed to minimize the number of sensors necessary for the horizontal balancing of the mobile inverted pendulum while maintaining the same level of the commercial performance. The inverted pendulum technique is getting attention and there have been many researches on the Segway since the US inventor Dean Kamen commercialized. One of the major problems of the Segway is that many sensors are required for the control of the Segway, which results in the high price. In this research, a single gyro and a tilt sensor are fused to obtain the absolute tilt information, which is applied for the control of the mobile inverted pendulum. A dynamic balancing technique has been developed and applied for a robust control system against disturbances. The intelligent handling and stable curving of the Segway as a next generation mobile tool are verified with a human loading.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.37-40
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• 2000

This paper represented the analytic results of outage probability, considering the effect of Rician fading, Interference and Interference-reduction techniques and simulated, when cellular system was constructed by using Stratospheric platform, one of the next generation wireless communication infras which provides high speed multimedia services.