• ETRI Journal
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• v.29 no.6
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• pp.707-715
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• 2007

In-phase/quadrature (I/Q) imbalances, which are generated by non-ideal transceiver components, are inevitable physical phenomena that cause the performance of practical communication systems to be degraded. In this paper, we provide a new closed-form expression for the bit error rate of hierarchical M-ary phase shift keying with I/Q phase and amplitude imbalances and analyze the effect of I/Q imbalances on BER performance over an additive white Gaussian noise channel.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1996.11a
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• pp.326-335
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• 1996

In this paper, we quantify the tradeoff between security and performance in secure data communication systems based on the queueing theory, and propose the optimization methods, such as the preprocessing, a message segmentation, compression, integration of compression and encryption and integration of user authentication and access control, which are able to reduce the delay induced by the security mechanisms and protocols. Moreover, we analyze the average delay for the secure data communication systems through the computer simulations, which are modeled by M/M/1, M/E$_2$/1 and M/H$_2$/1 queueing systems, respectively. We consider the DES, RSA digital signature and the combination of IDEA and RSA as security mechanisms for applying security services.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.711-718
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• 1999

Some of modern communication systems make use of broadband digital modulation with 5 MHz and 10 MHz. In the broadband communication systems, the nonlinear properties of power amplifier have a great effect on all systems. This paper analyzed the ACPR characteristics of WLL reverse link power amplifier with the varying AM and PM nonlinearities and suggests the required backoff from 1 dB compression point to satisfy the ACPR specifications. Also the comparions between the measured and the simulated characteristics are presrnted.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.1007-1010
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• 2005

In this paper, I propose the evolutional schemes of digital mobile communication systems based on 3GPP standards. The evolution process of those systems is going in for the purpose of support of high data rate service, radio link enhancement, If network support, and support of legacy service and realization of new enhanced service. It is essential for an efficient system configuration to analyze 3GPP network architecture based on standard and required technology for future IMS service.

• ETRI Journal
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• v.26 no.2
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• pp.149-160
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• 2004

In this paper, we present an interactive data broadcasting system compliant with the Advanced Television Systems Committee (ATSC) standards. The proposed system provides users not only with various data broadcasting services but also remote interactive services. For various data broadcasting services, we have adopted a synchronized data injector that calculates the transmission time of synchronized data accurately and multiplexes synchronized data with the data of an MPEG-2 audio-visual program according to the calculated transmission time. To support remote interactive services, we designed and implemented a return channel server connected on a bi-directional interaction channel. Test results show that the proposed system provides both an asynchronous and synchronized data broadcasting service and remote interactive service appropriately.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.919-928
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• 2012

The applications of computers and communication system and network technologies in nuclear power plants have expanded recently. This application of digital technologies to the instrumentation and control systems of nuclear power plants brings with it the cyber security concerns similar to other critical infrastructures. Cyber security risk assessments for digital instrumentation and control systems have become more crucial in the development of new systems and in the operation of existing systems. Although the instrumentation and control systems of nuclear power plants are similar to industrial control systems, the former have specifications that differ from the latter in terms of architecture and function, in order to satisfy nuclear safety requirements, which need different methods for the application of cyber security risk assessment. In this paper, the characteristics of nuclear power plant instrumentation and control systems are described, and the considerations needed when conducting cyber security risk assessments in accordance with the lifecycle process of instrumentation and control systems are discussed. For cyber security risk assessments of instrumentation and control systems, the activities and considerations necessary for assessments during the system design phase or component design and equipment supply phase are presented in the following 6 steps: 1) System Identification and Cyber Security Modeling, 2) Asset and Impact Analysis, 3) Threat Analysis, 4) Vulnerability Analysis, 5) Security Control Design, and 6) Penetration test. The results from an application of the method to a digital reactor protection system are described.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.103-111
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• 2021

In modern society, digital lifestyles are spreading to minimize contact with people and to receive contactless information. The spread trend has established an unmanned distribution system in which transactions through contactless technologies such as kiosks and chatbots are activated in face-to-face transactions with sellers and consumers. In order to streamline logistics supply worldwide, digital new deal based joint logistics hubs, unmanned courier storage platforms, and fresh logistics based last mile services have been developed into unmanned logistics systems, focusing on the intelligent logistics system automation process. Unmanned courier storage system installed in urban areas and home to daily logistics where volume is concentrated are provided with fresh logistics services through cold chain and receiving freights in contactless environments. Development is also underway to minimize safety accidents caused by courier services, such as managing various information based on the integrated control system. This paper defines the concept of integrated operation for the development of a platform for contactless unmanned courier storage device developed into next-generation logistics system. In addition, we intend to develop systems engineering-based output for deriving safety requirements and specifications by identifying risk sources that may occur in the operational scenario. Therefore, the goal is to establish a foundation for safety and reliability between interfaces of logistics systems to be installed in apartment and subway station environments that want to provide unmanned logistics services to various consumers.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.572-572
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• 2006

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.468-473
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• 1999

Neural networks for adaptive channel equalizers have been resorted to recently in digital communication systems. In this paper, the characteristics and the application areas and etc. for neural networks as adaptive channel equalizers are examined through simple examples.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1995.11a
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• pp.314-322
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• 1995

본 논문에서는 기존에 문태욱 등이 제안한 이동통신용 키분배 방식을 살펴보고, 이 세 가지 키분배 프로토콜의 문제점을 제기하며, 이를 해결할 수 있는 개선방안도 제시한다.