• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.58
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• pp.28-37
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• 2006

전파 자원은 국가의 무형 자산으로서 자원이 한정되어 있는 반면에 이에 대한 수요가 급증하면서 전파 자원의 가치가 점점 높아지고 있다. 특히 국내의 경우 IT839 전략으로 추진 중인 WiBro(Wireless Broadband), DMB(Digital Multimedia Broadcasting), Home Network, Telematics(Telecommunication Informatics), WCDMA(Wide Code Division Multiple Access), RFID/USN(Radio Frequency Identification/Ubiquitous Sensor Network) 등 무선 주파수를 이용하는 새로운 서비스가 증가하면서 주파수 자원에 대한 중요성은 더욱 강조되고 있다. 종래의 전파 정책이 정부가 정책을 세우고 이를 관리하는 Command-and-Control 위주였다면, 향후의 전파 정책은 OpYN1020en Spectrum 정책으로 전환될 것으로 전망된다. 본 고에서는 전파 자원의 효율적인 이용을 도모하는 일반적인 CR(Cognitive Radio) 기술에 대하여 언급하고, 이를 이동성이 없는 고정 환경에 적용하기 위한 IEEE 802.22 WRAN 시스템의 물리계층 전송 규격 사양, 프레임구조 및 현재 논의되고 있는 기술에 대하여 논의한다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.831-836
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• 2007

Overloaded Vehicles are one of biggest of hazard in durability decrease of roads and bridges. Thus, regulation was put in force about overloaded vehicles to reserve this problem. However, existing system had many problems. For these reasons, this paper presents solutions of U-intelligent overload vehicles regulation system based on manless and wireless for fixing of problems of existing system and construction of ITS. With this in mind, we studied about composition method of system. applications of USN, design of system controller, WCDMA/HSDPA, etc in this paper.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.208-210
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• 2004

무선과 이동성을 지원하기 위해서는 서로 다른 기술을 사용하고 있는 다양한 액세스 네트워크들간의 통신이 단절 없이 이루어져야 한다. 특히 멀티미디어 서비스와 실시간 서비스는 통신 단절, 패킷 지연과 밀접한 관련을 맺고 있다. 현재 iMT-2000 서비스의 개발로 인하여 WCDMA와 CDMA의 서비스가 동시에 이루어지고 있으나 이 두 가지 시스템은 인터페이스 및 트래픽 관리 등에서 다른 기술을 사용하고 있다 그러므로, 이종망간 핸드오프를 할 때, 통신 단절이 발생하게 된다. WCOMA 네트워크에서 통신을 하던 단말기가 그 지역을 벗어나 COMA 지역으로 이동하는 경우, 사용자는 이용하고 있던 서비스를 중단하고 다시 새로운 네트워크에서 서비스를 요청하여야 한다. 본 논문에서는 이기종 네트워크간의 핸드오프가 발생할 때 서비스의 단절 현상을 없애기 위해, Seamless Services를 지원하는 효율적인 핸드오프 모델과 절차를 제안한다.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.350-354
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• 2008

IP-based mobile communication system is one of the key research items in the mobile networks for a long time. But, due to some technical issues and no need of markets, it is still not full-fledged. Recently, CDMA and WCDMA service providers want to introduce IP-based network connectivity. Even though their efforts, the main network intra-structure depends on ATM or HDLC technology. This article describes a good example of commercialization of IP-based mobile communication systems. Our research is not experimental system but a in-service system - replacing the existing equipments with new IP-based systems. In this paper, we introduce IP related technologies used in our research such as IP-based ATCA(Advanced Telecommunications Computing Architecture) platform, HA(High Availability) redundancy, IP multicast, network redundancy techniques, multi-link bundling and IP header compression. These are already well-known to internet domain. We mix them with mobile communication systems concretely.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.6
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• pp.71-76
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• 2012

Recently, the huge growth of mobile data traffic has driven the earlier commercialization of LTE network and the evolution of LTE-Adv has been accelerated because of this trend of mobile traffic surges. Thus it has enabled the global connectivity and roaming capability due to continual standardization activities. The 3rd generation mobile communication system has been improved through incorporating technologies of HSDPA, MBMS and HSUPA etc continuously. Also, OFDMA/SC-FDMA-based LTE standardization has been under way. In this paper, the architectures of LTE network and protocol have been introduced and their inherent operation mechanisms have also been explored in order to give some insights about the LTE/LTE-Adv networks while their architectures are considered as most prominent candidate for worldwide standard by ITU-R and mobile operators for international communication networks.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.163-170
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• 2011

This study proposed the composition of a new long-code MMSE detector using the pilot channel that demonstrated the most excellent performance under Rayleigh fading in the previous studies. It analyzed and explained how to maintain the stability of the weight vector(introduction to the course of radio waves) in the receiver. In the operation of the receiver system to remove radio interference, the signal vector distortion received in the channel where fading was present achieved good results by compensating for signal errors. When there was distortion, the response characteristics of the received signals were superior to the common matching filter according to the computer simulation. The long-code MMSE receiver proposed in the study was able to prolong the cycle by $16{\times}T_b$ in the fading environment to fulfill the satisfaction.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.253-257
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• 2003

CDMA 방식의 디지털 이동통신 망은 기존의 2G 방식에서 IX, IxEV-DO을 거쳐 WCDMA로 비약적으로 발전하고 있으며, 이에 따라 무선망 운용 및 최적화 방법도 진화해가고 있다. 운용자들이 Field Tool을 사용하여 직접 Field 데이터를 측정, 분석하고 조치하는 방식이 가장 기본적인 방법이라면, Field 데이터와 Network 데이터를 함께 수집하여 분석하는, 보다. 발전된 방법도 사용되고 있다. 그러나, 이러한 방법도 여러 Tool에서 데이터를 off-line으로 수집한 후 분석 작업을 수동으로 반복 수행해야하는 번거로움이 있어, 실시간 on-line 무선망 최적화 시스템을 통한 체계적이고 과학적인 운용 방법을 생각해 볼 수 있다. 우선, 타 운용 Tool 들과의 on-line 연동으로 중앙 집중적 데이터베이스를 구축하여, 무선망에 관련된 모든 데이터에 대한 통합적인 관리가 필요하다. 이 데이터베이스를 이용하여, 실시간으로 무선망 성능 및 효율 저하 원인 분석을 실시하며, 분석된 결과는 기지국의 상태 및 문제점 도출에서부터 최종 처방까지 제시해준다. 본 논문에서는 이러한 솔루션을 구축하기 위한 다양한 네트웍 데이터 연동(성능, 장애, 구성, RF, 실측 데이터 등), 주요 KPI (Key Performance Indicator) 모니터링, 통계적 분석, 무선망 분석 등에 대해 고찰해본다.

• The KIPS Transactions:PartA
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• v.19A no.4
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• pp.195-204
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• 2012

M-commerce services are rapidly emerging with recent advances in mobile devices and wireless communications. Internet Shopping mall managers provide mobile phone users with their mobile shopping malls for m-commerce. However, these mobile shopping malls usually have their own sites which are not compatible with their Internet shopping malls, thus resulting in inefficiency to manage the two kinds of shopping malls. In this paper, we develop a M-commerce content provider system to effectively bring Internet shopping malls to mobile phones by extracting items only concerned to users from product documents. We then apply and evaluate the system over a specific internet shopping mall site. The results show that the system reduces considerably the amount of data transferred to user's mobile phones compared with using general web browsers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.40-47
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• 2009

This paper presents the method of measuring the feedback interference channel, which is developed between the transmit and receive antennas of a wireless repeater by receiving the transmit signal at the receive antenna of the identical repeater, and experiment results obtained by analyzing the measurements. This experiment uses 2 GHz WCDMA signal and is carried out near a highway. The high-speed mobiles on highways cause reflected signals with high Doppler frequencies and large energy. In order to characterize the feedback channel, the power delay profile and the scattering function are estimated by identifying the delay spread, the Doppler spread, the number of fingers, and the attenuation with delay. Since the feedback interference channel is constructed between the fixed TX and RX antennas, which is dependent upon the multipaths developed by moving or fixed objects around the antennas, the channel shows different properties comparing to the conventional channels between the base station and the mobile station. Therefore, the results presented in the paper are expected to provide guidelines for designing and evaluating wireless repeater systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.83-91
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• 2014

The passive UHF RFID tags for item-level tagging are now explosively used in the supply chain and retail applications as they have several advantages, the two most relevant are cost and a longer read range. However, the signal interference problem between RFID tags and smart devices in real world is expected according to the smart-phone and tablet market growth together. The performance of RFID tags can be significantly less. The popular examples are the read-success rates and read range reduction. Especially, KT Corp. recently emphasized the serious signal interference at 900 MHz of LTE and old RFID frequencies through their public demonstration. By popular demands, this paper suggests the interference tolerance measurement method between the passive UHF RFID tag and the transmitted signal from a smart device. In addition, we selected three passive UHF RFID tags(Inlay) available on the market and quantitatively evaluated read range reduction results by interference signals using the PCR(Performance Change Rates) index. As a result, the LTE system is about three times as effective as the WCDMA system in terms of interference effects, and the read range performance of two RFID tags about 60 % drop.