• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.186-190
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• 2002

본 논문에서는 WCDMA/TDD시스템에서 실외 환경에 셀 간 간섭 모델과 빌딩내의 층 간 간섭 모델을 비교하여 성능을 분석하였다. 실내 빌딩 환경에서 층 간 간섭 분석 모델을 고려 시, 건축 자재에 의한 전파 투과손실로 인해 인접 셀로부터 오는 간섭의 영향이 작아짐으로 실외환경을 고려한 셀 간 간섭 모델에 비해 성능이 좋음을 알 수 있었다. 따라서 WCDMA/TDD시스템은 광범위한 교외지역이나 피코 셀로 설계된 도심지역보다 층 간 간섭 모델을 기반으로 둔 빌딩내 사무실 환경을 고려한 시스템 설계에 더 적합할 것이라 사료된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1465-1468
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• 2004

기본적으로 무선 네트워크는 일정한 크기의 셀 단위로 구성된다. 통신 중인 단말은 이러한 셀 사이를 이동하게 되고, 셀과 셀 사이를 이동하는 것을 핸드오프라고 한다. 최근의 셀 크기는 보다 많은 사용자를 수용하기 위해 피코 셀 단위로까지 작아지고 있다. 이렇게 셀 단위가 작아지면, 더욱 빈번한 핸드오프가 일어나게 된다. 본 논문에서는 빈번한 핸드오프로 인한 연결 실패율을 줄이고자 지리적 정보를 토대로 이동성을 예측하고, 그 예측 결과를 사용하여 이동 단말의 속도에 따라 대역폭 예약을 다르게 하는 방식을 제안한다. 이 방식은 이동 단말의 속도와, 셀 내의 도로 사정, 도로 사정에 따른 다음 셀 이동 확률 등을 이용하여 대역의 예약범위와 예약 대역폭 량을 결정한다. 이러한 방법으로 좀 더 확실한 이동성 예측과 예약 대역폭 미사용에 따른 대역폭 낭비를 줄이는 효과를 볼 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.25-32
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• 2008

This paper presents the reflection and transmission measurements conducted at the 60GHz suitable to provide a high speed wide band service. Mean received power and standard deviation are calculated and used to compare the characteristics of radio wave propagation to the various obstacles between transmitting and receiving antennas at the frequency. The results show that the transmitted signal strength by the steel door and copper plate are about 40dB lower than in free space, those by the rubber plate, glass and styroform are about 3dB lower than in free space. Also, the re(looted signal strengths at the 60 degree grazing angle show that in case by the partition is about 23dB lower, by the surface of a wall is about 6dB lower than by the copper plate. The presented results can be used for the design of 60 GHz picocell communication network that the reflected and transmitted waves affect to the service area.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2233-2240
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• 2007

This paper presents the measured path loss exponents and standard deviations using measured data at 60GHz to analyze the propagation characteristics of millimeter wave bands having great demand for picocellular communications. In addition the angle of arrival(AOA) were measured to analyze the arrival direction of muitipath waves affecting the received signal strength. As results of analysis, the pathloss exponents in each environment are found to be lower than 2 for free space pathloss exponent. They were determined with the qualities of bottom materials affecting signal strength. The angles of arrival by multipath waves were different with the circumference structures between transmitter and receiver. That is, the multipath waves excluding direct and ground reflected wave were difficult to find in wide space such a gymnasium and playground, however the wall multipath waves were found to arrive at receiver in the corridor. The multipath waves at 60GHz can be known to hardly affect to the received signal strength because of weak signals compared with direct wave.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.316-318
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• 2000

미래의 무선망에서는 자원의 한계를 극복하기 위해서 셀 크기가 작은 마이크로/피코 셀 구조를 갖을 것으로 기대된다. 하지만, 이런 구조는 핸드오프의 증가를 가져오기 때문에 시간과 위치에 따라 망의 상태는 급격히 변동하게 된다. 이러한 점은 QoS 보장이 어렵거나 저하시키는 원인이 된다. 따라서, 본 논문은 멀티미디어 서비스 분포를 제어함으로써 망의 변동폭을 완화시켜 이동 QoS를 개선시키는 호 수락 알고리즘(RCAC)을 제안하였다. 실험 결과, 제안된 방식이 QoS를 개선시킬 수 있음을 확인할 수 있다.

• Journal of Convergence Society for SMB
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• v.1 no.1
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• pp.67-73
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• 2011

Handover in high speed mobile communication service, in particulary mobile WiMAX is supported efficiency mobility to 120km/h speed. But, in order to accommodate number of user increment in a cell, wireless network is increment to microcell and picocell by allocate bandwidth and by decrease cell size. handover is occurrent and increment connection failure ratio In this result. IEEE 802.16 standard is support seamless connection through handover optimization scheme. But because authentication process is abbreviate, network weakness is exposure. In this paper, we propose handover scheme for support realtime service as VoIP, Picure communication, Streaming Data Service in order to support partially encryption method. In experiment, proposed scheme is proof which process time is increment 20% more than previous scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.4
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• pp.30-44
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• 2003

In the microcell-or picocell-based system the frequent movements of mobiles bring about excessive traffics into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. Existing location estimation schemes consider only LOS model and have poor performance in presence of multi-path and shadowing. In this paper we study novel schemes which can increase estimation accuracy by considering NLOS environment and other multiple decision parameters than the received signal strength.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1641-1647
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• 2000

This paper presents an analysis of coverage and capacity for the multi-layer CDMA cellular system. The multi-layer CDMA system that shares a common frequency band consists of macrocells for outdoor users and picocells for indoor users. Though macrocells and picocells interfere with each other the capacity of the whole system can be increased, We have analyzed the effect of muual interference upon cell coverage soft handover areas and capacities. The parameters involved in the engineering of the system are discussed. The study results sow that we can control the service coverage of indoor picocells with the system parameters set properly. It is also show that the capacity of the whole system that the capacity of the whole system can be enhanced smoothly by deploying the indoor picocells within existing macrocells.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1509-1512
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• 2004

본 논문은 무선통신망 환경에서 이동체(Mobile Node)에 멀티미디어 서비스를 제공하기 위한 효율적인 핸드오프 알고리즘에 관한 연구로서 QoS에 미치는 영향이 큰 요소들에 대해 분석하고 이를 기반으로 효율적인 핸드오프 방안을 제시한다. 이를 위해 QoS와 밀접한 관련이 있는 이동체의 속도에 따른 핸드오프 호의 실패율(Blocking Rate)을 분석하였다. 또한 현재 각 이동통신 서비스 업체들이 제공중인 인구밀집지역에서의 무선 멀티미디어 서비스를 가정하여 피코셀(Pico Cell) 환경에서 멀티캐스트 그룹설정에 따른 핸드오프 호의 실패율을 분석하였으며, 이를 기반으로 무선통신망에서 향상된 QoS를 제공할 수 있는 핸드오프 방안을 제시하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1685-1690
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• 2006

The future mobile communication system should be operated with hierarchical cellular system for providing high quality multimedia services within limited wireless resources. In this paper, we have studied a call admission control scheme applied in hierarchical CDMA cellular system nested with macro, macro, and pico cells. When the proposed call admission control algorithm was applied we got 20% more system capacity than no admission control was applied.