• Proceedings of the Korean Society of Computer Information Conference
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• 2011.06a
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• pp.63-66
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• 2011

본 논문에서는 현재 3GPP에서 진행되고 있는 차세대 이동통신 기술 표준, 즉 LTE 시스템의 하향링크 전송방식의 수신성능을 향상시키기 위해 기지국(BS)과 단말(MS) 사이에 릴레이(RS) 설치를 제안하고, BS의 위치와 설치된 RS의 거리를 각각 500m, 1000m로 하고 RS의 전송방식을 OFDMA와 SC-FDMA를 선택함으로써 수신성능을 높이기 위한 연구를 수행하였다. 연구결과 RS의 위치가 BS와 가까울수록 RS에서는 SC-FDMA를 사용하는 것이 좋게 나왔고, 반대로 BS와 RS의 거리가 멀어질수록 RS에서는 OFDMA를 사용하는 것의 성능이 좋은 것으로 나왔다. 또한 BS와 MS 거리의 중심지역에서는 그 상황에 맞는 전송방식을 사용함으로써 시스템의 수신성능을 향상시킬 수 있었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.83-90
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• 2000

In this paper, a stacked circular-disk microstrip 1${\times}$4 array antenna was designed and manufactured and tested to apply in next generation mobile communication, on IMT-2000 system(up-link: 1.885 GHz∼2.025 GHz, down-link: 2.11 GHz∼2.2 GHz) base station which has dual frequency, broadband and high-gain characteristics. The experimental results are as follows : resonant frequency of 1.885 GHz and 2.178 GHz VSWR (1.064 , 1.432), return loss (-30.19 dB , -24.99 dB), band width (VSWR<2) are 402 MHz, -3dB beam width at radiation pattern are ${\alpha}$E-16.8$^{\circ}$, ${\alpha}$H-69$^{\circ}$(1.885 GHz) and ${\alpha}$E-l5.2$^{\circ}$, ${\alpha}$H-51.5$^{\circ}$(2.178 GHz), gain(13.7 dBi∼15.21 dBi).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.876-884
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• 2015

In this paper, a switched beamforming antenna system at 28 GHz frequency band is described for $5^{th}$ generation wireless communication. The butler matrix is used as a beamforming system and it produces linear spaced phase difference at four output ports. Array antenna is designed that can be steered in desired 4 different directions 28 GHz frequency band. Operation of designed butler matrix that composed of couplers and feedline is explained. The antenna system is designed in RO3003 substrate that has a height of 5 mil and dielectric constant of 3. The size of butler matrix is $20.3{\times}13.0mm^2$ and size of array antenna is $21.2{\times}19.9mm^2$. This system can be steered from $-34^{\circ}$ to $33^{\circ}$ and minimum sidelobe level is 12.9 dB.

• Journal of Korea Society of Digital Industry and Information Management
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• v.4 no.3
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• pp.69-75
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• 2008

The objective of this paper is to increase the performance by selecting the optimal value in outputs of two algorithms that are Generlized-Lagrange and LMS(Least Mean Square). This paper presents superior performance by mixed two of conventional algorithm arbitrary. Based on the analysis from various simulation, it is observed that proposed method is better performance in terms of practical WLL(Wireless Local Loop) environment.

• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.35-48
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL and CRRM. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate and the system service cost.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.162-165
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• 2017

In an effort to compensate the rising of the data throughput demand nowadays, there have been many research works to optimize the radio resource and increase the capacity of the network. At the present, small cell network, mmWave band and beamforming technology are leading the trend and becoming the core solutions of the fifth generation (5G) cellular networks. Since the propagation characteristics of radio wave in the mmWave band is quite different from the conventional bands, the communication systems which work in these bands have to be redesigned. In this paper, a 3D simulation model is discussed for cellular network at 60 GHz in outdoor environments. Coverage analysis and system performance is carried out for a small cell system in the typical urban environment including street canyon simulation scenario. In addition, the beamforming technique is considered to evaluate the throughput improvement. Simulation results show that the mmWave small cell systems is expected to be one of the major candidate technologies to satisfy the requirements of 5G in terms of data rate.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.1
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• pp.49-54
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• 2010

3GPP(Third Generation Partnership Project) LTE system that is the next step forward in cellular 3G services address the issues related to power saving at LTE base station. This is because that most of the energy in a typical telecommunication network is consumed by the wireless network's base station site. Power saving at LTE base station fall in with low-carbon green technology. This thesis proposes a power saving MAC protocol for LTE base station which utilizes different graded DRX/DTX(Discontinuous. Reception/Transmission). Considering traffic type in UE, proposed MAC protocol controls adaptive DRX/DTX cycle. The proposed method is more improve power saving performance than another method which is unchanged DRX/DTX by conditions. In this thesis, I propose an power saving MAC protocol in an environment where LTE base station are communicated with UE and prove improvement in performance through simulations.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.827-830
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• 2000

3GPP and ETSI adopted AMR(Adaptive Multi-Rate) as a standard for next generation IMT-2000 service. In this paper, we analyzed algorithm about AMR and optimized ANSI C source on the C complier and assembly language of Texas Instrument . The implemented AMR speech codec requires 28.2MIPS of complexity for encoder and 5.5MIPS for decoder. we performed real-time implementation of AMR speech codec using 82% of TMS320C5402 with 40 MIPS specification. We give proof that the output speech of the implemented speech codec on DSP board is identical with result of C source program simulation. Also the reconstructed speech is verified in the real-time environment consisted of microphone and speaker.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.334-336
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• 2000

인터넷의 폭발적인 증가와 다양한 무선 서비스에 대한 계속적인 수요 증가에 따라 용량이 크고, 데이터 전송 속도가 빠르며, 멀티미디어를 지원할 수 있는 무선 서비스가 필요하게 되었다. 비동기식 제3세대 이동통신시스템에서 단말과 인터넷망을 연결하는 GPRS network에서 GGSN의 인터넷 패킷 트래픽을 효과적으로 처리할 수 있는 방안이 연구되어져야 한다. GGSN은 기존의 라우터처럼 하드웨어적으로 구현되는 것이 이상적이지만 GTP (GPRS Tunneling Protocol)가 추가되므로 좀더 복잡한 형태의 gateway가 초기단계에서는 소프트웨어적으로 구현되어질 것이다. 이러한 GGSN의 성능과 용량을 최적화시키기 위한 패킷 트래픽 처리방안에 대한 연구가 필요하다. 본 논문에는 GGSN의 다운 링크상에서 입력되는 각 클래스별 트래픽 모델을 정립하고 트래픽에 대한 특성과 버퍼 관리에 대해 살펴본다.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2001.05a
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• pp.69-70
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• 2001

인터넷의 폭발적인 증가와 다양한 무선 서비스에 대한 계속적인 수요 증가에 따라 용량이 크고, 데이터 전송 속도가 빠르며, 멀티미디어를 지원할 수 있는 무선 서비스가 필요하게 되었다. 비동기식 제3세대 이동통신시스템에서 단말과 인터넷망을 연결하는 GPRS network에서 GGSN의 인터넷 패킷 트래픽을 효과적으로 처리할 수 있는 방안이 연구되어져야 한다. GGSN은 기존의 라우터 처럼 하드웨어적으로 구현되는 것이 이상적이지만 GTP(GPRS Tunneling Protocol) 가 추가되므로 좀더 복잡한 형태의 gateway가 초기단계에서는 소프트웨어적으로 구현되어 질것이다. 이러한 GGSN의 성능과 용량을 최적화 시키기 위한 패킷 트래픽 처리방안에 대한 연구가 필요하다. 본 논문에는 GGSN의 하향 링크상에 서 입력되는 각 클래스별 크래픽 모델을 정립하고 트래픽에 대한 특성과 버퍼 관리에 대해 살펴본다.