• Information and Communications Magazine
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• v.30 no.9
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• pp.78-84
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• 2013

최근 4세대 이동통신은 기술/경제적인 이유로 클라우드 기지국 (또는 C-RAN: Cloud Radio Access Network) 구조를 택하는 추세이다. C-RAN은 기존 일체형 기지국에서의 MAC/PHY 기능을 담당하는 BBU(Base Band Unit)와 RF신호 송수신 만을 담당하는 RRH(Remote Radio Head)로 분리된 기지국 구조를 가지며, RRH의 무선 송수신 신호는 중앙의 BBU에 집중되어 처리된다. 본고에서는 BBU와 RRH로 분리되어 설치/운용되는 C-RAN의 구조와 기지국 가상화 개념을 소개하며, 향후 이동통신시스템에서의 기술동향과 관련하여 C-RAN에서 발생할 수 있는 이슈들을 살펴본다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.359-362
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• 2010

BBU for 155mm projectile has been verified its stable performance and quality reliability through the production for several years. We have researched substitution test for flight test of BBU. Through this research, we expect the verification of quality stability and other collateral effect like the cost reduction and delivery on time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.04a
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• pp.109-109
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• 2001

• Electronics and Telecommunications Trends
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• v.28 no.3
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• pp.106-114
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• 2013

과거 이동통신용 기지국은 기저대역 처리부와 안테나를 포함하는 RF부가 일체형으로 제작되었으나, 4세대 이동통신에서는 기술/경제적인 이유로 BBU(Base Band Unit)와 RRH(Remote Radio Head)로 분리하여 구성되는 분산형 기지국 구조를 택하는 추세이다. BBU와 RRH 간 인터페이스로 널리 사용되어온 OBSAI, CPRI외에 2010년 ORI가 출현하여 표준화가 한창이다. ORI는 시장에서 널리 사용되는 CPRI(Common Public Radio Interface)의 Vendor Specific 부분으로 인해 제조사간 호환성이 보장되기 어려운 문제를 보완하기 위하여 탄생한 인터페이스 규격으로써, CPRI를 기반으로 하면서 표준으로써의 완성도를 높인 표준이라 할 수 있다. 또한 관련 표준으로는 유일하게 IQ 데이터 압축알고리즘의 표준화를 고려하고 있다. 본고에서는 ORI의 표준화 현황과 기술적인 이슈를 소개하고, 국내의 대응 현황을 알아본다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.327-330
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• 2006

Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base homing process. Overall fluid dynamic process is modeled by Wavier-Stokes equations for reacting flows with two-equation $k-\omega$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.479-483
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• 2005

BBU is the weapon system for the extension of range through the reduction of base drag in 155mm. It has been mass-produced since 2000. The purpose of this research is productivity increase through the reduction of process lead time. Development process is as follows. First, formulation tests about propellent and liner, Second, spin test and final firing test about end products.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4618-4639
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• 2018

One of the most innovative paradigms for the next-generation of wireless cellular networks is the cloud-radio access networks (C-RANs). In C-RANs, base station functions are distributed between the remote radio heads (RHHs) and base band unit (BBU) pool, and a communication link is defined between them which is referred as the fronthaul. This leveraging link is expected to reduce the CAPEX (capital expenditure) and OPEX (operating expense) of envisioned cellular architectures as well as improves the spectral and energy efficiencies, provides the high scalability, and efficient mobility management capabilities. The fronthaul link carries the baseband signals between the RRHs and BBU pool using the digital radio over fiber (RoF) based common public radio interface (CPRI). CPRI based optical links imposed stringent synchronization, latency and throughput requirements on the fronthaul. As a result, fronthaul becomes a hinder in commercial deployments of C-RANs and is seen as one of a major bottleneck for backbone networks. The optimization of fronthaul is still a challenging issue and requires further exploration at industrial and academic levels. This paper comprehensively summarized the current challenges and requirements of fronthaul networks, and discusses the recently proposed system architectures, virtualization techniques, key transport technologies and compression schemes to carry the time-sensitive traffic in fronthaul networks.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.652-655
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• 2010

BBU attached to the 155mm is the weapon system for the extension of range through the reduction of base drag. This research focus on the development of inhibitor formulation changing cure agent from DDI to IPDI. Development process is as follows. First, the formulation test about basic property Second, the study on the application of process. Third, the tests for the quality and aging properties. The test results are satisfied with the all of the requirments. In results, this research is contributed to the stable manufacturing in the instability of supplying of cure agent.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.92-97
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• 2007

Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base burning process. Overall fluid dynamic process is modeled by Navier-Stokes equations for reacting flows with two-equation $k-{\omega}$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.83-85
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• 2016

C-RAN (Cloud Radio Access Network) structure is the most popular approach for 5G stander, it employs CoMP (Coordinated Multiple Points Transmission/Reception) to enhance frequency utilization and increase throughput for cell-edge users. C-RAN mainly includes two parts: baseband units (BBU) and remote radio heads (RRH). In this paper we propose a new resource block allocation (spectrum allocation) scheme by the permutation and combination of BBUs, and we also use the CoMP (Coordinated Multiple Points Transmission/Reception) technique according to the different environment to improve the spectrum utilization and reduce resource waste in different environment. The simulation results expound that the scheme significantly enhances throughput and improves the spectrum utilization.