• Information and Communications Magazine
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• v.26 no.12
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• pp.35-48
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• 2009

본고에서는 LTE-Advance 및 802.16m 시스템에서 cell throughput 향상, cell coverage 확장 및 group mobility 지원을 위해 도입된 relaying 기술 및 이에 대한 표준화 동향에 대해 알아본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.18-25
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• 2013

In this paper, we propose a self-optimization scheme for indoor femtocell coverage in heterogeneous networks. If the femtocell coverage is larger than indoor area, neighbor cell users passing by the outer area of the femtocell coverage may request an unnecessary handover which incurs wasteful signaling overhead. On the other hand, if the coverage is smaller than the indoor area, some of indoor users might not be connected to the indoor femtocell. Therefore, we propose the method by which the femtocell coverage attains the exact indoor area employing self-organized scheme. Autonomous self TX power adjustment of the femtocell is possible because the proposed method utilizes handover request events and membership information of users that can be obtained by the femtocell itself. We show that the TX power obtained by the proposed algorithm converges to the optimal TX power that can be obtained analytically to attain the indoor coverage area.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11c
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• pp.2431-2434
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• 2002

본 논문에서는 전체 영역 경로 계획인 CCPP(Complete Coverage Path Planning)를 이용해 전 청소 영역을 청소하는 방법을 나타내고 청소영역을 해석 하였다. 그리고, Template방법에 CD(Cell Decomposition)을 접목시킨 방법을 이용해 청소영역을 청소 후 재 경로계획으로 청소 안된 영역을 효율적으로 청소하는 방법을 연구하였다. 또한 청소기의 회전 및 직선 모션에 따른 청소 영역을 비교 해석해 최적 시간과 거리에 따른 경로 계획을 살펴보았다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.639-642
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• 2003

본 논문에서는 청소로봇이 전 청소 영역을 CCPP(Complete Coverage Path Planning)를 이용해 경로를 생성한 후 재 경로계획 시 장애물의 미소한 변화로도 기존에 생성한 전 경로패턴을 바꾸지 않고 수정 할 수 있는 CD(Cell Decomposition)와 FN(Flow Network)을 이용한 CCPP 방식을 제안 하였다. 그리고 제안된 경로 계획에 대해 시뮬레이션으로 결과를 제시하였다.

• Journal of the Korea Society for Simulation
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• v.7 no.2
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• pp.63-78
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• 1998

The hierarchical cell structure consists of the macrocell and microcells to increase the system capacity and to achieve broad coverage. The hierarchical cell structure provides services for users in different mobility. In this paper, an analytical queueing model in mobile networks is proposed for the performance evaluation of the hierarchical cell structure. The model for networks with the multiple levels can simplify multi-dimensional ones into one-dimensional queueing model. The computational advantage will be growing as the layers are constructed in multiple levels. The computer simulation is provided for validating the proposed analytical model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.642-653
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• 2008

In this paper, we propose a 3-D finite element (FE) analysis model with combined physical behavior and kinematical impact factors for evaluation of residual stress in multi-impact shot peening. The FE model considers both physical behavior of material and characteristics of kinematical impact. The physical parameters include elastic-plastic FE modeling of shot ball, material damping coefficient, dynamic friction coefficient. The kinematical parameters include impact velocity and diameter of shot ball. Multi-impact FE model consists of 3-D symmetry-cell. We can describe a certain repeated area of peened specimen under equibiaxial residual stress by the cell. With the cell model, we investigate the FE peening coverage, dependency on the impact sequence, effect of repeated cycle. The proposed FE model provides converged and unique solution of surface stress, maximum compressive residual stress and deformation depth at four impact positions. Further, in contrast to the rigid and elastic shots, plastically deformable shot produces residual stresses closer to experimental solutions by X-ray diffraction. Consequently, it is confirmed that the FE model with peening factors and plastic shot is valid for multi-shot peening analyses.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.143-148
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• 2003

In this paper, we focused on the performance of reverse link in 1.8GHz CDMA 1x system including the Tower-Mount LNA in an urban environment. In order to study the benefit of TMLNA, Hata model is used and the effects of multiple cells are considered. Cell coverage extension ratio is proportional to the increased gain of TMLNA in CDMA cell site. However the cell coverage is not extended even if the noise figure of TMLNA is reduced in an urban area. When typical RSSI is between -70dBm and -80dBm, the increased gain and the reduced NF of TMLNA are not impact to the pole capacity of cell site. Namely, the benefit of TMLNA in an urban area is not the problem of capacity but the proble of sensitivity. The results are also shown that reverse link $E_b/N_o$ is improved by minimum 5dB and BER is lower than $10^{-6}$.

• ETRI Journal
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• v.37 no.5
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• pp.856-866
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• 2015

A heterogeneous network (HetNet) is a network topology composed by deploying multiple HetNets under the coverage of macro cells (MCs). It can improve network throughput, extend cell coverage, and offload network traffic; for example, the network traffic of a 5G mobile communications network. A HetNet involves a mix of radio technologies and various cell types working together seamlessly. In a HetNet, coordination between MCs and small cells (SCs) has a positive impact on the performance of the networks contained within, and consequently on the overall user experience. Therefore, to improve user-perceived service quality, HetNets require high-efficiency network protocols and enhanced radio technologies. In this paper, we introduce a 5G HetNet comprised of MCs and both fixed and mobile SCs (mSCs). The featured mSCs can be mounted on a car, bus, or train and have different characteristics to fixed SCs (fSCs). In this paper, we address the technical challenges related to mSCs. In addition, we analyze the network performance under two HetNet scenarios-MCs and fSCs, and MCs and mSCs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.628-631
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• 2014

Recently, the proliferation of new applications, e.g., mobile TV, Internet gaming, large file transfer, and the various of user terminals, e.g., smart phones and notebooks, has dramatically increased user traffic and network load. In order to meet this traffic growth, vendors and cellular operators are working on the development of new technologies and cellular standards. Within them, small cell deployment has been heralded as one of most promising way to increase both coverage and capacity of future cellular network. Small cell technology enables to improve capacity of cellular radio network by tight cooperation between small cell and macro cell in multi-tier network where small cells are densely deployed within macro cell coverage. In this paper, we describe the deployment scenarios for cooperation between macro cell and small cells and state-of-the-art technologies related to dense small cell deployment. Then, we also provide design principles and standardization trends for small cell enhancement in 3GPP.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.165-168
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• 1998

This paper describes the characteristics of CT-2 radio wave propagation at 900MHz range. Typical cell coverage of CT-2 based on picocellular design provides a 200m radius. The five sites of urban regions of Kwang Ju city were chosen to characterize propagation in various environments. On the basis of cell coverage data measured with field strength meter, average 75% of telepoint service was retained and it was lack 25% of overall gain. In some sites telepoint service was limited to two of four directions around a station. If specially designed collinear antenna with specific directivities are used in these shadow area, improved results will be acquired.