• Proceedings of the Korean Information Science Society Conference
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• 2010.06a
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• pp.287-292
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• 2010

컴퓨터의 성능을 향상하기 위해 주로 프로세서의 성능을 놓여 왔으나 발열 및 집적도 등의 문제로 인하여 한계를 가지게 되었고, 이를 해결하기 위하여 멀티 판로세서와 멀티 코어 시스템이 등장하였다. 이러한 시스템은 두 개 이상의 처리기를 사용하여 단일 처리기 시스템보다 놓은 성능을 갖으며 비교적 낮은 전력을 소모하기 때문에 점차 사용이 증가하고 있다. 운영체제도 이러한 다중 처리기 시스템을 위한 기능이 추가 되어 효율적으로 사용하여 성능을 놓이기 위해 변화하고 있다. 부하 분산 알고리즘 역시 예전의 스케줄러에는 들어있지 않는 기법이었으나 멀티 프로세서가 등장한 이후로 추가 되었다. 본 논문에서는 이 전 방식의 부하 분산 알고리즘에 유동적인 기준점을 추가하여 성능을 개선하고자 한다.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.06a
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• pp.307-311
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• 2001

신속조형시스템(RP : Rapid Prototyping)용 자료교환 표준인 STL의 자료구조는 단순하고, 조형용 2차원 단면 자료로의 전환이 용이하며, 생산 가공 기술로서의 현대적인 특성(신속성, 조형성, 경제성, 청정성 등)을 가지고 이는 장점이 있는 반면에, STL 3D 좌표값의 기준(좌표계의 원점)이 되는 크기 정보가 없다. 이런 문제를 구현된 STL 뷰어에서는, 스케일링(scaling) 기법과 선형적인 이동 기법을 사용하여 해결하였고, CAD 시스템으로 제작된 파일 자체의 문제점 패싯(facet) 중복, 정밀도, 법선 벡터 값의 오류 등도 검증기(verifier)와 오류 정정기(error corrector)글 구현하여 해결하였다. 제안된 방법으로 구현된 STL 뷰어는 시스템의 안정성과 확장성, 그리고 효율성 측면에서 우수한 성능을 보였으며, 슬라이싱(slicing), 경로 추적기(path tracer)의 전처리기의 역할을 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.650-652
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• 2000

본 논문은 최근에 그 수요가 증가하고 있는 리눅스를 기반으로 하여 안전한 운영체제의 설계 및 구현에 대하여 기술한다. 안전한 운영체제를 위해 사용되는 보안 기능들은 MAC(Mandatory Access Control), DAC(Discretionary Access Control), 그리고 SOP(Separate of privilege)과 같이 파일, 디렉토리, 그리고 디바이스와 같은 시스템 자원에 대한 접근을 제어하는 기능과 감사 추적(Auditing)기능, 그리고 사용자 인증기능 등이 있다. 접근제어란 컴퓨터자원, 통신자원, 정보자원 등에 대한 허가되지 않는 접근을 막는 것이다 본 논문에서는 리눅스 운영체제의 보안을 위해 필요한 접근 제어 기능과 다중 레벨의 사용자 인증기능의 설계 및 구현에 대해 기술한다. 또한 접근 제어기능 구현은 국제 표준화인 OSIX1003.le을 기준으로 하였다.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.1
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• pp.85-92
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• 2024

This study develops a Global Positioning System (GPS) Code Multipath Grid Map (CMGM) of each individual domestic reference station from the extracted code multipath of measurement data. Multipath corresponds to signal reflection/refraction caused by obstacles around the receiver antenna, and it is a major source of error that cannot be eliminated by differencing. From the receiver-independent exchange format (RINEX) data for two days, the associated code multipath of a satellite tracking arc is extracted. These code multipath data go through bias correction and interpolation to yield the CMGM with respect to the azimuth and elevation angles. The effect of the CMGM on multipath mitigation is then quantitatively analyzed to improve the Root Mean Square (RMS) of averaged pseudo multipath. Furthermore, the single point positioning (SPP) accuracy is analyzed in terms of the RMS of the horizontal and vertical errors. During two weeks in February 2023, the RMSs of the averaged pseudo multipath for five reference stations decreased by about 40% on average after CMGM application. Also, the SPP accuracies increased by about 7% for horizontal errors and about 10% for vertical errors on average after CMGM application. The overall quantitative analysis indicates that the proposed approach will reduce the convergence time of Differential Global Navigation Satellite System (DGNSS), Real-Time Kinematic (RTK), and Precise Point Positioning (PPP)-RTK correction information in real-time to use measurement data whose code multipath is corrected and mitigated by the CMGM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1076-1084
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• 2012

In the CS/CB(Coordinated Scheduling/Beamforming) scheme, the cell edge user throughput is increased by selecting MIMO (Multiple Input Multiple Output) precoders which can minimize the interferences from adjacent base stations (BSs). However, in current LTE(Long Term Evolution) systems, the serving cell is selected in the initialization stage by using the synchronization signals and cell specific reference signals transmitted by adjacent BSs with a single antenna. The selected BS in the initialization stage may not be the best one since the MIMO precoding gain has not been considered in the cell selection stage. In this paper, a new cell selection technique is proposed for LTE systems with MIMO precoder by taking into account the effect of the precoder in the initialization stage. The proposed technique enables a user equipment (UE) in the cell boundary to select the serving BS by using the information (channel rank, effective channel capacity, and effective SINR(Signal to Interference plus Noise Ratio)) acquired from cell specific reference signals of candidate BSs. It is verified by computer simulation that the proposed technique can increase the channel capacity significantly in the multi-cell environments, compared with the conventional CS/CB scheme.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.417-424
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• 2016

Russia recently began broadcasting the SDCM signal in order to provide SBAS service for the civil aviation in the Russian territory using its own geostationary satellites. The service coverage of the SDCM geostationary satellite, LUCH-5A and LUCH-5B, includes Korea peninsula, where the test signal from the pseudo random number (PRN) 140 is received. This paper shows that the position accuracy at the Chulwon GNSS site is improved to 0.8749 m (horizontal) and 0.9589 mm (vertical) by applying the received SDCM message to the RINEX data. Considering that the SDCM augments both GPS and GLONASS, the performance of multi-constellation SBAS was compared to that of GPS-only SBAS, and APV-I availability was improved by decreasing the protection level about 30 %. From the results, we can expect that the mult-constellation SBAS can contribute to the performance enhancement of the future KASS.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.73-80
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• 2019

Traffic Safety and efficient Road Traffic Policy of Traffic management came into effect over the certain size of the road like main road. Comparatively, Safety for Living street is deteriorated. Especially, Vehicle are usually priority to the life-zone street, even though Safety for the Passengers are essential to the life-zone street in the residential area. Improvement for the Living street has not been achieved In this study, To suggest Intersection Notifications standard of installation in Living Street, We execute on-site survey in priority to Gwangju Metropolitan City. Furthermore, After We suggest experimental value for the Intersection Notifications' standard of installation Prediction model in the Living street, Intersection Notifications compare & veritfy experimental value to the installation point's value to suggest the standard of installation in the living street. As a result, We can prevent frequent traffic accident in the Living Street. Furthermore, We are judged by installation of intersection Notifications considering stability and convenience to the passengers who are using the living street.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6C
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• pp.429-437
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• 2008

Multiple-input multiple-output (MIMO) techniques can be used for the spectral efficiency enhancement of the cellular systems, which can be categorized into spatial multiplexing (SM) and spatial diversity schemes. MIMO systems suffer a severe performance degradation due to the intercell interference from the adjacent cells as the mobile terminal moves toward the cell boundary. Therefore for the spectral efficiency enhancement, an appropriate transmission scheme for the given channel environment and reception scheme which can mitigate the intercell interference are required. In this paper, we propose an adaptive signal transmission/reception scheme for the spectral efficiency improvement of $M_R{\times}M_T$ MIMO systems, present the decision criteria for the adaptive operation of the proposed scheme, and demonstrate the performance gain. The proposed scheme performs adaptive transmission using spatial multiplexing and spatial diversity, and adaptive reception using maximal ratio combining (MRC) and intercell spatial demultiplexing (ISD) when the spatial diversity transmission is used at the transmitter. Spatial multiplexing/demultiplexing is performed at the high signal-to-interference ratio (SIR) range, and the transmit diversity in conjunction with the adaptive reception uses either conventional MRC or ISD which can mitigate the $M_R-1$ interference signals, based on the mobile location. For the performance evaluation of the proposed adaptive scheme, the probability density function (pdf) of the effective SIR for the transmission/reception methods in consideration are derived for $M_R{\times}M_T$ MIMO systems. Using the results, the average effective SIR and spectral efficiency are presented and compared with simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5C
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• pp.326-335
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• 2011

In this paper, we evaluate the performance of multi-antenna techniques adopted for the IEEE 802.16m standard. Base station is equipped with 4 or 8 antennas, and each mobile station (MS) has 2, 4, 8 antennas. The number of MSs is 4, and MIMO modes 0, 1, and 4 are evaluated. For each mimo mode, various number of data streams can be implemented, and the selected number of streams in the paper corresponds to the parameters adopted for hardware implementation. The error performance of various mimo modes presented in this paper was used as reference performance to verify successful hardware implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1355-1362
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• 2004

In this paper, we present the performance analysis of a multi-path searcher operating over Rayleigh fading channels when multiple transmit antennas are employed in the down-link of W-CDMA system. The simulation results for the receiver operating characteristics (ROC) for 1, 2, and 4 transmit antennas are presented to corroborate the theoretical analyses. We also propose a procedure to find the optimum parameters of double-dwell serial searcher according to the number of the multiple transmit antennas. Our analyses and simulations indicate that post-detection integration is not necessary when the number of transmit antennas is more than two. Finally, we found that increasing transmit diversity order does not necessarily improve the detection performance when the received pilot signal strength is relatively low. Therefore, this gives us a practical criterion on increasing transmit diversity order.