• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.505-513
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• 2009

Recently, researches on the construction information for construction of high-tech cities are under performed. RTLS(Real-Time location system) for gathering the dynamic location information of construction resources in construction sites, such as workers, materials and equipments, is one of the developments. Especially, construction resources can be managed efficiently with the dynamic location information and the improvement of safety and the reduction of cost are expected. To introduce the RTLS to the construction sites, the installation location of AP(Access Point) must be simulated using the 3-dimensional visibility analysis considering the propagation distance of AP. In this research, 3-dimensional signal simulation software based on the spatial data using surveying terrestrial LiDAR is developed. The simulated results are compared with the signal strength of field experiments for 4 test sites. As a result, the signal strength from the propagation model is most similar to that of field experiment at the front of the main building and the maul playground of Konkuk University. The visibilities in that sites are higher than other sites. among 4 test sites.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.551-560
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• 2011

Recently, There has been increasing concern about WLAN-based indoor positioning system. Most of the existing WLAN-based positioning systems use a fingerprinting method as a main approach. In the fingerprinting approach, the accuracy of the location of a mobile objects is proportional to the number of reference points. However, depending on the increasing number of reference points in the training phase, it requires more time and effort to create fingerprint database. To solve these problems, we propose the new indoor positioning algorithm that calculate the distance between a mobile objects and an AP using the information of surrounding environment WLAN based APs and applied the particle filter to the proposed algorithm in order to improve the accuracy of the estimated location in this paper. To implement this algorithm, at first environmental information database such as wall, iron door, glass door, partition etc. existing in the periphery of the AP should be established. The positioning use attenuation model and path loss model. Our experimental results with proposed algorithm are verified that the positioning accuracy was low but solved the problems with fingerprinting, compared with other positioning algorithms.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.367-367
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• 2020

최근 전세계적으로 기후변화로 인해 가뭄의 발생 가능성이 높아지고 있으며 그에 대한 인적피해와 경제적 손실로 인한 피해액은 증가하고 있다. 특히, 국내의 충남지역은 최근 강수량이 평년 대비 75% 수준으로 감소하고 있으며, 지속적인 가뭄이 발생하여 용수 확보에 어려움을 겪고 있다. 또한, 2015년에는 강수량 감소로 인해 보령댐을 상수원으로 사용하고 있는 충남 서북부지역 8개 시군의 용수공급에 큰 차질이 있었다. 지속적인 가뭄 상황이 반복되면서 기후변화의 영향에 따라 미래의 물공급량 변화 및 물부족에 대한 연구와 이를 분석하여 정확성을 높이는 물수지 분석모형이 지속적으로 개발되고 있다. 이에 본 연구에서는 가뭄이 발생한 충남지역을 대상으로 기후변화에 따른 미래 물부족 변화에 대한 경향성을 파악하고자 한다. 미래의 물부족 변화를 파악하기 위해 기상청 RCP 8.5 시나리오의 40년(2008~2047년) 중권역별 강수량과 잠재증발산량 일단위 자료를 수집하였다. 수집된 중권역별 기상자료를 하천유역별 일단위 기상자료를 활용하여 TANK 모델을 이용한 하천 일유출모의와 비유량법을 이용하여 저수지의 일유량을 산정하였다. 미래의 수혜면적변화와 생활/공업/농업 수요량 추정을 통해서 하천 및 저수지 물수지 분석을 진행하여 미래기간 30년에 대한 일단위 물수급을 산정하였다. 미래기간에 대한 분석은 기준기간 R0(2008~2017년) 대비, 미래기간 S1(2018~2027년), S2(2028~2037년), S3(2038~2047년)에 대한 연평균 물부족량과 경로별 경향성을 파악하였다. 대상지역의 물부족량에 대한 분석결과, 기준기간 대비 S1, S2, S3 기간에 각각 27.8%, 10.8%, 23.1% 감소하는 경향이 나타났다. 이는 미래의 강우량이 점차 증가하는 경향과 수혜면적 변화시 논과 밭 면적이 지속적인 감소로 인해 수요량에 영향을 받았을 것으로 판단된다. 본 연구 결과를 바탕으로 장래 하천유역의 가뭄에 대한 피해 예측 및 물수급 파악에 활용될 수 있을 것으로 판단된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.585-597
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• 2004

In this paper, we propose the functional models of optical burst switching (OBS) routers to apply GMPLS (Generalized Multiprotocol Label Switching) to optical networks based on OBS. In addition, we introduce a connection admission control (CAC) algorithms which are operated in this models and can accommodate the required QoS. Firstly, the characteristics of current GMPLS and OBS for the optical Internet are basically considered. With this consideration, the models are proposed to accept OBS features which include the recognition of data boundary with control information and the statistical multiplexing in terms of bursts. Secondly, we use an offset time decision (OTD) algorithm on behalf of controlling the connection admission with taking QoS parameters such as burst loss rate(BLR) and service-differentiation ratio(SDR) into consideration. The proposed CAC algorithms use the offered load of LSP (Label Switched Path), wavelength information, and QoS parameters as inputs of OTD algorithm. A call setup request will be accepted when the offset time decided by OTD algorithm is reasonable for guaranteeing its requested QoS. Simulation is used for performance evaluation. Results show the proposed schemes can guarantee the required QoS and those are better than the previous one in terms of channel utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9B
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• pp.778-790
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• 2004

In this paper, we propose the functional models of optical burst switching (OBS) routers to apply GMPLS (Generalized Multiprotocol Label Switching) to optical networks based on OBS. In addition, we introduce a connection admission control (CAC) algorithms which are operated in this models and can accommodate the required QoS. Firstly, the characteristics of current GMPLS and OBS for the optical Internet are basically considered. With this consideration, the models are proposed to accept OBS features which include the recognition of data bounda η with control information and the statistical multiplexing in terms of bursts. Secondly, we use an offset time decision (OTD) algorithm on behalf of controlling the connection admission with taking QoS parameters such as burst loss rate(BLR) and service-differentiation ratio(SDR) into consideration. The proposed CAC algorithms use the offered load of LSP (Label Switched Path), wavelength information, and QoS parame ‘ ers as inputs of OTD algorithm. A call setup request will be accepted when the offset time decided by OTD algorithm is reasonable for guaranteeing its requested QoS. Simulation is used for performance evaluation Results show the proposed schemes can guarantee the required QoS and those are better than the previous one in terms of channel utilization.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.63-77
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• 2015

Tsunami take away life, wash houses away and bring devastation to social infrastructures such as breakwaters, bridges and ports. The coastal structure targeted object in this study can be damaged mainly by the wave pressure together with foundation ground failure due to scouring and liquefaction. The increase of excess pore water pressure composed of oscillatory and residual components may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, the bore was generated using the water level difference, its propagation and interaction with a vertical revetment analyzed by applying 2D-NIT(Two-Dimensional Numerical Irregular wave Tank) model, and the dynamic wave pressure acting on the seabed and the surface boundary of the vertical revetment estimated by this model. Simulation results were used as input data in a finite element computer program(FLIP) for elasto-plastic seabed response. The time and spatial variations in excess pore water pressure ratio, effective stress path, seabed deformation, structure displacement and liquefaction potential in the seabed were estimated. From the results of the analysis, the stability of the vertical revetment was evaluated.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.62-68
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• 2016

The fingerprint, which is one of the methods of indoor localization using WiFi, has been frequently studied because of its ability to be implemented via wireless access points. This method has low positioning resolution and high computational complexity compared to other methods, caused by its dependence of reference points in the radio map. In order to compensate for these problems, this paper presents a radio map designed algorithm based on the log-distance path loss model fusing a WiFi and BLE fingerprint. The proposed algorithm designs a radio map with variable values using the log-distance path loss model and reduces distance errors using a median filter. The experimental results of the proposed algorithm, compared with existing fingerprinting methods, show that the accuracy of positioning improved by from 2.747 m to 2.112 m, and the computational complexity reduced by a minimum of 33% according to the access points.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.3
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• pp.51-58
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• 2010

According to dramatic increase of wireless communication demand, more spectrum resources are needed to support considerable and various wireless services, so cognitive radio(CR) was proposed to reuse unused frequency efficiently. Also, FCC revises its policies regarding the usage of the TV white spaces by unlicensed users. CR is an intelligent wireless communication system that is aware of the radio environment and is capable of adapting its operation to the statistical variations. Spectrum sensing is the key task of the CR systems. However, since spectrum sensing performance changes according to the received signal that is received various geography environment, regional characteristics are considered to estimate the path-loss. Therefore, for more accurate analysis and simulation, we demonstrate the spectrum sensing performance of CR system by various method applying Okumura-hata propagation model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.7
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• pp.449-458
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• 2014

In the context-aware services, localization is an important technical element. Due to the easy to use and low cost, it was widely enabled with RF properties such as RSSI. However, RSSI is known to be not appropriated for indoor localization, because it tends to show big variance in time and is greatly effected with the multipath. This paper proposes a distance estimation process and its constituted methods for indoor localization, by making use of the other WLAN's RF property, CSI(Channel State Information). Firstly we define a comprehensive localization process, and suggest a calibration algorithm of environment factors in the path loss propagation model. Then, by implementing them with a commercial WLAN module, an the proposed process and methods are evaluated in terms of usefulness.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.436-447
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• 2013

In this paper, Integrated circuit(IC) electromagnetic(EM) conducted immunity measurement and simulation using bulk current injection(BCI) and direct power injection(DPI) methods were conducted for 1.8 V I/O buffers. Using the equivalent circuit models developed for IC electromagnetic conducted immunity tests, we investigated the reliability of the frequency region where IC electromagnetic conducted immunity test is performed. The insertion loss for the noise injection path obtained from the simulation indicates that using only one conducted immunity test method cannot provide reliable conducted immunity test for broadband noise. Based on the forward power results, we analyzed the actual amount of EM noise injected to IC. We propose a more reliable immunity test methods for broad band noise.