• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.9
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• pp.789-794
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• 2014

The FPGA is used to the high speed digital satellite communication on the Digital Signal Process Unit of the next generation GEO communication satellite. The high capacity FPGA has the high power dissipation and it is difficult to satisfy the derating requirement of temperature. This matter is the major factor to degrade the equipment life and reliability. The thermal control at the equipment level has been worked through thermal conduction in the space environment. The FPGA of CCGA or BGA package type was mounted on printed circuit board, but the PCB has low efficient to the thermal control. For the FPGA heat dissipation, the heat sink was applied between part lid and housing of equipment and the performance of heat sink was confirmed via thermal vacuum test under the condition of space qualification level. The FPGA of high power dissipation has been difficult to apply for space application, but FPGA with heat sink could be used to space application with the derating temperature margin.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.49-61
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• 2015

Ground Based Augmentation System(GBAS) is a system that offers an aircraft within 23 NM radius from the airport precision positioning service and precision approach service using the concept of Differential Global Positioning System(DGPS). After GBAS ground equipment installing at the airport, functionalities and performances of GBAS should be verified through the GBAS ground and flight testing. This paper describes the methods and results for GBAS flight test using the flight inspection aircraft at Gimpo International Airport. From the test results, we confirmed that the VDB data was received without misleading within the VDB coverage of Gimpo International Airport, and VDB field strength, protection level, and course alignment accuracy met the evaluation's criteria.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.695-705
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• 2002

In this paper, we propose a simple open loop transmit diversity (TD) scheme for the wideband code division multiple access (W-CDMA) systems in Rician multipath fading channels such as rural area or satellite channels where line-of-sight (LOS) paths are in presence. The proposed scheme does not require any pre-processing of transmit data, resulting in simpler structure as compared to conventional closed loop transmit adaptive array (TxAA) and open loop space-time transmit diversity (STTD). We analytically derive the probability density function of signal-to-noise ratio at the Rake receiver output and the uncoded bit error rate performance of the proposed scheme. Extensive simulation is Performed to verify the analytical performance of the proposed scheme under typical Rician multipath fading channel environments. Moreover, comparative results with the conventional TxAA and STTD are also provided. Simulation results show that the proposed scheme shows slightly better performance than the conventional open loop STTD under the channels with very weak LOS components, however, it significantly outperforms the STTD under the channels with dominant LOS components, and achieves a close performance of ideal closed loop TxAA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.857-864
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• 1998

The infuluence of Doppler effects on the tracking performance of a noncoherent second-order delay locked loop (DLL) operating on a data modulated signal is investigated. For the perfoermance analysis we consider the tracking accuracy (steady state error and jitter) of the linear DLL and the reliability of the nonlinear loop. The nonlinear analysis concerning the loop reliability makes use of an asympototic expansion for the MTLL(mean time to lose lock) which has been derived by applying the singular perturbation method. In particular, we give optimal loop parameters and the optimal bandwidth of the bandpass filter in the loop arms to achieve a maximum MTLL. Since Doppler effects can be producesd comparatively in LEO system, we can espect the more reliable DLL loop design. by using the results of the circuit simulation, the delay lock loop is synthesized in FPGA, and verified to get the GPS data from the STR-2770 GPS simulator system. So, the synthesized logic circuit is shown be accurately performed.

• The Journal of the Convergence on Culture Technology
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• v.1 no.1
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• pp.79-85
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• 2015

According to the growing use of the personal GPS in the mobile device recently, the LBS (Local bases service), which processes and refines the GPS information, such as a position-tracking service, a public safety service, a local based information service, has increased steadily. Due to the refraction or reflection of GPS, however, it is impossible to use GPS around or in buildings. Therefore, it is necessary to correct the errors of GPS. We propose the method which corrects the errors of GPS and creates the refined trajectory using intersection region indexing. After analyzing the trajectory, receiving trajectories from many people and identifying the similarity between of trajectories, we will recommend the favorite route and useful information such as restaurant, convenience store, bus station and emergency call service.

• Journal of Digital Contents Society
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• v.9 no.3
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• pp.483-490
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• 2008

In this paper, we propose an active location acquisition terminal needing to construct an infrastructure based on a LBS and analyze the performance in real field. The proposed terminal is compounded with a GPS module and a CDMA module, so it can get the location information independently using satellite GPS signal and the proposed terminal can decide a user location with the location information of a base station in satellite GPS shadowed area. This is the distinguishable location acquisition method from the conventional A-GPS, and it complements a disadvantage of the conventional GPS. From these results, we can confirm that the proposed active location acquisition terminal is suitable to the requirements for the LBS which are the independent location acquisition ability, the continuity in the location information acquisition and the maintenance in the location information security.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.6
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• pp.659-667
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• 2009

In this study, an integrated GNSS Simulator called Inha GNSS Simulation System (IGSS) using 3D spatial information was developed and validated. Also positioning availability and accuracy improvement were evaluated under the integrated GNSS environment using IGSS. GPS and GLONASS satellite visibility predictions were compared with real observations, and their frequency of error were 6.4% and 7.5%, respectively. To evaluate positioning availability and accuracy improvement under the integrated GNSS environment, the Daejeon government complex area was selected to be the test site because the area has high-rise buildings and thus is susceptible to signal blockages. The test consists of three parts: the first is when only GPS was used; the second is when both GPS and GLONASS were simulated; and the last is when GPS, GLONASS, and Galileo were used all together. In each case, the number of visible satellites and Dilution Of Precision were calculated and compared.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.226-232
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• 2015

As the age of smart device has come, recently many application services related to smart phone are developing. The LBS(Location Based Service) technique is considered as one of the most important techniques to support location based application services. Usually the smart phone acquires the information of position by using the position recognition systems and sensors such as GPS(Global Positioning System) and G-Sensor. However, since the GPS signal from the satellite can hardly be received in the indoor environments, new LBS techniques for the indoor environment are required. In this paper, to solve the problem a position information transceiver using LED lights and smart phone camera sensor is proposed. We proved the possibility of the proposed positioning system through the experiments in the laboratory for the practical verification.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2073-2078
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• 2014

Based on the DGPS radio wave measurement in the coast of the yellow-sea, south-sea and east-sea, the DGPS service regions in the korean coastal ferry route are analyzed in this paper. The impact of obstacles on the propagation due to the archipelago and island regions are measured and analyzed in the point of service region. The ocean-based DGPS reference stations provide the wide DGPS ocean service regions with signal strength more than $40dB{\mu}V/m$ and signal-to-noise ratio more than 10 dB. Based on the overlapping of the service regions between the DGPS reference stations, the DGPS services with good quality are provided in the coastal ferry route segments. In case of regions where the propagation obstacles are scattered, the increasingly good service can be provided under conditions of output power reinforcement and antenna efficiency enhancement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11C
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• pp.1581-1591
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• 2004

In this paper, we investigate the design of three low-complexity joint estimation algorithms(LJEAs) for frequency offset and carrier phase. The proposed LJEAs are based on the interpolation technique of correlation values of the received signal in frequency and phase domains. With these algorithms, the estimation ranges $\Delta$f$_{d}$${\times}$T$_{s}$ . are less than 1/2N$_{s}$ , and 1/N$_{s}$ which are comparable to conventional algorithms. The Proposed LJEAs require only 2N$_{s}$ or 4N$_{s}$ complex multiplications which are very simple compared with the conventional algorithms. Nevertheless the estimation accuracies of the LJEAs are as good as those of the conventional algorithms. Suitable areas of application include joint estimation of frequency offset and carrier phase in burst-mode digital transmission such as satellite communications.