• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.309-317
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• 2024

Satellite and receiver Inter-Frequency Biases (IFBs) should be estimated or calibrated by pre-defined values for generating precise navigation messages and augmentation data in satellite navigation systems or the augmentation system. In this paper, a Kalman filter is designed and implemented to estimate the ionospheric delay and satellite/receiver IFBs using a regional receiver network. First, an ionospheric model and its filter parameter is defined based on previous studies. Second, a measurement model for estimating the relative satellite/receiver IFBs without any constraints is proposed. Third, a procedure for ensuring the continuity of estimation is proposed in this paper. To verify the performance of the designed filter, six Continuously Operating Reference Stations (CORSs) are selected. Finally, the stability and accuracy of satellite/receiver IFB estimation are analyzed.

• Journal of Aerospace System Engineering
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• v.14 no.6
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• pp.26-35
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• 2020

The national satellite operation network, which supports multiple satellites, was designated as a Critical Information Infrastructure (CII) in 2017. The network was designed independently from the control network and the information network to enhance physical security. Planning is underway to establish a bidirectional data interface between networks. The data transmission system allows data flow only to the physical layer and the data link layer; hence, only one file can be transferred at any one time. This means that when large amounts of data are being transmitted, no other data can be sent simultaneously in urgent situations. Thus, this paper discusses the design of flexible packets for the transmission of data between networks in an environment where physical security has been enhanced through network separation and based on this, presents a method for transmitting data effectively.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.169-180
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• 2019

In this study, a batch least square estimator that utilizes optical observation data is developed and utilized to determine geostationary orbits (GEO). Through numerical simulations, the effects of error sources, such as clock errors, measurement noise, and the a priori state error, are analyzed. The actual optical tracking data of a GEO satellite, the Communication, Ocean and Meteorological Satellite (COMS), provided by the optical wide-field patrol network (OWL-Net) is used with the developed batch filter for orbit determination. The accuracy of the determined orbit is evaluated by comparison with two-line elements (TLE) and confirmed as proper for the continuous monitoring of GEO objects. Also, the measurement residuals are converged to several arcseconds, corresponding to the OWL-Net performance. Based on these analyses, it is verified that the independent operation of electro-optic space surveillance systems is possible, and the ephemerides of space objects can be obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.666-676
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• 2004

We must design the buffer algorithm that protects traffic congestion and decreasing throughput at satellite communication network. It is important that buffer algorithm is satisfied with the good performance of transmission packet, responsibility of many connecting traffic and the 005 for connecting character. Old buffer algorithms are not the suitable algorithms when we have the satellite communication network environment. RED buffer algorithm is proposed by Floyd. It has a better performance than old buffer algorithm. But this algorithm is not well adapted a number of connecting TCP packet and changing network, so this algorithm has a bad Performance on satellite communication network that is many of connecting user at same time. This paper Propose the TARED(Target Adaptive RED). It has a good performance, adaptation and stability on satellite communication network and has not overflow and underflow of the buffer level.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.170.4-170
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• 2001

Safety and confidence of the communications network is the main purpose for the unmanned control systems, in terms of appling a satellite communications network to the water treatment and supply plant communication system. Since the unmanned control systems were applied in the industrial site, the lack of confidence on the communications network has been presented continuously as a main problem for the unmanned and automation systems. Therefore, satellite communications network was presented as one of the methods to solve this problem, supporting the wire used telecommunication. In addition to the safety of a communications network, there is the retrenchment of expenditure. This dual communications network has ...

• Journal of IKEEE
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• v.15 no.1
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• pp.86-95
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• 2011

In this paper, we propose a testbed system for the crisis management system of the power grid(CMS-PG) using satellite communication network. For the verification of CMS-PG, the proposed system composed of the simulator of satellite communication network and the simulator of phase measurement unit. Proposed satellite communication simulator can evaluate the delay and the robustness of the communication according to the rainfall and the humidity of local site. And the proposed simulator can calculates the voltage stability by hardware implementation using FPGA. Using the proposed testbed system, we adapted its function of crisis management system for the conventional power grid.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.896-899
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• 2002

In this paper, we present the experimentation and demonstration results of Korea-Japan high-speed satellite ATM network using Ka-band Koreasat-3. This experimentation consists of two items - TCP/IP and MPEG-2 video/audio transmission over 155Mbps ATM based satellite network. The goals of this experimentation are to measure TCP performance when the only standard mechanisms approved by IETF in order to improve TCP performance in LFN(long fat network) are used and to derive the effects of quality for the high definition video stream when MPEG-2 TS is transmitted through 155Mbps satellite ATM link. With on the results of the experiments, we demonstrated the applications suitable to the high-speed satellite ATM network. The first TCP/IP and MPEG-2 transmission experiments were done at the rate of 155Mbps using Ka-band KOREASAT-3 between Korea and Japan, and its results will be demonstrated with the ATM-based 3D-HDV(3 dimensional High definition video) and HDTV during 2002 Korea-Japan World Cup Soccer Game.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.9
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• pp.3152-3171
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• 2022

This work investigates the physical layer secrecy of a multi-antenna hybrid satellite-terrestrial relay networks (HSTRN) with jamming, in which a satellite aims to make communication with a destination user by means of a relay, along with spatially random eavesdroppers. In order to weaken the signals of eavesdroppers, the conventional relay can also generate intentional interference, besides forwarding the received signal. Shadowed-Rician fading is adopted in satellite link, while Rayleigh fading is adopted in terrestrial link, eavesdropper link and jamming link. The analytical and asymptotic formulas for the system secrecy outage probability (SOP) are characterized. Practical insights on the diversity order of the network are revealed according to the asymptotic behavior of SOP at high signal-to-noise ratio (SNR) regime. Then, analysis of the system throughput is examined to assess the secrecy performance. In the end, numerical simulation results are presented to validate the theoretical analysis and point out: (1) The secrecy performance of the considered network is affected by the channel fading scenario, the system configuration; (2) Decrease of the relay coverage airspace can provide better SOP performance; (3) Jamming from the relay can improve secrecy performance without additional network resources.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.382-388
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• 2022

Satellite communication for high altitude platform stations (HAPS) and low earth orbit (LEO) systems suffer from dust and sand (DU&SA) storms in the desert regions such as Saudi Arabia. These attenuations have a distorting effect on signal fidelity at high frequency of operations. This results signal to noise ratio (SNR) to dramatically decreasing and leads to wireless transmission error. The main focus in this paper is to propose common relations between HAPS and LEO for the atmospheric impairments affecting the satellite communication networks operating above Ku-band crossing the propagation path. A double phase three dimensional relationship for HAPS and LEO systems is then presented. The comparison model present the analysis of atmospheric attenuation with specific focus on sand and dust based on particular size, visibility, adding gaseous effects for different frequency, and propagation angle to provide system operations with a predicted vision of satellite parameters' values. Skillful decision and control system (SD&CS) is proposed to control applied parameters that lead to improve satellite network performance and to get the ultimate receiving wireless signal under bad weather condition.

• Journal of IKEEE
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• v.27 no.4
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• pp.456-463
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• 2023

In this paper, we introduce the SSResUNet network model, which integrates the SPADE structure with the U-Net network model for accurate land cover classification using high-resolution satellite imagery without requiring user intervention. The proposed network possesses the advantage of preserving the spatial characteristics inherent in satellite imagery, rendering it a robust classification model even in intricate environments. Experimental results, obtained through training on KOMPSAT-3A satellite images, exhibit superior performance compared to conventional U-Net and U-Net++ models, showcasing an average Intersection over Union (IoU) of 76.10 and a Dice coefficient of 86.22.