• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.722-724
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• 2010

CAS(Conditional Access System) was developed for paid-for service in cable and fixed satellite broadcast system and technology and market maturity are high. However, these assessment is limited by CAS in fixed broadcasting system. In case of digital mobile broadcast such as T-DMB is difficult to apply CAS technology of fixed broadcasting system because of a use method and technology characteristic. Expecially, in case T-DMB using limited resources, a CAS message which must transmit in each service channel can cause problems. It is desirable that system transmits the CAS message which transmitted by each service channel through logical CAS message-only channel. In order to make a logical CAS message channel, we need a multiplexing techniques for CAS message using in each channel. In this paper, we design the CAS message multiplexing techniques for composition of CAS message-only channel.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.811-818
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• 2013

In this paper, we have designed the elliptical dual offset gregorian antenna which can use Ka band earth station antennas in the fixed-satellite service. The structure of antenna is increasing the antenna gain by decreasing blockage areas and decreasing wind effects by shortening height of the antenna. The corrugate horn antenna for this antenna has symmetric radiation patterns and low side lobe levels that can meet ITU-R envelope. The distribution of electric field on a aperture of main reflector is calculated by an ray-tracing method that use the radiation pattern of the feed horn. The final geometric of antena is decided by choosing the distribution that comply with antenna requirement. The FEKO analysed electrical performance of this antenna. The fabricated antenna has 45.0dBi(@30.0GHz)/41.7dBi(@20.2GHz), high efficiency and low side lobe level that meet ITU-R S. 580-6 envelope.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.2
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• pp.75-82
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• 2021

Fields of high-precision positioning applications are growing fast across the mass market worldwide. Accordingly, the industry is focusing on developing methods of applying State-Space Representation (SSR) corrections on low-cost GNSS receivers. Among SSR correction types, this paper analyzes Safe Position Augmentation for Real Time Navigation (SPARTN) messages being offered by the SAfe and Precise CORrection DAta (SAPCORDA) company and validates positioning algorithms based on them. The first part of this paper introduces the SPARTN format in detail. Then, procedures on how to apply Basic-Precision Atmosphere Correction (BPAC) and High-Precision Atmosphere Correction (HPAC) messages are described. BPAC and HPAC messages are used for correcting satellite clock errors, satellite orbit errors, satellite signal biases and also ionospheric and tropospheric delays. Accuracies of positioning algorithms utilizing SPARTN messages were validated with two types of positioning strategies: Code-PPP using GPS pseudorange measurements and PPP-RTK including carrier phase measurements. In these performance checkups, only single-frequency measurements have been used and integer ambiguities were estimated as float numbers instead of fixed integers. The result shows that, with BPAC and HPAC corrections, the horizontal accuracy is 46% and 63% higher, respectively, compared to that obtained without application of SPARTN corrections. Also, the average horizontal and vertical RMSE values with HPAC are 17 cm and 27 cm, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.1
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• pp.115-125
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• 1998

This paper examined the feasibility of adding a new NGSO/MSS(Non-Geostationary orbit/Mobile satellite service) service link to a frequency band which is already allocated to fixed-service microwave(M/W) system. To achieve this goal, the NGSO/MSS handset performance under the influence of the M/W multiple stations and the influence of handsets on the M/W station were both analyzed. Sharing criterions were also obtained by means of coordination contour in the former case, and handset capacity in the latter case. As the results, it was proven that sharing was feasible only when the vertical distance between handset and trendline was above 4 km except front and back points of M/W antenna bore sight under influence of 9 hops(the distance between hops = 50 km) M/W system on the NGSO/MSS handset, and only when the capacity of handset was below $7.0\times10^{-14}$ handsets/ $m^{2}$ under influence of handsets on the M/W station.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.610-614
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• 2003

The bands 27.5 - 28.35GHz and 31.0 - 31.3GHz were allocated to the High Altitude Platform Station in WRC-2000. However, since these bands were already allocated to the existing fired-satellite service, the analysis on the interference effects between the existing FSS/GSO system and FS/HAPS system should be needed. To do study on the interference effects between above two systems, we can consider two frequency operational renditions, one is the Reverse mode and the other Forward mode. In this paper, we considered the Forward mode as the frequency operational condition and analyzed the interference effect from a number of GSO satellites to HAPS ground station due to the I/N values, the latitude of HAPS and the satellite separation. In future, these results will be vital data to share between HAPS and GSO systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.696-708
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• 1992

In this study, we have several objectives. First, In spite of a fixed bandwidth waste of reservation channel, we maximize the efficiency of transmission channel by the multiple access algorithm that performs channel reservation and data transmission independently, eliminating the frame structure of transmission channel and reserving it by the slot unit . Second, In order to improve the entire system performance, we accommodate the variation of traffic at each earth station more effectively, and accomplish the stable delay characteristics and the equlity of service #or users. For this purpose, we design the satellite channel that consists of reservation channel and transmission channel which are logically separate and operate Independently. We also design a demand assignment multiple access algorithm based on the satellite channel structure.

• Journal of IKEEE
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• v.28 no.3
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• pp.440-444
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• 2024

This paper presents a solution to the frequency coexistence problem between low earth orbit (LEO) satellite networks and other services by utilizing genetic algorithms. Non-terrestrial network (NTN) utilizing LEO satellites have mobility and need to address interference issues that may occur when sharing frequencies with terrestrial services according to propagation rules. In this study, we model the interference scenario based on the NTN operation scenario proposed by 3GPP, and derive the optimal channel allocation scheme for NTNs to protect terrestrial services while satisfying the minimum quality of service (QoS) through genetic algorithm. The simulation results show that the proposed method outperforms the existing fixed assignment method and graph coloring method, and enables efficient frequency sharing.

• Journal of the Korea Society of Computer and Information
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• v.11 no.5 s.43
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• pp.39-52
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• 2006

As accelerates the technical evolution of high-speed network and progresses the digitalization of broadcasting network, TV channel service through satellite/cable/terrestrial networks becomes more stable and mature. However, TV channel service using IP network such as IPTV is recently emerging. Especially, when it comes to current mosaic EPG(Electronic Program Guide) as a channel guide, the implementation of EPG via IP network is under developing. Furthermore, the personal target mosaic EPG is not provided at all in the IPTV. This paper proposes a construction method of mosaic system which can support fixed and personalized mosaic EPG using IP network for viewers. The fixed mosaic EPG is made several steps as follows ; First, H/E generates several mosaic A/V streams. Then, which are transmitted to the STB in terms of multicasting via IP network. Finally, mosaic EPG is displayed on TV through STB. In addition, this paper describes a construction model of the personalized A/V mosaic EPG that represents each person's favorite channels according to their tastes and interests. As for the contributions. The TV channel guide using IP network enable viewer to select channel more easily with practical adaptation of multi-channel expansibility and sufficient usability. In addition, through personal mosaic EPG, a number of viewers can compose their own mosaic EPG and enjoy a variety of channel easily in accordance with their preferences. Finally, the personal mosaic EPG can prohibit non-adult users from connecting adult-only contents more efficiently.

• Electronics and Telecommunications Trends
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• v.19 no.4 s.88
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• pp.89-95
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• 2004

본 문서에서는 WRC-2003 회의에서 결정된 차기 회기동안 연구하여야 할 연구 의제 중 1.19 ‘글로벌 인터넷 액세스를 위한 고정위성업무의 스펙트럼 연구’에 대해 2004년 4월에 개최된 ITU-R WP4A에서 논의된 사항을 중심으로 위성 인터넷 액세스 서비스의 배경 및 연구 현황에 대해 기술하였다. 고도화되는 무선 통신 환경에서 지역간 국가간 디지털 격차를 해소하기 위하여 광대역 인터넷 액세스를 위한 위성 시스템은 좋은 해결책이 될 수 있다. 또한, 글로벌 환경에서 사용 가능하도록 적절한 주파수 대역을 찾는 일 또한 중요한 이슈가 될 것으로 예상되며, 이에 대하여 계획된 고정위성업무 주파수 대역에 대해 본 서비스의 활용 가능성에 대하여 기술하였다.

• Electronics and Telecommunications Trends
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• v.19 no.4 s.88
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• pp.96-108
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• 2004

본 문서에서는 WRC-2003 회의에서 결정된 차기 회기동안 연구하여야 할 연구 의제 중 1.19 ‘글로벌 인터넷 액세스를 위한 고정위성업무의 스펙트럼 연구’에 대해 2004년 4월에 개최된 ITU-R WP4A에서 논의된 사항을 중심으로 위성 인터넷 액세스 서비스의 배경 및 연구 현황에 대해 기술하였다. 고도화되는 무선 통신 환경에서 지역간 국가간 디지털 격차를 해소하기 위하여 광대역 인터넷 액세스를 위한 위성 시스템은 좋은 해결책이 될 수 있다. 또한, 글로벌 환경에서 사용 가능하도록 적절한 주파수 대역을 찾는 일 또한 중요한 이슈가 될 것으로 예상되며, 이에 대하여 계획된 고정위성업무 주파수 대역에 대해 본 서비스의 활용 가능성에 대하여 기술하였다.