• Journal of Communications and Networks
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• 제13권5호
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• pp.494-498
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• 2011

Satellite digital multimedia broadcasting (S-DMB) systems use gap fillers (GFs) to provide wireless multimedia services to non-line-of-sight locations. GFs act as repeaters, and S-DMB systems require GF networks in order to guarantee mobile reception. Each GF covers a cell or sector. In order to provide contiguous coverage of an area comprising two or more cells or sectors, multiple GFs are needed. However, when multiple GFs are situated close to each other, interference is likely to occur. As a result, in this study, we have investigated system-level environments for planning the design of interference-free GF networks in S-DMB systems. Our investigations revealed that S-DMB services are unavailable because of quality deterioration caused by interference when the delay attributable to a GF and the satellite signals exceeds ${\pm}$256 chips and the distance between the GF and its reception terminal is greater than 4.6 km. On the basis of this analysis, we conducted a field test that confirmed that the above-mentioned time delay can be controlled in such a way as to ensure high quality S-DMB services.

• International Journal of Internet, Broadcasting and Communication
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• 제13권3호
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• pp.148-154
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• 2021

We propose the AI Smart Factory Model for integrated management of production processes in this paper .It is an integrated platform system for the production of food packaging containers, consisting of a platform system for the main producer, one or more production partner platform systems, and one or more raw material partner platform systems while each subsystem of the three systems consists of an integrated storage server platform that can be expanded infinitely with flexible systems that can extend client PCs and main servers according to size and integrated management of overall raw materials and production-related information. The hardware collects production site information in real time by using various equipment such as PLCs, on-site PCs, barcode printers, and wireless APs at the production site. MES and e-SCM data are stored in the cloud database server to ensure security and high availability of data, and accumulated as big data. It was built based on the project focused on dissemination and diffusion of the smart factory construction, advancement, and easy maintenance system promoted by the Ministry of SMEs and Startups to enhance the competitiveness of small and medium-sized enterprises (SMEs) manufacturing sites while we plan to propose this model in the paper to state funding projects for SMEs.

• ETRI Journal
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• 제27권5호
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• pp.635-638
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• 2005

Spatial audio coding (SAC) is an extremely high compact representation of encoded multi-channel audio material. This paper suggests a multi-channel audio service in the terrestrial digital multimedia broadcasting (T-DMB) system using a novel SAC tool, which is called a virtual source location information (VSLI)-based SAC tool. Intensive experiments are presented to evaluate the validity of the proposed VSLI-based SAC tool, and prototypical systems are also presented to demonstrate the reliability of the proposed multi-channel T-DMB system in real applications.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.527-530
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• 2002

The frequencies for HAPS used in fixed wireless access are allocated in the millimeter wave bands. The systems using these frequencies can have a serious impact on the radio communication qualities due to rain. In this paper, we compare the specific rain attenuation using CM(combined) raindrop size distribution with those using different sevral raindrop size distributions for the frequency bands 28/48㎓. The rain attenuations using CM raindrop size distribution for the path between the earth and HAPS platform according to the elevation angle are described.

• 방송공학회논문지
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• 제5권2호
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• pp.220-226
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• 2000

본 논문에서는 방송용 음성에 워터마크를 삽입하는 방법을 제시했다. 디지털 방송에서는 오디오와 음성을 일부러 구별하지는 않는다. 그러나 교육방송에서는 음성의 중요성이 비디오나 오디오에 비해 훨씬 크고 컨텐츠에서 차지하는 비중도 높다. 디지털 방송에서 중요한 이슈 가운데 하나가 바로 불법복제에 대한 대비책이다. 이 논문에서는 음성용으로 변형한 오디오 워터마크의 성능과 한계에 대해 설명하고, 공격에 대한 내성 결과를 제시했다. 그리고 음성 워터마크 연구에서 해결해야 할 과제들을 제시했다.

• ETRI Journal
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• 제38권5호
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• pp.799-806
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• 2016

In this paper, we propose an emergency wake-up alert system (EWAS) for providing accurate and rapid emergency information. The proposed system can provide an emergency wake-up alert service without an additional frequency allotment by utilizing the guard band of the Advanced Television Systems Committee (ATSC) Terrestrial Digital Television (DTV) system. The design target of the proposed system is to match the indoor reception coverage of EWAS with the outdoor reception coverage of the ATSC DTV system. To achieve this, the proposed system should be about 35.65 dB more robust than the ATSC DTV system. The simulation results show that the proposed system offers an emergency wake-up alert service supporting a data rate of up to 23 bps.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.556-558
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• 2008

Secure broadcasting is requirement for payment of TV systems, government or company. Hierarchical key management for access control provides efficient key management in those environment. Also, time-bound hierarchical key management technique generates different keys in each time period. In 2004, Tzeng proposed a time-bound cryptgraphic key assignment scheme for access control in a hierarchy and in 2008, Bertino et al proposed an efficient time-bound hierarchical key management scheme for secure broadcasting. Tzeng's scheme and Bertino et al's scheme are organized in different environment and primitive. In this paper, we analysis above two time-bound hierarchical key management scheme.

• ETRI Journal
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• 제27권1호
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• pp.43-52
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• 2005

In this paper, we introduce an adaptive radio resource allocation for IP-based mobile satellite services. We also present a synchronous multibeam CDMA satellite system using an orthogonal resource sharing mechanism among downlink beams for the adaptive packet transmission. The simulation results, using a Ka-band mobile satellite channel and various packet scheduling schemes, show that the proposed system and resource allocation scheme improves the beam throughput by more than two times over conventional systems. The simulation results also show that, in multibeam satellite systems, a system-level adaptation to a user's channel and interference conditions according to user locations and current packet traffic is more efficient in terms of throughput improvement than a user-level adaptation.

• 대한전자공학회논문지TC
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• 제46권11호
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• pp.61-65
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• 2009

신규 통신시스템을 도입할 경우 인접한 주파수 대역을 사용 중인 기존 통신시스템에 대한 간섭이 일정 수준 이하가 되도록 신규 통신 시스템의 송신 전력 및 중심 주파수를 설정하여야한다. 이를 위하여 기존 통신시스템의 최저 수신 성능 기준을 만족시키는 두 시스템 간 송신 전력 비 (Power ratio)인 보호비 (Protection ratio) 도출이 필수적이다. 본 논문에서는 전산 실험을 바탕으로 ATSC (Advanced Television Systems Committee) 디지털 방송 시스템과 WiBro (Wireless Broadband Internet) 시스템 간 보호비를 도출하는 방안을 제안한다. 이를 위하여 ATSC 디지털 방송시스템의 송수신기를 모델링하고 간섭 신호로 WiBro 시스템의 송신기를 모델링하여 두 시스템 간 보호비를 도출하였다. 이 결과는 아날로그 방송 종료 후 잉여 주파수에 신규 서비스를 도입할 경우 유용하게 활용될 수 있을 것으로 예상된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.139-142
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• 1998

This paper presents a method to determine the rolloff factors of both the digital terrestrial TV modulator and the bandpass filter (BPF) at the digital TV receiver input, using an analytical power spectral density model satisfying given co-channel and adjacent channel protection ratios for the digital terrestrial broadcasting services. Since the proposed method is very simple and effective to use, also can be used regardless of type of systems or modulation techniques, this method is expected to be applied to select some other digital terrestrial broadcasting system specifications.