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Development of Satellite and Terrestrial Convergence Technology for Internet Services on High-Speed Trains (Service Scenarios) (고속열차대상의 위성인터넷 서비스 제공을 위한 위성무선연동 기술(서비스 시나리오 관점))

Shin, Min-Su;Chang, Dae-Ig;Lee, Ho-Jin
- Journal of Satellite, Information and Communications
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- v.2 no.2
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- pp.69-74
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- 2007
Recently, the demands for the satellite broadband mobile communication services are increased. To provide these services, mobile satellite communication systems for the passengers or crews on the high-speed moving vehicles, are being developed for the last several years especially in the Europe and North America. However, most of these systems can provide only several hundred kbps of transmission rate and this is not enough performance to provide satellite internet service for the group users such as passengers on the high-speed train. Moreover, service availability with these systems is limited to be rather low because they don't have any countermeasure scheme for the N-LOS environment which happens often along the railway. This paper describes mobile broadband satellite communication system, which is on the development, to provide high data-rate internet services to the high-speed trains. This system is applied with the inter-networking scenarios of both satellite/terrestrial network and satellite/gap-filler network so that it can provide seamless service even in the train operating environment, and these inter-networking schemes result in high service availability. And this system also has the countermeasure schemes, such as upper layer FEC and antenna diversity, for the short fading which is occurred periodically on the railway due to the power supplying structures so that it can provide high speed internet services. Mobile DVB-S2 technology which is now being standardized in the DVB is used for the forward-link transmission and DVB-RCS for the return-link.
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Preparation of Glycidylmethacrylate-Divinylbenzene Copolymers Containing Phosphoric Acid Groups and Adsorption Characteristics of Uranium(I) - Preparation of Glycidylmethacrylate-Divinylbenzene Copolymers Containing Phosphoric Acid Groups and Their Adsorption Characteristics of Uranium - (인산기를 함유한 Glycidylmethacrylate-Divinylbenzene 공중합체의 제조와 우라늄 흡착특성(제1보) - 인산기를 함유한 GMA-DVB 공중합체의 제조와 물성 -)

Huh, Kwang-Sun;Sin, Se-Geun
- Applied Chemistry for Engineering
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- v.9 no.5
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- pp.680-688
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- 1998
The macroreticular (MR) type glycidylmethacrylate (GMA)-divinylbenzene (DVB) copolymer (polyglycidylmethacrylate) beads (RG) were prepared by a suspension polymerization using 0~100 vol % of 2,2,4-trimethylpentane (TMP) as a diluent. Macroreticular type cation exchange resins containing phosphoric acid groups (RGP) were prepared by the reaction of GMA-DVB copolymer and poly (glycidyl methacrylate) bead (RG) with phosphoric acid in the presence of benzene. In this study, the effect of degree of crosslinking and the amount of the diluent on physical properties and adsorbability of uranium of RGP resins were investigated respectively. The chemical and physical properties of RGP resins were affected by both of the amount of the diluent and the degree of crosslinking. The effect of degree of crosslinking on the adsorbed amount of uranium for RGP resins were decreased in the order of $$RGP-10(50){\sim_=}RGP-1(50)>RGP-2(50)>RGP-5(50)>RGP-0$$. The effect of the diluent amount were as follows RGP-2(100)>RGP-2(75)>RGP-2(50)>RGP-2(30)>RGP-2(0). The crosslinking degree effect on uranium adsorbability depended on pore structure, cation exchange capability and swelling ratio. On the other hand, the effect of the diluent amount were relied on surface area and pore structure raher than cation exchange capability.
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A Fully Digital Automatic Gain Control System with Wide Dynamic Range Power Detectors for DVB-S2 Application (넓은 동적 영역의 파워 검출기를 이용한 DVB-S2용 디지털 자동 이득 제어 시스템)

Pu, Young-Gun;Park, Joon-Sung;Hur, Jeong;Lee, Kang-Yoon
- Journal of the Institute of Electronics Engineers of Korea SD
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- v.46 no.9
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- pp.58-67
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- 2009
This paper presents a fully digital gain control system with a new high bandwidth and wide dynamic range power detector for DVB-S2 application. Because the peak-to-average power ratio (PAPR) of DVB-S2 system is so high and the settling time requirement is so stringent, the conventional closed-loop analog gain control scheme cannot be used. The digital gain control is necessary for the robust gain control and the direct digital interface with the baseband modem. Also, it has several advantages over the analog gain control in terms of the settling time and insensitivity to the process, voltage and temperature variation. In order to have a wide gain range with fine step resolution, a new AGC system is proposed. The system is composed of high-bandwidth digital VGAs, wide dynamic range power detectors with RMS detector, low power SAR type ADC, and a digital gain controller. To reduce the power consumption and chip area, only one SAR type ADC is used, and its input is time-interleaved based on four power detectors. Simulation and measurement results show that the new AGC system converges with gain error less than 0.25 dB to the desired level within $10{\mu}s$. It is implemented in a $0.18{\mu}m$ CMOS process. The measurement results of the proposed IF AGC system exhibit 80-dB gain range with 0.25-dB resolution, 8 nV/$\sqrt{Hz}$ input referred noise, and 5-dBm $IIP_3$ at 60-mW power consumption. The power detector shows the 35dB dynamic range for 100 MHz input.
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