Joon-Gyu Ryu

Gap Filler Architectures for Seamless DVB-S2/RCS Provision in the Railway Environment

In this paper, we study the provision of broadband interactive services to passengers of Korean high-speed train in the ISM 2.4 GHz band. We address in particular the design of tunnel gap-fillers (GFs) able to provide bi-directional connectivity to train-based terminals. The work has been developed in the broader context of interactive services provision for high-speed trains through satellite networks. First, a channel model for the in-tunnel propagation is derived. Taking into account the results of the propagation analysis, a comparison between commercial technologies (belonging to both the IEEE and the DVB standard families) is provided, showing the possible strengths and weaknesses of the proposed solutions with respect to architectural and performance point of views.

Forward link ACM for satellite communication public test-bed via COMS

This paper present the detailed design and the algorithm for forward link ACM(Adaptive Coding & Modulation) system to improve the link availability and system throughput in satellite communication services. To implement ACM system, the channel prediction and MODCOD decision methods is simulated. The channel prediction result shows that the 99% of predicted values in LMS(Least Mean Square) algorithm is within 3dB. Also this paper proposes the appropriate system architecture for ACM transmission.

The feasibility study on the 4K-UHD satellite broadcasting service in Ka-band

The goal of the paper is to present an efficient way for providing satellite UHD broadcasting services via Ka frequency band and, for the purpose, to develop a service adaptation and stabilization technology which is adaptive to the channel conditions including rain attenuation.

The design of satellite mesh protocol for the DVB-RCS TDMA networks

This paper presents satellite mesh connectivity architecture based on DVB-RCS and C2P protocol, especially in terms of connection control procedure. C2P protocol provides dynamic connectivities in the diverse network scenarios over DVB-RCS system. Satellite mesh connectivities are requested in many market sectors, such as enterprise networks and government/military segments. In these network types, voice and video communications and other data applications are the most probable services that require strongly reliable mesh connectivities. DVB created C2P protocol to be adequately able to operate with its DVB-RCS standard. However, C2P protocol is so complicated to understand that it needs to make simple architecture for specific network architecture. In this paper, satellite mesh connection control procedure is addressed for transparent satellite mesh network which is the only probable option in the country.

An open-loop power control method for mobile satellite system

In this paper, we propose an architecture of open-loop power control, which is applicable to Ku/Ka-band mobile satellite systems. When a mobile terminal tries to access a HUB system initially, the location of the mobile terminal is not fixed. If the transmission power of the mobile terminal is in a low state, the probability of initial access failure may be increased. For this, we propose an open-loop power control method which can be applied to mobile terminals which are located in any beam coverage. In the mobile environment, a communication channel can be changed dynamically, and our architecture can work in a dynamic environment.

Design and implementation of mobile satellite modulator based on MF-CDMA

In this paper a mobile satellite modulator based on MF-CDMA is designed and fabricated. The mobile satellite modulator can support maximally 384 kbit/s. To support maximum transmission rate of 384 kbit/s we need 3 frequency bands. The baseband I/Q quadrature modulation and Mux is implemented in the digital block. The output of the digital part is a low IF signal, 20/spl plusmn/4.35 MHz. And then the analog block converts this low IF signal to 950/spl sim/1450 MHz by the double conversion method. The mobile satellite modulator includes a 5-bit digital attenuator, RF switch and BPF. We implemented both digital part and analog part in one PCI card. We measured the mobile satellite modulators spurious rejection at about >55dBc and the output signal flatness is <5dB at 950/spl sim/1450 MHz. And the modulator shows good IMD3, -61 dBc.

Design and implementation of multifrequency TDMA modulator for satellite terminal based on DVB-RCS

In this paper, A fast frequency hopping satellite TDMA module based on the digital video broadcasting-return channel for satellite (DVB-RCS) is proposed and implemented. The DVB-RCS standard was finalized by DVB in 2000 and it is an alternative way for accessing the Internet via satellite. In the DVB-RCS standard, the multifrequency time division multiple access(MF-TDMA) is chosen for the return channel satellite access scheme. And this MF-TDMA scheme causes the implementation complexity and increase the modulator size. In this design and implementation, we bring to a focus minimizing the modulator size and direct interface to the outdoor unit. Also, for commercial usability, we developed a DVB-RCS modulator as the PCI card type.

Design & implementation of fast frequency hopping Tx IF module for satellite terminal based on DVB-RCS

In this paper the method for the minimization of satellite Tx IF module is presented. The proposed Tx IF module can support fast frequency hopping up to /spl plusmn/10 MHz around the center frequency within guard time, 6 usec. For minimizing Tx IF module, base-band I-Q signals are quadrature modulated to 820/spl plusmn/11.2 MHz band, after modulation it is up-converted to 950/spl sim/1450 MHz by wide band PLL. To support fast frequency hopping, the local oscillator (LO) of QPSK modulator is composed of DDS (Direct Digital Synthesizer) and fixed PLL (Phase Locked Loop). The Tx IF module includes a 5-bit digital attenuator, RF switch and BPF. We implemented both digital part and analog part were mounted in one PCI card.