The Gap Filler Technology for Mobile Satellite System

Abstract

To provide seamless broadband internet and broadcasting services to passengers of high speed train via satellite link, gap filling is key technology to extend the service coverage in NLOS environment, so to speak, tunnel. The XpeedSAT system is a Ka/Ku band broadband mobile multimedia access system based on DVB-S2/DVB-RCS+M standard for satellite TV, video multicasting, Internet through wireless LAN.In this paper we introduce the various gap filling technologies and compare pros and cons. Finally we propose the gap filling method for NLOS environment in XpeedSAT system.

Railway satellite channel at Ku band and above: Composite dynamic modeling for the design of fade mitigation techniques

“…where 525,600 are the minutes in a 365 days year. An application of Eqn (20) for the parameters in rows 6 and 7 of Table I is depicted in Figure 5 for an attenuation threshold A th = 6 dB.…”

“…On the other hand, tunnels, large train stations and dense urban areas correspond to the second category. In fact, in the latter case, direct communication to the satellite might not be feasible, and therefore, a transparent or non‐transparent terrestrial gap filler network must complement coverage to the train . Furthermore, open areas are characterized as nearly LOS because they may possibly suffer from a variety of channel phenomena: Diffraction because of power arches (PAs) that, depending on the link geometry, produce significant fading depths. Tree shadowing—usually of moderate degree. Doppler spread because of the movement of the train, especially at high train speeds. Multipath because of ground reflections, though insignificant when a directive antenna is used.…”

“…On the other hand, tunnels, large train stations and dense urban areas correspond to the second category. In fact, in the latter case, direct communication to the satellite might not be feasible, and therefore, a transparent or non-transparent terrestrial gap filler network must complement coverage to the train [19,20]. Furthermore, open areas are characterized as nearly LOS because they may possibly suffer from a variety of channel phenomena:…”

Dual ISM‐band gap‐filler microstrip antenna with two Y‐shaped slots for satellite internet service

“…It offers stable wireless internet service without time or space limitations, but is hindered when the train is passing through a tunnel, which blocks direct access to the satellite signal. A tunnel is a typical shadowing area, in which a gap filler is required for better communication between the satellite and the wireless terminal of the Korean high-speed train network [1][2][3]. A gap filler system requires three antennas: one installed outside the tunnel (Antenna 1), one installed inside the tunnel (Antenna 2), and one installed on the train (Antenna 3).…”

Admission control and handover management for high‐speed trains in vehicular geostationary satellite networks with terrestrial gap‐filling

“…In particular, we will demonstrate that low forced termination probability and high utilization can be achieved via inter-segment resource management without sacrificing much bandwidth in aggressive resource reservation strategies when the network load increases. Two solutions are currently available to provide multi-mode Return Channel Satellite Terminals (RCSTs) with a temporary point of attachment to the terrestrial infrastructure [2]. The first, known as the integral gap-filler, is suggested when the mobile terminals lose the line-of-sight (LOS) and ultimately the access to the serving satellite.…”