Gonzalo Seco Granados

Advanced fade countermeasures for DVB-S2 systems in railway scenarios

This paper deals with the analysis of advanced fade countermeasures for supporting DVB-S2 reception by mobile terminals mounted on high-speed trains. Recent market studies indicate this as a potential profitable market for satellite communications, provided that integration with wireless terrestrial networks can be implemented to bridge the satellite connectivity inside railway tunnels and large train stations. In turn, the satellite can typically offer the coverage of around 80% of the railway path with existing space infrastructure. This piece of work, representing the first step of a wider study, is focusing on the modifications which may be required in the DVB-S2 standard (to be employed in the forward link) in order to achieve reliable reception in a challenging environment such as the railway one. Modifications have been devised trying to minimize the impact on the existing air interface, standardized for fixed terminals.

Antenna diversity and GSE-based packet level FEC for DVB-S2 Systems in Railway scenarios

In this paper, we address the study of a broadband satellite system based on DVB-S2 for interactive services in a mobile scenario. In particular, we focus on the railway scenario when the train is moving with high speed under LOS (Line of Sight) conditions considering also the atmospheric effects for Ku band. We aim at the design of fading countermeasure to compensate the impact of short and medium term fading that is present in the LOS case, which is owed to the speed, the near environment (modelled by a Rice model) and the power arches. Long term signal blockage due to e.g. railway tunnels has not been considered in this study. With the purpose of compensating for these effects, the use of packet-level FEC and antenna diversity has been already proposed. In this paper, a further development of packet-level FEC, in combination or not with antenna diversity, is proposed. We propose a coding that differentiates classes of service thus avoiding guaranteeing quasi-error free PER performance for applications that do not need it with the consequent gain in capacity. Furthermore, we consider the adaptation layer to be based on the novel GSE (Generic Stream Encapsulation) encapsulation method currently under standardization process. Our results show that our proposed fade mitigation techniques yield improvements of average packet error rate.

Overview of Galileo System

This chapter provides an introduction to the Galileo program and architecture. It starts by presenting the program context, rationale and history, including the early definition phases and test beds and the GIOVE experimental satellites. It then presents an overview of the Galileo services. Later, an architectural overview is provided, including the Galileo segments: the Space Segment, the Ground Mission Segment, and the Ground Control Segment. The chapter also provides a description of Galileo’s contribution to the Search And Rescue services through COSPAS/SARSAT, and finalizes with an overview of the user segment and highlighting interoperability and compatibility issues with other GNSS.