GNSS-based Location Determination System Architecture for railway performance assessment in presence of local effects

GNSS plays a strategic role on the introduction of the Virtual Balise functionality and the train integrity. Thanks to GNSS, it could be possible to realize cost effective solutions to increase the safety in the regional lines, where the traffic density is lower. The train position estimation is implemented taking into account that the train is constrained to lie on the track (i.e. track constraint). In this way, we can express the position in terms of the curvilinear abscissa (progressive mileage) of the track corresponding to the train position. However, the impact of local effects such as multipath, foliage attenuation and shadowing in the railway environment plays a crucial role due to the presence of infrastructures like platform roofs, side walls, tunnel entrances, buildings and so on close to the trackside. In the paper, we analyse the impact of those threats on the train GNSS-based position estimation performance. At this aim, several scenarios have been generated by using both real data acquired on a railway test-bed in Sardinia, and synthetic data generated in the lab through ad hoc multipath and foliage models. A sensitivity analysis has been conducted, varying main scenarios parameters (e.g. height of obstacles, presence of trees and shadowing). The result of the performed analysis, in terms of availability, accuracy and integrity, are here presented. mitigations implemented by the ERTMS at system level are not considered since the attention is focused on GNSS only

Space and frequency multiplexing for MM-wave multi-gigabit point-to-point transmission links

During last 10 years, the use of frequencies at E-band from 71 GHz to 76 GHz, from 81 GHz to 86 GHz and from 92 GHz to 95 GHz to licensed users has been regulated in US, Europe, Australia and Japan. Due to the large amount of available bandwidth and reasonable atmospheric attenuation, these frequency bands are suitable for very high data rate radio communication for medium to long range wireless links. However, in order to convert the bandwidth availability into real capacity, suitable transmission techniques should be designed. In the present paper, we propose a space-frequency multiplexing technique using FDM, coded modulation and 4×4 MIMO spatial multiplexing for point-to-point multi-gigabit connection in the 81-86 GHz bandwidth. We tested the proposed system, considering different link distances, different values of pathloss and atmospheric and rain attenuations. Simulation results evidenced the possibility of achieving a 48 Gb/s net capacity over 5GHz bandwidth (spectral efficiency 9.6 b/s/Hz) with 99.98% availability at link distances up to 1 Km