The starting point for this project is the existing Indra Espacio's VSAT CDMA/DAMA network, originally designed to provide personal communications for fixed and portable terminals. That system has already been upgraded and field-tested for the mobile maritime environment. However, the railway environment has constraints, in addition to mobility, e.g., multi-path and obstacles along the way, which are common in the railway environment.
The architecture of the system to be deployed is based on:
- a satellite communications network, for covering the mobile environment between terrestrial Internet Service Providers (ISP) and trainsets, and
- an on-board test-bed communications network, covered by standard COTS Wi-Fi equipment, installed to distribute Internet access through one train coach.
The satellite communications network will be able to provide asymmetric two-way IP services to trains through a combination of two different technologies: a high-rate DVB-S broadcast communication technology for the forward link, and a DAMA/CDMA technology for the return link.
The use of CDMA allows, at the same traffic rate, a reduction in the size of the antenna and HPA power needed at the VSAT. They are both quite important when integrating a mobile station onto a train, bus, ship or aircraft. On the other hand, the DVB-S standard is designed to exploit the broadcast capability of satellite in forwarding digital TV content multiplexed with internet data streams.
The satellite network topology is of multi-star type, constituted by a satellite segment, a fixed ground segment with the NMS/HUB station which is able to manage the satellite network components and provide interconnection to Internet backbones, and the mobile user segment of MTS stations that interface with internet ser