Abstract
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.
Highlights
Satellite communications developed to a tremendous global success in the field of analog and digital audio/TV broadcasting by exploiting the inherent wide-area coverage for the distribution of content
Long columns appropriate to obtain low IP packet error rate (PER) when the duration of the fade events caused by power arches is large or when very spectrally efficient MODCODs are used; but this comes at the price of a large encoding and decoding delay, and an increased sensitivity to random baseband frame (BBFRAME) errors caused by noise and interference
It has been shown that the dimensioning of packet level forward error correction (FEC) is a complex task, that will be carried out following a cross-layer approach, the results presented in the previous section confirm that this technique, if properly designed, can guarantee reliable reception at the expenses of a limited increase in the system complexity and overhead
Summary
Satellite communications developed to a tremendous global success in the field of analog and digital audio/TV broadcasting by exploiting the inherent wide-area coverage for the distribution of content. Cons (i) Available tracking antennas and efficient satcom modems expensive (ii) High variable cost per MB (iii) Return bandwidth constrained by antenna size (iv) Satellite visibility seriously restricted on some rail routes (i) Geographic coverage of UMTS limited for years to come (ii) Coverage of railway lines often worse than roads (iii) GPRS/EDGE not really fast enough (iv) Inverse relationship between throughput and train speed (v) No QoS guarantees—affected by network congestion at peak times (vi) Organized country by country—data roaming charges are punitive (i) Existing standards not designed to support fast-moving terminals (ii) Proprietary equipment is more expensive (iii) No suitable public services yet in licensed bands—will licence-holders be allowed to provide mobile services?. (iv) Licence-exempt bands are low power, limited range (v) Infrastructure deployment (especially trackside) is expensive and time consuming analogue solutions have to be devised, which are not in the scope of the present work
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