Impact of Proactive Retransmissions on Forward TCP Throughput over DVB-S/S2 Railroad Satellite Links with Power Arches

High-speed trains are one of the major collective mobile communities that will exploit broadband satellite services. ETSI DVB-S/S2 and DVB-RCS specifications have enjoyed tremendous success and global acceptance. Recently, both EU and ESA have sponsored R&D programmes [1][2][4] to introduce mobility adaptations to DVB-S2 and DVB-RCS specifications. Power supply arches that are equidistantly placed over railway tracks pose a specific challenge for satellite transmission to high-speed trains. These structures result in quasi-periodic and quasi-deterministic deep fades, which are particularly deteriorating to TCP throughput over high bandwidth-delay-product satellite links. The focus of this article is mitigations for such deep fades that are triggered due to power arches. Specifically, the article considers proactive retransmissions of IP datagrams over the forward link to maintain high levels in forward TCP throughput. The article presents ns-based DVB-S2/RCS simulation results with several TCP variants (Reno, Newreno, and SACK). We present our conclusions regarding the applicability of the mitigation together with the performance levels that can be expected.