TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

Giovanni Giambene, Silvia Marchi, Sastri Kota
2012 EAI Endorsed Transactions on Ubiquitous Environments  
GEO satellite communication systems are an efficient approach for broadband Internet provision on highspeed trains, but some work is still needed to allow a seamless service. In the railway scenario, satellite communications suffer from strong variations in the received signal power and need suitable solutions to deal with long channel disruptions due to tunnels. The approach envisaged in this paper is based on a hybrid network (satellite and terrestrial WiFi coverage) and a Vertical Handover
more » ... HO) procedure to switch seamlessly from one segment to another whenever link quality degrades and a new segment is available. This paper deals with the TCP performance in the presence of VHOs (based on the IEEE 802.21 Media Independent Handover, MIH, standard) from the satellite to a terrestrial wireless segment and viceversa to cover tunnels. Details are provided for the adoption of MIH and MIPv6 in such a context, referring to the BSM standard. Design criteria for the WiFi coverage extension outside the tunnel are also presented. Finally, we have shown that TCP goodput behavior and convergence time can be improved by means of suitable accelerated TCP versions or using cross-layer methods. alternative hybrid approach with TCP acceleration and data compression is used by the 21Net operator [2] . Communication services to trains via GEO satellites are affected by short-term link unavailability events (shadowing, on the order of tens to hundreds of ms) due to power line structures, trees, buildings, and small obstacles, in general. While, long-term channel disruptions (blockage, on the order of seconds to minutes) are caused by relatively-long tunnels [3] . There are several approaches to deal with disruptions at different (4+ to PHY) layers, such as: Delay/Disruption Tolerant Network (DTN) • Performance Enhancing Proxy (PEP) • Accelerated TCP versions suitable for high Bandwidth-Delay Product (BDP) networks • Heterogeneous (hybrid) Networks (HetNet) with satellite and local wireless coverage • Repeaters (gap-fillers)
doi:10.4108/trans.ubienv.2012.e5 fatcat:b2y7k2tszrfhlll6j4wqs4jqma