Mobility management in DVB-RCS networks.

The undergoing spread of broadband Internet shows that high-speed services are now perceived as a commodity worldwide. Several research programmes have proposed low-cost mobility enhancements to the DVB-RCS standard to intercept the market segment represented by the increasing number of airlines, land-mobile, and maritime passengers. This thesis investigates link and network-layer mobility issues related to a multi-beam network topology with a particular emphasis on backward-compatible protocol modifications minimising the impact over the signalling mechanisms of the original DVB-RCS normative. The availability of GPS equipment onboard collective vehicles and their pattern predictability suggest using position and route information as driving parameters for mobility protocols. Estimations of the terminal residence time within spot-beams are used to prioritise ongoing communications over fresh traffic. Their superiority over distance- based schemes is demonstrated in congested airborne-railroad scenarios, whilst specific solutions are proposed to counteract the sensitivity of the signalling exchange to error modelling. Admission control in wireless networks determines the trade-off between QoS guarantee and resource utilisation. A novel scheme for inbound and outbound traffic estimation is proposed and compared with several existing static and probabilistic approaches. This is proved effective at reducing blocking probabilities without sacrificing much bandwidth in resource reservation. The mathematical characterisation of a threshold-based queuing mechanism for handover traffic is also presented and its accuracy confirmed via simulation results in airborne-railway scenarios. The integration with terrestrial cellular systems is investigated to ensure connectivity in urban centres. A hybrid satellite-terrestrial architecture is envisaged where gap-fillers provide service continuity when intra-satellite mobility cannot be guaranteed. It is proven that the temporary terrestrial diversion of active connections contributes to decrease blocking probabilities and to increase the network utilisation. Because such an approach incurs in roaming costs, an optimisation tool is developed that identifies the conditions under which vertical handover is preferable