To achieve fully mobile communications, considering different environments and modern service requirements, a multiple-segment architecture is the most suitable to guarantee service continuity with acceptable performance. Handover (HO) procedures can be invoked either out of necessity (if the current network connection is going off) or to improve performance (if different bandwidth or quality of service is required). In this scenario, to provide uninterrupted communication services, efficient intersegment HO capability must be implemented. The architecture considered includes a satellite segment and a number of Wi-Fi hot spots. A mobile node (MN) can switch from a segment to other exploiting services of mobile Internet protocol (MIP). This architecture introduces great flexibility and ensures capillary coverage; it also strongly affects Transmission Control Protocol (TCP)-based application performance. To efficiently face HO consequences, particularly when the TCP runs as a transport protocol, an innovative protocol architecture based on cross-layer (CL) exchange of information is proposed. Analyses of TCP dynamics during HOs and the performance improvement introduced with the proposed CL architecture, evaluated through the network simulator Ns-2, are presented.

Here, first, we analyze the undesired charge transfer occurring in charge pumps; afterwards we present a circuit which is less susceptible to this issue, resulting in significant improvements of the light load efficiency in charge pumps which must have a sufficiently high maximum current capability. SPICE simulations confirm the theoretical results.

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TCP Noordwijk has been designed and implemented to optimize short transfers (i.e. HTTP traffic) over satellite links, while assuring good performance for long transfers (i.e. FTP) as well. It was developed in the frame of an European Space Agency (ESA )project [††]. Its target scenario is a controlled communication environment adopting DVB-RCS standard between I-PEPs. A rich test campaign to both validate the protocol and evaluate performance improvements with respect to standard TCP has been performed using the Ns-2 simulator. This paper contributes to the evaluation of TCP-Noordwijk performance showing results of trials over a real DVB-RCS link, simulations to test protocol performance in a mobile satellite system (with a particular focus on high-speed trains) and tests on a satellite Linux-based emulation platform called SNEP

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