Cross-layer architecture for a satellite-Wi-Fi efficient handover

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

La costruzione di un mito: la vera storia del ponte del Risorgimento

This is the story of a bridge, some courageous men and, above all, about reinforced concrete that, as this story was unfolding, experienced a deep transformation; from a commercial system, protected by patents and restrained by rules governing its use, it developed into a free material at the disposal of any designer capable of fully exploiting its surprising and mysterious structural potential. The main character on this stage was the inventor of reinforced concrete himself, François Hennebique, or rather, the inventor of his most famous patent, filed in 1892, perfected in 1897, and about to expire in 1909 when this story started to unfold. The stage is Italy that more than any other Country was to enhance the properties of this material in all its variants, thanks to the debate that was triggered by the enduring and inexplicable strength of the work at the centre of the story: the Risorgimento Bridge in Rome. There is a rich bibliography on the bridge and many writings that were published at that time. Today’s new reading is made possible because we can compare the documents held in the archives of Giovanni Antonio Porcheddu’s company, Hennebique concessionaire for Northern Italy and builder of the bridge, with the records stored at the Fonds Bétons Armés Hennebique in Paris, and with those found in the Historic Archives of the Campidoglio, in spite of the intricate complexity of this office. The search has once again proven to be fascinating. The daily correspondence, whose sequence was reconstructed thanks to the documents found in the files of the offices in Turin, Rome and Paris, still today, after a hundred years, vividly reflects the audacity, preoccupation, pride, abilities and excitement of the main figure who designed and built the boldest bridge over the River Tiber

La costruzione di un mito: la vera storia del ponte del Risorgimento

This is the story of a bridge, some courageous men and, above all, about reinforced concrete that, as this story was unfolding, experienced a deep transformation; from a commercial system, protected by patents and restrained by rules governing its use, it developed into a free material at the disposal of any designer capable of fully exploiting its surprising and mysterious structural potential. The main character on this stage was the inventor of reinforced concrete himself, François Hennebique, or rather, the inventor of his most famous patent, filed in 1892, perfected in 1897, and about to expire in 1909 when this story started to unfold. The stage is Italy that more than any other Country was to enhance the properties of this material in all its variants, thanks to the debate that was triggered by the enduring and inexplicable strength of the work at the centre of the story: the Risorgimento Bridge in Rome. There is a rich bibliography on the bridge and many writings that were published at that time. Today’s new reading is made possible because we can compare the documents held in the archives of Giovanni Antonio Porcheddu’s company, Hennebique concessionaire for Northern Italy and builder of the bridge, with the records stored at the Fonds Bétons Armés Hennebique in Paris, and with those found in the Historic Archives of the Campidoglio, in spite of the intricate complexity of this office. The search has once again proven to be fascinating. The daily correspondence, whose sequence was reconstructed thanks to the documents found in the files of the offices in Turin, Rome and Paris, still today, after a hundred years, vividly reflects the audacity, preoccupation, pride, abilities and excitement of the main figure who designed and built the boldest bridge over the River Tiber

Enhancing transport layer in satellite systems

Satellite networks play a fundamental role in the provision of a broadband and global Internet access. Nonetheless, features of satellite systems imply worse performance of transport protocols, actually more suitable for wired terrestrial networks. In particular, TCP and UDP need enhancements to improve performance in various communication scenarios including both a satellite stand-alone network and satellite- terrestrial integrated networks. This paper addresses three specific study cases where performance of transport layer protocols is degraded. Analysis and performance evaluation have been carried out through two different platforms: a simulator based on Ns-2 and a Linux-based emulator

High light-load efficiency charge pumps

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

TCP Noordwijk for high-speed trains

In a scenario where people need to travel frequently for their business and leisure, spending a lot of time on high-speed trains, airplanes or ships, it is necessary to provide them a broadband Internet connection while moving. Broadband satellite systems, for their characteristics in terms of coverage and flexibility, can be the best solution for this type of scenarios. Nevertheless, although satellite systems allow a global coverage over the railways, the channel related to a high-speed train is characterized by frequent signal outages due to tunnels, steel covered bridges and powerline trellises. In particular, trellises, always and periodically present along the railroad, cause frequent obstructions of the line of sight, which implies packet loss that significantly affects TCP performance. In fact, standard TCP based on classical congestion control mechanisms is required to perform continuous restart of the algorithm. In this paper, the use of a new TCP protocol called TCP Noordwijk is proposed. It is based on burst transmission concept, which matches optimally with channel characteristics. The advantages with respect to the standard TCP will be shown

TCP performance on a railway satellite channel

High-speed rail is emerging in the world as an increasingly popular and efficient means of transportation used by a lot of people, who may also need a broadband Internet connection while travelling for their business and leisure. Satellite systems for their intrinsic characteristic, such as global coverage, reduced impact of Doppler effect due to link geometry and flexible bandwidth management, represent an excellent solution to provide broadband services in the identified scenario. Some problems specific of the railway propagation channel such as frequent signal outages due to the periodic electrical trellises, tunnels and steel covered bridges affect TCP/IP performance due to frequent packet losses occurring in bursts. In this paper, performance of TCP-based applications and error recovery mechanisms are investigated and the use of a new transport protocol named TCP-Noordwijk is introduced. TCP-Noordwijk leverages on a burst transmission and is particularly suited for the harsh satellite links. Results show that TCP-Noordwijk outperforms the other analyzed TCP versions

Performance evaluation of TCP Noordwijk over satellite systems for fixed and mobile services

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