Disseminazioni in reti peer-to-peer attraverso algoritmi di gossip a due fasi

Gli algoritmi di gossip sono utilizzati per la disseminazione di messaggi in una rete peer-to-peer. La tesi tratta lo sviluppo, l'implementazione e l'analisi di quattro nuovi algoritmi di gossip "a due fasi". Gli algoritmi sono stati sviluppati e testati con il simulatore LUNES per poi essere analizzati in vari confronti con gli algoritmi classici dell'ambito, ovvero Fixed Probability e Conditional Broadcast. Le prove sono state effettuate su varie tipologie di grafi, ovvero Random, Scale-free, Small-world e K-Regular.

Satellite IoT: a Study and Performance Analysis of GEO and LEO Systems

The study is divided into two main part: one focused on the GEO Satellite IoT and the other on the LEO Satellite IoT. Concerning the GEO Satellite IoT, the activity has been developed in the context of EUMETSAT Data Collection Service (DCS) by investigating the performance at the receiver within challenging scenarios. DCS are provided by several GEO Satellite operators, giving almost total coverage around the world. In this study firstly an overview of the DCS end-to-end architecture is given followed by a detailed description of both the tools used for the simulations: the DCP-TST (message generator and transmitter) and the DCP-RX (receiver). After generating several test messages, the performances have been evaluated with the addition of impairments (CW and sweeping interferences) and considerations in terms of BER and Good Messages are produced. Furthermore, a study on the PLL System is also conducted together with evaluations on the effectiveness of tuning the PLL Bw on the overall performance. Concerning the LEO Satellite IoT, the activity was carried out in the framework of the ASI Bidirectional IoT Satellite Service (BISS) Project. The elaborate covers a survey about the possible services that the project can accomplish and a technical analysis on the uplink MA. In particular, the LR-FHSS is proved to be a valid alternative for the uplink through an extensive analysis on its Network capacity and through the study of an analytic model for Success Probability with its Matlab implementation.

Spacecraft Collision Probability Calculation from Conjunction Data Message and High Precision Orbit Propagator

The increasing number of Resident Space Objects (RSOs) is a threat to spaceflight operations. Conjunction Data Messages (CDMs) are sent to satellite operators to warn for possible future collision and their probabilities. The research project described herein pushed forward an algorithm that is able to update the collision probability directly on-board starting from CDMs and the state vector of the hosting satellite which is constantly updated thanks to an onboard GNSS receiver. A large set of methods for computing the collision probability was analyzed in order to find the best ones for this application. The selected algorithm was then tested to assess and improve its performance. Finally, parts of the algorithm and external software were implemented on a Raspberry Pi 3B+ board to demonstrate the compatibility of this approach with computational resources similar to those typically available onboard modern spacecraft.