Positioning services for people and devices has become a necessity for nowadays society: the computation of precise position, both in single epoch and in real time, is in fact a fundamental aspect of many applications, such as guidance and control for people and transport, industrial applications, mass market, public security, assistive technologies and recreational purposes. From about 30 years outdoor positioning has been provided by the Global Navigation Satellite System (GNSS). At the beginning, positioning was based only on GPS constellation, using expensive and bulky dedicated receivers. Thanks to the technological development and the growing interest in the sector, over the years, the number of constellations has increased, constituting the GNSS. In addition, also the availability of receivers has increased, diversifying quality and pricing: for instance, nowadays, smartphones are equipped with cheap and miniaturized GNSS devices. Nowadays, thanks to the satellite coverage, we can consider open sky positioning an achieved goal worldwide. However, in urban environment, the obstructions caused by buildings degrade the positioning accuracy, even making it impossible in some configurations. This thesis aims to be the beginning of a complete analysis of the possible integration of the 5G signals to GNSS positioning in urban environment. The work is structured as follows and can be divided into two main phases: 1. Implementation of a software to perform GNSS point positioning. According to the available literature, we developed an open source Python library that is able to perform point positioning, starting from the computation of the ephemeris (position, velocity and clock offset of each satellite in each epoch) to the estimate of the position of the receiver by following the standard formulas and Least Squares approach. The software aims to be a complete solution that allows the user to perform point positioning starting from raw data, offering all the necessary functions for reading files, computing ephemerides and estimating unknowns. The software implementation, although it is not a research topic, is necessary for the future development of the thesis and to provide a complete open-source software available to everyone. 2. Geometric analysis of the advantages obtainable by integrating the 5G signals with GNSS in urban scenario, under the hypothesis of having Time of Arrival (ToA) observations from 5G. This second phase of work consists in an experimental study of the actual visibility of the GNSS satellites in urban environment: the analysis is carried out through the simulation of 4 scenarios of urban environments with buildings of different heights. The height of the buildings is decisive to differentiate the two classes: scenarios with tall buildings (24 meters high), which we will refer to as urban canyons, and scenarios with residential buildings (9 meters high), which will represent residential streets. Subsequently,the visibility of the satellites is analyzed for each scenario: signals that are not blocked by the presence of buildings are identified with a masking process. At the end, it is shown how the geometry and the number of satellites in view influence the positioning performance and it is studied how the introduction of 5G network for positioning can improve and ensure the performance of positioning in urban environment. This geometrical analysis is performed on the results obtained from the computation of Diluition of Precision (DOP) indices on both GNSS-only and GNSS+5G configurations.
I servizi di posizionamento per persone e dispositivi sono diventati una necessità per la società odierna: il calcolo della posizione precisa, sia in single epoch che in real time, è infatti un aspetto fondamentale di molte applicazioni, come guida e controllo per persone e trasporti, applicazioni industriali, mercato di massa, sicurezza pubblica, tecnologie per l’assistenza e scopi ricreativi. Da circa 30 anni il posizionamento outdoor è assicurato dal Sistema globale di navigazione satellitare (GNSS). All'inizio, il posizionamento si svolgeva appoggiandosi solo alla costellazione GPS, utilizzando ricevitori dedicati, i quali erano costosi e ingombranti. Grazie allo sviluppo tecnologico e al crescente interesse nel settore, negli anni, il numero di costellazioni è aumentato, andando a costituire il GNSS. Inoltre è aumentata la disponibilità dei ricevitori, diversificandone qualità e prezzo: per ad esempio, al giorno d'oggi, gli smartphone stessi sono dotati di dispositivi GPS economici e miniaturizzati. Oggi, grazie alla copertura satellitare, possiamo considerare il posizionamento in open-sky un traguardo raggiunto a livello mondiale. Tuttavia, in ambiente urbano, le ostruzioni causate dalla presenza di edifici degradano la precisione di posizionamento, rendendolo talvolta impossibile in alcune configurazioni. Questa tesi vuole essere l'inizio di un'analisi completa della possibile integrazione dei segnali 5G con il posizionamento GNSS in ambiente urbano. Il lavoro è strutturato come segue e può essere suddiviso in due fasi principali: 1. Implementazione di un software per eseguire il posizionamento del punto GNSS. Basandoci la letteratura disponibile, abbiamo sviluppato una libreria Python open source in grado di eseguire il posizionamento, a partire dal calcolo delle effemeridi (posizione, velocità e clock offset di ogni satellite in ogni epoca) alla stima della posizione del ricevitore seguendo le formule standard e applicando i Minimi Quadrati. Il software vuole essere una soluzione completa che permetta all'utente di eseguire il posizionamento partendo da dati grezzi, offrendo tutte le funzioni necessarie per la lettura dei file, il calcolo delle effemeridi e la stima delle incognite. L'implementazione del software, anche se non costituisce argomento di ricerca, è necessario per il futuro sviluppo della tesi e per poter fornire un software open source completo a disposizione di tutti. 2. Analisi geometrica dei vantaggi ottenibili dall’integrazione del 5G con GNSS in ambiente urbano, nell'ipotesi di avere osservazioni del tempo di arrivo (ToA) dal 5G. Questa seconda fase di lavoro consiste in uno studio sperimentale dell’effettiva visibilità dei satelliti GNSS in contesto urbano: l'analisi viene svolta attraverso la simulazione di 4 scenari di ambiente urbano con edifici di diversa altezza. L'altezza dell’edificio è determinante per differenziare due classi urbane principali: scenari con edifici alti (24 metri), a cui ci riferiremo come urban canyons, e scenari con edifici residenziali (9 metri), che rappresenteranno strade residenziali. Successivamente, per ogni scenario viene analizzata la visibilità dei satelliti: i segnali che non vengono bloccati dalla presenza degli edifici vengono individuati con un processo di masking. In conclusione, viene mostrato come la geometria, il numero di satelliti in vista e la loro disposizione influenza la performance di posizionamento e si studia come il l'introduzione della rete 5G per il posizionamento possa migliorare e garantire le prestazioni di posizionamento in ambiente urbano. Questa analisi geometrica viene eseguita sui risultati ottenuti dal calcolo degli indici di Diluition of Precision (DOP) sia sulla configurazione GNSS sia sulla configurazione ibrida GNSS+5G.
Integration of GNSS and 5G for precise urban positioning
ALGHISI, MARIANNA
2020/2021
Abstract
Positioning services for people and devices has become a necessity for nowadays society: the computation of precise position, both in single epoch and in real time, is in fact a fundamental aspect of many applications, such as guidance and control for people and transport, industrial applications, mass market, public security, assistive technologies and recreational purposes. From about 30 years outdoor positioning has been provided by the Global Navigation Satellite System (GNSS). At the beginning, positioning was based only on GPS constellation, using expensive and bulky dedicated receivers. Thanks to the technological development and the growing interest in the sector, over the years, the number of constellations has increased, constituting the GNSS. In addition, also the availability of receivers has increased, diversifying quality and pricing: for instance, nowadays, smartphones are equipped with cheap and miniaturized GNSS devices. Nowadays, thanks to the satellite coverage, we can consider open sky positioning an achieved goal worldwide. However, in urban environment, the obstructions caused by buildings degrade the positioning accuracy, even making it impossible in some configurations. This thesis aims to be the beginning of a complete analysis of the possible integration of the 5G signals to GNSS positioning in urban environment. The work is structured as follows and can be divided into two main phases: 1. Implementation of a software to perform GNSS point positioning. According to the available literature, we developed an open source Python library that is able to perform point positioning, starting from the computation of the ephemeris (position, velocity and clock offset of each satellite in each epoch) to the estimate of the position of the receiver by following the standard formulas and Least Squares approach. The software aims to be a complete solution that allows the user to perform point positioning starting from raw data, offering all the necessary functions for reading files, computing ephemerides and estimating unknowns. The software implementation, although it is not a research topic, is necessary for the future development of the thesis and to provide a complete open-source software available to everyone. 2. Geometric analysis of the advantages obtainable by integrating the 5G signals with GNSS in urban scenario, under the hypothesis of having Time of Arrival (ToA) observations from 5G. This second phase of work consists in an experimental study of the actual visibility of the GNSS satellites in urban environment: the analysis is carried out through the simulation of 4 scenarios of urban environments with buildings of different heights. The height of the buildings is decisive to differentiate the two classes: scenarios with tall buildings (24 meters high), which we will refer to as urban canyons, and scenarios with residential buildings (9 meters high), which will represent residential streets. Subsequently,the visibility of the satellites is analyzed for each scenario: signals that are not blocked by the presence of buildings are identified with a masking process. At the end, it is shown how the geometry and the number of satellites in view influence the positioning performance and it is studied how the introduction of 5G network for positioning can improve and ensure the performance of positioning in urban environment. This geometrical analysis is performed on the results obtained from the computation of Diluition of Precision (DOP) indices on both GNSS-only and GNSS+5G configurations.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/182952