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In the massive IoT era, billions of low-complexity devices are expected to be connected to the Internet, posing challenges to the infrastructure and the technologies which these communications rely on. In particular, the improvement of the Random Access (RA) procedure to serve a higher amount of users has high priority, being this the first procedure that any device has to perform to connect to the network. The objective of this thesis is to propose a novel approach to Non-Orthogonal Random Access (NORA), where multiple users can access the network using the same resources. This technology is even more important in Non-Terrestrial Networks, where cells can be several km wide and a massive amount of users have to be served in a short time window. Chapter 1 will present a brief introduction to the long range radio access standards for IoT with a focus on the chosen technology, Narrowband-IoT (NB-IoT). Then, Chapter 2 will analyze the steps of the RA procedure, detailing the rationale behind the RA preamble standardized in NB-IoT. This will be the ground for Chapter 3: after a State of the Art report on the NB-IoT RA procedure, along with the few published works on NORA, the proposed NORA technique will be presented. This includes the description of the slight modification to the RA preamble, which is required to ensure the detection of the preambles at the Base Station, and the definition of two detection algorithms for NORA. Chapter 4 will conclude this thesis, reporting the detection performance of the proposed algorithms. This evaluation will be carried out by means of simulation on MathWorks’ computing environment MATLAB.