## 1 Introduction  
The modernisation of the Global Navigation Satellite System (GNSS) and the constant improvement of their performance is driving the design of a plethora of applications with strict requirements on accuracy, precision and reliability of the estimated position [1]. Despite the impressive improvement of the quality of the broadcast signals and new processing techniques, the propagation of the signal through the ionosphere is still one of the limiting factors for precise positioning. In fact, it is well known that the GNSS signals while travelling through the upper layers of the atmosphere are affected in terms of delay, amplitude and phase, which turn out to be different with respect to the assumed propagation in free-space. Compensation of the ionospheric delay is applied by now in any GNSS receiver, either using models or external assistance for single frequency receivers, and it can be compensated by means of the iono-free combination of the measured pseudoranges in multi-frequency receivers [2]. However, due to the presence of a non-uniform distribution of the electron density in some layers of the ionosphere, electromagnetic signals are scattered in random directions, thus reaching the Earth through multiple paths. Signals on each path add in a phase-wise sense and interfere with each other, so that the received signal is then affected by deep amplitude fading and phase fluctuations. GNSS signals are indeed affected by scintillation effects, and their quality at the receiver might be strongly degraded. While moderate scintillations only increase noise in code and phase measurements, strong scintillation events severely disrupt the capabilities of GNSS receivers. Amplitude fading and rapid phase changes impact the receivers' tracking loops capabilities to follow the signal dynamics, resulting in cycle slips and Loss-of-Lock (LoL) in the tracking stage of the receiver [3]. Phase range measurements errors can be from 3 to 10 times larger [4], whereas, in the most severe situations, when more than one satellite-receiver link is concerned and the satellite visibility is poor, the receiver might completely fail [5]. At the same time, thanks to their global coverage and continuous availability, GNSS signals provide an excellent means to monitor the activity of the ionosphere. With multiple satellites from multiple constellations, the physical effects can be simultaneously measured through many pierce points. GNSS receivers have then become a convenient, cheap and widespread tool to study such phenomena [6; 7]. In this paper, we propose a technique to assess the intensity of scintillation on the signal amplitude, which is an alternative to the classical methods that require a GNSS receiver employing closed-loop architectures. Rather then relying on the traditional commercial receiver architecture, in which only the correlator outputs are available to the end user, this approach fully exploits the flexibility of a receiver architecture entirely designed according to software-radio approach [8]. Samples of the received signal at Radio Frequency (RF) are collected, sampled and digitized, at sampling frequencies of the order of millions of samples per second. Then, the bit-stream is stored on memories and processed by a fully-software GNSS receiver. This approach has gained consensus in recent years also in the space weather community [9; 10; 11], and it allows for an easier implementation of novel algorithms, specifically tailored to the scintillation monitoring and mitigation [12]. As a consequence, such techniques can be robust by design to the strong scintillations events causing LoLs in classical receivers' architectures. The paper is organized as follows: Section 2 will briefly recall the well known parameters used for scintillation detection and classification. Section 3 will discuss the flexibility given by a software-defined-radio approach for the design of novel methods to process the digitized GNSS signal, including the possibility to undertake different approaches for the scintillation monitoring.