Abstract
GPS-based systems have been widely used in different critical sectors, including civilian, military and commercial applications. Despite of being able to provide great benefi ts, under certain circumstances they show to be highly vulnerable to intentional interferences. In this context, this article aimed to evaluate the vulnerability range of this kind of systems, focusing on different kinds of environments and based on different propagation models, to which the simulations were performed. Results show high vulnerabilities of GPS-based systems even when operating in a well-protected urban environment, in a short range and under low-power sources of radiation. Graphs are presented with the range of effectiveness for different power levels of jammer in different situations. Evaluations are performed not only for the acquisition but also for the tracking processes of the GPS receivers, therefore being possible to establish a safe operation range for having a trustful GPS signal and mitigate malicious actions. The comparisons allow, as well, highlighting the importance of using the correct propagation model, in order to achieve consistent results, depending on the desired situation.
Highlights
ABStract: Global Positioning System (GPS)-based systems have been widely used in different critical sectors, including civilian, military and commercial applications
Even in military, where this dependency is not so clear, systems like Emitters Locating, Safe Communication and Multi-Static Radars depend on the time or frequency provided by GPS signals (Scott 2015)
We focus on the analysis of the L1 carrier frequency, which is the one used by the vast majority of civilian institutions outside the United States, as well as by the militaries that do not have authorization from the US Department of Defense (DoD) for using the encrypted data
Summary
GPS Systems The GPS system provides position and timing information anywhere on the globe, since the receiver has a line of sight to four or more satellites. In addition to the PRN codes, navigation data modulates the L1 and L2 carriers, providing the basic information for calculating the positions of satellites and estimating the receiver position on the globe. The GPS receivers provide the user position based on signals transmitted by satellites whose effective radiated power is approximately 280 Watts (in zenith direction). This signal arrives to the Earth surface with a power between –153 and –160 dBW, after travelling a distance of 20,200 km (Diggelen 2009). GPS Interference Basis and Phases of Operation In a simple way, in order to obtain the PNT information, a reference carrier shall be generated in the receiver and modulated with a replica of the desired C/A code. If a GPS receiver is already providing PNT information, only a J/S of 47 dB could avoid the generation of the information, but a J/S of 27 dB is enough to prevent a new acquisition process
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