The specific objective of this NAVISP project is the development of an SDR processor devoted to Low Earth Orbit (LEO) PNT applications. The LEO PNT system intends to provide services of accurate real-time positioning to complement the Global Navigation Satellite Systems (GNSS). A satellite constellation of LEO-PNT offers better signal power, that results in higher positioning accuracy and additional security capabilities such as navigation message encryptions. The LEO-PNT equipment receives the navigation signal from, for instance, Galileo and determines its position and time at that instant. This function can be complemented with ranging measurements from other satellites in the LEO-PNT constellation through Inter-Satellite Link (ISL). The equipment then generates its own GNSS signal with more accurate navigational data and transmits it to ground end-users.