Code Interference in GPS Observables and Implications in GPS Accuracy, Precision, and Applications

The Global Positioning System (GPS) provides satellite-based navigation signals that are employed in many fields, including agriculture, transportation, aviation, and military/personal navigation. In an effort to minimize interference among GPS satellites and enable GPS receivers to discern satellite identity, each satellite is assigned a specific pseudorandom noise (PRN) sequence that is used to modulate the phase of the corresponding signal. The codes that modulate the current GPS landscape are constructed in such a way that cross-correlation among codes is kept to a bounded minimum, which should prevent signal interference. In this study, the efficacy of the current PRN-based modulation system at high sampling rates is called into question as GPS signal power and phase data over the past decade show significant interference between satellite signals. Through the analysis of GPS signal power and carrier phase, irregularities were identified that correspond to supposed satellite-interference events. The current analysis will present evidence of this GPS signal interference and explore its implications in GPS-based ionospheric research.