Performance of data and pilot code/channel of modernized GPS signals

Ionospheric scintillation significantly impacts the performance and reliability of space-based navigation and communication systems.  Scintillation effects cause fluctuations in the amplitude and phase of (Global Navigation Satellite Systems) GNSS received signals. Significant variations in signal power causes loss in signal-to-noise ratio which, in combination with phase variations, can severely impact GNSS receiver performance by impairing signal acquisition or causing a loss of lock during tracking. Several studies, such as Delay et al. (2015), Jiao et al. (2016), and Moraes et al. (2017), have shown that modern GNSS signals are more vulnerable to ionospheric scintillation. This increased vulnerability arises from their lower operating frequencies, which make them more sensitive to small-scale plasma irregularities and rapid phase distortions caused by ionospheric irregularities. However, there is a notable lack of research on the performance of modernized GNSS observables, particularly regarding how different codes and channels perform across GNSS signal frequencies under ionospheric scintillation. To address this gap, this work evaluates the behavior of data and pilot codes/channels across different frequencies under challenging ionospheric conditions, focusing on signal availability, continuity using different signal and channel combinations. In terms of signal availability, the results reveal that L1 signals (C1C, C1X, L1X and L1C) exhibit the highest availability and resilience to ionospheric scintillation, followed by L5 and L2 signals (L5X, C5X, L2X, C2X), which exhibit moderate availability and reliability. The lowest signal availability is observed in the L2 signals (L2W, C2W), reflecting reduced performance.  The performance of modernized GPS signals during ionospheric scintillation varies by signal frequency.  The L5 signal is the most affected, showing the highest percentage of ionospheric scintillation index (S₄) values, indicating significant susceptibility to scintillation.  The L1 signal is the least affected, with the lowest S₄ percentages, suggesting greater resilience. The analysis demonstrates that the L1X signal exhibits the highest continuity, with the lowest percentage of data gaps, indicating superior robustness. In contrast, the L2X signal shows the highest susceptibility to interruptions, with the greatest percentage of data gaps, followed by the L5X signal, which displays slightly fewer gaps than L2X. The observed correlation between ionospheric scintillation intensity and signal loss highlights the frequency-dependent nature of signal disruptions, with L1X proving to be the most resilient and L2X the most vulnerable. These findings highlight the frequency-dependent nature of GNSS signal performance and the importance of selecting appropriate signal and channel combinations for reliable ionospheric estimations.