Assessing Ionospheric Scintillation Risk for Direct-to-Cellular Communications using Frequency-Scaled GNSS Observations

TL;DR

This study evaluates ionospheric scintillation's impact on Direct-to-Cellular satellite links by scaling GNSS observations to D2C frequencies, revealing diurnal and seasonal patterns and differences across bands to improve system resilience.

Contribution

It introduces a method to scale GNSS scintillation data to D2C frequencies and compares ground-based and space-based observations, providing insights into scintillation patterns relevant for D2C system design.

Findings

Scintillation peaks between 20-22 local time during equinoxes.

Higher D2C bands show less scintillation than lower bands.

Scintillation occurrence increases with solar activity.

Abstract

One of the key issues facing Direct-to-Cellular (D2C) satellite communication systems is ionospheric scintillation on the uplink and downlink, which can significantly degrade link quality. This work investigates the spatial and temporal characteristics of amplitude scintillation at D2C frequencies by scaling L-band scintillation observations from Global Navigation Satellite Systems (GNSS) receivers to bands relevant to D2C operation, including the low-band, and 3GPP's N255 and N256. These observations are then compared to scaled radio-occultation scintillation observations from the FORMOSAT-7/COSMIC-2 (F7/C2) mission, which can be used in regions that do not possess ground-based scintillation monitoring stations. As a proof of concept, five years of ground-based GNSS scintillation data from Sharjah, United Arab Emirates, together with two years of F7/C2 observations over the same region, corresponding to the ascending phase of Solar Cycle 25, are analyzed. Both space-based and ground-based observations indicate a pronounced diurnal scintillation peak between 20--22 local time, particularly during the equinoxes, with occurrence rates increasing with solar activity. Ground-based observations also reveal a strong azimuth dependence, with most scintillation events occurring on southward satellite links. The scintillation occurrence rate at the low-band is more than twice that observed at N255 and N256, highlighting the increased robustness of higher D2C bands to ionospheric scintillation. These results demonstrate how GNSS scintillation observations can be leveraged to characterize and anticipate scintillation-induced D2C link impairments, which help in D2C system design and the implementation of scintillation mitigation strategies.