Investigation of Ionospheric Scintillation Effects for Satellite Communications in VHF Band

Ionospheric scintillation refers to rapid fluctuations in signal amplitude and phase during trans-ionospheric propagation, which can degrade signal quality in satellite communications. This phenomenon is especially concerning for the VHF voice communication in aviation between air traffic controllers and aircrafts with satellite relays. Strong ionospheric scintillation can significantly affect the quality of analog amplitude-modulated VHF voice signals used in aviation. While much research on scintillation has focused on GNSS signals in the L-band, studies on VHF band scintillation remain limited. To address this gap, the Institute for Infocomm Research (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{I}^{\mathbf{2}} \mathbf{R}$</tex>), A*STAR in Singapore conducted scintillation measurements using ORBCOMM satellite signals (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$137-138 \text{MHz}$</tex>), and a technique for extracting scintillation effects from measured ORBCOMM signals was developed. This paper details the hardware and software developed by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I^{2} R$</tex> for decoding and processing ORBCOMM signals, presents the scintillation measurement results in VHF band.