Abstract
This paper presents studies of the effect of the Doppler frequency shift on the satellite link availability when regular smartphones are used as user equipment. The studies evaluated the NTN downlink channel showing how the availability of the link changes when using Doppler shift compensator at the satellite side and when it's not used. Additionally, the study simulates a typical NTN constellation in S-band and compares the link availability time when the Doppler shift compensator is used and is not. Conclusions are drawn about the challenges of using unmodified mobile phones for communication and how it might be affected by the Doppler shift.