  Evolving 5G New Radio (NR) to support non-terrestrial networks (NTNs),
particularly satellite communication networks, is under exploration in 3GPP.
The movement of the spaceborne platforms in NTNs may result in large timing
varying Doppler shift that differs for devices in different locations. Using
orthogonal frequency-division multiple access (OFDMA) in the uplink, each
device will need to apply a different frequency adjustment value to compensate
for the Doppler shift. To this end, the 3GPP Release-17 work on NTNs assumes
that an NTN device is equipped with a global navigation satellite system (GNSS)
chipset and thereby can determine its position and calculate the needed
frequency adjustment value using its position information and satellite
ephemeris data. This makes GNSS support essential for the NTN operation.
However, GNSS signals are weak, not ubiquitous, and susceptible to interference
and spoofing. We show that devices without access to GNSS signals can utilize
reference signals in more than one frequency position in an OFDM carrier to
estimate the Doppler shift and thereby determine the needed frequency
adjustment value for pre-compensating the Doppler shift in the uplink. We
analyze the performance, elaborate on how to utilize the NR reference signals,
and present simulation results. The solution can reduce the dependency of NTN
operation on GNSS with reasonable complexity and performance trade-off.
