Mechanisms are provided for a user equipment (UE) to determine a transmission frequency or a time advance for an uplink transmission from the UE to a base station in a non-terrestrial wireless network (NTN) without global navigation satellite systems (GNSS) information available to the UE. A communication connection between the UE and a base station can be established. The UE can determine that GNSS information is not available, and report to the base station that the GNSS information is not available. The UE can receive, from the base station, an indication of one or more parameters for an uplink transmission from the UE to synchronize the uplink transmission. The UE can determine, based on a current transmission frequency and the received indication of the one or more parameters, a next transmission frequency and transmit the uplink transmission at the determined next transmission frequency.