Systems and methods for managing doppler shift in cellular service signals from terrestrial user equipment at a satellite

A satellite computer system for a satellite, the satellite including at least one antenna configured to send and receive signals to terrestrial user equipment (UE) on a radio access network (RAN) via a plurality of directional beams, each of the beams having a beam footprint that defines a cell of the RAN, the satellite computer system comprising at least one processor in communication with a memory, the memory storing computer-readable instructions that are executable to cause the at least one processor to perform steps including:

• receiving, via the at least one antenna, a data stream on a first beam of the plurality of beams, the data stream including an uplink signal from a first UE, wherein the received uplink signal includes a Doppler shift due to one or more of an orbital motion of the satellite relative to the Earth and a motion of the first UE relative to the Earth;
• compensating the received data stream for a reference Doppler shift based on a trajectory of the satellite relative to a cell reference location within the beam footprint of the first beam, including converting the received uplink signal to a reference-location-compensated uplink signal, wherein the reference-location-compensated uplink signal retains a residual Doppler shift due to a difference in one or more of a location of the first UE relative to the cell reference location and a velocity of the first UE relative to the cell reference location;
• estimating a coarse portion of the residual Doppler shift;
• estimating a fine portion of the residual Doppler shift;
• and
• de-shifting the reference-location-compensated uplink signal by a shift frequency comprising the coarse portion and the fine portion.