Doppler compensation for non-terrestrial networks

Abstract

Various arrangements are presented for compensating for Doppler shift on a non-terrestrial orthogonal frequency division multiplexing (OFDM) network. An absolute position of a UE instance may be determined. A relative velocity of the UE instance with respect to a satellite of the non-terrestrial based OFDM network may be determined. A frequency delta due to Doppler shift may be determined. A transmit frequency at which uplink OFDM symbols are transmitted to a satellite of the non-terrestrial based OFDM network may be determined using the frequency delta.

Description

[Technical field]

[0001] [Cross Reference] This application claims the benefit of and priority to U.S. patent application Ser. No. 16 / 401,528, filed May 2, 2019, entitled “DOPPLER COMPENSATION FOR A NON-TERRESTRIAL NETWORK,” which is incorporated by reference in its entirety. [Background technology]

[0002] The amount of Doppler shift induced in an electromagnetic signal may be defined by Equation 1:

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[0003] In Equation 1, the change in frequency (ΔF) is equal to the nominal carrier frequency (F0) multiplied by the relative velocity component of the objects transmitting and receiving electromagnetic signals toward or away from each other, multiplied by the cosine of the angle between the objects divided by the speed of light. The higher the carrier frequency, the greater the change in frequency that will be caused by the Doppler shift. Also, the greater the velocity, the greater the change in frequency.

[0004] At lower frequencies, when an instance of user equipment, such as a mobile phone, is communicating with a fixed base station, the amount of Doppler shift introduced may be relatively small and may not have a significant effect on frequency. However, at higher frequencies, in situations where the UE is moving at high speed (e.g., on a high-speed train or airplane), the amount of Doppler shift may no longer be negligible. Summary of the Invention

[0005] Various arrangements are presented herein for compensating for Doppler shift on a non-terrestrial based network, such as an Orthogonal Frequency Division Multiplexing (OFDM) network. A user equipment (UE) instance may determine an absolute position of the UE instance. An angle between the UE instance and a satellite of the non-terrestrial based OFDM network may be determined. A relative velocity of the UE instance with respect to the satellite of the non-terrestrial based OFDM network may be determined. A frequency delta may be determined based on a nominal uplink carrier frequency, the relative velocity, and the angle. Using the frequency delta, a transmit frequency at which uplink OFDM symbols are transmitted to a satellite of the non-terrestrial based OFDM network may be adjusted. The UE instance may transmit the uplink OFDM symbols at the adjusted transmit frequency.

[0006] An embodiment of such an arrangement may include one or more of the following mechanisms, where determining a relative velocity of the UE instance with respect to a satellite of the non-terrestrial based OFDM network may include determining a velocity of the UE instance with respect to the Earth using Global Navigation Satellite System (GNSS) measurements. The satellite may be in a Low Earth Orbit (LEO) or a Medium Earth Orbit (MEO). Determining a relative velocity of the UE instance with respect to the satellite of the non-terrestrial based OFDM network may include accessing data indicating an orbit and an orbital velocity of the satellite. The satellite may be in a geostationary orbit. A frequency of a downlink OFDM symbol received from the satellite of the non-terrestrial based OFDM network may be measured. A frequency shift between an expected downlink frequency of the downlink OFDM symbol received from the satellite of the non-terrestrial based OFDM network and the measured frequency may be determined. Adjusting a transmission frequency at which the uplink OFDM symbol is transmitted to the satellite of the non-terrestrial based OFDM network may be further based on the determined frequency shift between an expected downlink frequency of the downlink OFDM symbol received from the satellite of the non-terrestrial based OFDM network and the measured frequency. The UE instance may communicate with a satellite of a non-terrestrial based OFDM network using a 5G New Radio (NR) radio access technology (RAT). The UE instance may be a smartphone. [Brief description of the drawings]

[0007] A further understanding of the nature and advantages of various embodiments may be realized by reference to the following figures. In the accompanying figures, similar components or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes between the similar components. When only a first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label, regardless of the second reference label.

[0008] [Figure 1] An embodiment is described in which an instance of a UE moves relative to a satellite of a non-terrestrial based network. [Diagram 2] An embodiment is described in which a UE changes its transmission frequency to compensate for Doppler shift. [Diagram 3] An embodiment of a method for instance in a UE to compensate for Doppler shift is described. [Figure 4] Another embodiment of a method for instance in a UE to compensate for Doppler shift based on an amount of Doppler shift measured in a downlink signal is described. [Diagram 5] An embodiment of a method for a UE instance to compensate for Doppler shift based on the amount of Doppler shift measured in a downlink signal and a frequency delta based on calculated velocity, position, and angle is described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Orthogonal Frequency Division Multiplexing (OFDM) is a method of digital signal modulation that allows narrowband channels to exist on subcarrier frequencies without guard bands between the subcarriers. For OFDM signal modulation to function properly, it is important that devices transmit precisely on their assigned subcarrier frequencies to reduce interference and crosstalk between the subcarrier frequencies. At low frequencies, when devices communicating with each other are stationary or nearly stationary, the Doppler effect may not need to be considered to avoid such interference and crosstalk. However, as frequency and relative speed increase, the Doppler effect can have a significant effect over frequency.

[0010] In a non-terrestrial based network (NTN), communication may occur between a user equipment (UE) instance and a satellite. If the satellite is in geostationary orbit, it may be effectively treated as stationary. However, the UE may potentially be moving at high speed. By way of example, the UE may be temporarily installed or permanently attached to a high speed train or airplane. By way of example, the UE may be used to provide WiFi to passengers so that they may access the Internet and other network-based services. If the satellite is in a non-geostationary orbit (e.g., LEO or MEO), the relative velocity component between the UE and the satellite may increase significantly due to the satellite's orbit around the Earth. As a simple example, referring to Equation 1, a satellite's orbit in LEO at 30 GHz may contribute a Doppler shift of 720 kHz.

[0011] The UE instance may be able to determine its position and velocity, such as by using a Global Navigation Satellite System (GNSS). The UE may further have access to data indicating the positions and orbits of the satellites. The UE may be able to determine the angle between the UE and the satellites, and the relative velocity components along the surface of the Earth toward or away from the satellites. The UE may then be able to calculate the amount of frequency shift that would be caused by the Doppler effect. The UE may then adjust its uplink transmission frequency, such as for transmission of OFDM symbols, to compensate for the Doppler effect.

[0012] Additionally or alternatively, the UE instance may be able to compare the received frequency of the downlink signal from the satellite with the expected frequency. The difference in frequency may be due to the Doppler effect. Using this change in frequency, the UE may be able to calculate the change in frequency that the Doppler effect would affect the uplink transmission, which may occur on a different frequency. This change in frequency may be combined (e.g., averaged) with the change in frequency calculated based on the position, velocity, and angle, or may be used in place of this calculation.

[0013] FIG. 1 illustrates an embodiment of a system 100 in which a UE instance 110 moves relative to a satellite 120 of a non-terrestrial based network. The non-terrestrial based network may use OFDM and may enable bidirectional communication with the UE instance. In some embodiments, the non-terrestrial based network may be a 5G New Radio (NR) network. In various embodiments, the satellite 120 may be in geostationary orbit or in LEO or MEO. The UE instances 110 (110-1, 110-2) may move in various directions approximately along the surface of the Earth 101 relative to the satellite 120 (although two UE instances 110 are illustrated, this number of UEs is for illustrative purposes only. In a real world implementation, a much larger number of UEs may be in communication with the satellite 120). The UE instances 110 may be smartphones, mobile phones, tablet computers, or other computerized devices that communicate with a satellite that is part of the NTN. In some embodiments, the UE instances may be used to provide network access to multiple other users. As an illustration, a mass transit vehicle such as a train or airplane may have installed UEs that enable WiFi or other network access for a large number of people. Such communications may be performed using 5G New Radio (NR) radio access technology (RAT). In an embodiment where the satellite 120 is in geostationary orbit, the satellite 120 may be treated as stationary. In such an embodiment, Doppler shifts in uplink transmissions (i.e., data transmissions from an instance of a UE to the satellite 120) may be entirely attributable to the movement of the particular UE instance. For example, if UE instance 110-1 is moving west at 600 km / hr, it may result in a significant amount of Doppler shift in uplink communications compared to UE instance 110-2 moving east at 100 km / hr.

[0014] Each of the UE instances 110 may be capable of determining its absolute position. By way of illustration, a Global Navigation Satellite System (GNSS) module may be installed in each UE instance. Such a GNSS module may use Global Positioning System (GPS), GLONASS, Galileo, Beidou, and / or other types of positioning systems. Each UE instance may 1) have access to data indicating the position of satellites 120, 2) be able to determine its absolute position using the GNSS module, and 3) be able to determine its ground speed (relative to the surface of the Earth), such as using multiple GNSS measurements. Using this information, each UE instance may determine 1) a relative velocity component indicating its speed along the surface of the Earth toward or away from the satellite, and 2) an angle 131. The angle 131 represents the difference between the uplink communication path 130 and approximately the surface of the Earth 101 (or the direction to a point 135 on the surface of the Earth 101 directly below the satellite 120). The angle 131 may be used as part of Equation 1. As an example, because UE instance 110-1 displaces a greater distance (distance 132) along the surface of the Earth 101 from satellite 120 than UE 110-2 (distance 142), movement of UE instance 110-1 may have a greater impact on the Doppler shift than movement of UE instance 110-2.

[0015] In a first set of embodiments, the satellite 120 is in a geostationary orbit. Thus, each UE instance may calculate the amount of frequency shift based on the absolute position of the UE instance, the relative velocity components along the surface of the Earth toward or away from the satellite, and the location of the satellite. In a second set of embodiments, the satellite 120 is in a LEO or MEO orbit. In such embodiments, the orbit and velocity of the satellite 120 need to be considered to determine the amount of Doppler shift that the orbit of the satellite around the Earth 101 will affect the uplink transmission. By way of illustration, if the velocity 111 of the UE instance 110-1 is moving directly away from the satellite 120 along the surface of the Earth 101 and the satellite 121 is moving in the opposite direction of the velocity 121, the Doppler shift in the uplink transmission may be significantly larger than the uplink transmission from the UE instance 110-2, which may be traveling at a velocity 112 (which may be the same speed as the velocity 111 but in the opposite direction). Because the velocity 112 is in the same direction as the velocity 121 of the satellite 120, the velocity may partially cancel the Doppler effect. UE instance 110-1 may determine a velocity component toward or away from point 135.

[0016] FIG. 2 illustrates an embodiment of an instance of a UE that changes its transmission frequency to compensate for Doppler shift. The illustrated UE instance is UE instance 110-1 of FIG. 1. Other instances of a UE may include the same or similar components. UE instance 110-1 may include a processing system 210, satellite orbit data 215, GNSS receiver 220, frequency controller 230, receiver 240, transmitter 250, and Doppler shift analyzer 260. Processing system 210 may include one or more processors. Processing system 210 may include one or more dedicated or general-purpose processors. Such dedicated processors may include processors specifically designed to perform the functions detailed herein. Such dedicated processors may be ASICs or FPGAs, which are general-purpose components physically and electrically configured to perform the functions detailed herein. Such general-purpose processors may execute dedicated software stored using one or more non-transitory processor-readable media, such as random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD).

[0017] The processing system 210 may receive absolute position measurements from the GNSS receiver 220 relative to the Earth 101. Based on the absolute position measurements, the processing system 210 may determine a velocity (which may indicate speed and direction) of the UE instance relative to the surface of the Earth. The processing system 210 may have access to a non-transitory processor-readable medium that may store satellite orbit data 215. The satellite orbit data 215 may store positions of geostationary satellites. The satellite orbit data 215 may store orbit information for LEO and / or MEO satellites that allows the processing system 210 to calculate the current position and velocity of the satellite from which the uplink transmission is transmitted. The processing system 210 may use Equation 1 to calculate the amount of Doppler shift caused by movement between the UE instance 110-1 and the satellite from which the uplink transmission is transmitted. The amount by which the frequency is adjusted (frequency delta) or the corrected carrier frequency may be output by the processing system 210 to the frequency controller 230. The frequency controller 230 may be configured to control the frequency at which uplink transmissions, such as OFDM symbols, are transmitted by the transmitter 250 .

[0018] The Doppler shift analyzer 260 may receive the downlink transmission from the satellite via the receiver 240. The receiver 240 may expect to receive the downlink transmission on a particular frequency. However, due to Doppler shifts caused by movement of the satellite and / or the UE instance 110-1, the downlink transmission may be received on a different frequency. The Doppler shift analyzer 260 may determine a frequency difference (or frequency delta) between the expected frequency at which the downlink transmission is received and the actual frequency at which the downlink transmission is received.

[0019] The processing system 210 may use the frequency delta observed by the Doppler shift analyzer 260 in addition to or instead of the calculated Doppler shift. Illustratively, in some embodiments, the change in frequency determined by the Doppler shift analyzer 260 may be averaged with the change in frequency calculated by the processing system 210. In other embodiments, the processing system 210 may select between using the change in frequency received from the Doppler shift analyzer 260 and using the change in frequency calculated based on observed conditions. Feedback may be received from the satellite indicating how well the uplink data transmitted by the UE instance 110-1 compensates for the Doppler shift. If the uplink transmission has sufficient error in the frequency correction, the processing system 210 may switch or adjust how it compensates for the Doppler shift using the change in frequency determined by the Doppler shift analyzer 260 and the change in frequency calculated.

[0020] A Doppler shift on a downlink communication may tend to cause less interference than a Doppler shift on an uplink transmission. Because all of the downlink transmissions originate from the same source (i.e., the satellite), each UE instance will observe all of the downlink transmissions shifted in the frequency domain. Because all of the downlink transmissions are shifted in the frequency domain, little or no interference occurs between such downlink transmissions.

[0021] 3 illustrates an embodiment of a method 300 for a UE instance to compensate for Doppler shift. The method 300 may be performed by a UE instance, such as UE instance 110-1. The UE instance may include components as detailed in connection with FIG. 2. At block 305, the UE instance may determine its absolute position with respect to the Earth. This absolute position may be determined using a GNSS component.

[0022] In block 310, a relative velocity component of the UE instance with respect to a satellite with which the UE instance is about to communicate or is already communicating may be determined or calculated. The relative velocity component may represent a velocity toward or away from a point on the Earth that is directly beneath the satellite's location. If the satellite has a geostationary orbit, the satellite may be treated as stationary. If the satellite is in a LEO or MEO orbit, the relative velocity component of the satellite toward or away from the UE instance may be added to the UE's velocity component (if in the opposite direction) or subtracted from the UE's velocity component (if in the same direction) to determine the relative velocity component.

[0023] In block 315, an angle between the UE instance and the satellite may be determined. The angle may be between a direct path to the satellite (e.g., uplink communication path 130) and a point on the Earth's surface directly below the satellite (e.g., point 135 in FIG. 1). The smaller the angle, the greater the effect of the relative velocity component of the Doppler shift on the uplink transmission as received by the satellite. To determine the angle, the position of the satellite may be required by the UE instance. The UE instance may access locally stored satellite orbit data or may access stored satellite data from a remote source, such as over a network.

[0024] At block 320, a frequency delta may be calculated by the UE instance using Equation 1. Equation 1 may be calculated by the UE instance and may use the relative velocity components at which the satellite and the UE move towards or away from each other and the angle calculated at block 315 to determine the frequency delta.

[0025] At block 325, the transmit frequency at which uplink data transmissions, such as OFDM symbols, are transmitted may be changed using a frequency delta. The frequency delta may be used to increase the transmit frequency or decrease the transmit frequency. If the relative velocity components indicate that the UE instance and the satellite are moving away from each other, the transmit frequency may be increased, and if the relative velocity components indicate that the UE instance and the satellite are moving towards each other, the transmit frequency may be decreased.

[0026] At block 330, the uplink OFDM symbol may be transmitted using the adjusted transmit frequency. By adjusting the frequency using the calculated frequency delta, the Doppler shift may be compensated for such that the subcarrier on which the OFDM symbol was transmitted, when received by the satellite, causes little or no interference with other subcarrier transmissions by other instances of the UE. Thus, the satellite may effectively receive the uplink transmission at the nominal subcarrier frequency (without any perceived Doppler shift).

[0027] FIG. 4 illustrates another embodiment of a method for a UE instance to compensate for Doppler shift based on an amount of Doppler shift measured on a downlink signal. Method 400 may be performed by a UE instance, such as UE instance 110-1. The UE instance may include components as detailed in connection with FIG. 2. Method 400 may be performed instead of or in addition to method 300. At block 401, a downlink signal may be received from a satellite. At block 405, a received frequency of the downlink signal may be determined by the UE instance. At block 410, the UE instance may determine a frequency at which it expects to receive the downlink signal. By way of illustration, a downlink message may include data indicating a frequency at which the data was transmitted, or the UE instance may have stored data indicating a frequency at which the downlink data is transmitted by the satellite. At block 415, a frequency delta between the expected frequency and the received frequency may be calculated by the UE instance.

[0028] Using Equation 2, which is equivalent to Equation 1, and using the frequency delta determined in block 415 and the nominal carrier frequency,

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[0029] Calculated from Eq.

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[0030] At block 425, the transmit frequency at which the uplink data transmission, such as OFDM symbols, is transmitted may be changed using the frequency delta calculated at block 420. The frequency delta may be used to increase or decrease the transmit frequency. If the relative velocity components indicate that the UE instance and the satellite are moving away from each other, the transmit frequency may be increased, and if the relative velocity components indicate that the UE instance and the satellite are moving towards each other, the transmit frequency may be decreased. At block 425, the uplink transmission, such as OFDM symbols, may be transmitted using the adjusted transmit frequency. By adjusting the frequency using the frequency delta calculated based on the measured Doppler shift of the downlink transmission, the Doppler shift may be compensated for to cause little or no interference with other subcarrier transmissions by other instances of the UE.

[0031] 5 illustrates an embodiment of a method for a UE instance to compensate for Doppler shift based on an amount of Doppler shift measured in a downlink signal and a frequency delta based on a calculated velocity, position, and angle. At block 505, the UE instance may determine its absolute position with respect to the Earth. This absolute position may be determined using a GNSS component.

[0032] At block 510, a relative velocity component of the UE instance with respect to a satellite with which the UE instance is about to communicate or is already communicating may be determined or calculated. The relative velocity component may represent a velocity toward or away from a point on the Earth that is directly beneath the satellite's location. If the satellite has a geostationary orbit, the satellite may be treated as stationary. If the satellite is in a LEO or MEO orbit, the relative velocity component of the satellite toward or away from the UE instance may be added to the UE's velocity component (if in the opposite direction) or subtracted from the UE's velocity component (if in the same direction) to determine the relative velocity component.

[0033] At block 515, an angle between the UE instance and the satellite may be determined. The angle may be between a direct path to the satellite (e.g., uplink communication path 130) and a point on the Earth's surface directly below the satellite (e.g., point 135 in FIG. 1). The smaller the angle, the greater the effect of the relative velocity component of the Doppler shift on the uplink transmission as received by the satellite. To determine the angle, the position of the satellite may be required by the UE instance. The UE instance may access locally stored satellite orbit data or may access stored satellite data from a remote source, such as over a network.

[0034] At block 520, a first frequency delta may be calculated by the UE instance using Equation 1. Equation 1 may be calculated by the UE instance and may use the relative velocity components by which the satellite and the UE are moving towards or away from each other and the angle calculated at block 515 to determine the frequency delta.

[0035] At block 525, a downlink signal may be received from the satellite. At block 530, a received frequency of the downlink signal may be determined by the UE instance. At block 535, the UE instance may determine a frequency at which it expects to receive the downlink signal. By way of illustration, the downlink message may include data indicating a frequency at which the data was transmitted, or the UE instance may have stored data indicating a frequency at which the downlink data is transmitted by the satellite. At block 540, a downlink frequency delta between the expected frequency and the received frequency may be calculated by the UE instance.

[0036] In block 545, to determine a second frequency delta to compensate for the Doppler shift of the uplink transmission, Equation 2, as detailed in connection with method 400, is used to calculate Equation 1 for a nominal carrier frequency for the uplink OFDM symbol transmission:

number

[0037] At block 550, either the first frequency delta or the second frequency delta is selected for use to adjust the uplink transmission frequency (e.g., of an OFDM symbol). In some embodiments, the first frequency delta and the second frequency delta are averaged together or otherwise combined. In some embodiments, weighting is used. By way of illustration, feedback may be received from a satellite from time to time indicating an amount of error in the frequency of the uplink transmission from the UE instance. Based on the feedback data, a weighting of the first frequency delta compared to the second frequency delta may be adjusted. In other embodiments, the feedback data may indicate whether the calculated first frequency delta or the calculated second frequency delta should be used to adjust the uplink transmission.

[0038] At block 555, the transmit frequency at which uplink data transmissions, such as OFDM symbols, are transmitted may be changed using the frequency delta combined at block 550. The frequency delta may be used to increase the transmit frequency or decrease the transmit frequency. If the relative velocity components indicate that the UE instance and the satellite are moving away from each other, the transmit frequency may be increased, and if the relative velocity components indicate that the UE instance and the satellite are moving towards each other, the transmit frequency may be decreased. At block 560, uplink transmissions, such as OFDM symbols, may be transmitted using the adjusted transmit frequency. The frequency may be adjusted using a frequency delta calculated based on a measured Doppler shift of the downlink transmission, so that the Doppler shift may be compensated for to cause little or no interference with other subcarrier transmissions by other instances of the UE.

[0039] The methods, systems, and devices discussed above are exemplary. Various configurations may omit, substitute, or add various procedures or components, as appropriate. Illustratively, in alternative configurations, the methods may be performed in an order different from that described, and / or various steps may be added, omitted, and / or combined. Also, features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. Also, because technology evolves, many of the elements are exemplary and do not limit the scope of the disclosure or claims.

[0040] Specific details are given in the description to provide a thorough understanding of the example configurations (including implementations). However, the configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques are shown without unnecessary detail to avoid obscuring the configurations. This description provides only example configurations and does not limit the scope, applicability, or configuration of the claims. Rather, the foregoing description of the configurations will provide one skilled in the art with an effective description for implementing the described technology. Various changes may be made in the function and arrangement of elements without departing from the spirit or scope of the disclosure.

[0041] Also, the configurations may be described as processes depicted as flow diagrams or block diagrams. Although each may be described as a sequential process of operations, many of the operations may be performed in parallel or simultaneously. Also, the order of operations may be rearranged. A process may have additional steps not included in the figures. Furthermore, the example methods may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. If implemented by software, firmware, middleware, or microcode, the program code or code segments to perform the necessary tasks may be stored in a non-transitory computer-readable medium, such as a storage medium. A processor may perform the tasks described.

[0042] While several example configurations have been described, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be components of a larger system, and other rules may take precedence over or otherwise modify the application of the invention. Also, some steps may be undertaken before, during, or after the above elements are considered.

Claims

1. 1. A method for compensating for Doppler shift on a non-terrestrial based Orthogonal Frequency Division Multiplexing (OFDM) network, comprising: measuring, by a user equipment (UE) instance, a frequency of downlink OFDM symbols received from a satellite of said non-terrestrial based OFDM network; determining a frequency shift between an expected downlink frequency of the downlink OFDM symbols received from the satellite of the non-terrestrial based OFDM network and the measured frequency; determining, by the UE instance, an absolute location of the UE instance; determining, by the UE instance, an angle between the UE instance and the satellite of the non-terrestrial based OFDM network; determining, by the UE instance, a relative velocity of the UE instance with respect to the satellites of the non-terrestrial based OFDM network; determining, by the UE instance, a frequency delta based on a nominal uplink carrier frequency, the relative velocity, and the angle; adjusting, by the UE instance, a transmission frequency at which uplink OFDM symbols are transmitted to the satellite of the non-terrestrial based OFDM network using the frequency delta; transmitting, by the UE instance, the uplink OFDM symbol at the adjusted transmission frequency; A method comprising:

2. Determining the relative velocity of the UE instance with respect to the satellites of the non-terrestrial based OFDM network comprises: determining a velocity of the UE instance relative to the Earth using Global Navigation Satellite System (GNSS) measurements; 2. A method for compensating for Doppler shift on a non-terrestrial based OFDM network according to claim 1, comprising:

3. 3. The method for compensating for Doppler shift on a non-terrestrial based OFDM network as claimed in claim 2, wherein the satellites are in low earth orbit (LEO) or medium earth orbit (MEO).

4. Determining the relative velocity of the UE instance with respect to the satellites of the non-terrestrial based OFDM network comprises: Accessing data indicating the orbit and orbital velocity of said satellite; 4. A method for compensating for Doppler shift on a non-terrestrial based OFDM network as claimed in claim 3, comprising:

5. 2. The method for compensating for Doppler shift on a non-terrestrial based OFDM network as recited in claim 1, wherein said satellites are in geostationary orbit.

6. 2. The method for compensating for Doppler shift on a non-terrestrial based OFDM network of claim 1, wherein adjusting the transmission frequency at which the uplink OFDM symbols are transmitted to the satellite of the non-terrestrial based OFDM network is further based on the determined frequency shift between the expected downlink frequency and the measured frequency of the downlink OFDM symbols received from the satellite of the non-terrestrial based OFDM network.

7. 2. The method for compensating for Doppler shift on a non-terrestrial based OFDM network of claim 1, wherein the UE instance communicates with the satellite of the non-terrestrial based OFDM network using a 5G New Radio (NR) radio access technology (RAT).

8. The method for compensating for Doppler shift on a non-terrestrial based OFDM network according to claim 7, wherein the UE instance is a smartphone.

9. 1. A system for compensating for Doppler shift on a non-terrestrial orthogonal frequency division multiplexing (OFDM) network, comprising: a satellite that is part of the non-terrestrial OFDM network; A user equipment (UE) instance, A transmitter; A receiver; 1. A processing system including one or more processors, measuring a frequency of a downlink OFDM symbol received from the satellite of the non-terrestrial based OFDM network; determining a frequency shift between an expected downlink frequency of the downlink OFDM symbols received from the satellite of the non-terrestrial based OFDM network and the measured frequency; determining an absolute location of the UE instance; determining an angle between the UE instance and the satellite of the non-terrestrial based OFDM network; determining a relative velocity of the UE instance with respect to the satellites of the non-terrestrial based OFDM network; determining a frequency delta based on a nominal uplink carrier frequency, the relative velocity, and the angle; using the frequency delta to adjust a transmission frequency at which uplink OFDM symbols are transmitted to the satellite of the non-terrestrial based OFDM network; causing the uplink OFDM symbols to be transmitted to the satellite at the adjusted transmission frequency; the processing system configured to The UE instance including Including, the system.

10. the processing system of the UE instance configured to determine the relative velocity of the UE instance with respect to the satellites of the non-terrestrial based OFDM network; determining a velocity of the UE instance relative to the Earth using Global Navigation Satellite System (GNSS) measurements; 10. The system for compensating for Doppler shift on a non-terrestrial based OFDM network of claim 9, comprising the processing system configured to:

11. 11. The system for compensating for Doppler shift on a non-terrestrial based OFDM network as recited in claim 10, wherein the satellites are in low earth orbit (LEO) or medium earth orbit (MEO).

12. the processing system of the UE instance configured to determine the relative velocity of the UE instance with respect to the satellites of the non-terrestrial based OFDM network; Accessing data indicating the orbit and orbital velocity of said satellite; The system for compensating for Doppler shift on a non-terrestrial based OFDM network of claim 11 , comprising the processing system of the UE instance configured to:

13. 10. The system for compensating for Doppler shift on a non-terrestrial based OFDM network as recited in claim 9, wherein said satellites are in geostationary orbits.

14. 10. The system for compensating for Doppler shifts on a non-terrestrial based OFDM network of claim 9, wherein the processing system of the UE instance configured to adjust the transmission frequency at which the uplink OFDM symbols are transmitted to the satellite of the non-terrestrial based OFDM network is further based on the determined frequency shift between the expected downlink frequency and the measured frequency of the downlink OFDM symbols received from the satellite of the non-terrestrial based OFDM network.

15. 10. The system for compensating for Doppler shift on a non-terrestrial based OFDM network of claim 9, wherein the UE instance communicates with the satellite of the non-terrestrial based OFDM network using a 5G New Radio (NR) radio access technology (RAT).

16. The system for compensating for Doppler shift on a non-terrestrial based OFDM network as recited in claim 15, wherein the UE instance is a smartphone.

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