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US-12628052-B2 - Epoch time acquisition for non-terrestrial networks (NTN) handover

US12628052B2US 12628052 B2US12628052 B2US 12628052B2US-12628052-B2

Abstract

Aspects are described for a user equipment (UE) comprising a transceiver configured to enable wireless communication with a serving cell and a target cell and a processor communicatively coupled to the transceiver. The processor is configured to receive a handover command from the serving cell. The handover command comprises an epoch index and ephemeris information of the target cell. The processor is further configured to determine an epoch time of the target cell based on the epoch index and perform time synchronization with the target cell using the epoch time and the ephemeris information.

Inventors

  • Jie Cui
  • Fangli XU
  • Chunxuan Ye
  • Yang Tang
  • Hong He
  • Qiming Li
  • Yuqin Chen
  • Dawei Zhang

Assignees

  • APPLE INC.

Dates

Publication Date
20260512
Application Date
20231113

Claims (16)

  1. 1 . A user equipment (UE) comprising: a transceiver configured to enable wireless communication with a serving cell and a target cell; and a processor communicatively coupled to the transceiver and configured to: receive, using the transceiver, a handover command from the serving cell, wherein the handover command comprises an epoch index and ephemeris information of the target cell; determine an epoch time of the target cell based on the epoch index; and perform time synchronization with the target cell using the epoch time and the ephemeris information, wherein to perform the time synchronization with the target cell using the epoch time and the ephemeris information of the target cell, the processor is further configured to determine that the target cell is associated with a geostationary orbit of a satellite.
  2. 2 . The UE of claim 1 , wherein to determine the epoch time, the processor is further configured to: determine that the epoch index corresponds to the serving cell; determine a current time index of the serving cell; and determine the epoch time based on the epoch index and the current time index.
  3. 3 . The UE of claim 1 , wherein the epoch index comprises one of a system frame number (SFN), a subframe number, or a slot index.
  4. 4 . The UE of claim 1 , wherein the handover command indicates whether the epoch index is in reference to timing of the serving cell.
  5. 5 . The UE of claim 1 , wherein the processor is further configured to: determine the epoch time based on the epoch index and an offset value, wherein the handover command includes the offset value.
  6. 6 . The UE of claim 1 , wherein the processor is further configured to: receive, using the transceiver, neighbor cell system information from the serving cell, wherein the neighbor cell system information comprise a second epoch index of the target cell; and determine the epoch time based on the second epoch index.
  7. 7 . A method of operating a user equipment (UE) comprising: receiving a handover command from a serving cell, wherein the handover command comprises an epoch index and ephemeris information of a target cell; determining an epoch time of the target cell based on the epoch index; and performing time synchronization with the target cell using the epoch time and the ephemeris information, wherein the performing the time synchronization with the target cell using the epoch time and the ephemeris information further comprises determining that the target cell is associated with a geostationary orbit of a satellite.
  8. 8 . The method of claim 7 , wherein the determining the epoch time further comprises: determine that the epoch index corresponds to the serving cell; determine a current time index of the serving cell; and determine the epoch time based on the epoch index and the current time index.
  9. 9 . The method of claim 7 , wherein the handover command indicates whether the epoch index is in reference to timing of the serving cell.
  10. 10 . The method of claim 7 , further comprising: determine the epoch time based on the epoch index and an offset value, wherein the handover command includes the offset value.
  11. 11 . The method of claim 7 , further comprising: receiving neighbor cell system information from the serving cell, wherein the neighbor cell system information comprise a second epoch index of the target cell; and determining the epoch time based on the second epoch index.
  12. 12 . A base station comprising: a transceiver configured to enable wireless communication with a user equipment (UE) and a second base station; and a processor communicatively coupled to the transceiver and configured to: generate a handover command that comprises an epoch index and ephemeris information of the second base station; transmit, using the transceiver, the handover command to the UE; generate a configuration message that indicates whether the epoch index is associated with: one of a closest past system frame number (SFN), a closest past subframe number, or a closest past slot index, or one of a closest future SFN index, a closest future subframe number, or a closest future slot index; and transmit, using the transceiver, the configuration message to the UE, wherein the epoch index is in reference to timing of the base station, and wherein the epoch index is associated with an epoch time for the UE to perform time synchronization with the second base station.
  13. 13 . The base station of claim 12 , wherein to generate the handover command, the processor is further configured to: transmit a request for information to the second base station; receive a response from the second base station, wherein the response includes a second epoch index and the ephemeris information; and convert the second epoch index to the epoch index.
  14. 14 . The base station of claim 12 , wherein to generate the handover command, the processor is further configured to: determine a time offset between the base station and the second base station, wherein the handover command includes the time offset.
  15. 15 . The base station of claim 14 , wherein the handover command further indicates whether the time offset is positive of negative.
  16. 16 . The base station of claim 12 , wherein the processor is further configured to: generate a configuration message that configures the UE whether to determine the epoch time based the epoch index or a second epoch index of neighbor cell system information; and transmit, using the transceiver, the configuration message to the UE.

Description

CROSS REFERENCES This application claims the benefit of U.S. Provisional Application No. 63/430,089 filed Dec. 5, 2022, titled “EPOCH TIME ACQUISITION FOR NON-TERRESTRIAL NETWORKS (NTN) HANDOVER,” the content of which is herein incorporated by reference in its entirety. BACKGROUND Field The described aspects generally relate to an epoch time acquisition process in wireless communications that a wireless network that includes one or more satellites. SUMMARY Some aspects of this disclosure relate to systems, apparatuses, and methods for implementing an epoch time acquisition in a non-terrestrial networks (NTN) handover procedure. For example, the systems, the apparatuses, and the methods are provided for determining an epoch time based on an epoch index of a target cell. Some aspects of this disclosure relate to a user equipment (UE) comprising a transceiver configured to enable wireless communication with a serving cell and a target cell and a processor communicatively coupled to the transceiver. The processor is configured to receive a handover command from the serving cell. The handover command comprises an epoch index and ephemeris information of the target cell. The processor is further configured to determine an epoch time of the target cell based on the epoch index and perform time synchronization with the target cell using the epoch time and the ephemeris information. Some aspects of this disclosure relate to a method of operating a UE. The method comprises receiving a handover command from a serving cell. The handover command comprises an epoch index and ephemeris information of a target cell. The method further comprises determining an epoch time of the target cell based on the epoch index and performing time synchronization with the target cell using the epoch time and the ephemeris information. Some aspects of this disclosure relate to a base station comprising a transceiver configured to enable wireless communication with a UE and a second base station and a processor communicatively coupled to the transceiver. The processor is configured to generate a handover command that comprises an epoch index and ephemeris information of the second base station and transmit the handover command to the UE. The epoch index is in reference to timing of the base station. The epoch index is associated with an epoch time for the UE to perform time synchronization with the second base station. This Summary is provided merely for the purposes of illustrating some aspects to provide an understanding of the subject matter described herein. Accordingly, the above-described features are merely examples and should not be construed to narrow the scope or spirit of the subject matter in this disclosure. Other features, aspects, and advantages of this disclosure will become apparent from the following Detailed Description, Figures, and Claims. BRIEF DESCRIPTION OF THE FIGURES The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the disclosure and enable a person of skill in the relevant art(s) to make and use the disclosure. FIG. 1 illustrates an example system implementing a non-terrestrial networks (NTN) handover procedure, according to some aspects of the disclosure. FIG. 2 illustrates a block diagram of an example system of an electronic device for the NTN handover procedure, according to some aspects of the disclosure. FIG. 3 illustrates an example method of the NTN handover procedure, according to aspects of the disclosure. FIG. 4 illustrates an example method of an epoch time acquisition process, according to aspects of the disclosure. FIG. 5 illustrates an example method of generating and transmitting a handover command, according to aspects of the disclosure. FIG. 6 illustrates an example of time index cycles, according to aspects of the disclosure. FIG. 7 is an example computer system for implementing some aspects of the disclosure or portion(s) thereof. The present disclosure is described with reference to the accompanying drawings. In the drawings, generally, like reference numbers indicate identical or functionally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. DETAILED DESCRIPTION Some aspects of this disclosure relate to systems, apparatuses, and methods for implementing an epoch time acquisition process in wireless communications. For example, the systems, the apparatuses, and the methods are provided for determining an epoch time based on an epoch index of a target cell. In some aspects, a UE communicates with a serving cell via a wireless connection to transmit and receive data. When the UE moves towards an edge of the serving cell, the UE can be configured to hand over to another cell. For example, the UE can establish a wireless connection with a