Method for synchronization between UEs according to change in reference synchronization source in V2X communication system, and device therefor
Provided are a method for synchronization between user equipments (UEs) according to a change in a reference synchronization source in a vehicle-to-everything (V2X) communication system, and a device therefor. A first transmission UE transmits information on a change in a reference synchronization source to at least one reception UE, and after a predetermined time, changes the reference synchronization source from the first transmission UE to a second transmission UE.
1 . A method comprising:
establishing, by a first device, connection between the first device and a second device;
receiving, from the second device, a first Sidelink Synchronization Signal Block (SL-SSB);
performing synchronization with the second device based on the first SL-SSB;
receiving, from the second device, sidelink services using the second device as a reference synchronization source;
receiving, from the second device, information about a change of the reference synchronization source; and
changing the reference synchronization source from the second device to a third device after a period of time,
wherein the information about the change of the reference synchronization source comprises a timing offset before and after the change of the reference synchronization source, and
wherein a Fast Fourier Transform (FFT) boundary is configured based on a timing with the second device as the reference synchronization source and the timing offset.
2 . The method of claim 1 , wherein broadcast services are provided from the second device within the FFT boundary.
3 . The method of claim 1 , wherein the information about the change of the reference synchronization source comprises information about a reference synchronization source activation time informing when the change of the reference synchronization source takes effect,
wherein the reference synchronization source activation time corresponds to the period of time.
4 . The method of claim 1 , wherein the information about the change of reference synchronization source comprises information about the third device.
5 . The method of claim 1 , wherein the information about the change of the reference synchronization source is transmitted from the second device, based on the second device receiving a second SL-SSB from the third device having a higher priority of the reference synchronization source than the second device.
6 . The method of claim 5 , wherein the information about the change of the reference synchronization source comprises an Identifier (ID) of the second SL-SSB.
7 . The method of claim 1 , wherein the timing offset comprises at least one of a System Frame Number (SFN) offset, a slot offset, a symbol offset, and/or a sample offset.
8 . The method of claim 1 , wherein the timing offset is expressed in sample units.
9 . The method of claim 1 , wherein the timing offset is a timing offset of SFN 0 or slot index 0.
10 . A first device comprising:
at least one transceiver;
at least one processor; and
at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed, cause the first device perform operations comprising:
establishing, by a first device, connection between the first device and a second device;
receiving, from the second device, a first Sidelink Synchronization Signal Block (SL-SSB);
performing synchronization with the second device based on the first SL-SSB;
receiving, from the second device, sidelink services using the second device as a reference synchronization source;
receiving, from the second device, information about a change of the reference synchronization source; and
changing the reference synchronization source from the second device to a third device after a period of time,
wherein the information about the change of the reference synchronization source comprises a timing offset before and after the change of the reference synchronization source, and
wherein a Fast Fourier Transform (FFT) boundary is configured based on a timing with the second device as the reference synchronization source and the timing offset.