Method and device for cell (re)selection in EFB-based non-terrestrial network

1 . A method of a user equipment (UE), the method comprising:

receiving, by a processor, configuration information of a cell service timer for each of at least one cell from a satellite;

decreasing, by the processor, the cell service timer indicating a time during which communication services can be provided for each of the at least one cell;

determining, by the processor, a candidate cell set including one or more cells for which the cell service timer exceeds a first preset value; and

performing, by the processor, a cell selection procedure for one cell belonging to the candidate cell set,

wherein the configuration information of the cell service timer for each of the at least one cell includes at least one of a value of the cell service timer for each of the at least one cell, location information of the UE, ephemeris information of the satellite, or elevation angle information of the satellite.

2 . The method of claim 1 , wherein the performing of the cell selection procedure for one cell belonging to the candidate cell set includes:

determining whether a number of cells belonging to the candidate cell set is 1; and

determining whether a reception quality of a first cell belonging to the candidate cell set exceeds a preset second value,

wherein upon concluding that the number of cells belonging to the candidate cell set is 1 and the reception quality of the first cell exceeds the preset second value, the first cell belonging to the candidate cell set is selected.

3 . The method of claim 1 , wherein the performing of the cell selection procedure for one cell belonging to the candidate cell set includes:

determining whether a number of cells belonging to the candidate cell set is 1;

in response that the number of cells belonging to the candidate cell set is not 1, determining a distance between a center of each of a plurality of cells belonging to the candidate cell set and a nadir of the satellite; and

selecting a candidate cell based on the distance between the center of each of the plurality of cells and the nadir of the satellite.

4 . The method of claim 1 , wherein the performing of the cell selection procedure for one cell belonging to the candidate cell set includes:

determining whether a number of cells belonging to the candidate cell set is 1;

in response that the number of cells belonging to the candidate cell set is not 1, determining traffic load information of a plurality of cells belonging to the candidate cell set; and

selecting a candidate cell based on the traffic load information of the plurality of cells.

5 . The method of claim 4 , wherein the performing of the cell selection procedure for one cell belonging to the candidate cell set includes:

determining whether a reception quality of the candidate cell exceeds a second preset value.

6 . The method of claim 1 , further including:

receiving, by the processor, variable measurement configuration information from the satellite; and

performing, by the processor, variable measurement procedures instead of general measurement procedures based on the variable measurement configuration information,

wherein a measurement periodicity for the variable measurement procedures is shorter than a measurement periodicity for the general measurement procedures.

7 . The method of claim 6 , wherein the variable measurement configuration information includes intermittent measurement configuration information and frequent measurement configuration information, intermittent measurement procedures are performed based on the intermittent measurement configuration information when a cell service timer of a cell selected in the cell selection procedure exceeds a threshold, and frequent measurement procedures are performed based on the frequent measurement configuration information when the cell service timer of the cell selected in the cell selection procedure is equal to or less than the threshold.

8 . The method of claim 1 , further including, after the performing of the cell selection procedure, triggering, by the processor, a cell reselection procedure when a cell service timer of a cell selected in the cell selection procedure is equal to or less than a threshold.

9 . A user equipment (UE) comprising:

a processor; and

a memory storing one or more instructions executable by the processor, wherein the one or more instructions are executed by the processor to perform:

receiving, by the processor, configuration information of a cell service timer for each of at least one cell from a satellite;

decreasing the cell service timer indicating a time during which communication services can be provided for each of the at least one cell;

determining a candidate cell set including one or more cells for which the cell service timer exceeds a first preset value; and

performing a cell selection procedure for one cell belonging to the candidate cell set,

wherein the configuration information of the cell service timer for each of the at least one cell includes at least one of a value of the cell service timer for each of the at least one cell, location information of the UE, ephemeris information of the satellite, or elevation angle information of the satellite.

10 . The UE of claim 9 , wherein the one or more instructions are further executed by the processor to perform:

determining whether a number of cells belonging to the candidate cell set is 1; and

determining whether a reception quality of a first cell belonging to the candidate cell set exceeds a preset second value,

wherein upon concluding that the number of cells belonging to the candidate cell set is 1 and the reception quality of the first cell exceeds the preset second value, the first cell belonging to the candidate cell set is selected.

11 . The UE of claim 9 , wherein the one or more instructions are further executed by the processor to perform:

determining whether a number of cells belonging to the candidate cell set is 1;

in response that the number of cells belonging to the candidate cell set is not 1, determining a distance between a center of each of a plurality of cells belonging to the candidate cell set and a nadir of the satellite; and

selecting a candidate cell based on the distance between the center of each of the plurality of cells and the nadir of the satellite.

12 . The UE of claim 9 , wherein the one or more instructions are further executed by the processor to perform:

determining whether a number of cells belonging to the candidate cell set is 1;

in response that the number of cells belonging to the candidate cell set is not 1, determining traffic load information of a plurality of cells belonging to the candidate cell set; and

selecting a candidate cell based on the traffic load information of the plurality of cells.

13 . The UE of claim 12 , wherein the one or more instructions are further executed by the processor to perform determining whether a reception quality of the candidate cell exceeds a second preset value.

14 . The UE of claim 9 , wherein the one or more instructions are further executed by the processor to perform:

receiving variable measurement configuration information from the satellite; and

performing variable measurement procedures instead of general measurement procedures based on the variable measurement configuration information,

wherein a measurement periodicity for the variable measurement procedures is shorter than a measurement periodicity for the general measurement procedures.

15 . The UE of claim 14 , wherein the variable measurement configuration information includes intermittent measurement configuration information and frequent measurement configuration information, intermittent measurement procedures are performed based on the intermittent measurement configuration information in response that a cell service timer of a cell selected in the cell selection procedure exceeds a threshold, and frequent measurement procedures are performed based on the frequent measurement configuration information in response that the cell service timer of the cell selected in the cell selection procedure is equal to or less than the threshold.

16 . The UE of claim 9 , wherein the one or more instructions are further executed by the processor to perform, after the performing of the cell selection procedure, triggering a cell reselection procedure when a cell service timer of a cell selected in the cell selection procedure is equal to or less than a threshold.