Method and apparatus for prioritizing LTE cells in wireless communication system supporting ENDC (E-UTRAN NR dual connectivity)

1. A method performed by a user equipment (UE) in a wireless communication system supporting Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network (E-UTRAN) New Radio (NR)-Dual Connectivity (ENDC), the method comprising:

receiving system information comprising information on an NR band list supported in the ENDC;

identifying, based on the system information, NR bands supported at Long Term Evolution (LTE) frequencies of LTE bands in a most recently used (MRU) LTE frequency list of the UE;

prioritizing the LTE frequencies in the MRU LTE frequency list, based on the supported NR bands and an ENDC capability of the UE; and

performing a cell selection based on the prioritized LTE frequencies in the MRU LTE frequency list,

wherein the ENDC capability of the UE indicates at least one NR band supported by the UE for each of the LTE bands supported by the UE,

wherein the LTE frequencies in the MRU LTE frequency list are prioritized based on whether the supported NR bands match the ENDC capability of the UE,

wherein the LTE frequencies in the MRU LTE frequency list comprise:

first MRU LTE frequencies that do not support the at least one NR band of the ENDC capability of the UE,

second MRU LTE frequencies supporting NR bands that do not match with the at least one NR band of the ENDC capability of the UE, and

third MRU LTE frequencies supporting NR bands that match with the at least one NR band of the ENDC capability of the UE,

wherein the third MRU LTE frequencies are prioritized over the first MRU LTE frequencies and the second MRU LTE frequencies,

wherein the UE prioritizes at least two of combinations of LTE and NR bands based on peak throughputs of the at least two combinations of LTE and NR bands in a case that the UE detects at least one LTE cell supporting at least two of the combinations of LTE bands and NR bands, and

wherein the peak throughputs are determined based on an available operator bandwidth corresponding to each of the combinations of LTE and NR bands.

2. The method of claim 1 , wherein the information on the NR band list indicates at least one NR band supported at each of the LTE frequencies of the LTE bands.

3. The method of claim 1 , further comprising:

initiating an LTE full band scan for preconfigured LTE bands based on the UE not being able to camp on any of the LTE frequencies in the MRU LTE frequency list;

identifying, with respect to a first LTE cell scanned during the LTE full scan, NR support provided at an LTE frequency of an associated LTE band supported by the first LTE cell; and

selecting the first LTE cell supporting the LTE frequency of the associated LTE band, if it is determined that the NR support provided at the LTE frequency of the associated LTE band matches the ENDC capability of the UE.

4. The method of claim 3 , further comprising selecting a second LTE cell supporting an LTE frequency of an associated LTE band through the LTE full band scan if it is determined that the NR support provided at the LTE frequency of the associated LTE band, supported by the first LTE cell, does not match the ENDC capability of the UE,

wherein a priority of the second LTE cell is lower than a priority of the first LTE cell.

5. The method of claim 4 , wherein priorities of LTE cells, supporting LTE frequencies of associated bands with the NR support, are determined based on at least one of:

a peak throughput provided by each LTE cell supporting an NR band in combination with an associated LTE band,

a number of NR bands supported by each associated LTE band,

a frequency range of each NR band supported by each associated LTE band, and

whether each NR band supported by each associated LTE band is a time division duplex (TDD) band or a frequency division duplex (FDD) band.

6. The method of claim 1 , further comprising:

detecting neighbouring LTE cells supporting LTE frequencies of associated LTE bands and satisfying predefined cell reselection criteria;

identifying NR support provided by each of the detected LTE frequencies of the associated LTE bands, based on system information received from the neighbouring LTE cells;

creating a candidate priority list comprising the neighbouring LTE cells, wherein the neighbouring LTE cells in the candidate priority list are prioritized for cell reselection based on NR support by the neighbouring LTE cells and the ENDC capability of the UE; and

performing the cell reselection among the neighbouring LTE cells based on the prioritized candidate priority list.

7. The method of claim 6 , wherein the performing the cell reselection comprises reselecting a first LTE cell among the neighbouring LTE cells, the reselected first LTE cell being either a best LTE cell in the candidate priority list in terms of satisfying the predefined cell reselection criteria or an LTE cell that is not inferior to the best LTE cell by a predefined threshold.

8. The method of claim 7 , wherein the predefined threshold is a value of a quality of service (QoS) parameter, and

wherein the QoS parameter comprises one of a signal strength, a bandwidth, and a bit error rate (BER).

9. The method of claim 6 , wherein the neighbouring LTE cells in the candidate priority list are prioritized based on at least one of:

a peak throughput provided by each LTE cell supporting an NR band in combination with an associated LTE band,

a number of NR bands supported by each associated LTE band,

a frequency range of each NR band supported by each associated LTE band, and

whether each NR band supported by each associated LTE band is a time division duplex (TDD) band or a frequency division duplex (FDD) band.

10. A user equipment (UE) in a wireless communication system supporting Evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network (E-UTRAN) New Radio (NR)-Dual Connectivity (ENDC), the UE comprising:

a communication interface; and

a processor configured to:

receive system information comprising information on an NR band list supported in the ENDC through the communication interface,

identify, based on the system information, NR bands supported at Long Term Evolution (LTE) frequencies of LTE bands in a most recently used (MRU) LTE frequency list of the UE,

prioritize the LTE frequencies in the MRU LTE frequency list, based on the supported NR bands and an ENDC capability of the UE, and

perform a cell selection based on the prioritized LTE frequencies in the MRU LTE frequency list,

wherein the ENDC capability of the UE indicates at least one NR band supported by the UE for each of the LTE bands supported by the UE, and

wherein the LTE frequencies in the MRU LTE frequency list are prioritized based on whether the supported NR bands match the ENDC capability of the UE,

wherein the LTE frequencies in the MRU LTE frequency list comprise:

first MRU LTE frequencies that do not support the at least one NR band of the ENDC capability of the UE,

second MRU LTE frequencies supporting NR bands that do not match with the at least one NR band of the ENDC capability of the UE, and

third MRU LTE frequencies supporting NR bands that match with the at least one NR band of the ENDC capability of the UE,

wherein the third MRU LTE frequencies are prioritized over the first MRU LTE frequencies and the second MRU LTE frequencies,

wherein the UE prioritizes at least two of combinations of LTE and NR bands based on peak throughputs of the at least two combinations of LTE and NR bands in a case that the UE detects at least one LTE cell supporting at least two of the combinations of LTE bands and NR bands, and

wherein the peak throughputs are determined based on an available operator bandwidth corresponding to each of the combinations of LTE and NR bands.

11. The UE of claim 10 , wherein the information on the NR band list indicates at least one NR band supported at each of the LTE frequencies of the LTE bands.

12. The UE of claim 10 , wherein the processor is further configured to:

initiate an LTE full band scan for preconfigured LTE bands based on the UE not able being to camp on any of the LTE frequencies in the MRU LTE frequency list,

identify, with respect to a first LTE cell scanned during the LTE full scan, NR support provided at an LTE frequency of an associated LTE band supported by the first LTE cell, and

select the first LTE cell supporting the LTE frequency of the associated LTE band, if it is determined that the NR support provided at the LTE frequency of the associated LTE band matches the ENDC capability of the UE.

13. The UE of claim 12 , wherein the processor is further configured to select a second LTE cell supporting an LTE frequency of an associated LTE band through the LTE full band scan if it is determined that the NR support provided at the LTE frequency of the associated LTE band, supported by the first LTE cell, does not match the ENDC capability of the UE, wherein a priority of the second LTE cell is lower than a priority of the first LTE cell.

14. The UE of claim 13 , wherein priorities of LTE cells, supporting LTE frequencies of associated bands with the NR support, are determined based on at least one of:

a peak throughput provided by each LTE cell supporting an NR band in combination with an associated LTE band,

a number of NR bands supported by each associated LTE band,

a frequency range of each NR band supported by each associated LTE band, and

whether each NR band supported by each associated LTE band is a time division duplex (TDD) band or a frequency division duplex (FDD) band.

15. The UE of claim 10 , wherein the processor is further configured to:

detect neighbouring LTE cells supporting LTE frequencies of associated LTE bands and satisfying predefined cell reselection criteria,

identify NR support provided by each of the detected LTE frequencies of the associated LTE bands, based on system information received from the neighbouring LTE cells,

create a candidate priority list comprising the neighbouring LTE cells, wherein the neighbouring LTE cells in the candidate priority list are prioritized for cell reselection based on the NR support by the neighbouring LTE cells and the ENDC capability of the UE, and

perform the cell reselection among the neighbouring LTE cells based on the prioritized candidate priority list.

16. The UE of claim 15 , wherein the processor is configured to reselect a first LTE cell among the neighbouring LTE cells, the reselected first LTE cell being either a best LTE cell in the candidate priority list in terms of satisfying the predefined cell reselection criteria or an LTE cell that is not inferior to the best LTE cell by a predefined threshold.

17. The UE of claim 16 , wherein the predefined threshold is a value of a quality of service (QoS) parameter, and

wherein the QoS parameter comprises one of a signal strength, a bandwidth, and a bit error rate (BER).

18. The UE of claim 15 , wherein the neighbouring LTE cells in the candidate priority list are prioritized based on at least one of:

a peak throughput provided by each LTE cell supporting an NR band in combination with an associated LTE band,

a number of NR bands supported by each associated LTE band,

a frequency range of each NR band supported by each associated LTE band, and

whether each NR band supported by each associated LTE band is a time division duplex (TDD) band or a frequency division duplex (FDD) band.