Method and apparatus for accessing new radio (NR) service in multi-rat dual connectivity (DC)

1. A method for accessing a New Radio (NR) service by a user equipment (UE) in a communication network supporting multiple-Radio Access Technology (multi-RAT) dual connectivity (DC), the method comprising:

determining whether a serving cell is an anchor band cell or a non-anchor band cell;

determining whether at least one secondary cell for the DC is the anchor band cell or the non-anchor band cell in case that the serving cell is the non-anchor band cell;

in case that the secondary cell is the anchor band cell, performing a measurement operation on at least one factor of the serving cell and the secondary cell to obtain measured values of the serving cell and the secondary cell, wherein the factor comprises at least one of a Reference Signals Received Power (RSRP) and a Reference Signals Received Quality (RSRQ);

in case that a difference between a measured value of the serving cell and a measured value of the secondary cell is greater than a measurement threshold, preparing a measurement report comprising the measured value of the serving cell and the measured value of the secondary cell for an event A2;

in case that the difference is less than or equal to the measurement threshold, preparing a modified measurement report by decreasing the measured value of the serving cell and increasing the measured value of the secondary cell for the event A2;

transmitting, the measurement report or the modified measurement report for the event A2 to the serving cell to perform a handover of the UE to the secondary cell; and

accessing the NR service by connecting with the secondary cell as a new serving cell.

2. The method of claim 1 , wherein the determining whether the secondary cell is the anchor band cell or the non-anchor band cell comprises:

receiving configurations of a plurality of neighbor cells from the serving cell; and

determining at least one of at least one neighbor anchor band cell and at least one neighbor non-anchor band cell from the neighbor cells using the received configurations,

wherein the secondary cell is one of the at least one neighbor anchor band cell.

3. The method of claim 1 , further comprising:

receiving a handover command to the secondary cell from the serving cell when the serving cell and the secondary cell are swapped based on the measurement report or the modified measurement report; and

initiating the handover to the secondary cell as the new serving cell,

wherein the secondary cell supports at least one NR cell.

4. The method of claim 1 , further comprising:

performing a measurement operation on at least one factor of at least one neighbor anchor band cell to obtain a measured value of the neighbor anchor band cell;

preparing a measurement report comprising the measured value of only the neighbor anchor band cell, among the neighbor anchor band cell and at least one neighbor non-anchor band cell, for at least one of an event A3 and an event A5; and

sending the measurement report comprising the measured value of only the neighbor anchor band cell to the serving cell to perform a handover of the UE to the neighbor anchor band cell,

wherein the secondary cell is one of the at least one neighbor anchor band cell.

5. The method of claim 4 , further comprising:

receiving a handover command to handover to the neighbor anchor band cell from the serving cell when the serving cell determines the neighbor anchor band cell as the new serving cell for the UE based on the received measurement report comprising the measured value of only the neighbor anchor band cell; and

initiating the handover to the neighbor anchor band cell,

wherein the neighbor anchor band cell supports at least one NR cell.

6. The method of claim 4 , further comprising:

delaying preparing and sending the measurement report comprising the measured value of only the neighbor anchor band cell, in case that a measured value of at least one neighbor non-anchor band cell satisfies the at least one of the event A3 and the event A5; and

decreasing the measured value of the neighbor non-anchor band cell compared to the measured value of the neighbor anchor band cell, and sending a measurement report including the measured value of the neighbor anchor band cell and the decreased measured value of the neighbor non-anchor band cell to the serving cell, in case that the measured value of the neighbor non-anchor band cell satisfies the at least one of the event A3 and the event A5.

7. The method of claim 1 , further comprising:

checking a plurality of cells for a cell selection when the UE is in a Radio Resource Control (RRC) idle state;

identifying at least one anchor band cell from the cells; and

prioritizing the anchor band cell.

8. A User Equipment (UE) in a communication network supporting multiple-Radio Access Technology (multi-RAT) dual connectivity (DC), the UE comprising:

a memory;

a transceiver; and

a processor coupled to the memory and the transceiver, and configured to:

determine whether a serving cell is an anchor band cell or a non-anchor band cell;

determine whether at least one secondary cell for the DC is the anchor band cell or the non-anchor band cell, in case that the serving cell is the non-anchor band cell;

in case that the secondary cell is the anchor band cell, perform a measurement operation on at least one factor of the serving cell and the secondary cell to obtain measured values of the serving cell and the secondary cell, wherein the factor comprises at least one of a Reference Signals Received Power (RSRP) and a Reference Signals Received Quality (RSRQ);

in case that a difference between a measured value of the serving cell and a measured value of the secondary cell is greater than a measurement threshold, prepare a measurement report comprising the measured value of the serving cell and the measured value of the secondary cell for an event A2;

in case that the difference is less than or equal to the measurement threshold, prepare a modified measurement report by decreasing the measured value of the serving cell and increasing the measured value of the secondary cell for the event A2;

transmit, the measurement report or the modified measurement report for the event A2 to the serving cell to perform a handover of the UE to the secondary cell; and

enable the UE to access a New Radio (NR) service by connecting with the secondary cell as a new serving cell.

9. The UE of claim 8 , wherein the processor is further configured to:

receive configurations of a plurality of neighbor cells from the serving cell; and

determine at least one of at least one neighbor anchor band cell and at least one neighbor non-anchor band cell from the neighbor cells using the received configurations,

wherein the secondary cell is one of the at least one neighbor anchor band cell.

10. The UE of claim 8 , wherein the processor is further configured to:

receive a handover command to the secondary cell from the serving cell when the serving cell and the secondary cell are swapped based on the measurement report or the modified measurement report; and

initiate the handover to the secondary cell as the new serving cell,

wherein the secondary cell supports at least one NR cell.

11. The UE of claim 8 , wherein the processor is further configured to:

perform a measurement operation on at least one factor of at least one neighbor anchor band cell to obtain a measured value of the neighbor anchor band cell;

prepare a measurement report comprising the measured value of only the neighbor anchor band cell, among the neighbor anchor band cell and at least one neighbor non-anchor band cell, for at least one of an event A3 and an event A5; and

send the measurement report comprising the measured value of only the neighbor anchor band cell to the serving cell to perform a handover of the UE to the at least one neighbor anchor band cell,

wherein the secondary cell is one of the at least one neighbor anchor band cell.

12. The UE of claim 11 , wherein the processor is further configured to:

receive a handover command to handover to the neighbor anchor band cell from the serving cell when the serving cell determines the neighbor anchor band cell as the new serving cell for the UE based on the received measurement report comprising the measured value of only the neighbor anchor band cell; and

initiate the handover to the neighbor anchor band cell,

wherein the neighbor anchor band cell supports at least one NR cell.

13. The UE of claim 8 , wherein the processor is further configured to:

delay preparing and sending the measurement report comprising the measured value of only the neighbor anchor band cell, in case that a measured value of at least one neighbor non-anchor band cell satisfies at least one of an event A3 and an event A5; and

decrease the measured value of the neighbor non-anchor band cell compared to the measured value of the neighbor anchor band cell, and sending a measurement report including the measured value of the neighbor anchor band cell and the decreased measured value of the neighbor non-anchor band cell to the serving cell, in case that the measured value of the neighbor non-anchor band cell satisfies the at least one of the event A3 and the event A5.

14. The UE of claim 8 , wherein the processor is further configured to:

check a plurality of cells for a cell selection, when the UE is in a Radio Resource Control (RRC) idle state;

identify at least one anchor band cell from the cells; and

prioritize the anchor band cell.