Method and apparatus for reporting buffer status report by RRC_INACTIVE state UE in mobile wireless communication system

1. A method performed by a terminal, the method comprising:

receiving, by the terminal and in a first cell, a first Radio Resource Control (RRC) message, wherein the first RRC message comprises a first set of parameters for a second resume procedure;

determining, by the terminal and in the first cell, one or more radio bearers configured for the second resume procedure based on the first set of parameters;

performing by the terminal cell selection from the first cell to a second cell;

receiving, by the terminal and in the second cell, a system information, wherein the system information comprises a second set of parameters for the second resume procedure;

initiating by the terminal and in the second cell, a first resume procedure or the second resume procedure based on

the first set of parameters; and

the second set of parameters;

re-establishing, by the terminal and in the second cell, Packet Data Convergence Protocol (PDCP) entity of Signaling Radio Bearer 1 (SRB1);

transmitting by the terminal and in the second cell, a second Radio Resource Control (RRC) message; and

receiving, by the terminal and in the second cell, a third RRC message,

wherein a cell group configuration for master cell group is restored before PDCP entities of the one or more radio bearers configured for the second resume procedure are re-established in case that the second resume procedure is initiated.

2. The method of claim 1 , wherein the cell group configuration for master cell group is restored after PDCP entities of the one or more radio bearers configured for the second resume procedure are re-established in case that the first resume procedure is initiated.

3. The method of claim 1 , wherein the first set of parameters comprises a Signaling Radio Bearer 2 (SRB2)-indicator and a Data Radio Bearer (DRB) list.

4. The method of claim 1 , wherein the second set of parameters comprises a first threshold and a second threshold.

5. The method of claim 4 , wherein the first threshold is related to a reference signal reception power and the second threshold is related to a data volume.

6. The method of claim 1 , wherein the second resume procedure is initiated in case that:

data volume of the radio bearers configured for the second resume procedure is smaller than a second threshold indicated in the second set of parameters; and

reference signal reception power is greater than a first threshold indicated in the second set of parameters.

7. The method of claim 1 , wherein the first resume procedure is initiated in case that:

data volume of the radio bearers configured for the second resume procedure is greater than a second threshold indicated in the second set of parameters; or

reference signal reception power is lower than a first threshold indicated in the second set of parameters.

8. The method of claim 1 , wherein the first RRC message further comprises:

a first identifier;

a second identifier; and

a count.

9. The method of claim 1 , wherein the second RRC message comprises:

a first identifier comprised in the first RRC message;

a Message Authentication Code for Integrity (MAC-I); and

a field indicating resume cause.

10. The method of claim 1 , wherein the third RRC message comprises:

parameters for the cell group configuration for master cell group; and

parameters for radio bearer configuration.

11. The method of claim 1 , wherein in case that the second resume procedure is initiated and after the cell group configuration for master cell group is restored:

PDCP entities of the one or more radio bearers configured for the second resume procedure are re-established; and

the one or more radio bearers configured for the second resume procedure are resumed.

12. The method of claim 1 , wherein in case that the first resume procedure is initiated and after the cell group configuration for master cell group is restored:

PDCP entities of Data Radio Bearers (DRBs) are re-established; and

DRBs are resumed.

13. The method of claim 1 , wherein in case that the second resume procedure is initiated:

the second RRC message is transmitted within a first Medium Access Control (MAC) Service Data Unit (SDU);

the first MAC SDU is comprised in a MAC Protocol Data Unit (PDU); and

the MAC PDU further comprises a second MAC SDU.

14. The method of claim 13 , wherein:

the first MAC SDU comprises a first MAC-I generated based on a first security key; and

the second MAC SDU comprises a second MAC-I generated based on a second security key.

15. The method of claim 14 , wherein:

the first security key is not derived from a count comprised in the first RRC message; and

the second security key is derived from the count comprised in the first RRC message.

16. The method of claim 13 , wherein the MAC PDU further comprises a Power Headroom Report (PHR).

17. The method of claim 16 , wherein, within the MAC PDU:

the first MAC SDU is placed before the second MAC SDU; and

the second MAC SDU is placed before the PHR.

18. The method of claim 1 , wherein the first resume procedure is to resume suspended RRC connection and the second resume procedure is for small data transmission in RRC_INACTIVE state.

19. A terminal in a wireless communication system, the terminal comprising:

a transceiver configured to transmit and receive a signal; and

a controller configured to control the transceiver to:

receive in a first cell a first Radio Resource Control (RRC) message, wherein the first RRC message comprises a first set of parameters for a second resume procedure;

determine in the first cell a one or more radio bearers configured for the second resume procedure based on the first set of parameters;

perform cell selection from the first cell to a second cell;

receive in the second cell a system information, wherein the system information comprises a second set of parameters for the second resume procedure;

initiate in the second cell a first resume procedure or the second resume procedure based on:

the first set of parameters; and

the second set of parameters;

re-establish in the second cell Packet Data Convergence Protocol (PDCP) entity of Signaling Radio Bearer 1 (SRB1);

transmit in the second cell a second Radio Resource Control (RRC) message; and

receive in the second cell a third RRC message,

wherein a cell group configuration for master cell group is restored before PDCP entities the one or more radio bearers configured for the second resume procedure are re-established in case that the second resume procedure is initiated.