Method and device for buffer status reporting

1. A method of reporting a buffer status of a terminal, the method comprising:

triggering a buffer status report (BSR) in a media access control (MAC) layer, based on a BSR triggering condition;

transmitting, to a base station, a scheduling request (SR) for transmitting uplink data;

receiving an uplink resource allocation grant (UL grant) from the base station, in response to the SR;

assembling a media access control protocol data unit (MAC PDU) including a BSR MAC control element (BSR MAC CE); and

cancelling all BSRs triggered prior to the MAC PDU assembly, at a time of transmitting the MAC PDU, in case that the BSR MAC CE includes buffer status information up to a last event that triggered the BSR prior to the MAC PDU assembly and the buffer status information covers all of more than one logical channel group (LCG) having data for transmission.

2. The method of claim 1 , further comprising canceling the triggered BSR when the uplink resource allocation grant is able to accommodate all pending data available for uplink transmission and is not sufficient to accommodate the BSR MAC CE and a MAC sub-header.

3. The method of claim 1 , further comprising:

triggering the SR, based on a certain SR triggering condition;

determining whether the triggered SR has been triggered prior to the MAC PDU assembly; and

determining whether to cancel the triggered SR, based on a result of the determination of whether the triggered SR has been triggered prior to the MAC PDU assembly.

4. The method of claim 3 , wherein the determining of whether to cancel the triggered SR comprises canceling the triggered SR, based on whether the BSR MAC CE contains buffer status information up to a certain event that triggers a BSR prior to the MAC PDU assembly.

5. The method of claim 3 , further comprising canceling the triggered SR when the uplink resource allocation grant is able to accommodate all pending data available for uplink transmission.

6. The method of claim 3 , further comprising stopping an sr-ProhibitTimer, when it is determined that the triggered SR is cancelled.

7. The method of claim 1 , wherein the cancelling of the BSR is performed when the MAC PDU is transmitted to the base station.

8. The method of claim 3 , wherein the determining of whether to cancel the triggered SR is performed when the MAC PDU is transmitted to the base station.

9. The method of claim 1 , wherein the triggering of the BSR is performed after the MAC PDU is assembled and before the MAC PDU is transmitted.

10. A user equipment (UE) for reporting a buffer status, the UE comprising:

a transceiver; and

one or more processors coupled with the transceiver,

wherein the is one or more processors are configured to:

trigger a buffer status report (BSR) in a media access control (MAC) layer, based on a BSR triggering condition,

transmit, to a base station, a scheduling request (SR) for transmitting uplink data,

receive an uplink resource allocation grant (UL grant) from the base station, in response to the SR,

assemble a media access control protocol data unit (MAC PDU) including a BSR MAC control element (BSR MAC CE), and

cancel all BSRs triggered prior to the MAC PDU assembly, at a time of transmitting the MAC PDU, in case that the BSR MAC CE includes buffer status information up to a last event that triggered the BSR prior to the MAC PDU assembly and the buffer status information covers all of more than one logical channel group (LCG) having data for transmission.

11. The UE of claim 10 , wherein the one or more processors are further configured to cancel the triggered BSR when the uplink resource allocation grant is able to accommodate all pending data available for uplink transmission and is not sufficient to accommodate the BSR MAC CE and a MAC sub-header.

12. The UE of claim 10 , wherein the one or more processors are further configured to:

trigger the SR, based on a certain SR triggering condition,

determine whether the triggered SR has been triggered prior to the MAC PDU assembly, and

determine whether to cancel the triggered SR, based on a result of the determination of whether the triggered SR has been triggered prior to the MAC PDU assembly.

13. The UE of claim 12 , wherein the one or more processors are further configured to cancel the triggered SR, based on whether the BSR MAC CE contains buffer status information up to a certain event that triggers a BSR prior to the MAC PDU assembly.