| CPC H04W 28/0278 (2013.01) [H04W 28/0252 (2013.01); H04W 76/11 (2018.02); H04W 76/15 (2018.02); H04W 80/02 (2013.01); H04W 88/02 (2013.01); H04W 88/08 (2013.01)] | 11 Claims |

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1. A method for transferring a buffer status report by a User Equipment (UE) that configures dual connectivity with a first Base Station (BS) and a second BS, which are connected through a non-ideal backhaul, the method comprising:
receiving, from the first BS, an RRC reconfiguration message including identification information for distinguishing a radio bearer to be transferred through the first BS or Component Carriers (CCs) of the first BS and a radio bearer to be transferred through the second BS or CCs of the second BS, wherein the identification information includes BS indication information for identifying whether a specific radio bearer is associated with the first BS or the second BS;
distinguishing logical channels to be mapped and transferred through the first BS or the CCs of the first BS and logical channels to be mapped and transferred through the second BS or the CCs of the second BS, in a medium access control (MAC) layer;
independently triggering a buffer status report for each of the first BS and second BS by distinguishing a buffer status of a logical channel group to be mapped and transferred through the first BS or the CCs of the first BS, and a buffer status of a logical channel group to be mapped and transferred through the second BS or the CCs of the second BS; and
transmitting, to the first BS, a first buffer status report associated with the logical group to be mapped and transferred through the first BS or the CCs of the first BS, and transmitting, to the second BS, a second buffer status report associated with the logical group to be mapped and transferred through the second BS or the CCs of the second BS,
wherein the identification information is included in radio bearer addition/modification information or logical channel configuration information, and
wherein the radio bearer addition/modification information includes an EPS bearer identifier, drb-Identity, pdcp-Config, rlc-Config, logical Channel Identity, and logical channel configuration information,
wherein the radio bearer addition/modification information is generated through a procedure through an X2 interface between the first BS and the second BS, and
wherein the CCs of the second BS is activated/deactivated by MAC control element (MAC CE) for indicating activation/deactivation of the CCs of the second BS,
wherein when the MAC CE for activating a specific CC of the second BS is received within a Transmission Time Interval (TTI), the specific CC of the second BS is activated within the TTI and a deactivation timer associated the specific CC of the second BS is started,
when the deactivation timer configured by an upper layer signaling expires, the specific CC of the second BS is deactivated.
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