Abstract: The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for performing a buffer status reporting in a D2D communication system, the method comprising: configuring a plurality of sidelink logical channels, wherein each of the plurality of sidelink logical channels has an associated priority and belongs to a LCG, and one or more of LCGs belong to a ProSe Destination; generating a SL BSR MAC CE including buffer sizes of LCGs in decreasing order of a LCG priority, wherein the LCG priority of a LCG is determined as a highest priority of a logical channel among priorities of logical channels belonging to the LCG; and transmitting a MAC PDU including the SL BSR MAC CE.

Abstract: Provided are a method for performing, by a user equipment (UE), transmission via only a primary path in a wireless communication system, and an apparatus supporting the same. The method may include: configuring a split bearer, which has multiple L2 entities for both a master cell group (MCG) and a secondary cell group (SCG); when the UE transits from a first state to a second state, reconfiguring the primary path of the split bearer autonomously; and performing the transmission via only the primary path of the split bearer, wherein the primary path is related to an L2 entity for the MCG.

Abstract: The present invention discloses a method of performing, by a user equipment (UE), wireless communications in a wireless communication system, the method comprising: receiving an activation command for activating a SPS resource; activating a cell related to the SPS resource if the cell is a deactivated cell; and activating the SPS resource on the activated cell.

Abstract: Provided is a cell reselection method performed by a terminal in a wireless communication system. The method includes: receiving first priority information for at least one frequency; receiving second priority information for the one or more frequencies; and selectively applying, based on the state of the terminal, any one of the first priority information and second priority information and performing cell reselection. The first priority information is provided through a connection rejection message and provides instructions on the priority for the one or more frequencies to be lowered. The second priority information is provided from a current cell through system information.