1. A method for transmitting, by a user equipment (UE), data in a wireless communication system, the method comprising:receiving a first uplink grant for a logical channel group (LCG) and a first LCG indicator of the LCG,
wherein the LCG is included in a plurality of LCGs having available data for transmission;
generating a Medium Access Control Protocol Data Unit (MAC PDU) containing only data of the LCG indicated by the first LCG indicator;
performing a logical channel prioritization procedure based on the data of the LCG contained in the MAC PDU; and
transmitting the MAC PDU using the first uplink grant,
wherein the first uplink grant and the first LCG indicator are received through a Downlink Control Information (DCI) included in a Physical Downlink Control Channel (PDCCH), and
wherein the DCI further includes a second uplink grant for another LCG and a second LCG indicator of the another LCG.