An operation method of a first communication node including a PHY layer, a MAC layer, and an RLC layer may comprise: delivering, by the MAC layer, first information requesting transmission of one or more RLC SDUs to the RLC layer; selecting, by the RLC layer, at least one RLC SDU based on the first information; performing, by the RLC layer, a segment operation on the at least one RLC SDU; delivering, by the RLC layer, an RLC PDU generated based on a result of the segment operation to the MAC layer; delivering, by the MAC layer, a MAC PDU generated based on the RLC PDU to the PHY layer; and transmitting, by the PHY layer, a PPDU generated based on the MAC PDU to a second communication node.