A method and apparatus for receiving first control information for resource allocation associated with a first RAT; receiving second control information for resource allocation associated with a second RAT; receiving a first protocol data unit, PDU based on the first control information; receiving a second PDU based on the second control information; generating a first service data unit, SDU, based on the first PDU and submitting, at the first layer associated with the first RAT, the first SDU to a second layer; and generating a second SDU based on the second PDU and submitting, at the first layer associated with the second RAT, the second SDU to the second layer, wherein the second layer is an upper layer of the first layer associated with the first RAT and the first layer associated with the second RAT.