Method and user equipment apparatus for optimizing radio resource for URLLC services in dual connectivity technology

Provided is a method for optimizing radio resource for Ultra-Reliable Low Latency Communication services in a Dual Connectivity technology. The method includes: receiving DownLink (DL) data by a UE using a first Radio Access Technology (RAT) from a base station; transmitting a first Acknowledgement (ACK) signal using the first RAT to the base station based on the DL data being successfully received; updating a Mapping Table Sequence Number of the DL data in a Mapping Table by the UE, based on the DL data being successfully received by the UE using the first RAT; checking the Mapping Table by the UE upon detecting an error in the received DL data using a second RAT; and sending a second ACK signal to the base station using the second RAT of the UE based on the Mapping Table Sequence Number of the DL data being found in the Mapping Table.