A method for a handover procedure comprises establishing a connection with a source network node of a first core network; receiving a radio resource control (RRC) message including an information element, wherein the information element indicates a second core network associated with a target network node; applying security parameters based on the second core network indicated in the information element; and performing a handover toward the target network node using the applied security parameters. The method provides an indication in RRC connection reconfiguration procedure to indicate the UE the core network of the target network node, so that the UE may recognize that this is an inter-system handover and apply corresponding security parameters for performing the handover without additional signaling.