A communication terminal comprising a first communication component configured for communication using a first radio access technology, a second communication component configured for communication using a second radio access technology, wherein the first communication component is configured to communicate speech data of a call using the first radio access technology; and a controller configured to control the second communication component to generate transport protocol packets comprising speech data of the call for uplink transmission of the speech data using the second radio access technology; andto switch the call from the first radio access technology to the second radio access technology access technology after the second communication component begins generation of transport protocol packets for uplink transmission.