Method and apparatus of traffic steering between a 3GPP access network and WLAN

A user equipment (UE) in a wireless communication system, the UE being capable of traffic steering between a 3rd generation partnership project (3GPP) access network and a wireless local area network (WLAN), the UE comprising:

• a memory;
• a transceiver;
• and
• a processor, operably coupled to the memory and the transceiver, that:
• controls the transceiver to receive signaling including at least one WLAN identifier (ID) from the 3GPP access network,
• controls the transceiver to receive radio access network (RAN) assistance information from the 3GPP access network,
• evaluates conditions for the traffic steering only on a primary cell (PCell) among a plurality of serving cells based on the received RAN assistance information which is only applicable for a WLAN for which a WLAN ID has been signaled to the UE, and
• when the conditions for the traffic steering are met on the PCell, performs the traffic steering between the 3GPP access network and the WLAN,
• wherein the RAN assistance information is applicable if access network discovery and selection function (ANDSF) policies are not applied to the UE.