Abstract: A Home Subscriber Server (HSS) determines whether roaming of voice communication via an IP Multimedia Subsystem (IMS) is supported in the Visited Public Land Mobile Network (VPLMN) or not, and transmits to a mobility management entity (MME) a signal that includes a ‘voice supported’ or ‘voice not supported’ indicator that indicates whether the roaming is supported or not. The MME receives the indicator from the HSS, and transmits to a User Equipment (UE) an ‘Attach Accept’ as a response to an ‘Attach Request’ for the VPLMN. The MME then transmits to the UE, based on the indicator received from the HSS, the ‘Attach Accept’ that includes an indicator that indicates whether the roaming is supported or not.

Abstract: The disclosure provides a mobile communication system, a communication control device, a mobility management entity, and a mobile communication method which can avoid a failure in making an emergency call via an IMS when a mobile station connects to a VPLMN. An HSS 100 judges whether or not an emergency call origination via an IMS 500 is supported in the VPLMN, and transmits a signal including an indicator, EM supported or EM not supported, which indicates whether or not the emergency call origination is supported, to an MME 300. The MME 300 receives the indicator from the HSS 100 and transmits, to the UE 20, Attach Accept responding to Attach Request to the VPLMN from a UE 20. Based on the indicator received from the HSS 100, the MME 300 transmits, to the UE 20, Attach Accept including the indicator which indicates whether or not the emergency call is supported.