Short message service (SMS) is a commonly used communications service nowadays. Different from a voice service, a short message service is to transport information such as text between a network and a user equipment (UE) through an SMS-service center (SMS-SC).
A conventional short message service depends on a Mobile Station International (MSI) Public Switched Telephone Network (PSTN)/Integrated Services Digital Network (ISDN) (MSISDN).
A short message may be sent between the calling terminal and the called terminal through a circuit switched (CS) domain or a packet switched (PS) domain or an Internet Protocol (IP) multimedia subsystem (IMS) network. With the appearance of new communications services and new terminals, although many new terminals (for example, machine type communications devices, devices with IMS subscription only) do not have an MSISDN, a short message is still required for communications.
When a short message is transferred in an IMS network, a called terminal is referred to as an IMS UE; when an existing calling terminal sends a short message to the IMS UE, the calling terminal first sends a short message service-submit message to a mobile switching center (MSC) or service general packet radio service (GPRS) support node (SGSN), the short message service-submit message is required to carry the MSISDN of the called terminal. Therefore, when the called terminal does not have an MSISDN, the called terminal cannot be identified, causing that a short message cannot be normally sent, that is, a terminal cannot send a short message to an IMS UE that does not have an MSISDN.