System and method for indicating emergency call back to user equipment

1. An apparatus, comprising:

a user equipment including a processor configured to recognize an Internet Protocol Multimedia Subsystem, IMS, call as an emergency call from a Public Safety Answering Point, PSAP, by an indication that is included in a Session Initiation Protocol, SIP, Invite message,

wherein the indication is a string of characters that identifies the PSAP as the source of the emergency call, and

wherein the indication is included in a P-Asserted-Identity Header of the SIP Invite message,

wherein the user equipment triggers an autonomous action when the user equipment does not receive an input in response to the emergency call within a predefined length of time after the user equipment receives the indication, and

wherein the autonomous action is at least one of:

sending an automated message to the PSAP;

sending a location of the user equipment to the PSAP; and

sending an automated message to an emergency-related entity other than the PSAP.

2. The apparatus of claim 1 , wherein the SIP Invite message comes from the PSAP.

3. The apparatus of claim 1 , wherein the processor is further configured to inspect all incoming SIP Invite messages for the indication.

4. A method for indicating an Internet Protocol Multimedia Subsystem, IMS, emergency call to a user equipment, comprising:

including in a Session Initiation Protocol, SIP, Invite message to the user equipment an indication that the emergency call is from a Public Safety Answering Point, PSAP,

wherein the indication is a string of characters that identifies to the user equipment the PSAP as the source of the emergency call, and

wherein the indication is included in a P-Asserted-Identity Header of the SIP Invite message,

wherein the indication triggers an autonomous action by the user equipment when the user equipment does not receive an input in response to the emergency call within a predefined length of time after the user equipment receives the indication,

wherein the autonomous action is at least one of:

sending an automated message to the PSAP;

sending a location of the user equipment to the PSAP; and

sending an automated message to an emergency-related entity other than the PSAP.

5. The method of claim 4 , wherein the SIP Invite message comes from the PSAP.

6. The method of claim 4 , wherein when the SIP Invite message is communicated to the user equipment via a Proxy Call Session Control Function, P-CSCF, the P-CSCF informs an access network to prepare and prioritize resources for the emergency call.

7. A system, comprising:

one or more processors; and

instructions that when executed by the one or more processors promote providing an indication in a SIP Invite message to a user equipment that an emergency call is from a Public Safety Answering Point, PSAP,

wherein the indication is a string of characters that identifies to the user equipment the PSAP as the source of the emergency call, and

wherein the indication is included in a P-Asserted-Identity Header of the SIP Invite message,

wherein the indication triggers an autonomous action by the user equipment when the user equipment does not receive an input in response to the emergency call within a predefined length of time after the user equipment receives the indication, and wherein the autonomous action is at least one of:

sending an automated message to the PSAP;

sending a location of the user equipment to the PSAP; and

sending an automated message to an emergency-related entity other than the PSAP.