Method and apparatus for maintaining a registration for an emergency service

1. A session control entity, comprising:

at least one processor; and

at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the session control entity to at least:

receive from a subscription entity a request to terminate a registration of a user, wherein the request comprises user identities;

based on the user identities, determine a status of various registrations of the user, comprising determining that the various registrations of the user include that the user is registered for an emergency service;

not terminating the registration of the user for the emergency service;

terminate at least one registration relating to the user, wherein the at least one registration does not comprise the registration for the emergency service, and transmit an indication to the subscription entity indicating that the user is registered for an emergency service based on the determination the user is registered for the emergency service, wherein the indication comprises an experimental result code of an internet protocol multimedia subsystem to indicate that the request to terminate the registration of the user is rejected because the user is registered for the emergency service.

2. The session control entity of claim 1 , wherein the user identities comprise at least one of:

a public identity, and

an Internet Protocol Multimedia Subsystem public user identity.

3. The session control entity of claim 1 , wherein the indication is transmitted at least one of:

responsive to the request,

in a rejection,

according to a diameter protocol, and

in Registration-Termination-Answer message.

4. The session control entity of claim 1 , wherein the request comprises at least one of:

a de-registration, and

a network initiated de-registration.

5. A subscription entity, comprising:

at least one processor; and

at least one memory including computer program code, where the at least one memory and the computer program code are configured, with the at least one processor, to cause the subscription entity to at least:

transmit, to a session entity, a request to terminate a registration of a user;

receive, from the session control entity, responsive to the request, an indication indicating that the user is registered for an emergency service, wherein the indication comprises an experimental result code of an internet protocol multimedia subsystem to indicate that the request to terminate the registration of the user is rejected because the user is registered for the emergency service; and

maintain the registration of the user active based on the received indication.

6. The subscription entity of claim 5 , wherein the indication is received at least one of:

responsive to the request,

in a rejection,

according to a diameter protocol, and

in Registration-Termination-Answer message.

7. The subscription entity of claim 5 , wherein the request to terminate comprises a network initiated de-registration.

8. A method, comprising:

receiving a request from a subscription entity to terminate a registration of a user, wherein the request comprises user identities;

based on the user identities, determining a status of various registrations of the user, comprising determining that the various registrations of the user include that the user is registered for an emergency service,

keeping the user registered for the emergency service, based on the determination the user is registered for the emergency service, and,

terminating at least one registration relating to the user, wherein the at least one registration does not comprise the registration for the emergency service,

transmitting an indication to the subscription entity indicating that the user is registered for an emergency service based on the determination the user is registered for the emergency service, wherein the indication comprises an experimental result code of an internet protocol multimedia subsystem to indicate that the request to terminate the registration of the user is rejected because the user is registered for the emergency service.

9. The method of claim 8 , wherein the request to terminate comprises a network initiated de-registration.

10. The method of claim 8 , wherein the Internet Protocol Multimedia Subsystem experimental result code is using text comprising DIAMETER_ERROR_EMERGENCY_REGISTRATION.

11. A method, comprising:

transmitting, by a subscription entity, a request to a session control entity to terminate a registration of a user, wherein the request comprises user identities;

receiving by the subscription entity, from the session control entity responsive to the request an indication indicating that the user is registered for an emergency service, wherein the indication comprises an experimental result code of an internet protocol multimedia subsystem to indicate that the request to terminate the registration of the user is rejected because the user is registered for the emergency service; and

maintaining the registration of the user active based on the received indication.

12. A non-transitory computer readable medium comprising computer program code when executed by a processor adapted to produce the steps of claim 8 .