Method, apparatus and computer program

1 . A user equipment comprising at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the user equipment at least to perform:

receiving, from a primary mission critical system, one or more user profile configuration documents, each user profile configuration document of the one or more user profile configuration documents comprising information associated with one or more partner mission critical systems to which the user equipment can migrate, and wherein the information comprises: for each respective partner mission critical system of the one or more partner mission critical systems, an identity of the respective partner mission critical system and a user equipment initial configuration associated with the respective partner mission critical system;

selecting a partner mission critical system to migrate to based on the following criteria:

the partner mission critical system is from among the one or more partner mission critical systems of at least one user profile configuration document of the one or more user profile configuration documents;

the partner mission critical system is associated with a public land mobile network code corresponding to a registered public land mobile network of the user equipment; and

when the public land mobile network code is associated with single network slice selection assistance information, the single network slice selection assistance information associated with the public land mobile network code is included in a list of allowed network slice selection assistance information;

selecting the user profile configuration document associated with the partner mission critical system that is selected for use in migration to the partner mission critical system that is selected; and

based on the user profile configuration document that is selected, performing the migration to the partner mission critical system that is selected.

2 . The user equipment of claim 1 , wherein selecting the partner mission critical system comprises:

indicating to a user of the user equipment, at least one of one or more partner mission critical systems that satisfy the criteria; and

receiving, via a user interface of the user equipment, user input selecting the partner mission critical system from among the at least one of the one or more partner mission critical systems that is indicated.

3 . The user equipment of claim 1 , wherein the selecting the user profile configuration document comprises selecting a user profile configuration document of the one or more user profile configuration documents that satisfies the following conditions:

the user profile configuration document contains a public land mobile network code corresponding to the registered public land mobile network of the user equipment; and

when the public land mobile network code is associated with single network slice selection assistance information, the associated single network slice selection assistance information is included in a list of allowed network slice selection assistance information.

4 . The user equipment of claim 3 , wherein a plurality of user profile configuration documents meet the conditions, and wherein the selecting the user profile configuration document of the one or more user profile configuration documents that satisfies the following conditions comprises: for selecting the user profile configuration document from among the plurality of user profile configuration documents.

5 . The user equipment of claim 4 , wherein the plurality of user profile configuration documents are associated with a plurality of precedence values, and wherein selecting the user profile configuration document of the one or more user profile configuration documents that satisfies the following conditions is based on the plurality of precedence values.

6 . The user equipment of claim 1 , wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform obtaining, from the primary mission critical system, security information for accessing the selected partner mission critical system.

7 . The user equipment of claim 6 , wherein the performing the migration comprises:

performing an authentication procedure with the partner mission critical system that is selected, based on the security information and the user equipment initial configuration associated with the partner mission critical system that is selected comprised in the user profile configuration document that is selected.

8 . The user equipment of claim 7 , wherein the performing the migration comprises, in response to successfully completing the authentication procedure, performing signalling plane migration to the partner mission critical system that is selected.

9 . The user equipment of claim 8 , wherein the performing the migration comprises:

in response to the performing the signalling plane migration, performing an authorization procedure on the partner mission critical system that is selected,

wherein the migration is successful when the authorization procedure is successfully completed.

10 . The user equipment of claim 8 , wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform:

receiving, from the partner mission critical system, information indicating one or more updates to at least one of: a user profile configuration document; a user equipment initial configuration document; or a service configuration document; and

updating locally stored information based on the information indicating the one or more updates.

11 . The user equipment of claim 10 , wherein the instructions, when executed by the at least one processor, further cause the user equipment at least to perform:

sending, to the partner mission critical system, a subscription request associated with at least one of; the user profile configuration document; the user equipment initial configuration document; or the service configuration document,

wherein the receiving the information indicating the one or more updates is based on the subscription request.

12 . The user equipment of claim 1 , wherein the selecting the partner mission critical system is performed before the selecting the user profile configuration document, or wherein the selecting the partner mission critical system is performed after the selecting the user profile configuration document.

13 . The user equipment of claim 1 , wherein the selecting the partner mission critical system comprises:

in an instance a plurality of candidate partner mission critical systems meets the criteria, selecting the partner mission critical system from the plurality of candidate mission critical systems.

14 . A method performed by a user equipment, the method comprising:

receiving, from a primary mission critical system, one or more user profile configuration documents, each user profile configuration document of the one or more user profile configuration documents comprising information associated with one or more partner mission critical systems to which the user equipment can migrate, and wherein the information comprises, for each respective partner mission critical system, an identity of the respective partner mission critical system and a user equipment initial configuration associated with the respective partner mission critical system;

selecting a partner mission critical system to migrate to based on the following criteria:

the partner mission critical system is from among the one or more partner mission critical systems of at least one user profile configuration document of the one or more user profile configuration documents;

the partner mission critical system is associated with a public land mobile network code corresponding to a registered public land mobile network of the user equipment; and

when the public land mobile network code is associated with single network slice selection assistance information, the single network slice selection assistance information associated with the public land mobile network code is included in a list of allowed network slice selection assistance information;

selecting the user profile configuration document associated with the partner mission critical system that is selected for use in migration to the partner mission critical system that is selected; and

based on the user profile configuration document that is selected, performing the migration to the partner mission critical system that is selected.

15 . The method of claim 14 , wherein a plurality of candidate partner mission critical systems meet the criteria, wherein the selecting the partner mission critical system comprises selecting the partner mission critical system from the plurality of candidate mission critical systems.