The MCX Service while operating in off-network mode comprises a set or collection of functions necessary to provide Mission Critical Services (e.g., MCPTT, MCVideo, MCData, etc.) using a ProSe direct (UE-to-UE) Communication path (ProSe direct communication path) for transport. The ProSe direct communication path does not traverse the network infrastructure. Users operating off the network are either out of network coverage (not served by a 3GPP network) (e.g., in a remote mountain area fighting a forest fire 20 miles from the nearest network) or have selected a ProSe direct communication path for MCX Service while in network coverage. MCX Users operating off the network need to be in ProSe direct communication range in order to communicate. MCX Users outside of the coverage of the fixed network might be first responders in a rural area assisting in a response to a plane crash, fire fighters in a remote mountain area fighting a forest fire or police officers inside a residence responding to a domestic issue. Off-network MCX Service communications are expected to be immediately accessible to users in the absence of the network. MCX Users in network coverage might be working in a confined area, such as fire fighters fighting a structure fire where direct UE-to-UE communication is more desirable and reliable. Users can communicate directly with one another without having to overcome the resistance of a building and distance to the nearest base station to communicate with other members of their team inside the building that are nearby. To operate off the network, an MCX UE is capable of automatically switching to a ProSe direct communication path for use of MCX Services when detecting an off-network (out of coverage) condition. In addition, a mechanism is provided for an authorized user to select (manually switch to) a ProSe direct communication path for use of off-network MCX Service communications (e.g., while in network coverage). When operating off the network, the MCX Service is provided by the MCX Service Application on the UE as compared to operations on the network, where the MCX Service Application on the UE interacts with an MCX Service server and the network to provide the MCX Service. The Off-Network MCX Service builds upon ProSe enablers to establish, maintain and terminate the signalling and communication path(s) among the off-network users. To the extent feasible, it is expected that the end user's experience is similar regardless if the MCX Service is used with a 3GPP network or based on the use of a ProSe direct communication path. The Off-Network MCX Service is intended to support communication between a group of users (a group communication), where each user has the ability to gain access to transmit in an arbitrated manner. However, the MCX Service also supports Private Communications between pairs of users. When operating off the network the MCX Service allows users to request the permission to transmit (transmit voice/audio) and provides a deterministic mechanism to arbitrate between requests that are in contention (i.e., Floor control). The Off-Network MCX Service provides a means for a user with higher priority (e.g., MCX Service Emergency condition) to override (interrupt) the current sender. The Off-Network MCX Service also supports a mechanism to limit the time a user transmits (has access to the resources) thus permitting users of the same or lower priority a chance to gain access to the resources. The Off-Network MCX Service provides the means for a user to monitor activity on a number of separate communications and enables the user to switch focus to a chosen communication. An Off-Network MCX User might join an already established MCX Service Group Communication (Late communication entry). In addition the Off-Network MCX Service supports MCX Service User IDs, aliases and user Location determination features. For operation off the network (e.g., when out of network coverage), an MCX UE is (pre-)provisioned by an MCX Service Administrator and/or authorized user with the following in order to use MCX Services:

1. An MCX Service User Profile associated with each of the intended MCX Users of the MCX UE that might be used for off-network operation;
   1. An alphanumeric identifier (with a minimum length of Nc3) (i.e., alias) for each MCX User;
   2. A number of off-network MCX Service Groups for use by the MCX User;
   3. An alphanumeric identifier (i.e., alias) for the authorized off-network MCX Service Groups;
   4. A Mission Critical Organization name if available, associated with each of the intended MCX Users or Administrator;
   5. A number of off-network MCX Users for Private Communications for which the MCX User is authorized;
2. Authentication and end-to-end security keys.

An MCX UE operating off the network is capable of transmitting the sender's Location information, MCX Service User ID, alias(es), off-network MCX Service Group ID, group alias and, if available, Mission Critical Organization name of the user who is transmitting (i.e., whose UE is transmitting) to all other users in a communication including MCX UEs operating off the network that are late entering a communication in progress. The Off-Network MCX Service uses the capabilities defined in ProSe TS 22.278, including the ProSe Relay capabilities defined in ProSe TS 22.278 and GCSE_LTE TS 22.468. MCX Service requirements specific to off-network use are defined in clause 7. Common MCX Service requirements defined in clause 5 apply whether the MCX Service is in use on the network or off the network.

[R-7.2-001] [R-7.2-002] [R-7.2-003]

1. An MCX Service User Profile associated with each of the intended MCX Users of the MCX UE that might be used for off-network operation:
   1. alphanumeric identifier (i.e., Alias ID) for the authorized off-network MCX Service Groups;
   2. a number of off-network MCX Service Groups for use by an MCX User;
   3. a MCX Service User ID associated with each of the intended MCX Users;
   4. an alphanumeric identifier (with a minimum length of Nc3) (i.e., alias) for each MCX Service User ID.
2. authentication and end to end security keys.

[R-7.2-004] [R-7.2-005]

[R-7.4-001] [R-7.4-002] [R-7.4-003] [R-7.4-004]

[R-7.5-001] [R-7.5-002]

[R-7.6-001]

• an application layer pre-emption capability;
• a capability to be pre-empted; and
• an application layer priority value.

[R-7.6-002] [R-7.6-003] [R-7.6-004] [R-7.6-005] [R-7.6-006] [R-7.6-007] [R-7.6-008] [R-7.6-009]

[R-7.8-001] [R-7.8-002] [R-7.8-003]

[R-7.9-001] [R-7.9-002]

[R-7.10-001] [R-7.10-002] [R-7.10-003]

[R-7.11-001] [R-7.11-002] [R-7.11-003]

[R-7.13-001] [R-7.13-002] [R-7.13-003] [R-7.13-004] [R-7.13-005]

[R-7.14-001] [R-7.14-001a] [R-7.14-002] [R-7.14-002a]

[R-7.16-001]