7  Functional model  Word‑p. 30

7.1  General

The functional model for the MC services architecture is defined as a series of planes to allow for the breakdown of the architectural description.

Further, each plane is expected to operate in an independent manner, providing services to the connected planes as and when requested by the connected plane, and requesting services from other planes as required.

As a consequence of this each plane should manage on its own behalf:

1. use of identities. Each plane is therefore responsible for the privacy of that plane's own identities; and
2. security for that plane. This does not preclude a plane requesting security services from another plane, but that is a decision made within the plane, as to whether to use offered security services or mechanisms within the plane itself.

7.2  Description of the planes

The following planes are identified:

1. application plane: The application plane provides all of the services (e.g. call control, floor control, video control, data control) required by the user together with the necessary functions to support MC service. It uses the services of the signalling control plane to support those requirements. For example, within the MCPTT service, the application plane also provides for the conferencing of media, and provision of tones and announcements; and
2. signalling control plane: The signalling control plane provides the necessary signalling support to establish the association of users involved in an MC service, such as an MCPTT call or other type of MC services. The signalling control plane also offers access to and control of services across MC services. The signalling control plane uses the services of the bearer plane.

Bearers supporting these planes are defined for LTE within TS 23.401. The resource control that is needed to support these planes is defined within TS 23.203. The application plane also relies on the use of multicast bearers established via procedures defined in TS 23.468 and TS 23.246.

7.3  Functional model description

7.3.1  On-network functional model

Each MC service can be represented by an application plane functional model. The functional model across MC services may be similar but is described by the individual functional entities and reference points that belong to that MC service. Within the application plane for an MC service there is a common set of functions and reference points. The common set is shared across services. This common set of functions and reference points is known as the common services core.

Figure 7.3.1-1 shows the functional model for the application plane for an MC system.

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Figure 7.3.1-1: Functional model for application plane for an MC system

The common services core functions and reference points shown in Figure 7.3.1-1 are shared across each MC service. The description of the functions and reference points specific to an MC service is contained in the corresponding MC service TS.

In the model shown in Figure 7.3.1-1, the following apply:

• A specific MC service server is an instantiation of a GCS AS in accordance with TS 23.468.
• The functional alias management client is an integrated functional entity of the configuration management client. The functional alias management client is described in subclause 7.4.2.2.12.
• The functional alias management server is an integrated functional entity of the configuration management server. The functional alias management server is described in subclause 7.4.2.2.13.

Figure 7.3.1-2 shows the functional model for the signalling control plane.

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Figure 7.3.1-2: Functional model for signalling control plane

Figure 7.3.1-3 shows the relationships between the reference points of the application plane of an MC service server and the signalling plane.

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Figure 7.3.1-3: Relationships between reference points of MC service application plane and signalling control planes

7.3.2  Off-network functional model  Word‑p. 34

Figure 7.3.2-1 shows the functional model for off-network operation.

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Figure 7.3.2-1: Functional model for MC service off-network operation

For a specific MC service, the description of off-network operation is contained in the corresponding MC service TS.

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