FD function of the MCData client and the MCData server is responsible to handle file distribution capability related requests and responses. The FD function of the MCData server is responsible for the distribution of file to the MCData communication participants. The FD function of the MCData server provides the following functionality:

• reception of uplink file data by means of the MCData-FD-2 reference point;
• replicate the file data as needed for distribution to those MCData communication participants using unicast transport;
• distribute downlink file data by IP unicast transmission to those MCData communication participants utilizing unicast transport by means of the MCData-FD-2 reference point; and
• distribute downlink file data using multicast downlink transport by means of the MCData-FD-3 reference point.

The media storage client is used to support FD function of the MCData client for file distribution capability. FD function of the MCData client interacts with media storage client for uploading and downloading file to or from the media storage function of the MCData content server.

This functional entity is responsible for transmission and reception control of MCData file data between the sending MCData UE, the MCData server, and the receiving MCData UE. Transmission and reception control function is used to provide arbitration between multiple data requests and apply the necessary policy to ensure that appropriate data is transmitted between the MCData UE. However, when the file distribution requests are exceeding a certain size, it may be necessary to control the data that is transmitted or received by the MCData UEs. The control is subject to criteria like application level priorities (e.g. user priority, group priority), service type, emergency nature of the communication, etc.

The media storage function is responsible for the storing of media uploaded by the media storage client of the MCData UE in case of MCData file distribution. It also supports download of stored media by the MCData UE in case of file distribution via media storage client. The media storage function supports partial download requests of stored media by the MCData UE via media storage client.

The MCData content server functional entity provides a repository area in the MCData trust domain allowing authorized MCData users to temporarily store files that are intended to share to other MCData users. It provides common pool of storage area (i.e. size) to all authorized MCData users to use, no personal space is allocated. An authorized MCData user can use the supported operations on the defined reference point to upload shared files and download the files that are shared to him. The MCData server will use the defined reference point to access the files stored in the MCData content server and support the necessary operational functionalities. As part of the file life cycle management the temporarily stored files will be removed periodically based on the Mission Critical service provider policy. An MCData content server may share files with another MCData content server in another MCData system to support interconnection. If the MBMS user service architecture described in TS 26.346 is utilized for file distribution, the MCData content server provides the stored file associated to the established MBMS session.

MCData-FD-1 reference point is used for MCData application signalling for establishing a session in support of MCData file distribution. The bearer is also used for both uplink and downlink unicast data (e.g., URL associated to file, file download completed report). The MCData-FD-1 reference point shall use the SIP-1 and SIP-2 reference points for transport and routing of SIP signalling. MCData-FD-1 reference point can be used as long as the file size does not exceed the capabilities (e.g. payload or transmission limits) provided by MCData-FD-1. Messages supported on this interface include the uplink and the downlink unicast file transaction between the MCData clients in MCData communication via the MCData server for:

• metadata (file size, type etc.) of the file being distributed;
• URL of the file being distributed;
• sending download completed report;
• small size file;
• conversation identifier for message thread indication; and
• application plane identities for the MCData user and MCData application.
  Messages supported on this interface may also include the MCData client providing the MCData server with
• MCData application signalling for establishing a file distribution session in support of MCData communication.

The MCData-FD-2 reference point, which exists between the FD functions of the MCData client and the MCData server, is used for unicast file transaction between MCData server and MCData client. The MCData-FD-2 reference point uses the SGi reference point defined in TS 23.002. Reference point MCData-FD-2 supports the following functions:

• file being distributed from and to the MCData client;
• conversation identifier for message thread indication; and
• application plane identities for the MCData user and MCData application.

The MCData-FD-3 reference point, which exists between the FD functions of the MCData client and the MCData server, is used by the FD function of the MCData server to send downlink multicast file data to the FD function of the MCData client. The MCData-FD-3 reference point uses the MB2-U interface defined in TS 23.468 or the xMB-U interface as defined in TS 26.348.

The MCData-FD-4 reference point, which exists between the media storage function and the media storage client, is used by the media storage client of MCData UE to upload and download file to the media storage function of the MCData content server. The MCData-FD-4 reference point uses the HTTP reference point.

The MCData-FD-5 reference point, which exists between FD function and the media storage function, is used by the FD function of MCData server to fetch the file in the MCData content server that was uploaded by the media storage client of a MCData UE for multicast delivery using MBMS. It also supports necessary operational functions such as size check for transmission control etc. The MCData-FD-5 reference point uses the HTTP reference point.

The MCData-FD-7 reference point, which exists between media storage function and the MCData message store, is used by the media storage function to fetch the file residing in the MCData message store and store in its repository for distribution. It is also used by the MCData message store to download the file contents from the media storage function.

DS function of the MCData client is responsible to handle DS capability related requests and responses for data streaming. FD function may interact with storage entity for retrieving the locally stored data for data streaming.

The data streaming and distribution function is responsible for the distribution of data stream to MCData communication participants. The data streaming and distribution function provides the following functionality:

• reception of uplink data stream transmission by means of the MCdata-DS-2 reference point;
• replicate the data stream as needed for distribution to those MCData communication participants using unicast transport;
• distribute downlink data stream by IP unicast transmission to those MCData communication participants utilizing unicast transport by means of MCdata-DS-2 reference point; and
• distribute downlink data stream using multicast downlink transport by means of the MCdata-DS-3 reference point.

This functional entity is responsible for transmission and reception control of data stream between the sending MCData UE, the MCData server, and the receiving MCData UE. Transmission and reception control function is used to provide arbitration between multiple data requests and apply the necessary policy to ensure that appropriate data is transmitted between the MCData UEs.

MCdata-DS-1 reference point is used for MCData application signalling for establishing a session in support of MCData data streaming. The bearer is also used for both uplink and downlink unicast stream download reports (e.g., stream start and stop records). The MCdata-DS-1 reference point shall use the SIP-1 and SIP-2 reference points for transport and routing of SIP signalling. Messages supported on this interface includes the uplink and the downlink unicast data stream between the MCData clients MCData communication via the MCData server for

• metadata of the data being streamed;
• URL of the data being streamed;
• sending stream download report;
• conversation identifier for message thread indication; and
• application plane identities for the MCData user and MCData application.

Messages supported on this interface may also include the MCData client providing the MCData server with

• MCData application signalling for establishing a UE data streaming session in support of MCData communication.

The MCdata-DS-2 reference point, which exists between the data streaming and distribution function and the DS function, is used to unicast data stream between the data streaming and distribution function of the MCData server and the DS function of the MCData client. The MCdata-DS-2 reference point uses the SGi reference point defined in TS 23.002. MCdata-DS-2 supports the following functions:

• stream data from MCData UE;
• stream data from network;
• data stream controls from the authorized MCData UE;
• stream data stream controls from the MCData UE over uplink;
• start and stop data stream from MCData UE over downlink;
• conversation identifier for message thread indication; and
• application plane identities for the MCData user and MCData application.

The MCdata-DS-3 reference point, which exists between the data streaming and distribution function and the DS function, is used by the data streaming and distribution function of the MCData server to send multicast data stream to the DS function of the MCData client. The MCdata-DS-3 reference point uses the MB2-U interface defined in TS 23.468.

IP connectivity function of the MCData client is responsible to handle IPcon capability related requests and responses.

The IPcon distribution function of the MCData server is responsible for the distribution of IP Data to MCData communication participants. The IPcon distribution function of the MCData server provides the following functionality:

• reception of uplink IP Data transmission by means of the MCData-IPcon-2 reference points;
• replicate the IP Data as needed for distribution to those MCData communication participants using unicast transport;
• distribute downlink data by IP unicast transmission to those MCData communication participants utilizing unicast transport by means of the MCData-IPcon-2 reference points; and
• distribute downlink IP Data using multicast downlink transport by means of the MCData-IPcon-3 reference point.

This functional entity is responsible for transmission and reception control of IP Data transaction between the sending MCData client, the MCData server, and the receiving MCData client. Transmission and reception control function is used to provide arbitration between multiple data requests and apply the necessary policy to ensure that appropriate IP Data are transmitted between the MCData clients.

MCData-IPcon-1 reference point is used for MCData application signalling for establishing a session in support of MCData IP connectivity.

MCData-IPcon-2 reference point carries bidirectional IP Data for point-to-point MCData IP connectivity over the media plane between the IPcon distribution function of the MCData server and the IPcon function of the MCData client(s).

MCData-IPcon-3 reference point carries downlink unidirectional IP Data over the media plane between the IPcon distribution function of the MCData server and the IPcon function of the MCData client(s).