Description
File Distribution is a service layer capability that facilitates the transfer of files from a content provider or application server to multiple recipient UEs. It is not a single protocol but a set of architectural functions and procedures defined across the service and application layer specifications. A key enabler for FD is the underlying broadcast/multicast bearer capabilities of the network, such as evolved Multimedia Broadcast Multicast Service (eMBMS) in 4G/5G or sidelink communication for direct device-to-device transfer. The FD service manages the session announcement, file delivery, and reception reporting.
The architecture typically involves a File Distribution Server (or Application Server), the broadcast/multicast core network (e.g., BM-SC for eMBMS), and the UEs. The process begins with the server preparing the file for distribution, often segmenting it into smaller source blocks for forward error correction (e.g., using Raptor or RaptorQ codes as defined for MBMS). This creates a repair flow alongside the source flow to allow UEs to recover lost packets without feedback. The service then announces the upcoming file distribution session via a service announcement mechanism, providing UEs with the necessary parameters to join the session, such as session description, timing, and TMGI (Temporary Mobile Group Identity).
During the distribution phase, the file data is delivered over the broadcast/multicast bearer. UEs monitor the transmission and use the repair data to reconstruct the original file. For ProSe-based FD, specified for public safety and V2X, the distribution can occur over PC5 sidelink interfaces between UEs without network infrastructure. Here, one UE (the distributor) can broadcast a file to neighboring UEs within proximity. The 3GPP specifications define protocols for session management, congestion control, and security for such direct FD. The service also includes mechanisms for the server to obtain delivery reports, indicating how many UEs successfully received the file, which is crucial for applications like firmware updates over-the-air (FOTA).
Purpose & Motivation
File Distribution was created to address the need for efficient, scalable, and network-friendly dissemination of bulk data to large groups of users or devices. Unicast delivery (a separate stream to each UE) is highly inefficient for popular content or mandatory updates, causing network congestion and wasting radio resources. FD leverages broadcast/multicast technologies to transmit the data once over a shared radio resource, serving all interested UEs within a coverage area simultaneously.
Its introduction in Rel-14 was strongly motivated by the evolution of Proximity Services (ProSe) for public safety and the emergence of Vehicle-to-Everything (V2X) communication. Use cases such as distributing safety-critical maps, software updates for vehicle fleets, or multimedia content to a crowd at an event required a standardized method for group file transfer. Prior to this, such services relied on proprietary applications or inefficient unicast pulls. FD standardizes the procedures, enabling interoperability between devices and networks from different vendors. It solves the problem of congested unicast links in dense scenarios (like stadiums or traffic jams) and supports off-network operation for public safety, where devices must share files directly when cellular infrastructure is unavailable or damaged.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (45 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-14, normative work from Rel-15.
In Release 15, the specification introduced the foundational application plane functional model for File Distribution (FD), defining the MCData-FD-1 through MCData-FD-5 and MCData-FD-7 reference points for signalling, unicast/multicast data transfer, and content server interactions. It also specified support for both mandatory and optional file delivery, along with unicast and broadcast delivery methods, within the MCData service. Furthermore, the release detailed the information flow and procedures for off-network File Distribution operations.
In Release 16, the MCData File Distribution function introduced new capabilities for emergency and imminent-peril communications, including one-to-one and group emergency FD sessions, as well as procedures to upgrade an ongoing one-to-one or group FD session to an emergency type. The release also added functional alias support for FD and specified the use of the MBMS download delivery method for multicast distribution. Furthermore, it clarified that for standalone FD, the UE uses the signalling plane for disposition notifications, while session-based FD uses the media plane.
- Interconnection for file distribution TS 23.282CR0138
- MCData File Distribution using the MBMS download delivery method TS 23.282CR0150
- Functional alias support for MCData File Distribution TS 23.282CR0157
- One-to-One Emergency MCData FD TS 23.282CR0185
- Group emergency MCData FD TS 23.282CR0186
- One-to-one FD Session upgrade to emergency session TS 23.282CR0187
+ 2 more changes
In Release 17, the File Distribution (FD) function introduced support for addressing based on a functional alias for one-to-one requests and enhanced integration with the MCData message store for depositing and distributing stored files. The release also brought significant enhancements and corrections for group standalone FD and one-to-one FD procedures using both HTTP and MBMS delivery methods, including clarified media plane control via the MB2 interface. Furthermore, it added an Emergency Indicator information element to FD requests and applied transmission and reception controls consistently across all FD HTTP procedures.
- File distribution addressing based on functional alias TS 23.282CR0181
- Providing stored files in MCData content server for FD over MBMS TS 23.282CR0232
- Depositing file contents distributed via FD communication using HTTP into MCData message store TS 23.282CR0252
- Distribution of file residing in MCData message store account of the MCData user TS 23.282CR0253
- MCData media plane control for FD using MBMS delivery via MB2 TS 24.582CR0025
- Enhancement of Group standalone FD using MBMS TS 23.282CR0234
+ 17 more changes
In Release 18, the File Distribution (FD) function was enhanced by introducing information flows and procedures for ad hoc group data communication specifically for FD and SDS services within MCData. This builds upon the existing FD capabilities for one-to-one and group communications, which support both unicast and broadcast delivery methods and mandatory download requests. The update formalizes the operational procedures for dynamic, ad hoc group scenarios within the established MCData service architecture.
- Information flows and procedures for the ad hoc group data communication for SDS and FD services of MCData TS 23.282CR0304
- Addition of ProSe LI reporting at the UDM Stage 2 TS 33.127CR0227
- Add new verified and e-mail agreed TTCN test cases in the TC lists in 37.579-5 (prose), Annex A TS 37.579CR0009
- Add new verified and e-mail agreed TTCN test cases in the TC lists in 37.579-5 (prose), Annex A TS 37.579CR0024
- Add new verified and e-mail agreed TTCN test cases in the TC lists in 37.579-5 (prose), Annex A TS 37.579CR0028
In Release 19, the File Distribution (FD) function introduced an Information Element for location within FD messages and defined new information flows and procedures to support ad hoc group standalone file distribution using HTTP. The release also included corrections to the existing FD file removal procedures to ensure proper operation.
- Addition of location Information Element to FD message TS 23.282CR0318
- Information flows and procedures to support ad hoc group standalone file distribution using HTTP procedures TS 23.282CR0349
- SMF enhancement for LI for 5G ProSe Communication via 5G ProSe UE-to-Network Relay - Stage 2 TS 33.127CR0272
- LI for 5G ProSe Direct Communication - Stage 2 TS 33.127CR0273
- Corrections to the FD file removal procedures TS 23.282CR0371
Explore further
Broader topics and technologies where FD plays a role.
Defining Specifications
3GPP specifications that define or reference FD, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.282 vk00 | MCData Functional Architecture & Info Flows | Rel-20 |
| TS 23.784 vg00 | Discreet Listening for Mission Critical Services | Rel-16 |
| TS 24.582 vj00 | MCData Media Plane Control Protocols | Rel-19 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 37.579 vi40 | Mission Critical services conformance testing | Rel-18 |
| TR 38.808 vh00 | Study on NR above 52.6 GHz to 71 GHz | Rel-17 |