Description
Background Data Transfer (BDT) is a standardized 5G service feature introduced in 3GPP Release 15 that enables network operators to manage and schedule data transmissions for applications that do not require immediate delivery. The service operates through a policy-based framework where the network determines optimal transmission windows based on network conditions, subscription profiles, and application requirements. BDT is implemented within the 5G Core Network's Policy Control Function (PCF) and Session Management Function (SMF), working in conjunction with the User Plane Function (UPF) to enforce scheduled data transfer policies.
The architecture of BDT involves several key components: the Application Function (AF) that requests background transfer capabilities, the Policy Control Function (PCF) that creates and manages BDT policies, the Session Management Function (SMF) that enforces these policies at the session level, and the User Plane Function (UPF) that implements the actual data transfer scheduling. The Network Exposure Function (NEF) may also be involved when third-party applications request BDT services through external APIs. The system uses standardized interfaces including N5 (PCF-AF), N7 (SMF-PCF), and N4 (SMF-UPF) to coordinate BDT operations across network functions.
BDT works through a multi-step process: first, an application or network function identifies traffic eligible for background transfer based on QoS requirements and application characteristics. The PCF then creates BDT policies specifying parameters such as maximum allowed delay, preferred time windows, data volume limits, and network conditions for activation. These policies are communicated to the SMF, which translates them into specific session rules. The UPF implements these rules by buffering, delaying, or scheduling data transmissions according to the established parameters. The system continuously monitors network conditions and can dynamically adjust BDT parameters to optimize performance.
The service supports various operational modes including time-based scheduling (specific time windows), network condition-based scheduling (when network load is below certain thresholds), and hybrid approaches. BDT policies can be applied at different granularities: per subscriber, per application, per data network name (DNN), or per network slice. The system includes mechanisms for policy conflict resolution, charging correlation for scheduled transfers, and reporting of BDT execution status to both network functions and external applications when authorized.
Purpose & Motivation
BDT was created to address the growing challenge of network congestion caused by massive amounts of non-urgent data traffic in 5G networks. As IoT deployments expanded and applications like software updates, cloud backups, and content synchronization became ubiquitous, networks faced increasing pressure from background traffic competing with latency-sensitive applications. Traditional approaches treated all data equally, leading to inefficient resource utilization during peak hours and degraded performance for critical services.
Previous 3GPP releases lacked standardized mechanisms for managing background traffic efficiently. Operators implemented proprietary solutions or relied on basic QoS differentiation, which proved insufficient for the scale and complexity of 5G use cases. The limitations included inability to coordinate transfers across multiple applications, lack of standardized APIs for third-party integration, and insufficient granularity in scheduling controls. BDT provides a standardized framework that enables predictable network behavior while maintaining service quality for all applications.
The technology solves several key problems: it reduces network congestion during peak hours by shifting non-urgent traffic to off-peak periods, improves energy efficiency for both network infrastructure and user devices by optimizing transmission timing, enables new business models for differentiated background data services, and provides tools for network operators to manage the explosion of machine-type communications in 5G networks. By creating a standardized approach, 3GPP ensured interoperability across vendors and enabled global deployment of efficient background data management solutions.
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (88 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Background Data Transfer (BDT) function was newly introduced, enabling an Application Function (AF) to negotiate future data transfer policies with the Policy Control Function (PCF) via the NEF using the Npcf_BDTPolicyControl_Create service. This framework allows the PCF to use network analytics to create policies, store them in the UDR, and later apply them to UE sessions by embedding a Background Data Transfer Reference ID into URSP and PCC rules, with mechanisms for policy re-negotiation triggered by network performance changes.
- Background Data Transfer data TS 29.519CR0014
- Correction for background data transfer for TS 23.503 TS 23.503CR0003
- BDT: clarification on network area information and ASP identifier TS 23.503CR0121
- BDT API Update TS 29.122CR0014
- Complete the openAPI definition for BDT API TS 29.122CR0017
- http details in BDT procedure TS 29.513CR0036
+ 4 more changes
In Release 16, the BDT function was enhanced to support the delivery of BDT policies directly to the UE via URSP rules and to enable dynamic policy re-negotiation. This re-negotiation can be triggered by changes in network conditions, utilizing analytics from the NWDAF, and involves notifying the Application Function with candidate replacement policies. Furthermore, the release formalized procedures for BDT warning notifications and integrated BDT policy control within PDU session management, allowing the PCF to retrieve and apply policies using a Background Data Transfer Reference ID.
- Update of TS 23.503 for Rel.16 BDT Notification TS 23.503CR0205
- Use of analytics for background data transfer TS 23.503CR0206
- Adding Support for Delivering Background Data Transfer Polices to the UE TS 23.503CR0242
- Removal of Editor's note for BDT warning notification and define send for notification in TS23.503 TS 23.503CR0256
- PDU session management for Background Data Transfer TS 23.503CR0271
- BDT Warning Notification Support TS 29.122CR0175
+ 24 more changes
In Release 17, enhancements to Background Data Transfer (BDT) included the generation of URSP rules based on the BDT policy and the introduction of a BDT policy re-negotiation procedure triggered by network performance analytics from the NWDAF. This re-negotiation allows the PCF to propose new candidate BDT policies to the AF when performance degrades, subsequently updating the URSP rules and validation criteria for affected UEs. The release also clarified procedures for applying a BDT policy to a UE's future PDU session using the Background Data Transfer Reference ID and refined the handling of query parameters and authorization results.
- URSP rule generation based on BDT policy and related information TS 23.503CR0632
- Faliure authorization result of BDT reference Id for ChargeableParty API request TS 29.122CR0324
- Handling of query parameters in Applied BDT Data TS 29.519CR0332
- Correction in the handling of individual Applied BDT Policy Data resource TS 29.519CR0347
- Clarify the BDT warning description with degraded Network performance TS 23.503CR0589
- Alignment of BDT policy re-negotiation TS 29.513CR0231
+ 1 more changes
In Release 18, the Background Data Transfer (BDT) function was enhanced with new service operations for the BDT_Configuration API, specifically adding Get, Update, and Delete capabilities. The release also introduced formal support for BDT_Negotiation_Notification procedures and clarified the storage of BDT warning notification indications and ASP addresses in the UDR. Furthermore, updates were made to the associated OpenAPI definitions, resources, and data models to support these expanded configuration and negotiation features.
- Updates to BDT on ASP Id TS 29.122CR0702
- BDT_Configuration_request API support with description update TS 29.549CR0194
- BDT_Configuration_request API support with resources and data model update TS 29.549CR0196
- BDT_Negotiation_notification support with description update TS 29.549CR0197
- BDT_Negotiation_Notification support with Notification message and data model update TS 29.549CR0198
- BDT_Configuration_request API support with open API update TS 29.549CR0199
+ 9 more changes
In Release 19, the BDT function was enhanced to integrate energy-related criteria directly into the policy negotiation and decision process, introducing a specific "Energy indicator" as a key input. This allows the PCF to calculate and propose BDT policies based on energy consumption information and operator energy policies, and to update the BDT negotiation procedure to incorporate this energy-based feedback. Furthermore, the release formalized the SDD_BDT API with its service operations and OpenAPI definition, while also introducing URSP rules provisioning to enable the delivery of BDT policies to UEs.
- BDT Energy Criteria TS 23.503CR1420
- Energy indicator for BDT policy TS 29.122CR0923
- SDD_BDT API definition TS 29.548CR0016
- SDD_BDT OpenAPI file TS 29.548CR0017
- SDD_BDT Service operations TS 29.548CR0018
- SDD_BDT API Annex TS 29.548CR0032
+ 19 more changes
In Release 20, the BDT (Background Data Transfer) function was newly introduced, enabling an Application Function to negotiate future data transfer policies with the network's Policy Control Function via the NEF. Key new capabilities include the negotiation of a specific time window and network conditions for BDT, the storage and application of these policies to UEs via URSP rules, and a re-negotiation procedure triggered by network performance analytics from an NWDAF.
- Adding BDT, PDTQ and UE policy control for network energy saving TS 23.503CR1612
Explore further
Broader topics and technologies where BDT plays a role.
Defining Specifications
3GPP specifications that define or reference BDT, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.503 vk00 | 5G Policy and Charging Control Framework | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 26.510 vj10 | Media Delivery APIs for 5GMS and RTC Systems | Rel-19 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TS 29.122 vj40 | T8 Reference Point for Northbound APIs | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.519 vj40 | UDR Usage for Policy & Exposure Data | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 29.548 vj40 | SEAL Data Delivery Server Services Stage 3 | Rel-19 |
| TS 29.549 vj40 | SEAL API Specification for Vertical Applications | Rel-19 |
| TS 29.554 vj10 | 5G Background Data Transfer Policy Control Service | Rel-19 |
