Description
The Packet Set Delay Budget (PSDB) is a Quality of Service (QoS) characteristic introduced in 5G System (5GS) to support deterministic communication, particularly for Industrial IoT and time-sensitive networking. Unlike the traditional Packet Delay Budget (PDB), which specifies a latency bound for individual packets, the PSDB applies to a 'Packet Set'. A Packet Set is defined as one or more packets that are temporally related, such as packets generated from a single sensor scan or a coordinated multi-actuator command. The PSDB defines the maximum allowed time from the generation of the first packet in the set at the source application until the successful delivery of the last packet in the set to the destination application, traversing the 5G system. This end-to-end delay includes all processing, queuing, and transmission delays across the UE, radio access network (RAN), user plane functions (UPF), and any associated time-sensitive networking (TSN) translators. The 5G core network uses the PSDB, along with other QoS parameters like the 5G QoS Identifier (5QI), to establish appropriate QoS Flows with the necessary resource allocation and scheduling policies in the RAN and core. For the RAN, supporting PSDB may require enhanced scheduling algorithms that consider the temporal relationship within a packet set, potentially prioritizing the delivery of the remaining packets in a set as the PSDB deadline approaches. The PSDB is a key enabler for the 5GS to act as a TSN bridge, integrating seamlessly with wired TSN networks that use similar group-based timing concepts. Its specification involves complex interaction between the Service Based Interface (SBI) for QoS policy control (via the PCF) and the N2/N4 interfaces for session management and forwarding rule enforcement.
Purpose & Motivation
The creation of the Packet Set Delay Budget (PSDB) was motivated by the stringent requirements of emerging industrial automation and control applications within the 5G framework. Traditional QoS mechanisms, designed for human-centric services like voice or video streaming, focus on the performance of individual packets (e.g., average delay, jitter). However, in a coordinated cyber-physical system, such as a robotic assembly line or motion control, the correct operation depends on the synchronized arrival of a related set of data packets at multiple endpoints. The failure or excessive delay of even one packet within a set can render the entire set useless and disrupt the control loop. The individual Packet Delay Budget (PDB) was insufficient to guarantee this collective timeliness. PSDB was introduced to address this gap, providing a QoS metric that aligns with the semantic requirements of deterministic applications. It allows the network to understand and enforce timing guarantees for logically grouped data, enabling 5G to support true deterministic latency for the first time. This evolution was driven by 3GPP's work on integration with IEEE Time-Sensitive Networking (TSN) and the needs of vertical industries under the umbrella of Ultra-Reliable Low-Latency Communication (URLLC) enhancements. PSDB solves the problem of providing temporal coordination over a wireless medium, a critical step for 5G's adoption in mission-critical industrial environments where wired TSN networks are prevalent.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (91 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Packet Set Delay Budget (PSDB) function was introduced as part of enhancements for URLLC services, specifically relating to 5QI, PDB, and PER attributes. This included clarifications on the support of the Delay Critical GBR resource type, which ensures packet transport with strict bounds on latency and reliability. Furthermore, procedures were defined for the SMF to determine the 5QI and ARP based on received downlink packets or Downlink Data Reports for QoS Flow establishment.
- Delay budget report and MAC CE adaptation for NR for TS 38.300 TS 38.300CR0042
- PS Data Off supporting non-IP data packet TS 23.501CR0680
- Corrections to RQoS logic when receiving DL packet with RQI TS 23.501CR0011
- Proposal of Specifying Packet Detection Rule TS 23.501CR0027
- Corrections and clarifications for the usage of Packet Filter Set TS 23.501CR0035
- Traffic mapping information that disallows UL packets TS 23.501CR0053
+ 6 more changes
In Release 16, the Packet Set Delay Budget (PSDB) function was enhanced as part of broader Ultra-Reliable Low Latency Communications (URLLC) support, with specific updates for QoS monitoring and bridge delay handling. The release introduced corrections and clarifications for the transfer, determination, and reporting of bridge delay parameters to improve latency bounds. Furthermore, it added procedures for UPF selection and for associating URLLC traffic to redundant PDU sessions to meet stringent delay budgets.
- New clause for URLLC supporting TS 23.501CR0810
- Introduction of QoS Monitoring to assist URLLC Service TS 23.501CR0990
- Description of URLLC features in NF description clauses TS 29.514CR0249
- 5G URLLC: Optimizing Redundancy TS 23.501CR1217
- Clarifications on URLLC support TS 23.501CR1643
- Support of forwarding of broadcast and multicast packets TS 23.501CR1659
+ 19 more changes
In Release 17, enhancements were made to the Packet Set Delay Budget (PSDB) function, including corrections to the residence time calculation for delay measurements and clarifications on bridge delay calculation. The release also introduced mechanisms for deriving uplink packet filters from downlink encapsulated IPsec protected packets and for mapping scheduled traffic information and propagation delays between TSN and 5GS clocks. Furthermore, it specified the handling of TSCAI calculation when UE-DS-TT residence time has not been provided.
- Enchantments for supporting Supported Analytics Delay mechanism TS 23.501CR2530
- Adding the usage of Redundant Transmission Experience analytics for URLLC service TS 23.501CR2581
- Packet Loss Rate measurements TS 23.501CR2587
- Introduction of Rel-17 IIoT/URLLC to TS 38.300 TS 38.300CR0416
- Correcting the residence time calculation for the delay measurements TS 23.501CR3198
- Clarify the Supported Analytics Delay TS 23.501CR2760
+ 10 more changes
In Release 18, the PSDB (Packet Set Delay Budget) function was enhanced by having PSER and PSDB supersede the PER and PDB per direction, providing a more refined framework for delay management. Furthermore, the release introduced explicit support for Packet Delay Variation monitoring and reporting as part of the QoS monitoring mechanism, which can be exposed to an Application Function. These updates were complemented by clarifications and corrections regarding SMF behavior for non-3GPP delay budgets and the handling of downlink packets for UEs outside a slice support area.
- PCF support of 5GS Packet Delay Variation monitoring based on QoS monitoring mechanism and exposed to AF TS 23.501CR3792
- Non-3GPP QoS and delay budget - 23.501 TS 23.501CR3912
- Update about the Packet Delay Variation description and add PDV in QoS monitoring parameters TS 23.501CR4506
- Support of Packet Delay Variation monitoring and reporting TS 29.514CR0519
- Support of the Packet Delay Variation monitoring TS 29.514CR0541
- Support of the measurement of Round-Trip delay over two QoS flows TS 29.514CR0607
+ 19 more changes
In Release 19, the PSDB (Packet Set Delay Budget) function was enhanced with new support for considering N6 interface delay. This included the introduction of an "Indication of considering N6 delay" in AF requests and the capability for the SMF to trigger N6 delay measurement, allowing the system to factor in transport network latency when managing QoS for packet sets. Furthermore, clarifications were provided on the use of PSDB within alternative QoS procedures.
- Adding the NAT information exposure and Packet Inspection functionality in the UPF NF profile TS 23.501CR5420
- Support of L-PSA UPF Selection Considering N6 Delay TS 23.501CR5437
- AF request and functionalities enhancement to support N6 delay measurement TS 23.501CR5443
- Support of the N6 delay indication TS 29.514CR0702
- Update the n6 delay indication handling in the PATCH TS 29.514CR0764
- Clarification on the PSDB and PSER in the alternative QoS TS 29.514CR0772
+ 7 more changes
Explore further
Broader topics and technologies where PSDB plays a role.
Defining Specifications
3GPP specifications that define or reference PSDB, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TR 38.835 vi01 | Technical Report on XR Enhancements for NR | Rel-18 |