Description
The 5G QoS Identifier (5QI) is a fundamental mechanism in 5G System (5GS) architecture for managing Quality of Service. It's a scalar value ranging from 1 to 255, where standardized values (1-89) have predefined QoS characteristics defined in 3GPP specifications, while dynamic values (90-254) can be assigned with operator-specific QoS parameters. Each 5QI value maps to a specific QoS profile containing five key parameters: Resource Type (GBR, Delay Critical GBR, or Non-GBR), Priority Level, Packet Delay Budget (PDB), Packet Error Rate (PER), and Averaging Window (for GBR flows only).
When a Protocol Data Unit (PDU) Session is established, the 5G Core Network (5GC) assigns one or more QoS Flows identified by their 5QI values. The Access and Mobility Management Function (AMF) communicates these QoS requirements to the Radio Access Network (RAN) via the N2 interface. The RAN then maps each QoS Flow to appropriate Data Radio Bearers (DRBs) using QoS Flow to DRB mapping rules. This hierarchical approach separates QoS control (in 5GC) from bearer management (in RAN), providing flexibility and scalability.
The 5QI mechanism works through standardized signaling procedures. During PDU Session Establishment or Modification, the Session Management Function (SMF) determines the appropriate 5QI based on the service requirements and subscriber profile. The SMF sends this information to the User Plane Function (UPF) for packet marking and to the RAN via the AMF. In the user plane, packets are marked with QoS Flow Identifiers (QFIs) derived from 5QI values, enabling consistent QoS treatment across network nodes. The RAN uses these markings to apply appropriate scheduling, admission control, and link layer configurations.
Key architectural components involved in 5QI implementation include the Policy Control Function (PCF), which provides policy rules containing 5QI assignments; the SMF, which enforces these policies; the UPF, which performs packet marking and rate policing; and the gNB, which implements radio resource scheduling based on 5QI parameters. The system supports both reflective QoS, where the UE can derive QoS rules from downlink traffic, and explicit QoS signaling via NAS and RRC protocols.
5QI plays a critical role in enabling network slicing and service differentiation. Different network slices can use different 5QI values to achieve their specific performance requirements. The standardized 5QI values cover a wide range of services including conversational voice, live streaming, autonomous driving, industrial automation, and massive IoT applications. This standardized approach ensures interoperability between different vendors' equipment and consistent QoS experience for end users.
Purpose & Motivation
5QI was created to address the limitations of previous QoS mechanisms in 4G/LTE networks, particularly the QCI (QoS Class Identifier). While QCI served well for 4G services, it lacked the granularity and flexibility needed for 5G's diverse use cases including ultra-reliable low-latency communications (URLLC), enhanced mobile broadband (eMBB), and massive machine-type communications (mMTC). The 4G system's bearer-based QoS model was too rigid for 5G's service-based architecture and network slicing requirements.
5QI solves several key problems: First, it provides finer granularity for delay-critical services with specific values for industrial automation, intelligent transport systems, and remote control applications. Second, it introduces the Delay Critical GBR resource type specifically for URLLC services requiring both guaranteed bitrate and strict latency bounds. Third, 5QI enables more efficient resource utilization through improved priority handling and the separation of QoS control from bearer management.
The historical context for 5QI development includes the need to support vertical industry requirements identified in 3GPP Study Items like TR 22.891 and TR 22.804. These studies revealed that previous QoS mechanisms couldn't adequately support services with conflicting requirements operating simultaneously on the same device, such as augmented reality (requiring high bandwidth) and vehicle-to-everything communication (requiring ultra-low latency). 5QI provides the foundation for meeting these diverse requirements through standardized yet flexible QoS profiles.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (32 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the 5G QoS Identifier (5QI) function was enhanced through clarifications and corrections, including fixes for URLLC attributes like PDB and PER, alignment with 4G QCI, and completion of the standardized 5QI characteristics table. The release also introduced the ability to use a preconfigured 5QI for the QoS Flow associated with the default QoS rule and provided corrections for subscribed 5QI and DRB 5QI handling. Furthermore, it established that the 5G system shall be able to provide services using satellite access, mapping QoS characteristics against specific 5QIs that account for the nature of the satellite link to provide the best performance with respect to jitter or required bit rates.
- 5G QoS fixes for URLLC services related attributes - PDB, PER, MDB, 5QI TS 23.501CR0087
- 5QI-QCI alignment TS 23.501CR0480
- Consistent Description of 5QI TS 23.501CR0583
- Clarifications for 5QI priority level TS 23.501CR0607
- Using preconfigured 5QI for QoS Flow associated with the default QoS rule TS 23.501CR0621
- Completion of 5QI characteristics table TS 23.501CR0676
+ 4 more changes
In Release 16, the 5QI function was enhanced by extending the standardized mapping table to accommodate new requirements, such as those for enhanced V2X services, and by introducing a new standardized 5QI value, 5QI 86. The release also included clarifications and corrections for the 5QI characteristics table, including specific updates for TSN (Time-Sensitive Networking) and static TSC (Time Sensitive Communication) QoS Flow establishment. Furthermore, modifications to standardized or pre-configured 5QI parameters were clarified, and an incorrect note for 5QI 3 was corrected.
- Extension of standardized 5QI to QoS characteristics mapping table to accommodate enhanced V2X requirements TS 23.501CR1735
- 5QI 86 introduction TS 24.501CR1697
- Corrections and alignments for the 5QI characteristics table TS 23.501CR1408
- TSN 5QI clarification and static TSC QoS Flow establishment TS 23.501CR1802
- Clarification on the Standardized or pre-configured 5QI parameters modification TS 23.501CR1816
- Incorrect NOTE 14 for 5QI 3 TS 23.501CR2299
In Release 17, the 5G QoS Identifier (5QI) function was expanded with new standardized 5QI values specifically designed to support Advanced Interactive Services (AIS). Furthermore, dedicated 5QI values were introduced to define QoS characteristics for services carried over satellite access, accounting for the unique nature of GEO, MEO, or LEO satellite links. These enhancements enable the system to select communication links that provide the best 5QI with respect to parameters like jitter or required bit rates for satellite-connected UEs.
- New 5QI values to support Advance Interactive Services (AIS) in 5G TS 23.501CR2701
- New standardized 5QI values for Advanced Interactive Services TS 23.501CR2740
- 5QI for satellite access TS 24.501CR3143
- 5QI value for services carried over satellite access/backhaul TS 29.513CR0284
- PDB value for 5QI 10 TS 23.501CR3029
- New 5QI values to support Advance Interactive Services (AIS) in 5G TS 24.501CR4501
+ 1 more changes
In Release 18, the 5G QoS Identifier (5QI) function was enhanced to support new service types, including V2X and A2X message delivery via Multicast/Broadcast Services (MBS) and services for AIML. The release also introduced support for a 5QI Priority Level within QoS constraints and applied the relaxation of 5QI delay requirements for first packets to RRC-INACTIVE mode and other best-effort 5QIs. Furthermore, specific considerations for mapping 5QI to account for the characteristics of satellite access networks were formalized.
- 5QI for V2X message delivery via MBS TS 23.501CR3881
- 5QI for A2X message delivery via MBS TS 23.501CR4249
- Support for 5QI Priority Level in QoS constraints TS 23.501CR3748
- 5QI for AIML services TS 23.501CR4473
- Relaxation of 5QI delay requirements for first packets should also apply for RRC-INACTIVE mode. TS 23.501CR4709
- Relaxation of 5QI delay requirements for first packets should also apply for RRC-INACTIVE mode and for other best effort 5QIs TS 23.501CR5043
+ 1 more changes
In Release 19, the 5QI function was updated to clarify its application for satellite access networks, such as those using GEO, MEO, or LEO satellites. The enhancements specify that the system must map QoS characteristics to specific 5QIs that account for the nature of satellite access to provide the best communication link with respect to jitter or required bit rates. Additionally, a correction was made to fix an erroneous description of a 5QI value.
Explore further
Broader topics and technologies where 5QI plays a role.
Defining Specifications
3GPP specifications that define or reference 5QI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 22.822 vg00 | Satellite Access in 5G Study | Rel-16 |
| TR 22.832 vh40 | Study on cyber-physical control in vertical domains | Rel-17 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.764 vh10 | Study on V2X Application Layer Enhancements | Rel-17 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 24.502 vj20 | 5G Core Access via Non-3GPP Networks; Stage 3 | Rel-19 |
| TS 24.890 vg00 | 5G NAS Protocol for 5GS Stage 3 | Rel-16 |
| TS 26.502 vj30 | 5G Multicast-Broadcast User Services Architecture | Rel-19 |
| TR 26.928 vj00 | Study on eXtended Reality (XR) in 5G | Rel-19 |
| TS 28.802 vf00 | Management Study for 5G Network Architecture | Rel-15 |
| TS 29.061 vj00 | Packet Domain Interworking for PLMN | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.518 vj50 | AMF Service Based Interface Protocol | Rel-19 |
| TS 29.520 vj40 | 5G Network Data Analytics Services Stage 3 | Rel-19 |
| TS 29.543 vj20 | 5G Data Transfer Policy Control Services Stage 3 | Rel-19 |
| TS 29.866 vj00 | IMS Disaster Prevention & Restoration Enhancement | Rel-19 |
| TS 29.890 vg00 | CT3 5G System Technical Report | Rel-16 |
| TS 37.473 vj00 | W1 Application Protocol (W1AP) Specification | Rel-19 |
| TS 37.483 vj10 | E1 Application Protocol (E1AP) | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 38.414 vj00 | NG Interface User Plane Protocol | Rel-19 |
| TS 38.423 vj10 | Xn Application Protocol (XnAP) specification | Rel-19 |
| TS 38.463 vj00 | E1 Application Protocol (E1AP) | Rel-19 |
| TS 38.473 vj10 | 5G F1 Application Protocol (F1AP) | Rel-19 |
