5QI

5QI stands for 5G Quality of Service Identifier. It is a numeric value used in 5G networks to identify the QoS profile associated with a given QoS flow within a PDU session. The 5QI allows the 5G core and radio access network to differentiate traffic classes and allocate resources accordingly, supporting differentiated service levels across diverse applications.

In practice, each QoS flow carries a 5QI, and the network uses a mapping from that 5QI to a set of QoS parameters that describe how the traffic should be treated. These parameters typically include aspects such as delay budget, reliability or resiliency class, and data rate guarantees (for example, maximum and/or guaranteed bit rates). The exact parameters and their values are defined in 3GPP specifications and may be tailored by network operators through their QoS catalogs. 5QI is a central mechanism for providing service differentiation in the 5G system and plays a key role in features like network slicing and support for diverse service categories.

The relationship between 5QI values and their QoS characteristics is not fixed universally; lower numerical values often imply stricter QoS requirements, but the precise interpretation depends on the operator’s 5QI catalog and the related 3GPP standards. 5QI is distinct from the older QCI concept used in 4G LTE, representing an evolution of the QoS framework for the 5G core.

Implementation-wise, 5QI is negotiated and signaled during PDU session setup, and network functions such as the Session Management Function and Policy Control Function use it to enforce scheduling, resource allocation, and QoS enforcement. QoS flows may be dynamically adjusted as conditions evolve, enabling flexible, application-aware service delivery.