5QI
5G QoS Identifier: a scalar value that maps to a standardized set of QoS characteristics (priority, delay budget, error rate) used to configure QoS flows in 5G.
The 5QI is a single number that acts as a pointer into a table of QoS behaviours, rather than a setting that carries the behaviour itself. When the SMF assigns a 5QI to a QoS flow, both the gNB and the core already know — from the standardised mapping in 3GPP TS 23.501 — what that value implies: a resource type (GBR or non-GBR), a priority level, a packet delay budget, and a packet error rate target. So one scalar configures scheduling, admission control, and how aggressively the radio protects those packets.
A few values are worth recognising on sight. 5QI 1 is conversational voice (GBR); 5QI 5 is IMS signalling (non-GBR, high priority); the 5QI 80s and 82–85 range covers low-latency and discrete-automation traffic. Operators can also define non-standardised 5QIs, but the standardised ones are what interoperate across vendors and roaming partners without prior agreement.
Frequently asked questions
- What's the difference between 5QI and QCI?
- They are the same idea in different generations. QCI is the LTE/EPC scalar that indexes a set of QoS characteristics for an EPS bearer; 5QI is its 5G successor for QoS flows. The 5G table reuses many of the familiar values (so QCI 1 voice and 5QI 1 voice line up) but extends the range with new low-latency and URLLC entries and adds finer control such as the averaging window and maximum data burst volume.
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