5QI — One number standing for a whole set of promises
Sessions, flows and slices
Where it sits
What it is
What it is. A single number standing for a whole set of QoS promises. TS 23.501 §5.7.2 makes it a scalar that "references 5G QoS characteristics", and Table 5.7.4-1 is the standardised mapping. It is the one parameter the core gives the RAN that changes how the scheduler behaves.
What one 5QI value carries: a resource type (GBR, Non-GBR, or Delay-critical GBR), a default priority level, a packet delay budget, a packet error rate, a default maximum data burst volume, and a default averaging window.
A few standardised rows, read out of Table 5.7.4-1:
| 5QI | Type | Priority | Delay budget | Error rate | Example service |
|---|---|---|---|---|---|
| 1 | GBR | 20 | 100 ms | 10⁻² | Conversational voice |
| 2 | GBR | 40 | 150 ms | 10⁻³ | Conversational video |
| 3 | GBR | 30 | 50 ms | 10⁻³ | Real-time gaming, V2X |
| 5 | Non-GBR | 10 | 100 ms | 10⁻⁶ | IMS signalling |
| 9 | Non-GBR | 90 | 300 ms | 10⁻⁶ | TCP — web, e-mail, file transfer |
| 80 | Non-GBR | 68 | 10 ms | 10⁻⁶ | Low-latency eMBB, augmented reality |
| 82 | Delay-critical GBR | 19 | 10 ms | 10⁻⁴ | Discrete automation |
| 85 | Delay-critical GBR | 21 | 5 ms | 10⁻⁵ | Electricity distribution — high voltage; remote driving |
| 87 | Delay-critical GBR | 25 | 5 ms | 10⁻³ | Motion tracking |
5QI 9 is the internet. Priority 90 — nearly the lowest in the table — a 300 ms budget and a 10⁻⁶ error rate. Ordinary web traffic is, by design, the thing that gives way to everything else. Almost every phone's default QoS flow is this row.
5QI 85 is where this table meets the rest of this folder. 5 ms delay budget at 10⁻⁵ packet error rate is URLLC written as a scheduling instruction, and it is very nearly TR 38.913 §7's target of 1−10⁻⁵ reliability. Everything the NR notes describe as the machinery for meeting it — short slots, high numerology, HARQ budgets, conservative CQI — exists to satisfy a row of this table.
"Delay-critical GBR" is a third resource type, not a label. Its rows are the only ones with a Maximum Data Burst Volume — 255, 500, 1354 or 17000 bytes — because a promise about latency is meaningless without a bound on how much arrives at once. The RAN is being told both how fast and how much.
The seam, stated plainly. The SMF puts the 5QI into a QoS profile and sends it "via AMF over N2 to AN". The base station's scheduler then has a delay budget and an error rate for that flow. That is the entire instruction the core gives the RAN about how to treat traffic — and everything in this folder's scheduling and link adaptation is the RAN's answer to it.
Read on
This concept is read as part of one argument in ref-session, alongside the rest of its group.
Before this concept, the hierarchy says to learn the following — the full chain, in order: