School of Specs 23.501v20.2.0

3GPP 23.501 v20.2.0 — the document's own text

5.31.19 QoS model for NB-IoT

Taught in 25. Small devices, small messages (The 5G system architecture, in depth).

5GC QoS model described in clause 5.7 applies to NB-IoT with the following requirements:

  • The default QoS rule shall be the only QoS rule of a PDU Session for a UE connected to 5GC via NB-IoT. There is only one QoS Flow (corresponding to the default QoS rule) per PDU session.
  • Reflective QoS is not supported over NB-IoT.
  • For NB-IoT, there is a 1:1 mapping between the QoS Flow corresponding to the default QoS of a PDU session and a Data Radio Bearer when user plane resources are active for that PDU session.
  • A maximum of two Data Radio Bearers are supported over NB-IoT. Therefore, at most two PDU sessions can have active user plane resources at the same time.
  • The capability of multiple UP resource support for NB-IoT UEs is indicated in the UE 5GMM Core Network Capability (see TS 24.501 [47]). During PDU Session Establishment or UP resource activation, the AMF checks if the UE can support the establishment of user plane resources (See clause 4.2.3.2 and clause 4.3.2.2.1 of TS 23.502 [3]).