School of Specs 23.501v20.2.0

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

5.32.5.5 UE Assistance Operation

Taught in 11. Using two accesses at once (The 5G system architecture, in depth).

When UE-assistance operation is authorized by the PCF in the PCC Rule, the SMF provides an indication for UE-assistance in the ATSSS Rule to the UE, as described in clause 5.32.8 and in the MAR to the UPF, as described in clause 5.8.5.8.

If the UE receives the UE-assistance indicator in an ATSSS rule (as specified in clause 5.32.8) and the UE decides to apply a different UL traffic distribution for an SDF than the default UL traffic distribution indicated in the Steering Mode component of the ATSSS rule (e.g. because the UE is running out of battery), then the following applies:

  • The UE may apply any split percentages for the UL traffic distribution of an SDF, based on implementation specific criteria.
  • The UE may send a PMF-UAD (UE Assistance Data) message to UPF that contains the split percentages that may be used by UPF for all DL traffic that the UE-assistance operation applies. The UPF acknowledges the reception of the PMF-UAD message by sending a PMF-UAD complete message to the UE.

NOTE: If the UE has multiple ATSSS rules that allow UE-assistance operation and the UE decides to use different UL split percentages for their respective SDFs, then the split percentages included in the PMF-UAD message are selected by the UE based on implementation specific criteria.

  • The UPF may apply the information in a received PMF-UAD message to align the DL traffic distribution for traffic that is allowed to use UE-assistance operation, i.e. traffic where the MAR contains a Steering Mode Indicator set to UE-assistance operation.
  • If the UE decides to terminate the UE assistance operation, the UE may send a PMF-UAT (UE Assistance Termination) message to the UPF indicating that the UE assistance operation is terminated and the UE performs the UL traffic distribution according to the split percentages in the ATSSS rule received from the network. If the UPF receives the PMF-UAT message, the UPF acknowledges the reception by sending a PMF-UAT complete message and performs DL traffic distribution by applying the split percentages included in the MAR.