AMF UE-AMBR updates from UDM

AMF UE-AMBR updates from UDM

AMF UE-AMBR updates from UDM is a feature that:

  • Enables the Access and Mobility Management Function (AMF) to receive real-time UE-AMBR values from Unified Data Management (UDM) using the Nudm_SDM_Notification service,

  • Ensures AMF delivers updated UE-AMBR values to the gNB using NGAP signaling to enforce consistent throughput in the radio access network, and

  • Allows updates to be applied immediately by sending UE Context Modification request for connected UEs or at the next state transition for idle UEs to maintain alignment between core and RAN policies.

Traditionally, UE-AMBR values are provided at registration, but this feature extends support to dynamic in-session updates for ongoing subscriber sessions.

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

AMF UE-AMBR updates from UDM

2026.03.0

You benefit from real-time enforcement of subscriber throughput limits because AMF now applies UE-AMBR updates from UDM during active sessions, not just at registration. Any changes to bit rate limits are promptly conveyed to the gNB for connected UEs or at the next connection if idle, ensuring consistent policy enforcement.

Configure AMF UE-AMBR updates from UDM

Follow these steps to configure AMF to apply CLI configured UE-AMBR values and ensure these values are correctly propagated to the gNB.

Procedure

Step 1

Enter the AMF configuration mode.

config

Step 2

Enter call control policy configuration mode under the AMF global configuration.

amf-global call-control-policy local

Use this mode to set policies for UE-AMBR behavior.

Step 3

Configure UE-AMBR uplink and downlink bit rates as required.

ue-ambr uplink uplink_value downlink downlink_value

Specify uplink and downlink bit rates in bits per second. Example:

  • ue-ambr uplink 200000000 downlink 300000000

    If no UE-AMBR value is configured in CLI or no value is recived from UDM then the default value is 256000 bps for both uplink and downlink UE-AMBR.

Step 4

Enable override for UDM-provided UE-AMBR values if required.

ue-ambr uplink uplink_value downlink downlink_value override-udm-ue-ambr

With override-udm-ue-ambr , locally configured CLI values take precedence for new subscribers. For existing subscribers, CLI value is considered when UE transitions from idle to active state.

  • Remove override-udm-ue-ambr to revert to UDM control.

Step 5

Save and commit the configuration.

Step 6

Verify applied UE-AMBR values using the AMF CLI.

Example:

show subscriber supi supi_value

Use this command to display current UE-AMBR values for a subscriber. Example output:

  • "SelectedSubs": { "UeAmbrUp": 200000000, "UeAmbrDown": 300000000 }

Note

 

Updated UE-AMBR values apply when the subscriber transitions from idle to connected mode.