| Protocol | rrc | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 38.331 | Spec Section | 6.2.2 |
| Direction | gNB -> UE | Message Type | MBS Configuration |
| Full message name | 5G NR - MBS Multicast Configuration |
|---|---|
| Protocol | RRC |
| Technology | 5G |
| Direction | gNB -> UE |
| Interface | Uu |
| Signaling bearer / channel | SRB1 / DL-DCCH |
| Typical trigger | Used when multicast-oriented MBS configuration must be delivered to the UE. |
| Main purpose | Carries the multicast-specific MBS configuration the UE needs to receive or maintain multicast service correctly. |
| Main specification | 3GPP TS 38.331, 6.2.2 |
| Release added | Release 17 |
| Procedures where used | MBS Multicast Service Configuration |
MBS Multicast Configuration is the NR RRC message used to provide dedicated MBS multicast configuration to the UE.
Carries the multicast-specific MBS configuration the UE needs to receive or maintain multicast service correctly.
MBS Multicast Configuration gives the UE dedicated multicast-service settings.
Call flow position: Sent when the network applies dedicated multicast configuration.
Typical state: UE is in connected mode with MBS multicast context.
Preconditions:
Next likely message: UE applies multicast configuration
Previous message(s): MBS Interest Indication
Next message(s): Multicast service reception handling
Security context: Sent as protected connected-mode signaling.
MBSMulticastConfiguration ::= SEQUENCE {
mbsMulticastConfig OCTET STRING
}
Engineers use the message to understand multicast-specific MBS configuration rather than general broadcast SI.
DL-DCCH-Message
message: mbsMulticastConfiguration
mbsMulticastConfig: present
| IE | Required | Description |
|---|---|---|
mbsMulticastConfig | Yes | Carries the multicast-specific MBS configuration relevant to the UE. |
mbsMulticastConfigCarries the multicast-specific MBS configuration relevant to the UE.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
Likely cause: Multicast configuration may be missing or not applied.
What to inspect: Check MBS Multicast Configuration and later multicast reception behavior.
Next step: Compare it with SIB24 and any interest indication sent by the UE.
It provides dedicated multicast MBS configuration to the UE.
Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.