| Protocol | rrc | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 38.331 | Spec Section | 6.2.2 |
| Direction | UE -> gNB | Message Type | Failure Reporting |
| Full message name | 5G NR - MCG Failure Information |
|---|---|
| Protocol | RRC |
| Technology | 5G |
| Direction | UE -> gNB |
| Interface | Uu |
| Signaling bearer / channel | SRB1 / UL-DCCH |
| Typical trigger | Used when the UE detects a failure condition related to the master cell group. |
| Main purpose | Lets the UE signal that the master cell group experienced a failure condition that the network needs to handle. |
| Main specification | 3GPP TS 38.331, 6.2.2 |
| Release added | Release 16 |
| Procedures where used | MCG Failure Reporting, Dual Connectivity Recovery |
MCG Failure Information is the NR RRC message used by the UE to report failure related to the master cell group.
Lets the UE signal that the master cell group experienced a failure condition that the network needs to handle.
MCG Failure Information tells the network that the master cell group has failed.
Call flow position: Sent after the UE detects a master-cell-group-related failure.
Typical state: UE is in connected mode and reports an MCG failure upward.
Preconditions:
Next likely message: Recovery or release handling
Previous message(s): RRC Reconfiguration
Next message(s): Recovery handling, Reconfiguration, RRC Release
Security context: Sent as protected connected-mode signaling.
MCGFailureInformation ::= SEQUENCE {
failureInfo OCTET STRING
}
The outer message is simple. The practical debugging value is in correlating the failure report with MCG state and the following recovery action.
UL-DCCH-Message
message: mcgFailureInformation
failureInfo: present
| IE | Required | Description |
|---|---|---|
failureInfo | Yes | Carries the information describing the MCG failure condition. |
failureInfoCarries the information describing the MCG failure condition.
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: The UE detected an MCG failure and reported it.
What to inspect: Check the failure information and the later recovery sequence.
Next step: Compare the MCG failure report with SCG or generic failure reporting if present.
It reports a master-cell-group-related failure from the UE to the network.
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.