What is RRCEarlyDataRequest-r15 in LTE?
It is the LTE RRC message the UE uses to start the control-plane early data branch and carry the first NAS payload.
| Protocol | lte-rrc | Network | lte |
|---|---|---|---|
| Spec | 3GPP TS 36.331 | Spec Section | 5.3.3, 6.2.2 |
| Direction | UE -> eNodeB | Message Type | CP-EDT Access |
| Full message name | LTE RRC Early Data Request-r15 |
|---|---|
| Protocol | LTE-RRC |
| Technology | LTE |
| Direction | UE -> eNodeB |
| Interface | Uu |
| Signaling bearer / channel | SRB0 / UL-CCCH |
| Typical trigger | The UE has a small NAS payload and the CP-EDT branch is allowed for the current access attempt. |
| Main purpose | Combines early access intent with the initial NAS payload so small data can be sent without a full ordinary setup path. |
| Main specification | 3GPP TS 36.331, 5.3.3, 6.2.2 |
| Release added | Release 15 |
| Procedures where used | Control Plane Early Data Transmission, Small Data Access |
| Related timers | T300 |
Uplink LTE RRC message used by the UE to request control-plane early data transmission.
Combines early access intent with the initial NAS payload so small data can be sent without a full ordinary setup path.
RRC Early Data Request-r15 is the LTE message the UE uses to start the control-plane early data branch with a small NAS payload.
Call flow position: UE entry message for the CP-EDT access branch.
Typical state: UE is idle and is trying to send small data without a normal full setup branch.
Preconditions:
Next likely message: RRCEarlyDataComplete-r15 or reject handling
Call flow position: Early access branch used when a small NAS payload is the main trigger.
Typical state: UE is still on the early CCCH path.
Preconditions:
Next likely message: RRCEarlyDataComplete-r15
Previous message(s): Random access completion, Broadcast information acquisition
Next message(s): RRCEarlyDataComplete-r15, RRCConnectionReject
Security context: Sent before normal connected-mode AS security activation on the early data entry path.
RRCEarlyDataRequest-r15 ::= SEQUENCE {
criticalExtensions CHOICE {
c1 CHOICE {
rrcEarlyDataRequest-r15 RRCEarlyDataRequest-r15-IEs,
spare3 NULL,
spare2 NULL,
spare1 NULL
},
criticalExtensionsFuture SEQUENCE {}
}
}
RRCEarlyDataRequest-r15-IEs ::= SEQUENCE {
establishmentCause-r15 EstablishmentCause,
dedicatedInfoNAS-r15 DedicatedInfoNAS,
nonCriticalExtension SEQUENCE {} OPTIONAL
}
Read this message as the CP-EDT entry request plus the first NAS payload.
UL-CCCH-Message
message c1 : rrcEarlyDataRequest-r15 : {
criticalExtensions c1 : rrcEarlyDataRequest-r15 : {
establishmentCause-r15 mo-Data,
dedicatedInfoNAS-r15 '271101'H
}
}
| IE | Required | Description |
|---|---|---|
s-TMSI-r15 | Optional | Temporary UE identity used when available on the early data path. |
establishmentCause-r15 | Yes | Shows why the early access was requested. |
dedicatedInfoNAS-r15 | Yes | NAS payload carried on the control-plane early data branch. |
s-TMSI-r15Temporary UE identity used when available on the early data path.
Presence: Optional
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.
establishmentCause-r15Shows why the early access was requested.
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.
dedicatedInfoNAS-r15NAS payload carried on the control-plane early data branch.
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 CP-EDT entry may have started correctly but the network did not accept or finish the branch.
What to inspect: Check this request, the carried NAS payload, and whether RRCEarlyDataComplete-r15 or reject handling appears.
Next step: Treat the issue as an early-data access problem rather than a normal full setup problem.
It is the LTE RRC message the UE uses to start the control-plane early data branch and carry the first NAS payload.
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.