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LTE RRCLTEUE -> eNodeB3GPP TS 36.331
LTE - RRCConnectionSetupComplete
Uplink LTE RRC message sent by the UE after applying RRCConnectionSetup to confirm setup completion and carry the initial dedicated NAS message.
Message Fact Sheet
Protocol
lte-rrc
Network
lte
Spec
3GPP TS 36.331
Spec Section
5.3.3, 6.2.2, Annex B
Direction
UE -> eNodeB
Message Type
Connection Control
Full message name
LTE - RRCConnectionSetupComplete
Protocol
LTE-RRC
Technology
LTE
Direction
UE -> eNodeB
Interface
Uu
Signaling bearer / channel
SRB1 / UL-DCCH
Typical trigger
The UE successfully applies RRCConnectionSetup and is ready to complete connection establishment and deliver the initial NAS payload.
Main purpose
Completes LTE RRC connection establishment, confirms that the UE applied the initial dedicated radio configuration, and transfers the first NAS message toward the core.
Main specification
3GPP TS 36.331, 5.3.3, 6.2.2, Annex B
Release added
Release 8
Procedures where used
RRC Connection Establishment, Initial Access, Paging Response from Idle
Related timers
T300
Related cause values
selectedPLMN-Identity helps tie the message to the broadcast PLMN choice used for access
What is RRCConnectionSetupComplete in simple terms?
Uplink LTE RRC message sent by the UE after applying RRCConnectionSetup to confirm setup completion and carry the initial dedicated NAS message.
Completes LTE RRC connection establishment, confirms that the UE applied the initial dedicated radio configuration, and transfers the first NAS message toward the core.
Why this message matters
RRCConnectionSetupComplete is the UE saying it applied the LTE setup message successfully and is now sending the first NAS message through the new connection.
Where this message appears in the call flow
LTE initial access
In the initial access path, RRCConnectionSetupComplete confirms setup and carries the first NAS payload into the next control stage.
Call flow position: UE confirmation message sent after applying RRCConnectionSetup and before later dedicated control continues.
Typical state: UE is moving from the early setup stage into stable connected-mode signaling.
Preconditions:
RRCConnectionSetup was received and applied successfully.
SRB1 is active.
The UE has an initial NAS message to transfer toward the network.
Next likely message: Security-related control or later dedicated LTE RRC signaling
Paging response path
In the paging response path, setup complete marks the handoff from fresh radio setup into the following NAS-driven continuation.
Call flow position: Completion message used after paging-triggered fresh access when a new dedicated LTE context has been created.
Typical state: UE is completing fresh setup after paging-driven access.
Preconditions:
Paging led to fresh access rather than reuse of an older context.
RRCConnectionSetup has already been applied.
Next likely message: Security-related continuation
Next message(s): Security-related continuation, Dedicated connected-mode control
Message direction and transport
Sender and receiver: UE -> eNodeB
Interface: Uu
Domain: Access-side radio control
Signaling bearer: SRB1
Logical channel: UL-DCCH
Transport / encapsulation: RRC over DCCH on SRB1 after the initial dedicated control configuration is applied
Security context: Sent after SRB1 is created but before the later dedicated security path fully changes subsequent signaling. Interpret it together with the early setup sequence.
Message Structure Overview
RRCConnectionSetupComplete is the UE-side confirmation that early LTE RRC setup succeeded.
The practical core of the message is selectedPLMN-Identity plus dedicatedInfoNAS.
This is the handoff point from LTE RRC connection establishment into the following NAS-driven control path.
The main reading path is simple: match the transaction identifier, confirm the PLMN choice, and inspect dedicatedInfoNAS because that is the payload that drives the next control-plane stage.
The transaction identifier should match the earlier RRCConnectionSetup.
selectedPLMN-Identity should align with the SIB1 PLMN list used during access.
dedicatedInfoNAS is often the most important field because it carries the initial NAS message.
Important Information Elements
IE
Required
Description
rrc-TransactionIdentifier
Yes
Transaction identifier matching the preceding RRCConnectionSetup.
selectedPLMN-Identity
Yes
Identifies which PLMN entry from SIB1 the UE selected for access.
registeredMME
Optional
Carries the registered MME information when the UE already has relevant EPS context.
dedicatedInfoNAS
Yes
Carries the initial NAS message, commonly Attach Request, TAU Request, or Service Request context depending on the scenario.
nonCriticalExtension
Optional
Release-extension branch used for later feature additions.
Detailed field explanation
rrc-TransactionIdentifier
Transaction identifier matching the preceding RRCConnectionSetup.
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.
selectedPLMN-Identity
Identifies which PLMN entry from SIB1 the UE selected for access.
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.
registeredMME
Carries the registered MME information when the UE already has relevant EPS context.
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.
dedicatedInfoNAS
Carries the initial NAS message, commonly Attach Request, TAU Request, or Service Request context depending on the scenario.
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.
nonCriticalExtension
Release-extension branch used for later feature additions.
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.
What to check in logs and traces
Confirm the message follows RRCConnectionSetup without an early failure or release.
Verify the transaction identifier matches the setup message.
Check selectedPLMN-Identity against the PLMN entry used from SIB1.
Decode dedicatedInfoNAS to confirm the expected NAS message is present.
Correlate the message with the following NAS or security-related continuation.
Common Issues and Troubleshooting
RRCConnectionSetup succeeds but the procedure still stalls.
Likely cause: RRCConnectionSetupComplete may be missing, malformed, or may carry unexpected NAS content.
What to inspect: Check whether the UE sent the message, whether dedicatedInfoNAS is present, and whether the transaction identifier matches.
Next step: Decode the NAS payload and correlate it with the expected access scenario.
The network receives setup complete but later NAS handling fails.
Likely cause: The issue may be in dedicatedInfoNAS rather than in the radio setup itself.
What to inspect: Decode the NAS container and compare it with the expected Attach, TAU, or service-trigger message.
Next step: Continue the analysis into the NAS procedure rather than staying only in LTE RRC.
PLMN-related access behavior looks wrong.
Likely cause: selectedPLMN-Identity may not match the intended PLMN entry from SIB1.
What to inspect: Compare selectedPLMN-Identity with the SIB1 PLMN list and access scenario.
Next step: Check broadcast configuration and UE PLMN selection assumptions.
LTE / 5G / Variant Comparison
Compared with LTE RRCConnectionSetup
RRCConnectionSetup creates the first dedicated control configuration. RRCConnectionSetupComplete confirms that configuration and carries the first NAS payload.
Compared with NR RRCSetupComplete
The LTE and NR setup-complete messages play the same procedural role, but the exact fields and surrounding access context differ between TS 36.331 and TS 38.331.
FAQ
What is RRCConnectionSetupComplete in LTE?
It is the uplink LTE RRC message the UE sends after applying RRCConnectionSetup to complete connection establishment.
What does RRCConnectionSetupComplete carry?
It carries selectedPLMN-Identity and the initial NAS message in dedicatedInfoNAS.
Why is RRCConnectionSetupComplete important?
It confirms that the early LTE RRC setup succeeded and it carries the NAS payload that drives the next control-plane stage.
What should I inspect first in RRCConnectionSetupComplete?
Start with the transaction identifier, selectedPLMN-Identity, and dedicatedInfoNAS.
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.
