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NAS5GUE to SMF via AMF3GPP TS 24.501
5G NAS - Remote UE Report
Remote UE Report is the 5GSM message the relay UE sends to inform the network that one or more 5G ProSe remote UEs connected or disconnected through the relay.
Message Fact Sheet
Protocol
nas
Network
5g
Spec
3GPP TS 24.501
Spec Section
8.3.19
Direction
UE to SMF via AMF
Message Type
5GSM remote UE reporting
Full message name
5G NAS - Remote UE Report
Protocol
NAS
Technology
5G
Direction
UE to SMF via AMF
Interface
N1
Signaling bearer / channel
NAS signaling / Usually carried on the uplink NAS path for the relay UE's PDU session
Typical trigger
A remote UE has connected or disconnected through the 5G ProSe relay and the relay UE must report the change.
Main purpose
Keeps the SMF informed about remote UE identities and the associated address information tied to the relay PDU session.
Main specification
3GPP TS 24.501, 8.3.19
Release added
Release 17
Procedures where used
5G ProSe layer-3 UE-to-network relay without N3IWF, Remote UE connection and disconnection reporting, Relay PDU session maintenance
What is Remote UE Report in simple terms?
Remote UE Report is the 5GSM message the relay UE sends to inform the network that one or more 5G ProSe remote UEs connected or disconnected through the relay.
Keeps the SMF informed about remote UE identities and the associated address information tied to the relay PDU session.
Why this message matters
Remote UE Report tells the network when a relay UE has newly connected or disconnected remote UEs, so the SMF can keep relay context accurate.
Where this message appears in the call flow
5G ProSe layer-3 UE-to-network relay without N3IWF
Call flow position: The relay UE sends this report after a remote UE connects or disconnects through the relay.
Typical state: The relay already has an active session and is tracking remote UE identity and address information.
Preconditions:
The relay UE has an established PDU session for relayed traffic.
A 5G ProSe remote UE has connected to or disconnected from the relay.
The SMF needs an updated view of the remote UE context.
Next likely message: Remote UE Report Response from the network
Relay Key Procedure
Call flow position: The report typically comes after relay access and key handling are already complete.
Typical state: Relay authentication and key establishment have already provided a usable relay path.
Preconditions:
Relay access security or keying has already been completed.
Next likely message: Relay UE continues reporting remote UE context as changes occur
Start with PDU Session ID to confirm which relay session the report belongs to.
Check PTI so the report can be correlated with the right 5GSM transaction.
The connected and disconnected context lists tell you whether the relay is adding or removing remote UEs.
Each remote UE context can carry identity, protocol, address information, and HPLMN context.
Important Information Elements
IE
Required
Description
PDU Session ID
Yes
Identifies the relay PDU session that carries the remote UE traffic.
PTI
Yes
Correlates the report with the correct 5GSM transaction.
Remote UE context connected
Optional
Carries one or more remote UE entries that have just become connected through the relay.
Remote UE context disconnected
Optional
Carries one or more remote UE entries that have just been removed from the relay context.
Detailed field explanation
PDU Session ID
Identifies the relay PDU session that carries the remote UE traffic.
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.
PTI
Correlates the report with the correct 5GSM transaction.
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.
Remote UE context connected
Carries one or more remote UE entries that have just become connected through the relay.
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.
Remote UE context disconnected
Carries one or more remote UE entries that have just been removed from the relay 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.
What to check in logs and traces
Confirm the report follows a visible relay or remote UE connection event.
Verify `PDU Session ID` and `PTI` first so the report matches the correct relay session.
Inspect the `Remote UE context connected` and `Remote UE context disconnected` lists for the expected identities.
Check whether the address information matches the expected IPv4, IPv6, or Ethernet service mode.
Correlate the NAS report with relay access logs and SMF context updates.
If the report is missing, verify the relay path, UL NAS delivery, and remote UE state.
Common Issues and Troubleshooting
The relay UE never sends the report.
Likely cause: The remote UE event may not have been detected, the relay may not have an active session, or the report path may be blocked.
What to inspect: Check relay state, PDU session status, UL NAS transport, and remote UE connect or disconnect logs.
Next step: Trace the relay event from the remote UE connection back to the SMF.
The network receives the report but does not update the relay context.
Likely cause: PTI or PDU Session ID mismatch, or the SMF may reject the payload as inconsistent with the current session.
What to inspect: Check PTI correlation, session identity, and SMF relay context logs.
Next step: Validate that the same relay session exists on both sides of the transaction.
The report contents look malformed.
Likely cause: The remote UE context may have an invalid ID format, unsupported protocol indication, or inconsistent address information.
What to inspect: Check the remote UE ID type, address information, and HPLMN ID encoding.
Next step: Compare the encoded context against the remote UE's actual access mode and address allocation.
FAQ
What does Remote UE Report do?
It reports newly connected or disconnected remote UEs to the network so the SMF can update relay context.
Who sends Remote UE Report?
The relay UE sends it to the SMF via the AMF.
When is Remote UE Report sent?
It is sent after a remote UE connects or disconnects through the 5G ProSe relay.
What are the important IEs in Remote UE Report?
Start with PDU Session ID and PTI, then inspect the Remote UE context connected and Remote UE context disconnected lists.
Can one Remote UE Report carry multiple remote UEs?
Yes. The report can contain multiple remote UE context entries in one message.
Is ASN.1 used for Remote UE Report?
No. It is a 5GSM NAS message defined by structured information elements in 3GPP TS 24.501.
What happens if Remote UE Report is missing?
The SMF may keep stale relay context, so the network view of connected or disconnected remote UEs can become inaccurate.
Does this message belong to normal PDU session establishment?
No. It is part of the 5G ProSe remote UE relay reporting flow, although it can coexist with PDU session procedures.
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.