3GPP TSG-RAN WG2 Meeting #130                                                        R2-2503431
St.Julians, Malta, May 19th – 23rd, 2025

Source:	CATT 
Title:	Discussion on Multi-hop Discovery and (Re)selection
Agenda Item:	8.13.2
Document for:	Discussion and Decision

Conclusion
According to the analysis in section 2, it is proposed:
Proposal 1: (RRC-6) The FFS if this case can occur or if the intermediate relay UE always establishes itself as a remote UE first can be deleted without further handling.
Proposal 2: (RRC-5) When the intermediate relay UE relay UE received a notification message from the last relay UE indicating a failure on UU, the intermediate relay UE may transmit a notification message downstream towards the remote UE without change the notification message content in Rel-19.
Proposal 3: When the parent UE in idle/inactive performs reselection, RAN2 uses the legacy PC5 notification message to indicate of the reselection for its child UE.
Proposal 4: Introduce a new cause value showing the parent PC5 link reselection happened in Rel-19.
Proposal 5: RAN2 agrees that no condition or timing is introduced for the intermediate relay UE notifies its child node in Rel-19.
Proposal 6: During the notification message transfer to its child UE, if the intermediate relay UE receives this notification(cause value of parent PC5 link reselection happened), it is left to intermediate relay UE implementation to trigger relay reselection or further forward this notification message to its child UE.
Proposal 7: During the notification message transfer to its child UE, if the remote UE receives this notification, relay reselection will be triggered.
Proposal 8: The role of UE can be used as AS condition to judge that whether a UE can be operated as an intermediate relay UE or not in case the network doesn’t configure an upper bound of Uu RSRP for the UE to operate as an intermediate relay UE.
Proposal 9: If RAN2 decides to leave the issue that whether a UE can be operated as an intermediate relay UE or not in case the network doesn’t configure an upper bound of Uu RSRP for the UE to operate as an intermediate relay UE to SA2, a LS is needed.

3GPP TSG-RAN WG2 Meeting #130	R2-2503490
St.Julians, Malta, May 19th – 23rd, 2025	

Agenda Item:	8.13.2
Source:	OPPO
Title:	Discovery and relay (re)selection for multi-hop U2N relay  
Document for:	Discussion, Agreement

Conclusion
We have the following observations:
Observation 1	The intermediate relay UE handles the received notification message before transmitting notification message to its connected child UE can avoid duplicated notification.
Observation 2	The path switching at the intermediate relay may cause change of serving cell ID/PLMN ID, hop number, and accumulated QoS information, which may invalidate both AS/upper layer relay (re)selection criteria at the child UE.
Observation 3	The intermediate Relay UE cannot validate the suitability of a new path for multiple downstream Remote UEs, as it lacks visibility into their relay (re)selection criteria. Consequently, notifications must always sent.
Observation 4	Since all relay reselection triggers necessitate releasing the PC5 link to the source Parent Relay UE, the legacy relayUE-PC5-RLF cause value (defined in R18) can be reused to signal this event.
Observation 5	Neither Model-A nor Model-B discovery transmissions are fully initialized by the intermediate Relay UE, i.e., depends on whether/when the discovery procedure is initialized at the Last Relay or Remote UE. So cannot reliably indicate path updates.
Observation 6	It is not clear whether the link modification defined in SA2 is only applied to L3 U2N Relay, and whether it can support all the cases that may happen for L2 U2N Relay.
Observation 7	With only two meetings left, there is no time for the LS to check with SA2 on the applicability to L2 U2N Relay and complete the design.
Observation 8	For L2 Multi-hop U2N Relay, the intermediate relay UE first acts as a remote UE for SI/Paging/data reception/transmission.
Observation 9	In L2 muti-hop U2N Relay, a UE should always have an available link towards the network before it serves a remote UE regardless of Model-B or Model-A. Which means the FFS case (PC5 link not established) is not a reasonable case for L2 multi-hop U2N Relay.

We have the following proposals:
Proposal 1	(RRC-5) Upon receiving NotificationMessageSidelink from parent relay, the intermediate Relay UE handles the received notification message first (e.g., trigger RRC Reestablishment, cell change or PC5 release) and then generates NotificationMessageSidelink to its connected child UE(s) based on the latest status.
Proposal 2	(RRC-5) In all relay reselection scenarios, upon PC5 link release between parent relay and the grand-parent relay, the parent relay notifies its child node(s) via NotificationMessageSidelink with the legacy cause value relayUE-PC5-RLF.
Proposal 3	(RRC-6) For L2 U2N Relay, RAN2 consider the intermediate relay UE always establishes connection with a parent relay by acting as a remote UE first.

3GPP TSG-RAN WG2 #130	R2-2503540
St Julian's, Malta, 19th May – 23rd May, 2025

Agenda Item:	8.13.2
Source:	NEC
Title:	Discussion on multi-hop relay discovery and relay reselection
Document for:	Discussion, Decision

Conclusion
In this contribution, we have discussed remaining issues for relay reselection, a brunch of proposals have been provided in the following:

Proposal 1	It is not necessary for the U2N intermediate relay UE to have a connected PC5 link with last relay UE when the actual U2N remote UE performing model B discovery.
Proposal 2	The message NotificationMessageSidelink can be reused to carry the indication for the child UE.
Proposal 3	Additional cause value indicating parent relay UE triggering relay reselection can be added in the indicationType within NotificationMessageSidelink
Proposal 4	The message is always needed without any exceptional cases when parent UE performing relay reselection.
 

3GPP TSG-RAN WG2 Meeting #130	           R2-2503668
St.Julians, Malta, May 19th – May 23rd, 2025	

Agenda item:	8.13.2
Source:	China Telecom
Title:	Discussion on multi-hop relay reselection
Document for:	Discussion

Conclusions
Based on the discussion above, we have the following proposals.
Proposal 1: If the first U2N relay UE performs path switch, send Notification message to notify the R19 U2N remote UE.
Observation 1: It is possible that R17 U2N Remote UE communicate with the network via a single R19 U2N Relay UE. And the R19 U2N Relay UE may select/switch from gNB to another U2N Relay UE.
Proposal 2: If the first U2N relay UE performs path switch or relay selection, it should trigger PC5-S link release toward the R17 U2N remote UE.

3GPP TSG-RAN WG2 Meeting #130	R2-2503725
St. Julians, Malta, 19-23 May 2025                                

Agenda item:	8.13.2
Source:	Apple
Title:	Relay discovery and selection for Multi-hop UE-to-NW Relay
WID/SID:	NR_SL_relay_multihop – Release 19
Document for:	Discussion and Decision
1 

Conclusion
In this contribution, we discuss the Relay discovery and selection for Multi-hop UE-to-NW Relay, and have the following proposals:
Proposal 1 	RAN2 confirms that there is valid case for the last relay UE to check AS conditions before responding to intermediate relay UE’s model B discovery request.
Proposal 2 	No suppression of indication is allowed when the IDLE/INACTIVE intermediate relay UE reselection under the same serving cell without changing the hop count.
Proposal 3 	When PC5 link is not established, the IDLE/INACTIVE relay UE send a broadcast signaling to notify the downstream nodes, which should be part of discovery message design.
Proposal 4 	When PC5 link is already established, the IDLE/INACTIVE relay UE send a NotificaitonMessageSidelink via unicast to notify the downstream nodes about the relay UE reselection.
Proposal 5 	Only mode 2 RA is supported for remote UE and intermediate relay UE.
4 

3GPP TSG-RAN WG2 Meeting #130	R2-2503901
St.Julians, Malta, May. 19th – 23rd, 2025	
	

Agenda Item	: 8.13.2
Source	: LG Electronics Inc.
Title	: Discussion on discovery and relay reslection
Document for	: Discussion and Decision
1.	

Conclusion
Proposal 1: For discovery model B, if there is an established PC5 link between the intermediate Relay UE and its parent UE, the intermediate Relay UE can send a response message toward the Remote UE without forwarding the solicitation message to its parent UE.  
Proposal 2: For discovery model B, if the intermediate Relay UE can generate the response message without forwarding the solicitation message, the intermediate Relay UE needs to check the PC5 AS condition before sending a discovery response message towards the Remote UE.
Proposal 3: When the intermediate Relay UE receives a notification message, the intermediate Relay UE can deliver the notification message as it is without changing the cause value.
Proposal 4: When a child UE in RRC_CONNECTED receives a notification message, the child UE performs the RRC reestablishment procedure regardless of the cause value.
Proposal 5: When a child UE in RRC_IDLE/INACTIVE receives a notification message, it’s up to the implementation of the child UE whether to keep or release the PC5 link. The child UE can check whether to change its cell ID via SIB from the parent UE.
Proposal 6: If the intermediate Relay UE in RRC_CONNECTED receives an indirect-to-indirect path switching command to the target first Relay UE in the same cell/gNB belonging to the source first Relay UE, the intermediate Relay UE doesn’t need to send a notification message to the child UE.
Proposal 7: If the intermediate Relay UE in RRC_IDLE/INACTIVE performs relay reselection and the target first Relay UE is in the same cell/gNB belonging to the source first Relay UE, the intermediate Relay UE doesn’t need to send a notification message to the child UE.
Proposal 8: In the discovery model A, the announcement discovery message may handle the hop count change if the hop count is changed due to the indirect-to-indirect path switching command or relay re-selection occurrence. 
Proposal 9: In the discovery model B, RAN 2 can ask to the SA2 how to handle the path information when the path information is changed (including the case hop count is changed). 
Proposal 10: RAN2 may need to discuss whether the discovery message should include which approaches (basic approach (approach 1), fast/parallel approach (approach 2), or both) are supported.
4.	

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3GPP TSG-RAN WG2 Meeting #130	R2-2503962
St Julian’s, Malta, May 19th – 23rd, 2025

Agenda item:	8.13.2
Source:	Spreadtrum, UNISOC
Title:	Discussion on notification message
Document for:	Discussion and Decision
1 

Conclusion
In this contribution we discuss the notification message for multi-hop relay, with the following proposals
Proposal 1: When the first relay UE occurred relay reselection and reselected relay UE belong to another cell, it should send Notification message to its connected remote UE.
Proposal 2: The notification message includes a new indication Type (i.e. relayUE-RelayReselection).
Proposal 3: Upon receiving NotificationMessageSidelink, the RRC_CONNECTED first relay UE will perform the RRC Reestablishment and then send NotificationMessageSidelink to its connected remote UE indicating the occurred RRC Reestablishment event.
Proposal 4: Upon receiving NotificationMessageSidelink, if the RRC_IDLE/INACTIVE first relay UE performs the PC5 link release and relay reselection, then it will send NotificationMessageSidelink to its connected remote UE indicating relay reselection. 
Proposal 5: Upon receiving NotificationMessageSidelink, if the RRC_IDLE/INACTIVE first relay UE maintains the PC5 link, it will send NotificationMessageSidelink to its connected remote UE indicating cell reselection.

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3GPP TSG-RAN WG2 Meeting #130  	                            R2-2504060
St.Julians, Malta, May 19th – 23rd, 2025							          (Resubmission of R2-2502497)       

Agenda Item:	8.13.2
Source: 	Sony
Title:	Multi-hop relay selection/re-selection
Document for:	Discussion 

Conclusion
We have observation as follows.
Observation: The QoS requirement may not be guaranteed for certain relay paths with different number of hops on the path, if only existing one hop L2 U2N relay criteria e.g., PC5 radio link quality of the first hop is considered for multi-hop relay selection/re-selection.

We propose RAN2 to discuss following proposals:
Proposal 1: RAN2 to discuss the criteria to select/re-select L2 U2N relay, in addition to the existing one hop L2 U2N relay criteria, with the introduction of multi-hop relay.

Proposal 2: Network configures a separate Uu signal strength threshold for remote UE to perform the multi-hop U2N relay selection.

  

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3GPP TSG-RAN WG2 #130	R2-2504161
St Julian’s, Malta, 19-23 May 2025

Agenda Item:	8.13.2
Source:	Ericsson
Title:	Discussion on relay discovery and relay (re)selection
Document for:	Discussion, Decision
1	

Conclusion
In the previous sections we made the following observations: 
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Based on the discussion in the previous sections we propose the following:
Proposal 1	When an intermediate relay UE receives a NotificationMessageSidelink message from the parent, the intermediate relay UE generate a new notification message and send it to the child UEs, with an updated cause that reflects its own response, such as relay reselection or re-establishment
Proposal 2	For Model A discovery, when the parent UE in idle/inactive performs relay reselection, the parent UE may trigger discovery message towards child UE(s). No RAN2 impact is assumed. FFS whether to inform SA2 on this.
Proposal 3	For Model B discovery, when the parent UE in idle/inactive performs relay reselection, the parent UE sends a NotificationMessageSidelink message to child UE(s) to trigger relay reselection. FFS on whether new cause is needed.
Proposal 4	Hop-Count can be categorized as an upper layer criterion and left to be handled by upper layer, and therefore, no need to be disclosed to AS layer.

4	

3GPP TSG-RAN WG2 #130					      		 R2-2504259
St. Julians, Malta – May 19 - 23, 2025		                   
Agenda item:	8.13.2
Source: 	Kyocera 
Title: 	Relay (re)selection under multihop relay
Document for:	Discussion

Conclusion 
In this contribution, we addressed the issues that may arise with the intermediate relay UE’s relay (re)selection procedure.  RAN2 is kindly asked to take into account the proposals below: 
Observation 1	For child UEs in IDLE/INACTIVE, the only benefit for the child UE to receive a notification/indication from its PC5 connected parent U2N relay UE, is to trigger it to perform relay reselection, followed by RRC Setup Request or RRC Resume Request if a suitable path can be found.
Observation 2	Since the parent U2N relay UE is assumed to be closer to the gNB and should, in general, have a better chance of finding a suitable path to the gNB than the child UE.
Observation 3	Making it mandatory for the parent U2N relay UE to send indication immediately to its PC5 connected child UE for all downstream UEs will result in many simultaneous relay reselection procedures.

Proposal 1	After successful relay reselection, the IDLE/INACTIVE parent U2N relay UE should not need to notify its PC5 connected child UE if the number of hops to the gNB has not increased.
Proposal 2	The parent U2N relay UE that experiences PC5-RLF in the upstream should have the option to decide if and when to send an indication to its PC5 connected child UE.
Observation 4	Leaving the indication to the parent U2N relay UE implementation does not preclude the child relay UE from using PC5-S signalling to release its PC5 connection to the parent U2N relay UE.
Proposal 3	RAN2 should consider whether the parent relay UE should indicate to the child UE when the number of hops increased upon successful relay reselection.
Proposal 4	RAN2 should consider whether the parent relay UE should indicate to the child UE the L2ID of the relay UE that experienced either the PC5 RLF or Uu RLF.
Proposal 5	All indications to the child UE should use legacy PC5-RRC signalling.
Proposal 6	RAN2 should consider whether the remote should perform RRC re-establishment procedure if the intermediate relay UE completes the RRC re-establishment procedure towards the same cell with the same number of hops (or fewer), and whether the intermediate relay UE needs to notify the remote UE.
Proposal 7	It may be further discussed whether it is necessary for the intermediate relay UE to notify the remote UE for the purpose of suspending UL data transmission prior to the intermediate relay UE’s completion of RRC re-establishment. 

3GPP TSG-RAN WG2 Meeting #130	R2-2504273
St Julian’s, Malta, May. 19th – 23rd, 2025
Agenda Item:	 8.13.2
Source:	 Huawei, HiSilicon
Title:	 Relay discovery and (re)selection for multi-hop Relay
Document for:  Discussion and Decision
1	

Conclusion 
Open issues items related to the Relay discovery and (re)selection.
Open issue RRC-6: Discovery Model B with no PC5 Link in multi hop scenario
Observation 1: The scenario where there is no established PC5 link between the last relay UE and the intermediate relay UE, and the intermediate relay UE sends/forwards the discovery solicitation message received from a nearby Remote UE before establishing itself as a Remote UE could happen when 
The intermediate relay UE has just powered on.
A UE that is capable of functioning as an intermediate relay UE, but not currently operating as a relay in a multi-hop configuration, participates in Model B discovery by forwarding the discovery Solicitation message.
Proposal 1: If the Last Relay UE needs to determine whether to send a discovery response message to the Intermediate Relay UE, it is proposed that the same SD-RSRP threshold condition used by the Intermediate Relay UE to decide whether to forward the solicitation message be applied. This ensures consistency and simplifies the decision-making process for discovery response handling.
Open issue RRC-6: Discovery Model B with no PC5 Link in multi hop scenario
Proposal 2: Upon receiving a NotificationMessageSidelink from the Last Relay UE, the Intermediate Relay UE generates a new notification message reflecting its own status or reaction (e.g., relay reselection). This newly generated message is always forwarded to the downstream child UE, enabling the directly or indirectly connected Remote UE to take appropriate action based on the most current and relevant context of its parent UE.

Other remaining FFS for Relay discovery and (re) selection
FFS detailed information in the indication and child UE handling
Proposal 3: Upon receiving a NotificationMessageSidelink from the Last Relay UE, the Intermediate Relay UE generates a new notification message reflecting its own status or reaction (e.g., relay reselection) with the new indication Type set to e.g. relayUE-RelayReselection

Proposal 4: Upon receiving a NotificationMessageSidelink from the parent Relay UE with the Indication Type set to e.g. relayUE-RelayReselection, the child UE performs a relay reselection to re-establish the connectivity with the network. 

FFS if there are exceptional cases where the indication can be suppressed
Proposal 5: The transmission of the NotificationMessageSidelink from the parent UE should not be suppressed, even when reselection occurs within the same serving cell and does not lead to a change in hop count.
FFS if the notification message is used or we rely on upper layer signalling
Proposal 6: A relay UE could, based on its implementation, either use upper layer signaling to trigger the release of the PC5 unicast link with its connected downstream child UE(s), or send a NotificationMessageSidelink to its connected L2 Uu-based Remote UE(s) and/or downstream child UE(s).

Detailed content of the discovery message for relay selection and reselection
Proposal 7: RAN2 should discuss whether/how to support indicating the hop number of the candidate Intermediate Relay UE to the U2N Remote UE during the discovery procedure in AS layer.
Proposal 8. It is beneficial for the Remote UE to know the link condition (SD-RSRP or SL-RSRP) of each hop over the path to select a better candidate relay UE or path.
Support of multiple RSC (Relay Service Code)
Proposal 9: RAN 2 needs to discuss whether support for multiple PC5 connections, each associated with different RSCs, is required between two relay UEs.

4	

3GPP TSG-RAN-WG2 Meeting #130	R2-2504358
19th– 23rd May, 2025
Agenda item	:		8.13.2
Source	: 	Sharp
Title	: 	discussion on Relay discovery and (re)selection for multi-hop relay
Document for	:	Discussion and Decision

Conclusion
In this paper, we provided following observations and proposals:
Proposal 1. When an intermediate relay UE transmits discovery message, the UE includes the cell access info received in parent UE’s discovery message.
Proposal 2. The intermediate relay UE always establishes RRC connection when receives RRC setup message from a child UE if there is no established PC5 link between the last relay UE and the intermediate relay UE.
Proposal 3. The agreed trigger conditions for relay reselection can be applied to L3 multi-hop relay but should only be an indication to higher layers.
Observation 1. SA2 agreed that intermediate relay UE which is also acting as a remote UE can initiate relay reselection while keeping PC5-RRC connection with child UEs.
Proposal 4. RAN2 confirm that intermediate relay UE which is also acting as a remote UE can initiate relay reselection while keeping PC5-RRC connection with child UEs.
Proposal 5. An intermediate relay UE always acts as a remote UE.
Proposal 6. Legacy cause value and a new flag indicating a UE is performing relay reselection should be indicated in notification message.
Proposal 7. Child UEs suspend UL transmission to avoid packet loss when it is indicated the intermediate relay UE reselection.
Proposal 8. Intermediate relay UE should indicate that relay reselection is ongoing to the remote UE regardless its RRC state.
Proposal 9. It is up to UE implementation (or upper layer) whether the child UE performs relay reselection or keeps current PC5 link when the child UE receives information indicating that relay reselection is ongoing from the parent UE.
Proposal 10. An intermediate relay UE should indicate the completion/failure of the relay reselection to a child UE.
Proposal 11. A mechanism for an intermediate relay UE to initiate relay reselection while retaining a child UE can be adopted for path switching performed by the intermediate relay UE.

3GPP TSG-RAN WG2 Meeting #130		R2-2504522
St.Julians, Malta, 19th – 23rd May 2025
Source:	vivo
Title:	Discussion on remaining issues on intermediate relay UE (re)selection and discovery
Agenda Item:		8.13.2
Document for:	Discussion and Decision

Conclusion
In this contribution, we discussed the discovery and intermediate relay UE (re)selection. We have the following Observations and Proposals: 
For discovery:
Observation 1: In SA2 TS 23.304, there is requirement for model-A that the intermediate relay UE should establish parent link before forwarding discovery message, but there is no similar description for model-B.
Proposal 1: RAN2 to confirm that the intermediate relay UE is not required to always establish itself as a remote UE first in multi-hop model-B discovery, and remove the FFS point on AS condition checking.
For intermediate relay UE (re)selection:
Observation 2: Rely on upper layer signalling discovery for notification message is not workable when there is no suitable relay found during intermediate relay UE (re)selection.
Observation 3: Rely on upper layer signalling except discovery message for notification message introduce more interaction with SA2 and is not realistic as SA2 has finalized their specification and work item.
Proposal 2: When intermediate relay UE detects PC5 RLF or receives notification on other links (e.g., failure on Uu), it performs relay reselection and does not transmit a notification message downstream if the reselected path is under the same serving cell without changing the hop count. For all other cases, a notification message downstream will be transmitted. 
Proposal 3: Reuse the AS signalling NotificationMessageSidelink and reuse one of the legacy cause values (e.g. PC5 RLF) to be included in it, for notification from intermediate relay UE to child nodes.
Proposal 4: Whenever receiving the notification message indicating relay (re)selection from first relay UE, the remote UE triggers the relay (re)selection.

3GPP TSG-RAN WG2 Meeting #130                                                              R2-2504546
St.Julians, Malta, May 19th- 23th, 2025

Agenda item:	8.13.2
Source:	Samsung
Title:	Considerations on relay discovery and (re)selection
WID/SID:	NR_SL_relay_enh2
Document for:	Discussion and Decision

Conclusion
In this contribution, we address some issues for the relay discovery and (re)selection, and have the following proposals:
Proposal 1-1: RAN2 is kindly asked to discuss how to determine whether the PC5 connection can be established with the discovered UE in multi-hop SL relay. 
Proposal 1-2: RAN2 is kindly asked to discuss whether the upstream hop count information is indicated to its child UE.
Proposal 1-3: RAN2 is kindly asked to discuss whether the number of supported downstream hops is indicated to its child UE. 
Proposal 2-1: RAN2 is kindly asked to agree that each intermediate relay UE can regenerate the information in the notification message. 
Proposal 2-2: RAN2 is kindly asked to agree that the Notification message can be used to indicate the PC5-S connection release. 
Proposal 2-3: RAN2 is kindly asked to agree that each intermediate relay UE can regenerate the notification message by adding its own link problem (e.g., PC5-RLF, PC5 connection release), and the corresponding relay UE’s local ID.
Proposal 2-4: RAN2 is kindly asked to agree that the idle/inactive relay UE can trigger its own notification message when the following condition is satisfied:
The reselected relay is served by a different cell from the one before PC5 RLF or PC5-S connection release 

3GPP TSG-RAN WG2 Meeting #130	R2-2504560
St.Julians, Malta,  May 19th – 23rd , 2025
Source:	Qualcomm Incorporated 
Title:	Discussion on notification when the intermediate relay UE performs relay reselection
Agenda Item:	8.13.2
Document for:	Discussion and Decision
Introduction & 

Conclusion
Relay UE (re)selection
Observation 1: For Model A discovery, SA2 agreed that the intermediate relay UE can perform relay reselection when the PC5 link is lost or link quality is below a threshold, and if it cannot complete the relay reselection, it may send re-selection indication and optionally with a cause value to the Remote UE via the established multi-hop relay path.
Observation 2: For Model B discovery, SA2 agreed that the intermediate relay UE sends reselection indication to the child UE when detecting link failure or link quality degradation.
For both Model A discovery and Model B discovery, no AS layer notification is needed to child UE when the intermediate relay UE performs relay reselection.
When the last relay UE performs HO, RLF, cell reselection, the last relay UE can notify the child UE.
When the intermediate relay UE receives notification from the parent relay UE, the intermediate relay UE could perform relay reselection acting as a Remote UE.