3GPP TSG RAN WG1 #120bis                        		     R1-2501828
Wuhan, China, April 7th – 11th, 2025

Source: 	vivo
Title:	Discussion on Low band carrier aggregation via switching
Agenda Item:	9.12.2
Document for:	Discussion and Decision

Conclusion
In this contribution, the following observations and proposals are summarized as follows: 
Proposal 1: For a SCell in a SDL carrier in R19 LB CA via switching, the PDCCH monitoring occasions should be configured in SDL carrier to support self-scheduling.
Proposal 2: The switching pattern configuration is UE-specific.
Proposal 3: Switching pattern should be released when SCell(SDL carrier) is deactivated or dormant.
Proposal 4: The configured switching pattern period should not beyond the maximum SSB periodicity, i.e. 160ms.
Proposal 5: The configured time switching pattern shall guarantee that UE does not stay continuously on SDL carrier for longer than 15 slots.
Proposal 6: for switching pattern indication, there are two alternatives:
Alt1: bitmap indication at N slot level
Alt2: starting slot/symbol indication and length indication
Proposal 7：When the switching period is not predefined in switching pattern or the predefined gap in the switching pattern is less than the switching period, the switching period location should be predefined. Otherwise, switching location is not need to be defined.
Proposal 8: If switching period location is defined, it can be located either in FDD carrier or SDL carrier configured by network.
Proposal 9: For DL/UL transmission on a serving cell, the symbols in invalid periods can be treated as the symbols semi-statically configured as TDD UL/DL symbols and similar UE behaviors can be defined.
Proposal 10: For low band carrier aggregation via switching, UE handles the overlapping among SPS PDSCHs after resolving overlapping with symbols in the slot indicated as invalid periods by semi-statically configured switching pattern including the switching gap.
Proposal 11: For periodic CSI-RS and semi-persistent CSI-RS on the serving cell configured in CSI report configuration in CSI-ReportConfig associated with the higher layer parameter reportQuantity comprising at least 'RI',
the UE is not expected to receive the periodic CSI-RS and semi-persistent CSI-RS during the invalid periods of the serving cell based on the configuration of switching pattern. 
The most recent CSI measurement occasion of semi-persistent CSI-RS resource or periodic CSI-RS resource on the serving cell occurs in valid time of the serving cell for CSI report configured by CSI-ReportConfig associated with the higher layer parameter reportQuantity comprising at least 'RI'.
the UE reports a CSI report only if receiving at least one CSI-RS transmission occasion of each periodic CSI-RS resource or semi-persistent CSI-RS resource on a serving cell in valid time of the serving cell, no later than CSI reference resource, and the UE drops the CSI report otherwise.

Proposal 12: If the higher layer parameter timeRestrictionForChannelMeasurements in CSI-ReportConfig is set to "Configured",
the UE shall derive the channel measurements for computing CSI reported in uplink slot n based on only the most recent, no later than the CSI reference resource, in cell DTX active time of a serving cell if cell DTX is activated, valid time of the carrier of the serving cell if a switching pattern for the serving cell, occasion of NZP CSI-RS associated with the CSI resource setting on the serving cell. 
the UE shall derive the interference measurements for computing the CSI value reported in uplink slot n based on the most recent, no later than the CSI reference resource, in cell DTX active time of a serving cell if cell DTX is activated, valid time of the carrier of the serving cell if a switching pattern for the serving cell, occasion of CSI-IM and/or NZP CSI-RS for interference measurement associated with the CSI resource setting on the serving cell. 
Proposal 13: For HARQ-ACK codebook generation of SPS PDSCHs, UE will not generate HARQ-ACK information for SPS PDSCH overlapping with symbols indicated as invalid periods of the serving cell based on semi-statically configured switching pattern including the switching gap.
Proposal 14: For type 1 HARQ-ACK codebook generation, a row of the TDRA table overlapping with the symbols in invalid periods of the serving cell is excluded when determining the set of occasions of candidate PDSCH receptions.
Proposal 15: During invalid periods of the serving cell, the UE configured with LB CA via switching is not expected to transmit the periodic SRS, or semi-persistent SRS for channel acquisition.
Proposal 16: UE performs UL multiplexing of PUCCH/PUSCH before considering limitations for UE transmission due to LB CA via switching.

3GPP TSG RAN WG1 #120bis			R1-2501886
Wuhan, China, April 7th – 11th, 2025
Agenda item:	9.12.2
Source: 	Spreadtrum, UNISOC
Title: 		Discussion on low band carrier aggregation via switching 
Document for:	Discussion and decision

Conclusion
In this contribution, we made the following observations and proposals.
Observation 1: two type of semi-static switching pattern can be considered for low band carrier aggregation via switching. 
Type 1: discontinuous with bitmap (e.g. PUCCH cell switching pattern)
Type 2: continuous region in a period (e.g. TDD DL UL switching pattern)
Semi-static switching pattern can be continuous region in a period.
Such as three parameters of starting slot offset and slot duration in a period for DL reception in SDL carrier, while the other time duration is for FDD carrier. 
The switching can occur at the slot boundary, and do not consider the switching happens at middle of the slot.
UE behaviours should be defined for deactivate carrier in Case 1 and Case 2
No DL reception on SDL carrier 2 during Case 1, including PDSCH/PDCCH/CSI-RS
No DL reception on FDD carrier 1 and No UL transmission on FDD carrier 1 during Case 2, including PUCCH/PUSCH/PRACH/SRS/PDSCH/PDCCH/CSI-RS

3GPP TSG RAN WG1 #120bis                                                                                  R1-2501893
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2
Source:	Lenovo
Title:	Discussion on NR low band CA via switching
Document for:	Discussion & Decision

Conclusion
In this contribution, we focus on the open issues for using a single DCI format to schedule one or multiple cells with one or multiple PUSCHs or PDSCHs per cell and have below observations and proposals:
Observation 1: The carrier switching pattern should be designed to guarantee DL transmission occasions for SSBs and reference signals on one carrier different from those on another carrier to avoid losing the synchronization on two carriers.
Observation 2: The carrier switching pattern should be designed to guarantee the HARQ-ACK feedback corresponding to PDSCHs on DL-only carrier can be transmitted on the paired carrier.
Observation 3: Rel-16 HARQ-ACK suspension and one-shot HARQ-ACK request can simplify the carrier switching pattern design to avoid frequent carrier switching for transmitting HARQ-ACK feedback for PDSCHs on Cell 2.
Observation 4: Rel-17 PUCCH cell switching pattern can be reused for designing the carrier switching pattern for low band CA via switching.

Proposal 1: For NR low band CA via switching, a periodical carrier switching pattern is configured by high layer parameter for a UE.
Proposal 2: The periodical carrier switching pattern is designed as a bitmap with each bit corresponding to one slot of a radio frame.

3GPP TSG RAN WG1 Meeting #120bis			R1-2501911
Wuhan, China, April. 7 – 11, 2025

Source:	ZTE
Title:	Discussion on low band carrier aggregation via switching
Agenda item:	9.12.2
Document for:	Discussion and Decision

Conclusion
In this contribution, we discuss the switching pattern design with following observations and proposals:
Proposal 1: RAN1 shall design a semi-static switching pattern and ensure the physical layer procedures workable when the switching pattern is configured.
Proposal 2: The following options should be considered for the semi-static switching pattern configuration.
Option 1: The configuration of the switching pattern includes the period of the switching pattern and the PCell (carrier1) duration.
Option 2: The configuration of the switching pattern includes the period of the switching pattern, the offset, and SCell duration.
Option 3: The configuration of the switching pattern includes a bitmap-like configuration for indicating the period of the switching pattern, the PCell duration and the SCell duration jointly.
Option 4: The configuration of the switching pattern can be achieved by configuring tdd-UL-DL-ConfigurationCommon for FDD PCell with reinterpretation on D/F/U slots/symbols.
Proposal 3: The semi-static switching pattern should be configured in symbol level.
Proposal 4:  The PCell duration and SCell duration should be less than or equal to 10ms, and the carrier switching period should be less than or equal to 20 ms.
Proposal 5: The gap location used for switching should be configured by the network.
Alt.1, The gap location can be configured in one of PCell duration and SCell duration, such as the start and end of the PCell duration, or the start and end of the SCell duration.
Alt.2, The gap location can be configured in both PCell duration and SCell duration, such as the start of the PCell duration and the SCell duration, or the end of the PCell duration and SCell duration.
Proposal 6: It should be clarified the UE behavior on the PDSCH/PUSCH repetition overlapping with the invalid duration, i.e., the PDSCH/PUSCH repetitions are omitted or postponed.

3GPP TSG RAN WG1 #120bis                                           R1-2501978
Wuhan, China, April 7th – 11th, 2025

Source:         CATT
Title:            Discussion on low band carrier aggregation via switching
Agenda Item:    9.12.2
Document for:   Discussion and Decision

Conclusion
In this contribution, the potential spec impacts for LBCA are discussed. The proposals are summarized as follows:
Proposal 1: The semi-static switching pattern of RRC configuration can be based on symbol level.
Proposal 2: The following two schemes on semi-static switching pattern of RRC configuration can be discussed
Alt-1: Joint one Configuration of Switching Patterns on a period P, some symbol(s) (e.g. a value is ‘1’) are indicated as CC-1, the others symbol(s) (e.g. a value is ‘0’) are regarded as CC-2.
Alt-2: Separate two Configuration of Switching Patterns on a period P, one pattern is for symbol(s) indication belonging to CC-1, the other pattern is for symbol(s) indication belonging to CC-1. Those symbol(s) not indicated by any pattern is reserved.
Proposal 3: The slot/symbol index of semi-static switching pattern is determined by downlink timing.
Proposal 4: It can be assumed that switching period is located on CC-2.
Proposal 5: the slot/symbols index of uplink transmission in case of switching is determined as following
For the switching from case-1 to case-2, the latest uplink transmission is no later than , n is the last downlink transmission symbol of CC-1
For the switching from case-2 to case-1, the earliest uplink transmission is no earlier than , n is the first downlink transmission symbols of CC-1
Proposal 6: When the UE receives a DCI scheduling the PDSCH and indicating to use the UL symbols at case 2 to transmit HARQ-ACK feedback, it can switch to case 1 to transmit the corresponding HARQ-ACK feedback, and then return to case 2.
Proposal 7: For the UCIs other than the HARQ-ACK feedback, i.e. SR and CSI report, for the resource of PUCCH can be up to gNB configuration, ensuring that it falls within the period of case 1.  
Proposal 8: When the UE is in case 2, it can switch to case 1 to start sending preamble, and then return to case 2 until the random access procedure is completed
Proposal 9: For the Type-1 HARQ-ACK codebook, the occasions for candidate PDSCH reception should be pruning based on the LBCA switching pattern for each of carrier.

3GPP TSG RAN WG1 #120bis	                                                              R1-2502046
Wuhan, China, April 7th – April 11th, 2025

Agenda item:	9.12.2
Source:		Ofinno
Title:		Discussion on a low-band CA with switching
Document for:	Discussion and Decision

Conclusion
The following captures our proposals. 
Configuration of a switching pattern should flexibly indicate different number of slots for a single time unit assigned to either cell. 
Specify whether and how to support a dormant BWP of the SDL carrier. 
Specify condition(s) to prioritize Case 1 on time slots allocated to Case 2. 
In switching gap determination, consider a TA of the FDD carrier.

3GPP TSG RAN WG1 #120bis Meeting		             		R1-2502203
Wuhan, China, April 7th – 11th, 2025	
Agenda item:	9.12.2
Source:	NEC
Title:	Discussion on low band carrier aggregation via switching 
Document for:	Discussion 

Conclusion
From the discussion, we discussed the issues to support low band carrier aggregation via switching and have the following proposals:
Proposal 1: Support special slot configuration including number of SDL symbols, number of FDD symbols and flexible number of gap symbols for FDD to SDL switching.
Proposal 2: Support special slot configuration considering cell specific and UE specific TA values for SDL to FDD switching.
Proposal 3: Support activation of semi-static FDD/SDL switching pattern upon RRC configuration.
Proposal 4: Support dynamic activation of semi-static FDD/SDL switching pattern after RRC configuration.
Proposal 5: DCI may include an indicator to update to one of the Special Slot configurations.  
Proposal 6: DCI can support cross-carrier scheduling with SDL carrier indication.
Proposal 7: DCI which schedules SDL carrier from FDD carrier may support multi-slot and multi-carrier scheduling with common scheduling information.

3GPP TSG-RAN WG1 Meeting #120bis	R1-2502216
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2
Source:	Huawei, HiSilicon
Title:	Discussion on low band CA via switching
Document for:	Discussion and Decision

Conclusion
In summary, our proposals and observations are the following,
Observation 1: When the switching happens on a slot boundary and if the switching period is located at the beginning of the switched-to carrier, it may overlay with PDCCH of the switched-to carrier.
Observation 2: Certain UE capabilities can help to mitigate the impact of switching on PDCCH, including supporting multi-carrier scheduling and supporting PDCCH monitoring occasion is not confined in the first 3 symbols in a slot.


To minimize the impact of switching on FDD PCell, the following aspects should be considered in the RAN1 design, 
SSB and CSI-RS that are common signals for all UEs in the PCell cannot be easily relocated. 
PDCCH monitoring at the first 3 symbols of a slot.
HARQ ACK/NACK on PUCCH format 1 and format 4 resource can span 14 symbols in a slot and can be shared with legacy UEs.
SRS validity for PUSCH scheduling.
UL and DL resources involved in PRACH procedure (at least for CBRA)
Relocations of signals and channel above on PCell should not be assumed for the coexistence between legacy UEs and the CA UEs with semi-static switching pattern

To minimize the impact of switching on UE implementation, RAN1 should strive for reusing existing UE behaviours and corresponding UE capabilities as much as possible.
SSB Configuration 1 is the baseline setting for RAN1 discussions. SSB Configuration 2 can be further considered if time permits.
FFS: the impact on SSB reception due to Rx switching gap
Regarding PDCCH monitoring, self-scheduling and multi-carrier scheduling (i.e. Rel-18 single DCI feature) are all considered.
Maximum time duration on one carrier should be considered in order to minimize its impacts on UE measurement/synchronization, which reply on SSB and CSI-RS receptions, and HARQ-ACK/NACK feedback on PUCCH.
To address compatibility with existing signal/channel, the switching pattern should be flexible enough for gNBs to guarantee that the resources of essential signal/channel CSI-RS, PDCCH, PUCCH and SRS are available to the UEs for the CA operation. Its impact on PDCCH may require to reuse some existing UE features on DL control channel.
FFS: Taking any existing UE capability as a prerequisite for this feature.
The switching pattern can be nested. It has a certain periodicity to repeat. Within each periodicity, UE can switch its Rx from and then back to FDD PCell.
Regarding the semi-static switching pattern, the RRC configuration should at least include its periodicity, starting time, time granularity of UE Reception on each carrier and the number and locations of switching occasions within a pattern.
A bitmap can be considered to configure the switching pattern where bit “1” in the bitmap refers to PCell DL reception while bit “0” to SCell DL reception. The starting time of the pattern is also configured.
Further discuss the applicability exception for potential collision handling between the semi-static pattern and existing signal/channels.
e.g., UE autonomous PRACH and PDCCH-ordered PRACH.
The switching patterns can be different for a being-activated SDL SCell and an activated SDL SCell, respectively.
FFS: The design of the switching pattern in each SCell scenario .

3GPP TSG RAN WG1 #120bis                                                                                R1-2502283
Wuhan, China, April 7th – 11st, 2025

Source:	OPPO
Title:	Discussion of low-band CA via switching
Agenda Item:	9.12.2
Document for:	Discussion and Decision

Conclusions
This contribution is concluded with the following proposals:
Proposal 1: ms-level or slot-level switching frequency is preferred. 
Proposal 2: RAN1 considers the following configuration options for FDD-SDL carrier switching pattern.
Option 1: The configurations include switching cycle, Offset and switching point(s) within switching cycle, e.g. relative offset for the 2nd carrier or duration for the 1st carrier.
The carrier order for switching aligns with carrier location within switching carrier set configuration
Option 2: The configurations include switching cycle, Offset and slot-level carrier-occupation bitmap within switching cycle.
Note: for both options, cycle offset relates to slot 0 within one frame
Proposal 3:  It is preferred for specification not to allow that the gap between the start of the first transmission or reception in switching-to carrier and the end of the last preceding transmission or reception in switching-from carrier is smaller than switching period, in which case it is not necessary to define the time mask for switching from RAN1 perspective; otherwise, the time mask for switching is configured by gNB.
Proposal 4: Collision issue should be avoided by proper switching pattern configuration and channel/signal resource allocation.

3GPP TSG RAN WG1 #120bis		R1-2502389
Wuhan, Hubei, China, April 7th – 11th, 2025
Agenda item:	9.12.2
Source:	Samsung
Title:	Discussion on low band carrier aggregation via switching
Document for:	Discussion and decision

Conclusion
The contribution discusses low band carrier aggregation via switching and the proposals and observations are summarized below.
Observation 1: For low band carrier aggregation via switching, FDD carrier should be the PCell and SDL carrier should be the SCell. 
Proposal 1: For low band carrier aggregation via switching, only one carrier operates at a time instance.
Dedicated RRC signaling configures the periodicity and offset for the carrier switching pattern. 
Support one switching point between two carriers within a periodicity.
The operation time period for PCell within a periodicity is configured by dedicated RRC signaling. 
PCell operates at the start of each periodicity and SCell operates at the remaining time within the periodicity
For the candidate values of the periodicity, at least support 5 ms.
Support slot level switching as baseline.
Proposal 2: For low band carrier aggregation via switching, 
The UE does not receive or transmit a semi-static signal/channel on a serving cell if the semi-static signal/channel overlaps with a non-operation period of the serving cell.
The UE does not expect to be scheduled with a transmission/reception on a serving cell by a DCI format and the transmission/reception overlaps with a non-operation period of the serving cell.
Proposal 3: For low band carrier aggregation via switching, carrier switching period is within the SCell operation period.
For a periodicity, a first carrier switching period starts after the end of PCell operation period and a second carrier switching period ends  before the start of PCell operation period of the next periodicity, where, TTA is defined in TS 38.211 clause 4.3.1.
The DL receptions on SCell are not allowed during the first and second carrier switching period and TTA period.
The transmissions and receptions on PCell are not impacted by carrier switching period.
Proposal 4: For low band carrier aggregation via switching, additional processing time should be introduced for the following cases if carrier switching happens between a DL reception and a UL transmission,
a PDCCH reception schedules a PUSCH transmission
a PDCCH reception indicates SRS transmission
a RAR schedules a PUSCH transmission
a PUCCH transmission with HARQ-ACK for a PDSCH or PDCCH reception
Proposal 5: For low band carrier aggregation via switching, 
If a UE is provided with Type-1 HARQ-ACK codebook, and a candidate PDSCH reception on a serving cell overlaps with a non-operation period of the serving cell, the candidate PDSCH reception is excluded from the set of occasions for candidate PDSCH receptions.
If a SPS PDSCH reception on a serving cell overlaps with a non-operation period of the serving cell, the UE does not receive the SPS PDSCH and does not transmit HARQ-ACK for the SPS PDSCH reception.

3GPP TSG RAN WG1 #120bis			R1-2502426
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2
Source:	Ericsson
Title:	Low band carrier aggregation through switching 
Document for:	Discussion, Decision
1	

Conclusion
In the previous sections we made the following observations: 
Observation 1	For lowband-lowband CA via switching, it is beneficial to support flexible configurability of switching patterns with sufficiently long duration. Such a flexible patterns allow for sharing of load between the FDD and SDL carriers for two groups of UEs and caters to different load sharing ratios, different DL-UL traffic ratios, different locations of broadcast signals, different configurations of DL reference signals, different settings for UL scheduling offset, different settings of PDSCH-to-HARQ timing, and different PUCCH configurations.
Based on the discussion in the previous sections we propose the following:
Proposal 1	For lowband-lowband CA via switching, a UE is semi-statically configured with switching pattern defined by a bitmap of length L, where each bit corresponds to a slot at 15 kHz SCS. The first bit of the bitmap corresponds to the first slot of the first radio frame (SFN 0). The pattern is assumed to be periodic with periodicity of L slots.
Proposal 2	For lowband-lowband CA via switching, the length of the bitmap for configuring the switching pattern is at least L = 40 slots @15 kHz SCS (4 radio frames).
Proposal 3	RAN1 to define a switching gap for switching from FDD to SDL bands in the last N1 symbols of a slot and for switching from SDL to FDD bands in the last N2 symbols of a slot.
FFS: Value(s) of N1 and N2 depending on RAN4 agreements, and whether N1 and N2 are the same or can be different, and whether N1 and/or N2 are the same for both UL and DL, or can be different.
Proposal 4	Support RRC configuration of N1 and N2
Proposal 5	The UE shall omit UL transmission and DL reception during the switching gap of N1 or N2 symbols.
Proposal 6	Send an LS to RAN4 with the above agreements
 

3GPP TSG RAN WG1 #120bis			                 R1-2502485
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2
Source: 	LG Electronics
Title: 	Discussion on low band CA operation via switching for Rel-19
Document for:	Discussion and decision

Conclusions
In this contribution, we discussed consideration points and potential issues for support of low band CA via semi-static switching pattern in Rel-19, and the following proposals are provided:

Proposal #1: It is necessary to decide the granularity of semi-static switching pattern by RRC configuration. (e.g. symbol level or slot level or frame level)

Proposal #2: It may need to discuss whether/how to define the location of switching gap between Case 1 and Case 2. (e.g. in switch-from carrier or switch-to carrier, in FDD carrier or SDL carrier)

Proposal #3: Consider how to handle (or what is the UE behaviour in) the situation that the semi-static switching pattern activates Case 2 during essential DL signal/channel transmission (e.g. SSB, CSS, CSI-RS for RRM/RLM/BFR) on FDD carrier 1.

Proposal #4: Consider UE behaviour in the situation that the semi-static switching pattern activates Case 2 during periodic UL signal/channel transmission occasion/resource (e.g. RACH occasion, SR PUCCH, CG PUSCH, PUXCH repetition) on FDD carrier 1.

Proposal #5: Consider the switching time from Case 2 (with PDSCH reception) to Case 1 (with HARQ-ACK transmission) in the determination of UE PDSCH processing time.

Proposal #6: Consider the slots to be invalid for PDSCH scheduling on carrier 1 (or 2) during Case 2 (or 1) in the construction of Type-1 HARQ-ACK codebook.
Consider DAI signaling by DL DCI in case of Type-2 codebook for the CA of carrier 1 and 2 via switching where only one carrier can be scheduled at a time.

3GPP TSG RAN WG1 #120bis	R1- 2502496
Wuhan, China, 07 – 11 April 2025

Agenda item:		9.12.2
Source:	Nokia
Title:	Principles for low-band CA via switching
WI code:	NR_LBCA_Sw
Release:	Rel-19
Document for:		Discussion and Decision

Conclusion
In this contribution we provided the initial Nokia view on how to define the low band carrier aggregation via switching feature and make the following proposals:
The switching pattern is configured by the RRC.
The switching pattern defines a non-overlapping FDD phase and an SDL phase and gaps referring to idle symbols for switching time between the phases.
The switching pattern can be configured as a single FDD-SDL phase pair (sub-pattern-1), or a concatenation of two separately parameterised FDD-SDL phase pairs (sub-pattern-1 and sub-pattern-2).
When the UE is in an FDD phase, it can transmit on the UL FDD and receive on the DL FDD, but it cannot receive on the DL SDL. Conversely, when the UE is in an SDL phase, it can receive on the DL SDL, but it cannot transmit on the FDD UL nor receive on the FDD DL.
The switching pattern consist of a maximum of 20 or 40 slots for a pattern with single FDD-SDL phase pair, and a maximum of 40 or 80 slots for a pattern with two concatenated FDD-SDL phase pairs.
The switching pattern consists of minimum of 4 or 5 slots
The switching pattern consist of a maximum of 20 slots for a pattern with single FDD-SDL phase pair, and a maximum of 40 slots for a pattern with two concatenated FDD-SDL phase pairs.
Switching gap is placed at the end of the slot
The DL reception after the switch starts at symbol#0 of the slot
The UL transmission on the FDD uplink starts at symbol#0 of the FDD UL slot after the switch
The switching pattern configuration allows for different switching gap length for FDD  SDL switch and for SDL  FDD switch.
Discuss the necessity of SSB on the SDL carrier
Discuss the necessity of TRS on the SDL carrier
PDSCH scheduling in FDD is managed by the PDCCH in FDD, while PDSCH scheduling in SDL is managed by the PDCCH in SDL.
PUSCH scheduling in FDD is managed by the PDCCH in FDD.
When the SDL carrier is deactivated or made dormant, the FDD cell should resume ‘normal’ operations, i.e. not apply any switching and be able to receive and transmit continuously on the FDD carrier.

3GPP TSG RAN WG1 #120bis                                                                                                R1-2502575
Wuhan, China, April 7th – 11th, 2025

Source:               TCL
Title:                    Low band carrier aggregation via switching
Agenda item:      9.12.2
Document for:    Discussion and Decision

Conclusion
In this contribution, the following proposals have been made:
Proposal 1: The switching time between band1 and band2 needs to report by UE, and a value of the switching time between band 1 and band2 should be considered. 
Proposal 2: Semi-static way for Rx switching pattern configuration low-low band aggregation in Rel-19 can be considered. 
Proposal 3: The switching time would better not to impact on the DL control information of a carrier. 
Proposal 4: The impacts on RRM measurement need to study when Rx switching for low-low band aggregation is configured. 
4. 

3GPP TSG RAN WG1 #120bis		             R1-2502634
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2
Source:	Apple
Title:	On low-band carrier aggregation via switching
Document for:	Discussion/Decision

Conclusion
In this contribution, we made the following observations/proposals on low-band carrier aggregation via switching:

Observation 1: All the Rx/Tx chains are associated with only one band at a time and no simultaneous association of Tx/Rx chains across the two bands are considered, as per the WI objectives

Observation 2: RAN1 specification work with respect to this feature is expected to be transparent in terms of the number of Rx or Tx at UE
Unlink UL Tx switching, there is no need to limit to specific number of Tx or Rx and it can be based on existing UE capabilities

Observation 3: considering only semi-static switching pattern in Rel-19, therefore, from timeline point of view, the specification could be relaxed and there is no strong reason to consider symbol-level switching

Observation 4: In Rel-19, since the switching is expected to be based on semi-static configuration of a pattern that triggers UE to switch between case 1 and case 2, therefore, in our view, network should be able to avoid scheduling that overlaps with the switching gap considering relaxed timeline

Observation 5: Considering that SSB patterns are known to network and configured on serving cell basis, therefore, it would be feasible for network to ensure alignment between switching pattern configuration and at least the SSB configuration in PCell in order to protect SSB by avoiding the conflict



Proposal 1: For case 2, since the SDL band is applied and it has no Tx chain associated, then it can be up to the UE implementation on what’s the state of UE’s Tx chain(s).

Proposal 2: New RRC configuration is introduced where a switching pattern can be semi-statically signaled to UE to switch between the two bands for which UE has reported the support:
UE is not expected to switch due to any additional semi-static and/or dynamic scheduling configuration, i.e. no overriding of the configured switching pattern 

Proposal 3: Switching pattern configuration similar to PUCCH cell switching can be considered as a starting point where a bitmap is applied to indicate the association of each time unit to one of the two bands, e.g. bit “0” indicates association with band 1 (FDD) and bit “1” indicates associated with band 2 (SDL)
FFS: candidate values for the exact duration of switching pattern and granularity of switching

Proposal 5: Similar to UL Tx switching, as a starting point, maximum of 1 switching per slot should be considered

Proposal 6: Slot-level switching is considered as the baseline for semi-static switching pattern, i.e. no switching between two bands within a slot
Proposal 7: Switching pattern configuration is applicable only when SCell is activated
If SCell is deactivated, then all symbols/slots are assumed to be valid for only PCell

Proposal 8: UE is not expected to be configured/scheduled with Tx/Rx at least on the symbols that may partially or fully overlap with the switching gap

Proposal 9: If network is not able to avoid overlap of certain channels/signals with the symbols that have switching gap, then further discussion is needed on whether/what channels/signals need to be prioritized/protected

Proposal 10: Network is expected to at least avoid conflict between the SSB configuration on PCell and the switching pattern configuration to the UE
UE is not expected to handle such conflict

Proposal 11: Network is not expected to allow misalignment at least between dynamically scheduled channels/signals and the switching pattern
If according to switching pattern, UE is switched to one band on a given slot, then UE is not expected to be scheduled by network on another band on the same given slot

3GPP TSG RAN WG1 #120bis			R1-2502635
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2

Source:	Moderator (Apple)
Title:	FL summary #1 of Low band carrier aggregation via switching
Document for:	Discussion/Decision

Summary of contribution 
R1-2501828 vivo
R1-2501886 Spreadtrum, UNISOC
R1-2501893 Lenovo
R1-2501911 ZTE Corporation, Sanechips
R1-2501978 CATT
R1-2502046 Ofinno
R1-2502216 Huawei, HiSilicon
R1-2502283 OPPO
R1-2502389 Samsung
R1-2502426/R1-2502935/R1-2502936  Ericsson
R1-2502485 LG Electronics
R1-2502496 Nokia
R1-2502575 TCL
R1-2502634/R1-2502593 Apple
R1-2502721 MediaTek Inc.
R1-2502784 NTT DOCOMO, INC.
R1-2502860 Qualcomm Incorporated
R1-2502203 NEC

3GPP TSG RAN WG1 #120bis			R1-2502636
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2

Source:	Moderator (Apple)
Title:	FL summary #2 of Low band carrier aggregation via switching
Document for:	Discussion/Decision

Summary of contribution 
R1-2501828 vivo
R1-2501886 Spreadtrum, UNISOC
R1-2501893 Lenovo
R1-2501911 ZTE Corporation, Sanechips
R1-2501978 CATT
R1-2502046 Ofinno
R1-2502216 Huawei, HiSilicon
R1-2502283 OPPO
R1-2502389 Samsung
R1-2502426/R1-2502935/R1-2502936  Ericsson
R1-2502485 LG Electronics
R1-2502496 Nokia
R1-2502575 TCL
R1-2502634/R1-2502593 Apple
R1-2502721 MediaTek Inc.
R1-2502784 NTT DOCOMO, INC.
R1-2502860 Qualcomm Incorporated
R1-2502203 NEC

3GPP TSG RAN WG1 #120bis			R1-2502637
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2

Source:	Moderator (Apple)
Title:	FL summary #3 of Low band carrier aggregation via switching
Document for:	Discussion/Decision

Summary of contribution 
R1-2501828 vivo
R1-2501886 Spreadtrum, UNISOC
R1-2501893 Lenovo
R1-2501911 ZTE Corporation, Sanechips
R1-2501978 CATT
R1-2502046 Ofinno
R1-2502216 Huawei, HiSilicon
R1-2502283 OPPO
R1-2502389 Samsung
R1-2502426/R1-2502935/R1-2502936  Ericsson
R1-2502485 LG Electronics
R1-2502496 Nokia
R1-2502575 TCL
R1-2502634/R1-2502593 Apple
R1-2502721 MediaTek Inc.
R1-2502784 NTT DOCOMO, INC.
R1-2502860 Qualcomm Incorporated
R1-2502203 NEC

3GPP TSG RAN WG1 #120bis                                                       R1-2502721
Wuhan, China, April 7th – 11th, 2025
 
Agenda item:	9.12.2
Source: 	MediaTek Inc.
Title: 	Low band carrier aggregation via switching
Document for:	Discussion and decision

Conclusion 
We have the following observations in this contribution. 
Observation 1: Symbol-based (i.e., intra-slot) switching patterns may require UE to support optional UE features such as cross-carrier scheduling.
Observation 2: Unlike UL Tx switching, for DL switching, if switching periods locate at or overlap with the beginning of a slot on the switching-to carrier, PDCCH will be impacted.
Observation 3: Per TS38.213, the 20ms SSB period is assumed for initial access. Hence, the SSB periodicity of 20ms can be considered as a typical configuration.
Observation 4: When the periodicity of a switching pattern is doubled (or larger) of an RS periodicity, it is not challenging for gNB to configure a switching pattern so that the RS is available at least once on each carrier within a configured switching pattern period.
Observation 5: When the band combination only consists of an FDD carrier and an SDL carrier and if the switching pattern is configured under the SCell configuration for the SDL carrier, there is no ambiguity for which carrier pair the configured switching pattern applies to.
Observation 6: In a future release, there may be ambiguity about which carrier/band pair to apply a configured switching pattern when there are more than one band pair that supports CA via switching in a future release.

We have the following proposals in this contribution. 
Proposal 1: If an issue can be avoided or resolved by gNB’s implementation, its impact on RAN1 specifications should be minimized.
Keep design simple and practical. Avoid overdesign.
Proposal 2: Optional UE features shall not be assumed or mandated, including cross-carrier scheduling, SSB-less SCell operation, etc.
Proposal 3: Regarding the switching pattern design methodology, RAN1 designs a switching pattern with configurable RRC parameters and specifies configuration constraints for base stations to follow.
Note: Network configuration flexibility is provided by configurable RRC parameters on the condition that configuration constraints should be specified and applied to avoid UE’s overdesign. 
Proposal 4: Once configured with a semi-static switching pattern, UE is in principle only expected to switch between the FDD carrier and the SDL carrier, according to the configured switching pattern. No additional switching is expected.
The base station shall not schedule or configure the UE in a way conflicting to the configured switching pattern. 
FFS: RACH procedure
Proposal 5: At least the following configuration constraints should be specified and applied for configuring a switching pattern to a UE:
gNB shall guarantee that SSBs are available to the UE on each carrier at least every X msec. 
X is at least <= 160. 
FFS: smaller X values, e.g., X<=2*SSB period on the carrier
UE-specific resources 
UE-specific resources shall not overlap with UE’s switching periods.
UE-specific uplink resources are only scheduled or configured within time duration that is within UE’s time on the FDD carrier and does not overlap with UE’s switching periods.
gNB shall not schedule or configure the UE in a way conflicting to the configured switching pattern.
For example, gNB shall not schedule UE on the FDD carrier during a time duration when UE is expected to be on the SDL carrier according to its configured switching pattern.
Cell-specific resources and common signals/channels  
At least some availability should be guaranteed.
FFS: Detailed constraints on availability of common channels and signals, e.g., PRACH, broadcast SIBs 
HARQ feedbacks 
For a received PDSCH at slot n on either FDD or SDL carrier, UE expects to be configured a K1 value so that it is on the FDD carrier at slot n+K1 according to its configured switching pattern. 
Note: K1 values are configured according to existing UE capabilities reported by UE.
Note: No new K1 values and HARQ process numbers are introduced for this feature.    
FFS: other constraints, for example, 
Periodic CSI-RS
Maximum number of switches during a time duration

Proposal 6: Symbol-based (i.e., intra-slot) switching patterns are not supported.
Proposal 7: Switching periods always locate at the end of the “switch-from” carrier to avoid impact on PDCCH.
Proposal 8: Support half-frame (i.e., 5ms) based switching patterns as a baseline.
FFS: necessity for slot-based switching patterns

Proposal 9: The RRC parameters for configuring a switching pattern include at least periodicity.
Support at least 40ms for the periodicity of switching patterns. FFS: other values
FFS: Other RRC parameters 

Proposal 10: For the configured switching pattern repeating every P msec/slots, RAN1 discusses whether to support a configurable time offset or the starting time is always aligned with SFN=0.
Proposal 11: To configure a semi-static switching pattern, select one of the following options for RRC configuration:
Option 1: the RRC configuration includes at least a periodicity and a bitmap.
Periodicity (P)
An integer multiple of a radio frame (10ms)
Support at least 40ms. FFS: other values
Bitmap: each bit in the bitmap indicates which carrier, FDD Carrier 1 (0) or SDL Carrier 2 (1), the UE is on during the corresponding duration 
Each bit corresponds a duration of [5 or 2] slots (i.e., msec).
FFS: Maximum size of the bitmap for the supported period(s)
Option 2: the RRC configuration includes at least the following parameters: 
Periodicity (P)
An integer multiple of a radio frame (10ms) 
Support at least 40ms. FFS: other values
Starting carrier within a period: FDD Carrier 1 (0) or SDL Carrier 2 (1) 
Number of switches within a period (N)
A switch is FDD->SDL or SDL->FDD.
FFS: maximum number of switches  
Length of each “duration” after (or before) a switch in a period
Definition of “duration”: In a period with N switches, there are total N+1 durations in the period.
FFS: equal duration only, maximum duration, minimum duration, and duration unit  
Note: For each agreed RRC parameter, its supported values are to be discussed in RAN1 by RAN1#121.    

Proposal 12: RAN1 discusses how to determine the band pair for a configured switching pattern and whether forward compatibility should be considered.
Proposal 13: A switching pattern is UE-specific and configured via dedicated RRC signaling.

3GPP TSG RAN WG1 #120bis			R1-2502784
Wuhan, China, April 7th – 11th, 2025

Source:	NTT DOCOMO, INC.
Title:	Discussion on Low band carrier aggregation via switching
Agenda Item:	9.12.2
Document for: 	Discussion and Decision

Conclusion
In this contribution, we discussed on semi-static switching pattern based on RRC configuration for switching between case 1 and 2. We have following observations and proposals:
Observation 1: Since the switching period is an overhead, it is better to avoid frequent switching within a short period of time. On the other hand, considering that only DL reception on SDL carrier 2 is available during case 2, too long duration of case 2 would not be practical.
Observation 2: For RAN1 discussion on semi-static switching pattern, the issue is whether/how to handle collision between semi-statically configured DL reception (or UL transmission) occasion and unavailable time domain resource according to the semi-static switching pattern.
Proposal 1: Following design principles for the semi-static switching pattern are considered.
The periodicity of semi-static switching pattern should be equal to or integer multiple of SSB periodicity of FDD cell.
At least one SSB occasion should be covered by case 1 duration in the semi-static switching pattern.
The maximum number of switching within a switching pattern periodicity or within a certain duration should be defined.
The maximum contiguous duration of Case 2 should be defined.
Proposal 2: Following options for the switching period location are considered.
Option 1: the switching period location is fixed by specification
1-1: it is fixed to either SDL carrier/symbol(s) side or FDD carrier/symbol(s) side
1-2: it is fixed to either switch-from carrier/symbol(s) side or switch-to carrier/symbol(s) side
Option 2: the switching period location is configured by NW
2-1: it is configured to either SDL carrier/symbol(s) side or FDD carrier/symbol(s) side
2-2: it is configured to either switch-from carrier/symbol(s) side or switch-to carrier/symbol(s) side
Proposal 3: UE does not expect to be scheduled to transmit or receive signal/channel on unavailable resource according to the semi-static switching pattern.
Proposal 4: The collision between part of occasions for configured transmission/reception or scheduled transmission/reception on multiple occasions and unavailable resource according to the semi-static switching pattern should be allowed, and only transmission/reception on the occasion colliding with unavailable re-source should be dropped.

3GPP TSG RAN WG1 Meeting #120bis    	            R1-2502860
Wuhan, China, April 7th – 11st, 2025

Source:	Qualcomm Incorporated
Title:	Low band carrier aggregation via switching
Agenda Item:	9.12.2
Document for: 	Discussion and Decision

Conclusion
In this contribution we have following proposals.

Proposal 1:
Discuss RAN1 aspects with the following pattern with 40 slots (40ms) periodicity as a reference:
(1) 6 slots on Case 1 (Tx/Rx on FDD carrier 1)
(2) 8 slots on Case 2 (Rx on SDL carrier 2)
(3) 6 slots on Case 1 (Tx/Rx on FDD carrier 1)
(4) 6 slots on Case 2 (Rx on SDL carrier 2)
(5) 8 slots on Case 1 (Tx/Rx on FDD carrier 1)
(6) 6 slots on Case 2 (Rx on SDL carrier 2)

Proposal 2:
Wait and see RAN4 progress if there is any RAN1 impact from SCell activation/deactivation for low-band CA via switching

Proposal 3:
Check if the reference pattern, potentially with a certain pattern adjustment, can accommodate C-DRX operation.

Proposal 4:
If slot-level granularity of switching pattern is sufficient, consider N-bit bit-map to indicate a switching pattern over N slots
At least N = 40. FFS support of the other values
Each bit in the N-bit bit-map indicates whether the corresponding slot belongs to Case 1 (Tx/Rx on FDD carrier 1) or Case 2 (Rx on SDL carrier 2) 
FFS: max number of switches per N slots

Proposal 5:
Consider switching period location of “switch-from carrier” and at the end of the last slot before the switch
A couple of last DL symbols at the end of the last slot before the switch become unavailable 
For switch from Case 2 (Rx on SDL carrier 2) to Case 1 (Tx/Rx on FDD carrier 1), UL slot/symbols on FDD become unavailable until the switching period ends

Proposal 6:
A UE does not expect a conflict between the semi-statically configured switching pattern (including switching periods) and semi-static DL/UL configured by dedicated RRC or dynamic DL/UL scheduled/triggered by unicast DCI
A UE prioritizes the semi-statically configured switching pattern over cell-specific DL/UL
FFS: special cases where the UE does not follow the switching pattern and proceed cell-specific DL/UL, e.g., RLF or BFD

3GPP TSG RAN WG1 #120bis			R1-2503110 
Wuhan, China, April 7th – 11th, 2025

Agenda Item:	9.12.2

Source:	Moderator (Apple)
Title:	FL summary #4 of Low band carrier aggregation via switching
Document for:	Discussion/Decision

Summary of contribution 
R1-2501828 vivo
R1-2501886 Spreadtrum, UNISOC
R1-2501893 Lenovo
R1-2501911 ZTE Corporation, Sanechips
R1-2501978 CATT
R1-2502046 Ofinno
R1-2502216 Huawei, HiSilicon
R1-2502283 OPPO
R1-2502389 Samsung
R1-2502426/R1-2502935/R1-2502936  Ericsson
R1-2502485 LG Electronics
R1-2502496 Nokia
R1-2502575 TCL
R1-2502634/R1-2502593 Apple
R1-2502721 MediaTek Inc.
R1-2502784 NTT DOCOMO, INC.
R1-2502860 Qualcomm Incorporated
R1-2502203 NEC