Section: 5.3.5.18.6 LTM cell switch execution
Content: Upon the indication by lower layers that an LTM cell switch procedure is triggered, or upon performing LTM cell switch following cell selection performed while timer T311 was running, as specified in 5.3.7.3, the UE shall: 1> release/clear all current dedicated radio configuration associated with the cell group for which the LTM cell switch procedure is triggered except for the following: - the logicalChannelIdentity and logicalChannelIdentityExt of RLC bearers configured in RLC-BearerConfig and the associated RLC entities, their state variables, buffers, and timers; - the UE variables VarLTM-Config, VarLTM-ServingCellNoResetID, and VarLTM-ServingCellUE-MeasuredTA-ID. 2> if the LTM cell switch is triggered on the MCG: - the MCG C-RNTI; - the AS security configurations associated with the master key; - for each SRB/DRB in current UE configuration which is using the master key: - keep the associated PDCP and SDAP entities, their state variables, buffers and timers; - release all fields related to the SRB/DRB configuration except for srb-Identity and drb-Identity; 2> else, if the LTM cell switch is triggered on the SCG: - the AS security configurations associated with the secondary key; - for each SRB/DRB in current UE configuration which is using the secondary key: - keep the associated PDCP and SDAP entities, their state variables, buffers and timers; - release all fields related to the SRB/DRB configuration except for srb-Identity and drb-Identity; 1> release/clear all current common radio configuration associated with the cell group for which the LTM cell switch procedure is triggered; 1> use the default values specified in 9.2.3 for timers T310, T311 and constants N310, N311 associate to cell group for which the LTM cell switch procedure is triggered; 1> if the value of field ltm-NoResetID contained within the LTM-Candidate IE in VarLTM-Config indicated by lower layers or for the selected cell in accordance with 5.3.7.3 is not equal to the value of ltm-ServingCellNoResetID within VarLTM-ServingCellNoResetID: 2> for each logicalChannelId and logicalChannelIdExt that is part of the current UE configuration for the cell group for which the LTM cell switch procedure is triggered: 3> after the end of this procedure, re-establish the corresponding RLC entity as specified in TS 38.322[ NR; Radio Link Control (RLC) protocol specification ]  [4], after applying the LTM configuration in ltm-CandidateConfig within LTM-Candidate IE in VarLTM-Config; 2> for each drb-Identity value that is part of the current UE configuration: 3> if this DRB is an AM DRB: 4> after the end of this procedure, trigger the PDCP entity of this DRB to perform data recovery as specified in TS 38.323[ NR; Packet Data Convergence Protocol (PDCP) specification ]  [5], after applying the LTM configuration in ltm-CandidateConfig within LTM-Candidate IE in VarLTM-Config; 2> replace the value of ltm-ServingCellNoResetID in VarLTM-ServingCellNoResetID with the value of ltm-NoResetID in the LTM-Candidate in VarLTM-Config indicated by lower layers or for the selected cell in accordance with 5.3.7.3;1> if the LTM-Candidate IE in VarLTM-Config indicated by lower layers or for the selected cell in accordance with 5.3.7.3 contains the field ltm-UE-MeasuredTA-ID: 2> replace the value of ltm-ServingCellUE-MeasuredTA-ID in VarLTM-ServingCellUE-MeasuredTA-ID with the value received within ltm-UE-MeasuredTA-ID; 1> if ltm-ConfigComplete is not included within the LTM-Candidate IE in VarLTM-Config indicated by lower layers or for the selected cell in accordance with 5.3.7.3: 2> consider ltm-ReferenceConfiguration in VarLTM-Config, associated with the cell group for which the LTM cell switch procedure is triggered, to be the current UE configuration for the fields and configurations which have been released and to be released by the actions above in this procedure; NOTE 1: When the UE considers the reference configuration to be the current UE configuration, the UE should store fields and configurations that are part of the reference configuration but should not execute any actions or procedures triggered by the reception of an RRCReconfiguration message which are described in clause 5.3.5.3. 1> if the LTM cell switch is triggered by an indication from lower layers: 2> apply the RRCReconfiguration message in ltm-CandidateConfig within LTM-Candidate IE in VarLTM-Config identified by the LTM candidate configuration identity received from lower layers according to clause 5.3.5.3; 1> else (LTM cell switch triggered upon cell selection performed while timer T311 was running): 2> apply the RRCReconfiguration message in ltm-CandidateConfig within LTM-Candidate IE in VarLTM-Config related to the LTM candidate configuration identity for the selected cell (i.e., in accordance with 5.3.7.3) according to clause 5.3.5.3; 1> release the radio bearer(s) and the logical channel(s) that are part of the current UE configuration but not part of the LTM candidate configuration either indicated by lower layers or for the selected cell in accordance with 5.3.7.3, or the LTM reference configuration (in case the LTM candidate configuration does not include ltm-ConfigComplete). NOTE 2: When ltm-ConfigComplete is not included for an LTM candidate configuration, before an LTM cell switch is triggered a UE implementation may generate and store an RRC reconfiguration message by applying the received LTM candidate configuration on top of the LTM reference configuration, and the stored RRC reconfiguration message is applied when the LTM cell switch is triggered.