5.1 Random Access procedure

38.3213GPPMedium Access Control (MAC) protocol specificationNRRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.1.1 Random Access procedure initialization

The Random Access procedure described in this clause is initiated by a PDCCH order, by the MAC entity itself, or by RRC for the events in accordance with TS 38.300 [2]. There is only one Random Access procedure ongoing at any point in time in a MAC entity. The Random Access procedure on an SCell shall only be initiated by a PDCCH order with ra-PreambleIndex different from 0b000000.

NOTE 1: If a new Random Access procedure is triggered while another is already ongoing in the MAC entity, it is up to UE implementation whether to continue with the ongoing procedure or start with the new procedure (e.g. for SI request).

NOTE 2: If there was an ongoing Random Access procedure that is triggered by a PDCCH order while the UE receives another PDCCH order indicating the same Random Access Preamble, PRACH mask index and uplink carrier, the Random Access procedure is considered as the same Random Access procedure as the ongoing one and not initialized again.

When a Random Access procedure is initiated, UE selects a set of Random Access resources as specified in clause 5.1.1b and initialises the following parameters for the Random Access procedure according to the values configured by RRC for the selected set of Random Access resources:

– prach-ConfigurationIndex: the available set of PRACH occasions for the transmission of the Random Access Preamble for Msg1. These are also applicable to the MSGA PRACH if the PRACH occasions are shared between 2-step and 4-step RA types;

– prach-ConfigurationPeriodScaling-IAB: the scaling factor defined in TS 38.211 [8] and applicable to IAB-MTs, extending the periodicity of the PRACH occasions baseline configuration indicated by prach-ConfigurationIndex;

– prach-ConfigurationFrameOffset-IAB: the frame offset defined in TS 38.211 [8] and applicable to IAB-MTs, altering the ROs frame defined in the baseline configuration indicated by prach-ConfigurationIndex;

– prach-ConfigurationSOffset-IAB: the subframe/slot offset defined in TS 38.211 [8] and applicable to IAB-MTs, altering the ROs subframe or slot defined in the baseline configuration indicated by prach-ConfigurationIndex;

– msgA-PRACH-ConfigurationIndex: the available set of PRACH occasions for the transmission of the Random Access Preamble for MSGA in 2-step RA type;

– preambleReceivedTargetPower: initial Random Access Preamble power for 4-step RA type;

– msgA-PreambleReceivedTargetPower: initial Random Access Preamble power for 2-step RA type;

– rsrp-ThresholdSSB: an RSRP threshold for the selection of the SSB for 4-step RA type. If the Random Access procedure is initiated for beam failure recovery, rsrp-ThresholdSSB used for the selection of the SSB within candidateBeamRSList refers to rsrp-ThresholdSSB in BeamFailureRecoveryConfig IE;

– rsrp-ThresholdCSI-RS: an RSRP threshold for the selection of CSI-RS for 4-step RA type. If the Random Access procedure is initiated for beam failure recovery, rsrp-ThresholdCSI-RS is equal to rsrp-ThresholdSSB in BeamFailureRecoveryConfig IE;

– msgA-RSRP-ThresholdSSB: an RSRP threshold for the selection of the SSB for 2-step RA type;

– rsrp-ThresholdSSB-SUL: an RSRP threshold for the selection between the NUL carrier and the SUL carrier;

– msgA-RSRP-Threshold: an RSRP threshold for selection between 2-step RA type and 4-step RA type when both 2-step and 4-step RA type Random Access Resources are configured in the UL BWP;

– rsrp-ThresholdMsg3: an RSRP threshold for MSG3 repetition (see clause 5.1.1b);

– featurePriorities: priorities for features, such as RedCap, NSAG(s), etc. (see clause 5.1.1d);

– msgA-TransMax: The maximum number of MSGA transmissions when both 4-step and 2-step RA type Random Access Resources are configured;

– candidateBeamRSList: a list of reference signals (CSI-RS and/or SSB) identifying the candidate beams for recovery and the associated Random Access parameters;

– recoverySearchSpaceId: the search space identity for monitoring the response of the beam failure recovery request;

– powerRampingStep: the power-ramping factor;

– msgA-PreamblePowerRampingStep: the power ramping factor for MSGA preamble;

– powerRampingStepHighPriority: the power-ramping factor in case of prioritized Random Access procedure;

– scalingFactorBI: a scaling factor for prioritized Random Access procedure;

– ra-PreambleIndex: Random Access Preamble;

– ra-ssb-OccasionMaskIndex: defines PRACH occasion(s) associated with an SSB in which the MAC entity may transmit a Random Access Preamble (see clause 7.4);

– msgA-SSB-SharedRO-MaskIndex: Indicates the subset of 4-step RA type PRACH occasions shared with 2-step RA type PRACH occasions for each SSB. If 2-step RA type PRACH occasions are shared with 4-step RA type PRACH occasions and msgA-SSB-SharedRO-MaskIndex is not configured, then all 4-step RA type PRACH occasions are available for 2-step RA type (see clause 7.4);

– ra-OccasionList: defines PRACH occasion(s) associated with a CSI-RS in which the MAC entity may transmit a Random Access Preamble;

– ra-PreambleStartIndex: the starting index of Random Access Preamble(s) for on-demand SI request;

– startPreambleForThisPartition: the first preamble associated with the set of Random Access Resources applicable to the Random Access procedure;

– preambleTransMax: the maximum number of Random Access Preamble transmission;

– ssb-perRACH-OccasionAndCB-PreamblesPerSSB: defines the number of SSBs mapped to each PRACH occasion for 4-step RA type and the number of contention-based Random Access Preambles mapped to each SSB;

– msgA-CB-PreamblesPerSSB-PerSharedRO: defines the number of contention-based Random Access Preambles for 2-step RA type mapped to each SSB when the PRACH occasions are shared between 2-step and 4-step RA types;

– msgA-SSB-PerRACH-OccasionAndCB-PreamblesPerSSB: defines the number of SSBs mapped to each PRACH occasion for 2-step RA type and the number of contention-based Random Access Preambles mapped to each SSB;

– numberOfPreamblesForThisPartition: the number of consecutive preambles associated with the set of Random Access Resources applicable to the Random Access procedure;

– msgA-PUSCH-ResourceGroupA: defines MSGA PUSCH resources that the UE shall use when performing MSGA transmission using Random Access Preambles group A;

– msgA-PUSCH-ResourceGroupB: defines MSGA PUSCH resources that the UE shall use when performing MSGA transmission using Random Access Preambles group B;

– msgA-PUSCH-Resource-Index: identifies the index of the PUSCH resource used for MSGA in case of contention-free Random Access with 2-step RA type;

– if groupBconfigured is configured, then Random Access Preambles group B is configured for 4-step RA type.

– Amongst the contention-based Random Access Preambles associated with an SSB (as defined in TS 38.213 [6]), the first numberOfRA-PreamblesGroupA included in groupBconfigured Random Access Preambles belong to Random Access Preambles group A. The remaining Random Access Preambles associated with the SSB belong to Random Access Preambles group B (if configured).

– if groupB-ConfiguredTwoStepRA is configured, then Random Access Preambles group B is configured for 2-step RA type.

– Amongst the contention-based Random Access Preambles for 2-step RA type associated with an SSB (as defined in TS 38.213 [6]), the first numberOfRA-PreamblesGroupA included in GroupB-ConfiguredTwoStepRA Random Access Preambles belong to Random Access Preambles group A. The remaining Random Access Preambles associated with the SSB belong to Random Access Preambles group B (if configured).

NOTE 3: If Random Access Preambles group B is supported by the cell Random Access Preambles group B is included for each SSB.

– if Random Access Preambles group B is configured for 4-step RA type:

– ra-Msg3SizeGroupA: the threshold to determine the groups of Random Access Preambles for 4-step RA type;

– msg3-DeltaPreamble: ∆_{PREAMBLE_Msg3} in TS 38.213 [6];

– messagePowerOffsetGroupB: the power offset for preamble selection included in groupBconfigured;

– numberOfRA-PreamblesGroupA: defines the number of Random Access Preambles in Random Access Preamble group A for each SSB included in groupBconfigured.

– if Random Access Preambles group B is configured for 2-step RA type:

– msgA-DeltaPreamble: ∆_{MsgA_PUSCH} in TS 38.213 [6];

– messagePowerOffsetGroupB: the power offset for preamble selection included in GroupB-ConfiguredTwoStepRA;

– numberOfRA-PreamblesGroupA: defines the number of Random Access Preambles in Random Access Preamble group A for each SSB included in GroupB-ConfiguredTwoStepRA;

– ra-MsgA-SizeGroupA: the threshold to determine the groups of Random Access Preambles for 2-step RA type.

– the set of Random Access Preambles and/or PRACH occasions for SI request, if any;

– the set of Random Access Preambles and/or PRACH occasions for beam failure recovery request, if any;

– the set of Random Access Preambles and/or PRACH occasions for reconfiguration with sync, if any;

– ra-ResponseWindow: the time window to monitor RA response(s) (SpCell only);

– ra-ContentionResolutionTimer: the Contention Resolution Timer (SpCell only);

– msgB-ResponseWindow: the time window to monitor RA response(s) for 2-step RA type (SpCell only).

In addition, the following information for related Serving Cell is assumed to be available for UEs:

– if Random Access Preambles group B is configured:

– if the Serving Cell for the Random Access procedure is configured with supplementary uplink as specified in TS 38.331 [5], and SUL carrier is selected for performing Random Access Procedure:

– P_CMAX,f,c of the SUL carrier as specified in TS 38.101-1 [14], TS 38.101-2 [15], and TS 38.101-3 [16].

– else:

– P_CMAX,f,c of the NUL carrier as specified in TS 38.101-1 [14], TS 38.101-2 [15], and TS 38.101-3 [16].

The following UE variables are used for the Random Access procedure:

– PREAMBLE_INDEX;

– PREAMBLE_TRANSMISSION_COUNTER;

– PREAMBLE_POWER_RAMPING_COUNTER;

– PREAMBLE_POWER_RAMPING_STEP;

– PREAMBLE_RECEIVED_TARGET_POWER;

– PREAMBLE_BACKOFF;

– PCMAX;

– SCALING_FACTOR_BI;

– TEMPORARY_C-RNTI;

– RA_TYPE;

– POWER_OFFSET_2STEP_RA;

– MSGA_PREAMBLE_POWER_RAMPING_STEP.

When the Random Access procedure is initiated on a Serving Cell, the MAC entity shall:

1> flush the Msg3 buffer;

1> flush the MSGA buffer;

1> set the PREAMBLE_TRANSMISSION_COUNTER to 1;

1> set the PREAMBLE_POWER_RAMPING_COUNTER to 1;

1> set the PREAMBLE_BACKOFF to 0 ms;

1> set POWER_OFFSET_2STEP_RA to 0 dB;

1> if the carrier to use for the Random Access procedure is explicitly signalled:

2> select the signalled carrier for performing Random Access procedure;

2> set the PCMAX to P_CMAX,f,c of the signalled carrier.

1> else if the carrier to use for the Random Access procedure is not explicitly signalled; and

1> if the Serving Cell for the Random Access procedure is configured with supplementary uplink as specified in TS 38.331 [5]; and

1> if the RSRP of the downlink pathloss reference is less than rsrp-ThresholdSSB-SUL:

2> select the SUL carrier for performing Random Access procedure;

2> set the PCMAX to P_CMAX,f,c of the SUL carrier.

1> else:

2> select the NUL carrier for performing Random Access procedure;

2> set the PCMAX to P_CMAX,f,c of the NUL carrier.

NOTE 4: Void.

1> perform the BWP operation as specified in clause 5.15;

1> select the set of Random Access resources applicable to the current Random Access procedure according to clause 5.1.1b;

1> if the Random Access procedure is initiated by PDCCH order and if the ra-PreambleIndex explicitly provided by PDCCH is not 0b000000; or

1> if the Random Access procedure was initiated for SI request (as specified in TS 38.331 [5]) and the Random Access Resources for SI request have been explicitly provided by RRC; or

1> if the Random Access procedure was initiated for SpCell beam failure recovery (as specified in clause 5.17) and if the contention-free Random Access Resources for beam failure recovery request for 4-step RA type have been explicitly provided by RRC for the BWP selected for Random Access procedure; or

1> if the Random Access procedure was initiated for reconfiguration with sync and if the contention-free Random Access Resources for 4-step RA type have been explicitly provided in rach-ConfigDedicated for the BWP selected for Random Access procedure:

2> set the RA_TYPE to 4-stepRA.

1> else if the BWP selected for Random Access procedure is configured with both 2-step and 4-step RA type Random Access Resources within the selected set of Random Access resources (as specified in clause 5.1.1b) and the RSRP of the downlink pathloss reference is above msgA-RSRP-Threshold; or

1> if the BWP selected for Random Access procedure is only configured with 2-step RA type Random Access resources within the selected set of Random Access resources according to clause 5.1.1b; or

1> if the Random Access procedure was initiated for reconfiguration with sync and if the contention-free Random Access Resources for 2-step RA type have been explicitly provided in rach-ConfigDedicated for the BWP selected for Random Access procedure:

2> set the RA_TYPE to 2-stepRA.

1> else:

2> set the RA_TYPE to 4-stepRA.

1> perform initialization of variables specific to Random Access type as specified in clause 5.1.1a;

1> if RA_TYPE is set to 2-stepRA:

2> perform the Random Access Resource selection procedure for 2-step RA type (see clause 5.1.2a).

1> else:

2> perform the Random Access Resource selection procedure (see clause 5.1.2).

5.1.1a Initialization of variables specific to Random Access type

The MAC entity shall:

1> if RA_TYPE is set to 2-stepRA:

2> set PREAMBLE_POWER_RAMPING_STEP to msgA-PreamblePowerRampingStep;

2> set SCALING_FACTOR_BI to 1;

2> apply preambleTransMax included in the RACH-ConfigGenericTwoStepRA;

2> if the Random Access procedure was initiated for reconfiguration with sync or for SCG activation; and

2> if cfra-TwoStep is configured for the selected carrier:

3> if msgA-TransMax is configured in the cfra-TwoStep:

4> apply msgA-TransMax configured in the cfra-TwoStep.

2> else if msgA-TransMax is included in the RACH-ConfigCommonTwoStepRA:

3> apply msgA-TransMax included in the RACH-ConfigCommonTwoStepRA.

2> if the Random Access procedure was initiated for SpCell beam failure recovery (as specified in clause 5.17); and

2> if beamFailureRecoveryConfig is configured for the active UL BWP of the selected carrier; and

2> if ra-PrioritizationTwoStep is configured in the beamFailureRecoveryConfig:

3> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority included in the ra-PrioritizationTwoStep in beamFailureRecoveryConfig;

3> if scalingFactorBI is configured in the ra-PrioritizationTwoStep in beamFailureRecoveryConfig:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if the Random Access procedure was initiated for reconfiguration with sync or for SCG activation; and

2> if rach-ConfigDedicated is configured for the selected carrier; and

2> if ra-PrioritizationTwoStep is configured in the rach-ConfigDedicated:

3> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority included in the ra-PrioritizationTwoStep in rach-ConfigDedicated;

3> if scalingFactorBI is configured in ra-PrioritizationTwoStep in the rach-ConfigDedicated:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if both ra-PrioritizationForSlicingTwoStep for a NSAG identity and ra-PrioritizationForAccessIdentityTwoStep are configured for the selected carrier; and

2> if the MAC entity is provided by upper layers with both this NSAG identity and Access Identity 1 or 2; and

2> if for at least one of these Access Identities the corresponding bit in the ra-PrioritizationForAI is set to one:

3> if enableRA-PrioritizationForSlicing is set to true:

4> if powerRampingStepHighPriority is configured in the ra-PrioritizationForSlicingTwoStep for this NSAG identity:

5> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

4> if scalingFactorBI is configured in the ra-PrioritizationForSlicingTwoStep for this NSAG identity:

5> set SCALING_FACTOR_BI to the scalingFactorBI.

3> else if enableRA-PrioritizationForSlicing is set to false:

4> if powerRampingStepHighPriority is configured in the ra-PrioritizationForAccessIdentityTwoStep:

5> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

4> if scalingFactorBI is configured in the ra-PrioritizationForAccessIdentityTwoStep:

5> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if ra-PrioritizationForSlicingTwoStep for a NSAG identity is configured for the selected carrier; and

2> if the MAC entity is provided by upper layers with this NSAG identity:

3> if powerRampingStepHighPriority is configured in the ra-PrioritizationForSlicingTwoStep for this NSAG identity:

4> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

3> if scalingFactorBI is configured in the ra-PrioritizationForSlicingTwoStep for this NSAG identity:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if ra-PrioritizationForAccessIdentityTwoStep is configured for the selected carrier; and

2> if the MAC entity is provided by upper layers with Access Identity 1 or 2; and

2> if for at least one of these Access Identities the corresponding bit in the ra-PrioritizationForAI is set to one:

3> if powerRampingStepHighPriority is configured in the ra-PrioritizationForAccessIdentityTwoStep:

4> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

3> if scalingFactorBI is configured in the ra-PrioritizationForAccessIdentityTwoStep:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> set MSGA_PREAMBLE_POWER_RAMPING_STEP to PREAMBLE_POWER_RAMPING_STEP.

1> else (i.e. RA_TYPE is set to 4-stepRA):

2> set PREAMBLE_POWER_RAMPING_STEP to powerRampingStep;

2> set SCALING_FACTOR_BI to 1;

2> set preambleTransMax to preambleTransMax included in the RACH-ConfigGeneric;

2> if the Random Access procedure was initiated for SpCell beam failure recovery (as specified in clause 5.17); and

2> if beamFailureRecoveryConfig is configured for the active UL BWP of the selected carrier:

3> start the beamFailureRecoveryTimer, if configured;

3> apply the parameters powerRampingStep, preambleReceivedTargetPower, and preambleTransMax configured in the beamFailureRecoveryConfig.

2> if the Random Access procedure was initiated for beam failure recovery (as specified in clause 5.17); and

2> if beamFailureRecoveryConfig is configured for the active UL BWP of the selected carrier; and

2> if ra-Prioritization is configured in the beamFailureRecoveryConfig:

3> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority included in the ra-Prioritization in beamFailureRecoveryConfig;

3> if scalingFactorBI is configured in ra-Prioritization in the beamFailureRecoveryConfig:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if the Random Access procedure was initiated for reconfiguration with sync or for SCG activation; and

2> if rach-ConfigDedicated is configured for the selected carrier; and

2> if ra-Prioritization is configured in the rach-ConfigDedicated:

3> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority included in the ra-Prioritization in rach-ConfigDedicated;

3> if scalingFactorBI is configured in ra-Prioritization in the rach-ConfigDedicated:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if both ra-PrioritizationForSlicing for a NSAG identity and ra-PrioritizationForAccessIdentity are configured for the selected carrier; and

2> if the MAC entity is provided by upper layers with both this NSAG identity and Access Identity 1 or 2; and

2> if for at least one of these Access Identities the corresponding bit in the ra-PrioritizationForAI is set to one:

3> if enableRA-PrioritizationForSlicing is set to true:

4> if powerRampingStepHighPriority is configured in the ra-PrioritizationForSlicing for this NSAG identity:

5> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

4> if scalingFactorBI is configured in the ra-PrioritizationForSlicing for this NSAG identity:

5> set SCALING_FACTOR_BI to the scalingFactorBI.

3> else if enableRA-PrioritizationForSlicing is set to false:

4> if powerRampingStepHighPriority is configured in the ra-PrioritizationForAccessIdentity:

5> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

4> if scalingFactorBI is configured in the ra-PrioritizationForAccessIdentity:

5> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if ra-PrioritizationForSlicing for a NSAG identity is configured for the selected carrier; and

2> if the MAC entity is provided by upper layers with this NSAG identity:

3> if powerRampingStepHighPriority is configured in the ra-PrioritizationForSlicing for this NSAG identity:

4> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

3> if scalingFactorBI is configured in the ra-PrioritizationForSlicing for this NSAG identity:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> else if ra-PrioritizationForAccessIdentity is configured for the selected carrier; and

2> if the MAC entity is provided by upper layers with Access Identity 1 or 2; and

2> if for at least one of these Access Identities the corresponding bit in the ra-PrioritizationForAI is set to one:

3> if powerRampingStepHighPriority is configured in the ra-PrioritizationForAccessIdentity:

4> set PREAMBLE_POWER_RAMPING_STEP to the powerRampingStepHighPriority.

3> if scalingFactorBI is configured in the ra-PrioritizationForAccessIdentity:

4> set SCALING_FACTOR_BI to the scalingFactorBI.

2> if RA_TYPE is switched from 2-stepRA to 4-stepRA during this Random Access procedure:

3> set POWER_OFFSET_2STEP_RA to (PREAMBLE_POWER_RAMPING_COUNTER – 1) × (MSGA_PREAMBLE_POWER_RAMPING_STEP – PREAMBLE_POWER_RAMPING_STEP).

NOTE: If enableRA-PrioritizationForSlicing is not configured in BWP-UplinkCommon and if both the provided NSAG identity and the provided Access Identity whose corresponding bit in the ra-PrioritizationForAI is set to one are configured with ra-Prioritization either in RACH-ConfigCommon or RACH-ConfigCommonTwoStepRA, it is up to UE implementation how to determine the values of PREAMBLE_POWER_RAMPING_STEP and SCALING_FACTOR_BI.

5.1.1b Selection of the set of Random Access resources for the Random Access procedure

The MAC entity shall:

1> if the BWP selected for Random Access procedure is configured with both set(s) of Random Access resources with MSG3 repetition indication and set(s) of Random Access resources without MSG3 repetition indication and the RSRP of the downlink pathloss reference is less than rsrp-ThresholdMsg3; or

1> if the BWP selected for Random Access procedure is only configured with the set(s) of Random Access resources with MSG3 repetition indication:

2> assume MSG3 repetition is applicable for the current Random Access procedure.

1> else:

2> assume MSG3 repetition is not applicable for the current Random Access procedure.

NOTE 1: Void.

1> if contention-free Random Access Resources have not been provided for this Random Access procedure and one or more of the features including RedCap and/or a specific NSAG(s) and/or SDT and/or MSG3 repetition is applicable for this Random Access procedure:

NOTE 2: The applicability of SDT is determined by MAC entity according to clause 5.27. The applicability of specific NSAG(s) is determined by upper layers when the Random Access procedure is initiated. The applicability of RedCap is also determined by upper layers when Random Access procedure is initiated and it is applicable to the Random Access procedures initiated by PDCCH orders and any Random Access procedure initiated by the MAC entity.

2> if none of the sets of Random Access resources are available for any feature applicable to the current Random Access procedure (as specified in clause 5.1.1c):

3> select the set(s) of Random Access resources that are not associated with any feature indication (as specified in clause 5.1.1c) for this Random Access procedure.

2> else if there is one set of Random Access resources available which can be used for indicating all features triggering this Random Access procedure:

3> select this set of Random Access resources for this Random Access procedure.

2> else (i.e. there are one or more sets of Random Access resources available that are configured with indication(s) for a subset of all features triggering this Random Access procedure):

3> select a set of Random Access resources from the available set(s) of Random Access resources based on the priority order indicated by upper layers as specified in clause 5.1.1d for this Random Access Procedure.

1> else if contention-free Random Access Resources have been provided for this Random Access procedure and RedCap is applicable for the current Random Access procedure and there is one set of Random Access resources available that is only configured with RedCap indication:

2> select this set of Random Access resources for this Random Access procedure.

1> else:

2> select the set of Random Access resources that are not associated with any feature indication (as specified in clause 5.1.1c) for the current Random Access procedure.

5.1.1c Availability of the set of Random Access resources

The MAC entity shall for each set of configured Random Access resources for 4-step RA type and for each set of configured Random Access resources for 2-step RA type:

1> if RedCap indication is configured for a set of Random Access resources:

2> consider the set of Random Access resources as not available for a Random Access procedure for which RedCap indication is not applicable.

1> if SDT indication is configured for a set of Random Access resources:

2> consider the set of Random Access resources as not available for the Random Access procedure which is not triggered for SDT.

1> if NSAG indication is configured for a set of Random Access resources:

2> consider the set of Random Access resources as not available for the Random Access procedure unless it is triggered for the corresponding NSAG indication.

1> if MSG3 repetition indication is configured for a set of Random Access resources:

2> consider the set of Random Access resources as not available for the Random Access procedure if MSG3 repetition is not applicable.

1> if a set of Random Access resources is not configured with any of the RedCap or SDT or NSAG(s) or MSG3 repetition indications:

2> consider the set of Random Access resources to not associated with any feature indication.

5.1.1d Selection of the set of Random Access resources based on feature prioritization

The MAC entity shall:

1> among the available sets of Random Access resources for this Random Access procedure (as specified in clause 5.1.1c), identify those configured with a feature which has the highest priority assigned in featurePriorities among all the features applicable to this Random Access procedure as specified in TS 38.331 [5].

1> if a single set of Random Access resources is identified:

2> select this set of Random Access resources.

1> else if more than one set of Random Access resources is identified:

2> repeat the procedure taking as an input the identified sets of Random Access resources and the feature applicable to the current Random Access procedure with the highest priority assigned in featurePriorities among all the features applicable to this Random Access procedure, except the features considered already.

1> else (i.e. no set of Random Access resources is identified):

2> repeat the procedure taking as an input the previous identified available sets of Random Access resources and the feature applicable to the current Random Access procedure with the highest priority assigned in featurePriorities among all the features applicable to this Random Access procedure, except the features considered already.

5.1.2 Random Access Resource selection

If the selected RA_TYPE is set to 4-stepRA, the MAC entity shall:

1> if the Random Access procedure was initiated for SpCell beam failure recovery (as specified in clause 5.17); and

1> if the beamFailureRecoveryTimer (in clause 5.17) is either running or not configured; and

1> if the contention-free Random Access Resources for beam failure recovery request associated with any of the SSBs and/or CSI-RSs have been explicitly provided by RRC; and

1> if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB amongst the SSBs in candidateBeamRSList or the CSI-RSs with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the CSI-RSs in candidateBeamRSList is available:

2> select an SSB with SS-RSRP above rsrp-ThresholdSSB amongst the SSBs in candidateBeamRSList or a CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the CSI-RSs in candidateBeamRSList;

2> if CSI-RS is selected, and there is no ra-PreambleIndex associated with the selected CSI-RS:

3> set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the SSB in candidateBeamRSList which is quasi-colocated with the selected CSI-RS as specified in TS 38.214 [7].

2> else:

3> set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected SSB or CSI-RS from the set of Random Access Preambles for beam failure recovery request.

1> else if the ra-PreambleIndex has been explicitly provided by PDCCH; and

1> if the ra-PreambleIndex is not 0b000000:

2> set the PREAMBLE_INDEX to the signalled ra-PreambleIndex;

2> select the SSB signalled by PDCCH.

1> else if the contention-free Random Access Resources associated with SSBs have been explicitly provided in rach-ConfigDedicated and at least one SSB with SS-RSRP above rsrp-ThresholdSSB amongst the associated SSBs is available:

2> select an SSB with SS-RSRP above rsrp-ThresholdSSB amongst the associated SSBs;

2> set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected SSB.

1> else if the contention-free Random Access Resources associated with CSI-RSs have been explicitly provided in rach-ConfigDedicated and at least one CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the associated CSI-RSs is available:

2> select a CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS amongst the associated CSI-RSs;

2> set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected CSI-RS.

1> else if the Random Access procedure was initiated for SI request (as specified in TS 38.331 [5]); and

1> if the Random Access Resources for SI request have been explicitly provided by RRC:

2> if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB is available:

3> select an SSB with SS-RSRP above rsrp-ThresholdSSB.

2> else:

3> select any SSB.

2> select a Random Access Preamble corresponding to the selected SSB, from the Random Access Preamble(s) determined according to ra-PreambleStartIndex as specified in TS 38.331 [5];

2> set the PREAMBLE_INDEX to selected Random Access Preamble.

1> else (i.e. for the contention-based Random Access preamble selection):

2> if at least one of the SSBs with SS-RSRP above rsrp-ThresholdSSB is available:

3> select an SSB with SS-RSRP above rsrp-ThresholdSSB.

2> else:

3> select any SSB.

2> if the RA_TYPE is switched from 2-stepRA to 4-stepRA:

3> if a Random Access Preambles group was selected during the current Random Access procedure:

4> select the same group of Random Access Preambles as was selected for the 2-step RA type.

3> else:

4> if Random Access Preambles group B is configured; and

4> if the transport block size of the MSGA payload configured in the rach-ConfigDedicated corresponds to the transport block size of the MSGA payload associated with Random Access Preambles group B:

5> select the Random Access Preambles group B.

4> else:

5> select the Random Access Preambles group A.

2> else if Msg3 buffer is empty:

3> if Random Access Preambles group B is configured:

4> if the potential Msg3 size (UL data available for transmission plus MAC subheader(s) and, where required, MAC CEs) is greater than ra-Msg3SizeGroupA and the pathloss is less than PCMAX (of the Serving Cell performing the Random Access Procedure) – preambleReceivedTargetPower – msg3-DeltaPreamble – messagePowerOffsetGroupB; or

4> if the Random Access procedure was initiated for the CCCH logical channel and the CCCH SDU size plus MAC subheader is greater than ra-Msg3SizeGroupA:

5> select the Random Access Preambles group B.

4> else:

5> select the Random Access Preambles group A.

3> else:

4> select the Random Access Preambles group A.

2> else (i.e. Msg3 is being retransmitted):

3> select the same group of Random Access Preambles as was used for the Random Access Preamble transmission attempt corresponding to the first transmission of Msg3.

2> select a Random Access Preamble randomly with equal probability from the Random Access Preambles associated with the selected SSB and the selected Random Access Preambles group;

2> set the PREAMBLE_INDEX to the selected Random Access Preamble.

1> if the Random Access procedure was initiated for SI request (as specified in TS 38.331 [5]); and

1> if ra-AssociationPeriodIndex and si-RequestPeriod are configured:

2> determine the next available PRACH occasion from the PRACH occasions corresponding to the selected SSB in the association period given by ra-AssociationPeriodIndex in the si-RequestPeriod permitted by the restrictions given by the ra-ssb-OccasionMaskIndex if configured (the MAC entity shall select a PRACH occasion randomly with equal probability amongst the consecutive PRACH occasions according to clause 8.1 of TS 38.213 [6] corresponding to the selected SSB).

1> else if an SSB is selected above:

2> determine the next available PRACH occasion from the PRACH occasions corresponding to the selected SSB permitted by the restrictions given by the ra-ssb-OccasionMaskIndex if configured, or ssb-SharedRO-MaskIndex if configured, or indicated by PDCCH (the MAC entity shall select a PRACH occasion randomly with equal probability amongst the consecutive PRACH occasions according to clause 8.1 of TS 38.213 [6] regardless the FR2 UL gap, corresponding to the selected SSB; the MAC entity may take into account the possible occurrence of measurement gaps and MUSIM gaps when determining the next available PRACH occasion corresponding to the selected SSB).

1> else if a CSI-RS is selected above:

2> if there is no contention-free Random Access Resource associated with the selected CSI-RS:

3> determine the next available PRACH occasion from the PRACH occasions, permitted by the restrictions given by the ra-ssb-OccasionMaskIndex if configured, corresponding to the SSB in candidateBeamRSList which is quasi-colocated with the selected CSI-RS as specified in TS 38.214 [7] (the MAC entity shall select a PRACH occasion randomly with equal probability amongst the consecutive PRACH occasions according to clause 8.1 of TS 38.213 [6] regardless the FR2 UL gap, corresponding to the SSB which is quasi-colocated with the selected CSI-RS; the MAC entity may take into account the possible occurrence of measurement gaps and MUSIM gaps when determining the next available PRACH occasion corresponding to the SSB which is quasi-colocated with the selected CSI-RS).

2> else:

3> determine the next available PRACH occasion from the PRACH occasions in ra-OccasionList corresponding to the selected CSI-RS (the MAC entity shall select a PRACH occasion randomly with equal probability amongst the PRACH occasions occurring simultaneously but on different subcarriers regardless the FR2 UL gap, corresponding to the selected CSI-RS; the MAC entity may take into account the possible occurrence of measurement gaps and MUSIM gaps when determining the next available PRACH occasion corresponding to the selected CSI-RS).

1> perform the Random Access Preamble transmission procedure (see clause 5.1.3).

NOTE 1: When the UE determines if there is an SSB with SS-RSRP above rsrp-ThresholdSSB or a CSI-RS with CSI-RSRP above rsrp-ThresholdCSI-RS, the UE uses the latest unfiltered L1-RSRP measurement.

NOTE 2: Void.

NOTE 3: If a RedCap UE in RRC_IDLE or RRC_INACTIVE mode is configured with a BWP indicated by initialDownlinkBWP-RedCap which is not associated with any SSB, SS-RSRP measurement is performed based on the SSB associated with the BWP indicated by initialDownlinkBWP.

5.1.2a Random Access Resource selection for 2-step RA type

If the selected RA_TYPE is set to 2-stepRA, the MAC entity shall:

1> if the contention-free 2-step RA type Resources associated with SSBs have been explicitly provided in rach-ConfigDedicated and at least one SSB with SS-RSRP above msgA-RSRP-ThresholdSSB amongst the associated SSBs is available:

2> select an SSB with SS-RSRP above msgA-RSRP-ThresholdSSB amongst the associated SSBs;

2> set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected SSB.

1> else (i.e. for the contention-based Random Access Preamble selection):

2> if at least one of the SSBs with SS-RSRP above msgA-RSRP-ThresholdSSB is available:

3> select an SSB with SS-RSRP above msgA-RSRP-ThresholdSSB.

2> else:

3> select any SSB.

2> if contention-free Random Access Resources for 2-step RA type have not been configured and if Random Access Preambles group has not yet been selected during the current Random Access procedure:

3> if Random Access Preambles group B for 2-step RA type is configured:

4> if the potential MSGA payload size (UL data available for transmission plus MAC subheader and, where required, MAC CEs) is greater than the ra-MsgA-SizeGroupA and the pathloss is less than PCMAX (of the Serving Cell performing the Random Access Procedure) – msgA-PreambleReceivedTargetPower – msgA-DeltaPreamble – messagePowerOffsetGroupB; or

4> if the Random Access procedure was initiated for the CCCH logical channel and the CCCH SDU size plus MAC subheader is greater than ra-MsgA-SizeGroupA:

5> select the Random Access Preambles group B.

4> else:

5> select the Random Access Preambles group A.

3> else:

4> select the Random Access Preambles group A.

2> else if contention-free Random Access Resources for 2-step RA type have been configured and if Random Access Preambles group has not yet been selected during the current Random Access procedure:

3> if Random Access Preambles group B for 2-step RA type is configured; and

3> if the transport block size of the MSGA payload configured in the rach-ConfigDedicated corresponds to the transport block size of the MSGA payload associated with Random Access Preambles group B:

4> select the Random Access Preambles group B.

3> else:

4> select the Random Access Preambles group A.

2> else (i.e. Random Access preambles group has been selected during the current Random Access procedure):

3> select the same group of Random Access Preambles as was used for the Random Access Preamble transmission attempt corresponding to the earlier transmission of MSGA.

2> select a Random Access Preamble randomly with equal probability from the 2-step RA type Random Access Preambles associated with the selected SSB and the selected Random Access Preambles group;

2> set the PREAMBLE_INDEX to the selected Random Access Preamble.

1> determine the next available PRACH occasion from the PRACH occasions corresponding to the selected SSB permitted by the restrictions given by the msgA-SSB-SharedRO-MaskIndex if configured, or ra-ssb-OccasionMaskIndex if configured, or ssb-SharedRO-MaskIndex if configured (the MAC entity shall select a PRACH occasion randomly with equal probability among the consecutive PRACH occasions allocated for 2-step RA type according to clause 8.1 of TS 38.213 [6] regardless the FR2 UL gap, corresponding to the selected SSB; the MAC entity may take into account the possible occurrence of measurement gaps and MUSIM gaps when determining the next available PRACH occasion corresponding to the selected SSB);

1> if the Random Access Preamble was not selected by the MAC entity among the contention-based Random Access Preamble(s):

2> select a PUSCH occasion from the PUSCH occasions configured in msgA-CFRA-PUSCH corresponding to the PRACH slot of the selected PRACH occasion, according to msgA-PUSCH-Resource-Index corresponding to the selected SSB;

2> determine the UL grant and the associated HARQ information for the MSGA payload in the selected PUSCH occasion;

2> deliver the UL grant and the associated HARQ information to the HARQ entity.

1> else:

2> select a PUSCH occasion corresponding to the selected preamble and PRACH occasion according to clause 8.1A of TS 38.213 [6];

2> determine the UL grant for the MSGA payload according to the PUSCH configuration associated with the selected Random Access Preambles group and determine the associated HARQ information;

2> if the selected preamble and PRACH occasion is mapped to a valid PUSCH occasion as specified in clause 8.1A of TS 38.213 [6]:

3> deliver the UL grant and the associated HARQ information to the HARQ entity.

1> perform the MSGA transmission procedure (see clause 5.1.3a).

NOTE 1: To determine if there is an SSB with SS-RSRP above msgA-RSRP-ThresholdSSB, the UE uses the latest unfiltered L1-RSRP measurement.

NOTE 2: If a RedCap UE in RRC_IDLE or RRC_INACTIVE mode is configured with a BWP indicated by initialDownlinkBWP-RedCap which is not associated with any SSB, SS-RSRP measurement is performed based on the SSB associated with the BWP indicated by initialDownlinkBWP.

5.1.3 Random Access Preamble transmission

The MAC entity shall, for each Random Access Preamble:

1> if PREAMBLE_TRANSMISSION_COUNTER is greater than one; and

1> if the notification of suspending power ramping counter has not been received from lower layers; and

1> if LBT failure indication was not received from lower layers for the last Random Access Preamble transmission; and

1> if SSB or CSI-RS selected is not changed from the selection in the last Random Access Preamble transmission:

2> increment PREAMBLE_POWER_RAMPING_COUNTER by 1.

1> select the value of DELTA_PREAMBLE according to clause 7.3;

1> set PREAMBLE_RECEIVED_TARGET_POWER to preambleReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) × PREAMBLE_POWER_RAMPING_STEP + POWER_OFFSET_2STEP_RA;

1> except for contention-free Random Access Preamble for beam failure recovery request, compute the RA-RNTI associated with the PRACH occasion in which the Random Access Preamble is transmitted;

1> instruct the physical layer to transmit the Random Access Preamble using the selected PRACH occasion, corresponding RA-RNTI (if available), PREAMBLE_INDEX, and PREAMBLE_RECEIVED_TARGET_POWER.

1> if LBT failure indication is received from lower layers for this Random Access Preamble transmission:

2> if lbt-FailureRecoveryConfig is configured:

3> perform the Random Access Resource selection procedure (see clause 5.1.2).

2> else:

3> increment PREAMBLE_TRANSMISSION_COUNTER by 1;

3> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

4> if the Random Access Preamble is transmitted on the SpCell:

5> indicate a Random Access problem to upper layers;

5> if this Random Access procedure was triggered for SI request:

6> consider the Random Access procedure unsuccessfully completed.

4> else if the Random Access Preamble is transmitted on an SCell:

5> consider the Random Access procedure unsuccessfully completed.

3> if the Random Access procedure is not completed:

4> perform the Random Access Resource selection procedure (see clause 5.1.2).

The RA-RNTI associated with the PRACH occasion in which the Random Access Preamble is transmitted, is computed as:

RA-RNTI = 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 × ul_carrier_id

where s_id is the index of the first OFDM symbol of the PRACH occasion (0 ≤ s_id < 14), t_id is the index of the first slot of the PRACH occasion in a system frame (0 ≤ t_id < 80), where the subcarrier spacing to determine t_id is based on the value of μ specified in clause 5.3.2 in TS 38.211 [8] for μ = {0, 1, 2, 3}, and for μ = {5, 6}, t_id is the index of the 120 kHz slot in a system frame that contains the PRACH occasion (0 ≤ t_id < 80), f_id is the index of the PRACH occasion in the frequency domain (0 ≤ f_id < 8), and ul_carrier_id is the UL carrier used for Random Access Preamble transmission (0 for NUL carrier, and 1 for SUL carrier).

5.1.3a MSGA transmission

The MAC entity shall, for each MSGA:

1> if PREAMBLE_TRANSMISSION_COUNTER is greater than one; and

1> if the notification of suspending power ramping counter has not been received from lower layers; and

1> if LBT failure indication was not received from lower layers for the last MSGA Random Access Preamble transmission; and

1> if SSB selected is not changed from the selection in the last Random Access Preamble transmission:

2> increment PREAMBLE_POWER_RAMPING_COUNTER by 1.

1> select the value of DELTA_PREAMBLE according to clause 7.3;

1> set PREAMBLE_RECEIVED_TARGET_POWER to msgA-PreambleReceivedTargetPower + DELTA_PREAMBLE + (PREAMBLE_POWER_RAMPING_COUNTER – 1) × PREAMBLE_POWER_RAMPING_STEP;

1> if this is the first MSGA transmission within this Random Access procedure:

2> if the transmission is not being made for the CCCH logical channel:

3> indicate to the Multiplexing and assembly entity to include a C-RNTI MAC CE in the subsequent uplink transmission.

2> if the Random Access procedure was initiated for SpCell beam failure recovery and spCell-BFR-CBRA with value true is configured:

3> if there is at least one Serving Cell of this MAC entity configured with two BFD-RS sets:

4> indicate to the Multiplexing and assembly entity to include an Enhanced BFR MAC CE or a Truncated Enhanced BFR MAC CE in the subsequent uplink transmission.

3> else:

4> indicate to the Multiplexing and assembly entity to include a BFR MAC CE or a Truncated BFR MAC CE in the subsequent uplink transmission.

2> else if the Random Access procedure was initiated for beam failure recovery of both BFD-RS sets of SpCell:

3> indicate to the Multiplexing and assembly entity to include an Enhanced BFR MAC CE or a Truncated Enhanced BFR MAC CE in the subsequent uplink transmission.

2> obtain the MAC PDU to transmit from the Multiplexing and assembly entity according to the HARQ information determined for the MSGA payload (see clause 5.1.2a) and store it in the MSGA buffer.

1> compute the MSGB-RNTI associated with the PRACH occasion in which the Random Access Preamble is transmitted;

1> instruct the physical layer to transmit the MSGA using the selected PRACH occasion and the associated PUSCH resource of MSGA (if the selected preamble and PRACH occasion is mapped to a valid PUSCH occasion), using the corresponding RA-RNTI, MSGB-RNTI, PREAMBLE_INDEX, PREAMBLE_RECEIVED_TARGET_POWER, msgA-PreambleReceivedTargetPower, and the amount of power ramping applied to the latest MSGA preamble transmission (i.e. (PREAMBLE_POWER_RAMPING_COUNTER – 1) × PREAMBLE_POWER_RAMPING_STEP);

1> if LBT failure indication is received from lower layers for the transmission of this MSGA Random Access Preamble:

2> instruct the physical layer to cancel the transmission of the MSGA payload on the associated PUSCH resource;

2> if lbt-FailureRecoveryConfig is configured:

3> perform the Random Access Resource selection procedure for 2-step RA type (see clause 5.1.2a).

2> else:

3> increment PREAMBLE_TRANSMISSION_COUNTER by 1;

3> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

4> indicate a Random Access problem to upper layers;

4> if this Random Access procedure was triggered for SI request:

5> consider this Random Access procedure unsuccessfully completed.

3> if the Random Access procedure is not completed:

4> if msgA-TransMax is applied (see clause 5.1.1a) and PREAMBLE_TRANSMISSION_COUNTER = msgA-TransMax + 1:

5> set the RA_TYPE to 4-stepRA;

5> perform initialization of variables specific to Random Access type as specified in clause 5.1.1a;

5> if the Msg3 buffer is empty:

6> obtain the MAC PDU to transmit from the MSGA buffer and store it in the Msg3 buffer;

5> flush HARQ buffer used for the transmission of MAC PDU in the MSGA buffer;

5> discard explicitly signalled contention-free 2-step RA type Random Access Resources, if any;

5> perform the Random Access Resource selection procedure as specified in clause 5.1.2.

4> else:

5> perform the Random Access Resource selection procedure for 2-step RA type (see clause 5.1.2a).

NOTE: The MSGA transmission includes the transmission of the PRACH Preamble as well as the contents of the MSGA buffer in the PUSCH resource corresponding to the selected PRACH occasion and PREAMBLE_INDEX (see TS 38.213 [6])

The MSGB-RNTI associated with the PRACH occasion in which the Random Access Preamble is transmitted, is computed as:

MSGB-RNTI = 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 × ul_carrier_id + 14 × 80 × 8 × 2

5.1.4 Random Access Response reception

Once the Random Access Preamble is transmitted and regardless of the possible occurrence of a measurement gap, the MAC entity shall:

1> if the contention-free Random Access Preamble for beam failure recovery request was transmitted by the MAC entity:

2> if the contention-free Random Access Preamble for beam failure recovery request was transmitted on a non-terrestrial network:

3> start the ra-ResponseWindow configured in BeamFailureRecoveryConfig at the PDCCH occasion as specified in TS 38.213 [6].

2> else:

3> start the ra-ResponseWindow configured in BeamFailureRecoveryConfig at the first PDCCH occasion as specified in TS 38.213 [6] from the end of the Random Access Preamble transmission.

2> monitor for a PDCCH transmission on the search space indicated by recoverySearchSpaceId of the SpCell identified by the C-RNTI while ra-ResponseWindow is running.

1> else:

2> if the Random Access Preamble was transmitted on a non-terrestrial network:

3> start the ra-ResponseWindow configured in RACH-ConfigCommon at the PDCCH occasion as specified in TS 38.213 [6].

2> else:

3> start the ra-ResponseWindow configured in RACH-ConfigCommon at the first PDCCH occasion as specified in TS 38.213 [6] from the end of the Random Access Preamble transmission.

2> monitor the PDCCH of the SpCell for Random Access Response(s) identified by the RA-RNTI while the ra-ResponseWindow is running.

1> if notification of a reception of a PDCCH transmission on the search space indicated by recoverySearchSpaceId is received from lower layers on the Serving Cell where the preamble was transmitted; and

1> if PDCCH transmission is addressed to the C-RNTI; and

1> if the contention-free Random Access Preamble for beam failure recovery request was transmitted by the MAC entity:

2> consider the Random Access procedure successfully completed.

1> else if a valid (as specified in TS 38.213 [6]) downlink assignment has been received on the PDCCH for the RA-RNTI and the received TB is successfully decoded:

2> if the Random Access Response contains a MAC subPDU with Backoff Indicator:

3> set the PREAMBLE_BACKOFF to value of the BI field of the MAC subPDU using Table 7.2-1, multiplied with SCALING_FACTOR_BI.

2> else:

3> set the PREAMBLE_BACKOFF to 0 ms.

2> if the Random Access Response contains a MAC subPDU with Random Access Preamble identifier corresponding to the transmitted PREAMBLE_INDEX (see clause 5.1.3):

3> consider this Random Access Response reception successful.

2> if the Random Access Response reception is considered successful:

3> if the Random Access Response includes a MAC subPDU with RAPID only:

4> consider this Random Access procedure successfully completed;

4> indicate the reception of an acknowledgement for SI request to upper layers.

3> else:

4> apply the following actions for the Serving Cell where the Random Access Preamble was transmitted:

5> process the received Timing Advance Command (see clause 5.2);

5> indicate the preambleReceivedTargetPower and the amount of power ramping applied to the latest Random Access Preamble transmission to lower layers (i.e. (PREAMBLE_POWER_RAMPING_COUNTER – 1) × PREAMBLE_POWER_RAMPING_STEP);

5> if the Random Access procedure for an SCell is performed on uplink carrier where pusch-Config is not configured:

6> ignore the received UL grant.

5> else:

6> process the received UL grant value and indicate it to the lower layers.

4> if the Random Access Preamble was not selected by the MAC entity among the contention-based Random Access Preamble(s):

5> consider the Random Access procedure successfully completed.

4> else:

5> set the TEMPORARY_C-RNTI to the value received in the Random Access Response;

5> if this is the first successfully received Random Access Response within this Random Access procedure:

6> if the transmission is not being made for the CCCH logical channel:

7> indicate to the Multiplexing and assembly entity to include a C-RNTI MAC CE in the subsequent uplink transmission.

6> if the Random Access procedure was initiated for SpCell beam failure recovery and spCell-BFR-CBRA with value true is configured:

7> if there is at least one Serving Cell of this MAC entity configured with two BFD-RS sets:

8> indicate to the Multiplexing and assembly entity to include an Enhanced BFR MAC CE or a Truncated Enhanced BFR MAC CE in the subsequent uplink transmission.

7> else:

8> indicate to the Multiplexing and assembly entity to include a BFR MAC CE or a Truncated BFR MAC CE in the subsequent uplink transmission.

6> else if the Random Access procedure was initiated for beam failure recovery of both BFD-RS sets of SpCell:

7> indicate to the Multiplexing and assembly entity to include an Enhanced BFR MAC CE or a Truncated Enhanced BFR MAC CE in the subsequent uplink transmission.

6> obtain the MAC PDU to transmit from the Multiplexing and assembly entity and store it in the Msg3 buffer.

NOTE: If within a Random Access procedure, an uplink grant provided in the Random Access Response for the same group of contention-based Random Access Preambles has a different size than the first uplink grant allocated during that Random Access procedure, the UE behavior is not defined.

1> if ra-ResponseWindow configured in BeamFailureRecoveryConfig expires and if a PDCCH transmission on the search space indicated by recoverySearchSpaceId addressed to the C-RNTI has not been received on the Serving Cell where the preamble was transmitted; or

1> if ra-ResponseWindow configured in RACH-ConfigCommon expires, and if the Random Access Response containing Random Access Preamble identifiers that matches the transmitted PREAMBLE_INDEX has not been received:

2> consider the Random Access Response reception not successful;

2> increment PREAMBLE_TRANSMISSION_COUNTER by 1;

2> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

3> if the Random Access Preamble is transmitted on the SpCell:

4> indicate a Random Access problem to upper layers;

4> if this Random Access procedure was triggered for SI request:

5> consider the Random Access procedure unsuccessfully completed.

3> else if the Random Access Preamble is transmitted on an SCell:

4> consider the Random Access procedure unsuccessfully completed.

2> if the Random Access procedure is not completed:

3> select a random backoff time according to a uniform distribution between 0 and the PREAMBLE_BACKOFF;

3> if the criteria (as defined in clause 5.1.2) to select contention-free Random Access Resources is met during the backoff time:

4> perform the Random Access Resource selection procedure (see clause 5.1.2).

3> else if the Random Access procedure for an SCell is performed on uplink carrier where pusch-Config is not configured:

4> delay the subsequent Random Access transmission until the Random Access Procedure is triggered by a PDCCH order with the same ra-PreambleIndex, ra-ssb-OccasionMaskIndex, and UL/SUL indicator TS 38.212 [9].

3> else:

4> perform the Random Access Resource selection procedure (see clause 5.1.2) after the backoff time.

The MAC entity may stop ra-ResponseWindow (and hence monitoring for Random Access Response(s)) after successful reception of a Random Access Response containing Random Access Preamble identifiers that matches the transmitted PREAMBLE_INDEX.

HARQ operation is not applicable to the Random Access Response reception.

5.1.4a MSGB reception and contention resolution for 2-step RA type

Once the MSGA preamble is transmitted, regardless of the possible occurrence of a measurement gap, the MAC entity shall:

1> start the msgB-ResponseWindow at the PDCCH occasion as specified in TS 38.213 [6], clause 8.2A;

1> monitor the PDCCH of the SpCell for a Random Access Response identified by MSGB-RNTI while the msgB-ResponseWindow is running;

1> if C-RNTI MAC CE was included in the MSGA:

2> monitor the PDCCH of the SpCell for Random Access Response identified by the C-RNTI while the msgB-ResponseWindow is running.

1> if notification of a reception of a PDCCH transmission of the SpCell is received from lower layers:

2> if the C-RNTI MAC CE was included in MSGA:

3> if the Random Access procedure was initiated for SpCell beam failure recovery or for beam failure recovery of both BFD-RS sets of SpCell (as specified in clause 5.17) and the PDCCH transmission is addressed to the C-RNTI:

4> consider this Random Access Response reception successful;

4> stop the msgB-ResponseWindow;

4> consider this Random Access procedure successfully completed.

3> else if the timeAlignmentTimer associated with the PTAG is running; or

3> if CG-SDT procedure is ongoing:

4> if the PDCCH transmission is addressed to the C-RNTI and contains a UL grant for a new transmission:

5> consider this Random Access Response reception successful;

5> stop the msgB-ResponseWindow;

5> consider this Random Access procedure successfully completed.

3> else:

4> if a downlink assignment has been received on the PDCCH for the C-RNTI and the received TB is successfully decoded:

5> if the MAC PDU contains the Absolute Timing Advance Command MAC CE:

6> process the received Timing Advance Command (see clause 5.2);

6> consider this Random Access Response reception successful;

6> stop the msgB-ResponseWindow;

6> consider this Random Access procedure successfully completed and finish the disassembly and demultiplexing of the MAC PDU.

2> if a valid (as specified in TS 38.213 [6]) downlink assignment has been received on the PDCCH for the MSGB-RNTI and the received TB is successfully decoded:

3> if the MSGB contains a MAC subPDU with Backoff Indicator:

4> set the PREAMBLE_BACKOFF to value of the BI field of the MAC subPDU using Table 7.2-1, multiplied with SCALING_FACTOR_BI.

3> else:

4> set the PREAMBLE_BACKOFF to 0 ms.

3> if the MSGB contains a fallbackRAR MAC subPDU; and

3> if the Random Access Preamble identifier in the MAC subPDU matches the transmitted PREAMBLE_INDEX (see clause 5.1.3a):

4> consider this Random Access Response reception successful;

4> apply the following actions for the SpCell:

5> process the received Timing Advance Command (see clause 5.2);

5> indicate the msgA-PreambleReceivedTargetPower and the amount of power ramping applied to the latest Random Access Preamble transmission to lower layers (i.e. (PREAMBLE_POWER_RAMPING_COUNTER – 1) × PREAMBLE_POWER_RAMPING_STEP);

5> if the Random Access Preamble was not selected by the MAC entity among the contention-based Random Access Preamble(s):

6> consider the Random Access procedure successfully completed;

6> process the received UL grant value and indicate it to the lower layers.

5> else:

6> set the TEMPORARY_C-RNTI to the value received in the Random Access Response;

6> if the Msg3 buffer is empty:

7> obtain the MAC PDU to transmit from the MSGA buffer and store it in the Msg3 buffer;

6> process the received UL grant value and indicate it to the lower layers and proceed with Msg3 transmission.

NOTE: If within a 2-step RA type procedure, an uplink grant provided in the fallback RAR has a different size than the MSGA payload, the UE behavior is not defined.

3> else if the MSGB contains a successRAR MAC subPDU; and

3> if the CCCH SDU was included in the MSGA and the UE Contention Resolution Identity in the MAC subPDU matches the CCCH SDU:

4> stop msgB-ResponseWindow;

4> if this Random Access procedure was initiated for SI request:

5> indicate the reception of an acknowledgement for SI request to upper layers.

4> else:

5> set the C-RNTI to the value received in the successRAR;

5> apply the following actions for the SpCell:

6> process the received Timing Advance Command (see clause 5.2);

6> indicate the msgA-PreambleReceivedTargetPower and the amount of power ramping applied to the latest Random Access Preamble transmission to lower layers (i.e. (PREAMBLE_POWER_RAMPING_COUNTER – 1) × PREAMBLE_POWER_RAMPING_STEP).

4> deliver the TPC, PUCCH resource Indicator, ChannelAccess-CPext (if indicated), and HARQ feedback Timing Indicator received in successRAR to lower layers.

4> consider this Random Access Response reception successful;

4> consider this Random Access procedure successfully completed;

4> finish the disassembly and demultiplexing of the MAC PDU.

1> if msgB-ResponseWindow expires, and the Random Access Response Reception has not been considered as successful based on descriptions above:

2> increment PREAMBLE_TRANSMISSION_COUNTER by 1;

2> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

3> indicate a Random Access problem to upper layers;

3> if this Random Access procedure was triggered for SI request:

4> consider this Random Access procedure unsuccessfully completed.

2> if the Random Access procedure is not completed:

3> if msgA-TransMax is applied (see clause 5.1.1a) and PREAMBLE_TRANSMISSION_COUNTER = msgA-TransMax + 1:

4> set the RA_TYPE to 4-stepRA;

4> perform initialization of variables specific to Random Access type as specified in clause 5.1.1a;

4> if the Msg3 buffer is empty:

5> obtain the MAC PDU to transmit from the MSGA buffer and store it in the Msg3 buffer;

4> flush HARQ buffer used for the transmission of MAC PDU in the MSGA buffer;

4> discard explicitly signalled contention-free 2-step RA type Random Access Resources, if any;

4> perform the Random Access Resource selection procedure as specified in clause 5.1.2.

3> else:

4> select a random backoff time according to a uniform distribution between 0 and the PREAMBLE_BACKOFF;

4> if the criteria (as defined in clause 5.1.2a) to select contention-free Random Access Resources is met during the backoff time:

5> perform the Random Access Resource selection procedure for 2-step RA type Random Access (see clause 5.1.2a).

4> else:

5> perform the Random Access Resource selection procedure for 2-step RA type Random Access (see clause 5.1.2a) after the backoff time.

Upon receiving a fallbackRAR, the MAC entity may stop msgB-ResponseWindow once the Random Access Response reception is considered as successful.

5.1.5 Contention Resolution

Once Msg3 is transmitted the MAC entity shall:

1> if the Msg3 transmission (i.e. initial transmission or HARQ retransmission) is scheduled with Type A PUSCH repetition:

2> if Msg3 is transmitted on a non-terrestrial network:

3> start or restart the ra-ContentionResolutionTimer in the first symbol after the end of all repetitions of the Msg3 transmission plus the UE-gNB RTT.

2> else:

3> start or restart the ra-ContentionResolutionTimer in the first symbol after the end of all repetitions of the Msg3 transmission.

1> else if Msg3 transmission (i.e. initial transmission or HARQ retransmission) is transmitted on a non-terrestrial network:

2> start or restart the ra-ContentionResolutionTimer in the first symbol after the end of the Msg3 transmission plus the UE-gNB RTT.

1> else:

2> start or restart the ra-ContentionResolutionTimer in the first symbol after the end of the Msg3 transmission.

1> monitor the PDCCH while the ra-ContentionResolutionTimer is running regardless of the possible occurrence of a measurement gap;

1> if notification of a reception of a PDCCH transmission of the SpCell is received from lower layers:

2> if the C-RNTI MAC CE was included in Msg3:

3> if the Random Access procedure was initiated by a PDCCH order and the PDCCH transmission is addressed to the C-RNTI; or

3> if the Random Access procedure was initiated by the MAC sublayer itself or by the RRC sublayer and the PDCCH transmission is addressed to the C-RNTI and contains a UL grant for a new transmission:

4> consider this Contention Resolution successful;

4> stop ra-ContentionResolutionTimer;

4> discard the TEMPORARY_C-RNTI;

4> consider this Random Access procedure successfully completed.

2> else if the CCCH SDU was included in Msg3 and the PDCCH transmission is addressed to its TEMPORARY_C-RNTI:

3> if the MAC PDU is successfully decoded:

4> stop ra-ContentionResolutionTimer;

4> if the MAC PDU contains a UE Contention Resolution Identity MAC CE; and

4> if the UE Contention Resolution Identity in the MAC CE matches the CCCH SDU transmitted in Msg3:

5> consider this Contention Resolution successful and finish the disassembly and demultiplexing of the MAC PDU;

5> if this Random Access procedure was initiated for SI request:

6> indicate the reception of an acknowledgement for SI request to upper layers.

5> else:

6> set the C-RNTI to the value of the TEMPORARY_C-RNTI;

5> discard the TEMPORARY_C-RNTI;

5> consider this Random Access procedure successfully completed.

4> else:

5> discard the TEMPORARY_C-RNTI;

5> consider this Contention Resolution not successful and discard the successfully decoded MAC PDU.

1> if ra-ContentionResolutionTimer expires:

2> if Msg3 transmission was transmitted on a non-terrestrial network:

3> if no PDCCH addressed to TC-RNTI indicating uplink grant for a Msg3 retransmission is received after the start of the ra-ContentionResolutionTimer:

4> discard the TEMPORARY_C-RNTI;

4> consider the Contention Resolution not successful.

2> else:

3> discard the TEMPORARY_C-RNTI;

3> consider the Contention Resolution not successful.

1> if the Contention Resolution is considered not successful:

2> flush the HARQ buffer used for transmission of the MAC PDU in the Msg3 buffer;

2> increment PREAMBLE_TRANSMISSION_COUNTER by 1;

2> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

3> indicate a Random Access problem to upper layers.

3> if this Random Access procedure was triggered for SI request:

4> consider the Random Access procedure unsuccessfully completed.

2> if the Random Access procedure is not completed:

3> if the RA_TYPE is set to 4-stepRA:

4> select a random backoff time according to a uniform distribution between 0 and the PREAMBLE_BACKOFF;

4> if the criteria (as defined in clause 5.1.2) to select contention-free Random Access Resources is met during the backoff time:

5> perform the Random Access Resource selection procedure (see clause 5.1.2);

4> else:

5> perform the Random Access Resource selection procedure (see clause 5.1.2) after the backoff time.

3> else (i.e. the RA_TYPE is set to 2-stepRA):

4> if msgA-TransMax is applied (see clause 5.1.1a) and PREAMBLE_TRANSMISSION_COUNTER = msgA-TransMax + 1:

5> set the RA_TYPE to 4-stepRA;

5> perform initialization of variables specific to Random Access type as specified in clause 5.1.1a;

5> flush HARQ buffer used for the transmission of MAC PDU in the MSGA buffer;

5> discard explicitly signalled contention-free 2-step RA type Random Access Resources, if any;

5> perform the Random Access Resource selection as specified in clause 5.1.2.

4> else:

5> select a random backoff time according to a uniform distribution between 0 and the PREAMBLE_BACKOFF;

5> if the criteria (as defined in clause 5.1.2a) to select contention-free Random Access Resources is met during the backoff time:

6> perform the Random Access Resource selection procedure for 2-step RA type as specified in clause 5.1.2a.

5> else:

6> perform the Random Access Resource selection for 2-step RA type procedure (see clause 5.1.2a) after the backoff time.

5.1.6 Completion of the Random Access procedure

Upon completion of the Random Access procedure, the MAC entity shall:

1> discard any explicitly signalled contention-free Random Access Resources for 2-step RA type and 4-step RA type except the 4-step RA type contention-free Random Access Resources for beam failure recovery request, if any;

1> flush the HARQ buffer used for transmission of the MAC PDU in the Msg3 buffer and the MSGA buffer.

Upon successful completion of the Random Access procedure initiated for DAPS handover, the target MAC entity shall:

1> indicate the successful completion of the Random Access procedure to the upper layers.