5.8 Transmission and reception without dynamic scheduling

38.3213GPPMedium Access Control (MAC) protocol specificationNRRelease 17TS

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

5.8.1 Downlink

Semi-Persistent Scheduling (SPS) is configured by RRC for a Serving Cell per BWP. Multiple assignments can be active simultaneously in the same BWP. Activation and deactivation of the DL SPS are independent among the Serving Cells.

For the DL SPS, a DL assignment is provided by PDCCH, and stored or cleared based on L1 signalling indicating SPS activation or deactivation.

RRC configures the following parameters when the SPS is configured:

– cs-RNTI: CS-RNTI for activation, deactivation, and retransmission;

– nrofHARQ-Processes: the number of configured HARQ processes for SPS;

– harq-ProcID-Offset: Offset of HARQ process for SPS;

– periodicity: periodicity of configured downlink assignment for SPS.

When the SPS is released by upper layers, all the corresponding configurations shall be released.

After a downlink assignment is configured for SPS, the MAC entity shall consider sequentially that the N^th downlink assignment occurs in the slot for which:

(numberOfSlotsPerFrame × SFN + slot number in the frame) =
[(numberOfSlotsPerFrame × SFN_{start time} + slot_{start time}) + N × periodicity × numberOfSlotsPerFrame / 10]
modulo (1024 × numberOfSlotsPerFrame)

where SFN_{start time} and slot_{start time} are the SFN and slot, respectively, of the first transmission of PDSCH where the configured downlink assignment was (re-)initialised.

NOTE: In case of unaligned SFN across carriers in a cell group, the SFN of the concerned Serving Cell is used to calculate the occurrences of configured downlink assignments.

5.8.1a Downlink for Multicast

MBS Semi-Persistent Scheduling (SPS) is configured by RRC on one Serving Cell per BWP. Multiple assignments can be active simultaneously in the same BWP.

For the DL MBS SPS, a DL assignment is provided by PDCCH, and stored or cleared based on L1 signalling indicating SPS activation or deactivation.

RRC configures the following parameters when the MBS SPS is configured:

– cs-RNTI: CS-RNTI for MBS SPS deactivation, PTP for PTM retransmission if configured;

– g-cs-RNTI: G-CS-RNTI for activation, deactivation, and retransmission;

– nrofHARQ-Processes: the number of configured HARQ processes for MBS SPS;

– harq-ProcID-Offset: Offset of HARQ process for MBS SPS;

– periodicity: periodicity of configured downlink assignment for MBS SPS.

When the MBS SPS is released by upper layers, all the corresponding configurations shall be released.

After a downlink assignment is configured for MBS SPS, the MAC entity shall consider sequentially that the N^th downlink assignment occurs in the slot for which:

where SFN_{start time} and slot_{start time} are the SFN and slot, respectively, of the first transmission of PDSCH where the configured downlink assignment was (re-)initialised.

5.8.2 Uplink

There are two types of transmission without dynamic grant:

– configured grant Type 1 where an uplink grant is provided by RRC, and stored as configured uplink grant;

– configured grant Type 2 where an uplink grant is provided by PDCCH, and stored or cleared as configured uplink grant based on L1 signalling indicating configured uplink grant activation or deactivation.

Type 1 and Type 2 are configured by RRC for a Serving Cell per BWP. Multiple configurations can be active simultaneously in the same BWP. For Type 2, activation and deactivation are independent among the Serving Cells. For the same BWP, the MAC entity can be configured with both Type 1 and Type 2.

Only configured grant Type 1 can be configured for CG-SDT. CG-SDT can only be configured on initial BWP.

RRC configures the following parameters when the configured grant Type 1 is configured:

– cs-RNTI: CS-RNTI for retransmission;

– cg-SDT-RSRP-ThresholdSSB: an RSRP threshold configured for SSB selection for CG-SDT;

– periodicity: periodicity of the configured grant Type 1;

– timeDomainOffset: Offset of a resource with respect to SFN = timeReferenceSFN in time domain;

– timeDomainAllocation: Allocation of configured uplink grant in time domain which contains startSymbolAndLength (i.e. SLIV in TS 38.214 [7]) or startSymbol (i.e. S in TS 38.214 [7]);

– nrofHARQ-Processes: the number of HARQ processes for configured grant;

– harq-ProcID-Offset: offset of HARQ process for configured grant configured with cg-RetransmissionTimer for operation with shared spectrum channel access;

– harq-ProcID-Offset2: offset of HARQ process for configured grant not configured with cg-RetransmissionTimer;

– timeReferenceSFN: SFN used for determination of the offset of a resource in time domain. The UE uses the closest SFN with the indicated number preceding the reception of the configured grant configuration.

RRC configures the following parameters when the configured grant Type 2 is configured:

– cs-RNTI: CS-RNTI for activation, deactivation, and retransmission;

– periodicity: periodicity of the configured grant Type 2;

– nrofHARQ-Processes: the number of HARQ processes for configured grant;

– harq-ProcID-Offset: offset of HARQ process for configured grant configured with cg-RetransmissionTimer for operation with shared spectrum channel access;

– harq-ProcID-Offset2: offset of HARQ process for configured grant not configured with cg-RetransmissionTimer.

RRC configures the following parameter when retransmissions on configured uplink grant is configured:

– cg-RetransmissionTimer: the duration after a configured grant (re)transmission of a HARQ process when the UE shall not autonomously retransmit that HARQ process;

– cg-SDT-RetransmissionTimer: the duration after a configured grant (re)trasnmission of a HARQ process of the initial CG-SDT transmission with CCCH message when the UE shall not autonomously retransmit the HARQ process.

Upon configuration of a configured grant Type 1 for a BWP of a Serving Cell by upper layers, the MAC entity shall:

1> store the uplink grant provided by upper layers as a configured uplink grant for the indicated BWP of the Serving Cell;

1> initialise or re-initialise the configured uplink grant to start in the symbol according to timeDomainOffset, timeReferenceSFN, and S (derived from SLIV or provided by startSymbol as specified in TS 38.214 [7]), and to reoccur with periodicity.

After an uplink grant is configured for a configured grant Type 1, the MAC entity shall consider sequentially that the N^th (N >= 0) uplink grant occurs in the symbol for which:

[(SFN × numberOfSlotsPerFrame × numberOfSymbolsPerSlot)
+ (slot number in the frame × numberOfSymbolsPerSlot) + symbol number in the slot] =
(timeReferenceSFN × numberOfSlotsPerFrame × numberOfSymbolsPerSlot
+ timeDomainOffset × numberOfSymbolsPerSlot + S + N × periodicity)
modulo (1024 × numberOfSlotsPerFrame × numberOfSymbolsPerSlot)

For an uplink grant configured for configured grant Type 1 for CG-SDT on the selected uplink carrier as in clause 5.27, when CG-SDT is triggered and not terminated, for each configured uplink grant valid according to TS 38.214 [7] for which the above formula is satisfied, the MAC entity shall:

1> if, after initial transmission for CG-SDT with CCCH message has been performed according to clause 5.4.1, PDCCH addressed to the MAC entity’s C-RNTI has not been received:

2> the SSB corresponding to the configured UL grant has the same SSB index as the SSB selected for initial transmission for CG-SDT with CCCH message (i.e., retransmission of initial transmission of CG-SDT):

3> select this SSB;

3> indicate the SSB index corresponding to the configured uplink grant to the lower layer;

3> consider this configured uplink grant as valid.

1> else if at least one SSB configured for CG-SDT with SS-RSRP above cg-SDT-RSRP-ThresholdSSB is available:

2> if at least one SSB corresponding to the configured uplink grant with SS-RSRP above the cg-SDT-RSRP-ThresholdSSB is available:

3> if this is the initial transmission of CG-SDT with CCCH message after the CG-SDT procedure is initiated as in clause 5.27 (i.e., initial transmission for CG-SDT):

4> select an SSB with SS-RSRP above cg-SDT-RSRP-ThresholdSSB amongst the SSB(s) associated with the configured uplink grant.

3> else if PDCCH addressed to C-RNTI has been received after the initial transmission of CG-SDT with CCCH message (i.e., subsequent new transmission for CG-SDT):

4> if SS-RSRP of the SSB selected for the previous transmission for CG-SDT is above cg-SDT-RSRP-ThresholdSSB and this SSB is associated with this configured uplink grant:

5> select this SSB.

4> else if SS-RSRP of the SSB selected for the previous transmission for CG-SDT is not above cg-SDT-RSRP-ThresholdSSB:

5> select an SSB with SS-RSRP above cg-SDT-RSRP-ThresholdSSB amongst the SSB(s) associated with the configured uplink grant.

3> if SSB is selected above:

4> indicate the SSB index to the lower layer;

43> consider this configured uplink grant as valid.

1> else if PDCCH addressed to C-RNTI after the initial transmission of the CG-SDT with CCCH message has been received:

2> if there is data available for transmission for at least one RB configured for SDT:

3> initiate Random Access procedure in clause 5.1.

After an uplink grant is configured for a configured grant Type 2, the MAC entity shall consider sequentially that the N^th (N >= 0) uplink grant occurs in the symbol for which:

[(SFN × numberOfSlotsPerFrame × numberOfSymbolsPerSlot)
+ (slot number in the frame × numberOfSymbolsPerSlot) + symbol number in the slot] =
[(SFN_{start time} × numberOfSlotsPerFrame × numberOfSymbolsPerSlot
+ slot_{start time} × numberOfSymbolsPerSlot + symbol_{start time}) + N × periodicity]
modulo (1024 × numberOfSlotsPerFrame × numberOfSymbolsPerSlot)

where SFN_{start time}, slot_{start time}, and symbol_{start time} are the SFN, slot, and symbol, respectively, of the first transmission opportunity of PUSCH where the configured uplink grant was (re-)initialised.

If cg-nrofPUSCH-InSlot or cg-nrofSlots is configured for a configured grant Type 1 or Type 2, the MAC entity shall consider the uplink grants occur in those additional PUSCH allocations as specified in clause 6.1.2.3 of TS 38.214 [7].

NOTE: In case of unaligned SFN across carriers in a cell group, the SFN of the concerned Serving Cell is used to calculate the occurrences of configured uplink grants.

When the configured uplink grant is released by upper layers, all the corresponding configurations shall be released and all corresponding uplink grants shall be cleared.

The MAC entity shall:

1> if at least one configured uplink grant confirmation has been triggered and not cancelled; and

1> if the MAC entity has UL resources allocated for new transmission:

2> if, in this MAC entity, at least one configured uplink grant is configured by configuredGrantConfigToAddModList:

3> instruct the Multiplexing and Assembly procedure to generate a Multiple Entry Configured Grant Confirmation MAC CE as defined in clause 6.1.3.31.

2> else:

3> instruct the Multiplexing and Assembly procedure to generate a Configured Grant Confirmation MAC CE as defined in clause 6.1.3.7.

2> cancel all triggered configured uplink grant confirmation(s).

For a configured grant Type 2, the MAC entity shall clear the configured uplink grant(s) immediately after first transmission of Configured Grant Confirmation MAC CE or Multiple Entry Configured Grant Confirmation MAC CE which confirms the configured uplink grant deactivation.

Retransmissions use:

– repetition of configured uplink grants; or

– received uplink grants addressed to CS-RNTI; or

– configured uplink grants with cg-RetransmissionTimer or cg-SDT-RetransmissionTimer configured.

5.8.3 Sidelink

There are two types of transmission without dynamic sidelink grant:

– configured grant Type 1 where an sidelink grant is provided by RRC, and stored as configured sidelink grant;

– configured grant Type 2 where an sidelink grant is provided by PDCCH, and stored or cleared as configured sidelink grant based on L1 signalling indicating configured sidelink grant activation or deactivation.

Type 1 and/or Type 2 are configured with a single BWP. Multiple configurations of up to 8 configured grants (including both Type 1 and Type 2, if configured) can be active simultaneously on the BWP.

RRC configures the following parameters when the configured grant Type 1 is configured, as specified in TS 38.331 [5] or TS 36.331 [21]:

– sl-ConfigIndexCG: the identifier of a configured grant for sidelink;

– sl-CS-RNTI: SLCS-RNTI for retransmission;

– sl-NrOfHARQ-Processes: the number of HARQ processes for configured grant;

– sl-PeriodCG: periodicity of the configured grant Type 1;

– sl-TimeOffsetCG-Type1: Offset of a resource with respect to reference logical slot defined by sl-TimeReferenceSFN-Type1 in time domain, referring to the number of logical slots in a resource pool;

– sl-TimeResourceCG-Type1: time resource location of the configured grant Type 1;

– sl-CG-MaxTransNumList: the maximum number of times that a TB can be transmitted using the configured grant;

– sl-HARQ-ProcID-offset: offset of HARQ process for configured grant Type 1;

– sl-TimeReferenceSFN-Type1: SFN used for determination of the offset of a resource in time domain. If it is present, the UE uses the first logical slot of associated resource pool after the starting time of the closest SFN with the indicated number preceding the reception of the sidelink configured grant configuration Type 1 as reference logical slot. If it is absent, the indicated reference SFN is zero.

RRC configures the following parameters when the configured grant Type 2 is configured, as specified in TS 38.331 [5]:

– sl-ConfigIndexCG: the identifier of a configured grant for sidelink;

– sl-CS-RNTI: SLCS-RNTI for activation, deactivation, and retransmission;

– sl-NrOfHARQ-Processes: the number of HARQ processes for configured grant;

– sl-PeriodCG: periodicity of the configured grant Type 2;

– sl-CG-MaxTransNumList: the maximum number of times that a TB can be transmitted using the configured grant;

– sl-HARQ-ProcID-offset: offset of HARQ process for configured grant Type 2.

Upon configuration of a configured grant Type 1, the MAC entity shall for each configured sidelink grant:

1> store the sidelink grant provided by RRC as a configured sidelink grant;

1> initialise or re-initialise the configured sidelink grant to determine PSCCH duration(s) and PSSCH duration(s) according to sl-TimeOffsetCG-Type1 and sl-TimeResourceCG-Type1, and to reoccur with sl-periodCG for transmissions of multiple MAC PDUs according to clause 8.1.2 of TS 38.214 [7].

NOTE 1: If the MAC entity is configured with multiple configured sidelink grants, collision among the configured sidelink grants may occur. How to handle the collision is left to UE implementation.

After a sidelink grant is configured for a configured grant Type 1, the MAC entity shall consider sequentially that the first slot of the S^th sidelink grant occurs in the logical slot for which:

CURRENT_slot = (sl-ReferenceSlotCG-Type1 + sl-TimeOffsetCG-Type1 + S × PeriodicitySL) modulo T’_max

where CURRENT_slot refers to current logical slot in the associated resource pool, and T’_max is the number of slots that belongs to the associated resource pool as defined in clause 8 of TS 38.214[7]. sl-ReferenceSlotCG-Type1 refers to reference logical slot defined by sl-TimeReferenceSFN-Type1.

After a sidelink grant is configured for a configured grant Type 2, the MAC entity shall consider sequentially that the first slot of S^th sidelink grant occurs in the logical slot for which:

CURRENT_slot = (sl-StartSlotCG-Type2 + S × PeriodicitySL) modulo T’_max

where sl-StartSlotCG-Type2 refers to the logical slot of the first transmission opportunity of PSSCH where the configured sidelink grant was (re)initialised.

When a configured sidelink grant is released by RRC, all the corresponding configurations shall be released and all corresponding sidelink grants shall be cleared.

The MAC entity shall:

1> if the configured sidelink grant confirmation has been triggered and not cancelled; and

1> if the MAC entity has UL resources allocated for new transmission:

2> instruct the Multiplexing and Assembly procedure to generate a Sidelink Configured Grant Confirmation MAC CE as defined in clause 6.1.3.34;

2> cancel the triggered configured sidelink grant confirmation.

For a configured grant Type 2, the MAC entity shall clear the corresponding configured sidelink grant immediately after first transmission of Sidelink Configured Grant Confirmation MAC CE triggered by the configured sidelink grant deactivation.