Content for  TS 38.321  Word version:  18.0.0

For IAB operation, in order to achieve time-domain synchronization across multiple backhaul hops, a timing adjustment may be provided to an IAB node by its parent node. Two different values may be provided, related to Case-1/Case-6, and Case-7 timing modes respectively. The Timing Delta MAC CE carries T_delta which is used to determine the IAB-DU DL Tx timing adjustment for the Case-1 timing mode, and to determine the IAB-DU DL Tx and IAB-MT UL Tx timing adjustment for the Case-6 timing mode. The Case-7 Timing advance offset MAC CE carries T_offset,2 which is used to determine the IAB-MT UL Tx timing adjustment for the Case-7 timing mode. Upon reception of a Timing Delta MAC CE the IAB node shall:

• apply the value of T_delta as specified in TS 38.213.

Upon reception of a Case-7 Timing advance offset MAC CE the IAB node shall:

• apply the value of T_offset,2 as specified in TS 38.213.

For IAB operation, the MAC entity on the IAB-DU or IAB-donor-DU reserves a sufficient number of symbols at the beginning and/or the end of slots where the child IAB-node switches operation from its IAB-DU to its IAB-MT function and operation from its IAB-MT to its IAB-DU function. The MAC entity on the IAB-DU or IAB-donor-DU informs the child node about the number of guard symbols it provides via the Provided Guard Symbols MAC CE. The IAB-MT on the child node may inform the parent IAB-DU or IAB-donor-DU about the number of guard symbols desired via the Desired Guard Symbols MAC CE. IAB-MT transmission timing modes are specified in clause 14 of TS 38.213. Upon reception of a Provided Guard Symbols MAC CE the MAC entity shall:

• indicate to lower layers the number of provided guard symbols and the SCS configuration for the indicated Serving Cell.

The MAC entity may: If the MAC entity has UL resources allocated for new transmission the MAC entity shall: For Case-1 timing mode, a separate value for the number of guard symbols is specified for each of the following eight switching scenarios (see Table 5.18.19-1).

For Case-6 and Case-7 timing modes, a separate value for the number of guard symbols is specified for each of the following eight switching scenarios (see Table 5.18.19-2):

If the UE is configured with pre-configured measurement gaps, the network may send DL MAC CE for Positioning Measurement Gap Activation/Deactivation Command to the UE as in clause 6.1.3.41. For the activated measurement gap, the UE shall follow the specified UE behaviour in clause 5.14. Upon the reception of the MAC CE for Positioning Measurement Gap Activation/Deactivation Command, the MAC entity shall:

If the UE is configured with pre-configured PPW, the network may send DL MAC CE for PPW Activation/Deactivation Command to the UE as in clause 6.1.3.42. For the activated PPW, the UE shall follow the specified UE behaviour in clause 5.24. Upon activation of DL BWP, the PPW(s) configured for that BWP are considered deactivated. Upon reconfiguration of PPW(s) of the active DL BWP, all the PPW(s) for that BWP are considered deactivated. Upon the reception of the MAC CE for PPW Activation/Deactivation Command, the MAC entity shall:

The network may activate and deactivate PUCCH power control set(s) for multiple TRP PUCCH repetition for a PUCCH resource or a PUCCH resource group of a Serving Cell by sending the PUCCH Power Control Set Update for multiple TRP PUCCH repetition MAC CE described in clause 6.1.3.46. The MAC entity shall:

The network may activate and deactivate the configured unified TCI states of a Serving Cell or a set of Serving Cells configured in simultaneousU-TCI-UpdateList1, simultaneousU-TCI-UpdateList2, simultaneousU-TCI-UpdateList3 or simultaneousU-TCI-UpdateList4 by sending the Unified TCI States Activation/Deactivation MAC CE described in clause 6.1.3.47. The configured unified TCI states are initially deactivated upon (re-)configuration by upper layers and after reconfiguration with sync. The MAC entity shall:

The network may provide and update the Differential Koffset of a Serving Cell in a non-terrestrial network by sending the Differential Koffset MAC CE described in clause 6.1.3.57. The MAC entity shall:

The network may activate and deactivate the configured beam failure detection resources of a Serving Cell by sending the BFD-RS indication MAC CE described in clause 6.1.3.58. The MAC entity shall:

Child IAB-DU Restricted Beam Indication MAC CE is used by an IAB-node to indicate to its child node spatial resources and associated frequency information where simultaneous transmission/reception from the IAB-MT and transmission from the IAB-DU cells is restricted. IAB-MT Recommended Beam Indication MAC CE is used by an IAB-node to indicate to its parent node recommendations for such a restriction. Time resources where these restrictions/recommendations can apply are indicated via RRC, while the MAC CE further selects from these time resources the specific time resource configuration (comprising a list of slot indices) to which information provided in the MAC CE applies. Upon reception of a Child IAB-DU Restricted Beam Indication MAC CE the IAB-node shall:

• apply the configuration signalled in the MAC CE to the time slots indicated in IAB-ResourceConfig (as specified in TS 38.331) which contains iab-ResourceConfigID parameter which matches the Resource Configuration ID field of the MAC CE.

The MAC entity may: If the MAC entity has UL resources allocated for new transmission the MAC entity shall:

DL TX Power Adjustment MAC CE is used by an IAB-node to indicate to its child node spatial resources and associated frequency information where the DL TX power adjustment contained in the MAC CE applies. Desired DL TX Power Adjustment MAC CE is used by an IAB-node to indicate to its parent node recommendations for such a restriction. Time resources where these restrictions/recommendations can apply are indicated via RRC, while the MAC CE further selects from these time resources the specific time resource configuration (comprising a list of slot indices) to which information provided in the MAC CE applies. Upon reception of a DL TX Power Adjustment MAC CE the IAB-node shall:

• apply the configuration signalled in the MAC CE to the time slots indicated in IAB-ResourceConfig (as specified in TS 38.331) which contains iab-ResourceConfigID parameter which matches the Resource Configuration ID field of the MAC CE.

The MAC entity may: If the MAC entity has UL resources allocated for new transmission the MAC entity shall:

Desired IAB-MT PSD range MAC CE is used by an IAB-node to indicate to its parent node a recommendation of spatial resources and associated frequency information where the desired PSD range, contained in the MAC CE (and provided to help with the node's UL TX power control) could apply. Time resources where these recommendations can apply are indicated via RRC, while the MAC CE further selects from these time resources the specific time resource configuration (comprising a list of slot indices) to which information provided in the MAC CE applies. The MAC entity may: If the MAC entity has UL resources allocated for new transmission the MAC entity shall:

Timing Case Indication MAC CE is used by an IAB-node to indicate to its child node timing modes which should apply to time resources indicated via RRC. Upon reception of a Timing Case Indication MAC CE the IAB-node shall:

• apply the configuration signalled in the MAC CE to the time slots indicated in IAB-ResourceConfig which contains iab-ResourceConfigID parameter (as specified in TS 38.331) which matches the Resource Configuration ID field of the MAC CE.

The Case-6 Timing Request MAC CE is used by the IAB-MT to inform its parent node whether Case-6 timing is required for simultaneous operation. The MAC entity may: If the MAC entity has UL resources allocated for new transmission the MAC entity shall:

NCR Downlink Backhaul Link Beam Indication MAC CE and NCR Uplink Backhaul Link Beam Indication MAC CE are used by a gNB to indicate to an NCR-node the beam to be used for the downlink and uplink backhaul transmission respectively between the gNB and the NCR-node. Upon reception of an NCR Downlink Backhaul Link Beam Indication MAC CE, the NCR-node shall:

• indicate to NCR-Fwd to apply the configuration contained in NCR Downlink Backhaul Link Beam Indication MAC CE as received by the NCR-MT.

Upon reception of an NCR Uplink Backhaul Link Beam Indication MAC CE, the NCR-node shall:

• indicate to NCR-Fwd to apply the configuration contained in the NCR Uplink Backhaul Link Beam Indication MAC CE as received by the NCR-MT.

NCR Access Link Beam Indication MAC CE is used by a gNB to indicate to an NCR-node the forwarding resources to be used for the semi-persistent access link transmission between the NCR-node and the UE(s) served by this device. Upon reception of an NCR Access Link Beam Indication MAC CE, the NCR-node shall:

• apply the configuration signalled in the MAC CE as received by NCR-MT to the forwarding resource lists indicated via RRC, and use it to operate the NCR-Fwd.

The network may activate and deactivate the configured unified TCI states of a Serving Cell or a set of Serving Cells configured in simultaneousU-TCI-UpdateList1, simultaneousU-TCI-UpdateList2, simultaneousU-TCI-UpdateList3 or simultaneousU-TCI-UpdateList4 by sending the Enhanced Unified TCI States Activation/Deactivation MAC CE described in clause 6.1.3.70 and 6.1.3.71. The configured unified TCI states are initially deactivated upon (re-)configuration by upper layers and after reconfiguration with sync. The MAC entity shall:

The network activates and deactivates PSI-based SDU discard by sending the PSI-Based SDU Discard Activation/Deactivation MAC CE described in clause 6.1.3.73. The PSI-based SDU discard is initially deactivated upon (re-)configuration by upper layers and after reconfiguration with sync. The MAC entity shall for each DRB configured with PSI-based SDU discard:

The network may instruct the UE to perform LTM cell switch procedure by sending the LTM Cell Switch Command MAC CE described in clause 6.1.3.75. The MAC entity shall:

The network may activate and deactivate the TCI states of LTM candidate cell(s) configured in CandidateTCI-State and CandidateTCI-UL-State by sending the Candidate Cell TCI States Activation/Deactivation MAC CE described in clause 6.1.3.76. The MAC entity shall: