Timing control for integrated access and backhaul (IAB)

1. An apparatus, comprising:

at least one processor; and

at least one memory comprising computer program code,

the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to

receive an indication that an integrated access and backhaul (IAB) node is capable of transmitting spatial division multiplexing (SDM);

determine a resource configuration and using the determined resource configuration to set a timing advance (TA) mode with two offsets comprising a first offset to be used with time division multiplexing (TDM) and a second offset to be used with at least one of spatial division multiplexing (SDM) or frequency division multiplexing (FDM); and

transmit a command, to the integrated access and backhaul (IAB) node, to start adjusting mobile termination (MT) uplink (UL) transmission (Tx) timing based on the determined resource configuration and the timing advance (TA).

2. The apparatus according to claim 1 , wherein, when the resource configuration indicates that at least one of SDM or FDM mode with timing alignment is used, MT timing follows the second offset and, when the resource configuration indicates not to use at least one of SDM or FDM mode with timing alignment, MT timing follows the first offset.

3. The apparatus according to claim 1 , further comprising receiving an uplink signal, from the TAB node, according to one of the first offset or the second offset that the MT timing follows, wherein the first offset is based on legacy TA control and the second offset aligns MT Tx with distributed unit (DU) Tx.

4. The apparatus according to claim 1 , wherein a time difference between the first offset and the second offset depends on a propagation delay (TP) on a link between a parent node and the IAB node, wherein said apparatus comprises the parent node.

5. The apparatus according to claim 1 , wherein, when multiple IAB nodes are present, scheduling of MT UL Tx with different UL reference timing is time division duplexed with respect to each other.

6. The apparatus according to claim 1 , wherein the transmitting of the command comprises providing the command to start adjusting the MT UL Tx timing at least partially based on the resource configuration.

7. The apparatus according to claim 1 , wherein, when multiple panels are present or available, the transmitting of the command comprises providing an explicit indication in downlink (DL) or uplink (UL) grant to indicate whether the first offset or the second offset should be applied.

8. The apparatus according to claim 1 , wherein the first offset supports simultaneous MT Tx and DU Tx via different panels, and the second offset supports simultaneous MT Tx and DU Tx via the same panel.

9. The apparatus according to claim 1 , wherein the MT UL Tx is determined based on a valid UL scheduling grant.

10. The apparatus according to claim 1 , wherein the MT UL Tx is determined based on information including at least one of MT resource configuration or dynamic slot format indication (SFI) indicated using downlink control information (DCI) format 2_0.

11. An apparatus, comprising:

at least one processor; and

at least one memory comprising computer program code,

the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to

transmit an indication to a parent node, that the apparatus is capable of transmitting spatial division multiplexing (SDM);

receive a command, from the parent node, to start adjusting mobile termination (MT) uplink (UL) transmission (Tx) timing based on a resource configuration,

wherein, when the resource configuration indicates that at least one of spatial division multiplexing (SDM) or frequency division multiplexing (FDM) mode with timing alignment is used, MT timing follows a second offset and, when the resource configuration indicates not to use at least one of SDM or FDM mode with timing alignment, MT timing follows a first offset.

12. The apparatus according to claim 11 , wherein the apparatus is initially operating according to time division multiplexing (TDM) mode and MT is operating according to legacy timing advance (TA) commands.

13. The apparatus according to claim 11 , wherein the first offset is based on legacy timing advance (TA) control and the second offset aligns MT UL Tx with distributed unit (DU) Tx.

14. The apparatus according to claim 11 , wherein a time difference between the first offset and the second offset depends on the propagation delay (TP) on a link between a IAB node and the parent node, wherein said apparatus comprises the IAB node.

15. The apparatus according to claim 11 , wherein the receiving of the command comprises receiving the command to start adjusting the MT UL Tx timing at least partially based on the resource configuration.

16. The apparatus according to claim 11 , wherein, when multiple panels are present, the receiving of the command comprises receiving an explicit indication in downlink (DL) or uplink (UL) grant to indicate whether the first offset or the second offset should be applied.

17. The apparatus according to claim 11 , wherein the first offset supports simultaneous MT Tx and DU Tx via different panels, and the second offset supports simultaneous MT Tx and DU Tx via the same panel.

18. The apparatus according to claim 11 , wherein the MT UL Tx is determined based on a valid UL scheduling grant.

19. The apparatus according to claim 11 , wherein the MT UL Tx is determined based on information including at least one of MT resource configuration or dynamic slot format indication (SFI) indicated using downlink control information (DCI) format 2_0.

20. A method, comprising:

receiving, at a parent node, an indication that an integrated access and backhaul (IAB) node is capable of transmitting spatial division multiplexing (SDM);

determining, at the parent node, a resource configuration and using the determined resource configuration to set a timing advance (TA) mode with two offsets comprising a first offset to be used with time division multiplexing (TDM) and a second offset to be used with at least one of spatial division multiplexing (SDM) or frequency division multiplexing (FDM); and

transmitting a command, to the integrated access and backhaul (IAB) node, to start adjusting mobile termination (MT) uplink (UL) transmission (Tx) timing based on the determined resource configuration and the timing advance (TA).