Timing advance acquisition in layer 1/layer 2-triggered mobility

1 . A first distributed unit for wireless communications, the first distributed unit associated with a first cell and comprising:

one or more memories storing processor-executable code; and

one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the first distributed unit to:

transmit, to a central unit associated with the first distributed unit, a first indication of a set of random access channel preambles for timing advance information acquisition in association with a triggered cell switch to the first cell;

receive, from a user equipment (UE) associated with a second cell, a random access channel message indicating a random access channel preamble of the set of random access channel preambles; and

transmit, to the central unit, a second indication of timing advance information associated with the random access channel message.

2 . The first distributed unit of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first distributed unit to:

receive, from the central unit, a request for the first distributed unit to allocate the set of random access channel preambles for the timing advance information acquisition, wherein the request includes an identifier of a second distributed unit, and wherein the first indication is transmitted in response to the request.

3 . The first distributed unit of claim 1 , wherein the second indication indicates an identifier of the first cell, an identifier associated with the random access channel preamble, the random access channel preamble, a random access channel occasion via which the random access channel message is received, a timestamp of reception of the random access channel message, an indication of a second distributed unit, or a combination thereof.

4 . The first distributed unit of claim 1 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the first distributed unit to:

receive, from the central unit, a third indication of respective allocations of one or more random access channel preambles of the set of random access channel preambles to respective distributed units of a set of distributed units associated with the central unit, wherein the second indication indicates a second distributed unit of the set of distributed units and associated with the second cell based at least in part on the random access channel preamble being included in a respective allocation of one or more random access channel preambles to the second distributed unit.

5 . The first distributed unit of claim 1 , wherein, to transmit the second indication, the one or more processors are individually or collectively operable to execute the code to cause the first distributed unit to:

transmit the second indication via non-UE associated signaling.

6 . The first distributed unit of claim 1 , wherein the triggered cell switch to the first cell is a layer 1 triggered cell switch or layer 2 triggered cell switch.

7 . A central unit for wireless communications, comprising:

one or more memories storing processor-executable code; and

one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the central unit to:

receive, from a first distributed unit associated with the central unit, a first indication of a set of random access channel preambles for timing advance information acquisition in association with a triggered cell switch to a first cell associated with the first distributed unit;

transmit, to a second distributed unit associated with the central unit, a second indication of one or more random access channel preambles of the set of random access channel preambles allocated to the second distributed unit for the timing advance information acquisition;

receive, from the first distributed unit, a third indication of timing advance information associated with a random access channel message indicating a random access channel preamble of the one or more random access channel preambles; and

transmit, to the second distributed unit, a fourth indication of the timing advance information.

8 . The central unit of claim 7 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the central unit to:

transmit, to the first distributed unit, a request for the first distributed unit to allocate the set of random access channel preambles for the timing advance information acquisition, wherein the request includes an identifier of the second distributed unit, and wherein the first indication is received in response to the request.

9 . The central unit of claim 7 , wherein, to transmit the fourth indication, the one or more processors are individually or collectively operable to execute the code to cause the central unit to:

transmit the fourth indication to the second distributed unit based at least in part on the third indication indicating the random access channel preamble and the random access channel preamble being included in the one or more random access channel preambles allocated to the second distributed unit.

10 . The central unit of claim 7 , wherein the one or more processors are individually or collectively further operable to execute the code to cause the central unit to:

transmit, to the first distributed unit, a fifth indication of the allocation of the one or more random access channel preambles to the second distributed unit,

wherein the third indication indicates the second distributed unit based at least in part on the fifth indication and the random access channel preamble being included in the one or more random access channel preambles allocated to the second distributed unit, and

wherein the fourth indication is transmitted to the second distributed unit based at least in part on the third indication indicating the second distributed unit.

11 . The central unit of claim 7 , wherein:

the third indication indicates an identifier of the first cell, an identifier associated with the random access channel preamble, a random access channel occasion via which the random access channel message is received at the first distributed unit, a timestamp of a reception of the random access channel message at the first distributed unit, or a combination thereof, and

the fourth indication indicates the identifier of the first cell, the identifier associated with the random access channel preamble, the random access channel occasion, the timestamp of the reception of the random access channel message at the first distributed unit, or a combination thereof.

12 . The central unit of claim 7 , wherein, to transmit the fourth indication, the one or more processors are individually or collectively operable to execute the code to cause the central unit to:

transmit the fourth indication to the second distributed unit based at least in part on the third indication indicating an identifier associated with the random access channel preamble and a random access channel occasion via which the random access channel message is received at the first distributed unit,

wherein a combination of the identifier and the random access channel occasion indicates the second distributed unit as having ordered a transmission of the random access channel message.

13 . The central unit of claim 7 , wherein, to transmit the second indication, the one or more processors are individually or collectively operable to execute the code to cause the central unit to:

transmit the second indication to a set of distributed units comprising the second distributed unit, the second indication indicating an allocation of the one or more random access channel preambles to each distributed unit of the set of distributed units,

wherein the fourth indication is transmitted to the set of distributed units based at least in part on the one or more random access channel preambles being allocated to each distributed unit of the set of distributed units.

14 . The central unit of claim 7 , wherein, to receive the third indication, the one or more processors are individually or collectively operable to execute the code to cause the central unit to:

receive the third indication via non-UE associated signaling.

15 . A second distributed unit for wireless communications, the second distributed unit associated with a second cell and comprising:

one or more memories storing processor-executable code; and

one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the second distributed unit to:

receive, from a central unit associated with the second distributed unit, a first indication of a set of random access channel preambles for timing advance information acquisition in association with a triggered cell switch to a first cell associated with a first distributed unit;

transmit, to a user equipment (UE) associated with the first cell, a second indication to transmit, to the first cell, a random access channel message indicating a random access channel preamble of the set of random access channel preambles;

receive from the central unit, a third indication of timing advance information associated with the random access channel message; and

transmit, to the UE, a fourth indication of the timing advance information.

16 . The second distributed unit of claim 15 , wherein the one or more memories and individually or collectively operable to execute the code to cause the second distributed unit to:

transmit the fourth indication via a random access response or via a cell switch indication for the UE to switch to the second cell.

17 . The second distributed unit of claim 15 , wherein the one or more memories and individually or collectively operable to execute the code to cause the second distributed unit to:

transmit, to the central unit, a request to be allocated the set of random access channel preambles for the timing advance information acquisition, wherein the first indication is received in response to the request.

18 . The second distributed unit of claim 15 , wherein the one or more memories and individually or collectively operable to execute the code to cause the second distributed unit to:

determine that the timing advance information is associated with the random access channel message transmitted by the UE based at least in part on transmission of the second indication.

19 . The second distributed unit of claim 15 , wherein the third indication indicates an identifier of the first cell, an identifier associated with the random access channel preamble, a random access channel occasion via which the random access channel message is received at the first distributed unit, a timestamp of a reception of the random access channel message at the first distributed unit, or a combination thereof.

20 . The second distributed unit of claim 19 , wherein the one or more memories and individually or collectively operable to execute the code to cause the second distributed unit to:

determine that the timing advance information is associated with the random access channel message transmitted by the UE based at least in part on the identifier of the first cell, the identifier associated with the random access channel preamble, the random access channel occasion, the timestamp, or a combination thereof.