Bandwidth parts operation in multiple active bandwidth parts

1. A method comprising:

receiving, by a wireless device, one or more configuration parameters for uplink bandwidth parts (BWPs) of a cell;

transmitting a first preamble, for a random-access procedure, via a first uplink BWP of the uplink BWPs;

receiving a random-access response comprising a backoff indicator;

starting a backoff window associated with the backoff indicator;

selecting, for transmission of a second preamble and during the backoff window, a second uplink BWP of the uplink BWPs that is different from the first uplink BWP; and

transmitting, via the second uplink BWP and based on the selecting, the second preamble for the random-access procedure.

2. The method of claim 1 , further comprising activating at least two uplink BWPs of the uplink BWPs, the at least two uplink BWPs comprising the first uplink BWP and the second uplink BWP.

3. The method of claim 2 , further comprising:

activating the first uplink BWP in a first slot; and

activating the second uplink BWP in a second slot.

4. The method of claim 1 , further comprising performing, for the random-access procedure, a first listen-before-talk (LBT) procedure comprising a first LBT on the first uplink BWP and a second LBT on the second uplink BWP.

5. The method of claim 4 , wherein the transmitting the first preamble via the first uplink BWP is based on selecting the first uplink BWP based on:

the first LBT being successful;

the second LBT being successful; and

at least one of: channel load metrics, LBT success rates, channel occupancies, and load histories of the first and second uplink BWPs.

6. The method of claim 4 , wherein the transmitting the first preamble via the first uplink BWP is based on selecting the first uplink BWP based on:

the first LBT being successful; and

the second LBT failing.

7. The method of claim 6 , wherein the first LBT on the first uplink BWP being successful comprises a channel on the first uplink BWP being idle.

8. The method of claim 6 , wherein the second LBT on the second uplink BWP failing comprises a channel on the second uplink BWP being busy.

9. The method of claim 1 , wherein the receiving the random-access response comprising the backoff indicator further comprises receiving the random-access response comprising a medium access control protocol data unit (MAC PDU) comprising the backoff indicator.

10. The method of claim 1 , wherein the starting the backoff window associated with the backoff indicator comprises starting a backoff timer associated with the backoff indicator.

11. The method of claim 10 , further comprising stopping the backoff timer based on the selecting the second uplink BWP.

12. The method of claim 11 , further comprising performing, for transmission of the second preamble, a second LBT procedure while the backoff timer is running.

13. The method of claim 12 , wherein the performing the second LBT procedure comprising a third LBT on the first uplink BWP and a fourth LBT on the second uplink BWP.

14. The method of claim 13 , further comprising performing the second LBT procedure during the backoff window.

15. The method of claim 14 , wherein the selecting the second uplink BWP is based on the second LBT procedure.

16. The method of claim 15 , wherein the selecting the second uplink BWP is based on:

the third LBT failing; and

the fourth LBT being successful.

17. The method of claim 15 , wherein the selecting the second uplink BWP is based on:

the third LBT being successful;

the fourth LBT being successful; and

at least one of: channel load metrics, LBT success rates, channel occupancies, and load histories of the first and second uplink BWPs.

18. The method of claim 1 , wherein the random-access procedure is a contention-based random-access procedure.

19. The method of claim 1 , wherein the random-access procedure is a contention-free random-access procedure.

20. The method of claim 1 , wherein the transmitting the second preamble comprises transmitting the second preamble during the backoff window.