Reliable transmission of multicast and broadcast services

1. A method comprising:

receiving, by a wireless device from a base station, parameters comprising:

a radio network temporary identifier (RNTI) associated with a multicast and broadcast service (MBS) session;

a first scrambling identity associated with the MBS session; and

a second scrambling identity associated with unicast transmissions;

receiving, based on the RNTI, a group common downlink control information (DCI) scheduling a transport block (TB) of the MBS session;

based on the group common DCI being received based on the RNTI, determining a scrambling identity for the TB being equal to the first scrambling identity; and

receiving the TB being scrambled with a scrambling sequence initialized by:

the determined scrambling identity; and

the RNTI.

2. The method of claim 1 , wherein:

the group common DCI is addressed to a plurality of wireless devices comprising the wireless device; and

the TB, scheduled by the group common DCI, is addressed to the plurality of wireless devices.

3. The method of claim 1 , comprising receiving the group common DCI based on cyclic redundancy check (CRC) bits, of the group common DCI, being scrambled by the RNTI.

4. The method of claim 1 , further comprising receiving a unicast DCI scheduling a second TB based on CRC bits, of the unicast DCI, being scrambled by a second RNTI, wherein the second RNTI is different from the RNTI.

5. The method of claim 4 , further comprising:

based on the unicast DCI being received based on the second RNTI, determining a scrambling identity for the second TB being equal to the second scrambling identity; and

receiving the second TB being scrambled with a second scrambling sequence initialized by:

the second scrambling identity; and

the second RNTI.

6. The method of claim 1 , wherein the parameters indicate common frequency resources, associated with the MBS session, within a bandwidth part (BWP) of a cell.

7. The method of claim 6 , comprising receiving the group common DCI and the TB in the common frequency resources within the BWP.

8. The method of claim 6 , wherein the parameters indicate:

a starting resource block (RB) of RBs of the common frequency resources; and

a number of the RBs.

9. The method of claim 8 , wherein an RB of the RBs comprises one or more resource elements in a frequency domain.

10. The method of claim 8 , wherein the RBs of the common frequency resources are a subset of RBs of the BWP.

11. A wireless device comprising:

one or more processors; and

memory storing instructions that, when executed by the one or more processors, cause the wireless device:

receive parameters, from a base station, comprising:

a radio network temporary identifier (RNTI) associated with a multicast and broadcast service (MBS) session;

a first scrambling identity associated with the MBS session; and

a second scrambling identity associated with unicast transmissions;

receive, based on the RNTI, a group common downlink control information (DCI) scheduling a transport block (TB) of the MBS session;

based on the group common DCI being received based on the RNTI, determine a scrambling identity for the TB being equal to the first scrambling identity; and

receive the TB being scrambled with a scrambling sequence initialized by:

the determined scrambling identity; and

the RNTI.

12. The wireless device of claim 11 , wherein:

the group common DCI is addressed to a plurality of wireless devices comprising the wireless device; and

the TB, scheduled by the group common DCI, is addressed to the plurality of wireless devices.

13. The wireless device of claim 11 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to receive the group common DCI based on cyclic redundancy check (CRC) bits, of the group common DCI, being scrambled by the RNTI.

14. The wireless device of claim 11 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to receive a unicast DCI scheduling a second TB based on CRC bits, of the unicast DCI, being scrambled by a second RNTI, wherein the second RNTI is different from the RNTI.

15. The wireless device of claim 14 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:

based on the unicast DCI being received based on the second RNTI, determine a scrambling identity for the second TB being equal to the second scrambling identity; and

receive the second TB being scrambled with a second scrambling sequence initialized by:

the second scrambling identity; and

the second RNTI.

16. The wireless device of claim 11 , wherein the parameters indicate common frequency resources, associated with the MBS session, within a bandwidth part (BWP) of a cell.

17. The wireless device of claim 16 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to receive the group common DCI and the TB in the common frequency resources within the BWP.

18. The wireless device of claim 16 , wherein the parameters indicate:

a starting resource block (RB) of RBs of the common frequency resources; and

a number of the RBs.

19. The wireless device of claim 18 , wherein an RB of the RBs comprises one or more resource elements in a frequency domain.

20. The wireless device of claim 18 , wherein the RBs of the common frequency resources are a subset of RBs of the BWP.