Techniques for contending for access to channels of a shared radio frequency spectrum band for broadcast/multicast transmissions

1. A method for wireless communications, comprising:

determining a previous contention window size for a transmission over a shared radio frequency spectrum band;

determining, based at least in part on a unicast reception status of at least a unicast transmission over the shared radio frequency spectrum band, a current contention window size for a first multipoint transmission on at least one channel of the shared radio frequency spectrum band, wherein the first multipoint transmission is targeted for a first plurality of user equipments (UEs), wherein determining the current contention window size further comprises:

increasing the current contention window size compared with the previous contention window size upon receiving one or more non-acknowledgements (NAKs) for the unicast transmission; or

decreasing the current contention window size or leaving the current contention window size the same compared with the previous contention window size upon receiving one or more acknowledgements (ACKs) for the unicast transmission; and

contending for access to the at least one channel of the shared radio frequency spectrum band for the first multipoint transmission based at least in part on the determined current contention window size.

2. The method of claim 1 , wherein the first multipoint transmission comprises a first broadcast transmission or a first multicast transmission.

3. The method of claim 1 , wherein the first multipoint transmission comprises a coordinated multipoint transmission.

4. The method of claim 1 , further comprising:

determining a load on the at least one channel of the shared radio frequency spectrum band;

wherein determining the current contention window size is further based at least in part on the determined load.

5. The method of claim 1 , further comprising:

multiplexing the at least one unicast transmission with the first multipoint transmission on the at least one channel of the shared radio frequency spectrum band; and

determining the unicast reception status based at least in part on identifying the one or more ACKs or NAKs received for the at least one unicast transmission;

wherein determining the current contention window size is further based at least in part on the ACKs or NAKs identified for the at least one unicast transmission.

6. The method of claim 1 , further comprising:

receiving, from each user equipment (UE) of a second plurality of UEs, an additional UE reception status of a second multipoint transmission on the at least one channel of the shared radio frequency spectrum band, wherein the second multipoint transmission is transmitted before the first multipoint transmission and targeted for the second plurality of UEs;

wherein determining the current contention window size is further based at least in part on the additional UE reception statuses.

7. The method of claim 6 , wherein each UE reception status of the second multipoint transmission comprises a UE block error rate (BLER) for the second multipoint transmission.

8. The method of claim 6 , further comprising:

receiving identifications of broadcast services of interest from each UE of at least the second plurality of UEs;

identifying the second plurality of UEs from the received identifications; and

triggering the second plurality of UEs to transmit the additional UE reception statuses for the second multipoint transmission.

9. The method of claim 6 , wherein the first plurality of UEs and the second plurality of UEs comprise a same plurality of UEs or different pluralities of UEs.

10. The method of claim 1 , wherein the at least one channel comprises at least a first channel and a second channel, and the first multipoint transmission comprises a multiple channel multipoint transmission over at least the first channel and the second channel.

11. The method of claim 10 , further comprising:

determining the unicast reception status based at least in part on the one or more ACKS or NAKs corresponding to the at least one unicast transmission, wherein the at least one unicast transmission is transmitted on one or more of a plurality of channels of the shared radio frequency spectrum band, the plurality of channels including the at least one channel on which the first multipoint transmission is transmitted.

12. The method of claim 1 , wherein the first multipoint transmission comprises a multicast-broadcast single-frequency network (MBSFN) transmission, a single cell enhanced multimedia broadcast multicast services (eMBMS) transmission, a single cell point to multipoint (SC-PTM) transmission, or a combination thereof.

13. The method of claim 1 , wherein determining, based at least in part on the unicast reception status of the shared radio frequency spectrum band, the contention window size further comprises:

increasing the current contention window size compared with the previous contention window size upon receiving more than a threshold number of NAKs for the unicast transmission.

14. The method of claim 1 , wherein determining the current contention window size is further based on a current Listen-Before-Talk (LBT) burst.

15. An apparatus for wireless communications, comprising:

a processor;

memory coupled to the processor; and

the processor and the memory configured to:

determine a previous contention window size for a transmission over a shared radio frequency spectrum band;

determine, based at least in part on a unicast reception status of at least a unicast transmission over the shared radio frequency spectrum band, a current contention window size for a first multipoint transmission on at least one channel of the shared radio frequency spectrum band, wherein the first multipoint transmission is targeted for a first plurality of user equipments (UEs), wherein determine the current contention window size further comprises:

increase the current contention window size compared with the previous contention window size upon receiving one or more non-acknowledgements (NAKs) for the unicast transmission; or

decrease the current contention window size or leave the current contention window size the same compared with the previous contention window size upon receiving one or more acknowledgements (ACKs) for the unicast transmission; and

contend for access to the at least one channel of the shared radio frequency spectrum band for the first multipoint transmission based at least in part on the determined current contention window size.

16. The apparatus of claim 15 , wherein the first multipoint transmission comprises a first broadcast transmission or a first multicast transmission.

17. The apparatus of claim 15 , wherein the first multipoint transmission comprises a coordinated multipoint transmission.

18. The apparatus of claim 15 , wherein the processor and the memory are configured to:

determine a load on the at least one channel of the shared radio frequency spectrum band;

wherein determine the current contention window size is further based at least in part on the determined load.

19. The apparatus of claim 15 , wherein the processor and the memory are configured to:

multiplex the at least one unicast transmission with the first multipoint transmission on the at least one channel of the shared radio frequency spectrum band; and

determine the unicast reception status based at least in part on identifying the one or more ACKs or NAKs received for the at least one unicast transmission;

wherein determine the current contention window size is further based at least in part on the ACKs or NAKs identified for the at least one unicast transmission.

20. The apparatus of claim 15 , wherein the processor and the memory are configured to:

receive from each user equipment (UE) of a second plurality of UEs, an additional UE reception status of a second multipoint transmission on the at least one channel of the shared radio frequency spectrum band, wherein the second multipoint transmission is transmitted before the first multipoint transmission and targeted for the second plurality of UEs;

wherein determine the current contention window size is further based at least in part on the UE reception statuses.

21. The apparatus of claim 20 , wherein each UE reception status of the second multipoint transmission comprises a UE block error rate for the second multipoint transmission.

22. The apparatus of claim 15 , wherein the at least one channel comprises at least a first channel and a second channel, and the first multipoint transmission comprises a multiple channel multipoint transmission over at least the first channel and the second channel.

23. The apparatus of claim 22 , wherein the processor and the memory are configured to:

determine the unicast reception status based at least in part on identifying the one or more ACKs or NAKs corresponding to the at least one unicast transmission, wherein the at least one unicast transmission is transmitted on one or more of a plurality of channels of the shared radio frequency spectrum band, the plurality of channels including the at least one channel on which the first multipoint transmission is transmitted;

wherein determining the current contention window size is further based at least in part on the plurality of ACKs or NAKs.

24. The apparatus of claim 15 , wherein the first multipoint transmission comprises a multicast-broadcast single-frequency network (MBSFN) transmission, a single cell enhanced multimedia broadcast multicast services (eMBMS) transmission, a single cell point to multipoint (SC-PTM) transmission, or a combination thereof.