MBMS and PMCH in unlicensed bands
Systems and methods are disclosed that enable multi-cast transmissions (e.g., Physical Multi-cast Channel (PMCH) transmissions) on carriers in unlicensed spectrum. In some embodiments, a method of operation of a radio access node to enable multi-cast transmissions on a carrier in an unlicensed spectrum comprises performing a Listen-Before-Talk (LBT) procedure on a carrier in an unlicensed spectrum based on random backoff and a contention window size prior to a multi-cast transmission. The method further comprises transmitting the multi-cast transmission if the LBT procedure determines that the carrier in the unlicensed spectrum is Idle. In this manner, multi-cast transmissions on the carrier in the unlicensed spectrum are enabled.
1. A method of operation of a radio access node to enable multi-cast transmissions on a carrier in an unlicensed spectrum, comprising:
performing a Listen-Before-Talk, LBT, procedure on a carrier in an unlicensed spectrum based on random backoff and a contention window size prior to a multi-cast transmission; and
transmitting the multi-cast transmission if the LBT procedure determines that the carrier in the unlicensed spectrum is Idle;
wherein a backoff counter for the LBT procedure is determined based on reception of preambles from radio access nodes of a same or different technology.
2. The method of claim 1 wherein the contention window size is a fixed contention window size.
3. The method of claim 2 wherein the fixed contention window size is defined based on any one or more of:
the fixed contention window size is set to a largest possible contention window size used in Category 4 LBT for downlink Physical Downlink Shared Channel, PDSCH, transmissions;
the fixed contention window size is set to a smallest possible contention window size used in Category 4 LBT for downlink PDSCH transmissions;
the fixed contention window size is predefined; and
the fixed contention window size is determined based on one or more observed operation channel conditions.
4. The method of claim 1 wherein the backoff counter for the LBT procedure is set to a deterministic value.
5. The method of claim 1 wherein the contention window size is an adaptive contention window size.
6. The method of claim 5 further comprising:
receiving feedback from a wireless device; and
configuring the adaptive content window size based on the feedback.
7. The method of claim 6 wherein the feedback comprises a number of subframes successfully decoded by the wireless device in one or more previous multi-cast transmissions.
8. The method of claim 6 wherein receiving the feedback comprises receiving the feedback in a portion of a last slot of a last Multi-cast Broadcast Single Frequency Network, MBSFN, subframe of a previous multi-cast transmission.
9. The method of claim 1 wherein the multi-cast transmission comprises one or more multi-cast transmissions, and at least one of the multi-cast transmissions is limited to a portion of a respective MBSFN subframe.
10. The method of claim 9 wherein the portion of the respective MBSFN subframe is a first slot of the MBSFN subframe.
11. The method of claim 9 wherein the portion of the respective MBSFN subframe is a second slot of the MBSFN subframe.
12. The method of claim 1 wherein the multi-cast transmission is a Physical Multi-cast Channel, PMCH, burst.