Handling of directional UL LBT failures

1 . A method of controlling wireless transmissions in a wireless communication system, the method comprising:

on a single serving transmission beam selected from a plurality of transmission beams, a wireless device sending listen before talk (LBT) based uplink wireless transmissions to an access node;

the wireless device detecting LBT failures on the single serving transmission beam; and

based on a number of the detected LBT failures on the single serving transmission beam exceeding a predetermined threshold for the beam, the wireless device sending a failure report to the access node, the failure report indicating the detected LBT failures on the single serving transmission beam.

2 . The method of claim 1 , wherein the failure report comprises an identifier of the serving transmission beam and identifies:

one or more candidate transmission beams for selection of a new serving transmission beam;

at least one synchronization block (SSB) or SSB group corresponding to the one or more candidate transmission beams;

channel state information reference signal (CSI-RS) resources associated with the one or more candidate transmission beams;

sounding reference signal (SRS) resources associated with the one or more candidate transmission beams; and

transmission configuration indicator (TCI) states associated with the one or more candidate transmission beams.

3 . The method of claim 1 , comprising the wireless device:

selecting a second transmission beam of the plurality of transmission beams;

sending the failure report on the second transmission beam;

performing a random access procedure on the second transmission beam; and

the wireless device sending the failure report by at least one message of the random access procedure.

4 . The method of claim 3 , comprising the wireless device:

sending the failure report by a random access preamble message of the random access procedure or a scheduled transmission, wherein the random access preamble message is:

provided with an indicator for indicating the failure report and a random access preamble that is allocated for indicating the failure report; and

sent on a random access occasion that is allocated for indicating the failure report.

5 . The method of claim 3 , comprising the wireless device sending the failure report by a radio resource control (RRC) message included in a message of the random access procedure, wherein the RRC message includes an indicator for indicating the failure report.

6 . The method of claim 3 , comprising the wireless device sending the failure report on one or more resources of an uplink control channel of the second transmission beam, wherein the one or more resources are configured for indicating the failure report.

7 . The method of claim 1 , comprising the wireless device reporting additional information associated with the failure report, wherein the additional information comprises at least one of: channel occupancy, LBT statistics, one or more radio quality indicators, one or more quality of service indicators, one or more buffer status reports, and one or more power headroom reports.

8 . The method of claim 1 , comprising the wireless device:

sending the failure report in response to the number of detected LBT failures reaching a threshold value;

monitoring the number of detected LBT failures by a counter;

starting a timer upon detecting an LBT failure;

sending the failure report in response to the counter reaching the threshold value; and

resetting the counter to zero, upon expiry of the timer before the counter reaches the threshold value, the wireless device.

9 . A method of controlling wireless transmissions in a wireless communication system, the method comprising:

on a single serving transmission beam selected from a plurality of transmission beams, an access node receiving listen before talk (LBT) based uplink wireless transmissions from a wireless device;

the access node receiving a failure report from the wireless device, the failure report indicating a number of detected LBT failures on the single serving transmission beam exceeding a predetermined threshold for the single serving transmission beam; and

based on the failure report, the access node controlling switching of the wireless device to a new serving transmission beam.

10 . The method of claim 9 , wherein the failure report comprises an identifier of the serving transmission beam and identifies one or more candidate transmission beams for selection of the new serving transmission beam.

11 . The method of claim 9 , comprising in response to the failure report, the access node initiating switching of the wireless device to a new serving transmission beam utilizing frequency resources that correspond to frequency resources used on the serving transmission beam.

12 . The method of claim 9 , comprising in response to the failure report, the access node initiating switching of the wireless device to a new serving transmission beam and to frequency resources that differ from the frequency resources used on the serving transmission beam.

13 . The method of claim 12 , wherein the frequency resources on a new transmission beam and the frequency resources on the transmission beam differ with respect to utilized frequency resources within a same bandwidth part (BWP).

14 . The method of claim 13 , wherein the frequency resources on the new transmission beam and the frequency resources on the transmission beam differ with respect to the utilized BWP.

15 . The method of claim 9 , comprising in response to the failure report, the access node initiating switching of the wireless device to another cell of the wireless communication system.

16 . A wireless device for a wireless communication system, the wireless device including:

processing circuitry and a memory, the memory containing instructions executable by the processor whereby the wireless device is configured to:

on a single serving transmission beam selected from a plurality of transmission beams, send listen before talk (LBT) based uplink wireless transmissions to an access node;

detect LBT failures on the single serving transmission beam; and

based on a number of the detected LBT failures on the single serving transmission beam exceeding a predetermined threshold for the beam, send a failure report to the access node, the failure report indicating the detected LBT failures on the single serving transmission beam.

17 . The wireless device of claim 16 , further configured to:

select a second transmission beam of the plurality of transmission beams;

send the failure report on the second transmission beam;

perform a random access procedure on the second transmission beam; and

the wireless device sending the failure report by at least one message of the random access procedure.

18 . The wireless device of claim 16 , further configured to:

send the failure report in response to the number of detected LBT failures reaching a threshold value;

monitor the number of detected LBT failures by a counter;

start a timer upon detecting an LBT failure;

send the failure report in response to the counter reaching the threshold value; and

reset the counter to zero, upon expiry of the timer before the counter reaches the threshold value, the wireless device.

19 . An access node for a wireless communication system, the access node including:

processing circuitry and a memory, the memory containing instructions executable by the processor whereby the access node wireless device is configured to:

on a single serving transmission beam selected from a plurality of transmission beams, receive listen before talk (LBT) based uplink wireless transmissions from a wireless device;

receive a failure report from the wireless device, the failure report indicating a number of detected LBT failures on the single serving transmission beam exceeding a predetermined threshold for the single serving transmission beam; and

based on the failure report, control switching of the wireless device to a new serving transmission beam.

20 . The access node of claim 19 , further configured to in response to the failure report, the access node initiating switching of the wireless device to a new serving transmission beam utilizing frequency resources that correspond to frequency resources used on the serving transmission beam.