Methods and apparatus for beam control in beamformed systems
Methods and apparatus are described. A method, implemented in a wireless transmit/receive unit (WTRU) includes monitoring a first control channel search space (SS) associated with a first normal beam set comprising a first beam set. The WTRU initiates extended monitoring and monitors, subsequent to a trigger based on a measurement by the WTRU, a control channel SS associated with an extended beam set comprising the first beam set and one or more additional beam sets. The WTRU determines a second beam set from the extended beam set. The determination is based on a received control channel beam switch command or based on a control channel SS in which a beam switch command is received. The WTRU monitors a second control channel SS associated with a second normal beam set comprising the determined second beam set.
1. A wireless transmit/receive unit (WTRU) comprising:
a processor; and
a transceiver,
wherein the WTRU is configured with a first set of beams for use for radio link quality measurements,
wherein the WTRU is further configured with a second set of beams for use for radio link quality measurements when a radio link quality of all beams of the first set of beams is below a first threshold,
wherein the processor and the transceiver are configured to monitor a first control channel search space using at least one beam of the first set of beams,
wherein the processor and the transceiver are further configured to evaluate a radio link quality of the second set of beams based on a radio link quality of all beams of the first set of beams being below the first threshold,
wherein the processor and the transceiver are further configured to identify at least one beam of the second set of beams that has a radio link quality above a second threshold, and
wherein the processor and the transceiver are further configured to monitor a second control channel search space using the at least one beam of the second set of beams.
2. The WTRU of claim 1 , wherein the processor and the transceiver are further configured to transmit, on configured random access channel (RACH) resources, based on the radio link quality of the one or more beams of the first set of beams being below the first threshold.
3. The WTRU of claim 1 , wherein the first control channel search space and the second control channel search space are physical downlink control channel (PDCCH) search spaces.
4. The WTRU of claim 1 , wherein the processor and the transceiver are further configured to evaluate the radio link quality of the second set of beams by performing measurements associated with a physical broadcast channel (PBCH) of beams of the second set of beams.
5. The WTRU of claim 1 , wherein the at least one beam of the first set of beams and beams of the second set of beams are each associated with a unique reference signal.
6. The WTRU of claim 1 , wherein the processor and the transceiver are further configured to indicate preferred beams of the second set of beams and an explicit WTRU ID.
7. The WTRU of claim 1 , wherein the processor and the transceiver are further configured to monitor the second control channel search space using the at least one beam of the second set of beams until the WTRU receives a beam switch command.
8. The WTRU of claim 1 , wherein the first threshold and the second threshold are the same.
9. The WTRU of claim 1 , wherein the first threshold and the second threshold are different.
10. A method comprising:
a wireless transmit/receive unit (WTRU), which is configured with a first set of beams for use for radio link quality measurements and configured with a second set of beams for use for radio link quality measurements when a radio link quality of all beams of the first set of beams is below a first threshold, monitoring a first control channel search space using at least one beam of the first set of beams,
evaluating a radio link quality of the second set of beams based on a radio link quality of all beams of the first set of beams being below a first threshold;
identifying at least one beam of the second set of beams that has a radio link quality above a second threshold; and
monitoring a second control channel search space using the at least one beam of the second set of beams.
11. The method of claim 10 , further comprising transmitting, on configured random access channel (RACH) resources, based on the radio link quality of the one or more beams of the first set of beams being below the first threshold.
12. The method of claim 10 , wherein the first control channel search space and the second control channel search space are physical downlink control channel (PDCCH) search spaces.
13. The method of claim 10 , wherein the evaluating the radio link quality of the second set of beams further comprises evaluating the radio link quality of the second set of beams by performing measurements associated with a physical broadcast channel (PBCH) of beams of the second set of beams.
14. The method of claim 10 , wherein the at least one beam of the first set of beams and beams of the second set of beams are each associated with a unique reference signal.
15. The method of claim 10 , wherein the processor and the transceiver are further configured to indicate preferred beams of the second set of beams and an explicit WTRU ID.
16. The method of claim 10 , further comprising monitoring the second control channel search space using the at least one beam of the second set of beams until the WTRU receives a beam switch command.
17. The method of claim 10 , wherein the first threshold and the second threshold are the same.
18. The method of claim 10 , wherein the first threshold and the second threshold are different.