Techniques for beam discovery and beamforming in wireless communications
Various aspects described herein relate to techniques for beam discovery and beamforming in wireless communications (e.g., 5th Generation (5G) New Radio (NR)). In an aspect, a method related to signaling for channel state information reference signals (CSI-RSs) in wireless communications is provided. The method includes receiving, by a user equipment (UE), a CSI-RS beam of a set of CSI-RS beams, and the CSI-RS beam includes a change indication message. The method further includes determining, by the UE, whether the set of CSI-RS beams have changed based on a value of the change indication message.
1. A method of wireless communications, comprising:
receiving, by a user equipment (UE), a channel state information reference signal (CSI-RS) beam of a set of CSI-RS beams, wherein the CSI-RS beam includes a change indication message; and
determining, by the UE, whether the set of CSI-RS beams has changed based on a value of the change indication message.
2. The method of claim 1 , further comprising:
determining, by the UE from a message received from a base station, time intervals during which the set of CSI-RS beams does not change.
3. The method of claim 1 , further comprising:
conducting, by the UE, a hierarchical beam search on all symbols of a CSI-RS burst.
4. The method of claim 3 , further comprising:
interrupting, by the UE, the hierarchical beam search in response to the value of the change indication message indicating that the set of CSI-RS beams has changed; and
entering, at the UE, a restore mode to search time-frequency locations of one or more previously identified or processed CSI-RS beams.
5. The method of claim 1 , wherein the change indication message is conveyed through a choice of a scrambling sequence used by the CSI-RS beam.
6. The method of claim 5 , wherein the scrambling sequence is selected based on at least one of a respective cell identification (ID) or a symbol number within a radio frame.
7. The method of claim 1 , wherein the set of CSI-RS beams are transmitted for a plurality of UEs.
8. The method of claim 1 , wherein the change indication message is a one-bit indication.
9. The method of claim 1 , wherein the value of the change indication message indicates whether a CSI-RS beam of the set of CSI-RS beams has been modified, inserted, or deleted.
10. The method of claim 1 , wherein the set of CSI-RS beams are transmitted in different spatial directions by one or more base stations.
11. An apparatus for wireless communications, comprising:
a receiver configured to receive a channel state information reference signal (CSI-RS) beam of a set of CSI-RS beams, wherein the CSI-RS beam includes a change indication message;
a memory configured to store instructions; and
at least one processor communicatively coupled with the receiver and the memory, wherein the at least one processor is configured to execute the instructions to determine whether the set of CSI-RS beams have changed based on a value of the change indication message.
12. The apparatus of claim 11 , wherein the at least one processor is configured to execute further instructions to determine, from a message received from a base station, time intervals during which the set of CSI-RS beams does not change.
13. The apparatus of claim 11 , wherein the at least one processor is configured to execute further instructions to conduct a hierarchical beam search on all symbols of a CSI-RS burst.
14. The apparatus of claim 13 , wherein the at least one processor is configured to execute further instructions to:
interrupt the hierarchical beam search in response to the value of the change indication message indicating that the set of CSI-RS beams has changed; and
enter a restore mode to search time-frequency locations of one or more previously identified or processed CSI-RS beams.
15. The apparatus of claim 11 , wherein the change indication message is conveyed through a choice of a scrambling sequence used by the CSI-RS beam.
16. The apparatus of claim 15 , wherein the scrambling sequence is selected based on at least one of a respective cell identification (ID) or a symbol number within a radio frame.
17. The apparatus of claim 11 , wherein the set of CSI-RS beams are transmitted for a plurality of UEs.
18. The apparatus of claim 11 , wherein the change indication message is a one-bit indication.
19. The apparatus of claim 11 , wherein the value of the change indication message indicating whether a CSI-RS beam of the set of CSI-RS beams has been modified, inserted, or deleted.
20. The apparatus of claim 11 , wherein the set of CSI-RS beams are transmitted in different spatial directions by one or more base stations.
21. An apparatus for wireless communications, comprising:
means for receiving a channel state information reference signal (CSI-RS) beam of a set of CSI-RS beams, wherein the CSI-RS beam includes a change indication message; and
means for determining whether the set of CSI-RS beams has changed based on a value of the change indication message.
22. The apparatus of claim 21 , further comprising:
means for determining, from a message received from a base station, time intervals during which the set of CSI-RS beams does not change.
23. The apparatus of claim 21 , further comprising:
means for conducting a hierarchical beam search on all symbols of a CSI-RS burst.
24. The apparatus of claim 23 , further comprising:
means for interrupting the hierarchical beam search in response to the value of the change indication message indicating that the set of CSI-RS beams have changed; and
means for entering a restore mode to search time-frequency locations of one or more previously identified or processed CSI-RS beams.
25. The apparatus of claim 21 , wherein the change indication message is conveyed through a choice of a scrambling sequence used by the CSI-RS beam.
26. A non-transitory computer-readable medium comprising code executable by at least one processor to:
receive a channel state information reference signal (CSI-RS) beam of a set of CSI-RS beams, wherein the CSI-RS beam includes a change indication message; and
determine whether the set of CSI-RS beams has changed based on a value of the change indication message.
27. The non-transitory computer-readable medium of claim 26 , further comprising code executable by the at least one processor to:
determine, from a message received from a base station, time intervals during which the set of CSI-RS beams does not change.
28. The non-transitory computer-readable medium of claim 26 , further comprising code executable by the at least one processor to:
conduct a hierarchical beam search on all symbols of a CSI-RS burst.
29. The non-transitory computer-readable medium of claim 28 , further comprising code executable by the at least one processor to:
interrupt the hierarchical beam search in response to the value of the change indication message indicating that the set of CSI-RS beams have changed; and
enter a restore mode to search time-frequency locations of one or more previously identified or processed CSI-RS beams.
30. The non-transitory computer-readable medium of claim 26 , wherein the change indication message is conveyed through a choice of a scrambling sequence used by the CSI-RS beam.