US-20260129689-A1 - EARLY BEAM REFINEMENT FOR A TWO-STEP RANDOM ACCESS CHANNEL (RACH) PROCEDURE

Abstract

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for beam refinement. One aspect provides a method for wireless communications at a user equipment (UE). The method includes: receiving, from a base station (BS), a set of synchronization signal blocks (SSBs) associated with a set of beams, respectively; transmitting, to the BS, a first message of a random access channel (RACH) process using one beam of the set of beams; receiving, from the BS, a second message of the RACH process, wherein the second message triggers a beam refinement process; and receiving a set of reference signals as part of the beam refinement process to identify one or more candidate refined beams.

Inventors

• In-soo Kim
• Yan Zhou
• Jing Sun
• Jing Jiang

Assignees

• QUALCOMM INCORPORATED

Dates

Publication Date

20260507

Application Date

20241107

Claims (20)

1. 1 . An apparatus for wireless communication, comprising: at least one memory comprising computer-executable instructions; and one or more processors configured to execute the computer-executable instructions and cause the apparatus to: receive, from a base station (BS), a set of synchronization signal blocks (SSBs) associated with a set of beams, respectively; transmit, to the BS, a first message of a random access channel (RACH) process using one beam of the set of beams; receive, from the BS, a second message of the RACH process, wherein the second message triggers a beam refinement process; and receive a set of reference signals as part of the beam refinement process to identify one or more candidate refined beams.
2. 2 . The apparatus of claim 1 , wherein the set of beams include wide beams, and wherein the one or more candidate refined beams include one or more narrow beams within the one beam of the set of beams.
3. 3 . The apparatus of claim 1 , wherein the second message triggers one of a set of beam refinement processes including the beam refinement process, the set of beam refinement processes including: a UE beam refinement process to refine a beam used by the UE for transmission or reception; a BS beam refinement process to refine a beam used by the BS for transmission or reception; and a BS and UE beam refinement process to refine the beams used by the UE and the BS for transmission or reception.
4. 4 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the apparatus to: transmit a third message including a beam report indicating the one or more candidate refined beams; receive a fourth message indicating a selected beam of the one or more candidate refined beams; and communicate with the BS using the selected beam after receiving the fourth message.
5. 5 . The apparatus of claim 1 , wherein the first message indicates one or more capabilities of the UE, and wherein the beam refinement process is in accordance with the one or more capabilities of the UE.
6. 6 . The apparatus of claim 5 , wherein the one or more capabilities include at least one of: a UE beam configuration indicating a number of beams supported by the UE; a type of beam refinement supported by the UE; reference signal (RS) measurement and reporting configuration of the UE indicating at least one of a number of beams that the UE can measure during the beam refinement process or a number of beams the UE can report as part of a beam reporting message; and a minimum gap between a beam sweep for the beam refinement process and transmission of the beam reporting message; or a minimum gap between receiving the second message and the beam sweep for the beam refinement process.
7. 7 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the apparatus to: transmit a third message including a beam report indicating the one or more candidate refined beams, wherein an acknowledgement that the second message is successfully decoded by the UE is multiplexed as part of the third message.
8. 8 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the apparatus to: transmit a third message including a beam report indicating the one or more candidate refined beams, the third message serving as an acknowledgement that the second message is successfully decoded by the UE.
9. 9 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the apparatus to: transmit a third message prior to receiving the set of reference signals, wherein the third message provides an acknowledgement that the second message is successfully decoded by the UE.
10. 10 . The apparatus of claim 9 , wherein the second message indicates a timing associated with at least one of receiving the set of reference signals or transmission of a beam report indicating the one or more candidate refined beams, the timing being indicated with reference to the third message.
11. 11 . The apparatus of claim 1 , wherein the second message indicates a timing associated with at least one of receiving the set of reference signals or transmission of a beam report indicating the one or more candidate refined beams, the timing being indicated with reference to the second message.
12. 12 . The apparatus of claim 1 , wherein the second message comprises a fallback random access response (RAR) triggering the beam refinement process.
13. 13 . The apparatus of claim 12 , wherein the RACH process comprises a two-step RACH process, and wherein the fallback RAR indicates to perform a four-step RACH process based on the two-step RACH process failing.
14. 14 . The apparatus of claim 13 , wherein the one or more processors are further configured to cause the apparatus to: transmit a third message of the four-step RACH process including a beam report indicating the one or more candidate refined beams; receive a fourth message of the four-step RACH process indicating a selected beam of the one or more candidate refined beams; and communicate with the BS using the selected beam after receiving the fourth message.
15. 15 . The apparatus of claim 13 , wherein the beam refinement process comprises a UE beam refinement process, the method further comprising: transmitting a third message of the four-step RACH process using a selected beam of the one or more candidate refined beams; and receiving a fourth message of the four-step RACH process using the selected beam.
16. 16 . An apparatus for wireless communication, comprising: at least one memory comprising computer-executable instructions; and one or more processors configured to execute the computer-executable instructions and cause the apparatus to: transmit, to a user equipment (UE), a set of synchronization signal blocks (SSBs) associated with a set of beams, respectively; receive, from the UE, a first message of a random access channel (RACH) process using one beam of the set of beams; transmit, to the UE, a second message of the RACH process, wherein the second message triggers a beam refinement process; and transmit a set of reference signals as part of the beam refinement process to identify one or more candidate refined beams.
17. 17 . The apparatus of claim 16 , wherein the second message triggers one of a set of beam refinement processes including the beam refinement process, the set of beam refinement processes including: a UE beam refinement process to refine a beam used by the UE for transmission or reception; a BS beam refinement process to refine a beam used by the BS for transmission or reception; and a BS and UE beam refinement process to refine the beams used by the UE and the BS for transmission or reception.
18. 18 . The apparatus of claim 16 , wherein the one or more processors are further configured to cause the apparatus to: receive a third message including a beam report indicating the one or more candidate refined beams; and transmit a fourth message indicating a selected beam of the one or more candidate refined beams.
19. 19 . The apparatus of claim 16 , wherein the first message indicates one or more capabilities of the UE, and wherein the beam refinement process is in accordance with the one or more capabilities of the UE.
20. 20 . The apparatus of claim 19 , wherein the one or more capabilities include at least one of: a UE beam configuration indicating a number of beams supported by the UE; a type of beam refinement supported by the UE; reference signal (RS) measurement and reporting configuration of the UE indicating at least one of a number of beams that the UE can measure during the beam refinement process or a number of beams the UE can report as part of a beam reporting message; and a minimum gap between a beam sweep for the beam refinement process and transmission of the beam reporting message; or a minimum gap between receiving the second message and the beam sweep for the beam refinement process.

Description

FIELD OF THE DISCLOSURE Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for beam refinement. DESCRIPTION OF RELATED ART Wireless communications systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, or other similar types of services. These wireless communications systems may employ multiple-access technologies capable of supporting communications with multiple users by sharing available wireless communications system resources with those users. Although wireless communications systems have made great technological advancements over many years, challenges still exist. For example, complex and dynamic environments can still attenuate or block signals between wireless transmitters and wireless receivers. Accordingly, there is a continuous desire to improve the technical performance of wireless communications systems, including, for example: improving speed and data carrying capacity of communications, improving efficiency of the use of shared communications mediums, reducing power used by transmitters and receivers while performing communications, improving reliability of wireless communications, avoiding redundant transmissions and/or receptions and related processing, improving the coverage area of wireless communications, increasing the number and types of devices that can access wireless communications systems, increasing the ability for different types of devices to intercommunicate, increasing the number and type of wireless communications mediums available for use, and the like. Consequently, there exists a need for further improvements in wireless communications systems to overcome the aforementioned technical challenges and others. SUMMARY One aspect provides a method for wireless communications at a user equipment (UE). The method includes: receiving, from a base station (BS), a set of synchronization signal blocks (SSBs) associated with a set of beams, respectively; transmitting, to the BS, a first message of a random access channel (RACH) process using one beam of the set of beams; receiving, from the BS, a second message of the RACH process, wherein the second message triggers a beam refinement process; and receiving a set of reference signals as part of the beam refinement process to identify one or more candidate refined beams. Another aspect provides a method for wireless communications at a base station (BS). The method includes: transmitting, to a user equipment (UE), a set of synchronization signal blocks (SSBs) associated with a set of beams, respectively; receiving, from the UE, a first message of a random access channel (RACH) process using one beam of the set of beams; transmitting, to the UE, a second message of the RACH process, wherein the second message triggers a beam refinement process; and transmitting a set of reference signals as part of the beam refinement process to identify one or more candidate refined beams. Other aspects provide: an apparatus operable, configured, or otherwise adapted to perform any one or more of the aforementioned methods and/or those described elsewhere herein; a non-transitory, computer-readable media comprising instructions that, when executed (e.g., directly, indirectly, after pre-processing, without pre-processing) by one or more processors of an apparatus, cause the apparatus to perform the aforementioned methods as well as those described elsewhere herein; a computer program product embodied on a computer-readable storage medium comprising code for performing the aforementioned methods as well as those described elsewhere herein; and/or an apparatus comprising means for performing the aforementioned methods as well as those described elsewhere herein. By way of example, an apparatus may comprise a processing system, a device with a processing system, or processing systems cooperating over one or more networks. The following description and the appended figures set forth certain features for purposes of illustration. BRIEF DESCRIPTION OF DRAWINGS The appended figures depict certain features of the various aspects described herein and are not to be considered limiting of the scope of this disclosure. FIG. 1 depicts an example wireless communications network. FIG. 2 depicts an example disaggregated base station (BS) architecture. FIG. 3 depicts aspects of an example base station and an example user equipment (UE). FIGS. 4A, 4B, 4C, and 4D depict various example aspects of data structures for a wireless communications network. FIG. 5A is a call flow diagram illustrating an example of a four-step random access procedure (RACH) procedure. FIG. 5B is a call flow diagram illustrating an example two-step RACH procedure. FIG. 6 is a diagram illustrating example beam management procedures in accordance with the present disclosure. FIG. 7 illustrates example signal communications for beam refinement after a four-step RACH proced