UE selection of contention-free and contention-based random access for handover
This disclosure generally relates to systems, devices, apparatuses, products, and methods for wireless communication. A communication system may include a user equipment (UE) that receives a configuration for contention-free random access (CFRA) and a configuration for contention-based random access (CBRA). The UE determines a first random access resource. The first random access resource maps to one or more beams from a target base station. The UE determines a beam quality associated with the first random access resource. The UE initiates a random access request using the CFRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is above a threshold beam quality. The UE initiates the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below the threshold beam quality.
1. A method of wireless communication, comprising:
receiving, at a user equipment (UE), a configuration for contention-free random access (CFRA) and a configuration for contention-based random access (CBRA);
determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
determining, by the UE, a beam quality associated with the first random access resource;
initiating, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is above a threshold beam quality; and
initiating, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below the threshold beam quality.
2. The method of claim 1 , further comprising:
determining that the first random access resource is the contention-free resource;
determining that the beam quality of the first random access resource is above the threshold beam quality; and
initiating, by the UE, the random access request using the CFRA based on the determination that the first random access resource is the contention-free resource and that the beam quality of the first random access resource is above the threshold beam quality.
3. The method of claim 1 , further comprising:
determining that the first random access resource is the contention-free resource;
determining that the beam quality of the first random access resource is below the threshold beam quality; and
initiating, by the UE, the random access request using the CBRA based on the determination that the first random access resource is the contention-free resource and that the beam quality of the first random access resource is below the threshold beam quality.
4. The method of claim 1 , wherein the threshold beam quality is a threshold provided to the UE by a base station.
5. The method of claim 1 , wherein the one or more beams from the target base station comprise channel state information reference signals (CSI-RS).
6. The method of claim 1 , further comprising:
receiving, at the UE, a random access response to the random access request using the CFRA, wherein the random access response identifies a next uplink transmission opportunity located after a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station; and
initiating, by the UE, CBRA at the next contention-based resource.
7. The method of claim 1 , further comprising:
failing, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the initiating the random access request using the CFRA; and
initiating, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.
8. The method of claim 1 , further comprising one of:
initiating, by the UE, another random access request using the CBRA at contention-based random access resources in addition to the initiating the random access request using the CFRA; or
initiating, by the UE, the another random access request using the CFRA at contention-free random access resources in addition to the initiating the random access request using the CBRA.
9. The method of claim 1 , further comprising receiving, at the UE, a random access configuration that includes identification for the UE to perform one of:
the initiating the random access request using the CFRA;
the initiating the random access request using the CBRA; or
initiating the random access request using both the CFRA and the CBRA.
10. The method of claim 1 , further comprising receiving, at the UE, a random access configuration that includes identification for the UE to perform, according to a predetermined priority, one of:
the initiating the random access request using the CFRA;
the initiating the random access request using the CBRA; or
initiating the random access request using both the CFRA and the CBRA.
11. An apparatus for wireless communication, the apparatus comprising:
at least one processor; and
a memory coupled with the at least one processor, wherein the at least one processor is configured to:
receive, at a user equipment (UE), a configuration for contention-free random access (CFRA) and a configuration for contention-based random access (CBRA);
determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
determine, by the UE, a beam quality associated with the first random access resource;
initiate, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is above a threshold beam quality; and
initiate, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below the threshold beam quality.
12. The apparatus of claim 11 , wherein the at least one processor is configured to:
determine that the first random access resource is the contention-free resource;
determine that the beam quality of the first random access resource is above the threshold beam quality; and
initiate, by the UE, the random access request using the CFRA based on the determination that the first random access resource is the contention-free resource and that the beam quality of the first random access resource is above the threshold beam quality.
13. The apparatus of claim 11 , wherein the at least one processor is configured to:
determine that the first random access resource is the contention-free resource;
determine that the beam quality of the first random access resource is below the threshold beam quality; and
initiate, by the UE, the random access request using the CBRA based on the determination that the first random access resource is the contention-free resource and that the beam quality of the first random access resource is below the threshold beam quality.
14. The apparatus of claim 11 , wherein the threshold beam quality is a threshold provided to the UE by a base station.
15. The apparatus of claim 11 , wherein the one or more beams from the target base station comprise channel state information reference signals (CSI-RS).
16. The apparatus of claim 11 , wherein the at least one processor is configured to:
receive, at the UE, a random access response to the random access request using the CFRA, wherein the random access response identifies a next uplink transmission opportunity located after a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station; and
initiate, by the UE, CBRA at the next contention-based resource.
17. The apparatus of claim 11 , wherein the at least one processor is configured to:
fail, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the random access request using the CFRA; and
initiate, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.
18. The apparatus of claim 11 , wherein the at least one processor is configured to:
initiate, by the UE, another random access request using the CBRA at contention-based random access resources in addition to the random access request using the CFRA; or
initiate, by the UE, the another random access request using the CFRA at contention-free random access resources in addition to the random access request using the CBRA.
19. The apparatus of claim 11 , wherein the at least one processor is configured to receive, at the UE, a random access configuration that includes identification for the UE to perform one of:
the random access request using the CFRA;
the random access request using the CBRA; or
the random access request using both the CFRA and the CBRA.
20. The apparatus of claim 11 , wherein the at least one processor is configured to receive, at the UE, a random access configuration that includes identification for the UE to perform, according to a predetermined priority, one of:
the random access request using the CFRA;
the random access request using the CBRA; or
the random access request using both the CFRA and the CBRA.
21. An apparatus for wireless communication, the apparatus comprising:
means for receiving, at a user equipment (UE), a configuration for contention-free random access (CFRA) and a configuration for contention-based random access (CBRA);
means for determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
means for determining, by the UE, a beam quality associated with the first random access resource;
means for initiating, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is above a threshold beam quality; and
means for initiating, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below the threshold beam quality.