Systems and methods for beam failure recovery enhancement
Systems and methods for beam failure recovery (BFR) are disclosed herein. A user equipment (UE) receives downlink (DL) reference signal(s) on corresponding beam(s) from a base station. The UE performs beam failure detection (BFD) on such beams used for user data to determine whether a beam failure has occurred, and candidate beam detection (CBD) on such beams not used for user data to identify candidate beams for recovering from the beam failure. The BFD and the CBD are based on both uplink (UL) channel performance considerations and DL channel performance considerations, as determined using the DL reference signal(s), such that a beam failure may be determined in the UL, the DL, or both, and a candidate beam may be identified for UL, DL, or both. The UE sends a beam failure recovery request BFRQ with this information to the base station, and the system changes beams accordingly.
1. A method of a base station, comprising:
sending, to a user equipment (UE), radio resource control (RRC) signaling indicating a first threshold to use at the UE for UL candidate beam detection (CBD) and a second threshold to use for DL CBD;
receiving, from the UE, one of a first beam failure recovery request (BFRQ) identifying a UL candidate beam and a second BFRQ identifying a DL candidate beam;
sending, to the UE, a beam failure recovery response (BFRR); and
using the one of the UL candidate beam and the DL candidate beam from the one of the first BFRQ and the second BFRQ to communicate with the UE;
wherein the RRC signaling further indicates a first contention free physical random access channel (CF-PRACH) resource used by the base station to receive the first BFRQ and a second CF-PRACH resource used by the base station to receive the second BFRQ.
2. The method of claim 1 , wherein the UL candidate beam is not used for DL communications with the UE and the DL candidate beam is not used for UL communications with the UE.
3. The method of claim 1 , wherein each of the first threshold and the second threshold is one of a layer 1 reference signal received power (L1-RSRP) threshold and a virtual power headroom (PHR) threshold.
4. The method of claim 1 , wherein:
the RRC signaling further indicates a third threshold to use at the UE for UL beam failure detection (BFD) and a fourth threshold to use for DL BFD.
5. The method of claim 4 , wherein:
each of the third threshold and the fourth threshold is one of a layer 1 reference signal received power (L1-RSRP) threshold, a hypothetical block error ratio (BLER) threshold, and a virtual power headroom (PHR) threshold.
6. The method of claim 1 , wherein the BFRR is sent to the UE in
a dedicated search space (SS) for the UE.
7. An apparatus of a base station, comprising:
one or more processors, and a memory storing instructions that, when executed by the one or more processors, configure the base station to:
send, to a user equipment (UE), radio resource control (RRC) signaling indicating a first threshold to use at the UE for UL candidate beam detection (CBD) and a second threshold to use for DL CBD;
receive, from the UE, one of a first beam failure recovery request (BFRQ) identifying a UL candidate beam and a second BFRQ identifying a DL candidate beam;
send, to the UE, a beam failure recovery response (BFRR); and
use the one of the UL candidate beam and the DL candidate beam from the one of the first BFRQ and the second BFRQ to communicate with the UE;
wherein the RRC signaling further indicates a first contention free physical random access channel (CF-PRACH) resource used by the base station to receive the first BFRQ and a second CF-PRACH resource used by the base station to receive the second BFRQ.
8. The apparatus of claim 7 , wherein the UL candidate beam is not used for DL communications with the UE and the DL candidate beam is not used for UL communications with the UE.
9. The apparatus of claim 7 , wherein each of the first threshold and the second threshold is one of a layer 1 reference signal received power (L1-RSRP) threshold and a virtual power headroom (PHR) threshold.
10. The apparatus of claim 7 , wherein:
the RRC signaling further indicates a third threshold to use at the UE for UL beam failure detection (BFD) and a fourth threshold to use for DL BFD.
11. The apparatus of claim 10 , wherein:
each of the third threshold and the fourth threshold is one of a layer 1 reference signal received power (L1-RSRP) threshold, a hypothetical block error ratio (BLER) threshold, and a virtual power headroom (PHR) threshold.
12. The apparatus of claim 7 , wherein the BFRR is sent to the UE in
a dedicated search space (SS) for the UE.
13. A non-transitory computer-readable storage medium including instructions that, when executed by one or more processors of a base station, cause the base station to:
send, to a user equipment (UE), radio resource control (RRC) signaling indicating a first threshold to use at the UE for UL candidate beam detection (CBD) and a second threshold to use for DL CBD;
receive, from the UE, one of a first beam failure recovery request (BFRQ) identifying a UL candidate beam and a second BFRQ identifying a DL candidate beam;
send, to the UE, a beam failure recovery response (BFRR); and
use the one of the UL candidate beam and the DL candidate beam from the one of the first BFRQ and the second BFRQ to communicate with the UE;
wherein the RRC signaling further indicates a first contention free physical random access channel (CF-PRACH) resource used by the base station to receive the first BFRQ and a second CF-PRACH resource used by the base station to receive the second BFRQ.
14. The non-transitory computer-readable storage medium of claim 13 , wherein the UL candidate beam is not used for DL communications with the UE and the DL candidate beam is not used for UL communications with the UE.
15. The non-transitory computer-readable storage medium of claim 13 , wherein each of the first threshold and the second threshold is one of a layer 1 reference signal received power (L1-RSRP) threshold and a virtual power headroom (PHR) threshold.
16. The non-transitory computer-readable storage medium of claim 13 , wherein:
the RRC signaling further indicates a third threshold to use at the UE for UL beam failure detection (BFD) and a fourth threshold to use for DL BFD.