Default beam for uplink transmission after beam failure recovery
A method of default uplink beam determination after a beam failure recovery (BFR) procedure in a beamforming system is proposed. For uplink (UL) transmission, the BS provides physical uplink control channel (PUCCH) resource configuration to UE. The configuration includes spatial relation information that indicates the spatial filter to be used by UE for the corresponding PUCCCH transmission. After BFR procedure is completed and before the first spatial relation information indication for a PUCCH resource is received by UE, a default UE TX beam for the PUCCH resource can be determined based on the UE TX beam used during the BFR procedure, e.g., the UE TX beam used to transmit a beam failure recovery request (BFRQ) during the BFR procedure.
1. A method comprising:
detecting a beam failure by a user equipment (UE) and identifying one or more new candidate beams in a beamforming communication network;
initiating a beam failure recovery (BFR) procedure using a new candidate beam selected from the one or more new candidate beams;
determining a default spatial filter for uplink transmissions after the BFR procedure is completed; and
performing a physical uplink control channel (PUCCH)-transmission on a PUCCH resource using the default spatial filter before receiving a first spatial relation information indication from the network for the PUCCH resource.
2. The method of claim 1 , wherein the one or more new candidate beams are identified based on measurements on reference signal resources corresponding to the one or more new candidate beams and a predefined criterion.
3. The method of claim 1 , wherein a dedicated physical random-access channel (PRACH) resource is associated with each corresponding reference signal resource for the new candidate beam identification.
4. The method of claim 3 , wherein the BFR procedure comprises the UE transmitting a beam failure recovery request (BFRQ) on a PRACH resource associated with a reference signal resource corresponding to the selected new candidate beam.
5. The method of claim 4 , wherein a spatial filter used for transmitting the BFRQ is determined as the default spatial filter for the PUCCH-transmission.
6. The method of claim 1 , wherein the BFR procedure is completed after the UE successfully receiving a network response.
7. The method of claim 6 , wherein the default spatial filter is determined upon a predefined time period is passed after the BFR procedure is completed.
8. The method of claim 1 , wherein the default spatial filter is used for the PUCCH-transmission during a time window from the BFR procedure is completed to the UE deriving a spatial filter for the PUCCH-transmission from the spatial relation information indication.
9. The method of claim 1 , wherein spatial relation information for the PUCCH resource is carried by an RRC signaling comprising one or more spatial relations.
10. The method of claim 9 , wherein a spatial relation is activated by a MAC CE when multiple spatial relations are carried by the RRC signaling.
11. A User Equipment (UE), comprising:
a beam monitoring circuit that detects a beam failure and identifies one or more new candidate beams in a beamforming communication network;
a beam failure recovery (BFR) handling circuit that initiates a BFR procedure using a new candidate beam selected from the one or more new candidate beams;
a beamforming circuit that determines a default spatial filter for uplink transmissions after the BFR procedure is completed; and
a transmitter that performs a physical uplink control channel (PUCCH)-transmission on a PUCCH resource using the default spatial filter before receiving a first spatial relation information indication from the network for the PUCCH resource.
12. The UE of claim 11 , wherein the one or more new candidate beams are identified based on measurements on reference signal resources corresponding to the one or more new candidate beams and a predefined criterion.
13. The UE of claim 11 , wherein a dedicated physical random-access channel (PRACH) resource is associated with each corresponding reference signal resource for the new candidate beam identification.
14. The UE of claim 13 , wherein the BFR procedure comprises the UE transmitting a beam failure recovery request (BFRQ) on a PRACH resource associated with a reference signal resource corresponding to the selected new candidate beam.
15. The UE of claim 14 , wherein a spatial filter used for transmitting the BFRQ is determined as the default spatial filter for the PUCCH-transmission.
16. The UE of claim 11 , wherein the BFR procedure is completed after the UE successfully receiving a network response.
17. The UE of claim 16 , wherein the default spatial filter is determined upon a predefined time period is passed after the BFR procedure is completed.
18. The UE of claim 11 , wherein the default spatial filter is used for the PUCCH-transmission during a time window from the BFR procedure is completed to the UE deriving a spatial filter for the PUCCH-transmission from the spatial relation information indication.
19. The UE of claim 11 , wherein spatial relation information for the PUCCH resource is carried by an RRC signaling comprising one or more spatial relations.
20. The UE of claim 19 , wherein a spatial relation is activated by a MAC CE when multiple spatial relations are carried by the RRC signaling.