Beam failure recovery for serving cell

Abstract

The present invention provides apparatuses, methods, computer programs, computer program products and computer-readable media regarding beam failure recovery for serving cell. The apparatus comprises means for composing, after a beam failure has been detected by a user equipment on a resource provided by a first serving cell of the user equipment, beam recovery signaling, the beam recovery signaling indicating at least one candidate beam to be used in beam failure recovery, means for transmitting, to a network entity, the beam recovery signaling on a resource provided by a second serving cell.

1 . An apparatus comprising:
 at least one processor; and   at least one memory including computer program code;   the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:   determine, after a beam failure has been detected by a user equipment on a first serving cell of the user equipment, whether at least one candidate beam is above a first threshold,   compose, based on the determining that none of the at least one candidate beam is above the first threshold, beam recovery signaling, the beam recovery signaling indicating the failed first cell and that no candidate beam is available for the failed first cell, and   transmit, to a network entity, the beam recovery signaling on a resource provided by a second serving cell.   
     
     
         2 . The apparatus according to  claim 1 , wherein the at least one processor and the computer program code are further configured to cause the apparatus to:
 detect at least one candidate beam existing on the resource provided by the first serving cell,   receive, from the network entity, a first quality threshold for a candidate beam to be used for the beam failure recovery,   determine whether a quality value of the at least one candidate beam for the beam failure recovery exceeds the first quality threshold.   
     
     
         3 . The apparatus according to  claim 2 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:
 if it is determined that there is at least one candidate beam associated with contention free random access, CFRA, signal and having a quality value exceeding the first quality threshold,   transmit the beam recovery signaling to the network entity using contention free random-access transmission to indicate at least one of candidates having quality value exceeding the first quality threshold.   
     
     
         4 . The apparatus according to  claim 2 :
 wherein the at least one processor and the computer program code configured to cause the apparatus to receive comprises the at least one processor and the computer program code configured to cause the apparatus to receive, from a network entity, a second threshold value for a candidate beam to be used for the beam failure recovery, and   the at least one processor and the computer program code configured to cause the apparatus to determine whether a quality value comprises the at least one processor and the computer program code configured to cause the apparatus to determine whether a quality value of the at least one candidate beam for the beam failure recovery exceeds the second quality threshold.   
     
     
         5 . The apparatus according to  claim 4 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:
 if it is determined that there is no candidate beam associated with CFRA signal having a quality value exceeding the first quality threshold and that there is at least one candidate beam having a quality value exceeding the first or second quality threshold,   transmit the beam recovery signaling to the network entity using a medium access control element, MAC CE, and includes a predetermined number of the at least one or more of the plurality of candidate beams having a quality value exceeding the second quality threshold in descending order of the quality value.   
     
     
         6 . The apparatus according to  claim 3 , wherein:
 the beam recovery signaling further includes information on the quality value of each candidate beam.   
     
     
         7 . The apparatus according to  claim 4 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:
 if it is determined that there is no candidate beam having a quality value exceeding the first and second quality threshold,   include, within the beam recovery signaling in the MAC CE, information on one candidate beam having the highest quality value among the detected candidate beams.   
     
     
         8 . The apparatus according to  claim 4 , wherein the at least one processor and the computer program code are configured to cause the apparatus to:
 if it is determined that there is no candidate beam having a quality value exceeding the first and second quality threshold,   indicate, by the user equipment to the network entity, that no candidate is available.   
     
     
         9 . The apparatus according to  claim 4 , wherein:
 if it is determined that there is one candidate beam existing on the first serving cell,   the beam recovery signaling includes the one candidate beam, wherein   the beam recovery signaling optionally includes information whether or not the candidate beam exceeds the first and second quality threshold, and   the quality value of the candidate beam is optionally signaled in a separate transmission to the network entity.   
     
     
         10 . The apparatus according to  claim 2 , wherein:
 a candidate beam having a quality value indicated by a channel state information reference signal, CSI-RS, is prioritized over a candidate beam having a quality value indicated by a synchronization signal block, SSB, if the quality value indicated by the CSI-RS is equal to or higher that the quality value indicated by the SSB including a predetermined offset value.   
     
     
         11 . The apparatus according to  claim 2 , wherein:
 the quality value and/or the threshold value is one of reference signal received power, RSRP, reference signal received quality, RSRQ, and signal-to-noise ratio, SINR.   
     
     
         12 . A method, comprising:
 determining, after a beam failure has been detected by a user equipment on a first serving cell of the user equipment, whether at least one candidate beam is above a first threshold, and   composing, based on the determining that none of the at least one candidate beam is above the first threshold, beam recovery signaling, the beam recovery signaling indicating the failed first cell and that no candidate beam is available for the failed first cell,   transmitting, to a network entity, the beam recovery signaling on a resource provided by a second serving cell.   
     
     
         13 . The method according to  claim 12 , further comprising:
 detecting at least one candidate beam existing on the resource provided by the first serving cell,   receiving, from the network entity, a first quality threshold for a candidate beam to be used for the beam failure recovery,   determining whether a quality value of the at least one candidate beam for the beam failure recovery exceeds the first quality threshold.   
     
     
         14 . The method according to  claim 13 , wherein
 if it is determined that there is at least one candidate beam associated with contention free random access, CFRA, signal and having a quality value exceeding the first quality threshold,   the beam recovery signaling is transmitted to the network entity using contention free random-access transmission to indicate at least one of candidates having quality value exceeding the first quality threshold.