Methods, devices, and systems for beam refinement during handover

Abstract

A method for performing handover of a user equipment (UE) from a first base station to a second base station is disclosed. The method includes receiving, by the UE, a radio resource control (RRC) message from the first base station, the RRC message comprising at least one preamble index and a physical random access channel (PRACH) resource associated with a channel state information-reference signal (CSI-RS) index, and performing, by the UE, random access (RA) with the second base station based on the received RRC message.

What is claimed is: 
     
         1 . A method for performing handover of a user equipment (UE) from a first base station to a second base station, the method comprising:
 receiving, by the UE, a radio resource control (RRC) message from the first base station, the RRC message comprising at least one preamble index and a physical random access channel (PRACH) resource associated with a channel state information-reference signal (CSI-RS) index;   performing, by the UE, random access (RA) with the second base station based on the received RRC message.   
     
     
         2 . The method of  claim 1 , further comprising:
 receiving, by the second base station, a handover request from the first base station;   allocating a plurality of preambles for the UE to perform at least one of downlink transmission beam selection and uplink transmission beam sweeping based on the handover request.   
     
     
         3 . The method of  claim 1 , further comprising:
 receiving, by the second base station, a handover request from the first base station;   allocating, by the second base station, a plurality of dedicated PRACH resource sets for the UE to perform at least one of downlink transmission beam selection and uplink transmission beam sweeping based on the handover request.   
     
     
         4 . The method of  claim 1 , further comprising:
 transmitting, by the first base station, a handover request to the second base station through an access and mobility management function (AMF).   
     
     
         5 . The method of  claim 4 , wherein the handover request comprises a measurement report of the second base station by the UE, the measurement report comprising the CSI-RS index. 
     
     
         6 . The method of  claim 1 , further comprising:
 selecting, by the UE, at least one of the preamble index and the PRACH resource based on reference signal received power measurements of the CSI-RS index.   
     
     
         7 . The method of  claim 1 , further comprising:
 receiving, by the UE, a random access response from the second base station on a Physical Downlink Shared Channel (PDSCH);   wherein antenna ports of a demodulation reference signal (DM-RS) for the random access response from the second base station to the UE are quasi co-located with one of an SS block and a CSI-RS resource selected by the UE for a preamble transmission and an association with the PRACH resource.   
     
     
         8 . The method of  claim 7 , further comprising:
 after receiving the random access response, determining, by the UE, that the DM-RS ports of the PDSCH is quasi co-located with one of the SS block and the CSI-RS resource selected by the UE for the preamble transmission and the association with the PRACH resource.   
     
     
         9 . A user equipment (UE) comprising:
 one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and   at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to:
 receive a radio resource control (RRC) message from the first base station, the RRC message comprising at least one preamble index and a physical random access channel (PRACH) resource associated with a channel state information-reference signal (CSI-RS) index; 
 perform random access (RA) with the second base station based on the received RRC message. 
   
     
     
         10 . The UE of  claim 9 , wherein the at least one processor is further configured to execute the computer-executable instructions to:
 perform at least one of downlink transmission beam selection and uplink transmission beam sweeping based on a plurality of preambles or a plurality of dedicated PRACH resource sets allocated by the second base station.   
     
     
         11 . The UE of  claim 10 , wherein the second base station allocates the plurality of preambles or the plurality of dedicated PRACH resource sets for the UE based on a handover request from the first base station. 
     
     
         12 . The UE of  claim 9 , wherein the at least one processor is further configured to execute the computer-executable instructions to:
 send a measurement report of the second base station to the first base station, the measurement report comprising the CSI-RS index.   
     
     
         13 . The UE of  claim 9 , wherein the at least one processor is further configured to execute the computer-executable instructions to:
 select at least one of the preamble index and the PRACH resource based on reference signal received power measurements of the CSI-RS index.   
     
     
         14 . The UE of  claim 9 , wherein the at least one processor is further configured to execute the computer-executable instructions to:
 receive, from the second base station, a random access response on a Physical Downlink Shared Channel (PDSCH); and   wherein antenna ports of a demodulation reference signal (DM-RS) for the random access response from the second base station to the UE are quasi co-located with one of an SS block and a CSI-RS resource selected by the UE for a preamble transmission and an association with the PRACH resource.   
     
     
         15 . The UE of  claim 14 , wherein the at least one processor is further configured to execute the computer-executable instructions to:
 after receiving the random access response, determine that the DM-RS ports of the PDSCH is quasi co-located with one of the SS block and the CSI-RS resource selected by the UE for the preamble transmission and the association with the PRACH resource.