Method and apparatus for random access in wireless communication systems

Abstract

Apparatuses and methods for random access procedures with multiple transmission reception points or cells in a wireless communication system. A method for performing random access (RA) procedures by a user equipment includes receiving a first configuration for RA. The method further includes initiating a first RA procedure with a first transmission-reception point (TRP) based on the first configuration and initiating a second RA procedure with a second TRP prior to completion of the first RA procedure. A method for operating a base station includes transmitting a first configuration for RA corresponding to a first TRP and transmitting a second configuration for RA corresponding to a second TRP. The first TRP and the second TRP are associated with a same cell.

What is claimed is: 
     
         1 . A method for performing random access (RA) procedures, the method comprising:
 receiving a first configuration for RA;   initiating a first RA procedure with a first transmission-reception point (TRP) based on the first configuration; and   initiating a second RA procedure with a second TRP prior to completion of the first RA procedure.   
     
     
         2 . The method of  claim 1 , wherein the first and second TRPs are associated with a same cell or with different cells. 
     
     
         3 . The method of  claim 1 , further comprising:
 receiving:
 a second configuration for RA, wherein the second configuration is different from the first configuration, 
 a first mapping between the first TRP and a first group of downlink reference signals (DL RSs), and 
 a second mapping between the second TRP and a second group of DL RSs; and 
   transmitting:
 for the first RA procedure, a first physical random access channel (PRACH) associated with a first DL RS from the first group of DL RSs, and 
 for the second RA procedure, a second PRACH associated with a second DL RS from the second group of DL RSs. 
   
     
     
         4 . The method of  claim 3 , wherein a DL RS is a synchronization signal and physical broadcast channel (SS/PBCH) block, or a channel state information (CSI) RS. 
     
     
         5 . The method of  claim 1 , further comprising:
 determining:
 a first downlink reference signal (DL RS) associated with the first RA procedure, 
 first random access occasions (ROs) associated with the first DL RS based on the first configuration, 
 a second DL RS associated with the second RA procedure, and 
 second ROs associated with the second DL RS, wherein the second ROs do not overlap in time with the first ROs; and 
   transmitting:
 a first physical random access channel (PRACH) in an RO from the first ROs, and 
 a second PRACH in an RO from the second ROs. 
   
     
     
         6 . The method of  claim 1 , further comprising:
 receiving:
 a first random access response (RAR) corresponding to the first RA procedure, wherein the first RAR includes a first temporary cell radio network temporary identifier (TC-RNTI) and a first uplink grant, and 
 a second RAR corresponding to the second RA procedure, wherein the second RAR includes a second TC-RNTI and a second uplink grant; and 
   transmitting:
 a first physical uplink shared channel (PUSCH) scheduled by the first uplink grant, wherein the first PUSCH includes first TRP-coordination assistance information, and 
 a second PUSCH scheduled by the second uplink grant, wherein the second PUSCH includes second TRP-coordination assistance information, 
   wherein the first TRP-coordination assistance information includes an indication for at least one of:
 whether the second RAR is received, 
 whether the second PUSCH includes the first TC-RNTI, and 
 a second downlink reference signal (DL RS) index associated with a second PRACH transmission that corresponds to the second RAR, and 
   wherein the second TRP-coordination assistance information includes an indication for at least one of:
 whether the first RAR is received, 
 whether the first PUSCH includes the second TC-RNTI, and 
 a first DL RS index associated with a first PRACH transmission that corresponds to the first RAR. 
   
     
     
         7 . The method of  claim 1 , wherein the first and second RA procedures are initiated by a downlink control information (DCI) format that includes:
 for the first RA procedure, at least one of:
 a first physical random access channel (PRACH) preamble index, 
 a first downlink reference signal (DL RS) index, 
 a first PRACH mask index, and 
 a first number of repetitions, and 
   for the second RA procedure, at least one of:
 a second PRACH preamble index, 
 a second DL RS index, 
 a second PRACH mask index, and 
 a second number of repetitions. 
   
     
     
         8 . A user equipment (UE) comprising:
 a transceiver configured to receive a first configuration for random access (RA); and   a processor operably coupled to the transceiver, the processor configured to initiate:
 a first RA procedure with a first transmission-reception point (TRP) based on the first configuration; and 
 a second RA procedure with a second TRP prior to completion of the first RA procedure. 
   
     
     
         9 . The UE of  claim 8 , wherein the first and second TRPs are associated with a same cell or with different cells. 
     
     
         10 . The UE of  claim 8 , wherein:
 the transceiver is further configured to receive:
 a second configuration for RA, wherein the second configuration is different from the first configuration, 
 a first mapping between the first TRP and a first group of downlink reference signals (DL RSs), and 
 a second mapping between the second TRP and a second group of DL RSs; and 
   the transceiver is further configured to transmit:
 for the first RA procedure, a first physical random access channel (PRACH) associated with a first DL RS from the first group of DL RSs, and 
 for the second RA procedure, a second PRACH associated with a second DL RS from the second group of DL RSs. 
   
     
     
         11 . The UE of  claim 8 , wherein a DL RS is a synchronization signal and physical broadcast channel (SS/PBCH) block, or a channel state information (CSI) RS. 
     
     
         12 . The UE of  claim 8 , wherein:
 the processor is further configured to determine:
 a first downlink reference signal (DL RS) associated with the first RA procedure, 
 first random access occasions (ROs) associated with the first DL RS based on the first configuration, 
 a second DL RS associated with the second RA procedure, and 
 second ROs associated with the second DL RS, wherein the second ROs do not overlap in time with the first ROs; and 
   the transceiver is further configured to transmit:
 a first physical random access channel (PRACH) in an RO from the first ROs, and 
 a second PRACH in an RO from the second ROs. 
   
     
     
         13 . The UE of  claim 8 , wherein:
 the transceiver is further configured to receive:
 a first random access response (RAR) corresponding to the first RA procedure, wherein the first RAR includes a first temporary cell radio network temporary identifier (TC-RNTI) and a first uplink grant, and 
 a second RAR corresponding to the second RA procedure, wherein the second RAR includes a second TC-RNTI and a second uplink grant; 
   the transceiver is further configured to transmit:
 a first physical uplink shared channel (PUSCH) scheduled by the first uplink grant, wherein the first PUSCH includes first TRP-coordination assistance information, and 
 a second PUSCH scheduled by the second uplink grant, wherein the second PUSCH includes second TRP-coordination assistance information; 
   the first TRP-coordination assistance information includes an indication for at least one of:
 whether the second RAR is received, 
 whether the second PUSCH includes the first TC-RNTI, and 
 a second downlink reference signal (DL RS) index associated with a second PRACH transmission that corresponds to the second RAR; and 
   the second TRP-coordination assistance information includes an indication for at least one of:
 whether the first RAR is received, 
 whether the first PUSCH includes the second TC-RNTI, and 
 a first DL RS index associated with a first PRACH transmission that corresponds to the first RAR. 
   
     
     
         14 . The UE of  claim 8 , wherein the first and second RA procedures are initiated by a downlink control information (DCI) format that includes:
 for the first RA procedure, at least one of:
 a first physical random access channel (PRACH) preamble index, 
 a first downlink reference signal (DL RS) index, 
 a first PRACH mask index, and 
 a first number of repetitions, and 
   for the second RA procedure, at least one of:
 a second PRACH preamble index, 
 a second DL RS index, 
 a second PRACH mask index, and 
 a second number of repetitions. 
   
     
     
         15 . A base station comprising:
 a processor; and   a transceiver operably coupled to the processor, the transceiver configured to transmit:
 a first configuration for random access (RA) corresponding to a first transmission-reception point (TRP); and 
 a second configuration for RA corresponding to a second TRP, wherein the first TRP and the second TRP are associated with a same cell. 
   
     
     
         16 . The base station of  claim 15 , wherein the transceiver is further configured to:
 transmit:
 a first mapping between the first TRP and a first group of downlink reference signals (DL RSs), and 
 a second mapping between the second TRP and a second group of DL RSs; and 
   receive:
 a first physical random access channel (PRACH) associated with a first DL RS from the first group of DL RSs, and 
 a second PRACH associated with a second DL RS from the second group of DL RSs. 
   
     
     
         17 . The base station of  claim 15 , wherein a DL RS is a synchronization signal and physical broadcast channel (SS/PBCH) block or a channel state information (CSI) RS. 
     
     
         18 . The base station of  claim 15 , wherein:
 the transceiver is further configured to transmit:
 a first random access response (RAR) in first slots of a first monitoring window that includes a third number of slots, and 
 a second RAR in second slots of a second monitoring window that includes a fourth number of slots, 
   the first RAR is associated with the first TRP,   the second RAR is associated with the second TRP,   the first and second monitoring windows overlap, and   the first and second slots do not overlap.   
     
     
         19 . The base station of  claim 15 , wherein:
 the transceiver is further configured to transmit:
 a first random access response (RAR) associated with the first TRP, wherein the first RAR includes a first temporary cell radio network temporary identifier (TC-RNTI) and a first uplink grant, and 
 a second RAR associated with the second TRP, wherein the second RAR includes a second TC-RNTI and a second uplink grant; 
   the transceiver is further configured to receive:
 a first physical uplink shared channel (PUSCH) scheduled by the first uplink grant, wherein the first PUSCH includes first TRP-coordination assistance information, and 
 a second PUSCH scheduled by the second uplink grant, wherein the second PUSCH includes second TRP-coordination assistance information; 
   the first TRP-coordination assistance information includes an indication for at least one of:
 whether the second RAR is transmitted, 
 whether the second PUSCH includes the first TC-RNTI, and 
 a second downlink reference signal (DL RS) index associated with a second PRACH transmission that corresponds to the second RAR; and 
   the second TRP-coordination assistance information includes an indication for at least one of:
 whether the first RAR is transmitted, 
 whether the first PUSCH includes the second TC-RNTI, and 
 a first DL RS index associated with a first PRACH transmission that corresponds to the first RAR. 
   
     
     
         20 . The base station of  claim 15 , wherein:
 the transceiver is further configured to transmit a downlink control information (DCI) format, and   the DCI format indicates to initiate first and second RA procedures and includes:
 for the first RA procedure, at least one of:
 a first physical random access channel (PRACH) preamble index, 
 a first downlink reference signal (DL RS) index, 
 a first PRACH mask index, and 
 a first number of repetitions, and 
 
 for the second RA procedure, at least one of:
 a second PRACH preamble index, 
 a second DL RS index, 
 a second PRACH mask index, and 
 a second number of repetitions.