Method and apparatus for non-codebook based uplink multiple-input and multiple-output

A method implemented by a transmission and reception point (TRP), the method comprising:

• sending an allocation of at least one sounding reference signal (SRS) resource in a uplink subframe to a user equipment (UE) for a first set of uplink transmission beams;
• receiving precoded SRSs sent in the at least one SRS resource, wherein the precoded SRSs are precoded with UE selected precoders and at least one rank;
• and
• sending an identification of one or more precoders for a second set of uplink transmission beams to the UE, wherein the second set of uplink transmission beams is selected from the first set of uplink transmission beams, and wherein the one or more precoders for the second set of uplink transmission beams are based on the precoded SRSs.

A user equipment (UE) comprising:

• a processor;
• and
• a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
• receive an allocation of at least one sounding reference signal (SRS) resource in an uplink subframe from a transmission and reception point (TRP) for a first set of uplink transmission beams;
• transmit precoded SRSs in the at least one SRS resource to the TRP, wherein the precoded SRSs are precoded with UE-selected precoders and at least one rank;
• and
• receive an identification of one or more precoders for a second set of uplink transmission beams, wherein the second set of uplink transmission beams is selected from the first set of uplink transmission beams, and wherein the one or more precoders are based on the precoded SRSs.

A transmission and reception point (TRP) comprising:

• a processor;
• and
• a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
• send an allocation of at least one sounding reference signal (SRS) resource in a uplink subframe to a user equipment (UE) for a first set of uplink transmission beams;
• receive precoded SRSs sent in the at least one SRS resource, wherein the precoded SRSs are precoded with UE selected precoders and at least one rank;
• and
• send an identification of one or more precoders for a second set of uplink transmission beams to the UE, wherein the second set of uplink transmission beams is selected from the first set of uplink transmission beams, and wherein the one or more precoders for the second set of uplink transmission beams are based on the precoded SRSs.