Apparatuses and methods for beam identification through the physical random access channel (PRACH) and efficient PRACH resource utilization

A method for beam identification through a PRACH, executed by a UE wirelessly connected to a cellular station, the method comprising:

• selecting a downlink reference signal associated with a candidate beam among a plurality of downlink reference signals comprising CSI-RS resources, SS blocks, or PBCH blocks;
• determining one set from a plurality of sets of PRACH preambles and RACH occasions for the selected downlink reference signal according to an association configured between the downlink reference signals and PRACH resources;
• and
• using the determined set of PRACH preamble and RACH occasion to perform a PRACH transmission to the cellular station,
• wherein the association between the downlink reference signal and the PRACH resource indicates the downlink reference signal selected by the UE to the cellular station,
• wherein the association between the downlink reference signal and the candidate beam indicates the candidate beam to the cellular station, and
• wherein the cellular station identifies the candidate beam indicated by the UE based on determination of the PRACH resource.

A cellular station, comprising:

• a wireless transceiver, configured to perform wireless transmission and reception to and from a UE;
• and
• a controller, configured to receive a PRACH transmission which utilizes a PRACH resource from the UE via the wireless transceiver, determine one of a plurality of downlink reference signals comprising CSI-RS resources, SS blocks, or PBCH blocks according to an association configured between the downlink reference signals and the PRACH resource, and identify a candidate beam associated with the determined downlink reference signal,
• wherein the association between the downlink reference signal and the PRACH resource indicates the downlink reference signal selected by the UE to the cellular station,
• wherein the association between the downlink reference signal and the candidate beam indicates the candidate beam to the cellular station, and
• wherein the cellular station identifies the candidate beam indicated by the UE based on determination of the PRACH resource, wherein the PRACH transmission comprising a PRACH preamble transmitted on a RACH occasion, and the association is configured between the downlink reference signals and the PRACH preamble, the RACH occasion, or a combination thereof.

A method for beam identification through a PRACH, executed by a cellular station wirelessly connected to a UE, the method comprising:

• receiving a PRACH transmission which utilizes a PRACH resource from the UE;
• determining one of a plurality of downlink reference signals comprising CSI-RS resources, SS blocks, or PBCH blocks according to an association configured between the downlink reference signals and the PRACH resource;
• and
• identifying a candidate beam associated with the determined downlink reference signal,
• wherein the association between the downlink reference signal and the PRACH resource indicates the downlink reference signal selected by the UE to the cellular station,
• wherein the association between the downlink reference signal and the candidate beam indicates the candidate beam to the cellular station, and
• wherein the cellular station identifies the candidate beam indicated by the UE based on determination of the PRACH resource, wherein the PRACH transmission comprising a PRACH preamble transmitted on a RACH occasion, and the association is configured between the downlink reference signals and the PRACH preamble, the RACH occasion, or a combination thereof.