Methods and apparatus for time-domain PRACH resource determination in wireless communication

1 . A baseband processor of a wireless equipment (UE) configured to perform operations comprising:

receiving Physical Random Access Channel (PRACH) configuration information including an indication of a first PRACH preamble format for a predefined subcarrier spacing (SCS) to enhance cell coverage, wherein the PRACH configuration information further includes a field that indicates a second PRACH preamble format in a time-domain based on a short sequence PRACH preamble format that extends the short sequence PRACH preamble format, wherein the short sequence PRACH preamble format is repeated over two consecutive time-domain random access channel (RACH) occasions (ROs) and the two consecutive ROs are linked to a synchronization signal block (SSB)/Channel State Information Reference Signal (CSI-RS) or two or more different SSBs/CSI-RSs;

receiving RACH configuration information;

transmitting a PRACH preamble using the first and second PRACH preamble formats over a PRACH to a base station (BS); and

based on a field comprised in the RACH configuration information that indicates that a listen before talk (LBT) procedure is not required before a RACH procedure, transmitting a RACH Message 1 as a short control signaling without performing the LBT procedure.

2 . The baseband processor of claim 1 , wherein the short sequence PRACH preamble format includes B4 format.

3 . The baseband processor of claim 1 , wherein the second PRACH preamble format doubles a guard period (GP) and a cyclic prefix duration (NCP).

4 . The baseband processor of claim 1 , wherein the second PRACH preamble format is defined in the time-domain based on a long sequence PRACH preamble format, and wherein the predefined SCS includes 120 kilohertz (kHz).

5 . The baseband processor of claim 1 , wherein the two consecutive ROs are allocated within a same frequency resource.

6 . The baseband processor of claim 1 , wherein a Random Access Radio Network Temporary Identifier (RA-RNTI) is calculated based on a merge of the two consecutive ROs.

7 . The baseband processor of claim 1 , wherein the operations further comprise:

receiving a PRACH configuration through signaling of a PRACH configuration index, wherein the PRACH configuration index indicates a number of PRACH slots within a 120 kilohertz (kHz) slot.

8 . The baseband processor of claim 7 , wherein a slot index of the predefined SCS is derived from 120 kHz.

9 . The baseband processor of claim 1 , wherein a slot number is between 0 to 79.

10 . The baseband processor of claim 1 , wherein a PRACH duration is 24 for the second PRACH preamble format.

11 . The baseband processor of claim 1 , wherein the two consecutive ROs are merged into an RO with the predefined SCS.

12 . The baseband processor of claim 1 , wherein a floor operation is added to calculate a time index of a PRACH transmission symbol.

13 . The baseband processor of claim 1 , wherein the predefined SCS includes 480 kilohertz (kHz) and 960 kHz.

14 . A user equipment (UE) device comprising:

at least one antenna;

at least one radio, wherein the at least one radio is configured to communicate with a second UE of a communication network using the at least one antenna; and

at least one processor coupled to the at least one radio, wherein the at least one processor is configured to perform operations comprising:

receiving Physical Random Access Channel (PRACH) configuration information including an indication of a first PRACH preamble format for a predefined subcarrier spacing (SCS) to enhance cell coverage, wherein the PRACH configuration information further includes a field that indicates a second PRACH preamble format in a time-domain based on a short sequence PRACH preamble format that extends the short sequence PRACH preamble format, wherein the short sequence PRACH preamble format is repeated over two consecutive time-domain random access channel (RACH) occasions (ROs) and the two consecutive ROs are linked to a synchronization signal block (SSB)/Channel State Information Reference Signal (CSI-RS) or two or more different SSBs/CSI-RSs;

receiving RACH configuration information;

transmitting a PRACH preamble using the first and second PRACH preamble formats over a PRACH to a base station (BS); and

based on a field comprised in the RACH configuration information that indicates that a listen before talk (LBT) procedure is not required before a RACH procedure, transmitting a RACH Message 1 as a short control signaling without performing the LBT procedure.

15 . A base station (BS) comprising a processor configured to perform operations comprising:

generating Physical Random Access Channel (PRACH) configuration information including an indication of a PRACH preamble format in a time-domain based on a short sequence PRACH preamble format for a predefined subcarrier spacing (SCS) to enhance cell coverage, wherein the short sequence PRACH preamble format is repeated over two consecutive time-domain random access channel (RACH) occasions (ROs) and the two consecutive ROs are linked to a synchronization signal block (SSB)/Channel State Information Reference Signal (CSI-RS) or two or more different SSBs/CSI-RSs;

generating RACH configuration information including a field that indicates that a listen before talk (LBT) procedure is not required before a RACH procedure;

transmitting the PRACH configuration information and the RACH configuration information to a user equipment (UE); and

receiving a RACH Message 1 from the UE as a short control signaling without the LBT procedure.

16 . The BS as in claim 15 , wherein the short sequence PRACH preamble format includes B4 format.