Method and user equipment for performing uplink transmissions and related base station

1 . A method for performing uplink transmissions by a User Equipment (UE), the method comprising:

receiving, from a base station, a Physical Random Access Channel (PRACH) configuration indicating a plurality of parameters and a first set of PRACH resources, each of the plurality of parameters corresponding to a respective one of the first set of PRACH resources;

initiating a Random Access (RA) procedure;

measuring a plurality of Downlink (DL) Reference Signals (RSs) to obtain a plurality of Reference Signal Received Power (RSRP) values;

selecting, among the plurality of DL RSs, a DL RS for the RA procedure after determining that all of the plurality of RSRP values are less than an RSRP threshold;

selecting a first PRACH resource from the first set of PRACH resources to transmit an RA preamble for the RA procedure, wherein the first PRACH resource corresponds to a first parameter of the plurality of parameters and is associated with the DL RS selected for the RA procedure; and

performing Multiple-PRACH (MP) transmissions on the first PRACH resource, the MP transmissions comprising transmitting the RA preamble a first number of times before the UE begins monitoring for a Random Access Response (RAR) that corresponds to the RA preamble, wherein:

the first set of PRACH resources is configured for the MP transmissions, and

the first number of times is determined by the first parameter.

2 . The method according to claim 1 , wherein the PRACH configuration further indicates a second set of PRACH resources that is configured for a Single-PRACH (SP) transmission, wherein the SP transmission comprises:

transmitting the RA preamble only once before the UE begins monitoring for the RAR that corresponds to the RA preamble.

3 . The method according to claim 1 , wherein the PRACH configuration is configured on a per-DL-RS basis.

4 . The method according to claim 1 , wherein:

a second PRACH resource of the first set of PRACH resources corresponds to a second parameter of the plurality of parameters,

the second parameter indicates a second number of times to transmit the RA preamble, and

the first number of times is different from the second number of times.

5 . The method according to claim 1 , further comprising:

determining whether to change from the first PRACH resource to a second PRACH resource of the first set of PRACH resources for transmitting the RA preamble based on at least one of:

a number of rounds in which the UE performs the MP transmissions, or

whether MP transmissions performed in two consecutive rounds are associated with the DL RS.

6 . The method according to claim 5 , further comprising:

receiving, from the base station, a counter threshold for configuring a counter;

monotonically changing a value of the counter after determining that the MP transmissions performed in the two consecutive rounds are associated with the DL RS; and

selecting the second PRACH resource for transmitting the RA preamble after determining that the value of the counter has reached the counter threshold.

7 . The method according to claim 6 , wherein a transmission power of transmitting the RA preamble on the second PRACH resource is higher than a transmission power of transmitting the RA preamble on the first PRACH resource.

8 . A User Equipment (UE) for performing uplink transmissions, the UE comprising:

at least one processor; and

at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the UE to:

receive, from a base station, a Physical Random Access Channel (PRACH) configuration indicating a plurality of parameters and a first set of PRACH resources, each of the plurality of parameters corresponding to a respective one of the first set of PRACH resources;

initiate a Random Access (RA) procedure;

measure a plurality of Downlink (DL) Reference Signals (RSs) to obtain a plurality of Reference Signal Received Power (RSRP) values;

select, among the plurality of DL RSs, a DL RS for the RA procedure after determining that all of the plurality of RSRP values are less than an RSRP threshold;

select a first PRACH resource from the first set of PRACH resources to transmit an RA preamble for the RA procedure, wherein the first PRACH resource corresponds to a first parameter of the plurality of parameters and is associated with the DL RS selected for the RA procedure; and

perform Multiple-PRACH (MP) transmissions on the first PRACH resource, the MP transmissions comprising transmitting the RA preamble a first number of times before the UE begins monitoring for a Random Access Response (RAR) that corresponds to the RA preamble,

wherein the first set of PRACH resources is configured for the MP transmissions, and the first number of times is determined by the first parameter.

9 . The UE according to claim 8 , wherein the PRACH configuration further indicates a second set of PRACH resources that is configured for a Single-PRACH (SP) transmission, wherein the SP transmission comprises:

transmitting the RA preamble only once before the UE begins monitoring for the RAR that corresponds to the RA preamble.

10 . The UE according to claim 8 , wherein the PRACH configuration is configured on a per-DL-RS basis.

11 . The UE according to claim 8 , wherein:

a second PRACH resource of the first set of PRACH resources corresponds to a second parameter of the plurality of parameters,

the second parameter indicates a second number of times to transmit the RA preamble, and

the first number of times is different from the second number of times.

12 . The UE according to claim 8 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to:

determine whether to change from the first PRACH resource to a second PRACH resource of the first set of PRACH resources for transmitting the RA preamble based on at least one of:

a number of rounds in which the UE performs the MP transmissions, or

whether MP transmissions performed in two consecutive rounds are associated with the DL RS.

13 . The UE according to claim 12 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the UE to:

receive, from the base station, a counter threshold for configuring a counter from the base station;

monotonically change a value of the counter after determining that the MP transmissions performed in the two consecutive rounds are associated with the DL RS; and

select the second PRACH resource for transmitting the RA preamble after determining that the value of the counter has reached the counter threshold.

14 . The UE according to claim 13 , wherein a transmission power of transmitting the RA preamble on the second PRACH resource is higher than a transmission power of transmitting the RA preamble on the first PRACH resource.