Method and apparatus for random access procedure

1. A method for a random access (RA) procedure performed by a user equipment (UE) having a specific access identity value, the method comprising:

receiving a mapping table via radio resource control (RRC) signaling from a base station, the mapping table including one or more access identity values and one or more backoff multipliers corresponding to the one or more access identity values;

transmitting a first RA preamble of the RA procedure to the base station;

receiving a random access response (RAR) in response to the first RA preamble from the base station, the RAR including a backoff value;

setting a resultant backoff value by multiplying the backoff value by a specific backoff multiplier corresponding to the specific access identity value of the UE in a case that the specific access identity value of the UE is included in the mapping table and an indication corresponding to the specific access identity value of the UE is not a specific value;

setting the resultant backoff value to the backoff value in a case that the specific access identity value of the UE is not included in the mapping table; and

transmitting a second RA preamble of the RA procedure to the base station after a duration indicated by the resultant backoff value expires.

2. The method of claim 1 , wherein each of the one or more access identity values is one of an access category value, an access class value, and a slice identity value.

3. The method of claim 1 , wherein the mapping table is included in a RACH- ConfigCommon Information Element (IE) in the RRC signaling.

4. The method of claim 1 , further comprising:

setting the resultant backoff value to the backoff value in a case that the specific access identity value of the UE is included in the mapping table and the indication is the specific value.

5. A user equipment (UE) having a specific access identity value, the UE comprising:

one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and

at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to:

receive a mapping table via radio resource control (RRC) signaling from a base station, the mapping table including one or more access identity values and one or more backoff multipliers corresponding to the one or more access identity values;

transmit a first random access (RA) preamble of the RA procedure to the base station;

receive a random access response (RAR) in response to the first RA preamble from the base station, the RAR including a backoff value;

set a resultant backoff value by multiplying the backoff value by a specific backoff multiplier corresponding to the specific access identity value of the UE in a case that the specific access identity value of the UE is included in the mapping table and an indication corresponding to the specific access identity value of the UE is not a specific value;

set the resultant backoff value to the backoff value in a case that the specific access identity value of the UE is not included in the mapping table; and

transmit a second RA preamble of the RA procedure to the base station after a duration indicated by the resultant backoff value expires.

6. The UE of claim 5 , wherein each of the one or more access identity values is one of an access category value, an access class value, and a slice identity value.

7. The UE of claim 5 , wherein the mapping table is included in a RACH-ConfigCommon Information Element (IE) in the RRC signaling.

8. The UE of claim 5 , wherein the at least one processor is further configured to execute the computer-executable instructions to set the resultant backoff value to the backoff value in a case that the specific access identity value of the UE is included in the mapping table and the indication is the specific value.

9. A method for a random access (RA) procedure performed by a base station, the method comprising:

transmitting a mapping table via radio resource control (RRC) signaling to a user equipment (UE) with a specific access identity value, the mapping table including one or more access identity values and one or more backoff multipliers corresponding to the one or more access identity values;

receiving a first RA preamble of the RA procedure from the UE;

transmitting a random access response (RAR) in response to the first RA preamble to the UE, the RAR including a backoff value; and

receiving a second RA preamble of the RA procedure from the UE, wherein:

a time interval between the first RA preamble and the second RA preamble is associated with a product of the backoff value and a specific backoff multiplier corresponding to the specific access identity value of the UE in a case that the specific access identity value of the UE is included in the mapping table and an indication corresponding to the specific access identity value of the UE is not a specific value, and

the time interval between the first RA preamble and the second RA preamble is associated with the backoff value in a case that the specific access identity value of the UE is not included in the mapping table.

10. The method of claim 9 , wherein each of the one or more access identity values is one of an access category value, an access class value, and a slice identity value.

11. The method of claim 10 , wherein the mapping table is included in a RACH-ConfigCommon Information Element (IE) in the RRC signaling.

12. The method of claim 9 , wherein the time interval between the first RA preamble and the second RA preamble is associated with the backoff value in a case that the specific access identity value of the UE is included in the mapping table and the indication is the specific value.