Physical random access channel (PRACH) format configuration

1. An apparatus comprising

processing circuitry, wherein, to facilitate a physical random access channel (PRACH) procedure, the processing circuitry is configured to cause a user equipment (UE) to:

decode system information block (SIB) information including configuration of a PRACH resource, wherein the configuration of a PRACH resource includes a plurality of PRACH instances;

determine a particular PRACH instance of the plurality of PRACH instances within the PRACH resource;

encode, for transmission to a base station, a PRACH preamble at the particular PRACH instance within the PRACH resource, wherein the PRACH preamble is associated with either a first preamble format or a second preamble format, depending on which PRACH instance is determined;

decode a random access channel response (RAR) message from the base station, the RAR message including an uplink grant for scheduling a physical uplink shared channel (PUSCH) transmission; and

encode data for transmission on the PUSCH based on the uplink grant,

wherein the RAR message is associated with a random access radio network temporary identifier (RA-RNTI), wherein the RA-RNTI is based on:

an index of an OFDM symbol;

a frequency index; and

a slot index;

wherein the RA-RNTI is associated with the particular PRACH instance inside the PRACH resource.

2. The apparatus of claim 1 , wherein the configuration of the PRACH resource includes a PRACH configuration index, wherein the PRACH preamble is transmitted with a starting symbol indicated by the PRACH configuration index.

3. The apparatus of claim 2 , wherein, when the first preamble format is one of formats A1, A2, and A3, the second preamble format is respectively one of formats B1, B2, and B3, and wherein formats A1-A3 have a zero guard period length, and formats B1-B3 have non-zero guard period length.

4. The apparatus of claim 3 , wherein, when the particular PRACH instance used for transmission of the PRACH preamble is a last PRACH instance within the PRACH resource, the PRACH preamble is one of the formats B1, B2, or B3.

5. The apparatus of claim 3 , wherein, when the particular PRACH instance used for transmission of the PRACH preamble is different from a last PRACH instance within the PRACH resource, the PRACH preamble is one of the formats A1, A2, or A3.

6. The apparatus of claim 2 , wherein said determining the particular PRACH instance includes randomly selecting the particular PRACH instance from the plurality of PRACH instances.

7. The apparatus of claim 2 , wherein the processing circuitry is configured to:

generate a hashing function based on a user equipment identifier (UE ID) associated with the apparatus; and

select the particular PRACH instance from the plurality of PRACH instances based on the generated hashing function.

8. The apparatus of claim 2 , wherein the processing circuitry is configured to:

select the particular PRACH occasion from the plurality of PRACH instances for transmission of the PRACH preamble based on a service priority indicator associated with the PUSCH transmission.

9. The apparatus of claim 1 , further comprising:

transceiver circuitry coupled to the processing circuitry; and

one or more antennas coupled to the transceiver circuitry.

10. The apparatus of claim 1 , wherein the OFDM symbol index is an index of the first OFDM symbol of the particular PRACH instance.

11. A method for operating a base station, the method comprising

encoding system information block (SIB) information including configuration of a PRACH resource, wherein the PRACH resource includes a plurality of PRACH instances;

decoding a PRACH preamble received at a particular one of the PRACH instances within the PRACH resource, wherein the PRACH preamble is based either on a first preamble format or a second preamble format;

encoding a random access channel response (RAR) message for transmission to a user equipment (UE), wherein the RAR message is encoded with a random access radio network temporary identifier (RA-RNTI) and includes an uplink grant for scheduling a physical uplink shared channel (PUSCH) transmission, wherein the RA-RNTI is based on:

an index of an OFDM symbol;

a frequency index; and

a slot index;

wherein the RA-RNTI is associated with the particular PRACH instance inside the PRACH resource; and

decoding data received on the PUSCH based on the uplink grant.

12. The method of claim 11 , wherein the base station is a next generation Node-B (gNB) or an evolved Node-B (eNB).

13. The method of claim 11 , wherein the base station comprises:

processing circuitry, wherein said encoding the SIB information, said decoding the PRACH preamble, and said encoding the RAR message are performed by the processing circuitry;

transceiver circuitry coupled to the processing circuitry; and

one or more antennas coupled to the transceiver circuitry.

14. The method of claim 11 , wherein the OFDM symbol index is an index of the first OFDM symbol of the particular PRACH instance.

15. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors of a user equipment (UE), wherein the instructions, when executed by the one or more processors, cause the UE to:

decode system information block (SIB) information including configuration of a PRACH resource, wherein the PRACH resource includes a plurality of PRACH instances;

encode, for transmission to a base station, a PRACH preamble at a particular one of the PRACH instances, within the PRACH resource, wherein the PRACH preamble is associated with either a first preamble format or a second preamble format, depending on which PRACH instance is determined; and

decode a random access channel response (RAR) message received from the base station in response to the PRACH preamble, the RAR message including an uplink grant for scheduling a physical uplink shared channel (PUSCH) transmission, wherein the RAR message is encoded with a random access radio network temporary identifier (RA-RNTI), wherein the RA-RNTI is based on:

an index of an OFDM symbol;

a frequency index; and

a slot index;

wherein the RA-RNTI is associated with the particular PRACH instance inside the PRACH resource.

16. The non-transitory computer-readable storage medium of claim 15 , wherein the configuration of the PRACH resource includes a PRACH configuration index, wherein the PRACH preamble is transmitted with a starting symbol indicated by the PRACH configuration index.

17. The non-transitory transitory computer-readable storage medium of claim 16 , wherein the instructions, when executed by the one or more processors, further cause the UE to:

determine the particular PRACH instance of the plurality of PRACH instances with the PRACH resource.

18. The non-transitory transitory computer-readable storage medium of claim 16 , wherein, when the first preamble format is one of formats A1, A2, and A3, the second preamble format is respectively one of formats B1, B2, and B3, and wherein formats A1-A3 have a zero guard period length, and formats B1-B3 have non-zero guard period length.

19. The non-transitory transitory computer-readable storage medium of claim 16 , wherein the instructions, when executed by the one or more processors, further cause the UE to:

select the particular PRACH instance from the plurality of PRACH instances for transmission of the PRACH preamble based on a service priority indicator associated with the PUSCH transmission.

20. The non-transitory computer-readable storage medium of claim 15 , wherein the OFDM symbol index is an index of the first OFDM symbol of the particular PRACH instance.