PUCCH resource configuration in two-step RACH

1. A method of wireless communication comprising:

receiving, by a user equipment (UE) from a base station (BS), a random access channel (RACH) response message as part of a two-step RACH procedure;

decoding, by the UE in response to a radio resource control (RRC) connection state corresponding to a connected state, a physical downlink control channel (PDCCH) of the RACH response message to obtain a resource indicator based on a downlink control information (DCI) of the PDCCH;

decoding, by the UE in response to the RRC connection state corresponding to a non-connected state, a physical downlink shared channel (PDSCH) of the RACH response message to obtain the resource indicator of the PDSCH;

determining, by the UE, physical uplink control channel (PUCCH) resources to use for a hybrid automatic repeat request (HARQ) procedure based on the resource indicator; and

transmitting, by the UE to the BS, a HARQ message using the PUCCH resources.

2. The method of claim 1 , wherein the DCI comprises DCI format 1_0.

3. The method of claim 1 , wherein the decoding in response to the RRC connection state corresponding to a connected state further comprises:

accessing, by the UE, the resource indicator in a PUCCH resource indicator field of the DCI.

4. The method of claim 3 , wherein the resource indicator comprises a length of four bits.

5. The method of claim 1 , wherein the decoding in response to the RRC connection state corresponding to a connect state further comprises:

accessing, by the UE, a first part of the resource indicator in a first field of the DCI;

accessing, by the UE, a second part of the resource indicator in a second field of the DCI following the first field with another field in between the first and second fields; and

combining, by the UE, the first part and the second part to form the resource indicator.

6. The method of claim 1 , further comprising:

decoding, by the UE prior to the transmitting, a physical downlink shared channel (PDSCH) of the RACH response message; and

determining, by the UE, a timing advance from the PDSCH of the RACH response message for the HARQ procedure.

7. The method of claim 1 , wherein the PUCCH resources determined from the PDSCH include dynamically selected configuration parameters.

8. The method of claim 1 , wherein the RACH message comprises a multicast message.

9. The method of claim 1 , wherein the RACH message comprises a unicast message.

10. The method of claim 1 , wherein the determining the PUCCH resources further comprises:

accessing, by the UE, a look-up table based on the resource indicator.

11. The method of claim 10 , wherein the look-up table comprises a first number of entries in response to the resource indicator comprising a length of four bits, and a second number of entries in response to the resource indicator comprising a length of three bits, the second number of entries comprising a subset of the first number of entries.

12. The method of claim 1 , wherein the decoding in response to the RRC connection state corresponding to a non-connected state further comprises:

applying, by the UE, a message B radio network temporary identifier (RNTI) to descramble and decode the PDSCH.

13. A method of wireless communication comprising:

receiving, by a base station (BS) from a user equipment (UE), a random access channel (RACH) message as part of a two-step RACH procedure;

including, by the BS, a resource indicator in downlink control information (DCI) in a physical downlink control channel (PDCCH) for use by the UE with a radio resource control (RRC) connection state corresponding to a connected state;

including, by the BS, the resource indicator in a physical downlink shared channel (PDSCH) for use by the UE with a RRC connection state corresponding to a non-connected state, the resource indicator related to physical uplink control channel (PUCCH) resources;

transmitting, by the BS to the UE, the PDCCH and the PDSCH as part of a RACH response message; and

receiving, by the BS from the UE, a hybrid automatic repeat request (HARQ) message using the PUCCH resources.

14. The method of claim 13 , further comprising:

configuring, by the BS, the DCI for inclusion in the PDCCH according to DCI format 1_0.

15. The method of claim 14 , wherein the configuring further comprises:

splitting, by the BS, the resource indicator into a first part and a second part;

adding, by the BS, the first part in a first field of the DCI; and

adding, by the BS, the second part in a second field of the DCI following the first field.

16. The method of claim 13 , wherein the RACH response message comprises a multicast message.

17. The method of claim 13 , wherein the RACH response message comprises a unicast message.

18. The method of claim 13 , wherein a look-up table associated with the resource indicator comprises a first number of entries in response to the resource indicator comprising a length of four bits, and a second number of entries in response to the resource indicator comprising a length of three bits, the second number of entries comprising a subset of the first number of entries.

19. The method of claim 13 , further comprising:

including, by the BS, a timing advance for the UE in a physical downlink shared channel (PDSCH) of the RACH response message; and

transmitting, by the BS to the UE, the PDSCH as another part of the RACH response message.

20. The method of claim 13 , further comprising:

scrambling, by the BS prior to the transmitting and as part of the RACH response message, a cyclic redundancy check (CRC) of a physical downlink control channel (PDCCH) with a message B radio network temporary identifier (RNTI).

21. A user equipment, comprising:

a transceiver configured to receive, from a base station (BS), a random access channel (RACH) response message as part of a two-step RACH procedure; and

a processor configured to:

decode, in response to a radio resource control (RRC) connection state corresponding to a connected state, a physical downlink control channel (PDCCH) of the RACH response message to obtain a resource indicator based on a downlink control information (DCI) of the PDCCH;

decode, in response to the RRC connection state corresponding to a non-connected state, a physical downlink shared channel (PDSCH) of the RACH response message to obtain the resource indicator of the PDSCH; and

determine physical uplink control channel (PUCCH) resources to use for a hybrid automatic repeat request (HARQ) procedure based on the resource indicator,

wherein the transceiver is further configured to transmit, to the BS, a HARQ message using the PUCCH resources.

22. The user equipment of claim 21 , wherein the DCI comprises DCI format 1_0.

23. The user equipment of claim 21 , wherein the processor is further configured to:

access the resource indicator in a PUCCH resource indicator field of the DCI.

24. The user equipment of claim 23 , wherein the resource indicator comprises a length of four bits.

25. The user equipment of claim 21 , wherein the processor is further configured to:

access a first part of the resource indicator in a first field of the DCI;

access a second part of the resource indicator in a second field of the DCI following the first field with another field in between the first and second fields; and

combine the first part and the second part to form the resource indicator.

26. The user equipment of claim 21 , wherein the processor is further configured to:

decode, prior to the transmission, a physical downlink shared channel (PDSCH) of the RACH response message; and

determine a timing advance from the PDSCH of the RACH response message for the HARQ procedure.

27. The user equipment of claim 21 , wherein the PUCCH resources determined from the PDSCH include dynamically selected configuration parameters.

28. The user equipment of claim 21 , wherein the RACH message comprises a multicast message.

29. The user equipment of claim 21 , wherein the RACH message comprises a unicast message.

30. The user equipment of claim 21 , wherein the processor is further configured to access a look-up table based on the resource indicator.

31. The user equipment of claim 30 , wherein the look-up table comprises a first number of entries in response to the resource indicator comprising four bits, and a second number of entries in response to the resource indicator comprising three bits, the second number of entries comprising a subset of the first number of entries.

32. The user equipment of claim 21 , wherein the processor is further configured, as part of the decode in response to the RRC connection state corresponding to a non-connected state, to:

apply a message B radio network temporary identifier (RNTI) to descramble and decode the PDSCH.

33. A base station, comprising:

a transceiver configured to receive, from a user equipment (UE), a random access channel (RACH) message as part of a two-step RACH procedure; and

a processor configured to:

include a resource indicator in downlink control information (DCI) in a physical downlink control channel (PDCCH) for use by the UE with a radio resource control (RRC) connection state corresponding to a connected state; and

include the resource indicator in a physical downlink shared channel (PDSCH) for use by the UE with a RRC connection state corresponding to an unconnected state, the resource indicator related to physical uplink control channel (PUCCH) resources;

wherein the transceiver is further configured to:

transmit, to the UE, the PDCCH and the PDSCH as part of a RACH response message; and

receive, from the UE, a hybrid automatic repeat request (HARQ) message using the PUCCH resources.

34. The base station of claim 33 , wherein the processor is further configured to:

configure the DCI for inclusion in the PDCCH according to DCI format 1_0.

35. The base station of claim 34 , wherein the processor is further configured to:

split the resource indicator into a first part and a second part;

add the first part in a first field of the DCI; and

add the second part in a second field of the DCI following the first field.

36. The base station of claim 33 , wherein the RACH response message comprises a multicast message.

37. The base station of claim 33 , wherein the RACH response message comprises a unicast message.

38. The base station of claim 33 , wherein a look-up table associated with the resource indicator comprises a first number of entries in response to the resource indicator comprising four bits, and a second number of entries in response to the resource indicator comprising three bits, the second number of entries comprising a subset of the first number of entries.

39. The base station of claim 33 , wherein:

the processor is further configured to include a timing advance for the UE in a physical downlink shared channel (PDSCH) of the RACH response message; and

the transceiver is further configured to transmit, to the UE, the PDSCH as another part of the RACH response message.

40. The base station of claim 33 , wherein the processor is further configured to:

scramble, as part of the RACH response message, a cyclic redundancy check (CRC) of a physical downlink control channel (PDCCH) with a message B radio network temporary identifier (RNTI).