2-step RACH initiated by PDCCH order

1. A method of operating a base station (BS) comprising:

configuring, by the BS, a different search space configuration for a physical downlink control channel (PDCCH) ordered physical random access channel (PRACH) for an ordered 2-step random access channel (RACH) procedure compared to a PRACH of a 4-step RACH procedure,

wherein a frequency domain resource assignment field in a downlink control information (DCI) format 1_0 used to trigger the ordered 2-step RACH procedure is used to indicate a frequency domain resource allocation of a MsgA physical uplink shared channel (PUSCH) transmission associated with the PRACH for the 2-step RACH procedure, and a remaining resource configuration for the MsgA PUSCH transmission including a time domain resource allocation is indicated by one or more reserved bits in the DCI format 1_0;

transmitting, by the BS, a PDCCH signal to a user equipment (UE), wherein the PDCCH signal includes an indication of the PDCCH ordered 2-step RACH procedure; and

receiving, by the BS, a first step of the 2-step RACH procedure, wherein the first step includes a PRACH preamble and an associated MsgA PUSCH from the UE.

2. The method of claim 1 , wherein the indication includes the one or more reserved bits in the DCI format 1_0, wherein the one or more reserved bits are configured to be interpreted by the UE to trigger transmission of the MsgA PUSCH.

3. The method of claim 1 , wherein the indication includes a MsgA PUSCH resource index in the DCI format 1_0, and an association rule between the PRACH and the MsgA PUSCH resource for the 2-step RACH procedure, wherein the association rule is previously configured by higher layers in the BS.

4. The method of claim 1 , wherein the indication includes one or more reserved states in a PRACH Mask index field in the DCI format 1_0.

5. The method of claim 1 , wherein the indication includes a truncated 10-bit field in the DCI format 1_0, wherein the truncated 10-bit field further indicates at least a portion of a MsgA PUSCH resource configuration.

6. The method of claim 1 , wherein the indication includes a radio network temporary identifier (RNTI) configured via a dedicated radio resource control signaling.

7. The method of claim 1 , further comprising indicating, by the BS, in a frequency domain resource assignment field in the DCI format 1_0, a frequency domain resource allocation for transmission by the UE of the MsgA PUSCH.

8. A non-transitory computer readable medium having instructions stored thereon that, when executed by one or more processors of a base station (BS), cause the BS to perform operations comprising:

configuring, by the BS, a different search space configuration for a physical downlink control channel (PDCCH) ordered physical random access channel (PRACH) for an ordered 2-step RACH procedure compared to a PRACH of a 4-step RACH procedure,

wherein a frequency domain resource assignment field in a downlink control information (DCI) format 1_0 used to trigger the ordered 2-step RACH procedure is used to indicate a frequency domain resource allocation of a MsgA physical uplink shared channel (PUSCH) transmission associated with the PRACH for the 2-step RACH procedure, and a remaining resource configuration for the MsgA PUSCH transmission including a time domain resource allocation is indicated by one or more reserved bits in the DCI format 1_0;

transmitting a PDCCH signal to a user equipment (UE), wherein the PDCCH signal includes an indication of the PDCCH ordered 2-step RACH procedure; and

receiving a first step of the 2-step RACH procedure, wherein the first step includes a PRACH preamble and an associated MsgA PUSCH from the UE.

9. The non-transitory computer readable medium of claim 8 , wherein the indication includes the one or more reserved bits in the DCI format 1_0, wherein the one or more reserved bits are configured to be interpreted by the UE to trigger transmission of the MsgA PUSCH.

10. The non-transitory computer readable medium of claim 8 , wherein the indication includes a MsgA PUSCH resource index in the DCI format 1_0, and an association rule between the PRACH and the MsgA PUSCH resource for the 2-step RACH procedure, wherein the association rule is previously configured by higher layers in the BS.

11. The non-transitory computer readable medium of claim 8 , wherein the indication includes one or more reserved states in a PRACH Mask index field in the DCI format 1_0.

12. The non-transitory computer readable medium of claim 8 , wherein the indication includes a truncated 10-bit field in the DCI format 1_0, wherein the truncated 10-bit field further indicates at least a portion of a MsgA PUSCH resource configuration.

13. The non-transitory computer readable medium of claim 8 , wherein the indication includes a radio network temporary identifier (RNTI) configured via a dedicated radio resource control signaling.

14. The non-transitory computer readable medium of claim 8 , wherein the operations further comprise indicating, by the BS, in a frequency domain resource assignment field in the DCI format 1_0, a frequency domain resource allocation for transmission by the UE of the MsgA PUSCH.

15. A base station (BS) comprising:

processor circuitry configured to:

configure, by the BS, a different search space configuration for a physical downlink control channel (PDCCH) ordered physical random access channel (PRACH) for an ordered 2-step RACH procedure compared to a PRACH of a 4-step RACH procedure,

wherein a frequency domain resource assignment field in a downlink control information (DCI) format 1_0 used to trigger the ordered 2-step RACH procedure is used to indicate a frequency domain resource allocation of a MsgA physical uplink shared channel (PUSCH) transmission associated with the PRACH for the 2-step RACH procedure, and a remaining resource configuration for the MsgA PUSCH transmission including a time domain resource allocation is indicated by one or more reserved bits in the DCI format 1_0:

generate a PDCCH signal, wherein the PDCCH signal includes an indication of the PDCCH ordered 2-step RACH procedure; and

radio front end circuitry coupled to the processor circuitry, and configured to:

transmit the PDCCH signal to a user equipment (UE); and

receive a first step of the 2-step RACH procedure, wherein the first step includes a PRACH preamble and an associated MsgA PUSCH from the UE.

16. The BS of claim 15 , wherein the indication includes one or more reserved bits in the DCI format 1_0, and wherein the one or more reserved bits are configured to be interpreted by the UE to trigger transmission of the MsgA PUSCH.

17. The BS of claim 15 , wherein the indication includes a MsgA PUSCH resource index in the DCI format 1_0, and an association rule between the PRACH and the MsgA PUSCH resource for the 2-step RACH procedure, wherein the association rule is previously configured by higher layers in the BS.

18. The BS of claim 15 , wherein the indication includes one or more reserved states in a PRACH Mask index field in the DCI format 1_0.

19. The BS of claim 15 , wherein the indication includes a truncated 10-bit field in the DCI format 1_0, wherein the truncated 10-bit field further indicates at least a portion of a MsgA PUSCH resource configuration.

20. The BS of claim 15 , wherein the indication includes a radio network temporary identifier (RNTI) configured via a dedicated radio resource control signaling.