Method and apparatus for performing random access

1. A method comprising:

receiving, by a wireless device from a base station, one or more messages comprising downlink control information (DCI) associated with a DCI format;

determining that a first field of the DCI corresponds to a predefined value;

determining that, based on the first field corresponding to the predefined value, the DCI is for a random access procedure associated with a physical downlink control channel (PDCCH) order;

determining, based on the determining that the DCI is for a random access procedure associated with a PDCCH order and based on a plurality of fields of the DCI, a random access channel (RACH) occasion associated with a synchronization signal/physical broadcasting channel (SS/PBCH) block, wherein the plurality of fields of the DCI comprise:

an SS/PBCH block index field having a value indicating the SS/PBCH block; and

a RACH index field having a value indicating one or more RACH occasions;

determining, based on the SS/PBCH block index field and the RACH index field, the RACH occasion associated with the SS/PBCH block; and

transmitting, based on the RACH occasion associated with the SS/PBCH block, a random access preamble.

2. The method of claim 1 , further comprising:

receiving information associated with a location of one or more transmission SS/PBCH blocks,

wherein determining the RACH occasion comprises determining, based on the SS/PBCH block indicated by the value of the SS/PBCH block index field, the RACH occasion.

3. The method of claim 1 , wherein the first field corresponds to a frequency domain resource assignment field of DCI format 1_0.

4. The method of claim 1 , wherein the DCI format is DCI format 1_0 associated with a physical downlink shared channel (PDSCH) scheduling.

5. The method of claim 1 , further comprising determining the DCI based on Cell Radio Network Temporary Identifier (C-RNTI).

6. The method of claim 1 , wherein the DCI comprises

an uplink/supplemental uplink (UL/SUL) indicator associated with the random access preamble.

7. The method of claim 2 , further comprising:

receiving, from the base station, configuration information comprising one or more of:

a physical RACH (PRACH) configuration period;

a transmission SS/PBCH block-PRACH mapping configuration period; or a number of SS/PBCH blocks per RACH occasion.

8. The method of claim 1 , further comprising:

determining, based on the determining that the DCI is for a random access procedure associated with a PDCCH order, an uplink/supplemental uplink (UL/SUL) indicator of the plurality of fields of the DCI,

wherein the transmitting the random access preamble comprises transmitting, based on the UL/SUL indicator, the random access preamble via an SUL carrier.

9. A method comprising:

determining, by a base station, a random access channel (RACH) occasion for a wireless device, wherein the RACH occasion is associated with a synchronization signal/physical broadcast channel (SS/PBCH) block;

generating downlink control information (DCI) corresponding to a DCI format, the DCI comprising:

a first field having a predefined value indicating that the DCI is for a random access procedure associated with a physical downlink control channel (PDCCH) order;

an SS/PBCH block index field having a value indicating the SS/PBCH block; and

an index field having a value indicating one or more RACH occasions,

wherein the RACH occasion for the wireless device is indicated by the values of the SS/PBCH block index field and the index field;

transmitting, to the wireless device, the DCI; and

receiving, from the wireless device and based on the RACH occasion, a random access preamble.

10. The method of claim 9 , further comprising:

transmitting information associated with a location of one or more SS/PBCH blocks.

11. The method of claim 9 , wherein the first field corresponds to a frequency domain resource assignment field of DCI format 1_0.

12. The method of claim 9 , wherein the DCI format is DCI format 1_0 associated with a physical downlink shared channel (PDSCH) scheduling.

13. The method of claim 12 , further comprising:

generating second DCI for a PDSCH scheduling, wherein the second DCI comprises a field having a value different from the predefined value; and

transmitting, to the wireless device, the second DCI.

14. The method of claim 9 , further comprising scrambling the DCI based on Cell Radio Network Temporary Identifier (C-RNTI).

15. The method of claim 9 , wherein the DCI comprises

an uplink/supplemental uplink (UL/SUL) indicator associated with the random access preamble.

16. A method comprising:

receiving, by a wireless device from a base station, one or more messages comprising downlink control information (DCI);

determining that the DCI corresponds to DCI format 1_0;

determining that, based on a value of a first field of the DCI format 1_0, the DCI is for a random access procedure associated with a physical downlink control channel (PDCCH) order;

determining, based on a synchronization signal/physical broadcast channel (SS/PBCH) block index field of the DCI and based on an index field associated with one or more random access channel (RACH) occasions, a RACH occasion associated with an SS/PBCH block indicated by the SS/PBCH block index field; and

transmitting, based on the RACH occasion associated the SS/PBCH block, a random access preamble.

17. The method of claim 16 , further comprising:

receiving information associated with a location of one or more SS/PBCH blocks,

wherein determining the RACH occasion comprises determining, based on the SS/PBCH block indicated by a value of the SS/PBCH block index field, the RACH occasion.

18. The method of claim 16 , wherein the first field corresponds to a frequency domain resource assignment field.

19. The method of claim 16 , further comprising:

receiving second DCI corresponding to the DCI format 1_0;

determining that a frequency domain resource assignment field has a value different from a predefined value, wherein the predefined value is associated with the random access procedure; and

retrieving, from the second DCI, information of a physical downlink shared channel (PDSCH) scheduling.

20. The method of claim 16 , further comprising determining the DCI based on Cell Radio Network Temporary Identifier (C-RNTI).

21. The method of claim 16 , wherein the DCI comprises

an uplink/supplemental uplink (UL/SUL) indicator associated with the random access preamble.