Methods providing RACH occasion indication for random access procedure initiated by PDCCH order and related wireless terminals and base stations

1. A method of operating a wireless terminal in communication with a network node, the method comprising:

receiving a Physical Downlink Control Channel, PDCCH, order from the network node, wherein the PDCCH order includes an identification for a Random Access CHannel, RACH, occasion to be used for a RACH message 1 preamble transmission, wherein the identification includes a first index that indicates a set of RACH occasions and a second index that indicates the RACH occasion associated with the set; and

responsive to the PDCCH order, transmitting a Message 1 preamble to the network node using the RACH occasion indicated by the first and second indexes together.

2. The method of claim 1 , wherein the first index is a synchronization signal block, SSB, index that indicates a set of RACH occasions that are associated with the SSB index.

3. The method of claim 2 , wherein the second index is a RACH occasion, RO, index that indicates the RACH occasion associated with the set of RACH occasions indicated by the SSB index.

4. The method of claim 1 , wherein the identification is provided in Downlink Control information, DCI, carried via the PDCCH order.

5. The method of claim 1 , wherein the Message 1 preamble is transmitted for a random access procedure, the method further comprising:

after transmitting the Message 1 preamble, receiving a Message 2 random access response of the random access procedure from the network node.

6. The method of claim 5 further comprising:

responsive to receiving the Message 2 random access response, transmitting a Message 3 for the random access procedure to the network node on an uplink channel.

7. The method of claim 6 further comprising:

after transmitting the Message 3, receiving a contention resolution message of the random access procedure from the network node.

8. The method of claim 1 , wherein the first index indicates a time resource of a plurality of time resources in a RACH configuration period.

9. A method of operating a network node in communication with a wireless terminal, the method comprising:

transmitting a Physical Downlink Control Channel, PDCCH, order to the wireless terminal, wherein the PDCCH order includes an identification for a Random Access CHannel, RACH, occasion to be used for a RACH message 1 preamble transmission from the wireless terminal, wherein the identification includes a first index that indicates a set of RACH occasions and a second index that indicates the RACH occasion associated with the set; and

receiving a Message 1 preamble from the wireless terminal using the RACH occasion indicated by the first and second indexes together.

10. The method of claim 9 , wherein the first index is a synchronization signal block, SSB, index that indicates a set of RACH occasions that are associated to the SSB index.

11. The method of claim 10 , wherein the second index is a RACH occasion, RO, index that indicates the RACH occasion associated with the set of RACH occasions indicated by the SSB index.

12. The method of claim 9 , wherein the identification is provided in Downlink Control information, DCI, carried via the PDCCH order.

13. The method of claim 9 , wherein the Message 1 preamble is received for a random access procedure, the method further comprising:

responsive to receiving the Message 1 preamble, transmitting a Message 2 random access response of the random access procedure to the wireless terminal.

14. The method of claim 13 further comprising:

after transmitting the Message 2 random access response, receiving a Message 3 for the random access procedure on an uplink channel from the wireless terminal.

15. The method of claim 14 further comprising:

after receiving the Message 3, transmitting a contention resolution message of the random access procedure to the wireless terminal.

16. The method of claim 9 , wherein the first index indicates a time resource of a plurality of time resources in a RACH configuration period.

17. A wireless terminal configured for communication with a network node, the wireless terminal comprising:

a transceiver configured to provide wireless communication with the network node in a wireless communication network; and

a processor circuit coupled with the transceiver, wherein the processor circuit is configured to provide wireless communication with the wireless communication network through the transceiver, wherein the processor circuit is further configured to,

receive a Physical Downlink Control Channel, PDCCH, order from the network node, wherein the PDCCH order includes an identification for a Random Access CHannel, RACH, occasion to be used for a RACH message 1 preamble transmission, wherein the identification includes a first index that indicates a set of RACH occasions and a second index that indicates the RACH occasion associated with the set, and

transmit a Message 1 preamble to the network node using the RACH occasion indicated by the first and second indexes together responsive to the PDCCH order.

18. The wireless terminal of claim 17 , wherein the first index is a synchronization signal block, SSB, index that indicates a set of RACH occasions that are associated with to the SSB index.

19. The wireless terminal of claim 17 , wherein the identification is provided in Downlink Control information, DCI, carried via the PDCCH order.

20. The wireless terminal of claim 17 , wherein the Message 1 preamble is transmitted for a random access procedure, wherein the processor circuit is further configured to,

receive a Message 2 random access response of the random access procedure from the network node after transmitting the Message 1 preamble.

21. The wireless terminal of claim 20 , wherein the processor circuit is further configured to:

after receiving the Message 2, transmitting a Message 3 for the random access procedure to the network node on an uplink channel; and

after transmitting the Message 3, receiving a contention resolution message of the random access procedure from the network node.

22. A network node configured for communication with a wireless terminal, the network node comprising:

a transceiver configured to provide wireless communication with a wireless terminal; and

a processor circuit coupled with the transceiver, wherein the processor circuit is configured to provide wireless communication with a wireless terminal through the transceiver, and wherein the processor circuit is further configured to,

transmit a Physical Downlink Control Channel, PDCCH, order to the wireless terminal, wherein the PDCCH order includes an identification for a Random Access CHannel, RACH, occasion to be used for a RACH message 1 preamble transmission from the wireless terminal, wherein the identification includes a first index that indicates a set of RACH occasions and a second index that indicates the RACH occasion associated with the set, and

receive a Message 1 preamble from the wireless terminal using the RACH occasion indicated by the first and second indexes together.

23. The network node of claim 22 , wherein the first index is a synchronization signal block, SSB, index that indicates a set of RACH occasions that are associated with the SSB index.

24. The network node of claim 22 , wherein the identification is provided in Downlink Control information, DCI, carried via the PDCCH order.

25. The network node of claim 22 , wherein the Message 1 preamble is received for a random access procedure, wherein the network node is further adapted to:

transmit a Message 2 random access response of the random access procedure to the wireless terminal responsive to receiving the Message 1 preamble.

26. The network node of claim 25 , wherein the processor circuit is further configured to:

after transmitting the Message 2, receiving a Message 3 for the random access procedure on an uplink channel from the wireless terminal; and

after receiving the Message 3, transmitting a contention resolution message of the random access procedure to the wireless terminal.