MESSAGE 2 OF A TWO-STEP RANDOM ACCESS PROCEDURE AND COEXISTENCE WITH FOUR-STEP RANDOM ACCESS PROCEDURE

• US 20200137803A1
• Filed: 10/23/2019
• Published: 04/30/2020
• Est. Priority Date: 10/24/2018
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Fakoorian, Seyed Ali Akbar, Zhang, Xiaoxia, Sun, Jing, Damnjanovic, Aleksandar, Yerramalli, Srinivas, Ozturk, Ozcan
• Granted Patent: US 11,140,720 B2
• Time in Patent Office: Days
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 1/1819 with retransmission of additional or different redundancy
• CPC Class Codes: H04L 1/1854 Scheduling and prioritising arrangements
• CPC Class Codes: H04L 1/1896 ARQ related signaling
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/0055 Physical resource allocation for ACK/NACK for physical mapping arrangements in ARQ protocols H04L1/1861
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal
• CPC Class Codes: H04W 72/30 Resource management for broadcast services
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/0891 for synchronized access
• CPC Class Codes: H04W 76/11 Allocation or use of connection identifiers

Abstract

Methods, systems, and devices for wireless communications are described. The method includes identifying that the user equipment (UE) is to use a two-step random access channel (RACH) procedure that includes a first message (e.g., uplink request message) and a second message (e.g., downlink response). The methods include sending, as a first message of the two-step RACH procedure, the uplink request message to a base station, receiving, from the base station, a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which the downlink response is to be received, and receiving the downlink response from the base station on the broadcast or multicast physical downlink shared channel. The physical downlink shared channel may be configured to provide downlink responses for one or multiple UEs.

Claims

1. A method for wireless communication at a user equipment (UE), comprising:

identifying that the UE is to use a two-step random access channel (RACH) procedure, the two-step RACH procedure including an uplink request message and a downlink response intended for the UE;

sending, as a first message of the two-step RACH procedure, the uplink request message to a base station;

receiving, from the base station, a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which the downlink response is to be received, the physical downlink shared channel being configured to provide downlink responses for multiple UEs; and

receiving the downlink response from the base station on the broadcast or multicast physical downlink shared channel, the downlink response being a second message of the two-step RACH procedure.

2. The method of claim 1, further comprising:

determining a group random access radio network temporary identifier;

decoding the physical downlink control channel based at least in part on the group random access radio network temporary identifier;

decoding the broadcast or multicast physical downlink shared channel in accordance with the indication received on the physical downlink control channel; and

identifying that downlink responses for multiple UEs included within the broadcast or multicast physical downlink shared channel are multiplexed at a media access control layer, wherein the downlink response intended for the UE is one of the multiplexed downlink responses.

3. The method of claim 2, wherein the physical downlink control channel includes one or more of a new data indicator, a redundancy version identifier, an acknowledgement resource indicator, or a hybrid automatic repeat request (HARQ) process identifier.

4. The method of claim 3, further comprising:

sending an acknowledgement (ACK) to the base station after successfully decoding the broadcast or multicast physical downlink shared channel and after identifying the downlink response intended for the UE.

5. The method of claim 4, wherein sending the ACK to the base station comprises:

transmitting the ACK using resources identified by a combination of the acknowledgement resource indicator included in the physical downlink control channel and an additional acknowledgement resource indicator included in the downlink response intended for the UE.

6. The method of claim 2, further comprising:

refraining from transmitting a negative acknowledgement (NACK) when decoding the broadcast or multicast physical downlink shared channel is unsuccessful or the downlink response intended for the UE is corrupted or unreadable.

7. The method of claim 6, further comprising:

receiving, based at least in part on refraining from transmitting a NACK, a retransmission of the downlink response intended for the UE.

8. The method of claim 7, wherein the retransmission includes each of the downlink responses included in the broadcast or multicast physical downlink shared channel.

9. The method of claim 7, wherein the retransmission includes fewer downlink responses than those included in the broadcast or multicast physical downlink shared channel.

10. The method of claim 2, further comprising:

refraining from transmitting any hybrid automatic repeat request (HARQ) feedback with respect to decoding the physical downlink control channel or decoding the broadcast or multicast physical downlink shared channel.

11. The method of claim 10, wherein the physical downlink control channel uses a larger transport block scaling than would be used if HARQ feedback were to be transmitted.

12. The method of claim 10, wherein the physical downlink control channel lacks one or more of a HARQ process identifier, a new data indicator, or a redundancy version identifier.

13. The method of claim 10, further comprising:

identifying an uplink grant in the downlink response intended for the UE, the uplink grant indicating resources for transmission by the UE of a confirmation message that confirms the UE received the downlink response intended for the UE or the broadcast or multicast physical downlink shared channel; and

transmitting the confirmation message based at least in part on the uplink grant.

14. The method of claim 1, wherein the downlink response intended for the UE includes one or more of a random access preamble index, a cell radio network temporary identifier, or a UE identifier.

15. A method for wireless communication at a base station:

receiving an uplink request message from a user equipment (UE);

identifying that the uplink request message is a first message of a two-step random access channel (RACH) procedure;

sending a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which a downlink response to the uplink request message intended for the UE is to be received, the downlink response being a second message of the two-step RACH procedure, the physical downlink shared channel being configured to provide a plurality of downlink responses to a corresponding plurality of UEs that includes the UE; and

sending the plurality of downlink responses, including the downlink response intended for the UE, to the plurality of UEs via the broadcast or multicast physical downlink shared channel.

16. The method of claim 15, further comprising:

multiplexing at a media access control layer of the broadcast or multicast physical downlink shared channel the downlink responses for the plurality of UEs, wherein the downlink response intended for the UE is one of the multiplexed downlink responses.

17. The method of claim 15, further comprising:

including in each of the plurality of downlink responses at least one of random access preamble index (RAPID), timing advance (TA), cell radio network temporary identifier, and UE identifier, or any combination thereof.

18. The method of claim 17, further comprising:

including in the broadcast or multicast physical downlink shared channel an acknowledgement/negative acknowledgement (ACK/NACK) resource indicator (ARI) for each of the plurality of downlink responses to indicate separate ACK/NACK feedback resources for each RAPID.

19. The method of claim 15, further comprising:

sending via the broadcast or multicast physical downlink shared channel a retransmission of at least some of the plurality of downlink responses.

20. The method of claim 19, further comprising:

sending the retransmission after failing to receive an ACK from any of the plurality of UEs within a given time period.

21. The method of claim 20, wherein the retransmission includes each of the plurality of downlink responses included in the transmission of the broadcast or multicast physical downlink shared channel.

22. The method of claim 20, wherein the retransmission includes fewer downlink responses than were included in the transmission of the broadcast or multicast physical downlink shared channel.

23. The method of claim 19, further comprising:

clearing a new data indicator (NDI); and

including in the retransmission of the plurality of downlink responses at least one of the downlink response intended for the UE second message from the plurality of downlink responses, at least one modified message sent previously in the transmission of the plurality of downlink responses, or at least one new message transmitted for the first time in the retransmission, or any combination thereof.

24. The method of claim 15, further comprising:

including an uplink grant in the physical downlink control channel, the uplink grant indicating resources for transmission by the UE of a confirmation message that confirms the UE received the downlink response intended for the UE.

25. The method of claim 24, further comprising:

confirming the UE receives the second message based at least in part on detecting a transmission on the resources indicated by the uplink grant.

26. The method of claim 15, further comprising:

refraining from including in the physical downlink control channel at least one of high availability resolution queue (HARQ) process identifier, new data indicator (NDI), and redundancy version identifier (RVID), or any combination thereof; and

using a space created by the refraining for transport block (TB) scaling.

27. The method of claim 15, further comprising:

including in the physical downlink control channel at least one of new data indicator (NDI), and redundancy version identifier (RVID) for retransmission support.

28. The method of claim 15, further comprising:

scrambling a cyclic redundancy check (CRC) of the physical downlink control channel by a group random access radio network temporary identifier (RA-RNTI).

29. An apparatus for wireless communication at a user equipment (UE), comprising:

a processor,

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to;

identify that the UE is to use a two-step random access channel (RACH) procedure, the two-step RACH procedure including an uplink request message and a downlink response;

send, as a first message of the two-step RACH procedure, the uplink request message to a base station;

receive, from the base station, a physical downlink control channel that comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which the downlink response is to be received, the physical downlink shared channel being configured to provide downlink responses for multiple UEs; and

receive the downlink response from the base station on the broadcast or multicast physical downlink shared channel, the downlink response being a second message of the two-step RACH procedure.

30. The apparatus of claim 29, wherein the instructions are further executable by the processor to cause the apparatus to:

determine a group random access radio network temporary identifier;

decode the physical downlink control channel based at least in part on the group random access radio network temporary identifier;

decode the broadcast or multicast physical downlink shared channel in accordance with the indication received on the physical downlink control channel; and

identify that downlink responses for multiple UEs included within the broadcast or multicast physical downlink shared channel are multiplexed at a media access control layer, wherein the downlink response intended for the UE is one of the multiplexed downlink responses.

31. The apparatus of claim 30, wherein the physical downlink control channel includes one or more of a new data indicator, a redundancy version identifier, an acknowledgement resource indicator, or a hybrid automatic repeat request (HARQ) process identifier.

32. The apparatus of claim 31, wherein the instructions are further executable by the processor to cause the apparatus to:

send an acknowledgement (ACK) to the base station after successfully decoding the broadcast or multicast physical downlink shared channel and after identifying the downlink response intended for the UE.

33. The apparatus of claim 32, wherein the instructions to send the ACK to the base station are executable by the processor to cause the apparatus to:

transmit the ACK using resources identified by a combination of the acknowledgement resource indicator included in the physical downlink control channel and an additional acknowledgement resource indicator included in the downlink response intended for the UE.

34. The apparatus of claim 30, wherein the instructions are further executable by the processor to cause the apparatus to:

refrain from transmitting a negative acknowledgement (NACK) when decoding the broadcast or multicast physical downlink shared channel is unsuccessful or the downlink response intended for the UE is corrupted or unreadable.

35. An apparatus for wireless communication at a base station, comprising:

a processor,

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to;

receive an uplink request message from a user equipment (UE);

identify that the uplink request message is a first message of a two-step random access channel (RACH) procedure;

send a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which a downlink response to the uplink request message intended for the UE is to be received, the downlink response being a second message of the two-step RACH procedure, the physical downlink shared channel being configured to provide a plurality of downlink responses to a corresponding plurality of UEs that includes the UE; and

send the plurality of downlink responses, including the downlink response intended for the UE, to the multiple UEs via the broadcast or multicast physical downlink shared channel.

36. The apparatus of claim 35, wherein the instructions are further executable by the processor to cause the apparatus to:

multiplex at a media access control layer of the broadcast or multicast physical downlink shared channel the downlink responses for the plurality of UEs, wherein the downlink response intended for the UE is one of the multiplexed downlink responses.

37. An apparatus for wireless communication at a user equipment (UE), comprising:

means for identifying that the UE is to use a two-step random access channel (RACH) procedure, the two-step RACH procedure including an uplink request message and a downlink response;

means for sending, as a first message of the two-step RACH procedure, the uplink request message to a base station;

means for receiving, from the base station, a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which the downlink response is to be received, the physical downlink shared channel being configured to provide downlink responses for multiple UEs; and

means for receiving the downlink response from the base station on the broadcast or multicast physical downlink shared channel, the downlink response being a second message of the two-step RACH procedure.

38. An apparatus for wireless communication at a base station, comprising:

means for receiving an uplink request message from a user equipment (UE);

means for identifying that the uplink request message is a first message of a two-step random access channel (RACH) procedure;

means for sending a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which a downlink response to the uplink request message intended for the UE is to be received, the downlink response being a second message of the two-step RACH procedure, the physical downlink shared channel being configured to provide a plurality of downlink responses to a corresponding plurality of UEs that includes the UE; and

means for sending the plurality of downlink responses, including the downlink response intended for the UE, to the multiple UEs via the broadcast or multicast physical downlink shared channel.

39. A non-transitory computer-readable medium storing code for wireless communication at a user equipment (UE), the code comprising instructions executable by a processor to:

identify that the UE is to use a two-step random access channel (RACH) procedure, the two-step RACH procedure including an uplink request message and a downlink response;

send, as a first message of the two-step RACH procedure, the uplink request message to a base station;

receive, from the base station, a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which the downlink response is to be received, the physical downlink shared channel being configured to provide downlink responses for multiple UEs; and

receive the downlink response from the base station on the broadcast or multicast physical downlink shared channel, the downlink response being a second message of the two-step RACH procedure.

40. A non-transitory computer-readable medium storing code for wireless communication at a base station, the code comprising instructions executable by a processor to:

receive an uplink request message from a user equipment (UE);

identify that the uplink request message is a first message of a two-step random access channel (RACH) procedure;

send a physical downlink control channel comprising an indication of resources of a broadcast or multicast physical downlink shared channel on which a downlink response to the uplink request message intended for the UE is to be received, the downlink response being a second message of the two-step RACH procedure, the physical downlink shared channel being configured to provide a plurality of downlink responses to a corresponding plurality of UEs that includes the UE; and

send the plurality of downlink responses, including the downlink response intended for the UE, to the multiple UEs via the broadcast or multicast physical downlink shared channel.