Reduced control channel monitoring for random access procedures

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

transmitting a first random access message during a random access procedure;

initiating a timer after transmitting the first random access message, wherein the first random access message includes an indication of a duration of the timer, and wherein initiation of the timer is based at least in part on inclusion of the indication of the duration of the timer in the first random access message;

monitoring, upon expiration of the timer, a physical downlink channel for a control message as part of the random access procedure; and

receiving, during the random access procedure, the control message on the physical downlink channel.

2 . The method of claim 1 , further comprising:

refraining from monitoring for the control message for a duration of the timer.

3 . The method of claim 1 , further comprising:

transmitting the first random access message comprises transmitting a first message of a four-step random access procedure; and

monitoring for the control message comprises monitoring for a second random access message of the four-step random access procedure.

4 . The method of claim 3 , further comprising:

initiating, at a first transmission time interval boundary of a next control resource set after expiration of the timer, a random access response monitoring window, wherein the monitoring occurs during the random access response monitoring window.

5 . The method of claim 1 , wherein:

transmitting the first random access message comprises transmitting a third message of a four-step random access procedure; and

monitoring for the control message comprises monitoring for a scheduling downlink control information message instructing the UE to send a retransmission of the third message of the four-step random access procedure,

wherein the method further comprises initiating, upon expiration of the timer, a contention resolution window, wherein the monitoring occurs during the contention resolution window.

6 . The method of claim 1 , wherein:

transmitting the first random access message comprises transmitting a third message of a four-step random access procedure; and

monitoring for the control message comprises monitoring for a retransmission of a fourth message of the four-step random access procedure.

7 . The method of claim 6 , further comprising:

initiating a contention resolution window after transmitting the third message of the four-step random access procedure;

monitoring, during the contention resolution window, for the fourth message of the four-step random access procedure;

determining, based at least in part on the monitoring, that the UE has failed to receive the fourth message of the four-step random access procedure;

identifying an uplink control resource allocated for transmitting feedback information; and

refraining from transmitting a feedback message indicating that the UE has successfully received the fourth message of the four-step random access procedure on the uplink control resource, wherein monitoring for the retransmission of the fourth message of the four-step random access procedure is based at least in part on refraining from transmitting the feedback message.

8 . The method of claim 1 , wherein:

transmitting the first random access message comprises transmitting a first message of a two-step random access procedure; and

monitoring for the control message comprises monitoring for a second random access message of the two-step random access procedure,

wherein the method further comprises: initiating, at a first transmission time interval boundary of a next control resource set after expiration of the timer, a random access response monitoring window, wherein the monitoring occurs during the random access response monitoring window.

9 . A method for wireless communications at a user equipment (UE), comprising:

transmitting a first random access message during a random access procedure, wherein transmitting the first random access message comprises transmitting a first message of a two-step random access procedure;

initiating a timer after transmitting the first random access message;

monitoring, upon expiration of the timer, a physical downlink channel for a control message as part of the random access procedure, wherein monitoring for the control message comprises monitoring for a retransmission of a second message of the two-step random access procedure; and

receiving, during the random access procedure, the control message on the physical downlink channel,

wherein the method further comprises:

initiating, at a first transmission time interval boundary of a next control resource set after expiration of the timer, a random access response monitoring window;

monitoring, during the random access response monitoring window, for the second message of the two-step random access procedure;

determining that the UE has failed to receive the second message of the two-step random access procedure; and

transmitting, on an uplink control resource allocated for transmitting feedback information, a feedback message indicating that the UE has not received the second message of the two-step random access procedure, and

wherein initiating the timer further comprises:

initiating the timer during the random access response monitoring window after a last transmission time interval boundary of the uplink control resource; or

identifying a fixed offset value, applying the fixed offset value after a last transmission time interval boundary of resources allocated for receiving the second message of the two-step random access procedure, and initiating the timer during the random access response monitoring window after the fixed offset value.

10 . The method of claim 9 , wherein initiating the timer comprises:

initiating the timer during the random access response monitoring window after the last transmission time interval boundary of the uplink control resource.

11 . The method of claim 9 , wherein initiating the timer further comprises:

identifying the fixed offset value;

applying the fixed offset value after the last transmission time interval boundary of resources allocated for receiving the second message of the two-step random access procedure; and

initiating the timer during the random access response monitoring window after the fixed offset value.

12 . The method of claim 1 , further comprising:

receiving system information comprising an indication of the duration of the timer.

13 . The method of claim 1 , further comprising:

receiving, in a previous random access message, an indication of the duration of the timer.

14 . The method of claim 1 , further comprising:

identifying one or more physical random access channel resources for transmitting the first random access message or a second random access message, wherein the identified one or more physical random access channel resources are associated with the timer, wherein initiating the timer is based at least in part on the identified one or more physical random access channel resources.

15 . The method of claim 1 , further comprising:

transmitting an indication that the UE is a reduced capacity UE, wherein initiating the timer is based at least in part on transmitting the indication.

16 . An apparatus for wireless communications at a user equipment (UE), comprising one or more memories coupled to one or more processors, wherein the one or more processors are configured to cause the apparatus to:

transmit a first random access message during a random access procedure;

initiate a timer after transmission of the first random access message, wherein the first random access message includes an indication of a duration of the timer, and wherein initiation of the timer is based at least in part on inclusion of the indication of the duration of the timer in the first random access message;

monitor, upon expiration of the timer, a physical downlink channel for a control message as part of the random access procedure; and

receive, during the random access procedure, the control message on the physical downlink channel.

17 . The apparatus of claim 16 , wherein the one or more processors are configured to cause the apparatus to:

refrain from monitoring for the control message for a duration of the timer.

18 . The apparatus of claim 16 , wherein:

to transmit the first random access message, the one or more processors are configured to cause the apparatus to transmit a first message of a four-step random access procedure; and

to monitor for the control message, the one or more processors are configured to cause the apparatus to monitor for a second random access message of the four-step random access procedure.

19 . The apparatus of claim 18 , wherein the one or more processors are configured to cause the apparatus to:

initiate, at a first transmission time interval boundary of a next control resource set after expiration of the timer, a random access response monitoring window,

wherein to monitor, the one or more processors are configured to cause the apparatus to monitor during the random access response monitoring window.

20 . The apparatus of claim 16 , wherein the one or more processors are configured to cause the apparatus to initiate, upon expiration of the timer, a contention resolution window, and wherein:

to transmit the first random access message, the one or more processors are configured to cause the apparatus to transmit a third message of a four-step random access procedure; and

to monitor for the control message, the one or more processors are configured to cause the apparatus to monitor during the contention resolution window and monitor for a scheduling downlink control information message instructing the UE to send a retransmission of the third message of the four-step random access procedure.

21 . The apparatus of claim 16 , wherein:

to transmit the first random access message, the one or more processors are configured to cause the apparatus to transmit a third message of a four-step random access procedure; and

to monitor for the control message, the one or more processors are configured to cause the apparatus to monitor for a retransmission of a fourth message of the four-step random access procedure.

22 . The apparatus of claim 21 , wherein the one or more processors are configured to cause the apparatus to:

initiate a contention resolution window after transmission of the third message of the four-step random access procedure;

monitor, during the contention resolution window, for the fourth message of the four-step random access procedure;

determine that the UE has failed to receive the fourth message of the four-step random access procedure;

identify an uplink control resource allocated for transmission of feedback information; and

refrain from transmitting a feedback message indicating that the UE has successfully received the fourth message of the four-step random access procedure on the uplink control resource.

23 . The apparatus of claim 16 , wherein:

to transmit the first random access message, the one or more processors are configured to cause the apparatus to transmit a first message of a two-step random access procedure; and

to monitor for the control message, the one or more processors are configured to cause the apparatus to monitor for a second random access message of the two-step random access procedure,

wherein the one or more processors are configured to cause the apparatus to:

initiate, at a first transmission time interval boundary of a next control resource set after expiration of the timer, a random access response monitoring window,

wherein to monitor, the one or more processors are configured to cause the apparatus to monitor during the random access response monitoring window.

24 . The apparatus of claim 16 , wherein the one or more processors are configured to cause the apparatus to:

receive system information comprising an indication of the duration of the timer.

25 . The apparatus of claim 16 , wherein the one or more processors are configured to cause the apparatus to:

receive, in a previous random access message, an indication of the duration of the timer.

26 . The apparatus of claim 16 , wherein the one or more processors are configured to cause the apparatus to:

identify one or more physical random access channel resources for transmission of the first random access message or a second random access message,

wherein the identified one or more physical random access channel resources are associated with the timer,

wherein initiation of the timer is based at least in part on the identified one or more physical random access channel resources.

27 . The apparatus of claim 16 , wherein the one or more processors are configured to cause the apparatus to:

transmit an indication that the UE is a reduced capacity UE,

wherein initiation of the timer is based at least in part on transmission the indication.

28 . An apparatus for wireless communications at a user equipment (UE), comprising one or more memories coupled to one or more processors, wherein the one or more processors are configured to cause the apparatus to:

transmit a first random access message during a random access procedure, wherein to transmit the first random access message, the one or more processors are configured to cause the apparatus to transmit a first message of a two-step random access procedure;

initiate a timer after transmission of the first random access message;

monitor, upon expiration of the timer, a physical downlink channel for a control message as part of the random access procedure, wherein to monitor for the control message, the one or more processors are configured to cause the apparatus to monitor for a retransmission of a second message of the two-step random access procedure; and

receive, during the random access procedure, the control message on the physical downlink channel,

wherein the one or more processors are configured to cause the apparatus to:

initiate, at a first transmission time interval boundary of a next control resource set after expiration of the timer, a random access response monitoring window;

monitor, during the random access response monitoring window, for the second message of the two-step random access procedure;

determine that the UE has failed to receive the second message of the two-step random access procedure; and

transmit, on an uplink control resource allocated for transmission of feedback information, a feedback message indicating that the UE has not received the second message of the two-step random access procedure, and

wherein to initiate the timer, the one or more processors are configured to cause the apparatus to:

initiate the timer during the random access response monitoring window after a last transmission time interval boundary of the uplink control resource; or

identify a fixed offset value, apply the fixed offset value after a last transmission time interval boundary of resources allocated for reception of the second message of the two-step random access procedure, and initiate the timer during the random access response monitoring window after the fixed offset value.

29 . The apparatus of claim 28 , wherein to initiate the timer, the one or more processors are configured to cause the apparatus to:

initiate the timer during the random access response monitoring window after the last transmission time interval boundary of the uplink control resource.

30 . The apparatus of claim 28 , wherein to initiate the timer, the one or more processors are configured to cause the apparatus to:

identify the fixed offset value;

apply the fixed offset value after the last transmission time interval boundary of resources allocated for reception of the second message of the two-step random access procedure; and

initiate the timer during the random access response monitoring window after the fixed offset value.