Patent Description:
<NPL>), discusses procedures for Two-Step RACH. <CIT> describes different configurations for message content and transmission in a random access procedure.

As defined by claim <NUM>, the invention provides a method of wireless communication performed by a user equipment, UE, comprising: transmitting an indication that includes a set of indexes corresponding to a set of downlink beams in uplink control information of a random access message, wherein each downlink beam of the set of downlink beams is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted, or wherein each downlink beam of the set of downlink beams is selected from a set of multiple downlink beams corresponding to the random access occasion; and monitoring for at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information, wherein the downlink beam is one of a plurality of downlink beams indicated in the uplink control information of the random access message, wherein the random access message is associated with a two-step random access channel procedure and the random access response instructs the UE to fall back to a four-step random access channel procedure. Preferred embodiments of the method of claim <NUM> are defined by claims <NUM> to <NUM>.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with reporting uplink control information (UCI) in a random access procedure, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG>, process <NUM> of <FIG>, process <NUM> of <FIG>, process <NUM> of <FIG>, and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively.

In some aspects, UE <NUM> may include means for transmitting an indication of a downlink beam in uplink control information of a random access message, wherein the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted, or wherein the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion; means for monitoring for at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information; and/or the like. Additionally, or alternatively, UE <NUM> may include means for transmitting at least one of a power headroom report or a buffer status report in uplink control information of a random access message; means for monitoring for at least one of a random access response or a downlink communication subsequent to the random access response based at least in part on the power headroom report or the buffer status report; and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>.

In some aspects, base station <NUM> may include means for receiving an indication of a downlink beam in uplink control information of a random access message, wherein the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion associated with the random access message, or wherein the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion; means for transmitting at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information; and/or the like. Additionally, or alternatively, UE <NUM> may include means for receiving at least one of a power headroom report or a buffer status report in uplink control information of a random access message; means for transmitting at least one of a random access response or a downlink communication subsequent to the random access response based at least in part on the power headroom report or the buffer status report; and/or the like. In some aspects, such means may include one or more components of base station <NUM> described in connection with <FIG>.

<FIG> is a diagram illustrating an example <NUM> of a two-step random access channel (RACH) procedure. As shown in <FIG>, a base station <NUM> and a UE <NUM> may communicate with one another to perform the two-step RACH procedure.

In a first operation <NUM>, the base station <NUM> may transmit, and the UE <NUM> may receive, one or more synchronization signal blocks (SSBs), system information (e.g., in one or more system information blocks (SIBs) and/or the like), and/or one or more reference signals (RSs) (e.g., channel state information reference signals (CSI-RSs) and/or the like). In a second operation <NUM>, the UE <NUM> may perform downlink (DL) synchronization (such as by using one or more SSBs), may decode system information (SI) that is included in one or more SIBs, and/or may perform one or more measurements of the RS(s). Based at least in part on performing the second operation <NUM>, the UE <NUM> may determine parameters for transmitting a random access message (RAM) in the two-step RACH procedure. For example, the UE <NUM> may determine one or more physical random access channel (PRACH) transmission parameters to be used to transmit the RAM, may determine one or more parameters for generating a preamble of the RAM, may identify one or more uplink resources on which the RAM is to be transmitted, may determine a downlink beam for the RACH procedure (e.g., a default downlink beam and/or a preferred downlink beam), and/or the like.

In a third operation <NUM>, the UE <NUM> may transmit a RAM preamble. In a fourth operation <NUM>, the UE <NUM> may transmit a RAM payload. As shown, the UE <NUM> may transmit the RAM preamble and the RAM payload as part of a first step of the two-step RACH procedure. The RAM is sometimes referred to as message A, msgA, or a first message in a two-step RACH procedure. The RAM preamble is sometimes referred to as a message A preamble, a msgA preamble, or a preamble. The RAM payload is sometimes referred to as a message A payload, a msgA payload, or a payload. The RAM may include some or all of the contents of message <NUM> (msg1) and message <NUM> (msg3) of a four-step RACH procedure. For example, the RAM preamble may include some or all contents of message <NUM> (such as a RACH preamble). The RAM payload may include some or all contents of message <NUM> (such as a UE identifier, uplink control information, a physical uplink shared channel (PUSCH) communication, and/or the like).

In a fourth operation <NUM>, the base station <NUM> may receive the RAM preamble transmitted by the UE <NUM>. If the base station <NUM> successfully receives and decodes the RAM preamble, the base station <NUM> may then receive and decode the RAM payload. In a fifth operation <NUM>, the base station <NUM> may transmit a random access response (RAR) (sometimes referred to as a RAR message). As shown, the base station <NUM> may transmit the RAR message as part of a second step of the two-step RACH procedure. The RAR message is sometimes referred to as message B, msgB, or a second message in a two-step RACH procedure. The RAR message may include some or all of the contents of message <NUM> (msg2) and message <NUM> (msg4) of a four-step RACH procedure. For example, the RAR message may include the detected RACH preamble identifier, the detected UE identifier, a timing advance value, contention resolution information, and/or the like.

<FIG> is a diagram illustrating an example <NUM> of a random access message that includes a random access message preamble and a random access message payload. As shown, the RAM of the two-step RACH procedure may include a RAM preamble and a RAM payload, as described above. The RAM preamble may include a PRACH preamble signal and a guard time (shown as GT, with a duration of TG). The RAM payload may include a demodulation reference signal (DMRS) and/or a physical uplink shared channel (PUSCH) communication, as well as a guard time (also shown as GT, with a duration of TG). As further shown, transmission of the RAM preamble and transmission of the RAM payload may be separated in time by a transmission guard time (shown as TxG, with a duration of Tg).

In some cases, performance of a wireless communication network may be improved by transmitting UCI, that may typically be transmitted after a RACH procedure is complete, in the RAM payload (e.g., in the PUSCH used for the RAM payload). For example, performance of the RACH procedure may be improved by such early reporting of UCI. Some techniques and apparatuses described herein permit a UE <NUM> to report a preferred downlink beam, a power headroom report, a buffer status report, and/or the like in UCI of a random access message (e.g., the RAM payload). A base station <NUM> may use this information to improve RACH communications and/or communications subsequent to the RACH procedure, such as by configuring and/or transmitting such communications based at least in part on the UCI received from the UE <NUM> in the random access message. Additional details are described below.

<FIG> is a diagram illustrating an example <NUM> of reporting UCI in a random access procedure, in accordance with various aspects of the present disclosure. As shown in <FIG>, a UE <NUM> and a base station <NUM> may communicate with one another to perform a <NUM>-step RACH procedure.

In a first operation <NUM>, the base station <NUM> may transmit, and the UE <NUM> may receive, one or more SSBs, system information (e.g., in one or more (SIBs) and/or the like), and/or one or more RSs (e.g., CSI-RSs and/or the like). In some aspects, different SSBs may be transmitted via different downlink beams, such as by using a beam-sweeping procedure.

In a second operation <NUM>, the UE <NUM> may determine a preferred downlink (DL) beam for communications with the base station <NUM> (e.g., for downlink communications from the base station <NUM> to the UE <NUM>. The UE <NUM> may determine the preferred downlink beam based at least in part on the SSB(s), the CSI-RS(s), and/or the like. For example, the UE <NUM> may measure one or more SSBs to determine an SSB with the best measurements, and may identify an SSB index of that SSB. The SSB index may correspond to a downlink beam via which the SSB was transmitted. Additionally, or alternatively, the UE <NUM> may measure CSI-RS on one or more downlink beams, and may select a preferred downlink beam based at least in part on the measurements (e.g., the downlink beam with the best CSI-RS measurements).

As shown by reference number <NUM>, in some aspects, the UE <NUM> may identify a preferred downlink beam that is different from a default downlink beam associated with a preamble to be used by the UE <NUM> in a random access message (e.g., a RAM preamble) and/or associated with a random access occasion (e.g., one or more time resources, one or more frequency resources, and/or the like) in which the UE <NUM> is to transmit the random access message.

In some cases, a random access occasion may correspond to a single default downlink beam. The correspondence between random access occasions and default downlink beams may be indicated in system information, may be prespecified (e.g., according to a wireless communication standard), and/or the like. In this case, when the UE <NUM> transmits a random access message (e.g., msgA) in a random access occasion, the base station <NUM> may transmit a random access response (e.g., msgB) via the default downlink beam corresponding to the random access occasion, and the UE <NUM> may monitor the default downlink beam for the random access response.

However, this may require the UE <NUM> to either wait to transmit the random access message in a random access occasion corresponding to a default beam that is the best beam identified by the UE <NUM>, or to transmit the random access message (without waiting) in a random access occasion corresponding to a sub-optimal downlink beam. By identifying a preferred downlink beam that is different from the default downlink beam and indicating the preferred downlink beam in UCI of the random access message (as described below), the UE <NUM> can achieve early transmission of the random access message in a random access occasion corresponding to an optimal downlink beam identified by the UE <NUM> (e.g., the preferred downlink beam).

In example <NUM>, the UE <NUM> is shown as identifying Beam <NUM> as the preferred downlink beam. In this case, Beam <NUM> may be the default downlink beam for the random access occasion (e.g., for all preambles, such as for <NUM> preambles when the UE <NUM> is permitted to select from a set of <NUM> preambles). Here, the UE <NUM> selects Beam <NUM>, which is different from the default downlink beam associated with the random access occasion.

In some cases, a random access occasion may correspond to multiple default downlink beams, and a set of preambles (e.g., random access preambles, RAM preambles, RACH preambles, and/or the like) may be partitioned into multiple subsets of preambles corresponding to the multiple default downlink beams. As indicated above, the correspondence between a default downlink beam and a corresponding combination of a random access occasion and a subset of preambles may be indicated in system information, may be prespecified, and/or the like. In this case, when the UE <NUM> transmits a random access message (e.g., msgA) with a selected preamble in a random access occasion, the base station <NUM> may transmit a random access response (e.g., msgB) via the default downlink beam corresponding to the random access occasion and the selected preamble, and the UE <NUM> may monitor the default downlink beam for the random access response.

However, this may still require the UE <NUM> to either wait to transmit the random access message in a random access occasion that is associated with a default beam (e.g., among different default beams corresponding to different sets of preambles) that is the best beam identified by the UE <NUM>, or to transmit the random access message (without waiting) in a random access occasion corresponding to a sub-optimal downlink beam. Furthermore, such preamble partitioning limits the number of possible preambles that can be used for a corresponding downlink beam, thereby increasing the likelihood of a preamble collision. By identifying a preferred downlink beam that is different from the default downlink beams associated with a random access occasion and indicating the preferred downlink beam in UCI of the random access message (as described below), the UE <NUM> can achieve early transmission of the random access message in a random access occasion corresponding to an optimal downlink beam identified by the UE <NUM> (e.g., the preferred downlink beam). Furthermore, preamble partitioning can be avoided, thereby reducing the likelihood of a preamble collision.

In example <NUM>, the UE <NUM> is shown as identifying Beam <NUM> as the preferred downlink beam. In this case, Beam <NUM> may be the default downlink beam for a first subset of preambles associated with the random access occasion (e.g., preambles <NUM> through <NUM>), and Beam <NUM> may be the default downlink beam for a second subset of preambles associated with the random access occasion (e.g., for preambles <NUM> through <NUM>). Here, the UE <NUM> selects Beam <NUM>, which is different from the default downlink beam associated with the random access occasion.

As shown by reference number <NUM>, in some aspects, the UE <NUM> may select a preferred downlink beam from a set of multiple downlink beams associated with the random access occasion. In this case, preamble partitioning may be avoided by permitting the UE <NUM> to select any one of the multiple downlink beams and any preamble for the random access message. In other words, a downlink beam in the set of multiple downlink beams can be selected by the UE <NUM> regardless of a preamble selected by the UE <NUM>. In some aspects, the correspondence between the random access occasion and the set of multiple downlink beams may be indicated in system information, may be prespecified (e.g., according to a wireless communication standard), and/or the like.

In example <NUM>, the set of downlink beams associated with a selected random access occasion is shown as {Beam <NUM>, Beam <NUM>}, representing Beam <NUM> and Beam <NUM>. Here, the UE <NUM> selects Beam <NUM> from the set (e.g., the UE <NUM> identifies Beam <NUM> as the preferred downlink beam). In some aspects, the UE <NUM> may identify the preferred downlink beam, and may then identify a random access occasion corresponding to a set of downlink beams that includes the preferred downlink beam. The UE <NUM> may transmit a random access message in the random access occasion (e.g., using any permitted preamble), and may indicate the preferred downlink beam in UCI of the random access message. In some cases, the UE <NUM> may still need to wait for a random access occasion corresponding to a set of downlink beams that includes the preferred downlink beam, but such a wait may be reduced as compared to a scenario where each random access occasion corresponds to a single downlink beam. Furthermore, this configuration may reduce system complexity.

In a third operation <NUM>, the UE <NUM> may transmit an indication of the preferred downlink beam in UCI of a random access message. For example, the random access message may be msgA, and may include a RAM preamble and a RAM payload. The UE <NUM> may transmit the indication of the preferred downlink beam in the RAM payload, such as in UCI of the RAM payload (e.g., in a PUSCH communication included in the RAM payload and/or in a media access control (MAC) protocol data unit (PDU)). In some aspects, the UE <NUM> may indicate the preferred downlink beam using an index. The index may include a beam index, an index indicated in an SSB transmitted via the preferred downlink beam, and/or the like. Additionally, or alternatively, if the random access occasion is associated with a set of multiple downlink beams, then the index may identify the preferred downlink beam from the set of multiple downlink beams (e.g., a first downlink beam in the set may be identified using a first index, a second downlink beam in the set may be identified using a second index, and so on).

In a fourth operation <NUM>, the base station <NUM> may receive the random access message (msgA). For example, the base station <NUM> may receive the RAM preamble and/or the RAM payload. If the base station <NUM> successfully receives and decodes the RAM preamble, the base station <NUM> may then receive and decode the RAM payload.

In a fifth operation <NUM>, the base station <NUM> may transmit a random access response (RAR), such as msgB or msg2. In some aspects, the base station <NUM> may transmit the RAR on the preferred downlink beam indicated by the UE <NUM>. Alternatively, the base station <NUM> may transmit the RAR on a default downlink beam associated with the random access occasion and/or the preamble used by the UE <NUM>. In some aspects, the base station <NUM> may transmit the RAR on both the default downlink beam and the preferred downlink beam to achieve performance improvements associated with spatial diversity. In some aspects, the random access occasion may be associated with a set of multiple downlink beams (which may or may not include a default beam for the random access occasion), and the base station <NUM> may transmit the RAR on more than one downlink beam included in the set (e.g., on all downlink beams included in the set) to achieve performance improvements associated with spatial diversity.

In a sixth operation <NUM>, the base station <NUM> may transmit a subsequent DL communication using the preferred downlink beam indicated by the UE <NUM>. The subsequent DL communication may include one or more messages that follow the RAR and/or that follow the RACH procedure, such as a physical downlink control channel (PDCCH) communication, a physical downlink shared channel (PDSCH) communication, a radio resource control (RRC) message (e.g., an RRC configuration message), and/or the like.

In a seventh operation <NUM>, the UE <NUM> may monitor for the RAR on the default downlink beam and/or the preferred downlink beam, such as when the random access occasion is associated with a single default downlink beam. In some aspects, to reduce system complexity, the UE <NUM> may be configured or required to monitor for the RAR on only the default downlink beam and not the preferred downlink beam. In this case, the default downlink beam may be used to transmit and/or receive the RAR, and the preferred downlink beam may be used to transmit and/or receive the one or more subsequent DL communications.

In some aspects, such as when the random access occasion is associated with a single default downlink beam, the UE <NUM> may monitor for the RAR on only the preferred downlink beam and not the default downlink beam. However, in some cases, this may result in the UE <NUM> missing the RAR if the base station <NUM> could not decode the UCI indicating the preferred downlink beam, in which case the base station <NUM> may transmit the RAR on the default downlink beam. Thus, in some aspects, the UE <NUM> may monitor for the RAR on both the preferred downlink beam and the default downlink beam. For example, the base station <NUM> may indicate (e.g., in system information, such as a SIB, remaining minimum system information (RMSI), and/or the like) a time division multiplexing (TDM) pattern to be used by the UE <NUM> to monitor different downlink beams for the RAR. The TDM pattern may indicate a first set of time domain resources (e.g., transmission time intervals (TTIs), such as slots, subframes, and/or the like) in which the default downlink beam is to be monitored, and may indicate a second set of time domain resources in which the preferred downlink beam is to be monitored. In some aspects, the first set of time domain resources and the second set of time domain resources may be mutually exclusive. For example, the first set of time domain resources may be even slots, and the second set of time domain resources may be odd slots, or vice versa.

Additionally, or alternatively, the UE <NUM> may monitor for the RAR on the preferred downlink beam and/or one or more other downlink beams included in a set of multiple downlink beams associated with a random access occasion. In some aspects, to reduce system complexity, the UE <NUM> may be configured or required to monitor for the RAR on only the preferred downlink beam and not any other downlink beams included in the set. However, in some cases, this may result in the UE <NUM> missing the RAR if the base station <NUM> could not decode the UCI indicating the preferred downlink beam, in which case the base station <NUM> may transmit the RAR on a different downlink beam included in the set (e.g., the set could include a default beam and one or more other beams). Thus, in some aspects, the UE <NUM> may monitor for the RAR on the preferred downlink beam and one or more other downlink beams included in the set. In a similar manner as described above, the base station <NUM> may indicate a TDM pattern to be used by the UE <NUM> to monitor different downlink beams for the RAR. The TDM pattern may indicate a first set of time domain resources in which the preferred downlink beam is to be monitored, may indicate a second set of time domain resources in which another downlink beam in the set is to be monitored, and so on (e.g., for all or a subset of beams included in the set), in a similar manner as indicated above.

As further shown in the seventh operation <NUM>, the UE <NUM> may monitor for the subsequent DL communication(s) on the preferred downlink beam. The subsequent DL communication(s) may include one or more messages that follow the RAR and/or that follow the RACH procedure, such as a PDCCH communication, a PDSCH communication, an RRC message, and/or the like. By indicating the preferred downlink beam in the random access message and receiving one or more communications from the base station <NUM> (e.g., the RAR and/or one or more subsequent DL communications) via the preferred downlink beam, performance may be improved. For example, communications via the preferred beam may have a higher throughput, a lower latency, a higher reliability, and/or the like as compared to communications via a non-preferred beam.

Although some operations are described above in connection with indicating a preferred downlink beam (e.g., a single preferred downlink beam) in UCI of a random access message, in some aspects, the UE <NUM> may indicate multiple downlink beams (e.g., including a preferred downlink beam) in the UCI of the random access message. For example, the UE <NUM> may indicate a set of indexes corresponding to a set of beams. In some aspects, the UE <NUM> may indicate, in the UCI, a ranking for the set of indexes corresponding to the set of beams such that a list of beams from most-preferred to least-preferred is indicated to the base station <NUM>. In some aspects, the UE <NUM> may determine whether to identify a beam in the list based at least in part on whether the beam satisfies a condition (e.g., a signal quality threshold, a signal power threshold, a reference signal received power (RSRP) threshold, a reference signal received quality (RSRQ) threshold, a signal-to-interference-plus-noise ratio (SINR) threshold, and/or the like). In some aspects, the list may include or may exclude a default beam associated with a random access occasion in which the random access message is transmitted.

Additionally, or alternatively, the UE <NUM> may indicate, in the UCI, one or more parameters for one or more of the beams included in the list, such as a measured signal quality, a measured signal power, a measured RSRP parameter, a measured RSRQ parameter, a measured SINR parameter, and/or the like. Additionally, or alternatively, the UE <NUM> may indicate, in the UCI, whether the beam corresponds to an SSB (and/or which SSB) or to a CSI-RS (and/or which CSI-RS) (e.g., if CSI-RS is configured for the UE <NUM>.

In some aspects, the base station <NUM> may indicate (e.g., in system information), a TDM pattern for monitoring different downlink beams for a RAR, as indicated above. In this case, when the UE <NUM> indicates multiple downlink beams in the UCI, the UE <NUM> may then monitor the indicated downlink beams according to the TDM pattern. For example, the UE <NUM> may monitor a first downlink beam, included in the multiple indicated downlink beams, on a first set of time domain resources, the UE <NUM> may monitor a second downlink beam, included in the multiple indicated downlink beams, on a second set of time domain resources, and so on, in a similar manner as described above. In some aspects, the base station <NUM> may be permitted to send the RAR on any single indicated downlink beam for scheduling flexibility. Additionally, or alternatively, the base station <NUM> may send the RAR on multiple downlink beams (e.g., all indicated downlink beams or a subset of the multiple downlink beams) for spatial diversity gains. However, in some aspects, to reduce system complexity, the UE <NUM> may be configured or required to monitor for the RAR on only a default downlink beam and not any other indicated beam. In this case, the default downlink beam may be used to transmit and/or receive the RAR, and one or more other downlink beams in the list (e.g., the best beam) may be used to transmit and/or receive the one or more subsequent DL communications.

Additionally, or alternatively, when the UE <NUM> indicates multiple downlink beams in UCI of the random access message, the base station <NUM> may indicate a set of downlink beams in the RAR. The set of downlink beams in the RAR may include all of the downlink beams indicated in the random access message or a subset of the downlink beams indicated in the random access message. The UE <NUM> may monitor the downlink beams indicated in the RAR according to a TDM pattern. As described above, in some aspects, the TDM pattern may be indicated in system information. Alternatively, the TDM pattern may be indicated in the RAR.

In some aspects, in addition to indicating a preferred downlink beam in the UCI of the random access message, the UE <NUM> may transmit a power headroom report (PHR) and/or a buffer status report (BSR) in the UCI of the random access message, as described in more detail elsewhere herein. The base station <NUM> may use the PHR and/or the BSR to configure and/or transmit the RAR and/or one or more subsequent downlink communications, as described in more detail elsewhere herein.

<FIG> is a diagram illustrating another example <NUM> of reporting UCI in a random access procedure, in accordance with various aspects of the present disclosure. As shown in <FIG>, a UE <NUM> and a base station <NUM> may communicate with one another to perform a <NUM>-step RACH procedure (but may fall back to a <NUM>-step RACH procedure in some aspects).

In a first operation <NUM>, the UE <NUM> may transmit an indication of the preferred downlink beam in UCI of a random access message (e.g., a first random access message), as described above in connection with <FIG>.

In a second operation <NUM>, the base station <NUM> may receive the random access message, and may attempt to decode the random access message. In some cases, the base station <NUM> may successfully decode the UCI (e.g., that indicates the preferred downlink beam), but may fail to successfully decode some other contents of the RAM payload (e.g., one or more media access control (MAC) protocol data units (PDUs) other than the UCI).

In this case, in a third operation <NUM>, the base station <NUM> may instruct the UE <NUM> to retransmit the random access message (e.g., as a retransmission of msgA of a <NUM>-step RACH procedure) and/or to fall back to a <NUM>-step RACH procedure (e.g., to transmit msg3 of a <NUM>-step RACH procedure). In either case, the preferred downlink beam may be used for one or more messages of the RACH procedure that follow the initial random access message (e.g., transmitted in the first operation <NUM>). For example, in some aspects, the base station <NUM> may transmit a RAR (e.g., msg2 or msgB') via the preferred downlink beam, in a similar manner as described above in connection with <FIG>. The RAR (e.g., a first RAR) may include the instruction and/or an indication that the preferred downlink beam is to be used in association with the RACH procedure (e.g., for monitoring a PDCCH for retransmission of the random access message or for a new random access message, for a random access response to the retransmission or the new random access message, and/or the like). Alternatively, in some aspects, the base station <NUM> may transmit the RAR via a default downlink beam, and may use the preferred downlink beam for one or more RACH messages that occur after the RAR, in a similar manner as described above in connection with <FIG>. In some aspects, the base station <NUM> may transmit the RAR on both the default downlink beam and the preferred downlink beam to achieve performance improvements associated with spatial diversity.

In a fourth operation <NUM>, based at least in part on receiving the instruction in the RAR, the UE <NUM> may perform PDCCH monitoring for an additional random access message based at least in part on the preferred downlink beam. For example, the UE <NUM> may monitor for the PDCCH on the preferred downlink beam. The base station <NUM> may transmit a PDCCH communication on the preferred downlink beam, and the UE <NUM> may receive the PDCCH communication on the preferred downlink beam. The PDCCH communication may include DCI for transmission of a new RAM (e.g., a retransmission of msgA of <NUM>-step RACH or a new transmission of msg3 of <NUM>-step RACH), such as a resource allocation for the new RAM, an MCS for the new RAM, a timing advance for the new RAM, and/or the like.

In a fifth operation <NUM>, the UE <NUM> may transmit another RAM (e.g., a second RAM) to the base station <NUM>. As described above, the second RAM may be a retransmission of the first RAM (e.g., msgA) transmitted in the first operation <NUM> when the UE <NUM> continues to perform the <NUM>-step RACH procedure, or may be an initial transmission of a random access message (e.g., msg3) of a <NUM>-step RACH procedure when the UE <NUM> falls back to the <NUM>-step RACH procedure. In some aspects, the UE <NUM> may transmit the second RAM based at least in part on a PDCCH communication, which may be received via the preferred downlink beam.

In some aspects, if the UE <NUM> does not successfully receive the second RAM (e.g., if the base station <NUM> fails to detect an uplink demodulation reference signal (DMRS) from the UE <NUM> in the resource(s) scheduled for the DMRS and/or the RAM payload in the PDCCH communication described in operation <NUM>), then the base station <NUM> may transmit an additional RAR. In some aspects, the base station <NUM> may transmit the additional RAR (e.g., and/or one or more subsequent RARs if there are additional failures) if a time period associated with RAR transmissions has not elapsed. The UE <NUM> may continue to monitor for RARs until the end of the time period (e.g., the end of a RAR window). In some aspects, a later-received RAR in the time period may override an earlier-received RAR in the time period. In some aspects, after receiving a RAR, the UE <NUM> may reset a contention resolution timer (e.g., associated with the RAR window) to permit reception of additional RARs upon additional failures. In some aspects, the UE <NUM> may monitor multiple beams during the time period when RARs are transmitted via the default beam. For example, the UE <NUM> may monitor for a RAR on the default beam, and may monitor for PDCCH (as described above in operation <NUM>) on the preferred beam.

In a sixth operation <NUM>, based at least in part on receiving and successfully decoding the second random access message, the base station <NUM> may transmit another RAR (e.g., a second RAR). In some aspects, the second RAR may be transmitted via the preferred downlink beam. The second RAR may include all or a portion of msgB when the UE <NUM> and the base station <NUM> continue to perform a <NUM>-step RACH procedure, or may be msg4 of a <NUM>-step RACH procedure when the UE <NUM> and the base station <NUM> fall back to the <NUM>-step RACH procedure.

In a seventh operation <NUM>, the UE <NUM> may monitor for the second RAR based at least in part on the preferred downlink beam. For example, the UE <NUM> may perform PDCCH monitoring and/or PDSCH monitoring for the second RAR based on the preferred downlink beam.

By indicating the preferred downlink beam in the first random access message and receiving one or more communications from the base station <NUM> (e.g., the first RAR and/or one or more subsequent RACH communications) via the preferred downlink beam, performance may be improved. For example, communications via the preferred beam may have a higher throughput, a lower latency, a higher reliability, and/or the like as compared to communications via a non-preferred beam.

<FIG> is a diagram illustrating another example <NUM> of reporting UCI in a random access procedure, in accordance with various aspects of the present disclosure. As shown in <FIG>, a base station <NUM> may communicate with multiple UEs <NUM>, shown as UE A (e.g., a first UE <NUM>) and UE B (e.g., a second UE <NUM>). The base station <NUM> and the UEs <NUM> may communicate to perform a <NUM>-step RACH procedure.

As shown by reference number <NUM>, UE A may transmit a random access message indicating, in UCI of the random access message, a preferred downlink beam (and/or indicating a PHR, a BSR, and/or the like). The content of the UCI transmitted by UE A is represented as UCI A. UE A may transmit the random access preamble on a first set of resources (e.g., time resources, frequency resources, spatial resources, and/or the like), represented as Resource(s) A. As shown, UE A may select a preamble for the random access message, represented by a random access preamble identifier (RAPID) of <NUM>.

As shown by reference number <NUM>, UE B may also transmit a random access message indicating, in UCI of the random access message, a preferred downlink beam (and/or indicating a PHR, a BSR, and/or the like). The content of the UCI transmitted by UE B is represented as UCI B. UE B may transmit the random access preamble on a second set of resources (e.g., time resources, frequency resources, spatial resources, and/or the like), represented as Resource(s) B. The second set of resources may be the same as and/or may overlap with the first set of resources, or may be different from and/or non-overlapping with the first set of resources. As shown by reference number <NUM>, UE B may select the same preamble for the random access message as the preamble selected by UE A, shown as RAPID <NUM>. As a result, the random access messages of UE A and UE B may collide.

As shown by reference number <NUM>, the base station <NUM> may detect the collision. Based at least in part on detecting the collision, the base station <NUM> may transmit one or more random access responses (RARs) that include collision mitigation information. The collision mitigation information included in a RAR may include, for example, a RAPID and UCI (e.g., all of the UCI or a portion of the UCI) transmitted in a random access message corresponding to the RAR, an RAPID and information that identifies one or more resources used for the UCI transmitted in the random access message corresponding to the RAR, an RAPID and a hashing identifier that is generated based at least in part on the UCI and/or the one or more resources, and/or the like.

As shown by reference number <NUM>, a UE <NUM> may identify information (e.g., downlink control information (DCI)) relating to a subsequent random access message (e.g., msg3 and/or a retransmission of msgA) by analyzing contents of multiple RARs to identify a RAR corresponding to the UE <NUM>. For example, if the RAR includes an RAPID and UCI for a corresponding random access message, the UE <NUM> may determine whether the UCI in the RAR matches UCI transmitted by the UE <NUM> in the random access message. If the UCI matches, then the UE <NUM> may determine that the RAR is intended for the UE <NUM>, and may use information in the RAR (e.g., DCI for a subsequent communication, a timing advance value, a resource allocation, and/or the like) to communicate with the base station <NUM>. If the UCI does not match, then the UE <NUM> may continue to monitor for a RAR corresponding to the UE <NUM> (or may restart a RACH procedure if a RAR for the UE <NUM> is not received within a time window).

As another example, if the RAR includes an RAPID and information that identifies resource(s) used to transmit UCI for a corresponding random access message, the UE <NUM> may determine whether the resources indicated in the RAR match the resources used by the UE <NUM> to transmit the UCI. If the resources match, then the UE <NUM> may determine that the RAR is intended for the UE <NUM>, and may use information in the RAR to communicate with the base station <NUM>. If the resources do not match, then the UE <NUM> may continue to monitor for a RAR corresponding to the UE <NUM> (or may restart a RACH procedure if a RAR for the UE <NUM> is not received within a time window).

As another example, if the RAR includes an RAPID and a hashing identifier generated from the UCI and/or the resource(s) for a corresponding random access message, the UE <NUM> may determine whether the hashing identifier indicated in the RAR (e.g., which is generated by the base station <NUM>) matches a hashing identifier generated by the UE <NUM> (e.g., using a same hashing algorithm as the base station <NUM>). If the hashing identifiers match, then the UE <NUM> may determine that the RAR is intended for the UE <NUM>, and may use information in the RAR to communicate with the base station <NUM>. If the hashing identifiers do not match, then the UE <NUM> may continue to monitor for a RAR corresponding to the UE <NUM> (or may restart a RACH procedure if a RAR for the UE <NUM> is not received within a time window).

Additionally, or alternatively, to mitigate and/or reduce the likelihood of a collision, the RAR may indicate a dedicated preamble and/or a dedicated random access occasion to be used by a UE <NUM> for a subsequent RACH attempt (e.g., retransmission of a random access message). For example, the base station <NUM> may assign a first preamble to a first UE <NUM>, and may assign a second (different) preamble to a second UE <NUM> based at least in part on detecting a collision between a random access message from the first UE <NUM> and a random access message from the second UE <NUM>. Additionally, or alternatively, the base station <NUM> may assign a first random access occasion to a first UE <NUM>, and may assign a second (different) random access occasion to a second UE <NUM> based at least in part on detecting the collision. A UE <NUM> may use a dedicated preamble and/or a dedicated random access occasion indicated by the base station <NUM> for a retransmission of the random access message.

Additionally, or alternatively, to mitigate and/or reduce the likelihood of a collision, a random access radio network temporary identifier (RA-RNTI) used by a UE <NUM> may be generated based at least in part on a preamble selected by the UE <NUM> and a PUSCH occasion selected by the UE <NUM> for transmission of the random access message. In this way, when different UEs <NUM> use the same preamble, those UEs <NUM> may be differentiated via different RA-RNTIs if the UEs <NUM> use different PUSCH occasions to transmit UCI for a random access message.

Using the techniques described above may reduce the likelihood of random access message collisions, mitigate random access message collisions after such collisions have occurred, and/or permit earlier detection of random access message collisions, thereby improving network performance.

<FIG> is a diagram illustrating another example <NUM> of reporting UCI in a random access procedure, in accordance with various aspects of the present disclosure. As shown in <FIG>, a UE <NUM> and a base station <NUM> may communicate with one another to perform a <NUM>-step RACH procedure.

In a first operation <NUM>, the UE <NUM> may transmit a power headroom report (PHR) and/or a buffer status report (BSR) in UCI of a random access message. As described above in connection with <FIG>, the random access message may be msgA, and may include a RAM preamble and a RAM payload. The UE <NUM> may transmit the PHR and/or the BSR in the RAM payload, such as in UCI of the RAM payload (e.g., in a PUSCH communication included in the RAM payload). In some aspects, the UE <NUM> may transmit the PHR and/or the BSR in the UCI, and may not transmit the preferred downlink beam (as described above) in the UCI. In some aspects, the UE <NUM> may indicate the preferred downlink beam and at least one of the PHR and/or the BSR in the UCI. In some aspects, one or more indexes and/or values to be used to report the PHR and/or the BSR may be indicated to the UE <NUM> in system information (e.g., RMSI and/or the like).

In a second operation <NUM>, the base station <NUM> may determine one or more parameters for a RAR and/or one or more subsequent downlink communications based at least in part on the PHR and/or the BSR. As described elsewhere herein, the one or more subsequent downlink communications may include one or more messages that follow the RAR and/or that follow the RACH procedure, such as a PDCCH communication (e.g., for uplink scheduling), a PDSCH communication, an RRC message, and/or the like. The one or more parameters may include, for example, a resource allocation for a communication (e.g., a set of time domain, frequency domain, and/or spatial domain resources), an MCS for the communication, a layer configuration for the communication (e.g., a number of MIMO layers to be used for the communication, one or more layer indexes, and/or the like), and/or the like.

In some aspects, the base station <NUM> may determine a layer configuration and/or an MCS based at least in part on the PHR. For example, the PHR may indicate whether the UE <NUM> has additional power headroom to support additional and/or multiple layers, whether the UE <NUM> has additional power headroom to support a different and/or a higher MCS, and/or the like. Additionally, or alternatively, the base station <NUM> may determine a resource allocation based at least in part on the BSR. For example, the BSR may indicate an amount of data queued for transmission by the UE <NUM>, which may indicate a number of resources needed for the transmission. Thus, the base station <NUM> may configure an appropriate resource allocation for the UE <NUM>. By using UCI rather than preamble partitioning to indicate a PHR and/or a BSR, network performance may be improved by avoiding preamble partitioning.

In a third operation <NUM>, the base station <NUM> may transmit a RAR, in a similar manner as described elsewhere herein. In a fourth operation <NUM>, the base station <NUM> may transmit the one or more subsequent downlink communications, in a similar manner as described elsewhere herein. As shown by reference number <NUM>, at least one of the RAR or the one or more subsequent downlink communications may be based at least in part on the PHR and/or the BSR. For example, the base station <NUM> may determine a layer configuration and/or an MCS for the RAR and/or the one or more subsequent downlink communications based at least in part on the PHR and/or the BSR. Additionally, or alternatively, the base station <NUM> may determine a resource allocation to be indicated to the UE <NUM> in an uplink grant (e.g., in the RAR and/or in a subsequent downlink communication).

In a fifth operation <NUM>, the UE <NUM> may monitor for a RAR and/or a downlink communication subsequent to the RAR based at least in part on the PHR and/or the BSR. For example, the UE <NUM> may monitor for a communication based at least in part on a layer configuration, an MCS, and/or the like, which may be based at least in part on the PHR and/or the BSR and/or which may be indicated to the UE <NUM> by the base station <NUM> based at least in part on the PHR and/or the BSR.

By indicating a PHR and/or a BSR in the random access message and receiving one or more communications from the base station <NUM> based at least in part on the PHR and/or the BSR, performance may be improved. For example, the base station <NUM> may configure one or more communications using the PHR and/or the BSR to achieve higher throughput, lower latency, higher reliability, and/or the like as compared to configuring such communication(s) without using the PHR and/or the BSR.

In a first operation <NUM>, the UE <NUM> may transmit a PHR and/or a BSR in UCI of a random access message (e.g., a first random access message), as described above in connection with <FIG>.

In a second operation <NUM>, the base station <NUM> may receive the random access message, and may attempt to decode the random access message. In some cases, the base station <NUM> may successfully decode the UCI (e.g., that indicates the PHR and/or the BSR), but may fail to successfully decode some other contents of the RAM payload (e.g., one or more MAC PDUs other than the UCI).

In a third operation <NUM>, the base station <NUM> may determine one or more parameters, associated with a RAR to be transmitted by the base station <NUM>, based at least in part on the PHR and/or the BSR. In some aspects, the one or more parameters may relate to an uplink grant to be included in a RAR. For example, the base station <NUM> calculate one or more parameters for the uplink grant (e.g., a resource allocation, a layer configuration, an MCS, and/or the like) based at least in part on the PHR and/or the BSR, in a similar manner as described above in connection with <FIG>. The uplink grant may be an uplink grant associated with a <NUM>-step RACH procedure, and the RAR may instruct the UE <NUM> to fall back to the <NUM>-step RACH procedure and to use the uplink grant for transmission of msg3. Additionally, or alternatively, the RAR may instruct the UE <NUM> to retransmit the random access message (e.g., as part of a continued <NUM>-step RACH procedure). In this case, the RAR may indicate an MCS, a resource allocation (e.g., a PUSCH resource allocation), and/or a layer configuration for the retransmission.

In a fourth operation <NUM>, the base station <NUM> may transmit the RAR to the UE <NUM>. As shown, the RAR may include msg2 or msgB', depending on whether the <NUM>-step RACH procedure is to continue or whether the UE <NUM> and the base station <NUM> are to fall back to the <NUM>-step RACH procedure. For <NUM>-step RACH fallback, the RAR may include an uplink grant for msg3, and the uplink grant may indicate and/or may be determined based at least in part on one or more parameters that are determined based at least in part on the PHR and/or the BSR. For <NUM>-step RACH, the RAR may instruct the UE <NUM> to retransmit the random access message, and may include one or more parameters for the retransmission.

In a fifth operation <NUM>, the UE <NUM> may transmit a second random access message to the base station <NUM>. As described above, the second RAM may be a retransmission of the first RAM (e.g., msgA) transmitted in the first operation <NUM> when the UE <NUM> continues to perform the <NUM>-step RACH procedure, or may be an initial transmission of a random access message (e.g., msg3) of a <NUM>-step RACH procedure when the UE <NUM> falls back to the <NUM>-step RACH procedure. In some aspects, the UE <NUM> may transmit the second RAM based at least in part on one or more parameters indicated in the RAR. For example, the UE <NUM> may transmit the RAM using a resource allocation, a layer configuration, and/or an MCS indicated in the RAR.

In a sixth operation <NUM>, based at least in part on receiving and successfully decoding the second random access message, the base station <NUM> may transmit a second RAR. The second RAR may include all or a portion of msgB when the UE <NUM> and the base station <NUM> continue to perform a <NUM>-step RACH procedure, or may be msg4 of a <NUM>-step RACH procedure when the UE <NUM> and the base station <NUM> fall back to the <NUM>-step RACH procedure. In some aspects, the second RAR may be transmitted based at least in part on the one or more parameters (e.g., using a resource allocation, an MCS, a layer configuration, and/or the like determined based at least in part on the PHR and/or the BSR).

In a seventh operation <NUM>, the UE <NUM> may monitor for the second RAR based at least in part on the one or more parameters. For example, the UE <NUM> may perform PDCCH monitoring and/or PDSCH monitoring for the second RAR using an indicated resource allocation, MCS, and/or the layer configuration.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where a UE (e.g., UE <NUM> and/or the like) performs operations associated with reporting uplink control information in a random access procedure.

As shown in <FIG>, in some aspects, process <NUM> may include transmitting an indication of a downlink beam in uplink control information of a random access message, wherein the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted, or wherein the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion (block <NUM>). For example, the UE (e.g., using transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit an indication of a downlink beam in uplink control information of a random access message, as described above. In some aspects, the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted. In some aspects, the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion.

As further shown in <FIG>, in some aspects, process <NUM> may include monitoring for at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information (block <NUM>). For example, the UE (e.g., using receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may monitor for at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information, as described above.

In a first aspect, a plurality of random access occasions configured for the UE each correspond to a single default beam, wherein the downlink beam is different from the default beam corresponding to the random access occasion in which the random access message is transmitted.

In a second aspect, alone or in combination with the first aspect, a plurality of random access occasions configured for the UE each correspond to multiple default beams, wherein the multiple default beams are each associated with a different set of preambles, wherein the downlink beam is different from the default beam corresponding to the random access occasion in which the random access message is transmitted and corresponding to the preamble of the random access message.

In a third aspect, alone or in combination with one or more of the first and second aspects, the random access response is received via the default beam or via the downlink beam.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process <NUM> includes monitoring at least one of the default beam or the downlink beam based at least in part on a time division multiplexing pattern indicated in system information.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the default beam is monitored for the random access response and the downlink beam is monitored for the downlink communication subsequent to the random access response.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the downlink beam is indicated using an index that identifies the downlink beam from the set of multiple downlink beams corresponding to the random access occasion.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, a set of preambles is not partitioned among different downlink beams included in the set of multiple downlink beams.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, process <NUM> includes monitoring at least one of the downlink beam or another downlink beam included in the set of multiple downlink beams based at least in part on a time division multiplexing pattern indicated in system information.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the random access message is associated with a two-step random access channel procedure and the random access response instructs the UE to use the downlink beam in association with a retransmission of the random access response or to fall back to a four-step random access channel procedure.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the UE is configured to monitor for random access responses until an end of a random access response window.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the random access response includes at least one of: a random access preamble identifier and the uplink control information transmitted in the random access message, a random access preamble identifier and information that identifies one or more resources used for the uplink control information transmitted in the random access message, or a random access preamble identifier and a hashing identifier that is based at least in part on at least one of the uplink control information or the one or more resources.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, a random access radio network temporary identifier for the UE is based at least in part on the preamble of the random access message and a physical uplink shared channel occasion in which the random access message is transmitted.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, the random access response identifies at least one of a dedicated preamble or a dedicated random access occasion to be used by the UE for a subsequent random access message.

In a fourteenth aspect, alone or in combination with one or more of the first through thirteenth aspects, the downlink beam is one of a plurality of downlink beams indicated in the uplink control information of the random access message.

In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, process <NUM> includes monitoring at least one of the plurality of downlink beams based at least in part on a time division multiplexing pattern indicated in system information.

In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, the random access response indicates a set of downlink beams to be monitored by the UE and a time division multiplexing pattern for monitoring the set of downlink beams.

In a seventeenth aspect, alone or in combination with one or more of the first through sixteenth aspects, the uplink control information further includes at least one of a power headroom report or a buffer status report.

As shown in <FIG>, in some aspects, process <NUM> may include transmitting at least one of a power headroom report or a buffer status report in uplink control information of a random access message (block <NUM>). For example, the UE (e.g., using transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit at least one of a power headroom report or a buffer status report in uplink control information of a random access message, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include monitoring for at least one of a random access response or a downlink communication subsequent to the random access response based at least in part on the power headroom report or the buffer status report (block <NUM>). For example, the UE (e.g., using receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may monitor for at least one of a random access response or a downlink communication subsequent to the random access response based at least in part on the power headroom report or the buffer status report, as described above.

In a first aspect, the random access message is associated with a two-step random access channel procedure and the random access response includes an uplink grant for retransmission of the random access message or fallback to a four-step random access channel procedure, wherein the uplink grant is determined based at least in part on at least one of the power headroom report or the buffer status report.

In a second aspect, alone or in combination with the first aspect, the random access response indicates one or more parameters for a retransmission of the random access message, wherein the one or more parameters are determined based at least in part on at least one of the power headroom report or the buffer status report.

In a third aspect, alone or in combination with one or more of the first and second aspects, the one or more parameters include at least one of a resource allocation, a modulation and coding scheme, or a layer configuration.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the random access response includes at least one of: a random access preamble identifier and the uplink control information transmitted in the random access message, a random access preamble identifier and information that identifies one or more resources used for the uplink control information transmitted in the random access message, or a random access preamble identifier and a hashing identifier that is based at least in part on at least one of the uplink control information or the one or more resources.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, a random access radio network temporary identifier for the UE is based at least in part on a preamble of the random access message and a random access occasion in which the random access message is transmitted.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the random access response identifies at least one of a dedicated preamble or a dedicated random access occasion to be used by the UE for a subsequent random access message.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the uplink control information further indicates a downlink beam, wherein the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted, or wherein the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a base station, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where a base station (e.g., base station <NUM> and/or the like) performs operations associated with reporting uplink control information in a random access procedure.

As shown in <FIG>, in some aspects, process <NUM> may include receiving an indication of a downlink beam in uplink control information of a random access message, wherein the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion associated with the random access message, or wherein the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion (block <NUM>). For example, the base station (e.g., using receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive an indication of a downlink beam in uplink control information of a random access message, as described above. In some aspects, the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion associated with the random access message. In some aspects, the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion.

As further shown in <FIG>, in some aspects, process <NUM> may include transmitting at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information (block <NUM>). For example, the base station (e.g., using transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information, as described above.

In a first aspect, a plurality of random access occasions each correspond to a single default beam, wherein the downlink beam is different from the default beam corresponding to the random access occasion in which the random access message is transmitted.

In a second aspect, alone or in combination with the first aspect, a plurality of random access occasions each correspond to multiple default beams, wherein the multiple default beams are each associated with a different set of preambles, wherein the downlink beam is different from the default beam corresponding to the random access occasion in which the random access message is transmitted and corresponding to the preamble of the random access message.

In a third aspect, alone or in combination with one or more of the first and second aspects, the random access response is transmitted via the default beam or via the downlink beam.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process <NUM> includes transmitting, in system information, a time division multiplexing pattern to be used for monitoring at least one of the default beam or the downlink beam.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the random access response is transmitted via the default beam and the downlink communication subsequent to the random access response is transmitted via the downlink beam.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, process <NUM> includes transmitting, in system information, a time division multiplexing pattern to be used for monitoring at least one of the downlink beam or another downlink beam included in the set of multiple downlink beams.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the random access message is associated with a two-step random access channel procedure and the random access response includes an instruction to use the downlink beam in association with a retransmission of the random access response or to fall back to a four-step random access channel procedure.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the base station is configured to retransmit random access responses upon detecting a failure until an end of a random access response window.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the random access response includes at least one of: a random access preamble identifier and the uplink control information received in the random access message, a random access preamble identifier and information that identifies one or more resources used for the uplink control information received in the random access message, or a random access preamble identifier and a hashing identifier that is based at least in part on at least one of the uplink control information or the one or more resources.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, a random access radio network temporary identifier is generated based at least in part on the preamble of the random access message and a physical uplink shared channel occasion in which the random access message is transmitted.

In a thirteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, the random access response identifies at least one of a dedicated preamble or a dedicated random access occasion to be used for a subsequent random access message.

In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, process <NUM> includes transmitting, in system information, a time division multiplexing pattern for monitoring at least one of the plurality of downlink beams.

In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, the random access response indicates a set of downlink beams to be monitored and a time division multiplexing pattern for monitoring the set of downlink beams.

As shown in <FIG>, in some aspects, process <NUM> may include receiving at least one of a power headroom report or a buffer status report in uplink control information of a random access message (block <NUM>). For example, the base station (e.g., using receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive at least one of a power headroom report or a buffer status report in uplink control information of a random access message, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include transmitting at least one of a random access response or a downlink communication subsequent to the random access response based at least in part on the power headroom report or the buffer status report (block <NUM>). For example, the base station (e.g., using transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit at least one of a random access response or a downlink communication subsequent to the random access response based at least in part on the power headroom report or the buffer status report, as described above.

In a first aspect, the one or more parameters include at least one of a resource allocation, a modulation and coding scheme, or a layer configuration.

In a second aspect, alone or in combination with the first aspect, the uplink control information further indicates a downlink beam, wherein the downlink beam is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted, or wherein the downlink beam is selected from a set of multiple downlink beams corresponding to the random access occasion.

Claim 1:
A method (<NUM>) of wireless communication performed by a user equipment, UE, comprising:
transmitting (<NUM>) an indication that includes a set of indexes corresponding to a set of downlink beams in uplink control information of a random access message, wherein each downlink beam of the set of downlink beams is different from a default beam corresponding to a preamble of the random access message and a random access occasion in which the random access message is transmitted, or wherein each downlink beam of the set of downlink beams is selected from a set of multiple downlink beams corresponding to the random access occasion; and
monitoring (<NUM>) for at least one of a random access response or a downlink communication subsequent to the random access response using the downlink beam indicated in the uplink control information, wherein the downlink beam is one of a plurality of downlink beams indicated in the uplink control information of the random access message, wherein the random access message is associated with a two-step random access channel procedure and the random access response instructs the UE to fall back to a four-step random access channel procedure.