Message 1 of a two-step random access procedure

Methods, systems, and devices for wireless communications are described. A user equipment (UE) may identify that the UE is configured to use a two-step random access channel (RACH) procedure. The two-step RACH procedure may include an uplink request message and a downlink response. The UE may transmit the uplink request message as part of the two-step RACH procedure, and the uplink request message may include a preamble portion that is one of a set of predefined sequences and a payload portion that includes a physical uplink shared channel waveform. The UE may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

BACKGROUND

The following relates generally to wireless communications, and more specifically to methods and techniques for configuring and transmitting a first message, or message 1, of a two-step random access procedure.

Some wireless systems may support random access procedures for establishing communications between a UE and a base station. The random access procedure may involve a series of handshake messages between the UE and the base station. In some cases, it may be desirable to reduce the latency associated with the random access procedure.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support message 1 of a two-step random access procedure. Generally, the described techniques provide for performing a two-step random access procedure based on an access request message (message 1) from a UE that includes a preamble portion and a payload portion. In some instances, the preamble of the access request message may serve as a demodulation reference signal for a payload portion of the access request message. In some cases, the payload portion of the access request message may be a physical uplink control channel waveform or a physical uplink shared channel waveform. The size of the payload portion of the access request message may be fixed or may be a function of a random access procedure use case.

A method of wireless communication at a UE is described. The method may include identifying that the UE is configured to use a two-step random access channel (RACH) procedure, the two-step RACH procedure including an uplink request message and a downlink response, transmitting the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and receiving the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response, transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for identifying that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response, means for transmitting the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and means for receiving the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response, transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an indication of the preamble portion before transmitting the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the preamble portion of the uplink request message as a demodulation reference signal for the payload portion of the uplink request message. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may also include transmitting additional demodulation reference signals for the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the preamble portion of the uplink request message using a preamble sequence that has a prime number sequence length, and transmitting the payload portion using resource elements that are a subset of a frequency span of the preamble portion.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the payload portion using a payload size that is based, at least in part, on whether the two-step RACH procedure is for initial access or for handover. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the payload portion using a fixed payload size.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the preamble portion of the uplink request message interleaved in time with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message without use of cyclic prefixes between resource elements of the preamble portion.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, via remaining minimum system information or radio resource control signaling, an association between the preamble portion of the uplink request message and the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the preamble portion of the uplink request message during a first transmission time interval, and transmitting, in accordance with the received association, the payload portion of the uplink request message during a second transmission time interval. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may also include transmitting the preamble portion of the uplink request message and the payload portion of the uplink request message without an intervening transmission time interval between the first transmission time interval and the second transmission time interval. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may also include transmitting the preamble portion of the uplink request message and the payload portion of the uplink request message with an intervening transmission time interval between the first transmission time interval and the second transmission time interval, wherein the intervening transmission time interval is available for non-RACH transmissions.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for selecting a preamble sequence from the plurality of predefined sequences for transmission of the preamble portion of the uplink request message, wherein only a portion of the predefined sequences are associated with two-step RACH procedures.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the payload portion of the uplink request message with an embedded demodulation reference signal to match dimensions of both the preamble portion and the payload portion.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include selecting a preamble sequence from the plurality of predefined sequences for transmission of the preamble portion of the uplink request message, wherein the selected preamble sequence shares a resource association with another preamble sequence of the plurality of predefined sequences, and applying an additional differentiating factor to the uplink request message to allow differentiation of the payload portion of the uplink request message. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the additional differentiating factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for selecting a preamble sequence from the plurality of predefined sequences for transmission of the preamble portion of the uplink request message, wherein the selected preamble sequence has a resource association with more than one payload resource, and applying an additional identifying factor to the uplink request message to allow identification of the payload portion of the uplink request message. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the additional identifying factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the payload portion during a time resource that is time-multiplexed with payload portions from additional UEs. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting the payload portion during a time resource that is code division-multiplexed with payload portions from additional UEs.

A method of wireless communication at a base station is described. The method may include receiving, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and transmitting a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

An apparatus for wireless communication at a base station is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

Another apparatus for wireless communication at a base station is described. The apparatus may include means for receiving, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and means for transmitting a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

A non-transitory computer-readable medium storing code for wireless communication at a base station is described. The code may include instructions executable by a processor to receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a plurality of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting an indication of the preamble portion to the UE before receiving the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the uplink request message may include receiving the preamble portion of the uplink request message, and using the preamble portion of the uplink request message as a demodulation reference signal for the payload portion of the uplink request message. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may also include receiving additional demodulation reference signals for the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message using a preamble sequence that has a prime number sequence length, and receiving the payload portion using resource elements that are a subset of a frequency span of the preamble portion.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the payload portion using a payload size that is based, at least in part, on whether the two-step RACH procedure is for initial access or for handover. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the payload portion using a fixed payload size.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message interleaved in time with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message without use of cyclic prefixes between resource elements of the preamble portion.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include transmitting, via remaining minimum system information or radio resource control signaling, an association between the preamble portion of the uplink request message and the payload portion of the uplink request message. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message during a first transmission time interval, and receiving, in accordance with the transmitted association, the payload portion of the uplink request message during a second transmission time interval.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message and the payload portion of the uplink request message without an intervening transmission time interval between the first transmission time interval and the second transmission time interval. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the preamble portion of the uplink request message and the payload portion of the uplink request message with an intervening transmission time interval between the first transmission time interval and the second transmission time interval, wherein the intervening transmission time interval is available for non-RACH transmissions.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving in the preamble portion a preamble sequence selected from the plurality of predefined sequences, wherein only a portion of the predefined sequences are associated with two-step RACH procedures. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the payload portion of the uplink request message with an embedded demodulation reference signal to match dimensions of both the preamble portion and the payload portion.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving in the preamble portion a preamble sequence selected from the plurality of predefined sequences, wherein the selected preamble sequence shares a resource association with another preamble sequence of the plurality of predefined sequences, and differentiating the payload portion of the uplink request message via a differentiating factor. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the differentiating factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving in the preamble portion a preamble sequence selected from the plurality of predefined sequences, wherein the selected preamble sequence has a resource association with more than one payload resource, and identifying the payload portion of the uplink request message via an identifying factor. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the identifying factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the payload portion during a time resource that is time-multiplexed with payload portions from additional UEs. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include receiving the payload portion during a time resource that is code division-multiplexed with payload portions from additional UEs.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the uplink request message may include applying the preamble portion of the uplink request message as a demodulation reference signal for the payload portion of the uplink request message, and scheduling non-RACH transmissions based on presence of the preamble portion and application of the preamble portion as a demodulation reference signal.

DETAILED DESCRIPTION

Some wireless systems support establishment of communications between a user equipment (UE) and a base station using a random access procedure that may enable a UE to synchronize with the base station. The UE may initiate the random access procedure when it is first powered up (e.g., at initial access), during a handover of the UE from one base station to another base station, when the UE needs to re-establish communications after an interruption, or under various other conditions, for example.

In some cases, a random access procedure may include transmission of a series of four handshake messages between the UE and the base station. Such messages may be unscheduled, for example, and may be transmitted on a shared random access channel (RACH). When the random access procedure is used in an unlicensed spectrum, the UE may perform a listen-before-talk (LBT) procedure before transmitting each message to ensure that the transmission channel is clear for use.

In a four-message random access procedure, the first message may be a message transmitted from the UE to the base station and may include a preamble waveform (e.g., a preamble sequence) that identifies the UE. The second message may be transmitted from the base station to the UE and may acknowledge receipt of the preamble and allocate transmission resources to the UE. The third message may be another message transmitted from the UE to the base station and may include a request for a radio resource control (RRC) connection. The fourth message may be transmitted from the base station to the UE and may include an RRC connection response. Once the fourth message is received and decoded by the UE, the UE may begin communications with the base station in, for example, RRC connected mode. This random access procedure may be referred to as a four-step random access procedure.

In some cases, it may be desirable or beneficial to reduce the latency and/or the number of LBT procedures associated with performing a random access procedure. Such reductions may improve communication efficiency and may be particularly useful for latency-sensitive communications. Thus, new random access procedures may be needed to reduce the latency associated with the random access procedure.

Aspects of the present disclosure may include a two-step random access procedure that includes transmission of a first message (message 1) from the UE to the base station and a second message (message 2) from the base station to the UE. In some cases, these two messages may essentially replace the four messages of a conventional four-step random access procedure. As described herein, in some cases, a UE may be configured to support both the two-step random access procedure and the four-step random access procedure.

In some cases, message 1 of the two-step random access procedure includes a preamble portion and a payload portion (which may be, for example, an RRC connection request or data), thereby combining features of the first message and the third message of a conventional four-step procedure. In some cases, the base station may respond with a downlink response. This downlink response may be referred to as message 2 of the two-step random access procedure.

As described herein, a two-step random access procedure may provide multiple benefits. For example, a two-step random access procedure as described herein may reduce the number of messages required for a random access procedure and may correspondingly, reduce the number of LBT procedures that may be performed by the UE when the UE is operating in an unlicensed spectrum. Such reductions may reduce the latency of the random access procedure. In addition, in some cases, the preamble portion of message 1 may be used as a reference signal for the payload portion of message 1, which may be particularly beneficial in the context of high Doppler operation (such as in vehicle to everything (V2X) systems) when a UE may be moving relatively quickly.

Aspects of the disclosure are initially described in the context of a wireless communications system. Aspects of the disclosure are further described in the context of a process flow. Aspects of the disclosure are further illustrated by and described with reference to message configuration diagrams, apparatus diagrams, system diagrams, and flowcharts that relate to configuring and transmitting message 1 of a two-step random access procedure.

In some cases, a UE115may perform a random access procedure to synchronize with the network under various circumstances, including at power-up (e.g., for initial access) or at a handover from one base station105to another base station105, for example. The random access procedure may enable the UE115to synchronize timing with the base station105and receive an allocation of uplink transmission resources. In some cases, a UE115may perform a two-step random access procedure. The UE115may initiate the procedure by transmitting an uplink request message (message 1) to a base station105. The uplink request message may include a preamble portion and a payload portion.

In some cases, the UE115may transmit the uplink request message to the base station using a transport channel, such as a shared RACH. Thus, the two-step random access procedure may be referred to as a two-step RACH procedure.

In some cases, the preamble portion of message 1 is a sequence, such as a Zadoff-Chu sequence or another type of sequence. In some cases, the sequence may have the property that cyclically shifted versions of the sequence are orthogonal to one another, such that the sequence may be used to reduce cross-correlation (e.g., interference) between transmissions.

In some cases, the preamble sequence (e.g., the sequence selected for the preamble portion) may be randomly selected from a set of predefined sequences. This may enable the base station105to distinguish between multiple UEs115trying to access the system simultaneously, since RACH is normally contention-based.

In some cases, the preamble portion (e.g., the preamble sequence) may be associated with a transmission occasion of a physical uplink shared channel (PUSCH). For example, the preamble portion may indicate an occasion during which the UE may transmit information to the base station on the PUSCH.

In some cases, the UE may receive an indication of the preamble portion from the base station before transmitting the uplink request message. For example, the base station may select a preamble sequence and may transmit an indication of the preamble sequence to the UE, and the indicated preamble sequence may be included by the UE in the preamble portion of the uplink request message.

In some cases, the payload portion includes either a physical uplink control channel (PUCCH) waveform or a PUSCH waveform. A PUCCH waveform may be used to convey signaling or control information, for example. A PUSCH waveform may be used to convey signaling information, uplink control information (UCI), or user data, for example.

In some cases, the base station105may respond to receiving message 1 from the UE115by transmitting a downlink response that enables the UE115to begin ongoing communication with the base station105(e.g., by establishing an RRC connection), thereby completing the two-step RACH procedure.

In some cases, a UE115may identify that the UE115is configured to use a two-step RACH procedure. The two-step RACH procedure may include an uplink request message and a downlink response. The UE115may transmit the uplink request message as part of the two-step RACH procedure. The uplink request message may include a preamble portion that is one of a set of predefined sequences and a payload portion that includes either a PUCCH waveform or a PUSCH waveform, where the preamble portion is associated with a transmission occasion of the PUSCH. The UE115may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

In some cases, a base station105may receive, as part of a two-step RACH procedure, an uplink request message from a UE. The uplink request message may include a preamble portion that is one of a set of predefined sequences and a payload portion that includes either a PUCCH waveform or a PUSCH waveform, where the preamble portion is associated with a transmission occasion of the PUSCH. The base station105may transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

UEs115may include a UE communications manager102, which may identify that the UE115is configured to use a two-step RACH procedure. The two-step RACH procedure may include an uplink request message and a downlink response. The UE communications manager102may transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes either a physical uplink control channel waveform or a physical uplink shared channel waveform, where the preamble portion is associated with a transmission occasion of the PUSCH. The UE communications manager102may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

One or more of the base stations105may include a base station communications manager101, which may receive, as part of a two-step RACH procedure, an uplink request message from a UE115. The uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes either a physical uplink control channel waveform or a physical uplink shared channel waveform, where the preamble portion is associated with a transmission occasion of the PUSCH. The base station communications manager101may transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

FIG. 2illustrates an example of a process200that supports a two-step random access procedure (e.g., a two-step RACH procedure) in accordance with aspects of the present disclosure. In some examples, process200may implement aspects of wireless communication system100. Process200may include communications between a base station205and a UE210, which may be examples of the corresponding devices described herein.

At215, UE210may identify that the UE210is configured to use a two-step RACH procedure. The UE210may identify that the UE210is configured to use the two-step RACH procedure based on configuration information previously received by UE210or based on a device setting of UE210, for example.

At220, UE210may transmit an uplink request message as part of the two-step RACH procedure. In some cases, the UE210may transmit the uplink request message on the RACH transport channel, for example. In some cases, the uplink request message may include a preamble portion that is one of a set of predefined sequences and a payload portion that includes either a PUCCH waveform or a PUSCH waveform. In some cases, the preamble portion is associated with a transmission occasion of the PUSCH.

At225, base station205may, in response to receiving the uplink request message from UE210, transmit a downlink response to UE210that may be received by UE210.

At230, UE210may, based on the downlink response message received from base station205, begin communicating with base station205. In some cases, UE210may begin communicating in RRC connected mode, for example.

Additional details regarding aspects of the uplink request message are described in more detail with reference toFIGS. 3 through 8.

FIG. 3illustrates an example of a message configuration300for an uplink request message of a two-step random access procedure in accordance with aspects of the present disclosure. In some examples, an uplink request message having message configuration300may be transmitted using aspects of wireless communication system100.

Message configuration300includes uplink request message305that may be transmitted from a UE210to a base station205as described with respect toFIG. 2. Uplink request message305may include a preamble portion310and a payload portion325.

Preamble portion310may include one or more preamble resource elements315-athrough315-b, each of which may include a symbol, such as an OFDM symbol, and a preamble cyclic prefix320. Preamble cyclic prefixes320may serve as guard intervals to reduce inter-symbol interference between preamble resource elements315, and/or may be used to support channel estimation or equalization. The preamble portion310may be associated with a PUCCH or PUSCH occasion (e.g., a transmission occasion during which the UE may transmit information on the PUCCH or PUSCH), for example. Preamble resource elements315may be indexed as shown from 0 to 11, for example, if there are twelve preamble resource elements in a frequency band. Other numbers of preamble resource elements are possible.

In some cases, preamble portion310is or includes one of a set of predefined sequences, such as Zadoff-Chu sequences or other type of sequences, for example. In some cases, the set of predefined sequences may be a set of 64 Zadoff-Chu sequences, for example. In some cases, the predefined sequence may be known to both the UE210and the base station205. In some cases, preamble portion310includes a sequence having a sequence length that is a prime number. In some cases, each of the sequences in the set of predefined sequences have corresponding sequence lengths that are prime numbers. The UE210may select the predefined sequence randomly, for example, or using a selection algorithm.

In some cases, base station205may transmit an indication of the preamble portion (e.g., a preamble sequence) to UE210, and UE210may select the predefined sequence based on the indication received from the base station205.

Payload portion325includes one or more payload resource elements330-athrough33-b, each of which may include a symbol, such as an OFDM or DFT-s-OFDM symbol, and a payload cyclic prefix335. Payload cyclic prefixes335may serve as guard intervals to reduce inter-symbol interference between payload resource elements330, and/or may be used to support channel estimation or equalization.

In some cases, the payload cyclic prefix335may be the same as the preamble cyclic prefix320. For example, the payload cyclic prefix335may have the same length as the preamble cyclic prefix320. In some cases, the payload cyclic prefix335may be different than the preamble cyclic prefix320. For example, the payload cyclic prefix335may have a different length than the preamble cyclic prefix320.

As depicted inFIG. 3, in some cases, the preamble portion310and the payload portion325are transmitted back-to-back; that is, there may not be a gap between the last preamble resource element and the first payload resource element. In this case, the payload portion325may be appended to the preamble portion310. In some cases, the preamble portion310and the payload portion325may be transmitted back-to-back on the same resources.

In some cases, the payload portion325may be transmitted as a PUCCH waveform or a PUSCH waveform. In some cases, payload portion325includes signaling or control information, such as an RRC request (e.g., a request for an RRC connection) for an initial access. The signaling or control information may be transmitted as a PUCCH waveform, for example. In some cases, payload portion325includes user data. Such user data may include, for example, data transmitted within a V2X system, such as a user (vehicle) location or speed. In some cases, the user data may be transmitted as a PUCCH or PUSCH waveform, for example. In some cases, the user data may be transmitted in a two-step RACH procedure during a handover, for example.

In some cases, the payload portion325may have a fixed payload size (which may include padding). That is, the payload portion325may be transmitted using the same fixed payload size regardless of whether the two-step RACH procedure is initiated for an initial access (e.g., on power up), for a handover, or for another reason.

In some cases, the payload portion325may have a payload size that is based on whether the two-step RACH procedure is initiated for an initial access or for a handover. For example, the payload portion325may be transmitted using a smaller payload size for an initial access (in which the payload may include an RRC connection request) and using a larger payload size for a handover (in which the payload may include user data), or vice versa.

As depicted inFIG. 3, in some cases, uplink request message305may be transmitted using interlaces350. An interlace350may be a set of frequency resources used for transmissions over a channel (e.g., PUCCH, PUSCH) to mitigate issues related to power spectral density limitations, for example. An interlace may include M resource block clusters345that are evenly spaced across the frequency span340(e.g., the system bandwidth available for the transmission), which may be, in this example, 20 MHz. Each resource block cluster345may include N interlaces350. In some cases, an interlace350may be associated with transmission of a preamble portion310.

In other cases, an uplink request message305may be transmitted without using interlaces; e.g., using a contiguous preamble format.

In some cases, the preamble portion305and payload portion325may have aligned resource element boundaries, as depicted inFIG. 3. In this case, an interlaced preamble (e.g., having a cyclic prefix for each sequence transmission) may be reused as a reference signal, such as a demodulation reference signal (DMRS) or other reference signal, for the payload portion325. Thus, in some cases, the preamble portion310of the uplink request message305may be transmitted as a DMRS for the payload portion325of the uplink request message305.

In conventional systems, a DMRS for a payload may be have a length that is a multiple of the number of resource elements associated with the payload. Therefore, the length of a DMRS is, in general, not a prime number. However, when the preamble portion310, which has a sequence length that is a prime number, is used as a DMRS for the payload portion325, the payload portion325may be transmitted using a number of resource elements that is the same prime number as the sequence length to enable the DMRS to be used as a reference signal for the payload portion325. In this case, this number of resource elements used to transmit the payload portion325may be a subset of the frequency span of the preamble portion310; that is, some resource elements330-bmay not be used. This scenario may be particularly relevant to the case of transmissions using DFT-s-OFDM symbols, for example.

In some cases, a preamble cyclic prefix320of a preamble resource element315in the preamble portion310may include a cyclic prefix extension; e.g., the preamble cyclic prefix320may be extended to a larger length or longer time period to enable the preamble portion310to be used as a DMRS for payload portion330.

In some cases, the uplink request message305may include one or more additional reference signals (e.g., one or more additional DMRS's or other reference signals) for the payload portion325, either in addition to or instead of the DMRS transmitted in the preamble portion310.

In some cases, the preamble portion310and payload portion325may have different user multiplexing capabilities. For example, the preamble portion310may be a PUCCH waveform, which may be designed to carry (e.g., accommodate transmissions from) multiple UEs using, for example, FDM and/or code division multiplexing (CDM). For example, the payload portion325may be a PUSCH waveform, which may not be designed to carry multiple UEs. In some cases, it may be possible to spatially separate transmissions from multiple UEs on a PUSCH waveform.

In some cases, the payload portion325may be frequency division multiplexed or code division multiplexed across UEs210.

In some cases, the uplink request message305may not include (e.g., may omit) HARQ information if the random access procedure is a contention-based random access procedure (CBRA); e.g., for use in NR-U or another unlicensed spectrum.

FIG. 4illustrates an example of a message configuration400for an uplink request message of a two-step random access procedure in accordance with aspects of the present disclosure. In some examples, an uplink request message having message configuration400may be transmitted using aspects of wireless communication system100.

Message configuration400includes uplink request message405, which may be transmitted by a UE210to a base station205as described with respect toFIG. 2. Uplink request message405may include a preamble portion410and a payload portion425. In some cases, the uplink request message405may be transmitted using interlaces. In some cases, the uplink request message405may be transmitted without using interlaces.

In message configuration400, preamble resource elements415of preamble portion410are interleaved in time (e.g., multiplexed in time) with payload resource elements440of payload portion425. In this example, the interleaved preamble resource elements415and payload resource elements440have resource element boundaries that are aligned in time, and the preamble portion410is distributed in time for better detection (e.g., better synchronization) under high Doppler conditions, such as in a V2X system in which UEs210may be moving relatively quickly. For example, a first preamble resource element415-a(e.g., a first preamble resource element spanning a frequency range at a given symbol) may be used as a DMRS for a corresponding first payload resource element440-a(e.g., for a payload resource element that is adjacent in time to the first preamble resource element), and a second preamble resource element415-cmay be used as a DMRS for a second payload resource element440-c, etc. In some cases, preamble resource elements415may be transmitted back-to-back with payload resource elements440(e.g., without a gap between resource elements).

FIG. 5illustrates an example of a message configuration500for an uplink request message of a two-step random access procedure in accordance with aspects of the present disclosure. In some examples, an uplink request message having message configuration500may be transmitted using aspects of wireless communication system100.

Message configuration500includes uplink request message505, which may be transmitted by a UE210to a base station205as described with respect toFIG. 2. Uplink request message505may include a preamble portion510and a payload portion525. In some cases, the uplink request message505may be transmitted using interlaces. In some cases, the uplink request message505may be transmitted without using interlaces. Preamble portion510may include preamble resource elements515-athrough515-b. Payload portion525may include payload resource elements530-athrough530-b.

In the example of message configuration500, the preamble portion510and the payload portion525are transmitted back-to-back; that is, there may not be a gap between the last preamble resource element515-band the first payload resource element530-a. In this case, the payload portion525may be appended to the preamble portion510. In some cases, the preamble portion510and the payload portion525may be transmitted back-to-back on the same resources.

In some cases, the first preamble resource element515-ain the preamble portion510may include a cyclic prefix520, and subsequent preamble resource elements515may be transmitted without the use of cyclic prefixes between the preamble resource elements515. That is, in some cases, only the first preamble resource element515-aof a preamble portion510may include a cyclic prefix520.

In some cases, the last preamble resource element515-bin the preamble portion510may include a guard time (GT)540. A guard time540may be a short time interval that provides a buffer between the last preamble resource element515-band the first payload resource element530-ato reduce the likelihood of inter-symbol interference.

FIG. 6illustrates an example of a message configuration600for an uplink request message of a two-step random access procedure in accordance with aspects of the present disclosure. In some examples, an uplink request message having message configuration600may be transmitted using aspects of wireless communication system100. Message configuration600may depict an example of a message configuration that may provide backward-compatibility with the four-message random access procedure, as described herein.

Message configuration600includes uplink request message605, which may be transmitted by a UE210to a base station205as described with respect toFIG. 2. Uplink request message605may include a preamble portion610and a payload portion625. In some cases, the uplink request message605may be transmitted using interlaces. In some cases, the uplink request message605may be transmitted without using interlaces.

In some cases, the first preamble resource element615-ain the preamble portion610may include a preamble cyclic prefix620, and the subsequent preamble resource elements may be transmitted without the use of preamble cyclic prefixes620between the preamble resource elements615. That is, in some cases, only the first preamble resource element615-aof a preamble portion610may include a preamble cyclic prefix620. In some cases, the last preamble resource element615-bin the preamble portion610may include a guard time (GT)640.

In some cases, it may be desirable for a communication system to support both two-step random access procedures and four-step random access procedures, by, for example, using the same physical RACH (PRACH) configuration for both types of procedures. In some cases, such as in NR, the PRACH configuration index may determine the RACH occasion (RO) (e.g., a transmission occasion during which a UE may transmit information) in the time domain. In some cases, the general PRACH configuration may be kept the same for the two-step procedure and four-step procedure, with the addition of an indication of the association between the preamble portion (e.g., the sequence) and the PUCCH/PUSCH resources allocated for transmission of the payload portion when the two-step random access procedure is used. That is, in some cases, a base station205may indicate, to the UE210, an association between a preamble and a payload resource (e.g., a PUCCH or PUSCH resource) for each RACH occasion.

The base station205may signal the association between the preamble and the PUCCH/PUSCH resources in remaining minimum system information (RMSI) transmitted by the base station205to the UE210. In this case, the PUCCH/PUSCH may be transmitted on a separate TTI (e.g., slot, mini-slot, resource element) than the preamble. That is, in some cases, message configuration600may provide better compatibility with a four-step RACH procedure by transmitting the preamble portion610of uplink request message605during a first TTI (e.g., a slot) and transmitting the payload portion625during a second TTI.

In some cases, the preamble portion610and the payload portion625may be transmitted with an intervening TTI; e.g., there may be a third TTI that is between the first TTI and the second TTI. In some cases, the intervening TTI may be available for non-RACH transmissions.

In some cases, the UE210may perform a first LBT procedure before transmitting the preamble portion610in the first TTI, and, because there is an intervening TTI during which the resources may be used by another UE, UE210may perform a second LBT procedure before transmitting the payload portion625in the second TTI. In some cases, the additional LBT procedure may introduce undesirable latency in the RACH procedure.

In some cases, however, a base station205may use the intervening TTI to perform a downlink transmission, thereby occupying the resources during the intervening TTI. In this case, the UE210may refrain from performing another LBT procedure before transmitting the payload portion625of the uplink request message605, thereby potentially reducing the latency of the RACH procedure and enabling a more efficient use of resources.

In some cases, a base station205may overprovision resources for the payload portion625to ensure that sufficient resources are available to accommodate potentially large payload sizes. However, in some cases, resources that have been provisioned by base station205for a preamble nay not be used; for example, a UE210may not use an allocated preamble resource to initiate a RACH procedure. In this case, the corresponding payload resource may also be unused.

In some cases, if there is a gap (e.g., an intervening TTI) between the preamble portion610and the payload portion625, a base station205may use DMRS detection in the preamble portion610to schedule (e.g., re-allocate) some of the corresponding payload portion625resources for which no preamble has been received (e.g., in the case when a UE does not initiate a RACH procedure on the preamble resource). In some cases, the base station205need only determine whether a UE215has transmitted or not. In some cases, a base station205may have a fairly short amount of time in which to reschedule the resources. If the base station205can process in a limited fashion due to smaller processing time, the base station205can schedule some other UEs only on the resources it can process.

The payload resources may or may not fully overlap with the preamble resources. For example, preambles on one interlace may correspond to the payload dimension across more than one interlace. In some cases, if a preamble portion overlaps a payload portion in frequency, then the preamble portion may be used as a DMRS for the payload portion. In some cases, as shown inFIG. 6, the preamble portion610may not overlap the payload portion625in frequency. In this case, the payload portion625may include an embedded DMRS that matches the dimension (e.g., the size or number of resource elements615,630) of the preamble portion610and/or the payload portion625.

In some cases, a first portion of the set of predefined sequences may be associated with two-step RACH procedures, and a second portion of the set of predefined sequences may be associated with four-step RACH procedures. For example, if the set of sequences includes 64 sequences, the first portion may include 16 of the sequences that are associated with the two-step procedure, and the second portion may include 48 of the sequences that are associated with the four-step procedure. Other partitionings are possible.

In this case, a UE210may be configured (e.g., using RMSI) to select a preamble sequence (e.g., a sequence to be included in the preamble portion) from the first portion of the set of predefined sequences to perform a two-step RACH procedure, and the UE210may be configured to select a preamble sequence from the second portion of the set of predefined sequences to perform a four-step RACH procedure. In this manner, the preamble sequence may be used to indicate which random access procedure (two-step or four-step) will be used.

In some cases, sequences that are included in the first portion of sequences may be associated with two-step PUSCH/PUCCH resources, and sequences that are included in the second portion of sequences may be associated with (different) four-step PUSCH/PUCCH resources.

In some cases, a preamble sequence may have a1:1correspondence with a payload resource, such that a single preamble sequence may be mapped to specific payload resources. In some cases, however, it may be possible to map multiple preamble sequences into the same payload (PUCCH/PUSCH) resource such that a preamble sequence shares a resource association with another preamble sequence. For example, preamble sequence1and sequence2may be mapped to the same PUSCH resource. In this case, a base station205may use additional information to distinguish between the two preamble sequences. In some cases, different preamble sequences may be associated with different DMRS ports (e.g., different antenna ports used to transmit the DMRS signal), or to different scrambling identifiers (for both the DMRS and/or for transmission of the payload portion). In this case, a base station205may use space division multiple access (SDMA) techniques to separate sequence1and sequence2. In some cases, a UE210may apply an additional differentiating factor, such as a different DMRS port or a different scrambling identifier, to the uplink request message to allow differentiation of the payload portion of the uplink request message. In some cases, a UE210may apply an additional identifying factor, such as a different DMRS port or a different scrambling identifier, to the uplink request message to allow identification of the payload portion of the uplink request message.

In some cases, UEs210can further hash into (e.g., index) the multiple payload resources/multiple DMRS ports/multiple scrambling IDs when multiple UEs210select the same preamble sequence. In some cases, this approach may help reduce collisions of transmissions from multiple UEs210when the same preamble sequence is selected by multiple UEs210.

FIG. 7illustrates an example of a message configuration700for an uplink request message of a two-step random access procedure in accordance with aspects of the present disclosure. In some examples, an uplink request message having message configuration700may be transmitted using aspects of wireless communication system100.

In some cases, message configurations300,400,500, and600may be examples of message configurations that may support a two-step RACH procedure when the UE210may use a relatively small timing advance (TA), such as for communications within relatively small cells with correspondingly small TAs. A TA may be an offset (e.g., an amount of time) that may be used to account for transmission time delays between a UE210and a base station205and thereby maintain synchronization of downlink and uplink transmissions. In some cases, if a cell is sufficiently small (as may be, for example, in NR systems), the TA may also be small, and may be covered (e.g., spanned) by the CP of the preamble portion of an uplink request message.

In some cases, however, the TA may be larger (or much larger) than the CP. Message configuration700may depict an example of a message configuration that may support a two-step RACH procedure when the UE210may use a relatively large TA. In this case, the UE210may transmit an uplink request message that includes a payload portion that is transmitted in a time-domain waveform and TDM-multiplexed with payloads for different UEs210.

For example, message configuration700includes uplink request message705, which may be transmitted by a UE210to a base station205as described with respect toFIG. 2. Uplink request message705may include a preamble portion710and a payload portion725.

In some cases, the first preamble resource element715-ain the preamble portion710includes a preamble cyclic prefix720, and the subsequent preamble resource elements715may be transmitted with or without the use of preamble cyclic prefixes720between the preamble resource elements715. In some cases, cyclic prefix720may cover (e.g., span) the TA to allow preamble timing and channel estimation in the frequency domain.

In some cases, payload portion725includes payload resource elements730-athrough740-c, each of which may or may not include a corresponding payload cyclic prefix735; e.g., payload cyclic prefix735may be optional. Payload portion725may include payload resource elements for a first UE (e.g., payload resource elements730-athrough730-c) TDM multiplexed with payload resource elements for a second UE (e.g., payload resource elements730-dthrough730-e). In some cases, payload resource elements730-dthrough730-efor the second UE may not include payload cyclic prefixes. In some cases, payload resource elements730-athrough730-cand payload resource elements730-dthrough730-emay include an embedded DMRS for their respective payload.

FIG. 8illustrates an example of a message configuration800for an uplink request message of a two-step random access procedure in accordance with aspects of the present disclosure. In some examples, an uplink request message having message configuration800may be transmitted using aspects of wireless communication system100. Message configuration800may depict an example of a message configuration that may support a two-step RACH procedure when the UE210may use a relatively large TA.

Message configuration800may be similar to message configuration700, but in this example, the payload portion may include a time-domain waveform with CDM-multiplexed payloads (rather than TDM-multiplexed payloads) for different UEs210.

For example, message configuration800includes uplink request message805, which may be transmitted by a UE210to a base station205as described with respect toFIG. 2. Uplink request message805may include a preamble portion810and a payload portion825.

In some cases, the first preamble resource element815-ain the preamble portion810includes a preamble cyclic prefix820, and the subsequent preamble resource elements815may be transmitted with or without the use of preamble cyclic prefixes820between the preamble resource elements815. In some cases, preamble cyclic prefix820may cover (e.g., span) the TA to allow preamble timing and channel estimation in the frequency domain.

In some cases, payload portion825includes payload resource elements830, each of which may or may not include a payload cyclic prefix835. Payload portion825may include payload resource elements for a first UE (e.g., payload resource elements830-athrough830-c) CDM multiplexed with payload resource elements for a second UE (e.g., payload resource elements830-dthrough830-f). In some cases, payload resource elements830-athrough830-cand payload resource elements830-dthrough830-fmay include a DMRS for the respective payload. In some cases, the payload and the DMRS in the payload portion825may also be CDM multiplexed using a different spreading code.

FIG. 9shows a block diagram900of a device905that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The device905may be an example of aspects of a UE115as described herein. The device905may include a receiver910, a UE communications manager915, and a transmitter920. The device905may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The UE communications manager915may identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response. The UE communications manager915may transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a physical uplink shared channel waveform, where the preamble portion is associated with a transmission occasion of the PUSCH. The UE communications manager915may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message. The UE communications manager915may be an example of aspects of the UE communications manager1210described herein.

The UE communications manager1015may be an example of aspects of the UE communications manager915as described herein. The UE communications manager1015may include an identifying manager1020, a request message manager1025, and a response manager1030. The UE communications manager1015may be an example of aspects of the UE communications manager1210described herein.

The identifying manager1020may identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response.

The request message manager1025may transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel.

The response manager1030may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

The transmitter1035may transmit signals generated by other components of the device1005. In some examples, the transmitter1035may be collocated with a receiver1010in a transceiver module. For example, the transmitter1035may be an example of aspects of the transceiver1220described with reference toFIG. 12. The transmitter1035may utilize a single antenna or a set of antennas.

FIG. 11shows a block diagram1100of a UE communications manager1105that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The UE communications manager1105may be an example of aspects of a UE communications manager915, a UE communications manager1015, or a UE communications manager1210described herein. The UE communications manager1105may include an identifying manager1110, a request message manager1115, a response manager1120, a preamble manager1125, a payload manager1130, a cyclic prefix manager1135, and an interleaving manager1140. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The identifying manager1110may identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response.

The request message manager1115may transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel.

In some examples, the request message manager1115may transmit the preamble portion of the uplink request message as a demodulation reference signal for the payload portion of the uplink request message. In some examples, the request message manager1115may transmit additional demodulation reference signals for the payload portion of the uplink request message.

In some examples, the request message manager1115may receive, via remaining minimum system information or radio resource control signaling, an association between the preamble portion of the uplink request message and the payload portion of the uplink request message.

In some examples, the request message manager1115may transmit the preamble portion of the uplink request message and the payload portion of the uplink request message without an intervening transmission time interval between the first transmission time interval and the second transmission time interval. In some examples, the request message manager1115may transmit the preamble portion of the uplink request message and the payload portion of the uplink request message with an intervening transmission time interval between the first transmission time interval and the second transmission time interval, where the intervening transmission time interval is available for non-RACH transmissions.

In some examples, the request message manager1115may apply an additional differentiating factor to the uplink request message to allow differentiation of the payload portion of the uplink request message. In some examples, the request message manager1115may apply an additional identifying factor to the uplink request message to allow identification of the payload portion of the uplink request message. In some cases, the additional differentiating factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications. In some cases, the additional identifying factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

The response manager1120may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

The preamble manager1125may transmit the preamble portion of the uplink request message using a preamble sequence that has a prime number sequence length.

In some examples, the preamble manager1125may transmit the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples, the preamble manager1125may transmit the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message without use of cyclic prefixes between resource elements of the preamble portion. In some examples, the preamble manager1125may transmit the preamble portion of the uplink request message during a first transmission time interval.

In some examples, the preamble manager1125may select a preamble sequence from the set of predefined sequences for transmission of the preamble portion of the uplink request message, where only a portion of the predefined sequences are associated with two-step RACH procedures. In some examples, the preamble manager1125may select a preamble sequence from the set of predefined sequences for transmission of the preamble portion of the uplink request message, where the selected preamble sequence shares a resource association with another preamble sequence of the set of predefined sequences. In some examples, the preamble manager1125may select a preamble sequence from the set of predefined sequences for transmission of the preamble portion of the uplink request message, where the selected preamble sequence has a resource association with more than one payload resource.

In some examples, the preamble manager1125may receive an indication of the preamble portion.

The payload manager1130may transmit the payload portion using resource elements that are a subset of a frequency span of the preamble portion.

In some examples, the payload manager1130may transmit the payload portion using a payload size that is based, at least in part, on whether the two-step RACH procedure is for initial access or for handover. In some examples, the payload manager1130may transmit the payload portion using a fixed payload size. In some examples, the payload manager1130may transmit, in accordance with the received association, the payload portion of the uplink request message during a second transmission time interval.

In some examples, the payload manager1130may transmit the payload portion of the uplink request message with an embedded demodulation reference signal to match dimensions of both the preamble portion and the payload portion. In some examples, the payload manager1130may transmit the payload portion during a time resource that is time-multiplexed with payload portions from additional UEs. In some examples, the payload manager1130may transmit the payload portion during a time resource that is code division-multiplexed with payload portions from additional UEs.

The cyclic prefix manager1135may generate a cyclic prefix for resource elements in the preamble portion and/or the payload portion.

In some cases, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

The interleaving manager1140may transmit the preamble portion of the uplink request message interleaved in time with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix.

In some cases, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

FIG. 12shows a diagram of a system1200including a device1205that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The device1205may be an example of or include the components of device905, device1005, or a UE115as described herein. The device1205may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a UE communications manager1210, an I/O controller1215, a transceiver1220, an antenna1225, memory1230, and a processor1240. These components may be in electronic communication via one or more buses (e.g., bus1245).

The UE communications manager1210may identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response, transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message.

The I/O controller1215may manage input and output signals for the device1205. The I/O controller1215may also manage peripherals not integrated into the device1205. In some cases, the I/O controller1215may represent a physical connection or port to an external peripheral. In some cases, the I/O controller1215may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In other cases, the I/O controller1215may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller1215may be implemented as part of a processor. In some cases, a user may interact with the device1205via the I/O controller1215or via hardware components controlled by the I/O controller1215.

The memory1230may include RAM and ROM. The memory1230may store computer-readable, computer-executable code1235including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory1230may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

FIG. 13shows a block diagram1300of a device1305that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The device1305may be an example of aspects of a base station105as described herein. The device1305may include a receiver1310, a base station communications manager1315, and a transmitter1320. The device1305may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver1310may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to message 1 of a two-step random access procedure, etc.). Information may be passed on to other components of the device1305. The receiver1310may be an example of aspects of the transceiver1620described with reference toFIG. 16. The receiver1310may utilize a single antenna or a set of antennas.

The base station communications manager1315may receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel, and transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message. The base station communications manager1315may be an example of aspects of the base station communications manager1610described herein.

The transmitter1320may transmit signals generated by other components of the device1305. In some examples, the transmitter1320may be collocated with a receiver1310in a transceiver module. For example, the transmitter1320may be an example of aspects of the transceiver1620described with reference toFIG. 16. The transmitter1320may utilize a single antenna or a set of antennas.

FIG. 14shows a block diagram1400of a device1405that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The device1405may be an example of aspects of a device1305, or a base station105as described herein. The device1405may include a receiver1410, a base station communications manager1415, and a transmitter1430. The device1405may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver1410may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to message 1 of a two-step random access procedure, etc.). Information may be passed on to other components of the device1405. The receiver1410may be an example of aspects of the transceiver1620described with reference toFIG. 16. The receiver1410may utilize a single antenna or a set of antennas.

The base station communications manager1415may be an example of aspects of the base station communications manager1315as described herein. The base station communications manager1415may include a message receiving manager1420and a downlink response manager1425. The base station communications manager1415may be an example of aspects of the base station communications manager1610described herein.

The message receiving manager1420may receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel waveform, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel.

The downlink response manager1425may transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

The transmitter1430may transmit signals generated by other components of the device1405. In some examples, the transmitter1430may be collocated with a receiver1410in a transceiver module. For example, the transmitter1430may be an example of aspects of the transceiver1620described with reference toFIG. 16. The transmitter1430may utilize a single antenna or a set of antennas.

FIG. 15shows a block diagram1500of a base station communications manager1505that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The base station communications manager1505may be an example of aspects of a base station communications manager1315, a base station communications manager1415, or a base station communications manager1610described herein. The base station communications manager1505may include a message receiving manager1510, a downlink response manager1515, a demodulation manager1520, a message transmitting manager1525, a preamble receiving manager1530, a payload receiving manager1535, and a scheduling manager1540. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The message receiving manager1510may receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel.

In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message. In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message using a preamble sequence that has a prime number sequence length.

In some examples, the message receiving manager1510may receive the payload portion using resource elements that are a subset of a frequency span of the preamble portion. In some examples, the message receiving manager1510may receive the payload portion using a payload size that is based, at least in part, on whether the two-step RACH procedure is for initial access or for handover. In some examples, the message receiving manager1510may receive the payload portion using a fixed payload size.

In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message interleaved in time with the payload portion of the uplink request message, each resource element of the preamble portion and each resource element of the payload portion having a cyclic prefix. In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message back-to-back with the payload portion of the uplink request message without use of cyclic prefixes between resource elements of the preamble portion.

In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message during a first transmission time interval. In some examples, the message receiving manager1510may receive, in accordance with the association transmitted via remaining minimum system information or radio resource control signaling, the payload portion of the uplink request message during a second transmission time interval. In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message and the payload portion of the uplink request message without an intervening transmission time interval between the first transmission time interval and the second transmission time interval. In some examples, the message receiving manager1510may receive the preamble portion of the uplink request message and the payload portion of the uplink request message with an intervening transmission time interval between the first transmission time interval and the second transmission time interval, where the intervening transmission time interval is available for non-RACH transmissions.

In some examples, the message receiving manager1510may receive in the preamble portion a preamble sequence selected from the set of predefined sequences, where only a portion of the predefined sequences are associated with two-step RACH procedures. In some examples, the message receiving manager1510may receive the payload portion of the uplink request message with an embedded demodulation reference signal to match dimensions of both the preamble portion and the payload portion.

In some cases, the cyclic prefix of the resource elements of the preamble portion of the uplink request message is different from the cyclic prefix of the resource elements of the payload portion of the uplink request message.

The downlink response manager1515may transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

The demodulation manager1520may use the preamble portion of the uplink request message as a demodulation reference signal for the payload portion of the uplink request message.

In some examples, the demodulation manager1520may receive additional demodulation reference signals for the payload portion of the uplink request message.

The message transmitting manager1525may transmit, via remaining minimum system information or radio resource control signaling, an association between the preamble portion of the uplink request message and the payload portion of the uplink request message.

In some examples, the message transmitting manager1525may transmit an indication of the preamble portion.

The preamble receiving manager1530may receive in the preamble portion a preamble sequence selected from the set of predefined sequences, where the selected preamble sequence shares a resource association with another preamble sequence of the set of predefined sequences.

In some examples, the preamble receiving manager1530may receive in the preamble portion a preamble sequence selected from the set of predefined sequences, where the selected preamble sequence has a resource association with more than one payload resource.

The payload receiving manager1535may differentiate the payload portion of the uplink request message via a differentiating factor.

In some examples, the payload receiving manager1535may identify the payload portion of the uplink request message via an identifying factor. In some examples, the payload receiving manager1535may receive the payload portion during a time resource that is time-multiplexed with payload portions from additional UEs. In some examples, the payload receiving manager1535may receive the payload portion during a time resource that is code division-multiplexed with payload portions from additional UEs. In some cases, the identifying factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

In some examples, the payload receiving manager1535may apply the preamble portion of the uplink request message as a demodulation reference signal for the payload portion of the uplink request message.

In some cases, the differentiating factor is one or more of use of different demodulation reference signal ports or use of different scrambling identifications.

The scheduling manager1540may schedule non-RACH transmissions based on presence of the preamble portion and application of the preamble portion as a demodulation reference signal.

FIG. 16shows a diagram of a system1600including a device1605that supports message 1 of a two-step random access procedure in accordance with aspects of the present disclosure. The device1605may be an example of or include the components of device1305, device1405, or a base station105as described herein. The device1605may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a base station communications manager1610, a network base station communications manager1615, a transceiver1620, an antenna1625, memory1630, a processor1640, and an inter-station base station communications manager1645. These components may be in electronic communication via one or more buses (e.g., bus1650).

The base station communications manager1610may receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes either a physical uplink control channel waveform or a physical uplink shared channel waveform and transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message.

The network base station communications manager1615may manage communications with the core network (e.g., via one or more wired backhaul links). For example, the network base station communications manager1615may manage the transfer of data communications for client devices, such as one or more UEs115.

In some cases, the wireless device may include a single antenna1625. However, in some cases the device may have more than one antenna1625, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory1630may include RAM, ROM, or a combination thereof. The memory1630may store computer-readable code1635including instructions that, when executed by a processor (e.g., the processor1640) cause the device to perform various functions described herein. In some cases, the memory1630may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor1640may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor1640may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor1640. The processor1640may be configured to execute computer-readable instructions stored in a memory (e.g., the memory1630) to cause the device1605to perform various functions (e.g., functions or tasks supporting message 1 of a two-step random access procedure).

The code1635may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code1635may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code1635may not be directly executable by the processor1640but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

At1705, the UE may identify that the UE is configured to use a two-step RACH procedure, the two-step RACH procedure including an uplink request message and a downlink response. The operations of1705may be performed according to the methods described herein. In some examples, aspects of the operations of1705may be performed by an identifying manager as described with reference toFIGS. 9 through 12.

At1710, the UE may transmit the uplink request message as part of the two-step RACH procedure, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that includes a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel. The operations of1710may be performed according to the methods described herein. In some examples, aspects of the operations of1710may be performed by a request message manager as described with reference toFIGS. 9 through 12.

At1715, the UE may receive the downlink response as part of the two-step RACH procedure and in response to the uplink request message. The operations of1715may be performed according to the methods described herein. In some examples, aspects of the operations of1715may be performed by a response manager as described with reference toFIGS. 9 through 12.

At1805, the base station may receive, as part of a two-step RACH procedure, an uplink request message from a UE, the uplink request message including a preamble portion that is one of a set of predefined sequences and a payload portion that a waveform of a physical uplink shared channel, where the preamble portion is associated with a transmission occasion of the physical uplink shared channel. The operations of1805may be performed according to the methods described herein. In some examples, aspects of the operations of1805may be performed by a message receiving manager as described with reference toFIGS. 13 through 16.

At1810, the base station may transmit a downlink response as part of the two-step RACH procedure and in response to the uplink request message. The operations of1810may be performed according to the methods described herein. In some examples, aspects of the operations of1810may be performed by a downlink response manager as described with reference toFIGS. 13 through 16.