Patent Description:
The following relates generally to wireless communications, and more specifically to front loading a sounding reference signal (SRS) and physical random access channel (PRACH).

These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-S-OFDM).

Some wireless communication systems may support a time division duplexing (TDD) based frame structure, such as a TDD fixed frame period. Generally, such a TDD based frame structure begins with a first device capturing the channel for a time period, e.g., a channel occupancy time (CoT), a transmission opportunity (TxOP), and the like, by performing a clear channel assessment (CCA) procedure on the channel. If the CCA procedure is successful, the first device controls the channel for the CoT, which may then be followed by an idle period. During the CoT, the first device may perform downlink transmissions to a second device and/or receive uplink transmissions from the second device. For example, the first device may perform a downlink transmission and provide a grant to the second device for resources for an uplink transmission. In some scenarios, gap periods between transmissions (e.g., between downlink and uplink transmissions, between successive uplink transmissions, and the like) during the CoT that exceed a threshold may require an additional CCA procedure to be performed by the second device before the uplink transmission can occur. The second device having to perform additional CCA procedures may delay such uplink transmissions, which increases latency and requires additional resources.

3GPP contribution R1-<NUM> discloses an approach for SRS design details.

The described techniques relate to improved methods, systems, devices, and apparatuses that support front loaded sounding reference signal (SRS) or physical random access channel (PRACH) preamble transmissions. References to an SRS transmission may refer to an SRS transmission, a SRS and a PRACH preamble transmission, and/or to a PRACH preamble transmission. Generally, the described techniques provide for front loading (e.g., during some of the first few symbols of an uplink portion) the SRS or PRACH preamble, where the SRS or PRACH preamble use frequency division multiplexing (FDM) with other reference signals (e.g., a demodulation reference signal (DMRS)), uplink data and/or control transmission(s), and/or other random access transmission(s).

Certain wireless communication systems may be configured with time division duplexing (TDD) based frame structure over a shared or unlicensed radio frequency spectrum band. For example, a first device (such as a base station) may capture the channel in the shared or unlicensed band by performing a clear channel assessment (CCA) procedure on the channel. Once captured, the first device may perform downlink and/or uplink communications on the channel for a time period, e.g., during corresponding downlink portions and uplink portions of the TDD frame. In some cases, the transmissions during the TDD frame may not require an additional CCA procedure unless there is a gap period that extends beyond a defined time period. For example, between downlink and uplink, between uplink and downlink transmissions, between successive uplink or downlink transmissions, and the like, the corresponding devices must perform an additional CCA procedure during the TDD frame if the gap period exceeds the defined time period or threshold. This increases latency and utilizes unnecessary resources.

Aspects of the disclosure are initially described in the context of a wireless communications system. Generally, aspects of the disclosure provide a mechanism where a second device (e.g., a user equipment (UE)) can avoid having to perform additional CCA procedure (s) by minimizing the gap period between downlink and uplink portions of the TDD frame. For example, a first device (e.g., a base station) may capture the channel by performing a CCA procedure on the channel. In some aspects, the channel may be a shared or unlicensed radio frequency spectrum band. The first device may capture the channel for a time period, e.g., for a channel occupancy time (CoT), a transmission opportunity (TxOP), and the like. The first device may perform downlink transmission(s) on the channel during the corresponding downlink portion(s) of the TDD frame. In some aspects, the downlink transmissions may include a grant of resources for the second device to use for uplink transmissions on the channel. In some aspects, the downlink transmissions may simply provide an indication of a time in which the second device can use the channel for uplink transmissions (e.g., may provide an indication of the uplink portion of the TDD frame).

In some aspects, the second device may identify a gap period that follows the downlink portion of the TDD frame. For example, the gap period may include the time between when the downlink portion ends and when the uplink portion begins. In some aspects, the second device may selectively perform a CCA procedure on the channel based on the gap period. For example, the second device may perform the CCA procedure when the gap period exceeds a defined threshold (e.g., is longer than a defined time period). However, the second device may skip the CCA procedure on the channel when the gap period does not exceed the defined threshold. In some aspects, this may include the second device transmitting an SRS or PRACH preamble in a set of initial symbols of the uplink portion of the TDD frame. For example, the gap period may include the first, or the first and second symbols of the TDD frame and the SRS or PRACH preamble may be transmitted in the second, or the second and third, and so on, symbols of the TDD frame. In some aspects, frontloading the SRS or PRACH preamble during the set of initial symbols of the uplink portion of the TDD frame may minimize a duration of the gap period and therefore reduce the occasions that the CCA procedure needs to be performed. In some aspects, the second device may also FDM the SRS or PRACH preamble with other transmissions (either from the second device or from other devices operating on the channel). For example, the second device may FDM the SRS or PRACH preamble with a demodulation reference symbol (DMRS), uplink control or data transmission(s), or other random access transmission(s). In some aspects, the FDM may be on a per-tone basis, on a per-comb basis, on a per-interlace basis, and the like.

Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to front loaded SRS.

<FIG> illustrates an example of a wireless communications system <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, a New Radio (NR) network, or a NR shared spectrum (NR-SS) network. In some cases, wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

In some examples, half-duplex communications may be performed at a reduced peak rate.

For example, wireless communications system <NUM> may use a transmission scheme between a first device (e.g., a base station <NUM>) and a second device (e.g., a UE <NUM>), where the first device is equipped with multiple antennas and the second devices are equipped with one or more antennas. The multiple signals may, for example, be transmitted by the first device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the second device via different antennas or different combinations of antennas. MIMO techniques include single-user MIMO (SU-MIMO) where multiple spatial layers are transmitted to the same second device, and multiple-user MIMO (MU-MIMO) where multiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a first device or a second device (e.g., a base station <NUM> or a UE <NUM>) to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a spatial path between the first device and the second device. The adjustment of signals communicated via the antenna elements may include a first device or a second device applying amplitude and phase offsets to signals carried via each of the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the first device or second device, or with respect to some other orientation).

In one example, a base station <NUM> may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE <NUM>. For instance, some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station <NUM> multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station <NUM> or a second device, such as a UE <NUM>) a beam direction for subsequent transmission and/or reception by the base station <NUM>. Some signals, such as data signals associated with a particular second device, may be transmitted by a base station <NUM> in a single beam direction (e.g., a direction associated with the second device, such as a UE <NUM>). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE <NUM> may receive one or more of the signals transmitted by the base station <NUM> in different directions, and the UE <NUM> may report to the base station <NUM> an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station <NUM>, a UE <NUM> may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE <NUM>), or transmitting a signal in a single direction (e.g., for transmitting data to a second device).

A second device (e.g., a UE <NUM>, which may be an example of a mmW second device) may try multiple receive beams when receiving various signals from the base station <NUM>, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a second device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, any of which may be referred to as "listening" according to different receive beams or receive directions. In some examples, a second device may use a single receive beam to receive along a single beam direction (e.g., when receiving a data signal).

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples, the carrier bandwidth may be referred to as a "system bandwidth" of the carrier or the wireless communications system <NUM>.

In a system employing MCM techniques, a resource element may include of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related.

Devices of the wireless communications system <NUM> (e.g., base stations <NUM> or UEs <NUM>) may have a hardware configuration that supports communications over a particular carrier bandwidth, or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system <NUM> may include base stations <NUM> and/or UEs <NUM> that can support simultaneous communications via carriers associated with more than one different carrier bandwidth.

A TTI in eCC may include of one or multiple symbol periods.

Wireless communications systems such as an NR system may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across the frequency domain) and horizontal (e.g., across the time domain) sharing of resources.

A UE <NUM> (e.g., a second device) may identify a gap period following a downlink portion of a TDD frame. The UE <NUM> may selectively perform, based at least in part on the gap period, a CCA on a channel of a radio frequency spectrum band. The UE <NUM> may transmit at least one of a SRS or a PRACH preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission.

A base station <NUM> (e.g., a first device) may perform a CCA on a channel of a radio frequency spectrum band prior to a downlink portion of a TDD frame. The base station <NUM> may perform, based at least in part on a success of the CCA, a downlink transmission during the downlink portion of the TDD frame. The base station <NUM> may receive, during a set of initial symbols of an uplink portion of the TDD frame that follows a gap period between the downlink portion of the TDD frame and the uplink portion of the TDD frame, at least one of a SRS or a PRACH preamble, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission.

<FIG> illustrates an example of a TDD frame configuration <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. In some examples, TDD frame configuration <NUM> may implement aspects of wireless communication system <NUM>. Aspects of TDD frame configuration <NUM> may be implement a by a base station and/or a UE, which may be examples of the corresponding devices described herein.

Generally, TDD frame configuration <NUM> includes a TDD frame <NUM>, with two TDD frames <NUM> being shown by way of examples and illustrated as TDD frame <NUM>-a and TDD frame <NUM>-b. In some aspects, TDD frame <NUM> may be a TxOP, a mini-slot, a partial slot, a slot, a subframe, and the like. In some aspects, TDD frame <NUM> may include one or more resource blocks. Each TDD frame <NUM> may include a communication portion <NUM> (illustrated as CoT) followed by an idle portion <NUM>. Thus, TDD frame <NUM>-a includes a communication portion <NUM>-a and an idle portion <NUM>-a and TDD frame <NUM>-b includes a communication portion <NUM>-b and an idle portion <NUM>-b. In some aspects, the communication portion <NUM> may be associated with a wireless device(s) performing uplink communications and/or downlink communications of control and/or data information. In some aspects, the idle portion <NUM> may be associated with a period in which the wireless device(s) refrain from communicating on the channel. In some aspects, TDD frame <NUM> may be used for communications on one or more channels in a shared or unlicensed radio frequency spectrum band, may have a corresponding bandwidth, and the like.

In some aspects, TDD frame configuration <NUM> may be an example of a fixed frame period in a frame based equipment (FBE) network. As one example, TDD frame <NUM> may support industrial IoT communications in a single or a multiple operator environment.

In some aspects, a first device may capture a TDD frame <NUM> by performing a CCA procedure on the channel. For example, the first device may monitor the channel for a period of time to detect signals and/or traffic on the channel and, if none is detected, determine that the CCA procedure is successful and transmit a signal to reserve the channel for the communication portion <NUM>. Generally, the CCA procedure may be performed prior to communications being performed on the channel, e.g., prior to a downlink portion or an uplink portion occurring during the corresponding communication portion <NUM>.

In some aspects, the first device may use the entire communication portion <NUM> to perform downlink communications. In other aspects, the first device may have one or more downlink portions and one or more uplink portions during the communication portion <NUM>. In some aspects, the first device may transmit a signal to a second device that carries or otherwise conveys an indication of a grant for the uplink communications on the second device. For example, the signal may include a grant of time/frequency resources that the second device is to use to perform the uplink communications. As another example, the signal may simply include an indication of a time when the second device is to begin performing the uplink communications, e.g., an indication of time associated with the uplink portion of the TDD frame <NUM>. Accordingly, the first device generally controls the channel during the communication portion <NUM> and can use the channel for uplink and/or downlink communications with the second device.

In some aspects, the first device may have multiple transmissions within the communication portion <NUM> (e.g., during the CoT) without performing additional CCA procedures, provided that a gap period between such transmissions does not exceed a defined threshold. Correspondingly, the second device may proceed with uplink transmissions without performing a CCA procedure, provided that a gap period between such transmissions also does not exceed the defined threshold, e.g., the uplink communications must begin within a defined period since the last downlink transmission by the first device. Aspects of the described techniques provide a mechanism that reduces the number of occasions that the second device must perform additional CCA procedure(s) by front loading and SRS or PRACH preamble transmission and also FDM the SRS or PRACH preamble with DMRS, uplink control or data transmission(s), and/or other random access transmission(s). Generally, the SRS or PRACH preamble may be FDM with DMRS, uplink control or data transmission(s), and/or the other random access transmission(s) from the second device and/or from other wireless devices. In some aspects, each wireless device utilizing TDD frame <NUM> may be preconfigured to implement such techniques and/or may be configured by the network to implement or initiate such techniques as warranted.

Therefore, the second device may identify the gap period following the downlink portion of the communication portion <NUM> of the TDD frame <NUM>. In some aspects, this may include the second device determining whether the gap period has exceeded the threshold or has not exceeded the threshold. If the gap period has not exceeded the threshold, the second device may proceed with performing uplink transmissions without performing a CCA procedure on the channel. If the gap period has exceeded the threshold, the second device may selectively perform the CCA procedure on the channel.

The second device may transmit an SRS or PRACH preamble during a set of initial symbols of the uplink portion of the TDD frame <NUM> the follows the gap period. In some aspects, the SRS or PRACH preamble may be FDM during the set of initial symbols with a DMRS, an uplink control or data transmission, and/or a random access transmission. In some aspects, the SRS or PRACH preamble may be FDM on a per-tone basis (e.g., using different combs for the SRS or PRACH preamble and the DMRS/uplink control and/or data, etc.) and/or on a per-interlace basis (e.g., using different interlaces for the SRS or PRACH preamble and the DMR/uplink control and/or data, etc.). In some aspects, front loading the SRS or PRACH preamble in accordance with the described techniques provides a mechanism where the second device can initiate an uplink transmission (e.g., the SRS or PRACH preamble) during the initial set of the symbols of the uplink portion of TDD frame <NUM> to minimize the gap period between the downlink portion and the uplink portion, and therefore reduce the likelihood of having to perform an additional CCA procedure(s).

Thus, the second device may transmit the SRS (or PRACH preamble) that can be multiplexed with a physical uplink shared channel (PUSCH) UE (e.g., a different device performing uplink control or data transmissions) in the frequency domain instead of TDM. This may reduce the sensing gap (e.g., the gap period) between SRS and PUSCH and avoid an additional CCA procedure.

In some aspects this may include DMRS and SRS being transmitted on different combs. For example, DMRS for PUSCH may be front loaded. The SRS is also front loaded and can be multiplexed on a different comb than the DMRS. In some aspects when additional SRS symbols are needed, the SRS can be frequency multiplexed with PUSCH data. The PUSCH data may rate match around the comb occupied by SRS resources.

In some aspects, this may include SRS being front loaded and FDM with data on a different comb. For example, DMRS for PUSCH may be TDM with SRS (e.g., to avoid SRS and DMRS on the same symbol).

In some aspects, this may include an interlaced SRS design. For example, the SRS may be transmitted on a given comb on a given interlace (e.g., SRS and PUSCH/physical uplink control channel (PUCCH)/PRACH are on different interlaces).

In some aspects, the described techniques can be utilized with SRS and/or with PRACH transmissions. For example, PRACH may be transmitted at the beginning of the uplink portion, e.g., front loaded PRACH. In some aspects for a given PRACH format, defined start symbol locations may be supported. PRACH may be FDM with other channels by transmitting on different interlaces, on different combs, and/or on different resource elements. When PRACH and other channel are multiplexed on different resource elements, comb based PRACH design can be utilized.

<FIG> illustrates an example of a resource block (RB) configuration <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. In some examples, RB configuration <NUM> may implement aspects of wireless communication system <NUM> and/or TDD frame configuration <NUM>. Aspects of RB configuration <NUM> may be implemented by a UE and/or a base station, which may be examples of corresponding devices described herein. It is to be understood that references to SRS being transmitted in accordance with RB configuration <NUM> may also refer to a PRACH preamble transmissions.

Generally, RB configuration <NUM> illustrates two example configurations for a RB <NUM>. Generally, the RB <NUM> may be an initial RB that occurs during an uplink portion of the TDD frame. For example, a first device (e.g., a base station) may perform a CCA procedure on the channel. If the CCA procedure is successful, the first device may capture the channel for some or all of the duration of the TDD frame and perform one or more downlink transmissions during corresponding downlink portions of the TDD frame. In some aspects, first device may also use the channel for uplink transmissions from a second device, e.g., the first device may provide a grant or other indication of time and/or frequency resources of the TDD frame for the second device to use for uplink communications. In some aspects, the uplink portion of the TDD frame may span one or more RBs <NUM>.

In some aspects, each of the two illustrated RB <NUM> configurations includes a plurality of tones (with <NUM> tones being shown by way of example only and labeled as <NUM>-<NUM> on the vertical axis) and a plurality of symbols (with <NUM> symbols being shown by way of example only and labeled as <NUM>-<NUM> on the horizontal axis). Other RB <NUM> configurations may also be used having more or fewer tones with more or fewer symbols.

The first example RB <NUM> configuration includes <NUM> OFDM symbol DMRS transmissions. Generally, the first example RB <NUM> configuration includes an SRS being multiplex in the frequency domain with a DMRS from four antenna ports. For example, the first example RB <NUM> configuration may include symbols <NUM> and <NUM> being used as non-uplink symbols <NUM>, e.g., symbols <NUM> and <NUM> may be a part of the downlink portion of the TDD frame and/or may be a part of the gap period between the downlink portion and the uplink portion. During symbol <NUM>, SRS <NUM> may be multiplexed in the frequency domain with DMRS <NUM>. For example, DMRS <NUM> may be transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, with SRS being transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of symbol <NUM>. In some aspects, the DMRS <NUM> may be transmitted from one or more antenna ports, with ports <NUM> and <NUM> being illustrated in the first example RB <NUM> configuration. In some aspects, the FDM techniques may correspond to different combs, with the DMRS <NUM> being transmitted on comb <NUM> (e.g., on a first comb consisting of tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) and the SRS being transmitted on comb <NUM> (e.g., on a second comb consisting of tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>). The remaining resources of the first example RB <NUM> configuration may be used for PUSCH <NUM> transmissions, e.g., one or more of tones <NUM>-<NUM> and/or symbols <NUM>-<NUM> may be used for PUSCH <NUM> transmissions.

The second example RB <NUM> configuration includes <NUM> OFDM symbol DMRS transmissions. Generally, the second example RB <NUM> configuration includes an SRS being multiplexed in the frequency domain with a DMRS from four antenna ports during two symbols. For example, the second example RB <NUM> configuration may include symbols <NUM> and <NUM> being non-uplink symbols <NUM>, e.g., symbols <NUM> and <NUM> may be a part of the downlink portion of the TDD frame and/or may be a part of the gap period between the downlink portion and the uplink portion. During symbols <NUM> and <NUM>, SRS <NUM> may be multiplexed in the frequency domain with DMRS <NUM>. For example, DMRS <NUM> may be transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, with SRS being transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of symbols <NUM> and <NUM>. In some aspects, the DMRS <NUM> may be transmitted from one or more antenna ports, with four ports <NUM>, <NUM>, <NUM>, and <NUM> being illustrated in the second example RB <NUM> configuration. In some aspects, the FDM techniques may correspond to different combs, with the DMRS <NUM> being transmitted on comb <NUM> (e.g., on a first comb consisting of tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) and the SRS <NUM> being transmitted on comb <NUM> (e.g., on a second comb consisting of tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) of symbols <NUM> and <NUM>. The remaining resources of the second example RB <NUM> configuration may be used for PUSCH <NUM> transmissions, e.g., one or more of tones <NUM>-<NUM> and/or symbols <NUM>-<NUM> may be used for PUSCH <NUM> transmissions.

<FIG> illustrates an example of a RB configuration <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. In some examples, RB configuration <NUM> may implement aspects of wireless communication system <NUM> and/or TDD frame configuration <NUM>. Aspects of RB configuration <NUM> may be implemented by a UE and/or a base station, which may be examples of the corresponding devices described herein. It is to be understood that references to SRS being transmitted in accordance with RB configuration <NUM> may also refer to a PRACH preamble transmissions.

Generally, RB configuration <NUM> illustrates two example configurations for a RB <NUM>. Generally, the RB <NUM> may be an initial RB that occurs during an uplink portion of the TDD frame. For example, a first device (e.g., a base station) may perform a CCA procedure on the channel. If the CCA procedure is successful, the first device may capture the channel for the TDD frame and perform one or more downlink transmissions during corresponding downlink portions of the TDD frame. In some aspects, first device may also use the channel for uplink transmissions from a second device, e.g., the first device may provide a grant or other indication of time and/or frequency resources of the TDD frame for the second device to use for uplink communications. In some aspects, the uplink portion of the TDD frame may span one or more RBs <NUM>.

In some aspects, each of the two illustrated RBs <NUM> configurations includes a plurality of tones (with <NUM> tones being shown by way of example only and labeled as <NUM>-<NUM> on the vertical axis) and a plurality of symbols (with <NUM> symbols being shown by way of example only and labeled as <NUM>-<NUM> on the horizontal axis). Other RB <NUM> configurations may also be used having more or fewer tones with more or fewer symbols.

The first example RB <NUM> configuration includes <NUM> OFDM symbol DMRS transmissions. Generally, the first example RB <NUM> configuration includes an SRS being multiplexed in the frequency domain with an uplink control or data transmissions. For example, the first example RB <NUM> configuration may include symbols <NUM> and <NUM> being used as non-uplink symbols <NUM>, e.g., symbols <NUM> and <NUM> may be a part of the downlink portion of the TDD frame and/or may be a part of the gap period between the downlink portion and the uplink portion. During symbol <NUM>, SRS <NUM> may be multiplexed in the frequency domain with PUSCH data <NUM>. For example, PUSCH data <NUM> may be transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, with SRS <NUM> being transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of symbol <NUM>. During symbol <NUM>, DMRS <NUM> may be multiplexed in the frequency domain with DMRS <NUM>. For example, DMRS <NUM> may be transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, with DMRS <NUM> being transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of symbol <NUM>. In some aspects, the DMRS <NUM> and DMRS <NUM> may be transmitted from one or more antenna ports, with ports <NUM> and <NUM> being illustrated for DMRS <NUM> and with ports <NUM> and <NUM> being illustrated for DMRS <NUM> in the first example RB <NUM> configuration. In some aspects, the FDM techniques may correspond to different combs, with the SRS <NUM> being transmitted on comb <NUM> (e.g., on a first comb consisting of tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) and the PUSCH data <NUM> being transmitted on comb <NUM> (e.g., on a second comb consisting of tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>). Similarly, DMRS <NUM> being transmitted on comb <NUM> and DMRS <NUM> being transmitted on comb <NUM>. The remaining resources of the first example RB <NUM> configuration may be used for PUSCH <NUM> transmissions, e.g., one or more of tones <NUM>-<NUM> and/or symbols <NUM>-<NUM> may be used for additional PUSCH <NUM> transmissions.

The second example RB <NUM> configuration includes <NUM> OFDM symbol DMRS transmissions. Generally, the second example RB <NUM> configuration includes an SRS being multiplexed in the frequency domain with an uplink control or data transmissions. For example, the second example RB <NUM> configuration may include symbols <NUM> and <NUM> being used as non-uplink symbols <NUM>, e.g., symbols <NUM> and <NUM> may be a part of the downlink portion of the TDD frame and/or may be a part of the gap period between the downlink portion and the uplink portion. During symbols <NUM> and <NUM>, SRS <NUM> may be multiplexed in the frequency domain with PUSCH data <NUM>. For example, PUSCH data <NUM> may be transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, with SRS <NUM> being transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of symbols <NUM> and <NUM>. During symbols <NUM> and <NUM>, DMRS <NUM> may be multiplexed in the frequency domain with DMRS <NUM>. For example, DMRS <NUM> may be transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, with DMRS <NUM> being transmitted on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of symbols <NUM> and <NUM>. In some aspects, the DMRS <NUM> and DMRS <NUM> may be transmitted from one or more antenna ports, with ports <NUM>, <NUM>, <NUM>, and <NUM> being illustrated for DMRS <NUM> and with ports <NUM>, <NUM>, <NUM>, and <NUM> being illustrated for DMRS <NUM> in the second example RB <NUM> configuration. In some aspects, the FDM techniques may correspond to different combs, with the SRS <NUM> being transmitted on comb <NUM> (e.g., on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) and the PUSCH data <NUM> being transmitted on comb <NUM> (e.g., on tones <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>). Similarly, DMRS <NUM> being transmitted on comb <NUM> and DMRS <NUM> being transmitted on comb <NUM>. The remaining resources of the second example RB <NUM> configuration may be used for PUSCH <NUM> transmissions, e.g., one or more of tones <NUM>-<NUM> and/or symbols <NUM>-<NUM> may be used for additional PUSCH <NUM> transmissions.

<FIG> illustrates an example of an interlace configuration <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. In some examples, interlace configuration <NUM> may implement aspects of wireless communication system <NUM> and/or TDD frame configuration <NUM>. Aspects of interlace configuration <NUM> may be implemented by a UE and/or a base station, which may be examples of the corresponding devices described herein.

Generally, the described techniques provide for a first device to capture the channel of a shared or unlicensed radio frequency spectrum band for a TDD frame. For example, the first device (e.g., base station) may perform a CCA procedure on the channel and, if successful, capture the channel for the TDD frame. The first device may perform downlink transmission(s) on the channel and/or use the channel for uplink transmissions from a second device (e.g., a UE). In some aspects, the channel may have an associated bandwidth <NUM> that includes a plurality of clusters <NUM> (with clusters <NUM>-a through <NUM>-m being shown by way of example only). Generally, each cluster <NUM> may support an interlace-based design where different types of transmissions are multiplexed in the frequency domain (e.g., on different interlaces). For example, a first cluster <NUM>-a may include an SRS interlace <NUM>-a, a PUSCH interlace <NUM>-a, and a PUCCH interlace <NUM>-a. The second cluster <NUM>-b may begin with a PRACH interlace <NUM>-a and continue with one or more additional interlaces (not shown). The final cluster <NUM>-m may include a PUSCH interlace <NUM>-m, a PUCCH interlace <NUM>-m, and a PRACH interlace <NUM>-m. Other cluster <NUM> configurations may also be used.

Accordingly, the second device may transmit the SRS (or PRACH preamble) in the SRS interlace <NUM>-a (e.g., a first interlace) of the channel bandwidth <NUM> and the DMRS, or uplink control or data transmission, or random access transmissions in corresponding PUSCH interlace <NUM>-a, PUCCH interlace <NUM>-a, PRACH interlace <NUM>-a (e.g., a second interlace) of the channel bandwidth <NUM>.

<FIG> illustrates an example of a process <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. In some examples, process <NUM> may implement aspects of wireless communication system <NUM>, TDD frame configuration <NUM>, RB configurations <NUM>/<NUM>, and/or interlace configuration <NUM>. Process <NUM> may include a base station <NUM> and a UE <NUM>, which may be examples of the corresponding devices described herein. In some aspects, base station <NUM> may refer to a first device and UE <NUM> may refer to a second device, or vice versa.

At <NUM>, base station <NUM> may perform a CCA procedure on a channel of a radio frequency spectrum band. The CCA procedure (or other LBT procedure) may be performed prior to a downlink portion of the TDD frame.

At <NUM>, base station <NUM> may transmit (and UE <NUM> may receive) a downlink transmission during a downlink portion of the TDD frame. In some aspects, base station <NUM> may transmit the downlink transmission based on the CCA procedure being successful, e.g., based on whether or not base station <NUM> captures the channel.

At <NUM>, UE <NUM> may identify a gap period following the downlink portion of the TDD frame. Broadly, the gap period may refer to the time period between the downlink portion and an uplink portion of the TDD frame.

At <NUM>, UE <NUM> may selectively perform a CCA procedure on the channel. For example, UE <NUM> may perform the CCA procedure when the duration of the gap period exceeds a threshold. As another example, UE <NUM> may transmit the SRS or PRACH preamble without performing a CCA procedure when the duration of the gap period is less than a threshold.

At <NUM>, UE <NUM> may transmit (and base station <NUM> may receive) an uplink transmission. In some aspects, the uplink transmission may include an SRS and/or a PRACH preamble transmitted in a set of initial symbols of the uplink portion of the TDD frame, e.g., the first one or more symbols following gap period. In some aspects, the SRS and/or PRACH preamble may be multiplexed in the frequency domain during the set of initial symbols with a DMRS, uplink control or data transmission(s), and/or a random access transmission(s).

In some aspects, this may include UE <NUM> identifying a first comb of a resource block and transmitting the SRS and/or PRACH preamble on the first comb. UE <NUM> may identify a second comb and transmit the DMRS, uplink control or data transmission(s), and/or a random access transmission(s) on the second comb.

In some aspects, the DMRS may be transmitted from one or more antenna ports. For example, the DMRS may be transmitted on a first set of antenna ports during a first subset of the set of initial symbols and transmitted from a second set of antenna ports during a second subset of the set of initial symbols.

In some aspects, this may include UE <NUM> transmitting the SRS or PRACH preamble multiplexed in the frequency domain with an uplink data transmission during a first subset of the set of initial symbols.

In some aspects, this may include UE <NUM> transmitting the SRS or PRACH preamble frequency domain multiplexed with the DMRS, uplink control or data transmission(s), and/or a random access transmission(s) on different interlaces of the channel bandwidth.

<FIG> shows a block diagram <NUM> of a device <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a UE <NUM> as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver <NUM> may 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 front loaded SRS, etc.). Information may be passed on to other components of the device <NUM>. The receiver <NUM> may be an example of aspects of the transceiver <NUM> described with reference to <FIG>. The receiver <NUM> may utilize a single antenna or a set of antennas.

The communications manager <NUM> may identify a gap period following a downlink portion of a TDD frame, selectively perform, based on the gap period, a CCA on a channel of a radio frequency spectrum band, and transmit at least one of a SRS or a PRACH preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission. The actions performed by the communications manager <NUM> as described herein may be implemented to realize one or more potential advantages. One implementation may allow a UE <NUM> to reduce latency and conserve resources by avoiding additional lengthy CCA procedures by minimizing the gap period between downlink and uplink portions of the TDD frame. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

If implemented in code executed by a processor, the functions of the communications manager <NUM>, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

<FIG> shows a block diagram <NUM> of a device <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a device <NUM> or a UE <NUM> as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager <NUM> may be an example of aspects of the communications manager <NUM> as described herein. The communications manager <NUM> may include a gap period manager <NUM>, a CCA manager <NUM>, and a SRS/PRACH manager <NUM>. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

The gap period manager <NUM> may identify a gap period following a downlink portion of a TDD frame.

The CCA manager <NUM> may selectively perform, based on the gap period, a CCA on a channel of a radio frequency spectrum band.

The SRS/PRACH manager <NUM> may transmit at least one of a SRS or a PRACH preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission.

<FIG> shows a block diagram <NUM> of a communications manager <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The communications manager <NUM> may be an example of aspects of a communications manager <NUM>, a communications manager <NUM>, or a communications manager <NUM> described herein. The communications manager <NUM> may include a gap period manager <NUM>, a CCA manager <NUM>, a SRS/PRACH manager <NUM>, a comb manager <NUM>, a port manager <NUM>, a FDM manager <NUM>, an interlace manager <NUM>, and a data manager <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The CCA manager <NUM> may selectively perform, based on the gap period, a CCA on a channel of a radio frequency spectrum band. In some examples, the CCA manager <NUM> may perform the CCA procedure when a duration of the gap period exceeds a threshold. In some examples, the CCA manager <NUM> may transmit the SRS or PRACH preamble without performing the CCA procedure when a duration of the gap period is less than a threshold.

The SRS/PRACH manager <NUM> may transmit at least one of a SRS or a PRACH preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission. In some cases, the set of initial symbols include one or more symbols immediately following the gap period.

The comb manager <NUM> may identify a first comb of a resource block, where the SRS or PRACH preamble is transmitted on the first comb of the resource block during the set of initial symbols. In some cases, the DMRS, or the uplink data transmission, or the uplink control transmission, or the random access transmission are transmitted on a second comb of the resource block.

The port manager <NUM> may transmit the DMRS from a first set of antenna ports during a first subset of the set of initial symbols. In some examples, the port manager <NUM> may transmit the DMRS from a second set of antenna ports during a second subset of the set of initial symbols.

The FDM manager <NUM> may transmit the SRS or PRACH preamble frequency-domain multiplexed with the uplink data transmission during a first subset of the set of initial symbols. In some examples, the FDM manager <NUM> may transmit the SRS or PRACH preamble frequency-domain multiplexed with the DMRS from a set of antenna ports during a second subset of the set of initial symbols. In some cases, the SRS or PRACH preamble and the DMRS are transmitted on different combs of a resource block.

The interlace manager <NUM> may transmit the SRS or PRACH preamble on a first interlace of a channel bandwidth and the DMRS, or uplink data transmission, or uplink control transmission, or random access transmission on a second interlace of the channel bandwidth.

The data manager <NUM> may transmit the uplink data transmission over a PUSCH. In some examples, the data manager <NUM> may transmit an additional uplink data transmission over a PUSCH during one or more symbols occurring after the set of initial symbols.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The device <NUM> may be an example of or include the components of device <NUM>, device <NUM>, or a UE <NUM> as described herein. The device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager <NUM>, an I/O controller <NUM>, a transceiver <NUM>, an antenna <NUM>, memory <NUM>, and a processor <NUM>. These components may be in electronic communication via one or more buses (e.g., bus <NUM>).

The communications manager <NUM> may identify a gap period following a downlink portion of a TDD frame, selectively perform, based on the gap period, a CCA on a channel of a radio frequency spectrum band, and transmit at least one of a SRS or a PRACH preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission.

However, in some cases, the device may have more than one antenna <NUM>, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

In some cases, the memory <NUM> may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor <NUM> may 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 processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (e.g., the memory <NUM>) to cause the device <NUM> to perform various functions (e.g., functions or tasks supporting front loaded SRS).

<FIG> shows a block diagram <NUM> of a device <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a base station <NUM> as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager <NUM> may perform a CCA on a channel of a radio frequency spectrum band prior to a downlink portion of a TDD frame, perform, based on a success of the CCA, a downlink transmission during the downlink portion of the TDD frame, and receive, during a set of initial symbols of an uplink portion of the TDD frame that follows a gap period between the downlink portion of the TDD frame and the uplink portion of the TDD frame, at least one of a SRS or a PRACH preamble, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

<FIG> shows a block diagram <NUM> of a device <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a device <NUM> or a base station <NUM> as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager <NUM> may be an example of aspects of the communications manager <NUM> as described herein. The communications manager <NUM> may include a CCA manager <NUM>, a downlink manager <NUM>, and a SRS/PRACH manager <NUM>. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

The CCA manager <NUM> may perform a CCA on a channel of a radio frequency spectrum band prior to a downlink portion of a TDD frame.

The downlink manager <NUM> may perform, based on a success of the CCA, a downlink transmission during the downlink portion of the TDD frame.

The SRS/PRACH manager <NUM> may receive, during a set of initial symbols of an uplink portion of the TDD frame that follows a gap period between the downlink portion of the TDD frame and the uplink portion of the TDD frame, at least one of a SRS or a PRACH preamble, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission.

<FIG> shows a block diagram <NUM> of a communications manager <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The communications manager <NUM> may be an example of aspects of a communications manager <NUM>, a communications manager <NUM>, or a communications manager <NUM> described herein. The communications manager <NUM> may include a CCA manager <NUM>, a downlink manager <NUM>, a SRS/PRACH manager <NUM>, a comb manager <NUM>, a port manager <NUM>, a FDM manager <NUM>, an interlace manager <NUM>, and a data manager <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The SRS/PRACH manager <NUM> may receive, during a set of initial symbols of an uplink portion of the TDD frame that follows a gap period between the downlink portion of the TDD frame and the uplink portion of the TDD frame, at least one of a SRS or a PRACH preamble, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission. In some examples, the SRS/PRACH manager <NUM> may receive the SRS or PRACH preamble from a first device and the DMRS, or uplink data transmission, or uplink control transmission, or random access transmission from a second device, the second device being different from the first device. In some examples, the SRS/PRACH manager <NUM> may receive the SRS or PRACH preamble and at least one of the DMRS, or uplink data transmission, or uplink control transmission, or random access transmission from a same device. In some cases, the set of initial symbols include one or more symbols immediately following the gap period.

The comb manager <NUM> may identify a first comb of a resource block, where the SRS or PRACH preamble is received on the first comb of the resource block during the set of initial symbols. In some examples, the comb manager <NUM> may identify a second comb of the resource block. In some examples, the comb manager <NUM> may receive one or more of: the DMRS, or the uplink data transmission, or the uplink control transmission, or the random access transmission on the second comb of the resource block.

The port manager <NUM> may receive the DMRS from a first set of antenna ports during a first subset of the set of initial symbols. In some examples, the port manager <NUM> may receive the DMRS from a second set of antenna ports during a second subset of the set of initial symbols.

The FDM manager <NUM> may receive the SRS or PRACH preamble frequency-domain multiplexed with the uplink data transmission during a first subset of the set of initial symbols. In some examples, the FDM manager <NUM> may receive the SRS or PRACH preamble frequency-domain multiplexed with the DMRS from a set of antenna ports during a second subset of the set of initial symbols. In some cases, the SRS or PRACH preamble and the DMRS are received on a different comb of a resource block.

The interlace manager <NUM> may receive the SRS or PRACH preamble on a first interlace of a channel bandwidth and the DMRS, or uplink data transmission, or uplink control transmission, or random access transmission on a second interlace of the channel bandwidth.

The data manager <NUM> may receive the uplink data transmission over a PUSCH. In some examples, the data manager <NUM> may receive an additional uplink data transmission over a PUSCH during one or more symbols occurring after the set of initial symbols.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The device <NUM> may be an example of or include the components of device <NUM>, device <NUM>, or a base station <NUM> as described herein. The device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager <NUM>, a network communications manager <NUM>, a transceiver <NUM>, an antenna <NUM>, memory <NUM>, a processor <NUM>, and an inter-station communications manager <NUM>. These components may be in electronic communication via one or more buses (e.g., bus <NUM>).

The communications manager <NUM> may perform a CCA on a channel of a radio frequency spectrum band prior to a downlink portion of a TDD frame, perform, based on a success of the CCA, a downlink transmission during the downlink portion of the TDD frame, and receive, during a set of initial symbols of an uplink portion of the TDD frame that follows a gap period between the downlink portion of the TDD frame and the uplink portion of the TDD frame, at least one of a SRS or a PRACH preamble, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a demodulation reference signal (DMRS), an uplink data transmission, an uplink control transmission, or a random access transmission.

The processor <NUM> may 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 processor <NUM> may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (e.g., the memory <NUM>) to cause the device #{device} to perform various functions (e.g., functions or tasks supporting front loaded SRS).

<FIG> shows a flowchart illustrating a method <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a communications manager as described with reference to <FIG>. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At <NUM>, the UE may identify a gap period following a downlink portion of a TDD frame. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a gap period manager as described with reference to <FIG>.

At <NUM>, the UE may selectively perform, based on the gap period, a CCA on a channel of a radio frequency spectrum band. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a CCA manager as described with reference to <FIG>.

At <NUM>, the UE may transmit at least one of a SRS or a PRACH preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a SRS/PRACH manager as described with reference to <FIG>.

At <NUM>, the UE may identify a first comb of a resource block, where the SRS or PRACH preamble is transmitted on the first comb of the resource block during the set of initial symbols. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a comb manager as described with reference to <FIG>.

<FIG> shows a flowchart illustrating a method <NUM> that supports front loaded SRS and PRACH in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by a base station <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a communications manager as described with reference to <FIG>. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described herein. Additionally or alternatively, a base station may perform aspects of the functions described herein using special-purpose hardware.

At <NUM>, the base station may perform a CCA on a channel of a radio frequency spectrum band prior to a downlink portion of a TDD frame. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a CCA manager as described with reference to <FIG>.

At <NUM>, the base station may perform, based on a success of the CCA, a downlink transmission during the downlink portion of the TDD frame. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a downlink manager as described with reference to <FIG>.

At <NUM>, the base station may receive, during a set of initial symbols of an uplink portion of the TDD frame that follows a gap period between the downlink portion of the TDD frame and the uplink portion of the TDD frame, at least one of a SRS or a PRACH preamble, where the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of: a DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a SRS/PRACH manager as described with reference to <FIG>.

At <NUM>, the base station may receive the uplink data transmission over a PUSCH. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a data manager as described with reference to <FIG>.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a FPGA or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable read only memory (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

Claim 1:
A method for wireless communication at a user equipment, UE (<NUM>), comprising:
identifying (<NUM>) a gap period following a downlink portion of a time division duplexing, TDD, frame;
selectively (<NUM>) performing, based at least in part on the gap period exceeding a threshold, a clear channel assessment, CCA, on a channel of a radio frequency spectrum band;
transmitting (<NUM>) at least one of a sounding reference signal, SRS, or a physical random access channel, PRACH, preamble in a set of initial symbols of an uplink portion of the TDD frame following the gap period, wherein the SRS or PRACH preamble is frequency-domain multiplexed during the set of initial symbols with one or more of:
a demodulation reference signal, DMRS, an uplink data transmission, an uplink control transmission, or a random access transmission;
transmitting the DMRS from a first set of antenna ports during a first subset of the set of initial symbols; and
transmitting the DMRS from a second set of antenna ports during a second subset of the set of initial symbols.