Patent Publication Number: US-2022240245-A1

Title: Generating a feedback codebook

Description:
CROSS REFERENCE 
     The present Application for Patent claims the benefit of U.S. Provisional Patent Application No. 63/140,676 by YANG et al., entitled “GENERATING A FEEDBACK CODEBOOK,” filed Jan. 22, 2021, assigned to the assignee hereof, and expressly incorporated by reference herein. 
    
    
     FIELD OF TECHNOLOGY 
     The following relates to wireless communications, including generating a feedback codebook. 
     BACKGROUND 
     Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. 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). A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). 
     SUMMARY 
     The described techniques relate to improved methods, systems, devices, and apparatuses that support generating a feedback codebook. Generally, the described techniques provide for a user equipment (UE) to transmit subslot-based feedback messages (e.g., via an uplink channel) associated with downlink transmissions (e.g., received via a downlink channel) when the uplink and downlink channels have different numerologies. For example, the UE may receive, from a base station, a configuration for the feedback messages which may indicate that the feedback messages are subslot-based and may additionally indicate an offset parameter (e.g., a K1 parameter). The UE and base station may generate the codebook for the feedback messages based on the UE being configured for subslot feedback and based on the numerologies for the downlink channel and uplink channel being different. For example, the UE may identify, for each uplink subslot, downlink transmissions that end in that subslot. Then, the UE may transmit a feedback message including feedback information associated with each downlink transmission ending in the subslot. Thus, the UE may be configured to provide subslot-based feedback messages to the base station in cases that the uplink and downlink channels have different numerologies. 
     A method for wireless communications at a UE is described. The method may include receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, and transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     An apparatus for wireless communications at a UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, generate a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, and transmit, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     Another apparatus for wireless communications at a UE is described. The apparatus may include means for receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, and means for transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     A non-transitory computer-readable medium storing code for wireless communications at a UE is described. The code may include instructions executable by a processor to receive, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, generate a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, and transmit, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying, for each of a set of multiple subslots of the uplink channel, a first quantity of downlink transmission opportunities ending during a respective subslot of the set of multiple subslots, where generating the feedback codebook may be based on the first quantity of the downlink transmission opportunities. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, each of the one or more feedback messages corresponds to one of the set of multiple subslots and may be associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the set of multiple subslots. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook based at least in part on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook independent whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying, for each of a set of multiple subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the set of multiple subslots and identifying, for each of the set of multiple subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the set of multiple subslots, where generating the feedback codebook may be based on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. 
     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 the downlink channel, a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, where both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel and generating a feedback message for transmission via the uplink channel including feedback associated with the first and second downlink transmissions based on both the first and second downlink transmissions ending within the same subslot. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel and identifying, based on the determining, a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel, where generating the feedback codebook may be based on the first quantity of downlink transmission opportunities and the second quantity of downlink transmission opportunities. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, where generating the feedback codebook is based at least in part on identifying the first quantity of slots. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration of the one or more feedback messages includes a subslot offset between receipt of the downlink transmissions and transmission of the one or more feedback messages, and transmitting the one or more feedback messages may be based on the subslot offset. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook for transmission of the one or more feedback messages for each of a set of multiple possible subslot offsets including at least the subslot offset. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, receiving the configuration may include operations, features, means, or instructions for receiving radio resource control (RRC) signaling indicating the configuration for transmission of the one or more feedback messages. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, slots of the downlink channel may be first transmission time intervals (TTIs) each having a first number of symbols, and subslots of the uplink channel may be second TTIs each with fewer than the first number of symbols. 
     A method for wireless communications at a base station is described. The method may include transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     An apparatus for wireless communications at a base station is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, generate a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     Another apparatus for wireless communications at a base station is described. The apparatus may include means for transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, and means for receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     A non-transitory computer-readable medium storing code for wireless communications at a base station is described. The code may include instructions executable by a processor to transmit, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel, generate a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions, and receive, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying, for each of a set of multiple subslots of the uplink channel, a first quantity of the downlink transmission opportunities ending during a respective subslot of the set of multiple subslots, where generating the feedback codebook may be based on the first quantity of the downlink transmission opportunities. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, each of the one or more feedback messages corresponds to one of the set of multiple subslots and may be associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the set of multiple subslots. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook based at least in part on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying, for each of a set of multiple subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the set of multiple subslots and identifying, for each of the set of multiple subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the set of multiple subslots, where generating the feedback codebook may be based on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, via the downlink channel, a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, where both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel, where one of the one or more feedback messages includes feedback associated with the first and second downlink transmissions based on both the first and second downlink transmissions ending within the same subslot. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel and identifying, based on the determining, a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel, where generating the feedback codebook may be based on the first quantity of downlink transmission opportunities and the second quantity of downlink transmission opportunities. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, where generating the feedback codebook is based at least in part on identifying the first quantity of slots. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration of the one or more feedback messages includes a subslot offset between receipt of the downlink transmissions and transmission of the one or more feedback messages, and receiving the one or more feedback messages may be based on the subslot offset. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, generating the feedback codebook may include operations, features, means, or instructions for generating the feedback codebook for transmission of the one or more feedback messages for each of a set of multiple possible subslot offsets including at least the subslot offset. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, transmitting the configuration may include operations, features, means, or instructions for receiving RRC signaling indicating the configuration for transmission of the one or more feedback messages. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, slots of the downlink channel may be first TTIs intervals each having a first number of symbols, and subslots of the uplink channel may be second TTIs each with fewer than the first number of symbols. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a wireless communications system that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIG. 2  illustrates an example of a wireless communications system that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIGS. 3 and 4  illustrate examples of feedback transmission schemes that support generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIG. 5  illustrates an example of a process flow that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIGS. 6 and 7  show block diagrams of devices that support generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIG. 8  shows a block diagram of a communications manager that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIG. 9  shows a diagram of a system including a device that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIGS. 10 and 11  show block diagrams of devices that support generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIG. 12  shows a block diagram of a communications manager that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIG. 13  shows a diagram of a system including a device that supports generating a feedback codebook in accordance with aspects of the present disclosure. 
         FIGS. 14 through 19  show flowcharts illustrating methods that support generating a feedback codebook in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In some wireless communications systems, a user equipment (UE) may receive downlink transmissions (e.g., downlink data transmissions) from a base station (e.g., via a downlink channel such as a physical downlink shared channel (PDSCH)). In some cases, the UE may be configured to transmit one or more feedback messages associated with the downlink transmissions. That is, the UE may transmit, via an uplink channel such as a physical uplink control channel (PUCCH), feedback messages indicating whether the UE successfully received and decoded the downlink transmissions. In some cases, the UE may be configured to transmit the feedback associated with a downlink transmission on a slot-basis. That is, the UE may transmit one feedback message associated with a slot including feedback for each downlink transmission received during that slot. In some other cases, the UE may be configured to transmit feedback messages associated with a transmission time interval (TTI) that is less than the slot (e.g., to reduce latency). For example, the UE may transmit one feedback message associated with a subslot and including feedback for downlink transmissions received during that subslot. 
     In some cases, the base station may transmit, to the UE, a configuration for the feedback messages. The configuration may indicate that the feedback messages are subslot-based and may additionally indicate a subslot offset parameter (e.g., a K1 parameter). Based on the configuration for the feedback messages, the UE and base station may generate the codebook for the feedback messages. For example, the UE may identify, for each uplink subslot, downlink transmissions that end in that subslot. Then, the UE may transmit a feedback message (e.g., within an uplink subslot indicated by the subslot offset parameter) including feedback information associated with each downlink transmission ending in the subslot. In some examples, the UE may be configured to provide feedback messages to the base station in cases that the uplink and downlink channels have different numerologies. 
     Aspects of the disclosure are initially described in the context of wireless communications systems. Aspects of the disclosure are then described in the context of feedback transmission schemes and a process flow. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to generating a feedback codebook. 
       FIG. 1  illustrates an example of a wireless communications system  100  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The wireless communications system  100  may include one or more base stations  105 , one or more UEs  115 , and a core network  130 . In some examples, the wireless communications system  100  may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system  100  may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof. 
     The base stations  105  may be dispersed throughout a geographic area to form the wireless communications system  100  and may be devices in different forms or having different capabilities. The base stations  105  and the UEs  115  may wirelessly communicate via one or more communication links  125 . Each base station  105  may provide a coverage area  110  over which the UEs  115  and the base station  105  may establish one or more communication links  125 . The coverage area  110  may be an example of a geographic area over which a base station  105  and a UE  115  may support the communication of signals according to one or more radio access technologies. 
     The UEs  115  may be dispersed throughout a coverage area  110  of the wireless communications system  100 , and each UE  115  may be stationary, or mobile, or both at different times. The UEs  115  may be devices in different forms or having different capabilities. Some example UEs  115  are illustrated in  FIG. 1 . The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115 , the base stations  105 , or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in  FIG. 1 . 
     The base stations  105  may communicate with the core network  130 , or with one another, or both. For example, the base stations  105  may interface with the core network  130  through one or more backhaul links  120  (e.g., via an S1, N2, N3, or other interface). The base stations  105  may communicate with one another over the backhaul links  120  (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations  105 ), or indirectly (e.g., via core network  130 ), or both. In some examples, the backhaul links  120  may be or include one or more wireless links. 
     One or more of the base stations  105  described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or a giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology. 
     A UE  115  may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE  115  may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, a UE  115  may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples. 
     The UEs  115  described herein may be able to communicate with various types of devices, such as other UEs  115  that may sometimes act as relays as well as the base stations  105  and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in  FIG. 1 . 
     The UEs  115  and the base stations  105  may wirelessly communicate with one another via one or more communication links  125  over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links  125 . For example, a carrier used for a communication link  125  may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP)) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system  100  may support communication with a UE  115  using carrier aggregation or multi-carrier operation. A UE  115  may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers. 
     The communication links  125  shown in the wireless communications system  100  may include uplink transmissions from a UE  115  to a base station  105 , or downlink transmissions from a base station  105  to a UE  115 . Carriers may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode). 
     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  100 . For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz)). Devices of the wireless communications system  100  (e.g., the base stations  105 , the UEs  115 , or both) may have hardware configurations that support 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  100  may include base stations  105  or UEs  115  that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE  115  may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth. 
     Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In a system employing MCM techniques, a resource element may consist 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. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements that a UE  115  receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE  115 . A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE  115 . 
     One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (Δf) and a cyclic prefix. In some examples, a UE  115  and base station  105  may communicate using channels having different numerologies. For example, an uplink channel (e.g., a PUCCH) between a UE  115  and base station  105  may have a first numerology while a downlink channel (e.g., a PDSCH) between the UE  115  and base station  105  may have a second numerology different from the first numerology. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE  115  may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time and communications for the UE  115  may be restricted to one or more active BWPs. 
     The time intervals for the base stations  105  or the UEs  115  may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T S =1/(Δf max ·N f ) seconds, where Δf max , may represent the maximum supported subcarrier spacing, and N f  may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023). 
     Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communications systems  100 , a slot may further be divided into multiple mini-slots (e.g., subslots) containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., N f ) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation. 
     A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system  100  and may be referred to as a TTI. In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system  100  may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)). 
     Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs  115 . For example, one or more of the UEs  115  may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs  115  and UE-specific search space sets for sending control information to a specific UE  115 . 
     In some examples, a base station  105  may be movable and therefore provide communication coverage for a moving geographic coverage area  110 . In some examples, different geographic coverage areas  110  associated with different technologies may overlap, but the different geographic coverage areas  110  may be supported by the same base station  105 . In other examples, the overlapping geographic coverage areas  110  associated with different technologies may be supported by different base stations  105 . The wireless communications system  100  may include, for example, a heterogeneous network in which different types of the base stations  105  provide coverage for various geographic coverage areas  110  using the same or different radio access technologies. 
     The wireless communications system  100  may be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system  100  may be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. The UEs  115  may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions). Ultra-reliable communications may include private communication or group communication and may be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT), mission critical video (MCVideo), or mission critical data (MCData). Support for mission critical functions may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low-latency may be used interchangeably herein. 
     In some examples, a UE  115  may also be able to communicate directly with other UEs  115  over a device-to-device (D2D) communication link  135  (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs  115  utilizing D2D communications may be within the geographic coverage area  110  of a base station  105 . Other UEs  115  in such a group may be outside the geographic coverage area  110  of a base station  105  or be otherwise unable to receive transmissions from a base station  105 . In some examples, groups of the UEs  115  communicating via D2D communications may utilize a one-to-many ( 1 :M) system in which each UE  115  transmits to every other UE  115  in the group. In some examples, a base station  105  facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs  115  without the involvement of a base station  105 . 
     The core network  130  may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network  130  may be an evolved packet core (EPC) or 5G core (5GC), which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs  115  served by the base stations  105  associated with the core network  130 . User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to IP services  150  for one or more network operators. The IP services  150  may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service. 
     Some of the network devices, such as a base station  105 , may include subcomponents such as an access network entity  140 , which may be an example of an access node controller (ANC). Each access network entity  140  may communicate with the UEs  115  through one or more other access network transmission entities  145 , which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs). Each access network transmission entity  145  may include one or more antenna panels. In some configurations, various functions of each access network entity  140  or base station  105  may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station  105 ). 
     The wireless communications system  100  may operate using one or more frequency bands, for example in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs  115  located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz. 
     The wireless communications system  100  may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system  100  may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations  105  and the UEs  115  may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples. 
     A base station  105  or a UE  115  may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station  105  or a UE  115  may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with a base station  105  may be located in diverse geographic locations. A base station  105  may have an antenna array with a number of rows and columns of antenna ports that the base station  105  may use to support beamforming of communications with a UE  115 . Likewise, a UE  115  may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port. 
     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 transmitting device or a receiving device (e.g., a base station  105 , a UE  115 ) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via 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 transmitting device or receiving device, or with respect to some other orientation). 
     The UEs  115  and the base stations  105  may support retransmissions of data to increase the likelihood that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique for increasing the likelihood that data is received correctly over a communication link  125 . HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ may improve throughput at the MAC (media access control) layer in poor radio conditions (e.g., low signal-to-noise conditions). In some examples, a device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval. 
     Additionally or alternatively, the UEs  115  may be configured to transmit feedback messages to the base stations  105  to provide feedback (e.g., acknowledgement (ACK) feedback, negative acknowledgement (NACK) feedback) associated with one or more downlink transmissions. That is, a UE  115  may receive downlink transmissions (e.g., downlink data transmissions) from a base station  105  and the UE  115  may be configured to transmit one or more feedback messages associated with the downlink transmissions via an uplink channel. In some examples, the UE  115  may generate a codebook for the feedback messages. For example, the UE  115  may generate a semi-static codebook (e.g., a Type 1 semi-static codebook) that is predetermined based on semi-static information configured by radio resource control (RRC) signaling. In another example, the UE  115  may generate a dynamic codebook (e.g., a Type 2 dynamic codebook) that is constructed based on indications received in DCI (downlink control information) (e.g., downlink assignment index (DAI) indications in the DCI). 
     In some cases, a UE  115  may transmit one feedback message associated with a slot including feedback for each downlink transmission received during that slot. The UE  115  may transmit the feedback message associated with the slot in a subsequent slot determined based on a slot offset parameter (K1) indicated to the UE  115  by the base station  105  (e.g., via RRC signaling, via DCI). To generate the feedback codebook, the UE  115  may identify the downlink transmission opportunities (e.g., time domain resource allocations (TDRAs)) within a slot of the downlink channel. The UE  115  may then determine a maximum quantity of non-overlapping downlink transmissions that can be scheduled within the slot of the downlink channel (e.g., based on identifying the downlink transmission opportunities). Then, the UE  115  may generate the feedback message (e.g., associated with the slot) based on the maximum quantity of non-overlapping downlink transmissions. For example, if the UE  115  determines a maximum number of two non-overlapping downlink transmissions that can be scheduled within the downlink slot, the UE  115  may generate a feedback message including two HARQ-ACK bits. In some cases, the UE  115  may be configured to determine the number of bits within the feedback message and how to map each downlink transmission opportunity to a bit within the feedback message. In some cases, the UE  115  may generate the feedback codebook for each possible slot offset parameter. 
     In some instances of the UE  115  transmitting feedback messages associated with a slot, the numerologies of the downlink channel and the uplink channel may be different. As a result, a slot of the downlink channel may be a different duration than a slot of the uplink channel. For example, one downlink slot may include multiple uplink slots (e.g., two uplink slots, three uplink slots, four uplink slots). Here, the UE  115  and base station  105  may generate the feedback codebook for each downlink slot according to a mixed numerology-based codebook generation procedure. In order to remove any feedback redundancy (e.g., resulting from more uplink slots than downlink slots due to the different numerologies of the uplink and downlink channels), the UE  115  may only determine a quantity of downlink transmission occasions within a slot of the downlink channel for a subset of the slots of the uplink channel. In one example, the UE  115  may determine the subset of the slots of the uplink channel (e.g., for determining the quantity of downlink transmission occasions within the slot of the downlink channel) according to Equation 1, shown below. 
       mod( n   u   −K 1+1,  N   UL   DL )=0   (1)
 
     That is, the UE  115  may determine the quantity of downlink transmission occasions for uplink slots n u −K1 with K1 values that satisfy Equation 1. Here, n u  may denote the uplink slot in which the UE  115  transmits the feedback message, and N UL   DL  may correspond to the number of uplink slots within a downlink slot. In an example where each downlink slot includes two uplink slots, the UE  115  may determine the quantity of downlink transmission occasions within a downlink slot within every other uplink slot. Additionally, the UE  115  may measure the slot offset (e.g., K1) with reference to the quantity of uplink slots. 
     In some other cases, the UE  115  may transmit feedback messages associated with a TTI that is less than a slot (e.g., a subslot) when the uplink and downlink channels have a same numerology. For example, the UE  115  may transmit a feedback message associated with a downlink slot including feedback for each downlink transmission received during that downlink slot. The UE  115  may transmit the feedback message associated with the downlink slot in a subsequent uplink subslot determined based on a subslot offset parameter (K1) indicated to the UE  115  by the base station  105  (e.g., via RRC signaling, via DCI). In some cases, transmitting subslot-based feedback messages may reduce latency when compared to transmitting slot-based feedback messages. To generate the feedback codebook for subslot-based feedback messages, the UE  115  and base station  105  may follow a subslot-based codebook generation procedure. For example, the UE  115  may identify, for each uplink subslot, the downlink transmission opportunities (e.g., TDRAs) ending within the respective uplink subslot. The UE  115  may then determine a maximum quantity of non-overlapping downlink transmissions that can be scheduled to end within the subslot of the uplink channel (e.g., based on identifying the downlink transmission opportunities). Then, the UE  115  may generate the feedback message (e.g., associated with the uplink subslot) based on the maximum quantity of non-overlapping downlink transmissions. 
     In the example of wireless communications system  100 , the UE  115  may be configured to generate subslot-based feedback messages. For example, the base station  105  may transmit, to UE  115 , a configuration for the feedback messages. The configuration may indicate that the feedback messages are subslot-based and may additionally indicate a subslot offset parameter (e.g., a K1 parameter). Based on the configuration for the feedback messages, the UE  115  and base station  105  may generate the codebook for the feedback messages. For example, the UE  115  may identify, for each uplink subslot, downlink transmissions that end in that subslot. Then, the UE  115  may transmit a feedback message (e.g., within an uplink subslot indicated by the subslot offset parameter) including feedback information associated with each downlink transmission ending in the subslot. In some examples, the UE  115  may be configured to provide feedback messages to the base station in cases that the uplink and downlink channels have different numerologies. 
       FIG. 2  illustrates an example of a wireless communications system  200  that supports generating a feedback codebook in accordance with aspects of the present disclosure. In some examples, the wireless communications system  200  may implement aspects of wireless communications system  100 . Wireless communications system  200  includes base station  105 - a  and UE  115 - a,  which may be examples of corresponding devices described herein. Base station  105 - a  may transmit downlink signals to UE  115 - a  via PDSCH  205 , and UE  115 - a  may transmit uplink signals to base station  105 - a  via PUCCH  210 . Wireless communications system  200  may support communications between base station  105 - a  and UE  115 - a  using subslots. In the example of wireless communications system  200 , UE  115 - a  may be configured to transmit subslot-based feedback messages associated with downlink transmissions  220 . 
     Base station  105 - a  and UE  115 - a  may be in communication via PDSCH  205  and PUCCH  210 . In some cases, PDSCH  205  and PUCCH  210  may have the same numerologies. In some other cases, PDSCH  205  and PUCCH  210  may have different numerologies. For example, the subslots of PDSCH  205  may have a different duration than the subslots of PUCCH  210 . Base station  105 - a  may transmit, via PDSCH  205 , an indication of feedback configuration  215  to UE  115 - a.  In some cases, base station  105 - a  may transmit the indication of feedback configuration  215  via RRC signaling. Feedback configuration  215  may indicate a configuration for transmitting feedback messages  225  via PUCCH  210 . For example, feedback configuration  215  may indicate that feedback messages  225  are subslot-based feedback messages. That is, feedback configuration  215  may indicate that UE  115 - a  is to determine, for each uplink subslot, a set of downlink transmission occasions to generate feedback for. Additionally, feedback configuration  215  may indicate a subslot offset (e.g., K1) for feedback messages  225 . The subslot offset may indicate an offset (e.g., a quantity of subslots of the PUCCH  210 ) between receipt of downlink transmissions  220  and transmission of feedback messages  225 . 
     After base station  105 - a  transmits feedback configuration  215  to UE  115 - a,  base station  105 - a  and UE  115 - a  may generate a feedback codebook for feedback messages  225 . Base station  105 - a  and UE  115 - a  may generate the feedback codebook according to a subslot-based codebook generation procedure (e.g., instead of a mixed numerology-based codebook generation procedure and independent of the numerologies of PDSCH  205  and PUCCH  210 ). That is, base station  105 - a  and UE  115 - a  may each identify, for each subslot of PUCCH  210 , a quantity of downlink transmission opportunities (e.g., PDSCH transmission opportunities) ending within that subslot. In some cases, a subslot of PUCCH  210  may overlap with two slots of PDSCH  205 . In some examples, base station  105 - a  and UE  115 - a  may generate the feedback codebook based on the numerologies for PDSCH  205  and PUCCH  210  being different. Here, base station  105 - a  and UE  115 - a  may each identify a quantity of downlink transmission opportunities in both slots of PDSCH  205  that end during the subslot of PUCCH  210 . In either case, UE  115 - a  and base station  105 - a  may generate the feedback codebook based on the quantity of downlink transmission opportunities that end each subslot of PUCCH  210 . Additionally, UE  115 - a  and base station  105 - a  may generate the feedback codebook for each possible subslot offset value. 
     When UE  115 - a  receives downlink transmissions  220  from base station  105 - a,  UE  115 - a  may be configured to transmit one or more feedback messages  225  associated with downlink transmissions  220  (e.g., based on receiving feedback configuration  215  and generating the feedback codebook). In some cases, each of the feedback messages  225  may correspond to one of the subslots of PUCCH  210  and may include feedback associated with the quantity of downlink transmission opportunities ending in that subslot of PUCCH  210 . 
       FIG. 3  illustrates an example of a feedback transmission scheme  300  that supports generating a feedback codebook in accordance with aspects of the present disclosure. In some examples, feedback transmission scheme  300  may implement aspects of wireless communications system  100  and wireless communications system  200 . For example, feedback transmission scheme  300  may be implemented for a UE to provide subslot-based feedback messages via a PUCCH  310  associated with downlink transmissions (e.g., received via a PDSCH  305 ). 
     PDSCH  305  and PUCCH  310  may be configured for communications between a UE and a base station. In some examples, PUCCH  310  may include a set of subslots  315 - a,    315 - b,    315 - c,    315 - d,    315 - e,    315 - f,    315 - g,  and  315 - h  (e.g., uplink subslots) and PDSCH  305  may include a set of slots  320 - a  and  320 - b.  In the example of feedback transmission scheme  300 , slots  320 - a  and  320 - b  of PDSCH  305  may have a first number of symbols, and subslots  315 - a,    315 - b,    315 - c,    315 - d,    315 - e,    315 - f,    315 - g,  and  315 - h  of PUCCH  310  may have a second number of symbols fewer than the first number of symbols. In some examples, each of the slots  320  may have more symbols than each of the subslots  315 . For example, PUCCH  310  may have a subcarrier spacing twice that of PDSCH  305 , and the length of each subslot  315  may be 7 OFDM symbols. Therefore, one slot of PUCCH  310  may contain two subslots  315 . 
     PDSCH  305  may include a set of downlink transmission opportunities  325 . For example, slot  320 - a  of PDSCH  305  may include downlink transmission opportunities  325 - a  and  325 - b.  Additionally, slot  320 - b  of PDSCH  305  may include downlink transmission opportunities  325 - c  and  325 - d.  In some cases, downlink transmission opportunities  325  may be slot-based downlink transmission opportunities. That is, the TDRA associated with each downlink transmission opportunity  325  may be defined with respect to slots  320 . In some other cases, downlink transmission opportunities  325  may be subslot-based downlink transmission opportunities. That is, the TDRA associated with each downlink transmission opportunity  325  may be defined with respect to the subslots of PDSCH  305 . After a UE receives an indication of a configuration for transmitting subslot-based feedback messages associated with downlink transmissions received via PDSCH  305 , the UE and the base station may generate a feedback codebook based on the feedback messages being subslot-based. In some examples, the UE and the base station may generate the feedback codebook based on the numerologies of PDSCH  305  and PUCCH  310  being different. That is, the base station and the UE may identify, for each subslot  315  of PUCCH  310 , a quantity of downlink transmission opportunities  325  ending during that subslot  315 . For example, the base station and UE may identify that downlink transmission opportunity  325 - a  ends during subslot  315 - a,  downlink transmission opportunity  325 - b  ends during subslot  315 - d,  downlink transmission opportunity  325 - c  ends during subslot  315 - e,  and downlink transmission opportunity  325 - d  ends during subslot  315 - h.    
     Based on the quantity of downlink transmission opportunities ending during each of the subslots  315 , the UE and the base station may generate the feedback codebook. In some cases, the UE and the base station may generate the feedback codebook based on each possible subslot offset value (e.g., each possible K1 value). That is, if the UE is configured to perform a subslot-based feedback procedure (e.g., the UE is configured with an RRC parameter subslotLengthForPUCCH), the UE may not use the mixed numerology-based codebook generation procedure, but instead use the subslot-based codebook generation procedure. For example, the UE and the base station may determine for the UE to transmit a feedback message via subslot  315 - g  in cases that the subslot offset value is two, three, or six. That is, in a case that the subslot offset value is equal to six, the UE and the base station may determine that a feedback message including feedback associated with downlink transmission opportunity  325 - a  may be transmitted within subslot  315 - g  of PUCCH  310  (e.g., because subslot  315 - g  occurs six subslots after subslot  315 - a  that downlink transmission opportunity  325 - a  ends during). Additionally, in a case that the subslot offset value is equal to three, the UE and the base station may determine that a feedback message including feedback associated with downlink transmission opportunity  325 - b  may be transmitted within subslot  315 - g.  Additionally, in a case that the subslot offset value is equal to two, the UE and the base station may determine that a feedback message including feedback associated with downlink transmission opportunity  325 - c  may be transmitted within subslot  315 - g.  The UE and the base station may perform similar determinations for each subslot  315  of PUCCH  310 . 
       FIG. 4  illustrates an example of a feedback transmission scheme  400  that supports generating a feedback codebook in accordance with aspects of the present disclosure. In some examples, feedback transmission scheme  400  may implement aspects of wireless communications system  100  and wireless communications system  200 . For example, feedback transmission scheme  400  may be implemented for a UE to provide subslot-based feedback messages via a PUCCH  410  associated with downlink transmissions (e.g., received via a PDSCH  405 ). Feedback transmission scheme  400  may illustrate an example of subslot-based feedback transmission in a case that one subslot  415  (e.g., a subslot  415 - d ) of PUCCH  410  overlaps with two slots  420  of PDSCH  405 . 
     PDSCH  405  and PUCCH  410  may be configured for communications between a UE and a base station. In some examples, PUCCH  410  may include a set of subslots  415 - a,    415 - b,    415 - c,    415 - d,    415 - e,    415 - f,  and  415 - g,  and PDSCH  405  may include a set of slots  420 - a  and  420 - b.  PDSCH  405  may include a set of downlink transmission opportunities  425 . For example, slot  420 - a  of PDSCH  405  may include downlink transmission opportunities  425 - a  and slot  420 - b  of PDSCH  405  may include downlink transmission opportunities  425 - b.  After a UE receives an indication of a configuration for transmitting subslot-based feedback messages associated with downlink transmissions received via PDSCH  405 , the UE and the base station may generate a feedback codebook based on the feedback messages being subslot-based. That is, the base station and the UE may identify, for each subslot  415  of PUCCH  410 , a quantity of downlink transmission opportunities  425  ending during that subslot  415 . In an example that one of the subslots  415  of PUCCH  410  overlaps (e.g., partially overlaps) with two slots  420  of PDSCH  405 , the UE and the base station may determine a quantity of downlink transmission opportunities  425  within both slots  420 - a  and  420 - b  of PDSCH  405 . For example, for each of the slots  420 - a  and  420 - b  that overlaps with subslot  415 - d  (e.g., starting with an earliest slot  420 - a  and then moving to the latest slot  420 - b ), the UE and the base station may determine whether that slot  420  includes a downlink transmission opportunity  425  ending during subslot  415 - d.  Here, the UE and the base station may determine that downlink transmission opportunities  425 - a  and  425 - b  end during subslot  415 - d.    
     Based on the quantity of downlink transmission opportunities ending during each of the subslots  415 , the UE and the base station may generate the feedback codebook. In some cases, the UE and the base station may generate the feedback codebook based on each possible subslot offset value (e.g., each possible K1 value). For example, the UE and the base station may determine, for a subslot offset value of three, to transmit a feedback message including feedback for downlink transmission opportunities  425 - a  and  425 - b  within subslot  415 - g.  That is, subslot  415 - g  occurs three subslots  415  after subslot  415 - d  (e.g., during which the downlink transmission opportunities  425 - a  and  425 - b  end). Feedback transmission scheme  400  illustrates an example K1 value of three, but the UE and the base station may additionally generate the feedback codebook for other subslot offset values. 
       FIG. 5  illustrates an example of a process flow  500  that supports generating a feedback codebook in accordance with aspects of the present disclosure. . In some examples, the process flow  500  may implement one or more aspects of wireless communications systems  100  and  200 . For example, process flow  500  may include a base station  105 - b  and a UE  115 - b,  which may be examples of corresponding wireless devices as described with reference to  FIGS. 1 and 2 . In the following description of process flow  500 , the operations between base station  105 - b  and UE  115 - b  and the may be transmitted in a different order than the order shown, or the operations performed by UE  115 - b  and the base station  105 - b  may be performed in different orders or at different times. Some operations may also be omitted from process flow  500 , and other operations may be added to process flow  500 . Further, while  FIG. 5  illustrates an example of communications between a base station  105 - b  and a UE  115 - b,  the techniques described herein may be applied to communications between any number of wireless devices. 
     At  505 , UE  115 - b  may receive, from base station  105 - b,  an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel (e.g., a PDSCH). The one or more feedback messages may be subslot-based transmissions in the uplink channel (e.g., a PUCCH). In some cases, each of the one or more feedback messages may correspond to one of multiple subslots. Additionally or alternatively, the configuration of one or more feedback messages may include a subslot offset between receipt of the downlink transmissions and transmissions of the one or more feedback messages, where transmitting the one or more feedback messages is based on the subslot offset. In some implementations, UE  115 - b  may receive RRC signaling indicating the configuration for transmission of the one or more feedback messages. 
     In some cases, at  510 , UE  115 - b  may determine that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel (e.g., in cases that the subslot of the uplink channel overlaps with the first and second slots of the downlink channel). Additionally, base station  105 - b  may also determine that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel at  515 . 
     At  520 , UE  115 - b  may identify, for each subslot of the multiple subslots of the uplink channel, a first quantity of downlink transmission opportunities ending during a respective subslot of the multiple of subslots. In some cases, each of the one or more feedback messages may be associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the multiple subslots. In some cases, UE  115 - b  may identify, for each subset of multiple subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the multiple subslots. Then, UE  115 - b  may identify, for each of the multiple subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the multiple subslots. In some other cases (e.g., in cases that the subslot of the uplink channel overlaps with the first and second slots of the downlink channel), UE  115 - b  may identify a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel based on determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel. In some examples, UE  115 - b  may identify a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, where generating the feedback codebook is based on identifying the first quantity of slots. 
     At  525 , base station  105 - b  may identify, for each of the multiple subslots of the uplink channel, a first quantity of downlink transmission opportunities ending during a respective subslot of the multiple subslots. In some cases, each of the one or more feedback messages may be associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the multiple subslots. In some cases, base station  105 - b  may identify, for each of the multiple subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the multiple subslots. Here, base station  105 - b  may identify, for each of the multiple subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the multiple subslots. Additionally or alternatively, base station  105 - b  may identify a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel based on determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel. 
     At  530 , UE  115 - b  may generate a feedback codebook for transmission of the one or more feedback messages based on one or more feedback messages being subslot-based transmissions and. In some cases, generating the feedback codebook may be based on the first quantity of the downlink transmission opportunities. In some cases, UE  115 - b  may generate the feedback codebook based on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. In some examples, UE  115 - b  may generate the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. Additionally or alternatively, UE  115 - b  may generate the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. In some other cases, UE  115 - b  may generate the feedback codebook based on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. In some cases, UE  115 - b  may generate the feedback codebook based on the first quantity of downlink transmission opportunities, where the first quantity of downlink transmission opportunities may be based on determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel. UE  115 - b  may generate the feedback codebook for transmission of one or more feedback messages for each possible subset offset of multiple possible subslot offsets including at least the subslot offset. 
     At  535 , base station  105 - b  may generate a feedback codebook for transmission of the one or more feedback messages based on one or more feedback messages being subslot-based transmissions. In some cases, generating the feedback codebook may be based on the first quantity of the downlink transmission opportunities. In some cases, base station  105 - b  may generate the feedback codebook based on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. In some examples, base station  105 - b  may generate the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. Additionally or alternatively, base station  105 - b  may generate the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. In some other cases, base station  105 - b  may generate the feedback codebook based on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. In some cases, base station  105 - b  may generate the feedback codebook based on the first quantity of downlink transmission opportunities, where the first quantity of downlink transmission opportunities may be based on determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel. UE  115 - b  may generate the feedback codebook for transmission of one or more feedback messages for each possible subset offsets of multiple possible subslot offsets including at least the subslot offset. 
     At  540 , UE  115 - b  may receive, via the downlink channel, one or more downlink transmissions from base station  105 - b.  For example, base station  105 - b  may transmit a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, where both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel. In some cases, UE  115 - b  may generate a feedback message for transmission via the uplink channel including feedback associated with the first and second downlink transmissions based on both the first and second downlink transmissions ending within the same subslot. 
     At  545 , UE  115 - b  may transmit, to base station  105 - b,  one or more feedback messages based on the feedback codebook via the uplink channel. In some cases, UE  115 - b  may generate a feedback message for transmission via the uplink channel including feedback associated with the first and second downlink transmissions based on both the first and second downlink transmissions ending within the same subslot. 
       FIG. 6  shows a block diagram  600  of a device  605  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The device  605  may be an example of aspects of a UE  115  as described herein. The device  605  may include a receiver  610 , a transmitter  615 , and a communications manager  620 . The device  605  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  610  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). Information may be passed on to other components of the device  605 . The receiver  610  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  615  may provide a means for transmitting signals generated by other components of the device  605 . For example, the transmitter  615  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). In some examples, the transmitter  615  may be co-located with a receiver  610  in a transceiver module. The transmitter  615  may utilize a single antenna or a set of multiple antennas. 
     The communications manager  620 , the receiver  610 , the transmitter  615 , or various combinations thereof or various components thereof may be examples of means for performing various aspects of generating a feedback codebook as described herein. For example, the communications manager  620 , the receiver  610 , the transmitter  615 , or various combinations or components thereof may support a method for performing one or more of the functions described herein. 
     In some examples, the communications manager  620 , the receiver  610 , the transmitter  615 , or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some examples, a processor and memory coupled with the processor may be configured to perform one or more of the functions described herein (e.g., by executing, by the processor, instructions stored in the memory). 
     Additionally or alternatively, in some examples, the communications manager  620 , the receiver  610 , the transmitter  615 , or various combinations or components thereof may be implemented in code (e.g., as communications management software or firmware) executed by a processor. If implemented in code executed by a processor, the functions of the communications manager  620 , the receiver  610 , the transmitter  615 , or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a central processing unit (CPU), an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., configured as or otherwise supporting a means for performing the functions described in the present disclosure). 
     In some examples, the communications manager  620  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  610 , the transmitter  615 , or both. For example, the communications manager  620  may receive information from the receiver  610 , send information to the transmitter  615 , or be integrated in combination with the receiver  610 , the transmitter  615 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  620  may support wireless communications at a UE in accordance with examples as disclosed herein. For example, the communications manager  620  may be configured as or otherwise support a means for receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The communications manager  620  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The communications manager  620  may be configured as or otherwise support a means for transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     By including or configuring the communications manager  620  in accordance with examples as described herein, the device  605  (e.g., a processor controlling or otherwise coupled with the receiver  610 , the transmitter  615 , the communications manager  620 , or a combination thereof) may support techniques for generating a feedback codebook which may improve reliability and resource efficiency, and decrease latency among other advantages. As such, supported techniques may include improved network operations and, in some examples, may promote network efficiencies, among other benefits. 
       FIG. 7  shows a block diagram  700  of a device  705  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The device  705  may be an example of aspects of a device  605  or a UE  115  as described herein. The device  705  may include a receiver  710 , a transmitter  715 , and a communications manager  720 . The device  705  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  710  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). Information may be passed on to other components of the device  705 . The receiver  710  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  715  may provide a means for transmitting signals generated by other components of the device  705 . For example, the transmitter  715  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). In some examples, the transmitter  715  may be co-located with a receiver  710  in a transceiver module. The transmitter  715  may utilize a single antenna or a set of multiple antennas. 
     The device  705 , or various components thereof, may be an example of means for performing various aspects of generating a feedback codebook as described herein. For example, the communications manager  720  may include a configuration manager  725 , a feedback codebook manager  730 , a feedback message manager  735 , or any combination thereof. The communications manager  720  may be an example of aspects of a communications manager  620  as described herein. In some examples, the communications manager  720 , or various components thereof, may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  710 , the transmitter  715 , or both. For example, the communications manager  720  may receive information from the receiver  710 , send information to the transmitter  715 , or be integrated in combination with the receiver  710 , the transmitter  715 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  720  may support wireless communications at a UE in accordance with examples as disclosed herein. The configuration manager  725  may be configured as or otherwise support a means for receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The feedback codebook manager  730  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The feedback message manager  735  may be configured as or otherwise support a means for transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
       FIG. 8  shows a block diagram  800  of a communications manager  820  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The communications manager  820  may be an example of aspects of a communications manager  620 , a communications manager  720 , or both, as described herein. The communications manager  820 , or various components thereof, may be an example of means for performing various aspects of generating a feedback codebook as described herein. For example, the communications manager  820  may include a configuration manager  825 , a feedback codebook manager  830 , a feedback message manager  835 , a downlink transmission opportunity manager  840 , a downlink transmission receiver  845 , or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The communications manager  820  may support wireless communications at a UE in accordance with examples as disclosed herein. The configuration manager  825  may be configured as or otherwise support a means for receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The feedback codebook manager  830  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The feedback message manager  835  may be configured as or otherwise support a means for transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     In some examples, the downlink transmission opportunity manager  840  may be configured as or otherwise support a means for identifying, for each of a set of multiple subslots of the uplink channel, a first quantity of downlink transmission opportunities ending during a respective subslot of the set of multiple subslots, where generating the feedback codebook is based on the first quantity of the downlink transmission opportunities. 
     In some examples, each of the one or more feedback messages corresponds to one of the set of multiple subslots and is associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the set of multiple subslots. 
     In some examples, to support generating the feedback codebook, the feedback codebook manager  830  may be configured as or otherwise support a means for generating the feedback codebook based on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different 
     In some examples, to support generating the feedback codebook, the feedback codebook manager  830  may be configured as or otherwise support a means for generating the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. 
     In some examples, to support generating the feedback codebook, the feedback codebook manager  830  may be configured as or otherwise support a means for generating the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. 
     In some examples, the downlink transmission opportunity manager  840  may be configured as or otherwise support a means for identifying, for each of a set of multiple subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the set of multiple subslots. In some examples, the downlink transmission opportunity manager  840  may be configured as or otherwise support a means for identifying, for each of the set of multiple subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the set of multiple subslots, where generating the feedback codebook is based on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. 
     In some examples, the downlink transmission receiver  845  may be configured as or otherwise support a means for receiving, via the downlink channel, a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, where both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel. In some examples, the feedback message manager  835  may be configured as or otherwise support a means for generating a feedback message for transmission via the uplink channel including feedback associated with the first and second downlink transmissions based on both the first and second downlink transmissions ending within the same subslot. 
     In some examples, the downlink transmission opportunity manager  840  may be configured as or otherwise support a means for determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel. In some examples, the downlink transmission opportunity manager  840  may be configured as or otherwise support a means for identifying, based on the determining, a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel, where generating the feedback codebook is based on the first quantity of downlink transmission opportunities and the second quantity of downlink transmission opportunities. In some examples, the downlink transmission opportunity manager  840  may be configured as or otherwise support a means for identifying a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, where generating the feedback codebook is based on identifying the first quantity of slots. 
     In some examples, the configuration of the one or more feedback messages includes a subslot offset between receipt of the downlink transmissions and transmission of the one or more feedback messages. In some examples, transmitting the one or more feedback messages is based on the subslot offset. 
     In some examples, to support generating the feedback codebook, the feedback codebook manager  830  may be configured as or otherwise support a means for generating the feedback codebook for transmission of the one or more feedback messages for each of a set of multiple possible subslot offsets including at least the subslot offset. 
     In some examples, to support receiving the configuration, the configuration manager  825  may be configured as or otherwise support a means for receiving RRC signaling indicating the configuration for transmission of the one or more feedback messages. 
     In some examples, slots of the downlink channel are first TTIs each having a first number of symbols. In some examples, subslots of the uplink channel are second TTIs each with fewer than the first number of symbols. 
       FIG. 9  shows a diagram of a system  900  including a device  905  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The device  905  may be an example of or include the components of a device  605 , a device  705 , or a UE  115  as described herein. The device  905  may communicate wirelessly with one or more base stations  105 , UEs  115 , or any combination thereof. The device  905  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager  920 , an input/output (I/O) controller  910 , a transceiver  915 , an antenna  925 , a memory  930 , code  935 , and a processor  940 . These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus  945 ). 
     The I/O controller  910  may manage input and output signals for the device  905 . The I/O controller  910  may also manage peripherals not integrated into the device  905 . In some cases, the I/O controller  910  may represent a physical connection or port to an external peripheral. In some cases, the I/O controller  910  may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. Additionally or alternatively, the I/O controller  910  may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller  910  may be implemented as part of a processor, such as the processor  940 . In some cases, a user may interact with the device  905  via the I/O controller  910  or via hardware components controlled by the I/O controller  910 . 
     In some cases, the device  905  may include a single antenna  925 . However, in some other cases, the device  905  may have more than one antenna  925 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver  915  may communicate bi-directionally, via the one or more antennas  925 , wired, or wireless links as described herein. For example, the transceiver  915  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  915  may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas  925  for transmission, and to demodulate packets received from the one or more antennas  925 . The transceiver  915 , or the transceiver  915  and one or more antennas  925 , may be an example of a transmitter  615 , a transmitter  715 , a receiver  610 , a receiver  710 , or any combination thereof or component thereof, as described herein. 
     The memory  930  may include random access memory (RAM) and read-only memory (ROM). The memory  930  may store computer-readable, computer-executable code  935  including instructions that, when executed by the processor  940 , cause the device  905  to perform various functions described herein. The code  935  may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, the code  935  may not be directly executable by the processor  940  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some cases, the memory  930  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  940  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  940  may be configured to operate a memory array using a memory controller. In some other cases, a memory controller may be integrated into the processor  940 . The processor  940  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  930 ) to cause the device  905  to perform various functions (e.g., functions or tasks supporting generating a feedback codebook). For example, the device  905  or a component of the device  905  may include a processor  940  and memory  930  coupled with the processor  940 , the processor  940  and memory  930  configured to perform various functions described herein. 
     The communications manager  920  may support wireless communications at a UE in accordance with examples as disclosed herein. For example, the communications manager  920  may be configured as or otherwise support a means for receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The communications manager  920  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The communications manager  920  may be configured as or otherwise support a means for transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     By including or configuring the communications manager  920  in accordance with examples as described herein, the device  905  may support techniques for generating a feedback codebook which may improve reliability and resource efficiency, and decrease latency among other advantages. As such, supported techniques may include improved network operations and, in some examples, may promote network efficiencies, among other benefits. 
     In some examples, the communications manager  920  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the transceiver  915 , the one or more antennas  925 , or any combination thereof. Although the communications manager  920  is illustrated as a separate component, in some examples, one or more functions described with reference to the communications manager  920  may be supported by or performed by the processor  940 , the memory  930 , the code  935 , or any combination thereof. For example, the code  935  may include instructions executable by the processor  940  to cause the device  905  to perform various aspects of generating a feedback codebook as described herein, or the processor  940  and the memory  930  may be otherwise configured to perform or support such operations. 
       FIG. 10  shows a block diagram  1000  of a device  1005  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The device  1005  may be an example of aspects of a base station  105  as described herein. The device  1005  may include a receiver  1010 , a transmitter  1015 , and a communications manager  1020 . The device  1005  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  1010  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). Information may be passed on to other components of the device  1005 . The receiver  1010  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  1015  may provide a means for transmitting signals generated by other components of the device  1005 . For example, the transmitter  1015  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). In some examples, the transmitter  1015  may be co-located with a receiver  1010  in a transceiver module. The transmitter  1015  may utilize a single antenna or a set of multiple antennas. 
     The communications manager  1020 , the receiver  1010 , the transmitter  1015 , or various combinations thereof or various components thereof may be examples of means for performing various aspects of generating a feedback codebook as described herein. For example, the communications manager  1020 , the receiver  1010 , the transmitter  1015 , or various combinations or components thereof may support a method for performing one or more of the functions described herein. 
     In some examples, the communications manager  1020 , the receiver  1010 , the transmitter  1015 , or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a DSP, an ASIC, an FPGA or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some examples, a processor and memory coupled with the processor may be configured to perform one or more of the functions described herein (e.g., by executing, by the processor, instructions stored in the memory). 
     Additionally or alternatively, in some examples, the communications manager  1020 , the receiver  1010 , the transmitter  1015 , or various combinations or components thereof may be implemented in code (e.g., as communications management software or firmware) executed by a processor. If implemented in code executed by a processor, the functions of the communications manager  1020 , the receiver  1010 , the transmitter  1015 , or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., configured as or otherwise supporting a means for performing the functions described in the present disclosure). 
     In some examples, the communications manager  1020  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  1010 , the transmitter  1015 , or both. For example, the communications manager  1020  may receive information from the receiver  1010 , send information to the transmitter  1015 , or be integrated in combination with the receiver  1010 , the transmitter  1015 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  1020  may support wireless communications at a base station in accordance with examples as disclosed herein. For example, the communications manager  1020  may be configured as or otherwise support a means for transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The communications manager  1020  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The communications manager  1020  may be configured as or otherwise support a means for receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     By including or configuring the communications manager  1020  in accordance with examples as described herein, the device  1005  (e.g., a processor controlling or otherwise coupled with the receiver  1010 , the transmitter  1015 , the communications manager  1020 , or a combination thereof) may support techniques for generating a feedback codebook which may improve reliability and resource efficiency, and decrease latency among other advantages. As such, supported techniques may include improved network operations and, in some examples, may promote network efficiencies, among other benefits. 
       FIG. 11  shows a block diagram  1100  of a device  1105  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The device  1105  may be an example of aspects of a device  1005  or a base station  105  as described herein. The device  1105  may include a receiver  1110 , a transmitter  1115 , and a communications manager  1120 . The device  1105  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  1110  may provide a means for receiving information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). Information may be passed on to other components of the device  1105 . The receiver  1110  may utilize a single antenna or a set of multiple antennas. 
     The transmitter  1115  may provide a means for transmitting signals generated by other components of the device  1105 . For example, the transmitter  1115  may transmit information such as packets, user data, control information, or any combination thereof associated with various information channels (e.g., control channels, data channels, information channels related to generating a feedback codebook). In some examples, the transmitter  1115  may be co-located with a receiver  1110  in a transceiver module. The transmitter  1115  may utilize a single antenna or a set of multiple antennas. 
     The device  1105 , or various components thereof, may be an example of means for performing various aspects of generating a feedback codebook as described herein. For example, the communications manager  1120  may include a configuration transmitter  1125 , a feedback codebook generator  1130 , a feedback message component  1135 , or any combination thereof. The communications manager  1120  may be an example of aspects of a communications manager  1020  as described herein. In some examples, the communications manager  1120 , or various components thereof, may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the receiver  1110 , the transmitter  1115 , or both. For example, the communications manager  1120  may receive information from the receiver  1110 , send information to the transmitter  1115 , or be integrated in combination with the receiver  1110 , the transmitter  1115 , or both to receive information, transmit information, or perform various other operations as described herein. 
     The communications manager  1120  may support wireless communications at a base station in accordance with examples as disclosed herein. The configuration transmitter  1125  may be configured as or otherwise support a means for transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The feedback codebook generator  1130  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The feedback message component  1135  may be configured as or otherwise support a means for receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
       FIG. 12  shows a block diagram  1200  of a communications manager  1220  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The communications manager  1220  may be an example of aspects of a communications manager  1020 , a communications manager  1120 , or both, as described herein. The communications manager  1220 , or various components thereof, may be an example of means for performing various aspects of generating a feedback codebook as described herein. For example, the communications manager  1220  may include a configuration transmitter  1225 , a feedback codebook generator  1230 , a feedback message component  1235 , a downlink transmission opportunity identifier  1240 , a downlink transmission transmitter  1245 , or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The communications manager  1220  may support wireless communications at a base station in accordance with examples as disclosed herein. The configuration transmitter  1225  may be configured as or otherwise support a means for transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The feedback codebook generator  1230  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The feedback message component  1235  may be configured as or otherwise support a means for receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     In some examples, the downlink transmission opportunity identifier  1240  may be configured as or otherwise support a means for identifying, for each of a set of multiple subslots of the uplink channel, a first quantity of the downlink transmission opportunities ending during a respective subslot of the set of multiple subslots, where generating the feedback codebook is based on the first quantity of the downlink transmission opportunities. 
     In some examples, each of the one or more feedback messages corresponds to one of the set of multiple subslots and is associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the set of multiple subslots. 
     In some examples, to support generating the feedback codebook, the feedback codebook generator  1230  may be configured as or otherwise support a means for generating the feedback codebook based on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. 
     In some examples, to support generating the feedback codebook, the feedback codebook generator  1230  may be configured as or otherwise support a means for generating the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. 
     In some examples, to support generating the feedback codebook, the feedback codebook generator  1230  may be configured as or otherwise support a means for generating the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. 
     In some examples, the downlink transmission opportunity identifier  1240  may be configured as or otherwise support a means for identifying, for each of a set of multiple subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the set of multiple subslots. In some examples, the downlink transmission opportunity identifier  1240  may be configured as or otherwise support a means for identifying, for each of the set of multiple subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the set of multiple subslots, where generating the feedback codebook is based on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. 
     In some examples, the downlink transmission transmitter  1245  may be configured as or otherwise support a means for transmitting, via the downlink channel, a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, where both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel, where one of the one or more feedback messages includes feedback associated with the first and second downlink transmissions based on both the first and second downlink transmissions ending within the same subslot. 
     In some examples, the downlink transmission opportunity identifier  1240  may be configured as or otherwise support a means for determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel. In some examples, the downlink transmission opportunity identifier  1240  may be configured as or otherwise support a means for identifying, based on the determining, a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel, where generating the feedback codebook is based on the first quantity of downlink transmission opportunities and the second quantity of downlink transmission opportunities. In some examples, the downlink transmission opportunity identifier  1240  may be configured as or otherwise support a means for identifying a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, where generating the feedback codebook is based on identifying the first quantity of slots. 
     In some examples, the configuration of the one or more feedback messages includes a subslot offset between receipt of the downlink transmissions and transmission of the one or more feedback messages. In some examples, receiving the one or more feedback messages is based on the subslot offset. 
     In some examples, to support generating the feedback codebook, the feedback codebook generator  1230  may be configured as or otherwise support a means for generating the feedback codebook for transmission of the one or more feedback messages for each of a set of multiple possible subslot offsets including at least the subslot offset. 
     In some examples, to support transmitting the configuration, the configuration transmitter  1225  may be configured as or otherwise support a means for receiving RRC signaling indicating the configuration for transmission of the one or more feedback messages. 
     In some examples, slots of the downlink channel are first TTIs each having a first number of symbols. In some examples, subslots of the uplink channel are second TTIs each with fewer than the first number of symbols. 
       FIG. 13  shows a diagram of a system  1300  including a device  1305  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The device  1305  may be an example of or include the components of a device  1005 , a device  1105 , or a base station  105  as described herein. The device  1305  may communicate wirelessly with one or more base stations  105 , UEs  115 , or any combination thereof. The device  1305  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a communications manager  1320 , a network communications manager  1310 , a transceiver  1315 , an antenna  1325 , a memory  1330 , code  1335 , a processor  1340 , and an inter-station communications manager  1345 . These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus  1350 ). 
     The network communications manager  1310  may manage communications with a core network  130  (e.g., via one or more wired backhaul links). For example, the network communications manager  1310  may manage the transfer of data communications for client devices, such as one or more UEs  115 . 
     In some cases, the device  1305  may include a single antenna  1325 . However, in some other cases the device  1305  may have more than one antenna  1325 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver  1315  may communicate bi-directionally, via the one or more antennas  1325 , wired, or wireless links as described herein. For example, the transceiver  1315  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  1315  may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas  1325  for transmission, and to demodulate packets received from the one or more antennas  1325 . The transceiver  1315 , or the transceiver  1315  and one or more antennas  1325 , may be an example of a transmitter  1015 , a transmitter  1115 , a receiver  1010 , a receiver  1110 , or any combination thereof or component thereof, as described herein. 
     The memory  1330  may include RAM and ROM. The memory  1330  may store computer-readable, computer-executable code  1335  including instructions that, when executed by the processor  1340 , cause the device  1305  to perform various functions described herein. The code  1335  may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, the code  1335  may not be directly executable by the processor  1340  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some cases, the memory  1330  may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices. 
     The processor  1340  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  1340  may be configured to operate a memory array using a memory controller. In some other cases, a memory controller may be integrated into the processor  1340 . The processor  1340  may be configured to execute computer-readable instructions stored in a memory (e.g., the memory  1330 ) to cause the device  1305  to perform various functions (e.g., functions or tasks supporting generating a feedback codebook). For example, the device  1305  or a component of the device  1305  may include a processor  1340  and memory  1330  coupled with the processor  1340 , the processor  1340  and memory  1330  configured to perform various functions described herein. 
     The inter-station communications manager  1345  may manage communications with other base stations  105 , and may include a controller or scheduler for controlling communications with UEs  115  in cooperation with other base stations  105 . For example, the inter-station communications manager  1345  may coordinate scheduling for transmissions to UEs  115  for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager  1345  may provide an X2 interface within an LTE/LTE-A wireless communications network technology to provide communication between base stations  105 . 
     The communications manager  1320  may support wireless communications at a base station in accordance with examples as disclosed herein. For example, the communications manager  1320  may be configured as or otherwise support a means for transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The communications manager  1320  may be configured as or otherwise support a means for generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The communications manager  1320  may be configured as or otherwise support a means for receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     By including or configuring the communications manager  1320  in accordance with examples as described herein, the device  1305  may support techniques for generating a feedback codebook which may improve reliability and resource efficiency, and decrease latency among other advantages. As such, supported techniques may include improved network operations and, in some examples, may promote network efficiencies, among other benefits. 
     In some examples, the communications manager  1320  may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the transceiver  1315 , the one or more antennas  1325 , or any combination thereof. Although the communications manager  1320  is illustrated as a separate component, in some examples, one or more functions described with reference to the communications manager  1320  may be supported by or performed by the processor  1340 , the memory  1330 , the code  1335 , or any combination thereof. For example, the code  1335  may include instructions executable by the processor  1340  to cause the device  1305  to perform various aspects of generating a feedback codebook as described herein, or the processor  1340  and the memory  1330  may be otherwise configured to perform or support such operations. 
       FIG. 14  shows a flowchart illustrating a method  1400  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The operations of the method  1400  may be implemented by a UE or its components as described herein. For example, the operations of the method  1400  may be performed by a UE  115  as described with reference to  FIGS. 1 through 9 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1405 , the method may include receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The operations of  1405  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1405  may be performed by a configuration manager  825  as described with reference to  FIG. 8 . 
     At  1410 , the method may include generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The operations of  1410  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1410  may be performed by a feedback codebook manager  830  as described with reference to  FIG. 8 . 
     At  1415 , the method may include transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. The operations of  1415  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1415  may be performed by a feedback message manager  835  as described with reference to  FIG. 8 . 
       FIG. 15  shows a flowchart illustrating a method  1500  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The operations of the method  1500  may be implemented by a UE or its components as described herein. For example, the operations of the method  1500  may be performed by a UE  115  as described with reference to  FIGS. 1 through 9 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1505 , the method may include receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The operations of  1505  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1505  may be performed by a configuration manager  825  as described with reference to  FIG. 8 . 
     At  1510 , the method may include identifying, for each of a set of multiple subslots of the uplink channel, a first quantity of downlink transmission opportunities ending during a respective subslot of the set of multiple subslots. The operations of  1510  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1510  may be performed by a downlink transmission opportunity manager  840  as described with reference to  FIG. 8 . 
     At  1515 , the method may include generating, based on the first quantity of the downlink transmission opportunities, a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The operations of  1515  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1515  may be performed by a feedback codebook manager  830  as described with reference to  FIG. 8 . 
     At  1520 , the method may include transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. The operations of  1520  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1520  may be performed by a feedback message manager  835  as described with reference to  FIG. 8 . 
       FIG. 16  shows a flowchart illustrating a method  1600  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The operations of the method  1600  may be implemented by a UE or its components as described herein. For example, the operations of the method  1600  may be performed by a UE  115  as described with reference to  FIGS. 1 through 9 . In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may perform aspects of the described functions using special-purpose hardware. 
     At  1605 , the method may include receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The operations of  1605  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1605  may be performed by a configuration manager  825  as described with reference to  FIG. 8 . 
     At  1610 , the method may include generating a feedback codebook for transmission of the one or more feedback messages according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure based on the one or more feedback messages being subslot-based transmissions. The operations of  1610  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1610  may be performed by a feedback codebook manager  830  as described with reference to  FIG. 8 . 
     At  1615 , the method may include transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. The operations of  1615  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1615  may be performed by a feedback message manager  835  as described with reference to  FIG. 8 . 
       FIG. 17  shows a flowchart illustrating a method  1700  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The operations of the method  1700  may be implemented by a base station or its components as described herein. For example, the operations of the method  1700  may be performed by a base station  105  as described with reference to  FIGS. 1 through 5 and 10 through 13 . In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the described functions. Additionally or alternatively, the base station may perform aspects of the described functions using special-purpose hardware. 
     At  1705 , the method may include transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The operations of  1705  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1705  may be performed by a configuration transmitter  1225  as described with reference to  FIG. 12 . 
     At  1710 , the method may include generating a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The operations of  1710  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1710  may be performed by a feedback codebook generator  1230  as described with reference to  FIG. 12 . 
     At  1715 , the method may include receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. The operations of  1715  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1715  may be performed by a feedback message component  1235  as described with reference to  FIG. 12 . 
       FIG. 18  shows a flowchart illustrating a method  1800  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The operations of the method  1800  may be implemented by a base station or its components as described herein. For example, the operations of the method  1800  may be performed by a base station  105  as described with reference to  FIGS. 1 through 5 and 10 through 13 . In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the described functions. Additionally or alternatively, the base station may perform aspects of the described functions using special-purpose hardware. 
     At  1805 , the method may include transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The operations of  1805  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1805  may be performed by a configuration transmitter  1225  as described with reference to  FIG. 12 . 
     At  1810 , the method may include identifying, for each of a set of multiple subslots of the uplink channel, a first quantity of the downlink transmission opportunities ending during a respective subslot of the set of multiple subslots. The operations of  1810  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1810  may be performed by a downlink transmission opportunity identifier  1240  as described with reference to  FIG. 12 . 
     At  1815 , the method may include generating, based on the first quantity of the downlink transmission opportunities, a feedback codebook for transmission of the one or more feedback messages based on the one or more feedback messages being subslot-based transmissions. The operations of  1815  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1815  may be performed by a feedback codebook generator  1230  as described with reference to  FIG. 12 . 
     At  1820 , the method may include receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. The operations of  1820  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1820  may be performed by a feedback message component  1235  as described with reference to  FIG. 12 . 
       FIG. 19  shows a flowchart illustrating a method  1900  that supports generating a feedback codebook in accordance with aspects of the present disclosure. The operations of the method  1900  may be implemented by a base station or its components as described herein. For example, the operations of the method  1900  may be performed by a base station  105  as described with reference to  FIGS. 1 through 5 and 10 through 13 . In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the described functions. Additionally or alternatively, the base station may perform aspects of the described functions using special-purpose hardware. 
     At  1905 , the method may include transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, where the one or more feedback messages are subslot-based transmissions in the uplink channel. The operations of  1905  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1905  may be performed by a configuration transmitter  1225  as described with reference to  FIG. 12 . 
     At  1910 , the method may include generating a feedback codebook for transmission of the one or more feedback messages according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure based on the one or more feedback messages being subslot-based transmissions. The operations of  1910  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1910  may be performed by a feedback codebook generator  1230  as described with reference to  FIG. 12 . 
     At  1915 , the method may include receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. The operations of  1915  may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of  1915  may be performed by a feedback message component  1235  as described with reference to  FIG. 12 . 
     The following provides an overview of aspects of the present disclosure: 
     Aspect 1: A method for wireless communications at a UE, comprising: receiving, from a base station, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel, wherein the one or more feedback messages are subslot-based transmissions in the uplink channel; generating a feedback codebook for transmission of the one or more feedback messages based at least in part on the one or more feedback messages being subslot-based transmissions; and transmitting, to the base station via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     Aspect 2: The method of aspect 1, further comprising: identifying, for each of a plurality of subslots of the uplink channel, a first quantity of downlink transmission opportunities ending during a respective subslot of the plurality of subslots, wherein generating the feedback codebook is based at least in part on the first quantity of the downlink transmission opportunities. 
     Aspect 3: The method of aspect 2, wherein each of the one or more feedback messages corresponds to one of the plurality of subslots and is associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the plurality of subslots. 
     Aspect 4: The method of any of aspects 1 through 3, wherein generating the feedback codebook comprises: generating the feedback codebook based at least in part on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. 
     Aspect 5: The method of any of aspects 1 through 4, wherein generating the feedback codebook comprises: generating the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. 
     Aspect 6: The method of any of aspects 1 through 5, wherein generating the feedback codebook comprises: generating the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. 
     Aspect 7: The method of any of aspects 1 through 6, further comprising: identifying, for each of a plurality of subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the plurality of subslots; and identifying, for each of the plurality of subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the plurality of subslots, wherein generating the feedback codebook is based at least in part on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. 
     Aspect 8: The method of any of aspects 1 through 7, further comprising: receiving, via the downlink channel, a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, wherein both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel; and generating a feedback message for transmission via the uplink channel comprising feedback associated with the first and second downlink transmissions based at least in part on both the first and second downlink transmissions ending within the same subslot. 
     Aspect 9: The method of any of aspects 1 through 8, further comprising: determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel; and identifying, based at least in part on the determining, a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel, wherein generating the feedback codebook is based at least in part on the first quantity of downlink transmission opportunities and the second quantity of downlink transmission opportunities. 
     Aspect 10: The method of any of aspects 1 through 9, further comprising: Some identifying a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, wherein generating the feedback codebook is based at least in part on identifying the first quantity of slots. 
     Aspect 11: The method of any of aspects 1 through 10, wherein the configuration of the one or more feedback messages comprises a subslot offset between receipt of the downlink transmissions and transmission of the one or more feedback messages, transmitting the one or more feedback messages is based at least in part on the subslot offset. 
     Aspect 12: The method of aspect 11, wherein generating the feedback codebook comprises: generating the feedback codebook for transmission of the one or more feedback messages for each of a plurality of possible subslot offsets comprising at least the subslot offset. 
     Aspect 13: The method of any of aspects 1 through 12, wherein receiving the configuration comprises: receiving RRC signaling indicating the configuration for transmission of the one or more feedback messages. 
     Aspect 14: The method of any of aspects 1 through 13, wherein slots of the downlink channel are first TTIs each having a first number of symbols, and subslots of the uplink channel are second TTIs each with fewer than the first number of symbols. 
     Aspect 15: A method for wireless communications at a base station, comprising: transmitting, to a UE, an indication of a configuration for transmission in an uplink channel of one or more feedback messages associated with downlink transmissions received via a downlink channel having a first numerology, wherein the one or more feedback messages are subslot-based transmissions in the uplink channel having a second numerology different from the first numerology; generating a feedback codebook for transmission of the one or more feedback messages based at least in part on the one or more feedback messages being subslot-based transmissions and based at least in part on the first numerology and the second numerology being different; and receiving, from the UE via the uplink channel, the one or more feedback messages in accordance with the feedback codebook. 
     Aspect 16: The method of aspect 15, further comprising: identifying, for each of a plurality of subslots of the uplink channel, a first quantity of the downlink transmission opportunities ending during a respective subslot of the plurality of subslots, wherein generating the feedback codebook is based at least in part on the first quantity of the downlink transmission opportunities. 
     Aspect 17: The method of aspect 16, wherein each of the one or more feedback messages corresponds to one of the plurality of subslots and is associated with respective ones of the first quantity of downlink transmission opportunities ending during the respective subslot of the plurality of subslots. 
     Aspect 18: The method of any of aspects 15 through 17, wherein generating the feedback codebook comprises: generating the feedback codebook based at least in part on a first numerology associated with the downlink channel and a second numerology associated with the uplink channel being different. 
     Aspect 19: The method of aspect 18, wherein generating the feedback codebook comprises: generating the feedback codebook independent of whether a first numerology associated with the downlink channel and a second numerology associated with the uplink channel are different. 
     Aspect 20: The method of aspect 18, wherein generating the feedback codebook comprises: generating the feedback codebook according to a subslot-based codebook generation procedure instead of according to a mixed numerology-based codebook generation procedure. 
     Aspect 21: The method of any of aspects 15 through 20, further comprising: identifying, for each of a plurality of subslots of the uplink channel, one or more downlink transmission opportunities that overlap a respective subslot of the plurality of subslots; and identifying, for each of the plurality of subslots, a subset of the one or more downlink transmission opportunities ending during the respective subslot of the plurality of subslots, wherein generating the feedback codebook is based at least in part on a first quantity of downlink transmission opportunities within the subset of the one or more downlink transmission opportunities. 
     Aspect 22: The method of any of aspects 15 through 21, further comprising: transmitting, via the downlink channel, a first downlink transmission within a first slot of the downlink channel and a second downlink transmission within a second slot of the downlink channel, wherein both the first downlink transmission and the second downlink transmission end within a same subslot of the uplink channel, wherein one of the one or more feedback messages comprises feedback associated with the first and second downlink transmissions based at least in part on both the first and second downlink transmissions ending within the same subslot. 
     Aspect 23: The method of any of aspects 15 through 22, further comprising: determining that a first slot of the downlink channel and a second slot of the downlink channel overlap with a subslot of the uplink channel; and identifying, based at least in part on the determining, a first quantity of downlink transmission opportunities within the first slot of the downlink channel and a second quantity of downlink transmission opportunities within the second slot of the downlink channel ending during the subslot of the uplink channel, wherein generating the feedback codebook is based at least in part on the first quantity of downlink transmission opportunities and the second quantity of downlink transmission opportunities. 
     Aspect 24: The method of any of aspects 15 through 23, further comprising: identifying a first quantity of slots of the downlink channel that overlap with a subslot of the uplink channel, wherein generating the feedback codebook is based at least in part on identifying the first quantity of slots. 
     Aspect 25: The method of any of aspects 15 through 24, wherein the configuration of the one or more feedback messages comprises a subslot offset between receipt of the downlink transmissions and transmission of the one or more feedback messages, receiving the one or more feedback messages is based at least in part on the subslot offset. 
     Aspect 26: The method of aspect 25, wherein generating the feedback codebook comprises: generating the feedback codebook for transmission of the one or more feedback messages for each of a plurality of possible subslot offsets comprising at least the subslot offset. 
     Aspect 27: The method of any of aspects 15 through 26, wherein transmitting the configuration comprises: receiving RRC signaling indicating the configuration for transmission of the one or more feedback messages. 
     Aspect 28: The method of any of aspects 15 through 27, wherein slots of the downlink channel are first TTIs each having a first number of symbols, and subslots of the uplink channel are second TTIs each with fewer than the first number of symbols. 
     Aspect 29: An apparatus for wireless communications at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 1 through 14. 
     Aspect 30: An apparatus for wireless communications at a UE, comprising at least one means for performing a method of any of aspects 1 through 14. 
     Aspect 31: A non-transitory computer-readable medium storing code for wireless communications at a UE, the code comprising instructions executable by a processor to perform a method of any of aspects 1 through 14. 
     Aspect 32: An apparatus for wireless communications at a base station, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 15 through 28. 
     Aspect 33: An apparatus for wireless communications at a base station, comprising at least one means for performing a method of any of aspects 15 through 28. 
     Aspect 34: A non-transitory computer-readable medium storing code for wireless communications at a base station, the code comprising instructions executable by a processor to perform a method of any of aspects 15 through 28. 
     It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined. 
     Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein. 
     Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. 
     Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (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 may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media. 
     As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of”) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.” 
     In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label. 
     The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.