Patent Publication Number: US-10771204-B2

Title: Half-duplex operation in new radio systems

Description:
CROSS REFERENCES 
     The present Application for Patent is a Continuation of U.S. patent application Ser. No. 15/711,143 by CHEN et al., entitled “HALF-DUPLEX OPERATION IN NEW RADIO SYSTEMS,” filed Sep. 21, 2017, which claims priority to U.S. Provisional Patent Application No. 62/453,946 by CHEN, et al., entitled “HALF-DUPLEX OPERATION IN NEW RADIO SYSTEMS,” filed Feb. 2, 2017, assigned to the assignee hereof. 
    
    
     BACKGROUND 
     The following relates generally to wireless communication and more specifically to half-duplex operation in New Radio (NR) systems. 
     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 code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a NR system). 
     A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). A base station may communicate with a UE using frequency resources (e.g., subcarriers) with scalable channel spacing (e.g., 15 kHz, 30 kHz, etc.) and time resources (e.g., slots) with variable durations (e.g., 0.5 ms, 0.25 ms, etc.). In such cases, the timing of uplink transmissions and downlink transmissions may conflict, and it may be challenging for some UEs (e.g., half-duplex UEs) to utilize resources efficiently. As a result, a wireless communications system may experience reduced throughput. 
     SUMMARY 
     Some wireless communications systems (e.g., New Radio (NR) systems) may support communication using time and frequency resources with different numerologies. For example, a base station may communicate with a user equipment (UE) using frequency resources (e.g., subcarriers) with scalable channel spacing and time resources (e.g., slots) with variable durations. A slot may include multiple symbols, and each symbol may be allocated for communication in a specific link direction (e.g., uplink, downlink, or sidelink). 
     For UEs configured to operate in a half-duplex mode, the base station may allocate sufficient time for the UE (or components of a UE) to transition between an uplink configuration and a downlink configuration. For example, a base station may coordinate with a UE to adjust the timing of transmissions, or the base station may allocate specific symbols to provide sufficient time for the UE to transition between configurations. In other cases, the UE may be scheduled for bidirectional communication on multiple carriers using carrier aggregation. In such cases, the base station may coordinate with the UE to avoid conflicting transmissions (i.e., simultaneous uplink and downlink transmissions). UEs or other devices may communicate directly with one another in a device-to-device configuration using the same or a similar scheme to allow half-duplex devices to transition between sending and receiving. 
     A method for wireless communication at a first wireless device is described. The method may include transmitting or receiving, to or from a second wireless device, signaling that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier, identifying a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier, and communicating on resources of the first carrier or the second carrier during the symbol period based at least in part on a capability of the first or second wireless device. 
     An apparatus for wireless communication at a first wireless device is described. The apparatus may include means for transmitting or receiving, to or from a second wireless device, signaling that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier, means for identifying a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier, and means for communicating on resources of the first carrier or the second carrier during the symbol period based at least in part on a capability of the first or second wireless device. 
     Another apparatus for wireless communication at a first wireless device is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be operable to cause the processor to transmit or receive, to or from a second wireless device, signaling that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier, identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier, and communicate on resources of the first carrier or the second carrier during the symbol period based at least in part on a capability of the first or second wireless device. 
     A non-transitory computer readable medium for wireless communication at a first wireless device is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to transmit or receive, to or from a second wireless device, signaling that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier, identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier, and communicate on resources of the first carrier or the second carrier during the symbol period based at least in part on a capability of the first or second wireless device. 
     In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink or a sidelink, and may be different from the first link direction. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the first wireless device operates in a half-duplex mode, and communicating on resources of the first carrier or the second carrier during the symbol period includes communicating on resources of the first carrier or the second carrier during the symbol period based at least in part on the capability of the first wireless device. 
     In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the first wireless device includes a UE and the second wireless device includes a base station. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the first wireless device includes a base station and the second wireless device includes a UE. Some examples of the method, apparatus, and non-transitory computer-readable medium described above may further include processes, features, means, or instructions for refraining from communicating on resources of the first carrier or the second carrier during the symbol period. 
     In some examples of the method, apparatus, and non-transitory computer-readable medium described above, communicating on resources of the first carrier or the second carrier during the symbol period includes communicating on resources of the first carrier or the second carrier during the symbol period based at least in part on a cell identity of the first carrier or the second carrier. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the cell identity indicates at least one of a primary cell (PCell), primary secondary cell (PSCell), or a secondary cell (SCell). 
     In some examples of the method, apparatus, and non-transitory computer-readable medium described above, communicating on resources of the first carrier or the second carrier during the symbol period includes communicating on resources of the first carrier or the second carrier during the symbol period based at least in part on a configuration of at least one of the first carrier and the second carrier. In some examples of the method, apparatus, and non-transitory computer-readable medium described above, the first carrier and the second carrier may be within a same frequency band. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a wireless communications system that supports half-duplex operation in New Radio (NR) systems in accordance with various aspects of the present disclosure; 
         FIG. 2  illustrates an example of a wireless communications system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIG. 3  illustrates an example of a wireless communications system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIGS. 4-16  illustrate aspects of half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIGS. 17-19  show block diagrams of a device or devices that support half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIG. 20  illustrates a block diagram of a system including a device that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIGS. 21-23  show block diagrams of a device or devices that support half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIG. 24  illustrates a block diagram of a system including a device, such as a base station, that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure; 
         FIGS. 25-28  illustrate methods for half-duplex operation in NR systems in accordance with various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As the demand for wireless data increases, the efficient use of resources becomes increasingly important. Accordingly, a wireless communications system (e.g., a New Radio (NR) system) may support the use of time and frequency resources with varying numerology (e.g., different subcarrier spacing and slot durations) to support more flexible allocation of resources. Efficient techniques for communicating using the different variations of time and frequency resources may be desirable to improve throughput in a wireless communications system. Specifically, a system may support communication with half-duplex operation using efficient techniques for transitioning between uplink and downlink configurations and for communicating over multiple carriers. 
     In some cases, a base station may allocate resources for uplink communication and downlink communication with a user equipment (UE). The base station may designate specific symbol periods for uplink communication and specific symbol periods for downlink communication. In some examples, the UE may be scheduled (or required) to transmit uplink signals during a symbol period and receive downlink signals during a subsequent symbol period. However, the UE may not have sufficient time to transition from an uplink configuration to a downlink configuration due to its radio frequency (RF) capabilities, etc. As such, the UE may not be able to receive some or all of the downlink information in the subsequent symbol (or, in other cases, the UE may not be able to make full use of a symbol (or symbols) for uplink communication), which may result in reduced throughput in a wireless communications system. 
     In other cases, a UE may be configured for carrier aggregation, and the UE may communicate using multiple carriers to increase bandwidth and throughput. The UE may be scheduled for an uplink transmission during a symbol period on resources of a carrier, and the UE may also be scheduled for a downlink transmission during the same symbol period on resources of a different carrier. However, the UE may not be capable of transmitting and receiving signals simultaneously. Thus, such scheduling may result in reduced throughput in a wireless communications system. 
     As described herein, a wireless communications system may support techniques for improving the timing of uplink and downlink communication and avoiding conflicting transmissions to improve throughput. In some examples, a base station may schedule sufficient time or set a timing advance for a UE to transition from an uplink configuration to a downlink configuration or vice versa based on a numerology of the resources allocated for uplink and downlink transmissions. In other examples, for carrier aggregation, a base station may coordinate with a UE to ensure that uplink transmissions scheduled during a specific symbol period on resources of a carrier do not interfere with downlink transmissions scheduled during the same symbol period on resources of another carrier. 
     Aspects of the disclosure introduced above are described below in the context of a wireless communications system. Examples of processes and signaling exchanges that support half-duplex operation in NR systems are then described. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to half-duplex operation in NR systems. 
       FIG. 1  illustrates an example of a wireless communications system  100  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The wireless communications system  100  includes base stations  105 , UEs  115 , and a core network  130 . In some examples, the wireless communications system  100  may be a Long Term Evolution (LTE) (or LTE-Advanced (LTE-A)) network, or an NR network. In some cases, wireless communications system  100  may support enhanced broadband communications, ultra-reliable (i.e., mission critical) communications, low latency communications, and communications with low-cost and low-complexity devices. 
     Base stations  105  may wirelessly communicate with UEs  115  via one or more base station antennas. Each base station  105  may provide communication coverage for a respective geographic coverage area  110 . Communication links  125  shown in 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 . Control information and data may be multiplexed on an uplink channel or downlink channel according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information transmitted during a transmission time interval (TTI) of a downlink channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region and one or more UE-specific control regions). 
     UEs  115  may be dispersed throughout the wireless communications system  100 , and each UE  115  may be stationary or mobile. A UE  115  may also be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE  115  may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, an appliance, an automobile, an automobile component, a train, a train component, or the like. 
     Base stations  105  may communicate with the core network  130  and with one another. For example, base stations  105  may interface with the core network  130  through backhaul links  132  (e.g., S1, etc.). Base stations  105  may communicate with one another over backhaul links  134  (e.g., X2, etc.) either directly or indirectly (e.g., through core network  130 ). Base stations  105  may perform radio configuration and scheduling for communication with UEs  115  or may operate under the control of a base station controller (not shown). In some examples, base stations  105  may be macro cells, small cells, hot spots, or the like. Base stations  105  may also be referred to as eNodeBs (eNBs)  105  or, in some cases, nodes. 
     The core network  130  may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. At least some of the network devices, such as base stations  105  may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with a number of UEs  115  through a number of other access network transmission entities, each of which may be an example of a smart radio head, or a transmission/reception point (TRP). In some configurations, various functions of each access network entity or base station  105  may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station  105 ). 
     In some cases, a UE  115  may be able to communicate directly with other UEs (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol) over a sidelink connection. One or more of a group of UEs  115  utilizing D2D communications may be within the coverage area  110  of a cell. Other UEs  115  in such a group may be outside the coverage area  110  of a cell, or otherwise unable to receive transmissions from a base station  105 . In some cases, groups of 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 cases, a base station  105  facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out independent of a base station  105 . 
     Some UEs  115 , such as MTC or IoT devices, may be low cost or low complexity devices, and may provide for automated communication between machines, i.e., Machine-to-Machine (M2M) communication. M2M or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station without human intervention. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging. In some cases, an MTC or IoT device may operate using half-duplex (one-way) communications at a reduced peak rate. The MTC or IoT device may support the use of guard periods (e.g., in units of symbols or subframes) and collision handling (e.g., for two adjacent transmissions in different directions and/or different sub-bands) to facilitate switching between uplink and downlink configurations and radio frequency retuning from one sub-band to another. 
     In some cases, UEs  115  and base stations  105  may support retransmissions of data to increase the chances that data is received successfully. Hybrid automatic repeat request (HARQ) feedback is one technique of increasing the likelihood that data is received correctly over a wireless 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 medium access control (MAC) layer in poor radio conditions (e.g., signal-to-noise conditions). In some cases, a wireless 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. 
     Time intervals in LTE or NR may be expressed in multiples of a basic time unit (which may be a sampling period of T s =1/30,720,000 seconds). Time resources may be organized according to radio frames of length 10 ms (T f =307200T s ), which may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include ten 1 ms subframes numbered from 0 to 9. A subframe may be further divided into two 0.5 ms slots, each of which contains 6 or 7 modulation symbol periods (depending on the length of the cyclic prefix prepended to each symbol). In some examples, the basic time unit is a slot. In some examples, the basic time unit is of shorter duration—e.g., one or more modulation symbol periods each having a duration of 1/14 of 1 ms. Excluding the cyclic prefix, each symbol may contain 2048 sample periods. Other symbol durations may also be employed. 
     In some cases, the subframe or slot may be the smallest scheduling unit, and may be referred to as a TTI. In other cases, a TTI may be shorter than a subframe or may be dynamically selected (e.g., in short TTI bursts or in selected component carriers using short TTIs). Timing between slots or within slots may be adjusted to account for half-duplex operation as described herein. 
     A resource element may consist of one symbol period and one subcarrier (e.g., a 15 KHz frequency range). In some cases, the numerology employed within a system (i.e., symbol size, subcarrier size, symbol-period duration, and/or TTI duration) may be selected or determined based on a type of communication. The numerology may be selected or determined in view of an inherent tradeoff between latency for low latency applications and efficiency for other applications, for example. In some cases, a resource block may contain 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each orthogonal frequency division multiplexing (OFDM) symbol, 7 consecutive OFDM symbols in the time domain (1 slot), or 84 resource elements. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of symbols that may be selected during each symbol period). Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate may be. Resource blocks may be defined according to other numerologies in various examples. 
     Wireless communications system  100  may support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation or multi-carrier operation. A carrier may also be referred to as a component carrier, a layer, a channel, etc. The terms “carrier,” “component carrier,” “cell,” and “channel” may be used interchangeably herein. A component carrier may be a primary cell (PCell), a secondary cell (SCell), or a primary SCell (PSCell). Both the PCell and SCell may be used to support communication with a UE  115 . However, the PCell may be used to maintain a radio resource control (RRC) connection with the UE  115 . In some cases, a UE  115  may be configured with multiple downlink component carriers and one or more uplink component carriers for carrier aggregation. Multiple base stations  105  (or cells) may communicate with a UE  115  in a dual connectivity configuration in which component carriers are aggregated. In some cases, a node (or some other network device) may transmit signaling to a UE  115  to configure the UE  115  for carrier aggregation. 
     In some cases, wireless communications system  100  may utilize enhanced component carriers (eCCs). An eCC may be characterized by one or more features including wider bandwidth, shorter symbol duration, shorter TTIs, and modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link). An eCC may also be configured for use in unlicensed spectrum or shared spectrum (where more than one operator is allowed to use the spectrum). In some cases, an eCC may utilize a different symbol duration than other CCs. For example, an eCC may utilize a reduced symbol duration as compared with symbol durations of the other CCs. A shorter symbol duration may be associated with increased subcarrier spacing. 
     A base station  105  or UE  115  may transmit bidirectional signals using frequency division duplexing (FDD) (e.g., using paired spectrum resources) or time division duplexing (TDD) (e.g., using unpaired spectrum resources). In some cases, specific frame structures for FDD (e.g., frame structure type 1) and TDD (e.g., frame structure type 2) may be defined. For TDD frame structures, each subframe may carry uplink or downlink signals, and special subframes may be used to switch between downlink and uplink configurations. Special subframes may carry downlink or uplink traffic and may include a guard period (GP) between downlink and uplink signals. In some examples, the time used to switch between an uplink and downlink configuration may differ for different categories of UEs  115  (e.g., half-duplex UEs  115 ). For example, a type 0 half-duplex UE  115  may be capable of transitioning between an uplink and downlink configuration faster (e.g., &lt;20 μs) than a type 1 half-duplex UE  115  (e.g., &gt;200 μs). In some cases, a UE  115  may signal its capability or type to a base station  105  for the base station  105  to use for scheduling communication with the UE  115 . 
     As discussed above, wireless communications system  100  may support the use of frequency resources with scalable carrier spacing (e.g., 15 kHz, 30 kHz, etc.) and variable slot durations (e.g., 0.5 μs, 0.25 μs, etc.). In some cases, the duration of guard periods allocated for transitioning between an uplink configuration and a downlink configuration may not be sufficient. In such cases, a wireless device (e.g., a half-duplex UE  115 ) may not be able to transition in time for a specific transmission, which may result in reduced throughput in a wireless communications system. Additionally, a wireless device may be configured for carrier aggregation, and the device may be scheduled for uplink communication on one carrier and downlink communication on another carrier during the same symbol period. However, some wireless devices (e.g., half-duplex UEs  115 ) may not support simultaneous bidirectional communication, and such scheduling may result in reduced throughput in a wireless communications system. 
     Wireless communications system  100  may support efficient techniques for communicating on time and frequency resources with various numerologies to improve throughput. For example, a base station  105  may allocate sufficient time for a UE  115  to transition from an uplink configuration to a downlink configuration and vice versa. In some cases, a base station  105  may coordinate with a UE  115  to adjust the timing of uplink transmissions or downlink transmissions to increase the duration of a transition period. In other cases, a base station  105  may allocate sufficient time for a UE  115  to transition between an uplink and downlink configuration. In addition, for a UE  115  utilizing carrier aggregation, a base station  105  may coordinate with the UE  115  to avoid scheduling the UE  115  for simultaneous bidirectional communication. However, in such cases where a UE  115  is scheduled for simultaneous uplink and downlink communication on resources of different carriers, the UE  115  may refrain from communicating on resources of one of the carriers based on, for example, a priority associated with each carrier. 
       FIG. 2  illustrates an example of a wireless communications system  200  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Wireless communications system  200  includes base station  105 - a  and UE  115 - a , which may be examples of a base station  105  and a UE  115  described with reference to  FIG. 1 . Base station  105 - a  may provide communication coverage for coverage area  110 - a . Base station  105 - a  may communicate with UE  115 - a  on resources of one or more carriers  205  using TDD or FDD. In some cases, base station  105 - a  and UE  115 - a  may communicate during slots  210  (e.g., self-contained slots). Slots  210  may include symbol periods allocated for downlink control and data  215 , uplink control and data  220 , and guard periods  225 . Slot  210 - a  may be an example of a downlink centric slot in an NR system, and slot  210 - b  may be an example of an uplink centric slot in an NR system. 
     In some cases, UE  115 - a  may be an example of a half-duplex UE  115 . Accordingly, UE  115 - a  may be restricted to communicating in a single direction (e.g., uplink or downlink) at a specific time instant. For communication using TDD or FDD, UE  115 - a  may utilize a guard period (or some other transition period) to transition between uplink and downlink configurations. However, in some cases, the duration of the guard period (or some other transition period) may not be sufficient for transitioning between an uplink and downlink configuration (e.g., within a slot or across slots). As described with reference to  FIG. 1 , if UE  115 - a  is not allocated sufficient time for transitioning between an uplink and downlink configuration, wireless communications system  200  may experience reduced throughput. 
     Wireless communications system  200  may support efficient techniques for allocating sufficient time for UE  115 - a  to transition between uplink and downlink configurations. In some examples, base station  105 - a  or UE  115 - a  may communicate based on a timing advance. For example, UE  115 - a  may transmit uplink signals earlier based on the timing advance. As such, UE  115 - a  may have sufficient time after the transmission to transition from an uplink configuration to a downlink configuration. In other examples, certain symbols may not be used for communication between base station  105 - a  or UE  115 - a  (e.g., symbol blanking), and UE  115 - a  may use this time to transition between an uplink and downlink configuration. For example, after an uplink transmission, UE  115 - a  may refrain from communicating during one or more subsequent symbol periods to allow sufficient time to transition to a downlink configuration. 
     Additionally, to allow for more efficient use of resources, base station  105 - a  may support techniques for allocating resources to reduce the amount of time used to transition between uplink and downlink configurations. Specifically, base station  105 - a  may bundle resources allocated for communication in a specific link direction by allocating multiple consecutive slots for communication in the same link direction (e.g., uplink or downlink) or by supporting long bursts for control transmissions (e.g., uplink or downlink control transmissions). UE  115 - a  may receive an indication of the allocation of the multiple consecutive slots in a system information block (SIB), a master information block (MIB), control information transmitted using RRC configured resources, downlink or uplink grants (e.g., for the same or different transport blocks), etc. In such cases, base station  105 - a  and UE  115 - a  may support acknowledgment/negative acknowledgment (ACK/NACK) bundling for HARQ transmissions. That is, base station  105 - a  and UE  115 - a  may transmit HARQ responses for a group of slots allocated for a specific link direction. As a result, the number of HARQ transmissions may be reduced and more resources may be available for data transmissions in wireless communications system  200 . 
       FIG. 3  illustrates an example of a wireless communications system  300  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Wireless communications system  300  includes base station  105 - b , base station  105 - c , and UE  115 - b , which may be examples of the corresponding devices described with reference to  FIG. 1 . Base station  105 - b  may provide communication coverage for coverage area  110 - b , and base station  105 - c  may provide communication coverage for coverage area  110 - c . Base station  105 - b  may communicate with UE  115 - b  on resources of a primary carrier or PCell and one or more secondary carriers or SCells, and base station  105 - c  may communicate with UE  115 - b  on resources of an SCell. In other examples, base station  105 - c  may communicate with UE  115 - b  on a PCell and/or SCell. As depicted in the example of  FIG. 3 , base station  105 - b  may transmit downlink signals on carrier  305  to UE  115 - b , and UE  115 - b  may transmit uplink signals on carrier  310  to base station  105 - c . The communications may be on a PCell or SCell depending on the particular configuration of UE  115 - b . Although not shown, UE  115 - b  may transmit to base station  105 - b  and receive from base station  105 - c  using resources of carriers  305  and  310 , respectively. 
     As indicated above, UE  115 - b  may support communication on multiple carriers to increase the bandwidth available for communication and, by extension, increase throughput. UE  115 - b  may support simultaneous communication in the same link direction (e.g., uplink or downlink) on resources of multiple carriers. That is, during a specific symbol period, UE  115 - b  may be capable of communicating with base station  105 - b  and base station  105 - c  in the same link direction. For communication in different link directions with base station  105 - b  and base station  105 - c , UE  115 - b  may utilize a guard period (or some other transition duration) to transition between an uplink and downlink configuration. However, in some cases, UE  115 - b  may be scheduled for uplink transmissions on carrier  305  and downlink transmissions on carrier  310  during the same symbol period. But UE  115 - b  (e.g., a half-duplex UE  115 ) may not be capable of supporting bidirectional communication in the same symbol period. Further, if the different carriers are within the same frequency band, downlink transmissions on carrier  305  may interfere with uplink transmissions on carrier  310 . 
     UE  115 - b  may support efficient techniques for communicating on resources of multiple carriers with different numerologies (e.g., different slot durations). Specifically, when UE  115 - b  is scheduled for bidirectional communication during a symbol period, UE  115 - b  may refrain from communicating on resources of a specific carrier. In some cases, a base station  105  may assign a priority to cells of base station  105 - b  and cells of base station  105 - c . If a PCell, e.g., associated with base station  105 - b , is assigned a higher priority (e.g., PCell driven design), UE  115 - b  may refrain from communicating on an SCell, e.g., associated with base station  105 - c , during the symbol period. Alternatively, if the SCell is assigned a higher priority (e.g., SCell driven design), UE  115 - b  may refrain from communicating on the PCell during the symbol period. In some cases, the priority associated with the PCell and SCell may be based on a numerology of time and frequency resources used to communicate with respective base stations  105  associated with the PCell and SCell. For example, if the slot durations used for communication with the PCell are shorter than the slot durations used for communication with the SCell, the base station  105  may determine to prioritize communication with the PCell. 
       FIG. 4  illustrates an example of resources  400  allocated for communication between wireless devices using TDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  on resources of a carrier during slots  405 . Slots  405  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  405  may be based on a nominal symbol period duration for symbols within the slot  405 , a numerology associated with one or more symbols within the slot  405 , a number of control symbols within the slot  405 , or a quantity of symbols of a specific link direction within the slot  405  within a carrier or across two or more carriers. In the example of  FIG. 4 , each slot  405  may include 14 symbols. However, in other examples, each slot  405  may include a different number of symbols (e.g., 12 symbols). Slots  405 - a  and  405 - b  may be examples of downlink centric slots. 
     Slot  405 - a  may be adjacent to slot  405 - b  in the time domain, and each slot may be self-contained. That is, each slot  405  may include symbols allocated for uplink communication and symbols allocated for downlink communication. In the example of  FIG. 4 , slot  405 - a  and slot  405 - b  may each include symbols allocated for communication of downlink control information  410 , downlink data  415 , and uplink control information  420 . In other examples, a slot may include symbols allocated for communication of downlink control information, downlink data, uplink control information, and uplink data. As illustrated, symbol  425  of slot  405 - a  (i.e., the last symbol of slot  405 - a ) may be allocated for an uplink transmission, and symbol  430  of slot  405 - b  (i.e., first symbol of slot  405 - b ) may be allocated for a downlink transmission. 
     To allow sufficient time to transition from an uplink configuration to a downlink configuration, the UE  115  may transmit uplink control information  420  in symbol  425  earlier based on a timing advance  435  (negative time offset). Consequently, the uplink transmission during symbol  425  may overlap with a previous symbol (e.g., allocated as a guard period). However, in some examples, the duration of the guard period allocated for the UE  115  to transition from a downlink configuration to an uplink configuration within slot  405 - a  may be excessive. Therefore, by transmitting the uplink control information  420  in symbol  425  earlier, the UE  115  may efficiently distribute the time allocated in the guard period to, for example, accommodate its RF capabilities. As a result, the UE  115  may have sufficient time to transition from downlink to uplink within slot  405 - a  and then from uplink to downlink across slots  405 - a  and  405 - b . In some cases, both full-duplex UEs  115  and half-duplex UEs  115  may communicate using a timing advance. 
     The timing advance may be a predetermined offset or may be indicated in a timing advance command from the base station  105 . In both cases, the base station  105  may transmit a message to the UE  115  to indicate whether the UE  115  should apply the timing advance to all transmissions or specific transmissions. Such an indication may be transmitted in a SIB, MIB, or using RRC signaling when the UE  115  accesses a cell, for example. In some cases, the timing advance offset may depend on the numerology (or structure) of slot  405 - a . The base station  105  may transmit an indication of the values associated with the numerology of slot  405 - a  to the UE  115  in a synchronization signal or SIB when the UE  115  initially accesses a cell. Additionally or alternatively, the UE  115  may derive the values associated with the numerology of slot  405 - a  based on a numerology of a control channel or data channel. 
     Although  FIG. 4  illustrates an example of transitioning from an uplink configuration to a downlink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. Additionally, although  FIG. 4  illustrates an example of transitioning between link directions across slots (i.e., inter-slot transitioning), the above techniques may apply to transitioning between link directions within a slot (i.e., intra-slot transitioning). 
       FIG. 5  illustrates an example of resources  500  allocated for communication between wireless devices using TDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  on resources of a carrier using slots  505 . Slots  505  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  505  may be based on a nominal symbol period duration for symbols within the slot  505 , a numerology associated with one or more symbols within the slot  505 , a number of control symbols within the slot  505 , or a quantity of symbols of a specific link direction within the slot  505  within a carrier or across two or more carriers. In the example of  FIG. 5 , each slot  505  may include 14 symbols. However, in other examples, each slot  505  may include a different number of symbols (e.g., 12 symbols). 
     Slot  505 - a  may be adjacent to slot  505 - b  in the time domain, and each slot may be self-contained. That is, each slot  505  may include symbols allocated for uplink communication and symbols allocated for downlink communication. In the example of  FIG. 5 , slot  505 - a  and slot  505 - b  may each include symbols allocated for communication of downlink control information  510 , downlink data  515 , and uplink control information  520 . In other examples, a slot may include symbols allocated for communication of downlink control information, downlink data, uplink control information, and uplink data. As illustrated, symbol  525  of slot  505 - a  may be allocated for an uplink transmission, and a subsequent symbol  540  of slot  505 - b  may be allocated for a downlink transmission. To allow time for transitioning from an uplink configuration to a downlink configuration, the UE  115  may refrain from communicating during symbol period  535 . In such cases, downlink control information  510  (and possibly other channels or signals such as demodulation reference signals (DMRS)) may be transmitted in a subsequent symbol (i.e., symbol  540 ). 
     Although  FIG. 5  illustrates an example of transitioning from an uplink configuration to a downlink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. Additionally, although  FIG. 5  illustrates an example of transitioning between link directions across slots (i.e., inter-slot transitioning), the above techniques may apply to transitioning between link directions within a slot (i.e., intra-slot transitioning). Further, the above techniques may be applied independently or in addition to applying a timing advance  530 . 
       FIG. 6  illustrates an example of resources  600  allocated for communication between wireless devices using TDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  on resources of a carrier using slots  605 . Slots  605  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  605  may be based on a nominal symbol period duration for symbols within the slot  605 , a numerology associated with one or more symbols within the slot  605 , a number of control symbols within the slot  605 , or a quantity of symbols of a specific link direction within the slot  605  within a carrier or across two or more carriers. In the example of  FIG. 6 , each slot  605  may include 14 symbols. However, in other examples, each slot  605  may include a different number of symbols (e.g., 12 symbols). 
     Slots  605 - a ,  605 - b , and  605 - c  may be adjacent in the time domain. Slot  605 - a  may include symbols allocated for downlink control information  610  and downlink data  615 , slot  605 - b  may include symbols allocated for uplink control information  620 , and slot  605 - c  may include symbols allocated for downlink control information  610  and downlink data  615 . In some cases, the UE  115  may refrain from communicating during symbol periods  625  to allow sufficient time for transitioning between uplink and downlink configurations. In such cases, the UE  115  may transmit a longer burst of uplink control information  620  during symbol periods  630 . The UE  115  may then use symbol periods  635  to transition back to a downlink configuration to receive downlink control information  610  and downlink data  615  in slot  605 - c . The number of symbols allocated for transitioning between configurations (or link directions) may be based on a type or capability (e.g., half-duplex configuration, RF switching time, FDD/TDD capability, carrier aggregation capability, etc.) of the UE  115 . Additionally, the number of symbols allocated for transitioning between configurations (or link directions) may depend on a slot structure. As an example, for short symbol durations, more symbols may be allocated for transitioning between configurations. 
     Although  FIG. 6  illustrates an example of transitioning from a downlink configuration to an uplink configuration then back to a downlink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. Additionally, although  FIG. 6  illustrates an example of transitioning between link directions across slots (i.e., inter-slot transitioning), the above techniques may apply to transitioning between link directions within a slot (i.e., intra-slot transitioning). Further, the above techniques may be applied independently or in addition to applying a timing advance. 
       FIG. 7  illustrates an example of resources  700  allocated for communication between wireless devices using TDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  on resources of a carrier using slots  705 . Slots  705  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  705  may be based on a nominal symbol period duration for symbols within the slot  705 , a numerology associated with one or more symbols within the slot  705 , a number of control symbols within the slot  705 , or a quantity of symbols of a specific link direction within the slot  705  within a carrier or across two or more carriers. In the example of  FIG. 7 , each slot  705  may include 14 symbols. However, in other examples, each slot  705  may include a different number of symbols (e.g., 12 symbols). 
     Slots  705 - a ,  705 - b , and  705 - c  may be adjacent in the time domain. Slot  705 - a  may include symbols allocated for downlink control information  710  and downlink data  715 , and slot  705 - c  may include symbols allocated for uplink control information  720 . Specifically, slot  705 - c  may be allocated for a long burst of uplink control information  720  to reduce the amount of time used for transitioning in a wireless communications system. In some cases, the UE  115  may refrain from communicating during slot  705 - b  to allow sufficient time for transitioning from a downlink configuration to an uplink configuration. The number of slots  705  allocated for transitioning between configurations (or link directions) may be based on a type or capability (e.g., half-duplex configuration, RF switching time, FDD/TDD capability, carrier aggregation capability, etc.) of the UE  115 . Additionally, the number of slots  705  allocated for transitioning between configurations may depend on a structure of the slot  705 . As an example, for short slot durations, more slots  705  may be allocated for transitioning between configurations. 
     Although  FIG. 7  illustrates an example of transitioning from a downlink configuration to an uplink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. Further, the above techniques may be applied independently or in addition to applying a timing advance. 
       FIG. 8  illustrates an example of resources  800  allocated for communication between wireless devices using TDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  on resources of a carrier using slots  805 . Slots  805  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  805  may be based on a nominal symbol period duration for symbols within the slot  805 , a numerology associated with one or more symbols within the slot  805 , a number of control symbols within the slot  805 , or a quantity of symbols of a specific link direction within the slot  805  within a carrier or across two or more carriers. In the example of  FIG. 8 , each slot  805  may include 14 symbols. However, in other examples, each slot  805  may include a different number of symbols (e.g., 12 symbols). 
     Slots  805  may be adjacent in the time domain. To reduce the amount of time used to transition between uplink and downlink configurations, the UE  115  may communicate in a single link direction in a given slot  805 . For example, the base station  105  may configure the UE  115  to refrain from communicating in a specific link direction in a given slot  805  (e.g., based on a type or capability of the UE  115 ). In the example of  FIG. 8 , the UE  115  may receive downlink control information  810  and downlink data  815  during slots  805 - a ,  805 - b , and  805 - c , and the UE  115  may refrain from communicating in the uplink direction during blanked symbols  825 . The UE  115  may then use slot  805 - d  to transition to an uplink configuration, and the UE  115  may transmit uplink control information  820  during slot  805 - e . To facilitate this operation, base station  105  may schedule the UE  115  to communicate (or operate) in the same link direction over a plurality of slots  805  such as by providing multi-slot downlink or uplink grants and refraining from scheduling (or requiring) the UE  115  to transition between configurations (or link directions) in a same slot  805 . In some cases, the uplink transmission in slot  805 - e  may be a long burst of uplink control information  820 . 
     When multiple consecutive slots  805  are used for communication in a single link direction, the base station  105  and UE  115  may support ACK/NACK bundling for HARQ transmissions. That is, the base station  105  and UE  115  may transmit HARQ responses for a group of slots  805  used for communication in a specific link direction. As a result, the number of HARQ transmissions may be reduced and more resources may be available for data transmissions in a wireless communications system. 
     Although  FIG. 8  illustrates an example of transitioning from a downlink configuration to an uplink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. 
       FIG. 9  illustrates an example of resources  900  allocated for communication between wireless devices using FDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  during slot  905 - a  on resources of carrier  910 - a  designated for downlink communication and during slot  905 - b  on resources of carrier  910 - b  designated for uplink communication. Slots  905  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  905  may be based on a nominal symbol period duration for symbols within the slot  905 , a numerology associated with one or more symbols within the slot  905 , a number of control symbols within the slot  905 , or a quantity of symbols of a specific link direction within the slot  905  within a carrier or across two or more carriers. In the example of  FIG. 9 , each slot  905  may include 14 symbols. However, in other examples, each slot  905  may include a different number of symbols (e.g., 12 symbols). 
     Slot  905 - a  may be adjacent to slot  905 - b  in the time domain. Slot  905 - a  may include symbols allocated for communication of downlink control information  915  and downlink data  920 , and slot  905 - b  may include symbols allocated for communication of uplink control information and data  925 . In some cases, the UE  115  may refrain from communicating during symbol periods  930 , and the UE  115  may use this time to transition from a downlink configuration to an uplink configuration. Similarly, the UE  115  may refrain from communicating during symbol period  935 , and the UE  115  may use this time to transition from an uplink configuration to a downlink configuration. 
     The UE  115  may refrain from communicating during certain symbol periods based on signaling received from the base station  105 . For example, the base station  105  may transmit an indication of symbols that are valid, and the UE  115  may refrain from communicating (e.g., symbol blanking) during other symbol periods based on the indication. The amount of symbols allocated to the UE  115  for switching between configurations may be based on, for example, the category of the UE  115  (e.g., type 0 and type 1 UEs) or the capability of the UE  115  (e.g., half-duplex or full-duplex). Further, the amount of symbols allocated to the UE  115  for switching between configurations may depend on the structure of a slot  905  (e.g., more symbols for shorter symbol durations). 
     Although  FIG. 9  illustrates an example of transitioning from a downlink configuration to an uplink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. The number of symbols allocated for transitioning from one configuration to another may vary based on the configurations (e.g., two (2) symbol periods for downlink to uplink and one (1) symbol period for uplink to downlink). 
       FIG. 10  illustrates an example of resources  1000  allocated for communication between wireless devices using FDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may support downlink communication with a UE  115  on resources of carrier  1010 - a  during slots  1005 - a ,  1005 - b ,  1005 - c , and  1005 - d , and the base station  105  may support uplink communication with the UE  115  on resources of carrier  1010 - b  during slot  1005 - e . The structure of each slot  1005  may be based on a nominal symbol period duration for symbols within the slot  1005 , a numerology associated with one or more symbols within the slot  1005 , a number of control symbols within the slot  1005 , or a quantity of symbols of a specific link direction within the slot  1005  within a carrier or across two or more carriers. In the example of  FIG. 10 , each slot  1005  may include 14 symbols. However, in other examples, each slot  1005  may include a different number of symbols (e.g., 12 symbols). 
     Slots  1005  may be adjacent to each other in the time domain. Slots  1005 - a ,  1005 - b ,  1005 - c , and  1005 - d  may each include symbols allocated for communication of downlink control information  1015  and downlink data  1020 , and slot  1005 - e  may include symbols allocated for uplink control information and data  1025 . To reduce the amount of time used for transitioning between uplink and downlink configurations, the base station  105  may allocate multiple subsequent slots for communication with the UE  115  in a specific link direction. For example, the base station  105  may allocate slots  1005 - a ,  1005 - b ,  1005 - c , and  1005 - d  for downlink communication. In such cases, the base station  105  and UE  115  may support ACK/NACK bundling for HARQ transmissions. That is, the base station  105  and UE  115  may transmit HARQ responses for a group of slots  1005  allocated for a specific link direction. As a result, the number of HARQ transmissions may be reduced and more resources may be available for data transmissions in a wireless communications system. 
     Although  FIG. 10  illustrates an example of transitioning from a downlink configuration to an uplink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. 
       FIG. 11  illustrates an example of resources  1100  allocated for communication between wireless devices using flexible duplex FDD in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. For flexible duplex FDD, a UE  115  may transmit uplink signals in a frequency band allocated for downlink communication and vice versa. A base station  105  may communicate with the UE  115  during slots  1105  on resources of a first carrier  1110 - a  designated for downlink communication and a second carrier  1110 - b  designated for uplink communication. The structure of each slot  1105  may be based on a nominal symbol period duration for symbols within the slot  1105 , a numerology associated with one or more symbols within the slot  1105 , a number of control symbols within the slot  1105 , or a quantity of symbols of a specific link direction within the slot  1105  within a carrier or across two or more carriers. In the example of  FIG. 11 , each slot  1105  may include 14 symbols. However, in other examples, each slot  1105  may include a different number of symbols (e.g., 12 symbols). 
     Slot  1105 - a  may be adjacent to slot  1105 - b  in the time domain, and each slot may be self-contained. That is, each slot  1105  may include symbols allocated for uplink communication and symbols allocated for downlink communication. In the example of  FIG. 11 , slot  1105 - a  and slot  1105 - b  may each include symbols allocated for communication of downlink control information  1115 , downlink data  1120 , and uplink control information  1125 . As illustrated, symbol  1130  of slot  1105 - a  may be allocated for an uplink transmission, and a subsequent symbol  1140  of slot  1105 - b  may be allocated for a downlink transmission. 
     To allow sufficient time to transition from an uplink configuration to a downlink configuration, the UE  115  may transmit uplink control information  1125  in symbol  1130  earlier based on a timing advance  1135  (negative time offset). Consequently, the uplink transmission during symbol  1130  may overlap with a previous symbol (e.g., allocated as a guard period). However, the duration of the guard period allocated for the UE  115  to transition from a downlink configuration to an uplink configuration within slot  1105 - a  may be excessive. Therefore, by transmitting the uplink control information  1125  in symbol  1130  earlier, the UE  115  may efficiently distribute the time allocated in the guard period. As a result, the UE  115  can have sufficient time to transition from downlink to uplink within slot  1105 - a  and then from uplink to downlink across slots  1105 - a  and  1105 - b . In some cases, both full-duplex UEs  115  and half-duplex UEs  115  may communicate using a timing advance. If a cell or the UE  115  does not support flexible duplex FDD, the timing advance offset may be zero (0) for UEs  115  served by the cell or specific to a UE  115 . However, if a cell or the UE  115  supports flexible duplex FDD, the timing advance offset may be greater than zero (0) (e.g., 20 μs) for UEs  115  served by the cell or specific to a UE  115 . 
     Although  FIG. 11  illustrates an example of transitioning from an uplink configuration to a downlink configuration, the above techniques may apply to transitioning between any two of a downlink configuration, uplink configuration, or sidelink configuration. Additionally, although  FIG. 11  illustrates an example of transitioning between link directions across slots (i.e., inter-slot transitioning), the above techniques may apply to transitioning between link directions within a slot (i.e., intra-slot transitioning). 
       FIG. 12  illustrates an example of resources  1200  allocated for communication using carrier aggregation in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  during slot  1205 - a  of a PCell  1210 - a  and during slots  1205 - b  and  1205 - c  of an SCell  1210 - b . Slots  1205  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  1205  may be based on a nominal symbol period duration for symbols within the slot  1205 , a numerology associated with one or more symbols within the slot  1205 , a number of control symbols within the slot  1205 , or a quantity of symbols of a specific link direction within the slot  1205  within a carrier or across two or more carriers. In some cases, the structure of slots  1205  used for communication on different carriers may be different. For example, symbols included in slot  1205 - a  of PCell  1210 - a  may have a longer duration than symbols included in slots  1205 - b  and  1205 - c  of SCell  1210 - b.    
     Slot  1205 - a  of PCell  1210 - a  may overlap with slots  1205 - b  and  1205 - c  of SCell  1210 - b  in the time domain, and each slot  1205  may be self-contained. That is, each slot  1205  may include symbols allocated for uplink communication and symbols allocated for downlink communication. Each slot  1205  may be a downlink centric slot. Specifically, slots  1205  may each include symbols allocated for communication of downlink control information  1215 , downlink data  1220 , and uplink control information  1225 . Slots  1205  may also include guard periods  1230  for transitioning between configurations (e.g., uplink and downlink). As illustrated, the UE  115  may be scheduled for simultaneous uplink and downlink communication on resources of different carriers in some symbols (e.g., symbol  1245 ). However, half-duplex UEs  115  may not be able to support simultaneous uplink and downlink communication. Further, if PCell  1210 - a  and SCell  1210 - b  are within the same frequency band, uplink transmissions and downlink transmissions scheduled during the same symbol period on these cells may interfere with each other (e.g., for half-duplex UEs  115  and full-duplex UEs  115 ). Accordingly, it may be appropriate for a wireless communications system to support techniques for preventing conflicting transmissions. 
     The UE  115  may support efficient techniques for coordinating with the base station  105  to prevent conflicting transmissions. In some cases, the base station  105  may establish different priorities for communication on resources of PCell  1210 - a  and for communication on resources of SCell  1210 - b , and the base station  105  may signal this information to the UE  115 . In some cases, the signaling may include an indication of a cell identity of the cell with the higher priority, and the UE  115  may prioritize communication on resources of that cell based on receiving the cell identity. The cell identity may indicate that the cell is a PCell, PSCell, or SCell. In the example of  FIG. 12 , the base station  105  may prioritize communication on PCell  1210 - a  (i.e., PCell driven design). 
     Accordingly, the UE  115  scheduled for simultaneous uplink and downlink communication may refrain from communicating on resources of SCell  1210 - b . For example, the UE  115  may refrain from communicating during symbol  1240  of SCell  1210 - b  (e.g., refrain from transmitting uplink control information  1225 ). Similarly, the UE  115  may refrain from communicating during symbols  1245  of SCell  1210 - b  (e.g., refrain from monitoring for downlink data  1220 ), and, in some cases, the base station  105  may refrain from transmitting downlink data  1220  on symbols  1245  of SCell  1210 - b . The process of refraining from transmitting or receiving on specific symbols may be referred to as symbol blanking, and symbol  1240  and symbols  1245  may be referred to as blanked symbols  1235 . 
     As indicated above, the decision to communicate on specific symbols may be based on a configuration of the carrier with the higher priority. In some cases, rather than refraining from transmitting during specific symbols, the UE  115  or base station  105  may align transmissions with the prioritized cell. For example, if symbols of a prioritized cell are allocated for downlink communication, the base station  105  or UE  115  may use the corresponding symbol or symbols of another cell for downlink communication. In such cases, the UE  115  may monitor for control information on one carrier and process data on another carrier. In addition, for full-duplex UEs  115 , the UE  115  may determine whether to perform symbol blanking based on whether the PCell  1210 - a  and SCell  1210 - b  are within the same frequency band (e.g., for intra-band carrier aggregation). 
     Although  FIG. 12  illustrates an example of symbols of a PCell  1210 - a  with longer durations than symbols of an SCell  1210 - b , the above techniques apply to various combinations of numerologies for different cells. For example, symbols of the SCell  1210 - b  may have longer durations than symbols of the PCell  1210 - a . Further, although  FIG. 12  illustrates an example of a downlink transmission scheduled on resources of a cell during the same symbol period as an uplink transmission scheduled on another cell, the above techniques may apply to any combination of uplink transmissions, downlink transmissions, or sidelink transmissions scheduled simultaneously on resources of different cells. 
       FIG. 13  illustrates an example of resources  1300  allocated for communication using carrier aggregation in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  during slot  1305 - a  of a PCell  1310 - a  and during slots  1305 - b  and  1305 - c  of an SCell  1310 - b . Slots  1305  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  1305  may be based on a nominal symbol period duration for symbols within the slot  1305 , a numerology associated with one or more symbols within the slot  1305 , a number of control symbols within the slot  1305 , or a quantity of symbols of a specific link direction within the slot  1305  within a carrier or across two or more carriers. In some cases, the structure of slots  1305  used for communication on different carriers may be different. For example, symbols included in slot  1305 - a  of PCell  1310 - a  may have a longer duration than symbols included in slots  1305 - b  and  1305 - c  of SCell  1310 - b.    
     Slot  1305 - a  of PCell  1310 - a  may overlap with slots  1305 - b  and  1305 - c  of SCell  1310 - b  in the time domain, and each slot  1305  may be self-contained. That is, each slot  1305  may include symbols allocated for uplink communication and symbols allocated for downlink communication. Each slot  1305  may be a downlink centric slot. Specifically, slots  1305  may each include symbols allocated for communication of downlink control information  1315 , downlink data  1320 , and uplink control information  1325 . Slots  1305  may also include guard periods  1330  for transitioning between uplink and downlink configurations. As illustrated, the UE  115  may be scheduled for simultaneous uplink and downlink communication on resources of different carriers in some symbols (e.g., symbol  1340 ). However, half-duplex UEs  115  may not be able to support simultaneous uplink and downlink communication. Further, if PCell  1310 - a  and SCell  1310 - b  are within the same frequency band, uplink transmissions and downlink transmissions scheduled during the same symbol period on these cells may interfere with each other (e.g., for half-duplex UEs  115  and full-duplex UEs  115 ). Accordingly, it may be appropriate for a wireless communications system to support techniques for preventing conflicting transmissions. 
     The UE  115  may support efficient techniques for coordinating with the base station  105  to prevent conflicting transmissions. In some cases, the base station  105  may establish different priorities for communication on resources of PCell  1310 - a  and for communication on resources of SCell  1310 - b , and the base station  105  may signal this information to the UE  115 . In some cases, the signaling may include an indication of a cell identity of the cell with the higher priority, and the UE  115  may prioritize communication on resources of that cell based on receiving the cell identity. The cell identity may indicate that the cell is a PCell, PSCell, or SCell. In the example of  FIG. 13 , the base station  105  may prioritize communication on SCell  1310 - b  (i.e., SCell driven design). 
     Accordingly, the UE  115  scheduled for simultaneous uplink and downlink communication may refrain from communicating on resources of PCell  1310 - b . For example, the UE  115  may refrain from communicating during symbol  1340  of PCell  1310 - a  (e.g., refrain from monitoring for downlink data  1320 ), and, in some cases, the base station  105  may refrain from transmitting downlink data  1320  during symbol  1340 . Similarly, the UE  115  and base station  105  may refrain from communicating during guard period  1330  of symbol  1345  of PCell  1310 - a  and refrain from transitioning to an uplink configuration until the guard period  1330  in slot  1305 - c  of SCell  1310 - b . The process of refraining from transmitting or receiving on specific symbols may be referred to as symbol blanking, and symbol  1340  and symbols  1345  may be referred to as blanked symbols  1335 . 
     As indicated above, the decision to communicate on specific symbols may be based on a configuration of the carrier with the higher priority. In some cases, rather than refraining from transmitting during specific symbols, the UE  115  or base station  105  may align transmissions with the prioritized cell. For example, if symbols of a prioritized cell are allocated for downlink communication, the base station  105  or UE  115  may use the corresponding symbol or symbols of another cell for downlink communication. In such cases, the UE  115  may monitor for control information on one carrier and process data on another carrier. In addition, for full-duplex UEs  115 , the UE  115  may determine whether to perform symbol blanking based on whether the PCell  1310 - a  and SCell  1310 - b  are within the same frequency band (e.g., for intra-band carrier aggregation). 
     Although  FIG. 13  illustrates an example of symbols of PCell  1310 - a  with longer durations than symbols of SCell  1310 - b , the above techniques apply to various combinations of numerologies for different cells. For example, symbols of SCell  1310 - b  may have longer durations than symbols of PCell  1310 - a . Further, although  FIG. 13  illustrates an example of a downlink transmission scheduled on a cell during the same symbol period as an uplink transmission scheduled on another cell, the above techniques may apply to any combination of uplink transmissions, downlink transmissions, or sidelink transmissions scheduled simultaneously on resources of different cells. 
       FIG. 14  illustrates an example of resources  1400  allocated for communication using carrier aggregation in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  during slot  1405 - a  of a PCell  1410 - a  and during slots  1405 - b  and  1405 - c  of an SCell  1410 - b . Slots  1405  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  1405  may be based on a nominal symbol period duration for symbols within the slot  1405 , a numerology associated with one or more symbols within the slot  1405 , a number of control symbols within the slot  1405 , or a quantity of symbols of a specific link direction within the slot  1405  within a carrier or across two or more carriers. In some cases, the structure of slots  1405  used for communication on different carriers may be different. For example, symbols included in slot  1405 - a  of PCell  1410 - a  may have a longer duration than symbols included in slots  1405 - b  and  1405 - c  of SCell  1410 - b.    
     Slot  1405 - a  of PCell  1410 - a  may overlap with slots  1405 - b  and  1405 - c  of SCell  1410 - b  in the time domain, and each slot  1405  may be self-contained. That is, each slot  1405  may include symbols allocated for uplink communication and symbols allocated for downlink communication. Slots  1405 - a  and  1405 - b  may be downlink centric slots, and slot  1405 - c  may be an uplink centric slot. Slots  1405 - a  and  1405 - b  may each include symbols allocated for communication of downlink control information  1415 , downlink data  1420 , and uplink control information  1425 , and slot  1405 - c  may include symbols allocated for downlink control information  1415 , uplink data  1430 , and uplink control information  1425 . Slots  1405  may also include guard periods  1435  for transitioning between uplink and downlink configurations. 
     As illustrated, the UE  115  may be scheduled for simultaneous uplink and downlink communication on resources of different carriers in some symbols (e.g., symbol  1445 ). However, half-duplex UEs  115  may not be able to support simultaneous uplink and downlink communication. Further, if PCell  1410 - a  and SCell  1410 - b  are within the same frequency band, uplink transmissions and downlink transmissions scheduled during the same symbol period on these cells may interfere with each other (e.g., for half-duplex UEs  115  and full-duplex UEs  115 ). Accordingly, it may be appropriate for a wireless communications system to support techniques for preventing conflicting transmissions. 
     The UE  115  may support efficient techniques for coordinating with the base station  105  to prevent conflicting transmissions. In some cases, the base station  105  may establish different priorities for communication on resources of PCell  1410 - a  and for communication on resources of SCell  1410 - b , and the base station  105  may signal this information to the UE  115 . In some cases, the signaling may include an indication of a cell identity of the cell with the higher priority, and the UE  115  may prioritize communication on resources of that cell based on receiving the cell identity. The cell identity may indicate that the cell is a PCell, PSCell, or SCell. In the example of  FIG. 14 , the base station  105  may prioritize communication on PCell  1410 - a  (i.e., PCell driven design). 
     Accordingly, the UE  115  scheduled for simultaneous uplink and downlink communication may refrain from communicating on resources of SCell  1410 - b . For example, the UE  115  may refrain from communicating during symbol  1445  of SCell  1410 - b  (e.g., refrain from transmitting uplink control information  1425 ). Similarly, the UE  115  may refrain from communicating during symbols  1450  of SCell  1410 - b  (e.g., refrain from transmitting uplink data  1430 ). The process of refraining from transmitting or receiving on specific symbols may be referred to as symbol blanking, and symbol  1445  and symbols  1450  may be referred to as blanked symbols  1440 . 
     As indicated above, the decision to communicate on specific symbols may be based on the configuration of the carrier with the higher priority. In some cases, rather than refraining from transmitting during specific symbols, the UE  115  or base station  105  may align transmissions with the prioritized cell. For example, if symbols of a prioritized cell are allocated for downlink communication, the base station  105  or UE  115  may use the corresponding symbol or symbols of another cell for downlink communication. In such cases, the UE  115  may monitor for control information on one carrier and process data on another carrier. In addition, for full-duplex UEs  115 , the UE  115  may determine whether to perform symbol blanking based on whether the PCell  1410 - a  and SCell  1410 - b  are within the same frequency band (e.g., for intra-band carrier aggregation). 
     Although  FIG. 14  illustrates an example of symbols of PCell  1410 - a  with longer durations than symbols of SCell  1410 - b , the above techniques apply to various combinations of numerologies for different cells. For example, symbols of SCell  1410 - b  may have longer durations than symbols of PCell  1410 - a . Further, although  FIG. 14  illustrates an example of a downlink transmission scheduled on a cell during the same symbol period as an uplink transmission scheduled on another cell, the above techniques may apply to any combination of uplink transmissions, downlink transmissions, or sidelink transmissions scheduled simultaneously on resources of different carriers. 
       FIG. 15  illustrates an example of resources  1500  allocated for communication using carrier aggregation in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  during slot  1505 - a  of a PCell  1510 - a  and during slots  1505 - b  and  1505 - c  of an SCell  1510 - b . Slots  1505  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  1505  may be based on a nominal symbol period duration for symbols within the slot  1505 , a numerology associated with one or more symbols within the slot  1505 , a number of control symbols within the slot  1505 , or a quantity of symbols of a specific link direction within the slot  1505  within a carrier or across two or more carriers. In some cases, the structure of slots  1505  used for communication on different carriers may be different. For example, symbols included in slot  1505 - a  of PCell  1510 - a  may have a longer duration than symbols included in slots  1505 - b  and  1505 - c  of SCell  1510 - b.    
     Slot  1505 - a  of PCell  1510 - a  may overlap with slots  1505 - b  and  1505 - c  of SCell  1510 - b  in the time domain, and each slot  1505  may be self-contained. That is, each slot  1505  may include symbols allocated for uplink communication and symbols allocated for downlink communication. Slots  1505 - a  and  1505 - b  may be downlink centric slots, and slot  1505 - c  may be an uplink centric slot. Slots  1505 - a  and  1505 - b  may each include symbols allocated for communication of downlink control information  1515 , downlink data  1520 , and uplink control information  1525 , and slot  1505 - c  may include symbols allocated for downlink control information  1515 , uplink data  1530 , and uplink control information  1525 . Slots  1505  may also include guard periods  1535  for transitioning between uplink and downlink configurations. 
     As illustrated, the UE  115  may be scheduled for simultaneous uplink and downlink communication on resources of different carriers in some symbols (e.g., symbol  1545 ). However, half-duplex UEs  115  may not be able to support simultaneous uplink and downlink communication. Further, if PCell  1510 - a  and SCell  1510 - b  are within the same frequency band, uplink transmissions and downlink transmissions scheduled during the same symbol period on these cells may interfere with each other (e.g., for half-duplex UEs  115  and full-duplex UEs  115 ). Accordingly, it may be appropriate for a wireless communications system to support techniques for preventing conflicting transmissions. 
     The UE  115  may support efficient techniques for coordinating with the base station  105  to prevent conflicting transmissions. In some cases, the base station  105  may establish different priorities for communication on resources of PCell  1510 - a  and for communication on resources of SCell  1510 - b , and the base station  105  may signal this information to the UE  115 . In some cases, the signaling may include an indication of a cell identity of the cell with the higher priority, and the UE  115  may prioritize communication on resources of that cell based on receiving the cell identity. The cell identity may indicate that the cell is a PCell, PSCell, or SCell. In the example of  FIG. 15 , the base station  105  may prioritize communication on SCell  1510 - b  (i.e., SCell driven design). 
     Accordingly, the UE  115  scheduled for simultaneous uplink and downlink communication may refrain from communicating on resources of PCell  1510 - a . For example, the UE  115  may refrain from communicating during symbol  1545  of PCell  1510 - a  (e.g., refrain from monitoring for downlink control information  1515 ). Similarly, the UE  115  may refrain from communicating during symbols  1550  of PCell  1510 - a  (e.g., refrain from monitoring for downlink data  1520 ). In some cases, the base station  105  may refrain from transmitting downlink data  1520  on symbol  1545  and symbols  1550  of PCell  1510 - a . The process of refraining from transmitting or receiving on specific symbols may be referred to as symbol blanking, and symbol  1545  and symbols  1550  may be referred to as blanked symbols  1540 . 
     As indicated above, the decision to communicate on specific symbols may be based on the configuration of the carrier with the higher priority. In some cases, rather than refraining from transmitting during specific symbols, the UE  115  or base station  105  may align transmissions with the prioritized cell. For example, if symbols of a prioritized cell are allocated for downlink communication, the base station  105  or UE  115  may use the corresponding symbol or symbols of another cell for downlink communication. In such cases, the UE  115  may monitor for control information on one carrier and process data on another carrier. In addition, for full-duplex UEs  115 , the UE  115  may determine whether to perform symbol blanking based on whether the PCell  1510 - a  and SCell  1510 - b  are within the same frequency band (e.g., for intra-band carrier aggregation). 
     Although  FIG. 15  illustrates an example of symbols of PCell  1510 - a  with longer durations than symbols of SCell  1510 - b , the above techniques apply to various combinations of numerologies for different cells. For example, symbols of SCell  1510 - b  may have longer durations than symbols of PCell  1510 - a . Further, although  FIG. 15  illustrates an example of a downlink transmission scheduled on a cell during the same symbol period as an uplink transmission scheduled on another cell, the above techniques may apply to any combination of uplink transmissions, downlink transmissions, or sidelink transmissions scheduled simultaneously on resources of different cells. 
       FIG. 16  illustrates an example of resources  1600  allocated for communication using carrier aggregation in a system that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. A base station  105  may communicate with a UE  115  during slots  1605 - a  and  1605 - b  of a PCell  1610 - a  and during slot  1605 - c  of an SCell  1610 - b . Slots  1605  may include a number of symbols each allocated for communication in a specific link direction or for transitioning between uplink, downlink, and sidelink configurations. The structure of each slot  1605  may be based on a nominal symbol period duration for symbols within the slot  1605 , a numerology associated with one or more symbols within the slot  1605 , a number of control symbols within the slot  1605 , or a quantity of symbols of a specific link direction within the slot  1605  within a carrier or across two or more carriers. In some cases, the structure of slots  1605  used for communication on different carriers may be different. For example, symbols included in slots  1605 - a  and  1605 - b  of PCell  1610 - a  may have a shorter duration than symbols included in slot  1605 - c  of SCell  1610 - b.    
     Slot  1605 - c  of SCell  1610 - b  may overlap with slots  1605 - a  and  1605 - b  of PCell  1610 - a  in the time domain, and each slot  1605  may be self-contained. That is, each slot  1605  may include symbols allocated for uplink communication and symbols allocated for downlink communication. Each slot  1605  may be a downlink centric slot. Specifically, slots  1605  may each include symbols allocated for communication of downlink control information  1615 , downlink data  1620 , and uplink control information  1625 . Slots  1605  may also include guard periods  1630  for transitioning between uplink and downlink configurations. As illustrated, the UE  115  may be scheduled for simultaneous uplink and downlink communication on resources of different carriers in some symbols (e.g., symbol  1640 ). However, half-duplex UEs  115  may not be able to support simultaneous uplink and downlink communication. Further, if PCell  1610 - a  and SCell  1610 - b  are within the same frequency band, uplink transmissions and downlink transmissions scheduled during the same symbol period on these cells may interfere with each other (e.g., for half-duplex UEs  115  and full-duplex UEs  115 ). Accordingly, it may be appropriate for a wireless communications system to support techniques for preventing conflicting transmissions. 
     The UE  115  may support efficient techniques for coordinating with the base station  105  to prevent conflicting transmissions. In some cases, the base station  105  may establish different priorities for communication on resources of PCell  1610 - a  and for communication on resources of SCell  1610 - b , and the base station  105  may signal this information to the UE  115 . In some cases, the signaling may include an indication of a cell identity of the cell with the higher priority, and the UE  115  may prioritize communication on resources of that cell based on receiving the cell identity. The cell identity may indicate that the cell is a PCell, PSCell, or SCell. In the example of  FIG. 16 , the base station  105  may prioritize communication on PCell  1610 - a  (i.e., PCell driven design). 
     Accordingly, the UE  115  scheduled for simultaneous uplink and downlink communication may refrain from communicating on resources of SCell  1610 - b . For example, the UE  115  may refrain from communicating during symbol  1640  of SCell  1610 - b  (e.g., refrain from monitoring for downlink data  1620 ). Similarly, the UE  115  may refrain from communicating during symbols  1645  of SCell  1610 - b  (e.g., refrain from transmitting uplink control information  1625 ). The process of refraining from transmitting or receiving on specific symbols may be referred to as symbol blanking, and symbol  1640  and symbols  1645  may be referred to as blanked symbols  1635 . 
     As indicated above, the decision to communicate on specific symbols may be based on a configuration of the carrier with the higher priority. In some cases, rather than refraining from transmitting during specific symbols, the UE  115  or base station  105  may align transmissions with the prioritized cell. For example, if symbols of a prioritized cell are allocated for downlink communication, the base station  105  or UE  115  may use the corresponding symbol or symbols of another cell for downlink communication. In such cases, the UE  115  may monitor for control information on one carrier and process data on another carrier. In addition, for full-duplex UEs  115 , the UE  115  may determine whether to perform symbol blanking based on whether the PCell  1610 - a  and SCell  1610 - b  are within the same frequency band (e.g., for intra-band carrier aggregation). 
     Although  FIG. 16  illustrates an example of symbols of PCell  1610 - a  with shorter durations than symbols of SCell  1610 - b , the above techniques apply to various combinations of numerologies for different cells. For example, symbols of PCell  1610 - a  may have longer durations than symbols of SCell  1610 - b . Further, although  FIG. 16  illustrates an example of a downlink transmission scheduled on a cell during the same symbol period as an uplink transmission scheduled on another cell, the above techniques may apply to any combination of uplink transmissions, downlink transmissions, or sidelink transmissions scheduled simultaneously on resources of different cells. 
       FIG. 17  shows a block diagram  1700  of a wireless device  1705  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Wireless device  1705  may be an example of aspects of a UE  115  as described with reference to  FIG. 1 . Wireless device  1705  may include receiver  1710 , UE communication manager  1715 , and transmitter  1720 . Wireless device  1705  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     Receiver  1710  may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to half-duplex operation in NR systems, etc.). Information may be passed on to other components of the device. The receiver  1710  may be an example of aspects of the transceiver  2035  described with reference to  FIG. 20 . 
     UE communication manager  1715  may be an example of aspects of the UE communication manager  2015  described with reference to  FIG. 20 . UE communication manager  1715  and/or at least some of its various sub-components 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 of the UE communication manager  1715  and/or at least some of its various sub-components may be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. 
     The UE communication manager  1715  and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, UE communication manager  1715  and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, UE communication manager  1715  and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure. 
     UE communication manager  1715  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot, and determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based on a structure of the first slot. UE communication manager  1715  may then coordinate with receiver  1710  and transmitter  1720  to communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. In some cases, the communication in the first link direction and the second link direction is based on a capability of the UE  115 . In some cases, the UE  115  may operate in a half-duplex mode. 
     The UE communication manager  1715  may receive signaling from a node that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier, and identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. UE communication manager  1715  may then coordinate with receiver  1710  and transmitter  1720  to communicate on resources of the first carrier or the second carrier during the symbol period based on a capability of the UE  115 , and refrain from communicating on resources of the first carrier or the second carrier during the symbol period. 
     In some cases, the communication on resources of the first or second carrier may be based on a cell identity of the first carrier or the second carrier, or both. In some cases, the cell identity indicates at least one of a PCell, PSCell, or a SCell. In some cases, the communication on resources of the first or second carrier may be based on a configuration of at least one of the first carrier and the second carrier. In some cases, the first carrier and the second carrier are within a same frequency band. 
     Transmitter  1720  may transmit signals generated by other components of the device. In some examples, the transmitter  1720  may be collocated with a receiver  1710  in a transceiver module. For example, the transmitter  1720  may be an example of aspects of the transceiver  2035  described with reference to  FIG. 20 . The transmitter  1720  may include a single antenna, or it may include a set of antennas. 
       FIG. 18  shows a block diagram  1800  of a wireless device  1805  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Wireless device  1805  may be an example of aspects of a wireless device  1705  or a UE  115  as described with reference to  FIGS. 1 and 17 . Wireless device  1805  may include receiver  1810 , UE communication manager  1815 , and transmitter  1820 . Wireless device  1805  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     Receiver  1810  may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to half-duplex operation in NR systems, etc.). Information may be passed on to other components of the device. The receiver  1810  may be an example of aspects of the transceiver  2035  described with reference to  FIG. 20 . 
     UE communication manager  1815  may be an example of aspects of the UE communication manager  2015  described with reference to  FIG. 20 . UE communication manager  1815  may include resource manager  1825 , transition period manager  1830 , and carrier aggregation manager  1835 . 
     Resource manager  1825  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink, or a sidelink, and is different from the first link direction. In some cases, the first slot includes one slot of a set of adjacent slots each designated for communication in the first link direction. 
     Transition period manager  1830  may determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based on a structure of the first slot. In some cases, the duration of the transition period may include one or more symbol periods, and transition period manager  1830  may coordinate with receiver  1810  and transmitter  1820  to refrain from communicating during the one or more symbol periods. In some cases, the structure of the first slot includes at least one of a nominal symbol period duration for symbols within the first slot, a numerology associated with one or more symbols within the first slot, a number of control symbols within the first slot, or a quantity of symbols of a link direction within the first slot within a carrier or across two or more carriers. 
     Additionally, UE communication manager  1815  may coordinate with receiver  1810  and transmitter  1820  to communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. In some cases, the communication in the first link direction and the second link direction is based on a capability of the UE  115 . In some cases, the UE  115  may operate in a half-duplex mode. 
     Carrier aggregation manager  1835  may receive signaling from a node that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier. 
     Resource manager  1825  may identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink or a sidelink, and is different from the first link direction. 
     Further, UE communication manager  1815  may coordinate with receiver  1810  and transmitter  1820  to communicate on resources of the first carrier or the second carrier during the symbol period based on a capability of the UE  115  and refrain from communicating on resources of the first carrier or the second carrier during the symbol period. In some cases, the communication on resources of the first or second carrier may be based on a cell identity of the first carrier or the second carrier, or both. In some cases, the cell identity indicates at least one of a PCell, PSCell, or a SCell. In some cases, the communication on resources of the first or second carrier may be based on a configuration of at least one of the first carrier and the second carrier. In some cases, the first carrier and the second carrier are within a same frequency band. 
     Transmitter  1820  may transmit signals generated by other components of the device. In some examples, the transmitter  1820  may be collocated with a receiver  1810  in a transceiver module. For example, the transmitter  1820  may be an example of aspects of the transceiver  2035  described with reference to  FIG. 20 . The transmitter  1820  may include a single antenna, or it may include a set of antennas. 
       FIG. 19  shows a block diagram  1900  of a UE communication manager  1915  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The UE communication manager  1915  may be an example of aspects of a UE communication manager  1715 , a UE communication manager  1815 , or a UE communication manager  2015  described with reference to  FIGS. 17, 18, and 20 . The UE communication manager  1915  may include resource manager  1920 , transition period manager  1925 , carrier aggregation manager  1930 , timing advance component  1935 , TDD communications manager  1940 , and FDD communications manager  1945 . Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     Resource manager  1920  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink, or a sidelink, and is different from the first link direction. In some cases, the first slot includes one slot of a set of adjacent slots each designated for communication in the first link direction. 
     Transition period manager  1925  may determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based on a structure of the first slot. In some cases, the duration of the transition period may include one or more symbol periods, and transition period manager  1925  may coordinate with a receiver and transmitter to refrain from communicating during the one or more symbol periods. In some cases, the structure of the first slot includes at least one of a nominal symbol period duration for symbols within the first slot, a numerology associated with one or more symbols within the first slot, a number of control symbols within the first slot, or a quantity of symbols of a link direction within the first slot within a carrier or across two or more carriers. 
     Additionally, UE communication manager  1915  may coordinate with a receiver and transmitter to communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. In some cases, the communication in the first link direction and the second link direction is based on a capability of a UE  115 . In some cases, the UE  115  may operate in a half-duplex mode. In some cases, TDD communications manager  1940  may coordinate with a receiver and transmitter to communicate during the first symbol period and the second symbol period on resources of the same carrier. In other cases, FDD communications manager  1945  may coordinate with a receiver and transmitter to communicate during the first symbol period on resources of a first carrier and during the second symbol period on resources of a second carrier. 
     Timing advance component  1935  may identify a timing advance associated with the first symbol period and coordinate with a transmitter and receiver to communicate during the first symbol period based on the timing advance. In some cases, the timing advance is based on a numerology of the first slot. In some cases, timing advance component  1935  may receive the timing advance associated with the first symbol period in one of a MIB, SIB, or an RRC message. 
     Carrier aggregation manager  1930  may receive signaling from a node that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier. 
     Resource manager  1825  may identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink or a sidelink, and is different from the first link direction. 
     Further, UE communication manager  1915  may coordinate with a receiver and transmitter to communicate on resources of the first carrier or the second carrier during the symbol period based on a capability of the UE  115 , and refrain from communicating on resources of the first carrier or the second carrier during the symbol period. In some cases, the communication on resources of the first or second carrier may be based on a cell identity of the first carrier or the second carrier, or both. In some cases, the cell identity indicates at least one of a PCell, PSCell, or a SCell. In some cases, the communication on resources of the first or second carrier may be based on a configuration of at least one of the first carrier and the second carrier. In some cases, the first carrier and the second carrier are within a same frequency band. 
       FIG. 20  shows a diagram of a system  2000  including a device  2005  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Device  2005  may be an example of or include the components of wireless device  1705 , wireless device  1805 , or a UE  115  as described above, e.g., with reference to  FIGS. 1, 17 and 18 . Device  2005  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE communication manager  2015 , processor  2020 , memory  2025 , software  2030 , transceiver  2035 , antenna  2040 , and I/O controller  2045 . These components may be in electronic communication via one or more busses (e.g., bus  2010 ). Device  2005  may communicate wirelessly with one or more base stations  105 . 
     Processor  2020  may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (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, processor  2020  may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor  2020 . Processor  2020  may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting half-duplex operation in NR systems). 
     Memory  2025  may include random access memory (RAM) and read only memory (ROM). The memory  2025  may store computer-readable, computer-executable software  2030  including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory  2025  may contain, among other things, a basic input/output system (BIOS) which may control basic hardware and/or software operation such as the interaction with peripheral components or devices. 
     Software  2030  may include code to implement aspects of the present disclosure, including code to support half-duplex operation in NR systems. Software  2030  may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software  2030  may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein. 
     Transceiver  2035  may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver  2035  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  2035  may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas. 
     In some cases, the wireless device may include a single antenna  2040 . However, in some cases the device may have more than one antenna  2040 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. 
     I/O controller  2045  may manage input and output signals for device  2005 . I/O controller  2045  may also manage peripherals not integrated into device  2005 . In some cases, I/O controller  2045  may represent a physical connection or port to an external peripheral. In some cases, I/O controller  2045  may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In other cases, I/O controller  2045  may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, I/O controller  2045  may be implemented as part of a processor. In some cases, a user may interact with device  2005  via I/O controller  2045  or via hardware components controlled by I/O controller  2045 . 
       FIG. 21  shows a block diagram  2100  of a wireless device  2105  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Wireless device  2105  may be an example of aspects of a base station  105  as described with reference to  FIG. 1 . Wireless device  2105  may include receiver  2110 , base station communication manager  2115 , and transmitter  2120 . Wireless device  2105  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     Receiver  2110  may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to half-duplex operation in NR systems, etc.). Information may be passed on to other components of the device. The receiver  2110  may be an example of aspects of the transceiver  2435  described with reference to  FIG. 24 . 
     Base station communication manager  2115  may be an example of aspects of the base station communication manager  2415  described with reference to  FIG. 24 . Base station communication manager  2115  and/or at least some of its various sub-components 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 of the base station communication manager  2115  and/or at least some of its various sub-components may be executed by a general-purpose processor, a DSP, an ASIC, 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 in the present disclosure. 
     The base station communication manager  2115  and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, base station communication manager  2115  and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, base station communication manager  2115  and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure. 
     Base station communication manager  2115  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot, and determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based on a structure of the first slot. Base station communication manager  2115  may coordinate with receiver  2110  and transmitter  2120  to communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. 
     The base station communication manager  2115  may transmit signaling to a UE  115  that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier, and identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. Base station communication manager  2115  may coordinate with receiver  2110  and transmitter  2120  to communicate on resources of the first carrier or the second carrier during the symbol period based on a capability of the UE  115  and refrain from communicating on resources of the first carrier or the second carrier during the symbol period. 
     In some cases, the UE  115  may operate in a half-duplex mode. In some cases, the communication on resources of the first carrier or the second carrier during the symbol period may be based on a cell identity of the first carrier or the second carrier. In some cases, the cell identify indicates at least one of a PCell, PSCell, or an SCell. In some cases, the communication on resources of the first carrier or the second carrier during the symbol period is based on a configuration of at least one of the first carrier and the second carrier. In some cases, the first carrier and the second carrier are within a same frequency band. 
     Transmitter  2120  may transmit signals generated by other components of the device. In some examples, the transmitter  2120  may be collocated with a receiver  2110  in a transceiver module. For example, the transmitter  2120  may be an example of aspects of the transceiver  2435  described with reference to  FIG. 24 . The transmitter  2120  may include a single antenna, or it may include a set of antennas. 
       FIG. 22  shows a block diagram  2200  of a wireless device  2205  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Wireless device  2205  may be an example of aspects of a wireless device  2105  or a base station  105  as described with reference to  FIGS. 1 and 21 . Wireless device  2205  may include receiver  2210 , base station communication manager  2215 , and transmitter  2220 . Wireless device  2205  may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses). 
     Receiver  2210  may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to half-duplex operation in NR systems, etc.). Information may be passed on to other components of the device. The receiver  2210  may be an example of aspects of the transceiver  2435  described with reference to  FIG. 24 . 
     Base station communication manager  2215  may be an example of aspects of the base station communication manager  2415  described with reference to  FIG. 24 . Base station communication manager  2215  may include resource manager  2225 , transition period manager  2230 , and carrier aggregation manager  2235 . 
     Resource manager  2225  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink, or a sidelink, and is different from the first link direction. In some cases, the first slot includes one slot of a set of adjacent slots each designated for communication in the first link direction. 
     Transition period manager  2230  may determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based on a structure of the first slot. In some cases, the duration of the transition period may include one or more symbol periods, and transition period manager  2230  may coordinate with receiver  2210  and transmitter  2220  to refrain from communicating during the one or more symbol periods. In some cases, the structure of the first slot includes at least one of a nominal symbol period duration for symbols within the first slot, a numerology associated with one or more symbols within the first slot, a number of control symbols within the first slot, or a quantity of symbols of a link direction within the first slot within a carrier or across two or more carriers, or both. 
     Base station communication manager  2215  may coordinate with receiver  2210  and transmitter  2220  to communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. 
     Carrier aggregation manager  2235  may transmit signaling to a UE  115  that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier. 
     Resource manager  2225  may identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink, or a sidelink, and is different from the first link direction. 
     Base station communication manager  2215  may coordinate with receiver  2210  and transmitter  2220  to communicate on resources of the first carrier or the second carrier during the symbol period based on a capability of the UE  115  and refrain from communicating on resources of the first carrier or the second carrier during the symbol period. In some cases, the UE  115  may operate in a half-duplex mode. In some cases, the communication on resources of the first carrier or the second carrier during the symbol period may be based on a cell identity of the first carrier or the second carrier. In some cases, the cell identify indicates at least one of a PCell, PSCell, or an SCell. In some cases, the communication on resources of the first carrier or the second carrier during the symbol period is based on a configuration of at least one of the first carrier and the second carrier. In some cases, the first carrier and the second carrier are within a same frequency band. 
     Transmitter  2220  may transmit signals generated by other components of the device. In some examples, the transmitter  2220  may be collocated with a receiver  2210  in a transceiver module. For example, the transmitter  2220  may be an example of aspects of the transceiver  2435  described with reference to  FIG. 24 . The transmitter  2220  may include a single antenna, or it may include a set of antennas. 
       FIG. 23  shows a block diagram  2300  of a base station communication manager  2315  that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The base station communication manager  2315  may be an example of aspects of a base station communication manager  2415  described with reference to  FIGS. 21, 22, and 24 . The base station communication manager  2315  may include resource manager  2320 , transition period manager  2325 , carrier aggregation manager  2330 , timing advance component  2335 , TDD communications manager  2340 , and FDD communications manager  2345 . Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     Resource manager  2320  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink, or a sidelink, and is different from the first link direction. In some cases, the first slot includes one slot of a set of adjacent slots each designated for communication in the first link direction. 
     Transition period manager  2325  may determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based on a structure of the first slot. In some cases, the duration of the transition period may include one or more symbol periods, and transition period manager  2325  may coordinate with a receiver and transmitter to refrain from communicating during the one or more symbol periods. In some cases, the structure of the first slot includes at least one of a nominal symbol period duration for symbols within the first slot, a numerology associated with one or more symbols within the first slot, a number of control symbols within the first slot, or a quantity of symbols of a link direction within the first slot within a carrier or across two or more carriers, or both. 
     Base station communication manager  2315  may coordinate with a receiver and transmitter to communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. In some cases, TDD communications manager  2340  may coordinate with the receiver and transmitter to communicate during the first symbol period and the second symbol period on resources of a same carrier. In other cases, FDD communications manager  2345  may coordinate with the receiver and transmitter to communicate during the first symbol period on resources of a first carrier and during the second symbol period on resources of a second carrier. 
     Timing advance component  2335  may identify a timing advance associated with the first symbol period and coordinate with a transmitter or receiver to communicate during the first symbol period based on the timing advance. In some cases, the timing advance is based on a numerology of the first slot. In some cases, timing advance component  2335  may transmit the timing advance associated with the first symbol period in one of a MIB, SIB, or an RRC message. 
     Carrier aggregation manager  2330  may transmit signaling to a UE  115  that indicates a carrier aggregation configuration including a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier. 
     Resource manager  2320  may identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. In some cases, the first link direction includes one of a downlink, an uplink, or a sidelink, and the second link direction includes one of a downlink, an uplink, or a sidelink, and is different from the first link direction. 
     Base station communication manager  2315  may coordinate with a receiver and transmitter to communicate on resources of the first carrier or the second carrier during the symbol period based on a capability of the UE  115  and refrain from communicating on resources of the first carrier or the second carrier during the symbol period. In some cases, the UE  115  may operate in a half-duplex mode. In some cases, the communication on resources of the first carrier or the second carrier during the symbol period may be based on a cell identity of the first carrier or the second carrier. In some cases, the cell identify indicates at least one of a PCell, PSCell, or an SCell. In some cases, the communication on resources of the first carrier or the second carrier during the symbol period is based on a configuration of at least one of the first carrier and the second carrier. In some cases, the first carrier and the second carrier are within a same frequency band. 
       FIG. 24  shows a diagram of a system  2400  including a device  2405 , such as a base station, that supports half-duplex operation in NR systems in accordance with various aspects of the present disclosure. Device  2405  may be an example of or include the components of base station  105  as described above, e.g., with reference to  FIG. 1 . Device  2405  may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including base station communication manager  2415 , processor  2420 , memory  2425 , software  2430 , transceiver  2435 , antenna  2440 , network communications manager  2445 , and inter-base station signaling manager  2450 . These components may be in electronic communication via one or more busses (e.g., bus  2410 ). Device  2405  may communicate wirelessly with one or more UEs  115 . 
     Processor  2420  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, processor  2420  may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor  2420 . Processor  2420  may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting half-duplex operation in NR systems). 
     Memory  2425  may include RAM and ROM. The memory  2425  may store computer-readable, computer-executable software  2430  including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory  2425  may contain, among other things, a BIOS which may control basic hardware and/or software operation such as the interaction with peripheral components or devices. 
     Software  2430  may include code to implement aspects of the present disclosure, including code to support half-duplex operation in NR systems. Software  2430  may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software  2430  may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein. 
     Transceiver  2435  may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver  2435  may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver  2435  may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas. 
     In some cases, the wireless device may include a single antenna  2440 . However, in some cases the device may have more than one antenna  2440 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. 
     Network communications manager  2445  may manage communications with the core network (e.g., via one or more wired backhaul links). For example, the network communications manager  2445  may manage the transfer of data communications for client devices, such as one or more UEs  115 . 
     Inter-base station signaling manager  2450  may manage communications with other base station  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-base station signaling manager  2450  may coordinate scheduling for transmissions to UEs  115  for various interference mitigation techniques such as beamforming or joint transmission. In some examples, inter-base station signaling  2450  may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations  105 . 
       FIG. 25  shows a flowchart illustrating a method  2500  for half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The operations of method  2500  may be implemented by a UE  115  or its components as described herein. For example, the operations of method  2500  may be performed by a UE communication manager as described with reference to  FIGS. 17 through 20 . In some examples, the UE  115  may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE  115  may perform aspects of the functions described below using special-purpose hardware. 
     At block  2505 , the UE  115  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot. The operations of block  2505  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2505  may be performed by a resource manager as described with reference to  FIGS. 17 through 20 . 
     At block  2510 , the UE  115  may determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based at least in part on a structure of the first slot. The operations of block  2510  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2510  may be performed by a transition period manager as described with reference to  FIGS. 17 through 20 . 
     At block  2515 , the UE  115  may communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. The operations of block  2515  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2515  may be performed by a transmitter or receiver as described with reference to  FIGS. 17 through 20 . 
       FIG. 26  shows a flowchart illustrating a method  2600  for half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The operations of method  2600  may be implemented by a base station  105  or its components as described herein. For example, the operations of method  2600  may be performed by a base station communication manager as described with reference to  FIGS. 21 through 24 . In some examples, the base station  105  may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station  105  may perform aspects of the functions described below using special-purpose hardware. 
     At block  2605 , the base station  105  may identify a first symbol period designated for communication in a first link direction and a second symbol period designated for communication in a second link direction, where the first symbol period is within a first slot and the second symbol period is within the first slot or a second slot. The operations of block  2605  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2605  may be performed by a resource manager as described with reference to  FIGS. 21 through 24 . 
     At block  2610 , the base station  105  may determine a duration of a transition period between the first symbol period and the second symbol period, where the duration of the transition period is based at least in part on a structure of the first slot. The operations of block  2610  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2610  may be performed by a transition period manager as described with reference to  FIGS. 21 through 24 . 
     At block  2615 , the base station  105  may communicate in the first link direction during the first symbol period and in the second link direction during the second symbol period. The operations of block  2615  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2615  may be performed by a transmitter or receiver as described with reference to  FIGS. 21 through 24 . 
       FIG. 27  shows a flowchart illustrating a method  2700  for half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The operations of method  2700  may be implemented by a UE  115  or its components as described herein. For example, the operations of method  2700  may be performed by a UE communication manager as described with reference to  FIGS. 17 through 20 . In some examples, the UE  115  may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE  115  may perform aspects of the functions described below using special-purpose hardware. 
     At block  2705 , the UE  115  may receive signaling from a node that indicates a carrier aggregation configuration comprising a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier. The operations of block  2705  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2705  may be performed by a carrier aggregation manager as described with reference to  FIGS. 17 through 20 . 
     At block  2710 , the UE  115  may identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. The operations of block  2710  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2710  may be performed by a resource manager as described with reference to  FIGS. 17 through 20 . 
     At block  2715 , the UE  115  may communicate on resources of the first carrier or the second carrier during the symbol period based at least in part on a capability of the UE  115 . The operations of block  2715  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2715  may be performed by a transmitter or receiver as described with reference to  FIGS. 17 through 20 . 
       FIG. 28  shows a flowchart illustrating a method  2800  for half-duplex operation in NR systems in accordance with various aspects of the present disclosure. The operations of method  2800  may be implemented by a base station  105  or its components as described herein. For example, the operations of method  2800  may be performed by a base station communication manager as described with reference to  FIGS. 21 through 24 . In some examples, a base station  105  may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station  105  may perform aspects of the functions described below using special-purpose hardware. 
     At block  2805 , the base station  105  may transmit signaling to a UE  115  that indicates a carrier aggregation configuration comprising a first carrier and a second carrier, where a numerology or slot duration of the first carrier is different from a numerology or slot duration of the second carrier. The operations of block  2805  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2805  may be performed by a carrier aggregation manager as described with reference to  FIGS. 21 through 24 . 
     At block  2810 , the base station  105  may identify a symbol period designated for communication in a first link direction on resources of the first carrier and designated for communication in a second link direction on resources of the second carrier. The operations of block  2810  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2810  may be performed by a resource manager as described with reference to  FIGS. 21 through 24 . 
     At block  2815 , the base station  105  may communicate on resources of the first carrier or the second carrier during the symbol period based at least in part on a capability of the UE  115 . The operations of block  2815  may be performed according to the methods described with reference to  FIGS. 1 through 12 . In certain examples, aspects of the operations of block  2815  may be performed by a transmitter or receiver as described with reference to  FIGS. 21 through 24 . 
     It should be noted that the methods described above describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Furthermore, aspects from two or more of the methods may be combined. 
     Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases may be commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). 
     An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications system (UMTS). 3GPP LTE and LTE-A are releases of Universal Mobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and GSM are described in documents from the organization named “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies. While aspects an LTE or an NR system may be described for purposes of example, and LTE or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE or NR applications. 
     In LTE/LTE-A networks, including such networks described herein, the term evolved node B (eNB) may be generally used to describe the base stations. The wireless communications system or systems described herein may include a heterogeneous LTE/LTE-A or NR network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB, next generation NodeB (gNB) or base station may provide communication coverage for a macro cell, a small cell, or other types of cell. The term “cell” may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context. 
     Base stations may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, eNB, gNB, Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area for a base station may be divided into sectors making up only a portion of the coverage area. The wireless communications system or systems described herein may include base stations of different types (e.g., macro or small cell base stations). The UEs described herein may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like. There may be overlapping geographic coverage areas for different technologies. 
     A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell is a lower-powered base station, as compared with a macro cell, that may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells (e.g., component carriers). 
     The wireless communications system or systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, the base stations may have different frame timing, and transmissions from different base stations may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations. 
     The downlink transmissions described herein may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. Each communication link described herein—including, for example, wireless communications system  100  and  200  of  FIGS. 1 and 2 —may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies). 
     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 “exemplary” 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, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     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. 
     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 above 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 modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, 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 conventional 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 above can 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. Also, as used herein, including in the claims, “or” as used in a list of items (for example, 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 exemplary 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.” 
     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 can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may comprise RAM, ROM, electrically erasable programmable read only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. 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, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave are included in the definition of 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. 
     The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled 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.