Patent Publication Number: US-2023163831-A1

Title: Beam switching in near-field operations

Description:
INTRODUCTION 
     Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for managing beam switching in near-field operations. 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, or other similar types of services. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources with those users (e.g., bandwidth, transmit power, or other resources). Multiple-access technologies can rely on any of code division, time division, frequency division orthogonal frequency division, single-carrier frequency division, or time division synchronous code division, to name a few. These and other multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. 
     Although wireless communication systems have made great technological advancements over many years, challenges still exist. For example, complex and dynamic environments can still attenuate or block signals between wireless transmitters and wireless receivers, undermining various established wireless channel measuring and reporting mechanisms, which are used to manage and optimize the use of finite wireless channel resources. Consequently, there exists a need for further improvements in wireless communications systems to overcome various challenges. 
     SUMMARY 
     One aspect provides a method for wireless communication by a user equipment (UE), comprising: receiving, from a network entity, a first indication indicating a same quasi co-location (QCL) mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs, wherein transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity; and selecting one of the multiple receive beams corresponding to the group of transmit and receive beam pairs, based on the distance between the UE and the network entity. 
     Another aspect provides a method for wireless communication by a network entity, comprising: transmitting, to a UE, a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs, wherein transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity; and transmitting, to the UE, a second indication indicating a selection of one of the multiple receive beams corresponding to the group of transmit and receive beam pairs, based on the distance between the UE and the network entity. 
     Other aspects provide: an apparatus operable, configured, or otherwise adapted to perform the aforementioned methods as well as those described elsewhere herein; a non-transitory, computer-readable media comprising instructions that, when executed by one or more processors of an apparatus, cause the apparatus to perform the aforementioned methods as well as those described elsewhere herein; a computer program product embodied on a computer-readable storage medium comprising code for performing the aforementioned methods as well as those described elsewhere herein; and an apparatus comprising means for performing the aforementioned methods as well as those described elsewhere herein. By way of example, an apparatus may comprise a processing system, a device with a processing system, or processing systems cooperating over one or more networks. 
     The following description and the appended figures set forth certain features for purposes of illustration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The appended figures depict certain features of the various aspects described herein and are not to be considered limiting of the scope of this disclosure. 
         FIG.  1    is a block diagram conceptually illustrating an example wireless communication network. 
         FIG.  2    is a block diagram conceptually illustrating aspects of an example base station (BS) and user equipment (UE). 
         FIGS.  3 A- 3 D  depict various example aspects of data structures for a wireless communication network. 
         FIG.  4    illustrates example quasi co-location (QCL) types for downlink (DL) transmissions. 
         FIG.  5    illustrates example transmission configuration indication (TCI) states. 
         FIG.  6 A  illustrates example near-field operation. 
         FIG.  6 B  illustrates example far-field operation. 
         FIG.  7 A  illustrates example array of a network entity. 
         FIG.  7 B  illustrates example distance between a center of array of a network entity and a UE. 
         FIG.  8    illustrates example performance of different beams on a single straight-line trajectory. 
         FIG.  9    illustrates another example performance of different beams on a single straight-line trajectory. 
         FIG.  10    is a flow diagram illustrating example operations for wireless communication by a UE. 
         FIG.  11    is a flow diagram illustrating example operations for wireless communication by a network entity. 
         FIG.  12    illustrates example transmitter beam and multiple receiver beams as a UE moves from one location to another location. 
         FIGS.  13 A- 13 C  illustrate different transmit and receive beam pairs mapped to a same transmission configuration indication (TCI) state. 
         FIG.  14    depicts aspects of an example communications device. 
         FIG.  15    depicts aspects of an example communications device. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present disclosure provide apparatuses, methods, processing systems, and computer-readable mediums for enabling beam switching in near-field operations. For example, different beams may become relevant in the near-field at both gNodeB (gNB) and user equipment (UE) depending on a distance between the gNB and the UE. 
     When the UE is in a greater distance from the gNB that exceeds a threshold distance determined by an antenna array size at the UE and wavelength, far-field operation prevails. In such cases, beams used for communication between the UE and gNB may stay suitable longer than when operating at closer distances. At closer distances, near-field operation prevails and which beams are suitable may change more rapidly. This rapid change may present a challenge for beam management. 
     Aspects of the present disclosure present techniques that may help support, in the near-field, efficient and swift beam switches to select a new beam based on the distance between the gNB and the UE (unlike a far-field operation where beams may stay relevant for far longer time-scales). As a result, the techniques presented herein may help improve overall system performance and user experience. 
     The technique described herein relates to beamformed communications between a transmitter device (e.g., the gNB) and a receiver device (e.g., the UE). Multiple transmit and receive beam pairs are mapped to a same transmission configuration indication (TCI) state identifier (ID) for different transmitter beams, and a same quasi co-location (QCL) state for different receiver beams. The multiple transmit and receive beam pairs are different from each other, and depend on a distance between the transmitter device and the receiver device. Based on the distance between the transmitter device and the receiver device, a beam switch is implemented and a new beam pair is selected. This beam switch may be autonomous or indication-based. 
     Introduction to Wireless Communication Networks 
       FIG.  1    depicts an example of a wireless communications network  100 , in which aspects described herein may be implemented. 
     Generally, wireless communications network  100  includes base stations (BSs)  102 , user equipments (UEs)  104 , one or more core networks, such as an Evolved Packet Core (EPC)  160  and 5G Core (5GC) network  190 , which interoperate to provide wireless communications services. 
     BSs  102  may provide an access point to EPC  160  and/or 5GC  190  for a UE  104 , and may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, delivery of warning messages, among other functions. BSs  102  may include and/or be referred to as a gNB, NodeB, eNB, ng-eNB (e.g., an eNB that has been enhanced to provide connection to both EPC  160  and 5GC  190 ), an access point, a base transceiver station, a radio BS, a radio transceiver, or a transceiver function, or a transmission reception point in various contexts. 
     BSs  102  wirelessly communicate with UEs  104  via communications links  120 . Each of BSs  102  may provide communication coverage for a respective geographic coverage area  110 , which may overlap in some cases. For example, small cell  102 ′ (e.g., a low-power BS) may have a coverage area  110 ′ that overlaps the coverage area  110  of one or more macrocells (e.g., high-power BSs). 
     The communication links  120  between BSs  102  and UEs  104  may include uplink (UL) (also referred to as reverse link) transmissions from UE  104  to BS  102  and/or downlink (DL) (also referred to as forward link) transmissions from BS  102  to UE  104 . The communication links  120  may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity in various aspects. 
     Examples of UEs  104  include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player, a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or other similar devices. Some of UEs  104  may be internet of things (IoT) devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, or other IoT devices), always on (AON) devices, or edge processing devices. UEs  104  may also be referred to more generally as a station, 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, or a client. 
     Communications using higher frequency bands may have higher path loss and a shorter range compared to lower frequency communications. Accordingly, certain BSs (e.g.,  180  in  FIG.  1   ) may utilize beamforming  182  with UE  104  to improve path loss and range. For example, BS  180  and UE  104  may each include a plurality of antennas, such as antenna elements, antenna panels, and/or antenna arrays to facilitate the beamforming. 
     In some cases, BS  180  may transmit a beamformed signal to UE  104  in one or more transmit directions  182 ′. UE  104  may receive the beamformed signal from BS  180  in one or more receive directions  182 ″. UE  104  may also transmit a beamformed signal to BS  180  in one or more transmit directions  182 ″. BS  180  may also receive the beamformed signal from UE  104  in one or more receive directions  182 ′. BS  180  and UE  104  may then perform beam training to determine the best receive and transmit directions for each of BS  180  and UE  104 . Notably, the transmit and receive directions for BS  180  may or may not be the same. Similarly, the transmit and receive directions for UE  104  may or may not be the same. 
     BS  102  includes beam component  199 , which may be configured perform operations  1100  of  FIG.  11   . UE  104  includes beam component  198 , which may be configured to perform operations  1000  of  FIG.  10   . 
       FIG.  2    depicts aspects of an example BS  102  and UE  104 . 
     Generally, BS  102  includes various processors (e.g.,  220 ,  230 ,  238 , and  240 ), antennas  234   a - t  (collectively  234 ), transceivers  232   a - t  (collectively  232 ), which include modulators and demodulators, and other aspects, which enable wireless transmission of data (e.g., data source  212 ) and wireless reception of data (e.g., data sink  239 ). For example, BS  102  may send and receive data between itself and UE  104 . 
     BS  102  includes controller/processor  240 , which may be configured to implement various functions related to wireless communications. In the depicted example, controller/processor  240  includes beam component  241 , which may be representative of beam component  199  of  FIG.  1   . Notably, while depicted as an aspect of controller/processor  240 , beam component  241  may be implemented additionally or alternatively in various other aspects of BS  102  in other implementations. 
     Generally, UE  104  includes various processors (e.g.,  258 ,  264 ,  266 , and  280 ), antennas  252   a - r  (collectively  252 ), transceivers  254   a - r  (collectively  254 ), which include modulators and demodulators, and other aspects, which enable wireless transmission of data (e.g., data source  262 ) and wireless reception of data (e.g., data sink  260 ). 
     UE  104  includes controller/processor  280 , which may be configured to implement various functions related to wireless communications. In the depicted example, controller/processor  280  includes beam component  281 , which may be representative of beam component  198  of  FIG.  1   . Notably, while depicted as an aspect of controller/processor  280 , beam component  281  may be implemented additionally or alternatively in various other aspects of UE  104  in other implementations. 
       FIGS.  3 A- 3 D  depict aspects of data structures for a wireless communication network, such as wireless communication network  100  of  FIG.  1   . In particular,  FIG.  3 A  is a diagram  300  illustrating an example of a first subframe within a 5 th  generation (5G) (e.g., 5G new radio (NR)) frame structure,  FIG.  3 B  is a diagram  330  illustrating an example of DL channels within a 5G subframe,  FIG.  3 C  is a diagram  350  illustrating an example of a second subframe within a 5G frame structure, and  FIG.  3 D  is a diagram  380  illustrating an example of UL channels within a 5G subframe. 
     Further discussions regarding  FIG.  1   ,  FIG.  2   , and  FIGS.  3 A- 3 D  are provided later in this disclosure. 
     Introduction to mmWave Wireless Communications 
     In wireless communications, an electromagnetic spectrum is often subdivided into various classes, bands, channels, or other features. The subdivision is often provided based on wavelength and frequency, where frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, or a subband. 
     5 th  generation (5G) networks may utilize several frequency ranges, which in some cases are defined by a standard, such as 3rd generation partnership project (3GPP) standards. For example, 3GPP technical standard TS 38.101 currently defines Frequency Range  1  (FR 1 ) as including 600 MHz-6 GHz, though specific uplink and downlink allocations may fall outside of this general range. Thus, FR 1  is often referred to (interchangeably) as a “Sub-6 GHz” band. 
     Similarly, TS 38.101 currently defines Frequency Range  2  (FR 2 ) as including 26-41 GHz, though again specific uplink and downlink allocations may fall outside of this general range. FR 2 , is sometimes referred to (interchangeably) as a “millimeter wave” (“mmW” or “mmWave”) band, despite being different from the extremely high frequency (EHF) band (30 GHz-300 GHz) that is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band because wavelengths at these frequencies are between 1 millimeter and 10 millimeters. 
     Communications using mmWave/near mmWave radio frequency band (e.g., 3 GHz-300 GHz) may have higher path loss and a shorter range compared to lower frequency communications. As described above with respect to  FIG.  1   , a base station (BS) (e.g.,  180 ) configured to communicate using mmWave/near mmWave radio frequency bands may utilize beamforming (e.g.,  182 ) with a user equipment (UE) (e.g.,  104 ) to improve path loss and range. 
     Overview of Beamforming 
     Beamforming (which may also be referred to as spatial filtering) is used in wireless and millimeter wave (mmW) application space to increase directional antenna array gain. Devices using wireless communication technologies (e.g., portable electronic devices) may include multiple transmission and reception antennas or arrays that are configured to transmit and receive communications over a single spatial stream/beam. In one example, beamforming may be used at a transmitter device (e.g., a gNodeB (gNB)) to shape and/or steer an overall antenna beam in a direction of a target receiver device (e.g., a user equipment (UE)). 
     Overview of Quasi Co-Location (QCL) and Transmission Configuration Indicator (TCI) 
     In some new radio (NR) applications, it is essential for a UE to know which assumptions the UE can make on a channel corresponding to different transmissions. For example, the UE may need to know which reference signals (RSs) the UE can use to estimate the channel in order to decode a signal. The signal may include a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH). In some cases, it may also be essential for the UE to be able to report relevant channel state information (CSI) to a gNB for scheduling, link adaptation, and/or beam management purposes. In NR, quasi co-location (QCL) and transmission configuration indicator (TCI) states are used to convey information about these assumptions. The QCL and the TCI state information may reduce processing at the UE side. 
     QCL configuration/relationship between signals refers to a relationship between antenna ports (and corresponding signaling beams) of respective transmissions. For example, the transmissions sharing a same antenna port may experience a same channel. In some cases, the transmissions from different antenna ports may experience radio channels that share some common characteristics (which are captured by QCL relationship). 
     Per 3rd Generation Partnership Project (3GPP) TS 38.214, “two antenna ports are said to be quasi-co-located if properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed.” For example, when some antenna ports are referred to as quasi co-located (QCL′d), it means that spatial parameters of a transmission on one antenna port may be inferred from spatial parameters of another transmission on a different antenna port. Accordingly, in operation, a receiving device (e.g., the UE) may be able to perform channel estimation for demodulating data or control information received on a first set of antenna ports based on RSs received on a second set of antenna ports that are QCL′d with the first set of antenna ports. The QCL relationship between the first set of antenna ports and the second set of antenna ports may improve the chances that the UE is able to successfully decode a downlink (DL) transmission from a transmitting device (e.g., the gNB). In some cases, the gNB may transmit to the UE an indication of which antenna ports are QCL′d such that the UE is able to identify additional RSs to use for channel estimation. 
     The gNB may configure a set of TCI states to use to indicate to the UE which beam weights are used in DL transmissions to the UE. Each TCI state is associated with a set of RSs (e.g., synchronization signal blocks (SSBs) or different types of channel state information reference signals (CSI-RSs)). As such, when the UE receives an indication of a particular TCI state from the gNB (e.g., in downlink control information (DCI) in a transmission time interval (TTI)), the UE may identify the beam weights used over the antenna ports to transmit the RSs associated with the TCI state. Accordingly, the UE may use the RSs associated with the TCI state to perform channel estimation for demodulating the data or control information received from the gNB. In some cases, the gNB may transmit the DCI to the UE to update the TCI states (e.g., based on current channel conditions). 
     QCL information and/or types may depend on or be a function of other information. For example, as illustrated in  FIG.  4   , QCL types for DL RSs (e.g., SSBs, CSI-RSs, etc.) indicated to a UE can be based on a higher layer parameter QCL-Type and may take one or a combination of the following types: QCL-TypeA, QCL-TypeB, QCL-TypeC, and QCL-TypeD. These four QCL types indicate which large scale channel characteristics or properties are common across different antenna ports. For example, the QCL-TypeA indicates Doppler shift, Doppler spread, average delay, and delay spread. The QCL-TypeB indicates Doppler shift and Doppler spread. The QCL-TypeC indicates Doppler shift and average delay. The QCL-TypeD indicates a spatial relationship (e.g., between antenna ports used for receiving uplink (UL) signals and antenna ports for transmitting DL data). 
     As further illustrated in  FIG.  4   , the QCL concept can be used for both PDCCH and PDSCH reception at the UE. The gNB can indicate to the UE that antenna port used by a specific SSB block is QCL with the PDCCH/PDSCH. The gNB can also indicate antenna port used by a CSI-RS is QCL with the PDCCH/PDSCH. The gNB can use a combination of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE), and DCI to convey this QCL information to the UE. 
     In some cases, the QCL-TypeA and the QCL-TypeB may be used to obtain CSI. The QCL-TypeC may be used to obtain measurements (e.g., reference signal received power (RSRP)). The QCL-TypeD may support beamforming, and help the UE to select an analog receive/transmit beam used over the radio frequency (e.g., during beam management procedures). For example, QCL Type-D mapping may indicate that a certain beam for a PDSCH is mapped to a RS resource (e.g., the SSB/CSI-RS). That is, the UE can receive the PDSCH with the same beam the UE uses for the SSB/CSI-RS resource based on the QCL mapping. In such cases, it does not mean that beam weights used for the PDSCH need to be directly obtained from the DL RS measurements, but the beam weights used for the PDSCH can be based on/derived from the DL RS measurements. 
     In NR, beamforming over multiple antennas with a set of beam weights at a gNB is associated with a TCI state operation. For example, a beam switch operation may correspond to change in a TCI state at the gNB side and/or beam weights used at a UE. The beam switch may be implemented on a per component carrier (CC) basis. In some cases, as illustrated in  FIG.  5   , a CC group-based TCI state update may be initiated, which may cause switching of beams/TCI states across multiple CCs with a single control signal (e.g., a MAC-CE message). 
     In some cases, multiple transmit/receive beams with a same gNB/transmission reception point (TRP) may be controlled with a single TCI state (e.g., near-field communications). This may be possible in a single frequency network (SFN) of multi-TRP (mTRP) system where a transmit/receive beam of one or more TRPs can be changed with the same TCI state (e.g., a SFN beam). However, such beam switch may not be possible in context of single gNB/TRP system. 
     Overview of Near-Field and Far-Field Systems 
     The present application relates to near-field systems. The difference between near-field and far-field systems typically relates to a distance separating transmit and receive nodes in the network. 
     As illustrated in  FIG.  6 A , when a transmit antenna (e.g., of a transmitter device/node such as a gNB) with a largest dimension/aperture D transmits a signal of a wavelength k, a receive antenna (e.g., of a receiver device/node such as a user equipment (UE)) is considered to be in a near-field if a distance separating the transmitting and receiving nodes is less than a Fraunhofer distance (defined as 2D 2 /λ) where D is equal to Nd (with d being an inter-antenna element spacing for a linear array of size N). As illustrated in  FIG.  6 B , a larger separation between the transmitting and receiving nodes places the receiver node in a far-field operation. The properties of transmitted electromagnetic waves change between the near- and far-fields. 
     A far-field distance may increase quadratically when there is an increase in array size/aperture. The far-field distance may increase linearly when there is an increase in a carrier frequency (e.g., for a same aperture). As a result, in some cases (e.g. for large arrays and higher carrier frequencies), the Fraunhofer distance at which far-field operation begins can be very large. 
     In conventional systems, UEs usually operate in a far-field (e.g., with respect to a gNB) and not in near-field. In such systems, a far-field distance may be at least 5 to 10 meters (m). However, in some other systems (e.g., a 6 th  generation (6G) system), a near-field operation may become significant due to increased importance in higher carrier frequencies (FR 4  and beyond) and larger arrays. In such systems, the near-field operation need not be near the gNB anymore. This is because, in such systems, a far-field distance may be quite large. For example, in some of these systems, the far-field distance is 20.48 m and 5.2 kilometer (km) with a 64×1 and 1024×1 array at 30 gigahertz (GHz), respectively. Also, for an aperture of 1 m, the far-field distance at 30 GHz and 120 GHz are approximately 200 m and 800 m, respectively. Example use-cases for the near-field operation in these systems include the use of assistive nodes (e.g., intelligent reflective surfaces (IRS), passive reflectarrays or repeater operations). 
     In some cases, when a receiver device gets closer to a transmitter device to be in a near-field, techniques (e.g., for beam switching) associated with a conventional system start failing. This is because directional/hierarchical beamforming design for such receiver devices implicitly assumes that these receiver devices are operating in a far-field. Accordingly, in such cases, a beam switching operation gets complex. For example, in the far-field operation, when a UE is moving away from or towards a gNB in a straight line, and an angle from the UE to the gNB does not change, the UE may continue to use a same beam (that was previously selected). However, in the same scenario in near-field, this is not possible. This is because even when the UE and the gNB are pointing at a same direction while the UE is moving towards or away from the gNB, beam weights previously used have to change. This disclosure describes improved techniques for the beam switching in near-field operations. 
     Aspects Related to Beam Switching in Near-Field Operations 
     While a user equipment (UE) is in a far field, as illustrated in  FIG.  6 B , the UE and a gNB may establish a beam pair (e.g., by steering energy in a certain direction from the gNB to the UE). The UE may then move from one location to another location. 
     As illustrated in  FIG.  6 A , when the UE moves closer to the gNB (and crosses a near- and far-field boundary), the UE is in a near-field. When the UE is in the near field, the earlier beam pair (that was suitable while the UE was in the far field) may not be appropriate and a new beam pair may have to be established (e.g., based on an angle and a distance between the UE and the gNB). 
     As illustrated in  FIG.  7 A , a gNB may include an array (e.g., a linear array of size N×1). As illustrated in  FIG.  7 B , when a UE is in a near-field, the UE is at a relative coordinate orientation of (y,z) from a center of the N×1 linear array of the gNB. In this example scenario, a new beam pair may be determined (e.g., based on values of y and z). The values of y and z may change when the UE moves. These distance values can be estimated with positioning signals (either NR-based or otherwise). 
     In one example scenario, the gNB and the UE may be positioned such that there may be a single straight-line trajectory between the gNB and the UE (e.g., equal to −51.3°). When the UE moves away or closer to the gNB, the angle between the gNB and the UE may not change. Over this single straight-line trajectory, different beams are used. Some beams may be from a far-field codebook. These beams may include five beams (e.g., beams  1  to  5 ). Some beams may be from a near-field codebook (e.g., a single near-field beam). 
     As illustrated in  FIG.  8   , a beamforming array gain is determined for all these six beams (e.g., based on a distance y between the gNB and the UE). As illustrated, all beams have oscillatory performance in the near-field (e.g., based on the beamforming array gain for all beams). However, even when there is the oscillatory performance from all beams, the performance of the near-field beam is still better (than other beams  1  to  5 ) at shorter near-field distances (e.g., due to the higher beamforming array gain). 
     In another example scenario, the UE may be moving away from the gNB in a straight line (=)−33.5°. While the UE is moving away from the gNB, the angle between the gNB and the UE may not change. As the distance y between the gNB and the UE increases, different beams may lead to a good performance depending on the distance y. However, as illustrated in  FIG.  9   , a third beam (beam  3 ) may have a best performance among all beams (e.g., due to the higher beamforming array gain). 
     As noted above, in a far-field operation, when there is no change in the angle between the gNB and the UE and only the distance between the gNB and the UE is changing, there is no need for beam switching (the same far-field beam works well independent of distance). Beam switching may only be needed when both the angle between the gNB and the UE changes. However, in a near-field operation, even though the angle between the gNB and the UE may not change when the UE is moving away or closer to the gNB, beam switching at both the gNB and the UE is still necessary (e.g., as a function of a distance between the gNB and the UE). This is because, as illustrated in above noted examples, different set of beam weights work at different distances between the gNB and the UE. 
     Also, in the far-field operation, a QCL mapping indicated to the UE may allow the UE to perform receive (Rx) beamforming even as the UE moves. However, in the near-field operation, such QCL mapping may not help the UE since beam switching as a function of distance between the gNB and the UE is necessary. In such near-field operation cases, different transmit and receive beams may be used for connectivity (e.g., for a same quasi co-location (QCL) mapping as a function of the distance between the gNB and the UE even though a same QCL mapping may suffice in the far-field). 
     Aspects of the present disclosure provide apparatuses, methods, processing systems, and computer-readable mediums for enabling (fast and efficient) beam switching in near-field operations. For example, different beams may become relevant in the near-field at both gNB and UE depending on a distance between the gNB and the UE. Accordingly, in the near-field, a swift beam switch may be implemented to select a new beam based on the distance between the gNB and the UE (unlike a far-field scenario where beams may stay relevant for far longer time-scales). 
     The techniques described herein generally relate to beamformed communications between a transmitter device (e.g., the gNB) and a receiver device (e.g., the UE). Multiple transmit beams from a set of multiple transmit and receive beam pairs are mapped to a same transmission configuration indication (TCI) state identifier (ID), and multiple receive beams from the set of multiple transmit and receive beam pairs are mapped to a same quasi co-location (QCL) state. The multiple transmit and receive beam pairs are different from each other in that at least one of the beams are different, and depend on a distance between the transmitter device and the receiver device. Based on the distance between the transmitter device and the receiver device, a beam switch may be implemented and a new beam pair selected. This beam switch may be autonomous or indication-based. 
       FIG.  10    illustrates example operations  1000  for wireless communication. The operations  1000  may be performed, for example, by a UE (e.g., such as UE  104  in wireless communication network  100  of  FIG.  1   ). The operations  1000  may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor  280  of  FIG.  2   ). Further, transmission and reception of signals by the UE in the operations  1000  may be enabled, for example, by one or more antennas (e.g., antennas  252  of  FIG.  2   ). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., the controller/processor  280 ) obtaining and/or outputting signals. 
     Operations  1000  begin, at  1010 , by receiving from a network entity a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs. Transmit and receive beam pairs are different from each other, and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity. For example, the UE may receive the first indication from the network entity using antenna(s) and/or receiver/transceiver components of UE  104  shown in  FIG.  1    or  FIG.  2    and/or of the apparatus shown in  FIG.  14   . 
     At  1020 , the UE selects one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity. For example, the UE may select one of the multiple receive beams corresponding to the group of transmit and receive beam pairs using a processor, antenna(s), and/or transceiver components of UE  104  shown in  FIG.  1    or  FIG.  2    and/or of the apparatus shown in  FIG.  14   . 
       FIG.  11    illustrates example operations  1100  for wireless communication. The operations  1100  may be performed, for example, by a network entity (e.g., such as BS  102  in wireless communication network  100  of  FIG.  1   ). The operations  1100  may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor  240  of  FIG.  2   ). Further, transmission and reception of signals by the network entity in the operations  1100  may be enabled, for example, by one or more antennas (e.g., antennas  234  of  FIG.  2   ). In certain aspects, the transmission and/or reception of signals by the network entity may be implemented via a bus interface of one or more processors (e.g., the controller/processor  240 ) obtaining and/or outputting signals. 
     Operations  1100  begin, at  1110 , by transmitting to a UE a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs. Transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity. For example, the network entity may transmit the first indication to the UE using antenna(s) and transmitter/transceiver components of BS  102  shown in  FIG.  1    or  FIG.  2    and/or of the apparatus shown in  FIG.  15   . 
     At  1120 , the network entity transmits to the UE a second indication indicating a selection of one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity. For example, the network entity may transmit the second indication to the UE using antenna(s) and transmitter/transceiver components of BS  102  shown in  FIG.  1    or  FIG.  2    and/or of the apparatus shown in  FIG.  15   . 
     The operations shown in  FIGS.  10  and  11    may be understood with reference to the  FIGS.  12 - 13 C . 
     As illustrated in  FIG.  12   , a receiver device (e.g., a UE) may move from one location (e.g., within a near-field) to another location (e.g., within the near field or in a far-field) with respect to a transmitter device (e.g., gNB). As the UE moves while the gNB remains stationary, a receive beam needs to be changed (while a transmitter beam may remain fixed). The UE selects a new receive beam based on a distance between a current location of the UE and the gNB. For example, the UE may select the new receive beam from multiple receive beams, which are mapped to a same QCL state (e.g., as a function of a distance between the UE and the gNB). 
     The multiple receive beams may include a first receive beam (Rx beam 1 ) based on a first location of the UE, a second receive beam (Rx beam 2 ) based on a second location of the UE, a third receive beam (Rx beam 3 ) based on a third location of the UE, a fourth receive beam (Rx beam  4 ) based on a fourth location of the UE, and a fifth receive beam (Rx beam 5 ) based on other locations such as a fifth and sixth locations of the UE. In the near-field, the first receive beam, the second receive beam, the third receive beam, and the fourth receive beam are different from each other based on a function of the distance between the UE and the gNB. In the far-field, the fifth receive beam may remain stationary as distance changes with angle remaining the same. 
     In one example, when the UE is in the first location, the UE may use the first receive beam (which is selected based on the distance between the first location of the UE and the gNB). As the UE moves from the first location to the second location, the UE may use the second receive beam (which is selected based on the distance between the second location of the UE and the gNB). The first receive beam and the second receive beam are mapped to a same QCLstate via a distance-dependent QCL mapping. The QCL mapping for these multiple receive beams may be performed via a radio resource control (RRC) configuration. 
     In certain aspects, multiple transmitter beams (e.g., corresponding to the group of transmit and receive beam pairs discussed above) are mapped to a same TCI state. For example, the TCI state may be mapped to the different transmitter beams as a function of the distance between the UE and the gNB. In such cases, a same TCI state identifier (ID) may be reused for the multiple transmitter beams and is a function of the distance between the UE and the gNB. 
     As illustrated in  FIGS.  13 A- 13 C , different transmit and receive beam pairs are mapped to a same TCI state and QCL mapping of these different beam pairs is performed (e.g., as a function of distance between the UE and the gNB). The transmit and receive beam pairs may include a first transmit and receive beam pair (including a first transmit beam and a first receive beam illustrated in  FIG.  13 A ), a second transmit and receive beam pair (including a second transmit beam and a second receive beam illustrated in  FIG.  13 B ), and a third transmit and receive beam pair (including a third transmit beam and a third receive beam illustrated in  FIG.  13 C ). 
     In certain aspects, the gNB may configure multiple distance dependent beams (e.g., the receive beams) in the same QCL mapping. The QCL mapping may be of different types. In one example, the QCL mapping may be a QCL Type A mapping. In another example, the QCL mapping may be a QCL Type B mapping. In another example, the QCL mapping may be a QCL Type C mapping. In another example, the QCL mapping may be a QCL Type D mapping. 
     In certain aspects, different TCI states may be defined corresponding to different gNB transmit beam weights. A beam switch across different beams may be based on a pre-defined criteria, which is a function of a distance between the UE and the gNB. 
     In certain aspects, a UE and/or a gNB may perform an autonomous beam switch. For example, both the UE and the gNB may autonomously switch a transmit and receive beam pair based on a distance between the UE and the gNB. In such autonomous beam switch cases, there may be some asymmetry between the UE and the gNB while performing autonomous beam switch. In one example, the asymmetry may be due to a latency/delay based on a poor estimation of the distance between the UE and the gNB. In another example, the asymmetry may be due to latencies from radio frequency (RF) circuits, which may cause slow beam switching at the UE or the gNB. To address this asymmetry, an indication indicating the switching of the transmit and receive beam pair may be transmitted. For example, in operation, when the UE moves towards the gNB, the UE can autonomously switch from a far-field beam to a near-field beam. After this beam switch, the UE may indicate the beam switch to the gNB (and further optimize the near-field beam over a few beam choices via a beam refinement procedure). Similarly, when the UE moves away from the gNB, the UE may then switch to an appropriate far-field beam. The UE may again send the indication of the beam switch to the gNB. Accordingly, the UE may consider autonomous beam switch (with the indication to the gNB after the beam switch) by configuring asymmetric distance-based switches (e.g., the far-field beam to the near-field beam at a first distance and the near-field beam to the far-field beam at a second distance). 
     In certain aspects, a UE and/or a gNB may perform indication-based beam switch. For example, the UE may perform the beam switch on receiving a beam switch indication from the gNB and the gNB may perform the beam switch on receiving the beam switch indication from the UE. The beam switch indication is similar to a beam switch request (BSR) when the beam switch indication is sent from the UE to the gNB. The beam switch indication is similar to a beam switch command (BSC) when the beam switch indication is sent from the gNB to the UE. In operation, a first node (e.g., the UE) may determine a distance to a second node (e.g., gNB). The first node may then send the beam switch indication to the second node. The second node may receive the beam switch indication from the first node. The second node may then switch the beam based on the beam switch indication. 
     In certain aspects, multiple different transmit beams corresponding to the group of transmit and receive beam pairs and mapped to different TCI states are grouped to a same TCI state group. The different transmit beams may depend on a distance between the UE and the gNB. For example, the TCI state group may be configured that may group together multiple TCI states and each of the multiple TCI states may map to a different transmit beam. 
     In some cases, a transmit beam is selected from the TCI state group for communications between the UE and the gNB based on the distance between the UE and the gNB. For example, individual TCI states within the TCI state group may be activated depending on the distance. In some cases, defining the TCI state group may lead to an overhead reduction as beams can be automatically switched based on a distance estimation (instead of configuring each TCI state separately). In some cases, the TCI state group may be applied across one or more component carriers (CCs). 
     Example Wireless Communication Devices 
       FIG.  14    depicts an example communications device  1400  that includes various components operable, configured, or adapted to perform operations for the techniques disclosed herein, such as the operations depicted and described with respect to  FIG.  10   . In some examples, communication device  1400  may be a UE  104  as described, for example with respect to  FIGS.  1  and  2   . 
     Communications device  1400  includes a processing system  1402  coupled to a transceiver  1408  (e.g., a transmitter and/or a receiver). Transceiver  1408  is configured to transmit (or send) and receive signals for the communications device  1400  via an antenna  1410 , such as the various signals as described herein. Processing system  1402  may be configured to perform processing functions for communications device  1400 , including processing signals received and/or to be transmitted by communications device  1400 . 
     Processing system  1402  includes one or more processors  1420  coupled to a computer-readable medium/memory  1430  via a bus  1406 . In certain aspects, computer-readable medium/memory  1430  is configured to store instructions (e.g., computer-executable code) that when executed by the one or more processors  1420 , cause the one or more processors  1420  to perform the operations illustrated in  FIG.  10   , or other operations for performing the various techniques discussed herein. 
     In the depicted example, computer-readable medium/memory  1430  stores code  1431  for receiving from a network entity a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs where transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity and code  1432  for selecting one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity. 
     In the depicted example, the one or more processors  1420  include circuitry configured to implement the code stored in the computer-readable medium/memory  1430 , including circuitry  1421  for receiving from a network entity a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs where transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity and circuitry  1422  for selecting one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity. 
     Various components of communications device  1400  may provide means for performing the methods described herein, including with respect to  FIG.  10   . 
     In some examples, means for transmitting or sending (or means for outputting for transmission) may include the transceivers  254  and/or antenna(s)  252  of the UE  104  illustrated in  FIG.  2    and/or transceiver  1408  and antenna  1410  of the communication device  1400  in  FIG.  14   . 
     In some examples, means for receiving (or means for obtaining) may include the transceivers  254  and/or antenna(s)  252  of UE  104  illustrated in  FIG.  2    and/or transceiver  1408  and antenna  1410  of the communication device  1400  in  FIG.  14   . 
     In some examples, means for receiving from a network entity a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs where transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity and means for selecting one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity, may include various processing system components, such as: the one or more processors  1420  in  FIG.  14   , or aspects of UE  104  depicted in  FIG.  2   , including receive processor  258 , transmit processor  264 , TX MIMO processor  266 , and/or controller/processor  280  (including beam component  281 ). 
     Notably,  FIG.  14    is an example, and many other examples and configurations of communication device  1400  are possible. 
       FIG.  15    depicts an example communications device  1500  that includes various components operable, configured, or adapted to perform operations for the techniques disclosed herein, such as the operations depicted and described with respect to  FIG.  11   . In some examples, communication device  1500  may be a BS  102  as described, for example with respect to  FIGS.  1  and  2   . 
     Communications device  1500  includes a processing system  1502  coupled to a transceiver  1508  (e.g., a transmitter and/or a receiver). Transceiver  1508  is configured to transmit (or send) and receive signals for the communications device  1500  via an antenna  1510 , such as the various signals as described herein. Processing system  1502  may be configured to perform processing functions for communications device  1500 , including processing signals received and/or to be transmitted by communications device  1500 . 
     Processing system  1502  includes one or more processors  1520  coupled to a computer-readable medium/memory  1530  via a bus  1506 . In certain aspects, computer-readable medium/memory  1530  is configured to store instructions (e.g., computer-executable code) that when executed by the one or more processors  1520 , cause the one or more processors  1520  to perform the operations illustrated in  FIG.  11   , or other operations for performing the various techniques discussed herein. 
     In the depicted example, computer-readable medium/memory  1530  stores code  1531  for transmitting to a UE a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs where transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity and code  1532  for transmitting to the UE a second indication indicating a selection of one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity. 
     In the depicted example, the one or more processors  1520  include circuitry configured to implement the code stored in the computer-readable medium/memory  1530 , including circuitry  1521  for transmitting to a UE a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs where transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity and circuitry  1522  for transmitting to the UE a second indication indicating a selection of one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity. 
     Various components of communications device  1500  may provide means for performing the methods described herein, including with respect to  FIG.  11   . 
     In some examples, means for transmitting or sending (or means for outputting for transmission) may include the transceivers  232  and/or antenna(s)  234  of the BS  102  illustrated in  FIG.  2    and/or transceiver  908  and antenna  910  of the communication device  1500  in  FIG.  15   . 
     In some examples, means for receiving (or means for obtaining) may include the transceivers  232  and/or antenna(s)  234  of the BS illustrated in  FIG.  2    and/or transceiver  1508  and antenna  1510  of the communication device  1500  in  FIG.  15   . 
     In some cases, rather than actually transmitting, for example, signals and/or data, a device may have an interface to output signals and/or data for transmission (a means for outputting). For example, a processor may output signals and/or data, via a bus interface, to a radio frequency (RF) front end for transmission. Similarly, rather than actually receiving signals and/or data, a device may have an interface to obtain the signals and/or data received from another device (a means for obtaining). For example, a processor may obtain (or receive) the signals and/or data, via a bus interface, from an RF front end for reception. In various aspects, an RF front end may include various components, including transmit and receive processors, transmit and receive multiple input multiple output (MIMO) processors, modulators, demodulators, and the like, such as depicted in the examples in  FIG.  2   . 
     In some examples, means for transmitting to a UE a first indication indicating a same QCL mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs where transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity and means for transmitting to the UE a second indication indicating a selection of one of the multiple receive beams corresponding to the group of transmit and receive beam pairs based on the distance between the UE and the network entity, may include various processing system components, such as: the one or more processors  1520  in  FIG.  15   , or aspects of the BS  102  depicted in  FIG.  2   , including receive processor  238 , transmit processor  220 , TX MIMO processor  230 , and/or controller/processor  240  (including beam component  241 ). 
     Notably,  FIG.  15    is an example, and many other examples and configurations of communication device  1500  are possible. 
     Example Clauses 
     Implementation examples are described in the following numbered clauses: 
     Clause 1: A method for wireless communication by a user equipment (UE), comprising: receiving, from a network entity, a first indication indicating a same quasi co-location (QCL) mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs, wherein transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity; and selecting one of the multiple receive beams corresponding to the group of transmit and receive beam pairs, based on the distance between the UE and the network entity. 
     Clause 2: The method alone or in combination with the first clause, wherein multiple transmit beams corresponding to the group of transmit and receive beam pairs are mapped to a same transmission configuration indication (TCI) state. 
     Clause 3: The method alone or in combination with one or more of the first and second clauses, wherein the QCL mapping for the multiple receive beams corresponding to the group of transmit and receive beam pairs is performed via a radio resource control (RRC) configuration. 
     Clause 4: The method alone or in combination with one or more of the first through third clauses, wherein the transmit and receive beam pairs in the same QCL mapping are configured by a network entity. 
     Clause 5: The method alone or in combination with one or more of the first through fourth clauses, wherein one or more types of the QCL mapping comprises at least one of a QCL Type A mapping, a QCL Type B mapping, a QCL Type C mapping, or a QCL Type D mapping. 
     Clause 6: The method alone or in combination with one or more of the first through fifth clauses, wherein the at least one processor is further configured to autonomously switch a transmit and receive beam pair, based on the distance between the UE and the network entity. 
     Clause 7: The method alone or in combination with one or more of the first through sixth clauses, wherein the at least one processor is further configured to transmit, to the network entity, an indication indicating the switching of the transmit and receive beam pair. 
     Clause 8: The method alone or in combination with one or more of the first through seventh clauses, wherein the at least one processor is further configured to switch a transmit and receive beam pair, based on a second indication indicating the switching of the transmit and receive beam pair from the network entity. 
     Clause 9: The method alone or in combination with one or more of the first through eighth clauses, wherein the second indication is based on the distance between the UE and the network entity. 
     Clause 10: The method alone or in combination with one or more of the first through ninth clauses, wherein multiple different transmit beams corresponding to the group of transmit and receive beam pairs and mapped to different transmission configuration indication (TCI) states are grouped to a same TCI state group, and wherein the different transmit beams depend on the distance between the UE and the network entity. 
     Clause 11: The method alone or in combination with one or more of the first through tenth clauses, wherein a transmit beam is selected from the TCI state group for communications between the UE and the network entity, based on the distance between the UE and the network entity. 
     Clause 12: The method alone or in combination with one or more of the first through eleventh clauses, wherein the TCI state group is applied across one or more component carriers (CCs). 
     Clause 13: A method for wireless communication by a network entity, comprising: transmitting, to a user equipment (UE), a first indication indicating a same quasi co-location (QCL) mapping for multiple receive beams corresponding to a group of transmit and receive beam pairs, wherein transmit and receive beam pairs are different from each other and grouping of the transmit and receive beam pairs is based on a distance between the UE and the network entity; and transmitting, to the UE, a second indication indicating a selection of one of the multiple receive beams corresponding to the group of transmit and receive beam pairs, based on the distance between the UE and the network entity. 
     Clause 14: The method alone or in combination with the thirteenth clause, wherein multiple transmit beams corresponding to the group of transmit and receive beam pairs are mapped to a same transmission configuration indication (TCI) state. 
     Clause 15: The method alone or in combination with the thirteenth and fourteenth clauses, wherein the QCL mapping for the multiple receive beams corresponding to the group of transmit and receive beam pairs is performed via a radio resource control (RRC) configuration. 
     Clause 16: The method alone or in combination with one or more of the thirteenth through fifteenth clauses, wherein the at least one processor is further configured to configure the transmit and receive beam pairs in the same QCL mapping. 
     Clause 17: The method alone or in combination with one or more of the thirteenth through sixteenth clauses, wherein one or more types of the QCL mapping comprises at least one of a QCL Type A mapping, a QCL Type B mapping, a QCL Type C mapping, or a QCL Type D mapping. 
     Clause 18: The method alone or in combination with one or more of the thirteenth through seventeenth clauses, wherein multiple different transmit beams corresponding to the group of transmit and receive beam pairs and mapped to different transmission configuration indication (TCI) states are grouped to a same TCI state group, and wherein the different transmit beams depend on the distance between the UE and the network entity. 
     Clause 19: The method alone or in combination with one or more of the thirteenth through eighteenth clauses, wherein a transmit beam is selected from the TCI state group for communications between the UE and the network entity, based on the distance between the UE and the network entity. 
     Clause 20: The method alone or in combination with one or more of the thirteenth through nineteenth clauses, wherein the TCI state group is applied across one or more component carriers (CCs). 
     Clause 21: An apparatus, comprising: a memory comprising executable instructions; one or more processors configured to execute the executable instructions and cause the apparatus to perform a method in accordance with any one of Clauses 1-20. 
     Clause 22: An apparatus, comprising means for performing a method in accordance with any one of Clauses 1-20. 
     Clause 23: A non-transitory computer-readable medium comprising executable instructions that, when executed by one or more processors of an apparatus, cause the apparatus to perform a method in accordance with any one of Clauses 1-20. 
     Clause 24: A computer program product embodied on a computer-readable storage medium comprising code for performing a method in accordance with any one of Clauses 1-20. 
     Additional Wireless Communication Network Considerations 
     The techniques and methods described herein may be used for various wireless communications networks (or wireless wide area network (WWAN)) and radio access technologies (RATs). While aspects may be described herein using terminology commonly associated with 3G, 4G, and/or 5G (e.g., 5G new radio (NR)) wireless technologies, aspects of the present disclosure may likewise be applicable to other communication systems and standards not explicitly mentioned herein. 
     5G wireless communication networks may support various advanced wireless communication services, such as enhanced mobile broadband (eMBB), millimeter wave (mmWave), machine type communications (MTC), and/or mission critical targeting ultra-reliable, low-latency communications (URLLC). These services, and others, may include latency and reliability requirements. 
     Returning to  FIG.  1   , various aspects of the present disclosure may be performed within the example wireless communication network  100 . 
     In 3GPP, the term “cell” can refer to a coverage area of a NodeB and/or a narrowband subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB), access point (AP), distributed unit (DU), carrier, or transmission reception point may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. 
     A macro cell may generally cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area (e.g., a sports stadium) and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) and UEs for users in the home). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS, home BS, or a home NodeB. 
     BSs  102  configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC  160  through first backhaul links  132  (e.g., an S1 interface). BSs  102  configured for 5G (e.g., 5G NR or Next Generation RAN (NG-RAN)) may interface with 5GC  190  through second backhaul links  184 . BSs  102  may communicate directly or indirectly (e.g., through EPC  160  or 5GC  190 ) with each other over third backhaul links  134  (e.g., X2 interface). Third backhaul links  134  may generally be wired or wireless. 
     Small cell  102 ′ may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell  102 ′ may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP  150 . Small cell  102 ′, employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. 
     Some BSs, such as BS  180  may operate in a traditional sub-6 GHz spectrum, in millimeter wave (mmWave) frequencies, and/or near mmWave frequencies in communication with the UE  104 . When BS  180  operates in mmWave or near mmWave frequencies, the BS  180  may be referred to as an mmWave BS. 
     The communication links  120  between BSs  102  and, for example, UEs  104 , may be through one or more carriers. For example, BSs  102  and UEs  104  may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, and other MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL than for UL). The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell). 
     Wireless communications network  100  further includes a Wi-Fi access point (AP)  150  in communication with Wi-Fi stations (STAs)  152  via communication links  154  in, for example, a 2.4 GHz and/or 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs  152 /AP  150  may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available. 
     Certain UEs  104  may communicate with each other using device-to-device (D2D) communication link  158 . The D2D communication link  158  may use the DL/UL WWAN spectrum. The D2D communication link  158  may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, 4G (e.g., LTE), or 5G (e.g., NR), to name a few options. 
     EPC  160  may include a Mobility Management Entity (MME)  162 , other MMEs  164 , a Serving Gateway  166 , a Multimedia Broadcast Multicast Service (MBMS) Gateway  168 , a Broadcast Multicast Service Center (BM-SC)  170 , and a Packet Data Network (PDN) Gateway  172 . MME  162  may be in communication with a Home Subscriber Server (HSS)  174 . MME  162  is the control node that processes the signaling between the UEs  104  and the EPC  160 . Generally, MME  162  provides bearer and connection management. 
     Generally, user Internet protocol (IP) packets are transferred through Serving Gateway  166 , which itself is connected to PDN Gateway  172 . PDN Gateway  172  provides UE IP address allocation as well as other functions. PDN Gateway  172  and the BM-SC  170  are connected to the IP Services  176 , which may include, for example, the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services. 
     BM-SC  170  may provide functions for MBMS user service provisioning and delivery. BM-SC  170  may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN), and may be used to schedule MBMS transmissions. MBMS Gateway  168  may be used to distribute MBMS traffic to the BSs  102  belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information. 
     5GC  190  may include an Access and Mobility Management Function (AMF)  192 , other AMFs  193 , a Session Management Function (SMF)  194 , and a User Plane Function (UPF)  195 . AMF  192  may be in communication with a Unified Data Management (UDM)  196 . 
     AMF  192  is generally the control node that processes the signaling between UEs  104  and 5GC  190 . Generally, AMF  192  provides QoS flow and session management. 
     All user Internet protocol (IP) packets are transferred through UPF  195 , which is connected to the IP Services  197 , and which provides UE IP address allocation as well as other functions for 5GC  190 . IP Services  197  may include, for example, the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services. 
     Returning to  FIG.  2   , various example components of BS  102  and UE  104  (e.g., the wireless communication network  100  of  FIG.  1   ) are depicted, which may be used to implement aspects of the present disclosure. 
     At BS  102 , a transmit processor  220  may receive data from a data source  212  and control information from a controller/processor  240 . The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), and others. The data may be for the physical downlink shared channel (PDSCH), in some examples. 
     A medium access control (MAC)-control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel such as a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), or a physical sidelink shared channel (PSSCH). 
     Processor  220  may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. Transmit processor  220  may also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), PBCH demodulation reference signal (DMRS), and channel state information reference signal (CSI-RS). 
     Transmit (TX) multiple-input multiple-output (MIMO) processor  230  may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) in transceivers  232   a - 232   t . Each modulator in transceivers  232   a - 232   t  may process a respective output symbol stream (e.g., for OFDM) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from the modulators in transceivers  232   a - 232   t  may be transmitted via the antennas  234   a - 234   t , respectively. 
     At UE  104 , antennas  252   a - 252   r  may receive the downlink signals from the BS  102  and may provide received signals to the demodulators (DEMODs) in transceivers  254   a - 254   r , respectively. Each demodulator in transceivers  254   a - 254   r  may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM) to obtain received symbols. 
     MIMO detector  256  may obtain received symbols from all the demodulators in transceivers  254   a - 254   r , perform MIMO detection on the received symbols if applicable, and provide detected symbols. Receive processor  258  may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE  104  to a data sink  260 , and provide decoded control information to a controller/processor  280 . 
     On the uplink, at UE  104 , transmit processor  264  may receive and process data (e.g., for the physical uplink shared channel (PUSCH)) from a data source  262  and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor  280 . Transmit processor  264  may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS)). The symbols from the transmit processor  264  may be precoded by a TX MIMO processor  266  if applicable, further processed by the modulators in transceivers  254   a - 254   r  (e.g., for SC-FDM), and transmitted to BS  102 . 
     At BS  102 , the uplink signals from UE  104  may be received by antennas  234   a - t , processed by the demodulators in transceivers  232   a - 232   t , detected by a MIMO detector  236  if applicable, and further processed by a receive processor  238  to obtain decoded data and control information sent by UE  104 . Receive processor  238  may provide the decoded data to a data sink  239  and the decoded control information to the controller/processor  240 . 
     Memories  242  and  282  may store data and program codes for BS  102  and UE  104 , respectively. 
     Scheduler  244  may schedule UEs for data transmission on the downlink and/or uplink. 
     5G may utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on the uplink and downlink. 5G may also support half-duplex operation using time division duplexing (TDD). OFDM and single-carrier frequency division multiplexing (SC-FDM) partition the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones and bins. Each subcarrier may be modulated with data. Modulation symbols may be sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers may be dependent on the system bandwidth. The minimum resource allocation, called a resource block (RB), may be 12 consecutive subcarriers in some examples. The system bandwidth may also be partitioned into subbands. For example, a subband may cover multiple RBs. NR may support a base subcarrier spacing (SCS) of 15 KHz and other SCS may be defined with respect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, and others). 
     As above,  FIGS.  3 A- 3 D  depict various example aspects of data structures for a wireless communication network, such as wireless communication network  100  of  FIG.  1   . 
     In various aspects, the 5G frame structure may be frequency division duplex (FDD), in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for either DL or UL. 5G frame structures may also be time division duplex (TDD), in which for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated for both DL and UL. In the examples provided by  FIGS.  3 A and  3 C , the 5G frame structure is assumed to be TDD, with subframe  4  being configured with slot format  28  (with mostly DL), where D is DL, U is UL, and X is flexible for use between DL/UL, and subframe  3  being configured with slot format  34  (with mostly UL). While subframes  3 ,  4  are shown with slot formats  34 ,  28 , respectively, any particular subframe may be configured with any of the various available slot formats  0 - 61 . Slot formats  0 ,  1  are all DL, UL, respectively. Other slot formats  2 - 61  include a mix of DL, UL, and flexible symbols. UEs are configured with the slot format (dynamically through DL control information (DCI), or semi-statically/statically through radio resource control (RRC) signaling) through a received slot format indicator (SFI). Note that the description below applies also to a 5G frame structure that is TDD. 
     Other wireless communication technologies may have a different frame structure and/or different channels. A frame (10 ms) may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-slots, which may include 7, 4, or 2 symbols. In some examples, each slot may include 7 or 14 symbols, depending on the slot configuration. 
     For example, for slot configuration  0 , each slot may include 14 symbols, and for slot configuration  1 , each slot may include 7 symbols. The symbols on DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. The symbols on UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also referred to as single carrier frequency-division multiple access (SC-FDMA) symbols) (for power limited scenarios; limited to a single stream transmission). 
     The number of slots within a subframe is based on the slot configuration and the numerology. For slot configuration  0 , different numerologies (μ)  0  to  5  allow for 1, 2, 4, 8, 16, and 32 slots, respectively, per subframe. For slot configuration  1 , different numerologies  0  to  2  allow for 2, 4, and 8 slots, respectively, per subframe. Accordingly, for slot configuration  0  and numerology μ, there are 14 symbols/slot and 2μ slots/subframe. The subcarrier spacing and symbol length/duration are a function of the numerology. The subcarrier spacing may be equal to 2 μ ×15 kHz, where μ is the numerology  0  to  5 . As such, the numerology μ=0 has a subcarrier spacing of 15 kHz and the numerology μ=5 has a subcarrier spacing of 480 kHz. The symbol length/duration is inversely related to the subcarrier spacing.  FIGS.  3 A- 3 D  provide an example of slot configuration  0  with 14 symbols per slot and numerology μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs. 
     A resource grid may be used to represent the frame structure. Each time slot includes a resource block (RB) (also referred to as physical RBs (PRBs)) that extends 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme. 
     As illustrated in  FIG.  3 A , some of the REs carry reference (pilot) signals (RS) for a UE (e.g., UE  104  of  FIGS.  1  and  2   ). The RS may include demodulation RS (DM-RS) (indicated as Rx for one particular configuration, where 100× is the port number, but other DM-RS configurations are possible) and channel state information reference signals (CSI-RS) for channel estimation at the UE. The RS may also include beam measurement RS (BRS), beam refinement RS (BRRS), and phase tracking RS (PT-RS). 
       FIG.  3 B  illustrates an example of various DL channels within a subframe of a frame. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol. 
     A primary synchronization signal (PSS) may be within symbol  2  of particular subframes of a frame. The PSS is used by a UE (e.g.,  104  of  FIGS.  1  and  2   ) to determine subframe/symbol timing and a physical layer identity. 
     A secondary synchronization signal (SSS) may be within symbol  4  of particular subframes of a frame. The SSS is used by a UE to determine a physical layer cell identity group number and radio frame timing. 
     Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the aforementioned DM-RS. The physical broadcast channel (PBCH), which carries a master information block (MIB), may be logically grouped with the PSS and SSS to form a synchronization signal (SS)/PBCH block. The MIB provides a number of RBs in the system bandwidth and a system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs), and paging messages. 
     As illustrated in  FIG.  3 C , some of the REs carry DM-RS (indicated as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at BS. UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether short or long PUCCHs are transmitted and depending on the particular PUCCH format used. The UE may transmit sounding reference signals (SRS). The SRS may be transmitted in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by BS for channel quality estimation to enable frequency-dependent scheduling on the UL. 
       FIG.  3 D  illustrates an example of various UL channels within a subframe of a frame. The PUCCH may be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and/or UCI. 
     Additional Considerations 
     The preceding description provides examples of physical downlink shared channel (PDSCH)-based channel state information (CSI) in communication systems. The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. The examples discussed herein are not limiting of the scope, applicability, or aspects set forth in the claims. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. For example, changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method that is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. 
     The techniques described herein may be used for various wireless communication technologies, such as 5G (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), 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), time division synchronous code division multiple access (TD-SCDMA), and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, and others. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and others. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). NR is an emerging wireless communications technology under development. 
     The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a DSP, an ASIC, a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available 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, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, a system on a chip (SoC), or any other such configuration. 
     If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user equipment (UE) (see  FIG.  1   ), a user interface (e.g., keypad, display, mouse, joystick, touchscreen, biometric sensor, proximity sensor, light emitting element, and others) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system. 
     If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product. 
     A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module. 
     As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). 
     As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like. 
     The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. Further, the various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering. 
     The following claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims. Within a claim, reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.” All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.