Patent Publication Number: US-2023163822-A1

Title: Beamforming for multi-aperture orbital angular momentum multiplexing based communication

Description:
FIELD OF THE DISCLOSURE 
     Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for beamforming for multi-aperture orbital angular momentum (OAM) multiplexing based communication. 
     BACKGROUND 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE). LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP). 
     A wireless network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs). A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP), a radio head, a transmit receive point (TRP), a New Radio (NR) BS, a 5G Node B, and/or the like. 
     The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New Radio (NR), which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL), using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM)) on the uplink (UL), as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. As the demand for mobile broadband access continues to increase, further improvements in LTE, NR, and other radio access technologies remain useful. 
     SUMMARY 
     In some aspects, a method of wireless communication performed by a receiver of orbital angular momentum (OAM) multiplexing based communication includes: receiving, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; transmitting, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and receiving, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, a method of wireless communication performed by a transmitter of OAM multiplexing based communication includes: transmitting, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; receiving, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and transmitting, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, a receiver of OAM multiplexing based communication includes: a memory; and one or more processors operatively coupled to the memory, the memory and the one or more processors configured to: receive, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; transmit, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and receive, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, a transmitter of OAM multiplexing based communication includes: a memory; and one or more processors operatively coupled to the memory, the memory and the one or more processors configured to: transmit, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; receive, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and transmit, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, a non-transitory computer-readable medium storing a set of instructions for wireless communication includes: one or more instructions that, when executed by one or more processors of a receiver of OAM multiplexing based communication, cause the receiver to: receive, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; transmit, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and receive, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, a non-transitory computer-readable medium storing a set of instructions for wireless communication includes: one or more instructions that, when executed by one or more processors of a transmitter of OAM multiplexing based communication, cause the transmitter to: transmit, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; receive, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and transmit, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, an apparatus for OAM multiplexing based communication includes: means for receiving, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; means for transmitting, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and means for receiving, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     In some aspects, an apparatus for OAM multiplexing based communication includes: means for transmitting, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair; means for receiving, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals; and means for transmitting, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information. 
     Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and/or processing system as substantially described herein with reference to and as illustrated by the drawings and specification. 
     The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements. 
         FIG.  1    is a diagram illustrating an example of a wireless network, in accordance with various aspects of the present disclosure. 
         FIG.  2    is a diagram illustrating an example of a base station in communication with a UE in a wireless network, in accordance with various aspects of the present disclosure. 
         FIG.  3    is a diagram illustrating an example of multi-aperture orbital angular momentum (OAM) multiplexing based communication, in accordance with various aspects of the present disclosure. 
         FIG.  4    is a diagram illustrating an example associated with beamforming for multi-aperture OAM multiplexing based communication, in accordance with various aspects of the present disclosure. 
         FIGS.  5  and  6    are diagrams illustrating example processes associated with beamforming for multi-aperture OAM multiplexing based communication, in accordance with various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein, one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. 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 which 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. 
     Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and/or the like (collectively referred to as “elements”). These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     It should be noted that while aspects may be described herein using terminology commonly associated with a 5G or NR radio access technologies (RAT), aspects of the present disclosure can be applied to other RATs, such as a 3G RAT, a 4G RAT, and/or a RAT subsequent to 5G (e.g., 6G). 
       FIG.  1    is a diagram illustrating an example of a wireless network  100 , in accordance with various aspects of the present disclosure. The wireless network  100  may be or may include elements of a 5G (NR) network, an LTE network, and/or the like. The wireless network  100  may include a number of base stations  110  (shown as BS  110   a , BS  110   b , BS  110   c , and BS  110   d ) and other network entities. A base station (BS) is an entity that communicates with user equipment (UEs) and may also be referred to as an NR BS, a Node B, a gNB, a 5G node B (NB), an access point, a transmit receive point (TRP), and/or the like. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used. 
     A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may 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 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 association with the femto cell (e.g., UEs in a closed subscriber group (CSG)). 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 or a home BS. In the example shown in  FIG.  1   , a BS  110   a  may be a macro BS for a macro cell  102   a , a BS  110   b  may be a pico BS for a pico cell  102   b , and a BS  110   c  may be a femto BS for a femto cell  102   c . A BS may support one or multiple (e.g., three) cells. The terms “eNB”, “base station”, “NR BS”, “gNB”, “TRP”, “AP”, “node B”, “5G NB”, and “cell” may be used interchangeably herein. 
     In some aspects, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some aspects, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless network  100  through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network. 
     Wireless network  100  may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS). A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in  FIG.  1   , a relay station  110   d  may communicate with macro BS  110   a  and a UE  120   d  in order to facilitate communication between BS  110   a  and UE  120   d . A relay station may also be referred to as a relay BS, a relay base station, a relay, and/or the like. 
     Wireless network  100  may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/or the like. These different types of BSs may have different transmit power levels, different coverage areas, and different impacts on interference in wireless network  100 . For example, macro BSs may have a high transmit power level (e.g., 5 to 40 watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 watts). 
     A network controller  130  may couple to a set of BSs and may provide coordination and control for these BSs. Network controller  130  may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul. 
     UEs  120  (e.g.,  120   a ,  120   b ,  120   c ) may be dispersed throughout wireless network  100 , and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, and/or the like. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. 
     Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, and/or the like, that may communicate with a base station, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as NB-IoT (narrowband Internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE). UE  120  may be included inside a housing that houses components of UE  120 , such as processor components, memory components, and/or the like. In some aspects, the processor components and the memory components may be coupled together. For example, the processor components (e.g., one or more processors) and the memory components (e.g., a memory) may be operatively coupled, communicatively coupled, electronically coupled, electrically coupled, and/or the like. 
     In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, and/or the like. A frequency may also be referred to as a carrier, a frequency channel, and/or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed. 
     In some aspects, two or more UEs  120  (e.g., shown as UE  120   a  and UE  120   e ) may communicate directly using one or more sidelink channels (e.g., without using a base station  110  as an intermediary to communicate with one another). For example, the UEs  120  may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, and/or the like), a mesh network, and/or the like. In this case, the UE  120  may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the base station  110 . 
     Devices of wireless network  100  may communicate using the electromagnetic spectrum, which may be subdivided based on frequency or wavelength into various classes, bands, channels, and/or the like. For example, devices of wireless network  100  may communicate using an operating band having a first frequency range (FR1), which may span from 410 MHz to 7.125 GHz, and/or may communicate using an operating band having a second frequency range (FR2), which may span from 24.25 GHz to 52.6 GHz. The frequencies between FR1 and FR2 are sometimes referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is often referred to as a “sub-6 GHz” band. Similarly, FR2 is often referred to as a “millimeter wave” band despite being different from the extremely high frequency (EHF) band (30 GHz-300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band. Thus, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like, if used herein, may broadly represent frequencies less than 6 GHz, frequencies within FR1, and/or mid-band frequencies (e.g., greater than 7.125 GHz). Similarly, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like, if used herein, may broadly represent frequencies within the EHF band, frequencies within FR2, and/or mid-band frequencies (e.g., less than 24.25 GHz). It is contemplated that the frequencies included in FR1 and FR2 may be modified, and techniques described herein are applicable to those modified frequency ranges. 
     As indicated above,  FIG.  1    is provided as an example. Other examples may differ from what is described with regard to  FIG.  1   . 
       FIG.  2    is a diagram illustrating an example  200  of a base station  110  in communication with a UE  120  in a wireless network  100 , in accordance with various aspects of the present disclosure. Base station  110  may be equipped with T antennas  234   a  through  234   t , and UE  120  may be equipped with R antennas  252   a  through  252   r , where in general T≥1 and R≥1. 
     At base station  110 , a transmit processor  220  may receive data from a data source  212  for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS(s) selected for the UE, and provide data symbols for all UEs. Transmit processor  220  may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., CQI requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. Transmit processor  220  may also generate reference symbols for reference signals (e.g., a cell-specific reference signal (CRS), a demodulation reference signal (DMRS), and/or the like) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor  230  may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs)  232   a  through  232   t . Each modulator  232  may process a respective output symbol stream (e.g., for OFDM and/or the like) to obtain an output sample stream. Each modulator  232  may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators  232   a  through  232   t  may be transmitted via T antennas  234   a  through  234   t , respectively. 
     At UE  120 , antennas  252   a  through  252   r  may receive the downlink signals from base station  110  and/or other base stations and may provide received signals to demodulators (DEMODs)  254   a  through  254   r , respectively. Each demodulator  254  may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator  254  may further process the input samples (e.g., for OFDM and/or the like) to obtain received symbols. A MIMO detector  256  may obtain received symbols from all R demodulators  254   a  through  254   r , perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor  258  may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE  120  to a data sink  260 , and provide decoded control information and system information to a controller/processor  280 . The term “controller/processor” may refer to one or more controllers, one or more processors, or a combination thereof. A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), and/or the like. In some aspects, one or more components of UE  120  may be included in a housing  284 . 
     Network controller  130  may include communication unit  294 , controller/processor  290 , and memory  292 . Network controller  130  may include, for example, one or more devices in a core network. Network controller  130  may communicate with base station  110  via communication unit  294 . 
     On the uplink, at UE  120 , a transmit processor  264  may receive and process data from a data source  262  and control information (e.g., for reports that include RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor  280 . Transmit processor  264  may also generate reference symbols for one or more reference signals. The symbols from transmit processor  264  may be precoded by a TX MIMO processor  266  if applicable, further processed by modulators  254   a  through  254   r  (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like), and transmitted to base station  110 . In some aspects, the UE  120  includes a transceiver. The transceiver may include any combination of antenna(s)  252 , modulators and/or demodulators  254 , MIMO detector  256 , receive processor  258 , transmit processor  264 , and/or TX MIMO processor  266 . The transceiver may be used by a processor (e.g., controller/processor  280 ) and memory  282  to perform aspects of any of the methods described herein, for example, as described with reference to  FIGS.  4 - 6   . 
     At base station  110 , the uplink signals from UE  120  and other UEs may be received by antennas  234 , processed by demodulators  232 , 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  120 . Receive processor  238  may provide the decoded data to a data sink  239  and the decoded control information to controller/processor  240 . Base station  110  may include communication unit  244  and communicate to network controller  130  via communication unit  244 . Base station  110  may include a scheduler  246  to schedule UEs  120  for downlink and/or uplink communications. In some aspects, the base station  110  includes a transceiver. The transceiver may include any combination of antenna(s)  234 , modulators and/or demodulators  232 , MIMO detector  236 , receive processor  238 , transmit processor  220 , and/or TX MIMO processor  230 . The transceiver may be used by a processor (e.g., controller/processor  240 ) and memory  242  to perform aspects of any of the methods described herein, for example, as described with reference to  FIGS.  4 - 6   . 
     Controller/processor  240  of base station  110 , controller/processor  280  of UE  120 , and/or any other component(s) of  FIG.  2    may perform one or more techniques associated with beamforming for multi-aperture orbital angular momentum (OAM) multiplexing based communication, as described in more detail elsewhere herein. For example, controller/processor  240  of base station  110 , controller/processor  280  of UE  120 , and/or any other component(s) of  FIG.  2    may perform or direct operations of, for example, process  500  of  FIG.  5   , process  600  of  FIG.  6   , and/or other processes as described herein. Memories  242  and  282  may store data and program codes for base station  110  and UE  120 , respectively. In some aspects, memory  242  and/or memory  282  may include a non-transitory computer-readable medium storing one or more instructions (e.g., code, program code, and/or the like) for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, interpreting, and/or the like) by one or more processors of the base station  110  and/or the UE  120 , may cause the one or more processors, the UE  120 , and/or the base station  110  to perform or direct operations of, for example, process  500  of  FIG.  5   , process  600  of  FIG.  6   , and/or other processes as described herein. In some aspects, executing instructions may include running the instructions, converting the instructions, compiling the instructions, interpreting the instructions, and/or the like. 
     In some aspects, UE  120  may include means for receiving, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair, means for transmitting, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals, means for receiving, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information, and/or the like. In some aspects, such means may include one or more components of UE  120  described in connection with  FIG.  2   , such as controller/processor  280 , transmit processor  264 , TX MIMO processor  266 , MOD  254 , antenna  252 , DEMOD  254 , MIMO detector  256 , receive processor  258 , and/or the like. 
     In some aspects, base station  110  may include means for transmitting, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair, means for receiving, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals, means for transmitting, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information, and/or the like. In some aspects, such means may include one or more components of base station  110  described in connection with  FIG.  2   , such as antenna  234 , DEMOD  232 , MIMO detector  236 , receive processor  238 , controller/processor  240 , transmit processor  220 , TX MIMO processor  230 , MOD  232 , antenna  234 , and/or the like. 
     While blocks in  FIG.  2    are illustrated as distinct components, the functions described above with respect to the blocks may be implemented in a single hardware, software, or combination component or in various combinations of components. For example, the functions described with respect to the transmit processor  264 , the receive processor  258 , and/or the TX MIMO processor  266  may be performed by or under the control of controller/processor  280 . 
     As indicated above,  FIG.  2    is provided as an example. Other examples may differ from what is described with regard to  FIG.  2   . 
       FIG.  3    is a diagram illustrating an example  300  of multi-aperture OAM multiplexing based communication, in accordance with various aspects of the present disclosure. As shown, a transmitter  305  and a receiver  310  may communicate with one another using OAM multiplexing based communication. According to various aspects, the transmitter  305  and/or the receiver  310  may be implemented in connection with one or more UEs (e.g., the UE  120  shown in  FIG.  1   , and/or the like), one or more base stations (e.g., the base station  110  shown in  FIG.  1   , and/or the like), one or more vehicles having one or more onboard UEs, and/or the like. 
     Communication based on OAM multiplexing may provide high-order spatial multiplexing as a means to increasing high data rates. In OAM multiplexing based communication, the transmitter  305  may radiate multiple coaxially propagating, spatially-overlapping waves (OAM mode l= . . . , −2, −1, 0, 1, 2, . . . ) each carrying a data stream through a transmitter aperture  315  to a receiver aperture  320 . An electromagnetic wave with a helical transverse phase of the form exp(iφl) may be used to carry an OAM mode waveform, where φ is the azimuthal angle and l is an unbounded integer (referred as the OAM order). Multiple OAM waves can be orthogonally transmitted using the same radio resources (time and/or frequency domains); thus, using OAM multiplexing can greatly improve communication spectrum efficiency. 
     To further increase the communication throughput, as shown in  FIG.  3   , multiple pairs of apertures (where each pair includes a transmitter aperture  315  and a corresponding receiver aperture  320 ) may be applied in parallel. In some cases, one pair of transmitter and receiver apertures can have M spatial-multiplexed channels (OAM modes), in which case, N pairs of apertures can have MN spatial multiplexed channels (OAM modes). The channels in one pair of apertures may be orthogonal and have no or trivial mutual interference. However, the channels in different pairs of apertures may be non-orthogonal and have mutual interference. 
     For example, as shown in  FIG.  3   , as a beam travels from the transmitter aperture  315  to the corresponding receiver aperture  320 , the outer bound (referred to herein as a radiation circle)  325 ,  330  of each beam mode expands. As shown, radiation circles  325  associated with waves with higher-order modes (e.g., l=3) expand faster than radiation circles  330  associated with waves with lower-order modes (e.g., l=1). As a result, the mutual interference is more severe among higher-order modes than among lower-order modes, and may cause a reduction in throughput, signal reliability, signal quality, and/or the like. 
     According to various aspects of the techniques and apparatuses described herein, a receiver of OAM multiplexing based communication may provide feedback to a transmitter to facilitate beamforming. As a result, aspects may facilitate a reduction in mutual interference between modes, thereby leading to an increase in throughput, signal reliability, signal quality, and/or the like. In some aspects, the transmitter may transmit one or more reference signals to the receiver. The receiver may determine OAM mode groupings and combining coefficients based on the reference signals and may feed back those OAM mode groupings and combining coefficients to the transmitter as beamforming information. The transmitter may transmit to the receiver data streams that are beamformed based at least in part on the beamforming information. In this way, aspects may facilitate reducing interference between antennas used for OAM multiplexing based communication. As a result, aspects may facilitate increases in throughput, signal reliability, signal quality, and/or the like. 
     As indicated above,  FIG.  3    is provided as an example. Other examples may differ from what is described with regard to  FIG.  3   . 
       FIG.  4    is a diagram illustrating an example  400  associated with beamforming for multi-aperture OAM multiplexing based communication, in accordance with various aspects of the present disclosure. As shown, a transmitter  405  of OAM multiplexing based communication and a receiver  410  of OAM multiplexing based communication may communicate with one another. 
     In some aspects, the transmitter  405  may be, be similar to, include, or be included in the transmitter  305  depicted in  FIG.  3   , and the receiver  410  may be, be similar to, include, or be included in, the receiver  310  shown in  FIG.  3   . In some aspects, the transmitter  405  and/or the receiver  410  may be, be similar to, include, or be included in, a UE (e.g., UE  120  shown in  FIG.  1   ), a base station (e.g., base station  110  shown in  FIG.  1   ), and/or the like. 
     As shown by reference number  415 , the transmitter  405  may transmit, and the receiver  410  may receive, a number of reference signals corresponding to a plurality of aperture pairs. In some aspects, each transmitter aperture may transmit one or more reference signals to a corresponding receiver aperture. In some aspects, a reference signal may correspond to an OAM mode of a corresponding aperture pair. 
     As shown by reference number  420 , the receiver  410  may determine beamforming information. In some aspects, the beamforming information may be based at least in part on one or more of the reference signals. In some aspects, the receiver  410  may determine the beamforming information by determining one or more characteristics of the reference signal, interference between two or more reference signals (inter-aperture interference, intra-aperture interference, and/or the like), and/or the like. In some aspects, the beamforming information may be configured to be used to beamform data streams so that the interference is reduced. 
     In some aspects, the beamforming information may indicate one or more OAM mode groups, one or more combining coefficients for two or more non-orthogonal OAM modes associated with an OAM mode group, one or more group-specific coefficients associated with an OAM mode group, a modulation and coding scheme (MCS) value corresponding to at least one OAM mode group, and/or the like. In some aspects, the beamforming information may be based at least in part on the determined inter-aperture interference, the determined intra-aperture interference, and/or the like. 
     In some aspects, the receiver  410  may measure inter-aperture interference and determine one or more OAM groups based at least in part on the inter-aperture interference. In some aspects, the receiver  410  may determine the OAM mode groups based at least in part on a condition being satisfied. The condition may be satisfied based at least in part on an OAM mode group of the OAM mode groups including one OAM mode or a plurality of non-orthogonal OAM modes, an OAM mode of a first OAM mode group being orthogonal to an OAM mode of a second OAM mode group, or a combination thereof. 
     In some aspects, the OAM mode groups may include at least one OAM mode group having a low-order OAM mode and at least one OAM mode group having a high-order OAM mode. For example, in some aspects, the OAM modes shown in  FIG.  3    may be grouped such that a first OAM mode group includes all of the channels (channel 2, channel 4, channel 6, and channel 8) having an OAM mode of l=3, a second OAM mode group that includes channel 1, a third OAM mode group that includes channel 3, a fourth OAM mode group that includes channel 5, a fifth OAM mode group that includes channel 7, and/or the like. In some aspects, an OAM mode group may be a beamformed port. The received signal of two OAM modes within one aperture pair are orthogonal, but due to energy divergence, the received signals of high-order OAM modes between two adjacent aperture pairs may be mutually interfered, while the low-order OAM modes between two adjacent aperture pairs still maintain orthogonality. Thus, grouping OAM modes in accordance with aspects described herein may facilitate orthogonality. 
     In some aspects, the beamforming information may indicate an index associated with an OAM mode. The index may indicate an OAM mode level corresponding to the OAM mode and an aperture pair identifier associated with the corresponding aperture pair. In some aspects, the beamforming information may indicate an order corresponding to the index and at least one additional index associated with at least one additional OAM mode. The order may be based at least in part on an order of mode levels within each aperture pair of the plurality of aperture pairs. In some aspects, the order may be based at least in part on an order of aperture pair identifiers corresponding to the plurality of aperture pairs. 
     For example, with reference to the modes depicted in  FIG.  3   , the order of the indexes may be based on the modes within each aperture: (aperture 1, mode 1), (aperture 1, mode 2), (aperture 2, mode 1), (aperture 2, mode 2), (aperture 3, mode 1), (aperture 3, mode 2), (aperture 4, mode 1), (aperture 4, mode 2). In some aspects, the indexes may be based on the OAM mode groups, and/or the like. 
     In some aspects, the beamforming information may include one or more combination coefficients for non-orthogonal modes in a group. In some aspects, a combining coefficient may be based at least in part on a plurality of channel gains associated with the two or more non-orthogonal OAM modes. The combining coefficient may include a conjugate value of a channel gain of the plurality of channel gains. 
     In some aspects, the receiver  410  may quantize an amplitude and a phase of a combining coefficient to generate a set of quantization bits, and may report the quantization bits to the transmitter  405  as part of the beamforming information. In some aspects, the receiver  410  may select, from a pre-configured codebook, a codeword that satisfies a similarity condition associated with the combining coefficient. The beamforming information may indicate an index associated with the codeword. In some aspects, the receiver  410  may determine a combining coefficient for a single OAM mode associated with an OAM mode group of a plurality of OAM mode groups. In some aspects, the combining coefficient may have a value of one. The receiver may refrain from including the combining coefficient in the beamforming information based at least in part on the combining coefficient having the value of one. 
     As shown by reference number  425 , the receiver  410  may transmit, and the transmitter  405  may receive, a feedback message. The feedback message may include the beamforming information. As shown by reference number  430 , the transmitter  405  may transmit, and the receiver  410  may receive, data streams that are beamformed based at least in part on the beamforming information. 
     As indicated above,  FIG.  4    is provided as an example. Other examples may differ from what is described with regard to  FIG.  4   . 
       FIG.  5    is a diagram illustrating an example process  500  performed, for example, by a receiver, in accordance with various aspects of the present disclosure. Example process  500  is an example where the receiver (e.g., receiver  410  shown in  FIG.  4   , and/or the like) performs operations associated with beamforming for multi-aperture OAM multiplexing based communication. 
     As shown in  FIG.  5   , in some aspects, process  500  may include receiving, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair (block  510 ). For example, the receiver (e.g., using receive processor  238 , receive processor  258 , controller/processor  240 , controller/processor  280 , memory  242 , memory  282 , and/or the like) may receive, from a transmitter of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, as described above. In some aspects, a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair. 
     As further shown in  FIG.  5   , in some aspects, process  500  may include transmitting, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals (block  520 ). For example, the receiver (e.g., using transmit processor  220 , transmit processor  264 , controller/processor  240 , controller/processor  280 , memory  242 , memory  282 , and/or the like) may transmit, to the transmitter, a feedback message comprising beamforming information based at least in part on the plurality of reference signals, as described above. 
     As further shown in  FIG.  5   , in some aspects, process  500  may include receiving, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information (block  530 ). For example, the receiver (e e.g., using receive processor  238 , receive processor  258 , controller/processor  240 , controller/processor  280 , memory  242 , memory  282 , and/or the like) may receive, from the transmitter, a plurality of data streams that are beamformed based at least in part on the beamforming information, as described above. 
     Process  500  may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein. 
     In a first aspect, the beamforming information indicates at least one of a plurality of OAM mode groups, wherein an OAM mode group of the plurality of OAM mode groups comprises the OAM mode, a combining coefficient for two or more non-orthogonal OAM modes associated with an OAM mode group of the plurality of OAM mode groups, a group-specific coefficient associated with the OAM mode group, a modulation and coding scheme value corresponding to at least one OAM mode group of the plurality of OAM groups, or a combination thereof. 
     In a second aspect, alone or in combination with the first aspect, the beamforming information further indicates an index associated with the OAM mode. 
     In a third aspect, alone or in combination with one or more of the first and second aspects, the index indicates: an OAM mode level corresponding to the OAM mode, and an aperture pair identifier associated with the corresponding aperture pair. 
     In a fourth aspect, alone or in combination with one or more of the first through third aspects, the beamforming information indicates an order corresponding to the index and at least one additional index associated with at least one additional OAM mode. 
     In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the order is based at least in part on an order of mode levels within each aperture pair of the plurality of aperture pairs. 
     In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the order is further based at least in part on an order of aperture pair identifiers corresponding to the plurality of aperture pairs. 
     In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, process  500  includes determining inter-aperture interference associated with two or more aperture pairs of the plurality of aperture pairs, determining intra-aperture interference associated with the corresponding aperture pair, or a combination thereof. 
     In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, process  500  includes determining the beamforming information based at least in part on at least one of the inter-aperture interference, the intra-aperture interference, or a combination thereof. 
     In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, process  500  includes determining a plurality of OAM mode groups based at least in part on a condition being satisfied. 
     In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the plurality of OAM mode groups comprises at least one OAM mode group having a low-order OAM mode, and at least one OAM mode group having a high-order OAM mode. 
     In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the condition is satisfied based at least in part on at least one of an OAM mode group of the plurality of OAM mode groups comprising one OAM mode or a plurality of non-orthogonal OAM modes, an OAM mode of a first OAM mode group being orthogonal to an OAM mode of a second OAM mode group, or a combination thereof. 
     In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, process  500  includes determining a combining coefficient for two or more non-orthogonal OAM modes associated with an OAM mode group of a plurality of OAM mode groups. 
     In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, the combining coefficient is based at least in part on a plurality of channel gains associated with the two or more non-orthogonal OAM modes. 
     In a fourteenth aspect, alone or in combination with one or more of the first through thirteenth aspects, the combining coefficient comprises a conjugate value of a channel gain of the plurality of channel gains. 
     In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, the OAM mode group comprises a beamformed port. 
     In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, process  500  includes quantizing an amplitude and a phase of the combining coefficient to generate a set of quantization bits, where the beamforming information indicates the set of quantization bits. 
     In a seventeenth aspect, alone or in combination with one or more of the first through sixteenth aspects, process  500  includes selecting, from a pre-configured codebook, a codeword that satisfies a similarity condition associated with the combining coefficient, where the beamforming information indicates an index associated with the codeword. 
     In an eighteenth aspect, alone or in combination with one or more of the first through seventeenth aspects, process  500  includes determining a combining coefficient for a single OAM mode associated with an OAM mode group of a plurality of OAM mode groups, where the combining coefficient has a value of one. 
     In a nineteenth aspect, alone or in combination with one or more of the first through eighteenth aspects, process  500  includes refraining from including the combining coefficient in the beamforming information based at least in part on the combining coefficient having the value of one. 
     In a twentieth aspect, alone or in combination with one or more of the first through nineteenth aspects, process  500  includes determining a group-specific coefficient associated with an OAM mode group of a plurality of OAM mode groups. 
     In a twenty first aspect, alone or in combination with one or more of the first through twentieth aspects, process  500  includes determining a modulation and coding scheme value corresponding to an OAM mode group of a plurality of OAM mode groups. 
     Although  FIG.  5    shows example blocks of process  500 , in some aspects, process  500  may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in  FIG.  5   . Additionally, or alternatively, two or more of the blocks of process  500  may be performed in parallel. 
       FIG.  6    is a diagram illustrating an example process  600  performed, for example, by a transmitter, in accordance with various aspects of the present disclosure. Example process  600  is an example where the transmitter (e.g., transmitter  410  shown in  FIG.  4   , and/or the like) performs operations associated with beamforming for multi-aperture OAM multiplexing based communication. 
     As shown in  FIG.  6   , in some aspects, process  600  may include transmitting, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, wherein a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair (block  610 ). For example, the transmitter (e.g., using transmit processor  220 , transmit processor  264 , controller/processor  240 , controller/processor  280 , memory  242 , memory  282 , and/or the like) may transmit, to a receiver of the OAM multiplexing based communication, a plurality of reference signals corresponding to a plurality of aperture pairs, as described above. In some aspects, a reference signal of the plurality of reference signals corresponds to an OAM mode of a corresponding aperture pair. 
     As further shown in  FIG.  6   , in some aspects, process  600  may include receiving, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals (block  620 ). For example, the transmitter (e.g., using receive processor  238 , receive processor  258 , controller/processor  240 , controller/processor  280 , memory  242 , memory  282 , and/or the like) may receive, from the receiver, a feedback message comprising beamforming information based at least in part on the plurality of reference signals, as described above. 
     As further shown in  FIG.  6   , in some aspects, process  600  may include transmitting, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information (block  630 ). For example, the transmitter (e.g., using transmit processor  220 , transmit processor  264 , controller/processor  240 , controller/processor  280 , memory  242 , memory  282 , and/or the like) may transmit, to the receiver, a plurality of data streams that are beamformed based at least in part on the beamforming information, as described above. 
     Process  600  may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein. 
     In a first aspect, the beamforming information indicates at least one of a plurality of OAM mode groups, wherein an OAM mode group of the plurality of OAM mode groups comprises the OAM mode, a combining coefficient for two or more non-orthogonal OAM modes associated with an OAM mode group of the plurality of OAM mode groups, a group-specific coefficient associated with the OAM mode group, a modulation and coding scheme value corresponding to at least one OAM mode group of the plurality of OAM groups, or a combination thereof. 
     In a second aspect, alone or in combination with the first aspect, the beamforming information further indicates an index associated with the OAM mode. 
     In a third aspect, alone or in combination with one or more of the first and second aspects, the index indicates an OAM mode level corresponding to the OAM mode and an aperture pair identifier associated with the corresponding aperture pair. 
     In a fourth aspect, alone or in combination with one or more of the first through third aspects, the beamforming information indicates an order corresponding to the index and at least one additional index associated with at least one additional OAM mode. 
     In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the order is based at least in part on an order of mode levels within each aperture pair of the plurality of aperture pairs. 
     In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the order is further based at least in part on an order of aperture pair identifiers corresponding to the plurality of aperture pairs. 
     In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the beamforming information is based at least in part on at least one of an inter-aperture interference associated with two or more aperture pairs of the plurality of aperture pairs, an intra-aperture interference associated with the corresponding aperture pair, or a combination thereof. 
     In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the beamforming information indicates a plurality of OAM mode groups based at least in part on a condition being satisfied. 
     In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the plurality of OAM mode groups comprises at least one OAM mode group having a low-order OAM mode and at least one OAM mode group having a high-order OAM mode. 
     In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the condition is satisfied based at least in part on at least one of an OAM mode group of the plurality of OAM mode groups comprising one OAM mode or a plurality of non-orthogonal OAM modes, an OAM mode of a first OAM mode group being orthogonal to an OAM mode of a second OAM mode group, or a combination thereof. 
     In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, the beamforming information indicates a combining coefficient for two or more non-orthogonal OAM modes associated with an OAM mode group of a plurality of OAM mode groups. 
     In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, the combining coefficient is based at least in part on a plurality of channel gains associated with the two or more non-orthogonal OAM modes. 
     In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, the combining coefficient comprises a conjugate value of a channel gain of the plurality of channel gains. 
     In a fourteenth aspect, alone or in combination with one or more of the first through thirteenth aspects, the OAM mode group comprises a beamformed port. 
     In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, the beamforming information indicates a set of quantization bits, and the set of quantization bits are based at least in part on quantization of an amplitude and a phase of the combining coefficient. 
     In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, the beamforming information indicates an index associated with a codeword, where the codeword is selected from a pre-configured codebook and satisfies a similarity condition associated with the combining coefficient. 
     In a seventeenth aspect, alone or in combination with one or more of the first through sixteenth aspects, the beamforming information does not indicate a combining coefficient for a single OAM mode associated with an OAM mode group of a plurality of OAM mode groups, where the combining coefficient has a value of one. 
     In an eighteenth aspect, alone or in combination with one or more of the first through seventeenth aspects, the beamforming information does not indicate the combining coefficient in the beamforming information based at least in part on the combining coefficient having a value of one. 
     In a nineteenth aspect, alone or in combination with one or more of the first through eighteenth aspects, the beamforming information indicates a group-specific coefficient associated with an OAM mode group of a plurality of OAM mode groups. 
     In a twentieth aspect, alone or in combination with one or more of the first through nineteenth aspects, the beamforming information indicates a modulation and coding scheme value corresponding to an OAM mode group of a plurality of OAM mode groups. 
     Although  FIG.  6    shows example blocks of process  600 , in some aspects, process  600  may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in  FIG.  6   . Additionally, or alternatively, two or more of the blocks of process  600  may be performed in parallel. 
     The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects. 
     As used herein, the term “component” is intended to be broadly construed as hardware, firmware, and/or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, and/or a combination of hardware and software. It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware, firmware, and/or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code—it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein. 
     As used herein, satisfying a threshold may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like. 
     Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. 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). 
     No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more.” Further, as used herein, the article “the” is intended to include one or more items referenced in connection with the article “the” and may be used interchangeably with “the one or more.” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like), and may be used interchangeably with “one or more.” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Also, as used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and/or,” unless explicitly stated otherwise (e.g., if used in combination with “either” or “only one of”).