Formula-Based Intercircular Precoding Weight Decision for Orbital Angular Momentum (OAM) Communication Systems

Abstract

Aspects of the present disclosure relate to a formula-based inter-circle precoding weight determination for an orbital angular momentum (OAM) communication system. Some aspects of the present disclosure relate to an apparatus and method for wireless communication, the apparatus including a processor, an antenna element including a first subset and a second subset of the antenna elements, and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the processor to transmit a first reference signal using a first OAM mode via the first subset of the antenna elements, transmit a second reference signal using the first OAM mode via the second subset of the antenna elements, and receive information indicating a subset of antenna elements of the plurality of antenna elements to use to transmit the first OAM mode. Other aspects, embodiments, and features are also claimed and described.

Description

[Technical field]

[0001]

[0001] The technology discussed below relates generally to wireless communication systems, and more particularly to transmitting and receiving reference signals. For example, some aspects of the disclosed technology may provide and enable techniques for calculating precoding weights for orbital angular momentum (OAM) transmission systems. [Background technology]

[0002]

[0002] In wireless communication, information is transmitted via electromagnetic radiation by modulating a carrier signal with one or more information signals. Many techniques for modulating a carrier signal are used in the art, including various analog and digital modulation techniques such as frequency modulation (FM), amplitude modulation (AM), phase-shift keying (PSK), and quadrature amplitude modulation (QAM), among other techniques. In a typical cellular wireless communication system, many such signals may be multiplexed (e.g., combined) onto a suitable carrier or band to enable simultaneous communication between multiple devices. Again, many techniques of multiplexing and multiple access are used in the art, including frequency-division multiplexing (FDM), time-division multiplexing (TDM), and orthogonal frequency-division multiplexing (OFDM), among other techniques.

[0003]

[0003] As the demand for mobile broadband access continues to grow, research and development continues to evolve wireless communications technologies not only to meet the growing demand for mobile broadband access, but also to evolve and improve the user experience with mobile communications. Summary of the Invention

[0004]

[0004] The following presents a simplified summary of one or more aspects of the present disclosure in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the present disclosure, nor is it intended to identify key or critical elements of all aspects of the present disclosure, nor is it intended to delineate the scope of any or all aspects of the present disclosure. Its sole purpose is to present some concepts of one or more aspects of the present disclosure in a simplified form as a prelude to the more detailed description that is presented later.

[0005] In one example, an apparatus configured for wireless communication is disclosed. In a more specific example, the apparatus includes a processor, a plurality of antenna elements including a first subset of antenna elements including at least a first antenna element and a second antenna element, and a second subset of antenna elements including at least a third antenna element and a fourth antenna element, and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the processor to transmit a first reference signal using a first orbital angular momentum (OAM) mode via the first subset of antenna elements, transmit a second reference signal using the first OAM mode via the second subset of antenna elements, and receive information indicating a subset of antenna elements of the plurality of antenna elements to use to transmit the first OAM mode.

[0006]

[0006] In another example, another device configured for wireless communication is disclosed. In a more specific example, the device includes a processor, a plurality of antenna elements including a first subset of antenna elements including at least a first antenna element and a second antenna element, and a second subset of antenna elements including at least a third antenna element and a fourth antenna element, and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the processor to receive an indication from a transmitting device including the third subset of antenna elements and the fourth subset of antenna elements that the third subset of antenna elements should be used to transmit a first reference signal for a first orbital angular momentum (OAM) mode, receive an indication from the transmitting device that the fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode, and transmit information indicating the subset of antenna elements of the plurality of antenna elements used to receive the first reference signal.

[0007] In yet another example, a method of wireless communication is disclosed. In a more detailed example, the method includes transmitting a first reference signal using a first orbital angular momentum (OAM) mode via a first subset of antenna elements of a plurality of antenna elements, transmitting a second reference signal using the first OAM mode via a second subset of antenna elements of the plurality of antenna elements, and receiving information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the first OAM mode.

[0008]

[0008] In yet another example, another method of wireless communication is disclosed. In a more specific example, the method includes: receiving, at a receiving device including a plurality of antenna elements including a first subset of antenna elements and a second subset of antenna elements, an indication that a third subset of antenna elements should be used to transmit a first reference signal for a first orbital angular momentum (OAM) mode from a transmitting device including a third subset of antenna elements and a fourth subset of antenna elements; receiving an indication from the transmitting device that the fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode; and transmitting information indicating a subset of antenna elements of the plurality of antenna elements used to receive the first reference signal. [Brief description of the drawings]

[0009] [Figure 1]

[0009] FIG. 1 is a schematic diagram of a radio access network in accordance with certain aspects of the present disclosure. [Diagram 2]

[0010] FIG. 1 is a schematic diagram of wireless communication between multiple antennas in accordance with some aspects of the present disclosure. [Diagram 3]

[0011] FIG. 2 is a block diagram conceptually illustrating an example of a hardware implementation for a transmitting device in accordance with certain aspects of the present disclosure. [Figure 4]

[0012] FIG. 2 is a block diagram conceptually illustrating an example of a hardware implementation for a receiving device in accordance with certain aspects of the present disclosure. [Diagram 5]

[0013] FIG. 1 is a schematic diagram of wireless communication via a uniform circular array (UCA) configuration supporting the use of orbital angular momentum (OAM) modes to multiplex communications, in accordance with certain aspects of the present disclosure. [Figure 6]

[0014] FIG. 1 is a schematic diagram of a coaxial multi-circle OAM configuration supporting secondary index modulation in accordance with certain aspects of the present disclosure. [Figure 7]

[0015] FIG. 1 is a call flow diagram illustrating an example process for determining inter-circuit precoding weights for an OAM communication system in accordance with certain aspects of the present disclosure. [Figure 8]

[0016] 1 is a flowchart illustrating an example process by which an OAM transmitting device determines circle-to-circle precoding weights for an OAM communication system, in accordance with certain aspects of the present disclosure. [Figure 9]

[0017] 1 is a flowchart illustrating an example process by which an OAM receiving device determines information for a transmitting device to determine circle-to-circuit precoding weights for an OAM communication system, in accordance with certain aspects of the disclosure. [Figure 10]

[0018] FIG. 13 is a call diagram illustrating transmission of reference signal configuration information and transmission of reference signals for multiple OAM modes using multiple equally-spaced circular array circles in accordance with certain aspects of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010]

[0019] In some aspects, the present disclosure provides wireless communication techniques that utilize the Orbital Angular Momentum (OAM) properties of electromagnetic (EM) waves to modulate a carrier wave to carry information and / or to multiplex information streams onto a common wireless resource. In particular, a Coaxial Multicircular Equal Circular Array (UCA) based antenna may be utilized to transmit reference signals for multiple OAM modes using a predefined sequence of resources such that a receiving device may determine which resources should be used to transmit a subsequent reference signal based on detection of the reference signal for a particular mode. Other aspects, embodiments, and features are also described and claimed.

[0011]

[0020] The detailed description set forth below in connection with the accompanying drawings describes various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The Detailed Description includes specific details intended to provide a thorough understanding of the various concepts. However, those skilled in the art will readily appreciate that these concepts may be practiced without these specific details. In some instances, the description provides well-known structures and components in block diagram form in order to avoid obscuring such concepts.

[0012]

[0021] While this description describes aspects and embodiments by way of illustration of some examples, one skilled in the art will appreciate that additional implementations and use cases may arise in many different arrangements and scenarios. The innovations described herein may be implemented across many different platform types, devices, systems, shapes, sizes, and packaging arrangements. For example, embodiments and / or applications may arise with integrated chip embodiments and other non-modular component-based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail / purchasing devices, medical devices, artificial intelligence (AI)-enabled devices, etc.). Some examples may or may not be specifically targeted to a use case or application, but a wide variety of applicability of the described innovation may arise. Implementations may range from chip-level or modular components to non-modular, non-chip-level implementations, and even aggregated, distributed, or OEM devices or systems incorporating one or more aspects of the described innovation. In some practical settings, devices incorporating the described aspects and features may also necessarily include additional components and features for implementing and practicing the claimed and described embodiments. For example, transmitting and receiving wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antennas, RF chains, power amplifiers, modulators, buffers, processor(s), interleavers, summers / analog summers, etc.). It is contemplated that the innovations described herein may be practiced in a variety of devices, chip-level components, systems, distributed configurations, end-user devices, etc., of various sizes, shapes, and configurations.

[0013]

[0022] In communication systems, modulation is a technique for systematically varying a carrier signal so that the transmitted signal contains information. Many techniques for modulating a carrier signal are used in the art, including various analog and digital modulation techniques. Modern wireless communication devices often employ quadrature amplitude modulation (QAM), in which pairs of quadrature (orthogonal) carrier signals have their amplitudes controlled to represent desired locations in the complex plane (sometimes called the Gaussian plane).

[0014]

[0023] Relatedly, multiplexing and multiple access are techniques that allow simultaneous communication of multiple signals and / or devices on the same channel. For example, the 5G New Radio (NR) specification utilizes orthogonal frequency division multiplexing (OFDM) with cyclic prefix (CP) to provide multiple access for uplink transmissions from mobile devices to base stations and multiplexing for downlink transmissions from base stations to mobile devices. In addition, for uplink transmissions, the 5G NR specification provides support for discrete Fourier transform-spread-OFDM (DFT-s-OFDM) with CP (also called single-carrier FDMA (SC-FDMA)). However, within the scope of this disclosure, multiplexing and multiple access are not limited to the above schemes. For example, a mobile device may provide uplink multiple access utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), sparse code multiple access (SCMA), resource spread multiple access (RSMA), orbital angular momentum (OAM) multiplexing, coaxial multi-circle antenna multiplexing, and / or other suitable multiplexing schemes. Further, a base station may multiplex DL transmissions to UEs utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), orbital angular momentum (OAM) multiplexing, coaxial multi-circle antenna multiplexing, and / or other suitable multiplexing schemes.

[0015] OAM

[0024] An EM transmission can be characterized as a wave that carries momentum. In some examples, this momentum can include angular momentum, including a spin angular momentum (SAM) component and an orbital angular momentum (OAM) component. In some cases, the SAM of an EM wave can be associated with the polarization of the EM wave. For example, an EM wave can be associated with different polarizations, such as left-handed, right-handed, and circular polarization. Thus, the SAM of an EM wave can have multiple (e.g., two) degrees of freedom.

[0016]

[0025] In some cases, the OAM of an EM wave may be associated with a field spatial distribution of the EM wave, which may be in the form of a helical or twisted wavefront shape. For example, an EM wave or light beam may be in a helical mode, sometimes referred to as an OAM mode, where such a helical mode may be characterized by a wavefront shaped as a helix with an optical vortex in the middle (e.g., at the beam axis), with each helical mode being associated with a different helical waveform structure. A helical mode (e.g., an OAM mode) may be defined or referred to by a mode index l, where the sign of the mode index l corresponds to the "handedness" (e.g., left or right) of one or more helices, and the magnitude of the mode index l (e.g., |l|) corresponds to the amount of different, but interleaved, helices of the EM wave.

[0017]

[0026] For example, for an EM wave associated with an OAM mode index of l=0, the EM wave is not a spiral, and the waveform of the EM wave is a multiple cut surface (e.g., the EM wave is a series of parallel surfaces). For an EM wave associated with an OAM mode index of l=+1, the EM wave may propagate in a right-handed direction (e.g., the EM wave may form a right-handed spiral rotating in a right-handed direction around the beam axis), and the wavefront of the EM wave may be shaped as a single spiral surface with a step length equal to the wavelength λ of the EM wave. Similarly, the phase delay over one revolution of the EM wave may be equal to 2π. Similarly, for an OAM mode index of l=-1, the EM wave may propagate in a left-handed direction (e.g., the EM wave may form a left-handed spiral rotating in a left-handed direction around the beam axis), and the wavefront of the EM wave may also be shaped as a single spiral surface with a step length equal to the wavelength λ of the EM wave. Similarly, the phase delay over one revolution of the EM wave may be equal to -2π.

[0018]

[0027] As a further example, for an OAM mode index of l=±2, an EM wave may propagate in either a right-handed (for l=+2) or left-handed (for l=-2) direction, and the wavefront of the EM wave may include two distinct, but interleaved, helical planes. In such an example, the step length of each helical plane may be equal to λ / 2. Similarly, the phase delay over one revolution of the EM wave may be equal to ±4π. In general terms, an EM wave of mode l may propagate in either a right-handed or left-handed direction (depending on the sign of l) and may include l distinct, but interleaved, helical planes, with a step length of each helical plane equal to π / |l|. Similarly, the phase delay over one revolution of the EM wave may be equal to 2lπ. In some cases, the EM wave may be extended infinitely (e.g., l∈Z, where Z is an unbounded set of integers) to provide a theoretically infinite number of degrees of freedom for the OAM of the EM wave. Therefore, the OAM of an EM wave can be associated with an infinite number of degrees of freedom.

[0019] OAM Modulation

[0028] In some examples, the OAM mode index l of an EM wave may correspond to or possibly function as (e.g., may be defined as) an additional dimension for multiplexing of signals or channels. For example, each OAM mode or state (which may be infinite) may function similarly (or equally) to a communication channel, such as a subchannel. In other words, an OAM mode or state may correspond to a communication channel, and vice versa. For example, a transmitting device or a receiving device may communicate separate signals using an EM wave having different OAM modes or states, similar to how a transmitting device or a receiving device may communicate separate signals over different communication channels. In some aspects, such use of OAM modes or states of an EM wave to carry different signals may be referred to as using an OAM beam.

[0020]

[0029] Additionally, in some examples, EM waves having different OAM modes (e.g., OAM states) may be mutually orthogonal with respect to one another (e.g., in a Hilbert sense where space may include an infinite set of axes and sequences may be infinite by always having another coordinate direction in which the next element of the sequence may proceed). Similarly, in a Hilbert sense, orthogonal OAM modes or OAM states may correspond to orthogonal communication channels (e.g., orthogonal sequences transmitted over a communication channel), and wireless communication systems employing the use of OAM beams based on a potentially infinite number of OAM modes or OAM states may logically achieve infinite capacity. Here, due to the mutual orthogonality between the OAM modes, a waveform of one OAM mode generally cannot be received by a receiver aperture configured for a different OAM mode. Logically, an infinite number of OAM states or OAM modes may be twisted together for multiplexing, and the capacity of the OAM link may approach infinity while preserving orthogonality between signals carried by different OAM modes (e.g., index l). However, in practice, crosstalk may exist between OAM modes at the receiver due to non-ideal factors (e.g., Tx / Rx axial and / or position placement errors, propagation divergence, etc.), and thus a reduced number of simultaneous OAM modes may be implemented between wireless devices. In some cases, the transmitting device may generate such OAM beams using a uniform circular array (UCA) configuration, as discussed with reference to Figures 6 and 7.

[0021] Wireless Communication Systems

[0030] The following disclosure presents various concepts that may be implemented across a wide variety of telecommunications systems, network architectures, and communication standards. Figure 1 illustrates an example of a radio access network (RAN) 100 operating in a wireless communication system that supports one-dimensional and / or two-dimensional index modulation in conjunction with coaxial multi-circle OAM transmission. The wireless communication system 100 may enable a UE 106 to conduct data communications with an external data network 110, such as (but not limited to) the Internet.

[0022]

[0031] The RAN 100 may implement any suitable wireless communication technology or technologies to provide radio access to one or more UEs. As an example, the RAN 100 may be implemented in accordance with the Third Generation Partnership Project (3G), often referred to as 5G. rd The RAN 100 may operate in accordance with the 5G Generation Partnership Project (3GPP) New Radio (NR) specifications. As another example, the RAN 100 may operate under a hybrid of the 5G NR standard and the Evolved Universal Terrestrial Radio Access Network (eUTRAN) standard, often referred to as LTE. 3GPP calls this hybrid RAN Next Generation RAN or NG-RAN. Of course, the RAN 100 may operate in accordance with any suitable 6G or other technology, and many other examples may be utilized within the scope of this disclosure.

[0023]

[0032] In FIG. 1, two base stations 110 and 112 are shown in cells 102 and 104, and a third base station 114 is shown controlling a remote radio head (RRH) 116 in cell 106. That is, a base station may have an integrated antenna or may be connected to an antenna or RRH by a feeder cable. Broadly, a base station is a network element in a RAN responsible for radio transmission and reception in one or more cells to or from UEs. In different technologies, standards, or contexts, a base station may be variously referred to by those skilled in the art as a base transceiver station (BTS), radio base station, radio transceiver, transceiver function, basic service set (BSS), extended service set (ESS), access point (AP), Node B (NB), eNode B (eNB), gNode B (gNB), or some other suitable technology.

[0024]

[0033] The geographic area covered by the RAN 100 may be divided into cellular regions (cells) that may be uniquely identified by user equipment (UE) based on an identification broadcasted from one access point or base station. FIG. 1 shows macro cells 102, 104, and 106, and small cell 108, each of which may include one or more sectors (not shown). A sector is a subarea of ​​a cell. All sectors within a cell are served by the same base station. Radio links within a sector may be identified by a single logical identification belonging to that sector. In a cell divided into sectors, multiple sectors within a cell may be formed by a group of antennas with each antenna responsible for communication with UEs in a portion of the cell.

[0025]

[0034] In the illustrated example, cells 102, 104, and 126 may be referred to as macro cells because base stations 110, 112, and 114 support cells having a large size. Additionally, base station 118 is shown among small cells 108 (e.g., micro cells, pico cells, femto cells, home base stations, home node Bs, home eNode Bs, etc.) that may overlap with one or more macro cells. In this example, cells 108 may be referred to as small cells because base station 118 supports cells having a relatively small size. Cell size determination may be made according to system design as well as component constraints.

[0026]

[0035] It should be appreciated that the RAN 100 may include any number of wireless base stations and cells. Additionally, relay nodes may be deployed to extend the size or coverage area of ​​a given cell. The base stations 110, 112, 114, 118 provide wireless access points to the core network for any number of mobile devices.

[0027]

[0036] The RAN 100 supports wireless communications for multiple mobile devices. A mobile device may be referred to as user equipment (UE) in 3GPP standards, but may also be referred to by those skilled in the art as a mobile station (MS), subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal (AT), mobile terminal, wireless terminal, remote terminal, handset, terminal, user agent, mobile client, client, or some other suitable terminology. A UE may be a device (e.g., a mobile device) that provides access to network services. A UE may take many forms and may include a variety of devices.

[0028]

[0037] Within this document, a "mobile" device (e.g., UE) does not necessarily have to be capable of moving and may be stationary. The term mobile device or mobile device broadly refers to a diverse range of devices and technologies. A UE may include several hardware structural components sized, shaped, and arranged to facilitate communication, such components may include antennas, antenna arrays, RF chains, amplifiers, one or more processors, etc., electrically coupled to each other. For example, some non-limiting examples of mobile devices include mobile, cellular (cell) phones, smartphones, session initiation protocol (SIP) phones, laptops, personal computers (PCs), notebooks, netbooks, smartbooks, tablets, personal digital assistants (PDAs), and a wide range of embedded systems, for example, those supporting the "Internet of things" (IoT). In addition, the mobile device may be an automobile or other transportation vehicle, a remote sensor or actuator, a robot or robotics device, a satellite radio, a global positioning system (GPS) device, an object tracking device, a drone, a multicopter, a quadcopter, a remote control device, eyewear, a wearable camera, a virtual reality device, a smart watch, a home and / or wearable device such as a health or fitness tracker, a digital audio player (e.g., an MP3 player), a camera, a game console, etc. In addition, the mobile device may be a digital home device or a smart home device such as a home audio, video, and / or multimedia device, an appliance, a vending machine, an intelligent lighting, a home security system, a smart meter, etc.In addition, the mobile devices may be smart energy devices, security devices, solar panels or arrays, city infrastructure devices (e.g., smart grids) that control power, lighting, water, etc., industrial automation and enterprise devices, logistics controllers, agricultural equipment, military defense equipment, vehicles, aircraft, ships, and weapons, etc. Furthermore, the mobile devices may provide connected medical support or telemedical support, e.g., remote health care. Telehealth devices may include telehealth monitoring devices and telehealth management devices, whose communications may be given preferential treatment or priority access over other types of information, e.g., with respect to priority access for transport of critical service data and / or associated QoS for transport of critical service data.

[0029]

[0038] The wireless communication between the RAN 100 and the UEs may be described as utilizing an air interface. The UEs and base stations may wirelessly communicate with each other over one or more communication links utilizing one or more carriers. The term "carrier" may refer to a set of radio frequency spectrum resources having a physical layer structure defined to support the communication links. A transmission over the air interface from a base station to one or more UEs may be referred to as a downlink (DL) transmission. According to some aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission that occurs at a scheduling entity (e.g., a base station). Another way to describe this scheme may be to use the term broadcast channel multiplexing. A transmission from a UE to a base station may be referred to as an uplink (UL) transmission. According to further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission that occurs at a scheduled entity (e.g., a UE).

[0030]

[0039] Generally, a base station may include a backhaul interface (not shown) to communicate with a backhaul portion of a wireless communications system. The backhaul may provide a link between the base station and a core network. Additionally, in some examples, the backhaul network may provide interconnection between the respective base stations. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, etc., using any suitable transport network. In some aspects, a portion of the backhaul network may be implemented using an OAM transmitter and an OAM receiver, each associated with a respective base station and / or a portion of the core network.

[0031]

[0040] In some examples, one or more base stations in the RAN 100 may be configured as an integrated access and backhaul (IAB) node, in which case the wireless spectrum may be used for both the access link (i.e., the wireless link with the UE) and the backhaul link. This approach may be referred to as wireless self-backhauling. By using wireless self-backhauling, rather than requiring each new base station deployment to equip itself with its own hardwired backhaul connection, the wireless spectrum utilized for communication between the base station and the UE may be utilized for backhaul communication, which may enable faster and easier deployment of dense small cell networks. Additionally or alternatively, OAM transmissions may be utilized for backhaul communication, which may reduce the impact of wireless backhaul communication on the wireless spectrum utilized for communication between the base station and the UE when the communication with the UE utilizes a different technology.

[0032]

[0041] 1 further includes a quadcopter or drone 120 that may be configured to function as a base station, i.e., in some examples, the cells may not necessarily be fixed, and the geographic area of ​​the cells may move according to the location of a mobile base station, such as the quadcopter 120.

[0033]

[0042] Each base station 110, 112, 114, 118, and 120 may be configured to provide an access point to the core network for all UEs in the respective cell. For example, UEs 122 and 124 may be in communication with base station 110, UEs 126 and 128 may be in communication with base station 112, UEs 130 and 132 may be in communication with base station 114 via RRH 116, UE 134 may be in communication with base station 118, and UE 136 may be in communication with mobile base station 120.

[0034]

[0043] In some examples, a mobile network node (e.g., the quadcopter 120) may be configured to function as a UE. For example, the quadcopter 120 may operate within the cell 102 by communicating with the base station 110.

[0035]

[0044] In further aspects of the RAN 100, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, two or more UEs (e.g., UEs 126 and 128) may communicate with each other using peer to peer (P2P) or sidelink signals 127 without relaying the communication through a base station (e.g., base station 112). In a further example, UE 138 is shown communicating with UEs 140 and 142, where UE 138 may function as a scheduling entity or primary sidelink device, and UEs 140 and 142 may function as scheduled entities or non-primary (e.g., secondary) sidelink devices. In yet another example, UEs may function as scheduling entities in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network and / or in a mesh network. In the example mesh network, UEs 140 and 142 may optionally communicate directly with one another in addition to communicating with scheduling entity 138. Thus, in a wireless communication system having a cellular, P2P, or mesh configuration with scheduled access to time-frequency resources, the scheduling entity and one or more scheduled entities may communicate utilizing the scheduled resources.

[0036]

[0045] In some examples, the RAN 100 may operate in the super high frequency (SHF) region, also known as the centimeter band (using frequency bands from 3 GHz to 30 GHz), the extremely high frequency (EHF) region of the spectrum, also known as the millimeter band (e.g., from 30 GHz to 300 GHz), or even higher frequency bands reaching the terahertz (THz) region. Also in some examples, the RAN 100 may support millimeter wave (mmW) communications between UEs and base stations, where EHF antennas on each device may be smaller and more closely spaced than UHF antennas. In some examples, this may facilitate the use of antenna arrays within the device. However, propagation of EHF transmissions may experience more atmospheric attenuation and may be shorter distances than SHF or UHF transmissions. The techniques disclosed herein may be employed over transmissions using one or more different frequency regions, and the designated use of bands over these frequency regions may vary by country or regulatory body.

[0037] A typical multi-antenna array

[0046] In some aspects of the disclosure, a wireless communications node or device may be configured with multiple antennas, for example, for beamforming, multiple-input multiple-output (MIMO), and / or orbital angular momentum (OAM) modulation techniques. FIG. 2 illustrates an example of wireless communications utilizing multiple antennas supporting beamforming, MIMO, and OAM. In some examples, the system of FIG. 2 may implement aspects of the RAN 100. The use of such multi-antenna techniques enables wireless communications systems to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity.

[0038]

[0047] Beamforming generally refers to the transmission or reception of directional signals. For beamformed transmission, the amplitude and phase of each antenna in an array of antennas may be precoded or controlled to create a desired (e.g., directional) pattern of constructive and destructive interference in the wavefront. In a MIMO system, the transmitter 202 includes multiple transmit antennas 204 (e.g., N transmit antennas) and the receiver 206 includes multiple receive antennas 208 (e.g., M receive antennas). Thus, there are N×M signal paths 210 from the transmit antennas 204 to the receive antennas 208. Each of the transmitter 202 and receiver 206 may be implemented, for example, within the scheduling entity 108, the scheduled entity 106, or any other suitable wireless communication device.

[0039]

[0048] In a MIMO system, spatial multiplexing may be used to transmit multiple different streams of data, also called layers, simultaneously on the same time-frequency resource. In some examples, a transmitter may send multiple data streams to a single receiver. In this way, a MIMO system takes advantage of the capacity gain and / or increased data rate associated with using multiple antennas in a rich scattering environment where channel variations may be tracked. Here, the receiver may track these channel variations and provide corresponding feedback to the transmitter. In the simplest case, a rank-2 (i.e., including two data streams) spatial multiplexing transmission in a 2×2 MIMO antenna configuration transmits two data streams via two transmit antennas 204. The signals from each transmit antenna 204 arrive at each receive antenna 208 along different signal paths 210. The receiver 206 may then reconstruct the data stream using the signals received from each receive antenna 208.

[0040]

[0049] The number of data streams or layers in a MIMO system corresponds to the rank of the transmission. In general, the rank of a MIMO system is limited by the number of transmit antennas 204 or receive antennas 208, whichever is less. In addition, other considerations, such as channel conditions at the receiving device as well as resources available for use by the transmitting device, may also affect the transmission rank. For example, a base station in a cellular RAN may assign a rank (and thus the number of data streams) for DL ​​transmission to a particular UE based on a rank indicator (RI) that the UE transmits to the base station. The UE may determine this RI based on the antenna configuration (e.g., the number of transmit and receive antennas) and the signal-to-interference-and-noise ratio (SINR) measured for each of the receive antennas. The RI may indicate, for example, the number of layers that can be supported under the current channel conditions. The base station may use the RI together with resource information (e.g., available resources and the amount of data to be scheduled for the UE) to assign a DL transmission rank to the UE.

[0041]

[0050] The transmitting device determines the precoding of one or more transmitted data streams based, for example, on known channel state information of the channel through which the transmitting device transmits the data stream(s). For example, the transmitting device may transmit one or more suitable reference signals (e.g., channel state information reference signal, or CSI-RS) that the receiving device may measure. The receiver may then report the measured channel quality information (CQI) back to the transmitting device. This CQI generally reports the current communication channel quality and, in some examples, reports the requested transport block size (TBS) for future transmissions to the receiver. In some examples, the receiver may further report a precoding matrix indicator (PMI) back to the transmitting device. This PMI generally reports the preferred precoding matrix of the receiving device that the transmitting device uses and may be indexed into a predefined codebook. The transmitting device may then utilize this CQI / PMI to determine a suitable precoding matrix for transmission to the receiver.

[0042]

[0051] In some cases, the RAN 100 may be an example of, or may support, an OAM-based communications system, and the transmitting device 202 and / or the receiving device 206 may communicate via an OAM beam. In some examples, the transmitting device 202 and / or the receiving device 206 may generate and steer an OAM beam based on selecting a set of antenna elements from a planar array of antenna elements (e.g., a planar array on the transmitting device 202 or the receiving device 206 that may be used for MIMO communications) based on which antenna elements fall within a determined area on the planar array associated with a uniform circular array (UCA) for OAM communications. Additionally or alternatively, one or more of the transmitting devices 202 or the receiving devices 206 may include components that provide spiral phase plate (SPP)-based OAM communications.

[0043]

[0052] In various examples, some or all of the wireless resources of the RAN 100 may be scheduled to carry one or more physical channels, such as a control channel, a shared channel, a data channel, etc. Other resources of the RAN 100 may also carry pilot or reference signals that may enable receiving devices to perform channel estimation of the corresponding channels.

[0044]

[0053] In DL transmission, a transmitting device (e.g., a base station or a scheduling entity) may allocate a set of wireless resources to carry DL control information, including one or more DL control channels that generally carry information originating from higher layers, to one or more receiving devices (e.g., UEs or scheduled entities). In addition, DL resources may be allocated to carry DL physical signals that generally do not carry information originating from higher layers. These DL physical signals may include synchronization signals, demodulation reference signals (DM-RS), phase-tracking reference signals (PT-RS), channel-state information reference signals (CSI-RS), etc.

[0045]

[0054] In an UL transmission, a transmitting device (e.g., a UE or a scheduled entity) may utilize a designated set of wireless resources to convey UL control information (UCI) to a receiving device (e.g., a base station or a scheduling entity). The UCI may originate from higher layers via one or more UL control channels. Additionally, the UL wireless resources may carry UL physical signals that do not typically carry information originating from higher layers, such as a demodulation reference signal (DM-RS), a phase tracking reference signal (PT-RS), a sounding reference signal (SRS), etc.

[0046]

[0055] In a sidelink (SL) transmission, a transmitting device (e.g., a UE or a scheduled entity, or a base station of the scheduling entity) may utilize a designated set of wireless resources to convey SL control information (SCI) to a receiving device (e.g., another UE or a scheduled entity, or another base station of the scheduling entity). Furthermore, the SL wireless resources may carry SL physical signals that do not typically carry information originating from higher layers, such as a demodulation reference signal (DM-RS), a phase tracking reference signal (PT-RS), a sounding reference signal (SRS), etc.

[0047]

[0056] In addition to control information, wireless resources may be allocated for user data or traffic data, which may be carried on one or more traffic channels.

[0048] Radio Resources

[0057] Those skilled in the art will appreciate that the various aspects of the present disclosure may be applied to DFT-s-OFDMA waveforms in substantially the same manner as described herein below, i.e., while some examples of the present disclosure may focus on OFDM links for clarity, it should be understood that the same principles may also be applied to DFT-s-OFDM waveforms.

[0049]

[0058] In some examples, a frame may refer to a predetermined duration for wireless transmission (e.g., 10 ms). Further, each frame may consist of a set of subframes (e.g., 10 subframes of 1 ms each). A given carrier may include one set of frames in the UL and another set of frames in the DL.

[0050]

[0059] A resource grid may represent time-frequency resources for a given antenna port. For example, in a MIMO implementation with multiple available antenna ports, multiple corresponding resource grids may be available for communication. As another example, as described below, different OAM modes may be orthogonal when transmitted using the same time, frequency, and / or code resources, and therefore may be associated with independent resource grids.

[0051]

[0060] The resource grid may be divided into multiple resource elements (REs). An RE, which is one subcarrier by one symbol, is the smallest individual portion of a time-frequency grid and may contain a single complex value representing data from a physical channel or signal. Depending on the modulation employed in a particular implementation, each RE may represent one or more bits of information. In some examples, a block of REs may be referred to as a physical resource block (PRB) or more simply a resource block (RB), which includes any suitable number of consecutive subcarriers in the frequency domain. In one example, an RB may include 12 subcarriers, a number that is independent of the numerology used. In some examples, depending on the numerology, an RB may include any suitable number of consecutive OFDM symbols in the time domain. This disclosure assumes, by way of example, that a single RB corresponds entirely to a single direction of communication (either transmission or reception for a given device).

[0052]

[0061] A UE typically utilizes only a subset of the resource grid. An RB may be the smallest unit of resource that a scheduler can allocate to a UE. Thus, the more RBs scheduled for the UE and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE. Although a UE may only use a subset of the resource grid (e.g., to allow other UEs to also communicate using the RAN), an OAM transmitter and an OAM receiver may utilize a much larger portion of the resource grid associated with one or more OAM modes. For example, there may not be other devices configured to use the same resources as is often the case when utilizing mobile resources in the RAN. An OAM transmitter and OAM receiver pair is generally closely spatially aligned, potentially reducing the ability to use the antenna to communicate with other devices that are not closely aligned.

[0053]

[0062] Resources used to transmit and / or receive a signal (e.g., a waveform) may include time-frequency resources, such as one or more REs, one or more RBs, etc., within a particular resource grid. Additionally or alternatively, resources may include a layer (e.g., a physical layer, a media access control (MAC) layer, a radio resource control (RRC) layer, etc.), a code (e.g., used to implement a code division multiple access scheme), an OAM mode, an array of antenna elements (e.g., a UCA circle, a portion of a ULA, a portion of a UPA, etc.).

[0054] Channel and Signal Description

[0063] Various REs within an RB may carry one or more physical channels, including a control channel, a shared channel, a data channel, etc. Other REs within an RB may also carry pilot or reference signals. These pilot or reference signals may enable receiving devices to perform channel estimation of the corresponding channels, which may enable coherent demodulation / detection of the control and / or data channels within the RB.

[0055]

[0064] In DL transmission, a transmitting device (e.g., a base station or a UE) may allocate one or more REs (e.g., in a control region) to carry one or more DL control channels. These DL control channels include DL control information (DCI), which generally carries information originating from higher layers to one or more receiving devices (e.g., UEs), such as a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), etc. In addition, a transmitting device may allocate one or more DL REs to carry DL physical signals, which generally do not carry information originating from higher layers. These DL physical signals may include a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a demodulation reference signal (DM-RS), a phase tracking reference signal (PT-RS), a channel state information reference signal (CSI-RS), etc.

[0056]

[0065] A base station (or other suitable transmitter device) may transmit synchronization signals PSS and SSS (collectively referred to as SS), and in some examples, the PBCH, in a synchronization signal block (SSB) that includes four consecutive OFDM symbols numbered via ascending time indexes from 0 to 3. In the frequency domain, the SSB may extend across 240 consecutive subcarriers, where the subcarriers may be numbered via ascending frequency indexes from 0 to 239. Of course, the present disclosure is not limited to this particular SSB configuration. Other non-limiting examples may utilize more or less than two synchronization signals, may include one or more supplemental channels in addition to the PBCH, may omit the PBCH, and / or may utilize non-consecutive symbols for the SSB within the scope of the present disclosure.

[0057]

[0066] The PDCCH may carry downlink control information (DCI) for one or more UEs in a cell, which may include, but is not limited to, power control commands, scheduling information, grants, and / or allocation of REs for DL ​​and UL transmissions.

[0058]

[0067] In an UL transmission, a transmitting device (e.g., a scheduled entity) may utilize one or more REs to carry one or more UL control channels, such as a physical uplink control channel (PUCCH), a physical random access channel (PRACH), etc. These UL control channels include UL control information (UCI), which generally carries information originating from higher layers. In addition, a UL RE may carry UL physical signals, such as a demodulation reference signal (DM-RS), a phase tracking reference signal (PT-RS), a sounding reference signal (SRS), etc., which generally do not carry information originating from higher layers. In some examples, the control information may include a scheduling request (SR), i.e., a request to the scheduling entity to schedule an uplink transmission. Here, in response to the SR transmitted on the control channel, the scheduling entity may transmit downlink control information, which may schedule resources for uplink packet transmission.

[0059]

[0068] The UL control information may also include hybrid automatic repeat request (HARQ) feedback, such as an acknowledgement (ACK) or negative acknowledgment (NACK), channel state information (CSI), or any other suitable UL control information. HARQ is a technique well known to those skilled in the art in which a receiving device may check the integrity of a packet transmission for accuracy, using any suitable integrity checking mechanism, such as, for example, a checksum or a cyclic redundancy check (CRC). If the receiving device confirms the integrity of the transmission, it may send an ACK; if not, it may send a NACK. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc.

[0060]

[0069] In addition to control information, one or more REs may be allocated for user or traffic data. Such traffic may be carried on one or more traffic channels, such as a physical downlink shared channel (PDSCH) for DL ​​transmissions or a physical uplink shared channel (PUSCH) for UL transmissions.

[0061]

[0070] Those skilled in the art will recognize that the channels or carriers described above are not necessarily all channels or carriers that may be utilized between a scheduling entity and one or more scheduled entities, and that other channels or carriers may be utilized in addition to those shown, such as other traffic channels, control channels, and feedback channels.

[0062] Block Diagram

[0071] 3 is a block diagram illustrating an example of a hardware implementation for a transmitting device 300 employing a processing system 314. For example, the transmitting device 300 may be a user equipment (UE), a base station, or any other wireless communication node, such as shown in any of FIGS.

[0063]

[0072] The transmitting device 300 may be implemented with a processing system 314 that includes one or more processors 304. Examples of the processors 304 include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), application specific integrated circuits (ASICs), state machines, gate logic, discrete hardware circuits, and other suitable hardware configured to perform various functions described throughout this disclosure. In various examples, the transmitting device 300 may be configured to implement any one or more of the functions described herein. That is, the processor 304 as utilized in the transmitting device 300 may be configured to implement (e.g., together with the memory 305) any one or more of the processes and procedures described below and illustrated in FIGS. 7-10.

[0064]

[0073] In this example, the processing system 314 may be implemented with a bus architecture, generally represented by bus 302. The bus 302 may include any number of interconnected buses and bridges, depending on the particular application and overall design constraints of the processing system 314. The bus 302 communicatively couples various circuits, including one or more processors (generally represented by processor 304), memory 305, and computer-readable media (generally represented by computer-readable media 306). The bus 302 may also link various other circuits, such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further. The bus interface 308 provides an interface between the bus 302 and the transceiver 310.

[0065]

[0074] The transceiver 310 provides a communication interface or means for communicating with various other devices over a transmission medium. In some aspects, the transceiver 310 includes (or is coupled to) multiple antennas 311 (e.g., each may include multiple antenna elements). The multiple antennas 311 may be configured similar to a uniform circular array (UCA) antenna described below and shown in FIG. 5, similar to a coaxial multi-circular UCA configuration described below and shown in FIG. 6, or some combination of the above. In some aspects, any structure that allows for OAM multiplexing of electromagnetic signals (e.g., RF signals, optical signals, etc.) may be applied, including, but not limited to, UCA antennas described by way of example. The multiple antennas 311 may include, or in some cases be configured using, any other suitably configured phase plates, spatial modulators, integrated circuits, any other suitable components, and / or any suitable combination thereof, for transmission over any suitable medium, including wireless air interfaces, optical fibers, etc. In some aspects, the transceiver 310 may be configured to provide any suitable number of simultaneous signals to the antennas 311. For example, a transceiver may be configured to implement multiple transceiver units (sometimes referred to as TXRUs) that may each transmit a signal (e.g., corresponding to a particular OAM mode) via a subset of antennas (e.g., corresponding to a particular uniform circular array (UCA), as described below with respect to FIGS. 5 and 6). In addition, in some aspects, such a TXRU may be configured to receive a signal (e.g., corresponding to a particular OAM mode) via a subset of antennas (e.g., corresponding to a particular uniform circular array (UCA), as described below with respect to FIGS. 5 and 6). As described below with respect to FIG. 7, the number of OAM modes that a UCA can simultaneously transmit and / or receive may be limited based on the number of TXRUs associated with the UCA. For example, a particular UCA may be configured to simultaneously transmit and / or receive any two OAM modes (e.g., modes 1 and 2, modes 1 and 3, etc.).

[0066]

[0075] Depending on the nature of the transmitting device 300, a user interface 312 (e.g., a keypad, a display, a speaker, a microphone, a joystick) may also be provided. Of course, such a user interface 312 is optional and may be omitted in some instances, such as a base station.

[0067]

[0076] In some aspects of the disclosure, the processor 304 may include a communications circuit 341 configured (e.g., in conjunction with the memory 305) for various functions, including, for example, coordinating with the transceiver controller circuit 342 and / or the transceiver controller instructions 362 to transmit a suitable waveform and / or transmit a reference signal to communicate information using one or more OAM modes. For example, the communications circuit 341 may be configured to implement one or more of the functions described below with respect to FIG. 7, e.g., including blocks 702, 710, and / or 722; with respect to FIG. 8, e.g., including blocks 802, 804, and / or 806; with respect to FIG. 10, e.g., including blocks 1010, 1014, 1016, 1018, and / or 1020.

[0068]

[0077] In some further aspects of the disclosure, the processor 304 may include a transceiver controller 342 configured (e.g., in cooperation with the memory 305 and / or the transceiver 310) for various functions including, for example, transmitting suitable waveforms (e.g., information or data streams) and / or reference signals (e.g., DM-RS, CSI-RS, etc.) as disclosed herein. For example, the transceiver controller 342 may be configured to implement one or more of the functions described below with respect to FIG. 7, e.g., including blocks 702, 710, and / or 722; with respect to FIG. 8, e.g., including blocks 802, 804, and / or 806; with respect to FIG. 10, e.g., including blocks 1010, 1014, 1016, 1018, and / or 1020.

[0069]

[0078] In some further aspects of the disclosure, the processor 304 may include a channel response determination circuit 343 configured (e.g., in cooperation with the memory 305) for various functions, including, for example, determining a channel response for a particular OAM mode and a particular pair of transmitting and receiving UCAs, determining precoding weights for a particular OAM mode based on information about the UCA circle. In some examples, the channel response determination circuit 343 may determine a channel response for a particular OAM mode based on a radius of the UCA used to receive the reference signal, a radius of the UCA used to transmit the reference signal, a distance between the transmitting and receiving UCAs, and a wavelength used to transmit the reference signal, and in some additional examples, the channel response determination circuit 343 may determine precoding weights for a particular OAM mode based on a channel response matrix associated with the particular OAM mode and one or more pairs of transmitting and receiving UCAs. For example, the channel response determination circuit 343 may be configured to implement one or more of the functions described below with respect to FIG. 7, including, for example, block 724.

[0070]

[0079] The processor 304 is responsible for managing the bus 302 and for general processing, including the execution of software stored on the computer-readable medium 306. The software, when executed by the processor 304, causes the processing system 314 to perform various functions described below for any particular apparatus. The computer-readable medium 306 and memory 305 may also be used for storing data that is manipulated by the processor 304 when executing software.

[0071]

[0080] One or more processors 304 in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on computer readable medium 306. Computer readable medium 306 may be a non-transitory computer readable medium. Non-transitory computer readable media include, by way of example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical disks (e.g., compact discs (CDs) or digital versatile discs (DVDs)), smart cards, flash memory devices (e.g., cards, sticks, or key drives), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, removable disks, and any other suitable medium for storing software and / or instructions that can be accessed and read by a computer. The computer readable medium 306 may be present within the processing system 314, may be external to the processing system 314, or may be distributed across multiple entities including the processing system 314. The computer readable medium 306 may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials.Those skilled in the art will recognize how to best implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

[0072]

[0081] In one or more examples, the computer-readable storage medium 306 may store computer-executable code including communication instructions 361 that configure the transmitting device 300 for various functions including, for example, receiving an information stream (e.g., a sequence of bits) for transmission and coordinating with the transceiver controller circuit 342 and / or the transceiver controller instructions 362 to transmit a suitable waveform. For example, the communication instructions 361 may be configured to cause the transmitting device 300 to implement one or more of the functions described below with respect to FIG. 7, e.g., including blocks 702, 710, and / or 722, with respect to FIG. 8, e.g., including blocks 802, 804, and / or 806, with respect to FIG. 10, e.g., including blocks 1010, 1014, 1016, 1018, and / or 1020.

[0073]

[0082] In one or more further examples, the computer-readable storage medium 306 may store computer-executable code including transceiver controller instructions 362 that configure the transmitting device 300 for various functions, including, for example, transmitting suitable waveforms (e.g., information or data streams) and / or reference signals (e.g., DM-RS, CSI-RS, etc.) disclosed herein. For example, the transceiver controller instructions 362 may be configured to cause the transmitting device 300 to implement one or more of the functions described below with respect to FIG. 7, e.g., including blocks 702, 710, and / or 722, with respect to FIG. 8, e.g., including blocks 802, 804, and / or 806, with respect to FIG. 10, e.g., including blocks 1010, 1014, 1016, 1018, and / or 1020.

[0074]

[0083] In one or more further examples, the computer-readable storage medium 306 may store computer-executable code including channel response determination instructions 363 that configure the transmitting device 300 for various functions, including, for example, determining a channel response for a particular OAM mode and a particular pair of transmitting and receiving UCAs, and determining precoding weights for the particular OAM mode based on information about the UCA circle. In some examples, the channel response determination instructions 363 may determine a channel response for a particular OAM mode based on a radius of a UCA used to receive a reference signal, a radius of a UCA used to transmit a reference signal, a distance between the transmitting and receiving UCAs, and a wavelength used to transmit a reference signal, and in some additional examples, the channel response determination instructions 363 may determine precoding weights for a particular OAM mode based on a channel response matrix associated with the particular OAM mode and one or more pairs of transmitting and receiving UCAs. For example, the channel response determination instructions 363 may be configured to implement one or more of the functions described below with respect to FIG. 7, including, for example, block 724.

[0075]

[0084] In one configuration, a transmitting device 300 for wireless communication includes means for transmitting a reference signal (e.g., a first reference signal, a second reference signal, etc.) using a particular Orbital Angular Momentum (OAM) mode (e.g., a first OAM mode, a second OAM mode, etc.), means for receiving information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit the first OAM mode, means for transmitting reference signal configuration information indicating that a first subset of reference signals of a plurality of reference signals is associated with the first OAM mode, a rank indicator associated with the first OAM mode, or channel quality information associated with the first OAM mode. from the receiving device, means for determining a channel response for a particular OAM mode based on a radius of a first UCA used to transmit a reference signal, a radius of a third UCA used by the receiving device to receive the reference signal, a distance between the first UCA and the third UCA, and a wavelength of a waveform used to transmit the first reference signal, and / or means for determining another channel response for a particular OAM mode based on a radius of a second UCA used to transmit another reference signal, a radius of the third UCA, a distance between the first UCA and the third UCA, and a wavelength of a waveform used to transmit the first reference signal. In one aspect, the above-mentioned means may be the processor 304 shown in FIG. 3 configured to perform the functions recited by the above-mentioned means. In another aspect, the above-mentioned means may be a circuit or any device configured to perform the functions recited by the above-mentioned means.

[0076]

[0085] Of course, in the above examples, the circuitry contained within the processor 304 is provided merely as an example, and other means for performing the described functions may be included within various aspects of the disclosure, including, but not limited to, instructions stored in the computer-readable storage medium 306 or any other suitable device or means employing the processes and / or algorithms described in any one of Figures 1, 2, 5, and / or 6, and described herein, e.g., with respect to Figures 7, 8, and / or 10.

[0077]

[0086] 4 is a conceptual diagram illustrating an example of a hardware implementation for an exemplary receiving device 400 employing a processing system 414. According to various aspects of the disclosure, the elements, or any portion of the elements, or any combination of the elements, may be implemented in a processing system 414 that includes one or more processors 404. For example, the receiving device 400 may be a user equipment (UE), a base station, or any other suitable wireless communications node, such as those shown in any of FIGS.

[0078]

[0087] In some aspects, the transceiver 410 includes (or is coupled to) multiple antennas 411 (e.g., each may include multiple antenna elements). The multiple antennas 411 may be configured as a uniform circular array (UCA) antenna, as described below and shown in FIG. 5, as a coaxial multi-circular UCA configuration, as described below and shown in FIG. 6, or some combination of two or more of the above. In some aspects, any structure that allows OAM multiplexing of electromagnetic signals (e.g., RF signals, optical signals, etc.) may be applied, including, but not limited to, the UCA antennas described by way of example. The multiple antennas 411 may include or possibly be configured using any other suitably configured phase plates, spatial modulators, integrated circuits, any other suitable components, and / or any suitable combination thereof, for transmission over any suitable medium, including wireless air interfaces, optical fibers, etc.

[0079]

[0088] The processing system 414 may be substantially similar to the processing system 314 shown in Figure 3, including the bus interface 408, the bus 402, the memory 405, the processor 404, and the computer-readable medium 406. Additionally, the receiving device 400 may include a user interface 412 and a transceiver 410 substantially similar to those described above in Figure 3. That is, the processor 404 as utilized in the receiving device 400 may be configured (e.g., in conjunction with the memory 405) to implement any one or more of the processes described below and illustrated in Figures 7, 9, and / or 10.

[0080]

[0089] In some aspects of the disclosure, the processor 404 may include a transceiver controller 441 configured (e.g., in cooperation with the memory 405) for various functions including, for example, receiving and sampling a waveform (including, in some examples, one or more reference signals) and storing samples of the received waveform in the memory 405. For example, the transceiver controller 441 may be configured to implement one or more of the functions described below with respect to FIG. 7, e.g., including blocks 706, 714, and / or 718, with respect to FIG. 9, e.g., including blocks 902, 904, and / or 906, and / or with respect to FIG. 10, e.g., including blocks 1010, 1014, 1016, 1018, and / or 1020.

[0081]

[0090] In some further aspects of the disclosure, the processor 404 may include a channel characterization circuit 442 configured (e.g., in conjunction with the memory 405) for various functions including, for example, measuring a channel based on a reference signal received using a particular OAM mode and determining a channel gain between a UCA used to transmit a reference signal using a particular OAM mode and a UCA used to receive a reference signal using a particular OAM mode. In some examples, the channel characterization circuit 442 may measure a channel based on a received reference signal (e.g., received CSI-RS) transmitted and received using a particular OAM mode, and in some other examples, the channel characterization circuit 442 may determine a channel gain between a UCA antenna that transmitted a reference signal (e.g., CSI-RS) using a particular OAM mode and a UCA antenna that received the reference signal. For example, the channel characterization circuit 442 may be configured to implement one or more of the functions described below with respect to FIG. 7, including, for example, block 716.

[0082]

[0091] In some further aspects of the disclosure, the processor 404 may include a channel selection circuit 443 configured (e.g., in conjunction with the memory 405) for various functions including, for example, determining which antennas (e.g., UCA antennas) to use to receive reference signals associated with various OAM modes and selecting which antenna(s) (e.g., UCA antennas) to use by a transmitting device (e.g., transmitting device 300) to transmit a particular OAM mode. In some examples, the channel selection circuit 443 may determine which antennas to use to receive reference signals (e.g., CSI-RS) associated with each OAM mode based on any suitable information (e.g., a maximum number of simultaneous OAM modes each transmitter UCA is configured to transmit, a maximum number of simultaneous OAM modes each receiver UCA is configured to receive, etc.), and in some other examples, the channel selection circuit 443 may select a transmitter UCA to use to transmit each OAM mode and / or allocate a receiver UCA to receive each OAM mode based on a channel gain between one or more pairs of UCAs used to transmit and receive each OAM mode. For example, the channel selection circuitry 443 may be configured to implement one or more of the functions described below with respect to FIG.

[0083]

[0092] Still further, the computer-readable storage medium 406 may store computer-executable code including transceiver controller instructions 461 that configure the receiving device 400 for various functions including, for example, receiving and sampling a waveform (including, in some examples, one or more reference signals) and storing samples of the received waveform in the memory 405. For example, the transceiver controller instructions 461 may be configured to cause the receiving device 400 to implement one or more of the functions described below with respect to FIG. 7, e.g., including blocks 706, 714, and / or 718, with respect to FIG. 9, e.g., including blocks 902, 904, and / or 906, and / or with respect to FIG. 10, e.g., including blocks 1010, 1014, 1016, 1018, and / or 1020.

[0084]

[0093] In some further examples, the computer-readable storage medium 406 may store computer-executable code including channel characterization instructions 462 that configure the receiving device 400 for various functions, including, for example, measuring a channel based on a reference signal received using a particular OAM mode and determining a channel gain between a UCA used to transmit a reference signal using a particular OAM mode and a UCA used to receive a reference signal using a particular OAM mode. In some examples, the channel characterization instructions 462 may measure a channel based on a received reference signal (e.g., received CSI-RS) transmitted and received using a particular OAM mode, and in some other examples, the channel characterization instructions 462 may determine a channel gain between a UCA antenna that transmitted a reference signal (e.g., CSI-RS) using a particular OAM mode and a UCA antenna that received the reference signal. For example, the channel characterization instructions 462 may be configured to perform one or more of the functions described below with respect to FIG. 7, including, for example, block 716.

[0085]

[0094] In some further examples, the computer-readable storage medium 406 may store computer-executable code including channel selection instructions 463 that configure the receiving device 400 for various functions including, for example, determining which antennas (e.g., UCA antennas) to use to receive reference signals associated with various OAM modes and selecting which antenna(s) (e.g., UCA antennas) to use by the transmitting device (e.g., transmitting device 300) to transmit a particular OAM mode. In some examples, the channel selection instructions 463 may determine which antennas to use to receive reference signals (e.g., CSI-RS) associated with each OAM mode based on any suitable information (e.g., a maximum number of simultaneous OAM modes each transmitter UCA is configured to transmit, a maximum number of simultaneous OAM modes each receiver UCA is configured to receive, etc.), and in some other examples, the channel selection instructions 463 may select which transmitter UCAs to use to transmit each OAM mode and / or allocate receiver UCAs to receive each OAM mode based on a channel gain between one or more pairs of UCAs used to transmit and receive each OAM mode. For example, the channel selection instructions 463 may be configured to implement one or more of the functions described below with respect to FIG.

[0086]

[0095] In one configuration, a receiving device 400 for wireless communication includes means for receiving an indication from a transmitting device (e.g., transmitting device 300) that a particular subset of antenna elements (e.g., corresponding to a particular UCA circle) should be used to transmit a first reference signal for a first OAM mode, means for receiving an indication from the transmitting device (e.g., transmitting device 300) that a particular subset of antenna elements (e.g., corresponding to a particular UCA circle) should be used to transmit a second reference signal for the first OAM mode, means for transmitting information indicating the subset of antenna elements used to receive the first reference signal, means for receiving the first reference signal, means for receiving the second reference signal, means for receiving reference signal configuration information from the transmitting device (e.g., transmitting device 300), and indicating that the first reference signal should be transmitted using the first UCA. The OAM mode determining means may include means for determining based on the channel configuration information, means for measuring a channel based on a first reference signal, means for determining a first channel gain between the first UCA and a UCA used to receive the first reference signal, means for determining a second channel gain between the first UCA and a UCA used to receive the second reference signal, means for receiving information indicative of a maximum number of OAM modes for which the transmitting device is configured to transmit simultaneously using the first UCA, means for selecting a UCA to be used for transmitting using the first OAM mode based on the first channel gain, the second channel gain, and the maximum number of OAM modes for which the transmitting device is configured to transmit simultaneously using the first UCA, and / or means for transmitting information indicative of a subset (e.g., UCA) of antenna elements of the transmitting device (e.g., transmitting device 300) for transmitting the first OAM mode. In one aspect, the above-mentioned means may be the processor 404 shown in FIG. 4 configured to perform the functions recited by the above-mentioned means. In another aspect, the above-mentioned means may be a circuit or any apparatus configured to perform the functions recited by the above-mentioned means.

[0087]

[0096] Of course, in the above examples, the circuitry contained within processor 404 is provided by way of example only, and other means for performing the described functions may be included within various aspects of the disclosure, including, but not limited to, instructions stored in computer-readable storage medium 406, or any other suitable FIG. 1, FIG. 2, FIG. 5, and / or FIG. 6, e.g., utilizing the processes and / or algorithms described herein with respect to FIG. 7, FIG. 9, and / or FIG. 10.

[0088]

[0097] In some aspects, the present disclosure provides wireless communication techniques that exploit the orbital angular momentum (OAM) properties of electromagnetic (EM) waves to modulate carriers to carry information and / or to multiplex reference signals onto a common wireless resource. Systems and devices employing OAM are currently under intense development due to its improved communications spectral efficiency, its ability to provide higher order spatial multiplexing (e.g., as described further below) potentially resulting in higher data rates, and its potential to enable low receiver complexity, and OAM is considered a strong candidate for future 6G communications technologies or an extension of existing 5G technologies.

[0089] UCA configuration

[0098] 5 illustrates an example of a uniform circular array (UCA) OAM configuration supporting information transmission with OAM mode selection and detection in accordance with some aspects of the disclosure. In some examples, the illustrated UCA OAM configuration may implement aspects of the RAN 100 and may be employed by the transmitting device 202 / 300 and the receiving device 206 / 400. In this example, the transmitting device (e.g., a UE or a base station) may include an OAM transmitter UCA antenna 505, and the receiving device (e.g., a UE or a base station) may include an OAM receiver UCA antenna 510.

[0090]

[0099] In some aspects, one or both of the OAM transmitter UCA antenna 505 or the OAM receiver UCA antenna 510 may be implemented as a planar array of antenna elements, which may be, or in some cases may function as, an example of a (massive or holographic) MIMO array or an intelligent surface. In some cases, the transmitting device may identify a set of antenna elements 515 of the planar array that forms the transmitter UCA, and the receiving device may identify a set of antenna elements 545 of the planar array that forms the receiver UCA.

[0091]

[0100] Upon selecting a set of antenna elements from the planar array, the OAM transmitter may apply weights 535 to each of the selected antenna elements 515 based on the OAM mode index l of the transmitted OAM beam and one or more spatial parameters associated with each antenna element. If a UCA method is used to generate an OAM beam, the transmitting device may identify a set of antenna elements 515 on a circular array of antenna elements and may load a first set of weights 520 to each of the identified antenna elements based on a first OAM mode index (e.g., l=0). Additionally, for other OAM mode indices, other weights may be used for the set of antenna elements 515, such as a second OAM mode index (e.g., l=+1) that may use a second set of weights 525 and a third OAM mode index (e.g., l=-1) that may use a third set of weights 530.

[0092]

[0101] For example, to generate an OAM beam with a selected OAM mode index (e.g., l=0), the OAM transmitter may load weights 535 onto each antenna element 515 on the UCA based on an angle 540 measured between a reference line on the UCA (e.g., the x-axis on a plane in which the UCA is located, whose origin is the center of the UCA) and the antenna element, the OAM mode index l, and i (e.g., for a complex-valued weight that may alternatively be denoted as j in some cases). In some cases, for example, the weight for antenna element n may be

[0093]

number

[0094] where φ n is equal to the angle 540 measured between a reference line on the UCA and antenna element n. By multiplying the respective beamforming weights 535 of each set of weights 520-530 on each antenna (e.g., w for the first set of weights 520, 1 =[w 1,1 ,w 1,2 ,...,w 1,8 ] T ), a signal port may be generated. The weights 535 of each antenna element 515 may be expressed as e iφl (where φ is the angle of antenna element 515 in the circle (e.g., angle 540 relative to antenna element 515-g) and l is the OAM mode index), each set of weights 520-530 provides a beamformed port that is equivalent to OAM mode l. iφl’ By using multiple OAM modes, multiple OAM modes are thereby generated.

[0095]

[0102] In the OAM receiver UCA antenna 510, the receiving device may have a circular arrangement of receive antenna elements 545. The channel matrix may be denoted as H from each transmit antenna to each receive antenna, where the beamformed channel matrix

[0096]

number

[0097] in the case of,

[0098]

number

[0099] Any two columns of are orthogonal, which means that the beamformed ports have no crosstalk. This allows OAM-based communication to efficiently achieve a high level of spatial multiplicity. Furthermore, the eigen-based transmit precoding weights and receive combining weights of UCA-based OAM are equal to a discrete Fourier transform (DFT) matrix that is independent of communication parameters (e.g., distance, aperture size, and carrier frequency). Therefore, UCA-based OAM can be implemented at a relatively low cost. In some cases, a receiving device may test multiple different OAM modes to determine the OAM mode used in a transmission (e.g., based on whether a particular OAM mode results in a successfully demodulated transmission), which may be used to identify one or more information bits of the transmission.

[0100]

[0103] In some aspects, when the central axes of the transmitter antenna (e.g., antenna 311) and the receiver antenna (e.g., antenna 411) are closely aligned (e.g., with a misalignment of less than 0.1 milliradians (mrad)), each OAM mode is orthogonal to each other's OAM mode. However, when the antennas are misaligned, nearby OAM modes may cause interference. For example, with a misalignment of 1 mrad, adjacent OAM modes may cause significant interference, and with larger misalignments, OAM modes that are farther away from a particular OAM mode may also cause interference.

[0101] Multiple Coaxial UCA Configurations

[0104] 6 illustrates an example of a coaxial multi-circle UCA OAM configuration that supports multiplexing and modulation of wireless transmissions by controlling OAM modes and coaxial UCA circles, in accordance with some aspects of the disclosure. In some examples, the illustrated coaxial multi-circle UCA OAM configuration may implement aspects of the RAN 100 and may be employed by the transmitting device 202 / 300 and the receiving device 206 / 400. In this example, the transmitting device (e.g., a UE or a base station) may include an OAM transmitter UCA antenna 605, and the receiving device (e.g., a UE or a base station) may include an OAM receiver UCA antenna 610.

[0102]

[0105] In some aspects, one or both of the OAM transmitter coaxial multi-circle UCA antenna 605 or the OAM receiver coaxial multi-circle UCA antenna 610 may be implemented as a planar array of coaxial UCA antenna elements, as described above and shown in FIG. 5. In various examples, the OAM transmitter may include the same number of UCA circles as the OAM receiver, but this is not necessarily the case. That is, a transmitting device 202 / 300 can communicate with a receiving device 206 / 400 using the same and different numbers of UCA circles.

[0103]

[0106] According to further aspects of the disclosure, a transmitting device may employ a subset (e.g., one or more) of its UCA circles from its transmitter UCA antenna 605 for a given transmission. For example, a transmitting device may multiplex multiple beams, streams, or waveforms onto a given wireless resource by transmitting each such stream with a different respective set of one or more UCA circles. In theory, streams transmitted over different sets of UCA circles may be orthogonal such that a receiving device can receive and separately recover those streams received over the same wireless resource (e.g., overlap in the time and frequency domains, use the same code, etc.).

[0104]

[0107] In a further aspect, the transmitting device may independently select or control an OAM mode for each of the multiplexed OAM beams. That is, the transmitting device may utilize a first set of one or more UCA circles to transmit a first OAM beam having a first OAM mode and a second set of one or more UCA circles to transmit a second OAM beam having a second OAM mode, where the first OAM mode (i.e., from the first set of one or more UCA circles) may be the same as or different from the second OAM mode (i.e., from the second set of one or more UCA circles). Various options and further details of such a system are provided in the following discussion.

[0105]

[0108] In the following description, for ease of explanation, reference is made to the UCA configuration as shown in FIG. 5 and FIG. 6. However, it should be appreciated that the present disclosure is not limited to this example. In addition, according to other aspects of the present disclosure, reference signal multiplexing using multiple OAM modes may be implemented using any structure that allows OAM multiplexing of electromagnetic signals (e.g., RF signals, optical signals, etc.) to be applied, including, but not limited to, a UCA antenna as described by way of example. Signals transmitted (e.g., multiplexed) using multiple OAM modes may be transmitted and / or received using any suitable transmitting and / or receiving components, which may include or, in some cases, be configured using any suitably configured phase plates, spatial modulators, integrated circuits, any other suitable components, and / or any suitable combination thereof, for transmission over any suitable medium, including wireless air interfaces, optical fibers, etc.

[0106]

[0109] In general, since different OAM modes are orthogonal when the transmit and receive antennas are aligned, precoding for different OAM modes in a multi-circle OAM communication system may be implemented separately. The OAM receiver may measure a reference signal for each circle for each mode and determine inter-circle precoding weights for each mode. The OAM receiver may then report the results of the measurements to the OAM transmitter. For example, the OAM receiver may report the amplitude and phase of each element of the precoding vector to the OAM transmitter based on the measurements of the reference signal. In such an example, as the number of modes and / or circles increases, the cost associated with the reporting (e.g., in reducing communication transmission capacity caused by signaling overhead) increases and may become prohibitively high. As another example, the OAM receiver may report codewords from an existing codebook (e.g., a precoding matrix indicator (PMI)) associated with MIMO communication. In such an example, the codebook may be defined based on antennas in a uniform linear array (ULA) and / or a uniform planar array (UPA). As described above, although the UCA includes multiple antennas, precoding in a multi-circle UCA communication system may be performed between UCA circles, not between different antenna elements (e.g., antenna element 515 in FIG. 5) of each UCA, and the antenna elements of the UCA are not arranged in a linear array or a planar array. Therefore, the UCA's inter-circle channel matrix does not match the DFT of the codebook defined for the ULA or UPA. This may lead to reduced beamforming gain and / or throughput compared to precoding that utilizes the characteristics of the OAM communication system configured with the multi-circle UCA.

[0107]

[0110] In a coaxial multi-circle OAM communication system, when the UCA circles of the transmitting device and the receiving device are aligned, the channel gain of the nth OAM mode is

[0108]

number

[0109] teeth,

[0110]

number

[0111] is proportional to In the formula, i is

[0112]

number

[0113] where λ is the wavelength of the center frequency used to transmit the OAM mode, and J n is the nth order Bessel function, and r tx is the radius of the outgoing UCA circle, and r rx is the receiving UCA circle, z is the distance between the antennas, and j is

[0114]

number

[0115] It is.

[0116] Formula-based inter-circle precoding weight determination

[0111] Figure 7 is a call flow diagram illustrating an example process of formula-based inter-circle precoding weight determination for an orbital angular momentum (OAM) communication system according to some aspects of the present disclosure. As described below, some or all of the illustrated features may be omitted in certain implementations within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process illustrated in Figure 7 may be performed by the transmitting device 300 illustrated in Figure 3 or the receiving device 400 illustrated in Figure 4. In some examples, the process of Figure 7 may be performed by any suitable device or means performing the functions or algorithms described below.

[0117]

[0112] At block 702, a transmitting device (eg, transmitting device 300) may transmit a signal 704 (eg, a waveform) including reference signal configuration information indicating which OAM mode is associated with each reference signal.

[0118] Furthermore, in some aspects, the reference signal configuration information may include information indicating which transmit antennas should be used to transmit each reference signal (e.g., corresponding to a particular UCA circle). In some aspects, the transmission of information indicating which transmit antennas should be used to transmit each reference signal may be omitted (e.g., if all UCA circles are configured to transmit reference signals for each OAM mode to be used).

[0119] In some aspects, the transmitting device 300 may transmit information over any suitable channel (e.g., any suitable physical layer channel, such as PDCCH, PUCCH, or PSCCH) over any suitable communication network (e.g., over a RAN, such as the RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the transmitting device 300 may transmit information using any suitable communication interface, such as a transceiver (e.g., the transceiver 310) and an antenna (e.g., the antenna 311). For example, in some aspects, the transmitting device 300 may transmit the signal 704 using a particular OAM mode and / or multiple OAM modes. As another example, the transmitting device 300 may transmit the signal 704 using any other suitable communication technique(s).

[0120] In some aspects, the transmitting device 300 may transmit the reference signal configuration information using any suitable signaling technique or combination of techniques. For example, the transmitting device 300 may transmit the reference signal configuration information using radio resource control (RRC) signaling. As another example, the transmitting device 300 may transmit the reference signal configuration information using MAC control element (MAC CE) signaling. As yet another example, the transmitting device 300 may transmit the reference signal configuration information using physical layer signaling (sometimes referred to as L1 signaling), such as via downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI), etc. Additionally or alternatively, the transmitting device 300 may transmit the reference signal configuration information using a combination of signaling techniques, such as one or more of RRC, MAC CE, DCI, UCI, SCI, and / or any other suitable signaling.

[0121] In some aspects, the reference signal configuration information may include information regarding channel state information reference signals (CSI-RSs) that the transmitting device 300 is scheduled to transmit. Reference signal configuration information including information regarding the CSI-RS may be referred to as CSI-RS configuration information.

[0122] In some aspects, the reference signal configuration information may identify which subset of antenna elements the transmitting device 300 is scheduled to use to transmit each reference signal (e.g., each CSI-RS). For example, the reference signal configuration information may specify that a first UCA circle is scheduled to transmit a first reference signal(s) and a second UCA circle is scheduled to transmit a second reference signal(s).

[0123] In some aspects, the reference signal configuration information may identify which subset of antenna elements (e.g., corresponding to UCA circles) is associated with each reference signal using any suitable technique or combination of techniques. For example, the reference signal configuration information may include CSI-RS resource information, and each UCA circle may be associated with a particular resource (e.g., CSI-RS resource described in 3GPP Technical Specification 38.214) used to transmit a reference signal (e.g., a first UCA circle of a transmitting device may be associated with a first CSI-RS resource, a second UCA circle of a transmitting device may be associated with a second CSI-RS resource, etc.). In such an example, reference signals associated with different OAM modes may be associated with a particular port of a resource (e.g., a first OAM mode may be associated with a first port of CSI-RS resources associated with a first UCA antenna, a second OAM mode may be associated with a second port of CSI-RS resources associated with a first UCA antenna, etc.).

[0124] As another example, the reference signal configuration information may include CSI-RS resource information, and each UCA circle may be associated with a particular resource set (e.g., a CSI-RS resource set as described in 3GPP Technical Specification 38.331) used to transmit reference signals (e.g., a first UCA circle of a transmitting device may be associated with a first CSI-RS resource set, a second UCA circle of a transmitting device may be associated with a second CSI-RS resource set, etc.). In such an example, reference signals associated with different OAM modes may be associated with particular resources of a resource set (e.g., a first OAM mode may be associated with a first resource of a CSI-RS resource set associated with a first UCA antenna, a second OAM mode may be associated with a second resource of a CSI-RS resource set associated with a first UCA antenna, etc.).

[0125] In some aspects, the reference signal configuration information may include a property associated with each resource (e.g., each port of each CSI-RS resource, each resource of each CSI-RS resource set, etc.) that indicates which OAM mode should be used to transmit each reference signal (e.g., each CSI-RS). In some aspects, the property may be an OAM mode index. For example, the OAM mode index may be indicated using one or more bits (e.g., bytes) in the reference signal configuration information. In such an example, a positive or negative OAM mode may be indicated using a bit (e.g., the first bit) to represent positive or negative, or using a complement code (e.g., two's complement).

[0126] In some aspects, the reference signal configuration information may include a property indicating a maximum number of simultaneous modes that each UCA circle (e.g., CSI-RS resources, a CSI-RS resource set, one or more ports associated with the CSI-RS resources, one or more resources associated with the CSI-RS resource set, etc.) of the transmitting device may transmit in. For example, the reference signal configuration information may include an indication that a first UCA antenna (e.g., associated with CSI-RS resource 1, associated with CSI-RS resource set 1, etc.) is configured to transmit up to a particular number of OAM modes (e.g., one mode, two modes, three modes, etc.) simultaneously, and an indication that a second UCA antenna (e.g., associated with CSI-RS resource 2, associated with CSI-RS resource set 2, etc.) is configured to transmit up to a particular number of OAM modes (e.g., one mode, two modes, three modes, etc.) simultaneously. In some aspects, a property indicating the maximum number of simultaneous modes that each UCA circle of a transmitting device may transmit may be included in the reference signal configuration information using any suitable number of bits associated with one or more of the UCA circles. As described above with respect to FIG. 3, the maximum number of OAM modes that a transmitting device 300 is configured to transmit (and / or receive) simultaneously using a particular UCA may be determined by the number of TXRUs associated with the UCA. For example, if the transmitting unit 300 includes two TXRUs associated with a first UCA, the UCA may be capable of transmitting no more than two OAM modes simultaneously. In some aspects, if the maximum number of simultaneous modes that a particular UCA circle of a transmitting device is configured to transmit is equal to or greater than the number of OAM modes that the transmitting device is configured to use, information related to the maximum number may be omitted from the reference signal configuration information.

[0127] At block 706, a receiving device (e.g., receiving device 400) may receive the signal 704. For example, in some aspects, the receiving device 400 may receive information over any suitable channel (e.g., any suitable physical layer channel, such as PDCCH, PUCCH, or PSCCH) over any suitable communication network (e.g., over a RAN, such as RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the receiving device may receive the signal 704 using any suitable communication interface, such as a transceiver (e.g., transceiver 410) and an antenna (e.g., antenna 411). In some aspects, the receiving device may receive the signal 704 by sampling and buffering a received wireless signal on an appropriate channel and applying suitable processing to the buffered signal, such as energy detection, demodulation (e.g., using a demodulation function associated with the OAM mode used to transmit and receive the signal 704 and based on a channel matrix), decoding, etc.

[0128] In some aspects, the receiving device 400 may store in memory the information received at block 706 and / or the information derived from the present invention received at block 706. For example, the receiving device 400 may store information indicating which OAM mode should be used to transmit a reference signal (e.g., CSI-RS). In a more specific example, the receiving device 400 may store a list indicating which OAM mode should be used to transmit a reference signal (e.g., as described above with respect to block 702). As another more specific example, the receiving device 400 may store a table indicating which OAM mode should be used to transmit a reference signal (e.g., as described above with respect to block 702). As yet another more specific example, the receiving device 400 may store a value or values ​​indicating which OAM mode should be used to transmit a reference signal.

[0129] As another example, the receiving device 400 may store information indicating which subset of antenna elements (e.g., which UCA circle) is associated with each reference signal. As yet another example, the receiving device 400 may store information indicating how many OAM modes each subset of antenna elements is capable of simultaneously transmitting.

[0130] At block 708, the receiving device (e.g., the receiving device 400) may determine one or more antenna elements to be used to receive a reference signal to be transmitted by the transmitting device. For example, the receiving device 400 may determine which subset of antenna elements (e.g., UCA circles) to use to receive the CSI-RS associated with each OAM mode. In such an example, the selection may be based on various considerations, such as the size of each subset of antenna elements used to receive the reference signal (e.g., the radius of each UCA circle), the number of OAM modes that a particular subset of antenna elements is configured to simultaneously receive (e.g., based on the number of TXRUs associated with the subset of antenna elements), the total number of OAM modes to be received, etc.

[0131] In a more specific example, the receiving device 400 may determine that a first UCA circle should be used to receive reference signal(s) transmitted using a first OAM mode (e.g., OAM mode 1), a second UCA circle should be used to receive reference signal(s) transmitted using the first OAM mode (e.g., OAM mode 1) and a second OAM mode (e.g., OAM mode 2), and a third UCA circle should be used to receive reference signal(s) transmitted using the second OAM mode (e.g., OAM mode 2). In such an example, the first and third UCA circles may be limited to simultaneously receive one OAM mode (e.g., if only one TXRU is associated with each UCA circle), while the second UCA circle may be configured to simultaneously receive multiple OAM modes (e.g., if two or more TXRUs are associated with the second UCA circle).

[0132]

[0127] In some aspects, the receiving device 400 may attempt to select a receiving antenna element to use to receive a reference signal to ensure that all reference signals to be transmitted by the transmitting device are associated with at least one receiving antenna (e.g., at least one UCA circle of the receiving device).

[0133] At block 710, a transmitting device (e.g., transmitting device 300) may transmit multiple signals 712 (e.g., as multiple waveforms and / or multiplexed signals on a single waveform), each including one or more reference signals. In some aspects, each reference signal transmitted at block 710 may be transmitted using a particular OAM mode and may be transmitted using a particular UCA circle.

[0134] In some aspects, the transmitting device 300 may transmit a signal on any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) over any suitable communication network (e.g., over a RAN, such as the RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the transmitting device 300 may transmit information using any suitable communication interface, such as a transceiver (e.g., the transceiver 310) and an antenna (e.g., the antenna 311). For example, in some aspects, the transmitting device 300 may transmit the signal 704 using a particular OAM mode and / or multiple OAM modes. As another example, the transmitting device 300 may transmit the signal 704 using any other suitable communication technique(s).

[0135] In some aspects, a transmitting device may transmit multiple reference signals in parallel (e.g., using the same UCA antenna or different UCA antennas). For example, because different OAM modes are generally orthogonal, a transmitting device may be configured to transmit reference signals associated with different OAM modes simultaneously. In such an example, a transmitting device may use a single UCA circle configured to transmit multiple OAM modes (e.g., using multiple TXRUs associated with the UCA circle) to simultaneously transmit reference signals (e.g., CSI-RS) for multiple modes. Alternatively, a transmitting device may use multiple UCA circles to simultaneously transmit reference signals (e.g., CSI-RS) for multiple modes when at least one of the UCA circles is configured to simultaneously transmit only a single OAM mode (e.g., the UCA circle is associated with a single TXRU).

[0136] At block 714, a receiving device (e.g., receiving device 400) may receive the reference signal transmitted in signal 712 using any suitable UCA antenna (and / or any other suitable antenna). For example, in some aspects, receiving device 400 may receive information over any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) over any suitable communication network (e.g., over a RAN, such as RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the receiving device may receive signal 712 using any suitable communication interface, such as a transceiver (e.g., transceiver 410) and an antenna (e.g., antenna 411). In some aspects, the receiving device can receive the signal 712 by sampling and buffering the received wireless signal on an appropriate channel and applying suitable processing to the buffered signal, such as energy detection, demodulation (e.g., based on a channel matrix, using a demodulation function associated with the OAM mode used to transmit and receive the signal 712), decoding, etc.

[0137] At block 716, the receiving device (e.g., the receiving device 400) may estimate a channel gain for a pair of transmitting and receiving antennas (e.g., a pair of UCA circles) based on the received reference signal. In some aspects, the receiving device 400 may use any suitable technique or combination of techniques to measure a channel between each UCA circle used to transmit a reference signal (e.g., CRI-RS) and each UCA circle used to receive a reference signal for an OAM mode. For example, based on information received in the reference signal configuration information, the receiving device may measure the channel and estimate a channel gain and / or any other suitable property associated with the channel based on the measurement of the channel (e.g., a channel quality indicator (CQI), a rank indicator (RI), etc.). In some aspects, the receiving device may estimate a channel gain h for a particular reference signal based on the OAM mode used to transmit the reference signal (e.g., based on the OAM mode indicated in the reference signal configuration information received at 706) based on a symbol x associated with the reference signal and the received signal y. For example, a receiving device may estimate a channel gain h based on the ratio of x and y (eg, using the relationship h=y / x).

[0138]

[0133] In some aspects, the receiving device 400 may determine which pair of transmit and receive antennas provides the best channel quality for a particular OAM mode (e.g., based on the channel gain associated with the pair). For example, the receiving device 400 may allocate the UCA circle of the receiving device 400 to all used OAM modes based on the number of OAM modes used by the transmitting device. As another example, the receiving device 400 may allocate the UCA circle of the receiving device 400 to a particular OAM mode based on the channel quality (e.g., channel gain) between the UCA circle and the UCA circle of the transmitting device for the particular OAM mode. In some aspects, the receiving device 400 may allocate less of the UCA circle of the receiving device 400 to the OAM mode than was used to receive the particular OAM mode in block 714.

[0139] In some aspects, the receiving device 400 may identify an OAM mode from which a transmitting antenna (e.g., a UCA circle of the transmitting device) should be received by a particular subset of receiving antenna elements based on a resource associated with the reference signal. For example, the receiving device 400 may determine that a first UCA circle (e.g., Rx circle 1) and a second UCA circle (e.g., Rx circle 2) should be used to receive a first OAM mode (e.g., OAM mode 1), and determine that a second UCA circle (e.g., Rx circle 2) and a third UCA circle (e.g., Rx circle 3) should be used to receive a second OAM mode (e.g., OAM mode 1). In such an example, the determination may be based in part on the first and third UCA circles (e.g., Rx circle 1 and Rx circle 3) being limited to receiving a single OAM mode and the second UCA circle (e.g., Rx circle 2) being capable of receiving at least two OAM modes.

[0140] In some aspects, the receiving device may select the transmit device resources to be used to transmit each OAM mode based on the number of OAM modes that the allocated receive antennas and / or transmit antennas are configured to transmit simultaneously. For example, the receiving device may select the port {port 1 of CSI-RS resource 1, port 1 of CSI-RS resource 2} for OAM mode 1 and the selected {port 2 of CSI-RS resource 2} for OAM mode 2 based on the number of simultaneous OAM modes that the transmit antennas are capable of transmitting (e.g., based on information received in reference signal configuration information) and / or based on channel measurements by the receiving device.

[0141] In some aspects, the receiving device 400 (and / or the transmitting device 300) may determine a matrix of possible transmit / receive pairs for each OAM mode based on the allocated Rx UCA circle and the selected Tx UCA circle. For example, if a receiving apparatus allocates Rx circle 1 and Rx circle 2 to be used to receive OAM mode 1, assigns Rx circle 2 and Rx circle 3 to be used to receive OAM mode 2, and selects {CSI-RS resource 1 port 1, CSI-RS resource 2 port 1} for OAM mode 1 and {CSI-RS resource 2 port 2} for OAM mode 2, then OAM mode 1 may be associated with a 2×2 channel matrix and OAM mode 2 may be associated with a 2×1 channel matrix.

[0142] At block 718, the receiving device (e.g., the receiving device 400) may transmit a signal 720 (e.g., a waveform) including information indicating which UCA circle(s) the receiving device 400 used (and / or expects to use) to receive a reference signal (and / or other communication). For example, the receiving device 400 may include, for each OAM mode, information indicating which UCA circle(s) the receiving device 400 used to receive a reference signal at 714. As another example, the receiving device 400 may include information indicating which UCAs the receiving device 400 has allocated at 716 to potentially receive future signals (e.g., reference signals, communication signals, etc.) for each OAM mode. Furthermore, in some aspects, the receiving device 400 may transmit information indicating the size of the UCA circle(s) used to receive a reference signal and / or allocated to receive future signals.

[0143] In some aspects, the receiving device 400 may transmit information over any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) over any suitable communication network (e.g., over a RAN, such as the RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the receiving device 400 may transmit information using any suitable communication interface, such as a transceiver (e.g., the transceiver 410) and an antenna (e.g., the antenna 411). For example, in some aspects, the receiving device 400 may transmit the signal 720 using a particular OAM mode and / or multiple OAM modes. As another example, the receiving device 400 may transmit the signal 720 using any other suitable communication technology(s).

[0144] In some aspects, the information transmitted in block 718 may include information indicating a radius of a UCA circle of the receiving device 400. For example, the receiving device 400 may receive information indicating that the radius of a first UCA circle (e.g., Rx circle 1) is r 1 The radius of the second UCA circle (for example, Rx circle 2) is r 2 The information may include information indicating that the

[0145] In some aspects, the receiving device 400 may include information in any suitable format indicating the radius of the UCA circle of the receiving device 400. For example, the receiving device 400 may include an information a field in which the identification information and / or circle radius information may be included (e.g., as a floating point value). In a more specific example, the receiving device 400 may include a list of radius values ​​(e.g., {r rx,1 ,r rx,2 ,...,r rx,n}).

[0146]

[0141] As another example, the receiving device 400 may include information indicating which UCA circles have been used (and / or are expected to be used) for which OAM modes, separate from information indicating the radius of each UCA circle.

[0147] In some aspects, the receiving device 400 may communicate information indicating the radius of each UCA circle separately from information indicating which UCA circle has been used (and / or is expected to be used) for each OAM mode. For example, the receiving device 400 may communicate the circle radius information with a lower periodicity than the information indicating which UCA circle has been used (and / or is expected to be used) for each OAM mode. In such an example, the receiving device 400 may communicate the circle radius information at any suitable time, such as during the process of initially establishing a connection between the transmitting device and the receiving device, periodically (e.g., at regular and / or irregular intervals, such as after a predetermined period of time has elapsed, after a connection has been interrupted, etc.), and / or at any other suitable time(s). The receiving device 400 may communicate information indicating which UCA circle(s) have been used (and / or are expected to be used) for each OAM mode periodically (e.g., at regular and / or irregular intervals), such as after (e.g., in response to) receiving a reference signal (e.g., CSI-RS) and / or measuring a channel gain.

[0148] In some aspects, the receiving device 400 may transmit information in any suitable format indicating which UCA circle(s) have been used (and / or are expected to be used) for each OAM mode at block 718. For example, the transmitting device 400 may transmit information indicating which UCA circle(s) have been used (and / or are expected to be used) for each OAM mode using a bitmap in which each bit corresponds to a UCA circle of the receiving device 400. In such an example, the bitmap may have a bit for each UCA circle (e.g., at least three bits if three UCA circles are present, at least four bits if four UCA circles are present, etc.), and the bit used to receive OAM mode 1 has a value (e.g., a binary 1 or a binary 0) indicating that a UCA circle was used. In a more specific example, if a first UCA circle (e.g., Rx circle 1) and a second UCA circle (e.g., Rx circle 2) are used to receive a first OAM mode (e.g., OAM mode 1), and a second UCA circle (e.g., Rx circle 2) and a third UCA circle (e.g., Rx circle 3) are used to receive a second OAM mode (e.g., OAM mode 2), the receiving device 400 may transmit a binary string "011" associated with OAM mode 1, indicating that Rx circle 1 and Rx circle 2 were used to receive OAM mode 1, and another binary string "110" associated with OAM mode 2, indicating that Rx circle 2 and Rx circle 3 were used to receive OAM mode 1. Note that in this example, the least significant bit is associated with Rx circle 1. However, this is an example, and the mapping of bits to OAM modes may be configured using any suitable scheme (e.g., the most significant bit may be associated with Rx circle 1).

[0149] In some aspects, the receiving device 400 may transmit information indicating which UCA circle(s) of the transmitting device are preferred by the receiving device for each OAM mode at block 718. For example, the receiving device 400 may indicate a CSI-RS port index or CSI-RS resource indicator (CRI) associated with a particular OAM mode and / or transmitting device UCA circle. In such an example, the receiving device 400 may transmit information indicating a preferred transmitting device UCA circle(s) (Tx UCA circle) for each OAM mode using a bitmap where each bit corresponds to a reference signal transmission resource. The bitmap has a bit (e.g., at least 4 bits if there are two Tx UCA circles each with two ports) for each port associated with each Tx UCA circle in the reference signal configuration information, and the bit is associated with a preferred transmission resource for OAM mode 1 with a value (e.g., binary 1 or binary 0) indicating a preference for the UCA circle. In a more specific example, a first port associated with a first UCA circle (e.g., port 1 for Tx circle 1) and a first port associated with a second UCA circle (e.g., port 1 for Tx circle 2) may be preferred for a first OAM mode (e.g., OAM mode 1), and a second port associated with the second UCA circle (e.g., port 2 for Tx circle 2) may be preferred for a second OAM mode (e.g., OAM mode 2). The receiving device 400 may communicate this information using a binary string “0101” associated with OAM mode 1, indicating that port 1 of CSI-resource 1 (associated with the two least significant bits) and port 1 of CSI-resource 2 (associated with the two most significant bits) are preferred by the receiving device for mode 1, and another binary string “1000” associated with OAM mode 2, indicating that port 2 of CSI-resource 2 (associated with the two least significant bits) is preferred by the receiving device for mode 2.

[0150]

[0145] In some aspects, the receiving device 400 may transmit, at block 718, a rank indicator (RI) and a channel quality information (CQI) for each OAM mode.

[0151] In some aspects, the receiver device 400 may transmit the information at block 718 using any suitable signaling technique and / or protocol. For example, the receiver device 400 may transmit the information at block 718 using radio resource control (RRC) signaling. As another example, the receiver device 400 may transmit the information at block 718 using medium access control (MAC) control element (CE) signaling. As another example, the receiver device 400 may transmit the information at block 718 using physical layer signaling (sometimes referred to as L1 signaling), such as via downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI). In such an example, the receiver device may transmit the information at block 718 as a CSI report.

[0152] At block 722, the transmitting device (e.g., transmitting device 300) may receive the signal 720 and information indicating which UCA circle the receiving device 400 has used (and / or expects to use) to receive the reference signal using any suitable UCA antenna (and / or any other suitable antenna). For example, in some aspects, the transmitting device 300 may receive the information over any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) over any suitable communication network (e.g., over a RAN, such as RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the receiving device may receive the signal 720 using any suitable communication interface, such as a transceiver (e.g., transceiver 410) and an antenna (e.g., antenna 411). In some aspects, the receiving device can receive signal 720 by sampling and buffering the received wireless signal on an appropriate channel and applying suitable processing to the buffered signal, such as energy detection, demodulation (e.g., based on a channel matrix using a demodulation function associated with the OAM mode used to transmit and receive signal 720), decoding, etc.

[0153] At block 724, the transmitting device (e.g., transmitting device 300) may determine precoding weights for multiple OAM modes based on information about the UCA circles used to receive the reference signal. As described above with respect to FIG. 6 and equation (1), the channel gain between any UCA transmitter / receiver circle pair may be calculated based on the radius of each circle, the distance between the circles, and the wavelength used to transmit the OAM mode.

[0154]

[0149] In some aspects, the transmitting device 300 may calculate a channel gain for each pair of a transmitting device antenna (eg, a Tx UCA circle) and a receiving device antenna (eg, an Rx UCA circle) (eg, based on equation (1)).

[0155] In some aspects, the transmitting device 300 may use information received from the receiving device to determine the pair of transmitter / receiver circles for which the gain should be calculated. For example, the transmitting device 300 may use information indicating which receiver UCA circle was used for each OAM (e.g., allocated by the receiving device). In a more specific example, the transmitting device 300 may use a bitmap associated with a first OAM mode to determine which Rx circle was used (and / or is expected to be used) to receive a reference signal associated with the first OAM mode, and may use a bitmap associated with a second OAM mode to determine which Rx circle was used (and / or is expected to be used) to receive a reference signal associated with the second OAM mode.

[0156]

[0151] As another example, the transmitting device 300 may use information indicating which transmitter UCA circle is preferred by the receiving device for each OAM mode. In a more specific example, the transmitting device 300 may use a bitmap associated with a first OAM mode to determine which Tx circle is preferred by the receiving device for transmitting communications using the first OAM mode, and may use a bitmap associated with a second OAM mode to determine which Tx circle is preferred by the receiving device for transmitting communications using the second OAM mode.

[0157] In some aspects, the transmitting device 400 may calculate a channel response matrix based on channel gains from various pairs of UCA circles of the transmitter and receiver. For example, the transmitting device 400 may calculate a channel response matrix based on the channel gains from various pairs of UCA circles of the transmitter and receiver (e.g., based on preference information from the receiving device) of Tx circle 1 and Tx circle 2 (whose radii r tx,1 ,r tx,2 is known to the OAM transmitter) should be used for the first OAM mode, Rx radius r rx,1 ,r rx,2

[0113] Assuming that OAM mode n has been reported to be used, and that a rank L for OAM mode n has been reported by the receiver device (e.g., as the RI associated with OAM mode n), the channel response matrix may be expressed as follows:

[0158]

number

[0159] During the ceremony, J. n is the nth order Bessel function, λ is the wavelength of the center frequency used to transmit the nth OAM mode, z is the distance between the antennas, and j is the

[0160]

number

[0161] In some aspects, z may be known to the transmitting device and / or receiving device (e.g., it may be provided as an input during a configuration process), may be measured by the transmitting device and / or receiving device (e.g., using a laser range finder, using global positioning data, etc.), and / or may be reported from another device (e.g., from the receiving device to the transmitting device, from the transmitting device to the receiving device, from a different device, etc.).

[0162] In some aspects, the transmitting device 400 may calculate a channel response matrix H for each OAM mode n. n , and H for OAM mode n can be calculated. n The transmitting device may determine the precoding vector by determining the L dominant singular vectors of H, where L is the rank associated with the OAM mode n. In some aspects, the transmitting device may use a singular value decomposition technique, such as n Any suitable technique or combination of techniques may be used to determine the L dominant singular vectors of the channel response matrix H n is H n =UDV H where D is a diagonal matrix, U and V are orthogonal or unitary matrices, and the columns of V correspond to the largest singular values ​​in D.

[0163]

[0154] In some aspects, utilizing a formula to calculate the channel response of the Tx / Rx circle pair may utilize OAM receiver feedback indicating the Tx / Rx circle selection result and the Rx radius based on the calculation at the receiving device. This may reduce feedback overhead compared to a scheme that reports the amplitude and phase of each element of the precoding vector to the transmitted signal. This may also improve accuracy compared to a scheme that uses PMI of the codebook developed for ULA and / or UPA. In some aspects, calculating the channel response matrix and / or precoding weights for the paired OAM mode may improve the beamforming gain and / or throughput of the OAM communication.

[0164]

[0155] FIG. 8 is a flowchart illustrating an example process by which an OAM transmitting device determines circle-to-circle precoding weights for an OAM communication system in accordance with certain aspects of the disclosure.

[0165] At block 802, a transmitting device (e.g., transmitting device 300) may transmit a reference signal (e.g., a channel state information reference signal (CSI-RS)) for a first orbital angular momentum (OAM) mode using a first subset of antenna elements (e.g., a first uniform circular array (UCA) circle). In some aspects, the transmitting device 300 may transmit the reference signal on any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) over any suitable communication network (e.g., over a RAN, such as the RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the transmitting device 300 may transmit the reference signal using any suitable communication interface, such as a transceiver (e.g., transceiver 310) and an antenna (e.g., antenna 311). For example, in some aspects, the transmitting device 300 may transmit the reference signal using a particular OAM mode and / or multiple OAM modes. As another example, the transmitting device 300 may transmit the reference signal using any other suitable communication technique(s).

[0166] At block 804, the transmitting device (e.g., transmitting device 300) may transmit another reference signal (e.g., CSI-RS) for the first OAM mode using a second subset of antenna elements (e.g., a second UCA circle). In some aspects, the transmitting device 300 may transmit the reference signal on any suitable channel (e.g., any suitable physical layer channel, such as PDCCH, PUCCH, or PSCCH) over any suitable communication network (e.g., over a RAN, such as RAN 200, and / or over a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the transmitting device 300 may transmit the reference signal using any suitable communication interface, such as a transceiver (e.g., transceiver 310) and an antenna (e.g., antenna 311). For example, in some aspects, the transmitting device 300 may transmit the reference signal using a particular OAM mode and / or multiple OAM modes. As another example, the transmitting device 300 may transmit the reference signal using any other suitable communication technique or techniques.

[0167]

[0158] In block 806, the transmitting device (e.g., the transmitting device 300) may receive information (e.g., from a receiving device, such as the receiving device 400) indicating a subset of antenna elements to use to transmit a communication (e.g., to the receiving device 400) via the first OAM mode.

[0168]

[0159] FIG. 9 is a flowchart illustrating an example process by which an OAM receiving device determines information for a transmitting device to determine circle-to-circuit precoding weights for an OAM communication system, in accordance with certain aspects of the disclosure.

[0169] At block 902, a receiving device (e.g., receiving device 400) may receive an indication of a subset of antenna elements (e.g., configured as a UCA circle) to be used to transmit a first reference signal (e.g., CSI-RS) for a first OAM mode. For example, in some aspects, receiving device 400 may receive a signal encoded with the indication on any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) via any suitable communications network (e.g., via a RAN, such as RAN 200, and / or via a D2D connection, using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the receiving device may receive the signal encoded with the indication using any suitable communications interface, such as a transceiver (e.g., transceiver 410) and an antenna (e.g., antenna 411). In some aspects, a receiving device may receive a signal encoded with the instructions by sampling and buffering a received wireless signal on an appropriate channel and applying suitable processing to the buffered signal, such as energy detection, demodulation (e.g., based on a channel matrix using a demodulation function associated with the OAM mode used to transmit and receive the signal), decoding, etc.

[0170] At block 904, a receiving device (e.g., receiving device 400) may receive an indication that another subset of antenna elements (e.g., configured as a second UCA circle) should be used to transmit a second reference signal (e.g., CSI-RS) for the first OAM mode. For example, in some aspects, receiving device 400 may receive a signal encoded with the indication on any suitable channel (e.g., any suitable physical layer channel, such as a PDCCH, a PUCCH, or a PSCCH) via any suitable communication network (e.g., via a RAN, such as RAN 200, and / or via a D2D connection using one or more DL slots, one or more UL slots, one or more SL slots, etc.). In some aspects, the receiving device may receive the signal encoded with the indication using any suitable communication interface, such as a transceiver (e.g., transceiver 410) and an antenna (e.g., antenna 411). In some aspects, a receiving device may receive a signal encoded with the instructions by sampling and buffering a received wireless signal on an appropriate channel and applying suitable processing to the buffered signal, such as energy detection, demodulation (e.g., based on a channel matrix using a demodulation function associated with the OAM mode used to transmit and receive the signal), decoding, etc.

[0171]

[0162] In some aspects, the instruction received at block 902 and the instruction received at block 904 may be received together (eg, in a single message).

[0172]

[0163] At block 906, the receiving device (e.g., the receiving device 400) may transmit information indicating a subset of antenna elements (e.g., a particular UCA circle of the receiving device) used to receive the first reference signal.

[0173]

[0164] FIG. 10 is a diagram illustrating transmission of reference signal configuration information and transmission of reference signals for multiple OAM modes using multiple equally-spaced circular array circles in accordance with some aspects of the present disclosure.

[0174] 10, the transmitting apparatus 300 includes a first UCA circle 1002 and a second UCA circle 1004, and the receiving apparatus includes a first UCA circle 1006 and a second UCA circle 1008. As described above with respect to block 702 of FIG. 7, the transmitting device 300 may transmit CSI-RS configuration information in block 1010, which may include CSI-RS resource information 1012.

[0175] In some aspects, the CSI-RS resource information 1012 may include information identifying a CSI-RS resource that may be associated with a particular UCA circle and / or a particular OAM mode. For example, the CSI-RS resource information 1012 may include information identifying a first CSI-RS resource (e.g., CSI-RS resource 1) having two ports associated with a first OAM mode and a second OAM mode, respectively (e.g., identified based on an OAM index value associated with each port). In such an example, the first CSI-RS resource may be associated with the UCA circle 1002 and may or may not explicitly identify an antenna associated with the CSI-RS resource. The CSI-RS resource information 1012 may also include information identifying a second CSI-RS resource (e.g., CSI-RS resource 2) having two ports associated with a first OAM mode and a second OAM mode, respectively.

[0176] As another example, the CSI-RS resource information 1012 may include information identifying a first CSI-RS resource set (e.g., CSI-RS resource set 1) having two ports associated with a first OAM mode and a second OAM mode, respectively (e.g., identified based on an OAM index value associated with each port). In such an example, the first CSI-RS resource set may be associated with the UCA circle 1002 and may or may not explicitly identify the antennas associated with the CSI-RS resources. The CSI-RS resource information 1012 may also include information identifying a second CSI-RS resource (e.g., CSI-RS resource 2) having two ports associated with a first OAM mode and a second OAM mode, respectively. The second CSI-RS resource set may be associated with the UCA circle 1004.

[0177] At block 1014, the transmitting device 300 may transmit the first CSI-RS using a first OAM mode (e.g., OAM mode 1), and at block 1016, the transmitting device 300 may transmit the second CSI-RS using a second OAM mode (e.g., OAM mode 2). In some aspects, the transmitting device may transmit the first CSI-RS and the second CSI-RS simultaneously (e.g., using the same transmission resources but different OAM modes) or consecutively (e.g., using different transmission resources and different OAM modes).

[0178]

[0169] The receiving device 400 may receive the first CSI-RS and the second CSI-RS using the UCA circle 1006 and / or the UCA circle 1008.

[0179] At block 1018, the transmitting device 300 may transmit the third CSI-RS using a first OAM mode (e.g., OAM mode 1), and at block 1020, the transmitting device 300 may transmit the fourth CSI-RS using a second OAM mode (e.g., OAM mode 2). In some aspects, the transmitting device may transmit the third CSI-RS and the fourth CSI-RS simultaneously (e.g., using the same transmission resource but using different OAM modes) or consecutively (e.g., using different transmission resources and different OAM modes). It should be noted that the first CSI-RS and the third CSI-RS may be transmitted simultaneously if they are transmitted using orthogonal resources (e.g., using different wavelength resources, different codes, etc.), but may be prohibited from being transmitted simultaneously if the transmission resources are the same in some cases (e.g., because two signals from different UCA circles with the same OAM mode are not orthogonal).

[0180]

[0171] The receiving device 400 may receive the third CSI-RS and the fourth CSI-RS using the UCA circle 1006 and / or the UCA circle 1008.

[0181] 7, the receiving device 400 may calculate channel gains for one or more pairs of transmitter and receiver antennas based on the received CSI-RS. As described above with respect to block 718 of FIG. 7, the receiving device 400 may report information to the transmitting device 300 that may be used to generate a precoding vector that may be used to transmit information between the transmitting device 300 and the receiving device 400.

[0182] Further examples with various characteristics:

[0173] Implementation examples are described in the following numbered clauses.

[0174] 1. An apparatus configured for wireless communications, comprising: a processor; a plurality of antenna elements including a first subset of antenna elements including at least a first antenna element and a second antenna element; and a second subset of antenna elements including at least a third antenna element and a fourth antenna element; and a memory coupled to the processor, wherein the processor is configured to transmit a first reference signal using a first orbital angular momentum (OAM) mode via the first subset of antenna elements, transmit a second reference signal using the first OAM mode via the second subset of antenna elements, and receive information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the first OAM mode.

[0175] 2. The apparatus of clause 1, wherein the first reference signal includes a first channel state information reference signal (CSI-RS) and the second reference signal includes a second CSI-RS.

[0176] 3. The apparatus described in clause 1, wherein execution of the instructions further causes the processor to transmit reference signal configuration information indicating that a first subset of reference signals among the plurality of reference signals is associated with a first OAM mode.

[0177] 4. The apparatus described in clause 3, wherein the reference signal configuration information indicates that a second subset of reference signals among the plurality of reference signals is associated with a second OAM mode.

[0178] 5. An apparatus as described in clause 3 or 4, wherein the reference signal configuration information indicates that a first subset of antenna elements should be used to transmit a first reference signal, and that a second subset of antenna elements should be used to transmit a second reference signal.

[0179] 6. An apparatus described in any one of clauses 3 to 5, wherein the reference signal configuration information includes information indicating that a first subset of antenna elements corresponds to a first CSI-RS resource and information indicating that a second subset of antenna elements corresponds to a second CSI-RS resource.

[0180] 7. The apparatus described in clause 6, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first port of a first CSI-RS resource, and information indicating that a second reference signal should be transmitted using a first port of a second CSI-RS resource.

[0181] 8. The apparatus described in clause 7, wherein the reference signal configuration information includes information indicating that the third reference signal should be transmitted using a second port of the first CSI-RS resource, and information indicating that the fourth reference signal should be transmitted using a second port of the second CSI-RS resource.

[0182] 9. An apparatus described in any one of clauses 3 to 5, wherein the reference signal configuration information includes information indicating that a first subset of antenna elements corresponds to a first CSI-RS resource set and information indicating that a second subset of antenna elements corresponds to a second CSI-RS resource set.

[0183] 10. The apparatus of clause 9, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first resource of a first CSI-RS resource set, and information indicating that a second reference signal should be transmitted using a first resource of a second CSI-RS resource set.

[0184] 11. The apparatus of claim 10, wherein the reference signal configuration information includes information indicating that a third reference signal should be transmitted using a second resource of the first CSI-RS resource set, and information indicating that a fourth reference signal should be transmitted using a second resource of the second CSI-RS resource set.

[0185] 12. The apparatus of any one of clauses 3 to 11, wherein the reference signal configuration information includes an OAM mode index parameter associated with the first reference signal indicating which OAM mode should be used to transmit the first reference signal.

[0186] 13. The apparatus of any one of clauses 1 to 12, wherein execution of the instructions further causes the processor to transmit a third reference signal using a third resource and a second OAM mode via a first subset of antenna elements, transmit a fourth reference signal using a fourth resource and the second OAM mode via a second subset of antenna elements, and receive information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the second OAM mode.

[0187] 14. The apparatus of clause 1, further comprising: a first uniform circular array (UCA) comprising a first subset of antenna elements, the first UCA having a first radius; and a second UCA comprising a second subset of antenna elements, the second UCA having a second radius and being coaxial with the first UCA.

[0188] 15. An apparatus described in any one of clauses 1 to 14, wherein the information indicating a subset of antenna elements among a plurality of antenna elements to be used to transmit a first OAM mode includes information indicating a radius of a first uniform circular array (UCA) used by the receiving device to receive a first reference signal, and information indicating a radius of a second UCA used by the receiving device to receive a second reference signal.

[0189] 16. The apparatus of clause 15, wherein execution of the instructions further causes the processor to receive a message including a first value corresponding to a radius of a first UCA used by the receiving device and a second value corresponding to a radius of a second UCA used by the receiving device.

[0190] 17. The apparatus of clause 16, wherein the message is received prior to information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode.

[0191] 18. The apparatus of clause 16, wherein the message includes information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the first OAM mode.

[0192] 19. An apparatus as described in any one of clauses 15 to 18, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit the first OAM mode includes a string of bits associated with the first OAM mode, each bit in the string of bits indicating whether a particular UCA of the receiving device has received the first OAM mode.

[0193] 20. An apparatus as described in any one of clauses 15 to 19, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit the first OAM mode includes a bitmap associated with the first OAM mode, a first string of bits in the bitmap indicating whether a first subset of antenna elements should be used to transmit the first OAM mode, and a second string of bits in the bitmap indicating whether a second subset of antenna elements should be used to transmit the first OAM mode.

[0194] 21. An apparatus as described in any one of clauses 15 to 20, wherein execution of the instructions further causes the processor to receive from the receiving device at least one of a rank indicator associated with the first OAM mode or channel quality information associated with the first OAM mode.

[0195] 22. The apparatus of any one of clauses 1 to 21, wherein execution of the instructions further causes the processor to receive information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode via one or more of radio resource control (RRC) signaling, medium access control (MAC) control element (CE) signaling, or physical layer signaling using at least one of downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI).

[0196] 23. The apparatus of any one of clauses 1-22, further comprising: a first uniform circular array (UCA) comprising a first subset of antenna elements, the first UCA having a first radius; and a second UCA comprising a second subset of antenna elements, the second UCA having a second radius and being coaxial with the first UCA, wherein execution of the instructions further causes the processor to determine a first channel response for the first OAM mode based on the first radius, a third radius of a third UCA used by the receiving device to receive the first reference signal, a distance between the first UCA and the third UCA, and a wavelength of a waveform used to transmit the first reference signal, and to determine a second channel response for the first OAM mode based on the second radius, a third radius of the third UCA used by the receiving device to receive the first reference signal, a distance between the first UCA and the third UCA, and the wavelength of a waveform used to transmit the first reference signal.

[0197] 24. Execution of the instruction further causes the processor to

[0183]

number

[0184] determining a first channel response based on n is the Bessel function corresponding to OAM mode n, and r tx,1 is the first radius of the first UCA, and r rx,1 is the third radius of the third UCA, λ is the wavelength of the waveform used to transmit the first reference signal, and j is

[0185]

number

[0186] 24. The apparatus of claim 23, wherein z is a distance between the first UCA and the third UCA.

[0198] 25. The apparatus of clause 23 or 24, wherein execution of the instructions further causes the processor to generate a channel response matrix using at least the first channel response, the second channel response, and a rank indicator (RI) L associated with the first OAM mode.

[0199] 26. The apparatus of clause 25, wherein execution of the instructions further causes the processor to determine a precoding weight vector for the first OAM mode based on the L dominant singular vectors of the channel response matrix.

[0200] 27. The apparatus of clause 26, wherein execution of the instructions further causes the processor to determine a precoding weight vector for the first OAM mode based on a singular value decomposition of the channel response matrix.

[0201] 28. The apparatus of any one of clauses 1 to 27, wherein execution of the instructions further causes the processor to transmit information indicating a maximum number of OAM modes in which the apparatus is configured to transmit simultaneously using the first subset of antenna elements.

[0202] 29. An apparatus configured for wireless communication comprising: a processor; a plurality of antenna elements including a first subset of antenna elements including at least a first antenna element and a second antenna element; and a second subset of antenna elements including at least a third antenna element and a fourth antenna element; and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the processor to receive an indication from a transmitting device including the third subset of antenna elements and a fourth subset of antenna elements that the third subset of antenna elements should be used to transmit a first reference signal for a first orbital angular momentum (OAM) mode, receive an indication from the transmitting device that the fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode, and transmit information indicative of the subset of antenna elements of the plurality of antenna elements used to receive the first reference signal.

[0203] 30. The apparatus of clause 29, wherein the first reference signal includes a first channel state information reference signal (CSI-RS) and the second reference signal includes a second CSI-RS.

[0204] 31. The apparatus of clause 29 or 30, wherein execution of the instructions further causes the processor to receive a first reference signal via a first subset of the antenna elements and receive a second reference signal via a second subset of the plurality of antenna elements.

[0205] 32. The apparatus of any one of clauses 29 to 31, wherein execution of the instructions further causes the processor to receive reference signal configuration information from a transmitting device, the reference signal configuration information including an indication that a first subset of reference signals of the plurality of reference signals are associated with a first OAM mode, the first subset of reference signals including a first reference signal and a second reference signal.

[0206] 33. The apparatus of clause 32, wherein execution of the instructions further causes the processor to determine that the first subset of antenna elements and the second subset of antenna elements should be used to receive a first reference signal, and that the first subset of antenna elements and the second subset of antenna elements should be used to receive a second reference signal, based on the reference signal configuration information and a maximum number of OAM modes for which the apparatus is configured to simultaneously receive using the first subset of antenna elements.

[0207] 34. The apparatus of clause 32 or 33, wherein execution of the instructions further causes the processor to determine based on the reference signal configuration information that the first reference signal should be transmitted using a first uniform circular array (UCA) comprising a third subset of antenna elements, receive the first reference signal via the first subset of antenna elements, measure a channel based on the first reference signal, and determine a channel gain between the first UCA and the first subset of antenna elements.

[0208] 35. The apparatus of any one of clauses 32-34, wherein execution of the instructions further causes the processor to determine based on the reference signal configuration information that the first reference signal should be transmitted using a first UCA having a third subset of antenna elements, receive the first reference signal via a second subset of antenna elements, measure a channel based on the first reference signal, and determine a channel gain between the first UCA and the second subset of antenna elements based on the channel measurement value.

[0209] 36. The apparatus of any one of clauses 32-35, wherein execution of the instructions further causes the processor to receive information indicating a maximum number of OAM modes in which the transmitting device is configured to transmit simultaneously using the first uniform circular array (UCA).

[0210] 37. The apparatus of clause 36, wherein execution of the instructions further causes the processor to determine a first channel gain between the first UCA and a first subset of antenna elements, determine a second channel gain between the first UCA and a second subset of antenna elements, and select a UCA to be used for transmitting using the first OAM mode based on the first channel gain, the second channel gain, and a maximum number of OAM modes for which the transmitting device is configured to simultaneously transmit using the first UCA.

[0211] 38. The apparatus of clause 37, wherein execution of the instructions further causes the processor to transmit information indicative of the selected UCA to the transmitting device.

[0212] 39. The apparatus of any one of clauses 32-38, wherein the reference signal configuration information includes an indication that a second subset of reference signals of the plurality of reference signals is associated with a second OAM mode.

[0213] 40. The apparatus of any one of clauses 32 to 39, wherein the reference signal configuration information includes an indication that a third subset of antenna elements should be used to transmit a first reference signal for the first OAM mode, and an indication that a fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode.

[0214] 41. The apparatus of any one of clauses 32 to 40, wherein the reference signal configuration information includes information indicating that a third subset of antenna elements corresponds to a first CSI-RS resource and information indicating that a fourth subset of antenna elements corresponds to a second CSI-RS resource.

[0215] 42. The apparatus of clause 41, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first port of a first CSI-RS resource, and information indicating that a second reference signal should be transmitted using a first port of a second CSI-RS resource.

[0216] 43. The apparatus of clause 42, wherein the reference signal configuration information includes information indicating that a third reference signal is to be transmitted using a second port of the first CSI-RS resource, and information indicating that a fourth reference signal is to be transmitted using a second port of the second CSI-RS resource.

[0217] 44. The apparatus of any one of clauses 32 to 41, wherein the reference signal configuration information includes information indicating that a first subset of antenna elements corresponds to a first CSI-RS resource set and information indicating that a second subset of antenna elements corresponds to a second CSI-RS resource set.

[0218] 45. The apparatus of clause 44, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first resource of a first CSI-RS resource set, and information indicating that a second reference signal should be transmitted using a first resource of a second CSI-RS resource set.

[0219] 46. ​​The apparatus of clause 45, wherein the reference signal configuration information includes information indicating that a third reference signal is to be transmitted using a second resource of the first CSI-RS resource set, and information indicating that a fourth reference signal is to be transmitted using a second resource of the second CSI-RS resource set.

[0220] 47. The apparatus of any one of clauses 32 to 46, wherein the reference signal configuration information includes an OAM mode index parameter associated with the first reference signal indicating which OAM mode should be used to transmit the first reference signal.

[0221] 48. The apparatus of any one of clauses 29 to 47, wherein execution of the instructions further causes the processor to receive a third reference signal using the second OAM mode via a first subset of antenna elements, receive a fourth reference signal using the second OAM mode via a second subset of antenna elements, and transmit information indicating the subset of antenna elements of the plurality of antenna elements used to receive the third reference signal and the subset of antenna elements of the plurality of antenna elements used to receive the fourth reference signal.

[0222] 49. The apparatus of any one of clauses 29 to 48, further comprising: a first receiver uniform circular array (UCA) comprising a first subset of antenna elements, the first receiver UCA having a first radius; and a second receiver UCA comprising a second subset of antenna elements, the second receiver UCA having a second radius and being coaxial with the first UCA.

[0223] 50. The apparatus of any one of clauses 29 to 49, wherein execution of the instructions further causes the processor to transmit information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode.

[0224] 51. The apparatus of clause 50, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit a first OAM mode includes information indicating a radius of a first uniform circular array (UCA) used by the apparatus to receive a first reference signal, and information indicating a radius of a second UCA used by the apparatus to receive a second reference signal.

[0225] 52. The apparatus of clause 51, wherein execution of the instructions further causes the processor to transmit a message including a first value corresponding to a radius of the first UCA and a second value corresponding to a radius of the second UCA.

[0226] 53. The apparatus of clause 52, wherein the message is transmitted prior to information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

[0227] 54. The apparatus of clause 52, wherein the message includes information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the first OAM mode.

[0228] 55. An apparatus as described in any one of clauses 51 to 54, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit the first OAM mode includes a string of bits associated with the first OAM mode, each bit in the string of bits indicating whether a particular UCA of the apparatus has received the first OAM mode.

[0229] 56. An apparatus as described in any one of clauses 51 to 55, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit the first OAM mode includes a bitmap associated with the first OAM mode, a first string of bits in the bitmap indicating whether a first subset of antenna elements should be used to transmit the first OAM mode, and a second string of bits in the bitmap indicating whether a second subset of antenna elements should be used to transmit the first OAM mode.

[0230] 57. An apparatus as described in any one of clauses 51 to 56, wherein execution of the instructions further causes the processor to transmit at least one of a rank indicator associated with the first OAM mode or channel quality information associated with the first OAM mode to the transmitting device.

[0231] 58. The apparatus of any one of clauses 51 to 57, wherein execution of the instructions further causes the processor to transmit information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode via one or more of radio resource control (RRC) signaling, medium access control (MAC) control element (CE) signaling, or physical layer signaling using at least one of downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI).

[0232] 59. The apparatus of any one of clauses 29 to 58, wherein execution of the instructions further causes the processor to transmit information indicating a subset of antenna elements of the plurality of antenna elements used to receive the first reference signal via one or more of radio resource control (RRC) signaling, medium access control (MAC) control element (CE) signaling, or physical layer signaling using at least one of downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI).

[0233] 60. A method of wireless communication, comprising: transmitting a first reference signal using a first orbital angular momentum (OAM) mode via a first subset of antenna elements of a plurality of antenna elements; transmitting a second reference signal using the first OAM mode via a second subset of antenna elements of the plurality of antenna elements; and receiving information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the first OAM mode.

[0234] 61. The method of clause 60, wherein the first reference signal comprises a first channel state information reference signal (CSI-RS) and the second reference signal comprises a second CSI-RS.

[0235] 62. The method of clause 60, further comprising transmitting reference signal configuration information indicating that a first subset of reference signals of the plurality of reference signals is associated with the first OAM mode.

[0236] 63. The method of clause 62, wherein the reference signal configuration information indicates that a second subset of reference signals of the plurality of reference signals is associated with a second OAM mode.

[0237] 64. The method of clause 62 or 63, wherein the reference signal configuration information indicates that a first subset of antenna elements should be used to transmit a first reference signal, and that a second subset of antenna elements should be used to transmit a second reference signal.

[0238] 65. The method of any one of clauses 62 to 64, wherein the reference signal configuration information includes information indicating that a first subset of antenna elements corresponds to a first CSI-RS resource and information indicating that a second subset of antenna elements corresponds to a second CSI-RS resource.

[0239] 66. The method of clause 65, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first port of a first CSI-RS resource, and information indicating that a second reference signal should be transmitted using a first port of a second CSI-RS resource.

[0240] 67. The method of clause 66, wherein the reference signal configuration information includes information indicating that the third reference signal is to be transmitted using a second port of the first CSI-RS resource, and information indicating that the fourth reference signal is to be transmitted using a second port of the second CSI-RS resource.

[0241] 68. The method of any one of clauses 62 to 64, wherein the reference signal configuration information includes information indicating that a first subset of antenna elements corresponds to a first CSI-RS resource set and information indicating that a second subset of antenna elements corresponds to a second CSI-RS resource set.

[0242] 69. The method of clause 68, wherein the reference signal configuration information includes information indicating that a first reference signal is to be transmitted using a first resource of a first CSI-RS resource set, and information indicating that a second reference signal is to be transmitted using a first resource of a second CSI-RS resource set.

[0243] 70. The method of clause 69, wherein the reference signal configuration information includes information indicating that a third reference signal is to be transmitted using a second resource of the first CSI-RS resource set, and information indicating that a fourth reference signal is to be transmitted using a second resource of the second CSI-RS resource set.

[0244] 71. A method according to any one of clauses 62 to 70, wherein the reference signal configuration information includes an OAM mode index parameter associated with the first reference signal indicating which OAM mode should be used to transmit the first reference signal.

[0245] 72. The method of any one of clauses 60 to 71, further comprising transmitting a third reference signal using a third resource and a second OAM mode via a first subset of antenna elements, transmitting a fourth reference signal using a fourth resource and the second OAM mode via a second subset of antenna elements, and receiving information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the second OAM mode.

[0246] 73. The method of claim 60, wherein a first subset of the antenna elements are included in a first uniform circular array (UCA) having a first radius, and a second subset of the antenna elements are included in a second UCA having a second radius and coaxial with the first UCA.

[0247] 74. A method according to any one of clauses 60 to 73, wherein the information indicating a subset of antenna elements among a plurality of antenna elements to be used for transmitting the first OAM mode includes information indicating a radius of a first uniform circular array (UCA) used by the receiving device to receive a first reference signal, and information indicating a radius of a second UCA used by the receiving device to receive a second reference signal.

[0248] 75. The method of clause 74, further comprising receiving a message including a first value corresponding to a radius of a first UCA used by the receiving device and a second value corresponding to a radius of a second UCA used by the receiving device.

[0249] 76. The method of clause 75, wherein the message is received prior to information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

[0250] 77. The method of clause 75, wherein the message includes information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

[0251] 78. A method according to any one of clauses 15 to 18, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used for transmitting the first OAM mode comprises a string of bits associated with the first OAM mode, each bit in the string of bits indicating whether a particular UCA of the receiving device has received the first OAM mode.

[0252] 79. A method according to any one of clauses 74 to 78, wherein the information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode comprises a bitmap associated with the first OAM mode, a first string of bits in the bitmap indicating whether the first subset of antenna elements should be used to transmit the first OAM mode, and a second string of bits in the bitmap indicating whether a second subset of antenna elements should be used to transmit the first OAM mode.

[0253] 80. The method of any one of clauses 74 to 79, further comprising receiving from the receiving device at least one of a rank indicator associated with the first OAM mode or channel quality information associated with the first OAM mode.

[0254] 81. The method of any one of clauses 1 to 21, further comprising receiving information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode via one or more of radio resource control (RRC) signaling, medium access control (MAC) control element (CE) signaling, or physical layer signaling using at least one of downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI).

[0255] 82. The method of any one of clauses 60-81, wherein a first subset of the antenna elements are included in a first uniform circular array (UCA) having a first radius, and a second subset of the antenna elements are included in a second UCA having a second radius and coaxial with the first UCA, the method further comprising: determining a first channel response for the first OAM mode based on the first radius, a third radius of a third UCA used by the receiving device to receive the first reference signal, a distance between the first UCA and the third UCA, and a wavelength of a waveform used to transmit the first reference signal; and determining a second channel response for the first OAM mode based on the second radius, a third radius of the third UCA used by the receiving device to receive the first reference signal, a distance between the first UCA and the third UCA, and the wavelength of a waveform used to transmit the first reference signal.

[0256] 83. Relationships

[0187]

number

[0188] and determining a first channel response based onn is the Bessel function corresponding to the OAM mode n, and r tx,1 is the first radius of the first UCA, and r rx,1 is the third radius of the third UCA, λ is the wavelength of the waveform used to transmit the first reference signal, and j is

[0189]

number

[0190] and z is a distance between the first UCA and the third UCA.

[0257] 84. The method of any one of clauses 82-83, further comprising generating a channel response matrix using at least the first channel response, the second channel response, and a rank indicator (RI) L associated with the first OAM mode.

[0258] 85. The method of clause 84, further comprising determining a precoding weight vector for the first OAM mode based on the L dominant singular vectors of the channel response matrix.

[0259] 86. The method of clause 85, further comprising determining a precoding weight vector for the first OAM mode based on a singular value decomposition of a channel response matrix.

[0260] 87. The method of any one of clauses 60-86, further comprising transmitting information indicating a maximum number of OAM modes in which the device is configured to transmit simultaneously using the first subset of antenna elements.

[0261] 88. A method of wireless communication, comprising: receiving, at a receiving device including a plurality of antenna elements including a first subset of antenna elements and a second subset of antenna elements, an indication from a transmitting device including a third subset of antenna elements and a fourth subset of antenna elements that a third subset of antenna elements should be used to transmit a first reference signal for a first orbital angular momentum (OAM) mode; receiving an indication from the transmitting device that the fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode; and transmitting information indicating the subset of antenna elements of the plurality of antenna elements used to receive the first reference signal.

[0262] 89. The method of clause 88, wherein the first reference signal comprises a first channel state information reference signal (CSI-RS) and the second reference signal comprises a second CSI-RS.

[0263] 90. The method of clause 88 or 89, further comprising receiving a first reference signal via a first subset of antenna elements of the plurality of antenna elements, and receiving a second reference signal via a second subset of the plurality of antenna elements.

[0264] 91. A method according to any one of clauses 88 to 90, further comprising receiving reference signal configuration information from a transmitting device, the reference signal configuration information including an indication that a first subset of reference signals of the plurality of reference signals are associated with a first OAM mode, the first subset of reference signals including a first reference signal and a second reference signal.

[0265] 92. The method of clause 91, further comprising determining, based on the reference signal configuration information and a maximum number of OAM modes that the method is configured to simultaneously receive using the first subset of antenna elements, that the first subset of antenna elements and the second subset of antenna elements should be used to receive a first reference signal, and that the first subset of antenna elements and the second subset of antenna elements should be used to receive a second reference signal.

[0266] 93. The method of clause 91 or 92, further comprising: determining based on reference signal configuration information that a first reference signal should be transmitted using a first uniform circular array (UCA) comprising a third subset of antenna elements; receiving the first reference signal via the first subset of antenna elements; measuring a channel based on the first reference signal; and determining a channel gain between the first UCA and the first subset of antenna elements.

[0267] 94. The method of any one of clauses 91 to 93, further comprising: determining based on reference signal configuration information that a first reference signal should be transmitted using a first UCA having a third subset of antenna elements; receiving the first reference signal via a second subset of antenna elements; measuring a channel based on the first reference signal; and determining a channel gain between the first UCA and the second subset of antenna elements based on the channel measurement value.

[0268] 95. The method of any one of clauses 91 to 94, wherein the transmission method further comprises receiving information indicating a maximum number of OAM modes that are configured to transmit simultaneously using the first uniform circular array (UCA).

[0269] 96. The method of clause 95, further comprising: determining a first channel gain between the first UCA and a first subset of antenna elements; determining a second channel gain between the first UCA and a second subset of antenna elements; and selecting a UCA to be used for transmitting using the first OAM mode based on the first channel gain, the second channel gain, and a maximum number of OAM modes for which the transmitting device is configured to simultaneously transmit using the first UCA.

[0270] 97. The method of clause 96, further comprising transmitting information to the transmitting device indicating the selected UCA.

[0271] 98. The method of any one of clauses 91-97, wherein the reference signal configuration information includes an indication that a second subset of reference signals of the plurality of reference signals is associated with a second OAM mode.

[0272] 99. A method according to any one of clauses 91 to 98, wherein the reference signal configuration information includes an indication that a third subset of antenna elements should be used to transmit a first reference signal for the first OAM mode, and an indication that a fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode.

[0273] 100. The method of any one of clauses 91-99, wherein the reference signal configuration information includes information indicating that a third subset of antenna elements corresponds to a first CSI-RS resource and information indicating that a fourth subset of antenna elements corresponds to a second CSI-RS resource.

[0274] 101. The method of clause 100, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first port of a first CSI-RS resource, and information indicating that a second reference signal should be transmitted using a first port of a second CSI-RS resource.

[0275] 102. The method of clause 101, wherein the reference signal configuration information includes information indicating that the third reference signal is to be transmitted using a second port of the first CSI-RS resource, and information indicating that the fourth reference signal is to be transmitted using a second port of the second CSI-RS resource.

[0276] 103. The method of any one of clauses 91 to 100, wherein the reference signal configuration information includes information indicating that a first subset of antenna elements corresponds to a first CSI-RS resource set and information indicating that a second subset of antenna elements corresponds to a second CSI-RS resource set.

[0277] 104. The method of clause 103, wherein the reference signal configuration information includes information indicating that a first reference signal should be transmitted using a first resource of a first CSI-RS resource set, and information indicating that a second reference signal should be transmitted using a first resource of a second CSI-RS resource set.

[0278] 105. The method of clause 104, wherein the reference signal configuration information includes information indicating that a third reference signal is to be transmitted using a second resource of the first CSI-RS resource set, and information indicating that a fourth reference signal is to be transmitted using a second resource of the second CSI-RS resource set.

[0279] 106. The method of any one of clauses 91 to 105, wherein the reference signal configuration information includes an OAM mode index parameter associated with the first reference signal indicating which OAM mode should be used to transmit the first reference signal.

[0280] 107. The method of any one of clauses 88-106, further comprising: receiving a third reference signal using a second OAM mode via a first subset of antenna elements; receiving a fourth reference signal using a second OAM mode via a second subset of antenna elements; and transmitting information indicating the subset of antenna elements of the plurality of antenna elements used to receive the third reference signal and the subset of antenna elements of the plurality of antenna elements used to receive the fourth reference signal.

[0281] 108. A method according to any one of clauses 88 to 107, wherein a first subset of the antenna elements is included in a first receiver uniform circular array (UCA) having a first radius, and a second subset of the antenna elements is included in a second receiver UCA having a second radius and coaxial with the first UCA.

[0282] 109. The method of any one of clauses 88-108, further comprising transmitting information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

[0283] 110. The method of clause 109, wherein the information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode includes information indicating a radius of a first uniform circular array (UCA) used by the method to receive a first reference signal, and information indicating a radius of a second UCA used by the method to receive a second reference signal.

[0284] 111. The method of clause 110, further comprising: sending a message including a first value corresponding to a radius of the first UCA and a second value corresponding to a radius of the second UCA.

[0285] 112. The method of clause 111, wherein the message is transmitted prior to information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

[0286] 113. The method of clause 111, wherein the message includes information indicating a subset of antenna elements of the plurality of antenna elements to use for transmitting the first OAM mode.

[0287] 114. A method according to any one of clauses 110 to 113, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used for transmitting the first OAM mode comprises a string of bits associated with the first OAM mode, each bit in the string of bits indicating whether a particular UCA of the method has received the first OAM mode.

[0288] 115. The method of any one of clauses 110 to 114, wherein the information indicating a subset of antenna elements of a plurality of antenna elements to be used to transmit the first OAM mode includes a bitmap associated with the first OAM mode, a first string of bits in the bitmap indicating whether a first subset of antenna elements should be used to transmit the first OAM mode, and a second string of bits in the bitmap indicating whether a second subset of antenna elements should be used to transmit the first OAM mode.

[0289] 116. The method of any one of clauses 110 to 115, further comprising transmitting at least one of a rank indicator associated with the first OAM mode or channel quality information associated with the first OAM mode to the transmission method.

[0290] 117. The method of any one of clauses 110 to 116, further comprising transmitting information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode via one or more of radio resource control (RRC) signaling, medium access control (MAC) control element (CE) signaling, or physical layer signaling using at least one of downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI).

[0291] 118. The method of any one of clauses 88 to 117, further comprising transmitting information indicating a subset of antenna elements of the plurality of antenna elements used to receive the first reference signal via one or more of radio resource control (RRC) signaling, medium access control (MAC) control element (CE) signaling, or physical layer signaling using at least one of downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI).

[0292] 119. An apparatus for wireless communication comprising a processor and a memory communicatively coupled to at least one processor, the processor being configured to perform a method according to any one of clauses 60 to 118.

[0293] 120. A non-transitory computer readable medium storing computer executable code, the computer executable code comprising code for causing a processor to perform any of the methods of clauses 60-118.

[0294] 121. An apparatus for wireless communication, comprising at least one means for performing a method according to any one of clauses 60 to 118.

[0191]

[0295] One or more of the components, steps, features, and / or functions shown in Figures 1-10 may be rearranged and / or combined into a single component, step, feature, or function, or embodied in several components, steps, or functions. Also, additional elements, components, steps, and / or functions may be added without departing from the novel features disclosed herein. The apparatus, devices, and / or components shown in Figures 1-10 may be configured to perform one or more of the methods, features, or steps described herein. Also, the novel algorithms described herein may be efficiently implemented in software and / or incorporated into hardware.

[0192]

[0296] It is understood that the specific order or hierarchy of steps in the disclosed methods are examples of example processes. Based on design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not intended to be limited to the specific order or hierarchy presented, unless specifically recited herein.

[0193]

[0297] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Thus, the claims are not limited to the aspects set forth herein, but are to be accorded all scope consistent with the language of the claims, and references to elements in the singular do not mean "one and only," unless expressly stated as such, but rather "one or more." Unless otherwise stated, the term "some" refers to one or more. A phrase referring to "at least one of" a list of items refers to any combination of those items, including a single element. As an example, "at least one of a, b, or c" is intended to cover a, b, c, a and b, a and c, b and c, and a, b, and c. All structural and functional equivalents of the elements of the various aspects described throughout this disclosure that are known or later become known to those skilled in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be made available to the public, regardless of whether such disclosure is expressly recited in the claims.

Claims

1. 1. An apparatus configured for wireless communication, comprising: A processor; a plurality of antenna elements including a first subset of antenna elements including at least a first antenna element and a second antenna element, and a second subset of antenna elements including at least a third antenna element and a fourth antenna element; a memory coupled to the processor; the memory storing instructions that, when executed by the processor, cause the processor to: transmitting a first reference signal using a first orbital angular momentum (OAM) mode via the first subset of antenna elements; transmitting a second reference signal using the first OAM mode via the second subset of antenna elements; receiving information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode; Device.

2. 2. The apparatus of claim 1, wherein the first reference signal comprises a first channel state information reference signal (CSI-RS) and the second reference signal comprises a second CSI-RS.

3. Execution of the instructions further causes the processor to: transmitting reference signal configuration information indicating that a first subset of reference signals of a plurality of reference signals is associated with the first OAM mode; 2. The apparatus of claim 1.

4. 4. The apparatus of claim 3, wherein the reference signal configuration information indicates that a second subset of reference signals of the plurality of reference signals is associated with a second OAM mode.

5. 4. The apparatus of claim 3, wherein the reference signal configuration information includes: information indicating that the first subset of antenna elements corresponds to a first CSI-RS resource; and information indicating that the second subset of antenna elements corresponds to a second CSI-RS resource.

6. Execution of the instructions further causes the processor to: a rank indicator associated with the first OAM mode; or Channel quality information associated with the first OAM mode. from a receiving device; 2. The apparatus of claim 1.

7. a first uniform circular array (UCA) comprising the first subset of antenna elements, the first UCA having a first radius; a second UCA comprising the second subset of antenna elements, the second UCA having a second radius and being coaxial with the first UCA; Further comprising: Execution of the instructions further causes the processor to: determining a first channel response for the first OAM mode based on the first radius, a third radius of a third UCA used by a receiving device to receive the first reference signal, a distance between the first UCA and the third UCA, and a wavelength of a waveform used to transmit a first reference signal; determining a second channel response for the first OAM mode based on the second radius, the third radius of the third UCA used by the receiving device to receive the first reference signal, the distance between the first UCA and the third UCA, and the wavelength of the waveform used to transmit a first reference signal.

2. The apparatus of claim 1.

8. 1. An apparatus configured for wireless communication, comprising: A processor; a plurality of antenna elements including a first subset of antenna elements including at least a first antenna element and a second antenna element, and a second subset of antenna elements including at least a third antenna element and a fourth antenna element; a memory coupled to the processor; the memory storing instructions that, when executed by the processor, cause the processor to: receiving an indication from a transmitting device including a third subset of antenna elements and a fourth subset of antenna elements that the third subset of antenna elements should be used to transmit a first reference signal for a first orbital angular momentum (OAM) mode; receiving an indication from the transmitting device that the fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode; transmitting information indicative of a subset of antenna elements of the plurality of antenna elements used to receive the first reference signal. Device.

9. Execution of the instructions further causes the processor to: receiving the first reference signal via the first subset of antenna elements of the plurality of antenna elements; receiving the second reference signal via the second subset of the plurality of antenna elements; 9. The apparatus of claim 8.

10. Execution of the instructions further causes the processor to: receiving reference signal configuration information from the transmitting device, the reference signal configuration information including an indication that a first subset of reference signals of a plurality of reference signals is associated with the first OAM mode, the first subset of reference signals including the first reference signal and the second reference signal; 9. The apparatus of claim 8.

11. Execution of the instructions further causes the processor to: determining, based on the reference signal configuration information, that the first reference signal should be transmitted using a first uniform circular array (UCA) comprising the third subset of antenna elements; receiving the first reference signal via the first subset of antenna elements; measuring a channel based on the first reference signal; determining a channel gain between the first UCA and the first subset of antenna elements; 11. The apparatus of claim 10.

12. Execution of the instructions further causes the processor to:

11. The apparatus of claim 10, further comprising: receiving information indicating a maximum number of OAM modes the transmitting device is configured to simultaneously transmit using a first uniform circular array (UCA).

13. Execution of the instructions further causes the processor to: determining a first channel gain between the first UCA and the first subset of antenna elements; determining a second channel gain between the first UCA and the second subset of antenna elements; 13. The apparatus of claim 12, further comprising: a UCA to be used for transmitting using the first OAM mode selected based on the first channel gain, the second channel gain, and the maximum number of OAM modes for which the transmitting device is configured to transmit simultaneously using the first UCA.

14. Execution of the instructions further causes the processor to:

10. The apparatus of claim 8, further comprising: transmitting information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

15. the information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode, information indicative of a radius of a first uniform circular array (UCA) used by the device to receive the first reference signal; information indicating a radius of a second UCA used by the device to receive the second reference signal; The apparatus of claim 14 , comprising:

16. 1. A method of wireless communication, comprising: transmitting a first reference signal using a first orbital angular momentum (OAM) mode via a first subset of antenna elements of the plurality of antenna elements; transmitting a second reference signal using the first OAM mode via a second subset of antenna elements of the plurality of antenna elements; receiving information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode; A method comprising:

17. 17. The method of claim 16, wherein the first reference signal comprises a first channel state information reference signal (CSI-RS) and the second reference signal comprises a second CSI-RS.

18. transmitting reference signal configuration information indicating that a first subset of reference signals of a plurality of reference signals is associated with the first OAM mode. The method of claim 16 further comprising:

19. 20. The method of claim 18, wherein the reference signal configuration information indicates that a second subset of reference signals of the plurality of reference signals is associated with a second OAM mode.

20. 20. The method of claim 18, wherein the reference signal configuration information includes: information indicating that the first subset of antenna elements corresponds to a first CSI-RS resource; and information indicating that the second subset of antenna elements corresponds to a second CSI-RS resource.

21. a rank indicator associated with the first OAM mode; or Channel quality information associated with the first OAM mode. receiving from the receiving device at least one of The method of claim 16 further comprising:

22. the first subset of antenna elements are comprised in a first uniform circular array (UCA) having a first radius; the second subset of antenna elements is contained within a second UCA having a second radius and coaxial with the first UCA; The method further comprising: determining a first channel response for the first OAM mode based on the first radius, a third radius of a third UCA used by a receiving device to receive the first reference signal, a distance between the first UCA and the third UCA, and a wavelength of a waveform used to transmit a first reference signal; determining a second channel response for the first OAM mode based on the second radius, the third radius of the third UCA used by the receiving device to receive the first reference signal, the distance between the first UCA and the third UCA, and the wavelength of the waveform used to transmit a first reference signal; The method of claim 16 further comprising:

23. 1. A method of wireless communication, comprising: receiving, at a receiving device including a plurality of antenna elements including a first subset of antenna elements and a second subset of antenna elements, from a transmitting device including a third subset of antenna elements and a fourth subset of antenna elements, an indication that the third subset of antenna elements should be used to transmit a first reference signal for a first orbital angular momentum (OAM) mode; receiving an indication from the transmitting device that the fourth subset of antenna elements should be used to transmit a second reference signal for the first OAM mode; transmitting information indicative of a subset of antenna elements of the plurality of antenna elements used to receive the first reference signal; A method comprising:

24. receiving the first reference signal via the first subset of antenna elements of the plurality of antenna elements; receiving the second reference signal via the second subset of the plurality of antenna elements; 24. The method of claim 23, further comprising:

25. receiving reference signal configuration information from the transmitting device; 24. The method of claim 23, further comprising: wherein the reference signal configuration information includes an indication that a first subset of reference signals of a plurality of reference signals is associated with the first OAM mode, the first subset of reference signals including the first reference signal and the second reference signal.

26. determining, based on the reference signal configuration information, that the first reference signal should be transmitted using a first uniform circular array (UCA) comprising the third subset of antenna elements; receiving the first reference signal via the first subset of antenna elements; measuring a channel based on the first reference signal; determining a channel gain between the first UCA and the first subset of antenna elements; 26. The method of claim 25, further comprising:

27. receiving information indicating a maximum number of OAM modes that the transmitting device is configured to simultaneously transmit using a first uniform circular array (UCA); 26. The method of claim 25, further comprising:

28. determining a first channel gain between the first UCA and the first subset of antenna elements; determining a second channel gain between the first UCA and the second subset of antenna elements; selecting a UCA to be used for transmitting using the first OAM mode based on the first channel gain, the second channel gain, and the maximum number of OAM modes for which the transmitting device is configured to simultaneously transmit using the first UCA; 30. The method of claim 27, further comprising:

29. transmitting information indicating a subset of antenna elements of the plurality of antenna elements to be used for transmitting the first OAM mode.

24. The method of claim 23, further comprising:

30. the information indicating a subset of antenna elements of the plurality of antenna elements to be used to transmit the first OAM mode, information indicative of a radius of a first uniform circular array (UCA) used by the method to receive the first reference signal; information indicative of a radius of a second UCA used by the method to receive the second reference signal; 30. The method of claim 29, comprising:

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