Patent Publication Number: US-2022217724-A1

Title: Power level determination for transmission of reference signals

Description:
FIELD OF THE DISCLOSURE 
     Aspects of the disclosure relate generally to wireless communications. In some implementations, examples are described for determining power level of resource elements utilized for transmission of reference signals between a base station and a user equipment. 
     BACKGROUND OF THE DISCLOSURE 
     Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (1G), a second-generation (2G) digital wireless phone service (including interim 2.5G networks), a third-generation (3G) high speed data, Internet-capable wireless service, a fourth-generation (4G) service (e.g., Long-Term Evolution (LTE), WiMax), and most recently a fifth-generation (5G) service. There are presently many different types of wireless communication systems in use, including cellular and personal communications service (PCS) systems. Examples of known cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), the Global System for Mobile communication (GSM), etc. 
     The fifth-generation (5G) mobile standard calls for higher data transfer speeds, greater numbers of connections, and better coverage, among other improvements. The 5G standard (also referred to as “New Radio” or “NR”), according to the Next Generation Mobile Networks Alliance, is designed to provide data rates of several tens of megabits per second to each of tens of thousands of users with, for example, a gigabit connection speeds to tens of users in a common location, such as on an office floor. Several hundreds of thousands of simultaneous connections are to be supported in order to support large sensor deployments. Consequently, there is a need for significantly enhancing the spectral efficiency of 5G mobile communications compared to the current 4G/LTE standard. Furthermore, there is also a corresponding need for enhancing signaling efficiencies and substantially reducing latency compared to current standards. 
     SUMMARY 
     The following presents a simplified summary relating to one or more aspects disclosed herein. Thus, the following summary should not be considered an extensive overview relating to all contemplated aspects, nor should the following summary be considered to identify key or critical elements relating to all contemplated aspects or to delineate the scope associated with any particular aspect. Accordingly, the following summary has the sole purpose to present certain concepts relating to one or more aspects relating to the mechanisms disclosed herein in a simplified form to precede the detailed description presented below. 
     Disclosed are systems, apparatuses, methods, and computer-readable media for determination of resource elements that form one or more tone pattern, and associated power levels for the resource elements utilized over a physical layer to transmit reference signals between a user equipment and a base station. 
     According to at least one example, a method of wireless communication includes: determining, by a receiving device, a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; determining, by the receiving device, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmitting, by the receiving device, one or more of the tone pattern or the plurality of power levels to the transmitting device. 
     In another example, an apparatus includes one or more memories having computer-readable instructions stored therein, and one or more processors. The one or more processors are configured to execute the computer-readable instructions to: determine a tone pattern for a reference signal for use in wireless communications between the apparatus and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; determine a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmit one or more of the tone pattern or the plurality of power levels to the transmitting device. 
     In another example, a non-transitory computer-readable medium is provided that includes stored thereon at least one instruction that, when executed by one or more processors, cause the one or more processors to: determine a tone pattern for a reference signal for use in wireless communications between the apparatus and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; determine a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmit one or more of the tone pattern or the plurality of power levels to the transmitting device. 
     In another example, an apparatus is provided. The apparatus includes: means for determining a tone pattern for a reference signal for use in wireless communications between the apparatus and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; means for determining a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and means for transmitting one or more of the tone pattern or the plurality of power levels to the transmitting device. 
     According to at least one example, a method of wireless communication includes: receiving, by a transmitting device, a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; receiving, by the transmitting device, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmitting, by the transmitting device and to a receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     In another example, an apparatus includes one or more memories having computer-readable instructions stored therein, and one or more processors. The one or more processors are configured to execute the computer-readable instructions to: receive a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; receive, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmit, to a receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels 
     In another example, a non-transitory computer-readable medium is provided that includes stored thereon at least one instruction that, when executed by one or more processors, cause the one or more processors to: receive a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; receive, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmit, to a receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     In another example, an apparatus is provided. The apparatus includes: means for: receiving a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; means for receiving a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and means for transmitting, to a receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     In some aspects, the apparatus is a receiving device such as a user device (e.g., user equipment (UE)) or a base station. In some aspects, the transmitting device is one of a user device (e.g., user equipment (UE)) or a base station. In some aspects, the receiving device and the transmitting device described above can be the same apparatus such as a user device or a base station. 
     This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings, and each claim. 
     Other objects and advantages associated with the aspects disclosed herein will be apparent to those skilled in the art based on the accompanying drawings and detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are presented to aid in the description of various aspects of the disclosure and are provided solely for illustration of the aspects and not limitation thereof. 
         FIG. 1  is a diagram illustrating an example wireless communications system, in accordance with some aspects of the present disclosure. 
         FIGS. 2A and 2B  are diagrams illustrating example wireless network structures, in accordance with some aspects of the present disclosure. 
         FIG. 3  is a diagram illustrating a design of a base station and a User Equipment (UE) device that enable transmission and processing of signals exchanged between the UE and the base station, in accordance with some aspects of the present disclosure. 
         FIG. 4  is a conceptual diagram illustrating an example of a frame structure, in accordance with some aspects of the present disclosure. 
         FIG. 5  is a conceptual diagram illustrating an example of a machine learning model that can be configured to facilitate tone placement optimization, in accordance with some aspects of the present disclosure. 
         FIG. 6  is a flow chart illustrating an example of a process of training a machine learning algorithm for tone pattern and power level determination, in accordance with some aspects of the present disclosure. 
         FIG. 7  is a flow chart illustrating an example of a process of communicating a customized tone pattern and associated power levels, in accordance with some aspects of the present disclosure. 
         FIGS. 8A-B  are conceptual diagrams illustrating non-limiting examples of customized irregular tone pattern arrangement, in accordance with some aspects of the present disclosure. 
         FIG. 9  is a flow chart illustrating an example of a process of communicating a customized tone pattern and associated power levels, in accordance with some aspects of the present disclosure. 
         FIG. 10  is a flow chart illustrating an example of a process of communicating a customized tone pattern and associated power levels, in accordance with some aspects of the present disclosure. 
         FIG. 11  is a flow chart illustrating an example of a process of communicating a reference signal using a tone pattern and associated power levels, in accordance with some aspects of the present disclosure. 
         FIG. 12  is a diagram illustrating example computing system of a user equipment (UE) device, according to some aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain aspects and embodiments of this disclosure are provided below for illustration purposes. Alternate aspects may be devised without departing from the scope of the disclosure. Additionally, well-known elements of the disclosure will not be described in detail or will be omitted so as not to obscure the relevant details of the disclosure. Some of the aspects and embodiments described herein may be applied independently and some of them may be applied in combination as would be apparent to those of skill in the art. In the following description, for the purposes of explanation, specific details are set forth in order to provide a thorough understanding of embodiments of the application. However, it will be apparent that various embodiments may be practiced without these specific details. The figures and description are not intended to be restrictive. 
     Systems, apparatuses, processes (also referred to as methods), and computer-readable media (collectively referred to herein as systems and techniques) are described herein for determining optimized tone patterns and/or power levels for resource elements utilized over a physical layer to transmit reference signals between a base station (e.g., an a 4G/LTE eNodeB, a 5G/new radio (NR) gNodeB, and/or other base station) and a user equipment (UE) device (referred to herein as a UE). 
     As noted above, the 5G mobile standard calls for higher data transfer speeds, greater numbers of connections, and better coverage, among other improvements. 5G is expected to support several hundreds of thousands of simultaneous connections. Consequently, there is room to improve the spectral efficiency of 5G mobile communications by enhancing signaling efficiencies and reducing latency. One aspect where such signaling efficiency and reduction in latency can be achieved is the communication of various uplink and downlink reference signals between user equipment and their respective serving base stations. 
     Reference signals are predefined signals occupying specific resource elements within a time-frequency grid of a resource block and may be exchanged on one or both of downlink and uplink physical communication channels. Each reference signal has been defined by the 3 rd  Generation Partnership Project (3GPP) for a specific purpose such as channel estimation, phase-noise compensation, acquiring downlink and/or uplink channel state information, time and frequency tracking, etc. 
     Example reference signals include, but are not limited to, Channel State Information-Reference Signal (CSI-RS), De-Modulation Reference Signal (DMRS), Sounding Reference Signal (SRS), among others. Some reference signals such as CSI-RS are downlink specific signals, while others such as DMRS are sent both on downlink and uplink communication channels. There are also uplink specific reference signals defined by the 3GPP. 
     Tone patterns can be defined as specific arrangements of resource elements in a given resource block for transmission of a reference signal. Tone patterns are currently pre-defined in the 5G communication standard and are known to both the user equipment and corresponding base station. In addition, estimated power used for transmission of a given resource element is known to the user equipment and base station. Accordingly, both the user equipment and base station have the necessary information in order to code and/or decode reference signals and perform corresponding measurements. 
     Pre-defined tone patterns may not be optimized for all environments. For instance, the arrangement or combination of resource elements used for transmission of a particular reference signal may not be optimized across all possible conditions under which a user equipment and base station may communicate. Furthermore, the power level of each resource element used for transmission of reference signals may not be optimized. Currently, resource element power levels are either fixed across all resource elements or are determined as a linear average of power of all resource elements in a given resource block. 
     The systems and techniques described herein include dynamically determining (or configuring) optimized tone patterns and/or dynamically determining and/or adjusting power levels (e.g., an energy per resource element (EPRE) or other power level) for resource elements of resource blocks used at the physical layer for transmission of various uplink and downlink reference signals between one or more UEs and their respective serving base stations. Determining the optimized tone patterns improves signal and spectral efficiency, can reduce overhead associated with transmission of reference signals, etc. (e.g., in 5G mobile systems). 
     In some examples, as described in more detail below, dynamic determination of tone patterns and/or power levels can be achieved through the use of machine learning models. For instance, a given condition under which a reference signal is to be communicated from a UE to a base station (and/or from a base station to a user equipment) can be provided as input to a trained machine learning model. Over time, the machine learning model can be trained to associate various conditions with different Resource Elements (REs) best suited for reference signal tone placement under different conditions in order to achieve an optimized output (e.g., spectral efficiency). Once trained, when such conditions can be provided as input, the machine learning model can process the input and can provide an optimized tone pattern and/or associated per resource element power levels for transmission of the underlying reference signal. 
     Additional aspects of the present disclosure are described in more detail below. 
     According to various aspects,  FIG. 1  illustrates an example wireless communications system  100 . The wireless communications system  100  (which may also be referred to as a wireless wide area network (WWAN)) can include various base stations  102  and various UEs  104 . 
     As used herein, the terms “user equipment” (UE) and “base station” are not intended to be specific or otherwise limited to any particular radio access technology (RAT), unless otherwise noted. In general, a UE may be any wireless communication device (e.g., a mobile phone, router, tablet computer, laptop computer, and/or tracking device, etc.), wearable (e.g., smartwatch, smart-glasses, wearable ring, and/or an extended reality (XR) device such as a virtual reality (VR) headset, an augmented reality (AR) headset or glasses, or a mixed reality (MR) headset), vehicle (e.g., automobile, motorcycle, bicycle, etc.), and/or Internet of Things (IoT) device, etc., used by a user to communicate over a wireless communications network. A UE may be mobile or may (e.g., at certain times) be stationary, and may communicate with a radio access network (RAN). As used herein, the term “UE” may be referred to interchangeably as an “access terminal” or “AT,” a “client device,” a “wireless device,” a “subscriber device,” a “subscriber terminal,” a “subscriber station,” a “user terminal” or “UT,” a “mobile device,” a “mobile terminal,” a “mobile station,” or variations thereof. Generally, UEs can communicate with a core network via a RAN, and through the core network the UEs can be connected with external networks such as the Internet and with other UEs. Of course, other mechanisms of connecting to the core network and/or the Internet are also possible for the UEs, such as over wired access networks, wireless local area network (WLAN) networks (e.g., based on IEEE 802.11 communication standards, etc.) and so on. 
     A base station may operate according to one of several RATs in communication with UEs depending on the network in which it is deployed, and may be alternatively referred to as an access point (AP), a network node, a NodeB (NB), an evolved NodeB (eNB), a next generation eNB (ng-eNB), a New Radio (NR) Node B (also referred to as a gNB or gNodeB), etc. A base station may be used primarily to support wireless access by UEs, including supporting data, voice, and/or signaling connections for the supported UEs. In some systems a base station may provide edge node signaling functions while in other systems it may provide additional control and/or network management functions. A communication link through which UEs can send signals to a base station is called an uplink (UL) channel (e.g., a reverse traffic channel, a reverse control channel, an access channel, etc.). A communication link through which the base station can send signals to UEs is called a downlink (DL) or forward link channel (e.g., a paging channel, a control channel, a broadcast channel, or a forward traffic channel, etc.). As used herein the term traffic channel (TCH) can refer to either an uplink, reverse or downlink, and/or a forward traffic channel. 
     The term “base station” may refer to a single physical transmission-reception point (TRP) or to multiple physical TRPs that may or may not be co-located. For example, where the term “base station” refers to a single physical TRP, the physical TRP may be an antenna of the base station corresponding to a cell (or several cell sectors) of the base station. Where the term “base station” refers to multiple co-located physical TRPs, the physical TRPs may be an array of antennas (e.g., as in a multiple-input multiple-output (MIMO) system or where the base station employs beamforming) of the base station. Where the term “base station” refers to multiple non-co-located physical TRPs, the physical TRPs may be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transport medium) or a remote radio head (RRH) (a remote base station connected to a serving base station). Alternatively, the non-co-located physical TRPs may be the serving base station receiving the measurement report from the UE and a neighbor base station whose reference RF signals (or simply “reference signals”) the UE is measuring. Because a TRP is the point from which a base station transmits and receives wireless signals, as used herein, references to transmission from or reception at a base station are to be understood as referring to a particular TRP of the base station. 
     A radio frequency signal or “RF signal” comprises an electromagnetic wave of a given frequency that transports information through the space between a transmitter and a receiver. As used herein, a transmitter may transmit a single “RF signal” or multiple “RF signals” to a receiver. However, the receiver may receive multiple “RF signals” corresponding to each transmitted RF signal due to the propagation characteristics of RF signals through multipath channels. The same transmitted RF signal on different paths between the transmitter and receiver may be referred to as a “multipath” RF signal. As used herein, an RF signal may also be referred to as a “wireless signal” or simply a “signal” where it is clear from the context that the term “signal” refers to a wireless signal or an RF signal. 
     Referring back to  FIG. 1 , the base stations  102  can include macro cell base stations (high power cellular base stations) and/or small cell base stations (low power cellular base stations). In an aspect, the macro cell base station may include eNBs and/or ng-eNBs where the wireless communications system  100  corresponds to an LTE network, or gNBs where the wireless communications system  100  corresponds to a NR network, or a combination of both, and the small cell base stations may include femtocells, picocells, microcells, etc. 
     In some implementations that support positioning of UEs, a base station may not support wireless access by UEs (e.g., may not support data, voice, and/or signaling connections for UEs), but may instead transmit reference signals to UEs to be measured by the UEs, and/or may receive and measure signals transmitted by the UEs. Such a base station may be referred to as a positioning beacon (e.g., when transmitting signals to UEs) and/or as a location measurement unit (e.g., when receiving and measuring signals from UEs). 
     The base stations  102  may collectively form a RAN and interface with a core network  170  (e.g., an evolved packet core (EPC) or a 5G core (5GC)) through backhaul links  122 , and through the core network  170  to one or more location servers  172  (which may be part of core network  170  or may be external to core network  170 ). In addition to other functions, the base stations  102  may perform functions that relate to one or more of transferring user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations  102  may communicate with each other directly or indirectly (e.g., through the EPC or 5GC) over backhaul links  134 , which may be wired and/or wireless. 
     The base stations  102  may wirelessly communicate with the UEs  104 . Each of the base stations  102  may provide communication coverage for a respective geographic coverage area  110 . In an aspect, one or more cells may be supported by a base station  102  in each coverage area  110 . A “cell” is a logical communication entity used for communication with a base station (e.g., over some frequency resource, referred to as a carrier frequency, component carrier, carrier, band, or the like), and may be associated with an identifier (e.g., a physical cell identifier (PCI), a virtual cell identifier (VCI), a cell global identifier (CGI)) for distinguishing cells operating via the same or a different carrier frequency. In some cases, different cells may be configured according to different protocol types (e.g., machine-type communication (MTC), narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB), or others) that may provide access for different types of UEs. Because a cell is supported by a specific base station, the term “cell” may refer to either or both of the logical communication entity and the base station that supports it, depending on the context. In addition, because a TRP is typically the physical transmission point of a cell, the terms “cell” and “TRP” may be used interchangeably. In some cases, the term “cell” may also refer to a geographic coverage area of a base station (e.g., a sector), insofar as a carrier frequency can be detected and used for communication within some portion of geographic coverage areas  110 . 
     While neighboring macro cell base station  102  geographic coverage areas  110  may partially overlap (e.g., in a handover region), some of the geographic coverage areas  110  may be substantially overlapped by a larger geographic coverage area  110 . For example, a small cell base station  102 ′ may have a coverage area  110 ′ that substantially overlaps with the coverage area  110  of one or more macro cell base stations  102 . A network that includes both small cell and macro cell base stations may be known as a heterogeneous network. A heterogeneous network may also include home eNBs (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG). 
     The communication links  120  between the base stations  102  and the UEs  104  may include uplink (also referred to as reverse link) transmissions from a UE  104  to a base station  102  and/or downlink (also referred to as forward link) transmissions from a base station  102  to a UE  104 . The communication links  120  may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links  120  may be through one or more carrier frequencies. Allocation of carriers may be asymmetric with respect to downlink and uplink (e.g., more or less carriers may be allocated for downlink than for uplink). 
     The wireless communications system  100  may further include a wireless local area network (WLAN) access point (AP)  150  in communication with WLAN stations (STAs)  152  via communication links  154  in an unlicensed frequency spectrum (e.g., 5 GHz). When communicating in an unlicensed frequency spectrum, the WLAN STAs  152  and/or the WLAN AP  150  may perform a clear channel assessment (CCA) or listen before talk (LBT) procedure prior to communicating in order to determine whether the channel is available. In some examples, the wireless communications system  100  can include devices (e.g., UEs etc.) that communicate with one or more UEs  104 , base stations  102 , APs  150 , etc. utilizing the ultra-wideband (UWB) spectrum. The UWB spectrum can range from 3.1 to 10.5 GHz. 
     The small cell base station  102 ′ may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell base station  102 ′ may employ LTE or NR technology and use the same 5 GHz unlicensed frequency spectrum as used by the WLAN AP  150 . The small cell base station  102 ′, employing LTE and/or 5G in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. NR in unlicensed spectrum may be referred to as NR-U. LTE in an unlicensed spectrum may be referred to as LTE-U, licensed assisted access (LAA), or MulteFire. 
     The wireless communications system  100  may further include a millimeter wave (mmW) base station  180  that may operate in mmW frequencies and/or near mmW frequencies in communication with a UE  182 . Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in this band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW and/or near mmW radio frequency band have high path loss and a relatively short range. The mmW base station  180  and the UE  182  may utilize beamforming (transmit and/or receive) over an mmW communication link  184  to compensate for the extremely high path loss and short range. Further, it will be appreciated that in alternative configurations, one or more base stations  102  may also transmit using mmW or near mmW and beamforming. Accordingly, it will be appreciated that the foregoing illustrations are merely examples and should not be construed to limit the various aspects disclosed herein. 
     Transmit beamforming is a technique for focusing an RF signal in a specific direction. Traditionally, when a network node (e.g., a base station) broadcasts an RF signal, it broadcasts the signal in all directions (omni-directionally). With transmit beamforming, the network node determines where a given target device (e.g., a UE) is located (relative to the transmitting network node) and projects a stronger downlink RF signal in that specific direction, thereby providing a faster (in terms of data rate) and stronger RF signal for the receiving device(s). To change the directionality of the RF signal when transmitting, a network node can control the phase and relative amplitude of the RF signal at each of the one or more transmitters that are broadcasting the RF signal. For example, a network node may use an array of antennas (referred to as a “phased array” or an “antenna array”) that creates a beam of RF waves that can be “steered” to point in different directions, without actually moving the antennas. Specifically, the RF current from the transmitter is fed to the individual antennas with the correct phase relationship so that the radio waves from the separate antennas add together to increase the radiation in a desired direction, while canceling to suppress radiation in undesired directions. 
     In receiving beamforming, the receiver uses a receive beam to amplify RF signals detected on a given channel. For example, the receiver can increase the gain setting and/or adjust the phase setting of an array of antennas in a particular direction to amplify (e.g., to increase the gain level of) the RF signals received from that direction. Thus, when a receiver is said to beamform in a certain direction, it means the beam gain in that direction is high relative to the beam gain along other directions, or the beam gain in that direction is the highest compared to the beam gain of other beams available to the receiver. This results in a stronger received signal strength, (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-interference-plus-noise ratio (SINR), etc.) of the RF signals received from that direction. 
     Receive beams may be spatially related. A spatial relation means that parameters for a transmit beam for a second reference signal can be derived from information about a receive beam for a first reference signal. For example, a UE may use a particular receive beam to receive one or more reference downlink reference signals (e.g., positioning reference signals (PRS), tracking reference signals (TRS), phase tracking reference signal (PTRS), cell-specific reference signals (CRS), channel state information reference signals (CSI-RS), primary synchronization signals (PSS), secondary synchronization signals (SSS), synchronization signal blocks (SSBs), etc.) from a base station. The UE can then form a transmit beam for sending one or more uplink reference signals (e.g., uplink positioning reference signals (UL-PRS), sounding reference signal (SRS), demodulation reference signals (DMRS), PTRS, etc.) to that base station based on the parameters of the receive beam. 
     Note that a “downlink” beam may be either a transmit beam or a receive beam, depending on the entity forming it. For example, if a base station is forming the downlink beam to transmit a reference signal to a UE, the downlink beam is a transmit beam. If the UE is forming the downlink beam, however, it is a receive beam to receive the downlink reference signal. Similarly, an “uplink” beam may be either a transmit beam or a receive beam, depending on the entity forming it. For example, if a base station is forming the uplink beam, it is an uplink receive beam, and if a UE is forming the uplink beam, it is an uplink transmit beam. 
     In 5G, the frequency spectrum in which wireless nodes (e.g., base stations  102  and/or  180 , UEs  104  and/or  182 ) operate is divided into multiple frequency ranges, FR1 (from 450 to 6000 MHz), FR2 (from 24250 to 52600 MHz), FR3 (above 52600 MHz), and FR4 (between FR1 and FR2). In a multi-carrier system, such as 5G, one of the carrier frequencies is referred to as the “primary carrier” or “anchor carrier” or “primary serving cell” or “PCell,” and the remaining carrier frequencies are referred to as “secondary carriers” or “secondary serving cells” or “SCells.” In carrier aggregation, the anchor carrier is the carrier operating on the primary frequency (e.g., FR1) utilized by a UE  104  and/or  182  and the cell in which the UE  104  and/or  182  either performs the initial radio resource control (RRC) connection establishment procedure or initiates the RRC connection re-establishment procedure. The primary carrier carries all common and UE-specific control channels, and may be a carrier in a licensed frequency (however, this is not always the case). 
     For example, still referring to  FIG. 1 , one of the frequencies utilized by the macro cell base stations  102  may be an anchor carrier (or “PCell”) and other frequencies utilized by the macro cell base stations  102  and/or the mmW base station  180  may be secondary carriers (“SCells”). In carrier aggregation, the base stations  102  and/or the UEs  104  may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100 MHz) bandwidth per carrier up to a total of Yx MHz (x component carriers) for transmission in each direction. The component carriers may or may not be adjacent to each other on the frequency spectrum. Allocation of carriers may be asymmetric with respect to the downlink and uplink (e.g., more or less carriers may be allocated for downlink than for uplink). The simultaneous transmission and/or reception of multiple carriers enables the UE  104  and/or  182  to significantly increase its data transmission and/or reception rates. For example, two 20 MHz aggregated carriers in a multi-carrier system would theoretically lead to a two-fold increase in data rate (i.e., 40 MHz), compared to that attained by a single 20 MHz carrier. 
     In order to operate on multiple carrier frequencies, a base station  102  and/or a UE  104  is equipped with multiple receivers and/or transmitters. For example, a UE  104  may have two receivers, “Receiver 1” and “Receiver 2,” where “Receiver 1” is a multi-band receiver that can be tuned to band (i.e., carrier frequency) ‘X’ or band ‘Y,’ and “Receiver 2” is a one-band receiver tuneable to band ‘Z’ only. In this example, if the UE  104  is being served in band ‘X,’ band ‘X’ would be referred to as the PCell or the active carrier frequency, and “Receiver 1” would need to tune from band ‘X’ to band ‘Y’ (an SCell) in order to measure band ‘Y’ (and vice versa). In contrast, whether the UE  104  is being served in band ‘X’ or band ‘Y,’ because of the separate “Receiver 2,” the UE  104  can measure band ‘Z’ without interrupting the service on band ‘X’ or band ‘Y.’ 
     The wireless communications system  100  may further include a UE  164  that may communicate with a macro cell base station  102  over a communication link  120  and/or the mmW base station  180  over an mmW communication link  184 . For example, the macro cell base station  102  may support a PCell and one or more SCells for the UE  164  and the mmW base station  180  may support one or more SCells for the UE  164 . 
     The wireless communications system  100  may further include one or more UEs, such as UE  190 , that connects indirectly to one or more communication networks via one or more device-to-device (D2D) peer-to-peer (P2P) links (referred to as “sidelinks”). In the example of  FIG. 1 , UE  190  has a D2D P2P link  192  with one of the UEs  104  connected to one of the base stations  102  (e.g., through which UE  190  may indirectly obtain cellular connectivity) and a D2D P2P link  194  with WLAN STA  152  connected to the WLAN AP  150  (through which UE  190  may indirectly obtain WLAN-based Internet connectivity). In an example, the D2D P2P links  192  and  194  may be supported with any well-known D2D RAT, such as LTE Direct (LTE-D), Wi-Fi Direct (Wi-Fi-D), Bluetooth®, and so on. 
     According to various aspects,  FIG. 2A  illustrates an example wireless network structure  200 . For example, a 5GC  210  (also referred to as a Next Generation Core (NGC)) can be viewed functionally as control plane functions  214  (e.g., UE registration, authentication, network access, gateway selection, etc.) and user plane functions  212 , (e.g., UE gateway function, access to data networks, IP routing, etc.) which operate cooperatively to form the core network. User plane interface (NG-U)  213  and control plane interface (NG-C)  215  connect the gNB  222  to the 5GC  210  and specifically to the control plane functions  214  and user plane functions  212 . In an additional configuration, an ng-eNB  224  may also be connected to the 5GC  210  via NG-C  215  to the control plane functions  214  and NG-U  213  to user plane functions  212 . Further, ng-eNB  224  may directly communicate with gNB  222  via a backhaul connection  223 . In some configurations, the New RAN  220  may only have one or more gNBs  222 , while other configurations include one or more of both ng-eNBs  224  and gNBs  222 . Either gNB  222  or ng-eNB  224  may communicate with UEs  204  (e.g., any of the UEs depicted in  FIG. 1 ). 
     Another optional aspect may include location server  230 , which may be in communication with the 5GC  210  to provide location assistance for UEs  204 . The location server  230  can be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc.), or alternately may each correspond to a single server. The location server  230  can be configured to support one or more location services for UEs  204  that can connect to the location server  230  via the core network, 5GC  210 , and/or via the Internet (not illustrated). Further, the location server  230  may be integrated with a component of the core network, or alternatively may be external to the core network. In some examples, the location server  230  can be operated by a carrier or provider of the 5GC  210 , a third party, an original equipment manufacturer (OEM), or other party. In some cases, multiple location servers can be provided, such as a location server for the carrier, a location server for an OEM of a particular device, and/or other location servers. In such cases, location assistance data can be received from the location server of the carrier and other assistance data can be received from the location server of the OEM. 
     According to various aspects,  FIG. 2B  illustrates another example wireless network structure  250 . For example, a 5GC  260  can be viewed functionally as control plane functions, provided by an access and mobility management function (AMF)  264 , and user plane functions, provided by a user plane function (UPF)  262 , which operate cooperatively to form the core network (i.e., 5GC  260 ). User plane interface  263  and control plane interface  265  connect the ng-eNB  224  to the 5GC  260  and specifically to UPF  262  and AMF  264 , respectively. In an additional configuration, a gNB  222  may also be connected to the 5GC  260  via control plane interface  265  to AMF  264  and user plane interface  263  to UPF  262 . Further, ng-eNB  224  may directly communicate with gNB  222  via the backhaul connection  223 , with or without gNB direct connectivity to the 5GC  260 . In some configurations, the New RAN  220  may only have one or more gNBs  222 , while other configurations include one or more of both ng-eNBs  224  and gNBs  222 . Either gNB  222  or ng-eNB  224  may communicate with UEs  204  (e.g., any of the UEs depicted in  FIG. 1 ). The base stations of the New RAN  220  communicate with the AMF  264  over the N2 interface and with the UPF  262  over the N3 interface. 
     The functions of the AMF  264  include registration management, connection management, reachability management, mobility management, lawful interception, transport for session management (SM) messages between the UE  204  and a session management function (SMF)  266 , transparent proxy services for routing SM messages, access authentication and access authorization, transport for short message service (SMS) messages between the UE  204  and the short message service function (SMSF) (not shown), and security anchor functionality (SEAF). The AMF  264  also interacts with an authentication server function (AUSF) (not shown) and the UE  204 , and receives the intermediate key that was established as a result of the UE  204  authentication process. In the case of authentication based on a UMTS (universal mobile telecommunications system) subscriber identity module (USIM), the AMF  264  retrieves the security material from the AUSF. The functions of the AMF  264  also include security context management (SCM). The SCM receives a key from the SEAF that it uses to derive access-network specific keys. The functionality of the AMF  264  also includes location services management for regulatory services, transport for location services messages between the UE  204  and a location management function (LMF)  270  (which acts as a location server  230 ), transport for location services messages between the New RAN  220  and the LMF  270 , evolved packet system (EPS) bearer identifier allocation for interworking with the EPS, and UE  204  mobility event notification. In addition, the AMF  264  also supports functionalities for non-3GPP access networks. 
     Functions of the UPF  262  include acting as an anchor point for intra-RAT and/or inter-RAT mobility (when applicable), acting as an external protocol data unit (PDU) session point of interconnect to a data network (not shown), providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering), lawful interception (user plane collection), traffic usage reporting, quality of service (QoS) handling for the user plane (e.g., uplink and/or downlink rate enforcement, reflective QoS marking in the downlink), uplink traffic verification (service data flow (SDF) to QoS flow mapping), transport level packet marking in the uplink and downlink, downlink packet buffering and downlink data notification triggering, and sending and forwarding of one or more “end markers” to the source RAN node. The UPF  262  may also support transfer of location services messages over a user plane between the UE  204  and a location server, such as a secure user plane location (SUPL) location platform (SLP)  272 . 
     The functions of the SMF  266  include session management, UE Internet protocol (IP) address allocation and management, selection and control of user plane functions, configuration of traffic steering at the UPF  262  to route traffic to the proper destination, control of part of policy enforcement and QoS, and downlink data notification. The interface over which the SMF  266  communicates with the AMF  264  is referred to as the N11 interface. 
     Another optional aspect may include an LMF  270 , which may be in communication with the 5GC  260  to provide location assistance for UEs  204 . The LMF  270  can be implemented as a plurality of separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spread across multiple physical servers, etc.), or alternately may each correspond to a single server. The LMF  270  can be configured to support one or more location services for UEs  204  that can connect to the LMF  270  via the core network, 5GC  260 , and/or via the Internet (not illustrated). The SLP  272  may support similar functions to the LMF  270 , but whereas the LMF  270  may communicate with the AMF  264 , New RAN  220 , and UEs  204  over a control plane (e.g., using interfaces and protocols intended to convey signaling messages and not voice or data), the SLP  272  may communicate with UEs  204  and external clients (not shown in  FIG. 2B ) over a user plane (e.g., using protocols intended to carry voice and/or data like the transmission control protocol (TCP) and/or IP). 
     In an aspect, the LMF  270  and/or the SLP  272  may be integrated with a base station, such as the gNB  222  and/or the ng-eNB  224 . When integrated with the gNB  222  and/or the ng-eNB  224 , the LMF  270  and/or the SLP  272  may be referred to as a “location management component,” or “LMC.” However, as used herein, references to the LMF  270  and the SLP  272  include both the case in which the LMF  270  and the SLP  272  are components of the core network (e.g., 5GC  260 ) and the case in which the LMF  270  and the SLP  272  are components of a base station. 
       FIG. 3  shows a block diagram of a design of a base station  102  and a UE  104  that enable transmission and processing of signals exchanged between the UE and the base station, in accordance with some aspects of the present disclosure. Design  300  includes components of a base station  102  and a UE  104 , which may be one of the base stations  102  and one of the UEs  104  in  FIG. 1 . Base station  102  may be equipped with T antennas  334   a  through  334   t , and UE  104  may be equipped with R antennas  352   a  through  352   r , where in general T≥1 and R≥1. 
     At base station  102 , a transmit processor  320  may receive data from a data source  312  for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS(s) selected for the UE, and provide data symbols for all UEs. Transmit processor  320  may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., CQI requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. Transmit processor  320  may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS)) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor  330  may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs)  332   a  through  332   t . The modulators  332   a  through  332   t  are shown as a combined modulator-demodulator (MOD-DEMOD). In some cases, the modulators and demodulators can be separate components. Each modulator of the modulators  332   a  to  332   t  may process a respective output symbol stream, e.g., for an orthogonal frequency-division multiplexing (OFDM) scheme and/or the like, to obtain an output sample stream. Each modulator of the modulators  332   a  to  332   t  may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals may be transmitted from modulators  332   a  to  332   t  via T antennas  334   a  through  334   t , respectively. According to certain aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information. 
     At UE  104 , antennas  352   a  through  352   r  may receive the downlink signals from base station  102  and/or other base stations and may provide received signals to demodulators (DEMODs)  354   a  through  354   r , respectively. The demodulators  354   a  through  354   r  are shown as a combined modulator-demodulator (MOD-DEMOD). In some cases, the modulators and demodulators can be separate components. Each demodulator of the demodulators  354   a  through  354   r  may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator of the demodulators  354   a  through  354   r  may further process the input samples (e.g., for OFDM and/or the like) to obtain received symbols. A MIMO detector  356  may obtain received symbols from all R demodulators  354   a  through  354   r , perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor  358  may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE  104  to a data sink  360 , and provide decoded control information and system information to a controller/processor  380 . A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), and/or the like. 
     On the uplink, at UE  104 , a transmit processor  364  may receive and process data from a data source  362  and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor  380 . Transmit processor  364  may also generate reference symbols for one or more reference signals (e.g., based at least in part on a beta value or a set of beta values associated with the one or more reference signals). The symbols from transmit processor  364  may be precoded by a TX-MIMO processor  366  if application, further processed by modulators  354   a  through  354   r  (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like), and transmitted to base station  102 . At base station  102 , the uplink signals from UE  104  and other UEs may be received by antennas  334   a  through  334   t , processed by demodulators  332   a  through  332   t , detected by a MIMO detector  336  if applicable, and further processed by a receive processor  338  to obtain decoded data and control information sent by UE  104 . Receive processor  338  may provide the decoded data to a data sink  339  and the decoded control information to controller (processor)  340 . Base station  102  may include communication unit  344  and communicate to a network controller  331  via communication unit  344 . Network controller  331  may include communication unit  394 , controller/processor  390 , and memory  392 . 
     In some aspects, one or more components of UE  104  may be included in a housing. Controller  340  of base station  102 , controller/processor  380  of UE  104 , and/or any other component(s) of  FIG. 3  may perform one or more techniques associated with implicit UCI beta value determination for NR. 
     Memories  342  and  382  may store data and program codes for the base station  102  and the UE  104 , respectively. A scheduler  346  may schedule UEs for data transmission on the downlink and/or uplink. 
     In some implementations, UE  104  may include means for determining a tone pattern for a reference signal for use in wireless communications between the UE  104  and the base station  102 , each tone of the tone pattern occupying a resource element in a resource block; determining a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmitting the reference signal using the tone pattern having the plurality of power levels. 
     In some implementations, base station  102  may include means for determining a tone pattern for a reference signal for use in wireless communications between the base station  102  and the UE  104 , each tone of the tone pattern occupying a resource element in a resource block; determining a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmitting the reference signal using the tone pattern having the plurality of power levels 
     As noted above, tone patterns can be defined as specific arrangement of resource elements in a given resource block for transmission of a reference signal between a UE such as one of UEs  104  and a base station such as base station  102 . Tone patterns are currently pre-defined in the 5G communication standard. Pre-defined tone patterns may not be optimized for all environments. For instance, the arrangement or combination of resource elements used for transmission of a particular reference signal may not be optimized across all possible conditions under which a user equipment and a base station operate. Therefore, signal efficiency and latency reduction for 5G mobile systems can be improved through a dynamic determination of optimal tone pattern configurations. 
     A resource block may be transmitted on UL or DL between the UE  104  and the base station  102  using a radio frame. Various radio frame structures may be used to support downlink and uplink transmissions between network nodes (e.g., base stations and UEs).  FIG. 4  is a diagram  400  illustrating an example of a downlink frame structure, according to some aspects of the disclosure. Other wireless communications technologies may have different frame structures and/or different channels. 
     NR (and LTE) utilizes OFDM on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. Unlike LTE, however, NR has an option to use OFDM on the uplink as well. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (resource block) may be 12 subcarriers (or 180 kHz). Consequently, the nominal fast Fourier transform (FFT) size may be equal to 128, 256, 512, 1024, or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e.,  6  resource blocks), and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10, or 20 MHz, respectively. 
     LTE supports a single numerology (subcarrier spacing, symbol length, etc.). In contrast, NR may support multiple numerologies (μ). For example, subcarrier spacing (SCS) of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz or greater may be available. Table 1 provided below lists some various parameters for different NR numerologies. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Max. nominal 
               
               
                   
                   
                   
                   
                   
                 Slot 
                 Symbol 
                 system BW 
               
               
                   
                 SCS 
                 Symbols/ 
                 Slots/ 
                 Slots/ 
                 Duration 
                 Duration 
                 (MHz) with 
               
               
                 μ 
                 (kHz) 
                 Sot 
                 Subframe 
                 Frame 
                 (ms) 
                 (μs) 
                 4 K FFT size 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 0 
                  15 
                 14 
                  1 
                  10 
                 1 
                 66.7 
                  50 
               
               
                 1 
                  30 
                 14 
                  2 
                  20 
                 0.5 
                 33.3 
                 100 
               
               
                 2 
                  60 
                 14 
                  4 
                  40 
                 0.25 
                 16.7 
                 100 
               
               
                 3 
                 120 
                 14 
                  8 
                  80 
                 0.125 
                 8.33 
                 400 
               
               
                 4 
                 240 
                 14 
                 16 
                 160 
                 0.0625 
                 4.17 
                 800 
               
               
                   
               
            
           
         
       
     
     In one example, a numerology of 15 kHz is used. Thus, in the time domain, a 10 millisecond (ms) frame is divided into 10 equally sized subframes of 1 ms each, and each subframe includes one time slot. In  FIG. 4 , time is represented horizontally (e.g., on the X axis) with time increasing from left to right, while frequency is represented vertically (e.g., on the Y axis) with frequency increasing (or decreasing) from bottom to top. 
     A resource grid may be used to represent time slots, each time slot including one or more time-concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs)) in the frequency domain.  FIG. 4  illustrates an example of a resource block (RB)  402 . The resource grid is further divided into multiple resource elements (REs). Referring to  FIG. 4 , the RB  402  includes multiple REs, including resource element (RE)  404 . The RE  404  may correspond to one symbol length in the time domain and one subcarrier in the frequency domain. In the numerology of  FIG. 4 , for a normal cyclic prefix, RB  402  may contain 12 consecutive subcarriers in the frequency domain and seven consecutive symbols in the time domain, for a total of 84 REs such as RE  404 . For an extended cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and six consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme. 
     Some of the REs carry downlink reference (pilot) signals (DL-RSs). A DL-RS may include, but is not limited to, PRS, TRS, PTRS, CRS, CSI-RS, DMRS, PSS, SSS, SSB, etc.  FIG. 4  illustrates example locations of REs carrying a DL-RS (with each RE being labeled with an “R”).  FIG. 4  and subsequent examples below will be described in relation to a CSI-RS and a TRS as illustrative examples of DL-RSs. However, the present disclosure is not limited thereto and the dynamic based techniques described herein for determining tone patterns can be equally applied to any other DL-RS and/or UL reference (pilot) signals (UL-RS). 
     A collection of resource elements (REs) that are used for transmission of reference signals is referred to as a tone pattern. The tone pattern can span multiple REs over a single RB, multiple REs over multiple RBs in the frequency domain and ‘N’ (e.g., 1 or more) consecutive symbol(s) within a slot in the time domain, or can span a single RE in a given RB. 
     Locations of REs (labeled “R”) in  FIG. 4  represent an example tone pattern for an example reference signal (e.g., a CSI-RS) in the RB  402 . The tone pattern illustrated in  FIG. 4  may be defined with REs having (time (subcarrier), frequency (OFDM symbol)) coordinates in the RB  402 . For example, in the example of  FIG. 4 , the tone pattern can be defined by REs with coordinates (2,4), (4,4), (6,4) and (8,4) in the RB  402 . These coordinates define the locations of the REs labeled “R” in  FIG. 4 . Various other tone patterns may be used for different reference signals of the 5G standard as defined by the 3GPP. The tone pattern shown in  FIG. 4 , as well as other tone patterns specified by 3GPP as part of the 5G standard, are pre-defined. For instance, when a reference signal is to be sent on a DL channel or an UL channel between the base station  102  and UE  104  (which can be in every RB, every second RB, etc.), one such pre-defined tone pattern is used. 
     Furthermore, a power level is associated with each RE in  FIG. 4  (labeled “R” or otherwise). The power level for each RE can be referred to as an energy per resource element (EPRE), which can be expressed in decibels (dBs). EPRE is typically a fixed value that is predetermined (e.g., average of power contributions of all the REs in the RB  402 ). 
     Relying on pre-defined tone patterns decoupled from conditions under which a UE and a base station communicate (channel conditions) and/or relying on fixed EPRE values for REs over which UE-base station communications take place may result in redundant and/or otherwise inefficient use of network resources for transmitting reference signals. One example of such inefficient use of network resources includes the overhead associated with transmission of reference signals, which can be reduced by implementing techniques described below for determining tone patterns and/or associated power levels for transmission of reference signals. Furthermore, in some examples, the systems and techniques described herein can provide the added advantage of frequency selectivity of a communication channel. For instance, when a receiving device configured to receive reference signals is aware of frequency selectivity of the communication channel, the receiving device can request a transmitting device to vary (e.g., boost) the power level (e.g., the EPRE value) of individual tones (e.g., REs) of the tone patterns used for transmission of reference signals, at frequencies at which channel response of the communication channel is relatively low. 
     Systems and techniques are described herein for a process of determining tone patterns and/or associated power levels (can also be referred to as optimized and/or customized tone patterns and/or associated power levels) used for transmission of references signals between UEs and base stations. In some cases, the systems and techniques can be implemented by a base station such as the base station  102 . In some examples, the systems and techniques can be implemented by a UE such as the UE  104 . The systems and techniques can determine and communicate a tone pattern and/or associated power levels based on current and/or prior conditions of a communication channel between a UE and a base station. Upon determination of a tone pattern for transmission of a reference signal between a UE and a base station, the systems and techniques described herein also determine a power level of each resource element in the tone pattern. In some cases, the power levels of the resource elements may be the same or different. Furthermore, the power levels of resource elements across different resource blocks may also be the same or different. In some cases, the systems and techniques described herein can also utilize a trained machine learning model for determining customized and/or optimized tone patterns and/or associated EPRE values for reference signal transmissions between UEs and base stations. 
     Configuring a UE and/or a base station to determine an optimized (and/or customized) tone pattern (e.g., each time a reference signal is to be sent on the DL channel to the UE or on the UL from the UE to the base station) and corresponding EPRE values can improve the efficiency of network resource utilization at the physical layer, and can reduce overhead associated with transmission of reference signals (e.g., based on EPRE=0 for some RS tones, as described herein), etc. 
     For example, under certain conditions, such as UE mobility conditions, environmental conditions, and/or transmission and reception capabilities of UEs and base stations (e.g., a UE having an advanced receiver that can estimate channels using lower RS tones, etc.), use of example tone pattern in  FIG. 4  may be redundant or inefficient. In such cases and in other cases, sending the reference signal over four different REs, as shown in  FIG. 4 , may be redundant. Using the systems and techniques described herein, under such conditions or others, the UE and/or base station can customize the tone pattern and/or associated EPRE values for transmission of reference signals. As a non-limiting example, sending the reference signal using fewer REs (e.g., 20 REs instead of 30 REs used by some of existing pre-defined and regular tone patterns), may suffice. Moreover, using fixed EPRE values in association with a tone pattern may also be redundant and/or inefficient. Varying the EPRE values of the various REs in an RB and/or across RBs for a selected tone pattern can increase signaling and/or spectral efficiencies. 
     In another example, environmental conditions may be such that signal reception at the UE  104  is sub-optimal (less than a threshold with the threshold being a configurable parameter determined based on experiments and/or empirical studies). In this instance, there may be a need to send a reference signal over more REs than used by pre-defined regular tone patterns (e.g., 40 REs instead of 30 REs). Moreover, using fixed EPRE values in association with a tone pattern may also be redundant and/or inefficient and thus varying the EPRE value of each RE (e.g., increasing the power level of some REs while keeping the EPRE values of others constant or lowering the other EPRE values) for a selected tone pattern can increase signaling and/or spectral efficiencies. In another example, depending on channel and device configurations, certain REs in a given RB may be reserved for communication of other pilot signals, which would intervene with REs to be used for transmission of reference signals. 
     While a number of example instances are described above under which use of a pre-defined tone pattern and/or EPRE values may be sub-optimal, there may be various other conditions in which the use of customized or alternative tone patterns and/or EPRE values compared to pre-defined tone patterns and pre-fixed EPRE values defined in the standard can be advantageous. A tone pattern and/or EPRE values may be determined by generating a new tone pattern and/or associated EPRE values based on channel conditions. In some cases, the new tone pattern and/or associated EPRE values is not defined in the 3GPP Standard. For instance, the new tone pattern and/or associated EPRE values can include a customized (e.g., irregular) placement of tones in a resource block with varying and RE-specific EPRE values. Illustrative examples of such new tone patterns are described below with respect to  FIG. 8A  and  FIG. 8B . In either case, whether determining a new tone pattern or using an existing pattern, making a determination of the best tone pattern to use for transmission of a reference signal and/or making a determination of resource element specific EPRE values can improve the spectral efficiency and reduce latency. 
     In some examples, the tone pattern and/or EPRE values optimization systems and techniques described herein can take into account channel conditions or other factors when determining optimized tone patterns and/or EPRE values. For instance, base stations and the UEs (e.g., the base station  102  and the UE  104  described above with reference to  FIG. 1 ) exchange various reference signals over time. Reference signals may be used by a base station or a UE to make one or more measurements including, but not limited to, channel throughput, channel distortion, Reference Signal Receive Power (RSRP) during mobility and beam management, frequency/time tracking, demodulation and UL reciprocity based pre-coding, path delay spread and Doppler spread, etc. 
     Such measurements may vary depending on channel conditions (e.g., environment conditions, mobility status, etc.) and the specific tone pattern over which reference signals are exchanged between a UE and a base station. By observing changes to measurements over time, UEs and base stations can learn the tone patterns and/or corresponding EPRE values that result in improved measurements for given underlying channel conditions. 
     In some examples, a machine learning model may be used to determine optimized tone patterns and/or EPRE values. For instance, as described in more detail below, a machine learning model may be trained using a training dataset to determine best tone patterns for reference signal transmission given a set of channel conditions. In some aspects, the training dataset can include channel conditions, different tone patterns over which UEs receive CSI-RS and TRS signals, resulting measurements made by the receiving UEs under such channel conditions and tone patterns, measured throughput, etc. Once trained, the machine learning model can receive as input channel conditions (e.g., one or more parameters associated with a communication channel between the UE  104  and the base station  102  to which it is connected such as mobility status of the UE  104 , environmental conditions in which the UE  104  is operating, etc.) and provide as output a recommended tone pattern for the base station  102  to use for sending CSI-RS and/or TRS on the DL channel to the UE  104 . 
     The machine learning model can be further trained using past EPRE values of previously utilized tone patterns such that the machine learning model can provide as output a particular recommended tone pattern (can be a new pattern or a previously known and/or utilized tone pattern) for a given channel condition as well as a recommended EPRE values for each RE associated with the recommended tone pattern. 
     Examples of a tone pattern optimization process will now be described with reference to  FIGS. 5-9 . 
       FIG. 5  illustrates an example neural architecture of a neural network  500  that can be trained for tone placement optimization and/or resource element specific EPRE values, in accordance with some aspects of the present disclosure. Example neural architecture of a neural network  500  may be defined by an example neural network description  502  in neural controller  501 . The neural network  500  is an example of a machine learning model that can be deployed and implemented at the base station  102  and/or at the UE  104 . The neural network  500  can be a feedforward neural network or any other known or to be developed neural network or machine learning model. 
     The neural network description  502  can include a full specification of the neural network  500 , including the neural architecture shown in  FIG. 5 . For example, the neural network description  502  can include a description or specification of architecture of the neural network  500  (e.g., the layers, layer interconnections, number of nodes in each layer, etc.); an input and output description which indicates how the input and output are formed or processed; an indication of the activation functions in the neural network, the operations or filters in the neural network, etc.; neural network parameters such as weights, biases, etc.; and so forth. 
     The neural network  500  can reflect the neural architecture defined in the neural network description  502 . In this non-limiting example, the neural network  500  includes an input layer  503 , which after being trained, can receive one or more sets of input data. The input data can be any type of data such as one or more parameters associated with a communication channel (e.g., environmental conditions associated with UL and DL communication channels between the UE  104  and the base station  102 , UE mobility status, etc.), various measurements made by the base station  102  and the UE  104  using previously transmitted reference signals, etc. 
     The neural network  500  can include the hidden layers  504 A through  504 N (collectively “ 504 ” hereinafter). The hidden layers  504  can include n number of hidden layers, where n is an integer greater than or equal to one. The number of hidden layers can include as many layers as needed for a desired processing outcome and/or rendering intent. In one illustrative example, any one of the hidden layer  504  can include data representing one or more of the data provided at the input layer  503  such as one or more parameters associated with a communication channel (e.g., environmental conditions associated with UL and DL communication channels between the UE  104  and the base station  102 , UE mobility status, etc.), previously utilized tone patterns for communication of reference signals and associated EPRE values, one or more measurements and associated throughputs made by the base station  102  and/or the UE  104  using the previously utilized tone patterns, a delta (difference) between the measurements made by the base station  102  and/or the UE  104  using the different tone patterns, etc. 
     The neural network  500  further includes an output layer  506  that provides an output resulting from the processing performed by hidden layers  504 . In one illustrative example, the output layer  506  can provide output data based on the input data. In one example context related to determination of a tone pattern for transmission of CSI-RS and/or TRS, the output data can include a recommended tone pattern to be used by the base station  102  for sending a CSI-RS and/or a TRS on the DL channel to the UE  104 . 
     The neural network  500 , in this example, is a multi-layer neural network of interconnected nodes. Each node can represent a piece of information. Information associated with the nodes is shared among the different layers and each layer retains information as information is processed. In some cases, the neural network  500  can include a feed-forward neural network. In other cases, the neural network  500  can include a recurrent neural network, which can have loops that allow information to be carried across nodes while reading in input. 
     Information can be exchanged between nodes through node-to-node interconnections between the various layers. The nodes of the input layer  503  can activate a set of nodes in the first hidden layer  504 A. For example, as shown, each input node of the input layer  503  is connected to each node of the first hidden layer  504 A. The nodes of the hidden layer  504 A can transform the information of each input node by applying activation functions to the information. The information derived from the transformation can then be passed to and can activate the nodes of the next hidden layer (e.g.,  504 B), which can perform their own designated functions. Example functions include convolutional, up-sampling, data transformation, pooling, and/or any other suitable functions. The output of hidden layer (e.g.,  504 B) can then activate nodes of the next hidden layer (e.g.,  504 N), and so on. The output of last hidden layer can activate one or more nodes of the output layer  506 , at which point an output is provided. In some cases, while nodes (e.g., nodes  508 A,  508 B,  508 C) in the neural network  500  are shown as having multiple output lines, a node has a single output and all lines shown as being output from a node represent the same output value. 
     In some cases, each node or interconnection between nodes can have a weight that is a set of parameters derived from training the neural network  500 . For example, an interconnection between nodes can represent a piece of information learned about the interconnected nodes. The interconnection can have a numeric weight that can be tuned (e.g., based on a training dataset), allowing the neural network  500  to be adaptive to inputs and able to learn as more data is processed. 
     The neural network  500  can be pre-trained to process the features from the data in the input layer  503  using different hidden layers  504  in order to provide the output through the output layer  506 . In some cases, the neural network  500  can adjust weights of nodes using a training process called backpropagation. Backpropagation can include a forward pass, a loss function, a backward pass, and a weight update. The forward pass, loss function, backward pass, and parameter update can be performed for one training iteration. The process can be repeated for a certain number of iterations for each set of training data until the weights of the layers are accurately tuned (e.g., meet a configurable threshold determined based on experiments and/or empirical studies). 
     The neural network  500  can include any suitable neural or deep learning type of network. One example includes a convolutional neural network (CNN), which includes an input layer and an output layer, with multiple hidden layers between the input and out layers. The hidden layers of a CNN include a series of convolutional, nonlinear, pooling (for downsampling), and fully connected layers. In other examples, the neural network  500  can represent any other neural or deep learning network, such as an autoencoder, a deep belief nets (DBNs), a recurrent neural network (RNN), etc. 
     Once trained, the neural network  500  can receive as input one or more parameters associated with a communication channel between the base station  102  and the UE  104 . Such parameters can include, but are not limited to, environmental conditions in which the base station  102  and the UE  104  are communicating (e.g., weather conditions, indoor/outdoor channel conditions, cellular or wireless connectivity, transmission capabilities and power of the base station  102  and/or the UE  104 , etc.), mobility status of the UE  104  (e.g., how fast the UE  104  is moving toward or away from the base station  102 , etc.), multipath characteristics of the channel, various measurements made by the base station  102  and the UE  104  using previously transmitted reference signals (e.g., tone patterns and/or associated EPRE values used in previous RBs for transmission of the reference signals), etc. The neural network  500  can then provide as output, a recommendation for a tone pattern to be used for transmission of an underlying reference signal as well as a recommendation on an EPRE value for each resource element associated with the tone pattern. As described in more detail below, the trained neural network  500  can be deployed at the UE  104  or alternatively at the base station  102 . 
     In some examples, a receiver (e.g., the base station  102  and/or the UE  104 ) can monitor, in real-time (e.g., as REs are received) or in near-real-time, received REs over time and/or frequency and may determine over a period of time that certain REs are better for the purpose of transmission of reference signals (RSs). In some cases, even RS tones used for data transmission can be interpreted as pilots after they are decoded. The receiver may also determine the optimized power distribution across the RS tones over which reference signals are received. Once an optimized power distribution is determined, the receiver can then feed the optimized pattern and/or associated EPREs across the RS tones of the optimized pattern back to a transmitter to be used for transmission of reference signals (e.g., which can be the same as the receiver or the other one of the base station  102  and/or the UE  104  as the transmitter). 
     Trained neural network  500  can log parameters, channel conditions, and/or other information (e.g., UE position, etc.), and can associate the same with various tone patterns (and/or corresponding EPRE values) used for reference signal transmission. As noted herein, the channel conditions can include indoor and/or outdoor channel conditions, UE mobility, multipath characteristics of the channel, any combination thereof, and/or other channel conditions. For example, the trained neural network  500  can remember which tone patterns (and/or associated EPRE values) were used for the logged information, so that they can be used in the future. Based on subsequent measurements and channel estimation processes, the trained neural network  500  can identify which tone patterns (and/or corresponding EPRE values) are best suited for a given set of parameters and/or channel conditions. In the future and upon occurrence or detection of such channel conditions, the trained neural network  500  is capable of identifying and using the best suited tone pattern(s) (and/or corresponding EPRE values) under the detected channel conditions for transmission of reference signals. In some examples, the trained neural network  500  can be continuously (e.g., in real-time) retrained and optimized each time reference signals are transmitted between the base station  102  and the UE  104  under various conditions. 
     As noted above, the output of the trained neural network, whether implemented at the base station  102  or the UE  104  can be a customized and new tone pattern not previously utilized for transmission of reference signals, or can be a previously utilized tone pattern determined to be the best tone pattern by the trained neural network  500  for the given set of one or more parameters provided as input. The output can further include determined resource element specific EPRE values for a determined tone pattern. 
       FIG. 6  is a flow chart of a process  600  of training a machine learning algorithm, such as neural network  500 , for tone pattern determination, in accordance with some aspects of the present disclosure. Operation of  FIG. 6  will be described in relation to  FIG. 5  and can be implemented at the base station  102  and/or the UE  104 . 
     At operation  610 , the neural controller  501  receives a description of the structure of the neural network  500  (e.g., from base station  102 ) including, but not limited to, the architecture of the neural network  500  and definition of layers, layer interconnections, input and output descriptions, activation functions, operations, filters, parameters such as weights, coefficients, biases, etc. In some examples, the description can be received from a device based on a user input received by the device (e.g., input via an input device, such as a keyboard, mouse, touchscreen, interface, and/or other type of input device). In some examples, operation  610  is optional and may not be performed in some cases. For example, in some cases, the neural network  500  can be UE specific (e.g., executed by the UE) and thus the description and specific configurations of the neural network  500  may be provided by the UE  104 . 
     At operation  620 , the neural network  500  is generated based on the description received at operation  610 . Using the description, neural controller  501  generates appropriate input, intermediate, and output layers with defined interconnections between the layers and/or any weights or coefficients assigned thereto. The weights and/or other coefficients can be set to initialized values, which will be modified during training, as described below. In some examples, operation  620  is optional and may not be performed in some cases (e.g., when the neural network  500  is UE specific). 
     At operation  630 , once the neural network  500  is defined, a training data set is provided to the input layer  503  of the neural network  500 . As described above, the training data set can include, but is not limited to, various tone patterns and/or associated EPRE values used for transmission of reference signals between the base station  102  and the UE  104 , environmental conditions in which the base station  102  and the UE  104  are communicating reference signals using such tone patterns and EPRE values, as described above. Environmental conditions can include, but are not limited to, weather conditions, cellular or wireless connectivity, transmission capabilities and power of the base station  102  and/or the UE  104 , etc., mobility status of the UE  104  (e.g., how fast the UE  104  is moving toward or away from the base station  102 , etc.), indoor/outdoor conditions, multipath characteristics of the channel, etc. Furthermore, various measurements made by the base station  102  and/or the UE  104  using previously transmitted reference signals (e.g., tone patterns and/or associated EPRE values used in previous RBs for transmission of the reference signals, etc.), one or more measurements and associated throughputs made by the base station  102  and/or the UE  104  using the previously utilized tone patterns, a delta (difference) between measurements made by the base station  102  and/or the UE  104  using the different tone patterns, etc., may be utilized in training the neural network  500 . In some examples, there may not be explicit dedicated training data for the purpose of training the neural network or a training data set may not necessarily be a predetermined set of conditions and associated tone patterns and associated EPRE values. For instance, in some cases, the neural network  500  may instead (or in conjunction with) be trained using an online learning approach, such as by using information associated with real-time live conditions under which the base station  102  and the UE  104  are communicating and transmitting reference signals using tone patterns and/or EPRE values codes. In such examples, the real-time data can be used for live training of the neural network  500  (e.g., as the UE  104  and/or base station  102  is in operation). 
     At operation  640 , the neural network  500  is trained using the training data set. In one example, the training of the neural network  500  is an iterative process repeated multiple times and each time validated against a test data set. The test data set may include a set of one or more parameters similar to those used as part of the training dataset and associated output tone patterns. During each iteration, the output at the output layer  506  is compared to the test data set and a delta between the output at the output layer  506  at that iteration and the optimized output defined in the test data set is determined. The weights and other coefficients of the various layers can be adjusted based on the delta. The iterative process may continue until the delta for any given set of input parameters is less than a threshold. The threshold may be a configurable parameter determined based on experiments and/or empirical studies. 
     At operation  650  and once the neural network  500  is trained, the trained neural network  500  is deployed at the base station  102  and/or the UE  104 . Once deployed at the base station  102  or the UE  104 , the trained neural network can periodically determine tone patterns and/or associated resource element specific EPRE values given a set of input parameters associated with the communication channel between the base station  102  and the UE  104 . The periodicity of the tone pattern and/or EPRE value determination can depend on any number of factors including, but not limited to a configured periodicity for transmission of reference signals, e.g., every subframe or RB, every other subframe or RB, every frame, etc. As the channel condition or other parameters change, the receiving device (e.g., the base station  102  or the UE  104  on which the trained neural network  500  is deployed) can re-train the neural network  500  to determine optimized tone pattern and/or channel conditions for the new conditions. 
     At operation  660 , a triggering condition for retraining the neural network  500  is detected. The command may be received after the trained neural network  500  is deployed and after each instance of determining a tone pattern and/or associated resource element specific EPRE values for a reference signal. The corresponding parameters used as input, the tone pattern and corresponding EPRE values are provided as part of the command received for retraining the neural network  500 . In another example, the command may be received upon a detection of a triggering condition, which will be further described below with reference to  FIGS. 7 and 9 . Examples of such triggering conditions can further include, but are not limited to, a threshold degradation in performance of tone patterns recommended by the neural network  500  for transmission of reference signal (where the threshold may be determined based on experiments and/or empirical studies), channel estimation errors when a reference signal is used for channel estimation (e.g., when channel estimation error reaches and/or exceeds a configurable threshold more than a number of times over a period of time, with the number of times and the period of time being configurable parameters determined based on experiments and/or empirical studies), etc. 
     At operation  670 , the neural network  500  is retrained using the corresponding parameters used as input and the tone pattern received as part of the command at operation  660 . The operation  660  and  670  for retraining the neural network  500  may be continuously repeated after the initial deployment of the trained neural network  500 . For instance, each time the trained neural network  500  determines a tone pattern and/or associated resource element specific EPRE values for transmission of a particular reference signal, the corresponding parameters used as input, the determined tone pattern and/or the determined resource element specific EPRE values are used as additional training data for retraining and optimizing the trained neural network  500 . 
       FIG. 7  is a flow chart of a process  700  of communicating a customized tone pattern and associated power levels, in accordance with some aspects of the present disclosure. The process  700  of  FIG. 7  will be described from the perspective of the UE  104 . It should be understood that the UE  104  may have one or more processors configured to execute one or more computer-readable instructions stored on one or more associated memories of the UE  104  to implement the steps of  FIG. 7 . In describing operations of  FIG. 7 , the UE  104  may be a receiving device and the base station  102  may be a transmitting device. 
     At operation  710 , the UE  104  determines one or more parameters associated with communications between the base station  102  and the UE  104 . Such communications between the base station  102  and the UE  104  can be over a communication channel used over a duration of time (e.g., current communication channel between the base station  102  and the UE  104 ). As described above, the one or more parameters include, but are not limited to, a location of the UE  104 , an environmental condition associated with the location of the UE  104 , a location of the base station  102 , an environmental condition associated with the location of the base station  102 , indoor/outdoor channel conditions, multipath characteristics of the channel, a mobility status of the UE  104  (e.g., how fast the UE  104  is moving toward or away from the base station  102 , etc.), various measurements made by the base station  102  and/or the UE  104  using previously transmitted reference signals (e.g., tone patterns used in previous RBs for transmission of reference signals), EPRE values associated with previously utilized tone patterns, any combination thereof, and/or other parameters. 
     At operation  720 , the UE  104  determines a tone pattern for a reference signal for use in future communication(s) between the base station  102  and the UE  104 . In one example, the UE  104  determines the tone pattern based on the one or more parameters determined at operation  710 . The tone pattern may identify one or more symbols and one or more locations within a resource block for the one or more symbols to be placed. In one example, the UE  104  may determine the tone pattern using a trained machine learning model (e.g., the trained neural network  500 ) of  FIG. 5 . As described above, the trained machine learning model can receive as input the one or more parameters determined at operation  710  and provide as output the tone pattern at operation  720 . In another example, one or more signal processing techniques may be applied to determine the tone pattern. For example, the UE  104  can have advance receiver capabilities built therein allowing the UE  104  to use fewer tones for transmission of a reference signal (e.g., which can be used for channel estimation). 
     In some examples, the tone pattern can be for a DL reference signal (e.g., a CSI-RS or other DL reference signal) to be transmitted by the base station  102  to the UE  104 . In one example, the tone pattern can be a new tone pattern such as customized irregular arrangement of REs with different (time, frequency) coordinates.  FIGS. 8A-B  illustrates non-limiting examples of customized irregular arrangement of REs, in accordance with some aspects of the present disclosure.  FIG. 8A  is an example of a configuration  800  of the RB  402  of  FIG. 4  having resource elements (REs)  404  as described above with reference to  FIG. 4 . The configuration  800  in  FIG. 8A  illustrates a customized and irregular arrangement of REs including an RE  802 , an RE  804 , and RE  806 . In contrast, the arrangement of the REs in  FIG. 4  are regular (pre-defined), as defined by the 3GPP standard. The REs  802 ,  804  and  806  shown in  FIG. 8A  are placed across the RB  402  without any set pattern (repetition or periodicity) to their placement within the RB  402 . In the example configuration  800 , the REs  802 ,  804  and  806  have (time, frequency) coordinates (2,4) (4,9) and (1,12), respectively, and define a non-limiting example of a customized irregular tone pattern. 
       FIG. 8B  is another example of a customized irregular tone arrangement shown as a configuration  850 . In this example, a tone pattern of the configuration  850  is defined by two clusters of REs, including cluster  852  and cluster  860 . The cluster  852  includes an RE  854 , an RE  856  and an RE  858 , while the cluster  860  includes an RE  862 , an RE  864 , an RE  866  and an RE  868 . Each cluster may be defined by REs that are within a threshold location of one another in the RB  402  in time and/or in frequency. For example, the REs  854 ,  856  and  858  of the cluster  852  are separated by at most one subcarrier (time) and/or one OFDM symbol (frequency). Accordingly, the REs  854 ,  856  and  858  are within the threshold of two OFDM symbols and two subcarriers of each other. In another example, the REs  862 ,  864 ,  866  and  868  of the cluster  860  are separated by at most one subcarrier (time) and/or two OFDM symbols (frequency). Accordingly, the REs  862 ,  864 ,  866  and  868  are within the threshold of three OFDM symbols and two subcarriers of each other. Accordingly, the thresholds in time and frequency may not be the same and may be different as shown with reference to example clusters  852  and  860  of  FIG. 8B . The clusters of REs, such as the clusters  852  and  860 , may also be referred to as clumps of REs. While  FIG. 8B  illustrates two example clusters as forming an example tone pattern, the present disclosure is not limited thereto and a tone pattern may be formed of a single cluster or more than two clusters. 
     In one example, the tone pattern can be one of a plurality of existing tone patterns defined by the 3GPP standard. An example of an existing tone pattern is shown in  FIG. 4  (i.e., the REs of the RB  402  designated with an “R”). The existing tone pattern of  FIG. 4  is an example of a regular (e.g., pre-defined) arrangement of REs for the tone pattern shown in  FIG. 4 . In another example, the tone pattern can be a periodic tone pattern, which has not been defined by the 3GPP standard. 
     At operation  730 , the UE  104  can determine a power level (e.g., an EPRE value) for each tone (RE) associated with the tone pattern determined at operation  720 . In one example, the UE  104  may determine an EPRE value (as an example of a power level) for each RE associated with the tone pattern using the trained machine learning model (e.g., the trained neural network  500 ). In another example, the UE  104  may determine the EPRE value based on a mapping table (e.g., stored on a memory of the UE  104 ). For example, the mapping table can include mappings of different RBs and/or different REs within each different RB to a set of EPRE values. In some examples, EPRE values may be expressed in dB. In one instance, each defined resource block and/or subset of REs in a RB may have an assigned EPRE value (e.g., the first three OFDM symbols across all subcarriers may have an EPRE value assigned thereto that is different than the EPRE value assigned to the last three OFDM symbols across all subcarriers in a resource block). Accordingly, each RE of the tone pattern determined at operation  720  may be assigned a corresponding EPRE value (e.g., according to the mapping table). 
     In another example, a list of quantized (discrete) EPRE values with corresponding dB values can be used for REs associated with the tone pattern determined at operation  720 . For example, with 2 bits (e.g.,  0  and  1 ), four different quantized EPRE values may be included in the list and, depending on the selected EPRE value for each RE, a corresponding combination of 2 bits may be used (e.g., transmitted), thus reducing overhead. The quantized EPRE values can be configured by the UE  104  and/or the base station  102 . The quantized EPRE values can be shared between the base station  102  and the UE  104  over radio resource control (RRC) layer. 
     The EPRE values determined at operation  730  may be the same for all REs associated with the tone pattern determined at operation  720 . In another example, the EPRE values for different REs associated with the tone pattern determined at operation  720 , may be different. In yet another example, EPRE values for different REs (e.g., whether the same or different within the same RB) may be different across different RBs. 
     At operation  740 , the UE  104  may facilitate transmission of the reference signal using the tone pattern determined at operation  720 . Furthermore, each RE associated with the tone pattern may have an EPRE value determined at operation  730 . Accordingly, for each reference signal to be transmitted on the DL channel, the UE  104  can determine an optimized tone pattern with optimized EPRE values. In one example, the reference signal for which the UE  104  determines a tone pattern and corresponding EPRE values may be a DL reference signal (e.g., a CSI-RS, a TRS, etc.), which is to be transmitted by the base station  102  to the UE  104  on the downlink channel. For instance, the UE  104  can facilitate the transmission by transmitting (sending) the tone pattern and/or the EPRE values determined at operation  730  to the base station  102 . The base station  102  can then use the tone pattern and/or EPRE values for transmitting the corresponding DL reference signal back to the UE  104 . In some examples, the UE  104  may transmit the determined tone pattern and the associated EPRE values to the base station  102  over one or more of a Physical Uplink Control Channel (PUCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     At operation  750 , the UE  104  can determine if a triggering condition for retraining the neural network  500  has occurred. In one example, the triggering condition can be a change in the mobility status of the UE  104 . In another example, the triggering condition can be the determination of the tone pattern at operation  720  and/or the determination of the associated EPRE values. Examples of such triggering conditions can further include, but are not limited to, a threshold degradation in performance of tone patterns recommended by the neural network  500  for transmission of reference signal (where the threshold may be determined based on experiments and/or empirical studies), channel estimation errors when a reference signal is used for channel estimation (e.g., when channel estimation error reaches and/or exceeds a configurable threshold more than a number of times over a period of time, with the number of times and the period of time being configurable parameters determined based on experiments and/or empirical studies), etc. 
     If, at operation  750 , the UE  104  determines that a triggering condition has not occurred, the process  700  reverts back to operation  710  and operations  710  through  750  may be periodically repeated, for example, depending on the frequency of transmission of reference signals between the base station  102  and the UE  104  (e.g., every subframe (1 ms), every other subframe, etc.). However, if at operation  750 , the UE  104  determines that the triggering condition has occurred, at operation  760 , the UE  104  can retrain the neural network  500  per operations  660  and  670  of  FIG. 6  described above. For instance, the one or more parameters determined at operation  710 , the tone pattern determined at operation  720  and/or the EPRE values determined at operation  730  may be provided as input to the input layer  503  of the neural network  500  for retraining the neural network  500 . In one example, the retraining may involve adjusting coefficients, biases and/or weights of different nodes (e.g., nodes  508 A,  508 B,  508 C) at different network layers of the neural network  500 . Thereafter, the process  700  may revert back to operation  710  and the UE  104  may perform the process of  FIG. 7  periodically depending on the frequency of transmission of reference signals between the base station  102  and the UE  104  (e.g., every subframe (1 ms), every other subframe, etc.). 
     As noted above, the process of determining a tone pattern and/or associated EPRE values using the trained neural network  500  of  FIG. 5  may be performed at the base station  102 .  FIG. 9  is a flow chart of an example process  900  of communicating a customized tone pattern and associated power levels, in accordance with some aspects of the present disclosure. The process  900  of  FIG. 9  is described from the perspective of the base station  102 . It should be understood that the base station  102  may have one or more processors configured to execute one or more computer-readable instructions stored on one or more associated memories of the base station  102  to implement the steps of FIG.  9 . In describing operations of  FIG. 9 , the base station  102  may be a receiving device and the UE  104  may be a transmitting device. 
     At operation  910 , the base station  102  determines one or more parameters associated with communications between the base station  102  and the UE  104 . Such communications between the base station  102  and the UE  104  can be over a communication channel used over a duration of time (e.g., a current communication channel between the base station  102  and the UE  104 ). As described above, the one or more parameters can include, but are not limited to, a location of the UE  104 , an environmental condition associated with the location of the UE  104 , a location of the base station  102 , an environmental condition associated with the location of the base station  102 , indoor/outdoor channel, multipath characteristics of the channel, a mobility status of the UE  104  (e.g., how fast the UE  104  is moving toward or away from the base station  102 , etc.), various measurements made by the base station  102  and/or the UE  104  using previously transmitted reference signals (e.g., tone patterns used in previous RBs for transmission of reference signals), EPRE values associated with previously utilized tone patterns, any combination thereof, and/or other parameters. 
     At operation  920 , the base station  102  determines a tone pattern for a reference signal for use in future communication(s) between the base station  102  and the UE  104 . In one example, the base station  102  determines the tone pattern based on the one or more parameters determined at operation  910 . The tone pattern may identify one or more symbols and one or more locations within a resource block for the one or more symbols to be placed. In one example, the base station  102  may determine the tone pattern using the trained machine learning model (e.g., the trained neural network  500 ) of  FIG. 5 . As described above, the trained machine learning model can receive as input the one or more parameters determined at operation  910  and provide as output the tone pattern at operation  920 . In another example, one or more signal processing may be applied to determine the tone pattern. For example, the base station  102  can have advance receiver capabilities built therein allowing the base station  102  to use fewer tones for a reference signal (e.g., which can be used for channel estimation). 
     The tone pattern can be for an UL reference signal (e.g., a DMRS or other UL reference signal) to be transmitted by the UE  104  to the base station  102  In one example, the tone pattern can be a customized irregular arrangement of REs with different (time, frequency) coordinates. Two non-limiting examples of customized irregular tone pattern arrangements have been described above with reference to  FIGS. 8A  and B. In another example, the tone pattern can be one of a plurality of existing tone patterns defined by the 3GPP standard. An example of an existing tone pattern is shown in  FIG. 4  (i.e., REs of the RB  402  designated with an “R”). In another example, the tone pattern can be a pre-defined regular tone pattern that has not been defined by the 3GPP standard. 
     At operation  930 , the base station  102  can determine a power level (e.g., an EPRE value) for each tone (RE) associated with the tone pattern determined at operation  920 . In one example, the base station  102  may determine the EPRE value for each RE associated with the tone pattern using the trained machine learning model (e.g., the trained neural network  500 ). In another example, the base station  102  may determine the EPRE value based on predefined values provided in a mapping table (e.g., stored on a memory of the base station  102 ). For example, the mapping table can include mappings of different RBs and/or different REs within each different RB to pre-specified EPRE values. In some examples, EPRE values may be expressed in dB. In one example, each defined resource block and/or subset of REs in a RB may have an assigned EPRE value (e.g., the first three OFDM symbols across all subcarriers may have an EPRE value assigned thereto that is different than the EPRE value assigned to the last three OFDM symbols across all subcarriers in a resource block). Accordingly, each RE of the tone pattern determined at operation  920  may be assigned a corresponding EPRE value (e.g., according to the mapping table). 
     In another example, a list of quantized (discrete) EPRE values with corresponding dB values can be used for REs associated with the tone pattern determined at operation  920 . For example, with 2 bits (e.g., 0 and 1), four different quantized EPRE values may be included in such list and depending on the selected EPRE value for each RE, a corresponding combination of 2 bits may be used, thus reducing overhead. The quantized EPRE values can be configured by the UE  104  and/or the base station  102 . The quantized EPRE values can be shared between the base station  102  and the UE  104  over radio resource control (RRC) layer. 
     The EPRE values determined at operation  930  may be the same for all REs associated with the tone pattern determined at operation  920 . In another example, the EPRE values for different REs associated with the tone pattern determined at operation  920 , may be different. In yet another example, EPRE values for different REs (whether the same or different within the same RB) may be different across different RBs. 
     At operation  940 , the base station  102  may facilitate transmission of the reference signal using the tone pattern determined at operation  920 . Furthermore, each RE associated with the tone pattern may have an EPRE value determined at operation  930 . Accordingly, for each reference signal to be transmitted on the UL channel, an optimized tone pattern with optimized EPRE values is determined. In one example, the reference signal for which the base station  102  determines a tone pattern and corresponding EPRE values may be an UL reference signal (e.g., a DMRS, etc.), which is to be transmitted by the UE  104  to the base station  102  on the uplink channel. For instance, the base station  102  facilitates the transmission by transmitting (sending) the determined tone pattern and/or the EPRE values determined at operation  930 , to the UE  104 . The UE  104  can then use the tone pattern and/or EPRE values for transmitting the corresponding UL reference signal back to the base station  102 . In this instance, the base station  102  may transmit the determined tone pattern and the associated EPRE values to the UE  104  over one or more of a Physical Downlink Control Channel (PDCCH), MAC Control Element (MAC-CE), or a Radio Resource Control layer. 
     At operation  950 , the base station  102  can determine if a triggering condition for retraining the neural network  500  has occurred. In one example, the triggering condition can be a change in the mobility status of the UE  104 . In another example, the triggering condition can be the determination of the tone pattern at operation  920  and/or the determination of the associated EPRE values. Examples of such triggering conditions can further include, but are not limited to, a threshold degradation in performance of tone patterns recommended by the neural network  500  for transmission of reference signal (where the threshold may be determined based on experiments and/or empirical studies), channel estimation errors when a reference signal is used for channel estimation (e.g., when channel estimation error reaches and/or exceeds a configurable threshold more than a number of times over a period of time, with the number of times and the period of time being configurable parameters determined based on experiments and/or empirical studies), etc. 
     If, at operation  950 , the base station  102  determines that a triggering condition has not occurred, the process  900  reverts back to operation  910  and operations  910  through  950  may be periodically repeated, for example, depending on the frequency of transmission of reference signals between the base station  102  and the UE  104 , e.g., every subframe (1 ms), every other subframe, etc. However, if at operation  950 , the base station  102  determines that the triggering condition has occurred, at operation  960 , the base station  102  can retrain the neural network  500  per operations  660  and  670  of  FIG. 6  described above. For instance, the one or more parameters determined at operation  910 , the tone pattern determined at operation  920  and/or the EPRE values determined at operation  930  may be provided to the input layer  503  of the neural network  500  for retraining the neural network  500 . In one example, the retraining may involve adjusting coefficients, biases and/or weights of different nodes (e.g., nodes  508 A,  508 B,  508 C) at different network layers of the neural network  500 . Thereafter, the process  900  may revert back to operation  910  and the base station  102  may perform the process of  FIG. 9  periodically depending on the frequency of transmission of reference signals between the base station  102  and the UE  104 , e.g., every subframe (1 ms), every other subframe, etc. 
       FIG. 10  is a flow chart of an example process  1000  of communicating a customized tone pattern and associated power levels for transmission of reference signals, in accordance with some aspects of the present disclosure. The process  1000  of  FIG. 10  is described from the perspective of a receiving device, which in some examples can be the base station  102  or the UE  104 . Furthermore, a transmitting device referenced in the description of  FIG. 10  can be one of the base station  102  or the UE  104  in some examples. 
     At operation  1010 , the process  1000  includes determining, by a receiving device, a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device. Each tone of the tone pattern can occupy a resource element in a resource block. In some cases, the receiving device can determine the tone pattern using a machine learning model. In some cases, the receiving device can determine the tone pattern as an irregular combination of a subset of resource elements in the resource block. In some aspects, the irregular combination of the subset of resource elements includes at least two clusters of resource elements. For instance, in each cluster, corresponding resource elements are within a threshold location of one another in at least one of time and frequency. In one illustrative example referring to  FIG. 8 , the REs  854 ,  856  and  858  of the cluster  852  are separated by at most one subcarrier (time) and/or one OFDM symbol (frequency). In some aspects, the receiving device can determine the tone pattern as one of a set of pre-defined tone patterns for the reference signal. In some cases, the reference signal is one or more of a Channel State Information-Resource Element (CSI-RS), a Demodulation Reference Signal (DMRS), and a Sounding Reference Signal (SRS). 
     At operation  1020 , the process  1000  includes determining, by the receiving device, a plurality of power levels for the tone pattern. The plurality of power levels can include a respective power level determined for each resource element associated with the tone pattern. In some cases, the respective power level for each resource element can be determined using a machine learning model. In some aspects, the receiving device can generate a mapping between resource blocks and power levels for resource elements in each of the resource blocks. The receiving device can determine the respective power level for each resource element of the resource block based on the mapping. In some cases, the receiving device can determine the respective power level for each resource element of the resource block using quantized power level values. In some aspects, the quantized power level values can be exchanged between the receiving device and the transmitting device over a Radio Resource Control (RRC) layer. 
     At operation  1030 , the process  1000  includes transmitting, by the receiving device, one or more of the tone pattern or the plurality of power levels to the transmitting device. For instance, the process  1000  can include transmitting, by the receiving device, the tone pattern, the plurality of power levels, or the tone pattern and the plurality of power levels to the transmitting device. In some cases, the receiving device is a user device and the transmitting device is a base station. In some cases, the receiving device is a base station and the transmitting device is a user device. In some cases, the receiving device (e.g., a user device, such as a UE device) can transmit the tone pattern and the plurality of power levels to the transmitting device (e.g., a base station, such as a gNB) over one or more of a Physical Uplink Control Channel (PUCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. In some cases, the receiving device (e.g., a base station, such as a gNB) can transmit the tone pattern and the plurality of power levels to the transmitting device (e.g., a user device, such as a UE device) over one or more of a Physical Downlink Control Channel (PDCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     At operation  1040 , the process may optionally include receiving, by the receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. In some cases, the transmitting device can receive the tone pattern and the plurality of power levels from the receiving device and in response, the transmitting device can send the reference signal back to the receiving device. For example, the reference signal can be sent over resource elements that correspond to the tone pattern and at the determined power levels. 
       FIG. 11  is a flow chart illustrating an example of a process of communicating a reference signal using a tone pattern and associated power levels, in accordance with some aspects of the present disclosure. The process  1100  of  FIG. 11  is described from the perspective of a transmitting device, which in some examples can be the base station  102  or the UE  104 . Furthermore, a receiving device referenced in the description of  FIG. 11  can be one of the base station  102  or the UE  104  in some examples. 
     At operation  1110 , the process  1100  includes receiving, by a transmitting device, a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block. In one example, the transmitting device may receive the tone pattern from a receiving device. In some cases, the receiving device (e.g., a user device, such as a UE device) can transmit the tone pattern to the transmitting device (e.g., a base station, such as a gNB) over one or more of a Physical Uplink Control Channel (PUCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. In some cases, the receiving device (e.g., a base station, such as a gNB) can transmit the tone pattern to the transmitting device (e.g., a user device, such as a UE device) over one or more of a Physical Downlink Control Channel (PDCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     Each tone of the tone pattern can occupy a resource element in a resource block. In some cases, the receiving device can determine the tone pattern using a machine learning model. In some cases, the receiving device can determine the tone pattern as an irregular combination of a subset of resource elements in the resource block. In some aspects, the irregular combination of the subset of resource elements includes at least two clusters of resource elements. For instance, in each cluster, corresponding resource elements are within a threshold location of one another in at least one of time and frequency. In one illustrative example referring to  FIG. 8 , the REs  854 ,  856  and  858  of the cluster  852  are separated by at most one subcarrier (time) and/or one OFDM symbol (frequency). In some aspects, the receiving device can determine the tone pattern as one of a set of pre-defined tone patterns for the reference signal. In some cases, the reference signal is one or more of a Channel State Information-Resource Element (CSI-RS), a Demodulation Reference Signal (DMRS), and a Sounding Reference Signal (SRS). 
     At operation  1120 , the process  1100  includes receiving, by the transmitting device, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern. In one example, the transmitting device may receive the plurality of power levels from the receiving device. In some cases, the receiving device (e.g., a user device, such as a UE device) can transmit the plurality of power levels to the transmitting device (e.g., a base station, such as a gNB) over one or more of a Physical Uplink Control Channel (PUCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. In some cases, the receiving device (e.g., a base station, such as a gNB) can transmit the plurality of power levels to the transmitting device (e.g., a user device, such as a UE device) over one or more of a Physical Downlink Control Channel (PDCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     The plurality of power levels can include a respective power level determined for each resource element associated with the tone pattern. In some cases, the respective power level for each resource element can be determined using a machine learning model. In some aspects, the receiving device can generate a mapping between resource blocks and power levels for resource elements in each of the resource blocks. The receiving device can determine the respective power level for each resource element of the resource block based on the mapping. In some cases, the receiving device can determine the respective power level for each resource element of the resource block using quantized power level values. In some aspects, the quantized power level values can be exchanged between the receiving device and the transmitting device over a Radio Resource Control (RRC) layer. 
     At operation  1130 , the process  1100  includes transmitting, by the transmitting device and to the receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. In some cases, once the transmitting device receives the tone pattern and the plurality of power levels from the receiving device and in response, the transmitting device can send the reference signal back to the receiving device. For example, the reference signal can be sent over resource elements that correspond to the tone pattern and at the determined one or more power levels. 
     With various examples of tone pattern and/or associated power levels optimization described above with reference to  FIGS. 4-11 ,  FIG. 12  will now be described illustrating components of the UE  104 . 
       FIG. 12  illustrates an example of a computing system  1270  of a user equipment (UE)  1207 . UE  1207  may be the same as the UE  104  described above with reference to  FIGS. 1-10 . In some examples, the UE  1207  can include a mobile phone, router, tablet computer, laptop computer, tracking device, wearable device (e.g., a smart watch, glasses, an XR device, etc.), Internet of Things (IoT) device, and/or other device used by a user to communicate over a wireless communications network. The computing system  1270  includes software and hardware components that can be electrically coupled via a bus  1289  (or may otherwise be in communication, as appropriate). For example, the computing system  1270  includes one or more processors  1284 . The one or more processors  1284  can include one or more CPUs, ASICs, FPGAs, APs, GPUs, VPUs, NSPs, microcontrollers, dedicated hardware, any combination thereof, and/or other processing device or system. The bus  1289  can be used by the one or more processors  1284  to communicate between cores and/or with the one or more memory devices  1286 . 
     The computing system  1270  may also include one or more memory devices  1286 , one or more digital signal processors (DSPs)  1282 , one or more subscriber identity modules (SIMS)  1274 , one or more modems  1276 , one or more wireless transceivers  1278 , an antenna  1287 , one or more input devices  1272  (e.g., a camera, a mouse, a keyboard, a touch sensitive screen, a touch pad, a keypad, a microphone, and/or the like), and one or more output devices  1280  (e.g., a display, a speaker, a printer, and/or the like). 
     The one or more wireless transceivers  1278  can transmit and receive wireless signals (e.g., signal  1288 ) via antenna  1287  to and from one or more other devices, such as one or more other UEs, network devices (e.g., base stations such as eNBs and/or gNBs, WiFi routers, etc.), cloud networks, and/or the like. As described herein, the one or more wireless transceivers  1278  can include a combined transmitter/receiver, discrete transmitters, discrete receivers, or any combination thereof. In some examples, the computing system  1270  can include multiple antennae. The wireless signal  1288  may be transmitted via a wireless network. The wireless network may be any wireless network, such as a cellular or telecommunications network (e.g., 3G, 4G, 5G, etc.), wireless local area network (e.g., a WiFi network), a Bluetooth™ network, and/or other network. In some examples, the one or more wireless transceivers  1278  may include an radio frequency (RF) front end including one or more components, such as an amplifier, a mixer (also referred to as a signal multiplier) for signal down conversion, a frequency synthesizer (also referred to as an oscillator) that provides signals to the mixer, a baseband filter, an analog-to-digital converter (ADC), one or more power amplifiers, among other components. The RF front-end can generally handle selection and conversion of the wireless signals  1288  into a baseband or intermediate frequency and can convert the RF signals to the digital domain. 
     In some cases, the computing system  1270  can include a coding-decoding device (or CODEC) configured to encode and/or decode data transmitted and/or received using the one or more wireless transceivers  1278 . In some cases, the computing system  1270  can include an encryption-decryption device or component configured to encrypt and/or decrypt data (e.g., according to the AES and/or DES standard) transmitted and/or received by the one or more wireless transceivers  1278 . 
     The one or more SIMS  1274  can each securely store an International Mobile Subscriber Identity (IMSI) number and a related key assigned to the user of the UE  1207 . The IMSI and the key can be used to identify and authenticate the subscriber when accessing a network provided by a network service provider or operator associated with the one or more SIMS  1274 . The one or more modems  1276  can modulate one or more signals to encode information for transmission using the one or more wireless transceivers  1278 . The one or more modems  1276  can also demodulate signals received by the one or more wireless transceivers  1278  in order to decode the transmitted information. In some examples, the one or more modems  1276  can include a 4G (or LTE) modem, a 5G (or NR) modem, a Bluetooth™ modem, a modem configured for vehicle-to-everything (V2X) communications, and/or other types of modems. In some examples, the one or more modems  1276  and the one or more wireless transceivers  1278  can be used for communicating data for the one or more SIMS  1274 . 
     The computing system  1270  can also include (and/or be in communication with) one or more non-transitory machine-readable storage media or storage devices (e.g., one or more memory devices  1286 ), which can include, without limitation, local and/or network accessible storage, a disk drive, a drive array, an optical storage device, a solid-state storage device such as a RAM and/or a ROM, which can be programmable, flash-updateable and/or the like. Such storage devices may be configured to implement any appropriate data storage, including without limitation, various file systems, database structures, and/or the like. 
     In various embodiments, functions may be stored as one or more computer-program products (e.g., instructions or code) in memory device(s)  1286  and executed by the one or more processor(s)  1284  and/or the one or more DSPs  1282 . The computing system  1270  can also include software elements (e.g., located within the one or more memory devices  1286 ), including, for example, an operating system, device drivers, executable libraries, and/or other code, such as one or more application programs, which may comprise computer programs implementing the functions provided by various embodiments, and/or may be designed to implement methods and/or configure systems, as described herein. 
     Specific details are provided in the description above to provide a thorough understanding of the embodiments and examples provided herein, but those skilled in the art will recognize that the application is not limited thereto. Thus, while illustrative embodiments of the application have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art. Various features and aspects of the above-described application may be used individually or jointly. Further, embodiments can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. For the purposes of illustration, methods were described in a particular order. It should be appreciated that in alternate embodiments, the methods may be performed in a different order than that described. 
     For clarity of explanation, in some instances the present technology may be presented as including individual functional blocks comprising devices, device components, steps or routines in a method embodied in software, or combinations of hardware and software. Additional components may be used other than those shown in the figures and/or described herein. For example, circuits, systems, networks, processes, and other components may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments. 
     Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. 
     Individual embodiments may be described above as a process or method which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed, but could have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function. 
     Processes and methods according to the above-described examples can be implemented using computer-executable instructions that are stored or otherwise available from computer-readable media. Such instructions can include, for example, instructions and data which cause or otherwise configure a general purpose computer, special purpose computer, or a processing device to perform a certain function or group of functions. Portions of computer resources used can be accessible over a network. The computer executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, firmware, and source code. Examples of computer-readable media that may be used to store instructions, information used, and/or information created during methods according to described examples include magnetic or optical disks, flash memory, USB devices provided with non-volatile memory, networked storage devices, and so on. 
     In some embodiments the computer-readable storage devices, mediums, and memories can include a cable or wireless signal containing a bitstream and the like. However, when mentioned, non-transitory computer-readable storage media expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals per se. 
     Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof, in some cases depending in part on the particular application, in part on the desired design, in part on the corresponding technology, etc. 
     The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed using hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof, and can take any of a variety of form factors. When implemented in software, firmware, middleware, or microcode, the program code or code segments to perform the necessary tasks (e.g., a computer-program product) may be stored in a computer-readable or machine-readable medium. A processor(s) may perform the necessary tasks. Examples of form factors include laptops, smart phones, mobile phones, tablet devices or other small form factor personal computers, personal digital assistants, rackmount devices, standalone devices, and so on. Functionality described herein also can be embodied in peripherals or add-in cards. Such functionality can also be implemented on a circuit board among different chips or different processes executing in a single device, by way of further example. 
     The instructions, media for conveying such instructions, computing resources for executing them, and other structures for supporting such computing resources are example means for providing the functions described in the disclosure. 
     The techniques described herein may also be implemented in electronic hardware, computer software, firmware, or any combination thereof. Such techniques may be implemented in any of a variety of devices such as general purposes computers, wireless communication device handsets, or integrated circuit devices having multiple uses including application in wireless communication device handsets and other devices. Any features described as modules or components may be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be realized at least in part by a computer-readable data storage medium comprising program code including instructions that, when executed, performs one or more of the methods, algorithms, and/or operations described above. The computer-readable data storage medium may form part of a computer program product, which may include packaging materials. The computer-readable medium may comprise memory or data storage media, such as random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic or optical data storage media, and the like. The techniques additionally, or alternatively, may be realized at least in part by a computer-readable communication medium that carries or communicates program code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer, such as propagated signals or waves. 
     The program code may be executed by a processor, which may include one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, an application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Such a processor may be configured to perform any of the techniques described in this disclosure. A general purpose processor may be a microprocessor; but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure, any combination of the foregoing structure, or any other structure or apparatus suitable for implementation of the techniques described herein. 
     The foregoing description provides example embodiments only, and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the example embodiments will provide those skilled in the art with an enabling description for implementing an example embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the application as set forth in the appended claims. 
     The terms “exemplary” and/or “example” are used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” and/or “example” is not necessarily to be construed as preferred or advantageous over other aspects. Likewise, the term “aspects of the disclosure” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. 
     One of ordinary skill will appreciate that the less than (“&lt;”) and greater than (“&gt;”) symbols or terminology used herein can be replaced with less than or equal to (“≤”) and greater than or equal to (“≥”) symbols, respectively, without departing from the scope of this description. 
     Where components are described as being “configured to” perform certain operations, such configuration can be accomplished, for example, by designing electronic circuits or other hardware to perform the operation, by programming programmable electronic circuits (e.g., microprocessors, or other suitable electronic circuits) to perform the operation, or any combination thereof. 
     The phrase “coupled to” refers to any component that is physically connected to another component either directly or indirectly, and/or any component that is in communication with another component (e.g., connected to the other component over a wired or wireless connection, and/or other suitable communication interface) either directly or indirectly. 
     Claim language or other language reciting “at least one of” a set and/or “one or more” of a set indicates that one member of the set or multiple members of the set (in any combination) satisfy the claim. For example, claim language reciting “at least one of A and B” or “at least one of A or B” means A, B, or A and B. In another example, claim language reciting “at least one of A, B, and C” or “at least one of A, B, or C” means A, B, C, or A and B, or A and C, or B and C, or A and B and C. The language “at least one of” a set and/or “one or more” of a set does not limit the set to the items listed in the set. For example, claim language reciting “at least one of A and B” or “at least one of A or B” can mean A, B, or A and B, and can additionally include items not listed in the set of A and B. 
     Illustrative aspects of the disclosure include: 
     Aspect 1: A method of wireless communication including determining, by a receiving device, a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; determining, by the receiving device, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmitting, by the receiving device, one or more of the tone pattern or the plurality of power levels to the transmitting device. 
     Aspect 2: The method of aspect 1, further including receiving, by the receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     Aspect 3: The method of any of aspects 1 or 2, further including determining the respective power level for each resource element using a machine learning model. 
     Aspect 4: The method of any of aspects 1 to 3, further including generating, by the receiving device, a mapping between resource blocks and power levels for resource elements in each of the resource blocks; and determining, by the receiving device, the respective power level for each resource element of the resource block based on the mapping. 
     Aspect 5: The method of any of aspects 1 to 4, further including determining, by the receiving device, the respective power level for each resource element of the resource block using quantized power level values 
     Aspect 6: The method of any of aspects 1 to 5, wherein the quantized power level values are exchanged between the receiving device and the transmitting device over a Radio Resource Control (RRC) layer. 
     Aspect 7: The method of any of aspects 1 to 6, further including determining the tone pattern using a machine learning model. 
     Aspect 8: The method of any of aspects 1 to 7, wherein the tone pattern is determined as one of a set of pre-defined tone patterns for the reference signal. 
     Aspect 9: The method of any of aspects 1 to 8, wherein the tone pattern is determined as an irregular combination of a subset of resource elements in the resource block. 
     Aspect 10: The method of any of aspects 1 to 9, wherein the irregular combination of the subset of resource elements includes at least two clusters of resource elements, wherein in each cluster, corresponding resource elements are within a threshold location of one another in at least one of time and frequency. 
     Aspect 11: The method of any of aspects 1 to 10, wherein the respective power level for each resource element in the resource block is different than respective power levels in another resource block used for transmission of the reference signal. 
     Aspect 12: The method of any of aspects 1 to 11, wherein the reference signal is one or more of a Channel State Information-Resource Element (CSI-RS), a Demodulation Reference Signal (DMRS), and a Sounding Reference Signal (SRS). 
     Aspect 13: The method of any of aspects 1 to 12, wherein the receiving device is a user device and the transmitting device is a base station. 
     Aspect 14: The method of any of aspects 1 to 13, wherein the receiving device is a base station and the transmitting device is user device. 
     Aspect 15: The method of any of aspects 1 to 14, wherein the receiving device transmits the tone pattern and the plurality of power levels to the transmitting device over one or more of a Physical Uplink Control Channel (PUCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     Aspect 16: The method of any of aspects 1 to 15, wherein the receiving device transmits the tone pattern and the plurality of power levels to the transmitting device over one or more of a Physical Downlink Control Channel (PDCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     Aspect 17: An apparatus includes one or more memories having computer-readable instructions stored therein, and one or more processors, the one or more processors are configured to execute the computer-readable instructions to determine a tone pattern for a reference signal for use in wireless communications between the apparatus and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; determine a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmit one or more of the tone pattern or the plurality of power levels to the transmitting device. 
     Aspect 18: The apparatus of aspect 17, wherein the one or more processors are further configured to execute the computer-readable instructions to receive the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     Aspect 19: The apparatus of any of aspects 17 or 18, wherein the one or more processors are configured to execute the computer readable instructions to determine the respective power level for each resource element using a machine learning model. 
     Aspect 20: The apparatus of any of aspects 17 to 19, wherein the one or more processors are further configured to execute the computer-readable instructions to generate a mapping between resource blocks and power levels for resource elements in each of the resource blocks; and determine the respective power level for each resource element of the resource block based on the mapping. 
     Aspect 21: The apparatus of any of aspects 17-20, wherein the one or more processors are further configured to execute the computer-readable instructions to determine the respective power level for each resource element of the resource block using quantized power level values. 
     Aspect 22: The apparatus of any of aspects 17-21, wherein the quantized power level values are exchanged between the apparatus and the transmitting device over a Radio Resource Control (RRC) layer. 
     Aspect 23: The apparatus of any of aspects 17-22, wherein the one or more processors are further configured to execute the computer-readable instructions to determine the tone pattern using a machine learning model. 
     Aspect 24: The apparatus of any of aspects 17-23, wherein the tone pattern is determined as one of a set of pre-defined tone patterns for the reference signal. 
     Aspect 25: The apparatus of any of aspects 17-24, wherein the tone pattern is determined as an irregular combination of a subset of resource elements in the resource block. 
     Aspect 26: The apparatus of any of aspects 17-25, wherein the irregular combination of the subset of resource elements includes at least two clusters of resource elements, wherein in each cluster, corresponding resource elements are within a threshold location of one another in at least one of time and frequency. 
     Aspect 27: The apparatus of any of aspects 17-26, wherein the respective power level for each resource element in the resource block is different than respective power levels in another resource block used for transmission of the reference signal. 
     Aspect 28: The apparatus of any of aspects 17-27, wherein the reference signal is one or more of a Channel State Information-Resource Element (CSI-RS), a Demodulation Reference Signal (DMRS), and a Sounding Reference Signal (SRS). 
     Aspect 29: The apparatus of any of aspects 17-28, wherein the receiving device is a user device and the transmitting device is a base station. 
     Aspect 30: The apparatus of any of aspects 17-29, wherein the receiving device is a base station and the transmitting device is user device. 
     Aspect 31: The apparatus of any of aspects 17-30, wherein the apparatus is configured to transmit the tone pattern and the plurality of power levels to the transmitting device over one or more of a Physical Uplink Control Channel (PUCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     Aspect 32: The apparatus of any of aspects 17-31, wherein the apparatus is configured to transmit the tone pattern and the plurality of power levels to the transmitting device over one or more of a Physical Downlink Control Channel (PDCCH), MAC Control Element (MAC-CE), or Radio Resource Control layer. 
     Aspect 33: One or more non-transitory computer-readable media comprising computer-readable instruction, which when executed by one or more processors of a receiving device, cause the receiving device to perform operations according to any of aspects 1 to 15. 
     Aspect 34: An apparatus including means for performing operations according to any of aspects 1 to 15. 
     Aspect 35: A method of wireless communication including receiving, by a transmitting device, a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; receiving, by the transmitting device, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmitting, by the transmitting device and to a receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     Aspect 36: An apparatus including one or more memories having computer-readable instructions stored therein, and one or more processors, the one or more processors are configured to execute the computer-readable instructions to receive a tone pattern for a reference signal for use in wireless communications between the receiving device and a transmitting device, each tone of the tone pattern occupying a resource element in a resource block; receive, a plurality of power levels for the tone pattern, the plurality of power levels including a respective power level determined for each resource element associated with the tone pattern; and transmit, to a receiving device, the reference signal using the tone pattern and having one or more of the plurality of power levels. 
     Aspect 37: One or more non-transitory computer-readable media comprising computer-readable instruction, which when executed by one or more processors of a receiving device, cause the receiving device to perform operations according to any of aspects 35 or 36. 
     Aspect 38: An apparatus including means for performing operations according to any of aspects 35 or 36.