WO2023033836A1

WO2023033836A1 - Apparatus and method of performing an anti-multipath function to calibrate an antenna array

Info

Publication number: WO2023033836A1
Application number: PCT/US2021/049091
Authority: WO
Inventors: Arkady Molev-Shteiman; Yi-Hsiu Wang
Original assignee: Zeku, Inc.
Priority date: 2021-09-03
Filing date: 2021-09-03
Publication date: 2023-03-09

Abstract

According to one aspect of the present disclosure, an apparatus of wireless communication is provided. The apparatus may include an antenna array. The antenna array may include a transmitter and a receiver configured to receive a measurement signal from the transmitter. The apparatus may include a radio. The radio may include a measurement circuit. The measurement circuit may be configured to estimate a joint delay function associated with the transmitter and receiver based on the measurement signal. The radio may include an anti-multipath circuit. The anti-multipath circuit may be configured to in response to the plurality of beams including a non- line-of-sight (NLOS) beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The radio may include a calibration circuit. The calibration circuit may be configured to calibrate the antenna array based on the channel delay function.

Description

APPARATUS AND METHOD OF PERFORMING AN ANTI-MULTIPATH FUNCTION TO CALIBRATE AN ANTENNA ARRAY BACKGROUND [0001] Embodiments of the present disclosure relate to apparatus and method for wireless communication. [0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. In wireless local area network (WLAN) communication (e.g., such as Wi-Fi) and in cellular communication (e.g., such as the 4th-generation (4G) Long Term Evolution (LTE) and the 5th-generation (5G) New Radio (NR)), the Institute of Electrical and Electronics Engineers (IEEE) and the 3rd Generation Partnership Project (3GPP) define various operations for calibrating an antenna array. SUMMARY [0003] Embodiments of apparatus and method for antenna array calibration are disclosed herein. [0004] According to one aspect of the present disclosure, an apparatus of wireless communication is provided. The apparatus may include an antenna array. The antenna array may include a transmitter and a receiver. The receiver may be configured to receive a measurement signal from the transmitter. The measurement signal may include a plurality of beams. The apparatus may include a radio. The radio may include a measurement circuit. The measurement circuit may be configured to estimate a joint delay function associated with the transmitter and receiver based on the measurement signal. The radio may include an anti-multipath circuit. The anti-multipath circuit may be configured to in response to the plurality of beams including an non- line-of-sight (NLOS) beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The radio may include a calibration circuit. The calibration circuit may be configured to calibrate the antenna array based on the channel delay function. [0005] According to another aspect of the disclosure, a radio chip is provided. The radio chip may include a measurement circuit. The measurement circuit may be configured to estimate a joint delay function associated with the transmitter and receiver based on the measurement signal. The radio chip may include an anti-multipath circuit. The anti-multipath circuit may be configured to in response to the plurality of beams including an NLOS beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The radio chip may include a calibration circuit. The calibration circuit may be configured to calibrate the antenna array based on the channel delay function. [0006] According to yet another aspect of the disclosure, a method of wireless communication is provided. The method may include receiving, by a receiver of an antenna array, a measurement signal from a transmitter of the antenna array, the measurement signal including a plurality of beams. The method may include estimating, by a measurement circuit, a joint delay function associated with the transmitter and receiver based on the measurement signal. The method may include in response to the plurality of beams including an NLOS beam, applying, by an anti- multipath circuit, an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The method may include calibrating, by a calibration circuit, the antenna array based on the channel delay function. BRIEF DESCRIPTION OF THE DRAWINGS [0007] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the pertinent art to make and use the present disclosure. [0008] FIG.1 illustrates an exemplary wireless network, according to some embodiments of the present disclosure. [0009] FIG. 2 illustrates a block diagram of an apparatus including a radio, a wireless network interface, and a host chip, according to some embodiments of the present disclosure. [0010] FIG. 3A illustrates a graphical representation of a joint delay function with oversampling that is an output of an anti-multipath function, according to certain aspects of the present disclosure. [0011] FIG. 3B illustrates an antenna array receiving a plurality of beams, according to some aspects of the disclosure. [0012] FIG.3C illustrates a graphical representation of a time autocorrelation function that set of beam parameters estimation circuits of FIG.2 may apply to a received signal, according to some embodiments of the present disclosure. [0013] FIG.3D illustrates a graphical representation of an angular autocorrelation function that set of beam parameters estimation circuits of FIG.2 may apply to a received signal, according to some embodiments of the present disclosure. [0014] FIG. 3E illustrates a graphical representation of a time-angular autocorrelation function that set of beam parameters estimation circuits of FIG.2 may apply to a received signal, according to some embodiments of the present disclosure. [0015] FIG.3F illustrates a diagram of an acquisition correlation and zoom-in procedure that may be implemented by a set of beam parameter estimation circuits of FIG. 2, according to some embodiments of the present disclosure. [0016] FIG. 3G illustrates a diagram of a beam cluster that includes a superposition of beams, according to some embodiments of the present disclosure. [0017] FIG.3H illustrates a diagram of a correlation cluster identified using the acquisition correlation and zoom-in procedure, according to some embodiments of the present disclosure. [0018] FIG.4 illustrates a flowchart of a method for wireless communication, according to some embodiments of the present disclosure. [0019] FIG. 5 illustrates a block diagram of an exemplary node, according to some embodiments of the present disclosure. [0020] FIG. 6A illustrates a block diagram of receivers and transmitters of an antenna array. [0021] FIG. 6B illustrates a block diagram of channels associated with the antenna array of FIG.6A. [0022] FIG.7 illustrates a graphical illustration of far-field multipath. [0023] Embodiments of the present disclosure will be described with reference to the accompanying drawings. DETAILED DESCRIPTION [0024] Although specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present disclosure. It will be apparent to a person skilled in the pertinent art that the present disclosure can also be employed in a variety of other applications. [0025] It is noted that references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” “some embodiments,” “certain embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of a person skilled in the pertinent art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. [0026] In general, terminology may be understood at least in part from usage in context. For example, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures or characteristics in a plural sense. Similarly, terms, such as “a,” “an,” or “the,” again, may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context. In addition, the term “based on” may be understood as not necessarily intended to convey an exclusive set of factors and may, instead, allow for existence of additional factors not necessarily expressly described, again, depending at least in part on context. [0027] Various aspects of wireless communication systems will now be described with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, units, components, circuits, steps, operations, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, firmware, computer software, or any combination thereof. Whether such elements are implemented as hardware, firmware, or software depends upon the particular application and design constraints imposed on the overall system. [0028] The techniques described herein may be used for various wireless communication networks, such as code division multiple access (CDMA) system, time division multiple access (TDMA) system, frequency division multiple access (FDMA) system, orthogonal frequency division multiple access (OFDMA) system, single-carrier frequency division multiple access (SC- FDMA) system, wireless local area network (WLAN) system, a global navigation satellites system (GNSS), and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio access technology (RAT), such as Universal Terrestrial Radio Access (UTRA), evolved UTRA (E-UTRA), CDMA 2000, etc. A TDMA network may implement a RAT, such as the Global System for Mobile Communications (GSM). An OFDMA network may implement a RAT, such as LTE or NR. A WLAN system may implement a RAT, such as Wi-Fi. The techniques described herein may be used for the wireless networks and RATs mentioned above, as well as other wireless networks and RATs. [0029] GNSS is frequently used for positioning services in various applications, such as pedestrian and vehicular navigation. To accurately determine its position, a user equipment (UE) or station (STA) is generally equipped with a GNSS receiver. The GNSS receiver uses the time difference between the time a signal is received versus when the signal was broadcast by a satellite vehicle (SV) to determine the receiver’s distance from the SV. A GNSS receiver that receives signals from four SVs can determine its position in three-dimensions (3D). Three of the SVs are used to determine latitude, longitude, and height, while a fourth SV is set to synchronize the receiver’s internal clock. [0030] In recent years, research into Angle-of-Arrival (AoA) and Time-of-Arrival (ToA) estimation have attracted significant attention for applications such as radar, sonar, mobile communications, and position estimation. GNSS AoA/ToA techniques typically utilize arrays of multiple antennas to measure the direction of incoming signals from several locations. Multipath and interference are the main sources of errors in positions estimated by GNSS signals. The interfering signals reduce the signal-to-noise ratio (SNR) and can cause receiver failure to detect SV signals. On the other hand, multipath distorts correlation peaks and affects discriminators. [0031] Similar issues may arise when multiple-input multiple-output (MIMO) and/or multi-use-MIMO (MU-MIMO) are used for position estimation. MIMO facilitates parallel delivery of multiple spatially multiplexed data signals, which are referred to as multiple spatial streams. Further, in multi-user MIMO (MU-MIMO), an access point (AP) may simultaneously transmit to multiple client user equipments (UEs), and beamforming may be used for directional signal transmission or reception. In MU-MIMO, the term “downlink” refers to communication, which may occur in parallel, from an AP (e.g., transmitted by the AP) to one or more stations (STAs), while the term “uplink” refers to communication, which may occur in parallel, to an AP (received by the AP) from one or more STAs. [0032] AoA refers to a direction of propagation of a radio-frequency wave incident on an antenna array relative to the orientation of the antenna array. As one example, AoA may be determined based on the Time Difference of Arrival (TDOA) or phase difference measurements of a radio wave received at individual elements of an antenna array. In some embodiments, the AoA may be determined by an STA (e.g., user equipment) based on signals exchanged with another STA (e.g., an access point (AP)). For example, an STA, such as a receiver, may resolve AoA based on signals exchanged with another STA. [0033] The term “Fine Timing Measurement” (FTM) refers to a message exchange protocol that may be used for positioning. FTM involves the exchange of FTM frames for range determination. For example, an initiating STA (e.g., non-AP STA) may start an FTM session and exchange FTM frames with a responding STA (e.g., an AP STA). The initiating STA may measure the time-of-flight (TOF), which is given by half the round trip delay. The initiating STA may determine its range based on exchanged frames, which may include timestamps corresponding to (a) the departure time of the FTM frame from the initiating STA and (b) the arrival time of the FTM frames at the responding station (e.g., an AP) during an FTM session. In some embodiments, such as MIMO/MU-MIMO, parameters such as Angle of Arrival (AoA), doppler speed, and delay may also be used to determine STA position. FTM frames (e.g., from an initiator) may use a dialog token to identify a corresponding FTM/FTM Acknowledgment (e.g., from a responder). FTM frames may include timestamp measurements at the AP and/or at an STA. The timestamp measurements may be used for range calculation and/or position determination. [0034] One or more frame structure and/or fields (OE/IE/data) in frames, broadcast messages, and/or message exchange protocols may be leveraged to determine one or more of (a) whether STA-AP positioning is available and/or whether an AP supports STA-AP positioning; and/or (b) whether AP-AP positioning is available and/or c) whether an AP is currently performing AP-AP positioning. In some embodiments, the disclosed techniques may be embodied in an application on an STA (e.g., an AP STA or a non-STA) as appropriate. The example message flows, frame formats, and/or information elements described herein may be compatible, in some respects, with specifications, diagrams, and guidelines found in some IEEE 802.11 standards. [0035] The AoA and ToA can be estimated using an antenna array of a STA. However, accurate determinations of AoA and/or ToA require accurate knowledge of the received signal, which may be used to calibrate the antenna array. However, due to differences in antenna systems of an antenna array, this requirement is difficult to meet because of mutual coupling between the antenna elements and the dissimilarity of the signal amplitude and phase between antennas, which degrade the AoA/ToA-determination performance. An example of an antenna array is illustrated in FIGs.6A and 6B. [0036] FIG.6A illustrates a block diagram of a conventional antenna array 600. FIG.6B illustrates a block diagram 601 of mutual coupling without the influence of reflection within the antenna array 600 of FIG.6A. Referring to FIG.6A, conventional antenna array 600 may include N receivers 602 and M transmitters 604. Receivers 602 and transmitters 604 may be part of a wireless network interface, e.g., such as an RF chip. [0037] One way to increase the reliability of determining AoA is to estimate normalized transmitter delay functions t_TXm - t_TX1 for one or more transmitter-transmitter pairs and normalized receiver delay functions t_RXn − t_RX1 for one or more receiver-receiver pairs within antenna array 600. Similarly, for ToA, joint delay functions t_TX1 − t_RX1 for one or more transmitter-receiver pairs in the antenna array 600 may be estimated. However, due to imperfections created during manufacture, the receiver 602 and transmitter 604 of each antenna system may have slightly different delay functions. If these delay functions remain unknown, errors in AoA and ToA may occur. [0038] Referring to FIG.6B, the delay function t_n,m between each transmitter-receiver pair may be measured. For simplicity of discussion, the delay function for two receivers 602 and two transmitters 604 will be discussed in terms of calibration. Thus, in this example, the total number of such experiments is four, as shown below in expression (1): (^1),

where t_CHm,n is the delay caused by mutual coupling between transmitter m and receiver n. [0039] In situations without the influence of reflection (e.g., multipath) the channel between antennas is known, as shown in FIG.6B. The first measurement provides the joint delay function between TX 1604-1 and RX 1602-1, as shown below in equation (2): (2).

[0040] Thus, using equation (2), the residual three equations of (1) may be normalized, as shown below in (3): (3),

which is equivalent to expression (4): _(4).

[0041] Therefore, the normalized transmitter-transmitter delay function tTX2 – tTX1 and the normalized receiver-receiver delay function t_RX2 – t_RX1 according to expression (5): (5).

[0042] Then, the delay function between transmitter n and receiver m t_n,m can be measured for subcarrier to estimate the channel ℎ_n,m ( ω ) between transmitter n and receiver m, where ω is the frequency. A Fourier transform may then be applied such that the transfer signal from frequency to time domain is obtained: ℎ_n,m ( t ). Further, the ToA as a maximum of channel impulse response time domain may be estimated according to expression (6): (_6).

[0043] However, estimating the normalized and joint delay functions can be challenging in scenarios where signal reflections create a multipath scenario. This is because multipath can introduce errors in the delay function measurement. Two types of multipath scenarios include far- field multipath and near-field multipath. FIG.7 illustrates a graphical representation 700 of a far- field multipath scenario. Far-field multipath may create multiple channel impulse responses, as seen in FIG.7. To suppress the influence of far-field multipath on the delay measurement, the first arriving line-of-sight (LOS) beam 750 may be selected for use in estimating the delay functions. [0044] Near-field multipath presents additional challenges, however. This is due to beam superposition. Beam superposition occurs when multiple overlapping beams are received in the same signal. An example of a near-field multipath scenario with beam superposition is illustrated in FIG. 3G. Present techniques fail to provide a mechanism by which to identify the maximum channel impulse response time, and hence, the LOS beam, within a superposition of beams. [0045] Thus, there exists an unmet need for a technique to calibrate an antenna array in scenarios in which beam superposition in a near-field multipath scenario occurs. [0046] To overcome these and other challenges, the present disclosure provides a calibration technique that can be applied in near-field multipath scenarios. For example, the present technique may apply an anti-multipath function to a transfer function in order to identify the maximum channel impulse response within a signal that includes a superposition of beams. The anti-multipath function may include any function that is configured to identify the maximum channel impulse response peak within a super position of beams. The maximum channel impulse response peak may be used to identify the LOS beam within the signal, which may be used to accurately calibrate the antenna array. Additional details of these and other techniques are provided below in connection with FIGs.1-5. [0047] Although some embodiments are described herein in connection with a WLAN or GNSS communication system, the same or similar techniques may be applied to a cellular communication system, as well. For example, a UE that receives a signal from a 5G NR base station via beamforming and/or millimeter-wave (mmW) signaling may experience multipath issues as these beams may reflect off nearby objects, which can deteriorate the accuracy of antenna calibration. Thus, the techniques described below may apply to calibrating an antenna array of a UE within a cellular communication system without departing from the scope of the present disclosure. [0048] FIG.1 shows a simplified architecture of a wireless communication system 100 in accordance with certain embodiments presented herein. System 100 may include non-access point (AP) stations (STAs) such as UEs 120-1 through 120-n (collectively referred to as UEs 120), and AP STAs such as APs 140-1 through 140-4 (collectively referred to as APs 140), which may communicate over a wireless communication network 130. Examples of UEs 120 may include, e.g., smartphones, vehicles, wearable devices, laptops, or any other device that can provide a navigation function to a user. In some embodiments, wireless communication network 130 may take the form of and/or may include one or more wireless local area networks (WLANs) or the internet. In some embodiments, UEs 120 and/or APs 140 may communicate with server 150 via wireless communication network 130. While system 100 illustrates some UEs 120 and APs 140, the number of UEs 120 and APs 140 in a wireless communication network (e.g., a WLAN) may be varied in accordance with various system parameters. In general, system 100 may include a smaller or larger number of UEs 120 and/or APs 140. [0049] In some embodiments, as outlined above, UE 120 may receive, measure and decode signals from one or more satellite vehicles (SVs) 180-1 through 180-4 and thereby, as is well known in the art, obtain a position fix, an accurate absolute time reference (such as global positioning system (GPS) time, Coordinated Universal Time (UTC) or a time for another GNSS which may be accurate to 50 nanoseconds (ns) or better in some embodiments) and a timing reference uncertainty. In some embodiments, the GNSS position fix, absolute time reference and/or absolute time synchronization information (e.g., GPS time, GNSS time, or UTC time) and timing reference uncertainty may be provided (e.g., by one or more UEs 120) to APs 140 by sending signaling information to APs 140 that includes a time reference such as using, for example, the Internet Network Time Protocol (NTP), IEEE 1588 Precision Time Protocol (PTP) and/or ITU- T Synchronous Ethernet. In some embodiments, APs 140, which receive the position fix, absolute time reference, and time reference uncertainty information, may optionally, modify the time reference uncertainty information to account for other inaccuracies and/or processing delays. In some embodiments, the absolute time and time reference uncertainty information may be modified by APs 140 based on the distance of UE 120 from AP 140, which may be determined from the position fix. For example, APs 140 may modify time reference uncertainty to adjust for Short Interframe Spacing (SIFS) delays, if appropriate. The terms “SIFS interval” or “SIFS delay” may refer to the amount of time (e.g., in microseconds) it takes for a wireless interface to process a received frame and to respond with a response frame. A SIFS interval may consist of the time delay arising from receiver radio frequency (RF) processing, Physical Layer Convergence Procedure (PLCP) delay, and the Medium Access Control (MAC) processing delay, which may depend on the physical layer used. [0050] In some embodiments, APs 140 and/or UEs 120 that are synchronized to or have access to a common time reference may transmit or re-transmit (unicast, multicast, or broadcast) the common time reference and time reference uncertainty to other STAs or devices on network 130. For example, an AP 140 synchronized to an absolute timing reference may transmit the timing reference and timing uncertainty information to other devices. As another example, a UE 120 may demodulate the Time-Of-Week (TOW) header to obtain an absolute (e.g., GNSS) time reference. In some embodiments, UE 120 may send the absolute time reference and timing reference uncertainty to one or more APs 140. Further, the timing reference and timing uncertainty may be requested by and/or provided to one or more UEs 120 that do not have access to the absolute timing reference source. [0051] In instances where one or more APs 140 experience clock degradation, maintaining timing synchronization by APs 140 may be facilitated by the timing information received by the APs 140 from UEs 120. In some embodiments, APs 140 may use the absolute time reference (e.g., GNSS time) for measurements and/or time stamps. For example, packets or frames sent or received by APs 140 may be timestamped using the absolute time reference. In some embodiments, multiple APs 140 on network 130 may be synchronized to a common absolute time reference (e.g., to GNSS time) via timing information received from UEs 120 to obtain a quasi-synchronous network. [0052] In some embodiments (e.g., in quasi-synchronized networks), APs 140 may estimate one-way delay for packets received from another device based on the timestamp indicating the time the packet was sent and the time that the packet was received at AP 140. In embodiments where one or more UEs 120 may also be synchronized to the absolute time reference (bounded by the timing reference uncertainty), then, APs 140 that are also synchronized to the absolute time reference may estimate one-way delay for packets (with the timing uncertainty) received from synchronized UEs 120 based on the timestamp indicating the time the packet was sent and time that the packet was received at AP 140. Conversely, a UE 120 may also estimate one-way delay for packets received from APs 140 that are synchronized to the common absolute time reference. [0053] In some embodiments, one or more UEs 120 and/or APs 140 in system 100 may comprise multiple antennas and may support multiple-input multiple-output (MIMO) and/or multi- user MIMO (MU-MIMO). UE 120 may receive and measure signals from APs 140, which may be used for position determination. In some embodiments, APs 140 may form part of a wireless communication network 130, such as a WLAN. For example, a WLAN may be an IEEE 802.11x network (e.g., such as IEEE 802.11ax, 802.11ay, or later version). Further, system 100 may comprise or take the form of an Extended Service Set (ESS) network, which may comprise a plurality of appropriately configured basic service set (BSS) networks, an Independent Basic Service Set (IBSS) network, an ad-hoc network, or a peer-to-peer (P2P) network (e.g., operating according to Wi-Fi Direct or similar protocols). [0054] In some embodiments, system 100 may support orthogonal frequency-division multiple access (OFDMA) communications, namely, conforming to the IEEE 802.11ax specification or variants thereof. OFDMA may facilitate multiple STAs to transmit and receive data on a shared wireless medium at the same time. For a wireless network using OFDMA, the available frequency spectrum may be divided into a plurality of resource units (RUs) each with a number of different frequency subcarriers, and distinct RUs may be assigned (e.g., by AP 140) to various wireless devices (e.g., UEs 120) at a given point in time. Accordingly, OFDMA may facilitate the concurrent transmission of wireless data by multiple wireless devices over the wireless medium using their assigned RUs. In some implementations, an AP may use a specific type of frame (such as a “trigger frame”) to allocate specific RUs to a number of wireless devices identified in the trigger frame. The trigger frame may indicate the RU size and location, power level, and other parameters to be used by identified wireless devices for uplink (UL) transmissions. In some embodiments, the AP may also use a trigger frame to solicit uplink (UL) multi-user (MU) data transmissions from wireless devices identified in the trigger frame. In some instances, the trigger frame may indicate or specify an order for identified wireless devices are to transmit UL data to the AP. [0055] In some embodiments, one or more UEs 120 and APs 140 may communicate over wireless communication network 130, which may be based on IEEE 802.11 or compatible standards. In some embodiments, UEs 120 and APs 140 may communicate using variants of the IEEE 802.11 standards. For example, UEs 120 and APs 140 may communicate using 802.11ac on the 5 GHz band, which may support multiple spatial streams including MIMO and MU-MIMO and. In some embodiments, UEs 120 and APs 140 may communicate using some of the above standards, which may further support one or more of Very High Throughput (VHT) (as described in the above standards) and High Efficiency WLAN (HEW), and/or beamforming with standardized sounding and feedback mechanisms. In some embodiments, UEs 120 and or APs 140 may additionally support legacy standards for communication with legacy devices. [0056] In some embodiments, an AP 140 may determine its availability for positioning at a first time and may transmit, based on the determination, information indicative of the AP’s availability for positioning. The information indicative of the AP’s availability for positioning may comprise at least one of AP availability for STA-AP location determination, or STA-AP location determination capability, or whether AP-AP AP positioning is being performed; or the next scheduled passive AP-AP ranging session, or some combination thereof. [0057] In some embodiments, the availability of AP 140 for positioning at a first time may be determined based on AP load or network load or channel load. For example, APs 140, which may form part of wireless communication network 130, may transmit management frames, which may include network related information. APs 140 may transmit (broadcast) management (e.g., beacon) frames periodically (e.g., every 120 ms) to announce the WLAN. For example, management frames, such as beacon frames, may include capability information, supported data rates, identification of network type (e.g., as an infrastructure network), a service set identifier (SSID) and/or a basic service set identifier (BSSID). In some embodiments, APs 140 may transmit a BSS Load element frame (e.g., with information related to the number of stations currently associated with an AP, channel utilization for available channels, available admission capacity, etc.), which may provide information on parameters related to AP load. In some embodiments, the BSS Load Element or similar information element (IE) may be transmitted by an AP 140 as part of a probe response frame or another WLAN management frame. [0058] Conventionally, network congestion may detrimentally affect STA positioning. For example, network congestion may cause an AP 140 to reject positioning requests from one or more UEs 120. When STA positioning requests are rejected, one or more UEs 120 may retry the positioning request, thereby potentially aggravating existing congestion. In other instances, the response to STA/UE 120 positioning requests may be delayed (e.g., by a responding STA/AP 140), thereby limiting the utility of the response. In addition, as the number of STAs associated with an AP increases, the ranging (RTT/FTM) measurements may consume significant system and network resources. For an AP with a high load relative to capacity, additional STA-AP positioning requests from UEs may aggravate congestion and detrimentally affect performance. [0059] Accordingly, in some embodiments, the availability of AP 140 for positioning at a first time may be determined based on AP load or network load or channel load. As one example, one or more APs 140 may transmit information indicative of AP load, network load, or channel load. For example, an AP 140 may provide information indicative of AP load in a BSS Load Element and/or another Field (e.g., in a management frame) field. As another example, an AP 140 may implicitly indicate higher AP load by disabling STA-AP positioning. As a further example, AP 140 may implicitly indicate lower AP load by signaling availability for STA-AP positioning. AP load, and/or network load and/or channel load-related information may also be implicitly indicated by temporarily indicating that AP 140 lacks support for STA-AP positioning or lacks STA-AP positioning capability. For example, capability information transmitted by APs 140 may be temporarily altered to indicate a lack of support STA-AP positioning. Further, the capability information may (additionally or alternatively) indicate support for AP-AP positioning and/or indicate performance (e.g., at a current time or some scheduled time) of AP-AP positioning. [0060] In some embodiments, UE 120 may initiate a location determination method to determine a location of UE 120 based on indications of availability for positioning received from one or more APs communicatively coupled to the STA. Each indication of availability may correspond to a distinct AP, and the location determination method may include either active UE- AP/STA-AP location determination by UE 120, or passive location determination. For example, in passive location determination, UE 120 may determine its location by sniffing AP-AP positioning session message exchanges, or by sniffing STA-AP positioning session message exchanges for other STAs/UEs. In some embodiments, the indication of availability (of an AP) for positioning may include information indicative of: (i) availability of an STA-AP positioning mode on the AP, or (ii) support for an STA-AP positioning capability on the AP, or availability of an AP-AP positioning mode on the AP, or (iii) support for an AP-AP positioning capability on the AP, or (iv) a current performance of AP-AP positioning by the AP, or (v) a scheduled performance of AP-AP positioning on the AP, or some combination thereof. In some embodiments, the information indicative of support for the STA-AP positioning capability on an AP, or the information indicative of support for the AP-AP positioning capability on the AP may be comprised in a capabilities field specifying the corresponding AP’s capabilities. [0061] In some embodiments, UEs 120 may determine or infer a network load and/or AP load and/or channel load based on (i)-(v) above. In some embodiments, UE 120 may determine a network load and/or AP load and/or channel load based, in part, on (i) parameters in a BSS Load Element and/or in other fields transmitted by the AP (e.g., in a management frame). Further, based on the AP positioning availability information and/or inferred/determined network/AP/channel load, one or more UEs 120 may request AP-AP positioning, or STA-AP positioning. For example, when the network load (e.g., as determined by UEs 120) is high or exceeds some threshold, or one or more APs signal unavailability or a lack of support for STA-AP positioning, then, UEs 120 may determine their respective position based on passive positioning. In some embodiments, UEs 120 may determine position by requesting and performing STA-AP positioning when AP/network/channel load is low, or APs 140 indicate support for STA-AP positioning and/or availability of STA-AP positioning at a current time (or at some specified time). For example, if the AP load or network load (e.g., as determined by UEs 120) indicates that AP load is low or does not exceed the threshold, or, if one or more APs 140 signal availability or support for STA-AP positioning, then STAs/UEs 120 may request STA-AP positioning and determine their respective positions actively by requesting STA-AP positioning. [0062] In some embodiments, UEs 120 and/or APs 140 may be coupled to one or more additional networks, such as a cellular carrier network, a satellite positioning network (shown in FIG.1), wireless personal area network (WPAN) access points, and the like (not shown in FIG.1). In some embodiments, UEs 120 and/or APs 140 may be coupled to a wireless wide area network (WWAN) (not shown in FIG. 1), A WWAN may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a Single-Carrier Frequency Division Multiple Access (SC-FDMA) network, Long Term Evolution (LTE), WiMax, and so on. [0063] A CDMA network may implement one or more radio access technologies (RATs) such as CDMA1000, Wideband-CDMA (W-CDMA), and so on. CDMA1000 includes IS-95, IS- 1000, and IS-856 standards. A TDMA network may implement Global System for Mobile Communications (GSM), Digital Advanced Mobile Phone System (D-AMPS), or some other RAT. GSM, W-CDMA, LTE, 5G NR are described in documents from 3GPP. CDMA1000 is described in documents from a consortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents are publicly available. [0064] As illustrated in FIG. 1, UE 120 may also communicate with server 150 through wireless communication network 130 and APs 140, which may be associated with wireless communication network 130. In some embodiments, APs 140 and/or UE 120 may receive location assistance, network traffic, network load, and/or other network related information from server 150, which, in some instances, may be relayed to UEs 120 through one or more APs 140. In some embodiments, server 150 may serve as a system controller and may interface with other less and/or wired networks, and/or facilitate communication between devices coupled to system 100 and devices on another work. [0065] Each element in FIG. 1 may be considered a node of wireless communication system 100. More detail regarding the possible implementation of a node is provided by way of example in the description of a node 500 in FIG.5. Node 500 may be configured as UE 120, AP 140, or server 150 in FIG.1. As shown in FIG.5, node 500 may include a processor 502, a memory 504, and a transceiver 506. These components are shown as connected to one another by a bus, but other connection types are also permitted. When node 500 is UE 120, additional components may also be included, such as a user interface (UI), sensors, and the like. Similarly, node 500 may be implemented as a blade in a server system when node 500 is configured as server 150. Other implementations are also possible. [0066] Transceiver 506 may include any suitable device for sending and/or receiving data. Node 500 may include one or more transceivers, although only one transceiver 506 is shown for simplicity of illustration. An antenna 508 is shown as a possible communication mechanism for node 500. Multiple antennas and/or arrays of antennas may be utilized for receiving multiple spatially multiplex data streams. Additionally, examples of node 500 may communicate using wired techniques rather than (or in addition to) wireless techniques. For example, AP 140 may communicate wirelessly to UE 120 and may communicate by a wired connection (for example, by optical or coaxial cable) to server 150. Other communication hardware, such as a network interface card (NIC), may be included as well. [0067] As shown in FIG. 5, node 500 may include processor 502. Although only one processor is shown, it is understood that multiple processors can be included. Processor 502 may include microprocessors, microcontroller units (MCUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout the present disclosure. Processor 502 may be a hardware device having one or more processing cores. Processor 502 may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Software can include computer instructions written in an interpreted language, a compiled language, or machine code. Other techniques for instructing hardware are also permitted under the broad category of software. [0068] As shown in FIG.5, node 500 may also include memory 504. Although only one memory is shown, it is understood that multiple memories can be included. Memory 504 can broadly include both memory and storage. For example, memory 504 may include random-access memory (RAM), read-only memory (ROM), static RAM (SRAM), dynamic RAM (DRAM), ferro- electric RAM (FRAM), electrically erasable programmable ROM (EEPROM), compact disc read only memory (CD-ROM) or other optical disk storage, hard disk drive (HDD), such as magnetic disk storage or other magnetic storage devices, Flash drive, solid-state drive (SSD), or any other medium that can be used to carry or store desired program code in the form of instructions that can be accessed and executed by processor 502. Broadly, memory 504 may be embodied by any computer-readable medium, such as a non-transitory computer-readable medium. [0069] Processor 502, memory 504, and transceiver 506 may be implemented in various forms in node 500 for performing wireless communication functions. In some embodiments, processor 502, memory 504, and transceiver 506 of node 500 are implemented (e.g., integrated) on one or more system-on-chips (SoCs). In one example, processor 502 and memory 504 may be integrated on an application processor (AP) SoC (sometimes known as a “host,” referred to herein as a “host chip”) that handles application processing in an operating system (OS) environment, including generating raw data to be transmitted. In another example, processor 502 and memory 504 may be integrated on a baseband processor (BP) SoC (sometimes known as a “modem,” referred to herein as a “radio”) that converts the raw data, e.g., from the host chip, to signals that can be used to modulate the carrier frequency for transmission, and vice versa, which can run a real-time operating system (RTOS). In still another example, processor 502 and transceiver 506 (and memory 504 in some cases) may be integrated on an RF SoC (sometimes known as a “transceiver,” referred to herein as a “wireless network interface”) that transmits and receives RF signals with antenna 508. It is understood that in some examples, some or all of the host chip, radio, and wireless network interface may be integrated as a single SoC. For example, a radio and a wireless network interface may be integrated into a single SoC that manages all the radio functions for GPSS communication, WLAN communication, WPAN communication, and/or cellular communication. [0070] Referring back to FIG. 1, in some embodiments, any suitable node of wireless communication system 100 (e.g., UE 120) may perform a calibration technique that can be applied in near-field multipath scenarios to calibrate its antenna array. For example, UE 120 applies an anti-multipath function to a transfer function in order to identify the maximum channel impulse response within a signal that includes a superposition of beams. The anti-multipath function may include any function that is configured to identify the maximum channel impulse response peak within a super position of beams. The maximum channel impulse response peak may be used to identify the LOS beam within the signal, which may be used to accurately calibrate the antenna array. Additional details of these and other techniques are provided below in connection with FIGs.2, 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, and 4. [0071] FIG.2 illustrates a block diagram of an apparatus 200 including a radio 202 (also referred to herein as “radio chip”), a wireless network interface 204, and a host chip 206, according to some embodiments of the present disclosure. Apparatus 200 may be implemented as UE 120 of wireless communication system 100 in FIG.1. In some embodiments, radio 202 is implemented by processor 502 and memory 504, and wireless network interface 204 is implemented by processor 502, memory 504, and transceiver 506, as described above with respect to FIG.5. When used for positioning determination within a WLAN communication system, radio 202 may be implemented as a WLAN radio or communication chip. On the other hand, when used for positioning determination within a GNSS communication system, radio 202 may be implemented as a GNSS receiver radio. Still further, when used for positioning determination within a cellular communication system, radio 202 may be implemented as a baseband chip, and wireless network interface 204 may be implemented as an RF chip. [0072] Besides the on-chip memory 218 (also known as “internal memory,” e.g., registers, buffers, or caches) on radio 202, wireless network interface 204, or host chip 206, apparatus 200 may further include an external memory 208 (e.g., the system memory or main memory) that can be shared by radio 202, wireless network interface 204, or host chip 206 through the system/main bus. Although radio 202 is illustrated as a standalone SoC in FIG.2, it is understood that in one example, radio 202 and wireless network interface 204 may be integrated as one SoC; in another example, radio 202 and host chip 206 may be integrated as one SoC; in still another example, radio 202, wireless network interface 204, and host chip 206 may be integrated as one SoC, as described above. [0073] In the uplink, host chip 206 may generate raw data and send it to radio 202 for encoding, modulation, and mapping. Interface 214 of radio 202 may receive the data from host chip 206. Radio 202 may also access the raw data generated by host chip 206 and stored in external memory 208, for example, using the direct memory access (DMA). Radio 202 may first encode (e.g., by source coding and/or channel coding) the raw data and modulate the coded data using any suitable modulation techniques, such as multi-phase shift keying (MPSK) modulation or quadrature amplitude modulation (QAM). Radio 202 may perform any other functions, such as symbol or layer mapping, to convert the raw data into a signal that can be used to modulate the carrier frequency for transmission. In the uplink, radio 202 may send the modulated signal to wireless network interface 204 via interface 214. Wireless network interface 204, through TX 250, may convert the modulated signal in the digital form into analog signals, i.e., RF signals, and perform any suitable front-end RF functions, such as filtering, digital pre-distortion, up-conversion, or sample-rate conversion. Antenna array 210 may transmit the RF signals provided by TX 250 of wireless network interface 204. [0074] In the downlink, antenna array 210 may receive RF signals from an access node or other wireless device. An RF signal may include K beams. The RF signals may be passed to RX 240 of wireless network interface 204. Wireless network interface 204 may perform any suitable front-end RF functions, such as filtering, IQ imbalance compensation, down-paging conversion, or sample-rate conversion, and convert the RF signals (e.g., transmission) into low-frequency digital signals (baseband signals) that can be processed by radio 202. [0075] As seen in FIG. 2, radio 202 may include a measurement circuit 260, an anti- multipath circuit 270, a calibration circuit 280, an AoA circuit 290, a ToA circuit 292, and a navigation circuit 294. Measurement circuit 260 may be configured to estimate a joint delay function associated with the transmitter and receiver based on the measurement signal. Anti- multipath circuit 270 may be configured to determine when a received signal includes an NLOS beam and apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array 210. Calibration circuit 280 may be configured to calibrate antenna array 210 based on the channel delay function. AoA circuit 290 may be configured to estimate, once antenna array 210 is calibrated, an AoA associated with the subsequent signals received by RX 240. ToA circuit 292 may be configured to estimate, once antenna array 210 is calibrated, a ToA associated with subsequent signals received by RX 240. Navigation circuit 294 may be configured to estimate positioning information of apparatus 200 based on the ToA and the AoA. [0076] The anti-multipath function used by anti-multipath circuit 270 may include any anti- multipath function configured to identify a LOS beam (channel impulse response maximum) within a received signal that includes a plurality of beams. One non-limiting example of an anti- multipath function that may be used by anti-multipath circuit 270 is described below in connection with FIGs.3A-3H. [0077] FIG. 3A illustrates a graphical representation 300 of a joint delay function with oversampling that is an output of an anti-multipath function, according to certain aspects of the present disclosure. FIG.3B illustrates a diagram 301 of antenna array 210, which receives a signal including a plurality of beams, according to some aspects of the disclosure. FIG.3C illustrates a graphical representation 303 of a time autocorrelation function that anti-multipath circuit 270 of FIG.2 may apply to a received signal, according to some embodiments of the present disclosure. FIG.3D illustrates a graphical representation 305 of an angular autocorrelation function that anti- multipath circuit 270 of FIG.2 may apply to a received signal, according to some embodiments of the present disclosure. FIG. 3E illustrates a graphical representation 307 of a time-angular autocorrelation function that anti-multipath circuit 270 of FIG. 2 may apply to a received signal, according to some embodiments of the present disclosure. FIG.3F illustrates a diagram 309 of an acquisition correlation and zoom-in procedure that may be implemented by anti-multipath circuit 270 of FIG. 2, according to some embodiments of the present disclosure. FIG. 3G illustrates a diagram 311 of a beam cluster that includes a superposition of K beams, according to some embodiments of the present disclosure. FIG.3H illustrates a diagram 313 of a correlation cluster identified using the acquisition correlation and zoom-in procedure, according to some embodiments of the present disclosure. FIGs.3A-3H will be described together. [0078] Referring to FIGs.2 and 3A, anti-multipath circuit 270 may apply an anti-multipath function to identify a channel impulse response maximum 375, which may be used it calibrate antenna array 210. The joint delay function may be measured by, e.g., measurement circuit 260. [0079] As shown in FIG.3B, antenna array 210 includes a plurality of antennas. Although depicted as a linear array, antenna array 210 may include a planar rectangular array with spacing between antennas equal to half-wavelength. The number of vertical antennas may be M_α , while the number of horizontal antennas may be M_β . Thus, the total antennas number is ( M_α × M_β ). A received signal may include Q bands, where the carrier frequency of each band q is denoted as f_q . Moreover, a received signal may include K beams 330, where each of the K beams has complex amplitude A_k , a two-dimensional electronics angle or AoA ( α_k , β_k ), speed v_k , and delay τ_k . [0080] The connection between AoA ( α , β )and the two-dimensional physical angle is described by the following expressions: (0.1),

where az is the azimuth and el is the elevation. [0081] The signal received by a receiver 602 with index ( m_α × m_β ) in band q at time t is equal to a superposition of K beams, as described below in expression (1.2): (_0.2),

where N_q,ma,mβ(t) is additive noise at antenna ( m_α × m_β ) at band q at time t. [0082] Moreover, each beam k in antenna ( m_α × m_β , ) band q at time t can be described according to expression (1.3):

where pn_q(t) is the pseudo-random number (PN) sequence of band q, BW is the signal bandwidth, and str_mα,_mβ (a_k,b_k) is the steering function. [0083] An example of steering function str_mα,_mβ (a_k,b_k) is shown below in expression (1.4): (0.4),

where is the doppler shift, j is mα is the antenna

row number, m_β is the antenna column number, M_α is the total number of rows in antenna array 210, and M_β is the total number of columns in antenna array 210. [0084] For simplicity, the PN sequence bandwidth of each band q may be considered identical. For a direct sequence spread spectrum, the PN sequence is a quadrature phase shift keying (QPSK) signal. For OFDM, the PN sequence signal has a Gaussian distribution. In both cases, the autocorrelation function of the PN code may be described according to expression (1.5): (0.5),

where ( )^∗ denotes a conjugate operation, E is the energy, t is time, and τ is delay. [0085] Anti-multipath circuit 270 may apply the anti-multipath function to perform joint estimation procedure that jointly estimates a set of beam parameters for each k beam of a received signal. The jointly estimated beam parameters may include, e.g., AoA (angle speed

and delay . Using the estimated set of beam parameters, the first arriving beam may be identified: (0.6).

[0086] Then, it may be verified that the first arriving beam has the maximum energy: (0.7).

[0087] By estimating complex amplitude for each k beam. Once the LOS beam is

identified, this beam may be used for antenna array calibration. Additional details of the anti- multipath function using joint beam parameter estimation are set forth below. [0088] Referring to FIGs. 2 and 3C, the process may begin when a signal including K beams is received by antenna array 210. Antenna array 210 may send the signal to RX 240, which may perform RF processing (as described above in connection with FIG. 2) before sending the signal to anti-multipath circuit 270. Anti-multipath circuit 270 may perform a joint estimation procedure as described below to estimate a set of beam parameters for each of the K beams of the received signal. To begin, anti-multipath circuit 270 may generate a set of correlation samples by applying an autocorrelation function to the signal received from RX 240. For example, the correlation function Cor_q between the received signal and beam k with angle (α, β), speed ν, and delay τ at band q may be defined according to expression (1.8): (0.8),

where S_{q,m a,mβ} arethe samples of an antenna at band q, row m_α, and column m_β, N_A is the accumulation length, T_C is the chip duration, M_V is the number of vertical antennas, M_H is the number of horizontal antennas, and BW is the bandwidth. [0089] From expressions (0.2), (0.3), (0.4) and (0.5) described above, it follows that the correlation function Cor_q is related to a sum of the amplitudes A_k of the K beams, as shown below in expression (1.9):

where N_A is the accumulation length, C_q(α ,β,ν, τ) is the single beam autocorrelation, α, β, ν, and τ are the set of parameters associated with the received signal, α_k, β_k, ν_k, and τ_k and are the set of beam parameters associated with beam k, N_q(α ,β,ν, τ) is the resulting noise, which may be defined according to expression (1.10): (0.10).

[0090] Meanwhile, C_q(α ,β,ν, τ) may be defined according to expression (1.11): (0.11).

[0091] Moreover, from expressions (0.3), (0.4) and (0.5), it follows that: (0.12), and

[0092] Examples of the beam autocorrelation function, where C_q(Δα=0, Δβ=0,ν = 0, Δt ) , are depicted in FIGs.3C-3E. [0093] Once autocorrelation is performed, anti-multipath circuit 270 may identify a search interval for an acquisition procedure. For example, from (0.1) it follows that initial angular ambiguity may be defined according to expression (1.14): 0 ≤α < 1 and 0 ≤ β < 1 (0.14). [0094] From (0.13) it follows that anti-multipath circuit 270 may check angular ambiguity with step Thus, anti-multipath circuit 270 may estimate the angular ambiguity

based on a first angular offset Δ_α, a second angular offset Δ_β, and an oversampling (OS) value. Here, Δ_α and Δ_β may be defined according to expression (1.15): (0.15).

[0095] The initial speed ambiguity interval may be defined by expression (1.16): (0.16).

[0096] Moreover, from expression (0.13) it follows that anti-multipath circuit 270 may check velocity/speed ambiguity with step Thus, anti-multipath circuit 270 may estimate the

speed ambiguity based on a speed offset Δ_ν and the OS value. Here, Δ_ν may be defined according to expression (1.17): (0.17).

[0097] Further, the initial delay ambiguity interval may be defined according to expression (1.18): 0 ≤ τ < max (τ) _(0.18). [0098] From expression (0.13) it also follows that anti-multipath circuit 270 may check delay ambiguity with step Thus, anti-multipath circuit 270 may estimate the delay ambiguity

based on a delay offset Δ_τ and the OS value. Here, Δ_τ may be defined according to expression (1.19): (0.19).

[0099] The oversampling value OS may be chosen according to a tradeoff between the number of correlation samples and computation complexity. To limit computation complexity, anti-multipath circuit 270 may set OS to 2, in some embodiments. [0100] Thus, using the intervals described above, it follows that the overall initial acquisition search interval used by anti-multipath circuit 270 may be defined according to expression (1.20):

[0101] The total number of correlation points N_ACQ in this interval may be defined according to expression (1.21): (0.21),

where N_α is the number of α correlation points in the interval, N_β is the number of β correlation points in the interval, N_ν is the number of ν correlation points in the interval, and N_τ is the number of τ correlation points in the interval. [0102] Referring to FIG.3F, during the initial acquisition procedure (also referred to herein as “the acquisition procedure”), anti-multipath circuit 270 may check all N_ACQ points and identify one or more correlation sample clusters 302a, 302b, 302c that exceed a thermal noise threshold, as defined by expression (1.22): (0.22).

[0103] Still referring to FIG. 3F, anti-multipath circuit 270 may select first cluster 302a and verify that this cluster has the maximum energy of all clusters. Then, anti-multipath circuit 270 may apply a zoom-in procedure to find the location of the main beam within this cluster. [0104] From autocorrelation expression (0.12), it follows that if first cluster 302a includes a single beam, the location of cluster maximum may be defined according to expression (1.23): (0.23).

[0105] However, multipath and/or a superposition of beams within first cluster 302a may insert errors in the beam parameters estimation

[0106] FIG.3G illustrates an example cluster 302d in which there is a superposition of two beams, namely beam k_x 306a and beam k_y 306b. The condition for beam k_x 306a and beam k_y 306b overlapping within cluster 302d may be defined according to expression (1.24):

where α_kx is the first electronic angle of beam k_x, α_ky is the first electronic angle of beam k_y, β_kx is the second electronic angle of beam k_x, β_ky is the second electronic angle of beam k_y, ν_kx is the speed of beam k_x, ν_ky is the speed of beam k_y, τ_kx is the delay of beam k_x, τ_ky is the delay of beam k_y, and intervals ( Δ_α , Δ_β , Δ_ν , Δ_τ ) are defined above according to expression (0.15), (0.17) and (0.19). [0107] Referring to FIG.3F, after the zoom-in procedure, anti-multipath circuit 270 may measure a plurality of correlation samples 304 (also referred to herein as “plurality of correlation points”) within first cluster 302a to estimate the set of beam parameters. Still referring to FIG.3F, it may be assumed that first cluster 302a is defined on the interval defined by expression (1.25): (0.25).

[0108] Thus, first cluster 302a may be described as a superposition of K beams 308 within the interval defined by expression (1.26): (0.26),

where intervals ( Δ_α, Δ_β,Δ_ν, Δ_τ) 310 are defined above by (0.15), (0.17) and (0.19). [0109] Here, anti-multipath circuit 270 may select an oversampling coefficient OS (e.g., OS = 256) that is much larger than the initial acquisition oversampling coefficient (e.g., OS = 2). Then, within first cluster 302a, anti-multipath circuit 270 we can measure N correlation samples 304 as defined by expression (1.27): (_0.27),

where n is the collective set of beam parameters associated with beam k at band q and defined by expressions (1.28) and (1.29): (_0.28), (0.29),

(0.30), and (0.31).

[0110] Thus, the correlation points are the product of K beams within first cluster 302a with the set of beam parameters defined by expression (1.32), (1.33) (1.34), (1.35), and (1.36): (0.32), where: (0.33), (0.34), (0.35), and (0.36).

[0111] From expression (0.9) it follows that: (_0.37),

where A_k is the complex amplitude of beam k and: (_0.38),

where n is defined by expression (0.28) and k is defined by expression (0.33). [0112] Expression (0.38) may be rewritten in matrix form as seen below in expressions (1.39) and (1.40): (^0.39),

and VectorCor = MatrixC · VectorA +VectorNoise (0.40). [0113] Thus, anti-multipath circuit 270 may apply an MMSE function to expression (1.40) to estimate a set of complex amplitude vectors

associated with the K beams of first cluster 302a, as shown below in expression (1.41):

[0114] To estimate the set of complex amplitudes for each of the K beams

of first cluster 302a, anti-multipath circuit 270 may select the amplitude vectors that are larger than a noise floor, as shown below in expression (1.42): (0.42).

[0115] From the set of complex amplitudes, anti-multipath circuit 270 may identify the beam ko with the maximum energy, as shown below in expression (1.43): (0.43).

[0116] Anti-multipath circuit 270 may identify the beam ko with the maximum energy, which may be associated with the channel impulse response maximum. Then, calibration circuit 280 may calibrate antenna array 210 based on the channel impulse response maximum. Then, AoA circuit 290 and ToA circuit 292 may estimate AoA and ToA, respectively, for subsequent signals. Based on the AoA and ToA, navigation circuit 294 may provide accurate navigation information for apparatus 200 even in multipath or beam superposition scenarios. [0117] FIG. 4 illustrates a flowchart of an exemplary method 400 of wireless communication, according to embodiments of the disclosure. Exemplary method 400 may be performed by an apparatus for wireless communication, e.g., such as UE 120, apparatus 200, radio 202, measurement circuit 260, anti-multipath circuit 270, calibration circuit 280, AoA circuit 290, ToA circuit 292, navigation circuit 294, and/or node 500. Method 400 may include steps 402-408 as described below. It is to be appreciated that some of the steps may be optional, and some of the steps may be performed simultaneously, or in a different order than shown in FIG.4. [0118] At 402, the radio may receive a signal comprising a plurality of beams. For example, referring to FIG.2, radio 202 may receive a signal with multiple beams from RX 240. [0119] At 404, the radio may perform a joint estimation procedure to estimate a set of beam parameters for each of the plurality of beams. For example, referring to FIGs. 2, measurement circuit 260 may estimate a joint delay function associated with the transmitter and receiver based on the measurement signal, e.g., based on equations (1)-(6). [0120] At 406, the radio may apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. For example, referring to FIGs. 2 and 3A-3H, anti-multipath circuit 270 may apply an anti-multipath function to the joint delay function to estimate the channel impulse response maximum, e.g., according to equations (1.1)-(1.43). [0121] At 408, the radio may calibrate the antenna array based on the channel delay function. For example, referring to FIG.2, calibration circuit 280 may calibrate antenna array 210 based on the channel delay function. [0122] In various aspects of the present disclosure, the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as instructions or code on a non-transitory computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computing device, such as node 500 in FIG. 5. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, HDD, such as magnetic disk storage or other magnetic storage devices, Flash drive, SSD, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a processing system, such as a mobile device or a computer. Disk and disc, as used herein, includes CD, laser disc, optical disc, digital video disc (DVD), and floppy disk where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. [0123] According to one aspect of the present disclosure, an apparatus of wireless communication is provided. The apparatus may include an antenna array. The antenna array may include a transmitter and a receiver. The receiver may be configured to receive a measurement signal from the transmitter. The measurement signal may include a plurality of beams. The apparatus may include a radio. The radio may include a measurement circuit. The measurement circuit may be configured to estimate a joint delay function associated with the transmitter and receiver based on the measurement signal. The radio may include an anti-multipath circuit. The anti-multipath circuit may be configured to in response to the plurality of beams including an NLOS beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The radio may include a calibration circuit. The calibration circuit may be configured to calibrate the antenna array based on the channel delay function. [0124] In some embodiments, the anti-multipath circuit may be configured to apply the anti-multipath function to the joint delay function to identify an LOS beam. [0125] In some embodiments, the anti-multipath circuit may be configured to apply the anti-multipath function by interpolating the joint delay function with an oversampling coefficient. [0126] In some embodiments, the anti-multipath circuit may be configured to apply the anti-multipath function by identifying a time-domain channel impulse response maximum from the interpolated joint delay function. In some embodiments, the time-domain channel impulse response maximum may be associated with an LOS beam of the plurality of beams. [0127] In some embodiments, the channel delay function may be estimated based on the time-domain channel impulse response maximum associated with the LOS signal. [0128] In some embodiments, the apparatus may include a ToA circuit configured to estimate, once the antenna array is calibrated, a ToA associated with subsequent signals received by the receiver. In some embodiments, the apparatus may include an AoA circuit configured to estimate, once the antenna array is calibrated, an AoA associated with the subsequent signals received by the receiver. [0129] In some embodiments, the apparatus may include a navigation circuit configured to estimate positioning information based on the ToA and the AoA. [0130] According to another aspect of the disclosure, a radio chip is provided. The radio chip may include a measurement circuit. The measurement circuit may be configured to estimate a joint delay function associated with the transmitter and receiver based on the measurement signal. The radio chip may include an anti-multipath circuit. The anti-multipath circuit may be configured to in response to the plurality of beams including an NLOS beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The radio chip may include a calibration circuit. The calibration circuit may be configured to calibrate the antenna array based on the channel delay function. [0131] In some embodiments, the anti-multipath circuit may be configured to apply the anti-multipath function to the joint delay function to identify an LOS beam. [0132] In some embodiments, the anti-multipath circuit may be configured to apply the anti-multipath function by interpolating the joint delay function with an oversampling coefficient. [0133] In some embodiments, the anti-multipath circuit may be configured to apply the anti-multipath function by identifying a time-domain channel impulse response maximum from the interpolated joint delay function. In some embodiments, the time-domain channel impulse response maximum may be associated with an LOS beam of the plurality of beams. [0134] In some embodiments, the channel delay function may be estimated based on the time-domain channel impulse response maximum associated with the LOS signal. [0135] In some embodiments, the apparatus may include a ToA circuit configured to estimate, once the antenna array is calibrated, a ToA associated with subsequent signals received by the receiver. In some embodiments, the apparatus may include an AoA circuit configured to estimate, once the antenna array is calibrated, an AoA associated with the subsequent signals received by the receiver. [0136] In some embodiments, the apparatus may include a navigation circuit configured to estimate positioning information based on the ToA and the AoA. [0137] According to yet another aspect of the disclosure, a method of wireless communication is provided. The method may include receiving, by a receiver of an antenna array, a measurement signal from a transmitter of the antenna array, the measurement signal including a plurality of beams. The method may include estimating, by a measurement circuit, a joint delay function associated with the transmitter and receiver based on the measurement signal. The method may include in response to the plurality of beams including an NLOS beam, applying, by an anti- multipath circuit, an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array. The method may include calibrating, by a calibration circuit, the antenna array based on the channel delay function. [0138] In some embodiments, the method may include identifying an LOS beam within the joint delay function based on the anti-multipath function. [0139] In some embodiments, the applying the anti-multipath function may include interpolating the joint delay function with an oversampling coefficient. [0140] In some embodiments, the applying the anti-multipath function may include identifying a time-domain channel impulse response maximum from the interpolated joint delay function. In some embodiments, the time-domain channel impulse response maximum may be associated with an LOS beam of the plurality of beams. [0141] In some embodiments, the channel delay function may be estimated based on the time-domain channel impulse response maximum associated with the LOS signal. [0142] In some embodiments, the method may include estimating, by a ToA circuit, a ToA associated with subsequent signals received by the receiver once the antenna array is calibrated. In some embodiments, the method may include estimating, by an AoA circuit, an AoA associated with the subsequent signals received by the receiver once the antenna array is calibrated. In some embodiments, the method may include estimating, by a navigation circuit, positioning information based on the ToA and the AoA. [0143] The foregoing description of the specific embodiments will so reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. [0144] Embodiments of the present disclosure have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. [0145] The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way. [0146] Various functional blocks, modules, and steps are disclosed above. The particular arrangements provided are illustrative and without limitation. Accordingly, the functional blocks, modules, and steps may be re-ordered or combined in different ways than in the examples provided above. Likewise, certain embodiments include only a subset of the functional blocks, modules, and steps, and any such subset is permitted. [0147] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

WHAT IS CLAIMED IS: 1. An apparatus of wireless communication, comprising: an antenna array comprising: a transmitter; and a receiver configured to receive a measurement signal from the transmitter, the measurement signal including a plurality of beams; a radio comprising: a measurement circuit configured to: estimate a joint delay function associated with the transmitter and receiver based on the measurement signal; an anti-multipath circuit configured to: in response to the plurality of beams including a non-line-of-sight (NLOS) beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array; and a calibration circuit configured to: calibrate the antenna array based on the channel delay function.

2. The apparatus of claim 1, wherein the anti-multipath circuit is configured to apply the anti- multipath function to the joint delay function to identify a line-of-sight (LOS) beam.

3. The apparatus of claim 1, wherein the anti-multipath circuit is configured to apply the anti- multipath function by: interpolating the joint delay function with an oversampling coefficient.

4. The apparatus of claim 3, wherein the anti-multipath circuit is further configured to apply the anti-multipath function by: identifying a time-domain channel impulse response maximum from the interpolated joint delay function, wherein the time-domain channel impulse response maximum is associated with a line-of-sight (LOS) beam of the plurality of beams.

5. The apparatus of claim 4, wherein the channel delay function is estimated based on the time-domain channel impulse response maximum associated with a line-of-sight (LOS) signal.

6. The apparatus of claim 1, further comprising: a time-of-arrival (ToA) circuit configured to: estimate, once the antenna array is calibrated, a ToA associated with subsequent signals received by the receiver; and an angle-of-arrival (AoA) circuit configured to: estimate, once the antenna array is calibrated, an AoA associated with the subsequent signals received by the receiver.

7. The apparatus of claim 6, further comprising a navigation circuit configured to: estimate positioning information based on the ToA and the AoA.

8. A radio chip, comprising: a measurement circuit configured to: estimate a joint delay function associated with a transmitter and receiver of an antenna array based on a measurement signal including a plurality of beams; an anti-multipath circuit configured to: in response to the plurality of beams including a non-line-of-sight (NLOS) beam, apply an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array; and a calibration circuit configured to: calibrate the antenna array based on the channel delay function.

9. The radio chip of claim 8, wherein the anti-multipath circuit is configured to apply the anti- multipath function to the joint delay function to identify a line-of-sight (LOS) beam.

10. The radio chip of claim 8, wherein the anti-multipath circuit is configured to apply the anti- multipath function by: interpolating the joint delay function with an oversampling coefficient.

11. The radio chip of claim 10, wherein the anti-multipath circuit is further configured to apply the anti-multipath function by: identifying a time-domain channel impulse response maximum from the interpolated joint delay function, wherein the time-domain channel impulse response maximum is associated with a line-of-sight (LOS) beam of the plurality of beams.

12. The radio chip of claim 11, wherein the channel delay function is estimated based on the time-domain channel impulse response maximum associated with a line-of-sight (LOS) signal.

13. The radio chip of claim 8, further comprising: a time-of-arrival (ToA) circuit configured to: estimate, once the antenna array is calibrated, a ToA associated with subsequent signals received by the receiver; and an angle-of-arrival (AoA) circuit configured to: estimate, once the antenna array is calibrated, an AoA associated with the subsequent signals received by the receiver.

14. The radio chip of claim 13, further comprising a navigation circuit configured to: estimate positioning information based on the ToA and the AoA.

15. A method of wireless communication, comprising: receiving, by a receiver of an antenna array, a measurement signal from a transmitter of the antenna array, the measurement signal including a plurality of beams; estimating, by a measurement circuit, a joint delay function associated with the transmitter and receiver based on the measurement signal; in response to the plurality of beams including a non-line-of-sight (NLOS) beam, applying, by an anti-multipath circuit, an anti-multipath function to the joint delay function to estimate a channel delay function associated with the antenna array; and calibrating, by a calibration circuit, the antenna array based on the channel delay function.

16. The method of claim 15, further comprising: identifying a line-of-sight (LOS) beam based on the anti-multipath function.

17. The method of claim 15, wherein the applying the anti-multipath function comprises: interpolating the joint delay function with an oversampling coefficient.

18. The method of claim 17, wherein the applying the anti-multipath function comprises: identifying a time-domain channel impulse response maximum from the interpolated joint delay function, wherein the time-domain channel impulse response maximum is associated with a line-of-sight (LOS) beam of the plurality of beams.

19. The method of claim 18, wherein the channel delay function is estimated based on the time- domain channel impulse response maximum associated with a line-of-sight (LOS) signal.

20. The method of claim 15, further comprising: estimating, by a time-of-arrival (ToA) circuit, a ToA associated with subsequent signals received by the receiver once the antenna array is calibrated; estimating, by an angle-of-arrival (AoA) circuit, an AoA associated with the subsequent signals received by the receiver once the antenna array is calibrated; and estimating, by a navigation circuit, positioning information based on the ToA and the AoA.