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 (3 GPP) define various operations for determining the angle-of- arrival (AoA) or time-of-arrival (ToA) of a received signal using 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 comprising a plurality of antenna systems. Each antenna system may include a receiver, a transmitter, and a set of MUXs configured to couple the receiver and the transmitter inside the antenna system. The apparatus may also include a radio that includes a calibration circuit. The calibration circuit may be configured to measure a plurality of joint transfer functions each associated with a receivertransmitter pair of the antenna array. The calibration circuit may be configured to estimate, based on the plurality of joint transfer functions, a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and a normalized receiver transfer function for each receiver-receiver pair of the antenna array.

[0005] According to another aspect of the present disclosure, a radio is provided. The radio may be configured to measure a plurality of joint transfer functions each associated with a receivertransmitter pair of an antenna array. The radio may be configured to estimate, based on the plurality of joint transfer functions, a normalized transmitter transfer function for each transmitter- transmitter pair of the antenna array and a normalized receiver transfer function for each receiverreceiver pair of the antenna array.

[0006] According to yet another aspect of the present disclosure, a method of wireless communication of a radio is provided. The method may include measuring, by a calibration circuit, a plurality of joint transfer functions each associated with a receiver-transmitter pair of an antenna array. The method may include estimating, by the calibration circuit, a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and a normalized receiver transfer function for each receiver-receiver pair of the antenna array. In some embodiments, the normalized transmitter transfer function and the normalized receiver transfer function may be estimated based on the plurality of joint transfer functions.

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. 3 illustrates a block diagram of an antenna array made up of a plurality of antenna systems, according to some embodiments of the present disclosure.

[0011] FIG. 4 illustrates a flow chart of an exemplary method of wireless communication, according to some embodiments of the present disclosure.

[0012] FIG. 5 illustrates a block diagram of an exemplary node, according to some embodiments of the present disclosure.

[0013] FIG. 6 illustrates a conventional antenna array made up of a plurality of conventional antenna systems.

[0014] Embodiments of the present disclosure will be described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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, 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.

[0020] In modern wireless systems, multiple antennas at the transmitter and receiver may be used to implement multiple input/multiple output (MEMO). MEMO 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 communication, which may occur in parallel, to an AP (received by the AP) from one or more STAs.

[0021] The term “Angle-of-Arrival” (AoA) refers to a direction of propagation of a radiofrequency 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 (also referred to herein as “antenna systems”) of an antenna array. In some embodiments, 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. [0022] 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) and/or Angle of Departure (AoD) 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.

[0023] In some embodiments, one or more of 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.

[0024] 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. 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 FIG. 6.

[0025] FIG. 6 illustrates a block diagram of a conventional antenna array 600. As shown, conventional antenna array 600 may include N number of different antenna systems 602. Each antenna system 602 may include a receiver 604, a transmitter 606, and an antenna 610. Receiver 604 and transmitter 606 may be part of an RF chip, for example. [0026] One way to increase the reliability of determining AoA is to estimate the intertransfer functions for each antenna system pair in the antenna array. Similarly, for ToA, the intratransfer function for each antenna system in the antenna array may be estimated. However, due to imperfections created during manufacture, the receiver 604 and transmitter 606 of each antenna system may have slightly different transfer functions. If these transfer functions remain unknown, then errors in AoA and ToA may occur. A radio coupled to the antenna array may be used to estimate the transfer functions. To support AoA estimation for each antenna system n, the radio may estimate, for each subcarrier ω , the normalized transmitter transfer function for transmitter n using equation (1) and the normalized receiver transfer function for receiver n using equation (2), as shown below:

[0027] On the other hand, to support ToA estimation for each antenna system n, the radio may estimate, for each subcarrier® , a joint transfer function using equation (3).

[0028] However, estimating the joint transfer function between receiver 604 and transmitter 606 in an intra-antenna system can be challenging since no direct channel between these elements is present in conventional antenna array 600. Moreover, existing techniques for estimating normalized transmitter and receiver transfer functions, as well as joint transfer functions, are computationally complex and consume an undesirable amount of power. Moreover, accuracy errors may be present in joint transfer functions, which are estimated using conventional techniques. These accuracy errors may be due to the lack of direct channel between receiver 604 and transmitter 606 inside antenna system 602.

[0029] Thus, there exists an unmet need for a technique to estimate the normalized transmitter and receiver transfer functions and the joint transfer functions that reduces computational complexity and power consumption, while increasing the accuracy of these computations.

[0030] To overcome these and other challenges, the present disclosure provides calibration hardware (e.g., a set of multiplexers (MUXs)) between the receiver and transmitter of each antenna system to estimate joint transfer functions more simply and with a greater degree of accuracy, as compared to conventional techniques. Thus, for each antenna system pair, the present disclosure computes four joint transfer functions: two intra-antenna system joint transfer functions and two inter-antenna system joint transfer functions. Then, the channel (mutual coupling) and normalized transmitter and receiver transfer functions can be estimated based on the four joint transfer functions estimated or the antenna system pair. These techniques reduce the computational complexity and power consumption and increase the accuracy in estimating normalized transmitter and receiver transfer functions, as well as the joint transfer functions. In so doing, the antenna array of the present disclosure may be calibrated more accurately and with less power consumption, as compared to conventional antenna arrays. Additional details of the present computational techniques, calibration hardware, and antenna array are provided below in connection with FIGs. 1-5.

[0031] 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-// (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. 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.

[0032] In some embodiments, as outlined above, UE 120 may receive, measure and decode signals from one or more satellite vehicles (SVs) 180 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 global navigation satellite system (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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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 multiuser 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 802.1 lx network (e.g., such as IEEE 802.1 lax, 802.1 lay, 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).

[0037] In some embodiments, system 100 may support orthogonal frequency-division multiple access (OFDMA) communications, namely, conforming to the IEEE 802.1 lax 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. [0038] 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.i l standards. For example, UEs 120 and APs 140 may communicate using 802.1 lac 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 or 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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, 5GNR 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.

[0047] 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

[0048] 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 user equipment 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

[0049] 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.

[0050] 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. [0051] 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), ferroelectric 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.

[0052] 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 WLAN communication, WPAN communication, and/or cellular communication.

[0053] Referring back to FIG. 1, in some embodiments, any suitable node of wireless communication system 100 (e.g., UE 120) may include a wireless network interface with calibration hardware (a set of MUXs) that couples the receiver and transmitter of each antenna system and a radio with a calibration circuit. The calibration circuit may be configured to estimate 1) intra-antenna system joint transfer functions based on the calibration hardware provided in the wireless network interface, 2) inter-antenna system joint transfer functions based on a channel between antenna systems, and 3) normalized transmitter and receiver transfer functions based on the intra and inter-antenna system joint transfer functions. Thus, for each antenna system pair, UE 120 computes four joint transfer functions: two intra-antenna system joint transfer functions and two inter-antenna system joint transfer functions. Then, the channel (mutual coupling) and normalized transmitter and receiver transfer functions can be estimated based on the four joint transfer functions estimated for the antenna system pair. These techniques reduce the computational complexity and power consumption and increase the accuracy in estimating normalized transmitter and receiver transfer functions, as well as the joint transfer functions. In so doing, the antenna array of user equipment 102 may be calibrated more accurately and with less power consumption, as compared to conventional antenna arrays. Additional details of the calibration hardware of the wireless network interface and calibration circuit of the radio are provided below in connection with FIGs. 2-4.

[0054] FIG. 2 illustrates a block diagram of an apparatus 200 including a radio 202, a wireless network interface 204, and a host chip 206, according to some embodiments of the present disclosure. Apparatus 200 may be implemented as user equipment 102 of wireless communication system 100 in FIG. 1. As shown in FIG. 2, apparatus 200 may include radio 202, wireless network interface 204, host chip 206, one or more antennas 210, and one or more antenna systems 230 that make up an antenna array. Each antenna system 230 may include, e g., a receiver (RX) 240, a transmitter (TX) 250, calibration hardware 260 (a set of MUXs), and an antenna 210. 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. 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.

[0055] 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. A plurality of antennas 210 (e g., an antenna array) may transmit the RF signals provided by TX 250 of wireless network interface 204.

[0056] In the downlink, antenna 210 may receive RF signals from an access node or other wireless device. 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. [0057] As seen in FIG. 2, wireless network interface 204 includes calibration hardware 260 (a set of MUXs) that couples RX 240 and TX 250 of each antenna system 230. Apparatus 200 may include an antenna array (see FIG. 3) that is made up of a plurality of antenna systems 230 Moreover, radio 202 may include calibration circuit 220 configured to estimate: 1) intra-antenna system joint transfer functions based on calibration hardware 260 provided in wireless network interface 204; 2) inter-antenna system joint transfer functions based on a channel between antenna systems 230; and 3) normalized transmitter and receiver transfer functions based on the intra and inter-antenna system j oint transfer functions. Thus, for each antenna system pair, calibration circuit 220 may compute four joint transfer functions: two intra-antenna system joint transfer functions and two inter-antenna system joint transfer functions. Then, calibration circuit 220 may estimate the channel (mutual coupling) and normalized transmitter and receiver transfer functions based on the four joint transfer functions estimated for the antenna system pair, as described in additional detail below in connection with FIG. 3. Calibration circuit 220 may input the normalized transmitter transfer functions and normalized receiver transfer functions into AoA estimation circuit 270, which may use these normalized transfer functions to estimate the AoA of a received signal. The joint transfer functions may be input into ToA estimation circuit 280, which may use the joint transfer functions to estimate the ToA of the received signal.

[0058] In some embodiments, radio 202 may include a position circuit 290 configured to determine a position of apparatus 200 in order to perform MEMO communication in accordance with the IEEE 802.1 lax or later protocol. Position circuit 290 may determine positioning or ranging information of apparatus 200 with respect to other STAs based on AoA information from AoA estimation circuit 270 and/or ToA information from ToA estimation circuit 280. The AoA information and ToA information may be obtained during active (e.g., STA-AP or passive (AP- AP) positioning sessions. Position circuit 290 may use information obtained during frame exchange, sounding, and ranging operation to determine the location of apparatus 200. In some embodiments, apparatus 200 may receive location assistance information such as the location of one or more APs from a network entity such as a system controller, a server communicatively coupled to apparatus 200, and/or one or more APs communicatively coupled to apparatus 200.

[0059] These antenna array calibration techniques described herein reduce the computational complexity and power consumption and increase the accuracy in estimating normalized transmitter and receiver transfer functions, as well as the joint transfer functions. In so doing, the antenna array (a plurality of antenna systems 230) of apparatus 200 may be calibrated more accurately and with less power consumption, as compared to conventional antenna arrays. Additional details of calibration hardware 260 of wireless network interface 204 and calibration circuit 220 of radio 202 are provided below in connection with FIG. 3.

[0060] FIG. 3 illustrates a block diagram of an antenna array 300 that may be included in apparatus 200 of FIG. 2, according to some embodiments of the present disclosure. As shown, antenna array 300 may include a first antenna system 230a and a second antenna system 230b. First antenna system 230a may include, e.g., RX1 240a, TX1 250a, first calibration hardware 260a (a first set of MUXs), and a first antenna 210a. Similarly, second antenna system 230b may include, e.g., RX2 240b, TX2 250b, second calibration hardware 260b (a second set of MUXs), and a second antenna 210b.

[0061] As illustrated in FIG. 3, first and second antenna systems 230a, 230b may experience mutual coupling via channel Moreover, RX1 240a and TX1 250a may be coupled within first antenna system 230a by first calibration hardware 260a, and RX2 240b and TX2 250b may be coupled within second antenna system 230b by second calibration hardware 260b. Based on this setup, calibration circuit 220 of radio 202 may estimate joint transfer functions for each antenna system pair of antenna array 300. For simplicity, only two antenna systems are depicted in FIG. 3, and the following computations for estimating transfer functions (which may be used to estimate AoA and ToA with a high degree of accuracy) are described in connection for only this antenna system pair. However, when antenna array 300 includes more than two antenna systems, calibration circuit 220 may perform the following computations for each antenna system pair in antenna array 300.

[0062] To begin, calibration circuit 220 may measure, for each subcarrier co, a plurality of joint transfer functions each associated with a receiver-transmitter pair of antenna array 300. Thus, the total number of joint transfer function measurements is four per subcarrier, as shown in the following set of equations (4). where is a first intra-antenna system joint transfer function associated with TX1 250a and RX1 240a of first antenna system 230a, is a first inter-antenna system joint transfer function associated with TX1 250a of first antenna system 230a and RX2 240b of second antenna system 230b, r ₂₁ (m) is a second inter-antenna joint transfer function associated with TX2250b of second antenna system 230b and RX1 240a of first antenna system 230a, and T ₂₂ (m) is a second intra-antenna system joint transfer function associated with TX2 250b and RX2 240b of second antenna system 230b.

[0063] With respect to the above set of equations (4), calibration circuit 220 may measure first intra-antenna joint transfer function and second intra-antenna j oint transfer function T ₂₂ (m) using first calibration hardware 260a and second calibration hardware 260b, respectively.

On the other hand, calibration circuit 220 may measure first inter-antenna j oint transfer function T ₁₂ (m) and second inter-antenna joint transfer function using channel which is the mutual coupling between first antenna 210a and second antenna 210b.

[0064] Based on the measurements of each of the four joint transfer functions, calibration circuit 220 may be configured to estimate a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array, a normalized receiver transfer function for each receiver-receiver pair of the antenna array, and channel C//(co). Each joint transfer function may be used to normalize the remaining three joint transfer functions. For ease of description, the following computations performed by calibration circuit 220 are provided for the example where first intra-antenna joint transfer function is used to normalize the residual joint transfer functions, which in this example include first inter-antenna system joint transfer function second inter-antenna joint transfer function , and second intra-antenna system joint transfer function

[0065] More specifically, calibration circuit 220 may normalize the residual joint transfer functions by as shown below in equation (5):

[0066] Once normalized, calibration circuit 220 may apply the natural logarithm of the three equations on the right side of the equal sign in the above equation (5), as shown below in equation (6):

[0067] As shown below in equations (7) and (8), equation (6) includes a linear system of three unknowns (see equation (7)) and three equations (see equation (8)).

[0068] The above matrix from equation (8) is non-singular (invertible).

Therefore, calibration circuit 220 may estimate the three unknowns (seen in equation (7)), as seen below in equation (9).

[0069] Then, calibration circuit 220 may apply a natural logarithm to equation (9) to estimate the channel the estimated normalized transmitter function T and the estimated normalized receiver function , as shown below in equation (10):

[0070] Then, for the first antenna system 230a/second antenna system 230b pair, calibration circuit 220 may perform the same normalization procedure shown above in equations (5)-(10), where first inter-antenna system joint transfer function is used to normalize the residual joint transfer functions, which in this example include first intra-antenna j oint transfer function second inter-antenna j oint transfer function and second intra-antenna system joint transfer function The normalization procedure may be performed four times until each of the transfer functions of equation (4) are used to normalize the residual transfer functions to estimate the parameters of equation (10). Once the normalization procedure has been performed using each of the transfer functions of equation (4), calibration circuit 220 may perform the same calculations (e.g., equations (4)-(l 0)) for each of the other antenna system pairs of antenna array 300.

[0071] Once estimated, the normalized transmitter transfer functions and normalized receiver transfer functions may be input to AoA estimation circuit 270, which may estimate AoA for a received signal based on these normalized transmitter and receiver transfer functions. Similarly, the joint transfer functions may be input into ToA estimation circuit 280, which may estimate the ToA for a received signal based on these joint transfer functions. Thus, by providing each antenna system 230 with calibration hardware 260, antenna array 300 can be calibrated using joint transfer functions, normalized transmitter transfer functions, and normalized receiver transfer functions that are calculated with reduced complexity and power consumption by calibration circuit 220, as compared to conventional techniques.

[0072] 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, calibration circuit 220, AoA estimation circuit 270, ToA estimation circuit 280, 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.

[0073] At 402, the radio may measure a plurality of joint transfer functions each associated with a receiver-transmitter pair of an antenna array. For example, referring to FIGs. 2 and 3, calibration circuit 220 may measure, for each subcarrier co, a plurality of joint transfer functions each associated with a receiver-transmitter pair of antenna array 300. Thus, the total number of joint transfer function measurements is four per subcarrier, as above in equation (4).

[0074] At 404, the radio may estimate a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and a normalized receiver transfer function for each receiver-receiver pair of the antenna array. In some aspects, the normalized transmitter transfer function and the normalized receiver transfer function may be estimated based on the plurality of joint transfer functions. For example, referring to FIGs. 2 and 3, based on the measurements of each of the four joint transfer functions, calibration circuit 220 may be configured to estimate a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array, a normalized receiver transfer function for each receiver-receiver pair of the antenna array, and channel C7/(co). Each joint transfer function may be used to normalize the remaining three joint transfer functions. For ease of description, the following computations performed by calibration circuit 220 are provided for the example where first intra-antenna joint transfer function is used to normalize the residual joint transfer functions, which in this example include first inter-antenna system joint transfer function second inter-antenna joint transfer function , and second intra-antenna system joint transfer function More specifically, calibration circuit 220 may normalize the residual joint transfer functions by T ₁₁ (m), as shown above in equation (5). Once normalized, calibration circuit 220 may apply the natural logarithm of the three equations on the right side of the equal sign in the above equation (5), as shown above in equation (6). As shown above in equations (7) and (8), equation (6) includes a linear system of three unknowns (see equation (7)) and three equations (see equation (8)). The above matrix from equation (8) is non-singular (invertible). Therefore, calibration circuit 220 may estimate the three unknowns (seen in equation (7)), as shown above in equation (9). Then, calibration circuit 220 may apply a natural logarithm to equation (9) to estimate the channel the estimated normalized transmitter function and the estimated normalized receiver function as shown above in equation (10). Then, for the first antenna system 230a/second antenna system 230b pair, calibration circuit 220 may perform the same normalization procedure shown above in equations (5)-(10), where first inter-antenna system joint transfer function T ₁₂ (n>) is used to normalize the residual joint transfer functions, which in this example include first intra-antenna joint transfer function T ₁₁ (m), second interantenna joint transfer function T ₂₁ (m), and second intra-antenna system joint transfer function The normalization procedure may be performed four times until each of the transfer functions of equation (4) are used to normalize the residual transfer functions to estimate the parameters of equation (10). Once the normalization procedure has been performed using each of the transfer functions of equation (4), calibration circuit 220 may perform the same calculations (e.g., equations (4)-(l 0)) for each of the other antenna system pairs of antenna array 300. [0075] At 406, the radio may estimate the AoA of a received signal based on the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array. For example, referring to FIGs. 2 and 3, once estimated, the normalized transmitter transfer functions and normalized receiver transfer functions may be input to AoA estimation circuit 270, which may estimate AoA for a received signal based on these normalized transmitter and receiver transfer functions.

[0076] At 408, the radio may estimate the ToA of the received signal based on the plurality of joint transfer functions. For example, referring to FIGs. 2 and 3, the joint transfer functions may be input into ToA estimation circuit 280, which may estimate the ToA for a received signal based on these joint transfer functions.

[0077] 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. [0078] According to one aspect of the present disclosure, an apparatus of wireless communication is provided. The apparatus may include an antenna array comprising a plurality of antenna systems. Each antenna system may include a receiver, a transmitter, and a set of MUXs configured to couple the receiver and the transmitter inside the antenna system. The apparatus may also include a radio that includes a calibration circuit. The calibration circuit may be configured to measure a plurality of joint transfer functions each associated with a receivertransmitter pair of the antenna array. The calibration circuit may be configured to estimate, based on the plurality of joint transfer functions, a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and a normalized receiver transfer function for each receiver-receiver pair of the antenna array.

[0079] In some embodiments, the plurality of joint transfer functions, the normalized transmitter transfer function, and the normalized receiver transfer function may be estimated for a plurality of subcarriers.

[0080] In some embodiments, each of the plurality of antenna systems of the antenna array may include a first antenna system and a second antenna system. In some embodiments, the first antenna system may include a first antenna. In some embodiments, the first antenna system may include a first receiver. In some embodiments, the first antenna system may include a first transmitter. In some embodiments, the first antenna system may include a first set of MUXs configured to couple the first receiver and the first transmitter. In some embodiments, the second antenna system may include a second antenna. In some embodiments, the second antenna system may include a second receiver. In some embodiments, the second antenna system may include a second transmitter. In some embodiments, the second antenna system may include a second set of MUXs configured to couple the second receiver and the second transmitter

[0081] In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring, using the first set of MUXs, a first intra-antenna joint transfer function associated with the first transmitter and the first receiver of the first antenna system. In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring a first inter-antenna joint transfer function associated with the first transmitter of the first antenna system, the second receiver of the second antenna system, and a channel between the first antenna system and the second antenna system. In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receivertransmitter pair of the antenna array by measuring a second inter-antenna j oint transfer function associated with the second transmitter of the second antenna system, the first receiver of the first antenna system, and the channel between the first antenna system and the second antenna system. In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring, using the second set of MUXs, a second intra-antenna joint transfer function associated with the second transmitter and the second receiver of the second antenna system. [0082] In some embodiments, the calibration circuit may be configured to estimate the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array by normalizing each of the first inter-antenna joint transfer function, the second inter-antenna joint transfer function, and the second intra-antenna joint transfer function based on the first intraantennajoint transfer function.

[0083] In some embodiments, the calibration circuit may be configured to estimate the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array by applying, after the normalizing, a natural logarithm to each of the first inter-antenna joint transfer function, the second inter-antenna joint transfer function, and the second intra-antenna joint transfer function to generate a system of three equations and three unknowns.

[0084] In some embodiments, the calibration circuit may be configured to estimate the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array applying a matrix to the system of three equations and three unknowns to estimate the channel, a first normalized transmitter transfer function associated with the second transmitter and the first transmitter, and a first normalized receiver transfer function associated with the second receiver and the first receiver.

[0085] According to another aspect of the present disclosure, a radio is provided. The radio may be configured to measure a plurality of joint transfer functions each associated with a receivertransmitter pair of an antenna array. The radio may be configured to estimate, based on the plurality of joint transfer functions, a normalized transmitter transfer function for each transmittertransmitter pair of the antenna array and a normalized receiver transfer function for each receiverreceiver pair of the antenna array.

[0086] In some embodiments, the plurality of joint transfer functions, the normalized transmitter transfer function, and the normalized receiver transfer function may be estimated for a plurality of subcarriers.

[0087] In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring, based on a first set of MUXs that couple a first receiver and a first transmitter within a first antenna system of the antenna array, a first intra-antenna joint transfer function associated with the first transmitter and the first receiver of the first antenna system. In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring a first inter-antenna joint transfer function associated with the first transmitter of the first antenna system, a second receiver of a second antenna system of the antenna array, and a channel between the first antenna system and the second antenna system. In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring a second inter-antenna joint transfer function associated with a second transmitter of the second antenna system, the first receiver of the first antenna system, and the channel between the first antenna system and the second antenna system. In some embodiments, the calibration circuit may be configured to measure the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array by measuring, based on a second set of MUXs that couple the second receiver and the second transmitter within the second antenna system of the antenna array, a second intra-antenna joint transfer function associated with the second transmitter and the second receiver of the second antenna system.

[0088] In some embodiments, the calibration circuit may be configured to estimate the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array by normalizing each of the first inter-antenna joint transfer function, the second inter-antenna joint transfer function, and the second intra-antenna joint transfer function based on the first intraantennajoint transfer function.

[0089] In some embodiments, the calibration circuit may be configured to estimate the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array by applying, after the normalizing, a natural logarithm to each of the first inter-antenna joint transfer function, the second inter-antenna joint transfer function, and the second intra-antenna joint transfer function to generate a system of three equations and three unknowns.

[0090] In some embodiments, the calibration circuit may be configured to estimate the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array by applying a matrix to the system of three equations and three unknowns to estimate the channel, a first normalized transmitter transfer function associated with the second transmitter and the first transmitter, and a first normalized receiver transfer function associated with the second receiver and the first receiver.

[0091] According to yet another aspect of the present disclosure, a method of wireless communication of a radio is provided. The method may include measuring, by a calibration circuit, a plurality of joint transfer functions each associated with a receiver-transmitter pair of an antenna array. The method may include estimating, by the calibration circuit, a normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and a normalized receiver transfer function for each receiver-receiver pair of the antenna array. In some embodiments, the normalized transmitter transfer function and the normalized receiver transfer function may be estimated based on the plurality of joint transfer functions.

[0092] In some embodiments, the method may include estimating the AoA of a received signal based on the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array. In some embodiments, the method may include estimating a ToA of the received signal based on the plurality of joint transfer functions.

[0093] In some embodiments, the plurality of joint transfer functions, the normalized transmitter transfer function, and the normalized receiver transfer function may be estimated for a plurality of subcarriers.

[0094] In some embodiments, the measuring the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array may include measuring, based on a first set of MUXs that couple a first receiver and a first transmitter within a first antenna system of the antenna array, a first intra-antenna joint transfer function associated with the first transmitter and the first receiver of the first antenna system. In some embodiments, the measuring the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array may include measuring, based on a second set of MUXs that couple a second receiver and a second transmitter within a second antenna system of the antenna array, a second intra-antenna joint transfer function associated with the second transmitter and the second receiver of the second antenna system.

[0095] In some embodiments, the measuring the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array may include measuring a first inter-antenna joint transfer function associated with the first transmitter of the first antenna system, the second receiver of a second antenna system of the antenna array, and a channel between the first antenna system and the second antenna system. In some embodiments, the measuring the plurality of joint transfer functions each associated with the receiver-transmitter pair of the antenna array may include measuring a second inter-antenna j oint transfer function associated with the second transmitter of the second antenna system, the first receiver of the first antenna system, and the channel between the first antenna system and the second antenna system.

[0096] In some embodiments, the estimating the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array may include normalizing each of the first inter-antenna joint transfer function, the second inter-antenna j oint transfer function, and the second intra-antenna joint transfer function based on the first intra-antenna joint transfer function. [0097] In some embodiments, the estimating the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array may include applying, after the normalizing, a natural logarithm to each of the first inter-antenna joint transfer function, the second inter-antenna j oint transfer function, and the second intra-antenna j oint transfer function to generate a system of three equations and three unknowns. In some embodiments, the estimating the normalized transmitter transfer function for each transmitter-transmitter pair of the antenna array and the normalized receiver transfer function for each receiver-receiver pair of the antenna array may include applying a matrix to the system of three equations and three unknowns to estimate the channel, a first normalized transmitter transfer function associated with the second transmitter and the first transmitter, and a first normalized receiver transfer function associated with the second receiver and the first receiver.

[0098] 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. [0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.