Sparse Antenna Array Calibration

Abstract

A system for communication may include an antenna array, where inter-element spacing of antennas of the antenna array may vary throughout the antenna array, an antenna manager coupled to each antenna and configured to transmit and receive ranging signals used to measure parameters indicative of distances between each antenna and other antennas, a calibration unit that determines a position of the antenna based on the measured parameters and a position of a reference antenna, and a communications manager that communicates with a terminal in accordance with beam coefficients determined for the antenna array based on the determined positions of the antennas.

Description

[Background technology]

[0001] The following generally relates to electronic communications, including sparse antenna array calibration.

[0002] Communication devices may communicate with each other using wired connections, wireless (e.g., radio frequency (RF)) connections, or both. Wireless communication between communication devices may be performed using a wireless spectrum designated for a service provider, a wireless technology, or both. In some examples, the amount of information that can be communicated over a wireless communication network is based on the amount of wireless spectrum designated for the service provider and the amount of frequency reuse in the area in which the service is provided. Wireless communications (e.g., cellular communications, satellite communications, etc.) may use beamforming and multiple-input multiple-output (MIMO) techniques for communication between devices to increase frequency reuse. However, providing high levels of frequency reuse in some types of communication systems, such as satellite communications, presents challenges. Summary of the Invention

[0003] A system for communication may include an antenna array, where inter-element spacing of antennas in the antenna array may vary throughout the antenna array. The system may also include an antenna manager coupled to each antenna and configured to transmit and receive ranging signals used to measure parameters indicative of distances between each antenna and other antennas. The system may also include a calibration unit that determines the positions of the antennas based on the measured parameters and the positions of a reference antenna. The system may also include a communications manager that communicates with a terminal according to beam coefficients determined for the antenna array based on the determined positions of the antennas. [Brief explanation of the drawings]

[0004] [Figure 1]FIG. 1 illustrates an example of a satellite communications system that supports sparse antenna array calibration in accordance with examples described herein. [Figure 2] FIG. 2 illustrates an example of a sparse antenna array that supports sparse antenna array calibration in accordance with examples described herein. [Figure 3] FIG. 3 illustrates an example of a communication network that supports sparse antenna array calibration in accordance with examples described herein. [Figure 4] FIG. 4 illustrates an example of a communications subsystem that supports sparse antenna array calibration according to examples described herein. [Figure 5] FIG. 5 illustrates an example of a communications subsystem that supports sparse antenna array calibration according to examples described herein. [Figure 6] FIG. 6 illustrates an example set of operations for sparse antenna array calibration according to examples described herein. [Figure 7] FIG. 7 illustrates an example set of operations for sparse antenna array calibration according to examples described herein. DETAILED DESCRIPTION OF THE INVENTION

[0005] A communication system (e.g., a satellite system) may include devices (e.g., satellites) with multiple antennas. The communication system may use these devices to support simultaneous communication by multiple terminals. In some examples, the communication system may use these devices to support beamformed communication. Beamformed communication may be used to increase utilization of communication resources, for example, by allowing wireless spectrum to be reused in different regions of a geographic area. In some examples, beamforming techniques may use multi-antenna devices to form a set of spot beams that cover a geographic area (e.g., in at least partially overlapping patterns).

[0006] Beamforming techniques can be used to increase spectrum utilization, but the resolution of beamforming techniques can be limited, for example, based on the size of the antenna array. In some examples, the coverage area of ​​a spot beam is based on the size of the satellite system's antenna array, the frequency used by the satellite system, or the orbit (e.g., geosynchronous orbit) used by the satellite system. For a typical satellite payload (e.g., an array-fed reflector with a reflector ranging from 10 to 30 meters), the coverage area of ​​a spot beam formed on the Earth's surface by the satellite system can be relatively large (e.g., hundreds or thousands of kilometers in diameter). Therefore, the use of current beamforming techniques to increase frequency resource reuse (e.g., by using smaller spot beams) can be limited.

[0007] To increase beamforming resolution and support an increased amount of users within a geographic area, the techniques described herein may use large sparse antenna arrays having antennas with different inter-element spacing across the antenna array. Current antenna arrays may have fixed and consistent inter-element spacing, and therefore, developing large antenna arrays using current techniques may be infeasible. In some examples, large sparse antenna arrays may span large distances (e.g., greater than a kilometer) based on using flexible antenna arrays. In some cases, the spacing between antennas in a flexible antenna array may not be fixedly set, and thus the antenna array may have different inter-element spacing. In some cases, the inter-element spacing may change over time (e.g., due to drift of the antennas relative to each other). In some cases, antennas in a large sparse antenna array may be grouped into sets of antennas (e.g., antenna subarrays), and each set of antennas may be used to form a beam (e.g., a discovery beam). Also, multiple sets of antennas in a large sparse antenna array may be used to form one or more beams (e.g., one or more communication beams).

[0008] A large sparse antenna array may be used (e.g., in combination with respective beam coefficients) to form beams within a geographic area using a geometric interpretation. In such cases, the beam coefficients may be selected based on the positions of the antennas of the sparse antenna array relative to the geographic area. In some examples, the positions of the antennas themselves may be determined before determining the positions of the antennas of the sparse antenna array relative to the geographic area. In some examples, an antenna manager may be coupled to each antenna of the large sparse antenna array. The antenna manager may be configured to transmit (e.g., via each antenna) and receive (e.g., via each antenna) ranging signals. The ranging signals may be used to measure parameters representing distances between each antenna and other antennas (e.g., by the antenna manager). The positions of the antennas may be determined (e.g., by a calibration unit) based on the measured parameters and the positions of a reference antenna. Based on determining the positions of the antennas, the sparse antenna array may be used to communicate with a terminal (e.g., in combination with a communications manager) according to beam coefficients determined for the antenna array using the determined positions of the antennas.

[0009] 1 illustrates an example of a satellite communication system 100 that supports sparse antenna array calibration in accordance with examples described herein. The satellite communication system 100 may include a ground system 135, a terminal 120, and a satellite system 101.

[0010] The ground system 135 may include a network of access nodes 140 configured to communicate with the satellite system 101. The access nodes 140 may be coupled to access node transceivers 145 configured to process signals received from and to be transmitted through corresponding access nodes 140. The access node transceivers 145 may also be configured to interface with a network 125 (e.g., the Internet) via, for example, a network device 130 (e.g., a network operations center, a satellite and gateway terminal command center, or other central processing center or device) that may provide an interface for communicating with the network 125.

[0011] Terminals 120 may include various devices configured to communicate signals with satellite system 101, which may include fixed terminals (e.g., terrestrial stationary terminals) or mobile terminals, such as terminals located on ships, aircraft, ground vehicles, etc. Terminals 120 may communicate data and information with access nodes 140 via satellite system 101. The data and information may be communicated to a destination device, such as network device 130, or some other device or distributed server associated with network 125.

[0012] The satellite system 101 may include a single satellite or a network of satellites deployed in space orbit (e.g., low Earth orbit, medium Earth orbit, geostationary orbit, etc.). One or more satellites included in the satellite system 101 may include multiple antennas (e.g., one or more antenna arrays). In some examples, one or more satellites with multiple antennas may each include one or more antenna panels including an array of uniformly distributed antennas (sometimes referred to as antenna elements). In some examples, a satellite may include an antenna array including antennas that are non-uniformly distributed over a large area. In some examples, the antennas may be connected to a central entity via wired or wireless links. Deploying antennas over a large area may increase the aperture size of the satellite's antenna array relative to an antenna array including uniformly distributed antennas (e.g., due to limitations associated with manufacturing and deploying large antenna arrays with uniformly distributed antennas). In some examples, a set of satellites, each including an antenna, may be non-uniformly distributed over a large area, and each satellite may communicate with a central entity (e.g., a central server or ground station). In such cases, the antennas of the set of satellites may be used to form an antenna array. In some examples, a set of satellites, each including an antenna subarray, may be distributed non-uniformly over a wide area, and each satellite may communicate with a central entity (e.g., a central server or a ground station), and the antenna subarray may include an array of uniformly distributed antennas. In such cases, the antenna subarrays of the set of satellites may be used to form an antenna array.

[0013] The satellite system 101 may use one or more satellites to support multiple-input multiple-output (MIMO) techniques to increase utilization of frequency resources used for communication, for example, by allowing the wireless spectrum to be reused in time and frequency in different geographic regions of a geographic area. Similarly, the satellite system 101 may use one or more satellites to support beamforming techniques to increase utilization of frequency resources used for communication.

[0014] MIMO techniques can be used to exploit multipath signal propagation and increase spectral efficiency by transmitting or receiving multiple signals via different spatial layers. The multiple signals can be transmitted by a transmitting device (e.g., a satellite system) via a set of antennas according to a set of weighting coefficients. Similarly, the multiple signals can be received by a receiving device (e.g., a satellite system) via a set of antennas according to a set of weighting coefficients. Each of the multiple signals can be associated with a separate spatial stream and can carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). MIMO techniques include single-user MIMO (SU-MIMO), in which multiple spatial layers are used to communicate with one device, and multi-user MIMO (MU-MIMO), in which multiple spatial layers are used to communicate with multiple devices.

[0015] To determine weighting coefficients to apply to the set of antennas such that N spatial layers are formed, an (M×N) MIMO matrix may be formed, where M may represent the number of antennas in the set of antennas. In some examples, M may be equal to N. The MIMO matrix may be determined based on the channel matrix and used to separate different spatial layers of the channel. In some examples, the weighting coefficients are selected to emphasize signals transmitted using different spatial layers while reducing interference of signals transmitted in other spatial layers. Thus, processing signals received at each antenna (e.g., signals received at the set of antennas) using the set of antennas using a MIMO matrix may result in multiple signals being output, each of the multiple signals may correspond to one of the spatial layers. The elements of the MIMO matrix used to form the spatial layers of the channel may be determined based on, for example, channel sounding probes received at the satellite system 101 from one or more devices. In some examples, the weighting coefficients used for MIMO communications may be referred to as beam coefficients, and the multiple signals or spatial layers may be referred to as beam signals.

[0016] Beamforming techniques may be used to shape or steer communication beams along a spatial path between the satellite system 101 and a geographic area. A communication beam may be formed by determining weighting coefficients for antenna elements of an antenna array that cause signals transmitted from or received at the antenna elements to be combined such that signals propagating in a particular direction relative to the antenna array are subject to constructive interference, while other signals are subject to destructive interference. Thus, beamforming may be used to transmit signals with energy focused in the direction of the communication beam and receive signals arriving in the direction of communication with increased signal power (relative to the absence of beamforming). Weighting coefficients may be used to apply an amplitude offset, a phase offset, or both to signals carried via the antenna. In some examples, weighting coefficients applied to an antenna may be used to form multiple beams associated with multiple directions, and multiple beams may be used to simultaneously communicate multiple signals having the same frequency. Weighting coefficients used for beamforming may be referred to as beam coefficients, and the multiple signals may be referred to as beam signals.

[0017] In some examples, beamforming techniques may be used by the satellite system 101 to form spot beams that are tiled (e.g., mosaicked) across a geographic area. In some examples, the wireless spectrum used by the satellite system 101 may be reused across a set of spot beams for communications between terminals 120 and the satellite system. In some examples, the wireless spectrum may be reused in non-overlapping spot beams, and adjacent geographic areas may be covered by overlapping spot beams that each use orthogonal resources (e.g., orthogonal time, frequency, or polarization resources).

[0018] To support an increased number of users within a geographic area, antenna arrays having antennas with different inter-element spacings across the antenna array (which may be referred to as large sparse antenna arrays) may be used to increase the resolution of beamforming techniques. That is, large sparse antenna arrays may be used (e.g., in combination with respective beam coefficients) to form communication beams having small coverage areas (e.g., less than 10 kilometers in diameter). A large sparse antenna array, such as antenna array 105, may include multiple antenna units 110 (e.g., hundreds or thousands of antennas) distributed non-uniformly throughout an area, e.g., in space. In some examples, each antenna unit 110 is or is located on an individual satellite. In other examples, the antenna units 110 are located on a single satellite, and each antenna unit 110 is tethered to a central location, e.g., via a physical connection.

[0019] Additionally, the distance between the antenna units 110 may be greater than the distance associated with the wavelength of a signal supported for communication by the large sparse antenna array, e.g., the distance between the antenna units 110 may be greater than the distance associated with the wavelength. In some examples, the distance between the antenna units 110 may be greater than 10 times the wavelength. In some examples, a first distance (d1) between a first one of the antenna units 110 and a second one of the antenna units 110, such as throughout the antenna array 105, may be different from a second distance (d2) between the second one of the antenna units 110 and a third one of the antenna units 110.

[0020] In some examples, a large sparse antenna array includes multiple antenna subarrays (e.g., tens or hundreds of antenna subarrays) that are distributed non-uniformly throughout an area. In some examples, the antenna subarrays may each include a group of antenna units 110. In some examples, an antenna subarray may include a single antenna unit 110, which may be combined with an antenna panel that includes a set of antenna elements that are uniformly distributed throughout the corresponding antenna subarray. In some examples, in addition to being large and sparse, the antenna array 105 may be random or semi-random such that the distance between the antenna units 110 of the antenna array 105 may be uncontrolled or partially controlled (e.g., unconstrained in one or more dimensions or allowed to drift in one or more dimensions relative to other antenna units 110).

[0021] To form small communication beams, a geometric relationship between geographic regions and antenna units 110 of the large sparse antenna array 105 may be used. In some examples, the geometric relationship between geographic regions and antenna units 110 of the large sparse antenna array 105 may also be used to simplify processing used for massive MIMO techniques, for example, based on limited directions of signal incidence, known location information for terminals, or any combination thereof.

[0022] In some examples, to support communicating using communication beams 117 having small coverage areas, the large sparse antenna array 105 may be used (e.g., in combination with respective beam coefficients) to form discovery beams 119 within the geographic area 150, where each discovery beam 119 may be formed by a corresponding set of antenna units 110 of the antenna array 105 and may cover a discovery area 155 within the geographic area 150. For example, each subarray may form a discovery beam 119, where the discovery beams may be tiled across the geographic area 150. Preambles transmitted from terminals 120 within the discovery area 155 of the discovery beam 119 may be detected using the large sparse antenna array 105 (e.g., each subarray may detect preambles transmitted from within the corresponding discovery area 155).

[0023] Based on detecting the preamble using the discovery beam 119, the presence of the terminal 120 within the discovery area 155 of the discovery beam 119 may be determined. Based on detecting the presence of the terminal 120, a set of antenna units 110 of the antenna array 105 (e.g., antennas from two or more subarrays, a substantial portion of the antenna units 110, a majority of the antenna units 110, or all of the antenna units 110) and corresponding beam coefficients may be selected to form a communications beam 117 (e.g., a small or narrow beam) having a beam coverage area 160 within the discovery area 155 that includes the location of the terminal 120. Signals detected at the antenna array 105 may then be processed according to the beam coefficients used to form the small communications beam 117, resulting in a beam signal for the small communications beam 117. In some examples, the beam signal may include one or more signals transmitted from one or more terminals located within the beam coverage area 160.

[0024] In some examples, the antenna array 105 includes multiple antenna subarrays, and each antenna subarray may be used to form a discovery beam 119 associated with a corresponding discovery area 155. Preambles from a set of terminals 120 may be detected using a subset of the discovery beams 119. Based on detecting terminals using the subset of the discovery beams 119, a communication beam 117 may be formed (e.g., using geometric interpretation or MIMO-based techniques) within the corresponding discovery area 155, and a beam coverage area 160 of the communication beam 117 may encompass the detected terminals 120. Communication may be performed between the antenna array 105 and the detected terminals 120 using the communication beams 117, and at least a subset of the communication beams 117 may reuse common time, frequency, and polarization resources.

[0025] The geometric relationship between the geographical region covered by the communications beam 117 and the antenna unit 110 may be used to determine beam coefficients of the antenna array 105 used to form the communications beam 117 (e.g., using geometric interpretation or geometrically informed MIMO). For example, the distance between the antenna unit 110 and the geographical region may be used to determine the value of the beam coefficient used to introduce a phase delay into the signal received at the antenna unit 110. The geometric relationship between the antenna unit 110 and the geographical region may also be used to determine the angle of arrival of the signal at the antenna unit 110. In some examples, the angle of arrival of the signal at the antenna unit 110 may be used to determine the value of the beam coefficient used to adjust the magnitude of the signal received at the antenna unit 110. In some examples, the relative position of the antenna unit 110 may be used to determine the beam coefficients of the antenna unit 110; for example, the beam coefficients of other antenna units 110 may be determined relative to the beam coefficients determined for the reference antenna unit 110.

[0026] To determine the geometric relationship between the antenna units 110 and geographic regions and / or between the antenna units 110, the location of each of the antenna units 110 may first be determined. For example, ground-based measurement techniques (e.g., radio detection and ranging (RADAR)) may be used to determine the location (e.g., x, y, z coordinates) of each antenna unit 110. Additionally or alternatively, the antenna units 110 may broadcast their locations to, for example, a central processing unit of the antenna array 105 to determine the distance between the antenna units 110 and the central location. In such a case, the central processing unit may also measure the angle of arrival for each of the broadcast signals used in conjunction with the determined distance to determine the location of the broadcast antenna units 110.

[0027] In some examples, each antenna unit 110 may transmit a ranging signal (e.g., a unique ranging signal) used to determine the distance between the transmitting antenna unit 110 and other antenna units 110 in the antenna array 105. Each antenna unit 110 may also receive ranging signals transmitted from other antenna units 110. In such cases, each antenna unit 110 may include an antenna 111 and an antenna manager 112. The antenna 111 may be a single antenna or multiple antennas. In some examples, the antenna 111 may be an antenna panel including a set of consistently spaced antenna elements (which may be referred to as an antenna subarray). The antenna manager 112 may be used to generate a ranging signal unique to the corresponding antenna unit 110. In some examples, the antenna manager 112 may generate a ranging signal that includes an identifier of the corresponding antenna unit 110 (e.g., each antenna unit 110 may be assigned an index), a timestamp indicating when the ranging signal was transmitted, Global Positioning System (GPS) coordinates, or any combination thereof. In some examples, each of the antenna units 110 is configured to simultaneously transmit ranging signals. The antenna manager 112 may also be used to receive ranging signals transmitted from other antenna units 110. In some examples, the antenna manager 112 is used to detect parameters associated with the received ranging signals (e.g., the time the ranging signal was received, the angle of arrival, the identifier of the transmitting antenna unit 110, etc.).

[0028] In some examples, the antenna manager 112 can transmit the detected parameters to a central processing unit (e.g., a calibration unit), which can determine the distance between each of the antenna units 110 (or, in some examples, the distance between each of the antennas 111 of the antenna units 110). In other examples, the antenna manager 112 can determine the distance between itself and each of the other antenna units based on the detected parameters and transmit the distance to the central processing unit. In such a case, the central processing unit can combine the received distances to determine the distance between each of the antenna units 110. In either case, after determining the distance between each of the antenna units 110, the central processing unit can use the distances to determine the position of each of the antenna units 110. In some examples, in addition to using the distances, the central processing unit can use the known positions of a set of antenna units 110 designated as reference antenna units (which may also be referred to as anchor antenna units) to determine the orientation of the antenna array 105. The central processing unit can use both the distance and the orientation of the antenna array 105 to determine the position of the antenna units 110. Determining the position of each of the antenna units 110 can be referred to as calibration.

[0029] By configuring each antenna unit 110 to transmit ranging signals and to receive ranging signals transmitted from other antenna units 110, and using anchor points to determine the orientation of the antenna array 105, the distance between antenna units 110 (and therefore the positions of the antenna units 110) can be determined with reduced delay, increased accuracy, and reduced complexity, e.g., relative to ground-based measurement techniques, position broadcast techniques, etc.

[0030] FIG. 2 illustrates an example of a sparse antenna array 205 that supports sparse antenna array calibration according to examples described herein.

[0031] The antenna array 205 includes antenna units 210, which may be distributed non-uniformly throughout the antenna array 205. In some examples, a set of antenna units 210 may be designated as reference antenna units. For example, the first antenna unit 210-1, the second antenna unit 210-2, and the third antenna unit 210-3 may be designated as reference antenna units. In some examples, the antenna position of the first antenna unit 210-1 may be designated as the origin of the antenna array 205. That is, if a three-dimensional x-y-z coordinate system is used, the antenna position of the first antenna unit 210-1 may be designated as (0,0,0). Each antenna unit 210 may include an antenna 211.

[0032] In some examples, the positions of other antenna units designated as reference antenna units may be determined relative to the position of the first antenna unit 210-1. For example, the antenna of the second antenna unit 210-2 may be positioned a unit spacing (e.g., a known distance, a distance equivalent to the wavelength of the communication signal, or a multiple of the wavelength of the communication signal) away from the antenna of the first antenna unit 210-1 in the x direction. That is, the position of the antenna of the second antenna unit 210-2 may be designated as (1,0,0). The antenna of the third antenna unit 210-3 may be positioned a unit spacing away from the antenna of the first antenna unit 210-1 in the y direction. That is, the position of the antenna of the third antenna unit 210-3 may be designated as (0,1,0). In some examples, the axes of the x-y-z coordinate system may not be fixed and may rotate with the antenna array 205 to maintain the preceding relationship between the antennas of the reference antenna units, regardless of the current orientation of the antenna array 205.

[0033] In some examples, the fourth reference antenna unit has an antenna located one unit distance away from the first antenna unit 210-1 in the Z direction. That is, the position of the antenna of the fourth reference antenna unit may be specified as (0,0,1). Other coordinate systems, such as a polar coordinate system, may be used to represent the position of the antenna unit 210 in the antenna array 205.

[0034] In some examples, the above configuration of the reference antenna units may be maintained using fixed connections 215 between the reference antenna units. For example, fixed connection 215-1 may connect antenna units 210-1 and 210-3, and fixed connection 215-2 may connect antenna units 210-1 and 210-2. In other examples, the above configuration of the reference antenna units may be maintained using other techniques, such as stationkeeping (e.g., thrusters) via command and control signaling.

[0035] Additionally or alternatively, the positions of the other reference antenna units may be determined using ground-based measurement techniques. For example, a ground station may use RADAR to determine the position of each of the reference antenna units. In some examples, the ground station may use RADAR to determine the positions of the other reference antenna units relative to the first antenna unit 210-1. In examples in which a mechanism for maintaining the relative positions of the reference antenna units is not used and ground-based measurement techniques are used, the positions of the reference antenna units may be configured differently; for example, the antenna position of the first antenna unit 210-1 may be (0,0,0), the antenna position of the second antenna unit 210-2 may be (2,0,1), and the antenna position of the third antenna unit 210-3 may be (0,1,3).

[0036] As described herein, each of the antenna units 210 (including the reference antenna unit) may transmit a ranging signal 220. Each ranging signal 220 transmitted by an antenna unit 210 may be unique, e.g., relative to the other antenna units, the fourth antenna unit 210-4 may transmit from antenna 211-4 a fourth ranging signal 220-4 (different components received by different antenna units 210 are shown) that is unique to the fourth antenna unit 210-4, the fifth antenna unit may transmit from antenna 211-5 a fifth ranging signal 220-5 (different components received by different antenna units 210 are shown) that is unique to the fifth antenna unit 210-5, etc.

[0037] In some examples, the ranging signal is transmitted using a frequency range that is specific to the transmitting antenna unit. In some examples, the ranging signal may be modulated using a modulation sequence that is specific to the transmitting antenna unit. In some examples, the modulation sequence used to modulate the ranging signal may be used to indicate the identity of the transmitting antenna unit. The modulation sequences used to transmit the ranging signal 220 may be selected to be orthogonal to one another. In some examples, the ranging signal may include information such as a timestamp indicating when the ranging signal was transmitted, the identity of the antenna unit that transmitted the ranging signal, the latest GPS coordinates of the antenna unit that transmitted the ranging signal, etc.

[0038] The ranging signal 220 may be transmitted using an out-of-band frequency. That is, the ranging signal 220 may be transmitted using a frequency band that is different (e.g., non-overlapping) from the frequency band used for the communication signal. In some examples, the ranging signal 220 is transmitted using a higher frequency band than the frequency band used for the communication signal, such that the frequency of the ranging signal may be higher than the carrier frequency of the communication signal. Using a higher frequency band may ensure that the wavelength of the ranging signal is smaller than the wavelength of the modulated communication signal. In some examples, the ranging signal is communicated using a frequency band above 60 GHz.

[0039] As described herein, each antenna unit 210 (including the reference antenna unit) may receive each component of the ranging signal transmitted from the other antenna units 210. The antenna manager 212 of the antenna unit may process each received ranging signal 220. In some examples, the antenna manager 212 determines parameters of the received ranging signal 220. For example, the antenna manager 212 may determine each antenna unit 210 that transmitted the received ranging signal 220. The antenna manager 212 may also determine the time when the ranging signal 220 was received. In some examples, a timing component provides a clock or time reference to the antenna unit 210. The antenna manager 212 may also determine the angle of arrival of the received ranging signal 220. The antenna manager 212 may also determine the GPS coordinates of each antenna unit 210 (e.g., antenna 211) that transmitted the received ranging signal 220.

[0040] In some examples, each antenna unit 210 transmits a response signal (e.g., of response signal 225) in response to the received ranging signal 220. In such cases, the antenna unit 210 may determine a set of parameters based on the response signal 225. For example, the antenna unit 210 may determine the time the response signal 225 was received, the angle of arrival of the response signal 225, the respective antenna unit 210 that transmitted the received response signal 225, the GPS coordinates of the respective antenna unit 210 that transmitted the received response signal 225, or any combination thereof. Techniques involving the response signal 225 may be referred to as round-trip signaling.

[0041] In some examples, the antenna manager 212 transmits the determined parameters to a central processing unit (e.g., a central processor), which may use these parameters to determine the distance between each of the antenna units 210 (or antennas 211) of the antenna array 205. Additionally or alternatively, the antenna manager 212 may itself determine the distance between the antenna units 210 (or antennas 211) based on the determined parameters, for example, by comparing the time the ranging signal was transmitted and the time the ranging signal was received divided by the speed at which the ranging signal travels (e.g., the speed of light). In some examples, the antenna manager 212 may determine the distance to other antenna units without using a common time reference, for example, based on knowing the time the ranging signal was transmitted and the time the response signal was received when a round-trip signal is used. The antenna units 210 may transmit the determined distance to the central processing unit. For example, antenna managers 212-4 and 212-5 of antenna units 210-4 and 210-5, respectively, may transmit the distances determined from ranging signals 220-4 and 220-5 to a central processing unit.

[0042] The central processing unit may determine the distance between each of the antenna units 210 of the antenna array 205 based on the received set of parameters or the distances received from the antenna units. The central processing unit may use the determined distances to determine the position of each of the antenna units 210. In some examples, the central processing unit may use a reference antenna unit to determine the orientation of the antenna array 205. The central processing unit may use both the determined distances, the known position of the reference antenna unit, and the orientation of the antenna array to determine the position of each of the antenna units. Techniques used by the central processing unit to determine the position of each of the antenna units are described in more detail herein and with respect to FIG. 3.

[0043] FIG. 3 illustrates an example of a communication network 300 that supports sparse antenna array calibration in accordance with examples described herein.

[0044] The communication network 300 illustrates a system for communicating using one or more of MIMO techniques, geometric interpretation techniques, and geometrically informed MIMO techniques. The communication network 300 also illustrates a system for calibrating the antenna array 305.

[0045] Communications network 300 may include antenna array 305, bus 315, beam manager 320, calibration unit 340, processor 347, communications manager 350, and memory 355. At least a portion (e.g., all) of communications network 300 may be located within a spatial segment of communications network 300 (e.g., within a satellite system). In some examples, portions of communications network 300 not included in a spatial segment may be located within a terrestrial segment of communications network 300 (e.g., within a terrestrial system). For example, antenna array 305, beam manager 320, calibration unit 340, processor 347, and memory 355 may be included in the spatial segment of communications network 300, while communications manager 350 may be included in the terrestrial segment of communications network 300. In another example, the antenna array 305 may be included in the spatial segment of the communication network 300, while the beam manager 320, calibration unit 340, processor 347, memory 355, and communication manager 350 may be included in the terrestrial segment of the communication network 300.

[0046] The antenna array 305 may be an example of the antenna array of FIGS. 1 and 2 and may include antenna units 310. The antenna units 310 may be an example of the antenna units described with reference to FIGS. 1 and 2. The spacing between the antenna units 310 may vary throughout the antenna array 305. In some examples, one or more of the antenna units 310 may be included in an antenna subarray (e.g., an antenna subarray with inconsistent spacing) or may include an antenna subarray (e.g., an antenna subarray with consistent antenna spacing), as described with reference to FIG. 1. In some examples, the distance (e.g., average distance) between the antenna units 310 is greater than a distance associated with the wavelength of the signals communicated using the antenna array 305. In some examples, the distance (e.g., average distance) between the antenna units 310 is greater than a distance associated with ten times the wavelength of the signals communicated using the antenna array 305.

[0047] The antenna unit 310 may include an antenna 311 and an antenna manager 312. In some examples, the antenna 311 may be a single antenna or an antenna panel including consistently spaced antenna elements. The antenna manager 312 may be used to manage the transmission and reception of ranging signals from each antenna unit 310. In some examples, a subset of the antenna units 310 (e.g., three or more of the antenna units 310) are designated as reference antenna units. In such cases, one reference antenna unit of the subset of antenna units 310 may be designated as the origin of the antenna array 305 and may be referred to as the origin reference antenna unit. That is, the origin reference antenna unit may be designated as having an xyz position of (0,0,0). In some examples, the reference antenna unit is a set of affine points in an absolute orientation relative to the satellite including the antenna array 305.

[0048] In some examples, the positions of other reference antenna units relative to the origin reference antenna unit may be known. In some examples, the positions of other reference antenna units may be known based on the architecture of the antenna array 305. For example, the antenna array 305 may be configured so that a second reference antenna has an x, y, and z position of (1, 0, 0) and a third reference antenna has an x, y, and z position of (0, 1, 0). In some examples, the antenna array 305 may be configured so that a fourth reference antenna has an x, y, and z position of (0, 0, 1). In some examples, the units of the x, y, and z coordinate system correspond to wavelengths used for communication signals. Also, in some examples, the axes of the coordinate system may rotate with the antenna array 305 to maintain the above coordinates regardless of the current orientation of the antenna array 305. In some examples, a fixed connection between the reference antenna units may be used to obtain a reference antenna unit configured with a previous coordinate.

[0049] In other examples, the positions of the other reference antenna units relative to the origin reference antenna unit may be known based on ground-based measurements. For example, the positions of the other reference antenna units relative to the origin reference antenna unit may be determined at a ground station using RADAR or light detection and ranging (LIDAR) techniques. In some examples, the ground station may signal the positions of the reference antenna units to the calibration unit 340.

[0050] The bus 315 may represent an interface through which signals may be exchanged between the antenna array 305 and a central location that may be used to distribute signals to the signal processing components of the communications network 300, such as the beam manager 320 and the calibration unit 340. The bus 315 may include a collection of wires connecting to each of the antennas. Additionally or alternatively, the bus 315 may be a wireless interface used to wirelessly communicate signaling between the antenna array 305 and the signal processing components, for example, according to a communications protocol.

[0051] The beam manager 320 may be configured to form beams including discovery beams, communication beams, geometric interpretation-based beams, MIMO-based beams, etc. In some examples, the beam manager 320 may be configured to form one or more discovery beams (e.g., a discovery beam covering the discovery area 155 of FIG. 1) within a geographic area covered by the antenna array 305 (e.g., geographic area 150 of FIG. 1). To form a discovery beam, the native antenna pattern of the set of antennas 311 of the antenna unit 310 may be used or may be combined with beamforming techniques, MIMO techniques, or a combination thereof.

[0052] The beam manager 320 may also be configured to form one or more communications beams (e.g., communications beams that form the beam coverage area 160 of FIG. 1). To form the communications beams, a geometric interpretation-based beamforming technique, a MIMO technique, or a geometry-informed MIMO technique may be used. The beam manager 320 may include a geometry component 325 and a MIMO component 330.

[0053] The geometric component 325 may be configured to form small communication beams (e.g., communication beams having diameters less than 10 km or less than 5 km) using a geometric relationship between the terminal's location and a set (e.g., including up to all) of the antenna units 310 of the antenna array 305. In some examples, the geometric component 325 may determine beam coefficients (e.g., phase shifts, amplitude components) that can be used to align in time signals detected at different antennas 311 of the antenna units 310 so that the signals can be added together according to the terminal's spatial location, increasing the signal strength of the transmitted signal associated with each of the detected signals. In some examples, the geometric component 325 may determine a first set of beam coefficients associated with a first beam coverage area, a second set of beam coefficients associated with a second beam coverage area, and so on. Thus, the geometric component 325 may independently determine multiple sets of beam coefficients and apply them to signals received from the antenna array 305, with each set of beam coefficients associated with a different beam coverage area.

[0054] The MIMO component 330 may be configured to use multipath signal propagation to form MIMO-based beams. In some examples, the MIMO component 330 may receive channel sounding probes from a set of transmitters (e.g., terminals), the structure of the channel sounding probes may be known to the MIMO component 330, and the channel sounding probes transmitted from different transmitters may be orthogonal to one another. The MIMO component 330 may use the channel sounding probes to estimate the channel between the antenna array 305 and the transmitter. Based on the estimated channel, the MIMO component 330 may determine beam coefficients (e.g., amplitude and phase shift) that can be used to account for the spatial layers of the channel. In some examples, the MIMO component 330 may determine beam coefficients that can be used to separate signals transmitted on spatial layers from one another, for example, by emphasizing the signals transmitted in the spatial layer and canceling interference from signals transmitted in other spatial layers, for each spatial layer. The MIMO component 330 may determine a single set of beam coefficients to apply to signals detected at a set (e.g., all) of antennas 311 of the antenna units 310 in the antenna array 305. The beam coefficients may be included in an M×N matrix, where the value of M may indicate the number of antenna units 310, the value of N may indicate the number of spatial layers, and the value of N may be less than or equal to the value of M.

[0055] The calibration unit 340 may be configured to determine the position (e.g., coordinates) of each of the antenna units 310 (or antennas 311) of the antenna array 305. The calibration unit 340 may be configured to determine the distance between each of the antenna units 310 (or antennas 311) of the antenna array 305. The calibration unit 340 may be configured to determine the orientation of the antenna array 305. In some examples, the calibration unit 340 uses the determined distance between each of the antenna units 310 and the orientation of the antenna array 305 to determine the position of each of the antenna units 310 (or antennas 311). In some examples, the beam manager 320 (e.g., either the geometry component 325 or the MIMO component 330) may use the positions of the antenna units 310 determined by the calibration unit 340 to determine beam coefficients for the antenna array 305 to form communication beams for communicating with one or more terminals, discovery beams, or both. The calibration unit 340 may include a positioning component 341 , a measurement component 342 , and a timing component 343 .

[0056] The positioning component 341 may be configured to determine the positions of a set of antenna units 310 designated as reference antenna units. In some examples, the positioning component 341 determines the positions of the reference antenna units based on the architecture of the antenna array 305. For example, the positioning component 341 may determine that a first reference antenna unit is at the origin of the antenna array 305 (e.g., (0,0,0)), a second reference antenna unit is at a point unit spacing away from the origin along a first axis (e.g., (1,0,0)), and a third reference antenna unit is at a point unit spacing away from the origin along a second axis (e.g., (0,0,1)). In some examples, the reference antenna units may be connected to each other by a fixed connection that maintains this geometric relationship between the reference antenna units. In some examples, the orbits of the reference antenna units may be controlled to maintain this geometric relationship. In such cases, the coordinate system may rotate with the antenna array 305 to maintain this geometric relationship between the reference antenna units.

[0057] In some examples, the positioning component 341 determines the location of the reference antenna units based on positioning coordinates broadcast by the reference antenna units, e.g., according to a fixed coordinate system. In some examples, the positioning component 341 determines the location of the reference antenna units based on positioning coordinates of the reference antenna units received from ground ranging stations that measure the location of each of the reference antenna units.

[0058] The measurement component 342 may be configured to determine the distance between each of the antenna units 310 (or antennas 311). In some examples, the measurement component 342 determines the distance between each of the antenna units 310 (or antennas 311) based on a set of parameters received from the antenna units 310, where the set of parameters may include a transmit timestamp and a receive timestamp. In some examples, the measurement component 342 determines the distance between each of the antenna units 310 based on a distance determined by and received from the antenna units 310. In some examples, the measurement component 342 determines the distance between each of the antenna units 310 based on a distance received from a ground-based ranging station. In some examples, the distance is expressed as a multiple of the wavelength of a primary communication frequency, e.g., the lowest frequency, the center frequency, or the highest frequency covered by the communication bandwidth. For example, if the communication bandwidth is in the range of 240 MHz to 380 MHz, the wavelength used as the unit of measurement may be selected as a wavelength of 240 MHz, 310 MHz, or 380 MHz. In other examples, the distance may be expressed as a multiple of different wavelengths relative to the primary communication frequency (eg, the wavelength corresponding to twice the highest frequency of the communication bandwidth).

[0059] In some examples, the measurement component 342 may arrange the determined distances in a matrix form that may be referred to as a Euclidean distance matrix. For example, the measurement component 342 may arrange, for all of the antenna units, in a first row, the determined distances between a first antenna unit and other antenna units (including the first antenna unit itself), in a second row, the determined distances between a second antenna unit and other antenna units (including the second antenna unit itself), etc. Such a matrix may be represented as TIFF0007785780000001.tif22170, where d 1,1 represents the distance between the first antenna unit and the first antenna unit itself, and d 1,Nrepresents the distance between the first antenna unit and the Nth antenna unit, and d N,1 represents the distance between the Nth antenna unit and the first antenna unit, and d N,N represents the distance between the Nth antenna unit and the Nth antenna unit. Such a matrix may have zeros along the diagonal, for example, because the distance between an antenna unit and itself may be equal to zero. The matrix may also be symmetric, i.e., assuming noise-free measurements, d i,j is d j,i Therefore, we can also define the matrix as TIFF0007785780000002.tif19170, and the entry d in the matrix i,j teeth, TIFF0007785780000003.tif10170, which is TIFF0007785780000004.tif14170, which is equivalent to It could be equivalent to TIFF0007785780000005.tif15170.

[0060] The measurement component 342 may also be configured to determine the orientation of the antenna array 305. In some examples, the measurement component 342 may determine the orientation of the antenna array 305 based on a reference antenna unit. In some cases, the measurement component 342 may determine the orientation of the antenna array 305 based on receiving positioning coordinates of the reference antenna unit relative to a fixed coordinate system and determining a rotated coordinate system (e.g., (0,0,0), (1,0,0), (0,1,0)) that provides a desired geometric relationship between the reference antenna units. The measurement component 342 may compare the fixed and rotated coordinate systems to determine the orientation of the antenna array 305. In other cases, the measurement component 342 may receive rotation information from the antenna unit 310, and the antenna manager 312 may determine an offset between the position of the antenna unit 310 and the position in the fixed coordinate system.

[0061] The positioning component 341 may be further configured to calculate the positions of the antenna units 310, for example, based on the determined distance between each of the antenna units 310. The positioning component 341 may arrange the positions of the antenna units in a matrix form. For example, the position of a first antenna unit may be represented by a first column of a matrix P, the position of a second antenna unit may be represented by a second column of the matrix, etc. Such a matrix may be TIFF0007785780000006.tif16170. In some examples, the positions of a subset of the antenna units, e.g., the reference antenna unit, are known. In such cases, the matrix may be TIFF0007785780000007.tif19170. The positioning component 341 may calculate the x, y, and z coordinates corresponding to the unknown position of the antenna unit based on a Euclidean distance matrix. In some examples, the determined matrix P may be It can be rotated relative to a fixed coordinate system by a matrix R, which can be expressed as TIFF0007785780000008.tif17170.

[0062] The timing component 343 may be configured to provide a common time reference to the antenna units 310. In some examples, the timing component 343 is configured to transmit (e.g., periodically) one or more signals that enable the antenna units 310 to synchronize their internal clocks.

[0063] The calibration unit 340 may also include a Kalman filter. In some examples, measurements (e.g., sets of parameters) received by the measurement component 342 may be applied to the Kalman filter and used to update a model of the position of the antenna unit 310. In such a case, if the antenna unit 310 is moving deterministically, the results of the Kalman filter may be used to later predict the position of the antenna unit 310.

[0064] In some examples, the positioning component 341 may be further configured to calculate an orientation of an antenna (e.g., antenna 111) of the antenna unit 310, for example, using signal strength measurements of ranging signals transmitted by the antenna unit 310 received at multiple other antenna units 310 and a known radiation pattern of the antenna 111 of the antenna unit 310. For example, the orientation of the antenna 111 may be determined by comparing relative signal strength measurements of the ranging signals in light of the determined relative distances between the antenna units 310.

[0065] The communications manager 350 may be configured to process beam signals received from the beam manager 320. The communications manager 350 may decode data symbols included in the beam signals. In some examples, the communications manager 350 may configure different modes in the beam manager 320. For example, the communications manager 350 may configure a first mode in the beam manager 320 used to discover terminals within a geographic area. While the first mode is configured, the beam manager 320 may form a discovery area using beamforming and / or MIMO techniques. The communications manager 350 may also configure a second mode in the beam manager 320 used to communicate with terminals within the geographic area using small beams. While the second mode is configured, the beam manager 320 may form a beam coverage area for communicating with the discovered terminals using geometric interpretation.

[0066] The processor 347 may include an intelligent hardware device (e.g., a general-purpose processor, a digital signal processor (DSP), a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (IC), a field-programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). The processor 347 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 355) to cause the communications network 300 to perform various functions (e.g., functions or tasks supporting sparse antenna array calibration). For example, the communications network 300 or a component of the communications network 300 may include the processor 347 and the memory 355 coupled to the processor 347, which are configured to perform various functions described herein.

[0067] Memory 355 may include random access memory (RAM) and / or read-only memory (ROM). Memory 355 may store computer-readable and computer-executable code. The code may include instructions that, when executed by processor 347, cause communication network 300 to perform various functions described herein. Code 360 ​​may be stored on a non-transitory computer-readable medium, such as system memory or another type of memory. In some cases, code 360 ​​may not be directly executable by processor 347, but may (e.g., when compiled and executed) cause a computer to perform functions described herein. In some cases, memory 355 may include a basic I / O system (BIOS), which may control basic hardware or software operations, such as interaction with peripheral components or devices, among other things.

[0068] In some examples, the beam manager 320, the calibration unit 340, the communications manager 350, or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry). The hardware may include a processor, a DSP, an ASIC, an FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting means for performing the functions described in this disclosure. In some examples, the processor and a memory coupled to the processor may be configured to perform one or more of the functions described herein (e.g., by the processor executing instructions stored in the memory).

[0069] Additionally or alternatively, the beam manager 320, the calibration unit 340, the communications manager 350, or various combinations or components thereof may be implemented in code 360 ​​executed by the processor 347 (e.g., as communications management software or firmware). When implemented in code 360 ​​executed by the processor 347, the functions of the beam manager 320, the calibration unit 340, the communications manager 350, or various combinations or components thereof may be performed by a general-purpose processor, a DSP, a central processing unit (CPU), an ASIC, an FPGA, or any combination of these or other programmable logic devices (e.g., configured as or otherwise supporting a means for performing the functions described in this disclosure).

[0070] The ranging station 365 may be configured to determine geometric information of the antenna array 305. In some examples, the ranging station 365 may be configured to determine the location of a set of antenna units 310 designated as reference antenna units. The ranging station 365 may also be configured to determine the distance between each of the antenna units 310. The ranging station 365 may be ground-based or satellite-based.

[0071] 4 illustrates an example of a communications subsystem 400 supporting sparse antenna array calibration, according to examples described herein. The communications subsystem 400 illustrates communications between an antenna array 405 and a terminal 420, processed using geometric relationships between the antenna units 410 of the antenna array 405 and the terminal 420. In some examples, a first set of signals 425 (signals 425-1 through 425-M) is transmitted between a first terminal 420-1 and the antenna array 405, and a second set of signals 430 (e.g., signals 430-1 through 430-N) is transmitted between a second terminal 420-2 and the antenna array 405. In some examples, the first set of signals 425 may relate to a single signal (e.g., a preamble or data signal) transmitted from the first terminal 420-1 to the antenna array 405, or the first set of signals 425 may be components (e.g., multipath components) of a signal transmitted from the first terminal 420-1. In other examples, the first set of signals 425 may be associated with a single signal (e.g., a preamble response or a data signal) acquired at the antenna array 405 for transmission to the first terminal 420-1, and the first set of signals 425 may be a component (e.g., an element) of a signal transmitted from the antenna array 405. Similarly, the second set of signals 430 may be associated with a single signal (e.g., a preamble or a data signal) transmitted from the second terminal 420-2 to the antenna array 405, or a single signal (e.g., a preamble response or a data signal) acquired at the antenna array 405 for transmission to the second terminal 420-2.

[0072] In some examples, the first set of antenna units 410 and first beam coefficients are used to form a discovery beam 419 having a discovery area 455. Signals received at the antenna array 405 using the first set of antenna units 410 and first beam coefficients may be analyzed to determine whether the signals include a preamble indicating the presence of a terminal. In some examples, the presence of the first terminal 420-1 is detected based on the first terminal 420-1 transmitting a preamble, and the first set of signals 425 may be a signal component of the preamble transmission. The preamble may include a repeating waveform. In some examples, the waveform may be modulated with a spreading code before transmission or may include coded data to increase the difficulty associated with spoofing the preamble. The preamble may also include positioning information, for example, in a second part of the preamble.

[0073] In some examples, the location of the first terminal 420-1 may be determined based on positioning information included in the preamble. Additionally or alternatively, the location of the first terminal 420-1 may be determined based on dithering beam coverage areas around the discovery area 455 after detecting the presence of the first terminal 420-1. The location of the first terminal 420-1 may be determined based on whether the signal quality associated with the first beam coverage area 460-1 meets a threshold, is higher than the signal quality associated with other beam coverage areas covered by the dithering operation, or both. The presence and location of the second terminal 420-2 may similarly be detected based on a preamble transmitted from the second terminal 420-2, and the second set of signals 430 may be signal components of the preamble transmission. Similarly, the location of the second terminal 420-2 may be determined based on dithering the beam coverage area 460-2 around the discovery area 455 after detecting the presence of the second terminal 420-2.

[0074] Second beam coefficients may be determined for the first terminal 420-1 based on the position of the first terminal 420-1. The second beam coefficients may also be determined based on the position of the antenna unit 410 relative to the first terminal 420-1, where the position of the antenna unit 410 may be determined as described above. In some cases, the second beam coefficients may also be determined based on the determined orientation of the antenna unit 410, where the orientation of the antenna unit may be determined as described above. The second beam coefficients may be used in conjunction with the second set of antenna units 410 to form a first communications beam 417-1 having a first beam coverage area 460-1. The second beam coefficients may be used to apply timing shifts (e.g., phase shifts) or amplitude weighting to signals detected at different antennas of the second set of antenna units 410 so that signals transmitted within the first beam coverage area 460-1 are distinguishable from signals transmitted in adjacent beam coverage areas. In some examples, the second beam coefficients may be represented using an M1×1 vector, where M1 may represent the number of antennas in the second set of antenna units 410 (e.g., 100 antennas, 1000 antennas, etc.). In some cases, the M1×1 vector may include coefficients for all of the antenna units 410, and some coefficients may be zero coefficients (e.g., the second set of antenna units 410 contributing to the first communication beam 417-1 may be a subset of the antenna units 410).

[0075] Third beam coefficients may be similarly determined for the second terminal 420-2. In some examples, the third beam coefficients may be represented using an M2×1 vector, where M2 may represent the number of antennas in the third set of antenna units 410 (e.g., 100 antennas, 1000 antennas, etc.). In some examples, the third set of antenna units 410 and the second set of antenna units 410 overlap (e.g., partially or completely).

[0076] In some examples, a first set of antenna units 410 associated with the discovery beam 419 may detect a first set of signals 425 within the discovery area 460, and second beam coefficients used to form the first communication beam 417-1 may be determined. Based on the determination, the second beam coefficients may be applied to a subsequent set of detected signals (e.g., corresponding to a subsequent data signal transmitted by the first terminal 420-1) output by the second set of antenna units 410 associated with the first communication beam 417-1. In some examples, the second set of antenna units 410 includes a majority (e.g., greater than 50%, 60%, 70%, 80%, or 90%) of the antenna units 410 in the antenna array 405. In some cases, the second set of antenna units 410 may include a portion (or all) of the first set of antenna units 410 associated with the discovery beam 419, and the second set of antenna units 410 may include a greater number of antenna units 410 than the first set of antenna units 410.

[0077] The first set of antenna units 410 associated with the discovery beam 419 may also detect a second set 430 of signals within the discovery area 460, and third beam coefficients used to form the second communications beam 417-2 may be determined. Based on the determination, the third beam coefficients may be applied to a subsequent set of detected signals (corresponding to a subsequent data signal transmitted by the second terminal 420-2) output by the third set of antenna units 410 associated with the second communications beam 417-2. The third set of antenna units 410 may overlap with the second set of antenna units 410, for example, include a portion of the second set of antenna units 410, or may be the same as the second set of antenna units 410. The second set of antenna units 410 may also include a majority (e.g., greater than 50%, 60%, 70%, 80%, or 90%) of the antenna units 410 in the antenna array 405.

[0078] Signal diagram 401 illustrates a first set of element signals 435 (e.g., element signals 435-1 through 435-M) detected at a second set of antenna units 410 associated with a first communications beam 417-1 and a second set of element signals 440 (e.g., element signals 440-1 through 440-N) detected at a third set of antenna units 410 associated with a second communications beam 417-2. Signal diagram 401 also illustrates the time delays associated with when first set of element signals 435 and second set of element signals 440 are detected at their respective antennas. First set of element signals 435 may correspond to first set of signals 425, and second set of element signals 440 may correspond to second set of signals 430. In some examples, first set of element signals 435 and first set of signals 425 may relate to data signals transmitted from first terminal 420-1. Additionally, second set of element signals 440 and second set of signals 430 may relate to data signals transmitted from second terminal 420-2.

[0079] Signal diagram 401 also shows the result of applying first beam coefficients 464-1 (which may correspond to second beam coefficients used to form first communications beam 417-1) to the first set of element signals 435 to obtain resultant element signals 465 (e.g., element signals 465-1 through 465-M). In some examples, each beam coefficient of first beam coefficients 464-1 may be applied to a respective antenna of the second set of antenna unit 410. Each beam coefficient of first beam coefficients 464-1 may be used to apply a time delay (e.g., a phase shift) or an amplitude weight, or both, to signals received at a respective antenna element, so that the resultant element signals 465 are aligned in time and may be combined with each other (e.g., summed via summing component 466) to form first beam signal 475-1 for first communications beam 417-1, and the signal-to-noise ratio (SNR) value of first beam signal 475-1 may be proportional to the number of element signals 465. In some examples, summing component 466 may include separate summing components used to sum the element signals obtained for each communications beam.

[0080] A second beam coefficient 464-2 (which may correspond to a third beam coefficient used to form the second communications beam 417-2) may similarly be applied to the second set of element signals 440, and the resulting element signals 470 (e.g., element signals 470-1 through 470-N) may be combined (e.g., summed via summing component 466) to obtain a second beam signal 475-2 for the second communications beam 417-2. Thus, the beam coefficients used to form the communications beam 417 may be independently determined and applied to signals received at the antenna unit 410.

[0081] In some examples, transmissions of associated data signals from the first terminal 420-1 and the second terminal 420-2 may overlap each other in time (e.g., partially or completely). In such cases, the first set of element signals 435 and the second set of element signals 440 may be superimposed to form a composite signal. Also in such cases, the first beam coefficients 464-1 may be applied to the composite signal to obtain a resulting element signal 465, and the second beam coefficients 464-2 may be applied to the composite signal to obtain a resulting element signal 470. In such cases, undesired signals in the composite signal may cause noise in the resulting beam signal 475 and may approach cancellation for many of the element signals.

[0082] In some examples, the following equation may be used to determine the beam signals received from the multiple communication beams 417: TIFF0007785780000009.tif33170In formula, TIFF0007785780000010.tif10170 corresponds to the signal received at the ith antenna of the set of antennas, f0 is the carrier frequency of the signal, t is the current time, TIFF0007785780000011.tif11170 is the time when the signal is received by the ith antenna, TIFF0007785780000012.tif11170 is the quantized estimate of the time delay between the signal received at the ith antenna and the earliest signal received at the set of antennas, TIFF0007785780000013.tif7170 is the phase of the signal. The time delay between the signal listed at the i-th antenna and the earliest signal received at the set of antennas represents the delay spread across the array at each i-th antenna. Subtracting the individual delays can align all signal samples, for example, as if they were all co-located at the "earliest signal" arrival location.

[0083] 5 illustrates an example of a communications subsystem 500 supporting sparse antenna array calibration according to examples described herein. Communications subsystem 500 illustrates communications between an antenna array 505 and terminals 520 that are processing using MIMO processing or geometry-informed MIMO processing. In some examples, first terminal 520-1 is an example of first terminal 520-1 of FIG. 5, and second terminal 520-2 is an example of second terminal 520-2 of FIG. 5.

[0084] The communication path between the terminal 520 and the antenna array 505 may be referred to as a channel. The channel may be composed of multiple spatial layers, and the multiple antenna units 510 of the antenna array 505 (along with sets of beam coefficients) may be used to expose the spatial layers of the channel. In some examples, a set of beam coefficients (which may also be referred to as MIMO coefficients) is selected to expose a first spatial layer of the channel containing the first terminal 520-1 and a second spatial layer of the channel containing the second terminal 520-2 (which may also be referred to as a communication beam or MIMO beam).

[0085] In some examples, beam coefficients are determined based on channel sounding probes transmitted from terminals 520. The channel sounding probes may have signal patterns known to the communication network and may be used to adapt the beam coefficients to ensure that a spatial layer is focused on each terminal (or group of terminals). The channel sounding probes may be orthogonal to one another. Estimation techniques such as maximum ratio combining (MRC), minimum mean square error (MMSE), zero forcing, successive interference cancellation, maximum likelihood estimation, or neural network MIMO detection techniques may be used to estimate the channel between the antenna array 505 and terminal 520 and determine the beam coefficients. Because the beam coefficients are formed using channel sounding probes received from multiple terminals, the resulting beam coefficients may depend on the channel sounding probes transmitted in different spatial layers. That is, the beam coefficients may be determined to reduce interference from the channel sounding probes relative to each other, and changes to one beam coefficient may result in changes to other beam coefficients. Therefore, the beam coefficients may be included in a single MIMO matrix (e.g., an M×N matrix, where M may represent the number of antenna units 510 and N may represent the number of spatial streams), and the elements of the matrix may be dependent on each other.

[0086] In some examples, the operations for determining beam coefficients use high-level processing and are very complex. The amount and complexity of processing may increase as the number of antennas and the number of spatial streams increase. In some examples, the geometric relationship between the terminal 520 and the antenna unit 510 may be used to simplify the operations for determining beam coefficients, for example, by constraining the channel matrix, reducing the set of possible beam coefficients, or both. In some examples, the channel sounding probe may experience less scattering based on the relative positions of the terminal 520 and the antenna array 505. Thus, the channel estimated using the channel sounding probe may be constrained, which may reduce the complexity associated with determining beam coefficients.

[0087] The geometric relationship between the terminal 520 and the antenna unit 510 may allow the set of possible beam coefficients to be reduced for one or more of the following reasons: the position of the antenna in space may reduce the amount of scattering and multipath components that are considered for terrestrial applications; the position of the antenna in space may reduce the angles at which signals transmitted from the terminal 520 may arrive; time delays at different antenna units 510 may be utilized to determine spatial information that facilitates the determination of beam coefficients;

[0088] Signal diagram 501 may show a first set of element signals 535 (e.g., element signals 535-1, 535-2, 535-3 through 535-M) received at antenna array 505, where each element signal 535 may be received at a respective antenna, e.g., first element signal 535-1 may correspond to the first antenna of antenna unit 510. Each element signal 535 may receive signal components associated with signals transmitted from first terminal 520-1 and second terminal 520-2 (and, in some examples, from other terminals), including direct path signals and multipath signals.

[0089] A MIMO matrix 540 may be applied to the element signals 535, and the elements of the MIMO matrix 540 may be predetermined using channel sounding probes transmitted from a set of terminals. After the MIMO matrix 540 is applied to the element signals 535, a set of beam signals 575 (e.g., beam signals 575-1 through 575-N) may be output, and the beam signals 575 may be associated with respective spatial layers of the channel exposed by the MIMO matrix 540.

[0090] 6 shows an example set of operations for sparse antenna array calibration, according to examples described herein. Process flow 600 may be performed by processing unit 615 and antenna units 610 (e.g., antenna units 610-1, 610-2 through 610-N) of antenna array 605. Processing unit 615 may include a calibration unit and a beam manager, as described with reference to FIG. 3. Antenna array 605 and antenna units 610 may be examples of antenna arrays and antenna units, respectively, as described with reference to FIGS. 1 through 5.

[0091] In some examples, process flow 600 illustrates an exemplary sequence of operations performed to support sparse antenna array calibration. For example, process flow 600 illustrates operations for discovering terminals and forming small communication beams using a sparse antenna array. One or more of the operations described in process flow 600 may be performed earlier or later in the process, omitted, replaced, supplemented, or combined with other operations. Also, additional operations not included in process flow 600 described herein may be included.

[0092] At 620, the antenna units 610 may each broadcast a ranging signal. Each ranging signal may be unique to the transmitting antenna unit. For example, each ranging signal may be modulated using a modulation sequence that is unique to the transmitting antenna unit. In some examples, the ranging signal may include information such as the identity of the transmitting antenna unit, the time the ranging signal was transmitted, the GPS coordinates of the transmitting antenna unit, or any combination thereof. In some examples, the antenna units 610 may each broadcast the ranging signals simultaneously. In other examples, the broadcast of the ranging signals may be staggered, for example, within a time window.

[0093] At 625, the antenna units 610 may each transmit a response signal in response to receiving the set of ranging signals. In some examples, the transmitting antenna units 610 may transmit the response signals using the same modulation sequence used to transmit the broadcast ranging signals. Each of the response signals may be transmitted a fixed or known time after receiving the respective ranging signal. In some examples, the response signals may include information such as the identity of the responding antenna unit, the time the response signal was transmitted, the GPS coordinates of the responding antenna unit, or any combination thereof.

[0094] In 630, the antenna units 610 may measure parameters of the ranging signals, the response signals, or both. Based on receiving the ranging signals transmitted by the other antenna units, each of the antenna units 610 may determine parameters of each of the received ranging signals. For example, the second antenna unit 610-2 may determine parameters (e.g., timing information, angle of arrival, received signal strength, etc.) of the ranging signal received from the first antenna unit 610-1, or vice versa. Based on receiving the response signals from the other antenna units, the receiving antenna units may determine parameters of the response signals. For example, the first antenna unit 610-1 may determine parameters (e.g., timing information, received signal strength, angle of arrival, etc.) of the response signal received from the second antenna unit 610-2 in response to the ranging signal transmitted by the first antenna unit 610-1, or vice versa. In some examples, the antenna units 610 determine which of the antenna units 610 the measured parameter belongs to based on identification information indicated by the corresponding ranging signal or response signal. For example, the antenna units 610 may decode the identification information from the corresponding ranging signal or response signal. Additionally or alternatively, the antenna units 610 may determine the identity of the corresponding antenna unit based on the index of the modulation sequence used for the ranging signal, e.g., each of the antenna units 610 may be assigned to use a respective modulation sequence of the set of modulation sequences.

[0095] In 635, each of the antenna units 610 may determine a distance between itself and the other antenna units based on, for example, measured parameters, information included in the ranging signal, and information included in the response signal. In some examples, the antenna units 610 may determine the distance using a timestamp received in the ranging signal. For example, the second antenna unit 610-2 may determine the distance between itself and the first antenna unit 610-1 based on the timestamp included in the ranging signal transmitted from the first antenna unit 610-1, the time the ranging signal was received at the second antenna unit 610-2, and the speed at which the ranging signal propagates. In examples where each of the ranging signals is transmitted simultaneously, the second antenna unit 610-2 may determine the distance between itself and the first antenna unit 610-1 based on the common transmission time, the time when the ranging signal transmitted by the first antenna unit 610-1 is received at the second antenna unit 610-2, and the speed at which the ranging signal propagates. In some examples, the antenna unit 610 may roughly determine the distance using GPS coordinates received in the ranging signal.

[0096] At 640, the antenna unit 610 may transmit ranging information to the processing unit 615. In some examples, the ranging information includes parameters measured by the antenna unit 610 for each of the other antenna units. In some examples, the ranging information includes the distance between the antenna unit 610 itself and the other antenna units, as determined by each of the antenna units 610.

[0097] At 645, the processing unit 615 may determine a distance between each of the antenna units 610, for example, based on the received parameters, the received distances, or a combination thereof. The processing unit 615 may generate a Euclidean distance matrix based on the distances, as described herein, with reference to FIG. 3, which may represent the distances between each of the antenna units 610.

[0098] At 650, the processing unit 615 may determine an orientation of the antenna array 605. In some examples, a subset of the antenna units 610 may be designated as reference antenna units with the origin of the antenna array 605 positioned at one of the reference antenna units, and the processing unit 615 may determine the orientation of the antenna array 605 using the reference antenna units, as described herein with reference to FIGS.

[0099] At 655, the processing unit 615 may determine the positions of the antenna units 610 based on the distances (e.g., a Euclidean distance matrix) determined between each of the antenna units 610. In some examples, the processing unit 615 may also use the orientation of the antenna array 605 to determine the positions of the antenna units 610. In some examples, the processing unit 615 may determine the orientation of each of the antenna units 610 relative to the orientation of the antenna array 605 based on the distances determined for each of the antenna units, the measured signal strength of the ranging signals or response signals, and the known antenna radiation pattern of the antenna units 610.

[0100] At 660, the processing unit 615 may determine beam coefficients for the antenna array 605. The beam coefficients may be used in combination with the antenna array 605 to form one or more communication beams having a beam coverage area that encompasses one or more terminals. The beam coefficients may be determined based on a determined orientation of the antenna array 605, a determined position of the antenna unit 610, and / or a determined orientation of the antenna unit 610 relative to the orientation of the antenna array 605.

[0101] At 665 , the processing unit 615 may receive communication signals from one or more terminals via the antenna unit 610 .

[0102] At 670, the processing unit 615 may apply the determined beam coefficients to the received communication signals to obtain one or more beam signals transmitted from one or more terminals. For example, the antenna unit 610 may send a representation of the received communication signals to the processing unit 615, and the processing unit 615 may apply the determined beam coefficients to obtain one or more beam signals. In some examples, the beam coefficients are applied at the antenna unit 610 to obtain components of one or more beam signals, and the antenna unit 610 sends the components of the one or more beam signals to the processing unit 615. The processing unit 615 may combine (e.g., add) the components of the one or more beam signals to obtain one or more beam signals.

[0103] At 675, the processing unit 615 may demodulate the beam signal and decode the resulting data signal.

[0104] 7 shows an example set of operations for sparse antenna array calibration, according to examples described herein. Method 700 may be performed by a component of a communications network, such as an antenna array, a ground system, a calibration unit, or a combination thereof, which may be examples of the communications networks (or components thereof) described with reference to FIGS. 1 and 3. In some examples, the communications network may execute a set of instructions to control functional elements of the communications network to perform the described functions. Additionally or alternatively, the communications network may perform aspects of the described functions using dedicated hardware.

[0105] At 705, the method 700 may include determining positions of a plurality of reference antennas and a plurality of reference antennas of an antenna array comprising the plurality of antennas, where a position of a first reference antenna of the plurality of reference antennas is at an origin of the antenna array and positions of other reference antennas of the plurality of reference antennas are determined relative to the first reference antenna, and where inter-element spacings of antennas of the plurality of antennas vary throughout the antenna array. The operations of 705 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 705 may be performed by a positioning component as described herein with reference to FIG. 3.

[0106] At 710, the method 700 may include receiving parameters representing distances between antennas of the antenna arrays from multiple antenna managers coupled to the multiple antenna arrays. The operations of 710 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 710 may be performed by a positioning component, as described herein with reference to FIG. 3.

[0107] At 715, the method 700 may include determining a distance between each antenna of the plurality of antennas based at least in part on the plurality of parameters. The operations of 715 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 715 may be performed by a positioning component, as described herein with reference to FIG. 3.

[0108] At 720, the method 700 may include determining a reference orientation of the antenna array based at least in part on the positions of the plurality of reference antennas. The operations of 720 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 720 may be performed by a positioning component, as described herein with reference to FIG. 3.

[0109] At 725, the method 700 may include calculating positions of the plurality of antennas based at least in part on the positions of the plurality of reference antennas, the distances between each of the plurality of antennas, and the reference orientation of the antenna array. The operations of 725 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 725 may be performed by a measurement component as described herein with reference to FIG. 3.

[0110] At 730, the method 700 may include providing the calculated locations of the multiple antennas to a communications manager. The operations of 730 may be performed according to examples disclosed herein. In some examples, aspects of the operations of 730 may be performed by a measurement component, as described herein with reference to FIG. 3.

[0111] In some examples, the devices described herein may perform a method or methods such as method 700. The apparatus may include features, circuits, logic, means, or instructions (e.g., an apparatus including a memory and a processor for executing instructions stored in the memory; a non-transitory computer-readable medium having code including instructions executable by the processor) for determining positions of a plurality of reference antennas of an antenna array including a plurality of reference antennas and the plurality of antennas, wherein a position of a first reference antenna of the plurality of reference antennas is at an origin of the antenna array, positions of other reference antennas of the plurality of reference antennas are determined relative to the first reference antenna, and inter-element spacing of the plurality of antennas varies throughout the antenna array; receiving parameters representing distances between antennas of the antenna array from a plurality of antenna managers coupled to the plurality of antennas; determining a distance between each antenna of the plurality of antennas based at least in part on the plurality of parameters; determining a reference orientation of the antenna array based at least in part on positions of the plurality of reference antennas; calculating positions of the plurality of antennas based at least in part on the positions of the plurality of reference antennas, the distances between each antenna of the plurality of antennas, and the reference orientation of the antenna array; and providing the calculated positions of the plurality of antennas to a communications manager.

[0112] In some examples, to calculate the positions of the multiple antennas, the device may include features, circuitry, logic, means, or instructions for calculating the calculated positions of the multiple antennas relative to an origin of the antenna array and according to a reference orientation based at least in part on a distance between each antenna of the multiple antennas.

[0113] In some examples, the set of parameters includes an indication of a distance between each antenna of the plurality of antennas, and determining the distance between each of the antennas of the plurality of antennas is based at least in part on the indication of the distance.

[0114] In some examples, the locations of the multiple reference antennas are determined based at least in part on multiple fixed connections between the multiple reference antennas.

[0115] In some examples, the apparatus may include features, circuitry, logic, means, or instructions for receiving measured positions of a plurality of reference antennas from a ground-based measurement station, the positions of the plurality of reference antennas being determined based at least in part on the measured distances.

[0116] It should be noted that these methods describe example implementations, and that the acts and steps may be rearranged or otherwise modified so that other implementations are possible. In some examples, aspects from two or more of the methods may be combined. For example, each aspect of the method may include steps or aspects of other methods, or other steps or techniques described herein.

[0117] In some examples, a system described herein may perform a method or methods such as method 700. The system may include an antenna array comprising a plurality of antennas, wherein inter-element spacing of antennas of the plurality of antennas varies throughout the antenna array; a plurality of antenna managers, each antenna manager of the plurality of antenna managers coupled to a respective antenna of the plurality of antennas, configured to transmit a respective ranging signal from the respective antenna of the plurality of antennas, receive a respective set of ranging signals from other antennas of the plurality of antennas, and measure a respective parameter indicative of a distance between the respective antenna and the other antennas based at least in part on receiving the respective sets of ranging signals; and a calibration unit for determining a position of a plurality of reference antennas, wherein the position of a first reference antenna of the plurality of reference antennas is determined by the antenna array. and a calibration unit configured to: determine a distance between each of the plurality of antennas based at least in part on parameters measured by the antenna manager; determine a reference orientation of the antenna array based at least in part on the positions of the plurality of reference antennas; and calculate positions of the plurality of antennas based at least in part on the positions of the plurality of reference antennas, the distance between each of the plurality of antennas, and the reference orientation of the antenna array; and a communications manager configured to communicate with the terminal according to beam coefficients determined for the antenna array based at least in part on the calculated positions of the plurality of antennas.

[0118] In some examples of the system, the system includes a beam manager configured to determine beam coefficients based at least in part on the calculated positions of the plurality of antennas relative to the antenna array.

[0119] In some examples of the system, to calculate the positions of the plurality of antennas, the calibration unit is further configured to calculate the calculated positions of the plurality of antennas relative to an origin of the antenna array according to a reference orientation based at least in part on a distance between each antenna of the plurality of antennas.

[0120] In some examples of the system, the plurality of antenna managers are configured to transmit parameters measured by the plurality of antenna managers to a calibration unit, and the calibration unit is configured to determine a distance between each antenna of the plurality of antennas based at least in part on receiving the parameters measured by the plurality of antenna managers.

[0121] In some examples of the system, each antenna manager of the plurality of antenna managers is configured to determine a distance between a respective antenna and other antennas of the plurality of antennas based at least in part on measuring a respective set of parameters, and to transmit an indication of the distance between the respective antenna and the other antennas to the calibration unit, and the calibration unit is configured to determine a distance between each antenna of the plurality of antennas based at least in part on the respective distance indications received from the plurality of antenna managers.

[0122] In some example systems, each ranging signal transmitted from multiple antennas is unique.

[0123] In some examples of the system, the ranging signal transmitted by an antenna manager of the plurality of antenna managers includes an identifier of the antenna manager, a timestamp when the ranging signal was transmitted, positioning coordinates of the antenna manager, or any combination thereof.

[0124] In some examples of the system, each ranging signal is transmitted in a first band that does not overlap with a second band used by the communications manager to communicate with the terminal.

[0125] In some examples of the system, a first frequency band used to transmit each ranging signal is higher than a second frequency band used to transmit the communication signal.

[0126] In some example systems, the wavelength of the ranging signal is smaller than the wavelength of the communication signal.

[0127] In some examples of the system, the bandwidth of the ranging signal is greater than the center frequency of the second frequency band.

[0128] In some examples, the system includes a timing component configured to provide a common time reference to multiple antenna managers.

[0129] In some examples of the system, a second antenna manager of the plurality of antenna managers is configured to determine a distance between a first antenna coupled with the first antenna manager of the plurality of antenna managers and a second antenna coupled with the second antenna manager based at least in part on the ranging signal received from the first antenna.

[0130] In some examples of the system, the second antenna manager is further configured to determine a distance between the first antenna and the second antenna based at least in part on a timestamp signaled by the ranging signal and a time the ranging signal was received.

[0131] In some examples of the system, a first antenna manager of the plurality of antenna managers is configured to determine a distance between a first antenna coupled to the first antenna manager and a second antenna coupled to a second antenna manager of the plurality of antenna managers based at least in part on a ranging signal transmitted by the first antenna manager and a response signal received from the second antenna in response to the ranging signal.

[0132] In some examples of the system, the first antenna manager is configured to determine a difference between a first time when the ranging signal is transmitted by the first antenna manager and a second time when the response signal is received from the second antenna, and the distance between the first antenna and the second antenna is based at least in part on the difference.

[0133] In some examples of the system, an antenna manager of the plurality of antenna managers is configured to determine, over a plurality of time periods, a plurality of distances between each antenna of the plurality of antennas and a second antenna based at least in part on a plurality of parameters measured over the plurality of time periods, and obtain a distance between each antenna and the second antenna based at least in part on a function of the plurality of distances.

[0134] In some examples of the system, each antenna manager of the plurality of antenna managers is configured to obtain, from a respective set of ranging signals, a set of GPS coordinates associated with other antennas of the plurality of antennas, and determine, based at least in part on the set of GPS coordinates, a coarse estimate of a distance between the coupled antenna and the other antennas of the plurality of antennas.

[0135] In some examples of the system, the antenna array includes a plurality of fixed connections between a plurality of reference antennas, and the calibration unit is configured to determine positions of the plurality of reference antennas based at least in part on the plurality of fixed connections.

[0136] In some examples, the system includes a ground-based measurement station configured to measure positions of a plurality of reference antennas to obtain measured positions and to signal the measured positions of the plurality of reference antennas to a calibration unit, the calibration unit configured to receive a signal including the measured positions of the plurality of reference antennas and to determine the positions of the plurality of reference antennas based at least in part on the signal.

[0137] The information and signals described herein may be represented using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0138] The various example blocks and modules described in connection with the disclosure herein may be implemented or performed using a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration).

[0139] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. Features implementing the functions may also be physically located in various locations, including being distributed such that portions of the functions are implemented in different physical locations.

[0140] Computer-readable media include both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media may be any available medium that can be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory, compact disk read-only memory (CDROM) or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other non-transitory medium that can be used to execute or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer or a general-purpose or special-purpose processor. Also, any connection may properly be referred to as a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of media. As used herein, disk and disc include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where a disk typically reproduces data magnetically while a disc reproduces data optically with a laser. Combinations of the above are also included within the scope of computer-readable media.

[0141] As used herein, including the claims, "or" used in a list of items (e.g., a list of items preceded by a phrase such as "at least one" or "one or more") indicates an inclusive list, such as, for example, the listing "at least one of A, B, or C" means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase "based on" should not be construed as a reference to a limited set of conditions. For example, an exemplary step described as "based on condition A" could be based on both condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted the same as the phrase "based at least in part on."

[0142] In the accompanying figures, similar components or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes among the similar components. If only a first reference label is used herein, the description is applicable to any one of the similar components having the same first reference label, regardless of a second reference label, or other subsequent reference label.

[0143] The description set forth herein with reference to the accompanying drawings describes exemplary configurations and does not represent every embodiment that may be implemented or that is within the scope of the claims. As used herein, the term "exemplary" means "serving as an example, instance, or illustration," and not "preferred" or "advantageous over other embodiments." The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, these technologies may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.

[0144] The description herein is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the embodiments and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A system (100) for communication, comprising: an antenna array (105) comprising a plurality of antennas (111), wherein inter-element spacings of antennas of the plurality of antennas (111) vary throughout the antenna array (105); a plurality of antenna managers (112), each of the plurality of antenna managers (112) being coupled to a respective antenna of the plurality of antennas (111); and transmitting a respective ranging signal (220, 620) from said respective antenna of said plurality of antennas (111); receiving respective sets of ranging signals (220, 620) from other antennas of the plurality of antennas (111); a plurality of antenna managers (112) configured to: measure, based at least in part on receiving the respective sets of ranging signals (220, 620), respective parameters indicative of distances between the respective antennas and the other antennas; A calibration unit (340) comprising: determining positions of a plurality of reference antennas (211), wherein a position of a first reference antenna (211-1) of the plurality of reference antennas (211) is at an origin of the antenna array (105), positions of other reference antennas of the plurality of reference antennas (211) are determined relative to the first reference antenna (211-1), and the plurality of antennas (111) includes the plurality of reference antennas (211); determining a distance between each antenna of the plurality of antennas (111) based at least in part on the parameters measured by the plurality of antenna managers (112); determining a reference orientation of the antenna array (105) based at least in part on the positions of the plurality of reference antennas (211); a calibration unit (340) configured to calculate positions of the plurality of antennas (111) based at least in part on the positions of the plurality of reference antennas (211), the distances between each antenna of the plurality of antennas (111), and the reference orientation of the antenna array (105); a communications manager (350) configured to communicate with a terminal (120) according to beam coefficients determined for the antenna array (105) based at least in part on the calculated positions of the plurality of antennas (111), the beam coefficients being used to form a plurality of beams.

2. The system (100) of claim 1, further comprising a beam manager (320) configured to determine the beam coefficients for the antenna array (105) based at least in part on the calculated positions of the plurality of antennas (111).

3. To calculate the calculated positions of the plurality of antennas (111), the calibration unit (340) 3. The system (100) of claim 1 or 2, further configured to calculate the calculated positions of the plurality of antennas (111) relative to the origin of the antenna array (105) according to the reference orientation based at least in part on the distance between each antenna of the plurality of antennas (111).

4. the plurality of antenna managers (112) are configured to transmit the parameters measured by the plurality of antenna managers (112) to the calibration unit (340); The system (100) of any one of claims 1 to 3, wherein the calibration unit (340) is configured to determine the distance between each antenna of the plurality of antennas (111) based at least in part on receiving the parameters measured by the plurality of antenna managers (112).

5. Each antenna manager of the plurality of antenna managers (112) determining the distance between each antenna and the other antennas of the plurality of antennas (111) based at least in part on measuring a respective set of parameters; and configured to transmit to the calibration unit (340) an indication of the distance between the respective antenna and the other antenna; The system (100) of any one of claims 1 to 3, wherein the calibration unit (340) is configured to determine the distance between each antenna of the plurality of antennas (111) based at least in part on the indication of the distance between the respective antenna and the other antenna received from the plurality of antenna managers (112).

6. The system (100) of any one of claims 1 to 5, wherein each of the ranging signals (220, 620) transmitted from the plurality of antennas (111) is unique.

7. 7. The system (100) of claim 1, wherein a ranging signal (220-4) transmitted by an antenna manager (212-4) of the plurality of antenna managers (112) includes an identifier of the antenna manager (212-4), a timestamp when the ranging signal (220-4) was transmitted, positioning coordinates of the antenna manager (212-4), or any combination thereof.

8. The system (100) of any one of claims 1 to 7, wherein the respective ranging signals (220, 620) are transmitted in a first band that does not overlap with a second band used by the communications manager (350) to communicate with a terminal (120).

9. 9. The system (100) of any one of claims 1 to 8, wherein a first frequency band used to transmit the respective ranging signals (220, 620) is higher than a second frequency band used to transmit communication signals.

10. The system (100) of claim 9, wherein the wavelength of the ranging signal (220, 620) is smaller than the wavelength of the communication signal.

11. 10. The system (100) of claim 9, wherein a bandwidth of the ranging signal (220, 620) is greater than a center frequency of the second frequency band.

12. The system (100) of any one of claims 1 to 11, further comprising a timing component (343) configured to provide a common time reference to the plurality of antenna managers (112).

13. a second antenna manager (212-5) of the plurality of antenna managers (112); 13. The system (100) of claim 1, configured to determine a distance between a first antenna (211-4) coupled to a first antenna manager (212-4) of the plurality of antenna managers (112) and a second antenna (211-5) coupled to the second antenna manager (212-5) based at least in part on a ranging signal (220-4) received from the first antenna (211-4).

14. The second antenna manager (212-5) 14. The system (100) of claim 13, further configured to determine the distance between the first antenna (211-4) and the second antenna (211-5) based at least in part on a timestamp signaled by the ranging signal (220-4) and a time at which the ranging signal (220-4) was received.

15. a first antenna manager (212-4) of the plurality of antenna managers (112); 13. The system (100) of claim 1, configured to determine a distance between a first antenna (211-4) coupled to the first antenna manager (212-4) and a second antenna (211-5) coupled to a second antenna manager (212-5) of the plurality of antenna managers (112) based at least in part on a ranging signal (220-4) transmitted by the first antenna manager (212-4) and a response signal (225) received from the second antenna (211-5) in response to the ranging signal (220-4).

16. The first antenna manager (212-4) 16. The system (100) of claim 15, configured to determine a difference between a first time when the ranging signal (220-4) was transmitted by the first antenna manager (212-4) and a second time when the response signal (225) was received from the second antenna (211-5), and the distance between the first antenna (211-4) and the second antenna (211-5) is determined based at least in part on the difference.

17. An antenna manager of the plurality of antenna managers (112) determining, over a plurality of time periods, a plurality of distances between each antenna of the plurality of antennas and a second antenna based at least in part on a plurality of parameters measured over the plurality of time periods; and 17. The system (100) of any one of claims 1 to 16, configured to obtain a distance between the respective antenna and the second antenna based at least in part on a function of the plurality of distances.

18. Each antenna manager of the plurality of antenna managers (112) obtaining sets of GPS coordinates associated with the other antennas of the plurality of antennas from the respective sets of ranging signals; and The system (100) of any one of claims 1 to 17, configured to determine a coarse estimate of a distance between a coupled antenna and the other antennas of the plurality of antennas (111) based at least in part on the set of GPS coordinates.

19. The antenna array (105) The system (100) of any one of claims 1 to 18, comprising a plurality of fixed connections (215) between the plurality of reference antennas (211), wherein the calibration unit (340) is configured to determine the positions of the plurality of reference antennas (211) based at least in part on the plurality of fixed connections (215).

20. a ground-based measurement station (365) configured to measure the positions of the plurality of reference antennas (211) to obtain measured positions, and to signal the measured positions of the plurality of reference antennas (211) to the calibration unit (340); The system (100) of any one of claims 1 to 19, wherein the calibration unit (340) is configured to receive signals including the measured positions of the plurality of reference antennas (211) and to determine the positions of the plurality of reference antennas (211) based at least in part on the signals.

21. 1. A method for communication, comprising: determining the positions of a plurality of reference antennas (211) of an antenna array (105), the antenna array (105) comprising the plurality of reference antennas (211) and a plurality of antennas (111); a first reference antenna (211-1) of the plurality of reference antennas (211) is located at the origin of the antenna array (105); The positions of other reference antennas of the plurality of reference antennas (211) are determined relative to the first reference antenna (211-1); determining that inter-element spacing of antennas of the plurality of antennas (111) varies across the antenna array (105); receiving, from a plurality of antenna managers (112) coupled to the plurality of antennas (111), parameters indicative of distances between antennas of the antenna array (105); determining a distance between each antenna of the plurality of antennas (111) based at least in part on the parameters received from the plurality of antenna managers (112); determining a reference orientation of the antenna array (105) based at least in part on the positions of the plurality of reference antennas (211); calculating positions of the plurality of antennas (111) based at least in part on the positions of the plurality of reference antennas (211), the distances between each antenna of the plurality of antennas (111), and the reference orientation of the antenna array (105); and providing the calculated locations of the plurality of antennas (111) to a communications manager (350).

22. Calculating the positions of the plurality of antennas (111) 22. The method of claim 21, comprising calculating the calculated positions of the plurality of antennas (111) relative to the origin of the antenna array (105) according to the reference orientation based at least in part on the distance between each antenna of the plurality of antennas (111).

23. the parameters include an indication of the distance between each antenna of the plurality of antennas (111); 23. The method of claim 21 or 22, wherein determining the distance between each antenna of the plurality of antennas (111) is based at least in part on the indication of the distance.

24. 24. The method of claim 21, wherein the locations of the plurality of reference antennas (211) are determined based at least in part on a plurality of fixed (215) connections between the plurality of reference antennas (211).

25. 25. The method of claim 21, further comprising receiving measured positions of the plurality of reference antennas from a ground-based measurement station, wherein the positions of the plurality of reference antennas are determined based at least in part on the measured positions.

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