Directivity Calibration in Wireless Communication

Abstract

A method of wireless communication includes performing a first measurement of a wavefront received at a first antenna of a base station configured to provide wireless communication access to user devices within a coverage area, and performing a second measurement of a wavefront received at a second antenna of the base station, wherein the first antenna and the second antenna are separated by a certain separation distance along a certain direction; deriving a compensation coefficient from the first measurement and the second measurement, the compensation coefficient being used for estimating an estimated angle of arrival (AOA); and performing subsequent communication by applying the compensation coefficient to a transmitted or received signal waveform to or from the user device.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority of U.S. Provisional Application No. 63 / 368,598, filed on July 15, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] (Technical Field) This document relates to wireless communication.

Background Art

[0003] (Background) Due to the explosive growth in the number of wireless user devices and the amount of wireless data that these devices can generate and consume, current wireless communication networks are rapidly exhausting their bandwidth to adapt to such high growth in data traffic and provide high - quality services to users.

[0004] Various efforts are being made in the telecommunications industry to propose next - generation wireless technologies that can keep pace with the demand for the performance of wireless devices and networks. Many of those activities involve situations where a large number of user devices can be served by a network.

Summary of the Invention

Means for Solving the Problems

[0005] (Summary) This document discloses techniques that can be used to achieve several operational improvements by a wireless network.

[0006] In one exemplary aspect, a wireless communication method is disclosed. The method includes performing a first measurement of a wavefront received at a first antenna of a base station configured to provide wireless communication access to user devices within a coverage area, performing a second measurement of a wavefront received at a second antenna of the base station, wherein the first antenna and the second antenna are separated by a certain separation distance along a certain direction, deriving a compensation coefficient from the first measurement and the second measurement, the compensation coefficient being used to estimate an estimated angle of arrival (AOA), and performing subsequent communication by applying the compensation coefficient to a transmitted or received signal waveform to or from the user device.

[0007] In another exemplary aspect, another wireless communication method is disclosed. The method includes determining, by a base station configured to provide wireless communication access using a first communication protocol, uplink alignment for a user device based on a first signal received in an uplink direction, the uplink alignment including one or more of aligning a phase, gain, timing, or polarization difference between different receiving-side antennas of the base station based on an estimated angle of arrival (AoA) for the user device, determining an estimated value of the estimated downlink alignment for the user device by transmitting, in a certain transmission pattern, a plurality of shaped interference signal transmissions to the user device, each of the shaped interference signals being shaped according to a current estimated value of the downlink alignment of the user device, the current estimated value of the downlink alignment being based on the uplink alignment or a previously received feedback signal received in response to a previous transmission of the shaped interference signal transmission, and performing a subsequence downlink transmission using the estimated downlink alignment.

[0008] In another exemplary aspect, a wireless communication device implementing the method described above is disclosed.

[0009] In yet another exemplary aspect, a wireless system in which one or more of the methods described above are implemented is disclosed.

[0010] In yet another exemplary aspect, the method may be embodied as processor-executable code and may be stored on a computer-readable program medium.

[0011] In yet another aspect, a wireless communication system operating by providing a single pilot tone for channel estimation is disclosed.

[0012] These and other features are described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are provided to facilitate further understanding of the present application and are used as a part thereof. Exemplary embodiments and their drawings are used to explain, rather than limit, the scope of the present technology.

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Best Mode for Carrying Out the Invention

[0027] (Detailed Description) To make the objectives, technical solutions, and advantages of the present disclosure clearer, various embodiments will be described in detail below with reference to the drawings. Unless otherwise noted, the embodiments and features in the embodiments of this document may be combined with each other.

[0028] The section headings in this document are used to improve the readability of the description and do not limit the discussion or embodiments to only individual sections in any way. Additionally, certain standard technical terms are used for illustrative purposes only, and the disclosed techniques are applicable to any wireless communication system.

[0029] 1. Introduction - Wireless Communication Environment

[0030] The wireless or time-varying nature of communication channels presents several challenges when designing transmission protocols suitable for wireless communication scenarios. Today, users expect their wireless devices to function everywhere and in various mobile or stationary situations.

[0031] The time-varying nature of wireless networks and the user's expectation of reliable high-bandwidth network connections at any time and anywhere create a tension between the amount of transmission resources that a wireless network can use for overhead signal communication for wireless channel calibration and, at the same time, allocating as much transmission bandwidth as possible to user data. The deployment of user devices and network devices with multiple antennas further exacerbates this problem because the wireless network may need to calibrate the wireless channels to / from each antenna of the multi-antenna device.

[0032] The techniques described in this application enable the calibration of uplink or downlink wireless network connections using various techniques that provide operational advantages as further described throughout this document.

[0033] 2. Exemplary Wireless System

[0034] FIG. 1 shows an example of a wireless communication system 100 in which a transmitter device 102 transmits a signal to a receiver 104. The signal can follow various wireless channels and multi - paths as depicted. Some reflectors such as buildings and trees may be static while others such as cars can be mobile scatterers. The transmitter device 102 can be, for example, a user device, a mobile phone, a tablet, a computer, or another Internet of Things (IoT) device such as a smart watch, a camera, etc. The receiver device 104 can be a network device such as a base station. Signals transmitted from the base station to the transmitter 102 can suffer from similar channel degradations produced by static or mobile scatterers. The techniques described in this document may be implemented by devices within the wireless communication system 100. The terms "transmitter" and "receiver" are used merely for convenience of explanation, and as further explained in this specification, depending on the direction of transmission (uplink or downlink), a network station may be on the transmission side or the receiving side, and a user device may be on the receiving side or the transmission side.

[0035] FIG. 2 shows a simplified wireless network to highlight certain aspects of the disclosed technology. A transmitter transmits a wireless signal to a receiver within the wireless network. Some transmissions within the network are variously called downlink or downstream transmissions, where network-side nodes such as base stations act as transmitters of the wireless signal, and one or more user devices act as receivers of these wireless signals. For some other transmissions, as depicted in FIG. 2, the direction of transmission may be opposite. Such transmissions are often called uplink or upstream transmissions. For such transmissions, one or more user devices act as transmitters of the wireless signal, and network-side nodes such as base stations act as receivers of these signals (as depicted in FIG. 2). Other types of transmissions within the network may include device-to-device transmissions, sometimes called direct or sideband transmissions. This document mainly uses the terms "downlink" and "uplink" for convenience purposes, but similar techniques may also be used in other situations where transmissions in both directions are implemented, e.g., upstream or incoming transmissions received by a wireless device and downstream or outgoing transmissions transmitted by a wireless device. For example, a downlink transmission can be an upstream transmission for a user device while also being a downstream transmission for a network device. Similarly, an uplink transmission can be an upstream transmission for a network device while also being a downstream transmission from a wireless device. Thus, for some embodiments, the disclosed techniques may also be described using terms such as "up" and "down" transmissions without incorporating any 3GPP (registered trademark)-specific or other wireless protocol-specific meanings into the terms "uplink" and "downlink".

[0036] In a frequency division multiplexing (FDM) network, transmissions to and from a base station may occupy different frequency bands (either continuously or intermittently). In a time division multiplexing (TDM) network, transmissions to and from a base station occupy the same frequency band but are separated in the time domain using a TDM mechanism such as time slot-based transmission. Other types of multiplexing are also possible (e.g., code division multiplexing, orthogonal time frequency space, or OTFS, multiplexing, spatial multiplexing, etc.). In general, various multiplexing schemes can be combined with each other. For example, in a spatially multiplexed system, transmissions to and from two different user devices may be isolated from each other using the directivity or orientation difference between two endpoints (e.g., network stations such as user devices and base stations).

[0037] Figure 3 depicts an example of an embodiment of angle of arrival (AoA) measurement. Here, RU represents a radio unit corresponding to the transmission / reception circuitry of a wireless communication device. The RU is equipped with a plurality of antenna ports, which are shown for convenience as two separate antennas. The antennas may be associated with a physical separation of Δs meters, referred to as the separation distance. The direction perpendicular to the separation distance direction may represent the boresight of the antenna array. Figure 1 shows that a particular handset or user device may be in a direction different from the boresight direction. The angle between the boresight direction and the handset direction may be represented as θ (theta). Due to this angle, the impinging wavefront from the handset may reach two different antenna ports at two different times Τ AoA in which it may reach two different antenna ports.

Number

[0038] In the formula, c represents the speed of light. In some embodiments, RU may perform measurements, as further disclosed herein, to measure the AoA of each user device, which may in turn be used in beamforming for communication with a particular user device. By performing beamforming, the transmission energy is focused in a specific direction, maximizing signal transmission in that direction, thereby achieving communication with the best quality (e.g., the highest signal-to-noise ratio) without causing interference to other user devices.

[0039] However, beamforming relies on the feed signals into the antenna array with appropriate complex weights. When the system is not calibrated due to imperfections in the RF path such as non-matching cables, connectors, trace lengths, impedances, antenna gains, etc., the intended complex weights are changed. This disrupts the beam pattern. Similarly, this also disrupts the angle-of-arrival measurements in the uplink.

[0040] Figure 4 shows an example of the impact of an uncalibrated TX or RX signal path on beamforming. Figure 4 depicts the transmit / receive chain of a multi-antenna port wireless communication device. For simplicity, the case of two antenna ports separated by a certain linear distance is shown. The antenna ports receive two slightly different versions of the same wavefront, represented as x0(f) and x1(f). The uncalibrated signal is modeled in the frequency domain as follows.

Number

[0041] c(f) is the calibration impairment, and τ, φ, and g are the delay, phase, and gain offsets, respectively.

[0042] Assuming a plurality of antennas in a uniform linear array, the following uncalibrated signal model is assumed using a UE at a certain angle of arrival (AoA) θ.

Number

[0043] As depicted in FIG. 4, the received signal can follow a receive chain that includes an antenna, a cable, a connector, and then continues with an amplifier, a filter, a mixer, analog / digital conversion, etc. On the transmission side, the typical signal processing is in the reverse direction, i.e., digital / analog conversion, followed by an amplifier, up-conversion, a cable, an antenna element, etc. Due to implementation tolerances, each transmission or receive chain can introduce a delay specific to that chain.

[0044] FIGS. 5A - 5C show beamforming achieved by various embodiments. FIG. 5A shows a case in which “ideal” beamforming can occur, where the weights w0 and w1 are selected to form a beam in the desired direction. As depicted, the main lobe of the energy can point in the desired direction (e.g., 15 degrees), and the side lobes are suppressed by 20 dB or better. Here, it is assumed that the AoA for the target user device is estimated as disclosed herein.

[0045] FIG. 5B shows another example where calibration impairments produce non-uniform distortions in the transmission or receive chain, respectively, and the resulting uncalibrated beam can be formed in a direction different from the desired direction as shown in FIG. 5A.

[0046] FIG. 5C shows an embodiment in which the AoA distortion is calibrated and the corresponding compensation gain is applied to produce a beam pattern that is close to the ideal beam pattern as shown in FIG. 5A. In the depicted embodiment, calibration coefficient matching is performed by applying the inverse ratio coefficient of the ratio between two different processing chains of two antenna ports. Alternatively, the coefficient matching can be applied to each signal processing path to match the signal distortion of each path to a uniform level.

[0047] FIG. 6 shows an example of an AoA calibration embodiment that is compatible with the Long Term Evolution (LTE) communication protocol. Some user devices 602 may be within the coverage area of a wireless network that implements LTE or the LTE protocol. The base station 600 may receive uplink signals from the user devices and perform uplink alignment as described herein (604). Uplink alignment may be performed on phase, gain, timing, and polarization used by the transmission signal. The results of the uplink alignment may be provided to the downlink calibration controller 606. The downlink calibration controller 606 may control a PDSCH (Physical Downlink Shared Channel) interference generator 608 that controls the function of interference shaping (610), and a transmission subsystem (612) that generates signals for downlink transmission to the user devices 602. Specifically, the downlink transmission may comply with the LTE / LTE protocol, but may include a shaped interference signal that is intentionally included within the downlink transmission and that aids in downlink channel calibration as described herein.

[0048] The downlink calibration controller 606 may receive feedback from the user device 602 in the form of, for example, ACK / NACK messages and other channel calibration feedback according to the LTE / LTE protocol. The feedback message may be used by the downlink calibration controller 606 to control the transmission pattern of the shaped interference signal as described herein. The ACK / NACK interpreter 614 may receive these messages and decode and interpret them for the downlink calibration controller 606. As further described throughout this document, 616 depicts the iterative or repeated transmission of a shaped interference signal to achieve convergence in the measurements for a particular UE.

[0049] FIG. 7 shows an example of an AoA calibration embodiment that is compatible with a new radio (NR) communication protocol, also referred to as the 5th generation or 5G protocol. Some user devices 702 may be within the coverage area of a wireless network that implements the 5G protocol. The base station 700 may receive uplink signals from the user devices and perform uplink alignment as described herein (704). Uplink alignment may be performed on phase, gain, timing, and polarization used by the transmission signal. The results of the uplink alignment may be provided to the downlink calibration controller 706. The downlink calibration controller 706 may control a channel state information (CSI) interference measurement generator 708 that controls the function of interference shaping (710) and a transmission subsystem (712) that generates a CSI reference signal for downlink transmission to the user device 702. Specifically, the downlink transmission may comply with the 5G protocol, but may include a shaped interference signal that is intentionally included within the downlink transmission and that aids in downlink channel calibration as described herein.

[0050] The downlink calibration controller 706 may receive feedback from the user device 702 in the form of, for example, channel quality information (CQI) messages such as CSI reports and other channel calibration feedback that complies with the 5G protocol. The feedback message may be used by the downlink calibration controller 706 to control the transmission pattern of the shaped interference signal as described herein. The feedback message may be analyzed and interpreted by a CSI interpreter 714. As further described throughout this document, 716 depicts the iterative or repeated transmission of a shaped interference signal to achieve convergence in the measurements for a particular UE.

[0051] 3. Example of Uplink Calibration

[0052] Regarding uplink calibration, in some embodiments, gain, phase, and timing alignment are performed independently per polarization. The gain is determined by measuring the difference in average received power per port. Phase and timing are determined in the phase domain and, along with phase and timing, suffer from ambiguity or aliasing due to the combination of AoA. Based on the relative UE location, by removing the AoA term, the phase and timing offsets can be isolated and measured.

[0053] FIG. 8 shows an example of an uplink calibration process. User device 802 may communicate with network-side radio station 804. The protocol used for this communication may be a legacy protocol such as LTE, 5G, or another protocol. Radio station 804 may process signals received at a plurality of antennas from each of the plurality of user devices 802. From the received signal waveforms, radio station 804 may extract various signals received according to the communication protocol. These transmission signals may include, for example, sounding reference signal SRS transmission, demodulation reference signal DMRS transmission, PUSCH (physical uplink shared channel), PRACH (physical random access) transmission, and the like. For each user device, radio station 804 may accumulate one or more transmissions of each type of signal from the user device received over a plurality of instances (808). The accumulated signals may be used to perform spatial learning (810). An anti-aliasing operation (812) may be performed on the result of the spatial learning to ensure removal of the aliased image. The resulting spatial information of the user device may be used to estimate gain, phase, and delay parameters (814). These results may be stored in calibration table 816 and made available for use by a scheduler that schedules transmission resources to / from each user device and the network. The scheduler may be implemented in a distributed unit (DU) or within a cloud-based service. The operations performed at 808-814 may also be performed either locally at radio station 804 or using cloud-based computing resources, or a combination thereof, similarly.

[0054] Figures 9 and 10 show examples of simulation results regarding calibration measurement accuracy. In the described examples, a 4G LTE sector configuration was used, in which a 1.95 GHz carrier frequency was used and a 10 MHz bandwidth was used for the frequency band. This system used four transmit antennas and four receive antennas. The initial calibration offsets applied to the antenna ports are listed in Table 1. The results obtained by processing 100 sounding reference signals (SRS) over 48 PRBs (physical resource blocks) and a variable SNR (signal-to-noise ratio) distribution with an average of -2 to 4 dB (the exemplary SNR distribution shown in the histogram below) achieved calibration with the accuracy shown in the graph depicted in Figure 9.

[0055] Referring to Figure 9, the horizontal axis indicates the average signal-to-noise ratio (SNR) of the SRS, while the vertical axis indicates typical phase, timing, and gain errors. Figure 10 shows the corresponding histogram, with the horizontal axis indicating SNR and the vertical axis indicating the count in the simulation.

Table 1

[0056] Table 2 below shows that the estimate converges to a low value after 100 iterations.

Table 2

[0057] FIG. 11 is an exemplary implementation of calibration process 1000, which may be implemented in a network device or using cloud-based distributed computing resources. Various logical operation groupings include calibration tables that are maintained based on previously performed calibrations (e.g., as described with reference to FIG. 8). The tables are generated and updated in response to the system reaching convergence as determined by convergence check operation 1004. When convergence check operation 1004 determines that convergence has not been reached, the interference parameters of the shaped interference may be updated (1008), and optionally, the interference filter may be updated (1010). Based on these updates, additional resources may be allocated for downstream transmission of the shaped interference (1012), which is then added to other ongoing transmissions in the network (1014) and transmitted from radio station 1016 to a user device (not explicitly shown) in the network. On the uplink side, transmissions received from the user device may be interpreted to check for convergence (1006). Convergence may be indicated when different settings of the shaped interference transmission do not result in significant changes in the feedback received from the targeted device (e.g., the difference in reported channel quality is below a threshold).

[0058] 4. Example of Downlink Calibration

[0059] Gain, phase, and timing alignment are performed independently per polarization. The parameter search is performed based on spatially directed contamination in the form of interference or reference signals. Subsequently, the polarizations are spatially aligned based on the similarity of the phase differences.

[0060] 5. Example of Alignment between Uplink and Downlink

[0061] Gain, phase, and timing alignment are performed independently per polarization. For uplink spatial channel information, parameter search is performed based on spatially directed contamination in the form of interference or reference signals. Thereafter, the polarizations are spatially aligned based on the similarity of the phase differences.

[0062] 6. Examples of Embodiments

[0063] FIG. 12 is a block diagram representation of a wireless hardware platform 1800, which may be used to implement the various methods described herein. The hardware platform 1800 may be incorporated within a base station or a user device. The hardware platform 1800 includes a processor 1802, a memory 1804, and transceiver circuitry 1806. The processor may execute instructions, for example, by reading from the memory 1804, control the operation of the transceiver circuitry 1806 and the hardware platform 1800, and implement the methods described herein. In some embodiments, the memory 1804 and / or the transceiver circuitry 1806 may be partially or fully contained within the processor 1802 (e.g., the same semiconductor package).

[0064] The following examples highlight some embodiments that use one or more of the techniques described herein.

[0065] For example, the angle of arrival or channel in the uplink direction may be measured using the following solutions.

[0066] 1. A method of wireless communication (e.g., method 1300 depicted in FIG. 13), configured to provide wireless communication access to user devices within a coverage area, performing a first measurement of a wavefront received at a first antenna of a base station (1302), and performing a second measurement of a wavefront received at a second antenna of the base station (1304), wherein the first antenna and the second antenna are separated by a certain separation distance along a certain direction, deriving a compensation coefficient from the first measurement and the second measurement (1306), wherein the compensation coefficient is used to estimate an estimated angle of arrival (AOA), and performing subsequent communication (1308) by applying the compensation coefficient to a transmitted or received signal waveform to or from a user device.

[0067] 2. The method according to solution 1, wherein the compensation coefficient is applied to a component of a received signal waveform received via the first antenna or the second antenna, or the compensation coefficient is applied to a component of a transmitted signal waveform transmitted via the first antenna or the second antenna.

[0068] 3. The method according to solution 1, wherein the compensation coefficient is applied by applying a first compensation coefficient to a first component of a received signal waveform received via the first antenna, a second compensation coefficient to a second component of a received signal waveform received via the second antenna, a first compensation coefficient to a first component of a transmitted signal waveform transmitted via the first antenna, and a second compensation coefficient to a second component of a transmitted signal waveform transmitted via the second antenna.

[0069] 4. The method according to any one of solutions 1-3, wherein the amplitude or phase of the compensation coefficient is a function of frequency. Some embodiments are disclosed with reference to Section 2, e.g., Equations 2 and 3.

[0070] 5. The method according to solution 4, wherein the compensation coefficient is stored in a calibration table and estimated periodically. Advantageously, the calibration table may be used by other layers of the protocol stack implementation.

[0071] 6. The cloud computing resources are used for estimating the AOA or determining a compensation factor for a user device by the method according to any one of Solutions 1-5.

[0072] For example, the channel in the downlink direction may be calibrated using the following preferred embodiments.

[0073] 7. A method of wireless communication (e.g., method 1400 depicted in FIG. 14), wherein a base station configured to provide wireless communication access using a first communication protocol determines (1402) uplink alignment for a user device based on a first signal received in the uplink direction, wherein the uplink alignment includes one or more of aligning the phase, gain, timing, or polarization difference between different receiving-side antennas of the base station based on an estimated angle of arrival (AoA) for the user device, and determining (1404) an estimated value of the estimated downlink alignment of the user device by transmitting a plurality of shaped interference signal transmissions to the user device in a certain transmission pattern, wherein each of the shaped interference signals is shaped according to a current estimated value of the downlink alignment of the user device, and the current estimated value of the downlink alignment is based on the uplink alignment or a previously received feedback signal received in response to a previous transmission of the shaped interference signal transmission, and performing (1406) a sub-sequence downlink transmission using the estimated downlink alignment.

[0074] 8. The method according to Solution 7, wherein each of the plurality of shaped interference transmissions is a spatially selective beam defined by an angular bandwidth, and the transmission pattern includes sweeping different ones of the plurality of shaped interference transmissions across an angular range.

[0075] 9. The method according to any one of Solutions 7-8, wherein the shaped interference signal is a noise signal.

[0076] 10. The formed interference signal is the method described in any of Solutions 7-8 that uses the transmission resources of the predefined reference signal of the legacy protocol.

[0077] 11. The legacy protocol includes the Long-Term Evolution (LTE) protocol, and the predefined reference signal is the method described in Solution 10 that occupies the physical downlink shared channel.

[0078] 12. The legacy protocol includes the 5th Generation New Radio (NR) protocol, and the predefined reference signal is the method described in Solution 10 that includes a channel state information reference signal.

[0079] 13. The previously received feedback signal is the method described in any of Solutions 7-12 that includes a reference signal measurement report.

[0080] 14. The previously received feedback signal is the method described in any of Solutions 7-12 that includes an ACK / NACK indicator.

[0081] 15. The previously received feedback signal is the method described in any of Solutions 7-12 that includes a channel state report.

[0082] 16. The multiple formed interference transmissions are the method described in any of Solutions 7-15 that includes interference transmission and is performed at different times.

[0083] 17. The multiple formed interference transmissions are the method described in any of Solutions 7-16 that includes interference transmission and is performed at different angles.

[0084] 18. The multiple formed interference transmissions are the method described in any of Solutions 7-17 that includes interference transmission and is performed using different ranks or antenna ports.

[0085] 19. The transmission pattern is the method described in any of Solutions 1-12 that defines the temporal sequence of transmission.

[0086] 20. The transmission pattern is the method described in any of Solutions 7-19 that defines the spatial sequence of transmission.

[0087] 21. The transmission pattern is the method described in any of Solutions 7-20 that defines the mapping of resource elements used for transmission.

[0088] 22. The shaped interference signal is the method described in any of Solutions 7-21 that includes data or control signal transmission to one or more other user devices.

[0089] 23. A wireless communication device comprising a processor and a transceiver, wherein the processor is configured to implement the method described in any one or more of the above solutions.

[0090] 24. A system comprising a plurality of wireless communication devices, wherein each device is configured to implement the method described in any one or more of the above solutions and comprises one or more processors.

[0091] 25. The techniques, methods, or devices disclosed in this document.

[0092] In the embodiments and solutions described above, in some embodiments, the first measurement and the second measurement include the calculations disclosed in Sections 1-5 of this document. In some embodiments, the measurement may capture the time instance at which the wavefront is received at the first or second antenna at that time using a locally activated time clock. In some embodiments, the measurements may be performed simultaneously such that both the first and second measurements are performed before starting the next sequence of measurements using the next received wavefront.

[0093] In the embodiments and solutions described above, in some embodiments, the compensation coefficient may be a real number, an integer, or a fraction, or a non-imaginary number. In some embodiments, the compensation coefficient is a complex number and may have a real part and an imaginary part, for example, representing a phase shift. In some embodiments, the compensation coefficient may be a single value. In some embodiments, the compensation coefficient may be a multi-dimensional value (e.g., a precoding or post-coding matrix).

[0094] In the embodiments and solutions described above, the shaped interference may be used to check the influence of the occupancy of a certain transmission resource by a signal on the signal reception quality by each UE. For example, in some embodiments, the shaped interference may be swept through a transmission pattern, in which the shaped interference is beamformed along different spatial directions, e.g., direction 1, direction 2, … direction N. Here, N may be a positive integer from 2 to 360 (e.g., one direction per radian). In some cases, the full sweep of the directivity may be split into a manageable number of sectors, e.g., 20 sectors that overlap by 50% with each other and provide 36 directional transmissions. Based on the uplink feedback from a specific user device, the direction that causes the worst degradation measured by the specific user device to the channel can be noted.

[0095] Alternatively, or in addition, the shaped interference may be swept across different time-frequency locations in the transmission scheme. For example, the interference signal may follow a specific sweep pattern (e.g., random hopping) among the resource elements received by the UE during channel measurement, and the feedback collected for each transmission may be used to perform uplink calibration.

[0096] Alternatively, or in addition, the shaped interference may be transmitted along a time-sequence transmission pattern. For example, the baseline sweep rate of the shaped interference signal for sweeping the entire cell may be predefined. Depending on the number of user devices in the cell, the time sequence may be increased (more frequent transmission of the shaped interference) or decreased. Similarly, the cell may further be divided into angular or radial sectors, and different time transmission patterns may be used for the division based on the desired accuracy / resolution, which may be a function of the presence of reflectors within the division or the number of UEs within the nature of that division of the radio channel. In some implementations, the number of shaped interference sweeps for a particular UE may depend on an estimated value of the rate at which the channel to / from the UE changes. For example, the transmission of shaped interference to a stationary or slow UE may be performed at a lower rate than the transmission of shaped interference to a mobile UE.

[0097] It should be understood that this book provides various techniques that can be used by embodiments for performing uplink calibration in which the signal paths of different antenna ports can be aligned in terms of gain, phase, timing, and polarization. The wireless communication device may be an integrated wireless unit or may include separate antennas. In various embodiments, the calibration may be performed using data signals or using reference signals. The techniques may be applied in both wideband situations where the signal used for calibration occupies the entire channel bandwidth or narrowband situations where the signal used for calibration occupies a bandwidth smaller than the channel. The calibration calculations may be performed by a processor in the wireless unit or may be performed using cloud-based computing resources. Also, it should be understood that the disclosed techniques may be applied to different duplexing schemes, such as TDD (Time Division Duplexing) or FDD (Frequency Division Duplexing). Further, the techniques may be used within any frequency band, such as the sub-6 GHz frequency band or the millimeter wave (mmWave) band. Also, it should be understood that the disclosed techniques do not impose specific requirements regarding the number of transmit or receive antennas and are generally applicable to NtNr situations (where Nt represents the number of transmit antennas and Nr represents the number of receive antennas).

[0098] Furthermore, it should be understood that this document discloses techniques that enable calibration of the signal path in the downlink direction to align gain, phase, timing, or polarization. In some embodiments, existing reference signals may be used to perform the alignment. For example, the previously disclosed CSI reference signals may be used. In some embodiments, shaped interference signals may be used in the downlink direction. In the feedback direction, existing reporting mechanisms such as Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), or ACK / NACK may be used. It should also be understood that the disclosed techniques may be applied to different duplexing schemes, such as Time Division Duplexing (TDD) or Frequency Division Duplexing (FDD). Furthermore, the techniques may be used within any frequency band, such as the sub-6 GHz frequency band or the millimeter wave (mmWave) band. It should also be understood that the disclosed techniques do not impose specific requirements regarding the number of transmit or receive antennas and are generally applicable to NtNr scenarios (where Nt represents the number of transmit antennas and Nr represents the number of receive antennas).

[0099] Furthermore, it should be understood that this document discloses techniques that may be used by embodiments to spatially align downlink and uplink transmissions between a network device and a user device, along with alignment of the corresponding polarization. The alignment may be achieved by calibrating the uplink and downlink based on reference signal transmission or data transmission. Such techniques may use existing mechanisms such as existing reference signals and existing feedback signals, as discussed throughout this document. It should also be understood that the disclosed techniques may be applied to different duplexing schemes, such as TDD or FDD. Furthermore, the techniques may be used within any frequency band, such as the sub-6 GHz frequency band or the mmWave band. It should also be understood that the disclosed techniques do not impose specific requirements regarding the number of transmit or receive antennas and are generally applicable to NtNr scenarios (where Nt represents the number of transmit antennas and Nr represents the number of receive antennas).

[0100] Furthermore, it should be understood that the calibration methods described above may be implemented using custom hardware such as user devices that are under the full control of the network device or are test devices deployed by the network operator. Alternatively, calibration may be performed based on user devices that are installed in known locations during the calibration phase.

[0101] The disclosed embodiments and other embodiments, modules, and functional operations described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, or in combinations of one or more of them, including the structures disclosed herein and their structural equivalents. The disclosed embodiments and other embodiments can be implemented as one or more computer program products, i.e., as one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, a data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter that generates a machine-readable propagated signal, or a combination of one or more of them. The term "data processing apparatus" includes, by way of example, all apparatus, devices, and machines for processing data, including programmable processors, computers, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program, e.g., code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal generated to encode information for transmission to a suitable receiver device.

[0102] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as modules, components, subroutines, or other units suitable for use within a computer environment. A computer program need not necessarily correspond to a file in a file system. The program can be stored in a part of a file that holds other programs or data (such as one or more scripts stored within a markup language document), in a single file dedicated to the program, or in multiple cooperating files (such as files that store one or more modules, subprograms, or portions of code). The computer program can be deployed so as to be executed on one computer, or located on one site, or distributed across multiple sites and executed on multiple computers interconnected by a communication network.

[0103] The processes and logical flows described in this specification can be implemented by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logical flows can also be implemented by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0104] Processors suitable for the execution of a computer program include, by way of example, both general and special microprocessors, as well as any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Essential elements of a computer are a processor for executing the instructions, and one or more memory devices for storing the instructions and data. Generally, a computer will also include, or be operatively coupled to, one or more mass storage devices for storing data, such as magnetic, magneto-optical disks, or optical disks, or receive data therefrom, or transfer data thereto, or both. However, a computer need not have such devices. Computer-readable media suitable for storing computer program instructions and data include, by way of example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices, magnetic disks, such as internal hard disks or removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks, including any form of non-volatile memory, media, and memory devices. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0105] This patent document contains many details, which should be construed as descriptions of features specific to particular embodiments rather than as limitations on the scope of the claimed invention or what may be claimed. In this document, a feature described in the context of a separate embodiment may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Also, although a feature may be described above as acting in a certain combination and may initially be claimed as such, one or more features from the claimed combination may in some cases be deleted from that combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Similarly, operations are depicted in the drawings in a particular order, but this should not be understood as requiring that the operations be performed in the particular order or sequential order shown in order to achieve a desirable result, or that all of the illustrated operations be performed.

[0106] Only some examples and implementations are disclosed. Variations, modifications, and extensions to the disclosed examples and implementations and other implementations can be made based on what is disclosed.

Claims

1. A method of wireless communication, comprising: performing a first measurement of a wavefront received at a first antenna of a base station, the base station being configured to provide wireless communication access to user devices within a coverage area; performing a second measurement of the wavefront received at a second antenna of the base station, the first antenna and the second antenna being separated by a separation distance along a direction; deriving a compensation coefficient from the first measurement and the second measurement, the compensation coefficient being used to estimate an estimated angle of arrival (AOA); performing subsequent communication by applying the compensation coefficient to a transmitted or received signal waveform to or from a user device A method comprising the steps of:

2. The method according to claim 1, wherein the compensation coefficient is applied to a component of the received signal waveform received via the first antenna or the second antenna, or the compensation coefficient is applied to a component of the transmitted signal waveform transmitted via the first antenna or the second antenna.

3. The compensation coefficient is applying a first compensation coefficient to a first component of the received signal waveform received via the first antenna and a second compensation coefficient to a second component of the received signal waveform received via the second antenna; applying a first compensation coefficient to a first component of the transmitted signal waveform transmitted via the first antenna and a second compensation coefficient to a second component of the transmitted signal waveform transmitted via the second antenna The method according to claim 1, wherein the method is applied by:

4. The method according to any one of claims 1 to 3, wherein an amplitude or a phase of the compensation coefficient is a function of a frequency.

5. The method according to claim 4, wherein the compensation coefficient is stored in a calibration table and is periodically estimated.

6. The method according to any one of claims 1 to 5, wherein cloud computing resources are used to estimate the AOA or to determine the compensation coefficient for the user device.

7. A method of wireless communication, comprising: A base station configured to provide wireless communication access using a first communication protocol determines uplink alignment for a user device based on a first signal received in an uplink direction, wherein the uplink alignment includes one or more of aligning a phase, gain, timing, or polarization difference between different receiving-side antennas of the base station based on an estimated angle of arrival (AoA) for the user device. In a certain transmission pattern, determining an estimated value of the estimated downlink alignment of the user device by transmitting a plurality of shaped interference signal transmissions to the user device, wherein each of the shaped interference signals is shaped according to a current estimated value of the downlink alignment of the user device, and the current estimated value of the downlink alignment is based on the uplink alignment or a previously received feedback signal received in response to a previous transmission of the shaped interference signal transmission. Performing a sub-sequence downlink transmission using the estimated downlink alignment. A method comprising.

8. Each of the plurality of shaped interference transmissions is a spatially selective beam defined by an angular bandwidth, and the transmission pattern includes sweeping different ones of the plurality of shaped interference transmissions across an angular range. The method according to claim 7.

9. The shaped interference signal is a noise signal. The method according to any one of claims 7-8.

10. The shaped interference signal uses a transmission resource of a predefined reference signal of a legacy protocol. The method according to any one of claims 7-8.

11. The legacy protocol comprises a Long-Term Evolution (LTE) protocol, and the predefined reference signal occupies a Physical Downlink Shared Channel. The method according to claim 10.

12. The legacy protocol comprises a 5th Generation New Radio (NR) protocol, and the predefined reference signal comprises a Channel State Information Reference Signal. The method according to claim 10.

13. The previously received feedback signal comprises a reference signal measurement report. The method according to any one of claims 9-12.

14. The previously received feedback signal comprises an ACK / NACK indicator, the method according to any of claims 9 - 12.

15. The previously received feedback signal comprises a channel state report, the method according to any of claims 9 - 12.

16. The plurality of shaped interference transmissions are performed at different times, the method according to any of claims 13 - 15, including interference transmission.

17. The plurality of shaped interference transmissions are performed at different angles, the method according to any of claims 13 - 16, including interference transmission.

18. The plurality of shaped interference transmissions are performed using different ranks or antenna ports, the method according to any of claims 7 - 17, including interference transmission.

19. The transmission pattern defines a temporal sequence of transmissions, the method according to any of claims 7 - 12.

20. The transmission pattern defines a spatial sequence of transmissions, the method according to any of claims 7 - 19.

21. The transmission pattern defines a map of resource elements used for transmission, the method according to any of claims 7 - 20.

22. The shaped interference signal comprises data or control signal transmission to one or more other user devices, the method according to any of claims 7 - 21.

23. A wireless communication device comprising a processor and a transceiver, wherein the processor is configured to implement the method according to any of claims 1 - 22.

24. A system comprising a plurality of wireless communication devices, each device comprising one or more processors configured to implement the method according to any of claims 1 - 22.

25. The techniques, methods, or devices disclosed in this document.

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