Air-based Phase Accuracy Estimation for Radio Transceiver Equipment

Abstract

A mechanism for OTA-based phase accuracy estimation for a first radio transceiver device is provided. A method is performed by a controller. The method includes: obtaining an estimated phase relationship between transceiver branches of the first radio transceiver device according to each position in a sequence of positions of a second radio transceiver device relative to the first radio transceiver device. Each estimated phase relationship is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device and the second radio transceiver device. The method includes: estimating an average phase relationship of at least one pair of transceiver branches of the first radio transceiver device by averaging the estimated phase relationships obtained at all positions in the sequence of positions. The phase accuracy of the first radio transceiver device is represented by the average phase relationship of at least one pair of transceiver branches.

Description

Technical Field

[0001] The embodiments presented herein relate to a method, a controller, a computer program, and a computer program product for over-the-air (OTA) based phase accuracy estimation in a radio transceiver device. Background Art

[0002] Active Antenna Systems (AAS) are an important part of both fourth generation (4G) telecommunication systems such as LTE (Long Term Evolution) and fifth generation (5G) telecommunication systems such as NR (New Radio). AAS is a general term that is commonly used to describe (radio) access nodes and other types of base stations that contain a large number of individual transmitter, receiver, and antenna elements that can be used for MIMO (Multiple Input Multiple Output) communication and beamforming as an integrated product.

[0003] In order to be able to control beamforming, the base station needs to be able to control the array excitation (in terms of amplitude and phase) with a certain accuracy. Therefore, the base station is calibrated at the factory as part of the manufacturing process and / or in the background during normal operation.

[0004] The term "beam quality" is a collective term for beamforming parameters such as peak EIRP (Effective Isotropic Radiated Power), sidelobe suppression, beam pointing error, beam width, etc. that are commonly used to characterize the AAS. The beam quality associated with the beam generated by the AAS is determined by the design, including the antenna and radio hardware and software algorithms such as the antenna calibration algorithm.

[0005] Calibration ensures that the excitation amplitude and phase relationship for each transceiver branch in the AAS meets the expectations. If this is not the case, this will have an impact on beamforming, thereby reducing the beam quality. The calibration data can be applied to the antenna excitation to compensate for errors due to aging, temperature, component variations, mechanical tolerances, etc.

[0006] Figure 1 An example of the degradation of beam quality due to array excitation phase error is illustrated, where the effect of Gaussian distributed phase error is visualized as a standard deviation of 30 degrees; σ = 0 represents the direction without any array excitation phase error, and σ = 60 represents the direction where the array excitation phase error has a standard deviation of 30 degrees. Assume that the AAS takes the form of a ULA (Uniform Linear Array) with 10 physical antenna elements (antenna element spacing of 0.9λ).

[0007] When deploying the AAS, factors such as hailstorms, material property degradation, external interference, etc. will interfere with the calibration process, which results in the degradation of uplink and downlink performance.

[0008] For AAS that supports communication via large spectra (shared multiple times with other services), advanced beamforming capabilities, and deployment scenarios, the complexity of OTA for network testing in outdoor sites has increased significantly. Therefore, network operators need to use mechanisms to monitor network performance, and regulatory agencies need to use mechanisms to monitor the parameters of licensing conditions in the deployed network.

[0009] Therefore, there is still a need for improved methods to ensure that AAS or other types of radio transceiver devices perform as expected, e.g., by having been successfully calibrated. Summary of the Invention

[0010] The purpose of the embodiments herein is to enable effective determination that radio transceiver devices such as AAS perform as expected.

[0011] According to a first aspect, a method for OTA-based phase accuracy estimation for a first radio transceiver device is proposed. The method is executed by a controller. The method includes: obtaining an estimated phase relationship between transceiver branches of the first radio transceiver device according to each position in a position sequence of a second radio transceiver device relative to the first radio transceiver device. Each estimated phase relationship is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device and the second radio transceiver device. The method includes: estimating an average phase relationship of at least one pair of transceiver branches of the first radio transceiver device by averaging the estimated phase relationships obtained at all positions in the position sequence. The phase accuracy of the first radio transceiver device is represented by the average phase relationship of at least one pair of transceiver branches.

[0012] According to a second aspect, a controller for OTA-based phase accuracy estimation for a first radio transceiver device is proposed. The controller includes a processing circuit. The processing circuit is configured to cause the controller to: obtain an estimated phase relationship between transceiver branches of the first radio transceiver device according to each position in a position sequence of a second radio transceiver device relative to the first radio transceiver device. Each estimated phase relationship is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device and the second radio transceiver device. The processing circuit is configured to cause the controller to: estimate an average phase relationship of at least one pair of transceiver branches of the first radio transceiver device by averaging the estimated phase relationships obtained at all positions in the position sequence. The phase accuracy of the first radio transceiver device is represented by the average phase relationship of at least one pair of transceiver branches.

[0013] According to a third aspect, a controller for OTA-based phase accuracy estimation of a first radio transceiver device is proposed. The controller includes an obtaining module configured to: obtain, for each position in a sequence of positions of a second radio transceiver device relative to the first radio transceiver device, an estimate of the phase relationship between transceiver branches of the first radio transceiver device. Each phase relationship estimate is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device and the second radio transceiver device. The controller includes an estimating module configured to: estimate an average phase relationship of at least one pair of transceiver branches of the first radio transceiver device by averaging the phase relationship estimates obtained at all positions in the sequence of positions. The phase accuracy of the first radio transceiver device is represented by the average phase relationship of at least one pair of transceiver branches.

[0014] According to a fourth aspect, a computer program for OTA-based phase accuracy estimation of a first radio transceiver device is proposed, the computer program including computer program code which, when run on a controller, causes the controller to perform the method according to the first aspect.

[0015] According to a fifth aspect, a computer program product including the computer program according to the fourth aspect and a computer-readable storage medium on which the computer program is stored is proposed. The computer-readable storage medium may be a non-transitory computer-readable storage medium.

[0016] Advantageously, the average phase relationship of the transceiver branches can be used to determine whether the first radio transceiver device is operating as expected.

[0017] Advantageously, the average phase relationship of the transceiver branches can be used to determine whether the first radio transceiver device has been successfully calibrated.

[0018] Advantageously, these aspects enable the functionality and performance of the first radio transceiver device to be tested in an outdoor field in a convenient and cost-effective manner. In addition, the effects of a multipath environment can be mitigated.

[0019] A more traditional method of testing the beam quality of a first radio transceiver device is to remove it from the field, take it to an advanced test site (such as an antenna test range), and perform the test. If the first radio transceiver device is not replaced during the test, this will be time-consuming, expensive, and mean extended system downtime.

[0020] Other objectives, features, and advantages of the attached embodiments will be apparent from the following detailed disclosure, from the attached dependent claims, and from the drawings.

[0021] In general, unless otherwise clearly defined herein, all terms used in the claims shall be interpreted according to their ordinary meanings in the relevant technical field. Unless otherwise clearly stated, all references to "an / the element, device, component, part, module, step, etc." shall be construed broadly as referring to at least one instance of the element, device, component, part, module, step, etc. Unless otherwise specified, the steps of any method disclosed herein need not be performed in the exact order disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present inventive concept will now be described by way of example with reference to the accompanying drawings, in which:

[0023] Figure 1 Schematically illustrates an example of beam quality degradation due to array excitation phase error according to an embodiment;

[0024] Figure 2 is a schematic diagram illustrating a communication network according to an embodiment;

[0025] Figure 3 and Figure 4 Schematically illustrates components of an access node according to an embodiment;

[0026] Figure 5 Schematically illustrates modules of a radio transceiver device according to an embodiment;

[0027] Figure 6 and Figure 11 is a flowchart of a method according to an embodiment;

[0028] Figure 7 Schematically illustrates an expected phase difference between two transceiver branches according to an embodiment;

[0029] Figure 8 , Figure 9 and Figure 10 show simulation results according to an embodiment;

[0030] Figure 12 is a schematic diagram showing functional units of a controller according to an embodiment;

[0031] Figure 13 is a schematic diagram showing functional modules of a controller according to an embodiment;

[0032] Figure 14 shows an example of a computer program product including a computer-readable storage medium according to an embodiment;

[0033] Figure 15 is a schematic diagram illustrating a telecommunication network connected to a host computer via an intermediate network according to some embodiments; and

[0034] Figure 16 FIG. is a schematic diagram showing a host computer communicating with a terminal device via a radio base station through a partial wireless connection according to some embodiments. DETAILED DESCRIPTION

[0035] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. However, the inventive concept may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Throughout the description, like numerals refer to like elements. Any step or feature shown by a dashed line should be considered optional.

[0036] As described above, there is still a need for improved methods to ensure that an AAS or other type of radio transceiver device has been successfully calibrated.

[0037] More specifically, currently, it can be challenging to evaluate the performance of the antenna calibration of a deployed radio transceiver device. The radio transceiver device can be sent back to the factory or laboratory for performance evaluation. This can be very expensive because there are a large number of deployed radio transceiver devices, and in many cases, they are located in remote and hard-to-reach places, usually on tall poles. In addition, when a functional failure occurs in the radio transceiver device, it may be difficult to identify the root cause from a network perspective. Network performance is usually related to increased interference from external sources (e.g., adjacent networks or other services). Even in reality, it is the performance of the radio transceiver device itself that degrades.

[0038] Accordingly, the embodiments disclosed herein relate to an OTA-based phase accuracy estimation mechanism for radio transceiver devices. Such a mechanism can be used to ensure that an AAS or other type of radio transceiver device has been successfully calibrated. To obtain such a mechanism, a controller, a method executed by the controller, and a computer program product including code (e.g., in the form of a computer program) are provided, which, when the code runs on the controller, causes the controller to execute the method.

[0039] Figure 2 FIG. is a schematic diagram of a communication network 100 in which the embodiments proposed herein can be applied. The communication network 100 includes a first radio transceiver device 110, a second radio transceiver device 120, and a controller 200. The wireless transmission of signals between the first radio transceiver device 110 and the second radio transceiver device 120 can be reflected by a physical object 150.

[0040] In some non - limiting examples, the first radio transceiver device 110 is a (radio) access node. Some non - limiting examples of a (radio) access node are: radio access network node, radio base station, base transceiver station, Node B (NB), evolved Node B (eNB), gNB, access point, and integrated access and backhaul (IAB) node. In some non - limiting examples, the second radio transceiver device 120 is a user equipment. Non - limiting examples of user equipment are portable wireless device, mobile station, mobile phone, cellular phone, wireless local loop phone, smart phone, laptop computer, tablet computer, network - equipped sensor, network - equipped vehicle, and Internet of Things device.

[0041] The controller 200 may be provided as a separate device or be collocated with, integrated with, or be part of another device (e.g., the first radio transceiver device 110, the second radio transceiver device 120) or another entity such as a network controller.

[0042] In Figure 2 the direct component of the signal is labeled as s 1 and s 2 while the component of the signal that has been reflected by the object 150 is labeled as and The controller 200 is at least configured to estimate the average phase relationship of the transceiver branches of the first radio transceiver device 110. More details of this operation and other aspects of the controller 200 will be disclosed below.

[0043] Figure 3 and Figure 4 illustrate the components of the (radio) access node 130 including the first radio transceiver device 110 and the in - field calibration modules 140a, 140b. Figure 3 and Figure 4 Provide an overview of the implementation of the beam quality measurement function for the case where the first radio transceiver device 110 acts as a transmitter (as in Figure 3 ) and a receiver (as in Figure 4 ) of the signals wirelessly transmitted between the first radio transceiver device 110 and the second radio transceiver device 120 respectively.

[0044] The first radio transceiver device 110 includes N transceiver branches 114a, 114b for the transmission (as in 1 s 2 s N ... s Figure 3 and reception (as in Figure 4 ) of N signals s 1 V2 , ..., V N (The) influence.

[0045] The on-site calibration modules 140a, 140b include a calibration memory 141, a logic control module 142, a measurement / processing module 143, a monitoring module 144, and an on-site calibration adjustment module 145. n C is a calibration factor provided by a calibration process (performed during production or during operation). The calibration memory stores the calibration factor C n . W n is the beam weight for calibrating the array. The calibration factor and the beam weight are multiplied by the signal, so C n and W n 's product forms the factor V n , V n which in turn is multiplied by the signal s n . The calibration factor C n and the beam weight W n (and thus the factor V n ) are different for the downlink and the uplink. The measurement / processing module is configured to receive signals corresponding to transmissions with one port at a time from a test receiver and compare the phase and amplitude differences between the ports with the expected values given by w n . The logic control module is configured to manage when beam quality measurements should be performed, control the on-site calibration module, and control other functions (e.g., the transmitter) to perform sufficient and timely operations. The monitoring module is configured to compare the deviation between the measured and expected phase and amplitude differences between the ports with a threshold and indicate their status as normal (ok) or abnormal (not ok). Optionally, the monitoring module is configured to update the calibration factor C n stored in the calibration memory. The on-site calibration module is configured to apply a correction factor when the deviation between the measured and expected phase and amplitude differences between the ports is greater than the threshold.

[0046] Figure 5 illustrates the modules of a radio transceiver device 110 according to an embodiment. The radio transceiver device 110 includes a baseband module (BB) 111, an antenna port mapping (APM) module 112, a transceiver array (TRA) module 113, a radio distribution network (RDN) module 115, and an antenna array (AA) module 116. The modules 111 - 116 are interconnected via interfaces summarized in Table 1. In this regard, the interface between the TRA module 113 and the RDN module 115 is defined by transceiver branches 114a, 114b.

[0047]

[0048] Table 1

[0049] Table 2 provides examples of the relationships between N LP 、N BB 、N RF and N AE for different implementations of the radio transceiver device 110.

[0050]

[0051] Table 2

[0052] Figure 6 is a flowchart illustrating an embodiment of a method for OTA-based phase accuracy estimation for a first radio transceiver device 110. The method is executed by a controller 200. The method is advantageously provided as a computer program 1320.

[0053] S102: The branch controller 200 obtains an estimate of the phase relationship between the transceiver branches of the first radio transceiver device 110 for each position in the position sequence of the second radio transceiver device 120 relative to the first radio transceiver device 110. Each phase relationship estimate is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device 110 and the second radio transceiver device 120.

[0054] S104: The controller 200 estimates the average phase relationship of at least one pair of transceiver branches of the first radio transceiver device 110 by averaging the phase relationship estimates obtained at all positions in the position sequence. The phase accuracy of the first radio transceiver device 110 is represented by the average phase relationship of at least one pair of transceiver branches.

[0055] In some aspects, for each combination of transceiver branch pairs, there will be a value of the average phase relationship. Thus, in some embodiments, by averaging the phase relationship estimates obtained at all positions in the position sequence for each pair of transceiver branches, an average phase relationship is estimated for each pair of transceiver branches, and the phase accuracy of the first radio transceiver device 110 is represented by the average phase relationship for each pair of transceiver branches. Further, the average phase relationship for a given transceiver branch can represent the phase difference between the given transceiver branch and a reference transceiver branch. For different pairs of transceiver branches, the average phase relationship can be different.

[0056] By considering measurements according to transceiver branches, the phase relationship between the transceiver branches can be estimated, and thus it can be checked whether, when a signal is wirelessly transmitted between the first radio transceiver device 110 and the second radio transceiver device 120, a specific beam generated at the first radio transceiver device 110 is as expected. Accordingly, the calibration of the first radio transceiver device 110 can be checked to see if the first radio transceiver device 110 is operating correctly.

[0057] Based on knowledge of the position and orientation of the first radio transceiver device 110 and knowledge of the position and orientation of the second radio transceiver device 120, the angular position of the second radio transceiver device 120 relative to the first radio transceiver device 110 can be obtained.

[0058] When the second radio transceiver device 120 is moved relative to the first radio transceiver device 110, the phases of the respective transceiver branches of the first radio transceiver device 110 are measured at several positions along the path. In some non-limiting examples, the direction of the path along which the second radio transceiver device 120 is moving is perpendicular or nearly perpendicular to the line of sight. In this regard, nearly perpendicular can be interpreted as deviating from perpendicular by at most 30° or at most 20° or at most 10°. However, it is not necessary to move the second radio transceiver device 120 relative to the first radio transceiver device 110 in such a way that the phase shift of the direct beam changes more slowly than the phase shift of the reflected beam. In some aspects, it is only necessary that the variation in the phase shift is different between the direct beam and the reflected beam. By calculating and using the average value at the measurement positions of the phase relationship between the transceiver branches, the reflection effect of the first radio transceiver device 110 in its specific environment can be mitigated.

[0059] This is in contrast to the uncertainty analysis of the test range, where the results of the uncertainty analysis sliding exercise will manifest as uncertainty values when the first radio transceiver device 110 is measured later, because the first radio transceiver device 110 is typically only measured in one position and the exact effect of the reflection will not be known in that specific position.

[0060] Embodiments related to more details of the OTA-based phase accuracy estimation of the first radio transceiver device 110 performed by the controller 200 will now be disclosed.

[0061] There can be different types of signals that are wirelessly transmitted between the first radio transceiver device 110 and the second radio transceiver device 120 and are used for the purposes disclosed above. In some embodiments, the signal is a dedicated test signal. In some examples, the signal is a reference signal.

[0062] In some examples, the first radio transceiver device 110 has a line-of-sight direction, the sequence of positions forms a path, and the path extends in a direction perpendicular to the line-of-sight direction. In other examples, the conditions for the path have fewer restrictions.

[0063] When estimating the phase for each transceiver branch, the phase variation (referred to as plane wave compensation) can be compensated. Thus, in some aspects, plane wave compensation is performed when estimating the average phase relationship. Plane wave compensation can be performed before or after estimating the average phase relationship (i.e., before or after step S104). Thus, according to an embodiment, the controller 200 is configured to perform one of the (optional) steps S104a, S104b:

[0064] S104a: The controller 200 performs plane wave compensation for the phase relationship estimation before estimating the average phase relationship.

[0065] S104b: The controller 200 performs plane wave compensation for the average phase relationship.

[0066] Thus, when plane wave compensation is performed before estimating the average phase relationship, step S104a is performed; and when plane wave compensation is performed after estimating the average phase relationship, step S104b is performed.

[0067] In some aspects, the average phase relationship is used to estimate the quality fraction for the transceiver branches of the first radio transceiver device 110. In particular, in some embodiments, the controller 200 is configured to perform the (optional) step S106:

[0068] S106: The controller 200 estimates the beam quality value of the first radio transceiver device 110 based on the average phase relationship of at least one pair of transceiver branches.

[0069] There can be different ways to define the beam quality. As will be disclosed in more detail below, in the line-of-sight direction, the higher the value of the phase difference between the transceiver branches, the lower the beam quality. In some embodiments, for wireless signal transmission and / or wireless signal reception at the first radio transceiver device 110, the beam quality value is related to the phase accuracy of the transceiver branches of the first radio transceiver device 110. In some examples, the beam quality value represents the worst phase deviation among all transceiver branches.

[0070] There can be different ways to determine the beam quality. In some embodiments, the beam quality value is estimated as the measured average phase relationship of at least one pair of transceiver branches compared to the expected phase relationship of at least one pair of transceiver branches.

[0071] In some aspects, not only the phase but also the amplitude needs to be considered. Therefore, in some embodiments, for the position sequence, an estimate of the amplitude relationship between the transceiver branches is obtained for each position of the second radio transceiver device 120 relative to the first radio transceiver device 110. Further, the average amplitude relationship of at least one pair of transceiver branches can be estimated by averaging the amplitude relationship estimates at all positions in the position sequence. Further, the amplitude accuracy of the first radio transceiver device 110 is represented by the average amplitude relationship of at least one pair of transceiver branches.

[0072] In some aspects, for each combination of transceiver branch pairs, there will be a value of the average amplitude relationship. Therefore, in some embodiments, by averaging the amplitude relationship estimates obtained for all positions in the position sequence for each pair of transceiver branches, an average amplitude relationship is estimated for each pair of transceiver branches, and the amplitude accuracy of the first radio transceiver device 110 is represented by the average amplitude relationship for each pair of transceiver branches. Further, the average amplitude relationship for a given transceiver branch can represent the amplitude difference between the given transceiver branch and a reference transceiver branch.

[0073] In some embodiments, the beam quality value is also estimated based on the average amplitude relationship. That is, the controller 200 can estimate the beam quality value of the first radio transceiver device 110 based on the average phase relationship and the average amplitude relationship of at least one pair of transceiver branches in step S108.

[0074] Further, for wireless signal transmission and / or wireless signal reception at the first radio transceiver device 110, the beam quality value can be further related to the amplitude accuracy of the transceiver branches of the first radio transceiver device 110. In some examples, the beam quality value represents the worst amplitude deviation among all transceiver branches.

[0075] The beam quality value can be estimated as the measured average amplitude relationship (compared to the expected amplitude relationship) between any given pair of transceiver branches.

[0076] The beam quality value can be estimated as a weighted combination of the measured phase relationship and the measured average amplitude relationship between any given pair of transceiver branches (compared to the expected phase relationship and amplitude relationship between the given pair of transceiver branches).

[0077] In some embodiments, a signal is wirelessly transmitted from the first radio transceiver device 110. Further, the beam quality can be specified in terms of the transmission amplitude and phase accuracy of each transceiver branch of the first radio transceiver device 110.

[0078] In some embodiments, for each position of the second radio transceiver device 120 relative to the first radio transceiver device 110, one transceiver branch is used at a time to transmit a signal. More specifically, a single transceiver branch is used at a time to wirelessly transmit a signal from the first radio transceiver device 110. Thus, the transceiver array module 113 can be configured to individually control each transceiver branch such that each transceiver branch is individually enabled and disabled one by one. Further, each enabled transceiver branch is used to wirelessly transmit a signal. Ideally, the second radio transceiver device 120 should receive signals with equal amplitudes from each transceiver branch (ignoring the differences in path losses between different transceiver branches and the second radio transceiver device 120), and the phases should be related by the relationship 360°·((r i -d) / λ), where r i is the distance between the second radio transceiver device 120 and transceiver branch i, where d is the distance between the second radio transceiver device 120 and one of the transceiver branches (as a reference transceiver branch), and λ is the radiation wavelength.

[0079] In some embodiments, signals are wirelessly transmitted from the second radio transceiver device 120. Further, beam quality can be specified in terms of the received amplitude and phase accuracy of each transceiver branch of the first radio transceiver device 110.

[0080] In some embodiments, for each position of the second radio transceiver device 120 relative to the first radio transceiver device 110, signals are received simultaneously in all transceiver branches. More specifically, signals are wirelessly transmitted from the second radio transceiver device 120 to the first radio transceiver device 110. Ideally, the signals received at the first radio transceiver device 110 have equal amplitudes in all transceiver branches (ignoring the differences in path losses between different transceiver branches and the second radio transceiver device 120), and the phase relationship should be given by 360°·((r i -d) / λ)i in the same manner as disclosed above.

[0081] As Figure 7 shown, above the beam weight phase difference, the expected phase difference between two transceiver branches can also include a phase difference Δα contribution. The phase difference is caused by the difference in distances between the antennas at the second radio transceiver device 120 and each antenna for different transceiver branches at the first radio transceiver device 110. For example, in Figure 7 in, for a transceiver branch 1 with position (x 11 , y 11 , z 11 ) and phase α 11 and a transceiver branch with position (x12 , y 12 , z 12 ) and phase α 12 between the transceiver branch 2 with and the antenna of the second radio transceiver device 120 having a position (x 2 , y 2 , z 2 ), the phase difference can be expressed as:

[0082]

[0083] Given the knowledge of the antenna position of the second radio transceiver device 120 and the position and orientation of the first radio transceiver device 110 as well as the antenna system geometry and configuration, this phase difference can be calculated and subsequently compensated for.

[0084] As described above, the calibration of the first radio transceiver device 110 can be checked to see if the first radio transceiver device 110 is operating correctly. Specifically, in some embodiments, the controller 200 is configured to perform (optional) steps S108 and S110:

[0085] S108: The controller 200 compares the value of the average phase relationship of at least one pair of transceiver branches with the expected phase relationship value of at least one pair of transceiver branches.

[0086] S110: When the value of the average phase relationship deviates from the expected phase relationship value by more than a threshold, the controller 200 provides a correction signal to the calibration module of the first radio transceiver device 110.

[0087] Thus, the controller 200 can implement a monitoring sub - function that checks the derived value of the average phase relationship with the expected excitation information stored in the calibration memory. The expected excitation information can be determined during production or during normal operation.

[0088] There can be different uses of the correction signal. In some embodiments, the correction signal is provided to initiate the calibration of the transceiver branches at the first radio transceiver device 110. In some examples, the correction signal is provided to pause the operation of the first radio transceiver device 110. The latter can be the case where the value of the average phase relationship deviates from the expected phase relationship value by more than a second threshold, where the second threshold is greater than the threshold used in step S110. If the derived value of the average phase relationship is deviating from the expected excitation, the fault signal defined by the correction signal can thus be set to a degraded performance or initiate a runtime calibration process.

[0089] There can be different examples of calibration signals. In some embodiments, the calibration signal is an alert signal. In other embodiments, the calibration signal is the value of the average phase relationship itself. Further, the difference between the value of the average phase relationship and the expected excitation can be used to calibrate the first radio transceiver device in-situ.

[0090] Aspects of how the embodiments disclosed herein can be applied during OTA-based phase accuracy estimation of the first radio transceiver device 110 to reduce the effects of reflections will now be disclosed.

[0091] When performing in-situ measurements on an installed radio transceiver device, such as a (radio) access node or other type of base station, reflections from surrounding objects, such as building walls, trees, vehicles, rocks, etc., may occur. This may potentially introduce errors in the transmit and receive beam quality measurements. However, by moving the second radio transceiver device 120 along a suitable path while performing a set of measurements (and then averaging them), the effects of reflections can be significantly reduced.

[0092] Consider measuring the phase difference (labeled as ) between two transceiver branches at the first radio transceiver device 110. Assume that a signal is wirelessly transmitted from the first radio transceiver device 110 to the second radio transceiver device 120. The direct components of the signals from the two transceiver branches at the first radio transceiver device 110 reaching the antenna of the second radio transceiver device 120 are labeled as s 1 and s 2 . The signals from the two transceiver branches at the first radio transceiver device 110 reaching the antenna of the second radio transceiver device 120 (after reflection from the object 150) are labeled as and See Figure 2 .

[0093] Without loss of generality, assume that the path lengths and path losses between the second radio transceiver device 120 and the two transceiver branches at the first radio transceiver device 110 are the same (i.e., the first radio transceiver device 110 and the second radio transceiver device 120 are on the line of sight relative to each other). Further:

[0094]

[0095]

[0096] Here, s a denotes the signal amplitude, and thus it is the same for the two signals s 1 and s 2 .

[0097] In addition, it is assumed that the beams for transmitting signals s 1 and s 2 are pointed at the second radio transceiver device 120. Furthermore, for a perfect beam, the phase difference between the transceiver branches is zero. Higher values of the phase difference between the transceiver branches correspond to lower beam quality.

[0098] Ideally, the desired phase difference can be obtained as:

[0099]

[0100] Here, ∠s 1 represents the phase of s 1 and ∠s 2 represents the phase of s 2 . However, if the measured values (labeled as y 1 and y 2 ) also include reflections from the object 150, then:

[0101]

[0102]

[0103] The estimated phase difference can be expressed as:

[0104]

[0105] Here, ∠y 1 represents the phase of y 1 and ∠y 2 represents the phase of y 2 . The reflected signal can be written as:

[0106]

[0107]

[0108] Here, is the amplitude of the reflection from the object 150 and is approximately the same for reflections from both transceiver branches. The difference differs from by a value given by the angle to the object 150. This will introduce an error in the estimation of .

[0109] Note that if there are M reflections, the expressions for y 1 and y 2 will take the following general form:

[0110]

[0111]

[0112] It should also be noted that in the presence of M reflections, for m = 1,..., M, the reflected signals will take the following general form:

[0113]

[0114]

[0115] Figure 8 Schematically illustrates how the error can affect in different ways, depending on the phase shift between the direct component of the signal (as given by and the reflected signal (as given by ). If the measurements can be obtained with different values of , then averaging these values will provide a better estimate than a single measurement.

[0116] One possible way to obtain the difference between the phase shifts is to perform a series of measurements along a path approximately perpendicular to the direction from the second radio transceiver device 120 to the first radio transceiver device 110. Furthermore, the value of will be approximately constant, while the value of

[0117] will vary. Furthermore, the measurements obtained can be averaged. sample Thus, considering a series of measurements k = 1...K, these measurements are performed as the measuring device moves along the path with a step size l The change in the phase shift of the signal is 2πl / λ per step, while the change in the phase shift of the reflection is 2πl 1 / λ. Furthermore:

[0118] l = l sample sinβ

[0119] l A = l sample sin(α 1 +β)

[0120] Ideally, the path can be chosen to be perpendicular to the direction from the second radio transceiver device 120 to the first radio transceiver device 110, resulting in l = 0, but values of β up to about 30° from the perpendicular direction still provide good performance. The phase shift will become:

[0121] ​

[0122]

[0123] Finally, the required estimation of the phase difference can be obtained as the average of the measurement sequence:

[0124]

[0125] Figure 9 shows an example at a frequency of 3.5 GHz and with a true value (corresponding to a rather small defect in the phase relationship between the two transceiver branches), a reflection amplitude lower than the signal by 10 dB, β = 5°, α A = 20°, l sample = 1 cm, K = 200.

[0126] To obtain an optimal estimate, the average should be taken over an integer number of periods of . In practice, this may not be possible, especially in the presence of more than one main reflection, which will result in more irregular measurement results. As shown in Figure 10 , by instead taking the average over a rather long measurement sequence, the influence of the precise selection of the number of samples will become smaller.

[0127] Next, a method for OTA-based phase accuracy estimation for a first radio transceiver device 110 will be disclosed with reference to Figure 11 at least some of the embodiments disclosed above.

[0128] S201: A second radio transceiver device 120 (RTD2) is placed within the coverage area of a first radio transceiver device 110 (RTD1).

[0129] S202: An operational connection is established between the first radio transceiver device 110 and the second radio transceiver device 120.

[0130] S203: A counter is initialized to k = 1.

[0131] S204: The second radio transceiver device 120 is moved along a path to position k.

[0132] S205: When the second radio transceiver device 120 is at position k, a signal is wirelessly transmitted between the first radio transceiver device 110 and the second radio transceiver device 120.

[0133] The signal is wirelessly transmitted from the first radio transceiver device 110 to the second radio transceiver device 120, or the signal is wirelessly transmitted from the second radio transceiver device 120 to the first radio transceiver device 110. Measurements are recorded and provided to the controller 200, which enables the controller 200 to estimate the phase relationship between the transceiver branches of the first radio transceiver device 110.

[0134] S206: Check whether the desired number of measurements K has been made, i.e., whether k = K. If so, proceed to step S207. If not, increment the counter, i.e., k := k + 1 and go back to step S205.

[0135] S207: The controller 200 obtains an estimate of the phase relationship between the transceiver branches of the first radio transceiver device 110 for each position in the sequence of positions of the second radio transceiver device 120 relative to the first radio transceiver device 110. Each phase relationship estimate is obtained from measurements of the signal wirelessly transmitted between the first radio transceiver device 110 and the second radio transceiver device 120.

[0136] S208: The controller 200 estimates the average phase relationship of the transceiver branches of the first radio transceiver device 110 by averaging the phase relationship estimates obtained for all positions in the position sequence. By averaging the phase relationship estimates obtained for all positions in the position sequence, an average phase relationship is estimated for each transceiver branch, and the phase accuracy of the first radio transceiver device 110 is represented by the average phase relationship per transceiver branch / per transceiver branch. Plane wave compensation can be performed as part of step S208, either before or after estimating the average phase relationship.

[0137] According to several functional units, Figure 12 schematically illustrates the components of the controller 200 according to an embodiment. The processing circuit 210 is provided by any combination of one or more of a suitable central processing unit (CPU), multi-processor, multi-controller, digital signal processor (DSP), etc. that can execute software instructions stored in a computer program product 1310 (such as Figure 14 in) (e.g., in the form of a storage medium 230). The processing circuit 210 can also be provided as at least one application specific integrated circuit (ASIC) or field programmable gate array (FPGA).

[0138] In particular, the processing circuitry 210 is configured to cause the controller 200 to perform a set of operations or steps as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the controller 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

[0139] Accordingly, the processing circuitry 210 is thus arranged to perform the method as disclosed herein. The storage medium 230 may further include a persistent storage device, which may be, for example, any one or a combination of a magnetic memory, an optical memory, a solid-state memory, or even a remotely mounted memory. The controller 200 may further include a communication interface 220, which is at least configured for communication with the first radio transceiver device 110 and the second radio transceiver device 120. Accordingly, the communication interface 220 may include one or more transmitters and receivers, which include analog and digital components. The processing circuitry 210 controls the general operation of the controller 200, for example, by sending data and control signals to the communication interface 220 and the storage medium 230, by receiving data and reports from the communication interface 220, and by retrieving data and instructions from the storage medium 230. Other components and related functions of the controller 200 are omitted so as not to obscure the concepts presented herein.

[0140] According to several functional modules, Figure 13 schematically illustrates the components of the controller 200 according to an embodiment. Figure 13 The controller 200 includes a plurality of functional modules; an obtaining module 210a is configured to perform step S102, and an estimating module 210b is configured to perform step S104. Figure 13 The controller 200 may further include a plurality of optional functional modules, such as a compensation module 210c configured to perform steps S104a and S104b, an estimating module 210d configured to perform step S106, a comparing module 210e configured to perform step S108, and a providing module 210f configured to perform step S110. Generally speaking, in one embodiment, each of the functional modules 210a-210f may be implemented only in hardware, while in another embodiment, it may be implemented by means of software, that is, the latter embodiment has computer program instructions stored on the storage medium 230, which, when running on the processing circuitry, cause the controller 200 to perform the corresponding steps as described above in connection with Figure 6 mentioned. Returning again to reference Figure 3 and Figure 4, the obtaining module 210a may at least partially implement the functions of the measurement / processing module. In addition, the estimation module 210b may at least partially implement the functions of the measurement / processing module. In addition, the comparison module 210e may at least partially implement the functions of the monitoring module. In addition, the providing module 210f may at least partially implement the functions of the on-site calibration module.

[0141] It should also be noted that although these modules correspond to parts of a computer program, they do not need to be separate modules therein, but rather their implementation in software depends on the programming language used. Preferably, one or more or all of the functional modules 210a - 210f may be implemented by the processing circuit 210 (possibly in cooperation with the communication interface 220 and / or the storage medium 230). Thus, the processing circuit 210 may be configured to retrieve instructions provided by the functional modules 210a - 210f from the storage medium 230 and execute these instructions, thereby performing any of the steps disclosed herein.

[0142] The controller 200 may be provided as a stand-alone device or as part of at least one other device. For example, the controller 200 may be provided in a node of a (radio) access network or in a node of a core network. Alternatively, the functions of the controller 200 may be distributed between at least two devices or nodes. These at least two nodes or devices may be part of the same network portion (such as a (radio) access network or a core network), or may be spread between at least two such network portions. Generally, instructions that need to be executed in real time may be executed in a device or node that is operationally closer to the cell compared to instructions that do not need to be executed in real time.

[0143] Thus, a first part of the instructions executed by the controller 200 may be executed in a first device, and a second part of the instructions executed by the controller 200 may be executed in a second device; the embodiments disclosed herein are not limited to any particular number of devices on which the instructions executed by the controller 200 may be executed. Thus, the method according to the embodiments disclosed herein is suitable for execution by a controller 200 residing in a cloud computing environment. Thus, although a single processing circuit 210 is illustrated in Figure 12 the processing circuit 210 may be distributed among multiple devices or nodes. This also applies to Figure 13 the functional modules 210a - 210f and Figure 14 the computer program 1320.

[0144] Figure 14An example of a computer program product 1310 including a computer-readable storage medium 1330 is shown. A computer program 1320 can be stored on the computer-readable storage medium 1330, and the computer program 1320 can cause a processing circuit 210 and entities and devices operably coupled thereto (such as a communication interface 220 and a storage medium 230) to perform a method according to the embodiments described herein. Thus, the computer program 1320 and / or the computer program product 1310 can provide components for performing any of the steps disclosed herein.

[0145] In Figure 14 the example of, the computer program product 1310 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-ray disc. The computer program product 1310 can also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM), and more specifically as a non-volatile storage medium in an external memory of a device (such as a USB (universal serial bus) memory or a flash memory (such as a compact flash memory)). Thus, although the computer program 1320 is schematically shown herein as tracks on the depicted optical disc, the computer program 1320 can be stored in any manner suitable for the computer program product 1310.

[0146] Figure 15 is a schematic diagram illustrating a telecommunications network connected to a host computer 430 via an intermediate network 420 according to some embodiments. According to an embodiment, the communication system includes a telecommunications network 410 (such as a 3GPP type cellular network), which includes an access network 411 and a core network 414. The access network 411 includes a plurality of radio access network nodes 412a, 412b, 412c, such as NB, eNB, gNB (each corresponding to Figure 2 a first radio transceiver device 110) or other types of wireless access points (each defining a corresponding coverage area or cell 413a, 413b, 413c). Each radio access network node 412a, 412b, 412c can be connected to the core network 414 via a wired or wireless connection 415. A first UE 491 located in the coverage area 413c is configured to be wirelessly connected to or paged by the corresponding network node 412c. A second UE 492 in the coverage area 413a can be wirelessly connected to the corresponding network node 412a. Although a plurality of UEs 491, 492 are illustrated in this example, the disclosed embodiments are equally applicable to cases where the only UE is in the coverage area or the only terminal device is connected to the corresponding network node 412. The UEs 491, 492 correspond to Figure 2The second radio transceiver device 120.

[0147] The telecommunication network 410 is itself connected to a host computer 430, which may be embodied in the hardware and / or software of a stand-alone server, a cloud-implemented server, a distributed server, or as processing resources in a server farm. The host computer 430 may be under the ownership or control of a service provider, or may be operated by or on behalf of a service provider. The connections 421 and 422 between the telecommunication network 410 and the host computer 430 may extend directly from the core network 414 to the host computer 430, or may be connected via an optional intermediate network 822. The intermediate network 420 may be one or more combinations of a public, private, or managed network; the intermediate network 420 (if any) may be a backbone network or the Internet; in particular, the intermediate network 420 may include two or more sub-networks (not shown).

[0148] Figure 15 The communication system as a whole realizes the connection between the connected UEs 491, 492 and the host computer 430. This connection may be described as an over-the-top (OTT) connection 450. The host computer 430 and the connected UEs 491, 492 are configured to use the access network 411, the core network 414, any intermediate network 420, and possibly other infrastructure (not shown) as intermediaries to transmit data and / or signaling via the OTT connection 450. The OTT connection 450 may be transparent in the sense that the participating communication devices through which the OTT connection 450 passes are unaware of the routing of the uplink and downlink communications. For example, it may not be necessary or required to inform the network node 412 about the past routing of an incoming downlink communication, where the incoming downlink communication has data originating from the host computer 430 that is to be forwarded (e.g., handed over) to the connected UE 491. Similarly, the network node 412 does not need to know the future routing of an outgoing uplink communication originating from the UE 491 to the host computer 430.

[0149] Figure 16 is a schematic diagram illustrating a host computer communicating with a UE via a radio access network node through a partial wireless connection according to some embodiments. Now reference will be made to Figure 16To describe an exemplary implementation according to an embodiment of the UE, radio access network node, and host computer discussed in the previous paragraphs. In communication system 500, host computer 510 includes hardware 515, which includes communication interface 516 configured to establish and maintain a wired or wireless connection to different communication devices in communication system 500. Host computer 510 also includes processing circuitry 518, which may have storage and / or processing capabilities. In particular, processing circuitry 518 may include one or more programmable processors, application specific integrated circuits, field programmable gate arrays, or a combination of components (not shown) suitable for executing instructions. Host computer 510 also includes software 511, which is stored in or accessible by host computer 510 and executable by processing circuitry 518. Software 511 includes host application 512. Host application 512 may be operable to provide services to remote users, such as UE 530 connected via an OTT connection 550 terminating at UE 530 and host computer 510. When providing services to remote users, host application 512 may provide user data transmitted using OTT connection 550.

[0150] Communication system 500 also includes radio access network node 520, which is provided in a telecommunications system and includes hardware 525 enabling it to communicate with host computer 510 and UE 530. Radio access network node 520 corresponds to Figure 2 the first radio transceiver device 110. Hardware 525 may include communication interface 526 for establishing and maintaining a wired or wireless connection to different communication devices in communication system 500, and radio interface 527 for at least establishing and maintaining a wireless connection 570 to UE 530 located within a coverage area (not shown in Figure 16 ). Communication interface 526 may be configured to facilitate connection 560 to host computer 510. Connection 560 may be direct, or it may pass through a core network (not shown in Figure 16 ) in the telecommunications system and / or through one or more intermediate networks external to the telecommunications system. In the illustrated embodiment, hardware 525 of radio access network node 520 also includes processing circuitry 528, which may include one or more programmable processors, application specific integrated circuits, field programmable gate arrays, or a combination of components (not shown) suitable for executing instructions. Radio access network node 520 also has software 521 stored internally or accessible via an external connection.

[0151] The communication system 500 also includes the UE 530 that has been mentioned. The hardware 535 of the UE 530 may include a radio interface 537, which is configured to establish and maintain a wireless connection 570 with a radio access network node serving the coverage area where the UE 530 is currently located. The hardware 535 of the UE 530 also includes a processing circuit 538, which may include one or more programmable processors, application specific integrated circuits, field programmable gate arrays, or a combination of components (not shown) suitable for executing instructions. The UE 530 also includes software 531, which is stored in or accessible by the UE 530 and executable by the processing circuit 538. The software 531 includes a client application 532. The client application 532 can be operable with the support of the host computer 510 to provide services to a human or non - human user via the UE 530. In the host computer 510, the executing host application 512 can communicate with the executing client application 532 via an OTT connection 550 terminating at the UE 530 and the host computer 510. When providing services to the user, the client application 532 can receive request data from the host application 512 and, in response to the request data, provide user data. The OTT connection 550 can convey both the request data and the user data. The client application 532 can interact with the user to generate the user data it provides.

[0152] Note that Figure 16 the host computer 510, radio access network node 520, and UE 530 shown in Figure 15 may be similar or identical to one of the host 430, network nodes 412a, 412b, 412c, and one of the UEs 491, 492 respectively. That is, the internal workings of these entities may be as Figure 16 shown, and independently, the surrounding network topology may be Figure 15 as shown.

[0153] In Figure 16 the OTT connection 550 has been abstractly drawn to illustrate communication between the host computer 510 and the UE 530 via the network node 520 without explicitly mentioning any intermediate devices and the exact message routing via these devices. The network infrastructure can determine the routing, which can be configured to hide from the UE 530 or the service provider operating the host computer 510, or both. When the OTT connection 550 is active, the network infrastructure can further make a decision by which it dynamically changes the routing (e.g., based on load - balancing considerations or network re - configuration).

[0154] The wireless connection 570 between the UE 530 and the radio access network node 520 is in accordance with the teachings of the embodiments described in this disclosure. One or more of the various embodiments may improve the performance of the OTT service provided to the UE 530 using the OTT connection 550, where the wireless connection 570 constitutes the last hop. More precisely, the teachings of these embodiments may reduce interference, as the classification ability of airborne UEs that can generate significant interference is improved.

[0155] For the purpose of monitoring data rate, latency, and other factors that are improved by one or more embodiments, a measurement process may be provided. There may also be optional network functions for reconfiguring the OTT connection 550 between the host computer 510 and the UE 530 in response to changes in the measurement results. The measurement process and / or network function for reconfiguring the OTT connection 550 may be implemented in the software 511 and hardware 515 of the host computer 510 or the software 531 and hardware 535 of the UE 530, or both. In an embodiment, sensors (not shown) may be deployed in or associated with the communication devices through which the OTT connection 550 passes; the sensors may participate in the measurement process by providing values of the monitored quantities illustrated above, or providing values of other physical quantities from which the monitored quantities can be calculated or estimated by the software 511, 531. The reconfiguration of the OTT connection 550 may include message format, retransmission settings, preferred routing, etc.; the reconfiguration need not affect the network node 520 and may be unknown or imperceptible to the radio access network node 520. Such processes and functions may be known and practiced in the art. In certain embodiments, the measurement may involve proprietary UE signaling that facilitates the host computer 510's measurement of throughput, propagation time, latency, etc. These measurements may be implemented when the software 511 and 531 that send messages (especially empty messages or "dummy" messages) using the OTT connection 550 monitor propagation time, errors, etc.

[0156] The inventive concept has been mainly described above with reference to several embodiments. However, as will be readily understood by those skilled in the art, other embodiments than those disclosed above may equally fall within the scope of the inventive concept as defined by the appended patent claims.

Claims

1. A method for over-the-air (OTA) based phase accuracy estimation for a first radio transceiver device (110) to mitigate the impact of reflections in its specific environment, the method being executed by a controller (200), the method comprising: obtaining (S102) an estimated phase difference between transceiver branches of the first radio transceiver device (110) for each position in a sequence of positions of a second radio transceiver device (120) relative to the first radio transceiver device (110), wherein each estimated phase difference is obtained from measurements of a signal wirelessly transmitted between the first radio transceiver device (110) and the second radio transceiver device (120); estimating (S104) an average phase relationship of at least one pair of the transceiver branches of the first radio transceiver device (110) by averaging the estimated phase differences obtained at all positions in the sequence of positions, wherein the phase accuracy of the first radio transceiver device (110) is represented by the average phase relationship of the at least one pair of the transceiver branches; comparing (S108) the value of the average phase relationship of the at least one pair of the transceiver branches with an expected phase relationship value of the at least one pair of the transceiver branches; and when the value of the average phase relationship deviates from the expected phase relationship value by more than a threshold, providing (S110) a correction signal to a calibration module of the first radio transceiver device (110).

2. The method according to claim 1, wherein, an average phase relationship is estimated for each pair of the transceiver branches by averaging the estimated phase differences obtained at all positions in the sequence of positions for each pair of the transceiver branches, and wherein the phase accuracy of the first radio transceiver device (110) is represented by the average phase relationship for each pair of the transceiver branches.

3. The method according to claim 1 or 2, further comprising: estimating (S106) a beam quality value of the first radio transceiver device (110) based on the average phase relationship of the at least one pair of the transceiver branches.

4. The method according to claim 3, wherein, for at least one of wireless signal transmission and wireless signal reception at the first radio transceiver device (110), the beam quality value is related to the phase accuracy of the transceiver branches of the first radio transceiver device (110).

5. The method according to claim 3, wherein, the beam quality value is estimated as a comparison of the measured average phase relationship of the at least one pair of the transceiver branches with the expected phase relationship of the at least one pair of the transceiver branches.

6. The method according to claim 3, wherein, For the position sequence, an estimated amplitude relationship between the transceiver branches is obtained for each position of the second radio transceiver device (120) relative to the first radio transceiver device (110), wherein an average amplitude relationship of at least a pair of the transceiver branches is estimated by averaging the estimated amplitude relationships at all positions in the position sequence, and wherein the amplitude accuracy of the first radio transceiver device (110) is represented by the average amplitude relationship of at least a pair of the transceiver branches.

7. The method according to claim 6, wherein, the beam quality value is further estimated based on the average amplitude relationship of at least a pair of the transceiver branches.

8. The method according to claim 7, wherein, for at least one of wireless signal transmission and wireless signal reception at the first radio transceiver device (110), the beam quality value is further related to the amplitude accuracy of the transceiver branches of the first radio transceiver device (110).

9. The method according to claim 1 or 2, further comprising: performing plane wave compensation (S104a, S104b) on the estimated phase difference before estimating the average phase relationship, or performing plane wave compensation (S104a, S104b) on the average phase relationship.

10. The method according to claim 1 or 2, wherein, the signal is wirelessly transmitted from the first radio transceiver device (110).

11. The method according to claim 10, wherein, for each position of the second radio transceiver device (120) relative to the first radio transceiver device (110), the signal is transmitted using one of the transceiver branches at a time.

12. The method according to claim 1 or 2, wherein, the signal is wirelessly transmitted from the second radio transceiver device (120).

13. The method according to claim 12, wherein, for each position of the second radio transceiver device (120) relative to the first radio transceiver device (110), the signal is received simultaneously in all of the transceiver branches.

14. The method according to claim 1, wherein, the calibration signal is an alarm signal or the value itself of the average phase relationship.

15. The method according to claim 1 or 14, wherein, the calibration signal is provided for initiating calibration of the transceiver branches at the first radio transceiver device (110).

16. The method according to claim 1 or 2, wherein, the signal is a dedicated test signal.

17. The method according to claim 1 or 2, wherein, the first radio transceiver device (110) has a line-of-sight direction, wherein the position sequence forms a path, and wherein the path extends in a direction perpendicular to the line-of-sight direction.

18. The method according to claim 1 or 2, wherein, The controller (200) is part of the first radio transceiver device (110), the second radio transceiver device (120), or the network controller (200).

19. The method according to claim 1 or 2, wherein, the first radio transceiver device (110) is part of an access node (130).

20. The method according to claim 1 or 2, wherein, the second radio transceiver device (120) is part of a user equipment (140).

21. A controller (200) for air-over-the-air (OTA) based phase accuracy estimation of a first radio transceiver device (110) for mitigating the impact of reflections in its specific environment, the controller (200) comprising processing circuitry (210) configured to cause the controller (200) to: Obtain an estimated phase difference between transceiver branches of the first radio transceiver device (110) for each position in a sequence of positions of a second radio transceiver device (120) relative to the first radio transceiver device (110), wherein, each estimated phase difference is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device (110) and the second radio transceiver device (120); Estimate an average phase relationship of at least one pair of the transceiver branches of the first radio transceiver device (110) by averaging the estimated phase differences obtained at all positions in the sequence of positions, wherein the phase accuracy of the first radio transceiver device (110) is represented by the average phase relationship of the at least one pair of the transceiver branches; Compare the value of the average phase relationship of the at least one pair of the transceiver branches with an expected phase relationship value of the at least one pair of the transceiver branches; and When the value of the average phase relationship deviates from the expected phase relationship value by more than a threshold, provide a correction signal to a calibration module of the first radio transceiver device (110).

22. The controller (200) according to claim 21, further configured to perform the method according to any one of claims 2 to 20.

23. A computer program (1320) for air-over-the-air (OTA) based phase accuracy estimation of a first radio transceiver device (110) for mitigating the impact of reflections in its specific environment, the computer program (1320) comprising computer code that, when run on the processing circuitry (210) of a controller (200), causes the controller (200) to: Obtain (S102) an estimated phase difference between transceiver branches of the first radio transceiver device (110) for each position in a sequence of positions of a second radio transceiver device (120) relative to the first radio transceiver device (110), wherein, Each estimated phase difference is obtained from measurements of signals wirelessly transmitted between the first radio transceiver device (110) and the second radio transceiver device (120). An average phase relationship of at least one pair of transceiver branches of the first radio transceiver device (110) is estimated (S104) by averaging the estimated phase differences obtained at all positions in the sequence of positions, wherein the phase accuracy of the first radio transceiver device (110) is represented by the average phase relationship of the at least one pair of transceiver branches; The value of the average phase relationship of the at least one pair of transceiver branches is compared (S108) with an expected phase relationship value of the at least one pair of transceiver branches; and When the value of the average phase relationship deviates from the expected phase relationship value by more than a threshold, a correction signal is provided (S110) to a calibration module of the first radio transceiver device (110).

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