WO2023123042A1

WO2023123042A1 - Method and apparatus for performing a beamformed test signaling

Info

Publication number: WO2023123042A1
Application number: PCT/CN2021/142449
Authority: WO
Inventors: Hao Zhang; Magnus Nilsson; Christian Braun
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-12-29
Filing date: 2021-12-29
Publication date: 2023-07-06

Abstract

A method is disclosed for a wireless communication node operating in a wireless communication system and controlling an antenna system. The method comprises obtaining information indicating a direction from the antenna system towards a location of interference sensitivity, and performing beamformed test signaling (e.g., over-the-air transmission of the test signal), wherein a beam direction of the beamformed test signaling and the indicated direction are different. For example, performing the beamformed test signaling may comprise orienting an emission pattern of the beamformed test signaling such that the emission pattern has an emission strength in the indicated direction which is lower than an emission strength threshold. The location of interference sensitivity may comprise a vehicular route, a location of a vehicular control station, or an area of operation of another wireless communication node. In some embodiments, the method is for antenna calibration of the antenna system, and the beamformed test signaling comprises beamformed antenna calibration signaling. Corresponding computer program product, apparatus, and wireless communication node are also disclosed.

Description

TEST SIGNALING CONTROL

TECHNICAL FIELD

The present disclosure relates generally to the field of wireless communication. More particularly, it relates to control of test signaling by a wireless communication node.

BACKGROUND

Test signaling (e.g., antenna calibration signaling) performed by a wireless communication node may be harmful to the operation of various electronic equipment operating at locations impacted by the test signaling.

Some attempts to reduce an interference signal and enhance data communication are made in US 6, 480, 153 B1. There, a calibration signal vector is injected into an array receiver/transmitter, a calibration coefficient is obtained by using that the transfer function of each channel is estimated by analyzing the signal injected, and an interference signal is eliminated by multiplying the received signal of a baseband and the calibration coefficient together. However, such approaches are not suitable for over-the-air antenna calibration approaches. Furthermore, the injected calibration signal may still be harmful to the operation of electronic equipment operating at locations impacted by the injected calibration signal.

Therefore, there is a need for alternative approaches to test signaling by wireless communication nodes.

SUMMARY

It should be emphasized that the term “comprises/comprising” (replaceable by “includes/including” ) when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a" , "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Generally, when an arrangement is referred to herein, it is to be understood as a physical product; e.g., an apparatus. The physical product may comprise one or more parts, such as controlling circuitry in the form of one or more controllers, one or more processors, or the like.

It is an object of some embodiments to solve or mitigate, alleviate, or eliminate at least some of the above or other disadvantages.

A first aspect is a method for a wireless communication node operating in a wireless communication system and controlling an antenna system. The method comprises obtaining information indicating a direction from the antenna system towards a location of interference sensitivity, and performing beamformed test signaling, wherein a beam direction of the beamformed test signaling and the indicated direction are different.

In some embodiments, the beamformed test signaling comprises radio frequency (RF) signaling.

In some embodiments, the method is for antenna calibration of the antenna system, and the beamformed test signaling comprises beamformed antenna calibration signaling.

In some embodiments, the method further comprises estimating transceiver branch channel variations based on the beamformed antenna calibration signaling, calculating calibration coefficients based on the estimated transceiver branch channel variations, and compensating for the transceiver branch channel variations according to the calculated calibration coefficients.

In some embodiments, obtaining the information indicating the direction comprises one or more of: retrieving the information from a storage device associated with the wireless communication node, receiving the information via signaling from an interference sensitivity monitoring node, receiving the information as input via a user interface, and determining the information based on spatial characteristics of incoming communication signaling from another wireless communication node operating in the wireless communication system.

In some embodiments, the location of interference sensitivity comprises one or more of: a geographical area, an angular extension, a geographical trace, and an angular trace.

In some embodiments, the information is further indicating a timing for the indicated direction, and/or a rate of change for the indicated direction.

In some embodiments, the information indicating the direction is dynamically updated.

In some embodiments, the location of interference sensitivity comprises one or more of: a vehicular route, a location of a vehicular control station, and an area of operation of another wireless communication node.

In some embodiments, the interference sensitivity relates to in-band interference and/or out-of-band interference in relation to a frequency band of the beamformed test signaling.

In some embodiments, performing the beamformed test signaling comprises orienting an emission pattern of the beamformed test signaling such that the emission pattern has an emission strength in the indicated direction which is lower than an emission strength threshold.

In some embodiments, performing the beamformed test signaling comprises placing a null of an emission pattern of the beamformed test signaling in association with the indicated direction.

In some embodiments, the method further comprises performing beamformed communication transmission from the wireless communication node, wherein a beam direction of the communication transmission and the indicated direction are different.

In some embodiments, the beamformed test signaling comprises two or more different and simultaneously used test signaling beams.

In some embodiments, the beamformed test signaling is performed for a subgroup of transceiver branches of the antenna system.

In some embodiments, the method further comprises selecting the transceiver branches of the subgroup.

In some embodiments, selecting the transceiver branches of the subgroup is based on a beam shape associated with a pattern of antenna elements of the antenna system that correspond to the transceiver branches.

In some embodiments, selecting the transceiver branches of the subgroup is based on an over-the-air coupling between another transceiver branch and each of the transceiver branches of the subgroup.

In some embodiments, the beamformed test signaling is performed simultaneously for two or more subgroups of transceiver branches, wherein any transceiver branch of the antenna system is comprised in at most one subgroup.

In some embodiments, the beamformed test signaling is performed for a subgroup comprises two or more different and simultaneously used test signaling beams.

In some embodiments, the interference sensitivity excludes sensitivity to interference between test signaling of the wireless communication node and communication transmission from the wireless communication node.

In some embodiments, the indicated direction is a direction of incoming communication signaling from another wireless communication node operating in the wireless communication system, and the method further comprises determining whether the indicated direction is stationary, wherein the beamformed test signaling is performed simultaneously with the incoming communication signaling when the indicated direction is stationary.

In some embodiments, determining whether the indicated direction is stationary comprises determining a rate of change for the indicated direction, and determining the indicated direction to be stationary when the rate of change is lower than a change rate threshold.

In some embodiments, performing the beamformed test signaling comprises over-the-air transmission of a beamformed test signal from a subgroup of transceiver branches of the antenna system, and over-the-air reception of the beamformed test signal by one or more other transceiver branches of the antenna system.

In some embodiments, performing the beamformed test signaling comprises, for at least one transceiver branch of the antenna system, injecting a test signal at a first position of the transceiver branch and extracting the test signal at a second position of the transceiver branch, wherein beamforming of the test signal is accomplished via application of a coupling network configured to process the test signal before injection and/or after extraction.

In some embodiments, the indicated direction comprises a plurality of indicated directions.

In some embodiments, performing the beamformed test signaling comprises injecting a beamformed test signal for transmission.

A second aspect is a computer program product comprising a non-transitory computer readable medium, having thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit and configured to cause execution of the method according to the first aspect when the computer program is run by the data processing unit.

A third aspect is an apparatus for a wireless communication node operating in a wireless communication system and controlling an antenna system. The apparatus comprises controlling circuitry configured to cause obtaining of information indicating a direction from the antenna system towards a location of interference sensitivity, and performance of beamformed test signaling, wherein a beam direction of the beamformed test signaling and the indicated direction are different.

A fourth aspect is a wireless communication node comprising the apparatus of the third aspect. In some embodiments, the wireless communication node further comprises the antenna system.

In some embodiments, any of the above aspects may additionally have features identical with or corresponding to any of the various features as explained above for any of the other aspects.

An advantage of some embodiments is that alternative approaches for test signaling by wireless communication nodes are provided.

An advantage of some embodiments is that test signaling (e.g., antenna calibration signaling) performed by a wireless communication node becomes less harmful (compared to other approaches for test signaling) to the operation of electronic equipment positioned at a location identified as interference sensitive.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

Figure 1 is a schematic drawing illustrating example principles of over-the-air antenna calibration signaling according to some embodiments;

Figure 2 is a schematic drawing illustrating example principles of antenna calibration signaling via a coupling network according to some embodiments;

Figure 3 is a flowchart illustrating example method steps according to some embodiments;

Figure 4 is a schematic block diagram illustrating example beamformed test signaling according to some embodiments;

Figure 5 is a schematic drawing illustrating example beamformed test signaling in relation to an indicated direction according to some embodiments;

Figure 6 is a collection of schematic drawings illustrating various types of example locations of interference sensitivity according to some embodiments;

Figure 7 is a schematic drawing illustrating an example antenna system and some corresponding examples of beamformed test signaling according to some embodiments;

Figure 8 is a schematic drawing illustrating example principles of beamformed test signaling in relation to communication reception according to some embodiments;

Figure 9 is a schematic block diagram illustrating an example apparatus according to some embodiments; and

Figure 10 is a schematic drawing illustrating an example computer readable medium according to some embodiments.

DETAILED DESCRIPTION

As already mentioned above, it should be emphasized that the term “comprises/comprising” (replaceable by “includes/including” ) when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a" , "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure will be described and exemplified more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the embodiments set forth herein.

Some embodiments may be particularly suitable for scenarios where massive multiple-input multiple-output (MIMO) and/or millimeter wavelength (mmW) frequencies are applied. Alternatively or additionally, some embodiments may be particularly suitable for fifth generation (5G) wireless communication (e.g., as advocated by the Third Generation Partnership Project, 3GPP, standardization) .

In the following, alternative approaches for test signaling (e.g., antenna calibration signaling) by wireless communication nodes will be exemplified. Some embodiments aim for reduction of interference caused by the test signaling, as experienced for location (s) identified as interference sensitive. Such a location is referred to herein as location of interference sensitivity (or a “critical” location) .

Generally, a location of interference sensitivity may be any location which is particularly sensitive to interference by radio frequency signals. Being particularly sensitive to interference by radio frequency signals may, for example, comprise requiring any radio frequency signals to have a signal strength (as experienced within the location of interference sensitivity) below an interference signal strength threshold value. Alternatively or additionally, the interference sensitivity may relate to one or more specified radio frequency intervals only, or to any radio frequencies.

Also generally, the location of interference sensitivity may have any suitable form. For example, the location of interference sensitivity may be defined geographically (in absolute terms, or in relation to the wireless communication node) ; for example, as one or more geographical point (s) , and/or one or more geographical area (s) , and/or one or more geographical trace (s) . Alternatively or additionally, the location of interference sensitivity may be defined angularly (in relation to the wireless communication node) ; for example, as one or more angular direction (s) , and/or one or more angular extension (s) (e.g., angular range (s) in one angular dimension or angular area (s) in two angular dimensions) , and/or one or more angular trace (s) .

Some examples locations that may be interference sensitive include (but are not limited to) vehicular routes, locations of vehicular control stations, and areas of operation of other wireless communication nodes.

Vehicular routes may, for example, be routes for autonomous vehicles, or routes for airplanes (e.g., takeoff/landing traces, runways, and/or taxing routes of an airport) , or satellite trajectories. In some embodiments, an angular extension which is vertically above horizon may be defined as a location of interference sensitivity (e.g., to avoid interference to airplanes and/or satellites) .

Locations of vehicular control stations may, for example, be a location of an airport control center, or a location of a satellite ground station.

Areas of operation of other wireless communication nodes may, for example, be a location of a wireless backhaul device (of the wireless communication system in which the wireless communication node operates, or of a coexisting wireless communication system other than the wireless communication system in which the wireless communication node operates) , or an area of operation for a coexisting wireless communication system other than the wireless communication system in which the wireless communication node operates, or a location of another wireless communication node operating in the wireless communication system in which the wireless communication node operates (e.g., co-located equipment and/or a wireless communication node performing communication transmission intended for the wireless communication node) .

According to some embodiments, the interference sensitivity excludes sensitivity to interference between test signaling of the wireless communication node and communication transmission from the wireless communication node. Thus, a communication transmission from the wireless communication node typically does not give rise to a location of interference sensitivity (i.e., the location of a receiver of such communication transmissions is typically not a location of interference sensitivity; at least not for that reason) . Hence, it should be noted that reduction of interference caused by test signaling to communication transmissions from the wireless communication node is typically not a goal for embodiments presented herein (even though it might be an additional consequence thereof) .

In the following description of embodiments, antenna calibration (AC) signaling will be used as a typical example of test signaling. It should be noted however, that test signaling may comprise any other applicable antenna system signaling which is not communication signaling. For example, the test signaling may –additionally or alternatively –be for multiple-input multiple-output digital pre-distortion (MIMO-DPD) control and/or for over-the-air inphase/quadrature (OTA IQ) compensation.

Generally, an antenna system as referred to herein may be any suitable antenna system. For example, the antenna system may be an advanced antenna system (AAS; a.k.a. an active antenna system) comprising a (typically relatively large) plurality of antenna elements. Each antenna element is typically associated with a respective transceiver branch of the wireless communication node controlling the antenna system. A transceiver branch may be associated with only a single antenna element, or with a group of two or more antenna elements.

Antenna calibration may adhere to any suitable general principles for antenna calibration (e.g., for massive MIMO radios) . For example, during an AC measurement phase (e.g., for downlink, DL, AC) , the antenna system may be arranged to transmit an AC signal from a subgroup of the transceiver branches (typically using a relatively sparse pattern –also termed AC TX pattern –of antenna elements of the antenna system) . Typically, sequential application of a plurality of AC TX patterns is required to achieve sufficient AC measurements.

Figures 1 and 2 illustrates two approaches for antenna calibration signaling; an over-the-air (OTA) approach and a coupling network approach. The illustrations relate to a

wireless communication node

100, 200 controlling an

antenna system

190, 290 that comprises a plurality of

antenna elements

116, 126, 136, 216, 226, 236. In the examples of Figures 1 and 2, each

antenna element

116, 126, 136, 216, 226, 236 is associated with a

respective transceiver branch

110, 120, 130, 210, 220, 230, and each transceiver branch is connectable (e.g., connected) to other circuitry of the

wireless communication node

100, 200, as illustrated by

connection points

112, 122, 132, 212, 222, 232.

Figure 1 schematically illustrates example principles of over-the-air antenna calibration signaling (a.k.a. mutual coupling based AC, MCAC) . According to these principles, the antenna calibration signaling comprises over-the-air (OTA) transmission of an

antenna calibration signal

181, 182 from a subgroup 120 of transceiver branches of the antenna system, and over-the-air (OTA) reception of the

antenna calibration signal

181, 182 by one or more

other transceiver branches

110, 130 of the antenna system.

Based on the OTA transmission and reception of the antenna calibration signaling, an analysis may be performed to determine differences between the transceiver branches, and corresponding adjustment (s) may be performed to mitigate the differences.

This approach may be particularly suitable for antenna calibration based on the mutual coupling between antenna elements.

Figure 2 schematically illustrates example principles of antenna calibration signaling via a coupling network (a.k.a. couplerbased AC) . According to these principles, the antenna calibration signaling comprises injecting, for at least one (e.g., all)

transceiver branch

210, 220, 230 of the antenna system, an antenna calibration signal at a first position (e.g., a first end) of the transceiver branch and extracting the antenna calibration signal at a second –different –position (e.g., a second end) of the transceiver branch.

Based on how the different transceiver branches affect the injected antenna calibration signal, an analysis may be performed to determine differences between the transceiver branches, and corresponding adjustment (s) may be performed to mitigate the differences.

A coupling network 280 may be used for the analysis and/or for the adjustment. The coupling network 280 may be connectable (e.g., connected) to the

transceiver branches

210, 220, 230 for injection and/or extraction of the antenna calibration signal. Such connections may be via connection points between the antenna system and the transceiver branches, as illustrated by 214, 224, 234, and/or via connection points at another end of the transceiver branches, as illustrated by 212, 222, 232, or within the transceiver branches. For example, the first end may be as represented by 214, 224, 234 and the second end may be represented by 212, 222, 232, or the first end may be as represented by 212, 222, 232 and the second end may be represented by 214, 224, 234.

Generally, the antenna calibration signal may be injected at any suitable connection point for a transceiver branch (e.g., at a connection points between the antenna system and the transceiver branch, at a connection point at the other end of the transceiver branches, or at any connection point within the transceiver branch) , and may be extracted at any other suitable connection point for the receiver branch.

The coupling network 280 may also be connectable (e.g., connected) to other circuitry of the wireless communication node 200, as illustrated by connection point 282.

A general problem with antenna calibration signaling (or other test signaling) is that it may cause interference (e.g., to ongoing traffic signaling, to system reference signaling, to coexisting equipment, etc. ) . Conventionally, antenna calibration signaling may comprise transmission of independent and orthogonal AC signals on the transceiver branches of the AC TX pattern. Thus, the AC emission corresponds to the basic emission pattern of the antenna system, and causes interference in all corresponding directions.

Some embodiments aim for reduction of such interference; by beamforming the antenna calibration signaling such that it is directed away from location (s) identified as interference sensitive.

Figure 3 illustrates an example method 300 according to some embodiments. The method 300 is for a wireless communication node operating in a wireless communication system and controlling an antenna system (e.g., any of the

wireless communication nodes

100, 200 described in connection with Figure 1 and 2) .

In step 310, information indicating a direction from the antenna system towards a location of interference sensitivity (e.g., as described above) is obtained. The interference sensitivity may relate to in-band interference in relation to a frequency band of the antenna calibration signaling and/or to out-of-band interference in relation to the frequency band of the antenna calibration signaling.

Generally, the information may indicate only a single direction, two or more (aplurality of) directions, or one or more ranges of directions. Alternatively or additionally, each indicated direction may relate to the location of interference sensitivity in any suitable way. For example, an indicated direction may be a direction toward a certain point (e.g., a mid-point) within the location of interference sensitivity, an indicated range of directions may span the location of interference sensitivity, etc.

Also generally, the location of interference sensitivity associated with the indicated direction (s) may comprise only a single location of interference sensitivity, or may comprise two or more location (s) of interference sensitivity (e.g., two or more geographical areas, two or more geographical traces, two or more angular extensions, two or more angular traces, etc. ) .

Obtaining the information in step 310 may be achieved using any suitable approach.

For example, the information may be retrieved in step 310 from a storage device associated with (e.g., comprised in) the wireless communication node (e.g., for scenarios where the information is hardcoded into the wireless communication node at deployment) .

Alternatively or additionally, the information may be received in step 310 via signaling from an interference sensitivity monitoring node. An interference sensitivity monitoring node might typically detect location (s) of interference sensitivity. Such detection may, for example, comprise detection of vehicles (e.g., airplanes of an airport) using any suitable vehicle detection approach (e.g., radar, video and image recognition, etc. ) . An interference sensitivity monitoring node may also transform the detected location (s) of interference sensitivity into direction (s) from the viewpoint of the wireless communication node. To this end, the interference sensitivity monitoring node could have knowledge regarding location and/or orientation and/or geometry of the antenna system controlled by the wireless communication node. Generally, information received via signaling from an interference sensitivity monitoring node may relate to instantaneously detected location (s) of interference sensitivity and/or to statistics collected over time for detected location (s) of interference sensitivity. Alternatively or additionally, information received via signaling from an interference sensitivity monitoring node may be valid until further notice, or may be valid only for a certain duration of time (e.g., starting when received, or at a later moment in time) .

Yet alternatively or additionally, the information may be received in step 310 via a user interface (e.g., input by a person operating, installing, and/or maintaining of the wireless communication node) . For example, such user interface may be comprised in the wireless communication node and/or in an interference sensitivity monitoring node.

Yet alternatively or additionally, step 310 may comprise determining the information based on spatial characteristics of incoming communication signaling from another wireless communication node operating in the wireless communication system. This scenario related to embodiments where the location of interference sensitivity is an area of operation of another wireless communication node performing communication transmission (i.e., communication signaling) intended for the wireless communication node performing the method 300. Thus, the location of interference sensitivity may correspond to an angular extension for the incoming communication signaling, and the indicated direction may be associated with (e.g., be equal to) a direction corresponding to a reception precoder for the incoming communication signaling.

In some embodiments, the information indicating the direction is dynamically updated (e.g., step 310 may be repeatedly performed) . For example, step 310 may be performed at a periodical time interval and/or responsive to a triggering event (e.g., before each –or some –antenna calibration signaling, when new information is received from the interference sensitivity monitoring node and/or the user interface, etc. ) . Dynamic updates of the information may comprise one or more of: adding one or more new indicated direction (s) , removing one or more previously indicated direction (s) , and changing (i.e., moving) one or more previously indicated direction (s) .

Any suitable combinations of the above examples may also be applied. For example, step 310 may comprise retrieving first information indicating some directions from a storage device comprised in the wireless communication node, receiving second information indicating some (e.g., other) directions via signaling from an interference sensitivity monitoring node, and combining the first and second information.

In step 340, beamformed antenna calibration signaling (or, more generally, test signaling) is performed (typically in the form of radio frequency (RF) signaling) based on the information obtained in step 310. The beamformed antenna calibration signaling is performed such that the beam direction of the antenna calibration signaling differs from the indicated direction of the information obtained in step 310. Thus, the antenna calibration signaling may be seen as being directed away from the indicated direction.

In some embodiments, step 340 may comprise letting the beam direction of the antenna calibration signaling differ from the indicated direction by an angular amount that is higher than an angular threshold value.

Alternatively or additionally, step 340 may comprise orienting an emission pattern of the antenna calibration signaling such that the emission pattern has an emission strength in the indicated direction which is lower than an emission strength threshold. For example, the emission strength threshold may be set in relation to a default emission strength (e.g., an emission strength of an emission pattern of conventional antenna calibration signaling; compare with 501 of Figure 5) . An example emission strength threshold that may be suitable in some scenarios represents a 20 dB reduction compared to a default emission strength.

Yet alternatively or additionally, step 340 may comprise placing a null of an emission pattern of the antenna calibration signaling in association with (e.g., at, in an angular vicinity of, closer than a null placing threshold to, etc. ) the indicated direction.

When step 340 comprises over-the-air transmission of the antenna calibration signal from a subgroup of transceiver branches of the antenna system, and over-the-air reception of the antenna calibration signal by one or more other transceiver branches of the antenna system, the beamformed antenna calibration signaling may be accomplished by application of conventional beamforming principles (e.g., applying beamforming weights) to the subgroup of transceiver branches transmitting the antenna calibration signal.

When step 340 comprises, for at least one transceiver branch of the antenna system, injecting the antenna calibration signal at a first position of the transceiver branch and extracting the antenna calibration signal at a second –different –position of the transceiver branch, the beamformed antenna calibration signaling may be accomplished via application of the coupling network (i.e., the coupling network may be seen as a beamformer) .

In some embodiments, the information obtained in step 310 is further indicating a timing for the indicated direction and/or a rate of change (e.g., associated with a speed/velocity or movement) for the indicated direction. In such embodiments, the method 300 may further comprise applying adaptation for such information, as illustrated by optional step 330, before performing the antenna calibration signaling. For example, step 330 may comprise controlling the antenna calibration signaling of step 340 to be directed away from an indicated direction that changes over time (e.g., due to mobility of a vehicle, or of a wireless communication node performing communication transmission intended for the wireless communication node performing the method 300) .

The method 300 may further comprise one or more of: estimating transceiver branch channel variations based on the antenna calibration signaling (as illustrated by optional step 350) , calculating calibration coefficients based on the estimated transceiver branch channel variations (as illustrated by optional step 360) , and compensating for the transceiver branch channel variations according to the calculated calibration coefficients (as illustrated by optional step 370) .

Steps

350, 360, 370 may be performed using any suitable approach (e.g., according to the prior art) .

As illustrated by optional step 380, the method 300 may further comprise performing communication (transmission and/or reception; e.g., with the antenna system calibrated via the compensation of step 370) .

Alternatively or additionally, communication signaling may be performed simultaneously with the antenna calibration signaling of step 340 according to some embodiments.

For example, step 340 may further comprise performing beamformed communication transmission from the wireless communication node (simultaneously with the antenna calibration signaling) , wherein a beam direction of the communication transmission is different from the indicated direction (e.g., in a similar manner as described for the beam direction of the antenna calibration signaling) . Typically, the beam direction of the communication transmission is also different from the beam direction of the antenna calibration signaling.

In some embodiments, step 340 may further comprise performing communication reception (simultaneously with the antenna calibration signaling) . This scenario is related to embodiments where the indicated direction is a direction of incoming communication signaling. Then, step 310 may further comprise determining whether the indicated direction is stationary. Determining whether the indicated direction is stationary may, for example, comprise determining a rate of change for the indicated direction, and the indicated direction may be determined to be stationary when the rate of change is lower than a change rate threshold. In this scenario, step 340 may be performed simultaneously with the incoming communication signaling when the indicated direction is stationary (wherein the beam direction of the antenna calibration signaling is different from the direction of the incoming communication signaling, i.e., the indicated direction) . When the indicated direction is not stationary, antenna calibration signaling may be performed separately from the incoming communication signaling, or may be performed simultaneously with the incoming communication signaling with adaptation for the mobility (such that the beam direction of the antenna calibration signaling is different from the changing direction of the incoming communication signaling) .

There are numerous variations to the performance of the beamformed antenna calibration signaling in step 340.

For example, the beamformed antenna calibration signaling may comprise only a single antenna calibration signaling beam, or may comprise two or more different and simultaneously used antenna calibration signaling beams.

Alternatively or additionally, the beamformed antenna calibration signaling may be performed for all transceiver branches of the antenna system, or may be performed for a subgroup of transceiver branches of the antenna system, wherein a subgroup of transceiver branches of the antenna system may be seen as a pattern of antenna elements.

In the latter case, the beamformed antenna calibration signaling may be performed for only one subgroup of transceiver branches of the antenna system, or for two or more subgroups of transceiver branches. A subgroup of transceiver branches typically comprises more than one transceiver branch, and less than all transceiver branches of the antenna system. Also typically, any transceiver branch of the antenna system is comprised in at most one subgroup. The subgroup (s) used for each execution of step 340 may differ over time (e.g., such that all necessary antenna calibration measurements can be performed over a sequence of executions of step 340) .

When the beamformed antenna calibration signaling is performed for one or more subgroup (s) of transceiver branches of the antenna system, the beamformed antenna calibration signaling may comprise only a single antenna calibration signaling beam for each subgroup, or may comprise two or more different and simultaneously used antenna calibration signaling beams for one or more of the subgroups.

When the beamformed antenna calibration signaling is performed for one or more subgroup (s) of transceiver branches of the antenna system, the method 300 may further comprise selecting the transceiver branches of the subgroup (s) , as illustrated by optional step 320. The selection may involve selecting one or more subarray (s) (e.g., panel (s) ) of the antenna system) , and/or selecting one or more transceiver branch (es) (e.g., within a selected subarray) , and/or selecting an antenna element orientation, and/or selecting an antenna element polarization (e.g., vertical or horizontal) .

The selection of step 320 may be based on any suitable considerations.

For example, the selection of step 320 may be based on which beam direction (s) and/or which beam shape (s) (e.g., beam width, side lobe pattern, etc. ) are achievable for a considered subgroup of transceiver branches (e.g., matching such information with the requirements of step 340; that the beam direction of the antenna calibration signaling should differ from the indicated direction of the information obtained in step 310) . Thus, the selection of a subgroup of transceiver branches may be based on a beam direction and/or a beam shape associated with the pattern of antenna elements of the antenna system that correspond to the transceiver branches.

Alternatively or additionally, the selection of step 320 may be based on an over-the-air coupling (i.e., mutual coupling) between another transceiver branch (abranch that might receive the OTA antenna calibration signaling) and each of the transceiver branches of the subgroup (branch that transmit the OTA antenna calibration signaling) . For example, a subgroup may be selected for which each potentially receiving branch can receive OTA antenna calibration signaling from at most one of the transceiver branches of the subgroup. Such considerations may be particularly important when beamforming is used for antenna calibration signaling since the beamforming may destroy any signal orthogonality between transceiver branches.

It may be noted that accurate antenna calibration is typically a prerequisite for proper beamforming. Hence, the beamforming of antenna calibration signaling (step 340) is typically not particularly precise during an initial antenna calibration process. However, adequate beamforming should typically be achieved after one or more initial antenna calibration process (es) , so the beamforming of antenna calibration signaling is expected to be more precise thereafter.

Figure 4 schematically illustrates an of example beamformed antenna calibration signaling according to some embodiments; in the form of example antenna calibration signaling for an antenna system 490. For example, the principles illustrated in Figure 4 may be applied by the wireless communication node performing the method 300 of Figure 3.

The example beamformed antenna calibration signaling of Figure 4 is illustrated for four

beams

491, 492, 493, 494 and four

transceiver branches

421, 422, 423, 424, but generalization to any number of beams and transceiver branches is possible.

According to Figure 4, antenna calibration signals 402 are subjected to beamforming weights 411 for a first beam 491, to beamforming weights 412 for a second beam 492, to beamforming weights 413 for a third beam 493, and to beamforming weights 414 for a fourth beam 494. Each

beam

491, 492, 493, 494 may carry a respective one of the antenna calibration signals 402.

The

beamforming weights

411, 412, 413, 414 are based on information 403 indicating direction (s) 498 from the antenna system towards location (s) of interference sensitivity (e.g., information obtained according to step 310 of Figure 3) . Thereby, the beamformed antenna calibration signaling may be performed such that the beam direction of the antenna calibration signaling 491, 492, 493, 494 differs from the indicated direction (s) 498 (e.g., as described for step 340 of Figure 3) .

The

beams

491, 492, 493, 494 are transmitted using

transceiver branches

421, 422, 423, 424, wherein each of the beams needs all four transceiver branches to be transmitted.

It should be noted that, while the antenna calibration signals 402 are typically orthogonal, the signals transmitted by the

different transceiver branches

421, 422, 423, 424 are typically not orthogonal.

In some embodiments there may also be communication (e.g., traffic) signaling simultaneously with the antenna calibration signaling. This is illustrated by traffic signals 410 being transmitted by a traffic signaling beam 499 (which may also have a direction different from the indicated direction 498) .

Figure 4 may be seen as illustrating a model for beamforming AC signals. Typically, the same AC signals 402 (e.g., X= [x ₁, x ₂, x ₃, x ₄] ^T; wherein x ₁, x ₂, x ₃, x ₄ are orthogonal signals in terms of, for example, code division, frequency division, or time division; and wherein each signal x _i corresponds to one AC beam) are injected to all the used

transceiver branches

421, 422, 423, 424, and each AC signal x _i is subject to a respective set of

beamforming weights

411, 412, 413, 414 to form a

corresponding beam

491, 492, 493, 494. Generally, the number of AC signals and/or the number of beams may be equal to, or larger than, the number of transceiver branches used for transmission.

The beamforming weights W for the AC signals may be expressed as:

where each row corresponds to the

beamforming weights

411, 412, 413, 414 of a respective AC signal x _i. For MCAC, it may be sufficient to apply only a single antenna calibration beam for each subgroup of transceiver branches. In such scenarios, the beamforming weight matrix W could consist of one row (i.e., W= [w ₁₁ w ₁₂ w ₁₃ w ₁₄] ^T) , and one AC signal x ₁ may be needed.

The receive signals in the coupling path (which could be a coupling path of a coupling network or an OTA path of a mutual coupling approach) may be expressed as Y= [y ₁, y ₂, y ₃, y ₄] ^T=H·WX+n, where n denotes noise, and H=[h ₁, h ₂, h ₃, h ₄] ^T denotes the channel information of the involved transceiver branches. An aim of antenna calibration is to estimate H and compensate accordingly. For example, an estimation may be expressed as H=Y./ (WX) -n. / (WX) . When W is a full rank matrix, the elements of H can be estimated and differences (e.g., in amplitude and phase) between transceiver branches can be determined.

The beamforming weights W can be defined such that all AC beams 491, 492, 493, 494 have directions that differ from the direction 498 towards a location of interference sensitivity, as described in connection with Figure 3. In some embodiments, the beamforming weights are also defined such that one or more (e.g., all) of the AC beams 491, 492, 493, 494 have directions that differ from the direction of a traffic beam 499. Alternatively or additionally, the beamforming weights may be defined such that one or more of the AC beams 491, 492, 493, 494 have directions that coincide (or substantially coincide) with the direction of a traffic beam 499, wherein those AC beams are made orthogonal to the traffic beam by means of time division and/or frequency division and/or code division.

Generally, the beamforming weights w _ij, where i is a beam index and j is a transceiver branch index, could be designed according to any suitable approach. For example, the beamforming weights could be designed according to

where

denotes the beam angle, p denotes a position of a set of one or more antenna elements of the antenna system that correspond to the transceiver branches used for transmission, ddenotes a distance between neighboring sets of antenna elements that correspond to the transceiver branches used for transmission, and λ denotes the wavelength.

Figure 5 schematically illustrates example beamformed antenna calibration signaling from an antenna system in relation to an indicated direction according to some embodiments. For example, the principles illustrated in Figure 5 may be applied by the wireless communication node performing the method 300 of Figure 3.

Figure 5 uses an angular representation of the signaling, where the distance from origin 510 (location of the antenna system) represents signal strength ranging from -40 dB to 10 dB. An indicated direction 500 from the antenna system towards a location of interference sensitivity is illustrated, together with an emission pattern 502 of antenna calibration signaling. The beam direction of the antenna calibration signaling differs from the indicated direction 500 and a null 503 of the emission pattern 502 of the antenna calibration signaling is placed at the indicated direction 500.

An emission pattern 501 of conventional antenna calibration signaling is also shown for reference, and it may be seen that the interference reduction achievable for the indicated direction is substantial (e.g. more than 20 dB) .

Defining boresight as the direction 520 (90 degrees) , the indicated direction 500 is -20 degrees from boresight (i.e., 20 degrees clockwise from boresight) as illustrated by 504. The beamforming weights of antenna calibration can be determined so that a beam null is placed at the direction 500, while beam peak is directed at +10 degrees from boresight (i.e., 10 degrees anti-clockwise from boresight) as illustrated by 505. Using four antenna ports (compare with subgroup 734 of Figure 7) , the beamforming weights in this example could be expressed as w ₁₁=1,

and

Figure 6 schematically illustrates various types of example locations of interference sensitivity according to some embodiments. The example locations of interference sensitivity are illustrated in relation to a wireless communication node 600. For example, the wireless communication node 600 may be configured to perform the method 300 of Figure 3.

Part (a) of Figure 6 illustrates a situation where the example location of interference sensitivity is a geographical area 610. Then, the

beams

611, 612 of the antenna calibration signaling may be configured to be different from a direction towards the geographical area 610 (compare with step 340 of Figure 3) .

Part (b) of Figure 6 illustrates a situation where the example location of interference sensitivity is a

geographical area

620, 630, which changes over time as illustrated by 640. Then, the

beams

621, 622, 631, 632 of the antenna calibration signaling may be configured such that the

beams

621, 622 of the antenna calibration signaling at a first point in time are different from a direction towards the geographical area 620 applicable for the first point in time, and such that the

beams

631, 632 of the antenna calibration signaling at a second (later) point in time are different from a direction towards the geographical area 630 applicable for the second point in time (compare with

steps

330, 340 of Figure 3) .

Part (c) of Figure 6 illustrates a situation where the example location of interference sensitivity is a geographical trace 650. Then, the

beams

651, 652, 653 of the antenna calibration signaling may be configured to be different from a direction towards the geographical trace 650 (compare with step 340 of Figure 3) . In some embodiments, different points or sections of the geographical trace 650 may be associated with different points in time and the

beams

651, 652, 653 of the antenna calibration signaling may be adaptable accordingly (in similarity with part (b) of Figure 6) .

Figure 7 schematically illustrates an example antenna system 700 and some corresponding examples of beamformed antenna calibration signaling according to some embodiments. For example, the example antenna system 700 may be controlled by the wireless communication node performing the method 300 of Figure 3.

The example antenna system 700 comprises four panels 710. Each panel comprises a number of antenna elements arranged in

sets

720, 721, 722. Each

set

720, 721, 722 of antenna elements is associated with a respective transceiver branch.

As mentioned earlier, beamformed antenna calibration signaling may be performed for a subgroup of transceiver branches of the antenna system, wherein a subgroup of transceiver branches of the antenna system may be seen as a pattern of antenna elements.

In Figure 7, a first subgroup of transceiver branches is exemplified by the four sets 731 associated with antenna calibration signaling on a first beam 741, a second subgroup of transceiver branches is exemplified by the four sets 732 associated with antenna calibration signaling on a second beam 742, a third subgroup of transceiver branches is exemplified by the four sets 733 associated with antenna calibration signaling on a third beam 743, and a fourth subgroup of transceiver branches is exemplified by the four sets 734 associated with antenna calibration signaling on a fourth beam 744.

One subgroup at a time may be used for beamformed antenna calibration signaling, or several subgroups may be used for simultaneous beamformed antenna calibration signaling. Alternatively or additionally, a subgroup may perform beamformed antenna calibration signaling using one beam at a time, or using several beams simultaneously.

As mentioned earlier, subgroup selection may involve one or more different considerations, such as beam shape and/or mutual coupling.

The beam shape (s) that are achievable may differ depending on the pattern of antenna elements corresponding to the subgroup. For example, it may be possible to form a more narrow beam when the pattern of antenna elements spans a larger area and/or has a larger distance d between neighboring sets of antenna elements (e.g., subgroup 731 may be able to form a more narrow beam than subgroup 733) .

Additionally or alternatively, the mutual coupling situation may differ depending on the pattern of antenna elements corresponding to the subgroup. For example, there may be a higher probability that each potentially receiving branch can receive OTA antenna calibration signaling from at most one of the transceiver branches of a subgroup when the pattern of antenna elements spans a larger area (e.g., for subgroup 731 it may be highly probable that the transceiver branches corresponding to the sets shown as horizontally striped 722 only receives OTA antenna calibration signaling from the transceiver branch corresponding to the upper left set 721, while such a characteristic may not be true for subgroup 733) .

As already mentioned, the beamforming weights w _ij could be designed according to any suitable approach.

For example, the beamforming weights could be designed according to

for any of the

subgroups

732 and 734, where

denotes the beam angle, and λ denotes the wavelength. For subgroup 732 p denotes the position in vertical direction of the set of antenna elements that correspond to the transceiver branch under consideration, and d denotes the vertical direction distance between neighboring sets of antenna elements of the subgroup. For subgroup 734 p denotes the position in horizontal direction of the set of antenna elements that correspond to the transceiver branch under consideration, and d denotes the horizontal direction distance between neighboring sets of antenna elements of the subgroup.

For any of the

subgroups

731 and 733, a two-dimensional beam can be generated using a combination of horizontal and vertical weight factors. For example, the beamforming weights could be designed according to

where

denotes the beam angle in horizontal direction, θ denotes the beam angle in vertical direction, p _h denotes the position in horizontal direction of the set of antenna elements that correspond to the transceiver branch under consideration, p _v denotes the position in vertical direction of the set of antenna elements that correspond to the transceiver branch under consideration, d _h denotes the horizontal direction distance between neighboring sets of antenna elements of the subgroup, d _v denotes the vertical distance between neighboring sets of antenna elements of the subset, and λ denotes the wavelength.

Figure 8 schematically illustrates example principles of beamformed antenna calibration signaling in relation to communication reception (e.g., for an uplink) according to some embodiments. For example, the principles illustrated by Figure 8 may be applied by the wireless communication node performing the method 300 of Figure 3.

The example principles illustrated by Figure 8 is for scenarios where communication reception may be performed simultaneously with the antenna calibration signaling (where the indicated direction may be a direction of incoming communication signaling) .

At a first point in time, a first communication reception (RX) 810 is performed. This enables determination of a first indicated direction towards the transmitting wireless communication node (as a location of interference sensitivity) based on spatial characteristics of the incoming communication signaling 811.

At a second point in time, a second communication reception (RX) 820 is performed from the same transmitting wireless communication node. This enables determination of a second indicated direction towards the transmitting wireless communication node (as a location of interference sensitivity) based on spatial characteristics of the incoming communication signaling 821.

When the first and second indicated directions are sufficiently similar (e.g., are equal, or corresponding to a rate of change lower than a change rate threshold) , the indicated direction may be determined to be stationary.

At a third point in time, a third communication reception (RX) 830 is performed from the same transmitting wireless communication node, and –when the indicated direction is stationary –antenna calibration signaling (AC) 840 is performed simultaneously (wherein the beam direction 841 of the antenna calibration signaling is different from the direction of the incoming communication signaling 831.

For example, determining whether the first and second indicated directions are sufficiently similar may comprise estimating a correlation coefficient

where H _u (t) and H _u (t+Δt) are channel estimates based on the first and second communication receptions (e.g. based on sounding reference signals, SRS) at the first and second points in time, t and t+Δt. The indicated direction may be determined to be stationary when ρ is close to 1 (e.g., above a threshold value) , and non-stationary otherwise (e.g., below the threshold value) .

Figure 9 schematically illustrates an example apparatus 900 according to some embodiments. The apparatus 900 is for a wireless communication node (WCN) 910 operating in a wireless communication system and controlling an antenna system 931. The wireless communication node may, for example, be a radio access node (e.g., a base station –BS, a radio unit –RU, etc. ) . Alternatively or additionally, the wireless communication node may comprise, or be connectable/connected to, the antenna system.

For example, the apparatus 900 may be comprisable/comprised in the wireless communication node 910, and/or may be configured to cause performance of (e.g., perform) one or more of the method steps described in connection with Figure 3.

The apparatus comprises a controller (CNTR; e.g., controlling circuitry or a control module) 920.

The controller 920 is configured to cause obtaining of information indicating a direction from the antenna system towards a location of interference sensitivity (compare with step 310 of Figure 3) .

To this end, the controller 920 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) , an interference sensitivity direction obtainer (ISD; e.g., obtaining circuitry or an obtaining module) 923. The obtainer 923 may be configured to obtain the information indicating the direction from the antenna system towards the location of interference sensitivity.

For example, the obtainer 923 may be configured to retrieve the information from a storage device (ST) 940 associated with the wireless communication node, and/or receive (e.g., via a transceiver, TX/RX, 930 of the wireless communication node) the information via signaling from an interference sensitivity monitoring node, and/or receive the information via a user interface (UI) 950, and/or determine the information based on spatial characteristics of communication signaling incoming to the wireless communication node (e.g., via the transceiver 930) .

The controller 920 is also configured to cause performance of beamformed test signaling (e.g., antenna calibration signaling) , wherein a beam direction of the test signaling and the indicated direction are different (compare with step 340 of Figure 3) .

To this end, the controller 920 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) , a test signaler (TS; e.g., test signaling circuitry or a test signal module) 921, comprising a beamformer (BF; e.g., beamforming circuitry or a beamformer module) 922. The test signaler 921 and the beamformer 922 may be configured to perform the beamformed test signaling (e.g., via the transceiver 930) .

As mentioned before, performance of the beamformed test signaling may comprise over-the-air transmission of a test signal from a subgroup of transceiver branches of the antenna system and over-the-air reception of the test signal by one or more other transceiver branches of the antenna system, or injection of a test signal at a first position of transceiver branches of the antenna system and extraction of the test signal at a second position of the transceiver branches of the antenna system. The transceiver branches may, for example, be comprised in the transceiver (TX/RX) 930.

When the test signaling is antenna calibration signaling, the controller 920 may also be configured to cause estimation of transceiver branch channel variations based on the antenna calibration signaling (compare with step 350 of Figure 3) , calculation of calibration coefficients based on the estimated transceiver branch channel variations (compare with step 360 of Figure 3) , and compensation of for the transceiver branch channel variations according to the calculated calibration coefficients (compare with step 370 of Figure 3) .

To this end, the controller 920 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) , an estimator (EST; e.g., estimating circuitry or an estimation module) 926, a calibration coefficient calculator (CCC; e.g., calculating circuitry or a calculation module) 927, and a compensator (COMP; e.g., compensating circuitry or a compensation module) 928. The estimator 926 may be configured to estimate transceiver branch channel variations based on the antenna calibration signaling. The calibration coefficient calculator 927 may be configured to calculate the calibration coefficients based on the estimated transceiver branch channel variations. The compensator 928 may be configured to compensate for the transceiver branch channel variations according to the calculated calibration coefficients.

When the beamformed test signaling is performed for a subgroup of transceiver branches of the antenna system, the controller 920 may also be configured to cause selection of the transceiver branches of the subgroup (compare with step 320 of Figure 3) .

To this end, the controller 920 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) , a selector (SEL; e.g., selecting circuitry or a selection module) 924. The selector 924 may be configured to select the transceiver branches of the subgroup.

When the obtained information indicates time related information (e.g., a timing for the indicated direction, a rate of change for the indicated direction, etc. ) the controller 920 may also be configured to cause adaptation accordingly (compare with step 330 of Figure 3) .

To this end, the controller 920 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) , a timing adaptor (TA; e.g., adapting circuitry or an adaptation module) 925. The timing adaptor 925 may be configured to apply adaptation according to the time related information.

The controller 920 may also be configured to cause performing communication signaling (transmission and/or reception; e.g., via the transceiver 930) separately form the test signaling (compare with step 380 of Figure 3) and/or simultaneously as the test signaling (compare with step 340 of Figure 3) .

The described embodiments and their equivalents may be realized in software or hardware or a combination thereof. The embodiments may be performed by general purpose circuitry. Examples of general purpose circuitry include digital signal processors (DSP) , central processing units (CPU) , co-processor units, field programmable gate arrays (FPGA) and other programmable hardware. Alternatively or additionally, the embodiments may be performed by specialized circuitry, such as application specific integrated circuits (ASIC) . The general purpose circuitry and/or the specialized circuitry may, for example, be associated with or comprised in an apparatus such as a wireless communication node.

Embodiments may appear within an electronic apparatus (such as a wireless communication node) comprising arrangements, circuitry, and/or logic according to any of the embodiments described herein. Alternatively or additionally, an electronic apparatus (such as a wireless communication node) may be configured to perform methods according to any of the embodiments described herein.

According to some embodiments, a computer program product comprises a non-transitory computer readable medium such as, for example, a universal serial bus (USB) memory, a plug-in card, an embedded drive, or a read only memory (ROM) . Figure 10 illustrates an example computer readable medium in the form of a compact disc (CD) ROM 1000. The computer readable medium has stored thereon a computer program comprising program instructions. The computer program is loadable into a data processor (PROC; e.g., a data processing unit) 1020, which may, for example, be comprised in a wireless communication node 1010. When loaded into the data processor, the computer program may be stored in a memory (MEM) 1030 associated with, or comprised in, the data processor. According to some embodiments, the computer program may, when loaded into, and run by, the data processor, cause execution of method steps according to, for example, the method illustrated in Figure 3, and/or any method steps otherwise described herein.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used.

Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims.

For example, the method embodiments described herein discloses example methods through steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims. Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence. Thus, the steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step.

In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means intended as limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. Furthermore, functional blocks described herein as being implemented as two or more units may be merged into fewer (e.g. a single) unit.

Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever suitable. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa.

Hence, it should be understood that the details of the described embodiments are merely examples brought forward for illustrative purposes, and that all variations that fall within the scope of the claims are intended to be embraced therein.

Claims

A method for a wireless communication node operating in a wireless communication system and controlling an antenna system, the method comprising:

obtaining (310) information indicating a direction (500) from the antenna system towards a location of interference sensitivity; and

performing (340) beamformed test signaling, wherein a beam direction of the beamformed test signaling and the indicated direction are different.
The method of claim 1, wherein the beamformed test signaling comprises radio frequency, RF, signaling.
The method of any of claims 1 through 2, wherein the method is for antenna calibration of the antenna system, and wherein the beamformed test signaling comprises beamformed antenna calibration signaling.
The method of claim 3, further comprising:

estimating (350) transceiver branch channel variations based on the beamformed antenna calibration signaling;

calculating (360) calibration coefficients based on the estimated transceiver branch channel variations; and

compensating (370) for the transceiver branch channel variations according to the calculated calibration coefficients.
The method of any of claims 1 through 4, wherein obtaining (310) the information indicating the direction comprises one or more of:

retrieving the information from a storage device associated with the wireless communication node;

receiving the information via signaling from an interference sensitivity monitoring node;

receiving the information as input via a user interface; and

determining the information based on spatial characteristics of incoming communication signaling from another wireless communication node operating in the wireless communication system.
The method of any of claims 1 through 5, wherein the location of interference sensitivity comprises one or more of: a geographical area, an angular extension, a geographical trace, and an angular trace.
The method of any of claims 1 through 6, wherein the information is further indicating a timing for the indicated direction, and/or a rate of change for the indicated direction.
The method of any of claims 1 through 7, wherein the information indicating the direction is dynamically updated.
The method of any of claims 1 through 8, wherein the location of interference sensitivity comprises one or more of:

a vehicular route;

a location of a vehicular control station; and

an area of operation of another wireless communication node.
The method of any of claims 1 through 9, wherein the interference sensitivity relates to in-band interference and/or out-of-band interference in relation to a frequency band of the beamformed test signaling.
The method of any of claims 1 through 10, wherein performing (340) the beamformed test signaling comprises orienting an emission pattern of the beamformed test signaling such that the emission pattern has an emission strength in the indicated direction which is lower than an emission strength threshold.
The method of any of claims 1 through 11, wherein performing (340) the beamformed test signaling comprises placing a null of an emission pattern of the beamformed test signaling in association with the indicated direction.
The method of any of claims 1 through 12, further comprising performing beamformed communication transmission from the wireless communication node, wherein a beam direction of the communication transmission and the indicated direction are different.
The method of any of claims 1 through 13, wherein the beamformed test signaling comprises two or more different and simultaneously used test signaling beams.
The method of any of claims 1 through 14, wherein the beamformed test signaling is performed for a subgroup (731) of transceiver branches of the antenna system.
The method of claim 15, further comprising selecting (320) the transceiver branches of the subgroup.
The method claim 16, wherein selecting (320) the transceiver branches of the subgroup is based on a beam shape associated with a pattern of antenna elements of the antenna system that correspond to the transceiver branches.
The method of any of claims 16 through 17, wherein selecting (320) the transceiver branches of the subgroup is based on an over-the-air coupling between another transceiver branch and each of the transceiver branches of the subgroup.
The method of any of claims 15 through 18, wherein the beamformed test signaling is performed simultaneously for two or more subgroups (731, 732, 733, 734) of transceiver branches, wherein any transceiver branch of the antenna system is comprised in at most one subgroup.
The method of any of claims 15 through 19, wherein the beamformed test signaling is performed for a subgroup comprises two or more different and simultaneously used test signaling beams.
The method of any of claims 1 through 20, wherein the interference sensitivity excludes sensitivity to interference between test signaling of the wireless communication node and communication transmission from the wireless communication node.
The method of any of claims 1 through 21, wherein the indicated direction is a direction of incoming communication signaling (810, 820, 830) from another wireless communication node operating in the wireless communication system, the method further comprising:

determining whether the indicated direction is stationary,

wherein the beamformed test signaling is performed (840) simultaneously with the incoming communication signaling (830) when the indicated direction is stationary.
The method of claim 22, wherein determining whether the indicated direction is stationary comprises determining a rate of change for the indicated direction, and determining the indicated direction to be stationary when the rate of change is lower than a change rate threshold.
The method of any of claims 1 through 23, wherein performing the beamformed test signaling comprises over-the-air transmission of a beamformed test signal from a subgroup of transceiver branches of the antenna system, and over-the-air reception of the beamformed test signal by one or more other transceiver branches of the antenna system.
The method of any of claims 1 through 23, wherein performing the beamformed test signaling comprises, for at least one transceiver branch of the antenna system, injecting a test signal at a first position of the transceiver branch and extracting the test signal at a second position of the transceiver branch, wherein beamforming of the test signal is accomplished via application of a coupling network configured to process the test signal before injection and/or after extraction.
The method of any of claims 1 through 25, wherein the indicated direction comprises a plurality of indicated directions.
The method of any of claims 1 through 26, wherein performing (340) the beamformed test signaling comprises injecting a beamformed test signal for transmission.
A computer program product comprising a non-transitory computer readable medium (1000) , having thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to any of claims 1 through 27 when the computer program is run by the data processing unit.
An apparatus for a wireless communication node operating in a wireless communication system and controlling an antenna system, the apparatus comprising controlling circuitry (920) configured to cause:

obtaining of information indicating a direction from the antenna system towards a location of interference sensitivity; and

performance of beamformed test signaling, wherein a beam direction of the beamformed test signaling and the indicated direction are different.
The apparatus of claim 29, wherein the beamformed test signaling comprises radio frequency, RF, signaling.
The apparatus of any of claims 29 through 30, wherein the apparatus is for antenna calibration of the antenna system, and wherein the beamformed test signaling comprises beamformed antenna calibration signaling.
The apparatus of claim 31, wherein the controlling circuitry is further configured to cause:

estimation of transceiver branch channel variations based on the beamformed antenna calibration signaling;

calculation of calibration coefficients based on the estimated transceiver branch channel variations; and

compensation of for the transceiver branch channel variations according to the calculated calibration coefficients.
The apparatus of any of claims 29 through 32, wherein the controlling circuitry is configured to cause the obtaining of the information indicating the direction by causing one or more of:

retrieval of the information from a storage device associated with the wireless communication node;

reception of the information via signaling from an interference sensitivity monitoring node;

reception of the information as input via a user interface; and

determination of the information based on spatial characteristics of incoming communication signaling from another wireless communication node operating in the wireless communication system.
The apparatus of any of claims 29 through 33, wherein the location of interference sensitivity comprises one or more of: a geographical area, an angular extension, a geographical trace, and an angular trace.
The apparatus of any of claims 29 through 34, wherein the information is further indicating a timing for the indicated direction, and/or a rate of change for the indicated direction.
The apparatus of any of claims 29 through 35, wherein the information indicating the direction is dynamically updated.
The apparatus of any of claims 29 through 36, wherein the location of interference sensitivity comprises one or more of:

a vehicular route;

a location of a vehicular control station; and

an area of operation of another wireless communication node.
The apparatus of any of claims 29 through 37, wherein the interference sensitivity relates to in-band interference and/or out-of-band interference in relation to a frequency band of the beamformed test signaling.
The apparatus of any of claims 29 through 38, wherein the controlling circuitry is configured to cause the performance of beamformed test signaling by causing orientation of an emission pattern of the beamformed test signaling such that the emission pattern has an emission strength in the indicated direction which is lower than an emission strength threshold.
The apparatus of any of claims 29 through 39, wherein the controlling circuitry is configured to cause the performance of beamformed test signaling by causing placement of a null of an emission pattern of the beamformed test signaling in association with the indicated direction.
The apparatus of any of claims 29 through 40, wherein the controlling circuitry is further configured to cause performance of beamformed communication transmission from the wireless communication node, wherein a beam direction of the communication transmission and the indicated direction are different.
The apparatus of any of claims 29 through 41, wherein the beamformed test signaling comprises two or more different and simultaneously used test signaling beams.
The apparatus of any of claims 29 through 42, wherein the beamformed test signaling is performed for a subgroup of transceiver branches of the antenna system.
The apparatus of claim 43, wherein the controlling circuitry is further configured to cause selection of the transceiver branches of the subgroup.
The apparatus claim 44, wherein the selection of the transceiver branches of the subgroup is based on a beam shape associated with a pattern of antenna elements of the antenna system that correspond to the transceiver branches.
The apparatus of any of claims 44 through 45, wherein the selection of the transceiver branches of the subgroup is based on an over-the-air coupling between another transceiver branch and each of the transceiver branches of the subgroup.
The apparatus of any of claims 43 through 46, wherein the beamformed test signaling is performed simultaneously for two or more subgroups of transceiver branches, wherein any transceiver branch of the antenna system is comprised in at most one subgroup.
The apparatus of any of claims 43 through 47, wherein the beamformed test signaling is performed for a subgroup comprises two or more different and simultaneously used test signaling beams.
The apparatus of any of claims 29 through 48, wherein the interference sensitivity excludes sensitivity to interference between test signaling of the wireless communication node and communication transmission from the wireless communication node.
The apparatus of any of claims 29 through 49, wherein the indicated direction is a direction of incoming communication signaling from another wireless communication node operating in the wireless communication system, the controlling circuitry being further configured to cause:

determination of whether the indicated direction is stationary; ,

wherein the performance of beamformed test signaling is caused to be simultaneous with the incoming communication signaling responsive to the indicated direction being determined as stationary.
The apparatus of claim 50, wherein the controlling circuitry is configured to cause determination of whether the indicated direction is stationary by causing determination of a rate of change for the indicated direction, and determination of the indicated direction as stationary responsive to the rate of change being lower than a change rate threshold.
The apparatus of any of claims 29 through 51, wherein the performance of beamformed test signaling comprises over-the-air transmission of a beamformed test signal from a subgroup of transceiver branches of the antenna system, and over-the-air reception of the beamformed test signal by one or more other transceiver branches of the antenna system.
The apparatus of any of claims 29 through 51, wherein the performance of beamformed test signaling comprises, for at least one transceiver branch of the antenna system, injection of a test signal at a first position of the transceiver branch and extraction of the test signal at a second position of the transceiver branch, wherein beamforming is accomplished via application of a coupling network configured to process the test signal before injection and/or after extraction.
The apparatus of any of claims 29 through 53, wherein the indicated direction comprises a plurality of indicated directions.
The apparatus of any of claims 29 through 54, wherein the performance of the beamformed test signaling comprises injection of a beamformed test signal for transmission.
A wireless communication node comprising the apparatus of any of claims 29 through 55.
The wireless communication node of claim 56, further comprising the antenna system.