Transmission of data signals from subarrays of an antenna array

Abstract

There is provided techniques for transmission of a data signal from subarrays of an antenna array of a transceiver device. Each of the subarrays comprises elements. A method is performed by the transceiver device. The method comprises transmitting the data signal in a traffic beam from the antenna array with an absolute phase difference between each pair of neighboring elements. The absolute phase difference depends on how many elements there are per subarray and on a phase difference selected based on a report received from an intended receiver of the data signal.

Description

[0001]TRANSMISSION OF DATA SIGNALS FROM SUBARRAYS OF AN ANTENNA ARRAY TECHNICAL FIELD Embodiments presented herein relate to a method, a transceiver device, a computer program, and a computer program product for transmission of a data signal from subarrays of an antenna array of the transceiver device. BACKGROUND In wireless communication systems, the use of frequency bands at comparatively high frequencies implies a link budget challenge due to increased pathloss. If the antenna area of antenna arrays used forfrequencies in the range of 3.5 GHz is to be maintained at the double frequency whilst at the same timealso persevering the link budget, this implies that the amount of elements (and radio branches) in theantenna array needs to be increased about four times.A common technique for determining a beam direction with good signal strength between a network node(with multiple radio branches) and a user equipment (UE) is referred to as “Closed Loop Feedback”. Thebasics of such a scheme is that the network node would transmit multiple reference signals mapped todifferent subarrays of the antenna array at the network node. When the UE has detected all individualreference signals, the UE can combine them with an agreed set of weights (referred to as a codebook insome telecommunication systems) and determine the best set of weights. The result is then communicatedto the network node. The network node can use the recommendation from the UE or use other weights ifthe network node has access to any extra information to support such a decision. To get the maximum beam pointing resolution (and beamforming gain), one reference signal per subarray is required. However, the transmission of reference signals will reduce the overall system efficiency due to its overhead. It is therefore of interest to keep the number of reference signal to a minimum. Thecurrent trend with larger arrays and a desire to minimize the number of reference signals pose a problemin this respect. Another problem is that the number of reference signals might be limited, and thus not chosen freely.The same reasoning applies also in the case where the UE (if it its equipped with an antenna arraycomprising multiple radio branches, or subarrays) transmitting reference signals towards the networknode.As a non-limiting illustrative example, assume an antenna arrays with 16 columns and 8 reference signals.In this case there will be 2 columns for every reference signal. In, for example, the New Radio (NR)telecommunication system, the reference signals are referred to as channel state information referencesignals (CSI-RSs). The basic solution for an antenna array with 16 columns and an 8 column CSI-RS codebook is to map each CSI-RS signal to two columns and thereby create 8 virtual subarrays of 2columns each, as in Fig. 1.The resulting beamwidth of the virtual subarray will be determined by the width of the virtual subarray. Acolumn separation of 0.5λ (where λ is the wavelength) yields a 1λ wide virtual subarray. Fig. 2 shows theresulting CSI-RS horizontal far-field pattern, which is labelled as CSI-RS DS1, where DS is short for digital sector. In this respect, digital sector is a term used to indicate that the CSI-RS resource has an intended angular coverage. Fig.2 also includes the resulting traffics beams used for the downlink datasignal. They are labelled DS1-tr together with the nominal scan direction of the beam. The antenna arrayfor these results has 4 rows and 16 columns and each of the subarrays has 6 elements in elevation. As canbe seen in Fig. 2, the beamwidth of such virtual subarray is a bit narrow for a typical 3-sector cell. Thedirectivity at ф = + / −60 degrees is 15-20 dB lower than the peak directivity at ф = 0 degrees. Thedifference for typical 3-sector cell deployments is in the 5-10 dB range. For illustrative purposes, butwithout loss of generality, nominal scan directions are used in this example rather than the exact weightsof any specific codebook. This difference is not important to the overall conclusions, it is just asimplification done to yield easier comparisons.One way to mitigate this coverage issue is to configure multiple CSI-RS sets, i.e., to sweep the CSI-RSsignals in multiple horizontal directions. In this respect, the use of virtual subarrays with typicallyseparation of 1λ (i.e., 2 ∙ 0.5λ) will create grating lobes when the desired traffic beam is steered too farfrom the direction of the virtual subarray beam. Fig. 3 shows the traffic beams for the DS1 CSI-RSmapping and the traffic beams for the DS2 CSI-RS mapping. In this figure it is possible to see how grating lobes produced from one DS enter the angular range of the other DS, see box 310. If simultaneous transmissions are done to one UE in DS1 and a second UE in DS2 (MU-MIMO) poor signal-to-interference ratio (SIR) can occur from the grating lobes. The poor SIR can also be referred to as poorBeam Isolation. One way to mitigate this poor beam isolation resulting from grating lobes is to introduce extra CSI-RS directions and put restrictions on the allowed beams for the UE to report. However, this will introduce overhead. Hence, there is still a need for techniques that can improve the beam isolation. SUMMARY An object of embodiments herein is to improve the beam isolation whilst avoiding, or at least mitigating or reducing the above issues. A particular object is to remove grating lobes of the data signals in an effort to improve the beam isolation.According to a first aspect there is presented a method for transmission of a data signal from subarrays ofan antenna array of a transceiver device. Each of the subarrays comprises elements. The method isperformed by the transceiver device. The method comprises transmitting the data signal in a traffic beamfrom the antenna array with an absolute phase difference ∆^∗between each pair of neighboring elements.The absolute phase difference ∆^∗ depends on how many elements there are per subarray and on a phasedifference ∆^^^^^^selected based on a report received from an intended receiver of the data signal. According to a second aspect there is presented a transceiver device for transmission of a data signal fromsubarrays of an antenna array of the transceiver device. Each of the subarrays comprises elements. Thetransceiver device comprises processing circuitry, and wherein the processing circuitry is configured tocause the transceiver device to transmit the data signal in a traffic beam from the antenna array with anabsolute phase difference ∆^∗ between each pair of neighboring elements. The absolute phase difference∆^∗depends on how many elements there are per subarray and on a phase difference ∆^^^^^^selectedbased on a report received from an intended receiver of the data signal.According to a third aspect there is presented a computer program for transmission of a data signal from subarrays of an antenna array of a transceiver device, where each of the subarrays comprises elements.The computer program comprises computer code which, when run on processing circuitry of thetransceiver device, causes the transceiver device to perform actions. One action comprises the transceiver device to transmit the data signal in a traffic beam from the antenna array with an absolute phase difference ∆^∗between each pair of neighboring elements. The absolute phase difference ∆^∗depends on how many elements there are per subarray and on a phase difference ∆^^^^^^selected based on a report received from an intended receiver of the data signal. According to a fourth aspect there is presented a computer program product comprising a computer program according to the third aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.Advantageously, these aspects enable for data transmissions with reduced presence of grating lobes.Advantageously, these aspects yield improved beam isolation, multi-user multiple-input multiple-output(MU-MIMO) performance and intercell interference.Advantageously, these aspects are applicable in systems where there are more available subarrays thanavailable reference signals, e.g., antenna systems with 16 columns (or rows) and a codebook with 8columns (or rows).Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. BRIEF DESCRIPTION OF THE DRAWINGS The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 schematically illustrates an antenna array according to an example;Fig. 2 shows a CSI-RS horizontal far-field pattern according to an example;Fig.3 shows traffic beams for a first digital sector CSI-RS mapping according to an example;Fig. 4 is a schematic diagram illustrating a communications system according to embodiments;Fig.5 schematically illustrates an antenna array according to an example; Fig.6 schematically illustrates an antenna array according to an embodiment;Fig. 7 is a flowchart of methods according to embodiments;Fig.8 shows traffic beams with phases applied according to an embodiment; Fig.9 shows the envelope patterns using reference signals in three digital sectors and the corresponding envelope of the data signal for the first digital sector according to an embodiment; Fig.10 shows the envelopes of the reference signals and the data signals for a configuration with a singledigital sector in the elevation domain according to an embodiment;Fig. 11 is a schematic diagram showing structural units of a transceiver device according to anembodiment;Fig. 12 is a schematic diagram showing functional modules of a transceiver device according to anembodiment; andFig. 13 shows one example of a computer program product comprising computer readable storagemedium according to an embodiment. DETAILED DESCRIPTION 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. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example 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. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.Fig. 4 is a schematic diagram illustrating a communications system 100 where embodiments presentedherein can be applied. The communications system 100 comprises two transceiver devices 100a, 100b; anetwork node 100a and a user equipment 100b configured to communicate with each other over awireless (radio) channel. The network node 100a could be a (radio) access network node, (radio) basestation, base transceiver station; node B, evolved node B, gNB, access point, integrated access andbackhaul node, transmission and reception point, or the like. The user equipment could be a portable wireless device, mobile station, mobile phone, handset, wireless local loop phone, smartphone, laptop computer, tablet computer, network equipped sensor device, network equipped vehicle, Internet of Things device, gaming device, or the like. As noted above there is still a need for techniques that can improve the beam isolation. As will be further disclosed below, according to the herein disclosed embodiments, the grating lobes areremoved and the beam isolation is improved. In further detail, denoted by ∆^^^^ the phase differencebetween two columns (or rows) in a subarray. For transmission of reference signals in reference beams,the value of ∆^^^^ is given by ∆^^^^,^^^ which can be calculated according to:∆^^^^,^^^ = ^ ∙ ^^ ∙ sin(^^^^)where ^^^^ is the beampointing direction of the reference signal, ^^ is the column (or row) separation ofthe antenna, and ^ equals the wave number; ^ = 2^ / ^ with ^ being the wavelength, see the antenna array500 in Fig. 5 composed of subarrays 510a to 510N having elements 520-1a to 520-MN. On the otherhand, for transmission of data signals in data beams, the value of ∆^^^^ is determined from ∆^^^^^^where the value of ∆^^^^^^ is determined by the selected codebook, see the antenna array 600 in Fig. 6composed of subarrays 610a to 610N and elements 620-1a to 620-MN 8collectively herein referred to as elements 620-xy).Grating lobes will be produced when the difference between ∆^^^^^^ and 2 ∙ ∆^^^^,^^^ becomes largei.e., when the phase gradient produced for the traffic beam is different from the phase gradient produced for the reference beam. According to the herein disclosed embodiments, the value of ∆^^^^for the data signals is replaced to avoid such grating lobes. That is, for the data signals, ∆^^^^is no longer equal to ∆^^^^,^^^as used during the transmission of the reference signals. How the value of ∆^^^^for the data signals can bedetermined to avoid grating lobes will be disclosed below.The embodiments disclosed herein in particular relate to techniques for transmission of a data signal fromsubarrays 610a:610M of an antenna array 600. In order to obtain such techniques there is provided atransceiver device 100a, 100b, a method performed by the transceiver device 100a, 100b, a computer program product comprising code, for example in the form of a computer program, that when run on atransceiver device 100a, 100b, causes the transceiver device 100a, 100b to perform the method.Fig. 7 is a flowchart illustrating embodiments of methods for transmission of a data signal from subarrays610a:610M of an antenna array 600 of the transceiver device 100a, 100b. Each of the subarrays610a:610M comprises elements 620-xy. The methods are performed by the transceiver device 100a,100b. The methods are advantageously provided as computer programs.S110: The transceiver device 100a, 100b transmits the data signal in a traffic beam from the antenna array600 with an absolute phase difference ∆^∗ between each pair of neighboring elements 620-xy. That is, theabsolute phase difference ∆^∗ is applied to the signal as transmitted from the antenna array 600. Theabsolute phase difference ∆^∗ depends on how many elements 620-xy there are per subarray 610a:610Mand on a phase difference ∆^^^^^^selected based on a report received from an intended receiver of the data signal.Advantageously, this method enables data transmissions with reduced presence of grating lobes.Advantageously, this method yields improved beam isolation, multi-user multiple-input multiple-output (MU-MIMO) performance and intercell interference. Advantageously, this method is applicable in systems where there are more available subarrays610a:610M than available reference signals, e.g., antenna systems with 16 columns (or rows) and acodebook with 8 columns (or rows).In Fig. 8 is shown the traffic beams when the phase has been applied according to step S110. Theimprovement with respect to Fig.3 can be seen when comparing the angular range marked by the box810; Fig. 3 contains several grating lobes that have been removed in Fig. 8 (i.e. which are present in box310 but not in box 810). In some embodiments, the transceiver device 100a, 100b is a network node 100a or a user equipment 100b. In case the transceiver device is a network node 100a, the intended receiver could be a user equipment, or another network node. Likewise, in case the transceiver device is a user equipment 100b, the intended receiver could be a network node, or another user equipment.Embodiments relating to further details of transmission of a data signal from subarrays 610a:610M of anantenna array 600 as performed by the transceiver device 100a, 100b will now be disclosed withcontinued reference to Fig.7.There may be different ways for the absolute phase difference ∆^∗ to depend on how many elements 620-xy there are per subarray 610a:610M and on the phase difference ∆^^^^^^ . In general terms, for asubarray 610a:610M with 2 elements 620-xy, ∆^∗ can be set to half the value of ∆^^^^^^. that is, ∆^∗ =∆^^^^^^ / 2. Thus, generally, the absolute phase difference ∆^∗ can be set to ∆^^^^^^ / ^ for a subarray610a:610M with ^ elements 620-xy and uniform element separation. This selection of the absolute phasedifference ∆^∗avoids grating lobes to be produced. Therefore, in some embodiments, the absolute phase difference ∆^∗is where ^ is the number of elements 620-xy per subarray 610a:610M, and where ^ is an error tolerancevalue. Typically, ^ ≪ 1, for example ^ < 0.1 or even ^ < 0.01.In some aspects, having the absolute phase difference ∆^∗ at the output of the antenna array 600 isachieved by applying a two-step procedure. In a first step of the two-step procedure, first phasedifferences are applied to the subarrays 610a:610M (with one first phase difference per subarray610a:610M). In a second step of the two-step procedure, second phase differences are applied to theelements 620-xy within each subarray 610a:610M (with one second phase difference per element). Inparticular, in some embodiments, the absolute phase difference ∆^∗is achieved by applying a first set ofrelative phases ^^^∗ to the subarrays 610a:610M and applying a second set of relative phases ^^^∗ to theelements 620-xy within each of the subarrays 610a:610M. Here, one first relative phase value ^^^∗ isapplied to each subarray 610a:610M, and one second relative phase value ^^^∗is applied to each of the elements 620-xy.In some embodiments, the first set of relative phases ^^^∗ as applied to the subarrays 610a:610M isdefined as ^^^∗ = {0, ∆^^^^^^ , … , (^ − 1) ∙ ∆^^^^^^},where ^ is number of subarrays 610a:610M, and where one respective value of ^^^∗ is applied per eachof the subarrays 610a:610M. In other words, for subarray 610a:610M 1 ≤ ^ ≤ ^, the relative phase^^^∗ = (^ − 1) ∙ ∆^^^^^^ is applied.Further, in some embodiments, the second set of relative phases ^^^∗ as applied to the elements 620-xywithin each of the subarrays 610a:610M is defined as where ^ is number of elements 620-xy per subarray 610a:610M, and where one respective value of is applied per each of the elements 620-xy in each of the subarrays 610a:610M. In other words, forelement 1 ≤ ^ ≤ ^, the relative phase ^^^∗ = (^ − 1) ∙ ∆^^^^^^ / ^ is applied.As disclosed above, the phase difference ∆^^^^^^is selected based on a report received from an intended receiver of the data signal. There can be different such reports. In some cases, for example when thetransceiver device is a network node 100a and the intended receiver is a user equipment 100b, the reportcan be a Channel State Information (CSI) report. More particularly, the phase difference ∆^^^^^^might be given by the Precoding Matrix Indicator (PMI) as provided in the CSI report. That is, in some embodiments, the report is a CSI report comprising a PMI and the phase difference ∆^^^^^^is based onthe PMI. In this respect, in some examples, he phase difference is derivable from the PMI. In this way, bymeans of the PMI, the user equipment 100b can indicate a certain precoder (which implies a certain phase difference ∆^^^^^^). Therefore, since the PMI can be mapped to a certain phase difference ∆^^^^^^, the network node 100a can thereby select the absolute phase difference ∆^∗based on the received PMI.Further aspects of the antenna array 600, and how properties of the antenna array 600 might impact theselection of the absolute phase difference ∆^∗, will be disclosed next. In some examples, the transceiver device 100a, 100b is configured to transmit reference signals (as disclosed above) and each reference signal is mapped to at least two columns and / or at least two rows ofthe antenna array 600. That is, in some embodiments, the antenna array 600 is composed of ^ columnsand ^ rows, and each subarray 610a:610M is mapped to one of the ^ columns and / or one of the ^ rows.Each subarray 610a:610M might correspond to at least one column or at least one row of the antennaarray 600. In some examples, the antenna array 600 comprises exactly ^ = 16 columns, and there areexactly 8 available reference signals. Further aspects of the report received from the intended receiver of the data signal will be disclosed next. The report received from the intended receiver of the data signal might be received in response to the transceiver device 100a, 100b having transmitted one or more reference signals to this intended receiver.In this respect, there might be more available subarrays 610a:610M than available reference signals. Insome embodiments, the transceiver device 100a, 100b is configured to perform (optional) steps S102 toS106 for transmitting the reference signals and for receiving the report before transmitting the data signalin step S110.S102: The transceiver device 100a, 100b maps the reference signals to the subarrays 610a:610M. Eachreference signal is mapped to its own set of at least two subarrays 610a:610M.S104: The transceiver device 100a, 100b transmits the reference signals according to the mapping andtowards the intended receiver.S106: The transceiver device 100a, 100b receives the report from the intended receiver.The risk that the intended receiver in the report indicates a direction corresponding to a grating lobe (i.e.,a grating lobe direction) can be reduced by having a proper isolation between the grating lobes of onedigital sector and the main beams of other digital sectors. In further detail, if the beam isolation seen by the intended receiver during codebook evaluation, or beamselection, for which the reference signals as transmitted in step S104 might be used, is insufficient for twodigital sectors, one option is to use three digital sectors e.g., with a respective direction of ^^^^ =[−40040]°. There might then still be grating lobes, but the beam isolation (between digital sectors) willimprove compared to having only two digital sectors. Hence, the risks for the intended receiver to report adirection in the grating lobe direction can be reduced significantly.A more detailed analysis of the risk of improper beam selection for the case with three digital sectors willbe presented next. Fig. 9 shows the traffic envelope patterns of multiple reference signals in three digitalsectors (DS1, DS2, DS3) and the corresponding envelope of the data signal for the first digital sector(DS1). It can be observed that the data signal is reduced in the 5-45 degree direction due to the removal ofgrating lobes. The issue of improper beam selection can be minimized if the reference signals from DS2and DS3 are sufficiently stronger than the grating lobes of DS1. That is, there would be no reason for theintended receiver to select the relatively weak grating lobes from DS1 when the intended receiver canselect the stronger signal from DS2 or DS3. There is a 5-7 dB margin between the grating lobes of thereference signals for DS1 and the main beams of the reference signals in DS2 and DS3. This can beconsidered as a safe margin with very small risk of improper beam selection. In some aspects, the peak directivity in the main beam direction differs between the reference signals andthe data signal. In this respect, the directivity of the data signal might increase slightly due to the removalof the grating lobe. However, since the difference is relatively small (about 0.5-2 dB) and can be madeknown to the transceiver device 100a, 100b, the transceiver device 100a, 100b can therefore compensatefor this. In particular, in some embodiments, a change in peak directivity in a main beam direction as caused by transmitting the data signal with the absolute phase difference ∆^∗between each pair ofneighboring elements 620-xy is adjusted to be dependent on the absolute phase difference ∆^∗.Fig. 10 shows the envelopes of the reference signals and the data signals for a configuration with a singledigital sector in the elevation domain. An antenna array 600 consisting of 8 × 8 fixed subarrays610a:610M where each fixed subarray 610a:610M consists of 3 × 1 elements 620-xy. It can be observedthat the grating lobes from reference signal beams can create interference to the horizon (θ≈90°). As seenin the envelope for the data signals, this interference is removed by the herein disclosed embodiments.The risk of poor coverage when the intended receiver is in directions θ≈120° and θ≈170° can be regardedas negligible due to angular spread. Further, it can be secured that the intended receiver is in a properdirection, e.g. in the main beam direction of the reference signal. Therefore, in some embodiments, the transceiver device 100a, 100b is configured to perform (optional) step S108 before transmitting the data signal in step S110.S108: The transceiver device 100a, 100b confirms that the intended receiver is not negatively impactedby loss of energy as caused by using the absolute phase difference ∆^∗between each pair of neighboringelements 620-xy during the transmission of the data signal.In this way the transceiver device 100a, 100b can confirm that the intended receiver is located in the main lobe direction of one of the traffic beams before the transceiver device 100a, 100b transmits the data signal with the phase difference set as in step S110.The herein disclosed embodiments for using the absolute phase difference ∆^∗ during transmission ofdata signals are applicable for both horizontal-domain beamforming and vertical-domain beamforming.For vertical-domain beamforming, in case the transceiver device is a network node 100a, the area closestto the network node 100a might not be covered by main beams but only by sidelobes. This might requiresome additional compensation when selecting the absolute phase difference ∆^∗.Fig. 11 schematically illustrates, in terms of a number of structural units, the components of a transceiverdevice 100a, 100b according to an embodiment. Processing circuitry 110 is provided using anycombination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computerprogram product 1310 (as in Fig. 13), e.g. in the form of a storage medium 130. The processing circuitry110 may further be provided as at least one application specific integrated circuit (ASIC), or fieldprogrammable gate array (FPGA).Particularly, the processing circuitry 110 is configured to cause the transceiver device 100a, 100b toperform a set of operations, or steps, as disclosed above. For example, the storage medium 130 may storethe set of operations, and the processing circuitry 110 may be configured to retrieve the set of operationsfrom the storage medium 130 to cause the transceiver device 100a, 100b to perform the set of operations.The set of operations may be provided as a set of executable instructions.Thus, the processing circuitry 110 is thereby arranged to execute methods as herein disclosed. The storagemedium 130 may also comprise persistent storage, which, for example, can be any single one orcombination of magnetic memory, optical memory, solid state memory or even remotely mountedmemory. The transceiver device 100a, 100b may further comprise a communications (comm.) interface120 at least configured for communications with another transceiver device for transmission of the datasignal in accordance with the herein disclosed embodiments. As such the communications interface 120 may comprise one or more transmitters and receivers, comprising analogue and digital components, andin particular the antenna array 600. The processing circuitry 110 controls the general operation of thetransceiver device 100a, 100b e.g. by sending data and control signals to the communications interface120 and the storage medium 130, by receiving data and reports from the communications interface 120,and by retrieving data and instructions from the storage medium 130. Other components, as well as therelated functionality, of the transceiver device 100a, 100b are omitted in order not to obscure the conceptspresented herein.Fig. 12 schematically illustrates, in terms of a number of functional modules, the components of atransceiver device 100a, 100b according to an embodiment. The transceiver device 100a, 100b of Fig.12comprises a transmit module 110e configured to perform step S110. The transceiver device 100a, 100b ofFig. 12 may further comprise a number of optional functional modules, such as any of a map module110a configured to perform step S102, a transmit module 110b configured to perform step S104, a receivemodule 110c configured to perform step S106, and a confirm module 110d configured to perform stepS108.In general terms, each functional module 110a:110e may in one embodiment be implemented only inhardware and in another embodiment with the help of software, i.e., the latter embodiment havingcomputer program instructions stored on the storage medium 130 which when run on the processingcircuitry makes the transceiver device 100a, 100b perform the corresponding steps mentioned above inconjunction with Fig 12. It should also be mentioned that even though the modules correspond to parts of a computer program, they do not need to be separate modules therein, but the way in which they are implemented in software is dependent on the programming language used. Preferably, one or more or allfunctional modules 110a:110e may be implemented by the processing circuitry 110, possibly incooperation with the communications interface 120 and / or the storage medium 130. The processingcircuitry 110 may thus be configured to from the storage medium 130 fetch instructions as provided by afunctional module 110a:110e and to execute these instructions, thereby performing any steps as disclosedherein.The transceiver device 100a, 100b may be provided as a standalone device or as a part of at least onefurther device. For example, the transceiver device 100a, 100b may be provided in a network node of aradio access network. Alternatively, functionality of the transceiver device 100a, 100b may be distributedbetween at least two devices, or nodes. These at least two nodes, or devices, may either be part of thesame network part (such as a radio access network or a core network) or may be spread between at leasttwo such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. Thus, a first portion of the instructions performed by the transceiver device100a, 100b may be executed in a first device, and a second portion of the of the instructions performed bythe transceiver device 100a, 100b may be executed in a second device; the herein disclosed embodimentsare not limited to any particular number of devices on which the instructions performed by the transceiverdevice 100a, 100b may be executed. Hence, the methods according to the herein disclosed embodimentsare suitable to be performed by a transceiver device 100a, 100b residing in a cloud computationalenvironment. Therefore, although a single processing circuitry 110 is illustrated in Fig. 11 the processingcircuitry 110 may be distributed among a plurality of devices, or nodes. The same applies to thefunctional modules 110a:110e of Fig. 12 and the computer program 1320 of Fig. 13.Some (radio) access network architectures define network nodes (or gNBs) comprising multiple component parts or nodes: a central unit (CU), one or more distributed units (DUs), and one or more radiounits (RUs). The protocol layer stack of the network node is divided between the CU, the DUs and theRUs, with one or more lower layers of the stack implemented in the RUs, and one or more higher layers of the stack implemented in the CU and / or DUs. The CU is coupled to the DUs via a fronthaul higherlayer split (HLS) network; the CU / DUs are connected to the RUs via a fronthaul lower-layer split (LLS)network. The DU may be combined with the CU in some embodiments, where a combined DU / CU may be referred to as a CU or simply a baseband unit. A communication link for communication of user data messages or packets between the RU and the baseband unit, CU, or DU is referred to as a fronthaul network or interface. Messages or packets may be transmitted from the network node in the downlink(i.e., from the CU to the RU) or received by the network node in the uplink (i.e., from the RU to the CU).Fig. 13 shows one example of a computer program product 1310 comprising computer readable storagemedium 1330. On this computer readable storage medium 1330, a computer program 1320 can be stored,which computer program 1320 can cause the processing circuitry 110 and thereto operatively coupledentities and devices, such as the communications interface 120 and the storage medium 130, to executemethods according to embodiments described herein. The computer program 1320 and / or computerprogram product 1310 may thus provide means for performing any steps as herein disclosed.In the example of Fig. 13, the computer program product 1310 is illustrated as an optical disc, such as aCD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product1310 could also be embodied as a memory, such as a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasableprogrammable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, suchas a compact Flash memory. Thus, while the computer program 1320 is here schematically shown as atrack on the depicted optical disk, the computer program 1320 can be stored in any way which is suitablefor the computer program product 1310.The inventive concept has mainly been described above with reference to a few embodiments. However,as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed aboveare equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A transceiver device (100a, 100b) for transmission of a data signal from subarrays (610a:610M) ofan antenna array (600) of the transceiver device (100a, 100b), wherein each of the subarrays (610a:610M)comprises elements (620-1a:620-MN), wherein the transceiver device (100a, 100b) comprises processing circuitry (110), and wherein the processing circuitry (110) is configured to cause the transceiver device (100a, 100b) to: transmit the data signal in a traffic beam from the antenna array (600) with an absolute phasedifference ∆^∗between each pair of neighboring elements (620-1a:620-MN), wherein the absolute phasedifference ∆^∗ depends on how many elements (620-1a:620-MN) there are per subarray (610a:610M) andon a phase difference ∆^^^^^^ selected based on a report received from an intended receiver of the datasignal.

2. The transceiver device (100a, 100b) according to claim 1, wherein the absolute phase difference∆^∗iswhere ^ is number of elements (620-1a:620-MN) per subarray (610a:610M), and where ^ is an errortolerance value.

3. The transceiver device (100a, 100b) according to claim 1 or 2, wherein the absolute phasedifference ∆^∗ is achieved by applying a first set of relative phases ^^^∗ to the subarrays (610a:610M)and applying a second set of relative phases ^^^∗ to the elements (620-1a:620-MN) within each of thesubarrays (610a:610M).

4. The transceiver device (100a, 100b) according to claim 3, wherein the first set of relative phases^^^∗ as applied to the subarrays (610a:610M) is defined as^^^∗ = {0, ∆^^^^^^ , … , (^ − 1) ∙ ∆^^^^^^},where ^ is number of subarrays (610a:610M), and where one respective value of ^^^∗ is applied per eachof the subarrays (610a:610M).

5. The transceiver device (100a, 100b) according to claim 3 or 4, wherein the second set of relativephases ^^^∗ as applied to the elements (620-1a:620-MN) within each of the subarrays (610a:610M) isdefined aswhere ^ is number of elements (620-1a:620-MN) per subarray (610a:610M), and where one respectivevalue of ^^^∗ is applied per each of the elements (620-1a:620-MN) in each of the subarrays (610a:610M).

6. The transceiver device (100a, 100b) according to any preceding claim, wherein the report is aChannel State Information, CSI, report comprising a Precoding Matrix Indicator, PMI, and wherein thephase difference ∆^^^^^^ is based on the PMI.

7. The transceiver device (100a, 100b) according to any preceding claim, wherein the antenna array(600) is composed of ^ columns and ^ rows, and wherein each subarray (610a:610M) is mapped to atleast one of the ^ columns and / or at least one of the ^ rows.

8. The transceiver device (100a, 100b) according any preceding claim, wherein there are moreavailable subarrays (610a:610M) than available reference signals, and wherein the processing circuitry(110) further is configured to cause the transceiver device (100a, 100b) to map the reference signals to the subarrays (610a:610M), wherein each reference signal is mapped to its own set of at least two subarrays (610a:610M); transmit the reference signals according to the mapping and towards the intended receiver; andreceive the report from the intended receiver.

9. The transceiver device (100a, 100b) according to claim 8, wherein the antenna array (600)comprises exactly ^ = 16 columns, and wherein there are exactly 8 available reference signals.

10. The transceiver device (100a, 100b) according to any preceding claim, wherein a change in peakdirectivity in a main beam direction as caused by transmitting the data signal with the absolute phasedifference ∆^∗ between each pair of neighboring elements (620-1a:620-MN) is adjusted to be dependenton the absolute phase difference ∆^∗.

11. The transceiver device (100a, 100b) according to any preceding claim, wherein the processingcircuitry (110) further is configured to cause the transceiver device (100a, 100b) to: confirm that the intended receiver is not negatively impacted by loss of energy as caused by usingthe absolute phase difference ∆^∗ between each pair of neighboring elements (620-1a:620-MN) duringthe transmission of the data signal.

12. The transceiver device (100a, 100b) according to any preceding claim, wherein the transceiverdevice (100a, 100b) is a network node (100a) or a user equipment (100b).

13. A method for transmission of a data signal from subarrays (610a:610M) of an antenna array (600)of a transceiver device (100a, 100b), wherein each of the subarrays (610a:610M) comprises elements(620-1a:620-MN), the method being performed by the transceiver device (100a, 100b), the method comprising: transmitting (S110) the data signal in a traffic beam from the antenna array (600) with an absolutephase difference ∆^∗between each pair of neighboring elements (620-1a:620-MN), wherein the absolutephase difference ∆^∗ depends on how many elements (620-1a:620-MN) there are per subarray(610a:610M) and on a phase difference ∆^^^^^^ selected based on a report received from an intendedreceiver of the data signal.

14. The method according to claim 13, wherein there are more available subarrays (610a:610M) thanavailable reference signals, and wherein the method further comprises: mapping (S102) the reference signals to the subarrays (610a:610M), wherein each reference signal is mapped to its own set of at least two subarrays (610a:610M); transmitting (S104) the reference signals according to the mapping and towards the intended receiver; and receiving (S106) the report from the intended receiver.

15. The method according to claim 13 or 14, wherein the method further comprises:confirming (S108) that the intended receiver is not negatively impacted by loss of energy as causedby using the absolute phase difference ∆^∗between each pair of neighboring elements (620-1a:620-MN) during the transmission of the data signal.

16. A computer program (1320) for transmission of a data signal from subarrays (610a:610M) of anantenna array (600) of a transceiver device (100a, 100b), wherein each of the subarrays (610a:610M)comprises elements (620-1a:620-MN), the computer program comprising computer code which, when runon processing circuitry (110) of the transceiver device (100a, 100b), causes the transceiver device (100a,100b) to: transmit (S110) the data signal in a traffic beam from the antenna array (600) with an absolutephase difference ∆^∗between each pair of neighboring elements (620-1a:620-MN), wherein the absolutephase difference ∆^∗ depends on how many elements (620-1a:620-MN) there are per subarray(610a:610M) and on a phase difference ∆^^^^^^ selected based on a report received from an intendedreceiver of the data signal.

17. A computer program product (1310) comprising a computer program (1320) according to claim 16,and a computer readable storage medium (1330) on which the computer program is stored.

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