Selection of beam weights for an array of elements

Abstract

There is provided techniques for selecting beam weights for an array of elements. A method is performed by a controller. The method comprises obtaining a lens identifier of a lens as the lens is mounted in front of the array of elements. The method comprises selecting the beam weights of the array of elements based on a combination of the lens identifier and a target radiation pattern for the array of elements.

Description

[0001] SELECTION OF BEAM WEIGHTS FOR AN ARRAY OF ELEMENTS

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a controller, a computer program, and a computer program product for selecting beam weights for an array of elements.

[0004] BACKGROUND

[0005] In wireless communication networks, the number of wireless devices is increasing day by day alongside the demand for higher throughput. Consequently, there is an ongoing search for physical-layer technologies that enables the throughput over the air interface between served user equipment and serving network nodes to be increased, as well as enabling performance re-configurability in order to adapt the system to different scenarios and reduce design and implementation efforts and cost.

[0006] Array antennas (also referred to as antenna arrays) are commonly employed at network nodes to add the capability of adaptation to communication settings, including channel conditions and serving multiple user equipment. This can be achieved by various types of beamforming, i.e., by radiating energy according to a spatial radiation pattern. Radiation patterns can be shaped to have various properties such as beamwidths, pointing directions, etc. The properties are controlled by the complex-valued weights applied to the array elements. These weights can be generated either with analog means or digital means. Basically, the properties of the weights are constrained by the element types and the array topology. In general terms, for a given array implementation, the achievable radiation properties are bounded by the overall dimensions of the array and the grid points at which the elements are placed in the array. Not only network nodes benefit from beamforming. Multi-antenna user equipment can also utilize beamforming for reception purpose in the downlink or for transmissions in the uplink.

[0007] Different requirements on service angular range and / or Effective Isotropic Radiated Power (EIRP) of a network node lead to different optimal array configurations. For example, rural flat areas require a very small angular range of coverage in elevation, whilst covering high rise buildings from the outside would require a very wide elevation angular scan range. In the first case, the need for high antenna gain would motivate having large subarrays in vertical direction, while in the latter case the large elevation scan range would not allow such large arrays. This leads to the need of a wide range of different arrays to cater for all the different deployment needs.

[0008] Reconfigurable intelligent surfaces (RISs) enable the control of the propagation environment by reflect! ng / scatteri ng incident waves according to an impedance profile. Similarly to the aforementioned array antennas, the RIS radiation properties are determined by the radiation elements and the array topology. A typical RIS consists of hundreds, or even thousands, of elements, and the configuration can be represented by a matrix consisting of reflection coefficients; the impedance and the reflection coefficient are two ways of describing the same thing. In more detail, a RIS might be provided as a planar array or a periodical grid of certain unit cells, that is / are used to redirect the signal propagation path to, e.g., overcome mid-term link blockages. That is, whenever the direct link between the transmitter and receiver is blocked, e.g., by a building, communication can take an indirect route in two stages: transmitter-RIS and RIS-receiver. When the RIS has a line-of-sight path to both the transmitter and receiver, while the direct transmitter-receiver is blocked, the RIS can create a virtual line-of-sight path via itself between the transmitter and the receiver. The radiation configurations of a RIS are controlled by the phase shifts applied to the reflective elements of the RIS.

[0009] In certain settings, the radiation properties of a network node or an RIS do not suffice. By adding a lens in front of the array antenna of the network node or in front of the elements of the RIS, the radiation characteristics can be changed. Some ways the radiation characteristics can be changed are: extending the scanning range (thus reducing scanning loss), increasing directivity, reducing grating lobes, polarization transformation, and beam pattern shaping. One example of using a lens for extending the scan range is provided in F. Sun, et. al., “A General Method for Designing a Radome to Enhance the Scanning Angle of a Phased Array Antenna,” Progress In Electromagnetics Research, 2014, where a Graded Index Lens (GRIN) with anisotropic permittivity designed using transformation optics is placed on top of an array. Further, an example of a dispersing, homogeneous dielectric lens has been reported in E. Gandini et al., ‘A Dielectric Dome Antenna With Reduced Profile and Wide Scanning Capability,” IEEE Transactions on Antennas and Propagation, 2021 .

[0010] The lenses can be implemented in different ways. One example is homogenous dielectric lens-shaped lenses. However, the same function can be achieved with flat lenses using meta-surfaces or transmit arrays. GRIN lenses can be implemented either using metamaterials or mixing different materials with different permittivity in the correct ratios, most commonly mixing some dielectric and air by making the material with varying porosity.

[0011] From a technical point-of-view, the beam pattern of an antenna array is limited by the pattern of its single antenna element. That is, radiated signals in directions close to the array endfire will be significantly attenuated in comparison to those signals radiated close to the array boresight. Vice versa, an antenna array has a limited maximum gain, which might not suffice for a given deployment where the beam might need to be focused even further. Similar arguments apply for the RIS and its elements. Here, lenses might be used for beam pattern reconfigurability.

[0012] However, each lens is tailored to a specific use case, and achieving a desired beam pattern for another use case might not be possible for a given combination of network node (or RIS) and lens. This opens up for the possibility to have several different lenses in combination with the network node (or RIS), each optimized for a specific use case. However, when a new lens is placed in front of the network node (or the RIS), also the beam weights as used by the network node need to be adapted (and similar for the RIS). This requires some extra training, thus requiring radio resources that otherwise could have been used for served user equipment.

[0013] SUMMARY

[0014] An object of embodiments herein is to address the above issues.

[0015] A particular object is to enable selection of beam weights for an array of elements without suffering from the above issues.

[0016] A particular object is to enable selection of beam weights for an array of elements when placing a lens in front of a network node or RIS without requiring any extra training.

[0017] According to a first aspect there is presented a method for selecting beam weights for an array of elements. The method is performed by a controller. The method comprises obtaining a lens identifier of a lens as the lens is mounted in front of the array of elements. The method comprises selecting the beam weights of the array of elements based on a combination of the lens identifier and a target radiation pattern for the array of elements.

[0018] According to a second aspect there is presented a controller for selecting beam weights for an array of elements. The controller comprises processing circuitry. The processing circuitry is configured to cause the controller to obtain a lens identifier of a lens as the lens is mounted in front of the array of elements. The processing circuitry is configured to cause the controller to select the beam weights of the array of elements based on a combination of the lens identifier and a target radiation pattern for the array of elements.

[0019] According to a third aspect there is presented a computer program for selecting beam weights for an array of elements. The computer program comprises computer code which, when run on processing circuitry of a controller, causes the controller to perform actions. One action comprises the controller to obtain a lens identifier of a lens as the lens is mounted in front of the array of elements. One action comprises the controller to select the beam weights of the array of elements based on a combination of the lens identifier and a target radiation pattern for the array of elements.

[0020] 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.

[0021] According to a fifth aspect there is presented a system for selecting beam weight of an array of elements. The system comprises a controller according to the second aspect, an array of elements, and a lens, where the lens is mounted in front of the array of elements.

[0022] Advantageously, these aspects enable selection of beam weights for an array of elements without suffering from the above issues.

[0023] Advantageously, these aspects enable selection of beam weights for an array of elements when placing a lens in front of a network node or RIS without requiring any extra training.

[0024] Advantageously, these aspects counteract the shortcomings of a network node or IS with respects to coverage, as well as adding reconfigurability depending on the deployment. For example, the limited scanning range due to directive array element pattern can be extended by applying a dispersive lens on top of the array. Alternatively, applying a collimating lens could extend the coverage by providing a higher antenna gain than what an array without a lens can support.

[0025] Advantageously, according to these aspects, the lens, if made of a suitable dielectric material, can act as a radome which is a component that sometimes needs to be included in a radio system in order to provide mechanical protection from environmental conditions. The radome is usually transparent from the electromagnetic point of view, and sometimes it even deteriorates the array antenna performance, thus needing to consider its effect beforehand to counter-back such degradation. However, by adding lensing functionality to the radome it is possible to improve the performance of the array antenna as well as providing a mechanical cover.

[0026] Advantageously, according to these aspects, the number of needed different variants of array antennas and RIS configurations can be reduced compared to prior art. This is achieved by only modifying the lens placed on top of the array antennas or RIS and then updating the beam weights of the array antennas or RIS accordingly.

[0027] 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.

[0028] 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.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0031] Fig. 1 is a schematic diagram illustrating communication networks according to embodiments;

[0032] Fig. 2 schematically illustrates a system according to an embodiment;

[0033] Fig. 3 is a flowchart of methods according to embodiments;

[0034] Fig. 4 schematically illustrates using different lenses to achieve different desired beam patterns according to embodiments;

[0035] Fig. 5 schematically illustrates a lens according to an embodiment;

[0036] Figs. 6 and 7 show simulation results according to embodiments;

[0037] Fig. 8 is a schematic diagram showing structural units of a controller according to an embodiment;

[0038] Fig. 9 is a schematic diagram showing functional modules of a controller according to an embodiment; and

[0039] Fig. 10 shows one example of a computer program product comprising computer readable storage medium according to an embodiment. DETAILED DESCRIPTION

[0040] 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.

[0041] Fig. 1 is a schematic diagram illustrating communication network 100a, 100b where embodiments presented herein can be applied. In Fig. 1 (a) is illustrated an example where a network node 150, by means of a transmission and reception point 120, provides network access to a user equipment 140 over a wireless link 130. A lens 270 is placed in front of the transmission and reception point 120 so as to alter the radiation characteristics of the transmission and reception point 120. In Fig. 1 (b) is illustrated an example where network node 150, by means of a transmission and reception point 120, provides network access to a user equipment 140 via an RIS 160 over wireless links 130a, 130b. A lens 270 is placed in front of the RIS 160 so as to alter the of scattering (reflecting) characteristics of the RIS 160.

[0042] In general term, when fitting a lens in front of a transmission and reception point 120 or an RIS 160, the radiation characteristics of an antenna array in a transmission and reception point 120, or the scattering (reflecting) characteristics of elements in an RIS 160 change. This might prompt the beam weights to be adjusted so as to achieve a target beam pattern. Furthermore, the radiation characteristics of an antenna array in a transmission and reception point 120, or the scattering (reflecting) characteristics of elements in a RIS 160 can be tailored to different scenarios using different lenses 270. As will be disclosed hereinafter, the lenses 270 can be easily interchangeable and the beam weights adjusted accordingly by using a certain type of identification system. In this way, a controller placed in the transmission and reception point 120 or RIS 160 can automatically identify which lens 270 is placed in front it and can thereby use the correct set of beam weights for that specific lens 270.

[0043] The embodiments disclosed herein in particular relate to techniques for selecting beam weights for an array of elements 240. In order to obtain such techniques, there is provided a controller 800, 900, a method performed by the controller 800, 900, a computer program product comprising code, for example in the form of a computer program, that when run on a controller 800, 900, causes the controller 800, 900 to perform the method. Embodiments of a system 200 for selecting beam weight of an array of elements 240, and embodiments of methods for selecting beam weights for an array of elements 240 will be disclosed next with parallel references to the system 200 in Fig. 2 and the flowchart of Fig. 3. The methods are performed by the controller 800, 900. The methods are advantageously provided as computer programs 1020. The method is based on adjusting beam weights to produce a desired beam pattern 420a, 420b (see, Fig. 4) when a lens 270 is mounted in front of an array of elements 240. In this respect, the array of elements 240 can define an antenna array of radiating elements in a transmission and reception point 120 or an array of scattering (reflecting) elements in an RIS 160, etc. The system 200 comprises a controller 800, 900, an array of elements 240, and a lens 270, where the lens 270 is mounted in front of the array of elements 240. The array of elements 240 can be part of either a transmission and reception point 120, an RIS 160, or some other piece of equipment, such as a remote radio unit, or the like. The lens 270 might be part of a lens unit 260.

[0044] S102: The controller 800, 900 obtains a lens identifier (ID) of a lens 270 as the lens 270 is mounted in front of the array of elements 240.

[0045] There can be different ways for the controller 800, 900 to obtain the lens ID. In some aspects, the lens 270 (or lens unit 260) is equipped with a tag 280, such as an RFID tag, a QR code, etc. and the controller 800, 900 is provided with a tag reader 220 for reading the tag 280. That is, in some embodiments, the lens 270 (or lens unit 260) comprises a tag 280 that holds the lens ID, the controller 800 comprises a tag reader 220, and the controller 800 is configured to obtain the lens ID by instructing the tag reader 220 to read the lens ID from the tag 280. In some aspects, the lens 270 (or lens unit 260) and the controller 800 provided with wireless communication interfaces, such as near-field communication (NFC) interfaces or Bluetooth interfaces, for communication with each other. That is, in some embodiments, the lens 270 (or lens unit 260) comprises a wireless transmitter 285, the controller 800 comprises a wireless receiver 225, and the controller 800 is configured to obtain the lens ID by instructing the wireless receiver 225 to receive the lens ID from the wireless transmitter 285. In this way, with some type of a lens ID integrated within the lens 270 (or lens unit 260), the controller 800, 900 can automatically identify the attached lens 270 and adapt the beam weights as needed for the specific lens 270 to form a target radiation pattern 420a, 420b.

[0046] S106: The controller 800, 900 select the beam weights of the array of elements 240 based on a combination of the lens ID and a target radiation pattern 420a, 420b for the array of elements 240. In some embodiments, the array of elements 240 comprises antenna elements (marked by “x” in Fig. 2), and the beam weights define either phase shifts or complex-valued excitation weights of the antenna elements. In this respect, the beam weights might define phase shifts, in terms of reflection coefficients or reflection phase, of the antenna elements when the array of elements 240 is part of an RIS 160. Further in this respect, the beam weights might define complex-valued excitation weights of the antenna elements when the array of elements 240 is part of a transmission and reception point 120.

[0047] There can be different ways for the controller 800, 900 to select the beam weights.

[0048] In some aspects, the beam weights are obtained from a look-up table 230, 290 for the particular lens 270. That is, in some embodiments, the beam weights are selectable by being retrievable from a lookup table 230, 290. Which beam weights to retrieve can then be defined by the combination of lens ID and target radiation pattern 420a, 420b. The look-up table 230, 290 might either be part of the transmission and reception point 120 or RIS 160 on the one hand or the lens 270 (or lens unit 260) on the other hand. In this way the controller 800, 900 might obtain the beam weights from a lookup table 230, 290 of codebook weights for each type of lens 270. Those beam weights can be pre-designed for a particular array of elements 240, a set of expected lenses 270 and a set of target radiation patterns 420a, 420b. In case the lens 270 (or lens unit 260) is provided with such a lookup table 290 and the lens 270 is put in front of a RIS 160, the RIS 160 might communicate to the network node the lens ID and the network node can adjust its operation according to the known phase shifts the RIS 160 will have. This is since the network node is also assumed to know how the lens 270 in question will affects the radiation patter of the RIS.

[0049] In some aspects, the beam weights are obtained from a memory in the lens 270 (or lens unit 260) or in the transmission and reception point 120 or RIS 160. That is, in some embodiments, the beam weights are selectable by being retrievable from a storage 235, 295, where the storage 235, 295 is either associated with the lens 270 (or lens unit 260) or with the controller 800, 900. Which beam weights to retrieve can then be defined by the combination of lens ID and target radiation pattern 420a, 420b. Hence, the lens 270 (or lens unit 260) might not only have a lens ID but a storage 295 comprising the relevant beam weights.

[0050] In some aspects, the beam weights are downloaded from the network based on the tag information provided. That is, in some embodiments, the beam weights are selectable by being downloadable from a network. Which beam weights to be downloaded can be defined by the combination of lens ID and target radiation pattern 420a, 420b. In some aspects, the beam weights are pre-designed based on a given lens 270, a given array and a given target radiation pattern 420a, 420b. That is, in some embodiments, the beam weights are selectable from sets of beam weights, where each set of beam weights is designed for a given combination of lens 270 and target radiation pattern 420a, 420b.

[0051] In some aspects, the beam weights are computed by either the controller 800, 900 or the lens unit 260 given the desired radiation pattern and the lens shape. In some examples, as will be further disclosed below, the beam weights are computable using an inverse excitation method.

[0052] Embodiments relating to further details of selecting beam weights for an array of elements 240 as performed by the controller 800 will now be disclosed with continued reference to Fig. 2 and Fig. 3.

[0053] In the case the array of elements 240 is part of a RIS 160, also the incident wave might be considered when selecting the beam weights. In some examples, the wave incident from the network node on the RIS 160 to be static, and then factoring in the beam weights needed to compensate for the oblique incident angle can be regarded as a type of calibration.

[0054] Aspects where the controller 800, 900 is at a RIS 160 and communicates with a network node 150 to set the RIS configuration will be disclosed next.

[0055] In some aspects the controller 800, 900 sets the beam weights by itself, and the network node 150 could then adjust its operation according to the beam weights the RIS 160 will have. That is, in some embodiments, the array of elements 240 is part of a reflective intelligent surface 160, the reflective intelligent surface 160 is configured to reflect radio waves towards, and / or from, a transmission and reception point 120 controlled by a network node 150. The controller 800, 900 might then be configured to perform (optional) step S104.

[0056] S104: The controller 800, 900 sends the lens ID to the network node 150.

[0057] As noted above, in some aspects the controller 800 receives the beam weights from the network node 150. That is, in some embodiments, controller 800, 900 might then be configured to perform (optional) step S106a as part of selecting the beam weights of the array of elements 240 in step S106.

[0058] S106a: The controller 800, 900 receives the beam weights from the network node 150, for the controller 800 to thereby select the beam weights. This also encompass the case as described above where the beam weights downloads the beam weights from the network as such (i.e., where the beam weights are selectable by being downloadable from the network).

[0059] In some non-limiting examples, the target radiation pattern 420a, 420b is defined in terms of at least one of: beam range, beam directivity, grating lobe shaping, polarization transformation, beam shaping.

[0060] Fig. 4 illustrates two examples of using different lenses to achieve different desired beam patterns 420a, 420b. In Fig. 4(a) is illustrated an array of elements 240 with beam weights giving rise to a first beam pattern 410a. A first desired beam patterns 420a is obtained when a concave (or diverging) lens 270 is placed in front of the array of elements 240. The array of elements 240 could thus be fitted with a lens 270 that disperses the radiation in, for example, elevation, extending the scan range beyond what is possible with the array of elements 240 alone, for extreme scan range coverage, as in the example in Fig. 4(a). In Fig. 4(b) is illustrated an array of elements 240 with beam weights giving rise to a second beam pattern 410b. A second desired beam patterns 420b is obtained when a convex (or converging) lens 270 is placed in front of the array of elements 240. The lens 270 can have any shape in general, i.e., the lens 270 does not have to be rotationally symmetric. An array of elements 240 could, e.g., be complemented with a lens 270 that collimates its radiation or scattering (reflection) in elevation while leaving the azimuth radiation or scattering (reflection) characteristics unaltered. In this way, the antenna gain would increase, while the beam widths and scan range in elevation would decrease, as in the example in Fig. 4(b). Another set of lenses could modify the radiation or scattering (reflecting) characteristics in azimuth alone. Yet other lenses could be used that affect both the elevation and azimuth radiation or scattering (reflecting) characteristics simultaneously.

[0061] A non-limiting and illustrative example of pre-designing the beam weights based on a given lens 270, a given array of elements 240 and a given target radiation pattern 420a, 420b will be disclosed next.

[0062] For illustrative purposes, and without loss of generality, the amplitude excitation is considered uniform, and hence beamforming can be performed by changing the phase distribution, to adapt the scanning functionality of the array of elements 240. Given a two-dimensional array of elements 240 and a particular lens 270 shown in Fig. 5, the phase of the wave propagating from the array to the aperture plane is mainly composed of three parts: i) the phase distribution <t»aof the array antenna, ii) the phase change Cwhen propagating in the air and the lens, and iii) the phase that finally reaches the aperture plane. An example incident wave, with wave direction 0£, on the inner lens surface is refracted and the wave propagates inside the dielectric lens. The wave is refracted again after going through the outer surface, and propagates in the wave direction 0O. So, <t»ais a vector of the phases of the array of elements 240. Cis a vector of the total phase contribution due to the electrical path length from the array to the aperture plane (defined by dl ■ kl + d2 ■ k2 + d3 ■ k3, where dl, d2, d3 are the distances as indicated in Fig. 5, and kl, k2, k3 are the wave numbers in the regions rl, r2, r3. =

[0063] <t»a+ Cis the resulting phase distribution in the aperture plane 510, which is perpendicular to the boresight direction of the array of elements 240, corresponding to the symmetry axis 520.

[0064] In one illustrative example, considering a street outdoor scenario where a collimating lens is used to provide high gain and a coverage of ±30°, to determine the beamforming weights, the inverse excitation method can be applied to obtain the array excitation phase distribution that achieves directive beams pointing at the target range of scanning angles. According to the inverse excitation method, given an incident plane wave as excitation source at different angles 0reverse, observation points can be placed at each antenna array element position. In this way, the corresponding phase distribution needed to get the target different output radiation angles from the lens can be extracted. This can be done by means of, e.g., the CST full wave simulation tool. As a result of applying the inverse excitation method, the phase of the wave arriving at the aperture (see, Fig. 5) is ensured to be uniform so that higher gain can be achieved and, thereby, obtaining the largest radiation aperture efficiency and gain after the wave propagates through the lens. Given the pre-designed lens, and a two-dimensional array of elements 240 of size Lxx Ly, following the above procedure, and considering that a coverage of ±30° is to be achieved, the phase excitation profile <Pacan be numerically obtained for different pointing angles 0O.

[0065] Simulation results will be disclosed next with reference to Fig. 6 and Fig. 7 which shows the gain (in d Bi) as a function of pointing angles 0O(in degrees). The left-hand side of Fig. 6 shows an increase of gain of 0.5 dBi from 0 to 30° while maintaining the gain performance at the remaining scanning range. This is not an optimized lens, and better gain values could be obtained, by for example sweeping the position of the lens with respect to the array of elements 240. In the same way, a pre-designed lens can be applied and obtain the beam weights for the scenario of scanning range extension from 60° to 80°. The corresponding performance gain of some 0.5-1 dBi can be seen at the right-hand side of Fig. 7.

[0066] The herein disclosed embodiments are not limited to any specific communication standard. The herein disclosed embodiments can be applied in any communication system where array of elements 240 are used, and where there is a benefit of adapting the radiation characteristics or the scattering (reflecting) characteristics to the deployment scenario. The herein disclosed embodiments are not limited to any specific type of lenses 270. For example, the lens 270 might be a meta-material lens (also referred to as a meta dome), a dielectric lens (single layer or multilayer), a graded index lens (e.g., made of different dielectric materials), or a lens that could be changed between states (such as a (semi-)transparent surface lens).

[0067] Fig. 8 schematically illustrates, in terms of a number of structural units, the components of a controller 800 according to an embodiment. Processing circuitry 810 is provided using any combination 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 computer program product 1010 (as in Fig. 10), e.g. in the form of a storage medium 830. The processing circuitry 810 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0068] Particularly, the processing circuitry 810 is configured to cause the controller 800 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 830 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 830 to cause the controller 800 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

[0069] Thus the processing circuitry 810 is thereby arranged to execute methods as herein disclosed. The storage medium 830 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The controller 800 may further comprise a communications (comm.) interface 820 at least configured for communications with other entities, functions, nodes, and devices, as illustrated in Fig. 2. As such the communications interface 820 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 810 controls the general operation of the controller 800 e.g. by sending data and control signals to the communications interface 820 and the storage medium 830, by receiving data and reports from the communications interface 820, and by retrieving data and instructions from the storage medium 830. Other components, as well as the related functionality, of the controller 800 are omitted in order not to obscure the concepts presented herein.

[0070] Fig. 9 schematically illustrates, in terms of a number of functional modules, the components of a controller 900 according to an embodiment. The controller 900 of Fig. 9 comprises an obtain module 910 configured to perform step S102, and a select module 930 configured to perform step S106. The controller 900 of Fig. 9 may further comprise a number of optional functional modules, such as any of a send module 920 configured to perform step S104, and a receive module 940 configured to perform step S106a. In general terms, each functional module 910:940 may in one embodiment be implemented only in hardware and in another embodiment with the help of software, i.e., the latter embodiment having computer program instructions stored on the storage medium 830 which when run on the processing circuitry makes the controller 900 perform the corresponding steps mentioned above in conjunction with Fig 9. 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 all functional modules 910:940 may be implemented by the processing circuitry 810, possibly in cooperation with the communications interface 820 and / or the storage medium 830. The processing circuitry 810 may thus be configured to from the storage medium 830 fetch instructions as provided by a functional module 910:940 and to execute these instructions, thereby performing any steps as disclosed herein.

[0071] The controller 800, 900 may be provided as a standalone device or as a part of at least one further device. For example, the controller 800, 900 may be provided in the network node or the RIS. Alternatively, functionality of the controller 800, 900 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the radio access network or the core network) or may be spread between at least two 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 controller 800, 900 may be executed in a first device, and a second portion of the of the instructions performed by the controller 800, 900 may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the controller 800, 900 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a controller 800, 900 residing in a cloud computational environment. Therefore, although a single processing circuitry 810 is illustrated in Fig. 8 the processing circuitry 810 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 910:940 of Fig. 9 and the computer program 1020 of Fig. 10.

[0072] Further in this respect, 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 radio units (RUs). The protocol layer stack of the network node is divided between the CU, the DUs and the RUs, 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 higher layer 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 200 in the downlink (i.e., from the CU to the RU) or received by the network node 200 in the uplink (i.e., from the RU to the CU). In this respect, the controller 800, 900 might be part of either the CU, the DU, or the RU.

[0073] Fig. 10 shows one example of a computer program product 1010 comprising computer readable storage medium 1030. On this computer readable storage medium 1030, a computer program 1020 can be stored, which computer program 1020 can cause the processing circuitry 810 and thereto operatively coupled entities and devices, such as the communications interface 820 and the storage medium 830, to execute methods according to embodiments described herein. The computer program 1020 and / or computer program product 1010 may thus provide means for performing any steps as herein disclosed.

[0074] In the example of Fig. 10, the computer program product 1010 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1010 could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more 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, such as a compact Flash memory. Thus, while the computer program 1020 is here schematically shown as a track on the depicted optical disk, the computer program 1020 can be stored in any way which is suitable for the computer program product 1010.

[0075] 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 above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1 . A controller (800, 900) for selecting beam weights for an array of elements (240), wherein the controller (800, 900) comprises processing circuitry (810), and wherein the processing circuitry (810) is configured to cause the controller (800, 900) to: obtain a lens identifier (ID) of a lens (270) as the lens (270) is mounted in front of the array of elements (240); select the beam weights of the array of elements (240) based on a combination of the lens identifier (ID) and a target radiation pattern (420a, 420b) for the array of elements (240).

2. The controller (800, 900) according to claim 1 , wherein the lens (270) comprises a tag (280) that holds the lens identifier (ID), wherein the controller (800, 900) comprises a tag reader (220), and wherein the controller (800, 900) is configured to obtain the lens identifier (ID) by instructing the tag reader (220) to read the lens identifier (ID) from the tag (280).

3. The controller (800, 900) according to claim 1 , wherein the lens (270) comprises a wireless transmitter (285), wherein the controller (800, 900) comprises a wireless receiver (225), and wherein the controller (800, 900) is configured to obtain the lens identifier (ID) by instructing the wireless receiver (225) to receive the lens identifier (ID) from the wireless transmitter (285).

4. The controller (800, 900) according to any preceding claim, wherein the beam weights are selectable by being retrievable from a look-up table (230, 290), and wherein which beam weights to retrieve is defined by the combination of lens identifier (ID) and target radiation pattern (420a, 420b).

5. The controller (800, 900) according to any of claims 1 to 3, wherein the beam weights are selectable by being retrievable from a storage (235, 295), wherein the storage (235, 295) is either associated with the lens (270) or with the controller (800, 900), and wherein which beam weights to retrieve is defined by the combination of lens identifier (ID) and target radiation pattern (420a, 420b).

6. The controller (800, 900) according to any of claims 1 to 3, wherein the beam weights are selectable by being downloadable from a network, and wherein which beam weights to be downloaded is defined by the combination of lens identifier (ID) and target radiation pattern (420a, 420b).

7. The controller (800, 900) according to any of claims 1 to 3, wherein the beam weights are selectable from sets of beam weights, wherein each set of beam weights is designed for a given combination of lens (270) and target radiation pattern (420a, 420b).

8. The controller (800, 900) according to any preceding claim, wherein the beam weights are computable using an inverse excitation method.

9. The controller (800, 900) according to any preceding claim, wherein the array of elements (240) is part of any of: a transmission and reception point (120), a remote radio unit, a reflective intelligent surface (160).

10. The controller (800, 900) according to any of claims 1 to 9, wherein the array of elements (240) is part of a reflective intelligent surface (160), wherein the reflective intelligent surface (160) is configured to reflect radio waves towards, and / or from, a transmission and reception point (120) controlled by a network node (150), and wherein the processing circuitry (810) further is configured to cause the controller (800, 900) to: send the lens identifier (ID) to the network node (150).11 . The controller (800, 900) according to claim 10, wherein the processing circuitry (810) further is configured to cause the controller (800, 900) to: receive the beam weights from the network node (150), for the controller (800, 900) to thereby select the beam weights.

12. The controller (800, 900) according to any preceding claim, wherein the array of elements (240) comprises antenna elements (x), and wherein the beam weights define either phase shifts or complexvalued excitation weights of the antenna elements (x).

13. The controller (800, 900) according to any preceding claim, wherein the target radiation pattern (420a, 420b) is defined in terms of at least one of: beam range, beam directivity, grating lobe shaping, polarization transformation, beam shaping.

14. A system (200) for selecting beam weight of an array of elements (240), the system comprising a controller (800, 900) according to any preceding claim, the array of elements (240), and a lens (270), wherein the lens (270) is mounted in front of the array of elements (240).

15. A method for selecting beam weights for an array of elements (240), the method being performed by a controller (800, 900), the method comprising: obtaining (S102) a lens identifier (ID) of a lens (270) as the lens (270) is mounted in front of the array of elements (240); selecting (S106) the beam weights of the array of elements (240) based on a combination of the lens identifier (ID) and a target radiation pattern (420a, 420b) for the array of elements (240).

16. A computer program (1020) for selecting beam weights for an array of elements (240), the computer program comprising computer code which, when run on processing circuitry (810) of a controller (800, 900), causes the controller (800, 900) to: obtain (S102) a lens identifier (ID) of a lens (270) as the lens (270) is mounted in front of the array of elements (240); select (S106) the beam weights of the array of elements (240) based on a combination of the lens identifier (ID) and a target radiation pattern (420a, 420b) for the array of elements (240).

17. A computer program product (1010) comprising a computer program (1020) according to claim 16, and a computer readable storage medium (1030) on which the computer program is stored.

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