Digital controllable scatterer controller and method therefor

Abstract

A digital controllable scatterer (DCS) controller for controlling a DCS to simultaneously serve a subset of a plurality of receivers, where the DCS includes a plurality of scattering elements arranged on a scattering surface. The DCS controller is configured to determine a single user codeword for each receiver of the plurality of receivers, where the single user codeword defines a set of scattering elements of the scattering surface of the DCS for the respective receiver and defines a respective phase shift configuration for each scattering element of the set of scattering elements. The DCS controller is configured to determine a desired signal gain for each of the plurality of receivers and determine a subset of receivers based on the desired signal gain. The DCS controller is configured to determine a subset of scattering elements of the scattering surface for each receiver in the subset of receivers and determine a multi-user codeword based on the subset.

Description

Technical Field

[0001] The present disclosure generally relates to the field of wireless communication, and more particularly, to a digital controllable scatterer (DCS) controller and a method for use in a DCS controller. Background Art

[0002] Generally, a digital controllable scatterer (DCS) is defined as a large surface having a large number of independently configurable scattering elements. The DCS has channel programming capabilities as well as focusing capabilities that can be used to focus energy towards a given user equipment (UE). The focusing capabilities enable the DCS to serve UEs that cannot be directly served while controlling the achieved signal-to-noise ratio (SNR). However, it is technically challenging to serve multiple UEs simultaneously through the same DCS. Generally, the codeword, i.e., the phase configuration of the DCS, is designed to focus on a given position in space. This means that when two users (or UEs) are separated in space, it becomes infeasible to focus simultaneously and maintain the required link budget because the two corresponding codewords are significantly different and cannot provide the required SNR level to each UE to ensure proper communication. Additionally, the DCS, being a large surface, can be divided into sub-regions, each of which can be dedicated to serving a given UE. Then the question becomes: which region or regions of the DCS should be associated with each UE in a given set of UEs to ensure proper service to each UE at the required SNR. This problem is solved by dividing the DCS into vertical and / or horizontal sub-regions, where each sub-region is assigned to a specific user. Although the proposed solution is easy to implement, it is not preferred because various parameters are not considered, such as the structure and orientation of the optimal service plane for focusing energy towards the target user, the orientation of the optimal beamformer, the SNR level of each target UE, etc.

[0003] Currently, different methods have been developed to configure the phases of one or more digital controllable scatterers (DCSs) in a multi-user (MU) scenario, where these phases are optimized based on an objective function. Examples of the objective function include sum rate, minimum mean square error (MMSE), outage, minimum interference, maximum effective rank, maximum minimum singular value, geometric mean of SINR, worst-case sum rate, etc. Different works have considered various assumptions of channel state information (CSI), such as full perfect CSI, full noise CSI, or statistical CSI. To simplify the CSI requirements and / or the algorithms for solving the optimization problem, many alternative options have been considered, for example, each DCS is only associated with one user, beam training, Bayesian optimization, random beamforming, DCS partitioning, radio environment mapping, etc. Despite the above solutions, there are technical problems in configuring DCSs to serve multiple users simultaneously while maintaining the required SNR level for each user.

[0004] Therefore, based on the above discussion, it is necessary to overcome the above disadvantages associated with the conventional ways of configuring the phases of DCSs in the MU scenario. Summary of the Invention

[0005] The present disclosure provides a digital controllable scatterer (DCS) controller and a method for use in the DCS controller. The present disclosure provides a solution to the existing problem of configuring DCSs to serve multiple users simultaneously while maintaining the required SNR level for each user. The objective of the present disclosure is to provide a solution that at least partially overcomes the problems encountered in the prior art and provides an improved DCS controller and a method for use in the DCS controller.

[0006] One or more objectives of the present disclosure are achieved by the technical solutions provided in the appended independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.

[0007] In one aspect, the present disclosure provides a digital controllable scatterer (DCS) controller for controlling DCSs to serve a subset of multiple receivers (Rxs) simultaneously, where the multiple receivers (Rxs) at least include a first receiver (Rx 1 ) and a second receiver (Rx 2 ) located at different positions, and where the DCS includes a plurality of scattering elements arranged on a scattering surface, and the DCS controller is configured to: for the multiple receivers (Rxs i) determines a single-user codeword (C i ), where the single-user codeword is the corresponding receiver (Rx i ) defines a scattering element set of the scattering surface of the DCS, and defines a corresponding phase shift configuration for each scattering element in the scattering element set. The DCS controller is also used to i ) determines the required signal gain (G i ), and based on the required signal gain (G 1 , G 2 ) determines the receiver subset (Rx 1 , Rx 2 The DCS controller is further configured to provide a DCS controller for the receiver subset (Rx 1 , Rx 2 ) in each receiver (Rx i ) determines the scattering element subset (S) of the scattering surface i ), where the determination is for the receiver (Rx i ) of the scattering element subset (S i ) to satisfy the receiver (Rx i ) of the desired signal gain (G i ), subset (S i ) are disjoint. The DCS controller is further configured to determine a multi-user codeword (C m ), wherein the multi-user codeword (C m ) define a phase configuration for a subset of all scattering elements of the (scattering) surface of the DCS; based on the multi-user codeword (C m ) controls the DCS to perform data transmission.

[0008] The disclosed DCS controller is used to control the DCS so that the DCS serves a subset of multiple receivers simultaneously while maintaining a desired SNR level for each receiver. Alternatively, the DCS controller is used to provide a plurality of receivers based on a multi-user codeword (C m)Control the DCS, where the multi - user codeword enables the DCS to serve a subset of multiple receivers simultaneously with a single multi - user codeword, and the single multi - user codeword can be constructed as a function of multiple single - user codewords. The DCS controller is used to generate single - user codewords using the virtual ellipsoid technique. The single - user codewords define the set of scattering elements of the DCS for each receiver. Thereafter, the DCS controller is used to determine the required signal gain for each of the multiple receivers and determine the receiver subset based on the required signal gain. Thereafter, beamforming is used at the transmitter, and the beamforming is used to focus the energy on the assigned DCS elements, and the assigned DCS elements further scatter the focused energy towards each of the multiple receivers.

[0009] In one implementation, the DCS controller is further used to determine the receiver subset (Rx 1 、C 2 ) based on the single - user codewords (C 1 、Rx 2 ).

[0010] In another implementation, the DCS controller is further used to determine the receiver subset (Rx 1 、G 2 ) based on the required signal gains (G 1 、Rx 2 ) such that the total required signal gain (∑G i ) of the determined receiver subset does not exceed the characteristics of the DCS.

[0011] In another implementation, the DCS controller is further used to determine that the total required signal gain (∑G * =∑S i ) of the determined receiver subset does not exceed the characteristics of the DCS by determining that the total surface (S i ) of the subset of the scattering elements does not exceed the scattering surface of the DCS.

[0012] In another implementation, the DCS controller is further used to determine the receiver subset based on the Lagrangian optimization solution that maximizes the system metric subject to the constraints of the available resources on the DCS.

[0013] Using the Lagrangian optimization solution means simplifying the calculation of the system metric.

[0014] In another implementation, the system metric is based on the number of users served by the DCS.

[0015] In one implementation, the system metric is based on the maximum number of users that the DCS can serve simultaneously.

[0016] In another implementation, the system metric is throughput, which is the sum rate of the rates of each served user.

[0017] The maximum throughput can be obtained by maximizing the number of co-scheduled user equipments through DCS.

[0018] In another implementation, the DCS controller is further configured to determine the subset of receivers based on Lagrangian optimization by: determining an optimal constant (μ i ) based on the required signal-to-noise-ratio (SNR) values of two or more receivers (Rx * ), and solving the Lagrangian optimization by moving the optimal constant (μ * ) until the total surface of the subset of the scattering elements reaches the surface of the DCS.

[0019] The multi-user codeword (C m ) enables DCS to serve a subset of multiple receivers located at different positions simultaneously.

[0020] In another implementation, the DCS controller is further configured to determine a scattering pattern focused on a receiver (Rx i ), the scattering pattern corresponding to the reflection pattern from a perfect electric conductor having an ellipsoidal shape, the ellipsoid having a first focus (F 1 ) as the transmitter (Tx) position and a second focus (F i ) as the position of the receiver (Rx 2 ), wherein the single-user codeword (C i ) is determined based on the scattering pattern.

[0021] Using an ellipsoid to generate the single-user codeword (C i ) can simplify the calculation.

[0022] In another implementation, the DCS controller is further configured to determine the set of scattering elements for a receiver (Rx i ) by: determining a first plane that contains the major axis of the ellipsoid and intersects the ellipsoid; determining a first intersection line as the line where the first plane intersects the DCS surface. The DCS controller is further configured to determine a second plane that contains the major axis of the ellipsoid and intersects the ellipsoid; determining a second intersection line as the line where the second plane intersects the DCS surface. The DCS controller is further configured to place the receiver (Rx iThe set of scattering elements of ) is determined as a part of the DCS surface between the first intersection line and the second intersection line.

[0023] Determining the set of scattering elements of the receiver (Rx i ) as a part of the DCS surface between the first intersection line and the second intersection line provides an accurate set of scattering elements.

[0024] In another implementation, the DCS controller is further configured to translate at least one of the first intersection line and the second intersection line to provide a higher required gain (G i ) to the receiver (Rx i ).

[0025] Higher gain can be achieved by using at least one of the first intersection line and the second intersection line.

[0026] In another implementation, the DCS controller is further configured to configure the scattering elements of the DCS according to the following equation:

[0027]

[0028] where

[0029] Tx is the position of the transmitter,

[0030] Rx i is the position of the i-th receiver,

[0031] M is the position of the scattering element on the DCS surface,

[0032] V is a point on the ellipsoid, where the line between M and Rx i intersects the ellipsoid,

[0033] is the phase shift applied by the DCS at point M,

[0034] δ M is the path difference between the path through the DCS at point M and the path through the ellipsoidal PEC seen at the receiver from the same point M,

[0035] λ is the wavelength of the transmitted signal.

[0036] In another implementation, the DCS controller is further configured to determine the subset of receivers by receiving scheduling information indicating which receivers are scheduled to be activated, and only determine the required signal gain of the receivers scheduled to be activated.

[0037] Receiving scheduling information reduces the search space of the optimization process. The scheduling information can be adjusted according to requirements at a given moment in time.

[0038] In another implementation, the DCS controller is further configured to determine the subset of receivers by receiving scheduling information indicating which receivers are scheduled to be prioritized, and to determine the subset of receivers to include the prioritized receivers.

[0039] In another implementation, the DCS includes scattering elements, and the DCS controller is further configured to determine the multi - user codeword (C i ) based on the subset of scattering elements (S m ) by: assigning phase shifts specified by the codeword C i to the scattering elements of the subset S i , and aggregating these scattering elements and the corresponding phase shifts into the multi - user codeword (C m ).

[0040] In another implementation, the subset (S i ) of scattering elements of the DCS surface for a receiver (Rx i ) consists of contiguous scattering elements.

[0041] In another implementation, the subset (S i ) of scattering elements of the DCS surface for a receiver (Rx i ) is defined by a strip having a first angle (α) between two principal cutting planes and a second angle (β) representing the opening of the strip calculated (or defined) at the center of the ellipsoid, wherein the first angle and the second angle (α, β) are determined to achieve a gain (G i ) for the corresponding subset (S i ), and wherein the width of the strip reflects the beamwidth to be used by a transmitter (Tx).

[0042] In another implementation, the subset (S i ) of scattering elements of the DCS surface for a receiver (Rx i ) consists of non - contiguous scattering elements.

[0043] In another implementation, the DCS controller further includes determining a beamformer (P i ) for the transmitter (Tx), and the beamformer (P i ) is focused towards the strip identified for the receiver (Rx i ).

[0044] In another aspect, the present disclosure provides a method for use in a DCS controller for controlling a DCS to simultaneously serve a subset of a plurality of receivers (Rx), the plurality of receivers (Rx) comprising at least a first receiver (Rx) located at different locations. 1 ) and the second receiver (Rx 2 ), wherein the DCS comprises a plurality of scattering elements arranged on a scattering surface, and the method comprises: providing the plurality of receivers (Rx i ) determines a single-user codeword (C i ), wherein the single-user codeword is used for the corresponding receiver (Rx i ) of the DCS of the (scattering) surface of the (scattering) surface, and defining a corresponding phase shift configuration for each scattering element in the scattering element set. The method further comprises: i ) determines the required signal gain (G i ); Based on the required signal gain (G 1 , G 2 ) determines the receiver subset (Rx 1 , Rx 2 ), wherein the total required signal gain (∑G i ) does not exceed the characteristics of the DCS. The method also includes: for the receiver subset (Rx 1 , Rx 2 ) in each receiver (Rx i ) determines the scattering element subset (S i ), where the receiver (Rx i ) of the subset (S i ) to satisfy the receiver (Rx i ) of the desired signal gain (G i ), subset (S i ) are disjoint. The method further comprises: determining a multi-user codeword (C m ), wherein the multi-user codeword (C m ) define the phase configuration for all subsets of scattering elements of the (scattering) surface of the DCS; based on the multi-user codeword (C m ) controls the DCS to perform data transmission.

[0045] The method achieves all the advantages and technical effects of the DCS controller disclosed herein.

[0046] It should be noted that all devices, components, circuits, units, and modules described in this application can be implemented in hardware components or any type of combination thereof. All steps performed by various entities described in this application and the functions described as being performed by various entities are intended to mean that the corresponding entities are adapted or used to perform the corresponding steps and functions. Even in the description of the following specific embodiments, where the specific functions or steps to be performed by external entities are not reflected in the description of the specific detailed components of the entity performing that specific step or function, those skilled in the art should be aware that these methods and functions can be implemented in the corresponding software or hardware components, or in any combination of such components. It should be understood that the features of the present disclosure are readily combinable in various combinations without departing from the scope of the present disclosure as defined by the appended claims.

[0047] Additional aspects, advantages, features, and objectives of the present disclosure will become apparent from the accompanying drawings and the detailed description of the illustrative implementations explained in conjunction with the following appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above-described invention content and the following detailed description of the illustrative embodiments can be better understood when read in conjunction with the accompanying drawings. To illustrate the present disclosure, exemplary structures of the present disclosure are shown in the drawings. However, the present disclosure is not limited to the specific methods and tools disclosed herein. In addition, those skilled in the art should understand that the drawings are not drawn to scale. Where possible, like elements are denoted by the same reference numerals.

[0049] Embodiments of the present disclosure will now be described by way of example only with reference to the following figures, wherein:

[0050] Figure 1 is an environmental diagram showing communication between multiple user equipments (MUEs) through a digital controllable scatterer (DCS) according to an embodiment of the present disclosure;

[0051] Figure 2 is a flowchart showing the configuration of a DCS to serve multiple user equipments according to an embodiment of the present disclosure;

[0052] Figure 3 is a diagram depicting the selection of an ellipsoid for codeword calculation provided by an embodiment of the present disclosure;

[0053] Figure 4 is a diagram showing the calculation of a set of scattering elements for a receiver provided by an embodiment of the present disclosure;

[0054] Figure 5 is a diagram depicting the calculation of the phase shift of the scattering elements of a DCS provided by an embodiment of the present disclosure;

[0055] Figure 6 is a diagram depicting the geometric structure of the ellipsoid provided by an embodiment of the present disclosure;

[0056] Figure 7 is a three - dimensional (3D) graphical representation provided by an embodiment of the present disclosure, which depicts the equivalent points of the ellipsoid simulated by the DCS based on the calculated phase shift matrix;

[0057] Figure 8 shows the mapping of the nominal beam directions on the DCS in the case of ellipsoid - based codewords according to an embodiment of the present disclosure;

[0058] Figure 9 shows the calculation of the DCS surface assigned to each user equipment provided by an embodiment of the present disclosure;

[0059] Figure 10 is an alternative implementation for calculating the DCS surface assigned to each user equipment provided by another embodiment of the present disclosure;

[0060] Figure 11 is a flowchart of the method in the DCS controller provided by an embodiment of the present disclosure;

[0061] Figures 12A to 12C shows the arrangement of a subset of the scattering elements of the scattering surface of the DCS provided by different embodiments of the present disclosure;

[0062] Figure 13 shows an exemplary configuration of the scattering surface of the DCS provided by an embodiment of the present disclosure.

[0063] In the drawings, underlined numbers are used to indicate the item in which the underlined number is located or the item adjacent to the underlined number. Non - underlined numbers are related to the item identified by the line associating the non - underlined number with the item. When a number is non - underlined and accompanied by an associated arrow, the non - underlined number is used to identify the general item to which the arrow points. Detailed Description of the Invention

[0064] The following detailed description shows embodiments of the present disclosure and the ways in which these embodiments can be implemented. Although some modes of implementing the present disclosure have been disclosed, those skilled in the art should recognize that there may be other embodiments for implementing or practicing the present disclosure.

[0065] Figure 1It is an environmental diagram showing communication between multiple user equipment (MUE) through a digital controllable scatterer (DCS) according to an embodiment of the present disclosure. Refer to Figure 1 , an environmental diagram 100 is shown, which includes a DCS controller 102 for controlling the DCS 104. The DCS 104 includes a plurality of scattering elements 106 arranged on a scattering surface 108. A transmitter 110 (which can also be denoted as Tx) and a plurality of receivers 112 are also shown, such as a first receiver 112A (which can also be denoted as Rx 1 ), a second receiver 112B (which can also be denoted as Rx 2 ), up to an Nth receiver 112N (which can also be denoted as Rx N ). The DCS 104 is represented by a dashed box, which is for illustrative purposes only and does not form part of the circuit.

[0066] The DCS controller 102 may include suitable logic, circuitry, and / or interfaces for controlling the DCS 104. Examples of the DCS controller 102 may include, but are not limited to, integrated circuits, coprocessors, microprocessors, microcontrollers, complex instruction set computing (CISC) processors, application-specific integrated circuit (ASIC) processors, reduced instruction set (RISC) processors, very long instruction word (VLIW) processors, central processing unit (CPU), and other processors or circuitry. Additionally, the DCS controller 102 may refer to one or more individual controllers, control devices, or control units that are part of a machine. In one implementation, the DCS controller 102 may further include a memory and a network interface. The memory may be used to store the generated multi-user codewords. Examples of the implementation of the memory may include, but are not limited to, electrically erasable programmable read-only memory (EEPROM), dynamic random access memory (DRAM), random access memory (RAM), read-only memory (ROM), hard disk drive (HDD), flash memory, secure digital (SD) card, solid-state drive (SSD), and / or CPU cache memory. Examples of the implementation of the network interface may include, but are not limited to, communication interfaces, computer ports, network sockets, network interface controller (NIC), and any other network interface devices. The DCS controller 102 may be located at the same location or a different location from the location of the DCS 104. Alternatively, the DCS controller 102 and the DCS 104 may or may not be collocated.

[0067] The DCS 104 may include suitable logic, circuitry, and / or interfaces for serving each receiver in a subset of the multiple receivers 112 simultaneously, where the receiver subset is obtained as a result of a selection process (i.e., resource allocation, scheduling constraints, etc.). Each of the multiple receivers 112 is located at a different position. The DCS 104 may be implemented in the form of an intelligent reflective surface (IRS), a reflective intelligent surface (RIS), or a large intelligent surface (LIS), where a plurality of scattering elements 106 (i.e., a large number of scattering elements), also referred to as cell elements, are arranged on the scattering surface 108.

[0068] The transmitter 110 (i.e., Tx) may include suitable logic, circuitry, and / or interfaces for simultaneously transmitting a signal of interest to a subset of the multiple receivers 112 by using the DCS 104. Examples of the transmitter 110 (i.e., Tx) may include, but are not limited to, Internet-of-Things (IoT) devices, smartphones, machine type communication (MTC) devices, computing devices, evolved universal mobile telecommunications system (UMTS) terrestrial radio access (E-UTRAN) NR dual connectivity (EN-DC) devices, servers, IoT controllers, drones, custom hardware for wireless communication, transmitters, or any other portable or non-portable electronic device.

[0069] Each of the multiple receivers 112 may include suitable logic, circuitry, and / or interfaces for receiving the signal of interest transmitted by the transmitter 110 via the DCS 104. Examples of each of the multiple receivers 112 may include, but are not limited to, Internet-of-Things (IoT) controllers, servers, smartphones, custom hardware for wireless communication, receivers, or any other portable or non-portable electronic device. The multiple receivers 112 may also be referred to as multiple user equipment (MUE) or multiple users.

[0070] In operation, the DCS controller 102 is used to control the digitally controllable scatterer (DCS) 104 to simultaneously serve a subset of a plurality of receivers 112 (Rx), and the plurality of receivers 112 (Rx) at least includes a first receiver 112A (Rx 1 ) and a second receiver 112B (Rx 2 ), wherein the DCS 104 includes a plurality of scattering elements 106 arranged on the scattering surface 108. The DCS controller 102 is used to control the DCS 104 to simultaneously focus energy in a given area where the plurality of receivers 112 are located. The DCS 104 is divided into a plurality of sub-regions. Each of these regions is assigned to a given UE and is thus configured using a specific codeword for the intended UE. In addition, the selected region is only a set of scattering elements (i.e., the plurality of scattering elements 106). Each scattering element in the plurality of scattering elements 106 represents a surface that can be converted into a radar cross section (RCS) and thus represents a gain factor.

[0071] The DCS controller 102 is used to determine a single-user codeword (C i ) for each of the plurality of receivers 112 (Rx i ), wherein the single-user codeword defines a set of scattering elements of the (scattering) surface of the DCS 104 for the corresponding receiver (Rx i ) and defines a corresponding phase shift configuration for each scattering element in the set of scattering elements. The single-user codeword (C i ) is selected from a codebook or constructed according to a codeword generation process. A codeword is generated as a single-user codeword for each UE in the considered UE (i.e., a subset of the plurality of receivers 112), that is, as if the UE were alone. In addition, for the corresponding receiver (Rx i ), a single-user codeword (C i ) is calculated for the set of scattering elements arranged on the scattering surface 108 of the DCS 104. Alternatively, the single-user codeword (C i ) identifies a region in the DCS 104 that is more suitable for serving the corresponding receiver (Rx i ) or user i. In addition, the single-user codeword defines a corresponding phase shift configuration for each scattering element in the set of scattering elements. The set of scattering elements and the corresponding phase shift configuration defined by the single-user codeword (C i ) are associated with the gain (G i ) of the i-th UE. A subset of the set of scattering elements defined by the single-user codeword (C i ) selected for serving the i-th UE is used to modify the gain perceived by the i-th UE. This is used to design a multi-user (MU) codeword.

[0072] The DCS controller 102 is also used to determine the required signal gain (G i ) for each of the plurality of receivers 112 (Rx i ), and determine a subset of receivers (Rx 1 , G 2 ) based on the required signal gain (G 1 ). After determining a single-user codeword for each of the plurality of receivers 112 (Rx 2 ), the nominal direction of the acquired focused beam is calculated, and the projection of the focused beam on the DCS 104 is identified based on the single-user codeword. Alternatively, a subset of scattering elements of the phase shift configuration is identified by a grid of nominal directions for beam construction. The nominal direction can be obtained through codeword construction, so no additional calculation is required. Thereafter, the dimensions of the space allocated for each of the plurality of receivers 112 (Rx i ) on the DCS 104 are identified. Finally, determining the allocated space requires identifying the contours of these regions. This can be reduced to calculating the width and height of a parallelogram around the nominal direction identified for the identified maximum contributing element. This calculation takes into account the following several constraints: (i) The first constraint includes the required gain towards a given UE obtained through the DCS 104. This can be clearly transformed according to the surface directly related to the RCS. (ii) The second constraint includes DCS constraints (e.g., the size of the DCS 104). (iii) The third hidden constraint is optional but can be easily taken into account in this framework, i.e., the scheduling constraint, which can be considered when selecting the codewords that need to be stacked simultaneously on the DCS 104. This is done based on the required signal gain (G i ) for each of the plurality of receivers 112 (Rx i ). After evaluating the required signal-to-noise ratio (SNR) and propagation loss for each receiver (or UE), the link budget can be calculated for each of the plurality of receivers 112, thereby providing the required gain from the DCS 104 in terms of focused gain. Then the provided gain is transformed onto the surface of the DCS 104. The DCS controller 102 is used to determine a subset of receivers from the plurality of receivers 112 (i.e., Rx i ) based on the required signal gain (G 1 , G 2 ), such as the first receiver 112A (i.e., Rx i ) and the second receiver 112B (i.e., Rx 1 2 ).

[0073] The DCS controller 102 is also used for the subset of receivers (Rx 1 ​, Rx 2 ) each receiver (Rx i ) determines a subset (S i ) of the scattering elements of the scattering surface 108, wherein the subset (S i ) of the scattering elements of the scattering surface 108 for the receiver (Rx i ) is determined to meet the required signal gain (G i ) of the receiver (Rx i ), and the subsets (S i ) are disjoint. The DCS controller 102 is used to determine, for each receiver (Rx 1 , Rx 2 ) of the subset of receivers (Rx i ), a subset (S i ) of the scattering elements from the plurality of scattering elements 106 arranged on the scattering surface 108. The subset (S i ) of the scattering elements of the scattering surface 108 for each receiver (Rx i ) is identified such that the subset (S i ) meets the required signal gain (G i ) of each receiver (Rx i ). The subsets (S i ) of the scattering elements of the scattering surface 108 for each receiver (Rx i ) are different from each other and have no common elements.

[0074] The DCS controller 102 is also used to determine a multi-user codeword (C m ) based on the subsets, wherein the multi-user codeword (C m ) defines a phase configuration for all subsets of the scattering elements of the scattering surface 108 of the DCS 104, and controls the DCS 104 to perform data transmission based on the multi-user codeword (C m ). The DCS controller 102 is used to determine a multi-user codeword (C m ) based on the subset of the scattering elements of the (scattering) surface of the DCS 104 according to Equation (1):

[0075]

[0076] where 1 i is an indicative function of the selected DCS elements for user i, ⊙ is the Hadamard matrix product, K is the total number of users in the selected subset of users, C i is the single-user codeword for user i, C m is the multi-user codeword, and the multi-user codeword defines a phase configuration for all subsets of the scattering elements of the (scattering) surface of the DCS 104. The DCS controller 102 is also used to based on the multi-user codeword (C m)Control the DCS 104 to perform data transmission.

[0077] According to one embodiment, the DCS controller 102 is further configured to determine a subset of receivers (Rx 1 , C 2 ) based on single-user codewords (C 1 , Rx 2 ). The single-user codewords (C 1 , C 2 ) provide potential configuration states of the set of scattering elements of the DCS 104 and corresponding phase shift configurations of each scattering element in the set of scattering elements. The set of scattering elements identifies regions on the DCS 104 that are more suitable for assignment to each receiver. Therefore, based on the single-user codewords (C 1 , C 2 ), a subset of receivers (Rx 1 , Rx 2 ) is determined.

[0078] According to one embodiment, the DCS controller 102 is further configured to determine a subset of receivers (Rx 1 , G 2 ) based on the required signal gains (G 1 , Rx 2 ) such that the total required signal gain (∑G i ) of the determined subset of receivers does not exceed the characteristics of the DCS 104. The total required signal gain (∑G 1 ) of the determined subset of receivers (i.e., the first receiver 112A (i.e., Rx 2 ) and the second receiver 112B (i.e., Rx i )) does not exceed the characteristics of the DCS 104. The characteristics of the DCS 104 include not only the scattering surface 108 but also the number of receivers (or user devices) that can be served simultaneously by the DCS 104, the rate of serving each receiver (or user device), and the total reflected energy from the DCS 104.

[0079] According to one embodiment, the DCS controller 102 is further configured to determine a subset of receivers by receiving scheduling information indicating which receivers are scheduled to be activated, and only determine the required signal gains of the receivers that are scheduled to be activated. In one implementation, the DCS controller 102 can be used to receive scheduling information before determining the required signal gains for each of the multiple receivers 112. The scheduling information indicates which of the multiple receivers 112 are scheduled to be activated, and then, the DCS controller 102 is used to only determine the required signal gains of the receivers that are scheduled to be activated.

[0080] According to one embodiment, the DCS controller 102 is further configured to determine a subset of receivers by receiving scheduling information indicating which receivers are scheduled to be prioritized, and to determine the subset of receivers to include the prioritized receivers. In one implementation, the scheduling information may include information about which receivers from among the plurality of receivers 112 are scheduled to be prioritized. After receiving the scheduling information, the DCS controller 102 is configured to determine only the required signal gain for the receivers scheduled to be prioritized.

[0081] According to one embodiment, the DCS controller 102 is further configured to determine a multi-user codeword (C m ) based on a subset of scattering elements by: determining the corresponding phase shifts for each subset of the scattering elements and subset of the DCS 104, and aggregating these scattering elements and corresponding phase shifts into the multi-user codeword (C m ). The multi-user codeword (C m ) enables the focusing of the required energy towards the respective users (i.e., the plurality of receivers 112) to be served by the DCS 104. To generate the multi-user codeword (C m ), the following inputs are considered: (i) a set of codewords or codebooks for serving a single user by the DCS 104, (ii) a set of users (i.e., the plurality of receivers 112) to be served by the DCS 104, and (iii) the required gain for achieving the communication-enabling SNR for each considered user. Using the above inputs, the structure of each codeword for each receiver is estimated. Thereafter, the resulting structures and phase shifts are aggregated in order to generate a multi-user codeword for a subset of the plurality of receivers 112 to be served by the DCS 104. In addition, the regions to be assigned to each codeword to achieve the required SNR are calculated. The scattering elements and corresponding phase shifts to be used for each codeword are identified.

[0082] According to one embodiment, the DCS 104 includes scattering elements, and the DCS controller 102 is further configured to determine a multi-user codeword (C i ) based on a subset of scattering elements (S m ) by: assigning the phase shifts specified by its corresponding single-user codeword (C i ) to the scattering elements of each subset of scattering elements (S i ), and aggregating these scattering elements (S i ) and the corresponding phase shifts of all subsets of scattering elements into the multi-user codeword (C m ). The DCS 104 includes scattering elements (i.e., a plurality of scattering elements 106). The phase shifts specified by the single-user codeword C i are assigned to the scattering elements defined by the subset of scattering elements (S i ).

[0083] According to one embodiment, the DCS controller 102 is included in the DCS 104. In one implementation, the DCS controller 102 may be included by the DCS 104. In another implementation, the DCS controller 102 may be located outside the DCS 104.

[0084] According to one embodiment, the DCS controller 102 is included in a base station. In one implementation, the DCS controller 102 may be used in a communication node. In different implementation scenarios, the communication node may act as a base station or as an access point (AP).

[0085] According to one embodiment, the DCS controller 102 is included in a stand-alone device. In one implementation, the DCS controller 102 may be included by a base station that may be used to operate as a stand-alone device. In another implementation, the DCS controller 102 may be included by an access point that may be used to operate as a stand-alone device.

[0086] Therefore, the DCS controller 102 is used to control the DCS 104 such that the DCS 104 serves a subset of multiple users simultaneously while maintaining the required SNR level for each user. Alternatively, the DCS controller 102 is used to control the DCS 104 based on a multi-user codeword (C m ) such that the DCS 104 can serve a subset of multiple users simultaneously through a single multi-user codeword C constructed as a function of single-user codewords m . The DCS controller 102 is used to generate single-user codewords using virtual ellipsoid techniques. Single-user codewords are calculated for a set of scattering elements of the DCS 104 for each receiver. Thereafter, the DCS controller 102 is used to determine the required signal gain for each of the multiple receivers 112 and determine a subset of receivers based on the required signal gain. Thereafter, beamforming is used at the transmitter 110, and the beamforming is used to focus energy on the assigned DCS elements, and the assigned DCS elements further reflect the focused energy towards each of the multiple receivers 112. The generated phase pattern is applied to the respective DCS elements and concentrates an appropriate or required amount of energy onto each of the multiple served user devices.

[0087] Figure 2 is a flowchart showing the configuration of a DCS to serve a subset of multiple user devices simultaneously according to an embodiment of the present disclosure. Figure 2 is described in connection with Figure 1 the elements in. Referring to Figure 2 , a flowchart 200 including steps 202 to 216 is shown. ( Figure 1The DCS controller 102 is used to execute the flow chart 200. In addition, the information provided in the dashed box (or dashed line) (i.e., the scheduling information) is optional and is particularly useful for enhancing the process.

[0088] In step 202, the codeword (i.e., the single-user codeword (C i )) is selected from the codebook or constructed by following the codeword generation process.

[0089] In step 204, a codeword is generated for each UE under consideration (i.e., a subset of the plurality of receivers 112) as a single-user codeword C i , that is, as if the UE were alone.

[0090] Steps 202 and 204 involve the selection or construction of the single-user codeword C i . Scheduling information about the plurality of receivers 112 is received before estimating the signal gain required for each of the plurality of receivers 112.

[0091] In step 206, based on the generated codeword, the nominal direction of the acquired focused beam (e.g., radiation beam or scattering beam or impact beam) is calculated, and the projection of the focused beam on the DCS 104 is identified. Thereafter, the signal gain required for each of the plurality of receivers 112 is estimated.

[0092] In step 208, the dimensions of the space allocated on the DCS 104 for a subset of the plurality of receivers 112 are identified based on the required gain estimated for each of the plurality of receivers 112.

[0093] In step 210, based on the required signal gain (G 1 , G 2 ), a subset of receivers from the plurality of receivers (i.e., Rx i ) 112 is determined, such as a first receiver (i.e., Rx 1 ) 112A and a second receiver (i.e., Rx 2 ) 112B.

[0094] In step 212, a subset of scattering elements (S 1 and Rx 2 ) is determined for each receiver (i.e., Rx i ) from the plurality of scattering elements 106. In addition, a multi-user codeword (C i ) is generated based on the single-user codeword (C i ) and the subset of scattering elements (S m ) of the (scattering) surface of the DCS 104 according to equation (1).

[0095] Steps 206 to 212 result in the multi-user codeword (C m) generation.

[0096] In step 214, configure DCS 104 according to the generated multi - user codewords (C m ). Alternatively, configure the phase distribution of DCS 104 according to the generated multi - user codewords (C m ).

[0097] In step 216, start data transmission after configuring the phase configuration of DCS 104. Alternatively, one or more transmitters (e.g., transmitter 110) start sending data to each of the multiple receivers 112 through DCS 104.

[0098] Figure 3 is a diagram depicting the ellipsoid selection for codeword calculation provided by an embodiment of the present disclosure. Figure 3 is described in combination with Figure 1 and Figure 2 elements. Referring to Figure 3 , FIG. 300 is shown, which describes the ellipsoid selection for codeword calculation for the configuration of DCS 104. Also shown are ellipsoid 302, transmitter 304, receiver 306, and point T 308 on ellipsoid 302.

[0099] Transmitter 304 corresponds to transmitter 110 (of Figure 1 ). Similarly, receiver 306 corresponds to one of the multiple receivers 112 (of Figure 1 ).

[0100] FIG. 300 shows a geometric structure where ellipsoid 302 is selected for its focusing characteristics. To maintain the desired focusing ability of ellipsoid 302 (e.g., in three - dimensional (3D)), it is considered that the two semi - axes of ellipsoid 302 (i.e., the semi - minor axis and the semi - third axis) have the same size. This consideration, together with the tangency condition, is used for calculation simplification because it makes the constructed solution unique for focusing from transmitter 304 towards receiver 306, without changing the output phase configuration solution depending on modulo operation. Additionally, shown is transmitter 304 (i.e., Tx) with focus F 1 , receiver 306 (i.e., Rx) with focus F 2 , plane representing DCS 104 and ellipsoid 302 tangent to plane * ). Ellipsoid 302 (which can also be represented as the unique ellipsoid ε 1 ) is tangent to DCS 104 at point T 308 and has foci F 2is obtained with it as the focus. The ellipsoid 302 is defined with three axes, where the major axis is the axis connecting the two foci (e.g., F 1 and F 2 ), which is called the first major axis. The two minor axes are also defined in a plane orthogonal to the first major axis and include the center of the ellipsoid 302. If the two semi - minor axes are equal, a spheroid is formed. This means that the intersection of any plane with normal vector with the ellipsoid 302 provides a circle.

[0101] Once the ellipsoid 302 is constructed, the codeword calculation can begin. The energy from the transmitter 304 to the receiver 306 can be focused with a perfect electrical conductor shaped like the designed ellipsoid 302. Thus, the DCS 104 is configured such that the scattering pattern of the DCS 104 mimics the reflection pattern from a perfect electrical conductor shaped like the ellipsoid 302 (i.e., the optimally constructed ellipsoid), and thus the DCS 104 obtains all its focusing characteristics (i.e., the focusing characteristics of the ellipsoid 302). Therefore, mapping the reflection behavior from a perfect electrical conductor shaped like the ellipsoid 302 to the scattering from the DCS 104 amounts to providing a phase - shift configuration for the DCS 104 that produces the correct (i.e., exactly the same) path difference for each point of the DCS 104, e.g., as detailed in Figure 5 . Alternatively, for each controllable element of the DCS 104, the correct path difference is applied as a phase - shift in such a way that the path difference through the DCS 104 matches the path difference observed through the ellipsoid 302.

[0102] The specific construction process of the codewords is described in detail, for example, in Figure 7 . The set of constructed or calculated codewords spanning the considered space constitutes a codebook. By construction, the codebook is a structured partially ordered set (poset) that can be directly sorted using an absolute or relative distance metric in the space (i.e., related to the coordinates in three - dimensional space). Since the construction of the codewords is geometry - based, the codewords can be obtained as an analytical solution as a function of the relative positions of the transmitter 304, the receiver 306, and the DCS 104. Thus, the system only needs to store one expression (e.g., a mathematical expression).

[0103] According to one embodiment, the DCS controller 102 is also used to determine the scattering pattern focused on the receiver (Rx i ), which corresponds to the reflection pattern from a perfect electrical conductor having an ellipsoidal shape, the ellipsoid having a first focus (F 1 ) at the transmitter (Tx) position and a second focus (F i ) at the receiver (Rx 2 ) position, where the single - user codeword (Ci ) is determined based on a scattering pattern. The scattering pattern corresponds to the pattern resulting from reflection from a perfect electrical conductor in the shape of an ellipsoid (e.g., ellipsoid 302). The ellipsoid 302 is tangent to the plane of the DCS 104 (as Figure 3 shown). The ellipsoid 302 has a first focus (F 1 ) at the location of the transmitter 304, and a second focus (F 2 ) at the location of the receiver 306. Additionally, the single-user codeword (C i ) associated with each receiver is determined based on the scattering pattern, as described in detail, for example, in Figure 5 .

[0104] Figure 4 is a diagram showing the calculation of the set of scattering elements provided for a receiver in an embodiment of the present disclosure. Figure 4 is described in connection with Figure 1 , Figure 2 and Figure 3 in the elements. Referring to Figure 4 , a diagram 400 showing the calculation of the set of scattering elements for a receiver (e.g., Figure 3 the receiver 306) is shown. Also shown are a first plane 402, a second plane 404, a first intersection line 406, and a second intersection line 408.

[0105] According to one embodiment, the DCS controller 102 is further configured to determine a set of scattering elements for the receiver 306 (Rx i ) by determining a first plane 402 that contains the major axis of the ellipsoid 302 and intersects the ellipsoid 302. The DCS controller 102 is further configured to determine the first intersection line 406 as the line of intersection of the first plane 402 with the surface of the DCS 104, and to determine a second plane 404 that contains the major axis of the ellipsoid 302 and intersects the ellipsoid 302. The DCS controller 102 is further configured to determine the second intersection line 408 as the line of intersection of the second plane 404 with the surface of the DCS 104, and to determine the set of scattering elements for the receiver 306 (Rx i) The set of scattering elements of the DCS 104 is determined as a portion of the surface of the DCS 104 between the first intersection line 406 and the second intersection line 408. FIG. 400 shows the construction of the ellipsoid for the receiver 306, and then, the set of scattering elements of the DCS 104 is calculated. For this calculation, the DCS controller 102 is used to consider a first plane 402 containing the major axis of the ellipsoid 302, and the first plane 402 intersects the ellipsoid 302. Thereafter, the DCS controller 102 is used to determine the first intersection line 406 where the first plane 402 intersects the DCS 104. The DCS 104 is represented as a planar structure. The DCS controller 102 is used to consider a second plane 404 containing the major axis of the ellipsoid 302, and the second plane 404 intersects the ellipsoid 302. Thereafter, the DCS controller 102 is used to determine the second intersection line 408 where the second plane 404 intersects the DCS 104. The second plane 404 is different from the first plane 402. The DCS controller 102 uses the portion of the surface of the DCS 104 between the first intersection line 406 and the second intersection line 408 to determine the set of scattering elements for the receiver 306. Alternatively, the portion of the surface of the DCS 104 between the first intersection line 406 and the second intersection line 408 is used to focus energy towards the receiver 306.

[0106] According to one embodiment, the DCS controller 102 is further used to translate at least one of the first intersection line 406 and the second intersection line 408 to provide a higher desired gain (G i ) to the receiver 306 (Rx i ). The DCS controller 102 is used to translate a region of at least one of the first intersection line 406 and the second intersection line 408 to provide a higher desired gain (which may also be expressed as ) to the receiver 306. A higher desired gain can be achieved by changing the angle between the first plane 402 and the second plane 404 around the major axis of the ellipsoid 302.

[0107] Figure 5 FIG. 500 is a diagram describing the calculation of the phase shift of the scattering elements of the DCS provided by the embodiments of the present disclosure. Figure 5 FIG. 500 is described in connection with the elements in Figure 1 , Figure 2 , Figure 3 and Figure 4 . Referring to Figure 5 , FIG. 500 shows a diagram describing the calculation of the phase shift of the scattering elements of the DCS 104 (of Figure 1 ). An ellipse 502 is also shown.

[0108] In FIG. 500, the structured codewords based on the ellipsoid 302 are used to encode the phase shifts of the DCS 104 for focusing between the transmitter 304 and the receiver 306. Different codewords are calculated for different Rxs. The different single-user codewords form a structured single-user codebook (a codebook where one codeword is designed to serve only one user at a time), as a partially ordered set with respect to the focusing metric. In FIG. 500, the codewords are related to the spatial positioning of the foci. Thus, the codewords are generated by a construction based on the behavior of an analog rotating ellipsoid (e.g., ellipsoid 302). That is, the two semi-axes have the same size. The ellipsoid 302 can also be constructed by rotating an ellipse about its major axis. For simplicity, the ellipsoid 302 tangent to the DCS 104 (i.e., ε * ) is selected, and the ellipsoid 302 simplifies the expression of the code. The construction of the ellipsoid 302 can be carried out in two ways. The first is analytical, where the parameters of the ellipsoid 302 are provided, and the second is geometric. Based on the ellipsoid 302 (i.e., ε * ), the phase shifts of the respective elements of the DCS 104 are calculated. In one implementation, a point M on the DCS 104 (in FIG. 500) is shown, which is located at the center of the scattering element of the DCS 104. In addition, an ellipse E is constructed as the intersection of the plane (T x MR x ) and the ellipsoid 302 (i.e., ε * ), represented by the dashed line 502 in Figure 5 . Thereafter, the DCS controller 102 calculates the phase of the signal at the receiver 306, which propagates from the transmitter 304 to the receiver 306 through the ray reflected at the point M on the DCS 104. The ray reflected from the DCS 104 is denoted as MRx (i.e., at the point M) and intersects the ellipse E at the point V. The reflected ray from the ellipsoid 302 is drawn as the dashed line VRx. To ensure that the DCS 104 simulates the reflection behavior of the ellipsoid 302 and obtains the focusing characteristics, the paths T x V R x and T x M R x should both present the same phase. To achieve the same phase, the phase at the point M of the DCS 104 needs to be compensated by the following path difference, as shown in equation (2) below:

[0109]

[0110] According to one embodiment, the DCS controller 102 is also used to configure the scattering elements of the DCS 104 according to the following equation:

[0111]

[0112] Among them,

[0113] Tx is the position of the transmitter 304,

[0114] Rx i is the position of the receiver i 306,

[0115] M is the position of the scattering element on the surface of the DCS 104

[0116] V is a point on the ellipsoid 302, at which the line between M and Rx i intersects the ellipsoid 302,

[0117] is the phase shift at point M,

[0118] δ M is the path difference between the path through the DCS 104 at point M and the other paths through the ellipsoidal PEC as seen at the receiver 306 as if coming from the same point M, and λ is the wavelength of the transmitted signal.

[0119] All these quantities are geometrically constructed and can be calculated in closed-form expressions as functions of the coordinates of Tx, Rx, and M and the definition of the DCS 104 plane. By calculating the path difference δ for all points M corresponding to the centers of the scattering elements of the DCS 104 M the resulting phase of each scattering element is calculated. The obtained codewords are defined as the set given by equation (3):

[0120] c(Tx,Rx,DCS) = {φ M , M ∈ DCS} (3)

[0121] Finally, the codebook is the aggregation of all codewords for the transmitter 304 and the receiver 306 at given positions in the region of interest.

[0122] Figure 6 is a diagram depicting the geometric construction of the ellipsoid provided by the embodiments of the present disclosure. Figure 6 is described in conjunction with Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 in the elements of. Referring to Figure 6 , a diagram 600 depicting the geometric construction of an ellipsoid (e.g., Figure 3 the ellipsoid 302) is shown.

[0123] Diagram 600 shows the geometric construction of a prolate ellipsoid (i.e., the ellipsoid 302) that is tangent to a plane (e.g., DCS 104) and has a transmitter 304 (i.e., T x) and the receiver 306 (i.e., R x )'s specific foci. Alternatively, FIG. 600 shows a geometric method of constructing a rotational ellipsoid (i.e., ellipsoid 302) based on simple geometric operations. The construction process is as follows: First, construct the symmetric point Rx′ of the receiver 306 (i.e., Rx) with respect to the DCS 104 plane. Thereafter, consider the line Rx′Tx, and consider the point T at the intersection of the line Rx′Tx and the DCS 104 plane. Then, the point T is the tangent point of the ellipsoid 302 and the DCS 104 plane. Finally, construct an ellipse with foci Rx and Tx and passing through the point T. The ellipsoid 302 is simply constructed by rotating the ellipse about its major axis (i.e., Rx′Tx). The construction process is shown in detail, for example, in Figure 8 .

[0124] In addition to the geometric construction of the ellipsoid 302, an analytical method can also be used for the construction of the ellipsoid 302. All geometric operations can be converted into their analytical equivalent operations, where the application of the geometric operations to the coordinates of the considered points provides an analytical expression of the ellipsoid 302.

[0125] Figure 7 is a three-dimensional (3D) graphical representation provided by an embodiment of the present disclosure, which describes the equivalent points of the ellipsoid simulated by the DCS based on the calculated phase shift matrix. Figure 7 is combined with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 in the elements described. Referring to Figure 7 , a 3D graphical representation 700 is shown, which describes the equivalent points of the ellipsoid (e.g., Figure 3 's ellipsoid 302) simulated by the DCS 104 based on the calculated phase shift matrix.

[0126] Referring to Figure 7 , a 3D graphical representation 700 is shown, which includes an X-axis 702, a Y-axis 704, and a Z-axis 706, which are used to represent the equivalent points of the ellipsoid 302 simulated by the DCS 104 based on the calculated phase shift matrix.

[0127] According to one embodiment, the DCS controller 102 is used to select at least one single-user codeword (C i ) from the stored single-user codewords. In one implementation, the codebook is considered fixed, where specific points in space have been preselected. In this case, calculate the area covered by the DCS 104. Therefore, for each point, calculate and store the state of the DCS 104. Then, the codebook will be a look-up table or of size A 2D matrix, where S is the number of scattering elements on the DCS 104, is the cardinality of the codebook and is the number of relevant points considered in the region.

[0128] According to one embodiment, the DCS controller 102 is used to construct at least one single-user codeword (C i ) in the single-user codewords. In one implementation, the codebook (i.e., the structured codebook) can be constructed using an explicit equation form of the ellipsoid 302, which compresses the description of the codebook into the description of the ellipsoid equation. In this case, the closed-form expression is used to simply generate the codeword for a given point in space by substituting the coordinates of the target point and the coordinates of the foci (e.g., the foci of the transmitter 304 (or the foci of the receiver 306)).

[0129] As Figure 6 shown, the closed-form expression of the tangent ellipsoid is obtained. Also, the coordinates of the two foci and the equation of the plane defining the DCS 104 are obtained, which are used to calculate the path difference of each scattering element M(x M , y M , z M ) of the DCS 104 and update the phase shift correction φ M to be applied. For any focus in space and any point on the DCS 104, the closed-form expression of the codeword is defined by the corresponding Cartesian expression given by Equation (4) below.

[0130]

[0131] Using the closed-form expression, the codebook does not require more storage or look-up tables because the values of the codewords can be instantaneously calculated for the set of scattering elements M that make up the DCS 104. In addition, the codeword calculation can be simplified by considering the real-world deployment scenario and the underlying assumptions. In fact, it can be assumed that the DCS 104 plane and one of the foci (usually the Tx) are known and fixed, so the codeword is only a function of the receiving point in space. The various points regarded as reflection elements on the DCS 104 are predefined as fixed components on the DCS 104 according to Equation (5):

[0132] φ M = f(Rx) (5)

[0133] Figure 8 Shows the mapping of the nominal beam direction on the DCS in the case of the ellipsoid-based codeword according to an embodiment of the present disclosure. Figure 8 is combined with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 ,Figure 6 and Figure 7 described by the elements in. Refer to Figure 8 , which shows FIG. 800, which describes the mapping of the nominal beam direction on the DCS 104 in the case of a codeword based on the ellipsoid 302. In FIG. 800, shown on the DCS 104 for the first receiver Rx 1 the first set 806 identified and for the second receiver Rx 2 the second set 808 identified. Also shown is a surface 804, which is defined by the intersection of the ellipsoid calculated for Rx Figure 4 as described in and the cutting planes 402 and 404 selected for Rx 1 . Further, shown is another surface 802 defined by the intersection of the ellipsoid calculated for Rx 1 and a second set of cutting planes selected for Rx 2 . 2

[0134] In FIG. 800, Figure 7 the single-user codebook constructed in is used to calculate the multi-user codeword. In this case, the representation of the nominal direction of the codeword seen at the DCS 104 is very simple. By construction, this is provided by the DCS 104 plane, which passes through the transmitter 304, the receiver 306 and is tangent to the tangent point of the ellipsoid 302 and the DCS 104. The geometric structure obtained is a line. In FIG. 800, consider the digital aperture around the nominal direction highlighted by a subset of the ellipsoid 302. The projection of the beam aperture around the nominal direction provides the highlighted strip as shown in FIG. 800. The intersection of these strips with the DCS 104 provides the range of achievable gain.

[0135] Figure 9 Shows the calculation of the DCS surface assigned to each user equipment provided by an embodiment of the present disclosure. Figure 9 is described in combination with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 the elements in. Refer to Figure 9 , which shows a bar chart 900, which shows the calculation of the surface on the DCS 104 assigned to each receiver (or user equipment).

[0136] According to one embodiment, the DCS controller 102 is also used to determine the total surface (S * = ∑S i ​) without exceeding the scattering surface of the DCS 104 to determine the total required signal gain (∑G of the determined subset of receivers i ) not exceeding the characteristics of the DCS 104. The subset of receivers (i.e., the first receiver 112A (Rx 1 ) and the second receiver 112B (Rx 2 )) is determined in such a way that the total required gain (∑G i ) of the subset of receivers does not exceed the characteristics of the DCS 104. For example, the characteristics of the DCS 104 are described in detail in Figure 1 . In addition, the total surface (S * = ∑S i ) of the subset of scattering elements associated with the subset of receivers does not exceed the scattering surface of the DCS 104 (i.e., the scattering surface 108). The scattering surface 108 of the DCS 104 is associated with multiple users.

[0137] According to one embodiment, the DCS controller 102 is further configured to determine a subset of receivers based on a Lagrangian optimization solution that maximizes a system metric subject to the constraints of the available resources on the DCS 104. The subset of receivers (i.e., the first receiver 112A (Rx 1 ) and the second receiver 112B (Rx 2 )) is determined based on the Lagrangian optimization solution that maximizes the system metric while satisfying the required area requirements and constraints.

[0138] According to one embodiment, the system metric is based on the number of users served by the DCS 104. In one implementation, the system metric can be defined as the maximum number of receivers (or users) that can be served simultaneously by the DCS 104.

[0139] According to one embodiment, the system metric is throughput, which is the sum rate of the rates of each served user. In one implementation, the system metric can be defined as maximizing the throughput by maximizing the sum rate of the rates of each user served by the DCS 104.

[0140] A potential optimization implementation starts with considering for each UE (Rx i ): (i) the associated codeword (i.e., the single-user codeword C i ) and the potential configuration states of the elements of the DCS 104, (ii) the required gain G i = αS i proportional to the surface G i. Finding the set of pairable UEs boils down to coloring the DCS 104 under the constraints of the available resources (i.e., the surface S of the DCS 104). Then, this problem can be formulated as a standard optimization problem. For the Max-SR criterion, and after writing down the KKT, the following conditions are obtained in the form of equation (6):

[0141]

[0142] According to one embodiment, the DCS controller 102 is further configured to determine a subset of receivers based on Lagrangian optimization by: determining an optimal constant (μ i ) based on the required signal-to-noise-ratio (SNR) values of two or more receivers (Rx * ), and solving the Lagrangian optimization by moving the optimal constant (μ * ) until the total surface of the subset of scattering elements reaches the surface of the DCS 104. The calculation of the Lagrangian optimization provides the optimal constant (μ i ) that needs to be calculated based on the required SNR values of two or more receivers (Rx * ) and is a function of the allocated surface on the DCS 104. The solution of the Lagrangian optimization is obtained by moving the optimal constant (μ * ) and calculating the surface until the surface reaches the total surface of the DCS 104 (i.e., the available resources). Figure 9 The shaded part in

[0143] Figure 10 highlights the surface allocated to each UE. Figure 10 is an alternative implementation provided by another embodiment of the present disclosure for calculating the DCS surface allocated to each user equipment. Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 and Figure 9 described in the elements of. Referring to Figure 10 , FIG. 1000 is shown, which shows that the DCS 104 is planar.

[0144] According to one embodiment, the subset of scattering elements (S i ) of the DCS 104 surface for a receiver (Rx i ) consists of consecutive scattering elements. As shown in Figure 9 , the set of UEs that can be served simultaneously by the DCS 104 can be written in the form of equation (7):

[0145]

[0146] And a subset of the scattering elements associated with the UE set (i.e., the associated desired surface) is Alternatively, for a receiver (Rx i )(e.g., Figure 3 receiver 306), a subset (S i ) of the scattering elements on the surface of the DCS 104 consists of contiguous scattering elements.

[0147] According to one embodiment, a subset (S i ) of the scattering elements arranged on the scattering surface 108 of the DCS 104 for a receiver (Rx i ) is defined by strips having a first angle (α) between two principal cutting planes and a second angle (β) representing the opening of the strip calculated (or defined) at the center of an ellipsoid (e.g., ellipsoid 302), wherein the first angle and the second angle (α, β) are determined to achieve the gain (G i ) of the corresponding subset (S i ), wherein the width of the strip reflects the beam width to be used by a transmitter (Tx). The regions on the DCS 104 are divided into strips having a first angle (α) between two principal cutting planes and a second angle (β) representing the opening of the strip calculated (or defined) at the center of an ellipsoid (e.g., ellipsoid 302). Thus, the strips can be controlled by using the first angle (α) and the second angle (β).

[0148] According to one embodiment, a subset of the scattering elements on the DCS surface for a receiver (Rx i ) consists of non - contiguous scattering elements. In one implementation, a subset of the scattering elements on the surface of the DCS 104 for a receiver (Rx i ) consists of non - contiguous scattering elements.

[0149] According to one embodiment, it includes determining a beamformer (P i ) of a transmitter (Tx), and the beamformer (P i ) focuses towards the strip identified for a receiver (Rx i ). Then, the width of the region can be selected to meet the S i condition and reflect the beam width used at the transmitter 304. Then, the problem obtained is a bin - packing problem of a parallelogram with variable dimensions.

[0150] Figure 11 is a flowchart of a method in a DCS controller provided by an embodiment of the present disclosure. Figure 11 is in combination with Figure 1 、Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 and the elements in. Refer to Figure 11 , which shows a method 1100 including steps 1102 to 1112. Step 1108 includes two sub-steps 1108A and 1108B. The method 1100 is executed by the DCS controller 102 of ( Figure 1 ).

[0151] A method 1100 for the DCS controller 102 is provided, and the DCS controller 102 is used to control the DCS 104 to simultaneously serve a subset of a plurality of receivers 112 (R xi ), and the plurality of receivers 112 (Rx i ) at least include a first receiver 112A (Rx 1 ) and a second receiver 112B (Rx 2 ) located at different positions. Among them, the DCS 104 includes a plurality of scattering elements 106 arranged on the scattering surface 108. The DCS controller 102 is used to control the DCS 104 to simultaneously focus energy in a given area where the receivers (i.e., the subset) being simultaneously served from the plurality of receivers 112 are located. The DCS 104 is divided into sub-regions. Each of these regions is assigned to a given UE, and thus is configured using a specific codeword for the intended UE.

[0152] In step 1102, the method 1100 includes: determining a single-user codeword (C i ) for each receiver among a plurality of receivers (Rx i ), where the single-user codeword defines a phase configuration for a set of scattering elements of the (scattering) surface of the DCS 104 for the corresponding receiver (Rx i ) and defines a corresponding phase shift configuration for each scattering element in the set of scattering elements. The single-user codeword (C i ) is selected from a codebook or constructed according to a codeword generation process. A codeword is generated for each UE among the UEs under consideration (i.e., the plurality of receivers 112) as a single-user codeword, that is, as if the UE is alone. For example, it is described in detail in Figure 1 .

[0153] In step 1104, the method 1100 further includes determining a required signal gain (G i ) for each receiver among the plurality of receivers 112 (Rx i)。After determining the single-user codewords for each of the plurality of receivers (Rx) 112, the nominal direction of the acquired focused beam is calculated, and the projection of the focused beam on the DCS 104 is identified based on the single-user codewords. Thereafter, the dimensions of the space allocated for each of the plurality of receivers 112 (Rx i ) are identified. This is done based on the desired signal gain (G i ) for each of the plurality of receivers (Rx i ) 112. After evaluating the desired signal-to-noise ratio (SNR) and propagation loss for each receiver (or UE), a link budget can be calculated for each of the plurality of receivers 112 to provide the desired gain from the DCS 104 in terms of beamforming gain. The provided gain is then transformed onto the surface of the DCS 104.

[0154] In step 1106, method 1100 further includes: determining a subset of receivers (Rx 1 , G 2 ) based on the desired signal gains (G 1 , Rx 2 ), wherein the total desired signal gain (∑G i ) of the determined subset of receivers does not exceed the characteristics of the DCS 104. The DCS controller 102 is used to determine a subset of receivers from the plurality of receivers 112 (i.e., Rx) based on the desired signal gains (G 1 , G 2 ), such as the first receiver 112A (i.e., Rx 1 ) and the second receiver 112B (i.e., Rx 2 ).

[0155] In step 1108, method 1100 further includes determining a subset of scattering elements (S 1 , Rx 2 ) for each receiver (Rx i ) in the subset of receivers (Rx i ). The DCS controller 102 is used to determine, for each receiver (Rx 1 , Rx 2 ) in the subset of receivers (Rx i ), a subset of scattering elements (S i ) from the plurality of reflecting elements 108 arranged on the scattering surface 108.

[0156] In sub-step 1108A, step 1108 includes determining a subset (S i ) of scattering elements for the receiver (Rx i ) to satisfy the receiver (Rx i) the required signal gain (G i ). A subset (S i ) of scattering elements of the scattering surface for each receiver (Rx i ) is identified such that the subset (S i ) satisfies the required signal gain (G i ) for each receiver (Rx i ).

[0157] In sub-step 1108B, step 1108 includes that the subsets (S i ) are disjoint. Subsets (S i ) of scattering elements of the scattering surface for each receiver (Rx i ) are different from each other and have no common elements.

[0158] In step 1110, method 1100 further includes: determining a multi-user codeword (C m ) based on the subset of scattering elements, wherein the multi-user codeword (C m ) defines all subsets of scattering elements of the scattering surface of DCS 104. The DCS controller 102 is used to determine the multi-user codeword (C m ) based on the subset of scattering elements of the (scattering) surface of DCS 104 according to equation (1), as detailed, for example, in Figure 1 .

[0159] In step 1112, method 1100 further includes: controlling DCS 104 to perform data transmission based on the multi-user codeword (C m ). The multi-user codeword (C m , which can also be represented as C MU ) defines the phase configuration of all subsets of scattering elements of the (scattering) surface of DCS 104. The DCS controller 102 is also used to control DCS 104 to perform data transmission based on the multi-user codeword (C m ).

[0160] Steps 1102 to 1112 (and sub-steps 1108A to 1108B) are merely illustrative, and other alternatives may be provided without departing from the scope of the claims herein, wherein one or more steps are added, one or more steps are deleted, or one or more steps are provided in a different order.

[0161] In one aspect, a computer program product includes program instructions for performing method 1100 when executed by one or more processors in the DCS controller 102. In another aspect, the computer program product includes a non-transitory storage medium storing the program instructions.

[0162] A computer program product is provided, including a non-transitory storage medium storing computer-readable code modules. In such an embodiment, the computer program product includes computer-readable code that, when run in the DCS controller 102, causes the DCS controller 102 to execute method 1100. The computer program product can be implemented as an algorithm and embedded in software stored in a non-transitory computer-readable storage medium. The non-transitory computer-readable storage module can include, but is not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the above devices. Examples of implementations of the computer-readable storage medium include, but are not limited to, electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), read only memory (ROM), hard disk drive (HDD), flash memory, secure digital (SD) card, solid-state drive (SSD), computer-readable storage medium, and / or CPU buffer memory.

[0163] Figures 12A to 12C Shows an arrangement of a subset of a plurality of scattering elements of the scattering surface of the DCS provided by different embodiments of the present disclosure. Figures 12A to 12C Is combined with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 and the elements in. Referring to Figure 12A , FIG. 1200A shows a subset of a plurality of scattering elements 106 of the scattering surface 108 of the DCS 104 described for the first receiver 112A (i.e., Rx 1 ) and the second receiver 112B (i.e., Rx 2 ), the subset consisting of consecutive scattering elements. For example, each of the first dashed box 1202 and the second dashed box 1204 shows a subset of a plurality of scattering elements 106 of the scattering surface 108 of the DCS 104 for the first receiver 112A (i.e., Rx 1 ) and the second receiver 112B (i.e., Rx 2 ) consisting of consecutive scattering elements.

[0164] Now refer to Figure 12B , which shows FIG. 1200B depicting a subset of the plurality of scattering elements 106 of the scattering surface 108 of the DCS 104 for the first receiver 112A (i.e., Rx 1 ) and the second receiver 112B (i.e., Rx 2 ), the subset being composed of non - contiguous scattering elements.

[0165] Now refer to Figure 12C , which shows FIG. 1200C depicting a subset of the plurality of scattering elements 106 of the scattering surface 108 of the DCS 104 for the first receiver 112A (i.e., Rx 1 ) and the second receiver 112B (i.e., Rx 2 ), the subset being composed of non - contiguous interlaced scattering elements.

[0166] Figure 13 FIG. [reference number not provided] shows an exemplary configuration of the scattering surface of the DCS provided by an embodiment of the present disclosure. Figure 13 is described in conjunction with the elements in Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 . Referring to Figure 13 , FIG. 1300 shows an exemplary configuration of the scattering surface 108 of the DCS 104. Alternatively, the DCS 104 can have a different configuration or a different shape. For example, the DCS 104 can have a planar or non - planar structure.

[0167] The embodiments of the present disclosure described above may be modified without departing from the scope of the present disclosure as defined by the appended claims. Expressions such as "comprising", "combining", "having", "being", etc. used to describe and claim the present disclosure are intended to be interpreted in a non-exclusive manner, such that items, components or elements not explicitly described are also present. References to the singular should also be interpreted as relating to the plural. The term "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments, or does not exclude incorporating features of other embodiments. The term "optionally" as used herein means "provided in some embodiments and not provided in other embodiments". It should be understood that certain features of the present disclosure described in the context of separate embodiments for clarity may also be provided in combination in a single embodiment. Conversely, the various features of the present invention described in the context of a single embodiment for brevity may also be provided separately or in any suitable combination or as a suitable embodiment of any other description of the present disclosure.

Claims

1. A digital controllable scatterer (DCS) controller (102) for controlling a DCS (104) to serve a subset of the plurality of receivers (112) simultaneously, the plurality of receivers (112) including at least a first receiver (112A) and a second receiver (112B) located at different positions, wherein, the DCS (104) includes a plurality of scattering elements (106) arranged on a scattering surface (108), and the DCS controller (102) is configured to: ● Determine a single-user codeword for each of the plurality of receivers (112), wherein the single-user codeword defines a set of scattering elements of the scattering surface of the DCS 104 for the corresponding receiver, and defines a corresponding phase shift configuration for each scattering element in the set of scattering elements; ● Determine the required signal gain for each of the plurality of receivers (112); ● Determine a subset of receivers based on the required signal gain; ● Determine a subset of scattering elements of the scattering surface for each receiver in the subset of receivers, wherein, ■ Determine the subset of scattering elements of the scattering surface for the receiver to meet the required signal gain of the receiver, ■ The subsets are disjoint; ● Determine a multi-user codeword based on the subsets, wherein the multi-user codeword defines the phase configuration for all subsets of scattering elements of the scattering surface (108) of the DCS (104); ● Control the DCS (104) to perform data transmission based on the multi-user codeword.

2. The DCS controller (102) according to claim 1, wherein, the DCS controller (102) is further configured to determine the subset of receivers based on the single-user codeword.

3. The DCS controller (102) according to claim 1 or 2, wherein, the DCS controller (102) is further configured to determine the subset of receivers based on the required signal gain such that the total required signal gain of the determined subset of receivers does not exceed the characteristics of the DCS (104).

4. The DCS controller (102) according to claim 1, 2 or 3, wherein, the DCS controller (102) is further configured to determine that the total required signal gain of the determined subset of receivers does not exceed the characteristics of the DCS (104) by determining that the total surface of the subset of scattering elements does not exceed the scattering surface of the DCS (104).

5. The DCS controller (102) according to claim 4, wherein, the DCS controller (102) is further configured to determine the subset of receivers based on a Lagrangian optimization solution that maximizes a system metric subject to constraints on the available resources on the DCS (104).

6. The DCS controller (102) according to claim 5, wherein, the system metric is based on the number of users served by the DCS (104).

7. The DCS controller (102) according to claim 6, wherein, The system metric is the throughput, which is the sum rate of the rates of each served user.

8. The DCS controller (102) according to claim 5, 6 or 7, wherein, The DCS controller (102) is further configured to determine the receiver subset based on the Lagrangian optimization by: determining an optimal constant based on the required signal-to-noise ratio (SNR) values of the two or more receivers, and solving the Lagrangian optimization by moving the optimal constant μ * , until the total surface of the subset of the scattering elements reaches the surface of the DCS (104).

9. The DCS controller (102) according to any one of the preceding claims, wherein, The DCS controller (102) is further configured to determine the multi - user codeword based on the subset of scattering elements by: determining the reflection elements of the DCS (104) and the corresponding phase shifts of each subset of the subset, and aggregating these reflection elements and corresponding phase shifts into the multi - user codeword.

10. The DCS controller (102) according to any one of the preceding claims, wherein, The DCS controller (102) is further configured to determine a scattering pattern focused on the receiver, the scattering pattern corresponding to a reflection pattern from a perfect electric conductor having the shape of an ellipsoid (302), the ellipsoid (302) having a first focus at the position of the transmitter (304) and a second focus at the position of the receiver (306), wherein the single - user codeword is determined based on the scattering pattern.

11. The DCS controller (102) according to claim 10, wherein, The DCS controller (102) is further configured to determine the set of scattering elements for the receiver (306) by: determining a first plane (402) that contains the major axis of the ellipsoid (302) and intersects the ellipsoid (302); determining a first intersection line (406) as the line of intersection of the first plane (402) and the surface of the DCS (104); determining a second plane (404) that contains the major axis of the ellipsoid (302) and intersects the ellipsoid (302); determining a second intersection line (408) as the line of intersection of the second plane (404) and the surface of the DCS (104); determining the set of scattering elements of the receiver (306) as a portion of the surface of the DCS (104) between the first intersection line (406) and the second intersection line (408).

12. The DCS controller (102) according to claim 11, wherein, The DCS controller (102) is further configured to translate at least one of the first intersection line (406) and the second intersection line (408) to provide a higher required gain to the receiver (306).

13. The DCS controller (102) according to claim 10, 11 or 12, wherein, The DCS controller (102) is further configured to configure the scattering elements of the DCS (104) according to the following equation: wherein, Tx is the position of the transmitter (304), Rx i is the position of the receiver i(306), M is the position of the scattering element on the surface of the DCS (104), V is a point on the ellipsoid (302), where the line between M and Rx i intersects the ellipsoid (302). is the phase shift applied by the DCS (104) at point M, δ m is the path difference between the path through the DCS (104) at point M and the path through the ellipsoidal PEC seen at the receiver (306) from the same point M. λ is the wavelength of the transmitted signal.

14. The DCS controller (102) according to any one of the preceding claims, wherein, The DCS controller (102) is configured to select at least one single-user codeword from the stored single-user codewords.

15. The DCS controller (102) according to any one of the preceding claims, wherein, the DCS controller (102) is configured to construct at least one single-user codeword among the single-user codewords.

16. The DCS controller (102) according to any one of the preceding claims, wherein, the DCS controller (102) is further configured to determine the subset of receivers by receiving scheduling information indicating which receivers are scheduled to be activated, and to determine the required signal gain of only the receivers scheduled to be activated.

17. The DCS controller (102) according to any one of the preceding claims, wherein, the DCS controller (102) is further configured to determine the subset of receivers by receiving scheduling information indicating which receivers are scheduled to be prioritized, and to determine the subset of receivers to include the prioritized receivers.

18. The DCS controller (102) according to any one of the preceding claims, wherein, the DCS (104) includes scattering elements, and the DCS controller (102) is further configured to determine the multi-user codeword based on the subset of scattering elements by: assigning phase shifts specified by their corresponding single-user codewords to the scattering elements of each subset of scattering elements, and aggregating these scattering elements and the corresponding phase shifts of all subsets of scattering elements into the multi-user codeword.

19. The DCS controller (102) according to any one of the preceding claims, wherein, the subset of scattering elements on the surface of the DCS (104) for the receiver (306) consists of consecutive scattering elements.

20. The DCS controller (102) according to any one of the preceding claims, wherein, the subset of scattering elements on the surface of the DCS (104) for the receiver is defined by a strip having a first angle between two principal cutting planes and a second angle representing the opening of the strip calculated (or defined) at the center of the ellipsoid (302), wherein the first angle and the second angle are determined to achieve the gain of the corresponding subset, and the width of the strip reflects the beamwidth to be used by the transmitter (304).

21. The DCS controller (102) according to any one of claims 1 to 20, wherein, the subset of scattering elements on the surface of the DCS (104) for the receiver consists of non-consecutive scattering elements.

22. The DCS controller (102) according to claim 20 or 21, further comprising a beamformer for the transmitter (304) that focuses towards the strip identified for the receiver (306).

23. The DCS controller (102) according to any one of the preceding claims, wherein, the DCS controller (102) is included in the DCS (104).

24. The DCS controller (102) according to any one of claims 1 to 22, wherein, The DCS controller (102) is included in a base station.

25. The DCS controller (102) according to any one of claims 1 to 22, wherein, the DCS controller (102) is included in a stand-alone device.

26. A method (1100) for use in a DCS controller (102), wherein, the DCS controller (102) is configured to control a DCS (104) to serve a subset of a plurality of receivers (112) simultaneously, the plurality of receivers (112) including at least a first receiver (112A) and a second receiver (112B) located at different positions, wherein the DCS (104) includes a plurality of scattering elements (106) arranged on a scattering surface (108), and the method (1100) includes: ● determining a single-user codeword for each of the plurality of receivers (112), wherein the single-user codeword defines a phase configuration for a set of scattering elements of the scattering surface (108) of the DCS (104) for the corresponding receiver and defines a respective phase shift configuration for each scattering element in the set of scattering elements; ● determining a required signal gain for each of the plurality of receivers (112); ● determining a subset of receivers based on the required signal gain, wherein a total required signal gain of the determined subset of receivers does not exceed the characteristics of the DCS (104); ● determining a subset of scattering elements for each receiver in the subset of receivers, wherein, ■ determining the subset for the receiver to meet the required signal gain of the receiver, ■ the subsets are disjoint; ● determining a multi-user codeword based on the subset of scattering elements, wherein the multi-user codeword defines all subsets of scattering elements of the scattering surface (108) of the DCS (104); ● controlling the DCS (104) to perform data transmission based on the multi-user codeword.

27. A computer program product comprising program instructions for performing the method (1100) according to claim 26 when executed by one or more processors in a DCS controller (102).

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