WO2023117050A1

WO2023117050A1 - Communication arrangement including digitally controlled scatteres, method and computer program for the operation thereof

Info

Publication number: WO2023117050A1
Application number: PCT/EP2021/086925
Authority: WO
Inventors: Mustapha Amara; Melissa DUARTE GELVEZ; Mohamed Kamoun; Maxime Guillaud
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2021-12-21
Filing date: 2021-12-21
Publication date: 2023-06-29
Also published as: CN118435527A; EP4445505A1

Abstract

A communication arrangement and a method for the operation thereof are provided. The communication arrangement includes a plurality of digitally controllable scatterers, DCSs, group construction circuitry, DCS coupling quantity calculation circuitry, group selection circuitry and DCS control circuitry. Each DCS is configured to provide one or more phase shift patterns for electromagnetic radiation reflected thereon. The group construction circuitry is configured to construct, for a plurality of communication nodes, CNs, a set of groups of CNs. Each group of CNs is associated with a respective phase shift pattern of a respective DCS of the plurality of DCSs. Each group of CNs includes one or more CNs that are co-schedulable on a communication channel that is formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group. The DCS coupling quantity calculation circuitry is configured to calculate one or more DCS coupling quantities. Each DCS coupling quantity is indicative of an interference level between at least two communication channels via at least two DCSs of the plurality of DCSs. The group selection circuitry is configured to select, for a first CN, a first group of CNs that includes the first CN and to select, for a second CN, a second group of CNs that includes the second CN. At least the second group of CNs is selected on the basis of the one or more DCS coupling quantities and the selected first group of CNs. The DCS control circuitry is configured to operate each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs to provide the phase shift pattern associated with the respective group of CNs.

Description

COMMUNICATION ARRANGEMENT INCLUDING DIGITALLY CONTROLLED SCATTERES, METHOD AND COMPUTER PROGRAM FOR THE OPERATION THEREOF

TECHNICAL FIELD

This application relates to the technical field of communication arrangements, more specifically to communication arrangements including digitally controllable scatterers, and to methods and computer programs for the operation thereof.

BACKGROUND

In the technical field of radio communication, a capacity of a radio channel between communication nodes (CNs) can be improved by providing multiple antennas in some or all of the communication nodes. Such techniques are denoted as Multiple-Input and Multiple-Output (MIMO) technologies. A CN can be, for example, a Base Station (BS) or a User Equipment (UE). MIMO technologies allow to exploit a spatial diversity of the propagation channel of electromagnetic waves for improving channel capacity compared to Single-Input Single-Output (SISO) techniques wherein a single antenna is provided at each communication node.

For further improving radio communication, it has been proposed to move from solutions where channel diversity that occurs due to the propagation of electromagnetic waves in the environment of the communication nodes is exploited to solutions where the propagation channel can be manipulated and adapted to specific needs. This can be done by introducing programmable surfaces called Digitally Controllable Scatterers (DCS), wherein a large number of reflective or scattering elements is provided on large surfaces. DCSs can, for example, be implemented in the form of so-called Reflective Intelligent Surfaces (RIS), Intelligent Reflective Surfaces (IRS) or Large Intelligent Surfaces (LIS). The reflection phase shift of each element composing the surface can be controlled on its own. This enables shaping the propagation channel by adapting to the requirement and the environment.

Fig. 1 schematically illustrates a DCS 100, a CN 101 and a CN102. The CN 101 can, for example, be a BS, and the CN 102 can, for example, be a UE communicating with the BS. The DCS 100 includes a plurality of scattering elements 103, one of which is exemplarily denoted by reference numeral 104. The scattering elements 103 are adapted such that incident electromagnetic radiation, in particular electromagnetic radiation in a particular frequency range that is used for radio communication is reflected with a phase shift that can be electronically controlled. Examples of scattering elements include antennas connected to phase shifting circuitry and meta-materials.

In Fig. 1, electromagnetic radiation emitted by the CN 101 is schematically illustrated by dotted arrows. Electromagnetic radiation from the CN 101 that is reflected by the DCS 100 towards the CN 102 is schematically illustrated by dashed arrows. The reflection of electromagnetic radiation at the DCS 100 contributes to a communication channel from the CN 101 to the CN 102. The overall communication channel can be decomposed into two main components, which are the non-DCS channel 106, wherein electromagnetic radiation propagates from the CN 101 to the CN 102 without reflection at the DCS 100 and the DCS channel 105. The DCS channel 105 consists of two components: the channel between the DCS 100 and the CN 101, and the channel between the DCS 100 and the CN 102.

By appropriately selecting the reflection phase shifts for the DCS 100, the communication between the CNs 101 and 102 can be improved. Thus, for example, a higher signal to noise ratio and/or a higher rate of data transmission between the CNs 101, 102 can be obtained. Additionally, there can be situations wherein the non-DCS channel 106 is not available which can, for example, be the case when the line of sight between the CNs 101, 102 is blocked by a large building. In such situations, the DCS channel 105 can still be available, so that communication between the CNs 101, 102 via the DCS is still possible.

In communication arrangements, user scheduling is performed for organizing the communication between the CNs. Techniques for user scheduling in environments with various configurations and constraints, but without DCSs are known. However, user scheduling in communication environments where one or more DCSs are present can have issues associated therewith. For example, if the reflection phase shifts of the scattering elements of a DCS are controlled so that electromagnetic radiation from the BS is reflected to a first UE for improving the communication between the BS and the first UE, it may not be possible to simultaneously use the DCS for reflecting electromagnetic radiation from the BS to a second UE, in particular when, seen from the DCS, the second UE is in a different direction than the first UE. Additionally, there can be a cross-interference between electromagnetic radiation from the BS reflected to a UE via a first DCS and electromagnetic radiation from the BS reflected to the UE via a second DCS, which can substantially reduce the signal-to-noise ratio.

Previous approaches have dealt with scheduling in a single DCS scenario, and there are theoretical works that try to assess theoretical limits in terms of capacity bounds. The latter are done through theoretical analysis of a physical layer involving several DCS and UEs with no scheduling constraints. The approach relies on formulating mixed-integer linear programming (MILP) problems that are solved theoretically or through heuristics in order to evaluate theoretical bounds. MILP problems are difficult to solve, since they are NP -complete. Hence, what is missing are techniques which address the above- mentioned issues in a practical manner and allow to enhance the overall data throughput of the system.

SUMMARY

The present disclosure provides communication arrangements, methods and computer programs which help to address some or all of the above-mentioned issues.

According to an aspect, a communication arrangement includes a plurality of digitally controllable scatterers, DCSs, group construction circuitry, DCS coupling quantity calculation circuitry, group selection circuitry and DCS control circuitry. Each DCS is configured to provide one or more phase shift patterns of the respective DCS for electromagnetic radiation reflected thereon. The group construction circuitry is configured to construct, for a plurality of communication nodes, CNs, a set of groups of CNs. Each group of CNs is associated with a respective phase shift pattern of a respective DCS of the plurality of DCSs. Each group of CNs includes one or more CNs of the plurality of CNs that are co-schedulable on a communication channel that is formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group. The DCS coupling quantity calculation circuitry is configured to calculate one or more DCS coupling quantities. Each DCS coupling quantity of the plurality of DCS coupling quantities is indicative of an interference level between at least two communication channels via at least two DCSs of the plurality of DCSs. The group selection circuitry is configured to select, for a first CN of the plurality of CNs, a first group of CNs from the plurality of groups of CNs that includes the first CN and to select, for a second CN of the plurality of CNs, a second group of CNs from the plurality of groups of CNs that includes the second CN. At least the second group of CNs is selected on the basis of the one or more DCS coupling quantities and the selected first group of CNs. The DCS control circuitry is configured to operate each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs to provide the phase shift pattern associated with the respective group of CNs.

In a possible implementation, the communication arrangement further includes scheduling circuitry configured to co-schedule a communication of the first CN and the second CN while each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs provides the phase shift pattern associated with the respective group of CNs. The first CN communicates via the DCS associated with the first group of CNs. The second CN communicates via the DCS associated with the second group of CNs.

In a possible implementation, one of the first group of CNs and the second group of CNs additionally includes at least one third CN of the plurality of CNs. The scheduling circuitry is configured to coschedule the at least one third CN on the communication channel via the DCS associated with the one of the first group of CNs and the second group of CNs.

In a possible implementation, the other of the first group of CNs and the second group of CNs additionally includes at least one fourth CN of the plurality of CNs. The scheduling circuitry is configured to co-schedule the at least one fourth CN on the communication channel via the DCS associated with the other of the first group of CNs and the second group of CNs.

In a possible implementation, the group selection circuitry is configured to receive a first list defining a subset of the plurality of CNs that includes the first CN and the second CN and an associated priority of each CN of the subset of the plurality of CNs. In a possible implementation, the first CN has a higher priority than the second CN. The group selection circuitry is configured to select the second group of CNs from a subset of the set of groups of CNs that are not associated with a combination of the DCS associated with the first group of CNs and any phase shift pattern of the DCS associated with the first group of CNs that is different from the phase shift pattern associated with the first group of CNs.

In a possible implementation, the group selection circuitry is configured to process the CNs of the subset of the plurality of CNs defined by the first list in an order of decreasing priority. The group selection circuitry selects, for each CN of the subset of the plurality of CNs defined by the first list, a respective group of CNs from the set of groups of CNs that is not associated with a combination of a DCS associated with an already selected group of CNs that was selected for a CN of the subset of the plurality of CNs defined by the first list having a higher priority and any phase shift pattern of the DCS associated with the already selected group of CNs that is different from the phase shift pattern associated with the already selected group of CNs. The selection is performed on the basis of the one or more DCS coupling quantities.

In a possible implementation, the group selection circuitry is configured to provide to the scheduling circuitry a second list including one of more CNs from the selected groups of CNs that are not part of the subset of the plurality of CNs defined by the first list.

In a possible implementation, the scheduling circuitry is configured to provide an updated first list to at least the group selection circuitry. The updated first list is based on the first list and the second list. The group selection circuitry is configured to provide an updated second list on the basis of the updated first list.

In a possible implementation, the group construction circuitry is configured to obtain, for the plurality of CNs and for at least a part of the phase shift patterns of at least a part of the plurality of DCSs, a plurality of channel correlation quantities. Each channel correlation quantity is representative of a correlation between a respective pair of the communication channels for the plurality of CNs that are formed via the DCSs of the at least a part of the plurality of DCSs when the DCSs provide the at least a part of the phase shift patterns and to which the plurality of CNs are connectable. Additionally, the group construction circuitry is configured to construct the set of groups of CNs on the basis of the channel correlation quantities.

In a possible implementation, the group construction circuitry is configured to construct the set of groups of CNs by including, into each group of CNs, one or more CNs of the plurality of CNs that are selected such that, for each pair of the communication channels that are formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group and to which the selected CNs are connectable, the respective channel correlation quantity is greater than a predetermined threshold value.

In a possible implementation, the group construction circuitry is configured to obtain, for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCS, a channel estimate matrix for each CN of the plurality of CNs and to determine a respective channel correlation quantity on the basis of each pair of the determined channel estimate matrices.

In a possible implementation, the group construction circuitry is configured to determine, for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCSs, a respective coverage area, to obtain, for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCS, a channel estimate matrix for those CNs of the plurality of CNs that are in the coverage area of the respective phase shift pattern of the respective DCS, and to determine a respective channel correlation quantity on the basis of each pair of the determined channel estimate matrices.

In a possible implementation, the group construction circuitry is configured to determine the respective coverage area for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCSs on the basis of a position of a base station, a respective position of each DCS of at least a part of the plurality of DCSs and a respective reflection pattern associated with each phase shift pattern of the at least a part of the phase shift patterns of the at least a part of the plurality of DCSs.

In a possible implementation, the group construction circuitry is configured to calculate, for each pair of the determined channel estimate matrices, the respective channel correlation quantity on the basis of at least one of a sum of singular values of the pair of channel estimate matrices, a common subspace of the pair of channel estimate matrices and a rank of the common subspace of the pair of channel estimate matrices.

In a possible implementation, the DCS coupling quantity calculation circuitry is configured to calculate a respective DCS coupling quantity for each pair of phase shift patterns of the phase shift patterns of the plurality of DCSs.

In a possible implementation, the group selection circuitry is configured to provide a decision tree that defines, for each group of CNs of the set of groups of CNs, a set of co-schedulable groups of CNs. The set of co-schedulable groups of CNs includes groups of CNs associated with a phase shift pattern of one of the plurality of DCSs for which the DCS coupling quantity with the phase shift pattern of the DCS associated with the respective group of CNs is less than a predetermined threshold value.

In a possible implementation, the group selection circuitry is configured to select the second group of CNs from the set of co-schedulable groups of CNs for the first group of CNs. In a possible implementation, the group selection circuitry is configured to obtain, from the DCS coupling quantity calculation circuitry, a respective DCS coupling quantity for a plurality of pairs of phase shift patterns of the plurality of DCSs that include the phase shift pattern of the DCS associated with the first group of CNs, to construct a set of co-schedulable groups of CNs that is restricted to groups of CNs associated with a phase shift pattern of one of the plurality of DCSs for which the DCS coupling quantity with the phase shift pattern of the DCS associated with the first group of CNs is less than a predetermined threshold value, and to select the second group of CNs on the basis of the set of co- schedulable groups of CNs.

In a possible implementation, the DCS coupling quantity calculation circuitry is configured to perform the calculation of the DCS coupling quantity for each pair of phase shift patterns of the plurality of DCSs on the basis of a coverage area of a first phase shift pattern of a first DCS of the pair and a coverage area of a second phase shift pattern of a second DCS of the pair.

In a possible implementation, the DCS coupling quantity calculation circuitry is configured to perform the calculation of the DCS coupling quantity for each pair of phase shift patterns of the plurality of DCSs on the basis of a radiation pattern of a first phase shift pattern of a first DCS of the pair and a radiation pattern of a second phase shift pattern of a second DCS of the pair.

In a possible implementation, the DCS coupling quantity calculation circuitry is configured to perform the calculation of the DCS coupling quantity for each pair of phase shift patterns of the plurality of DCSs on the basis of an average energy that is captured by the CNs of a group of CNs from the set of groups of CNs that is associated with a first phase shift pattern of a first DCS of the pair from a communication channel that is formed via a second DCS of the pair when the second DCS of the pair provides a second phase shift pattern of the second DCS of the pair.

In a possible implementation, the communication arrangement further includes circuitry for calculating an overall channel estimate matrix for each of the plurality of CNs and each phase shift pattern of each DCS of the plurality of DCSs. The group construction circuitry is configured to construct the set of groups of CNs on the basis of the overall channel estimate matrix. The DCS coupling quantity calculation circuitry is configured to calculate the one or more DCS coupling quantities on the basis of the overall channel estimate matrix.

According to a second aspect, a method is provided wherein a set of groups of communication nodes, CNs, is constructed for a plurality of CNs. Each group of CNs is associated with a respective phase shift pattern of a respective digitally controllable scatterer, DCS of a plurality of DCSs. Each group of CNs includes one or more CNs of the plurality of CNs that are co-schedulable on a communication channel that is formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group. One or more DCS coupling quantities are calculated. Each DCS coupling quantity of the plurality of DCS coupling quantities is indicative of an interference level between at least two communication channels via at least two DCSs of the plurality of DCSs. For a first CN of the plurality of CNs, a first group of CNs that includes the first CN is selected from the plurality of groups of CNs. For a second CN of the plurality of CNs, a second group of CNs that includes the second CN is selected from the plurality of groups of CNs. The second group of CNs is selected on the basis of the plurality of DCS coupling quantities and the first group of CNs. Each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs is operated to provide the phase shift pattern associated with the respective group of CNs.

According to a third aspect, a computer program includes instructions which, when carried out on a computer, cause the computer to perform a method according to the second aspect.

BRIEF DESCRIPTION OF DRAWINGS

In the following, embodiments will be described with reference to the drawings, wherein:

Fig. 1 shows communication channels in an arrangement including a DCS and two CNs;

Figs. 2a, 2b and 2c show a communication arrangement;

Fig. 3 shows a BS;

Fig. 4 shows a DCS;

Figs. 5a to 5d show configurations of scattering surfaces of DCSs;

Fig. 6 shows input/output exchanges performed in embodiments;

Fig. 7 shows input/output exchanges performed in embodiments;

Fig. 8 shows a structure of an overall coupling matrix;

Fig. 9 shows an exchange of signals in a method of communication; and

Fig. 10 shows an exchange of signals in another method of communication.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described with reference to the Figures.

Figs. 2a, 2b and 2c show schematic views of a communication arrangement 200 according to an embodiment. The communication arrangement 200 includes a plurality of DCSs 201-205 and a plurality of communication nodes (CNs) 206-218. As shown in Figs. 2a, 2b and 2c, the CNs 206 to 217 can be user equipments (UEs), and the CN 218 can be a base station (BS). The UEs 206-217 can be mobile equipments of various types such as, for example, mobile phones, tablet or laptop computers, or wearable devices.

The present disclosure is not limited to embodiments where a single BS is provided, as shown in Figs. 2a, 2b and 2c. In other embodiments, a plurality of BSs can be provided. Thus, there is at least one BS. Furthermore, the number of UEs need not be 12, and the number of DCSs need not be 5, as shown in Figs. 2a, 2b and 2c. Generally, there can be K UEs and D DCSs that are spread over an area of interest which can, for example, be an area covered by the BS 218. In further embodiments, CNs other than UEs can be provided instead of some or all of the UEs 206-217.

Fig. 3 shows a schematic block diagram of a configuration of the BS 218 according to an embodiment. The BS 218 can include antennas 301, 302. The number of antennas can be two, as shown in Fig. 3. In other embodiments, a greater number of antennas can be provided. Providing two or more antennas can allow performing communication in accordance with MIMO technologies. In further embodiments, a single antenna can be provided.

The BS 218 can include transmitter circuitry 303 and receiver circuitry 304, which are connected to the antennas 301, 302, and can be used for transmitting and/or receiving signals for transmitting and/or receiving various types of information, and/or signals that can be used for channel estimation such as, for example, pilot signals. Additionally, the BS 218 can include computation circuitry 305, which can include a processor and memory. The computation circuitry 305 can be used for carrying out various algorithms, as will be described below. Thus, the computation circuitry 305 can be used for performing various types of data processing at the BS 218 so that the computation circuitry 305 can be configured so as to include circuitry for various purposes. In particular, the computation circuitry 305 can include scheduling circuitry 306 and physical layer circuitry 307. The scheduling circuitry 306 and the physical layer circuitry 307 can handle different layers of a communication model, wherein the scheduling circuitry 306 provides a higher layer than the physical layer circuitry 307. The physical layer circuitry 307 can include group construction circuitry 308, DCS coupling quantity calculation circuitry 309, group selection circuitry 310 and DCS control circuitry 311. Optionally, in some embodiments, the physical layer circuitry 307 can also include circuitry 312 for calculating an overall channel estimate matrix. The group construction circuitry 308, the DCS coupling quantity calculation circuitry 309, the group selection circuitry 310, the DCS control circuitry 311 and the circuitry 312 for calculating an overall channel estimate matrix will be described in more detail below.

Fig. 4 schematically illustrates a configuration of the DCS 201 according to an embodiment. The DCS 201 can be implemented in the form of an Intelligent Reflective Surface (IRS) or Reflective Intelligent Surface (RIS). In embodiments, some or all of the other DCSs 202-205 of the communication arrangement 200 shown in Figs. 2a, 2b and 2c can have features corresponding to those of the DCS 201. The DCS 201 includes a scatering surface 401 and a controller 402. The scatering surface 401 includes a plurality of scatering elements 406, one of which is exemplarily denoted by reference numeral 407. The plurality of scatering elements 406 can be adapted such that reflection phase shifts of the scatering elements 406 for electromagnetic radiation are electronically controllable.

In some embodiments, each of the scatering elements 406 can include an antenna and phase shifting circuitry. The phase shift provided by the phase shifting circuitry can be electronically controlled so as to provide the reflection phase shift of the scatering element. In other embodiments, the scatering elements can include meta-material elements configured to provide a reflection phase shift for electromagnetic radiation in the predetermined frequency range that can be electronically controlled. By controlling the reflection phase shifts of the scatering elements 406, directions into which electromagnetic radiation impinging on the scatering surface 401 of the DCS is scatered can be controlled.

The reflection phase shift patern provided by the scatering elements 406 of the DCS 201 can be represented by phase shift matrix Φ . In a communication arrangement such as the communication arrangement 200 shown in Figs. 2a, 2b and 2c that includes D DCSs, an index d can be used for denoting the individual DCSs. For example, the DCSs 201, 202, 203, 204, 205 can be denoted by indices d = 1, d = 2, d = 3, d = 4 and d = 5, respectively. Each DCS d can be configured with a phase shift patern represented by a phase shift matrix that generates a space and frequency filter denoted as

where I is an index denoting a selected phase shift patern in a set of potential L_d phase shift patterns for DCS d. Controlling the configuration of the scatering elements of each of a plurality of DCSs in accordance with a respective phase shift patern will also be denoted as “channel programming” herein.

The DCS 201 can further include a controller 402. The controller 402 can include interface circuitry 403 for connecting the controller 403 to the scatering elements 406 of the DCS 201, and computation circuitry 404, which can include a processor and a memory so that the computation circuitry 404 can be configured as circuitry for various purposes. In particular, the computation circuitry 404 can include circuitry 405 for controlling the reflection phase shifts of the scatering elements 406.

The present disclosure is not limited to embodiments wherein each of the DCSs 201, 202, 203 has a scatering surface 401 that is substantially planar, as shown in Fig. 4. In other embodiments, some or all of the DCSs can include scatering surfaces having a non-planar configuration, as will be described in the following with reference to Figs. 5a, 5b and 5c.

Fig. 5a schematically illustrates a scatering surface 501a, which can be used as an alternative to the scatering surface 401 of the DCS 201 shown in Fig. 4. The scatering surface 501a includes a plurality of scatering elements 406, one of which is exemplarily denoted by reference numeral 407. The scatering surface 501a has a non-planar configuration, wherein a front side of the scatering surface 501a is convex. The front side of the scattering surface 501a is the side on which, in the operation of the DCS 201, the electromagnetic radiation reflected at the scattering surface 501a impinges. For example, in embodiments, the scattering surface 501a can be mounted on a wall of a building. In such embodiments, the front side of the scattering surface 501a is the side of the scattering surface that is averted from the wall.

Fig. 5b schematically illustrates a scattering surface 501b, which can be used as another alternative to the scattering surface 401 of the DCS 201 shown in Fig. 4. The scattering surface 501b includes a plurality of scattering elements 406, one of which is exemplarily denoted by reference numeral 407. The scattering surface 501b has a non-planar configuration, wherein the front side of the scattering surface 501b is concave.

Fig. 5c schematically illustrates a scattering surface 501c, which can be used as a further alternative to the scattering surface 401 of the DCS 201 shown in Fig. 4. The scattering surface 501c includes a plurality of scattering elements 406, one of which is exemplarily denoted by reference numeral 407. The scattering surface 501c has a non-planar configuration, wherein the front side of the scattering surface 501c includes portions having a different curvature. For example, the front side of the scattering surface 501c can include convex portions, concave portions and/or saddle-shaped portions.

Moreover, the present disclosure is not limited to embodiments wherein the scattering surface of the DCS 201 is provided in a single piece. Fig. 5d schematically illustrates a scattering surface 50 Id, which can be used as a further alternative to the scattering surface 401 of the DCS 201 shown in Fig. 4. The scattering surface 501d includes a plurality of DCS blocks 502, 503, 504, 505, which can be distributed. Thus, the scattering surface 501d is not provided as a single piece. The scattering surface 501d includes a plurality of scattering elements, wherein each of the DCS blocks 502-505 includes a subset of the scattering elements. The DCS blocks 502-505 can have a non-planar configuration, as shown in Fig. 5d. In other implementations, some or all of the DCS blocks 502-505 can be planar. The scattering elements of the DCS blocks 502-505 can be operated in a coordinated manner, so that the scattering surface 501d is provided as a virtual DCS scattering surface.

Reference is made to Figs. 2a, 2b and 2c again. In Fig. 2a, DCS channels created by a reflection of signals from the BS 218 at the DCSs 201-205 for a particular configuration of the respective phase shift patterns of the DCSs are schematically illustrated by arrows. As shown, for example, by reflecting signals from the BS 218 at the DCSs 201, 202 and/or 203 towards the UE 215, DCS communication channels between the BS 218 and the UE 215 can be provided. Thus, the UE 215 can be served, even if it is totally hidden in a dead spot of the BS 218, for example due to a building arranged in the line of sight between the BS 218 and the UE 215. Similar DCS communication channels can also be provided for other UEs and/or other DCSs. Additionally, in Fig. 2a, a non-DCS channel between the BS 218 and the UE 208 is schematically illustrated by an arrow between the BS 218 and the UE 208. Similar non- DCS channels can also exist for other UEs.

Fig. 2b illustrates the impact of channel programming on the UEs that can be served in the communication arrangement 200. For example, by providing a phase shift pattern in accordance with an optimized selected phase shift matrix for DCS 201 (the lower index 1 denoting DCS 201 and the

upper index 1 denoting a first phase shift pattern of DCS 201) a subset of UEs such as, for example, UE 215 can be served by the scattered beam that is generated when the electromagnetic radiation from the BS 218 is reflected at the DCS 201, whereas other UEs such as, for example, UE 216 can be rendered totally inaccessible. On the other hand, adapting the DCS 201 for serving UE 216, for example by providing a phase shift pattern in accordance with phase shift matrix can make it impossible to serve

UE 215. These constraints can be crucial and should be taken into account in the scheduling.

Fig. 2c depicts another issue occurring when multiple DCSs are used, namely inter-DCS interference. While adapting the phases for two non-collocated DCS panels, for each of the DCSs the best phase shift pattern for serving a respective target UE might be chosen. This might be, for example for the DCS

201 in order to serve UE 215 and for DCS 202 in order to serve UE 217. In doing so, the radiation

pattern of the DCS 202 can overlap with the one generated by the DCS 201, thus generating interference at UE 215 which can lead to a drastic drop of its signal-to-noise ratio (SNR). This might even result in severing the communication link. In this situation, scheduling the two UEs 215 and 217 at the same time can become impossible, although two independent DCSs 201, 202 are used.

In addition to the two issues described above with reference to Figs. 2b and 2c, allocating the resources so as to optimize DCS configurations for serving a set of scheduled UEs can drastically consume resources while limiting service to the set of scheduled UEs.

Embodiments described herein provide tools for opportunistic extra UEs scheduling while avoiding the problems of cross DCS interference and selecting the optimal phase shifts for each of a plurality DCSs in order to achieve minimal scheduling goals. This can effectively result in more UEs being served on the unused resources and in a more effective utilization of the available resources without degrading the serving of the initially targeted UEs, so that the overall throughput of the system can be enhanced.

In embodiments disclosed herein, extra UEs can be co-scheduled and served on the same generated resources, wherein the term “resource” is used to denote the time/frequency slots commonly called resource blocks (RBs) in communication systems, as well as spatial beams. The extra UEs are selected on the basis of a set of groups of UEs that are constructed based on potentially available communication channels which are created through configuring the various available DCSs. From the set of groups of UEs, the most appropriate groups are selected in order to fulfill scheduling constraints. Procedures according to embodiments disclosed herein define the phase shift patterns of the various DCSs, program the communication channels to optimally serve the required UEs and provide a list of extra UEs that can be opportunistically served on the same resources.

Fig. 6 illustrates an overview over various input/output (I/O) exchanges performed in embodiments described herein.

At steps 601 to 604 various inputs are provided. Steps 601 to 604 do not need to be performed in a particular order. Furthermore, steps 601 to 604 do not need to be performed separately. In embodiments, some or all of steps 601 to 604 can be performed together by simultaneously providing data relating to the some or all of steps 601 to 604. At step 601, a list of UEs that need to be scheduled is provided as input. These UEs need to be served during a next timeslot. The list of UEs can be provided by a scheduler such as, for example, the scheduling circuitry 306 of the BS 218 illustrated in Fig. 3. The UEs of the list can be selected by the scheduler in accordance with known techniques, for example based on a metric.

At step 602, partial or fully acquired channel state information (CSI) is provided as input, which can be used for group construction, for example by the group construction circuitry 308 of the BS 218 illustrated in Fig. 3.

At step 603, knowledge about cross-interference between DCSs such as, for example, coverage areas and/or radiation patterns associated with particular phase shift patterns of the DCSs can be provided as input, which can be used for calculating DCS coupling quantities, for example by the DCS coupling quantity calculation circuitry 309 of the BS 218 illustrated in Fig. 3. Step 603 is optional. In embodiments without step 603, the DCS coupling quantities can be calculated on the basis of the CSI provided at step 602.

At step 604, scheduling constraints are provided as input. The scheduling constraints can include, for example, a respective priority of each UE and, optionally, data transmission rate constraints, and can be used for group selection, for example by the group selection circuitry 310 of the BS 218 shown in Fig. 3. In embodiments, the scheduling constraints can be provided in form of a list that defines, for each of the UEs to be scheduled, an associated priority. This list needs not be provided separately from the list provided at step 601. In some embodiments, a single list defining the UEs to be scheduled and an associated priority can be provided by the scheduler.

At step 605, various types of processing are performed, for example by the group construction circuitry 308, the DCS coupling quantity calculation circuitry 309 and the group selection circuitry 310 of the BS 218 shown in Fig. 3. In particular, the group construction circuitry 308 can construct, for a plurality of UEs, a set of groups of UEs. Each group of UEs is associated with a respective phase shift pattern of a respective DCS. Each group of UEs includes one or more UEs that are co-schedulable on a communication channel that is formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group.

Then, the DCS coupling quantity calculation circuitry 309 can calculate one or more DCS coupling quantities. Each DCS coupling quantity of the plurality of DCS coupling quantities is indicative of an interference level between at least two communication channels via at least two DCSs. In some embodiments, a respective DCS coupling quantity can be calculated for each pair of phase shift patterns of the phase shift patterns of the DCSs.

Then, the group selection circuitry can select, for a first UE of the list of UEs to be scheduled that was provided at step 601, a first group of UEs that includes the first UE. Then, it can select, for a second UE of the list of UEs to be scheduled, a second group of UEs that includes the second UE. At least the second group of UEs is selected on the basis of the one or more DCS coupling quantities and the selected first group of UEs. By selecting the second group of UEs on the basis of DCS coupling quantities, interference levels between electromagnetic radiations that are reflected by different DCSs can be avoided or at least minimized. By selecting the second group of UEs on the basis of the first group, constraints can be considered. For example, since a DCS cannot apply two different phase shift patterns at the same time, the second group can be selected so that it is not associated with the same DCS and a different phase shift pattern as the first group. Thereafter, a selection of respective groups for further UEs from the list of UEs to be scheduled that was provided at step 601 can be performed. In embodiments, the selection of groups for the UEs from the list of UEs to be scheduled can be performed in an order of decreasing priority of UEs.

At step 606, as an output of the processing, an exhaustive list of UEs that can be co-scheduled is provided and the resources used for serving them are specified. Co-scheduled UEs are UEs that share one or more resources, like for example a time resource or a frequency resource, or both. For the co-scheduled UEs, a definition containing additional information such as their respective DCS association and their respective DCS phase shift pattern configuration can be provided at step 606. The co-scheduled UEs can be UEs that are included in the groups of UEs that were selected for the UEs of the list of UEs to be scheduled that was provided at step 601, but which are not included in the list of UEs to be scheduled. For example, if the first group of UEs that is selected for the first UE includes a third UE that was not included in the list of UEs to be scheduled, the third UE can be co-scheduled on a communication channel via the DCS associated with the first group of UEs. Similarly, if the second group of UEs that is selected for the second UE includes a fourth UE that was not included in the list of UEs to be scheduled, the fourth UE can be co-scheduled on a communication channel via the DCS associated with the second group of UEs.

At step 607, each of the DCSs can be configured with a selected phase shift pattern, for example by the DCS control circuitry 311 of the BS 218 shown in Fig. 3. For this purpose, the DCS control circuitry 311 can send a signal to the controller 402 (see Fig. 4) of the respective DCS, which causes the circuitry 405 to control the reflection phase shifts of the scattering elements 406 of the DCS in accordance with the selected phase shift pattern of the DCS. The phase shift patterns of the DCSs are selected such that each DCS associated with a respective one of the groups selected at step 605 provides the phase shift pattern associated with the respective group.

Fig. 7 shows a more detailed overview over I/O exchanges performed in embodiments described herein, where the various functionalities in the processing block are expanded as compared to Fig. 6, and their interactions with the various I/O blocks are detailed. Similar to the embodiments described above with reference to Fig. 6, at steps 701, 702, 703, 704, various inputs are provided. Features of steps 701, 702, 703 and 704 can correspond to features of steps 601, 602, 603 and 604, respectively, and a detailed description thereof will be omitted.

As will be detailed in the following, the processing illustrated by Fig. 7 includes a succession of four main processing stages.

The first processing stage, which can be performed, for example, by the group construction circuitry 308 of the BS 218 illustrated in Fig. 3, includes step 705 of constructing per DCS and per potential DCS phase shift pattern configuration a set of groups of UEs. Each group identifies co-schedulable UEs, which are UEs that can share resources, for example a same time resource, a same frequency resource and/or a same spatial beam. The choice of UEs assigned to a group is based on selection criteria. Various criteria can be taken into consideration such as, among others, power coupling, common subspace and rank of common subspaces. In embodiments, step 705 can require only the knowledge of the CSI between the DCS and UEs (full or partial) or any other type of information that can provide an information about coupling between UEs, given a particular phase shift pattern of the DCS. At this step, only an approximate/partial CSI information is required, depending on the criteria used and the level of accuracy that is imposed by the application. In some embodiments, this CSI can even be a predicted version computed based on previous CSI updated through tracking/prediction.

The second processing stage which can be performed, for example, by the DCS coupling quantity calculation circuitry 309 of the BS 218 illustrated in Fig. 3, includes step 706 of constructing sets of DCSs with phase shift patterns such that the cross interference between the DCSs in a set is minimal. Two methods can be adopted here depending on the available inputs. In some embodiments, a totally independent approach can be adopted where the coupling between DCSs providing respective phase shift patterns is computed on the basis of estimated coverage areas or radiation patterns, respectively. These computations can then be done offline based on their relative positions and the codebooks of their phase shifts. In other embodiments, a second approach for computing the coupling between DCSs can be employed that is more UE centric and takes into account a global aggregated CSI information representing a group of UEs (based on the previously constructed groups) for a given DCS and a given selected phase shift pattern. This approach can adapt better to the actual configuration (i.e. different UEs present in the environment) but may require more online computation.

The third processing stage, which can be performed, for example, by the group selection circuitry 310 of the BS 218 illustrated in Fig. 3, can include step 707 wherein these two kinds of information, i.e. the constructed UE groups and the low interfering DCS, are combined for performing a first discrimination where sets of groups that can be co-scheduled are identified. The final decision on the selection of groups is then taken at step 708, which can also be performed by the group selection circuitry 310, and where groups that are going to be co-scheduled are identified based on a scheduling constraint where main groups of UEs are selected in order to serve the high priority UEs. This provides a set of selected groups. Additionally, a set of DCSs with associated phase shift patterns is provided for each time slot at step 709.

As an output at step 710, all selected groups and thus all UEs in those set of sets of UEs that can be coscheduled are provided. These groups contain, in addition to the main UEs required to be scheduled with their respective DCS associations, extra UEs that can be co-scheduled on the same resources. This list is fed back to a scheduler at a higher level, for example to the scheduling circuitry 306 of the BS 218 illustrated in Fig. 3, in order to serve the main UEs and to opportunistically schedule the extra UEs.

As an additional output which can be provided, for example, to the DCS control circuitry of the BS 218 illustrated in Fig. 3, at step 711 a configuration set including the phase shift patterns of all DCSs in the propagation environment is provided.

Thereafter, in some embodiments, at step 712, channel estimates can be performed for providing channel state information (CSI) for the selected UEs with the assigned and configured DCSs. For this purpose, the DCSs can be operated in accordance with the phase shift patterns provided at step 711, and the BS and the UEs can be operated for determining the CSI in accordance with conventional techniques of channel estimation such as least squares estimation and/or minimum mean square error (MMSE) estimation.

In the following, further embodiments will be described, which allow a joint optimization of the scheduling and channel programming under propagation and scheduling constraints. The embodiments include three main steps, which will be denoted as group construction step, group selection step and output step.

The group construction step which, in embodiments, can be performed by the group construction circuitry 308 of the BS described above with reference to Fig. 3 is addressed at the physical layer and provides information that can be used for co-scheduling UEs on the same physical resources, i.e., resource blocks (RBs). The group construction step therefore provides groups of UEs that can be coscheduled on communication channels over the same DCS d while configured with the same phase shift pattern . Here, I is the index denoting phase shift patterns among the set L_d of potential phase shift patterns for DCS d. The group construction step provides groups of UEs which are assigned to a

DCS d and a phase shift pattern and can have a rank . Every subset of a group is a valid group.

In the group selection step which, in embodiments can be performed by the group selection circuitry 310 of the BS 218 described above with reference to Fig. 3, a DCS scheduling plan is defined in order to assess the optimal assignment of phase shift patterns for the DCSs. The objective here is to take

into account the mutual coupling between active DCSs considering their respective phase shift pattern configurations. For taking into account the mutual coupling between the active DCSs, DCS coupling quantities which, in embodiments, can be calculated by the DCS coupling quantity calculation circuitry 309 of the BS 218 described above with reference to Fig. 3 can be used. In the group selection step, groups of UEs that can be co-scheduled at the same time with little interference are aggregated, wherein compatible groups that can be scheduled in the same time slot can be collected in tuples. Two groups and served respectively by DCS d_k and d_k, with phase shift patterns and respectively,

can be co-scheduled if the interference between them is minimal.

In the output step, a list of extra UEs that can be co-scheduled given the new state of shaped communication channels that can be provided by operating the DCSs to provide the phase shift patterns associated with the groups of UEs selected at the group selection step as well as assignments of UEs to respective DCSs is provided as a feedback. Additionally, in the output step, signals instructing each of the DCSs to provide the phase shift pattern associated with one or more selected groups to which it is assigned can be sent to the DCSs. In embodiments, this can be done by the DCS control circuitry 311 of the BS 218 described above with reference to Fig. 3. The control circuitry 402 (see Fig. 4) of each DCS can then operate the scattering elements 406 of the respective DCS in accordance with the respective phase shift pattern.

In the following, the group construction step, the group selection step and the output step will be described in more detail.

Group construction step

The group construction step can use some input data such as channel state information between the DCS and the UEs. For grouping UEs that are co-schedulable on a communication channel via a given DCS or can be served directly through the BS, channel estimate matrices for

downlink communication channels between the DCS and the various visible UEs, as well as channel estimate matrices for the non-DCS communication channels from the BS to the UEs can be

acquired or computed, and a set of overall channels can

be constructed. Here, K represents the number of UEs served by the considered BS, D represents the number of DCSs associated with it and L_d is a set of potential phase shift patterns for DCS d. The downlink communication channels can be estimated through several ways.

In some embodiments, channel estimates of a relatively low accuracy can be used for the group construction step. For this purpose, each DCSs d can be operated in accordance with multiple phase shift patterns of the set and conventional techniques of channel estimation can be

employed for determining a respective global communication channel from the BS to each UE k

when the DCS d provides the phase shift pattern I. Then, a respective estimate H_d of a communication channel between the BS and each DCS d can be computed by averaging the determined global communication channels over the UEs and phase shift patterns:

The channel estimates H_d can then be used for computing channel estimate matrices of communication channels between each DCS d providing phase shift pattern I and each UE k:

Additionally, an estimate of the non-DCS channel can be calculated by averaging out the contributions of the DCSs for all potential the average being performed over all phase shift patterns of all DCSs:

In other embodiments, the generated fdter F( Φ ) can be computed on the basis of the considered phase shift pattern Φ of a DCS and the channel estimate matrices for the respective DCS can be computed by means of an accurate scattering model of the DCS. Other known solutions based on a priori knowledge and channel tracking can also be applied to alleviate computational complexity. In further embodiments, techniques for channel estimation as described in International patent application No. PCT/EP2021/068936 or International patent application No. PCT/EP2021/057912, the disclosure of which is incorporated herein by reference, can be used.

Based on the input data which include the channel estimate matrices, the UEs can be clustered in accordance with a selected set of criteria. The criteria allow to identify UEs that can potentially use the same resources for communication via a given DCS with a defined phase shift pattern. In embodiments, the criteria can be channel correlation quantities such as power, rank, common subspace, energy transferred in the common space, relative common space, and any combination of all of these.

Taking into account the selected criteria and applying the acquired channel estimate matrices, a coupling matrix denoted can be constructed. The elements of the coupling matrix

can be channel correlation quantities which are representative of correlations between communication channels for the plurality of UEs that are formed via each of the DCSs when the DCSs provide the respective phase shift patterns and to which the plurality of UEs is connectable. Only half of this coupling matrix need to be computed thanks to its symmetric structure. The entries of the coupling matrix provide an easy to interpret measure of correlation between UEs. The higher the scalar value, the higher the coupling.

The clustering process can then be performed by thresholding the coupling matrix, wherein elements C > C_min are assigned a first value, for example a value of 1, and the other elements of the coupling matrix are assigned a second value, for example a value of 0 so as to provide a binarized matrix. Reading the binarized matrix column-wise or row-wise and selecting, in each row or column, combinations of UE, DCS and phase shift patterns corresponding to elements of the coupling matrix having the first value provides sets of UEs with highly coupled channel estimate matrices. These UEs are then regrouped into groups of UEs. A UE can appear in multiple groups with and without the same configuration

of the phases on the various DCSs.

In some embodiments, in the group construction step, additional refining constraints can also be applied in order to ensure a target criteria such as, for example, a minimum number of degrees of freedom (for example, a rank of the channel matrix for the group) min_dim and/or a minimum number of co-scheduled UEs).

Each group of UEs generated in the group construction step has a DCS associated therewith for serving the UEs of the group, as well as a specific phase shift pattern of the associated DCS. Therefore, the group of UEs for the phase shift pattern

applied to the DCS d in order to focus the energy in the common subspace of UEs is denoted a with

The output of the group construction step is a set of potential groups of UEs associated to a DCS with a given phase shift pattern or directly to the BS. However, these groups are not used for scheduling or for selecting phase shift patterns for the DCSs, as one of the main problems, cross DCS interference, has not been resolved. However, using the groups can drastically reduce the problem dimensionalities in the group selection step by going from a huge set of UEs to a well-structured sets of clusters with correlated UEs.

Group selection step

The group selection step can resolve the cross-DCS interference. Starting points of the group selection step are the previously constructed sets of UEs and their associated DCSs d as well as their associated

phase shift patterns The group selection step can identify the groups that can be co-scheduled at the

same time and it can identify their corresponding phase shift patterns in order to minimize the DCS cross interference. In order to acquire input information relating to DCS interference for this step, two approaches can be considered.

The first approach is UE independent and the actual instantaneous distribution of the UEs is not taken into account. The input that is taken into account is information about the DCSs, their relative positions and their respective radiation/scattering patterns as a function of the potential selected phase shift patterns. Based on this input, the cross interference, which is also called leakage between DCSs, can be estimated. Considering knowledge of the deployment of the DCS, their respective sets of phase shift patterns and the deployment environment, this estimation can be performed offline and a DCS coupling matrix between DCSs which defines DCS coupling quantities can be generated. The DCS coupling matrix can also be updated or even calculated through an online method. The DCS coupling matrix is denoted C_DCS where the rows and columns are indexed by a respective DCS index and a respective phase shift pattern index. Thus, the elements of C_DCS are coupling values between DCSs d and

d' using phase shift patterns I and I'.

The second approach is based the actual distribution of the UEs, which has an influence on the communication channels of the UEs. Based on the acquired CSI information, the constructed groups of UEs for each DCS and each potential phase shift pattern, a representation of cross-interference between groups can be calculated, for example in terms of common space and/or energy leakage. This information can then be used to construct the DCS coupling matrix defining DCS coupling quantities. Alternatively, the DCS coupling matrix can be constructed directly based on global information acquired through conventional channel estimation where through the DCS and H_0,k are known. The

DCS coupling matrix is denoted C_DCS, where the rows and columns are indexed by a respective DCS index and a phase shift pattern index. Thus, the elements of C_DCS are coupling values between

DCSs d and d' using phase shift patterns I and I'.

As a further input for the group selection step, in addition to the input information relating to DCS interference, scheduling constraints can be provided. The scheduling constraints can be obtained from higher layers. The scheduling information can include priorities that can for example be generated UE- based, considering prior scheduling of the UEs and their traffic requests. Additionally or alternatively, the priorities can be generated by specific feeds such as high priority and low priority feeds. Generally, the priorities can be combinations of these parameters and further parameters.

Taking into account the scheduling constraints can help not only to define a structured way in constructing the network of DCS and their respective configurations, but also to respect priorities for ensuring a minimal quality of service (QoS). In embodiments, the group selection step can be performed in accordance with the following algorithm:

Algorithm S2_0 (for group selection step): 1. Order the UEs in a list 11 based on the selected criteria, for example, the priorities.

2. Start with the highest priority UEs in 11 and select the best group (for example, in

terms of SNR based on channels for serving the target UEs.

3. Lock that group (G*) as used.

4. Mark the corresponding DCS as active and fix its corresponding phase shift pattern as identified in G*.

5. Parse the list of groups and mark all highly correlated ones as unavailable. The correlation decision is done based on C_DCS.

7. Incrementally add groups in the order of decreasing priorities of UEs and by selecting groups minimizing coupling based on C_DCS, looping back to step 2 as long as groups are available and

In some embodiments, the group selection step can be further enhanced by incorporating extra constraints such as the number of pairable UEs, which can be added to the selection process.

Output step

In the output step, the sets of selected UEs, their respective DCS assignments and, optionally, their channel qualities (CSI, SNR, CQI,...) can be communicated. In particular, the selected groups are fed back to the scheduler. Based thereon, the scheduler can add the extra UEs present

in the groups to its scheduling list and serve them in an opportunistic manner if there is traffic aimed for them in the queues. Additionally, the phase shift patterns of the DCSs associated with the selected groups can be provided to the DCSs for operating the DCSs in accordance with the phase shift patterns.

In some embodiments, an iteration through the group construction step and the group selection step can be performed in order to further jointly optimize the assignment of UEs and DCSs and to further improve the programming of the propagation channel.

Embodiments disclosed herein can have several advantages. In particular, the total throughput can be maximized, which is achieved through a better aggregation of UEs that are served simultaneously, and the cross interference between DCS can be minimized in a dynamic fashion based on the requests. The available resources can be efficiently used due to the insertion of the DCSs in the propagation environment. The configuration of the DCSs, i.e. channel programming and scheduling can be jointly optimized. The number of UEs served at a given time slot can be enhanced as they are chosen to minimize cross-interference, and groups of UEs are co-schedulable on the same RB. Techniques disclosed herein can provide tools for the scheduler which can allow to ensure that high priority traffic (e.g. with time constraint) is always properly conveyed to its destination. Compared to very complex MILP optimization problems, which are encountered in prior art techniques, a low complexity recursive solution is provided. Moreover, techniques disclosed herein can make it easy to insert several criteria at any step, which can be considered throughout the process until the output is provided.

In the following, specific embodiments will be described in detail.

Embodiment 1, group construction step: per DCS computations

In the following, an embodiment of the group construction step will be described. In this embodiment, the construction of the groups of UEs is done in such a way that they can be served at the same time by a communication channel via a DCS. As each newly selected phase shift pattern matrix adopted for DCS d changes the propagation environment, it is of advantage to consider the i

mpact of each configuration on the various UEs.

In this embodiment, a per DCS computation is performed, and an algorithm as described in the following Algorithm S1_1 is applied at DCS d. Independently, and for all present DCS, the algorithm computes a coupling matrix

_d between the communication channels of the UEs for each potential phase shift pattern that each DCS may apply. The elements of the coupling matrix are channel

correlation quantities, each being representative of a correlation between a respective pair of the communication channels to which the UEs are connectable, and which are formed via the DCSs d when the DCS d provides the phase shift pattern

For determining the elements of the coupling matrix for each UE, a respective channel estimate

matrix can be obtained for each UE and each phase shift pattern of each DCS, and the elements of the coupling matrix can be determined on the basis thereof. Multiple criteria can be considered for

computing the elements of the coupling matrix such as perceived energy (i.e. the sum of singular

values of channels common subspaces and/or rank of common subspace that is an important

metric to identify the number of UEs separable in the spatial dimension.

From the coupling matrix and based on a predefined threshold C_min as well as the selected criteria that have been considered in constructing the coupling matrix the algorithm identifies all potential

combinations of UEs that are highly coupled and sets them as an independent group. Thus, into each group one or more UEs are included that are selected such that for each pair of the communication channels that are formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group and to which the selected CNs are connectable, the respective channel correlation quantity is greater than a predetermined threshold value.

Multiple groups overlapping or disjoint ones can be constructed and any subset of a group is another group. These groups are then forwarded to the group construction step where cross-DCS interference is considered.

Proceed to the group selection step.

Embodiment 2, group construction step: coverage and position information for complexity reduction

In the following, another embodiment of the group construction step will be described, wherein positions of UEs are taken into account. Localization, positioning and UE tracking are possible in 4G and 5G communication technologies, where they have been integrated into some services with varying degrees of accuracy, depending on the constraints and applications. They are also basic functionalities for future communication systems. Thus, in communication arrangements, information relating to positions of UEs is available, which can be used to reduce the complexity of the group construction step. Using this information along with the position of the BS, the positions of the DCSs and the reflection patterns of the DCSs as a function of their respective phase shift patterns allows to determine respective coverage areas of the DCSs, which enables preselecting the UEs considered in the computation of the coupling matrix for DCS d with phase shift so that complexity of the computation of the coupling

matrix can be reduced. Additionally, the requirements on channel state information (CSI acquisition) can be reduced. Algorithm Sl_2 provides an implementation of the group construction step. The algorithm starts by physically associating a set of UEs for each DCS d with phase shift

The association is

done based on the location P_k of UE k ∈ X and the coverage area

of DCS d with phase shift

such that where ε is a tolerance factor extending the area In some implementations,

the coverage area can be precomputed and provided or computed especially when the possible phase shift patterns of the DCSs are fixed. In other implementations, they can be dynamically computed and/or updated by computing radiation and/or scattering patterns of the DCSs. After providing the set of UEs the CSI information can be acquired for each UE in and the processing can be continued

as described above for Algorithm Sl_1. Thus, for each phase shift pattern I of each DCS d. a channel estimate matrix is obtained for those UEs that are in the coverage area of the respective phase shift

pattern of the respective DCS, and a respective channel correlation quantity is determined on the basis of each pair of the determined channel estimate matrices

Proceed to the group selection step.

Embodiment 3, group selection step: coverage area and/or radiation pattern based computation

In the following, an embodiment of the group selection step will be described, where configurations of the DCSs that result in a level of cross DCS interference that is acceptable and are thus nonexclusive configurations of the DCSs are identified. The computations of this embodiment can be performed offline based on a predefined set of potential phase shift patterns and their impact in terms of radiation and/or scattering patterns. Considering that the incident signals come essentially from the BS and using the positions of the various DCSs, a coverage area that is denoted as can be computed. The coverage

areas can then be used to compute a leakage power between the various DCSs in their various configurations, thus constructing a respective DCS coupling matrix having elements

. The are DCS coupling quantities, wherein a respective DCS coupling quantity is

provided for each pair of phase shift patterns of the DCSs which is computed on the basis of the coverage area dl_d ^l of the first phase shift pattern I of the first DCS d of the pair and the second phase shift pattern I' of the second DCS d' of the pair. Additionally and/or alternatively, closed form expressions for the radiated power of the DCSs can be computed, and for each pair of phase shift patterns of the DCSs, a DCS coupling quantity can be calculated on the basis of a radiation pattern of a first phase shift pattern of a first DCS of the pair and a radiation pattern of a second phase shift pattern of a second DCS of the pair. In some embodiments, the DCS coupling quantities

can be calculated on the basis of an average energy that is captured by the UEs of a group of UEs from the set of groups of UEs that is associated with a first phase shift pattern I of a first DCS d of the pair from a communication channel that is formed via a second DCS d' of the pair when the second DCS d' of the pair provides a second phase shift pattern I' of the second DCS d'of the pair.

These computations can be done offline or online, and they can be partially or fully updated on the fly. For example, if a new phase shift pattern of a DCS is considered, then only a column needs to be added to the DCS coupling matrix. To the contrary, if a phase shift pattern of a DCSs is removed, the DCS coupling matrix can be updated by deleting the entries corresponding to the phase shift pattern in the coupling matrix.

Then, the DCS coupling matrix can be used to perform a selection process of the groups of UEs. Two approaches can be considered here. In the first approach, as described in Algorithm S2_1, the selection is decoupled into two functions. The first function constructs mutually exclusive sets of DCSs d and phase shift patterns I (this needs to be computed once). Based on the mutually exclusive sets of DCSs and phase shift patterns, mutually exclusive groups of UEs that are associated with the respective DCSs and phase shift patterns can be selected from that is updated every time the groups of UEs are

recomputed. This provides a decision tree for the selection of active groups based on a selected scheduling criterion. The decision tree defines, for each group of CNs, a set of co-schedulable groups of CNs. The set of co-schedulable groups of CNs includes groups of CNs associated with a phase shift pattern of one of the plurality of DCSs for which the DCS coupling quantity with the phase shift pattern of the DCS associated with the respective group of CNs is less than a predetermined threshold value. The second function performs the selection of active groups. For example, considering priority as a scheduling constraint, the groups of UEs that are going to be served are selected. In doing so, starting with the highest priority UE, the best serving configuration and thus the associated group is selected. Each selection in the recursive process defines the next arm in the decision tree and the remaining available groups as described in Algorithm S2_0. Thus, the UEs that are going to be served are processed in an order of decreasing priority. For each of the UEs to be served, a group of UEs is selected that is not associated with a combination of a DCS of an already selected group that was selected for a UE having a higher priority and a phase shift pattern of the DCS associated with the already selected group that is different from the phase shift pattern associated with the already selected group. The selection is performed on the basis of the DCS coupling quantities. Algorithm S2_1:

Select the subtree of the decision tree associated with G*

End While

Proceed to the output step.

In the second approach, as described in Algorithm S2_2, the two functionalities are done jointly and the scheduling constraints are taken into account since the start. The main difference with the first approach is that only groups that are co-schedulable with the previously identified and selected groups are computed. Similar to Algorithm S2_l, the UEs that are going to be served are processed in an order of decreasing priority. For each of the UEs to be served, a group of UEs is selected that is not associated with a combination of a DCS of an already selected group that was selected for a UE having a higher priority and a phase shift pattern of the DCS associated with the already selected group that is different from the phase shift pattern associated with the already selected group. The selection is performed on the basis of the DCS coupling quantities.

Exclude all groups highly coupled with G*

End While

Proceed to the output step.

Embodiment 4, group selection step: CSI-based computation

In the following, an embodiment of the group selection step that is alternative to embodiment 3 is described. In this embodiment, the considered inputs are not related to DCS capabilities but rather to the actual state of UEs, their distribution and perceived communication channels. This approach, although more consuming in terms of computations and involving additional constraints on the online processing, can have advantages associated therewith, as constraints related to the DCS cross-interference can be relaxed, in particular when UEs are not uniformly distributed over the entire area.

In this embodiment, the computation of the DCS coupling matrix C_DCS is performed not on the basis of the radiation and/or scattering patterns of the DCSs but rather on the perceived interference by the grouped UEs.

In the following, one possible implementation will be described wherein the selection of co-schedulable groups and the consideration of scheduling constraints are done jointly. Alternatively, as detailed above in the description of embodiment 3, it is also possible to first provide a decision tree based on the DCS coupling matrix, and to then select groups of UEs that are going to be served on the basis of the decision tree and the scheduling constraints.

Starting from the output provided by the group construction step and additionally considering the channel estimate matrices for all UEs in a given group, if available, or an aggregated representative channel for the group of UE, the group selection step can be performed as described in Algorithm S2_3.

The main difference between embodiment 4 and embodiment 3 lies in the computation of the DCS coupling quantities which are computed as the aggregated captured

energy coming from an external DCS with any potential phase configuration. This does not represent the leakage between two DCS with a given configuration, but represents the leakage only as far as it impacts impacting existing or scheduled UEs through the selected group G*. Thus, harmless leakage which does not affect the operation of the UEs can be kept, which can allows relaxing the constraints resulting from the interference between DCSs.

Embodiment 5, output step

This embodiment presents a potential implementation of the output step where the extra UEs are finally taken into account in the scheduling process. Thus, all the UEs provided in the groups constructed in the group construction step and selected in the group selection step can be served. The scheduler is not aware of the potential co-scheduling of the extra UEs until it is provided with the list from the lower layers.

As described in Algorithm S3_1, the scheduler then rearranges the extra UEs after assessing their potentially achievable rates and based on their queued streams to jointly serve them along with the main UEs in the same group. At this step, rate adjustment and pairing can be done based on a main amount of resources allocated to the main UEs (i.e. the initially planned UEs) so as to appropriately serve the main UEs.

Algorithm S3_1:

Processing:

Allocate resources for priority UEs (i.e, UEs initially planned for scheduling)

Select extra UEs that have queued traffic

Based on allocated resources for the main resources select proper UEs to maximize a criteria (e.g. aggregated throughput)

Embodiment 6, group construction and selection steps: joint construction of groups and DCS couplings

In the following, an embodiment providing an alternative implementation of the group construction step and the group selection step will be described with reference to Fig. 8. In embodiments 1 to 5 described above, the computations for the group construction step and the group selection step are performed independently. This independence is essentially a result of the difference in the required input data for the processing.

However, as described above in the context of embodiment 4, the group selection step can be performed on the basis of channel estimation matrices which, as described in the context of embodiments 1 and 2, are also used for the group construction step. Thus, the group selection step can be performed using the same input data as the group construction step, but through a different processing procedure.

As will be described in the following, it is actually possible to aggregate the processing in a common fashion. This can be done by computing a huge aggregated overall channel estimate matrix for each UE and each phase shift pattern of each DCS of where the CSI matrices of the various are stacked. In

implementations, the calculation of the overall channel estimate matrix can be performed by a BS, for example by the circuitry 312 for calculating an overall channel estimate matrix of the BS 218 described above with reference to Fig. 3. Based on the overall channel estimate matrix, an overall coupling matrix is computed by multiplying the overall channel estimate matrix and its transpose.

A structure of such an overall coupling matrix 800 is schematically illustrated in Fig. 8. The overall coupling matrix 800 includes diagonal blocks 801-805. Each of the diagonal blocks is representative of an inter-UE coupling for the plurality of UEs for one phase shift pattern I of one DCS d. Thus, the diagonal blocks 801-805 can be used for the group construction step. Additionally, the overall coupling matrix 800 includes off-diagonal blocks, some of which are exemplarily denoted by reference numerals 806-813 in Fig. 8. The off-diagonal blocks 806-813 are representative of the energy collected by UEs from a different DCS d' when they should be served by DCS d. This information can be extracted by computing the mean energy in each of the off-diagonal blocks 806-813 of the overall coupling matrix 800 for providing the DCS coupling quantities. Although, in this embodiment, a large number of DCS coupling quantities is calculated, it can be interesting from a processing delay perspective when hardware and tools for large matrix multiplication are used such as optical CPUs.

Embodiment 7: Iterative version

In the following, an embodiment will be described which provides an iterative version where the scheduling is jointly optimized with the grouping and selection process, and where an alternating optimization is used.

The process starts as in the previously described embodiments by the scheduler providing a list of UEs to schedule. After performing the group construction step and the group selection step in accordance with any of the above-described embodiments 1 to 6, a list of UEs is provided to the scheduler. The scheduler then processes the extra UEs and feeds back an updated list of UEs with an updated constraint based on the scheduled resources per UE (especially the more critical UEs) with the objective to maximize the total throughput.

This new list is then processed in accordance with the group construction step and the group selection step in order to provide an alternative channel programming, which can allow to better serve the UEs of the new list (including the extra UEs), potentially by adding new or alternative groups. Algorithm Sl-3_Iter describes an implementation of the process where the convergence criterion is maximizing the total data throughput R. The iteration is terminated when an absolute value of a difference between the available data throughput R obtained after an iteration and the data throughput C obtained after the preceding iteration is less than or equal to a convergence constant ε. Before the iteration, an initialization can be performed, wherein initial values R = 0 and C = — ∞ can be set.

Operate scheduler to provide a list of UEs with their respective priorities

Run any alternative of implementation of the group construction step Run any alternative of implementation of the group selection step Run any alternative of implementation of the output step, i.e. update UE lists based on the requests

Compute the estimated achievable throughput R

End While

Perform DCS configuration

Allocate UEs to DCSs

Allocate resources

In the following, embodiments of an exchange of signals and information between a base station, a DCS and a UE will be described with reference to Figs. 9 and 10.

Embodiment 8: signal exchange

Fig. 9 illustrates signal exchanges between a BS, a DCS and a UE, which, in some implementations, can have features corresponding to those of the BS 218, the DCSs 201-205 and the UEs 206-217 described above with reference to Figs. 2a, 2b, 2c, 3 and 4. For simplicity, in Fig. 9, only one DCS and one UE are shown. In implementations, more than one DCS and more and one UE can be present, each of which can be operated as described in the following.

The BS can include a layer LI including physical layer circuitry which, in some implementations, can have features corresponding to those of the physical layer circuitry 307 described above with reference to Fig. 3, and a layer L2 including scheduling circuitry which, in some implementations, can have features corresponding to those of the scheduling circuitry 306 described above with reference to Fig. 3. Various components of a wireless network can communicate through the layers LI and L2.

At step 901, the scheduling circuitry can make a scheduling decision, and select a set of UEs based on their traffic requests and stream types generating an ordered list with priorities. This can be performed in accordance with known techniques from conventional cellular communication systems.

At step 902, this list is forwarded to the lower layers, in particular to the physical layer circuitry, requesting channel estimation and resource allocation. The channel estimation can be performed as described above, taking into account that in a propagation environment including one or more DCSs, the communication channels are not static but programmable through the various DCSs. Then, at step 903 a channel estimation procedure over the various DCSs and UEs is performed, which can include communications between the physical layer circuitry, the DCSs and the UEs that are performed at step 904. Thereafter, at step 905, the BS performs the group construction and group selection processes in accordance with any of the embodiments described above. This can be done by the physical layer circuitry, using scheduling constraints and/or an ordering of UEs according to a priority thereof, which can be provided by the scheduling circuitry. At step 906, the output step is performed, wherein a list representing the groups of UEs obtained from the group construction and the group selection is then fed back to the scheduling circuitry. The list can include the assignments of the UEs to the groups. Additionally, at step 907, an appropriate channel quality indicator (CQI) for each UE can be fed back to the scheduling circuitry.

At step 908, this information is then processed by the scheduler in order to add those extra UEs to the list of UEs for serving them in an opportunistic manner. In addition to the main output, configmation instructions used for setting the corresponding phases for each of the DCSs are produced, which

are provided to the DCSs at step 909.

Embodiment 9: signal exchange in iterative method

Fig. 10 illustrates signal exchanges between a BS, a DCS and a UE, which can have features corresponding to those of the BS 218, the DCSs 201-205 and the UEs 206-217 described above with reference to Figs. 2a, 2b, 2c, 3 and 4. For simplicity, in Fig. 10, only one DCS and one UE are shown. In implementations, more than one DCS and more and one UE can be present, each of which can be operated as described in the following.

In this embodiment, steps 901 to 908 can be performed as described above with reference to Fig. 9 wherein, at step 908, the scheduling circuitry obtains an updated list including extra UEs. Features of steps 901 to 908 can correspond to those of steps 901 to 908 in embodiment 8, and a detailed description thereof will be omitted.

In order to further optimize the selection of groups of UEs, after step 908, an iterative process including steps 1001-1008 can be performed. Features of the iterative process can correspond to those of embodiment 7 described above.

In particular, at step 1001, an initialization can be performed, wherein a value of a data transmission rate R after an iteration and a value of a data transmission rate C after the preceding iteration are set to initial values, for example to values R = 0 and C = — ∞ .

Then, at step 1002, the scheduling circuitry can forward the updated list of UEs that was created at step 908 to the physical layer circuitry. At step 1003, the physical layer circuitry of the BS performs the group construction and group selection processes, the result of which is fed back to the scheduling circuitry at step 1004. At step 1005, an appropriate channel quality indicator (CQI) for each UE is fed back to the scheduling circuitry. Then, at step 1006, the scheduling circuitry updates the list of UEs with the information fed back at steps 1004, 1005 and updates the priorities of the UEs. At step 1007, the scheduling circuitry estimates the data throughput rate gained by introducing the extra UEs, and updates the values of R and C as described above in the context of embodiment 7. At step 1008, the scheduling circuitry determines if convergence is achieved, for example by determining if |R — C| < ε with a convergence constant ε. If convergence is not achieved, steps 1002-1007 are iterated. Otherwise, at step 1009, configuration instructions for setting the corresponding phases

for each of the DCSs are produced on the basis of the latest selected groups and provided to the DCSs.

The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the scope of protection of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the scope of protection of this application. Therefore, the scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A communication arrangement, comprising: a plurality of digitally controllable scatterers, DCSs, each DCS being configmed to provide one or more phase shift patterns of the respective DCS for electromagnetic radiation reflected thereon; group construction circuitry configmed to construct, for a plurality of communication nodes, CNs, a set of groups of CNs, each group of CNs being associated with a respective phase shift pattern of a respective DCS of the plurality of DCSs, wherein each group of CNs comprises one or more CNs of the plurality of CNs that are co-schedulable on a communication channel that is formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group;

DCS coupling quantity calculation circuitry configured to calculate one or more DCS coupling quantities, each DCS coupling quantity of the plurality of DCS coupling quantities being indicative of an interference level between at least two communication channels via at least two DCSs of the plurality of DCSs; group selection circuitry configured to select, for a first CN of the plurality of CNs, a first group of CNs from the plurality of groups of CNs that comprises the first CN and to select, for a second CN of the plurality of CNs, a second group of CNs from the plurality of groups of CNs that comprises the second CN, wherein at least the second group of CNs is selected on the basis of the one or more DCS coupling quantities and the selected first group of CNs; and

DCS control circuitry configured to operate each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs to provide the phase shift pattern associated with the respective group of CNs.

2. The communication arrangement according to claim 1, further comprising scheduling circuitry configured to co-schedule a communication of the first CN and the second CN while each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs provides the phase shift pattern associated with the respective group of CNs, wherein the first CN communicates via the DCS associated with the first group of CNs and the second CN communicates via the DCS associated with the second group of CNs.

3. The communication arrangement according to claim 2, wherein one of the first group of CNs and the second group of CNs additionally comprises at least one third CN of the plurality of CNs, and wherein the scheduling circuitry is configured to co-schedule the at least one third CN on the communication channel via the DCS associated with the one of the first group of CNs and the second group of CNs.

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4. The communication arrangement according to claim 3, wherein the other of the first group of CNs and the second group of CNs additionally comprises at least one fourth CN of the plurality of CN, and wherein the scheduling circuitry is configured to co-schedule the at least one fourth CN on the communication channel via the DCS associated with the other of the first group of CNs and the second group of CNs.

5. The communication arrangement according to any of the preceding claims, wherein the group selection circuitry is configured to receive a first list defining a subset of the plurality of CNs that comprises the first CN and the second CN and an associated priority of each CN of the subset of the plurality of CNs.

6. The communication arrangement according to claim 5, wherein the first CN has a higher priority than the second CN and wherein the group selection circuitry is configured to select the second group of CNs from a subset of the set of groups of CNs that are not associated with a combination of the DCS associated with the first group of CNs and any phase shift pattern of the DCS associated with the first group of CNs that is different from the phase shift pattern associated with the first group of CNs.

7. The communication arrangement according to claim 5 or 6, wherein the group selection circuitry is configured to process the CNs of the subset of the plurality of CNs defined by the first list in an order of decreasing priority, and wherein the group selection circuitry selects, for each CN of the subset of the plurality of CNs defined by the first list, a respective group of CNs from the set of groups of CNs that is not associated with a combination of a DCS associated with an already selected group of CNs that was selected for a CN of the subset of the plurality of CNs defined by the first list having a higher priority and any phase shift pattern of the DCS associated with the already selected group of CNs that is different from the phase shift pattern associated with the already selected group of CNs, the selection being performed on the basis of the one or more DCS coupling quantities.

8. The communication arrangement according to claim 7, wherein the group selection circuitry is configured to provide to the scheduling circuitry a second list comprising one of more CNs from the selected groups of CNs that are not part of the subset of the plurality of CNs defined by the first list.

9. The communication arrangement according to claim 8, wherein the scheduling circuitry is configmed to provide an updated first list to at least the group selection circuitry, the updated first list being based on the first list and the second list, and the group selection circuitry is configmed to provide an updated second list on the basis of the updated first list.

10. The communication arrangement according to any of the preceding claims, wherein the group construction circuitry is configured to obtain, for the plurality of CNs and for at least a part of the phase shift patterns of at least a part of the plurality of DCSs, a plurality of channel correlation quantities, each channel correlation quantity being representative of a correlation between a respective pair of the communication channels for the plurality of CNs that are formed via the DCSs of the at least a part of the plurality of DCSs when the DCSs provide the at least a part of the phase shift patterns and to which the plurality of CNs are connectable, and to construct the set of groups of CNs on the basis of the channel correlation quantities.

11. The communication arrangement according to claim 10, wherein the group construction circuitry is configured to construct the set of groups of CNs by including, into each group of CNs, one or more CNs of the plurality of CNs that are selected such that, for each pair of the communication channels that are formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group and to which the selected CNs are connectable, the respective channel correlation quantity is greater than a predetermined threshold value.

12. The communication arrangement according to claim 10 or 11, wherein the group construction circuitry is configured to obtain, for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCS, a channel estimate matrix for each CN of the plurality of CNs and to determine a respective channel correlation quantity on the basis of each pair of the determined channel estimate matrices.

13. The communication arrangement according to claim 10 or 11, wherein the group construction circuitry is configured to determine, for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCSs, a respective coverage area, to obtain, for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCS, a channel estimate matrix for those CNs of the plurality of CNs that are in the coverage area of the respective phase shift pattern of the respective DCS, and to determine a respective channel correlation quantity on the basis of each pair of the determined channel estimate matrices.

14. The communication arrangement according to claim 13, wherein the group construction circuitry is configured to determine the respective coverage area for each of the at least a part of the phase shift patterns of the at least a part of the plurality of DCSs on the basis of a position of a base station, a respective position of each DCS of at least a part of the plurality of DCSs and a respective reflection pattern associated with each phase shift pattern of the at least a part of the phase shift patterns of the at least a part of the plurality of DCSs.

15. The communication arrangement according to any of claims 12 to 14, wherein the group construction circuitry is configured to calculate, for each pair of the determined channel estimate matrices, the respective channel correlation quantity on the basis of at least one of a sum of singular values of the pair of channel estimate matrices, a common subspace of the pair of channel estimate matrices and a rank of the common subspace of the pair of channel estimate matrices.

16. The communication arrangement according to any of the preceding claims, wherein the DCS coupling quantity calculation circuitry is configured to calculate a respective DCS coupling quantity for each pair of phase shift patterns of the phase shift patterns of the plurality of DCSs.

17. The communication arrangement according to claim 16, wherein the group selection circuitry is configured to provide a decision tree that defines, for each group of CNs of the set of groups of CNs, a set of co-schedulable groups of CNs, the set of co-schedulable groups of CNs comprising groups of CNs associated with a phase shift pattern of one of the plurality of DCSs for which the DCS coupling quantity with the phase shift pattern of the DCS associated with the respective group of CNs is less than a predetermined threshold value.

18. The communication arrangement according to claim 17, wherein the group selection circuitry is configured to select the second group of CNs from the set of co-schedulable groups of CNs for the first group of CNs.

19. The communication arrangement according to any of claims 1 to 15, wherein the group selection circuitry is configured to obtain, from the DCS coupling quantity calculation circuitry, a respective DCS coupling quantity for a plurality of pairs of phase shift patterns of the plurality of DCSs that comprise the phase shift pattern of the DCS associated with the first group of CNs, to construct a set of co- schedulable groups of CNs that is restricted to groups of CNs associated with a phase shift pattern of one of the plurality of DCSs for which the DCS coupling quantity with the phase shift pattern of the DCS associated with the first group of CNs is less than a predetermined threshold value, and to select the second group of CNs on the basis of the set of co-schedulable groups of CNs.

20. The communication arrangement according to any of claims 16 to 19, wherein the DCS coupling quantity calculation circuitry is configured to perform the calculation of the DCS coupling quantity for each pair of phase shift patterns of the plurality of DCSs on the basis of a coverage area of a first phase shift pattern of a first DCS of the pair and a coverage area of a second phase shift pattern of a second DCS of the pair.

21. The communication arrangement according to any of claims 16 to 19, wherein the DCS coupling quantity calculation circuitry is configured to perform the calculation of the DCS coupling quantity for each pair of phase shift patterns of the plurality of DCSs on the basis of a radiation pattern of a first phase shift pattern of a first DCS of the pair and a radiation pattern of a second phase shift pattern of a second DCS of the pair.

22. The communication arrangement according to any of claims 16 to 19, wherein the DCS coupling quantity calculation circuitry is configured to perform the calculation of the DCS coupling quantity for each pair of phase shift patterns of the plurality of DCSs on the basis of an average energy that is captured by the CNs of a group of CNs from the set of groups of CNs that is associated with a first phase shift pattern of a first DCS of the pair from a communication channel that is formed via a second DCS of the pair when the second DCS of the pair provides a second phase shift pattern of the second DCS of the pair.

23. The communication arrangement according to claim 22, further comprising circuitry for calculating an overall channel estimate matrix for each of the plurality of CNs and each phase shift pattern of each DCS of the plurality of DCSs, wherein the group construction circuitry is configured to construct the set of groups of CNs on the basis of the overall channel estimate matrix and wherein the DCS coupling quantity calculation circuitry is configured to calculate the one or more DCS coupling quantities on the basis of the overall channel estimate matrix.

24. A method, comprising: constructing, for a plurality of communication nodes, CNs, a set of groups of CNs, each group of CNs being associated with a respective phase shift pattern of a respective digitally controllable scatterer, DCS of a plurality of DCSs, wherein each group of CNs comprises one or more CNs of the plurality of CNs that are co-schedulable on a communication channel that is formed via the DCS associated with the respective group when the DCS associated with the respective group provides the phase shift pattern associated with the respective group; calculating one or more DCS coupling quantities, each DCS coupling quantity of the plurality of DCS coupling quantities being indicative of an interference level between at least two communication channels via at least two DCSs of the plurality of DCSs; for a first CN of the plurality of CNs, selecting a first group of CNs from the plurality of groups of CNs that includes the first CN; for a second CN of the plurality of CNs, selecting a second group of CNs from the plurality of groups of CNs that includes the second CN, wherein the second group of CNs is selected on the basis of the plurality of DCS coupling quantities and the first group of CNs; operating each DCS of the plurality of DCSs that is associated with at least one of the first group of CNs and the second group of CNs to provide the phase shift pattern associated with the respective group of CNs.

25. A computer program comprising instructions which, when carried out on a computer, cause the computer to perform a method according to claim 24.