Controller for setting a reflective phase of a cell in a

Abstract

Techniques for setting reflection phases of cells in a reconfigurable smart surface are provided. The cells are divided into subsets of cells, each of which has at least two cells. The reflection phase of each cell in each subset of cells is controlled by a respective local controller of each subset of cells. The central controller is configured to communicate control messages with the local controllers. The central controller comprises a processing circuit. The processing circuitry is configured to cause the central controller to send a first control message to a first one of the local controllers. The first control message includes a description of a first reflected phase dedicated to a first subset of cells, the reflected phase of the first subset of cells being controlled by the first local controller.

Description

Technical Field

[0001] Embodiments presented herein relate to methods, central controllers, local controllers, computer programs and computer program products for setting the reflection phase of cells in a reconfigurable smart surface. Background Art

[0002] Reconfigurable smart surfaces (RIS) offer opportunities for improved wireless communications. In particular, millimeter wave spectrum, which is the spectrum used in fifth and sixth generation telecommunication systems, is expected to gain significant benefits. This spectrum presents severe challenges in terms of propagation and coverage, for example, due to its support for very high frequency ranges of tens of GHz. These challenges are greater than those for spectrum with lower frequencies, for example for the so-called sub-6 GHz bands.

[0003] The use of RIS may vary, but in general, RIS can be configured to reflect wireless signals in a controlled manner, for example, to direct the transmitted signal in a certain direction. This can be used, for example, to improve the coverage, range, and efficiency of the overall system. RIS is also commonly referred to as large smart surface, smart reflective array, smart reflective surface, passive smart mirror, artificial radio space, and metasurface.

[0004] In short, the surface of RIS includes multiple (e.g., hundreds or thousands) antenna elements, or simply elements. Each element can be individually configured or controlled to dynamically adjust the reflective properties of the surface. Figure 1 A typical RIS 110 is shown, comprising a central controller 200 individually connected to all units 112a, 112b, ..., 112M. Figure 2 1 is a schematic diagram illustrating a communication network 100, wherein a RIS 110 is shown to facilitate communications between a network node 120 and a user device 140 over wireless links 130a, 130b. This may represent a scenario where a physical object 150 obstructs the line of sight between the network node 120 and the user device 140. Other usage scenarios may involve the RIS being part of or connected to a wireless device for enhancing communications for the device.

[0005] In some implementation examples, the RIS does not include any radio frequency (RF) chain for generating or amplifying the signal, but instead provides a unit to modify the properties of the signal through its reflection. The central controller is configured to send control signals to adjust the properties of each unit in the RIS. An example of this situation is disclosed in the following document: A. Araghi et al., "Reconfigurable Intelligent Surface (RIS) in the Sub-6 GHz Band: Design, Implementation, and Real-World Demonstration", IEEE Access, Vol. 10, pp. 2646-2655, 2022, doi: 10.1109 / ACCESS.2022.3140278. One problem with this technique for configuring the unit is the implementation complexity when scaling the RIS to a very large number of units. Future uses of the RIS may contain thousands of units. It is conceivable to consider using printed electronics to solve some of the manufacturing problems in the manufacturing problem, but this has another set of challenges related to scaling and how to manage the control of a large number of interconnected units. Printed electronics have limitations when it comes to miniaturization and the number of layers that can be used (compared to silicon-based manufacturing processes). Connecting each unit to a central controller leads to several challenges.

[0006] One challenge is the wiring congestion between the central controller and the units. This is mainly due to the large number of units, which therefore limits the scalability of RIS. In addition, the large number of units increases the computational load of the central controller.

[0007] Another challenge is that due to changes in the radio propagation environment, signal processing needs to be performed by the central unit. Such changes may cause reprocessing of the entire RIS and thus reconfiguration of all its units. In other words, the central unit must understand and calculate the panel layout based on the unit layout.

[0008] These issues imply a very complex hardware design (which has high cost and high implementation complexity), as well as increased hot spots due to uneven power consumption in the RIS (e.g., due to more complex circuit design). Furthermore, in practice, it can limit the ability to scale up the physical size of the RIS. Thus, issues regarding scalability and complexity may arise, including uneven power consumption. Summary of the invention

[0009] An object of the embodiments herein is to provide a technique for setting the reflection phase of a cell of a RIS that solves the above-mentioned problems.

[0010] According to a first aspect, a central controller for setting a reflection phase of a cell in a reconfigurable smart surface is provided. The cells are divided into cell subsets, each cell subset having at least two cells. The reflection phase of each of the cells in each cell subset is controlled by a corresponding local controller of each cell subset. The central controller is configured to transmit control messages with the local controllers. The central controller includes a processing circuit. The processing circuit is configured to cause the central controller to send a first control message to a first local controller of the local controllers. The first control message includes a description of a first reflection phase dedicated to a first cell subset, and the reflection phase of the first cell subset is controlled by the first local controller.

[0011] According to a second aspect, a method for setting a reflection phase of a cell in a reconfigurable smart surface is provided. The cells are divided into cell subsets, each cell subset having at least two cells. The reflection phase of each of the cells in each cell subset is controlled by a corresponding local controller of each cell subset. The method is performed by a central controller of the reconfigurable smart surface. The central controller is configured to transmit control messages with the local controllers. The method includes sending a first control message to a first local controller of the local controllers. The first control message includes a description of a first reflection phase dedicated to a first cell subset, and the reflection phase of the first cell subset is controlled by the first local controller.

[0012] According to a third aspect, a computer program for setting the reflection phase of a unit in a reconfigurable smart surface is proposed, the computer program comprising computer program code which, when run on a processing circuit of a central controller, causes the central controller to perform the method according to the second aspect.

[0013] According to a fourth aspect, a local controller for setting a reflection phase of a unit in a reconfigurable smart surface is proposed. The local controller is configured to set the reflection phase of a unit in a first unit subset including at least two units of the unit. The local controller is configured to transmit a control message to an adjacent local controller in the reconfigurable smart surface. Each adjacent local controller of the adjacent local controllers is configured to set the reflection phase of a unit in a corresponding second unit subset, each second unit subset in the second unit subset having at least two units. The local controller includes a processing circuit. The processing circuit is configured to cause the local controller to receive a first control message. The first control message includes a description of a first reflection phase dedicated to the first unit subset. The processing circuit is configured to cause the local controller to send a second control message to a second local controller in the adjacent local controller. The second control message includes a description of a second reflection phase of a second unit subset dedicated to the second local controller. The second reflection phase is based on the first reflection phase and a geometric relationship between the first unit subset and the second unit subset of the second local controller in the reconfigurable smart surface. The processing circuit is configured to cause the local controller to set the reflection phase of each unit in the first unit subset according to the description of the first reflection phase.

[0014] According to a fifth aspect, a method for setting a reflection phase of a unit in a reconfigurable smart surface is proposed. The method is performed by a local controller of the reconfigurable smart surface. The local controller is configured to set the reflection phase of a unit in a first unit subset including at least two units of the unit. The local controller is configured to transmit a control message to an adjacent local controller in the reconfigurable smart surface. Each adjacent local controller of the adjacent local controllers is configured to set the reflection phase of a unit in a corresponding second unit subset, and each second unit subset in the second unit subset has at least two units. The method includes receiving a first control message. The first control message includes a description of a first reflection phase dedicated to the first unit subset. The method includes sending a second control message to a second local controller in the adjacent local controllers. The second control message includes a description of a second reflection phase of a second unit subset dedicated to the second local controller. The second reflection phase is based on the first reflection phase and a geometric relationship between the first unit subset and the second unit subset of the second local controller in the reconfigurable smart surface. The method includes setting the reflection phase of each unit in the first unit subset according to the description of the first reflection phase.

[0015] According to a sixth aspect, a computer program for setting the reflection phase of a unit in a reconfigurable smart surface is proposed, the computer program comprising computer program code, which, when run on a processing circuit of a local controller, causes the local controller to perform the method according to the fifth aspect.

[0016] According to a seventh aspect, a computer program product and a computer readable storage medium are provided, the computer program product comprising a computer program according to at least one of the third aspect and the sixth aspect, the computer program being stored on the computer readable storage medium. The computer readable storage medium may be a non-transitory computer readable storage medium.

[0017] According to an eighth aspect, a system for setting a reflection phase of a unit in a reconfigurable smart surface is provided. The system comprises a central controller according to the first aspect and at least one local controller according to the fourth aspect.

[0018] Advantageously, these aspects provide a RIS that does not suffer from the problems disclosed above.

[0019] Advantageously, these aspects provide a RIS that is easily scalable to large sizes. The implementation can be done in the same way independent of the RIS size, without increasing the number of interconnects and the length of the interconnects, all connected to a central controller. Thus, the manufacturing and assembly will be very similar, independent of the RIS size, creating a RIS that is easily scalable and has great flexibility.

[0020] Advantageously, these aspects enable the RIS to be flexible in shape, enabling the RIS to be not only of different sizes, but also of different shapes, without the central controller having to take any immediate action based on information given of new additions or changes to the RIS.

[0021] Advantageously, these aspects enable the central controller to be greatly simplified compared to a central unit configured for fully centralized unit-specific management. The central controller does not have to support a large number of connections (or the bandwidth required for such connections), and does not need to calculate each and every individual unit configuration. Instead, the central controller will only need to determine control messages (such as gradient settings) and send them to local controllers in the RIS. This reduces the required computational complexity, memory for handling large collections of units, and physical packaging size of the central controller, and it also enables the use of a very similar central controller independent of the size of the RIS, which reduces design complexity.

[0022] Advantageously, these aspects free the central controller from the task of managing the interconnections with the individual units, since the disclosed technique is based on information propagation between controllers.The central controller is responsible for calculating the overall gradient across the entire RIS, which may or may not take into account the geometry and physical size of the entire RIS.

[0023] Advantageously, these aspects improve robustness. Since the unit subset controllers can be connected to neighbors on all faces and have two-way communication, control messages are less prone to interruption, but many backup paths can be found or operated simultaneously in the event of failure of some local controllers. The central controller is connected to more than one local controller to reduce the time required to set up or change the overall RIS configuration.

[0024] Advantageously, these aspects enable low and evenly distributed power consumption, which is beneficial in terms of heat dissipation. Since the central controller will have lower complexity than traditional centralized control, the heat dissipation in the central controller is lower. Since high temperatures at a certain location may be difficult to handle in electronic design, the aspects disclosed herein reduce design complexity.

[0025] Other objectives, features and advantages of the disclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the accompanying drawings.

[0026] Generally, unless otherwise explicitly defined herein, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field. Unless otherwise explicitly stated, all references to "a / an / the unit, device, component, member, module, step, etc." will be publicly interpreted as referring to at least one instance of the unit, device, component, member, module, step, etc. Unless otherwise explicitly stated, the steps of any method disclosed herein do not have to be performed in the exact order disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present inventive concept will now be described by way of example and with reference to the accompanying drawings, in which:

[0028] Figure 1 is a schematic diagram of a RIS according to an example;

[0029] Figure 2 is a schematic diagram illustrating a communication network according to an example;

[0030] Figure 3 is a schematic diagram of a RIS according to an embodiment;

[0031] Figure 4 is a schematic diagram of a controller according to an embodiment;

[0032] Figure 5 is a schematic diagram of a RIS according to an embodiment;

[0033] Figure 6 is a schematic diagram of reflection in RIS according to an embodiment;

[0034] Figure 8 and Fig. 9is a flow chart of a method according to an embodiment;

[0035] Fig. 9 is a schematic diagram of a unit and a unit subset according to an embodiment;

[0036] Fig.10 is a schematic diagram showing functional units of a central controller according to an embodiment;

[0037] Fig.11 is a schematic diagram showing functional modules of a central controller according to an embodiment;

[0038] Fig.12 is a schematic diagram showing functional units of a local controller according to an embodiment;

[0039] Fig.13 is a schematic diagram showing functional modules of a local controller according to an embodiment; and

[0040] Fig.14 An example of a computer program product comprising computer readable means according to an embodiment is shown. DETAILED DESCRIPTION

[0041] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the embodiments described herein; rather, these embodiments are provided by way of example so that the disclosure will be thorough and complete and the scope of the inventive concept will be fully conveyed to those skilled in the art. Throughout the description, like numbers refer to like units. Any steps or features shown with dashed lines should be considered optional.

[0042] Embodiments disclosed herein relate to techniques for setting the reflection phase of the units 112a:112M of the RIS 110. To achieve such techniques, a central controller 200, a method performed by the central controller 200, a computer program product including code (e.g., in the form of a computer program) is provided, which, when run on a processing circuit of the central controller 200, causes the central controller 200 to perform the method. To achieve such techniques, a local controller 300a, a method performed by the local controller 300a, and a computer program product including code (e.g., in the form of a computer program) is provided, which, when run on a processing circuit of the local controller 300a, causes the local controller 300a to perform the method.

[0043] Rather than using a single master controller connected to all units in RIS 110, where such connections to each unit would be complex and expensive, a distributed control system is disclosed below in which a combination of a central controller and multiple local controllers are used.

[0044] The central controller may include a receiver to obtain commands from other devices in the communication network, such as the wireless device 140 or the network node 120. In one or more examples, the central controller and the RIS may be operably connected to one or more wireless devices to enhance communication for one or more wireless devices. The central controller may then be configured to receive a control command from the wireless device 140 or the network node 120, wherein the control command includes a configuration for setting the reflection phase of the unit 112a:112M of the RIS110. Each local controller is connected to a group of nearby units (denoted as a unit subset) to control the phase of their reflection. Therefore, the central controller is configured to send a first control message to at least one local controller (hereinafter denoted as the first local controller) of the local controllers 300a:300K. The first control message includes a description of a first reflection phase dedicated to the first unit subset 114a, the reflection phase of the first unit subset 114a being controlled by the first local controller 300a. Then, the number of interconnections between the units and the controllers becomes manageable in terms of distance and the number of units involved. The local controllers connect to their neighbors to propagate the control settings through the RIS110. As the control settings propagate between adjacent local controllers, the phase settings are adjusted depending on the propagation direction so that the entire system becomes self-configuring. Different shapes of RIS 110 can be used without complex configuration, as the local connections between the local controllers will define all phase relationships of the system.

[0045] Figure 3 An example of a proposed architecture for control of cells in the RIS 110 is shown. Control messages for setting the reflection phase of cells in the RIS 110 are injected by the central controller 200 and then propagated from the local controller 300a to the local controllers 300b:300K, where each local controller 300a:300K is associated with its own cell subset (not shown). In some examples, each of the local controllers 300a:300K is embedded in, integrated with, or part of one cell 112a:112M of each cell subset 114a:114d.

[0046] In order to reflect an incident plane wave in a certain direction, the phase of the reflection of the unit should have a linear gradient across the surface, which gives a simple local phase relationship that is independent of the absolute position of the unit in the surface. This can be expressed as a certain increase (or decrease) in the horizontal direction from one unit to the next unit, and a certain increase (or decrease) in the vertical direction from one unit to another unit. That is, in some examples, the description of the first reflected phase defines a phase value and a phase gradient for the reflected phase that is specific to the first local controller 300a. The local controller can know the relative positions of its units (i.e., the subset of units it controls) in the RIS110, so it can calculate their relative phases from the horizontal and vertical increments.

[0047] Each local controller is connected to its neighboring local controllers and can be connected to its neighboring local controllers in all directions (here represented as north, south, east and west for non-limiting and illustrative purposes). When a local controller receives a control message from one of its neighboring local controllers, the local controller checks whether a new gradient is commanded, that is, whether the gradient is different from its current setting. If the gradient is not different, no action is required. This means that the control message is irrelevant and can be ignored. This prevents irrelevant control messages from continuing to propagate in the parts of RIS110 that have received the update. If the gradient indicated in the control message is different from its current setting, the local controller will, for example, calculate a new phase setting for the units in its unit subset based on the new gradient and the starting phase informed by the control message, and also propagate the control message to the other local controllers.

[0048] For phase relationships that are more complex than a linear gradient across the surface, the control message may include information such as an expression for calculating the phase, and the local coordinates or starting point for the cell in the RIS 110 that is managed by the local controller. The control message may also contain the local coordinates of the receiving or sending local controller. The control message may also contain a more complex equation for the phase, such as a high-order polynomial as a function of both the horizontal and vertical coordinates. In particular, in some examples, the description of the first reflected phase is provided in either of the following ways: an initial phase value specific to the first local controller 300a and a phase gradient for the reflected phase, or: coordinates for the first subset of cells 114a in the RIS 110 and coefficients of an expression for calculating the phase value of the reflected phase of the cell at the coordinates in the RIS 110. In some examples, the first subset of cells 114a includes a plurality of cells, wherein a separate reflected phase is set for each of the plurality of cells. The description of the first reflection phase may then still specify a reflection phase for exactly one of the plurality of cells, but wherein the reflection phase for exactly one of the plurality of cells is used as a reference when setting reflection phases for the remaining cells in the first cell subset 114a.

[0049] The control message may also set different ranges for the gradient, such as creating limits on the area of ​​RIS110 in which the cells need to be set. This will be referred to later as the valid area. After the control message has been checked, the local controller passes the control message to its other ports, notifies its neighboring local controllers of the new gradient, and calculates the starting phase or local coordinates for that neighbor. For example, the starting phase may be the southwest corner when communicating with the east and north ports and the northeast corner when communicating with the west and south ports, respectively. The connections may be to all available neighboring local controllers, or some connections may remain unconnected, as long as the control message is able to propagate to all intended parts of RIS110. Reference is here Figure 4 , which shows the connection between local controllers 300a:300d. Figure 4 As shown in , the (first) control message received by the (first) local controller 300a is received from a fourth local controller 300d in the adjacent local controllers 300b:300K, or from the central controller 200 of the RIS110. In some examples, the local controllers 300a:300K are configured to transmit control messages with the adjacent local controllers 300b:300K via a bidirectional connection. By having a bidirectional connection and connections with several adjacent local controllers, control messages can be propagated through the system in many different paths. This creates robustness. Even if some local controllers may fail, this will not prevent the unit subsets of other local controllers in the RIS110 from being updated.

[0050] It also creates flexibility in the shape, e.g. Figure 5 Schematically shown in FIG, where a wall 510 with doors 520 and windows 530 can be covered with a RIS 110 without the need for a complex configuration of a central controller. This represents an example where the RIS 110 has a planar surface over which the units 112a:112M are distributed, and where the planar surface has a non-rectangular and / or asymmetrical shape.

[0051] The architecture is scalable, so the size of the RIS 110 can be changed by just adding more cell subsets with corresponding local controllers. In addition, the shape of the RIS 110 can be made flexible; each cell subset and its local controller can be considered as a tile. To further increase the degree of freedom, the distance between tiles can be flexible, so when a local controller calculates the starting phase for its neighboring local controllers, a distance offset is used (e.g., read from non-volatile memory) instead of assuming the same distance as between cells within its own cell subset.

[0052] The control message may contain a high-resolution gradient, such as a phase increment in the horizontal and vertical directions, and a high-resolution starting phase of a unit of the local controller receiving the control message, or a high-resolution phase of a unit of the local controller sending the control message. In addition, the phase increment in the horizontal and vertical directions may not be an integer multiple of the phase control resolution of the unit. The local controller may use a higher resolution phase internally. A quantization is then performed to obtain the actual phase setting of the unit. Therefore, in some examples, setting the reflection phase of each unit in the first unit subset 114a according to the description of the first reflection phase includes: the local controller 300a quantizes the phase value of the reflection phase dedicated to the local controller 300a. This enables an increased effective resolution of the phase gradient of the system.

[0053] To reconfigure RIS110, in one or more examples, a control message may be sent to any local controller in the system. In one or more examples, for the fastest reconfiguration, a local controller close to the center of RIS110 may be selected so that the information of the control message may propagate in all directions.

[0054] One of the ports of the selected local controller is connected to the central controller. For even faster response (and / or very large RIS 110), the central controller may provide control messages to more than one local controller, so that the control messages may be spread from multiple points. This may be a situation where fast updates are required, for example, for RIS 110 participating in beam scanning or beam tracking. Therefore, the central controller may be configured to send a second control message to a second local controller 300b of the local controllers 300a:300K, wherein the second control message includes a description of a second reflection phase dedicated to the second unit subset 114b, the reflection phase of the second unit subset 114b being controlled by the second local controller 300b. Figure 3 The dashed lines in show an example of such a system, where there are four injection points in RIS 110. This also increases robustness, as the system is more vulnerable to damage to local controllers close to or where control messages are injected from the central controller. The central controller must have access to geometric information about RIS 110. Otherwise, discontinuities may form between subsets of units receiving updates from different injection points.

[0055] In one or more examples, the control message may describe a linear phase shift, i.e., a phase gradient, on the RIS110. The control message may then also contain a starting phase so that the local controller knows where the previous local controller expects the phase gradient to continue. This is important for avoiding discontinuities between unit subsets belonging to different local controllers so that the RIS110 behaves like a single surface in which all units contribute constructively to the desired reflection. The control message should then contain either the phase of the sending local controller or the expected phase of the receiving local controller. Both alternatives are feasible, and it should be decided which alternative to use and to stick to it throughout the RIS110. It should also be decided where the starting phase is specified in the unit subset of the receiving or sending local controller. For example, again depending on the communication direction of the control message, it can be located in the center of the unit subset, or it can be located in the middle of the face, such as in the middle of the east face when communicating with an adjacent local controller on the east face, or it can be located in a corner unit.

[0056] In other examples, the control message may describe a more complex function for the phase, such as a high-order polynomial in two coordinates of the local controller. The control message should then include coordinates instead of the starting phase, and when the control message is passed to the neighboring local controller, the coordinates of the control message are updated in a similar manner to the starting phase. The coordinates of the receiving or sending local controller are then calculated and included in the control message, and similar points as used for the starting phase can be used, such as the center of a subset of cells, the center of a face, and corners.

[0057] When the coordinates are calculated and transmitted, the control message may further include information of a valid area so that only cells in certain areas of the RIS 110 are updated. The description of the first reflected phase may then be valid only for cells in a valid area of ​​the RIS 110, wherein the valid area defines a subset of cells within the RIS 110. The validity check may be performed either at the receiving local controller or at the sending local controller. If the check is performed at the receiving local controller, then upon receiving the control message it should be checked whether the local controller is in the valid area, and if it is not in the valid area, the control message should be ignored. Conversely, if the check is performed at the sending local controller, then before sending any control message it should be checked which neighboring local controllers have a subset of cells in the valid area, and only sent to these local controllers.

[0058] With a linear phase gradient on the RIS 110, an incident plane wave will be reflected into another plane wave where the direction of the main lobe can be different from that of a mirror located in the same plane as the RIS 110. Figure 6 , by arrows representing the wavefronts of radio waves incident on and outgoing from RIS 110, Figure 6 The reflection angles of the RIS 110 according to two examples are schematically shown. If all cells have the same phase setting, the RIS 110 will behave as a regular mirror, but if a phase gradient is introduced, this provides the possibility to direct the reflection into other directions (see Figure 6 (a)). If a nonlinear phase function is introduced, the RIS 110 can be configured to behave as a curved mirror, concentrating the radio waves into space (see Figure 6 (b)).

[0059] Reference now Figure 7 , which shows a method for setting the reflection phase of the units 112a:112M of the RIS 110 as performed by the central controller 200 of the RIS 110 according to an embodiment. The units 112a:112M are divided into unit subsets 114a:114d, each unit subset 114a:114d having at least two units 112a:112M. The reflection phase of each unit 112a:112M in the units 112a:112M in each unit subset 114a:114d is controlled by the corresponding local controller 300a:300K of each unit subset 114a:114d. The central controller 200 is configured to communicate control messages with the local controllers 300a:300K.

[0060] S104: The central controller 200 sends a first control message to the first local controller 300a among the local controllers 300a:300K. The first control message includes a description of a first reflection phase dedicated to the first unit subset 114a, the reflection phase of the first unit subset 114a being controlled by the first local controller 300a.

[0061] As disclosed above, the central controller may include a receiver to obtain commands from other devices in the communication network (eg, the network node 120). Then, the central controller 200 may be configured to perform (optional) step S102.

[0062] S102: The central controller 200 receives a control command from a wireless device or a network node 120, the control command including a configuration for setting the reflection phase of the units 112a:112M of the RIS 110. The description of the first reflection phase is set according to the configuration.

[0063] As disclosed above, the central controller may provide control messages to more than one local controller, so the control messages may be diffused from multiple points.Then, the central controller 200 may be configured to perform (optional) step S106.

[0064] S106: The central controller 200 sends a second control message to the second local controller 300b among the local controllers 300a:300K, wherein the second control message includes a description of a second reflection phase dedicated to the second unit subset 114b, and the reflection phase of the second unit subset 114b is controlled by the second local controller 300b.

[0065] Reference now Figure 8 , which illustrates a method for setting the reflection phase of the cells 112a:112M of the RIS 110 as performed by a local controller 300a of the RIS 110 according to an embodiment. The local controller 300a is configured to set the reflection phase of the cells 112a:112M in a first cell subset 114a, the first cell subset 114a including at least two cells of the cells 112a:112M. The local controller 300a is configured to transmit control messages with adjacent local controllers 300b:300K in the RIS 110. Each of the adjacent local controllers 300b:300K is configured to set the reflection phase of the cells 112a:112M in a respective second cell subset 114b:114d, each of the second cell subsets 114b:114d having at least two cells 112a:112M.

[0066] S202: The local controller 300a receives a first control message. The first control message includes a description of a first reflection phase dedicated to the first unit subset 114a.

[0067] S210: The local controller 300a sends a second control message to a second local controller 300b among the adjacent local controllers 300b: 300K. The second control message includes a description of a second reflection phase of the second unit subset 114b dedicated to the second local controller 300b. The second reflection phase is based on the first reflection phase and a geometric relationship in the RIS110 between the first unit subset 114a and the second unit subset 114b of the second local controller 300b.

[0068] S212: The local controller 300a sets the reflection phase of each unit in the first unit subset 114a according to the description of the first reflection phase.

[0069] As disclosed above, the local controller may check whether a new gradient is commanded, ie whether the gradient is different from its current setting.The local controller 300a may then be configured to perform (optional) step S204.

[0070] S204: The local controller 300a verifies before sending the second control message that the description of the first reflection phase results in an update of the description of the second reflection phase that was most recently sent.

[0071] As disclosed above, the description of the first reflection phase may be valid only for cells in the active area of ​​the RIS 110. Then, the local controller 300a may be configured to perform (optional) step S206.

[0072] S206: The local controller 300a verifies that the first cell subset 114a is included in the cells in the valid area before setting the reflection phase of each cell in the first cell subset 114a.

[0073] As disclosed above, the local controller 300a may communicate control messages with more than one other local controller.Then, the local controller 300a may be configured to perform (optional) step S208.

[0074] S208: The local controller 300a sends a third control message to a third local controller 300c among the adjacent local controllers 300b:300K. The third control message includes a description of a third reflection phase of the second unit subset 114b dedicated to the third local controller 300c. The third reflection phase is based on the first reflection phase and a geometric relationship in the RIS110 between the first unit subset 114a and the second unit subset 114b of the third local controller 300c.

[0075] Next reference Fig. 9 , Fig. 9 It is used to illustrate how the phases of the units 112a : 112M of the RIS 110 can be set. Fig. 9 1 shows four unit subsets 114a:114d of the RIS 110, wherein each unit subset 114a:114d is controlled by its own local controller (not shown). Accordingly, each unit subset 114a:114d consists of 25 units, provided in a 5×5 subarray, wherein the three units of the unit subset 114a are identified by reference numerals 112a, 112b, and 112c.

[0076] Consider the case where the local controller of cell subset 114a propagates a control message to its neighbors to the north, east, and west, i.e., to the local controllers of cell subsets 114c, 114d, and 114b, respectively. Further assume that in this case, the gradient of each cell in the north direction is a 21 degree increase, and the gradient of each cell in the east direction is a 7 degree increase. Further assume that the phase of the center cell in each cell subset is used when transmitting the control message, and the expected receiver phase is used. Cell 112a is the center cell in cell subset 114a. Further assume that the local controller for cell subset 114a has just received the gradient information, as well as the information that the center cell 112a should be at 57 degrees. Further assume that this is a new value that should be propagated through cell subset 114a and provided to the local controllers of cell subsets 114b, 114c, and 114d.

[0077] To the west, i.e., to the local controller of cell subset 114b, the center cell phase will be equal to the actual center cell phase minus the increment times 5 (where 5 is the center-to-center distance between the two 5×5 subarrays), which is equal to 57-7·5=57-35=22 degrees. Therefore, the control message with the new gradient sent to the local controller of cell subset 114b will specify a center cell phase of 22 degrees. In the control message sent to the north (i.e., to the local controller of cell subset 114c), the center cell phase will be 57+21·5=57+105=162 degrees. In the control message sent to the east (i.e., to the local controller of cell subset 114d), the center cell phase will be 57+35=92 degrees. Each local controller can then calculate the phase value for each of the remaining cells in its cell subset based on the received center cell phase and gradient and apply it to the resolution of the phase shifter after quantization. If the phase value exceeds 360 degrees, 360 degrees may be subtracted from the result, and if the phase result is negative, 360 degrees may be added to the result. This ensures that each phase value will be in the interval 0 to 360 degrees. Alternatively, subtraction and addition may be applied to keep all phase values ​​within +180 degrees and -180 degrees.

[0078] In summary, at least some embodiments have disclosed a method of controlling a RIS 110 using a set of distributed local controllers of identical design, wherein each local controller is configured to set the reflection phase of its own subset of units and propagate control message units to neighboring local controllers. The control message is initially sent from a central controller to one or several of the local controllers, and then propagated from one local controller to one or more other local controllers through the interconnect until the units of the entire RIS 110 have been updated.

[0079] Fig.10 The components of the central controller 200 according to an embodiment are schematically shown in the form of a plurality of functional units. The processing circuit 1110 is provided using any combination of one or more of the following: a suitable central processing unit (CPU), a multiprocessor, a microcontroller, a digital signal processor (DSP), etc., which are capable of executing a computer program product 1510a (e.g., stored in the form of a storage medium 1130) Fig.14 The processing circuit 1110 may also be provided as at least one application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0080] Specifically, the processing circuit 1110 is configured to cause the central controller 200 to perform a set of operations or steps as disclosed above. For example, the storage medium 1130 may store the set of operations, and the processing circuit 1110 may be configured to retrieve the set of operations from the storage medium 1130 to cause the central controller 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Therefore, the processing circuit 1110 is thereby arranged to perform the method disclosed herein.

[0081] The storage medium 1130 may also include persistent storage, which may be, for example, any single memory or combination of magnetic storage, optical storage, solid-state storage, or even remotely mounted storage.

[0082] The central controller 200 may further include a communication interface 1120 for communicating with the network node 120 and at least one of the local controllers 300a:300d. Thus, the communication interface 1120 may include one or more transmitters and receivers, including analog and digital components.

[0083] The processing circuit 1110 controls the general operation of the central controller 200, such as by sending data and control signals to the communication interface 1120 and the storage medium 1130, by receiving data and reports from the communication interface 1120, and by retrieving data and instructions from the storage medium 1130. Other components of the central controller 200 and related functions are omitted to avoid obscuring the concepts presented herein.

[0084] Fig.11 The components of the central controller 200 according to the embodiment are schematically shown in the form of a plurality of functional modules. Fig.11 The central controller 200 includes a sending module 210b configured to perform step S104. Fig.11 The central controller 200 may also include a plurality of optional functional modules, such as any one of a receiving module 210a configured to perform step S102 and a sending module 210c configured to perform step S106. In general, each functional module 210a:210c may be implemented in hardware or software. Preferably, one or more or all functional modules 210a:210c may be implemented by a processing circuit 1110, possibly in cooperation with a communication interface 1120 and / or a storage medium 1130. Therefore, the processing circuit 1110 may be arranged to obtain instructions as provided by the functional modules 210a:210c from the storage medium 1130 and execute these instructions, thereby performing any steps of the central controller 200 as disclosed herein.

[0085] Fig.12 The components of the local controller 300a according to an embodiment are schematically shown in the form of a plurality of functional units. The processing circuit 1310 is provided using any combination of one or more of the following: a suitable central processing unit (CPU), a multiprocessor, a microcontroller, a digital signal processor (DSP), etc., which are capable of executing a computer program product 1510b (e.g., stored in the form of a storage medium 1330) Fig.14 The processing circuit 1310 may also be provided as at least one application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0086] Specifically, the processing circuit 1310 is configured to cause the local controller 300a to perform a set of operations or steps as disclosed above. For example, the storage medium 1330 may store the set of operations, and the processing circuit 1310 may be configured to retrieve the set of operations from the storage medium 1330 to cause the local controller 300a to perform the set of operations. The set of operations may be provided as a set of executable instructions. Therefore, the processing circuit 1310 is thereby arranged to perform the method as disclosed herein.

[0087] The storage medium 1330 may also include persistent storage, which may be, for example, any single memory or combination of magnetic storage, optical storage, solid-state storage, or even remotely mounted storage.

[0088] The local controller 300a may also include a communication interface 1320 for communicating with units of its own subset of units, with other local controllers 300b:300d, and possibly with the central controller 200. Thus, the communication interface 1320 may include one or more transmitters and receivers, including analog and digital components.

[0089] The processing circuit 1310 controls the general operation of the local controller 300a, such as by sending data and control signals to the communication interface 1320 and the storage medium 1330, by receiving data and reports from the communication interface 1320, and by retrieving data and instructions from the storage medium 1330. Other components of the local controller 300a and related functions are omitted to avoid obscuring the concepts presented herein.

[0090] Fig.13 The components of the local controller 300a according to the embodiment are schematically shown in the form of a plurality of functional modules. Fig.13 The local controller 300a includes multiple functional modules; a receiving module 310a configured to execute step S202, a sending module 310e configured to execute step S210, and a setting module 310f configured to execute step S212. Fig.13 The local controller 300a may also include a plurality of optional functional modules, such as any one of a verification module 310b configured to perform step S204, a sending module 310c configured to perform step S206, and a verification module 310d configured to perform step S208. In general, each functional module 310a:310f may be implemented in hardware or software. Preferably, one or more or all functional modules 310a:310f may be implemented by a processing circuit 1310, possibly in cooperation with a communication interface 1320 and / or a storage medium 1330. Therefore, the processing circuit 1310 may be arranged to obtain instructions provided by the functional modules 310a:310f from the storage medium 1330 and execute these instructions, thereby performing any steps of the local controller 300a disclosed herein.

[0091] Fig.14An example of a computer program product 1510a, 1510b comprising a computer readable device 1530 is shown. On the computer readable device 1530, a computer program 1520a may be stored, which may cause the processing circuit 1110 and entities and devices operatively coupled thereto (e.g., communication interface 1120 and storage medium 1130) to perform methods according to embodiments described herein. Thus, the computer program 1520a and / or the computer program product 1510a may provide means for performing any steps of the central controller 200 as disclosed herein. On the computer readable device 1530, a computer program 1520b may be stored, which may cause the processing circuit 1310 and entities and devices operatively coupled thereto (e.g., communication interface 1320 and storage medium 1330) to perform methods according to embodiments described herein. Thus, the computer program 1520b and / or computer program product 1510b may provide means for performing any of the steps of the local controller 300a disclosed herein.

[0092] exist Fig.14 In the example of , the computer program products 1510a, 1510b are shown as an optical disc, such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) or a Blu-ray Disc. The computer program products 1510a, 1510b may also be implemented as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM) or an electrically erasable programmable read-only memory (EEPROM), and more specifically, may be implemented as a non-volatile storage medium of a device in an external memory, such as a USB (Universal Serial Bus) memory or a flash memory, such as a compact flash. Therefore, although the computer programs 1520a, 1520b are schematically shown herein as tracks on the depicted optical disc, the computer programs 1520a, 1520b may be stored in any manner suitable for the computer program products 1510a, 1510b.

[0093] The inventive concept has mainly been described above with reference to several embodiments. However, as readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept as defined by the appended patent claims.

Claims

1. A central controller (200) for setting the reflection phase of a unit (112a:112M) of a reconfigurable smart surface (110), wherein: The units (112a:112M) are divided into unit subsets (114a:114d), each unit subset (114a:114d) having at least two units (112a:112M), wherein the reflection phase of each unit in the units (112a:112M) in each unit subset (114a:114d) is controlled by a corresponding local controller (300a:300K) of each unit subset (114a:114d), wherein the central controller (200) is configured to transmit control messages with the local controllers (300a:300K), wherein the central controller (200) comprises a processing circuit (1110), and wherein the processing circuit (1110) is configured to cause the central controller (200) to: A first control message is sent to a first local controller (300a) among the local controllers (300a:300K), wherein the first control message includes a description of a first reflection phase dedicated to a first unit subset (114a), and the reflection phase of the first unit subset (114a) is controlled by the first local controller (300a).

2. The central controller (200) according to claim 1, wherein: Each of the local controllers (300a:300K) is embedded in, integrated with, or part of one unit (112a:112M) of each unit subset in the unit subset (114a:114d).

3. The central controller (200) according to any one of the preceding claims, wherein: The processing circuit (1110) is configured to enable the central controller (200): A control command is received from a wireless device (140) or a network node (120), wherein the control command comprises a configuration for setting the reflection phase of the unit (112a:112M) of the reconfigurable smart surface (110), and wherein the description of the first reflection phase is set according to the configuration.

4. The central controller (200) according to any one of the preceding claims, wherein: The description of the first reflection phase is valid only for cells in an active area of ​​the reconfigurable smart surface (110), wherein the active area defines a subset of the cells within the reconfigurable smart surface (110).

5. The central controller (200) according to any one of the preceding claims, wherein: The description of the first reflection phase defines a phase value of the reflection phase and a phase gradient for the reflection phase that are specific to the first local controller (300a).

6. The central controller (200) according to any one of the preceding claims, wherein: The description of the first reflected phase is provided in either the following manner: an initial phase value specific to the first local controller (300a) and a phase gradient for the reflected phase, or: coordinates of the first subset of cells (114a) in the reconfigurable smart surface (110) and coefficients of an expression for calculating a phase value of the reflected phase for the cells at the coordinates in the reconfigurable smart surface (110).

7. The central controller (200) according to any one of the preceding claims, wherein: The processing circuit (1110) is configured to enable the central controller (200): A second control message is sent to a second local controller (300b) among the local controllers (300a:300K), wherein the second control message includes a description of a second reflection phase dedicated to a second unit subset (114b), and the reflection phase of the second unit subset is controlled by the second local controller (300b).

8. The central controller (200) according to any one of the preceding claims, wherein: The reconfigurable smart surface (110) has a planar surface, the units (112a: 112M) are distributed on the planar surface, and the planar surface has a non-rectangular and / or asymmetrical shape.

9. A local controller (300a) for setting the reflection phase of a unit (112a:112M) of a reconfigurable smart surface (110), wherein: The local controller (300a) is configured to set the reflection phase of a cell (112a:112M) in a first cell subset (114a), the first cell subset (114a) including at least two cells in the cells (112a:112M), wherein the local controller (300a) is configured to transmit a control message to an adjacent local controller (300b:300K) in the reconfigurable smart surface (110), wherein the adjacent local controller (300b:300K) Each adjacent local controller in a second unit subset (114b:114d) is configured to set the reflection phase of the unit (112a:112M) in the corresponding second unit subset (114b:114d), each second unit subset in the second unit subset (114b:114d) having at least two units (112a:112M), wherein the local controller (300a) comprises a processing circuit (1310), and wherein the processing circuit (1310) is configured to cause the local controller (300a) to: receiving a first control message, wherein the first control message comprises a description of a first reflection phase specific to the first subset of units (114a); sending a second control message to a second local controller (300b) of the adjacent local controllers (300b:300K), wherein the second control message includes a description of a second reflection phase of the second unit subset (114b) dedicated to the second local controller (300b), and wherein the second reflection phase is based on the first reflection phase and a geometric relationship between the first unit subset (114a) and the second unit subset (114b) of the second local controller (300b) in the reconfigurable smart surface (110); and The reflection phase of each element in the first subset of elements (114a) is set according to the description of the first reflection phase.

10. The local controller (300a) according to claim 9, wherein: The local controller (300a) is embedded in, integrated with, or part of one unit (112a:112M) in the first subset of units (114a:114d).

11. The local controller (300a) according to claim 9 or 10, wherein: The first control message is received from a fourth local controller (300d) among the adjacent local controllers (300b:300K) or from a central controller (200) of the reconfigurable smart surface (110).

12. The local controller (300a) according to any one of claims 9 to 11, wherein: The processing circuit (1310) is configured to cause the local controller (300a): Before sending the second control message, verifying the description of the first reflection phase results in an update of the most recently sent description of the second reflection phase.

13. The local controller (300a) according to any one of claims 9 to 12, wherein: The description of the first reflection phase is valid only for cells in an active area of ​​the reconfigurable smart surface (110), and wherein the processing circuit (1310) is configured to cause the local controller (300a): Before setting the reflection phase of each cell in the first cell subset (114a), it is verified that the first cell subset (114a) is included in the cells in the active area.

14. The local controller (300a) according to any one of claims 9 to 13, wherein: The description of the first reflection phase defines a phase value of the reflection phase and a phase gradient for the reflection phase that are specific to the local controller (300a).

15. The local controller (300a) according to claim 14, wherein: According to the description of the first reflection phase, setting the reflection phase of each unit in the first subset of units (114a) comprises quantizing the phase value of the reflection phase specific to the local controller (300a).

16. The local controller (300a) according to any one of claims 9 to 15, wherein: The description of the first reflected phase is provided in either the following manner: an initial phase value specific to the local controller (300a) and a phase gradient for the reflected phase, or: coordinates of the first subset of cells (114a) in the reconfigurable smart surface (110) and coefficients of an expression for calculating a phase value of the reflected phase for the cells at the coordinates in the reconfigurable smart surface (110).

17. The local controller (300a) according to any one of claims 9 to 16, wherein: The first subset of cells (114a) comprises a plurality of cells, and wherein a separate reflection phase is set for each cell of the plurality of cells.

18. The local controller (300a) according to claim 17, wherein: The description of the first reflection phase specifies the reflection phase for exactly one of the plurality of cells, and wherein the reflection phase for exactly one of the plurality of cells is used as a reference when setting the reflection phase for the remaining cells in the first subset of cells (114a).

19. The local controller (300a) according to any one of claims 9 to 18, wherein: The processing circuit (1310) is configured to cause the local controller (300a): A third control message is sent to a third local controller (300c) among the adjacent local controllers (300b:300K), wherein the third control message includes a description of a third reflection phase of the second unit subset (114c) dedicated to the third local controller (300c), and wherein the third reflection phase is based on the first reflection phase and a geometric relationship between the first unit subset (114a) and the second unit subset (114c) of the third local controller (300c) in the reconfigurable smart surface (110).

20. The local controller (300a) according to any one of claims 9 to 19, wherein: The local controller (300a) is configured to transmit the control message to the adjacent local controller (300b:300K) via a bidirectional connection.

21. A system for setting the reflection phase of a unit (112a:112M) of a reconfigurable smart surface (110), the system comprising a central controller (200) according to any one of claims 1-8 and at least one local controller (300a) according to any one of claims 9-20.

22. A method for setting the reflection phase of a unit (112a:112M) of a reconfigurable smart surface (110), wherein: The cells (112a:112M) are divided into cell subsets (114a:114d), each cell subset (114a:114d) having at least two cells (112a:112M), wherein the reflection phase of each cell in the cells (112a:112M) in each cell subset (114a:114d) is controlled by a corresponding local controller (300a:300K) of each cell subset (114a:114d), wherein the method is performed by a central controller (200) of the reconfigurable smart surface (110), wherein the central controller (200) is configured to transmit control messages with the local controllers (300a:300K), and wherein the method comprises: A first control message is sent (S104) to a first local controller (300a) among the local controllers (300a:300K), wherein the first control message includes a description of a first reflection phase dedicated to a first unit subset (114a), and the reflection phase of the first unit subset (114a) is controlled by the first local controller (300a).

23. A method for setting the reflection phase of a unit (112a:112M) of a reconfigurable smart surface (110), wherein: The method is performed by a local controller (300a) of the reconfigurable smart surface (110), wherein the local controller (300a) is configured to set the reflection phase of a cell (112a:112M) in a first cell subset (114a), the first cell subset (114a) comprising at least two cells of the cells (112a:112M), wherein the local controller (300a) is configured to communicate with adjacent cells in the reconfigurable smart surface (110). A method for transmitting a control message to a local controller (300b:300K) of the adjacent local controllers (300b:300K), wherein each of the adjacent local controllers (300b:300K) is configured to set the reflection phase of the unit (112a:112M) in the corresponding second unit subset (114b:114d), each second unit subset in the second unit subset (114b:114d) having at least two units (112a:112M), and wherein the method comprises: Receiving (S202) a first control message, wherein the first control message comprises a description of a first reflection phase specific to the first subset of units (114a); sending (S210) a second control message to a second local controller (300b) of the adjacent local controllers (300b:300K), wherein the second control message comprises a description of a second reflection phase of the second unit subset (114b) dedicated to the second local controller (300b), and wherein the second reflection phase is based on the first reflection phase and a geometric relationship between the first unit subset (114a) and the second unit subset (114b) of the second local controller (300b) in the reconfigurable smart surface (110); and According to the description of the first reflection phase, the reflection phase of each unit in the first unit subset (114a) is set (S212).

24. A computer program (1520a) for setting a reflection phase of a cell (112a:112M) of a reconfigurable smart surface (110), wherein: The cells (112a:112M) are divided into cell subsets (114a:114d), each cell subset (114a:114d) having at least two cells (112a:112M), wherein the reflection phase of each cell in the cells (112a:112M) in each cell subset (114a:114d) is controlled by a corresponding local controller (300a:300K) of each cell subset (114a:114d), and the computer program comprises computer code which, when executed on a processing circuit (210) of a central controller (200) of the reconfigurable smart surface (110) configured to transmit control messages to the local controllers (300a:300K), causes the central controller (200) to: A first control message is sent (S104) to a first local controller (300a) among the local controllers (300a:300K), wherein the first control message includes a description of a first reflection phase dedicated to a first unit subset (114a), and the reflection phase of the first unit subset (114a) is controlled by the first local controller (300a).

25. A computer program (1520b) for setting the reflection phase of a unit (112a:112M) of a reconfigurable smart surface (110), the computer program comprising computer code, when the computer code is run on a processing circuit (1310) of a local controller (300a) of the reconfigurable smart surface (110), wherein: The local controller (300a) is configured to set the reflection phase of a cell (112a:112M) in a first cell subset (114a), the first cell subset (114a) comprising at least two cells of the cells (112a:112M), wherein the local controller (300a) is configured to transmit a control message to an adjacent local controller (300b:300K) in the reconfigurable smart surface (110), wherein each adjacent local controller of the adjacent local controllers (300b:300K) is configured to set the reflection phase of a cell (112a:112M) in a corresponding second cell subset (114b:114d), each second cell subset of the second cell subset (114b:114d) having at least two cells (112a:112M), such that the local controller (300a): Receiving (S202) a first control message, wherein the first control message comprises a description of a first reflection phase specific to the first subset of units (114a); sending (S210) a second control message to a second local controller (300b) of the adjacent local controllers (300b:300K), wherein the second control message comprises a description of a second reflection phase of the second unit subset (114b) dedicated to the second local controller (300b), and wherein the second reflection phase is based on the first reflection phase and a geometric relationship between the first unit subset (114a) and the second unit subset (114b) of the second local controller (300b) in the reconfigurable smart surface (110); and According to the description of the first reflection phase, the reflection phase of each unit in the first unit subset (114a) is set (S212).

26. A computer program product (1510a, 1510b) comprising a computer program (1520a, 1520b) according to at least one of claims 24 and 25, and a computer readable storage medium (1530) on which the computer program is stored.

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