Inter-cell interference suppression in RIS assisted wireless networks

Abstract

Methods and apparatus for inter-cell interference mitigation under a reconfigurable intelligent surface (RIS) assisted wireless network are disclosed. In one embodiment, a first network node (e.g., a base station or UE) in a first cell includes a transceiver; and a processor coupled to the transceiver, where the processor is configured to: receive, via the transceiver from a second network node in a second cell, an indication of an optimal reflection coefficient of a second RIS in the second cell, where the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and determining the optimal reflection coefficient of the first RIS in the first cell according to the indication of the optimal reflection coefficient of the second RIS, so as to suppress the interference of the first cell on the second cell.

Description

Technical Field

[0001] The subject matter disclosed herein relates generally to wireless communications, and more particularly to methods and apparatus for inter-cell interference suppression in reconfigurable smart surface (RIS)-assisted wireless networks. Background Art

[0002] The following abbreviations are defined herein, at least some of which may be used in the following description: new radio (NR), very large scale integration (VLSI), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), compact disc read-only memory (CD-ROM), local area network (LAN), wide area network (WAN), user equipment (UE), evolved Node B (eNB), next-generation Node B (gNB), uplink (UL), downlink (DL), central processing unit (CPU), graphics processing unit (GPU), field programmable gate array (FPGA), orthogonal frequency division multiplexing (OFDM), radio resource control (RRC), user entity / equipment (mobile terminal), transmitter (TX), receiver (RX), reconfigurable smart surface (RIS), large smart surface (LIS), smart reflecting surface (IRS), electromagnetic (EM), radio frequency (RF), sixth generation (6G), base station (BS), transmission reception point (TRP), signal-to-interference-plus-noise ratio (SINR), received signal received power (RSRP), channel state information (CSI).

[0003] Reconfigurable smart surfaces (RIS), which can alternatively be referred to as large smart surfaces (LIS), intelligent reflective surfaces (IRS), or smart metasurfaces, are an emerging technology. RIS are large, thin metasurfaces of metallic or dielectric materials that include an array of passive subwavelength scattering elements with a specially designed physical structure. These elements can be controlled in a software-defined manner to alter the electromagnetic (EM) properties (e.g., phase shift and / or amplitude attenuation) of the reflection of an incident radio frequency (RF) signal. By jointly controlling the phase of all scattering elements, the reflected radiation pattern of the incident RF signal can be arbitrarily tuned in real time, thereby creating new degrees of freedom for optimizing overall wireless network performance. RIS can effectively control the response of electromagnetic waves in real time and is considered one of the potential key technologies for 6G systems.

[0004] Figure 1Figure 2 illustrates a typical deployment of a RIS in a modern mobile communication system, where the RIS is controlled by a base station (BS)—such as a gNB or TRP—via a dedicated interface. (Note that if the RIS is considered a new node class in a 6G network, an interface may be defined.) The RIS forwards signals from the BS to the target user equipment (UE). That is, in addition to the direct link from the BS to the UE, the RIS also forms a cascade link between the BS and the UE.

[0005] The present invention is directed to an inter-cell interference suppression solution in a RIS-assisted wireless network. Summary of the Invention

[0006] Disclosed are a method and apparatus for inter-cell interference suppression in a wireless network assisted by a reconfigurable smart surface (RIS).

[0007] In one embodiment, a first network node (e.g., a base station or a UE) in a first cell includes a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receive, from a second network node in a second cell via the transceiver, an indication of an optimal reflection coefficient of a second RIS in the second cell, wherein the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and determine, based on the indication of the optimal reflection coefficient of the second RIS, an optimal reflection coefficient of the first RIS in the first cell for suppressing interference of the first cell to the second cell.

[0008] In some embodiments, the optimal reflection coefficient of the first RIS results in a reflection direction of the first RIS that is orthogonal to a reflection direction of the second RIS caused by the optimal reflection coefficient of the second RIS.

[0009] In some embodiments, the processor is further configured to receive, via the transceiver, a matching map of the first RIS and the second RIS; and the processor is configured to determine the optimal reflection coefficient of the first RIS based on an indication of the optimal reflection coefficient of the second RIS, which is an index of the optimal reflection coefficient of the second RIS, and the matching map. In particular, the matching map includes a plurality of pairs, each pair including a reflection coefficient of the first RIS and a reflection coefficient of the second RIS, and the optimal reflection coefficient of the first RIS is determined from any pair including the optimal reflection coefficient of the second RIS, other than a pair including the optimal reflection coefficient of the second RIS and the reflection coefficient of the first RIS that results in optimal signal transmission through the first RIS.

[0010] In some embodiments, the first network node is a first base station unit in a first cell, and the second network node is a second base station unit in a second cell. The optimal reflection coefficient of the second RIS is determined based on an SINR or RSRP reported by a UE in the second cell to the second network node, wherein the SINR or RSRP is calculated for each candidate reflection coefficient of the second RIS. The processor may be configured to receive an indication of the optimal reflection coefficient of the second RIS from the second base station unit via the transceiver over an Xn interface.

[0011] In some embodiments, the first network node is a first UE in a first cell, and the second network node is a second UE in a second cell. The optimal reflection coefficient of the second RIS may be determined by the second UE based on an SINR or RSRP calculated for each candidate reflection coefficient of the second RIS. The processor may be configured to receive an indication of the optimal reflection coefficient of the second RIS from the second UE via a transceiver via a PC5 interface. Alternatively, the processor may be configured to receive an indication of the optimal reflection coefficient of the second RIS from a base station unit in the first cell via a transceiver via RRC signaling or a MAC CE.

[0012] In another embodiment, a method performed at a base station or a UE includes: receiving an indication of an optimal reflection coefficient of a second RIS in the second cell from a second network node in the second cell, wherein the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and determining, based on the indication of the optimal reflection coefficient of the second RIS, an optimal reflection coefficient of the first RIS in the first cell for suppressing interference of the first cell to the second cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments illustrated in the accompanying drawings. Understanding that these drawings depict only some embodiments and are therefore not to be considered limiting of scope, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0014] Figure 1 The diagram shows the typical deployment of RIS in modern mobile communication systems;

[0015] Figure 2 The figure shows a RIS-assisted downlink multi-cell wireless system;

[0016] Figure 3 A process according to a first embodiment is illustrated;

[0017] Figure 4 illustrates a process according to a second embodiment;

[0018] Figure 5illustrates a process according to a third embodiment;

[0019] Figure 6 illustrates a process according to a fourth embodiment;

[0020] Figure 7 is a schematic flow chart illustrating an embodiment of a method; and

[0021] Figure 8 is a schematic block diagram illustrating an apparatus according to one embodiment. DETAILED DESCRIPTION

[0022] As will be appreciated by those skilled in the art, certain aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Thus, the embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may generally be referred to herein as a "circuit," "module," or "system." Furthermore, the embodiments may take the form of a program product embodied in one or more computer-readable storage devices storing machine-readable code, computer-readable code, and / or program code, hereinafter referred to as "code." The storage device may be tangible, non-transitory, and / or non-transmitting. The storage device may not embody signals. In one embodiment, the storage device employs only signals for accessing the code.

[0023] Certain functional units described in this specification may be labeled "modules" to more specifically emphasize their independent implementation. For example, a module may be implemented as a hardware circuit comprising custom very large scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, or programmable logic devices.

[0024] Modules can also be implemented with code and / or software for execution by various types of processors. The identified code module can, for example, include one or more physical or logical executable code blocks, which can, for example, be organized as objects, procedures, or functions. However, the executable files of the identified modules do not need to be physically located together, but can include different instructions stored in different locations that, when logically joined together, include the module and achieve the purpose of the module.

[0025] In fact, code module can comprise single instruction or many instructions, and can even be distributed on several different code segments, among different programs and across several memory devices.Similarly, operational data can be identified and illustrated in this article in module, and can be embodied and organized in the data structure of any suitable type in any suitable form.This operational data can be collected as single data set, or can be distributed in different locations, including being distributed on different computer-readable storage devices.When a module or the part of a module is implemented with software, the software portion is stored on one or more computer-readable storage devices.

[0026] Any combination of one or more computer-readable media may be utilized. The computer-readable medium may be a computer-readable storage medium. The computer-readable storage medium may be a storage device that stores code. The storage device may be, for example, but need not be, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0027] A non-exhaustive list of more specific examples of storage devices would include the following: an electrical connection having one or more conductors, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0028] The code for performing the operations of the embodiments may comprise any number of lines and may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Python, Ruby, Java, Smalltalk, C++, and the like, as well as conventional procedural programming languages ​​such as the "C" programming language and / or machine languages ​​such as assembly language. The code may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be established to an external computer (e.g., via the Internet using an Internet service provider).

[0029] References throughout this specification to "one embodiment," "an embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, unless expressly specified otherwise, the appearance of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but do mean "one or more, but not all, embodiments." Unless expressly specified otherwise, the terms "comprise," "comprising," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise. An enumerated list of items does not imply that any or all items are mutually exclusive, unless expressly specified otherwise. The terms "a," "an," and "the" also mean "one or more," unless expressly specified otherwise.

[0030] In addition, the features, structures or characteristics of the various embodiments can be combined in any suitable manner. In the following description, many specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of the embodiments. However, those skilled in the art will recognize that the embodiments can be practiced without one or more of the specific details or using other methods, components, materials, etc. In other instances, well-known structures, materials or operations are not shown or described in detail to avoid any ambiguity in the various aspects of the embodiments.

[0031] Aspects of various embodiments are described below with reference to schematic flow charts and / or schematic block diagrams of methods, devices, systems, and program products according to embodiments. It will be understood that each block in the schematic flow charts and / or schematic block diagrams, as well as combinations of blocks in the schematic flow charts and / or schematic block diagrams, can be implemented by code. The code can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to generate a machine, such that instructions executed by the processor of the computer or other programmable data processing device create means for implementing the functions specified in the schematic flow charts and / or schematic block diagrams of one or more blocks.

[0032] The code may also be stored in a storage device that is capable of directing a computer, other programmable data processing apparatus, or other device to function in a specific manner so that the instructions stored in the storage device produce an article of manufacture including instructions that implement the functions specified in one or more blocks of the schematic flowchart and / or schematic block diagram.

[0033] The code may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operating steps are executed on the computer, other programmable apparatus, or other device to produce a computer-implemented process, so that the code executed on the computer or other programmable apparatus provides a process for implementing the functions specified in one or more blocks of the flowchart and / or block diagram.

[0034] The schematic flowcharts and / or schematic block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of devices, systems, methods, and program products according to various embodiments. In this regard, each block in the schematic flowcharts and / or schematic block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing a specified logical function.

[0035] It should also be noted that in some alternative implementations, the functions indicated in the blocks may not occur in the order indicated in the figures. For example, depending on the functionality involved, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order. Other steps and methods are contemplated that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated figures.

[0036] Although various arrow types and line types may be employed in the flowcharts and / or block diagrams, they are understood not to limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the depicted embodiments. For example, arrows may indicate waiting or monitoring periods of unspecified duration between enumerated steps of the depicted embodiments. It will also be noted that each block of the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by a dedicated hardware-based system or a combination of dedicated hardware and code that performs the specified functions or actions.

[0037] The description of an element in each figure may refer to an element in a previous figure. The same reference numerals refer to the same elements in all figures, including alternative embodiments of the same elements.

[0038] In cellular networks, multiple cells can operate on the same frequency to improve spectrum utilization. Each cell can have a gNB placed at the center of the cell, serving a set of UEs. Cells operating on the same carrier frequency are referred to as co-channel cells. A UE in one co-channel cell, especially one located at the cell edge, may experience interference from another co-channel cell (or multiple co-channel cells), which can be referred to as inter-cell interference. To enhance system performance, inter-cell interference must be eliminated or at least mitigated.

[0039] The present disclosure relates to mitigating inter-cell interference in RIS-assisted wireless networks.

[0040] exist Figure 2 Figure 2 shows a multi-cell wireless system with RIS-assisted downlink. Cell-edge users (or cell-edge UEs) are located between the source cell and a neighboring cell. This means that users can be served by both the source cell and the neighboring cell. Each cell has a gNB and a RIS. Specifically, the source cell includes the source gNB and RIS#1; and the neighboring cell includes the target gNB and RIS#2.

[0041] Cell-edge users can receive signals from four links: a direct link from the source gNB, a cascade link from the source gNB via RIS#1, a direct link from the target gNB, and a cascade link from the target gNB via RIS#2. Incidentally, since the path loss effect between gNBs and RISs in different cells is relatively weak, the cascade link from the source gNB via RIS#2 and the cascade link from the target gNB via RIS#1 are omitted.

[0042] Without loss of generality, it is assumed that all RIS (e.g., RIS#1 and RIS#2) have the same number of reflective elements (e.g., reflective elements, of which >=1).

[0043] The channel gain from the source gNB directly to the cell edge user is expressed as The channel gain from the source gNB to RIS#1 is expressed as ; and the channel gain from RIS#1 to the cell edge user is expressed as Similarly, the channel gain from the target gNB directly to the cell edge user is expressed as The channel gain from the target gNB to RIS#2 is expressed as ; and the channel gain from RIS#2 to the cell edge user is expressed as .

[0044] There can be one source cell and multiple neighboring cells (e.g., one source cell and adjacent cells). ( From 1 to The diagonal reflection matrix of the RIS in the cell (where each cell is assumed to have one RIS) is given by Indicates that, It is in The first RIS in the community ( From 1 to ) reflection coefficient, where It is The amplitude of the element, and It is The phase of the element.

[0045] For simplicity, in the following description, it is assumed that there is only one neighboring cell. This means that the first cell is the source cell and the second cell is the neighboring cell. Therefore, the RIS of the source cell (e.g., Figure 2 The diagonal reflection matrix of RIS#1 in is given by indicates; and the RIS of the neighboring cells (e.g., Figure 2 The diagonal reflection matrix of RIS#2 in is given by express.

[0046] The symbols of the transmission at the gNB in ​​the first cell (i.e., the source cell) are represented by denoted by ; and the symbol of the transmission at the gNB in ​​the second cell (i.e., the neighboring cell) is represented by Therefore, the overall received signal including interference and noise at the cell edge user is given by Given, where It is an expectation signal. is the inter-cell interference signal, and yes Additive white Gaussian noise in follows a Gaussian distribution (or normal distribution), where the mathematical expectation (or mean) is 0 and the variance is ).

[0047] Therefore, the signal to interference plus noise ratio (SINR) of the cell-edge user in the source cell can be modeled as Equation #1: ,in Indicates the transmit power per resource block in each cell.

[0048] From formula #1, we can see that by reducing the interference between cells The system performance can be improved. In particular, the diagonal reflection matrix of RIS#2 (i.e. ) can be configured to change the reflection direction of the signal reflected by RIS#2, resulting in channel gain Like this, and Both can be changed to suppress inter-cell interference.

[0049] ,in, , m=1 to , It is The amplitude of the element, and It is The phase of the element.

[0050] The combination of can be called the reflection coefficient of RIS#2. Each of the (i.e., amplitude) and (i.e., phase). For simplicity, it is assumed that the amplitude of each element is fixed to 1, such as for far-field communication. This means Each of these can be viewed as depending on the (i.e., phase). Thus, where m is a number from 1 to of Each combination of (i.e., Each combination of corresponds to the reflection direction of the signal reflected by RIS#2. Therefore, if it is assumed that the amplitude of each element is fixed to 1, then The combination of can also be called the reflection coefficient of RIS#2. Each reflection coefficient of RIS#2 can result in a different reflection direction of RIS#2.

[0051] The RIS can be controlled by the gNB of the cell where the RIS is deployed, or by the UE in the cell. In the first scenario, each gNB in ​​the cell can control and configure the phase of each element of the RIS (or the reflection coefficient of the RIS) in the cell. In the second scenario, any UE in the cell can control and configure the phase of each element of the RIS (or the reflection coefficient of the RIS) in the cell.

[0052] The first embodiment relates to a first solution in a first scenario. Figure 3 The process of the first embodiment is illustrated.

[0053] UE can be Figure 2 A cell-edge user is shown in the cell-edge region between the source and target gNBs. The source gNB controls RIS#1; and the target gNB controls RIS#2.

[0054] In step 310, the UE in the RRC_CONNECTED state receives downlink data. Specifically, the UE can receive useful signals on both the first direct link from the source gNB and the first tandem link from the source gNB via RIS#1. Additionally, the UE can receive interfering signals on both the second direct link from the target gNB and the second tandem link from the target gNB via RIS#2.

[0055] RIS#1 can be controlled in the same way as RIS#2. That is, the diagonal reflection matrix of RIS#1 (i.e. ) can be configured to change the reflection direction of the signal reflected by RIS#1. ,in, , m=1 to , It is The amplitude of the element, and It is The phase of the element. The combination of can be called the reflection coefficient of RIS#1. Similarly, assume that the amplitude of each element is fixed to 1. Therefore, The combination of can also be called the reflection coefficient of RIS#1. Each reflection coefficient of RIS#1 can result in a different reflection direction of RIS#1.

[0056] For the purpose of illustration, assume that RIS#1 has ( >=1) candidate reflection coefficients; and RIS#2 has ( >=1) candidate reflection coefficients.

[0057] In step 320, RIS#2 is configured with Under any of the reflection coefficients, the UE calculates the received useful signal and the received interference signal for the configurable RIS#1. For each of the reflection coefficients, SINR (eg, L1-SINR) or RSRP (eg, L1-RSRP) is calculated.

[0058] In step 330, the UE can send a measurement report (e.g., a CSI report) to the source gNB, where the measurement report includes the calculated SINR or RSRP for each of the reflection coefficients of RIS#1.

[0059] In step 340, after receiving the measurement report, if all calculated SINR or RSRP (for all If the reflection coefficients of the two signals are all below a predefined threshold, the source gNB can determine that the signal quality is poor and that the poor signal quality is caused by strong interference (e.g., inter-cell interference). or Determine the optimal reflection coefficient of RIS#1. Among the signal qualities resulting from the various reflection coefficients, the reflection coefficient that results in the best signal quality is determined as the optimal reflection coefficient for RIS#1. The source gNB assigns this optimal reflection coefficient to RIS#1 to increase the received signal.

[0060] In step 350, the source gNB decides to suppress inter-cell interference. Specifically, the source gNB can trigger an inter-cell interference suppression message to one or more neighboring gNBs (e.g., the target gNB) via the Xn interface by sending the optimal reflection coefficient of RIS#1 to the target gNB.

[0061] In step 360, after receiving the inter-cell interference suppression message including the optimal reflection coefficient of RIS#1, the target gNB determines an optimal reflection coefficient of RIS#2 that can maximally suppress transmission via RIS#2 based on the optimal reflection coefficient of RIS#1 (which means that interference on the second cascade link from the target gNB via RIS#2 can be minimized). For example, a reflection coefficient of RIS#2 that results in a reflection direction of RIS#2 being orthogonal to a reflection direction of RIS#1 resulting from the optimal reflection coefficient of RIS#1 can be determined as the optimal reflection coefficient of RIS#2 to reduce inter-cell interference.

[0062] In step 370, the target gNB assigns the optimal reflection coefficient of RIS#2 to RIS#2.

[0063] The optimal reflection coefficient of RIS#2 (ie, the optimal phase combination of elements) can make the inter-cell interference Smaller so that inter-cell interference in the RIS-assisted link from the adjacent cell can be suppressed.

[0064] The second embodiment relates to a second solution in the first scenario. Figure 4 The process of the second embodiment is illustrated.

[0065] According to the second embodiment, in order to reduce system processing time, the directional relationship between RIS#1 and RIS#2 is considered to suppress inter-cell interference. Considering that different reflection coefficients of RIS can lead to different reflection directions of RIS, a matching mapping between RIS#1 and RIS#2 can be established. To make the explanation simpler, it is assumed that RIS#1 has three (3) reflection directions (e.g., ) of the discrete reflection coefficients, and RIS#2 has two (2) discrete reflection coefficients that result in two reflection directions (e.g., {1, }) are shown in Table 1, where (m, n) refers to the discrete reflection coefficient with the first The reflection direction of RIS#1 with the reflection coefficient is the same as that of Reflection coefficient of RIS#2 shows the signal effect between the reflection directions.

[0066] right RIS#1_Index 1 RIS#1_Index 2 RIS#1_Index 3 RIS#2_Index 1 For (1, 1) For (2, 1) For (3, 1) RIS#2_Index 2 For (1, 2) For (2, 2) For (3, 2)

[0067] Table 1

[0068] Examples of pairs and their values ​​are shown in Table 2.

[0069]

[0070] In step 405, both the source gNB and the target gNB receive matching mappings between their RISs (e.g., between RIS#1 and RIS#2).

[0071] Steps 410, 420, 430, 440, and 450 are substantially the same as steps 310, 320, 330, 340, and 350, respectively. Some differences are described below: In step 440, the optimal reflection coefficient is the index of one of the candidate reflection coefficients. For example, index 3 of RIS#1 can be determined. In step 450, the optimal reflection coefficient of RIS#1 transmitted is index 3 of RIS#1.

[0072] In step 460, upon receiving the inter-cell interference suppression message including the optimal reflection coefficient of RIS#1 (i.e., the index of the optimal reflection coefficient of RIS#1), the target gNB queries the matching mapping containing pair information to find which reflection direction of RIS#2 achieves optimal signal transmission to the UE. For example, when the optimal reflection coefficient of RIS#1 transmitted is index 3, the pair (3, 1) is the pair where the third reflection coefficient of RIS#1 is the optimal reflection coefficient received from RIS#1 of the source gNB, and the first reflection coefficient of RIS#2 achieves optimal signal transmission to the UE via RIS#2. This means that if the signal transmission to the UE via RIS#2 acts as interference, the pair (3, 1) is not optimal. In other words, (3, x) where x is not 1 can be selected. In other words, the reflection coefficient x of RIS#2 (where x is not 1) can be selected as the optimal reflection coefficient for RIS#2 to suppress inter-cell interference. In the example of Table 2, in addition to the pair (3, 1), only the pair (3, 2) exists. Therefore, the second reflection coefficient of RIS#2 (i.e., the reflection coefficient index is 2) is selected as the optimal reflection coefficient of RIS#2 to suppress inter-cell interference. Incidentally, if there are multiple pairs other than the pair (3, 1), one of the multiple pairs can be randomly selected. In other words, the reflection coefficient of RIS#2 in any pair (3, x) where x is not 1 can be selected.

[0073] Step 470 is the same as step 370 .

[0074] The third embodiment relates to the first solution in the second scenario. Figure 5 The process of the third embodiment is illustrated.

[0075] UE#1 is a cell edge user, which can Figure 2, shown at the cell edge area between the source gNB and the target gNB. UE#1 controls RIS#1. UE#2 ( Figure 2 UE#2 is a user within the coverage of a neighboring cell. UE#2 controls RIS#2.

[0076] In step 510, UE#1 in the RRC_CONNECTED state receives downlink data. Specifically, UE#1 is able to receive useful signals on both the first direct link from the source gNB and the first tandem link from the source gNB via RIS#1. In addition, UE#1 is also able to receive interference signals on both the second direct link from the target gNB and the second tandem link from the target gNB via RIS#2. Assume that RIS#1 has ( >=1) candidate reflection coefficients; and RIS#2 has ( >=1) candidate reflection coefficients.

[0077] In step 520, RIS#2 is configured with Under any of the reflection coefficients, UE#1 calculates the received useful signal and the received interference signal for the RIS#1 that can be configured. For each of the reflection coefficients, SINR (eg, L1-SINR) or RSRP (eg, L1-RSRP) is calculated.

[0078] In step 530, if all calculated SINRs or RSRPs (for all reflection coefficients) are all below a predefined threshold, UE#1 determines that the signal quality is poor and that the poor signal quality is caused by strong interference (e.g., inter-cell interference). Therefore, UE#1 can use or Determine the optimal reflection coefficient of RIS#1. UE#1 assigns the optimal reflection coefficient of RIS#1 to RIS#1.

[0079] In step 540 , UE# 1 decides to suppress inter-cell interference (eg, by triggering an inter-cell interference suppression event).

[0080] Two options (eg, Option A and Option B) are presented to implement step 540 .

[0081] In Option A, it is assumed that a sidelink protocol can be enabled between UE#1 and UE#2, where UE#2 in the neighboring cell can control RIS#2. In step 540a1, UE#1 sends an inter-cell interference suppression message to UE#2 via the PC5 interface by sending the optimal reflection coefficient of RIS#1.

[0082] In Option B, it is assumed that the sidelink protocol cannot be enabled between UE#1 and UE#2. In step 540b1, UE#1 sends the optimal reflection coefficient of RIS#1 to the source gNB. For example, the optimal reflection coefficient RIS#1 can be included in a CSI report to be sent to the source gNB. In step 540b2, the source gNB sends an inter-cell interference mitigation message to one or more neighboring gNBs (e.g., the target gNB) via the Xn interface by sending the optimal reflection coefficient of RIS#1. In step 540b3, the target gNB transmits the optimal reflection coefficient of RIS#1 to UE#2, for example, via higher layer signaling such as RRC signaling or via a MAC CE.

[0083] In step 550 , UE# 2 can generate the optimal reflection coefficient of RIS# 2 in the same manner as described in step 360 .

[0084] In step 560, UE#2 assigns the optimal reflection coefficient of RIS#2 to RIS#2.

[0085] The fourth embodiment relates to the second solution in the second scenario. Figure 6 The process of the second embodiment is illustrated.

[0086] The fourth embodiment is similar to the second embodiment, that is, the directional relationship between RIS#1 and RIS#2 is taken into consideration to suppress inter-cell interference, so as to reduce system processing time.

[0087] In step 605, the matching mapping between RISs (e.g., between RIS#1 and RIS#2) is received by both UE#1 capable of controlling RIS#1 and UE#2 capable of controlling RIS#2. For example, the matching mapping between RIS#1 and RIS#2 can be broadcast in the source cell (including RIS#1) and the neighboring cell (including RIS#2).

[0088] Steps 610, 620, 630, and 640 are substantially the same as steps 510, 520, 530, and 540, respectively. Some differences are described below: In step 640, the optimal reflection coefficient is an index to one of the candidate reflection coefficients. For example, index 3 can be determined for RIS#1.

[0089] In step 650 , the optimal reflection coefficient of RIS#2 is generated in the same manner as described in step 460 .

[0090] Step 660 is the same as step 560 .

[0091] Figure 77 is a schematic flow chart illustrating an embodiment of a method 700 according to the present application. In some embodiments, the method 700 is performed by a first network node, such as a base station of a serving cell or a UE. In certain embodiments, the method 700 may be performed by a processor that executes program code, such as a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, etc.

[0092] The method 700 may include: 702 receiving an indication of an optimal reflection coefficient of a second RIS in the second cell from a second network node in the second cell, wherein the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and 704 determining an optimal reflection coefficient of the first RIS in the first cell based on the indication of the optimal reflection coefficient of the second RIS, for suppressing interference of the first cell to the second cell.

[0093] In some embodiments, the optimal reflection coefficient of the first RIS results in a reflection direction of the first RIS that is orthogonal to a reflection direction of the second RIS caused by the optimal reflection coefficient of the second RIS.

[0094] In some embodiments, the method further includes: receiving a matching map for the first RIS and the second RIS; and determining the optimal reflection coefficient of the first RIS based on an indication of the optimal reflection coefficient of the second RIS, which is an index of the optimal reflection coefficient of the second RIS, and the matching map. In particular, the matching map includes a plurality of pairs, wherein each pair includes a reflection coefficient of the first RIS and a reflection coefficient of the second RIS, and the optimal reflection coefficient of the first RIS is determined from any pair including the optimal reflection coefficient of the second RIS, except for a pair including the optimal reflection coefficient of the second RIS and the reflection coefficient of the first RIS that results in optimal signal transmission through the first RIS.

[0095] In some embodiments, the first network node is a first base station unit in a first cell, and the second network node is a second base station unit in a second cell. The optimal reflection coefficient of the second RIS may be determined based on an SINR or RSRP reported by a UE in the second cell to the second network node, wherein the SINR or RSRP is calculated for each candidate reflection coefficient of the second RIS. The method may further include receiving an indication of the optimal reflection coefficient of the second RIS from the second base station unit via an Xn interface.

[0096] In some embodiments, the first network node is a first UE in a first cell, and the second network node is a second UE in a second cell. The optimal reflection coefficient of the second RIS may be determined by the second UE based on the SINR or RSRP calculated for each candidate reflection coefficient of the second RIS. The method may further include receiving an indication of the optimal reflection coefficient of the second RIS from the second UE via a PC5 interface. Alternatively, the method may further include receiving an indication of the optimal reflection coefficient of the second RIS from a base station unit in the first cell via RRC signaling or MAC CE.

[0097] Figure 8 is a schematic block diagram illustrating an apparatus according to one embodiment.

[0098] refer to Figure 8 , the UE (i.e., remote unit) includes a processor, a memory, and a transceiver as a transmitter and / or receiver. The base station (e.g., gNB) includes a processor, a memory, and a transceiver as a transmitter and / or receiver. The processor (e.g., the processor of the UE or the processor of the gNB) implements Figure 7 The functions, processes and / or methods proposed in.

[0099] A first network node (e.g., a base station or a UE) in a first cell includes a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to receive, from a second network node in a second cell via the transceiver, an indication of an optimal reflection coefficient of a second RIS in the second cell, wherein the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and determine, based on the indication of the optimal reflection coefficient of the second RIS, an optimal reflection coefficient of the first RIS in the first cell for suppressing interference of the first cell to the second cell.

[0100] In some embodiments, the optimal reflection coefficient of the first RIS results in a reflection direction of the first RIS that is orthogonal to a reflection direction of the second RIS caused by the optimal reflection coefficient of the second RIS.

[0101] In some embodiments, the processor is further configured to receive, via the transceiver, a matching map of the first RIS and the second RIS; and the processor is configured to determine the optimal reflection coefficient of the first RIS based on an indication of the optimal reflection coefficient of the second RIS, which is an index of the optimal reflection coefficient of the second RIS, and the matching map. In particular, the matching map includes a plurality of pairs, wherein each pair includes a reflection coefficient of the first RIS and a reflection coefficient of the second RIS, and the optimal reflection coefficient of the first RIS is determined from any pair including the optimal reflection coefficient of the second RIS, other than a pair including the optimal reflection coefficient of the second RIS and the reflection coefficient of the first RIS that results in optimal signal transmission via the first RIS.

[0102] In some embodiments, the first network node is a first base station unit in a first cell, and the second network node is a second base station unit in a second cell. The optimal reflection coefficient of the second RIS is determined based on an SINR or RSRP reported by a UE in the second cell to the second network node, wherein the SINR or RSRP is calculated for each candidate reflection coefficient of the second RIS. The processor may be configured to receive an indication of the optimal reflection coefficient of the second RIS from the second base station unit via the transceiver over an Xn interface.

[0103] In some embodiments, the first network node is a first UE in a first cell, and the second network node is a second UE in a second cell. The optimal reflection coefficient of the second RIS may be determined by the second UE based on an SINR or RSRP calculated for each candidate reflection coefficient of the second RIS. The processor may be configured to receive an indication of the optimal reflection coefficient of the second RIS from the second UE via a transceiver via a PC5 interface. Alternatively, the processor may be configured to receive an indication of the optimal reflection coefficient of the second RIS from a base station unit in the first cell via a transceiver via RRC signaling or a MAC CE.

[0104] The radio interface protocol layer can be implemented by a processor. A memory is connected to the processor to store various pieces of information used to drive the processor. A transceiver is connected to the processor to transmit and / or receive radio signals. Of course, the transceiver can be implemented as a transmitter for transmitting radio signals or a receiver for receiving radio signals.

[0105] The memory may be located inside or outside the processor and connected to the processor through various well-known means.

[0106] In the above-described embodiments, the components and features of the embodiments are combined in a predetermined form. Unless otherwise explicitly stated, each component or feature should be considered as an option. Each component or feature can be implemented without being associated with other components or features. In addition, the embodiments can be configured by associating some components and / or features. The order of the operations described in the embodiments can be changed. Some components or features of any embodiment can be included in another embodiment, or replaced with components and features corresponding to another embodiment. It is obvious that claims that are not explicitly cited in the claims are combined to form an embodiment or are included in a new claim.

[0107] The embodiments may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, the exemplary embodiments described herein may be implemented using one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like, according to the hardware implementation.

[0108] The embodiments may be practiced in other specific forms. The embodiments described are to be considered in all respects as illustrative only and not restrictive. The scope of the present invention is therefore indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalents of the claims are intended to be included within their scope.

Claims

1. A first network node in a first cell, comprising: transceiver; as well as a processor coupled to the transceiver, wherein the processor is configured to: receiving, via the transceiver, from a second network node in a second cell, an indication of an optimal reflection coefficient for a second RIS in the second cell, wherein the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and According to the indication of the optimal reflection coefficient of the second RIS, an optimal reflection coefficient of the first RIS in the first cell is determined to suppress interference of the first cell to the second cell.

2. The first network node according to claim 1, wherein: The optimal reflection coefficient of the first RIS causes a reflection direction of the first RIS to be orthogonal to a reflection direction of the second RIS caused by the optimal reflection coefficient of the second RIS.

3. The first network node according to claim 1, wherein: The processor is further configured to receive, via the transceiver, a matching mapping of the first RIS and the second RIS; and The processor is configured to determine an optimal reflection coefficient of the first RIS based on the indication of the optimal reflection coefficient of the second RIS and the matching map, the indication being an index of the optimal reflection coefficient of the second RIS. The first network node according to claim 3 , wherein: The matching map includes a plurality of pairs, each pair of the plurality of pairs includes a reflection coefficient of the first RIS and a reflection coefficient of the second RIS, and The optimal reflection coefficient of the first RIS is determined from any pair including the optimal reflection coefficient of the second RIS other than a pair including the optimal reflection coefficient of the second RIS and the reflection coefficient of the first RIS that results in optimal signal transmission via the first RIS. The first network node according to claim 1 , wherein: The first network node is a first base station unit in the first cell, and the second network node is a second base station unit in the second cell. The first network node according to claim 5 , wherein: The optimal reflection coefficient of the second RIS is determined according to the SINR or RSRP reported by the UE in the second cell to the second network node, wherein the SINR or RSRP is calculated for each candidate reflection coefficient of the second RIS.

7. The first network node according to claim 5, wherein: The processor is configured to receive the indication of the optimal reflection coefficient of the second RIS from the second base unit via the transceiver over an Xn interface.

8. The first network node according to claim 1, wherein: The first network node is a first UE in the first cell, and the second network node is a second UE in the second cell.

9. The first network node according to claim 8, wherein: The optimal reflection coefficient of the second RIS is determined by the second UE according to the SINR or RSRP calculated for each candidate reflection coefficient of the second RIS.

10. The first network node according to claim 8, wherein: The processor is configured to receive the indication of the optimal reflection coefficient of the second RIS from the second UE via the transceiver over a PC5 interface.

11. The first network node according to claim 8, wherein: The processor is configured to receive the indication of the optimal reflection coefficient of the second RIS from a base station unit in the first cell via the transceiver through RRC signaling or MAC CE.

12. A method performed at a first network node in a first cell, comprising: receiving, from a second network node in a second cell, an indication of an optimal reflection coefficient for a second RIS in the second cell, wherein the first cell is a neighboring cell of the second cell and has the same frequency as the second cell; and According to the indication of the optimal reflection coefficient of the second RIS, an optimal reflection coefficient of the first RIS in the first cell is determined to suppress interference of the first cell to the second cell.

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