A method of RIS subcarrier-based watermarking in OFDM

Abstract

The invention relates to wireless communication systems, and more particularly to propose a novel method of RIS Subcarrier Based Watermarking in multicarrier transmission systems.

Description

[0001] DESCRIPTION

[0002] A METHOD OF RIS SUBCARRIER-BASED WATERMARKING IN OFDM

[0003] TECHNICAL FIELD

[0004] The invention relates to wireless communication systems, and more particularly to discovery of reconfigurable intelligent surface (RIS) subcarrier-based watermarking in OFDM in a wireless communication network.

[0005] PRIOR ART

[0006] RISs are a sort of new technology that can be utilized instead of conventional receiving wires to transmit and get electromagnetic waves. In the prior art, it is emphasized that reconfigurable intelligent surface (RIS) is of critical importance in the field of telecommunications. Identifying the RIS reflected path / link is also another among the important issues in telecommunications.

[0007] Reconfigurable Intelligent Surfaces (RISs) are emerging as a transformative technology in wireless communication, with the capability to dynamically alter the propagation environment. These surfaces comprise numerous reflecting elements, each with a controllable reflection coefficient, allowing for adaptive beamforming. While conventionally RISs remain transparent to User Equipment (UE), certain applications necessitate RIS identification, such as in scenarios involving localization, uplink transmission power conservation, and enhancement of physical layer security. While new technologies offer new solutions to the relevant technical field, they can also bring about different problems such as discovery and presence of RIS, distinguishing of signal paths in the environment / region.

[0008] The current technical problem in wireless communications is difficulty in distinguishing the paths that an OFDM signal may take, especially in environments rich with reflective surfaces like RISs. Traditional Power Delay Profiles (PDPs) cannot reliably distinguish between multiple RIS-reflected signals due to similar time-of-arrival and power levels. Since PDP is not distinguished in multicarrier systems, RIS watermarking is a must for RIS identification.

[0009] Several approaches to RIS-assisted identification have been discussed in literature. One method involves scheduling RIS activations sequentially, with each RIS reflecting beams within designated time slots, enabling the UE to discern the unique RIS activation sequence. Other propositions include unique phase configurations at the RIS to mark signals a method that necessitates advanced receiver design to decode the phase-configured signals. Alternatively, the modulation of RIS elements' states (on / off) can induce distinguishable power fluctuations at the receiver, and temporal coding patterns may be used for frequency conversion or introducing frequency offsets at the RIS, including polarization alterations.

[0010] Furthermore, delay estimation techniques have been considered, leveraging the relative positions of RISs and gNBs; these approaches equate relative distances to signal delays at the receiver. However, the variable proximity of UEs to different RISs undermines the reliability of this method, given that the shortest path does not universally correspond to the nearest RIS. Despite the potential benefits of RIS side signal watermarking, it poses several significant challenges that must be addressed. The complexity of RIS hardware is a primary concern; the fundamental design of RIS elements is largely passive, and incorporating watermarking capabilities would necessitate a more complex design. This could lead to increased hardware complexity and associated costs. Also, there is the risk of distortion of beam direction; implementing watermarking on the RIS could interfere with the meticulous phase shifts essential for accurate beamforming, potentially distorting the beam path and diminishing the quality of signal directionality. Finally, the issues associated with watermark detection cannot be overlooked. The process of detecting watermarks is rendered more difficult by the presence of channel impairments and noise, which are further distorted by the phase variations inherent in the RIS operation. These challenges require careful re-evaluation of RIS watermarking strategies, ensuring that the proposed solutions are easily implemented and easily detected at the receiver, without adding additional complexity to RIS and receiver designs. As RIS is known, adjusting the phases of the elements on the RIS surface is possible, that is, the phase to be added to the signal, the amplitude values and polarization of the elements. When the signals come to the RIS, the element that the signal hits give a certain amount of phase. When the phases of the signals are adjusted, the signal can be passively beamformed to increase the power at the desired point. Traditional methods do not have a situation such as scheduling RISs in different time periods. When it is not scheduled, an action needs to be taken. In traditional methods, either the phase or the amplitude is changed. In the literature, there are various patent documents related to RIS. Some of them are explained below.

[0011] Patent document US1 1546194B1 relates to reconfigurable intelligent surface link identification. In a communication system, a direct link and an indirect link (through RIS) may be maintained simultaneously but may need to be treated separately. However, the base station and / or the UE (4) may be unable to differentiate between signals transmitted via the direct link and the indirect link. Therefore, the base station and / or the UE (4) may treat signals transmitted via the direct link and the indirect link the same, resulting in reduced communication performance and / or efficiency.

[0012] This patent provides some techniques for identifying RIS links. Various aspects of the present disclosure relate to wireless communication. In some respects, a receiver may receive, from a transmitter, an indication of a modulation signature associated with a reconfigurable intelligent surface (RIS). The receiver may receive a signal that uses the modulation signature, wherein the modulation signature identifies a link associated with the RIS and the transmitter.

[0013] An RIS may be associated with a modulation signature. The modulation signature may identify the RIS and / or a beam state associated with the RIS. The modulation signature may be associated with a modulation of signals reflected by the RIS in phase, polarization, and / or amplitude. For example, the RIS may modulate impinging signals in phase, polarization, and / or amplitude to indicate the modulation signature associated with the RIS. A receiver (e.g., a UE (4) and / or a base station) may receive a signal that uses the modulation signature, indicating that the signal is transmitted via an indirect link (e.g., the RIS link).

[0014] Another approach is described in patent document WO2022252176A1 . This patent document relates to the identification of reconfigurable intelligent surfaces. The present disclosure provides a reconfigurable intelligent surface (RIS), a wireless device, and methods for identifying radio signals therefrom. A method at a RIS for facilitating a first wireless device in identifying radio signals from the RIS comprises: receiving, from a second wireless device, a sequence of radio signals; adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to determine that the adjusted sequence of radio signals comes from the RIS; and transmitting, to the first wireless device, the adjusted sequence of radio signals. In some embodiments, the step of adjusting the received sequence of radio signals in the analog domain comprises at least one of: replacing at least one of the received radio signals with a zero-power signal; applying a phase shift to at least one of the received radio signals; and applying a frequency shift to at least one of the received radio signals.

[0015] In some embodiments, the step of replacing at least one of the received radio signals with a zero-power signal comprises: determining at least one of the received radio signals according to the criterion; and replacing the at least one determined radio signal with a zero-power signal. In some embodiments, the step of applying phase shift to at least one of the received radio signals comprises: determining at least one of the received radio signals according to the criterion; and applying the phase shift to the at least one determined radio signal. In some embodiments, for each of the at least one determined radio signal, a signal-specific phase shift or a common phase shift is applied.

[0016] In another embodiment, the step of applying a frequency shift to at least one of the received radio signals comprises: determining at least one of the received radio signals according to the criterion; and applying the frequency shift to the at least one determined radio signal. In some embodiments, for each of the at least one determined radio signal, a signal-specific frequency shift or a common frequency shift is applied. In some embodiments, the step of adjusting the received sequence of radio signals in the analog domain further comprises: adjusting the received sequence of radio signals in the analog domain to enable the first wireless device to further determine one or more of: -geometry information of the RIS and / or the second wireless device; and - information about signal delay introduced by the RIS. In some embodiments, one of the first wireless device and the second wireless device is a User Equipment (UE), and the other of the first wireless device and the second wireless device is a Radio Access Network (RAN) node. In some embodiments, the criterion is received from the RAN node.

[0017] Another patent document is US2022232422A1 . The document relates to reconfigurable intelligent surface (RIS) scheduling again. Reconfigurable intelligent surface (RIS) scheduling provided with respect to wireless communication networks is described. A base station or other network entity may serve as a central node to accommodate RIS sense and / or control requests from user equipments (UEs). A RIS scheduling protocol according to some aspects may provide a technique for avoiding potential collisions at the RIS sense and / or control phases of operation with respect to RISs deployed in a wireless communication network. Using RIS scheduling, wireless communication networks may avoid or otherwise mitigate situations in which multiple sensing signals negatively impact RIS detection procedures, multiple control signals causing signal processing problems and / or control issues, and / or interference results from uncoordinated control of multiple RISs. Other aspects and features are also claimed and described.

[0018] Here this patent file also mentions that an RIS can be scheduled or requested for the purpose of positioning:

[0019] A RIS request received according to some aspects of the disclosure may include one or more parameters useful with respect to scheduling. A RIS request may, for example, include information with respect to a subject RIS of the RIS request, information regarding the desired use of the RIS by a UE, etc. In some examples, the one or more parameters may include time resources (e.g., information identifying one or more time slots, subframes, frames, etc.), frequency resources (e.g., information identifying one or more subchannels, channels, etc.), or a combination thereof, such as may be preferred otherwise requested for use (e.g., for communication, sensing and / or positioning, etc.) by a UE with respect to the RIS. Additionally or alternatively, the one or more parameters may include RIS identification (e.g., information identifying one or more subject RISs), one or more RIS states (e.g., information identifying one or more phase shift, reflection angle, etc. states a RIS is capable of which are desired for use by the UE), RIS state pattern (e.g., information identifying one or more sequences of RIS states to be implemented by a RIS for the UE), or a combination thereof, such as may be preferred or otherwise requested for use (e.g., for communication, sensing and / or positioning, etc.) by a UE with respect to a RIS. The one or more parameters may additionally or alternatively include target UE identification (e.g., a UE for which a sidelink is to be established via a RIS), information regarding communication via or with the RIS (e.g., information identifying a type of communication link to be established via a RIS, such as sidelink, carrier aggregation, backhaul, etc., information indicating that the RIS is to be used for sensing, positioning, etc.), or a combination thereof.

[0020] Another approach to RIS is explained in the patent document WO2022182417A1 , which relates to reconfigurable intelligent surface discovery procedures. In this document, improved methods, systems, devices, and apparatuses that support reconfigurable intelligent surface discovery procedures based on wireless sensing. The described techniques allow for a UE to obtain RIS information and use that information for RIS-assisted communications. The UE may communicate with a base station (BS) to receive RIS information regarding one or more RISs in a coverage area. The UE may request the RIS information, or the BS may send the RIS information without a request. The UE may use the RIS information to locate one or more RISs by sweeping a signal around the possible locations of the RIS. The UE may use various techniques to distinguish the RIS from other environmental objects based on return signals received at the UE. Once the RIS is discovered and located, the UE may use one or more RISs to communicate with the base station or another UE.

[0021] Techniques described in this patent provide the UE with a new protocol or procedure for RIS discovery and acquisition of RIS information. Techniques described in this patent enable the UE to obtain RIS information from the BS. The UE may request the RIS information from the BS, or the BS may send the UE the RIS information without a request. The UE may sweep a sensing signal toward the potential location of the RIS based on the RIS information, which may include the location of the RIS. Once the UE locates the RIS, the UE may use the RIS to transmit a UL wireless communication to the base station or the UE.

[0022] This patent is about discovering and finding the positions of RISs. However, assuming that the positions of the RISs are known on the UE side. In this patent, RISs are discovered by signaling between the UE and BS. This may be complicated since many transmissions between the UE and BS may be required for RIS discovery. Another disadvantage of this method may be the amount of information needed to be transferred between the UE and BS for RIS discovery.

[0023] Another patent document in the state of the art is WO2022147415A1 . This document relates to time and frequency resource level muting of reconfigurable intelligent surfaces. This method in the document introduces a resource-level muting bitmap for reconfigurable intelligent surfaces (RISs). Here, the resource-level muting bitmap identifies sets of time and frequency resources during which the RIS should be enabled to reflect a transmission beam or disabled from reflecting a transmission beam and requesting RIS to be enabled or disabled according to the resource-level muting bitmap. This method can be performed by both BS and UE. The base station (BS) transmits positioning reference signals (PRSs). The BS transmits the first, second, and third PRSs to the RIS1 , RIS2, and the UE, respectively. RIS1 and RIS2 reflect the incoming signal to the UE. Since the PRSs reach the UE at different times, the UE can perform measurements using these PRSs for positioning. For example, the UE can measure reference signal timing difference (RSTD). After measuring RSTD, the UE can report the measured RSTD, and the network estimates the position of the UE using the measured RSTD. If the UE knows the locations of RISs, it can estimate its own position. In this method, different time and frequency resources should be used to perform positioning, causing a waste of resources. Therefore, there is no solution to make RIS Discovery and to enable the user to identify the RIS in the environment.

[0024] Another patent document in the state of the art is WO2022133444A1 . The document relates to reconfigurable intelligent surface-aided positioning . This patent document is about positioning using reconfigurable intelligent surfaces (RISs). In this method, the base station (BS) transmits a set of positioning reference signals (PRSs). The BS transmits the first, second, and third PRSs to the RIS1 , RIS2, and the UE, respectively. RIS1 and RIS2 reflect the incoming signal to the UE. Since the PRSs reach the UE at different times, the UE can perform measurements using these PRSs for positioning. For example, the UE can measure reference signal timing difference (RSTD). After measuring RSTD, the UE can report the measured RSTD, and the network estimates the position of the UE using the measured RSTD. If the UE knows the locations of RISs, it can estimate its own position. In this method, different time and frequency resources should be used to perform positioning, causing a waste of resources. Therefore, there is no proposed solution to make RIS Discovery and to enable the user to identify the RIS in the environment.

[0025] All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0026] BRIEF DESCRIPTION OF THE INVENTION

[0027] The present invention generally relates to a method of Reconfigurable Intelligent Surface (RIS) discovery and identification to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0028] The invention is a method for RIS discovery and identification which could be crucial for physical layer security, power saving and rough localization such as Enhanced Cell ID, etc. The invention is directed to detecting the presence of RIS in the environment / region. It is not purely for localization purposes but is related to RIS identification. The processing is done on the RIS side.

[0029] For applications beyond localization, RIS-side watermarking remains viable. By leveraging the inherent capabilities of standard RIS infrastructure, an innovative watermarking method is proposed. The invention proposes a Reconfigurable Intelligent Surface (RIS) identification scheme for Orthogonal Frequency Division Multiplexing (OFDM)-based systems.

[0030] The motivation behind designing a novel Reconfigurable Intelligent Surface (RIS) identification scheme for Orthogonal Frequency Division Multiplexing (OFDM)-based systems stems from the inherent limitations of existing single carrier system approaches in handling frequency-selective channels prevalent in modern communication environments.

[0031] Given OFDM's critical role in achieving high spectral efficiency and robustness against multipath fading and inter-symbol interference in these high-speed communication standards, the development of an effective RIS identification scheme tailored to OFDM is crucial. Such a scheme would enable the intelligent manipulation of signal propagation environments for enhanced signal quality and network performance, addressing a key challenge in realizing the full potential of RIS-enhanced OFDM systems in next-generation wireless communications.

[0032] This method would entail selectively enhancing (preferably certain) subcarriers by aligning the RIS phase response with the channel response of those subcarriers, particularly under frequency-selective channel conditions.

[0033] The main purpose of the invention is to make RIS discovery and identification and to enable the user to identify the RIS or RISs in the environment. Thanks to invention, it is possible to identify the single / multi pie RISs in the environment by allowing each RIS to selectively amplify specific OFDM subcarriers or subblocks thereby creating a unique spectral signature identifiable at the receiver. This selective amplification not only makes identification possible but also enhances the signal strength on designated subcarriers.

[0034] Another purpose of the invention is to create an optimized phase response by considering the channel responses of all subcarriers and strengthen the entire signal after identification step.

[0035] The proposed system offers several advantages over prior art: Selective RIS Amplification: By configuring RISs to boost particular subcarriers or subblocks, invention ensures that each RIS provides a distinct contribution to the signal, which can be reliably identified and utilized by the receiver.

[0036] Robustness in Fading Environments: Assigning multiple subcarriers to RISs for amplification, especially those with high channel correlation, enhances system robustness. This is critical in scenarios where certain subcarriers are subject to deep fading.

[0037] Versatile Applications: by enabling the RIS recognition by the UE, the invention can aid in uplink transmission when direct LoS is unavailable, contribute to physical layer security by controlling the signal's propagation paths, and provide rough estimates of UE location, augmenting existing positioning methods like Enhanced Cell ID.

[0038] Two-Phase Operation: The identification phase allows for the system to recognize the RISs involved before transitioning to the communication phase, where the RISs optimize the signal by considering the channel responses of all subcarriers of said signal . This dynamic adaptability ensures efficient system operation.

[0039] Channel Selectivity Adaptation: The system adapts the size of the subblocks targeted by RISs based on the channel selectivity, which means it can operate effectively across a range of channel conditions.

[0040] In the RISs that are closest to each other, it is ensured that the most distant subcarrier / subcarriers / subblock possible is selected.

[0041] The usage areas of the invention can also be used in physical layer security. In other words, knowing which RIS the signal is coming from, if the UE transmits and receives through identified RIS i, other users cannot receive the signal because the RIS directs the signal to us. The usage areas of the invention can also be used in physical layer security. In other words, knowing which RIS the signal is coming from, if the signal is received only in that direction, other users cannot receive the signal because the RIS directs the signal to us. Another usage area; rough localization (Enhanced +Cell ID), RIS discovery or using RIS in the uplink transmission for power saving.

[0042] RIS can be used for physical layer security, for user uplink (power saving), for UEs to use in sidelink communication, for rough localization to contribute to Enhance Cell ID method, etc.

[0043] In the first aspect, the embodiment of the present application relates to a method of Reconfigurable Intelligent Surface Identification (RIS) method, which can be executed by a network device, or by a component of the network device (such as a processor, a chip, or a chip system, etc.), or can be implemented by all or logical modules or software implementations of some network device functions or computer implemented device.

[0044] The RIS method proposed by the embodiment of the present application can be applied to the 5G, 6G or similar networks.

[0045] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method of Reconfigurable Intelligent Surface Identification (RIS).

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present disclosure, in accordance with one or more various examples, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict examples of the disclosure. These drawings are provided to facilitate the reader's understanding of the disclosure and should not be considered limiting the breadth, scope, or applicability of the disclosure. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.

[0048] Figure 1 : An example scenario of RIS Assisted Transmission

[0049] Figure 2: An Example for Power Spectral Densities of Representative Scenarios Figure 3: Two phase operation process Figure 4: Representing the distance to each base station and the location of the user (Prior Art).

[0050] REFERENCE LIST

[0051] The reference numbers of the elements included in the figures are explained below.

[0052] A Base station 1

[0053] B Base station 2

[0054] C Base station 3

[0055] D1 distance between A and UE

[0056] D2 distance between B and UE

[0057] D3 distance between C and UE

[0058] 2 RIS 1

[0059] 3 RIS 2

[0060] 4 UE

[0061] 5 Incoming signal

[0062] DETAILED DESCRIPTION OF THE INVENTION

[0063] In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only to make the subject more understandable.

[0064] The present invention generally relates to a method of Reconfigurable Intelligent Surface (RIS) discovery which is shown in figure 3. The invention provides to make RIS discovery and to enable the user to identify the RIS in the environment.

[0065] This invention proposes a method for how to watermarking OFDM-based signals on the RIS side.

[0066] A computer implemented Reconfigurable Intelligent Surface (RIS) Identification method for marking Orthogonal Frequency-Division Multiplexing (OFDM)-based signals in RIS wherein the method comprises, adjusting the power of the subcarrier on the RIS side in OFDM based systems by selectively enhancing (preferably certain subcarriers) by aligning the RIS phase response with the channel response of those subcarriers, under frequency-selective channel conditions. This invention introduces a novel method of identifying and utilizing Reconfigurable Intelligent Surfaces (RISs) in wireless communication systems, particularly enhancing the use of Orthogonal Frequency-Division Multiplexing (OFDM) signals in environments with multiple RISs. This method addresses challenges in signal identification due to multipath propagation and provides a robust framework for signal enhancement, security, and potential localization improvements.

[0067] The invention proposes adjusting the response of RIS only based on the channel of a certain subcarrier / subcarriers / subblock. When it is chosen, it is possible to boost the power of the signal corresponding to that subcarrier / subcarriers / subblock. It does not increase the others that much. Signal adjustment is done by RIS.

[0068] Thanks to invention, by detecting the index / indices of boosted subcarrier / subblocks, it is possible to understand from which RIS the signal is reflected.

[0069] The invention provides to determine which RIS will amplify which subcarrier / subcarriers / subblocks. Hence, it is possible to understand which signal is coming from the RIS. In OFDM / multicarrier-based systems, a method of watermarking is offered by adjusting / manipulating the power of the subcarrier / subcarriers / subblock on the RIS side in the proposed invention.

[0070] The proposed RIS identification method for watermarking OFDM-based signals by RIS is dependent on the computer-implemented method. The method can be implemented by a processor of a network device for RIS identification method (which is shown in figure 3) for marking OFDM-based signals in RIS wherein the method comprises,

[0071] • Determining subcarrier(s) / subblock associated with each RIS,

[0072] • Configuring RISs based on the channel response of the selected subcarrier / subcarriers / subblock,

[0073] • Performing RIS identification at the user equipment (UE (4)) side,

[0074] • Selecting an RIS or multiple RISs to establish a communication link,

[0075] • Configuring the selected RISs by an optimized phase response by taking into account the channel responses of all subcarriers and strengthening the entire signal. The method does this;

[0076] In multicarrier transmission, the bandwidth is divided into multiple sub-bands which are called subcarriers. In the OFDM system, symbols are transmitted in parallel using orthogonal subcarriers. Each subcarrier is located at different frequencies and the frequency separation between adjacent subcarriers is called subcarrier spacing. Multiple adjacent / nonadjacent subcarriers may form a subblock. The receiver can decode the signal by using OFDM decoding procedures.

[0077] Each subcarrier experiences a flat fading channel and the correlation of the channel responses between subcarriers depends on channel conditions such as frequency selectivity. As the frequency selectivity of the channel increases the correlation for channel responses of subcarriers decreases. While channel correlation is maximum between consecutive subcarriers, the correlation decreases as the frequency separation between subcarriers increases.

[0078] In communication systems, the concept of frequency-flat channels refers to those in which the channel characteristics exhibit minimal variation across different frequencies. This uniformity often results in challenges when attempting to discern signals, as variations in the channel that might aid in signal differentiation are absent.

[0079] In contrast, frequency-selective channels display significant variation in their response at different frequencies. This variation can be advantageous for signal processing, as it allows for more distinct identification and extraction of signals.

[0080] If an example is given for the environment where the method will be applied, there is at least one RIS and user equipment (UE (4)) in an environment / region. A signal was reflected from this RIS to the user. The base station focused the signal to the user using one of the RISs. Let's assume BS is not in LOS of the UE. In an example, a method for wireless communication at first user equipment (UE (4)) in a wireless communications system is described, including receiving, from a base station, information associated with one or more reconfigurable intelligent surfaces (RISs) in the wireless communications system. Fig.1 shows a system model diagram depicting the placement of RISs in the environment and their relation to the base station (BS) and user equipment (UE (4)). There could be multiple RISs in the environment, as seen in Fig.1 . The RIS-1 (2), RIS- 2 (3) or both could be active during transmission. The aim is to identify which RISs are used on the UE (4) side and obtain insight into their effectiveness.

[0081] Fig.2 is a spectral analysis plot, showing the power distribution across subcarriers after RIS enhancement. When only a single RIS is activated in the region, it can be observed that only a certain subblock of the OFDM block is relatively boosted where the RIS identity can be found by analyzing subcarrier / subcarriers / subblock power distribution. The left-hand side of Fig.2 shows the case when only a single RIS is activated where there is a clear peak in the power spectral density plot. When there is more than a single RIS activated in the environment, each RIS can watermark different subcarriers / subblock on the OFDM block as seen in the right-hand side Fig.5 where there are two distinct peaks representing two different RISs. The RIS-1 (2) could be selected for communication by the UE (4) since it is probably closer and more effective compared to RIS-2 (3) based on the UE (4) interpretation.

[0082] The flowchart in Fig.3 describes the two-phase operation process: the identification phase followed by the communication phase. In the identification phase, first certain subcarriers / subblock are allocated for each RIS, thus RISs can configure themselves based on the channel response of allocated subcarriers / subblock. After the UE identifies the RISs in the environment, it can make a decision about which RIS / RISs will be used to establish a communication link. Then, in the communication phase, the selected RISs are configured to enhance the capacity of the communication by considering the whole OFDM block rather than a certain subcarriers / subblock.

[0083] Method comprising of two phases. One of the phases is the identification phase which is comprising;

[0084] • Determining subcarriers / subblock associated with each RIS (In this step, depending on communication parameters such as channel selectivity, bandwidth, subcarrier spacing, number of RIS in the environment, the base station / network determines the number / size and indexes of subcarrier / subblocks that should be assigned to a RIS.),

[0085] • Configuration of RISs based on the channel response of the selected at least one subcarrier or subblock (In this step, providing to boost specified at least one subcarrier or subblocks by adjusting the phase responses (It can be assumed that there is a backhaul link between RIS and BS. According to communication parameters, which RIS will power which subcarriers can be provided to the RIS via backhaul by the BS.) of the elements in the RIS.),

[0086] • Performing RIS identification at the UE side (The UE can use several methods to decide RIS ID / IDs by analyzing the directed signal from RIS / RISs. For instance, by examining the magnitude of the subcarriers in the frequency domain, the UE could employ a thresholding technique to distinguish between boosted and non-boosted subcarriers. Subcarriers with magnitudes exceeding a predefined threshold would be identified as boosted, thereby revealing the unique signature of the RIS. This method enables the UE to accurately deduce the RIS ID based on the specific pattern of subcarrier enhancements, even in environments where multiple RISs may influence the signal.).

[0087] Another phase is the communication phase which is comprising;

[0088] • Selecting an RIS or multiple RISs to establish a communication link (In this step, the selection can be made according to the quality of the signal coming from the RIS or to increase communication security.),

[0089] • Configuring the selected RISs by configuring them with an optimized phase response considering the channel responses of all subcarriers and strengthening the entire signal.

[0090] Quality of the signal: After the successful identification of Reconfigurable Intelligent Surfaces (RISs) by the User Equipment (UE), the next critical step is to select the most suitable RIS to establish or enhance the communication link with the Base Station (BS). This selection process is pivotal for optimizing the communication channel's quality and overall network performance. Here’s how the selection process can be conceptualized: 1 . Signal quality metrics such as SNR, BER, or Channel capacity.

[0091] 2. Comparative analysis: By comparing the signal quality metrics associated with each RIS, the UE can determine which RIS provides the most significant improvement in the communication link.

[0092] 3. Dynamic Selection: the selection process can be dynamic, allowing the UE to switch between RISs based on real-time evaluations of signal quality. This adaptability is crucial in mobile scenarios or changing environmental conditions, where the optimal RIS for communication might vary over time.

[0093] Considerations for RIS Selection

[0094] Latency: The process of RIS identification and selection should be efficient to minimize latency, especially in applications requiring real-time communication.

[0095] Power Consumption: The selection algorithm should consider the power consumption of the UE, especially in scenarios where the UE might have limited battery life.

[0096] Environmental Factors: Changes in the environment, such as physical obstructions or variations in atmospheric conditions, can affect the RIS's performance, requiring the selection process to be responsive to such changes.

[0097] By carefully selecting the best RIS based on signal quality improvement, the UE can ensure an optimized communication link with the BS. This process underscores the importance of intelligent decision-making in RIS-enabled networks, leveraging the unique capabilities of RIS technology to enhance wireless communications efficiently.

[0098] Other embodiments of invention:

[0099] • Subcarriers are detected according to the power of subcarrier(s) or subblocks at the receiver to determine from which RIS the signal is reflected.

[0100] • Communication parameters are channel selectivity, bandwidth, subcarrier spacing and / or number of RIS in the environment.

[0101] • Steps of the computer implemented method of Reconfigurable Intelligent Surface (RIS) Identification for marking Orthogonal Frequency-Division Multiplexing (OFDM) / multicarrier-based signals in RIS wherein the method steps are done in RIS side adjusting the power of the subcarrier on the RIS side steps are done in RIS side.

[0102] • Configuring RISs by providing to boost specified subcarrier(s) or subblocks by adjusting the phase responses of the elements in the RIS. Adjusting the phase responses is configured by using a backhaul link according to the communication parameter.

Claims

CLAIMS1. A computer implemented method of Reconfigurable Intelligent Surface (RIS) Identification for marking Orthogonal Frequency-Division Multiplexing (OFDM) / multicarrier-based signals in RIS wherein the method comprises, adjusting the power of the subcarrier on the RIS side in OFDM / multicarrier- based systems by selectively enhancing at least one subcarrier or subblock by aligning the RIS phase response with the channel response of subcarriers, under frequency-selective channel conditions.

2. The method according to claim 1 , wherein said subcarriers are detected according to the power of subcarrier(s) or subblocks at the receiver to determine from which RIS the signal is reflected.

3. The method according to claim 1 , characterized in that comprising the following steps:• Determining subcarrier(s) / subblock associated with each Reconfigurable Intelligent Surface (RIS) by base station or network according to communication parameters,• Configuring RISs based on the channel response of the at least one selected subcarrier or subblock by adjusting their phase responses,• Performing RIS identification at user equipment side,• Selecting an RIS or multiple RISs to establish a communication link,• Configuring the selected RISs by configuring them with an optimized phase response taking into account the channel responses of all subcarriers and strengthening the entire signal.

4. The method according to claim 3, wherein said configuring RISs by providing to boost specified subcarrier(s) or subblocks by adjusting the phase responses of the elements in the RIS.

5. The method according to claim 3, wherein said steps are done in RIS side.

6. The method according to claim 3, wherein said adjusting the phase responses are configured by using backhaul link according to communication parameter.

7. The method according to claim 3, wherein said communication parameters are channel selectivity, bandwidth, subcarrier spacing and / or number of RIS in the environment.

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