A method of base station (BS) side watermarking system for RIS identification

Abstract

The invention proposes a novel Base Station (BS) side watermarking for RIS identification, which overcomes the difficulties by shifting the complexity from RIS hardware to the more capable BS.

Description

[0001] A Method of Base Station (BS) Side Watermarking System for RIS Identification

[0002] TECHNICAL FIELD

[0003] The invention relates to wireless communication systems, and more particularly to identification of reconfigurable intelligent surface (RIS) in a wireless communication network. The invention proposes a novel method of Base Station (BS) side watermarking system for RIS identification.

[0004] PRIOR ART

[0005] In the prior art, it is emphasized that localization is of critical importance in the field of telecommunications. With developing technology, localization capabilities in communication systems significantly increase the user experience. Localization involves the ability to precisely determine and transmit user location information, enabling a wide range of applications from cellular networks to sensor networks. This technique focuses on the advantages of localization in telecommunication systems, such as the effectiveness of location-based services, rapid response in cases of emergency, and improving overall network performance. Localization is also among the important issues in 5G, 6G localization in telecommunications, and it is necessary to know from which location the signal is coming from correctly.

[0006] There are some approaches used for localization in 5G, some of them are dependent on RAT (Radio Access network) and some are independent methods. As it is known, the most commonly used localization is the use of GPS. There is also a network-based localization system. It is done using base stations.

[0007] Some localization techniques in the prior art;

[0008] Trilateration: The position solution is obtained by computing the intersection between geometric forms. Several types of measurements can be used, such as time of arrival (ToA), or received signal strength (RSS). In this method, as the user, it is assumed that the user location is unknown. Therefore, it is necessary to receive a signal from three points whose location knew. When knowing the distance between the base station and the user, the distance is found by knowing how long the signal travels. The distance to each base station represents a circle which is shown in figure 4. The intersection point of these circles gives the location of the user.

[0009] When determining the location of a user, at least 3 base stations are needed. However, if there are 1 or 2 base stations in the environment, the location of the user cannot be determined. In order to determine the location, even if the scenario is considered where there is only one base station in the environment and the angle of departure of the signal, the time it reaches the target is known; Such a precise angle of departure estimation cannot be performed. For example, in 5G, beamforming is applied at the base station. Let's say there are 64 or 16 beams to serve a cell. In practice, since the widths of these beams are very wide, high number of antennas are needed to obtain a sharp beam. It is very costly and requires a very complex structure for its implementation. Therefore, a clear precise measurement cannot be made with current applications. The disadvantage of this method is that there must be a strict synchronization between the base stations and the user. That is, the moment the signal is emitted and the moment the user receives it must be highly synchronized so that the distance can be measured accurately. And here it is assumed that the signal is direct (line of sight). Therefore, this method is not always a reliable method(Time of Arrival (ToA) because it has such problems and limitations in practice.

[0010] Multilateration Method (Time of difference of arrival (TDoA)):

[0011] Again, it is assumed that a signal is received from three base stations. It accepts the first signal as the beginning of time. It looks at how much later the subsequent signals arrive. Therefore, it looks at the time difference in the arrival times of the signals. Here, geometrically, a parabolic shape is formed, not round, and the parabolas are located according to the intersection point. The problem here is that the three base stations have to be synchronized to each other. In this method, since the arrival time difference of the signals are considered, the signals must come out of all three base stations at the same time for accurate positioning. T riangulation. Estimated angle of arrivals (AoA) or estimated angle of departures (AoD) are used to estimate position of the user by intersecting at least two known directions of the incoming signal. When the angle of departure of the signals from the base stations is known, the intersection points of these angles give the location of the user (three base stations are assumed.)

[0012] Enhanced Cell ID (E-CID):

[0013] This method does not provide location information of the user (UE) clearly. The known transmitter position is assigned to be the position of the terminal. The cell-ID method, where the position provided is the one of the serving base stations. This is the most widely adopted method in conventional GSM networks. The operations used here are given below.

[0014] Which base station you are connected to means that you are approximately in that coverage area of that base station (CELL ID). Sector antennas are used in base stations, for example, in 4G, for example, 120 degrees facing three sides. Then that base station sends a signal to the user or receives a signal from the user. Then, looking at the strength of that signal, looking at the distance of the user, the region where the user is located is determined accuracy is a low in this method.

[0015] RF pattern matching (RFPM) method:

[0016] Measurements are taken from certain points in the network. According to the incoming signal strength, the measured point is determined offline. Then online is a method that allows to estimate the location according to the previously determined point. The resolution of this method is not very high. This method also known as fingerprinting, the algorithm is based on finding the best match for a certain signal measurement, such as RSS, time delay or channel spread, from the database of fingerprints.

[0017] Hybrid method:

[0018] A combination of the previous localization algorithms can be implemented to improve the overall performance. In 5G localization systems,, the signals transmitted from the base stations to the user (downlink) are referred to as positioning reference signals (PRS). Here, the user receives PRSs and solves his own position according to the PRS. There is also a reverse situation as uplink. One user equipment (for example: telephone, etc.) sends sounding reference signal (SRS) signals into the air and 3 different base stations catch them in the air. Since the signal from that user will reach the neighboring base stations at different times, the measurement is made using this time difference.

[0019] To sum up the challenges of current cellular localization methods;

[0020] Coverage: the transmit power and the number of BSs mainly define the cost of the network deployment. Cellular networks are primarily designed for communications; thus, the cell coverage is optimized to reduce the number of deployed BSs to serve a certain service area.

[0021] Intercell Interference: The transmit power is optimized depending on if the user at the cell edge or at the center of the cell. The position can be successfully estimated by the TDoA based trilateration if the mobile radio receives signals from three or more BSs. However, only at the cell edge is a good reception of several BSs concurrently ensured. This limitation is due to the near-far effect problem, where the nearest BS masks the neighboring BSs.

[0022] Uncontrolled multipath: In practice, apart from the LOS (Line of Sight) path, other signal components reach the UE after being scattered by the surrounding objects. If such components are not resolved at the UE, they interfere with the LOS signal and deteriorate the localization accuracy. If the NLOS (non-Line of Sight) components are resolvable in at least one domain (angle, delay, or Doppler), they can be separated from the LOS signal, but, more importantly, they can contribute to UE (user equipment) localization and environmental mapping.

[0023] Synchronization: Trilateration requires a precise estimation of the distance between transmitter and receiver. Therefore, the unknown synchronization errors of the involved clocks on both ends affect the position accuracy.

[0024] Identifying the RIS reflected path / link is also among the important issues in telecommunications. 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.

[0025] In the realm of 5G localization, prevalent methodologies include Enhanced Cell ID, Time of Arrival (ToA), Time Difference of Arrival (TDoA), and RF Pattern Matching. ToA and TDoA are particularly prevalent, wherein the UE receives Positioning Reference Signals (PRS) from a minimum of three gNBs. These methods, however, impose stringent synchronization demands between the UE and gNBs in ToA and among multiple gNBs for TDoA. Additionally, they require the allocation of multiple resource blocks for distinct PRS emissions and are susceptible to intercell interference, thus leading to reduced effectiveness, particularly in indoor localization contexts. Given these limitations, RIS-assisted localization has been proposed as a promising alternative, capable of generating additional signal paths that can potentially supplant those from neighboring gNBs. Nonetheless, this introduces the challenge of UE's identification of RIS-originated signal paths.

[0026] Several approaches to RIS-assisted localization 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 origin of PRS. 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.

[0027] Since all of these techniques mark the signal on the RIS side, it is very difficult to distinguish them on the user side, that is, on the receiver side, and even to decode them correctly, because the signal is marked in the RIS and goes through the channel. There is also a power fluctuation in the channel, polarization can be changed in the channel. Therefore, marking in RIS is not a very reliable method.

[0028] 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. Firstly, 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. Secondly, the control and flexibility of watermarking at the RIS are limited. Central networks may find their oversight and ability to dynamically tailor the watermarking process significantly reduced when this process is embedded within the RIS framework. Thirdly, 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 necessitate a careful reconsideration of RIS watermarking strategies, ensuring that any proposed solutions are robust against the intricacies of RIS- enhanced communication environments by channel impairments and noise, compounded by the RIS's phase variations.

[0029] 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 focused 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 is changed or the amplitude is changed. In literature, there are various patent documents related to RIS. Some of them are explained below.

[0030] 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.

[0031] This patent provides some techniques for identifying RIS links. Various aspects of the present disclosure relate to wireless communication. In some aspects, 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.

[0032] 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).

[0033] Another approach is described in patent document WO2022252176A1 . This patent document relates to identification of reconfigurable intelligent surface. 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Here this patent file also mentions that an RIS can be scheduled or requested for the purpose of positioning:

[0039] 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.

[0040] The another approach about RIS is explained in the patent document WO2022182417A1 that 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 provide for a UE to obtain RIS information and use that information for RIS-assisted communications. The UE may communicate with a base station to receive RIS information regarding one or more RISs in a coverage area. The UE may request the RIS information, or the base station (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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The current technical problem in wireless communications involves 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.

[0046] It possible to understand that RIS side watermarking is not feasible. There are some reasons why feasibility is not possible. These can be listed as follows; Complexity of RIS Hardware, Limited Control and Flexibility, Distortion of Beam Direction and Watermark Detection Issues. To explain the complexity of RIS Hardware: Traditional RISs are passive elements introducing phase changes to incident signals. Watermarking would require more sophisticated control over the RIS elements to embed patterns intentionally. This could increase the complexity and cost of the RIS hardware. Another problem is Limited Control and Flexibility: If the watermarking is done at the RIS side, the central network (e.g., the BS or core network) might have limited control over the watermarking process, making it harder to adjust or update the watermarking schemes dynamically. Another additional problem is Distortion of Beam Direction: If watermarking is introduced at the RIS, it means that specific patterns or modulations are added to the signal intentionally. This could interfere with the phase shifts set for beamforming, thereby affecting the direction and focus of the beam. Another problem that makes it not feasible is Watermark Detection Issues: The combination of channel impairments, noise, and the inherent nature of RIS (which can introduce varying phase shifts) might make the detection of watermarks at the Rx challenging.

[0047] All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result. BRIEF DESCRIPTION OF THE INVENTION

[0048] The present invention relates to a method for Reconfigurable Intelligent Surface Identification (RIS) to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0049] The present invention relates generally to the field of wireless communications, and more specifically to identifying the RIS reflected path / link.

[0050] The invention proposes a novel Base Station (BS) side watermarking for RIS identification, which overcomes the aforementioned difficulties by shifting the complexity from RIS hardware to the more capable BS. This invention enhances control over the watermarking process, ensures the integrity of beam direction, and simplifies watermark detection.

[0051] An object of the invention is to develop a method to provide to identify RIS by using Base Station (BS) side watermarking and localizing the RIS at the same time.

[0052] The invention proposes RIS assisted localization based on RIS activation scheme. Single carrier waveform is used in the invention.

[0053] In this invention, signal manipulation is done by the base station. As it is known, base stations are active devices. Let's assume there are three base stations in the environment / region. When a signal comes from any base station, it is understood that the signal comes from the base station in question. When the other two base stations are replaced with RIS, there is a need to know which RIS the signal is reflected from, so that distance measurement can be made. Here, in order to know the locations of the RISs, there is a need to know which RIS the signal is coming from. At this point, the present invention relates to a method providing a solution how to identify RISs by the user. Thanks to invention, the signal to be reflected from the RIS is marked at the base station before the signal leaves the base station. In this way, the invention provides to know which RIS the signal is coming from.

[0054] Another remarkable feature of the invention is that in the invention, a single time signal is sent to the base station and the user receives this signal. There is no such thing as scheduling RISs in three time periods or different time periods. When it is not scheduled, an action needs to be taken.

[0055] In traditional methods, either the phase is changed, or the amplitude is changed. Watermarking is done on the RIS side. With the invention in question, RIS watermarking is performed by BS rather than RIS itself while RIS only functions as a passive beamformer. The signal to be reflected from the RIS is marked at the base station before the signal leaves the base station.

[0056] One of the aims of the invention is to keep the RIS relatively passive. It is not desired that there be any extra load or processing capability on the RIS.

[0057] Advantages of the invention:

[0058] • Centralized control,

[0059] • Simpler RIS design,

[0060] • Reduced interference with beamforming,

[0061] • Improved watermarking reliability,

[0062] • Flexibility in watermarking.

[0063] The proposed RIS identification method is dependent on computer implemented method. In the first aspect, the embodiment of the present invention relates to a method of Reconfigurable Intelligent Surface Identification (RIS) method, which can be executed by an apparatus for wireless communication at a base station in a wireless communications system (the apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory), or 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.

[0064] Yet another object of the invention is to provide RIS localization by using one Base station and at least two RIS in the area.

[0065] Aim of using two RIS that there are three coordinates (x, y, z); three different signals need to be obtained. When using two RIS connected to one base station instead of three base stations, obtain three different paths and three different signals.

[0066] It is known that RIS is used instead of base stations. However, in the invention, it is possible to distinguish which RIS the incoming signal is coming from. Therefore, the invention proposes a different method that allows distinguishing which RIS the signal comes from.

[0067] Another embodiment of the invention;

[0068] • Watermarking with orthogonal codes,

[0069] • Phase introduction,

[0070] • Cyclic shifts.

[0071] RIS can create controllable multipaths. So that makes it possible to;

[0072] • Drastically reduces the required number of BSs,

[0073] • RIS are passive technology. In this way, it provides to use low energy.

[0074] • Synchronization is done by naturally,

[0075] • RIS can also have a very large antenna aperture.

[0076] One another aspect of the invention also used smart repeaters instead of RIS.

[0077] Since the signal originates from a single base station and is reflected from the RIS. Thanks to this invention, there is no need to synchronize with other (neighboring Base stations, for example: gNB). It is possible to control the multipath. Otherwise, it is possible to create additional and identifiable paths with RIS and NCR. Moreover, intercell interference problems can be handled. Processing is done in its own cell. Since RIS indoor is also used, indoor localization is increased.

[0078] The RIS method proposed by the embodiment of the present application can be applied to the 5G, 5G beyond, 6G or similar networks.

[0079] Based on the foregoing narratives, an invention proposes a Base Station (BS) side watermarking system for link identification via RIS. Utilizing a multi-channel beamforming gNB, localization signals can be concurrently dispatched through direct and RIS-reflected paths within a single time slot. A watermarking scheme implemented on the Base Station (BS) side offers distinct advantages: it centralizes control, allowing for a more straightforward design of the Reconfigurable Intelligent Surfaces (RIS). This approach avoids the complications that watermark embedding could introduce to RIS operations, ensuring that beamforming remains robust, and the beam direction is maintained without degradation due to watermarking. Furthermore, it enhances the robustness of the watermarking process, facilitating more reliable identification at the receiver side.

[0080] 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 (RIS) Identification.

[0081] Other aspects, features, and embodiments will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary aspects in conjunction with the accompanying figures. While features may be discussed relative to certain aspects and figures below, all aspects can include one or more of the advantageous features discussed herein. In other words, while one or more aspects may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various aspects discussed herein. It should be understood that such exemplary aspects can be implemented in various devices, systems, and methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] 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.

[0083] Figure 1 : Transmission Scenario is shown.

[0084] Figure 2: Expected PDP is shown (PDP vs Delay).

[0085] Figure 3: Proposed BS Side Watermarking Scheme is shown.

[0086] Figure 4: Representing the distance to each base station and the location of the user (Prior Art).

[0087] REFERENCE LIST

[0088] The reference numbers of the elements included in the figures are explained below.

[0089] 1 BS

[0090] 2 RIS 1

[0091] 3 RIS 2

[0092] 4 UE

[0093] DETAILED DESCRIPTION OF THE INVENTION

[0094] 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.

[0095] To achieve all the objects mentioned above and that will emerge from the following detailed description.

[0096] The present invention relates to a method BS (Base Station) (1 ) side watermarking for RIS identification. The invention is a method where RIS is determined on the base station side. The invention answers that how does a user distinguish PRS signals from base stations? question. It is an invention that emerged with the idea of how to distinguish which base station this signal came from when a user captures PRS signals. To achieve this, the invention proposes a method for RIS identification at the base station side.

[0097] The proposed invention is a computer implemented method of reconfigurable intelligent surface (RIS) identification comprises; using base station side watermarking method for reconfigurable intelligent surface (RIS) identification.

[0098] The computer implemented method of reconfigurable intelligent surface (RIS) identification for BS (1 ) side watermarking comprises; identifying RIS and localization at the same time by using a multi-channel beamforming gNB, dispatching localization signals concurrently through direct and RIS-reflected paths within a single time slot.

[0099] For the method to be implemented, there must be at least the following elements in the region / environment;

[0100] • At least one RIS (It is possible to use more than one RIS especially for localization) in figure 1 and figure 3),

[0101] • At least one UE (user equipment) (4),

[0102] • At least one BS (base station) (1 ),

[0103] • At least one LMF network element.

[0104] Reconfigurable Intelligent Surfaces (RISs) which is providing focus of signal to user.

[0105] User equipment can be any communication device that means which provides radio frequency signal transmission and radio frequency signal reception device. Such communication means are well known in the art.

[0106] The base station which generates a PRS signal in the invention.

[0107] Location management function (LMF), a network entity provides positioning functionality by means to determine the geographic position of a mobile device based on downlink and uplink location measuring radio signals. The LMF receives measurements and assistance information from the next generation radio access network (NG-RAN) and the mobile device, otherwise known as the user equipment (UE), via the access and mobility management function (AMF) over the NLs interface to compute the position of the UE. The LMF configures the UE (4) using the LTE positioning protocol (LPP) via AMF. LMF serves as a centralized location server in a Core Network (CN).

[0108] A computer implemented method which is suitable for being used with a communication network comprising

[0109] • At least one RIS,

[0110] • At least one user equipment,

[0111] • At least one base station,

[0112] • At least one location management function network element, the method is configured to provide RIS identification for BS (1 ) side watermarking and comprises the steps of;

[0113] • Requesting a positioning by the user equipment (UE) (4) in the cell region,

[0114] • Assigning positioning sequence IDs to primary network element Base Station,

[0115] • Assigning remaining positioning sequence IDs to secondary network elements which are RISs and informing the user by LMF,

[0116] • Generating positioning sequence signals locally according to these positioning sequence IDs by the user equipment (UE) (4),

[0117] • Transmitting positioning sequences by the base station through direct or RIS assisted links (Here, techniques such as Space Division Multiplexing or Multichannel beamforming can be used when transmitting.) When the user equipment (UE) (4) captures localization signals, correlating between captured localization signals and the signals which are produced in locally by user,

[0118] • As a result of the correlation, determining the time according to the point that gives the highest correlation (peak) (using known correlation techniques in the prior art),

[0119] • Identifying to RIS according to correlation result.

[0120] The highest correlation (peak) point in correlation result, identifies which to understand which RIS the signal came. In the invention, a base station can send signals to three different locations. For example, 2 RIS, 1 UE. The distances of this base station to the RISs and the UE (4) are unknown. In figure 3, LMFs assign position sequence IDs to base stations. For instance, if a UE (4) requests location information, the LMF assigns a positioning sequence ID to the primary network elements, i.e. the BS; then if there are redundant positioning IDs (which often happens), the LMF assigns the positioning ID to secondary network elements, i.e. the RISs used in the localization process. These are not unique to the base stations but are assigned by the LMF. The base station also generates a PRS signal according to this ID.

[0121] One of the features that makes the difference is that the PRS signal is assigned only to the base station.

[0122] When the cell region is observed, there are too many positioning sequence IDs which is called redundant.

[0123] So, emerging of invention go ahead and assign these IDs to the primary base stations. Then, transferring the remaining IDs to the secondary network, that is, RISs (subelements of the base station. These are: RIS1 (2) and RIS2 (3), and they work depending on this base station, as shown in figure 3). It will assign the IDs remaining in the network subelement. Thus, the base station will generate and send the signals via RIS1 (2) according to the positioning sequence ID assigned to RIS1 (2). Likewise, the base station will generate and send the signals it will send via RIS2 (3) according to the positioning sequence IDs assigned to RIS2 (3). This feature is one of the most innovative and distinctive features of the invention.— In this method, xi, X2, X3 were produced according to different positioning IDs.

[0124] Reconfigurable Intelligent Surface (RIS) link identification by user equipment (UE) (4) has multifaceted benefits, encompassing physical layer security enhancements and improved power efficiency. RIS link identification helps in mitigating man-in-the-middle (MITM) attacks where an attacker could intercept or alter the communication between two parties without their knowledge. By recognizing RIS in their environment, UEs can leverage RIS in uplink transmissions, leading to significant power savings. This is particularly advantageous in mobile or remote devices where power conservation is crucial. Additionally, the ability of UEs (4) to identify and interact with RIS enables more precise Cell ID-based localization, offering improved accuracy in positioning and tracking services. This combination of features not only supports the security at the physical layer but also optimizes operational efficiency and enhances location-based services, making RIS link identification a valuable asset in modern wireless communication systems.

[0125] Therefore, there are 3 embodiments of the invention, and three different modifications have been proposed for the same signal.

[0126] 1stembodiment: multiplication with orthogonal codes.

[0127] 2ndembodiment: predetermined phase shift.

[0128] 3rdembodiment: cyclic shift.

[0129] These three methods (multiplication with orthogonal codes, predetermined phase shift, cyclic shift) and BS (1 ) side watermarking can be used for RIS Identification and UE localization.

[0130] Multiplication with orthogonal codes;

[0131] Assuming that there is no redundant positioning sequence ID to assign secondary network elements i.e. RISs, LMF only assigns positioning sequence ID to BS. Accordingly, PRS signal is generated. Let this signal be xi. However, it is assumed that X2 and X3 are derivative signals of xi and considering the scenario of being different from xi ; in this case, the function is used. To obtain xi by making changes in x.

[0132] One can generate N different sequences, such Here, the x signal is multiplied by different orthogonal sequences. To obtain X2 and X3, it is obtained by multiplying it with the orthogonal signal. So there is a signal multiplied with three different orthogonal sequences creating three different signals. Therefore, correlation is made by multiplying the same localization signal with three different orthogonal ones. When detected, it will be identified which base station and via which RIS the signal came. The computer implemented method which is suitable for being used with a communication network comprising

[0133] • At least one reconfigurable intelligent surface (RIS),

[0134] • At least one user equipment (UE) (4),

[0135] • At least one base station (BS),

[0136] • At least one location management function network element, the method is configured to provide BS (1 ) side watermarking with orthogonal codes for reconfigurable intelligent surface identification and comprises the steps of

[0137] • Requesting a positioning to base station (BS) (1 ) by the user equipment (UE (4)) in the cell region,

[0138] • Assigning the one positioning sequence ID to BS (1 ) by Location Management function (LMF) network element and informing the user by LMF,

[0139] • Generating localization signal based on the sequence ID assigned to the BS and by multiplying this signal by different orthogonal sequences to obtain unique localization signals, here generating N different sequences as base station,

[0140] • T ransmitting generated signals by the BS (1 ) through direct link or RIS assisted links.

[0141] • When the user equipment (UE) (4) captures localization signals, correlation is performed between received localization signal and locally generated copies of the localization signals.,

[0142] • Detecting the signal as a which base station and via which RIS the signal came.

[0143] Another embodiment of the invention;

[0144] Another method is phase shifting. This method is applying phase shifts to the signal x1 at the base station. Phase shift introduction is done at the BS (1 ) side instead of the RIS side. Given different phase shifts, results in different phase shifted versions of x1 which are x2, x3. By looking at the amount of phase shifts, the user (user equipment) can understand which path it is coming from (the technical person in the relevant technical field can easily understand it). What happens here is that since it sends the same PRS signal with different phase shifts, it will be understood from which base station and through which RIS the signal comes from. This embodiment is the application of a pre-determined phase shift to the signal. The computer implemented method which is suitable for being used with a communication network comprising

[0145] • At least one reconfigurable intelligent surface (RIS),

[0146] • At least one user equipment (UE) (4),

[0147] • At least one base station (BS) (1 ),

[0148] • At least one location management function network element, the method is configured to provide BS side watermarking by phase introduction for reconfigurable intelligent surface identification and comprises the steps of;

[0149] • Requesting a positioning to base station (BS) (1 ) by the user equipment (UE) (4) in the cell region,

[0150] • Applying pre-determined phase shifts to the signal,

[0151] • Sending of localization signals with phase shift to user equipment (UE) (4).

[0152] The third another embodiment of the invention is shifting the signal (cyclic shift). Shifted by the amount of one symbol, two symbols etc. The user can understand how much cyclic shift there is in the correlator and detect the signal. By looking at the user, prs signal, it can be understood which base station it came from, and by looking at how much shift there is, which RIS it came from.

[0153] Transmitting phase shifted version of localization signal to UE through direct and RIS assisted linksThe computer implemented method which is suitable for being used with a communication network comprising

[0154] • At least one reconfigurable intelligent surface (RIS),

[0155] • At least one user equipment (UE) (4),

[0156] • At least one base station (BS),

[0157] • At least one location management function network element, the method is configured to provide BS (1 ) side watermarking by cyclic shifting for reconfigurable intelligent surface identification and comprises the steps of;

[0158] • Requesting a positioning to base station (BS) (1 ) by the user equipment (UE) (4) in the cell region,

[0159] • Applying a distinct cyclic shift to the original localization signal for each RIS, • T ransmitting generated signals by the BS (1 ) through direct link or RIS assisted links,

[0160] • Correlating the signal by looking at how much shift there is at the user PRS signal which base station it came from. (By looking at how many symbols the signal shifts as a result of correlation, a certain number of shifts corresponds to a RIS. Thus, by looking at how much it has shifted, it is possible to understand which RIS it is coming from.)

[0161] Figure 1 demonstrates the BS (1 ) equipped with multi-channel beamforming capabilities. The BS (1 ) can transmit localization signals towards multiple RISs and the direct path simultaneously. Each signal directed towards an RIS (RIS 1 , RIS 2) or direct path is uniquely watermarked by the BS (1 ).

[0162] Figure 2 illustrates a Power Delay Profile (PDP) in a wireless communication system, which graphically represents the received signal power over various time delays. This profile identifies three significant peaks that correspond to different propagation paths: a direct Line-of-Sight (LoS) path and two indirect paths via Reconfigurable Intelligent Surfaces (RIS 1 (2) and RIS 2 (3)).

[0163] In positioning and localization, the PDP is utilized to discern the signals arriving from assorted directions. Typically, the LoS path would present the shortest delay and potentially the highest power level, as it’s the most direct transmission with minimal obstructions. The signals reflected by RIS 1 (2) and RIS 2 (3) exhibit longer delays due to the extra distance they travel upon reflection.

[0164] The interpretation of Power Delay Profile (PDP) data for accurate positioning within a wireless communication system presents several challenges. Variability in signal strength means that the path with the highest received power is not always the direct Line-of-Sight (LoS) path. Instead, it might be a signal reflected from an RIS, which could be stronger due to constructive interference or more favorable conditions in the reflected path, potentially misleading positioning algorithms. Additionally, the ambiguity in identifying the origin of received signals is a significant issue. When signals are reflected by RIS 1 (2) and RIS 2 (3), distinguishing between them based solely on their arrival time and power is problematic, as these characteristics can be quite similar if the RISs are located at similar distances from the User Equipment (UE) (4). Moreover, the UE's position relative to the RISs is dynamic, which impacts the signal's timing and power, rendering the PDP an inconsistent measure for determining distance or signal source, since it does not account for the variable nature of the UE's (4) location. These challenges underscore the insufficiency of relying solely on PDP for accurate localization. While PDP provides valuable insight into the signal propagation environment, the potential for signal strength anomalies, the ambiguity in signal origins, and the varying positions of the UE (4) necessitate a more sophisticated method for signal identification. This is where the need to individually identify the taps associated with each RIS becomes essential. A reliable RIS identification method would allow a localization system to correctly attribute each tap in the PDP to its source, thereby enabling precise positioning by accurately factoring in the unique delays and power levels of the signals reflected by different RISs.

[0165] Figure 3 shows the signalsX1, x2> and x3transmitted by the BS (1 ) towards the UE (4) and RISs. The signals are embedded with distinct modifications, such as different localization sequences, using orthogonal codes, applying cyclic shifts, or predetermined phase shifts, serving as watermarks to be recognized by the UE. The proposed system allows for accurate identification of the signals' paths, improving localization accuracy.

[0166] By applying distinct watermarking techniques at the BS, the system embeds a unique signature into each signal transmitted towards different RISs and the direct path, simplifying the UE's task of path identification. These signatures could be different types of localization signals assigned by the network (LMF) to each entity in the system. In a centralized manner, Location Management Function (LMF) can assign positioning sequence IDs to the neighboring BSs (1 ) and acknowledge the UE (4) of these assignments. In a typical environment there will be redundant number of positioning sequences which could be assigned to secondary network equipment (e.g., RIS) which serves in the network but is connected to a certain BS (1 ) and controlled by the said BS. In such a case, if available, the redundant sequences could be assigned to those said RISs to further identify the RIS links. The assignment process can be held in a cascaded manner where the first set of positioning sequences are assigned to the BSs, then the second set of positioning sequences assigned to the secondary network equipment such as RISs. In such a caseX1represents the signal generated based on the positioning sequence ID from first set of sequences; and x2and x3represent the signal generated based on second set of sequence IDs. The positioning sequences could be generated using Gold Sequences as used in PRS signals in 5G NR or could be any type of sequences with good auto correlation and poor cross correlation properties.

[0167] In case where the network assigns positioning sequence IDs to only BSs, BS (1 ) can decide to watermark the signal based on manipulating the assigned positioning sequence x with length L which is generated according to the assigned positioning sequence ID.

[0168] One can generate N different sequences suchX£= f(x, a£), i = In one embodiment, the a£could represent the orthogonal sequence where each a£is associated with an RIS connected to said BS, such that

[0169] The receiver can identify which RIS has been used by correlating the received signal with locally generated sequences for all x£-

[0170] In another embodiment, the a£could represent pre-determined phase shift where eacha=ejdi is associated with an RIS connected to said BS, such that f(x, a£) = x ejei, where i = {i; The receiver can identify the link by measuring the phase shift at the correlator output.

[0171] In another embodiment, the a£could represent the amount of cyclic shift and associated with an RIS connected to said BS, such that / (x, a£) outputs x£which is the cyclic shifted version of x by a£elements where a£= {o, ..., L - 1 }. The receiver can understand the amount of cyclic shift which represent the RIS path.

[0172] Another embodiment of the invention are; • The Positioning sequence IDis assigned only to the base station.

[0173] • Use of smart repeaters instead of RIS.

[0174] • Remaining positioning IDs could be redundant IDs.

[0175] • Positioning sequence signals could be PRS signals.

[0176] • Space Division Multiplexing or Multi-channel beamforming techniques are used during transmission of localization signals.

[0177] The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the art may exhibit similar embodiments in light of the above-mentioned facts without drifting apart from the main theme of the invention.

Claims

AMENDED CLAIMS received by the International Bureau on 24 July 2025 (24.07.2025)1. A computer implemented method of reconfigurable intelligent surface (RIS) identification comprises; using base station side watermarking method for reconfigurable intelligent surface (RIS) identification.

2. The computer implemented method according to claim 1 of reconfigurable intelligent surface (RIS) identification for base station side watermarking comprises; identifying RIS and localization at the same time by using a multichannel beamforming gNB, dispatching localization signals concurrently through direct and RIS-reflected paths within a single time slot.

3. A computer implemented method according to claim 1 , which is suitable for being used with a communication network comprising• At least one reconfigurable intelligent surface (RIS),• At least one user equipment (UE) (4),• At least one base station (BS) (1 ),• At least one Location management function network element, the method is configured to provide base station side watermarking for reconfigurable intelligent surface identification and comprises the steps of;• Requesting a positioning to base station (BS) (1 ) by the user equipment (UE) (4) in the cell region,• Assigning positioning sequence IDs to primary network element Base Station, Assigning remaining positioning sequence IDs to secondary network elements which are RISs and informing the user by LMF,• Generating positioning sequence signals locally according to these positioning sequence IDs by the user equipment (UE) (4),• Transmitting positioning sequences by the base station through direct or RIS assisted links when the user equipment (UE) (4) captures localization signals, correlating between captured localization signals and the signals which are produced in locally by user,• According to result of the correlation, determining the time according to the point that gives the highest correlation (peak) and identifying to RIS according to correlation result.31AMENDED SHEET (ARTICLE 19)4. The computer implemented method according to claim 1 , which is suitable for being used with a communication network comprising• At least one reconfigurable intelligent surface (RIS),• At least one user equipment (UE) (4),• At least one base station (BS) (1 ),• At least one Location management function network element, the method is configured to provide base station side watermarking with orthogonal codes for reconfigurable intelligent surface identification and comprises the steps of• Requesting a positioning to base station (BS) (1 ) by the user equipment (UE) (4) in the cell region,• Assigning the one positioning sequence ID to BS (1 ) by Location management function (LMF) network element and informing the user by LMF,• Generating localization signal based on the sequence ID assigned to the BS and by multiplying this signal by different orthogonal sequences to obtain unique localization signals, here generating, N different sequences asbase station• Transmitting generated signals by the BS through direct link or RIS assisted links.• When the user equipment (UE) (4) captures localization signals, performing correlation between received localization signal and locally generated copies of the localization signals.,• Detecting the signal as a which base station and via which RIS the signal came.

5. The computer implemented method according to claim 1 , which is suitable for being used with a communication network comprising• At least one reconfigurable intelligent surface (RIS),• At least one user equipment (UE) (4),• At least one base station (BS) (1 ),• At least one Location management function network element, the method is configured to provide BS (1 ) side watermarking by phase introduction for reconfigurable intelligent surface identification and comprises the steps of;• Requesting a positioning to base station (BS) (1 ) by the user equipment (UE) (4) in the cell region,• Applying pre-determined phase shifts to the signal,32AMENDED SHEET (ARTICLE 19)• Sending of localization signals with phase shift to user equipment (UE) (4),6. The computer implemented method according to claim 1 , of transmitting phase shifted version of localization signal to UE through direct and RIS assisted links which is suitable for being used with a communication network comprising• At least one reconfigurable intelligent surface (RIS),• At least one user equipment (UE) (4),• At least one base station (BS) (1 ),• At least one Location management function network element, the method is configured to provide BS (1 ) side watermarking by cyclic shifting for reconfigurable intelligent surface identification and comprises the steps of;• Requesting a positioning to base station (BS) (1 ) by the user equipment (UE) (4) in the cell region,• Applying a distinct cyclic shift to the original localization signal for each RIS,• Transmitting generated signals by the base station (BS) (1 ) through direct link or RIS assisted links,• Corelating the signal by looking how much shift there is at the user PRS signal which base station it came from.

7. The method of according to any one of the preceding claims, wherein said use of smart repeaters in order to RIS.

8. The method of according to claim 2, wherein multiplication with orthogonal codes method, predetermined phase shift method, cyclic shift method or base station side watermarking method is used to said signal localization.

9. The method of according to claim 3 or claim 4, wherein said the positioning sequence ID is assigned only to the base station.

10. The method of according to claim 3, wherein said remaining positioning IDs are redundant IDs.

11. The method of according to claim 3, wherein said positioning sequence signals are PRS signals.

12. The method of according to claim 1 or claim 3, wherein space division multiplexing or multi-channel beamforming techniques are used during transmission of localization signals.33AMENDED SHEET (ARTICLE 19)

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