Ris-assisted base station positioning method, device and system in complex environment

Abstract

The application provides a RIS-assisted base station positioning method, device and system in a complex environment, and relates to the technical field of wireless positioning. The beam pointing of the RIS to the target is determined through RIS beam scanning, the pitch angle and the azimuth angle between the RIS and the target are calculated according to the beam pointing and the OFDM signal transmitted by the base station, and the position information of the target is calculated according to the pitch angle, the azimuth angle and the distance between the RIS and the target. The RIS-assisted base station positioning method in the complex environment provided by the application separates the echo signal of the target reflected by the RIS from the total signal of the target received by the base station through the OFDM signal and a reasonable design of the direction codebook, and finally positions the target by using the separated signal and the RIS beam scanning. Compared with the base station positioning in a multipath-assisted shielding environment, the application can achieve higher positioning accuracy with only one RIS, the RIS can more flexibly control the amplitude and phase of the signal, and the reliability of target positioning is improved.

Description

Technical Field

[0001] This invention belongs to the field of wireless positioning technology, specifically relating to a RIS-assisted base station positioning method, device, and system in complex environments. Background Technology

[0002] Base station target localization in complex environments is an important research area. In complex environments such as cities and indoors, obstacles such as buildings and trees can cause signal attenuation and multipath interference, making target localization difficult. Traditional positioning technologies such as the Global Positioning System (GPS) suffer from limitations in accuracy and reliability in such environments.

[0003] Existing technology 1: A target localization system using a RIS-assisted multi-anchor point approach is proposed. This system optimizes the RIS phase shift design when there are obstacles between the target and the RIS, and when multiple RIS are present, achieving a certain level of localization accuracy. However, the introduction of multiple anchor points leads to resource waste. Furthermore, there is a direct line-of-sight path between each anchor point and the target; in this case, a single anchor point can complete the localization, making the role of the RIS less significant. Existing technology 2: A one-step localization algorithm for OFDM transmitters is proposed, effectively addressing multipath interference and suitable for situations with different incident angles along multiple paths. This algorithm fully utilizes the time-domain characteristics of the received signal to construct an extended covariance matrix to counteract the damage to the orthogonality of OFDM signals caused by Doppler frequency shift. However, this algorithm introduces multiple receivers, each equipped with multiple antennas, resulting in high costs. Moreover, this algorithm is designed for two-dimensional scenarios, while the target, transmitter, and receiver are typically located in a three-dimensional scene. Existing technology 3: Based on the situation where the line-of-sight path of the target node and anchor node is missing due to obstacle occlusion, a direct localization algorithm based on convex optimization with intelligent reflective surface assistance is proposed. This algorithm can effectively estimate the position parameters of the target node when the line-of-sight path is missing. However, when the line-of-sight path of the target node and anchor node is missing due to obstacle occlusion, four RIS are required to complete the localization scenario. In this case, the root mean square error of localization is large and the localization accuracy is not high. Furthermore, this algorithm introduces a convex optimization algorithm, which increases the complexity of the localization algorithm.

[0004] Therefore, while existing multipath-assisted base station positioning schemes in obstructed environments can achieve a certain level of positioning accuracy, in real-world positioning scenarios, the positioning signal transmitted by the base station cannot be guaranteed to be reflected back to the target via multipath propagation, as multipath propagation is uncontrollable. Furthermore, existing RIS-assisted target positioning in obstructed environments only operates under ideal conditions. In actual positioning scenarios, the positioning signal transmitted by the base station is subject to reflection, refraction, and scattering from objects such as buildings, complicating the signal propagation path and interfering with the positioning signal reflected by the RIS, thus leading to inaccurate positioning. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, the present invention provides a RIS-assisted base station positioning method, apparatus, and system in complex environments.

[0006] The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a RIS-assisted base station positioning method in complex environments, comprising:

[0008] Based on the OFDM signal transmitted by the base station, the RIS direction codebook is designed and obtained;

[0009] Based on the RIS direction codebook, the OFDM signal, the communication information during the target propagation process, the RIS information, and the base station information, the initial echo signal of the target received by the base station is calculated, and the total signal of the target received by the base station is calculated based on the initial echo signal of the target received by the base station.

[0010] The total signal of the target received by the base station is subjected to phase shift removal processing to obtain the total signal of the target received by the base station after phase shift removal processing. The echo signal of the target reflected by the RIS is calculated based on the total signal of the target received by the base station after phase shift removal processing. The distance between the RIS and the target is calculated based on the echo signal of the target reflected by the RIS.

[0011] The beam direction of the RIS to the target is determined by RIS beam scanning. The elevation angle and azimuth angle between the RIS and the target are calculated based on the beam direction and the OFDM signal transmitted by the base station. The position information of the target is calculated based on the elevation angle, the azimuth angle and the distance between the RIS and the target.

[0012] Optionally, the step of designing the RIS direction codebook based on the OFDM signal transmitted by the base station includes:

[0013] Based on the number of subcarriers and symbols of the OFDM signal transmitted by the base station, a RIS direction codebook is designed, wherein the initial RIS direction codebook of the nth subcarrier during the kth symbol period [B]. n,k Represented as:

[0014] [B] n,k =e -j2πnk / N (1)

[0015] n = 1, 2, ..., N, k = 1, 2, ..., K, where n represents the subcarrier of the current OFDM signal, N represents the number of subcarriers of the OFDM signal transmitted by the base station, k represents the number of symbols of the current OFDM signal, K represents the number of symbols of the OFDM signal transmitted by the base station, and j represents the imaginary factor.

[0016] Transform B into a column vector to obtain b, when γ 3k-2 =b,γ 3k-1 =2b,γ 3k =3b, where γ is the directional codebook of the transformed RIS.

[0017] Optionally, the communication information, RIS information, and base station information during the target propagation process include:

[0018] The multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, the RIS reflection path signal gain, the RIS signal time delay of the target, the turning vector corresponding to the angle between the base station and the RIS, the turning vector corresponding to the angle between the target and the RIS, the radial velocity of the target relative to the RIS, the cross-path signal time delay of the target, the OFDM echo signal of the RIS reflection path, and the noise signal corresponding to the target.

[0019] Optionally, the initial echo signal of the target received by the base station includes: the initial echo signal of the target reflected by multipath, the initial echo signal of the target reflected by RIS, and the initial echo signal of the target reflected by cross-path.

[0020] Optionally, the step of calculating the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, communication information during target propagation, RIS information, and base station information, and calculating the total signal of the target received by the base station based on the initial echo signal of the target received by the base station, includes:

[0021] Based on the multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, and the wavelength of the OFDM signal, the initial echo signal of the multipath-reflected target is calculated. The initial echo signal received by the base station from the m-th target of the multipath reflection is [Y]. o,m ] n,k :

[0022] [Y o,m ] n,k =g o,m [X(τ o,m )] n,k ⊙[C(v o,m )] n,k (2)

[0023] Where m represents the m-th target, g o,m Let τ be the multipath signal gain corresponding to the m-th target. o,m Let X(τ) be the time delay of the multipath signal corresponding to the m-th target. o,m The expression τ represents the time delay τ of the multipath signal corresponding to the m-th target added to the OFDM signal of multipath reflection. o,m C(v) o,m This indicates that the radial velocity information of the m-th target relative to the multipath has been captured. v o,m Let T be the radial velocity of the m-th target relative to the multipath. sym λ is the sum of the duration of a single symbol and the duration of the cyclic prefix of the OFDM signal, and λ is the wavelength of the OFDM signal.

[0024] Based on the RIS direction codebook, RIS reflection path signal gain, target RIS signal time delay, turning vector corresponding to the angle between the base station and the RIS, turning vector corresponding to the angle between the target and the RIS, target radial velocity relative to the RIS, and OFDM echo signal of the RIS reflection path, the initial echo signal of the target reflected by the RIS is calculated. The initial echo signal of the m-th target reflected by the RIS received by the base station is [Y]. r,m ] n,k :

[0025]

[0026] Among them, g r,m For the RIS reflection path signal gain, [A(φ m )] n,k =[a(θ)] T diag(γ k )a(φ m ) represents the RIS phase shift of the m-th target on the n-th subcarrier in the k-th symbol, γ k For the k-th symbol, the RIS direction codebook is given, where a(θ) is the turning vector corresponding to the angle between the base station and the RIS, and a(φ) is the direction vector. m Let ) be the turning vector corresponding to the angle between the m-th target and RIS, and T denote the matrix transpose operation, v r,m Let C(v) be the radial velocity of the m-th target relative to RIS. r,m X(τ) represents capturing the radial velocity information of the m-th target relative to RIS. r,m () represents the OFDM echo signal of the RIS reflection path. τ r,m Let Δ be the RIS signal time delay for the m-th target. f This indicates the subcarrier spacing of the OFDM signal; This represents a vector of length K with elements all equal to 1.

[0027] The initial echo signal of the target reflected from the cross-path is calculated based on the target's cross-path signal time delay, the target's radial velocity relative to the RIS, the target's radial velocity relative to the multipath, the turning vector corresponding to the angle between the base station and the RIS, and the OFDM echo signal of the RIS reflection path. The initial echo signal of the m-th target reflected from the cross-path is [Y]. ro,m ] n,k :

[0028]

[0029] Among them, g ro,m For the cross-path signal gain, τ ro,m Let X(τ) be the time delay of the cross-path signal for the m-th target. ro,m The cross-path reflection OFDM signal is supplemented with the time delay τ of the cross-path signal corresponding to the m-th target. ro,m ,[A(φ m )] n,k =[a(θ)] T diag(γ k )a(φ m ) represents the RIS phase shift of the m-th target on the n-th subcarrier in the k-th symbol, γ k For the k-th symbol, the RIS direction codebook is given, where a(θ) is the turning vector corresponding to the angle between the base station and the RIS, and a(φ) is the direction vector. m ) is the steering vector corresponding to the angle between the m-th target and the RIS;

[0030] The total signal of the target received by the base station is [Y m ] n,k :

[0031] [Y m ] n,k =[Y o,m ] n,k +[Y r,m ] n,k +2[Y ro,m ] n,k +[N m ] n,k (5)

[0032] Among them, [N m ] n,k The noise signal of the m-th target when the n-th subcarrier is the k-th symbol.

[0033] Optionally, the step of performing phase-shift removal processing on the total target signal received by the base station to obtain the phase-shift removed total target signal received by the base station, and calculating the echo signal of the target reflected by the RIS based on the phase-shift removed total target signal received by the base station, and calculating the distance between the RIS and the target using the echo signal of the target reflected by the RIS, includes:

[0034] According to formula (1) and the target RIS phase shift [A(φ] m )] n,k ,get:

[0035] [A(φ m )] n,3k =3[A(φ m )] n,3k-2 ,[A(φ m )] n,3k-1 =2[A(φ m )] n,3k-2 ,but

[0036]

[0037] The total signal of the m-th target received by the base station is subjected to phase shift removal processing to obtain the phase shift removed total signal of the m-th target received by the base station [W]. m ] n,k :

[0038] [W m ] n,k =[Y m ] n,k ⊙[A(-φ m )] n,k ⊙[A(-φ m )] n,k (6);

[0039] After phase shift removal processing, the echo signal of the target reflected by the RIS corresponding to the m-th target is,

[0040]

[0041]

[0042] After phase shift removal processing, the echo signal of the multipath reflection target corresponding to the m-th target is,

[0043]

[0044]

[0045] After phase-shift removal processing, the echo signal of the target reflected by the intersecting path corresponding to the m-th target is,

[0046]

[0047] The matrix is ​​represented as:

[0048]

[0049] The matrix is ​​transformed to obtain the echo signal W of the target reflected by the RIS corresponding to the m-th target after matrix transformation. r,m ,

[0050]

[0051] W r,m Perform a two-dimensional FFT and extract the x and y coordinates corresponding to the peak values ​​of the signal after the two-dimensional FFT processing, which are respectively x m and y m x m That is, the sum of the distances between the m-th target and the RIS, and between the RIS and the base station, y m Let be the radial velocity of the m-th target relative to RIS, and let d be the distance between RIS and the m-th target. m d m =x m -d br , where d br This represents the distance between the base station and the RIS.

[0052] Optionally, the step of determining the beam pointing of the RIS to the target through RIS beam scanning, calculating the elevation angle and azimuth angle between the RIS and the target based on the beam pointing and the OFDM signal transmitted by the base station, and calculating the target's position information based on the elevation angle, the azimuth angle, and the distance between the RIS and the target includes:

[0053] When the base station transmits four OFDM signals, and the RIS receives each of the four OFDM signals, it divides the four received signals in each RIS area into four beam directions, A, B, C, and D, based on the beam scanning results. The beam directions of A, B, C, and D are as follows:

[0054] G A,m =Sa[(θ m -θ r,m +B s ) / B w ]·Sa[(φ m -φ r,m +B s ) / Bw ];

[0055] G B,m =Sa[(θ m -θ r,m -B s ) / B w ]·Sa[(φ m -φ r,m +B s ) / B w ];

[0056] G C,m =Sa[(θ m -θ r,m -B s ) / B w ]·Sa[(φ m -φ r,m -B s ) / B w ];

[0057] G D,m =Sa[(θ m -θ r,m +B s ) / B w ]·Sa[(φ m -φ r,m -B s ) / B w ];

[0058] Where, θ m Let φ be the azimuth angle of RIS relative to the m-th target. m Let θ be the pitch angle of RIS relative to the m-th target. r,m Let φ be the initial azimuth angle corresponding to the beam pointing of RIS relative to the m-th target. r,m Let B be the initial elevation angle corresponding to the beam pointing of RIS relative to the m-th target. s For the beam offset relative to the beam direction, B w The beamwidth of the RIS;

[0059] Based on the four beam directions and x m Calculate the amplitude g of the echo signal. A,m ,g B,m ,g C,m ,g D,m When echo delay Let c be the speed of light. The echo signals of the four OFDM signals A, B, C, and D are calculated as follows:

[0060] Y A,m =g A,m X(τ r,m );

[0061] Y B,m =g B,m X(τ r,m );

[0062] Y C,m =g C,m X(τ r,m );

[0063] Y D,m =g D,m X(τ r,m );

[0064] The echo signals of the four OFDM signals are combined into three signals, and the sum signal s corresponding to the m-th target is represented as Y. s,m The difference signal d corresponding to the m-th target is represented as Y. d,m The difference signal q corresponding to the m-th target is represented by Y. q,m ;

[0065] Y s,m =Y A,m +Y B,m +Y C,m +Y D,m ;

[0066] Y d,m =Y A,m +Y D,m -(Y B,m +Y C,m );

[0067] Y q,m =Y A,m +Y B,m -(Y C,m +Y D,m );

[0068] The lookup table ranges θ for azimuth and elevation angles are set according to the beamwidth respectively. s and φ s Calculate the pointers of A, B, C, and D for each value within the lookup table range.

[0069] G A1 (n)=Sa[(θ s (n)+B s ) / B w ]·Sa[(φ s (n)+B s ) / B w ];

[0070] G B1 (n)=Sa[(θ s (n)-B s ) / Bw ]·Sa[(φ s (n)+B s ) / B w ];

[0071] G C1 (n)=Sa[(θ s (n)-B s ) / B w ]·Sa[(φ s (n)-B s ) / B w ];

[0072] G D1 (n)=Sa[(θ s (n)+B s ) / B w ]·Sa[(φ s (n)-B s ) / B w ];

[0073] Combine the pointers to A, B, C, and D corresponding to each value within the lookup table range, G s (n) represents the lookup table range and the beam pointing s, G d (n) represents the difference beam pointing d and G within the lookup table range. q (n) represents the difference beam pointing q within the lookup table range;

[0074]

[0075] Calculate the sum-difference ratio within the lookup table range using the combination formula (15), R. t (n) represents the ratio of the difference beam pointing d to the sum beam pointing s within the lookup table range, R p (n) represents the ratio of the difference beam pointing q to the sum beam pointing s within the lookup table range.

[0076] R t (n)=G d (n) / G s (n); R p (n)=G q (n) / G s (n);

[0077] Find Y respectively s,m (x 1,m ,y 1,m ), Y d,m (x 1,m ,y 1,m ), Y q,m (x 1,m ,y 1,m The phase angle of ) is A s,mA d,m A q,m , where x 1,m =d m y 1,m =y m According to Determine the signs of the azimuth and elevation angles of the m-th target; where S θ,m S represents the sign of the azimuth angle of the m-th target relative to RIS. φ,m A represents the sign of the pitch angle of the m-th target relative to RIS. s,m A d,m A q,m They represent Y respectively s,m Y d,m Y q,m The corresponding phase angle;

[0078] Calculate the sum-difference ratio of the signal at the m-th target.

[0079] R θ,m =|Y d,m (x 1,m ,y 1,m ) / Y s,m (x 1,m ,y 1,m )|,

[0080] R φ,m =|Y q,m (x 1,m ,y 1,m ) / Y s,m (x 1,m ,y 1,m (16)

[0081] R θ,m and R φ,m R is the ratio of each sum and difference within the lookup table range. t (n), R p (n) is used for comparison.

[0082] p θ,m =min|S θ,m ·R θ,m -R t (n)|;p φ,m =min|S φ,m ·R φ,m -R p (n)|;

[0083] According to θ m =θ s,m (p θ,m )+θ r,m ;φ m =φs,m (p φ,m )+φ r,m ; Calculate the azimuth angle θ between RIS and the target. m and pitch angle φ m ,

[0084] According to formula p m (1)=p r (1)+d m cos(φ m cos(θ) m );

[0085] p m (2) = p r (2)+d m cos(φ m sin(θ) m );

[0086] p m (3) = p r (3)+d m sin(φ m );

[0087] Calculate the position p of the m-th target m p m =[p m (1),p m (2),p m (3)]; (17)

[0088] p r Let p be the coordinates of RIS. r (1) represents the coordinates of RIS in the x-dimensional space, p r (2) represents the coordinates of RIS in the y-dimensional space, p r (3) represents the coordinates of RIS in the z-dimensional dimension.

[0089] Secondly, the present invention provides a RIS-assisted base station positioning device in a complex environment, comprising: a design unit and a computing unit;

[0090] The design unit is used to design a RIS direction codebook based on the OFDM signal transmitted by the base station.

[0091] The calculation unit is used to calculate the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, the communication information during the target propagation process, the RIS information, and the base station information, and to calculate the total signal of the target received by the base station based on the initial echo signal of the target received by the base station.

[0092] The calculation unit is further configured to perform phase shift removal processing on the total signal of the target received by the base station to obtain the total signal of the target received by the base station after phase shift removal processing, and calculate the echo signal of the target reflected by RIS based on the total signal of the target received by the base station after phase shift removal processing, and calculate the distance between RIS and the target through the echo signal of the target reflected by RIS.

[0093] The computing unit is further configured to determine the beam direction of the RIS to the target through RIS beam scanning, calculate the elevation angle and azimuth angle between the RIS and the target based on the beam direction and the OFDM signal transmitted by the base station, and calculate the target's position information based on the elevation angle, the azimuth angle and the distance between the RIS and the target.

[0094] Thirdly, the present invention provides a RIS-assisted base station positioning system in a complex environment, comprising: a processor, a storage medium, and a bus, wherein the storage medium stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the storage medium via the bus, and the processor executes the machine-readable instructions to perform the steps of the method described in the first aspect above.

[0095] Fourthly, the present invention provides a storage medium storing a computer program, which, when executed by a processor, performs the steps of the method described in the first aspect above.

[0096] The present invention provides a RIS-assisted base station positioning method in complex environments, comprising: designing a RIS direction codebook based on the OFDM signal transmitted by the base station; calculating the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, communication information during target propagation, RIS information, and base station information, and calculating the total signal of the target received by the base station based on the initial echo signal of the target received by the base station; performing phase shift removal processing on the total signal of the target received by the base station to obtain the phase shift removed total signal of the target received by the base station, and calculating the echo signal of the target reflected by the RIS based on the phase shift removed total signal of the target received by the base station, and calculating the distance between the RIS and the target based on the echo signal of the target reflected by the RIS; determining the beam pointing of the RIS towards the target through RIS beam scanning, calculating the elevation angle and azimuth angle between the RIS and the target based on the beam pointing and the OFDM signal transmitted by the base station, and calculating the position information of the target based on the elevation angle, azimuth angle, and the distance between the RIS and the target. The RIS-assisted base station positioning method in complex environments provided by this invention utilizes OFDM signals and a rationally designed direction codebook. Simultaneously, by using the total target signal received by the base station, the echo signal reflected from the RIS is separated, and the separated signal, along with RIS beam scanning, is used for final target positioning. Compared to base station positioning in multipath-assisted obstructed environments, this invention requires only one RIS to achieve higher positioning accuracy than multipath-assisted methods. The RIS can more flexibly adjust the amplitude and phase of the signal, improving the reliability of target positioning.

[0097] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0098] Figure 1 This is a flowchart illustrating the RIS-assisted base station positioning method in a complex environment provided in this embodiment.

[0099] Figure 2 A system model diagram of the RIS-assisted base station positioning method in complex environments provided in this embodiment of the invention;

[0100] Figure 3 A two-dimensional FFT result diagram of a single target echo signal provided in an embodiment of the present invention;

[0101] Figure 4 This invention provides a trend of the root mean square error of location as a function of the standard deviation of base station measurement error during single-target positioning, as shown in the embodiments of the present invention.

[0102] Figure 5 This invention provides an embodiment of the problem showing how the root mean square error of the location changes with the distance between the RIS and the target during multi-target localization in a complex environment.

[0103] Figure 6 A schematic diagram of a RIS-assisted base station positioning device in a complex environment provided in an embodiment of the present invention;

[0104] Figure 7 This is a schematic diagram of the structure of a RIS-assisted base station positioning system in a complex environment, as provided in an embodiment of the present invention. Detailed Implementation

[0105] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0106] To improve the reliability of target positioning in complex environments, this invention provides a RIS-assisted base station positioning method in complex environments. Figure 1 This is a flowchart illustrating the RIS-assisted base station positioning method in complex environments provided in this embodiment, as shown below. Figure 1 As shown, the steps include:

[0107] S101. Based on the OFDM signal transmitted by the base station, design and obtain the RIS direction codebook;

[0108] Optionally, S101 includes: designing a RIS direction codebook based on the number of subcarriers and symbols of the OFDM signal transmitted by the base station, wherein the initial RIS direction codebook of the nth subcarrier during the kth symbol [B]. n,k Represented as:

[0109] [B] n,k =e -j2πnk / N (1)

[0110] n = 1, 2, ..., N, k = 1, 2, ..., K, where n represents the subcarrier of the current OFDM signal, N represents the number of subcarriers of the OFDM signal transmitted by the base station, k represents the number of symbols of the current OFDM signal, K represents the number of symbols of the OFDM signal transmitted by the base station, and j represents the imaginary factor.

[0111] Transform B into a column vector to obtain b, when γ 3k-2 =b,γ 3k-1 =2b,γ 3k =3b, where γ is the directional codebook of the transformed RIS.

[0112] It should be noted that, in this embodiment of the invention, the execution entity of the RIS-assisted base station positioning method in this complex environment comprises: a base station, a RIS, and a system of M targets. The base station transmits four identical OFDM signals at fixed intervals. There are obstacles obstructing the view between the base station and the targets. The base station has two antennas: one for transmitting signals and the other for receiving signals. The signals transmitted by the base station propagate in free space. The RIS unit is M1×M2, and the spacing between the units is d=λ / 2, where λ is the signal wavelength. br d represents the distance between the base station and the RIS. rm Let be the distance between RIS and the target.

[0113] S102. Based on the RIS direction codebook, OFDM signal, communication information during target propagation, RIS information, and base station information, calculate the initial echo signal of the target received by the base station, and calculate the total signal of the target received by the base station based on the initial echo signal of the target received by the base station.

[0114] Optionally, the communication information, RIS information, and base station information during the target propagation process include:

[0115] The multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, the RIS reflection path signal gain, the RIS signal time delay of the target, the turning vector corresponding to the angle between the base station and the RIS, the turning vector corresponding to the angle between the target and the RIS, the radial velocity of the target relative to the RIS, the cross-path signal time delay of the target, the OFDM echo signal of the RIS reflection path, and the noise signal corresponding to the target.

[0116] Optionally, the initial echo signal of the target received by the base station includes: the initial echo signal of the target reflected by multipath, the initial echo signal of the target reflected by RIS, and the initial echo signal of the target reflected by cross-path.

[0117] Optionally, S102 specifically includes:

[0118] Based on the multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, and the wavelength of the OFDM signal, the initial echo signal of the multipath-reflected target is calculated. The initial echo signal received by the base station from the m-th target of the multipath reflection is [Y]. o,m ] n,k :

[0119] [Y o,m ] n,k =g o,m [X(τ o,m )] n,k ⊙[C(vo,m )] n,k (2)

[0120] Where m represents the m-th target, g o,m Let τ be the multipath signal gain corresponding to the m-th target. o,m Let X(τ) be the time delay of the multipath signal corresponding to the m-th target. o,m The expression τ represents the time delay τ of the multipath signal corresponding to the m-th target added to the OFDM signal of multipath reflection. o,m C(v) o,m This indicates that the radial velocity information of the m-th target relative to the multipath has been captured. v o,m Let T be the radial velocity of the m-th target relative to the multipath. sym λ is the sum of the duration of a single symbol and the duration of the cyclic prefix of the OFDM signal, and λ is the wavelength of the OFDM signal.

[0121] Based on the RIS direction codebook, RIS reflection path signal gain, target RIS signal time delay, turning vector corresponding to the angle between the base station and the RIS, turning vector corresponding to the angle between the target and the RIS, target radial velocity relative to the RIS, and OFDM echo signal of the RIS reflection path, the initial echo signal of the target reflected by the RIS is calculated. The initial echo signal of the m-th target reflected by the RIS received by the base station is [Y]. r,m ] n,k :

[0122]

[0123] Among them, g r,m For the RIS reflection path signal gain, [A(φ m )] n,k =[a(θ)] T diag(γ k )a(φ m ) represents the RIS phase shift of the m-th target on the n-th subcarrier in the k-th symbol, γ k For the k-th symbol, the RIS direction codebook is given, where a(θ) is the turning vector corresponding to the angle between the base station and the RIS, and a(φ) is the direction vector. m Let ) be the turning vector corresponding to the angle between the m-th target and RIS, and T denote the matrix transpose operation, v r,m Let C(v) be the radial velocity of the m-th target relative to RIS. r,m X(τ) represents capturing the radial velocity information of the m-th target relative to RIS. r,m () represents the OFDM echo signal of the RIS reflection path. τ r,m Let Δ be the RIS signal time delay for the m-th target.f This indicates the subcarrier spacing of the OFDM signal; This represents a vector of length K with elements all equal to 1.

[0124] The initial echo signal of the target reflected from the cross-path is calculated based on the target's cross-path signal time delay, the target's radial velocity relative to the RIS, the target's radial velocity relative to the multipath, the turning vector corresponding to the angle between the base station and the RIS, and the OFDM echo signal of the RIS reflection path. The initial echo signal of the m-th target reflected from the cross-path received by the base station is [Y]. ro,m ] n,k :

[0125]

[0126] Among them, g ro,m For the cross-path signal gain, τ ro,m Let X(τ) be the time delay of the cross-path signal for the m-th target. ro,m The cross-path reflection OFDM signal is supplemented with the time delay τ of the cross-path signal corresponding to the m-th target. ro,m ,[A(φ m )] n,k =[a(θ)] T diag(γ k )a(φ m ) represents the RIS phase shift of the m-th target on the n-th subcarrier in the k-th symbol, γ k For the k-th symbol, the RIS direction codebook is given, where a(θ) is the turning vector corresponding to the angle between the base station and the RIS, and a(φ) is the direction vector. m ) is the steering vector corresponding to the angle between the m-th target and the RIS;

[0127] The total signal of the target received by the base station is [Y m ] n,k :

[0128] [Y m ] n,k =[Y o,m ] n,k +[Y r,m ] n,k +2[Y ro,m ] n,k +[N m ] n,k (5)

[0129] Among them, [N m ] n,k The noise signal of the m-th target when the n-th subcarrier is the k-th symbol.

[0130] S103. Perform phase shift removal processing on the total signal of the target received by the base station to obtain the total signal of the target received by the base station after phase shift removal processing. Calculate the echo signal of the target reflected by RIS based on the total signal of the target received by the base station after phase shift removal processing. Calculate the distance between RIS and the target based on the echo signal of the target reflected by RIS.

[0131] Optionally, S103 specifically includes:

[0132] According to formula (1) and the target RIS phase shift [A(φ] m )] n,k ,get:

[0133] [A(φ m )] n,3k =3[A(φ m )] n,3k-2 ,[A(φ m )] n,3k-1 =2[A(φ m )] n,3k-2 ,but

[0134]

[0135] The total signal of the m-th target received by the base station is subjected to phase shift removal processing to obtain the phase shift removed total signal of the m-th target received by the base station [W]. m ] n,k :

[0136] [W m ] n,k =[Y m ] n,k ⊙[A(-φ m )] n,k ⊙[A(-φ m )] n,k (6);

[0137] To simplify the formula description, the formula is calculated by grouping three symbols together according to the number K of OFDM signals transmitted by the base station.

[0138] After phase shift removal processing, the echo signal of the target reflected by the RIS corresponding to the m-th target is,

[0139]

[0140]

[0141] After phase shift removal processing, the echo signal of the multipath reflection target corresponding to the m-th target is,

[0142]

[0143]

[0144] After phase-shift removal processing, the echo signal of the target reflected by the intersecting path corresponding to the m-th target is,

[0145]

[0146] The matrix is ​​represented as:

[0147]

[0148] The matrix is ​​transformed to obtain the echo signal W of the target reflected by the RIS corresponding to the m-th target after matrix transformation. r,m ,

[0149]

[0150] W r,m Perform a two-dimensional FFT and extract the x and y coordinates corresponding to the peak values ​​of the signal after the two-dimensional FFT processing, which are respectively x m and y m x m That is, the sum of the distances between the m-th target and the RIS, and between the RIS and the base station, y m Let be the radial velocity of the m-th target relative to RIS, and let d be the distance between RIS and the m-th target. m d m =x m -d br , where d br This represents the distance between the base station and the RIS.

[0151] S104. Determine the beam direction of the RIS to the target through RIS beam scanning. Calculate the elevation and azimuth angles between the RIS and the target based on the beam direction and the OFDM signal transmitted by the base station. Calculate the target's position information based on the elevation, azimuth angles, and the distance between the RIS and the target.

[0152] Optionally, S104 specifically includes:

[0153] When the base station transmits four OFDM signals, and the RIS receives each of the four OFDM signals, it divides the four received signals in each RIS area into four beam directions, A, B, C, and D, based on the beam scanning results. The beam directions of A, B, C, and D are as follows:

[0154] G A,m =Sa[(θ m -θr,m +B s ) / B w ]·Sa[(φ m -φ r,m +B s ) / B w ];

[0155] G B,m =Sa[(θ m -θ r,m -B s ) / B w ]·Sa[(φ m -φ r,m +B s ) / B w ];

[0156] G C,m =Sa[(θ m -θ r,m -B s ) / B w ]·Sa[(φ m -φ r,m -B s ) / B w ];

[0157] G D,m =Sa[(θ m -θ r,m +B s ) / B w ]·Sa[(φ m -φ r,m -B s ) / B w ];

[0158] Where, θ m Let φ be the azimuth angle of RIS relative to the m-th target. m Let θ be the pitch angle of RIS relative to the m-th target. r,m Let φ be the initial azimuth angle corresponding to the beam pointing of RIS relative to the m-th target. r,m Let B be the initial elevation angle corresponding to the beam pointing of RIS relative to the m-th target. s For the beam offset relative to the beam direction, B w The beamwidth of the RIS;

[0159] Based on the four beam directions and x m Calculate the amplitude g of the echo signal. A,m ,g B,m ,g C,m ,g D,m When echo delay Let c be the speed of light. The echo signals of the four OFDM signals A, B, C, and D are calculated as follows:

[0160] Y A,m =g A,m X(τ r,m );

[0161] Y B,m =g B,m X(τ r,m );

[0162] Y C,m =g C,m X(τ r,m );

[0163] Y D,m =g D,m X(τ r,m );

[0164] The echo signals of the four OFDM signals are combined into three signals, and the sum signal s corresponding to the m-th target is represented as Y. s,m The difference signal d corresponding to the m-th target is represented as Y. d,m The difference signal q corresponding to the m-th target is represented by Y. q,m ;

[0165] Y s,m =Y A,m +Y B,m +Y C,m +Y D,m ;

[0166] Y d,m =Y A,m +Y D,m -(Y B,m +Y C,m );

[0167] Y q,m =Y A,m +Y B,m -(Y C,m +Y D,m );

[0168] The lookup table ranges θ for azimuth and elevation angles are set according to the beamwidth respectively. s and φ s Calculate the pointers of A, B, C, and D for each value within the lookup table range.

[0169] G A1 (n)=Sa[(θ s (n)+B s ) / B w ]·Sa[(φ s (n)+Bs ) / B w ];

[0170] G B1 (n)=Sa[(θ s (n)-B s ) / B w ]·Sa[(φ s (n)+B s ) / B w ];

[0171] G C1 (n)=Sa[(θ s (n)-B s ) / B w ]·Sa[(φ s (n)-B s ) / B w ];

[0172] G D1 (n)=Sa[(θ s (n)+B s ) / B w ]·Sa[(φ s (n)-B s ) / B w ];

[0173] Combine the pointers to A, B, C, and D corresponding to each value within the lookup table range, G s (n) represents the lookup table range and the beam pointing s, G d (n) represents the difference beam pointing d and G within the lookup table range. q (n) represents the difference beam pointing q within the lookup table range;

[0174]

[0175] Calculate the sum-difference ratio within the lookup table range using the combination formula (15), R. t (n) represents the ratio of the difference beam pointing d to the sum beam pointing s within the lookup table range, R p (n) represents the ratio of the difference beam pointing q to the sum beam pointing s within the lookup table range.

[0176] R t (n)=G d (n) / G s (n); R p (n)=G q (n) / G s (n);

[0177] Find Y respectively s,m (x 1,m ,y1,m ), Y d,m (x 1,m ,y 1,m ), Y q,m (x 1,m ,y 1,m The phase angle of ) is A s,m A d,m A q,m , where x 1,m =d m y 1,m =y m According to Determine the signs of the azimuth and elevation angles of the m-th target; where S θ,m S represents the sign of the azimuth angle of the m-th target relative to RIS. φ,m A represents the sign of the pitch angle of the m-th target relative to RIS. s,m A d,m A q,m They represent Y respectively s,m Y d,m Y q,m The corresponding phase angle;

[0178] Calculate the sum-difference ratio of the signal at the m-th target.

[0179] R θ,m =|Y d,m (x 1,m ,y 1,m ) / Y s,m (x 1,m ,y 1,m )|,

[0180] R φ,m =|Y q,m (x 1,m ,y 1,m ) / Y s,m (x 1,m ,y 1,m (16)

[0181] R θ,m and R φ,m R is the ratio of each sum and difference within the lookup table range. t (n), R p (n) is used for comparison.

[0182] p θ,m =min|S θ,m ·R θ,m -R t (n)|;p φ,m =min|S φ,m ·R φ,m -Rp (n)|;

[0183] According to θ m =θ s,m (p θ,m )+θ r,m ;φ m =φ s,m (p φ,m )+φ r,m ; Calculate the azimuth angle θ between RIS and the target. m and pitch angle φ m ,

[0184] According to formula p m (1)=p r (1)+d m cos(φ m cos(θ) m );

[0185] p m (2) = p r (2)+d m cos(φ m sin(θ) m );

[0186] p m (3) = p r (3)+d m sin(φ m );

[0187] Calculate the position p of the m-th target m p m =[p m (1),p m (2),p m (3)]; (17)

[0188] p r Let p be the coordinates of RIS. r (1) represents the coordinates of RIS in the x-dimensional space, p r (2) represents the coordinates of RIS in the y-dimensional space, p r (3) represents the coordinates of RIS in the z-dimensional dimension.

[0189] It should be noted that this invention uses both a phase shift matrix and a lookup table method for angle estimation, which can improve the accuracy of angle estimation and thus improve the accuracy of target positioning.

[0190] In this embodiment of the invention, when the OFDM signal transmitted by the base station passes through the RIS, the RIS uses the OFDM signal transmitted by the base station to perform beam scanning. When the OFDM signal power within one symbol time is greater than the signal power within the previous symbol time and the next symbol time, [F] n,k Record it as 1, otherwise record it as 0. The target is to satisfy both of the following conditions.

[0191] (1)[F] n,k The value is 1;

[0192] (2)[F] n,k For the same subcarrier, the values ​​of the first three symbols and the last three symbols of any symbol k are all 0.

[0193] Figure 2 The diagram shows a system model of the RIS-assisted base station positioning method in a complex environment provided in this embodiment of the invention. To verify the RIS-assisted base station positioning method in a complex environment provided by this invention, a simulation experiment was conducted.

[0194] Simulation conditions: The base station transmits an OFDM signal with N = 3000 subcarriers and K = 256 transmitted symbols. The base station location is p. b =[0,0,20], RIS position p r = [50, 50, 50], the m-th target position is p m The number of RIS units is M1 = M2 = 64, the number of Monte Carlo simulation experiments is 1000, and the coordinate origin of the RIS-assisted base station positioning method in this complex environment is selected at the base station location in the Z coordinate direction at a position of -20m.

[0195] Figure 3 A two-dimensional FFT result image of a single target echo signal provided in an embodiment of the present invention, as shown below. Figure 3 As shown in (a), without using the RIS phase-shift design to distinguish signals, the two-dimensional FFT result of the base station received signal has three peaks. It is impossible to identify which peak corresponds to the RIS reflected signal, which leads to the inability to utilize the peaks to obtain distance and velocity information, thus preventing target localization. Figure 3 As shown in (b), after using the RIS phase shift design to distinguish the signal, the two-dimensional FFT result of the base station received signal has only one peak, which is the peak corresponding to the RIS reflected signal. The distance and velocity corresponding to this peak can be obtained, thereby completing the target localization.

[0196] Figure 4This paper presents the trend of root mean square error (RMSE) of single-target localization as a function of the standard deviation of base station measurement error in an embodiment of the present invention. Since multipath propagation cannot achieve multi-target localization, only single-target localization results are compared. The RMSE of RIS-assisted localization in complex environments is compared with that of multipath-assisted localization. At least four multipath paths are required in three-dimensional space to complete localization. Clearly, as the standard deviation of base station measurement error increases, the RMSE of both multipath-assisted localization and RIS-assisted localization also increases. Figure 4 As can be seen, with the same standard deviation of measurement error, the root mean square error (RMSE) of RIS-assisted localization is smaller than that of four-path assisted localization. Furthermore, it can be observed that as the standard deviation of measurement error increases, the RMSE curve of four-path assisted localization increases faster than that of RIS-assisted localization. Simulation results further confirm the superiority of RIS-assisted localization over multipath assisted localization in complex environments.

[0197] Figure 5 This invention illustrates the variation of the root mean square error (RMSE) of a target location with the distance between the RIS (Range Target Error) and the target during multi-target localization in a complex environment, as provided in an embodiment of the invention. Ten targets were uniformly generated, each 100m apart. Figure 5 As can be seen, the root mean square error increases with the increase of the distance between the RIS and the target. This is because the signal strength attenuates with increasing distance, resulting in a decrease in the signal-to-noise ratio and thus a larger positioning error. Simulation results demonstrate that this invention can be used in multi-target positioning scenarios.

[0198] The present invention provides a RIS-assisted base station positioning method in complex environments, comprising: designing a RIS direction codebook based on the OFDM signal transmitted by the base station; calculating the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, communication information during target propagation, RIS information, and base station information, and calculating the total signal of the target received by the base station based on the initial echo signal of the target received by the base station; performing phase shift removal processing on the total signal of the target received by the base station to obtain the phase shift removed total signal of the target received by the base station, and calculating the echo signal of the target reflected by the RIS based on the phase shift removed total signal of the target received by the base station, and calculating the distance between the RIS and the target based on the echo signal of the target reflected by the RIS; determining the beam pointing of the RIS towards the target through RIS beam scanning, calculating the elevation angle and azimuth angle between the RIS and the target based on the beam pointing and the OFDM signal transmitted by the base station, and calculating the position information of the target based on the elevation angle, azimuth angle, and the distance between the RIS and the target. The RIS-assisted base station positioning method in complex environments provided by this invention utilizes OFDM signals and a rationally designed direction codebook. Simultaneously, by using the total target signal received by the base station, the echo signal reflected from the RIS is separated, and the separated signal, along with RIS beam scanning, is used for final target positioning. Compared to base station positioning in multipath-assisted obstructed environments, this invention requires only one RIS to achieve higher positioning accuracy than multipath-assisted methods. The RIS can more flexibly adjust the amplitude and phase of the signal, improving the reliability of target positioning.

[0199] Figure 6 This is a schematic diagram of a RIS-assisted base station positioning device in a complex environment provided in an embodiment of the present invention, as shown below. Figure 6 As shown, the device includes: a design unit 601 and a calculation unit 602;

[0200] The design unit 601 is used to design a RIS direction codebook based on the OFDM signal transmitted by the base station.

[0201] The calculation unit 602 is used to calculate the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, the communication information during the target propagation process, the RIS information, and the base station information, and to calculate the total signal of the target received by the base station based on the initial echo signal of the target received by the base station.

[0202] The calculation unit 602 is further configured to perform phase shift removal processing on the total signal of the target received by the base station to obtain the total signal of the target received by the base station after phase shift removal processing, and calculate the echo signal of the target reflected by RIS based on the total signal of the target received by the base station after phase shift removal processing, and calculate the distance between RIS and the target through the echo signal of the target reflected by RIS.

[0203] The computing unit 602 is further configured to determine the beam direction of the RIS to the target through RIS beam scanning, calculate the elevation angle and azimuth angle between the RIS and the target based on the beam direction and the OFDM signal transmitted by the base station, and calculate the target's position information based on the elevation angle, the azimuth angle and the distance between the RIS and the target.

[0204] Figure 7 A schematic diagram of the structure of a RIS-assisted base station positioning system in a complex environment provided in an embodiment of the present invention includes: a processor 710, a storage medium 720, and a bus 730. The storage medium 720 stores machine-readable instructions executable by the processor 710. When the electronic device is running, the processor 710 communicates with the storage medium 720 via the bus 730, and the processor 710 executes the machine-readable instructions to perform the steps of the above-described method embodiment. Specific implementation methods and technical effects are similar and will not be repeated here.

[0205] The method provided in this invention can be applied to electronic devices. Specifically, the electronic device can be a desktop computer, a portable computer, a smart mobile terminal, a server, etc. No limitation is made herein; any electronic device that can implement this invention falls within the protection scope of this invention.

[0206] The memory may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0207] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0208] It should be noted that, for the embodiments of the device / electronic device / storage medium / computer program product, since they are basically similar to the method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments.

[0209] It should be noted that the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. The implementations described in the following exemplary embodiments do not represent all implementations consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure.

[0210] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0211] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A RIS-assisted base station positioning method in complex environments, characterized in that, include: Based on the OFDM signal transmitted by the base station, the RIS direction codebook is designed and obtained; Based on the RIS direction codebook, the OFDM signal, the communication information during the target propagation process, the RIS information, and the base station information, the initial echo signal of the target received by the base station is calculated, and the total signal of the target received by the base station is calculated based on the initial echo signal of the target received by the base station. The total signal of the target received by the base station is subjected to phase shift removal processing to obtain the total signal of the target received by the base station after phase shift removal processing. The echo signal of the target reflected by the RIS is calculated based on the total signal of the target received by the base station after phase shift removal processing. The distance between the RIS and the target is calculated based on the echo signal of the target reflected by the RIS. The beam direction of the RIS to the target is determined by RIS beam scanning. The elevation angle and azimuth angle between the RIS and the target are calculated based on the beam direction and the OFDM signal transmitted by the base station. The position information of the target is calculated based on the elevation angle, the azimuth angle and the distance between the RIS and the target. The step of designing the RIS direction codebook based on the OFDM signal transmitted by the base station includes: Based on the number of subcarriers and symbols of the OFDM signal transmitted by the base station, a RIS direction codebook is designed, where the first... The subcarrier at the ... RIS initial direction codebook during one symbol period Represented as: ；（1） , , This represents the subcarrier of the current OFDM signal. This indicates the number of subcarriers in the OFDM signal transmitted by the base station. The symbol representing the current OFDM signal. Indicates the number of symbols in the OFDM signal transmitted by the base station. Represents imaginary factors; Will Obtained by column vectorization ,when , , , This is the directional codebook for the modified RIS; The initial echo signal of the target received by the base station includes: the initial echo signal of the target reflected by multipath, the initial echo signal of the target reflected by RIS, and the initial echo signal of the target reflected by cross-path. The step of calculating the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, communication information during target propagation, RIS information, and base station information, and calculating the total signal of the target received by the base station based on the initial echo signal of the target received by the base station, includes: Based on the multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, and the wavelength of the OFDM signal, the initial echo signal of the multipath-reflected target is calculated. The base station receives the first echo signal from the multipath reflection. The initial echo signal of each target is : ；（2） in, Indicates the first One goal, For the first The multipath signal gain corresponding to each target For the first The time delay of the multipath signal corresponding to each target Adding the first to the OFDM signal representing multipath reflection The time delay of the multipath signal corresponding to each target , Indicates capturing the first Radial velocity information of the target relative to the multipath. ; For the first The radial velocity of the target relative to the multipath. This is the sum of the duration of a single symbol and the duration of the cyclic prefix in the OFDM signal. The wavelength of the OFDM signal; Based on the RIS direction codebook, RIS reflection path signal gain, target RIS signal time delay, turning vector corresponding to the angle between the base station and the RIS, turning vector corresponding to the angle between the target and the RIS, target radial velocity relative to the RIS, and OFDM echo signal of the RIS reflection path, the initial echo signal of the target reflected by the RIS is calculated. The base station receives the first echo signal from the RIS reflection path. The initial echo signal of each target is : ；（3） in, For RIS reflection path signal gain, For the first The subcarrier When the symbol is the first RIS phase shift of each target For the first Each symbol represents the RIS direction codebook. This is the turning vector corresponding to the angle between the base station and the RIS. For the first The turning vectors corresponding to the angles of each target and the RIS, where T represents the matrix transpose operation. For the first The radial velocity of the target relative to RIS, Indicates capturing the first Radial velocity information of the target relative to RIS This is the OFDM echo signal of the RIS reflection path. ; For the first The RIS signal time delay of each target This indicates the subcarrier spacing of the OFDM signal; The representative length is A vector whose element value is 1; The initial echo signal of the target reflected from the cross-path is calculated based on the target's cross-path signal time delay, the target's radial velocity relative to the RIS, the target's radial velocity relative to the multipath, the turning vector corresponding to the angle between the base station and the RIS, and the OFDM echo signal of the RIS reflection path. The base station receives the first echo signal from the cross-path reflection. The initial echo signal of each target is : ；（4） in, For cross-path signal gain, For the first Time delay of cross-path signals for each target Adding the first to the OFDM signal representing cross-path reflection Time delay of the cross-path signal corresponding to each target , For the first The subcarrier When the symbol is the first RIS phase shift of each target For the first Each symbol represents the RIS direction codebook. This is the turning vector corresponding to the angle between the base station and the RIS. For the first The steering vector corresponding to the angle of each target and the RIS; The total signal received by the base station from the target is : ；（5） in, For the first The subcarrier When the symbol is the first Noise signal of each target.

2. The RIS-assisted base station positioning method in complex environments according to claim 1, characterized in that, The communication information, RIS information, and base station information during the target propagation process include: The multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, the RIS reflection path signal gain, the RIS signal time delay of the target, the turning vector corresponding to the angle between the base station and the RIS, the turning vector corresponding to the angle between the target and the RIS, the radial velocity of the target relative to the RIS, the cross-path signal time delay of the target, the OFDM echo signal of the RIS reflection path, and the noise signal corresponding to the target.

3. The RIS-assisted base station positioning method in complex environments according to claim 1, characterized in that, The process of performing phase-shift removal processing on the total target signal received by the base station to obtain the phase-shift removed total target signal received by the base station, calculating the target echo signal reflected by the RIS based on the phase-shift removed total target signal received by the base station, and calculating the distance between the RIS and the target using the target echo signal reflected by the RIS includes: Based on formula (1) and the target RIS phase shift ,get: , ,but ， ； The first received by the base station The total signal of the n targets is subjected to phase shift removal processing to obtain the nth target received by the base station after phase shift removal processing. The total signal of the target : (6); After phase shift removal processing, the first The echo signal of the target reflected by the RIS corresponding to each target is, ;（7） ;（8） After phase shift removal processing, the first The echo signals of the multipath reflection targets corresponding to each target are: ； （9） ；（10） After phase shift removal processing, the first The echo signals reflected from the intersecting paths corresponding to each target are: ；（11） ；（12） The matrix is ​​represented as: ；（13） Transform the matrix to obtain the transformed matrix. The RIS echo signal of the target corresponding to each target , ；（14） Will Perform two-dimensional FFT processing, and then extract the peak values ​​of the signal after the two-dimensional FFT processing. coordinates and The coordinates are extracted as follows: and , That is, the first The sum of the distances between the target and the RIS and between the RIS and the base station. For the first The radial velocity of the first target relative to the RIS, and the RIS relative to the first... The distance between the targets is , ,in, This represents the distance between the base station and the RIS.

4. The RIS-assisted base station positioning method in complex environments according to claim 3, characterized in that, The step of determining the beam direction of the RIS towards the target through RIS beam scanning, calculating the elevation and azimuth angles between the RIS and the target based on the beam direction and the OFDM signal transmitted by the base station, and calculating the target's position information based on the elevation angle, the azimuth angle, and the distance between the RIS and the target includes: When the base station transmits four OFDM signals, and the RIS receives each of the four OFDM signals, it divides the four received signals in each RIS region into four groups based on the beam scanning results. Four beams pointing, The beam directions are as follows: ； ； ； ； in, For RIS relative to the first The azimuth of the target. For RIS relative to the first The pitch angle of the target, For RIS relative to the first The beam of each target is pointed to the corresponding initial azimuth angle. For RIS relative to the first The beam pointing to each target corresponds to the initial elevation angle. For beam offset relative to the beam direction, The beamwidth of the RIS; Based on the four beam directions and Calculate the amplitude of the echo signal. When echo delay , For the speed of light, calculate The echo signals of the four OFDM signals are as follows: ； ； ； ； The echo signals of the four OFDM signals are combined into three signals, the first... The sum of signals corresponding to each target Represented as , No. The difference signal corresponding to each target Represented as , No. The difference signal corresponding to each target Represented as ; ； ； ； Set the lookup table ranges for azimuth and elevation angles according to the beamwidth respectively. and Calculate the value corresponding to each value within the lookup table range. The direction, ； ； ； ； For each value within the lookup range Combine the pointers, Within the lookup table range and beam pointing , For the lookup table range, the difference beam pointing , For the lookup table range, the difference beam pointing ; ； ；（15） ； Calculate the sum-difference ratio within the lookup table range using the combination formula (15). For the lookup table range, the difference beam pointing and beam pointing The ratio, For the lookup table range, the difference beam pointing and beam pointing The ratio, ； ； Find them separately , , The phase angle is , , ,in , According to ; , judge the first The sign of the target's azimuth and elevation angles; among which... Indicates the first The positive and negative azimuth angle of the target relative to RIS Indicates the first The positive and negative pitch angles of the target relative to RIS They represent , , The corresponding phase angle; Calculate the signal at the 1st The sum and difference at each target location ， ；（16） Will and Compared with each sum and difference within the lookup table range , Comparison, ； ； according to ; ; Calculate the azimuth angle between RIS and the target. and pitch angle , According to the formula ; ； ； Calculate the first The location of the target , (17) For the coordinates of RIS, Let be the coordinates of RIS in the x-dimensional dimension. Let be the coordinates of RIS in the y-dimensional dimension. Let be the coordinates of RIS in the z-dimensional dimension.

5. A RIS-assisted base station positioning device in a complex environment, characterized in that, include: Design unit and computing unit; The design unit is used to design a RIS direction codebook based on the OFDM signal transmitted by the base station. The calculation unit is used to calculate the initial echo signal of the target received by the base station based on the RIS direction codebook, the OFDM signal, the communication information during the target propagation process, the RIS information, and the base station information, and to calculate the total signal of the target received by the base station based on the initial echo signal of the target received by the base station. The calculation unit is further configured to perform phase shift removal processing on the total signal of the target received by the base station to obtain the total signal of the target received by the base station after phase shift removal processing, and calculate the echo signal of the target reflected by RIS based on the total signal of the target received by the base station after phase shift removal processing, and calculate the distance between RIS and the target through the echo signal of the target reflected by RIS. The computing unit is also used to determine the beam direction of the RIS to the target through RIS beam scanning, calculate the elevation angle and azimuth angle between the RIS and the target based on the beam direction and the OFDM signal transmitted by the base station, and calculate the position information of the target based on the elevation angle, the azimuth angle and the distance between the RIS and the target. The initial echo signal of the target received by the base station includes: the initial echo signal of the target reflected by multipath, the initial echo signal of the target reflected by RIS, and the initial echo signal of the target reflected by cross-path. The design unit is specifically used to design a RIS direction codebook based on the number of subcarriers and symbols of the OFDM signal transmitted by the base station, wherein the first... The subcarrier at the ... RIS initial direction codebook during one symbol period Represented as: ；（1） , , This represents the subcarrier of the current OFDM signal. This indicates the number of subcarriers in the OFDM signal transmitted by the base station. The symbol representing the current OFDM signal. Indicates the number of symbols in the OFDM signal transmitted by the base station. Represents imaginary factors; Will Obtained by column vectorization ,when , , , This is the directional codebook for the modified RIS; The calculation unit is specifically used to calculate the initial echo signal of the multipath-reflected target based on the multipath signal gain corresponding to the target, the multipath signal time delay corresponding to the target, the multipath radial velocity corresponding to the target, and the wavelength of the OFDM signal. The base station receives the first echo signal from the multipath reflection. The initial echo signal of each target is : ；（2） in, Indicates the first One goal, For the first The multipath signal gain corresponding to each target For the first The time delay of the multipath signal corresponding to each target Adding the first to the OFDM signal representing multipath reflection The time delay of the multipath signal corresponding to each target , Indicates capturing the first Radial velocity information of the target relative to the multipath. ; For the first The radial velocity of the target relative to the multipath. This is the sum of the duration of a single symbol and the duration of the cyclic prefix in the OFDM signal. The wavelength of the OFDM signal; Based on the RIS direction codebook, RIS reflection path signal gain, target RIS signal time delay, turning vector corresponding to the angle between the base station and the RIS, turning vector corresponding to the angle between the target and the RIS, target radial velocity relative to the RIS, and OFDM echo signal of the RIS reflection path, the initial echo signal of the target reflected by the RIS is calculated. The base station receives the first echo signal from the RIS reflection path. The initial echo signal of each target is : ；（3） in, For RIS reflection path signal gain, For the first The subcarrier When the symbol is the first RIS phase shift of each target For the first Each symbol represents the RIS direction codebook. This is the turning vector corresponding to the angle between the base station and the RIS. For the first The turning vectors corresponding to the angles of each target and the RIS, where T represents the matrix transpose operation. For the first The radial velocity of the target relative to RIS, Indicates capturing the first Radial velocity information of the target relative to RIS This is the OFDM echo signal of the RIS reflection path. ; For the first The RIS signal time delay of each target This indicates the subcarrier spacing of the OFDM signal; The representative length is A vector whose element value is 1; The initial echo signal of the target reflected from the cross-path is calculated based on the target's cross-path signal time delay, the target's radial velocity relative to the RIS, the target's radial velocity relative to the multipath, the turning vector corresponding to the angle between the base station and the RIS, and the OFDM echo signal of the RIS reflection path. The base station receives the first echo signal from the cross-path reflection. The initial echo signal of each target is : ；（4） in, For cross-path signal gain, For the first Time delay of cross-path signals for each target Adding the first to the OFDM signal representing cross-path reflection Time delay of the cross-path signal corresponding to each target , For the first The subcarrier When the symbol is the first RIS phase shift of each target For the first Each symbol represents the RIS direction codebook. This is the turning vector corresponding to the angle between the base station and the RIS. For the first The steering vector corresponding to the angle of each target and the RIS; The total signal received by the base station from the target is : ；（5） in, For the first The subcarrier When the symbol is the first Noise signal of each target.

6. A RIS-assisted base station positioning system in a complex environment, characterized in that, include: The processor, storage medium, and bus, wherein the storage medium stores machine-readable instructions executable by the processor, and when the processor is running, the processor communicates with the storage medium via the bus, and the processor executes the machine-readable instructions to perform the steps of the method as described in any one of claims 1-4.

7. A storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, performs the steps of the method as described in any one of claims 1-4.

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