A Metasurface Wireless Sensing Enhancement Method Based on Tree Structure

Abstract

This application belongs to the field of wireless sensing, metasurfaces, and integrated sensing technology. It discloses a metasurface-based wireless sensing enhancement method based on a tree structure, comprising: Step 1, configuring a single set of wireless transceiver devices, a master metasurface, and several slave metasurfaces; Step 2, constructing a composite channel with aggregated channel state information; Step 3, initial phase configuration and time-series coding generation; Step 4, establishing pose error models for the master metasurface and each slave metasurface based on the obtained initial discrete phase state and time-varying phase sequence; Step 5, calculating the pose compensation phase offset of the metaatoms according to the pose error models, optimizing the pose compensation parameters and discrete phase configuration of the master and slave metasurfaces, and generating a calibrated time-varying control phase. This application can significantly improve the spatial diversity capability and angular resolution of wireless sensing systems, and is suitable for wireless sensing scenarios such as human posture monitoring, fine environmental imaging, and passive human-computer interaction.

Description

Technical Field

[0001] This application belongs to the field of wireless sensing, metasurface and integrated sensing and communication (ISAC) technology, specifically relating to a metasurface wireless sensing enhancement method based on a tree structure. Background Technology

[0002] With the increasing prevalence of metasurfaces in wireless sensing scenarios, utilizing metasurfaces to reflect commercial wireless signals to expand the spatial perspective of sensing and thus achieve fine-grained sensing such as human posture and environmental imaging has become a current research hotspot. Although traditional single-piece independent metasurface beamforming schemes have a simple architecture, they are limited by physical aperture, resulting in limited spatial angular resolution and spatial sensing diversity capabilities, making it difficult to achieve large-scale, multi-view synchronous sensing. If multiple independent metasurfaces are densely deployed in space, each one requires a separate access point (AP) feed or RF transmission feed, which leads to high system deployment costs, complex hardware wiring, and increased space occupation.

[0003] To reduce deployment costs, existing technologies have proposed a master-slave hierarchical metasurface architecture. The core idea is to use a master metasurface (Master RIS) to wirelessly drive multiple distributed slave metasurfaces (Slave RIS), thus eliminating the need for multiple independent transmitter feeds. However, this system still faces significant bottlenecks in practical engineering implementation and high-precision sensing applications: First, the incident wavefront received by the slave metasurfaces is a complex aliased wavefront formed by numerous micro-element reflections from the master metasurface. The two-stage cascaded channels between the metasurfaces cannot be directly separated and observed at the receiver. If a traditional unit-by-unit exhaustive calibration scheme is used, the latency and computational load will increase exponentially, failing to meet the requirements of real-time sensing. Second, in practical engineering deployments, there will inevitably be uncontrollable spatial translation and attitude rotation deviations between the master and slave metasurfaces. These minute six-degree-of-freedom (6-DoF) geometric pose errors will be amplified by cascading on the two-stage reflection links, causing severe inaccuracies in the preset phase compensation scheme, leading to beam pointing distortion, and resulting in problems at the receiver. The received signal strength (RSS) is significantly attenuated, directly damaging the signal-to-noise ratio of the sensed signal. Third, multiple control reflection path signals generated from the metasurface are spatially superimposed and severely aliased at the receiver. Existing technologies struggle to directly and losslessly separate the independent sensed signal corresponding to each virtual viewpoint from the aliased Channel State Information (CSI), leading to difficulties in multi-view feature extraction and extremely poor robustness in 3D human pose estimation imaging in non-line-of-sight (NLoS) scenarios. Summary of the Invention

[0004] To address the aforementioned technical challenges, this application provides a metasurface-based wireless sensing enhancement method based on a tree structure. This method utilizes a Wi-Fi passive sensing system as its carrier, leveraging a master-slave hierarchical metasurface architecture to reduce the deployment requirements of multiple independent feed sources. It can compensate for beam distortion caused by pose shifts between master and slave metasurfaces and achieve decoupling of signals from different reflection paths through a timing coding mechanism. Simultaneously, it supports large-scale deployment of multiple slave metasurfaces, significantly improving the spatial diversity and angular resolution of the wireless sensing system. This method is suitable for wireless sensing scenarios such as human posture monitoring, fine environmental imaging, and passive human-computer interaction.

[0005] To achieve the above objectives, this application employs the following technical solution:

[0006] This application discloses a metasurface wireless sensing enhancement method based on a tree structure. The metasurface wireless sensing enhancement method specifically includes the following steps:

[0007] Step 1: Build a master-slave hierarchical metasurface architecture: Configure a single set of wireless transceivers, a master metasurface, and... A tree-like metasurface sensing architecture is constructed by connecting multiple slave metasurfaces to a master metasurface. The master metasurface is divided into a beamguide subarray and a virtual viewpoint subarray. It is an integer greater than or equal to 2;

[0008] Step 2: Construct the aggregated channel state information composite channel: Based on the propagation components of the transmitted signal after reflection from the main metasurface, the beamguide subarray, the virtual viewpoint subarray, and each secondary metasurface, establish the virtual viewpoint reflection link of the main metasurface and the cascaded reflection link from the main metasurface to the secondary metasurfaces, and aggregate the propagation components to obtain the aggregated channel state information composite channel corresponding to the tree-like metasurface sensing architecture.

[0009] Step 3: Initial Phase Configuration and Timing Coding Generation: Based on the target reflection direction and the propagation direction between the primary and secondary metasurfaces, the azimuth and elevation angles of the corresponding propagation paths are substituted into the aggregated channel state information composite channel constructed in Step 2. The continuous phase offset of each metasurface unit under ideal deployment conditions is calculated, and the continuous phase offset is quantized into the initial discrete phase state to obtain the initial phase configuration. At the same time, independent time-varying phase sequences are assigned to different virtual propagation paths, so that different paths have distinguishable timing identifiers while performing directional reflection.

[0010] Step 4: Establishing the pose error model: Based on the initial discrete phase state and time-varying phase sequence obtained in Step 3, establish the pose error model of the master metasurface and each slave metasurface. The pose error model includes translation offset and rotation offset.

[0011] Step 5, Pose Compensation Parameter Optimization and Time-Varying Phase Calibration: Calculate the pose compensation phase offset of the superatom based on the pose error model, and optimize the pose compensation parameters and discrete phase configuration of the master and slave metasurfaces alternately using a block coordinate descent algorithm with the goal of maximizing the received signal strength or equivalent channel gain. Correct the time-varying phase sequence while maintaining the time discriminability of different virtual reflection paths, and generate the calibrated time-varying control phase to compensate for deployment errors and calibrate beam pointing.

[0012] A further improvement in this application is that step 1 specifically includes the following steps:

[0013] Step 1.1: Configure a single wireless transceiver unit, a main metasurface, and... A secondary metasurface, which does not require an independent wired feed, has its incident signal provided by directional reflection from the beamguide subarray of the primary metasurface;

[0014] Step 1.2: Functionally divide the main metasurface: Divide the main metasurface into a beamguide subarray and a virtual viewpoint subarray. The beamguide subarray is used to directionally reflect the incident wireless signal to the secondary metasurface, and the virtual viewpoint subarray is used to directionally reflect the incident wireless signal to the target area to form a virtual observation viewpoint.

[0015] Step 1.3: Establish the mapping relationship between the metasurface and the virtual observation viewpoint: Each metasurface applies a controllable phase shift to the incident signal from the main metasurface and reflects it to the target area. Each metasurface forms an independent virtual observation viewpoint, thereby achieving multi-directional spatial coverage under the condition of a single set of wireless transceivers.

[0016] A further improvement in this application is that step 2 specifically includes the following steps:

[0017] Step 2.1, at the receiving end of the wireless transceiver device Receives CSI signals, the CSI signals including transmitted signals reflected by the main metasurface beamguide subarray to the first The reflection component formed by the metasurface after reflection. The transmitted signal is directly reflected to the target area by the virtual viewpoint subarray of the primary metasurface, forming the viewpoint reflection component of the primary metasurface. And the direct clutter components corresponding to the direct path and environmental multipath. ;

[0018] Step 2.2, the metasurface reflection component The viewpoint reflection component of the principal metasurface and direct clutter components Modeled as a composite channel with aggregated channel state information for:

[0019]

[0020] in, Indicates the time-varying phase shift, the first The reflection component corresponding to the metasurface Represented as:

[0021]

[0022] Principal metasurface viewpoint reflection component Represented as:

[0023]

[0024] in, This represents the channel from the transmitter to the main metasurface beamguide subarray. Indicates the main metasurface beamguide array to the first A cascaded channel from the metasurface, Indicates the first From metasurface to receiver The channel, This represents the channel from the transmitter to the virtual viewpoint subarray of the main metasurface. This indicates the virtual viewpoint subarray of the main metasurface to the receiving end. The channel, For the first A diagonal phase shift matrix from the metasurface, Main metasurface beamguide subarray This represents the virtual viewpoint subarray of the main metasurface. This indicates the transpose operation.

[0025] A further improvement in this application is that step 3 specifically includes the following steps:

[0026] Step 3.1, Calculation of continuous phase offset: For the first... A metasurface, among which... ,when When is the master metasurface, when It is from the metasurface, in the first In a local coordinate system of a metasurface, the metasurface is placed Face, let the first Superatomic positions for:

[0027]

[0028] in, Indicates the first A superatom in Coordinates in direction Indicates the first A superatom in Coordinates in the direction;

[0029] Step 3.2, let the first... The target emission direction of the metasurface is determined by the azimuth angle. and pitch angle Confirmed, number The unit reflection vector of a metasurface is Then the first The first metasurface Superatomic positions Phase offset on for:

[0030] ;

[0031] in, For the first The position of a superatom, For the first The position of a superatom The geometric center, The equivalent incident source location includes the equivalent phase center of the wireless transceiver, the primary metasurface, or the previous hop metasurface. For subcarrier wavelength, Denotes the Euclidean norm;

[0032] Step 3.3, Binary Phase Quantization: For continuous phase offsets By performing a uniform binarization approximation, the discrete phase state is obtained. for:

[0033]

[0034] Therefore, we obtain the first... The initial binary phase configuration of the metasurface;

[0035] Step 3.4, Metasurface Timing Encoding: For the first... Each metasurface is defined with a length of... Temporal coding vector for:

[0036] ,

[0037] in, Indicates the first Applying within the first time slot Temporal encoding vectors of a metasurface;

[0038] Step 3.5, Time-varying phase superposition: For the first... The metasurface, in the first Within each time slot, the corresponding timing coding vector Superimposed on the initial binary phase of all superatoms, we obtain the first... The time-varying total phase of a superatom for:

[0039]

[0040] in, The time slot number, The duration of a single time slot, Indicates the first The end time corresponding to each time slot;

[0041] Step 3.6, Time-varying channel model construction: Apply the time-series coding vector defined in step 3.4 to both the primary and secondary metasurfaces. Aggregate channel state information to composite channel Modulation is a time-varying form that changes dynamically with time. for:

[0042]

[0043] in, and These represent the time-coded phases of the main metasurface beamguide subarray and the virtual viewpoint subarray, respectively, with a duration of... Within one time-series coding cycle, by collecting The measurements from each time slot are used to obtain the time-coded CSI vector. .

[0044] A further improvement in this application is that, in step 4, the pose error model of the metasurface is defined as follows:

[0045] For the master metasurface and each slave metasurface, establish pose error models respectively, and let the metasurfaces be numbered as follows: ,in , Indicates the primary metasurface. Indicates from the metasurface, for the first A metasurface is defined to represent a 6-DOF pose error. for:

[0046]

[0047] in, This is the translation offset. Indicates the first A metasurface surrounds , , Euler angles for rotational offset of the three coordinate axes.

[0048] A further improvement in this application is in step 5.1, based on the pose error model. , No. The first metasurface The actual position of each superatom Corrected to position vector for:

[0049] ;

[0050] If the first The unit vector of the reference reflection direction of each metasurface is Then, the corrected reflection direction vector after considering rotation error for:

[0051] ;

[0052] Step 5.2, Pose Compensation Phase Calculation: Calculate the corrected position vector obtained in Step 5.1. With the corrected reflection direction vector Substitute phase offset Calculate the first The first metasurface Pose compensation phase offset of each superatom for:

[0053] ;

[0054] Step 5.3: For the discrete phase metasurface, the pose compensation phase offset is... Quantization is performed according to the phase resolution of the metasurface to obtain the corrected multi-level discrete phase states. for:

[0055]

[0056] in, This represents the phase quantization function. For a binary phase metasurface, the output of the phase quantization function is 0 or... For a multi-bit phase metasurface, the output of the phase quantization function is the corresponding multi-level discrete phase state.

[0057] Step 5.4: Construct the pose compensation phase shift matrix: Based on the corrected multi-level discrete phase state obtained in Step 5.3 Construct the first Pose compensation phase shift matrix of a metasurface for:

[0058]

[0059] in, Indicates the first The number of superatoms contained in each metasurface, and the pose compensation phase shift matrix of the beamguide subarray and the virtual viewpoint subarray divided by the main metasurface, are used to construct the beamguide subarray respectively. Pose compensation phase shift matrix of virtual viewpoint subarray ;

[0060] Step 5.5: Combine the timing coding vector from Step 3. Then in the first Within the first time slot, the first The first metasurface The total phase of each superatom for:

[0061]

[0062] in, Indicates the first Applying within the first time slot The temporal encoding vector of each metasurface, based on the total phase Get the first Time-varying pose compensation phase shift matrix for each time slot for:

[0063]

[0064] Step 5.6: Construct the composite channel of aggregated channel state information after pose compensation: The time-varying pose compensation phase shift matrix obtained in Step 5.5... Substituting the aggregated channel state information composite channel constructed in step 2, we obtain the equivalent CSI after considering pose error compensation. For the first... The metasurface reflection component after being relayed by the main metasurface beamguide subarray from the metasurface Represented as:

[0065]

[0066] Corrected reflection components of the virtual viewpoint subarray of the master metasurface for:

[0067]

[0068] in, , , It is a diagonal phase shift matrix that includes the pose compensation phase;

[0069] Step 5.7: In a two-hop scenario containing only one master metasurface and one target slave metasurface, jointly optimize the pose error parameters of the master metasurface with the goal of maximizing the received signal strength. and from metasurface pose error parameters The optimization objective is expressed as:

[0070]

[0071] in, Represent the two-hop equivalent channel after pose error compensation for the master metasurface and the first slave metasurface; jointly optimize the pose error parameters of the master metasurface. and from metasurface pose error parameters A two-stage optimization strategy is adopted:

[0072] Phase 1, Master Hypersurface Optimization: Estimating the pose error parameters of the master hypersurface. Configure the main metasurface towards Directional beamforming, calculating and quantizing the initial phase matrix, by maximizing End RSS solver for optimal pose compensation parameters of the master metasurface for:

[0073]

[0074] in, The block diagonal phase shift matrix of the master metasurface;

[0075] The second stage involves metasurface optimization, fixing the optimal pose compensation parameters of the master metasurface. Activate the target from the metasurface, configure the main metasurface beamguide subarray towards the direction of the target from the metasurface, and construct the link signal. ; Calculate and quantize the initial phase matrix from the metasurface based on spatial coordinates. Substitute into step 5.6 The metasurface reflection component after being relayed by the main metasurface beamguide subarray from the metasurface The optimal pose compensation parameters from the metasurface are solved by maximizing the receiver RSS. for:

[0076] ;

[0077] Step 5.8, Phased Optimization Solution: A block coordinate descent strategy is adopted to alternately optimize the pose error model. Translation and rotation components, including a fixed rotation matrix. Optimize translation vector Fixed translation vector Update the rotation matrix Iterate until the received RSS converges, completing the collaborative configuration of a single master-slave metasurface pair;

[0078] Step 5.9, Multi-slave metasurface extension configuration: In the multi-slave metasurface scenario, the two-stage optimization strategy described in Step 5.7 is extended to multiple slave metasurfaces to obtain the pose compensation parameter set for the multiple metasurfaces. ;

[0079] Step 5.10: Update the metasurface control state based on the optimization results: based on the set of pose compensation parameters for the multiple metasurfaces obtained in Step 5.9. Update the discrete phase configuration of the master metasurface and each slave metasurface respectively. For the first... A metasurface will have its optimal pose compensation parameters adjusted. Substitute the phase offset from step 4.2 The compensation phase of each superatom is recalculated and quantized to obtain the final control phase. Further combined with timing-coded phase , generate the first The final time-varying control phase within each time slot for:

[0080]

[0081] The final time-varying control phase The superatomic control circuits sent to the corresponding metasurfaces enable the master metasurface and each slave metasurface to maintain the expected beam steering, virtual viewpoint generation, and multipath reflection enhancement effects even in the presence of installation deviations, positional offsets, or attitude errors.

[0082] A further improvement to this application is that step 5.9 includes the following steps:

[0083] Step 5.9.1: Based on the two-stage optimization strategy described in 5.7, extend it to multiple secondary metasurfaces, perform pose compensation optimization on the primary metasurface, and obtain the optimal pose compensation parameters of the primary metasurface. ;

[0084] Step 5.9.2: Fix the optimal pose compensation parameters of the master metasurface. Under these conditions, each slave metasurface is activated sequentially, and the optimal pose compensation parameters for each slave metasurface are solved separately. for:

[0085]

[0086] in, After solving all the pose compensation parameters from the metasurface, a set of pose compensation parameters for multiple metasurfaces is obtained. .

[0087] The beneficial effects of this application are:

[0088] This application possesses advantages such as low deployment cost, strong robustness to pose errors, interference-free separation of multi-viewpoint signals, system scalability, high beamforming accuracy, and significant improvement in sensing and imaging resolution, specifically:

[0089] 1) The architecture is streamlined, requiring only a single emitter to drive multiple metasurfaces;

[0090] 2) It can compensate for pose deviations and ensure stable beamforming;

[0091] 3) Multi-view collaborative sampling significantly improves wireless sensing imaging resolution.

[0092] This application overcomes the spatial resolution limitations of single-view wireless sensing without requiring an independent wired feed for each metasurface, significantly improving the system's angular resolution, path diversity, and sensing accuracy. It provides a scalable technical solution for the deployment of large-scale, low-cost, and high-precision wireless sensing systems. Attached Figure Description

[0093] Figure 1 This is a schematic diagram of the overall process of this application.

[0094] Figure 2 This is a schematic diagram of the basic cascaded channel model corresponding to the sensing enhancement method of this application.

[0095] Figure 3 This is a schematic diagram of the surface control effect of the present application.

[0096] Figure 4 This is a schematic diagram of the deployment of pose deviation modeling in this application.

[0097] Figure 5 This is a schematic diagram of the hierarchical collaborative optimization results of this application. Detailed Implementation

[0098] The embodiments of this application will be disclosed below with reference to the drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit this application. That is, in some embodiments of this application, these practical details are not necessary. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0099] This application provides a metasurface wireless sensing enhancement method based on a tree-structured architecture. This method is applicable to scenarios such as home fitness, rehabilitation training, cameraless human-computer interaction, and privacy-preserving human posture perception. In these scenarios, the human body being sensed does not need to wear any sensors; the system constructs multi-view observation capabilities through indoor wireless signals, achieving non-contact sensing of human movements and posture changes. Figure 1 As shown, the overall process includes five main steps: master-slave hierarchical metasurface architecture construction, construction of aggregated channel state information composite channel, initial phase configuration and timing coding generation, pose error model establishment, pose compensation parameter optimization and time-varying phase calibration.

[0100] Specifically, the metasurface wireless sensing enhancement method includes the following steps:

[0101] Step 1: Build a master-slave hierarchical metasurface architecture: Configure a single set of wireless transceivers, a master metasurface, and... A tree-like metasurface sensing architecture is constructed by connecting multiple slave metasurfaces to a master metasurface. The master metasurface is divided into a beamguide subarray and a virtual viewpoint subarray. For integers greater than or equal to 2, the specific steps are as follows:

[0102] Step 1.1: Configure a single wireless transceiver unit, a main metasurface, and... A secondary metasurface, which does not require an independent wired feed, has its incident signal provided by directional reflection from the beamguide subarray of the primary metasurface;

[0103] Step 1.2: Functionally divide the main metasurface: Divide the main metasurface into a beamguide subarray and a virtual viewpoint subarray. The beamguide subarray is used to directionally reflect the incident wireless signal to the secondary metasurface, and the virtual viewpoint subarray is used to directionally reflect the incident wireless signal to the target area to form a virtual observation viewpoint.

[0104] Step 1.3: Establish the mapping relationship between the metasurface and the virtual observation viewpoint: Each metasurface applies a controllable phase shift to the incident signal from the main metasurface and reflects it to the target area. Each metasurface forms an independent virtual observation viewpoint, thereby achieving multi-directional spatial coverage under the condition of a single set of wireless transceivers.

[0105] Step 2: Construct the aggregated channel state information composite channel: Based on the propagation components of the transmitted signal after reflection from the main metasurface, the beamguide subarray, the virtual viewpoint subarray, and each secondary metasurface, establish the virtual viewpoint reflection link of the main metasurface and the cascaded reflection link from the main metasurface to the secondary metasurfaces, and aggregate the propagation components to obtain the aggregated channel state information composite channel corresponding to the tree-like metasurface sensing architecture. Figure 2 This describes the tree-like cascaded propagation path formed by the master metasurface and multiple slave metasurfaces, and the multi-virtual viewpoint signal formation mechanism under this architecture, such as... Figure 2 As shown, step 2 specifically includes the following steps:

[0106] Step 2.1, at the receiving end of the wireless transceiver device Receives CSI signals, the CSI signals including transmitted signals reflected by the main metasurface beamguide subarray to the first The reflection component formed by the metasurface after reflection. The transmitted signal is directly reflected to the target area by the virtual viewpoint subarray of the primary metasurface, forming the viewpoint reflection component of the primary metasurface. And the direct clutter components corresponding to the direct path and environmental multipath. ;

[0107] Step 2.2, the metasurface reflection component The viewpoint reflection component of the principal metasurface and direct clutter components Modeled as a composite channel with aggregated channel state information for:

[0108]

[0109] in, This represents the time-varying phase shift introduced by hardware, the first... The reflection component corresponding to the metasurface for:

[0110]

[0111] Principal metasurface viewpoint reflection component Represented as:

[0112]

[0113] in, This represents the channel from the transmitter to the main metasurface beamguide subarray. Indicates the main metasurface beamguide array to the first A cascaded channel from the metasurface, Indicates the first From metasurface to receiver The channel, This represents the channel from the transmitter to the virtual viewpoint subarray of the main metasurface. This indicates the virtual viewpoint subarray of the main metasurface to the receiving end. The channel, For the first A diagonal phase shift matrix from the metasurface, Main metasurface beamguide subarray This represents the virtual viewpoint subarray of the main metasurface. This indicates the transpose operation.

[0114] Step 3, Initial Phase Configuration and Timing Coding Generation: Based on the target reflection direction and the propagation direction between the primary and secondary metasurfaces, the azimuth and elevation angles of the corresponding propagation paths are substituted into the aggregated channel state information composite channel constructed in Step 2. The continuous phase offset of each metasurface unit under ideal deployment conditions is calculated, and the continuous phase offset is quantized into an initial discrete phase state, i.e., a 1-bit discrete phase state, to obtain the initial phase configuration. Simultaneously, independent time-varying phase sequences are assigned to different virtual propagation paths, enabling different paths to have distinguishable timing identifiers while performing directional reflection. Step 3 specifically includes the following steps:

[0115] Step 3.1, Calculation of continuous phase offset: For the first... A metasurface, among which... ,when When is the master metasurface, when It is from the metasurface, in the first In a local coordinate system of a metasurface, the metasurface is placed Face, let the first Superatomic positions for:

[0116]

[0117] in, Indicates the first A superatom in Coordinates in direction Indicates the first A superatom in Coordinates in the direction;

[0118] Step 3.2, let the first... The target emission direction of the metasurface is determined by the azimuth angle. and pitch angle Confirmed, number The unit reflection vector of a metasurface is Then the first The first metasurface Superatomic positions Phase offset on for:

[0119] ;

[0120] in, For the first The position of a superatom, For the first The position of a superatom The geometric center, The equivalent incident source location includes the equivalent phase center of the wireless transceiver, the primary metasurface, or the previous hop metasurface. For subcarrier wavelength, Denotes the Euclidean norm;

[0121] Step 3.3, Binary Phase Quantization: For continuous phase offsets By performing a uniform binarization approximation, the discrete phase state is obtained. for:

[0122]

[0123] Therefore, we obtain the first... The initial binary phase configuration of the metasurface;

[0124] Step 3.4, Metasurface Timing Coding: To distinguish multiple metasurface reflections and facilitate subsequent channel separation, a unique timing code is assigned to each metasurface. Specifically, for the first metasurface... Each metasurface is defined with a length of... Temporal coding vector for:

[0125] ,

[0126] in, Indicates the first Applying within the first time slot The temporal coding vectors of each metasurface; the temporal coding vectors of different metasurfaces are different from each other or have low cross-correlation, so that the reflection paths of different metasurfaces have distinguishable phase characteristics in the time dimension. The global phase shift is uniformly superimposed on all superatoms on the same metasurface, so it will not change the spatial phase gradient inside the metasurface, thus maintaining the original beamforming direction.

[0127] Step 3.5, Time-varying phase superposition: For the first... The metasurface, in the first Within each time slot, the corresponding timing coding vector Superimposed on the initial binary phase of all superatoms, we obtain the first... The time-varying total phase of a superatom for:

[0128]

[0129] in, The time slot number, The duration of a single time slot, Indicates the first The end time corresponding to each time slot;

[0130] Step 3.6, Time-varying channel model construction: Apply the time-series coding vector defined in step 3.4 to both the primary and secondary metasurfaces. Aggregate channel state information to composite channel Modulation is a time-varying form that changes dynamically with time. for:

[0131]

[0132] in, and These represent the time-coded phases of the main metasurface beamguide subarray and the virtual viewpoint subarray, respectively, with a duration of... Within one time-series coding cycle, by collecting The measurements from each time slot are used to obtain the time-coded CSI vector. .

[0133] Step 4: Establishment of Pose Error Model: Based on the initial discrete phase state and time-varying phase sequence obtained in Step 3, establish pose error models for the master metasurface and each slave metasurface. The pose error model includes translational offset and rotational offset. Specifically, in Step 4, the pose error model of the metasurface is defined as follows:

[0134] For the master metasurface and each slave metasurface, establish pose error models respectively, and let the metasurfaces be numbered as follows: ,in , Indicates the primary metasurface. Indicates from the metasurface, for the first A metasurface is defined to represent a 6-DOF pose error. for:

[0135]

[0136] in, This is the translation offset. Indicates the first A metasurface surrounds , , Euler angles for rotational offset of the three coordinate axes.

[0137] Step 5, Pose Compensation Parameter Optimization and Time-Varying Phase Calibration: Calculate the pose compensation phase offset of the superatom based on the pose error model. With the goal of maximizing received signal strength or equivalent channel gain, alternately optimize the pose compensation parameters and discrete phase configuration of the primary and secondary metasurfaces using a block coordinate descent algorithm. Correct the time-varying phase sequence while maintaining the time-sequence distinguishability of different virtual reflection paths, generating a calibrated time-varying control phase to compensate for deployment errors and calibrate beam pointing. Specifically, this includes the following steps:

[0138] Step 5.1: Based on the pose error model , No. The first metasurface The actual position of each superatom Corrected to position vector for:

[0139]

[0140] If the first The unit vector of the reference reflection direction of each metasurface is Then, the corrected reflection direction vector after considering rotation error for:

[0141] ;

[0142] Step 5.2, Pose Compensation Phase Calculation: Calculate the corrected position vector obtained in Step 5.1. With the corrected reflection direction vector Substitute phase offset Calculate the first The first metasurface Pose compensation phase offset of each superatom for:

[0143] ;

[0144] Step 5.3: For the discrete phase metasurface, the pose compensation phase offset is... Quantization is performed according to the phase resolution of the metasurface to obtain the corrected multi-level discrete phase states. for:

[0145]

[0146] in, This represents the phase quantization function. For a binary phase metasurface, the output of the phase quantization function is 0 or... For a multi-bit phase metasurface, the output of the phase quantization function is the corresponding multi-level discrete phase state.

[0147] Step 5.4: Construct the pose compensation phase shift matrix: Based on the corrected multi-level discrete phase state obtained in Step 5.3 Construct the first Pose compensation phase shift matrix of a metasurface for:

[0148]

[0149] in, Indicates the first The number of superatoms contained in each metasurface, and the pose compensation phase shift matrix of the beamguide subarray and the virtual viewpoint subarray divided by the main metasurface, are used to construct the beamguide subarray respectively. Pose compensation phase shift matrix of virtual viewpoint subarray ;

[0150] Step 5.5: Combine the timing coding vector from Step 3. Then in the first Within the first time slot, the first The first metasurface The total phase of each superatom for:

[0151]

[0152] in, Indicates the first Applying within the first time slot The temporal encoding vector of each metasurface, based on the total phase Get the first Time-varying pose compensation phase shift matrix for each time slot for:

[0153]

[0154] Step 5.6: Construct the composite channel of aggregated channel state information after pose compensation: The time-varying pose compensation phase shift matrix obtained in Step 5.5... Substituting the aggregated channel state information composite channel constructed in step 2, we obtain the equivalent CSI after considering pose error compensation. For the first... The metasurface reflection component after being relayed by the main metasurface beamguide subarray from the metasurface Represented as:

[0155]

[0156] Corrected reflection components of the virtual viewpoint subarray of the master metasurface for:

[0157]

[0158] in, , , It is a diagonal phase shift matrix that includes the pose compensation phase;

[0159] Step 5.7: In a two-hop scenario containing only one master metasurface and one target slave metasurface, jointly optimize the pose error parameters of the master metasurface with the goal of maximizing the received signal strength. and from metasurface pose error parameters The optimization objective is expressed as:

[0160]

[0161] in, This represents the two-hop equivalent channel after compensation for the pose error of the primary metasurface and the first secondary metasurface;

[0162] To reduce the complexity of joint optimization, the pose error parameters of the master metasurface are jointly optimized. and from metasurface pose error parameters A two-stage optimization strategy is adopted:

[0163] The first stage, master metasurface optimization: estimating the pose error parameters of the master metasurface based on the known "Tx→master metasurface→Rx" link. Configure the main metasurface towards Directional beamforming, calculating and quantizing the initial phase matrix, by maximizing End RSS solver for optimal pose compensation parameters of the master metasurface for:

[0164]

[0165] in, The block diagonal phase shift matrix of the master metasurface;

[0166] The second stage involves metasurface optimization, fixing the optimal pose compensation parameters of the master metasurface. Activate the target from the metasurface, configure the main metasurface beamguide subarray towards the direction of the target from the metasurface, and construct the link signal. ; Calculate and quantize the initial phase matrix from the metasurface based on spatial coordinates. Substitute into step 5.6 The metasurface reflection component after being relayed by the main metasurface beamguide subarray from the metasurface The optimal pose compensation parameters from the metasurface are solved by maximizing the receiver RSS. for:

[0167] ;

[0168] Step 5.8, Phased Optimization Solution: Employ a block coordinate descent (BCD) strategy to alternately optimize the pose error model. Translation and rotation components, including a fixed rotation matrix. Optimize translation vector Fixed translation vector Update the rotation matrix Iterate until the received RSS converges, completing the collaborative configuration of a single master-slave metasurface pair;

[0169] Step 5.9, Multi-slave metasurface extension configuration: In the multi-slave metasurface scenario, the two-stage optimization strategy described in Step 5.7 is extended to multiple slave metasurfaces to obtain the pose compensation parameter set for the multiple metasurfaces. First, the two-stage optimization strategy described in section 5.7 is extended to multiple secondary metasurfaces, and pose compensation optimization of the primary metasurface is performed to obtain the optimal pose compensation parameters of the primary metasurface. ;

[0170] Then, fix the optimal pose compensation parameters of the master metasurface. Under these conditions, each secondary metasurface is activated sequentially, and the optimal pose compensation parameters for the nth secondary metasurface are solved respectively. for:

[0171]

[0172] in, After solving all the pose compensation parameters from the metasurface, a set of pose compensation parameters for multiple metasurfaces is obtained. .

[0173] Step 5.10: Update the metasurface control state based on the optimization results: based on the set of pose compensation parameters for the multiple metasurfaces obtained in Step 5.9. Update the discrete phase configuration of the master metasurface and each slave metasurface respectively. For the first... A metasurface will have its optimal pose compensation parameters adjusted. Substitute the phase offset from step 4.2 The compensation phase of each superatom is recalculated and quantized to obtain the final control phase. Further combined with the timing-coded phase in step 3 , generate the first The final time-varying control phase within each time slot for:

[0174]

[0175] The final time-varying control phase The superatomic control circuits sent to the corresponding metasurfaces enable the master metasurface and each slave metasurface to maintain the expected beam steering, virtual viewpoint generation, and multipath reflection enhancement effects even in the presence of installation deviations, positional offsets, or attitude errors.

[0176] Figure 3 (a) in the figure is a comparison between the beamforming results based on phase control and the theoretical prediction results; Figure 3 (b) in the figure shows the effect of CSI phase modulation based on timing coding. Figure 3 (c) in the figure represents time coding without metasurface.

[0177] Figure 4 (a) in the diagram is a schematic of the ideal deployment posture; Figure 4 (b) in the diagram is a schematic diagram of the translational deviation; Figure 4 (c) in the diagram is a schematic diagram of rotational deviation.

[0178] Figure 5 (a) in the figure is the convergence curve during the pose error compensation optimization process; Figure 5 (b) in the figure shows the beamforming result at an azimuth angle of 30° after pose compensation.

[0179] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A metasurface wireless sensing enhancement method based on a tree-structured architecture, characterized in that: The metasurface wireless sensing enhancement method specifically includes the following steps: Step 1: Master-Slave Hierarchical Metasurface Architecture Setup: Configure a single set of wireless transceivers, a master metasurface, and... A tree-like metasurface sensing architecture is constructed by connecting multiple slave metasurfaces to a master metasurface. The master metasurface is divided into a beamguide subarray and a virtual viewpoint subarray. It is an integer greater than or equal to 2; Step 2: Construct the aggregated channel state information composite channel: Based on the propagation components of the transmitted signal after reflection from the main metasurface, the beamguide subarray, the virtual viewpoint subarray, and each secondary metasurface, establish the virtual viewpoint reflection link of the main metasurface and the cascaded reflection link from the main metasurface to the secondary metasurfaces, and aggregate the propagation components to obtain the aggregated channel state information composite channel corresponding to the tree-like metasurface sensing architecture. Step 3: Initial Phase Configuration and Timing Coding Generation: Based on the target reflection direction and the propagation direction between the primary and secondary metasurfaces, the azimuth and elevation angles of the corresponding propagation paths are substituted into the aggregated channel state information composite channel constructed in Step 2. The continuous phase offset of each metasurface unit under ideal deployment conditions is calculated, and the continuous phase offset is quantized into the initial discrete phase state to obtain the initial phase configuration. At the same time, independent time-varying phase sequences are assigned to different virtual propagation paths, so that different paths have distinguishable timing identifiers while performing directional reflection. Step 4: Establishing the pose error model: Based on the initial discrete phase state and time-varying phase sequence obtained in Step 3, establish the pose error model of the master metasurface and each slave metasurface. The pose error model includes translation offset and rotation offset. Step 5, Pose Compensation Parameter Optimization and Time-Varying Phase Calibration: Calculate the pose compensation phase offset of the superatom based on the pose error model, and optimize the pose compensation parameters and discrete phase configuration of the master and slave metasurfaces alternately using a block coordinate descent algorithm with the goal of maximizing the received signal strength or equivalent channel gain. Correct the time-varying phase sequence while maintaining the time discriminability of different virtual reflection paths, and generate the calibrated time-varying control phase to compensate for deployment errors and calibrate beam pointing.

2. The metasurface wireless sensing enhancement method based on a tree structure according to claim 1, characterized in that: Step 1 specifically includes the following steps: Step 1.1: Configure a single wireless transceiver unit, a main metasurface, and... A secondary metasurface, which does not require an independent wired feed, has its incident signal provided by directional reflection from the beamguide subarray of the primary metasurface; Step 1.2: Functionally divide the main metasurface: Divide the main metasurface into a beamguide subarray and a virtual viewpoint subarray. The beamguide subarray is used to directionally reflect the incident wireless signal to the secondary metasurface, and the virtual viewpoint subarray is used to directionally reflect the incident wireless signal to the target area to form a virtual observation viewpoint. Step 1.3: Establish the mapping relationship between the metasurface and the virtual observation viewpoint: Each metasurface applies a controllable phase shift to the incident signal from the main metasurface and reflects it to the target area. Each metasurface forms an independent virtual observation viewpoint, thereby achieving multi-directional spatial coverage under the condition of a single set of wireless transceivers.

3. The metasurface wireless sensing enhancement method based on a tree structure according to claim 2, characterized in that: Step 2 specifically includes the following steps: Step 2.1, at the receiving end of the wireless transceiver device Receives CSI signals, the CSI signals including transmitted signals reflected by the main metasurface beamguide subarray to the first The reflection component formed by the metasurface after reflection. The transmitted signal is directly reflected to the target area by the virtual viewpoint subarray of the primary metasurface, forming the viewpoint reflection component of the primary metasurface. And the direct clutter components corresponding to the direct path and environmental multipath. ; Step 2.2, the metasurface reflection component The viewpoint reflection component of the principal metasurface and direct clutter components Modeled as a composite channel with aggregated channel state information for: in, Indicates the time-varying phase shift, the first The reflection component corresponding to the metasurface Represented as: Principal metasurface viewpoint reflection component Represented as: in, This represents the channel from the transmitter to the main metasurface beamguide subarray. Indicates the main metasurface beamguide array to the first A cascaded channel from the metasurface, Indicates the first From metasurface to receiver The channel, This represents the channel from the transmitter to the virtual viewpoint subarray of the main metasurface. This indicates the virtual viewpoint subarray of the main metasurface to the receiving end. The channel, For the first A diagonal phase shift matrix from the metasurface, Main metasurface beamguide subarray This represents the virtual viewpoint subarray of the main metasurface. This indicates the transpose operation.

4. The metasurface wireless sensing enhancement method based on a tree structure according to claim 3, characterized in that: Step 3 specifically includes the following steps: Step 3.1, Calculation of continuous phase offset: For the first... A metasurface, among which... ,when When is the master metasurface, when It is from the metasurface, in the first In a local coordinate system of a metasurface, the metasurface is placed Face, let the first Superatomic positions for: in, Indicates the first A superatom in Coordinates in direction Indicates the first A superatom in Coordinates in the direction; Step 3.2, let the first... The target emission direction of the metasurface is determined by the azimuth angle. and pitch angle Confirmed, number The unit reflection vector of a metasurface is Then the first The first metasurface Superatomic positions Phase offset on for: ； in, For the first The position of a superatom, For the first The position of a superatom The geometric center, The equivalent incident source location includes the equivalent phase center of the wireless transceiver, the primary metasurface, or the previous hop metasurface. For subcarrier wavelength, Denotes the Euclidean norm; Step 3.3, Binary Phase Quantization: For continuous phase offsets By performing a uniform binarization approximation, the discrete phase state is obtained. for: Therefore, we obtain the first... The initial binary phase configuration of each metasurface; Step 3.4, Metasurface Timing Encoding: For the first... Each metasurface is defined with a length of... Temporal coding vector for: ， in, Indicates the first Applying within the first time slot Temporal encoding vectors of a metasurface; Step 3.5, Time-varying phase superposition: For the first... The metasurface, in the first Within each time slot, the corresponding timing coding vector Superimposed on the initial binary phase of all superatoms, we obtain the first... The time-varying total phase of a superatom for: in, The time slot number, The duration of a single time slot, Indicates the first The end time corresponding to each time slot; Step 3.6, Time-varying channel model construction: Apply the time-series coding vector defined in step 3.4 to both the primary and secondary metasurfaces. Aggregate channel state information to composite channel Modulation is a time-varying form that changes dynamically with time. for: in, and These represent the time-coded phases of the main metasurface beamguide subarray and the virtual viewpoint subarray, respectively, with a duration of... Within one time-series coding cycle, by collecting The measurements from each time slot are used to obtain the time-coded CSI vector. .

5. The metasurface wireless sensing enhancement method based on a tree structure according to claim 4, characterized in that: In step 4, the pose error model of the metasurface is defined as follows: For the master metasurface and each slave metasurface, establish pose error models respectively, and let the metasurfaces be numbered as follows: ,in , Indicates the primary metasurface. Indicates from the metasurface, for the first A metasurface is defined to represent a pose error with 6 degrees of freedom. for: in, This is the translation offset. Indicates the first A metasurface surrounds , , Euler angles for rotational offset of the three coordinate axes.

6. The metasurface wireless sensing enhancement method based on a tree structure according to claim 5, characterized in that: Step 5 specifically includes the following steps: Step 5.1: Based on the pose error model , No. The first metasurface The actual position of each superatom Corrected to position vector for: If the first The unit vector of the reference reflection direction of each metasurface is Then, the corrected reflection direction vector after considering rotation error for: ； Step 5.2, Pose Compensation Phase Calculation: Calculate the corrected position vector obtained in Step 5.

1. With the corrected reflection direction vector Substitute phase offset Calculate the first The first metasurface Pose compensation phase offset of each superatom for: ； Step 5.3: For the discrete phase metasurface, the pose compensation phase offset is... Quantization is performed according to the phase resolution of the metasurface to obtain the corrected multi-level discrete phase states. for: in, This represents the phase quantization function. For a binary phase metasurface, the output of the phase quantization function is 0 or... For a multi-bit phase metasurface, the output of the phase quantization function is the corresponding multi-level discrete phase state. Step 5.4: Construct the pose compensation phase shift matrix: Based on the corrected multi-level discrete phase state obtained in Step 5.3 Construct the first Pose compensation phase shift matrix of a metasurface for: in, Indicates the first The number of superatoms contained in each metasurface, and the pose compensation phase shift matrix of the beamguide subarray and the virtual viewpoint subarray divided by the main metasurface, are used to construct the beamguide subarray respectively. Pose compensation phase shift matrix of virtual viewpoint subarray ; Step 5.5: Combine the timing coding vector from Step 3. Then in the first Within the first time slot, the first The first metasurface The total phase of each superatom for: in, Indicates the first Applying within the first time slot The temporal encoding vector of each metasurface, based on the total phase Get the first Time-varying pose compensation phase shift matrix for each time slot for: Step 5.6: Construct the composite channel of aggregated channel state information after pose compensation: The time-varying pose compensation phase shift matrix obtained in Step 5.5... Substituting the aggregated channel state information composite channel constructed in step 2, we obtain the equivalent CSI after considering pose error compensation. For the first... The metasurface reflection component after being relayed by the main metasurface beamguide subarray from the metasurface Represented as: Corrected reflection components of the virtual viewpoint subarray of the master metasurface: in, , , It is a diagonal phase shift matrix that includes the pose compensation phase; Step 5.7: In a two-hop scenario containing only one master metasurface and one target slave metasurface, jointly optimize the pose error parameters of the master metasurface with the goal of maximizing the received signal strength. and from metasurface pose error parameters The optimization objective is expressed as: in, This represents the two-hop equivalent channel after pose error compensation for the master metasurface and the first slave metasurface, and the joint optimization of the master metasurface pose error parameters. and from metasurface pose error parameters A two-stage optimization strategy is adopted: Phase 1, Master Hypersurface Optimization: Estimating the pose error parameters of the master hypersurface. Configure the main metasurface towards Directional beamforming, calculating and quantizing the initial phase matrix, by maximizing End RSS solver for optimal pose compensation parameters of the master metasurface for: in, The block diagonal phase shift matrix of the master metasurface; The second stage involves metasurface optimization, fixing the optimal pose compensation parameters of the master metasurface. Activate the target from the metasurface, configure the main metasurface beamguide subarray towards the target from the metasurface, and construct the link signal. ; Calculate and quantize the initial phase matrix from the metasurface based on spatial coordinates. Substitute into step 5.6 The metasurface reflection component after being relayed by the main metasurface beamguide subarray from the metasurface The optimal pose compensation parameters from the metasurface are solved by maximizing the receiver RSS. for: ； Step 5.8, Phased Optimization Solution: A block coordinate descent strategy is adopted to alternately optimize the pose error model. Translation and rotation components, including a fixed rotation matrix. Optimize translation vector Fixed translation vector Update the rotation matrix Iterate until the received RSS converges, completing the collaborative configuration of a single master-slave metasurface pair; Step 5.9, Multi-slave metasurface extension configuration: In the multi-slave metasurface scenario, the two-stage optimization strategy described in Step 5.7 is extended to multiple slave metasurfaces to obtain the pose compensation parameter set for the multiple metasurfaces. ; Step 5.10: Update the metasurface control state based on the optimization results: based on the set of pose compensation parameters for the multiple metasurfaces obtained in Step 5.

9. Update the discrete phase configuration of the master metasurface and each slave metasurface respectively. For the first... Each metasurface will have its optimal pose compensation parameters adjusted accordingly. Substitute the phase offset from step 4.2 The compensation phase of each superatom is recalculated and quantized to obtain the final control phase. Further combining timing-coded phase , generate the first The final time-varying control phase within each time slot for: The final time-varying control phase The superatomic control circuits sent to the corresponding metasurfaces enable the master metasurface and each slave metasurface to maintain the expected beam steering, virtual viewpoint generation, and multipath reflection enhancement effects even in the presence of installation deviations, positional offsets, or attitude errors.

7. The metasurface wireless sensing enhancement method based on a tree structure according to claim 6, characterized in that: Step 5.9 includes the following steps: Step 5.9.1: Based on the two-stage optimization strategy described in 5.7, extend it to multiple secondary metasurfaces, perform pose compensation optimization on the primary metasurface, and obtain the optimal pose compensation parameters of the primary metasurface. ; Step 5.9.2: Fix the optimal pose compensation parameters of the master metasurface. Under these conditions, each slave metasurface is activated sequentially, and the optimal pose compensation parameters for each slave metasurface are solved separately. for: in, After solving all the pose compensation parameters from the metasurface, a set of pose compensation parameters for multiple metasurfaces is obtained. .

Images