Phase-free integrated sensing and backscatter communication method based on inverse scattering and related device

Abstract

The invention discloses a phase-free integrated sensing and backscatter communication method based on inverse scattering and a related device. According to the invention, the load impedance of the tag is dynamically modulated, so that a receiving antenna receives pilot signals in different modulation states to enhance backscattering; estimating a clutter tag structure combination power component and a tag antenna power component according to the RSSI of the collected pilot signal, thereby sensing and identifying a tag; and transmitting a data signal to a receiving antenna by adopting ASK modulation through the tag, collecting the received RSSI of the receiving antenna, and performing signal demodulation by utilizing a zero-forcing algorithm, thereby effectively enhancing the reliability of backscatter communication.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and in particular, to a phase-free integrated sensing and backscatter communication method and related devices based on inverse scattering. Background Art

[0002] Backscatter communication can effectively reduce the energy consumption brought about by the rapid development of the Internet of Things. Low-power data transmission can be achieved by using reflected radio frequency signals from the environment or dedicated sources. Since the current transmission power requirements are as low as nanowatts to microwatts, backscatter technology is particularly suitable for energy-constrained application scenarios. For this reason, integrated sensing and communication (ISAC) systems have attracted great attention. It can further improve efficiency by combining sensing and communication functions, optimizing spectrum and hardware usage, reducing costs, and supporting location-aware and environmental-aware applications. In this context, the precise positioning of passive tag antennas is crucial for location-based services, enabling automatic target recognition and applications in biomedical systems and environmental monitoring. Therefore, integrating positioning into backscatter systems has become an important research hotspot.

[0003] Existing indoor positioning methods (such as time of arrival (ToA), angle of arrival (AoA), and direction of arrival (DoA), etc.) are widely used, but have obvious limitations. Although these positioning methods can achieve precise positioning, they require multiple receivers to determine the position by identifying the intersection of detection directions. Synthetic aperture radar (SAR) technology can also be used for passive tag positioning, but its strong dependence on mechanical scanning greatly limits the imaging speed.

[0004] In contrast, phase-free imaging technology relies on intensity measurements (such as received signal strength indicator (RSSI)), and demonstrates unique advantages in the fields of indoor radio frequency (RF) and microwave imaging. By eliminating the need for coherent phase information, this method has the advantages of reducing hardware complexity and cost, making phase-free technology particularly applicable in the microwave band because capturing accurate phase measurement values in this band is inherently quite challenging.

[0005] From the perspective of electromagnetics, RSSI-based imaging is generally classified as Inverse Scattering Problems (ISPs). Since ISPs are inherently ill-conditioned and non-linear, methods such as the Born approximation (BA) and Rytov approximation (RA), contrast source inversion, and non-linear deep learning have been developed to address these challenges. Among them, non-linear techniques, including subspace optimization and iterative methods such as the distorted wave Born iterative method (DBIM) and the distorted wave Rytov iterative method (DRIM), have made significant progress in reconstructing strong scattering scenarios. These methods show the potential for high-fidelity imaging and precise positioning of clutter scatterers with time-invariant reflectivity. However, the existing research on non-phase inverse scattering methods mainly focuses on static clutter scatterers, and the application of time-varying reflectivity has not been widely explored. This limitation hinders the full utilization of non-phase inverse scattering technology in integrated sensing and communication (ISAC) systems, thus affecting the poor detection accuracy of the non-phase system for tags in chaotic environments containing clutter scatterers and the low backscatter communication performance. Summary of the Invention

[0006] The present invention provides a non-phase integrated sensing and backscatter communication method and related device based on inverse scattering to solve the technical problems of poor detection accuracy of the existing non-phase system for tags and low backscatter communication performance.

[0007] The present invention provides a non-phase integrated sensing and backscatter communication method based on inverse scattering, and the method includes:

[0008] Transmitting a pilot signal to a tag through a transmitting antenna, modulating the load impedance of the tag so that the tag generates a first pilot signal and a second pilot signal, and backscattering the first pilot signal and the second pilot signal to a receiving antenna;

[0009] Receiving the first pilot signal and the second pilot signal through the receiving antenna, measuring a first RSSI and a second RSSI; determining a clutter-tag structure combined power component and a tag antenna power component according to the first RSSI and the second RSSI;

[0010] Estimating a clutter-tag structure combined reflection coefficient and a tag antenna reflection coefficient respectively based on the clutter-tag structure combined power component and the tag antenna power component;

[0011] When the transmitting antenna senses and identifies the tag through the clutter-tag structure combined reflection coefficient and the tag antenna reflection coefficient, the tag uses ASK modulation to transmit a data signal to the receiving antenna, and measures the received RSSI of the receiving antenna;

[0012] Based on the zero-forcing algorithm, a demodulation operation is performed through the received RSSI, the combined power component of the clutter tag structure, and the tag antenna power component to obtain the bit symbols of the data signal.

[0013] Optionally, the step of respectively estimating the combined reflection coefficient of the clutter tag structure and the tag antenna reflection coefficient based on the combined power component of the clutter tag structure and the tag antenna power component includes:

[0014] Using the compressive sensing algorithm, a first underdetermined equation is constructed based on the combined power component of the clutter tag structure, and the first underdetermined equation is solved by the two-step iterative shrinkage threshold algorithm to obtain the combined reflection coefficient of the clutter tag structure;

[0015] Using the compressive sensing algorithm, a second underdetermined equation is constructed based on the tag antenna power component, and the second underdetermined equation is solved by the two-step iterative shrinkage threshold algorithm to obtain the tag antenna reflection coefficient.

[0016] Optionally, the step of when the transmitting antenna senses and identifies the tag through the combined reflection coefficient of the clutter tag structure and the tag antenna reflection coefficient, and then the tag uses ASK modulation to transmit a data signal to the receiving antenna and measures the received RSSI of the receiving antenna includes: When the transmitting antenna senses the clutter scatterer and the tag through the combined reflection coefficient of the clutter tag structure and identifies the tag from the clutter scatterer through the tag antenna reflection coefficient, the tag uses ASK modulation to transmit a data signal to the receiving antenna and measures the received RSSI of the receiving antenna.

[0017] Optionally, the step of performing a demodulation operation through the received RSSI, the combined power component of the clutter tag structure, and the tag antenna power component based on the zero-forcing algorithm to obtain the bit symbols of the data signal includes:

[0018] Performing a subtraction operation on the received RSSI and the combined power component of the clutter tag structure to obtain the received signal of the receiving antenna;

[0019] Inputting the received signal of the receiving antenna and the tag antenna power component into a preset backscatter communication model and using the zero-forcing algorithm to solve to obtain a decision reflection coefficient;

[0020] Setting the average value of the reflection coefficient of the first pilot signal and the reflection coefficient of the second pilot signal as the decision threshold;

[0021] Judge the decision reflection coefficient and the decision threshold. If the decision reflection coefficient is greater than the decision threshold, the bit symbol of the demodulated data signal is bit 1; otherwise, the bit symbol of the demodulated data signal is bit 0.

[0022] Optionally, the first underdetermined equation is specifically:

[0023]

[0024] Where: represents the l1 norm, represents the clutter label structure combined reflection coefficient, represents the clutter label structure combined power component, represents the measurement matrix;

[0025] The second underdetermined equation is specifically:

[0026]

[0027] Where: represents the tag antenna reflection coefficient, represents the tag antenna power component.

[0028] Optionally, the preset backscatter communication model is specifically:

[0029]

[0030] Where: represents the th received signal, represents the th data symbol, represents the th additive white Gaussian noise of the data symbol.

[0031] Optionally, the decision reflection coefficient is expressed as:

[0032]

[0033] Where: represents the th decision reflection coefficient, represents the linear detection matrix.

[0034] The present invention also provides a phase-free integrated sensing and backscatter communication device based on inverse scattering, including:

[0035] A modulation module, configured to transmit a pilot signal to a tag via a transmitting antenna, modulate the load impedance of the tag such that the tag generates a first pilot signal and a second pilot signal, and backscatter the first pilot signal and the second pilot signal to a receiving antenna;

[0036] A power component determination module, configured to receive the first pilot signal and the second pilot signal via the receiving antenna, measure a first RSSI and a second RSSI; and determine a clutter tag structure combined power component and a tag antenna power component according to the first RSSI and the second RSSI;

[0037] A reflection coefficient estimation module, configured to respectively estimate a clutter tag structure combined reflection coefficient and a tag antenna reflection coefficient based on the clutter tag structure combined power component and the tag antenna power component;

[0038] A signal transmission module, configured to, when the transmitting antenna senses and identifies the tag via the clutter tag structure combined reflection coefficient and the tag antenna reflection coefficient, transmit a data signal to the receiving antenna by ASK modulation using the tag, and measure a received RSSI of the receiving antenna;

[0039] A demodulation module, configured to perform a demodulation operation based on a zero-forcing algorithm through the received RSSI, the clutter tag structure combined power component and the tag antenna power component to obtain bit symbols of the data signal.

[0040] The present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above-described non-phase integrated sensing and backscatter communication method are implemented.

[0041] The present invention further provides a computer program product, including a computer program, and when the computer program is executed by a processor, the steps of the above-described non-phase integrated sensing and backscatter communication method are implemented.

[0042] It can be seen from the above technical solutions that the present invention has the following advantages:

[0043] A method and related device for phase - less integrated sensing and backscatter communication based on inverse scattering. The method includes: transmitting a pilot signal to a tag through a transmitting antenna, modulating the load impedance of the tag so that the tag generates a first pilot signal and a second pilot signal, and backscattering the first pilot signal and the second pilot signal to a receiving antenna; receiving the first pilot signal and the second pilot signal through the receiving antenna, and measuring a first RSSI and a second RSSI; determining a clutter - tag structure combined power component and a tag antenna power component according to the first RSSI and the second RSSI; respectively estimating a clutter - tag structure combined reflection coefficient and a tag antenna reflection coefficient based on the clutter - tag structure combined power component and the tag antenna power component; when the transmitting antenna senses and identifies the tag through the clutter - tag structure combined reflection coefficient and the tag antenna reflection coefficient, the tag uses ASK modulation to transmit a data signal to the receiving antenna, and measures the received RSSI of the receiving antenna; based on the zero - forcing algorithm, performing a demodulation operation through the received RSSI, the clutter - tag structure combined power component and the tag antenna power component to obtain the bit symbols of the data signal.

[0044] In the present invention, by dynamically modulating the load impedance of the tag, the clutter - tag structure combined reflection coefficient and the tag antenna reflection coefficient are obtained, so that the clutter scatterer and the tag can be accurately sensed and identified; at the same time, the zero - forcing algorithm is used for signal demodulation, which can improve the reliability of backscatter communication, and thus solves the technical problems that the existing phase - less system has poor detection accuracy for tags and low backscatter communication performance. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a flowchart of the steps of a method for phase - less integrated sensing and backscatter communication based on inverse scattering provided by an embodiment of the present invention;

[0047] Figure 2 It is a schematic diagram of a phase - less integrated sensing and backscatter communication system provided by an embodiment of the present invention;

[0048] Figure 3 It is a schematic diagram for analyzing the sensing and identification results of three tags and a closed clutter scatterer provided by an example of the present invention;

[0049] Figure 4 Schematic diagram of the scattered RSSI response of the receiving antenna provided for the example of the present invention;

[0050] Figure 5 Data symbols of ASK modulation provided for the example of the present invention (k) bit error rate performance;

[0051] Figure 6 Block diagram of a phase - less integrated sensing and backscatter communication device based on inverse scattering provided for the embodiment of the present invention. Detailed implementation manners

[0052] The embodiment of the present invention provides a phase - less integrated sensing and backscatter communication method and related device, which are used to solve the technical problems that the existing phase - less system has poor detection accuracy for tags and low backscatter communication performance.

[0053] To make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] Please refer to Figure 1 , the present invention proposes a phase - less integrated sensing and backscatter communication method; the method includes:

[0055] Step 101: Transmit a pilot signal to the tag through a transmitting antenna, modulate the load impedance of the tag so that the tag generates a first pilot signal and a second pilot signal, and backscatter the first pilot signal and the second pilot signal to the receiving antenna.

[0056] It should be noted that the present invention is applied to a phase - less integrated sensing and backscatter communication system. Please refer to Figure 2 , this system integrates sensing and backscatter communication using backscatter technology, realizes accurate tag positioning and identification, and at the same time realizes backscatter communication.

[0057] Figure 2The phase-free integrated sensing and backscatter communication system constructed for this embodiment is applicable to a typical indoor environment. In the figure, a plurality of clutter scatterers (Clutter) and tags (Tag) are arranged in the test area range DOI. The test area range DOI covers an area of Lx×Ly and is divided into a grid of Nx×Ny pixels, where Nx = Lx / Δx and Ny = Ly / Δy. Nx represents the number of pixels divided in the x direction, Δx represents the length occupied by each pixel in the x direction, Ny represents the number of pixels divided in the y direction, and Δy represents the length occupied by each pixel in the y direction. Then each pixel occupies the area of.

[0058] Along the boundary B of DOI, M = 20 transceivers with uniform intervals operate at a frequency of 2.4 GHz. Among them, the spatial position of the transmitting antenna m is represented by r m and the spatial position of the receiving antenna m' is represented by r m’ . All antennas are located on the boundary B. The distance between the transmitting antenna m and the test point n in DOI is denoted as r m,n , and for the same test point n and the receiving antenna m', the distance is denoted as r n,m’ . Since each node cannot act as a transmitter and a receiver simultaneously, the system is configured for independent measurements, where M = 20 and L represents the number of independent measurements of the transceiver antennas. In addition, in the subsequent calculation parameters, the subscripts m and m' respectively refer to the parameters related to the transmitting and receiving antennas.

[0059] In the proposed system, each transmitting antenna m generates a vertically polarized time-harmonic incident electric field, which propagates through the test points in DOI and interacts with the clutter scatterers. The total electric field generated under this interaction is the superposition of the incident field and the scattered field

[0060]

[0061] and can be expressed as: In addition, the scattered field

[0062]

[0063] at the DOI boundary can be calculated using the Lippmann-Schwinger integral equation as: where \(j\) is the unit imaginary number, \(\omega\) is the angular frequency, \(\mu_0\) is the vacuum permeability; \(\overline{G}(r,r')\) represents that all position points are located within the DOI region; represents the Green's function, (·) represents the zero-order Hankel function of the first kind, represents the free space wave number.

[0064] In practical applications, the scattered fields in formulas (1) and (2) will be captured by the receiving antenna m' and converted into voltage. Then the Green's function involved in formula (2) can be converted into the electric field radiated by the receiving antenna m' in the transmission mode of unit excitation, and the result is:

[0065]

[0066] in, represents the voltage generated by the receiving antenna m' receiving the scattered field generated by the transmitting antenna m; a represents the normalization factor; represents the electric field radiated by the receiving antenna m' in the transmit mode with unit excitation.

[0067] The inverse scattering problem aims to measure the The relative permittivity distribution is estimated from However, there are two unknowns involved in solving equation (2): and , making the problem both ill-posed and nonlinear.

[0068] To solve this problem, this embodiment applies the RA (Rytov Approximation) approximation algorithm, which is particularly effective in a phase-free framework.

[0069] According to the RA approximation algorithm, the transmitting antenna m is located at The total field at is expressed as:

[0070]

[0071] in, represents the complex phase of the scattered field generated by the transmitting antenna m.

[0072] By converting the total field into the logarithmic domain using the Rytov transform, equation (4) can be reformulated as:

[0073]

[0074] By applying this transformation to the voltage measurement and neglecting the terms under weak scattering conditions , formula (3) can be reformulated as a linear problem as follows:

[0075]

[0076] in, is the background voltage measurement value (without clutter scatterers), Denotes the total voltage measured at the receiving antenna (with clutter scatterers); at this time is the only unknown, thus simplifying the solution process.

[0077] In order to convert Equation (6) to be applicable under the non-phase frame and expressed in exponential form, Equation (6) can be expressed as:

[0078]

[0079] Multiply Equation (7) by its complex conjugate and take the base-10 logarithm to obtain the RSSI received power change (dB), as follows:

[0080]

[0081] Where: is the power change, with the unit of dB; thus, a linear relationship between the RSSI change and the relative permittivity distribution is established.

[0082] In antenna scattering theory, the scattered field from a tag is determined by the impedance matching between its antenna and the connected load impedance, and this relationship is described by the reflection coefficient as:

[0083]

[0084] Where: denotes the antenna impedance is the complex conjugate of denotes the load impedance; when the load impedance matches the complex conjugate of the antenna impedance, i.e., , the reflection coefficient becomes zero at this time.

[0085] Among them, for a specific modulation symbol c related to a certain reflection coefficient q , its corresponding load impedance can be expressed as:

[0086]

[0087] When the transmitting antenna m irradiates the tag, the scattered field within the DOI region located at can be expressed as:

[0088]

[0089] Where, corresponds to the electric field related to the structural mode of the tag, is the field radiated by the antenna mode of the tag, is the scattered field of the tag antenna mode, ​is the load impedance and the antenna impedance, is the current when conjugate complex matching occurs.

[0090] It should be noted that for the tag, its scattered field includes the scattered fields of the structural mode and the antenna mode. Among them, the scattered field of the tag's structural mode is not affected by the load impedance and is determined by physical properties such as shape, size, position, and composition. The scattered field of the tag's antenna mode depends on the load conditions and can be modulated to facilitate data transmission in backscatter communication, which also makes it possible to identify the tag from clutter scatterers.

[0091] For simplicity, when the DOI region contains tags and clutter scatterers, the scattered field of the clutter scatterer is denoted as , then in formula (4) can be expressed as:

[0092]

[0093] Since and are independent of the load impedance of the tag, they can be combined into a constant field .

[0094] Then, according to formulas (1) and (2), the relative permittivity distribution can be decomposed as:

[0095]

[0096] In the formula, is associated with the structural modes of the clutter scatterer and the tag, corresponds to the antenna mode of the tag.

[0097] Similarly, the RSSI in formula (8) can be decomposed as:

[0098]

[0099] Among them, represents the power associated with the structural modes of the clutter scatterer and the tag, represents the power associated with the antenna mode of the tag.

[0100] Combined with formula (8) again, the decibel (dB) expressions of the components decomposed from RSSI are specifically as follows. The decibel (dB) expression of the power associated with the structural modes of the clutter scatterer and the tag is shown in formula (15), and the power The decibel (dB) expression is as shown in formula (16);

[0101]

[0102]

[0103] Combining formula (15) and formula (16), the inverse problem can thus be transformed into estimating and from the measured RSSI, thereby sensing and identifying clutter scatterers and tags, which helps to more accurately identify the position of the tag.

[0104] Therefore, the present invention uses the method of extracting and by backscatter communication, thereby enhancing the sensing and identification capabilities. The process starts by transmitting two pilot signals to the tag through the transmitting antenna, and the two pilot signals respectively correspond to the reflection coefficients = and = Γ2, which are respectively related to the load impedances Z L1 and Z L2 and backscatter the first pilot signal and the second pilot signal to the receiving antenna.

[0105] Step 102, receive the first pilot signal and the second pilot signal through the receiving antenna, and measure the first RSSI and the second RSSI; determine the clutter tag structure combined power component and the tag antenna power component according to the first RSSI and the second RSSI.

[0106] Among them, combining formula (13), the RSSI received by these pilot signals can be expressed as:

[0107]

[0108]

[0109] Where: represents the first RSSI, represents the second RSSI.

[0110] Then, and can be deduced as:

[0111]

[0112]

[0113] Given independent measurement values, Can form a clutter tag structure combined power component , where each element . Similarly, there is a tagged antenna power component , where each element .

[0114] Among them , m = 1, 2..., M−1, m is determined by = 1 + ceil(m / M),..., M. Although the backscatter communication system theoretically supports high-order modulation schemes, such as 4- or 8-ary modulation, in this embodiment, for simplicity, consider = 0.5 and = 1, where = 1 represents the strongest reflection degree (i.e., corresponding to the maximum RSSI), while = 0.5 corresponds to a medium reflection degree, indicating that there is sufficient power difference, which is easy for subsequent detection and demodulation, and is also easy to implement in hardware.

[0115] Step 103, based on the clutter tag structure combined power component and the tagged antenna power component, estimate the clutter tag structure combined reflection coefficient and the tagged antenna reflection coefficient respectively.

[0116] This step specifically includes the following sub-steps:

[0117] Sub-step 1031, use the compressive sensing algorithm to construct the first underdetermined equation based on the clutter tag structure combined power component, and solve the first underdetermined equation through the two-step iterative shrinkage threshold algorithm to obtain the clutter tag structure combined reflection coefficient.

[0118] In the initial stage, can be used to accurately sense the clutter scatterers and tags. According to Equation (15), there is:

[0119]

[0120] Among them, represents the clutter tag structure combined reflection coefficient, , which is composed of at all N positions; represents the measurement matrix, H contains elements × .

[0121] A direct method to recover from the measurement in Equation (21) is to calculate the inverse of , so that , however, this method is usually not feasible because the L observations are not completely independent, leading to an ill-posed problem where the number of observations is typically less than the number of unknowns N.

[0122] Therefore, the matrix H is usually non-invertible. To solve this problem, compressive sensing (CS) technology can be used for image reconstruction. For sparse objects or scatterers, a first underdetermined equation is constructed, and then Equation (21) can be reformulated as:

[0123]

[0124] where: represents the l1 norm.

[0125] Then, the two-step iterative shrinkage thresholding (TwIST) algorithm is used to solve Equation (22). The TwIST algorithm iteratively updates the estimated reflection coefficients by applying shrinkage and thresholding operations, thereby achieving the recovery of the sparse reflection coefficients .

[0126] Sub-step 1032: Use the compressive sensing algorithm to construct a second underdetermined equation based on the tag antenna power components, and solve the second underdetermined equation through the two-step iterative shrinkage thresholding algorithm to obtain the tag antenna reflection coefficients.

[0127] Since represents the reflection coefficients of the clutter scatterers and the tag structure patterns, with the help of the clutter-tag structure combined reflection coefficient the clutter scatterers and the tag can be accurately sensed. However, only recovering the clutter-tag structure combined reflection coefficient is not sufficient to identify the tag from the clutter scatterers. To identify the tag, the tag antenna reflection coefficient also needs to be recovered.

[0128] To identify the tag, we focus on , which isolates the contribution of the antenna pattern. According to Equation (16), we have:

[0129]

[0130] where: .

[0131] Similar to recovering , a second underdetermined equation is constructed:

[0132]

[0133] Similarly, the TwIST algorithm is used to solve Equation (24) so that the tag can be identified.

[0134] Step 104. After the transmitting antenna senses and identifies the tag by combining the reflection coefficient and the tag antenna reflection coefficient through the clutter tag structure, the tag uses ASK modulation to transmit a data signal to the receiving antenna, and the received RSSI of the receiving antenna is measured.

[0135] It can be understood that after the transmitting antenna senses and identifies the tag by combining the reflection coefficient and the tag antenna reflection coefficient through the clutter tag structure, the backscatter communication stage can be entered: the tag transitions to data transmission through backscatter communication, and this process uses amplitude shift keying (ASK) modulation, where the tag alternates between two load impedances Z L1 and Z L2 , corresponding to the reflection coefficients and respectively; the k-th data symbol transmitted by the tag is denoted as .

[0136] For each transmitted data symbol, the RSSI received at the antenna is measured and denoted as the vector in = . Based on the relationship in Equation (14), the measured th received RSSI is related to the transmitted data symbol as:

[0137]

[0138] Step 105. Based on the zero-forcing algorithm, a demodulation operation is performed through the received RSSI, the combined power component of the clutter tag structure, and the power component of the tag antenna to obtain the data symbol of the data signal.

[0139] This step specifically includes the following sub-steps:

[0140] Sub-step 1051. A subtraction operation is performed on the received RSSI and the combined power component of the clutter tag structure to obtain the received signal of the receiving antenna.

[0141] By removing the combined power component of the clutter tag structure from , the received signal y(k) is further defined to obtain , where represents the th received signal.

[0142] Sub-step 1052. The received signal of the receiving antenna and the power component of the tag antenna are input into a preset backscatter communication model and solved using the zero-forcing algorithm to obtain the decision reflection coefficient.

[0143] Considering the noise effect, the preset backscatter communication model can be expressed as:

[0144]

[0145] wherein, represents the additive white Gaussian noise (AWGN) of the -th data symbol, which is characterized by zero mean and covariance matrix σ 2 L . Here, can be regarded as the channel vector of the preset backscatter communication model. The preset backscatter communication model can operate as a single-input multiple-output (SIMO) system. In addition, the channel state information (CSI) of can be obtained in the sensing phase.

[0146] To optimize symbol detection, the zero-forcing (ZF) technique is applied, and the linear detection matrix of the optimal linear detector is defined as ; then, the relationship between the received signal after applying the detector and the decision reflection coefficient can be expressed as:

[0147]

[0148] Sub-step 1053, set the average value of the reflection coefficient of the first pilot signal and the reflection coefficient of the second pilot signal as the decision threshold.

[0149] wherein, the decision threshold is defined as and midpoint .

[0150] Sub-step 1054, judge the decision reflection coefficient and the decision threshold. If the decision reflection coefficient is greater than the decision threshold, the bit symbol of the demodulated data signal is bit 1; otherwise, the bit symbol of the demodulated data signal is bit 0.

[0151] Specifically, when , it is determined that the data symbol of the data signal is symbol , and the bit symbol of the demodulated data signal is bit 1. Otherwise, it is determined as symbol , and bit 0 is demodulated.

[0152] In addition, to evaluate the performance of the backscatter communication system, the bit error rate (BER) can be analyzed. The bit error rate (BER) is expressed as , where Q(·) represents the Q function.

[0153] Exemplarily, the present invention also provides corresponding simulation experiments to verify the application performance of the present solution.

[0154] 1) Regarding sensing and recognition performance:

[0155] In this example, the sensing and recognition capabilities of the proposed solution are evaluated through three configurations. The first configuration includes one tag and one clutter scatterer, the second configuration includes two tags and one clutter scatterer, and the third configuration includes three tags and one clutter scatterer. For each configuration, a copper dipole antenna with a radius of 10 mm (0.08λ) and a height of 56.5 mm (0.452λ) is used as the tag, and the antenna impedance is 75 ohms; modulation is performed with a load impedance of 225 ohms and infinity, and the corresponding reflection coefficients are 0.5 and 1.

[0156] To evaluate the perception and recognition quality of the reconstructed images and compare them with the ground truth, we use the peak signal-to-noise ratio (PSNR) and the structural similarity index measure (SSIM). A higher PSNR value or an SSIM value closer to 1 indicates better image quality. Here, the sensing and recognition results in the third configuration, i.e., in the presence of multiple tags, are mainly analyzed, as Figure 3 shown.

[0157] The third configuration includes four tags and a nearby copper rectangular clutter scatterer, and the reconstruction results are as Figure 3 shown. In Figure 3 , the blue curve represents the actual boundary of the clutter scatterer, and the green curve represents the tag boundary. In the sensing stage, Figure 3 (a) shows that the system accurately reconstructs the positions of all four tags and the clutter scatterer. In the recognition stage, the system successfully identifies individual tags, as Figure 3 (b)-(e) shown. In addition, various combinations of two or three tags can also be reconstructed and recognized, as Figure 3 (f)-(p) shown. Finally, the system achieves the simultaneous recognition of four tags, as Figure 3 (q) shown. These analysis results highlight the robustness of the proposed solution in the case of multiple tags and clutter scatterers.

[0158] In summary, the reconstruction results demonstrate the effectiveness of the proposed tagless system. By leveraging tag characteristics and the inverse scattering method, the tagless system can accurately locate and identify multiple tags and clutter scatterers with a resolution of 100 mm (0.8λ). This ability is particularly valuable in challenging environments where clutter scatterers may interfere with accurate tag localization and recognition.

[0159] 2) Regarding backscatter communication performance:

[0160] To verify the backscatter communication ability of the proposed system, we consider a scenario involving a single copper dipole antenna (tag) and a copper clutter scatterer within the DOI. The load impedance of the tag is at = 225 ohms and is modulated between = ∞, corresponding to the theoretical reflection coefficients = 0.5 and Γ2 = 1, respectively. The total RSSI response includes the contributions from the structural modes of the tag and clutter scatterers, as well as the antenna modes of the tag under two impedance conditions ( = 225 ohms and = ∞), as shown in Figure 4 (a). Figure 4 (b) gives the RSSI distribution of the isolated structural modes of the clutter scatterers and the tag based on Equation (19). In addition, Figure 4 (c) shows the RSSI distribution of the isolated antenna mode of the tag under the same impedance conditions. To further analyze the system, Figure 4 (d) shows = 225 ohms and = ∞, the normalized RSSI ratio of the total RSSI value with respect to the RSSI value under = ∞. The results show that the normalized RSSI ratio is stable at 1 or 0.5, which is in good agreement with the theoretical analysis. At the same time, this expected change in RSSI provides a basis for reliable data communication using amplitude shift keying (ASK) modulation.

[0161] 107 trials were carried out using Monte Carlo simulation to further analyze the bit error rate (BER) performance of the proposed non-phase integrated sensing and backscatter communication system, and at the same time analyze the uplink bit error rate of the backscatter communication system using the ZF technique for signal detection. Among them, the relationship between the bit error rate and the signal-to-noise ratio is as shown in Figure 5 . The simulation results are in good agreement with the theoretical bit error rate results, verifying the accuracy and reliability of the system.

[0162] A non-phase integrated sensing and backscatter communication method based on inverse scattering provided by the present invention has the following advantages:

[0163] 1. The present invention can perform the functions of sensing and communication within a specified domain of interest (DOI) by dynamically modulating the load impedance of the tag to distinguish the tag from clutter scatterers and achieve the separate extraction of the structural mode and antenna mode of the received signal strength indicator (RSSI).

[0164] 2. A sparse-based method is combined with inverse scattering technology to process non-phase measurements. The RSSI corresponding to the structural modes of the clutter scatterers and the tag is used for initial detection of the tag and clutter, while the RSSI corresponding to the antenna structure mode of the tag is used for accurate identification of individual tags.

[0165] 3. The RSSI corresponding to the extracted antenna pattern can be used to derive channel state information (CSI) to improve the performance of backscatter communication; the bit error rate (BER) performance can be improved by the zero-forcing (ZF) technique to enhance communication reliability.

[0166] 4. Compared with traditional synthetic aperture radar imaging systems, since the present invention does not rely on phased arrays, mechanical, and electrical scanning mechanisms, the imaging speed is faster and the complexity is greatly reduced.

[0167] 5. This solution can achieve powerful backscatter communication while sensing and identifying tags in a complex environment without phase information.

[0168] Please refer to Figure 6 , the present invention also provides a phase-free integrated sensing and backscatter communication device based on inverse scattering, including:

[0169] A modulation module 201, configured to transmit a pilot signal to a tag through a transmitting antenna, modulate the load impedance of the tag so that the tag generates a first pilot signal and a second pilot signal, and backscatter the first pilot signal and the second pilot signal to a receiving antenna;

[0170] A power component determination module 202, configured to receive the first pilot signal and the second pilot signal through the receiving antenna, measure a first RSSI and a second RSSI; determine a clutter tag structure combined power component and a tag antenna power component according to the first RSSI and the second RSSI;

[0171] A reflection coefficient estimation module 203, configured to respectively estimate a clutter tag structure combined reflection coefficient and a tag antenna reflection coefficient based on the clutter tag structure combined power component and the tag antenna power component;

[0172] A signal transmission module 204, configured to, when the transmitting antenna senses and identifies the tag through the clutter tag structure combined reflection coefficient and the tag antenna reflection coefficient, transmit a data signal to the receiving antenna by using ASK modulation on the tag, and measure the received RSSI of the receiving antenna;

[0173] A demodulation module 205, configured to perform a demodulation operation based on the zero-forcing algorithm through the received RSSI, the clutter tag structure combined power component, and the tag antenna power component to obtain the bit symbols of the data signal.

[0174] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the phase-free integrated sensing and backscatter communication method as described above are implemented.

[0175] The present invention also provides a computer program product, including a computer program, which implements the steps of the non-phase integrated sensing and backscatter communication method as described above when executed by a processor.

[0176] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0177] In several embodiments provided by the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed mutual coupling, direct coupling, or communication connection can be through some interfaces, indirect coupling, or communication connection of devices or units, and can be in electrical, mechanical, or other forms.

[0178] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0179] In addition, in each embodiment of the present invention, the functional units can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0180] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0181] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of various embodiments of the present invention.

Claims

1. A phase-free integrated sensing and backscattering communication method based on inverse scattering, characterized in that: The method comprises: Transmitting a pilot signal to a tag through a transmitting antenna, modulating a load impedance of the tag so that the tag generates a first pilot signal and a second pilot signal, and backscattering the first pilot signal and the second pilot signal to a receiving antenna; Receiving the first pilot signal and the second pilot signal through the receiving antenna, measuring and obtaining a first RSSI and a second RSSI; determining a clutter tag structure combined power component and a tag antenna power component according to the first RSSI and the second RSSI; Based on the clutter tag structure combined power component and the tag antenna power component, respectively estimating the clutter tag structure combined reflection coefficient and the tag antenna reflection coefficient; After the transmitting antenna senses and identifies the tag through the reflection coefficient of the clutter tag structure combination and the tag antenna reflection coefficient, the tag is modulated by ASK to transmit a data signal to the receiving antenna, and the receiving RSSI of the receiving antenna is measured; Based on the zero forcing algorithm, a demodulation operation is performed through the received RSSI, the clutter tag structure combined power component and the tag antenna power component to obtain the bit symbol of the data signal.

2. The phase-free integrated sensing and backscattering communication method according to claim 1, characterized in that: The step of respectively estimating the clutter tag structure combination reflection coefficient and the tag antenna reflection coefficient based on the clutter tag structure combination power component and the tag antenna power component comprises: A first underdetermined deterministic equation is constructed based on the clutter tag structure combined power component by using a compressed sensing algorithm, and the first underdetermined deterministic equation is solved by a two-step iterative shrinkage threshold algorithm to obtain a clutter tag structure combined reflection coefficient; A compressed sensing algorithm is used to construct a second underdetermined deterministic equation based on the tag antenna power component, and the second underdetermined deterministic equation is solved by a two-step iterative shrinkage threshold algorithm to obtain the tag antenna reflection coefficient.

3. The phase-free integrated sensing and backscattering communication method according to claim 1, characterized in that: The step of transmitting a data signal to a receiving antenna by using ASK modulation through the tag after the transmitting antenna senses and identifies the tag through the combined reflection coefficient of the clutter tag structure and the reflection coefficient of the tag antenna, and measuring the receiving RSSI of the receiving antenna comprises: after the transmitting antenna senses the clutter scatterer and the tag through the combined reflection coefficient of the clutter tag structure and identifies the tag from the clutter scatterer through the reflection coefficient of the tag antenna, transmitting a data signal to the receiving antenna by using ASK modulation through the tag, and measuring the receiving RSSI of the receiving antenna.

4. The phase-free integrated sensing and backscattering communication method according to claim 1, characterized in that: The step of obtaining the bit symbol of the data signal by performing a demodulation operation based on the zero forcing algorithm through the received RSSI, the clutter tag structure combined power component and the tag antenna power component comprises: Subtracting the received RSSI from the power component of the clutter tag structure combination to obtain a received signal of the receiving antenna; Inputting the received signal of the receiving antenna and the power component of the tag antenna into a preset backscatter communication model and solving them using a zero-forcing algorithm to obtain a decision reflection coefficient; Setting an average value of a reflection coefficient of the first pilot signal and a reflection coefficient of the second pilot signal as a decision threshold; The decision reflection coefficient and the decision threshold are judged. If the decision reflection coefficient is greater than the decision threshold, the bit symbol of the demodulated data signal is bit 1; otherwise, the bit symbol of the demodulated data signal is bit 0.

5. The phase-free integrated sensing and backscattering communication method according to claim 2, characterized in that: The first underdetermined deterministic equation is specifically: Where: represents the l1 norm, represents the reflection coefficient of the clutter tag structure combination, represents the combined power component of the clutter tag structure, represents the measurement matrix; The second underdetermined determination equation is specifically: Where: represents the tag antenna reflection coefficient, Represents the tag antenna power component.

6. The phase-free integrated sensing and backscattering communication method according to claim 4, characterized in that: The preset backscatter communication model is specifically: Where: Indicates The received signal, Indicates data symbols, Indicates Additive white Gaussian noise of the data symbols.

7. The phase-free integrated sensing and backscattering communication method according to claim 6, characterized in that: The decision reflection coefficient is expressed as: Where: Indicates The decision reflection coefficient, represents the linear detection matrix.

8. A phase-free integrated sensing and backscattering communication device based on backscattering, characterized in that: include: A modulation module, configured to transmit a pilot signal to a tag through a transmitting antenna, modulate a load impedance of the tag so that the tag generates a first pilot signal and a second pilot signal, and backscatter the first pilot signal and the second pilot signal to a receiving antenna; A power component determination module, configured to receive the first pilot signal and the second pilot signal through the receiving antenna, measure a first RSSI and a second RSSI; determine a clutter tag structure combined power component and a tag antenna power component according to the first RSSI and the second RSSI; A reflection coefficient estimation module, used to estimate the clutter tag structure combination reflection coefficient and the tag antenna reflection coefficient respectively based on the clutter tag structure combination power component and the tag antenna power component; A signal transmission module, used for transmitting a data signal to a receiving antenna by ASK modulation through the tag after the transmitting antenna senses and identifies the tag through the reflection coefficient of the clutter tag structure combination and the reflection coefficient of the tag antenna, and measuring the receiving RSSI of the receiving antenna; The demodulation module is used to perform a demodulation operation based on a zero forcing algorithm through the received RSSI, the clutter tag structure combined power component and the tag antenna power component to obtain the bit symbol of the data signal.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the phase-free integrated sensing and backscattering communication method as described in any one of claims 1 to 7 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the phase-free integrated sensing and backscattering communication method as described in any one of claims 1 to 7 are implemented.

Images