CN112911267A - Indoor imaging method and device based on WiFi channel state information - Google Patents
Indoor imaging method and device based on WiFi channel state information Download PDFInfo
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Abstract
An exemplary embodiment of the present invention provides an indoor imaging method based on WIFI channel state information, including: extracting a channel state signal, wherein the channel state signal at least comprises complex amplitude information of the WIFI signal on a transmission path; combining the omnidirectional radiation model of the channel state signal and the transmission path to carry out path decomposition on the channel state signal to obtain monochromatic plane wave signals of the channel state signal in different propagation directions; and preprocessing each monochromatic plane wave signal to distinguish amplitude and phase information of different depths of each transmission path, and imaging the detected object according to the amplitude and phase information to obtain an image of the detected object. The method does not depend on parameters such as bandwidth and dominant frequency of the WIFI signal, so that the final imaging resolution is improved, and imaging information can be enriched.
Description
Technical Field
The exemplary embodiment of the invention relates to the technical field of wireless communication, in particular to an indoor imaging method and device based on WiFi channel state information.
Background
The microwave imaging technology is a popular subject technology, and has wide application in the fields of industrial detection, radar reconnaissance, medical rescue and the like by virtue of good penetrating performance and the characteristic of basically no radiation damage to a human body. However, the existing microwave imaging equipment has the characteristics of large volume, high price, no concealment and the like, so that the microwave imaging equipment is not convenient to use in daily life all the time. And the common WiFi commercial equipment which is widely used and low in price at present can just make up the defect, and can meet the basic requirement of daily indoor imaging.
At present, an orthogonal frequency division multiplexing system is adopted in a WiFi technology based on an 802.11n protocol, and a Channel response, that is, Channel State Information (CSI), superimposed by a multipath signal can be acquired in space. CSI describes the attenuation factors of the signal in each transmission path in the frequency and time domains, such as signal scattering, environmental attenuation, distance attenuation, etc., in the form of complex amplitudes. Therefore, by measuring the wireless signals by using the CSI, fine-grained Channel Frequency Responses (CFRs) of each subcarrier can be obtained, and rich surrounding environment information can be captured, thereby realizing imaging of indoor objects.
The main principle of the WiFi imaging technology is as follows: the signal of the transmitter is transmitted to the surface of an object, then the signal reaches a receiver through a series of processes of reflection, transmission and diffraction, the frequency domain signal distribution of the surface of the object is obtained through backward transmission of the received CSI signal, then Two-Dimensional in-vertical discrete Fourier Transform (IFFT 2) is carried out on discrete points on a plane to obtain the signal intensity, and the three-Dimensional view of the object is recovered. However, the complex amplitude of the channel response presented by CSI during signal propagation and reception is noisy and cannot fully reflect the change of the signal passing through the environment. Meanwhile, due to the fact that the WIFI signal is used for transmitting data instead of an imaging design, each channel is only 20MHz in bandwidth, the resolution ratio is low, and the outline of a target object in the environment cannot be accurately distinguished. Therefore, these problems must be addressed to achieve imaging with commercial WiFi devices.
Disclosure of Invention
In view of the above, an object of the exemplary embodiments of the present invention is to provide an indoor imaging method and apparatus based on WiFi channel state information, so as to solve the problem of low image resolution of a target object during WiFi imaging.
Based on the above object, an exemplary embodiment of the present invention provides an indoor imaging method based on WIFI channel state information, including:
extracting a channel state signal, wherein the channel state signal at least comprises complex amplitude information of the WIFI signal on a transmission path;
combining the omnidirectional radiation model of the channel state signal and the transmission path to carry out path decomposition on the channel state signal to obtain monochromatic plane wave signals of the channel state signal in different propagation directions;
and preprocessing each monochromatic plane wave signal to distinguish amplitude and phase information of different depths of each transmission path, and imaging the detected object according to the amplitude and phase information to obtain an image of the detected object.
In another possible implementation manner of the embodiment of the present invention, with reference to the above description, the preprocessing the monochromatic plane wave signals includes:
and extracting the phase and the amplitude of each monochromatic plane wave signal, and eliminating phase noise generated by line-of-sight propagation, multipath propagation and equipment errors.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the method further includes:
the resolution and the noise of the image information are processed separately to expand the information comprised by the image.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the method further includes:
simplifying the omnidirectional radiation of the WIFI signals in a scalar diffraction manner so that the channel state signals are represented by electric field vectors;
simplification is made by the following formula:
wherein E isθElectric vector for WiFi signal propagation in space, I0Is the feed current, r is the signal propagation distance, and θ is the angle of signal propagation.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the method further includes:
the received channel state signal is linearly transformed by introducing a reference antenna.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the receiving antenna of the image is shifted by a preset spatial frequency to form a receiving surface of the image information;
the signal of each point of the receiving surface is the superposition composition of the monochromatic plane waves, and is expressed by a formula as follows:
wherein A ist(x, y,0) denotes a rear surface of the WIFI signal transmission object, fxAnd fyDistribution represents spatial frequency components of X-axis and Y-axis, "0" represents a point represented by a monochromatic plane wave on the receiving surface;
and obtaining data of a receiving surface through the formula, and acquiring signal amplitude and phase information of any depth to generate the image.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the method further includes:
the monochromatic plane waves are combined to form an integral signal, and reflections and external disturbances are filtered from the integral signal.
In a second aspect, an exemplary embodiment of the present invention further provides an indoor imaging apparatus based on WIFI channel state information, including:
the extraction module is used for extracting a channel state signal, wherein the channel state signal at least comprises complex amplitude information of the WIFI signal on a transmission path;
the analysis module is used for carrying out path decomposition on the channel state signal by combining the omnidirectional radiation model of the channel state signal and the transmission path to obtain monochromatic plane wave signals of the channel state signal in different propagation directions;
and the imaging module is used for preprocessing each monochromatic plane wave signal to distinguish amplitude and phase information of different depths of each transmission path, and imaging the detected object according to the amplitude and phase information to obtain an image of the detected object.
In the above-mentioned indoor imaging device based on WIFI channel state information, the imaging module is further configured to:
and extracting the phase and the amplitude of each monochromatic plane wave signal, and eliminating phase noise generated by line-of-sight propagation, multipath propagation and equipment errors.
The above-mentioned indoor imaging device based on WIFI channel state information, the device further includes:
and the optimization module is used for respectively processing the resolution and the noise of the image information so as to expand the information included in the image.
As can be seen from the foregoing, according to the indoor imaging method and apparatus based on WiFi channel state information provided by the exemplary embodiment of the present invention, since the bandwidth and the dominant frequency of the WiFi signal are both relatively low, and therefore, when the WiFi signal is directly used for indoor imaging, the resolution is relatively low, the present invention does not depend on parameters such as the bandwidth and the dominant frequency of the WiFi signal, but by introducing the reference antenna and setting the aperture and the spatial frequency of the receiving surface, the difference between the complex amplitude information of the original CSI signal and the CSI signal after transmitting the detected object is made, and the final imaging resolution is improved by combining the image information such as the brightness related to the image represented by the phase and the amplitude of the complex amplitude, and the imaging information can be richer.
Drawings
In order to more clearly illustrate the exemplary embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only exemplary embodiments of the present invention, and for those skilled in the art, other drawings may be obtained based on these drawings without inventive effort.
FIG. 1 is a schematic illustration of a propagation path for indoor imaging in an exemplary embodiment of the invention;
FIG. 2 is a schematic illustration of the results of imaging an image of an exemplary embodiment of the present invention;
fig. 3 is a schematic basic flow chart of an indoor imaging method based on WiFi channel state information according to an exemplary embodiment of the present invention;
FIG. 4 is a schematic flow chart illustrating the practice of an exemplary embodiment of the present invention;
FIG. 5 is a schematic diagram of an apparatus embodying exemplary embodiments of the present invention;
FIG. 6 is a schematic diagram of the basic structure of an apparatus according to an exemplary embodiment of the present invention;
fig. 7 is a schematic diagram of an electronic device implementing an indoor imaging method based on WiFi channel state information according to an exemplary embodiment of the invention.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
It should be noted that technical terms or scientific terms used in the exemplary embodiments of the present invention should have a general meaning as understood by those having ordinary skill in the art to which the present disclosure pertains, unless otherwise defined. The use of "first," "second," and similar language in the exemplary embodiments of the invention is not intended to imply any order, quantity, or importance, but rather the intention is to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
It should be noted that the bandwidth of the WIFI signal is small, the image is blurred during direct imaging, and the WIFI signal cannot be used for commercial use, and the method of the present invention is not dependent on the bandwidth, but is set by a delicate device, so that when a receiving surface collects a detected object or CSI data after transmission of the detected object according to a preset aperture and spatial frequency, the image of the detected object is quickly generated according to relevant parameters in the complex amplitude information of the CSI data.
In one implementation of the exemplary embodiment of the present invention, fig. 1 shows a schematic diagram of an application scenario of the method of the present invention, where the application scenario includes:
in the process that a WiFi signal passes through a transmitting end 102 of a commercial WiFi device to reach a receiving plane 103, passes through a surrounding wall 104 and is directly irradiated to an object to be imaged 101, and the like, a plurality of static paths including direct paths 105 and 106, reflected paths 107 and 109, and a diffraction path 108 caused by the object to be imaged reaching a receiving surface are generated.
The distribution of the frequency domain signals on the surface of the detected object can be obtained by carrying out backward propagation through the received CSI signals, and then the signal intensity can be obtained by carrying out two-dimensional inverse Fourier transform, and the three-dimensional view of the detected object can be recovered.
The receiving surface is formed by the receiving antenna in a vertical horizontal plane in the moving process and generally comprises two parameters of an aperture and a spatial frequency, so that the receiving surface is not related to parameters such as bandwidth and/or main frequency of a WIFI signal in the imaging process, and the wavelength, the aperture and the CSI signal of original data of the transmitting end have certain errors, so that the reference antenna is introduced into the antennas of the transmitter and the receiver when the detected object is imaged, and the errors of the CSI signal are eliminated to a certain extent.
According to the expression of the complex amplitude of the CSI signal and the ratio of the receiving antenna to the reference antenna, a linear relation exists, and the linear relation does not influence the image information formed by final imaging, so that fluctuation which is influenced by imaging is eliminated in the calculation process, and the indoor imaging is further refined.
In one implementation of the exemplary embodiment of the present invention, by making the phase in the complex amplitude closer to the actual value, the error caused by the external environment can be eliminated as much as possible.
In the implementation manner of the exemplary embodiment of the present invention, the detected object is a cross-shaped object, the image information formed after the WIFI signal penetrates through the object is shown in fig. 2, and the cross-shaped outline in fig. 2 is the indoor image information formed after the WIFI signal penetrates through the detected object.
In the implementation manner of the exemplary embodiment of the present invention, the transmitting end of the WIFI signal is installed with an Intel5300 network card whose protocol is 802.11n, and the kernel of the network card can realize that the generated WIFI signal is converted into an original CSI signal (channel state signal) during transmission after being modified.
The invention relates to an indoor imaging method and device based on WiFi channel state information, which are mainly applied to a scene of realizing indoor imaging through a WIFI signal, and the basic idea is as follows: the method is independent of parameters such as bandwidth and main frequency of a WIFI signal, and by introducing a reference antenna and setting aperture and spatial frequency of a receiving surface, difference between original CSI signals and complex amplitude information of the CSI signals after the CSI signals penetrate through a detected object is achieved, and a mode of combining image information such as brightness related to an image and represented by phases and amplitudes of complex amplitudes is achieved, so that final imaging resolution is improved, and imaging information can be enriched.
As shown in fig. 3, a basic flow diagram of an indoor imaging method based on WiFi channel state information in an exemplary embodiment of the present invention specifically includes the following steps:
in step 110, extracting a channel state signal, where the channel state signal at least includes complex amplitude information of the WIFI signal on a transmission path;
a channel state signal is extracted from a transmitter of the WIFI signal.
In step 120, the channel state signal is subjected to path decomposition by combining the omnidirectional radiation model of the channel state signal and the transmission path, so as to obtain monochromatic plane wave signals of the channel state signal in different propagation directions;
in step 130, after preprocessing each monochromatic plane wave signal, to distinguish amplitude and phase information of different depths of each transmission path, an imaging process is performed on the detected object according to the amplitude and phase information, so as to obtain an image of the detected object.
Specifically, in a more specific implementation scenario of an exemplary embodiment of the present invention, the method includes:
step 1: a signal propagation model is introduced, parameters of the signal propagation model are shown in FIG. 1, in a given indoor environment, the propagation process of a WIFI signal is analyzed, the propagation of the WiFi signal is simplified into a signal propagation part and a signal diffraction part, the signal propagation comprises direct signal propagation, signal transmission propagation, diffraction propagation after an object is measured and the like, for the indoor wall and other diffraction parts and the non-transmittable direct signal part, the influence on imaging is small and can be ignored, the calculation amount is reduced, and the subsequent analysis is facilitated.
In an implementation manner of the exemplary embodiment of the present invention, the method further includes synthesizing the monochromatic plane waves to form an overall signal, and filtering the reflected and external interference from the overall signal, specifically, filtering the diffracted portion of the wall and the direct portion of the signal which is not transmitted, so as to make the filtered monochromatic plane waves easier to calculate.
Step 2: introducing a diffraction imaging algorithm, diffracting the converted CSI signals after the converted CSI signals pass through the surface of the detected object, and dividing the complex amplitude signals into the superposition of monochromatic plane wave signals in different propagation directions by using an angular spectrum diffraction theory;
the diffractive imaging algorithm will be described in detail later.
And step 3: phase and amplitude extraction is carried out on the CSI signals received through diffraction, and phase noise is eliminated;
and 4, step 4: imaging reduction is carried out on the preprocessed CSI signal, and signal amplitude and phase information at any depth in a path can be obtained;
and 5: the resolution of the received image is improved, noise points in the image are reduced, and the received image result information is richer.
In the exemplary embodiment of the present invention, the transmission and reception of signals may be implemented by a transmitter and a receiver, that is, an existing Wi-Fi device is provided with a transmitting antenna, the receiver receives signals through a receiving antenna, and the antennas on the devices perform CSI data acquisition.
In the process, an introduced reference antenna is fixed at any point near a receiving end by pulling one antenna out of a receiver, and then CSI data from the transmitting end to the point are collected, the data received by the receiving antenna and the reference antenna are different, and the received data is fixed due to the fixed position of the reference antenna, so that when the CSI data received by the receiving antenna in the moving process changes, parameter information such as amplitude and phase related to images in the CSI data at different positions of the receiving surface can be determined by taking the data of the reference antenna as reference.
The ratio of the CSI data of the receive antenna and the reference antenna is phase subtraction with respect to phase, i.e. a phase linear transformation occurs on the original phase.
In step 1, in the exemplary embodiment of the present invention, mutual influence between signals caused by mimo during propagation of WiFi signals and influence of air medium on receiving effect are not considered, so that the WiFi signals are considered as omnidirectional radiation propagating in free space, and thus, the calculation complexity can be reduced by using scalar diffraction, and only electric field vector needs to be considered.
The situation that the WiFi electric field vector propagates in the free space is simplified as follows:
wherein EθElectric vector for propagation of WiFi transmitter signal in space, I0Is the feed current, r is the signal propagation distance, and θ is the angle of signal propagation.
In step 2, since the signals do not all travel along straight lines in the process of arriving at the receiver from the surface of the object to be detected and diffraction occurs, it is necessary to find the diffraction distribution relationship of the CSI signal and to represent the signal at any point in space by using complex amplitude information of other points. Since, in the imaging scene, the observation point (receiving surface) is not in the near-field range from the diffraction aperture (the aperture formed by the diffraction of the detected object, such as a cross-shaped aperture), and the diffraction aperture (the size of the receiving surface) is much larger than the wavelength of the irradiated wave, scalar diffraction theory can be adopted, without considering the coupling relationship between the electric vector and the magnetic vector.
In step 3, due to the complexity of the reason for forming the CSI data, in a real system environment, the measurement result of the CSI is determined by three factors, namely line-of-sight propagation, multipath propagation and equipment error of the signal transmitted to the receiver. Therefore, there is a need to eliminate CSI amplitude offset and CSI phase offset caused by different channels. By carrying out ratio processing on CSI data received by the receiving antenna and the reference antenna, random error interference such as time delay and the like can be eliminated, only linear transformation is introduced to the receiving antenna, and no influence is caused on an imaging result in subsequent diffraction calculation.
In step 4, by using the theory of angular spectrum diffraction, the amplitude and phase of the signal at any point can be digitally reconstructed from the antenna CSI information recorded at the receiving surface, and then the signal amplitude is used to calculate the field intensity of the plane, so as to restore all the information of the plane.
Angle spectrum diffraction theory, kirchhoff diffraction formula:
complex amplitude information of a point (x, y, z) at an arbitrary depth is obtained using all points (x, y,0) on the receiving surface.
In step 5, incoherent white light is used to reduce the intensity of noise spots, the intensities under a plurality of subcarriers in the CSI data are averaged, the imaging result is further optimized, and an image including richer holographic imaging information is obtained.
Further, fig. 4 shows a basic flowchart of an indoor imaging method based on WiFi channel state information according to an exemplary embodiment of the present invention.
In step S01, a signal propagation model is introduced, and assuming that mutual influence between signals and influence of air medium on the receiving effect caused by mimo in the WiFi propagation process are not considered, the WiFi signal may be further approximated to the propagation process of the half-wave symmetric array antenna, and since the electric field vector distribution and the magnetic field vector distribution are both scalars, only the electric field vector needs to be considered here. The electric field distribution radiated by the single half-wave antenna in the free space can be simplified as follows:
wherein EθElectric vector for propagation of WiFi transmitter signal in space, I0Is the feed current, r is the signal propagation distance, and θ is the angle of signal propagation. The direct process signal propagation of the WiFi transmitter can be solved.
In step S02, a diffraction imaging algorithm is introduced, and after obtaining the signal from the WiFi transmitter to the front surface of the object, it is necessary to study the process of the signal from the front surface of the object to be detected to the back surface of the object to be detected through transmission and the subsequent diffraction of the signal. The diffraction imaging algorithm can be decomposed into the following two steps:
1. a propagation process of signal transmission to the rear surface of the detected object;
2. the signal is diffracted into a propagation process reaching the receiver.
Wherein 1, the signal is transmitted to reach the propagation process of the rear surface of the detected object. For the signal transmission section, assume that the incident signal is Ai(x0,y0) The complex amplitude transmission of the diffraction plane aperture is T (x)0,y0) Then, the signal A of the rear surface of the detected object is detectedt(x0,y0) Comprises the following steps:
At(x0,y0)＝Ai(x0，y0)*T(x0，y0)
it can be seen that the phenomenon of bandwidth broadening occurs on the rear surface of the detected object, a monochromatic plane wave different from the WiFi signal propagation direction is introduced, the plane waves are diffracted waves, a series of diffracted waves are generated from the signal on the rear surface of the detected object, and then the diffracted waves are superimposed on the receiving surface to obtain the signal on the receiving surface.
Wherein the propagation process of diffraction to the receiver occurs for the signal. In practical indoor imaging experiments, signals are generally treated as scalar fields, namely transverse and longitudinal axis independent treatment, and the coupling relation of electric vectors and magnetic vectors is not considered, namely scalar diffraction theory is adopted. In this way, as long as the observation point is not within the near field range from the diffraction aperture, and the diffraction aperture is much larger than the wavelength of the illuminating wave, the difference between the result and the vector field is small, which is completely met in the method of the present invention.
In the invention, the observation point is a receiving surface, the diffraction hole refers to the position of the detected object which is diffracted, generally the outline of the detected object, the aperture is the size of the receiving surface, and the spatial frequency refers to the distance between the points of the receiving surface.
The scalar diffraction theory adopted by the invention is kirchhoff diffraction theory, the signal of each point on the receiving surface is regarded as the superposition composition of a plurality of monochromatic plane waves transmitted from the aperture, and the signal of each point is expressed by the following formula:
wherein A ist(x, y,0) denotes the rear surface of the object after transmission, fxAnd fyThe distribution represents spatial frequency components of the X-axis and the Y-axis. The formula shows that the data of the receiving surface can be obtained to obtain the signal amplitude and phase information of any depth, and the image of the WIFI signal passing through the detected object can be generated through the formula.
In step S03, phase and amplitude extraction is performed on the diffracted and received CSI signals, the measured data describes not only the channel characteristics in the pass band but also the characteristics of the signal processing circuit in the baseband, and the method of the exemplary embodiment of the present invention can eliminate the influence of these noises through preprocessing.
The general CSI equation is expressed as follows:
the left side H of the formulai,j,kIndicating the CSI from the i-th transmitting antenna transmission channel to the j-th receiving antenna under the nth channel, the first item on the right side indicating the multipath channel of the signal from the transmitting end to the receiving end, di,j,nDenotes the distance from the i-th transmitting antenna to the j-th receiving antenna in the n-th channel, fkRepresenting the carrier frequency, c represents the speed of light; the second term of the equation represents Cyclic Shift Diversity (CSD), τ from the i transmit antennasiRepresenting a time delay; the third term and the fourth term of the equation respectively represent Sampling Time Offset (STO) and Sampling Frequency Offset (SFO), and ρ and η respectively represent corresponding Sampling Offset coefficients; the last term of the equation represents the beamforming, qi,j、ξi,jRespectively representing the phase and amplitude of the beam formation.
Therefore, the reason for forming the CSI data is complex, and the phase and the amplitude obtained by measurement have certain transformation. Because only the fifth wave beam forming process in the formula influences the amplitude, and the wave beam forming process is linear processing, finally, amplitude information obtained by different frequency data packets synchronously shows regular change, and the influence on the final imaging effect is not great. For the phase, one antenna on the receiving device can be placed on one side and fixed differently to be used as a reference antenna for eliminating the delay offset.
In step S04, the preprocessed CSI signals are subjected to image restoration. After noise in the environment is eliminated, amplitude and phase information of an object plane at any depth from the point can be obtained from the complex amplitude of the receiving recording surface through the back propagation of kirchhoff diffraction, namely, the intensity information of each point on the receiving surface is obtained, and therefore a hologram of the plane can be constructed.
In step S05, the resolution of the received image is increased and noise points in the image are reduced. In order to further optimize the holographic imaging result, incoherent white light is adopted to reduce the intensity of noise spots, and the intensity under a plurality of subcarriers in the CSI data is subjected to average processing. This process suppresses speckle interference by making use of WiFi radiation that is actually white light.
This approach can recover a white light image from the reconstruction of each frequency, similar to the filtering techniques in digital holography. Compared with other denoising optimization technologies, the method cannot reduce the spatial resolution because the method reserves the phase information of each frequency component during acquisition and only executes a non-coherent averaging algorithm in the process of reconstructing the image.
Fig. 5 is a schematic view of a device between an imaging receiving surface and a detected object, where the object is a detected object and is in a cross shape, a transmitting antenna in the figure is a transmitting antenna of a WIFI transmitter, a receiving antenna is a receiving antenna of a receiver, a reference antenna is fixed in position, and is not shown in the figure, the aperture is an aperture of the receiving surface, the receiving surface is the same as an observation point, and the receiving surface is formed by moving the receiving antenna.
It is to be appreciated that the method can be performed by any apparatus, device, platform, cluster of devices having computing and processing capabilities.
Based on the same inventive concept, fig. 6 is a schematic structural diagram of an indoor imaging device based on WIFI channel state information according to an embodiment of the present invention, where the device may be implemented by software and/or hardware, is generally integrated in an intelligent terminal, and may be implemented by an indoor imaging method based on WIFI channel state information. As shown in the figure, the present embodiment provides an indoor imaging device based on WIFI channel state information corresponding to any of the above method embodiments, which mainly includes an extraction module 610, an analysis module 620, and an imaging module 630.
The extracting module 610 is configured to extract a channel state signal, where the channel state signal at least includes complex amplitude information of the WIFI signal on a transmission path;
the analysis module 620 is configured to perform path decomposition on the channel state signal in combination with the omnidirectional radiation model of the channel state signal and the transmission path to obtain monochromatic plane wave signals of the channel state signal in different propagation directions;
the imaging module 630 is configured to perform preprocessing on each monochromatic plane wave signal to distinguish amplitude and phase information of different depths of each transmission path, and perform imaging processing on a detected object according to the amplitude and phase information to obtain an image of the detected object.
In the above indoor imaging apparatus based on WIFI channel state information, the imaging module 630 is further configured to:
and extracting the phase and the amplitude of each monochromatic plane wave signal, and eliminating phase noise generated by line-of-sight propagation, multipath propagation and equipment errors.
The above-mentioned indoor imaging device based on WIFI channel state information, the device further includes:
and the optimization module is used for respectively processing the resolution and the noise of the image information so as to expand the information included in the image.
The imaging module is further configured to simplify omnidirectional radiation of the WIFI signals by scalar diffraction such that the channel state signals are represented by electric field vectors;
simplification is made by the following formula:
wherein E isθElectric vector for WiFi signal propagation in space, I0Is the feed current, r is the signal propagation distance, and θ is the angle of signal propagation.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the apparatus further includes a reference module, configured to:
the received channel state signal is linearly transformed by introducing a reference antenna.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the imaging module is further configured to: moving a receiving antenna of the image by a preset spatial frequency to form a receiving surface of image information;
the signal of each point of the receiving surface is the superposition composition of the monochromatic plane waves, and is expressed by a formula as follows:
wherein A ist(x, y,0) denotes a rear surface of the WIFI signal transmission object, fxAnd fyDistribution represents spatial frequency components of X-axis and Y-axis, "0" represents a point represented by a monochromatic plane wave on the receiving surface;
and obtaining data of a receiving surface through the formula, and acquiring signal amplitude and phase information of any depth to generate the image.
In another possible implementation manner of the embodiment of the present invention, in combination with the above description, the apparatus further includes a signal selection module, configured to:
the monochromatic plane waves are combined to form an integral signal, and reflections and external disturbances are filtered from the integral signal.
For convenience of description, the indoor imaging device based on the WIFI channel state information is respectively described by dividing functions into various modules, and certainly, when the indoor imaging device based on the WIFI channel state information is implemented in the exemplary embodiment of the present invention, the functions of the modules may be implemented in the same software and/or hardware, and the indoor imaging device based on the WIFI channel state information provided in the above embodiment may execute the indoor imaging method based on the WIFI channel state information provided in any embodiment of the present invention, and has functional modules and beneficial effects corresponding to the execution of the method.
Based on the same inventive concept, corresponding to the indoor imaging method based on WIFI channel state information in any of the above embodiments, one or more embodiments of the present specification further provide an electronic device, which includes a memory, a processor, and a computer program stored in the memory and operable on the processor, and when the processor executes the computer program, the indoor imaging method based on WIFI channel state information in any of the above embodiments is implemented.
The foregoing description has been directed to specific embodiments of this disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.
For convenience of description, the above devices are described as being divided into various modules by functions, and are described separately. Of course, the functionality of the various modules may be implemented in the same one or more software and/or hardware in implementing the exemplary embodiments of this invention.
Fig. 7 is a schematic diagram illustrating a more specific hardware structure of an electronic device according to this embodiment, where the electronic device may include: a processor 1010, a memory 1020, an input/output interface 1030, a communication interface 1040, and a bus 1050. Wherein the processor 1010, memory 1020, input/output interface 1030, and communication interface 1040 are communicatively coupled to each other within the device via bus 1050.
The processor 1010 may be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits, and is configured to execute related programs to implement the technical solutions provided in the embodiments of the present disclosure.
The Memory 1020 may be implemented in the form of a ROM (Read Only Memory), a RAM (Random Access Memory), a static storage device, a dynamic storage device, or the like. The memory 1020 may store an operating system and other application programs, and when the technical solution provided by the embodiment of the present disclosure is implemented by software or firmware, the relevant program codes are stored in the memory 1020 and called by the processor 1010 to execute the WIFI channel state information based indoor imaging method according to the embodiment of the present disclosure.
The input/output interface 1030 is used for connecting an input/output module to input and output information. The i/o module may be configured as a component in a device (not shown) or may be external to the device to provide a corresponding function. The input devices may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output devices may include a display, a speaker, a vibrator, an indicator light, etc.
The communication interface 1040 is used for connecting a communication module (not shown in the drawings) to implement communication interaction between the present apparatus and other apparatuses. The communication module can realize communication in a wired mode (such as USB, network cable and the like) and also can realize communication in a wireless mode (such as mobile network, WIFI, Bluetooth and the like).
Bus 1050 includes a path that transfers information between various components of the device, such as processor 1010, memory 1020, input/output interface 1030, and communication interface 1040.
It should be noted that although the above-mentioned device only shows the processor 1010, the memory 1020, the input/output interface 1030, the communication interface 1040 and the bus 1050, in a specific implementation, the device may also include other components necessary for normal operation. In addition, those skilled in the art will appreciate that the above-described apparatus may also include only those components necessary to implement the embodiments of the present description, and not necessarily all of the components shown in the figures.
The electronic device of the above embodiment is used to implement the corresponding indoor imaging method based on the WIFI channel state information in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiment, which are not described herein again.
Exemplary embodiments of the present invention also provide a non-transitory computer readable storage medium, including permanent and non-permanent, removable and non-removable media, that can implement information storage by any method or technology, corresponding to the method of any exemplary embodiment of the present invention, based on the same inventive concept. The information may be computer readable instructions, data structures, programs, modules of the programs themselves, or other data. Examples of the storage medium of the computer include, but are not limited to: phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technologies, compact disc read only memory (CD-ROM), Digital Versatile Disc (DVD) or other optical storage, magnetic tape storage or other magnetic storage devices, or any other non-transmission medium, may be used to store information that may be accessed by a computing device for performing WIFI channel state information based room imaging methods described in exemplary embodiments of the invention.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the idea of the present disclosure, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the exemplary embodiments of the present invention as described above, which are not provided in detail for the sake of brevity.
In addition, well-known power/ground connections to Integrated Circuit (IC) chips and other components may or may not be shown within the provided figures for simplicity of illustration and discussion, and so as not to obscure the exemplary embodiments of the invention. Furthermore, devices may be shown in block diagram form in order to avoid obscuring exemplary embodiments of the present invention, and this also takes into account the fact that specifics with respect to implementation of such block diagram devices are highly dependent upon the platform within which the exemplary embodiments of the present invention are to be implemented (i.e., specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the disclosure, it should be apparent to one skilled in the art that the example embodiments of the disclosure can be practiced without, or with variation of, these specific details. Accordingly, the description is to be regarded as illustrative instead of restrictive.
While the present disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. For example, other memory architectures (e.g., dynamic ram (dram)) may use the discussed embodiments.
The exemplary embodiments of the invention are intended to embrace all such alternatives, modifications and variances that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of the exemplary embodiments of the invention are intended to be included within the scope of the disclosure.
Claims (10)
1. An indoor imaging method based on WIFI channel state information is characterized by comprising the following steps:
extracting a channel state signal, wherein the channel state signal at least comprises complex amplitude information of the WIFI signal on a transmission path;
combining the omnidirectional radiation model of the channel state signal and the transmission path to carry out path decomposition on the channel state signal to obtain monochromatic plane wave signals of the channel state signal in different propagation directions;
and preprocessing each monochromatic plane wave signal to distinguish amplitude and phase information of different depths of each transmission path, and imaging the detected object according to the amplitude and phase information to obtain an image of the detected object.
2. The WIFI channel state information based indoor imaging method of claim 1, wherein the preprocessing each of the monochromatic plane wave signals includes:
and extracting the phase and the amplitude of each monochromatic plane wave signal, and eliminating phase noise generated by line-of-sight propagation, multipath propagation and equipment errors.
3. The WIFI channel state information based indoor imaging method of claim 1, the method further comprising:
the resolution and the noise of the image information are processed separately to expand the information comprised by the image.
4. The WIFI channel state information based indoor imaging method of claim 1, the method further comprising:
simplifying the omnidirectional radiation of the WIFI signals in a scalar diffraction manner so that the channel state signals are represented by electric field vectors;
simplification is made by the following formula:
wherein E isθElectric vector for WiFi signal propagation in space, I0Is the feed current, r is the signal propagation distance, and θ is the angle of signal propagation.
5. The WIFI channel state information based indoor imaging method of any one of claims 1 to 4, wherein the method further comprises:
the received channel state signal is linearly transformed by introducing a reference antenna.
6. The WIFI channel status information-based indoor imaging method according to any one of claims 1 to 4, wherein a receiving antenna of the image is moved by a preset spatial frequency to form a receiving surface of image information;
the signal of each point of the receiving surface is the superposition composition of the monochromatic plane waves, and is expressed by a formula as follows:
wherein A ist(x, y,0) denotes a rear surface of the WIFI signal transmission object, fxAnd fyDistribution represents spatial frequency components of X-axis and Y-axis, "0" represents a point represented by a monochromatic plane wave on the receiving surface;
and obtaining data of a receiving surface through the formula, and acquiring signal amplitude and phase information of any depth to generate the image.
7. The WIFI channel state information based indoor imaging method of claim 6, the method further comprising:
the monochromatic plane waves are combined to form an integral signal, and reflections and external disturbances are filtered from the integral signal.
8. An indoor imaging device based on WIFI channel state information, comprising:
the extraction module is used for extracting a channel state signal, wherein the channel state signal at least comprises complex amplitude information of the WIFI signal on a transmission path;
the analysis module is used for carrying out path decomposition on the channel state signal by combining the omnidirectional radiation model of the channel state signal and the transmission path to obtain monochromatic plane wave signals of the channel state signal in different propagation directions;
and the imaging module is used for preprocessing each monochromatic plane wave signal to distinguish amplitude and phase information of different depths of each transmission path, and imaging the detected object according to the amplitude and phase information to obtain an image of the detected object.
9. The WIFI channel state information based indoor imaging device of claim 1, wherein the imaging module is further configured to:
and extracting the phase and the amplitude of each monochromatic plane wave signal, and eliminating phase noise generated by line-of-sight propagation, multipath propagation and equipment errors.
10. The WIFI channel state information based indoor imaging device of claim 1, the device further comprising:
and the optimization module is used for respectively processing the resolution and the noise of the image information so as to expand the information included in the image.
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| CN110443206A (en) * | 2019-08-07 | 2019-11-12 | 北京邮电大学 | A kind of human body attitude image generating method and device based on Wi-Fi signal |
| US20200311420A1 (en) * | 2019-03-29 | 2020-10-01 | Board Of Trustees Of Michigan State University | Imaging System Using WiFi Signals |
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| CN110245588A (en) * | 2019-05-29 | 2019-09-17 | 西安交通大学 | A kind of fine granularity estimation method of human posture based on radio frequency signal |
| CN110443206A (en) * | 2019-08-07 | 2019-11-12 | 北京邮电大学 | A kind of human body attitude image generating method and device based on Wi-Fi signal |
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