A real-time breathing detection method based on wireless channel

Abstract

The present invention discloses a real-time respiration detection method based on a wireless channel, which is applied to a receiving device in a communication base station. The method comprises: receiving a reference signal, which is sent by a transmitting device in the communication base station and reaches the receiving device via different paths, and which includes multiple subcarriers; detecting whether a target person is present in the environment based on channel state information (CSI) data obtained from the reference signal; determining a first respiratory frequency of the target person based on the multiple subcarriers when the target person is present in the environment; performing autocorrelation on each subcarrier to obtain a periodic signal corresponding to the target person's respiration for each subcarrier; determining available subcarriers from the multiple subcarriers based on the periodic signal and the first respiratory frequency; and calculating a final second respiratory frequency of the target person using the periodic signal corresponding to the available subcarriers. The present invention can ensure the accuracy of respiratory frequency detection while saving costs, and has the advantages of being non-invasive and convenient.

Description

Technical Field

[0001] The present invention belongs to the field of radio technology, and in particular relates to a real-time breathing detection method based on a wireless channel. Background Art

[0002] In recent years, methods for respiration detection based on home Wi-Fi infrastructure have garnered widespread attention. While Wi-Fi's Received Signal Strength (RSS) is commonly used for sensing, RSS suffers from low detection accuracy and susceptibility to noise. In contrast, Channel State Information (CSI) is more sensitive to respiration. The introduction of the Fresnel zone concept provides theoretical guidance for the relationship between location and performance in Wi-Fi CSI-based respiration detection, resulting in more accurate results.

[0003] In existing technologies, the HRD method selects the subcarrier with the largest variance based on the variance of the CSI amplitude. However, variance is not a good selection criterion, and individual subcarriers are easily affected, resulting in large errors. The ResBeat method estimates the target person's respiratory rate by modeling the amplitude and phase difference of the CSI and, after filtering and noise reduction, selecting the subcarrier with the highest respiratory energy. This method offers high accuracy but requires a longer time window and has lower temporal resolution. Furthermore, these methods do not consider situations where the target person temporarily leaves the detection environment, which is not conducive to cost savings. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a real-time respiration detection method based on a wireless channel. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] The present invention provides a real-time breathing detection method based on a wireless channel, which is applied to a receiving device in a communication base station;

[0006] The method comprises:

[0007] receiving a reference signal, where the reference signal is sent by a transmitting device in a communication base station and reaches a receiving device via different paths, and the reference signal includes multiple subcarriers;

[0008] Detecting whether a target human body exists in an environment based on channel state information (CSI) data obtained from the reference signal;

[0009] When a target human body exists in the environment, determining a first respiratory frequency of the target human body according to the multiple subcarriers;

[0010] Performing autocorrelation on each of the subcarriers to obtain a periodic signal of the target human body breathing corresponding to each subcarrier;

[0011] determining an available subcarrier from the plurality of subcarriers according to the periodic signal and the first respiratory frequency;

[0012] The final second respiratory frequency of the target human body is calculated using the periodic signal corresponding to the available subcarrier.

[0013] In one embodiment of the present invention, the step of detecting whether a target human body exists in an environment based on channel state information (CSI) data obtained from the reference signal includes:

[0014] Acquire CSI data from the reference signal, and segment the CSI data using a preset window;

[0015] Obtain the amplitudes of the multiple subcarriers corresponding to each segment of CSI data and perform fast Fourier transform, and record the frequency point f corresponding to the highest energy point of the i-th subcarrier within the preset respiratory frequency range from the result of the fast Fourier transform. i,max ;

[0016] Count the number of subcarriers P corresponding to each frequency point r ;

[0017] According to the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max , detect whether there is a target human body in the environment.

[0018] In one embodiment of the present invention, according to the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max ,The steps of detecting whether there is a target human body in the environment include:

[0019] Compare the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max and a first preset threshold value; the first preset threshold value is 70% of the number of subcarriers;

[0020] When the number of subcarriers corresponding to each frequency point P r The maximum value (P r ) max When the value is greater than the first preset threshold, it indicates that the target human body exists in the environment; otherwise, it indicates that the target human body does not exist in the environment.

[0021] In one embodiment of the present invention, when a target human body exists in the environment, the step of determining the first respiratory frequency of the target human body according to the multiple subcarriers includes:

[0022] The maximum value (P r ) max The corresponding frequency point is determined as the first respiratory frequency of the target human body.

[0023] In one embodiment of the present invention, the step of determining an available subcarrier from the plurality of subcarriers according to the periodic signal and the first respiratory frequency includes:

[0024] For the periodic signal corresponding to each subcarrier, determine the frequency, the amplitude of the first peak, and the amplitude of the first trough of the periodic signal;

[0025] Calculating a first difference between the amplitude of the first peak and the amplitude of the first trough;

[0026] calculating a second difference between the first respiratory frequency and the frequency of the periodic signal;

[0027] Whether each subcarrier is an available subcarrier is determined according to the first difference, the second difference, and the amplitude of the first peak.

[0028] In one embodiment of the present invention, the step of determining whether each subcarrier is an available subcarrier based on the first difference, the second difference, and the amplitude of the first peak includes:

[0029] determining whether the second difference is less than a second preset threshold and whether both the amplitude of the first peak and the first difference are greater than a third preset threshold;

[0030] If so, the subcarrier corresponding to the periodic signal is determined as an available subcarrier.

[0031] In one embodiment of the present invention, the step of calculating the final second respiratory frequency of the target human body using the periodic signal corresponding to the available subcarrier includes:

[0032] The frequency average of the periodic signal corresponding to the available subcarrier is calculated to obtain a final second respiratory frequency of the target human body.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention provides a real-time respiration detection method based on wireless channels. This method utilizes existing base stations to transmit and receive modulated reference signals. A receiving device demodulates the CSI data from the received reference signals and analyzes the CSI data to detect the presence of a target person in the environment, thus reducing overhead. Furthermore, when a target person is present in the environment, the present invention performs autocorrelation processing on each subcarrier, selects an available subcarrier based on the resulting periodic signal, and then fuses the frequencies of the available subcarriers corresponding to the periodic signal to determine the target person's respiratory rate. This method not only ensures the accuracy of respiratory rate detection but also offers the advantages of being non-invasive and convenient.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of a real-time breathing detection method based on a wireless channel provided by an embodiment of the present invention;

[0037] Figure 2a This is a schematic diagram of a result of human detection in an environment provided by an embodiment of the present invention;

[0038] Figure 2b is another schematic diagram of the results of human detection in an environment provided by an embodiment of the present invention;

[0039] Figure 3 1 is a waveform diagram of a periodic signal provided by an embodiment of the present invention;

[0040] Figure 4 1 is a waveform diagram of a periodic signal slightly longer than one respiratory cycle provided by an embodiment of the present invention;

[0041] Figure 5 3 is a waveform diagram of periodic signals corresponding to all subcarriers provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0043] Figure 1 This is a flow chart of a real-time breathing detection method based on a wireless channel provided by an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a real-time breathing detection method based on a wireless channel, which is applied to a receiving device in a communication base station;

[0044] The above methods include:

[0045] S1. Receive a reference signal. The reference signal is sent by a transmitting device in a communication base station and reaches a receiving device via different paths. The reference signal includes multiple subcarriers.

[0046] S2. Detect whether a target human body exists in the environment based on the channel state information (CSI) data obtained from the reference signal;

[0047] S3. When a target human body exists in the environment, determining a first respiratory frequency of the target human body according to the multiple subcarriers;

[0048] S4. Perform autocorrelation on each subcarrier to obtain a periodic signal of the target human body's breathing corresponding to each subcarrier;

[0049] S5. Determine an available subcarrier from a plurality of subcarriers according to the periodic signal and the first respiratory frequency;

[0050] S6. Calculate the final second respiratory frequency of the target human body using the periodic signal corresponding to the available subcarrier.

[0051] This embodiment can utilize existing 4G communication base stations for real-time respiration detection. Specifically, the communication base station includes a receiving device R and a transmitting device T. During the detection process, the transmitting device T sends a modulated reference signal. The reference signal reaches the receiving device through different paths, such as the LOS path, reflection from the ground and walls, and reflection from the target person. These signals with different propagation paths are superimposed at the receiving antenna of the receiving device R. Therefore, the reference signal received by the receiving device R actually includes environmental information and the target person's respiration information.

[0052] In the above steps S2-S3, the receiving device R extracts CSI data from the received reference signal. The CSI data includes the amplitude characteristics and phase characteristics of the corresponding reference signal. Figure 2a This is a schematic diagram of a result of human detection in an environment provided by an embodiment of the present invention. Figure 2b This is another schematic diagram of the results of human detection in the environment provided by the embodiment of the present invention. Figure 2a As shown in the figure, in the absence of human presence, there is almost no periodic motion in the environment, and the reference signal received by the receiving device R will not be affected by periodicity. At this time, the CSI data demodulated by the receiving antenna is messy noise, which is converted into randomly distributed frequency points in the frequency domain. Generally speaking, human breathing is periodic, so when a person breathes normally, the rise and fall of the chest will also show periodic changes, and the signal will therefore be affected by periodic motion, such as Figure 2b As shown, a frequency point in the frequency domain will have concentrated energy, that is, the vertical coordinate of this frequency point will be higher than the vertical coordinates of other frequency points. Therefore, this embodiment can detect whether there is a target human body in the environment through CSI data.

[0053] If a target person is present in the environment, the approximate respiratory frequency of the target person, i.e., the first respiratory frequency, is calculated, and further precise respiratory frequency detection is performed. Specifically, autocorrelation is performed on each subcarrier to obtain a periodic signal, which is then low-pass filtered to remove high-frequency noise. For example, if a reference signal includes 200 subcarriers, 200 periodic signals will be obtained after autocorrelation processing. This embodiment selects an available subcarrier from the 200 subcarriers based on information such as the frequency of the periodic signal, the amplitude of the first peak, and the amplitude of the first trough. Ultimately, the precise second respiratory frequency of the target person in the environment is determined based on the periodic signals of the available subcarriers.

[0054] Optionally, in step S2, the step of detecting whether a target human body exists in the environment based on the channel state information CSI data obtained from the reference signal includes:

[0055] S201, obtaining CSI data from a reference signal, and segmenting the CSI data using a preset window;

[0056] S202, obtain the amplitudes of multiple subcarriers corresponding to each segment of CSI data and perform fast Fourier transform, and record the frequency point f corresponding to the highest energy point of the i-th subcarrier within the preset respiratory frequency range from the result of the fast Fourier transform. i,max ;

[0057] S203: Count the number of subcarriers P corresponding to each frequency point. r ;

[0058] S204, according to the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max , detect whether there is a target human body in the environment.

[0059] It should be understood that during the real-time detection process, the receiving antenna will continuously demodulate the CSI data from the received reference signal, so the CSI data can be segmented using a preset window; wherein, the larger the window length of the preset window, the higher the frequency resolution and the lower the time resolution. Considering that step S2 is only for detecting the presence of personnel, there is no need to set an excessively high frequency resolution. For example, in this embodiment, the window length T of the preset window is set to W 20s.

[0060] Still taking the reference signal including 200 subcarriers as an example, after segmenting the CSI data, the amplitude of the 200 subcarriers corresponding to each segment of CSI data is fast Fourier transformed, and the preset respiratory frequency range f is recorded based on the result of the fast Fourier transform. W The frequency point f corresponding to the highest energy point of each subcarrier i,max, and then count each frequency point f i,max The corresponding number of subcarriers P r , so according to the number of subcarriers P r The maximum value (P r ) max Detect whether there is a target human body in the environment.

[0061] Optionally, the preset respiratory frequency range f W is [0.16Hz, 0.5Hz].

[0062] In the above step S203, according to the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max ,The steps of detecting whether there is a target human body in the environment include:

[0063] Compare the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max and a first preset threshold; the first preset threshold is 70% of the number of subcarriers;

[0064] When the number of subcarriers corresponding to each frequency point P r The maximum value (P r ) max When it is greater than the first preset threshold, it indicates that the target human body exists in the environment; otherwise, it indicates that the target human body does not exist in the environment.

[0065] Based on the above analysis, it can be seen that when there are people in the environment, the reference signal is affected by the periodic movement of breathing during propagation, and energy concentration will appear at a certain frequency point in the frequency domain. However, considering the influence of factors such as multipath on some subcarriers, there may be a situation where the frequency point with the maximum energy does not correspond to the breathing frequency. Therefore, this embodiment sets a first preset threshold. Specifically, when (P r ) max When it is greater than the first preset threshold, it means that only more than 70% of the subcarriers have f i,max Only when they are at the same frequency point can we judge that there is a target human body in the environment. On the contrary, if (P r ) max If the value is less than or equal to the first preset threshold, it indicates that the target human body does not exist in the current environment, and only the next segment of CSI data needs to be waited for, which is beneficial to saving costs.

[0066] In addition, it should be understood that this embodiment can eliminate the influence of low-frequency components and high-frequency components by presetting the respiratory frequency range, thereby making the detection result more accurate.

[0067] Optionally, when a target human body exists in the environment, the step of determining a first respiratory frequency of the target human body according to multiple subcarriers includes:

[0068] The maximum value (P r ) max The corresponding frequency point is determined as the first respiratory frequency of the target human body.

[0069] It should be noted that, since a higher frequency resolution is not set when the CSI data is segmented, according to (P r ) max The determined frequency point is only the approximate breathing frequency of the target human body.

[0070] In view of this, this embodiment further performs accurate frequency detection.

[0071] Figure 3 FIG is a waveform diagram of a periodic signal provided by an embodiment of the present invention. Figure 3 In the above step S5, the step of determining an available subcarrier from a plurality of subcarriers according to the periodic signal and the first respiratory frequency includes:

[0072] S501: For a periodic signal corresponding to each subcarrier, determine the frequency, the amplitude of the first peak, and the amplitude of the first trough of the periodic signal;

[0073] S502, calculating a first difference between the amplitude of the first peak and the amplitude of the first trough;

[0074] S503, calculating a second difference between the first respiratory frequency and the frequency of the periodic signal;

[0075] S504: Determine whether each subcarrier is an available subcarrier according to the first difference, the second difference, and the amplitude of the first peak.

[0076] Figure 4 : is a waveform diagram of a periodic signal slightly longer than a respiratory cycle provided by an embodiment of the present invention. Figure 3-4 As shown, the horizontal axis represents the time delay and the vertical axis represents the amplitude. In the periodic signal corresponding to each subcarrier, the horizontal axis corresponding to the first peak is the period, and its reciprocal corresponds to the frequency. Figure 4 The respiratory frequency can be calculated by the above method if the periodic signal length is slightly longer than one respiratory cycle. ACF Slightly longer than a breathing cycle, such as 5s, gradually sliding the window can achieve the purpose of real-time breathing detection.

[0077] Figure 5 : is a waveform diagram of a periodic signal corresponding to all subcarriers provided in an embodiment of the present invention. Specifically, Figure 5 As shown in the figure, multiple subcarriers correspond to multiple periodic signals. However, due to the influence of the environment and multipath, some subcarriers cannot obtain a good periodic signal waveform. Therefore, the following three indicators can be used to screen the subcarriers:

[0078] (1) The frequency of the first peak in the periodic signal, used to measure the respiratory rate of the target person;

[0079] (2) The amplitude of the first peak. The larger the peak amplitude, the greater the energy of the periodic signal contained.

[0080] (3) The difference between the amplitudes of the first peak and the first trough is used to measure the possibility of the existence of a peak.

[0081] Optionally, in step S504, the step of determining whether each subcarrier is an available subcarrier according to the first difference, the second difference, and the amplitude of the first peak includes:

[0082] Determining whether the second difference is less than a second preset threshold and whether both the amplitude of the first peak and the first difference are greater than a third preset threshold;

[0083] If so, the subcarrier corresponding to the periodic signal is determined as an available subcarrier.

[0084] In this embodiment, the larger the first difference between the amplitude of the first peak and the amplitude of the first trough, and the larger the amplitude of the first peak, the stronger the respiratory information contained in the subcarrier corresponding to the periodic signal. Therefore, when the second difference is less than the second preset threshold, and both the amplitude of the first peak and the first difference are greater than the third preset threshold, the subcarrier corresponding to the periodic signal is determined to be a usable subcarrier.

[0085] In the above step S6, the step of calculating the final second respiratory frequency of the target human body using the periodic signal corresponding to the available subcarrier includes:

[0086] The frequency average of the periodic signal corresponding to the available subcarrier is calculated to obtain the final second respiratory frequency of the target human body.

[0087] It can be seen from the above embodiments that the beneficial effects of the present invention are:

[0088] The present invention provides a real-time respiration detection method based on wireless channels. This method utilizes existing base stations to transmit and receive modulated reference signals. A receiving device demodulates the CSI data from the received reference signals and analyzes the CSI data to detect the presence of a target person in the environment, thus reducing overhead. Furthermore, when a target person is present in the environment, the present invention performs autocorrelation processing on each subcarrier, selects an available subcarrier based on the resulting periodic signal, and then fuses the frequencies of the available subcarriers corresponding to the periodic signal to determine the target person's respiratory rate. This method not only ensures the accuracy of respiratory rate detection but also offers the advantages of being non-invasive and convenient.

[0089] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0090] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0091] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art can understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims.

Claims

1. A real-time breathing detection method based on wireless channels, characterized in that: Receiving equipment used in communication base stations; The method comprises: receiving a reference signal, where the reference signal is sent by a transmitting device in a communication base station and reaches a receiving device via different paths, and the reference signal includes multiple subcarriers; Detecting whether a target human body exists in an environment based on channel state information (CSI) data obtained from the reference signal; When a target human body exists in the environment, determining a first respiratory frequency of the target human body according to the multiple subcarriers; Performing autocorrelation on each of the subcarriers to obtain a periodic signal of the target human body breathing corresponding to each subcarrier; determining an available subcarrier from the plurality of subcarriers according to the periodic signal and the first respiratory frequency; Calculating a final second respiratory frequency of the target human body using the periodic signal corresponding to the available subcarrier; The step of detecting whether a target human body exists in an environment based on the channel state information CSI data obtained from the reference signal includes: Acquire CSI data from the reference signal and segment the CSI data using a preset window; obtain the amplitude of the multiple subcarriers corresponding to each segment of CSI data and perform fast Fourier transform, and record the frequency point f corresponding to the highest energy point of the i-th subcarrier within the preset respiratory frequency range from the result of the fast Fourier transform. i,max ; Count the number of subcarriers P corresponding to each frequency point r ; According to the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max , detect whether there is a target human body in the environment; According to the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max ,The steps of detecting whether there is a target human body in the environment include: Compare the number of subcarriers P corresponding to each frequency point r The maximum value (P r ) max and the first preset threshold; the first preset threshold is 70% of the number of subcarriers; when the number of subcarriers corresponding to each frequency point P r The maximum value (P r ) max When the value is greater than a first preset threshold, it indicates that the target human body exists in the environment; otherwise, it indicates that the target human body does not exist in the environment; When a target human body exists in the environment, the step of determining a first respiratory frequency of the target human body according to the multiple subcarriers includes: The maximum value (P r ) max The corresponding frequency point is determined as the first respiratory frequency of the target human body.

2. The real-time breathing detection method based on wireless channel according to claim 1, characterized in that The step of determining an available subcarrier from the plurality of subcarriers according to the periodic signal and the first respiratory frequency includes: For the periodic signal corresponding to each subcarrier, determine the frequency, the amplitude of the first peak, and the amplitude of the first trough of the periodic signal; Calculating a first difference between the amplitude of the first peak and the amplitude of the first trough; calculating a second difference between the first respiratory frequency and the frequency of the periodic signal; Whether each subcarrier is an available subcarrier is determined according to the first difference, the second difference, and the amplitude of the first peak.

3. The real-time breathing detection method based on wireless channel according to claim 2, characterized in that: The step of determining whether each subcarrier is an available subcarrier according to the first difference, the second difference, and the amplitude of the first peak includes: determining whether the second difference is less than a second preset threshold and whether both the amplitude of the first peak and the first difference are greater than a third preset threshold; If so, the subcarrier corresponding to the periodic signal is determined as an available subcarrier.

4. The real-time breathing detection method based on wireless channel according to claim 3, characterized in that: The step of calculating the final second respiratory frequency of the target human body using the periodic signal corresponding to the available subcarrier comprises: The frequency average of the periodic signal corresponding to the available subcarrier is calculated to obtain a final second respiratory frequency of the target human body.

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