Wireless sensor network signal attenuation compensation method in mine tunnel multipath environment

Abstract

The application discloses a wireless sensor network signal attenuation compensation method in a mine tunnel multipath environment and relates to the technical field of mine wireless communication and signal processing. The specific implementation scheme is as follows: a receiving device measures and obtains a multipath propagation response distribution by performing propagation response measurement on periodic wireless detection transmission, performs statistical fusion on each path in a preset statistical time range after phase unwrapping and linear phase correction, calculates the stability of a propagation path and selects a structure stable propagation path, determines wireless transmission matching parameters according to the structure stable propagation path set and feeds back the wireless transmission matching parameters to a transmitting device, and the transmitting device adjusts a transmission time and a transmission amplitude distribution according to the wireless transmission matching parameters, so that the electromagnetic wave components of each structure stable propagation path are superposed in phase at the receiving device. According to the application, the statistically stable propagation path in the mine tunnel can be selectively pre-compensated, and the received signal amplitude is enhanced.

Description

Technical Field

[0001] This application relates to the field of wireless communication and signal processing technology in mines, specifically to a method for compensating for signal attenuation in wireless sensor networks in multipath environments of mine roadways. Background Technology

[0002] In the environment of mine roadways, wireless sensor network nodes are deployed at different locations in the roadway to monitor parameters such as gas concentration, temperature, and equipment operating status. The transmitting and receiving nodes communicate via radio electromagnetic waves. Since mine roadways are narrow and confined spaces, electromagnetic waves will be reflected multiple times at the roof, floor, and side walls of the roadway during propagation, in addition to the direct path, forming multiple wireless propagation paths. Each wireless propagation path has different propagation delays, amplitude attenuation, and phase changes. These paths overlap at the receiving node, resulting in multipath fading, which causes significant fluctuations in the received signal strength and seriously affects the communication reliability of the wireless sensor network. In existing technologies, channel estimation and equalization compensation methods are commonly used to address signal attenuation issues in multipath environments in mine roadways. The receiving node uses pilot sequences periodically transmitted by the transmitting node to estimate the wireless propagation channel in real time, obtaining the channel's frequency response or impulse response. Then, inverse filtering is applied to the received signal using methods such as zero-forcing equalization or minimum mean square error equalization to compensate for signal distortion caused by multipath propagation. These methods require high real-time channel estimation, necessitating the retransmission of pilot sequences and channel estimation within each channel coherence time, thus consuming significant communication bandwidth. Another existing technology employs a time-reversal mirror method. The receiving node first receives the probe signal transmitted by the transmitting node, records the channel impulse response, and then reverses the time of the impulse response to use it as precoding coefficients, feeding them back to the transmitting node. The transmitting node uses these precoding coefficients to precode subsequent signals, automatically achieving time alignment and phase focusing at the receiving node after the signal propagates through the multipath channel. This method utilizes the spatial focusing effect of multipath propagation and eliminates the need for frequent updates to the channel estimation results. The existing technologies have the following shortcomings: When estimating and compensating for multipath propagation, the existing methods include all distinguishable wireless propagation paths obtained from channel estimation in the compensation process without distinguishing the statistical stability of the propagation paths. Propagation paths formed by fixed reflective structures such as the roof, floor, and side walls of mine roadways remain statistically stable over a long period of time, with their propagation delay, amplitude, and phase parameters changing slowly. However, propagation paths caused by random scatterers such as moving mine cars, personnel, or temporarily stacked equipment in the roadway have parameters that change rapidly over time and are not statistically stable. Compensating for statistically unstable random scattering paths together with statistically stable structural paths not only does not help improve signal quality but also introduces additional compensation errors due to the time fluctuations of unstable path parameters, thus reducing the compensation effect. Summary of the Invention

[0003] In view of this, the purpose of this application is to provide a method for signal attenuation compensation of wireless sensor networks in a multipath environment of mine roadways. By selecting structurally stable propagation paths from the multipath propagation environment of mine roadways and performing pre-compensation based on these paths, the electromagnetic wave components of each structurally stable propagation path can be superimposed in phase at the receiving device, thereby achieving the effect of compensating for signal attenuation and improving communication reliability.

[0004] According to a first aspect of this application, a method for compensating for signal attenuation in a wireless sensor network under multipath conditions in mine roadways is provided, comprising: The receiving device measures the propagation response of the wireless detection transmission periodically transmitted by the transmitting device, and obtains the multipath propagation response distribution including the propagation delay parameters, amplitude attenuation parameters and phase change parameters of each wireless propagation path. Phase difference calculation is performed on the phase change parameters of the same wireless propagation path in multiple consecutive multipath propagation response distributions to extract the propagation phase drift caused by the local oscillator frequency deviation between transceivers. Based on the propagation phase drift, phase unwrapping and linear phase correction processing are performed on each multipath propagation response distribution path by path. Within a preset statistical time range, the processed multipath propagation response distribution is statistically fused path by path to obtain the statistical propagation response parameters and amplitude fluctuation characteristic parameters corresponding to each wireless propagation path. The propagation path stability is obtained from these two parameters. Propagation paths whose propagation path stability exceeds a preset threshold are determined as structurally stable propagation paths, thus forming a set of structurally stable propagation paths. By determining the wireless transmission matching parameters based on the set of structurally stable propagation paths, the wireless transmission matching parameters are associated with the propagation path stability, the conjugate value of the statistical propagation response parameters, and the propagation delay parameters corresponding to each structurally stable propagation path. The wireless transmission matching parameters are sent to the transmitting device. The transmitting device adjusts the transmission time and transmission amplitude distribution according to the wireless transmission matching parameters, so that the electromagnetic wave components of each structurally stable propagation path after the electromagnetic wave propagates through the multipath of the mine roadway are superimposed in phase at the receiving device. The receiving device periodically re-executes the above steps to update the set of structurally stable propagation paths and the wireless transmission matching parameters, forming a closed-loop adaptive wireless propagation in the mine roadway.

[0005] In some embodiments, obtaining the multipath propagation response distribution, which includes propagation delay parameters, amplitude attenuation parameters, and phase change parameters for each wireless propagation path, specifically includes: The receiving device receives the wireless detection transmission periodically transmitted by the transmitting device, extracts the propagation response parameters from the known detection waveform in the received signal, and determines the propagation delay parameters, amplitude attenuation parameters, and phase change parameters corresponding to each wireless propagation path based on the matching relationship between the received signal and the known detection waveform. The set of propagation delay parameters, amplitude attenuation parameters, and phase change parameters corresponding to all wireless propagation paths is taken as the multipath propagation response distribution.

[0006] In some embodiments, extracting the propagation phase drift caused by the local oscillator frequency deviation between the transceivers specifically includes: Phase unwrapping is performed on the phase change parameters of the same wireless propagation path in multiple continuously acquired multipath propagation response distributions to eliminate phase jumps generated by the phase change parameters within the periodic value range. Differential calculations are performed on the phase change parameters of two adjacent measurements after unwinding to obtain the phase difference sequence corresponding to the wireless propagation path; linear fitting is performed based on the time relationship between the phase difference sequence and the corresponding propagation response measurement time, and the slope of the fitted line is determined as the propagation phase drift rate caused by the local oscillator frequency deviation between the transceiver devices; the propagation phase drift is determined based on the propagation phase drift rate and the propagation response measurement time interval. Based on the propagation phase drift, linear phase correction is performed path-by-path on the multipath propagation response distribution, specifically including: Using the moment of the first propagation response measurement as the phase reference zero point, the time offset of the measurement moment corresponding to each propagation response measurement relative to the moment of the first propagation response measurement is obtained; the propagation phase drift is multiplied by the time offset to obtain the cumulative phase drift of that propagation response measurement. For each wireless propagation path in the multipath propagation response distribution obtained after phase unwrapping processing in this propagation response measurement, the phase change parameter of the wireless propagation path is subtracted from the cumulative phase drift; the multipath propagation response distribution after the above processing is the multipath propagation response distribution after phase correction processing.

[0007] In some embodiments, obtaining the statistical propagation response parameters and amplitude fluctuation characteristic parameters corresponding to each wireless propagation path specifically includes: Obtain the total number of frames of all multipath propagation response distributions after phase correction processing within a preset statistical time range; for any wireless propagation path, construct the complex amplitude value of the wireless propagation path in this measurement by using the amplitude attenuation parameter of the wireless propagation path in the multipath propagation response distribution after each phase correction processing as the modulus and the phase change parameter after phase correction processing as the argument. The statistical propagation response parameters of the wireless propagation path are obtained by summing all the complex amplitude values ​​corresponding to the wireless propagation path in the entire multipath propagation response distribution and dividing the result of the complex summation by the total number of frames. The statistical propagation response parameters of each wireless propagation path are obtained by traversing all wireless propagation paths. For any wireless propagation path, obtain the amplitude attenuation parameter in the multipath propagation response distribution after phase correction processing for each frame within the preset statistical time range, and obtain the magnitude of the statistical propagation response parameter of the wireless propagation path; subtract the magnitude of the statistical propagation response parameter from the amplitude attenuation parameter of each frame to obtain the amplitude deviation value of each frame; perform an arithmetic mean on the squares of the amplitude deviation values ​​of all frames, and perform a square root operation on the result of the arithmetic mean to obtain the amplitude fluctuation characteristic parameter of the wireless propagation path; traverse all wireless propagation paths to obtain the amplitude fluctuation characteristic parameter corresponding to each wireless propagation path.

[0008] In some embodiments, the propagation path stability is obtained from statistical propagation response parameters and amplitude fluctuation characteristic parameters, specifically including: For any wireless propagation path, obtain the magnitude of the statistical propagation response parameter of the wireless propagation path, obtain a preset positive constant, add the preset positive constant to the amplitude fluctuation characteristic parameter of the wireless propagation path to obtain the fluctuation adjustment value; divide the magnitude of the statistical propagation response parameter by the fluctuation adjustment value to obtain the propagation path stability of the wireless propagation path; traverse all wireless propagation paths to obtain the propagation path stability corresponding to each wireless propagation path. The set of structurally stable propagation paths specifically includes: A preset threshold value is obtained, and the propagation path stability of all wireless propagation paths is compared with the preset threshold value one by one. Wireless propagation paths with a propagation path stability greater than the preset threshold value are determined as structurally stable propagation paths. All structurally stable propagation paths constitute a set of structurally stable propagation paths, which includes the propagation delay parameter, statistical propagation response parameter, and propagation path stability of each structurally stable propagation path.

[0009] In some embodiments, the wireless transmission matching parameters are associated with the propagation path stability, the conjugate value of the statistical propagation response parameters, and the propagation delay parameters corresponding to each structurally stable propagation path, specifically including: For each structurally stable propagation path, the inverse of the propagation delay parameter of the structurally stable propagation path is taken as the matching delay position corresponding to the structurally stable propagation path; the conjugate operation is performed on the statistical propagation response parameter of the structurally stable propagation path to obtain the statistical propagation response conjugate value; the propagation path stability of the structurally stable propagation path is multiplied by the statistical propagation response conjugate value to obtain the weighted conjugate value of the structurally stable propagation path. The normalized reference value is obtained by summing the products of the propagation path stability of each structurally stable propagation path and the square of the magnitude of its respective statistical propagation response parameter. The weighted conjugate value of the structurally stable propagation path is divided by the normalized reference value to obtain the matching weighting coefficient corresponding to the structurally stable propagation path. All matching delay positions and the matching weighting coefficients corresponding to each matching delay position are used together as the wireless transmission matching parameters.

[0010] In some embodiments, the transmitting device adjusts the transmission timing and transmission amplitude distribution according to wireless transmission matching parameters, specifically including: The transmitting device extracts all matching delay positions and the matching weighting coefficients corresponding to each matching delay position from the wireless transmission matching parameters; based on the matching delay positions and matching weighting coefficients, it performs multipath pre-compensation processing on the wireless signal to be transmitted, so that the wireless signal to be transmitted generates a delay offset in the time domain that matches the propagation delay parameters of each structurally stable propagation path, and generates an amplitude adjustment that matches each matching weighting coefficient; the signal with the generated delay offset and amplitude adjustment is transmitted through the wireless propagation channel in the mine roadway. After electromagnetic waves propagate through multiple paths in a mine tunnel, the electromagnetic wave components of each structurally stable propagation path are superimposed in phase at the receiving device, specifically including: The wireless signals transmitted by the transmitting device, after adjustment of transmission time and amplitude distribution, propagate along the stable propagation paths of each structure in the mine roadway. Since the linear phase correction process has eliminated the propagation phase drift caused by the local oscillator frequency deviation, and the transmitting device has reversed the transmission time of each electromagnetic wave component according to the propagation delay parameter of the corresponding stable propagation path during the transmission time adjustment, each electromagnetic wave component arrives at the receiving device simultaneously and has phase consistency, and the amplitudes of each electromagnetic wave component are superimposed in phase at the receiving device.

[0011] In some embodiments, the receiving device periodically re-executes each step to update the set of structurally stable propagation paths and the wireless transmission matching parameters, specifically including: The receiving device acquires a preset update period and, using this preset update period as the time interval, re-executes each step at the arrival of each preset update period. During each re-execution, it recalculates the propagation path stability of each wireless propagation path based on the latest measured multipath propagation response distribution, re-selects and forms a set of structurally stable propagation paths, redetermines the wireless transmission matching parameters, and transmits them to the transmitting device via the backhaul wireless link. One embodiment of the above application has the following advantages or beneficial effects: This application obtains the multipath propagation response distribution through propagation response measurement, providing raw measurement data for subsequent statistical fusion. Phase unwrapping and linear phase correction eliminate the cumulative influence of local oscillator frequency deviation on phase estimation, ensuring the consistency of phase data in long-term statistical observation. Within a preset statistical time range, the phase-corrected multipath propagation response distribution is statistically fused to obtain statistical propagation response parameters and amplitude fluctuation characteristic parameters. The propagation path stability is calculated, and statistically stable structural propagation paths are selected, eliminating the interference of random scattering paths on compensation. This application generates wireless transmission matching parameters based on a set of structurally stable propagation paths, giving reliable paths a greater compensation weight. The wireless transmission matching parameters are fed back to the transmitting device for multipath pre-compensation processing, enabling the electromagnetic wave components of each structurally stable propagation path to be superimposed in phase at the receiving device, thereby enhancing the amplitude of the received signal. By periodically re-executing the above steps, the set of structurally stable propagation paths and the wireless transmission matching parameters can adaptively track changes in the multipath environment of the mine roadway, forming a closed-loop adaptive compensation.

[0012] Other effects of the above-mentioned alternative methods will be described below in conjunction with specific embodiments. Attached Figure Description

[0013] The accompanying drawings are provided for a better understanding of this solution and do not constitute a limitation of this application. Wherein: Figure 1 This is a schematic diagram of a wireless sensor network signal attenuation compensation method in a multipath environment of a mine roadway provided in an embodiment of this application; Figure 2 This is a schematic diagram of a fitting curve for amplitude fluctuation characteristic parameters and propagation path stability provided in an embodiment of this application; Figure 3 This is a schematic diagram of a statistical propagation response parameter magnitude-propagation path stability fitting curve provided in an embodiment of this application. Detailed Implementation

[0014] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0015] To facilitate understanding of this application, the embodiments of this application will be briefly described below: This application provides a method for signal attenuation compensation of wireless sensor networks in a multipath environment in mine roadways. It is applied to a communication system composed of wireless sensor nodes in a mine roadway. A mine roadway is a narrow and confined space, and its cross-sectional shape is usually rectangular or arched. The roadway wall is composed of coal wall, rock wall or concrete support structure. Wireless sensor nodes are deployed at different locations in the roadway to monitor environmental parameters and equipment operating status. When the transmitting node sends a wireless signal to the receiving node, the electromagnetic wave propagates in the roadway not only through a direct path, but also undergoes multiple reflections at the roadway roof, floor and side walls, forming numerous wireless propagation paths. These wireless propagation paths have different propagation distances and reflection times, resulting in different propagation delays, amplitude attenuations and phase changes of the signal components of each path at the receiving node. After superposition, they produce a multipath fading effect, causing deep fading at specific frequencies, resulting in large fluctuations in the received signal strength, which seriously affects the reliability of communication. Existing methods for compensating for attenuation of wireless communication signals in mine roadways typically employ channel estimation and equalization techniques. These methods estimate the channel's frequency response or impulse response in real time and then perform inverse filtering or maximum likelihood detection on the distorted signal at the receiver to recover the original transmitted symbols. However, real-time channel estimation requires periodic transmission of pilot sequences, consuming limited communication bandwidth resources. When mine cars or personnel move within the roadway, the multipath propagation environment changes rapidly, and the update rate of channel estimation cannot keep up with the speed of environmental changes, leading to a decrease in compensation effectiveness. More importantly, existing methods compensate for all propagation paths obtained from channel estimation indiscriminately, failing to distinguish between stable propagation paths formed by fixed structures in the roadway and unstable propagation paths caused by random scatterers. The parameters of random scattering paths change rapidly over time, and including them in the compensation will introduce additional errors. The method in this application, through long-term statistical observation, selects structurally stable propagation paths determined by fixed structures from the complex multipath propagation environment of mine roadways. These paths are then used to construct wireless transmission matching parameters, and pre-compensation is performed on the signal at the transmitting end. This ensures that the electromagnetic wave components of each structurally stable propagation path are superimposed in phase at the receiving device, enhancing the received signal amplitude and compensating for signal attenuation. This method utilizes only statistically stable propagation paths for compensation, eliminating interference from random scattering paths and effectively improving the communication reliability of wireless sensor networks in mine roadways.

[0016] See Figure 1 This is a flowchart illustrating a wireless sensor network signal attenuation compensation method in a multipath environment of mine roadways, as provided in an embodiment of this application. Figure 1 The execution subject of the method shown can be a combination of software and / or hardware, specifically, it can be one or more of various types of terminals, hardware systems, cloud computing, etc.

[0017] See Figure 2 , Figure 2 A schematic diagram of the amplitude fluctuation characteristic parameter-propagation path stability fitting curve provided in the embodiments of this application is shown below. Figure 2 As shown, the horizontal axis represents the amplitude fluctuation characteristic parameter, and the vertical axis represents the propagation path stability. The data points are taken from the statistical fusion results of the aforementioned 30 wireless propagation paths. The fitted curve shows a monotonically decreasing trend. This trend indicates that wireless propagation paths with smaller amplitude fluctuation characteristic parameters have higher propagation path stability, corresponding to structurally stable propagation paths formed by fixed reflective structures in mine roadways. Wireless propagation paths with larger amplitude fluctuation characteristic parameters have lower propagation path stability, corresponding to unstable propagation paths caused by random scatterers in roadways. The data points fluctuate around the fitted curve, reflecting that the propagation path stability is also affected by the magnitude of the statistical propagation response parameter. Even if the amplitude fluctuation characteristic parameters of two paths are similar, the difference in average propagation intensity will lead to different stability. This distribution characteristic is consistent with the path statistical characteristics in the actual multipath propagation environment of mine roadways.

[0018] See Figure 3 This is a schematic diagram of the statistical propagation response parameter magnitude-propagation path stability fitting curve provided in the embodiments of this application, as shown below. Figure 3As shown, the horizontal axis represents the magnitude of the statistical propagation response parameter, and the vertical axis represents the propagation path stability. The data points are taken from the statistical fusion results of the aforementioned 30 wireless propagation paths. The fitted curve shows a monotonically increasing trend, which indicates that wireless propagation paths with larger magnitudes of the statistical propagation response parameter have higher propagation path stability. These paths correspond to propagation paths formed by fixed reflective surfaces such as the roof, floor, and side walls in mine roadways, and have strong average propagation intensity and good statistical stability. The data points fluctuate around the fitted curve, reflecting that the propagation path stability is also affected by the amplitude fluctuation characteristic parameter. Even if the average propagation intensity of two paths is similar, the difference in the degree of amplitude fluctuation will lead to different stability. This distribution characteristic is consistent with the physical characteristics of paths in the actual multipath propagation environment of mine roadways.

[0019] Figure 1 The method for compensating for signal attenuation in a wireless sensor network under multipath conditions in a mine roadway includes steps S101 to S105, as detailed below: Step S101: The receiving device measures the propagation response of the periodically transmitted wireless detection transmission from the transmitting device, and obtains the multipath propagation response distribution including propagation delay parameters, amplitude attenuation parameters, and phase change parameters for each wireless propagation path; The purpose of this step is to obtain the propagation delay parameters, amplitude attenuation parameters, and phase change parameters of each wireless propagation path between the transmitting and receiving devices in the mine roadway by measurement, so as to provide the raw data basis for subsequent statistical analysis and pre-compensation. The transmitting device periodically transmits wireless detection data according to a preset detection period. This wireless detection data carries a detection waveform known in advance by the receiving device. In this embodiment, the known detection waveform is a pseudo-random sequence with good autocorrelation characteristics. The reason for choosing such a sequence as the detection waveform is that its autocorrelation function exhibits a sharp main peak at zero delay and a lower amplitude at non-zero delay. This characteristic is beneficial for the receiving device to accurately distinguish wireless propagation paths with different propagation delays after receiving a signal containing multipath superposition. The length and bandwidth of the detection waveform are determined according to the multipath delay extension range of the mine roadway and the required multipath resolution. Specifically, the bandwidth of the detection waveform determines the minimum delay interval between two wireless propagation paths that the receiving device can distinguish. The larger the bandwidth, the smaller the minimum delay interval that can be distinguished. The period of the detection waveform should be less than the time interval between two adjacent propagation response measurements within the preset statistical time range described in the subsequent step S103, so as to ensure that a sufficient number of measurement samples can be collected within the preset statistical time range. The receiving device receives periodically transmitted wireless probe data from the transmitting device, extracts propagation response parameters from the known probe waveforms in the received signal, and determines the propagation delay parameters, amplitude attenuation parameters, and phase change parameters corresponding to each wireless propagation path based on the matching relationship between the received signal and the known probe waveforms. Specifically, the receiving device down-converts the received wireless probe signal to baseband to obtain a received baseband signal. The receiving device then performs a time-domain sliding correlation operation between the received baseband signal and a locally stored baseband copy of the known probe waveform. The time-domain sliding correlation operation involves sliding the baseband copy of the known probe waveform point-by-point along the time axis. For each sliding sampling point, the integral of the conjugate product of the received baseband signal and the baseband copy of the known probe waveform at that sliding position over the duration of the probe waveform is calculated. This integral result is the correlation response value at that sliding position. When the sliding position matches the propagation delay of a certain wireless propagation path, the signal component in the received baseband signal contributed by that wireless propagation path is perfectly aligned with the baseband copy of the known probe waveform, and a peak value appears in the correlation response value. The time position of the correlation response peak is the propagation delay parameter of the wireless propagation path. The magnitude of the complex response value of the correlation response peak is the amplitude attenuation parameter of the wireless propagation path. The argument of the complex response value of the correlation response peak is the phase change parameter of the wireless propagation path. The receiving device sets a preset detection threshold to distinguish the correlation response peak corresponding to the real wireless propagation path from false peaks caused by noise or sidelobes. The preset detection threshold is determined as follows: During the initialization phase, the receiving device collects environmental noise samples during the silent period when the transmitting device does not transmit wireless probe data, calculates the power estimate of the environmental noise, and sets the preset detection threshold as a preset multiple of the environmental noise power estimate. The selection of this preset multiple needs to strike a balance between the detection probability and the false alarm probability: if the multiple is too low, noise peaks will be misjudged as valid paths, increasing the interference components in subsequent statistical fusion; if the multiple is too high, real paths with smaller amplitudes will be missed, possibly losing some structurally stable propagation paths. In this embodiment, the preset multiple ranges from 5 to 10 times, which corresponds to an empirical value where the false alarm probability is lower than the acceptable level in engineering practice. The receiving device only determines peaks with correlation response values ​​exceeding the preset detection threshold as valid correlation response peaks, and each valid correlation response peak corresponds to a distinguishable wireless propagation path. In multiple consecutive propagation response measurements, the receiving device needs to track the same wireless propagation path between two adjacent measurements so that the subsequent step S102 can perform cross-frame processing on the phase change parameters of the same wireless propagation path. The path tracking method is based on the nearest neighbor matching criterion of propagation delay parameters: for the k-th wireless propagation path identified in the m-th measurement, in the m+1-th measurement, find the wireless propagation path with the smallest difference between the propagation delay parameters and the propagation delay parameters of the path; if the difference does not exceed the preset delay matching tolerance, then the two wireless propagation paths are determined to be the same wireless propagation path; the value of the preset delay matching tolerance should be greater than the delay resolution of a single propagation response measurement, and less than the minimum propagation delay interval between two adjacent wireless propagation paths in the mine roadway. In some embodiments, the preset delay matching tolerance is set to 2 to 3 times the reciprocal of the probe waveform bandwidth. This setting is based on the fact that the delay resolution of a single propagation response measurement is determined by the reciprocal of the probe waveform bandwidth. Setting the tolerance to 2 to 3 times this resolution allows for reliable path tracing within the range of normal errors in delay estimation, while avoiding mismatching two wireless propagation paths with similar but different delay intervals as the same path. Through this path tracing method, the receiving device can establish a time-varying parameter sequence for each wireless propagation path in multiple consecutive propagation response measurements, which can be used for subsequent phase difference calculations and statistical fusion processing. The set of propagation delay parameters, amplitude attenuation parameters, and phase change parameters corresponding to all distinguishable wireless propagation paths is taken as the multipath propagation response distribution obtained by a single propagation response measurement. In mine roadways, some distinguishable wireless propagation paths are formed by fixed reflection structures of electromagnetic waves on the roof, floor, and side walls. The propagation delay and loss of these paths are determined by the fixed geometric dimensions of the roadway and the electromagnetic parameters of the walls. Under conditions where there are no significant structural changes in the roadway environment, their parameters remain statistically stable over a long period of time. Other distinguishable wireless propagation paths are caused by scatterers such as moving mine cars, personnel, or temporarily stacked equipment within the roadway. The parameters of these paths change rapidly with the movement of the scatterers and do not have statistical stability over time. The core objective of the subsequent steps in this embodiment is to statistically fuse multiple multipath propagation response distributions obtained from multiple propagation response measurements, distinguish between statistically stable structurally stable propagation paths and statistically unstable random scattering paths, and use only structurally stable propagation paths for pre-compensation. In this embodiment, starting with the first propagation response measurement, multiple propagation response measurements are performed continuously according to a preset measurement cycle to obtain multi-frame multipath propagation response distributions, which are used for local oscillator frequency offset estimation and statistical fusion processing in subsequent steps.

[0020] Step S102: Perform phase difference operation on the phase change parameters of the same wireless propagation path in multiple consecutive multipath propagation response distributions, extract the propagation phase drift caused by the local oscillator frequency deviation between the transceivers, and perform phase unwinding and linear phase correction processing on each multipath propagation response distribution according to the propagation phase drift. The purpose of this step is to extract the propagation phase drift caused by the local oscillator frequency deviation between the receiving and transmitting devices from multiple multipath propagation response distributions obtained from consecutive propagation response measurements, and to use this propagation phase drift to correct the phase change parameters in each multipath propagation response distribution in order to eliminate the influence of the local oscillator frequency deviation on subsequent statistical fusion processing. The technical logic of this step is based on the following physical understanding: In a wireless sensor network communication system in a mine roadway, the receiving device and the transmitting device each use independent local oscillators for frequency conversion, and there is a local oscillator frequency deviation between the two local oscillators. This local oscillator frequency deviation will cause the phase change parameter obtained in each propagation response measurement to contain an additional phase component that accumulates linearly over time. The rate of change of this additional phase component is proportional to the local oscillator frequency deviation. At the same time, environmental disturbances such as personnel walking and equipment moving in the mine roadway will also cause fluctuations in the phase change parameter, but such fluctuations do not have strict time linearity. By constructing a time series of the phase change parameters of the same wireless propagation path in multiple propagation response measurements and linearly fitting its trend, the linear phase drift caused by the local oscillator frequency deviation can be separated from other nonlinear environmental disturbances. In some embodiments, the specific implementation of step S102 is divided into three sub-steps: phase unwinding processing, propagation phase drift rate extraction, and linear phase correction processing. In the phase unwinding sub-step, the receiving device performs phase unwinding processing on the phase change parameters of the same wireless propagation path in multiple continuously acquired multipath propagation response distributions to eliminate phase jumps generated by the phase change parameters within the periodic value range. The phase change parameter is determined by the argument of the complex response value of the correlation response peak in step S101. Since the output range of the argument operation is limited to the periodic value range from negative π to positive π, when the real physical phase changes continuously with time and exceeds this periodic value range, the phase change parameter output by the argument operation will jump, that is, it will suddenly jump from a value close to positive π to a value close to negative π, or from a value close to negative π to a value close to positive π. This periodic jump will destroy the continuity of the phase change parameter in time, making it impossible to obtain the correct phase change trend by directly performing differential operation or linear fitting on the phase change parameter. The purpose of phase unwinding is to eliminate the aforementioned periodic jumps and restore the continuous temporal sequence of phase change parameters. In this embodiment, the specific operation of phase unwinding is as follows: using the phase change parameters obtained from the first propagation response measurement as a benchmark, starting from the second propagation response measurement, the difference between the phase change parameters obtained in the current measurement and the phase change parameters after unwinding in the previous measurement is compared sequentially; when the difference is greater than a preset positive jump threshold, it is determined that the phase change parameters of the current measurement and all subsequent measurements have undergone a positive periodic jump, and 2π is subtracted from the phase change parameters of the current measurement and all subsequent measurements; when the difference is less than a preset negative jump threshold, it is determined that the current measurement... If a negative periodic jump occurs in the phase change parameters of the current measurement and all subsequent measurements, 2π is added to the phase change parameters of the current measurement and all subsequent measurements. If the absolute value of this difference does not exceed a preset jump threshold, it is determined that no periodic jump has occurred, and the phase change parameters of the current measurement remain unchanged. In this embodiment, the preset positive jump threshold is π, and the preset negative jump threshold is negative π. The setting is based on the periodic range of the phase change parameters being 2π. When the difference between the phase change parameters of two adjacent measurements exceeds half a period, i.e., π, it can be determined that a periodic jump has occurred. The above phase unwrapping process is performed independently on each wireless propagation path to obtain the phase change parameter sequence of each wireless propagation path after phase unwrapping. In the propagation phase drift rate extraction sub-step, the receiving device performs differential operation and linear fitting on the phase change parameter sequence of the same wireless propagation path obtained after unwinding processing to extract the propagation phase drift rate caused by the local oscillator frequency deviation between the transceiver devices. Specifically, for each wireless propagation path, the receiving device performs a differential operation on the phase change parameters of two adjacent propagation response measurements after unwinding. That is, it subtracts the unwinded phase change parameter of the previous propagation response measurement from the unwinded phase change parameter of the subsequent propagation response measurement to obtain the phase difference sequence corresponding to the wireless propagation path. Each element in the phase difference sequence represents the increment of the phase change between two adjacent measurements. This increment is composed of the linear cumulative phase increment caused by the local oscillator frequency deviation and the random phase fluctuation caused by environmental disturbances. The receiving device uses the values ​​of each element in the phase difference sequence as the ordinate and the corresponding propagation response measurement time as the abscissa to form a set of data points in a rectangular coordinate system. Linear fitting is then performed on this set of data points. The goal of the fitting is to find a straight line that minimizes the sum of squared residuals between the line and each data point. In this embodiment, the linear fitting uses the least squares method, and the slope of the fitted line represents the average rate of change of the phase difference over time. Since the phase drift caused by the local oscillator frequency deviation has a linear cumulative characteristic over time, its contribution to the phase difference sequence is a constant increment, which corresponds to the slope of the fitted line in the fitting result. Random phase fluctuations caused by environmental disturbances do not have a linear characteristic over time and are separated as residuals during the fitting process. Therefore, the slope of the fitted line is the propagation phase drift rate caused by the local oscillator frequency deviation between the transceiver devices, and the unit of the propagation phase drift rate is radians per unit time. In some embodiments, the number of data points participating in linear fitting is at least three to ensure the statistical reliability of the fitting results; when the number of available data points is less than three, the receiving device continues to collect new multipath propagation response distributions until the number of data points meets the requirements before performing linear fitting. Furthermore, after completing the linear fitting, the receiving device calculates the goodness of fit between the fitted line and each data point. The goodness of fit is measured by the correlation coefficient, which ranges from 0 to 1. The closer the goodness of fit is to 1, the more dominant the linear component caused by the local oscillator frequency deviation is in the phase difference sequence, and the more reliable the fitting result is. When the goodness of fit is lower than the preset goodness of fit threshold, it indicates that the contribution of environmental disturbances in the phase difference sequence is too large, and the data contains too many nonlinear random fluctuations. At this time, the fitting result obtained based on the current number of data points is unreliable. The receiving device continues to collect new multipath propagation response distributions to increase the number of data points involved in the fitting. The number of data points is increased, and linear fitting and goodness-of-fit calculation are re-executed until the goodness-of-fit reaches the preset goodness-of-fit threshold. The purpose of increasing the number of data points is to use more observation samples to smooth out the effects of random fluctuations, so that the linear trend caused by the local oscillator frequency deviation can be highlighted on a longer observation time scale. In this embodiment, the preset goodness-of-fit threshold ranges from 0.8 to 0.9. The setting of this range is based on the general criteria for judging the strength of linear correlation in statistics, that is, when the correlation coefficient is above 0.8, it is considered that there is a strong linear correlation between the two variables, and the fitted line can reliably reflect the linear relationship between the variables. The receiving device determines the propagation phase drift based on the propagation phase drift rate and the propagation response measurement time interval. The propagation phase drift refers to the cumulative phase change caused by the local oscillator frequency deviation between two adjacent propagation response measurements, and its value is equal to the propagation phase drift rate multiplied by the time interval between two adjacent propagation response measurements. In the linear phase correction processing sub-step, the receiving device performs linear phase correction processing on each path according to the multipath propagation response distribution based on the propagation phase drift. Specifically, the receiving device uses the moment of the first propagation response measurement as the phase reference zero point. The physical meaning of this phase reference zero point is that the phase state of each wireless propagation path at the moment of the first propagation response measurement is used as the correction benchmark. The phase drift caused by the local oscillator frequency deviation in each subsequent propagation response measurement is calculated and corrected relative to this benchmark. The receiving device obtains the time offset of the measurement moment corresponding to each propagation response measurement relative to the moment of the first propagation response measurement. This time offset is equal to the difference between the measurement moment of the current propagation response measurement and the moment of the first propagation response measurement. The receiving device multiplies the propagation phase drift by the time offset to obtain the cumulative phase drift of the current propagation response measurement. The cumulative phase drift represents the total cumulative amount of phase drift caused by the local oscillator frequency deviation during the time period from the moment of the first propagation response measurement to the moment of the current propagation response measurement. For each wireless propagation path in the multipath propagation response distribution obtained after phase unwrapping processing in this propagation response measurement, the receiving device subtracts the cumulative phase drift corresponding to this propagation response measurement from the phase change parameter of the wireless propagation path. After this subtraction operation, the linear cumulative phase component caused by the local oscillator frequency deviation in each propagation response measurement is eliminated, and the remaining phase information mainly reflects the true phase change of the propagation characteristics of each wireless propagation path. The multipath propagation response distribution after the above processing is the multipath propagation response distribution after phase correction processing. The multipath propagation response distribution after phase correction processing will be used for statistical fusion processing in the subsequent step S103. Since the phase drift caused by the local oscillator frequency deviation has been eliminated, the result of the complex arithmetic mean in the statistical fusion processing can more accurately reflect the long-term stable propagation characteristics of each wireless propagation path under the static structure of the mine roadway, which is conducive to accurately calculating the propagation path stability and reliably screening structurally stable propagation paths.

[0021] Step S103: Within a preset statistical time range, statistical fusion is performed on all processed multipath propagation response distributions path by path to obtain the statistical propagation response parameters and amplitude fluctuation characteristic parameters corresponding to each wireless propagation path. The propagation path stability is obtained from the two parameters. Propagation paths whose propagation path stability exceeds a preset threshold are determined as structurally stable propagation paths, thus forming a set of structurally stable propagation paths. The purpose of this step is to perform path-by-path statistical fusion on the multipath propagation response distribution after phase correction processing obtained in step S102 within a preset statistical time range, extract the long-term stable propagation characteristics of each wireless propagation path from a statistical perspective, calculate the propagation path stability based on the characteristics, and select structurally stable propagation paths that are determined by the fixed structure of the mine roadway and maintain statistical stability in time to form a set of structurally stable propagation paths. The technical logic of this step is based on the following physical understanding: Wireless propagation paths in mine roadways can be divided into two categories. The first category consists of paths formed by electromagnetic waves propagating between fixed reflecting surfaces such as the roof, floor, and side walls of the roadway. The propagation delay parameters, amplitude attenuation parameters, and phase change parameters of these paths remain statistically stable under the condition that the roadway geometry and the electromagnetic properties of the walls do not change significantly. The second category consists of paths caused by random scatterers such as moving mine cars, personnel, or temporarily stacked equipment in the roadway. The parameters of these paths change rapidly with the movement of the scatterers and do not have statistical stability in time. By taking the complex arithmetic mean of the complex amplitude values ​​obtained from multiple measurements, the statistical consistency of phase information can be used to distinguish between two types of paths: for statistically stable paths, the complex amplitude values ​​of each measurement have similar phases in the complex plane, and the magnitude is enhanced after complex summation; for statistically unstable paths, the complex amplitude values ​​of each measurement have randomly distributed phases in the complex plane, and the magnitude is weakened after complex summation due to phase cancellation. Based on this, the propagation path stability can be constructed by combining amplitude fluctuation characteristic parameters, which can further quantify the stability of each path and provide a basis for screening structurally stable propagation paths. In some embodiments, the specific implementation of step S103 is divided into four sub-steps: complex arithmetic mean statistics, amplitude fluctuation characteristic parameter statistics, propagation path stability calculation, and structural stable propagation path screening. In the complex arithmetic mean statistical sub-step, the receiving device performs a complex arithmetic mean on the multipath propagation response distribution after phase correction processing for each path to obtain the statistical propagation response parameters corresponding to each wireless propagation path. Specifically, the receiving device first acquires the total number of frames of all multipath propagation response distributions after phase correction processing within a preset statistical time range; the total number of frames refers to the total number of multipath propagation response distributions obtained by the receiving device after successfully completing propagation response measurement, phase unwinding processing and linear phase correction processing within the preset statistical time range. The duration of the preset statistical time range is determined by the upper limit of the statistical time range under which the multipath propagation delay structure of the mine roadway remains unchanged. The unchanged multipath propagation delay structure of the mine roadway means that under the condition that there is no personnel movement or equipment movement in the roadway, the propagation delay parameters and amplitude attenuation parameters of each wireless propagation path do not exceed the preset fluctuation range for a continuous period of time. The upper limit of the statistical time range is determined as follows: In the learning phase of the initial deployment of the wireless sensor network communication system in the mine roadway, the receiving device performs long-term continuous propagation response measurement on the wireless propagation environment of the mine roadway. For each wireless propagation path, the maximum continuous time length during which the deviation of its propagation delay parameter does not exceed the preset delay deviation threshold is statistically calculated. The minimum or median of the maximum continuous time length corresponding to all wireless propagation paths is taken as the upper limit of the statistical time range. Specifically, the propagation path stability is calculated based on the statistical propagation response parameters and amplitude fluctuation characteristic parameters. The calculation formula is as follows:

[0022] in, For the index of wireless propagation path, greater than or equal to 1 and less than or equal to 1 integers, This represents the total number of all wireless propagation paths that the receiving device can distinguish in a single propagation response measurement. It is a positive integer. Indicates the first The statistical propagation response parameters of the wireless propagation path, which are derived from the first... The complex amplitude values ​​of all phase-corrected values ​​within a preset statistical time range for each wireless propagation path are obtained by performing a complex arithmetic mean: The real parts of all complex amplitude values ​​are summed and then divided by the total number of frames to obtain... The real part; summing the imaginary parts of all complex amplitude values ​​and dividing by the total number of frames, yields... The imaginary part, modulus This indicates the average propagation strength of the wireless propagation path within a preset statistical time range. The argument represents the average propagation phase of the wireless propagation path within a preset statistical time range; For statistical propagation response parameters The modulus of is a real number greater than or equal to 0, and this modulus is determined by [the modulus of is determined by ] The square root of the sum of the squares of the real and imaginary parts is obtained by performing a square root operation. For the first The amplitude fluctuation characteristic parameter of each wireless propagation path is a real number greater than or equal to 0. The physical meaning is the root mean square fluctuation of the amplitude attenuation parameter of the wireless propagation path within a preset statistical time range. The calculation process is as follows: calculate the amplitude attenuation parameter and the magnitude of the statistical propagation response parameter for each frame of the wireless propagation path within a preset statistical time range. The difference is used to obtain the amplitude deviation value of that frame; the amplitude deviation values ​​of all frames are squared and then the arithmetic mean is taken. The square root of the arithmetic mean is then taken to obtain the result. , The larger the value, the more drastic the amplitude of the wireless propagation path changes over time, and the more unstable the propagation characteristics. The smaller the value, the more smoothly the amplitude of the wireless propagation path changes over time, and the more stable the propagation characteristics. This is a preset positive constant, and represents a real number greater than zero. The value of should be much smaller than the typical value of the amplitude fluctuation characteristic parameter of the normal wireless propagation path in the mine roadway, so that Only In the extreme case of zero or close to zero The calculation results are affected, while When within the normal range The impact is negligible. The value range is 0.1 to 0.5 times the amplitude normalization value corresponding to the background noise of the receiving device. The amplitude normalization value corresponding to the background noise of the receiving device refers to the statistical average value of the noise amplitude under the condition that there is only noise and no effective signal at the input of the receiving device. This represents the fluctuation adjustment value, which is a real number greater than zero. It is used as the denominator in the formula for calculating the stability of the propagation path to ensure that the denominator is never zero. Indicates the first The path stability of a wireless propagation path is a dimensionless positive real number. The physical meaning of this is the average propagation strength of the wireless propagation path under a unit fluctuation degree, which is used to comprehensively measure the long-term effective propagation capability and time-varying stability of the wireless propagation path. The larger the value, the more stable and reliable the propagation characteristics are, indicating that the wireless propagation path has small time-varying fluctuations while maintaining strong propagation capabilities. Propagation path stability The determination rule is: the receiving device calculates all... wireless propagation path The median of the sequence is set as a preset threshold value, which is the median multiplied by a preset coefficient. The preset coefficient ranges from 1.5 to 3.0. The receiving device will collect all wireless propagation paths. Each value is compared with a preset threshold value, and then... Wireless propagation paths exceeding a preset threshold are determined to be structurally stable propagation paths. The specific data on wireless propagation path number and propagation path stability are shown in Table 1.

[0023] Table 1

[0024] In this data analysis, we systematically evaluated the statistical characteristics of 30 wireless propagation paths identified by the receiving device in a single propagation response measurement. Table 1 contains the statistical propagation response parameters, magnitude fluctuation characteristic parameters, preset positive constants, and propagation path stability for each wireless propagation path. These data are designed to reflect the propagation characteristics of different wireless propagation paths in mine roadways and their stability within the statistical time range. The propagation path stability is calculated by dividing the magnitude of the statistical propagation response parameter by the sum of the amplitude fluctuation characteristic parameter and a preset positive constant. The preset positive constant is 0.010, used to prevent numerical overflow during division when the amplitude fluctuation characteristic parameter approaches zero. Its value is much smaller than the typical value of the normal amplitude fluctuation characteristic parameter, only providing numerical protection in extreme cases. Through data analysis, we observed significant differences in the propagation characteristics of each wireless propagation path. The magnitude of the statistical propagation response parameter for wireless propagation path 15 is 0.756, and the amplitude fluctuation characteristic parameter is only 0.015. The calculated... The propagation path stability is 30.240, the highest among all wireless propagation paths, indicating that this wireless propagation path not only has a strong average propagation intensity within the preset statistical time range, but also has minimal amplitude fluctuation over time, exhibiting extremely stable propagation characteristics. The statistical propagation response parameter modulus of wireless propagation path 23 is 0.856, the amplitude fluctuation characteristic parameter is 0.031, and the propagation path stability is 20.878, also demonstrating high stability characteristics. This type of wireless propagation path physically corresponds to the structurally stable propagation path formed by electromagnetic waves propagating between fixed reflecting surfaces such as the roof, floor, and side walls of a mine roadway. The statistical propagation response parameter magnitude of wireless propagation path 6 is 0.156, the amplitude fluctuation characteristic parameter is 0.389, and the propagation path stability is only 0.391. The statistical propagation response parameter magnitude of wireless propagation path 25 is 0.112, the amplitude fluctuation characteristic parameter is 0.378, and the propagation path stability is 0.289, which is the lowest among all wireless propagation paths. The amplitude fluctuation characteristic parameter of this type of wireless propagation path is significantly larger than the statistical propagation response parameter magnitude, indicating that its propagation intensity is weak and the amplitude varies drastically over time. Physically, this corresponds to the propagation path caused by random scattering objects such as moving mine cars, personnel, or temporary equipment in the roadway. The distribution of data points exhibits a clear nonlinear relationship. Paths with larger statistical propagation response parameter magnitudes have higher propagation path stability. However, the propagation path stability is also significantly affected by the amplitude fluctuation characteristic parameter. For example, the statistical propagation response parameter magnitude of wireless propagation path 12 is 0.673, which is similar to 0.651 of wireless propagation path 3. However, the amplitude fluctuation characteristic parameter of wireless propagation path 12 is 0.067, which is slightly larger than 0.056 of wireless propagation path 3. This results in its propagation path stability of 8.740 being slightly lower than that of wireless propagation path 3 (9.864). This characteristic of data points fluctuating around the fitted curve truly reflects the physical scenario of a mixture of structurally stable paths and random scattering paths in the wireless propagation environment of mine roadways.

[0025] In this embodiment, the preset delay deviation threshold is set to 3 to 5 times the reciprocal of the probe waveform bandwidth. This setting is based on the fact that the measurement accuracy of the propagation delay parameter is limited by the bandwidth of the probe waveform; the reciprocal of the bandwidth is the delay resolution. When the delay deviation is within 3 to 5 times this resolution, the propagation delay structure of the propagation path can be considered to have not undergone substantial change. The preset statistical time range should be less than the upper limit of the statistical time to ensure that all multipath propagation response distributions collected within the preset statistical time range reflect the same stable multipath propagation environment. In this embodiment, the preset statistical time range is 0.5 to 0.8 times the upper limit of the statistical time, ensuring the number of statistical samples while avoiding the inclusion of data introduced by environmental changes due to an excessively long statistical time range. For any wireless propagation path identified and tracked in step S101, the receiving device uses the amplitude attenuation parameter of the wireless propagation path in the multipath propagation response distribution after each phase correction process as the modulus of the complex amplitude value, and the phase change parameter of the wireless propagation path in the multipath propagation response distribution after the same phase correction process as the argument of the complex amplitude value, to construct the complex amplitude value of the wireless propagation path in this measurement. The complex amplitude value is constructed as follows: the real part of the complex amplitude value is equal to the product of the amplitude attenuation parameter and the cosine of the phase change parameter, and the imaginary part of the complex amplitude value is equal to the product of the amplitude attenuation parameter and the sine of the phase change parameter. The receiving device performs a complex summation of all complex amplitude values ​​corresponding to the multipath propagation response distribution of the wireless propagation path within a preset statistical time range. The complex summation method is as follows: the real parts of all complex amplitude values ​​are summed to obtain the accumulated real part, and the imaginary parts of all complex amplitude values ​​are summed to obtain the accumulated imaginary part. The accumulated real part and the accumulated imaginary part together constitute the complex summation result. The receiving device divides the real part of the complex summation result by the total number of frames to obtain the real part of the statistical propagation response parameter. The imaginary part of the complex summation result is divided by the total number of frames to obtain the imaginary part of the statistical propagation response parameter. The real part and the imaginary part of the statistical propagation response parameter together constitute the statistical propagation response parameter of the wireless propagation path. The receiving device traverses all wireless propagation paths to obtain the statistical propagation response parameter corresponding to each wireless propagation path. The physical meaning of the statistical propagation response parameter is that the magnitude of the statistical propagation response parameter represents the average propagation intensity of the wireless propagation path within a preset statistical time range, and the argument of the statistical propagation response parameter represents the average propagation phase of the wireless propagation path within the preset statistical time range. The reason for using the complex arithmetic mean instead of the amplitude arithmetic mean is that the complex arithmetic mean can retain the statistical consistency characteristics of the phase information in each measurement. For a statistically stable path determined by the fixed structure of the tunnel, the complex amplitude values ​​of each measurement point in similar directions on the complex plane, and the magnitude is enhanced after complex accumulation. For a statistically unstable path caused by random scatterers, the complex amplitude values ​​of each measurement change randomly in direction on the complex plane, and the magnitude is weakened after complex accumulation due to phase cancellation. Therefore, the magnitude of the statistical propagation response parameter itself contains information about the statistical stability of the path. In the amplitude fluctuation characteristic parameter statistics sub-step, the receiving device performs amplitude fluctuation variance statistics on the multipath propagation response distribution after phase correction processing for each path to obtain the amplitude fluctuation characteristic parameters corresponding to each wireless propagation path. Specifically, for any wireless propagation path, the receiving device acquires the amplitude attenuation parameter in the multipath propagation response distribution after phase correction processing for each frame within a preset statistical time range, and acquires the magnitude of the statistical propagation response parameter calculated in the aforementioned complex arithmetic mean statistical sub-step for the wireless propagation path; the receiving device subtracts the magnitude of the statistical propagation response parameter from the amplitude attenuation parameter of each frame to obtain the amplitude deviation value of each frame, which represents the degree of deviation of the actual amplitude of the wireless propagation path from its statistical average amplitude in this measurement; the receiving device performs an arithmetic mean on the squares of the amplitude deviation values ​​of all frames, that is, it sums up the squares of the amplitude deviation values ​​of all frames and divides them by the total number of frames to obtain the arithmetic mean of the squares of the amplitude deviations; the receiving device performs a square root operation on the arithmetic mean, and uses the result of the square root operation as the amplitude fluctuation characteristic parameter of the wireless propagation path; the receiving device traverses all wireless propagation paths to obtain the amplitude fluctuation characteristic parameter corresponding to each wireless propagation path. The physical meaning of the amplitude fluctuation characteristic parameter is the root mean square fluctuation of the amplitude of the wireless propagation path within a preset statistical time range. It is used to measure the time-varying severity of the amplitude attenuation parameter of the wireless propagation path. The larger the amplitude fluctuation characteristic parameter, the more drastic the amplitude of the wireless propagation path changes over time, and the more unstable its propagation characteristics are. The smaller the amplitude fluctuation characteristic parameter, the smoother the amplitude of the wireless propagation path changes over time, and the more stable its propagation characteristics are. When calculating the amplitude fluctuation characteristic parameter, the magnitude of the statistical propagation response parameter is used as the reference benchmark instead of calculating the amplitude arithmetic mean separately. This is because the magnitude of the statistical propagation response parameter has extracted the comprehensive stability characteristics of amplitude and phase in each measurement through complex arithmetic mean. Using the magnitude as the reference benchmark can maintain the consistency of amplitude and phase information in the stability evaluation system. In the propagation path stability calculation sub-step, the receiving device calculates the propagation path stability based on the statistical propagation response parameters and amplitude fluctuation characteristic parameters; Specifically, for any wireless propagation path, the receiving device obtains the magnitude of the statistical propagation response parameters of the wireless propagation path, obtains a preset positive constant, and adds the preset positive constant to the amplitude fluctuation characteristic parameters of the wireless propagation path. The result of the addition operation is the fluctuation adjustment value. The receiving device divides the magnitude of the statistical propagation response parameters by the fluctuation adjustment value. The result of the division operation is the propagation path stability of the wireless propagation path. The receiving device traverses all wireless propagation paths to obtain the propagation path stability corresponding to each wireless propagation path. The physical meaning of propagation path stability is the average propagation strength of a wireless propagation path under a unit fluctuation. It is used to comprehensively measure the long-term effective propagation capability and time-varying stability of the wireless propagation path. In the formula for calculating propagation path stability, the numerator is the magnitude of the statistical propagation response parameter, representing the long-term average propagation strength of the wireless propagation path, reflecting the path's contribution to signal transmission; the denominator is the sum of the amplitude fluctuation characteristic parameter and a preset positive constant, representing the degree of propagation uncertainty of the wireless propagation path, reflecting the path's instability over time. The larger the propagation path stability obtained by dividing the two, the larger the propagation path stability is, indicating that the wireless propagation path maintains strong propagation capability while having small time-varying fluctuations, and therefore its propagation characteristics are more stable and reliable. The smaller the propagation path stability is, the smaller the propagation path stability is, the weaker the propagation strength or the larger the time-varying fluctuations, and therefore its propagation characteristics are less reliable. In some embodiments, the function of the preset positive constant is to prevent the denominator from becoming zero and causing the propagation path stability value to overflow when the amplitude fluctuation characteristic parameter is close to zero. The value of the preset positive constant should be much smaller than the typical value of the amplitude fluctuation characteristic parameter, so that the preset positive constant only plays a value protection role when the amplitude fluctuation characteristic parameter is extremely small or zero, and its impact on the calculation result of propagation path stability is negligible when the amplitude fluctuation characteristic parameter is within the normal range. The value of the preset positive constant is based on the amplitude normalization value corresponding to the background noise of the receiving device, and the typical value range is 0.1 to 0.5 times the amplitude normalization value corresponding to the background noise of the receiving device. The amplitude normalization value corresponding to the background noise of the receiving device refers to the statistical average value of the noise amplitude under the condition that there is only noise and no effective signal at the input of the receiving device. In the structurally stable propagation path selection sub-step, the receiving device determines wireless propagation paths whose propagation path stability exceeds a preset threshold as structurally stable propagation paths, thus forming a set of structurally stable propagation paths. Specifically, the receiving device acquires a preset threshold value, which is determined based on the statistical distribution characteristics of the propagation path stability of all wireless propagation paths. In some embodiments, the receiving device calculates the median of the propagation path stability sequence of all wireless propagation paths and sets the preset threshold value as the median multiplied by a preset coefficient, the preset coefficient ranging from 1.5 to 3.0. The physical basis for this setting is that the median can reflect the central trend of the propagation path stability sequence. Setting the preset threshold value as a preset multiple of the median can filter out wireless propagation paths with propagation stability significantly higher than the average level. These filtered paths physically correspond to propagation paths formed by fixed reflective surfaces such as the tunnel roof, floor, and side walls. Their geometric propagation structure remains unchanged in a short time and is therefore defined as structurally stable propagation paths. The receiving device compares the propagation path stability of each wireless propagation path with a preset threshold value. Wireless propagation paths with a propagation path stability greater than the preset threshold value are determined to be structurally stable propagation paths, while wireless propagation paths with a propagation path stability less than or equal to the preset threshold value are determined to be non-structurally stable propagation paths and are not used in subsequent pre-compensation processing. All wireless propagation paths determined to be structurally stable propagation paths constitute a set of structurally stable propagation paths. The set of structurally stable propagation paths includes the propagation delay parameters, statistical propagation response parameters, and propagation path stability of each structurally stable propagation path. These parameters will be used to generate wireless transmission matching parameters in the subsequent step S104.

[0026] Step S104: Determine the wireless transmission matching parameters based on the set of structurally stable propagation paths, and associate the wireless transmission matching parameters with the propagation path stability, the conjugate value of the statistical propagation response parameters, and the propagation delay parameters corresponding to each structurally stable propagation path. The purpose of this step is to generate wireless transmission matching parameters to guide the transmitting device to perform pre-compensation based on the set of structurally stable propagation paths obtained in step S103. These wireless transmission matching parameters are composed of the matching delay position and matching weighting coefficients corresponding to each structurally stable propagation path. In essence, they are a set of time-reversed conjugate matched filter coefficients, which enable the transmitting device to pre-compensate the propagation delay and phase shift of each structurally stable propagation path when transmitting signals, thereby achieving in-phase superposition of the electromagnetic wave components of each structurally stable propagation path at the receiving device. The technical logic of this step is based on time-reversal signal processing theory and channel matching principle. In the classic time-reversal communication theory, after the transmitter obtains the channel impulse response, it reverses the time and precodes it at the transmitter. After the signal propagates through the same multipath channel, each multipath component will automatically achieve time and phase alignment at the receiver, forming a spatial focusing and time compression effect. This embodiment makes two key improvements based on this theory: First, it only matches statistically stable and structurally stable propagation paths, eliminating the interference of random scattering paths and avoiding the additional errors introduced by including unstable paths in the matching parameters; Second, it introduces propagation path stability as a weighting factor, so that paths with high stability receive a larger transmission weight and paths with low stability receive a smaller transmission weight, further improving the reliability and robustness of pre-compensation. In some embodiments, the specific implementation of step S104 is divided into four operation steps: time reversal matching, conjugate phase compensation, stability weighting, and energy normalization. In the time-reversal matching operation, for each structurally stable propagation path in the set of structurally stable propagation paths, the receiving device inverts the propagation delay parameter of that structurally stable propagation path, using this inverse as the corresponding matching delay position. Inverting the propagation delay parameter means making the delay value negative, which physically means advancing the transmission time relative to the reference time by the corresponding delay value. After the signal propagates through the mine roadway via multiple paths, the structurally stable propagation path itself will introduce a positive delay, meaning the signal component will arrive later than the reference time. By transmitting the signal component corresponding to this path at the transmitting end by the corresponding advance time, the advance at the transmitting end cancels out the propagation lag of the path, and the signal component will arrive at the receiving device exactly at the reference time. After performing the above time-reversal operation on all structurally stable propagation paths, the electromagnetic wave components of each structurally stable propagation path will theoretically arrive at the receiving device simultaneously, achieving time alignment. In the conjugate phase compensation operation, the receiving device performs a conjugate operation on the statistical propagation response parameters of the stable propagation path of the structure to obtain the conjugate value of the statistical propagation response. The conjugate operation means keeping the real part of the complex value unchanged and taking the opposite of the imaginary part. The argument of the statistical propagation response parameter represents the average propagation phase of the stable propagation path of the structure within a preset statistical time range, that is, the phase offset accumulated when the electromagnetic wave propagates along the path. After taking the conjugate of the statistical propagation response parameter, the argument of the conjugate value of the statistical propagation response is equal to the opposite of the argument of the statistical propagation response parameter. The purpose of this operation is to apply a phase pre-compensation amount equal in magnitude and opposite in sign to the channel propagation phase offset to the signal component of the path at the transmitting end in advance, so that after the signal component actually propagates through the mine roadway, the phase offset introduced by the channel is canceled by the pre-compensation at the transmitting end, and the phase of the signal component at the receiving device is restored to be consistent with the transmission reference phase. Specifically, the formula for calculating the pre-compensated transmitted signal is as follows:

[0027] in, For continuous time variables, The waveform of the original baseband symbol to be transmitted by the transmitting device is in complex baseband signal form and is time-dependent. Complex numerical functions, For the first The propagation delay parameter of the stable propagation path of the structure is a real number greater than or equal to zero. This parameter comes from the time position of the relevant response peak in the propagation response measurement in step S101. In this formula, This indicates that the original baseband symbol waveform is shifted to the left in the time domain. Seconds, meaning in advance Launch in seconds; For the first The emission pre-compensation coefficient corresponding to the stable propagation path of the structure is a complex number. The direct value is the calculated matching weighting coefficient. ,Right now , The modulus value represents the modulus of the first... The amplitude adjustment applied to the signal component corresponding to the stable propagation path of the bar structure. The argument represents the amount of phase pre-adjustment applied to that signal component; The baseband transmitted signal after multipath pre-compensation processing is in complex baseband signal form and is time-dependent. Complex numerical functions, Depend on It is composed of superimposed time-domain components, each component corresponding to a structurally stable propagation path, and its waveform is the original baseband symbol waveform advanced in the time domain. seconds and multiplied by the pre-compensation coefficient The result; In the stability-weighted operation, the receiving device multiplies the propagation path stability of the structurally stable propagation path by the conjugate value of the statistical propagation response, obtaining the weighted conjugate value of the structurally stable propagation path. The weighted conjugate value is a complex number whose magnitude is equal to the product of the propagation path stability and the magnitude of the conjugate value of the statistical propagation response, and whose argument is equal to the argument of the conjugate value of the statistical propagation response. The physical meaning of this operation is that, using propagation path stability as a weighting factor, the relative importance of each structurally stable propagation path in the pre-compensation processing is adjusted. Structurally stable propagation paths with higher propagation path stability have a higher statistical propagation response value. The more accurately the response parameters reflect the long-term stable propagation characteristics of the path, the more reliable the pre-compensation effect. Therefore, a larger weighting coefficient is assigned to them, resulting in a larger magnitude of the weighted conjugate value. For structurally stable propagation paths with lower propagation path stability, the greater the temporal fluctuation of their propagation parameters, the worse the predictability of the pre-compensation effect. Therefore, a smaller weighting coefficient is assigned to them, resulting in a smaller magnitude of the weighted conjugate value. Through stability weighting, the wireless transmission matching parameters can adaptively focus on utilizing those statistically most reliable structurally stable propagation paths, reducing the potential adverse effects of paths with large statistical fluctuations on the pre-compensation effect. In the energy normalization operation, the receiving device calculates the matching weighting coefficients corresponding to the weighted conjugate values ​​of all structurally stable propagation paths, so that all matching weighting coefficients satisfy the preset energy constraint conditions. Specifically, the receiving device accumulates the product of the propagation path stability of each structurally stable propagation path and the square of the magnitude of the statistical propagation response parameter of each path to obtain a normalized reference value. For any structurally stable propagation path, the square of the magnitude of the statistical propagation response parameter represents the average propagation energy of the structurally stable propagation path, and the product of the propagation path stability and the energy value represents the weighted energy contribution of the structurally stable propagation path. The normalized reference value obtained by accumulating the weighted energy contributions of all structurally stable propagation paths physically represents the total weighted energy of all structurally stable propagation paths. The receiving device divides the weighted conjugate value of the structurally stable propagation path by a normalized reference value to obtain the matching weighting coefficient corresponding to the structurally stable propagation path. The matching weighting coefficient is a complex value, and its magnitude represents the amplitude adjustment amount applied by the transmitting device to the signal component corresponding to the structurally stable propagation path in the pre-compensation process, that is, the transmission amplitude weight obtained by the structurally stable propagation path in the pre-compensation. The argument of the matching weighting coefficient represents the phase adjustment amount applied to the signal component, that is, the phase pre-adjustment amount that needs to be applied to the structurally stable propagation path in the pre-compensation. The operation of dividing the matching weighting coefficient by the normalized reference value ensures that the sum of the squares of the magnitudes of the matching weighting coefficients corresponding to all structurally stable propagation paths satisfies the preset energy constraint condition. The total transmission power after the pre-compensation process remains constant and does not change due to the change in the number of paths in the set of structurally stable propagation paths. This normalization process ensures that the power amplifier of the transmitting device always operates within the preset linear range, avoiding signal distortion caused by excessive pre-compensation gain. Specifically, the formula for calculating the matching weighting coefficient is as follows:

[0028] in, The total number of structurally stable propagation paths in the set of structurally stable propagation paths, which is a positive integer. The value is determined by the propagation path stability. The comparison result with the preset threshold value is determined. Less than or equal to , This is an index for the structural stability propagation path, used to identify the specific structural stability propagation path currently being computed for matching weighting coefficients. greater than or equal to 1 and less than or equal to 1 integers, and The distinction lies in: This is only used to identify paths that have been determined to be structurally stable propagation paths, and the value range is [value range missing]. , Used to identify all distinguishable paths, with a value range of [value range missing]. ; This is the traversal index of the structurally stable propagation path, used to traverse all paths in the summation operation of the denominator. A stable propagation path with a defined structure. greater than or equal to 1 and less than or equal to 1 integers, and The distinction lies in: Identify the specific path currently being computed. In the summation operation of the denominator, all structurally stable paths are traversed; For the first The statistical propagation response parameter of the stable propagation path is a complex number, and the method for obtaining this parameter is the same as in Formula 1. The acquisition method is the same, that is, it is obtained by performing a complex arithmetic mean of the complex amplitude values ​​after all phase correction processing of the path within the preset statistical time range; For the first The conjugate value of the statistical propagation response of a stable propagation path with a linear structure is a complex number. The real part is The imaginary part is ,but The real part is The imaginary part is ; For the first The path stability of a stable propagation path is a dimensionless positive real number. For the first The statistical propagation response parameters of a stable propagation path with a complex structure are given by subscript . Iterate through all the values ​​in the summation operation of the denominator. A stable propagation path with a single structure; For the first Statistical propagation response parameters of a stable propagation path with a linear structure The square of the modulus of is a real number that is greater than or equal to zero. For the first The path stability of a stable propagation path is a dimensionless positive real number. For the first The stability of a propagation path is the product of the square of the magnitude of its statistical propagation response parameter. This represents the normalization reference value, which is a real number greater than zero; this value represents all values. The sum of the weighted energy contributions of each of the structurally stable propagation paths; For the first The matching weighting coefficients corresponding to each structurally stable propagation path are complex numbers, and the matching weighting coefficients of all structurally stable propagation paths satisfy the following normalization constraint: ; The receiving device uses all the matching delay positions and the matching weighting coefficients corresponding to each matching delay position as wireless transmission matching parameters. The wireless transmission matching parameters completely describe the pre-compensation operation that the transmitting device needs to perform on its signal to be transmitted: at each time advance determined by the matching delay position, the corresponding pre-compensation signal component is generated according to the amplitude and phase adjustment determined by the matching weighting coefficients; the wireless transmission matching parameters will be used for the multipath pre-compensation processing of the transmitting device in the subsequent step S105. Specifically, the formula for calculating the matching delay position is:

[0029] in, For the first The matching delay position corresponding to the stable propagation path of the structure is a real number less than or equal to zero; The physical meaning is that the transmitting device should advance the signal component corresponding to the path in the time domain. The second-by-second emission is used to counteract the effects of the propagation path. Second propagation delay.

[0030] Step S105: Send the wireless transmission matching parameters to the transmitting device. The transmitting device adjusts the transmission time and transmission amplitude distribution according to the wireless transmission matching parameters so that the electromagnetic wave components of each structurally stable propagation path after the electromagnetic wave propagates through the multipath of the mine roadway are superimposed in phase at the receiving device. The receiving device periodically re-executes the above steps to update the set of structurally stable propagation paths and the wireless transmission matching parameters, forming a closed-loop adaptive wireless propagation in the mine roadway. The purpose of this step is to send the wireless transmission matching parameters generated in step S104 to the transmitting device through the backhaul wireless link. The transmitting device performs multipath pre-compensation processing on the wireless signal to be transmitted based on the wireless transmission matching parameters, and transmits the pre-compensated signal through the wireless propagation channel in the mine roadway. This enables the electromagnetic wave components of each structurally stable propagation path to be superimposed in phase at the receiving device. The receiving device also periodically re-executes all the aforementioned steps to update the set of structurally stable propagation paths and the wireless transmission matching parameters, thereby achieving continuous adaptive tracking of changes in the multipath environment of the mine roadway. In some embodiments, the specific implementation of step S105 is divided into four sub-steps: wireless transmission matching parameter feedback, multipath pre-compensation processing and transmission, in-phase superposition reception, and closed-loop adaptive update. In the wireless transmission matching parameter feedback sub-step, the receiving device sends the wireless transmission matching parameters generated in step S104 to the transmitting device through the backhaul wireless link. The backhaul wireless link is a dedicated wireless communication link between the receiving device and the transmitting device, used to transmit the feedback control parameters calculated by the receiving device to the transmitting device. In some embodiments, the backhaul wireless link can adopt the same physical layer communication method as the wireless probe transmission, and a dedicated time slot is divided in the communication frame structure for the transmission of feedback data. In other embodiments, the backhaul wireless link can use an independent low-speed wireless link to reduce the resource consumption of the main communication link. The data content transmitted by the backhaul wireless link includes the matching delay position and matching weighting coefficient corresponding to each structurally stable propagation path. Since the amount of data for wireless transmission matching parameters depends on the number of paths in the set of structurally stable propagation paths, and this amount of data is much smaller than the amount of data transmitted in normal communication, the backhaul wireless link can meet the requirements by using low-speed transmission. To ensure the reliability of feedback data transmission, the transmission rate can be reduced and redundancy checks can be added for transmission. In the multipath pre-compensation processing and transmission sub-step, after receiving the wireless transmission matching parameters, the transmitting device performs multipath pre-compensation processing on the wireless signal to be transmitted according to the wireless transmission matching parameters, and transmits the pre-compensated signal through the wireless propagation channel of the mine roadway. Specifically, the transmitting device extracts all matching delay positions and the matching weighting coefficients corresponding to each matching delay position from the received wireless transmission matching parameters. The matching delay position is a time sequence, where each element is a negative delay value, representing the amount of time that the corresponding signal component needs to be transmitted before the reference time. The matching weighting coefficient is a complex number sequence, where the modulus of each complex number represents the amplitude weight that needs to be applied to the corresponding signal component during transmission, and the argument of each complex number represents the phase pre-adjustment amount that needs to be applied to the corresponding signal component during transmission. The transmitting device performs multipath pre-compensation processing on the wireless signal to be transmitted based on the matching delay position and matching weighting coefficients. Multipath pre-compensation processing refers to the process of generating multiple components, offsetting delays, and adjusting amplitude and phase of the wireless signal to be transmitted in the time domain, and then superimposing the adjusted components into a composite signal. One implementation of multipath pre-compensation processing is a tapped delay line filter structure. The transmitting device maps the matching delay position to the delay position of each tap in the tapped delay line and maps the matching weighting coefficients to the complex gain coefficients of each tap. The baseband symbol sequence to be transmitted is input into the tapped delay line filter, and the output of the filter is the pre-compensated baseband signal with time delay offset and amplitude and phase adjustment. After multipath pre-compensation processing, the wireless signal to be transmitted generates a time delay offset in the time domain that matches the propagation delay parameters of each structurally stable propagation path, and generates an amplitude adjustment that matches each matching weighting coefficient. The matching relationship between the time delay offset and the propagation delay parameter is that the time delay offset is the negative of the propagation delay parameter, that is, the transmitter advances the signal component by the time corresponding to the propagation delay of that path. The matching relationship between the amplitude adjustment and the matching weighting coefficient is that the amplitude adjustment is equal to the magnitude of the matching weighting coefficient, and the phase pre-adjustment is equal to the argument of the matching weighting coefficient. The transmitting device upconverts the pre-compensated baseband signal, which has generated time delay offset and amplitude adjustment, to the carrier frequency through a digital-to-analog converter and radio frequency front-end, generates a pre-compensated wireless signal, and transmits the pre-compensated wireless signal through the wireless propagation channel in the mine roadway through the antenna. In the in-phase superposition receiving sub-step, the pre-compensated wireless signal, after adjustment of transmission time and transmission amplitude distribution, transmitted by the transmitting device, propagates along each structurally stable propagation path in the mine roadway. Each structurally stable propagation path introduces corresponding propagation delay and phase shift to the signal components. Since the transmitting device has already reversed the transmission time of each electromagnetic wave component according to the propagation delay parameter of the corresponding structurally stable propagation path during the transmission time adjustment, that is, the advance amount of the transmitting end is equal to the propagation lag amount, each electromagnetic wave component arrives at the receiving device simultaneously after propagating on its respective structurally stable propagation path, thus achieving time alignment. Regarding phase consistency, after the receiving device receives the signal components contributed by each structurally stable propagation path, when performing channel equalization on each signal component, its equivalent baseband response is the product of the statistical propagation response parameters of the structurally stable propagation path and the corresponding matching weighting coefficients. After substituting the construction rules of the matching weighting coefficients in step S104 into this product, the argument of the matching weighting coefficients is equal to the negative of the argument of the statistical propagation response parameters. Therefore, the sum of the argument of the statistical propagation response parameters and the argument of the matching weighting coefficients is 0, and the phase term in the statistical propagation response parameters is completely canceled out. At the same time, since the linear phase correction process in step S102 has eliminated the propagation phase drift caused by the local oscillator frequency deviation, each electromagnetic wave component has phase consistency at the receiving device, that is, the phases of each component tend to be the same. Since all electromagnetic wave components arrive simultaneously and have phase consistency, the amplitudes of each electromagnetic wave component are superimposed in phase at the receiving device. The amplitude of the received signal obtained after in-phase superposition is equal to the sum of the amplitudes of the signal components contributed by each structurally stable propagation path. Compared with the case of random phase superposition of each component without pre-compensation, the amplitude of the received signal is enhanced, realizing the compensation for signal attenuation caused by multipath propagation in mine roadways. Specifically, matching weighted coefficients Substitute the first Equivalent baseband response at the receiver of a stable propagation path with a strip structure ,get:

[0031] because It is a dimensionless positive real number. The numerator is a real number greater than or equal to zero. For real numbers greater than or equal to zero, since the denominator It is a positive real number greater than zero, therefore The result is a positive real number, which proves that after compensation by matching weighted coefficients, the th The received response of a stable propagation path with a linear structure does not contain an imaginary part; statistical propagation response parameters are used. The propagation phase shift contained therein is completely canceled out, all The received responses of the stable propagation path of the bar structure are all positive real numbers, and the phases of each electromagnetic wave component are completely consistent, achieving in-phase superposition at the receiving device; In the closed-loop adaptive update sub-step, the receiving device periodically re-executes steps S101 to S105 to update the set of structurally stable propagation paths and wireless transmission matching parameters, thereby achieving continuous adaptive tracking of multipath environmental changes in mine roadways. Specifically, the receiving device acquires a preset update cycle. The duration of the preset update cycle is determined based on the changing state of the wireless propagation environment in the mine roadway. The changing state of the wireless propagation environment in the mine roadway refers to the time-varying rate of the wireless propagation environment, which is determined by a combination of factors such as the frequency of personnel movement, the frequency of equipment movement, and the operating status of the ventilation system. In some embodiments, the changing state of the environment can be divided into multiple levels, each level corresponding to a preset update cycle value. During operation periods when personnel and equipment are frequently active in the roadway, the changing state of the environment is at a higher level, and the preset update cycle is set to a shorter value, typically ranging from 0.1 seconds to 1 second. During maintenance or shutdown periods when personnel and equipment are sparsely active in the roadway, the changing state of the environment is at a lower level, and the preset update cycle is set to a longer value, typically ranging from 1 second to 10 seconds. The duration of the preset update cycle should be greater than the duration of the preset statistical time range to ensure that the receiving device has completed the statistical fusion processing of all multipath propagation response distributions within the preset statistical time range for each update, and generates new wireless transmission matching parameters based on the complete statistical fusion data. The receiving device re-executes steps S101 to S105 at each preset update period. During each re-execution, the propagation path stability of each wireless propagation path is recalculated based on the latest measured multipath propagation response distribution. The set of structurally stable propagation paths is re-selected, and the wireless transmission matching parameters are re-determined and sent to the transmitting device through the backhaul wireless link. In some embodiments, when the existing set of structurally stable propagation paths fails due to the initial startup or significant changes in the mine roadway environment, the receiving device needs to perform a cold start procedure. The specific operation of the cold start procedure is as follows: the receiving device first performs several rounds of complete propagation response measurement, local oscillator frequency offset estimation and phase correction processing, and statistical fusion processing. It then uses the accumulated initial multipath propagation response distribution to construct the first set of structurally stable propagation paths and the first wireless transmission matching parameter. During the cold start phase, the transmitting device does not perform pre-compensation processing and transmits the original waveform of the wireless signal to be transmitted. After the first wireless transmission matching parameter is successfully generated and fed back to the transmitting device, it enters the closed-loop adaptive tracking state, and the transmitting device begins to perform multipath pre-compensation processing based on the wireless transmission matching parameter. Through the aforementioned closed-loop adaptive update mechanism, the receiving device can continuously track changes in the wireless propagation environment of the mine roadway. When environmental changes cause changes in the propagation characteristics of the original structurally stable propagation path or the emergence of a new structurally stable propagation path, the receiving device can update the set of structurally stable propagation paths and wireless transmission matching parameters in a timely manner, so that the multipath pre-compensation processing always matches the current multipath propagation environment of the mine roadway and maintains the continuous effectiveness of the in-phase superposition effect.

[0032] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0033] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0034] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for compensating signal attenuation in wireless sensor networks under multipath environments in mine roadways, characterized in that, include: The receiving device measures the propagation response of the wireless detection transmission periodically transmitted by the transmitting device, and obtains the multipath propagation response distribution including the propagation delay parameters, amplitude attenuation parameters and phase change parameters of each wireless propagation path. Phase difference calculation is performed on the phase change parameters of the same wireless propagation path in multiple consecutive multipath propagation response distributions to extract the propagation phase drift caused by the local oscillator frequency deviation between transceivers. Based on the propagation phase drift, phase unwrapping and linear phase correction processing are performed on each multipath propagation response distribution path by path. Within a preset statistical time range, the processed multipath propagation response distribution is statistically fused path by path to obtain the statistical propagation response parameters and amplitude fluctuation characteristic parameters corresponding to each wireless propagation path. The propagation path stability is obtained from these two parameters. Propagation paths whose propagation path stability exceeds a preset threshold are determined as structurally stable propagation paths, thus forming a set of structurally stable propagation paths. By determining the wireless transmission matching parameters based on the set of structurally stable propagation paths, the wireless transmission matching parameters are associated with the propagation path stability, the conjugate value of the statistical propagation response parameters, and the propagation delay parameters corresponding to each structurally stable propagation path. The wireless transmission matching parameters are sent to the transmitting device. The transmitting device adjusts the transmission time and transmission amplitude distribution according to the wireless transmission matching parameters, so that the electromagnetic wave components of each structurally stable propagation path after the electromagnetic wave propagates through the multipath of the mine roadway are superimposed in phase at the receiving device. The receiving device periodically re-executes the above steps to update the set of structurally stable propagation paths and the wireless transmission matching parameters, forming a closed-loop adaptive wireless propagation in the mine roadway.

2. The method according to claim 1, characterized in that, Obtain the multipath propagation response distribution, including propagation delay parameters, amplitude attenuation parameters, and phase change parameters for each wireless propagation path. Specifically, this includes: The receiving device receives the wireless detection transmission periodically transmitted by the transmitting device, extracts the propagation response parameters from the known detection waveform in the received signal, and determines the propagation delay parameters, amplitude attenuation parameters, and phase change parameters corresponding to each wireless propagation path based on the matching relationship between the received signal and the known detection waveform. The set of propagation delay parameters, amplitude attenuation parameters, and phase change parameters corresponding to all wireless propagation paths is taken as the multipath propagation response distribution.

3. The method according to claim 1, characterized in that, Extracting the propagation phase drift caused by the local oscillator frequency deviation between the transceiver devices, specifically including: Phase unwrapping is performed on the phase change parameters of the same wireless propagation path in multiple continuously acquired multipath propagation response distributions to eliminate phase jumps generated by the phase change parameters within the periodic value range. Differential calculations are performed on the phase change parameters of two adjacent measurements after unwinding to obtain the phase difference sequence corresponding to the wireless propagation path; linear fitting is performed based on the time relationship between the phase difference sequence and the corresponding propagation response measurement time, and the slope of the fitted line is determined as the propagation phase drift rate caused by the local oscillator frequency deviation between the transceiver devices; the propagation phase drift is determined based on the propagation phase drift rate and the propagation response measurement time interval. Based on the propagation phase drift, linear phase correction is performed path-by-path on the multipath propagation response distribution, specifically including: Using the moment of the first propagation response measurement as the phase reference zero point, the time offset of the measurement moment corresponding to each propagation response measurement relative to the moment of the first propagation response measurement is obtained; the propagation phase drift is multiplied by the time offset to obtain the cumulative phase drift of that propagation response measurement. For each wireless propagation path in the multipath propagation response distribution obtained after phase unwrapping processing in this propagation response measurement, the phase change parameter of the wireless propagation path is subtracted from the cumulative phase drift; the multipath propagation response distribution after the above processing is the multipath propagation response distribution after phase correction processing.

4. The method according to claim 3, characterized in that, Obtain the statistical propagation response parameters and amplitude fluctuation characteristic parameters corresponding to each wireless propagation path, specifically including: Obtain the total number of frames of all multipath propagation response distributions after phase correction processing within a preset statistical time range; for any wireless propagation path, construct the complex amplitude value of the wireless propagation path in this measurement by using the amplitude attenuation parameter of the wireless propagation path in the multipath propagation response distribution after each phase correction processing as the modulus and the phase change parameter after phase correction processing as the argument. The statistical propagation response parameters of the wireless propagation path are obtained by summing all the complex amplitude values ​​corresponding to the wireless propagation path in the entire multipath propagation response distribution and dividing the result of the complex summation by the total number of frames. The statistical propagation response parameters of each wireless propagation path are obtained by traversing all wireless propagation paths. For any wireless propagation path, obtain the amplitude attenuation parameter in the multipath propagation response distribution after phase correction processing for each frame within the preset statistical time range, and obtain the magnitude of the statistical propagation response parameter of the wireless propagation path; subtract the magnitude of the statistical propagation response parameter from the amplitude attenuation parameter of each frame to obtain the amplitude deviation value of each frame; perform an arithmetic mean on the squares of the amplitude deviation values ​​of all frames, and perform a square root operation on the result of the arithmetic mean to obtain the amplitude fluctuation characteristic parameter of the wireless propagation path; traverse all wireless propagation paths to obtain the amplitude fluctuation characteristic parameter corresponding to each wireless propagation path.

5. The method according to claim 4, characterized in that, The stability of the propagation path is obtained from statistical propagation response parameters and amplitude fluctuation characteristic parameters, specifically including: For any wireless propagation path, obtain the magnitude of the statistical propagation response parameter of the wireless propagation path, obtain a preset positive constant, add the preset positive constant to the amplitude fluctuation characteristic parameter of the wireless propagation path to obtain the fluctuation adjustment value; divide the magnitude of the statistical propagation response parameter by the fluctuation adjustment value to obtain the propagation path stability of the wireless propagation path; traverse all wireless propagation paths to obtain the propagation path stability corresponding to each wireless propagation path. The set of structurally stable propagation paths specifically includes: A preset threshold value is obtained, and the propagation path stability of all wireless propagation paths is compared with the preset threshold value one by one. Wireless propagation paths with a propagation path stability greater than the preset threshold value are determined as structurally stable propagation paths. All structurally stable propagation paths constitute a set of structurally stable propagation paths, which includes the propagation delay parameter, statistical propagation response parameter, and propagation path stability of each structurally stable propagation path.

6. The method according to claim 5, characterized in that, This associates the wireless transmission matching parameters with the propagation path stability, the conjugate value of the statistical propagation response parameters, and the propagation delay parameters corresponding to each structurally stable propagation path. Specifically, this includes: For each structurally stable propagation path, the inverse of the propagation delay parameter of the structurally stable propagation path is taken as the matching delay position corresponding to the structurally stable propagation path; the conjugate operation is performed on the statistical propagation response parameter of the structurally stable propagation path to obtain the statistical propagation response conjugate value; the propagation path stability of the structurally stable propagation path is multiplied by the statistical propagation response conjugate value to obtain the weighted conjugate value of the structurally stable propagation path. The normalized reference value is obtained by summing the products of the propagation path stability of each structurally stable propagation path and the square of the magnitude of its respective statistical propagation response parameter. The weighted conjugate value of the structurally stable propagation path is divided by the normalized reference value to obtain the matching weighting coefficient corresponding to the structurally stable propagation path. All matching delay positions and the matching weighting coefficients corresponding to each matching delay position are used together as the wireless transmission matching parameters.

7. The method according to claim 6, characterized in that, The transmitting device adjusts the transmission timing and amplitude distribution according to the wireless transmission matching parameters, specifically including: The transmitting device extracts all matching delay positions and the matching weighting coefficients corresponding to each matching delay position from the wireless transmission matching parameters; based on the matching delay positions and matching weighting coefficients, it performs multipath pre-compensation processing on the wireless signal to be transmitted, so that the wireless signal to be transmitted generates a delay offset in the time domain that matches the propagation delay parameters of each structurally stable propagation path, and generates an amplitude adjustment that matches each matching weighting coefficient; the signal with the generated delay offset and amplitude adjustment is transmitted through the wireless propagation channel in the mine roadway. After electromagnetic waves propagate through multiple paths in a mine tunnel, the electromagnetic wave components of each structurally stable propagation path are superimposed in phase at the receiving device, specifically including: The wireless signals transmitted by the transmitting device, after adjustment of transmission time and amplitude distribution, propagate along the stable propagation paths of each structure in the mine roadway. Since the linear phase correction process has eliminated the propagation phase drift caused by the local oscillator frequency deviation, and the transmitting device has reversed the transmission time of each electromagnetic wave component according to the propagation delay parameter of the corresponding stable propagation path during the transmission time adjustment, each electromagnetic wave component arrives at the receiving device simultaneously and has phase consistency, and the amplitudes of each electromagnetic wave component are superimposed in phase at the receiving device.

8. The method according to claim 7, characterized in that, The receiving device periodically re-executes each step to update the set of structurally stable propagation paths and the wireless transmission matching parameters, specifically including: The receiving device obtains a preset update cycle and, with the preset update cycle as the time interval, re-executes each step when the preset update cycle arrives. During each re-execution, the propagation path stability of each wireless propagation path is recalculated based on the latest measured multipath propagation response distribution, a new set of structurally stable propagation paths is selected, the wireless transmission matching parameters are re-determined, and the data is sent to the transmitting device through the backhaul wireless link.

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