A wireless communication channel modeling method based on a tunnel construction scene

Abstract

The application provides a wireless communication channel modeling method based on a tunnel construction scene, and aims to solve the problems that the channel modeling in the current tunnel construction field does not conform to the actual needs of the construction site, is complicated to calculate, has low accuracy and is not expandable and universal. The application comprises three parts of a theoretical calculation method, a computer simulation method and an actual measurement method. The actual measurement method selects a transmitter and a receiver and determines the installation positions of the transmitter and the receiver from the perspective of the construction site requirements. The theoretical calculation method calculates the received power of a receiving point by using an improved ray tracing method based on the tunnel construction scene. The computer simulation method performs simulation based on a WinProp wave propagation solution simulation modeling method. The simulation results are compared with the results obtained by the theoretical calculation method and the actual measurement method to verify the application. The application has the advantages of conforming to the construction site requirements, being simple to calculate, having high accuracy and being expandable and universal.

Description

Technical Field

[0001] This invention relates to the technical field of tunnel construction, and in particular to a method for modeling wireless communication channels in tunnel construction scenarios. Background Technology

[0002] With the continuous increase in population and the gradual advancement of urbanization, underground rail transit has received more attention and importance. The shield tunneling method utilizes a tunnel boring machine (TBM) for excavation, primarily used in urban subway tunnel construction. During excavation, segment assembly provides support to prevent ground collapse. Generally, the tunnel diameter after segment assembly is between 6.2 and 6.5 meters, with a standard segment width of 1.5 meters. To improve the excavation efficiency, construction quality, and safety of TBMs, the domestic TBM industry has begun to propose the concept of intelligent TBMs. Ensuring full-line networking during tunnel construction is a prerequisite for achieving interconnectivity among various devices in intelligent TBMs. Therefore, wireless networking in tunnel construction scenarios is a key issue that urgently needs to be researched and solved. To solve the problem of full-line networking within the tunnel, it is necessary to study the modeling of wireless communication channels in tunnel construction scenarios. This will provide theoretical guidance for on-site work during actual deployment, ensuring the signal strength, communication bandwidth, latency, and other indicators of the network.

[0003] Tunnels are narrow, confined spaces exhibiting unique waveguide effects. Signals propagating within a waveguide experience less power attenuation compared to free-space propagation, with a path loss exponent less than 2. Furthermore, waveguides possess high-pass filter characteristics; high-frequency signals propagating in a tunnel experience less power attenuation with distance compared to low-frequency signals, including multipath signals. Current tunnel channel modeling generally falls into static and dynamic scenario modeling. Dynamic scenario modeling is suitable for clustered mobile devices but is complex and less accurate. For example, patent CN 114499721 A discloses a method for modeling channel communication between vehicles, and patent CN 109639378 A discloses a method for modeling vehicle-to-vehicle communication in rectangular tunnels. Since most tunnel construction scenarios are static, modeling is based on static scenarios. To ensure accuracy, current tunnel channel modeling employs a combination of theoretical calculations and actual measurements. Most of these methods utilize omnidirectional antennas with SISO (Single-Input Single-Output) transceivers to perform theoretical calculations in tunnel scenarios, followed by on-site measurements. For example, patent CN107276705 A uses an omnidirectional antenna transceiver, which requires consideration of circumferential electromagnetic radiation during calculation, resulting in a large computational load, long calculation time, and high computational complexity. Compared to SISO transmission, MIMO (Multiple-Input Multiple-Output) wireless transmission technology fully utilizes spatial resources, maximizing spectrum utilization and power efficiency. Patent CN 114465682 A proposes a mine MIMO channel modeling method. This method derives system-related functions by establishing models of direct and scattered signal components, primarily calculating channel capacity for power allocation. Similarly, patent CN 105721087 B also establishes a three-dimensional model of the tunnel, divides it, and calculates the transfer function during propagation. Because the scattering points of rectangular tunnels are easy to divide, both methods are mostly applicable to rectangular tunnels. Calculations for other cross-section tunnels are more complex and time-consuming, failing to meet the actual on-site construction needs. During on-site measurements, measurements are typically taken in the middle of the tunnel. However, the location of the receiver during measurement can lead to significant errors in the results, affecting accuracy. Therefore, considering practical construction needs, the measurement location should be fixed on the tunnel sidewall to avoid interfering with transport vehicles and personnel. Furthermore, using an omnidirectional antenna during measurements results in relatively low antenna gain, leading to weaker received signals and greater noise at longer distances, thus impacting measurement accuracy. Summary of the Invention

[0004] To address the technical problems of large data processing volume and low accuracy in existing tunnel construction mixed spraying support technologies, this invention proposes a wireless communication channel modeling method based on tunnel construction scenarios. This method solves the problems of current channel modeling in the tunnel construction field not meeting the actual needs of the construction site, being computationally complex, having low accuracy, and lacking scalability and universality.

[0005] To achieve the above objectives, the technical solution of this invention is implemented as follows: a wireless communication channel modeling method based on tunnel construction scenarios, comprising three parts: a theoretical calculation method, a computer simulation method, and an actual measurement method; the actual measurement method selects the transmitter and receiver from the perspective of on-site construction requirements and determines the installation positions of the transmitter and receiver; the theoretical calculation method calculates the received power of the receiving point using an improved ray tracing method based on the tunnel construction scenario, according to the installation positions of the transmitter and receiver; the computer simulation method performs simulation based on the WinProp radio wave propagation solution simulation modeling method, according to the antenna parameters of the transmitter and receiver and the installation positions of the transmitter and receiver; the simulation results are compared and verified with the results obtained by the theoretical calculation method and the actual measurement method.

[0006] Preferably, the actual measurement method is based on the actual on-site construction requirements, which determines the antenna type and radiation angle of the transmitter and receiver, as well as the measurement interval for each interval.

[0007] Preferably, the transmitter's transmitting antenna is a directional antenna, oriented towards the working face inside the tunnel; the transmitter uses MIMO wireless transmission; and the receiver is a spectrum scanner with an omnidirectional antenna for measuring signal field strength.

[0008] Preferably, the directional antenna is a dual-polarized directional flat panel antenna with a radiation angle of 15-25 degrees; the transmitter has a frequency range of 5150-5850Hz.

[0009] Preferably, in the axial direction, both the transmitter and receiver are deployed at the segment joint; in the cross-sectional direction, both the transmitter and receiver are located in the horizontal plane where the tunnel axis is located, and the measurement interval is an integer multiple of the segment width; both the transmitter and receiver are located on the same side wall in the horizontal plane of the tunnel axis.

[0010] The improved ray tracing method combines the advantages of the Spot Sphere Receiver (SBR) and Image tracing methods. The traditional SBR method cannot determine the location of the reflection point, while the Image method, although it can, treats the receiver as a virtual point, which is not realistic. Therefore, the advantages of both methods are combined: the Image tracing method is used to obtain the location of the reflection point at the center of the receiver, and the SBR method is used to obtain the field strength within a certain range at the receiver, thus enabling more accurate theoretical modeling. Specifically, the three-dimensional ray propagation in the SBR method is mapped to two-dimensional ray propagation within the horizontal plane containing the axis. For the transmitter, the wavefronts of all emitted rays, which are spherical waves, are mapped to plane waves. For the receiver, at shorter distances, the receiving sphere, with the antenna and receiver lengths as its diameter, is mapped to a semi-circular receiving surface. At longer distances, the radius of the semi-circular receiving surface increases accordingly by a coefficient, but cannot exceed the radius of the tunnel. Here, the radius of the receiving surface is limited by restricting the angular interval of the emitted rays, and the center of the semi-circular receiving surface is assumed to be located at the joint of adjacent tunnel segments. The angular interval of the transmitter's emitted waves can be determined according to the formula... Obtain, R re It is the radius of the circular receiving surface, d max It is the maximum propagation distance during measurement; when the distance between the transmitter and receiver is l, the angular range of the emitted ray is... Where d is the tunnel diameter, the emitted electromagnetic wave number is:

[0011] Preferably, when the circular tunnel is a straight section, the reflection path length and reflection angle are calculated using the center of the semi-circular receiving surface, i.e., the joint of the tunnel segments, as an example. The improved ray tracing method is implemented by using a Cartesian coordinate system to calculate the distance and reflection angle between the transmitter and receiver, taking the transmitter's location point P as an example. s Point P, the location of the receiver, is the origin of the Cartesian coordinate system. r With point P s The spacing between them is l = l g ×N meters, where, l g Where N is the width of the tunnel segment and N represents the number of tunnel segments; the reflection angle θ is calculated using trigonometric functions. r and the angle of incidence θ i for Where d is the tunnel diameter;

[0012] The incident diameter length l was calculated using the Pythagorean theorem. i With the reflection path length l r for reflectivity θ r Incident diameter length l i and reflection diameter length l rSubstituting these values ​​into the formula for calculating the received power in the ray tracing method, we can obtain the received power at the receiving point.

[0013] Preferably, when the circular tunnel is curved, the reflection path length and reflection angle are calculated using the center of the semi-circular receiving surface, i.e., the joint of the tunnel segments, as an example. The improved ray tracing method is as follows: the distance and reflection angle between the receiver and transmitter are calculated using a polar coordinate system, where the curve axis is a transition curve with a radius of R meters; the two sidewalls of the tunnel form an inner circle and an outer circle, the difference in radius between the inner and outer circles is the tunnel diameter d meters, and the origin of the polar coordinate system is the center O of the transition curve between the inner and outer circles. The position of the transmitter is... Location of the receiver The location is at a radius of On the circle, with the width l of the tube segment on the circle. g The arc length is divided into several equal parts by the distance between the transceivers, where the straight-line distance between the transceivers is point P. s and point P r The chord length l of the arc c The centerline of the transmitter and receiver intersects the inner circle at point F, the outer circle at point W, and the chord length l. c They intersect at point C, connect points F and P. s The angle between the line containing the incident light and the center line is the angle θ. i Connect point F and point P r The angle between the line and the center line is the reflection angle θ. r Because the division is equally spaced, the arc lengths of the transmitter and receiver locations... and the included angle θ = θ u ×N, θ u For the width of a single segment l g The corresponding radians; then the chord length. Similarly, we can obtain the distance from point W to point P. r chord length l wpr From point W to point P s chord length l wps for

[0014] The length of line segment WC can be obtained using the Pythagorean theorem. Therefore, the length l of line segment CF can be obtained. cf Finally, the incident angle θ can be obtained. i and reflection angle θ r Incident diameter length l psf and reflection path length l prf for Substituting these values ​​into the formula for calculating the received power in the ray tracing method, we can obtain the received power at the receiving point.

[0015] Preferably, the method for calculating the received power using the ray tracing method is as follows:

[0016] The electric field of the direct path is calculated as follows:

[0017] The electric field of the reflection path is calculated as follows:

[0018] The electric field at the receiving point is: E total =E D +∑E R ;

[0019] Where E0 is the electric field at the reference point; d D and d R These are the total path lengths of the direct path and the reflected path, respectively, and the incident path length l when the tunnel is a straight section. i and reflection diameter length l r Or, the incident radius length l when the tunnel is a curve. psf and reflection path length l prf ;R i The reflection coefficient represents the i-th reflection along the reflection path; q is the total number of reflections along the reflection path. λ is the wavelength of the electromagnetic wave;

[0020] The total power of the receiving point is:

[0021]

[0022] Among them, P t It is the antenna's transmit power; G t and G r These are the gains of the transmitting antenna and the receiving antenna, respectively. ε is the wave impedance in free space, μ0 is the permeability, and ε0 is the permittivity.

[0023] Preferably, the method for calculating the reflection coefficient is as follows:

[0024] Considering the polarization of electromagnetic waves, the incident electric field is decomposed into two components: perpendicular polarization and parallel polarization. The reflection coefficient is then calculated for each component. The decomposition process is as follows:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] Among them, E p and E n These represent the components of the electric field in the parallel and perpendicular polarization directions, respectively; E i and E r These are the incident electric field and the reflected electric field, respectively. and Let R represent unit vectors parallel to and perpendicular to the plane of incidence, respectively; p R n ε1 and ε2 are the reflection coefficients in the horizontal and vertical directions, respectively; ε2 and ε1 are the dielectric constants.

[0031] Preferably, when a battery-powered rail transport vehicle enters the tunnel during construction, it significantly affects the propagation of radio waves within the tunnel. Therefore, it is necessary to solve for and model the radio waves in the area where the battery-powered vehicle is located. During tunnel construction, the height of the battery-powered vehicle exceeds the plane containing the tunnel axis. Therefore, when the battery-powered vehicle moves, due to obstruction, the opposite side of the transmitter's location is a region with relatively weak field strength, while the same side experiences a change in field strength due to the offset of the reflecting surface, and the same side is a region with relatively strong field strength. The calculation method for the field strength on the same side is similar to the improved ray tracing method, except that the reflecting surface is offset inward, which can be considered as a reduction in the tunnel diameter. Due to obstruction, the field strength on the opposite side cannot be reached by the direct path. Therefore, only the field strength of the reflection path is considered in the calculation. Also, due to obstruction, only the reflection from the top surface of the tunnel can be considered. The calculation point P for the field strength on the opposite side is... ops and the location P of the transmitter s Connecting the two lines, the intersection of the line and the top surface of the tunnel is the reflection point P. f From point P ops Point P s With point P f The three points form a two-dimensional plane, similar to the horizontal plane containing the axis, also centered on the emission point P. s A Cartesian coordinate system is established with the origin as the reference point. The reflection path and reflection angle are calculated in the same way as the improved ray tracing method. It should be noted that the field strength of the direct path is 0. Since the length of the electric railcar is generally tens of meters, it can be considered as a straight road relative to the curve radius of thousands of meters in the tunnel. Thus, the field strength distribution model of the same side and opposite side of the area where the electric railcar is located is obtained.

[0032] Preferably, the WinProp-based simulation modeling method for solving radio wave propagation is as follows: An antenna diagram of the transmitter is established based on the transmitter selected according to the actual measurement method, including the polarization radiation angle and gain of the antenna diagram; a two-dimensional and three-dimensional model of the tunnel is established, including the length of the straight sections and curves of the tunnel, the turning radius, the tunnel diameter, the tunnel wall material, the distribution of obstacles, and the receiver position; the orientation and transmission power of the transmitter antenna in the three-dimensional model of the tunnel are defined, and the installation position of the transmitter antenna is defined; a simulation algorithm is selected for simulation calculation; the simulation algorithm is a 3D-SRT ray tracing model or an SBR ray tracing model.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. Based on the actual needs of tunnel construction, this paper proposes a channel modeling method that combines theoretical calculations, computer simulations, and actual measurements. This method has the advantages of meeting the needs of on-site construction, being simple to calculate, highly accurate, scalable, and versatile. It lays the foundation for interconnection and networking of various equipment in tunnel construction and has important guiding significance.

[0035] 2. This invention compares and verifies the results from three dimensions: theoretical calculation, computer simulation, and actual measurement. It improves the understanding of electromagnetic wave propagation solutions and the accuracy of channel models in tunnel construction scenarios, and has great guiding significance for network planning within tunnels. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This invention is a schematic diagram of the installation and deployment of transmitters and receivers inside a tunnel.

[0038] Figure 2 for Figure 1 The left view.

[0039] Figure 3 A schematic diagram illustrating the calculation of ray angle and receiving area for the improved ray tracing method.

[0040] Figure 4 This is a schematic diagram of the improved ray tracing method for straight-line calculation in this invention.

[0041] Figure 5 This is a schematic diagram of the improved ray tracing method for curve calculation in this invention.

[0042] In the diagram, 1 represents the tunnel, 2 represents the transmitter, 3 represents the tunnel axis, 4 represents the receiver, 5 represents the tunnel segment, and 6 represents the tunnel face. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, a wireless communication channel modeling method based on tunnel construction scenarios is presented. This method is suitable for actual construction site needs, is computationally simple, highly accurate, and possesses scalability and versatility. The invention comprises three parts: a theoretical calculation method, a computer simulation method, and an actual measurement method. The theoretical calculation method uses an improved ray tracing method based on tunnel construction scenarios to calculate the received power at the receiving points. The computer simulation method is based on the WinProp radio wave propagation solution simulation modeling method to simulate the power at each receiving point. The actual measurement method is the method used during on-site measurement, including the installation positions of transmitter 2 and receiver 4, the type and radiation angle of the antenna used, and the measurement interval for each interval. The measurement interval is specified; in this invention, the width of one tunnel segment is selected.

[0045] The actual measurement method is based on the on-site construction requirements. Considering the narrow and confined characteristics of the tunnel, transmitter 2 uses a dual-polarized directional flat panel antenna with a radiation angle of 17° and a gain of 18dBi, oriented towards the tunnel face 6. The transmitter uses a 2T2R MIMO configuration, operating at a frequency of 5.55GHz with a bandwidth of 40MB. Receiver 4 is a KEYSIGHT N9914A spectrum scanner with a 4dBi omnidirectional antenna. Both theoretical and simulation calculations are performed using this transceiver. Theoretical calculations require specifying the wavelength and antenna gain; the wavelength can only be specified when the frequency is given. Simulation calculations require determining the antenna position, direction, gain, transmit power, and frequency. The 17° radiation angle and 5.55GHz frequency of transmitter 2's directional antenna can be modified according to different scenarios. For example, changes in the antenna's size will affect the radiation angle, which is not limited to 17°; a preferred radiation angle is 15-25 degrees. Within the scope permitted by national regulations, and not limited to any particular frequency band (the 5.8 GHz band ranges from 5150-5850 Hz), the transmitter's communication protocol is not restricted. The receiver is not limited to Keysight Technologies' spectrum analyzers; other high-precision spectrum analyzers such as Rohde & Schwarz FSH8, TFN FAT801, and Cord GD7500 are also acceptable. The receiver's antenna gain is not limited to 4dBi; any omnidirectional antenna with arbitrary gain can be used, matched with the spectrum analyzer for signal strength measurement.

[0046] The actual measurement method involves fixing one end of the transmitter to one side of the tunnel wall, and then measuring the field strength with the receiver for each tunnel segment width (1.5m). This allows us to determine the magnitude of the field strength at different locations. Figure 1 and Figure 2 As shown, in the actual measurement method, when installing transmitter 2 and receiver 4 during the construction of tunnel 1, in order not to affect on-site construction, improve convenience, and protect the integrity of the tunnel segments, transmitter 2 and receiver 4 are both deployed at the joints of tunnel segments 5 in the axial direction. In the cross-sectional direction, transmitter 2 and receiver 4 are both located in the horizontal plane where tunnel axis 3 is located, and the measurement interval is an integer multiple of the width of tunnel segment 5. This deployment method is followed in both theoretical calculations and simulation calculations.

[0047] The theoretical calculation method refers to an improved ray tracing method based on a tunnel construction scenario. The distance between transmitter 2 and receiver 4 is an integer multiple of the width of segment 5, where the standard segment width is 1.5 meters. The ray tracing method calculates based on the reflection, refraction, and diffraction of electromagnetic waves. The components of refraction and diffraction within the tunnel are very small and negligible. For reflection, a specified number of reflections serves as a boundary; beyond this number, the reflected electromagnetic wave component is considered very small and no longer included in the calculation. In the improved ray tracing method, transmitter 2 and receiver 4 are both located on the same sidewall within the horizontal plane of the tunnel axis. Transmitter 2 is a directional antenna facing the construction direction of the tunnel face 6; therefore, in the improved ray tracing method, the portion behind transmitter 2 can be considered as having no electromagnetic wave propagation. When electromagnetic waves propagate on the top and bottom surfaces, since tunnel 1 has a circular cross-section, they can ultimately be included in the direct path range. Therefore, the final considered reflecting surface is the sidewall opposite the installation position.

[0048] like Figure 3 As shown, the improved ray tracing method combines the advantages of the Spot Sphere Receiver (SBR) method and the Image method. The traditional SBR method cannot determine the location of the reflection point, while the Image method, although it can, treats the receiver as a virtual point, which is not entirely accurate. Therefore, this invention combines the advantages of both methods, using the Image method to obtain the reflection point location at the center of the receiver and the SBR method to obtain the field strength within a certain range at the receiver, thus enabling more accurate theoretical modeling. The specific method is as follows: the three-dimensional ray propagation in the SBR method is mapped to two-dimensional ray propagation within the horizontal plane containing the axis. For the transmitter, the wavefronts of all emitted rays, which are spherical waves, are mapped to plane waves. For the receiver, at shorter distances, the receiving sphere with the antenna and receiver lengths as diameters is mapped to a semi-circular receiving surface. At longer distances, the radius of the semi-circular receiving surface increases accordingly by a coefficient, but cannot exceed the radius of the tunnel. Here, the radius of the receiving surface is limited by restricting the angular interval of the emitted rays, and it is assumed that the center of the semi-circular receiving surface is located at the joint of adjacent tunnel segments. The angular interval of the transmitter's emitted waves can be determined according to the formula... Obtain, R re It is the radius of the circular receiving surface, d max It is the maximum propagation distance during measurement; when the distance between the transmitter and receiver is l, the angular range of the emitted ray is... Where d is the tunnel diameter, the emitted electromagnetic wave number is:

[0049] like Figure 4As shown, in the improved ray tracing method, when tunnel 1 is a straight section, the reflection diameter and reflection angle are calculated using the center of the semi-circular receiving surface, i.e., the joint of the tunnel segments, as an example; the distance and reflection angle between transmitter 2 and receiver 4 are calculated using a Cartesian coordinate system, with the location P of transmitter 2 as the reference point. s Point P is the origin of the two-dimensional coordinate system, and the location of receiver 4 is P. r Point and P s The distance between the points is l = 1.5 × N meters, where N represents the number of tunnel segments. Given the tunnel diameter d and the transceiver spacing l, the reflection angle θ can be calculated using trigonometric functions. r According to the reflection theorem, the incident angle θ i Equal to the reflection angle θ r Therefore, the incident diameter length l can be calculated using the Pythagorean theorem. i With the reflection path length l r , reflectivity θ r Incident diameter length l i and reflection diameter length l r Substituting these values ​​into the formula for calculating the received power using the ray tracing method, we can obtain the received power at the receiving point. The calculation formula is shown below:

[0050]

[0051]

[0052] The distance between transmitter 2 and receiver 4 is l = 1.5 × N, where N is the number of tube segments.

[0053] like Figure 5 As shown, in the improved ray tracing method, when tunnel 1 is a curve, the reflection path length and reflection angle are calculated using the center of the semi-circular receiving surface, i.e., the joint of the tunnel segments, as an example. The distance between the transceiver and the reflection angle are calculated using a polar coordinate system, where the curve axis is a transition curve with a radius of R meters. In the curve, the two sidewalls of the tunnel form two circles, the difference in radius between the inner and outer circles being the tunnel diameter d meters. The origin of the polar coordinate system is O, the center of the transition curve, and the location of transmitter 2 is... Position point of receiver 4 The location is at a radius of The circle is divided into several equal parts with an arc length of 1.5 meters, and the straight-line distance between the transceiver and the point is point P. s and point P r The chord length l of the arc c The centerline of the transceiver's location intersects the inner circle at point F, the outer circle at point W, and the chord length at point C. Connect point F with point P, the location of the transmitter. s The angle between the incident angle and the centerline is the angle θ. iConnection point F and the location point P of the receiver r The angle between the centerline and the reflection angle θ is the reflection angle. r Because the division is at equal intervals, the angle θ is 1.5 meters per unit arc length. u Since it is known, the arc length l of the transceiver's location is... a The included angle θ is known, therefore the chord length l can be obtained. c Similarly, we can obtain the distance from point W to point P. r chord length l wpr From point W to point P s chord length l wps According to the Pythagorean theorem, the length l of line segment WC can be obtained. wc Therefore, the length l of line segment CF can be obtained. cf Finally, the incident angle θ can be obtained. i and reflection angle θ r Incident diameter length l psf and reflection path length l prf Substituting this into the formula for calculating the received power in the ray tracing method, we can obtain the received power at the receiving point.

[0054]

[0055] θ=θ u ×N (4)

[0056]

[0057]

[0058]

[0059]

[0060] Where N is the number of segments, θ u The unit radius corresponds to 1.5m of tunnel segment.

[0061] After obtaining the incident diameter, reflected diameter, incident angle, and reflected angle, these values ​​are substituted into the calculation formula for the ray tracing method to obtain the received power at the receiving point. The ray tracing method calculation is divided into direct diameter field strength calculation and reflected diameter field strength calculation, and the calculation methods are as follows:

[0062] The electric field of the direct path is:

[0063]

[0064] The electric field of the reflection path is:

[0065]

[0066] The electric field at the receiving point is:

[0067] E total =E D +∑E R (11)

[0068] Where E0 is the electric field at the reference point, typically taken as the electric field at a distance of 1m from the emission point; d D and d R These are the total path lengths of the direct path and the reflected path, respectively, and the incident path length l obtained when the tunnel is a straight section. i and reflection diameter length l r The incident diameter length l obtained when the tunnel is a curve psf and reflection path length l prf ;R i The reflection coefficient represents the i-th reflection along the reflection path; q is the total number of reflections along the reflection path. λ is the wavelength of the electromagnetic wave.

[0069] The total power of the receiving point is:

[0070]

[0071] Among them, P t It is the antenna's transmit power; G t and G r These are the gains of the transmitting antenna and the receiving antenna, respectively. It is the wave impedance in free space. μ0 is the permeability, and ε0 is the permittivity.

[0072] It is important to note that the calculation of the reflection coefficient in a tunnel scenario needs to consider the polarization of the electromagnetic wave. Electromagnetic waves may strike the tunnel sidewall at various angles, and the electric field of the incident wave will be at an arbitrary angle to the incident surface, not always perpendicularly or parallelly polarized. Therefore, the incident electric field needs to be decomposed into two components: perpendicularly polarized and parallelly polarized, and the reflection coefficient needs to be calculated separately for each component. The specific decomposition process is as follows:

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] Among them, E p and E n These represent the components of the electric field in the parallel and perpendicular polarization directions, respectively; E i and Er These are the incident electric field and the reflected electric field, respectively. and R represents the unit vectors parallel to and perpendicular to the incident plane, respectively. p R n ε1 and ε2 are the reflection coefficients in the horizontal and vertical directions, respectively; ε2 and ε1 are the dielectric constants.

[0079] When battery-powered rail transport vehicles enter the tunnel during construction, they significantly affect the propagation of radio waves within the tunnel. Therefore, it is necessary to solve for and model the radio waves in the area where the battery-powered vehicles are located. During tunnel construction, the height of the battery-powered vehicles exceeds the plane containing the tunnel axis. Therefore, due to obstruction, the opposite side of the transmitter's location is a region with relatively weak field strength, while the same side experiences a change in field strength due to the offset of the reflecting surface, and the same side is a region with relatively strong field strength. The calculation method for the field strength on the same side is similar to the improved ray tracing method, except that the reflecting surface is offset inward, which can be considered as a reduction in the tunnel diameter. Due to obstruction, the field strength on the opposite side cannot be reached by the direct path; therefore, only the field strength of the reflection path is considered in the calculation. Also, due to obstruction, only the top surface of the tunnel can be considered for reflection. The calculation point P for the field strength on the opposite side is... ops and the location P of the transmitter s Connecting the two lines, the intersection of the line and the top surface of the tunnel is the reflection point P. f From point P ops Point P s With point P f The three points form a two-dimensional plane, similar to the horizontal plane containing the axis, also centered on the emission point P. s A Cartesian coordinate system is established with the origin as the reference point. The reflection path and reflection angle are calculated in the same way as the improved ray tracing method. It should be noted that the field strength of the direct path is 0. Since the length of the electric railcar is generally tens of meters, it can be considered as a straight road relative to the curve radius of thousands of meters in the tunnel. Thus, the field strength distribution model of the same side and opposite side of the area where the electric railcar is located is obtained.

[0080] The computer simulation method described is based on WinProp radio wave propagation solving software. First, an antenna diagram of the transmitter is established according to the actual measurement method, with key parameters including the polarization radiation angle and gain. Second, two-dimensional and three-dimensional models of the tunnel are established, with key parameters including the tunnel plan, straight and curved lengths, turning radii, tunnel diameter, tunnel wall material, obstacle distribution, and receiver location. The two-dimensional model shows the tunnel's orientation and diameter; the three-dimensional model is derived from the two-dimensional model plus the tunnel diameter and obstacle distribution. Next, the orientation and transmission power of the transmitter antenna in the three-dimensional tunnel model are defined, along with the antenna's installation location and specifications. Finally, a simulation algorithm is selected, such as the 3D-SRT ray tracing model or the DPM dominant path model. After these operations are completed, simulation calculations can be performed to obtain the received power at the receiving point.

[0081] The simulation results from the computer simulation method are exported and compared with the values ​​obtained from theoretical calculations and actual measurements for verification. The received power at the receiving point is compared; for example, a series of values ​​are obtained using theoretical calculations and simulations, and these values ​​are compared with the values ​​obtained from actual measurements. Based on the error, the parameters of the transmitter and receiver in the actual measurements are adjusted.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for modeling wireless communication channels in a tunnel construction scenario, characterized in that, It consists of three parts: theoretical calculation methods, computer simulation methods, and actual measurement methods. The actual measurement methods select transmitters and receivers from the perspective of on-site construction needs and determine the installation locations of transmitters and receivers. The theoretical calculation method uses an improved ray tracing method based on the tunnel construction scenario to calculate the received power of the receiving point, according to the installation positions of the transmitter and receiver. The computer simulation method uses WinProp's radio wave propagation solution simulation modeling method to perform simulations based on the antenna parameters of the transmitter and receiver, as well as the installation positions of the transmitter and receiver. The simulation results were compared and verified with those obtained by theoretical calculations and actual measurement methods. In the axial direction, both the transmitter and receiver are deployed at the segment joints; in the cross-sectional direction, both the transmitter and receiver are located in the horizontal plane containing the tunnel axis, with the measurement interval being an integer multiple of the segment width; both the transmitter and receiver are located on the same side wall within the horizontal plane of the tunnel axis. The improved ray tracing method combines the ray receiving sphere method and the mirror method. The mirror method is used to obtain the reflection point location at the receiver center, while the ray receiving sphere method is used to obtain the field strength within a certain range at the receiver, thus enabling more accurate theoretical modeling. The specific method is as follows: the three-dimensional ray propagation in the ray receiving sphere method is mapped to two-dimensional ray propagation within the horizontal plane of the axis. For the transmitter, the spherical waves of the wavefronts of all emitted rays are mapped to plane waves. For the receiver, at shorter distances, the receiving sphere with a diameter equal to the length of the antenna and receiver is mapped to a semi-circular receiving surface. At longer distances, the radius of the semi-circular receiving surface is multiplied by a coefficient but does not exceed the radius of the tunnel. The radius of the receiving surface is limited by restricting the angular interval of the emitted rays, and the center of the semi-circular receiving surface is assumed to be located at the joint of adjacent tunnel segments. The angular interval of the transmitter's emitted radio waves... , It is the radius of the circular receiving surface. It is the maximum propagation distance measured when the distance between the transmitter and receiver is [missing information]. At that time, the range of the emitted rays is ,in, If is the tunnel diameter, then the emitted electromagnetic wave number is: .

2. The wireless communication channel modeling method based on tunnel construction scenarios according to claim 1, characterized in that, The actual measurement method is based on the actual on-site construction requirements, which determines the antenna type, installation position and radiation angle of the transmitter and receiver, as well as the measurement interval for each interval.

3. The wireless communication channel modeling method based on tunnel construction scenarios according to claim 2, characterized in that, The transmitter's transmitting antenna is a directional antenna, pointing towards the working face inside the tunnel; the transmitter uses MIMO wireless transmission; the receiver is a spectrum scanner with an omnidirectional antenna for measuring signal field strength.

4. The wireless communication channel modeling method based on tunnel construction scenarios according to claim 3, characterized in that, The directional antenna is a dual-polarized directional flat panel antenna with a radiation angle of 15-25 degrees; the transmitter's frequency band is 5150-5850Hz.

5. The method for modeling wireless communication channels in a tunnel construction scenario according to any one of claims 1-4, characterized in that, When the circular tunnel is straight, the reflection path length and reflection angle are calculated using the center of the semi-circular receiving surface, i.e., the joint of the tunnel segments, as an example. The improved ray tracing method is implemented as follows: the distance and reflection angle between the transmitter and receiver are calculated using a Cartesian coordinate system, taking the location of the transmitter as an example. The location of the receiver is the origin of the Cartesian coordinate system. With point The spacing between them l= Rice, of which, Where N is the width of the tunnel segment and N represents the number of tunnel segments; the reflection angle is calculated using trigonometric functions. and angle of incidence for ,in, The diameter of the tunnel; The incident diameter length was calculated using the Pythagorean theorem. With reflection path length for ; reflectivity Incident diameter length and reflection diameter length Substituting these values ​​into the formula for calculating the received power in the ray tracing method, we can obtain the received power at the receiving point.

6. The wireless communication channel modeling method based on tunnel construction scenarios according to claim 5, characterized in that, When the circular tunnel has a curve, the reflection radius and reflection angle are calculated using the center of the semi-circular receiving surface, i.e., the joint of the tunnel segments, as an example. The improved ray tracing method uses a polar coordinate system to calculate the distance and reflection angle between the receiver and transmitter, where the curve axis is the radius. A gentle curve; the tunnel's two sidewalls form an inner and an outer circle, the difference between their radii being the tunnel diameter. Meters, the center of the inner and outer circles with a gentle curve. The origin of the polar coordinate system is the location of the transmitter. Location of the receiver The location is at a radius of On the circle, the width of the tube segment The arc length is divided into several equal parts by the spacing, where the straight-line distance between the transceivers is a point. and points chord length of the arc The centerline of the transmitter and receiver intersects the inner circle at point [point missing]. It intersects the outer circle at point . , and chord length Intersect at point Connection point and points The angle between the line containing the incident light and the centerline is the angle of incidence. Connect point F and point The angle between the line and the center line is the angle of reflection. Because the division is equally spaced, the arc lengths of the transmitter and receiver locations... and included angle , Width of a single segment The corresponding radians; then the chord length. Similarly, we can obtain the point. Time String length ,point Time String length for ; According to the Pythagorean theorem, the line segment is obtained. length Therefore, the line segment can be obtained. length Finally, the angle of incidence can be obtained. and reflection angle Incident diameter length and reflection path length for Substituting this into the formula for calculating the received power in the ray tracing method, we can obtain the received power at the receiving point.

7. The wireless communication channel modeling method based on tunnel construction scenarios according to claim 4 or 6, characterized in that, The method for calculating the received power at the receiving point using the ray tracing method is as follows: The electric field of the direct path is calculated as follows: ; The electric field of the reflection path is calculated as follows: ; The electric field at the receiving point is: ; in, It is the electric field at the reference point; and These are the total path lengths of the direct path and the reflected path, respectively. Indicates the first [item] on the reflection path The reflection coefficient of secondary reflection; It is the total number of reflections along the reflection path; , It is the wavelength of electromagnetic waves; The total power of the receiving point is: ； in, It is the antenna's transmission power; and These are the gains of the transmitting antenna and the receiving antenna, respectively. It is the wave impedance in free space. It is the permeability. It is the dielectric constant.

8. The wireless communication channel modeling method based on tunnel construction scenario according to claim 7, characterized in that, The method for calculating the reflection coefficient is as follows: Considering the polarization of electromagnetic waves, the incident electric field is decomposed into two components: perpendicular polarization and parallel polarization. The reflection coefficient is then calculated for each component. The decomposition process is as follows: ； ， ， ， ； in, and These represent the components of the electric field in the parallel and perpendicular polarization directions, respectively. and These are the incident electric field and the reflected electric field, respectively. and These represent unit vectors parallel to and perpendicular to the plane of incidence, respectively. , These are the reflection coefficients in the horizontal and vertical directions, respectively; , It is the dielectric constant.

9. The wireless communication channel modeling method based on tunnel construction scenarios according to claim 8, characterized in that, When a battery-powered rail transport vehicle enters the tunnel during construction, radio wave calculations and modeling are performed on the area where the vehicle is located. During tunnel construction, the height of the vehicle exceeds the plane containing the tunnel axis. Due to obstruction, the opposite side of the transmitter's location experiences a relatively weak field strength, while the same side experiences a change in field strength due to the offset of the reflecting surface, and the same side is a relatively strong field strength area. The field strength calculation method for the same side utilizes an improved ray tracing method, but the inward offset of the reflecting surface can be considered as a reduction in the tunnel diameter. Due to obstruction, the field strength on the opposite side cannot be reached by the direct path; therefore, only the field strength of the reflected path is considered in the calculation. Similarly, due to obstruction, only the top surface of the tunnel is considered for reflection. The calculation point for the field strength on the opposite side is... Location of the transmitter The point where the line intersects the tunnel ceiling is the reflection point. From point ,point Point reflection Forming a two-dimensional plane, with the emission point A Cartesian coordinate system is established with the origin as the origin. The reflection path and reflection angle are calculated using an improved ray tracing method. The field strength of the direct path is 0, thus obtaining the field strength distribution model of the same side and opposite side of the area where the electric railcar is located.

10. The method for modeling wireless communication channels in a tunnel construction scenario according to claim 8 or 9, characterized in that, The WinProp-based simulation modeling method for solving radio wave propagation is as follows: An antenna diagram of the transmitter is established based on the transmitter selected according to the actual measurement method, including the polarization radiation angle and gain of the antenna diagram; a two-dimensional and three-dimensional model of the tunnel is established, including the length of the straight sections and curves of the tunnel, the turning radius, the tunnel diameter, the tunnel wall material, the distribution of obstacles, and the receiver position; the orientation and transmission power of the transmitter antenna in the three-dimensional model of the tunnel are defined, and the installation position of the transmitter antenna is defined; a simulation algorithm is selected for simulation calculation; the simulation algorithm is either a 3D-SRT ray tracing model or an SBR ray tracing model.

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