A design method of a visible light communication system model for vehicles based on pedestrian interference

Abstract

The application discloses a design method of a vehicle visible light communication system model based on pedestrian interference, and belongs to the technical field of visible light communication. The method uses two headlamps of a vehicle as two transmitters, additionally sets two photodetectors as two receivers, uses diversity multiplexing technology, introduces a pedestrian interference model, uses a market weighted headlamp illumination intensity model and real road reflection data to establish a two-input two-output vehicle visible light communication system model, and specifically comprises the following steps: establishing the pedestrian interference model; establishing the headlamp illumination intensity model; analyzing received optical power of a line-of-sight link and a non-line-of-sight link; analyzing system noise; and analyzing a system received signal. The application establishes the model based on real traffic conditions, improves the authenticity of the system model, thereby improving the accuracy of experimental results, provides a theoretical basis for vehicle visible light communication, and has practical application value.

Description

Technical Field

[0001] This invention relates to the field of visible light communication technology, and in particular to a design method for a vehicle-mounted visible light communication system model based on pedestrian interference. Background Technology

[0002] Visible light communication typically uses light-emitting diodes (LEDs) as transmitters, modulating the emitted light to carry information, and photodetectors as receivers. Visible light communication has advantages such as wide spectrum resources, free access, and no electromagnetic interference, thus it is considered a promising complementary technology to vehicular wireless communication. Therefore, it has received widespread attention and research from numerous scholars in recent years.

[0003] Research on the practical application of visible light communication in vehicles is difficult to realize. Therefore, the verification and performance testing of visible light communication solutions for vehicles are mostly carried out by establishing simulation models or conducting simulation studies in the laboratory. However, most of the two-input two-output visible light communication system models for vehicles established by researchers at present only consider the impact of natural factors such as weather or turbulence on the system, which has some limitations. Summary of the Invention

[0004] To address the shortcomings of existing vehicle-mounted two-input two-output visible light communication system models, which consider relatively few factors, this invention aims to provide a design method for a vehicle-mounted visible light communication system model based on pedestrian interference. Using real data, this method establishes a vehicle-mounted two-input two-output visible light communication system model based on pedestrian interference, thereby improving communication quality and maximizing communication range.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A design method for a vehicle-mounted visible light communication system model based on pedestrian interference includes the following steps:

[0007] Step 1, Establishment of the pedestrian interference model;

[0008] Step 2, Establishment of the headlight intensity model for automobiles;

[0009] Step 3: Received optical power analysis of line-of-sight and non-line-of-sight links;

[0010] Step 4, System noise analysis;

[0011] Step 5: System received signal analysis.

[0012] A further improvement to the technical solution of the present invention is that step 1 specifically includes:

[0013] Data on pedestrian crossings at intersections without traffic lights is collected. The probability that the number of pedestrians arriving within a certain time interval is a certain value is expressed as:

[0014]

[0015]

[0016] Equation (1) is a formula for describing the characteristics of pedestrian arrival using the Poisson distribution, and Equation (2) is a formula for describing the characteristics of pedestrian arrival using the negative binomial distribution. m is the number of pedestrians arriving within a certain time interval, and p and r are parameters in the negative binomial distribution.

[0017] By statistically analyzing the frequency of vehicle yielding behavior and pedestrian-vehicle conflicts at unsignaled crosswalks, the probability of such conflicts is denoted as p. aff By treating pedestrian traffic during vehicle-pedestrian conflicts as interference with the vehicle-mounted two-input two-output visible light communication system, the interference probability p of pedestrian traffic on a crosswalk without a signal can be obtained. dis for:

[0018]

[0019] Among them, f dij (θ1,θ2) is defined by the following formula:

[0020]

[0021] Where, d length Let y be the longitudinal distance between the two vehicles. crowd Let θ2-θ1 be the distance between the pedestrian group's location and the center line of the following vehicle, θ2-θ1 be the angle of dynamic interference from the pedestrians in the system, and Ψ be the half-angle received by the photodetector. The distance y between the pedestrian group's location and the center line of the following vehicle varies with the distance y. corwd and the longitudinal distance d between the two vehicles length As the situation changes, the angle of interference will also change, and consequently, the probability of interference will also change.

[0022] A further improvement to the technical solution of this invention is that, in step 2, the illuminance of the light emitted by the car headlight at the illuminated point is:

[0023]

[0024] Among them, I M (ξ,ζ) represents the statistically weighted luminous intensity (cd) of the lamps in the market, where ξ and ζ are the horizontal and vertical angles between the direction of the headlight beam and the positive direction of the headlight. S is the luminous flux (lm); S is the corresponding reflective area of ​​the road surface (m²). 2); Ω is the solid angle of the ray (sr); θ is the angle between the ray emitted from the car headlight and the normal to the illuminated plane; d is the straight-line distance (m) between the ray emission point and the illuminated point.

[0025] A further improvement to the technical solution of the present invention is that step 3 specifically includes the following steps:

[0026] Step 3.1, in a vehicle-mounted two-input two-output visible light communication system, the power received by the j-th photodetector from the system's line-of-sight link is as follows:

[0027]

[0028] Where i, j = 1, 2; A r ξ is the effective detection area of ​​the photodetector; ij and ζ ij Let θ be the horizontal and vertical angles between the line-of-sight link formed by the i-th headlight and the j-th photodetector and the direction of the headlight beam emission; ij d is the angle between the line-of-sight link formed by the i-th headlight and the j-th photodetector and the normal to the surface of the photodetector; ij Let LER be the distance between the i-th headlight and the j-th photodetector; LER is the luminous efficacy of the automotive headlight.

[0029] Step 3.2, considering the occlusion effect of pedestrian traffic on the line-of-sight link in the vehicular two-input two-output visible light communication system, the power received by the j-th photodetector from the line-of-sight link is expressed by the following formula:

[0030]

[0031] Step 3.3, in a vehicle-mounted two-input two-output visible light communication system, the power calculation process of the photodetector received from the system's non-line-of-sight link:

[0032] When the light emitted by the car headlights is reflected off the road surface, the luminous intensity at reflection point A is:

[0033]

[0034] Where, β A Let I be the angle between the backward extension of the projection of the incident ray onto the road surface at reflection point A and the projection of the reflected ray onto the road surface; Tx-A (ζ A ,ξ A The luminous intensity of light emitted by automotive headlights to satisfy the reflection condition is represented by the statistically weighted luminous intensity of market-weighted lamps, γ. A r(β) is the angle of incidence of the ray, i.e., the angle between the incident ray and the normal to the road surface. A ,tanγA ) represents the simplified brightness coefficient of the road surface; ζ A and ξ A h represents the horizontal and vertical angles between the link formed by the reflection point A and the light emitted from the headlight, and the direction of the headlight's light emission; Tx-A The vertical height of the car's headlights from the road surface;

[0035] The reflected light from a single headlight at reflection point A is taken as the luminous intensity. The illuminance at point A on the road surface, which is a secondary light source, is:

[0036]

[0037] Among them, S A Let A be the area of ​​the reflection point A;

[0038] The power received by the photodetector from reflection point A is:

[0039]

[0040] Where, d Tx-A θ is the straight-line distance from reflection point A to the j-th photodetector; A-Rx Let be the angle between the non-line-of-sight link formed by reflection point A and the j-th photodetector and the normal direction of the photodetector surface; LER is the luminous efficacy of the automotive headlight.

[0041] In a vehicular two-input two-output visible light communication system, the optical power received by the photodetector from the non-line-of-sight link varies depending on its installation location, and there is more than one reflection area that meets the reflection conditions. Therefore, the total power received by the photodetector from the non-line-of-sight link is:

[0042]

[0043] Among them, A k and A′ k These are different road surface areas that satisfy the reflection conditions; θ Ak-Rx1 and θ Ak′-Rx2 These represent the angles between different light rays that satisfy the reflection conditions and the normal direction of the PD surface; and These represent the transmission distance of the reflected light rays.

[0044] A further improvement to the technical solution of the present invention is that step 4 specifically includes the following steps:

[0045] Step 4.1, the formula for calculating shot noise caused by sunlight in the background environment is as follows:

[0046]

[0047] Where R is the responsivity of the photodetector; q is the electron charge; B is the system bandwidth; I bg I0 is the received background noise current; I2 is the noise bandwidth factor of the background noise;

[0048] Step 4.2, the formula for calculating inter-symbol interference noise caused by multipath effect is as follows:

[0049]

[0050] Step 4.3: The formula for calculating the thermal noise caused by electron motion is as follows:

[0051]

[0052] Where k is the Boltzmann constant; T k Γ is the absolute temperature; G is the open-loop voltage gain; Γ is the transistor channel noise factor; g m It is the transistor's back conductivity; η is the fixed capacitance per unit area of ​​the photodetector; I3 is the transistor's channel noise current due to thermal noise.

[0053] A further improvement to the technical solution of the present invention is that step 5 specifically includes the following steps:

[0054] Step 5.1: Select links based on constraints and interference probabilities;

[0055] In a vehicle-mounted two-input two-output visible light communication system, it is assumed that a photodetector can receive signals from different LEDs through diversity reception technology. In order to improve the quality of service, it is stipulated that an LED can only serve one photodetector at a time. At the same time, in order to enhance its anti-interference capability, it is stipulated that each photodetector needs to be connected to an LED to enhance the stability of the communication system.

[0056] The interference probability of each of the four links is calculated and sorted. The link with the lowest interference probability is selected first. This strategy can effectively reduce the maximum interference probability of the system links, thereby effectively reducing the degree of interference.

[0057] Step 5.2: The emitted light is modulated using on / off keying modulation technology, and the information is received by direct detection using a photodetector. The signal-to-noise ratio of the received signal is defined as:

[0058]

[0059] Among them, SNR j Let p be the signal-to-noise ratio of the signal received by the j-th photodetector. dis-ij P represents the interference probability of the selected link. ijThe line-of-sight power of the selected link;

[0060] Step 5.3: Perform equal-gain combining on the signals received by the two photodetectors. The calculation formula is as follows:

[0061]

[0062] Among them, SNR Total This represents the final signal-to-noise ratio of the system.

[0063] Step 5.4, the system bit error rate is calculated as follows:

[0064]

[0065] Where Q(x) is a function used to calculate the tail probability of the standard Gaussian distribution.

[0066] Compared with the prior art, the beneficial technical effects of the present invention are:

[0067] 1. In this invention, the vehicle-mounted two-input two-output visible light communication system uses the two headlights of a car as two transmitters and two additional photodetectors as two receivers. Diversity multiplexing technology is used to establish a model of the vehicle-mounted two-input two-output visible light communication system. The pedestrian interference model is introduced into the vehicle-mounted two-input two-output visible light communication system, which improves the realism and reliability of the vehicle-mounted two-input two-output visible light communication system model based on pedestrian interference. This, in turn, improves the accuracy of the simulation results of the system model, and provides a reliable theoretical basis and experimental guidance for future technical research.

[0068] 2. In this invention, after introducing a pedestrian interference model, a market-weighted headlight intensity model and real road reflection data are used to establish the model based on real traffic conditions, which improves the realism of the system model and thus improves the accuracy of the experimental results. Based on the constraints of the four links and the probability of interference, the four links are selected and then equal gain merging is performed, providing a theoretical basis and practical value for vehicle visible light communication. Attached Figure Description

[0069] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0070] Figure 1 This is a schematic diagram of a vehicle-mounted two-input two-output visible light communication system with pedestrian interference in an embodiment of the present invention;

[0071] Figure 2 This is a schematic diagram illustrating that pedestrian traffic flow conforms to a Poisson distribution and a negative binomial distribution in an embodiment of the present invention;

[0072] Wherein: (a) pedestrian traffic flow follows a Poisson distribution; (b) pedestrian traffic flow follows a negative binomial distribution;

[0073] Figure 3 This is a schematic diagram of line-of-sight links and non-line-of-sight links in a visible light communication system according to an embodiment of the present invention;

[0074] Figure 4 This is a schematic diagram of the actual road surface reflection situation in an embodiment of the present invention;

[0075] Figure 5 This refers to the bit error rate of the vehicle visible light system when the lateral distance is 2m in this embodiment of the invention and the pedestrian traffic flow conforms to a negative binomial distribution.

[0076] Figure 6 This refers to the bit error rate of the vehicle visible light system when the lateral distance is 3m in this embodiment of the invention and the pedestrian traffic flow conforms to a negative binomial distribution.

[0077] Among them: 1. Left headlight; 2. Right headlight; 3. Left photodetector; 4. Right photodetector; 5. Line-of-sight link; 6. Incident light; 7. Outgoing light. Detailed Implementation

[0078] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0079] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0080] like Figure 1-4As shown, a design method for a vehicle-mounted visible light communication system model based on pedestrian interference is presented. This method introduces the interference caused by pedestrians crossing intersections without traffic lights, affecting the vehicle-mounted two-input two-output visible light communication system. The system uses a vehicle headlight as the transmitter and two additional photodetectors as receivers. Diversity multiplexing is employed to establish the vehicle-mounted two-input two-output visible light communication system model. Based on a market-weighted statistical model of vehicle headlight illumination intensity and real road reflection data, the optical power of the line-of-sight and non-line-of-sight links is calculated. Real data is used to establish the system model, making it more realistic and reliable. The specific implementation steps are as follows:

[0081] Step 1, Establishment of the pedestrian interference model;

[0082] Specifically, it includes the following:

[0083] The pedestrian interference model is an expression derived by comprehensively considering the probability of a certain value being encountered when crossing an intersection without traffic lights within a certain time interval, and the probability of pedestrian-vehicle conflict. The expression for the probability of m pedestrians crossing an intersection without traffic lights within a certain time interval is:

[0084]

[0085]

[0086] Equation (1) is a formula for describing the characteristics of pedestrian arrival using the Poisson distribution, and Equation (2) is a formula for describing the characteristics of pedestrian arrival using the negative binomial distribution. m is the number of pedestrians arriving within a certain time interval, and p and r are parameters in the negative binomial distribution.

[0087] By statistically analyzing the frequency of vehicle yielding behavior and pedestrian-vehicle conflicts at unsignaled crosswalks, the probability of such conflicts is denoted as p. aff If pedestrian traffic during a vehicle-pedestrian conflict is considered as interference to the vehicle-mounted two-input two-output visible light communication system, then the interference probability p of pedestrian traffic on a crosswalk without signal can be obtained. dis for:

[0088]

[0089] Among them, f dij (θ1,θ2) can be defined by the following formula:

[0090]

[0091] Where, d length Let y be the longitudinal distance between the two vehicles. crowdLet θ2-θ1 be the distance between the pedestrian group's location and the center line of the following vehicle, θ2-θ1 be the angle of dynamic interference from the pedestrians in the system, and Ψ be the half-angle received by the photodetector. The distance y between the pedestrian group's location and the center line of the following vehicle varies with the distance y. corwd and the longitudinal distance d between the two vehicles length As the situation changes, the angle of interference will also change, and consequently, the probability of interference will also change.

[0092] Step 2, Establishment of the headlight intensity model for automobiles;

[0093] Specifically, it includes the following:

[0094] The illuminance distribution of automotive headlights is obtained by measuring the illuminance distribution of different vehicles based on their market share and then weighting the results. The illuminance of the emitted light from the automotive headlights at the illuminated point is:

[0095]

[0096] Among them, I M (ξ,ζ) represents the statistically weighted luminous intensity (cd) of the lamps in the market, where ξ and ζ are the horizontal and vertical angles between the direction of the headlight beam and the positive direction of the headlight. S is the luminous flux (lm); S is the corresponding reflective area of ​​the road surface (m²). 2 ); Ω is the solid angle of the ray (sr); θ is the angle between the ray emitted from the car headlight and the normal to the illuminated plane; d is the straight-line distance (m) between the ray emission point and the illuminated point.

[0097] Step 3: Received optical power analysis of line-of-sight and non-line-of-sight links;

[0098] Specifically, the following steps are included:

[0099] Formulas for the optical power received by the photodetector in line-of-sight links and non-line-of-sight links are defined, and interference caused by pedestrians passing through is considered in line-of-sight links.

[0100] Step 3.1, in a vehicle-mounted two-input two-output visible light communication system, the power received by the j-th photodetector from the system's line-of-sight link is as follows:

[0101]

[0102] Where i, j = 1, 2; A r ξ is the effective detection area of ​​the photodetector; ij and ζ ij Let θ be the horizontal and vertical angles between the line-of-sight link formed by the i-th headlight and the j-th photodetector and the direction of the headlight beam emission; ijd is the angle between the line-of-sight link formed by the i-th headlight and the j-th photodetector and the normal to the surface of the photodetector; ij Let be the distance between the i-th headlight and the j-th photodetector; LER is the luminous efficacy of the car headlight.

[0103] Step 3.2, considering the obstruction effect of pedestrian traffic on the line-of-sight link in the vehicular two-input two-output visible light communication system, the power received by the j-th photodetector from the line-of-sight link can be expressed by the following formula:

[0104]

[0105] Step 3.3, in a vehicle-mounted two-input two-output visible light communication system, the power calculation process of the photodetector received from the system's non-line-of-sight link:

[0106] When the light emitted by the car headlights is reflected off the road surface, the luminous intensity at reflection point A is:

[0107]

[0108] Where, β A Let I be the angle between the backward extension of the projection of the incident ray onto the road surface at reflection point A and the projection of the reflected ray onto the road surface; Tx-A (ζ A ,ξ A The luminous intensity of light emitted by automotive headlights to satisfy the reflection condition is represented by the statistically weighted luminous intensity of market-weighted lamps, γ. A r(β) is the angle of incidence of the ray, i.e., the angle between the incident ray and the normal to the road surface. A ,tanγ A ) represents the simplified brightness coefficient of the road surface; ζ A and ξ A h represents the horizontal and vertical angles between the link formed by the reflection point A and the light emitted from the headlight, and the direction of the headlight's light emission; Tx-A This refers to the vertical height of the car's headlights from the road surface.

[0109] The reflected light from a single headlight at reflection point A is taken as the luminous intensity. The illuminance at point A on the road surface, which is a secondary light source, is:

[0110]

[0111] Among them, S A Let A be the area of ​​the reflection point.

[0112] The power received by the photodetector from reflection point A is:

[0113]

[0114] Where, d Tx-A θ is the straight-line distance from reflection point A to the j-th photodetector; A-Rx Let be the angle between the non-line-of-sight link formed by reflection point A and the j-th photodetector and the normal direction of the photodetector surface; LER is the luminous efficacy of the automotive headlight.

[0115] In a vehicular two-input two-output visible light communication system, the optical power received by the photodetector from the non-line-of-sight link varies depending on its installation location, and there is more than one reflection area that meets the reflection conditions. Therefore, the total power received by the photodetector from the non-line-of-sight link is...

[0116]

[0117] Among them, A k and A′ k These are different road surface areas that meet the reflection conditions; and These represent the angles between different light rays that satisfy the reflection conditions and the normal direction of the PD surface; and These represent the transmission distance of the reflected light rays.

[0118] Step 4, System noise analysis;

[0119] Specifically, the following steps are included:

[0120] Step 4.1, the formula for calculating shot noise caused by sunlight in the background environment is as follows:

[0121]

[0122] Where R is the responsivity of the photodetector; q is the electron charge; B is the system bandwidth; I bg I0 is the received background noise current; I2 is the noise bandwidth factor of the background noise.

[0123] Step 4.2, the formula for calculating inter-symbol interference noise caused by multipath effect is as follows:

[0124]

[0125] Step 4.3, the formula for calculating the thermal noise caused by electron motion is as follows:

[0126]

[0127] Where k is the Boltzmann constant; T k Γ is the absolute temperature; G is the open-loop voltage gain; Γ is the transistor channel noise factor; g mIt is the transistor's back conductivity; η is the fixed capacitance per unit area of ​​the photodetector; I3 is the transistor's channel noise current due to thermal noise.

[0128] Step 5: System received signal analysis;

[0129] Specifically, the following steps are included:

[0130] Step 5.1: Select links based on constraints and interference probabilities;

[0131] In a vehicle-mounted two-input two-output visible light communication system, it is assumed that a photodetector can receive signals from different LEDs through diversity reception technology. In order to improve the quality of service, it is stipulated that an LED can only serve one photodetector at a time. At the same time, in order to enhance its anti-interference capability, it is stipulated that each photodetector needs to be connected to an LED to enhance the stability of the communication system.

[0132] The interference probability of each of the four links is calculated and sorted. The link with the lowest interference probability is selected first. This strategy can effectively reduce the maximum interference probability of the system links, thereby effectively reducing the degree of interference.

[0133] Step 5.2: The emitted light is modulated using on / off keying modulation technology, and the information is received by direct detection using a photodetector. The signal-to-noise ratio of the received signal is defined as:

[0134]

[0135] Among them, SNR j Let p be the signal-to-noise ratio of the signal received by the j-th photodetector. dis-ij P represents the interference probability of the selected link. ij The line-of-sight power of the selected link.

[0136] Step 5.3: Perform equal-gain combining on the signals received by the two photodetectors. The calculation formula is as follows:

[0137]

[0138] Among them, SNR Total This represents the final signal-to-noise ratio of the system.

[0139] Step 5.4, the system bit error rate is calculated as follows:

[0140]

[0141] Where Q(x) is a function used to calculate the tail probability of the standard Gaussian distribution.

[0142] Step 6: System simulation.

[0143] Specifically, the following steps are included:

[0144] Step 6.1 configured the vehicle-mounted two-input two-output visible light communication system model as follows: Figure 1-4 As shown, during the daytime low beam (50% luminous intensity), the distance between the left headlight 1 and right headlight 2 of the vehicle emitting the signal is 1.2m, and the height above the road surface is 0.66m. The distance between the left photodetector 3 and right photodetector 4 of the vehicle receiving the signal is 1.2m. The two vehicles are in adjacent lanes, and the lateral distance between their center lines is 2m and 3m, respectively. The left headlight 1 of the vehicle emitting the signal and the left photodetector 3 of the vehicle receiving the signal form a line-of-sight link 5. The right headlight 2 of the vehicle emitting the signal and the road surface reflection point form an incident light 6. The road surface reflection point and the receiving vehicle form an outgoing light 7.

[0145] Table 1 shows the key parameters for system modeling.

[0146] Table 1 System Model Parameter Table

[0147]

[0148]

[0149] Step 6.2: The left headlight 1 and right headlight 2 of the vehicle emitting the signal emit light of a certain intensity. The line-of-sight and non-line-of-sight optical power received by the left photodetector 3 and right photodetector 4 of the receiving vehicle are calculated according to formulas (7) and (11). Based on the line-of-sight and non-line-of-sight optical power, the system noise is calculated. According to the constraints and interference probability, the four links of the vehicle-mounted two-input two-output visible light communication system are selected for equal-gain combining, and the bit error rate is calculated.

[0150] Step 6.3: Calculate the relationship between the bit error rate when using conventional equal-gain combining and when using link-selection-based equal-gain combining according to formula (17), as shown in the appendix. Figure 5 , 6 As shown. According to the appendix Figure 5 , 6 It can be seen that when pedestrian traffic follows a negative binomial distribution, the system has better communication performance and a larger effective communication range when using link selection-based equal-gain merging.

[0151] In the specific embodiments, the impact of different pedestrian traffic volumes and different lateral distances between two vehicles on the system's bit error rate performance was analyzed. However, this invention is not limited to the above performance analysis used to analyze vehicle-mounted two-input two-output visible light communication based on pedestrian interference.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for a vehicle-mounted visible light communication system model based on pedestrian interference, characterized in that, Includes the following steps: Step 1, Establishment of the pedestrian interference model; Specifically, the pedestrian interference model is an expression derived from collected pedestrian data at intersections without traffic lights within a certain time interval, taking into account the probability of pedestrian-vehicle conflicts. It uses a Poisson distribution or a negative binomial distribution to calculate the probability of m pedestrians crossing an intersection without traffic lights within a certain time interval. Let m be the number of pedestrians actually arriving within a specific time interval; the probability of a pedestrian-vehicle conflict is denoted as p by statistically analyzing the frequency of vehicle yielding behavior and pedestrian-vehicle conflicts at unsignalized crosswalks. aff By treating pedestrian traffic during vehicle-pedestrian conflicts as interference with the vehicle-mounted two-input two-output visible light communication system, the interference probability p of pedestrian traffic on a crosswalk without a signal can be obtained. dis for: (3) Among them, f dij (θ1,θ2) is defined by the following formula: (4) Where, d length Let y be the longitudinal distance between the two vehicles. crowd Let θ2-θ1 be the distance between the pedestrian group's location and the center line of the following vehicle, θ2-θ1 be the angle of dynamic interference from the pedestrians in the system, and Ψ be the half-angle received by the photodetector. The distance y between the pedestrian group's location and the center line of the following vehicle varies with the distance y. corwd and the longitudinal distance d between the two vehicles length As the angle of interference changes, so does the probability of interference. Step 2, Establishment of the headlight intensity model for automobiles; The illuminance of the light emitted by the car headlights at the illuminated point is: (5) Among them, I M (ξ,ζ) represents the statistically weighted luminous intensity of the lamps in the market; ξ and ζ are the horizontal and vertical angles between the emission direction of the car headlight and the positive direction of the car headlight; φ is the luminous flux; S is the corresponding reflective area of ​​the road surface; Ω is the solid angle of the light ray; θ is the angle between the emitted light ray from the car headlight and the normal to the illuminated plane; d is the straight-line distance between the light emission point and the illuminated point; Step 3, analysis of received optical power of line-of-sight link and non-line-of-sight link; Specifically, the following steps are included: Step 3.1, in a vehicle-mounted two-input two-output visible light communication system, the power received by the j-th photodetector from the system's line-of-sight link is as follows: (6) Where i, j = 1, 2; A r ξ is the effective detection area of ​​the photodetector; ij and ζ ij Let θ be the horizontal and vertical angles between the line-of-sight link formed by the i-th headlight and the j-th photodetector and the direction of the headlight beam emission; ij d is the angle between the line-of-sight link formed by the i-th headlight and the j-th photodetector and the normal to the surface of the photodetector; ij Let LER be the distance between the i-th headlight and the j-th photodetector; LER is the luminous efficacy of the automotive headlight. Step 3.2, considering the occlusion effect of pedestrian traffic on the line-of-sight link in the vehicular two-input two-output visible light communication system, the power received by the j-th photodetector from the line-of-sight link is expressed by the following formula: (7) Step 3.3, in a vehicle-mounted two-input two-output visible light communication system, the power calculation process of the photodetector received from the system's non-line-of-sight link: When the light emitted by the car headlights is reflected off the road surface, the luminous intensity at reflection point A is: (8) Where, β A Let I be the angle between the backward extension of the projection of the incident ray onto the road surface at reflection point A and the projection of the reflected ray onto the road surface; Tx-A (ζ A ,ξ A The luminous intensity of light emitted by automotive headlights to satisfy the reflection condition is represented by the statistically weighted luminous intensity of market-weighted lamps, γ. A r(β) is the angle of incidence of the ray, i.e., the angle between the incident ray and the normal to the road surface. A , tan γ A ) represents the simplified brightness coefficient of the road surface; ζ A and ξ A h represents the horizontal and vertical angles between the link formed by the reflection point A and the light emitted from the headlight, and the direction of the headlight's light emission; Tx-A The vertical height of the car's headlights from the road surface; The reflected light from a single headlight at reflection point A is taken as the luminous intensity. The illuminance at point A on the road surface, which is a secondary light source, is: (9) Among them, S A Let A be the area of ​​the reflection point A; The power received by the photodetector from reflection point A is: (10) in, Let be the straight-line distance from reflection point A to the j-th photodetector; Let be the angle between the non-line-of-sight link formed by reflection point A and the j-th photodetector and the normal direction of the photodetector surface; LER is the luminous efficacy of the automotive headlight. In a vehicular two-input two-output visible light communication system, the optical power received by the photodetector from the non-line-of-sight link varies depending on its installation location, and there is more than one reflection area that meets the reflection conditions. Therefore, the total power received by the photodetector from the non-line-of-sight link is: (11) in, and These are different road surface areas that meet the reflection conditions; and These represent the angles between different light rays that satisfy the reflection conditions and the normal direction of the PD surface; and These represent the transmission distance of the reflected light rays; Step 4, system noise analysis; specifically including the following steps: Step 4.1, the formula for calculating shot noise caused by sunlight in the background environment is as follows: (12) Where R is the responsivity of the photodetector; q is the electron charge; B is the system bandwidth; I bg I0 is the received background noise current; I2 is the noise bandwidth factor of the background noise; Step 4.2, the formula for calculating inter-symbol interference noise caused by multipath effect is as follows: (13) Step 4.3: The formula for calculating the thermal noise caused by electron motion is as follows: (14) Where k is the Boltzmann constant; T k Γ is the absolute temperature; G is the open-loop voltage gain; Γ is the transistor channel noise factor; g m η is the reverse conductivity of the transistor; η is the fixed capacitance per unit area of ​​the photodetector; I3 is the transistor channel noise current due to thermal noise. Step 5: System received signal analysis.

2. The design method for a vehicle-mounted visible light communication system model based on pedestrian interference according to claim 1, characterized in that, Step 5 specifically includes the following steps: Step 5.1: Select links based on constraints and interference probabilities; In a vehicle-mounted two-input two-output visible light communication system, it is assumed that a photodetector can receive signals from different LEDs through diversity reception technology. In order to improve the quality of service, it is stipulated that an LED can only serve one photodetector at a time. At the same time, in order to enhance its anti-interference capability, it is stipulated that each photodetector needs to be connected to an LED to enhance the stability of the communication system. The interference probability of each of the four links is calculated and sorted. The link with the lowest interference probability is selected first. This strategy can effectively reduce the maximum interference probability of the system links, thereby effectively reducing the degree of interference. Step 5.2: The emitted light is modulated using on / off keying modulation technology, and the information is received by direct detection using a photodetector. The signal-to-noise ratio of the received signal is defined as: (15) Among them, SNR j Let p be the signal-to-noise ratio of the signal received by the j-th photodetector. dis-ij P represents the interference probability of the selected link. ij The line-of-sight power of the selected link; Step 5.3: Perform equal-gain combining on the signals received by the two photodetectors. The calculation formula is as follows: (16) Among them, SNR Total This represents the final signal-to-noise ratio of the system. Step 5.4, the system bit error rate is calculated as follows: (17) Where Q(x) is a function used to calculate the tail probability of the standard Gaussian distribution.

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