A method for constructing a two-input two-output visible light communication system model under pedestrian interference

Abstract

The application discloses a kind of construction methods of workshop two-input two-output visible light communication system model under pedestrian interference, and visible light communication system is based on market weighted beam model as two transmitters with automobile headlamps, with photodetector as two receivers, the receiving optical power of photodetector corresponding to the position of pedestrian is calculated, the influence of pedestrian interference between two cars on visible light communication receiving optical power is analyzed, the influence of pedestrian interference on visible light communication system link is considered, an improved maximum ratio combining mode is proposed, compared with general combining mode, the signal-to-noise ratio and bit error rate of visible light communication system corresponding to the position of pedestrian are solved, the signal-to-noise ratio performance of visible light communication system under pedestrian interference is improved, and a theoretical basis and experimental guidance are provided for visible light communication between cars with interference model.

Description

Technical Field

[0001] This invention relates to a method for constructing a two-input two-output visible light communication system model in a workshop under pedestrian interference, and belongs to the field of visible light communication. Background Technology

[0002] Visible light communication, as a key technology for next-generation communication, can be applied to automotive lighting in urban transportation systems. It uses the light emitted by automotive headlights and the visible light band as a carrier of information, eliminating the need for wired channels as a transmission medium. It is a communication method that directly transmits light signals in the air.

[0003] When a visible light communication system for a workshop is applied to automotive lighting in an urban transportation system, the impact of pedestrian interference on the system cannot be ignored, as pedestrian traffic is a very important part of the urban transportation system.

[0004] Furthermore, since experimental equipment for vehicle-to-vehicle visible light communication is quite expensive, the verification and performance testing of vehicle-to-vehicle visible light communication schemes are mostly achieved by establishing simulation models. However, existing studies have not considered the obstacles and interference present in outdoor visible light communication, nor have they established models of visible light communication systems with obstacles and interference, making the verification and performance testing of vehicle-to-vehicle visible light communication schemes unreliable.

[0005] Therefore, how to model a two-input two-output visible light communication system in a vehicle-to-vehicle communication vehicle (V2V) system that is affected by pedestrian interference, and how to reduce the impact of pedestrian interference on the V2V system, are important research areas for the further development of V2V technology between vehicles. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for constructing a model of a two-input two-output visible light communication system in a workshop under pedestrian interference. By studying the visible light communication link, a practical model of the two-input two-output visible light communication system in a workshop under pedestrian interference is established. This method can improve the performance of the two-input two-output visible light communication system in the presence of obstacles and provides a reliable theoretical basis and experimental guidance for future technical research.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for constructing a two-input, two-output visible light communication system model in a workshop under pedestrian interference is disclosed. This method uses two market-weighted headlight beams as transmitters and two photodetectors as receivers. It introduces a visible light communication model under pedestrian interference and an improved merging method to address this interference. The model is built based on real traffic environment characteristics, thus making the experimental data of the system model more realistic. The method includes the following steps:

[0009] Step 1: Creating the car headlight model;

[0010] Step 2: Line-of-sight link analysis under pedestrian interference;

[0011] Step 3: Analysis of non-line-of-sight links under pedestrian interference;

[0012] Step 4: System noise analysis;

[0013] Step 5: Analysis of merging methods.

[0014] A further improvement to the technical solution of this invention is that: the headlight intensity distribution in step 1 is obtained based on a market-weighted headlight beam model, and the intensity expression is:

[0015] I T (α, β)(1)

[0016] Wherein, α and β are the horizontal and vertical angles between the direction of the emitted light from the car headlight and the direction of the headlight axis;

[0017] The illuminance of the light emitted by a car headlight at any illuminated point on the surface is:

[0018]

[0019] Where φ is the luminous flux; S is the corresponding reflective area of ​​the road surface; ω is the solid angle of the ray; r is the straight-line distance between the ray emission point and the illuminated point; and θ is the angle between the ray emitted by the car headlight and the normal to the illuminated plane.

[0020] A further improvement of the technical solution of the present invention is that: when a pedestrian moves in a straight line at a zebra crossing, the light emitted by the headlights of the car (L1) and headlights of the car (L2) to the photodetectors of the car (P1) and photodetectors of the car (P2) is a line-of-sight link (3); under pedestrian interference, the line-of-sight link will be blocked and interfered with.

[0021] Step 2 specifically includes the following steps:

[0022] Step 2.1: The light-receiving area A caused by pedestrian interference in the line-of-sight link from the i-th headlight to the j-th photodetector. r-ij The expression is:

[0023]

[0024] in, This represents the light-receiving area when i and j are the same. This represents the light-receiving area when i and j are different. When i is 1, the coordinate axis is established with L1 as the origin, and when i is 2, the coordinate axis is established with L2 as the origin.

[0025] Step 2.2: The light-receiving area mentioned in the previous step The expressions are as follows:

[0026]

[0027] In this coordinate system, the pedestrian's coordinates are (da, ha), where r represents the radius of the photodetector, and hp is the distance from the center of the photodetector to the shadow (transition variable). D represents the pedestrian's side width, also known as thickness. W represents the pedestrian's frontal width, also known as width. V This indicates the longitudinal distance between the two vehicles.

[0028]

[0029] Among them, D PD This indicates the distance between two photodetectors.

[0030] Step 2.3: Given A r-ij The expression for the optical power received through the line-of-sight link under pedestrian interference is:

[0031]

[0032] in, A represents the power generated when the i-th headlight illuminates the j-th photodetector under a line-of-sight link. r-ij Let θ be the light-receiving area caused by the line-of-sight link from the i-th headlight to the j-th photodetector; LER is the luminous efficacy of the headlight; θ 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 be the straight-line distance between the i-th headlight and the j-th photodetector.

[0033] The further improvement of the technical solution of the present invention is that: the light emitted by the headlight one (L1) and headlight two (L2) of the car is reflected by the road surface and enters the light received by the car photodetector one (P1) and photodetector two (P2) as the non-line-of-sight link (4) of the system model. The beam road surface reflection mode is regarded as the Lambert mode. When pedestrians move in a straight line at the zebra crossing, pedestrian interference will affect the non-line-of-sight link.

[0034] Step 3 specifically includes the following steps:

[0035] Step 3.1: The non-line-of-sight link beam's reflection mode on the road surface is considered to be a Lambertian profile. Assuming the Lambertian index m = 1, the reflected radiation intensity is:

[0036]

[0037] Where ρ is the diffuse reflectance and φ is the polar angle of the scattered light;

[0038] Step 3.2: When a pedestrian obstructs the visible light communication system, the expression for the pedestrian obstruction angle γ is:

[0039]

[0040] Among them, the angle between the critical light level blocked by pedestrians and the direction of the headlight axis. and The pedestrian's coordinates in the coordinate system are (da, ha). D represents the pedestrian's side profile width, also known as thickness; W represents the pedestrian's frontal width, also known as width. V This indicates the longitudinal distance between the two vehicles.

[0041] Step 3.3: The received optical power of the non-line-of-sight link in the visible light communication system under pedestrian interference is:

[0042]

[0043] in, The luminous intensity of the light emitted by the i-th headlight with a blocking angle of γ, reaching the j-th photodetector via a non-line-of-sight link; when i is 1, the established coordinate axis uses L1 as the origin, and when i is 2, the established coordinate axis uses L2 as the origin; A r d and h represent the light-receiving area of ​​the photodetector and its height above the ground, respectively; ij Let θ be the direct path between the non-line-of-sight link of the light emitted from the i-th headlight to the j-th photodetector and the perpendicular projection of the road surface reflection point A and the photodetector; θ is the angle between the road surface normal and the incident light ray, ρ is the road surface diffuse reflectivity, and φ is the angle between the road surface normal and the incident light ray. ij Let ψ be the angle between the road surface normal and the reflected light from the road surface in the non-line-of-sight link from the i-th headlight to the j-th photodetector. ij Let di be the angle between the reflected ray from the i-th headlight's emission light to the j-th photodetector's non-line-of-sight link and the normal to the photodetector's plane, and let dS be the area of ​​the incident ray reflected onto the road surface. T This is the shortest distance from the headlight to the reflection point A;

[0044] Step 3.4: The received optical power of the non-line-of-sight link from the i-th headlight to the j-th photodetector under pedestrian interference is expressed as:

[0045]

[0046] Where S is the reflection area of ​​the non-line-of-sight link on the road surface, and the reflection point A is located within the reflection area S.

[0047] A further improvement of the technical solution of this invention is that: this model is used to analyze the performance of a two-input two-output visible light communication system between vehicles during the daytime, therefore ambient light will have a significant impact on signal transmission; under ambient light conditions, shot noise, inter-symbol interference noise, and thermal noise represented by additive white Gaussian noise will have a significant impact on signal transmission.

[0048] Step 4 includes the following steps:

[0049] Step 4.1: The interference of shot noise on the received signal of the system model is calculated as follows:

[0050]

[0051] is the variance of the scattering noise from the i-th headlight beam to the j-th photodetector; q is the electron charge; R is the response speed of the photodetector; B is the system bandwidth; I bg I0 is the received background noise current; I2 is the noise bandwidth coefficient of the background noise.

[0052] Step 4.2: The formula for calculating inter-symbol interference noise is as follows:

[0053]

[0054] in, Let be the variance of the inter-symbol interference noise of the j-th photodetector;

[0055] Step 4.3: The formula for calculating thermal noise in the form of additive Gaussian white noise is as follows:

[0056]

[0057] in, T is the variance of thermal noise; 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.

[0058] A further improvement to the technical solution of the present invention is that step 5 includes the following steps:

[0059] Step 5.1: Information is transmitted using binary on / off keying modulation technology and direct detection technology with a photodetector. The signal-to-noise ratio of the acquired signal is defined as:

[0060]

[0061] Among them, SNR ijLet be the signal-to-noise ratio from the i-th headlight to the j-th photodetector;

[0062] Step 5.2: The light path emitted by the i-th headlight and incident on the j-th photodetector via the line-of-sight link and non-line-of-sight links is denoted as link-ij. This model includes four links: link11, link21, link12, and link12. The signal-to-noise ratio of the four links is then combined with equal gain, calculated as follows:

[0063] SNR EGC =0.5·(SNR) 11 +SNR 21 )+0.5·(SNR 12 +SNR 22 (15)

[0064] SNR EGC The signal-to-noise ratio of a visible light communication system under pedestrian interference after equal-gain combining processing;

[0065] Step 5.3: Perform maximum ratio combining on the signal-to-noise ratios of the four links, calculated as follows:

[0066]

[0067] SNR MRC The signal-to-noise ratio of a visible light communication system under pedestrian interference after maximum ratio combining processing;

[0068] Step 5.4: To address the impact of pedestrian interference on visible light communication systems, an improved maximum ratio combining method is proposed, calculated as follows:

[0069]

[0070] SNR NEW The signal-to-noise ratio (SNR) of a visible light communication system under pedestrian interference is the result of improved maximum ratio combining. NEW The optimal signal-to-noise ratio for system performance;

[0071] Step 5.5: The formula for calculating the bit error rate of a visible light communication system under pedestrian interference is as follows:

[0072]

[0073] Where Q(x) is a function used to calculate the tail probability of the standard Gaussian distribution.

[0074] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0075] This invention is based on the photoelectric detector receiving light power generated by pedestrian location and an improved merging method to solve this interference scenario. It establishes a model based on a real traffic environment, which improves the practicality of the workshop two-input two-output visible light communication system model under pedestrian interference and provides experimental guidance for visible light communication when there are obstacles and interference.

[0076] This invention studies the interference of obstacles in a workshop two-input two-output visible light communication system model, and further analyzes and improves the performance of the workshop two-input two-output visible light communication system when obstacles exist, providing a reliable theoretical basis and experimental guidance for future technical research. Attached Figure Description

[0077] Figure 1 This invention provides a schematic diagram of two-input two-output visible light communication in a workshop under pedestrian interference and a schematic diagram of illuminance calculation.

[0078] Figure 2 This is a schematic diagram of the line-of-sight link analysis under pedestrian interference according to the present invention;

[0079] Figure 3 This is a schematic diagram of non-line-of-sight link analysis under pedestrian interference according to the present invention;

[0080] Figure 4 This is a graph showing the relationship between the received optical power of the photodetector of this invention and the longitudinal distance of a pedestrian.

[0081] Where: (a) pedestrian lateral distance = 20m, (b) pedestrian lateral distance = 21m,

[0082] (c) Pedestrian lateral distance = 22m, (d) Pedestrian lateral distance = 23m;

[0083] Figure 5 This is a graph showing the relationship between the longitudinal distance of pedestrians and the bit error rate when the lateral distance of pedestrians is 20m, processed by different merging methods according to the present invention;

[0084] Among them: L1, headlight one; L2, headlight two; P1, photodetector one; P2, photodetector two; 3, line-of-sight link; 4, non-line-of-sight link. Detailed Implementation

[0085] 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.

[0086] A method for constructing a two-input two-output visible light communication system model in a workshop under pedestrian interference is described below:

[0087] Step 1: Creating a car headlight model

[0088] The headlights were weighted according to current sales data for the corresponding vehicle model to obtain the illuminance distribution at different emission angles in low beam mode along the positive direction of the lamp axis. To describe a real-world visible light communication system in a factory, the horizontal intensity of the emitted light from automotive headlights is asymmetrical. (See attached...) Figure 1 As shown, the illuminance of the market-weighted beam model for headlight L1 and headlight L2 is expressed as follows:

[0089] I T (α, β)(1)

[0090] Where α and β are the horizontal and vertical angles between the emitted light rays of the car headlight and the direction of the headlight axis.

[0091] The formula for the illuminance of any position on the road surface or photodetector surface illuminated by the emitted light is:

[0092]

[0093] Where φ is the luminous flux (lm); S is the corresponding reflective area of ​​the road surface (m2); ω is the solid angle of the light ray (sr); r is the straight-line distance (m) between the light ray emission point and a point on the illuminated road surface or between the light ray emission point and the surface of the photodetector; θ is the angle between the direction of the light ray emitted by the car headlight and the normal to the illuminated road surface or the direction of the light ray emitted by the headlight and the normal to the surface of the photodetector.

[0094] Step 2: Handling line-of-sight links under pedestrian interference

[0095] The model of a two-input two-output visible light communication system in a workshop under pedestrian interference, with road communication scenarios, is attached. Figure 2 As shown, a pedestrian moves in a straight line at a zebra crossing. During model communication, the light emitted by headlights L1 and L2 to photodetectors P1 and P2 constitutes line-of-sight link 3. Under pedestrian interference, the line-of-sight link may be obstructed or interfered with.

[0096] Step 2.1: The light-receiving area A caused by pedestrian interference in the line-of-sight link from the i-th headlight to the j-th photodetector. r-ij The expression is:

[0097]

[0098] in, This represents the light-receiving area when i and j are the same. This represents the light-receiving area when i and j are different. When i is 1, the coordinate axis is established with L1 as the origin, and when i is 2, the coordinate axis is established with L2 as the origin.

[0099] Step 2.2: The light-receiving area mentioned in the previous step The expressions are as follows:

[0100]

[0101] In this coordinate system, the pedestrian's coordinates are (da, ha), where r represents the radius of the photodetector, and hp is the distance from the center of the photodetector to the shadow (transition variable). D represents the pedestrian's side width, also known as thickness. W represents the pedestrian's frontal width, also known as width. V This indicates the longitudinal distance between the two vehicles.

[0102]

[0103] Among them, D PD This indicates the distance between two photodetectors.

[0104] Step 2.3: Given A r-ij The expression for the optical power received through the line-of-sight link under pedestrian interference is:

[0105]

[0106] in, A represents the power generated when the i-th headlight illuminates the j-th photodetector under a line-of-sight link. r-ij Let θ be the light-receiving area caused by the line-of-sight link from the i-th headlight to the j-th photodetector; LER is the luminous efficacy of the headlight; θ 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 θ be the straight-line distance between the i-th headlight and the j-th photodetector. In the environment of this study, its θ... ij Since it is much smaller than the half-angle of the field of view ψ, we do not need to consider the case where it exceeds the half-angle of the field of view, and the constraint conditions are always satisfied.

[0107] Step 3: Non-line-of-sight link processing under pedestrian interference

[0108] The light emitted by the car's headlights L1 and L2 is reflected off the road surface and enters the light received by the car's photodetectors P1 and P2. This constitutes the non-line-of-sight link 4 in the system model. The beam reflection pattern is considered a Lambertian mode. A pedestrian moving in a straight line at a zebra crossing will cause interference that affects the non-line-of-sight link, specifically as follows: Figure 3 As shown.

[0109] Step 3.1: The non-line-of-sight link beam's reflection mode on the road surface is considered to be a Lambertian profile. Here, it is assumed that the Lambertian exponent m = 1, which results in the reflected radiation intensity as follows:

[0110]

[0111] Where ρ is the diffuse reflectance and φ is the polar angle of the scattered light.

[0112] Step 3.2: When a pedestrian obstructs the visible light communication system, the expression for the pedestrian obstruction angle γ is:

[0113]

[0114] Among them, the angle between the critical light level blocked by pedestrians and the direction of the headlight axis. and The pedestrian's coordinates in the coordinate system are (da, ha). D represents the pedestrian's side profile width, also known as thickness; W represents the pedestrian's frontal width, also known as width. V This indicates the longitudinal distance between the two vehicles.

[0115] Step 3.3: The received optical power of the non-line-of-sight link in the visible light communication system under pedestrian interference is:

[0116]

[0117] in, The luminous intensity of the light emitted by the i-th headlight with a blocking angle of γ, reaching the j-th photodetector via a non-line-of-sight link; when i is 1, the established coordinate axis uses L1 as the origin, and when i is 2, the established coordinate axis uses L2 as the origin; A r d and h represent the light-receiving area of ​​the photodetector and its height above the ground, respectively; ij Let θ be the direct path between the non-line-of-sight link of the light emitted from the i-th headlight to the j-th photodetector and the perpendicular projection of the road surface reflection point A and the photodetector; θ is the angle between the road surface normal and the incident light ray, ρ is the road surface diffuse reflectivity, and φ is the angle between the road surface normal and the incident light ray. ij Let ψ be the angle between the road surface normal and the reflected light from the road surface in the non-line-of-sight link from the i-th headlight to the j-th photodetector. ij Let di be the angle between the reflected ray from the i-th headlight's emission light to the j-th photodetector's non-line-of-sight link and the normal to the photodetector's plane, and let dS be the area of ​​the incident ray reflected onto the road surface. T This is the shortest distance from the headlight to the reflection point A;

[0118] Step 3.4: The received optical power of the non-line-of-sight link from the i-th headlight to the j-th photodetector under pedestrian interference is expressed as:

[0119]

[0120] Where S is the reflection area of ​​the non-line-of-sight link on the road surface, and the reflection point A is located within the reflection area S.

[0121] Step 4: System Noise Processing

[0122] For optical wireless communication, noise typically originates from ambient light and artificial light. This model is used to analyze the performance of a two-input, two-output visible light communication system between vehicles during the day, so ambient light can significantly impact signal transmission. Under ambient light conditions, shot noise, inter-symbol interference (ISI), and thermal noise represented by additive white Gaussian noise can all significantly affect signal transmission.

[0123] Step 4.1: The interference of shot noise on the system is as follows:

[0124]

[0125] in, is the variance of the scattering noise of the light emitted by headlight i to photodetector j; q is the electron charge; R is the response speed of the photodetector; B is the system bandwidth; I bg I is the received background noise current; I2 is the noise bandwidth coefficient of the background noise.

[0126] Step 4.2: The inter-symbol interference noise caused by the multipath effect is as follows:

[0127]

[0128] in, Let be the variance of the inter-symbol interference noise of the photodetector j.

[0129] Step 4.3: The thermal noise represented by additive Gaussian white noise is:

[0130]

[0131] in, T is the variance of thermal noise; 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.

[0132] Step 5: Merging Method Processing

[0133] Step 5.1: The model uses binary amplitude shift keying (BPS) modulation technology and direct detection calculation by photodetectors to modulate and receive information. Therefore, the signal-to-noise ratio of the acquired signal is defined as:

[0134]

[0135] Among them, SNR ij Let be the signal-to-noise ratio from headlight i to photodetector j.

[0136] Step 5.2: The light path emitted by the i-th headlight and incident on the j-th photodetector via the line-of-sight link and non-line-of-sight links is denoted as link-ij. This model includes four links: link11, link21, link12, and link12. The signal-to-noise ratio of the four links is then combined with equal gain, calculated as follows:

[0137] SNR EGC =0.5·(SNR) 11 +SNR 21 )+0.5·(SNR 12 +SNR 22 (15)

[0138] SNR EGC The signal-to-noise ratio of a visible light communication system under pedestrian interference after equal-gain combining processing.

[0139] Step 5.3: Perform maximum ratio combining on the signal-to-noise ratios of the four links, calculated as follows:

[0140]

[0141] SNR MRC The signal-to-noise ratio of a visible light communication system under pedestrian interference is the result of maximum ratio combining.

[0142] Step 5.4: To address the impact of pedestrian interference on visible light communication systems, an improved maximum ratio combining method is proposed, calculated as follows:

[0143]

[0144] SNR NEW The signal-to-noise ratio (SNR) of a visible light communication system under pedestrian interference is the result of improved maximum ratio combining. NEW The optimal signal-to-noise ratio for system performance.

[0145] Step 5.5: The formula for calculating the bit error rate of a visible light communication system under pedestrian interference is as follows:

[0146]

[0147] Where Q(x) is a function used to calculate the tail probability of the standard Gaussian distribution.

[0148] Step 6: Visible Light Communication System Simulation

[0149] Step 6.1: The two-input, two-output visible light communication system model for the workshop was configured as follows: pedestrian width 0.306m, pedestrian thickness 0.212m, low beam headlights (50% luminous intensity) during the day, distance between headlights L1 and L2 1.2m, height from the road surface 0.66m, distance between photodetectors P1 and P2 1.2m, height from the road surface 0.66m. Table 1 shows the key parameters for system modeling.

[0150] Table 1 System Model Parameter Table

[0151]

[0152]

[0153] Step 6.2: Headlights L1 and L2 emit light of a certain intensity. Considering pedestrian interference, calculate the line-of-sight and non-line-of-sight optical power received by photodetector P1 and photodetector P2 according to steps 2 and 3. The optical power received by the visible light communication system when the pedestrian is in different positions is shown in the attached figure. Figure 4 As shown. According to the appendix Figure 4 It can be seen that pedestrians blocking light has a significant impact on the received optical power of visible light communication systems. Since the light intensity of headlights varies in different directions, the impact on visible light communication systems also varies depending on the location of the pedestrian.

[0154] Step 6.3: Based on Step 5, apply different combining methods to the visible light communication system to obtain the bit error rate after equal gain combining, the bit error rate after maximum ratio combining, and the bit error rate after the proposed improved maximum ratio combining method to address pedestrian interference, as shown in the appendix. Figure 5 As shown, it can be concluded that the proposed improved maximum ratio combining method achieves the best bit error rate performance.

[0155] In the specific embodiments, the line-of-sight link receiving power and non-line-of-sight link receiving power of the visible light communication system under pedestrian interference were analyzed, and the proposed improved merging method improved the performance of the visible light communication system. However, the present invention is not limited to the above performance analysis used to analyze the two-input two-output visible light communication in the workshop under pedestrian interference.

[0156] The embodiments described above are merely illustrative of the working method of the present invention and are not intended to limit the scope of the invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this utility model. Any aspects not covered in this invention are applicable to the prior art.

Claims

1. A method for constructing a model of a two-input, two-output visible light communication system in a workshop under pedestrian interference, characterized in that: Two market-weighted headlight beams were used as transmitters, and two photodetectors were used as receivers. A visible light communication model under pedestrian interference and an improved merging method to address this interference were introduced. The model was built based on real traffic environment characteristics, making the experimental data of the system model more realistic. The specific steps included: Step 1: Creating the car headlight model; Step 2: Line-of-sight link analysis under pedestrian interference: When a pedestrian moves in a straight line at a zebra crossing, the light emitted by the car's headlights L1 and L2 to the receiving car's photodetectors P1 and P2 during model communication constitutes the line-of-sight link (3); under pedestrian interference, the line-of-sight link will be subject to obstruction interference; Step 2 specifically includes the following steps: Step 2.1: The light-receiving area caused by pedestrian interference in the line-of-sight link from the i-th headlight to the j-th photodetector. The expression is: in, This represents the light-receiving area when i and j are the same. This represents the light-receiving area when i and j are different. When i is 1, the coordinate axis is established with L1 as the origin, and when i is 2, the coordinate axis is established with L2 as the origin. Step 2.2: The light-receiving area mentioned in the previous step , The expressions are as follows: Where the pedestrian's coordinates in the coordinate system are (da, ha), r represents the radius of the photodetector, hp is the distance from the center of the photodetector to the shadow, i.e., the transition variable; D represents the pedestrian's side width, also known as thickness; W represents the pedestrian's frontal width, also known as width; D V Indicates the longitudinal distance between the two vehicles; Among them, D PD This indicates the distance between two photodetectors; Step 2.3: Given The expression for the optical power received through the line-of-sight link under pedestrian interference is: in, The power generated when the i-th headlight illuminates the j-th photodetector under a line-of-sight link; The light-receiving area is caused by the line-of-sight link from the i-th headlight to the j-th photodetector; LER is the luminous efficacy of the headlight. Let be 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; Let be the straight-line distance between the i-th headlight and the j-th photodetector; Step 3: Analysis of non-line-of-sight links under pedestrian interference; Step 4: System noise analysis; Step 5: Analysis of merging methods.

2. The method for constructing a workshop two-input two-output visible light communication system model under pedestrian interference as described in claim 1, characterized in that: The headlight intensity distribution in step 1 is obtained based on a market-weighted headlight beam model, and the intensity expression is: in, and The horizontal and vertical angles between the direction of the light emitted by the car headlights and the direction of the headlight axis. The illuminance of the light emitted by a car headlight at any illuminated point on the surface is: in, S is the luminous flux; S is the corresponding reflective area of ​​the road surface. is the solid angle of the ray; r1 is the straight-line distance between the ray's exit point and the illuminated point; The angle between the light emitted from the car's headlights and the normal to the illuminated plane.

3. The method for constructing a workshop two-input two-output visible light communication system model under pedestrian interference as described in claim 1, characterized in that: The light emitted by the headlights L1 and L2 of the car is reflected by the road surface and enters the light of the photodetectors P1 and P2 of the car as the non-line-of-sight link of the system model (4). The beam road surface reflection mode is regarded as the Lambert mode. When pedestrians move in a straight line at the zebra crossing, pedestrian interference will affect the non-line-of-sight link. Step 3 specifically includes the following steps: Step 3.1: The non-line-of-sight link beam's reflection mode on the road surface is considered to be a Lambertian profile. Assuming the Lambertian index m = 1, the reflected radiation intensity is: in, Diffuse reflectance It is the polar angle of the scattered light; Step 3.2: When a pedestrian obstructs the visible light communication system, the pedestrian obstruction angle. The expression is: Among them, the angle between the critical light level blocked by pedestrians and the direction of the headlight axis. , and , The pedestrian's coordinates in the coordinate system are (da, ha); D represents the pedestrian's side width, also known as thickness; W represents the pedestrian's frontal width, also known as width. Step 3.3: The received optical power of the non-line-of-sight link in the visible light communication system under pedestrian interference is: in, The angle of obstruction is The light emitted by the i-th headlight reaches the luminous intensity of the j-th photodetector via a non-line-of-sight link; when i is 1, the established coordinate axis is based on L1 as the origin, and when i is 2, the established coordinate axis is based on L2 as the origin. h and h represent the light-receiving area of ​​the photodetector and its height above the ground, respectively. The direct path between the non-line-of-sight link road surface reflection point A and the vertical projection of the photodetector from the light emitted by the i-th headlight to the j-th photodetector; Let be the angle between the road surface normal and the incident ray. The diffuse reflectance of the road surface. Let the angle between the road surface normal and the reflected light from the road surface in the non-line-of-sight link from the i-th headlight to the j-th photodetector be a given value. Let be the angle between the reflected ray from the i-th headlight's emission light to the j-th photodetector's non-line-of-sight link and the normal to the photodetector's plane. The area of ​​the road surface reflected by the incident light. This is the shortest distance from the headlight to the reflection point A; Step 3.4: The non-line-of-sight link received optical power of the light emitted by the i-th headlight under pedestrian interference, reflected by the road surface, and transmitted to the j-th photodetector is expressed as: in, The non-line-of-sight link's reflection area on the road surface is shown, and reflection point A is located within the reflection area. Inside; It is the half-angle of the field of view of the PD receiving light, which is the angle between the non-line-of-sight link of the light emitted by the i-th headlight reflected from the ground to the j-th photodetector and the normal of the PD surface. Beyond the half-angle of the PD's receiving light field At this time, the PD cannot receive the non-line-of-sight link power introduced by road surface reflection, and the received optical power is 0.

4. The method for constructing a workshop two-input two-output visible light communication system model under pedestrian interference as described in claim 1, characterized in that: This model is used to analyze the performance of a two-input two-output visible light communication system between vehicles during the day. Therefore, ambient light will have a significant impact on signal transmission. Under ambient light conditions, shot noise, inter-symbol interference noise, and thermal noise represented by additive white Gaussian noise will have a significant impact on signal transmission. Step 4 includes the following steps: Step 4.1: The interference of shot noise on the received signal of the system model is calculated as follows: It is the variance of the scattering noise from the light emitted by the i-th headlight to the j-th photodetector; R is the electron charge; R is the response speed of the photodetector; B is the system bandwidth. It is the received background noise current; It is the noise bandwidth coefficient of the background noise; Step 4.2: The formula for calculating inter-symbol interference noise is as follows: in, Let be the variance of the inter-symbol interference noise of the j-th photodetector; Step 4.3: The formula for calculating thermal noise in the form of additive Gaussian white noise is as follows: in, denoted as , where is the variance of the thermal noise; k is the Boltzmann constant. Where is the absolute temperature; G is the open-loop voltage gain; For transistor channel noise factor; The reverse conductivity of the transistor; I0 is the fixed capacitance per unit area of ​​the photodetector; I3 is the thermal noise current of the transistor channel. This represents the light-receiving area of ​​the photodetector.

5. The method for constructing a workshop two-input two-output visible light communication system model under pedestrian interference as described in claim 1, characterized in that: Step 5 includes the following steps: Step 5.1: Information is transmitted using binary on / off keying modulation technology and direct detection technology with a photodetector. The signal-to-noise ratio of the acquired signal is defined as: in, Let be the signal-to-noise ratio from the i-th headlight to the j-th photodetector; Step 5.2: The light path emitted by the i-th headlight and incident on the j-th photodetector via the line-of-sight link and non-line-of-sight link is denoted as link-ij. This model includes four links: link11, link21, link12, and link12. The signal-to-noise ratio of the four links is then combined with equal gain, as calculated by the following formula: The signal-to-noise ratio of a visible light communication system under pedestrian interference after equal-gain combining processing; Step 5.3: Perform maximum ratio combining on the signal-to-noise ratios of the four links, calculated as follows: The signal-to-noise ratio of a visible light communication system under pedestrian interference after maximum ratio combining processing; Step 5.4: To address the impact of pedestrian interference on visible light communication systems, an improved maximum ratio combining method is proposed, calculated as follows: The signal-to-noise ratio of a visible light communication system under pedestrian interference is the result of improved maximum ratio combining. The optimal signal-to-noise ratio for system performance; Step 5.5: The formula for calculating the bit error rate of a visible light communication system under pedestrian interference is as follows: in, This is a function used to calculate the tail probability of a standard Gaussian distribution.

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