Wireless optical communication transmitter position optimization method based on digital twin technology

Abstract

The present application belongs to the cross field of digital twin and wireless optical communication. Since the wireless optical communication system transmits information by visible light, the data transmission is affected by the transmission environment, building distribution and terrain, etc., and is prone to light path deviation. The present application provides a wireless optical communication transmitter position optimization method based on digital twin technology, acquires actual urban environment data, photoelectric equipment performance parameters and simulates the laser transmission process, uses digital twin technology to build a wireless optical communication system in the actual urban environment, optimizes the wireless optical communication system working in the actual urban environment based on an intelligent algorithm, optimizes the transmitter position in the built wireless optical communication system through the interaction of genetic algorithm and digital twin, reduces the engineering demand of field test, and provides system support for further research on the transmitter position optimization of wireless optical communication.

Description

TECHNICAL FIELD

[0001] The present application relates to a wireless optical communication transmitter position optimization system based on digital twin technology, and more particularly to a wireless optical communication system transmitter position optimization method based on Unreal Engine. BACKGROUND

[0002] Wireless optical communication has the characteristics of high transmission rate, low transmission power, high reception power, large transmission capacity, etc. With the maturity of atmospheric communication technology, its application will be more and more widely used. In cities with large population and prosperous business, it is very difficult to build a full-coverage optical fiber line, and wireless optical communication can be used for short-distance transmission and information transmission as long as the transmission path is not blocked. Therefore, wireless optical communication plays an increasingly important role in cities. However, there are still many problems in its application: first, the influence of atmospheric medium. Since the transmission medium of the wireless optical communication system is the atmosphere, the quality of the communication transmission is greatly affected by the atmosphere. If the weather is too bad, the signal of the wireless optical communication will quickly decay; second, the contradiction between transmission distance and signal quality is prominent. The transmission distance of wireless optical communication is inversely proportional to the signal quality. The longer the transmission distance, the worse the signal quality; third, the alignment problem between the transmitter and the receiver. In the existing optimization process, whether the transmitter and the receiver can communicate is determined according to whether there is a line-of-sight obstruction between them. If the transmitter and the receiver lack the corresponding line-of-sight transmission condition, communication cannot be realized. If the communication equipment is located in a high place with a wide field of view, it will be affected by strong winds, heavy snow and other weather conditions, and the optical path will easily deviate. SUMMARY

[0003] In view of the deficiencies in the prior art, the purpose of the present application is to provide a wireless optical communication transmitter position optimization method based on digital twin technology. The present application realizes the simulation of wireless optical communication in actual urban environment, and optimizes the position of the transmitter based on the built wireless optical communication system, thereby improving the communication quality and providing an auxiliary means for engineering design.

[0004] To achieve the above purpose, the present application provides the following technical scheme:

[0005] A wireless optical communication transmitter position optimization method based on digital twin technology, which uses digital twin technology and Unreal Engine to model the wireless optical communication system in actual urban environment, simulates laser transmission, and optimizes the wireless optical communication system working in actual urban environment based on intelligent algorithm, and optimizes the position of the transmitter in the built wireless optical communication system, including the following steps:

[0006] Step 1. Use Unreal Engine and digital twin technology to import optical and electrical equipment performance parameters and atmospheric communication environment data:

[0007] The aperture, length and field angle of the photoelectric device are used to simulate the light source and light path in the optical design software Zemax, and the internal structure of the photoelectric device is exported, the external structure of the photoelectric device is modeled by using the three-dimensional modeling software Solidworks, and the combination of the external structure and the internal structure of the photoelectric device is integrated into the Unreal Engine, wherein the photoelectric device includes a laser transmitter and a laser detector, and then the atmospheric communication environment is simulated by using the Unreal Engine;

[0008] Step 2. Build the actual city environment and the communication system client vehicle based on the Unreal Engine:

[0009] The actual city environment data is obtained by shooting the buildings, roads and surrounding facilities by using the unmanned aerial vehicle, the obtained actual city environment data is imported into the modeling software RealityCapture, the buildings, roads and surrounding facilities in the actual city environment data are modeled, the three-dimensional model of the modeled buildings, roads and surrounding facilities is visualized in the Unreal Engine, a car is placed on the visualized road, a laser detector of the photoelectric device is installed on the car, the car is interacted with the client by using the blueprint class in the Unreal Engine, and the operator inputs the control of the movement of the car through the peripheral device;

[0010] Step 3. According to the optical design software simulation light transmission process, the combination of the photoelectric device obtained in step 1 and the actual city environment completed in step 2 is combined, and the light wave beam during laser transmission is simulated in real time based on the completed actual environment;

[0011] Step 4. In the completed actual environment, the position distribution of the transmitter is optimized by using the genetic algorithm and the digital twin interaction.

[0012] Further, in step 3, the light wave beam during laser transmission is simulated in real time, and the specific steps are as follows:

[0013] Step 3.1 Install the laser transmitter in the combination of the photoelectric device obtained in step 1 to the building in the simulated environment, and calculate the signal-to-noise ratio of the light communication transmission through the change of the atmospheric communication environment, the distance between the car and the laser transmitter, and whether there is an obstruction in the transmission line of sight between the car and the laser transmitter;

[0014] Step 3.2 The width of the light wave beam during laser transmission is simulated in real time by using the beam broadening formula.

[0015] Further, in step 4, the optimization process of the position distribution of the transmitter is as follows:

[0016] Step 4.1 Determine the encoding mode, determine the gene sequence of the individuals in the population according to the encoding mode, and then initialize the individuals in the population;

[0017] Step 4.2, sampling the road in the city environment built in step 2, the car moves to a sampling point, the car-mounted detector and the transmitter placed on the building perform optical communication, and the fitness value of the individual is calculated;

[0018] Step 4.3, judging whether the fitness value meets the termination condition of optimization: whether the change of the fitness value of the adjacent population is less than 5% twice, if it meets, the optimization ends, if it does not meet, a new population is obtained through the set selection, crossover and mutation operators, the fitness value of the individuals in the new population is calculated and whether the fitness value of the individuals in the new population meets the termination condition of optimization is judged, if the termination condition is still not met, a new population is obtained again through the set selection, crossover and mutation operators and its fitness value is calculated, until the termination condition is met.

[0019] Further, the encoding method is to encode the buildings where the transmitters can be placed and the positions of the transmitters that can be placed on each building where the transmitters can be placed in the three-dimensional model built in steps 1-3, if a position point has a transmitter, it is represented by 1, if there is no transmitter, it is represented by 0, and the transmitter device column is encoded in real domain according to the number of specific device categories.

[0020] Further, the specific way of optical communication is as follows:

[0021] Step 4.2.1, establishing a twin environment of the actual city environment obtained in step 2 and the atmospheric communication environment in step 1;

[0022] Step 4.2.2, placing a car on the road in the environment, and randomly sampling on the road, the car reaches a sampling point and the transmitter placed in the individual performs data communication according to the following process once:

[0023] First, judging whether there is a line-of-sight obstruction between the transmitter placed in the individual and the car, if there is an obstruction, the corresponding SNR=0, where SNR represents the signal-to-noise ratio of the communication signal; when there is no line-of-sight obstruction in the communication link, the SNR is calculated according to the optical physical transmission formula, the environmental optical characteristics and the geometric relationship of the transmission link, then the car moves, at each sampling point of the road, it is judged whether there is a line-of-sight obstruction between the car and the transmitter placed in the individual, and the SNR is calculated, where

[0024]

[0025] In the above formula, where h represents the height difference between the transmitter and the laser, Cn2 is the atmospheric turbulence structure constant, which is the vertical path wind speed, v g is the near-surface wind speed, L pis the transmission distance, i.e., the distance between the transmitter and the detector, k is the wave number, i.e. is the wavelength of the laser.

[0026] Further, the adaptation value is calculated according to the signal-to-noise ratio distribution of the entire urban area and the economic benefit of the transmitter category, and the specific calculation formula is:

[0027] f (h) = ω l f l (h) + ω e f e (h)

[0028] Wherein, f l and f e correspond to the signal-to-noise ratio distribution and the economic benefit of the objective function, defined as:

[0029]

[0030]

[0031] ω l , ω e are the weight values of f l and f e , ω l + ω e = 1, t represents the number of positions of the divided road, p i represents the price of each transmitter

[0032] In summary, the application has the following beneficial effects:

[0033] The application adopts digital twin technology to model the wireless optical communication system in the actual urban environment, reduces the engineering demand of field test, and provides system support for further research on transmitter position optimization of wireless optical communication; based on intelligent algorithm, the transmitter position optimization of the wireless optical communication system working in the actual urban environment can reduce the need for manual system deployment, and provides an auxiliary means for engineering design. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a method flowchart of the application, Figure 2 is an optimization flowchart. DETAILED DESCRIPTION

[0035] The application will be further described in detail below in combination with the drawings.

[0036] As Figure 1As shown, the present application proposes a wireless optical communication transmitter position optimization method based on digital twin technology, acquires actual urban environment data, optoelectronic device performance parameters and simulates laser transmission process, uses digital twin technology to build a wireless optical communication system in the actual urban environment, optimizes the wireless optical communication system working in the actual urban environment based on intelligent algorithm, and optimizes the transmitter position in the built wireless optical communication system through the interaction of genetic algorithm and digital twin. The specific steps are as follows:

[0037] Step 1. Use Unreal Engine and digital twin technology to import optoelectronic device performance parameters and atmospheric communication environment data: specifically including modeling of optoelectronic devices and simulation of atmospheric communication environment, optoelectronic devices including laser transmitter and laser detector, the structure of optoelectronic device consisting of external structure and internal structure, wherein the external structure is modeled by using three-dimensional modeling software Solidworks, the internal structure is simulated by using optical design software Zemax to simulate the light source and light path and export, then the external structure and internal structure are combined into the optoelectronic device combination and integrated into the Unreal Engine; The simulation of atmospheric communication environment is completed based on Unreal Engine, which simulates normal environment and snow environment in Unreal Engine. Through digital twin technology, the data and behavior of physical entities or processes are converted into digital models for analysis, optimization and prediction. The model of optoelectronic device is integrated into Unreal Engine for digital processing to analyze its parameters and provide environment for subsequent system building.

[0038] Step 2. Build actual urban environment and communication system client vehicle based on Unreal Engine: The modeling of actual urban scene is completed by three-dimensional design software RealityCapture, which uses unmanned aerial vehicle to shoot buildings, roads and surrounding facilities to obtain actual urban environment data, imports the obtained environment data into RealityCapture to model buildings, roads and surrounding facilities in the data, and visualizes the three-dimensional model of the modeled buildings, roads and surrounding facilities in Unreal Engine; The communication client vehicle refers to placing a car on the visualized road, mounting the laser detector of the optoelectronic device on the car, and using the blueprint class in Unreal Engine to realize the interaction between the car and the client, and the operator controls the movement of the car through the external input device.

[0039] Step 3. Simulate the light transmission process according to the optical design software, and then combine it with the actual urban environment built in step 2 in real time: Specifically, install the laser transmitter in the photoelectric device combination obtained in step 1 on the building, and calculate the signal-to-noise ratio of the transmitted optical communication through the changes in the atmospheric communication environment, the distance between the car and the laser transmitter, and whether there is an obstruction in the transmission line of sight between the car and the laser transmitter. Simulate the light wave beam width in real time during laser transmission in the built environment. Simulate the light transmission process through the optical transmission simulation software Zemax to obtain the initial light intensity, and then calculate the light intensity after attenuation through the light intensity attenuation coefficient τ a The formula calculates the light intensity after attenuation, where P t (0) is the power of the light source, P r (L) is the power after transmission distance L, β a and β s respectively represent the absorption coefficient and the scattering coefficient, and the beam widening formula is as follows:

[0040]

[0041] where ω0 represents the initial beam radius, and are the diffraction and atmospheric turbulence beam spread angles respectively, z is the transmission distance, and ρ T is the atmospheric turbulence coherence length, where k = 2π / λ, λ is the wavelength, is the atmospheric refractive index structure constant, and L is the maximum transmission distance.

[0042] Calculate the radius ω of the transmitted light beam, and finally visualize the light beam in the Unreal Engine.

[0043] Step 4. Use genetic algorithm and digital twin interaction to optimize the position distribution of the transmitter in the system built in steps 1, 2 and 3. The position distribution optimization process is as follows:

[0044] Step 4.1 Determine the encoding method, determine the gene sequence of individuals in the population according to the encoding method, and then initialize the individuals in the population.

[0045] Step 4.2 Sample the roads in the urban environment built in step 2. The car-mounted detector performs optical communication with the transmitter placed on the building every time the car moves to a sampling point. Calculate the fitness value of the individual. The specific way of optical communication is as follows:

[0046] Step 4.2.1 Establish a twin environment for the actual urban environment obtained in step 2 and the atmospheric communication environment in step 1;

[0047] Step 4.2.2 Place a small car on the road in the environment and perform random sampling on the road. Each time the car reaches a sampling point, it communicates with the transmitter placed on the building in the individual according to the following process:

[0048] like Figure 2 The flowchart shown is for optimization. In the transmitter installation location optimization problem, the first thing to consider is the encoding issue. The specific encoding method is as follows: In the actual urban environment built in step 2, the locations of buildings where transmitters can be placed are encoded. If a transmitter is placed at a certain location, it is represented by 1; if no transmitter is placed, it is represented by 0. The transmitter device column is encoded in real number field according to the number of specific device categories.

[0049] Individual representation: Each individual is represented as a vector h = (s1, s2, ..., s... k ,id), where s j =(x j y j , z j ) represents the position of the j-th transmitter, K is the number of buildings in the entire area where transmitters can be placed, i.e. the maximum number of transmitters that can be placed in the optimization. In the actual layout, n(h) represents the actual number of transmitters placed for individual h (n(h)≤K), and id represents the equipment type.

[0050] Initialize the population: Set the number of individuals in the population to M. Set s ij Let represent the coordinates of the j-th transmitter in the i-th individual, where i = 1, 2, ..., M, j = 1, 2, ..., K, and K represents the number of buildings in the entire area where transmitters can be placed. The M individuals in the initial population are represented as...

[0051] H1={h i =(s i1 s i2 , ..., s ik |i = 1, 2, ..., M}

[0052] Initialization method for M individuals: Each individual randomly places a transmitter on one of the K buildings where transmitters can be placed, and the transmitter device list is randomly set according to the number of specific device categories.

[0053] Adaptive function calculation: the actual urban environment obtained in step 2 and the atmospheric communication environment in step 1 are used to establish a twin environment. At the same time, a small car is placed on the road in the environment, and random sampling is performed on the road. The small car performs data communication with the transmitter placed in the individual according to the following process every time it reaches a sampling point: first, it is determined whether there is a line-of-sight obstruction between the transmitter placed in the individual and the small car. If there is an obstruction, the corresponding SNR=0, where SNR represents the signal-to-noise ratio of the communication signal; when there is no line-of-sight obstruction, the SNR is calculated according to the optical physics transmission formula, the optical properties of the environment, and the geometric relationship of the transmission link. Then, through the movement of the small car, it is determined whether there is a line-of-sight obstruction between the small car and the transmitter placed in the individual at each sampling point on the road, and the SNR is calculated, wherein

[0054]

[0055] In the above formula:

[0056]

[0057]

[0058] h represents the height difference between the transmitter and the laser, v RMS is the vertical path wind speed, which represents the atmospheric turbulence structure constant, v g is the near-surface wind speed, L p is the transmission distance, i.e., the distance between the laser transmitter and the detector, k is the wave number, i.e. λ is the wavelength, thereby obtaining the SNR distribution of the entire region. Then, the economic benefit is determined by the price of the transmitter type and the number of transmitters placed in the individual. Finally, the adaptive function f(h) is defined by the SNR distribution of the entire region and the economic benefit:

[0059] f(h) = ω l f l (h) + ω e f e (h)

[0060] where f l and f e correspond to the objective functions of the SNR distribution and the economic benefit, respectively, and are defined as:

[0061]

[0062]

[0063] ω l , ω e are the weight values set by humans for the two objectives (ω l + ωe =1), t represents the number of positions of the divided road, p i represents the price of each transmitter.

[0064] Setting of selection operator, crossover operator and mutation operator: selection operator: fitness proportionate method is adopted, in which the selection probability of each individual is proportional to its fitness value, and the i-th individual is selected with probability

[0065]

[0066] wherein M represents the number of individuals in the population, and selected for crossover; crossover operator: adjacent two individuals in the parent are crossed through uniform crossover, specifically, a 0 / 1 sequence G consistent with the individual structure is first randomly generated, and for adjacent two individuals in the parent, if G j =0, the corresponding j-th gene value does not undergo crossover, and if G j =1, the corresponding j-th gene value undergoes crossover; mutation operator: for the generated offspring, C genes in the M chromosomes are randomly selected, and according to a mutation probability P m , the selected genes are inverted, and the values of C and P m are specified by input parameters.

[0067] Step 4.3: judging whether the fitness value meets the termination condition of optimization: whether the change of the fitness values of two adjacent populations is less than 5%, if yes, the optimization is ended, and if not, a new population is obtained through the set selection, crossover and mutation operators, the fitness values of the individuals in the new population are calculated, and whether the fitness values of the individuals in the new population meet the termination condition of optimization is judged, if the termination condition is still not met, a new population is obtained again through the set selection, crossover and mutation operators, and the fitness values thereof are calculated, until the termination condition is met.

[0068] The application firstly utilizes digital twin technology to receive performance parameters of the receiving end and the transmitting end equipment, atmospheric communication environment data; secondly, utilizes Unreal Engine to build a city environment and a communication system client carrier based on geographic remote sensing information; then, simulates an optical transmission process according to an optical transmission simulation software, and further simulates an optical wave beam during laser transmission in real time based on the built environment; finally, obtains optimal wireless optical communication system configuration parameters in the current environment through genetic algorithm and digital twin interaction with the performance, position and variable parameters of the wireless optical communication system equipment. The application utilizes digital twin technology to model the wireless optical communication system in the actual environment, reduces the engineering demand of field test, optimizes the wireless optical system working in the actual environment based on the intelligent algorithm, can reduce the manual work required for system deployment, and provides an auxiliary means for engineering design.

[0069] The above merely describes the preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-described embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall also be considered as falling within the protection scope of the present application.

Claims

1. A method for optimizing the location of a wireless optical communication transmitter based on digital twin technology, characterized in that: This paper utilizes digital twin technology and Unreal Engine to model a wireless optical communication system in a real urban environment, simulates laser transmission, and optimizes the system based on intelligent algorithms. Specifically, it optimizes the transmitter's location within the constructed wireless optical communication system, including the following steps: Step 1. Using Unreal Engine and digital twin technology, access the performance parameters of optoelectronic equipment and atmospheric communication environment data: The aperture, length, and field of view of the optoelectronic device are used to simulate the light source and optical path in the optical design software Zemax and derive the internal structure of the optoelectronic device. The external structure of the optoelectronic device is modeled using the 3D modeling software Solidworks. The combination of the external and internal structures of the optoelectronic device is integrated into the Unreal Engine. The optoelectronic device includes a laser emitter and a laser detector. Then, the atmospheric communication environment is simulated using the Unreal Engine. Step 2. Build a realistic city environment and communication system client vehicle based on Unreal Engine: Drones are used to photograph buildings, roads, and surrounding facilities to obtain data on the actual urban environment. The obtained data is then imported into the modeling software RealityCapture to model the buildings, roads, and surrounding facilities in the actual urban environment data. The 3D models of the completed buildings, roads, and surrounding facilities are then visualized in Unreal Engine. A car is placed on the visualized road, and a laser detector of photoelectric equipment is installed on the car. The Blueprint class in Unreal Engine is used to enable the car to interact with the client. The operator controls the movement of the car through peripheral input. Step 3. Based on the optical design software, simulate the light transmission process and combine it with the optoelectronic device assembly obtained in Step 1 and the actual urban environment modeled in Step 2. Simulate the light beam during laser transmission in real time based on the actual environment modeled. Step 4. In the actual environment where the modeling is complete, the position distribution of the transmitters is optimized using a genetic algorithm in conjunction with the digital twin. The optimization process for the transmitter position distribution is as follows: Step 4.1 Determine the encoding method, determine the gene sequence of individuals in the population based on the encoding method, and then initialize the individuals in the population; Step 4.2 Sample the roads in the urban environment built in Step 2. Each time the car moves to a sampling point, the detector mounted on the car communicates optically with the transmitter placed on the building to calculate the individual's fitness value. Step 4.3 Determine if the fitness value meets the optimization termination condition: Is the change in fitness value between two adjacent populations less than 5%? If so, the optimization ends. If not, a new population is obtained by setting selection, crossover, and mutation operators. The fitness value of individuals in the new population is then calculated, and it is determined whether the fitness value of individuals in the new population meets the optimization termination condition. If the termination condition is still not met, a new population is obtained again by setting selection, crossover, and mutation operators, and its fitness value is calculated until the termination condition is met. The encoding method described above involves encoding the buildings on which transmitters can be placed and the locations on each building that can house a communication transmitter in the 3D model completed in steps 1 to 3. A location point where a transmitter is placed is represented by 1, and a location point where no transmitter is placed is represented by 0. The transmitter device column is encoded in the real number field according to the number of specific device categories. The fitness value is calculated based on the signal-to-noise ratio distribution of the entire urban area and the economic benefits of the transmitter type. The specific calculation formula is as follows: in, and The objective functions corresponding to the signal-to-noise ratio distribution and economic benefits, respectively, are defined as follows: , They are and The weight value, + =1, where t represents the number of locations of the divided roads. This indicates the price of each transmitter.

2. The method for optimizing the location of a wireless optical communication transmitter based on digital twin technology according to claim 1, characterized in that: In step 3, the optical beam during laser transmission is simulated in real time. The specific steps are as follows: Step 3.1 Install the laser emitter in the optoelectronic device assembly obtained in Step 1 onto a building in the simulated environment. Calculate the signal-to-noise ratio of the transmitted optical communication based on changes in the atmospheric communication environment, the distance between the vehicle and the laser emitter, and whether there are any obstructions in the line-of-sight transmission distance between the vehicle and the laser emitter. Step 3.2 Simulate the beamwidth of the laser transmission in real time using the beamwidth formula.

3. The method for optimizing the location of a wireless optical communication transmitter based on digital twin technology according to claim 1, characterized in that: The specific method for performing optical communication is as follows: Step 4.2.1 Establish a twin environment between the actual urban environment obtained in Step 2 and the atmospheric communication environment in Step 1; Step 4.2.2 Place a small car on the road in the environment and perform random sampling on the road. Each time the car reaches a sampling point, it communicates with the transmitter placed in the individual according to the following process: First, determine if there is line-of-sight obstruction in the communication link between the transmitter placed in the individual and the vehicle. If obstruction exists, the corresponding SNR = 0, where SNR represents the signal-to-noise ratio of the communication signal. When there is no line-of-sight obstruction, calculate the SNR based on the optical physical transmission formula, environmental optical characteristics, and the geometric relationship of the transmission link. Then, as the vehicle moves, at each sampling point along the road, determine if there is line-of-sight obstruction in the communication link between the vehicle and the transmitter placed in the individual, and calculate the SNR accordingly. In the above formula Where h represents the height difference between the transmitter and the laser. The atmospheric turbulence structure constant represents the vertical path wind speed. It is the near-surface wind speed, L p The transmission distance is the distance between the transmitter and the detector, and k is the wavenumber. λ is the laser wavelength.

Images