Visible Light Communication Mobile Terminal Dynamic Tracking Method and System

Abstract

This invention relates to the field of visible light communication technology, and particularly to a dynamic tracking method and system for visible light communication mobile terminals. The RIS module initializes the light field of the transmitting light source; an image sensor fixed at the receiving end transmits the captured image of the light source to a computer; the computer obtains the relative orientation information of the transmitting and receiving ends through subtle features of the light source shape in the image, and obtains the relative distance between the transmitting and receiving ends through image grayscale features. Combining direction and distance, the computer estimates the relative position of the transmitting and receiving ends; the computer controls the RIS module to adjust the light field of the light source based on the relative position information, enabling the light source to dynamically track the receiving terminal. This invention obtains the relative position information of the transmitting and receiving ends through the image sensor at the receiving end, and the RIS module adjusts the position, range, and intensity of the light spot according to the position information, ensuring wide-area coverage of optical communication while still meeting the light intensity requirements for high-speed communication.

Description

Technical Field

[0001] This invention relates to the field of visible light communication technology, and in particular to a method and system for dynamic tracking of visible light communication mobile terminals. Background Technology

[0002] With the continuous development of technology, the Industrial Internet has placed demands on wireless communication, including deep coverage, ultra-low latency, and secure communication. Traditional wireless communication modes such as 5G / WiFi face numerous problems such as limited frequency bands and electromagnetic interference. The emergence of Visible Light Communication (VLC) has opened up new spectrum resources for the Industrial Internet, and it is irreplaceable in the fields of short-to-medium distance, high-speed, and high-density wireless interconnection.

[0003] When discussing the communication environment in the context of the Industrial Internet, a prominent characteristic is "movement." In modern smart factories, movement is often large-scale and frequent. Workers and intelligent mobile devices (such as automated guided vehicles and autonomous robots) move back and forth between different areas, constantly exchanging information. In this context, visible light communication inevitably faces a trade-off between signal strength and coverage. Limited by the total power of the light source, achieving the required signal strength for high-speed communication necessitates sacrificing signal coverage, but limited coverage cannot handle the relative movement of the transmitting and receiving ends. Conversely, sacrificing signal strength for increased coverage compromises communication speed.

[0004] To address the aforementioned contradictions, signal reception issues in dynamic scenarios can be resolved through real-time dynamic tracking of the receiver. After acquiring the real-time location information of the receiver, the light source transmitter emits a narrow beam in a directional manner to cover the receiver and dynamically adjusts it based on the receiver's position. This solution satisfies both the wide-area coverage requirements for terminal movement and the local high light intensity requirements for efficient communication, effectively solving the visible light communication problem in dynamic scenarios.

[0005] In existing dynamic visible light communication solutions, communication and positioning studies are typically conducted independently. For example, Agheli et al.'s 2022 evaluation showed that RIS (Radio-Resistant Component Analysis) improved data transmission rates for Free Space Optical (FSO) communication by 44%. While this method of improving communication performance through RIS dynamic system optimization explains the source of location information and how it guides RIS parameter configuration, it fails to mention the interaction between communication performance and this location information. On the other hand, research on improving positioning performance based on visible light generally does not address how to leverage the improved positioning performance to further enhance communication signals. While Ma et al. from China University of Mining and Technology analyzed the relationship between visible light communication and positioning and proposed a design framework for a VLPC system using DC for positioning and AC for communication, they also failed to propose or utilize the mutually reinforcing relationship between the two to achieve overall performance improvement. Summary of the Invention

[0006] This invention aims to address the problem that existing solutions cannot achieve intelligent control of the light field, which prevents the light field from adjusting accordingly to changes in the position of the mobile terminal. This results in the inability to simultaneously meet the needs of mobile receivers and high-speed communication under power-limited conditions. The invention proposes a dynamic tracking method and system for visible light communication mobile terminals. By obtaining the relative position information of the transceiver through the image sensor at the receiving end, the RIS module adjusts the position, range, and intensity of the light spot according to the position information of the transceiver, ensuring wide-area coverage of optical communication while still meeting the light intensity required for high-speed communication.

[0007] To achieve the above objectives, the technical solution adopted is:

[0008] A method for dynamic tracking of visible light communication mobile terminals, comprising:

[0009] The RIS module initializes the light field of the emitted light source;

[0010] The image sensor fixed at the receiving end transmits the captured light source image to the computer;

[0011] The computer obtains the relative orientation information of the transmitting and receiving ends through the subtle features of the image light source shape, obtains the relative distance between the transmitting and receiving ends through the image grayscale features, and estimates the relative position of the transmitting and receiving ends by combining the direction and distance.

[0012] The computer controls the RIS module to adjust the light field of the light source based on the relative position information, so that the light source dynamically tracks the receiving terminal.

[0013] According to the visible light communication mobile terminal dynamic tracking method of the present invention, the RIS module further initializes the light field of the transmitting light source so that the light field covers the entire motion range of the communication receiving end.

[0014] According to the visible light communication mobile terminal dynamic tracking method of the present invention, the computer further obtains the relative orientation information of the transceiver end through subtle features of the image light source shape, including:

[0015] The computer uses image recognition algorithms to deduce the relative positions of the light source and the receiver based on the imaging shape and position of the light source in the image.

[0016] According to the visible light communication mobile terminal dynamic tracking method of the present invention, obtaining image grayscale features further includes:

[0017] The average grayscale distribution of the captured image is fitted as follows:

[0018]

[0019] In the formula, α and β are linear fitting coefficients, which are related to the light source's emission power, the light source's mounting height, and the parameters of the image sensor; f represents the lens focal length that provides the same focusing effect as RIS, and L represents the distance between the focusing lens and the LED light source. The θ represents the exit angle, and θ is the incident angle of the light beam reaching the receiver.

[0020] According to the visible light communication mobile terminal dynamic tracking method of the present invention, the computer further adopts an equal gradient phase distribution method for RIS configuration to offset the direction of the light beam; the computer adopts a non-equal gradient phase distribution method for RIS configuration to change the spot range and intensity.

[0021] According to the visible light communication mobile terminal dynamic tracking method of the present invention, the computer further performs RIS configuration using an equal gradient phase distribution method, including:

[0022] When the light source is placed horizontally, the center of the light spot is located directly below the light source (0,0). To move the center of the light spot to the location of the receiver (x... R ,y R Taking the straight line from the emitter to the center of the beam spot as the reference axis, and the angle of incidence of the beam onto the RIS as 0°, the phase shift gradient applied to the RIS is expressed as:

[0023]

[0024] In the formula, ΔΘ represents the phase shift gradient applied by RIS, and n i λ is the spatial refractive index, λ is the incident light wavelength, (u,v) are the coordinate axes of the RIS dimming surface, and d is the distance between the receiver and the light source.

[0025] According to the visible light communication mobile terminal dynamic tracking method of the present invention, the computer further performs RIS configuration using a non-uniform gradient phase distribution method, including:

[0026] The phase distribution of the non-uniform gradient portion is configured with reference to the thickness function of an ideal lens, as expressed as:

[0027]

[0028] According to the visible light communication mobile terminal dynamic tracking method of the present invention, the light source dynamic tracking receiving terminal further includes:

[0029] With a sufficiently high feedback refresh rate, after the light field of the light source is adjusted, the position of the receiving end has changed slightly, but it is still within the illumination range of the light source. At this time, the relative position of the transmitting and receiving ends is repeatedly acquired and the light field of the light source is adjusted to maintain the dynamic tracking of the light source on the moving receiving terminal.

[0030] Furthermore, this invention also proposes a dynamic tracking system for visible light communication mobile terminals, comprising a transmitter LED, an image sensor, a computer, and a RIS module, wherein:

[0031] An image sensor, fixed at the receiving end, transmits the captured image of the light source to a computer.

[0032] The computer obtains the relative orientation information of the transceiver end through the subtle features of the image light source shape, obtains the relative distance between the transceiver end through the image grayscale features, and estimates the relative position of the transceiver end by combining the direction and distance; the computer controls the RIS module to adjust the light field of the light source based on the relative position information.

[0033] The RIS module adjusts the beam at the transmitting end to track and focus the position of the receiving end.

[0034] The beneficial effects achieved by adopting the above technical solution are:

[0035] Visible light communication systems utilize mobile communication terminals in many application scenarios, such as industrial workshops. These terminals require both wide-area coverage of the visible light emitting source to meet their mobility needs and high light intensity in the local area where the receiving end is located to meet their high-speed communication requirements. To address the contradiction between wide-area coverage and high local light intensity in mobile scenarios, this invention proposes a dynamic tracking method for visible light communication mobile terminals. This method uses an image sensor at the receiving end to acquire the relative position information of the transmitting and receiving ends. Based on this position information, a computer-controlled RIS module automatically adjusts the position, range, and intensity of the light spot to track the communication receiving end in real time, thus supporting high-speed visible light communication for mobile terminals. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0037] Figure 1 This is a framework diagram of the visible light communication mobile terminal dynamic tracking method according to an embodiment of the present invention;

[0038] Figure 2 This embodiment of the invention achieves different light-emitting characteristics by adjusting the distance L between the focusing lens and the LED light source;

[0039] Figure 3 This is a schematic diagram of the grayscale distribution calculated based on the model and the grayscale distribution measured using the assembled transmitter and CMOS camera according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram illustrating how the equal gradient phase distribution changes the position of the light spot according to an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram illustrating how a non-uniform gradient phase distribution can be used to change the range and intensity of the light spot, according to an embodiment of the present invention. Detailed Implementation

[0042] The exemplary solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art.

[0043] like Figure 1 As shown, this embodiment discloses a dynamic tracking method for visible light communication mobile terminals. This method simultaneously achieves wide-area coverage and fixed-point signal enhancement for visible light communication; it includes the following steps:

[0044] Step S101: The RIS module initializes the light field of the emitted light source.

[0045] RIS is a novel electromagnetic wave manipulation device composed of subwavelength phase modulation units, typically meta-surface or liquid-crystal (LC) arrays. RIS can alter the propagation form of light waves through reflection, transmission, and even diffraction. It can be deployed at any location in the receiving end, transmitting end, or propagation medium, and can change the direction, range, intensity, and even wavelength of the light beam.

[0046] In the initial stage, the receiving and transmitting ends of the communication system are unaware of each other's location information. Therefore, during the initial acquisition phase, the RIS module needs to adjust the light field of the transmitting light source to cover the entire range of motion of the receiving end as much as possible. During this stage, the light field of the transmitting light source exhibits wide-area coverage characteristics, with the light intensity evenly distributed over a wide range. Although the receiving end is illuminated by the light source, the signal-to-noise ratio is not high, which cannot meet the requirements of high-speed visible light communication.

[0047] Step S102: The image sensor fixed at the receiving end transmits the captured light source image to the computer.

[0048] Step S103: The computer obtains the relative orientation information of the transmitting and receiving ends through the subtle features of the image light source shape, obtains the relative distance between the transmitting and receiving ends through the image grayscale features, and estimates the relative position of the transmitting and receiving ends by combining the direction and distance.

[0049] Under the premise of wide-area coverage by the light source, the receiving end is located under the illumination of the light source. At this time, the image sensor fixed at the receiving end captures an image of the light source. After the image is transmitted to the computer, the computer can use image recognition algorithms to deduce the relative positions of the light source and the receiving end based on the imaging shape and position information of the light source in the image.

[0050] Because of the linear relationship between illuminance and captured image grayscale, and because a given light source has a definite power-illuminance conversion relationship, it is reasonable to assume that for a given light source, the relationship between optical power and grayscale can also be expressed as linear. Therefore, the image grayscale distribution model can be obtained by linearly fitting the power distribution. The radiant flux reaching the receiver can be expressed as:

[0051]

[0052] Where Ω(θ)=A R cosθ / d 2 =A R cos 3 θ / h 2 Let θ be the solid angle of the effective receiving surface covered by the beam, θ be the incident angle of the beam reaching the receiving end, d be the distance between the receiving end and the light source, h be the perpendicular distance between the receiving plane and the light source, and A be the solid angle of the beam covering the effective receiving surface. R For effective receiving area. For the equivalent radiation model of the light source, P T Where f is the transmission power, and f is the focal length of the lens that provides the same focusing effect as RIS. Let P be the emission angle, and L represent the distance from the condenser lens to the LED light source. Here, it is assumed that the image sensor has sufficiently high dynamic range and responsivity to render the entire incident flux into the image; therefore, the received power P is... R =Φ R Substitute Ω(θ) and have to:

[0053]

[0054] Following the idea that power and gray level have an approximately linear relationship, the average gray level distribution of the captured image is fitted as follows:

[0055]

[0056] Here, α and β are linear fitting coefficients, which are related to the light source emission power, the light source mounting height, and the parameters of the image sensor.

[0057] By adjusting the distance L between the condenser lens and the LED light source, light source characteristics with different degrees of focusing can be obtained, such as... Figure 2 As shown, the transmitter is positioned 185cm above the platform. An image sensor is used to acquire the average grayscale distribution of the light source image at different horizontal positions on the platform. Based on the measured results, the coefficients α and β in the above formula are fitted, and then substituted into the formula to obtain the grayscale distribution calculated by the model, as shown below. Figure 3 As shown in the figure, the distance L between the condenser lens and the LED light source was set to three values: 72mm, 77mm, and 81mm. It can be seen from the figure that as the value of L increases, the emissivity of the emitted light gradually decreases, the area of ​​the light spot on the platform gradually shrinks, while the brightness at the center of the light spot gradually increases. The grayscale distribution obtained by linear fitting with different L values ​​also matches the actual measurement results well.

[0058] Step S104: The computer controls the RIS module to adjust the light field of the light source according to the relative position information, so that the light source dynamically tracks the receiving terminal.

[0059] A transmissive RIS dimming panel is mounted at the front end of the light source. Then, based on the relative positions of the transmitter and receiver, the RIS is configured using a combination of equal-gradient and non-equal-gradient phases. That is, the transmissive RIS dimming panel at the front end of the light source not only deflects the direction of the light beam but also converges the beam to change the spot size and intensity. Therefore, this embodiment proposes using a combination of equal-gradient and non-equal-gradient phases to achieve a high signal-to-noise ratio at the receiver, meeting the requirements of high-speed visible light communication.

[0060] The equal gradient phase distribution is used to configure the beam shift (change the position of the beam spot). The phase shift gradient applied by RIS is calculated according to the generalized Snell's law, such as... Figure 4 As shown, when the light source is placed horizontally, the center of the light spot is located directly below the light source (0,0). To move the center of the light spot to the location of the receiving terminal (x... R ,y R Taking the straight line from the emitter to the center of the beam spot as the reference axis, and the angle of incidence of the beam onto the RIS as 0°, the phase shift gradient applied to the RIS is expressed as:

[0061]

[0062] In the formula, n i λ is the spatial refractive index, λ is the incident light wavelength, (u,v) are the coordinate axes of the RIS dimming surface, and when placed horizontally, their directions are the same as (x,y); ΔΘ represents the phase shift gradient applied to the RIS.

[0063] Non-uniform gradient phase distribution is used for focusing (changing the intensity and range of the light spot) to achieve, for example... Figure 5 The light-gathering effect shown, with the phase distribution of the non-uniform gradient portion configured according to the thickness function of an ideal lens, is expressed as:

[0064]

[0065] The focusing effect of RIS is equivalent to that of a focusing lens with a focal length of f. According to the above formula, by changing the parameter configuration of the non-uniform gradient part, different degrees of focusing effect can be achieved using RIS.

[0066] The receiver is always in motion relative to the transmitting light source, so the relative positions of the transmitter and receiver will constantly change. When the feedback refresh frequency is high enough, after the light field of the light source is adjusted, the position of the receiver has changed slightly, but it is still within the illumination range of the light source. At this time, the relative positions of the transmitter and receiver are repeatedly acquired and the light field of the light source is adjusted to maintain the dynamic tracking of the light source on the moving receiver.

[0067] If the receiving terminal moves too fast and exceeds the radiation range of the light source, the system feedback refresh frequency can be increased by improving computer performance to reduce computation time or improving the response characteristics of the RIS module. Alternatively, the spot size can be appropriately increased at the expense of a certain signal-to-noise ratio to ensure that the receiving terminal remains within the irradiation range of the light source within a cycle.

[0068] Corresponding to the above method, this embodiment also proposes a visible light communication mobile terminal dynamic tracking system, including a transmitter LED, an image sensor, a computer, and a RIS module, wherein:

[0069] An image sensor, fixed at the receiving end, transmits the captured image of the light source to a computer.

[0070] The computer obtains the relative orientation information of the transmitting and receiving ends through the subtle features of the image light source shape, obtains the relative distance between the transmitting and receiving ends through the image grayscale features, and estimates the relative position of the transmitting and receiving ends by combining the direction and distance; the computer controls the RIS module to adjust the light field of the light source based on the relative position information.

[0071] The RIS module adjusts the beam at the transmitting end to track and focus the position of the receiving end.

[0072] In this invention, estimating the relative position of the transceiver is a prerequisite for dynamic tracking. This invention utilizes images captured by the image sensor at the receiving end, identifying relative orientation information through subtle features of the light source shape and relative distance information through image grayscale features, thereby estimating the relative position of the transceiver. This invention also proposes a RIS (Radio Reflector Array) control method, which involves mounting a transmissive RIS dimming panel at the front end of the light source. Then, based on the relative position of the transceiver, the RIS is configured using a superposition of equal-gradient and non-equal-gradient phases. This changes the direction of the offset beam while simultaneously converging the beam, altering the spot size and intensity, achieving a high signal-to-noise ratio at the receiving end, thus meeting the requirements of high-speed visible light communication.

[0073] Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0075] The units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations are not considered to be beyond the scope of this invention.

[0076] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This invention is not limited to any particular combination of hardware and software.

[0077] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dynamic tracking method for a visible light communication mobile terminal, characterized in that, include: Step 1: The RIS module initializes the light field of the emitted light source; Step 2: The image sensor fixed at the receiving end transmits the captured light source image to the computer; Step 3: The computer obtains the relative orientation information of the transmitting and receiving ends through the subtle features of the image light source shape, obtains the relative distance between the transmitting and receiving ends through the image grayscale features, and estimates the relative position of the transmitting and receiving ends by combining the direction and distance. The computer obtains the relative distance between the transmitting and receiving ends through image grayscale features, specifically including: First, the computer extracts the average grayscale value of the captured light source image. Next, based on the average gray-scale distribution model Combining the geometric relationship cosθ=h / d, the relative distance d between the transmitter and receiver is calculated by solving the equation. In the equation, α and β are linear fitting coefficients, which are related to the light source's emission power, the light source's mounting height, and the parameters of the image sensor; f represents the focal length of the lens that provides the same focusing effect as RIS; and L represents the distance from the focusing lens to the LED light source. The emission angle is represented by θ, which is the incident angle of the light beam reaching the receiver, and h is the perpendicular distance between the receiving plane and the light source. Step 4: The computer controls the RIS module to adjust the light field of the light source based on the relative position information, so that the light source dynamically tracks the receiving terminal.

2. The visible light communication mobile terminal dynamic tracking method according to claim 1, characterized in that, The RIS module initializes the light field of the transmitting light source, ensuring that the light field covers the entire range of motion of the communication receiver.

3. The visible light communication mobile terminal dynamic tracking method according to claim 1, characterized in that, Computers obtain relative location information between the transmitting and receiving ends by observing subtle features of the image's light source shape, including: The computer uses image recognition algorithms to deduce the relative positions of the light source and the receiver based on the imaging shape and position of the light source in the image.

4. The visible light communication mobile terminal dynamic tracking method according to claim 1, characterized in that, The computer uses an equal gradient phase distribution method for RIS configuration, offsetting the direction of the beam, including: When the light source is placed horizontally, the center of the light spot is located directly below the light source (0,0). To move the center of the light spot to the location of the receiver (x... R ,y R Taking the straight line from the emitter to the center of the beam spot as the reference axis, and the angle of incidence of the beam onto the RIS as 0°, the phase shift gradient applied to the RIS is expressed as: In the formula, ΔΘ represents the phase shift gradient applied by RIS, and n i λ is the spatial refractive index, λ is the incident light wavelength, (u,v) are the coordinate axes of the RIS dimming surface, and d is the distance between the receiver and the light source. The computer uses a non-uniform gradient phase distribution method for RIS configuration to change the spot size and intensity, including: The phase distribution of the non-uniform gradient portion is configured with reference to the thickness function of an ideal lens, as expressed as:

5. The visible light communication mobile terminal dynamic tracking method according to claim 1, characterized in that, The light source dynamic tracking receiver terminal includes: With a sufficiently high feedback refresh rate, after the light field of the light source is adjusted, the position of the receiving end has changed slightly, but it is still within the illumination range of the light source. At this time, the relative position of the transmitting and receiving ends is repeatedly acquired and the light field of the light source is adjusted to maintain the dynamic tracking of the light source on the moving receiving terminal.

6. A dynamic tracking system for visible light communication mobile terminals, characterized in that, To implement the visible light communication mobile terminal dynamic tracking method as described in claim 1, the system includes a transmitter LED, an image sensor, a computer, and a RIS module, wherein: An image sensor, fixed at the receiving end, transmits the captured image of the light source to a computer. The computer obtains the relative orientation information of the transceiver end through the subtle features of the image light source shape, obtains the relative distance between the transceiver end through the image grayscale features, and estimates the relative position of the transceiver end by combining the direction and distance; the computer controls the RIS module to adjust the light field of the light source based on the relative position information. The RIS module adjusts the beam at the transmitting end to track and focus the position of the receiving end.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1-5.

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