Method and system for multi-beam visible light communication for mobile scenarios

Abstract

The present application relates to the technical field of visible light communication, and particularly relates to a multi-beam visible light communication method and system for a mobile scene, wherein first, a position sensor collects the positions of each receiving terminal in a target space under a lamp, and feeds back the position information to a computer; then, after the computer receives the position information, a fast CGH algorithm based on a G-S algorithm for a mobile scene is used to generate a hologram to load a control RIS module, the phase of an incident light beam is changed through the RIS module; a single light beam of a signal source is used to generate multiple light beams for tracking the positions of the receiving terminals through a Fourier lens, and then the light beams are adjusted through a lens system and irradiated onto corresponding receiving terminals in the target space. The present application can dynamically adjust the coverage range of a transmitting light beam according to the real-time positions of multi-user mobile communication terminals, and ensure the stability of communication of multiple receiving terminals in a movement process.

Description

Technical Field

[0001] This invention relates to the field of visible light communication technology, and in particular to a multi-beam visible light communication method and system for mobile scenarios. Background Technology

[0002] Visible Light Communication (VLC) transmits signals by loading them onto optical fibers in the visible light band. This technology utilizes the properties of visible light for information transmission, converting data into visible light signals through modulation and encoding, and then using optical communication equipment for transmission and reception.

[0003] With the development of the Industrial Internet of Things (IIoT) and the increasing demand for production efficiency, smart factories are gradually moving towards denser infrastructures. To cope with these densely packed smart mobile devices and ensure their orderly and efficient operation, the need for mobile multi-user visible light communication (VLP) capable of simultaneously transmitting data to all devices within a certain range is growing. Existing multi-user VLP solutions for mobile scenarios include... Figure 1 As shown. Wide-area coverage broadcasting is a relatively primitive and simple method, covering the entire workspace with a single signal source, resulting in the lowest complexity and cost. However, the signal strength received by each user is weak, and the communication efficiency between users is very low due to time-division multiple access. Massive multiple-input multiple-output (MIMO) technology can provide efficient parallel data transmission. However, in dynamic scenarios, each signal source needs to be equipped with a complex beam deflection control system and its corresponding drive circuit, becoming large-scale point-to-point tracking. Obviously, this method greatly increases the system complexity and cost, and also requires consideration of various issues such as the coordination of multiple signals. In addition, dividing the workspace into multiple cells using the controllable irradiation range of the visible light transmitter is a low-complexity and efficient solution, and also the most widely used. In traditional multi-cell methods, multiple signal sources are regularly deployed in space as access points for each cell. Each cell has a limited coverage area and communicates independently. However, there are unavoidable overlapping areas between cells. Interference between adjacent signal sources in these areas, as well as the time delay caused by cell handover during movement, severely affect system performance. The RIS-based reconfigurable cell solution addresses these issues of traditional visible light multi-cell communication methods. With the assistance of RIS, cells in a VLC system can be arbitrarily generated and reconfigured in real time according to actual scenario requirements. This avoids cell overlap and resolves crosstalk issues, reduces the frequency of cell handover by mobile devices, and significantly reduces latency caused by cell traversal during movement through control-end synchronization. Compared to traditional multi-cell methods, the dynamic reconfigurable cell multi-user solution is more efficient and flexible.

[0004] The existing scheme for constructing a dynamic link using a RIS mainly shifts the direction of incident light waves by applying a certain phase shift gradient. However, considering the influence of the RIS pixel size, the range of the cell light spot that can be generated by this scheme is limited, and it is difficult to generate multiple light spots to correspond to different mobile users. SUMMARY

[0005] The present application aims to solve the problem that the current scheme cannot adjust the light field coverage in real time according to the real-time position of the mobile terminal, resulting in that under the condition of limited power, the mobile attribute and high signal-to-noise ratio communication demand of multiple users cannot be met at the same time. A multi-beam visible light communication method and system for mobile scenarios are proposed, which can dynamically adjust the coverage range of the transmitted light beam according to the real-time position of the multi-user mobile communication terminal, and ensure the stability of the communication of the multiple receiving terminals in the movement process.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted is:

[0007] A multi-beam visible light communication method for mobile scenarios, comprising:

[0008] First, the position sensor collects the positions of each receiving terminal in the target space under the lamp, and feeds back the position information to the computer;

[0009] Then, the computer generates a hologram using a fast CGH algorithm for mobile scenarios based on the G-S algorithm after receiving the position information, loads the control RIS module, and changes the phase of the incident light beam through the RIS module;

[0010] And use a Fourier lens to generate multiple light beams that track the positions of the receiving terminals from a single light beam of the signal source, and then adjust them through a lens system and irradiate them onto the corresponding receiving terminals in the target space.

[0011] According to the multi-beam visible light communication method for mobile scenarios, further, the fast CGH algorithm for mobile scenarios based on the G-S algorithm for generating a hologram comprises:

[0012] The initial image of the target light spot is divided into several sub-images, each of which contains a light spot;

[0013] In the iteration loop, the inverse FT operation is performed on each sub-image, and the phase of the sub-hologram of the light spot is extracted k ;

[0014] FT operation is performed on these k , and the phase is extracted to replace the phase of the original sub-image; then the above steps are repeated until the optimized target light spot image passes the quality evaluation;

[0015] Assuming that the kth spot has a position offset in time Δt, the spot at time (t+Δt) is obtained by superimposing a phase shift Δψ k onto the sub-hologram at time t, without repeating the G-S iteration.

[0016] According to the multi-beam visible light communication method for a moving scene, further, assuming that the kth spot has a position offset in time Δt The offset spot is expressed as:

[0017]

[0018] where FT[·] represents the Fourier transform operation, A and φ are the amplitude and phase distribution on the holographic image plane, respectively, λ is the wavelength of light, f is the focal length of the Fourier lens, ψ is the phase distribution loaded on the RIS, (x, y) is the coordinate on the holographic image plane, (u, v) is the simplified coordinate on the RIS surface, and i represents the imaginary unit.

[0019] According to the multi-beam visible light communication method for a moving scene, further, a plurality of spots of the target space are obtained at the back focal plane of the Fourier lens.

[0020] According to the multi-beam visible light communication method for a moving scene, further, the axial position and lateral magnification of the generated spot are adjusted by the lens system, so that the spot is projected on the receiver with a proper size.

[0021] Further, the present application also provides a multi-beam visible light communication system for a moving scene, for implementing the multi-beam visible light communication method for a moving scene as described above, which comprises a position sensor, a computer, an RIS module, a Fourier lens and a lens system; wherein:

[0022] The position sensor collects the positions of each receiving terminal in the target space under the lamp, and feeds back the position information to the computer;

[0023] The computer generates a hologram to load the control RIS module by using a fast CGH algorithm for a moving scene based on the G-S algorithm after receiving the position information;

[0024] The RIS module changes the phase of the incident light beam;

[0025] The Fourier lens generates a plurality of light beams to track the positions of the receiving terminals from the single light beam of the signal source;

[0026] The lens system adjusts the spot generated by the Fourier lens.

[0027] By adopting the above technical solution, the beneficial effects are:

[0028] In view of the problem of dynamic tracking of multiple beams in a multi-user visible light communication system in a mobile scenario, the method for multiple-beam visible light communication in a mobile scenario provided by the application obtains real-time position information of a receiving terminal through a position sensor, and then feeds back the information to a computer, which generates a corresponding CGH as an input of a RIS module by using a mobile scenario fast CGH algorithm, so as to adjust the coverage range of the beam in real time, realize real-time dynamic tracking of the beam to the receiving terminal, and ensure the stability of communication of multiple receiving terminals in the process of movement. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings of the embodiments of the application will be briefly introduced hereinafter. The drawings are only used to show some embodiments of the application, and the application is not limited to the drawings.

[0030] Figure 1 is a schematic diagram of four existing multiple-user mobile terminal visible light communication modes;

[0031] Figure 2 is an architecture diagram of the method for multiple-beam visible light communication in a mobile scenario according to the embodiment of the application;

[0032] Figure 3 is a flowchart of the mobile scenario fast CGH algorithm according to the embodiment of the application;

[0033] Figure 4 is a structural diagram of the multiple-beam visible light communication system in a mobile scenario according to the embodiment of the application. DETAILED DESCRIPTION

[0034] Hereinafter, the example solutions of the embodiments of the application will be clearly and completely described with reference to the drawings of the embodiments of the application. Unless otherwise defined, the technical terms or scientific terms used in the application should be understood as the general meanings understood by persons having ordinary skills in the art.

[0035] As shown in Figure 2 , the embodiment discloses a method for multiple-beam visible light communication in a mobile scenario, which comprises the following steps:

[0036] Step S101: The position sensor collects the positions of each receiving terminal in the target space under the lamp, and feeds back the position information to the computer.

[0037] Step S102, after receiving the position information, the computer generates a hologram using a mobile scene fast CGH algorithm based on the G-S algorithm to load the control RIS module. The phase of the incident light beam is changed through the RIS module, so as to control the light field to converge around the mobile terminal, and the beam coverage range is updated in real time according to the change of the receiver terminal position. The involved terms are explained as follows: RIS: Reconfigurable Intelligent Surfaces (RIS). CGH: Computer-Generated Hologram (CGH).

[0038] Step S103, a single light beam of the signal source is generated into multiple light beams tracking the position of the receiving terminal by using a Fourier lens, and then irradiated on the corresponding receiving terminal in the target space after adjustment by a lens system, so as to finally realize the multi-beam high-efficiency visible light communication demand of multiple mobile users.

[0039] The purpose of the method is to use a single red LD (laser diode) to generate multiple light spots on a receiving plane, each light spot covering a photodiode (PD) receiver respectively, and the light spots can be adjusted according to the position of the receiver. By inputting a pure phase GCH to the RIS, a target spot image can be obtained on the back focal plane of the Fourier lens, which is used to shape the incident light beam, as in ③ of Figure 2 The axial position and transverse magnification of the generated light spots are adjusted by the lens system, so that the light spots are projected on the receiver with appropriate size.

[0040] According to the analysis of the above part, the light field generated on the receiving plane is covered by the CGH, so the quality of the generated CGH significantly affects the stability of the received signal. How to generate a high-quality pure phase CGH is an important task in the scheme. However, a more practical problem is that the operation of a high-quality pure phase CGH is too time-consuming, and when applied to a mobile scene, it is often impossible to achieve real-time multi-spot reconstruction. If the refresh speed of the generated light spot is insufficient, the target user in the mobile state cannot be locked in real time, and the signal will be interrupted. If the CGH quality is low, the generated light spot intensity is also weak, and the user signal quality will also be poor, and the generated high-order diffracted light will cause serious interference to other cells. Therefore, it is a basic requirement for the application of holographic beam shaping method in mobile multi-user communication to ensure the quality of the light spot and have a high enough refresh rate.

[0041] According to the Fresnel diffraction formula, the light field on the holographic image plane can be expressed as:

[0042]

[0043] where FT[·] denotes the Fourier transform (FT) operation, A and φ are the amplitude and phase distribution on the hologram image plane, respectively, λ is the wavelength of light, f is the focal length of the Fourier lens, ψ is the phase distribution loaded on the RIS, (x, y) is the coordinate on the hologram image plane, (u, v) is the simplified coordinate on the RIS surface, and i represents the imaginary unit. Since the intensity of the signal light is detected, φ is not affected in this process. The function of the CGH algorithm is to estimate the pure phase solution ψ, which can achieve the target amplitude A.

[0044] To improve the calculation speed and maintain the image quality, the embodiment proposes a moving scene fast CGH algorithm based on the (Gerchberg-Saxton) G-S algorithm. The G-S algorithm is a method of searching for the optimal value by constantly updating the result in the FT and inverse FT (IFT) iterative cycle. The calculation is simplified according to the spatial correlation between the moving target pictures without loss of resolution. The process of the moving scene fast CGH algorithm is shown in Figure 3 , which contains the following steps.

[0045] Taking the case of three receiving terminals as an example, the target spot image contains three light spots at arbitrary positions.

[0046] (1) Since FT is a linear operation, the target spot initial image can be divided into three sub-images before entering the G-S iterative cycle. Each sub-image contains a light spot.

[0047] (2) In the iterative cycle, the inverse FT (IFT) operation is performed on each sub-image, and the phase ψ k of the sub-hologram of the light spot is extracted.

[0048] (3) FT operation is performed on these ψ k , and the phase is extracted to replace the phase of the original sub-image; then the above steps are repeated until the optimized target spot image passes the quality evaluation.

[0049] (4) Assuming that the kth light spot has a position offset According to the characteristics of FT, the offset light spot can be expressed as:

[0050]

[0051] This means that the light spot at time (t+Δt) is obtained by superimposing the phase shift Δψ k on the sub-hologram at time t, without repeating the G-S iteration.

[0052] The pattern generated on the back focal plane of the Fourier lens is too small, and the adjustable space is very limited, so the scheme proposes to use a lens system composed of multiple coaxial lenses to adjust the generation position and magnification of the generated light spot, and project the pattern on the receiving plane.

[0053] Corresponding to the above method, the embodiment also proposes a multi-beam visible light communication system for a mobile scene, as shown in the figure, the system comprises a position sensor, a computer, an RIS module, a Fourier lens and a lens system; wherein: Figure 4

[0054] The position sensor collects the positions of each receiving terminal in the target space under the lamp, and feeds back the position information to the computer.

[0055] The computer generates a hologram using a fast CGH algorithm based on the G-S algorithm after receiving the position information to load the control RIS module.

[0056] The RIS module changes the phase of the incident light beam.

[0057] The Fourier lens generates a plurality of light beams tracking the positions of the receiving terminals from a single light beam of the signal source.

[0058] The lens system adjusts the light spot generated by the Fourier lens.

[0059] The present application uses the beamforming technology of digital holography to construct multiple dynamic light cells, realizes multi-beam efficient visible light communication in a mobile scene, and proposes to load the corresponding computer-generated hologram (CGH) to the RIS, so as to generate the required light field distribution on the receiving plane. Further, the present application proposes to design a suitable optical system to generate the required light spot distribution in a larger range.

[0060] Because the light power intensity generated on the receiving plane is the Fourier transform (FT) of the phase shift ψ on the spatial light modulator, which is determined by the CGH. In addition, the Gerchberg-Saxton (G-S) algorithm is a method for searching for the optimal value of ψ by continuously updating the results in the FT and inverse FT (IFT) iterative cycle. Therefore, the present application proposes to use the G-S algorithm to realize a fast CGH algorithm with pure phase in a mobile scene, which has low computational complexity, can meet the requirements of high refresh rate while ensuring the quality of the light spot, and can better realize the light field tracking of multiple moving terminals, and ensure the stability of communication of multiple receiving terminals in the movement process.

[0061] Unless otherwise specified, the relative steps, numerical expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0062] ​The various embodiments are described in the specification in a progressive manner, each embodiment focusing on different aspects of the other embodiments, and the same or similar parts between the embodiments can be mutually referred to. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method.

[0063] The units and method steps of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been described in the above description in general terms. Whether these functions are performed 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 implementation does not exceed the scope of the present application.

[0064] Those skilled in the art can understand that all or part of the steps in the above method can be instructed by a program to complete the relevant hardware, and the program can be stored in a computer readable storage medium, such as a read-only memory, a magnetic disk or an optical disk, etc. Alternatively, all or part of the steps of the above embodiments can also be implemented using one or more integrated circuits, and accordingly, each module / unit in the above embodiments can be implemented in the form of hardware or in the form of a software function module. The present application is not limited to any specific form of combination of hardware and software.

[0065] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present application, which are used to illustrate the technical solutions of the present application, and are not limiting. The protection scope of the present application is not limited thereto, although the present application 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 modify or easily think of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed by the present application, or make equivalent replacements to some of the technical features; and these modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for multi-beam visible light communication for mobile scenarios, characterized in that, Comprise: First, the position sensor acquires the position of each receiving terminal in the target space under the lamp, and feeds back the position information to the computer; Then the computer receives the position information and generates a hologram using the fast CGH algorithm for mobile scenes based on the G-S algorithm to load the RIS module to change the phase of the incident light beam; And use the Fourier lens to generate multiple beams to track the position of the receiving terminal from a single beam of the signal source, and then adjust the generated light spots through the lens system and irradiate them on the corresponding receiving terminal in the target space; Wherein the fast CGH algorithm for mobile scenes based on the G-S algorithm to generate a hologram comprises: The initial image of the target spot is divided into several sub-images, and each sub-image contains a spot. During the iteration loop, the inverse FT operation is performed for each sub-image separately and the phase ψ k is extracted; For these ψ k The FT operation is performed and the phase is extracted to replace the phase of the original sub-image; then the above steps are repeated until the optimized target spot image passes the quality evaluation; According to the Fresnel diffraction formula, the light field on the holographic image plane is represented as: Assume that the kth spot has a position shift By superimposing the phase shift Δψ k on the sub-hologram at time t to obtain the spot at time (t + Δt), the G-S iteration does not need to be repeated; the shifted spot is represented as: In the formula, FT[·] represents the Fourier transform operation, A and φ are the amplitude and phase distribution on the holographic image plane respectively, λ is the wavelength of light, f is the focal length of the Fourier lens, ψ is the phase distribution loaded on the RIS, (x, y) is the coordinate on the holographic image plane, (u, v) is the simplified coordinate on the RIS surface, and i represents the imaginary unit.

2. The method of claim 1, wherein, Obtain multiple spots in the target space on the back focal plane of the Fourier lens.

3. The method of claim 2, wherein, Adjust the axial position and lateral magnification of the generated light spots through the lens system to project the light spots on the receiver with appropriate size.

4. A multi-beam visible light communication system for mobile scenarios, characterized in that, A system for implementing the method for mobile scene multi-beam visible light communication according to any one of claims 1-3, comprising a position sensor, a computer, an RIS module, a Fourier lens and a lens system; wherein: The position sensor acquires the position of each receiving terminal in the target space under the lamp, and feeds back the position information to the computer; The computer receives the position information and generates a hologram using the fast CGH algorithm for mobile scenes based on the G-S algorithm to load the RIS module; The RIS module changes the phase of the incident light beam; The Fourier lens generates multiple beams to track the position of the receiving terminal from a single beam of the signal source; The lens system adjusts the light spots generated by the Fourier lens.

5. A computer apparatus comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 4. The processor executes the computer program to implement the steps of the method according to any one of claims 1-3.

6. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method according to any one of claims 1-3.

Images