Multi-beam visible light communication method and system for mobile scene

Abstract

The invention relates to the technical field of visible light communication, in particular to a multi-beam visible light communication method and system for a mobile scene, and the method comprises the steps: firstly collecting the position of each receiving terminal in a target space under a lamp through a position sensor, and feeding back the position information to a computer; after the computer receives the position information, a hologram is generated by adopting a moving scene rapid CGH algorithm based on a G-S algorithm to load and control an RIS module, and the phase of an incident beam is changed through the RIS module; a Fourier lens is used for generating a plurality of light beams for tracking the position of a receiving terminal from a single light beam of a signal source, and the light beams are adjusted through a lens system and then irradiated to a receiving terminal corresponding to a target space. According to the invention, the coverage range of the emitted light beam can be dynamically adjusted according to the real-time position of the multi-user mobile communication terminal, and the communication stability of the multi-receiving terminal in the movement process is ensured.

Description

Technical Field

[0001] The present 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 Art

[0002] Visible Light Communication (VLC) is the transmission of signals by loading them onto light in the visible light band. This technology uses the characteristics of visible light to transmit information, converts data into visible light signals through modulation and coding, and uses optical communication equipment to send and receive.

[0003] With the development of industrial Internet of Things and the increasing demand for production efficiency, smart factories are gradually moving towards a dense direction. In order to cope with these dense smart mobile devices and ensure their orderly and efficient operation, there is an increasing demand for mobile multi-user visible light communication that can simultaneously transmit data to all devices within a certain range. Existing multi-user visible light communication solutions in mobile scenarios are as follows: Figure 1 As shown. Large-scale coverage broadcasting is a relatively primitive and simple method. It covers the entire workspace with a single signal source, with the lowest complexity and cost. However, the signal strength received by each user in this method is weak, and the communication efficiency between users is very low through time division multiple access. Large-scale multiple-input multiple-output (MIMO) technology can provide efficient parallel data transmission. In dynamic scenes, each signal source needs to be equipped with a complex beam deflection control system and its corresponding drive circuit, which becomes a large-scale point-to-point tracking. Obviously, this method greatly increases the complexity and cost of the system, and also needs to consider various issues such as the coordination of multiple signals. In addition, using the controllable irradiation range of the visible light transmitter to divide the workspace into multiple cells is a low-complexity and efficient solution, and it is also the most widely used solution. In the traditional multi-cell method, multiple signal sources are regularly deployed in space as access points for each cell. Each cell has a limited coverage range and communicates independently with each other. However, there are inevitable overlapping areas between cells. The interference of adjacent signal sources in these areas and the delay caused by cell switching during movement seriously affect the performance of the system. The reconfigurable cell solution based on RIS can solve these problems of the traditional visible light multi-cell communication method. With the help of RIS, the units in the VLC system can be arbitrarily generated and reconstructed in real time according to the actual scene requirements. On the one hand, this can avoid overlap between cells and solve the problem of crosstalk between cells. On the other hand, it can reduce the frequency of mobile devices switching cells, and through the synchronization of the control end, it can greatly reduce the delay caused by shuttling cells during movement. Compared with the traditional multi-cell method, the multi-user solution of the dynamically reconfigurable cell is more efficient and flexible.

[0004] The existing schemes for constructing dynamic links using RIS mainly apply a certain phase shift gradient to the incident light wave to offset its direction. However, considering the influence of RIS pixel size, the movable range of the cell light spot generated by this scheme is limited, and it is difficult to generate multiple light spots to correspond to different mobile users. Summary of the invention

[0005] The present invention aims to solve the problem that the current solution cannot adjust the light field coverage in time according to the real-time position of the mobile terminal, resulting in the inability to simultaneously meet the mobility attributes and high signal-to-noise ratio communication requirements of multiple users under power-limited conditions. A multi-beam visible light communication method and system for mobile scenarios are proposed, which can dynamically adjust the coverage of the transmitted light beam according to the real-time position of the multi-user mobile communication terminal, thereby ensuring the stability of communication of multiple receiving terminals during movement.

[0006] To achieve the above purpose, the technical solution adopted is:

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

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

[0009] Then, after receiving the position information, the computer uses the mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram to load and control the RIS module, and changes the phase of the incident light beam through the RIS module;

[0010] A Fourier lens is used to convert the single light beam of the signal source into multiple light beams that track the position of the receiving terminal, which are then adjusted through the lens system and irradiated onto the receiving terminal corresponding to the target space.

[0011] According to the multi-beam visible light communication method for mobile scenes of the present invention, further, using a mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram includes:

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

[0013] In the iterative cycle, the inverse FT operation is performed on each sub-image, and the phase ψ of the sub-hologram of the spot is k Extract it;

[0014] For these k Perform FT operation and extract the phase to replace the phase of the original sub-image; then repeat the above steps until the optimized target spot image passes the quality assessment;

[0015] Assume that within the time Δt, the kth light spot has a position offset; by shifting the phase Δψ k The light spot at time (t+Δt) is obtained by superimposing it onto the sub-hologram at time t without repeating the GS iteration.

[0016] According to the multi-beam visible light communication method for mobile scenes of the present invention, further, assuming that within the time Δt, the kth light spot has a position offset The shifted 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) are the coordinates on the holographic image plane, (u, v) are the simplified coordinates on the RIS surface, and i represents the imaginary unit.

[0019] According to the multi-beam visible light communication method for mobile scenes of the present invention, further, multiple light spots in the target space are obtained on the rear focal plane of the Fourier lens.

[0020] According to the multi-beam visible light communication method for mobile scenes of the present invention, further, the axial position and lateral magnification of the generated light spot are adjusted by the lens system, and the light spot is projected onto the receiver with an appropriate size.

[0021] Furthermore, the present invention also provides a multi-beam visible light communication system for mobile scenes, which is used to implement the multi-beam visible light communication method for mobile scenes as described above, and the system includes a position sensor, a computer, a RIS module, a Fourier lens and a lens system; wherein:

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

[0023] After receiving the location information, the computer uses the mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram to load and control the RIS module;

[0024] RIS module, which changes the phase of the incident beam;

[0025] Fourier lens, which converts the single beam of the signal source into multiple beams that track the position of the receiving terminal;

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

[0027] The beneficial effects achieved by adopting the above technical solution are:

[0028] In view of the multi-beam dynamic tracking problem faced by multi-user visible light communication systems in mobile scenarios, the multi-beam visible light communication method for mobile scenarios proposed in the present invention obtains the real-time position information of the receiving terminal through a position sensor, and then feeds it back to the computer. The computer uses the mobile scenario fast CGH algorithm to generate the corresponding CGH as the input of the RIS module, adjusts the coverage of the beam in real time, realizes real-time dynamic tracking of the beam to the receiving terminal, and ensures the stability of communication of multiple receiving terminals during movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0030] Figure 1 It is a schematic diagram of four existing visible light communication modes for multi-user mobile terminals;

[0031] Figure 2 is an architecture diagram of a multi-beam visible light communication method for mobile scenarios according to an embodiment of the present invention;

[0032] Figure 3 is a flowchart of a fast CGH algorithm for mobile scenarios according to an embodiment of the present invention;

[0033] Figure 4 It is a structural schematic diagram of a multi-beam visible light communication system for mobile scenarios according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings of specific embodiments of the present invention to clearly and completely describe the exemplary scheme of the embodiment of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field.

[0035] like Figure 2 As shown, this embodiment discloses a multi-beam visible light communication method for a mobile scene, comprising the following steps:

[0036] Step S101: The position sensor collects the position 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 location information, the computer uses the mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram to load and control the RIS module, and changes the phase of the incident light beam through the RIS module, thereby controlling the light field to converge around the mobile terminal, and updating the beam coverage in real time according to the change of the receiver terminal position. The terms involved are explained as follows: RIS: Reconfigurable Intelligent Surfaces (RIS). CGH: Computer-Generated Hologram (CGH).

[0038] Step S103: Use a Fourier lens to convert the single light beam of the signal source into multiple light beams that track the position of the receiving terminal, and then adjust them through the lens system and irradiate them onto the receiving terminal corresponding to the target space, ultimately achieving multi-beam efficient visible light communication needs that meet the needs of multiple mobile users.

[0039] The purpose of this method is to use a single red LD (laser diode) to generate multiple light spots on the receiving plane, each of which covers a photodiode (PD) receiver and can be adjusted according to the receiver position. By adapting the pure phase GCH to the RIS input, the target light spot image can be obtained at the back focal plane of the Fourier lens to shape the incident light beam, such as Figure 2 The axial position and lateral magnification of the generated light spot are adjusted by the lens system, and the light spot is projected onto the receiver with an appropriate size.

[0040] According to the analysis in the above section, the light field coverage generated on the receiving plane is determined 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 this 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 mobile scenarios, it is often impossible to achieve real-time multi-spot reconstruction. If the refresh rate of the generated light spot is insufficient, the moving target user cannot be locked in real time, and the signal will be interrupted. If the quality of the CGH is low, the intensity of the generated light spot is also weak, the user signal quality will also be poor, and the generated high-order diffraction light will cause more serious interference to other cells. Therefore, it is the basic requirement for the application of holographic beamforming methods in mobile multi-user communications to ensure both the quality of the light spot and a sufficiently high 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[·] represents the Fourier transform (FT) operation, A and φ are the amplitude and phase distribution on the holographic image plane, 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) are the coordinates on the holographic image plane, (u, v) are the simplified coordinates 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] In order to improve the calculation speed and maintain the image quality, this embodiment proposes a fast CGH algorithm for moving scenes based on the (Gerchberg-Saxton) GS algorithm. The GS algorithm is a method for searching for the optimal value by continuously updating the results in the FT and inverse FT (IFT) iteration loop. Without losing resolution, the calculation is simplified according to the spatial correlation between moving target pictures. The process of the fast CGH algorithm for moving scenes is as follows: Figure 3 As shown, the following steps are included.

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

[0046] (1) Since FT is a linear operation, before entering the GS iteration loop, the target spot initial image can be divided into three sub-images. Each sub-image contains a spot.

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

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

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

[0050]

[0051] This means that by shifting the phase by Δψ k The light spot at time (t+Δt) is obtained by superimposing it onto the sub-hologram at time t without repeating the GS iteration.

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

[0053] Corresponding to the above method, this embodiment also proposes a multi-beam visible light communication system for mobile scenes, such as Figure 4 As shown, the system includes a position sensor, a computer, a RIS module, a Fourier lens and a lens system; wherein:

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

[0055] After receiving the location information, the computer uses the mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram to load and control the RIS module.

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

[0057] The Fourier lens converts the single beam of the signal source into multiple beams that track the position of the receiving terminal.

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

[0059] The present invention uses the beamforming technology of digital holography to construct multiple dynamic optical cells, realize multi-beam efficient visible light communication in mobile scenarios, and proposes that by loading the corresponding computer-generated hologram (CGH) into RIS, the required light field distribution can be generated on the receiving plane. Further, the present invention proposes that by designing a suitable optical system, the required light spot distribution can be generated in a larger range.

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

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

[0062] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0063] The units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person of ordinary skill in the art may use different methods to implement the described functions for each specific application, but such implementation is not considered to be beyond the scope of the present invention.

[0064] Those skilled in the art will appreciate that all or part of the steps in the above method can be completed by instructing related hardware through a program, 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 embodiment can also be implemented using one or more integrated circuits, and accordingly, each module / unit in the above embodiment can be implemented in the form of hardware or in the form of software function modules. The present invention 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 only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A multi-beam visible light communication method for mobile scenes, characterized in that: include: First, the position sensor collects the position of each receiving terminal in the target space under the light and feeds the position information back to the computer; Then, after receiving the position information, the computer uses the mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram to load and control the RIS module, and changes the phase of the incident light beam through the RIS module; A Fourier lens is used to convert the single light beam of the signal source into multiple light beams that track the position of the receiving terminal, which are then adjusted through the lens system and irradiated onto the receiving terminal corresponding to the target space.

2. The multi-beam visible light communication method for mobile scenes according to claim 1, characterized in that: The hologram is generated by the fast CGH algorithm for mobile scenes based on the GS algorithm, including: The target light spot initial image is divided into several sub-images, each of which contains a light spot; In the iterative cycle, the inverse FT operation is performed on each sub-image, and the phase ψ of the sub-hologram of the spot is k Extract it; For these k Perform FT operation and extract the phase to replace the phase of the original sub-image; then repeat the above steps until the optimized target spot image passes the quality assessment; Assume that within the time Δt, the kth light spot has a position offset; by shifting the phase Δψ k The light spot at time (t+Δt) is obtained by superimposing it onto the sub-hologram at time t without repeating the GS iteration.

3. The multi-beam visible light communication method for mobile scenes according to claim 2, characterized in that: Assume that within the time Δt, the kth light spot has a position offset The shifted spot is expressed as: 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) are the coordinates on the holographic image plane, (u, v) are the simplified coordinates on the RIS surface, and i represents the imaginary unit.

4. The multi-beam visible light communication method for mobile scenes according to claim 1, characterized in that: Multiple light spots in the target space are obtained at the rear focal plane of the Fourier lens.

5. The multi-beam visible light communication method for mobile scenes according to claim 4, characterized in that: The axial position and lateral magnification of the generated light spot are adjusted through the lens system, and the light spot is projected onto the receiver with an appropriate size.

6. A multi-beam visible light communication system for mobile scenarios, characterized in that: Used to implement the multi-beam visible light communication method for mobile scenes as described in any one of claims 1 to 5, the system includes a position sensor, a computer, a RIS module, a Fourier lens and a lens system; wherein: The position sensor collects the position of each receiving terminal in the target space under the light and feeds the position information back to the computer; After receiving the location information, the computer uses the mobile scene fast CGH algorithm based on the GS algorithm to generate a hologram to load and control the RIS module; RIS module, which changes the phase of the incident beam; Fourier lens, which converts the single beam of the signal source into multiple beams that track the position of the receiving terminal; The lens system adjusts the light spot generated by the Fourier lens.

7. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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