Multi-user MISO visible light communication transmission method based on liquid crystal RIS

Abstract

The invention discloses a multi-user MISO visible light communication transmission method based on a liquid crystal RIS. The method comprises the following steps: (1) optimizing LC-RIS parameters through an artificial fish swarm algorithm; (2) calculating a signal sent by an LED transmitter according to the ZF precoding matrix which enables the channel capacity to be maximized and is obtained in the step (1); and (3) calculating a signal received by the receiver according to the step 1 and the step 2. According to the invention, the system sum rate is maximized under the conditions that the LED light power is insufficient and the incident light loss rate of a traditional visible light receiver is too high.

Description

Technical Field

[0001] The present invention relates to the technical field of optical wireless communication, and in particular to a multi-user MISO visible light communication transmission method based on liquid crystal RIS. Background Art

[0002] The beam propagation direction of the traditional VLC system is usually fixed and the coverage is limited. In addition, a convex lens is used in the visible light receiver to focus the incident light on the surface of the photodetector, which will cause loss of the intensity of the incident light. However, with the gradual deepening of the research on mirror array-based optical RIS and the rapid development of metamaterials, the LC-RIS-assisted VLC system has gradually entered the research field of scholars. Different from the research on mirror array-based optical RIS deployed on the wall, LC-RIS is mainly deployed in VLC receivers for beam steering and light intensity amplification.

[0003] At present, the research on LC-RIS-based VLC systems is mainly focused on single-user VLC systems, and it is found that the system has significant improvements in data rate and energy efficiency performance. However, the situation of multiple LC-RIS-assisted VLC receivers in multi-user scenarios has not been deeply explored. Compared with the single-user scenario, the optimization problem in the multi-light source-multi-user environment is more complicated and requires comprehensive consideration of multiple factors. How to obtain the channel state information of each user in real time and how to optimize multiple LC-RIS simultaneously to maximize the system capacity are currently unresolved problems. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a multi-user MISO visible light communication transmission method based on liquid crystal RIS to solve the problems of low LED light power and high incident light loss rate of traditional visible light receivers.

[0005] Technical solution: The multi-user MISO visible light communication transmission method based on liquid crystal RIS described in the present invention comprises the following steps: (1) The multi-user MISO visible light communication system based on liquid crystal RIS optimizes the parameters of LC-RIS through artificial fish school algorithm; (2) Calculate the signal sent by the LED transmitter according to the ZF precoding matrix that maximizes the channel capacity obtained in step (1); (3) Calculate the signal received by the receiver.

[0006] Furthermore, in step (1), the multi-user MISO visible light communication system based on liquid crystal RIS is specifically as follows: L LEDs are distributed indoors as transmitting ends, there are K users at the receiving end, and each receiving end is composed of a single photodetector based on LC-RIS.

[0007] Furthermore, step (1) includes the following steps: (11) Set the parameters of the artificial fish swarm algorithm: Set the step length , crowding factor , maximum number of attempts , perception range , maximum number of iterations , the initial optimal solution The refractive index vectors of multiple LC-RIS to be optimized are expressed as ,in, are the initial values ​​of N randomly generated LC-RIS refractive index vectors; (12) The refractive index vector of LC-RIS is Time users and rate It is calculated by the following method: Assume that the angular reflectivity of the light signal emitted by the lth LED transmitter when it reaches the kth LC-RIS top interface is expressed as ; in, is the relative refractive index of the kth LC-RIS, For air medium, The refractive index of the kth LC-RIS, is the incident angle from the lth LED transmitter to the kth LC-RIS top interface, The angular transmittance of light when it reaches the top interface of LC-RIS is Similarly, the angular reflectivity of the light signal when it leaves the LC-RIS is: ; in, The angular transmittance of light when it leaves LC-RIS is , the transmission coefficient of the kth LC-RIS , the amplification gain coefficient of the kth LC-RIS , in, is the wavelength of the incident light, E is the external electric field, is the electro-optic coefficient. The gain of the signal emitted by the kth LED transmitter after passing through the lth LC-RIS is ; in, is the LOS channel gain from the lth LED transmitter to the kth receiver, d is the depth of LC-RIS, and the channel gain at the kth photodetector is expressed as , the total channel gain of the VLC system is , the pseudo-inverse based ZF precoding is ,in , is the equal channel gain of the parallel subchannels. Considering that the ZF precoding based on pseudo-inverse completely eliminates MUI, the signal interference noise ratio at the kth user is expressed as ,in, is the covariance of the pulse amplitude modulation symbol transmitted to the kth user, is the variance of the noise, and the achieved rate at user k is , the system users and rate are ; (13) Calculation and The Euclidean distance is less than The number of initial values ​​of the refractive index vector m, and find the refractive index vector at the center of the initial value of the refractive index vector ,Will Substituting into operation (12) we get the user and rate as , like ,but Updated to , in, is a random number between [0, 1], when When Randomly select a new refractive index vector within the perception range ,Will Substituting into operation (12) we get the user and rate as ,like ,but Towards One step forward in the direction If you try Still not satisfied ,but remain unchanged; (14) Calculation and The Euclidean distance is less than The number m of initial values ​​of the refractive index vectors, and finding the refractive index vector that maximizes the user sum rate among the initial values ​​of the refractive index vectors ,Will Substituting into operation (12), we get the user and rate as, ,if ,but Updated to Otherwise, execute the above operation (13) Operation at the time; (15) Compare the user and rate sizes after executing operation (13) and operation (14), and select the LC-RIS refractive index when the user and rate are the largest as the optimal solution. Define the LC-RIS refractive index vector at this time as According to operation (12), the user and rate are ; (16) When When the value of Y is updated , the optimal solution for this iteration is ,when , the optimal solution of this iteration is the optimal solution obtained in the previous iteration.

[0008] Further, step (2) is specifically as follows: According to the optimization algorithm of step (1), the ZF precoding matrix that maximizes the user sum rate is obtained. , then the signal vector transmitted by multiple LEDs Expressed as ; in, represents the pulse amplitude modulation symbol transmitted to all users, is the DC bias added to the signal, the signal transmitted by the lth LED Expressed as , yes The element in row l, column k.

[0009] Furthermore, step (3) is as follows: The signal received by the kth user is expressed as , Where m yes The kth column of It is additive Gaussian noise composed of shot noise and thermal noise.

[0010] The present invention provides a multi-user MISO visible light communication transmission system based on liquid crystal RIS, comprising: Fish School Module: It is used to optimize the parameters of LC-RIS by artificial fish school algorithm in multi-user MISO visible light communication system based on liquid crystal RIS; Calculation module: used to calculate the signal sent by the LED transmitter according to the ZF precoding matrix that maximizes the channel capacity obtained in the fish school module; Receiving module: used to calculate the signal received by the receiver.

[0011] Furthermore, in the fish school module, the multi-user MISO visible light communication system based on liquid crystal RIS is specifically as follows: L LEDs are distributed indoors as transmitters, there are K users at the receiving end, and each receiving end is composed of a single photodetector based on LC-RIS.

[0012] Furthermore, the fish school module is as follows: (a) Setting the parameters of the artificial fish swarm algorithm: Set the step length , crowding factor , maximum number of attempts , perception range , maximum number of iterations , the initial optimal solution The refractive index vectors of multiple LC-RIS to be optimized are expressed as ,in, are the initial values ​​of N randomly generated LC-RIS refractive index vectors; (b) The refractive index vector of LC-RIS is Time users and rate It is calculated by the following method: Assume that the angular reflectivity of the light signal emitted by the lth LED transmitter when it reaches the kth LC-RIS top interface is expressed as ; in, is the relative refractive index of the kth LC-RIS, For air medium, The refractive index of the kth LC-RIS, is the incident angle from the lth LED transmitter to the kth LC-RIS top interface, The angular transmittance of light when it reaches the top interface of LC-RIS is Similarly, the angular reflectivity of the light signal when it leaves the LC-RIS is: ; in, The angular transmittance of light when it leaves LC-RIS is , the transmission coefficient of the kth LC-RIS , the amplification gain coefficient of the kth LC-RIS , in, is the wavelength of the incident light, E is the external electric field, is the electro-optic coefficient. The gain of the signal emitted by the kth LED transmitter after passing through the lth LC-RIS is ; in, is the LOS channel gain from the lth LED transmitter to the kth receiver, d is the depth of LC-RIS, and the channel gain at the kth photodetector is expressed as , the total channel gain of the VLC system is , the pseudo-inverse based ZF precoding is ,in , is the equal channel gain of the parallel subchannels. Considering that the ZF precoding based on pseudo-inverse completely eliminates MUI, the signal interference noise ratio at the kth user is expressed as ,in, is the covariance of the pulse amplitude modulation symbol transmitted to the kth user, is the variance of the noise, and the achieved rate at user k is , the system users and rate are ; (c) Calculation and The Euclidean distance is less than The number of initial values ​​of the refractive index vector m, and find the refractive index vector at the center of the initial value of the refractive index vector ,Will Substituting into operation (b) we get the user and rate as , like ,but Updated to , in, is a random number between [0, 1], when When Randomly select a new refractive index vector within the perception range ,Will Substituting into operation (b) we get the user and rate as ,like ,but Towards One step forward in the direction If you try Still not satisfied ,but remain unchanged; (d) Calculation and The Euclidean distance is less than The number m of initial values ​​of the refractive index vectors, and finding the refractive index vector that maximizes the user sum rate among the initial values ​​of the refractive index vectors ,Will Substituting into operation (b) we get the user and rate as, ,if ,but Updated to Otherwise, perform the above operation (c) Operation at the time; (e) Compare the user and rate sizes after executing operation (c) and operation (d), and select the LC-RIS refractive index when the user and rate are the largest as the optimal solution. Define the LC-RIS refractive index vector at this time as According to operation (b), the user and rate are ; (f) When When the value of Y is updated , the optimal solution for this iteration is ,when , the optimal solution of this iteration is the optimal solution obtained in the previous iteration.

[0013] Furthermore, in the calculation module, the ZF precoding matrix that maximizes the user sum rate is obtained according to the optimization algorithm in the fish school module. , then the signal vector transmitted by multiple LEDs Expressed as ; in, represents the pulse amplitude modulation symbol transmitted to all users, is the DC bias added to the signal, the signal transmitted by the lth LED Expressed as , yes The element in row l, column k.

[0014] Furthermore, in the receiving module, the details are as follows: The signal received at the kth user is expressed as , Where m yes The kth column of It is additive Gaussian noise composed of shot noise and thermal noise.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: based on each LC-RIS refractive index constraint, the artificial fish swarm optimization algorithm is used to simultaneously optimize the values ​​of multiple LC-RIS refractive indices, which effectively improves the system capacity and fully taps the transmission potential of multi-user VLC based on LC-RIS. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the system model of the present invention; Figure 2 The relationship between the random time and rate of user position and the emitted optical power of the present invention (670nm); Figure 3 The relationship between the rate and the transmitted optical power when the user position is fixed in the present invention; Figure 4 The user position and LED position coordinates of the present invention; Figure 5 The relationship between the speed and FOV (670nm) when the user position is fixed in the present invention; Figure 6This is the relationship between the speed and FOV when the user position is random in the present invention. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown, an embodiment of the present invention provides a multi-user MISO visible light communication transmission method based on liquid crystal RIS, comprising the following steps: Step 1: The multi-user MISO visible light communication system based on liquid crystal RIS consists of L LEDs distributed indoors as transmitters, and K users at the receiving end. Each receiving end consists of a single photodetector based on LC-RIS. The fish school algorithm is used to calculate the parameters of LC-RIS, which is implemented by the following steps: (11) Set the parameters of the artificial fish swarm algorithm: Set the step length , crowding factor , maximum number of attempts , perception range , maximum number of iterations , the initial optimal solution The refractive index vectors of multiple LC-RIS to be optimized are expressed as ,in, are the initial values ​​of N randomly generated LC-RIS refractive index vectors; (12) The refractive index vector of LC-RIS is Time users and rate It is calculated by the following method: Assume that the angular reflectivity of the light signal emitted by the lth LED transmitter when it reaches the kth LC-RIS top interface is expressed as ; in, is the relative refractive index of the kth LC-RIS, For air medium, The refractive index of the kth LC-RIS, is the incident angle from the lth LED transmitter to the kth LC-RIS top interface, The angular transmittance of light when it reaches the top interface of LC-RIS is Similarly, the angular reflectivity of the light signal when it leaves the LC-RIS is: ; in, The angular transmittance of light when it leaves LC-RIS is , the transmission coefficient of the kth LC-RIS , the amplification gain coefficient of the kth LC-RIS , in, is the wavelength of the incident light, E is the external electric field, is the electro-optic coefficient. The gain of the signal emitted by the kth LED transmitter after passing through the lth LC-RIS is ; in, is the LOS channel gain from the lth LED transmitter to the kth receiver, d is the depth of LC-RIS, and the channel gain at the kth photodetector is expressed as , the total channel gain of the VLC system is , the pseudo-inverse based ZF precoding is ,in , is the equal channel gain of the parallel subchannels. Considering that the ZF precoding based on pseudo-inverse completely eliminates MUI, the signal interference noise ratio at the kth user is expressed as ,in, is the covariance of the pulse amplitude modulation symbol transmitted to the kth user, is the variance of the noise, and the achieved rate at user k is , the system users and rate are ; (13) Calculation and The Euclidean distance is less than The number of initial values ​​of the refractive index vector m, and find the refractive index vector at the center of the initial value of the refractive index vector ,Will Substituting into operation (12) we get the user and rate as , like ,but Updated to , in, is a random number between [0, 1], when When Randomly select a new refractive index vector within the perception range ,Will Substituting into operation (12) we get the user and rate as ,like ,but Towards One step forward in the direction If you try Still not satisfied ,but remain unchanged; (14) Calculation and The Euclidean distance is less than The number m of initial values ​​of the refractive index vectors, and finding the refractive index vector that maximizes the user sum rate among the initial values ​​of the refractive index vectors ,Will Substituting into operation (12), we get the user and rate as, ,if ,but Updated to Otherwise, execute the above operation (13) Operation at the time; (15) Compare the user and rate sizes after executing operation (13) and operation (14), and select the LC-RIS refractive index when the user and rate are the largest as the optimal solution. Define the LC-RIS refractive index vector at this time as According to operation (12), the user and rate are ; (16) When When the value of Y is updated , the optimal solution for this iteration is ,when , the optimal solution of this iteration is the optimal solution obtained in the previous iteration.

[0019] Step 2: According to the optimization algorithm in step 1, the ZF precoding matrix that maximizes the user sum and rate is obtained. According to the optimization algorithm in step (1), the ZF precoding matrix that maximizes the user sum and rate is obtained. , then the signal vector transmitted by multiple LEDs Expressed as ; in, represents the pulse amplitude modulation symbol transmitted to all users, is the DC bias added to the signal, the signal transmitted by the lth LED Expressed as , yes The element in row l, column k.

[0020] Step 3: From steps 1 and 2, the signal received by the kth user is expressed as , Where m yes The kth column of It is additive Gaussian noise composed of shot noise and thermal noise.

[0021] like Figure 2As shown, after the algorithm is repeatedly executed one hundred times using the Monte Carlo simulation method, the relationship between the transmitted optical power and the system sum rate under different transmission schemes when the user position is random is compared. When the transmitted optical power of the transmitter increases from 1W to 10W, the system sum rate after LC-RIS optimization is always greater than the system sum rate before LC-RIS optimization and the system sum rate using only ZF precoding. The experimental results show that LC-RIS located in front of the receiver can not only amplify and steer the incident light beam, but also further verify the superiority of the artificial fish school optimization algorithm adopted by the present invention.

[0022] like Figure 3 As shown in the figure, when the user position is fixed, the effect of the beam wavelength on the system sum rate is very small when only ZF precoding is used. However, after adding LC-RIS in front of the receiver, it can be clearly seen that when the beam wavelength is 510nm, the system sum rate is significantly higher than the system sum rate when the beam wavelength is 670nm.

[0023] like Figure 4 As shown, the user position parameters and the position parameters of the LED transmitter when using a fixed position, that is, Figure 3 and Figure 5 The positional parameters used in .

[0024] like Figure 5 As shown, the maximum system sum rate is achieved at low FOV values ​​because a smaller FOV results in a higher condenser gain, which effectively concentrates the incident light and enhances the received signal strength. Conversely, a higher FOV results in a decrease in condenser gain, thereby reducing the corresponding system sum rate.

[0025] like Figure 6 As shown in the figure, under different FOV conditions, after LC-RIS optimization, the system sum rate when the beam wavelength is 510nm is always greater than the system sum rate when the beam wavelength is 670nm, while when only ZF precoding is used, when the FOV is 50° to 60°, the system sum rate when the beam wavelength is 510nm is higher than the system sum rate when the beam wavelength is 670nm, however, when the FOV is in the range of 60° to 90°, the system sum rate when the beam wavelength is 510nm is lower than the system sum rate when the beam wavelength is 670nm.

Claims

1. A multi-user MISO visible light communication transmission method based on liquid crystal RIS, characterized in that: The following steps are involved: (1) The multi-user MISO visible light communication system based on liquid crystal RIS optimizes the parameters of LC-RIS through artificial fish school algorithm; (2) Calculate the signal sent by the LED transmitter according to the ZF precoding matrix that maximizes the channel capacity obtained in step (1); (3) Calculate the signal received by the receiver.

2. According to claim 1, a multi-user MISO visible light communication transmission method based on liquid crystal RIS is characterized in that: In step (1), the multi-user MISO visible light communication system based on liquid crystal RIS is specifically as follows: L LEDs are distributed indoors as transmitting ends, there are K users at the receiving end, and each receiving end is composed of a single photodetector based on LC-RIS.

3. According to claim 2, a multi-user MISO visible light communication transmission method based on liquid crystal RIS is characterized in that: Step (1) includes the following steps: (11) Set the parameters of the artificial fish swarm algorithm: Set the step length , crowding factor , maximum number of attempts , perception range , maximum number of iterations , the initial optimal solution The refractive index vectors of multiple LC-RIS to be optimized are expressed as ,in, are the initial values ​​of N randomly generated LC-RIS refractive index vectors; (12) The refractive index vector of LC-RIS is Time users and rate It is calculated by the following method: Assume that the angular reflectivity of the light signal emitted by the lth LED transmitter when it reaches the kth LC-RIS top interface is expressed as ； in, is the relative refractive index of the kth LC-RIS, For air medium, The refractive index of the kth LC-RIS, is the incident angle from the lth LED transmitter to the kth LC-RIS top interface, The angular transmittance of light when it reaches the top interface of LC-RIS is Similarly, the angular reflectivity of the light signal when it leaves the LC-RIS is: ； in, The angular transmittance of light when it leaves LC-RIS is , the transmission coefficient of the kth LC-RIS , the amplification gain coefficient of the kth LC-RIS , in, is the wavelength of the incident light, E is the external electric field, is the electro-optic coefficient. The gain of the signal emitted by the kth LED transmitter after passing through the lth LC-RIS is ; in, is the LOS channel gain from the lth LED transmitter to the kth receiver, d is the depth of LC-RIS, and the channel gain at the kth photodetector is expressed as , the total channel gain of the VLC system is , the pseudo-inverse based ZF precoding is ,in , is the equal channel gain of the parallel subchannels. Considering that the ZF precoding based on pseudo-inverse completely eliminates MUI, the signal interference noise ratio at the kth user is expressed as ,in, is the covariance of the pulse amplitude modulation symbol transmitted to the kth user, is the variance of the noise, and the achieved rate at user k is , the system users and rate are ; (13) Calculation and The Euclidean distance is less than The number of initial values ​​of the refractive index vector m, and find the refractive index vector at the center of the initial value of the refractive index vector ,Will Substituting into operation (12) we get the user and rate as , like ,but Updated to , in, is a random number between [0, 1], when When Randomly select a new refractive index vector within the perception range ,Will Substituting into operation (12) we get the user and rate as ,like ,but Towards One step forward in the direction If you try Still not satisfied ,but remain unchanged; (14) Calculation and The Euclidean distance is less than The number m of initial values ​​of the refractive index vectors, and finding the refractive index vector that maximizes the user sum rate among the initial values ​​of the refractive index vectors ,Will Substituting into operation (12), we get the user and rate as, ,if ,but Updated to Otherwise, execute the above operation (13) Operation at the time; (15) Compare the user and rate sizes after executing operation (13) and operation (14), and select the LC-RIS refractive index when the user and rate are the largest as the optimal solution. Define the LC-RIS refractive index vector at this time as According to operation (12), the user and rate are ; (16) When When the value of Y is updated , the optimal solution for this iteration is ,when , the optimal solution of this iteration is the optimal solution obtained in the previous iteration.

4. The multi-user MISO visible light communication transmission method based on liquid crystal RIS according to claim 3 is characterized in that: Step (2) is as follows: According to the optimization algorithm of step (1), the ZF precoding matrix that maximizes the user sum rate is obtained. , then the signal vector transmitted by multiple LEDs Expressed as ; in, represents the pulse amplitude modulation symbol transmitted to all users, is the DC bias added to the signal, the signal transmitted by the lth LED Expressed as , yes The element in row l, column k.

5. The multi-user MISO visible light communication transmission method based on liquid crystal RIS according to claim 4, characterized in that: Step (3) is as follows: The signal received by the kth user is expressed as , Where m yes The kth column of It is additive Gaussian noise composed of shot noise and thermal noise.

6. A multi-user MISO visible light communication transmission system based on liquid crystal RIS, characterized in that: include: Fish School Module: It is used to optimize the parameters of LC-RIS by artificial fish school algorithm in multi-user MISO visible light communication system based on liquid crystal RIS; Calculation module: used to calculate the signal sent by the LED transmitter according to the ZF precoding matrix that maximizes the channel capacity obtained in the fish school module; Receiving module: used to calculate the signal received by the receiver.

7. The multi-user MISO visible light communication transmission system based on liquid crystal RIS according to claim 6, characterized in that: In the fish school module, the multi-user MISO visible light communication system based on liquid crystal RIS is as follows: L LEDs are distributed indoors as transmitters, there are K users at the receiving end, and each receiving end is composed of a single photodetector based on LC-RIS.

8. The multi-user MISO visible light communication transmission system based on liquid crystal RIS according to claim 7, characterized in that: The fish school module is as follows: (a) Setting the parameters of the artificial fish swarm algorithm: Set the step length , crowding factor , maximum number of attempts , perception range , maximum number of iterations , the initial optimal solution The refractive index vectors of multiple LC-RIS to be optimized are expressed as ,in, are the initial values ​​of N randomly generated LC-RIS refractive index vectors; (b) The refractive index vector of LC-RIS is Time users and rate It is calculated by the following method: Assume that the angular reflectivity of the light signal emitted by the lth LED transmitter when it reaches the kth LC-RIS top interface is expressed as ； in, is the relative refractive index of the kth LC-RIS, For air medium, The refractive index of the kth LC-RIS, is the incident angle from the lth LED transmitter to the kth LC-RIS top interface, The angular transmittance of light when it reaches the top interface of LC-RIS is Similarly, the angular reflectivity of the light signal when it leaves the LC-RIS is: ； in, The angular transmittance of light when it leaves LC-RIS is , the transmission coefficient of the kth LC-RIS , the amplification gain coefficient of the kth LC-RIS , in, is the wavelength of the incident light, E is the external electric field, is the electro-optic coefficient. The gain of the signal emitted by the kth LED transmitter after passing through the lth LC-RIS is ; in, is the LOS channel gain from the lth LED transmitter to the kth receiver, d is the depth of LC-RIS, and the channel gain at the kth photodetector is expressed as , the total channel gain of the VLC system is , the pseudo-inverse based ZF precoding is ,in , is the equal channel gain of the parallel subchannels. Considering that the ZF precoding based on pseudo-inverse completely eliminates MUI, the signal interference noise ratio at the kth user is expressed as ,in, is the covariance of the pulse amplitude modulation symbol transmitted to the kth user, is the variance of the noise, and the achieved rate at user k is , the system users and rate are ; (c) Calculation and The Euclidean distance is less than The number of initial values ​​of the refractive index vector m, and find the refractive index vector at the center of the initial value of the refractive index vector ,Will Substituting into operation (b) we get the user and rate as , like ,but Updated to , in, is a random number between [0, 1], when When Randomly select a new refractive index vector within the perception range ,Will Substituting into operation (b) we get the user and rate as ,like ,but Towards One step forward in the direction If you try Still not satisfied ,but remain unchanged; (d) Calculation and The Euclidean distance is less than The number m of initial values ​​of the refractive index vectors, and finding the refractive index vector that maximizes the user sum rate among the initial values ​​of the refractive index vectors ,Will Substituting into operation (b) we get the user and rate as, ,if ,but Updated to Otherwise, perform the above operation (c) Operation at the time; (e) Compare the user and rate sizes after executing operation (c) and operation (d), and select the LC-RIS refractive index when the user and rate are the largest as the optimal solution. Define the LC-RIS refractive index vector at this time as According to operation (b), the user and rate are ; (f) When When the value of Y is updated , the optimal solution for this iteration is ,when , the optimal solution of this iteration is the optimal solution obtained in the previous iteration.

9. The multi-user MISO visible light communication transmission system based on liquid crystal RIS according to claim 8, characterized in that: In the calculation module, according to the optimization algorithm in the fish school module, the ZF precoding matrix that maximizes the user and rate is obtained , then the signal vector transmitted by multiple LEDs Expressed as ; in, represents the pulse amplitude modulation symbol transmitted to all users, is the DC bias added to the signal, the signal transmitted by the lth LED Expressed as , yes The element in row l, column k.

10. The multi-user MISO visible light communication transmission system based on liquid crystal RIS according to claim 9, characterized in that: In the receiving module, the details are as follows: The signal received by the kth user is expressed as , Where m yes The kth column of It is additive Gaussian noise composed of shot noise and thermal noise.

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