Visible light communication system and method based on CDMA (Code Division Multiple Access)

Abstract

The invention relates to the technical field of green communication, and discloses a visible light communication system and method based on CDMA (Code Division Multiple Access), the system comprises a transmitting end module, a visible light channel module, a receiving end module and a dynamic optimization module, by combining a CDMA multiple access technology and OFDM (Orthogonal Frequency Division Multiplexing) modulation, multi-user efficient access and spectrum resource dynamic allocation are realized, and the visible light communication efficiency is improved. User data streams are distinguished based on orthogonal spreading codes, and multi-user interference is effectively suppressed; through an OFDM subcarrier mapping and self-adaptive power allocation algorithm, the subcarrier transmitting power is optimized, the spectrum utilization rate is improved, the problem of resource allocation rigidness in a traditional TDMA / FDMA technology is solved, the communication capacity and the data transmission efficiency in a multi-user scene are remarkably improved, and by measuring the signal-to-noise ratio and the path loss of a channel in real time, the transmission efficiency of the multi-user scene is improved. And the spreading code length and the OFDM modulation order are dynamically adjusted, and signal attenuation and distortion caused by complex illumination conditions and a multipath effect are reduced.

Description

Technical Field

[0001] The present invention relates to the field of green communication technologies, and particularly to a visible light communication system and method based on CDMA. Background Art

[0002] Optical communication technologies using light in the visible light range have attracted much attention in recent years. Along with the rapid increase in lighting devices using light-emitting devices such as light-emitting diodes, developing data communication technologies that use infrastructure including indoor and outdoor lighting to achieve more convenient and higher-rate data communication is the future development direction of optical communication technologies.

[0003] The main defects of existing visible light communication systems include: (1) Low multi-user access efficiency and weak interference suppression ability; (2) Insufficient channel dynamic adaptation ability and difficulty in coping with light changes and multipath effects; (3) Lack of an adaptive parameter optimization mechanism, and system performance is limited by fixed configurations.

[0004] In view of the above problems, the present invention provides a visible light communication system and method based on CDMA, which combines CDMA multiple access technology, OFDM modulation and a dynamic optimization visible light communication scheme to improve multi-user capacity, anti-interference ability and environmental adaptability, and meet the high-reliability communication requirements in complex scenarios. Summary of the Invention

[0005] (I) Technical Problems to be Solved In view of the deficiencies of the prior art, the present invention provides a visible light communication system and method based on CDMA, which solves the problems raised in the above background art.

[0006] (II) Technical Solutions To achieve the above objectives, the present invention provides the following technical solutions: A visible light communication method based on CDMA, the method comprising the following steps: S1. CDMA-encode multiplexed user data streams through a visible light transmitting module to generate multiplexed spread spectrum signals, and perform OFDM modulation on each spread spectrum signal to generate multiplexed subcarrier modulation signals; S2. Based on the dynamic characteristics of the visible light channel, adjust the transmission power of each subcarrier modulation signal through an adaptive power allocation algorithm to generate multiplexed subcarrier signals with optimized power; S3. Synthesize the power-optimized signals into a composite optical signal through an LED array and transmit it to a free space channel; S4. Receive the composite optical signal through a photodetector of a visible light receiving module and convert it into an electrical signal to generate a received baseband signal; S5. Synchronize the received baseband signal, including clock recovery and carrier frequency offset compensation, to generate a synchronized baseband signal; S6. Demodulate the synchronized baseband signal by OFDM, extract multiple subcarrier signals, and equalize the subcarrier signals based on the channel estimation result to generate equalized multiple spread-spectrum signals; S7. Use a multi-user detection algorithm to perform CDMA decoding on the equalized multiple spread-spectrum signals, separate each user data stream, and calculate the bit error rate index; S8. Dynamically adjust the CDMA spreading code length and OFDM modulation order according to the bit error rate index to generate an adaptive parameter configuration instruction; S9. Update the CDMA encoding and OFDM modulation parameters based on the adaptive parameter configuration instruction to achieve dynamic optimization of the visible light communication system.

[0007] Preferably, the specific steps of S1 include: S11. Assign a unique orthogonal spreading code to each user data stream , where is the total number of users; S12. Perform a time-domain convolution operation on the user data stream and the spreading code to generate a spread-spectrum signal: , where, is the spread-spectrum signal, is the user data stream, is the spreading code, represents the time-domain convolution operation; S13. Perform OFDM modulation on each spread-spectrum signal , including subcarrier mapping, IFFT transformation, and cyclic prefix addition, to generate a subcarrier-modulated signal .

[0008] Preferably, the implementation steps of the adaptive power allocation algorithm in S2 include: S21. Measure the signal-to-noise ratio and path loss of the visible light channel, where is the subcarrier index; S22. Calculate the subcarrier power weight based on and : , where is the power weight of the subcarrier, is the signal-to-noise ratio, is the path loss;​​​ S23. Adjust the transmit power of the subcarrier signal according to the weight to generate a power optimization signal: , S51. Detect the training sequence in the received baseband signal through a sliding correlator to complete symbol timing synchronization; S52. Estimate the carrier frequency offset using the frequency-domain pilot signal , and compensate for the frequency offset through frequency-domain rotation to generate a frequency offset compensation signal; S53. Use a phase-locked loop to perform phase tracking on the frequency offset compensation signal to generate a synchronized baseband signal.

[0009] Preferably, the implementation steps of the equalization process in S6 include: S61. Estimate the subcarrier channel response matrix through the least squares algorithm

[0010] S62. Construct an equalization matrix: , is the equalization matrix, is the channel response matrix, is a diagonal matrix; S63. Perform frequency-domain equalization on the subcarrier signal to generate an equalized signal: , where is the subcarrier signal, is the equalized signal, is the equalization matrix; Preferably, the multi-user detection algorithm in S7 is an iterative detection algorithm based on interference cancellation, and the specific steps include: S71. Initialize the estimated value of the user data , S72. For the i-th iteration, calculate the multi-user interference: , is the sum of the multi-user interference, is the estimated value of the user data; S73. Eliminate the interference from the received signal to generate an updated signal: S74. Demodulate and make a decision on to generate an updated estimated value ; S75. Repeat steps S72 - S74 until convergence or the maximum number of iterations is reached.

[0011] ​​Preferably, the rule for adaptive parameter adjustment in S8 is: The rule for adaptive parameter adjustment is: If the bit error rate BER , then increase the spreading code length to: , and reduce the OFDM modulation order to

[0012] If the bit error rate BER , then reduce the spreading code length to: , and increase the OFDM modulation order to .

[0013] A visible light communication system based on CDMA, the system includes: A transmitting end module, a visible light channel module, a receiving end module, and a dynamic optimization module; The transmitting end module includes: A CDMA encoding unit, generating multiple paths of orthogonal spreading signals; An OFDM modulation unit, performing subcarrier mapping and IFFT transformation on the spreading signals; A power distribution unit, dynamically adjusting the transmitting power of subcarriers; An LED driving unit, driving an LED array to emit a composite optical signal; The receiving end module includes: A photoelectric conversion unit, converting an optical signal into an electrical signal; A synchronization processing unit, performing clock recovery and frequency offset compensation; An OFDM demodulation unit, extracting subcarrier signals and equalizing; A multi-user detection unit, separating user data streams; The dynamic optimization module includes: A bit error rate analysis unit, calculating communication quality indicators; A parameter adjustment unit, dynamically configuring spreading codes and modulation parameters.

[0014] Preferably, the CDMA encoding unit uses a Gold sequence as the spreading code, and its generation formula is: , where is the sequence spreading code, and are preferred m sequences, is the th user's delay parameter.

[0015] Preferably, the LED driving unit adopts a hybrid modulation method of pulse width modulation and amplitude modulation, and its driving signal expression is: , where and are modulation coefficients, is the LED bias current.

[0016] (III) Beneficial effects Compared with the prior art, the present invention provides a visible light communication system and method based on CDMA, which has the following beneficial effects: 1. By combining CDMA multiple access technology and OFDM modulation, multi-user efficient access and dynamic allocation of spectrum resources are realized. User data streams are distinguished based on orthogonal spreading codes, effectively suppressing multi-user interference; through OFDM subcarrier mapping and adaptive power allocation algorithm, the transmission power of subcarriers is optimized, improving the spectrum utilization rate, solving the problem of rigid resource allocation in traditional TDMA / FDMA technology, and significantly improving the communication capacity and data transmission efficiency in multi-user scenarios.

[0017] 2. By designing an adaptive parameter adjustment mechanism based on the dynamic characteristics of the visible light channel, the environmental adaptability and anti-interference ability of the system are enhanced. By measuring the channel signal-to-noise ratio and path loss in real time, the spreading code length and OFDM modulation order are dynamically adjusted to reduce signal attenuation and distortion caused by complex illumination conditions and multipath effects; combined with the interference cancellation iterative algorithm and frequency domain equalization technology, the influence of inter-symbol interference and frequency offset is suppressed, enabling the system to maintain a low bit error rate and high communication reliability in a dynamic environment.

[0018] 3. The system performance is autonomously improved through hybrid modulation and dynamic optimization module. The LED array is driven by the PWM and AM hybrid modulation method, taking into account both the modulation depth of the optical signal and the lighting stability; based on the real-time feedback of the bit error rate index, the spreading code configuration and modulation parameters are automatically optimized, reducing manual intervention, ensuring that the system can still operate stably in complex scenarios of noise interference and occlusion, and expanding the applicability of visible light communication in fields such as smart home and industrial Internet of Things.

[0019] 4. Through modular design and algorithm collaboration, the scalability and deployment flexibility of the system are improved. The transmitter and receiver modules integrate functions such as CDMA coding, OFDM modulation, and multi-user detection, supporting multi-device collaborative work; the dynamic optimization module operates independently and can adapt to different LED light sources and channel environments, providing reliable technical support for the large-scale application of future visible light communication networks. Description of the drawings

[0020] Figure 1 is a schematic diagram of the overall system architecture of the present invention; Figure 2 This is the flowchart of the method of the present invention. Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Please refer to Figure 1 , a visible light communication system and method based on CDMA, the method includes the following steps: S1. Perform CDMA encoding on multiple user data streams through a visible light emission module to generate multiple spread spectrum signals, and perform OFDM modulation on each spread spectrum signal to generate multiple subcarrier modulation signals; S2. Based on the dynamic characteristics of the visible light channel, adjust the transmission power of each subcarrier modulation signal through an adaptive power allocation algorithm to generate multiple subcarrier signals with optimized power; S3. Synthesize the power-optimized signals into a composite optical signal through an LED array and transmit it to the free space channel; S4. Receive the composite optical signal through a photodetector of the visible light receiving module and convert it into an electrical signal to generate a received baseband signal; S5. Perform synchronization processing on the received baseband signal, including clock recovery and carrier frequency offset compensation, to generate a synchronized baseband signal; S6. Perform OFDM demodulation on the synchronized baseband signal, extract multiple subcarrier signals, and perform equalization processing on the subcarrier signals based on the channel estimation result to generate multiple equalized spread spectrum signals; S7. Use a multi-user detection algorithm to perform CDMA decoding on the multiple equalized spread spectrum signals, separate each user data stream, and calculate the bit error rate index; S8. Dynamically adjust the CDMA spread spectrum code length and OFDM modulation order according to the bit error rate index to generate an adaptive parameter configuration instruction; S9. Update the CDMA encoding and OFDM modulation parameters based on the adaptive parameter configuration instruction to achieve dynamic optimization of the visible light communication system.

[0023] Further, the specific steps of S1 include: S11. Allocate a unique orthogonal spread spectrum code for each user data stream , where is the total number of users; S12. Multiply the user data stream by the spread spectrum code Perform time-domain convolution operation to generate a spread-spectrum signal:

[0024] wherein, is the spread-spectrum signal, is the user data stream, is the spreading code, represents the time-domain convolution operation; S13. Perform OFDM modulation on each path of spread-spectrum signal , including subcarrier mapping, IFFT transformation, and cyclic prefix addition, to generate a subcarrier modulation signal .

[0025] Furthermore, the implementation steps of the adaptive power allocation algorithm in S2 include: S21. Measure the signal-to-noise ratio and path loss of the visible light channel, wherein is the subcarrier index; S22. Calculate the subcarrier power weight based on and :

[0026] is the power weight of the subcarrier, is the signal-to-noise ratio, is the path loss; S23. Adjust the transmission power of the subcarrier signal according to the weight to generate a power-optimized signal:

[0027] Furthermore, the specific steps of the synchronization process in S5 include: S51. Detect the training sequence in the received baseband signal through a sliding correlator to complete symbol timing synchronization; S52. Estimate the carrier frequency offset using the frequency-domain pilot signal, and compensate for the frequency offset through frequency-domain rotation to generate a frequency-offset compensation signal; S53. Use a phase-locked loop to perform phase tracking on the frequency-offset compensation signal to generate a synchronized baseband signal.

[0028] Furthermore, the implementation steps of the equalization process in S6 include: S61. Estimate the subcarrier channel response matrix

[0029] through the least squares algorithm; S62. Construct an equalization matrix: , is the equalization matrix, is the channel response matrix, is the diagonal matrix.

[0030] S63. Perform frequency-domain equalization on the subcarrier signal to generate an equalized signal: , where is the subcarrier signal, is the equalized signal, is the equalization matrix; The multi-user detection algorithm in S7 is an iterative detection algorithm based on interference cancellation, and the specific steps include: S71. Initialize the estimated value of user data , S72. For the i-th iteration, calculate the multi-user interference: , is the total multi-user interference, is the estimated value of user data; S73. Eliminate the interference from the received signal to generate an updated signal: , S74. Demodulate and make a decision on to generate an updated estimated value ; S75. Repeat steps S72 - S74 until convergence or the maximum number of iterations is reached.

[0031] The rule for adaptive parameter adjustment in S8 is: If the bit error rate BER , then increase the spreading code length to: , and reduce the OFDM modulation order to

[0032] If the bit error rate BER , then reduce the spreading code length to: , and increase the OFDM modulation order to .

[0033] A visible light communication system based on CDMA includes: A transmitter module, a visible light channel module, a receiver module, and a dynamic optimization module; Among them, the transmitter module includes: CDMA coding unit, generating multiple orthogonal spreading signals; OFDM modulation unit, performing subcarrier mapping and IFFT transformation on the spreading signals; power allocation unit, dynamically adjusting the transmission power of subcarriers; LED driving unit, driving the LED array to emit composite optical signals; The receiving end module includes: Optoelectronic conversion unit, converting the optical signal into an electrical signal; Synchronization processing unit, performing clock recovery and frequency offset compensation; OFDM demodulation unit, extracting subcarrier signals and equalizing; Multi-user detection unit, separating user data streams; The dynamic optimization module includes: Bit error rate analysis unit, calculating communication quality indicators; Parameter adjustment unit, dynamically configuring spreading codes and modulation parameters.

[0034] The CDMA coding unit uses the Gold sequence as the spreading code, and its generation formula is: , where is the sequence spreading code, and are the preferred m sequences, is the th user's delay parameter.

[0035] The LED driving unit adopts a hybrid modulation method of pulse width modulation and amplitude modulation, and its driving signal expression is: , where and are the modulation coefficients, is the LED bias current.

[0036] Embodiment 1: Visible light communication method based on CDMA S1. CDMA coding and OFDM modulation of multi-user data streams: S11. At the transmitting end, assign a unique orthogonal Gold sequence spreading code to each user , and the user data stream is a binary bit sequence, and the spreading signal is generated through time-domain convolution operation: , where the spreading code length , and the chip rate is 10 Mbps; S12. For each path of spreading signal Perform OFDM modulation: Map the signal to 52 subcarriers, perform a 64-point IFFT transform and add a cyclic prefix to generate a subcarrier modulation signal .

[0037] S2. Adaptive power allocation and LED driving: S21. The receiving end measures the signal-to-noise ratio of each subcarrier through the channel estimation module and the path loss .

[0038] S22. Calculate the subcarrier power weight: , where is the signal-to-noise ratio, is the path loss, is the power weight.

[0039] S23. Adjust the transmission power to generate an optimized signal: , where is the power weight, is the modulation signal, .

[0040] S24. Convert to an optical signal through the LED driving unit, and use PWM-AM hybrid modulation to drive the LED array to transmit the composite optical signal to free space.

[0041] S3. Optical signal reception and synchronization processing: S31. The photodetector at the receiving end captures the optical signal and converts it into an electrical signal, and generates a received baseband signal through a low-noise amplifier; S33. Estimate the carrier frequency offset Δf using the pilot subcarrier, and compensate for the frequency offset through frequency-domain rotation to generate a synchronized baseband signal; S4. OFDM demodulation and multi-user detection: S41. Perform an FFT transform on the synchronized signal, extract the subcarrier data, and estimate the channel response matrix through the least squares algorithm, and construct an equalization matrix: , where is the equalization matrix, is the channel response matrix, is the signal-to-noise ratio, is the diagonal matrix.

[0042] S42. Demodulate the equalized signal and use the iterative interference cancellation algorithm to separate the user data streams: Initialize the estimated value , at the th iteration, calculate the interference , update the signal after eliminating the interference , generate the decision , converge after 3 iterations, and output the final user data ; where is the sum of multi-user interference, is the estimated value of the user data.

[0043] S5. Dynamic parameter optimization: S51. The bit error rate analysis unit calculates the current BER; S52. After updating the parameters, re-execute S1 - S4 to achieve system adaptive optimization; Embodiment 2: Visible light communication system based on CDMA: Please refer to Figure 1 , the system provided in this embodiment includes the following modules: Transmitter module: CDMA encoding unit: Implement Gold sequence generation using FPGA: ( ); OFDM modulation unit: Based on the AD9361 radio frequency chip, supporting 64-point IFT and dynamic subcarrier allocation; Power distribution unit: Integrate the MAX9930 power amplifier and adjust the gain according to the real-time SNR; LED driver unit: Use the LTC3459 driver chip to output a mixed modulation signal; Receiver module: Optoelectronic conversion unit: APD module combined with a TIA amplifier; Synchronization processing unit: Implement symbol synchronization and frequency offset compensation using Xilinx Zynq-7000.

[0044] Multi-user detection unit: Run the iterative interference cancellation algorithm based on ARM Cortex-A9, with a delay less than 1 ms.

[0045] Dynamic optimization module: Bit error rate analysis unit: Real-time statistics of BER and feedback to the transmitter through UART.

[0046] Parameter adjustment unit: Dynamically switch the spreading code length and modulation mode according to BER: Collaboration process: 1. The transmitter modulates the user data by CDMA-OFDM and transmits it by the LED array; 2. The receiver captures the signal and demodulates it, and separates the data stream through multi-user detection; 3. The dynamic optimization module adjusts the parameters according to the BER and updates them to the transmitter to complete the closed-loop optimization.

[0047] It should be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0048] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A visible light communication method based on CDMA, characterized in that: The method includes the following steps: S1. CDMA-encode multiple user data streams through a visible light emission module to generate multiple spread spectrum signals, and perform OFDM modulation on each spread spectrum signal to generate multiple subcarrier modulation signals; S2. Based on the dynamic characteristics of the visible light channel, adjust the transmission power of each subcarrier modulation signal through an adaptive power allocation algorithm to generate multiple subcarrier signals with optimized power; S3. Synthesize the power-optimized signals into a composite optical signal through an LED array and transmit it to the free space channel; S4. Receive the composite optical signal through a photodetector of the visible light receiving module and convert it into an electrical signal to generate a received baseband signal; S5. Perform synchronization processing on the received baseband signal, including clock recovery and carrier frequency offset compensation, to generate a synchronized baseband signal; S6. Perform OFDM demodulation on the synchronized baseband signal, extract multiple subcarrier signals, and perform equalization processing on the subcarrier signals based on the channel estimation result to generate multiple equalized spread spectrum signals; S7. Use a multi-user detection algorithm to perform CDMA decoding on the multiple equalized spread spectrum signals, separate each user data stream, and calculate the bit error rate index; S8. Dynamically adjust the CDMA spreading code length and OFDM modulation order according to the bit error rate index to generate an adaptive parameter configuration instruction; S9. Update the CDMA encoding and OFDM modulation parameters based on the adaptive parameter configuration instruction to achieve dynamic optimization of the visible light communication system.

2. The visible light communication method based on CDMA according to claim 1, wherein The specific steps of S1 include: S11. Assign a unique orthogonal spreading code to each user data stream , where is the total number of users; S12. Convolve the user data stream with the spreading code in the time domain to generate a spread spectrum signal: Among them, is a spread spectrum signal, is the user data stream, is the spreading code, represents the time-domain convolution operation; S13. For each spread spectrum signal perform OFDM modulation, including subcarrier mapping, IFFT transformation, and cyclic prefix addition, to generate a subcarrier modulated signal .

3. The visible light communication method based on CDMA according to claim 1, characterized in that, The implementation steps of the adaptive power allocation algorithm in S2 include: S21. Measure the signal-to-noise ratio and path loss of the visible light channel and path loss , where is the subcarrier index; S22. Based on and calculate the subcarrier power weight: is the power weight of the subcarrier, is the signal-to-noise ratio, is the path loss; S23. Adjust the transmission power of the subcarrier signal according to the weight to generate a power optimization signal: .​ 4. The visible light communication method based on CDMA according to claim 1, characterized in that The specific steps of the synchronization processing in S5 include: S51. Detect the training sequence in the received baseband signal through a sliding correlator to complete symbol timing synchronization; S52. Estimate the carrier frequency offset using the frequency-domain pilot signal , and discuss frequency offset compensation by frequency-domain rotation to generate a frequency-offset compensation signal; S53. Use a phase-locked loop to perform phase tracking on the frequency offset compensation signal to generate a synchronized baseband signal.

5. The visible light communication method based on CDMA according to claim 1, characterized in that The implementation steps of the equalization processing in S6 include: S61. Estimate the subcarrier channel response matrix through the least squares algorithm S62. Construct an equalization matrix: ， is the equalization matrix, is the channel response matrix, is the diagonal matrix; S63. Perform frequency domain equalization on the subcarrier signal to generate an equalized signal: ， wherein is a subcarrier signal, is an equalization signal, is an equalization matrix.

6. The visible light communication method based on CDMA according to claim 1, characterized in that The multi-user detection algorithm in S7 is an iterative detection algorithm based on interference cancellation, and the specific steps include: S71. Initialize the estimated value of user data ; S72. For the i-th iteration, calculate the multi-user interference: ， is the sum of multi-user interference, is the estimated value of user data; S73. Eliminate the interference from the received signal to generate an updated signal: is the balanced signal, is the sum of multi-user interference; S74. Demodulate and make a decision on to generate an updated estimated value ; S75. Repeat steps S72 - S74 until convergence or the maximum number of iterations is reached.

7. The visible light communication method based on CDMA according to claim 1, wherein The rule of adaptive parameter adjustment in S8 is: If the bit error rate BER , then increase the spreading code length to: ， and reduce the OFDM modulation order to If the bit error rate BER , then reduce the spreading code length to: ， and increase the OFDM modulation order to .

8. A CDMA-based visible light communication system for implementing the CDMA-based visible light communication method according to any one of claims 1-7, characterized in that, The system includes: a transmitting end module, a visible light channel module, a receiving end module, and a dynamic optimization module; The transmitting end module includes: a CDMA encoding unit that generates multiple orthogonal spread spectrum signals; an OFDM modulation unit that performs subcarrier mapping and IFFT transformation on the spread spectrum signals; a power allocation unit that dynamically adjusts the subcarrier transmission power; an LED driving unit that drives the LED array to emit a composite optical signal; The receiving end module includes: a photoelectric conversion unit that converts the optical signal into an electrical signal; a synchronization processing unit that performs clock recovery and frequency offset compensation; an OFDM demodulation unit that extracts the subcarrier signal and equalizes it; a multi-user detection unit that separates the user data stream; The dynamic optimization module includes: an error rate analysis unit that calculates communication quality metrics; and a parameter adjustment unit that dynamically configures the spreading code and modulation parameters.

9. The visible light communication system based on CDMA according to claim 8, wherein The CDMA encoding unit uses a Gold sequence as the spreading code, and its generation formula is: ， Among them is the sequence spreading code, and is the preferred m-sequence, is the delay parameter of the nth user.

10. The visible light communication system based on CDMA according to claim 8, characterized in that, The LED driving unit adopts a hybrid modulation method of pulse width modulation and amplitude modulation, and its driving signal expression is: ， wherein and are modulation coefficients, is the LED bias current.

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