Visible light communication system and signal processing method

Abstract

The invention discloses a visible light communication system and a signal processing method. The visible light communication system comprises a plurality of optical filters of different colors and a signal processing module, the optical filters are used for receiving visible light signals, and the optical filters of different colors are used for receiving visible light signals of different wavelengths; the signal processing module is used for receiving the visible light signals transmitted by the optical filters respectively, converting the visible light signals into digital signals and demodulating the digital signals by adopting a preset modulation method to obtain communication signals, and the communication signals are used for supporting network communication of the visible light communication system. The preset modulation method is used for demodulating each carrier signal after demodulating the digital signal into a plurality of carrier signals. The technical problem that a visible light communication system in related technologies cannot support multi-user parallel communication is solved.

Description

Technical Field

[0001] The present application relates to the technical field of visible light communication, and in particular to a visible light communication system and a signal processing method. Background Art

[0002] With the development of wireless networks, people are increasingly relying on wireless networks for daily information transmission, but wireless networks have the disadvantages of limited spectrum resources, low communication security, susceptibility to interference and limited capacity. Visible Light Communication (VLC) is an emerging communication technology that uses light in the visible light band to transmit information. Due to its advantages such as fast transmission rate, high network, rich spectrum resources and high security, it occupies a vital position in future communication technology. In the visible light communication system, the optical transmitter is responsible for generating the modulated optical signal, and the optical receiver is responsible for receiving and demodulating the optical signal. Since the optical receiver is generally set in the lighting system, the optical receiver is easily interfered by the ambient light, which seriously affects the transmission quality of the communication signal. In addition, the visible light communication system in the related technology cannot support multi-user parallel communication.

[0003] To address the above-mentioned problems, no effective solution has been proposed yet. Summary of the invention

[0004] The embodiments of the present application provide a visible light communication system and a signal processing method to at least solve the technical problem in the related art that the visible light communication system cannot support multi-user parallel communication.

[0005] According to one aspect of an embodiment of the present application, a visible light communication system is provided, comprising: a plurality of filters of different colors and a signal processing module, wherein the filters are used to receive visible light signals, wherein the filters of different colors are used to receive visible light signals of different wavelengths; the signal processing module is used to receive the visible light signals respectively transmitted by the plurality of filters, convert the visible light signals into digital signals, and demodulate the digital signals using a preset modulation method to obtain communication signals, wherein the communication signals are used to support network communication of the visible light communication system, and the preset modulation method is used to demodulate the digital signals into a plurality of carrier signals, and then demodulate each carrier signal respectively.

[0006] Optionally, a preset modulation method is used to demodulate the digital signal to obtain a communication signal, including: obtaining modulation and demodulation parameters, wherein the modulation and demodulation parameters at least include: a modulation order and a preset frequency series, the preset frequency series includes multiple preset frequencies, and the preset frequency series is an arithmetic progression; decomposing a long data stream composed of all digital signals into multiple discrete signals according to the preset frequency series, wherein the discrete signals are in the form of complex values, and each discrete signal corresponds to a preset frequency; for each discrete signal, demodulating the discrete signal according to the modulation order to obtain a partial communication signal, wherein the modulation order is used for the number of bits carried in the discrete signal; and generating a communication signal according to multiple partial communication signals.

[0007] Optionally, a long data stream consisting of all digital signals is decomposed into multiple discrete signals according to a preset frequency, including: using a Fourier transform method to determine the frequency domain information of each digital signal, wherein the frequency domain information includes: phase and amplitude; and determining the complex value corresponding to each digital signal based on the frequency domain information.

[0008] Optionally, the discrete signal is demodulated according to the modulation order to obtain a partial communication signal, including: obtaining signal spatial distribution information corresponding to the modulation order, wherein the signal spatial distribution information corresponding to different modulation orders is different, and the signal spatial distribution information is used to record frequency domain information of multiple modulation parameters, wherein the frequency domain information includes: phase and amplitude; determining the distance value between the discrete signal and each modulation parameter to obtain multiple distance values ​​corresponding to the discrete signal; determining the modulation parameter corresponding to the distance value with the smallest numerical value as the target modulation parameter corresponding to the discrete signal; determining the bit sequence corresponding to the target modulation parameter in a preset mapping table, wherein the bit sequence is the partial communication signal corresponding to the discrete signal, and the preset mapping table is used to record the mapping relationship between the modulation parameter and the bit sequence.

[0009] Optionally, the visible light communication system also includes: a transmitter, which is used to send a training sequence, wherein the training sequence is a bit sequence; the modulation order is obtained during the initialization of the visible light communication system by the following method: the transmitter sends the training sequence to the signal processing module through a transmission channel; obtains multiple processing results output by the signal processing module according to multiple different training modulation orders for demodulating the training sequence, wherein the processing results are bit sequences; determines a channel evaluation index of the transmission channel under the training modulation order according to the training sequence and processing results corresponding to each training modulation order, wherein the channel evaluation index includes: a bit error rate; determines a target channel evaluation index with the smallest value among multiple channel evaluation indicators, and determines the training modulation order corresponding to the target channel evaluation index as the modulation order.

[0010] Optionally, the signal processing module includes: a photodiode, an analog signal processing module, and an analog-to-digital converter; converting the visible light signal into a digital signal includes: absorbing the photon energy of the visible light signal through the photodiode, and under the excitation of the photon energy, outputting a current signal to the analog signal processing module, wherein the intensity of the current signal is directly proportional to the brightness of the visible light signal; converting the current signal into a voltage signal through the analog signal processing module, and outputting the voltage signal to the analog-to-digital converter; converting the voltage signal into a digital signal through the analog-to-digital converter.

[0011] Optionally, the analog signal processing module includes: a signal amplifier, a signal conversion device; converting the current signal into a voltage signal includes: receiving the current signal through the signal amplifier, amplifying the current signal, and outputting the amplified target current signal to the signal conversion device; converting the target current signal into a voltage signal through the signal conversion device.

[0012] According to another aspect of an embodiment of the present application, a signal processing method is also provided, including: receiving visible light signals of different wavelengths through multiple filters of multiple different colors; converting the visible light signal into a digital signal, and demodulating the digital signal using a preset modulation method to obtain a communication signal, wherein the communication signal is used to support network communication, and the preset modulation method is used to indicate that after the digital signal is demodulated into multiple carrier signals, each carrier signal is demodulated separately.

[0013] Optionally, a preset modulation method is used to demodulate the digital signal to obtain a communication signal, including: obtaining modulation and demodulation parameters, wherein the modulation and demodulation parameters at least include: a modulation order and a preset frequency series, the preset frequency series includes multiple preset frequencies, and the preset frequency series is an arithmetic progression; decomposing a long data stream composed of all digital signals into multiple discrete signals according to the preset frequency series, wherein the discrete signals are in the form of complex values, and each discrete signal corresponds to a preset frequency; for each discrete signal, demodulating the discrete signal according to the modulation order to obtain a partial communication signal, wherein the modulation order is used for the number of bits carried in the discrete signal; and generating a communication signal according to multiple partial communication signals.

[0014] According to another aspect of an embodiment of the present application, a signal processing device is also provided, including: a receiving module, used to receive visible light signals of different wavelengths through multiple filters of multiple different colors; a processing module, used to convert the visible light signal into a digital signal, and demodulate the digital signal using a preset modulation method to obtain a communication signal, wherein the communication signal is used to support network communication, and the preset modulation method is used to indicate that the digital signal is demodulated into multiple carrier signals and then each carrier signal is demodulated separately.

[0015] In an embodiment of the present application, a visible light communication system is provided, and the visible light communication system includes: a plurality of filters of different colors and a signal processing module, wherein the filters are used to receive visible light signals, wherein the filters of different colors are used to receive visible light signals of different wavelengths; the signal processing module is used to receive the visible light signals respectively transmitted by the plurality of filters, convert the visible light signals into digital signals, and demodulate the digital signals using a preset modulation method to obtain communication signals, wherein the communication signals are used to support network communication of the visible light communication system, and the preset modulation method is used to demodulate the digital signals into a plurality of carrier signals, and then demodulate each carrier signal respectively; the visible light communication system transmits different visible light signals by using a plurality of filters respectively. The method for supporting multi-user parallel communication is realized in the formula, wherein each filter receives visible light of the corresponding wavelength, and each user end uses an optical signal of a specific wavelength, thereby achieving the purpose of simultaneously transmitting multiple visible light signals of different wavelengths, thereby realizing the technical effect of multi-user parallel transmission; in addition, the preset modulation method assists the visible light system in performing user parallel communication, and the preset modulation method is used to separate and demodulate the digital signal converted from the visible light signal (that is, decompose it into multiple carrier signals and then demodulate them separately), thereby achieving the purpose of improving the spectrum efficiency of data transmission, enhancing the anti-interference ability of the visible light communication system, thereby realizing the technical effect of improving the performance of the visible light communication system, and further solving the technical problem that the visible light communication system in the related art cannot support multi-user parallel communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 is a structural schematic diagram of a visible light communication system according to an embodiment of the present application;

[0018] Figure 2 is a flowchart of a signal processing method according to an embodiment of the present application;

[0019] Figure 3 is a flowchart of an execution of a preset modulation method according to an embodiment of the present application;

[0020] Figure 4 is a structural diagram of a signal processing device according to an embodiment of the present application;

[0021] Figure 5 It is the test result of downlink transmission of a three-color multi-lamp bead prototype according to the embodiment of the present application;

[0022] Figure 6It is the test result of uplink transmission of a three-color multi-lamp bead prototype according to the embodiment of the present application;

[0023] Figure 7 It is a hardware structure block diagram of a computer terminal for implementing a signal processing method according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] In order to better understand the embodiments of the present application, the technical terms involved in the embodiments of the present application are explained as follows:

[0027] Amplitude: The strength or size of a signal’s waveform, usually representing the voltage or power level of the signal. In modulation, changes in amplitude can be used to carry information. For example, in amplitude modulation (AM), the amplitude of the signal varies with the amplitude of the modulating signal, thus carrying information.

[0028] Phase: It is the position of the signal waveform relative to a reference point. It describes the position of the initial point of the signal waveform in time. In modulation technology, the change of phase can be used to encode information; in quadrature amplitude modulation (QAM), the combination of phase and amplitude is used to represent different signal states, and each state corresponds to a different combination of information bits.

[0029] In the related art, the visible light communication system cannot support multi-user parallel communication; in addition, the optical receiver in the visible light communication system is generally set in the lighting system, so the optical receiver is easily interfered by the ambient light, which seriously affects the transmission quality of the communication signal, and there are problems such as low performance and low spectrum efficiency of the visible light communication system. In order to solve this problem, the embodiments of the present application provide relevant solutions, which are described in detail below.

[0030] Figure 1 is a schematic diagram of the structure of a visible light communication system provided in an embodiment of the present application, such as Figure 1 As shown, the visible light communication system includes: a plurality of filters 10 of different colors, and a signal processing module 12, wherein the filters 10 are used to receive visible light signals, wherein the filters 10 of different colors are used to receive visible light signals of different wavelengths; the signal processing module 12 is used to receive visible light signals respectively transmitted by the plurality of filters, convert the visible light signals into digital signals, and demodulate the digital signals using a preset modulation method to obtain communication signals, wherein the communication signals are used to support network communication of the visible light communication system, and the preset modulation method is used to demodulate the digital signals into a plurality of carrier signals, and then demodulate each carrier signal respectively.

[0031] In the visible light communication system provided in the embodiment of the present application, optical elements such as lenses and reflectors are added to the receiving end (i.e., the optical receiver). Specifically, optical elements such as lenses and reflectors are installed in front of the photodetector (contained in the signal processing module 12) at the receiving end to focus and guide the light beam; the photodetector is used to accurately convert the visible light signal into an electrical signal. Figure 1The visible light communication system shown uses filters 10 of different colors at different receiving ends, and wavelength division multiplexing is achieved through multiple filters 10 of different colors, wherein wavelength division multiplexing is to achieve multi-user parallel transmission by assigning each user to a specific wavelength in the visible light band; since independent regulation can be achieved in the wavelength domain, when the wavelength division multiplexing method is used for multi-user parallel transmission, it can be ensured that visible light of different bands does not interfere with each other, thereby improving the transmission performance of the visible light communication system. In specific implementation, firstly, the corresponding wavelengths are defined for the receiving ends corresponding to different users, and then the narrow-band transmission medium film structure of the corresponding wavelength is designed on the surface of the photodetector for direct integration, so that the receiving end itself can have wavelength selectivity, ensuring that the visible light communication system can support multi-user parallel transmission. For example, the visible light communication system is set as a three-color light Fidelity (LiFi) wireless communication system, the laser is set as a user-end transmitter (i.e., transmitter) for sending visible light signals to the optical receiver, a lens or a reflector is set between the optical receiver and the laser, and a filter 10 is installed before the lens or the reflector. If the visible light communication system includes three user ends, and these three user ends correspond to the wavelength of red light, the wavelength of green light, and the wavelength of blue light, respectively, then these three user ends can use a red light filter 10, a green light filter 10, and a blue light filter 10, respectively, wherein the red light filter only allows light in the red band to pass through, the green light filter only allows light in the green band to pass through, and the blue light filter only allows light in the blue band to pass through.

[0032] Optionally, a preset modulation method is used to demodulate the digital signal to obtain a communication signal, including: obtaining modulation and demodulation parameters, wherein the modulation and demodulation parameters at least include: a modulation order and a preset frequency series, the preset frequency series includes multiple preset frequencies, and the preset frequency series is an arithmetic progression; decomposing a long data stream composed of all digital signals into multiple discrete signals according to the preset frequency series, wherein the discrete signals are in the form of complex values, and each discrete signal corresponds to a preset frequency; for each discrete signal, demodulating the discrete signal according to the modulation order to obtain a partial communication signal, wherein the modulation order is used for the number of bits carried in the discrete signal; and generating a communication signal according to multiple partial communication signals.

[0033] In the visible light communication system provided in the embodiment of the present application, the signal processing module 12 uses a preset signal modulation method (i.e., a preset modulation method) that complies with the Gigabit Home Networking (G.hn) standard to demodulate the digital signal generated by the visible light signal conversion. The G.hn standard stipulates that the received signal is first decomposed into multiple carrier signals and then each carrier signal is demodulated separately, so that high-speed data transmission can be achieved in a channel with limited spectrum. Therefore, in this embodiment, the received digital signal is also first decomposed into multiple carrier signals and then each carrier signal is demodulated separately. In this embodiment, the digital signal generated by the visible light conversion is an orthogonal frequency division multiplexing (OFDM) signal, which adopts quadrature amplitude modulation (QAM). Therefore, the preset modulation method includes: OFDM demodulation and QAM demapping. During OFDM demodulation, the received digital signal needs to be mapped to subcarrier signals of different frequencies to achieve the decomposition of the digital signal. The above-mentioned subcarrier is a high-frequency sine wave used to carry information signals in communication, and different subcarrier signals have different frequencies. QAM carries digital information by simultaneously changing the amplitude and phase of the carrier. In QAM modulation, the modulation order needs to be pre-set. The modulation order is used to indicate that each subcarrier signal is modulated by the carrier. The number of information bits carried by a modulation symbol (i.e., signal point). The higher the modulation order, the more information each information symbol carries during QAM modulation. Therefore, in this embodiment, when demodulating a digital signal, the signal processing module 12 first needs to obtain modulation and demodulation parameters, including the modulation order (e.g., 16th order or 64th order) and a preset frequency series. The preset frequency series contains multiple preset frequencies with equal frequency intervals, which are used to indicate which frequency subcarrier signals the received digital signal is decomposed into. For example, the frequency interval can be set to 6×24.4140625 kHz to form an arithmetic progression. The system uses FFT (Fast Fourier Transform) to convert digital signals from the time domain to the frequency domain to obtain discrete signals at each preset frequency point; in the Fourier transform formula, these discrete signals are in the form of complex values ​​composed of amplitude and phase; through the above method, the digital signal sequence (i.e., long data stream) obtained by optical signal conversion is decomposed into multiple discrete signals; next, QAM modulation is performed. During QAM modulation, for each discrete signal, the system performs demodulation processing based on the modulation order to obtain the network layer (MAC layer) bit stream (i.e., part of the communication signal) corresponding to this discrete signal; finally, the communication signals corresponding to all discrete signals are merged to generate the final communication signal that can be used for network communication. In the above process, the OFDM signal is decomposed into multiple subcarriers for transmission.The signal on each subcarrier is modulated by QAM, and the number and modulation order of subcarrier signals can be adjusted according to the channel conditions and system performance requirements. This mechanism allows the system to reduce the number of subcarriers when the channel conditions are poor, and avoid using subcarriers with poor signal quality due to noise, fading or other factors. In this way, the visible light communication system can focus resources on subcarriers with higher quality, thereby improving the stability and reliability of data transmission.

[0034] According to some optional embodiments of the present application, a long data stream composed of all digital signals is decomposed into multiple discrete signals according to a preset frequency, including: using a Fourier transform method to determine the frequency domain information of each digital signal, wherein the frequency domain information includes: phase and amplitude; determining the complex value corresponding to each digital signal based on the frequency domain information.

[0035] As mentioned in the previous embodiment, the preset modulation method is divided into two parts: OFDM demodulation and QAM modulation. In this embodiment, when performing OFDM demodulation, the digital signal is decomposed into multiple discrete signals by following the Fourier transform (FFT) method. Each digital signal will generate frequency domain information after Fourier transform, including phase and amplitude. According to these frequency domain information, the discrete signal corresponding to each digital signal can be represented as a complex value, where the real part of the complex value represents the amplitude information and the imaginary part represents the phase information. In this way, each discrete signal contains complete frequency domain characteristics, and the original bit stream can be accurately restored in the subsequent demodulation process; the above-mentioned process of OFDM demodulation following the Fourier transform method can be expressed as the following formula: Wherein, X(k) is the frequency domain signal (the spectrum of the (k)th subcarrier), x(n) is the time domain signal (the signal value at the (n)th sampling point), N is the number of transformation points (i.e., the number of subcarriers, i.e., the number of preset frequencies contained in the preset frequency sequence), j is the imaginary unit, It is a complex rotation factor, which is used to convert the time domain signal to the frequency domain. It reflects the frequency characteristic-related operation relationship such as phase rotation in the process of transforming the discrete signal in the time domain to the discrete signal in the frequency domain.

[0036] According to other optional embodiments of the present application, a discrete signal is demodulated according to a modulation order to obtain a partial communication signal, including: obtaining signal spatial distribution information corresponding to the modulation order, wherein the signal spatial distribution information corresponding to different modulation orders is different, and the signal spatial distribution information is used to record frequency domain information of multiple modulation parameters, wherein the frequency domain information includes: phase and amplitude; determining a distance value between the discrete signal and each modulation parameter to obtain multiple distance values ​​corresponding to the discrete signal; determining the modulation parameter corresponding to the distance value with the smallest numerical value as the target modulation parameter corresponding to the discrete signal; determining a bit sequence corresponding to the target modulation parameter in a preset mapping table, wherein the bit sequence is a partial communication signal corresponding to the discrete signal, and the preset mapping table is used to record the mapping relationship between the modulation parameter and the bit sequence.

[0037] In this embodiment, when the signal processing module 12 performs QAM modulation, demodulation is performed according to the signal space distribution information corresponding to the modulation order. For each discrete signal, the signal processing module 12 calculates the Euclidean distance between it and all modulation parameters (constellation points) in the signal space to obtain a series of distance values. The modulation parameter corresponding to the shortest distance value is the modulation parameter (i.e., the target modulation parameter) corresponding to the discrete signal when QAM modulation is performed; the above process is actually determining which point in the constellation diagram best matches the signal point. In QAM modulation, the constellation point is a specific position in the signal space, which is used to represent the information state carried by a modulation symbol. These constellation points are distributed in a two-dimensional coordinate system, usually defined by amplitude and phase. The two-dimensional coordinate system in which the constellation points are distributed is called a constellation diagram. Each constellation point (representing a debugging parameter) corresponds to a specific amplitude and phase combination, thereby representing one or more bits of data. In QAM modulation, after the modulation order is determined, the number of bits carried by each modulation parameter is determined. For example, if the modulation order is 16, 16 constellation points (i.e., modulation parameters) are recorded in the constellation diagram (i.e., signal space distribution information), and each point corresponds to 4 bits of information; if the modulation order is 64, 64 constellation points (i.e., modulation parameters) are recorded in the constellation diagram (i.e., signal space distribution information), and each point corresponds to 6 bits of information; when the signal processing module 12 performs QAM demodulation, this mechanism can be recorded in a list (i.e., a preset mapping table), then the signal processing module 12 can convert the target modulation parameters into a bit sequence (i.e., part of the communication signal) carrying a signal with a corresponding number of bits by searching the preset mapping table.

[0038] According to some optional embodiments of the present application, the visible light communication system also includes: a transmitter 14, which is used to send a training sequence, wherein the training sequence is a bit sequence; the modulation order is obtained during the initialization of the visible light communication system by the following method: the transmitter 14 sends the training sequence to the signal processing module through the transmission channel; obtains multiple processing results output by the signal processing module according to multiple different training modulation orders for demodulating the training sequence, wherein the processing results are bit sequences; determines a channel evaluation index of the transmission channel under the training modulation order according to the training sequence and processing results corresponding to each training modulation order, wherein the channel evaluation index includes: a bit error rate; determines a target channel evaluation index with the smallest value among multiple channel evaluation indicators, and determines the training modulation order corresponding to the target channel evaluation index as the modulation order.

[0039] The modulation order used by the signal processing module 12 when performing QAM modulation is determined by negotiation between the transmitter 14 and the receiving end in the visible light communication system. The transmitter 14 detects the accuracy of restoring the bit sequence (i.e., outputting the communication signal) when the receiving end uses different modulation orders by sending a known bit sequence (i.e., training sequence) to the receiving end, and selects the modulation order used when the accuracy is the highest as the modulation order used in the application process of the visible light communication system. Specifically, in this embodiment, when the system is initialized, the transmitter 14 sends a known training sequence (bit sequence) to the signal processing module 12. The signal processing module 12 demodulates the training sequence each time using a different preset modulation order (i.e., training modulation order) (such as three times using the following preset modulation orders 4-QAM, 16-QAM, and 64-QAM, respectively). After each demodulation using the modulation order, the signal processing module 12 outputs the modulation result (i.e., the processing result), wherein the modulation result is also a bit sequence, which is the restoration result of the known bit sequence (i.e., the training sequence) by the signal processing module 12. Therefore, by comparing the known bit sequence (i.e., the training sequence) with its corresponding modulation result (i.e., the processing result), the bit error rate when the signal processing module 12 uses a certain preset modulation parameter can be obtained. In this embodiment, the bit error rate corresponding to different preset modulation orders is used as a channel evaluation index for evaluating the performance of the transmission channel between the transmitter 14 and the receiving end. Finally, the modulation order corresponding to the bit error rate (i.e., the target channel evaluation index) with the smallest value is selected as the modulation order used when applying the visible light communication system to achieve the best channel performance and data transmission rate.

[0040] According to some optional embodiments of the present application, the signal processing module 12 includes: a photodiode 120, an analog signal processing module 122, and an analog-to-digital converter 124; converting the visible light signal into a digital signal includes: absorbing the photon energy of the visible light signal through the photodiode 120, and under the excitation of the photon energy, outputting a current signal to the analog signal processing module 122, wherein the intensity of the current signal is directly proportional to the brightness of the visible light signal; converting the current signal into a voltage signal through the analog signal processing module 122, and outputting the voltage signal to the analog-to-digital converter 124; converting the voltage signal into a digital signal through the analog-to-digital converter 124.

[0041] In the visible light communication system provided in the embodiment of the present application, after receiving the visible light signal filtered by the optical filter, the signal processing module 12 first converts it into an analog signal, and then converts it into a digital signal through the analog-to-digital converter 124. In this embodiment, the photodiode 120 and the analog signal processing module 122 are first used to convert the visible light signal into an analog signal, wherein the photodiode 120 can be an avalanche photodiode (APD) or a PIN photodiode, which is used to absorb the photon energy in the visible light signal and generate a current driven by the photon energy to achieve the effect of converting the visible light signal into a current signal (an analog signal), wherein the higher the illumination intensity of the visible light, the greater the photon energy it contains, and the higher the intensity of the converted current signal. For the case where the visible light signal is weak, a signal amplifier can be added to the output end of the photodiode 120 to increase the generated current signal. In addition, if the avalanche diode is selected, since it has the function of amplifying the signal itself, it only needs to arrange a corresponding amplification circuit for it to achieve the effect of the signal method. Both voltage signals and current signals are analog signals, but voltage signals are easier to transmit and amplify in circuits than current signals, because voltage signals can be directly amplified by resistors, while current signal amplification requires the use of current mirrors or more complex circuit structures. Therefore, the visible light system of the embodiment of the present application converts the visible light signal into an analog signal, which means converting the visible light signal into a voltage signal. Therefore, an analog signal processing module 122 is connected to the output end of the photodiode 120 to convert the current signal into a voltage signal, wherein the analog signal processing module 122 can be a transimpedance amplifier (TIA). Finally, since the signal modulation method (i.e., the preset modulation method) in the embodiment of the present application needs to be executed for a digital signal, an analog-to-digital converter 124 is connected to the output end of the analog signal processing module 122 to convert the analog signal (i.e., the voltage signal) into a digital signal.

[0042] Optionally, the analog signal processing module 122 includes: a signal amplifier 1220 and a signal conversion device 1222; converting the current signal into a voltage signal includes: receiving the current signal through the signal amplifier 1220, amplifying the current signal, and outputting the amplified target current signal to the signal conversion device 1222; converting the target current signal into a voltage signal through the signal conversion device 1222.

[0043] In this embodiment, the analog signal processing module 122 may also be other hardware devices that integrate a signal amplifier 1220 and a signal conversion device 1222. In this way, there is no need to add an additional amplifier at the output end of the photodiode 120; wherein the signal amplifier 1220 is used to receive the current signal from the photodiode 120, amplify it, and ensure that the signal strength meets the requirements of subsequent processing; the signal conversion device 1222 is used to receive the current signal (i.e., the target current signal) after amplification by the signal amplifier 1220, and convert it into a voltage signal, which is then transmitted continuously and finally converted into a digital signal by the analog-to-digital converter (ADC) 124. The digital signal will serve as the input of the signal processing module 12, and the signal processing module 12 uses a preset modulation method to demodulate the digital signal.

[0044] According to an embodiment of the present application, a method embodiment of signal processing is also provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0045] Figure 2 is a flowchart of a signal processing method according to an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0046] Step S202 , receiving visible light signals of different wavelengths through a plurality of filters of different colors.

[0047] The signal processing method provided in the embodiment of the present application can also be applied to Figure 1 Other visible light communication systems other than the visible light communication system shown may also be applied in other devices for realizing signal demodulation functions; when other devices apply the signal processing method in the embodiments of the present application, in order to realize parallel transmission of users, filters of different colors are installed in the device, and filters of different colors receive visible light signals of different wavelengths, and different wavelengths correspond to different user terminals.

[0048] Step S204, converting the visible light signal into a digital signal, and demodulating the digital signal using a preset modulation method to obtain a communication signal, wherein the communication signal is used to support network communication, and the preset modulation method is used to indicate that after the digital signal is demodulated into multiple carrier signals, each carrier signal is demodulated separately.

[0049] In step S204, the received visible light signal is processed. Since the ultimate goal is to achieve network communication based on visible light, the visible light signal needs to be converted into a communication signal of the network layer (i.e., the MAC layer) in step S204 to achieve network communication. In step S204, a signal modulation method (i.e., a preset modulation method) that complies with the G.hn standard is used to demodulate the digital signal generated by the conversion of the visible light signal. The G.hn standard stipulates that the received signal is first decomposed into multiple carrier signals and then each carrier signal is demodulated separately, that is, the preset modulation method includes: OFDM demodulation and QAM demapping.

[0050] Optionally, a preset modulation method is used to demodulate the digital signal to obtain a communication signal, including: obtaining modulation and demodulation parameters, wherein the modulation and demodulation parameters at least include: a modulation order and a preset frequency series, the preset frequency series includes multiple preset frequencies, and the preset frequency series is an arithmetic progression; decomposing a long data stream composed of all digital signals into multiple discrete signals according to the preset frequency series, wherein the discrete signals are in the form of complex values, and each discrete signal corresponds to a preset frequency; for each discrete signal, demodulating the discrete signal according to the modulation order to obtain a partial communication signal, wherein the modulation order is used for the number of bits carried in the discrete signal; and generating a communication signal according to multiple partial communication signals.

[0051] Figure 3 is an execution flow chart of the preset modulation method. Since the G.hn standard stipulates that the received signal is first decomposed into multiple carrier signals and then each carrier signal is demodulated separately, high-speed data transmission can be achieved in a channel with limited spectrum. Therefore, Figure 3As shown, when the preset modulation method is executed in step S204, the received digital signal is first decomposed into multiple carrier signals, and then each carrier signal is demodulated separately. In this embodiment, the digital signal generated by visible light conversion is an orthogonal frequency division multiplexing signal (Orthogonal Frequency-Division Multiplexing, OFDM), and the signal is modulated by quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM); during OFDM demodulation, the received digital signal needs to be mapped to subcarrier signals of different frequencies (f0, f1, f2, f3, f4, f5) to achieve the decomposition of the digital signal. The above-mentioned subcarrier is a high-frequency sine wave used to carry information signals in communication, and different subcarrier signals have different frequencies; QAM carries digital information by simultaneously changing the amplitude and phase of the carrier; in QAM modulation, the modulation order needs to be set in advance, and the modulation order is used to indicate that when QAM modulation is performed, each modulation symbol (i.e., signal The higher the modulation order, the more information each information symbol carries during QAM modulation. Therefore, in this embodiment, when demodulating a digital signal, the signal processing module 12 first needs to obtain modulation and demodulation parameters, including the modulation order (for example, 16th order or 64th order) and a preset frequency series. The preset frequency series includes a plurality of preset frequencies with equal frequency intervals, which are used to indicate which frequency subcarrier signals the received digital signal is decomposed into. For example, the frequency interval can be set to 6×24.4140625 kHz to form an arithmetic progression. The system uses FFT (Fast Fourier Transform) to convert digital signals from the time domain to the frequency domain to obtain discrete signals at each preset frequency point; in the Fourier transform formula, these discrete signals are in the form of complex values ​​composed of amplitude and phase; through the above method, the digital signal sequence (i.e., long data stream) obtained by optical signal conversion is decomposed into multiple discrete signals; next, QAM modulation is performed. During QAM modulation, for each discrete signal, the system performs demodulation processing based on the modulation order to obtain the network layer (MAC layer) bit stream (i.e., part of the communication signal) corresponding to this discrete signal; finally, the communication signals corresponding to all discrete signals are merged to generate the final communication signal that can be used for network communication. In the above process, the OFDM signal is decomposed into multiple subcarriers for transmission. The signal on each subcarrier is QAM modulated, and the number of subcarrier signals and the modulation order can be adjusted according to the channel conditions and system performance requirements. This mechanism allows the system to reduce the number of subcarriers when the channel conditions are poor, and avoid using those subcarriers with poor signal quality due to noise, fading or other factors. In this way, the visible light communication system can focus resources on higher quality subcarriers, thereby improving the stability and reliability of data transmission. Figure 3As shown, after QAM modulation, different subcarrier signals are converted into corresponding short bit streams (i.e., part of the communication signal) (Y[0], Y[1], Y[2], Y[3], Y[4], Y[5]). Finally, these multiple short bit streams are merged into a long bit stream (i.e., communication signal) for supporting network communication.

[0052] Through the above steps, it is possible to achieve the technical effect of using filters of different colors to realize multi-user parallel transmission, and to use a preset modulation method that complies with the G.hn standard to improve frequency utilization and high-speed data transmission.

[0053] Figure 4 is a structural diagram of a signal processing device provided according to an embodiment of the present application, such as Figure 4 As shown, the device includes: a receiving module 40, which is used to receive visible light signals of different wavelengths through multiple filters of multiple different colors; a processing module 42, which is used to convert the visible light signal into a digital signal, and demodulate the digital signal using a preset modulation method to obtain a communication signal, wherein the communication signal is used to support network communication, and the preset modulation method is used to indicate that the digital signal is demodulated into multiple carrier signals and then each carrier signal is demodulated separately.

[0054] It should be noted that Figure 4 The preferred implementation of the illustrated embodiment can be found in Figure 2 The relevant description of the illustrated embodiment will not be repeated here.

[0055] It should be noted that the various modules in the above-mentioned signal processing device can be program modules (for example, a set of program instructions that implement a certain specific function) or hardware modules. For the latter, it can be expressed in the following forms, but is not limited to this: the expression form of each of the above-mentioned modules is a processor, or the functions of each of the above-mentioned modules are implemented by a processor.

[0056] Based on the method provided in the embodiment of the present application, a three-color multi-lamp bead prototype (a visible light communication system that can realize parallel communication of three user terminals) is designed to verify the method provided in the embodiment of the present application. The multi-lamp bead LiFi prototype user-end receiving module includes an APD receiver; the user-end transmitting module is a laser, and the receiving module includes a filter, and the signal is demodulated in the signal processing module according to the QAM+OFDM demodulation process. The prototype has three user terminals, and the filters used are red, green and blue filters respectively. The downlink of the prototype is that the headlight end (RGB-LED) sends a visible light signal, and the user end receives it; the uplink is that the user-end laser sends a signal, and the headlight end receives it. The Ethernet physical layer chip, G.hn digital baseband processing chip, analog front-end and other chips are all integrated on a circuit board, realizing the integration of the signal processing module. The user end of the three-color multi-lamp prototype is three miniaturized devices. The three devices have the ability to communicate through the universal serial bus (USB). The three devices are connected as a whole through a USB splitter. The downlink is composed of three discrete detection demodulators, which independently receive the red, green and blue signals respectively. They are connected to the computer through the USB bus, which can realize independent reception communication for three users. The data paths of three users can be merged by using a bridge method or a custom network service software method. Each demodulation module using a detection demodulator uses an analog front end (i.e., analog signal processing module 1220) and a digital baseband processing chip that conforms to the G.hn standard. It can demodulate the G.hn analog signal output by the APD using the FFT method model OFDM, and perform QAM symbol mapping to convert it into an Ethernet MAC layer signal. The uplink of the user end uses an 850 nanometer (nm) LED for backhaul. Figure 5 This is the test result of the downlink transmission of the three-color multi-lamp bead prototype. Taking the red light channel as an example, the downlink transmission of the prototype is tested. At the transmitting end, the data is encoded according to the G.hn standard, QAM+OFDM modulated, and then the red light LED is modulated to convert the electrical signal into an optical signal and send it into free space. At the receiving end, APD is used as a photodetector for reception, and the G.hn module is used to perform OFDM demodulation and QAM symbol demapping of the analog signal, convert it into an Ethernet digital signal, and save the data on the computer. The saved data is processed to perform channel estimation for the prototype, obtain the constellation diagram used for QAM demodulation, and determine the channel evaluation indicators of the channel (such as bit error rate and signal-to-noise ratio). The independent variables of the bit error rate and signal-to-noise ratio are SC (that is, the number of subcarriers), and the output is as follows: Figure 5 The test results shown, Figure 5In the test results of the channel estimation (frequency response-subcarrier diagram) shown, Hk1 and Hk2 are the results of channel estimation based on two different training sequences, Hk is the average of the two, and Hk ISFA is the result after smoothing using an iterative spectral flattening algorithm (ISFA). Figure 6 This is the test result of the uplink transmission of the three-color multi-lamp bead prototype. Taking the red light channel as an example, the uplink transmission of the prototype is tested. The data is encoded and modulated at the transmitting end and input into the red light LED, and the electrical signal is converted into an optical signal and sent into free space. A photoelectric detector is used at the receiving end to receive and save the data. The saved data is processed to obtain the following Figure 6 The prototype shown in the figure performs channel estimation on the uplink and uses a constellation diagram when performing QAM modulation on the uplink channel to calculate the bit error rate and signal-to-noise ratio of the uplink channel. Figure 5 and Figure 6 It can be seen from the test results that in actual experiments, when the method provided in the embodiment of the present application is used to process visible light signals, the downlink rate is close to 100 megabits per second (Mbps) and the uplink rate reaches 25Mbps, which verifies the feasibility of using the multi-lamp bead wavelength division multiplexing technology provided in the embodiment of the present application to build a multi-user access network.

[0057] The method embodiments provided in the embodiments of the present application can be executed in a mobile terminal, a computer terminal or a similar computing device. Figure 7 FIG. 1 shows a hardware structure block diagram of a computer terminal for implementing a signal processing method. Figure 7 As shown, the computer terminal 70 may include one or more (shown as 702a, 702b, ..., 702n in the figure) processors 702 (the processor 702 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA), a memory 704 for storing data, and a transmission device 706 for communication functions. In addition, it may also include: a display, an input / output interface (I / O interface), a universal serial bus (USB) port (which may be included as one of the ports of the BUS bus), a network interface, a power supply and / or a camera. It can be understood by those skilled in the art that Figure 7 The structure shown is only for illustration and does not limit the structure of the above electronic device. Figure 7 More or fewer components as shown, or with Figure 7 Different configurations are shown.

[0058] It should be noted that the one or more processors 702 and / or other data processing circuits described above may generally be referred to herein as "data processing circuits". The data processing circuits may be embodied in whole or in part as software, hardware, firmware, or any other combination thereof. In addition, the data processing circuit may be a single independent processing module, or may be incorporated in whole or in part into any of the other components in the computer terminal 70. As described in the embodiments of the present application, the data processing circuit acts as a processor control (e.g., selection of a variable resistor terminal path connected to an interface).

[0059] The memory 704 can be used to store software programs and modules of application software, such as program instructions / data storage devices corresponding to the signal processing method in the embodiment of the present application. The processor 702 executes various functional applications and data processing by running the software programs and modules stored in the memory 704, that is, realizing the above-mentioned signal processing method. The memory 704 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 704 may further include a memory remotely arranged relative to the processor 702, and these remote memories may be connected to the computer terminal 70 via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0060] The transmission device 706 is used to receive or send data via a network. The specific example of the above network may include a wireless network provided by a communication provider of the computer terminal 70. In one example, the transmission device 706 includes a network adapter (Network Interface Controller, NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 706 can be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0061] The display may be, for example, a touch screen liquid crystal display (LCD) that enables a user to interact with a user interface of the computer terminal 70 .

[0062] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0063] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0064] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0065] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0066] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0067] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the relevant technology or all or part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, disk or optical disk, etc. Various media that can store program codes.

[0068] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A visible light communication system, characterized in that: include: Multiple filters of different colors and signal processing modules, among which, The optical filter is used to receive visible light signals, wherein the optical filters of different colors are used to receive visible light signals of different wavelengths; A signal processing module is used to receive the visible light signals transmitted by the multiple filters respectively, convert the visible light signals into digital signals, and demodulate the digital signals using a preset modulation method to obtain communication signals, wherein the communication signals are used to support network communication of the visible light communication system, and the preset modulation method is used to demodulate the digital signals into multiple carrier signals and then demodulate each of the carrier signals respectively.

2. The visible light communication system according to claim 1, characterized in that: The digital signal is demodulated by a preset modulation method to obtain a communication signal, including: Acquire modulation and demodulation parameters, wherein the modulation and demodulation parameters at least include: a modulation order and a preset frequency sequence, the preset frequency sequence includes a plurality of preset frequencies, and the preset frequency sequence is an arithmetic progression; Decomposing a long data stream consisting of all the digital signals into a plurality of discrete signals according to the preset frequency sequence, wherein the discrete signals are in the form of complex values, and each of the discrete signals corresponds to one of the preset frequencies; For each of the discrete signals, demodulate the discrete signal according to the modulation order to obtain a partial communication signal, wherein the modulation order is used for the number of bits carried in the discrete signal; The communication signal is generated based on a plurality of the partial communication signals.

3. The visible light communication system according to claim 2, characterized in that: Decomposing a long data stream consisting of all the digital signals into a plurality of discrete signals according to the preset frequency, including: Using Fourier transform method to determine the frequency domain information of each digital signal, wherein the frequency domain information includes: phase and amplitude; A complex value corresponding to each of the digital signals is determined according to the frequency domain information.

4. The visible light communication system according to claim 2, characterized in that: Demodulating the discrete signal according to the modulation order to obtain a partial communication signal, including: Acquire signal spatial distribution information corresponding to the modulation order, wherein the signal spatial distribution information corresponding to different modulation orders is different, and the signal spatial distribution information is used to record frequency domain information of multiple modulation parameters, wherein the frequency domain information includes: phase and amplitude; Determine a distance value between the discrete signal and each modulation parameter, and obtain a plurality of distance values ​​corresponding to the discrete signal; Determine the modulation parameter corresponding to the distance value with the smallest value as the target modulation parameter corresponding to the discrete signal; A bit sequence corresponding to the target modulation parameter is determined in a preset mapping table, wherein the bit sequence is the portion of the communication signal corresponding to the discrete signal, and the preset mapping table is used to record a mapping relationship between the modulation parameter and the bit sequence.

5. The visible light communication system according to claim 2, characterized in that: The visible light communication system further includes: a transmitter, the transmitter being used to send a training sequence, wherein the training sequence is a bit sequence; The modulation order is obtained by the following method during the initialization of the visible light communication system: The transmitter sends the training sequence to the signal processing module through a transmission channel; Acquire multiple processing results output by the signal processing module after demodulating the training sequence according to multiple different training modulation orders, wherein the processing results are bit sequences; Determining a channel evaluation index of the transmission channel under the training modulation order according to the training sequence corresponding to each training modulation order and the processing result, wherein the channel evaluation index includes: a bit error rate; A target channel evaluation index having the smallest value is determined among the multiple channel evaluation indexes, and the training modulation order corresponding to the target channel evaluation index is determined as the modulation order.

6. The visible light communication system according to claim 1, characterized in that: The signal processing module includes: a photodiode, an analog signal processing module, and an analog-to-digital converter; converting the visible light signal into a digital signal includes: The photodiode absorbs the photon energy of the visible light signal, and under the excitation of the photon energy, outputs a current signal to the analog signal processing module, wherein the intensity of the current signal is directly proportional to the brightness of the visible light signal; Converting the current signal into a voltage signal through the analog signal processing module, and outputting the voltage signal to the analog-to-digital converter; The voltage signal is converted into the digital signal by the analog-to-digital converter.

7. The visible light communication system according to claim 6, characterized in that: The analog signal processing module includes: a signal amplifier and a signal conversion device; converting the current signal into a voltage signal includes: receiving the current signal through the signal amplifier, amplifying the current signal, and outputting the amplified target current signal to the signal conversion device; The target current signal is converted into the voltage signal by the signal conversion device.

8. A signal processing method, characterized in that: include: Receiving visible light signals of different wavelengths through a plurality of filters of different colors; The visible light signal is converted into a digital signal, and the digital signal is demodulated using a preset modulation method to obtain a communication signal, wherein the communication signal is used to support network communication, and the preset modulation method is used to indicate that after the digital signal is demodulated into multiple carrier signals, each of the carrier signals is demodulated separately.

9. The method according to claim 8, characterized in that The digital signal is demodulated by a preset modulation method to obtain a communication signal, including: Acquire modulation and demodulation parameters, wherein the modulation and demodulation parameters at least include: a modulation order and a preset frequency sequence, the preset frequency sequence includes a plurality of preset frequencies, and the preset frequency sequence is an arithmetic progression; Decomposing a long data stream consisting of all the digital signals into a plurality of discrete signals according to the preset frequency sequence, wherein the discrete signals are in the form of complex values, and each of the discrete signals corresponds to one of the preset frequencies; For each of the discrete signals, demodulate the discrete signal according to the modulation order to obtain a partial communication signal, wherein the modulation order is used for the number of bits carried in the discrete signal; The communication signal is generated based on a plurality of the partial communication signals.

10. A signal processing device, characterized in that: include: A receiving module, used for receiving visible light signals of different wavelengths through a plurality of filters of different colors; A processing module is used to convert the visible light signal into a digital signal, and demodulate the digital signal using a preset modulation method to obtain a communication signal, wherein the communication signal is used to support network communication, and the preset modulation method is used to indicate that the digital signal is demodulated into multiple carrier signals and then each of the carrier signals is demodulated separately.

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