CN114978315A - SCMA (Single chip multiple Access) assisted visible light communication coding and decoding method and system based on fitting method - Google Patents

SCMA (Single chip multiple Access) assisted visible light communication coding and decoding method and system based on fitting method Download PDF

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CN114978315A
CN114978315A CN202210894908.6A CN202210894908A CN114978315A CN 114978315 A CN114978315 A CN 114978315A CN 202210894908 A CN202210894908 A CN 202210894908A CN 114978315 A CN114978315 A CN 114978315A
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fitting
codebook
signals
polynomial
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CN114978315B (en
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余礼苏
刘超良
王玉皞
余修鹏
陈俊源
王正海
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Nanchang University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention provides a fitting method-based SCMA assisted visible light communication coding and decoding method and system, wherein the coding method comprises the following steps: constructing a mother codebook, performing constellation rotation on the mother codebook according to the factor graph matrix to obtain a corresponding codebook, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook; acquiring bit signals, and performing codebook mapping on the bit signals through a target codebook to superpose a plurality of bit signals to obtain real part signals and imaginary part signals; filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the direct current bias is added to the positive and real signals to drive the light emitting diodes with different primary colors to generate signal light, the signal to be emitted is loaded on a visible light channel, and Gaussian white noise is superposed to convert the signal light into an aliasing white light signal. Overfitting is prevented by optimizing the polynomial fitting coefficients.

Description

SCMA (Single chip multiple Access) assisted visible light communication coding and decoding method and system based on fitting method
Technical Field
The invention relates to the technical field of wireless communication, in particular to a fitting method-based SCMA assisted visible light communication coding and decoding method and system.
Background
The 5G technology is now applied to people's real life, and then people focus on the next generation mobile communication technology, i.e. the 6G technology, which is expected to be used in visible light communication and non-orthogonal multiple access technologies. The visible light communication technology has the advantages of high safety, good confidentiality, strong anti-electromagnetic interference capability, integration of communication and illumination functions and no electromagnetic pollution. The Sparse Code Multiple Access (SCMA) technology is a non-orthogonal Multiple Access technology in which Multiple users share spectrum resources, and combines a Low Density Signature (LDS) technology and a Code Division Multiple Access (CDMA) technology together to solve the problem of system overload. The conventional SCMA decoding technique employs a Message Passing Algorithm (MPA), combines a priori probability, and iteratively updates a posteriori probability messages between user nodes and resource nodes using a factor graph, so as to decode codewords originally sent by each user as accurately as possible. Compared with a Maximum Likelihood (ML) detection method, although the algorithm complexity of the MPA decoder is reduced, the complexity increases exponentially with the number of users, so that the decoding efficiency is low, and the deployment requirement of a future 6G system cannot be met. In addition, for the multi-user detection of non-orthogonal multiple access, a technique called Successive Interference Cancellation (SIC) can also be adopted, and the SIC decoding technique can greatly reduce the decoding complexity of the decoding technique compared with the MPA decoding technique, but a great disadvantage of the SIC decoding technique is that the decoding performance of the SIC decoding technique is inferior to that of the MPA, especially under the condition of high signal-to-noise ratio.
Aiming at the problem of high complexity caused by the MPA decoding algorithm adopted by the existing SCMA-based visible light communication system, a plurality of improved MPA algorithms are provided, such as the MPA algorithm based on a log domain, the MPA decoding algorithm based on a serial mode, the MPA decoding algorithm based on partial code words and other algorithms for reducing the MPA decoding complexity, the algorithms are only improved on the basis of the original MPA decoding algorithm, another channel decoding strategy is not provided, the improved algorithms reduce the complexity of the original MPA decoding algorithm and simultaneously reduce the performance of a receiver to a certain extent, and the improved methods are explained to replace the low complexity of the algorithm by sacrificing the decoding accuracy. While reducing the decoding complexity of the MPA algorithm in the SCMA system, the decoding performance of the system must be considered, and the decoding performance of the system is mainly measured by using a Bit Error Rate (BER) value. Meanwhile, researchers propose that successive interference cancellation technology is used in an SCMA system to reduce the decoding complexity of the SCMA system, however, the drawback of the successive interference cancellation technology is not negligible, firstly, compared with the traditional SIC receiver, the SIC receiver adopted in the SCMA system is more complex and requires stronger signal processing capability; secondly, it can be known from the above process that the best receiving effect is determined according to the user sequence of the signal power rows, and in the actual process, the power of the user is constantly changed, which requires the SIC receiver to constantly sequence the user power; thirdly, as can be seen from the SIC structure diagram, each stage of processing will generate a certain time delay, and the generated time delay is very large in the actual multi-stage processing process. The former problem is solved by the future increase of the chip processing capability, and the latter two problems need further research on relevant processing algorithms.
Polynomial regression, where the regression function is the regression of a regression variable polynomial. The polynomial regression model is one of linear regression models, in which case the regression function is linear with respect to the regression coefficients. Polynomial regression has wide application since either function can be approximated by a polynomial. A Regression analysis method that studies polynomials between a dependent variable and one or more independent variables is called Polynomial Regression (PR). If the independent variable is only one, the method is called univariate polynomial regression; if there are more than one independent variable, it is called multivariate polynomial regression. In a univariate regression analysis, if the relationship between the dependent variable y and the independent variable x is non-linear, but no suitable functional curve can be found to fit, a univariate polynomial regression can be used.
In the existing visible light communication technology based on SCMA assistance, according to the codebook structure of an SCMA system and a user coding mapping principle, a code word of a single user and a code word superposed and synthesized by each user can be subjected to codebook design in a polynomial regression fitting mode and subjected to interference-free parallel decoding on the single user by utilizing a polynomial relationship. However, one unavoidable problem of the polynomial fitting method is that overfitting occurs, and how to avoid the overfitting phenomenon in the fitting process and ensure the fitting accuracy is an urgent problem to be solved.
Disclosure of Invention
Based on this, the invention aims to provide a fitting method-based SCMA assisted visible light communication coding and decoding method and system, which are used for solving the technical problems that in the prior art, the decoding complexity is too high and the polynomial fitting method is easy to over-fit.
One aspect of the present application provides a fitting method-based SCMA assisted visible light communication encoding method, where the method includes:
constructing a mother codebook, performing constellation rotation on the mother codebook according to a factor graph matrix to obtain a corresponding codebook corresponding to each user, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook;
acquiring bit signals of a plurality of users, and performing codebook mapping on the bit signals through the target codebook to enable the bit signals to be subjected to signal superposition to obtain complex signals, wherein the complex signals comprise real part signals and imaginary part signals;
filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal;
and adding direct current bias to the positive real number signal to drive the light emitting diodes with different primary colors to generate signal light, loading the signal to be emitted to a visible light channel, and adding white Gaussian noise to convert the signal light into an aliasing white light signal.
In addition, according to the SCMA assisted visible light communication encoding method based on the fitting method of the present invention, the following additional technical features may be provided:
further, the step of obtaining the target codebook by fitting according to the corresponding codebook in combination with the polynomial fitting coefficient includes:
obtaining the highest fitting times and the initial fitting times of the polynomial;
carrying out polynomial regression coefficient fitting on the codeword signal of the single user and the superimposed codeword signal, storing a polynomial fitting coefficient and calculating a correlation score;
judging whether the calculated correlation score is larger than a preset value or not;
and if so, increasing the fitting times according to the initial fitting times to obtain target fitting times, returning to execute the step of fitting the polynomial regression coefficients of the codeword signals of the single user and the superposed codeword signals, judging whether a polynomial fitting coefficient with the highest correlation score meeting the conditions exists or not until the target fitting times are greater than the highest fitting times, and if so, acquiring and storing the polynomial fitting coefficient with the highest correlation score meeting the conditions.
Further, the step of fitting according to the corresponding codebook and the polynomial fitting coefficient to obtain the target codebook comprises:
obtaining a polynomial fitting coefficient with the highest correlation score meeting the condition;
judging whether polynomial fitting coefficients of all users are obtained or not according to the number of the users;
and if so, obtaining a target codebook meeting the conditions according to the obtained polynomial fitting coefficients of all the users.
If not, resetting the polynomial maximum fitting times, and returning to the step of obtaining the polynomial maximum fitting times and the initial fitting times until obtaining the polynomial fitting coefficients of all users.
Further, the step of determining whether there is a polynomial fitting coefficient having the highest correlation score satisfying the condition further includes:
and if the polynomial fitting coefficient with the highest correlation score meeting the condition does not exist, returning to the step of constructing the mother codebook until the polynomial fitting coefficient with the highest correlation score meeting the condition is obtained.
Further, in the step of fitting the codeword signal of the single user with the superimposed codeword signal by a polynomial regression coefficient, the fitting relation is:
Figure 235954DEST_PATH_IMAGE001
wherein x is j Is shown asjCode word signals of the users mapped by the corresponding code books; x represents a code word signal superposed by each user; a. the n A matrix of coefficients representing the fit of the respective users,Nis the highest number of fits that are made,Jrepresenting the number of users;nrepresenting the current number of fits.
Another aspect of the present application provides a fitting method-based SCMA assisted visible light communication decoding method, where the method includes:
obtaining a white light signal, separating the white light signal into a plurality of signal lights through a plurality of optical filters with different primary colors, and converting the signal lights into electric signals through a photoelectric detector;
removing direct current bias from the electric signals, carrying out channel equalization on the electric signals subjected to direct current bias removal to obtain an equalization matrix, carrying out filtering processing on the signals subjected to channel equalization through a matched filter, and combining the equalization matrix and polynomial fitting coefficients to obtain estimated code word signals of each user;
and converting the code word signal into a complex signal, and decoding the complex signal through decoding judgment to obtain an input bit signal of each user.
In addition, according to the SCMA assisted visible light communication decoding method based on the fitting method of the present invention, the following additional technical features may be further included:
further, the step of decoding the complex signal by decoding decisions to obtain the input bit signal of each user comprises:
acquiring a complex signal and carrying out normalization processing on the complex signal;
and decoding the complex signal after the normalization processing through decoding judgment to obtain an input bit signal of each user.
According to the SCMA assisted visible light communication coding and decoding method based on the fitting method, the mother codebook is constructed, constellation rotation is carried out on the mother codebook according to the factor graph matrix so as to obtain the corresponding codebook corresponding to each user, fitting is carried out according to the corresponding codebook and the polynomial fitting coefficient so as to obtain the target codebook, and the polynomial fitting coefficient is optimized so as to prevent the over-fitting phenomenon; filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the direct current bias is added to the positive and real number signals to drive the light emitting diodes with different primary colors to generate signal light, the signal to be emitted is loaded to a visible light channel, and the Gaussian white noise is added to convert the signal light into an aliasing white light signal, so that the technical problem that the polynomial fitting method in the prior art is easy to generate overfitting is solved.
Another aspect of the present application further provides a signal coding mapping transmitting end, including:
the construction module is used for constructing a mother codebook, performing constellation rotation on the mother codebook according to a factor graph matrix to obtain a corresponding codebook corresponding to each user, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook;
a bit signal acquiring module, configured to acquire bit signals of multiple users, perform codebook mapping on the bit signals through the target codebook, so that the multiple bit signals are subjected to signal superposition to obtain a complex signal, where the complex signal includes a real part signal and an imaginary part signal;
the superposition module is used for filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal;
and the conversion module is used for adding direct current bias to the positive real number signal to drive the light emitting diodes with different primary colors to generate signal light, loading a signal to be emitted to a visible light channel, and superposing Gaussian white noise to convert the signal light into an aliasing white light signal.
Another aspect of the present application further provides a receiving and decoding end, including:
the white light signal acquisition module is used for acquiring a white light signal, separating the white light signal into a plurality of signal lights through a plurality of optical filters with different primary colors, and converting the signal lights into electric signals through a photoelectric detector;
the direct current bias removing module is used for removing direct current bias from the electric signals, carrying out channel equalization on the electric signals subjected to direct current bias removal to obtain an equalization matrix, carrying out filtering processing on the signals subjected to channel equalization through a matched filter, and combining the equalization matrix and polynomial fitting coefficients to obtain estimated code word signals of each user;
and the decoding module is used for converting the code word signal into a complex signal and decoding the complex signal through decoding judgment so as to obtain an input bit signal of each user.
The present application also provides a fitting method-based SCMA assisted visible light communication system, including a signal encoding mapping transmitting end, a receiving decoding end and a visible light channel, where the signal encoding mapping transmitting end is the signal encoding mapping transmitting end, and the receiving decoding end is the receiving decoding end;
the visible light channel is a transmission medium of visible light signals in space, and is used for data connection between the signal coding mapping sending end and the receiving decoding end.
Drawings
Fig. 1 is a flowchart of a fitting method-based SCMA assisted visible light communication encoding method according to a first embodiment of the present invention;
FIG. 2 is a detailed flowchart of step S101;
FIG. 3 is a flowchart of a SCMA assisted visible light communication decoding method based on a fitting method according to a second embodiment of the present invention;
FIG. 4 is a detailed flowchart of step S203;
FIG. 5 is a system diagram of a SCMA assisted visible light communication system based on a fitting method according to a fifth embodiment of the present invention;
fig. 6 is a diagram showing a correspondence relationship between a superimposed signal and a single-user signal according to a fifth embodiment of the present invention;
FIG. 7 is a comparison graph of the prediction and test accuracy of a single-user signal and a superimposed signal using polynomial fitting according to a fifth embodiment of the present invention;
fig. 8 is a graph of the average ber of each user obtained by decoding based on the polynomial fitting relationship in the fifth embodiment of the present invention.
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Several embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The invention provides a fitting method-based SCMA (sparse code multiple access) auxiliary visible light communication system, and aims at the problem that complexity of a decoding algorithm is increased rapidly due to SCMA multi-user signal superposition, a polynomial regression-based mode is provided for fitting the relation between a code word signal of a single user and a superposition code word signal, and meanwhile, polynomial fitting coefficients and polynomial regression times are optimized, so that an overfitting phenomenon is prevented;
meanwhile, in order to better find an ideal polynomial fitting coefficient and regression times, the codebook is specially designed, and an optimal fitting scheme can be found under the condition of optimization constraint through the specially designed codebook.
At the decoding end, the application performs channel equalization on the received superposed signal by using a polynomial matching coefficient and Minimum Mean Square Error (MMSE).
The codebook and the decoding mode designed by the method can realize parallel decoding, the decoding modes of all users are not interfered mutually, and compared with the traditional multi-user detection mode, the decoding mode can greatly improve the decoding efficiency and reduce the decoding complexity.
Example one
Referring to fig. 1, a fitting method-based SCMA assisted visible light communication encoding method in a first embodiment of the present invention is shown, the method including steps S101-S104:
s101, constructing a mother codebook, performing constellation rotation on the mother codebook according to the factor graph matrix to obtain a corresponding codebook corresponding to each user, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook.
In some optional embodiments, referring to fig. 2, the step of fitting the corresponding codebook with the polynomial fitting coefficients to obtain the target codebook includes steps S1011 to S1014:
s1011, obtaining the highest fitting times and the initial fitting times of the polynomial;
s1012, fitting a polynomial regression coefficient between the code word signal of the single user and the code word signal after superposition, storing the polynomial fitting coefficient and calculating a correlation score;
in the step of fitting the codeword signal of a single user with the superimposed codeword signal by a polynomial regression coefficient, the fitting relation is:
Figure 422216DEST_PATH_IMAGE002
wherein x is j Denotes the firstjCode word signals of the users mapped by the corresponding code books; x represents a code word signal superposed by each user; a. the n A matrix of coefficients representing the fit of the respective users,Nis the highest number of fits that are made,Jrepresenting the number of users;nrepresenting the current number of fits.
S1013, judging whether the calculated correlation score is larger than a preset value;
and S1014, if the calculated correlation score is larger than a preset value, increasing the fitting times according to the initial fitting times to obtain target fitting times, returning to the step of executing polynomial regression coefficient fitting of the code word signal of the single user and the superposed code word signal until the target fitting times are larger than the highest fitting times, judging whether a polynomial fitting coefficient with the highest correlation score meeting the condition exists, and if the polynomial fitting coefficient with the highest correlation score meeting the condition exists, acquiring and storing the polynomial fitting coefficient with the highest correlation score meeting the condition.
Further, the step of determining whether there is a polynomial fitting coefficient having the highest correlation score satisfying the condition further includes:
and if the polynomial fitting coefficient with the highest correlation score meeting the condition does not exist, returning to the step of constructing the mother codebook until the polynomial fitting coefficient with the highest correlation score meeting the condition is obtained.
In some optional embodiments, the step of fitting the corresponding codebook with the polynomial fitting coefficients to obtain the target codebook comprises:
and acquiring a polynomial fitting coefficient with the highest correlation score meeting the condition.
And judging whether polynomial fitting coefficients of all users are obtained or not according to the number of the users.
And if the polynomial fitting coefficients of all the users are obtained, obtaining a target codebook meeting the conditions according to the obtained polynomial fitting coefficients of all the users.
And if the polynomial fitting coefficients of all the users are not obtained, resetting the polynomial highest fitting times, and returning to the step of obtaining the polynomial highest fitting times and the initial fitting times until the polynomial fitting coefficients of all the users are obtained.
S102, obtaining bit signals of a plurality of users, and performing codebook mapping on the bit signals through a target codebook to enable the plurality of bit signals to be subjected to signal superposition to obtain complex signals, wherein the complex signals comprise real part signals and imaginary part signals.
S103, filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal.
S104, adding direct current bias to the positive and real signals to drive the light emitting diodes with different primary colors to generate signal light, loading the signal to be emitted to a visible light channel, and adding white Gaussian noise to convert the signal light into an aliasing white light signal.
In summary, in the SCMA assisted visible light communication encoding method based on the fitting method in the above embodiments of the present invention, the master codebook is constructed, the master codebook is constellation-rotated according to the factor graph matrix to obtain the corresponding codebook corresponding to each user, the target codebook is obtained by fitting according to the corresponding codebook in combination with the polynomial fitting coefficient, and the polynomial fitting coefficient is optimized to prevent the over-fitting phenomenon; filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the method comprises the steps of adding direct current bias to a positive and real number signal to drive light emitting diodes with different primary colors to generate signal light, loading a signal to be emitted to a visible light channel, and adding Gaussian white noise to convert the signal light into an aliasing white light signal, so that the technical problem that the polynomial fitting method in the prior art is easy to generate overfitting is solved.
Example two
Referring to fig. 3, a SCMA assisted visible light communication decoding method based on fitting method in a second embodiment of the present invention is shown, the method includes steps S201-S203:
s201, obtaining a white light signal, separating the white light signal into a plurality of signal lights through a plurality of filters with different primary colors, and converting the signal lights into electric signals through a photoelectric detector.
S202, removing direct current bias from the electric signals, performing channel equalization on the electric signals after the direct current bias is removed to obtain an equalization matrix, performing filtering processing on the signals after the channel equalization through a matched filter, and combining the equalization matrix and polynomial fitting coefficients to obtain estimated code word signals of each user.
Specifically, the expression of the equalization matrix is:
Figure 551846DEST_PATH_IMAGE003
wherein the content of the first and second substances,Prepresents the power of the signal; h is a channel matrix;Tis a symbol transposing the matrix;σis the noise standard deviation; and I is an identity matrix.
And S203, converting the code word signal into a complex signal, and decoding the complex signal through decoding judgment so as to obtain an input bit signal of each user.
In some alternative embodiments, referring to fig. 4, the step of decoding the complex signal by decoding decision to obtain the input bit signal of each user includes steps S2031 to S2032:
s2031, acquiring a complex signal, and normalizing the complex signal;
s2032, decoding the complex signal after normalization processing through decoding judgment to obtain the input bit signal of each user.
In summary, in the SCMA assisted visible light communication decoding method based on the fitting method in the above embodiments of the present invention, the master codebook is constructed, the master codebook is constellation-rotated according to the factor graph matrix to obtain the corresponding codebook corresponding to each user, the target codebook is obtained by fitting according to the corresponding codebook in combination with the polynomial fitting coefficient, and the polynomial fitting coefficient is optimized to prevent the over-fitting phenomenon; respectively filtering the real part signal and the imaginary part signal through an in-phase filter and an orthogonal filter, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the direct current bias is added to the positive and real number signals to drive the light emitting diodes with different primary colors to generate signal light, the signal to be emitted is loaded to a visible light channel, and the Gaussian white noise is added to convert the signal light into an aliasing white light signal, so that the technical problem that the polynomial fitting method in the prior art is easy to generate overfitting is solved.
EXAMPLE III
The embodiment provides a signal coding mapping transmitting end, including:
the construction module is used for constructing a mother codebook, performing constellation rotation on the mother codebook according to a factor graph matrix to obtain a corresponding codebook corresponding to each user, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook;
a bit signal acquiring module, configured to acquire bit signals of multiple users, perform codebook mapping on the bit signals through the target codebook, so that the multiple bit signals are superimposed to obtain a complex signal, where the complex signal includes a real part signal and an imaginary part signal;
the superposition module is used for respectively filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal;
and the conversion module is used for adding direct current bias to the positive real number signal to drive the light emitting diodes with different primary colors to generate signal light, loading a signal to be emitted to a visible light channel, and superposing Gaussian white noise to convert the signal light into an aliasing white light signal.
In some optional embodiments, in the building module, the step of fitting according to the corresponding codebook and combining with a polynomial fitting coefficient to obtain the target codebook may include:
the acquisition module is used for acquiring the highest fitting times and the initial fitting times of the polynomial;
the polynomial regression coefficient fitting module is used for carrying out polynomial regression coefficient fitting on the codeword signals of the single user and the superposed codeword signals, storing the polynomial fitting coefficients and calculating the correlation score;
the first judgment module is used for judging whether the calculated correlation score is larger than a preset value or not;
the first execution module is used for increasing the fitting times according to the initial fitting times to obtain target fitting times when the calculated correlation score is larger than a preset value, returning to execute the step of performing polynomial regression coefficient fitting on the code word signal of the single user and the superposed code word signal, and judging whether a polynomial fitting coefficient with the highest correlation score meeting the condition exists or not until the target fitting times are larger than the highest fitting times;
the second judgment module is used for judging whether a polynomial fitting coefficient with the highest correlation score meeting the condition exists or not;
the second execution module is used for acquiring and storing the polynomial fitting coefficient with the highest correlation score meeting the condition if the polynomial fitting coefficient with the highest correlation score meeting the condition exists;
and the third execution module is used for returning to the step of constructing the mother codebook if the polynomial fitting coefficient with the highest correlation score meeting the condition does not exist until the polynomial fitting coefficient with the highest correlation score meeting the condition is obtained.
In some optional embodiments, in the building module, the step of fitting according to the corresponding codebook and combining with a polynomial fitting coefficient to obtain the target codebook includes:
an obtaining unit configured to obtain a polynomial fitting coefficient having a highest correlation score satisfying the condition;
the judging unit is used for judging whether polynomial fitting coefficients of all users are obtained or not according to the number of the users;
the first execution unit is used for obtaining a target codebook meeting the conditions according to the obtained polynomial fitting coefficients of all the users when the polynomial fitting coefficients of all the users are obtained;
and the second execution unit is used for resetting the polynomial highest fitting times when the polynomial fitting coefficients of all the users are not obtained, and returning to execute the step of obtaining the polynomial highest fitting times and the initial fitting times until the polynomial fitting coefficients of all the users are obtained.
The signal coding and mapping transmitting terminal constructs a mother codebook, performs constellation rotation on the mother codebook according to the factor graph matrix to obtain a corresponding codebook corresponding to each user, performs fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook, and optimizes the polynomial fitting coefficient to prevent an over-fitting phenomenon; filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the direct current bias is added to the positive and real number signals to drive the light emitting diodes with different primary colors to generate signal light, the signal to be emitted is loaded to a visible light channel, and the Gaussian white noise is added to convert the signal light into an aliasing white light signal, so that the technical problem that the polynomial fitting method in the prior art is easy to generate overfitting is solved.
Example four
The present embodiment provides a receiving and decoding end, including:
the white light signal acquisition module is used for acquiring a white light signal, separating the white light signal into a plurality of signal lights through a plurality of optical filters with different primary colors, and converting the signal lights into electric signals through a photoelectric detector;
the direct current bias removing module is used for removing direct current bias from the electric signals, carrying out channel equalization on the electric signals subjected to direct current bias removal to obtain an equalization matrix, carrying out filtering processing on the signals subjected to channel equalization through a matched filter, and combining the equalization matrix and polynomial fitting coefficients to obtain estimated code word signals of each user;
and the decoding module is used for converting the code word signal into a complex signal and decoding the complex signal through decoding judgment so as to obtain an input bit signal of each user.
In some optional embodiments, the decoding module comprises:
the normalization processing unit is used for acquiring the complex signals and carrying out normalization processing on the complex signals;
and the decoding unit is used for decoding the normalized complex signals through decoding judgment so as to obtain the input bit signals of each user.
The receiving and decoding end constructs a mother codebook, performs constellation rotation on the mother codebook according to the factor graph matrix to obtain a corresponding codebook corresponding to each user, performs fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook, and optimizes the polynomial fitting coefficient to prevent an over-fitting phenomenon; filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the direct current bias is added to the positive and real number signals to drive the light emitting diodes with different primary colors to generate signal light, the signal to be emitted is loaded to a visible light channel, and the Gaussian white noise is added to convert the signal light into an aliasing white light signal, so that the technical problem that the polynomial fitting method in the prior art is easy to generate overfitting is solved.
EXAMPLE five
The present embodiment provides a fitting method based SCMA assisted visible light communication system, please refer to fig. 5, which includes a signal encoding mapping transmitting end, a visible light channel, and a receiving decoding end, where the visible light channel is a transmission medium of a visible light signal in a space and is used for data connection between the signal encoding mapping transmitting end and the receiving decoding end.
At a signal coding mapping transmitting end, a polynomial fitting coefficient which is not over-fitted and has the best fitting accuracy is found through polynomial fitting, and at this time, a codebook structure under the fitting relation is considered to be also the best, for convenience of explanation and without loss of generality, it is assumed that signals of 6 users are subjected to signal superposition after being mapped by a codebook designed by the application, and the SCMA codebook structure and the coding principle know that the signals subjected to the SCMA codebook mapping are complex signals which cannot be directly loaded on visible light for transmission, so that the application processes the complex signals at the signal coding mapping transmitting end, and respectively takes a real part signal and an imaginary part signal to be filtered by an in-phase filter which can be subjected to orthogonal filtering, and the implementation principle is as follows:
Figure 897376DEST_PATH_IMAGE004
；
wherein
Figure 391943DEST_PATH_IMAGE005
、
Figure 393397DEST_PATH_IMAGE006
Representing a set of real-pulse hilbert transform pairs,
Figure 123456DEST_PATH_IMAGE007
、
Figure 962973DEST_PATH_IMAGE008
representing the real and imaginary parts, signs, respectively, of a signal taking complex code words
Figure 487496DEST_PATH_IMAGE009
Which represents a convolution operation, is a function of,
Figure 976246DEST_PATH_IMAGE010
representing the positive real number codeword signal obtained through filtering processing.
Further, the signals passing through the filter are superposed again to become real signals, and after the direct current bias is added, the superposed and synthesized four paths of signals drive the light emitting diodes with different primary colors, so that the signals to be sent are successfully loaded on the light waves, only the direct gain of a visible light channel is considered in the application, and the channel gain expression is as follows:
Figure 385361DEST_PATH_IMAGE011
whereinmWhich represents the order of the lambertian radiation,
Figure 439905DEST_PATH_IMAGE012
，
Figure 604170DEST_PATH_IMAGE013
representing the half-power angle of the LED emission,
Figure 517900DEST_PATH_IMAGE014
indicating the signal emission angle from the emitting end of the LED to the receiving end,A rx representing the receiving area of the PD photodetector,n c which represents the refractive index of the receiving lens,
Figure 324182DEST_PATH_IMAGE015
which represents the field of view of the PD detector,dindicating the direct link distance between the LED and the receiver,
Figure 702073DEST_PATH_IMAGE016
which represents the angle of incidence of the light rays,
Figure 443764DEST_PATH_IMAGE017
is shown in
Figure 969424DEST_PATH_IMAGE018
A function of the rectangle in between,T s is the gain factor of the filter.
The signal light passes through a visible light channel and is superposed with white Gaussian noise to become an aliasing white light signal, in order to correctly decode a transmitted signal, the signal light of different primary colors is separated by using optical filters of different primary colors, then the optical signal is converted into an electric signal through a photoelectric detector, four paths of obtained electric signals are subjected to direct current bias removal, then the signal is subjected to channel equalization to reduce the influence of channel disturbance and noise, the equalized signal is filtered through a matched filter to respectively obtain an in-phase real part signal and an orthogonal imaginary part signal, the processed signal is multiplied by a fitting coefficient by a representation relation of polynomial fitting mentioned above to obtain a single user estimation signal, the signal at the moment is also a real signal, and the obtained real signal is converted into a complex form at the beginning, and then, carrying out decoding judgment on the single user, wherein the step of decoding judgment is explained in detail in the following decoding algorithm, so that the decoded bit stream of each user is obtained, and the complete communication flow of the whole system is ended.
Further, referring to fig. 6 and fig. 7, in light of the above mentioned codebook structure problem, the present application describes a structure of a 6 × 4 codebook, where 6 × 4 indicates that 6 users share 4 orthogonal spectrum resources, where the 4 orthogonal spectrum resources are equivalent to four-primary LED lamps in the system, and the structure of the codebook is as follows:
step 1: constructing a mother codebook
Figure 782659DEST_PATH_IMAGE019
In whichα=3；R 2 /R 1 = 1/0.63; wherein the determination is madeR 1 AndR 2 the value of any one of the mother codebooks is determined accordingly, and the value can be set firstlyR 1 Has a value of 1, C MC Representing a mother codebook;
step 2: according to the factor graph
Figure 185696DEST_PATH_IMAGE020
Rotation angle matrix
Figure 754081DEST_PATH_IMAGE021
Determining a codebook for each user
Figure 439140DEST_PATH_IMAGE022
WhereinjIs shown asjIndividual user, v j Representing a mapping matrix, v j By
Figure 728170DEST_PATH_IMAGE023
To obtain wherein F j The jth column of the factor graph F is shown,
Figure 877392DEST_PATH_IMAGE024
the transpose of the matrix is represented,
Figure 226464DEST_PATH_IMAGE025
and
Figure 398820DEST_PATH_IMAGE026
respectively representing a rotation angle matrix
Figure 616174DEST_PATH_IMAGE027
To (1) ajThe 1 st and 2 nd elements of the column;
finding a relation between the input code word of the single user and the superposed signal according to the above-mentioned mode of fitting according to a polynomial, wherein the fitting step is as follows;
step 1: considering the situation that 6 users share 4 orthogonal spectrum resource blocks, and then the codebook structure of each user is known, considering that in a 6 × 4 SCMA visible light communication system, each user occupies two orthogonal spectrum resource blocks for signal transmission, and the SCMA transmitted signal is in a complex form, while polynomial fitting cannot fit imaginary numbers, for this reason, the present application considers that a real part and an imaginary part are fitted separately, and signals on different resource blocks are fitted separately, and the specific process is as follows:
for the present applicationJIndicating the number of usersJ= 6; by usingKWhich indicates the number of resource blocks,K= 4; before passing through the channel, the superimposed signal of each user can be represented as:
Figure 495269DEST_PATH_IMAGE028
，
wherein x j Denotes the firstjThe code word signal mapped by the codebook corresponding to each user,
Figure 343139DEST_PATH_IMAGE029
in which
Figure 799528DEST_PATH_IMAGE030
Representing a userjTo be transmittednAnMA binary digital signal;
and 2, step: finding out the position of each user occupied resource block, and storing the position information,
Figure 194475DEST_PATH_IMAGE031
whereinfindRepresenting in matlab softwarefindThe inquiry function can inquire the position of the resource block occupied by each user, and according to the factor graph F, the number of the resource blocks occupied by each user is two, so that the users can inquire the resource block occupied by each userjThe polynomial fitting steps are:
step 2.1: according to the relation between input and output to be fitted, the method takes the superposed code word signal as an independent variable and takes the code word of a single user as a dependent variable, and the fitting relation is as follows:
Figure 787131DEST_PATH_IMAGE032
，
wherein x is j Is shown asjCode word signals of the users mapped by the corresponding code books; x represents a code word signal superposed by each user; a. the n A matrix of signals representing the fit of the respective users,Nis the highest number of fits that are made,Jrepresenting the number of users;nrepresenting the current number of fits.
Step 2.2: according to step 2.1, for the userjOccupied first resource blockj Position of (1) Fitting the real part of the image, and optimizing,
Figure 805902DEST_PATH_IMAGE033
Figure 421691DEST_PATH_IMAGE034
wherein the content of the first and second substances, a 0 ，a 1 ，a n representing the fitting coefficient, R2_ score represents the correlation score of the fitting effect.
Step 2.3: in the same way, for the userjOccupied first resource blockj Position of (1) Fitting the imaginary part of the signal, and optimizing,
Figure 184111DEST_PATH_IMAGE035
Figure 37797DEST_PATH_IMAGE036
wherein the content of the first and second substances,b 0 ，b 1 ，b n representing the fitting coefficient, R2_ score represents the correlation score of the fitting effect.
Step 2.4: in the same way, for the userjOccupied second resource blockj Position of (2) The real part of (a) is fitted and optimized,
Figure 758629DEST_PATH_IMAGE037
Figure 64976DEST_PATH_IMAGE038
wherein, the first and the second end of the pipe are connected with each other,c 0 ，c 1 ，c n representing the fitting coefficient, R2_ score represents the correlation score of the fitting effect.
Step 2.5: for users in the same wayjOccupied second resource blockj Position of (2) Fitting the imaginary part of the signal, and optimizing,
Figure 162245DEST_PATH_IMAGE039
Figure 198334DEST_PATH_IMAGE040
wherein the content of the first and second substances,d 0 ，d 1 ，d n representing the fitting coefficient, R2_ score represents the correlation score of the fitting effect.
Similarly, the fitting of other user signals follows the above steps, and the obtained relational expression of the code words of the single user and the superposition signal of each user is as follows:
Figure 463968DEST_PATH_IMAGE041
；
and step 3: decoding the received signal without loss of generality, the application assumes that the expression of the received signal after the mixed and overlapped optical signal is detected by the photoelectric detector through the optical filter and the direct current offset is removed as follows:
Figure 647825DEST_PATH_IMAGE042
wherein h is j Is shown asjA channel gain matrix of each user in a visible light channel, wherein w represents a received total Gaussian white noise matrix;
this application will provideyThe expression of (c) is further simplified as: y = Hx + w,
where Y represents the received signal matrix, H represents the channel matrix, x represents the codeword signal superimposed by each user, and w represents the noise matrix.
In order to make the received data closer to the transmitted data as much as possible, the Minimum Mean Square Error (MMSE) algorithm is adopted in the application, and a matrix G is found through the MMSE algorithm, so that the distance difference between GY and x is minimum, namely
Figure 424151DEST_PATH_IMAGE043
Where GY represents the estimated transmit codeword signal superimposed by each user, which greatly reduces the effect of channel disturbance and noise on signal detection, according to the general derivation process of MMSE algorithmAnd finally, obtaining the expression of the G matrix as follows:
Figure 845905DEST_PATH_IMAGE003
；
and 4, step 4: after the received signal is processed by MMSE algorithm, the expression of the received signal at this time is changed into
Figure 49485DEST_PATH_IMAGE044
At this time, the estimated signal obtained by multiplying the fitting coefficient of the polynomial is:
Figure 392741DEST_PATH_IMAGE045
；
consider that in an ideal case GH = I, I denotes the identity matrix, so there is
Figure 97392DEST_PATH_IMAGE046
，
Figure 514598DEST_PATH_IMAGE047
，
Figure 279292DEST_PATH_IMAGE048
Representing the estimated codeword signals superimposed by the respective users, x representing the codeword signals superimposed by the respective users,f(x, w) a polynomial matrix representing the codeword signal x and the noise w superimposed on each user;
in order to better eliminate the effect of noise on the decoded signal, the present application normalizes the received signal so that in the case of a high signal-to-noise ratio, i.e. where the noise w tends to zero,fthe value of (x, w) tends to zero, i.e.
Figure 280484DEST_PATH_IMAGE049
Therefore, the performance is very advantageous at high signal-to-noise ratio by using the coefficient matching relation.
After the code word signal of a single user is obtained by multiplying the coefficients, the method adopts decoding judgment again, and the steps of the decoding judgment are as follows:
step 4.1: the position of the resource block occupied by the decoding user at this time is found through the factor graph F, and the implementation method is as follows:
Figure 523246DEST_PATH_IMAGE050
，
wherein, the first and the second end of the pipe are connected with each other,
Figure 122855DEST_PATH_IMAGE051
is shown as
Figure 668237DEST_PATH_IMAGE051
A user, here will be
Figure 782823DEST_PATH_IMAGE051
The position of the resource block occupied by an individual user in the factor graph F is stored in k,findrepresenting in matlab softwarefindThe query function can query the position of the resource block occupied by each user;
step 4.2: decode to obtain
Figure 704643DEST_PATH_IMAGE051
The signal transmitted by each user is specifically realized as follows:
Figure 424337DEST_PATH_IMAGE052
；
Figure 265254DEST_PATH_IMAGE053
；
wherein the content of the first and second substances,mis shown asiThe decoded value corresponding to each of the symbols,normrepresenting in matlab softwarenormTaking a 2-norm function, wherein min represents that min in matlab software takes a minimum function,yrepresenting the codeword signal received at the receiving end,decXwhich represents the decoding of the recovered signal,iis shown asiThe number of the signals is such that,decX（j,i）represents decoding tojA user transmitsiA signal, k represents the position of the resource block occupied by the user;
through the above steps, the bit information of the single user is detected.
Referring to fig. 8, a performance simulation diagram of an SCMA assisted visible light communication system based on a fitting method, which is provided by the present application and adopts encoding and decoding provided by the present invention, is given, and it can be clearly seen from the diagram that the bit error rate of the system of the present application is continuously reduced along with the continuous increase of the signal-to-noise ratio, so that the present application verifies from a theoretical analysis and simulation level that the codebook design and decoding method of the SCMA assisted visible light communication system based on the fitting method provided by the present application has better decoding accuracy.
In conclusion, in the SCMA assisted visible light communication system based on the fitting method, the mother codebook is constructed, the mother codebook is subjected to constellation rotation according to the factor graph matrix to obtain the corresponding codebook corresponding to each user, the fitting is performed according to the corresponding codebook and the polynomial fitting coefficient to obtain the target codebook, and the polynomial fitting coefficient is optimized to prevent the over-fitting phenomenon; filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal; the direct current bias is added to the positive and real number signals to drive the light emitting diodes with different primary colors to generate signal light, the signal to be emitted is loaded to a visible light channel, and the Gaussian white noise is added to convert the signal light into an aliasing white light signal, so that the technical problem that the polynomial fitting method in the prior art is easy to generate overfitting is solved.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A SCMA assisted visible light communication coding method based on a fitting method is applied to a signal coding mapping sending end, and is characterized by comprising the following steps:
constructing a mother codebook, performing constellation rotation on the mother codebook according to a factor graph matrix to obtain a corresponding codebook corresponding to each user, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook;
acquiring bit signals of a plurality of users, and performing codebook mapping on the bit signals through the target codebook to enable the bit signals to be subjected to signal superposition to obtain complex signals, wherein the complex signals comprise real part signals and imaginary part signals;
filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal;
and adding direct current bias to the positive real number signal to drive the light emitting diodes with different primary colors to generate signal light, loading the signal to be emitted to a visible light channel, and adding white Gaussian noise to convert the signal light into an aliasing white light signal.
2. The fitting method-based SCMA assisted visible light communication encoding method of claim 1, wherein the step of fitting according to the corresponding codebook in combination with polynomial fitting coefficients to obtain the target codebook comprises:
obtaining the highest fitting times and the initial fitting times of the polynomial;
carrying out polynomial regression coefficient fitting on the codeword signal of the single user and the superimposed codeword signal, storing a polynomial fitting coefficient and calculating a correlation score;
judging whether the calculated correlation score is larger than a preset value or not;
and if so, increasing the fitting times according to the initial fitting times to obtain target fitting times, returning to execute the step of fitting the polynomial regression coefficients of the codeword signals of the single user and the superposed codeword signals, judging whether a polynomial fitting coefficient with the highest correlation score meeting the conditions exists or not until the target fitting times are greater than the highest fitting times, and if so, acquiring and storing the polynomial fitting coefficient with the highest correlation score meeting the conditions.
3. The fitting method-based SCMA assisted visible light communication encoding method of claim 2, wherein fitting according to the corresponding codebook with polynomial fitting coefficients to obtain a target codebook comprises:
obtaining a polynomial fitting coefficient with the highest correlation score meeting the condition;
judging whether polynomial fitting coefficients of all users are obtained or not according to the number of the users;
if yes, obtaining a target codebook meeting the conditions according to the obtained polynomial fitting coefficients of all the users;
if not, resetting the polynomial maximum fitting times, and returning to the step of obtaining the polynomial maximum fitting times and the initial fitting times until obtaining the polynomial fitting coefficients of all users.
4. The fitting method-based SCMA assisted visible light communication encoding method of claim 2, wherein the step of determining whether there is a polynomial fitting coefficient with the highest correlation score that satisfies the condition further comprises:
and if the polynomial fitting coefficient with the highest correlation score meeting the condition does not exist, returning to the step of constructing the mother codebook until the polynomial fitting coefficient with the highest correlation score meeting the condition is obtained.
5. The SCMA-assisted visible light communication encoding method according to claim 2, wherein in the step of fitting polynomial regression coefficients to the codeword signals of a single user and the superimposed codeword signals, the fitting relation is:
Figure 763180DEST_PATH_IMAGE001
wherein x is j Denotes the firstjCode word signals of the users mapped by the corresponding code books; x represents the code word signal superposed by each user; a. the n A matrix of coefficients representing the fit of the respective users,Nis the highest number of fits that are made,Jrepresenting the number of users;nrepresenting the current number of fits.
6. A SCMA assisted visible light communication decoding method based on a fitting method is applied to a receiving decoding end, and is characterized in that the method comprises the following steps:
obtaining a white light signal, separating the white light signal into a plurality of signal lights through a plurality of optical filters with different primary colors, and converting the signal lights into electric signals through a photoelectric detector;
removing direct current bias from the electric signals, carrying out channel equalization on the electric signals subjected to direct current bias removal to obtain an equalization matrix, carrying out filtering processing on the signals subjected to channel equalization through a matched filter, and combining the equalization matrix and polynomial fitting coefficients to obtain estimated code word signals of each user;
and converting the code word signal into a complex signal, and decoding the complex signal through decoding judgment to obtain an input bit signal of each user.
7. The fitting method-based SCMA assisted visible light communication decoding method of claim 6, wherein the step of decoding the complex signal by decoding decision to get the input bit signal of each user comprises:
acquiring a complex signal and carrying out normalization processing on the complex signal;
and decoding the complex signal after the normalization processing through decoding judgment to obtain an input bit signal of each user.
8. A signal code mapping transmitting end, comprising:
the construction module is used for constructing a mother codebook, performing constellation rotation on the mother codebook according to a factor graph matrix to obtain a corresponding codebook corresponding to each user, and fitting according to the corresponding codebook and a polynomial fitting coefficient to obtain a target codebook;
a bit signal acquiring module, configured to acquire bit signals of multiple users, perform codebook mapping on the bit signals through the target codebook, so that the multiple bit signals are superimposed to obtain a complex signal, where the complex signal includes a real part signal and an imaginary part signal;
the superposition module is used for filtering the real part signal and the imaginary part signal through an in-phase filter and a quadrature filter respectively, and superposing the filtered real part signal and the filtered imaginary part signal to obtain a positive real part signal;
and the conversion module is used for adding direct current bias to the positive real number signal to drive the light emitting diodes with different primary colors to generate signal light, loading a signal to be emitted to a visible light channel, and superposing Gaussian white noise to convert the signal light into an aliasing white light signal.
9. A receiving and decoding end, comprising:
the white light signal acquisition module is used for acquiring a white light signal, separating the white light signal into a plurality of signal lights through a plurality of optical filters with different primary colors, and converting the signal lights into electric signals through a photoelectric detector;
the direct current bias removing module is used for removing direct current bias from the electric signals, performing channel equalization on the electric signals subjected to direct current bias removal to obtain an equalization matrix, performing filtering processing on the signals subjected to channel equalization through a matched filter, and combining the equalization matrix and polynomial fitting coefficients to obtain estimated code word signals of each user;
and the decoding module is used for converting the code word signal into a complex signal and decoding the complex signal through decoding judgment so as to obtain an input bit signal of each user.
10. An SCMA-assisted visible light communication system based on a fitting method, comprising a signal encoding mapping transmitting end, a receiving decoding end and a visible light channel, wherein the signal encoding mapping transmitting end is the signal encoding mapping transmitting end according to the claim 8, and the receiving decoding end is the receiving decoding end according to the claim 9;
the visible light channel is a transmission medium of visible light signals in space, and is used for data connection between the signal coding mapping sending end and the receiving decoding end.
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