CN110855363B - Optimal dimming control visible light communication system and method based on distortion strategy - Google Patents

Optimal dimming control visible light communication system and method based on distortion strategy Download PDF

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CN110855363B
CN110855363B CN201911129913.2A CN201911129913A CN110855363B CN 110855363 B CN110855363 B CN 110855363B CN 201911129913 A CN201911129913 A CN 201911129913A CN 110855363 B CN110855363 B CN 110855363B
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distortion
ofdm
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CN110855363A (en
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江明
陈贤煜
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Sun Yat Sen 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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F18/00—Pattern recognition
    • G06F18/20—Analysing
    • G06F18/23—Clustering techniques
    • 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
    • H04B10/54—Intensity modulation
    • H04B10/541—Digital intensity or amplitude 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
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/548—Phase or frequency modulation
    • H04B10/556—Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
    • H04B10/5561—Digital phase modulation

Abstract

The invention provides a distortion strategy-based optimized dimming control visible light communication system, which comprises a transmitter and a receiver, and also provides a communication method, wherein the communication method comprises a carrier modulation process of the transmitter, wherein a TR subcarrier is inserted into an OFDM symbol, signal distortion constraint is carried out on other OFDM subcarriers carrying information, and then a modulated signal is sent to the receiver; the receiver transmits the obtained series of subcarriers to a distorted signal solving module, the distorted signal solving module calculates the real amplification factor of the useful signal, under the condition of not changing the bandwidth, the potential influence of signal distortion on effective signal transmission is analyzed and mined, and under the condition of giving dimming constraint, the signal distortion can provide more effective signal amplification capability, so that the communication is more reliable; meanwhile, the superiority of the L1 norm under the condition of solving large distortion is utilized, a clustering algorithm is adopted to ensure that some wrong local optimum points are avoided, and the performance and the transmission efficiency of the visible light communication system are effectively improved.

Description

Optimal dimming control visible light communication system and method based on distortion strategy
Technical Field
The invention relates to the technical field of visible light communication dimming control, in particular to a distortion strategy-based visible light communication system for optimizing dimming control, and further relates to a distortion strategy-based visible light communication method for optimizing dimming control.
Background
Currently, advanced dimming approaches are divided into two categories: digital dimming and analog dimming. The digital dimming mode achieves the aim of dimming by changing a waveform structure, and the analog dimming mode achieves dimming by directly adjusting light-emitting diode (LED) bias and specific waveforms [1 ]. For digital dimming, the main implementation mainly uses encoding for dimming pulse-width modulation (PWM) [2], and some schemes for modification on this basis. The digital dimming technology has certain limitations because the digital dimming technology changes the waveform duty ratio or performs dimming operation in a pulse mode or other modes through an encoding technology, which possibly reduces the communication rate of a system or increases the bandwidth of the system, and increases the complexity of signal processing of a user terminal. For analog dimming, the corresponding main implementation modes are asymmetric hybrid optical orthogonal frequency division multiplexing (AHO-OFDM) [3], high power frequency-efficient orthogonal frequency division multiplexing system [4], which is mostly composed of asymmetric shaped optical orthogonal frequency division multiplexing (QAM) with high spectral efficiency and pulse amplitude modulated discrete single tone (PAM-DMT) with low efficiency, and thus the total transmission efficiency is not high.
Disclosure of Invention
The invention provides an optimized dimming control visible light communication system based on a distortion strategy, aiming at overcoming the technical defects that the communication rate of the system is reduced or the bandwidth of the system is increased and the complexity of a user terminal for processing signals is finally increased in the existing digital dimming mode and the technical defect that the transmission efficiency is low in the existing analog dimming mode.
The invention also provides an optimized dimming control visible light communication method based on the distortion strategy.
In order to solve the technical problems, the technical scheme of the invention is as follows:
an optimized dimming control visible light communication system based on a distortion strategy comprises a transmitter, wherein an enhanced convex optimized dimming control frame is arranged on the transmitter, and the enhanced convex optimized dimming control frame comprises an optical-orthogonal frequency division multiplexing (O-OFDM) subsystem, a Tone Reservation (TR) subsystem, a signal distortion constraint module and an out-of-band distortion optimization module; wherein:
the O-OFDM subsystem is used for generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol; the TR subsystem is used for inserting the corresponding optimized subcarrier signals into corresponding positions of subcarriers reserved in the OFDM symbols; the signal distortion constraint module carries out signal distortion constraint on other OFDM symbols carrying information, and the out-of-band distortion optimization module carries out optimization and converts the OFDM symbols into electrical O-OFDM signals; and finally, converting the electrical O-OFDM signal into an optical signal by the transmitter and transmitting the optical signal in a corresponding VLC channel.
A distortion strategy-based optimized dimming control visible light communication system comprises a receiver, wherein a distortion signal solving module is arranged on the receiver and is used for solving effective signal distortion and solving out-of-band distortion; wherein:
the receiver obtains a series of subcarriers after optical-electrical conversion, transmits the subcarriers to the distortion signal solving module, and the distortion signal solving module calculates the real amplification factor of the useful signal, so as to demodulate the corresponding signal.
A distortion strategy-based optimized dimming control visible light communication method comprises a carrier modulation process of a transmitter, and comprises the following steps:
the optical-orthogonal frequency division multiplexing O-OFDM subsystem generates an orthogonal frequency division multiplexing OFDM symbol;
the tone reservation TR subsystem inserts TR subcarriers into OFDM symbols;
the signal distortion constraint module carries out signal distortion constraint on other OFDM symbols carrying information;
the out-of-band distortion optimization module optimizes the signals after the signal distortion constraint and converts the signals into electrical O-OFDM signals;
and finally, converting the electrical O-OFDM signals into optical signals on a transmitter, and transmitting the optical signals into corresponding VLC channels for transmission.
The carrier modulation process of the transmitter specifically comprises:
defining the frequency domain FD signal subcarrier index needing to be transmitted in each OFDM symbol as a set I in an O-OFDM subsystem s ＝{P s ,s＝1,2,...,N s And P is s ≤N s /2-1，N s Represents the total number of sub-carriers of useful information sent by one OFDM symbol; wherein, the value frequency domain FD signal X of the original signal to be transmitted s Expressed as:
Figure RE-GDA0002346881170000021
by means of I l And I h Represents the range of photocurrent passed through the transmitter, where the dimming level η is expressed as:
Figure RE-GDA0002346881170000031
wherein, the dimming level eta is set by the actual situation, so as to obtain the corresponding photocurrent average value I av (ii) a Thus, the parameter I needed in the OFDM symbol is obtained s 、X s 、I av 、I l And I h ；
In tone reservation, TR, subsystem, the index of the TR sub-carriers is defined as set I i ＝{P i ,s＝1,2,...,N i }，P i ≤N i /2-1，N i Represents the total number of TR sub-carriers carried by one OFDM symbol; thus, inserting TR subcarriers into an OFDM symbol includes:
I s ∪I i ＝{1,2,...,N/2-1}
Figure RE-GDA0002346881170000032
wherein N is i +N s (N/2) -1, and in addition, X is used i Denotes a TR subcarrier variation used in frequency domain FD; in the signal distortion constraint module, the variable xi is used 1 Quantifying the degree of signal distortion by the variable xi 2 The energy of the TR subcarrier signal is quantized, so in the time-frequency transform of the signal, the corresponding fourier transform matrix is:
Figure RE-GDA0002346881170000033
wherein, W N ＝e -j2π/N Thus, the frequency domain FD signal X corresponding to the transmitted signal is:
X＝W D s
wherein the parameter s represents the valid signal,
Figure RE-GDA0002346881170000034
n is the total number of inverse fast Fourier transforms, R + Representing positive real numbers, which are represented by the parameter I s 、X s 、I av 、I l And I h Determining; and then carrying out signal distortion constraint on the obtained signal X, optimizing the signal after the signal distortion constraint by an out-of-band distortion optimization module, converting the signal into an electrical O-OFDM signal, and finally transmitting the electrical O-OFDM signal by a transmitter.
The signal distortion constraint expression specifically includes:
defining decimation matrices
Figure RE-GDA0002346881170000035
And
Figure RE-GDA0002346881170000036
which extracts the true signal portion and the TR signal portion of the signal X, respectively; defining p as the amplification factor of the useful signal, d as the minimum value of the values of the decision distances from all the really transmitted signal points to the corresponding constellation diagram, and maximizing the minimum value to obtain the best communication performance, wherein the expression of the corresponding total optimization is as follows:
Figure RE-GDA0002346881170000037
s.t.X＝W D s
max s≤I h
min s≥I l
Figure RE-GDA0002346881170000041
Figure RE-GDA0002346881170000042
0≤d≤d i,j ,i∈I s ,x j ∈Y i
Figure RE-GDA0002346881170000043
setting the constellation diagram set in the process as A, and normalizing the energy of all constellation points in A to 1; let parameter x i Taken from the sets A, x i Is Y i In which there is x j ∈Y i (ii) a When the constellation diagram is amplified by p times, the corresponding point is set as px i The point transmitted by the transmitter is x * Then its neighbor point x j ，x j ∈K i The distance of the formed decision curve is specifically expressed as:
Figure RE-GDA0002346881170000044
i.e., the transformation is expressed as:
Figure RE-GDA0002346881170000045
wherein the content of the first and second substances,
Figure RE-GDA0002346881170000046
the specific process of optimizing the signal after the signal distortion constraint by the out-of-band distortion optimization module is as follows:
let the signal transmitted by the transmitter be
Figure RE-GDA0002346881170000047
Where L is the over-sampling rate used to describe the out-of-band distortion, assuming that the receiver is expected to receive a down-sampled signal of
Figure RE-GDA0002346881170000048
Wherein
Figure RE-GDA0002346881170000049
Down-sampling the signal with a receiver, defining an oversampled fourier transform matrix:
Figure RE-GDA00023468811700000410
wherein, W NL ＝e -j2π/NL Then, define the variable xi 3 Quantizing the degree of out-of-band distortion, then optimizing the signal distortion constraint to:
Figure RE-GDA00023468811700000411
s.t.X L ＝W L s L
X＝W D Ds L
max s L ≤I h
min s L ≥I l
Figure RE-GDA0002346881170000051
Figure RE-GDA0002346881170000052
Figure RE-GDA0002346881170000053
Figure RE-GDA0002346881170000054
wherein E is L3 Represents extracting X L Of the broadband external signal.
The method comprises a carrier distortion signal solving process of a receiver, and specifically comprises the following steps:
the receiver obtains a series of subcarriers after optical-electrical conversion, transmits the subcarriers to the distortion signal solving module, and demodulates the carrier signals by the distortion signal solving module to obtain the real amplification factor of the useful signals, thereby finally demodulating the corresponding signals.
The receiver specifically performs cyclic prefix removal processing, serial-parallel conversion processing and fast Fourier transform processing on an optical signal received from an optical channel through optical-electrical conversion to obtain a series of subcarriers; wherein:
the frequency FD signal received by the k-th subcarrier is represented as:
Y[k]＝H[k]X[k]+N[k]
wherein X [ k ] denotes the kth signal of the frequency domain FD signal X; n [ k ] is complex additive white Gaussian noise with zero mean, representing the noise vector of the kth signal corresponding to X [ k ]; h [ k ] is a channel transfer function CTF with respect to a channel impulse response CIR, and represents a channel of a k-th signal corresponding to X [ k ].
Wherein, in the distortion signal solving module, the signal amplification factor needs to be solved
Figure RE-GDA0002346881170000055
Useful signal of original signal to be transmitted
Figure RE-GDA0002346881170000056
And signals used for transmitting TR sub-carriers
Figure RE-GDA0002346881170000057
Further, the CTF of the effective signal subcarrier is defined as
Figure RE-GDA0002346881170000058
CTF corresponding to TR subcarrier is
Figure RE-GDA0002346881170000059
Definition of
Figure RE-GDA00023468811700000510
Wherein, with respect to the variables
Figure RE-GDA00023468811700000511
Is a dual variable of the inequality constraint of
Figure RE-GDA00023468811700000512
About signal amplification factor
Figure RE-GDA00023468811700000513
Is a dual variable of the inequality constraint of
Figure RE-GDA00023468811700000514
In the blind estimation process, according to the variables
Figure RE-GDA00023468811700000515
Variables of
Figure RE-GDA00023468811700000516
Variables of
Figure RE-GDA00023468811700000517
Updating the sequence of (a); wherein:
at the time of the 0-th instance,
Figure RE-GDA00023468811700000518
is initialized to:
Figure RE-GDA00023468811700000519
wherein, the first and the second end of the pipe are connected with each other,
Figure RE-GDA0002346881170000061
denotes the Hadamard product, F s Each element of (1) is H s The reciprocal of each element in (1); y represents a vector Y [ k ]](ii) a If obtained
Figure RE-GDA0002346881170000062
To an optimal solution
Figure RE-GDA0002346881170000063
Using maximum likelihood decisions
Figure RE-GDA0002346881170000064
Is judged by
Figure RE-GDA0002346881170000065
While
Figure RE-GDA0002346881170000066
The points of the corresponding constellation diagram are obtained through maximum likelihood estimation, and the judgment expression is as follows:
Figure RE-GDA0002346881170000067
if it concerns the variable
Figure RE-GDA0002346881170000068
Is the optimal solution of dual variables of the inequality constraint of
Figure RE-GDA0002346881170000069
When the value is equal to 0, the value,
Figure RE-GDA00023468811700000610
comprises the following steps:
Figure RE-GDA00023468811700000611
wherein the parameters
Figure RE-GDA00023468811700000612
Representing a diagonal matrix as an integral variable; if it is related to a variable
Figure RE-GDA00023468811700000613
Is the optimal solution of the dual variable of the inequality constraint of
Figure RE-GDA00023468811700000614
When not equal to 0, solving the function
Figure RE-GDA00023468811700000615
Zero point of (2), wherein
Figure RE-GDA00023468811700000616
Is composed of
Figure RE-GDA00023468811700000617
The corresponding derivatives are:
Figure RE-GDA00023468811700000618
thus, the function is scaled by Newton's method
Figure RE-GDA00023468811700000619
Is solved, and the obtained zero point is obtained
Figure RE-GDA00023468811700000620
Substituting the numerical value into the following formula to obtain
Figure RE-GDA00023468811700000621
Comprises the following steps:
Figure RE-GDA00023468811700000622
wherein, the first and the second end of the pipe are connected with each other,
Figure RE-GDA00023468811700000623
is a number N i ×N i The identity matrix of (1); after the update is finished
Figure RE-GDA00023468811700000624
Then, if regarding the variables
Figure RE-GDA00023468811700000625
Is the optimal solution of dual variables of the inequality constraint of
Figure RE-GDA00023468811700000626
When the value is equal to 0, the value,
Figure RE-GDA00023468811700000627
comprises the following steps:
Figure RE-GDA00023468811700000628
wherein, the first and the second end of the pipe are connected with each other,
Figure RE-GDA00023468811700000629
the representation is taken as the real part of x,
Figure RE-GDA00023468811700000630
representing the imaginary part of x; defining parameters
Figure RE-GDA00023468811700000631
Figure RE-GDA00023468811700000632
And
Figure RE-GDA00023468811700000633
the parameters r and i are spliced into a large vector v ri And r is s And i s Spliced into another large vector
Figure RE-GDA0002346881170000071
Then, the l1 norm optimal solution algorithm is adopted for solving:
first to v ri Is subjected to sequencing to obtain
Figure RE-GDA0002346881170000072
And its corresponding data v about the original data ri Is ordered as W ri Using v just obtained ri Index ordering W of ri For is to
Figure RE-GDA0002346881170000073
Is reordered to obtain
Figure RE-GDA0002346881170000074
Next, according to the formula (1), there are:
Figure RE-GDA0002346881170000075
taking N from 2 to 2N s And step size is 1, calculate:
Figure RE-GDA0002346881170000076
judgment of
Figure RE-GDA0002346881170000077
If yes, continuing to update n if not, and if yes,:
Figure RE-GDA0002346881170000078
if the above-mentioned variables relate to
Figure RE-GDA0002346881170000079
Is the optimal solution of dual variables of the inequality constraint of
Figure RE-GDA00023468811700000710
When the value is not equal to 0, the value,
Figure RE-GDA00023468811700000711
comprises the following steps:
Figure RE-GDA00023468811700000712
updating
Figure RE-GDA00023468811700000713
Then, the objective function of the receiver is obtained as follows:
Figure RE-GDA00023468811700000714
will be updated
Figure RE-GDA00023468811700000715
As
Figure RE-GDA00023468811700000716
And substituting in an equation to obtain the numerical value of the objective function and finish the solving process of the distortion signal.
After the solving process of the distortion signal, the numerical value of the objective function is processed by adopting a clustering algorithm, so that the influence of a series of local minimum values on the result on the final pair variable is avoided
Figure RE-GDA00023468811700000717
The accurate judgment of (2) is specific:
pre-aggregating vector c of stored cost function and storing optimal value
Figure RE-GDA0002346881170000081
Vector c of p To obtain a ternary tuple (a) i ，ι i ，f i ) I is 1, …, Label, wherein a i Is a vector of class i, consisting of vector c p Is of a group of i Is a i Mean, f, of the corresponding elements located in the vector c i Is a vector a i Is the total number of categories; the operation effectively avoids influence on the last pair caused by a series of local minimum values found by a heuristic algorithm
Figure RE-GDA0002346881170000082
And (4) accurate judgment.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
according to the optimal dimming control visible light communication system and method based on the distortion strategy, the potential influence of signal distortion on effective signal transmission is analyzed and mined under the condition that the bandwidth is not changed, and under the condition of given dimming constraint, the signal distortion can provide more effective signal amplification capability, so that the communication is more reliable; meanwhile, the advantage of the L1 norm under the condition of solving large distortion is utilized, and a clustering algorithm is adopted to ensure that the method does not fall into some wrong local optimum points, so that the performance and the transmission efficiency of the visible light communication system are effectively improved.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a graph of the bit error rate BER at a dimming level of 0.25;
FIG. 3 is a graph of the bit error rate BER at a dimming level of 0.5;
fig. 4 is a diagram of the maximum spectral efficiency that can be achieved by different schemes at different dimming levels.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
The invention adopts an optimized dimming control visible light communication system based on a distortion strategy, which comprises a transmitter, wherein an enhanced convex optimized dimming control frame is arranged on the transmitter, and the enhanced convex optimized dimming control frame comprises an optical-orthogonal frequency division multiplexing (O-OFDM) subsystem, a Tone Reservation (TR) subsystem, a signal distortion constraint module and an out-of-band distortion optimization module; wherein:
the O-OFDM subsystem is used for generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol; the TR subsystem is used for inserting the corresponding optimized subcarrier signals into corresponding positions of subcarriers reserved in the OFDM symbols; the signal distortion constraint module carries out signal distortion constraint on other OFDM symbols carrying information, and the out-of-band distortion optimization module carries out optimization and converts the OFDM symbols into electrical O-OFDM signals; and finally, converting the electrical O-OFDM signal into an optical signal by the transmitter and transmitting the optical signal in a corresponding VLC channel.
More specifically, the optimized dimming control visible light communication system based on the distortion strategy comprises a receiver, wherein a distortion signal solving module is arranged on the receiver and is used for solving effective signal distortion and solving out-of-band distortion; wherein:
the receiver obtains a series of subcarriers after optical-electrical conversion, transmits the subcarriers to the distortion signal solving module, and the distortion signal solving module calculates the real amplification factor of the useful signal, thereby demodulating the corresponding signal.
Example 2
More specifically, as shown in fig. 1, a distortion-strategy-based optimized dimming control visible light communication method includes a carrier modulation process of a transmitter, including:
the optical-orthogonal frequency division multiplexing O-OFDM subsystem generates an orthogonal frequency division multiplexing OFDM symbol;
the tone reservation TR subsystem inserts TR subcarriers into OFDM symbols;
the signal distortion constraint module carries out signal distortion constraint on other OFDM symbols carrying information;
the out-of-band distortion optimization module optimizes the signals after the signal distortion constraint and converts the signals into electric O-OFDM signals;
and finally, converting the electrical O-OFDM signals into optical signals on a transmitter, and transmitting the optical signals to a corresponding VLC channel for transmission.
The carrier modulation process of the transmitter specifically includes:
defining the frequency domain FD signal subcarrier index needing to be transmitted in each OFDM symbol as a set I in an O-OFDM subsystem s ＝{P s ,s＝1,2,...,N s H, and P s ≤N s /2-1，N s Represents the total number of sub-carriers of useful information sent by one OFDM symbol; wherein, the value frequency domain FD signal X of the original signal to be transmitted s Expressed as:
Figure RE-GDA0002346881170000091
by means of I l And I h Represents the range of photocurrent passed through the transmitter, where the dimming level η is expressed as:
Figure RE-GDA0002346881170000092
wherein, the dimming level eta is set by the actual situation, so as to obtain the corresponding photocurrent average value I av (ii) a Thus, the parameter I needed in the OFDM symbol is obtained s 、X s 、I av 、I l And I h ；
In tone reservation, TR, subsystem, the index of the TR sub-carriers is defined as set I i ＝{P i ,s＝1,2,...,N i }，P i ≤N i /2-1，N i Represents the total number of TR subcarriers carried by one OFDM symbol; thus, inserting TR subcarriers into an OFDM symbol includes:
I s ∪I i ＝{1,2,...,N/2-1}
Figure RE-GDA0002346881170000101
wherein N is i +N s (N/2) -1, furthermore, X i Denotes a TR subcarrier variation used in frequency domain FD; in the signal distortion constraint module, the variable xi is used 1 Quantifying the degree of signal distortion by the variable xi 2 The energy of the TR subcarrier signal is quantized, so in the time-frequency transform of the signal, the corresponding fourier transform matrix is:
Figure RE-GDA0002346881170000102
wherein, W N ＝e -j2π/N Thus, the frequency domain FD signal X corresponding to the transmitted signal is:
X＝W D s
wherein the parameter s represents the valid signal,
Figure RE-GDA0002346881170000103
n is the total number of inverse fast Fourier transforms, R + Representing positive real numbers, represented by the parameter I s 、X s 、I av 、I l And I h Determining; and then carrying out signal distortion constraint on the obtained signal X, optimizing the signal after the signal distortion constraint by an out-of-band distortion optimization module, converting the signal into an electrical O-OFDM signal, and finally transmitting the electrical O-OFDM signal by a transmitter.
The signal distortion constraint expression specifically includes:
defining decimation matrices
Figure RE-GDA0002346881170000104
And
Figure RE-GDA0002346881170000105
which extracts the true signal part and the TR signal part in the signal X respectively; defining p as the amplification factor of the useful signal, d as the minimum value of the values of the decision distances from all the really transmitted signal points to the corresponding constellation diagram, and maximizing the minimum value to obtain the best communication performance, wherein the expression of the corresponding total optimization is as follows:
Figure RE-GDA0002346881170000106
s.t.X＝W D s
max s≤I h
min s≥I l
Figure RE-GDA0002346881170000111
Figure RE-GDA00023468811700001110
0≤d≤d i,j ,i∈I s ,x j ∈Y i
Figure RE-GDA0002346881170000112
setting the constellation diagram set in the process as A, and normalizing the energy of all constellation points in A to 1; let parameter x i Taken from the set A, x i Is Y i In which there is x j ∈Y i (ii) a When the constellation diagram is amplified by p times, the corresponding point is set as px i The point transmitted by the transmitter is x * Then its neighbor point x j ，x j ∈K i The distance of the formed decision curve is specifically expressed as:
Figure RE-GDA0002346881170000113
i.e., the transformation is expressed as:
Figure RE-GDA0002346881170000114
wherein, the first and the second end of the pipe are connected with each other,
Figure RE-GDA0002346881170000115
the specific process of optimizing the signal after the signal distortion constraint by the out-of-band distortion optimization module is as follows:
let the signal transmitted by the transmitter be
Figure RE-GDA0002346881170000116
Where L is the over-sampling rate used to describe the out-of-band distortion, assuming that the receiver is expected to receive a down-sampled signal of
Figure RE-GDA0002346881170000117
Wherein
Figure RE-GDA0002346881170000118
Down-sampling the signal with a receiver, defining an oversampled fourier transform matrix:
Figure RE-GDA0002346881170000119
wherein, W NL ＝e -j2π/NL Then, define the variable xi 3 Quantizing the degree of out-of-band distortion, then optimizing the signal distortion constraint to:
Figure RE-GDA00023468811700001111
s.t.X L ＝W L s L
X＝W D Ds L
max s L ≤I h
min s L ≥I l
Figure RE-GDA0002346881170000121
Figure RE-GDA0002346881170000122
Figure RE-GDA0002346881170000123
Figure RE-GDA0002346881170000124
wherein E is L3 Representation extraction X L Of the broadband external signal.
The method comprises a carrier distortion signal solving process of a receiver, and specifically comprises the following steps:
the receiver obtains a series of subcarriers after optical-electrical conversion, the subcarriers are transmitted to the distortion signal solving module, the distortion signal solving module demodulates the carrier signals to obtain the real amplification factor of the useful signals, and finally the corresponding signals are demodulated.
The receiver specifically performs cyclic prefix removal processing, serial-parallel conversion processing and fast Fourier transform processing on an optical signal received from an optical channel through optical-electrical conversion to obtain a series of subcarriers; wherein:
the frequency FD signal received by the kth subcarrier is expressed as:
Y[k]＝H[k]X[k]+N[k]
wherein X [ k ] denotes the kth signal of the frequency domain FD signal X; n [ k ] is complex additive white Gaussian noise with zero mean, representing the noise vector of the kth signal corresponding to X [ k ]; h [ k ] is a channel transfer function CTF with respect to a channel impulse response CIR, and represents a channel of a k-th signal corresponding to X [ k ].
Wherein, in the distortion signal solving module, the signal amplification factor needs to be solved
Figure RE-GDA0002346881170000125
Useful signal of original signal to be transmitted
Figure RE-GDA0002346881170000126
And signals used for transmitting TR sub-carriers
Figure RE-GDA0002346881170000127
Further, the CTF of the effective signal subcarrier is defined as
Figure RE-GDA0002346881170000128
CTF corresponding to TR subcarrier is
Figure RE-GDA0002346881170000129
Definition of
Figure RE-GDA00023468811700001210
Wherein, with respect to the variables
Figure RE-GDA00023468811700001211
Is a dual variable of the inequality constraint of
Figure RE-GDA00023468811700001212
About signal amplification factor
Figure RE-GDA00023468811700001213
Is a dual variable of the inequality constraint of
Figure RE-GDA00023468811700001214
In the blind estimation process, according to the variables
Figure RE-GDA00023468811700001215
Variables of
Figure RE-GDA00023468811700001216
Variables of
Figure RE-GDA00023468811700001217
Updating the sequence of (a); wherein:
at the time of the 0-th instance,
Figure RE-GDA00023468811700001218
is initialized to:
Figure RE-GDA00023468811700001219
wherein, the first and the second end of the pipe are connected with each other,
Figure RE-GDA00023468811700001220
denotes the Hadamard product, F s Each element of (1) is H s The reciprocal of each element in (1); y represents a vector Y [ k ]](ii) a If obtained
Figure RE-GDA00023468811700001221
To an optimal solution
Figure RE-GDA00023468811700001222
Using maximum likelihood decisions
Figure RE-GDA00023468811700001223
Is judged by
Figure RE-GDA00023468811700001224
While
Figure RE-GDA0002346881170000131
The corresponding points of the constellation diagram are obtained through maximum likelihood estimation, and the judgment expression is as follows:
Figure RE-GDA0002346881170000132
if it is related to a variable
Figure RE-GDA0002346881170000133
Is the optimal solution of dual variables of the inequality constraint of
Figure RE-GDA0002346881170000134
When the value is equal to 0, the value,
Figure RE-GDA0002346881170000135
comprises the following steps:
Figure RE-GDA0002346881170000136
wherein the parameters
Figure RE-GDA0002346881170000137
Representing a diagonal matrix as an integral variable; if it is related to a variable
Figure RE-GDA0002346881170000138
Is the optimal solution of dual variables of the inequality constraint of
Figure RE-GDA0002346881170000139
When not equal to 0, first solveFunction(s)
Figure RE-GDA00023468811700001310
Of (2), wherein
Figure RE-GDA00023468811700001311
Is composed of
Figure RE-GDA00023468811700001312
The corresponding derivatives are:
Figure RE-GDA00023468811700001313
thus, the function is scaled by Newton's method
Figure RE-GDA00023468811700001314
Is solved, and the obtained zero point is obtained
Figure RE-GDA00023468811700001315
Substituting the numerical value into the following formula to obtain
Figure RE-GDA00023468811700001316
Comprises the following steps:
Figure RE-GDA00023468811700001317
wherein the content of the first and second substances,
Figure RE-GDA00023468811700001318
is a number N i ×N i The identity matrix of (1); after the update is finished
Figure RE-GDA00023468811700001319
Then, if regarding the variables
Figure RE-GDA00023468811700001320
Is constrained by an inequality ofThe optimal solution for the dual variables is
Figure RE-GDA00023468811700001321
When the value is equal to 0, the value,
Figure RE-GDA00023468811700001322
comprises the following steps:
Figure RE-GDA00023468811700001323
wherein the content of the first and second substances,
Figure RE-GDA00023468811700001324
the representation is taken as the real part of x,
Figure RE-GDA00023468811700001325
representing the imaginary part of x; defining parameters
Figure RE-GDA00023468811700001326
Figure RE-GDA00023468811700001327
And
Figure RE-GDA00023468811700001328
stitching the parameters r and i into a large vector v ri And r is s And i s Spliced into another large vector
Figure RE-GDA00023468811700001329
Then, the l1 norm optimal solution algorithm is adopted for solving:
first, for v ri Is subjected to sequencing to obtain
Figure RE-GDA0002346881170000141
And its corresponding data v about the original data ri Is ordered as W ri Using v just obtained ri Index ordering W of ri To pair
Figure RE-GDA0002346881170000142
Is reordered to obtain
Figure RE-GDA0002346881170000143
Next, according to the formula (1), there are:
Figure RE-GDA0002346881170000144
taking N from 2 to 2N s And step size is 1, calculate:
Figure RE-GDA0002346881170000145
judgment of
Figure RE-GDA0002346881170000146
If yes, continuing to update n if not, and if yes,:
Figure RE-GDA0002346881170000147
if the above-mentioned variables relate to
Figure RE-GDA0002346881170000148
Is the optimal solution of dual variables of the inequality constraint of
Figure RE-GDA0002346881170000149
When the value is not equal to 0, the value,
Figure RE-GDA00023468811700001410
comprises the following steps:
Figure RE-GDA00023468811700001411
updating
Figure RE-GDA00023468811700001412
Then, the objective function of the receiver is obtained as follows:
Figure RE-GDA00023468811700001413
will be updated
Figure RE-GDA00023468811700001414
As
Figure RE-GDA00023468811700001415
And substituting in an equation to obtain the numerical value of the objective function and finish the solving process of the distortion signal.
After the solving process of the distortion signal, the numerical value of the objective function is processed by adopting a clustering algorithm, so that the influence of a series of local minimum values on the result on the final pair variable is avoided
Figure RE-GDA00023468811700001416
The accurate judgment of (1) specifically:
pre-aggregating vector c of stored cost function and storing optimal value
Figure RE-GDA00023468811700001417
Vector c of p To obtain a ternary tuple (a) i ，ι i ，f i ) I is 1, …, Label, wherein a i Is a vector of class i, consisting of vector c p Is the composition of the adjacent elements in i Is a i Mean, f, of the corresponding elements located in the vector c i Is a vector a i Is the total number of categories; the operation effectively avoids a series of local minimum values found by a heuristic algorithm from influencing the final pair
Figure RE-GDA0002346881170000152
And (4) accurate judgment.
In a specific implementation process, the distortion strategy-based optimal dimming control visible light communication system and method provided by the invention analyze and mine the potential influence of signal distortion on effective signal transmission under the condition of not changing bandwidth, and under the condition of giving dimming constraint, the signal distortion can provide more effective signal amplification capability, so that the communication is more reliable; meanwhile, the advantages of the L1 norm solution under the large distortion scene are utilized, and the clustering algorithm is adopted to ensure that the method is not trapped in some wrong local optimal points, so that the performance and the transmission efficiency of the visible light communication system are effectively improved.
Example 3
To more fully illustrate the benefits of the present invention, the following simulation analyses and results further illustrate the effectiveness and advancement of the present invention. Assuming a conventional indoor scene, a size of 5x5x4m is used 3 Wherein the VLC channel model maximum reflection order is set to four, and the room center is located at (0, 0). The LED is centrally located and the user device employs a single photo-detector (PD) to receive the signal transmitted from the LED. Note that the field of view (FOV) angle of the PD may affect the performance of the VLC system. As an example, [5 ] is used]Configuration a in (2) sets the FOV to 70 °. Unless otherwise stated, the parameters in table 1 apply to most scenarios tested in the present invention. Where M is the modulation order of MQAM.
Figure RE-GDA0002346881170000151
Figure RE-GDA0002346881170000161
In the implementation, the method of the present invention is compared with other advanced algorithms, as shown in fig. 2 and 3. Therein, depicted are Bit Error Rate (BER) plots for different algorithms at dimming levels equal to 0.25, 0.5, respectively, where the abscissa is the noise variance of the receiver. In the figure, the CB-DCF algorithm proposed by the scheme adopts a 64QAM modulation mode, the highest spectral efficiency is 2.60 bits/s/Hz, other algorithms such as AHO-OFDM adopt 64QAM and 8PAM, and the parameters use the beta specified in the text ACO ＝β PAM ＝3，The highest frequency spectrum efficiency is 2.24 bit/s/Hz; the combined HACO and NHACO system proposed by Yang, using 128QAM and 8PAM, with parameters using the β specified in the text ACO ＝β PAM The highest spectral efficiency is 2.49bit/s/Hz, 4. As can be seen from fig. 2 and fig. 3, the system of AHO-OFDM and combining HACO and NHACO is easy to have error flat in the case of low noise of the receiver, and the effect is not good, while the BER obtained by CB-CDF shows waterfall type drop, and obviously as the signal-to-noise ratio increases, the performance becomes better.
In the implementation process, as shown in fig. 4, the scheme can obtain spectral efficiency under different dimming levels. AHO-OFDM and systems combining HACO and NHACO are used as a comparison, and different constellations, different modulation schemes are used to evaluate the achievable spectral efficiency in order to meet the requirements of a particular BER. In particular, the BER at the target is 2X 10 -3 The noise variance of the receiver is-110 dBm and the associated spectral efficiency is plotted. It can be found that in the interval of dimming level between 20% and 80%, the performance of the proposed scheme is significantly better than AHO-OFDM and systems combining HACO and NHACO.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
[1]Y.Yang,Z.Zeng,J.Cheng and C.Guo,“An Enhanced DCO-OFDM Scheme for Dimming Control in Visible Light Communication Systems,”IEEE Photonics Journal,vol.8,no.3,pp.1–13,June 2016.
[2]S.Kim and S.Y.Jung,“Modified Reed Muller Coding Scheme Made From the Bent Function for Dimmable Visible Light Communications,”IEEE Photonics Technology Letters,vol.25,no.1,pp.11–13,Jan.2013.
[3]Q.Wang,Z.Wang,and L.Dai,“Asymmetrical hybrid optical ofdm for visible light communications with dimming control,”IEEE Photonics Technology Letters, vol.27,no.9,pp.974–977,May 2015.
[4]F.Yang and J.Gao,“Dimming Control Scheme With High Power and Spectrum Efficiency for Visible Light Communications,”IEEE Photonics Journal,vol. 9,no.1,pp.1–12,Feb.2017.
[5]J.R.Barry,J.M.Kahn,W.J.Krause,E.A.Lee and D.G. Messerschmitt,“Simulation of multipath impulse response for indoor wireless optical channels,”IEEE Journal on Selected Areas in Communications,vol.11,no.3,pp. 367–379,Apr.1993.

Claims (6)

1. An optimized dimming control visible light communication system based on a distortion strategy, comprising a transmitter, characterized in that: the transmitter is provided with an enhanced convex optimization dimming control frame, and the enhanced convex optimization dimming control frame comprises an optical-orthogonal frequency division multiplexing (O-OFDM) subsystem, a Tone Reservation (TR) subsystem, a signal distortion constraint module and an out-of-band distortion optimization module; the O-OFDM subsystem is used for generating an Orthogonal Frequency Division Multiplexing (OFDM) symbol; the TR subsystem is used for inserting the corresponding optimized subcarrier signals into corresponding positions of subcarriers reserved in the OFDM symbols; the signal distortion constraint module carries out signal distortion constraint on other OFDM symbols carrying information, and the out-of-band distortion optimization module carries out optimization and converts the OFDM symbols into electrical O-OFDM signals; finally, the transmitter converts the electrical O-OFDM signals into optical signals to be transmitted in the corresponding VLC channels;
the system comprises a receiver and a control module, wherein the receiver is provided with a distortion signal solving module for solving effective signal distortion and out-of-band distortion; the receiver obtains a series of subcarriers after optical-electrical conversion, the subcarriers are transmitted to the distortion signal solving module, and the distortion signal solving module calculates the real amplification factor of the useful signal, so that the corresponding signal is demodulated;
wherein, executing a carrier modulation process on the transmitter specifically comprises:
defining the frequency domain FD signal subcarrier index needing to be transmitted in each OFDM symbol as a set I in an O-OFDM subsystem s ＝{P s ,s＝1,2,...,N s And P is s ≤N s /2-1，N s Represents the total number of sub-carriers of useful information sent by one OFDM symbol; wherein, the value frequency domain FD signal X of the original signal to be transmitted s Expressed as:
Figure FDA0003764814280000011
by means of I l And I h Representing the range of photocurrent passed in the transmitter, where the dimming level η is expressed as:
Figure FDA0003764814280000012
wherein, the dimming level eta is set according to actual conditions, thereby obtaining a corresponding photocurrent average value I av (ii) a Thus, the parameter I needed in the OFDM symbol is obtained s 、X s 、I av 、I l And I h ；
In tone reservation, TR, subsystem, the index of the TR sub-carriers is defined as set I i ＝{P i ,s＝1,2,...,N i }，P i ≤N i /2-1，N i Represents the total number of TR subcarriers carried by one OFDM symbol; thus, the TR subcarrier is inserted into the OFDM symbol, and there are:
I s ∪I i ＝{1,2,...,N/2-1}
Figure FDA0003764814280000021
wherein N is i +N s (N/2) -1, furthermore, X i Denotes a TR subcarrier variation used in frequency domain FD; in the signal distortion constraint module, the variable xi is used 1 QuantizationDegree of signal distortion, using variable xi 2 The energy of the TR subcarrier signal is quantized, so in the time-frequency transform of the signal, the corresponding fourier transform matrix is:
Figure FDA0003764814280000022
wherein, W N ＝e -j2π/N Thus, the frequency domain FD signal X corresponding to the transmitted signal is:
X＝W D s
wherein the parameter s represents the valid signal,
Figure FDA0003764814280000023
n is the total number of inverse fast Fourier transforms, R + Representing positive real numbers, represented by the parameter I s 、X s 、I av 、I l And I h Determining; then, carrying out signal distortion constraint on the obtained signal X, optimizing the signal after the signal distortion constraint by an out-of-band distortion optimization module, converting the signal into an electrical O-OFDM signal, and finally transmitting the electrical O-OFDM signal by a transmitter;
wherein, the signal distortion constraint expression is specifically as follows:
defining decimation matrices
Figure FDA0003764814280000024
And
Figure FDA0003764814280000025
which extracts the true signal portion and the TR signal portion of the signal X, respectively; defining p as the amplification factor of the useful signal, d as the minimum value of the values of the decision distances from all the really transmitted signal points to the corresponding constellation diagram, maximizing the minimum value to obtain the best communication performance, and the corresponding overall optimization expression is as follows:
Figure FDA0003764814280000026
s.t.X＝W D s
maxs≤I h
mins≥I l
Figure FDA0003764814280000027
Figure FDA0003764814280000028
0≤d≤d i,j ,i∈I s ,x j ∈Y i
Figure FDA0003764814280000029
setting the constellation diagram set in the process as A, and normalizing the energy of all constellation points in A to 1; let parameter x i Taken from the sets A, x i Is Y i In which there is x j ∈Y i (ii) a When the constellation diagram is amplified by p times, the corresponding point is set as px i The point transmitted by the transmitter is x * Then its neighbor point x j ，x j ∈K i The distance of the formed decision curve is specifically expressed as:
Figure FDA0003764814280000031
i.e., the transformation is expressed as:
Figure FDA0003764814280000032
wherein the content of the first and second substances,
Figure FDA0003764814280000033
the specific process of optimizing the signal after the signal distortion constraint by the out-of-band distortion optimization module is as follows:
let the signal transmitted by the transmitter be
Figure FDA0003764814280000034
Where L is the over-sampling rate, assuming that the receiver is expected to receive a down-sampled signal of
Figure FDA0003764814280000035
Wherein
Figure FDA0003764814280000036
For obtaining a receiver down-sampled signal, defining an oversampled fourier transform matrix:
Figure FDA0003764814280000037
wherein, W NL ＝e -j2π/NL Then, define the variable xi 3 Quantizing the degree of out-of-band distortion, then optimizing the signal distortion constraint to:
Figure FDA0003764814280000038
s.t.X L ＝W L s L
X＝W D Ds L
maxs L ≤I h
mins L ≥I l
Figure FDA0003764814280000039
Figure FDA00037648142800000310
Figure FDA00037648142800000311
Figure FDA0003764814280000041
wherein E is L3 Represents extracting X L Of the wideband external signal.
2. A distortion strategy-based optimized dimming control visible light communication method is characterized by comprising the following steps: a carrier modulation process comprising a transmitter, comprising:
the optical-orthogonal frequency division multiplexing O-OFDM subsystem generates an orthogonal frequency division multiplexing OFDM symbol;
the tone reservation TR subsystem inserts TR subcarriers into OFDM symbols;
the signal distortion constraint module carries out signal distortion constraint on other OFDM symbols carrying information;
the out-of-band distortion optimization module optimizes the signal after the signal distortion constraint and converts the signal into an electrical O-OFDM signal;
finally, converting the electrical O-OFDM signals into optical signals on a transmitter, and transmitting the optical signals to a corresponding VLC channel for transmission;
the carrier modulation process of the transmitter specifically includes:
defining the frequency domain FD signal subcarrier index needing to be transmitted in each OFDM symbol as a set I in an O-OFDM subsystem s ＝{P s ,s＝1,2,...,N s And P is s ≤N s /2-1，N s Represents the total number of sub-carriers of useful information sent by one OFDM symbol; wherein the FD signal X of the original signal to be transmitted is the numerical frequency domain s Expressed as:
X s ＝[X s [0],X s [1],...,X s [N s -1]] T ∈C Ns×1
by means of I l And I h Represents the range of photocurrent passed through the transmitter, where the dimming level η is expressed as:
Figure FDA0003764814280000042
wherein, the dimming level eta is set by the actual situation, so as to obtain the corresponding photocurrent average value I av (ii) a Thus, the parameter I needed in the OFDM symbol is obtained s 、X s 、I av 、I l And I h ；
In tone reservation, TR, subsystem, the index of the TR sub-carriers is defined as set I i ＝{P i ,s＝1,2,...,N i }，P i ≤N i /2-1，N i Represents the total number of TR subcarriers carried by one OFDM symbol; thus, inserting TR subcarriers into an OFDM symbol includes:
I s ∪I i ＝{1,2,...,N/2-1}
Figure FDA0003764814280000043
wherein N is i +N s (N/2) -1, and in addition, X is used i Denotes a TR subcarrier variation used in frequency domain FD; in the signal distortion constraint module, the variable xi is used 1 Quantifying the degree of signal distortion using the variable ξ 2 The energy of the TR subcarrier signal is quantized, so in the time-frequency transform of the signal, the corresponding fourier transform matrix is:
Figure FDA0003764814280000051
wherein, W N ＝e -j2π/N Thus, the frequency domain FD signal X corresponding to the transmitted signal is:
X＝W D s
wherein the parameter s represents the valid signal,
Figure FDA0003764814280000052
n is the total number of inverse fast Fourier transforms, R + Representing positive real numbers, which are represented by the parameter I s 、X s 、I av 、I l And I h Determining; then, carrying out signal distortion constraint on the obtained signal X, optimizing the signal after the signal distortion constraint by an out-of-band distortion optimization module, converting the signal into an electrical O-OFDM signal, and finally transmitting the electrical O-OFDM signal by a transmitter;
the signal distortion constraint expression specifically includes:
defining decimation matrices
Figure FDA0003764814280000053
And
Figure FDA0003764814280000054
which extracts the true signal portion and the TR signal portion of the signal X, respectively; defining p as the amplification factor of the useful signal, d as the minimum value of the values of the decision distances from all the really transmitted signal points to the corresponding constellation diagram, and maximizing the minimum value to obtain the best communication performance, wherein the expression of the corresponding total optimization is as follows:
Figure FDA0003764814280000055
s.t.X＝W D s
maxs≤I h
mins≥I l
Figure FDA0003764814280000056
Figure FDA0003764814280000057
0≤d≤d i,j ,i∈I s ,x j ∈Y i
Figure FDA0003764814280000058
setting the constellation diagram set in the process as A, and normalizing the energy of all constellation points in A to 1; let parameter x i Taken from the set A, x i Is Y i In which there is x j ∈Y i (ii) a When the constellation diagram is amplified by p times, the corresponding point is set as px i The point transmitted by the transmitter is x * Then its neighbor point x j ，x j ∈K i The distance of the formed decision curve is specifically expressed as:
Figure FDA0003764814280000061
i.e. the transformation is expressed as:
Figure FDA0003764814280000062
wherein, the first and the second end of the pipe are connected with each other,
Figure FDA0003764814280000063
the specific process of optimizing the signal after the signal distortion constraint by the out-of-band distortion optimization module is as follows:
let the signal transmitted by the transmitter be
Figure FDA0003764814280000064
Where L is the over-sampling rate, assuming that the receiver is expected to receive a down-sampled signal of
Figure FDA0003764814280000065
Wherein
Figure FDA0003764814280000066
For obtaining a receiver down-sampled signal, an oversampled fourier transform matrix is defined:
Figure FDA0003764814280000067
wherein, W NL ＝e -j2π/NL Then, define the variable xi 3 Quantizing the degree of out-of-band distortion, then optimizing the signal distortion constraint to:
Figure FDA0003764814280000068
s.t.X L ＝W L s L
X＝W D Ds L
maxs L ≤I h
mins L ≥I l
Figure FDA0003764814280000069
Figure FDA00037648142800000610
Figure FDA00037648142800000611
Figure FDA00037648142800000612
wherein E is L3 Representation extraction X L Of the broadband external signal.
3. The optimized dimming control visible light communication method based on the distortion strategy as claimed in claim 2, wherein: the method comprises a carrier distortion signal solving process of a receiver, and specifically comprises the following steps:
the receiver obtains a series of subcarriers after optical-electrical conversion, the subcarriers are transmitted to the distortion signal solving module, the distortion signal solving module demodulates the carrier signals to obtain the real amplification factor of the useful signals, and finally the corresponding signals are demodulated.
4. The optimized dimming control visible light communication method based on the distortion strategy as claimed in claim 3, wherein: the receiver specifically performs cyclic prefix removal processing, serial-parallel conversion processing and fast Fourier transform processing on an optical signal received from an optical channel through optical-electrical conversion to obtain a series of subcarriers; wherein:
the frequency FD signal received by the k-th subcarrier is represented as:
Y[k]＝H[k]X[k]+N[k]
wherein X [ k ] denotes the kth signal of the frequency domain FD signal X; n [ k ] is complex additive white Gaussian noise with zero mean, representing the noise vector of the kth signal corresponding to X [ k ]; h [ k ] is a channel transfer function CTF with respect to a channel impulse response CIR, and represents a channel of a k-th signal corresponding to X [ k ].
5. The optimized dimming control visible light communication method based on the distortion strategy as claimed in claim 4, wherein: in the distortion signal solving module, the signal amplification factor needs to be calculated
Figure FDA0003764814280000071
Useful signal of original signal to be transmitted
Figure FDA0003764814280000072
And signals used for transmitting TR sub-carriers
Figure FDA0003764814280000073
Definition ofCTF of the useful signal sub-carrier is
Figure FDA0003764814280000074
CTF corresponding to TR subcarrier is
Figure FDA0003764814280000075
Definition of
Figure FDA0003764814280000076
Wherein, with respect to the variables
Figure FDA0003764814280000077
Is a dual variable of the inequality constraint of
Figure FDA0003764814280000078
About signal amplification factor
Figure FDA0003764814280000079
Is a dual variable of the inequality constraint of
Figure FDA00037648142800000710
In the blind estimation process, according to the variables
Figure FDA00037648142800000711
Variables of
Figure FDA00037648142800000712
Variables of
Figure FDA00037648142800000713
Updating the sequence of (a); wherein:
at the time of the 0-th clock,
Figure FDA00037648142800000714
is initialized to:
Figure FDA00037648142800000715
wherein the content of the first and second substances,
Figure FDA00037648142800000716
denotes the Hadamard product, F s Each element of (1) is H s The reciprocal of each element in (1); y represents a vector Y [ k ]](ii) a If obtained
Figure FDA00037648142800000717
To an optimal solution
Figure FDA00037648142800000718
Using maximum likelihood decision to obtain
Figure FDA00037648142800000719
Is judged by
Figure FDA00037648142800000720
While
Figure FDA00037648142800000721
The points of the corresponding constellation diagram are obtained through maximum likelihood estimation, and the judgment expression is as follows:
Figure FDA00037648142800000722
if it concerns the variable
Figure FDA00037648142800000723
Is the optimal solution of dual variables of the inequality constraint of
Figure FDA00037648142800000724
When the value is equal to 0, the value,
Figure FDA00037648142800000725
comprises the following steps:
Figure FDA00037648142800000726
wherein the parameters
Figure FDA0003764814280000081
Representing a diagonal matrix as an integral variable; if it is related to a variable
Figure FDA0003764814280000082
Is the optimal solution of dual variables of the inequality constraint of
Figure FDA0003764814280000083
When not equal to 0, solving the function
Figure FDA0003764814280000084
Of (2), wherein
Figure FDA0003764814280000085
Is composed of
Figure FDA0003764814280000086
The corresponding derivatives are:
Figure FDA0003764814280000087
thus, the function is scaled by Newton's method
Figure FDA0003764814280000088
Is solved, and the obtained zero point is obtained
Figure FDA0003764814280000089
Substituting the numerical value into the following formula to obtain
Figure FDA00037648142800000810
Comprises the following steps:
Figure FDA00037648142800000811
wherein the content of the first and second substances,
Figure FDA00037648142800000812
is a number N i ×N i The identity matrix of (1); after the update is finished
Figure FDA00037648142800000813
Then, if regarding the variables
Figure FDA00037648142800000814
Is the optimal solution of dual variables of the inequality constraint of
Figure FDA00037648142800000815
When the value is equal to 0, the value,
Figure FDA00037648142800000816
comprises the following steps:
Figure FDA00037648142800000817
wherein the content of the first and second substances,
Figure FDA00037648142800000818
the representation is taken as the real part of x,
Figure FDA00037648142800000819
representing the imaginary part of x; defining parameters
Figure FDA00037648142800000820
Figure FDA00037648142800000821
And
Figure FDA00037648142800000822
the parameters r and i are spliced into a large vector v ri And r is s And i s Spliced into another large vector
Figure FDA00037648142800000823
Then, the l1 norm optimal solution algorithm is adopted to solve:
first, for v ri Is subjected to sequencing to obtain
Figure FDA00037648142800000824
And its corresponding data v about the original data ri Is ordered as W ri Using v just obtained ri Index ordering W of ri To pair
Figure FDA00037648142800000825
Is reordered to obtain
Figure FDA00037648142800000826
Next, according to the formula (1), there are:
Figure FDA0003764814280000091
taking N from 2 to 2N s And step size is 1, calculate:
Figure FDA0003764814280000092
judgment of
Figure FDA0003764814280000093
If the result is true, continuing to update n if the result is false, and if true, performing:
Figure FDA0003764814280000094
if the above-mentioned variables relate to
Figure FDA0003764814280000095
Is the optimal solution of dual variables of the inequality constraint of
Figure FDA0003764814280000096
When the value is not equal to 0, the value,
Figure FDA0003764814280000097
comprises the following steps:
Figure FDA0003764814280000098
updating
Figure FDA0003764814280000099
Then, the objective function of the receiver is obtained as follows:
Figure FDA00037648142800000910
will be updated
Figure FDA00037648142800000911
As
Figure FDA00037648142800000912
And substituting in an equation to obtain the numerical value of the objective function and finish the solving process of the distortion signal.
6. The optimized dimming control visible light communication method based on the distortion strategy as claimed in claim 5, wherein: after the solving process of the distortion signal, the numerical value of the objective function is processed by adopting a clustering algorithm, so that the influence of a series of local minimum values obtained by the result is avoidedLast pair of variables
Figure FDA00037648142800000913
The accurate judgment of (1) specifically:
pre-aggregating vector c of stored cost function and storing optimal value
Figure FDA00037648142800000914
Vector c of p Obtaining a triplet (a) i ，l i ，f i ) I is 1, …, Label, wherein a i Is a vector of class i, consisting of vector c p Composition of the neighboring elements of (1) i Is a i Mean, f, of the corresponding elements located in the vector c i Is a vector a i Is the total number of categories; the operation effectively avoids influence on the last pair caused by a series of local minimum values found by a heuristic algorithm
Figure FDA0003764814280000101
And (4) accurate judgment.
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