CN111600651A - Dimming control method and system for visible light communication system - Google Patents

Dimming control method and system for visible light communication system Download PDF

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CN111600651A
CN111600651A CN202010352068.1A CN202010352068A CN111600651A CN 111600651 A CN111600651 A CN 111600651A CN 202010352068 A CN202010352068 A CN 202010352068A CN 111600651 A CN111600651 A CN 111600651A
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张剑
郭家宁
张艳语
李琳
左昱
陈如翰
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Information Engineering University of PLA Strategic Support Force
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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
    • H04B10/501—Structural aspects
    • 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
    • H04B10/66—Non-coherent receivers, e.g. using direct detection

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Abstract

The embodiment of the invention discloses a dimming control method and a system of a visible light communication system, wherein the method comprises the following steps: the binary transmission data stream is subjected to high-order mapping according to the dimming level gamma and the original code weight value
Figure DDA0002472240200000011
And a threshold value T n × (l)max‑1)/2＝K×(lmax-1) obtaining the values of the check bits and the number of the complement bits by looking up a table, each uncoded transmitted codeword having a code length n, K being a positive integer, liIndicating the power level of the ith slot, lmaxThe maximum power grade number of each time slot is; according to the original code of the input data bitThe encoder outputs a transmission code word x, the transmission code word x is a transmission optical signal, and the transmitting end modulates the transmission signal into the transmission optical signal; the receiving end converts the transmission optical signal into an electric signal; the receiving end carries out rapid maximum likelihood demodulation on the received signal and outputs a demodulated signal; the receiving end carries out high-order parity check decoding on the demodulated signal and outputs a decoding result, and dual functions of communication and dimming control are realized in the realization process of the indoor visible light communication system.

Description

Dimming control method and system for visible light communication system
Technical Field
The embodiment of the invention relates to the technical field of visible light communication, in particular to a dimming control method and system of a visible light communication system.
Background
Visible Light Communication (VLC) uses an indoor lighting white Light LED (Light emitting diode) as a Light source, high-speed bright and dark flashing signals carried by the LED are used for transmitting information, and a receiving end uses a photoelectric detector for receiving the Light signals. In recent years, with the rapid development of LEDs, the realization of visible light communication systems has become a reality. As a system for coupling communication and illumination depth, visible light communication is required to not only seek high efficiency and reliability in communication, but also meet the needs of users for illumination.
For dimming control, the essence is to realize the required dimming level by adjusting the average electric/optical power of the transmission signal, so as to achieve the purpose of dimming control. Currently, the dimming schemes used by VLC are mainly divided into two types according to their working modes: a Continuous Current Regulation (CCR) technique for realizing dimming control by directly changing a Current value, which may be regarded as analog dimming; the other is based on a coded modulation dimming technology, which can be regarded as digital dimming, and under the condition that the driving current value is not changed, the average power of the optical signal is changed through communication means such as constellation design, channel coding and the like.
At present, a high-order weight threshold check code (ML-WTCC) dimming control scheme is generally adopted, and the spectrum efficiency is improved through high-order expansion of the Weight Threshold Check Code (WTCC). The realization principle is that: for the ML-WTCC signal, the code length of each uncoded transmission code word is n, n is even number, that is, each symbol is divided into n equal time slots, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2,/iIndicates the power level of the ith slot, wherei∈(0,1,2,…,lmax-1). At the same time, ω denotes the code weight of the transmitted codeword, i.e.
Figure BDA0002472240180000021
And omega is more than or equal to 0 and less than or equal to n (l)max-1) judging the size relation between the code weight omega and the threshold value T to obtain the value (0 or l) of the check bitmax-1) by changing lmaxAnd n, and adding a complement symbol to achieve the purpose of dimming control. However, in the implementation process of the indoor visible light communication system, the error code performance of the system can be improved as much as possible while the dual control of communication and dimming control cannot be realized.
Disclosure of Invention
The embodiment of the invention provides a dimming control method and system of a visible light communication system, which are used for solving the problem that in the realization process of an indoor visible light communication system in the prior art, the error code performance of the system is improved while the dual control of communication and dimming control cannot be realized.
The embodiment of the invention adopts the following technical scheme:
in a first aspect, a dimming control method for a visible light communication system is provided, where the method includes:
the transmitting terminal generates a binary transmission data stream according to the acquired transmission data stream of the visible light communication;
the transmitting end obtains the dimming level;
the transmitting end carries out high-order parity check coding on the binary transmission data stream;
the transmitting terminal modulates the transmission signal into a transmission optical signal;
the receiving end converts the transmitted optical signal into an electric signal;
the receiving end carries out rapid maximum likelihood demodulation on the received signal and outputs a demodulated signal;
the receiving end carries out high-order parity check decoding on the demodulated signal and outputs a decoding result;
the transmitting end carries out high-order parity check coding on the binary transmission data stream and comprises the following steps:
the binary transmission data stream is subjected to high-order mapping according to the dimming level gamma and the original code weight value
Figure BDA0002472240180000022
And a threshold value T n × (l)max-1)/2＝K×(lmax-1) obtaining the value of the check bits and the number of the complement bits by looking up the table. Each uncoded transmission code word has a code length of n, n is an even number, K is a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2;
according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, wherein the transmission code word x is a transmission optical signal.
In a second aspect, a dimming control system of a visible light communication system is provided, the system comprising:
the signal source module is used for generating a binary transmission data stream by the transmitting terminal according to the acquired transmission data stream of the visible light communication;
the dimming controller module is used for acquiring dimming grade by the transmitting terminal;
the high-order parity check code coding module is used for the transmitting end to carry out high-order parity check coding on the binary transmission data stream;
the electro-optical conversion module is used for modulating the transmission signal into a transmission optical signal by the transmitting end;
the photoelectric conversion module is used for converting the transmission optical signal into an electric signal at the receiving end;
the demodulation module is used for the receiving end to carry out rapid maximum likelihood demodulation on the received signal and output a demodulated signal;
the high-order parity check code decoding module is used for the receiving end to carry out high-order parity check decoding on the demodulation signal and output a decoding result;
wherein, the high-order parity check code coding module is used for:
according to the dimming level gamma, the code weight value
Figure BDA0002472240180000031
And a threshold value T n × (l)max-1)/2＝K×(lmax-1) obtaining the value of the check bit a and the number of the complement bits by looking up a table, each uncoded transmitted codeword having a code length n, n being an even number, K being a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2;
according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, and the transmission code word x is an optical signal transmitted by a transmitting end.
The embodiment of the invention adopts at least one technical scheme which can achieve the following beneficial effects:
in the embodiment of the invention, the code weight value is calculated according to the dimming level gamma
Figure BDA0002472240180000032
And a threshold value T n × (l)max-1)＝K×(lmax-1) obtaining the value of the check bit a and the number of the complementary bits by looking up a table, the code length of each uncoded transmitted codeword being n (n is an even number), K is a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2; according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, and the transmitting end modulates the transmission signal into a transmission optical signal; the receiving end converts the transmitted optical signal into an electric signal; the receiving end carries out rapid maximum likelihood demodulation on the received signal and outputs a demodulated signal; the receiving end carries out high-order parity check code decoding on the demodulated signal and outputs a decoding result, and dual functions of communication and dimming control are realized in the realization process of the indoor visible light communication system.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a flowchart illustrating a dimming control method of a visible light communication system according to an embodiment of the present disclosure;
fig. 2 is one of simulation effect diagrams of a dimming control method of a visible light communication system according to an embodiment of the present disclosure;
fig. 3 is a second simulation effect diagram of the dimming control method of the visible light communication system according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a dimming control system of a visible light communication system according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more clear, the technical solutions of the present application will be clearly and completely described below with reference to the specific embodiments of the present specification and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments in the present specification without any inventive step are within the scope of the present application.
The embodiment of the invention provides a dimming control method and system of a visible light communication system, which are used for solving the problem that in the realization process of an indoor visible light communication system in the prior art, the double control of communication and dimming control cannot be realized, and the error code performance of the system is improved. Embodiments of the present invention provide a dimming control method for a visible light communication system, and an execution subject of the method may be, but is not limited to, an application program, a system, or a device or a system capable of being configured to execute the method provided by the embodiments of the present invention.
Fig. 1 is a flowchart of a dimming control method of a visible light communication system according to an embodiment of the present invention, and as shown in fig. 1, the method may include:
step 101, the transmitting terminal generates a binary transmission data stream according to the acquired transmission data stream of the visible light communication.
When the dimming control of the visible light communication signal is needed, the transmission data stream of the visible light communication is obtained, and the transmission data stream is converted into a binary transmission data stream.
And 102, the transmitting end acquires the dimming level.
The dimming level may be set according to the current environment, and the embodiment of the present invention is not particularly limited.
And 103, the transmitting end carries out high-order parity check code coding on the binary transmission data stream.
It is understood that the acquired binary transmission data stream is subjected to a high order parity check code encoding according to the dimming level.
The high-order parity check coding of the binary transmission data stream by the transmitting end can be specifically realized as follows:
the binary transmission data stream is subjected to high-order mapping according to the dimming level gamma and the original code weight value
Figure BDA0002472240180000051
And a threshold value T n × (l)max-1)/2＝K×(lmax-1) obtaining the values of the check bits and the number of the complement bits by looking up a table, each uncoded transmitted codeword having a code length n (n is an even number), K is a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2;
according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, wherein the transmission code word x is a transmission optical signal.
The steps can be realized as follows:
if omega 'is less than or equal to T and omega' is odd number, the transmission code word x is output as [1, l%n,l(n-1),…,l2,l1]；
If omega 'is less than or equal to T and omega' is even number, the transmission code word x is output as [0, l%n,l(n-1),…,l2,l1]；
If ω '> T and ω' is an odd number, then
Figure BDA0002472240180000061
If ω '> T and ω' is an even number, then
Figure BDA0002472240180000062
Illustratively, the implementable code is:
determining the number n of time slots and the modulation order l according to the dimming level gammamaxThe expression is:
Figure BDA0002472240180000063
Figure BDA0002472240180000071
when n is 2, lmaxFor example, when 4, the code word is shown in table 1:
TABLE 1
Uncoded codeword Encoding code word Uncoded codeword Encoding code word
00 000 03 103
01 101 30 130 10
10 110 22 211
11 011 13 220
02 002 31 202
20 020 23 310
12 112 32 301 15
21 121 33 200
The flexibility of using higher-order parity-check codes allows the check symbols to be not only 0 (or 1),xlam-2 (or l)max-1). When omega' is less than or equal toT, the check symbol can be a or a +1, and when omega' > T, the check bit can be lmax-1-a or lmax-1- (a +1), wherein the condition a < (l) needs to be satisfiedmax-1)/2-1。
For example: when n is 2, lmaxWhen ω' ≦ T, its check symbol may be 0 (or 1), 2 (or 3); if ω' > T has a check symbol of 6 (or 7), 6 (or 5), 4 (or 5), it corresponds to the dimming level shown in table 2 (table 2 is when n is 2, lmaxWhen the check symbol is 8, the dimming level corresponding to the different check symbols) as follows:
TABLE 2
Check bit 0,1 1,2 2,3
4,5 0.3155 0.3393 0.3690
5,6 0.3393 0.3631 0.3929
6,7 0.3571 0.3810 0.4107
Where the first row represents the parity bits where ω '≦ T and the first column represents the parity bits where ω' > T. As can be seen from the table, the difference between adjacent dimming levels is small, and it is derived theoretically that the difference between adjacent dimming levels is further reduced as n increases, so that the dimming can be approximately regarded as any dimming.
And 104, modulating the transmission signal into a transmission optical signal by the transmitting end.
The steps can be realized as follows: and electro-optical conversion is carried out on the transmission data through the transmitting end LED to generate a transmission optical signal.
Step 105, the receiving end converts the transmitted optical signal into an electrical signal.
The steps can be realized as follows: the transmitted optical signal passes through a channel, is detected by a photodiode at a receiving end and is converted into an electrical signal, and the received signal can be represented as y ═ hx + n, wherein x represents the transmitted signal, n is the mean value 0 and the variance σ is2＝N0A gaussian white noise of/2, the electro-optic channel gain can be considered as h ═ 1.
The embodiment of the invention utilizes a Lambertian radiation model for modeling, and because a line-of-sight link of an optical link is dominant, a reflection link is not considered in the invention, and the channel gain can be recorded as:
Figure BDA0002472240180000081
wherein A represents the light receiving area of the receiving end PD, d represents the distance between the emitting end LED and the PD, and m represents the parameter of the Lambertian Lambert model; Ψ and φ are the incident angle and the irradiance angle, respectively; t isS(Ψ) and g (Ψ) are an optical filter gain and a concentrator gain, respectively, and the field of view (FOV) of the PD is ΨC。
For the PD receiver, the optical channel is slowly time-varying, so the channel can be considered as a static link. Since receiver preamplifier noise is the dominant noise and is signal independent, the channel can be modeled as an Additive White Gaussian Noise (AWGN) channel. While assuming that the Channel State Information (CSI) is known at both the receiving end and the transmitting end. The received electrical signal may be written as:
y＝rhx+n
where r denotes a photoelectric conversion coefficient, and x and y denote a transmission signal and a reception signal, respectively. And h is the channel gain as described above, and n is zero mean, variance σ2Additive White Gaussian Noise (AWGN).
Without loss of generality, assume that the photoelectric conversion factor r is 1.
Suppose that: rn,wFor a high-order codeword set with length n and code weight ω, | Rn,wAnd | is the number of codewords in the codeword set, wherein,
Figure BDA0002472240180000091
from the above definition, | Rn|＝(lmax)nThe total number of code words in the code word set is obtained, and the length of the code word after being coded is n +1, and the amplitude of a single symbol is l max1, so the total power can be derived as:
Ppeak＝(lmax-1)(n+1)(lmax)n
the expression of the dimming level γ is calculated as:
Figure BDA0002472240180000092
wherein k is a positive integer,
Figure BDA0002472240180000093
represents a check digit of which a and b are respectively 0 < gamma < 0.5, omega '< T and omega' > T, and c and d are respectively 0.5 < gamma < 1, omega '< T and omega' > T.
And 106, the receiving end carries out rapid maximum likelihood demodulation on the received signal and outputs a demodulated signal.
And step 107, the receiving end decodes the high-order parity check code of the demodulation signal and outputs a decoding result.
The steps can be realized as follows: obtaining a weight value omega of each transmission code word according to the code word y of the receiving end; and outputting a decoding result according to the dimming level gamma and the parity of the code weight value omega.
Specifically, the minimum euclidean distance judgment of the receiving end constellation is carried out on each transmission symbol; calculating a code weight value omega for each transmission code word; if omega is an even number, determining that the judgment is accurate; if omega is odd number and the dimming level gamma is gamma, the unified minimum Euclidean distance judgment is carried out on the whole receiving end code word y to output a decoding character string x containing check bitsd。
And data recovery is carried out according to the inverse process of the encoding process:
if gamma is more than 0 and less than or equal to 0.5,
Figure BDA0002472240180000101
or
Figure BDA0002472240180000102
Then
Figure BDA0002472240180000103
If gamma is more than 0 and less than or equal to 0.5,
Figure BDA0002472240180000104
or
Figure BDA0002472240180000105
Then
Figure BDA0002472240180000106
If gamma is more than 0.5 and less than 1,
Figure BDA0002472240180000107
or
Figure BDA0002472240180000108
Then
Figure BDA0002472240180000109
If gamma is more than 0.5 and less than 1,
Figure BDA00024722401800001010
or
Figure BDA00024722401800001011
Then
Figure BDA00024722401800001012
Illustratively, the implementation algorithm may be summarized as:
For i＝1:n+1
Figure BDA00024722401800001013
0＜q＜lmaxand q is an integer
End
If
Figure BDA00024722401800001014
Is not even
The received signal y needs to be re-judged by using the minimum Euclidean distance criterion
Figure BDA00024722401800001015
Figure BDA0002472240180000111
In practical application, the simulation images obtained through MATLAB simulation experiment verification are shown in fig. 2 and fig. 3. In fig. 2, the solid line is a high-order coding scheme, the dotted line is a binary coding scheme, and the line 1 indicates the spectral efficiency of the scheme proposed by the present invention. In fig. 3, line 1 shows the error performance of the proposed scheme, and line 2 shows the error performance of the comparison scheme. It can be seen from fig. 2 and fig. 3 that, by increasing the minimum euclidean distance of the high-order coding, the error code performance is improved relative to other coding modes under the condition that the high-order coding spectrum efficiency is ensured to be the same as that of other high-order coding schemes.
In the embodiment of the invention, the code weight value is calculated according to the dimming level gamma
Figure BDA0002472240180000112
And a threshold value T n × (l)max-1)＝K×(lmax-1) obtaining the value of the check bit a and the number of the complement bits by looking up a table, each uncoded transmitted codeword having a code length n, n being an even number, K being a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2; according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, and the transmitting end modulates the transmission signal into a transmission optical signal; the receiving end converts the transmitted optical signal into an electric signal; the receiving end carries out rapid maximum likelihood demodulation on the received signal and outputs a demodulated signal; the receiving end carries out high-order parity check code decoding on the demodulated signal and outputs a decoding result, and dual control of communication and dimming control is realized in the realization process of the indoor visible light communication system.
The dimming control method of the visible light communication system according to the embodiment of the present specification is described in detail above with reference to fig. 1 to 3, and the dimming control method of the visible light communication system according to the embodiment of the present specification is described in detail below with reference to fig. 4.
Fig. 4 is a schematic structural diagram of a system of a dimming control method for a visible light communication system according to an embodiment of the present disclosure, and as shown in fig. 4, the system may include:
the signal source module 401 is configured to generate a binary transmission data stream according to the acquired transmission data stream of the visible light communication at the transmitting end;
a dimming controller module 402 for the transmitting end to obtain a dimming level;
a high-order parity check code encoding module 403, configured to perform high-order parity check encoding on a binary transmission data stream by a transmitting end;
an electrical-to-optical conversion module 404, configured to modulate a transmission signal into a transmission optical signal at a transmitting end;
a photoelectric conversion module 405, configured to receive the transmission optical signal and convert the transmission optical signal into an electrical signal;
a demodulation module 406, configured to perform fast maximum likelihood demodulation on the received signal by the receiving end, and output a demodulated signal;
a high-order parity check code decoding module 407, configured to perform high-order parity check decoding on the demodulated signal by the receiving end and output a decoding result;
the high-order parity check code encoding module 403 is configured to:
according to the dimming level gamma, the code weight value
Figure BDA0002472240180000121
And a threshold value T n × (l)max-1)/2＝K×(lmax-1) obtaining the value of the check bit a and the number of the complement bits by looking up a table, each uncoded transmitted codeword having a code length n, n being an even number, K being a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2;
according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, and the transmission code word x is an optical signal transmitted by a transmitting end.
In an embodiment, the higher-order parity-check code encoding module 403 may include:
a first output unit for outputting a transmission codeword x [1, l ] if ω 'is ≦ T and ω' is an odd numbern,l(n-1),…,l2,l1]；
If omega 'is less than or equal to T and omega' is even number, the transmission code word x is output as [0, l%n,l(n-1),…,l2,l1]；
If ω '> T and ω' is an odd number, then
Figure BDA0002472240180000122
If ω '> T and ω' is an even number, then
Figure BDA0002472240180000123
In an embodiment, the high-order parity-check code decoding module 407 may include:
the obtaining unit is used for obtaining a code weight value omega of each transmission code word according to the code word y of the receiving end;
and the second output unit is used for outputting a decoding result according to the dimming level gamma and the parity of the code weight value omega.
In an embodiment, the high-order parity-check code decoding module 407 may include:
the first decision unit is used for carrying out minimum Euclidean distance decision of a receiving end constellation on each transmission symbol;
the calculation unit is used for calculating a code weight value omega of each transmission code word;
the determining unit is used for determining that the judgment is accurate if omega is an even number;
a second decision unit, configured to perform uniform minimum euclidean distance decision on the whole receiving codeword y to output a decoding string x containing check bits if ω is an odd number and the dimming level γ is reachedd。
In one embodiment, data recovery is performed in accordance with the inverse of the encoding process:
if gamma is more than 0 and less than or equal to 0.5,
Figure BDA0002472240180000131
or
Figure BDA0002472240180000132
Then
Figure BDA0002472240180000133
If gamma is more than 0 and less than or equal to 0.5,
Figure BDA0002472240180000134
or
Figure BDA0002472240180000135
Then
Figure BDA0002472240180000136
If gamma is more than 0.5 and less than 1,
Figure BDA0002472240180000137
or
Figure BDA0002472240180000138
Then
Figure BDA0002472240180000139
If gamma is more than 0.5 and less than 1,
Figure BDA00024722401800001310
or
Figure BDA00024722401800001311
Then
Figure BDA00024722401800001312
In an embodiment, the electro-optical conversion module 404 may include:
and the production unit is used for performing electro-optical conversion on the transmission data through the transmitting end LED to generate a transmission optical signal.
In an embodiment, the photoelectric conversion module 405 may include:
a detection conversion unit for transmitting optical signal through channel, detecting by photodiode at receiving end and converting into electric signal, wherein the received signal can be represented as y ═ hx + n, where x represents transmitted signal, n is mean value 0 and variance σ2＝N0White Gaussian noise of/2.
In one embodiment, the channel gain can be expressed as:
Figure BDA00024722401800001313
wherein A represents the light receiving area of the receiving end PD, d represents the distance between the emitting end LED and the PD, and m represents the parameter of the Lambertian Lambert model; Ψ and φ are the incident angle and the irradiance angle, respectively; t isS(Ψ) and g (Ψ) are an optical filter gain and a concentrator gain, respectively, and the field of view (FOV) of the PD is ΨC。
In the embodiment of the invention, the code weight value is calculated according to the dimming level gamma
Figure BDA0002472240180000141
And a threshold value T n × (l)max-1)＝K×(lmax-1) obtaining the value of the check bit a and the number of the complementary bits by looking up a table, the code length of each uncoded transmitted codeword being n (n is an even number), K is a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2; according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, and the transmitting end modulates the transmission signal into a transmission optical signal; the receiving end converts the transmitted optical signal into an electric signal; the receiving end carries out rapid maximum likelihood demodulation on the received signal and outputs a demodulated signal; the receiving end carries out high-order parity check code decoding on the demodulated signal and outputs a decoding result, and dual functions of communication and dimming control are realized in the realization process of the indoor visible light communication system.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (9)

1. A dimming control method of a visible light communication system is characterized by comprising the following steps:
the transmitting terminal generates a binary transmission data stream according to the acquired transmission data stream of the visible light communication;
the transmitting end obtains the dimming level;
the transmitting end carries out high-order parity check coding on the binary transmission data stream;
the transmitting terminal modulates the transmission signal into a transmission optical signal;
the receiving end converts the transmitted optical signal into an electric signal;
the receiving end carries out maximum likelihood demodulation on the received signal and outputs a demodulated signal;
the receiving end carries out high-order parity check decoding on the demodulated signal and outputs a decoding result;
the transmitting end carries out high-order parity check coding on the binary transmission data stream and comprises the following steps:
the binary transmission data stream is subjected to high-order mapping according to the dimming level gamma and the original code weight value
Figure FDA0002472240170000011
And a threshold value T n × (l)max-1)/2＝K×(lmax-1) obtaining the value of the check bits and the number of the complement bits by looking up the table. Each uncoded transmission code word has a code length of n, n is an even number, K is a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2;
according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, wherein the transmission code word x is a transmission optical signal.
2. The method of claim 1, wherein the encoder outputs a transport codeword x based on the original code weight value ω 'of the input data bits in relation to the threshold value T, and the parity of ω', comprising:
if omega 'is less than or equal to T and omega' is odd number, the transmission code word x is output as [1, l%n,l(n-1),…,l2,l1]；
If omega 'is less than or equal to T and omega' is even number, the transmission code word x is output as [0, l%n,l(n-1),…,l2,l1]；
If ω '> T and ω' is an odd number, then
Figure FDA0002472240170000012
If ω '> T and ω' is an even number, then
Figure FDA0002472240170000013
3. The method of claim 1, wherein the receiving end performs high-order parity-check decoding on the demodulated signal and outputs a decoding result, comprising:
obtaining a weight value omega of each transmission code word according to the code word y of the receiving end;
and outputting a decoding result according to the dimming level gamma and the parity of the code weight value omega.
4. The method of claim 3, wherein the receiving end performs high-order parity-check decoding on the demodulated signal and outputs a decoding result, comprising:
carrying out minimum Euclidean distance judgment of a receiving end constellation on each transmission symbol;
calculating a code weight value omega for each transmission code word;
if omega is an even number, determining that the judgment is accurate;
if omega is odd number and the dimming level gamma is gamma, the unified minimum Euclidean distance judgment is carried out on the whole receiving end code word y to output a decoding character string x containing check bitsd。
5. Method according to claim 4, characterized in that the data recovery is performed according to the inverse of the encoding process:
if gamma is more than 0 and less than or equal to 0.5,
Figure FDA0002472240170000021
or
Figure FDA0002472240170000022
Then
Figure FDA0002472240170000023
If gamma is more than 0 and less than or equal to 0.5,
Figure FDA0002472240170000024
or
Figure FDA0002472240170000025
Then
Figure FDA0002472240170000026
If gamma is more than 0.5 and less than 1,
Figure FDA0002472240170000027
or
Figure FDA0002472240170000028
Then
Figure FDA0002472240170000029
If gamma is more than 0.5 and less than 1,
Figure FDA00024722401700000210
or
Figure FDA00024722401700000211
Then
Figure FDA00024722401700000212
6. The method of claim 1, wherein the transmitting end modulates the transmission signal into a transmission optical signal, comprising:
and electro-optical conversion is carried out on the transmission data through the transmitting end LED to generate a transmission optical signal.
7. The method of claim 1, wherein the receiving end receives and converts the transmitted optical signal into an electrical signal, comprising:
the transmitted optical signal passes through a channel, is detected by a photodiode at a receiving end and is converted into an electrical signal, and the received signal can be represented as y ═ hx + n, wherein x represents the transmitted signal, n is the mean value 0 and the variance σ is2＝N0White Gaussian noise of/2.
8. The method of claim 7, wherein the channel gain is expressed as:
Figure FDA0002472240170000031
wherein A represents the light receiving area of the receiving end PD, d represents the distance between the emitting end LED and the PD, and m represents the parameter of the Lambertian Lambert model; Ψ and φ are the incident angle and the irradiance angle, respectively; t isS(Ψ) and g (Ψ) are an optical filter gain and a concentrator gain, respectively, and the field of view (FOV) of the PD is ΨC。
9. A dimming control system for a visible light communication system, comprising:
the signal source module is used for generating a binary transmission data stream by the transmitting terminal according to the acquired transmission data stream of the visible light communication;
the dimming controller module is used for acquiring dimming grade by the transmitting terminal;
the high-order parity check code coding module is used for the transmitting end to carry out high-order parity check coding on the binary transmission data stream;
the electro-optical conversion module is used for modulating the transmission signal into a transmission optical signal by the transmitting end;
the photoelectric conversion module is used for converting the transmission optical signal into an electric signal at the receiving end;
the demodulation module is used for the receiving end to carry out maximum likelihood demodulation on the received signal and output a demodulated signal;
the high-order parity check code decoding module is used for the receiving end to carry out high-order parity check decoding on the demodulation signal and output a decoding result;
wherein, the high-order parity check code coding module is used for:
according to the dimming level gamma, the code weight value
Figure FDA0002472240170000032
And a threshold value T n × (l)max-1)/2＝K×(lmax-1) obtaining the value of the check bit a and the number of the complement bits by looking up a table, each uncoded transmitted codeword having a code length n, n being an even number, K being a positive integer, liIndicating the power level of the ith slot, lmaxFor maximum power class number of each time slot, lmaxIs an integer power of 2;
according to the relation between the original code weight value omega 'of the input data bit and the threshold value T and the parity of omega', the encoder outputs a transmission code word x, and the transmission code word x is an optical signal transmitted by a transmitting end.
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