CN107453808B - A kind of nonlinear μ rule method and system of reduction visible light communication system light source led - Google Patents
A kind of nonlinear μ rule method and system of reduction visible light communication system light source led Download PDFInfo
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- CN107453808B CN107453808B CN201610367297.4A CN201610367297A CN107453808B CN 107453808 B CN107453808 B CN 107453808B CN 201610367297 A CN201610367297 A CN 201610367297A CN 107453808 B CN107453808 B CN 107453808B
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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
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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
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5059—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input
- H04B10/50593—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input to control the modulating signal amplitude including amplitude distortion
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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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
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- H04L25/00—Baseband systems
- H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
- H04L25/40—Transmitting circuits; Receiving circuits
- H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
- H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
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Abstract
The present invention provides a kind of nonlinear μ rule method and system of reduction visible light communication system light source led, can eliminate signal distortion caused by LED nonlinear characteristic from the signal of transmission itself, improve the reliability of system.The described method includes: obtaining signal to be sent in transmitting terminal；It is multiplied to after the signal progress μ rule log-compressed to be sent of acquisition with preset pre-distortion coefficients, obtains μ rule compressed signal；μ rule compressed signal is sent.The present invention is suitable for visible light multi-carrier communication technical field.
Description
Technical field
The present invention relates to visible light multi-carrier communication technical fields, particularly relate to a kind of reduction visible light communication system light source
The nonlinear μ of LED restrains method and system.
Background technique
With the continuous development of wireless communication technique and lighting industry, it is seen that light-emitting diode (LED) is wireless
Communication is as a kind of new technology communicated using white light LEDs, resourceful, energy-saving safe, message capacity with visible light
Greatly, tranmitting frequency is high, transmission rate is fast, without electromagnetic interference, do not need the advantages that radio frequency card.Visible LED channel radio
Letter with good application prospect, occupies an important position and is worth in future communications field, logical by indoor visible light of LED
Believe signal optical source, has many advantages, such as energy-saving, intelligence, informationization, safe, electromagnetic-radiation-free.
Visible light communication system has the advantages that many can make up Radio-Frequency Wireless Communication system defect, but visible light communication system
Light source led is non-linear in system causes signal distortion to be to influence one of the greatest problem of its system performance.Intrinsic non-of light source led
Linear propagation characteristics are to lead to one of maximum nonlinear device of non-linear effects in VISIBLE LIGHT SYSTEM.LED is electric current driving
One way conducting device, luminous flux is directly proportional to forward current, and there is centainly non-linear between the two.Due to visible light
The modulation bandwidth of wireless communication system is influenced by the nonlinear characteristic of LED, and the linear transfer of light source led is limited in scope, because
This is in the transmission process of LED component, and when signal amplitude is higher than the saturation threshold of LED linear range, the amplitude of signal is by nothing
Method normally exports, and it is distorted signal that amplitude is LED saturation threshold that such high-amplitude value signal, which is just distorted,.The high-amplitude to be distorted
Value multi-carrier signal enters visible light communication channel, and receiving end can not recover original signal after receiving, this is non-linear by LED
The caused reliability for influencing not only to reduce visible light wireless communication system can also reach LED saturation threshold because of a large amount of signals, make
It obtains LED and work is driven with saturation current for a long time, to reduce the service life of light source led.
In the prior art, change LED bias current, which can be used as one kind, can mitigate light source led in visible light wireless communication
The methods of non-linear effects analyze and calculate and send signal specifically, the central value of detection LED linear transmission range
Average current value sets LED bias current to the central value of LED linear transmission range, so that sending the average current of signal
It is worth close to bias current value.This method is configured according to device itself, easy to operate, and still, there is no the letters from transmission
Non-linear reduction processing number is done in itself.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of nonlinear μ rules of reduction visible light communication system light source led
Method and system, to solve the problems, such as to handle present in the prior art without doing non-linear reduction from the signal of transmission itself.
In order to solve the above technical problems, to provide a kind of reduction visible light communication system light source led non-thread for the embodiment of the present invention
Property μ restrain method, comprising:
In transmitting terminal, signal to be sent is obtained；
It is multiplied to after the signal progress μ rule log-compressed to be sent of acquisition with preset pre-distortion coefficients, obtains μ
Restrain compressed signal；
μ rule compressed signal is sent.
Further, described in transmitting terminal, obtaining signal to be sent includes:
In transmitting terminal, original signal to be sent is obtained, baseband modulation is carried out to the original signal to be sent；
Modulated signal after baseband modulation is converted into parallel signal；
Inverse fast fourier transform is carried out to the parallel signal, obtains the multi-carrier signal of multidiameter delay；
Plus cyclic prefix and parallel serial conversion is carried out to the multi-carrier signal of the multidiameter delay, is generated described to be sent
Signal.
Further, the μ rule compressed signal indicates are as follows:
Wherein, xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates μ rule system
Number；X (n) indicates that the signal to be sent obtained, Sgn<>indicate piecewise function.
Further, the method also includes:
In receiving end, exponential flareout transformation is carried out to the signal received, is indicated by the transformed signal of exponential flareout
Are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) signal that receiving end receives is indicated；xc(n) table
Show that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain pending
The number of delivering letters, Sgn<>indicate piecewise function.
Further, the pre-distortion coefficients indicate are as follows:
Wherein, ILEDIndicate light source led saturation current threshold value, Ix(n)Indicate the maximum current value of signal to be sent.
Further, described in receiving end, exponential flareout transformation is carried out to the signal received, later, further includes:
The transformed signal of the exponential flareout is successively executed go cyclic prefix, serial to parallel conversion, Fast Fourier Transform (FFT),
Base band demodulating, parallel serial conversion operation, to recover the original signal of transmitting terminal transmission.
The embodiment of the present invention also provides a kind of nonlinear μ rule system of reduction visible light communication system light source led, comprising:
Module is obtained, for obtaining signal to be sent in transmitting terminal；
Compression module, for the signal to be sent of acquisition carry out after μ rule log-compressed with preset predistortion
Multiplication obtains μ rule compressed signal；
Sending module, for sending μ rule compressed signal.
Further, the acquisition module includes:
Modulation unit carries out the original signal to be sent for obtaining original signal to be sent in transmitting terminal
Baseband modulation；
Converting unit, for the modulated signal after baseband modulation to be converted to parallel signal；
Converter unit obtains the multicarrier of multidiameter delay for carrying out inverse fast fourier transform to the parallel signal
Signal；
Generation unit plus cyclic prefix and carries out parallel serial conversion for the multi-carrier signal to the multidiameter delay, raw
At the signal to be sent.
Further, the μ rule compressed signal indicates are as follows:
Wherein, xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients,ILEDIndicate light source led saturation
Current threshold, Ix(n)Indicate the maximum current value of signal to be sent；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) is indicated
The signal to be sent obtained, Sgn<>indicate piecewise function.
Further, the system also includes:
Module is expanded, for exponential flareout transformation being carried out to the signal received, being converted by exponential flareout in receiving end
Signal afterwards indicates are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) signal that receiving end receives is indicated；xc(n) table
Show that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain pending
The number of delivering letters, Sgn<>indicate piecewise function；
Inverse transform module, for the transformed signal of the exponential flareout is successively executed go cyclic prefix, serial to parallel conversion,
Fast Fourier Transform (FFT), base band demodulating, parallel serial conversion operation, to recover the original signal of transmitting terminal transmission.
The advantageous effects of the above technical solutions of the present invention are as follows:
In above scheme, in transmitting terminal, μ rule log-compressed processing is carried out to the signal to be sent of acquisition, is reduced to be sent
The peak-to-average power ratio of signal, and the signal after log-compressed is multiplied with preset pre-distortion coefficients, μ rule compressed signal is obtained,
The predistortion compression processing for realizing signal to be sent can be avoided the nonlinear distortion shadow of light source led in visible light communication system
It rings, then obtained μ rule compressed signal is sent.In this way, non-linear reduction processing is done from signal to be sent itself, with
Guarantee that signal to be sent normally exports in the light source led range of linearity, so that it is abnormal to eliminate signal caused by LED nonlinear characteristic
Become, improves the reliability of system.
Detailed description of the invention
Fig. 1 is the process that the nonlinear μ of reduction visible light communication system light source led provided in an embodiment of the present invention restrains method
Schematic diagram one；
Fig. 2 is the process that the nonlinear μ of reduction visible light communication system light source led provided in an embodiment of the present invention restrains method
Schematic diagram two.
Fig. 3 is transmitting terminal schematic illustration provided in an embodiment of the present invention.
Fig. 4 is DCO-OFDM signal CCDF/PAPR simulation curve schematic diagram provided in an embodiment of the present invention；
Fig. 5 is that the DCO-OFDM signal waveform provided in an embodiment of the present invention for inputing to LED and LED output compares signal
Figure；
Fig. 6 is the visible light communication DCO-OFDM error rate of system emulation provided in an embodiment of the present invention based on algorithms of different
Curve synoptic diagram；
Fig. 7 is the structure that the nonlinear μ of reduction visible light communication system light source led provided in an embodiment of the present invention restrains system
Schematic diagram.
Specific embodiment
To keep the technical problem to be solved in the present invention, technical solution and advantage clearer, below in conjunction with attached drawing and tool
Body embodiment is described in detail.
The present invention it is existing not from the signal of transmission itself do non-linear reduction handle aiming at the problem that, a kind of drop is provided
The nonlinear μ of low visible light communication system light source led restrains method and system.
Embodiment one
Referring to shown in Fig. 1, a kind of nonlinear μ of reduction visible light communication system light source led provided in an embodiment of the present invention
Rule method, comprising:
Step 101: in transmitting terminal, obtaining signal to be sent；
Step 102: to the signal to be sent of acquisition carry out after μ rule log-compressed with preset pre-distortion coefficients phase
Multiply, obtains μ rule compressed signal；
Step 103: μ rule compressed signal is sent.
The nonlinear μ of reduction visible light communication system light source led described in the embodiment of the present invention restrains method, in transmitting terminal,
μ rule log-compressed processing is carried out to the signal to be sent of acquisition, reduces peak-to-average power ratio (the Peak to of signal to be sent
Average Power Ratio, PAPR), and the signal after log-compressed is multiplied with preset pre-distortion coefficients, obtain μ rule
Compressed signal realizes the predistortion compression processing of signal to be sent, it is non-linear to can be avoided light source led in visible light communication system
Distortion effect, then by the obtained μ rule compressed signal send.In this way, doing non-linear drop from signal to be sent itself
Reduction process is caused with guaranteeing that signal to be sent normally exports in the light source led range of linearity to eliminate LED nonlinear characteristic
Signal distortion, improve the reliability of system.
μ provided in an embodiment of the present invention restrains method abbreviation μ law, and the μ law is as a kind of non-uniform quantizing method, energy
It is enough that non-homogeneous companding is carried out to signal to be sent, the peak-to-average power ratio of signal to be sent is reduced, avoids signal to be sent because of light source
The distortion of severe signal caused by LED limited modulation range, it is ensured that receiving end can not recovered by LED non-linear effects and accurately
The signal that transmitting terminal is sent, thus the reliability of lifting system.
In the embodiment of the present invention, the visible light communication system can be visible light direct current biasing light orthogonal frequency division multiplexing
(Direct Current-Biased Optical Orthogonal Frequency Division Multiplexing,
DCO-OFDM) system, the signal to be sent are ofdm signal, which is a kind of multi-carrier signal, it is seen that light is logical
Have big signal probability of occurrence small by the DCO-OFDM signal that light source led emits in letter system, small signal probability of occurrence is big
Feature, μ law can distinguish high low signal, and different non-linear compandings is carried out to it, and μ law is applied to visible light DCO-OFDM
It can effectively reduce the peak-to-average power ratio of multi-carrier signal in system, so that the amplitude of DCO-OFDM signal to be sent is controlled in light
In the LED linear region of source, to guarantee that signal to be sent normally exports in the light source led range of linearity, so that it is non-linear to eliminate LED
Signal distortion caused by characteristic improves the reliability of system.
In the specific embodiment of the nonlinear μ rule method of aforementioned reduction visible light communication system light source led, further
Ground, described in transmitting terminal, obtaining signal to be sent includes:
In transmitting terminal, original signal to be sent is obtained, baseband modulation is carried out to the original signal to be sent；
Modulated signal after baseband modulation is converted into parallel signal；
Inverse fast fourier transform is carried out to the parallel signal, obtains the multi-carrier signal of multidiameter delay；
Plus cyclic prefix and parallel serial conversion is carried out to the multi-carrier signal of the multidiameter delay, is generated described to be sent
Signal.
In the embodiment of the present invention, as shown in Figures 2 and 3, in transmitting terminal, obtaining signal specific steps to be sent be can wrap
It includes:
1) baseband modulation carries out baseband modulation to sent original signal (for example, binary signal) in transmitting terminal, obtains
To serial band passband signals；M-ary Quadrature Amplitude modulation (Multiple is carried out to sent original signal
Quadrature Amplitude Modulation, MQAM) constellation mapping, obtain serial MQAM signal；
2) obtained serial MQAM signal is gone here and there and is become by serioparallel exchange (Serial to Parallel, S/P)
It changes, it is made to be transformed to the signal of N (N IFFT point number) road parallel transmission, the signal of the road the N parallel transmission can indicate are as follows: letter
Number X.
3) inverse fast fourier transform (Inverse Fast Fourier Transform, IFFT), signal X carry out N point
IFFT transformation, obtains the parallel ofdm signal in the road N, carries out multi-carrier modulation to signal X, can be improved the transmission rate of system,
Guarantee signal orthogonalization and without intersymbol interference.
4) ofdm signal parallel to the obtained road N plus cyclic prefix (Cyclic Prefix, CP) and carries out and goes here and there change
(Parallel to Serial, P/S) is changed, it is made to be transformed to the ofdm signal x of 1 tunnel serial transmission, signal x delivers letters as pending
Number.In addition the main function of cyclic prefix is that interchannel caused by eliminating intersymbol interference and multipath transmisstion to the greatest extent is dry
It disturbs；Carry out parallel-serial conversion main purpose with change signal transfer mode, become believing after mode of serial transmission is more suitable for
It is transmitted in road.
In step 4), ofdm signal is obtained after parallel serial conversion to be indicated are as follows:
Wherein, x (n) expression obtains ofdm signal after parallel serial conversion, and N indicates DCO-OFDM system subcarrier number, X table
Show the signal of the road the N parallel transmission obtained after serioparallel exchange, T indicates the ofdm signal period, and n indicates the of multi-carrier OFDM signal
N frame symbol, i indicate imaginary number i, and k indicates kth subcarriers.Then, cyclic prefix is added to the x (n), before plus circulation
Ofdm signal after sewing carries out μ and restrains compression processing, in the communications, in addition before and after cyclic prefix to the denotational description of ofdm signal without
It influences, that is to say, that multi-carrier OFDM signal can also be expressed as x (n) plus after cyclic prefix.Wherein, μ restrains compression processing
It specifically includes:
Carry out μ rule log-compressed to plus the ofdm signal after cyclic prefix (μ restrains non-linear compression)；
The ofdm signal obtained after μ restrains log-compressed is multiplied with pre-set pre-distortion coefficients, obtains meeting LED
The μ transmitted in the range of linearity restrains compressed signal xc(n)。
It, should also be pre- to before carrying out μ rule compression processing plus the ofdm signal after cyclic prefix in the embodiment of the present invention
First set corresponding pre-distortion coefficients m, to avoid the nonlinear distortion effect of LED light source in visible light communication system, guarantee to
Signal is sent to transmit within the scope of light source led linear transfer.Pre-distortion coefficients m is equal to light source led in visible light communication system
Saturation current threshold value ILEDWith signal maximum current value I to be sentx(n)Ratio, i.e.,In this way, in conjunction with light source led
Saturation current threshold value carries out self-adapting compressing to signal to be sent, can overcome multicarrier high-amplitude value signal after light source led
The non-linear distortion suffered influences, so that the communication system for having light source led obtains higher transmission reliability.
In the embodiment of the present invention, for visible light DCO-OFDM system, pre-distortion coefficients m is visible light DCO-OFDM system
Middle light source led saturation current threshold value and the ratio plus the ofdm signal maximum current value after cyclic prefix.
In the specific embodiment of the nonlinear μ rule method of aforementioned reduction visible light communication system light source led, further
Ground, the μ restrain compressed signal xc(n) it indicates are as follows:
Wherein, xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates μ rule system
Number；X (n) indicates that the signal to be sent obtained, Sgn<>indicate piecewise function.
In the embodiment of the present invention, A is for guaranteeing
In the embodiment of the present invention, as shown in figure 3, the μ restrains compressed signal xcIt (n), must before passing through light source led transmitter
Compressed signal load direct current biasing must be restrained to the μ and makes DCO-OFDM signal, to guarantee that all negative signals are all positive letter
Number to drive light source led to work normally, μ rule compressed signal is made to enter visible light communication channel.
In the specific embodiment of the nonlinear μ rule method of aforementioned reduction visible light communication system light source led, further
Ground, the method also includes:
In receiving end, exponential flareout transformation is carried out to the signal received, is indicated by the transformed signal of exponential flareout
Are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) signal that receiving end receives is indicated；xc(n) table
Show that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain pending
The number of delivering letters, Sgn<>indicate piecewise function.
In the specific embodiment of the nonlinear μ rule method of aforementioned reduction visible light communication system light source led, further
Ground, it is described in receiving end, exponential flareout transformation is carried out to the signal received, later, further includes:
The transformed signal of the exponential flareout is successively executed go cyclic prefix, serial to parallel conversion, Fast Fourier Transform (FFT),
Base band demodulating, parallel serial conversion operation, to recover the original signal of transmitting terminal transmission.
In the embodiment of the present invention, in receiving end, the signal y that receivescIt (n) is DCO-OFDM signal, it is necessary first to institute
State yc(n) it carries out direct current biasing to handle, then undergoes the inverse transformation with transmitting terminal contrary, to ensure accurately to recover transmitting terminal
The original signal of transmission, wherein y can be still expressed as by removing direct current biasing treated to receive signalc(n)。
In the embodiment of the present invention, the inverse transformation with transmitting terminal contrary is specifically included:
Firstly, removing direct current biasing treated signal y to what receiving end receivedc(n) carrying out the compression of μ rule, (μ restrains compressed package
Include: μ rule log-compressed and μ rule log-compressed after is multiplied with preset pre-distortion coefficients) inverse transformation with realize reception signal into
The non-linear expansion of row, i.e. exponential flareout convert, the DCO-OFDM signal y converted by exponential flareoute(n) it can indicate are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) what expression receiving end received goes at direct current biasing
Signal after reason；xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；
X (n) indicates that the signal to be sent obtained, Sgn<>indicate piecewise function.
Then, as shown in Fig. 2, signal y transformed to the exponential flareoute(n) cyclic prefix, string are carried out and is become
It changes, N point quick Fourier transformation (Fast Fourier Transform, FFT) transformation, base band demodulating (solution baseband modulation), simultaneously
The inverse transformation of string transformation these and transmitting terminal transformation contrary, finally recovers the original signal of transmitting terminal transmission.
μ law in the embodiment of the present invention belongs to a kind of predistortion companding technology, is expanded using log-compressed characteristic and index
It opens characteristic and non-linear companding is carried out to multi-carrier signal, to meet signal transmission in the linear region of light source led, from being distorted shadow
It rings.To send end signal according to light source led saturation current threshold value and signal maximum current value to be sent two value adaptively into
The compression of row μ rule (μ rule compression includes: to be multiplied after μ restrains log-compressed and μ rule log-compressed with preset pre-distortion coefficients) processing,
To guarantee that signal amplitude to be sent is adapted to transmit within the scope of LED linear, signal distortion caused by avoiding LED non-linear；It is connecing
Receiving end carries out exponential flareout processing to μ rule compressed signal, accurately to restore the original signal of transmitting terminal transmission, and guarantees communication system
The transmission quality of system.
μ law provided in an embodiment of the present invention ensure that multi-carrier signal mean power does not change while compressed signal
Become, reason is that μ rule technology acts on originally and is largely expanded to small signal, carries out lesser degree expansion to big signal
, finally the signal after expansion is multiplied with pre-distortion coefficients m again, obtaining peak-to-average power ratio reduces and meet LED linear range
The DCO-OFDM signal of transmission.μ law provided in an embodiment of the present invention plays great work to the inhibition of LED non-linear effects
With, can be avoided because light source led it is non-linear caused by irrecoverable signal distortion so that send signal light source led input before
Identical waveform is all kept with after light source led output.
In the embodiment of the present invention, the emulation platform that can also build a visible light DCO-OFDM system implements the present invention
The μ law that example provides is verified.Wherein, the simulation parameter used are as follows: DCO-OFDM sub-carrier number N is 128, the DCO- of input
OFDM symbol number is 10000, using 4QAM modulation system.
Fig. 4 is imitative for DCO-OFDM signal complementary cumulative distribution function (CCDF)/PAPR provided in an embodiment of the present invention
True curve.Emulation is directed to visible light DCO-OFDM system multi-carrier DCO-OFDM signal, and wherein sub-carrier number N=128, is adopted
It is modulated with 4QAM.Fig. 4 compares the peak-to-average power ratios (PAPR) of two kinds of system signals in showing, is primal system respectively, that is, does not have
Using the DCO-OFDM system of μ law provided in an embodiment of the present invention, and μ law provided in an embodiment of the present invention is used
DCO-OFDM system.Abscissa indicates the threshold value of PAPR, unit dB in Fig. 4, and ordinate indicates that input signal PAPR is more than
The probability of a certain threshold value, i.e. CCDF.Referring to Fig. 4 it is found that μ law provided in an embodiment of the present invention can significantly reduce DCO-
The PAPR of ofdm system.
Fig. 5 is to input to the DCO-OFDM signal waveform that LED and LED is exported shown in the embodiment of the present invention to compare figure.
Distinct methods have been respectively compared in Fig. 5 to the eradicating efficacy of LED non-linear effects, original signal and tradition μ rule (original μ rule) letter
Number all by the nonlinear influence of LED, it is equivalent to and experienced expendable clipping.And it uses the embodiment of the present invention and provides
μ law signal not by the nonlinear influence of LED, undergo the predistortion of μ law provided in an embodiment of the present invention to compress
It completely transmits and comes out out of LED linear region afterwards.Referring to Fig. 5 it is found that μ law provided in an embodiment of the present invention can significantly disappear
Except light source led non-linear effects, the features such as signal waveform amplitude are not changed before and after light source led output.
Fig. 6 is the visible light communication DCO-OFDM error rate of system emulation provided in an embodiment of the present invention based on algorithms of different
Curve.Abscissa indicates that signal-to-noise ratio, ordinate indicate the signal error rate under different signal-to-noise ratio in Fig. 6.Referring to Fig. 6 it is found that phase
Than coming in the original DCO-OFDM signal without any DCO-OFDM signal for eliminating LED Nonlinear Processing and experience tradition μ rule
It says, undergoes the bit error rate (Bit Error Rate, BER) of μ law provided in an embodiment of the present invention compared with the above two, have significant
It reduces, when signal-to-noise ratio (Signal Noise Ratio, SNR) is 25dB, undergoes the mistake of μ law provided in an embodiment of the present invention
Code rate can reach 10-5Below.
To sum up, through experiment it is found that compared with the scheme for not using μ law provided in an embodiment of the present invention, using the present invention
The μ law that embodiment provides can not only reduce the peak-to-average power ratio of DCO-OFDM system, moreover it is possible to effectively inhibit visible light DCO-
The bring signal distortion of LED nonlinear characteristic influences in ofdm system, significantly reduces the error code of visible light DCO-OFDM system
Rate, thus the whole performance for promoting DCO-OFDM system.
Embodiment two
The present invention also provides a kind of specific embodiment parties of the nonlinear μ rule system of reduction visible light communication system light source led
Formula, since the nonlinear μ rule system of reduction visible light communication system light source led provided by the invention and aforementioned reduction visible light are logical
Believe that the specific embodiment of the nonlinear μ rule method of system source LED is corresponding, the reduction visible light communication system light source led
Nonlinear μ rule system can realize mesh of the invention by executing the process step in above method specific embodiment
, therefore the explanation in the nonlinear μ rule method specific embodiment of above-mentioned reduction visible light communication system light source led,
It is also applied for the specific embodiment of the nonlinear μ rule system of reduction visible light communication system light source led provided by the invention,
It will not be described in great detail in present invention specific embodiment below.
Referring to shown in Fig. 7, the embodiment of the present invention also provides a kind of reduction visible light communication system light source led nonlinear μ
Rule system, comprising:
Module 11 is obtained, for obtaining signal to be sent in transmitting terminal；
Compression module 12, for the signal to be sent of acquisition carry out after μ rule log-compressed with preset pre- mistake
True coefficient is multiplied, and obtains μ rule compressed signal；
Sending module 13, for sending μ rule compressed signal.
The nonlinear μ of reduction visible light communication system light source led described in the embodiment of the present invention restrains system, in transmitting terminal,
μ rule log-compressed processing is carried out to the signal to be sent of acquisition, reduces the peak-to-average power ratio of signal to be sent, and by log-compressed
Signal afterwards is multiplied with preset pre-distortion coefficients, obtains μ rule compressed signal, realizes at the predistortion compression of signal to be sent
Reason can be avoided the nonlinear distortion effect of light source led in visible light communication system, then the obtained μ restrained compressed signal
It sends.In this way, non-linear reduction processing is done from signal to be sent itself, to guarantee that signal to be sent is linear in light source led
It is normally exported in range, to eliminate signal distortion caused by LED nonlinear characteristic, improves the reliability of system.
In the specific embodiment of the nonlinear μ rule system of aforementioned reduction visible light communication system light source led, further
Ground, the acquisition module include:
Modulation unit carries out the original signal to be sent for obtaining original signal to be sent in transmitting terminal
Baseband modulation；
Converting unit, for the modulated signal after baseband modulation to be converted to parallel signal；
Converter unit obtains the multicarrier of multidiameter delay for carrying out inverse fast fourier transform to the parallel signal
Signal；
Generation unit plus cyclic prefix and carries out parallel serial conversion for the multi-carrier signal to the multidiameter delay, raw
At the signal to be sent.
In the specific embodiment of the nonlinear μ rule system of aforementioned reduction visible light communication system light source led, further
Ground, the μ rule compressed signal indicate are as follows:
Wherein, xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients,ILEDIndicate light source led saturation
Current threshold, Ix(n)Indicate the maximum current value of signal to be sent；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) is indicated
The signal to be sent obtained, Sgn<>indicate piecewise function.
In the specific embodiment of the nonlinear μ rule system of aforementioned reduction visible light communication system light source led, further
Ground, the system also includes:
Module is expanded, for exponential flareout transformation being carried out to the signal received, being converted by exponential flareout in receiving end
Signal afterwards indicates are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) signal that receiving end receives is indicated；xc(n) table
Show that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain pending
The number of delivering letters, Sgn<>indicate piecewise function；
Inverse transform module, for the transformed signal of the exponential flareout is successively executed go cyclic prefix, serial to parallel conversion,
Fast Fourier Transform (FFT), base band demodulating, parallel serial conversion operation, to recover the original signal of transmitting terminal transmission.
The above is a preferred embodiment of the present invention, it is noted that for those skilled in the art
For, without departing from the principles of the present invention, it can also make several improvements and retouch, these improvements and modifications
It should be regarded as protection scope of the present invention.
Claims (3)
1. a kind of nonlinear μ of reduction visible light communication system light source led restrains method characterized by comprising
In transmitting terminal, signal to be sent is obtained；
It is multiplied to after the signal progress μ rule log-compressed to be sent of acquisition with preset pre-distortion coefficients, obtains μ rule pressure
Contracting signal；
μ rule compressed signal is sent；
Wherein, described in transmitting terminal, obtaining signal to be sent includes:
In transmitting terminal, original signal to be sent is obtained, baseband modulation is carried out to the original signal to be sent；
Modulated signal after baseband modulation is converted into parallel signal；
Inverse fast fourier transform is carried out to the parallel signal, obtains the multi-carrier signal of multidiameter delay；
Plus cyclic prefix and parallel serial conversion is carried out to the multi-carrier signal of the multidiameter delay, generates the letter to be sent
Number；
Wherein, the μ rule compressed signal indicates are as follows:
Wherein, xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；x
(n) indicate that the signal to be sent obtained, Sgn<>indicate piecewise function；
Wherein, the method also includes:
In receiving end, exponential flareout transformation is carried out to the signal received, is indicated by the transformed signal of exponential flareout are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) signal that receiving end receives is indicated；xc(n) μ is indicated
Restrain compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain to be sent
Signal, Sgn<>indicate piecewise function；
Wherein, the pre-distortion coefficients indicate are as follows:
Wherein, ILEDIndicate light source led saturation current threshold value, Ix(n)Indicate the maximum current value of signal to be sent.
2. the nonlinear μ of reduction visible light communication system light source led according to claim 1 restrains method, which is characterized in that
It is described in receiving end, exponential flareout transformation is carried out to the signal received, later, further includes:
The transformed signal of the exponential flareout is successively executed and goes cyclic prefix, serial to parallel conversion, Fast Fourier Transform (FFT), base band
Demodulation, parallel serial conversion operation, to recover the original signal of transmitting terminal transmission.
3. a kind of nonlinear μ of reduction visible light communication system light source led restrains system characterized by comprising
Module is obtained, for obtaining signal to be sent in transmitting terminal；
Compression module, for the signal to be sent of acquisition carry out after μ rule log-compressed with preset pre-distortion coefficients
It is multiplied, obtains μ rule compressed signal；
Sending module, for sending μ rule compressed signal；
Wherein, the acquisition module includes:
Modulation unit carries out base band to the original signal to be sent for obtaining original signal to be sent in transmitting terminal
Modulation；
Converting unit, for the modulated signal after baseband modulation to be converted to parallel signal；
Converter unit obtains the multi-carrier signal of multidiameter delay for carrying out inverse fast fourier transform to the parallel signal；
Generation unit plus cyclic prefix and carries out parallel serial conversion for the multi-carrier signal to the multidiameter delay, generates institute
State signal to be sent；
Wherein, the μ rule compressed signal indicates are as follows:
Wherein, xc(n) indicate that μ restrains compressed signal；M indicates pre-distortion coefficients,ILEDIndicate light source led saturation current
Threshold value, Ix(n)Indicate the maximum current value of signal to be sent；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain
Signal to be sent, Sgn<>indicate piecewise function；
Wherein, the system also includes:
Module is expanded, it is transformed by exponential flareout for carrying out exponential flareout transformation to the signal received in receiving end
Signal indicates are as follows:
Wherein, ye(n) the transformed signal of exponential flareout is indicated；yc(n) signal that receiving end receives is indicated；xc(n) μ is indicated
Restrain compressed signal；M indicates pre-distortion coefficients；A indicates normalization constant；μ indicates that μ restrains coefficient；X (n) indicates to obtain to be sent
Signal, Sgn<>indicate piecewise function；
Inverse transform module, for the transformed signal of the exponential flareout is successively executed go cyclic prefix, serial to parallel conversion, quickly
Fourier transformation, base band demodulating, parallel serial conversion operation, to recover the original signal of transmitting terminal transmission.
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| CN109561043B (en) * | 2019-01-08 | 2020-12-22 | 桂林电子科技大学 | Mixed type peak-to-average power ratio suppression method in DCO-OFDM system |
| CN110048773B (en) * | 2019-03-15 | 2020-10-09 | 哈尔滨工业大学（深圳） | Visible light communication method, signal processing method, system and storage medium |
| CN115001576B (en) * | 2022-05-20 | 2023-08-15 | 复旦大学 | micro-LED predistortion method and system based on visible light communication system, storage medium and intelligent terminal |
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| CN102624664A (en) * | 2011-01-10 | 2012-08-01 | 中兴通讯(美国)公司 | Method and system for optical orthogonal frequency division multiplexing with hadamard transform combined with companding transform |
| CN103825855A (en) * | 2013-12-04 | 2014-05-28 | 北京科技大学 | Method reducing peak average power ratio in OFDM system based on amplitude limiting technology |
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| CN1588938A (en) * | 2004-09-16 | 2005-03-02 | 西安电子科技大学 | OFDM communication system and method for reducing peak uniform power tatio |
| CN102624664A (en) * | 2011-01-10 | 2012-08-01 | 中兴通讯(美国)公司 | Method and system for optical orthogonal frequency division multiplexing with hadamard transform combined with companding transform |
| CN103825855A (en) * | 2013-12-04 | 2014-05-28 | 北京科技大学 | Method reducing peak average power ratio in OFDM system based on amplitude limiting technology |
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