CN104796195A - Visible light multi-carrier transmission method using multiplicative clipping - Google Patents

Abstract

The invention discloses a visible light multi-carrier transmission method using multiplicative clipping. Positive value signals in each set of symmetrical time domain signals are reserved according to the characteristics of PAM-DMT modulation signals, and zero setting is conducted on negative value signals. The maximum optical signal threshold value is set as eta c, and when the data bit is larger than eta c, clipping is conducted after the data bit is multiplied with a given constant alpha. Then, the signal values at symmetrical positions are changed into preset fixed signal values from 0 so that the symmetrical position can serve as mark bits. A system receiving end determines signal clipping positions and the mark bits through an MAP detection method, signal recovery is conducted according to the multiplicative clipping principle used by a sending end, and therefore the sending signal detection is completed. By means of the method, the PAPR of emitted light signals is effectively reduced through multiplicative clipping, the method is easy to achieve, the system energy utilization rate is increased while the PAPR is restrained, the requirements a system for the linear ranges of power amplifiers and light-emitting diodes, the nonlinear distortion of signals in the electric domain and the light domain is reduced, and the overall performance of the system is improved.

Description

A kind of visible ray multicarrier transmitting method adopting multiplicative slicing

Technical field

The present invention relates to a kind of visible ray multicarrier transmitting method adopting multiplicative slicing, belong to wireless light communication technology.

Background technology

The impact covered owing to not being subject to growing radio frequency, and enjoy a large amount of frequency spectrum resources, visible light communication has caused in field of wireless transmission of future generation and has paid close attention to widely.Because current optical communication system generally adopts intensity modulated/direct-detection (IM/DD), that is: the intensity of signal to light is modulated, and therefore will ensure that time-domain signal is arithmetic number.Binary system on off keying modulation (OOK) is although realize simple, and energy efficiency is very poor.In order to improve message transmission rate and the availability of frequency spectrum, simultaneously to anti-multipath fading, the discrete multitone techniques (DMT) derivative and next from OFDM (OFDM) is introduced.

In order to ensure the positive solid of time-domain signal, two the optical communication DMT schemes be widely adopted now are non-symmetrical clipping light-orthogonal frequency division multiplexi (ACO-OFDM) and direct current biasing light-orthogonal frequency division multiplexi (DCO-OFDM).The input frequency domain signal vector of the two all meets conjugate symmetry property, after inverse fast fourier transform (IFFT), just can obtain real number time-domain signal.In order to obtain non-negative time-domain signal, it is 0 that negative value is directly cut by the former, and the latter adds a direct current biasing on signal.In ACO-OFDM scheme, only have 1/4 subcarrier to be used to transmission of signal, the availability of frequency spectrum is very low, reduces capacity usage ratio; And in DCO-OFDM scheme, have 1/2 subcarrier to be used to transmission of signal, but added direct current biasing also reduces capacity usage ratio.

Also has a kind of scheme adopting pulse amplitude Discrete Multitone modulation (PAM-DMT).In the program, half subcarrier is used to the symbol passing through PAM modulation, and does not need direct current biasing.Frequency-region signal vector meets conjugation symmetry, therefore after IFFT conversion, obtains real number time-domain signal.Often pair of bipolarity time-domain signal amplitude is identical, and symbol is contrary, therefore cuts negative value time-domain signal for 0 can't reduce transmitted information.

Due to the superposition that ofdm signal is multiple sine wave, when group variable number acquires a certain degree, according to central-limit theorem, OFDM symbol waveform will be a Gaussian random process, its envelope extremely unstable.When the same phase time of data of IFFT input, its output will produce very large peak value, therefore can cause excessive peak-to-average force ratio (PAPR).

No matter be ACO-OFDM, DCO-OFDM, or PAM-DMT, all there is the problem that PAPR is too high.The too high requirement that not only can improve modulus and the digital to analog converter range of linearity of PAPR, and signal can be made easily to enter inelastic region by during circuit, thus cause distorted signals, great impact is produced on entire system performance.In photosystem, not only power amplifier has non-linear, and light-emitting diode (LED) also has non-linear, and therefore the too high nonlinear effect caused of PAPR is more serious.Therefore, the PAPR reducing visible light communication system is necessary very much.

Summary of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides a kind of visible ray multicarrier transmitting method adopting multiplicative slicing.According to the modulation signal feature of PAM-DMT, on time-domain signal symmetric sampling position, signal amplitude is identical, and symbol is contrary.Often will organize in symmetrical temporal signal and retain on the occasion of signal, the zero setting of negative value signal.Setting maximum light signal threshold values is η _c, when data bit is greater than η _ctime, data bit is multiplied by given constant α and carries out slicing, then, change symmetric position signal value into fixed signal value flag as marker bit by 0, thus reach the effect reducing PAPR.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

A kind of visible ray multicarrier transmitting method adopting multiplicative slicing, it is characterized in that: often pair of time-domain signal of PAM-DMT (pulse amplitude-Discrete Multitone modulation) system is after asymmetric slicing, wherein a time-domain signal is data bit, and another one time-domain signal is 0; Data bit is valid data, when the valid data value of data bit is greater than the threshold value η of the maximum permission of systems radiate signal _ctime, another one time-domain signal doubly, is changed to fixed value flag by 0 by the α by data bit time-domain signal slicing being former time-domain signal value simultaneously, thus reaches the effect reducing PAPR (peak-to-average force ratio); Wherein α is multiplicative clipping factor, for be greater than 0 and be less than 1 fixed value, such as α=1/2, flag represents the marking signal of mark multiplicative clipping operation.

Said method specifically comprises the steps:

(1) transmitting terminal is according to PAM-DMT mode, adopts individual sub-carrier transmission, through the complex frequency domain symbolic vector of ovennodulation, is specially: the binary signal that information source produces obtains through PAM (pulse amplitude modulation) individual frequency domain symbol, using these frequency domain symbols as the imaginary part of individual complex frequency domain symbol, sets to 0 the real part of complex frequency domain symbol, obtains complex frequency domain symbolic vector wherein N is PAM-DMT system subcarrier sum;

(2) in PAM-DMT system, carry out visible ray modulation to obtain real number time-domain signal, frequency-region signal maps demand fulfillment conjugate symmetry property, namely needs to carry out frequency domain symbol mapping according to formula below on sub-carriers:

Wherein, X [n] represents the frequency-region signal that the n-th subcarrier carries, and subscript * represents and gets conjugation;

(3) N point IFFT (inverse fast fourier transform) operation is carried out to frequency domain signal X [n], obtains time-domain signal x (k) as follows:

$x\left(k\right)=\frac{1}{\sqrt{N}}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}X\left[n\right]e^{j2\mathrm{\πkn}/N}$

Wherein, k represents the sampling instant position of time-domain symbol, and x (k) represents a kth time-domain signal;

(4), in the time-domain signal obtained in step (3), the numerical value often organizing symmetrical temporal signal value [x (k), x (N-k)] is identical, and symbol is contrary; Asymmetric negative value elimination is carried out to all time-domain signals, obtains nonnegative real number time-domain signal x _c(k); Removal process carries out according to following formula:

$x_c\left(k\right)=\left\{\begin{array}{cc}x\left(k\right),& x\left(k\right)\&GreaterEqual;0\\ 0,& x\left(k\right)<0\end{array}\right.$

Wherein, x _ck () is the kth time-domain signal after asymmetric negative value slicing;

(5) according to the non-linear domain definite threshold η of transmitting in PAM-DMT system with light-emitting diode (LED) _c, to time-domain signal x _c(k), (k=1,2 ..., N) and carry out multiplicative slicing: first, when data bit signal value is greater than η _ctime, this data bit signal value is multiplied by α and carries out slicing, and place marking signal value flag in symmetric position; Then, still η is greater than by after multiplicative slicing _cdata bit signal value be reduced to η _c; Obtain the kth group symmetric signal [x after multiplicative slicing thus _dc(k), x _dc(N-k)] as follows:

$[x_{\mathrm{dc}}\left(k\right),x_{\mathrm{dc}}(N-k)]=\left\{\begin{array}{ccc}[x_c\left(k\right),0],& x_c\left(k\right)\&le;{\mathrm{\&eta;}}_c,x_c(N-k)=0& \left(a\right)\\ [0,x_c(N-k)],& x_c\left(k\right)=0,x_c(N-k)\&le;{\mathrm{\&eta;}}_c& \left(b\right)\\ [\mathrm{\&alpha;}{x}_c\left(k\right),\mathrm{flag}],& {\mathrm{\&eta;}}_c<x_c\left(k\right)\&le;{\mathrm{\&eta;}}_c/\mathrm{\&alpha;},x_c(N-k)=0& \left(c\right)\\ [\mathrm{flag},\mathrm{\&alpha;}{x}_c(N-k)],& x_c\left(k\right)=0,{\mathrm{\&eta;}}_c<x_c(N-k)\&le;{\mathrm{\&eta;}}_c/\mathrm{\&alpha;}& \left(d\right)\\ [{\mathrm{\&eta;}}_c,\mathrm{flag}],& x_c\left(k\right)>{\mathrm{\&eta;}}_c/\mathrm{\&alpha;},x_c(N-k)=0& \left(e\right)\\ [\mathrm{flag},{\mathrm{\&eta;}}_c],& x_c\left(k\right)=0,x_c(N-k)>{\mathrm{\&eta;}}_c/\mathrm{\&alpha;}& \left(f\right)\end{array}\right.$

Wherein, flag gets fixed value 0.3 η _c;

(6) by the nonnegative real number time-domain signal x after slicing _dc=[x _dc(0), x _dc(1) ..., x _dc(N-1)] be sent to optical communication transmission module, adopt intensity modulated, convert the electrical signal to light intensity signal;

(7) at receiving terminal, light intensity signal is converted to time domain signal of telecommunication y by photodiode _dc=[y _dc(0), y _dc(1) ..., y _dc(N-1)], respectively for often organizing symmetric signal [y _dc(k), y _dc(N-k)] classical MAP (maximum a posteriori criterion) is adopted to carry out input, detected by MAP and estimate the multiplicative slicing type of this signal combination in step (5), namely the situation (a) in step (5) in multiplicative slicing formula, (b), (c), (d), (e), (f), recover the time-domain signal y through negative value slicing thus _c; Concrete recovery operation is as follows: when this group Received signal strength MAP is detected as situation (a) or (b), data are not done to change; When belonging to situation (c) or (d), data bit is divided by α, and symmetric position Received signal strength is marker bit, direct zero setting; When situation belongs to (e) or (f), data bit divided by α, symmetric position zero setting;

(8) y obtained in step (7) _cin, on the occasion of remaining unchanged, symmetric position places the identical and value that symbol is contrary of amplitude, obtains original time-domain signal detected value y, and carries out FFT (fast fourier transform), obtain frequency domain and receive vectorial Y;

(9) part carrying effective information in Y is got get the value of wherein imaginary part, obtained the binary data sent by PAM demodulation.

Beneficial effect: the present invention proposes a kind of low peak average ratio transmission of visible light scheme adopting multiplicative slicing method on asymmetric slicing PAM-DMT basis, there is following advantage: 1, make full use of visible light communication PAM-DMT technical characterstic, under the prerequisite as far as possible retaining original signal information, carry out the process of multiplicative slicing, reduce the peak-to-average force ratio of system; 2, do not need to transmit extra side information, do not waste frequency resource and can effectively reduce system peak-to-average power ratio; 3, after multiplicative slicing, the gross energy of time-domain signal is reduced, improve the capacity usage ratio 4 of system, low PAPR can reduce the requirement of system to power amplifier and LED linear scope, 5, reduce PAPR and can reduce the nonlinear distortion caused due to power amplifier and LED nonlinear characteristic, improve the overall performance of system.

Accompanying drawing explanation

Fig. 1 is the system block diagram adopting the low peak average ratio visible ray multicarrier transmitting method of multiplicative slicing method on asymmetric slicing PAM-DMT basis that the present invention proposes;

Fig. 2 is the transmitting terminal signal transacting schematic diagram of the low peak average ratio visible ray multicarrier transmitting method adopting multiplicative slicing; Wherein 2 (a) is for meeting the imaginary values of the frequency-region signal of conjugation symmetry in PAM-DMT optical transmission system; 2 (b) is the time-domain signal through IFFT change; 2 (c) is the time-domain signal after negative value slicing; 2 (d) is the time-domain signal after multiplicative slicing, and wherein α gets 1/2;

Fig. 3 is the complementary accumulated probability scatter chart of PAPR of the present invention and original PAM-DMT system;

Fig. 4 is bit error rate-signal to noise ratio (BER-SNR) the Performance comparision figure of the present invention and direct slicing PAM-DMT.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

A kind of multiplicative slicing transmission plan for pulse amplitude-Discrete Multitone modulation (PAM-DMT) visible ray multi-carrier communications systems: according to the modulation signal feature of PAM-DMT, on time-domain signal symmetric sampling position, signal amplitude is identical, and symbol is contrary.Often will organize in symmetrical temporal signal and retain on the occasion of signal, the zero setting of negative value signal.Setting maximum light signal threshold values is η _c, when data bit is greater than η _ctime, data bit is multiplied by given constant α and carries out slicing, then, change symmetric position signal value into fixed signal value flag as marker bit by 0.The method effectively reduces the peak-to-average force ratio (PAPR) of utilizing emitted light signal by multiplicative slicing, method realizes simple, system capacity utilance is improve while suppression PAPR, reduce the requirement of system to power amplifier and light-emitting diode (LED) range of linearity, decrease the nonlinear distortion of signal in electricity, area of light, improve the overall performance of system.

As shown in Figure 1, be real-time block diagram of the present invention, detailed process is as follows:

(1) transmitting terminal is according to PAM-DMT mode, adopts individual sub-carrier transmission, through the complex frequency domain symbolic vector of ovennodulation, is specially: the binary signal that information source produces obtains through PAM (pulse amplitude modulation) individual frequency domain symbol, using these frequency domain symbols as the imaginary part of individual complex frequency domain symbol, sets to 0 the real part of complex frequency domain symbol, obtains complex frequency domain symbolic vector wherein N is PAM-DMT system subcarrier sum;

(2) in PAM-DMT system, carry out visible ray modulation to obtain real number time-domain signal, frequency-region signal maps demand fulfillment conjugate symmetry property, namely needs to carry out frequency domain symbol mapping according to formula below on sub-carriers:

Wherein, X [n] represents the frequency-region signal that the n-th subcarrier carries, and subscript * represents and gets conjugation;

(3) N point IFFT (inverse fast fourier transform) operation is carried out to frequency domain signal X [n], obtains time-domain signal x (k) as follows:

$x\left(k\right)=\frac{1}{\sqrt{N}}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X\left[n\right]e^{j2\mathrm{\&pi;kn}/N}$

Wherein, k represents the sampling instant position of time-domain symbol, and x (k) represents a kth time-domain signal;

(4), in the time-domain signal obtained in step (3), the numerical value often organizing symmetrical temporal signal value [x (k), x (N-k)] is identical, and symbol is contrary; Asymmetric negative value elimination is carried out to all time-domain signals, obtains nonnegative real number time-domain signal x _c(k); Removal process carries out according to following formula:

$x_c\left(k\right)=\left\{\begin{array}{cc}x\left(k\right),& x\left(k\right)\&GreaterEqual;0\\ 0,& x\left(k\right)<0\end{array}\right.$

Wherein, x _ck () is the kth time-domain signal after asymmetric negative value slicing;

(5) according to the non-linear domain definite threshold η of transmitting in PAM-DMT system with light-emitting diode (LED) _c, to time-domain signal x _c(k), (k=1,2 ..., N) and carry out multiplicative slicing: first, when data bit signal value is greater than η _ctime, this data bit signal value is multiplied by α and carries out slicing, and place marking signal value flag in symmetric position; Then, still η is greater than by after multiplicative slicing _cdata bit signal value be reduced to η _c; Obtain the kth group symmetric signal [x after multiplicative slicing thus _dc(k), x _dc(N-k)] as follows:

$[x_{\mathrm{dc}}\left(k\right),x_{\mathrm{dc}}(N-k)]=\left\{\begin{array}{ccc}[x_c\left(k\right),0],& x_c\left(k\right)\&le;{\mathrm{\&eta;}}_c,x_c(N-k)=0& \left(a\right)\\ [0,x_c(N-k)],& x_c\left(k\right)=0,x_c(N-k)\&le;{\mathrm{\&eta;}}_c& \left(b\right)\\ [\mathrm{\&alpha;}{x}_c\left(k\right),\mathrm{flag}],& {\mathrm{\&eta;}}_c<x_c\left(k\right)\&le;{\mathrm{\&eta;}}_c/\mathrm{\&alpha;},x_c(N-k)=0& \left(c\right)\\ [\mathrm{flag},\mathrm{\&alpha;}{x}_c(N-k)],& x_c\left(k\right)=0,{\mathrm{\&eta;}}_c<x_c(N-k)\&le;{\mathrm{\&eta;}}_c/\mathrm{\&alpha;}& \left(d\right)\\ [{\mathrm{\&eta;}}_c,\mathrm{flag}],& x_c\left(k\right)>{\mathrm{\&eta;}}_c/\mathrm{\&alpha;},x_c(N-k)=0& \left(e\right)\\ [\mathrm{flag},{\mathrm{\&eta;}}_c],& x_c\left(k\right)=0,x_c(N-k)>{\mathrm{\&eta;}}_c/\mathrm{\&alpha;}& \left(f\right)\end{array}\right.$

Wherein, flag gets fixed value 0.3 η _c;

(6) by the nonnegative real number time-domain signal x after slicing _dc=[x _dc(0), x _dc(1) ..., x _dc(N-1)] be sent to optical communication transmission module, adopt intensity modulated, convert the electrical signal to light intensity signal;

(7) at receiving terminal, light intensity signal is converted to time domain signal of telecommunication y by photodiode _dc=[y _dc(0), y _dc(1) ..., y _dc(N-1)], respectively for often organizing symmetric signal [y _dc(k), y _dc(N-k)] classical MAP (maximum a posteriori criterion) is adopted to carry out input, detected by MAP and estimate the multiplicative slicing type of this signal combination in step (5), namely the situation (a) in step (5) in multiplicative slicing formula, (b), (c), (d), (e), (f), recover the time-domain signal y through negative value slicing thus _c; Concrete recovery operation is as follows: when this group Received signal strength MAP is detected as situation (a) or (b), data are not done to change; When belonging to situation (c) or (d), data bit is divided by α, and symmetric position Received signal strength is marker bit, direct zero setting; When situation belongs to (e) or (f), data bit divided by α, symmetric position zero setting;

(8) y obtained in step (7) _cin, on the occasion of remaining unchanged, symmetric position places the identical and value that symbol is contrary of amplitude, obtains original time-domain signal detected value y, and carries out FFT (fast fourier transform), obtain frequency domain and receive vectorial Y;

(9) part carrying effective information in Y is got get the value of wherein imaginary part, obtained the binary data sent by PAM demodulation.

Below in conjunction with accompanying drawing, the present invention is made further instructions.

As shown in Figure 2, the imaginary values of the frequency-region signal of conjugation symmetry is met as shown in 2 (a); The time-domain signal obtained after IFFT change, as shown in 2 (b), meets x (k)=-x (N-k); Through the time-domain signal of negative value slicing as shown in 2 (c); 2 (d) is through the time-domain signal of multiplicative slicing, exceedes threshold values η _csignal be multiplied by α, and place a flag value as marking in the symmetric position being originally 0.Wherein α gets 1/2, flag and gets 0.3 η _c.

The PAPR complimentary cumulative distribution curve of the system after Fig. 3 gives original optical communication PAM-DMT system and uses the present invention.System all adopts 64-PAM to modulate, sub-carrier number N=256, thresholding η _c=8dB, marker bit constant flag=0.3 η _c, α=1/2.Adopt this method effectively can reduce the PAPR of system as can be observed from Figure, thus reduce the requirement to the range of linearity of the devices such as transmitting terminal power amplifier, LED, reduce the nonlinear distortion of signal in electricity, area of light, improve overall system receptivity.

Fig. 4 illustrates bit error rate of the present invention (BER) performance, adopts 64-PAM modulation, sub-carrier number N=256, thresholding η _cin=8dB, figure, more direct slicing PAM-DMT and bit error rate of the present invention are with the change of signal to noise ratio (SNR), and the present invention can significantly improve BER performance relative to direct slicing as can be observed from Figure.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (2)

1. adopt a visible ray multicarrier transmitting method for multiplicative slicing, it is characterized in that: often pair of time-domain signal of PAM-DMT system is after asymmetric slicing, and wherein a time-domain signal is data bit, and another one time-domain signal is 0; Data bit is valid data, when the valid data value of data bit is greater than the threshold value η of the maximum permission of systems radiate signal _ctime, another one time-domain signal doubly, is changed to fixed value flag by 0 by the α by data bit time-domain signal slicing being former time-domain signal value simultaneously, thus reaches the effect reducing PAPR; Wherein α is multiplicative clipping factor, for be greater than 0 and be less than 1 fixed value, flag represents the marking signal of mark multiplicative clipping operation.

2. the visible ray multicarrier transmitting method of employing multiplicative slicing according to claim 1, is characterized in that: specifically comprise the steps:

(1) transmitting terminal is according to PAM-DMT mode, adopts individual sub-carrier transmission, through the complex frequency domain symbolic vector of ovennodulation, is specially: the binary signal that information source produces obtains through PAM individual frequency domain symbol, using these frequency domain symbols as the imaginary part of individual complex frequency domain symbol, sets to 0 the real part of complex frequency domain symbol, obtains complex frequency domain symbolic vector wherein N is PAM-DMT system subcarrier sum;

(2) in PAM-DMT system, carry out visible ray modulation to obtain real number time-domain signal, frequency-region signal maps demand fulfillment conjugate symmetry property, namely needs to carry out frequency domain symbol mapping according to formula below on sub-carriers:

Wherein, X [n] represents the frequency-region signal that the n-th subcarrier carries, and subscript * represents and gets conjugation;

(3) carry out N point IFFT to frequency domain signal X [n] to operate, obtain time-domain signal x (k) as follows:

$x\left(k\right)=\frac{1}{\sqrt{N}}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X\left[n\right]e^{j2\mathrm{\&pi;kn}/N}$

Wherein, k represents the sampling instant position of time-domain symbol, and x (k) represents a kth time-domain signal;

(4), in the time-domain signal obtained in step (3), the numerical value often organizing symmetrical temporal signal value [x (k), x (N-k)] is identical, and symbol is contrary; Asymmetric negative value elimination is carried out to all time-domain signals, obtains nonnegative real number time-domain signal x _c(k); Removal process carries out according to following formula:

$x_c\left(k\right)=\left\{\begin{array}{cc}x\left(k\right),& x\left(k\right)\&GreaterEqual;0\\ 0,& x\left(k\right)<0\end{array}\right.$

Wherein, x _ck () is the kth time-domain signal after asymmetric negative value slicing;

(5) according to the non-linear domain definite threshold η of transmitting light-emitting diode in PAM-DMT system _c, to time-domain signal x _c(k), (k=1,2 ..., N) and carry out multiplicative slicing: first, when data bit signal value is greater than η _ctime, this data bit signal value is multiplied by α and carries out slicing, and place marking signal value flag in symmetric position; Then, still η is greater than by after multiplicative slicing _cdata bit signal value be reduced to η _c; Obtain the kth group symmetric signal [x after multiplicative slicing thus _dc(k), x _dc(N-k)] as follows:

$[x_{\mathrm{dc}}\left(k\right),x_{\mathrm{dc}}(N-1)]=\left\{\begin{array}{ccc}[x_c\left(k\right),0],& x_c\left(k\right)\&le;{\mathrm{\&eta;}}_c,x_c(N-k)=0& \left(a\right)\\ [0,x_c(N-k)],& x_c\left(k\right)=0,x_c(N-k)\&le;{\mathrm{\&eta;}}_c& \left(b\right)\\ [{\mathrm{\&alpha;x}}_c\left(k\right),\mathrm{flag}],& {\mathrm{\&eta;}}_c<x_c\left(k\right)\&le;{\mathrm{\&eta;}}_c/\mathrm{\&alpha;},x_c(N-k)=0& \left(c\right)\\ [\mathrm{flag},{\mathrm{\&alpha;x}}_c(N-k)],& x_c\left(k\right)=0,{\mathrm{\&eta;}}_c<x_c(N-k)\&le;{\mathrm{\&eta;}}_c/\mathrm{\&alpha;}& \left(d\right)\\ [{\mathrm{\&eta;}}_c,\mathrm{flag}],& x_c\left(k\right)>{\mathrm{\&eta;}}_c/\mathrm{\&alpha;},x_c(N-k)=0& \left(e\right)\\ [\mathrm{flag},{\mathrm{\&eta;}}_c],& x_c\left(k\right)=0,x_c(N-k)>{\mathrm{\&eta;}}_c/\mathrm{\&alpha;}& \left(f\right)\end{array}\right.$

Wherein, flag gets fixed value 0.3 η _c;

(6) by the nonnegative real number time-domain signal x after slicing _dc=[x _dc(0), x _dc(1) ..., x _dc(N-1)] be sent to optical communication transmission module, adopt intensity modulated, convert the electrical signal to light intensity signal;

(7) at receiving terminal, light intensity signal is converted to time domain signal of telecommunication y by photodiode _dc=[y _dc(0), y _dc(1) ..., y _dc(N-1)], respectively for often organizing symmetric signal [y _dc(k), y _dc(N-k)] classical MAP is adopted to carry out input, detected by MAP and estimate the multiplicative slicing type of this signal combination in step (5), namely the situation (a) in step (5) in multiplicative slicing formula, (b), (c), (d), (e), (f), recover the time-domain signal y through negative value slicing thus _c; Concrete recovery operation is as follows: when this group Received signal strength MAP is detected as situation (a) or (b), data are not done to change; When belonging to situation (c) or (d), data bit is divided by α, and symmetric position Received signal strength is marker bit, direct zero setting; When situation belongs to (e) or (f), data bit divided by α, symmetric position zero setting;

(8) y obtained in step (7) _cin, on the occasion of remaining unchanged, symmetric position places the identical and value that symbol is contrary of amplitude, obtains original time-domain signal detected value y, and carries out FFT, obtain frequency domain and receive vectorial Y;

(9) part carrying effective information in Y is got get the value of wherein imaginary part, obtained the binary data sent by PAM demodulation.