CN102394723A - White-light LED modulation method combined with asymmetric Turbo coding - Google Patents

Abstract

The invention aims to provide a white-light LED modulation method combined with asymmetric Turbo coding. The method comprises the following steps: binary random signals are generated and subjected to asymmetric Turbo coding, and the coded sequence is subjected to 16QAM (Queued Access Method) modulation at first and then discrete Fourier transform; the transformed data is transformed to the time domain through inverse discrete Fourier transform after being subjected to local mapping and then transformed to the time domain and added with cyclic prefix; the signals are subjected to digital-to-analog conversion and sent to a white-light LED wireless optical channel; the received signals are subjected to analog-digital conversion and the cyclic prefix is removed; the signals are subjected to discrete Fourier transform and then single-carrier de-mapping; and the signals receiving the above treatment is subjected to inverse discrete Fourier transform, then 16 QAM demodulation and at last asymmetric Turbo decoding. The white-light LED modulation method provided by the invention can strike an average of the error ratio within the whole signal-to-noise ratio range of the system, and lowers the peak power rate of the system.

Description

White light LEDs modulator approach in conjunction with asymmetric Turbo coding

Technical field

What the present invention relates to is a kind of modulator approach of communication technical field.

Background technology

At present, to the research based on the visible light communication system of white light LEDs mainly concentrate on light source and layout thereof, optimal LED lamp number, modulating/demodulating and encoding and decoding technique, overcome intersymbol interference and these several aspects of multipath effect.Research is the white light LEDs communication system that has combined the OFDM technology the most widely, though utilize the OFDM technology to have to overcome intersymbol interference, suppress multipath effect, improve the advantage of the availability of frequency spectrum.But its peak power ratio and the error rate are high, and complex equipments.

Summary of the invention

The object of the present invention is to provide the white light LEDs modulator approach that can reduce peak power ratio and on the basis of existing coded system, improve the asymmetric Turbo coding of combination of the error rate.

The objective of the invention is to realize like this:

The present invention combines the white light LEDs modulator approach of asymmetric Turbo coding, it is characterized in that:

(1) generate L binary system signal u to be sent at random, it is v that signal u to be sent is sent into first constraint length, and generator polynomial is g ₁=[A B] (encode, simultaneously as the output x of system by the component coder of A ≠ B) _SDirectly deliver to and carry out serial/parallel transducer, it is v ' that while u sends into second constraint length through the interleaved sequence u ' behind the random interleaver, and generator polynomial is g ₂=[C D] component coder (C=D), the verification sequence u that then two component coders is exported ₁And u ₂Through the output x behind the residual matrix _pWith the output x of system _STogether at the codeword sequence c that through generation code check behind the parallel/serial transducer is 1/3;

(2) the sequence c after will encoding carries out the 16QAM modulation, and makes the discrete Fourier transform operation transform behind the plural number that will generate to frequency domain;

(3) data after frequency domain is with conversion carry out returning time domain and adding the Cyclic Prefix that length is L ' through discrete fourier inverse transformation operation transform after the local mapping;

The digital signal that (4) will add Cyclic Prefix converts analog signal into, sends into white light LEDs wireless optical channel then;

The analog signal conversion that contains noise that (5) will receive is digital signal and removes Cyclic Prefix;

(6) signal is transformed to frequency domain through discrete Fourier transform, and carry out the mapping of separating of local mapping;

(7) signal is made the discrete fourier inverse transformation, return to time domain, and sequence of complex numbers is done the 16QAM demodulation, be reduced to binary transmission signal u;

(8) utilize the method for max log posterior probability binary sequence to be done the decoding of asymmetric Turbo code.

The present invention can also comprise:

1, described white light LEDs wireless optical Channel Models can be expressed as following form:

wherein y (t) be the reception signal after t passes through white light LEDs wireless optical channel constantly; X (t) is that t transmits through what generate behind the D/A switch constantly; R is the sensitivity of receiver; Be about to the conversion efficiency that light signal converts the signal of telecommunication into; H (t) is the impulse response of the white light LEDs wireless optical channel under the line-of-sight channel situation; Convolution algorithm is carried out in symbol

expression, and n (t) is the additive white Gaussian noise with the x that transmits (t) equal in length;

The radiation intensity of the light signal of emission is designated as R (φ),

φ ∈ [pi/2, pi/2], P _SThe angle of the light that the power of expression signal transmitter, φ are represented to launch, n representes the modulus of radiant matter, the gross power of this model etching system emission when t does

N _tBe the number of rays that t arrives receiver constantly, p _i(t) be in the t power of i ray constantly, the gross power of P (t) expression t moment transmitter;

The impulse response of channel can be write as following form: $h(t;R)\≈\frac{n+1}{2\mathrm{\π}}{\mathrm{Cos}}^n\left(\mathrm{\ψ}\right)\mathrm{D\Ω\; Rect}\left(\frac{\mathrm{\θ}}{\mathrm{FOV}}\right),$ Wherein R representes the distance between transmitter and the receiver, h (t; Channel impulse response when R) the expression t moment, distance was R, Angle θ is

With (r _S-r _R) between an angle,

Refer to the normal line vector of receiver, r _SAnd r _RBe respectively to arrive the distance of reflecting surface and receive the distance that light arrives reflecting surface, can obtain by computes through emission light:

Angle ψ is

With (r _R-r _S) between an angle, wherein

Refer to the normal line vector of transmitter, can obtain by computes:

N is the radiant matter modulus of common Lambert's model, A _RBe the receiving area of receiver, FOV is an angle of visibility, in the formula

Be rectangular function, be defined as following form: $\mathrm{Rect}\left(x\right)=\left\{\begin{array}{c}1,\left|x\right|\≤1\\ 0,\left|x\right|>0\end{array}\right.,$ X wherein is an independent variable, promptly $x=\frac{\mathrm{\θ}}{\mathrm{FOV}}.$

Advantage of the present invention is: the present invention has utilized asymmetric Turbo coding techniques, its system's error rate in whole signal to noise ratio scope of can compromising; The SC-FDMA modulation technique has been applied in the white light LEDs communication system, has reduced the peak power ratio of system.

Description of drawings

Fig. 1 is a flow chart of the present invention;

Fig. 2 is the coding structure block diagram of asymmetric Turbo code;

Fig. 3 is the sketch map of single carrier mapping mode;

Fig. 4 is lambert's radiation model;

Fig. 5 is the channel model of white light communication;

Fig. 6 is line-of-sight channel impulse response;

Fig. 7 is the Turbo coding of symmetry and the ber curve of asymmetrical Turbo coding.

Embodiment

For example the present invention is done description in more detail below in conjunction with accompanying drawing:

In conjunction with Fig. 1～7, the white light LEDs modulator approach in conjunction with asymmetric Turbo coding may further comprise the steps:

(1) generate L binary system signal u to be sent at random, it is v that signal u to be sent is sent into first constraint length, and generator polynomial is g ₁=[A B] (encode, simultaneously as the output x of system by the component coder of A ≠ B) _SDirectly deliver to and carry out serial/parallel transducer, it is v ' that while u sends into second constraint length through the interleaved sequence u ' behind the random interleaver, and generator polynomial is g ₂=[C D] component coder (C=D), the verification sequence u that then two component coders is exported ₁And u ₂Through the output x behind the residual matrix _pWith the output x of system _STogether at the codeword sequence c that through generation code check behind the parallel/serial transducer is 1/3;

(2) the sequence c after will encoding carries out the 16QAM modulation, and makes the discrete Fourier transform operation transform behind the plural number that will generate to frequency domain;

(3) data after frequency domain is with conversion carry out returning time domain and adding the Cyclic Prefix that length is L ' through discrete fourier inverse transformation operation transform after the local mapping;

The digital signal that (4) will add Cyclic Prefix converts analog signal into, sends into white light LEDs wireless optical channel then;

The analog signal conversion that contains noise that (5) will receive is digital signal and removes Cyclic Prefix;

(6) signal is transformed to frequency domain through discrete Fourier transform, and carry out the mapping of separating of local mapping;

(7) signal is made the discrete fourier inverse transformation, return to time domain, and sequence of complex numbers is done the 16QAM demodulation, be reduced to binary transmission signal u;

(8) utilize the method for max log posterior probability binary sequence to be done the decoding of asymmetric Turbo code.

Described white light LEDs wireless optical Channel Models can be expressed as following form:

wherein y (t) be the reception signal after t passes through white light LEDs wireless optical channel constantly; X (t) is that t transmits through what generate behind the D/A switch constantly; R is the sensitivity of receiver; Be about to the conversion efficiency that light signal converts the signal of telecommunication into; H (t) is the impulse response of the white light LEDs wireless optical channel under the line-of-sight channel situation; Convolution algorithm is carried out in symbol

expression, and n (t) is the additive white Gaussian noise with the x that transmits (t) equal in length;

The radiation intensity of the light signal of emission is designated as R (φ),

φ ∈ [pi/2, pi/2], P _SThe angle of the light that the power of expression signal transmitter, φ are represented to launch, n representes the modulus of radiant matter, the gross power of this model etching system emission when t does

N _tBe the number of rays that t arrives receiver constantly, p _i(t) be in the t power of i ray constantly, the gross power of P (t) expression t moment transmitter;

The impulse response of channel can be write as following form: $h(t;R)\≈\frac{n+1}{2\mathrm{\π}}{\mathrm{Cos}}^n\left(\mathrm{\ψ}\right)\mathrm{D\Ω\; Rect}\left(\frac{\mathrm{\θ}}{\mathrm{FOV}}\right),$ Wherein R representes the distance between transmitter and the receiver, h (t; Channel impulse response when R) the expression t moment, distance was R,

Angle θ is

With (r _S-r _R) between an angle, Refer to the normal line vector of receiver, r _SAnd r _RBe respectively to arrive the distance of reflecting surface and receive the distance that light arrives reflecting surface, can obtain by computes through emission light:

Angle ψ is

With (r _R-r _S) between an angle, wherein Refer to the normal line vector of transmitter, can obtain by computes: N is the radiant matter modulus of common Lambert's model, A _RBe the receiving area of receiver, FOV is an angle of visibility, in the formula

Be rectangular function, be defined as following form: $\mathrm{Rect}\left(x\right)=\left\{\begin{array}{c}1,\left|x\right|\≤1\\ 0,\left|x\right|>0\end{array}\right.,$ X wherein is an independent variable, promptly

Native system is when having adopted the SC-FDMA modulation technique, and in conjunction with asymmetrical Turbo coding method, the general structure block diagram of its system is as shown in Figure 1.The binary sequence that generates is sent into asymmetric Turbo coding wherein; And then the signal after will encoding is input in the SC-FDMA system; Through optical channel, the optical channel here refers to white light LEDs wireless optical channel, and being in harmonious proportion encodes exports original transmission signal through separating accordingly then.Below with specific explanations each step wherein.

Fig. 2 is the coding block diagram of asymmetric Turbo code, generates 256 binary system signal u to be sent at random, and 256 random numbers are here easyly got arbitrarily in order to calculate, and it is 3 that signal u to be sent is sent into first constraint length, and generator polynomial is g ₁=[7 5] component coder is encoded, simultaneously as the output x of system _SDirectly deliver to and carry out serial/parallel transducer, it is 3 that while u sends into second constraint length through the interleaved sequence u ' behind the random interleaver, and generator polynomial is g ₂=[5 5] component coder, the verification sequence u that then two component coders is exported ₁And u ₂Through the output x behind the residual matrix _pWith the output x of system _STogether at the codeword sequence c that through generation code check behind the parallel/serial transducer is 1/3.Codeword sequence c length behind the coding is 768, after carrying out 16QAM modulation, makes the discrete Fourier transform operation transform to frequency domain after generating length and be 192 plural number.What adopt at frequency domain is the local mapping mode, and as shown in Figure 3, the subcarrier that among the figure each user is distributed is designated as x _N, the N here represents the N number of sub-carrier, supposes that each user is divided into to join N=0, and 1,2,3, totally 4 number of sub-carrier are used for the transmission of data; X _KExpression is through the subcarrier of frequency domain after the discrete Fourier transform, and the K here represents the subcarrier of K frequency domain, K=0,1,2,3; User's sum is designated as l; Suppose that total l=3 user carries out the transmission of signal, in the figure after the mapping, every continuous 4 number of sub-carrier are represented user's information transmitted; Then be designated as M, M=l*N=3*4=12 through the total number of subcarriers in local mapping back.The parameter here is easy and choose arbitrarily in order to carry out emulation, under the actual conditions, as long as satisfy relational expression M=l*N.Then under the local distribution condition, the data of one of them user's transmission directly continuous being mapped on the four adjacent number of sub-carrier are transmitted.Returning time domain through discrete fourier inverse transformation operation transform at last and adding length is 18 Cyclic Prefix, and through generating the x (t) that transmits behind the D/A switch, x (t) expression t transmitting constantly sends to x (t) in the white light LEDs wireless optical channel and transmit.

White light LEDs wireless optical Channel Models can be expressed as following form:

wherein y (t) be the reception signal after t passes through white light LEDs wireless optical channel constantly; X (t) is that t transmits through what generate behind the D/A switch constantly; R is the sensitivity of receiver; Be about to the conversion efficiency that light signal converts the signal of telecommunication into; Usually getting r=1 is to choose according to the actual value of the clever sensitivity of existing actual reception; H (t) is the impulse response of the white light LEDs wireless optical channel under the line-of-sight channel situation; Convolution algorithm is carried out in symbol expression, and n (t) is the additive white Gaussian noise with the x that transmits (t) equal in length.

The radiation intensity of light signal of emission is designated as R (φ), and it is meant the power of the machine of penetrating with a certain fixing unit angular emission bright dipping, uses lambert's radiation model representation as shown in Figure 4 usually, and its mathematical expression form is:

φ ∈ [pi/2, pi/2], the P here _SThe angle of the light that the power of expression signal transmitter, φ are represented to launch, n representes the modulus of radiant matter, it is confirmed that by the emission angle of transmitter along with the increase of emission angle, modulus also increases thereupon.Coefficient wherein

Be to be P in order to make R (φ) can cover whole transmitting power _SThe radiating surface of dome-type, the radiant matter modulus of common Lambert's model is got n=1 usually.The gross power of this model etching system emission when t is: Here N _tBe the number of rays that t arrives receiver constantly, p _i(t) be in the t power of i ray constantly, the gross power of P (t) expression t moment transmitter.

Fig. 5 is white light Channel Models figure, and the impulse response of channel can be similar to is write as following form: $h(t;R)\≈\frac{n+1}{2\mathrm{\π}}{\mathrm{Cos}}^n\left(\mathrm{\ψ}\right)\mathrm{D\Ω\; Rect}\left(\frac{\mathrm{\θ}}{\mathrm{FOV}}\right),$ Wherein R representes the distance between transmitter and the receiver, h (t; Channel impulse response when R) the expression t moment, distance was R,

Angle θ is

With (r _S-r _R) between an angle, wherein

Refer to the normal line vector of receiver, r _SAnd r _RBe respectively to arrive the distance of reflecting surface and receive the distance that light arrives reflecting surface, can obtain by computes through emission light:

Angle ψ is With (r _R-r _S) between an angle, wherein

Refer to the normal line vector of transmitter, can obtain by computes:

N is that the radiant matter modulus of common Lambert's model is got n=1 usually.A _RBe the receiving area of receiver, get A _R=1cm ², angle of visibility FOV=60 °.In the formula

Be rectangular function, be defined as following form: $\mathrm{Rect}\left(x\right)=\left\{\begin{array}{c}1,\left|x\right|\≤1\\ 0,\left|x\right|>0\end{array}\right.,$ X wherein is an independent variable, promptly

Fig. 6 gets parameter θ=30 °, ψ=30 °, FOV=60 °, A _R=1cm ², the channel impulse response that obtains through emulation during R=1m.Under actual conditions, these parameters are to choose according to the practical layout of white light array and transmitter and receiver.

Fig. 7 contrasts the Turbo coding of symmetry with the ber curve that asymmetrical Turbo encodes; As can be seen from the figure; Asymmetrical Turbo coded system signal to noise ratio less than 5 condition under, its error rate of system curve is in the centre position of two asymmetric encoding curves; Signal to noise ratio greater than 10 condition under; Its error rate of system curve still is in the centre position of two asymmetric encoding curves, and this explains that the error rate that asymmetric Turbo coded system can make system compromises the performance of the Turbo coding of symmetry in whole signal to noise ratio scope.

Claims (2)

1. combine the white light LEDs modulator approach of asymmetric Turbo coding, it is characterized in that:

(1) generate L binary system signal u to be sent at random, it is v that signal u to be sent is sent into first constraint length, and generator polynomial is g ₁=[A B] (encode, simultaneously as the output x of system by the component coder of A ≠ B) _SDirectly deliver to and carry out serial/parallel transducer, it is v ' that while u sends into second constraint length through the interleaved sequence u ' behind the random interleaver, and generator polynomial is g ₂=[C D] component coder (C=D), the verification sequence u that then two component coders is exported ₁And u ₂Through the output x behind the residual matrix _pExport xS at the codeword sequence c that through generation code check behind the parallel/serial transducer is 1/3 with system;

(2) the sequence c after will encoding carries out the 16QAM modulation, and makes the discrete Fourier transform operation transform behind the plural number that will generate to frequency domain;

(3) data after frequency domain is with conversion carry out returning time domain and adding the Cyclic Prefix that length is L ' through discrete fourier inverse transformation operation transform after the local mapping;

The digital signal that (4) will add Cyclic Prefix converts analog signal into, sends into white light LEDs wireless optical channel then;

The analog signal conversion that contains noise that (5) will receive is digital signal and removes Cyclic Prefix;

(6) signal is transformed to frequency domain through discrete Fourier transform, and carry out the mapping of separating of local mapping;

(7) signal is made the discrete fourier inverse transformation, return to time domain, and sequence of complex numbers is done the 16QAM demodulation, be reduced to binary transmission signal u;

(8) utilize the method for max log posterior probability binary sequence to be done the decoding of asymmetric Turbo code.

2. the white light LEDs modulator approach of the asymmetric Turbo coding of combination according to claim 1; It is characterized in that: described white light LEDs wireless optical Channel Models can be expressed as following form:

wherein y (t) be the reception signal after t passes through white light LEDs wireless optical channel constantly; X (t) is that t transmits through what generate behind the D/A switch constantly; R is the sensitivity of receiver; Be about to the conversion efficiency that light signal converts the signal of telecommunication into; H (t) is the impulse response of the white light LEDs wireless optical channel under the line-of-sight channel situation; Convolution algorithm is carried out in symbol

expression, and n (t) is the additive white Gaussian noise with the x that transmits (t) equal in length;

The radiation intensity of the light signal of emission is designated as R (φ),

φ ∈ [pi/2, pi/2], P _SThe angle of the light that the power of expression signal transmitter, φ are represented to launch, n representes the modulus of radiant matter, the gross power of this model etching system emission when t does N _tBe the number of rays that t arrives receiver constantly, p _i(t) be in the t power of i ray constantly, the gross power of P (t) expression t moment transmitter;

The impulse response of channel can be write as following form: $h(t;R)\≈\frac{n+1}{2\mathrm{\π}}{\mathrm{Cos}}^n\left(\mathrm{\ψ}\right)\mathrm{D\Ω\; Rect}\left(\frac{\mathrm{\θ}}{\mathrm{FOV}}\right),$ Wherein R representes the distance between transmitter and the receiver, h (t; Channel impulse response when R) the expression t moment, distance was R, Angle θ is

With (r _S-r _R) between an angle,

Refer to the normal line vector of receiver, r _SAnd r _RBe respectively to arrive the distance of reflecting surface and receive the distance that light arrives reflecting surface, can obtain by computes through emission light:

Angle ψ is

With (r _R-r _S) between an angle, wherein

Refer to the normal line vector of transmitter, can obtain by computes: N is the radiant matter modulus of common Lambert's model, A _RBe the receiving area of receiver, FOV is an angle of visibility, in the formula

Be rectangular function, be defined as following form: $\mathrm{Rect}\left(x\right)=\left\{\begin{array}{c}1,\left|x\right|\≤1\\ 0,\left|x\right|>0\end{array}\right.,$ X wherein is an independent variable, promptly $x=\frac{\mathrm{\θ}}{\mathrm{FOV}}.$

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