CN103248600B - The method for peak suppression that in a kind of ofdm system, multi signal represents - Google Patents

Abstract

The method for peak suppression that in ofdm system, multi signal represents, belongs to wireless communication technology field.First adopt U the phase sequence preset to be multiplied respectively with OFDM frequency-region signal, pass through after spectral aliasing point IFFT, generates U the time-domain alternative signals of times lack sampling; Then calculate cubic measure (Cubic Metric, the CM) value of U time-domain alternative signals, in U time-domain alternative signals, choose the phase sequence corresponding to time-domain alternative signals of the less M of CM value; Again the M a selected phase sequence is multiplied with OFDM frequency-region signal, by the IFFT of JN point, generates M time-domain alternative signals; Calculating finally by CM value, choosing the minimum alternative signal of CM value as transmitting.The present invention utilizes the thought of lack sampling to improve traditional SLM algorithm, and by simulating, verifying, the present invention can obtain good inhibition, and the complexity of whole process is reduced greatly.

Description

The method for peak suppression that in a kind of ofdm system, multi signal represents

Technical field

The invention belongs to wireless communication technology field, relate to OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) the baseband signal peak value suppression technology in system, the baseband signal peak value suppression technology of (Multiple signal presentation, MSR) is represented in particular to multi signal undistorted in ofdm system.

Background technology

Compared with single-carrier system, transmitting of ofdm communication system is carrier signal superposition on multiple subchannel, and the amplitude of the baseband signal of generation, by a very large scope fluctuation, has unsteadiness.General papr (Peak-to-Average Power Ratio, PAPR) weighs the peak value wave characteristic of ofdm signal.From existing research, the approach solving multicarrier peak value fluctuation problem has two: one to be the range of linearity being increased amplifier by linear technique, improve the efficiency of amplifier, but this fundamentally can not solve multi-carrier signal peak value problem, also very responsive to the Parameters variation of system signal; Two is carry out peak value to multicarrier baseband signal to suppress process.

Baseband signal peak value suppression technology can be divided into predistortion and undistorted two large classes.Undistorted technology, under the prerequisite not introducing distorted signals or additional noise, adopts the method for linear transformation, is reconstructed traditional ofdm signal, avoids the signal after processing to occur larger peak value.Undistorted method signal transmission performance loss is less, channel circumstance strong adaptability.

Undistorted baseband signal peak value suppression technology roughly comprises coding (Coding), preserved sub-carrier (Tone Reservation, TR) and multi signal and represents methods such as (Multiple signal presentation, MSR).Wherein the basic thought of MSR is: transmitting terminal generates the multiple alternative signal representing same group of subcarrier information by signal map, and therefrom searches for Optimal Signals for sending according to low peak average ratio criterion.These class methods can not change the transmitting power of signal, also do not have loss of spectral efficiency, are thus paid close attention to widely.

According to the difference of the mapping generating mode of alternative signal, MSR has diversified way of realization.Wherein, the mode based on phase rotating is extensively studied with its convenience realized.Choose for user (Selective Mapping, the SLM) method for peak suppression that in existing ofdm system, multi signal represents, employs U the phase sequence preset, is multiplied respectively with OFDM frequency-region signal, then by IFFT, generate U time-domain alternative signals.Calculating finally by PAPR, choosing the minimum alternative signal of PAPR as transmitting.For SLM method, the generation of each alternative signal needs an extra IFFT, and complexity is higher.

Summary of the invention

The present invention proposes the method for peak suppression that in a kind of ofdm system, multi signal represents, can realize the computation complexity basis to the baseband signal peak value suppression in ofdm system reduced in peak value process of inhibition.

Basic ideas of the present invention are: first adopt U the phase sequence preset to be multiplied respectively with OFDM frequency-region signal, pass through after spectral aliasing point IFFT(inverse fast Fourier transform), generate U the time-domain alternative signals of times lack sampling; Then calculate cubic measure (Cubic Metric, the CM) value of U time-domain alternative signals, in U time-domain alternative signals, choose the phase sequence corresponding to time-domain alternative signals of the less M of C M value; Again the M a selected phase sequence is multiplied with OFDM frequency-region signal, by the IFFT of JN point, generates M time-domain alternative signals; Calculating finally by CM value, choosing the minimum alternative signal of CM value as transmitting.The SLM method for peak suppression that the present invention represents with multi signal in existing ofdm system compares, core difference is that the selection mode of alternative signal is different: the SLM method for peak suppression that in existing ofdm system, multi signal represents, being calculated by PAPR after generation U time-domain alternative signals, choosing the minimum alternative signal of PAPR as transmitting; And the present invention is calculated by CM value, in alternative signal, select the minimum alternative signal of CM value as transmitting.

Technical solution of the present invention is as follows:

The method for peak suppression that in ofdm system, multi signal represents, as shown in Figure 1, comprises the following steps:

Step 1: preset U group phase sequence u=1 ..., U, by its respectively with OFDM frequency domain signal X=[X ₀..., X _n-1] ^hbe multiplied, obtain signal X ^u.That is:

X ^u=diag(Φ ^u)X，u=1,…,U （1）

Wherein N is ofdm system sub-carriers quantity,

Step 2: the signal X that step 1 is obtained ^ucarry out spectral aliasing, obtain the signal after aliasing $X_P^u=[X_{0,P}^u,...,X_{i,P}^u,...,X_{\frac{N}{P}-1,P}^u{]}^H,$ U=1 ..., U; Wherein aliasing process is:

$X_{i,P}^u=\underset{j=0}{\overset{P-1}{\mathrm{\Σ}}}{X}_{i+j\frac{N}{P}}^u,i=\mathrm{0,1},\·\·\·,\frac{N}{P}-1;u=1,\·\·\·,U---\left(2\right)$

Wherein for lack sampling multiple;

Step 3: the aliasing signal that step 2 is obtained carry out point IFFT, generates U the time-domain alternative signals of times lack sampling $s_P^u=[s_{0,P}^u,...,s_{k,P}^u,...,s_{\frac{N}{P}-1,P}^u{]}^H,$ U=1 ..., U, that is:

$s_{k,P}^u=\frac{1}{\sqrt{N/P}}\underset{i=0}{\overset{N/P-1}{\mathrm{\Σ}}}{X}_{i,P}^u{e}^{\frac{j2\mathrm{\πk}}{N/P}},k=\mathrm{0,1},...,\frac{N}{P}-1;u=1,...,U---\left(3\right)$

Step 4: U time-domain alternative signals in calculation procedure 3 cM value, u=1 ..., U, wherein e [x] represents the desired value of sequence x; Choose M(M≤U) organize phase sequence corresponding to the less time-domain alternative signals of CM value, be designated as: m=0,1 ..., M, and ${\mathrm{\Φ}}^m\⋐{\mathrm{\Φ}}^u;$

Step 5: the M group phase sequence that step 4 is obtained with OFDM frequency domain signal X=[X ₀..., X _n-1] ^hbe multiplied, m=0,1 ..., M, obtains signal , that is:

${\tilde{X}}^m=\mathrm{diag}\left({\mathrm{\Φ}}^m\right)X,m=\mathrm{0,1},...,M---\left(4\right)$

Wherein

Step 6: the signal that step 5 is obtained carry out the IFFT of JN point, generate the time-domain alternative signals of M J times of over-sampling ${\tilde{s}}_J^m=[s_{0,J}^m,...,s_{k,J}^m,...,s_{\mathrm{JN}-1,J}^m{]}^H,$ That is:

${\tilde{s}}_{k,J}^m=\frac{1}{\sqrt{\mathrm{JN}}}\underset{i=0}{\overset{\mathrm{JN}-1}{\mathrm{\Σ}}}{\tilde{X}}_i^m{e}^{\frac{j2\mathrm{\πk}}{\mathrm{JN}}},k=\mathrm{0,1},...,\mathrm{JN}-1;m=\mathrm{0,1},...,M---\left(5\right)$

Wherein J is over-sampling multiple;

Step 7: M time-domain signal in calculation procedure 6 cM value ${\mathrm{CM}}_m^{\′}=20{\log }_{10}\left\{\mathrm{rms}\right[{\left(\frac{\left|{\tilde{s}}_J^m\right|}{\mathrm{rms}\left[{\tilde{s}}_J^m\right]}\right)}^3\left]\right\},$ M=1 ..., M, wherein e [x] represents the desired value of sequence x;

Step 8: the signal that in selecting step 7, CM value is minimum as transmitting, that is:

$\hat{s}=\underset{{\tilde{s}}_J^m,1\≤m\≤M}{\min }\left\{{\mathrm{CM}}_m^{\′}\right\}---\left(6\right)$

For the SLM peak value realizing lower complexity suppresses, the present invention uses CM value to describe the peak value fluctuation situation of ofdm signal, and one or more phase sequence estimated with OFDM undersampled signal suppresses the peak value of ofdm signal as the phase sequence of actual signal.

In order to describe the amplitude fluctuations characteristic of ofdm signal more fully, needing to carry out over-sampling to transmitting, then suppressing peak-to-average force ratio by method for peak suppression.For traditional SLM method, the generation of each alternative signal needs an extra IFFT, more due to the existence of over-sampling, makes whole process complexity higher.The present invention utilizes the thought of lack sampling to improve traditional SLM algorithm, and by simulating, verifying, new method can obtain good inhibition, and the complexity of whole process is reduced greatly.In a word, low complex degree is the outstanding feature of this programme.

Accompanying drawing explanation

Fig. 1 is ofdm system method for peak suppression generally overall flow schematic diagram.

Fig. 2 is ofdm system method for peak suppression spy row (M=1) overall flow schematic diagram.

Embodiment

The method for peak suppression that in ofdm system, multi signal represents, as shown in Figure 1, comprises the following steps:

Step 1: preset U group phase sequence u=1 ..., U, by its respectively with OFDM frequency domain signal X=[X ₀..., X _n-1] ^hbe multiplied, obtain signal X ^u.That is:

X ^u=diag(Φ ^u)X，u=1,…,U （1）

Wherein N is ofdm system sub-carriers quantity,

Step 2: the signal X that step 1 is obtained ^ucarry out spectral aliasing, obtain the signal after aliasing $X_P^u=[X_{0,P}^u,...,X_{i,P}^u,...,X_{\frac{N}{P}-1,P}^u{]}^H,$ U=1 ..., U; Wherein aliasing process is:

$X_{i,P}^u=\underset{j=0}{\overset{P-1}{\mathrm{\Σ}}}{X}_{i+j\frac{N}{P}}^u,i=\mathrm{0,1},...,\frac{N}{P}-1;u=1,...,U---\left(2\right)$

Wherein for lack sampling multiple;

Step 3: the aliasing signal that step 2 is obtained carry out point IFFT, generates U the time-domain alternative signals of times lack sampling $s_P^u=[s_{0,P}^u,...,s_{k,P}^u,...,s_{\frac{N}{P}-1,P}^u{]}^H,$ U=1 ..., U, that is:

$s_{k,P}^u=\frac{1}{\sqrt{N/P}}\underset{i=0}{\overset{N/P-1}{\mathrm{\Σ}}}{X}_{i,P}^u{e}^{\frac{j2\mathrm{\πk}}{N/P}},k=\mathrm{0,1},...,\frac{N}{P}-1;u=1,...,U---\left(3\right)$

Step 4: U time-domain alternative signals in calculation procedure 3 cM value, u=1 ..., U, wherein e [x] represents the desired value of sequence x; Choose M(M≤U) organize phase sequence corresponding to the less time-domain alternative signals of CM value, be designated as: m=0,1 ..., M, and ${\mathrm{\Φ}}^m\⋐{\mathrm{\Φ}}^u;$

Step 5: the M group phase sequence that step 4 is obtained with OFDM frequency domain signal X=[X ₀..., X _n-1] ^hbe multiplied, m=0,1 ..., M, obtains signal X that is:

${\tilde{X}}^m=\mathrm{diag}\left({\mathrm{\Φ}}^m\right)X,m=\mathrm{0,1},...,M---\left(4\right)$

Wherein

Step 6: the signal that step 5 is obtained carry out the IFFT of JN point, generate the time-domain alternative signals of M J times of over-sampling ${\tilde{s}}_J^m=[s_{0,J}^m,...,s_{k,J}^m,...,s_{\mathrm{JN}-1,J}^m{]}^H,$ That is:

${\tilde{s}}_{k,J}^m=\frac{1}{\sqrt{\mathrm{JN}}}\underset{i=0}{\overset{\mathrm{JN}-1}{\mathrm{\Σ}}}{\tilde{X}}_i^m{e}^{\frac{j2\mathrm{\πk}}{\mathrm{JN}}},k=\mathrm{0,1},...,\mathrm{JN}-1;m=\mathrm{0,1},...,M---\left(5\right)$

Wherein J is over-sampling multiple;

Step 7: M time-domain signal in calculation procedure 6 cM value m=1 ..., M, wherein e [x] represents the desired value of sequence x;

Step 8: the signal that in selecting step 7, CM value is minimum as transmitting, that is:

$\hat{s}=\underset{{\tilde{s}}_J^m,1\≤m\≤M}{\min }\left\{{\mathrm{CM}}_m^{\′}\right\}---\left(6\right)$

Main innovation of the present invention is when doing SLM process, one or more phase sequence estimated with lack sampling ofdm signal suppresses the peak value of ofdm signal as the phase sequence of actual signal, and use CM value to describe the peak value fluctuation situation of ofdm signal, as selecting the index sending signal.This programme greatly reduces computational complexity rejection is reasonable simultaneously.

Computer Simulation shows, when points N=8192 of ofdm signal, and phase sequence group U=256, lack sampling multiple over-sampling multiple J=4, the CM value calculating 4 times of oversampled signals is: 17.9304, the CM value of 4 times of oversampled signals after traditional SLM algorithm is: 17.1559, and as M=50, the CM value of 4 times of oversampled signals after the inventive method is: 17.1668; As M=10, the CM value of 4 times of oversampled signals after the inventive method is: 17.2538; As M=1, the CM value of 4 times of oversampled signals after the inventive method is: 17.5369.Can have thus, the present invention can suppress the peak value of ofdm signal preferably, and when M increases, the CM value that the present invention calculates is more close to the CM value after original 4 times of oversampled signals SLM, and performance is also better.

Those of ordinary skill in the art will appreciate that, embodiment described here is to help reader understanding's implementation method of the present invention, should be understood to that protection scope of the present invention is not limited to so special statement and embodiment.Those of ordinary skill in the art can make various other various concrete distortion and combination of not departing from essence of the present invention according to these technology enlightenment disclosed by the invention, and these distortion and combination are still in protection scope of the present invention.

Claims (1)

1. the method for peak suppression that in ofdm system, multi signal represents, comprises the following steps:

Step 1: preset U group phase sequence by its respectively with OFDM frequency domain signal X=[X ₀..., X _n-1] ^hbe multiplied, obtain signal X ^u, that is:

X ^u＝diag(Φ ^u)X，u＝1,…,U (1)

Wherein N is ofdm system sub-carriers quantity,

Step 2: the signal X that step 1 is obtained ^ucarry out spectral aliasing, obtain the signal after aliasing wherein aliasing process is:

Wherein for lack sampling multiple;

Step 3: the aliasing signal that step 2 is obtained carry out point IFFT, generates U the time-domain alternative signals of times lack sampling that is:

Step 4: U time-domain alternative signals in calculation procedure 3 cM value, wherein e [x] represents the desired value of sequence x; Choose M (M≤U) and organize phase sequence corresponding to the less time-domain alternative signals of CM value, be designated as: and

Step 5: the M group phase sequence that step 4 is obtained with OFDM frequency domain signal X=[X ₀..., X _n-1] ^hbe multiplied, m=1 ..., M, obtains signal that is:

Wherein

Step 6: the signal that step 5 is obtained carry out the IFFT of JN point, generate the time-domain alternative signals of M J times of over-sampling that is:

Wherein J is over-sampling multiple;

Step 7: M time-domain signal in calculation procedure 6 cM value CM ' _m, wherein e [x] represents the desired value of sequence x;

Step 8: the signal that in selecting step 7, CM value is minimum as transmitting, that is:

。