CN105245240A - Power microwave communication system wavelet noise reduction method - Google Patents

Abstract

The invention provides a power microwave communication system wavelet noise reduction method. The method comprises the steps that b, according to different communication signals, a wavelet primary function is selected and wavelet decomposition level is determined; c, the signals are filtered to acquire a wavelet coefficient; d, according to the preset wavelet decomposition level, threshold quantization processing is carried out on the wavelet coefficient to acquire a quantized wavelet coefficient; and e, a reconstructed signal is acquired through wavelet reconstruction filtering. According to the invention, the original signals are decomposed into a series of approximate components and detail components through wavelet decomposition; detail component processing and wavelet reconstruction are carried out to extract useful communication signals; weak signal characteristics are extracted in a strong noise background; noise in the signals can be effectively reduced and even eliminated; wireless communication demodulation signal to noise ratio and signal relevance can be significantly improved; phase distortion and bit error rate are reduced; the power microwave communication performance is improved; and the problems of large electromagnetic background noise and many signal harmonic components of power communication are solved.

Description

The wavelet de-noising method of electric power microwave telecommunication system

Technical field

The present invention relates to field of power, particularly relate to a kind of wavelet de-noising method of electric power microwave telecommunication system.

Background technology

Power telecom network, in order to ensure that the safe and stable operation of electric power system arises at the historic moment, is power network schedule automation, the network operation marketization and the basis of management modernization; It is the important means guaranteeing power grid security, stable, economical operation.At present, main in power telecom network transmission means has power line carrier communication, digital microwave telecommunication, SDH optical fiber communication 3 kinds.Power line communication is as communication mode traditional in electric power system; be widely used in power telecom network; but along with the development of bearer service and powerline network; power line communication can not meet the requirement of modern power systems running in controls, protection information etc. Large Copacity, in real time, in reliable, safe transmission etc., be applicable to county's tune, the quantity of information requirement such as to adjust little situation.Fiber-optic communications traffic capacity is large, loss is little, signal cross-talk is little, become the main flow transmission means of power telecom network gradually, but its shortcoming is also particularly evident, the transmission medium of optical fiber communication is optical fiber, long distance optical cable any point along the line fracture, all will cause communication disruption, and optical cable and power line are joint used, once interrupt, need interruption maintenance.Digital microwave telecommunication, satellite are called as three large pillars of modern communications transmission together with optical fiber, digital microwave applying flexible, fast, networking is convenient, against natural disaster ability is strong, along with the development of advanced modulation demodulation techniques, microwave transmission capacity also improves constantly, the experience of various countries shows, when being not suitable for using optical fiber or natural calamity occurring, always first recover telecommunication service by communication, in power telecom network, microwave communication and optical fiber communication complement one another, and have stronger survivability and reliability by making powerline network.But the phase distortion degree of wireless communication signals and the error rate, have a significant impact electric power microwave communication performance, unspecial, way to solve the problem that signal harmonic component many large for power communication electromagnetic background noise in prior art.

Summary of the invention

In view of this, the invention provides a kind of wavelet de-noising method of electric power microwave telecommunication system, to solve the problem.

The wavelet de-noising method of electric power microwave telecommunication system provided by the invention, comprises

B. according to different signals of communication, choose wavelet basis function and determine wavelet decomposition level;

C. signal is carried out filtering process, obtain wavelet coefficient;

D. according to the wavelet decomposition level preset, threshold value quantizing process is carried out to wavelet coefficient, obtain the wavelet coefficient after quantizing;

E. reconstruction signal is obtained by wavelet reconstruction filtering.

Further, described steps d also comprises, and carries out threshold value quantizing process according to following formula,

$T=\mathrm{\σ}\sqrt{2log\left(N{\log }_{2}N\right)},\mathrm{\σ}=\frac{mid\left(\right|d_{1,k}\left|\right)}{0.6745}$

Wherein, σ is that noise criteria is poor, mid (| d _{1, k}|) be the absolute value intermediate value of ground floor high frequency coefficient, 0.6745 is the regulation coefficient of noise criteria difference, and N is the length of signal, and T is small echo quantization threshold.

Further, also comprise after described step e

F. judge wavelet reconstruction level, described wavelet reconstruction level is identical with wavelet decomposition level.

Further, described step f also comprises

If wavelet reconstruction level does not reach default wavelet decomposition hierachy number, then return step e;

If reach default wavelet decomposition hierachy number, then the signal obtained is the signal after noise reduction;

Further, the level of wavelet decomposition described in step b is 3 grades of decomposition.

Further, wavelet coefficient described in step b comprises Coefficients of Approximation and detail coefficients.

Further, step c also comprises

C1. input signal is through low pass filter, and the low frequency coefficient of acquisition is Coefficients of Approximation; Input signal through high pass filter, the high frequency coefficient of acquisition and detail coefficients;

C2. even number extraction is carried out to described Coefficients of Approximation and detail coefficients.

Further, steps d also comprises and carries out interpolation sampling to two sample datas of two wavelet coefficient sequences of the Coefficients of Approximation after quantizing and detail coefficients respectively.

Further, also comprise before step b

A. by receive signal through frequency-conversion processing, be converted to intermediate-freuqncy signal, and described intermediate-freuqncy signal be converted to digital signal.

Further, carry out threshold value quantizing process according to soft-threshold function to wavelet coefficient, described soft-threshold function is

$W_{j,k}^{*}=\left\{\begin{array}{c}sgn\left(W_{j,k}\right)\left(\right|W_{j,k}|-T),\left|W_{j,k}\right|\≥T\\ 0,\left|W_{j,k}\right|\≤T\end{array}\right.$

In formula, sgn () is the function judging sign, W _j,kfor the high frequency coefficient of WAVELET PACKET DECOMPOSITION, T is small echo quantization threshold.

Beneficial effect of the present invention: the wavelet de-noising method of electric power microwave telecommunication system provided by the invention, by wavelet decomposition, primary signal is decomposed into a series of approximation component and details coefficients, after process details coefficients, then through wavelet reconstruction, thus extract useful signal of communication; The present invention extracts small-signal feature under strong noise background, effectively can reduce the noise in even erasure signal, significantly can promote radio communication demodulation signal to noise ratio and signal correction degree, reduce phase distortion degree and the error rate, improve electric power microwave communication performance, solve the problem that power communication electromagnetic background noise is large, signal harmonic component is many.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described:

Fig. 1 is schematic flow sheet of the present invention.

Fig. 2 is the performance simulation figure of the embodiment of the present invention.

Embodiment

Below in conjunction with drawings and Examples, the invention will be further described: Fig. 1 is schematic flow sheet of the present invention; Fig. 2 is the performance simulation figure of the embodiment of the present invention.

As described in Figure 1, the wavelet de-noising method of the electric power microwave telecommunication system in the present embodiment, comprises

A. by receive signal through frequency-conversion processing, be converted to intermediate-freuqncy signal, and described intermediate-freuqncy signal be converted to digital signal;

B. according to different signals of communication, choose wavelet basis function and determine wavelet decomposition level;

C. signal is carried out filtering process, obtain wavelet coefficient;

D. according to the wavelet decomposition level preset, threshold value quantizing process is carried out to wavelet coefficient, obtain the wavelet coefficient after quantizing;

E. reconstruction signal is obtained by wavelet reconstruction filtering.

F. judge wavelet reconstruction level, described wavelet reconstruction level is identical with wavelet decomposition level,

If wavelet reconstruction level does not reach default wavelet decomposition hierachy number, then return step e;

If reach default wavelet decomposition hierachy number, then the signal obtained is the signal after noise reduction;

In the present embodiment, for different signals of communication, choose the wavelet basis of such signal characteristic applicable, just can obtain better de-noising effect.Such as, for the MPSK complex signal of electric power microwave telecommunication system, select the rbio2.2 wavelet basis in ReverseBiorthogonal wavelet systems, there is optimum de-noising effect, draw low-pass filter coefficients h1 and the high pass filter coefficient g1 of this wavelet basis.

In the present embodiment, after wavelet basis function is determined, need the level determining wavelet decomposition.Wavelet decomposition level is relevant with equalisation of over-sampled signals multiple, and the Received signal strength in the present embodiment adopts 8 times of over-samplings, and wavelet decomposition level is 3 grades of decomposition.

In the present embodiment, wavelet coefficient comprises Coefficients of Approximation and detail coefficients, and after wavelet basis is determined, input signal, through low pass filter h1, obtains low frequency coefficient and Coefficients of Approximation Ap1; Input signal, through high pass filter g1, obtains high frequency coefficient and detail coefficients Det1, then carries out even number extraction to Coefficients of Approximation Ap1 and detail coefficients Det1, Ap1 and Det1 sequence length is reduced by half respectively.According to the wavelet decomposition level preset, if do not reach 3 grades of decomposition, then AP1 and Det1 sequence proceeds iteration, till reaching 3 grades of decomposition levels; If reached 3 grades of decomposition, then adopt soft-threshold function to carry out threshold value quantizing process to wavelet coefficient, obtained wavelet coefficient AP2 and Det2 after quantizing;

Wherein, described small echo quantization threshold is determined according to formula (1).

$T=\mathrm{\σ}\sqrt{2log\left(N{\log }_{2}N\right)},\mathrm{\σ}=\frac{mid\left(\right|d_{1,k}\left|\right)}{0.6745}---\left(1\right)$

In formula, σ is that noise criteria is poor, mid (| d _{1, k}|) be the absolute value intermediate value of ground floor high frequency coefficient, 0.6745 is the regulation coefficient of noise criteria difference, and N is the length of signal.

Wherein, described soft-threshold function is such as formula shown in (2):

$W_{j,k}^{*}=\left\{\begin{array}{c}sgn\left(W_{j,k}\right)\left(\right|W_{j,k}|-T),\left|W_{j,k}\right|\≥T\\ 0,\left|W_{j,k}\right|\≤T\end{array}\right.---\left(2\right)$

Wherein, sgn () is the function judging sign, W _j,kfor the high frequency coefficient of WAVELET PACKET DECOMPOSITION, T is small echo quantization threshold.

In the present embodiment, interpolation sampling is carried out to signal, the present embodiment adopts odd number to insert 0 liter of sampling: namely between two sample datas of wavelet coefficient sequence A P2 and Det2, insert 0 respectively, data sequence AP2 after liter sampling is by reconstruction low pass filter h2, rise the data sequence Det2 after sampling by reconstruct high pass filter g2, obtain reconstruction signal.

Wherein, the relation of described wavelet reconstruction filter h2 and g2 and described wavelet decomposition filter h1, g1 is such as formula shown in (3).

$\begin{array}{c}{h}_2\left(n\right)=h_1^{*}(-n)\\ g_2\left(n\right)=g_1^{*}(-n)\end{array}---\left(3\right)$

Wavelet reconstruction level in the present embodiment is corresponding with wavelet decomposition level, is 3 grades of reconstruct, if do not reach 3 grades of reconstruct, then returns and re-starts iteration, if reached 3 grades of reconstruct, then wavelet de-noising completes.After wavelet reconstruction completes, obtain the digital signal after noise reduction, follow-up digital demodulated signal process can be carried out.

As shown in Fig. 2 (a) (b) (c) (d), triangular nodes curve is 8PSK noisy signal, circular node curve is signal after wavelet de-noising, as seen from the figure, smooth signal is obtained by wavelet reconstruction, realize extracting small-signal feature under strong noise background, improve demodulation signal to noise ratio and signal correction degree significantly, reduce phase distortion degree and the error rate.

What finally illustrate is, above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although with reference to preferred embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to technical scheme of the present invention or equivalent replacement, and not departing from aim and the scope of technical solution of the present invention, it all should be encompassed in the middle of right of the present invention.

Claims (10)

1. a wavelet de-noising method for electric power microwave telecommunication system, is characterized in that: comprise

B. according to different signals of communication, choose wavelet basis function and determine wavelet decomposition level;

C. signal is carried out filtering process, obtain wavelet coefficient;

D. according to the wavelet decomposition level preset, threshold value quantizing process is carried out to wavelet coefficient, obtain the wavelet coefficient after quantizing;

E. reconstruction signal is obtained by wavelet reconstruction filtering.

2. the wavelet de-noising method of electric power microwave telecommunication system according to claim 1, is characterized in that: described steps d also comprises, carries out threshold value quantizing process according to following formula,

Wherein, σ is that noise criteria is poor, mid (| d _{1, k}|) be the absolute value intermediate value of ground floor high frequency coefficient, 0.6745 is the regulation coefficient of noise criteria difference, and N is the length of signal, and T is small echo quantization threshold.

3. the wavelet de-noising method of electric power microwave telecommunication system according to claim 1, is characterized in that: also comprise after described step e

F. judge wavelet reconstruction level, described wavelet reconstruction level is identical with wavelet decomposition level.

4. the wavelet de-noising method of electric power microwave telecommunication system according to claim 3, is characterized in that: described step f also comprises

If wavelet reconstruction level does not reach default wavelet decomposition hierachy number, then return step e;

If reach default wavelet decomposition hierachy number, then the signal obtained is the signal after noise reduction.

5. the wavelet de-noising method of electric power microwave telecommunication system according to claim 3, is characterized in that: the level of wavelet decomposition described in step b is 3 grades of decomposition.

6. the wavelet de-noising method of electric power microwave telecommunication system according to claim 1, is characterized in that: wavelet coefficient described in step b comprises Coefficients of Approximation and detail coefficients.

7. the wavelet de-noising method of electric power microwave telecommunication system according to claim 6, is characterized in that: step c also comprises

C1. input signal is through low pass filter, and the low frequency coefficient of acquisition is Coefficients of Approximation; Input signal through high pass filter, the high frequency coefficient of acquisition and detail coefficients;

C2. even number extraction is carried out to described Coefficients of Approximation and detail coefficients.

8. the wavelet de-noising method of electric power microwave telecommunication system according to claim 6, is characterized in that: steps d also comprises carries out interpolation sampling to two sample datas of two wavelet coefficient sequences of the Coefficients of Approximation after quantizing and detail coefficients respectively.

9. the wavelet de-noising method of electric power microwave telecommunication system according to claim 1, is characterized in that: also comprise before step b

A. by receive signal through frequency-conversion processing, be converted to intermediate-freuqncy signal, and described intermediate-freuqncy signal be converted to digital signal.

10. the wavelet de-noising method of electric power microwave telecommunication system according to claim 2, is characterized in that: carry out threshold value quantizing process according to soft-threshold function to wavelet coefficient, described soft-threshold function is

In formula, sgn () is the function judging sign, W _j,kfor the high frequency coefficient of WAVELET PACKET DECOMPOSITION, T is small echo quantization threshold.