CN103607363B - A kind of method of signal to noise ratio blind estimate - Google Patents

Abstract

A kind of method that the invention discloses signal to noise ratio blind estimate, the method includes: the grandfather tape messenger received is carried out Hilbert transform, it is thus achieved that corresponding complex baseband signal；Utilize predetermined bandwidth that described complex baseband signal is carried out low-pass filtering, it is thus achieved that corresponding band-limited signal；Described band-limited signal is carried out successively M times up-sample with N times of down-sampling after, use singular value decomposition algorithm estimate signal to noise ratio.By using method disclosed by the invention to improve stability and accuracy, expand the scope of application.

Description

A kind of method of signal to noise ratio blind estimate

Technical field

The present invention relates to wireless technical field, a kind of method particularly relating to signal to noise ratio blind estimate.

Background technology

Signal to noise ratio is a key character parameter of modulated signal, exactly estimate signal to noise ratio for understand the characteristic of channel and Optimal energy allocation in communication is significant.

All the time, forefathers have been proposed for a lot of effective signal-to-noise ratio estimation algorithm, are broadly divided into blind estimate and non-blind Estimating, (a square signal to noise ratio variance ratio is estimated for such as maximal possibility estimation, SSME (segmentation symbol moments estimation), SNV Meter), Eigenvalues Decomposition method etc..But use these algorithms often to have a lot of constraints, be based especially on priori The non-blind estimate of knowledge, greatly limit the range of application of algorithm.

In many actual application scenarios, lack the prior information of signal during signal-to-noise ratio (SNR) estimation, it is necessary to carry out blind estimate.Special Value indicative decomposition method is exactly the Typical Representative of Algorithm for Blind Estimation of SNR, its estimated accuracy apparently higher than other algorithms, but Require that noise should keep smooth power spectral density in whole frequency domain.But in actual satellite communication system In, modulated signal, often without molding filtration, has passed through a band filter before end digitized the most in front of the receiver, Owing to band-pass filtering property is undesirable, actual sample frequency and band filter bandwidth are frequently not integral multiple and close System, causes the noise after sampling no longer to have white power spectrum characteristic, and now Eigenvalues Decomposition method cannot be proved effective.

Summary of the invention

A kind of method that it is an object of the invention to provide signal to noise ratio blind estimate, improves stability and accuracy, expands applicable Scope.

It is an object of the invention to be achieved through the following technical solutions:

(corresponding with claim).

As seen from the above technical solution provided by the invention, by signal is carried out complex base band conversion, low-pass filtering and on Down-sampling conversion achieves and completed the whitening processing to noise component(s) before signal-to-noise ratio (SNR) estimation.By above-mentioned process, improve The robustness of singular value decomposition algorithm and accuracy, expand the scope of application of this algorithm.

Accompanying drawing explanation

In order to be illustrated more clearly that the technical scheme of the embodiment of the present invention, required use in embodiment being described below Accompanying drawing is briefly described, it should be apparent that, the accompanying drawing in describing below is only some embodiments of the present invention, for From the point of view of those of ordinary skill in the art, on the premise of not paying creative work, it is also possible to obtain according to these accompanying drawings Other accompanying drawings.

The schematic diagram of a kind of BPSK modulating system that Fig. 1 provides for the embodiment of the present invention one；

The flow chart of the method for a kind of signal to noise ratio blind estimate that Fig. 2 provides for the embodiment of the present invention one；

The curve synoptic diagram of the signal-to-noise ratio (SNR) estimation average utilizing the inventive method to obtain that Fig. 3 provides for the embodiment of the present invention one；

The curve synoptic diagram of the signal to noise ratio relative error utilizing the inventive method to obtain that Fig. 4 provides for the embodiment of the present invention one；

The curve signal of the signal-to-noise ratio (SNR) estimation average that the method utilizing prior art that Fig. 5 provides for the embodiment of the present invention one obtains Figure；

The curve signal of the signal to noise ratio relative error that the method utilizing prior art that Fig. 6 provides for the embodiment of the present invention one obtains Figure.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clearly and completely Describe, it is clear that described embodiment is only a part of embodiment of the present invention rather than whole embodiments.Based on Embodiments of the invention, it is every other that those of ordinary skill in the art are obtained under not making creative work premise Embodiment, broadly falls into protection scope of the present invention.

Embodiment one

The schematic diagram of a kind of digital signal modulation mode that Fig. 1 provides for the embodiment of the present invention, it is illustrated that for BPSK (two-phase phase Move keying) modulation, under practical situation, it would however also be possible to employ other digital modulation mode, such as, QPSK (orthogonal phase shift Keying), 8PSK (eight phase phase-shift keying (PSK)s) etc..

The flow chart of the Fig. 2 a kind of method of signal to noise ratio blind estimate for providing for the embodiment of the present invention one.As in figure 2 it is shown, should Method mainly comprises the steps:

Step 21, the grandfather tape messenger received is carried out Hilbert transform, it is thus achieved that corresponding complex baseband signal.

The embodiment of the present invention can use following formula calculate:

$r_L\left(n\right)=\mathrm{hilbert}\left(r\left(n\right)\right)\·e^{-j2\mathrm{\π}{f}_{c}n/f_s};$

Wherein, r_LN () is the complex baseband signal obtained, r (n) is the grandfather tape messenger received, f_sFor sample frequency, Hilbert represents Hilbert transform, f_cFor signal carrier frequency, n be described in the sequence number of grandfather tape messenger that receives, j is empty Number unit.

Step 22, utilize predetermined bandwidth that described complex baseband signal is carried out low-pass filtering, it is thus achieved that corresponding band-limited signal.

Using the low pass filter of a high-order that complex baseband signal is carried out bandlimiting filtering in the embodiment of the present invention, its exponent number should Ensure that the intermediate zone of wave filter is sufficiently narrow, ideal low-pass filter can be approximately.

Bandwidth W of low pass filter should be slightly below 1/2nd of original tape bandpass filter bandwidth, simultaneously with two points of sample frequency One of keep integer ratio relation, i.e.M and N is positive integer, concrete value can according to the actual requirements or Experience determines.

Step 23, described band-limited signal is carried out successively M times up-sample with N times of down-sampling after, use singular value decomposition algorithm Estimate signal to noise ratio.

The band-limited signal that will obtain after filtering, first carries out M times and up-samples, then carry out N times of down-sampling；Its purpose is to Signal spectrum after making conversion on the premise of meeting Nyquist's theorem is full of whole frequency range, now by realization to whole The whitening processing of noise in individual frequency range.

Then, this signal is carried out autocorrelation matrix singular value decomposition and estimates signal to noise ratio.

On the other hand, in order to further illustrate technical scheme, there is preferable accuracy and reliability, below base Technical scheme in the embodiment of the present invention has carried out emulation experiment, and design parameter is as shown in table 1.

Systematic parameter	Value
		Signal carrier frequency	15MHz
Sample frequency	60MHz
		Character rate	3M Baud
Modulation system	BPSK/QPSK/8PSK
		SNR ranges	[0dB,40dB]
Band filter bandwidth	22MHz
		Sampling multiple M/N	1/3
Low pass filter bandwidth	10MHz
		Autocorrelation matrix dimension	300
Cycle-index	100

Table 1 emulation experiment parameter list

Setting signal source in this emulation experiment as 0,1 sequence randomly generated, noise is white Gaussian noise, low-pass filtering Device selects chebyII (Chebyshev II) type, and exponent number is 20 rank, and stopband attenuation is 50dB.

In emulation experiment, in the range of [0,40] dB, selecting stepping is 2.5, for each signal to noise ratio (SNR), respectively Carry out 100 independent emulation, calculate estimation average and the relative error average of these 100 simulation results, use side of the present invention The performance of method and the estimation performance before not having albefaction are made comparisons, and draw corresponding curve and observe.

As shown in figures 3 to 6, wherein, it is equal that Fig. 3-Fig. 4 is respectively the signal-to-noise ratio (SNR) estimation using the method for the present invention to obtain to its result Value and relative error curve；Fig. 5-Fig. 6 is respectively the signal to noise ratio using the method not carrying out whitening processing in prior art to obtain Estimate average and relative error curve.Simulation result shows, in [0,30] dB in a big way, for various modulation systems, The method signal-to-noise ratio (SNR) estimation value that the present invention improves is more accurate, and error is less than 2dB, and in [0,20] dB, error is less than 1dB, has preferable accuracy and reliability；Review the thousand of the performance not doing whitening processing, estimated value and actual value difference In, complete mistake, cause the reason of this result be exactly noise be not albefaction.

Through the above description of the embodiments, those skilled in the art it can be understood that to above-described embodiment permissible Realized by software, it is also possible to the mode adding necessary general hardware platform by software realizes.Based on such reason Solving, the technical scheme of above-described embodiment can embody with the form of software product, and this software product can be stored in one In individual non-volatile memory medium (can be CD-ROM, USB flash disk, portable hard drive etc.), including some instructions with so that One computer equipment (can be personal computer, server, or the network equipment etc.) performs the present invention, and each is implemented Method described in example.

The above, the only present invention preferably detailed description of the invention, but protection scope of the present invention is not limited thereto, Any those familiar with the art in the technical scope of present disclosure, the change that can readily occur in or replace Change, all should contain within protection scope of the present invention.Therefore, protection scope of the present invention should be with claims Protection domain is as the criterion.

Claims (3)

1. the method for a signal to noise ratio blind estimate, it is characterised in that the method includes:

The grandfather tape messenger received is carried out Hilbert transform, it is thus achieved that corresponding complex baseband signal；

Utilize predetermined bandwidth that described complex baseband signal is carried out low-pass filtering, it is thus achieved that corresponding band-limited signal；

Described band-limited signal is carried out successively M times up-sample with N times of down-sampling after, use singular value decomposition algorithm estimate noise Ratio.

Method the most according to claim 1, it is characterised in that the described signal to receiving carries out Hilbert change The formula changed is:

$r_L\left(n\right)=hilbert\left(r\right(n\left)\right)\·e^{-j2{\mathrm{\πf}}_{c}n/f_s};$

Wherein, r_LN () is the complex baseband signal obtained, r (n) is the grandfather tape messenger received, f_sFor sample frequency, Hilbert represents Hilbert transform, f_cFor signal carrier frequency, n be described in the sequence number of grandfather tape messenger that receives, j is empty Number unit.

Method the most according to claim 1, it is characterised in that described utilize predetermined bandwidth that described complex radical is taken a message Number carrying out low-pass filtering includes:

Bandwidth W of described low pass filter is:

$W=\frac{M\·f_s}{2N};$

Wherein, f_sFor sample frequency.