CN101867543B - A kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation - Google Patents

Abstract

The invention discloses a kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation, said method comprising the steps of: arranging signal to noise ratio register initial value is SNR ₁, counter n=0; Make n=n+1; According to signal-to-noise ratio (SNR) estimation value, carry out the preamble detecting of the n-th frame; Extract the data for signal-to-noise ratio (SNR) estimation in the leader block of the n-th frame, carry out channel estimating, obtain the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _n; By the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _nas the SNR of preamble detecting carrying out the (n+1)th frame _n+1, carry out the preamble detecting of the (n+1)th frame, until all detect complete to all frames.The present invention introduces signal-to-noise ratio (SNR) estimation value in preamble detecting, well eliminate the impact of signal to noise ratio on preamble detecting, particularly when signal to noise ratio is very low, avoid the generation of false-alarm under deep fade and false dismissal phenomenon, the threshold value simultaneously avoiding preamble detecting changes with the change of signal to noise ratio.

Description

A kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation

Technical field

The present invention relates to wireless communication technology, particularly relate to a kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation.

Background technology

In a wireless communication system, except the interference by various noise, the multipath transmisstion transmitted also affects transfer of data.Along with the raising of message transmission rate, more and more higher transmission bandwidth causes serious time dispersive, contains the multipath ripple of experience decay and time delay, cause frequency selective fading, thus cause the problems such as serious intersymbol interference and deep fade in Received signal strength.Single-carrier frequency domain equalization system (SC-FDE, SingleCarrierFrequencyDomainEqualization), is a kind of system effectively to anti-multipath jamming in broad band wireless transmission, can well solves the problem.

SC-FDE technology needs insert Cyclic Prefix and carry out frequency domain equalization, and this method sends signal with partitioned organization simultaneously, synchronously requires high to receiving terminal, quite responsive to synchronism deviation.The partitioned organization of general SC-FDE system is in units of frame, and as shown in Figure 1, every frame is made up of n data block and 1 leader block.

A most crucial problem in digital communication technology field is exactly stationary problem, and synchronous matter of utmost importance is exactly that frame arrives detection, signal detected for determining whether.For block transmission system, also need original position---the frame head detecting every transmission frame number certificate, the frame head of every frame data only detected, what could judge to receive is useful signal, just can carry out follow-up process.There is mistake in preamble detecting, receiver will be caused cannot to process whole frame data normally, and this directly affects the reliability of receiver.

Broadband wireless Mobile Transmission channel, there are time-varying characteristics in channel, therefore certainly exists the moment of deep fade, and now receiving terminal signal to noise ratio is very low, probably signal frame head cannot be detected, that is: said false dismissal; Meanwhile, if there is interference in signal transmission band, also frame head may be detected when signal frame head does not also arrive, that is: said false-alarm.

In existing single-carrier frequency domain equalization system, preamble detecting algorithm generally uses the detection algorithm based on leader block, algorithm mainly utilizes the symmetry characteristic of characteristic sequences in leader block---the two-part correlation properties in front and back, carry out slip to signal to be correlated with, time by comparing correlation and determining with fixing threshold value, frame head detected.

Existing method is comparatively large in interference, will inevitably occur the phenomenon of false-alarm and false dismissal, and for different channel conditions, also need in good time amendment threshold value when signal to noise ratio is lower, otherwise algorithm possibly cannot normally run.And timely modification threshold value, then need to introduce adaptive algorithm, this will increase the complexity of preamble detecting algorithm greatly, is difficult to realize.

Summary of the invention

The invention provides a kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation, detect the false-alarm that occurs and false dismissal problem in order to solve arriving at frame of existing in prior art.

For reaching above-mentioned purpose, the invention provides a kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation, said method comprising the steps of:

S101, arranging signal to noise ratio register initial value is SNR ₁, counter n=0;

S102, makes n=n+1; According to signal-to-noise ratio (SNR) estimation value, carry out the preamble detecting of the n-th frame;

S103, extracts the data for signal-to-noise ratio (SNR) estimation in the leader block of the n-th frame, carries out channel estimating, obtains the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _n;

S104, by the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _nas the SNR of preamble detecting carrying out the (n+1)th frame _n+1, carry out the preamble detecting of the (n+1)th frame, until all detect complete to all frames.

Further, in step s 102, according to signal-to-noise ratio (SNR) estimation value, carry out the preamble detecting of the n-th frame, specifically comprise the following steps:

S1021, if the sampled signal sequence of the n-th frame reception end is r (k), k=1,2,3.......}, the sliding window length for preamble detecting is mL sampled point, and wherein m is the sampling number of a code element:

S1022, the original position of sliding window point d is set to d=1;

S1023, be original position with d, obtain the long sampled value for mG sampled point of two windows continuously:

R _i＝(r(d+m(i-1)G),…,r(d+miG-1)) ^T，

Wherein, T represents transposition; I=1,2; G=32, represents the Baud Length obtained;

S1024, determine R1, correlation P (d) of R2:

$P\left(d\right)={R_1}^H{R}_2=\underset{k=d}{\overset{d+mG-1}{\Σ}}{r}^{*}\left(k\right)r(k+mG);$

Wherein, r represents R ₁conjugation; r ^*(k) represent r (k), conjugation;

S1025, determine the average energy of two windows got:

$R\left(d\right)=\frac{1}{2}\underset{k=d}{\overset{d+2mG-1}{\Σ}}{\left|r\left(k\right)\right|}^2;$

S1026, calculating M (d):

$M\left(d\right)=\frac{{\left|P\left(d\right)\right|}^2({\mathrm{SNR}}_n+1)}{{\left(R\right(d\left)\right)}^2{\mathrm{SNR}}_n};$

Judge whether M (d) is more than or equal to predetermined threshold value M _a, if so, then stop mobile sliding window, sliding window original position point is now the frame header position of Frame; Otherwise, the original position of mobile sliding window point is added 1, returns step S1023.

Further, described predetermined threshold value M _a=0.7.

Further, for the unique word sequence of the sequence of preamble detecting to be N number of length be G code element.

Further, step S103, obtains the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame by the following method _n:

S1032, extracts the pilot data being used for signal-to-noise ratio (SNR) estimation from the Received signal strength that the leader block of the n-th frame is corresponding wherein, pilot data overall length is 2M;

S1033 is right carry out fast Fourier transform, obtain

S1034, in cast out odd number value of frequency point, obtain the data that length is M

S1035, calculates σ ²:

${\mathrm{\σ}}^2=\frac{{\left|R\left(2\right)\right|}^2+{\left|R\left(4\right)\right|}^2+\mathrm{...}+{\left|R\left(M\right)\right|}^2}{2M};$

S1036, obtains signal-to-noise ratio (SNR) estimation SNR _n:

${\mathrm{SNR}}_n=\frac{1}{{\mathrm{\σ}}^2}.$

Further, before step S1032, also comprise:

S1031, carries out energy normalized process to the Received signal strength of the n-th frame.

Further, arranging described signal to noise ratio register initial value is SNR ₁=100db.

Beneficial effect of the present invention is as follows:

The present invention introduces signal-to-noise ratio (SNR) estimation value in preamble detecting, well eliminate the impact of signal to noise ratio on preamble detecting, particularly when signal to noise ratio is very low, avoid the generation of false-alarm under deep fade and false dismissal phenomenon, the threshold value simultaneously avoiding preamble detecting changes with the change of signal to noise ratio.

Accompanying drawing explanation

Fig. 1 is the structural representation of the Frame of SC-FDE system in prior art;

Fig. 2 is the flow chart of a kind of frame arrival detection method based on signal-to-noise ratio (SNR) estimation of the embodiment of the present invention;

Fig. 3 is a kind of flow chart based on carrying out frame detection in the frame arrival detection method of signal-to-noise ratio (SNR) estimation of the embodiment of the present invention;

Fig. 4 be the embodiment of the present invention a kind of based in the frame arrival detection method of signal-to-noise ratio (SNR) estimation for the structural representation of the sequence of preamble detecting;

Fig. 5 is a kind of structural representation based on pilot data in the frame arrival detection method of signal-to-noise ratio (SNR) estimation of the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing and embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, do not limit the present invention.

The present invention utilizes the estimated value of the signal to noise ratio of Received signal strength to carry out preamble detecting, change along with signal to noise ratio changes by estimating of such preamble detecting, avoid the phenomenon of false-alarm and false dismissal, simultaneously thresholding can keep a fixing value, do not need to make adjustment along with the change of channel circumstance, well solve the problem that preamble detecting under wireless channel is made mistakes.

As shown in Figure 2, the concrete steps of the present embodiment method are as follows:

A, the initial value arranging signal to noise ratio register in single-carrier frequency domain equalization system is SNR ₁=100db, counter n=0;

B、n＝n+1；

C, utilizes signal-to-noise ratio (SNR) estimation value, in conjunction with the correlation properties of leader block data, carries out the preamble detecting of the n-th frame;

D, extracts the data for signal-to-noise ratio (SNR) estimation in the leader block of the n-th frame, carries out channel estimating, obtains the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _n;

E, by the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _nas the SNR of preamble detecting carrying out the (n+1)th frame _n+1, carry out the preamble detecting of the (n+1)th frame, until all detect complete to all frames.

In above-mentioned steps, for step C, as shown in Figure 3, comprise the following steps:

C1, if the sampled signal sequence of the n-th frame reception end is r (k), k=1,2,3.......}, the sliding window length for preamble detecting is mL sampled point, and wherein m is the sampling number of a code element:

C2, is set to d=1 by the original position of sliding window point d;

C3 take d as original position, obtains the long sampled value for mG sampled point of two windows continuously:

R _i＝(r(d+m(i-1)G),…,r(d+miG-1)) ^T，

Wherein, T represents transposition; I=1,2; G=32, represents the Baud Length obtained;

C4, determines R1, correlation P (d) of R2:

$P\left(d\right)={R_1}^H{R}_2=\underset{k=d}{\overset{d+mG-1}{\Σ}}{r}^{*}\left(k\right)r(k+mG);$

Wherein, R ₁ ^hr represents R ₁conjugation; r ^*(k) represent r (k), conjugation;

C5, determines the average energy of two windows got:

$R\left(d\right)=\frac{1}{2}\underset{k=d}{\overset{d+2mG-1}{\Σ}}{\left|r\left(k\right)\right|}^2;$

C6, calculates M (d):

$M\left(d\right)=\frac{{\left|P\left(d\right)\right|}^2({\mathrm{SNR}}_n+1)}{{\left(R\right(d\left)\right)}^2{\mathrm{SNR}}_n};$

Judge whether M (d) is more than or equal to predetermined threshold value M _a, if so, then stop mobile sliding window, sliding window original position point is now the frame header position of Frame, otherwise, the original position of mobile sliding window point is added 1, returns step C3.

Wherein, predetermined threshold value is M _a=0.7, UW (UniqueWord, unique word) the sequence composition of to be N number of length the be G code element of the particular sequence for preamble detecting, as shown in Figure 4.UW sequence is generally chu sequence, frank-zadoff sequence, the PN sequence that IEEE802.16a standard specifies.

For step D, comprise the following steps:

D1, carries out energy normalized process to present frame Received signal strength, as long as carry out processing through existing digital AGC (AUTOGAINCONTROL, automatic growth control) chip;

D2, extracts the pilot data (being also simultaneously the pilot data for channel estimating) being used for signal-to-noise ratio (SNR) estimation from the Received signal strength that leader block is corresponding wherein, pilot data overall length is 2M, as shown in Figure 5, is made up of the UW data of two M length;

D3 is right carry out FFT (FastFourierTransform, fast Fourier transform) conversion to obtain

D4, in cast out odd number value of frequency point, obtain the data that length is M

D5, calculates σ ²:

${\mathrm{\σ}}^2=\frac{{\left|R\left(2\right)\right|}^2+{\left|R\left(4\right)\right|}^2+\mathrm{...}+{\left|R\left(M\right)\right|}^2}{2M};$

D6, obtains signal-to-noise ratio (SNR) estimation SNR _n:

${\mathrm{SNR}}_n=\frac{1}{{\mathrm{\σ}}^2}.$

In preamble detecting, introduce signal-to-noise ratio (SNR) estimation value, well eliminate the impact of signal to noise ratio on preamble detecting, particularly when signal to noise ratio is very low.Doing so avoids the phenomenon of false-alarm under deep fade and false dismissal, avoid the thresholding M of preamble detecting simultaneously _athe requirement changed along with the change of signal to noise ratio, and thresholding how to change be very doubt.

The accuracy of noise estimation value directly affects the reliability of adaptive algorithm.General noise Estimation Algorithm all completes in time domain.The present invention is when estimated snr, for the feature of SC-FDE system, do not changing on the basis of data frame structure, pilot data for channel estimating is transformed to frequency domain thus obtains noise estimation value accurately, use energy normalized process before treatment simultaneously, simplify signal-to-noise ratio estimation algorithm.

Obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.

Claims (6)

1. based on a frame arrival detection method for signal-to-noise ratio (SNR) estimation, it is characterized in that, said method comprising the steps of:

S101, arranging signal to noise ratio register initial value is SNR ₁, counter n=0;

S102, makes n=n+1; According to signal-to-noise ratio (SNR) estimation value, carry out the preamble detecting of the n-th frame;

S103, extracts the data for signal-to-noise ratio (SNR) estimation in the leader block of the n-th frame, carries out channel estimating, obtains the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _n;

S104, by the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame _nas the SNR of preamble detecting carrying out the (n+1)th frame _n+1, carry out the preamble detecting of the (n+1)th frame, until all detect complete to all frames;

In step s 102, according to signal-to-noise ratio (SNR) estimation value, carry out the preamble detecting of the n-th frame, specifically comprise the following steps:

S1021, if the sampled signal sequence of the n-th frame reception end is r (k), k=1,2,3.......}, the sliding window length for preamble detecting is mL sampled point, and wherein m is the sampling number of a code element:

S1022, the original position of sliding window point d is set to d=1;

S1023, be original position with d, obtain the long sampled value for mG sampled point of two windows continuously:

R _i＝(r(d+m(i-1)G)，…，r(d+miG-1)) ^T，

Wherein, T represents transposition; I=1,2; G=32, represents the Baud Length obtained;

S1024, determine R ₁, R ₂correlation P (d):

Wherein, R ₁ ^hrepresent R ₁conjugation; r ^*k () represents the conjugation of r (k);

S1025, determine the average energy of two windows got:

S1026, calculating M (d):

Judge whether M (d) is more than or equal to predetermined threshold value M _a, if so, then stop mobile sliding window, sliding window original position point is now the frame header position of Frame; Otherwise, the original position of mobile sliding window point is added 1, returns step S1023.

2., as claimed in claim 1 based on the frame arrival detection method of signal-to-noise ratio (SNR) estimation, it is characterized in that, described predetermined threshold value M _a=0.7.

3. as claimed in claim 1 based on the frame arrival detection method of signal-to-noise ratio (SNR) estimation, it is characterized in that, the unique word sequence of to be N number of length the be G code element of the sequence for preamble detecting.

4., as claimed in claim 1 based on the frame arrival detection method of signal-to-noise ratio (SNR) estimation, it is characterized in that, step S103, obtain the signal-to-noise ratio (SNR) estimation value SNR of the n-th frame by the following method _n:

S1032, extracts the pilot data being used for signal-to-noise ratio (SNR) estimation from the Received signal strength that the leader block of the n-th frame is corresponding wherein, pilot data overall length is 2M;

S1033 is right carry out fast Fourier transform, obtain

S1034, in cast out odd number value of frequency point, obtain the data that length is M

S1035, calculates σ ²:

S1036, obtains signal-to-noise ratio (SNR) estimation SNR _n:

5., as claimed in claim 4 based on the frame arrival detection method of signal-to-noise ratio (SNR) estimation, it is characterized in that, before step S1032, also comprise:

S1031, carries out energy normalized process to the Received signal strength of the n-th frame.

6., as claimed in claim 1 based on the frame arrival detection method of signal-to-noise ratio (SNR) estimation, it is characterized in that, arranging described signal to noise ratio register initial value is SNR ₁=100db.