CN104754605A - Timing synchronization method applied to OFDM-WLAN radio frequency testing system - Google Patents

Abstract

The invention discloses a timing synchronization method applied to OFDM-WLAN radio frequency testing system; the method is as follows: firstly, using a vector signal analyzer for processing WLAN radio frequency signal emitted by a device to be tested, transforming the WLAN radio frequency signal into the digital base band signal of FS; secondly, processing the obtained digital base band signal, obtaining the rising edge position and the falling edge position of the data frame according to the change of the power value, intercepting the data between the rising edge position and the falling edge position as integrated frame data r(n); thirdly, using the obtained data r(n) and adopting L-STF for realizing timing synchronization, and computing to obtain the timing metric function M(n); finally, detecting the peak value position of the timing metric function M(n) to obtain the accurate timing estimated position. The timing synchronization method applied to OFDM-WLAN radio frequency testing system can obtain accurate timing synchronization by using L-STF only, compared with conventional method of using L-STF and L-LTF for estimating the timing position, the timing synchronization step is simplified and the synchronization precision is improved.

Description

A kind of time synchronization method being applicable to OFDM-WLAN radio frequency test system

Technical field

The present invention relates to OFDM-WLAN radio frequency test system, particularly relate to a kind of time synchronization method being applicable to OFDM-WLAN radio frequency test system.

Background technology

WLAN (wireless local area network) (WLAN) is mainly used in the wireless access of subrange, the WLAN (wireless local area network) occurred the earliest can trace back to the ALOHANet based on package formula technology developed for 1971, and it utilizes wireless transmission to replace the network technology of wire transmission first time.It is after IEEE in 1997 has formulated 802.11 standards that WLAN (wireless local area network) really starts commercialization, through development for many years, and the life circulating people that wireless local area network technology is deep.

802.11 standards are WLAN (wireless local area network) series standards that Institute of Electrical and Electric Engineers (IEEE) is formulated, and are mainly used in the local radio communication that 2.4GHz and 5GHz exempts from licence plate frequency range.Present stage, common version comprised 802.11a, 802.11b, 802.11g, 802.11n, and the 802.11ac issued recently.IEEE 802.11ac is carry out using for reference and optimizing on the basis of 802.11n as up-to-date WLAN standard, and it not only possesses the flexibility of wireless technology but also supports the Large Copacity of gigabit Ethernet.802.11ac equally adopts OFDM (OFDM) technology as physical layer modulation method with 802.11a/g/n, OFDM technology be based upon multi-carrier communication basis on develop.OFDM technology synchronously uses orthogonal subcarrier to replace the large subcarrier of spacing to substantially increase bandwidth efficiency, but the orthogonality of the subcarrier of OFDM causes it very responsive to carrier shift, if orthogonality is destroyed, will cause carrier-in-interference.And the accuracy of Timing Synchronization correctly estimates the prerequisite of carrier shift, and if the inaccurate meeting of Timing Synchronization causes intersymbol interference, also can influential system performance.

Radio frequency test system has great significance to production wlan device.Radio frequency test system can be tested the index such as the power of wlan product, frequency spectrum, frequency shift (FS), relatively planisphere error, the manufacturer of wlan device must guarantee that the radio-frequency performance of product meets the standard of IEEE formulation, to guarantee that the performance of product meets operating specification.The quality of simultaneous techniques can affect the overall performance of radio frequency test system, and traditional time synchronization method is combined by L-STF and L-LTF, complex steps, and Timing Synchronization precision is not high yet.

Summary of the invention

Goal of the invention: the object of this invention is to provide one and only adopt L-STF just can realize precise timing synchronization, and step is simply applicable to the time synchronization method of OFDM-WLAN radio frequency test system.

Technical scheme: for reaching this object, the present invention by the following technical solutions:

The time synchronization method being applicable to OFDM-WLAN radio frequency test system of the present invention, comprises the following steps:

S1: utilize VSA to process the WLAN radiofrequency signal that to be measured equipment is launched, being converted into sample rate is F _sdigital baseband signal;

S2: Timing Synchronization process is carried out to the digital baseband signal obtained in step S1, obtain leading edge position and the trailing edge position of Frame according to the change of performance number, the data between intercepting leading edge position and trailing edge position are as complete frame data r (n);

S3: utilize the data r (n) obtained in step S2, realize Timing Synchronization by L-STF, calculate timing metric function M (n);

S4: by the peak of timing metric function M (n) obtained in detecting step S3, obtain accurate timing estimation position.

Further, in described step S2, leading edge position is calculated by following step:

S2.11: from the sampled point after the pre-trigger time, calculates the power of two adjacent integrating ranges; Wherein, integrating range length is multiplied by the comparator time delay that is spaced apart of two adjacent integrating range starting points, and integrating range length is determined jointly by the time of integration and sample rate;

S2.12: the ratio judging two adjacent integrating range power, namely whether the ratio of a rear integrating range power and previous integrating range power reaches the threshold value R preset _t; If reach threshold value R _t, then step S2.13 is carried out; Otherwise, skip the size of time according to integration and skip to down a pair adjacent integrating range, and repeat the operation of step S2.11;

A rear integrating range in S2.13: obtain in step S2.12 two adjacent integrating ranges is as zequin, the performance number of each integrating range of calculated for subsequent, judges whether the ratio of the previous integrating range power in the two adjacent integrating ranges obtained in each integrating range power follow-up and step S2.12 all reaches threshold value R successively _t; If all reach threshold value R _t, then step S2.14 is carried out; Otherwise, repeat the operation of step S2.11;

S2.14: using the index value of the starting point of the rear integrating range in two adjacent integrating ranges described in step S2.13 as leading edge position.

Further, in described step S2, trailing edge position is calculated by following step:

S2.21: from described leading edge position, calculates the power of two adjacent integrating ranges; Wherein, integrating range length is multiplied by the comparator time delay that is spaced apart of two adjacent integrating range starting points, and integrating range length is determined jointly by the time of integration and sample rate;

S2.22: the ratio judging two adjacent integrating range power, namely whether the ratio of previous integrating range power and a rear integrating range power reaches the threshold value R preset _t; If reach threshold value R _t, then step S2.23 is carried out; Otherwise, skip the size of time according to integration and skip to down a pair adjacent integrating range, and repeat the operation of step S2.21;

A rear integrating range in S2.23: obtain in step S2.22 two adjacent integrating ranges is as zequin, the performance number of each integrating range of calculated for subsequent, whether the previous integrating range power in the two adjacent integrating ranges obtained in determining step S2.12 successively and the ratio of each integrating range power follow-up all reach threshold value R _t; If all reach threshold value R _t, then step S2.24 is carried out; Otherwise, repeat the operation of step S2.21;

S2.24: using the index value of the starting point of the previous integrating range in two adjacent integrating ranges described in step S2.23 as trailing edge position.

Further, described step S3 is obtained by following step:

S3.1: utilize the data r (n) obtained in described step S2 to calculate the data C (n) of delay aperture C:

$\begin{array}{c}C\left(n\right)=\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+2L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+3L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+4L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+L)r(n+k+2L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+L)r(n+k+3L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+L)r(n+k+4L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+2L)r(n+k+3L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+2L)r(n+k+4L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+3L)r(n+k+4L)\end{array}$

Wherein, L is the length of 1/5th L-STF periodic sequences;

S3.2: utilize the data r (n) obtained in described step S2 to calculate the data P (n) of delay aperture P:

$P\left(n\right)=\frac{1}{5}\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}({\left|r(n+k)\right|}^2+{\left|r(n+k+L)\right|}^2+{\left|r(n+k+2L)\right|}^2+{\left|r(n+k+3L)\right|}^2+{\left|r(n+k+4L)\right|}^2)$

Wherein, L is the length of 1/5th L-STF periodic sequences;

S3.3: calculate timing metric function

Further, described step S4 is obtained by following step:

S4.1: suitable threshold value T is set _h, in chronological order, the value that M (n) is engraved when each and threshold value T _hcompare successively, when the value of M (n) is greater than threshold value T _htime just think that peak value is about to occur, the value of the value of the moment d that record is corresponding and M (d) corresponding to d moment;

S4.2: if the value of the M (n) occurred after the d moment obtained in step S4.1 is greater than the value of M (d), then more the value of new record M (d) and d is the value of current time;

S4.3: if the value of M (n) corresponding to all moment after the d moment obtained in step S4.2 is all less than the value of M (d), then using the peak value of the value of M (d) as described timing metric function M (n), corresponding moment d is as described timing estimation position.

Beneficial effect: the time synchronization method being applicable to OFDM-WLAN radio frequency test system provided by the invention, just accurate Timing Synchronization can be realized by means of only L-STF, compared to the method utilizing L-STF and L-LTF Combined estimator timing position in conventional method, simplify the step of Timing Synchronization, improve synchronous precision.

Accompanying drawing explanation

Fig. 1 is flow chart of the present invention;

Fig. 2 is the schematic diagram that leading edge position detects;

Fig. 3 is the schematic diagram of trailing edge position probing;

Fig. 4 is the flow chart of step S3;

Fig. 5 is the structure chart of a L-STF;

Fig. 6 is the timing metric curve of conventional method;

Fig. 7 is timing metric curve of the present invention.

Embodiment

Below in conjunction with specific embodiment, illustrate the present invention further, these embodiments should be understood only be not used in for illustration of the present invention and limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to the various equivalent form of value of the present invention has all fallen within the application's claims limited range.

In order to technology contents of the present invention is described better, accompanying drawing is coordinated to be described as follows especially exemplified by specific embodiment.Time synchronization method in the present embodiment is that PXI3000 train of radio frequency (RF) the modularization instrument of producing at Ai Fasi (Aeroflex) realizes, use the data of the BCM43526 chip emission 802.11ac standard of Botong (Broadcom) company, bandwidth is 20MHz.

According to preferred embodiment of the present invention, the time synchronization method being applicable to OFDM-WLAN radio frequency test system as shown in Figure 1, comprises the following steps:

S1: utilize Botong's control software design to control to be measured BCM43526 launches that standard is 802.11ac, bandwidth for 20MHz, MCS be the Wave data of 8; Utilize PXI3035 VSA to carry out the conversion of radio frequency to base band data to the data received, its sample rate F is set _sfor 40MHz; At this moment, the periodic sequence of to be length be 320 sampled points of the L-STF in 802.11ac signal, comprise the part that 10 length repeated are 32 sampled points, be expressed as t1 to t10, the structure chart of L-STF as shown in Figure 5.

S2: Timing Synchronization process is carried out to the base band data obtained in step S1, obtain leading edge position and the trailing edge position of Frame according to the change of performance number, the data between intercepting leading edge position and trailing edge position are as complete frame data r (n);

S3: utilize the data r (n) obtained in step S2, realize Timing Synchronization by L-STF, calculate timing metric function M (n);

S4: by the peak of timing metric function M (n) obtained in detecting step S3, obtain accurate timing estimation position.

Wherein, in step S2, the acquisition of leading edge position as shown in Figure 2, arranges pre-trigger time pre_trigger=30, sample rate F _s=40e ⁶hz, threshold value R _t=15dB, minimum time MinOnTime=20e ^-6s, comparator postpone ComDelay=3, the time of integration InTime=20e ^-8s, integration skips time InSkipTime=150e ^-9s.The detection of leading edge position comprises the following steps:

S2.11: from base band data pre_trigger sampled point, calculates the power of two adjacent integrating ranges, as shown in first pair of integrating range that Fig. 2 bend shadow region represents; Wherein, integrating range length is multiplied by the comparator time delay that is spaced apart of two adjacent integrating range starting points, and integrating range length InPoint is by InTime and the sample rate F time of integration _scommon decision, here InPoint=round (InTime × Fs)=8;

S2.12: the ratio judging two adjacent integrating range power, namely whether the ratio of a rear integrating range power and previous integrating range power reaches the threshold value R preset _tif reach threshold value R _t, then step S2.13 is carried out; Otherwise the size skipping time InSkipTime according to integration skips to down a pair adjacent integrating range, as shown in second pair of integrating range that vertical line shadow region in Fig. 2 represents, and repeats the operation of step S2.11;

A rear integrating range in S2.13: obtain in step S2.12 two adjacent integrating ranges is as zequin, and the performance number of each integrating range of calculated for subsequent, as shown in Figure 2, if the ratio of the power of two vertical line shadow regions meets be greater than threshold value R _tcondition, then continue calculated for subsequent 1,2,3 ... the power of each integrating range, the number MCount of integrating range is determined by minimum time MinOnTime, Mcount=MinOnTime/InTime=100 in example, then judges whether the power ratio of the previous integrating range in the two adjacent integrating ranges obtained in each integrating range power and step S2.12 in follow-up 100 integrating ranges reaches the threshold value R preset _t; If all reach threshold value R _t, then step S2.14 is carried out; Otherwise, repeat the operation of step S2.11;

S2.14: using the index value of the starting point of the rear integrating range in two adjacent integrating ranges described in step S2.13 as leading edge position.

The detection method of similar leading edge position, in step S2, the acquisition of trailing edge position as shown in Figure 3, arranges pre-trigger time pre_trigger=30, sample frequency F _s=40e ⁶hz, threshold value R _t=15dB, minimum time MinOnTime=20e ^-6s, comparator postpone ComDelay=3, the time of integration InTime=20e ^-8s, integration skips time InSkipTime=150e ^-9s.The detection of trailing edge position comprises the following steps:

S2.21: from the leading edge position obtained, calculates the power of two adjacent integrating ranges, as shown in first pair of integrating range that Fig. 3 bend shadow region represents; Wherein, integrating range length is multiplied by the comparator time delay that is spaced apart of two adjacent integrating range starting points, and integrating range length InPoint is by InTime and the sample rate F time of integration _scommon decision, here InPoint=round (InTime × Fs)=8;

S2.22: the ratio judging the power of two adjacent integrating ranges, namely whether the ratio of previous integrating range power and a rear integrating range power reaches the threshold value R preset _t; If reach threshold value R _t, then step S2.23 is carried out; Otherwise the size skipping time InSkipTime according to integration skips to down a pair adjacent integrating range, as shown in second pair of integrating range that vertical line shadow region in Fig. 3 represents, and repeats the operation of step S2.21;

A rear integrating range in S2.23: obtain in step S2.22 two adjacent integrating ranges is as zequin, and the performance number of each integrating range of calculated for subsequent, as shown in Figure 3, if the ratio of the power of two vertical line shadow regions meets be greater than threshold value R _tcondition, then continue calculated for subsequent 1,2,3 ... the power of each integrating range, the number of integrating range is determined by minimum time MinOnTime, Mcount=MinOnTime/InTime=100 in example, in the previous integrating range power in the two adjacent integrating ranges then obtained in determining step S2.22 and follow-up 100 integrating ranges, whether the ratio of each integrating range power reaches the threshold value R preset _t; If all reach threshold value R _t, then step S2.24 is carried out; Otherwise, repeat the operation of step S2.21;

S2.24: using the index value of the starting point of the previous integrating range in two adjacent integrating ranges described in step S2.23 as trailing edge position.

In addition, as shown in Figure 4, utilize the concrete steps of the correlation of L-STF acquisition timing metric function as follows:

S3.1: utilize the data r (n) obtained in step S2 to calculate the data C (n) of delay aperture C:

$\begin{array}{c}C\left(n\right)=\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+64)+\underset{k=0}{\mathrm{\Σ}}{r}^{*}(n+k)r(n+k+128)\\ +\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+192)+\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+256)\\ +\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k+64)r(n+k+128)+\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k+64)r(n+k+192)\\ +\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k+64)r(n+k+256)+\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k+128)r(n+k+192)\\ +\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k+128)r(n+k+256)+\underset{k=0}{\overset{63}{\mathrm{\Σ}}}{r}^{*}(n+k+192)r(n+k+256)\end{array}$

Wherein, L is the length of 1/5th L-STF periodic sequences, and the periodic sequence of L-STF to be total length the be repetition of 320, so L=64.

S3.2: utilize the data r (n) obtained in described step S2 to calculate the data P (n) of delay aperture P:

$P\left(n\right)=\frac{1}{5}\underset{k=0}{\overset{63}{\mathrm{\Σ}}}({\left|r(n+k)\right|}^2+{\left|r(n+k+64)\right|}^2+{\left|r(n+k+128)\right|}^2+{\left|r(n+k+192)\right|}^2+{\left|r(n+k+256)\right|}^2)$

Wherein, L is the length of 1/5th L-STF periodic sequences, and the periodic sequence of L-STF to be total length the be repetition of 320, so L=64.

S3.3: calculate timing metric function

Finally, step S4 is obtained by following step:

S4.1: suitable threshold value T is set _h=0.5, in chronological order, the value that M (n) is engraved when each and threshold value T _hcompare successively, when the value of M (n) is greater than threshold value T _htime just think that peak value is about to occur, the value of the value of the moment d that record is corresponding and M (d) corresponding to d moment;

S4.2: if the value of the M (n) occurred after the d moment obtained in step S4.1 is greater than the value of M (d), then more the value of new record M (d) and d is the value of current time;

S4.3: if the value of the M (n) occurred after the d moment obtained in step S4.2 is all less than M (d) value, then using the peak value of the value of M (d) as described timing metric function M (n), corresponding moment d is as described timing estimation position.

As shown in Figure 6, timing metric curve of the present invention as shown in Figure 7 for the timing metric curve of conventional method.The result of comparison diagram 6 and Fig. 7 can be found out, time synchronization method timing metric curve when only utilizing L-STF of conventional method there will be related platform, and because in 802.11ac frame structure, unnecessary peak value has appearred in the existence of VHT-STF, sync bit can be caused like this to be difficult to locate accurately, L-LTF must to be recycled and carry out once accurate Timing Synchronization; And this method only utilizes L-STF just can obtain to only have the timing metric curve of a sharp-pointed peak value, eliminating timing metric curve in conventional method there is the problem of related platform, the position of peak value need be found just to judge the position of Timing Synchronization.Therefore, this method improves the precision of timing, simplifies the step of timing, is applicable to being used in the base band signal process of radio frequency test system.

Claims (5)

1. be applicable to a time synchronization method for OFDM-WLAN radio frequency test system, it is characterized in that: comprise the following steps:

S1: utilize VSA to process the WLAN radiofrequency signal that to be measured equipment is launched, being converted into sample rate is F _sdigital baseband signal;

S2: Timing Synchronization process is carried out to the digital baseband signal obtained in step S1, obtain leading edge position and the trailing edge position of Frame according to the change of performance number, the data between intercepting leading edge position and trailing edge position are as complete frame data r (n);

S3: utilize the data r (n) obtained in step S2, realize Timing Synchronization by L-STF, calculate timing metric function M (n);

S4: by the peak of timing metric function M (n) obtained in detecting step S3, obtain accurate timing estimation position.

2. the time synchronization method being applicable to OFDM-WLAN radio frequency test system according to claim 1, is characterized in that: in described step S2, leading edge position is calculated by following step:

S2.11: from the sampled point after the pre-trigger time, calculates the power of two adjacent integrating ranges; Wherein, integrating range length is multiplied by the comparator time delay that is spaced apart of two adjacent integrating range starting points, and integrating range length is determined jointly by the time of integration and sample rate;

S2.12: the ratio judging two adjacent integrating range power, namely whether the ratio of a rear integrating range power and previous integrating range power reaches the threshold value R preset _t; If reach threshold value R _t, then step S2.13 is carried out; Otherwise, skip the size of time according to integration and skip to down a pair adjacent integrating range, and repeat the operation of step S2.11;

A rear integrating range in S2.13: obtain in step S2.12 two adjacent integrating ranges is as zequin, the performance number of each integrating range of calculated for subsequent, judges whether the ratio of the previous integrating range power in the two adjacent integrating ranges obtained in each integrating range power follow-up and step S2.12 all reaches threshold value R successively _t; If all reach threshold value R _t, then step S2.14 is carried out; Otherwise, repeat the operation of step S2.11;

S2.14: using the index value of the starting point of the rear integrating range in two adjacent integrating ranges described in step S2.13 as leading edge position.

3. the time synchronization method being applicable to OFDM-WLAN radio frequency test system according to claim 1, is characterized in that: in described step S2, trailing edge position is calculated by following step:

S2.21: from described leading edge position, calculates the power of two adjacent integrating ranges; Wherein, integrating range length is multiplied by the comparator time delay that is spaced apart of two adjacent integrating range starting points, and integrating range length is determined jointly by the time of integration and sample rate;

S2.22: the ratio judging two adjacent integrating range power, namely whether the ratio of previous integrating range power and a rear integrating range power reaches the threshold value R preset _t; If reach threshold value R _t, then step S2.23 is carried out; Otherwise, skip the size of time according to integration and skip to down a pair adjacent integrating range, and repeat the operation of step S2.21;

A rear integrating range in S2.23: obtain in step S2.22 two adjacent integrating ranges is as zequin, the performance number of each integrating range of calculated for subsequent, whether the previous integrating range power in the two adjacent integrating ranges obtained in determining step S2.12 successively and the ratio of each integrating range power follow-up all reach threshold value R _t; If all reach threshold value R _t, then step S2.24 is carried out; Otherwise, repeat the operation of step S2.21;

S2.24: using the index value of the starting point of the previous integrating range in two adjacent integrating ranges described in step S2.23 as trailing edge position.

4. the time synchronization method being applicable to OFDM-WLAN radio frequency test system according to claim 1, is characterized in that: described step S3 is obtained by following step:

S3.1: utilize the data r (n) obtained in described step S2 to calculate the data C (n) of delay aperture C:

$\begin{array}{c}C\left(n\right)=\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+2L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+3L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k)r(n+k+4L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+L)r(n+k+2L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+L)r(n+k+3L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+L)r(n+k+4L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+2L)r(n+k+3L)\\ +\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+2L)r(n+k+4L)+\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}{r}^{*}(n+k+3L)r(n+k+4L)\end{array}$

Wherein, L is the length of 1/5th L-STF periodic sequences;

S3.2: utilize the data r (n) obtained in described step S2 to calculate the data P (n) of delay aperture P:

$P\left(n\right)=\frac{1}{5}\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}({\left|r(n+k)\right|}^2+{\left|r(n+k+L)\right|}^2+{\left|r(n+k+2L)\right|}^2+{\left|r(n+k+3L)\right|}^2+{\left|r(n+k+4L)\right|}^2)$

Wherein, L is the length of 1/5th L-STF periodic sequences;

S3.3: calculate timing metric function

5. the time synchronization method being applicable to OFDM-WLAN radio frequency test system according to claim 1, is characterized in that: described step S4 is obtained by following step:

S4.1: suitable threshold value T is set _h, in chronological order, the value that M (n) is engraved when each and threshold value T _hcompare successively, when the value of M (n) is greater than threshold value T _htime just think that peak value is about to occur, the value of the value of the moment d that record is corresponding and M (d) corresponding to d moment;

S4.2: if the value of the M (n) occurred after the d moment obtained in step S4.1 is greater than the value of M (d), then more the value of new record M (d) and d is the value of current time;

S4.3: if the value of M (n) corresponding to all moment after the d moment obtained in step S4.2 is all less than the value of M (d), then using the peak value of the value of M (d) as described timing metric function M (n), corresponding moment d is as described timing estimation position.