CN103152767A - Uplink synchronous detection method for resisting frequency deviation in wireless communication system - Google Patents

Abstract

The invention provides an uplink synchronous detection method for resisting frequency deviation in a wireless communication system. According to a protocol, the computation result of Sr-pre, n(k)*Csing, s(k) can be known to be a sequence consisting of +1 and -1 and is set to be Zn; e<j[pi/4+(pi/2)k]> can be removed by using a twiddle factor of which the rotation direction is opposite; (Rn')<2> is subjected to fast Fourier transform, the frequency spectrum is analyzed, frequency deviation delta f can be obtained by calculating the position of the highest peak value in the frequency spectrum, and the precision of the delta f is solved to be Sample/(2*FFTn), wherein the FFTn is a fast Fourier transform point and the Sample is sampling rate; and under the condition that the Signal to Noise Ratio is relatively good, the loss of the Signal to Noise Ratio of the (Rn')<2> is only 3db, and when the Signal to Noise Ratio is 1, the loss of the Signal to Noise Ratio of the (Rn')<2> is only 5db, and the calculation of the frequency deviation performance is hardly affected. By adopting the method, the uplink synchronous detection performance can be effectively improved.

Description

Be used for the uplink synchronous detection method of frequency offset resistant in a kind of wireless communication system

Technical field

The present invention relates to a kind of uplink synchronous detection method, particularly be used for the uplink synchronous detection method of frequency offset resistant in a kind of wireless communication system.

Background technology

In wireless communication system, must synchronize before carrying out data interaction with terminal in the base station, comprising down-going synchronous and two processes of uplink synchronous: (1) down-going synchronous generally all comprises main synchronous and auxiliary synchronous two channels, terminal is completed down-going synchronous according to main synchronous and auxiliary sync bit relation, terminal complete and the base station between down-going synchronous after the data of ability correct reception base station; (2) the uplink synchronous process is to be initiated the prefix part of Physical Random Access Channel by terminal, the uplink synchronous process is detected to complete to the prefix part of the Physical Random Access Channel that terminal is initiated in the base station, after base station and terminal are completed uplink synchronous, the reception that the data basestation that terminal sends could be correct.

In wireless communication system, the prefix part that is used for the Physical Random Access Channel of uplink synchronous process is all to have good autocorrelation and cross correlation, so in the situation that the non-constant of signal to noise ratio still has extraordinary detection performance, thereby success rate and the accuracy of uplink synchronous have been guaranteed.

In the uplink synchronous process, if there is larger frequency deviation in wireless communication system, this terminal of example high ferro is in the situation that high-speed motion, the frequency deviation that Doppler effect produces, can cause autocorrelation and the cross correlation of the prefix part of Physical Random Access Channel sharply to worsen along with the increase of frequency deviation, can cause detecting like this hydraulic performance decline, the success rate of uplink synchronous reduces, finally cause terminal uplink synchronous difficulty, affect the data interaction between terminal and base station.

Summary of the invention

The present invention proposes to be used in a kind of wireless communication system the uplink synchronous detection method of frequency offset resistant, and the method can improve the uplink synchronous in uplink synchronous detection performance, particularly broadband CDMA system effectively

Detect performance.

Technical scheme of the present invention is achieved in that

Because the prefix sequence generation of Physical Random Access Channel in each wireless communication protocol is different, therefore the present invention describes the prefix testing process of whole Physical Random Access Channel in detail take Wideband Code Division Multiple Access (WCDMA) (WCDMA) system as example, according to the description of agreement 3GPP agreement TS25.213, can know that the sequence of PRACH prefix part is:

$\mathrm{Cpre},n,s\left(k\right)=\mathrm{Sr}-\mathrm{pre},n\left(k\right)\&times;\mathrm{Csig},s\left(k\right){\&times;e}^{j(\frac{\mathrm{\&pi;}}{4}+\frac{\mathrm{\&pi;}}{2}k)},k=\mathrm{0,1,2,3},...,4095;---\left(8\right)$

Can know according to agreement, Sr-pre, n (k) * Csig, s (k) operation result be one group by+1 and-1 sequence that forms, the present invention utilizes this sequence to carry out frequency deviation to estimate, be made as Zn.

Can be understood as a twiddle factor, utilize the opposite twiddle factor of direction of rotation

It can be removed, the calculating process that frequency deviation is estimated does not exert an influence.

Can think that the prefix signal of the Physical Random Access Channel that receives is dimerous by signal Zn' and noise Nn with frequency deviation, so Rn is expressed as following formula:

Rn=Zn'+Nn (9)

Wherein Zn' can be expressed as:

Wherein,

Be initial phase, f is frequency deviation.

Receiving the signal to noise ratio of signal this moment is:

SNR=Zn'/Nn (11)

At first to remove twiddle factor before calculating frequency deviation

Multiply by a twiddle factor that direction of rotation is opposite

Get final product, owing to removing the twiddle factor process, noise is not exerted an influence, so noise section do not change, the signal Rn' that can obtain removing after twiddle factor can be expressed as following formula:

${\mathrm{Rn}}^{\&prime;}=\mathrm{Rn}\&times;e^{j(\frac{\mathrm{\&pi;}}{4}-\frac{\mathrm{\&pi;}}{2}n)}=\mathrm{Zn}\&times;e^{(\mathrm{\&phi;}+2\mathrm{\&pi;}\&CenterDot;f\&CenterDot;n)}---\left(12\right)$

After Rn' is carried out square operation, can be just the signal of complete 1 known array that forms and noise composition receiving signal intensity, so just can find the solution its frequency deviation, the signal indication of this moment be (Rn') ²As shown in formula (6), owing to having carried out square operation by (Rn') ²The frequency deviation of the frequency deviation result of calculating and primary reception signal Rn is the relation of 2 times:

(Rn') ²=e ^{2·(φ+2π·f·n)}+Nn' (13)

To (Rn') ²The method that can adopt conjugation related operation method to find the solution phase difference of finding the solution of frequency deviation is found the solution frequency deviation, but the method easily is subjected to noise jamming, affects computational solution precision, in the situation that signal to noise ratio can't be calculated frequency deviation accurately less than 5db.The prefix of utilizing Physical Random Access Channel is all a long sequence this point, and the present invention has adopted a kind of method of new calculating frequency deviation, to (Rn') ²Carry out fast Fourier transform, then its frequency spectrum is analyzed, ask that in its frequency spectrum, the peak-peak position just can obtain frequency deviation Δ f, this method is in the situation that noise still can be calculated frequency deviation accurately for-25db, the precision of finding the solution frequency deviation Δ f is Sample/ (2 * FFTn), wherein FFTn is that fast Fourier transform is counted, and Sample is sample rate.

This moment, correspondence received signal (Rn') ²Signal to noise ratio can be released by formula (2) (4):

SNR'=SNR ²/(2×SNR+1) (14)

Can find out in signal to noise ratio preferably in situation, (Rn') from formula (7) ²Signal to noise ratio only lost 3db, in the situation that signal to noise ratio is 1, (Rn') ²Signal-to-Noise also only lost 5db, almost there is no what impact concerning the performance of calculating frequency deviation.

Beneficial effect of the present invention: detect with General Physics Random Access Channel prefix and compare, the present invention has increased and utilizes the Physical Random Access Channel prefix to carry out frequency deviation to estimate and carry out these two steps of compensate of frequency deviation to received signal, effectively having promoted the detection performance of Physical Random Access Channel prefix when having larger frequency deviation in the wireless communication system; The method not only can be in the situation that do not know that the prefix sequence of Physical Random Access Channel calculates frequency deviation, and still can calculate accurately frequency deviation in can signal to noise ratio very little situation.

Description of drawings

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, the below will do to introduce simply to the accompanying drawing of required use in embodiment or description of the Prior Art, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is used for the processing block diagram of the uplink synchronous detection method of frequency offset resistant in wireless communication system of the present invention.

Fig. 2 is used for the flow chart of the uplink synchronous detection method of frequency offset resistant in wireless communication system of the present invention.

Embodiment

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 clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Based on the embodiment in the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that obtains under the creative work prerequisite.

With reference to Fig. 1 and Fig. 2, be used for the uplink synchronous detection method of frequency offset resistant in a kind of wireless communication system, detect with General Physics Random Access Channel prefix and compare, the present invention has increased and utilizes the Physical Random Access Channel prefix to carry out frequency deviation to estimate and carry out these two steps of compensate of frequency deviation to received signal, effectively having promoted the detection performance of Physical Random Access Channel prefix when having larger frequency deviation in the wireless communication system.in wireless communication system, the prefix of Physical Random Access Channel is detected the impact of performance for eliminating frequency deviation, the present invention had first done frequency deviation and has estimated and two steps of compensate of frequency deviation before the prefix of Physical Random Access Channel detects, wherein, frequency deviation algorithm for estimating part, the prefix testing process that general frequency deviation algorithm for estimating can't be applied to Physical Random Access Channel has two reasons: (1) detection signal need to be known array, then known array is carried out conjugation related operation method and calculate frequency deviation, and Physical Random Access Channel prefix testing process is that unknown signaling is detected, (2) in the smaller situation of noise, the frequency offset estimation result error is larger, can not meet the demands.Therefore the present invention has adopted a kind of new method to calculate frequency deviation, this method not only can be in the situation that do not know that the prefix sequence of Physical Random Access Channel calculates frequency deviation, and still can calculate accurately frequency deviation in can signal to noise ratio very little situation.The prefix of Physical Random Access Channel is all autocorrelation and the extraordinary sequence of cross correlation that is generated as the basis by+1 and-1 Zn sequence that forms take a group in wireless communication system, the present invention utilizes by+1 and-1 these characteristics that form, after the Zn sequence is carried out square operation, with its known array that becomes one complete 1, so just frequency deviation can have been calculated.

In the situation that noise is smaller, general its error calculated of frequency offset calculation method can be very large, can't use, therefore the present invention has adopted a kind of new method to calculate frequency deviation, because the prefix of Physical Random Access Channel is all a long sequence, therefore can utilize these characteristics to use fast Fourier transform to find the solution frequency deviation to the method for its spectrum analysis, this computational methods are affected by noise very little, and computational accuracy is only counted relevant with sample rate to fast Fourier transform.Because the prefix sequence generation of Physical Random Access Channel in each wireless communication protocol is different, therefore the present invention describes the prefix testing process of whole Physical Random Access Channel in detail take Wideband Code Division Multiple Access (WCDMA) (WCDMA) system as example, according to the description of agreement 3GPP agreement TS25.213, can know that the sequence of PRACH prefix part is:

$\mathrm{Cpre},n,s\left(k\right)=\mathrm{Sr}-\mathrm{pre},n\left(k\right)\&times;\mathrm{Csig},s\left(k\right){\&times;e}^{j(\frac{\mathrm{\&pi;}}{4}+\frac{\mathrm{\&pi;}}{2}k)},k=\mathrm{0,1,2,3},...,4095;---\left(15\right)$

Can know according to agreement, Sr-pre, n (k) * Csig, s (k) operation result be one group by+1 and-1 sequence that forms, the present invention utilizes this sequence to carry out frequency deviation to estimate, be made as Zn.

Can be understood as a twiddle factor, utilize the opposite twiddle factor of direction of rotation It can be removed, the calculating process that frequency deviation is estimated does not exert an influence.

Can think that the prefix signal of the Physical Random Access Channel that receives is dimerous by signal Zn' and noise Nn with frequency deviation, so Rn is expressed as following formula:

Rn=Zn'+Nn (16)

Wherein Zn' can be expressed as:

Wherein,

Be initial phase, f is frequency deviation.

Receiving the signal to noise ratio of signal this moment is:

SNR=Zn'/Nn (18)

At first to remove twiddle factor before calculating frequency deviation

Multiply by a twiddle factor that direction of rotation is opposite

Get final product, owing to removing the twiddle factor process, noise is not exerted an influence, so noise section do not change, the signal Rn' that can obtain removing after twiddle factor can be expressed as following formula:

${\mathrm{Rn}}^{\&prime;}=\mathrm{Rn}\&times;e^{j(\frac{\mathrm{\&pi;}}{4}-\frac{\mathrm{\&pi;}}{2}n)}=\mathrm{Zn}\&times;e^{(\mathrm{\&phi;}+2\mathrm{\&pi;}\&CenterDot;f\&CenterDot;n)}---\left(19\right)$

After Rn' is carried out square operation, can be just the signal of complete 1 known array that forms and noise composition receiving signal intensity, so just can find the solution its frequency deviation, the signal indication of this moment be (Rn') ²As shown in formula (6), owing to having carried out square operation by (Rn') ²The frequency deviation of the frequency deviation result of calculating and primary reception signal Rn is the relation of 2 times:

(Rn') ²=e ^{2·(φ+2π·f·n)}+Nn' (20)

To (Rn') ²The method that can adopt conjugation related operation method to find the solution phase difference of finding the solution of frequency deviation is found the solution frequency deviation, but the method easily is subjected to noise jamming, affects computational solution precision, in the situation that signal to noise ratio can't be calculated frequency deviation accurately less than 5db.The prefix of utilizing Physical Random Access Channel is all a long sequence this point, and the present invention has adopted a kind of method of new calculating frequency deviation, to (Rn') ²Carry out fast Fourier transform, then its frequency spectrum is analyzed, ask that in its frequency spectrum, the peak-peak position just can obtain frequency deviation Δ f, this method is in the situation that noise still can be calculated frequency deviation accurately for-25db, the precision of finding the solution frequency deviation Δ f is Sample/ (2 * FFTn), wherein FFTn is that fast Fourier transform is counted, and Sample is sample rate.

This moment, correspondence received signal (Rn') ²Signal to noise ratio can be released by formula (2) (4):

SNR'=SNR ²/(2×SNR+1) (21)

Can find out in signal to noise ratio preferably in situation, (Rn') from formula (7) ²Signal to noise ratio only lost 3db, in the situation that signal to noise ratio is 1, (Rn') ²Signal-to-Noise also only lost 5db, almost there is no what impact concerning the performance of calculating frequency deviation.

After utilizing the frequency deviation Δ f that calculates in the frequency deviation estimation to do compensate of frequency deviation to received signal, the detection performance of the prefix of Physical Random Access Channel will no longer be subject to the impact of frequency deviation, thereby reach the purpose of frequency offset resistant, promote the detection performance of the prefix of Physical Random Access Channel with this.

The above is only preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (1)

1. be used for the uplink synchronous detection method of frequency offset resistant in a wireless communication system, it is characterized in that, the method is: according to the description of agreement 3GPP agreement TS25.213, can know that the sequence of PRACH prefix part is:

$\mathrm{Cpre},n,s\left(k\right)=\mathrm{Sr}-\mathrm{pre},n\left(k\right)\&times;\mathrm{Csig},s\left(k\right)\&times;e^{j(\frac{\mathrm{\&pi;}}{4}+\frac{\mathrm{\&pi;}}{2}k)},k=\mathrm{0,1,2,3},...,4095;---\left(1\right)$

Can know according to agreement, Sr-pre, n (k) * Csig, s (k) operation result be one group by+1 and-1 sequence that forms, be made as Zn;

Can be understood as a twiddle factor, utilize the opposite twiddle factor of direction of rotation It can be removed;

Therefore Rn is expressed as following formula:

Rn=Zn'+Nn(2)

Wherein Zn' can be expressed as:

Wherein,

Be initial phase, f is frequency deviation;

Receiving the signal to noise ratio of signal this moment is:

SNR=Zn'/Nn (4)

The signal Rn' that can obtain removing after twiddle factor can be expressed as following formula:

${\mathrm{Rn}}^{\&prime;}=\mathrm{Rn}\&times;e^{j(\frac{\mathrm{\&pi;}}{4}-\frac{\mathrm{\&pi;}}{2}n)}=\mathrm{Zn}\&times;e^{(\mathrm{\&phi;}+2\mathrm{\&pi;}\&CenterDot;f\&CenterDot;n)}+\mathrm{Nn}---\left(5\right)$

After Rn' is carried out square operation, can be just the signal of complete 1 known array that forms and noise composition receiving signal intensity, so just can find the solution its frequency deviation, the signal indication of this moment be (Rn') ²As shown in formula (6), owing to having carried out square operation by (Rn') ²The frequency deviation of the frequency deviation result of calculating and primary reception signal Rn is the relation of 2 times:

${\left({\mathrm{Rn}}^{\&prime;}\right)}^2=e^{2\&CenterDot;(\mathrm{\&phi;}+2\mathrm{\&pi;}\&CenterDot;f\&CenterDot;n)}+{\mathrm{Nn}}^{\&prime;}---\left(6\right)$

To (Rn') ²Carry out fast Fourier transform, then its frequency spectrum is analyzed, asked that in its frequency spectrum, the peak-peak position just can obtain frequency deviation Δ f, the precision of finding the solution frequency deviation Δ f is Sample/ (2 * FFTn), wherein FFTn is that fast Fourier transform is counted, and Sample is sample rate;

This moment, correspondence received signal (Rn') ²Signal to noise ratio can be released by formula (2) (4):

SNR'=SNR ²/(2×SNR+1)(7)

Can draw at last, (Rn') ²Signal to noise ratio only lost 3db, in the situation that signal to noise ratio is 1, (Rn') ²Signal-to-Noise also only lost 5db, almost there is no what impact concerning the performance of calculating frequency deviation.

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