CN1756411A - WCDMA system access channel frequency deviation estimating method - Google Patents

Abstract

The invention relates to a estimation method for access channel frequency off-set in WCDMA, which comprises following steps: 1. detecting the predecessor part of access channel signal without frequency off-set compensation to obtain multi-path position with maximal energy; 2. removing interference and sign to the data of said multi-path position, dividing result into some small segments; 3. taking coherent integration treatment to every segment data, calling the result as symbol; 4. calculating auto-correlation function of different data; 5. calculating estimation value of phase rotation angle of adjacent symbols; 6. calculating frequency off-set estimation value. This method increases precision and decreases consumption to hardware resource.

Description

WCDMA system cut-in channel frequency deviation estimating method

Technical field

The present invention relates to the access channel frequency deviation estimating method of wireless communication system, the access channel frequency deviation estimating method of particularly a kind of Wideband Code Division Multiple Access (WCDMA) (WCDMA) communication system up link.

Background technology

Along with the fast development of mobile communication, people require also more and more higher to the quality of mobile communication and the type of service that provides thereof, and the proposition of 3G (Third Generation) Moblie and development have met people's this demand just, therefore get most of the attention.Wideband Code Division Multiple Access (WCDMA) (WCDMA) is (the 3rdGeneration Partnership Project of 3-G (Generation Three mobile communication system) standardization body, 3GPP) the Radio Transmission Technology of Ti Chuing (Radio TransmissionTechnology, RTT) scheme, it not only can provide high-quality voice service, and can provide and the similar multimedia service of fixed network.

In Wideband Code Division Multiple Access (WCDMA) (WCDMA) system, access channel is one of them very important part, and professional beginning all is to set up service link again after the experience access channel inserts earlier.The signal that the access channel receiving system will detect comprises two parts, promptly leading and message, as shown in Figure 1.Wherein leading have the signature of 16 bits to repeat formation 256 times, as shown in Figure 2.Wherein detection of preamble is being undertaken three big tasks: 1, detect this and leadingly whether comprise effective signature; 2, detect to contain how many effectively multipaths in this access channel; 3, frequency offset estimating.What the present invention relates to is exactly the method for frequency offset estimating wherein.

In the prior art, default usually several frequency deviations (be generally 4 ,+/-200Hz ,+/-800Hz, use Δ f respectively _i, i=0,1,2,3) and carry out compensate of frequency deviation to received signal, for certain signature, corresponding each frequency deviation all has a ceiling capacity (to use MaxEnerger _iΔ f is adopted in expression _iThe maximum energy value that obtains, i=0,1,2,3), if MaxEnerger so _iMaximum in 4 ceiling capacities, just with Δ f _iFrequency offset estimating value as this time detection of preamble.This frequency offset estimating value will be used for the initial frequency deviation compensation that the leading message part afterwards of access channel is separated timing.Because the real system intermediate frequency is bigger than normal generally-1500 to 1500Hz scopes (3GPP requirement system can do with the frequency deviation in this scope).In the current method,, show the following aspects to very coarse of the estimation of frequency deviation:

1, no matter how high signal to noise ratio is, all accurately impossible as long as actual frequency deviation not on default several frequency deviations, is estimated so.

2, actual frequency deviation from preset value far away (such as+/-1500Hz), frequency offset estimating value that obtains and actual frequency deviation differ too big, this will reduce receptivity.

3, default a plurality of frequency deviation values will consume a large amount of hardware resources.

Wherein the loss that the message demodulation performance is brought of the deviation of frequency offset estimating value and actual frequency deviation as shown in Figure 6.

Summary of the invention

Technical problem to be solved by this invention provides a kind of WCDMA system cut-in channel frequency deviation estimating method, overcomes shortcomings such as frequency offset estimating is not accurate enough in the prior art, the consumption hardware resource is too big.

To achieve these goals, the invention provides a kind of WCDMA system cut-in channel frequency deviation estimating method, estimate the frequency deviation of access channel according to the anglec of rotation of signal among the coherent integration result.

Concrete, a kind of WCDMA system cut-in channel frequency deviation estimating method provided by the invention is applied to the up link of WCDMA system, and its characteristics are, comprise the steps:

Step 1 detects the leading part in the access channel signal under the situation of not doing compensate of frequency deviation, thereby obtains the multi-path location of energy maximum;

Step 2 is carried out descrambling earlier with the reception data of the multi-path location of energy maximum and is separated signature and handle, and result is divided into some segments again;

Step 3 is carried out coherent integration with the data in every segment and is handled, and the result that integration obtains is referred to as symbol;

Step 4 is calculated the auto-correlation function between the distinct symbols;

Step 5 is calculated the estimated value that phase angle rotates between the adjacent-symbol;

Step 6 is calculated the frequency offset estimating value according to intersymbol phase angle difference and intersymbol time difference.

Above-mentioned WCDMA system cut-in channel frequency deviation estimating method, its characteristics are, in step 1, specifically comprise the steps:

The relevant execution descrambling operation of elder generation with scrambler;

Carry out through fast hadamard transform again and separate signature operation, from multipath, find the multi-path location of energy maximum.

Above-mentioned WCDMA system cut-in channel frequency deviation estimating method, its characteristics be, in step 2, is by descrambling being separated data behind the signature with can be by 4096 Integer N that divide exactly _ChipFor unit is divided into the m segment, wherein $m=\frac{4096}{N_{\mathrm{chip}}}.$

Above-mentioned WCDMA system cut-in channel frequency deviation estimating method, its characteristics be, in step 3, and this symbol $S_i={\mathrm{se}}^{j2\mathrm{\π\Δf}{t}_i},$ I=0 wherein ..., m-1; S is the signal that does not have frequency deviation, and Δ f is a frequency deviation, t _iBe the time.

Above-mentioned WCDMA system cut-in channel frequency deviation estimating method, its characteristics be, in step 4, can by following formula calculate auto-correlation function R between the distinct symbols (i, k),

$R(i,k)=S_{i+k}*{\stackrel{\‾}{S}}_i,$

I=0 wherein ..., m-2; K=1 ..., m-1; R (i k) is plural number,

The result's that the expression coherent integration obtains symbol S _iConjugate of symbol.

Above-mentioned WCDMA system cut-in channel frequency deviation estimating method, its characteristics are, in step 5, can calculate the estimated value that phase angle rotates between the adjacent-symbol by following formula

$\mathrm{\Δ}{\mathrm{\θ}}_{i,k}=\frac{a\tan \left(\frac{\mathrm{Imag}\left(R(i,k)\right)}{\mathrm{Real}\left(R(i,k)\right)}\right)}{k},$

$\mathrm{\Δ}\widehat{\mathrm{\θ}}=\frac{1}{(m-1)*(m-2)}\underset{i=0}{\overset{m-2}{\mathrm{\Σ}}}\underset{k=1}{\overset{m-1}{\mathrm{\Σ}}}\mathrm{\Δ}{\mathrm{\θ}}_{i,k}$

Imag wherein, Real represents to get plural R (i, imaginary part k) and real part respectively; Atan (x) expression is to the x tangent computing of negating.

Above-mentioned WCDMA system cut-in channel frequency deviation estimating method, its characteristics are, and be in step 6, poor according to the phase angle between the adjacent-symbol And the time difference T between the adjacent-symbol calculates frequency offset estimating value Δ f:

$\mathrm{\Δf}=\frac{\mathrm{\Δ}\widehat{\mathrm{\θ}}}{2\mathrm{\π}*T}.$

The method of the frequency offset estimating that the present invention proposes compared with prior art, its advantage is:

1, signal to noise ratio is high more, it is accurate more to estimate, even deviation levels off to 0, as Fig. 4, shown in Figure 5, because signal to noise ratio is higher, promptly interference is littler comparatively speaking among Fig. 5, is disturbing under the little situation, the frequency deviation that mode by phase angle rotation estimates is more accurate, so the standard variance of frequency offset estimating value (the standard variance representative estimates that frequency deviation departs from the average departure situation of actual frequency deviation) obvious littler than among Fig. 4 just.And with respect to traditional frequency deviation estimating method, because it has only fixing several default frequency deviation, so signal to noise ratio is high more also of no use.

Even 2 frequency deviations very big (such as+/-1500Hz), it is too big that frequency offset estimating value and actual frequency deviation value can not differ, and as Fig. 4, shown in Figure 5, the standard variance of frequency offset estimating value is more steady, can not become big and too far away partially, thereby improve the access channel receptivity with frequency deviation with true frequency deviation.

3, the frequency deviation not only estimated of the inventive method is more accurate than prior art, and required hardware resource is less than the default required hardware resource of a plurality of frequency deviations of prior art far away.

Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.

Description of drawings

Fig. 1 is a WCDMA system uplink access channel signal schematic representation;

Fig. 2 is a WCDMA system uplink Access Channel Preamble part schematic diagram;

Fig. 3 is the concrete implementation step schematic diagram of the present invention;

The standard variance of the estimation frequency deviation that emulation obtained when Fig. 4 was EcI0=-20dB;

The standard variance of the estimation frequency deviation that emulation obtained when Fig. 5 was EcI0=-15dB;

The loss that Fig. 6 brings the message demodulation performance for the frequency offset estimating deviation.

Embodiment

The principle of frequency deviation estimating method of the present invention is as follows:

Suppose that not having the signal of frequency deviation is S, the signal when so frequency deviation being arranged is se ^{J2 π Δ ft}, wherein Δ f is a frequency deviation, and unit is Hz (hertz), and t is the time, the s of unit (second).Suppose t1, t2 is two different moment, and $S_i={\mathrm{se}}^{j2\mathrm{\π\Δf}{t}_i},$ Use S _iExpression S _iConjugate of symbol, so $S_2*{\stackrel{\‾}{S}}_1={\left|S\right|}^2{e}^{j2\mathrm{\π\Δf}(t_2-t_1)}={\left|S\right|}^2{e}^{\mathrm{j\Δ\θ}}=f(\mathrm{\Δf},\mathrm{\Δt}),$ Wherein, △ t=t ₂-t ₁

$\tan \mathrm{gent}\left(\mathrm{\Δ\θ}\right)=\frac{\mathrm{Imag}\left(f(\mathrm{\Δf},\mathrm{\Δt})\right)}{\mathrm{Real}\left(f(\mathrm{\Δf},\mathrm{\Δt})\right)},$

Imag wherein, Real represent to get the imaginary part and the real part of plural number respectively.

So 2 π Δ f Δ t=Δ θ=atan (f (Δ f, Δ t))

That is: $\mathrm{\Δf}=\frac{a\tan \left(f(\mathrm{\Δf},\mathrm{\Δt})\right)}{2\mathrm{\π\Δt}}$ Be the frequency offset estimating value.

Below in conjunction with drawings and Examples technical scheme of the present invention is described in further detail, according to following described embodiment, the technical staff in same field can be easy to realize the present invention.

As shown in Figure 3, method of the present invention mainly may further comprise the steps:

Step 301, under the situation of not doing compensate of frequency deviation, detect leadingly, specifically comprise elder generation's descrambling operation of relevant execution with scrambler, pass through FHT (fast hadamard transform) execution again and separate signature operation, from multipath, find the multi-path location of energy maximum.

Step 302, the first descrambling of reception data (the whole leading 4096 chip data that comprise) of the multi-path location of energy maximum is separated signature, again descrambling is separated data behind the signature with N _Chip(can be by 4096 integers of dividing exactly such as 256 or 512 etc.) for unit is divided into some segments, be established $m=\frac{4096}{N_{\mathrm{chip}}}.$

Data coherency integration in step 303, the every segment, the result that integration obtains is referred to as symbol (complex symbol) here, uses S _iExpression, wherein $S_i={\mathrm{se}}^{j2\mathrm{\π\Δf}{t}_i},$ I=0 wherein ..., m-1; S is the signal that does not have frequency deviation, and Δ f is a frequency deviation, t _iBe the time.

Auto-correlation function R between step 304, the calculating distinct symbols (i, k),

$R(i,k)=S_{i+k}*{\stackrel{\‾}{S}}_i,i=0,...,m-2,k=1,...,m-1.$

(i k) is plural number to R.

The estimated value that phase angle rotates between step 305, the calculating adjacent-symbol:

$\mathrm{\Δ}{\mathrm{\θ}}_{i,k}=\frac{a\tan \left(\frac{\mathrm{Imag}\left(R(i,k)\right)}{\mathrm{Real}\left(R(i,k)\right)}\right)}{k},$

$\mathrm{\Δ}\widehat{\mathrm{\θ}}=\frac{1}{(m-1)*(m-2)}\underset{i=0}{\overset{m-2}{\mathrm{\Σ}}}\underset{k=1}{\overset{m-1}{\mathrm{\Σ}}}\mathrm{\Δ}{\mathrm{\θ}}_{i,k};$

Imag wherein, Real represent to get the imaginary part and the real part of plural number respectively; Atan (x) expression is to the x tangent computing of negating.

Step 306, poor according to the phase angle between the adjacent-symbol

And the time difference T between the adjacent-symbol (unit: second) calculating frequency offset estimating value:

$\mathrm{\Δf}=\frac{\mathrm{\Δ}\widehat{\mathrm{\θ}}}{2\mathrm{\π}*T}$

The frequency offset estimating value that obtains like this, more more accurate than the frequency offset estimating value that the method for presetting several frequency deviations in the prior art obtains.

Fig. 4 and Fig. 5 are simulation result, can obtain two conclusions from figure: according to frequency deviation estimating method of the present invention, at first, though actual frequency deviation depart under the bigger situation (such as+/-1500Hz) still can estimate frequency deviation more exactly; Secondly, (EcI0 is a conception of species of expression signal to noise ratio among the WCDMA to EcI0=-15 than EcI0=-20 signal to noise ratio height, EcI0 (dB of unit)=10*log (energy of the energy of 1 chip signal/1 chip noise)), y axle among the figure " standard variance of the frequency offset estimating value that obtains in the emulation " is an index of explanation accuracy of estimation, standard variance is more little, illustrate that estimation is accurate more, it is more accurate to estimate when as can be seen from the figure signal to noise ratio is big.

According to the inventive method, only need to calculate the amount of calculation of a default frequency deviation, estimate after the frequency deviation, only need go to compensate data with this frequency deviation from antenna port, and carry out detection of preamble (amount of calculation of this part is very little) to obtaining some bigger multipaths of energy in the step 301, and adopt 4 default frequency deviations in the prior art usually, therefore adopt the inventive method, only need significantly reduce resource requirement than 1/4 slightly more point of prior art resource requirement.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (7)

1, a kind of WCDMA system cut-in channel frequency deviation estimating method is applied to the up link of WCDMA system, it is characterized in that, comprises the steps:

Step 1 detects the leading part in the access channel signal under the situation of not doing compensate of frequency deviation, thereby obtains the multi-path location of energy maximum;

Step 2 is carried out descrambling earlier with the reception data of the multi-path location of energy maximum and is separated signature and handle, and result is divided into some segments again;

Step 3 is carried out coherent integration with the data in every segment and is handled, and the result that integration obtains is referred to as symbol;

Step 4 is calculated the auto-correlation function between the distinct symbols;

Step 5 is calculated the estimated value that phase angle rotates between the adjacent-symbol;

Step 6 is calculated the frequency offset estimating value according to intersymbol phase angle difference and intersymbol time difference.

2, WCDMA system cut-in channel frequency deviation estimating method according to claim 1 is characterized in that, in step 1, specifically comprises the steps:

The relevant execution descrambling operation of elder generation with scrambler;

Carry out through fast hadamard transform again and separate signature operation, from multipath, find the multi-path location of energy maximum.

3, WCDMA system cut-in channel frequency deviation estimating method according to claim 2 is characterized in that, in step 2, is by descrambling being separated data behind the signature with can be by 4096 Integer N that divide exactly _ChipFor unit is divided into the m segment, wherein $m=\frac{4096}{N_{\mathrm{chip}}}.$

4, WCDMA system cut-in channel frequency deviation estimating method according to claim 3 is characterized in that, in step 3, and this symbol $S_i={\mathrm{Se}}^{j2\mathrm{\π\Δf}{t}_i}$ , i=0 wherein ..., m-1; S is the signal that does not have frequency deviation, and Δ f is a frequency deviation, t _iBe the time.

5, WCDMA system cut-in channel frequency deviation estimating method according to claim 4 is characterized in that, in step 4, can by following formula calculate auto-correlation function R between the distinct symbols (i, k),

R(i，k)＝S _i+k* S _i，

I=0 wherein ..., m-2; K=1 ..., m-1; (i k) is plural number, S to R _iThe result's that the expression coherent integration obtains symbol S _iConjugate of symbol.

6, WCDMA system cut-in channel frequency deviation estimating method according to claim 5 is characterized in that, in step 5, can calculate the estimated value that phase angle rotates between the adjacent-symbol by following formula

${\mathrm{\Δ\θ}}_{i,k}=\frac{a\tan \left(\frac{\mathrm{Im\; ag}\left(R(i,k)\right)}{\mathrm{Re\; al}\left(R(i,k)\right)}\right)}{k},$

$\mathrm{\Δ}\widehat{\mathrm{\θ}}=\frac{1}{(m-1)*(m-2)}\underset{i=0}{\overset{m-2}{\mathrm{\Σ}}}\underset{k=1}{\overset{m-1}{\mathrm{\Σ}}}{\mathrm{\Δ\θ}}_{i,k}$

Imag wherein, Real represents to get plural R (i, imaginary part k) and real part respectively; Atan (x) expression is to the x tangent computing of negating.

7, WCDMA system cut-in channel frequency deviation estimating method according to claim 6 is characterized in that, and is in step 6, poor according to the phase angle between the adjacent-symbol And the time difference T between the adjacent-symbol calculates frequency offset estimating value Δ f:

$\mathrm{\Δf}=\frac{\mathrm{\Δ}\widehat{\mathrm{\θ}}}{2\mathrm{\π}*T}.$

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