CN101442339A - Method and apparatus for estimating noise power - Google Patents

Abstract

The embodiment of the invention discloses a method and a device for estimating noise power. The method comprises the following steps: dividing an nth item and an (n+4)th item of a common pilot channel CPICH descrambling-despreading signs on a strongest path in a time slot into a group; subtracting the grouped nth item and the (n+4)th item; and estimating the noise power according to a subtracted result. The embodiment of the invention utilizes the CPICH descrambling-despreading signs on the strongest path to be divided into groups and subtracted, can effectively eliminate span interference in estimation of the noise power under the condition of double-antenna transmission, and improve accuracy of the estimation of the noise power.

Description

A kind of noise power estimation approach and device

Technical field

The present invention relates to the communications field, relate in particular to a kind of noise power estimation approach and device.

Background technology

In WCDMA (Wideband Code Division Multiple Access, Wideband Code Division Multiple Access (WCDMA)) system receiver algorithm, no matter be RAKE receiver, still balanced receiver all needs to carry out noise power and estimates.In RAKE receiver, noise power is estimated to influence asking for of LLR (Log-Likelihood Ratio, log-likelihood ratio).In balanced receiver, noise power estimates that not only influencing LLR asks for, and also influences asking for of equalizing coefficient.Therefore the noise power estimation performance directly influences the performance of whole receiver.

After existing noise power estimation scheme adopts CPICH channel descrambling and de-spreading, remove each 1 symbol end to end in the time slot, adjacent two symbols is formed one group then, offsets in the group, asks mould square, asks average mode to obtain the noise power estimated value again.

In implementing process of the present invention, the inventor finds to exist at least in the prior art following problem:

Under the two antenna transmit situation, existing Noise Estimation scheme can not be eliminated between the footpath that multipath channel brings and disturb, thereby influences the accuracy that noise power is estimated, and then has influenced the demodulation performance of whole receiver.

Summary of the invention

The embodiment of the invention provides a kind of noise power estimation approach and device, when carrying out the noise power estimation to be implemented in, eliminates and disturbs between the footpath the noise power estimation effect, improves the accuracy of noise power estimation.

The embodiment of the invention provides a kind of noise power estimation approach, may further comprise the steps:

The n item and the n+4 item of the Common Pilot Channel CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group;

N item and n+4 item after the described grouping are subtracted each other;

According to the described estimating noise power as a result that subtracts each other.

The device that the embodiment of the invention provides a kind of noise power to estimate comprises:

Grouped element is used for the n item and the n+4 item of the Common Pilot Channel CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group;

Subtract each other the unit, be used for n item and n+4 item after the described grouped element grouping are subtracted each other;

Estimation unit is used for subtracting each other the estimating noise power as a result that the unit subtracts each other according to described.

Compared with prior art, the embodiment of the invention has the following advantages at least:

The embodiment of the invention is divided into one group with the n item and the n+4 item of the CPICH descrambling and de-spreading symbol on the most powerful path in the time slot, subtract each other in the group, thereby can under the situation of two antenna transmit, effectively eliminate between the footpath in the noise power estimation and disturb, improve the accuracy that noise power is estimated.

Description of drawings

The schematic flow sheet of the method that Fig. 1 provides for the embodiment of the invention;

The schematic flow sheet of method under concrete application scenarios that Fig. 2 provides for the embodiment of the invention;

The received signal modeling schematic diagram of the WCDMA system that Fig. 3 provides for the embodiment of the invention;

CPICH under the two antenna transmit that Fig. 4 provides for the embodiment of the invention sends symbol pattern;

The structural representation of the device that Fig. 5 provides for the embodiment of the invention;

The detailed structure schematic diagram of the device that Fig. 6 provides for the embodiment of the invention.

Embodiment

Below in conjunction with drawings and Examples the present invention is introduced.

The embodiment of the invention provides a kind of noise power estimation approach, as shown in Figure 1, may further comprise the steps:

Step s101 is divided into one group with the n item and the n+4 item of the Common Pilot Channel CPICH descrambling and de-spreading symbol on the most powerful path in the time slot;

Step s102 subtracts each other n item and n+4 item after the grouping;

Step s103 is according to the above-mentioned estimating noise power as a result that subtracts each other.

By the method that adopts the embodiment of the invention to provide, the n item and the n+4 item of the CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group, subtract each other in the group, thereby can be under the situation of two antenna transmit, effectively eliminate between the footpath in the noise power estimation and disturb, improve the accuracy that noise power is estimated.

Below in conjunction with a concrete application scenarios the present invention is described in further detail.Wherein, be example with the Noise Estimation under the WCDMA system.

The embodiment of the invention provides a kind of noise power estimation approach, as shown in Figure 2, may further comprise the steps:

Step s201 is the received signal modeling of WCDMA system.

The received signal modeling of WCDMA system as shown in Figure 3.Wherein, c ₀, c ₁.., c ₂₅₅PN sign indicating number for CPICH; H (0), h (1) ..., h (L-1) is an equivalent channel, i.e. the convolution of RC filter and actual channel; ..., x (k-1), x (k), x (k+1) ... be each modulation symbol that sends on the CPICH channel; Y (0), y (1) ... be received signal.

Step s202 obtains the general formula of received signal according to above-mentioned modeling.

This formula can for:

y(0)＝x(k)c ₀h(0)+x(k-1)c ₂₅₅h(1)+…+x(k-1)c _256-(L-1)h(L-1)+n ₀

y(1)＝x(k)c ₁h(0)+x(k)c ₀h(1)+x(k-1)c ₂₅₅h(2)+…+x(k-1)c _257-(L-1)h(L-1)+n ₁

.

.

.

y(L-2)＝x(k)c _L-2h(0)+x(k)c _L-3h(1)+…+x(k)c ₀h(L-2)+x(k-1)c ₂₅₅h(L-1)+n _L-2

y(L-1)＝x(k)c _L-1h(0)+x(k)c _L-2h(1)+…+x(k)c ₀h(L- ¹)+n _L-1 (1)

y(L)＝x(k)c _Lh(0)+x(k)c _L-1h(1)+…+x(k)c ₁h(L-1)+n _L

.

.

.

y(255)＝x(k)c ₂₅₅h(0)+x(k)c ₂₅₄h(1)+…+x(k)c _255-(L-1)h(L-1)+n ₂₅₅

y(256)＝x(k+1)c ₀h(0)+x(k)c ₂₅₅h(1)+…+x(k)c _256-(L-1)h(L-1)+n ₂₅₆

.

.

.

y(255+(L-1))＝x(k+1)c _L-2h(0)+…+x(k+1)c ₀h(L-2)+x(k)c ₂₅₅h(L-1)+n _255+(L-1)

Formula (1) can be noted by abridging and is:

$y\left(j\right)=\left\{\begin{array}{cc}\underset{i=0}{\overset{j}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-i}h\left(i\right)+\underset{i=j+1}{\overset{L-1}{\mathrm{\&Sigma;}}}x(k-1){\mathrm{<figure-callout\; id="256"\; label="c"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">c</figure-callout>}}_{256+j-i}h\left(i\right)+{\mathrm{<figure-callout\; id="0"\; label="n\; j"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">n</figure-callout>}}_j& 0\&le;j<L-1\\ \underset{i=0}{\overset{L-1}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-i}h\left(i\right)+n_j& L-1\&le;j\&le;255\\ \underset{i=0}{\overset{j-256}{\mathrm{\&Sigma;}}}x(k+1)c_{j-256-i}h\left(i\right)+\underset{i=j-256+1}{\overset{L-1}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-i}h\left(i\right)+{\mathrm{<figure-callout\; id="256"\; label="n\; j"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">n</figure-callout>}}_j& 256\&le;j\&le;255+(L-1)\end{array}\right.---\left(2\right)$

Step s203, the CPICH received signal on the descrambling and de-spreading most powerful path.

If footpath l _mBe most powerful path, general 0＜l _m＜L-1, then the operation of the descrambling and de-spreading on the most powerful path can be formulated as:

$r\left(n\right)=\underset{j=l_m}{\overset{l_m+255}{\mathrm{\&Sigma;}}}y\left(j\right)c_{j-l_m}^{*}$

$=\underset{j=l_m}{\overset{L-2}{\mathrm{\&Sigma;}}}\{\underset{i=0}{\overset{j}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-i}h\left(i\right)+\underset{i=j+1}{\overset{L-1}{\mathrm{\&Sigma;}}}x(k-1){\mathrm{<figure-callout\; id="256"\; label="c"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">c</figure-callout>}}_{256+j-i}h\left(i\right)+n_j\}{c}_{j-l_m}^{*}$

$+\underset{j=L-1}{\overset{255}{\mathrm{\&Sigma;}}}\{\underset{i=0}{\overset{L-1}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-i}h\left(i\right)+n_j\}{c}_{j-l_m}^{*}$

$+\underset{j=256}{\overset{l_m+255}{\mathrm{\&Sigma;}}}\{\underset{i=0}{\overset{j-256}{\mathrm{\&Sigma;}}}x(k+1)c_{j-256-i}h\left(i\right)+\underset{i=j-256+1}{\overset{L-1}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-i}h\left(i\right)+n_j\}{c}_{j-l_m}^{*}$

$=\underset{j=l_m}{\overset{l_m+255}{\mathrm{\&Sigma;}}}x\left(k\right)c_{j-l_m}h\left(l_m\right)c_{j-l_m}^{*}$

$+\underset{j=l_m}{\overset{L-2}{\mathrm{\&Sigma;}}}\left\{\underset{i\&NotEqual;l_m}{\overset{j}{\underset{i=0}{\mathrm{\&Sigma;}}}}x\left(k\right)c_{j-i}h\left(i\right)+\underset{i=j+1}{\overset{L-1}{\mathrm{\&Sigma;}}}x(k-1){\mathrm{<figure-callout\; id="256"\; label="c"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">c</figure-callout>}}_{256+j-i}h\left(i\right)\right\}{c}_{j-l_m}^{*}$

$+\underset{j=L-1}{\overset{255}{\mathrm{\&Sigma;}}}\left\{\underset{i\&NotEqual;l_m}{\overset{L-1}{\underset{i=0}{\mathrm{\&Sigma;}}}}x\left(k\right)c_{j-i}h\left(i\right)+n_j\right\}{c}_{j-l_m}^{*}$

$+\underset{j=256}{\overset{l_m+255}{\mathrm{\&Sigma;}}}\{\underset{i=0}{\overset{j-256}{\mathrm{\&Sigma;}}}x(k+1)c_{j-256-i}h\left(i\right)+\underset{i\&NotEqual;l_m}{\overset{L-1}{\underset{i=j-256+1}{\mathrm{\&Sigma;}}}}x\left(k\right)c_{j-i}h\left(i\right)\}{c}_{j-l_m}^{*}---\left(3\right)$

$+\underset{j=l_m}{\overset{l_m+255}{\mathrm{\&Sigma;}}}{n_{j}c}_{j-l_m}^{*}$

First is target descrambling and de-spreading symbol in the formula (3), and second is distracter, the 3rd

Be noise item, $E\left\{{\left|\right|\underset{j=l_m}{\overset{l_m+255}{\mathrm{\&Sigma;}}}{n}_j{c}_j^{*}\left|\right|}^2\right\}={\mathrm{SF}}_{\mathrm{CPICH}}{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">c</figure-callout>}}^2.$ From formula (3) as can be seen, in the symbol that obtains behind the CPICH descrambling and de-spreading, target descrambling and de-spreading symbol and noise item are arranged not only, also have distracter.

Distracter in the formula (3) can be written as:

$\mathrm{Inter}$

$+\underset{j=l_m}{\overset{L-2}{\mathrm{\&Sigma;}}}\left\{\underset{i\&NotEqual;l_m}{\overset{j}{\underset{i=0}{\mathrm{\&Sigma;}}}}x\left(k\right)c_{j-i}h\left(i\right)+\underset{i=j+1}{\overset{L-1}{\mathrm{\&Sigma;}}}x(k-1){\mathrm{<figure-callout\; id="256"\; label="c"\; filenames="A200810187289E00121.png"\; state="\{\{state\}\}">c</figure-callout>}}_{256+j-i}h\left(i\right)\right\}{c}_{j-l_m}^{*}$

$+\underset{j=L-1}{\overset{255}{\mathrm{\&Sigma;}}}\left\{\underset{i\&NotEqual;l_m}{\overset{L-1}{\underset{i=0}{\mathrm{\&Sigma;}}}}x\left(k\right)c_{j-i}h\left(i\right)+n_j\right\}{c}_{j-l_m}^{*}---\left(4\right)$

$+\underset{j=256}{\overset{l_m+255}{\mathrm{\&Sigma;}}}\{\underset{i=0}{\overset{j-256}{\mathrm{\&Sigma;}}}x(k+1)c_{j-256-i}h\left(i\right)+\underset{i\&NotEqual;l_m}{\overset{L-1}{\underset{i=j-256+1}{\mathrm{\&Sigma;}}}}x\left(k\right)c_{j-i}h\left(i\right)\}{c}_{j-l_m}^{*}---\left(3\right)$

From formula (4) as can be seen, distracter is not only relevant with displacement autocorrelation, the channel of PN sign indicating number, also with the CPICH channel on before and after to send symbol x (k-1) relevant with x (k+1).

Fig. 4 is under the two antenna transmit, the transmission symbol pattern of CPICH.

As can be seen from Figure 4: under the situation of two antenna transmit, the transmission symbol pattern of CPICH repeats every 4 symbols, therefore the front and back symbol of i symbol is with identical with the front and back symbol of i+4 symbol, and then the influence of the front and back transmission symbol that i symbol and the distracter of i+4 symbol are subjected in the formula 4 is identical.For becoming channel slowly, channel remains unchanged substantially in continuous 5 symbols (i symbol～i+4 symbol), and 4 of the mark spaces that then descrambling and de-spreading on the most powerful path is obtained subtract each other, and formula (4) just equals 0, promptly can eliminate fully between the footpath and disturb.And because the front and back symbol difference of adjacent two symbols, disturbing between the footpath that is subjected to thus can't be by the elimination of subtracting each other of adjacent two symbols in the prior art.

Step s204 obtains receiving symbol r (n) and r (n+4) according to the general expression of CPICH descrambling and de-spreading symbol.

Suppose the received signal on the descrambling and de-spreading most powerful path, the CPICH descrambling and de-spreading symbol in the time slot that obtains is respectively r (0), r (1) ..., r (9).Then remove respectively 1 symbol of the interior head and the tail of time slot, r (1) and r (5), r (2) and r (6), r (3) and r (7), r (4) and r (8) are divided into groups respectively, the target descrambling and de-spreading symbol of every group of interior two symbols is identical with distracter.

Step s205 subtracts each other receiving symbol r (n) and r (n+4).

To offset i.e. v (1)=r (1)-r (5), v (2)=r (2)-r (6), v (3)=r (3)-r (7), v (4)=r (4)-r (8) in the above-mentioned class symbol group.Because the target descrambling and de-spreading symbol of two symbols is identical with distracter in every group, so r (n) subtracts each other a back residual noise item with r (n+4).

Step s206 carries out noise power according to the above-mentioned result who subtracts each other and estimates.

The above-mentioned remaining noise item in back that subtracts each other is asked mould square to ask on average to obtain noise power-value again; Concrete, the noise power of estimation equals

${\mathrm{\&sigma;}}^2=\frac{{\left|v\left(1\right)\right|}^2{\left|v\left(2\right)\right|}^2+{\left|v\left(3\right)\right|}^2+{\left|v\left(4\right)\right|}^2}{8}$

The method that the embodiment of the invention provides is not only applicable to the situation of two antenna transmit, is equally applicable to other situation, and for example the situation of single-antenna transmission does not repeat them here.

By the method that adopts the embodiment of the invention to provide, the n item and the n+4 item of the CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group, subtract each other in the group, thereby can be under the situation of two antenna transmit, effectively eliminate between the footpath in the noise power estimation and disturb, improve the accuracy that noise power is estimated.

The device that the embodiment of the invention provides a kind of noise power to estimate as shown in Figure 5, comprising:

Grouped element 51 is used for the n item and the n+4 item of the CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group.

Suppose the received signal on the descrambling and de-spreading most powerful path, the CPICH symbol in the time slot that obtains is respectively r (0), r (1) ..., r (9).This unit removes respectively 1 symbol of the interior head and the tail of time slot, and r (1) and r (5), r (2) are divided into groups respectively with r (6), r (3) and r (7), r (4) and r (8), and the target descrambling and de-spreading symbol of every group of interior two symbols is identical with the interference symbol.

Subtract each other unit 52, be used for n item and n+4 item after grouped element 51 groupings are subtracted each other.

Offset i.e. v (1)=r (1)-r (5), v (2)=r (2)-r (6), v (3)=r (3)-r (7), v (4)=r (4)-r (8) in the class symbol group of this unit with grouped element 51.Because the target descrambling demodulation symbol of two symbols is identical with distracter in every group, so r (n) subtracts each other a back residual noise item with r (n+4).

Estimation unit 53 is used for according to subtracting each other the estimating noise power as a result that unit 52 subtracts each other.

This unit subtracts each other the remaining noise item in back and asks mould square to ask on average to obtain noise power-value again the above-mentioned unit 52 that subtracts each other.

As shown in Figure 6, this device also comprises:

Modeling unit 54 is used to the received signal modeling.

Formula unit 55 is used for obtaining according to the modeling of modeling unit 54 formula of the CPICH received signal on the most powerful path.

Descrambling and de-spreading unit 56 is used for the formula that descrambling and de-spreading formula unit 55 obtains and obtains CPICH descrambling and de-spreading symbol.

Estimation unit 53 comprises:

Ask mould squaring cell 531, be used for asking mould square subtracting each other the result who subtracts each other unit 52;

Averaging unit 532 is used for the mould square result that asks who asks mould squaring cell 531 is asked on average, obtains the estimated value of noise power.

By the device that adopts the embodiment of the invention to provide, the n item and the n+4 item of the CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group, subtract each other in the group, thereby can be under the situation of two antenna transmit, effectively eliminate between the footpath in the noise power estimation and disturb, improve the accuracy that noise power is estimated.

Through the above description of the embodiments, those skilled in the art can be well understood to the present invention and can realize by hardware, also can realize by the mode that software adds necessary general hardware platform.Based on such understanding, technical scheme of the present invention can embody with the form of software product, it (can be CD-ROM that this software product can be stored in a non-volatile memory medium, USB flash disk, portable hard drive etc.) in, comprise some instructions with so that computer equipment (can be personal computer, server, the perhaps network equipment etc.) carry out the described method of each embodiment of the present invention.

In a word, the above is preferred embodiment of the present invention only, is not to be used to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1, a kind of noise power estimation approach is characterized in that, may further comprise the steps:

The n item and the n+4 item of the Common Pilot Channel CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group;

N item and n+4 item after the described grouping are subtracted each other;

According to the described estimating noise power as a result that subtracts each other.

2, the method for claim 1 is characterized in that, described n item and n+4 item with the Common Pilot Channel CPICH descrambling and de-spreading symbol on the most powerful path in the time slot was divided into before one group, also comprised:

Carry out modeling to received signal;

Obtain the formula of the CPICH received signal on the most powerful path according to described modeling;

The described formula of descrambling and de-spreading obtains the CPICH descrambling and de-spreading symbol on the most powerful path;

Remove each symbol of head and the tail of described CPICH descrambling and de-spreading symbol in the time slot.

3, method as claimed in claim 1 or 2 is characterized in that, described CPICH descrambling and de-spreading symbol comprises target descrambling and de-spreading symbol, distracter and noise item.

4, the method for claim 1 is characterized in that, the estimating noise power as a result that described basis is subtracted each other comprises:

The described result who subtracts each other is asked mould square;

The described result of mould square that asks is asked on average, obtain the estimated value of described noise power.

5, method as claimed in claim 1 or 2 is characterized in that, described CPICH is for becoming channel slowly.

6, a kind of device of noise power estimation is characterized in that, comprising:

Grouped element is used for the n item and the n+4 item of the Common Pilot Channel CPICH descrambling and de-spreading symbol on the most powerful path in the time slot are divided into one group;

Subtract each other the unit, be used for n item and n+4 item after the described grouped element grouping are subtracted each other;

Estimation unit is used for subtracting each other the estimating noise power as a result that the unit subtracts each other according to described.

7, device as claimed in claim 6 is characterized in that, also comprises:

Modeling unit is used for carrying out to received signal modeling;

The formula unit is used for obtaining according to the modeling of described modeling unit the formula of the CPICH received signal on the most powerful path;

The descrambling and de-spreading unit is used for formula that the described formula of descrambling and de-spreading unit obtains and obtains CPICH descrambling and de-spreading symbol on the most powerful path;

The head and the tail unit is used to remove each symbol of head and the tail of the CPICH descrambling and de-spreading symbol that described descrambling and de-spreading unit obtains in the time slot.

8, device as claimed in claim 6 is characterized in that, described estimation unit comprises:

Ask mould square subelement, be used for the described result who subtracts each other is asked mould square;

Average subelement is used for the described mould square result that asks of mould square subelement that asks is asked on average, obtains the estimated value of described noise power.

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