CN1181631C - Method and device for estimating head-path delay difference of different base station signals in WCDMA system - Google Patents

Abstract

The present invention discloses a time delay difference estimation method and a device for initial paths of different base station signals in a WCDMA system. Firstly, a search window signal is obtained by matched filtering and non-coherent accumulation; after the approximate position of an initial path is obtained through multi-path judgment, an initial path signal is intercepted from the search window; then, the cross correlation and the peak values of the initial path intercepted signals of different base stations are detected to obtain the initial path time delay difference among different base station signals, and the initial path intercepted signals of different base stations are obtained by the method of the present invention. The method and the device of the present invention effectively enhance the estimation precision of the initial path time delay difference, and consequently enhance the estimation precision to mobile station positions.

Description

Different base station signal in the WCDMA system first footpath delay inequality method of estimation and device

Technical field

The present invention relates to a kind of method and apparatus of estimating the first footpath delay inequality of different base station signal of WCDMA (WCDMA mobile communication system).

Background technology

In the WCDMA system, if adopt OTDOA (Observed Time DifferenceOf Arrival) localization method that travelling carriage is positioned, need at first estimate the poor of distance between different base station and the travelling carriage, and the difference of the distance between different base station and the travelling carriage can be estimated by the difference of signal transmission delay.In the wireless communications environment of land, owing to exist building and ground etc. to radio wave reflection, scattering and diffraction phenomenon, and cause the signal of transmitter emission to produce so-called multipath signal at receiving terminal through different propagated to receiver.Wherein, first footpath is meant detected article one footpath in the multipath signal, first footpath time delay is that the best of signal transmission delay between transmitter and the receiver is approached, and therefore accurately estimates the first footpath delay inequality of the different base station signal that travelling carriage receives, and is most important to the precision that improves mobile position estimation.

The method of estimating the first footpath delay inequality of different base station signal in the prior art mainly contains following two kinds:

A kind of is to obtain the search window signal by matched filtering and noncoherent accumulation, obtains multipath signal through multi-path judging, the footpath of estimating then to inform against the time delay, directly the first footpath time delay of different base station is subtracted each other the delay inequality that obtains first footpath.This method is simple, is easy to realize, when the first footpath estimation that obtains when multi-path judging was very accurate, the first footpath delay inequality that obtains was also very accurate accordingly.But in practice, because the mutual superposition of waveform between the multipath, and multipath has decay through behind the dissemination channel, make actual detected to first footpath have certain error.Therefore, estimate that in this way first footpath delay inequality can produce bigger error if under the multidiameter fading channel environment, make.

Another kind method be to the signal of different base station through after the matched filtering, directly carry out cross-correlation, its principle is as follows:

It is as follows to suppose to carry out two input signals that delay inequality estimates:

S wherein ₁(t), s ₂(t) be input signal x ₁(t), x ₂(t) signal component, n ₁(t), n ₂(t) be the noise component(s) of input signal, D is signal s ₁(t) with signal s ₂(t) delay inequality.

Utilize the incoherent characteristics of signal component and noise component(s), the cross-correlation function R of input signal _X1x2(τ) be:

$R_{x_1{x}_2}\left(\mathrm{\τ}\right)=a{R}_{s_1{s}_2}(\mathrm{\τ}-D)+R_{n_1{n}_2}\left(\mathrm{\τ}\right)$

R wherein _S1s2(τ) be the signal component s of input signal ₁(t), s ₂(t) cross-correlation function.If the noise of two input signals is incoherent mutually, then $R_{n_1{n}_2}\left(\mathrm{\τ}\right)=0,$ So cross-correlation function R of input signal _X1x2(τ) can be reduced to:

$R_{x_1{x}_2}\left(\mathrm{\τ}\right)=a{R}_{s_1{s}_2}\left(\mathrm{\τ}\right)*\mathrm{\δ}(\mathrm{\τ}-D)$

This shows, if the signal component s of hypothesis input signal ₁(t), s ₂(t) waveform has correlation, then input signal x ₁(t), x ₂(t) cross-correlation function R _X1x2(τ) get maximum constantly at D.Thereby the maximum of the cross-correlation function by detecting two signals can obtain the delay inequality of two signals.

But the shortcoming of the method is the requirement input signal has waveform similarity, and in practice, the signal of different base station emission produces multidiameter delay through behind the different channels, and such multipath signal no longer has waveform similarity.

Summary of the invention

The objective of the invention is at deficiency of the prior art, the method and apparatus of the first footpath of a kind of effective estimation different base station signal delay inequality is provided.

For achieving the above object, the method that the present invention adopts is: the first footpath of the different base station signal delay inequality method of estimation in a kind of WCDMA system, and its step is as follows:

At first the base station signal that travelling carriage is received carries out matched filtering and noncoherent accumulation obtains search window, then search window is carried out the judgement of head footpath, obtains the roughly time delay in first footpath;

Again the search window signal is carried out the intercepting of head footpath, obtain first footpath intercept signal;

The first footpath intercept signal that different base station is obtained respectively carries out cross-correlation, obtains the first footpath delay inequality between the different base station signal.

Adopt said method to estimate the device of the first footpath of different base station signal delay inequality, comprise matched filtering unit, noncoherent accumulation unit, and first footpath decision unit, first footpath interception unit, cross-correlation unit and first footpath delay inequality decision unit; Wherein:

The matched filtering receiving element is used for carrying out to the received signal matched filtering; The noncoherent accumulation unit is used for the result of matched filtering is carried out noncoherent accumulation, obtains the search window signal; First footpath decision unit is used for search window is carried out threshold judgement, and the roughly time delay that obtains first footpath is estimated; First footpath interception unit estimates to intercept the footpath signal of informing against according to the roughly time delay in head footpath from search window; Cross-correlation unit is used for the first footpath signal after the intercepting is carried out computing cross-correlation; First footpath delay inequality decision unit is used for the result of cross-correlation is carried out the peak value detection, obtains the delay inequality in first footpath.

Owing to adopted above method and device, by the search window signal being carried out the intercepting of head footpath, eliminated other footpaths when carrying out cross-correlation to head influence directly; Signal after head directly intercepted carries out computing cross-correlation, has overcome noise to the accurately influence of time delay judgement of head footpath, has improved the precision that first footpath delay inequality is estimated.

Description of drawings

Fig. 1 is a first footpath delay inequality method of estimation implementation schematic diagram in the prior art;

Fig. 2 is the implementation schematic diagram of a kind of execution mode of the inventive method;

Fig. 3 is the schematic diagram of a kind of execution mode of first footpath intercepting in the inventive method.

Fig. 4 is the first footpath of a present invention delay inequality estimation unit structural representation.

Embodiment

Figure 1 shows that the implementation of a kind of first footpath delay inequality method of estimation in the prior art, obtain the search window signal by matched filtering and noncoherent accumulation, obtain multipath signal through multi-path judging, estimate then to inform against the footpath the time delay, directly the first footpath time delay of different base station is subtracted each other the delay inequality that obtains first footpath.

With reference to the inventive method execution mode shown in Figure 2, at first the base station signal that travelling carriage is received carries out matched filtering and noncoherent accumulation obtains search window, then search window is carried out the judgement of head footpath, obtains first roughly time delay directly;

Again the search window signal is carried out the intercepting of head footpath, obtain first footpath intercept signal;

The first footpath intercept signal that different base station is obtained respectively carries out cross-correlation, obtains the first footpath delay inequality between the different base station signal.

Wherein, x1, x2 are the search window signal, and it can be the multipath of judging search window according to certain thresholding that search window is carried out the judgement of first footpath, and described thresholding is chosen according to the noise energy of search window, is estimated as benchmark with the noise energy to search window.Search window signal x1, x2 are carried out head footpath intercepting, are that the time delay with the head footpath is the center, about respectively intercept several chips, obtain intercept signal x1 ', x2 ', the quantitative range of intercepting chip can be 0.5 to 5.Shown in Figure 3 is a kind of execution mode of first footpath intercepting in the inventive method, suppose to comprise the 0th～8 chip shown in Fig. 3 left side by the search window signal that obtains behind matched filtering and the noncoherent accumulation, obtain the Position Approximate in first footpath after directly adjudicating by head on the 1st chip, at this moment, with the 1st chip is the center, about respectively intercept 1 chip, it is constant to keep original search window signal time delay distribute power in this scope, and in other positions of search window, its time delay distribute power is changed to 0, obtains the first footpath intercept signal shown in Fig. 3 right side.

The first footpath intercept signal that different base station is obtained respectively carries out cross-correlation, the step that obtains the first footpath delay inequality between the different base station signal can be the related operation that slides of the first footpath intercept signal with two different base stations, the relevant result that slides is carried out peak value detect, the position of maximum correspondence is estimated as the first footpath delay inequality of these two base stations.

Adopt the inventive method to estimate the device of the first footpath of different base station signal delay inequality, comprise matched filtering unit 1, noncoherent accumulation unit 2, and first footpath decision unit 3, first footpath interception unit 4, cross-correlation unit 5 and first footpath delay inequality decision unit 6; Wherein:

Matched filtering receiving element 1 is used for carrying out to the received signal matched filtering; Noncoherent accumulation unit 2 is used for the result of matched filtering is carried out noncoherent accumulation, obtains the search window signal; First footpath decision unit 3 is used for search window is carried out threshold judgement, and the roughly time delay that obtains first footpath is estimated; First footpath interception unit 4 estimates to intercept the footpath signal of informing against according to the roughly time delay in head footpath from search window; Cross-correlation unit 5 is used for the first footpath signal after the intercepting is carried out computing cross-correlation; First footpath delay inequality decision unit 6 is used for the result of cross-correlation is carried out the peak value detection, obtains the delay inequality in first footpath.

Claims (5)

1. A method for estimating first-path delay difference of different base station signals in a WCDMA system: It is characterized by: First, match filtering and non-coherent accumulation are performed on the base station signal received by the mobile station to obtain the search window, and then the first path judgment is performed on the search window to obtain the approximate time delay of the first path; Then perform head-path interception on the search window signal to obtain the first-path intercept signal; Cross-correlate the first-path intercepted signals obtained by different base stations to obtain the first-path time delay difference between different base station signals. Perform peak detection, and use the position corresponding to the maximum value as the first-path delay difference estimation of the two base stations. 2. The method for estimating the first-path time delay difference of different base station signals according to claim 1, characterized in that: said first-path judgment of the search window is to judge the multipath of the search window according to a certain threshold, and said threshold is based on The noise energy of the search window is selected. 3. The method for estimating the first-path time delay difference of different base station signals according to claim 1, characterized in that: said first-path interception of the search window signal takes the time delay of the first-path as the center, and several pieces are intercepted on the left and right sides. chips. 4. The method for estimating the first-path delay difference of different base station signals according to claim 3, characterized in that the number of intercepted chips on the left and right sides ranges from 0.5 to 5 with the first-path delay as the center. 5. A device for estimating first-path delay difference of different base station signals in a WCDMA system, comprising a matched filter unit and a non-coherent accumulation unit, characterized in that the device also includes a first-path judgment unit, a first-path interception unit, and a cross-correlation unit And the head-path delay difference judgment unit; wherein: The matched filter receiving unit is used to perform matched filtering on the received signal; the non-coherent accumulation unit is used to perform non-coherent accumulation on the matched filtering results to obtain the search window signal; the first-path judgment unit is used to perform threshold judgment on the search window to obtain The approximate time delay estimation of the first path; the first path interception unit intercepts the first path signal from the search window according to the approximate time delay estimation of the first path; the cross correlation unit is used to perform cross correlation calculation on the intercepted first path signal; The delay difference judging unit is used for performing peak detection on the cross-correlation result to obtain the time delay difference of the first path.