CN1474196A - High precision anti-multipath narrow band correlated distance detecting system in radio positioning - Google Patents

Abstract

The present invention relates to radio positioning technology based on time or time difference, and is used for frequency spreading communication system to detect the signal arrival time or arrival time difference. The narrow band correlated ranging system adopts one leading correlator and one lagging correlator, and has shorted correlation interval between the leading correlator and the lagging correlator to reduce the measurement error caused by multipath interfernce. Operating the output correlation result of the two correlators can obtain the error information of initial time estimation and obtain precise time of arrival or time difference of arrival. The ranging system of the present invention has raised time detecting precision, effective suppression on the effect of noise and multipath and thus raised positioning precision.

Description

The relevant range measurement system in the arrowband of high precision, anti-multipath in the wireless location

Technical field

The present invention relates to a kind of range measurement system that is used for wireless location, particularly relate to adopt based on time of arrival (toa) or time of arrival difference wireless location in range measurement system.

Background technology

Nowadays, the portable terminal positioning service has caused people's common concern, and has obtained very fast development because of its application prospects.The most frequently used wireless location technology has field intensity localization method (SS at present, signal strength), based on time of arrival (toa) (TOA, time of arrive) or signal arrival time difference (TDOA, time difference of arrive) location technology, based on electric wave incident angle (AOA, angle of arrive), mixed location method etc.Wherein two kinds of time-based location technologies of TOA and TDOA realize relatively easily having obtained using the most widely because precision is relative higher.In time-based positioning system, the precision of time measurement and anti-interference are the key factors that finally obtains the higher location estimation of precision.

In the actual wireless communication environments, various interference ubiquities, wherein multi-path influence is to cause one of time measurement main error.Because the reflection of ground and surrounding buildings thing, transmit often via many different paths, with different time arrival receiving antennas, these arrive ripple and are called the multipath ripple, because the difference of their intensity, travel-time and the bandwidth that transmits etc., and make amplitude, phase place and the generation disperse of time delay aspect of the received signal after synthetic, thereby cause distortion or decline.Multipath transmisstion can make signal arrive the required time lengthening of receiving end usually, and it may cause intersymbol interference, thereby causes signal stained.Because the existence of multipath is even if also can bring negative effect to the mensuration of signal transmission delay under the situation that has line-of-sight propagation between portable terminal and the base station.Therefore multipath is to cause various signal characteristic measured values the fundamental cause of error to occur, and the inhibition that multipath is disturbed is one of locator key technology.

In wireless location system, traditional propagation delay is measured the general received signal method relevant with reference signal that adopt and is obtained, and when adopting the TOA/TDOA method to position, the major parameter that influence time is estimated is time delay τ ₀With frequency displacement f ₀, usual way is to adopt two-dimensional correlation search (frequency domain search and time domain search) to carry out TOA and FOA (arriving frequency, frequency ofarrive) estimation.Yet when multipath signal exists, cause the peak value of received signal and pseudo-random code related function deviation to be arranged with actual peak value, and because the characteristic of spread spectrum system, traditional latency measurement can't play inhibiting effect to 1.0 chips (chip) with the interference of interior multipath signal, thereby cause measuring accuracy to descend, and may cause wrong signal time delay measurement.

At present quite a few about the patented technology of multipath inhibition aspect.For example: the anti-multipath technology that is used to adopt the positioning system that arrives the angle technology, its Chinese number of patent application is 01124493.3, denomination of invention is the arrival angle estimating apparatus and the method for tool multipath interference suppression unit, it provides a kind of arrival angle estimating apparatus of tool multipath interference suppression unit, adopt the antenna of space diversity to come the incident angle of detected wireless signals, this invention is used for based on the wireless location that arrives angle (AOA).Other the detection and the search that are mostly to be used for multipath are to communicate control and to improve communication quality.As Chinese patent application number is 00111563, denomination of invention is the patent of the method and apparatus of code division multiple address communication system Multipath searching, adopt a kind of method and apparatus of code division multiple address communication system Multipath searching, mainly utilize a kind of adaptive threshold technology that can change, its method adopts the multichannel sliding correlation detector to carry out local P N sign indicating number address and input signal is made related operation, output to a Multipath searching controller through the correlation behind the related operation and search for, and can find multipath rapidly.Chinese patent application number is 00119528, denomination of invention be a kind of new code division multiple access system Multipath searching and distribution method disclosure of the Invention Multipath searching and distribution method in a kind of RAKE receiver that is applicable to wideband CDMA system, improve the performance of RAKE receiver.

Yet the patent of anti-multipath aspect does not all also relate to time-based wireless location system at present, can't be implemented in the effect that anti-multipath disturbs in the time-based wireless location system.

Summary of the invention

The object of the present invention is to provide a kind of range measurement system that is used for based on the wireless location system of time or mistiming, particularly the relevant distance-finding method in arrowband.But adopt this system's anti-multipath to disturb, improve the time detecting precision, and then improve the bearing accuracy of positioning system.

According to purpose of the present invention, the invention provides a kind of range measurement system that improves the time detecting precision, suppresses the multipath interference that has, be used for a spread spectrum communication system, poor with the time of arrival or the time of arrival of detection signal.In the relevant range measurement system in arrowband of the present invention, on the basis of original correlator, adopt a leading correlator and lag correlation device, on the basis that original time detecting is estimated, leading correlator adopts a reference code that is ahead of punctual local signal, the lag correlation device adopts a reference code that lags behind punctual local signal, and two correlators are done further tracking and detection near the TOA of initial detecting or TDOA.In addition, adopt one to select the device at the interval between the lead and lag correlator to change related interval, shorten this and can change the relevant output result in arrowband at interval.Output correlated results to two correlators carries out computing, can obtain the control information that initial time is estimated, thereby initial time is estimated to correct.

The present invention also provides a kind of can suppress the distance measuring equipment that multipath disturbs, comprise a leading correlator in I road, an I road lag correlation device, the leading correlator in Q road, a Q road lag correlation device, four correlators are used for that signal is carried out lead and lag and are correlated with, a shift register that produces reference signal, a Discr. mode selector, can select different associative modes and Discr. output mode, an arithmetic unit is used for the correlated results of leading correlator and lag correlation device is carried out computing.

Adopt the arrowband of the present invention range measurement system of being correlated with, can improve time detecting precision, the influence of noise and multipath is had the good restraining effect, play critical effect finally obtaining the higher positioning result of precision.In order to obtain better effect, need to increase some hardware facilities, improve sampling rate, need higher digital signal processing speed simultaneously, the also corresponding raising of computation complexity, but these can be implemented under the condition of current science and technology and processor technology.

Description of drawings

Fig. 1 arrowband of the present invention correlative measurement is apart from system chart

Arrowband correlator in Fig. 2 system of the present invention is realized block diagram

The arrowband of Fig. 3 related interval d=0.5chip curve of output of being correlated with

The arrowband of Fig. 4 related interval d=1chip curve of output of being correlated with

Fig. 5 arrowband correlated results relatively

Embodiment

With the TOA detection is the example explanation, and the arrowband correlative measurement is seen accompanying drawing 1 apart from system principle diagram.Wherein, coherent detection correlation search obtains to TOA according to a preliminary estimate for adopting original TOA method of estimation, and the relevant Narrowcorrelation in arrowband is for to be realized by the lead and lag correlator.Obtain the relevant result in arrowband by the interval that changes between the lead and lag correlator.

R _Fe(τ _k) for shifting to an earlier date the cross correlation results of reference signal and received signal, R _Fl(τ _k) being the cross correlation results of hysteresis reference signal and received signal, the arrowband correlator is output as d τ _k, its computing formula is

dτ _k＝[R _fe(τ _k)] ²-[R _fl(τ _k)] ² (1)

The realization functional block diagram of the arrowband correlator in the system of the present invention is seen accompanying drawing 2.Received signal obtains baseband signal behind intermediate-frequency filter, obtain I road and Q road sampled signal by the AD analog to digital conversion, respectively with reference PN signal simple crosscorrelation.The operator scheme of Discr. has two kinds of noncoherent patterns and a kind of relevant pattern, and wherein, the I road is all relevant respectively with the lead and lag reference code with Q road sampled signal, and correlated results is respectively I _EK, Q _EK, I _LK, Q _LK, for subtracting the after-power pattern in advance; I road and Q road sampled signal all with to subtract the hysteresis reference code on time and in advance relevant respectively, are the dot product pattern, in addition, also have a kind of Coherence Mode.Operator scheme can be finished by the select command of Discr..

Incoherent Discr. is subtracting under the after-power pattern in advance, and Discr. is output as ${\mathrm{d\τ}}_k=I_{\mathrm{EK}}^2+Q_{\mathrm{EK}}^2-I_{\mathrm{LK}}^2-Q_{\mathrm{LK}}^2---\left(2\right)$

Under the dot product pattern, Discr. is output as

dτ _k＝I _E-L，KI _PK+Q _E-L，KQ _PK (3)

A kind of typical relevant Discr. has following form:

dτ _k＝I _E-L，Ksign(I _PK) (4)

When the form of expression of having determined received signal, d τ _kAverage just can obtain, thereby obtain the curve of output of Discr., and tracking error track, wherein Discr. output is the function of time delay spacing d.

If received signal is $x\left(t\right)=\underset{i=0}{\overset{M}{\mathrm{\Σ}}}{a}_i\left(t\right)d\left(t\right)\mathrm{PN}[t-{\mathrm{\τ}}_i\left(t\right)]\cos [{\mathrm{\ω}}_{c}t+{\mathrm{\θ}}_i\left(t\right)]---\left(5\right)$

PN (t) wherein, d (t) is respectively pseudo-random code and data message, and i=0 represents direct signal, and other M is multipath signal, α _i, τ _i, θ _iRepresent amplitude, time delay and phase delay respectively.

Advanced code and hysteresis coded signal after the local reference signal modulation are respectively $x_L(T+\frac{d}{2})=\mathrm{PN}(t-{\widehat{\mathrm{\τ}}}_0+\frac{d}{2})\cos \left[({\mathrm{\ω}}_c-{\mathrm{\ω}}_{\mathrm{IF}})t\right]---\left(6\right)$ $x_E(T-\frac{d}{2})=\mathrm{PN}(t-{\widehat{\mathrm{\τ}}}_0-\frac{d}{2})\cos \left[({\mathrm{\ω}}_c-{\mathrm{\ω}}_{\mathrm{IF}})t\right]---\left(7\right)$

ω wherein _IFBe the intermediate frequency angular frequency.

Input signal carries out relevant respectively with the lead and lag signal and obtains through after the if bandpas filter filtering $R_E\left({\widehat{\mathrm{\τ}}}_0\right)=\frac{1}{2}\underset{i=0}{\overset{m}{\mathrm{\Σ}}}{a}_{i}d\left(t\right)R({\widehat{\mathrm{\τ}}}_0-{\mathrm{\τ}}_i+\frac{d}{2})\cos ({\mathrm{\ω}}_{\mathrm{IF}}t+{\mathrm{\θ}}_i)----\left(8\right)$ $R_L\left({\widehat{\mathrm{\τ}}}_0\right)=\frac{1}{2}\underset{I=0}{\overset{m}{\mathrm{\Σ}}}{a}_{i}d\left(t\right)R({\widehat{\mathrm{\τ}}}_0-{\mathrm{\τ}}_i-\frac{d}{2})\cos ({\mathrm{\ω}}_{\mathrm{IF}}t+{\mathrm{\θ}}_i)----\left(9\right)$

Top two signals respectively square, with low frequency filter filtering ω=2 ω _IFThe frequency multiplication component after subtract each other, the output control curve S that obtains Discr. is $S\left(\mathrm{\&zeta;}\right)=\frac{1}{8}\underset{i=0}{\overset{M}{\mathrm{\&Sigma;}}}{a_i}^2[R(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}+\frac{d}{2}){]}^2+\frac{1}{4}\underset{i<j}{\mathrm{\&Sigma;}}{a}_i{a}_j\&CenterDot;R(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}+\frac{d}{2})R(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{dj}}+\frac{d}{2})\cos ({\mathrm{\&theta;}}_j-{\mathrm{\&theta;}}_i)---\left(10\right)$ $-\frac{1}{8}\underset{i=0}{\overset{M}{\mathrm{\&Sigma;}}}{a_i}^2[R(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}-\frac{d}{2}){]}^2+\frac{1}{4}\underset{i<j}{\mathrm{\&Sigma;}}{a}_i{a}_j\&CenterDot;R(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}-\frac{d}{2})R(\mathrm{\&zeta;}{-\mathrm{\&tau;}}_{\mathrm{dj}}-\frac{d}{2})\cos ({\mathrm{\&theta;}}_j-{\mathrm{\&theta;}}_i)$

For simplifying therebetween, consider to have only the situation of a multipath, the autocorrelation function of PN sign indicating number is

$S\left(\mathrm{\&zeta;}\right)=\frac{1}{8}\left\{\right[\underset{i=0}{\overset{1}{\mathrm{\&Sigma;}}}{a}_i\cos ({\mathrm{\&theta;}}_i-{\mathrm{\&theta;}}_0)R_{\mathrm{PN}}(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}+\frac{d}{2})]+[\underset{i=0}{\overset{1}{\mathrm{\&Sigma;}}}{a}_i\cos ({\mathrm{\&theta;}}_i-{\mathrm{\&theta;}}_0)R_{\mathrm{PN}}(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}-\frac{d}{2})\left]\right\}\&times;---\left(11\right)$ $\left\{\right[\underset{i=0}{\overset{1}{\mathrm{\&Sigma;}}}{a}_j\cos ({\mathrm{\&theta;}}_i-{\mathrm{\&theta;}}_0)R_{\mathrm{PN}}(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}+\frac{d}{2})]-[\underset{i=0}{\overset{1}{\mathrm{\&Sigma;}}}{a}_i\cos ({\mathrm{\&theta;}}_i-{\mathrm{\&theta;}}_0)R_{\mathrm{PN}}(\mathrm{\&zeta;}-{\mathrm{\&tau;}}_{\mathrm{di}}-\frac{d}{2})\left]\right\}$

Because Discr. is followed the tracks of is output control curve at the zero point of slope for the negative range of linearity, and first factor in the formula (11) is permanent in zero in the range of linearity, considers second factor, i.e. S (ζ ₀)=0 can get by simple calculating:

Wherein ${\mathrm{\&tau;}}_p=\frac{[a_0+a_1\cos ({\mathrm{\&theta;}}_1-{\widehat{\mathrm{\&theta;}}}_0)]d}{{2a}_0}---\left(13\right)$ ${\mathrm{\&tau;}}_q=T_c-\frac{d}{2}+\frac{a_{1}d\cos ({\mathrm{\&theta;}}_1-{\widehat{\mathrm{\&theta;}}}_0)}{{2a}_0}---\left(14\right)$

ζ ₀(* c) is exactly the error that multipath effect causes, when ${\mathrm{\&theta;}}_1-{\widehat{\mathrm{\&theta;}}}_0=0$ Or during π, ζ ₀Reach maximal value ${\mathrm{\&zeta;}}_{0m}=\&PlusMinus;\frac{a_{1}d}{{2a}_0}.$ Under the situation that has a plurality of multipath signals to exist, the multipath error analytical expression is difficult to obtain, but when the amplitude of multipath signal was smaller, the maximal value that still can similarly obtain multipath error was ${\mathrm{\&zeta;}}_{0m}=\frac{d}{{2a}_0}\max \left[\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{a}_i\cos ({\mathrm{\&theta;}}_i-{\widehat{\mathrm{\&theta;}}}_0)\right].$

The correlation properties of PN sign indicating number make it to the bigger multipath signal of time-delay inhibiting effect be arranged in the spread spectrum system, also can draw this result from formula (12), when ${\mathrm{\&tau;}}_{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="A0311788000111.png"\; state="\{\{state\}\}">d</figure-callout>}1}>T_c+\frac{d}{2}$ The time, multipath error is zero; The maximal value of multipath error is when having only a multipath signal ${\mathrm{\&zeta;}}_{0m}=\&PlusMinus;\frac{a_{1}d}{{2a}_0},$ Illustrate that the factor that influences multipath error mainly is the amplitude alpha of multipath signal _iWith the time interval d of the advanced code and the sign indicating number that lags behind, the time interval d that reduces advanced code and hysteresis sign indicating number can reduce multipath error.

The enforcement of range measurement system of the present invention is to carry out a series of relevant treatment.Concrete implementation example is as follows.

1. at first the signal that receives is obtained baseband signal behind wave filter, received signal and the local reference signal that produces that will carry out after the AD conversion are carried out preliminary coherent detection, obtain initial estimation to TOA and FOA by two-dimensional time-domain and frequency domain detection.

2. near the TOA that obtains, carry out further relevant treatment.Employing is with respect to the leading local signal of the leading d/2d of punctual local signal and the hysteresis local signal of hysteresis d/2, between the two be spaced apart d, anticipating signal carries out relevant with received signal respectively with local signal.By reducing d at interval, can improve the precision that TOA estimates, and bring improvement the multipath rejection.

3. adopt ${\mathrm{d\&tau;}}_k=I_{\mathrm{EK}}^2+Q_{\mathrm{EK}}^2-I_{\mathrm{LK}}^2-Q_{\mathrm{LK}}^2$ The coherent signal that obtains is calculated, obtain the measuring error of TOA, thereby TOA is corrected.

In order to compare, the two sampling data and the four sampling data of the received signal that collects are carried out the arrowband relevant treatment respectively, obtain different Discr. curves of output.Related interval d=1chip during the arrowband of 2 sampling data is relevant, related interval d=0.5chip during the arrowband of 4 sampling data is relevant, from Fig. 3 and Fig. 4 as seen, the TOA measuring error that multipath effect causes in the arrowband correlated results of 2 sampling data is 0.615 sample, and corresponding distance is 0.615 * 203 * 10 ^-9* 3 * 10 ⁸=37.4535m, and the TOA measuring error that multipath effect causes in the arrowband correlated results of 4 sampling data only is 0.4124 sample, corresponding distance is 0.4124 * 203 * 10 ^-9* 3 * 10 ⁸=25.1152m has brought the performance improvement of 12.3383m thus, thereby has verified by shortening the relevant spacing in arrowband and can effectively reduce the TOA that measuring error that multipath effect brings is more approached actual value.

Claims (3)

1. the relevant range measurement system in the arrowband of high precision, anti-multipath in the wireless location is with the time of arrival (TOA) or the time of arrival poor (TDOA) of detection signal.This system comprises:

On the basis of original correlator, adopt a leading correlator and lag correlation device, on the basis that original time detecting is estimated, leading correlator adopts a reference code that is ahead of punctual local signal, the lag correlation device adopts a reference code that lags behind punctual local signal, and two correlators are done further tracking and detection near the TOA of initial detecting or TDOA.

Adopt one to select the device at the interval between the lead and lag correlator to change related interval, shorten this and can change the relevant output result in arrowband at interval.

Output correlated results to two correlators carries out computing, can obtain the control information that initial time is estimated, initial time is estimated to correct.

2. one kind can be suppressed the distance measuring equipment that multipath disturbs, and comprising:

The leading correlator in I road, an I road lag correlation device, the leading correlator in Q road, a Q road lag correlation device, four correlators are used for that signal is carried out lead and lag and are correlated with a shift register that produces reference signal, a Discr. mode selector, can select different associative modes and Discr. output mode, an arithmetic unit is used for the correlated results of leading correlator and lag correlation device is carried out computing.

3. associative mode that selection as claimed in claim 2 is different and Discr. output mode select incoherent Discr. in the pattern that subtracts after-power in advance in the native system, Discr. is output as ${\mathrm{d\&tau;}}_k=I_{\mathrm{EK}}^2+Q_{\mathrm{EK}}^2-I_{\mathrm{LK}}^2-Q_{\mathrm{LK}}^2.$

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