DE102006001794A1 - Satellite navigation system e.g. global positioning system, receiver interferences reducing method, involves influencing residual error based on eigen characteristic reflections, which are inferred back due to detector types characteristics - Google Patents

Abstract

The method involves utilizing several different correlation detector types for estimation and minimization of a residual error relating to distance during multi-path channel estimation, while receiving digital radio signals in the receiver. The residual error is influenced differently according to its respective delay-dependent error envelop eigen characteristic reflections. The reflections are inferred back due to the different, delay-dependent eigen characteristics of the different correlation detector types.

Description

The The invention relates to a method of reducing multipath reception caused disturbances in a receiver a satellite navigation system, e.g. GPS or Galileo, received Signals of a navigation satellite using a multipath reception suppressive correlation.

At the Receiving signals in satellite navigation systems, e.g. GPS (Global Positioning System) or the future Galileo, it comes under to receive reflection signals due to multipath propagation effects the satellite signals. These reflection signals are a disturbance, which affects the accuracy of navigation receivers. Therefore, reflection signals or their interference should be reduced.

in the Related to the combination of satellite navigation and others Positioning method, e.g. using mobile and e-maps and / or sensors for example Acceleration, air pressure, magnetic field, inertial forces, Doppler frequency shift is the best possible Position determination an evaluation of each procedure and thus a weighting of their results required. An essential Criterion for the evaluation of the distance measurement to a satellite in the The framework of a satellite radio navigation system is multipath reception.

It is previously known, an estimate of the multipath channel with so-called Multipath Estimating receivers make. But the estimates made here are often erroneous and thus give bad results, still remains a big residual error in the multipath case.

It also receivers are used for this purpose, which largely suppress the reception of reflected signals using a special correlator, so that essentially only the direct received signal is evaluated. Such special correlators suppressing the multipath reception are, for example, the so-called double-delta correlator and the strobe correlator ^TM and are in the conference contribution of M. Irsigler, GW Hein, B. Eissfeller: "Multipath Performance Analysis for Future GNSS Signals" Proceedings of the National Technical Meeting of the Satellite Division of the Institute of Navigation, ION NTM 2004, 26.-28. January 2004, San Diego California.

task The present invention is to provide a method with the multipath reception can be detected and evaluated and in particular the residual error of the distance measurement in the multipath case can be assessed and minimized.

According to the invention, referring to a method for reducing multipath reception caused disturbances refers to the above-mentioned type, this object is achieved in an advantageous manner solved by that remaining for evaluation and minimization of multipath channel estimation, the distance related residual errors when receiving digital Radio signals in the receiver used in parallel several different types of correlation detectors which are corresponding to their respective delay-dependent error envelope characteristic Reflections affect the residual error differently, and that due to the different, known, delay-dependent characteristics of the different types of correlation detectors on the respective present Reflection closed becomes.

In Advantageously, at least two of the following are given Correlation detector types, namely the "wide" correlator, the "Narrow" correlator and the "Double Delta (ΔΔ)" correlator, where the "double delta (ΔΔ)" correlator is preferred is included in every case.

Of the fundamental The purpose of the present invention is to functionally design a satellite navigation receiver such that in parallel with several correlation detector types, e.g. a "Narrow" correlator and a "Double Delta (ΔΔ)" correlator can. Act on different types of correlators in a receiver differs from a satellite reflection signals on the residual error. In particular, e.g. a "Double Delta (ΔΔ)" correlator Delay (Delay) area, in which he says Multipath is quite insensitive. Kick a reflection with such a delay up, so learns this correlator detector type will only make a small error, while "narrow" correlators or "wide" correlators will bigger mistake do. On the basis of the respectively known characteristic of the different Detector types can thus be deduced to the particular reflection present.

The Method according to the present invention uses, in general terms, the different eigencharacteristic (error envelopes) from different types of detectors that differ that a reflection with a certain delay different detector errors generated.

The output information of the different types of correlation detectors may suitably be used to evaluate the multipath test error and thus indicate the variance of a position estimate due to multipath propagation.

In a multipath channel estimation performing by means of a multi-detector method according to the invention receiver can advantageously still a Apriori information about the approximate location reflection to improve channel estimation. Such a multi-detector receiver So in the case of a Multipath Estimating Receiver, in which the apriori information about the approximate Location of reflections leads to the improvement of channel estimation, a additional Improvement.

By the method according to the present invention will thus become one of Distance related residual error minimization and evaluation by different achieved delay dependent detector sensitivities. About that lets out This represents a significant improvement in multipath estimating Achieve receivers.

advantageous Further developments and embodiments of the invention are in the to the claim 1 directly or indirectly rückbeziehenden dependent claims specified.

The The invention will be explained below with reference to the accompanying drawings. It demonstrate:

1 in a diagram, the error envelope eigencharacteristics of a "Narrow" -Korrelators on the one hand for the case of a BOC (1,1) signal shown in dashed lines and the other for the case of the solid line case of a BOC (1.5 , 1.5) signal,

2 in a diagram, the error envelope inherent characteristics of a "double delta (ΔΔ)" - correlator on the one hand for the case of a BOC (1,1) signal shown in dashed lines and the other for the case of a BOC shown in solid lines (1.5,1.5) signal,

3 FIG. 3 is a block diagram of three different cooperating receiver tracking loops, each operating according to the method of the invention with a different type of correlator.

4 in a block diagram, three different cooperating receiver tracking loops, each of which also operates according to the method of the invention with a different type of correlator, but from the reliability information for the best possible distance estimation a particularly suitable type of correlator is selected, and

5 in a further block diagram, three different cooperating receiver tracking loops, each of which also operates according to the method according to the invention with a different type of correlator, but for the best possible range estimation so-called multipath estimators are used, which the channel impulse response of the multipath channel in particular by means of a Apriori Estimate information that is improved by applying the multicorrelator principle of the invention.

In 1 is the dependence of the error envelope eigen characteristic of a distance measurement, measured in meters [m], as a function of the multipath delay, measured in nanoseconds [ns], on the one hand for a BOC (1,1) for a "Narrow" -correlator Signal (dashed line) and on the other for a BOC (1.5, 1.5) signal (solid line).

In 2 In comparison, for a "Double Delta (ΔΔ)" correlator, the dependence of the error envelope eigen characteristic of a distance measurement, measured in meters [m], as a function of the multipath delay, measured in nanoseconds [ns], is also for a BOC (1,1) signal (dashed line) and on the other for a BOC (1.5,1.5) signal (solid line) shown.

From the comparison of the two in 1 and 2 As can be seen clearly from the diagrams shown, the two types of correlator to be compared have completely different error envelope characteristics. For the case of a BOC (1,1) signal (dashed line trace), which is planned for Galileo L1, it is clearly evident that the "Double Delta (ΔΔ)" correlator, for example, provides very low residual errors when reflected in the delay range between 100 ns and 400 ns.

In 3 are three different, often also referred to as a tracking loop DLL tracking loops (DLL) of a satellite navigation receiver imaged, each of which de works with a different type of correlator. The first DLL tracking loop 1 is with a "wide" correlator, the second DLL tracking loop 2 with a "Narrow" correlator and the third DLL tracking loop 3 equipped with a "Double Delta (ΔΔ)" correlator. Are the signals originating from a satellite in the receiver via its antenna 4 received without previous multipath propagation, that is in three subtractors 5 . 6 and 7 he put difference of the processes limited to the thermal noise. In particular, the squaring and integration of these difference processes gives a small performance, especially if the received signals originate from the same frontend and have been converted with the same analog / digital converter.

Now, if the receiver is placed in a multipath environment, the "wide" correlator will be most affected by this effect. This is followed by the "Narrow" correlator. The "Double Delta (ΔΔ)" correlator is the most insensitive type of correlator against multipath, as in the diagram in 2 shows. The performance of the three processes can now be suitably used to detect the existence of multipath reception and to provide reliability information with the aid of, in particular, measured apriori statistics. This reliability information can be used in an exemplary development of the method according to the present invention by means of the known soft-location (SoLo) algorithm in order to obtain an improved position information. For this purpose, the reliability information is used to model a blurred ball (in cross-section similar to a rice edge) and thus to obtain from the combination of several of these balls an improved position solution.

at the known soft-location (SoLo) method, the data of different localization sensors as two- or three-dimensional Probability density functions that implicitly represent a Statement about include the accuracy of the respective localization methods and define an interface to the attitude and / or motion information suitable to process. The soft-location (SoLo) method is e.g. out K. Wendlandt, A. Ouhmich, M. Angermann, P. Robertson: "Implementation of Soft Location on mobile devices ", International Symposium on Indoor Localization and Position Finding, July 2nd 2002, DGON, Bonn (Germany) known.

A Another development of the invention is that the signals of such a navigation satellite to be omitted, the one unreliable solution supplies.

Notwithstanding the determination of reliability information, the receiver's task is to achieve the best possible range estimation. In this case, how will 4 1, which uses reliability information to identify a particular one of the three DLL tracking loops, each equipped with a different type of correlator 1 to 3 select. The appropriate selection is made via an electronic switch 8th to the pseudo orange output controlling logic box 9 from the three reliability information provided by the subtractors 5 . 6 and 7 be derived. In particular, the "Double Delta (ΔΔ)" correlator is a good solution only for the multipath channel. For the AWGN (Additive White Gaussian Noise) channel, the "Narrow" Correlator the optimal reception detector. Although the "wide" correlator provides a worse pseudo-orange solution, it is much more robust in channels with a low receive level.

insofar can the knowledge about the existence of multipath reception are used to the particular to select a suitable detector.

• Fall 1A: Geringer Signalpegel → Umschalten auf "Wide"-Korrelator.
• Fall 1B: Hoher Signalpegel → Umschalten auf "Narrow"-Korrelator.

For this purpose, case 1 with an AWGN channel is cited as the first exemplary embodiment. In this case, the difference processes show low performance, possibly in relation to the "double-delta (ΔΔ)" correlator process. It follows thus:

• Case 1A: Low signal level → Switch to "Wide" correlator.
• Case 1B: High Signal Level → Switch to Narrow Correlator.

When second embodiment case 2 with a multipath channel is given. In In this case, the difference processes show: high or higher powers → switching on "Double Delta (ΔΔ)" correlator.

Thus, notwithstanding the determination of reliability information, it has already been stated that the task of the receiver is to achieve the best possible distance estimation. Typically, so-called multipath channel estimators are used for this, which estimate the channel impulse response of the multipath channel, in particular with the aid of the apriori information. This apriori information can be improved if it is known in which delay range a reflection is likely. In this case will be appropriate 5 the DLL tracking loop 1 with "Wide" correlator, the DLL tracking loop 2 with "Narrow" correlator, the DLL tracking loop 3 with "Double Delta (ΔΔ)" correlator and the three subtractors 5 . 6 . 7 reliability information processes used to obtain the measured and, for example, in tables stored apriori information for the multipath channel estimator 10 continue to improve. Here is the idea: If it is known, namely from the reliability process 1 that the multipath is in the "long multipath area", the corresponding apriori information of this area must, of course, be weighted higher than the remaining probability (WSK).

In case of a short multipath reception must be weighted differently. The improvement of apriori statistics necessarily improves the accuracy of the estimate.

regardless this is about the reliability processes an estimate reached the multipath performance, which can then be used to channel estimation to improve.

1

DLL tracking loop with "wide" correlator

2

DLL tracking loop with "Narrow" correlator

3

DLL tracking loop with "Double Delta (ΔΔ)" correlator

4

antenna

5

subtractor

6

subtractor

7

subtractor

8th

electronic switch

9

Logic Box

10

channel estimator

Claims (10)

A method for reducing multipath reception disturbances of a navigation satellite signal received in a satellite navigation system receiver, eg GPS or Galileo, using a multipath reception suppressing correlation, characterized in that for evaluating and minimizing residual distance errors remaining in multipath channel estimation of digital radio signals in the receiver in parallel several different correlation detector types ( 1 . 2 . 3 ), in which reflections have different effects on the residual error according to their respective delay-dependent error envelope eigencharacteristics, and that due to the different, known, delay-dependent intrinsic characteristics of the different types of correlation detectors, the respective present reflection is deduced. Method according to claim 1, characterized in that at least two of the following correlation detector types are used, namely the "wide" correlator ( 1 ), the "Narrow" correlator ( 2 ) and the "Double Delta (ΔΔ)" correlator ( 3 ), wherein preferably in each case the "Double Delta (ΔΔ)" - correlator is included. A method according to claim 1 or 2, characterized in that the output information of the different in their type correlation detectors ( 1 . 2 . 3 ) can be used to evaluate the multipath test error, thus indicating the variance of a position estimate due to multipath propagation. Method according to one of the preceding claims, characterized by use in a multipath channel estimation receiver, i. in a so-called Multipath Estimating Receiver, in which a Apriori information about the approximate Location of reflection leads to improvement of channel estimation. Method according to one of the preceding claims, characterized in that by combining the output information of the type-different correlation detectors ( 1 . 2 . 3 ) and possibly the apriori information reliability information is obtained. Method according to claim 5, characterized in that that the determination of the position information data based on the reliability information by Algorithms according to the known soft-location (SoLo) method, where the different reliability information are represented as probability density functions that implicitly a statement about the accuracy of the reliability information include and define an interface to the position information suitable to process. Method according to one of the preceding claims, characterized characterized in that in the receiver the signals of such a navigation satellite are omitted the one unreliable solution supplies. Method according to Claim 5, characterized in that, in order to obtain the best possible distance estimation, the reliability information is used to select the type of correlator which is particularly suitable in type, in particular the "double delta" correlator ( 3 ) is a good solution for the multipath channel only, the "Narrow" correlator ( 2 ) for the AWGN (Additive White Gaussian Noise) channel is the optimal receive detector type and the "wide" correlator ( 1 ) provides a worse pseudo-orange solution, but is much more robust in channels with a low reception level. Method according to claims 4 and 5, characterized that to achieve the best possible distance estimation so-called Multipath estimator using the apriori information the channel impulse response of the multipath channel, that the apriori information by knowing that delay range be improved, in which a reflection is likely and that in this case the reliability information processes to be used for the measured and stored Apriori information continue to improve. Method according to claim 9, characterized in that that over the reliability processes one Priori estimate the multipath power performed which is then used to improve channel estimation.