DE102008024248B4 - Method for generating field strength profiles for the reception testing of mobile radio receivers - Google Patents

Abstract

Method for creating field strength profiles (FP) for testing the reception of mobile radio receivers under laboratory conditions, whereby a field strength profile (FP) has at least one field strength profile (FV1, FV2, FV3, FV4) dependent on the distance (S), time and speed for at least one Transmission frequency (SF1, SF2, SF3, SF4), and the field strength curve (FV1, FV2, FV3, FV4) is measured, filtered and statistically modeled, and the measured field strength curve (FV1, FV2, FV3, FV4) in at least two individual route sections (SA1, SA2), whereby for each route section (SA1, SA2) of the measured field strength curve (FV1, FV2, FV3, FV4) parameters with regard to the minimum field strength (Fmin) and the maximum field strength (Fmax) and the resulting difference (ΔF) can be determined.

Description

Technical area

The invention relates to a method for generating field strength profiles for the reception testing of mobile radio reception devices, for example car radios, under laboratory conditions.

State of the art

From the DE 10 2006 032 270 A1 a method for testing a mobile radio receiving device under laboratory conditions is known, wherein the radio receiving device signal-carrying radio waves with a predetermined frequency and field strength (a radio field profile was obtained in advance by field measurements and / or simulation calculations) exposed and a power-determining output of the radio receiving device is detected and evaluated. The radio receiving device is acted upon in a time-extended test program with the radio waves of a pre-stored field strength-time curve and the output measured as a function of field strength.

From the article "Multipath Hardware and Software Mobile Cannel Simulator" Briso-Rodriguer, C .; Alonso-Montes, J.I .; IEEE 53rd Vehicular Technology Conference, 6-9 May 2001, vol. 4, pp 3060-3063 a method for the simulation of mobile radio channels is known. An input signal is successively delayed and multiplied by a transfer function for each history path. The delay and the variables of the transfer function can be parameterized individually. By means of this method complex environments can be reproduced.

If a radio field profile is obtained by field measurements, the field strength profile, for example due to shadowing or multipath propagation, may be exposed to various fading influences.

Object of the invention

The invention is based on the object of providing a method for simulating lost fading effects under field conditions measured under real conditions.

Solution of the task

The object is achieved by a method according to claim 1.

Advantages of the invention

In order to be able to replicate largely real environmental conditions reproducibly under laboratory conditions in a test of mobile radio reception devices, for example car radios, field strength profiles of different transmission frequencies, for example a radio station, are measured, filtered and statically modeled under real conditions. The field strength profile obtained by measurement and filtering does not take into account any lost course components, in particular fading. For their replication statistically modeled field strength gradients are added to the previous field strength course. The field strength profile resulting from the summation of the filtered field strength profile and the statistically modeled field strength profile at least partially forms a field strength profile according to the invention.

Based on the resulting field strength profiles, laboratory tests of mobile radio reception devices, such as car radios, can be carried out so that objective quality evaluations can be achieved by means of the laboratory results. In the laboratory tests, the individual field strength curves can be played in parallel, offset or one after the other.

With the method according to the invention, the reception conditions along a considered route can be detected with a relatively low metrological effort and processed for reproduction in the laboratory. For reproduction in the laboratory, the possibilities of directly recording and reproducing the recorded data and modeling the reception conditions are available with statistical means. In the present method, a mixture of both methods is used, taking into account the respective advantages of both approaches.

In an advantageous embodiment of the invention, the field strength profile is measured continuously or discontinuously. Possible criteria for the selection of a type of measurement (continuous or discontinuous) may be the data volume, the degree of compression of the "required" field strength values, the measurement technique and special features of the measured test section.

In the method according to the invention, only individual values (interpolation points) of the measured field strength values can be used both in the continuous measurement and in the discontinuous measurement. The criteria for node selection can be set individually and may depend on the characteristics of the received signal. An example of this can be a dense sequence of supporting values in areas that have a require high local resolution, while in areas with relatively constant received signal characteristics a lower node rate is required.

The conditioning of the measured field strength profiles comprises a filtering by means of low-pass filtering of the second order. By means of the low-pass filtering, an antialiasing of the field strength profile can be achieved.

In an advantageous embodiment of the invention, the measured Feldstäkeverlauf is statistically modeled by means of a logarithmic normal distribution and a subsequent Rayleigh distribution. By means of the logarithmic normal distribution there is a simulation of shadowing, so-called "slow fading". The local resolution should assume a typical for effects of "slow fading" value of about 10 m. The subsequent Rayleigh distribution replicates the so-called "fast fading" caused by multipath propagation. The local resolution of this modeling should also assume a typical value, here for effects of "almost fading". This value is in the range of half the wavelength of the considered frequency range, so for example at 1.67 m for an FM frequency of 100 MHz. In the considered FM broadcasting scenario, Doppler effects are within the coherence frequency and therefore play a negligible role.

In an advantageous embodiment of the invention, the above-mentioned measured supporting values mark individually considered road sections of the test track.

For each section individual field strength parameters are determined. Examples of corresponding parameters are the minimum and maximum field strength, which can also be refined with respect to outliers, and the resulting fluctuation range (difference between minimum and maximum field strength).

The classification of outliers can be carried out, for example, by determining an area of the field strength distribution within a route section, this area covering 66% of the field strength values occurring. Ordinary field strength values are then within this range and outliers outside it. The choice of the range can be made depending on the desired test situation.

In an advantageous embodiment of the invention, the field strength parameters are subjected to statistical modeling. Advantageously, the parameter of the minimum field strength is low-pass filtered for each route section and the fluctuation range (difference between the maximum and minimum field strength) is statistically modeled. Instead of the fluctuation range, the maximum field strength can be statistically modeled. If the field strength distribution is divided into "normal" field strength values and "outliers", the low-pass filtering and the statistical modeling can be carried out correspondingly for the "outliers".

In order to achieve a field strength curve according to the invention, the field strength values of the low-pass filtering and of the statistical modeling are summed up.

drawings

Show it:

1 : a section of a measured field strength curve of a radio station with different transmission frequencies with DC channel interference;

2 : a section of the measured field strength profile of a transmission frequency with interpolation points;

3 : the field strength history 2 with sections and parameters;

4 : the field strength history 3 after a second-order low-pass filtering;

5 : the field strength history 3 after a statistical modeling by means of a logarithmic. Normal distribution;

6 : the summed field strength curve from the 4 and 5 after a statistical modeling by means of a Rayleigh distribution;

7 : a section of a field strength profile.

In 1 a section of measured field strength curves FV1, FV2, FV3, FV4 of a radio transmitter RS with three different transmission frequencies SF1, SF2, SF4 along a distance S is shown. In addition, there is a foreign radio station, which sends SF3 with its transmission frequency on the same frequency as RS (SF2 = SF3) and thus causes a co-channel interference GK. The field strength profiles FV1, FV2, FV3, FV4 were recorded during a test drive in rural areas, for example. The individual field strength curves FV1, FV2, FV3, FV4 were measured discontinuously. Each measured field strength value forms a support point, which in 2 are shown.

Due to low transmission power of the individual transmission frequencies SF1, SF2, SF3, SF4 occur frequent alternative frequency change AF. Furthermore, in the illustrated field strength curves FV1, FV2, FV3, FV4, the above-mentioned co-channel interference GK can be recognized by a foreign radio station and losses of all alternative frequencies AFV for a specific time period.

The basis for the creation of field strength profiles (datasets) can be measured runs, whereby GPS data and a video with the filmed display of a reference radio are used. The car radio can be operated in test mode in order to read the currently received field strength F.

The 2 shows the field strength curve FV1 for the transmission frequency SF1 according to 1 , The measurement of the field strength profile FV1 was carried out discontinuously and depending on the conditions in the track part, so that each measured value forms a support point ST1, ST2.

In the 3 is the field strength curve FV1 off 2 divided into sections SA1, SA2 shown. The in the 3 shown sections SA1, SA2 are not equidistant and result from the in 2 marked three adjacent support points.

Field strength parameters are determined for each route section SA1, SA2. For the determination, the data recorded during the test drive for the field strength course FV1 within the considered track section SA1, SA2 are used, possible parameters are the minimum field strength Fmin and the maximum field strength Fmax. From both parameters, the difference .DELTA.F can be formed as a further parameter. Furthermore, it is possible to classify the field strength values located in each route section SA1, SA2. The classification can be carried out separately for the entire field strength profile FV1 or for each segment SA1, SA2. By means of the classification, field strength value ranges can be formed, according to which field strength values lying outside of this range B are declared as so-called outliers. In the 3 the range is approximately 66% of the total field strength value range in the considered section SA1, SA2. This means that for the section SA1 (or in total) the minimum field strength Fmin and the maximum field strength Fmax are determined. Their difference ΔF is set as 100%. A region B is formed around the determined mean value, which covers 2/3 of all occurring field strength values. All field strength values that are larger or smaller than the 2/3 range B are assigned to the outliers. In 3 an outlier of a maximum field strength FmaxA is shown in the section SA2.

The 4 shows the field strength curve FV1 after a low-pass filtering TP second order. The low-pass filtering TP is based on the parameters minimum field strength Fmin and minimum field strength outliers for each line segment SA1, SA2. The field strength curve FV1 on which the low-pass filtering TP is based forms on the one hand the minimum field strength Fmin (a minimum field strength Fmin for each route segment SA1, SA2) which are expanded according to the respective route length and on the other hand the minimum field strength values outliers (a minimal field strength value for each route segment SA1, SA2) Outliers), which are expanded according to the respective route length. If, for example, in the first path section SA1, which is in the range between 0 and 800 meters, the minimum field strength value Fmin is 35 dBμV and in the second path section SA2, which is greater than 800 meters and 1000 meters, the minimum field strength value Fmin is 40 dBμV, then the the resulting field strength curve FV1 in the range between 0 meters and 800 meters the value 35 dBμV (minimum field strength value Fmin in the first section SA1) and in the range greater 800 meters and 1000 meters the value 40 dBμV (minimum field strength value Fmin in the second section SA2).

In 5 the field strength course FV1 is shown according to a statistical modeling by means of a logarithmic normal distribution logN. For this modeling, each section of the route is subjected to an equidistant division, which is based on the effects typical of "slow fading" and thus enables a local resolution of the modeling of, for example, 10 m. For this purpose, the in 3 shown differences .DELTA.F from minimum field strength Fmin and maximum field strength Fmax based. Alternatively, for the statistical modeling of the parameter maximum field strength Fmax can be used.

In 6 is the in 5 shown field strength course FV1 according to a statistical modeling with a Rayleigh distribution RY shown. For this modeling, each section of the line is subjected to a further finer equidistant division, which is based on the effects typical for "fast fading" and thus enables a local resolution of the modeling of half the wavelength of the frequency range used (for example, 1.67 m at 100 MHz). , For statistical modeling by means of Rayleigh distribution RY the in 3 shown differences .DELTA.F from minimum field strength Fmin and maximum field strength Fmax based. Alternatively, for the statistical modeling of the parameter maximum field strength Fmax can be used.

7 shows an inventive field strength profile FP of a radio station RS. This field strength profile FP is based on the in 1 shown field strength curves FV1, FV2, FV3, FV4. In the 7 shown field strength curves FV1, FV2, FV3, FV4 result from the summation of the low-pass filtered field strength profile TP ( 4 ) and of the statistically modeled (by means of a logarithmic normal distribution logN ( 5 ) and a Rayleigh distribution RY ( 6 )) Field strength course of FV1.

The in the 7 shown field strength curves FV1, FV2, FV3, FV4 are arranged one behind the other or partially in parallel.

Depending on the desired test situation, the respective number and arrangement of the field strength profiles FV1, FV2, FV3, FV4 can vary in a field strength profile FP.

LIST OF REFERENCE NUMBERS

• AF

  Alternatively, frequency change

  AFV

  Alternatively frequency loss

  B

  Area

  F

  field strength

  fmin

  minimal field strength

  Fmax

  maximum field strength

  FmaxA

  maximum field strength outliers

  FP

  Field strength profile

  FV1

  Field strength curve

  FV2

  Field strength curve

  FV3

  Field strength curve

  F4V

  Field strength curve

  GK

  Co-channel interference

  log N

  logarithmic normal distribution

  RS

  radio stations

  RY

  Rayleigh

  S

  route

  SA1

  stretch

  SA2

  stretch

  SF1

  transmission frequency

  SF2

  transmission frequency

  SF3

  transmission frequency

  SF4

  transmission frequency

  ST1

  support point

  ST2

  support point

  ST3

  support point

  TP

  Low-pass filtering

  .DELTA.F

  difference

Claims (10)

Method for generating field strength profiles (FP) for the reception testing of mobile radio receivers under laboratory conditions, wherein a field strength profile (FP) at least one of the distance (S), the time and the speed dependent field strength course (FV1, FV2, FV3, FV4) for at least one Transmission frequency (SF1, SF2, SF3, SF4) and the field strength profile (FV1, FV2, FV3, FV4) is measured, filtered and statically modeled, and the measured field strength profile (FV1, FV2, FV3, FV4) in at least two individual sections (SA1, SA2), wherein for each section (SA1, SA2) of the measured field strength profile (FV1, FV2, FV3, FV4) parameters with respect to the minimum field strength (Fmin) and the maximum field strength (Fmax) and the resulting difference (.DELTA.F) are determined. A method according to claim 1, characterized in that the measurement is carried out continuously. A method according to claim 1, characterized in that the measurement is discontinuous. A method according to claim 1, characterized in that the filtering is effected by means of low-pass filtering (TP) second order. Method according to Claim 1, characterized in that the statistical modeling is carried out by means of logarithmic normal distribution (logN) and Rayleigh distribution (RY). A method according to claim 1, characterized in that additional parameters with respect to the minimum field strength and the maximum field strength (FmaxA) of field strength values that are outside a range (B) of the field strength values in the respective link section (SA1, SA2), and the resulting difference be determined. Method according to claim 1 or 6, characterized in that the parameter difference (ΔF), which is formed from minimum field strength (Fmin) and maximum field strength (Fmax), is statistically modeled. Method according to Claim 7, characterized in that the parameter difference (ΔF), which is formed from minimum field strength (Fmin) and maximum field strength (Fmax), is statistically modeled by means of logarithmic normal distribution (logN) and subsequent Rayleigh distribution (RY). A method according to claim 1 or 6, characterized in that the parameter minimum field strength (Fmin) is filtered by means of a low-pass filtering (TP) second order. Method according to claim 8 and 9, characterized in that the values of the filtered field strength profile (FV1, FV2, FV3, FV4) and the statistically modeled field strength profile (FV1, FV2, FV3, FV4) are summed.

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