Prediction of attenuation of radio signals caused by buildings

The invention relates to a method for predicting the building attenuation at Radio signals, in particular radio signals in the GSM mobile radio system, by the preamble of claim 1.

The present invention is based on the object, a method of propose the aforementioned type, which allows the building damping a building known design practice different at each location Stories based less easy to identify parameter to be determined.

This object is achieved by the specified in patent claim 1.

With the described method the building attenuation can substantially knowing the width and the floor height of the building virtually for Anywhere in different floors are determined.

It is important to design the building. The most common types are Reinforced concrete, reinforced concrete frame and masonry structures.

The usual types can be classified in the following way:

<ul><li>- Masonry (brick, sand-lime, aerated concrete or Bimsbaustein) with or without plastering or cladding with sand or sand-lime brick.</li><li>- Reinforced concrete or reinforced concrete frame constructions. Reinforced concrete exterior walls often covered with natural stone. In the Stahlbetonskelettbauten External walls mostly with curtain-reinforced concrete or metal panels provided. The use of metallized glass surfaces usually comes in this type before.</li><li>- Iron lattice construction with glass or plastic surfaces.</li><li>- Industrial buildings with metal walls.</li></ul>

For the last two building types are currently no measured data available. Thus, the method for calculating the damping building can in this Cases are not used. but you may find that, under the Building types, the first two are most common.

In the prediction of the pathloss within the building is first the building attenuation determined on the ground floor of the building. Based on determined attenuation on the ground floor may be aware of the type of electromagnetic wave propagation and the consideration of the so-called bullet profit each pathloss anywhere any floor to determine the building.

To determine the path loss in buildings RF Em were pfangspegelmessungen with a mobile measuring system in thirteen Objects carried out. Seven of them are reinforced or Stahlbetonskelettbauten. The rest are made of masonry.

Advantage of the method is the simplicity of its application and achieved high accuracy of the predictions.

Now, the new feature is only a reference to a Execution path drawing depicting explained. Here, assume the Drawing and its description further essential features and Benefits out of innovation.

In which:

<b>Fig.</b> 1 Schematic structure of a field strength measurement system;

<b>Fig.</b> 2 Definition of the energy radiation direction with respect the outer wall and the average angle of incidence of the energy beam;

<b>Fig.</b> 3 illustrate the definition of D₁ and d₂;

<b>Fig.</b> 4 approximation of attenuation of the reference outer wall function the mean angle of incidence of the energy beam for reinforced concrete structures;

<b>Fig.</b> 5 approximation of attenuation of the reference outer wall function the mean angle of incidence of radiation energy for masonry;

<b>Fig.</b> 6 measured values ​​and approximate equations for the dependent of B Damping term in reinforced concrete and masonry structures;

<b>Fig.</b> 7 measured values ​​and the approximate equation of k₁;

<b>Fig.</b> 8 measured values ​​of k₂ and their approximate equation;

<b>Fig.</b> 9A traces of the RF receiver voltage at d2 = 7.5m and their Averaging function (dashed lines) from the 3 rd to 6 th floor;

<b>Fig.</b> 9B traces of the RF receiver voltage at d2 = 7.5m and their Averaging function (dashed line) from the 7 th to the 17 th floor;

<b>Fig.</b> 10 approximation of the building damping and profile of the mean value of the Measurements on the ground floor and in the basement of a Masonry building (no line of sight);

<b>Fig.</b> 11 approximation of the building damping and profile of the mean value of the Measurements on the ground floor of a brick building (No line of sight);

<b>Fig.</b> 12 approximation of the building damping and profile of the mean value of the Values ​​in the 6-th floor of a reinforced concrete frame building, (Line of sight exists from the 6-th floor).

<b>Fig.</b> 1 shows the schematic structure of a mobile measuring system for measuring the H F-reception voltage level. The H F-reception voltage level from Active power stations is measured in dB microvolts.

The vertically polarized λ / 2-dipole antenna was respectively at a height of 1.6m arranged above the ground. Your<b>3</b>-dB bandwidth approximately corresponds to the D1 Frequency range. The measuring system provides a second 200 values, from which are formed at 0.15 m distances level averages. The measurement data are detected by the computer.

Building attenuation on the ground floor

According to <b>Fig.</b> 2 are used to determine the path loss on the ground floor (EC) of a building <b>1</b> the following auxiliary terms are defined:

<ul><li>- Energy radiation direction <b>3</b> for building</li><li>- Reference outer wall <b>2</b> the building</li><li>- Mean angle of incidence β of the energy radiation</li><li>- Mean elevation angle to the transmitting antenna</li></ul>

The energy radiation direction <b>3</b> is by the connecting line of the transmitting antenna <b>4</b> to the receiving antenna <b>5</b> , said the receiving antenna <b>5</b> in the geometric center of the Building outline is.

The closest to the transmitting antenna and above by the connecting line cut building wall, reference outer wall <b>2</b> called.

The above-mentioned compound of the line <b>3</b> and the reference outer wall <b>3</b> included angle β is as average angle of incidence of the energy beam considered (0 ° &lt;β ≦ 90 °).

The connecting line from the transmitting antenna <b>4</b> the center of the reference outer wall <b>2</b> in half the building height determines the average elevation angle for Transmit antenna.

In practice, the heights of the transmitting and receiving antennas <b>4</b>. <b>5</b> above the Soil usually much smaller than the distance between them. In this case, the Deviation of elevation and angle of incidence of their average values ​​- calculated at any point of the building - negligible.

Depending on the dimensions of the building, see <b>Fig.</b> 3, the Pathloss in dB with a ground floor of a building

a = Uex - U (d1, d2) (1)

To be defined. In equation (1) d₁ and d₂ in meters Distances from the the outer walls in the direction of the components of the vector in the Energy radiation direction <b>2</b> (<b>Fig.</b> 3), U_ex in dBĩV the average value of the RF Reception voltage level outside the building <b>1</b> along the reference outer wall <b>2</b>, And U (d₁, d₂) In dBĩV the RF receiver voltage on the ground of the building <b>1</b>,

The measurement results have shown that the function a (d₁, d₂) At various Values ​​of d₂ remains approximately the same. Thus, the building attenuation can in EC in dB simplified as a function of the variable d₁ describe:

a = U_ex-U (D₁) (2)

The domain of equation (2) is:

3 ≦ d₁ ≦ B-3 (3)

In equation (3) B is the width of the building in meters <b>1</b> perpendicular to Reference outer wall <b>2</b> in the immediate vicinity of the reference outer wall <b>2</b> was the Reception level not measured. To ensure the accuracy of equation (2) not to deteriorate, the above restriction of the domain of d₁ necessary.

The measurements have shown that the building attenuation in equation (2) having the following quadratic function

a = a_W + a_B - k₁(d₁-k₂)² (4)

can be approximated.

In equation (4), A_W or a_B both in dB attenuation of Reference outer wall or a dependent of the width of the building attenuation term. Both damping terms also depend on the structure of the building. The slope of the attenuation curve is the coefficient k₁ affected, which is a function of B is. The dependent also from the B coefficient k₂ effected in m a shift of the attenuation curve to the right.

The results show an almost identical course for a_EC at Reinforced concrete, and reinforced concrete frame buildings. For this reason, in the further only the term used reinforced concrete buildings.

In the following the determination of a_W, a_B, k₁ and k₂ described. Being aware of This function makes the building attenuation can be calculated.

Determination of attenuation of the reference outer wall

The attenuation of the reference outer wall depends on the mean angle of incidence β of Energy radiation and from the substance of the exterior walls. The latter is determined by the design.

In <b>Fig.</b> 4 are in the form of the small squares in the measured values Reinforced concrete structures for the attenuation of the reference outer wall and their Approximation by the function

a_W = 7 + 0.0019 (β-85)² (5)

shown for outer wall thicknesses of 0.3 m to 0.7 m. Wall thicknesses outside this interval in practice rare. The value of a_W = 21dB at β ≈ 1 ° in <b>Fig.</b> 4 is the result of a measurement with GMSK modulated Transmission signal.

In concrete structures sometimes happens that the glass surfaces in the Exterior walls are damped metallic. The thickness of the metal layer is allg. the more times the skin depth. In this case, the incident Beams independently β greatly attenuated by the incident angle. Thus shall Equation (5) does not, the attenuation of the reference outer wall can be in this Cases with a_W = 21dB closer.

<b>Fig.</b> 5 shows as small squares the values ​​of a_W and their approximation by the function

a_W = 5 + 0.0014 (β-85)² (6)

for masonry structures in outer wall thickness of 0.5 m to 1.3 m. This area the wall thickness includes most occurring in practice cases.

Damping term, which is dependent on the width of the building

From measurement results, the effect of the width of the building on which was Building damping determined in a range of B = 10 m to 100 m. The form registered squares measured values ​​and their approximations

a_B = 3 + 0.0014 (B + 40)² for reinforced concrete (7)

or.

a_B = 0.0011 (B + 40)² for masonry structures (8)

are in <b>Fig.</b> shown. 6

Calculating the coefficients of the building attenuation curve

The coefficient k₁ affects the slope of the attenuation curve. It can be from the measurement results (registered as small squares) with

k₁ = 0.61 (B-5) (9)

approximate (<b>Fig.</b> 7). The empirically determined constant 0.6 in equation (9) has the dimension dB / m.

By k₂ A shift to the right in the course of building attenuation caused. This displacement reaches its maximum at a d₁ &lt;B. If d₁ ≈ B-3 reduces the damping due to the superposition of waves from the energy radiation towards the building with the other Exterior walls penetrated reflected waves.

The measured values ​​of k₂ (Shown as small squares) and their approximation

k₂ = 3 + 0.58B (10)

are in <b>Fig.</b> shown. 8

Owned by a_W, a_B, k₁ and k₂ can now building attenuation (a_s) in the EC for reinforced concrete structures by substituting the equations (5), (7), (9) and (10) in Equation (4) with

a_S = 10 + 0.0019 (β-85)² + 0.0014 (B + 40)²-0.6 / (B-5) (d₁-3-0.58B)² (11)

or. for masonry structures (a_M) By the substitution of the equations (6), (8), (9) and (10) in equation (4) with

a_M = 5 + 0.0014 (β-85)² + 0.0011 (B + 40)²-0.61 (B-5) (d₁-3-0.58B)² (12)

to calculate.

For metallized glass surfaces in reinforced concrete buildings have a_W = 21dB in Equation (4) be used and the result is:

a_S = 24 +0.0014 (β-40)²-0.6 / (B-5) (d₁-3-0.58B)²

Determining the building damping in different floors

The building attenuation is in higher floors by extending the Equation (4) having an additional term, the so-called. Bullet gain to capture.

The measurements have shown that the attenuation characteristic in higher floors also on the nature of the electromagnetic wave propagating to the building depends. Accordingly, in the determination of the building damping must be carried out the following cases:

<ul><li>- No line of sight between the transmitter antenna and the building</li><li>- Optical sight is (ie, the first Fresnel ellipse is free of obstacles) from a particular floor</li><li>- Spread on clear view of the whole building</li></ul>

No line of sight between the transmitter antenna and the building

Using the equation (11) can be the building attenuation in the ith floor a Stahlbetonbautes (a_Si) The following example calculate:

a_Si = a_S-4i, I = 1,2,. , ., P (13)

In the equation, i is the ordinal number of floors. The first floor (1st floor) corresponds to i = 1, etc. The top floor is denoted by i = p.

The reduction in the attenuation of 4 dB / floor over the ground floor equal to the average of measured values. This effect can be with Diffraction explain the waves of obstacles. The HF receiving level, and thus the Building attenuation varies with the angle of diffraction. With increasing amount of Receiving antenna decreases the angle of diffraction, the diffraction loss is smaller, which the building attenuation decreases.

In reinforced concrete structures the damping in the basement is not calculated, because here the RF Reception level averaging at outdoor supply most of the Receiver sensitivity of mobile phones is.

In masonry building attenuation in higher floors using Equation (12) determines:

a_mi = a_M - 4i (14)

The attenuation curve in UG (a_MUG) Can be in this case with

a_MUG = a_M + 13 (15)describe. The damping gain of 13dB vs.. To (<b>12</b>) Corresponds to the Average value of measurement results. A climb in damping following main reasons:

<ul><li>- Part of the reference outer wall is located at the ground, whereby the Waves suffer greater Eindringungsdämpfung.</li><li>- The reinforced concrete floor in the basement to increase damping.</li></ul>

Optical view is from a certain height of the receiving antenna

The m-th floor is the minimum receiving antenna height, from which the first Fresnel ellipse between the transmitting antenna and the reference outer wall free of Obstructions.

The determination of the building damping with reinforced concrete buildings from the first to takes place for m-th floor with the equation (13), where i = 1,2 ,. , ., M. From the Floor m + 1 to p can be the building damping with i = m in equation (13) predict. The measurements have shown that the attenuation in optical View remains approximately constant despite the rising level of the receiving antenna. In extreme height may, however, an increase in the building attenuation occur. Larger change in the elevation angle to the receiver antenna leads namely to greater decrease of the transmit antenna gain in the vertical plane. at Measurements up to a height of about 20 floors did not occur this effect.

The change of the building damping to the receiving antenna at height lack of sight can be with diffraction theory the example of a DUT verify. In Table 1, the theoretical values ​​of the Diffraction loss in different floors of the townhouse in Bonn in following data summarized:

<ul><li>- Transceiver distance: 1.8 km</li><li>- RF carrier frequency of the transmitter: 953.6 MHz</li><li>- Terrain heights at the transmitting antenna and the measurement object above sea level: 55 m or 59 m</li><li>- Transmitting antenna height above ground: 36.5 in</li><li>- Distance of the sharp-edged obstacle from the transmitting antenna: 1.6 km</li><li>- Obstacle height above sea level: 79 m.</li><li>- Floor height of the measurement object: about 3.5 in.</li></ul>

Table 1

Theoretical diffraction loss in different storey heights the Town House in Bonn

<tgroup cols="2"><tbody><entry align="left">Diffraction loss (dB)</entry><entry align="left">Height of the receive antenna above the ground (M)</entry><row><entry align="left">-14.1</entry><entry align="left">12.4 (3rd floor)</entry></row><row><entry align="left">-9.7</entry><entry align="left">15.9 (4th floor)</entry></row><row><entry align="left">-4.7</entry><entry align="left">19.4 (5th floor)</entry></row><row><entry align="left">-0.5</entry><entry align="left">22.9 (6th floor)</entry></row></tbody></tgroup>

The table shows that the decrease in diffraction loss at the successive floors 4 to 5 dB. From the 6 th floor is the first Fresnel ellipsoid practically free from obstacles that the diffraction loss fluctuates around 0 dB. The measurement results for the townhouse (<b>image</b> 9A) show that the change of the RF receiving voltage from the 3-th to 6-th floor, the Calculating values ​​approaching. From the 7 th to the 17 th floor then varies the RF receive power about its mean value (<b>image</b> 9B).

For the calculation of the building damping with masonry from the first until mth Stock apply the equation (14), where i = 1,2 ,. , ., M. From poles m + 1 to p, the damping with i = m in the equation (14) can predict.

The determination of the building attenuation in the basement is by the equation (15).

Optical view is available for the whole building

When spread on a clear view is not a lawful amendment of Building attenuation in function of the height of the reception antenna recognizable. It fluctuates around its value for the EC, which in itself reinforced concrete or Masonry with equation (11) or (12) can be calculated.

In the application of equation (11) or (12) it is assumed that the Change in the elevation angle in dependence on the received antenna height is negligible. This requirement is in practice often fulfilled. in the the opposite case, the change of the transmitting antenna gain in be significant vertical plane. Then, the gain change in the must Equations are considered.

The building attenuation in the basement of a masonry structure can with equation (15) to be appreciated.

Accuracy of the prediction of the building damping

In the <b>Fig.</b> 10, 11 and 12 are the averages of the measurement data for the Building damping and its approximation s according to equation (4) for three Building shown. These examples reflect the average Accuracy of the method. The deviation between the measured curve and the Approximation is usually not greater than 4 dB.

The deviations of the measured values ​​from their mean can be personalized with Gaussian Normal distribution describe. The dispersion (σ), in the case of

<ul><li>- Cartographic Institute of UNI-Bonn at σ ≈ 4dB</li><li>- Geographical Institute of UNI-Bonn at σ ≈ 5dB</li><li>- Townhouse-Bonn at σ ≈ 2dB.</li></ul>

The achievable accuracy of the prediction is by the huge differences limited under the buildings and in the electromagnetic wave propagation.

The main differences in the features of the building are made in the

<ul><li>- Thickness and trim the outer walls</li><li>- Number, direction, thickness and material of the inner walls</li><li>- The number, distribution and size of the interiors and the corridors</li><li>- Number and size of windows and openings in building exterior walls</li><li>- Shape and length of the building</li><li>- Height floor.</li></ul>

The electromagnetic wave propagation is due to the changing itself Conditions in the reflections, scattering and diffraction, etc. at any Building different.

A further increase in the accuracy of the prediction could probably be achieved by further measurements.

The method described here indicates approximate formulas that allow Propagation attenuation practically different in buildings anywhere Floors can be predicted in height above the ground in approximately 1.6. in the current state, the process at the most common types, ie used in reinforced concrete, masonry and Stahlbetonskelett- will.

was for the prediction of the building attenuation in the basement of concrete structures no formula developed because here the RF-input level mean value in Outdoor supply most of the receiver sensitivity of D1-Mo biltelefonen located.

To calculate the path loss within a building, the following information is required:

<ul><li>- Geographical position of the base station antenna (BS antenna) and the building</li><li>- Height of the BS antenna above the ground</li><li>- Distance between the BS antenna and the building</li><li>- Type of electromagnetic wave propagation (see Section 5).</li><li>- Type and width of the building</li><li>- The number and amount of stories</li><li>- Coating of glass surfaces.</li></ul>

With optical sight to the building must be determined, from which Floor the first Fresnel ellipse is free of obstacles. For this purpose, the knowledge The following additional data is required:

<ul><li>- Terrain elevation above sea level at the BS antenna and the object</li><li>- H F-carrier frequency of the BS transmitter</li><li>- Distance of the obstacle from the BS transmit antenna</li><li>- Obstacle height above sea level.</li></ul>

The calculation of the first Fresnel zone can be spared in any a greater inaccuracy in the prediction of the building attenuation in higher Storeys in your portfolio. Experience has shown that the change in the Building attenuation in urban areas from the 6-th floor negligible.

Numerals, symbols and abbreviations

LIST OF REFERENCE NUMBERS

<b>1</b>

building

<b>2</b>

Reference outer wall

<b>3</b>

Energy radiation direction

<b>4</b>

transmitting antenna

<b>5</b>

receiving antennaSymbols:a damping curve in the ground floor of a buildinga_B

Damping term, the structural fabric of the building and the width dependsa_Si

Building attenuation in the ith floor of a reinforced concrete buildinga_mi

Building attenuation in the ith floor of a brick buildinga_S

Building attenuation on the ground for reinforced concrete or Stahlbetonskelettbautena_MUG

Building attenuation in UGa_W

Attenuation of the reference outer walla_M

Building attenuation in the EC for masonry structuresB width of the building perpendicular to the reference outer wallβ Mean angle of incidence of the energy beamd₁

Vertical distance from the reference outer wall in the buildingd₂

Distance from the neighboring with the reference outer wall exterior walli ordinal number of floorsk₁

Coefficient, which affects the slope of the attenuation curve buildingk₂

Coefficient for the displacement of the building attenuation curveU (d₁

) RF receiver voltage in ECU_ex

along average of HF receiver voltage level outside the building the reference outer wallAbbreviations:BS base stationEC FloorHF High FrequencyOG floorUG basement