Mobile radio coverage planning method in building, involves positioning of virtual transmission antennas for augmentation of coverage region

The invention relates to a process for the planning of mobile radio coverage within Building, in particular using a prediction method for the occurring in the building RF reception power level, wherein the transmitting antenna for Supply of the building is disposed within the building.

The Maxwell's equations, the electromagnetic wave propagation be described analytically in any case where the initial and Limits are given.

From DE 197 03 916 A1 is a method for prediction of the building damping or the RF receiver power level within a building at Known mobile radio systems, wherein it is assumed here that the Transmission antenna is arranged outside of the building.

In the wave propagation in buildings, in an arrangement of Transmitting antenna within the building, the building structures are so complex that the starting point for the application of Maxwell's equations not can be determined. Thus, in this case, no closed form solution exists said equations.

With the currently existing method for predicting HF Received power levels in buildings, the so-called semi-empirical Models, the RF receive power level may only floor, where the Transmitting antenna is located and are predicted only in their immediate vicinity.

The object of the invention is a method for planning the provide mobile coverage inside buildings, that of a prediction RF reception power level allowed at any place of the building.

This object is achieved by the features of independent claim 1 dissolved.

With the planning process of the invention based on a Approximation methods for determining the expected RF receiver performance can the GSM radio coverage plan in the floors of a building. The to Supply necessary GSM transmitters are housed in the building. The Supply planning is carried out according to the following steps:

<ul><li>- There is a transmitter (with the transmitting antenna) on a stationary available Location of the building to be supplied is positioned.</li><li>- With the approximation method of the invention is the size of the cabin (Service area) determined within the building. When the supply is not sufficient, is examined as to whether the service area with the can extend change the channel parameters on the whole building.</li><li>- When the power supply to a transmitter is not possible, ent on a Speaking place a second transmitter positioned. Subsequently, the size of the Useful cell (coverage area) determined for this channel.</li><li>- With any more repetitions of the above procedure is fully achieved steady supply of the building.</li></ul>

It has been found that the radio coverage of a building, in many cases with is only a transmitter.

With the invention, a radio planning and prediction is of the HF Received power level in the downlink in buildings with sufficient accuracy below up to the sixth floor and above the floor, in which the transmitting antenna is positioned, is possible. The transmitter can at any location the building will be erected. The method may for the most frequently occurring building types, ie Stahlbetonskelett- and masonry building be used.

The advantage of the invention is that the planning of radio coverage in Buildings can be dispensed with elaborate series of measurements. There are also no complicated calculations based on semi-empirical models, z. B. Raytracing, necessary. The proposing method provides very fast sufficiently accurate results about the expected radio coverage in a Building and the same great for a number of levels. With Except for a few building parameters such as inter alia Building dimensions are for performing the process no further Input parameters required.

Advantageous refinements and developments of the invention will be made the dependent claims.

Hereinafter, the invention by way of example, with reference is made to described the drawing figures. From the drawings and their Description arising other features and advantages of the invention. It shows:

<b>Fig.</b> 1: the possible structure of a signal generator to perform Measurements within a building;

<b>Fig.</b> 2: the possible structure of a mobile test receiver for Carrying out measurements within a building;

<b>Fig.</b> 3: a diagram of a typical RF receiver voltage level in Depending on the distance traveled;

<b>Fig.</b> 4 is a horizontal cross-section of one floor of a building where the transmitting antenna S (0,0).

<b>Fig.</b> 5 to 11: measurement values ​​of the received power level and whose Approximation for different floors of a building.

In the <b>Fig.</b> 1 to 3 is a typical measurement system to perform Measurements shown within a building. The measurement system consists of a Measuring and a mobile measurement receiving system.

according to the Measuring <b>Fig.</b> 1 supplies a GMSK-modulated transmit signal. The level values ​​are at the output of each stage in the case of P_t = 1 W shown.

The downlink radio channels used for the measurements are GSM measurement channels. The power amplifier <b>3</b> amplifies the input signal of the GSM generator <b>2</b> around about 48 dB. The insulators<b>4</b>. <b>5</b> at the output of the signal generator <b>2</b> and power amplifier <b>3</b> ensure good impedance matching. The reflected Signals are suppressed by at least 20 dB. This is the emergence of disturbing intermodulation products especially on the non-linear Transfer characteristic of the power amplifier are prevented. the insulator<b>5</b> can a power meter <b>6</b> be followed.

The transmitting antenna <b>7</b> is a vertically polarized λ / 2 dipole. The half-width in the vertical plane is 78 °. The antenna gain is 2 dBi in the frequency range of 870-960 MHz. The VSWR at the antenna input is about 1.15. The height of the antenna base on the floor, in the transmission antenna on 1.67 m set.

The RF receiver voltage level (U_r in dB microvolts) is in accordance with <b>Fig.</b> 2 with a mobile measurement receiving system <b>8th</b> detected. The measurement accuracy is ± 1.5 dB in the level range of -10 dB microvolts. , , +60 DB microvolts.

The measuring receiver <b>9</b> has the same antenna <b>10</b> at the same height above the ground as the transmitter. The RF gain bandwidth of the receiver<b>9</b> is between 0.4 GHz and 1 GHz. The IF bandwidth is B₀ = 120 KHz.

The measurement system delivers 200 readings per second, from which at 0.15 m Distances arithmetic averages are. The measured data are from a computer <b>11</b> detected. an odometer pulse<b>12</b> provides the impetus for the Averaging distance. multiplexer<b>13</b> performs the task of a central unit. With Help a digitizer <b>14</b> the measurement data of the measured route assigned will.

The measuring station <b>1</b> is possible in the mean building height (average Floor) situated at a suitable disposal site.

With the mobile test receiver <b>8th</b> are level measurements possible on each Unit area of ​​the floors done. <b>Fig.</b> 3 shows a typical diagram of the RF receiver voltage U_r along a measuring path as an example. The distance measurement section is the evaluation of the computer <b>11</b> determined.

From the RF receiver voltage levels and the associated coordinates of Measurement points will create a file for each floor of the building.

Subsequently, the reference RF Empfangsleistungspege (P_rre in dBm) with Conversion of the U_rValues ​​calculated in RF receiver performance. the equation

P_{r ref} = U_r - 107 - G_t - G_r + a_r - 10th log (P_t/ 1 W) + 10th log (B / B₀) (1)

describes the case where the transmitting and receiving antennas and lossless isotropic, the antenna feed without loss to the receiving antenna and P_t = 1 W. In (1) B denotes the 3-dB bandwidth of the GMSK-modulated transmission signal in kHz.

The design and construction of buildings can be through the fabric of the outer walls characterize and influence the electromagnetic wave propagation in Building. The radio coverage with internal transmitter is mainly in larger public buildings applied. These are mostly offices, corporate buildings, Institutions, warehouses, etc. The following types come to this Building types in most cases:

<ul><li>- Reinforced concrete frame construction with masonry or reinforced concrete outer walls. The Fairing plaster or natural stone.</li><li>- Masonry buildings (brick, sand-lime, aerated concrete or Bimsbaustein) with or without plaster or natural stone cladding.</li></ul>

The glass surfaces in the outer walls are mostly not vaporized metallic.

The results of the reference to the <b>Fig.</b> 1 measuring method described to 3 can be sufficient by the approximation method according to the invention accurately predict.

In developing the procedure was striven necessary Initial parameters, ie the necessary building data, to a minimum to reduce. Thus, the application of the model is not an extensive Building database possible.

Under the current state are for the approximation method following Building parameters are required:

<ul><li>- Building</li><li>- Latitude and longitude of the building between the inner sides of the outer walls</li><li>- By number and height of floors</li><li>- Type of glazing</li></ul>

The listed data are usually of the conventional specifications, for the each building is available, refer to.

In the following, the approximation of the equation (1) and then the Prediction of the HF-receiving power described in the general case.

The investigations have shown that P_{r ref} two with the following function real variables (P_ra(X, y) in dBm)

P_ra(X, y) = s [(| x | - Max (x₁, | X₂|))² + (| Y | - Max (y₁, | Y₂|))² ] - F (2)

can be approximated.

The image of equation (2) is a surface in three dimensional space. By on the x, P_ra-Koordinatenebenen Parallel cut surfaces, ie, y = y_j = constant formed section curves of the face. The into the x, P_ra Level projected section curves give P_ra(X, y_j):P_ra(X, y_j) = S [(| x |) - Max (x₁ | x₂|))² + (| Y_j| - Max (y₁, | Y₂|))² ] - F (3)

In equation (3) denotes the absolute value of the independent variable | x | the absolute value of the distance from the transmitting antenna in the x-direction. The constant Value | y_j| means the absolute value of the distance from the transmitting antenna in the y- Direction.

<b>Fig.</b> 4 illustrates the distances x₁, x₂, y₁, y₂ in m from the transmitting antenna <b>17</b> the origin of the rectangular coordinate system (x, y, P_ra) Up to the corresponding insides of the external walls of buildings <b>16</b> the building <b>15</b>,

In equation (3) s determines the curve slope of the approximation curves:

s = (5.2. 10^-3/ (Max (x_Max, y_Max) - 10) - 2.5. 10^-5). (I - 8.5)⁴/ (| Y_j| + 35) + 0002, (4)

in whichx_Max = Max (x₁, | X₂|) And y_Max = Max (y₁, | Y₂|) Are

It is assumed that x_Max or y_Max greater than 10 m in accordance with the in practice occurring building dimensions.

The parameter i in equation (4), the floors are numbered. At the Reference floor, where the transmitting antenna is equivalent to i = 0. The here downward and upward successive floors are with i = 1, 2,. , ., 5 designated.

The function f in equation (3) causes a displacement curve.

For the UG a building

f = 1:07. 10^-2 , x_Max , y_Max+ 74

for all other floors applies:f = 1:07. 10^-2 , x_Max , y_Max+ 63 (6)

with P_ra(X, y_j) Can be the reference receive RF power level at any place of considered approximate floor.

In the above, was the approximation of P_{r ref} by P_ra(X, y_j) Described. in the Possession of P_ra(X, y_j), The power level at the receiver input (P_r in dBm) with

P_r = P_ra(X, y_j) + G_t + G_r - a_r + 10th log (P_t/ W 1) (7)

in any capacity at the base of the transmitting antenna, for any antennas and Antennæ be charged to the receiving antenna.

The size of the cabin, i.e., the coverage area of ​​the transmitting antenna, depends on the transmitter and receiver parameters. These are the power at the Foot point of the transmitting antenna (P_t in W), the gain of the transmitting or Receiving antenna (G_t in dBi) or (G_r in dBi) relative to the isotropic radiator and the Damping of the supply line to the receiving antenna (a_r in dB).

The gain of the transmitting antenna may be made of the radiation patterns in the Elevation and azimuthal plane for each point S (x, y) of the observed Floor will be charged.

Using an example now to a comparison of the measured values ​​with the approximation done. Listed below are the construction data of the surveyed building of Directorate Telekom in Cologne and presented the position data of the transmitting antenna. The Transmitting antenna is located on the 2nd floor. The observed object is a Reinforced concrete frame building with exterior walls made of sand-lime brick.Building: reinforced concrete skeletonExternal walls: sand-lime brick Building width (m): 62.5Building length (m): 52.5Number of floors: 7Location of the transmitting antenna: 2. OGx₁ (M): 60x₂ (M): -2.5y₁ (M): 50y₂ (M): -2.5

In the <b>Fig.</b> 5 to 11 are the measurement results and their approximations for the considered building shown.

Each figure shows selected measurement and approximate values ​​for a particular Floor of the building. The abscissa is the distance in the x direction in meters applied from the transmitting antenna. On the ordinate the measured RF Received power values ​​and the related approximate expected the Received power. The distance in the y direction from the transmitting antenna is in each case multiple values ​​fixed.

The measurement curves are recognized by their marks of the measuring points. The Approximation curves are drawn as pure lines without marking. The mating curves are characterized by a double arrow.

The accuracy of the approximation is for planning the radio coverage sufficient. The deviation between the measurement and approximate values ​​is in the Typically less than ± 10 dB downstairs EC and in the higher floors. The Inaccuracy of the approximation in the basement UG can in certain cases, if z. B. below the basement ceiling many metal tube extend bigger.

Symbols used

a_r

Attenuation of the supply line to the receiving antennaB 3-dB bandwidth of the GMSK-modulated transmission signalB₀

IF bandwidth of the measuring receiverf partial function in P_ra

(X, y)G_r

Gain of the receiving antenna with respect to the isotropic radiatorG_t

Gain of the transmitting antenna relative to the isotropic radiatori ordinal number of stories based on the reference floorP power level at the receiver inputP_ra

Approximate function of P_{r ref}

P_{r ref}

Reference receive RF power levelP_t

Power at the foot point of the transmitting antennaS (0,0) position of the transmitting antenna in the origin of the Cartesian coordinates system (x = 0, y = 0)s part in the function P_ra

(X, y)x distance from the transmitting antenna in the x-directionx₁

Distance from the transmitting antenna to the inside of Building outer wall in the positive x-directionx₂

Distance from the transmitting antenna to the inside of Building outer wall in the negative x-directiony distance from the transmitting antenna in the y-directiony₁

Distance from the transmitting antenna to the inside of Building exterior wall in the positive y directiony₂

Distance from the transmitting antenna to the inside of Building exterior wall in the negative y-directionU_r

RF reception voltage levelλ the wavelength in the air

LIST OF REFERENCE NUMBERS

<b>1</b>

measuring

<b>2</b>

GSM Generator

<b>3</b>

power amplifier

<b>4</b>

insulator

<b>5</b>

insulator

<b>6</b>

power meter

<b>7</b>

antenna

<b>8th</b>

measuring receivers

<b>9</b>

measuring receivers

<b>10</b>

antenna

<b>11</b>

calculator

<b>12</b>

odometer pulse

<b>13</b>

multiplexer

<b>14</b>

digitizing

<b>15</b>

building

<b>16</b>

Building outer wall

<b>17</b>

transmitting antenna