LOS AÑOS FINALES DEL SIGLO XX

Suburban From -5 to -3

Industrial From -5 to -3

Open in urban From -6 to -4

Open From -12 to -10

Water From -14 to -12

The Standard Propagation Model is derived from the Hata formulae, valid for urban environments. The above values are normalized for urban clutter types (0 dB for urban clutter class). Positive values correspond to more dense clutter classes and negative values to less dense clutter classes.

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2.6 WLL Propagation Model

2.6.1 WLL Path Loss Formula

Where is the free space loss calculated using the formula entered in the model properties, is the diffraction loss calculated using the 3-obstacle Deygout method, and is the diffraction multiplying factor defined in the model properties.

2.6.2 Calculations in

^Atoll

Free Space Loss

For free space loss calculation, see "Free Space Loss" on page 86.

Diffraction

Atoll calculates diffraction loss along the transmitter-receiver profile built from DTM and clutter maps. Therefore, losses due to clutter are taken into account in diffraction losses. Atoll takes clutter height information from the clutter heights file if available in the .atl document. Otherwise, it considers average clutter height specified for each clutter class in the clutter classes file description.

The Deygout construction (considering 3 obstacles) is used. This method is described under "Diffraction" on page 86. The final diffraction losses are determined by multiplying the diffraction losses calculated using the Deygout method by the Diffraction multiplying factor defined in the model properties.

• Receiver Clearance

Define receiver clearance (m) per clutter class when clutter height information is either statistical or semi-deterministic. Both ground altitude and clutter height are considered along the whole profile except over a specific distance around the receiver (clearance), where Atoll proceeds as if there was only the DTM map (see SPM part). Atoll uses the clearance information to model streets.

If the clutter is deterministic, do not define any receiver clearance (m) per clutter class. In this case, clutter height information is accurate enough to be used directly without additional information such as clearance (Atoll can locate streets).

• Receiver Height

Entering receiver height per clutter class enables Atoll to consider the fact that receivers are fixed and located on the roofs.

• Visibility

If the option ‘Line of sight only’ is not selected, Atoll computes L_model on each calculation bin using the formula defined above. When selecting the option ‘Line of sight only’, Atoll checks for each calculation bin if the Diffraction loss (as defined in the Diffraction loss: Deygout part) calculated along profile equals 0.

• In this case, receiver is considered in ‘line of sight’ and Atoll computes L_model on each calculation bin using the formula defined above.

• Otherwise, Atoll considers that L_model tends to infinity.

• It is not possible to calibrate the unmasked version of the SPM using measurement data.

• Using the SPM, you can also calculate the angles of incidence by creating a new instance of the SPM with the following characteristics:

Type: Atoll.StdPropagModelIncidence.1

Signature: {659F0B9E-2810-4e59-9F0D-DA9E78E1E64B}

• The "masked" version of the algorithm has not been changed. It still takes into account Atoll.ini options. However, the "unmasked" version does not take Atoll.ini options into account.

• It’s highly recommended to use one method (Atoll.ini options) or the other one (new identifier & signature) but not to combine both.

L_model = L_FS+F_DiffL_Diff

L_FS L_Diff

F_Diff

2.7 ITU-R P.526-5 Propagation Model

2.7.1 ITU 526-5 Path Loss Formula

Where is the free space loss calculated using the formula entered in the model properties and is the diffraction loss calculated using the 3-obstacle Deygout method.

2.7.2 Calculations in

^Atoll

Free Space Loss

For free space loss calculation, see "Free Space Loss" on page 86.

Diffraction

Atoll calculates diffraction loss along the transmitter-receiver profile is built from the DTM map. The Deygout construction (considering 3 obstacles), with or without correction, is used. These methods are described under "Diffraction" on page 86.

2.8 ITU-R P.370-7 Propagation Model

2.8.1 ITU 370-7 Path Loss Formula

If d<1 km, If d>1000 km, If 1<d<1000 km,

d is the distance between the transmitter and the receiver (km).

2.8.2 Calculations in

^Atoll

Free Space Loss

For free space loss calculation, see "Free Space Loss" on page 86.

Corrected Standard Loss

This formula is given for a 60 dBm (1kW) transmitter power.

where,

C_n is the field strength received in dBV/m,

is a correction factor for effective receiver antenna height (dB), A_cl is the correction for terrain clearance angle (dB),

f is the frequency in MHz.

• C_n Calculation

The C_n value is determined from charts C_n=f(d, H_Txeff).

In the following part, let us assume that C_n=E_n(d,H_Txeff) (where E_n(d,H_Txeff) is the field received in dBV/m) is read from charts for a distance, d (in km), and an effective transmitter antenna height, H_Txeff (in m).

First of all, Atoll evaluates the effective transmitter antenna height, , as follows:

If , L_model = L_FS+L_Diff

L_FS L_Diff

L_model = L_FS L_model = 1000

L_model = max L _FSCorrectedStandardLoss

CorrectedStandardLoss 60 C– _n A_H

Rxeff

– –A_cl–108,75+31,54 20– logf

=

A_H

Rxeff

H_Txeff 0d3km H_Txeff = H_0Tx+H_Tx–H_0Rx

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If , If ,

where,

is the transmitter antenna height above the ground (m).

is the ground height (ground elevation) above sea level at the transmitter (m).

is the average ground height (m) above sea level for the profile between a point 3 km from transmitter and the receiver (located at d km from transmitter).

is the average ground height (m) above sea level for the profile between a point 3 km and another 15 km from transmitter.

Then, depending on d and H_Txeff, Atoll determines C_n using bilinear interpolation as follows.

If 37.5 H_Txeff 1200, C_n= E_n(d,H_Txeff)

Otherwise, Atoll considers (d is stated in km)

Therefore, If H_Txeff < 37.5

If , we have

Else C_n=E_n(d, 37.5) – E_n(d_horizon, 37.5) + E_n(25, 37.5) If H_Txeff > 1200

If , we have

Else C_n=E_n(d, 1200) – E_n(d_horizon, 1200) + E_n(142, 1200)

• A_HRxeff Calculation

where,

H_Rx is the user-defined receiver height, c is the height gain factor.

• A_cl Calculation If f 300 MHz,

Otherwise,

With where,

is the clearance angle (in radians) determined according to the recommendation 370-7 (figure 19), f is the frequency stated in MHz.

c values are provided in the recommendation 370-7; for example, c=4 in a rural case.

3d15km H_Txeff = H_0Tx+H_Tx–H₀3 d;  15d H_Txeff = H_0Tx+H_Tx–H₀3 15; 

H_Tx H_0Tx H₀3 d; 

H₀3 15; 

d_horizon = 4,1 H_Txeff

dd_horizon C_n = E_nd+25 d– _horizon37,5

dd_horizon C_n = E_nd+142 d– _horizon1200

A_H

Rxeff

c

6--- 20 H_Rx ---10

 

 

 log

=

 A_cl = 8,1–6,9+20log  0,1– ²+1+ 0,1– 

A_cl = 14,9–6,9+20log  0,1– ²+1+ 0,1– 

 – 4000 f

300

---



=



2.9 Erceg-Greenstein (SUI) Propagation Model

Erceg-Greenstein propagation model is a statistical path loss model derived from experimental data collected at 1.9 GHz in 95 macrocells. The model is for suburban areas, and it distinguishes between different terrain categories called the Stanford University Interim Terrain Models. This propagation model is well suited for distances and base station antenna heights that are not well-covered by other models. The path loss model applies to base antenna heights from 10 to 80 m, base-to-terminal distances from 0.1 to 8 km, and three distinct terrain categories.

The basic path loss equation of the Erceg-Greenstein propagation model is:

Where . This is a fixed quantity which depends upon the frequency of operation. d is the distance between the base station antenna and the receiver terminal and d₀ is a fixed reference distance (100 m). a(H_BS) is the correction factor for base station antenna heights, H_BS:

Where , and a, b, and c are correction coefficients which depend on the SUI terrain type.

The Erceg-Greenstein propagation model is further developed through the correction factors introduced by the Stanford University Interim model. The standards proposed by the IEEE working group 802.16 include channel models developed by Stanford University. The basic path loss equation with correction factors is presented below:

Where a(f) is the correction factor for the operating frequency, , with f being the operating

frequency in MHz. a(H_R) is the correction factor for the receiver antenna height, , where d depends on the terrain type.

2.9.1 SUI Terrain Types

The SUI models are divided into three types of terrains², namely A, B and C.

• Type A is associated with maximum path loss and is appropriate for hilly terrain with moderate to heavy tree densities.

• Type B is characterised with either mostly flat terrains with moderate to heavy tree densities or hilly terrains with light tree densities.

• Type C is associated with minimum path loss and applies to flat terrain with light tree densities.

The constants used for a, b, and c are given in the table below.

• a(H_R) = 0 for H_R = 2 m.

• References:

• [1] V. Erceg et. al, “An empirically based path loss model for wireless channels in suburban environments,” IEEE J. Select Areas Commun., vol. 17, no. 7, July 1999, pp. 1205-1211.

• [2] Abhayawardhana, V.S.; Wassell, I.J.; Crosby, D.; Sellars, M.P.; Brown, M.G.;

"Comparison of empirical propagation path loss models for fixed wireless access systems," Vehicular Technology Conference, 2005. IEEE 61st Volume 1, 30 May-1 June 2005 Page(s):73 - 77 Vol. 1

2. The word ‘terrain’ is used in the original definition of the model rather than ‘environment’. Hence it is used interchangeably with ‘environment’ in this description.

Model Parameter Terrain A Terrain B Terrain C

a 4.6 4.0 3.6

b (m^-1) 0.0075 0.0065 0.005

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2.9.2 Erceg-Greenstein (SUI) Path Loss Formula

The Erceg-Greenstein (SUI) propagation model formula can be simplified from the following equation:

(1)

to the equation below:

(2) Where,

• f is the operating frequency in MHz

• d is the distance from the transmitter to the received in m in equation (1) and in km in equation (2)

• H_BS is the transmitter height in m

• H_R is the receiver height in m

The above equation is divided into two parts in Atoll:

Where,

The above path loss formulas are valid for d > d₀, i.e. d > 100 m. For d < 100 m, the path loss has been restricted to the free space path loss with correction factors for operating frequency and receiver height:

instead of

Where a(f) and a(Hr) have the same definition as given above. Simplifying the above equation, we get, , or

The above equation is not user-modifiable in Atoll except for the coefficient of , i.e. 26. Atoll uses the same coefficient as the one you enter for in Atoll for the case d > d₀.

2.9.3 Calculations in

^Atoll

The Erceg-Greenstein (SUI) propagation model takes DTM into account between the transmitter and the receiver, and it can also take clutter into account at the receiver location.

1^st step: For each pixel in the calculation radius, Atoll determines the clutter bin on which the receiver is located. This clutter bin corresponds to a clutter class. Atoll uses the Erceg-Greenstein (SUI) path loss formula assigned to this clutter class to evaluate path loss.

2^nd step: This step depends on whether the ‘Add diffraction loss’ option is selected or not.

• If the ‘Add diffraction loss’ option is not selected, 1^st step gives the final path loss result.

• If the ‘Add diffraction loss’ option is selected, Atoll proceeds as follows:

a. It extracts a geographic profile between the transmitter and the receiver using the radial calculation method.

b. It determines the largest obstacle along the profile in accordance with the Deygout method and evaluates losses due to diffraction . For more information on the Deygout method, see "3 Knife-edge Deygout Method"

on page 87.

The final path loss is the sum of the path loss determined in 1^st step and .

c (m) 12.6 17.1 20

X 10.8 10.8 20

Model Parameter Terrain A Terrain B Terrain C

You can get the same resulting equation by setting a(hBS) = 2.

PL 20 Log₁₀ 4d₀

Shadow fading is computed in Atoll independent of the propagation model. For more information on the shadow fading calculation, see "Shadow Fading Model" on page 90.

2.10 ITU-R P.1546-2 Propagation Model

This propagation model is based on the P.1546-2 recommendations of the ITU-R. These recommendations extend the P.370-7 recommendations, and are suited for operating frequencies from 30 to 3000 MHz. The path loss is calculated by this propagation model with the help of graphs available in the recommendations. The graphs provided in the recommendations represent field (or signal) strength, given in , as a function of distance for:

• Nominal frequencies, : 100, 600, and 1000 MHz

The graphs provided for 100 MHz are applicable to frequencies from 30 to 300 MHz, those for 600 MHz are applicable to frequencies from 300 to 1000 MHz, and the graphs for 1000 MHz are applicable to frequencies from 1000 to 3000 MHz. The method for interpolation is described in the recommendations (Annex 5, § 6).

• Transmitter antenna heights, : 10, 20, 37.5, 75, 150, 300, 600, and 1200 m

For any values of from 10 to 3000 m, an interpolation or extrapolation from the appropriate two curves is used, as described in the recommendations (Annex 5, § 4.1). For below 10 m, the extrapolation to be applied is given in Annex 5, § 4.2. It is possible for the value of to be negative, in which case the method is given in Annex 5, § 4.3.

• Time variability, : 1, 10, and 50 %

The propagation curves represent the field strength values exceeded for 1, 10 and 50 % of time.

• Receiver antenna height, : 10 m

For land paths, the graphs represent field strength values for a receiver antenna height above ground, equal to the representative height of the clutter around the receiver. The minimum value of the representative height of clutter is 10 m. For sea paths, the graphs represent field strength values for a receiver antenna height of 10 m.

For other values of receiver antenna height, a correction is applied according to the environment of the receiver. The method for calculating this correction is given in Annex 5, § 9.

These recommendations are not valid for transmitter-receiver distances less than 1 km or greater than 1000 km. Therefore in Atoll, the path loss between a transmitter and a receiver over less than 1 km is the same as the path loss over 1 km. Similarly, the path loss between a transmitter and a receiver over more than 1000 km is the same as the path loss over 1000 km.

Moreover, these recommendations are not valid for transmitter antenna heights less than the average clutter height surrounding the transmitter.

2.10.1 Calculations in

^Atoll

The input to the propagation model are the transmission frequency, transmitter and receiver heights, the distance between the transmitter and the receiver, the precentage of time the field strength values are exceeded, the type of environment (i.e., land or sea), and the clutter at the receiver location.

In the following calculations, is the transmission frequency, is the transmitter-receiver distance, and is the percentage of time for which the path loss has to be calculated.

The following calculations are performed in Atoll to calculate the path loss using this propagation model.

2.10.1.1 Step 1: Determination of Graphs to be Used

First of all, the upper and lower nominal frequencies are determined for any given transmission frequency. The upper and lower nominal frequencies are the nominal frequencies (100, 600, and 2000 MHz) between which the transmission frequency

is located, i.e., .

Once and are known, along with the information about the percentage of time and the type of path (land or sea), the sets of graphs which will be used for the calculation are also known.

• The cold sea graphs are used for calculations over warm and cold sea both.

• The mixture of land and sea paths is not supported by Atoll.

db V m   f_n

h₁ h₁

h₁ h₁

t

h₂

f d t

f_n1 f f_n2

f_n1 f_n1 t

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2.10.1.2 Step 2: Calculation of Maximum Field Strength

A field strength must not exceed a maximum value, , which is given by:

for land paths, and

for sea paths.

Where is the free space field strength for 1 kW ERP, is an enhancement for sea graphs.

2.10.1.3 Step 3: Determination of Transmitter Antenna Height

The transmitter antenna height to be used in the calculation depends on the type and length of the path.

• Land paths

• Sea paths

Here, all antenna heights (i.e., , , and ) are in expressed in m. is the antenna height above ground and is the effective height of the transmitter antenna, which is its height over the average level of the ground between distances of

and d km from the transmitter in the direction of the receiver.

2.10.1.4 Step 4: Interpolation/Extrapolation of Field Strength

The interpolations are performed in series in the same order as described below. The first interpolation/extrapolation is performed over the field strength values, , from the graphs for transmitter antenna height to determine . The second interpolation/extrapolation is performed over the interpolated/extrapolated values of to determine . And, the thrid and final interpolation/extrapolation is performed over the interpolated/extrapolated values of to determine . Step 4.1: Interpolation/Extrapolation of Field Strength for Transmitter Antenna Height

If the value of coincides with one of the eight heights for which the field strength graphs are provided, namely 10, 20, 37.5, 75, 150, 300, 600, and 1200 m, the required field strength is obtained directly from the corresponding graph. Otherwise:

• If

The field strength is interpolated or extrapolated from field strengths obtained from two curves using the following equation:

Where if , otherwise is the nearest nominal effective height below ,

if , otherwise is the nearest nominal effective height above , is the field strength value for at the required distance, and is the field strength value for at the required distance.

• If

• For land path if the transmitter-receiver distance is less than the smooth-Earth horizon distance

, i.e., if ,

, or because

• For land path if the transmitter-receiver distance is greater than or equal to the smooth-Earth horizon distance

, i.e., if ,

, or because

Where is the field strength value read for the transmitter-receiver distance of y from the graph available for the transmitter antenna height of x.

If in the above equation, even though , the field strength is determined from linear extrapolation for Log (distance) of the graph given by:

Where is penultimate tabulation distance (km), is the final tabulation distance (km), is the field strength value for , and is the field strength value for .

• For sea path, should not be less than 1 m. This calculation requires the distance at which the path has 0.6 of the first Fresnel zone just unobstructed by the sea surface. This distance is given by:

(km)

Where (km) with (frequency-dependent term), and

(asymptotic term defined by the horizon distance).

If the 0.6 Fresnel clearance distance for the sea path where the transmitter antenna height is 20 m is also calculated as:

(km)

Once and are known, the field strength for the required distance is given by:

Where is the maximum field strength at the required distance as calculated in "Step 2: Calculation of Maximum Field Strength" on page 81, is for ,

, , and

is the field strength calculated as described for land paths. and are field strengths interpolated

for distance y and , respectively, and .

• If

A correction is applied to the field strength, , calculated in the above description in order to take into account the diffraction and tropospheric scattering. This correction is the maximum of the diffraction correction,, and tropospheric scattering correction, .

Where with and ,

, and is 1.35 for 100 MHz, 3.31 for 600 MHz, 6.00 for 2000 MHz.

with , (radius of the Earth), and is the

effective Earth radius factor for mean refractivity conditions.

In document (1)LA MODIFICACION DE LA CIUDAD (página 131-142)