This propagation model is fully described in Recommendation ITU-R P.1546-6. Only land terrain profiles are implemented in SEAMCAT. The ranges of application are the same as for the ITU-R P.1546-4 and ITU-R P.1546-5, save for the frequency range that in this model is extended to as high as 4 GHz.
In the section about Algorithm description, only the parts of Recommendation ITU-R P.1546-6 that are different from Recommendation ITU-R P.1546-4 and ITU-R P.1546-5 are listed.
It must be emphasised that the measurements and modelling in this Recommendation intrinsically include the effect of terminal clutter, so it would be inappropriate to add a calculation of clutter separately.
Input parameters
SEAMCAT Interface to the ITU-R P.1546-6 propagation model
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Table: ITU-R P.1546-6 propagation model
Description | Symbol | Type | Unit | Comments | ||||||
Variations |
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| Variation in basic transmission loss | ||||||
| p | D | % | Time variability for which the field strength value is exceeded: 1% - 50% | ||||||
General environment around the Rx |
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| Environment of the propagation around the Rx with representative values of clutter height in m: open/uncluttered (10), rural (10), suburban (10), urban (15), dense urban (20). | ||||||
Representative clutter height around the Rx | R2 | S | m | User-specified clutter height at the Rx which overwrites any predefined value when selected | ||||||
General environment around the Tx |
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| Environment of the propagation around the Tx with representative values of clutter height in m: open/uncluttered (10), rural (10), suburban (10), urban (15), dense urban (20). For the open/uncluttered environment, the clutter correction at the Tx is not computed. | ||||||
Representative clutter height around the Tx | R1 | S | m | User-specified clutter height at the Tx which overwrites any predefined value when selected | ||||||
Location probability | q | D | % | Location variability: 1% - 99% (default value: 50%) | ||||||
User specified standard deviation | S | dB | User-specified standard deviation value which overwrites any predefined value when selected | |||||||
System |
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| Mobile or Broadcasting DTT (determines the appropriate value of standard deviation of location variability) | ||||||
Prediction resolution | wa | S | m | The width of the square area over which variability applies. Not applicable for Broadcasting DTT | ||||||
Average profile height around the Rx | S | m | The average level of the terrain height between distances of 3 and 15 km from the Rx antenna in the direction of the Tx antenna. If Tx-Rx distance d is less than 15 km, then the terrain height is averaged between distances 0.2 d and d km. | |||||||
Average profile height around the Tx | S | m | The average level of the terrain height between distances of 3 and 15 km from the Tx antenna in the direction of the Rx antenna. If Tx-Rx distance d is less than 15 km, then the terrain height is averaged between distances 0.2 d and d km. | |||||||
Terrain clearance angle (at the Rx) | tca | S | deg | The h2 terminal's clearance angle as calculated in Section 11, noting that this is the elevation angle relative to the local horizontal | ||||||
Terrain clearance angle (at the Tx) | eff1 | S | deg | The h1 terminal's terrain clearance angle calculated using the method in Paragraph 4.3 case a), whether or not h1 is negative | ||||||
Terrain height above sea level at the Rx |
| S | m | Terrain height in meters above sea level at the receiver/mobile. This parameter is used in combination with the antenna height (from the Rx local environment) and the average profile height around the Rx to compute the effective antenna height. | ||||||
Terrain height above sea level at the Tx |
| S | m | Terrain height in meters above sea level at the transmitter/base. This parameter is used in combination with the antenna height (from the Tx local environment) and the average profile height around the Tx to compute the effective antenna height. | ||||||
Terminal designations | S | When selected the algorithm will consider the option a), b) and c) of ITU-R. 1546-6 Annex 5 §1.1. By default it is selected. |
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Values of standard deviation are dependent on the prediction resolution and frequency, and empirical studies have shown a spread. In the case where terrain data is being used and the variation over a small area is required representative values of σL are given by Equation (34). The representative values relate to the 50th percentile of the cumulative distributions of measured standard deviation of location variability.
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where:
f: required frequency (MHz)
wa: prediction resolution (m).
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When using this Recommendation without terrain information the variation across the service area might be a more appropriate measure of σL. In this case no dependency on frequency is found however the environment type will impact the standard deviation of location variability values. Representative values of σL are 8, 10 and 12 dB for urban, suburban and open areas respectively.
Percentage location q can vary between 1 and 99. This Recommendation is not valid for percentage locations less than 1% or greater than 99%. The values given in Table 2 have been found appropriate for the planning of digital terrestrial television (DTT) services, this was found to be equivalent to the 93rd percentile of the measurement CDF for rooftop height antenna for a 100 × 100 m area.
Table 2: Values of variability used in certain planning situations
| Standard deviation (dB) |
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100 MHz | 600 MHz | 2 000 MHz | ||
Broadcasting, DTT | 5.5 | 5.5 | 5.5 | |
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