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A17.10.1 A17.10.1

ITM propagation model also know as Longley-Rice was developed to estimate radio transmission loss over irregular terrain for VHM, UHF, SHF frequency band. Computing of signal loss based on electromagnetic theory and on statistical analyses. It has been complemented by empirical dependences, during tests and measurements.

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At the beginning necessary geometry parameters are calculated, based on input parameters. Then, depending on the range in which the transceiver and receiver are, ITM model compute reference attenuation A_ref – the median attenuation relative to a free space. Reference attenuation is a function of distance d, what is illustrated below. On cumulative attenuation comprises reference attenuation and attenuation of quantailes A(­q­_T, q_L, q_s) – which are calculated based on normal distribution, as variability of time, localization, reliability.

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F475 F475

Figure 475: Reference attenuation as function of distance

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