The hart of every RF simulation tool is the prediction model. There are many models that predict RF propagation but the most known is the 'Hata-Okumura' model. This model is 'the mother of all models'.

Over the years new models have been developed where the growth of commercial cellular networks like GSM UMTS, and now WiMAX are the main drive. These networks operate in th UHF and SHF bands (450 to 2400 MHZ). Other frequency's are used for broadcast of Radio and TV (VHF and UHF, 50-800 MHz) and a small portion for PAMR and PMR networks. Their focus is in the VHF and low UHF frequency's (50-500 MHz).

The prediction models used for these networks are devided by coverage distance. For GSM, DCS and UMTS (900-2400 MHz) these models are limited to predictions over a short range. Due to the nature of broadcast the distance over wich predictions are made is extensively bigger than for cellular networks.

The difference in range for the model is devided in to two main categories:

This choice is influenced strongly by the en-user terminal. A if a uplink is required, a hand held terminal will limit the coverage because these devices have limited transmit power and poor antenna performance. In the case of broadcast A Radio receiver does not need to talk back to the broadcaster so bigger powers do no harm to the link budget.

When prediction over small distances are required to be accurate it is important that the influence of local buildings (clutter) is taken in account. when predictions are performed over bigger distances the dominance of clutter decreases and eventually can be left out of the calculations. This simplifies the formula for calculating RF propagation.

Accurate RF predictions require detailed clutter and height data bu this data is generally expensive and only affordable when income out of the exploitation of a radio network is high. For amateurradio, emergency services, and students for example it is not realistic to have this accurate data available. Therefore low budget and easy accessable data must be accessed. Radio Mobile uses geodata that is available on the internet for free.

Based on the Hata model many other models have been derived. Also models have been improved for their specific purpose. But some general models have been almost the same and available for free. On very well known model is the Longley-Rice model. This model is accurate over a wide range of frequencys and over various distances. Based on this model the US Institute for Telecommunications Science (ITS) created a propagation prediction model know as the Irregular Terrain Model or ITM.

Radio Mobile uses the ITM model.

To understand the operation and limitations of the model I have collected information about the Longly-Rise and ITM model on this website.

The chapters cover general and background information about the propagation model in Radio Mobile. Also specific implementations in Radio Mobile are discribed.