**3.5 Global aggregate traffic intensity model**

Integration of individual modules in the global aggregate traffic intensity model is schematically illustrated in Fig. 7. Instead of simulating individual sources and destinations, a geographic distribution of relative traffic source intensity is calculated for any location on the surface of the Earth. The cumulative traffic intensity of sources within its coverage area are mapped to the currently serving satellite. Satellite footprint coverage areas on the Earth, overlaid over geographic distribution of traffic sources and destinations, are identified from the satellite positions in a given moment.

Fig. 7. Global aggregate traffic intensity model.

With the normalized cumulative traffic on each satellite, which is proportional to the intensity of traffic sources in the satellite's coverage area, it is possible to modulate the selected traffic source generator (not shown in Fig. 7). Thus data packets are actually generated considering the relative traffic intensity experienced by a particular satellite.

The destination satellite is selected for each packet in accordance with the traffic flow pattern. The probability of selecting a given satellite as a destination node is proportional to its coverage share in the destination region divided by the sum of all coverage shares in that region. Thus, although in a simplified manner, the model is taking into consideration also multiple coverage. In the case of using different traffic source models to generate distinct types of traffic by global aggregate traffic intensity model, one should also consider different, service specific traffic flow patterns.
