Fig. 2
From: Heterogeneous wireless IoT architecture for natural disaster monitorization
Density Solar Cycle 1945–2018 [22]. In this figure, we can see the variation of density solar Cycle. This figure allows us to preview the state of the ionosphere. The ionospheric channel varies constantly, and we must be able to constantly work with this variation. In this scenario where technology will have to live a long time, we have to foresee these long-term variations