The 433 MHz band is gaining relevance as an alternative to the 2.4 GHz band for machine-to-machine communications using low-power wireless technologies. Currently, two standards are being developed that use the 433 MHz band, DASH7 Mode 2 and IEEE 802.15.4f. The article presents propagation models based on measurements conducted at the 433 MHz and 2.4 GHz bands that can be used for link budget calculations in both outdoor and indoor environments depending on node height. The results obtained show that the 433 MHz band has a larger communication range in both indoor and outdoor environments despite the negative effects of having a larger Fresnel zone. In addition, indoor propagation measurements are conducted in line-of-sight and nonline-of-sight conditions to determine the suitability of channel hopping to combat the effects of multipath propagation. Contrary to the 2.4 GHz band, the results show that channel hopping at 433 MHz does not provide any link robustness advantage because the channel coherence bandwidth is larger than the whole band bandwidth, and thus, all channels are highly correlated.

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The tremendous growth of low power wireless technologies oriented to smart city applications has conduced to evaluate the propagation aspects under typical communication scenarios in urban environments where in contrast to cellular technologies the transmitter and or the receiver antenna can be deployed at different heights near ground. Thus, the authors introduce a unified empiric parametrised propagation model with validated parameters from the measurements to study the propagation characteristics in near‐ground scenarios. The proposed model considers the antenna's height as well as external power losses because of objects that may block the line‐of‐sight to the receiver. The main results of this research demonstrate that in near‐ground wireless links, the wireless range is severely reduced because of diffraction caused by ground. However, in scenarios where the receiver is always higher than the transmitter the diffraction is null and the path loss slope is less than free space, with the consequence of a considerably higher wireless range. The propagation model presented here is a valuable tool for network planning where typical cellular propagation models might not be appropriate.

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