# LaRoAwan and Urban Waste Management--A Trial
## 5 Evaluation
### Radio Coverage  
As expected, the reduced distance scenario presented no challenges to the LoRa technology, with all data received. However, the longer distance scenario (\(\approx 5\) km), proved  
Figure 10: Map showing the distance from the sensor to the LoRa Gateway at Amoreiras. Figure 9: Map showing the distances from the LoRa GW at ISEL to sensors at (**a**) the underground containers (RU); (**b**) at ISEL. to be too demanding, and not a single transmission of the sensor installed in Belem was ever heard at Amoreiras. A more detailed analysis of the terrain profile and the longer distance, shown in Figure 11, shows that there will be no line of sight between the location of the container installation and the nearest gateway, due to the morphology of the terrain, namely Monsanto (a large municipality managed forest/park), but also due to the urban landscape existing on the radio link. The scenario of the underground container presented challenges in terms of good reception of the signal due not only to the installation site, but also due to the metallic construction of the container, particularly the steel cover and pavement applied on the cover upper surface. This installation context prevents, for example, direct radio communication with the legacy sensors currently installed with GSM/GPRS technology, requiring the placement of an external antenna, outside of the waste container, in order for it to work correctly. Installing an external antenna voids the watertightness of the waste container and is undesirable. Figure 12 shows the terrain profile between the ISEL gateway and the underground waste container, where it is also visible that there is no line-of-sight communication. This factor aggravates the existing bad radio conditions, but it is a good opportunity to study the performance of technology in unfavorable situations. The figure also shows the direct beam and diffraction path. This high obstruction results from buildings on the radio propagation path to the nearer gateway. In Figure 13, the values reported by the filling level measurement sensor are presented from its installation to its removal. It should be noted that for about two months, starting in day n + 45, up to day n + 112, there were no measurements, due to a fault in the existing gateway. This situation led to the need to replace the gateway with new equipment that entered service on day n + 112. Figure 11: Distance profile between the waste container at Belem and the LoRa gateway at Amoreiras. Figure 12: Distance profile between the waste container at Spacio Shopping and the LoRa gateway at ISEL. The evolution of the spreading factor due to the ADR (Adaptive Data Rate) of the LoRa is visible in the initial part of the chart. This automatic adaptation mechanism allows the system to switch spreading factor (between 7 and 12) according to the radio conditions, allowing to optimize the relationship between the transmission rate, duty cycle and energy consumption, leading to greater spectral and energy consumption efficiency. A lower spreading factor led to a higher transmission rate and a lower channel occupation time. However, it requires a better signal-to-noise ratio (SNR), which is only possible if the attenuation of the radio link is low and the level of noise and interference too. On the contrary, a maximum spreading factor leads to a lower rhythm and consequently much longer emission times, with greater energy consumption. Thus, the system uses the spreading factor that optimizes this equation. In the figure it is possible to observe that the first messages were received with SF10 BW125, which corresponds to a spreading factor of 10. However, there is a lack of continuous reception of messages, caused by a high error rate. Thus, it is possible to observe the transition to the spreading factor 11 and, later, to the maximum of 12. From that point, the frequency of receiving messages increases.