## 3 Results and Discussion
### The Antenna Range  
The designed antenna will be discussed in detail in a follow-up paper. Figure 10 shows the RSSI values as a function of time. These are the data of only one of the columns with concrete M1, since, during the test, the device placed in the second column faced battery issues. The node was evaluated over a week, until the batteries ran out. On the first day, 31 January 2023, the node was mounted to the rebar. At 10 am, the concrete was poured, resulting in a significant drop in the RSSI value (\(-\)30 dB). After a day, the concrete columns were demolded, resulting in a variation (\(\pm\)5 dB) in the RSSI due to the high variability in its environment during demolding. After the demolding, the columns were left to rest inside the laboratory under controlled atmosphere (temperature of 20 \(\pm\) 2 \({}^{\circ}\)C and relative humidity of 60 \(\pm\) 5%), resulting in a flat RSSI behavior. On the seventh day, the columns were placed outside of the laboratory, exposed to realistic environmental conditions resulting in an uptick of the RSSI (+10 dB). One day after moving the columns outside there was an increase in the RSSI value to \(-\)100 dB (+15 dB compared to its inside location). This increase in RSSI is due to the blocking nature of the laboratory (e.g., for a building with reinforced concrete). This difference in reception is well known and characterized in the mobile community (e.g., the 3 GPP 3D-UMa model [37]).  
Figure 10: The RSSI values as a function of time. It is clear from the results that the communication link was robust against the many changes in its environment.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**First Day of Pouring** & \multicolumn{2}{c}{**Day after**} & \multicolumn{2}{c}{**Three Months after Pouring**} & \multicolumn{2}{c}{**Accelerated**} \\ \hline \(\epsilon_{\mathrm{r}}\) [\(-\)] & \(\sigma\) [S/m] & \(\epsilon_{\mathrm{r}}\) [\(-\)] & \(\sigma\) [S/m] & \(\epsilon_{\mathrm{r}}\) [\(-\)] & \(\sigma\) [S/m] & \(\epsilon_{\mathrm{r}}\) [\(-\)] & \(\sigma\) [S/m] \\
30 & 1.75 & 6 & 0.35 & 5 & 0.075 & 5 & 0.075 \\ \hline \The robustness of the communication link is measured as follows. The node tries to send a package every hour. When a package is not received, the node will try to resend the package. Due to the time it takes to resend the package, the time between each package will determine the number of retransmissions (ignoring the drift in the RTS clock of the device). Figure 11 gives the cumulative histogram of the time intervals of the received packages. It shows that more than 98.5% of the packages were received within a second. This is a manifestation of a robust communication link.  
Figure 12 shows the cell tower with the most retrieved packages. This tower was located 500 m from the transmitting device. Therefore, we conclude that a range of at least 500 m is achieved from the nodes embedded in the concrete to the LTE cell tower, surpassing the predetermined goal of 100 m. We achieved a long-range communication link from in-to-out concrete to an LTE cell tower.  
Figure 11: The cumulative distribution of the time between packages as a measure of communication link robustness. Every hour (3600 s), the node tried to send a package. The cumulative histogram shows that more than 98% of the packages were received within time.  
Figure 12: The place of the columns with the nodes and the connected cell tower. A range of 500 m has been achieved.