## 5 Conclusions  
This study examines the influence of vegetation on radio wave propagation in real-world scenarios for IoT-based smart agriculture applications in a corn field at 0.9 GHz and 2.4 GHz. All measurements were conducted in a corn field at stage R3, during which the corn leaves and stalk almost do not change and the kernels contain approximately 80% moisture. The results indicate that increasing the receiving antenna height above the corn height, from 2.0 m to 3.4 m, expanded the coverage area. The maximum communication distance for near-ground installation of the sensor node (where the transmitter is \(\lambda/3\) m above ground) in a corn field, with a base station (receiving) antenna height of 3.4 m, was found to be 105 m at 0.9 GHz and 45 m at 2.4 GHz in the obstructed line-of-sight (O-LoS) scenario for co-polarized H-H antennas. Moreover, a more significant increase in the communication distance between the transmitting and receiving antennas was observed when the transmitting antenna height was increased from \(\lambda/3\) m (0.11 m at 0.9 GHz and 0.04 m at 2.4 GHz) to 0.5 m above ground level. The maximum communication distance for above-ground installation of the sensor node (0.5 m above ground) in a corn field, with a base station antenna height of 3.4 m, was found to be 140 m at 0.9 GHz \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\(\text{h}_{\text{Rx}}\)*} & \multirow{2}{*}{\(\text{h}_{\text{Tx}}\)*} & \multirow{2}{*}{**Frequency**} & \multirow{2}{*}{**Polarization**} & \multicolumn{4}{c}{**Mean Absolute Percentage Error**} \\ \cline{5-8}  & & & & & **Basic Free-Space Loss** & **Multi-Slope Model** & **Weissberger Model** & **COST-235 Model** \\ \hline \multirow{8}{*}{3.4} & 0.9 & H & 24.4 & 8.3 & 10.6 & 22.9 \\  & 2.4 & H & 25.2 & 12.2 & 14.8 & 13.5 \\  & 0.9 & V & 33.8 & 14.7 & 21.0 & 9.4 \\  & 2.4 & V & 32.4 & 20.2 & 22.7 & 5.7 \\ \cline{1-1} \cline{2-8}  & 0.9 & H & 17.9 & 8.2 & 6.2 & 33.7 \\  & 2.4 & H & 20.6 & 20.4 & 7.5 & 19.1 \\  & 0.9 & V & 31.34 & 22.2 & 16.6 & 14.0 \\  & 2.4 & V & 26.8 & 26.6 & 14.3 & 12.6 \\ \hline \hline \end{tabular}  
* \(\text{h}_{\text{Rx}}\) and \(\text{h}_{\text{Tx}}\) are receiving and transmitting antenna heights in meters. ** The frequency indicated in the table is in GHz. *** H—horizontal and V—vertical polarization.  
\end{table} 
Table 6: A comparison of the mean absolute percentage errors of Weissberger, COST-235, and Multi-slope models when they are used to predict the loss-versus-distance trend in several scenarios in a corn field at a receiving antenna height of 3.4 m.  
and 65 m at 2.4 GHz in the O-LoS scenario for co-polarized H-H antennas. Also, the results show that, for vertical polarization Tx-Rx antennas, the received signal experienced higher attenuation than for horizontal ones, especially at 0.9 GHz. In contrast, at 2.4 GHz, antenna polarization had minimal impact on the coverage area. In addition, we identify the three models suitable for planning radio coverage in a cornfield in the following scenarios: (1) Multi-slope model for the near-ground node connectivity scenario with omnidirectional in-elevation-plane antennas and horizontal polarization; (2) Weissberger model for above-ground node connectivity scenario with omnidirectional in-elevation-plane antennas and horizontal polarization; and (3) COST-235 model for omnidirectional in-azimuth-plane vertical polarized antennas of nodes and base stations in both near- and above-ground scenarios. This work provides insights into radio wave propagation in a corn field in different scenarios, making it suitable for radio coverage planning in the presence of crops where plants are grown in rows with vertically oriented stalks (such as corn, sunflower, etc.) to ensure reliable and resilient wireless communications in IoT-based smart agriculture. Conceptualization, B.N.A., N.T.A. and G.L.A. ; methodology, B.N.A., N.T.A. and G.L.A. ; software, N.T.A. and B.N.A. ; validation, B.N.A., N.T.A. and G.L.A. ; formal analysis, N.T.A. and G.L.A. ; investigation, B.N.A., N.T.A.