# Unmanned Aerial System-Based Data Ferrying over a Sensor Node Station Network in Maize
## 2 Materials and Methods
### Proposed UAS Data Ferrying Designs
#### 2.1.4 Decision Matrix  
Proposed designs were assessed based on the design objective for a typical US mid-west maize field (area > 50 ha), the criteria, and the constraints. The proposed designs were evaluated based on an evaluation matrix where points were allocated to the four criteria, and two constraints. The evaluation results are provided in a matrix (Table 1) with scores for each criterion and constraint explained below:  
Criteria 1 (wireless technology): The six wireless technology protocol designs were analyzed and assigned points from 1 to 3 (1 being less desirable and 3 being highly desirable). Since the GPRS wireless protocol has a communication range between 1-10 km and a high-power consumption (560 mW), the GPRS was assigned a point value of 1. The ZigBee wireless protocol has a communication range of 100 m and has lower power consumption (36.9 mW) but the line-of-sight between the sensor node and the coordinator node must be available, so the potential for canopy interference could be an issue. Thus, the ZigBee wireless protocol was awarded a point value of 2. Because the LoRa wireless protocol has a long range (5 km) and low power consumption (100 mW), it was rated at 3 points. Criteria 2 (UAS): The two UAS systems were evaluated and given points from 1 to 2 (with 2 being the more desirable rating). The fixed-wing UAS was rated 1 out of 2 points because of its limitations of low maneuverability, higher cost, and tedious take-off and landing. The multi-rotor UAS was rated 2 points because of its better maneuverability and more controlled take-off and landing as compared to the fixed-wing UAS. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \begin{tabular}{c} **Criteria 1** \\ **Wireless Technology** \\ \end{tabular} & \begin{tabular}{c} **Criteria 2** \\ **UAS** \\ \end{tabular} & \begin{tabular}{c} **Criteria 3** \\ **Power Supply** \\ \end{tabular} & \begin{tabular}{c} **Criteria 4** \\ **Data Storage** \\ \end{tabular} & \
\begin{tabular}{c} **Constraint 1** \\ **Cost** \\ \end{tabular} &
\begin{tabular}{c} **Constraint 2** \\ **Adoptability** \\ \end{tabular} & \multirow{2}{*}{**Total**} \\ \hline Design A & 2 & 1 & 1 & 1 & 3 & 3 & 11 \\ \hline Design B & 3 & 2 & 2 & 2 & 4 & 5 & 18 \\ \hline Design C & 1 & 1 & 2 & 2 & 4 & 3 & 13 \\ \hline Design D & 2 & 2 & 1 & 1 & 5 & 5 & 16 \\ \hline Design E & 3 & 1 & 1 & 1 & 3 & 3 & 12 \\ \hline Design F & 1 & 2 & 2 & 2 & 5 & 4 & 16 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The unmanned aerial systems (UAS) data ferry decision matrix table for six proposed designs based on the four criteria and two constraints with the total points for each design. Criteria 3 (power supply): The two types of power supplies studied were given points from 1 to 2. Since the power supply to the wireless communication setup tethered from the UAS could potentially add load on the UAS battery, it was rated 1 out of 2 points. An inexpensive and light external power source mounted on the UAS was determined as a better alternative than tethering the power from UAS since it could sufficiently accommodate the power requirements of the whole system and not add power load to the UAS. Thus, it was assigned 2 points. Criteria 4 (data storage): Two data storage modes were considered (on-board UAS memory and cloud storage) and awarded points from 1 to 2. Data transmitted over a single flight would be small (around 2 megabits), so cloud storage would not be very helpful in this scenario as it would add unnecessary complexity. Cloud data storage was given 1 out of 2 points, while an on-board UAS memory card was given 2 points. Constraint 1 (cost): Cost-effectiveness of each system design was evaluated with points ranging from 1-5. Low points were allocated to the design with higher costs. As much as 2 points could be allocated for the cost of the wireless technology protocol, as much as 2 points could be allocated for the UAS cost, and 0 to 1 point for the power source for the wireless communication.