## 2 Materials and Methods
### Proposed Wireless Network
Flooding in this case is also demonstrated in Figure 6. For both scenarios, each experiment was repeated twenty times, and the average results are reported. We note that, in these experiments, we sent real data packets in every sampling period from the transmitter to the receiver, and we included the sensor information. As illustrated in Section 5.2, in the ongoing work of our research group, a three-axis accelerometer and Gyro sensors using the GY-521 module for monitoring applications have been included in the XBee3. Figure 2: Example of the proposed sensor node deployment process (before the data collection phase. Figure 4: The test field layouts. Figure 3: Test scenarios #1 and #2. ## 4 Evaluation Metrics

To study the performances of the proposed multi-hop network introduced above, three performance metrics were measured and evaluated, including the RSSI level of the three hops, the PDR, and the ETED, as shown in Equations (1)-(3). Figure 5: Illustration of sensor node deployment and environments. Figure 6: An example of water flooding during the rainy season for field #2. \[\left[RSSI_{relay1,i},RSSI_{relay2,i},RSSI_{receiver,j}\right]=\left\{ \begin{array}{l} Avg.\:from\:all\:RSSI\:samples;\:for\:transmitter\:to\:relay1\\ Avg.\:from\:all\:RSSI\:samples;\:for\:relay1\:to\:relay2\\ Avg.\:from\:all\:RSSI\:samples;\:for\:relay2\:to\:reciver\\ \end{array} \right.\]

\[\left[Avg.RSSI_{relay1,i},Avg.RSSI_{relay2,i},Avg.RSSI_{receiver,j}\right]= \left\{ \begin{array}{l}\frac{1}{N}\sum\limits_{i=1}^{N}RSSI_{relay1,i}\\ \frac{1}{N}\sum\limits_{i=1}^{N}RSSI_{relay2,i}\\ \frac{1}{N}\sum\limits_{i=1}^{N}RSSI_{receiver,i}\end{array} \right. \tag{1}\]

\[PDR=\frac{Num.received\:packets\:at\:receiver}{Num.\:sent\:packets\:by\:transmitter} \times 100 \tag{2}\]

\[ETED(at\:receiver)=Finish\:time\:to\:receive\:the\:last\:packet\:-\:Staring\:time\:to\: receive\:the\:first\:packet \tag{3}\]

The RSSI indicates the signal power at the receiver side. In this work, both the raw RSSIs and average RSSIs of all wireless links, including transmitter-to-relay 1, relay 1-to-relay 2, and relay 2-to-receiver, were collected. A weak RSSI level can represent poor signal quality when the RSSI is significantly influenced by environmental factors [11, 16, 17]. The PDR represents the success level of the delivery of data from the transmitter to the receiver [18], while the ETED measures how long the network processes data transmissions. To cope with the time synchronization problem of all nodes in the network, the ETED is calculated at the receiver's side with its clock. It is the difference between the finish time of the receipt of the last data packet and the starting time of the receipt of the first data packet. As mentioned before, each experiment (test scenarios #1 and #2) was repeated twenty times, and the average RSSI, PDR, and ETED were measured and reported. ## 5 Experimental Results and Discussion

### Communication Performances

The raw RSSI signals, the average RSSIs of all wireless links, the average PDR, and the average ETEDs for test scenarios #1 and #2 are demonstrated in Figures 7-10, respectively. We note that the results in Figure 7 are examples of raw RSSI signals measured and collected from test scenario # 1 (test times 5 and 15). Such signals could be displayed in real time during the test using the graphical user interface (GUI) window implemented on the computer. The average RSSI results are shown in Figure 8.

Figure 8: Average RSSIs of hops 1 to 3 for test scenarios #1 and #2. Figure 7: Examples of raw RSSI signals collected from test scenario #1 (test times 5 and 15). The signals could be displayed in real time during the test in the GUI window. Note that the y-axis is the RSSI level in dBm, and RSSI B, C, and D refer to hops 3, 2, and 1. Figure 10: ETED results. Figure 9: PDR results. The experimental results also indicate that the multi-hop network with the communication protocol and the sensor node deployment solution presented in this work could provide an average PDR of 100% for both test scenarios.