## 2 Materials and Methods
### Proposed Wireless Network
This means that the transmitter could successfully send all data packets to the receiver via hop-by-hop, while the receiver could also completely receive all data streams. We note that we performed the experiments over three days in March 2023, which corresponds to the summer season in Thailand. The weather each day was quite stable. Therefore, we could obtain excellent PDRs. However, for long-term testing, the PDR may be varied due to environmental factors, so this issue should be considered for future study. Not only the PDR but also the average ETEDs obtained good results: 21,091.6 ms and 21,079 ms, for test scenarios 1 and 2, respectively. For the results here, at each test, 100 packets could be sent hop-by-hop for every sampling time (i.e., 200 ms) with a real-time response. We note that, for theoretical calculation, the ETE delay should be 20,000 ms (100 packets * 200 ms) for each test. The average ETEDs for both cases are small and very close. However, as mentioned above, long-term test should explore this point. The experimental results in this section indicate the achievement of our objective since the implemented multi-hop network with the sensor node deployment solution obtained accepted RSSI levels, a 100% PDR, and a small ETED for the mountainous forest environment with sloping areas and the watercourse environment. We believe that our methodology and results can help users and researchers carefully consider and deploy 2.4 GHz IEEE 802.15.4 multi-hop WSNs in their work. ### Sensing Results

Since, in this work, we developed the multi-hop network, the design and implementation of its wireless networks, an autonomous protocol, node deployment, and test cases related to communication evaluation were focused. For the results, as in Section 5.1, to satisfy practical use, we sent real data packets in every sampling period from the transmitter to the receiver and included the sensor information. 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. It can be used to support both test scenarios #1 and #2, with scenarios such as landslide and huge water flooding monitoring [19; 20; 21; 22]. To show the potential of our system, the proposed device and the real-time three-axis acceleration and gyro signals (i.e., acceleration: Ax, Ay, and Az; and angular velocity: Gx, Gy, and Gz) [23; 24] with three different vibration behaviors collected from the multi-hop network are illustrated as examples in Figures 11 and 12, respectively. However, long-term use and performance evaluation in various scenarios should be further explored. Also, the integration of other related sensors (i.e., those recording temperature, moisture, position, etc.) and the implementation of data packet formats to achieve wireless communication capacity and satisfy applications should be further studied. Figure 12: _Cont._

## 6 Conclusions

In this paper, we demonstrated the realistic test of a 2.4 GHz multi-hop wireless network for mountainous forest and watercourse environments. A multi-hop network using IEEE 802.15.4 XBee3 micro-modules and a communication protocol among nodes were developed. The wireless node deployment solution being able to maintain reliable communications for practical testing was also presented. The system was tested in two different scenarios: a mountainous forest and watercourse, which refer to environmental and flooding monitoring applications. Wireless network performances were evaluated through the RSSI level of each hop, the PDR, as the successful rate of packet transmission, and the ETED from the transmitter to the receiver. The experimental results confirm the success of the multi-hop WSN deployment and communication. In future work, we will include more nodes in multi-hop networks where line and mesh topologies will be taken into account. Relay nodes will be integrated with sensors, and multi-source transmission in a multi-hop network will be tested.