Development and Field Testing of a Wireless Data Relay System for Amphibious Drones

Round 1

Reviewer 1 Report (Previous Reviewer 2)

The revision is fine to me.

Author Response

Thank you very much for taking your valuable time to review. We are truly grateful for your understanding and it is an honor that you have reviewed our paper presentation.

Reviewer 2 Report (New Reviewer)

This article addresses amphibious drones' restricted wireless data transmission range through a developed relay system. Field tests demonstrated successful data transmission over 757 meters, but obstacles such as shoreline vegetation presented challenges, necessitating confirmation of a continuous drone path. The paper is well-structured and effectively conveys the concept. However, it lacks a discussion on related works and comparisons with existing literature. Additionally, the authors could enhance the articulation of the study's contributions compared to previous works in the field.

OK

Author Response

Thank you very much for taking your valuable time to review our manuscript. In the introduction, we have provided a more detailed overview of the paper that closely aligns with the content of our study. The description was added for clearly identify our challenge as wireless data relay in amphibious settings. This information has been included in the revised manuscript on pages 2, lines 75–78.

To ensure the impact of the vegetation in the test site on wireless communication, we have presented estimates using the most frequently used model introduced in a relevant review. This discussion has been added to the revised manuscript on pages 26–27, lines 1184–1193.

We have cited previous research on drone swarms, estimating the number of drones operable in our system. We have also referenced recent studies on high-speed communication using millimeter waves, highlighting the clear need for future drone relays. This information can be found in the revised manuscript on pages 27–28, lines 1208–1250.

Reviewer 3 Report (New Reviewer)

This paper presents the development and testing of a wireless data relay system for multiple amphibious drones. The idea is of interest and the manuscript is well written. I suggest the following:

1. The authors should focus more on the novelty of their work in the Introduction and state clearly their contributions.

2. The title is misleading, because it contains the word multiple, but the results are mainly based on a single relay. A theoretical analysis and background for multiple relays should at least be described.

3. At which other frequencies the radio relay can be extended? Can the specific scenario support mm-waves?

4. It is recommended that the authors provide the bit rate or throughput performance of their relay scenario. This would increase the technical content of the manuscript as well as the novelty.

Minor edits will be required throughout the text.

Author Response

Thank you very much for providing many important suggestions. Following your feedback, the following modifications have been made:

1. We have added detailed information on the references in the introduction and included descriptions focusing on the most relevant study to clearly identify the unresolved issues in amphibious drones. This addition is on page 2, lines 75-78 of the revised manuscript.
2. As you pointed out, the content of this study is limited to the verification of a single relay. While the concept aims for the use of a larger number of drones, various parameters related to the connectivity of multiple communication nodes and communication traffic are likely to be involved in the operation of numerous drones. Therefore, we have avoided unwarranted speculation and removed the word "multiple" from the paper title and abstract. We are highly interested in addressing such challenges in future research, and further investigation is deemed necessary.                  To demonstrate the effectiveness of the drone relay concept in this study, we estimated the upper limit of the drone swarm size under two assumptions: measured throughput and theoretical throughput limits. This description has been added to the revised manuscript on pages 27, lines 1208–1226 and pages 27–28, lines 1231–1243.
3. As you suggested, drone data relay at various frequencies has been verified in previous studies for aerial operations. Although legal regulations led us to use the 2.4 GHz band (an ISM band) in this study, it is anticipated that longer-distance wireless relay using longer wavelengths would be possible in the absence of legal issues. Even shorter wavelengths, such as millimeter waves, may be applicable to the relay concept in this study, but the introduction of antenna technologies like high-speed beamforming is essential for hardware implementation. Millimeter waves offer the potential for improved communication speed and increased channels, enabling faster routing and connection of numerous drones. This addition is on page 28, lines 1244–1250 of the revised manuscript.
4. Thank you for your valuable and insightful feedback. In the outdoor operation tests, we limited the serial bus speed to 9600 bps to ensure a stable response time for the water quality sensors. However, using a faster sensor could lead to improved communication speed. We have added a detailed description on the theoretical maximum throughput for an optimized hardware setting with negligible latency. This addition is on page 27, lines 1227–1231.

Round 2

Reviewer 3 Report (New Reviewer)

The authors addressed the raised concerns. Thank you.

Minor editing will be required.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The paper lacks scientific knowledge / deepness. Both in the mathematical and the telecommunications fields.

It reads as a report of work-done, touching integration and physical design of the many parts of the system, but does not argue how the relay system is resilient. Throughput and other networking metrics are in need.

I don't really seem the formalization of the problem at hands.

Some portions of text sound unnatural, but the english it self is good.

Reviewer 2 Report

1)The paper is well-written and organized. However, the manuscript is more like a report than a scientific contribution at this moment. Please clear what the scientific contributions are.

2)Please illustrate the necessity of integrating water quality monitoring systems into relay drones.

3)Page 12, Figure 7, There is no relay drone in the picture.

4)Both figures and tables must come immediately after the first time it is mentioned in the text, not far away.

Both figures and tables must come immediately after the first time it is mentioned in the text, not far away.