Joint Hovering Height, Power, and Rate Optimization for Air-to-Ground UAV-RSMA Covert Communications

Round 1

Reviewer 1 Report

Please provide further details on how the covert rate maximization problem (P1) is divided into its three sub-problems: optimizing transmit power allocation, common rate allocation, and UAV hovering height. 

To strengthen your claim, kindly provide further details on how the covert rate significantly decreases in the benchmark scheme compared to the UAV-RSMA scheme. This emphasizes the unrivaled covert performance of the proposed UAV-RSMA scheme.

Please provide the error margin for the affirmation that the curves in Figure 3 also demonstrate the superiority of the proposed scheme over that of the benchmark scheme. 

Would it be possible to incorporate a section dedicated to related works and potentially include additional references to your work? This could provide valuable context and credibility to your research. 

Please rewrite this sentence to provide a more precise understanding: " To combat the effects of imperfect channel state information at transmitter (CSIT) on secrecy performance, IUI mitigation and secrecy sum-rate maximization were jointly designed under a worst-case uncertainty channel model for RSMA, which significantly enhanced secrecy rate performance over that of NOMA"

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper investigates the covert communications in the air-to-ground UA V-RSMA. Based on that, the authors establish the covert rate optimization model and analyzed the impact of the system parameters. Overall, this paper studied an interesting topic, and the mathematic works are sound. Nevertheless, the authors need to address the following concerns before suggesting a publication.

1.       The effect of distance is not considered in the expression of the signal-to-interference-plus-noise ratio, does this have a negative impact on the accuracy of the model?

2.       The authors should elaborate the derivations of several new results that are presented in the paper without reference or derivation. If the derivations break the flow of the paper, they can be added to the annex.

3.       In Figure4, there is a typo that “H=80”, which should be “H=80m”.

4.       In a practical scenario, where the number of available channels and the battery capacity of the UAV are limited, is the proposed algorithm still feasible under the low latency constraint?

5.       The description of the experimental simulation section is not comprehensive enough, it is better to add more covert comparison experimental results.

6.       The explanation and discussion of the results presented in the paper also needs improvements. The new insights from the work should be more clearly highlighted.

7.       Besides, authors can refer to “Securing Collaborative Environment Monitoring in Smart Cities Using Blockchain Enabled Software-Defined Internet of Drones” to consider the connected  UAVs scenarios and add some discussion about such application.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Overall, in the paper, the authors have presented the system model and proof of the propositions in a detailed manner and is highly appreciated. However, the "simulation results" section can be improved by adding more graphical comparison of the proposed optimization method with other existing methods using other performance metrics.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

In this paper, the authors investigate the covert communications in the air-to-ground unmanned aerial vehicle aided rate-splitting multiple access system with the aim to maximize the covert rate. The authors, In order to achieve the maximum covert rate consider system parameters such as transmit power allocation, common rate allocation, and UAV's hovering height in the optimization process. They design and propose a alternating optimization algorithm to achieve to optimal solution according to non-convex nature of the covert rate maximization problem. Based on the simulation results, the authors clarify the superior performance of the proposed alternating optimization algorithm's hiding rate and demonstrate that the suggested RSMA drone scheme achieves a higher hiding rate compared to conventional designs. The paper is well written and well structured and the topic is highly relevant.

Nevertheless, I have four main concerns:

1.       The research domain has not been clearly specified in the article. It is better to categorize the literature review before the literature review section and define the research domain using a tree diagram.

2.       It is advisable to conclude the literature review section by comparing different methods using a table and highlighting the strengths and weaknesses of each method.

3.       The writing quality of the article is generally good in terms of grammar. However, there are some issues in certain parts, as mentioned below as examples:

3.1   In line 100, there is an extra space before the preposition "to".

3.2   In line 234, it is better to remove the comma after "".

3.3   In the first row of line 243, there is an extra "▢" that needs to be removed.

3.4   In the fifth row of line 243, "its" should be replaced with "it's".

3.5   In the fourth row of line 256, the value "[?]" should be replaced with the desired reference.

4.       It is advisable to compare the proposed methods in section 4 not only with benchmarks but also with one of the latest and best works presented in the field of research. This work should have been evaluated in the literature review section and can be used as a reference for comparison and evaluation purposes.

1.       The writing quality of the article is generally good in terms of grammar. However, there are some issues in certain parts, as mentioned below as examples:

1.1   In line 100, there is an extra space before the preposition "to".

1.2   In line 234, it is better to remove the comma after "".

1.3   In the first row of line 243, there is an extra "▢" that needs to be removed.

1.4   In the fifth row of line 243, "its" should be replaced with "it's".

1.5   In the fourth row of line 256, the value "[?]" should be replaced with the desired reference.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf