Spectral Efficiency Beamforming Scheme for UAV MIMO Communication via Budgeted Combinatorial Multi-Armed Bandit

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Journal: Electronics (ISSN 2079-9292)

Manuscript ID: electronics-3993208

Title: Spectral Efficiency Beamforming Scheme for UAV MIMO Communication via Budgeted Combinatorial Multi-Armed bandit

Authors: Jing Gao , Yunxing Xiang , Yunchao Song * , Jing Zhu , Jun Wang , Xiaohui You , Ge Wang , Tianbao Gao

 

This article recommends a two-stage beamforming scheme (BC-MAB) to improve spectral and energy efficiency of UAV MIMO systems under relatively low power. To minimize pilot overhead and improve performance, it selectively selects RF chains with an optimal bang-per-buck ratio. After reviewing the manuscript, my specific comments are below:

 

 

1. The abstract should briefly describe the problem, solution, outcomes, and quantifiable improvements (in %) over benchmarks.

 

2. The introduction reviews previous work without delving into specific limitations in past methods that this work overcomes. Also, the introduction should provide a clear research gap followed by the essential novelty points.

 

3. The motivation for incorporating BC-MAB with UAV beamforming is not well-established. What makes a budgeted combinatorial approach more effective than simpler MAB or reinforcement learning models? Why or why not?

 

4. Technical innovation and quantitative advantage should be explicitly acknowledged in the contributions.

 

5. What is the specific differentiation between current studies and previous literature on UAV-MIMO, such as [19] or other recent works?

 

6. Add a comparison table in section 2 (Related Work). Also, discuss the weaknesses of existing techniques/methods and justify how your approach performs better.

 

7. The system model assumes perfect CSI, fixed altitude, and solar energy input, but fails to consider or address practical differences in reality. Add sensitivity analysis or justification.

 

8. Differences in variables defined and assumptions made for Equations (1)–(4) are not well-defined. For example, the selection and measurement of τt and Ts are uncertain.

 

9. The formulation in (6a)–(7b) does not contain any specific constraints on UAV power or energy dynamics, making the optimization process incomplete.

 

10. Some symbols (e.g., Ft_RF, Lt, NRF, Dt) have been included without any meaningful definitions or consistency, enhancing the notation coherence and consistency.

 

11. The Algorithm 1 proposed is a (heuristic greedy) and does not provide any formal proof of convergence or performance limitations. Also, there is no complexity analysis for Algorithm 1 in terms of its scalability for large antenna arrays or real-time UAVs. In addition, Input/output parameters and iteration termination criteria are not explicitly specified; the pseudocode is informal, making it redundant.

 

 

12. The simulation setup doesn't make any reference to how parameters such as noise power, channel estimation error, or solar recharging dynamics affect the results. (No reference is made to the simulation parameters)?. Also, the source or rationale for settings (e.g., Pc = 240 mW, αp = 0.35, P = 2 W) must be clarified, with appropriate citations.

 

13. There are comparisons made using comparable methods like (JHPC, SOMP, and full-digital), but they are not fully implemented or referenced with uniform parameter setups, making the comparison unjustifiable.

 

14. Figures 3-9 lack a quantitative discussion. You describe qualitative trends, but statistical results, convergence metrics and computational costs are not presented (missing).

 

15. The conclusion does not contain any quantitative evidence or critical thinking. It simply restates the methodology without summarizing measurable performance gains, practical implications, or analytical insights. You should strengthen the conclusion by adding key numerical results, limitations, and providing clear directions for future work, rather than solely mentioning multi-UAV scenarios.

 

16. The paper has several grammar and typographical issues need to be addressed.

 

17. References [2] and [5] are duplicated.

Comments on the Quality of English Language

The paper has several grammar and typographical issues need to be addressed.

Author Response

Please see the attached response letter for detailed responses.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article proposes a two-stage beamforming scheme based on a budgeted combinatorial multi-armed bandit (BC-MAB) for UAV MIMO systems. The work technically sounds; however, I have the following comments.

• The authors are recommended to add a section on related works to provide the novelty of the work compared to existing studies.
• All acronyms and initialisms should be defined the first time they appear in the text. This should be in the abstract as well as the article. Many acronyms are not defined. Additionally, abbreviations should be defined once, and then they can be used without redefinition.
• It is recommended to add a discussion of selecting the discrete Fourier transform (DFT) for channel modeling.
• Are there no other constraints related to the UAV movement, trajectory, orientation, speed,…?
• For better presentation, move the simulation parameters to a table.
• Add details related to the simulation environment.
• Results lack a clear discussion. Further discussion is needed to clarify the results.
• References should be updated; most of the references are out of date. It is recommended to replace with recent relevant references.

Author Response

Please see the attached response letter for detailed responses.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed all my concerns; I have no more comments.