Study of Power and Trajectory Optimization in UAV Systems Regarding THz Band Communications with Different Fading Channels

Round 1

Reviewer 1 Report

This report presents a comprehensive study on the performance of UAV systems in Terahertz (THz) communication under different channel fading types. The proposed system aims to optimize THz channels by enhancing the uplink and downlink transmission trajectories between UAVs and users, with the objective of reducing transmission power. The analysis considers various fading channels such as Nakagami-m, Rician, Rayleigh, Log-normal, and Weibull. The results demonstrate that as the average signal-to-noise ratio (SNR) increases, the bit error rate (BER) and outage probability decrease significantly. Among the fading channels, Nakagami-m exhibits superior performance. The findings provide valuable insights for future designs and deployments of THz communication systems and highlight the potential of THz communication in challenging channel environments. Further research is recommended to explore the full potential of THz communication and investigate cooperative UAV systems in reducing BER and co-channel interference.

Author Response

1- This report presents a comprehensive study on the performance of UAV systems in Terahertz (THz) communication under different channel fading types. The proposed system aims to optimize THz channels by enhancing the uplink and downlink transmission trajectories between UAVs and users, with the objective of reducing transmission power. The analysis considers various fading channels such as Nakagami-m, Rician, Rayleigh, Log-normal, and Weibull. The results demonstrate that as the average signal-to-noise ratio (SNR) increases, the bit error rate (BER) and outage probability decrease significantly. Among the fading channels, Nakagami-m exhibits superior performance. The findings provide valuable insights for future designs and deployments of THz communication systems and highlight the potential of THz communication in challenging channel environments. Further research is recommended to explore the full potential of THz communication and investigate cooperative UAV systems in reducing BER and co-channel interference.

[A]-1

Thank you for your advice. The introduction section has been rewritten in the revised manuscript and future research works are mentioned in the conclusion.

Many researchers are working hard to explore the potential of THz communication. In this field, the use of cooperative UAV systems is considered as a promising approach to reduce the bit error rate (BER) and minimize co-channel interference. Collaborative UAV systems provide a communication environment where UAVs in a network can collaborate by sharing their information and resources. These systems can increase the signal strength, apply signal processing techniques and correct channel-related errors by communicating with each other. Thus, cooperative UAV systems can play an important role in future wireless communication systems to reduce BER in THz communication and minimize co-channel interference. However, more research and development studies are needed in this area. I will address this issue more detail in my future work.

 

Author Response File: Author Response.docx

Reviewer 2 Report

This study examines UAVs' potential in 5G and 6G networks and explores THz-band communications for fast UAV communication. It analyzes UAV performance in THz networks, considering fading channels and optimizing transmission power. The study derives equations for UAV location and user power optimization, supported by analytical formulations and numerical results. This paper deals with a hot area of investigation at the moment.  I have looked at the mathematics and it looks sound. The simulation results are based on the known fading models. Herein are some comments that need clarification:

*In the introduction, it would be beneficial to provide more specific details about the potential applications of UAVs in 5G and 6G networks. What are some specific use cases or industries where UAVs can be utilized effectively?

*Clarify why terahertz (THz)-band communications are being considered as a potential option for 6G networks. What advantages does THz-band communication offer over other frequency bands?

*Expand on the methodology used to analyze the performance of UAV communications in THz networks. How were the different fading channels selected and what criteria were used to evaluate their influence on the performance? Additionally, it is well-known that as the frequency used increases, the signal becomes highly susceptible to environmental effects, resulting in a smaller coverage area. In the context of 6G, where the radius of the cell is expected to be less than 200m, have you taken this challenge into consideration in your analysis and mathematical model?

*Discuss the practical implications and potential challenges of implementing the proposed optimization algorithm in real-world scenarios. Are there any limitations or assumptions that should be considered?

*It is essential to support your study with relevant literature that demonstrates how the fading models used in this study are applicable to THz frequencies. Additionally, please ensure that references are provided to support the information presented in Table 2.

*Provide more details about the analytical formulations for capacity, outage probability, and bit error rate (BER). How were these formulations derived, and how do they account for the specific performance-influencing factors considered in the study?

Readable

Author Response

1- In the introduction, it would be beneficial to provide more specific details about the potential applications of UAVs in 5G and 6G networks. What are some specific use cases or industries where UAVs can be utilized effectively?    

[A]-1

Thank you for your comments. I have added a paragraph about some specific use cases or industries where UAVs can be utilized effectively.

 

There are a number of specific use cases and industries where UAVs have a variety of potential applications in wireless communication networks such as 5G and 6G. For example, in the logistics and transportation sector, UAVs can play an important role thanks to their fast and effective payload capacity. UAVs may be preferred in cases such as rapid delivery of emergency medical supplies or rapid shipment of critical parts. In the agricultural sector, UAVs can be an effective tool for phytosanitary monitoring, productivity improvement and irrigation management. In the field of security and monitoring, UAVs can be used effectively in issues such as border security, fire monitoring, disaster management and crime prevention. The media and entertainment industry are another area where UAVs can be used for creative shooting and impressive visual effects. Also, infrastructure monitoring and maintenance is another area where UAVs are useful. UAVs can perform unmanned visual inspections of structures such as bridges, power lines, buildings and detect abnormal conditions. Thanks to their ability to provide easy access to high points, UAVs can facilitate infrastructure monitoring processes. With the development and improvement of advanced technologies, it is predicted that UAVs will be used more effectively in different industries.

 

2- Clarify why terahertz (THz)-band communications are being considered as a potential option for 6G networks. What advantages does THz-band communication offer over other frequency bands?    

[A]-2

Thank you very much for your comment. I appreciate the reviewer's comment. I have added a paragraph to clarify why terahertz (THz)-band communications are being considered as a potential option for 6G networks.

 

First, because of its large bandwidth, the THz band enables for high data rates. To address the need for higher data rates, 6G networks may deliver substantially higher data rates by employing the THz spectrum. Second, within the frequency spectrum, the THz band allows numerous parallel channels. This capability enables 6G networks to support a huge number of users. Third, because the THz band has minimal latency, it is a feasible option for ultra-low latency applications. THz communication enables real-time engagement by providing a quick and dependable connection. As a consequence of its features such as fast data rates, large capacity, and low latency, THz band communication is being explored as a viable alternative for 6G networks.

 

3- Expand on the methodology used to analyze the performance of UAV communications in THz networks. How were the different fading channels selected and what criteria were used to evaluate their influence on the performance? Additionally, it is well-known that as the frequency used increases, the signal becomes highly susceptible to environmental effects, resulting in a smaller coverage area. In the context of 6G, where the radius of the cell is expected to be less than 200m, have you taken this challenge into consideration in your analysis and mathematical model?      

[A]-3

Thank you for your comment. I have added a paragraph why I chose these fading channels. In this study, cellular radius and coverage area are not considered.  However, I will consider this challenge for future studies.

 

They are commonly used elements for selecting different fading channels in the THz band and evaluating their effects on performance. The use of fading profile, environmental conditions, and frequency-dependent fading criteria are important to improve the efficiency of THz communication and to determine the most suitable channels. Based on these criteria, analysis and evaluation of different channels can be made. For this reason, Rayleigh, Rician, Nakagami-m, Weibull and Lognormal fading channels were determined to provide the best for communication performance.

 

4- Discuss the practical implications and potential challenges of implementing the proposed optimization algorithm in real-world scenarios. Are there any limitations or assumptions that should be considered?    

[A]-4

Thank you very much for your concern. I appreciate the reviewer’s concern.

 

The power and trajectory optimization algorithm of the UAV system will be under the influence of various factors when applied in real-world scenarios. These factors include atmospheric conditions, obstacles, the presence and movement of other users, and radio frequency interference. The performance of the algorithm should be evaluated together with the impact of these factors in real scenarios. It is important to optimize the communication power of the UAV. Power management should be done by considering communication distance, target communication speed, fading levels and other factors. The algorithm should be optimized to ensure maximum communication performance with minimum power consumption of the UAV. The trajectory of the UAV can have an impact on the communication performance. In order to maximize the communication quality, the UAV needs to choose and follow the optimum trajectory. This allows the UAV to reach the targeted contact points in the best possible way. The algorithm should include appropriate metrics and control strategies for trajectory optimization.

Some limitations and assumptions must be taken into account in the practical applications of the algorithm. For example, limitations on UAV operations such as air traffic, airport management and regulations should be considered. In addition, assumptions such as real-time damping forecasts based on current weather data can affect the accuracy of the algorithm. Potential challenges include real-time fading prediction, dynamic air traffic management, multi-UAV coordination, use of error correction mechanisms during data transmission, and regulatory requirements. These factors are important challenges that must be addressed in order to be successful in practical applications of the algorithm.

 

5- It is essential to support your study with relevant literature that demonstrates how the fading models used in this study are applicable to THz frequencies. Additionally, please ensure that references are provided to support the information presented in Table 2.

[A]-5

Thank you very much for the detailed examination of the manuscript.

The values used in Table 2 are given by considering the references [5, 8, 12].

 

6- Provide more details about the analytical formulations for capacity, outage probability, and bit error rate (BER). How were these formulations derived, and how do they account for the specific performance-influencing factors considered in the study?   

[A]-6 Thank you for your comment. I appreciate the reviewer’s concern. I took pdfs of some formulas from the relevant references and adapted them to the proposed system. References are provided for the pdfs I have used from other works in the manuscript.

 

Author Response File: Author Response.docx

Reviewer 3 Report

I have the following comments:

1. The title Power and Trajectory Optimization of UAVs System .....  has to be justified. But the results did not discuss about those techniques. The Figure 3 seem to be trivial with reference to power optimization.

2. No details of Trajectory Optimization is found with respect to UAV

3. The paper is of study or survey paper as it discusses the available Nakagami-m, Rician, Weibull, log-normal fading and Rayleigh fading channels for THz channel.

4. The title can be renamed as "Study of Power and Trajectory Optimization of UAVs System in THz-2 Band Communications under Different Fading Channels"

5. The Authors need to mention the novelty in the abstract although the present contributions of this study is not valid.

 

Author Response

1- The title Power and Trajectory Optimization of UAVs System .....  has to be justified. But the results did not discuss about those techniques. The Figure 3 seem to be trivial with reference to power optimization.    

[A]-1

Thank you for your comments. I have revised the conclusion. I have changed Figure 3.

 

I proposed an optimization problem to find the best path between the UAV and the users while addressing each user's communication needs. To address this issue, I proposed an iterative technique that separates the original optimization problem into three subproblems to optimize three variables: UAV position, user power, and user bandwidth.

 

2- No details of Trajectory Optimization is found with respect to UAV.    

[A]-2

Thank you very much for your comment. Equation 7-11 includes trajectory optimization in Section 3.2.

 

3- The paper is of study or survey paper as it discusses the available Nakagami-m, Rician, Weibull, log-normal fading and Rayleigh fading channels for THz channel. The title can be renamed as "Study of Power and Trajectory Optimization of UAVs System in THz-2 Band Communications under Different Fading Channels"

[A]-3

Thank you very much for your comment. I appreciate the reviewer’s concerns. The title has been changed as Study of Power and Trajectory Optimization of UAVs System in THz Band Communications under Different Fading Channels.

 

4- The Authors need to mention the novelty in the abstract although the present contributions of this study is not valid.

[A]-4

Thank you very much for your comment. In the revised manuscript, abstract is updated based on your comments.

Nakagami-m, Rician, Weibull, and Rayleigh fading channels are all taken into consideration along with log-normal fading. Moreover, an optimization algorithm for the THz channel is presented, which is to minimize the transmission power by optimizing the trajectory of uplink and downlink transmissions between the UAV and users. The equations of the UAVs location and the transmission power optimization of each user are derived.

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I am satisfied with the latest revision.

Readable 

Reviewer 3 Report

The Authors have made significant changes

The manuscript may be accepted