Power and Element Allocation Design for RIS–NOMA IoV Networks

Round 1

Reviewer 1 Report

Dear Authors, 

This paper presents a cooperative non-orthogonal multiple access (NOMA) based Internet of Vehicles (IoV) network that utilizes a reconfigurable intelligent surface (RIS) to enhance signal transmission. The proposed system is unique in that it uses a new power allocation scheme to address the varying channel conditions created by the intelligently controlled RIS. The paper investigates two power allocation schemes and derives the number of elements needed to guarantee the same transmission data sum-rate under different channel qualities. The results og simulation experiments are provided to verify the correctness and superiority of the proposed schemes.

The strengths of this paper are that it presents a novel approach to enhancing signal transmission in IoV networks, and it provides a detailed analysis of the proposed power allocation schemes. The proposed system is well-motivated and the results of the numerical and simulation experiments are clearly presented. However, there are also several areas that could be improved in the paper:

1- The inclusion of more simulations to further validate the proposed method, and the discussion on the comparison with other existing methods for the same problem.

2- More detailed explanations of the mathematical derivations used in the analysis of the power allocation schemes.

3- More advanced analytical models to support the proposed system. For example, the authors could incorporate more advanced mathematical models to describe the channel conditions and the signal transmission process. These models could provide a more in-depth understanding of the system behaviour and help to explain the results of the simulations better.

4- Incorporating more complex scenarios and network configurations in their analysis, such as multi-user and multi-cell systems.

5- Providing a mathematical analysis of the proposed power allocation schemes. This can include deriving closed-form expressions for the system performance metrics, such as the sum rate or bit-error rate, and providing a theoretical analysis of the system's behaviour under different channel conditions and network configurations.

6- Comparing the proposed system with other existing NOMA-RIS schemes and providing a comprehensive analysis of the advantages and disadvantages of the proposed system over the existing ones.

7- The paper only shows simulation results, it does not show any optimization algorithms or any analysis of feasibility, which is an essential aspect of the proposed system. The authors could consider adding a section on the optimization algorithm used to obtain the power allocation schemes and the complexity analysis of the algorithm. Furthermore, they could also provide a feasibility analysis of the proposed system, including the cost, energy consumption, and the required hardware and software resources.

Best regards

Author Response

Please refer to the attachment named "Response_1.26".

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper focuses on using a cooperative non-orthogonal multiple access (NOMA) network for the Internet of Vehicles (IoV), which is supported by a reconfigurable intelligent surface (RIS) to improve signal transmission. In order to address this problem and offer a better channel gain for transmitting signals, new power allocation schemes are presented. Due to the intelligent regulation of RIS, the channel condition of our proposed IoV system differs from that of standard NOMA and RIS schemes. Two power allocation techniques are examined in this study for various reflecting element counts as well as the element counts serving for near or far user, respectively.

Comments:

The motivation to use RIS can be clearly highlighted in the Introduction section. Also, the motivation to use RIS and NOMA needs to be clarified.

Literature review can be improved by citing recent work in this area. Works such as "Reliable Communications for Cybertwin driven 6G IoVs using Intelligent Reflecting Surfaces", can be cited to improve the work in this area. 

Trends in Figure 2 and Figure 4 needs to be clarified more clearly. The reason of increase and decrease in rate needs to be discussed. 

The discussion on results with respect to mobility in IoV needs to be highlighted. 

Future work can be added to highlight the improvements that can be done in this work.

Author Response

Please refer to the attachment named "Response_1.26".

Author Response File: Author Response.pdf

Reviewer 3 Report

In this paper, the authors proposed and analyzed the performance of a RIS-NOMA IoV network. However, the abstract and introduction sections are written very poorly, and many sentences are not grammatically correct and cannot be understood by readers.

1. For instance, the authors claim that their work considers the impact of 'rate variety', which was not studied in previous works [20-23]. What do the authors mean by this phrase, is it referring to variable data rates? What causes the variation?

2. Throughout the paper, the authors refer to the phrase 'elements number'. This is grammatically wrong and is not making sense. Are the authors referring to the number of antenna elements in the RIS?

3. The authors have proposed an IoV system, but have not commented on the impact of mobility of the vehicles. What is the speed of the vehicles in the simulation and performance evaluation? The authors need to provide more details regarding the impact of Doppler.

Author Response

Please refer to the attachment named "Response_1.26".

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

Thank you for your hard work on this paper. I have reviewed the responses to the three reviewers and am pleased to see that all comments have been addressed.

I look forward to the publication of this paper in the near future. Best regards.

Author Response

Please refer to the response letter.

Author Response File: Author Response.pdf

Reviewer 2 Report

Authors have addressed the comments of the last round and I suggest acceptance of the paper.

Author Response

Please refer to the response letter.

Author Response File: Author Response.pdf