Reconfigurable Intelligent Surface Physical Model in Channel Modeling
Round 1
Reviewer 1 Report
Reconfigurable Intelligent Surface Physical model in Channel
Modeling
General comment:
“The RIS physical model is proposed to facilitate channel modeling in system simulation. Based on impinging EM wave of the last bounce to RIS, the scattering field intensity of the target point is obtained by using geometric optics and electric filed surface integration method of physical optics.The feasibility of the model are verified by comparison between simulation and test results.
Other Comments:
-
The manuscript discusses the physical model in channel modeling and experimental evaluation has been done and results are presented.
-
The cited references consider some of the basic works that are very essential. However, there are many recent works on physical layer modeling other than the papers mentioned. It would be great if those were also included to have a better understanding of state-of-the-art techniques.
-
Many abbreviations, notations, and concepts are introduced directly in the middle. This makes the manuscript and the overall contributions challenging to understand. Example, PEC, GO, PO, etc:
-
It will be easier to understand the overall flow if there is a table for mathematical notations and schematic illustrations of the simulation.
-
The references to the source basic equations are not mentioned. Further, some of the equations require explanations before and after it is written.
-
The contributions should be mentioned more clearly and so the details of attaining the channel model proposed are missing.
-
The results should be discussed in detail to gain better clarity.
-
Overall, the manuscript should be structured again to have a better understanding.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The article proposed an implementation-independent RIS physical model with key electromagnetic characteristics to facilitate RIS-assisted wireless transmission channel modeling in system simulation. The RIS panel with radiation pattern element can solve the scattered field at the target point using the physical optics far-field integration method based on geometric optics and electromagnetic scattering theory. The main contribution of the article is considering the polarization effect in the modeling. The author verified the model with two specific simulation and experiment results.
There are some problems in the manuscript as follows:
1) The title can be more specific to highlight the main contribution of the article, as the content mainly focuses on the calculation of reflected field intensity and scattered field at the target field point;
2) The author should note that RISs are not limited to reflection surfaces but also include transmission types; the description of RISs in the Abstract and Introduction should be more rigorous.
3) Only two specific panels are used to verify the model, which is insufficient.
4) The reason for choosing the specific parameters, such as the base and receiving station locations, RIS azimuth angle, and incident wave vector polarization angle, should be explained. Also, one set of parameters is not enough to validate the model.
5) In section3, the simulation and experiment results should be explained more, especially the difference between simulation and measurement.
6) The simulation and experiment results should also be compared with the theoretical model and explain their connections.
7) The language should be improved. For example, in line 96, the acronyms "GO" and "PO" appear for the first time without explanation.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper studies the channel modeling problem of RIS-aided communication. To this end, the authors propose a hybrid method based on geometric and physical optics to determine the scattered field by the RIS. Finally, the theoretical model is evaluated against measured data. The theme under consideration has been extensively investigated in a stream of recent works [R1-R6]. As such, it is not clear what is the novelty of this paper compared to the existing literature. Moreover, it is poorly written as explained below.
1) The format of acronyms should be improved. For example, electromagnetic(EM) -> electromagnetic (EM).
2) Line 12: polarization of reflection EM wave -> polarization of the incident EM wave.
3) Line 13: crucial in RIS channel modeling -> crucial to RIS channel modeling
4) Line 17: electric filed -> electric field
5) Line 18: the model are verified -> the model is verified
6) Line 27: EM wave[1] -> EM wave [1]; please add a space before each reference.
7) Line 42: RIS is modelled as multiple virtual base stations; this sentence is not correct, the RIS is a planar structure of reflecting elements.
8) The title of section 2 has redundant words, i.e., RIS Panel Physical Model Abstraction Basis -> RIS Physical Model
9) Line: 94-95: center element of the infinite panel is used as the basis of the RIS element model -> for the sake of channel modeling, we consider an infinite RIS to characterise the response of an individual element.
10) Throughout the text, conduction PEC -> PEC
11) Comma or period is missing at the end of each equation
[R1] A. Diaz-Rubio, S. Kosulnikov and S. Tretyakov, "On the Integration of Reconfigurable Intelligent Surfaces in Real-World Environments: A Convenient Approach for Estimation Reflection and Transmission.," IEEE Antennas and Propagation Magazine, 2022.
[R2] V. Degli-Esposti, E. M. Vitucci, M. Di Renzo and S. Tretyakov, "Reradiation and Scattering from a Reconfigurable Intelligent Surface: A General Macroscopic Model," IEEE Transactions on Antennas and Propagation, 2022.
[R3] A. Díaz-Rubio and S. A. Tretyakov, "Macroscopic Modeling of Anomalously Reflecting Metasurfaces: Angular Response and Far-Field Scattering," IEEE Transactions on Antennas and Propagation, vol. 69, no. 10, pp. 6560-6571, Oct. 2021.
[R4] W. Tang et al., "Wireless Communications With Reconfigurable Intelligent Surface: Path Loss Modeling and Experimental Measurement," IEEE Transactions on Wireless Communications, vol. 20, no. 1, pp. 421-439, Jan. 2021.
[R5] M. Najafi, V. Jamali, R. Schober and H. V. Poor, "Physics-Based Modeling and Scalable Optimization of Large Intelligent Reflecting Surfaces," IEEE Transactions on Communications, vol. 69, no. 4, pp. 2673-2691, Apr. 2021.
[R6] K. Dovelos, S. D. Assimonis, H. Quoc Ngo, B. Bellalta and M. Matthaiou, "Intelligent Reflecting Surfaces at Terahertz Bands: Channel Modeling and Analysis," 2021 IEEE International Conference on Communications Workshops (ICC Workshops), 2021.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Authors
Please rewrite the conclusion results section (Section 4) aligning your abstract and contributions (and tone the information in the current version) ...ideally this will be your conclusion and please add future work along with the conclusion.
Thanks and Regards
Reviewer1
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The revised version has improved a lot.
As the novelty of the paper is proposing the channel model, adequate simulation and experiment are necessary to prove the model. The author should provide more comparisons or explanations for this.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The presentation of the revised paper has been significantly improved. Prior to acceptance, though, the authors should clarify how their channel modelling approach differs from those developed by S. A. Tretyakov and others [R1]. This would be in terms of model complexity and accuracy. Why similar modelling approaches are not included/discussed in the simulation results?
[R1] A. Díaz-Rubio, S. Kosulnikov and S. A. Tretyakov, "On the Integration of Reconfigurable Intelligent Surfaces in Real-World Environments: A Convenient Approach for Estimation Reflection and Transmission," IEEE Antennas and Propagation Magazine, vol. 64, no. 4, pp. 85-95, Aug. 2022.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 3 Report
After two revision rounds, the manuscript still contains minor text errors. For example, the reference in line 168 is missing: "In the first polarization direction []".
More importantly, the proposed modeling approach is not adequately described. Does the total field computed by geometric optics correspond to the tangential component on the IRS element? To my knowledge, the total tangential field component is needed to apply physical optics, which is usually determined assuming a PEC. Please mention that point in the paper.
Last but not least, the discussion on the difference between this work and the state-of-the-art is not added to the revised manuscript. You could consider your response to report 2.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
