A Clutter Loss Model for Satellite Communication Systems

Round 1

Reviewer 1 Report

The paper presents very useful material in frequency management applications. Thus it is worth of publication. However, there are a few points that need clarifying to make the contents clearer:

- On Page 2, line 79, the authors say "The clutter loss statistics are finally gathered from a number of simulated scenarios (rays) sufficiently high 80 to guarantee statistical reliability."

It is not clear the usage of "scenarios" and "rays" as equivalent concepts. Please explain.

- On Page 8, Eq. 7, total diffraction loss after several edges is computed as the sum of individual diffractions. It is not clear how these diffraction values are computed more specifically how the "v" parameter is computed. I am assuming that each v value is computed by keeping the corresponding edge and disregarding the rest. However, this contradicts the various recommended approaches to multiple screen diffraction, for example in ITU-R Rec. P.526, such as Epstein and Peterson, Deygout, etc.

Please clarify.

- On Page 9, Eq. 9, the authors calculate the loss in the second path. It seems that the authors assumption is that that the second ray, initially, carries the power that is not lost in path 1. In the authors terms (1-l_B1). I do not agree with this (please convince me I am wrong). The only loss the second ray undergoes at B1 is l_R,B1.

- One more thing regarding the naming convention, variable names called "l" seem to indicate loss as a power ratio (not dB.) However, the way these "l" are employed, they are not "losses" they are "gains", that is l=1/g.

I think that this naming convention leads to misunderstandings, however, I would not object to the authors keeping on using this convention.

- It is clear that the overall clutter loss is the result of the power sum of two rays and that isotropic antennas are assumed. On Page 10, there is mention of other assumptions on possible antennas, namely fixed arrays and adaptive arrays which are more representative of 5G base stations. Please elaborate on the need or not to account for the atennas.

- On Page 12, Line 364, the text says: "The results achieved with a uniform random horizontal incidence angle between 0° and 60° are presented in Figure 11 and Figure 12 ..." Please explain the choice of angle range.

- On Page 14, Line 399, it says "In this context, a “receiver” is to be intended as an infinitesimal sphere in space that collects the information of all rays reaching 400 it: amplitude, ..." What is meant by "infinitesimal sphere", isn't the ray-tracing tool using a point to point approach (not small sphere)

Author Response

The reply to the reviewer is in the uploaded pdf file.

Author Response File: Author Response.pdf

Reviewer 2 Report

 This work presents a model to predict clutter loss during wireless communications system design.  The model is validated up to 10GHz.

Explain the near monotonic shape of the proposed model to the more discontinuous results of ray tracing in Figure 17. 

English needs improvement.

Author Response

The reply to the reviewer is also in the uploaded pdf file.

This work presents a model to predict clutter loss during wireless communications system design.  The model is validated up to 10GHz.

The authors would like to thank the reviewer for his/her review and his/her comment that helped improve the manuscript.

Explain the near monotonic shape of the proposed model to the more discontinuous results of ray tracing in Figure 17.

The ray tracing simulation does consider (due to high computation time) a limited area of the city, i.e. a limited number of buildings with their actual heights and distances: the derived statistics are expected to have a more limited stability if compared to the Montecarlo simulation, which considers a very high number of realizations (several rays, each of which will interact with a random building scenario) generated on the basis of the building height and distance statistics. The purpose of the comparison of the Montecarlo and ray tracing simulations is to confirm the same order of magnitude for the clutter loss, by using two very different approaches. This concept has been clarified in the manuscript just before Figure 17 with the following sentence:

“In fact, for the comparison, it must be taken into account that the ray-tracing simulation a limited area of the city, i.e. a limited number of buildings with their actual heights and distances: the derived statistics are expected to have a more limited stability if compared to the Montecarlo simulation, which considers a very high number of realizations (several rays, each of which will interact with a random building scenario) generated on the basis of the building height and distance statistics. Indeed, the purpose of the comparison between the Montecarlo simulation and the ray tracing calculations was to confirm the same order of magnitude for the clutter loss by using two very different approaches.”

English needs improvement.

As the authors are not English native speakers, they have submitted the paper to the editing services provided by MDPI to improve the English quality.

Author Response File: Author Response.pdf

Reviewer 3 Report

1.  A novel clutter loss model in urban and suburban environment for frequencies up to 10 GHz is proposed. The model relies on the Montecarlo simulation approach presented in the Report ITU-R P.2402-0, but some limitations have been removed to extend its applicability to more complex scenarios and possibly increase its accuracy for U6G systems.

2.  In the figure 11, clutter loss cumulative distributions: comparison between the proposed model and the ITU-R P.2402 one, for elevation angles of 15, 40 and 70 degrees in London (base station height uni-formly distributed between 4 and 6 m) should be demonstrated in detail.

3.  In the figure 12, clutter loss cumulative distributions: comparison between the proposed model and the ITU-R P.2402 one for elevation angles of 15, 40 and 70 degrees in Melbourne (base station height uniformly distributed between 4 and 6 m) should be demonstrated in detail.

4.     The manuscript cites 19 references; the number of the references should be increased.

5.     Revise the English thoroughly before submission.

Author Response

The reply to the reviewer is also in the uploaded pdf file.

1. A novel clutter loss model in urban and suburban environment for frequencies up to 10 GHz is proposed. The model relies on the Montecarlo simulation approach presented in the Report ITU-R P.2402-0, but some limitations have been removed to extend its applicability to more complex scenarios and possibly increase its accuracy for U6G systems.

The authors would like to thank the reviewer for his/her review and his/her comments that helped improve the manuscript.

2. In the figure 11, clutter loss cumulative distributions: comparison between the proposed model and the ITU-R P.2402 one, for elevation angles of 15, 40 and 70 degrees in London (base station height uniformly distributed between 4 and 6 m) should be demonstrated in detail.

The reviewer is right: The results in Figures from 11 to 14 were not sufficiently commented in the text. The following sentence has been added before Figure 11:

“Figures 11-14 show that the statistics from the proposed Monte Carlo simulation provide similar or larger clutter loss values if compared to the results obtained by the report ITU R P.2402 model, for elevation angles of +15° and +40°. The proposed Monte Carlo simulation yields lower values than the ITU-R approach in the low probability range, for the 70° elevation angle. These observations are even more evident for the antenna height of 18 m and for Melbourne, which is characterized by taller and more distant buildings (see Figures 2 and 3). The reason behind the differences in the results highlighted above is likely due to the fact that, in the proposed Monte Carlo simulation, more realistic reflections coefficients are used, as well as an unlimited number of wave reflections and diffractions. As expected, for negative elevation angles, the clutter loss values are much larger; however, concerning frequency interference studies, this result is compensated by the usual larger power radiated by the base station towards the users on the ground. As expected, the analytical model described in Section 5.2 is close to the simulations results especially in the low probability range which is the most important for interference studies.”.

3. In the figure 12, clutter loss cumulative distributions: comparison between the proposed model and the ITU-R P.2402 one for elevation angles of 15, 40 and 70 degrees in Melbourne (base station height uniformly distributed between 4 and 6 m) should be demonstrated in detail.

Please refer to the answer to the previous comment.

4. The manuscript cites 19 references; the number of the references should be increased.

The authors agree with the reviewer about the limited number of references. Unfortunately, a very limited number of papers is available in the literature on this topic, despite the fact that the authors have made a quite intensive search to collect different approaches and results to potentially improved their work. If the reviewer is aware of any publications on this topic that was not considered in the present work, the authors would be very happy to them into account.

5. Revise the English thoroughly before submission.

As the authors are not English native speakers, we have submitted the paper to the editing services provided by MDPI to improve the English quality.

Author Response File: Author Response.pdf

Reviewer 4 Report

This manuscript introduces a new model for the 10 GHz band that provides reliable predictions of noise loss primarily during the design of wireless communication systems. The model relies on the Montecarlo simulation method proposed in the ITU-R P.2402-0 report. Still, some limitations have been removed to extend its applicability to more complex scenarios and possibly improve its accuracy for U6G systems. In addition, this manuscript proposes an analytical method to simulate the spurious loss statistics obtained by properly fitting the statistics obtained for the cities of London and Melbourne. Finally, the proposed model is validated by comparing its results with commercial ray tracers' results. Indeed, I found the idea original and exciting. Thus, I can recommend this manuscript for publication in Electronics.

Author Response

The reply to the reviewer is also in the uploaded pdf file.

This manuscript introduces a new model for the 10 GHz band that provides reliable predictions of noise loss primarily during the design of wireless communication systems. The model relies on the Montecarlo simulation method proposed in the ITU-R P.2402-0 report. Still, some limitations have been removed to extend its applicability to more complex scenarios and possibly improve its accuracy for U6G systems. In addition, this manuscript proposes an analytical method to simulate the spurious loss statistics obtained by properly fitting the statistics obtained for the cities of London and Melbourne. Finally, the proposed model is validated by comparing its results with commercial ray tracers' results. Indeed, I found the idea original and exciting. Thus, I can recommend this manuscript for publication in Electronics.

The authors would like to thank the reviewer for his/her review and appreciation of the work.

Author Response File: Author Response.pdf