A Simplistic Downlink Channel Estimation Method for NB-IoT

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please see the attached file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

NA

Author Response

Dear respected Reviewer,

Thank you very much for your work and for pointing out the aspects of the paper that require improvement. Please find below the list of modifications that were introduced in the revised version to address your comments.

Comment 1. The paper's structure needs refinement. The introduction should provide a more detailed background of the problem and its significance in the context of NB-IoT. Additionally, the literature review is somewhat limited; including more recent and relevant references could strengthen the paper's foundations.

• The content of Section I was organized into the following subsections: 1.1 Channel estimation in NB-IoT downlink, 1.2 Related work, 1.3 Contributions, and 1.4 Organization of the paper.
• Subsection 1.3 was expanded to emphasize the paper’s actual contribution.
• The list of cited references was significantly extended. More recent and relevant references have been added.

 

Comment 2. The paper presents an interesting approach to channel estimation. However, the methodology and experiments require further elaboration. It would be beneficial to include a more detailed description of the simulation setup, parameter settings, and a discussion of potential limitations and sources of error.

• The photograph of the measurement test bed has been added (Figure 5).
• The newly added subsection 5.4 can serve as a reference for comparing the methods described in the literature mentioned. Also, this subsection mentions possible sources of measurement error that are relevant to hardware test scenarios.

Comment 3. The results are presented in a somewhat superficial manner. More in-depth analysis and discussions of the findings are needed. Explain the implications of the results, and consider comparing them to other existing methods for a better understanding of the proposed approach's performance.

• Subsection 5.4 “Comparison with other channel estimation methods”, has been added to extend the scope of the presented results.
• A second paragraph has been added in section 6, which highlights the impact of the described work on NB-IoT development and suggests possible directions for further research.
• The comparison of the obtained results with other existing studies is somewhat limited due to the reasons mentioned in the paper. All previous studies were based on simulations, whereas the tests described in this paper involve capturing and analyzing live signals. Due to this limitation, it is generally not possible to assess metrics like Bit Error Rate since the original bit stream is typically unavailable. Similarly, it is not possible to accurately evaluate the mean squared error (MSE) because the original values of the channel coefficients are unknown. This is why alternative indicators were introduced for quality assessment. However, a rough estimation of MSE, based solely on information obtained from the received signal, is provided in Subsection 5.4.

Comment 4. The paper contains several grammatical and language issues that need correction. Consider proofreading and editing to improve the overall readability and professionalism of the paper. Including a section on future work would be beneficial

• The entire paper was thoroughly proofread by a professional English lecturer.

I hope that you will find the introduced improvements satisfactory.

Thank you once again.

Sincerely,
Jarosław Magiera

Reviewer 2 Report

Comments and Suggestions for Authors

This study investigates a downlink channel estimation method for NB-IoT links. Author presented a three stage linear interpolation based calculation method.

 

1- Introduction should be extended and contributions should be listed explicitly. 
            I. Introduction, I.A. Related Work, I.B. Contributions and I.C. Organization of the paper.

2- Please move Figure 1 to a new chapter to give some preliminary information or remove.

3- Comparison with existing studies for results need to be for Figures 6,7,8,9,10.

4- Actual picture of the measurement system should be added for Section 4.

 

Comments on the Quality of English Language

It needs to undergo Grammar check.

Author Response

Dear respected Reviewer,

Thank you very much for your work and for pointing out the aspects of the paper that require improvement. Please find below the list of modifications that were introduced in the revised version to address your comments.

1- Introduction should be extended and contributions should be listed explicitly. 
            I. Introduction, I.A. Related Work, I.B. Contributions and I.C. Organization of the paper.

• The content of Section I was organized into the following subsections: 1.1 Channel estimation in NB-IoT downlink, 1.2 Related work, 1.3 Contributions, and 1.4 Organization of the paper.
• Subsection 1.3 was extended to emphasize the paper’s actual contribution.

2- Please move Figure 1 to a new chapter to give some preliminary information or remove.

• Figure 1 was placed inside subsection 1.1, and the role of NRS in the channel estimation procedure was further explained

3- Comparison with existing studies for results need to be for Figures 6,7,8,9,10.

• Subsection 5.4 “Comparison with other channel estimation methods”, was added to extend the scope of the presented results. This subsection can serve as a reference for comparing the methods described in the literature mentioned. Also, this subsection mentions possible sources of measurement error that are relevant to hardware test scenarios.
• The comparison of the obtained results with other existing studies is somewhat limited due to the reasons mentioned in the paper. All previous studies were based on simulations, whereas the tests described in this paper involve capturing and analyzing live signals. Due to this limitation, it is generally not possible to assess metrics like Bit Error Rate since the original bit stream is typically unavailable. Similarly, it is not possible to accurately evaluate the mean squared error (MSE) because the original values of the channel coefficients are unknown. This is why alternative indicators were introduced for quality assessment. However, a rough estimation of MSE, based solely on information obtained from the received signal, is provided in Subsection 5.4.

4- Actual picture of the measurement system should be added for Section 4.

• The photograph of the measurement test bed has been added (Figure 5).

The paper needs to undergo Grammar check

• The entire paper was thoroughly proofread by a professional English lecturer.

I hope that you will find the introduced improvements satisfactory.

Thank you once again.

Sincerely,
Jarosław Magiera

Reviewer 3 Report

Comments and Suggestions for Authors

In this work, the authors propose a downlink channel estimation method for narrowband internet-of-things (NB-IoT) links, consisting of three steps. The authors provide an overview of the proposed method, explaining the involved steps and elaborating on the evaluation methodology.  Additionally, they present the approach for capturing and processing the waveforms, as well as the utilized hardware equipment. Finally, they evaluate the proposed method and compare it against a baseline one that is implemented in the Matlab LTE Toolbox.

The overall organization and structure of the paper are considered good. Furthermore, the proposed estimation method and approach for processing the waveforms are described in detail. In addition, the evaluation results indicate that the proposed method performs better compared to the baseline method. Nevertheless, the paper is focused on a widely investigated topic, while the proposed method is only compared against one specific Matlab implementation. In this respect, the references of this work are a bit dated. Finally, there are some additional recommendations to be considered as follows:
1) Adding a paragraph that highlights the contributions of this work will be beneficial for the readers.
2) The state-of-art paragraph should be expanded by including more recent research works.
3) Adding a flowchart or algorithm that summarizes the main steps of the proposed method would assist the readers.
4) Including a complexity analysis, in addition to the estimation duration, would increase the contributions of this work.
5) A paragraph discussing future extensions of this work can be added in the conclusion.

Author Response

Dear respected Reviewer,

Thank you very much for your work and for pointing out the aspects of the paper that require improvement. Please find below the list of modifications that were introduced in the revised version to address your comments.

 

1) Adding a paragraph that highlights the contributions of this work will be beneficial for the readers.

• The content of Section I was organized into the following subsections: 1.1 Channel estimation in NB-IoT downlink, 1.2 Related work, 1.3 Contributions, and 1.4 Organization of the paper.
• Subsection 1.3 was expanded to emphasize the paper’s actual contribution.

2) The state-of-art paragraph should be expanded by including more recent research works.

• The list of cited references was significantly extended. More recent and relevant references have been added.

3) Adding a flowchart or algorithm that summarizes the main steps of the proposed method would assist the readers.

• The proposed method is described step-by-step in Section 2.
• The photograph of the measurement test bed was added (Figure 5).

4) Including a complexity analysis, in addition to the estimation duration, would increase the contributions of this work.

• Regarding the comment on the analysis of the computational complexity, there is no framework which could be used to accurately determine the number of operations required for channel estimation using the described methods. This is why a simplified approach, based on comparing the processing time on the same hardware platform, was applied.

5) A paragraph discussing future extensions of this work can be added in the conclusion.

• A second paragraph has been added in Section 6, which highlights the impact of described work on the NB-IoT development and points the possible directions for continuation of this research.

I hope that you will find the introduced improvements satisfactory.

Thank you once again.

Sincerely,
Jarosław Magiera

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Authors responded all the comments raised by reviewer. I have no further comments.

Comments on the Quality of English Language

Proofreading is needed.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have thoroughly addressed my comments. I support the publication of this work.