An Ultra-Wideband Indoor Localization Algorithm with Improved Cubature Kalman Filtering Based on Sigmoid Function

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

 

Thank you for your manuscript. It focuses on enhancing the precision and reducing the deviation of ultra-wideband (UWB) indoor positioning systems in non-line-of-sight environments through an improved cubature Kalman filter (CKF) utilizing the Sigmoid function. The proposed method addresses the inaccuracies caused by non-Gaussian noise and state estimation performance degradation, demonstrating significant improvements in positioning accuracy—up to 39.29% better than the standard squared range difference model. This paper, aimed at addressing the challenges in UWB indoor localization, contributes to the field by offering a more stable, accurate, and robust algorithm for dynamic positioning in complex environments. However, the paper cannot be published in the present form. In the following, some remarks are proposed that should be addressed to improve the quality of the paper. Therefore, a major revision is required before the paper can be accepted for publication.

 

Abstract

 

Ensure the abstract clearly states the problem being addressed, the main contribution of the study, and the results. It should be concise yet informative enough to give a reader a complete overview of the research without needing to read the full paper.

 

Highlight the objective of the research more distinctly and briefly describe the methodology used, particularly the introduction of the Sigmoid function in the improved cubature Kalman filter (CKF) for UWB indoor localization. This will help readers understand the novelty of the approach.

 

Provide a quantitative summary of the results to emphasize the improvement in positioning accuracy. Mentioning the specific percentage improvement helps, but clarifying the conditions or scenarios where these improvements were observed would add value.

 

1. Introduction

 

Provide a clearer, more comprehensive background on UWB indoor localization challenges, particularly in non-line-of-sight conditions. This sets the stage for why the study's focus is important.

 

Expand the literature review to include a broader range of existing solutions and their limitations. 

More explicitly state the research gap the study aims to fill. 

 

Make the research objectives more explicit and directly linked to the identified research gap. This can include specific mention of how the Sigmoid function is expected to improve CKF for UWB localization.

 

Offer a brief preview of the methodology used in the study to address the research objectives. 

Highlight the anticipated contribution and its significance to the field of indoor localization.

 

2. SRD Model Based on TDOA Algorithm

 

Provide more detailed explanations or examples of how the TDOA algorithm is implemented and utilized within the context of UWB indoor localization. 

 

Include a comparison between the SRD model based on the TDOA algorithm and other existing models. Highlight the benefits and limitations to provide a clearer rationale for the choice of this model.

 

Elaborate on the methodological choices made in developing the SRD model. Discuss any assumptions, limitations, and the rationale behind specific decisions.

 

Discuss how the SRD model impacts the accuracy and reliability of UWB indoor localization. Provide data or references to studies that support the claims made.

 

3. Improved CKF Localization Algorithm Based on Volume Criterion

 

Enhance the explanation of the volume criterion and its integration into the CKF algorithm. 

 

Include a comparative analysis of the improved CKF algorithm against standard CKF approaches. Highlighting specific scenarios where improvements are noted can illustrate the algorithm's efficacy.

 

Please include more comprehensive experimental results or case studies demonstrating the algorithm's performance in real-world conditions.

 

Discuss any limitations or challenges encountered with the improved CKF algorithm. 

 

Elaborate on the practical implications of using the improved algorithm in UWB indoor localization. Discuss how it can be implemented in existing systems.

 

4. Experimental Validation and Analysis

 

Integrate a broader range of environmental conditions and obstacles in the experimental setup to test the algorithm's adaptability.

 

Implement cross-validation techniques to ensure the robustness and reliability of the results.

 

Include a comparative performance analysis with the latest algorithms in UWB localization to establish the proposed method's competitive advantage.

 

Detail the statistical significance of the results to underscore the improvements and validate the findings.

 

5. Conclusions

 

Highlight the primary achievements of the research more clearly, summarizing the key contributions and findings in a concise manner.

 

Emphasize the practical implications of the research findings for the field of UWB indoor localization, providing a clear link between the study's results and their potential applications.

 

Include future research directions more explicitly, outlining potential areas for further investigation or development based on the current study's limitations and findings.

 

Highlight the novelty and value of the improved CKF algorithm with the Sigmoid function, making sure the reader grasps the significance of this contribution to the existing body of knowledge.

 

General comments

 

Provide a deeper analysis and interpretation of the results, discussing the implications and how they contribute to the field.

 

Strengthen the conclusion by clearly summarizing the findings, their significance, and potential future research directions.

 

Conduct a thorough language and grammar check to enhance readability.

 

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Conduct a thorough language and grammar check to enhance readability.

Author Response

请参阅附件。

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have written an article of 12 pages, plus one consisting of references, concerning the problems of degradation of positioning accuracy and large deviation of ultra-wideband when localizing a dynamic target.

 

The authors address unsatisfactory positioning accuracy under non-line-of-sight conditions and propose an improved adaptive algorithm combining the Sigmoid function and the singular value decomposition method.

 

By experimental means, they verify the superior stability and position accuracy of the cubature Kalman filtering algorithm. According to the results, it is able to reduce points dispersing away from the real trajectory during the ranging process of UWB dynamic positioning and it improves the outliers in the non-visual range environment during the ranging process.

 

I consider the chosen methods of evaluating precision in "Chapter 3.3. Precision Evaluation Methods" to be appropriate.

 

The authors outline the future aims of the work, planning to use the method for a multi-sensor fusion.

A few minor adjustments:

• The citation on line 45 would be better just after the text on the same page.

• Place the "3.1. Decomposition of Estimated Covariance Array by SVD Method" on the following page.

• Figure 3 and its descriptions are quite confined, I recommend making more space around it.
• The Fig 8. descryptions are quite small. It would also be fitting to thicken the border of the small chart found within the bigger chart.

 

Comments on the Quality of English Language

The English of the article is understandable, and its proficiency is fitting. Nonetheless, I would like to propose a few adjustments:

• Check for missing articles

• for example 

• (327) When using the UWB positioning...
• (329) Based on the SRD model of the TDOE algorithm...
• (335) ...checkpoints for UWB positioning in a non-line-of-sight environment
• Remove the word "and" at the beginning of your sentences. Either replace it with "also" or "as well", or omit it entirely.
• (30/31) And they are different that traditional positioning techniques... → They are (also/as well) different from/than traditional positioning techniques...
• (336) And this paper also compares... → This paper also compares...
• Consider replacing "ultra wide band" with "ultra-wideband".
• (46) However, the Kalman filter algorithm is used the premise that the model is a linear Gaussian mode → ...is used with the premise.../ ...algorithm uses the premise...

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents an interesting experimental study on the application of cubature Kalman filtering (CKF) to enhance the accuracy of ultra-wideband (UWB) indoor positioning in non-line-of-sight environments. It proposes the utilization of the Sigmoid function to update the measurement noise matrix over time, thereby enhancing estimation accuracy under non-Gaussian noise conditions. Furthermore, the combination of CKF and the squared range difference (SRD) model of the time difference of arrival (TDOA) algorithm employs singular value decomposition (SVD) decomposition to solve the problem that the estimated covariance matrix cannot meet the positive qualitative requirements in real-time.

 

The paper can be recommended for publication after the following minor corrections:

Conducting a comprehensive literature review to address previous studies that discussed the proposed method.

Introducing a separate section to highlight the study's original contributions.

Implementing a larger font size for figures' labels and legends, ensuring uniformity across all figures.

Proofreading the paper for minor language errors.

Comments on the Quality of English Language

Proofreading the paper for minor language errors is recommended.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The article presents an important and current topic regarding indoor location systems. My comments about the article:

• Chapter no. 1: The chapter is too short, the literature analysis is very limited, and the number of analyzed publications could be more extensive. Additionally, it is difficult to understand how the mentioned publications are connected with the purpose of the work, as there is no description here.

• Chapters no. 2 and 3: The mathematical relationships presented are consistent, but there are some errors. In Figure 1, "location label" appears and the text refers to "target M". Additionally, there is mention of the xyz coordinate system, which is not marked in the figure. Large Hk or Fk matrices (lines 121, 126) should be in a separate paragraph. The chapters are approximately 5 pages long, while the entire work, excluding the bibliography, is 12 pages long. This is too much, I would recommend shortening the redundant descriptions (e.g. subsections 3.1.1 and 3.1.2).

• Chapter 4: The description of the experiment needs to be more extensive because key information is missing. In Figure 3 - the xyz coordinate system that appears in the text is missing. How was the real transmitter movement path determined (ground truth)? In Figure 4 - please mark the location of the receivers. Various units of distance measurement are used throughout the work, cm, dm, etc. Please choose one measure, preferably meters, and use it uniformly throughout the work. Most of the drawings have poor resolution and small font size, some values are difficult to read.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 5 Report

Comments and Suggestions for Authors

The paper is properly formatted and written. It is clear what the contribution is. The work produced is quite reliable. I have the following suggestions for the authors to take into account when the work is revised:

- A summary table of prior research is required, together with an analysis of its limitations and the authors' respective contributions to this earlier work.

- In order to help the authors improve the localization algorithm that was described, it is required to add feedback regarding the shortcomings of the work presented in this research.

- Is the proposed localization algorithm for the indoor instance still applicable for the outside situation?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 6 Report

Comments and Suggestions for Authors

1. The article does not provide analysis parameters.

2. How should the presented room dimensions and the modeling results presented in Figs. 4 to 9 be understood?

3. What is the UWB range being analyzed?

4. The authors do not declare what the status of the submission is

Work done using software, line 230. How do the mathematical dependencies presented in the submission relate to this software? See point 1.

5. Lack of emphasis on the authors' contribution - mechanical data entry into the program.

6. Nothing follows from the conclusions

Comments on the Quality of English Language

1. The article does not provide analysis parameters.

2. How should the presented room dimensions and the modeling results presented in Figs. 4 to 9 be understood?

3. What is the UWB range being analyzed?

4. The authors do not declare what the status of the submission is

Work done using software, line 230. How do the mathematical dependencies presented in the submission relate to this software? See point 1.

5. Lack of emphasis on the authors' contribution - mechanical data entry into the program.

6. Nothing follows from the conclusions

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The suggestions have been addressed

Author Response

Dear reviewer,

 

Thank you very much for handling my manuscript again. We really appreciate you for your carefulness and conscientiousness. We will work harder in the future, to improve our scientific research ability and writing ability.

 

Sincerely,

Yunzhu Lv, Songlin Liu *, Yipin Gao, Jun Dai, Zongbin Ren, Yang Liu

Reviewer 4 Report

Comments and Suggestions for Authors

The authors responded to all comments included in the comments. The issue of different units (dm, cm) remains, although the authors suggest that the results may be unreadable when using one unit in all document (meter). Given the significant improvement of the listed problems and the increase in the work's quality, I think the article can be accepted in its current form.

Author Response

Dear reviewer,

 

Thank you very much for handling my manuscript again. We really appreciate you for your carefulness and conscientiousness. We will work harder in the future, to improve our scientific research ability and writing ability.

 

Sincerely,

 

Yunzhu Lv, Songlin Liu *, Yipin Gao, Jun Dai, Zongbin Ren, Yang Liu

Reviewer 6 Report

Comments and Suggestions for Authors

The authors responded very sparingly to my objections.

When specifying the UWB frequency band, they give me its values, so it is not visible in the drawings.

There is no coordinate system and therefore no location of the transmitter and, accordingly, the receivers, see relation 1.

We are dealing with a rectangular room, and the calculations and measurements are for a square. The provided dependencies are well known in the literature, even in this one.

Comments on the Quality of English Language

The authors responded very sparingly to my objections.

When specifying the UWB frequency band, they give me its values, so it is not visible in the drawings.

There is no coordinate system and therefore no location of the transmitter and, accordingly, the receivers, see relation 1.

We are dealing with a rectangular room, and the calculations and measurements are for a square. The provided dependencies are well known in the literature, even in this one.

Author Response

Please see the attachment.

Author Response File: Author Response.docx