Comments on abstract, title, references

The paper aims to give an introduction to cover the current technologies used for indoor positioning, before diving deep in UWB positioning. The abstract clearly mentions that though the title gave an idea that it will focus only on UWB. I think the title should be changed to be more inclusive to other indoor positioning systems,

Comments on introduction/background

The introduction clearly describes the work done in the paper. It starts by elaborating the need for indoor positioning. Then it continues to create a framework for quality assessments of IPSs and the challenges that need to be overcome. The paper jumps to reference harvesting for UWB positioning by using key words like "Localization" & UWB. This makes sense to the relevancy of the scope. The papers also points out previous papers by the authors that covers parts of the indoor positioning used in this paper. Background greatly focuses on different IPSs and the performance metrics, then it focuses on the technologies. They have described the terms in details and in organized tables. No more modifications are needed in this part.

Comments on methodology

The paper doesn't really have a contribution based on invention as much as completing a survey over the Indoor positioning systems with focus on UWB. The paper scans through many recent references from specific sources and clearly organize them in tables. The tables describes a relevant brief from each paper and make it easy for reviewers to go back to the references to check them. I find this paper a good start for any one who wants to work on UWB positioning. However, they clearly lacked the focus on the equations that are used ( section 4 and all its subsections), though this can be understood since they clearly referenced the sources. In any case, I think that the equations are irrelevant to the comparison and should be removed.

Comments on data and results

The outcome form each section and reference is clearly identified through the text and the tables provided. No more modifications are required in this section.

Comments on discussion and conclusions

The discussion sums up the papers reviewed in an organized way. However, some of the points mentioned need to be updated such as the problem of interference between GPS and UWB and the proposed solutions. This part needs to have more recent publications referenced as I think it is not an important issue as described. The conclusion part focus on the interference part more than the other parts, and hence the conclusion is not entirely balanced. The conclusion should also focus on accuracy, update rate and other key factors of UWB positioning specifically and other IPSs generally.