Review of Indoor Positioning: Radio Wave Technology

SL

Comments

Author Response

1

Please check if all acronyms are explained in the text.

All acronyms are explained in the text.

2

What is the source of all Figures?

All figures in this manuscript are extracted idea from references without copying.

Figure 1 and 7 has been created by own idea, Figure 2,3,4,5, and 6 has been extracted idea from these references  [35,50, 51, 64] [107] [116] etc.,

Figure 9,10,11 and 12 are based on these references [50], [93], [160], [162], [167], [168], [170], [175] etc.

3

Table 4 and 5, the unit must be separated from value, e.g. 3 m

Thanks for point out this issue.

The specific modification is mentioned in Table 4 and Table 5.

4

line 784, what means: "with3.97 ?

The word “with 3.97” pointed out the mean localization error with tolerance 0.59 m by using un labelled data.  The specific modifications are mentioned on Line 878 and in Table 5.

SL

Comments

Author Response

1

The manuscript aims to provide a survey on positioning using signals from wireless networks. However, this is an extremely wide topic and thus it is very complicated to provide an overview of all the methods techniques and algorithms in a single paper.

The paper has intended to the comprehensive description regarding of indoor positioning behaviours and the useful algorithms.  Moreover, radio wave signals and non-radio wave signals are inclusively expressed.

2

Authors tried to review everything which makes this paper not going deeply into any topic. Thus authors do not highlight any open questions or topic that should be covered in future research, which should be the outcome of the review paper.

Thank you very much for your comments.

All topics in the manuscript are nearly approached to the validation of recent research papers.

3

POA (Phase of arrival) is usually used for the measurements of distance and not the direction of the signal as it is depicted in figure 1. Moreover, it is not clear what is the difference between AoA and DoA.

POA is used for the distance measurements. The specific modification is depicted in Figure 1.

DoA can be estimated by looking at the angle of arrival (AoA). The objective of the DoA-based radio positioning system is the estimation of the AoA, that’s to say the AoA associated to the LOS component.

The specific modification is mentioned on Line 353-355.

4

Moreover, a part of the information presented in the paper is not quite correct. For example Table 1, which should be considered as part of the contribution of the review paper, includes the following statements:  

"Disadvantage of RSS: Needs fingerprinting database"

I cannot agree with this statement as RSS can also be used for distance estimation and in such case no fingerprinting database is required.

In Table 1, some statements have been repaired and checked.

The word “Needs fingerprinting database" is required when RRS is used for mapping or science analysis methods.

5

Almost all other parameters in Table 1 include advantage "No need fingerprinting database". This statement is not false, however, all the techniques could be used with a fingerprinting database as well.

Thanks for point out this issue. The note points in Table 1 have been checked and repaired. The specific modification is mentioned in Table 1.

6

Some Parameters are not described in the text of the manuscript. It is not clear what is the difference between RTT and RTOF. (Both use roundtrip time measurements, don't they?)

The RTT technique, also known as RTOF, measures the round-trip. RTOF has been removed from Figure 1 due to the same RTT. The specific modification is mentioned on Line 278 to 279.

7

Statements that POA "Increase accuracy by changing frequency of the signal", DOA "Improve capacity, connectivity, spectrum", CSI "more strong to multipath noise" are kind of misleading. Since we are talking about parameters (or measurements) which represent input to a localization algorithm these cannot do anything with the signal, they cannot improve capacity or connectivity. There have been cases when the implementation of AoA based positioning reduced these parameters in WiFi systems.

Uncertain statements have been excluded from Table. The specific modification is mentioned in Table 1.

8

Some of the parameters in table 1 are not dissuaded in the text itself.

Some parameters in table 1 have been excluded by summarizing. The specific modification is consistently mentioned in Table 1 and the text.

9

Figure 7 does show communication technologies not "localization technologies". This name is incorrect since most of the technologies in the figure are not primarily developed for positioning purposes, which also leads to problems in the implementation of positioning systems based on these technologies.

Thanks for point out this issue. The word “indoor positioning systems” are used in Figure instead of “localization technologies". The specific modification is mentioned in Figure 7.

10

Same applies for Table 2, I find the title misleading.

The specific modification is mentioned in Table 2.

11

It is not clear what is the contribution of the paper, there should be some directions for future research provided in the conclusion section. These should be based on "unsolved problems" that were identified during the review.

Thank you very much for your comments. The specific modification is added in the conclusion section emphasis on guided comments.

SL

Comments

Author Response

1

The authors made a review of radio-wave-based indoor positioning systems, and organize the paper by firstly classifying the parameters that are used for positioning estimation, secondly listing different technologies, such as WIFI, BLE, UWB, etc., then enumerating the positioning algorithms, including fingerprint, machine learning solution, etc. The manuscript is well structured, and the review is comprehensive in its focus, would be a good reference for junior researchers interested in RF-based IPS. The references are also mostly the latest researches from the literature.

Thank you very much for your comments. We really appreciate your valuable time and the effort for this review. The manuscript has been revised based on your suggestions.

2

Just a suggestion, Table 2 lists the advantages and disadvantages of the radio technologies used for IPS. It would be good to give some hard numbers to strengthen the technologies' differences, especially power consumption, unit price. For example, the author stated that Zigbee and BT technology both enjoy the advantage of low power, but actually BLE, that normally used for IPS, consumes current only in tens of uA with a battery as a power source, and Zigbee, in contrast, consumes tens of mA current with a battery-powered source, which makes a huge difference when stating that both of them are "low power" solutions. So as the unit price. Some hard numbers will give potential readers a clear review.

Thank you very much for suggestion.

We have mentioned power consumption 0.367mW for BLE and 17.68mW for ZigBee according to the reference [107]. The specific modifications have been been mentioned in Table 2.

3

And some minor writing errors:

Line 65: two comma in the same place.

Line 351: "Radio signals based positioning" should be in a new line as the title of section three.

Line 818: Referred to a wrong figure, Figure 13, instead of Figure 12.

Line 820: The table reference should be in the right format (Roman numerals) as before.

Line 1076: 'DOA' should be 'POA': Phase of Arrival

Table 5: in the  . Some format errors are resulting in strange question marks. Please have a look.

The minor writing errors were checked and followed by guided comments.

For Line 65, the specific modification is mentioned on Line 65.

For Line 351, title "Radio signals based positioning" moved to next line. The specific modification is mentioned on Line 427.

For Line 818, figure number is changed. The specific modification is mentioned on Line 917.

For Line 820, the table reference is revised with right format. The specific modification is mentioned on Line 919.

For Line 1076, 'DOA' corrected 'POA'. The specific modification is mentioned on line 1164 and 1208.

Format errors in Table. 5 has been checked. The specific modification is mentioned in the performance column.

SL

Comments

Author Response

1

The paper extensively introduces measurement parameters (e.g. TDOA), measurement technologies (e.g. WiFi), and positioning algorithms (e.g. fingerprinting), specially related to Radio Frequency (RF) band signals. The contents are well organized and tabularized which allows readers to easily follow the paper. However, the paper can be improved by adding some suggestions or opinions of the authors on what parameters, technologies, and/or algorithms are advantageous in general IPS field in the Conclusion section.

Thank you very much for your comments. The specific modification is added in the conclusion section by the following emphasis on guided comments.

Recently, WiFi based positioning systems have been mostly used due to its low cost and implementation with existing infrastructure.

Moreover, super-resolution methods have been widely used for high resolution DOA or TDOA estimation.

Fingerprinting have been also developed using machine learning and deep learning to get high accuracy.

Therefore, we extensively introduce about it.

2

 In Introduction, it is suggested to add a table like Table, which compares performance of IPS among the seven segments in the electromagnetic spectrum. 

Thank you for your suggestion. The number of paper pages are now excessively due to some implementation in the manuscript. However, the significant pros and cons are expressed in the text instead of Table.

3

  - A paragraph starting from Line 75 (L75) can be detailed by adding pros and cons of magnetic field based IPS and INS based IPS, like done in the other paragraphs.

Magnetic field-based IPS and INS based IPS have been identified by adding pros and cons. The specific modification is complemented at starting from Line 98.

4

  - What is the definition of range-free approach in L173? Doesn't it still use distance as information to navigate like range-based approach? If not, how it obtains the target position.

Range-free method does not need angle or distance measurements among nodes, which also explains in subsection 4.6 and Table 3.

5

- Figure 7 is suggested to be redrawn by categorizing technologies with RF-based and non-RF-based technologies.

Thanks for indicating in Figure requirement.

Figure 7 has been redrawn by categorizing technologies with RF-based and non-RF-based technologies.

6

- Like written earlier, the authors' suggestions and/or opinions are suggested to be added in Conclusion.

Thank you very much for your comments.

The specific modification is mentioned in the conclusion

7

- The Nomenclature can be organized in alphabetical order. And, not all acronyms are identified. For example, POA and DPOA are missing.

The Nomenclature has been arranged in alphabetical order. All acronyms are mentioned details with abbreviation names.

8

  - Often some English expressions are felt to be redundant or indirect to convey messages clearly. For example, in Abstract, 'information collection within the offline' can be converted to 'offline information collection.'

The phrase 'information collection within the offline' converted to 'offline information collection’ in Abstract. The specific modification has now been revised in paragraphs.

9

  - Some typos are found. For example, in the paragraph starting from Line 65(L65), there are a redundant comma in the first phrase, a space is needed before 'Infrared', and 'which is' has to be corrected in L70. In L217, 'have proposed' into 'have been proposed.' In L513, 'were' into 'have been.' In 748, 'be' has to be added before 'perfect.'

Thanks for details point out.

The comma and space have been removed and added. The specific modification is mentioned on line 65.

The word 'which is' revised to the correct word. The specific modification is mentioned on line 70.

The tense “have proposed” revised “have been proposed”. The specific modification is mentioned on Line 277.

The tense 'were' revised ‘have been’. The specific modification is mentioned on Line 596-597.

The tense 'be' added before 'perfect.' The specific modification is mentioned on line 838.

10

- In L384, please add the reason why the fingerprinting localization algorithms are applied the most.

The specific modification is mentioned on Line 464-465.

11

  - Suggest to separate the paragraphs in L698 using the first sentence with "Generally, [...]."

Thank you very much for suggestion. The specific modification on Line 782.