Enhancing OLSR Protocol by an Advanced Greedy Forwarding Mechanism for VANET in Smart Cities

Round 1

Reviewer 1 Report

This paper has been improved since last submission. However, the overall contribution is still limited. The presentation of this paper need to be improved. The authors use a lot of bullets and the equations do not appear in the correct form. 

Author Response

Dear Reviewer,

Thank you very much for your constructive comments concerning our manuscript. The comments are valuable and helpful for revising and improving the quality of our paper, and all our researches. We have studied the comments carefully and have made corrections which we hope meet with approval. The letter which provides a point-by-point response to the comments is in the attachment.

Once again, thank you very much for your comments and suggestions.

Best regards,

MyDriss Laanaoui et al.

Answers

1. Is the content succinctly described and contextualized with respect to previous and present theoretical background and empirical research (if applicable) on the topic?

I revised the content succinctly more described and contextualized with respect to previous and present theoretical background and empirical research on the topic. In the abstract. [Lines: 16 to 24] and 1. Introduction: [lines: 51 to 71]

2. Are all the cited references relevant to the research?

Thanks a lot for the reviewer’s positive comment.

3. Are the research design, questions, hypotheses and methods clearly stated?

The research design, problem, methodology and solutions are briefly summarized in 1. Introduction [Lines 51 to 71] and 4. Proposed work [Lines 206 to 223]. Also, we added a schema to illustrate the two parts of our approach

4. Are the arguments and discussion of findings coherent, balanced and compelling

I revised the arguments and discussion of findings to be more coherent, balanced, compelling, and clear. 5. Discussion [Lines 465 to 532] and figure 3 [line 221].

5. For empirical research, are the results clearly presented?

Thank you very much for your advice. We have improved the presentation of the result of our empirical research in our revised manuscript in 4. Proposed work [Lines 206 to 223] also in Discussion [Lines 465 to 532].

6. Is the article adequately referenced?

Thanks a lot for the reviewer’s positive comment.

7. Are the conclusions thoroughly supported by the results presented in the article or referenced in secondary literature?

Thanks a lot for the reviewer’s positive comment.

8. This paper has been improved since last submission. However, the overall contribution is still limited. The presentation of this paper need to be improved. The authors use a lot of bullets and the equations do not appear in the correct form.

Thank you very much for your advice. We have improved our paper to clarify our proposition. So, we illustrate with Figure 3 [line 221], and we comment to explain the features of our proposition in 4. Proposed work [Lines 206 to 223]. In addition, we use the bullets just to summarize information, and if the order is not important. We changed the bullet to number in the algorithm because the order is important in 4.1 Optimization of OLSR for VANET communication [Lines 258 to 265] and in 1. Introduction [Lines 45 to 49] transformed to text. Bullets in Line 287 changed to table including simulation parameters. As for the equations, the text following equations in my paper became a paragraph in 4.1 Optimization of OLSR for VANET communication [Lines 251 and 252], 4.3 Injection of the GFA mechanism into the OLSR protocol [Lines 362 to 367].

Author Response File: Author Response.docx

Reviewer 2 Report

First of all, I really like the research topic and the paper’s approach. But the research work has serious weaknesses.

The main problem, and very critical, is the section of the scientific literature review and the conclusion that OLSR is the best protocol. I strongly disagree with this conclusion, and many reviews of the scientific literature achieve the same conclusion. I cite a few: 

Al-Sultan, S., Al-Doori, M. M., Al-Bayatti, A. H., & Zedan, H. (2014). A comprehensive survey on vehicular Ad Hoc network. Journal of Network and Computer Applications, 37(1), 380–392. https://doi.org/10.1016/j.jnca.2013.02.036

Sharef, B. T., Alsaqour, R. A., & Ismail, M. (2014). Vehicular communication ad hoc routing protocols: A survey. Journal of Network and Computer Applications, 40(1), 363–396. https://doi.org/10.1016/j.jnca.2013.09.008

Tripp-Barba, C., Zaldívar-Colado, A., Urquiza-Aguiar, L., & Aguilar-Calderón, J. A. (2019). Survey on routing protocols for vehicular ad Hoc networks based on multimetrics. Electronics (Switzerland), 8(10), 1–32. https://doi.org/10.3390/electronics8101177

Abu Taleb, A. (2018). VANET routing protocols and architectures: An overview. Journal of Computer Science, 14(3), 423–434. https://doi.org/10.3844/jcssp.2018.423.434

After this selection of the OLSR protocol, the rest of the paper is of no scientific interest. 

Author Response

Dear Reviewer,

Thank you very much for your constructive comments concerning our manuscript. The comments are valuable and helpful for revising and improving the quality of our paper, and also to situate and defend our researches. We have studied the comments carefully and have made corrections which we hope meet with approval. The letter which provides a point-by-point response to the comments is in the attachment.

Once again, thank you very much for your comments and suggestions.

Best regards,

MyDriss Laanaoui et al.

 

Response to Reviewer Comments

1. Is the content succinctly described and contextualized with respect to previous and present theoretical background and empirical research (if applicable) on the topic?

Thanks very much for your advice, I revised the content succinctly more described and contextualized with respect to previous and present theoretical background and empirical research on the topic. In the abstract. [Lines: 16 to 24] and 1. Introduction: [lines: 51 to 71]

2. Are all the cited references relevant to the research?

Thanks very much for your advice, we have improved and added other references relevant to research.

3. Are the research design, questions, hypotheses and methods clearly stated?

Thanks very much for your advice and information. The research design, problem, methodology and solutions are briefly summarized in 1. Introduction [Lines 51 to 71] and 4. Proposed work [Lines 206 to 223]. Also we added a schema to illustrate the two parts of our approach.

4. Are the arguments and discussion of findings coherent, balanced and compelling?

I revised the arguments and discussion of findings to be more coherent, balanced, compelling, and clear. 5. Discussion [Lines 465 to 532] and figure 3 [line 221].

5. For empirical research, are the results clearly presented?

Thank you very much for your advice. We have improved the presentation of the result of our empirical research in our revised manuscript in 4. Proposed work [Lines 206 to 223] also in Discussion [Lines 465 to 532].

6. Is the article adequately referenced?

Thank you very much for your advice. We have improved the references in our revised manuscript so that our paper is adequately referenced.

7. Are the conclusions thoroughly supported by the results presented in the article or referenced in secondary literature?

Thank you very much for your advice. We have improved the conclusions in our revised manuscript.

 

 

 

For the articles:

 

 

“Al-Sultan, S., Al-Doori, M. M., Al-Bayatti, A. H., & Zedan, H. (2014). A comprehensive survey on vehicular Ad Hoc network. Journal of Network and Computer Applications, 37(1), 380–392. https://doi.org/10.1016/j.jnca.2013.02.036”

The authors doesn’t inform that OLSR is not suitable for VANET, but there is some challenges and problems to overcame in order to adapt the protocol to VANET environment. The criteria were respect in my proposition. I simulate G-OLSR in terms of Packet delivery ratio and End to end delay to save the information efficiency because of the topology change. In addition, the integration of Greedy Forwarding Advanced will enhance the behaviours of G-OLSR because we consider the position. (The article is published in 2014)

 

“Sharef, B. T., Alsaqour, R. A., & Ismail, M. (2014). Vehicular communication ad hoc routing protocols: A survey. Journal of Network and Computer Applications, 40(1), 363–396. https://doi.org/10.1016/j.jnca.2013.09.008”

The author confirms (in page 9) that OLSR consists of well-known unicast routing protocols for MANETs, ​​which have been successfully adapted to VANETs. The problem for OLSR is just the cost for maintaining routes. In our proposition, the use of GFA overcame this problem.

 

Tripp-Barba, C., Zaldívar-Colado, A., Urquiza-Aguiar, L., & Aguilar-Calderón, J. A. (2019). Survey on routing protocols for vehicular ad Hoc networks based on multimetrics. Electronics (Switzerland), 8(10), 1–32. https://doi.org/10.3390/electronics8101177

In this paper, the authors announce the main characteristics for a protocol adapted to VANET. and among these characteristics, there are PDR and EED, and these are the metrics that we considered for the verification of our proposal. In several protocols cited in this article, we find the use of the Dijikstra algorithm, which is also the core of our G-OLSR proposal. In addition, the authors don’t announce that OLSR can’t be enhanced to be suitable for VANET.

 

 

Abu Taleb, A. (2018). VANET routing protocols and architectures: An overview. Journal of Computer Science, 14(3), 423–434. https://doi.org/10.3844/jcssp.2018.423.434

In article : « SALLUM, Eduardo El Akkari, DOS SANTOS, Guilherme, ALVES, Mario, et al. Performance analysis and comparison of the DSDV, AODV and OLSR routing protocols under VANETs. In : 2018 16th international conference on intelligent transportation systems telecommunications (ITST). IEEE, 2018. p. 1-7 ». 

The authors summurize ; in “Table 1: PREVIOUS RESULTS ON THE PERFORMANCE ANALYSIS OF THE AODV, OLSR AND DSDV ROUTING PROTOCOLS“ page 1; the results givens in a several research using different simulators. OLSR presents the best results in terms of PDR and EED.

 

In article : «AMINA, Bengag et MOHAMED, Elboukhari. Performance evaluation of VANETs routing protocols using SUMO and NS3. In : 2018 IEEE 5th International Congress on Information Science and Technology (CiSt). IEEE, 2018. p. 525-530».

In the literature review (page 1), the authors announce that OLSR outperforms AODV and DSDV in urban environment by using NS-3 and VanetMobiSim as tools in term of PDR, end to end delay and routing overhead.

The authors compare the existing routing protocols in VANET environment using the NS3 version 25 as network simulator, combining with SUMO 0.25 as road traffic simulator, extracting a real-world urban map downloaded from the Open Street Map. (As done in our research). The results prove that OLSR outperforms other existing protocols.

 

The main idea of our research is to combine the advantages of OLSR and Greedy Forwarding Advanced; which another amelioration for GF in this paper; to adapt OLSR for VANET environment.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors have investigated the evaluation of the optimized link state routing protocol in the vehicular ad hoc network in term of end to end delay and packet delivery ratio. The modified OLSR protocol is more efficient for vehicular ad hoc network. The manuscript is interesting and useful for the design and application of vehicular communication systems. The paper is acceptable to be published in Smart Cities, provided the following issue can be addressed

 

1. Some abbreviations should be clarified when they appear for the first time.
2. The introduction part should be improved, with more details on the developed work in this manuscript
3. There are two Figure 3, two Figure 2, while no Figure 5 and Figure 6. Please pay careful attention on format.
4. Add some discussion regarding the impact of the proposed protocol on the capacity of the vehicular ad hoc network.
5. Add some discussion either in the Discussion or the Introduction Section regarding other potential optical wireless techniques that can be applied in vehicular communication systems.

See e.g.

W Hu et al., High-dimensional feature based non-coherent detection for multi-intensity modulated ultraviolet communications, Journal of Lightwave Technology, 2022.

K Wang et al., Evolution of short-range optical wireless communications, Optical Fiber Communications Conference, 2022.

Author Response

Dear Reviewer,

Thank you very much for your constructive comments concerning our manuscript. The comments are valuable and helpful for revising and improving the quality of our paper, and all our researches. We have studied the comments carefully and have made corrections which we hope meet with approval. The letter which provides a point-by-point response to the comments is in the attachment.

Once again, thank you very much for your comments and suggestions.

Best regards,

MyDriss Laanaoui et al.

Author Response File: Author Response.docx

Reviewer 4 Report

The followings are my comments on this paper:

• Consider rephrasing the title. The "by a new forwarding mechanism" is a bit vague.
• I suggest adding a list of contributions in the Introduction section.
• The authors can improve the introduction by showing the novelty and briefly describing how the paper solves the given problem. For this reason, the authors can borrow some sentences from the abstract.
• Line 81 typo "proto-actif"
• Line 83 typo "objet". Please recheck the paper for any more typos.
• Table 1. "cons" header should be in Title Case.
• In section 3, the comparison from Ref 15 and 16 shows OLSR wins. Meanwhile, from Ref 17 and 18, GPSR wins. However, is it possible to compare OLSR and GPSR? Is there any paper that compares them? This can be used to argue why the paper's idea is to combine GFA with OLSR. 
• Line 175-176, The integration of "greedy forwarding" mechanism also adapts more the protocols to the VANET environment. What does this sentence mean? Please rephrase any other confusing sentences.
• Please make Figure 3 bigger, and change the contents to English.
• Figure 3 is not mentioned in the paragraph. Please make sure that all Tables and Figures are mentioned.
• Figure 2 should be Figure 4
• Figure 3 should be Figure 5.
• Figure 4 should be Figure 6.
• Figure 6-9 is blurry, please fix it. Change the contents to English.
• Section 4.3 seems like the core idea of the paper, but only a little information is provided here. The authors can add any diagram or explanations on how the authors combine GFA and OLSR.
• Please fix Equation 3.
• Fix indentation of algorithms on Page 12 and 13.
• Fix the chart legend in Figure 12 and 13.
• Figure 5 should be Figure 13.
• Consider integrating the Discussion section into the previous sections when the analysis of the experiments are described.
• Check the formatting of the References.

Author Response

Dear Reviewer,

Thank you very much for your constructive comments concerning our manuscript. The comments are valuable and helpful for revising and improving the quality of our paper, and all our researches. We have studied the comments carefully and have made corrections which we hope meet with approval. The letter which provides a point-by-point response to the comments is in the attachment.

Once again, thank you very much for your comments and suggestions.

Best regards,

MyDriss Laanaoui et al.

 

Response

1. Is the content succinctly described and contextualized with respect to previous and present theoretical background and empirical research (if applicable) on the topic?

I revised the content succinctly more described and contextualized with respect to previous and present theoretical background and empirical research on the topic. In the abstract. [Lines: 16 to 24] and 1. Introduction: [lines: 51 to 71]

2. Are all the cited references relevant to the research?

Thanks very much for your advice, we have improved and added other references relevant to research.

3. Are the research design, questions, hypotheses and methods clearly stated?

The research design, problem, methodology and solutions are briefly summarized in 1. Introduction [Lines 51 to 71] and 4. Proposed work [Lines 206 to 223]. Also we added a schema to illustrate the two parts of our approach.

4. Are the arguments and discussion of findings coherent, balanced and compelling

I revised the arguments and discussion of findings to be more coherent, balanced, compelling, and clear. 5. Discussion [Lines 465 to 532] and figure 3 [line 221].

5. For empirical research, are the results clearly presented?

Thank you very much for your advice. We have improved the presentation of the result of our empirical research in our revised manuscript in 4. Proposed work [Lines 206 to 223] also in Discussion [Lines  465 to 532  ].

6. Is the article adequately referenced?

Thank you very much for your advice. We have improved the references in our revised manuscript so that our paper is adequately referenced.

7. Are the conclusions thoroughly supported by the results presented in the article or referenced in secondary literature?

Thank you very much for your advice. We have improved the conclusions in our revised manuscript

8. Consider rephrasing the title. The "by a new forwarding mechanism" is a bit vague.

Thank you very much for your advice, the new title reflect the proposition “Enhancing OLSR protocol by an advanced greedy forwarding mechanism for VANET in Smart cities”

9. I suggest adding a list of contributions in the Introduction section.

Thank you very much for your advice, I added a new list of existing contribution in the introduction.

10. The authors can improve the introduction by showing the novelty and briefly describing how the paper solves the given problem. For this reason, the authors can borrow some sentences from the abstract.

Thank you very much for your advice, we have improved our paper to clarify our proposition. in the abstract. [Lines: 16 to 19] and 1. Introduction: [lines: 52 to 71]

11. In section 3, the comparison from Ref 15 and 16 shows OLSR wins. Meanwhile, from Ref 17 and 18, GPSR wins. However, is it possible to compare OLSR and GPSR? Is there any paper that compares them? This can be used to argue why the paper's idea is to combine GFA with OLSR. 

Thank you very much for your advice and information, we have improved the literature study in 3. Literature review [Lines 196 to 201].

1. Line 175-176, the integration of "greedy forwarding" mechanism also adapts more the protocols to the VANET environment. What does this sentence mean? Please rephrase any other confusing sentences.

Thank you very much for your advice and information, we have changed this sentence in our revised manuscript.

1. Please make Figure 3 bigger, and change the contents to English

Thank you very much for your advice and information, we have improved the figures in our revised manuscript.

14. Figure 2 should be Figure 4; Figure 3 should be Figure 5; Figure 4 should be Figure 6; Figure 5 should be Figure 13.

Thank you for your advice, I have verified all figures in our revised manuscript, all figures are in the order of citation.

15. Section 4.3 seems like the core idea of the paper, but only a little information is provided here. The authors can add any diagram or explanations on how the authors combine GFA and OLSR.

Thank you very much for your advice and information, we have detailed more our proposition, we introduce the two features of our protocol in section 4. Proposed work [Lines 206 to 223] illustrated by Figure 3, the first one is detailed in section 4.1 where we explained the GFA and simulated in section 4.2. We explain in section 4.3 the second step where our protocol use the information collected in first step.

16. Please fix Equation 3.

Thank you very much for your advice, we have fixed the equations in the correct form like in template.

17. Fix indentation of algorithms on Page 12 and 13.

Thank you very much for your advice and information, we have improved the format of algorithms in our revised manuscript.

18. Fix the chart legend in Figure 12 and 13.

Thank you very much for your advice, we have fixed the legend of figure 12 and 13 in our revised manuscript

19. Consider integrating the Discussion section into the previous sections when the analysis of the experiments are described.

Thank you very much for your advice, we have integrated a discussion in every parts of simulation, and as in the template, we add a section “Discussion” for analyzing the simulations in global and conclude with a limitations and perspectives.

20. Check the formatting of the References.

Thank you very much for your advice. We have formatted the references in our revised manuscript.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I still think that OLSR is not the best option for VANETs. And the reasons are the ones you indicate in the introduction. “In particular, the high mobility of vehicles in this network requires adapting routing information to the frequent change of the topology. Therefore, we must reduce the convergence time for routing algorithms to find the path from source to the destination, which can enhance the end-to-end delay and will minimize the latency time to discover neighbors.”

Accepting that OLSR could be an option, I review the rest of the paper.

First, a general comment, complete proofreading of the English language is mandatory. There are parts of the paper that I am not able to understand.

Section 4 needs to be rewritten. The proposal is not clear. It is very difficult to follow the logical structure. Basically, it is a new factor, the advanced Greedy Forwarding Mechanism (GFA). Is the proposal just a minor change from previous works [22] and [23]? How can OLSR compute this factor? How does this factor apply to OLSR routing?

And more important, what is the purpose of G-OLSR? In one part of the paper, it seems that the network is intended to be formed by the intersections (nodes) and the streets (links), but in other parts, it seems that the network is formed by the cars themselves and the communications between them. Following the same comment, does the OLSR protocol run only on the cars, or does it require infrastructure (at the street intersections)? 

The proposal also lacks details to bring the proposal to the real world. Do all cars in a city form a single OLSR network? If there are several OLSR networks, how is it decided which car belongs to which network? What happens to the cars that are just connected (neighbor discovery)?

Regarding the proposed metric in formula 1, the main contribution of the paper, I do not understand that it only has the X component. The map of a city is in 2D. The coordinate is not scalar, it is vectorial (2D), and also the velocities are not scalar, they are vectorial (2D). 

Related to this last point, how does a car in the network know the current position of all the cars in the network? And how does it know the coverage range of each car? Each car has a different converter range, which depends both on the car's own radio and antenna, and on the propagation environment. 

One last comment on the proposal. Why is WiFi used as a communication protocol? Why have other protocols designed for VANETs, such as Dedicated short-range communications (DSRC), been discarded?

Now some comments about the simulations and results. 

First of all, I was expecting some simulations to validate the claims in the introduction: adapting routing information to the frequent change of the topology, reducing the convergence time for routing algorithms, and reducing the time to discover neighbors.

Many details are missing in the experimental framework, for example, the HELLO frequency, the TC frequency, data rate (packet size and frequency), duration of the simulation,...

On the first set of simulations (section 4.2). The results cannot be generalized. A simple 4-node simulation with constant velocities allows us to exemplify the proposal but not generalize it to all cases. Simulations with more realistic cases are mandatory, streets not in straight lines, more cars, not all of them driving in the same direction, not with constant speeds, and cars entering and leaving the simulated segment,...

On the first set of simulations (section 4.4). First, again, a single simulation cannot validate anything. The results depend on the distribution of the cars. Multiple simulations with different initial distributions of cars, even speeds, must be performed. 

Important metrics to compare are missing, for example, number of HOPs, number of segments, number of intersections,... And justify the number of data sources and sinks. Why 10? Where are they located? Why only 4 data packets? Why a pause time of 0?

Reviewer 4 Report

The authors have addressed all of my previous comments.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The presentation of this paper is very poor, with a lot of grammar mistakes and typos, for example, in the abstract, it should be “exchange information” instead of “change information”. The full name of “OLSR” is only mentioned in line 58 of page 2. More than one figures have the same labels. The equations do not appear in the correct form.

 

The comparison of the existing protocols is not very effective. The authors list the advantages and disadvantages of each scheme using bullets. However, they may have different application scenarios and the bullets do not provide much insight. A better way for comparison is to use tables.  

 

The analysis in Section 5 is based on the special case created by the authors, which does not provide much insight on the actual performance of the proposed scheme.

 

The final simulation results need further explanation. The gain of the modified greedy-OLSR comes at the cost of higher complexity. The discussion of the drawbacks is missing. Furthermore, for the last figure, it is not clear why the latency first decrease, then increase and decrease again with the density.

Reviewer 2 Report

This paper explores Intelligent Transport System ‘ITS’ transport. The topic is interesting. Here are my comments to improve the paper:

1- in the abstract, you need to include the major aspects of the entire paper in a prescribed sequence that includes: 1) the overall purpose of the study and the research problem(s) you investigated; 2) the basic design of the study; 3) major findings or trends found as a result of your analysis; and, 4) a brief summary of your interpretations and conclusions. At the moment, some of these aspects are missing.

2- abstract line 11, it should ‘exchanging information’

3- abstract line 14, you say "prove that the OLSR protocol presents the best performance". This is a big claim. How do you do that? Either explain how you prove it or rewrite the sentence in a humbler way. Again, you haven’t said anything about the methodology in your abstract.

4- In the introduction, make clearer what knowledge gaps you identified and how your research addresses them. Also, make the research objectives/questions clearer. Answer the “so what?” question. Why investigating such matter is important? End the introduction with an outline of the paper; what comes next?

5- The novelty/originality should be clearly justified that the manuscript contains sufficient contributions to the new body of knowledge from the international perspective.  What new things (new theories, new methods, or new policies) can the paper contribute to the existing international literature? This point must be reasonably justified by a Literature Review, clearly introduced in Introduction Section, and completely discussed in Discussion Section.

6- you didn’t include any references in the introduction. You need to acknowledge the existing research on these topical matters.

7- What are the limitations of your study?

8- you need to include a discussion section where you clearly discuss your arguments. this is one of the major areas of improvement for your paper. Your discussion section should be at least 750 words.

9- section 3, should this be ‘literature review’?

10- there are issues with your referencing, for example line 132, you cannot say ‘in [10] the authors’. Look at MDPI’s referencing guide.