A Multi-Hop Data Dissemination Algorithm for Vehicular Communication
Round 1
Reviewer 1 Report
In this paper, it proposed a multihop data dissemination mechanism using LCL algorithm. This is one of important issues in VANET. According to the two kinds of simulation scenarios, the results shows that the proposed method has achieved higher coverage rate and message delivery ratio. However, the following issues should be discussed to improve the quality of the paper.
- The equation (1) is presented as an informal mathematical expression. The definition of symbol Hi should be presented more clearly. Is it an angle, number or direction?
- The equation (2) is wrong. The left side of the equation is not equal to the right side. The symbol d is undefined.
- It shows the symbol dCx in line 325, but the symbol dCy is showed in Figures 8. According to the inconsistent symbol, it made me feel really confused.
- The definition of llane is misunderstanding. In line 334, it is an average length of road lane. But in algorithm 1, it shows that it is the width of lane. The symbol E is undefined in algorithm 1.
- According to the description in pages 8-9, it is hard to understand how to derive Eq. (7) from Eq. (5) and Eq. (6). It should be included sufficient explanation.
- In section 5, it is better to show the figure of 3*3 Manhattan grid. In the scenario of multilane, the number of lanes should be listed in simulation parameters.
- In line 426, it shows the “relay coverage”, but the simulation results only discuss about “coverage rate”. It should to show the definition of coverage rate.
- The simulation results shows performance of the proposed method and compare with APTt and DBF methods. What are APTt and DBF methods? What is the difference between LCLA and other methods?
- According to the simulation results and conclusion, it is hard to understand the proposed method is better than others. For example, it shows that the LCLA has the best end to end delay in Figure 11(a), but it is not in Figure 12(a) (i.e. APTt is the best) It is recommended to indicate the conditions under which the proposed method is more effective.
- Some typos should be corrected. (Lines 34, 319, 322, 324, 327, …, 485) No dot after the word “Figure”.
- Please keep the experimental results consistent so that readers can understand. It is recommended to adjust the order of simulation results. (Figure 12(c) and Figure 12(d))
- The reference paper [29] should be listed in the right ordered. The reference paper [3] should be mentioned in the paper.
- Since the content of Section 3 is too short, it is recommended to adjust its title and content to the subsection of Section 4.
Author Response
Reviewer: 1
[Reviewer 1, Comment #1]
The equation (1) is presented as an informal mathematical expression. The definition of symbol Hi should be presented more clearly. Is it an angle, number or direction?
[Author’s Response to Comment #1]
As your correctly pointed out, in Eq. (1) was not properly defined. We have corrected the Eq. (1) and defined as a heading angle of vehicle . We have corrected Eq. (1) as follows.
[Reviewer 1, Comment #2]
The equation (2) is wrong. The left side of the equation is not equal to the right side. The symbol d is undefined.
[Author’s Response to Comment #2]
We appreciate your kind correction of Eq. (2). We modified Eq. (2) and removed undefined variable . The current state of the Eq.(2) is shown as:
[Reviewer 1, Comment #3]
It shows the symbol dCx in line 325, but the symbol dCy is showed in Figures 8. According to the inconsistent symbol, it made me feel really confused.
[Author’s Response to Comment #3]
We apologies for making you bit confused regarding the notation . We found this typo and changed it though entire manuscript.
[Reviewer 1, Comment #4]
The definition of lane is misunderstanding. In line 334, it is an average length of road lane. But in algorithm 1, it shows that it is the width of lane. The symbol E is undefined in algorithm 1.
[Author’s Response to Comment #4]
We have made a mistake. In this paragraph (lines 350~359), we meant lane width, but it was written a lane length. We have corrected them as per your kind request. We appreciate of your attentiveness.
[Reviewer 1, Comment #5]
According to the description in pages 8-9, it is hard to understand how to derive Eq. (7) from Eq. (5) and Eq. (6). It should be included sufficient explanation.
[Author’s Response to Comment #5]
The Eq. (7) is a timer calculation formula used by APTt algorithm. According to this equation, if potential transmitter obtains smaller overlapped area, it waits shorter time before performing the transmission. In this formulation, we added the result of Eq.(6) in order to have acute alignment of transmitter with the previous transmitter. This increases the chance to select relay node from the same road and reduces the cases shown in Figure 8.
[The following sentences has been added/modified to the manuscript]
“The Eq.(7) is timer calculation formula used by APTt algorithm proposed in [17]. If potential transmitter obtains smaller overlapped area, it gets shorter back-off timer. Similarly, in our method, if transmitter obtains smaller area in upper sector, it achieves earlier retransmission of received message. Here, aligns relay node to the precious transmitter.”
[Reviewer 1, Comment #6]
In section 5, it is better to show the figure of 3*3 Manhattan grid. In the scenario of multilane, the number of lanes should be listed in simulation parameters.
[Author’s Response to Comment #6]
We have added the number of lanes in the table 1 where main simulation parameters are listed. We have added a figure of 3 by 3 Manhattan Grid figures as figure 11.
[The following sentences has been added/modified to the manuscript]
On Page 13 Line 408
Figure 11. 3 by 3 Manhattan grid urban network
[Reviewer 1, Comment #7]
In line 426, it shows the “relay coverage”, but the simulation results only discuss about “coverage rate”. It should to show the definition of coverage rate.
[Author’s Response to Comment #7]
We have changed “coverage rate” to “relay coverage”, since we had defined relay coverage in simulation parameters section. We appreciate your kind remark.
[Reviewer 1, Comment #8]
The simulation results shows performance of the proposed method and compare with APTt and DBF methods. What are APTt and DBF methods? What is the difference between LCLA and other methods?.
[Author’s Response to Comment #8]
Following paragraph is added to give additional details regarding reference methods.
[The following sentences has been added/modified to the manuscript]
On Page 6 Line 225
“In simulation stage, we compared our method with algorithms introduced in [17-18]. In [17], authors proposed area-based message dissemination approach that orders the transmission according to the gained additional area that would be covered by potential transmission. Their method integrates a timer and probabilistic area-based transmission and therefore, it is called APTt algorithm. In [17], authors considered only the gain in new additional area and they neglected a dissemination direction and positional distance. As long as vehicle (receiver) maintains the smallest overlapped area, it becomes transmitter. This may cause message dissemination in undesired direction. On the other hand, authors of [18] propose distance based forwarding scheme. According to this method, the farthest (Euclidian distance ) node within wireless range of transmitter obtains the shortest back-off time. In [18], authors highlighted the effect of spurious forwarding phenomenon and they claimed that their method reduced effect of this problem. However, this method only effective in highway scenario and this may also propagate the emergency messages towards undesired direction. In this paper, we propose LCL based relay selection scheme. Our approach allows each one-hop neighbor node calculates its retransmission back-off timer upon receiving the event messages. This back-off timer value is directly proportional to the area that is yields by a receiver in the upper sector of source’s wireless range. Once, the back-off timer of a receiver elapse, it executes retransmission. If during this period, it detects the retransmission of the same message by another neighbor, it suppresses the retransmission. Our method considers positional distance and message dissemination direction. Therefore, it provides the smallest back-off timer to the vehicle moving in the same road and aligned to the latest position of transmitter. So, proposed method can be considered as a timer/delay based rebroadcast method.”
[Reviewer 1, Comment #9]
According to the simulation results and conclusion, it is hard to understand the proposed method is better than others. For example, it shows that the LCLA has the best end to end delay in Figure 11(a), but it is not in Figure 12(a) (i.e. APTt is the best) It is recommended to indicate the conditions under which the proposed method is more effective.
[Author’s Response to Comment #9]
The followings details are included as per your kind recommendation
Page 17, Line 536
“Our method performs a slightly more latency a conventional back-off period in MAC layer. In APTt algorithm, CSMA/CA algorithm is disabled in MAC layer. A transmitter does not have to select back-off counter and it neglects existing contention in the network. Therefore, whenever the vehicles disseminate the message using APTt algorithm, they immediately retransmit once their timer expires. Another reason can be the multiple retransmissions permitted by our method to relay nodes. As our method lets multiple retransmissions only for the relay nodes, and thus it may cause additional contention in the wireless channel. Since emergency messages are important for vehicles safety, we apply multiple retransmission to achieve higher coverage rate especially in sparse density. Therefore, the proposed method performs an additional delay since multiple relay nodes compete to access wireless channel”
[Reviewer 1, Comment #10]
Some typos should be corrected. (Lines 34, 319, 322, 324, 327, …, 485) No dot after the word “Figure”.
[Author’s Response to Comment #10]
Thanks for noticing the error constantly made after “Figure”. We have removed all dots (full stop) used after the word “Figure”. All changes are shown in the revised manuscript.
[Reviewer 1, Comment #11]
Please keep the experimental results consistent so that readers can understand. It is recommended to adjust the order of simulation results. (Figure 12(c) and Figure 12(d))
[Author’s Response to Comment #11]
We have changed the ordering of Figure 12(c) and Figure 12(d). As we added more figures, the number of Figure 12(c) and Figure 12(d) has been changed to Figure 13(c) and Figure 13(d) respectively.
[Reviewer 1, Comment #12]
The reference paper [29] should be listed in the right ordered. The reference paper [3] should be mentioned in the paper.
[Author’s Response to Comment #12]
We changed reference paper [29] to [33] by following the sequential order. We highly appreciate your kind notice on this reference. We have used reference [3] in the correct place in line 34.
[Reviewer 1, Comment #13]
Since the content of Section 3 is too short, it is recommended to adjust its title and content to the subsection of Section 4.
[Author’s Response to Comment #13]
We merged Section 3 and Section 4 as the content of Section 3 was very small. In the current manuscript, Section 3 became a Subsection 3.1. Then, Sections were changed as follow: Section 1 Introduction; Section 2 is related work; Section 3 is the proposed method; Section 4 is simulation parameters; Section 5 is performance analysis and simulation results; Section 6 is conclusion.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Authors propose a multihop data dissemination algorithm for vehicular communication. The topic addressed is interesting and the article is well written. The first part of the paper is devoted in discussing the state-of-the-art methodologies for vehicular communication. The proposed algorithm is then detailed and result simulations are shown.
Both the theoretical and experimental part are satisfactory. The article is technically sound.
Some minor comments:
-As regards the English language, the paper contains some typos, so that it should be deeply re-read by authors
-Figure 3(a) instead of Figure.3(a) (use the same formalism for all the references in the article)
-equation 2: please define R and d
- please, consider discussion the relationship between your way to formalize the protocol and other formal approaches to the same problem, e.g. https://doi.org/10.1007/978-3-319-19237-6_18
Author Response
Reviewer: 2
Both the theoretical and experimental part are satisfactory. The article is technically sound.
Some minor comments:
[Reviewer 2, Comment #1]
As regards the English language, the paper contains some typos, so that it should be deeply re-read by authors.
[Author’s Response to Comment #1]
We highly appreciate your remark on typos and English corrections. We reread the entire manuscript and we changed errors and typos.
[Reviewer 2, Comment #2]
Figure 3(a) instead of Figure.3(a) (use the same formalism for all the references in the article)
[Author’s Response to Comment #2]
The names of all figures have been changed from Figure.3(a) to Figure 3(a). Thanks for your kind suggestion.
[Reviewer 2, Comment #3]
equation 2: please define R and d
[Author’s Response to Comment #3]
We appreciate your kind correction of Eq. (2). We modified Eq. (2) and removed undefined variable . The current state of the Eq.(2) is shown as:
[Reviewer 2, Comment #4]
please, consider discussion the relationship between your way to formalize the protocol and other formal approaches to the same problem, e.g. https://doi.org/10.1007/978-3-319-19237-6_18
[Author’s Response to Comment #3]
In proposed method, we considered only few states that can directly impact on message dissemination performance. Each vehicle should be in idle state while one of them is transmitting its data through shared wireless channel. Once the message is sent, each vehicle must be in receiving state to safely receive the data sent by the transmitter. Then, all receivers stay in the waiting state as they calculate their back-off timers. Then, again one of them goes in forwarding state to forward the data received from the initial transmitter. The algorithm 1 and 2 can be explained by the similar method presented in https://doi.org/10.1007/978-3-319-19237-6_18. However, in the current manuscript we rather used many running examples where we explained all cases in detail. Therefore, we used current form of Algorithm 1 and 2 to present only basic steps conducted in our method.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The author has almost fulfill my review comments. However, the Eq. (2) is still incorrect. The error must be corrected.
Comments for author File: 
Comments.pdf
Author Response
[Reviewer 1, Comment]
The author has almost fulfill my review comments. However, the Eq. (2) is still incorrect. is equal to . But is not equal to . The error must be corrected.
[Author’s Response to the Comment ]
We appreciate your kind effort to improve the Eq. (2). We accept the mistake indicated by you and kindly send you our apologies. We modified Eq. (2). The current state of the Eq.(2) is:
Author Response File: Author Response.docx
