Motion Prediction Based TDMA Protocol in VANETs

Round 1

Reviewer 1 Report

The article proposes a motion-prediction based TDMA protocol, which aims to predicts the network topology in the next frame in order to select the better forwarding node. The experimental results for highway and urban scenarios are presented.

Comments:

1. Avoid mass citation (such as [2]-[7]), but rather use each reference to support a different point or claim.
2. The contributions stated on p. 59-69 are rather the summary of the work done. Rewrite this part of the paper to emphasize how your work advances over the state-of-the-art in this are of research.
3. Explicitly state the novelty of this paper at the end of section 1.
4. The overview of related work is rather short considering that this research domain is very active. Discuss the difference of the approach presented in this paper from the one proposed in “Dynamic Scheduling Algorithm for Delay-Sensitive Vehicular Safety Applications in Cellular Network”.
5. Present more informative and detailed captions of figures as some are very short.
6. 143, “vehicle speed follows a normal distribution” -> this assumption is not supported. Other authors reported vehicle speed following beta distribution.
7. How does the topology in second scenario (urban) differ from the first scenario (highway)? Note that Fig. 1 shows only 2 lanes rather than 8 lanes (L. 249).
8. The proposed method should be validated on real-world dataset rather than on the simulated data.
9. Add critical discussion section to discuss the limitations of your method and threats-to-validity of the simulation results.
10. Expand conclusions, provide main numerical results to support your claims, formulate implications or recommendations for further research in this area.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper, the authors propose a motion-prediction based TDMA protocol, which predicts the network topology in the next frame to select the better forwarding node to improve the network performance. The following text presents some observations and comments for improvement of the paper before acceptance.

1. TDMA MAC protocol assigns each node a particular time slot to avoid contention and collision. Apparently this approach seems perfect, however it’s not simple process as it requires continuous coordination and this cause significant overhead. Slot allocation/re-allocation to the nodes within a cluster significantly degrades the performance of TDMA protocol as nodes are frequently changing in a cluster. The author shall consider its impact on the proposed approach.
2. Eq. 1 assume even distribution of nodes which is over simplification of the model and against reality. Nodes can be close be together on one side and further apart on the side.
3. Elaborate Eq. 3, how p is transformed into ᵠ where ᵠ is direction of movement?
4. Some information are missing regarding the simulation setup, for instance, number of active nodes sending the data and data sending rate of individual node. This is important to study channel utilization.
5. What’s the impact of changing various parameters on the number of collisions in the two selected scenarios?
6. Paper write-up and English grammar needs revision as some of the sentences are difficult to comprehend. I suggest thorough revision of paper text to improve its readability.

Minor Comments

1. Line 103 – UTSP [24] uses the rode side units -> road side units
2. Line 104 “and Access Category of the vehicles” avoid un-necessary capitalization
3. Eq. 2, is that u or µ? Make correction.
4. Fig. 3 (b) Legend is same for all graphs.
5. Line 212 Fig. 6 is referenced but it’s not correct. 

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper proposes a motion-prediction based TDMA protocol (MPTDMA), in the rapidly changing Vehicular Ad Hoc Network (VANET), to improve the transmission efficiency by uniquely analyzing and predicting the real-time movement. At-scale NS2 simulations were used to evaluate the performance of the proposed design in both highway and urban scenarios, making comparisons with ADHOC MAC and VeMAC protocols.

This study investigates an interesting research question. Literature review should be enhanced. The methodology is adequately explained and seems convincing. The results should be better investigated. A discussion of methods and results is lacking. The conclusions seem properly supported. The contribution to research literature is significant.

• “1. Introduction” section: The study background, motivations and objectives are adequately delineated but its novelty should be better and clearly highlighted.
• “2. Related work” section: This section is rather concise. The knowledge and ideas that have been established on the specific topic should be deepened, highlighting strengths and weaknesses.
• “5. Performance Evaluation” section: This section presents also the output of the performance analysis of NS2 highway and urban simulation but, the discussion of the results is very brief (for the urban scene is lacking) and does not even offer a cursory description of the high-level findings. The description of the results for the urban simulation is almost non-existent. More exploration is required here.
• The discussion should be improved: a more extensive interpretation and a clearer explanation of the findings, and a critical comparison with other considered protocols (ADHOC MAC and VeMAC) needs to be addressed. Any limitation of the proposed model should be also declared. I recommend to add a specific “Discussion” section
• The contribution of the paper to the research literature should be better delineated.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The revisions are ok. The paper can be accepted for publication.

Reviewer 2 Report

All my comments are addressed and I am satisfied with the revised version.