In this paper, the authors proposed an energy saving MAC protocol for data gathering in UAV-WSN. This paper has severe flaws regarding the problem formulation, technical soundness, and simulation results. My detailed comments are listed as follows:
1. It is not clear why the proposed MAC protocol is specific to UAV networks, and the description of state-of-the-art works are unsatisfactory. The references related are still outdated. More recent work should be added, such as:
Ma, Xiaoyan, Rahim Kacimi, and Riadh Dhaou. "Adaptive hybrid MAC protocols for UAV-assisted mobile sensor networks." Consumer Communications & Networking Conference (CCNC), 2018 15th IEEE Annual. IEEE, 2018.
Qin, Yuan, David Boyle, and Eric Yeatman. "A novel protocol for data links between wireless sensors and UAV based sink nodes." Internet of Things (WF-IoT), 2018 IEEE 4th World Forum on. IEEE, 2018.
Song, Xiao Ou. "Dynamic MAC Protocol Designed for UAV Collision Avoidance System." Conference on Complex, Intelligent, and Software Intensive Systems. Springer, Cham, 2017.
The significance and effectiveness of this work are unclear and the presentation is not convincing. The importance of this work needs to be highlighted in the light of related works.
2. Please give the structure of all the frames. Why the length of the beacon frame is 100 bits?
3. Why the UAV cannot stop or slow its movement during the mission?
4. Where is the average energy consumption in sleep mode? The sleep mode is not same as idle mode.
5. The overall quality of English language and presentation are poor and revision is needed in many parts. For example,
(1) Write the title of Sec. II in Title Case (standard capitalization);
(2) The figures could be improved (better resolution etc.).
(3) ¡°The NSL-MAC able to reduce ¡¦¡±->¡°The NSL-MAC is able to reduce ¡¦¡±
(4)¡°where the UAV has A constant speed during the flight ¡¦¡±->¡°where the UAV has a constant speed during the flight period¡¦¡±
(6) The format of the reference should be the same.
Comments to the Author
This letter proposes NSL-MAC which is an energy saving MAC protocol for UAV-assisted data gathering in WSNs. The application scenario in this letter is interesting and important. However, the technical content and novelty of this letter are not enough for publication. The detailed comments are as follows:
1, Although the proposed NSL-MAC is used for UAV-assisted data gathering in WSNs, the similar scenarios can be found in UAV-assisted relay communications and reconnaissance. However, the authors do not survey them.
2, The main contribution of this letter has divided the superframe into four periods. The procedure is reasonable, however, many details are ignored. For example, in the registration period, how to handle the collision among so many nodes? Therefore, I think the proposed NSL-MAC is not practical.
3, The nodes become active only when they are in the communication coverage of the UAV. However, because the UAV is mobile, the authors must discuss some issues brought by the mobility of UAV. For example, perhaps the node is in the coverage in the registration period and the UAV assigns some slots to it, but if it is out of the coverage in the gathering period, how to handle?
4, When evaluating the different performance, you should not compare with different protocols. You should have fixed comparative protocols.
5, The presentation needs to be improved. For example, there are too many typos, the authors should check the manuscript carefully. In addition, the format of simulation figures needs to be unified and beautified.
Comments to the Author
In this paper, the authors propose a MAC protocol to improve energy efficiency for UAV sensor networks. This paper has severe flaws regarding the system and simulation results. My detailed comments are listed as follows:
1. Why the coverage area of the UAV is ¡î£¨R/2£©^2+H^2?
2. What is the biggest difference between the proposed MAC protocol and other protocols? The authors need to emphasize the innovative nature of this work.
3. Why the proposed MAC protocol achieves a better PDR than AO-ALOHA?
4. Why the average throughput of the proposed MAC protocol obtains higher throughput when the number of nodes is increasing?
5. All references and figures should be in the same format.