Dear Prof. Kim:
Manuscript ID JCN18-DIV3-034.R1 entitled "Channel-Aware Cooperative Routing in Underwater Acoustic Sensor Networks" which you submitted to the Journal of Communications and Networks, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.
The reviewer(s) have recommended publication, but also suggest some revisions to your manuscript. Therefore, I invite you to respond to the reviewer(s)' comments and revise your manuscript.
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Once again, thank you for submitting your manuscript to the Journal of Communications and Networks and I look forward to receiving your revision.
Prof. Di Wu
Editor, Journal of Communications and Networks
Reviewer(s)' Comments to Author:
Comments to the Author
Most of the requests of this reviewer were satisfied. However, the reviewer still has questions about the following items, and the authors would like to consider them again.
Why did the authors set the slot time to 0.2 seconds? It can be understood that the slot time becomes larger because the speed of the sound wave is slower than the propagation speed of the radio wave, but the reason why the value is 0.2 seconds is not explained in the manuscript. In general, the slot time of IEEE 802.11 is defined in consideration of the time for signal detection(CCA), the time it takes for the radio waves to travel(round trip time), and the time it takes for the signal to be transmitted. The size of the slot time is related to the result of packet transmission delay and energy consumption according to the time that the node waits to transmit. Therefore, the reviewer believes that a reason for setting such a value is necessary when changing the slot time.
In addition, the slot time of the text is 0.2 seconds, and the slot time of the table is 0.18 seconds. Please recap what you have done with the standard.
The authors hypothesized that the communication environment is stable and set a value of 0.5 for the stability factor. However, there is no description of what the definition of a stable communication environment is and why the stabilization factor should be set to 0.5. If the effect on the stabilization factor cannot be shown in this paper, it is also possible to mention separately as a later study item.
Comments to the Author
Revised paper is well improved with additional simulation results especially with a variation of the number of nodes. However, some parts are insufficient for the reviewers' comments.
Additional revisions are needed for publishing the paper.
* On Comment 2 of Reviewer 2
Though the reviewer 2 requested to add evaluation of the relationship between the performance (delivery ratio and end-to-end delay) and the distance between the sink and source sensor nodes, it is not included in the revised paper. Though a graph for presenting the average number of hops per meter is added in the revised paper, the number of hops and the Euclid distance between source and destination are different. The reviewer is concerned with the performance of the proposed protocol when the distance between the source and destination is long.
* On Comment 2 of Reviewer 2
Though the no_reTx field is introduced in the revised version, the way a receiver of a packet updates the field is not written. Also, though the author mentioned that no_reTx is "a metaphor for number of retransmissions," the usage of the word "metaphor" seems strange and inappropriate to be used in the context.
If a packet from a node that can be sent from any node is damaged, the ID of the sender may be also damaged or not be damaged. If the correctness of the header and the payload of a packet are checked separately with error detection code, the receiver can send NACK to the sender only if the header is not damaged and the payload is damaged. The authors should clarify how the error in a packet is treated in the simulation. Is it assumed that the sender ID is not damaged in the simulation?
* On Comment 4 of Reviewer 2
Though algorithm 1 is updated according to the reviewer 2's comment, line 5-7 in the revised paper are not needed.
* On Comment 5 of Reviewer 3
Though the reviewer mentioned that "Time calculation by unidirectional communication requires time synchronization between two nodes or packet exchange through bidirectional communication, " the revised paper does not answer to the mention. Since a local clock of computers easily drift, and it is very difficult to synchronize clocks on different computers without communication nor GPS, some assumption is needed for time synchronization in the revised paper or the detailed description how to measure ToA should be included. However, neither is in the revised paper.
Fig. 15 and 16: The top part of the title of Y-axis is hidden.