Asynchronous Pattern-Designed Channel Access Protocol in Underwater Acoustic Wireless Sensor Networks

Round 1

Reviewer 1 Report

The authors present an automatic retransmitting protocol for underwater wireless sensor networks that is able to guarantee an 100% transmission success ratio.

The proposed protocol is well described but some implementation settings must be better clarified. For example:
- The total number of sensor nodes is pre-defined and fixed?
- It is possible to add a new sensor node in the network?
- After the end of a complete time window, how much time is required for the communication buoy to process the SIC mechanism and for the sensor nodes transmit new frames?
- The mobility of nodes and/or the distance to the buoy node can't impact in the timeline from figure 3? If yes, what is the impact in all the proposed protocol and presented results?
- The algorithm 1 is used in the rx node (buoy)? If yes, what is the meaning/effect of the randomly generated probability? What happens if p > Prob_b?
- In figure 6 and respective explanation, it's not clear the comparison. Why should TDMA use a time window of 128 for 7 nodes transmission?
- It is guaranteed that SIC can always recover one of the conflicting frames?

There are several typos, that must be corrected:
- line 64: sender transmit
- line 73: access,
- line 259: the performance the receiving
- input text in algorithm 1: maxi mum
- line 450: it's time slot or time window? Window = total time for a complete transmission from all the nodes; Slot = time for a node frame transmission. Is it wright?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This work is correct, there are some small things that can be fixed.

In section 3.3 lines 309 and 313, the letter y is defined two times differently. The only difference is that in line 303 it is used in italic and in line 313 not. Is it the same or represent different concepts?

In the line 313 I think that the "receiving node." should be "receiving node,"

In equation 6, how is modeled h_j-1.

In equation 8, how the distance is obtained? The expression 7 uses A(l_a, f_a), you need to know the distance.

In Algorithm 1, "maxi mum" there is an extra whitespace.

 What represents ????_?? What represents NodeCol?

The Algorithm 1, should be reviewed. I have not found errors, but it is a bit difficult to understand because some variables are not defined.

The section 4 needs to be revised. It should include some information about the simulator and the model used.

It should be interesting to test the protocol using a discrete event tool such  as Ns3, Omnet++ ... .

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The Asynchronous Pattern-Designed Random Access (APDRA) protocol is presented by the authors. The proposed algorithm establishes retransmission time intervals for data frames based on pattern design that increases the access probability. They also include a successive interference cancellation (SIC) decoding technique at the receiver. By switching from the traditional method of rejecting conflicting data frames to repeated decoding, authors claim that this process increases the effectiveness of transmission. The proposed protocol is simulated against conventional underwater media access control protocols and current retransmission techniques, and results are compared. The outcomes shows that the APDRA protocol improves the transmission success ratio and also somewhat shortens the access delay.

The paper is interesting and worth publishing. However, it needs minor revision before publishing.

1) In Algorithm 1 on page 11, the conflict matrix variable NodeCol mentioned in Line 10 hasn't been defined before its first use.

2) The cons of the algorithm have been briefly described but have not been reflected in the results. The results are too good to be true. For example, Figures 5, 7 and 8 show as if the proposed algorithm doesn't have any downside. The authors should also show the scenarios where the cons of the technique are also highlighted.

I suggest that the authors carefully go over the manuscript and correct any typos and other minor English language errors.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors improved the paper to an acceptable level.

Reviewer 3 Report

All my concerns have been addressed.