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%\title{Response to the reviewers of \bf "Perimeter-based Coverage Optimization to Improve Lifetime in Wireless Sensor Networks"}
%\author{Ali Kadhum Idrees, Karine Deschinkela, Michel Salomon and Raphael Couturier}

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\today
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\vspace{-0.5cm}\hspace{-2cm}FEMTO-ST Institute, UMR 6174 CNRS

\hspace{-2cm}University Bourgogne Franche-Comt\'e

\hspace{-2cm}IUT Belfort-Montb\'eliard, BP 527, 90016 Belfort Cedex, France.

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\begin{center}
Detailed changes and addressed issues in the revision of the article

``Perimeter-based Coverage Optimization \\
to Improve Lifetime in Wireless Sensor Networks''\\

by Ali Kadhum Idrees, Karine Deschinkel, Michel Salomon and Raph\"ael Couturier

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Dear Editor and Reviewers,

First of all, we would like to thank you very much for your kind help to improve
our article  named: ``Perimeter-based Coverage Optimization  to Improve Lifetime
in  Wireless  Sensor Networks''.  We  highly  appreciate the  detailed  valuable
comments of the reviewers on our  article. The suggestions are quite helpful for
us and we incorporate them in the revised article. We are happy to submit to you
a revised version that considers most of your remarks and suggestions to improve
the quality of our article.

As below, we  would like to clarify  some of the points raised  by the reviewers
and we hope the reviewers and the  editors will be satisfied by our responses to
the comments and the revision for the original manuscript.

%Journal: Engineering Optimization
%Reviewer's Comment to the Author Manuscript id GENO-2015-0094
%Title: \bf "Perimeter-based Coverage Optimization to Improve Lifetime in Wireless Sensor Networks"
%Authors: Ali Kadhum Idrees, Karine Deschinkela, Michel Salomon and Raphael Couturier

\section*{Response to Reviewer No. 1 Comments}

This paper  proposes a  scheduling technique  for WSN  to maximize  coverage and
network lifetime.  The novelty of this  paper is the integration  of an existing
perimeter  coverage   measure  with  an  existing   integer  linear  programming
model. Here are few comments:\\




\noindent  {\bf  3.}  The  communication and  information  sharing  required  to
cooperate and make these decisions was not discussed.\\

\textcolor{blue}{\textbf{\textsc{Answer:}  The   communication  and  information
    sharing required to  cooperate and make these decisions is  discussed at the
    end of page 8.  Position coordinates,  remaining energy, sensor node ID, and
    number of one-hop neighbors are exchanged.}}\\

\textcolor{red}{\textbf{\textsc{Reviewer's response:} I see at the end of page 8 the description of the INFO packet. However, you are not including any description of the position coordinates, remaining energy, sensor node ID, etc. in the write up. I suggest adding this into the write up to make the communication clear.}}\\


\noindent {\bf  6.} The  authors have  performed a  thorough review  of existing
coverage  methodologies.  However,  the clarity  in the  literature review  is a
little off. Some of the descriptions of the  method s used are very vague and do
not bring out their key contributions.  Some references are not consistent and I
suggest using the journals template to adjust them for overall consistency.\\

\textcolor{red}{\textbf{\textsc{Reviewer's response:}  I do like the way you have presented the different literature related to each aspect of
the problem. I think I was just concerned that the sentences presenting each work are not very
clear. After reading through them however, everything is clear. I like the addition of the last
paragraph and believe it is definitely needed since you are directly comparing these
methodologies.}}


\textcolor{blue}{\textbf{\textsc{Answer:} References have been carefully checked
    and seem to be consistent with the journal template. In Section~2, ``Related
    literature'',  we refer  to papers  dealing  with coverage  and lifetime  in
    WSN. Each  paragraph of this section  discusses the literature related  to a
    particular aspect of the problem : 1. types of coverage, 2. types of scheme,
    3. centralized versus distributed protocols,  4. optimization method. At the
    end of each  paragraph we position our  approach. We have also  added a last
    paragraph  about  our  previous  work  on  DiLCO  protocol  to  explain  the
    difference with PeCO. }}\\

\noindent {\bf 7.} The methodology is implemented in OMNeT++ (network simulator)
and tested  against 2 existing algorithms  and a previously developed  method by
the authors.   The simulation results  are thorough  and show that  the proposed
method improves the  coverage and network lifetime compared with  the 3 existing
methods. The results are similar to previous work done by their team.\\

\textcolor{red}{\textbf{\textsc{Reviewer's response:}  
I agree that you should show the same performance indicators and that this paper is
about the way you formulated the problem. The mathematical optimization model is the main
contribution but it’s less convincing since the results are slightly better if not the same for the two
methodologies you have developed. Could you include some other measure that shows that the
PeCO is better? Maybe include computation time or something that is as convincing as the energy
consumed per sensor.}}

\textcolor{blue}{\textbf{\textsc{Answer:} Although  the study conducted  in this
    paper reuses the  same protocol presented in our previous  work, we focus in
    this  paper on  the mathematical  optimization model  developed to  schedule
    nodes  activities.   We deliberately  chose  to  keep the  same  performance
    indicators to  compare the results  obtained with this new  formulation with
    other existing algorithms.}}\\

\noindent {\bf 8.}  Since this paper  is attacking the coverage problem, I would
like  to  see more  information  on  the amount  of  coverage  the algorithm  is
achieving. It seems that  there is a tradeoff in this  algorithm that allows the
network to increase  its lifetime but does not improve  the coverage ratio. This
may be an  issue if this approach  is used in an application  that requires high
coverage ratio. \\

\textcolor{blue}{\textbf{\textsc{Answer:} Your  remark is very interesting.  Indeed,
    Figures 8(a) and (b) highlight this  result. The PeCO protocol allows to achieve
    a coverage  ratio greater than $50\%$  for far more periods  than the others
    three  methods, but  for applications  requiring  a high  level of  coverage
    (greater than  $95\%$), the DiLCO method is  more efficient. It is  explained at
    the end of Section 5.2.4.}}\\

\textcolor{red}{\textbf{\textsc{Reviewer's response:}   
I’m glad you added the explanation. I am confused with your conclusion in the last
sentence though, “DiLCO is better for coverage ratios near 100%, but in that case PeCO is not
ineffective for the smallest network sizes”. I suggest adjusting it to something like this. “DiLCO
outperforms PeCO when the coverage ratio is required to be >90%, but PeCo extends the network
lifetime significantly when coverage ratio can be relaxed. “ Also, can you add applications where
you would want to have a coverage ratio of 50%? This seems like a very small ratio and as you
increase it, DiLCO becomes the methodology that has the maximum network lifetime. If you don’t
include application examples, your statement “Indeed there are applications that do not require a
100$\%$ coverage of the area to be monitored.” stronger. }}





We are very grateful to the  reviewers who, by their recommendations, allowed us
to improve the quality of our article.

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Best regards\\
The authors
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