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13 %\title{Response to the reviewers of \bf "Perimeter-based Coverage Optimization to Improve Lifetime in Wireless Sensor Networks"}
14 %\author{Ali Kadhum Idrees, Karine Deschinkela, Michel Salomon and Raphael Couturier}
22 \vspace{-0.5cm}\hspace{-2cm}FEMTO-ST Institute, UMR 6174 CNRS
24 \hspace{-2cm}University Bourgogne Franche-Comt\'e
26 \hspace{-2cm}IUT Belfort-Montb\'eliard, BP 527, 90016 Belfort Cedex, France.
31 Revision of the manuscript ``Perimeter-based Coverage Optimization to Improve Lifetime in Wireless Sensor Networks''\\
33 by Ali Kadhum Idrees, Karine Deschinkel, Michel Salomon and Raph\"ael Couturier
38 Dear Editor and Reviewers,\\
39 Comments (here in red color) raised by the reviewer n\textsuperscript{o}1 after a first revision have been carefully considered. Please find below our answers highlighted in green. We also highlighted the changes we made in the manuscript by using coloured text. We did our best to satisfy your requests.
41 %Journal: Engineering Optimization
42 %Reviewer's Comment to the Author Manuscript id GENO-2015-0094
43 %Title: \bf "Perimeter-based Coverage Optimization to Improve Lifetime in Wireless Sensor Networks"
44 %Authors: Ali Kadhum Idrees, Karine Deschinkela, Michel Salomon and Raphael Couturier
46 \section*{Response to Reviewer No. 1 Comments}
53 \noindent {\textbf{3. \textsc{Reviewer's comment:} } } The communication and information sharing required to
54 cooperate and make these decisions was not discussed.\\
56 \textcolor{blue}{\textbf{\textsc{Answer:} The communication and information
57 sharing required to cooperate and make these decisions is discussed at the
58 end of page 8. Position coordinates, remaining energy, sensor node ID, and
59 number of one-hop neighbors are exchanged.}}\\
61 \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.}}\\
63 \textcolor{green}{\textbf{\textsc{Answer:} Right, we have included more description about the INFO packet and the ActiveSleep packet at the end of section~3.}}\\
65 \noindent {\textbf{7. \textsc{Reviewer's comment:}}} The methodology is implemented in OMNeT++ (network simulator)
66 and tested against 2 existing algorithms and a previously developed method by
67 the authors. The simulation results are thorough and show that the proposed
68 method improves the coverage and network lifetime compared with the 3 existing
69 methods. The results are similar to previous work done by their team.\\
71 \textcolor{blue}{\textbf{\textsc{Answer:} Although the study conducted in this
72 paper reuses the same protocol presented in our previous work, we focus in
73 this paper on the mathematical optimization model developed to schedule
74 nodes activities. We deliberately chose to keep the same performance
75 indicators to compare the results obtained with this new formulation with
76 other existing algorithms.}}\\
78 \textcolor{red}{\textbf{\textsc{Reviewer's response:}
79 I agree that you should show the same performance indicators and that this paper is
80 about the way you formulated the problem. The mathematical optimization model is the main
81 contribution but it's less convincing since the results are slightly better if not the same for the two
82 methodologies you have developed. Could you include some other measure that shows that the
83 PeCO is better? Maybe include computation time or something that is as convincing as the energy
84 consumed per sensor.}}\\
86 \textcolor{green}{\textbf{\textsc{Answer:} In fact, we defined in section 5.1 a new performance metric linked to the energy, called Energy Saving Ratio (ESR). We added a new section (5.2.3) in the result part related to this performance metric which shows that our PeCO protocol provides better energy saving compared with other approaches.}}\\
90 \noindent {8. \textbf{\textsc{Reviewer's comment:}}} Since this paper is attacking the coverage problem, I would
91 like to see more information on the amount of coverage the algorithm is
92 achieving. It seems that there is a tradeoff in this algorithm that allows the
93 network to increase its lifetime but does not improve the coverage ratio. This
94 may be an issue if this approach is used in an application that requires high
97 \textcolor{blue}{\textbf{\textsc{Answer:} Your remark is very interesting. Indeed,
98 Figures 8(a) and (b) highlight this result. The PeCO protocol allows to achieve
99 a coverage ratio greater than $50\%$ for far more periods than the others
100 three methods, but for applications requiring a high level of coverage
101 (greater than $95\%$), the DiLCO method is more efficient. It is explained at
102 the end of Section 5.2.4.}}\\
104 \textcolor{red}{\textbf{\textsc{Reviewer's response:}
105 I'm glad you added the explanation. I am confused with your conclusion in the last
106 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
107 you would want to have a coverage ratio of $50\%$? This seems like a very small ratio and as you
108 increase it, DiLCO becomes the methodology that has the maximum network lifetime. If you don't
109 include application examples, your statement "Indeed there are applications that do not require a
110 100$\%$ coverage of the area to be monitored." stronger. }}\\
112 \textcolor{green}{\textbf{\textsc{Answer:} Thank you so much for your suggestion, we modified the sentence at the end of Section 5.2.5. (previously Section 5.2.4.). As recommended, we added some applications examples. We also changed the figure 10 (previously figure 9) by replacing DilCO/50 and PecO/50 by DilCO/70 and PeCO/70.}}\\