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[ThesisAli.git] / CHAPITRE_06.tex

diff --git a/CHAPITRE_06.tex b/CHAPITRE_06.tex
index 33c8fa3d4f52faf855ee6679076e57206277a74c..66f0e6a60a94373c698e2f3f696b9dc13ab15d1e 100644 (file)
--- a/CHAPITRE_06.tex
+++ b/CHAPITRE_06.tex
@@ -132,7 +132,7 @@ In the PeCO protocol,  the  scheduling  of  the  sensor nodes'  activities  is f
 
 \noindent The  WSN area of interest is, in a  first step, divided  into regular homogeneous subregions  using a divide-and-conquer  algorithm. In a  second step our  protocol  will  be  executed  in a distributed way in each subregion simultaneously to schedule nodes' activities for one sensing period. Sensor nodes  are assumed to be deployed  almost uniformly over the  region. The regular subdivision  is made such that the number of hops between  any pairs of sensors inside a subregion is less than or equal to 3.
 
 
 \noindent The  WSN area of interest is, in a  first step, divided  into regular homogeneous subregions  using a divide-and-conquer  algorithm. In a  second step our  protocol  will  be  executed  in a distributed way in each subregion simultaneously to schedule nodes' activities for one sensing period. Sensor nodes  are assumed to be deployed  almost uniformly over the  region. The regular subdivision  is made such that the number of hops between  any pairs of sensors inside a subregion is less than or equal to 3.
 

-As  shown in  Figure~\ref{fig2}, node  activity  scheduling is  produced by  our protocol in a periodic manner. Each period is divided into 4 stages: Information (INFO)  Exchange,  Leader Election,  Decision  (the  result of  an  optimization problem),  and  Sensing.   For  each  period, there  is  exactly  one  set  cover responsible for  the sensing task.  Protocols  based on a periodic  scheme, like PeCO, are more  robust against an unexpected  node failure. On the  one hand, if a node failure is discovered before  taking the decision, the corresponding sensor
+As shown in  Figure~\ref{fig2}, node  activity  scheduling is  produced by  our protocol in a periodic manner. Each period is divided into 4 stages: Information (INFO)  Exchange,  Leader Election,  Decision  (the  result of  an  optimization problem),  and  Sensing.   For  each  period, there  is  exactly  one  set  cover responsible for  the sensing task.  Protocols  based on a periodic  scheme, like PeCO, are more  robust against an unexpected  node failure. On the  one hand, if a node failure is discovered before  taking the decision, the corresponding sensor

 node will  not be considered  by the optimization  algorithm. On  the other hand, if the sensor failure happens after  the decision, the sensing task of the network will be temporarily affected: only  during the period of sensing until a new period starts, since a new set cover will take charge of the sensing task in the next period. The energy consumption and some other constraints can easily be taken  into  account since  the  sensors  can  update  and then  exchange  their information (including their  residual energy) at the beginning  of each period. However, the pre-sensing  phases (INFO Exchange, Leader  Election, and Decision)
 are energy consuming, even for nodes that will not join the set cover to monitor the area.
 
 node will  not be considered  by the optimization  algorithm. On  the other hand, if the sensor failure happens after  the decision, the sensing task of the network will be temporarily affected: only  during the period of sensing until a new period starts, since a new set cover will take charge of the sensing task in the next period. The energy consumption and some other constraints can easily be taken  into  account since  the  sensors  can  update  and then  exchange  their information (including their  residual energy) at the beginning  of each period. However, the pre-sensing  phases (INFO Exchange, Leader  Election, and Decision)
 are energy consuming, even for nodes that will not join the set cover to monitor the area.
 


@@ -209,7 +209,14 @@ The sensors  inside a same  region cooperate to  elect a leader.   The selection
 \item larger  remaining energy;
 \item and then  in case  of equality,  larger index.
 \end{enumerate}
 \item larger  remaining energy;
 \item and then  in case  of equality,  larger index.
 \end{enumerate}

-Once chosen, the leader collects information  to formulate and solve the integer program  which allows  to construct  the set  of active  sensors in  the sensing stage.
+Once chosen, the leader collects information  to formulate and solve the integer program  which allows  to construct  the set  of active  sensors in  the sensing stage. \textcolor{blue}{The flowchart of PeCO protocol executed in each sensor node is presented in Figure \ref{flow6}.} 
+
+\begin{figure}[ht!]
+\centering
+\includegraphics[scale=0.45]{Figures/ch6/Algo3.pdf} % 70mm
+\caption{The flowchart of PeCO protocol.}
+\label{flow6}
+\end{figure} 

 
 
 \section{Perimeter-based Coverage Problem Formulation}
 
 
 \section{Perimeter-based Coverage Problem Formulation}