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[Sensornets15.git] / Example.tex

diff --git a/Example.tex b/Example.tex
index c30cff51112364dea3d5a5c685cef7ee903e0bec..06be2737b984dd37e7e399b71be63edb87edfb7f 100644 (file)
--- a/Example.tex
+++ b/Example.tex
@@ -26,7 +26,8 @@
 
 %\title{Authors' Instructions  \subtitle{Preparation of Camera-Ready Contributions to SCITEPRESS Proceedings} }
 
 
 %\title{Authors' Instructions  \subtitle{Preparation of Camera-Ready Contributions to SCITEPRESS Proceedings} }
 

-\title{Distributed Lifetime Coverage Optimization Protocol in Wireless Sensor Networks}
+\title{Distributed Lifetime Coverage Optimization Protocol \\
+  in Wireless Sensor Networks}

 
 \author{Ali Kadhum Idrees$^{a,b}$, Karine Deschinkel$^{a}$,\\ Michel Salomon$^{a}$, and Rapha\"el Couturier$^{a}$\\
 $^{a}$FEMTO-ST Institute, UMR 6174 CNRS, \\ University  Bourgogne  Franche-Comt\'e, Belfort, France\\
 
 \author{Ali Kadhum Idrees$^{a,b}$, Karine Deschinkel$^{a}$,\\ Michel Salomon$^{a}$, and Rapha\"el Couturier$^{a}$\\
 $^{a}$FEMTO-ST Institute, UMR 6174 CNRS, \\ University  Bourgogne  Franche-Comt\'e, Belfort, France\\


@@ -78,20 +79,30 @@ email: ali.idness@edu.univ-fcomte.fr,\\ $\lbrace$karine.deschinkel, michel.salom
 \label{sec:introduction}
 
 \noindent 
 \label{sec:introduction}
 
 \noindent 

-Energy efficiency is  a crucial issue in wireless  sensor networks since sensory
+Energy efficiency is  a crucial issue in wireless sensor  networks since sensory

 consumption, in  order to  maximize the network  lifetime, represents  the major
 difficulty when designing WSNs. As a consequence, one of the scientific research
 challenges in  WSNs, which has  been addressed by  a large amount  of literature
 during the  last few  years, is  the design of  energy efficient  approaches for
 consumption, in  order to  maximize the network  lifetime, represents  the major
 difficulty when designing WSNs. As a consequence, one of the scientific research
 challenges in  WSNs, which has  been addressed by  a large amount  of literature
 during the  last few  years, is  the design of  energy efficient  approaches for

-coverage and connectivity~\cite{conti2014mobile}.   Coverage reflects how well a
+coverage and connectivity~\cite{conti2014mobile}.  Coverage  reflects how well a

 sensor  field is  monitored. On  the one  hand we  want to  monitor the  area of
 sensor  field is  monitored. On  the one  hand we  want to  monitor the  area of

-interest in the most efficient way~\cite{Nayak04}.  On the other hand we want to
-use  as little energy  as possible.   Sensor nodes  are battery-powered  with no
-means  of recharging  or replacing,  usually  due to  environmental (hostile  or
-unpractical environments)  or cost reasons.   Therefore, it is desired  that the
-WSNs are deployed  with high densities so as to  exploit the overlapping sensing
-regions of some sensor  nodes to save energy by turning off  some of them during
-the sensing phase to prolong the network lifetime. \textcolor{blue}{A WSN can use various types of sensors such as \cite{ref17,ref19}: thermal, seismic, magnetic, visual, infrared, acoustic, and radar. These sensors are capable of observing  different physical conditions such as: temperature, humidity, pressure, speed, direction, movement, light, soil makeup, noise levels, presence or absence of certain kinds of objects, and mechanical stress levels on attached objects. Consequently, there is a wide range of WSN applications such as~\cite{ref22}: health-care, environment, agriculture, public safety, military, transportation systems, and industry applications.}
+interest in the most  efficient way~\cite{Nayak04}, \textcolor{blue}{which means
+  that we want to maintain the best coverage as long as possible}.  On the other
+hand  we  want  to  use  as   little  energy  as  possible.   Sensor  nodes  are
+battery-powered  with  no means  of  recharging  or  replacing, usually  due  to
+environmental (hostile or unpractical environments) or cost reasons.  Therefore,
+it is desired  that the WSNs are  deployed with high densities so  as to exploit
+the overlapping sensing  regions of some sensor nodes to  save energy by turning
+off  some   of  them   during  the   sensing  phase   to  prolong   the  network
+lifetime.  \textcolor{blue}{A WSN  can  use  various types  of  sensors such  as
+  \cite{ref17,ref19}:  thermal, seismic,  magnetic, visual,  infrared, acoustic,
+  and  radar.  These  sensors  are   capable  of  observing  different  physical
+  conditions  such  as:  temperature,   humidity,  pressure,  speed,  direction,
+  movement, light,  soil makeup,  noise levels, presence  or absence  of certain
+  kinds  of  objects,   and  mechanical  stress  levels   on  attached  objects.
+  Consequently, there is a wide  range of WSN applications such as~\cite{ref22}:
+  health-care, environment, agriculture, public safety, military, transportation
+  systems, and industry applications.}

 
 In this  paper we design  a protocol that  focuses on the area  coverage problem
 with  the objective  of maximizing  the network  lifetime. Our  proposition, the
 
 In this  paper we design  a protocol that  focuses on the area  coverage problem
 with  the objective  of maximizing  the network  lifetime. Our  proposition, the


@@ -116,9 +127,10 @@ framework of the  DiLCO approach and the coverage problem  formulation.  In this
 paper  we   made  more  realistic   simulations  by  taking  into   account  the
 characteristics of  a Medusa II sensor  ~\cite{raghunathan2002energy} to measure
 the energy consumption and the computation  time.  We have implemented two other
 paper  we   made  more  realistic   simulations  by  taking  into   account  the
 characteristics of  a Medusa II sensor  ~\cite{raghunathan2002energy} to measure
 the energy consumption and the computation  time.  We have implemented two other

-existing \textcolor{blue}{and distributed approaches}(DESK ~\cite{ChinhVu}, and GAF  ~\cite{xu2001geography}) in order to  compare their performances
-with our approach.  We also focus on performance analysis based on the number of
-subregions. 
+existing \textcolor{blue}{and distributed approaches} (DESK ~\cite{ChinhVu}, and
+GAF ~\cite{xu2001geography})  in order  to compare  their performances  with our
+approach.   We  also focus  on  performance  analysis  based  on the  number  of
+subregions.

 % MODIF - END
 
 The remainder  of the  paper continues with  Section~\ref{sec:Literature Review}
 % MODIF - END
 
 The remainder  of the  paper continues with  Section~\ref{sec:Literature Review}


@@ -290,23 +302,37 @@ and each sensor node will have five possible status in the network:
 \end{itemize}
 %\end{enumerate}
 
 \end{itemize}
 %\end{enumerate}
 

-An outline of the  protocol implementation is given by Algorithm~\ref{alg:DiLCO}
+An outline of the protocol  implementation is given by Algorithm~\ref{alg:DiLCO}

 which describes  the execution of  a period  by a node  (denoted by $s_j$  for a
 which describes  the execution of  a period  by a node  (denoted by $s_j$  for a

-sensor  node indexed by  $j$). At  the beginning  a node  checks whether  it has
-enough energy to stay active during the next sensing phase. If yes, it exchanges
-information  with  all the  other  nodes belonging  to  the  same subregion:  it
-collects from each node its position coordinates, remaining energy ($RE_j$), ID,
-and  the number  of  one-hop neighbors  still  alive. Once  the  first phase  is
-completed, the nodes  of a subregion choose a leader to  take the decision based
-on  the  following  criteria   with  decreasing  importance:  larger  number  of
-neighbors, larger remaining energy, and  then in case of equality, larger index.
-After that,  if the sensor node is  leader, it will execute  the integer program
-algorithm (see Section~\ref{cp})  which provides a set of  sensors planned to be
-active in the next sensing phase. As leader, it will send an Active-Sleep packet
-to each sensor  in the same subregion to  indicate it if it has to  be active or
-not.  Alternately, if  the  sensor  is not  the  leader, it  will  wait for  the
-Active-Sleep packet to know its state for the coming sensing phase.
-
+sensor node  indexed by  $j$). At  the beginning  a node  checks whether  it has
+enough  energy  \textcolor{blue}{(its energy  should  be  greater than  a  fixed
+  treshold $E_{th}$)} to  stay active during the next sensing  phase. If yes, it
+exchanges information with all the other  nodes belonging to the same subregion:
+it collects from each node  its position coordinates, remaining energy ($RE_j$),
+ID,  and the  number of  one-hop neighbors  still alive.   \textcolor{blue}{INFO
+  packet contains two parts: header and  data payload. The sensor ID is included
+  in  the header,  where the  header  size is  8  bits. The  data part  includes
+  position coordinates (64 bits), remaining energy  (32 bits), and the number of
+  one-hop live neighbors (8 bits). Therefore the  size of the INFO packet is 112
+  bits.} Once the  first phase is completed,  the nodes of a  subregion choose a
+leader to  take the  decision based  on the  following criteria  with decreasing
+importance: larger  number of  neighbors, larger remaining  energy, and  then in
+case of equality,  larger index.  After that,  if the sensor node  is leader, it
+will  solve an  integer program  (see Section~\ref{cp}).   \textcolor{blue}{This
+  integer program  contains boolean variables  $X_j$ where ($X_j=1$)  means that
+  sensor $j$ will be active in the  next sensing phase. Only sensors with enough
+  remaining energy are  involved in the integer  program ($J$ is the  set of all
+  sensors  involved).  As  the  leader consumes  energy  (computation energy  is
+  denoted by $E^{comp}$) to solve the  optimization problem, it will be included
+  in the integer program only if it has enough energy to achieve the computation
+  and to  stay alive during the  next sensing phase, that  is to say if  $RE_j >
+  E^{comp}+E_{th}$. Once  the optimization problem  is solved, each  leader will
+  send an ActiveSleep packet to each sensor in the same subregion to indicate it
+  if it has to be active or not.  Otherwise, if the sensor is not the leader, it
+  will wait for the ActiveSleep packet to  know its state for the coming sensing
+  phase.}
+%which provides a set of  sensors planned to be
+%active in the next sensing phase.

 
 \begin{algorithm}[h!]                
 
 
 \begin{algorithm}[h!]                
 


@@ -354,7 +380,7 @@ We formulate the coverage optimization problem with an integer program.
 The objective function consists in minimizing the undercoverage and the overcoverage of the area as suggested in \cite{pedraza2006}. 
 The area coverage problem is expressed as the coverage of a fraction of points called primary points. 
 Details on the choice and the number of primary points can be found in \cite{idrees2014coverage}. The set of primary points is denoted by $P$
 The objective function consists in minimizing the undercoverage and the overcoverage of the area as suggested in \cite{pedraza2006}. 
 The area coverage problem is expressed as the coverage of a fraction of points called primary points. 
 Details on the choice and the number of primary points can be found in \cite{idrees2014coverage}. The set of primary points is denoted by $P$

-and the set of sensors by $J$. As we consider a boolean disk coverage model, we use the boolean indicator $\alpha_{jp}$ which is equal to 1 if the primary point $p$ is in the sensing range of the sensor $j$. The binary variable $X_j$ represents the activation or not of the sensor $j$. So we can express the number of  active sensors  that cover  the primary  point $p$ by $\sum_{j \in J} \alpha_{jp} * X_{j}$. We deduce the overcoverage denoted by $\Theta_p$ of the primary point $p$ :
+and the set of alive sensors by $J$. As we consider a boolean disk coverage model, we use the boolean indicator $\alpha_{jp}$ which is equal to 1 if the primary point $p$ is in the sensing range of the sensor $j$. The binary variable $X_j$ represents the activation or not of the sensor $j$. So we can express the number of  active sensors  that cover  the primary  point $p$ by $\sum_{j \in J} \alpha_{jp} * X_{j}$. We deduce the overcoverage denoted by $\Theta_p$ of the primary point $p$ :

 \begin{equation}
  \Theta_{p} = \left \{ 
 \begin{array}{l l}
 \begin{equation}
  \Theta_{p} = \left \{ 
 \begin{array}{l l}


@@ -398,9 +424,14 @@ X_{j} \in \{0,1\}, &\forall j \in J
 \end{array}
 \right.
 \end{equation}
 \end{array}
 \right.
 \end{equation}

-The objective function is a weighted sum of overcoverage and undercoverage. The goal is to limit the overcoverage in order to activate a minimal number of sensors while simultaneously preventing undercoverage. Both  weights $w_\theta$  and $w_U$ must  be carefully  chosen in
-order to  guarantee that the  maximum number of  points are covered  during each
-period.
+The objective function is a weighted sum of overcoverage and undercoverage. The goal is to limit the overcoverage in order to activate a minimal number of sensors while simultaneously preventing undercoverage.  \textcolor{blue}{ By
+    choosing  $w_{U}$ much  larger than $w_{\theta}$,  the coverage  of a
+    maximum of  primary points  is ensured.  Then for the  same number  of covered
+    primary points,  the solution  with a  minimal number  of active  sensors is
+    preferred. }
+%Both  weights $w_\theta$  and $w_U$ must  be carefully  chosen in
+%order to  guarantee that the  maximum number of  points are covered  during each
+%period.

 % MODIF - END
 
 
 % MODIF - END