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 \section{Introduction}
 \label{ch1:sec:01}
 The wireless networking has received more attention and fast growth in the last decade. The growing demand for the use of wireless applications and emerging the wireless devices such as portable computers, cellular phones, and personal digital assistants (PDAs) have led to develop different infrastructures of wireless networks. The wireless networks can be classified into two classes based on the network architecture~\cite{ref154,ref155}: Infrastructure-based networks that consist of a fixed network structure such as cellular networks and wireless local-area networks
 \section{Introduction}
 \label{ch1:sec:01}
 The wireless networking has received more attention and fast growth in the last decade. The growing demand for the use of wireless applications and emerging the wireless devices such as portable computers, cellular phones, and personal digital assistants (PDAs) have led to develop different infrastructures of wireless networks. The wireless networks can be classified into two classes based on the network architecture~\cite{ref154,ref155}: Infrastructure-based networks that consist of a fixed network structure such as cellular networks and wireless local-area networks

-(WLANs); and Infrastructureless networks that constructed dynamically by the cooperation of the wireless nodes in the network, where each node capable of sending the packets and taking the decision based on the network status. Examples of such type of networks include mobile ad hoc networks and wireless sensor networks. Figure~\ref{WNT} shows the taxonomy of wireless networks.
+(WLANs); and Infrastructureless networks that are constructed dynamically by the cooperation of the wireless nodes in the network, where each node is capable of sending the packets and taking the decision based on the network status. Examples of such type of networks include mobile ad hoc networks and wireless sensor networks. Figure~\ref{WNT} shows the taxonomy of wireless networks.

 
 \begin{figure}[h!]
 \centering
 
 \begin{figure}[h!]
 \centering


@@ -22,14 +22,16 @@ The wireless networking has received more attention and fast growth in the last
 \label{WNT}
 \end{figure}
 
 \label{WNT}
 \end{figure}
 

-In recent years, there is increasing interest in Wireless Sensor Networks (WSNs) by many researchers around the world. WSNs are considered as one of the most researched fields in the last decade due to the extensive research in this discipline. It represents a special case of the Ad Hoc networks. Recent advances in wireless networking, Micro-Electro-Mechanical Systems (MEMS), and embedded computing technologies have led to construct low-cost, small-sized, and low-power sensor nodes. These sensor nodes can perform detection, computation, and data communication of surrounding environment. A WSN includes a large number of sensor nodes that can sense, process, and transmit data over a wireless communication. The sensor nodes communicate with each other by using multi-hop wireless communications and cooperate together to monitor the area of interest. The measured data is reported to a monitoring center called sink for further analysis~\cite{ref1,ref2}. The WSN receives the orders from the end user by means of the sink. These orders specify data aggregation, computation and delivery missions to wireless sensor nodes, after that the sensed measurements are received from the WSN by the sink~\cite{ref3}. The cooperation among the wireless sensor nodes in WSNs has been led to several advantages over the traditional wireless ad-hoc networks, like self-organization, rapid deployment, flexibility, and inherent intelligent-processing capability~\cite{ref5}.
+In recent years, there is increasing interest in Wireless Sensor Networks (WSNs) by many researchers around the world. 
+%WSNs are considered as one of the most researched fields in the last decade due to the extensive research in this discipline. 
+It represents a special case of the Ad Hoc networks. Recent advances in wireless networking, Micro-Electro-Mechanical Systems (MEMS), and embedded computing technologies have led to construct low-cost, small-sized, and low-power sensor nodes. These sensor nodes can perform detection, computation, and data communication of surrounding environment. A WSN includes a large number of sensor nodes that can sense, process, and transmit data over a wireless communication. The sensor nodes communicate with each other by using multi-hop wireless communications and cooperate together to monitor the area of interest. The measured data is reported to a monitoring center called sink for further analysis~\cite{ref1,ref2}. The WSN receives the orders from the end user by means of the sink. These orders specify data aggregation, computation and delivery missions to wireless sensor nodes, after that the sensed measurements are received from the WSN by the sink~\cite{ref3}. The cooperation among the wireless sensor nodes in WSNs has been led to several advantages over the traditional wireless ad-hoc networks, like self-organization, rapid deployment, flexibility, and inherent intelligent-processing capability~\cite{ref5}.

 
 
 \section{Wireless Sensor Network Architecture} 
 \label{ch1:sec:02}
 A typical WSN architecture consists of a set of a typical wireless sensor nodes, which are capable of sensing the surrounded physical phenomenon such as fire in the forest (see~figure~\ref{wsn}), and then send the sensed data to a controller node called a sink. One or more sink in WSN are responsible for collecting and processing the received sensed data, and then send that data through the Internet to the end-user. 
 
 
 
 \section{Wireless Sensor Network Architecture} 
 \label{ch1:sec:02}
 A typical WSN architecture consists of a set of a typical wireless sensor nodes, which are capable of sensing the surrounded physical phenomenon such as fire in the forest (see~figure~\ref{wsn}), and then send the sensed data to a controller node called a sink. One or more sink in WSN are responsible for collecting and processing the received sensed data, and then send that data through the Internet to the end-user. 
 

-In this WSN architecture, the basic element is a typical wireless sensor node that composed of four major units~\cite{ref17,ref18}: sensing, computation, communication, and power. In addition, there are three optional units, which can be combined with the sensor node such as localization system, mobilizer, and power generator. Figure~\ref{twsn} shows the components of a typical wireless sensor node~\cite{ref17}.
+In this WSN architecture, the basic element is a typical wireless sensor node that is composed of four major units~\cite{ref17,ref18}: sensing, computation, communication, and power. In addition, there are three optional units, which can be combined with the sensor node such as localization system, mobilizer, and power generator. Figure~\ref{twsn} shows the components of a typical wireless sensor node~\cite{ref17}.

 
 \begin{figure}[h!]
 \centering
 
 \begin{figure}[h!]
 \centering


@@ -41,9 +43,9 @@ In this WSN architecture, the basic element is a typical wireless sensor node th
 \begin{enumerate} [(I)]
 \item \textbf{Sensing Unit:} consists of two main parts: sensors and analog to digital converters (ADCs). It is responsible for sensing the physical phenomena. The analog signal produced by the sensors is converted into digital data by ADC. The resulted digital data is sent to the computation unit  for further processing.
 
 \begin{enumerate} [(I)]
 \item \textbf{Sensing Unit:} consists of two main parts: sensors and analog to digital converters (ADCs). It is responsible for sensing the physical phenomena. The analog signal produced by the sensors is converted into digital data by ADC. The resulted digital data is sent to the computation unit  for further processing.
 

-\item \textbf{Computation Unit:} The main purpose of this unit is to manage and manipulate the instructions that related to sensing, communication, and self-organization. This allows to the sensor node cooperates with other sensor nodes in order to perform the allocated sensing tasks. It is composed of a processor chip, an active short-term memory for storing the sensed data, an internal flash memory for storing program instructions, and an internal timer.
+\item \textbf{Computation Unit:} The main purpose of this unit is to manage and manipulate the instructions that are related to sensing, communication, and self-organization. This allows the sensor node to cooperate with other sensor nodes in order to perform the allocated sensing tasks. It is composed of a processor chip, an active short-term memory for storing the sensed data, an internal flash memory for storing program instructions, and an internal timer.

 
 

-\item \textbf{Communication Unit:} It is responsible for all data transmission and reception of the sensor node that are performed by the transceiver circuitry. A transceiver circuit is composed of a mixer, frequency synthesizer, voltage-controlled oscillator (VCO), phase-locked loop (PLL), demodulator, and power amplifiers, all of which consume valuable power~\cite{ref19}.
+\item \textbf{Communication Unit:} It is responsible for all data transmission and reception of the sensor node that are performed by the transceiver circuitry. A transceiver circuit is composed of a mixer, frequency synthesizer, voltage-controlled oscillator (VCO), phase-locked loop (PLL), demodulator, and power amplifiers. They consume valuable power~\cite{ref19}.

 
 \item \textbf{Power Unit:} This unit represents the most significant part of wireless sensor node.  It supplies the other units by the needed power. 
 
 
 \item \textbf{Power Unit:} This unit represents the most significant part of wireless sensor node.  It supplies the other units by the needed power. 
 


@@ -53,11 +55,11 @@ Furthermore, additional components can be incorporated into wireless sensor node
 
 \begin{enumerate} [(I)]         
 
 
 \begin{enumerate} [(I)]         
 

-\item \textbf{Localization System:} It is important that the wireless sensor node is equipped with a location finding system because it is necessary for many WSN applications. It is required for routing algorithms and sensing coverage algorithms, which need information about the location of the wireless sensor nodes. The location finding system is composed of a Global Positioning System (GPS) or a discovery algorithm that executes a localization system to provides information about the location of wireless sensor node using distributed computation.
+\item \textbf{Localization System:} It is important that the wireless sensor node is equipped with a location finding system because it is necessary for many WSN applications. It is required for routing algorithms and sensing coverage algorithms, which need information about the location of the wireless sensor nodes. The location finding system is composed of a Global Positioning System (GPS) or a discovery algorithm that executes a localization system to provide information about the location of wireless sensor node using distributed computation \cite{ref232,ref233}.

 
 

-\item \textbf{Mobilizer:} The mobility function is sometimes needed in many applications to move the wireless sensor node from one location to another so as to perform a certain task in WSN. Therefore, it is necessary that the wireless sensor node equipped with the mobilizer system for such applications. A high energy consumption is needed to support the mobility in wireless sensor node, and it should be supported efficiently. The movement of wireless sensor node is controlled by the mobility function with cooperation with the sensing unit and the computation unit.
+\item \textbf{Mobilizer:} The mobility function is sometimes needed in many applications to move the wireless sensor node from one location to another so as to perform a certain task in WSN. Therefore, it is necessary to equip the node  with the mobilizer system for such applications. A high energy consumption is needed to support the mobility in wireless sensor node, and it should be supported efficiently. The movement of wireless sensor node is controlled by the mobility function with cooperation with the sensing unit and the computation unit.

 
 

-\item \textbf{Power Generator:} Several applications in WSNs need to operate for a longer time. So, it is essential to equip the wireless sensor node with additional power source in order to prolong the network lifetime. The better energy source to generate the power for outdoor applications is a solar cell. An another power harvesting mechanisms~\cite{ref20,ref21} for thermal, motion, vibration, micro water flow, Biological, pressure gradients, and electromagnetic radiation energy harvesting can be used to yield increasing power output to extend the network lifetime. 
+\item \textbf{Power Generator:} Several applications in WSNs need to operate for a longer time. So, it is essential to equip the wireless sensor node with additional power source in order to prolong the network lifetime. The better energy source to generate the power for outdoor applications is a solar cell. An another power harvesting mechanisms~\cite{ref20,ref21} like thermal, motion, vibration, micro water flow, biological, pressure gradients, and electromagnetic radiation energy harvesting can be used to yield increasing power output and to extend the network lifetime. 

 \end{enumerate}
 
 \begin{figure}[h!]
 \end{enumerate}
 
 \begin{figure}[h!]


@@ -118,7 +120,7 @@ A network consists of a low-cost wireless sensor nodes, which are equipped with
 \item \textbf{Health-care Applications:} There is increasing interest and extensive research in the health-care applications. Two types of health-care systems are recognized~\cite{ref22}: vital status monitoring and remote health-care surveillance. In vital status monitoring applications, sick persons are wearing the sensors in order to oversee the state of their health and to allow medical staff to monitor and control the patient's status expeditiously. The most general used vital signs are ECG, pulse oximetry, body temperature, heart rate, and blood pressure~\cite{ref27}. These applications include  mass-casualty disaster monitoring, vital sign monitoring in hospitals, and sudden fall or epilepsy seizure detection. On the other hand, remote health-care surveillance refers to the health services that do not require continuous existence of health care. These applications include elderly monitoring, providing support to a physically impaired person, gather clinically relevant information for rehabilitation supervision~\cite{ref28}, location tracking, and medication intake monitoring~\cite{ref27}.
 
 
 \item \textbf{Health-care Applications:} There is increasing interest and extensive research in the health-care applications. Two types of health-care systems are recognized~\cite{ref22}: vital status monitoring and remote health-care surveillance. In vital status monitoring applications, sick persons are wearing the sensors in order to oversee the state of their health and to allow medical staff to monitor and control the patient's status expeditiously. The most general used vital signs are ECG, pulse oximetry, body temperature, heart rate, and blood pressure~\cite{ref27}. These applications include  mass-casualty disaster monitoring, vital sign monitoring in hospitals, and sudden fall or epilepsy seizure detection. On the other hand, remote health-care surveillance refers to the health services that do not require continuous existence of health care. These applications include elderly monitoring, providing support to a physically impaired person, gather clinically relevant information for rehabilitation supervision~\cite{ref28}, location tracking, and medication intake monitoring~\cite{ref27}.
 
 

-\item \textbf{ Environment and agriculture Applications:}
+\item \textbf{ Environment and agriculture Applications}

 \indent Several WSNs applications have been developed for the precision agriculture, cattle monitoring, and environmental monitoring.
 
 \indent Precision agriculture refers to the science of using the innovative and modern technology to improve the crop production. The WSNs are the main technology for developing of precision agriculture~\cite{ref29}. This technology contributes to increasing the agricultural yields, improving quality, and reducing costs whilst decreasing the damaging impact on the environment. The wireless sensors are distributed over the target field so as to monitor the main parameters such as soil moisture, atmospheric temperature, and creating a decision support system \cite{ref22}. The wireless sensors can be used in agricultural services like Irrigation, fertilization,  pest control, animal and pastures monitoring, horticulture(e.g., greenhouse and viticulture)~\cite{ref30}. 
 \indent Several WSNs applications have been developed for the precision agriculture, cattle monitoring, and environmental monitoring.
 
 \indent Precision agriculture refers to the science of using the innovative and modern technology to improve the crop production. The WSNs are the main technology for developing of precision agriculture~\cite{ref29}. This technology contributes to increasing the agricultural yields, improving quality, and reducing costs whilst decreasing the damaging impact on the environment. The wireless sensors are distributed over the target field so as to monitor the main parameters such as soil moisture, atmospheric temperature, and creating a decision support system \cite{ref22}. The wireless sensors can be used in agricultural services like Irrigation, fertilization,  pest control, animal and pastures monitoring, horticulture(e.g., greenhouse and viticulture)~\cite{ref30}. 


@@ -193,16 +195,16 @@ nodes in order to achieve their tasks efficiently.
 \label{emwsn}
 \end{figure}
 
 \label{emwsn}
 \end{figure}
 

-\subsection{Energy-Efficient Routing:}
+\subsection{Energy-Efficient Routing}

 
 \indent The energy-efficient routing is a significant factor in the design of WSN protocols in order to satisfy the main constraints in the hardware, power, and other resources of wireless sensor nodes~\cite{ref42}. Many challenging factors need to be taken into consideration in designing a routing protocol for WSN such as limited energy capacity, node deployment, sensor location, dynamic network, hardware resource constraints, data aggregation, latency, scalability, and fault tolerance.
 
 
 
 \indent The energy-efficient routing is a significant factor in the design of WSN protocols in order to satisfy the main constraints in the hardware, power, and other resources of wireless sensor nodes~\cite{ref42}. Many challenging factors need to be taken into consideration in designing a routing protocol for WSN such as limited energy capacity, node deployment, sensor location, dynamic network, hardware resource constraints, data aggregation, latency, scalability, and fault tolerance.
 
 

-\subsubsection{Routing Metric based on Residual Energy:} Lifetime maximization can be achieved by using the residual power of wireless sensor node as a routing metric that should be taken into account in executing the routing protocol in WSNs. The routing protocols should be concentrated on the remaining power of sensor nodes during taking the decision to select the next hop toward the destination. They should not only depend on the shortest path solution.  They prioritize routes on the basis of an energy metric (sometimes with other routing metrics). Therefore,  it is called energy-aware routing protocols.~\cite{ref45,ref46}.
+\subsubsection{Routing Metric based on Residual Energy} Lifetime maximization can be achieved by using the residual power of wireless sensor node as a routing metric that should be taken into account in executing the routing protocol in WSNs. The routing protocols should be concentrated on the remaining power of sensor nodes during taking the decision to select the next hop toward the destination. They should not only depend on the shortest path solution.  They prioritize routes on the basis of an energy metric (sometimes with other routing metrics). Therefore,  it is called energy-aware routing protocols.~\cite{ref45,ref46}.

 
 

-\subsubsection{Multipath Routing:} Represents an efficient strategy that provides reliability, security, and load balancing in order to forward packets in a limited energy and constrained resources (computation, communication, and storage) networks like WSNs~\cite{ref50}. The single path routing is simple and scalable, but it is not efficient for energy-constrained networks such as WSNs. Many multipath routing protocol summarized in~\cite{ref50,ref51}.
+\subsubsection{Multipath Routing} Represents an efficient strategy that provides reliability, security, and load balancing in order to forward packets in a limited energy and constrained resources (computation, communication, and storage) networks like WSNs~\cite{ref50}. The single path routing is simple and scalable, but it is not efficient for energy-constrained networks such as WSNs. Many multipath routing protocol summarized in~\cite{ref50,ref51}.

 
 

-\subsection{Cluster Architectures:}
+\subsection{Cluster Architectures}

 
 \indent In this strategy, the wireless sensor nodes are grouped into several groups that called clusters, each group of wireless sensor nodes are managed by a single sensor node, which is called cluster head. The cluster head takes the responsibility for managing the activities of the wireless sensor nodes in the cluster and it communicates and coordinates with other cluster heads or with the base station in the WSN. This mechanism conserves the energy in WSNs by means of~\cite{ref43,ref22}:
 
 
 \indent In this strategy, the wireless sensor nodes are grouped into several groups that called clusters, each group of wireless sensor nodes are managed by a single sensor node, which is called cluster head. The cluster head takes the responsibility for managing the activities of the wireless sensor nodes in the cluster and it communicates and coordinates with other cluster heads or with the base station in the WSN. This mechanism conserves the energy in WSNs by means of~\cite{ref43,ref22}:
 


@@ -217,7 +219,7 @@ nodes in order to achieve their tasks efficiently.
 \indent In addition, the clustering supports network scalability in WSNs~\cite{ref43,ref44}. The clustering approach represents an efficient mechanism for scalability of WSN and providing energy-efficient data aggregation by minimizing the consumption of a limited energy by means of grouping the sensor nodes and organizing them hierarchically. Several important design considerations that should be taken into account during designing clustering algorithms such as limited energy, network lifetime, limited abilities, application dependency, secure communication, cluster formation, cluster head selection, synchronization, data aggregation, repair mechanisms, and Quality of Service (QoS)~\cite{ref161}.
 
 
 \indent In addition, the clustering supports network scalability in WSNs~\cite{ref43,ref44}. The clustering approach represents an efficient mechanism for scalability of WSN and providing energy-efficient data aggregation by minimizing the consumption of a limited energy by means of grouping the sensor nodes and organizing them hierarchically. Several important design considerations that should be taken into account during designing clustering algorithms such as limited energy, network lifetime, limited abilities, application dependency, secure communication, cluster formation, cluster head selection, synchronization, data aggregation, repair mechanisms, and Quality of Service (QoS)~\cite{ref161}.
 
 

-\subsection{Scheduling Schemes:}
+\subsection{Scheduling Schemes}

 
 \indent Many scheduling schemes have been suggested so as to decrease the energy depletion and improve the lifetime of WSNs~\cite{ref58,ref59}. These schemes deal with scheduling the states of wireless sensor nodes and putting the idle sensor nodes into sleep mode (i.e, turn off the radio unit) to save the energy. Figure~\ref{wsns} summarizes the scheduling schemes in WSNs. In this figure, the scheduling schemes are classified into two main branches~\cite{ref56,ref57}: 
 \begin{itemize}
 
 \indent Many scheduling schemes have been suggested so as to decrease the energy depletion and improve the lifetime of WSNs~\cite{ref58,ref59}. These schemes deal with scheduling the states of wireless sensor nodes and putting the idle sensor nodes into sleep mode (i.e, turn off the radio unit) to save the energy. Figure~\ref{wsns} summarizes the scheduling schemes in WSNs. In this figure, the scheduling schemes are classified into two main branches~\cite{ref56,ref57}: 
 \begin{itemize}


@@ -234,7 +236,7 @@ nodes in order to achieve their tasks efficiently.
 \end{figure}
 
 
 \end{figure}
 
 

-\subsubsection{Wake up Scheduling Schemes:}
+\subsubsection{Wake up Scheduling Schemes}

 
 \indent This section demonstrates the scheduling schemes from the point of view of schedule composition process and the framework of the wake-up schedule. In these scheduling schemes, the wake-up interval refers to the period of time at which the radio unit is turned on so as to send or receive the packets. On the other hand, the sleep interval refers to a period of time at which the radio unit is turned off so as to retain the energy of wireless sensor node. Some schemes divide the time into equal length durations of time and are called slotted schemes. The other schemes work with the time in continuous way and are called unslotted schemes. The sleep and wake up intervals are defined for the unslotted schemes, whilst for the slotted schemes, these intervals are represented as multiple slots. The wake-up schedule represents a set of a wake-up and sleep intervals, which are produced for one period. This schedule replicates to each period and it can be changed by the wake-up scheduling scheme during the different periods of time. The final goal of this wake-up schedule is to permit to exchange the data among the wireless sensor nodes in WSN during the wake-up interval. As shown in figure~\ref{wsns}, the requirement for synchronization has been categorized the wake-up scheduling into three categories~\cite{ref57}:
 
 
 \indent This section demonstrates the scheduling schemes from the point of view of schedule composition process and the framework of the wake-up schedule. In these scheduling schemes, the wake-up interval refers to the period of time at which the radio unit is turned on so as to send or receive the packets. On the other hand, the sleep interval refers to a period of time at which the radio unit is turned off so as to retain the energy of wireless sensor node. Some schemes divide the time into equal length durations of time and are called slotted schemes. The other schemes work with the time in continuous way and are called unslotted schemes. The sleep and wake up intervals are defined for the unslotted schemes, whilst for the slotted schemes, these intervals are represented as multiple slots. The wake-up schedule represents a set of a wake-up and sleep intervals, which are produced for one period. This schedule replicates to each period and it can be changed by the wake-up scheduling scheme during the different periods of time. The final goal of this wake-up schedule is to permit to exchange the data among the wireless sensor nodes in WSN during the wake-up interval. As shown in figure~\ref{wsns}, the requirement for synchronization has been categorized the wake-up scheduling into three categories~\cite{ref57}:
 


@@ -280,7 +282,7 @@ nodes in order to achieve their tasks efficiently.
 
 
 
 
 
 

-\subsubsection{Topology Control Schemes:}
+\subsubsection{Topology Control Schemes}

 
 \indent The topology control schemes deal with the redundancy in the WSNs. The WSN is always deploying with high density and in a random way, where a large number of wireless sensor nodes are usually throwing by the airplane over the area of interest. The purpose of deploying a dense WSN is to cope with the sensor failure during or after the WSN deployment and to maximize the network lifetime by means of exploiting the overlapping among the sensor nodes in the network by putting the redundant sensor nodes into sleep mode in order to benefit from it later. The major goal of topology control protocols is to dynamically adapt network topology based on requirements of application so as to minimize the number of active sensor nodes, achieve the tasks of the network, and prolong the network lifetime~\cite{ref56,ref22}. Many factors can be used to decide which sensor nodes should be turned on or off and when. The topology control schemes have been classified into two categories~\cite{ref56}: 
  
 
 \indent The topology control schemes deal with the redundancy in the WSNs. The WSN is always deploying with high density and in a random way, where a large number of wireless sensor nodes are usually throwing by the airplane over the area of interest. The purpose of deploying a dense WSN is to cope with the sensor failure during or after the WSN deployment and to maximize the network lifetime by means of exploiting the overlapping among the sensor nodes in the network by putting the redundant sensor nodes into sleep mode in order to benefit from it later. The major goal of topology control protocols is to dynamically adapt network topology based on requirements of application so as to minimize the number of active sensor nodes, achieve the tasks of the network, and prolong the network lifetime~\cite{ref56,ref22}. Many factors can be used to decide which sensor nodes should be turned on or off and when. The topology control schemes have been classified into two categories~\cite{ref56}: 
  


@@ -291,7 +293,7 @@ nodes in order to achieve their tasks efficiently.
 \end{enumerate}
 
 
 \end{enumerate}
 
 

-\subsection{Data-Driven Schemes:}
+\subsection{Data-Driven Schemes}

 
 \indent Data-driven approaches aim to decrease the amount of data sent to the sink whilst maintaining the accuracy of sensing within an acceptable level. Therefore, removing unwanted data during the transmission and restriction the sensing tasks during data acquisition can be participating in reducing the energy consumption in WSNs. 
 %Several data-driven schemes have been proposed in~\cite{ref86,ref87,ref88,ref89,ref90}.
 
 \indent Data-driven approaches aim to decrease the amount of data sent to the sink whilst maintaining the accuracy of sensing within an acceptable level. Therefore, removing unwanted data during the transmission and restriction the sensing tasks during data acquisition can be participating in reducing the energy consumption in WSNs. 
 %Several data-driven schemes have been proposed in~\cite{ref86,ref87,ref88,ref89,ref90}.


@@ -303,26 +305,26 @@ Data driven schemes are classified into two main approaches~\cite{ref59,ref22}:
 \subsubsection{Energy Efficient Data Acquisition Schemes} are concentrated on the energy consumption reduction in the sensing unit. These schemes are divided into adaptive sampling, hierarchical sampling, and model-based active sampling. In adaptive sampling, the amount of data that acquired from the transducer can be reduced by spatial or temporal correlation between data. These approaches are more efficient to be used in centralized fusion, but it consumes more energy due to requiring a high processing. While, the hierarchical sampling are more efficient when there are different types of sensors are installed on the nodes. These approaches are more energy efficient and application specific. The model-based approaches are similar to data prediction schemes. These approaches aim to decrease the data samples by using computed models and conserve the energy by means of data acquisition. 
 %\end{enumerate} 
 
 \subsubsection{Energy Efficient Data Acquisition Schemes} are concentrated on the energy consumption reduction in the sensing unit. These schemes are divided into adaptive sampling, hierarchical sampling, and model-based active sampling. In adaptive sampling, the amount of data that acquired from the transducer can be reduced by spatial or temporal correlation between data. These approaches are more efficient to be used in centralized fusion, but it consumes more energy due to requiring a high processing. While, the hierarchical sampling are more efficient when there are different types of sensors are installed on the nodes. These approaches are more energy efficient and application specific. The model-based approaches are similar to data prediction schemes. These approaches aim to decrease the data samples by using computed models and conserve the energy by means of data acquisition. 
 %\end{enumerate} 
 

-\subsection{Battery Repletion:}
+\subsection{Battery Repletion}

 
 \indent In the last years, extensive researches have been focused on energy harvesting and wireless charging techniques. These solutions represent alternate energy sources to recharge wireless sensor batteries without human intervention~\cite{ref91,ref59}.
 
 
 \indent In the last years, extensive researches have been focused on energy harvesting and wireless charging techniques. These solutions represent alternate energy sources to recharge wireless sensor batteries without human intervention~\cite{ref91,ref59}.
 

-\subsubsection{Energy Harvesting:} In energy harvesting, several sources of environmental energy have been developed so as to enable the wireless sensors to acquire energy from the surrounding environment like solar, wind energy, vibration based energy harvesting, radio signals for scavenging RF power, Thermoelectric generators, and shoe-mounted piezoelectric generator to power artificial organs~\cite{ref59}. 
+\subsubsection{Energy Harvesting} In energy harvesting, several sources of environmental energy have been developed so as to enable the wireless sensors to acquire energy from the surrounding environment like solar, wind energy, vibration based energy harvesting, radio signals for scavenging RF power, Thermoelectric generators, and shoe-mounted piezoelectric generator to power artificial organs~\cite{ref59}. 

 
 

-\subsubsection{Wireless Charging:}In wireless charging, the wireless power can be transmitted between the devices without requiring to the connection between the transmitter and the receiver. These techniques are participating in increasing the availability of WSNs and prolonging the network lifetime. Wireless charging in WSNs can be performed by using two manners: magnetic resonant coupling and electromagnetic radiation~\cite{ref22}.
+\subsubsection{Wireless Charging}In wireless charging, the wireless power can be transmitted between the devices without requiring to the connection between the transmitter and the receiver. These techniques are participating in increasing the availability of WSNs and prolonging the network lifetime. Wireless charging in WSNs can be performed by using two manners: magnetic resonant coupling and electromagnetic radiation~\cite{ref22}.

 
 

-\subsection{Radio Optimization:}
+\subsection{Radio Optimization}

 
 \indent In wireless sensor node, the radio is the most energy-consuming unit for draining the battery power. Extensive researches have been focused on decreasing the power depletion due to wireless communication by means of optimizing the radio parameters such as coding and modulation schemes; transmission power and antenna
 direction; and cognitive radio and Cooperative communications schemes~\cite{ref22}.
 
 
 \indent In wireless sensor node, the radio is the most energy-consuming unit for draining the battery power. Extensive researches have been focused on decreasing the power depletion due to wireless communication by means of optimizing the radio parameters such as coding and modulation schemes; transmission power and antenna
 direction; and cognitive radio and Cooperative communications schemes~\cite{ref22}.
 

-\subsection{Relay nodes and Sink Mobility:}
+\subsection{Relay nodes and Sink Mobility}

 \indent The relay node placement and the mobility of the sink can be considered as energy-efficient strategies, which are used to minimize the consumption of the energy and extend the lifetime of WSNs.
 %\begin{enumerate} [(I)]
 \indent The relay node placement and the mobility of the sink can be considered as energy-efficient strategies, which are used to minimize the consumption of the energy and extend the lifetime of WSNs.
 %\begin{enumerate} [(I)]

-\subsubsection{Relay node placement:} 
+\subsubsection{Relay node placement} 

 In WSN, some wireless sensor nodes in a certain region may die and this creates a hole in the WSN. This problem can be solved by placing the wireless sensor nodes in sensing field using optimal distribution or by deploying a small number of relay wireless sensor nodes with powerful capabilities. The major goal of relay nodes is the communication with other wireless sensor nodes or relay nodes~\cite{ref52}. This solution can enhance the power balancing and avoiding the overloaded wireless sensor nodes in a particular region in WSN.
 
 In WSN, some wireless sensor nodes in a certain region may die and this creates a hole in the WSN. This problem can be solved by placing the wireless sensor nodes in sensing field using optimal distribution or by deploying a small number of relay wireless sensor nodes with powerful capabilities. The major goal of relay nodes is the communication with other wireless sensor nodes or relay nodes~\cite{ref52}. This solution can enhance the power balancing and avoiding the overloaded wireless sensor nodes in a particular region in WSN.
 

-\subsubsection{Sink Mobility:} 
+\subsubsection{Sink Mobility} 

 In the WSNs include a static sink, the wireless sensor nodes, which are near the sink drain their power more rapidly compared with other sensor nodes, and this leads to WSN disconnection and limited network lifetime~\cite{ref53}. Sending all the data in WSN to the sink maximizes the overload on the sensor nodes near to sink. In order to overcome this problem and prolong the network lifetime, it is necessary to use a mobile sink to move within the area of WSN so as to collect the sensory data from the static sensor nodes over a single hop communication.  The mobile sink avoids the multi-hop communication and conserves the energy at the static sensor nodes near to the base station, extending the lifetime of WSN~\cite{ref54,ref55}.
 
  
 In the WSNs include a static sink, the wireless sensor nodes, which are near the sink drain their power more rapidly compared with other sensor nodes, and this leads to WSN disconnection and limited network lifetime~\cite{ref53}. Sending all the data in WSN to the sink maximizes the overload on the sensor nodes near to sink. In order to overcome this problem and prolong the network lifetime, it is necessary to use a mobile sink to move within the area of WSN so as to collect the sensory data from the static sensor nodes over a single hop communication.  The mobile sink avoids the multi-hop communication and conserves the energy at the static sensor nodes near to the base station, extending the lifetime of WSN~\cite{ref54,ref55}.
 
  


@@ -411,7 +413,7 @@ The coverage protocols have proposed in this dissertation use the binary disc se
 
 
 
 
 
 

-\section{Design Issues for Coverage Problems:}
+\section{Design Issues for Coverage Problems}

 \label{ch1:sec:11}
 \indent Several design issues should be considered in order to produce solutions for the coverage problems in WSNs. These design issues can be classified into~\cite{ref103}:
 
 \label{ch1:sec:11}
 \indent Several design issues should be considered in order to produce solutions for the coverage problems in WSNs. These design issues can be classified into~\cite{ref103}:
 


@@ -433,7 +435,7 @@ The coverage protocols have proposed in this dissertation use the binary disc se
 
 \end{enumerate}
 
 
 \end{enumerate}
 

-\section{Energy Consumption Modeling:} 
+\section{Energy Consumption Modeling} 

 \label{ch1:sec:9}
 \indent The WSNs have been received a lot of interests because the low energy consumption of the sensor nodes.  One of the most critical issues in WSNs is to reduce the energy consumption of the limited power battery of the sensor nodes so as to prolong the network lifetime as long as possible. In order to model the energy consumption, four states for a sensor node are used~\cite{ref140}:  transmission, reception, listening, and sleeping. In addition, two states should be taken into account: computation and sensed data acquisition. The main tasks of each of these states include:
 
 \label{ch1:sec:9}
 \indent The WSNs have been received a lot of interests because the low energy consumption of the sensor nodes.  One of the most critical issues in WSNs is to reduce the energy consumption of the limited power battery of the sensor nodes so as to prolong the network lifetime as long as possible. In order to model the energy consumption, four states for a sensor node are used~\cite{ref140}:  transmission, reception, listening, and sleeping. In addition, two states should be taken into account: computation and sensed data acquisition. The main tasks of each of these states include: