**5. Deployment model of nodes**

Wireless transmission is an important factor that allowed WSN to deploy successfully. It has been increased in recent years and has been appeared even in smart house systems [1, 2]. Many communication technologies, such as IrDA, Bluetooth, and Zigbee, GSM/GPRS (General Packet Radio Service), PSTN (Public Switched Telephone Network), etc. have been developed for different locations [16, 18]. A kind of real-time system in which multiple sensors connected simultaneously to one gateway unit it become indispensable, and they are transformed into wireless sensor networks (WSNs) [10]. A mobile sensor sends data to the nearest sensor which is transferred later to the BS via the shortest path as it is shown in **Figure 2**. Indeed, when a sensor has to inform the administrator of an event or simply send the information collected, it must first pass this information to the sink (see. **Figure 2**). It is the one that will transfer the understood information to the administrator through an extensive network such as the Internet or more simply via the satellite. Conversely, when the administrator wants to send information or requests to the

**49**

**Figure 5.**

*OSI MODEL and their signification [4, 8, 10, 18].*

*Design Model and Deployment Fashion of Wireless Sensor Networks*

of potential applications that we will see later in this chapter.

various sensors of the network or one, in particular, the two will have to go through

The routing algorithm is used to accomplish this task to support multi-hop communication inside the network by the nodes [9]. So, we will understand how to communicate this data and how to monitor the information shared between nodes. These data are typically relayed from node to another and these links are dynamically built on -demand (reactive routing) or dynamically re-computed (proactiverouting) [3, 12]. Proactive routing protocol: they are presented on the same routing principle as wired networks. The routes in this type of routing are calculated in advance - each node encountered updates several routing tables by exchanging packets between neighbors. Also, they luckily tend to have a communication brink between them for reason that path computation is generated upon request or the occurrence of specific events from the application data to the sink node. Preferentially, the node should be able to enter and leave the network [1].

It turns out that the use of these technologies makes information more accessible by the user. This would significantly improve people's living quality. Especially that wired network has some problems, such as inconvenience and high cost, unsatisfactory security assurance [2]. Therefore, their concept in sensing with their capabilities in transferring the data into a signal has paved the way for the creation of a lot

*DOI: http://dx.doi.org/10.5772/intechopen.94256*

the sink to reach its targets [4, 11].

#### *Design Model and Deployment Fashion of Wireless Sensor Networks DOI: http://dx.doi.org/10.5772/intechopen.94256*

*Wireless Sensor Networks - Design, Deployment and Applications*

modules in more detail [5, 6, 9, 14].

to our next point.

**5. Deployment model of nodes**

standable by the processing unit.

shows all of these different modules. In our case, let us dwell on each of these

• Captive Unit: it is the module for which wireless sensors have been developed. It breaks down itself into two subunits. The "sensor" or receiver will recognize the event to be monitored by the sensor. Then, it will perceive the analog signals emitted by the receiver to transform them into a digital signal under-

• The Processing Unit: Consisting of a processor, and sometimes even a small storage memory operates using an operating system specially designed for this type of medium (for example: open source TinyOS). This unit executes communication protocols by allowing the node to collaborate with the rest of the network. Under certain conditions, the processing unit can analyze the

• The Transceiver Unit: it takes care of the operations on the transmission and reception of data. This emission is either optical or the radio-frequency type.

• The Power Unit: being the major constraint of this technology, it was necessary to insert a module within the sensors allowing sparse management of the energy in the sensor. Therefore, it will be responsible for distributing the energy available in the sensor optimally; for example, by putting inactive components on standby. It will also be responsible for managing the energy

recharging system, but it provided that a module for this purpose.

• Location Finding System: it provides the location information required by certain routing protocols. Usually, it is a Global Positioning System (GPS).

• Mobilizer: in the case, certain larger sensors are possible to move them. This system what will have the task assigned to it. The different components of the sensor node described above define its possibilities. In other words, they let you know what a sensor is capable of doing and how far it can do it. It brings us

Wireless transmission is an important factor that allowed WSN to deploy successfully. It has been increased in recent years and has been appeared even in smart house systems [1, 2]. Many communication technologies, such as IrDA, Bluetooth, and Zigbee, GSM/GPRS (General Packet Radio Service), PSTN (Public Switched Telephone Network), etc. have been developed for different locations [16, 18]. A kind of real-time system in which multiple sensors connected simultaneously to one gateway unit it become indispensable, and they are transformed into wireless sensor networks (WSNs) [10]. A mobile sensor sends data to the nearest sensor which is transferred later to the BS via the shortest path as it is shown in **Figure 2**. Indeed, when a sensor has to inform the administrator of an event or simply send the information collected, it must first pass this information to the sink (see. **Figure 2**). It is the one that will transfer the understood information to the administrator through an extensive network such as the Internet or more simply via the satellite. Conversely, when the administrator wants to send information or requests to the

observed data in order to reduce the task at the well node.

**48**

various sensors of the network or one, in particular, the two will have to go through the sink to reach its targets [4, 11].

It turns out that the use of these technologies makes information more accessible by the user. This would significantly improve people's living quality. Especially that wired network has some problems, such as inconvenience and high cost, unsatisfactory security assurance [2]. Therefore, their concept in sensing with their capabilities in transferring the data into a signal has paved the way for the creation of a lot of potential applications that we will see later in this chapter.

The routing algorithm is used to accomplish this task to support multi-hop communication inside the network by the nodes [9]. So, we will understand how to communicate this data and how to monitor the information shared between nodes. These data are typically relayed from node to another and these links are dynamically built on -demand (reactive routing) or dynamically re-computed (proactiverouting) [3, 12]. Proactive routing protocol: they are presented on the same routing principle as wired networks. The routes in this type of routing are calculated in advance - each node encountered updates several routing tables by exchanging packets between neighbors. Also, they luckily tend to have a communication brink between them for reason that path computation is generated upon request or the occurrence of specific events from the application data to the sink node. Preferentially, the node should be able to enter and leave the network [1].

**Figure 5.** *OSI MODEL and their signification [4, 8, 10, 18].*

We can use any kind of protocol to communicate the information, and careful protocol design is needed as well as a successful target application [4, 8, 10]. So, the routes are determined before they are used. Since host nodes are mobile. So, it causes frequent and unpredictable topological changes in the network [17]. Dealing with the formation and maintenance of WSN Network is very difficult. In recent years, a lot of routing protocols have been proposed for WSNs, out of two major protocols AODV which is a reactive routing protocol because its uses and efficiency in energy consumption represents a significant performance factor that limits node capacity [8, 11].

Also, each layer of the model communicates with an adjacent layer (that of the top or that of the lower part). Each layer uses the services of the sub-bases and provides some to that of higher level.

As it was mentioned above each layer has its own significant. And to give more detail (see **Figure 5**).

#### **6. Vulnerabilities and challenges in WSN**

Wireless sensor network is an interconnection among hundreds, thousands, or millions of sensor nodes. It is capable of sensing, data processing, and communication tasks. During this process, Maintenance and route computation are needed to involve a minimum number of nodes [20].

So, their flexibility is provided by each node which acts as a router to forward each other's packets to enable out of range communication and to forward each other the data packets which is multi-hop; because Their less capable hardware and limited capability such as node limitation, network limitations, physical limitations, the inherent vulnerabilities of wireless communication like physical vulnerability and other related to wireless technology, also, the dense deployment nature in public and hostile environments in many applications, the restricted field of sensing and sensitive nature of collected data, unattended operation [4, 11].

This minimal configuration and lack of infrastructure, also the quick deployment makes WSNs convenient for emergency operations especially for military operations [2, 5]. In WSN, multi-hop routing, higher latency in packet transmission may achieve difficult synchronization which is due to network congestion and processing intermediate nodes.

Being limited by computation resources, WSN process the following limitations as it is shown in **Figure 6** because the position of the sensor nodes in a wireless sensor network (WSN) is of paramount importance for their design and for their implementation that will intersect with their architecture and design requirements in parallel with their specifications techniques like energy consumption, connectivity and coverage. Let us started with the first metric which is the coverage.

**51**

*Design Model and Deployment Fashion of Wireless Sensor Networks*

the reporting period may range from months to years.

some specific network scenarios (e.g., a controllable WSN) [11, 18].

Coverage ensures the monitoring area by at least one sensor node while connectivity is required to make sure that every sensor node is directly connected to the sink node or indirectly connected to this last via any other sensor nodes [1, 11, 19]. Two sensor nodes that are outside the communicate directly [11, 19]. Consequently, connectivity cannot be guaranteed. Most applications in WSNs involve batterypowered nodes with limited energy where their batteries may not be convenient for recharging or replacing [7]. Thus, it is very crucial to find a way to reduce the energy consumption because it is inconvenient to keep on changing the battery specially if WSN is installed in remote area. The desired coverage can be assured as the locations of sensor nodes are carefully planned according to certain requirements. A wireless sensor network (WSN) has to maintain a desirable sensing coverage and periodically report sensed data to the administrative center (i.e., base station), and

Coverage and lifetime are two paramount problems in a WSN due to constraint of associated battery power [5]. All the existing theoretical analyses on the coverage and lifetime are primarily focused on the random uniform distribution of sensors or

Coverage and connectivity can be optimized by deploying a large number of sensor nodes. Unfortunately, the connectivity cannot remain unchanging at any working time. The sensor network is a broadcast network in which any signal can be captured by adversaries at any time. These features make wireless ad-hoc sensor networks more vulnerable than wired networks. This presents real challenges in the

This factor is of paramount importance during the design and implementation

Another concern in WSN, is about energy efficiency. In WSN, each sensor node may need to support multiple communication models including unicast, multicast, and broadcast. Therefore, due to the limited battery lifetime, security mechanisms for sensor networks must be energy efficient [1, 10]. Especially, the number of message transmissions and the amount of expensive computation should be a few as

implementation of the following security requirements for WSNs [4, 11, 19].

of WSN network which ensure the network lifetime in its operating system.

Since the transmission distance also affects the energy consumption, it is another factor to be considered [8]. Due to these factors, a sensor node placement algorithm for WSN is needed to ensure that the position of deployed sensor nodes is able to provide maximum coverage, minimum energy without jeopardizing connectivity although the communication methods and protocols of the sensor node may affect the coverage, connectivity and energy consumption, they are only considered after the sensor node positions have been determined [4, 19]. Romoozi [16] stated that these is a tradeoff between energy consumption and network coverage. Bigger coverage is achieved if the distance between two sensor nodes is further [16]. However, their energy consumption will be higher due to longer distance data transmission. The tradeoff between system lifetime and system reliability is a

paramount design consideration for wireless sensor networks [2, 4, 11].

*DOI: http://dx.doi.org/10.5772/intechopen.94256*

**6.1 Coverage**

**6.2 Connectivity**

**6.3 Energy consumption**

possible [17, 19].

#### **Figure 6.**

*WSN challenges [1, 3, 7, 8, 18, 19].*

#### **6.1 Coverage**

*Wireless Sensor Networks - Design, Deployment and Applications*

capacity [8, 11].

detail (see **Figure 5**).

operation [4, 11].

processing intermediate nodes.

provides some to that of higher level.

**6. Vulnerabilities and challenges in WSN**

involve a minimum number of nodes [20].

We can use any kind of protocol to communicate the information, and careful protocol design is needed as well as a successful target application [4, 8, 10]. So, the routes are determined before they are used. Since host nodes are mobile. So, it causes frequent and unpredictable topological changes in the network [17]. Dealing with the formation and maintenance of WSN Network is very difficult. In recent years, a lot of routing protocols have been proposed for WSNs, out of two major protocols AODV which is a reactive routing protocol because its uses and efficiency in energy consumption represents a significant performance factor that limits node

Also, each layer of the model communicates with an adjacent layer (that of the top or that of the lower part). Each layer uses the services of the sub-bases and

As it was mentioned above each layer has its own significant. And to give more

Wireless sensor network is an interconnection among hundreds, thousands, or millions of sensor nodes. It is capable of sensing, data processing, and communication tasks. During this process, Maintenance and route computation are needed to

So, their flexibility is provided by each node which acts as a router to forward each other's packets to enable out of range communication and to forward each other the data packets which is multi-hop; because Their less capable hardware and limited capability such as node limitation, network limitations, physical limitations, the inherent vulnerabilities of wireless communication like physical vulnerability and other related to wireless technology, also, the dense deployment nature in public and hostile environments in many applications, the restricted field of sensing and sensitive nature of collected data, unattended

This minimal configuration and lack of infrastructure, also the quick deployment makes WSNs convenient for emergency operations especially for military operations [2, 5]. In WSN, multi-hop routing, higher latency in packet transmission may achieve difficult synchronization which is due to network congestion and

Being limited by computation resources, WSN process the following limitations

as it is shown in **Figure 6** because the position of the sensor nodes in a wireless sensor network (WSN) is of paramount importance for their design and for their implementation that will intersect with their architecture and design requirements in parallel with their specifications techniques like energy consumption, connectiv-

ity and coverage. Let us started with the first metric which is the coverage.

**50**

**Figure 6.**

*WSN challenges [1, 3, 7, 8, 18, 19].*

Coverage ensures the monitoring area by at least one sensor node while connectivity is required to make sure that every sensor node is directly connected to the sink node or indirectly connected to this last via any other sensor nodes [1, 11, 19]. Two sensor nodes that are outside the communicate directly [11, 19]. Consequently, connectivity cannot be guaranteed. Most applications in WSNs involve batterypowered nodes with limited energy where their batteries may not be convenient for recharging or replacing [7]. Thus, it is very crucial to find a way to reduce the energy consumption because it is inconvenient to keep on changing the battery specially if WSN is installed in remote area. The desired coverage can be assured as the locations of sensor nodes are carefully planned according to certain requirements. A wireless sensor network (WSN) has to maintain a desirable sensing coverage and periodically report sensed data to the administrative center (i.e., base station), and the reporting period may range from months to years.

Coverage and lifetime are two paramount problems in a WSN due to constraint of associated battery power [5]. All the existing theoretical analyses on the coverage and lifetime are primarily focused on the random uniform distribution of sensors or some specific network scenarios (e.g., a controllable WSN) [11, 18].

#### **6.2 Connectivity**

Coverage and connectivity can be optimized by deploying a large number of sensor nodes. Unfortunately, the connectivity cannot remain unchanging at any working time. The sensor network is a broadcast network in which any signal can be captured by adversaries at any time. These features make wireless ad-hoc sensor networks more vulnerable than wired networks. This presents real challenges in the implementation of the following security requirements for WSNs [4, 11, 19].

#### **6.3 Energy consumption**

This factor is of paramount importance during the design and implementation of WSN network which ensure the network lifetime in its operating system.

Another concern in WSN, is about energy efficiency. In WSN, each sensor node may need to support multiple communication models including unicast, multicast, and broadcast. Therefore, due to the limited battery lifetime, security mechanisms for sensor networks must be energy efficient [1, 10]. Especially, the number of message transmissions and the amount of expensive computation should be a few as possible [17, 19].

Since the transmission distance also affects the energy consumption, it is another factor to be considered [8]. Due to these factors, a sensor node placement algorithm for WSN is needed to ensure that the position of deployed sensor nodes is able to provide maximum coverage, minimum energy without jeopardizing connectivity although the communication methods and protocols of the sensor node may affect the coverage, connectivity and energy consumption, they are only considered after the sensor node positions have been determined [4, 19]. Romoozi [16] stated that these is a tradeoff between energy consumption and network coverage. Bigger coverage is achieved if the distance between two sensor nodes is further [16]. However, their energy consumption will be higher due to longer distance data transmission. The tradeoff between system lifetime and system reliability is a paramount design consideration for wireless sensor networks [2, 4, 11].


#### **Table 1.**

*Nodes' constraints in WSN [1, 3, 7, 8, 12, 19].*

Due to distributed nature of these networks and their deployment in remote areas, the node constraints have been summarized in **Table 1**.

They are fully distributed, and adaptive regarding frequent changes [2]. Their deployment in ubiquitous and pervasive applications, inherently; a wireless sensor network is an interconnection among hundreds, thousands or millions of sensor nodes. Sensor node is capable of sensing, data processing and communication tasks. During this process, Maintenance and route computation are needed to involve minimum number of nodes [4].

#### **7. Areas of application of the WSN**

The basic objectives of wireless sensor networks generally depend on the applications; however, the following tasks are common to several applications.

They have a large catalog of applications where they can be found. We have already mentioned a few that shows just a range of possibilities. Among them, we can try to name few [5–7, 11, 13, 15, 20] in where they can determine the values of some parameters according to a given situation. For example, in an environmental network, one can seek to know the temperature, the atmospheric pressure, the amount of sunlight, and the relative humidity in a number of sites, etc. [12, 17].

Detect the occurrence of events that we are interested in and it estimates the parameters of the events detected. In traffic control networks, one may want to detect the movement of vehicles through an intersection and estimate the speed and the direction of the vehicle [5, 12]. Classify the object detected, e. g in a traffic network is a vehicle a car, a bus, etc. [6]. So, they are fully distributed and adaptive regarding frequent changes. Their deployment in ubiquitous and pervasive applications,

The ease of deployment of wireless sensor networks (WSN) in a harsh and hostile environment has paved the way for the use of several applications.

Wireless Sensor Networks (WSNs) have recently attracted a lot of interest in the research community due to their wide range of applications and have a vast area of application for real-time event detection. Their simplification in wiring and harness

**53**

*Design Model and Deployment Fashion of Wireless Sensor Networks*

helps in improving people's living quality. They are implicated in smart homes in these last years. Some applications already exist using WSN especially in the

**Mission-critical applications** in wireless sensor networks (WSN) such as fire alarms, radiation leaks, and monitoring in hostile environments should have a fast, reliable, and tolerant response to protocol failures routing. Otherwise, these applications will not be able to function properly and it will bring unexpected material,

Using the miniaturization of micro-sensors, the increasingly low cost, the wide range of types of sensors available (thermal, optical, vibration, etc.) as well as the wireless communication medium allow the application of sensors in several fields

In **the Military sector** as in many other technologies, the military sector was the initial engine for the development of sensor networks. The rapid deployment, the reduced cost, the self-organization, and the fault tolerance of sensor networks are characteristics that make this type of network an appreciable tool in such a field. Currently, WSNs can be an integral part of a command, control, communication,

**The Medical field,** Sensor networks are widely used in the medical field. This class includes applications such as: providing a help interface for the disabled, collecting better human physiological information, as well as, facilitating the diagnosis of certain diseases, continuously monitoring the sick and doctors inside the hospital. Also, they can be used to ensure permanent monitoring of the vital organs of human beings thanks to micro-sensors which can be swallowed or implanted on the patient (blood sugar monitoring, cancer detection, …). They can also facilitate the diagnosis of some diseases by carrying out physiological measurements such as: blood pressure, heartbeat, temperature. Each sensor must have a very specific task

**The Architectural domain** Transformation of buildings into intelligent environments is capable of recognizing people, interpreting their actions, and reacting

**The environmental field** is fairly varied field. The sensors are used to detect the pollution level of factories as well as to monitor the activity of a volcano. For example, we can mention the real-time detection of forest fires and faster industrial risks and reduce the leakage of toxic products (gas, chemicals, radioactive elements, petroleum, etc.). to detect natural disasters (forest fires, earthquakes, etc.). It detects fumes of toxic products (gases, chemicals, petroleum, etc.) in industrial

**The security domain** is the most important and sensitive area or sector in which

the sensors can be in buildings in order to detect alterations in their structure or else be used to detect intrusions by building a distributed alarm system, monitoring railways, to prevent accidents, or the detection of water leaks in dams to avoid

Wireless sensor networks have the potential for many applications (military, security, environment, medicine, commerce, etc.). The choice and model of a WSN

**The commercial domain** is among domains where sensor networks have proven their usefulness. Several applications can be listed in this sector, such as: monitoring the condition of the equipment, controlling and automating the machining pro-

for using it. It is mainly a remote monitoring of a patient [12, 16].

*DOI: http://dx.doi.org/10.5772/intechopen.94256*

following fields [6, 12, 14, 16–18]:

financial or human losses [2, 9, 11].

surveillance, reconnaissance, etc. [2, 16].

sites such as nuclear or oil plants [12, 15, 17].

including:

to them [12, 14].

cesses, etc. [7, 13, 14].

possible damage [2, 9, 12].

**8. Conclusion**

#### *Design Model and Deployment Fashion of Wireless Sensor Networks DOI: http://dx.doi.org/10.5772/intechopen.94256*

*Wireless Sensor Networks - Design, Deployment and Applications*

**Constraint Description**

Energy constraints Smaller memory capacity

Memory limitations Limited memory capacity

Unreliable communication Open air medium

Higher latency in communication Limited radio spectrum

Node limitations Frequent path beak

Heterogeneous nature of sensor nodes Limited battery power

Physical limitations Lack of tamper resistant packaging

Limited battery life

Processing power Low computational power Low bandwidth

Wireless transmission

Affects multiple access,

No centralized infrastructure

Inherent limitations in sensor networks

interference

Design constraint

Due to distributed nature of these networks and their deployment in remote

They are fully distributed, and adaptive regarding frequent changes [2]. Their deployment in ubiquitous and pervasive applications, inherently; a wireless sensor network is an interconnection among hundreds, thousands or millions of sensor nodes. Sensor node is capable of sensing, data processing and communication tasks. During this process, Maintenance and route computation are needed to involve

The basic objectives of wireless sensor networks generally depend on the appli-

They have a large catalog of applications where they can be found. We have already mentioned a few that shows just a range of possibilities. Among them, we can try to name few [5–7, 11, 13, 15, 20] in where they can determine the values of some parameters according to a given situation. For example, in an environmental network, one can seek to know the temperature, the atmospheric pressure, the amount of sunlight, and the relative humidity in a number of sites, etc. [12, 17]. Detect the occurrence of events that we are interested in and it estimates the parameters of the events detected. In traffic control networks, one may want to detect the movement of vehicles through an intersection and estimate the speed and the direction of the vehicle [5, 12]. Classify the object detected, e. g in a traffic network is a vehicle a car, a bus, etc. [6]. So, they are fully distributed and adaptive regarding frequent changes. Their deployment in ubiquitous and pervasive applications, The ease of deployment of wireless sensor networks (WSN) in a harsh and

cations; however, the following tasks are common to several applications.

hostile environment has paved the way for the use of several applications.

Wireless Sensor Networks (WSNs) have recently attracted a lot of interest in the research community due to their wide range of applications and have a vast area of application for real-time event detection. Their simplification in wiring and harness

areas, the node constraints have been summarized in **Table 1**.

minimum number of nodes [4].

*Nodes' constraints in WSN [1, 3, 7, 8, 12, 19].*

**Table 1.**

**7. Areas of application of the WSN**

**52**

helps in improving people's living quality. They are implicated in smart homes in these last years. Some applications already exist using WSN especially in the following fields [6, 12, 14, 16–18]:

**Mission-critical applications** in wireless sensor networks (WSN) such as fire alarms, radiation leaks, and monitoring in hostile environments should have a fast, reliable, and tolerant response to protocol failures routing. Otherwise, these applications will not be able to function properly and it will bring unexpected material, financial or human losses [2, 9, 11].

Using the miniaturization of micro-sensors, the increasingly low cost, the wide range of types of sensors available (thermal, optical, vibration, etc.) as well as the wireless communication medium allow the application of sensors in several fields including:

In **the Military sector** as in many other technologies, the military sector was the initial engine for the development of sensor networks. The rapid deployment, the reduced cost, the self-organization, and the fault tolerance of sensor networks are characteristics that make this type of network an appreciable tool in such a field. Currently, WSNs can be an integral part of a command, control, communication, surveillance, reconnaissance, etc. [2, 16].

**The Medical field,** Sensor networks are widely used in the medical field. This class includes applications such as: providing a help interface for the disabled, collecting better human physiological information, as well as, facilitating the diagnosis of certain diseases, continuously monitoring the sick and doctors inside the hospital. Also, they can be used to ensure permanent monitoring of the vital organs of human beings thanks to micro-sensors which can be swallowed or implanted on the patient (blood sugar monitoring, cancer detection, …). They can also facilitate the diagnosis of some diseases by carrying out physiological measurements such as: blood pressure, heartbeat, temperature. Each sensor must have a very specific task for using it. It is mainly a remote monitoring of a patient [12, 16].

**The Architectural domain** Transformation of buildings into intelligent environments is capable of recognizing people, interpreting their actions, and reacting to them [12, 14].

**The commercial domain** is among domains where sensor networks have proven their usefulness. Several applications can be listed in this sector, such as: monitoring the condition of the equipment, controlling and automating the machining processes, etc. [7, 13, 14].

**The environmental field** is fairly varied field. The sensors are used to detect the pollution level of factories as well as to monitor the activity of a volcano. For example, we can mention the real-time detection of forest fires and faster industrial risks and reduce the leakage of toxic products (gas, chemicals, radioactive elements, petroleum, etc.). to detect natural disasters (forest fires, earthquakes, etc.). It detects fumes of toxic products (gases, chemicals, petroleum, etc.) in industrial sites such as nuclear or oil plants [12, 15, 17].

**The security domain** is the most important and sensitive area or sector in which the sensors can be in buildings in order to detect alterations in their structure or else be used to detect intrusions by building a distributed alarm system, monitoring railways, to prevent accidents, or the detection of water leaks in dams to avoid possible damage [2, 9, 12].

## **8. Conclusion**

Wireless sensor networks have the potential for many applications (military, security, environment, medicine, commerce, etc.). The choice and model of a WSN depends greatly on the need for the application as well as the type of sensors used. In this chapter, we had the opportunity to discover what is a WSN, and the elements that go with it to lead an application to a specific domain. The advance of technology allowed the creation of prototype WSNs, but the hardware and software both have a way to go before WSNs are cost-effective, practical, and useful. To sum up, it emerged from this first chapter that thanks to their small size, their relatively low cost and their various functional characteristics, sensor networks offer us a truly immense range of possibilities. They can be used both on a civil level and in specialized fields. Unfortunately, the various constraints mentioned still hamper in their use. Indeed, the amount of energy is a big brake on this technology which continues fortunately to develop. On the other hand, another concern in this technology is the assurance of the conduct of information. So, the assurance as a captured phenomenon has been transmitted to the administrator. In this regard, the requirement for the security of its wireless sensor networks is one of the main obstacles. Securing a network of sensors amounts set up the various security services in this network, while taking into account its different characteristics. More precisely, it is to secure the routing protocols of the network layer; and it will be the main point of another next chapter.
