# Software Defined Networks in Wireless Sensor Architectures
## 3 Wireless Sensor Networks
### Wireless Sensor Networks Applicability  
WSNs are highly useful in several fields of research, overall in computer science and telecommunications. Such networks provide a great applicability from the point of view of monitoring to obtain important information in a system or an environment. Figure 4 provides an organized tree of WSN applicability. The most common application of WSN is area monitoring, which consists of deploying sensors in a place to detect some phenomenon that wants to be monitored. An example of area monitoring is the use of this type of network to detect fire, gas, enemy intrusion among others. WSN are also used in smart grids and energy control systems in order to measure the quantity of energy that a user or application is using, and, at the same time, they are able to regulate such energy consumption. In this way, WSNs are extremely useful in smart buildings at controlling the indoor climate, controlling parking lots, turning on light bulbs in corridors and so on. Another great applicability is found in the health care field [49; 50]. Medical applications can help patients to detect and to tackle possible diseases with enough time to apply an effective treatment. It is divided into two types: implanted or wearable. Regarding implanted devices, they are composed of the artifacts that are introduced into the human body. Moreover, they monitor human information such as human tension and sugar levels among others. Nowadays, fitness information is gaining importance since the quantity of people practising sports is growing. In this way, other types of sensor networks applicable to health care have appeared, the wearable devices. These devices are used on the surface of the human body surface or close to vital organs, in order to measure data from the body (number of steps in a day, consumed calories, cardiac frequency, etc.). Figure 4: Summary of WSN applicability. In addition, other fields in which to apply sensor networks is environmental or earth sensing. There are several examples of these kinds of sensor networks, but the most important are the following: firstly, air pollution monitoring WSNs are deployed in some cities to measure the concentration of dangerous gases for the population. These dangerous gases come from cars and factories among others. The advantage of wireless sensors with respect to the wired sensors is the mobility to test data readings in different places or areas across the city. Secondly, a WSN can be set up in a forest in order to detect if a fire has been initiated. In this case, network nodes have been deployed with sensors to measure the percentage of gases, temperature and humidity. The advantage in this field is the capacity to detect prematurely a fire and how it is expanding across the forest. Thirdly, a WSN is very useful to detect slight movements on the floor. Sensors within network nodes are able to gather data, which is very important to in order to get a pattern or an occurrence of landslides. The advantage in this applicability is the reduction in the reaction time before a soil movement happens. Following this topic, WSN can be effectively used in the prevention of natural disasters like floods [51], hurricanes, volcano eruptions, etc. In this way, [PERSON] et al. [52] propose WSN to study seismic signals in a volcano. The proposed deployment consists of 16 sensor networks with a seismometer and a microphone that gather seismic and acoustic data from the volcano. These sensors send collected data to a gateway node that is also situated near the volcano, and, after that, it transmits the data via free wave radio to an observatory. Fourthly, a direct human involving factor is the water quality. WSNs are established in oceans and rivers as well as underground water reserves. The use of sensor networks provides an accurate water status as input to a system that determines if the water is drinkable. Another important applicability of WSN is in industrial monitoring.