# A Comprehensive Survey on Real-Time Applications of WSN
## 3 Applications of WSN
### Underwater Sensor Network  
Wireless sensor networks (WSNs) are an emerging technology today, and are made up of a large number of separated tiny embedded sensor nodes that are used in monitoring and sending data from their surroundings [53]. The research in the underwater environment is facing many challenges in localization, node mobility, end to end delay, dynamic topology, energy consumption, and effective communication. In underwater wireless sensor networks, routing is different from the terrestrial wireless sensor networks due to a limited bandwidth, node mobility, and end to end delay in data packet transmission. Existing routing protocols have been analyzed which investigate the optimization performance of network services, node mobility, end to end delay, and energy draining of sensor nodes. Large numbers of routing protocol have been developed for those that are working in Underwater Wireless Sensor Network (UWSN). These protocols evaluate the performance efficiency with respect to an end to end delay, node mobility, network throughput, and energy consumption, etc. [54]. Figure 6, shows the real-time example of underwater sensor network implemented in Aquarium of Zaragoza. The UWSN consists of four different numbers of sensor nodes. Nodes that are anchored to the sea bottom have randomly floated with the water current. Anchored nodes sense data within range environments and route the sensed data toward the surface sink in multi-hop fashion or through autonomous underwater vehicles (AUVs). The autonomous underwater vehicles (AUVs), unmanned underwater vehicles (UUVs) move in water in a fixed pattern to communicate with sensor nodes through a short range and high rate data link. AUVs near the base station negotiate to the sink node to forward the collected data. In UWSN, link failure is a burning issue due to node mobility. Node mobility will create holes in the network causing an increase in the end to end delay in data transmission. The efficient underwater communication poses significant problems due to the intrinsic absorption nature of water. The acoustic signal also faces many problems due to a high error rate, low available bandwidth, node mobility, lower propagation speed, and high end to end delay. In recent years, the wireless sensor network applications have spanned into different fields for use in weather monitoring; water pollution monitoring such as biological, chemical, nuclear, and micro-organism tracking; and disaster prevention. UWSN is also widely used in underwater oil and gas pipeline corrosion detection and military security applications. In order to design an efficient UWSN routing protocol, researchers face many challenges which attenuate the medium, such as node mobility, end-to-end propagation delay, and energy saving [55]. Table 7, depicts the example of the real-time applications for underwater sensor networks. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**References** & **Application** & **Sensors** & **City Deployed in** \\ \hline [PERSON] et al. (2006) [51] & \begin{tabular}{c} FFSS—Forest Fire \\ Surveillance System \\ \end{tabular} & \
\begin{tabular}{c} Temperature, Humidity, \\ Light Sensors \\ \end{tabular} & Daegu, Korea \\ \hline [PERSON] et al. (2007) [52] & FWI—Fire Weather Index &
\begin{tabular}{c} Temperature, Humidity, \\ Moisture, Temperature \\ \end{tabular} & Columbia, Canada \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Examples of prototyped applications for forest monitoring. [PERSON] et al., 2011 investigated and deployed real-time sensors for flood retort development in Portsmouth, England. The authors delineated the semantic sensor web architecture which involved several heterogeneous databases and data sets. The architecture provides an insight into the mechanism for discovering the data sets, defining incorporation-integrated views, real time streaming, visualization, and communication with the obtained information.