Underwater wireless communications have assumed a very vital role in marine activities for military and private commercial purposes like environmental monitoring, underwater exploration, as well as scientific data collection. Underwater wireless communication networks (UWCNs) involves the interaction, coordination and informative relationship between sensors in order to carry out sensing and monitoring functions. Because about 71% of the earth’s surface is water, the relevance of underwater communication network (UWCN) in a vast range of applications like coastal surveillance systems, underwater vehicle (AUV) operation, environmental research, linking submarines to land, collection of data for water monitoring autonomous oil-rig maintenance, among many others, continues to rise. However useful and necessary they are, underwater networks remain very challenging due to several factors like the harsh conditions – severe attenuation and multi-path dispersion – of underwater channels.
Power and Battery: Due to the use of acoustic signals and its longer distance coverage, underwater wireless networks consume so much power and unlike the sensors of terrestrial wireless networks, underwater wireless sensors cannot use solar energy to recharge the battery. This is one challenge that has proven worrisome to both researchers and scientists and the only feasible way to solve it is if the sensors were designed to self-charge.
Communication Signals: Today, a majority of underwater wireless networks make use of acoustic signals to communicate between sensors. Underwater acoustics is the use of the propagation of sound in water but due to attenuation, propagation delay and high error rates, acoustic signals tend to be more challenging than helpful. The obvious solution to this problem is to try using another kind of signal. Optical signal which has previously been used to communicate sensors appear to be a great direction to turn to for underwater wireless communication.
Distributed Localization and Time Synchronization: In terrestrial wireless network communications, Global Positioning System (GPS) is used to give location and synchronize time or Time-Difference-of-Arrival (TDoA)is used to calculate the distance according to the speed of the signals. However, in underwater wireless network communications, distance between two sensors is very hard to get wether of not positions are known. Methods like Angle-of-Arrival (AoA) and Time-of-Arrival (ToA) are sometimes used as GPS signals do not work underwater but the accuracy is usually largely affected by the underwater environment.
This is a huge problem in underwater wireless networking as data without location information is as good as useless. Hence, more concern and work should be put in to figure out how to get an accurate distance between two underwater sensors.
Routing Protocols: With underwater Wireless Communication network protocol designs, saving energy is a major concern, especially for long-term aquatic monitoring and sensing applications and due to its node mobility, most of the energy-efficient protocols designed for terrestrial wireless networking are not feasible. Hence, more concern should be given to the architect of underwater wireless networks.
Other challenges facing underwater wireless communication include propagation delay, shadow zones, bandwidth amongst so many others. It’s prone nature to failure, extremely high cost and memory problems also consist a challenging block to underwater networking.
Today, Underwater Wireless Sensor Networks (UWSN) has garnered a staggering amount of attention from researchers, scientists and even private businesses. However, when compared to Terrestrial Wireless Sensor Networks (WSN), Underwater Sensor Networks presents one with an intricate complexity.