Energy efficient routing protocols and efficient bandwidth techniques in Underwater Wireless Sensor Networks - a survey

The underwater wireless remote sensors convey messages in a range, where there is no possible human intervention. It is difficult to replace the battery in order to sustain energy in an acoustic environment. Moreover, considering the environment, solar energy cannot be used to recharge for batteries. These sensors are required to be awake for an extended period, taking in consideration that they have constrained energy limitations. One of the difficulties in submerged remote sensor systems is the uneven utilization of the energy resources. This will eventually result in lessening the lifetime of the sensors in the underwater networks. When compared to regular wireless sensor networks, Underwater Wireless Sensor Networks (UWSN) have a harsher surrounding, which could be translated into high energy constraints, low bandwidth, decreased throughput, and propagation delay. In multi-hop communication, the distance between the anchor node and the normal node is more considerable; which leads to more consumption of energy. On the other hand, since the distance is longer, it results into signal attenuation, ending into frequency power loss. The speed of the sound in deep ocean should be considered as the depth of the ocean increases. The variation of the speed of the sound results into this specific loss. A typical power spectral density occurs when the combined attenuation and noise are combined. Resulting into a decline of 18 dB within the duration of ten years. Among the layers of acoustic sensor network physical UWSN conventions are outlined in a manner that the energy utilization is compensated. While packets are being forwarded, the energy consumption must be less or balanced, else energy holes are created. In such cases, the energy efficiency, lifetime, and throughput are expanded. In this paper, we are summarizing most of the current energy based routing protocols. The provided information could be useful to analyze and design protocols for wireless underwater sensor networks by reducing energy consumption.