Avoiding Routing Voids With Selective Transmission Power in Underwater Wireless Sensor Networks

Underwater wireless sensor networks have been deployed lately to facilitate many applications such as underwater world surveillance and exploration. It relies mainly on acoustic waves for carrying the sensed data from underwater nodes to a surface sink. However, many challenges are faced by such networks including long propagation delays, low bandwidth, the difficulty of obtaining exact location, mobility, and sparsity of deployment. An efficient and simple routing strategy that is based on depth information is used to tackle the problem of localization. However, all protocols adopting the classical depth-based routing don't work well for sparse underwater wireless sensor networks and consume high energy in a dense network. To overcome this, we propose a routing strategy that combines the simplicity of the depth-based routing technique with the acoustic modem capability of switching between a discrete set of transmission power levels. Each level is associated with a range at which the signal-to-noise ratio (SNR) is above the acoustic receiver threshold. In our strategy, nodes increment their transmission power level until at least one forwarder is found within a depth below the sender depth. Our technique shows that using selective transmission power with DBR enhances the delivery ratio and reduces the consumed energy with a slight increase in end-to-end delays.