A Localization Free Variable Transmit Power Routing Protocol for Underwater Wireless Sensor Networks

In underwater wireless sensor networks (UWSNs), adjusting the transmit power of a sensor node in response to the time-varying characteristics of the aquatic medium is one of the promising techniques to combat the hostile environment. It can be used to mitigate the unwanted effects of noise, fading and attenuation on data and reliably deliver it from source to destination utilizing more transmit power. For favorable channel conditions, data packets can be reached to destination at the expense of lower energy consumption. In this chapter, we propose a localization-free variable transmit power routing (LF-VTPR) protocol for UWSNs. The proposed protocol adjusts the transmit power level of the data to send in proportion to the latest link quality states of the routing trajectories. The proposed work is unique and never been done in that it does not involve calculation of position information of nodes. All the conventional and variable transmit power routing protocols that involve localization of nodes require that the three dimensional position coordinates of sensor nodes must be known. Localization is energy inefficient for the limited battery life of sensor nodes in underwater communications. Also, it is difficult to achieve when nodes change their positions with water currents. The LF-VTPR uses the depth and response time information of sensor nodes to forward data to final destination. Simulation results reveal that the scheme outperforms some of the existing schemes in terms of throughput and end-to-end delay.