Abstract
The unique characteristics of underwater wireless sensor networks (UWSN) pose many constraints in transmission of data packets and energy efficiency is one of them. The battery powered underwater acoustic nodes require sophisticated protocols to control the nodes' active and sleep periods in order to increase the nodes lifetime. In the terrestrial networks a number of variants of Receiver Initiated MAC (RI-MAC) protocols utilize the nodes active and sleep cycles with the aim to improve the energy efficiency of the overall network. Motivated by the significance of less costly and energy efficient RI-MAC protocol, we present its two variants for the UWSN. In the first protocol, Duty Cycle Scheduling based on Residual Energy (RidE), each sender node to adjust its duty-cycle based on its residual energy. In the second protocol, Duty Cycle scheduling based on Next Wake-up Time (NeWT), each node calculates its duty cycle according to the duty cycle of last awake node, this allows the nodes to avoid any data collision and utilize their sleep modes efficiently to conserve their energy. The simulation results show that, RidE alleviates the need of additional re-transmissions as all the sender nodes overhear the communication with the receiver and plan their communication accordingly at the cost of additional energy consumption. Whereas, in NeWT energy consumption is minimized as the nodes stay awake for shorter period.