Exploiting the Collision-Free Region with Slotting Access for Data-Gathering in the Linear UANs.

Long transmission range and non-negligible propagation delay are the unique features of medium accessing in underwater acoustic networks (UANs). In this paper, we study the medium access control (MAC) problem during data gathering from large-scale regular linear UANs where the underwater sensors are deployed in a one-dimensional chain with equal distance. We suppose each underwater sensor in the linear network are capable to transmit their packets to the receiver through one-hop transmission directly. During the data-gathering mission, the underwater sensors and the receiver construct a star-connected topology. In star-connected topology, it is possible to exploit the collision-free regions and reuse the medium while adopting the slotting technique. On this basis, we propose a slotted-based lightweight scheduling MAC (SLS-MAC) protocol. By jointly designing the slot length and scheduling the receiver position, the SLS-MAC can achieve collision-free data gathering and spatial reuse in the sink node. In the ideal case, the SLS-MAC can achieve almost 1 in normalized network throughput. Considering the limitation of the physical modem, in the worse case, the achievable normalized network throughput of SLS-MAC is also greater than 0.5, which is much greater than conventional slotted access MAC. The NS-3 simulator is used to validate our analysis and evaluate the network performance of the proposed SLS-MAC.