A Scheduled and Slotted MAC Protocol for Underwater Acoustic Networks

Unlike terrestrial wireless networks, which employ radio waves to communicate, underwater acoustic networks (UANs) employ acoustic waves to communicate. The long propagation delay and limited bandwidth of UANs pose great challenges for MAC protocol design. But the long propagation delay in underwater acoustic channel permits multiple packets to be “pipelined” concurrently in the underwater channel. To utilize this characteristic of underwater acoustic channel, we propose a slotted FAMA-based MAC protocol (slotted C-FAMA) for underwater acoustic networks in this paper. In this protocol, we use control packets (RTS; CTS, ACK and NACK) for handshaking and time-slotted based to allocate the time for each node to communicate. Every control packet is transmitted from the source node to the destination node at the beginning of each time-slot to avoid collision. The simulations show that the slotted C-FAMA is able to achieve high and stable throughput performance, and increase channel utilization while maintaining low collision rate.